JP2015097206A - Electrode active material, manufacturing method thereof, and power storage device arranged by use of electrode active material - Google Patents
Electrode active material, manufacturing method thereof, and power storage device arranged by use of electrode active material Download PDFInfo
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本発明は、チタン化合物からなる電極活物質及びその製造方法に関する。また、前記電極活物質を用いた蓄電デバイスに関する。 The present invention relates to an electrode active material comprising a titanium compound and a method for producing the same. The present invention also relates to an electricity storage device using the electrode active material.
リチウム二次電池は、軽量、高エネルギー密度という特徴から、ポータブル機器を中心に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としては、放電電位が高く、安全性に優れたリチウムチタン複合酸化物やチタン酸化合物が注目されている。例えば、Li4Ti5O12で表されるスピネル型(特許文献1)、Li2Ti3O7で表されるラムスデライト型(特許文献2)等のリチウムチタン複合酸化物や、HxLiy−xTizO4(0<x≦y、0.8≦y≦2.7、1.3≦z≦2.2)(特許文献3)で表されるチタン酸水素リチウムを、電極活物質に用いる技術が知られている。あるいは、H2Ti12O25で表されるチタン酸化合物(特許文献4)、HxMyTi1.73Oz(0.5≦x+y≦1.07、0≦y/(x+y)≦0.2、3.85≦z≦4.0、MはLi以外のアルカリ金属)(特許文献5)、A2Ti3O7(AはNa、Li、Hから選ばれる少なくとも一種)(特許文献6)等で表される化合物等や、ブロンズ型に類似する結晶構造を有するチタン酸化合物とスピネル型のリチウムチタン複合酸化物の混合物(特許文献7)を用いる技術も知られている。また、負電極において集電体と接する側にスピネル型リチウムチタン複合酸化物層を、セパレーターと対向する側にラムスデライト型リチウムチタン複合酸化物又はアナターゼ型酸化チタンの層を、それぞれ負極活物質として用いた非水電解質電池(特許文献8)も提案されている。 In recent years, lithium secondary batteries have been rapidly spread mainly in portable devices because of their light weight and high energy density. As an electrode active material for a lithium secondary battery, a lithium-titanium composite oxide or titanic acid compound having a high discharge potential and excellent safety has been attracting attention. For example, a lithium-titanium composite oxide such as a spinel type represented by Li 4 Ti 5 O 12 (Patent Document 1) and a ramsdellite type represented by Li 2 Ti 3 O 7 (Patent Document 2), or H x Li Lithium hydrogen titanate represented by y-x Ti z O 4 (0 <x ≦ y, 0.8 ≦ y ≦ 2.7, 1.3 ≦ z ≦ 2.2) (Patent Document 3) is used as an electrode. Techniques used for active materials are known. Alternatively, titanate compounds represented by H 2 Ti 12 O 25 (Patent Document 4), H x M y Ti 1.73 O z (0.5 ≦ x + y ≦ 1.07,0 ≦ y / (x + y) ≦ 0.2, 3.85 ≦ z ≦ 4.0, M is an alkali metal other than Li (Patent Document 5), A 2 Ti 3 O 7 (A is at least one selected from Na, Li, and H) (Patent) A technique using a compound represented by Document 6) or the like, or a mixture of a titanic acid compound having a crystal structure similar to the bronze type and a spinel type lithium titanium composite oxide (Patent Document 7) is also known. In addition, a negative electrode active material includes a spinel type lithium titanium composite oxide layer on the side in contact with the current collector and a ramsdellite type lithium titanium composite oxide or anatase type titanium oxide layer on the side facing the separator, respectively. The nonaqueous electrolyte battery used (Patent Document 8) has also been proposed.
上記のように電極活物質は各種存在するが、それぞれ電気容量や高率充放電特性、充放電サイクル特性などに優劣がある。例えば、Li4Ti5O12で表されるスピネル型リチウムチタン複合酸化物は充放電サイクル特性に優れるが、電池容量は高くない。また、Li2Ti3O7で表されるラムスデライト型リチウムチタン複合酸化物は、理論容量は高いが実際の電池系で取り出せる電気容量は充分でなく、充放電サイクル特性も劣るとともに、別の課題として、合成には1000℃を超える高温加熱工程が必要とされる。H2Ti12O25で表されるチタン酸化合物は、電気容量が高いが、特に近年検討が盛んになってきた高出力用途への適用のために高率充放電特性の改善が求められるようになってきた。従って、現在、蓄電デバイスは様々な用途に向け開発検討がなされているが、用途ごとに最も重視される性能に応じて、他の性能を犠牲にしながら電極活物質が選択されている状況にある。この問題の解決策として、例えば、特許文献8の技術が提案されている。 As described above, there are various types of electrode active materials, but each has superiority or inferiority in electric capacity, high rate charge / discharge characteristics, charge / discharge cycle characteristics, and the like. For example, a spinel type lithium titanium composite oxide represented by Li 4 Ti 5 O 12 is excellent in charge / discharge cycle characteristics, but the battery capacity is not high. In addition, the Ramsdelite-type lithium titanium composite oxide represented by Li 2 Ti 3 O 7 has a high theoretical capacity, but the electric capacity that can be taken out in an actual battery system is not sufficient, and the charge / discharge cycle characteristics are inferior. As a problem, the synthesis requires a high-temperature heating step exceeding 1000 ° C. Although the titanic acid compound represented by H 2 Ti 12 O 25 has a high electric capacity, it seems that improvement of high rate charge / discharge characteristics is required particularly for application to high-power applications that have been actively studied in recent years. It has become. Therefore, at present, development of power storage devices is being studied for various applications, but depending on the performance most important for each application, electrode active materials are being selected while sacrificing other performances. . As a solution to this problem, for example, the technique of Patent Document 8 has been proposed.
ここで、特許文献8の技術は、個々の活物質の長所を生かすため、電池内部での各活物質の配置を工夫したものであり、容量とサイクル特性のトータルバランスを高めることができる優れた技術である。しかしながら、ラムスデライト型リチウムチタン複合酸化物単独使用時ほどの電気容量は得られず、また、スピネル型リチウムチタン複合酸化物単独使用時ほどのサイクル特性も得られず、両者の平均的な性能となってしまうという問題がある。 Here, the technique of Patent Document 8 is a device in which the arrangement of each active material inside the battery is devised in order to take advantage of the individual active materials, and is capable of improving the total balance between capacity and cycle characteristics. Technology. However, the electric capacity is not as high as when using a ramsdellite-type lithium-titanium composite oxide alone, and the cycle characteristics are not as good as when using a spinel-type lithium-titanium composite oxide alone. There is a problem of becoming.
本発明は、優れた電池特性、例えば電気容量や高率充放電特性を示す電極活物質を提供することを目的とする。 An object of this invention is to provide the electrode active material which shows the outstanding battery characteristic, for example, an electrical capacity, and a high rate charge / discharge characteristic.
本発明者らは、鋭意研究を重ねた結果、スピネル型結晶構造を有するリチウムチタン化合物相と、一次元トンネル構造を有する特定のチタン化合物相、とを少なくとも含む電極活物質を蓄電デバイスの活物質に用いると、スピネル型リチウムチタン化合物の容量や高率充放電容量と一次元トンネル構造チタン化合物の容量や高率充放電容量とから計算された理論的な電池容量や高率充放電容量に比べ高い値を示し、時には、それぞれの化合物を単独で活物質として用いた場合のそれぞれが長所としている電池特性と同等もしくはそれを超える電池特性を示すことを見出し、本発明を完成させた。 As a result of intensive studies, the present inventors have developed an electrode active material containing at least a lithium titanium compound phase having a spinel crystal structure and a specific titanium compound phase having a one-dimensional tunnel structure as an active material for an electricity storage device. Compared to the theoretical battery capacity and high rate charge / discharge capacity calculated from the capacity and high rate charge / discharge capacity of spinel type lithium titanium compound and the capacity and high rate charge / discharge capacity of one-dimensional tunnel structure titanium compound The inventors have found that the present invention has been completed by showing high battery values, sometimes showing battery characteristics equivalent to or exceeding the battery characteristics of each compound when used alone as an active material.
即ち、本発明は、
(1)スピネル型結晶構造を有するリチウムチタン化合物相と、一般式として(式1)で表される一次元トンネル構造を有するチタン化合物相、の少なくとも二相を有する電極活物質であり、
(式1)H2-XAXTinO2n+1(Aはアルカリ金属であり、Xは0≦X≦2を満たす実数であり、nはn≧6を満たす整数である。)
(2)前記の一次元トンネル構造を有するチタン化合物相が、式1中のnが6,8,12,18,24のいずれか一種又は二種以上である上記(1)の電極活物質であり、
(3)上記(1)又は(2)に記載の電極活物質を正極又は負極に用いた蓄電デバイスであり、
(4)スピネル型結晶構造を有するリチウムチタン化合物の含有物と、一般式として前記式1で表される一次元トンネル構造を有するチタン化合物の含有物、を混合する工程を有する電極活物質の製造方法であり、
(5)前記(4)で作製した混合物を焼成する工程を有する電極活物質の製造方法、
である。
That is, the present invention
(1) An electrode active material having at least two phases of a lithium titanium compound phase having a spinel crystal structure and a titanium compound phase having a one-dimensional tunnel structure represented by (Formula 1) as a general formula,
(Equation 1) H 2-X A X Ti n O 2n + 1 (A is an alkali metal, X is a real number satisfying 0 ≦ X ≦ 2, n is an integer satisfying n ≧ 6.)
(2) The electrode active material according to the above (1), wherein the titanium compound phase having the one-dimensional tunnel structure is any one or two or more of 6, 8, 12, 18, and 24 in Formula 1. Yes,
(3) An electricity storage device using the electrode active material according to (1) or (2) as a positive electrode or a negative electrode,
(4) Production of an electrode active material having a step of mixing a lithium titanium compound-containing material having a spinel crystal structure with a titanium compound-containing material having a one-dimensional tunnel structure represented by Formula 1 as a general formula Is the way
(5) A method for producing an electrode active material comprising a step of firing the mixture produced in (4),
It is.
本発明の、スピネル型結晶構造を有するリチウムチタン化合物相と、一次元トンネル構造を有する特定のチタン化合物相、を少なくとも含む電極活物質を用いると、それぞれを単独で活物質として用いた場合の特性と同等又はそれを超える特性を有する蓄電デバイスが得られる。 When an electrode active material containing at least a lithium titanium compound phase having a spinel crystal structure and a specific titanium compound phase having a one-dimensional tunnel structure according to the present invention is used, the characteristics when each is used alone as an active material An electric storage device having characteristics equivalent to or exceeding the above can be obtained.
本発明は、スピネル型結晶構造を有するリチウムチタン化合物相と、一般式として前記式1で表される一次元トンネル構造を有するチタン化合物相(以降、「トンネル構造チタン化合物」と記載することもある)、の少なくとも二相を有する電極活物質である。スピネル型結晶構造を有するリチウムチタン化合物は特に限定されるものではないが、その一例に、一般式として、Li4Ti5O12(式2)で表されるリチウムチタン複合酸化物が挙げられる。式2の化合物を例に説明すると、式2のような一般式で代表される化合物相であれば、リチウムやチタン,酸素の一部が他の元素に置換されていてもよいし、化学量論組成のものだけでなく、一部の元素が欠損又は過剰となる非化学量論組成のものでもよい。式2のリチウムチタン複合酸化合物は、粉末X線回折測定(CuKα線使用)において、X線回折パターンのピークが、2θが18.5°および35.7°,43.3°,47.4°,57.3°,62.9°,66.1°の位置(いずれも誤差±0.5°程度)に少なくとも存在する。なお、異種元素で置換すると、前記のピーク位置には若干のシフトが認められる。 The present invention may be described as a lithium titanium compound phase having a spinel crystal structure and a titanium compound phase having a one-dimensional tunnel structure represented by the above formula 1 as a general formula (hereinafter referred to as “tunnel structure titanium compound”). ), An electrode active material having at least two phases. Although the lithium titanium compound having a spinel crystal structure is not particularly limited, an example thereof includes a lithium titanium composite oxide represented by Li 4 Ti 5 O 12 (formula 2). Taking the compound of formula 2 as an example, if it is a compound phase represented by a general formula such as formula 2, a part of lithium, titanium, or oxygen may be substituted with other elements, Not only a stoichiometric composition but also a non-stoichiometric composition in which some elements are deficient or excessive. The lithium-titanium complex acid compound of Formula 2 has an X-ray diffraction pattern peak of 2θ of 18.5 °, 35.7 °, 43.3 °, 47.4 in powder X-ray diffraction measurement (using CuKα ray). It exists at least at the positions of 5 °, 57.3 °, 62.9 °, and 66.1 ° (all of which have an error of about ± 0.5 °). Note that, when substituted with a different element, a slight shift is observed at the peak position.
一般式として式1で表される一次元トンネル構造を有するチタン化合物とは、TiO6八面体が稜共有と頂点共有を介して連結することによりトンネル構造が形成された構造を有し、水素又はアルカリ金属元素がそのトンネル構造内に一次元的に配列することで多量に挿入されることができる化合物である。このようなチタン酸化合物としては例えば一般式としてH2Ti12O25(式3)やH1.5Li0.5Ti6O13、Li2Ti18O37で表されるチタン酸化合物が挙げられる。本発明において式1のnの値としては、n=6,8,12,18,24が好ましく、n=12,18であるとより好ましい。一次元トンネル構造には特に制限はないが、TiO6八面体が稜共有で2つ連結した2辺と頂点共有で1つ連結した2辺とで取り囲まれたトンネル構造(いわゆる2×1のトンネル構造)以外のサイズのトンネル構造が少なくとも存在することが好ましい。例えばn=12の場合、いわゆる2×1と3×1で表される2種類のトンネル構造が存在し、n=8の場合、4×1のトンネル構造が、n=6の場合、3×1のトンネル構造が存在する。アルカリ金属Aとしてはリチウム、ナトリウム、カリウムなどが挙げられ、特にリチウムが好ましい。式1のような一般式で代表されるものであれば、水素やチタン,酸素の一部が他の元素に置換されていてもよいし、化学量論組成のものだけでなく、一部の元素が欠損又は過剰となる非化学量論組成のものでもよい。式3のチタン酸化合物は、空間群P21/mで表され、粉末X線回折測定(CuKα線使用)において、X線回折パターンのピークが、2θ=14.0°,24.8°,28.7°,30.3°,31.1°,43.5°,44.5°,48.6°,57.6°,59.0°の位置に存在する(いずれも誤差±0.5°程度)。なお、異種元素で置換すると、前記のピーク位置には若干のシフトが認められる。また、ブロンズ型に類似する構造を有するチタン酸化合物(特許文献7)のX線回折パターンには、2θ=23.9°,33.4°の位置にピークが存在するが、これら2つのピークは、式3のチタン酸化合物のX線回折パターンには認められない。このため、両者は明確に区別される。 A titanium compound having a one-dimensional tunnel structure represented by Formula 1 as a general formula has a structure in which a TiO6 octahedron is connected through edge sharing and vertex sharing, and a hydrogen or alkali It is a compound in which metal elements can be inserted in a large amount by one-dimensionally arranging in the tunnel structure. Examples of such titanic acid compounds include titanic acid compounds represented by general formulas such as H 2 Ti 12 O 25 (formula 3), H 1.5 Li 0.5 Ti 6 O 13 , and Li 2 Ti 18 O 37. Can be mentioned. In the present invention, the value of n in Formula 1 is preferably n = 6, 8, 12, 18, 24, and more preferably n = 12,18. There is no particular limitation on the one-dimensional tunnel structure, but a tunnel structure surrounded by two sides of two TiO6 octahedrons connected by a shared edge and two sides connected by a shared vertex (a so-called 2 × 1 tunnel structure) It is preferable that at least a tunnel structure having a size other than () exists. For example, when n = 12, there are two types of tunnel structures represented by so-called 2 × 1 and 3 × 1, and when n = 8, a 4 × 1 tunnel structure is 3 × There is one tunnel structure. Examples of the alkali metal A include lithium, sodium, and potassium, and lithium is particularly preferable. As long as it is represented by a general formula such as Formula 1, a part of hydrogen, titanium, or oxygen may be substituted with another element, and not only a stoichiometric composition but also a part of A non-stoichiometric composition in which elements are deficient or excessive may be used. The titanic acid compound of Formula 3 is represented by the space group P2 1 / m, and in the powder X-ray diffraction measurement (using CuKα ray), the peak of the X-ray diffraction pattern is 2θ = 14.0 °, 24.8 °, 28.7 °, 30.3 °, 31.1 °, 43.5 °, 44.5 °, 48.6 °, 57.6 °, and 59.0 ° (all have an error of ± 0) About 5 °). Note that, when substituted with a different element, a slight shift is observed at the peak position. In addition, in the X-ray diffraction pattern of the titanate compound having a structure similar to the bronze type (Patent Document 7), there are peaks at 2θ = 23.9 ° and 33.4 °. Is not observed in the X-ray diffraction pattern of the titanate compound of formula 3. For this reason, both are clearly distinguished.
本発明の電極活物質は、スピネル型結晶構造を有するリチウムチタン化合物相と、トンネル構造チタン化合物相の少なくとも二相がそれぞれ別相として存在している電極活物質をさし、粉末X線回折測定により確認することができる。電極活物質の形状は後述の通り粒子状であることが好ましいが、両相の存在状態としては、一次粒子内に両相が共存してもよく、各単相からなる一次粒子が両相共存二次粒子や凝集体を形成していてもよく、各単相からなる一次粒子,二次粒子,凝集体などが独立に存在していてもよく、一方の相が一次粒子として存在し、他方の相が二次粒子として存在するなど、その存在形態は問わず、リチウムチタン化合物とトンネル構造チタン化合物との間になんらの結合状態の無い混合物であってもよい。なお、一次粒子は各単相からなることが好ましい。もちろん、前記二相以外の別相の存在を排除するものではない。なお、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。 The electrode active material of the present invention refers to an electrode active material in which at least two phases of a lithium titanium compound phase having a spinel crystal structure and a tunnel structure titanium compound phase exist as separate phases, and powder X-ray diffraction measurement Can be confirmed. As described later, the shape of the electrode active material is preferably particulate. However, both phases may coexist in the primary particles, and the primary particles composed of each single phase coexist in both phases. Secondary particles or aggregates may be formed, and primary particles, secondary particles, aggregates, etc., each consisting of a single phase may exist independently, one phase exists as primary particles, and the other The phase may be present as secondary particles, and the mixture may be a mixture without any bonding state between the lithium titanium compound and the tunnel structure titanium compound. In addition, it is preferable that a primary particle consists of each single phase. Of course, it does not exclude the presence of another phase other than the two phases. The secondary particles in the present invention are in a state in which the primary particles are firmly bonded to each other, and easily disintegrated in industrial operations such as normal mixing, pulverization, filtration, water washing, transportation, weighing, bagging, and deposition. Most of them remain as secondary particles.
前記電極活物質は粒子状であることが好ましく、その平均粒子径(電子顕微鏡法による平均一次粒子径で表し、異方性形状の場合は長軸長とする。)は、特に制限を受けないが、通常は、0.05〜100μmの範囲が好ましく、0.1〜20μm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、針状、棒状、板状等の異方性形状、不定形状等特に制限は無いが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。二次粒子を含む電極活物質粒子の平均粒子径(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(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く、2〜30m2/gの範囲がより一層好ましい。粒子形状も、一次粒子と同様に制限は無く、様々な形状のものを用いることができる。 The electrode active material is preferably in the form of particles, and the average particle size (represented by the average primary particle size by electron microscopy and the major axis length in the case of an anisotropic shape) is not particularly limited. However, the range of 0.05 to 100 μm is usually preferable, and the range of 0.1 to 20 μm is more preferable. The particle shape is not limited, but isotropic shape such as spherical shape, polyhedral shape, isotropic shape such as needle shape, rod shape, plate shape, indefinite shape, etc. Powder characteristics such as fluidity, adhesion, and filling properties are improved, and when used as an electrode active material, battery characteristics such as cycle characteristics are also improved, which is preferable. The average particle diameter (median diameter by laser scattering method) of the electrode active material particles containing secondary particles is preferably in the range of 0.1 to 20 μm. Although the specific surface area (BET method) 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, still more preferably in the range of 2~30m 2 / g . The particle shape is not limited as in the case of the primary particles, and various shapes can be used.
スピネル型結晶構造を有するリチウムチタン化合物相と、トンネル構造チタン化合物相の存在比は特に制限は無く、二相共存による本発明の相乗効果が得られるのであれば、任意の割合としてよいが、その比は質量比で0.1:9.9〜9.9:0.1が好適であり、3:7〜7:3がより好適である。 The abundance ratio of the lithium titanium compound phase having the spinel crystal structure and the tunnel structure titanium compound phase is not particularly limited, and any ratio may be used as long as the synergistic effect of the present invention can be obtained by the coexistence of two phases. The mass ratio is preferably 0.1: 9.9 to 9.9: 0.1, and more preferably 3: 7 to 7: 3.
本願発明の電極活物質が優れた電池特性を示す理由は明確ではないが、スピネル型結晶構造のリチウムチタン化合物はリチウムイオンの挿入・脱離速度に優れた材料であり、トンネル構造チタン化合物は多量のリチウムイオンをそのトンネル内に吸蔵することができる容量特性に優れた材料であるため、それらが共存することによる相乗効果に起因するものと本発明者らは考えている。 The reason why the electrode active material of the present invention exhibits excellent battery characteristics is not clear, but a spinel-type crystal structure lithium titanium compound is an excellent material for inserting and desorbing lithium ions, and a large amount of tunnel structure titanium compound. The present inventors consider that the lithium ion is occluded in the tunnel and is excellent in capacity characteristics, and thus is caused by a synergistic effect due to the coexistence of these materials.
前記電極活物質の一次粒子あるいは二次粒子の粒子表面には、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種が被覆されていても良い。なお、ここでいう被覆とは表面を完全に覆った層だけでなく、当該物質が表面に島状に点在する状態も含む。これらの被覆種は、1種を被覆することも、2種以上を積層したり、混合物や複合化物として被覆することもでき、特に、炭素で被覆すると電気伝導性が良くなるので、電極活物質として用いる場合には好ましい。炭素の被覆量は、TiO2換算の各化合物に対し、C換算で0.05〜10重量%の範囲が好ましい。この範囲より少ないと所望の電気伝導性が得られず、多いと却って特性が低下する。より好ましい含有量は、0.1〜5重量%の範囲である。尚、炭素の含有量は、CHN分析法、高周波燃焼法等により分析できる。あるいは、チタン、リチウム、水素、酸素以外の異種元素を、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。 The particle surfaces of the primary particles or secondary particles of the electrode active material are coated with at least one selected from inorganic compounds such as carbon, silica, and alumina, and organic compounds such as surfactants and coupling agents. Also good. Note that the term “coating” as used herein includes not only a layer that completely covers the surface but also a state in which the substance is scattered in an island shape on the surface. These coating species can be coated as a single species, or can be laminated as two or more species, or can be coated as a mixture or composite. Especially, when coated with carbon, the electrical conductivity is improved. When using as, it is preferable. Coating amount of carbon, for each compound of terms of TiO 2, 0.05 to 10 wt% is preferable in C terms. If it is less than this range, the desired electrical conductivity cannot be obtained, while if it is more, the characteristics deteriorate. A more preferable content is in the range of 0.1 to 5% by weight. The carbon content can be analyzed by a CHN analysis method, a high frequency combustion method, or the like. Alternatively, a different element other than titanium, lithium, hydrogen, and oxygen can be contained in the crystal lattice by doping, etc., as long as the crystal form is not inhibited.
次に、本発明は、スピネル型結晶構造を有するリチウムチタン化合物の含有物と、一般式として前記式1で表される一次元トンネル構造を有するチタン化合物の含有物、とを混合する工程を有する電極活物質の製造方法である。 Next, the present invention includes a step of mixing the inclusion of a lithium titanium compound having a spinel crystal structure with the inclusion of a titanium compound having a one-dimensional tunnel structure represented by the above-described formula 1 as a general formula. It is a manufacturing method of an electrode active material.
式1で表されるトンネル構造チタン化合物は、公知の方法で得ることができる。例えば、M2TiyO2y+1(Mはアルカリ金属元素を表し、yは2より大きい整数である)(式4)の化学組成をとる化合物と酸性化合物とを反応させ、その後加熱脱水することにより得られる。式4中のMで表されるアルカリ金属元素としては、リチウム、ナトリウム、カリウム、ルビジウム、セシウム等が挙げられ、中でもナトリウム、カリウム、セシウムは工業的に有利に実施できるので好ましい。酸性化合物としては、塩酸、硫酸、硝酸、フッ酸等の無機酸を用いると反応が進み易く、塩酸、硫酸であれば工業的に有利に実施できるので好ましい。 The tunnel structure titanium compound represented by Formula 1 can be obtained by a known method. For example, by reacting a compound having a chemical composition of M 2 Ti y O 2y + 1 (M represents an alkali metal element and y is an integer greater than 2) (formula 4) with an acidic compound, and then dehydrating by heating can get. Examples of the alkali metal element represented by M in Formula 4 include lithium, sodium, potassium, rubidium, cesium, and the like. Among them, sodium, potassium, and cesium are preferable because they can be implemented industrially advantageously. As the acidic compound, use of an inorganic acid such as hydrochloric acid, sulfuric acid, nitric acid, or hydrofluoric acid is preferable because the reaction can easily proceed, and hydrochloric acid or sulfuric acid can be advantageously implemented industrially.
式4の化合物は、チタン化合物とアルカリ金属化合物とを、乾式または湿式で所望の比率で混合した後、焼成することで得られる。チタン化合物としては、チタン酸化物やチタン塩化物等の無機チタン塩、及び、チタンアルコキシド等の有機チタン化合物を用いることができ、アルカリ金属化合物としては、リチウム、ナトリウム、カリウム、ルビジウム、セシウム等のアルカリ金属の炭酸塩、水酸化物等を用いることができる。中でも、チタン酸化物とアルカリ金属炭酸塩を用いるのが好ましい。尚、本発明では、チタン酸化物とは、チタンと酸素の化合物及びその含水素化合物、含水物または水和物を包含する化合物を意味し、例えば、二酸化チタン(TiO2)等の酸化チタンのほか、メタチタン酸(TiO2・H2O)、オルトチタン酸(TiO2・2H2O)、ペルオキソチタン酸等が挙げられ、これらから選ばれる1種あるいは2種以上を用いることができる。また、結晶性の化合物であっても、非晶質であってもよく、結晶性の場合は、ルチル型、アナターゼ型、ブルッカイト型等のいずれであってもよく、結晶形にも特に制限を受けない。焼成温度は600〜1000℃の範囲が好ましく、この範囲より低いと反応が進み難く、この範囲より高いと生成物同士の焼結が生じ易い。更に好ましい範囲は、700〜900℃である。反応を促進し、且つ生成物の焼結を抑制するために、焼成を2回以上繰り返して行うこともできる。焼成には、流動炉、静置炉、ロータリーキルン、トンネルキルン等の公知の焼成炉を用いることができる。焼成雰囲気としては、大気中及び非酸化性雰囲気を適宜選択できる。焼成機器は、焼成温度等に応じて適宜選択する。焼成後、必要に応じて、粉砕を行っても良い。粉砕は、ハンマーミル、ピンミル、遠心粉砕機等の衝撃粉砕機、ローラーミル等の摩砕粉砕機、ロールクラッシャー、ジョークラッシャー等の圧縮粉砕機、ジェットミル等の気流粉砕機等を用いて乾式で行なっても良く、サンドミル、ボールミル、ポットミル等を用いて湿式で行っても良い。 The compound of Formula 4 is obtained by mixing a titanium compound and an alkali metal compound in a desired ratio in a dry or wet manner, and then firing. As the titanium compound, inorganic titanium salts such as titanium oxide and titanium chloride, and organic titanium compounds such as titanium alkoxide can be used. As the alkali metal compound, lithium, sodium, potassium, rubidium, cesium and the like can be used. Alkali metal carbonates, hydroxides, and the like can be used. Among these, it is preferable to use titanium oxide and alkali metal carbonate. In the present invention, the titanium oxide means a compound containing titanium and oxygen and a hydrogen-containing compound, a hydrate or a hydrate thereof. For example, titanium oxide such as titanium dioxide (TiO 2 ) In addition, metatitanic acid (TiO 2 · H 2 O), orthotitanic acid (TiO 2 · 2H 2 O), peroxotitanic acid, and the like can be used, and one or more selected from these can be used. Further, it may be a crystalline compound or amorphous, and in the case of crystallinity, it may be any of rutile type, anatase type, brookite type, etc. I do not receive it. The firing temperature is preferably in the range of 600 to 1000 ° C. When the temperature is lower than this range, the reaction hardly proceeds. When the temperature is higher than this range, the products are easily sintered. A more preferable range is 700 to 900 ° C. In order to accelerate the reaction and suppress the sintering of the product, the firing can be repeated twice or more. For firing, a known firing furnace such as a fluidized furnace, a stationary furnace, a rotary kiln, or a tunnel kiln can be used. As the firing atmosphere, air and a non-oxidizing atmosphere can be appropriately selected. The firing equipment is appropriately selected according to the firing temperature and the like. You may grind | pulverize as needed after baking. The pulverization is dry using an impact pulverizer such as a hammer mill, a pin mill, or a centrifugal pulverizer, a grinding pulverizer such as a roller mill, a compression pulverizer such as a roll crusher or a jaw crusher, or an airflow pulverizer such as a jet mill. It may be carried out by a wet method using a sand mill, a ball mill, a pot mill or the like.
以下では、式1におけるn=12の場合(式3)を例に製造方法を述べる。前記式3のチタン酸化合物は、式4の化学組成をとる化合物と酸性化合物とを反応させた後、適宜洗浄、固液分離、乾燥を行い、150〜400℃の範囲の温度で加熱脱水することで得られる。式4中のyの値は2より大きければ特に制限は無いが、3〜5の範囲の整数であるのが好ましい。具体的には、Na2Ti3O7、K2Ti4O9、Cs2Ti5O11等が挙げられる。酸性化合物としては、塩酸、硫酸、硝酸、フッ酸等の無機酸を用いることができる。酸性化合物の量や濃度には特に制限は無いが、式4の化合物に含まれるアルカリ金属イオンの反応当量以上で、遊離酸の濃度を2規定以下にするのが好ましい。酸性化合物と式4の化合物との反応温度に特に制限は無いが、式4の化合物の構造が変化し難い100℃未満の範囲の温度で行なうのが好ましい。加熱脱水には、流動炉、静置炉、ロータリーキルン、トンネルキルン等の公知の焼成炉を用いることができ、加熱雰囲気は、大気中、不活性ガス中のいずれであっても良い。好適な加熱脱水温度は、用いた式4の化合物種にも依存するが、例えばNa2Ti3O7と硫酸水溶液を用いた場合は230〜270℃の範囲であると式3の化合物の結晶性が高くなり易く、且つ、単相が得られ易い。230〜270℃の範囲を外れると、H2Ti12O25相に加え、他の相が存在し易くなる。 Hereinafter, the manufacturing method will be described by taking the case of n = 12 in Formula 1 (Formula 3) as an example. The titanic acid compound of the formula 3 is reacted with a compound having the chemical composition of the formula 4 and an acidic compound, and then appropriately washed, solid-liquid separated and dried, and heated and dehydrated at a temperature in the range of 150 to 400 ° C. Can be obtained. The value of y in Formula 4 is not particularly limited as long as it is greater than 2, but is preferably an integer in the range of 3 to 5. Specifically, Na 2 Ti 3 O 7, K 2 Ti 4 O 9, Cs 2 Ti 5 O 11 and the like. As the acidic compound, inorganic acids such as hydrochloric acid, sulfuric acid, nitric acid, and hydrofluoric acid can be used. Although there is no restriction | limiting in particular in the quantity and density | concentration of an acidic compound, It is preferable to make the density | concentration of a free acid 2 N or less above the reaction equivalent of the alkali metal ion contained in the compound of Formula 4. Although there is no restriction | limiting in particular in the reaction temperature of an acidic compound and the compound of Formula 4, It is preferable to carry out at the temperature of the range of less than 100 degreeC in which the structure of the compound of Formula 4 does not change easily. For heat dehydration, a known firing furnace such as a fluidized furnace, a stationary furnace, a rotary kiln, a tunnel kiln can be used, and the heating atmosphere may be either in the air or in an inert gas. A suitable heat dehydration temperature depends on the compound type of the formula 4 used, but for example, when Na 2 Ti 3 O 7 and a sulfuric acid aqueous solution are used, the crystal of the compound of the formula 3 is in the range of 230 to 270 ° C. The properties are likely to be high and a single phase is easily obtained. When the temperature is outside the range of 230 to 270 ° C., other phases are likely to exist in addition to the H 2 Ti 12 O 25 phase.
なお、式3で表される化合物のHの一部をアルカリ金属で置換した、H2−xAxTi12O25(Aはアルカリ金属)(式5)の化合物は、式3の化合物とアルカリ金属化合物とを反応させる工程を含む製造方法によって得られる。アルカリ金属化合物としては、リチウム、ナトリウム、カリウム、ルビジウム、セシウム等のアルカリ金属の炭酸塩、水酸化物等を用いることができる。式3の化合物とアルカリ金属化合物を反応させるには、両者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、水性媒体を用いてスラリー化するのが更に好ましい。水性媒体を用いる場合は、アルカリ金属の水酸化物、炭酸塩等の水溶性アルカリ金属化合物を用いるのが好ましい。固相中で反応を行なう場合は、加熱によって、アルカリ金属化合物が溶融塩となって、式3の化合物と反応すると考えられ、アルカリ金属化合物としては、比較的融点が低いアルカリ金属の硝酸塩、塩化物塩、硫酸塩を用いるのが好ましい。加熱温度は、用いるアルカリ金属化合物によって適宜設定されるが、通常は、150〜400℃の範囲が好ましい。式5中のxの値の範囲は、アルカリ金属化合物による水素イオンの置換量を制御することで定まる。例えば、式3の化合物に含まれる水素イオンの一部をリチウムイオンと置換し、式5中のxの範囲を0<x≦2に調整すれば、一般式としてH2−xLixTi12O25(0<x≦2)の化学組成をとる化合物が得られる。 Note that by replacing part of the H of the compound represented by Formula 3 with an alkali metal, the compound of H 2-x A x Ti 12 O 25 (A is an alkali metal) (Equation 5) can be prepared by reacting a compound of formula 3 It is obtained by a production method including a step of reacting with an alkali metal compound. As the alkali metal compound, carbonates or hydroxides of alkali metals such as lithium, sodium, potassium, rubidium, and cesium can be used. In order to react the compound of Formula 3 and the alkali metal compound, a method of contacting them by mixing them in a liquid phase may be used, or they may be contacted and heated by mixing them in a solid phase. . When the reaction is performed in the liquid phase, the reaction is preferably performed in a slurry, and more preferably slurried using an aqueous medium. When using an aqueous medium, it is preferable to use water-soluble alkali metal compounds such as alkali metal hydroxides and carbonates. When the reaction is carried out in the solid phase, it is considered that the alkali metal compound becomes a molten salt by heating and reacts with the compound of formula 3, and as the alkali metal compound, an alkali metal nitrate or chloride having a relatively low melting point can be used. It is preferable to use a physical salt or a sulfate. Although heating temperature is suitably set with the alkali metal compound to be used, the range of 150-400 degreeC is preferable normally. The range of the value of x in Formula 5 is determined by controlling the amount of hydrogen ion substitution by the alkali metal compound. For example, if a part of hydrogen ions contained in the compound of formula 3 is replaced with lithium ions and the range of x in formula 5 is adjusted to 0 <x ≦ 2, the general formula H 2−x Li x Ti 12 A compound having a chemical composition of O 25 (0 <x ≦ 2) is obtained.
得られた式5の化合物は、必要に応じて洗浄、固液分離した後、乾燥する。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。 The obtained compound of the formula 5 is washed, solid-liquid separated if necessary, and then dried. 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3のチタン酸化合物の二次粒子を製造するには、式4の化合物と酸性化合物とを反応させる工程において、更に(1)式4の化合物を造粒してから酸性化合物と反応させるか、又は(2)式4の化合物を酸性化合物と反応させてから造粒する工程が含まれていれば良い。また、式5のチタン酸の二次粒子を製造するには、式3のチタン酸化合物とアルカリ金属化合物とを反応させる工程において、更に(1)式3のチタン酸化合物とアルカリ金属化合物とを共に造粒後に反応させるか、(2)式3のチタン酸化合物を造粒してからアルカリ金属化合物と反応させるか、又は(3)式3のチタン酸化合物をアルカリ金属化合物と反応させてから造粒する工程が含まれていれば良い。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、原料化合物あるいは反応生成物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 order to produce secondary particles of the titanic acid compound of formula 3, in the step of reacting the compound of formula 4 and the acidic compound, (1) whether the compound of formula 4 is further granulated and then reacted with the acidic compound. Or (2) a step of granulating after reacting the compound of formula 4 with an acidic compound may be included. Moreover, in order to produce the secondary particles of titanic acid of formula 5, in the step of reacting the titanic acid compound of formula 3 and the alkali metal compound, (1) a titanic acid compound of formula 3 and an alkali metal compound are further added. Either after reacting after granulation, (2) granulating the titanate compound of formula 3 and then reacting with the alkali metal compound, or (3) reacting the titanate compound of formula 3 with the alkali metal compound. The process of granulating should just be included. 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. Dry granulation includes methods such as dehydrating a slurry containing a raw material compound or reaction product, drying and pulverizing; dehydrating the slurry, molding and drying; spray drying the slurry, and the like. Of these, spray drying is industrially preferable.
H2Ti8O17の化合物やH2Ti6O13の化合物も、式4の化合物、例えばK2Ti4O9やNa2Ti3O7を原料に調製することができる。また、H2Ti18O37の化合物は、式3のチタン酸化合物を更に300〜600℃の温度で焼成することにより得られる。これらの化合物についても、式3のチタン酸化合物と同様に、水素の一部をアルカリ金属で置換したり、造粒したりして用いることができる。 A compound of H 2 Ti 8 O 17 and a compound of H 2 Ti 6 O 13 can also be prepared from compounds of formula 4, such as K 2 Ti 4 O 9 or Na 2 Ti 3 O 7 as raw materials. The compound of H 2 Ti 18 O 37 is obtained by sintering at a temperature of titanate compounds of Formula 3 further 300 to 600 ° C.. These compounds can also be used by substituting a part of hydrogen with an alkali metal or granulated, like the titanic acid compound of formula 3.
式2のスピネル型結晶構造を有するリチウムチタン化合物は、チタン化合物とリチウム化合物とを、乾式または湿式で所望の比率で混合した後、焼成することで得られる。チタン化合物としては、段落(0020)で述べた、式4の化合物の調製に用いることができるものと同様のチタン化合物を用いることができる。焼成温度は600〜1000℃の範囲が好ましく、この範囲より低いと反応が進み難く、この範囲より高いと生成物同士の焼結が生じ易い。更に好ましい範囲は、650〜900℃である。反応を促進し、且つ生成物の焼結を抑制するために、焼成を2回以上繰り返して行うこともできる。焼成には、前述の公知の焼成炉を用いることができる。焼成雰囲気としては、大気中及び非酸化性雰囲気を適宜選択できる。焼成機器は、焼成温度等に応じて適宜選択する。焼成後、焼結の程度に応じて、粉砕を行っても良い。粉砕には、前述の粉砕機、粉砕方式を採用することができる。 The lithium titanium compound having the spinel crystal structure of Formula 2 is obtained by mixing a titanium compound and a lithium compound in a desired ratio in a dry or wet manner and then firing the mixture. As the titanium compound, the same titanium compound as described in paragraph (0020), which can be used for preparing the compound of formula 4, can be used. The firing temperature is preferably in the range of 600 to 1000 ° C. When the temperature is lower than this range, the reaction hardly proceeds. When the temperature is higher than this range, the products are easily sintered. A more preferable range is 650 to 900 ° C. In order to accelerate the reaction and suppress the sintering of the product, the firing can be repeated twice or more. For the firing, the above-mentioned known firing furnace can be used. As the firing atmosphere, air and a non-oxidizing atmosphere can be appropriately selected. The firing equipment is appropriately selected according to the firing temperature and the like. After firing, pulverization may be performed according to the degree of sintering. For the pulverization, the aforementioned pulverizer and pulverization method can be employed.
式2のスピネル型結晶構造を有するリチウムチタン化合物の二次粒子を製造するには、リチウム化合物とチタン化合物とを反応させる工程において、更に(1)リチウム化合物とチタン化合物とを共に造粒後に反応させるか、(2)チタン化合物を造粒してリチウム化合物と反応させるか、又は(3)リチウム化合物をチタン化合物と反応させてから造粒する工程が含まれていれば良い。造粒には、前述の造粒方法を適宜用いることができるが、噴霧乾燥が工業的に好ましい。 In order to produce secondary particles of a lithium titanium compound having a spinel type crystal structure of Formula 2, in the step of reacting the lithium compound and the titanium compound, (1) reaction after the granulation of the lithium compound and the titanium compound together Or (2) granulating the titanium compound to react with the lithium compound, or (3) granulating the lithium compound after reacting with the titanium compound. For granulation, the above granulation methods can be used as appropriate, but spray drying is industrially preferable.
スピネル型結晶構造を有するリチウムチタン化合物含有物と、トンネル構造チタン化合物含有物の混合は、任意の方法で行うことができ、例えば、各化合物粒子を乾式や湿式で混合する方法が挙げられる。乾式混合は、例えば、流体エネルギー粉砕機、衝撃粉砕機等の乾式粉砕機や、ヘンシェルミキサー、スーパーミキサー等の高速攪拌機等を用い、両者を攪拌、混合することで行うことができる。湿式混合は、例えば、両化合物をスラリーに分散させ、サンドミル、ボールミル、ポットミル、ダイノミルなどの湿式粉砕機を通して混合しても良い。場合によっては、混合後のスラリーをスプレードライなどの噴霧乾燥機で噴霧乾燥しても良い。また、各化合物個別に、バインダー、導電材などと混合した電極合剤スラリーを調製し、両電極合剤スラリーを混合することで上記工程を行ってもよい。 The lithium titanium compound-containing material having a spinel crystal structure and the tunnel structure titanium compound-containing material can be mixed by any method, for example, a method of mixing each compound particle by a dry method or a wet method. Dry mixing can be performed by, for example, using a dry pulverizer such as a fluid energy pulverizer or an impact pulverizer, or a high-speed stirrer such as a Henschel mixer or a supermixer, and stirring and mixing them. In the wet mixing, for example, both compounds may be dispersed in a slurry and mixed through a wet pulverizer such as a sand mill, a ball mill, a pot mill, or a dyno mill. In some cases, the mixed slurry may be spray-dried by a spray dryer such as spray-drying. Moreover, the said process may be performed by preparing the electrode mixture slurry mixed with the binder, the electrically conductive material, etc. for each compound individually, and mixing both electrode mixture slurries.
また、本発明の電極活物質の製造においては、前記混合を行った後、該混合物を焼成するのが、蓄電デバイスに用いた際の高率充放電特性が向上するため、好適である。焼成温度は150〜400℃の範囲が好ましい。焼成温度が高いとトンネル構造チタン化合物の相転移が起きてしまい、蓄電デバイスに用いた際の電池特性の向上が小さくなる。好適な焼成温度は式1中のxの値(アルカリ金属置換量)にも依存するが、式3のチタン酸化合物であれば、更に好ましい範囲は230〜270℃である。焼成時間は特に制限は無いが、5時間程度が工業的に好ましい。反応を促進するために、焼成を2回以上繰り返して行うこともできる。焼成には、前述の公知の焼成炉を用いることができる。焼成雰囲気としては、大気中及び非酸化性雰囲気を適宜選択できる。焼成機器は、焼成温度等に応じて適宜選択する。焼成後、焼結の程度に応じて、粉砕を行っても良い。粉砕には、前述の粉砕機、粉砕方式を採用することができる。 In addition, in the production of the electrode active material of the present invention, it is preferable that the mixture is fired after the mixing because the high rate charge / discharge characteristics when used in an electricity storage device are improved. The firing temperature is preferably in the range of 150 to 400 ° C. When the firing temperature is high, the phase transition of the tunnel structure titanium compound occurs, and the improvement in battery characteristics when used in an electricity storage device is reduced. A suitable firing temperature depends on the value of x in the formula 1 (alkali metal substitution amount), but if it is a titanic acid compound of the formula 3, a more preferable range is 230 to 270 ° C. The firing time is not particularly limited, but about 5 hours is industrially preferable. In order to accelerate the reaction, the firing can be repeated twice or more. For the firing, the above-mentioned known firing furnace can be used. As the firing atmosphere, air and a non-oxidizing atmosphere can be appropriately selected. The firing equipment is appropriately selected according to the firing temperature and the like. After firing, pulverization may be performed according to the degree of sintering. For the pulverization, the aforementioned pulverizer and pulverization method can be employed.
スピネル型結晶構造を有するリチウムチタン化合物と、トンネル構造チタン化合物を少なくとも含む電極活物質について、二次粒子を製造するには、両化合物を混合する工程において、(1)トンネル構造チタン化合物とスピネル型結晶構造を有するリチウムチタン化合物とを共に造粒後に混合させるか、(2)トンネル構造チタン化合物又はスピネル型結晶構造を有するリチウムチタン化合物の一方を造粒してから他方の化合物と混合させるか、(3)トンネル構造チタン化合物とスピネル型結晶構造を有するリチウムチタン化合物と混合させてから造粒するか、又は(4)トンネル構造チタン化合物前駆体(式4の化合物を酸性化合物と反応させた後、加熱脱水する前のもの)とスピネル型結晶構造を有するリチウムチタン化合物とを混合後造粒してから加熱脱水する工程、が含まれていれば良い。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、トンネル構造チタン化合物、スピネル型結晶構造を有するリチウムチタン化合物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 order to produce secondary particles of a lithium titanium compound having a spinel crystal structure and an electrode active material containing at least a tunnel structure titanium compound, in the step of mixing both compounds, (1) tunnel structure titanium compound and spinel type Or after mixing together with a lithium titanium compound having a crystal structure, or (2) granulating one of a tunnel structure titanium compound or a lithium titanium compound having a spinel crystal structure and then mixing with the other compound, (3) Granulation after mixing with tunnel structure titanium compound and lithium titanium compound having spinel crystal structure, or (4) tunnel structure titanium compound precursor (after reacting compound of formula 4 with acidic compound) Before heating and dehydration) and a lithium titanium compound having a spinel crystal structure. Heating dehydration from the rear granulation, it is sufficient that contain. 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, a slurry containing a tunnel structure titanium compound and a lithium titanium compound having a spinel crystal structure is dehydrated, dried and pulverized; the slurry is dehydrated, molded and dried; and the slurry is spray dried. Among them, spray drying is industrially preferable.
噴霧乾燥するのであれば、用いる噴霧乾燥機としては、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の乾燥機を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したり、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適量、加えても良い。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, a spray dryer such as a disk type, a pressure nozzle type, a two-fluid nozzle type, or a four-fluid nozzle type can be appropriately selected depending on the properties and processing capacity of the slurry. . The secondary particle size can be controlled, for example, by adjusting the solid content concentration in the slurry, or by rotating the number of rotations of the disk in the case of the above-described disk type, and spraying in the case of a pressure nozzle type, two-fluid nozzle type, four-fluid nozzle type, etc. This can be done by controlling the size of the sprayed droplets by adjusting the pressure and 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 appropriate amount of an organic binder may be added when the slurry has a low viscosity and is difficult to granulate, or in order to further facilitate the control of the particle diameter. 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、本発明の電極活物質を含有する電極を構成部材として用いた蓄電デバイスは、電池特性、特に高容量で、高率充放電特性に優れ、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 electrode active material of the present invention as a constituent member has battery characteristics, particularly high capacity, excellent high-rate charge / discharge characteristics, and reversible lithium insertion / extraction reaction. Therefore, it is an electricity storage device that 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、これらは電極、対極及びセパレーターと電解液とを含み、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、適宜成形または電極基板に塗布して得られる。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、正極には公知の材料、例えば、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。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、例えば、多孔性ポリエチレンフィルムなどを用いることができ、電解質としては、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、1,2−ジメトキシエタンなどの溶媒にLiPF6、LiClO4、LiCF3SO3、LiN(CF3SO2)2、LiBF4などのリチウム塩を溶解させた電解液、固体電解質、溶融塩など、常用の材料を用いることができる。蓄電デバイスの構造としては電極活物質を除き、上記の他、周知のものが使用でき、特に限定されない。 Specific examples of the electricity storage device include a lithium battery, a capacitor, and the like, which include an electrode, a counter electrode, a separator, and an electrolyte solution. The electrode includes a conductive material such as carbon black and a fluororesin as the electrode active material. It is obtained by adding a binder such as or the like, and forming or coating the electrode substrate appropriately. 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 known material for the positive electrode, for example, lithium such as lithium / manganese composite oxide, lithium / cobalt composite oxide, lithium / nickel composite oxide, lithium / vanadine composite oxide Transition metal complex oxides and olivine compounds such as lithium / iron / complex phosphate compounds can be used. In the case of a capacitor, an asymmetric capacitor using the electrode active material and graphite can be used. For example, a porous polyethylene film or the like can be used as the separator. As an electrolyte, a solvent such as propylene carbonate, ethylene carbonate, dimethyl carbonate, 1,2-dimethoxyethane, LiPF 6 , LiClO 4 , LiCF 3 SO 3 is used. Conventional materials such as an electrolytic solution in which a lithium salt such as LiN (CF 3 SO 2 ) 2 or LiBF 4 is dissolved, a solid electrolyte, or a molten salt can be used. The structure of the electricity storage device is not particularly limited, except for the electrode active material, and other well-known ones 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.
実験1
(原料であるH2Ti12O25の製造)
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、純水を1284gを加え、攪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:藤崎電機社製)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、メジアン径が5.5μmの試料を得た。
Experiment 1
(Production of raw material H 2 Ti 12 O 25 )
1284 g of pure water was added 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, and the mixture was 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 Co., Ltd.). The obtained spray-dried product was heated and fired at 800 ° C. for 10 hours in the atmosphere using an electric furnace to obtain a sample having a median diameter of 5.5 μm.
得られた試料のICP発光分析法(ICPS−7500:島津製作所社製)による化学組成分析を行ったところ、Na:Ti=1.99:3.00であった。また、X線粉末回折装置(RINT2550V:リガク社製)により、良好な結晶性を有する、単斜晶系、空間群P21/mの結晶構造のNa2Ti3O7の単一相であることが明らかになった。 When the chemical composition analysis of the obtained sample by ICP emission analysis (ICPS-7500: manufactured by Shimadzu Corporation) was performed, it was Na: Ti = 1.99: 3.00. Further, it is a single phase of Na 2 Ti 3 O 7 having a monoclinic system and a crystal structure of space group P2 1 / m having good crystallinity by an X-ray powder diffractometer (RINT2550V: manufactured by Rigaku Corporation). It became clear.
得られたNa2Ti3O7 1077gに、純水4210gを加え、スラリー化し、64%硫酸657gを加え、攪拌しながら60℃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3326gにしてから再分散させ、64%硫酸34gを加え、攪拌しながら70℃の条件で5時間反応させてから、ろ過水洗乾燥して試料を得た。 4210 g of pure water was added to 1077 g of the obtained Na 2 Ti 3 O 7 to make a slurry, 657 g of 64% sulfuric acid was added, and the mixture was reacted for 5 hours at 60 ° C. with stirring, and then washed with filtered water. Pure water was added to the filter cake to make 3326 g, and then re-dispersed. 34 g of 64% sulfuric acid was added, reacted for 5 hours at 70 ° C. with stirring, washed with filtered water and dried to obtain a sample.
得られた試料について、ICP発光分析法により、化学組成を分析したところ、ナトリウムは検出されず、ほぼ完全にプロトン交換されたH2Ti3O7の化学式で妥当であった。さらに、X線粉末回折装置により、良好な結晶性を有する、単斜晶系、空間群C2/mの結晶構造のH2Ti3O7の単一相であることが明らかとなった。 When the chemical composition of the obtained sample was analyzed by ICP emission spectrometry, sodium was not detected, and the chemical formula of H 2 Ti 3 O 7 which was almost completely proton-exchanged was appropriate. Furthermore, it was revealed by an X-ray powder diffractometer that the crystal has a monoclinic system and a single phase of H 2 Ti 3 O 7 having a crystal structure of the space group C2 / m having good crystallinity.
このようにして得られたH2Ti3O7の粒子形状を走査型電子顕微鏡(SEM)(JSM−5400:日本電子社製)により調べたところ、サブミクロン〜ミクロンオーダーの等方的又は棒状の形状を有していた。 The particle shape of the H 2 Ti 3 O 7 obtained in this way was examined with a scanning electron microscope (SEM) (JSM-5400: manufactured by JEOL Ltd.). It had the shape of
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、試料Aを得た。 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 Sample A.
得られた試料Aについて、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。また、X線粉末回折装置により、X線回折データを測定し、良好な結晶性を有する、単斜晶系、空間群P2/mの結晶構造のH2Ti12O25の単一相であることが明らかとなった。そのX線回折図形を図1に示す。 The obtained sample A, the loss on heat in the temperature range of 250 to 600 ° C., measured using a differential thermal balance, heat loss is was calculated by assuming that corresponds to the structure water, of H 2 Ti 12 O 25 The chemical composition was confirmed to be reasonable. In addition, X-ray diffraction data is measured by an X-ray powder diffractometer, and it is a single phase of H 2 Ti 12 O 25 having a monoclinic system and a crystal structure of space group P2 / m having good crystallinity. It became clear. The X-ray diffraction pattern is shown in FIG.
このようにして得られたH2Ti12O25粒子の走査型電子顕微鏡(SEM)写真を図2に示す。前駆体であるH2Ti3O7の形状がほぼ保持されたサブミクロン〜ミクロンオーダーの等方的又は棒状の形状を有していた。 A scanning electron microscope (SEM) photograph of the H 2 Ti 12 O 25 particles thus obtained is shown in FIG. It had an isotropic or rod-like shape on the order of submicron to micron, in which the shape of the precursor H 2 Ti 3 O 7 was almost retained.
(Li4Ti5O12の製造)
4.5モル/リットルの水酸化リチウム水溶液340ミリリットルに、ルチル型とアナターゼ型の混晶の二酸化チタン(PT−401M:石原産業製)125gを添加し分散させた。このスラリーを攪拌しながら液温を80℃に保ち、オルトチタン酸を、TiO2換算で25g分散させた水性スラリー250ミリリットルを添加して、チタン化合物及びリチウム化合物を含むスラリーを得た。このスラリーを噴霧乾燥機(GB210‐B型:ヤマト科学社製)を用いて、入口温度190℃、出口温度80℃の条件で噴霧乾燥を行い、乾燥造粒物を得た後、乾燥造粒物を大気中700℃の温度で3時間焼成を行い、試料Bを得た。
(Production of Li 4 Ti 5 O 12 )
125 g of rutile type and anatase type mixed crystal titanium dioxide (PT-401M: manufactured by Ishihara Sangyo Co., Ltd.) was added and dispersed in 340 ml of a 4.5 mol / liter lithium hydroxide aqueous solution. While stirring the slurry, the liquid temperature was kept at 80 ° C., and 250 ml of an aqueous slurry in which 25 g of orthotitanic acid was dispersed in terms of TiO 2 was added to obtain a slurry containing a titanium compound and a lithium compound. This slurry is spray-dried under conditions of an inlet temperature of 190 ° C. and an outlet temperature of 80 ° C. using a spray dryer (GB210-B type: manufactured by Yamato Kagaku Co., Ltd.) to obtain a dry granulated product, and then dry granulation The product was calcined at 700 ° C. in the atmosphere for 3 hours to obtain Sample B.
得られた試料Bについて、X線粉末回折装置により、X線回折データを測定し、良好な結晶性を有する、スピネル型結晶構造のLi4Ti5O12の単一相であることを確認した。そのX線回折図形を図3に示す。 The obtained sample B, the X-ray powder diffractometer, measuring the X-ray diffraction data, with a good crystallinity was confirmed to be a single phase of Li 4 Ti 5 O 12 having a spinel type crystal structure . The X-ray diffraction pattern is shown in FIG.
このようにして得られたLi4Ti5O12の粒子形状を走査型電子顕微鏡(SEM)により調べたところ、0.01〜1μm程度の一次粒子が、球状や多面体状に集合して二次粒子を形成しており、メジアン径は5.7μm、BET法で測定した比表面積は11m2/gであった。 When the particle shape of the Li 4 Ti 5 O 12 obtained in this way was examined by a scanning electron microscope (SEM), primary particles of about 0.01 to 1 μm aggregated in a spherical or polyhedral shape and were secondary. Particles were formed, the median diameter was 5.7 μm, and the specific surface area measured by the BET method was 11 m 2 / g.
(混合物の作製)
このようにして得られたH2Ti12O25 7gと、Li4Ti5O12 3gに、純水50gを加え、超音波分散を5分間行い、スラリーを作製した。このスラリーを、100℃の乾燥機に投入し、純水を蒸発させ、蒸発乾固物を得た。引き続き、この蒸発乾固物を電気炉にて260℃で5時間、大気中で焼成し、試料Cを得た。また、H2Ti12O25を5g、Li4Ti5O12を5g、純水を50gとした以外は同様の手順で試料Dを、H2Ti12O25を3g、Li4Ti5O12を7g、純水を50gとした以外は同様の手順で試料Eを得た。試料DのX線回折図形を図4に示す。図4から、試料DはH2Ti12O25相とLi4Ti5O12相がそれぞれ別相として存在していることがわかる。本実験の試料C〜Eが本発明の活物質であり、それぞれ実施例1〜3とし、本発明の原料である試料A,Bを比較例1,2とする。
(Production of mixture)
50 g of pure water was added to 7 g of H 2 Ti 12 O 25 thus obtained and 3 g of Li 4 Ti 5 O 12 , and ultrasonic dispersion was performed for 5 minutes to prepare a slurry. This slurry was put into a dryer at 100 ° C. to evaporate pure water to obtain an evaporated dry product. Subsequently, this evaporated and dried product was calcined in the electric furnace at 260 ° C. for 5 hours in the air to obtain Sample C. Further, sample D was prepared in the same procedure except that 5 g of H 2 Ti 12 O 25 , 5 g of Li 4 Ti 5 O 12 and 50 g of pure water were used, 3 g of H 2 Ti 12 O 25 , Li 4 Ti 5 O Sample E was obtained in the same procedure except that 12 was changed to 7 g and pure water was changed to 50 g. The X-ray diffraction pattern of Sample D is shown in FIG. From FIG. 4, it can be seen that in Sample D, the H 2 Ti 12 O 25 phase and the Li 4 Ti 5 O 12 phase exist as separate phases. Samples C to E of this experiment are active materials of the present invention, which are Examples 1 to 3, respectively. Samples A and B which are raw materials of the present invention are Comparative Examples 1 and 2, respectively.
(蓄電デバイスの作製)
電極活物質として上記手順で得られた、試料A〜Eを、導電剤としてのアセチレンブラック粉末(デンカブラック(登録商標)(粉状):電気化学工業社製)、及び結着剤としてのポリフッ化ビニリデン(PVdF)樹脂(KFポリマーL‐#1120:クレハ社製 溶媒N‐メチル‐2‐ピロリドン)と重量比で100:10:10(PVdFは樹脂分)で混合し、固形分濃度が30%になるようN-メチル‐2‐ピロリドンを加え、自転・公転ミキサー(泡とり練太郎ARE−310:シンキー社製)で2000rpmで15分混合を行って、ペーストを調製した。このペーストをアルミ箔(IN30‐H18(20μm):富士加工紙株式会社製)上に塗布し、120℃の温度で10分乾燥した後、直径12mmの円形に打ち抜き、17MPaでプレスして電極とした。この直径12mmに切り出した電極の活物質重量が2.5mgになるよう塗布量(塗布厚)を調整した。
(Production of electricity storage device)
Samples A to E obtained by the above procedure as the electrode active material were mixed with acetylene black powder (DENKA BLACK (registered trademark) (powder): manufactured by Denki Kagaku Kogyo Co., Ltd.) as a conductive agent and polyfluoride as a binder. It is mixed with vinylidene chloride (PVdF) resin (KF polymer L- # 1120: Solvent N-methyl-2-pyrrolidone manufactured by Kureha Co., Ltd.) at a weight ratio of 100: 10: 10 (PVdF is the resin content), and the solid content concentration is %, N-methyl-2-pyrrolidone was added, and the mixture was mixed at 2000 rpm for 15 minutes with a rotation / revolution mixer (Awatori Netaro ARE-310: manufactured by Sinky Corporation) to prepare a paste. This paste was applied onto an aluminum foil (IN30-H18 (20 μm): manufactured by Fuji Processing Paper Co., Ltd.), dried for 10 minutes at a temperature of 120 ° C., punched into a circle with a diameter of 12 mm, pressed at 17 MPa, did. The coating amount (coating thickness) was adjusted so that the active material weight of the electrode cut into a diameter of 12 mm was 2.5 mg.
この電極を120℃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正極として組み込んだ。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(リチウムフォイル:本城金属社製)を直径12mmの円形に成形したものを用いた。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1:2)を用いた。 This electrode was vacuum-dried at 120 ° C. for 4 hours, and then incorporated as a positive electrode in a sealable coin cell in a glove box having a dew point of −70 ° C. or lower. 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 (lithium foil: manufactured by Honjo Metal Co., Ltd.) formed into a circle having a diameter of 12 mm was used. A mixed solution (volume ratio 1: 2) of ethylene carbonate and dimethyl carbonate in which LiPF6 was dissolved at a concentration of 1 mol / liter was used as the non-aqueous electrolyte.
電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厚スペーサー及びウエーブワッシャ(いずれもSUS316製)をのせ、その上から非水電解液を溢れるほど滴下し、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、本発明の蓄電デバイス(デバイスc〜e)及び比較の蓄電デバイス(デバイスa,b)を得た。なお、上記の0.5mm厚スペーサー及びウエーブワッシャ等の電池部材にはCR2032用パーツセット(宝泉社)を用いた。 The electrode was placed in the lower can of the coin-type cell, a porous polypropylene film was placed thereon as a separator, and a nonaqueous electrolyte was dropped from above. Furthermore, a negative electrode, a 0.5 mm thick spacer for adjusting the thickness, and a wave washer (both made of SUS316) are placed thereon, and the nonaqueous electrolyte is dripped over the top so that the upper can with a polypropylene gasket is attached. The outer peripheral edge portion was covered and sealed to obtain an electricity storage device (devices c to e) of the present invention and comparative electricity storage devices (devices a and b). In addition, a CR2032 parts set (Hosen Co., Ltd.) was used for battery members such as the above-mentioned 0.5 mm thick spacers and wave washers.
蓄電デバイス(デバイスa〜e)について、セル作製後3時間熟成した後、0.25Cで2サイクル充放電するコンディショニングを行った。コンディショニング2サイクル目の放電容量を初期容量とした。その後、種々の電流量で放電容量(mAh/g)を測定した。測定は、電圧範囲を1〜2.5Vに、充電電流は0.25Cに、放電電流は0.25C〜50Cの範囲に設定して行った。環境温度は25℃とした。尚、ここで1Cとは満充電後に1時間で完全放電できる電流値を言うが、本評価では、デバイスbでは0.4mAが、その他のデバイスでは0.5mAが1C電流値に相当するものとして測定を行った。 About the electrical storage device (device ae), after aging for 3 hours after cell preparation, the conditioning which charges / discharges 2 cycles at 0.25C was performed. The discharge capacity at the second cycle of conditioning was taken as the initial capacity. Thereafter, the discharge capacity (mAh / g) was measured with various current amounts. The measurement was performed with the voltage range set to 1 to 2.5 V, the charging current set to 0.25 C, and the discharging current set to the range 0.25 C to 50 C. The environmental temperature was 25 ° C. In addition, 1C means a current value that can be completely discharged in 1 hour after full charge. In this evaluation, 0.4 mA is equivalent to 1 C current value in the device b and 0.5 mA in other devices. Measurements were made.
表1は比較例の測定結果である。試料Aは容量特性に優れ、試料Bは高率放電容量に優れることがわかる。 Table 1 shows the measurement results of the comparative example. It can be seen that Sample A is excellent in capacity characteristics and Sample B is excellent in high rate discharge capacity.
表2は、各電流値における比較例1および比較例2の測定結果と試料A,Bの混合比70:30から加重平均(試料Aの容量×試料Aの混合比(0.7)+試料Bの容量×試料Bの混合比(0.3))して求められる試料Cの容量計算値(mAh/g)と、及びデバイスcの容量実測値(mAh/g)である。また、表2における1C電流値の計算値は、比較例1および比較例2の実測値と試料A,Bの混合比70:30を用いて算出(比較例1の1C電流値(0.5mA)×試料Aの配合比(0.7)+比較例2の1C電流値(0.4mA)×試料Bの配合比(0.3))したものである。デバイスcはいずれの電流値においても計算値を上回る放電容量を示し、更に、0.25〜2Cの電流値においては、試料A,Bをそれぞれ単独で用いたデバイスa,bを超える放電容量を示しており、予想し得ない効果が認められた。 Table 2 shows a weighted average from the measurement results of Comparative Example 1 and Comparative Example 2 and the mixing ratio of samples A and B at each current value of 70:30 (capacity of sample A × mixing ratio of sample A (0.7) + sample. (Capacitance of B × mixing ratio of sample B (0.3)), calculated capacity of sample C (mAh / g), and actual capacity of device c (mAh / g). In addition, the calculated value of the 1C current value in Table 2 is calculated using the actual measurement value of Comparative Example 1 and Comparative Example 2 and the mixing ratio 70:30 of Samples A and B (1C current value of Comparative Example 1 (0.5 mA). ) × mixing ratio of sample A (0.7) + 1C current value of comparative example 2 (0.4 mA) × mixing ratio of sample B (0.3)). The device c shows a discharge capacity exceeding the calculated value at any current value, and further, at a current value of 0.25 to 2C, the discharge capacity exceeding the devices a and b using the samples A and B alone, respectively. As shown, an unexpected effect was observed.
表3は、各電流値における比較例1および比較例2の測定結果と試料A,Bの混合比50:50から加重平均(試料Aの容量×試料Aの混合比(0.5)+試料Bの容量×試料Bの混合比(0.5))して求められる試料Dの容量計算値(mAh/g)と、デバイスdの容量実測値(mAh/g)である。また、表3における1C電流値の計算値は、比較例1および比較例2の実測値と試料A,Bの混合比50:50を用いて算出(比較例1の1C電流値(0.5mA)×試料Aの配合比(0.5)+比較例2の1C電流値(0.4mA)×試料Bの配合比(0.5))したものである。デバイスdはいずれの電流値においても計算値を上回る放電容量を示し、更に、0.5〜3Cの電流値においては、デバイスa,bを超える放電容量を示しており、予想し得ない効果が認められた。 Table 3 shows the measurement results of Comparative Example 1 and Comparative Example 2 at each current value and the weighted average (mixing ratio of sample A × mixing ratio of sample A (0.5) + sample) from the mixing ratio of samples A and B of 50:50. (Capacitance of B × mixing ratio of sample B (0.5)), calculated capacity of sample D (mAh / g), and actual capacity of device d (mAh / g). Further, the calculated value of the 1C current value in Table 3 was calculated using the actual measurement value of Comparative Example 1 and Comparative Example 2 and the mixing ratio 50:50 of Samples A and B (1C current value of Comparative Example 1 (0.5 mA). ) × Sample A blending ratio (0.5) + 1C current value of Comparative Example 2 (0.4 mA) × Sample B blending ratio (0.5)). The device d shows a discharge capacity that exceeds the calculated value at any current value, and further shows a discharge capacity that exceeds the devices a and b at a current value of 0.5 to 3 C, which has an unexpected effect. Admitted.
表4は、各電流値における比較例1および比較例2の測定結果と試料A,Bの混合比30:70から加重平均(試料Aの容量×試料Aの混合比(0.3)+試料Bの容量×試料Bの混合比(0.7))して求められる試料Eの容量計算値(mAh/g)と、デバイスeの容量実測値(mAh/g)である。また、表4における1C電流値の計算値は、比較例1および比較例2の実測値と試料A,Bの混合比30:70を用いて算出(比較例1の1C電流値(0.5mA)×試料Aの配合比(0.3)+比較例2の1C電流値(0.4mA)×試料Bの配合比(0.7))したものである。デバイスeはいずれの電流値においても計算値を上回る放電容量を示しており、予想し得ない効果が認められた。 Table 4 shows the measurement result of Comparative Example 1 and Comparative Example 2 at each current value and the weighted average (mixing ratio of sample A × mixing ratio of sample A (0.3) + sample) from the mixing ratio of samples A and B of 30:70. The calculated capacity (mAh / g) of the sample E and the actual measured capacity (mAh / g) of the device e, which are obtained by multiplying the volume of B by the mixing ratio of the sample B (0.7). Further, the calculated value of the 1C current value in Table 4 is calculated using the actually measured value of Comparative Example 1 and Comparative Example 2 and the mixing ratio 30:70 of Samples A and B (1C current value of Comparative Example 1 (0.5 mA). ) × mixing ratio of sample A (0.3) + 1C current value of comparative example 2 (0.4 mA) × mixing ratio of sample B (0.7)). The device e showed a discharge capacity exceeding the calculated value at any current value, and an unexpected effect was recognized.
以上の結果について実電流値をx軸にとりグラフ化したものを図5に示す。図5から明らかなように、100mA以上の電流値でも、実施例1〜3の本発明の電極活物質を用いたデバイスc〜eは、高率放電容量に優れるデバイスbと同等の放電容量を示し、高率放電容量に優れることがわかる。更に、低率放電時の容量において特にデバイスcやデバイスdは、容量の低いスピネル型結晶構造リチウムチタン化合物である試料Bを配合しているにもかかわらず、高容量に特徴のあるトンネル構造チタン化合物を用いたデバイスaを超える放電容量を示すことがわかる。 FIG. 5 is a graph showing the actual current values plotted on the x-axis for the above results. As is clear from FIG. 5, the devices c to e using the electrode active materials of the present invention of Examples 1 to 3 have a discharge capacity equivalent to that of the device b excellent in high rate discharge capacity even at a current value of 100 mA or more. It can be seen that the high-rate discharge capacity is excellent. Furthermore, in the capacity at the time of low-rate discharge, the device c and the device d have a tunnel structure titanium which is characterized by a high capacity, even though the sample B which is a spinel type crystal structure lithium titanium compound having a low capacity is blended. It can be seen that the discharge capacity exceeds the device a using the compound.
実験2
試料Dの作製において、蒸発乾固物の電気炉での焼成を行わなかった以外は試料Dと同様の手順で試料Fを得た。本実験の試料Fが本発明の活物質であり、実施例4とする。また、試料Fと実験1で作製した試料Dを用いて、実験1と同様の手順で蓄電デバイスd’及び蓄電デバイスfを作製した。
Experiment 2
In the preparation of Sample D, Sample F was obtained in the same procedure as Sample D, except that the evaporated and dried product was not fired in an electric furnace. Sample F of this experiment is the active material of the present invention, and is Example 4. Further, using Sample F and Sample D prepared in Experiment 1, an electricity storage device d ′ and an electricity storage device f were prepared in the same procedure as in Experiment 1.
蓄電デバイスd’,fを用いて、放電電流を0.25C〜5Cの範囲に設定した以外は実験1と同様の手順で高率放電容量を測定した。0.25Cでの放電容量を100としたときの、各放電電流値における放電容量の比率(容量維持率)を表5に示す。 The high rate discharge capacity was measured in the same procedure as in Experiment 1 except that the discharge current was set in the range of 0.25C to 5C using the electricity storage devices d 'and f. Table 5 shows the ratio of discharge capacity (capacity maintenance ratio) at each discharge current value when the discharge capacity at 0.25 C is 100.
表5中、試料A,Bを混合後、焼成を行った試料Dを用いたデバイスd’及びfの高率放電容量測定は、1C電流値を0.5mAとして行っている。一方、表5における1C電流値の計算値では1C電流値は0.45mAである(表1における試料Aの1C電流値(0.5mA)×試料Aの配合比(0.5)+表1における試料Bの1C電流値(0.4mA)×試料Bの配合比(0.5))。従って、デバイスd’及びfでは、計算値のそれと比較して、各測定電流値において10%以上の高負荷がかかっている(+10%以上の大電流を流している)ことになる。それにもかかわらず、デバイスfでも充分な高率放電特性が得られることがわかる。また、デバイスd’の測定結果から明らかなように、混合後焼成を行うことで更に高率放電特性が向上していることがわかる。 In Table 5, the high-rate discharge capacity measurement of the devices d 'and f using the sample D that was baked after mixing the samples A and B was performed with a 1C current value of 0.5 mA. On the other hand, in the calculated value of the 1C current value in Table 5, the 1C current value is 0.45 mA (1C current value of sample A (0.5 mA) in Table 1 × mixing ratio of sample A (0.5) + Table 1) 1C current value of sample B (0.4 mA) × mixing ratio of sample B (0.5)). Therefore, in the devices d 'and f, compared with the calculated value, a high load of 10% or more is applied at each measured current value (a large current of + 10% or more is flowing). Nevertheless, it can be seen that a sufficiently high discharge characteristic can be obtained even with the device f. Further, as is apparent from the measurement result of the device d ', it can be seen that the high rate discharge characteristics are further improved by performing the firing after mixing.
実験3
実験1とは異なる製法で得られたスピネル型結晶構造を有するリチウムチタン化合物を用いて、本発明の効果を検証した。
Experiment 3
The effect of the present invention was verified using a lithium titanium compound having a spinel crystal structure obtained by a production method different from Experiment 1.
(Li4Ti5O12の製造)
炭酸リチウム粉末187gと、ルチル型の二酸化チタン(CR−EL:石原産業製)500gをヘンシェルミキサーにて1800rpmで10分間混合した。この混合物を電気炉にて、大気中940℃の温度で3時間焼成を行い、試料Gを得た。
(Production of Li 4 Ti 5 O 12 )
187 g of lithium carbonate powder and 500 g of rutile titanium dioxide (CR-EL: manufactured by Ishihara Sangyo) were mixed at 1800 rpm for 10 minutes with a Henschel mixer. This mixture was baked in an electric furnace at a temperature of 940 ° C. for 3 hours in the atmosphere to obtain a sample G.
得られた試料Gについて、X線粉末回折装置により、X線回折データを測定し、良好な結晶性を有する、スピネル型結晶構造のLi4Ti5O12の単一相であることを確認した。粒子形状を走査型電子顕微鏡(SEM)により調べたところ、サブミクロン〜ミクロンオーダーの大きさの不定形粒子であった。 The obtained sample G, the X-ray powder diffractometer, measuring the X-ray diffraction data, with a good crystallinity was confirmed to be a single phase of Li 4 Ti 5 O 12 having a spinel type crystal structure . When the particle shape was examined with a scanning electron microscope (SEM), it was found to be amorphous particles having a size of submicron to micron order.
(混合物の作製)
実験1と同様の方法で得られたH2Ti12O25(試料A)5gと、上記実験3で得られたLi4Ti5O12(試料G)5gに、純水50gを加え、超音波分散を5分間行い、スラリーを作製した。このスラリーを、100℃の乾燥機に投入し、純水を蒸発させ、蒸発乾固物を得た。引き続き、この蒸発乾固物を電気炉にて260℃で5時間、大気中で焼成し、試料Hを得た。本実験の試料Hが本発明の活物質であり、実施例5とし、試料Gを比較例3とする。
(Production of mixture)
50 g of pure water was added to 5 g of H 2 Ti 12 O 25 (Sample A) obtained in the same manner as in Experiment 1 and 5 g of Li 4 Ti 5 O 12 (Sample G) obtained in Experiment 3 above. Sonic dispersion was performed for 5 minutes to prepare a slurry. This slurry was put into a dryer at 100 ° C. to evaporate pure water to obtain an evaporated dry product. Subsequently, this evaporated and dried product was baked in the electric furnace at 260 ° C. for 5 hours in the air, and sample H was obtained. Sample H of this experiment is the active material of the present invention, and is Example 5. Sample G is Comparative Example 3.
試料A,G,Hを電極活物質として用いてリチウム二次電池を調製し、その充放電サイクル特性を評価した。電池の形態や測定条件について説明する。 Samples A, G, and H were used as electrode active materials to prepare lithium secondary batteries, and their charge / discharge cycle 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四フッ化エチレン樹脂を重量比で5:4:1で混合し、乳鉢で練り合わせ、直径10mmの円形に成型してペレット状とした。ペレットの重量は10mgであった。このペレットに直径10mmに切り出したアルミニウム製のメッシュを重ね合わせ、9MPaでプレスして電極とした。 Each sample, acetylene black powder as a conductive agent, and polytetrafluoroethylene resin as a binder are mixed at a weight ratio of 5: 4: 1, kneaded in a mortar, and molded into a circle with a diameter of 10 mm. It was in a pellet form. The weight of the pellet was 10 mg. An aluminum mesh cut out to a diameter of 10 mm was superimposed on this pellet and pressed at 9 MPa to form an electrode.
この電極を100℃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評価用セルに正極として組み込んだ。評価用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 electrode was vacuum-dried at a temperature of 100 ° C. for 4 hours and then incorporated as a positive electrode in a sealable coin-type evaluation cell in a glove box having a dew point of −70 ° C. or lower. The evaluation cell used was made of stainless steel (SUS316) and had an outer diameter of 20 mm and a height of 3.2 mm. 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. 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.
電極は評価用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。作製したデバイスはそれぞれデバイスa,g,hとした。 The electrode was placed in the lower can of the evaluation 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. The devices produced were devices a, g, and h, respectively.
充放電容量の測定は、電圧範囲を1.0〜2.5Vに、充放電電流を0.2mAに設定して、室温下、定電流で行った。2サイクル目と10,20、30サイクル目の充放容量を測定し、(各サイクル時の放電容量/2サイクル目の放電容量)×100(%)をサイクル特性とした。この値が大きい程、サイクル特性が優れている。結果を表6に示す。実施例5の本発明の活物質Hを用いたデバイスhは比較例のデバイスa,gと同等以上のサイクル特性を示すことがわかる。 The charge / discharge capacity was measured at a constant current at room temperature with the voltage range set to 1.0 to 2.5 V and the charge / discharge current set to 0.2 mA. The charge / discharge capacities at the second cycle, 10, 20, and 30 cycles were measured, and (discharge capacity at each cycle / discharge capacity at the second cycle) × 100 (%) was defined as the cycle characteristics. The larger this value, the better the cycle characteristics. The results are shown in Table 6. It can be seen that the device h using the active material H of the present invention in Example 5 exhibits cycle characteristics equivalent to or higher than those of the devices a and g of the comparative example.
実験4
実験3の充放電を60℃で行った以外は実験3と同様にして高温サイクル特性を評価した。結果を表7に示す。実施例5の本発明の活物質Hを用いたデバイスhは比較例のデバイスa,gと同等以上のサイクル特性を示すことがわかる。
Experiment 4
The high-temperature cycle characteristics were evaluated in the same manner as in Experiment 3 except that the charge / discharge in Experiment 3 was performed at 60 ° C. The results are shown in Table 7. It can be seen that the device h using the active material H of the present invention in Example 5 exhibits cycle characteristics equivalent to or higher than those of the devices a and g of the comparative example.
また、試料A,G,Hを用いて実験1と同様にデバイスを作製し、50C放電容量の0.25C放電容量比を測定した結果、試料Aでは18%、試料Gでは23%であったのに対し、両者を混合した試料Hでは38%を示し、予想し得ない効果が認められた。
In addition, a device was fabricated using Samples A, G, and H in the same manner as in Experiment 1, and the 0.25C discharge capacity ratio of the 50C discharge capacity was measured. As a result, Sample A was 18% and Sample G was 23%. On the other hand, Sample H in which both were mixed showed 38%, and an unexpected effect was observed.
本発明の電極活物質は、一次元トンネル構造を有する特定のチタン化合物と、スピネル型結晶構造を有するリチウムチタン化合物の混合物からなるが、それぞれを単独で活物質として用いた場合の電池特性を超える電池特性、例えば初期容量、高率充放電容量を示し、優れた材料である。そのため、リチウム二次電池等の蓄電デバイス電極材料として実用性の高いものである。 The electrode active material of the present invention comprises a mixture of a specific titanium compound having a one-dimensional tunnel structure and a lithium titanium compound having a spinel type crystal structure, which exceeds the battery characteristics when each is used alone as an active material. It shows battery characteristics such as initial capacity and high rate charge / discharge capacity, and is an excellent material. Therefore, it is highly practical as a power storage device electrode material such as a lithium secondary battery.
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.
Claims (6)
一般式として(式1)で表される一次元トンネル構造を有するチタン化合物の含有物とを混合する工程、次いで、前記混合物を焼成する工程を含む電極活物質の製造方法。
(式1)H2-XAXTinO2n+1(式中、Aはアルカリ金属であり、Xは0≦X≦2を満たす実数であり、nはn≧6を満たす整数である。) Inclusion of a lithium titanium compound having a spinel crystal structure;
The manufacturing method of the electrode active material including the process of mixing the content of the titanium compound which has a one-dimensional tunnel structure represented by (Formula 1) as a general formula, and the process of baking the said mixture then.
(Equation 1) H 2-X A X Ti n O 2n + 1 ( wherein, A is an alkali metal, X is a real number satisfying 0 ≦ X ≦ 2, n is an integer satisfying n ≧ 6 .)
スピネル型結晶構造を有するリチウムチタン化合物相と、
一般式として(式1)で表される一次元トンネル構造を有するチタン化合物相との少なくとも二相を有する電極活物質。
(式1)H2-XAXTinO2n+1(式中、Aはアルカリ金属であり、Xは0≦X≦2を満たす実数であり、nはn≧6を満たす整数である。) Manufactured by the method according to any one of claims 1 to 4,
A lithium titanium compound phase having a spinel crystal structure;
An electrode active material having at least two phases with a titanium compound phase having a one-dimensional tunnel structure represented by (Formula 1) as a general formula.
(Equation 1) H 2-X A X Ti n O 2n + 1 ( wherein, A is an alkali metal, X is a real number satisfying 0 ≦ X ≦ 2, n is an integer satisfying n ≧ 6 .)
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