JP6109672B2 - Ceramic cathode-solid electrolyte composite - Google Patents

Ceramic cathode-solid electrolyte composite Download PDF

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JP6109672B2
JP6109672B2 JP2013157914A JP2013157914A JP6109672B2 JP 6109672 B2 JP6109672 B2 JP 6109672B2 JP 2013157914 A JP2013157914 A JP 2013157914A JP 2013157914 A JP2013157914 A JP 2013157914A JP 6109672 B2 JP6109672 B2 JP 6109672B2
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positive electrode
solid electrolyte
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garnet
plate
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隆太 杉浦
隆太 杉浦
小林　伸行
伸行 小林
七瀧　努
七瀧　　努
嘉彦 山村
嘉彦 山村
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Description

本発明は、正極−固体電解質複合体に関するものであり、より詳しくは全固体蓄電素子用の正極−固体電解質複合体に関する。   The present invention relates to a positive electrode-solid electrolyte composite, and more particularly to a positive electrode-solid electrolyte composite for an all-solid-state energy storage device.

近年、リチウムイオン二次電池が高いエネルギー密度の観点から注目されている。しかしながら、現在広く使用されているリチウムイオン二次電池は、可燃性の有機溶媒にリチウム塩を溶解した有機電解液が主流であるため、液漏れ等に対する安全性の確保が重要な課題となっている。これに対して、電解液の代わりに固体電解質を用いた全固体電池が、可燃性の有機溶媒を使用する必要が無い安全性の高い電池として提案されている。   In recent years, lithium ion secondary batteries have attracted attention from the viewpoint of high energy density. However, since lithium ion secondary batteries currently widely used are mainly organic electrolytes in which lithium salts are dissolved in flammable organic solvents, it is important to ensure safety against liquid leakage and the like. Yes. On the other hand, an all-solid battery using a solid electrolyte instead of an electrolytic solution has been proposed as a highly safe battery that does not require the use of a flammable organic solvent.

特許文献１（国際公開第２０１１／１３２６２７号公報）には、正極層、負極層及び固体電解質層の焼結によって一体化された全固体二次電池が開示されている。この全固体二次電池は、正極層、負極層及び固体電解質層の各々のグリーンシートを積層し、その積層体を同時焼結して作製されている。このような同時焼結製法で、密着性の高い界面を形成するためには熱処理温度を高くせざるを得ない。その結果、各層間で元素拡散により組成変動が生じたり、界面層に非常に抵抗の高い反応層が形成されるなど、各部材が本来有する良好な機能を最大限に発揮させることが困難であった。   Patent Document 1 (International Publication No. 2011/132627) discloses an all-solid secondary battery integrated by sintering of a positive electrode layer, a negative electrode layer, and a solid electrolyte layer. This all-solid-state secondary battery is produced by laminating green sheets of a positive electrode layer, a negative electrode layer, and a solid electrolyte layer, and simultaneously sintering the laminate. In order to form an interface with high adhesion by such a simultaneous sintering method, the heat treatment temperature must be increased. As a result, it is difficult to maximize the good functions inherent to each member, such as composition fluctuations caused by element diffusion between layers, and formation of a reaction layer with extremely high resistance in the interface layer. It was.

非特許文献１（加藤健久、外８名、「界面制御によるＬｉ７Ｌａ３Ｚｒ２Ｏ１２／ＬｉＣｏＯ２の抵抗低減」、電気化学会第７９回大会、大会予稿集Ｐ９３、３Ｃ１３、２０１２年３月）には、それら熱処理時の元素拡散を抑制する手段として、Ｌｉ−Ｎｂ−Ｏ系材料を正極と固体電解質の界面に形成することが開示されている。しかしながら、Ｌｉ−Ｎｂ−Ｏ系材料は、組成の制御が難しく、かつ、組成のずれに抵抗値が敏感である。このため、低抵抗な界面を安定的に形成することが難しく、更なる界面の制御が望まれている。 Non-Patent Literature 1 (Takehisa Kato, 8 others, “Reduction of Li 7 La 3 Zr 2 O 12 / LiCoO 2 resistance by interface control”, 79th Annual Meeting of the Electrochemical Society, Proceedings P93, 3C13, 2012 (March) discloses that a Li—Nb—O-based material is formed at the interface between the positive electrode and the solid electrolyte as a means for suppressing element diffusion during the heat treatment. However, it is difficult to control the composition of Li—Nb—O-based materials, and the resistance value is sensitive to a shift in composition. For this reason, it is difficult to stably form a low-resistance interface, and further control of the interface is desired.

一方、リチウムイオン伝導性を有する固体電解質として、Ｌｉ７Ｌａ３Ｚｒ２Ｏ１２（以下、ＬＬＺという）系の組成を有するガーネット型のセラミックス材料が注目されている。例えば、特許文献２（特開２０１１−０５１８００号公報）には、ＬＬＺの基本元素であるＬｉ，Ｌａ及びＺｒに加えてＡｌを加えることで、緻密性やリチウムイオン伝導率を向上できることが開示されている。特許文献３（特開２０１１−０７３９６２号公報）には、ＬＬＺの基本元素であるＬｉ、Ｌａ及びＺｒに加えてＮｂ及び／又はＴａを加えることで、リチウムイオン伝導率を更に向上できることが開示されている。特許文献４（特開２０１１−０７３９６３号公報）には、Ｌｉ、Ｌａ、Ｚｒ及びＡｌを含み、Ｌａに対するＬｉのモル比を２．０〜２．５とすることで、緻密性を更に向上できることが開示されている。 On the other hand, as a solid electrolyte having lithium ion conductivity, a garnet-type ceramic material having a Li 7 La 3 Zr 2 O 12 (hereinafter referred to as LLZ) composition has attracted attention. For example, Patent Document 2 (Japanese Patent Laid-Open No. 2011-051800) discloses that the addition of Al in addition to Li, La and Zr, which are basic elements of LLZ, can improve the density and lithium ion conductivity. ing. Patent Document 3 (Japanese Patent Laid-Open No. 2011-073962) discloses that lithium ion conductivity can be further improved by adding Nb and / or Ta in addition to Li, La and Zr, which are basic elements of LLZ. ing. Patent Document 4 (Japanese Patent Laid-Open No. 2011-073963) includes Li, La, Zr, and Al, and the density can be further improved by setting the molar ratio of Li to La to 2.0 to 2.5. Is disclosed.

国際公開第２０１１／１３２６２７号公報International Publication No. 2011-132627 特開２０１１−０５１８００号公報JP 2011-051800 A 特開２０１１−０７３９６２号公報JP 2011-073962 A 特開２０１１−０７３９６３号公報JP 2011-073963 A

加藤健久、外８名、「界面制御によるＬｉ７Ｌａ３Ｚｒ２Ｏ１２／ＬｉＣｏＯ２の抵抗低減」、電気化学会第７９回大会、大会予稿集Ｐ９３、３Ｃ１３、２０１２年３月Takehisa Kato and 8 others, "Reduction of Li7La3Zr2O12 / LiCoO2 resistance by interface control", 79th Annual Meeting of the Electrochemical Society, Proceedings P93, 3C13, March 2012

本発明者らは、今般、正極と固体電解質の接合に際し、特定組成の界面を意図的に形成することにより、低抵抗の正極−固体電解質複合体を提供できるとの知見を得た。   The inventors of the present invention have recently found that a low-resistance positive electrode-solid electrolyte composite can be provided by intentionally forming an interface having a specific composition when joining a positive electrode and a solid electrolyte.

したがって、本発明の目的は、低抵抗の正極−固体電解質複合体を提供することにある。   Accordingly, an object of the present invention is to provide a positive electrode-solid electrolyte composite having low resistance.

本発明の一態様によれば、
層状岩塩型構造を有する正極活物質を含むセラミックス焼結体からなる板状正極と、
リチウムイオン伝導性を有するセラミックスからなる固体電解質と、
前記板状正極及び前記固体電解質の間に介在し、（ＬａＸＬｉｙ）（Ｎｂ２Ｏ６）（式中、３ｘ＋ｙ＝２、０．４０≦ｘ≦０．５４、及び０．３８≦ｙ≦０．８０である）の化学式で表されるリチウムイオン伝導性複合酸化物からなる界面層と、
を備えた、セラミック正極−固体電解質複合体が提供される。 According to one aspect of the invention,
A plate-like positive electrode comprising a ceramic sintered body containing a positive electrode active material having a layered rock salt structure;
A solid electrolyte made of a ceramic having lithium ion conductivity;
(La X Li y ) (Nb 2 O 6 ) (where 3x + y = 2, 0.40 ≦ x ≦ 0.54, and 0.38 ≦ y) interposed between the plate-like positive electrode and the solid electrolyte. An interface layer composed of a lithium ion conductive composite oxide represented by a chemical formula of ≦ 0.80;
A ceramic positive electrode-solid electrolyte composite is provided.

本発明によるセラミック正極−固体電解質複合体の構成を示す模式断面図である。It is a schematic cross section which shows the structure of the ceramic positive electrode-solid electrolyte composite by this invention.

正極−固体電解質複合体
図１に、本発明によるセラミック正極−固体電解質複合体の一例を模式的に示す。図１に示されるセラミック正極−固体電解質複合体１０は、板状正極１２と固体電解質１４とを備えてなる。板状正極１２は層状岩塩型構造を有する正極活物質を含むセラミックス焼結体からなる一方、固体電解質１４はリチウムイオン伝導性を有するセラミックスからなる。板状正極１２と固体電解質１４の間には、（ＬａＸＬｉｙ）（Ｎｂ２Ｏ６）（式中、３ｘ＋ｙ＝２、０．４０≦ｘ≦０．５４、及び０．３８≦ｙ≦０．８０である）の化学式で表されるリチウムイオン伝導性複合酸化物からなる界面層１６が存在する。すなわち、板状正極１２と固体電解質１４は上記組成の界面層１６を介して間接的に接合されており、直接的には接合されていない。板状正極１２と固体電解質１４が直接的に接合される場合には、焼成等の処理を経ることで、これらの界面に意図していない組成の高抵抗な層が形成されてしまい、界面抵抗を上昇させてしまう。このような界面抵抗の高い正極−固体電解質複合体を用いて電池として構成すると、電池の内部抵抗が高くなるため、高速充放電を実現する上で不利となる。この点、本発明にあっては、上記組成の界面層１６を板状正極１２と固体電解質１４の間に意図的に形成することで、意図していない組成の高抵抗な層の形成を効果的に回避することができる。 Positive - the solid electrolyte composite Figure 1, the ceramic cathode according to the invention - an example of a solid electrolyte composite body is shown schematically. A ceramic positive electrode-solid electrolyte composite 10 shown in FIG. 1 includes a plate-like positive electrode 12 and a solid electrolyte 14. The plate-like positive electrode 12 is made of a ceramic sintered body containing a positive electrode active material having a layered rock salt structure, while the solid electrolyte 14 is made of a ceramic having lithium ion conductivity. Between the plate-like positive electrode 12 and the solid electrolyte 14, (La X Li y ) (Nb 2 O 6 ) (where 3x + y = 2, 0.40 ≦ x ≦ 0.54, and 0.38 ≦ y ≦ There is an interface layer 16 made of a lithium ion conductive composite oxide represented by the chemical formula (0.80). That is, the plate-like positive electrode 12 and the solid electrolyte 14 are indirectly joined through the interface layer 16 having the above composition, and are not joined directly. When the plate-like positive electrode 12 and the solid electrolyte 14 are directly joined, a high-resistance layer having an unintended composition is formed on the interface through a treatment such as firing, and the interface resistance Will rise. When such a positive electrode-solid electrolyte composite having a high interface resistance is used as a battery, the internal resistance of the battery is increased, which is disadvantageous in realizing high-speed charge / discharge. In this respect, in the present invention, the interface layer 16 having the above composition is intentionally formed between the plate-like positive electrode 12 and the solid electrolyte 14, thereby effectively forming a high-resistance layer having an unintended composition. Can be avoided.

界面層１６は、（ＬａＸＬｉｙ）（Ｎｂ２Ｏ６）（式中、３ｘ＋ｙ＝２、０．４０≦ｘ≦０．５４、及び０．３８≦ｙ≦０．８０である）の化学式で表されるリチウムイオン伝導性複合酸化物からなる。このような数値範囲内の組成は、リチウムイオンの拡散経路が連続的に繋がった結晶構造を採りやすく、物質自体のリチウムイオン伝導率が高く、しかも正極−固体電解質間の接合性も良いという優れた利点をもたらす。そして、このような組成の界面層を意図的に形成させつつ正極活物質と固体電解質を一体化接合してリチウムイオン二次電池を構成すると、良好な界面形成を実現しながら、内部抵抗が低く、かつ、高出力の電池が得られる。これらの利点を得る観点から、上記化学式中、０．４２≦ｘ≦０．５２及び０．４４≦ｙ≦０．７４であるのがより好ましく、さらに好ましくは０．４５≦ｘ≦０．５０及び０．４４≦ｙ≦０．６５である。 The interface layer 16 has a chemical formula of (La X Li y ) (Nb 2 O 6 ) (where 3x + y = 2, 0.40 ≦ x ≦ 0.54, and 0.38 ≦ y ≦ 0.80). It consists of lithium ion conductive complex oxide represented by these. The composition within such a numerical range is easy to adopt a crystal structure in which the diffusion paths of lithium ions are continuously connected, the lithium ion conductivity of the substance itself is high, and the bondability between the positive electrode and the solid electrolyte is also excellent. Brings benefits. When a lithium ion secondary battery is formed by integrally bonding the positive electrode active material and the solid electrolyte while intentionally forming an interface layer having such a composition, the internal resistance is reduced while realizing good interface formation. And a high output battery is obtained. From the viewpoint of obtaining these advantages, it is more preferable that 0.42 ≦ x ≦ 0.52 and 0.44 ≦ y ≦ 0.74 in the above chemical formula, and more preferably 0.45 ≦ x ≦ 0.50. And 0.44 ≦ y ≦ 0.65.

界面層１６は１０ｎｍ〜１００ｎｍの厚さを有するのが好ましく、より好ましくは１０ｎｍ〜７０ｎｍ、さらに好ましくは１０ｎｍ〜５０ｎｍである。これらの範囲内であると化学的にも物理的にも安定した界面層を形成できる。１０ｎｍ以上の厚さであると、複合酸化物の層として欠陥が発生しにくくなり、正極活物質と固体電解質との間の元素拡散を優位に抑制することができ、その結果、界面抵抗の低減を効果的に実現することができる。また、１００ｎｍ以下の厚さであると、拡散距離の増大に伴う界面抵抗の上昇を抑制できる。   The interface layer 16 preferably has a thickness of 10 nm to 100 nm, more preferably 10 nm to 70 nm, and still more preferably 10 nm to 50 nm. Within these ranges, a chemically and physically stable interface layer can be formed. When the thickness is 10 nm or more, defects are unlikely to occur as a composite oxide layer, and element diffusion between the positive electrode active material and the solid electrolyte can be preferentially suppressed, resulting in a reduction in interface resistance. Can be realized effectively. Moreover, the raise of the interface resistance accompanying the increase in a diffusion distance can be suppressed as it is the thickness of 100 nm or less.

板状正極１２は、層状岩塩構造を有する正極活物質を含むセラミックス焼結体からなる板状物である。層状岩塩構造を有する正極活物質はリチウム−遷移金属系複合酸化物であるのが好ましい。層状岩塩構造は、リチウムイオンの吸蔵により酸化還元電位が低下し、リチウムイオンの脱離により酸化還元電位が上昇する性質がある。中でもＮｉを多く含む組成は特に好ましい。ここで、層状岩塩構造とは、リチウム以外の遷移金属系層とリチウム層とが酸素原子の層を挟んで交互に積層された結晶構造、すなわち、リチウム以外の遷移金属等のイオン層とリチウムイオン層とが酸化物イオンを挾んで交互に積層された結晶構造（典型的にはα−ＮａＦｅＯ２型構造：立方晶岩塩型構造の［１１１］軸方向に遷移金属とリチウムとが規則配列した構造）をいう。層状岩塩構造を有するリチウム−遷移金属系複合酸化物の典型例としては、ニッケル酸リチウム、マンガン酸リチウム、ニッケル・マンガン酸リチウム、ニッケル・コバルト酸リチウム、コバルト・ニッケル・マンガン酸リチウム、コバルト・マンガン酸リチウム等が挙げられ、これらの材料にＭｇ，Ａｌ，Ｓｉ，Ｃａ，Ｔｉ，Ｖ，Ｃｒ，Ｆｅ，Ｃｕ，Ｚｎ，Ｇａ，Ｇｅ，Ｓｒ，Ｙ，Ｚｒ，Ｎｂ，Ｍｏ，Ａｇ，Ｓｎ，Ｓｂ，Ｔｅ，Ｂａ，Ｂｉ等の元素が１種以上更に含まれていてもよい。好ましい正極活物質は、コバルト酸リチウム、ニッケル−マンガン−コバルト酸リチウム、ニッケル酸リチウム、及びニッケル−コバルト−アルミニウム酸リチウムからなる群から選択される化合物を主成分として含んでなる。正極−固体電解質複合体の内部抵抗の低さから高出力が得られることに加え、これらの好ましい化合物を用いることで、負極としてのリチウムに対する平均電位を高くすることができ、高容量密度も得られる。 The plate-like positive electrode 12 is a plate-like material made of a ceramic sintered body containing a positive electrode active material having a layered rock salt structure. The positive electrode active material having a layered rock salt structure is preferably a lithium-transition metal composite oxide. The layered rock salt structure has the property that the redox potential decreases due to occlusion of lithium ions, and the redox potential increases due to elimination of lithium ions. Among these, a composition containing a large amount of Ni is particularly preferable. Here, the layered rock salt structure is a crystal structure in which transition metal layers other than lithium and lithium layers are alternately stacked with an oxygen atom layer interposed therebetween, that is, an ion layer and lithium ions of transition metals other than lithium. Crystal structure in which layers are alternately stacked with oxide ions (typically α-NaFeO 2 type structure: structure in which transition metal and lithium are regularly arranged in the [111] axis direction of cubic rock salt type structure ). Typical examples of the lithium-transition metal composite oxide having a layered rock salt structure include lithium nickelate, lithium manganate, nickel / lithium manganate, nickel / lithium cobaltate, cobalt / nickel / lithium manganate, cobalt / manganese. Examples of these materials include Mg, Al, Si, Ca, Ti, V, Cr, Fe, Cu, Zn, Ga, Ge, Sr, Y, Zr, Nb, Mo, Ag, Sn, and Sb. , Te, Ba, Bi, etc. may further contain one or more elements. A preferred positive electrode active material comprises as a main component a compound selected from the group consisting of lithium cobaltate, nickel-manganese-lithium cobaltate, lithium nickelate, and nickel-cobalt-lithium aluminumate. In addition to being able to obtain high output from the low internal resistance of the positive electrode-solid electrolyte complex, by using these preferred compounds, the average potential for lithium as the negative electrode can be increased, and high capacity density is also obtained. It is done.

典型的には、正極活物質は、複数の結晶粒子からなる多結晶体であり、これら複数の結晶粒子が配向されてなるのが好ましい。この配向は、層状岩塩構造の（００３）面が板状正極の板面（主面（principal surface））と交差するように配向しているのが好ましく、より好ましくは（００３）以外の面（例えば（１０４）面）が板状正極の板面と平行に配向しているのが好ましい。このような配向により、リチウムイオン等のイオンの挿脱が容易となりイオン伝導度が上がるとともに、蓄電素子を構成した場合におけるレート特性が向上する。このような板状正極における配向度は、板状正極の板面からのＸ線回折における、（１０４）面による回折強度に対する（１０３）面による回折強度（ピーク強度）の比率［００３］／［１０４］で評価することができ、好ましい［００３］／［１０４］比は２以下であり、より好ましくは１以下であり、さらに好ましくは０．５以下である。なお、このような低い［００３］／［１０４］比は、板状正極の板面や内部において板面と平行に（００３）面が出現している割合が減っていることを意味する。   Typically, the positive electrode active material is a polycrystal composed of a plurality of crystal particles, and the plurality of crystal particles are preferably oriented. This orientation is preferably oriented so that the (003) plane of the layered rock salt structure intersects the plate surface (principal surface) of the plate-like positive electrode, more preferably a plane other than (003) ( For example, the (104) plane) is preferably oriented parallel to the plate surface of the plate-like positive electrode. Such an orientation facilitates insertion / removal of ions such as lithium ions, increases ion conductivity, and improves rate characteristics when a power storage element is configured. The degree of orientation in such a plate-like positive electrode is the ratio of the diffraction intensity (peak intensity) of the (103) plane to the diffraction intensity of the (104) plane in the X-ray diffraction from the plate surface of the plate-like positive electrode [003] / [ 104], and a preferable [003] / [104] ratio is 2 or less, more preferably 1 or less, and further preferably 0.5 or less. Note that such a low [003] / [104] ratio means that the ratio of the appearance of the (003) plane parallel to the plate surface in the plate surface or inside of the plate-like positive electrode is reduced.

板状正極１２は、正極活物質を含むセラミックス焼結体からなる。このセラミックス焼結体は正極活物質以外にも導電動剤等の任意成分を含むものであってもよいが、このような任意成分を実質的に含まない構成とすることも可能である。例えば、結晶粒子が配向されてなる正極活物質を用いる場合には、導電助剤等を使用することなくイオン移動度を向上させることができるので、活物質充填率を最大限に高めることができる。したがって、板状正極１２は正極活物質のみから実質的になる（consisting essential1y of）のが好ましく、より好ましくは正極活物質のみからなる（consisting of）。   The plate-like positive electrode 12 is made of a ceramic sintered body containing a positive electrode active material. This ceramic sintered body may contain an optional component such as a conductive mobilizer in addition to the positive electrode active material, but it is also possible to have a configuration substantially free of such an optional component. For example, in the case of using a positive electrode active material in which crystal particles are oriented, ion mobility can be improved without using a conductive aid or the like, so that the active material filling rate can be maximized. . Accordingly, the plate-like positive electrode 12 preferably consists essentially of the positive electrode active material (consisting essential 1y of), and more preferably consists only of the positive electrode active material (consisting of).

板状正極１２及びそれを構成する正極活物質は気孔を有するのが好ましい。板状正極中に気孔が存在することで、充放電によるリチウムイオンの挿脱に伴う膨張ないし収縮によって生じうる応力を緩和することができる。さらに、接合時に生じる熱膨張係数の違いに起因する割れやクラックの発生を抑制する。これにより、緻密な板同士の接合で起こりうる界面での剥離も効果的に防止することができる。正極活物質は３〜３０％の空隙率を有するのが好ましく、より好ましくは５〜２５％であり、さらに好ましくは１０〜２０％である。空隙率（voidage）は、板状正極における気孔（開気孔及び閉気孔を含む）の体積比率であり、気孔率（porosity）と称されることもあり、板状正極の嵩密度と真密度とから算出可能である。   The plate-like positive electrode 12 and the positive electrode active material constituting the plate-like positive electrode 12 preferably have pores. The presence of pores in the plate-like positive electrode can relieve stress that may be caused by expansion or contraction associated with insertion / extraction of lithium ions due to charge / discharge. Furthermore, the generation | occurrence | production of the crack resulting from the difference in the thermal expansion coefficient produced at the time of joining and a crack is suppressed. As a result, it is possible to effectively prevent peeling at the interface that may occur when the dense plates are joined together. The positive electrode active material preferably has a porosity of 3 to 30%, more preferably 5 to 25%, and still more preferably 10 to 20%. The voidage is a volume ratio of pores (including open pores and closed pores) in the plate-like positive electrode, and is sometimes referred to as porosity, and the bulk density and true density of the plate-like positive electrode It can be calculated from

板状正極１２の寸法は特に限定されないが、厚さは単位面積当りの活物質容量の観点から、０．１〜３００μｍが好ましく、より好ましくは１０〜２００μｍ、さらに好ましくは５０〜１００μｍであり、板面の大きさは板面内の反り抑制と電極作製の容易さの観点から、０．５ｍｍ平方〜１０ｍｍ平方が好ましく、より好ましくは１ｍｍ平方〜５ｍｍ平方である。   Although the dimension of the plate-like positive electrode 12 is not particularly limited, the thickness is preferably 0.1 to 300 μm, more preferably 10 to 200 μm, and still more preferably 50 to 100 μm, from the viewpoint of the active material capacity per unit area. The size of the plate surface is preferably 0.5 mm square to 10 mm square, more preferably 1 mm square to 5 mm square, from the viewpoint of suppressing warpage in the plate surface and ease of electrode production.

本発明の好ましい態様によれば、板状正極が複数用意され、これら複数の板状正極が板状固体電解質上にタイル状に配列されてなる。これにより、電極内で活物質をより高密度に充填可能になるという利点がある。   According to a preferred aspect of the present invention, a plurality of plate-like positive electrodes are prepared, and the plurality of plate-like positive electrodes are arranged in a tile shape on the plate-like solid electrolyte. Accordingly, there is an advantage that the active material can be filled in the electrode with higher density.

板状正極１２には固体電解質１４と反対側に集電体がさらに設けられていてもよい。集電体としては、金、銀、銅、アルミニウム、ニッケル等で形成された膜や箔であってよく、例えばスパッタリング法により形成される。   The plate-like positive electrode 12 may further be provided with a current collector on the side opposite to the solid electrolyte 14. The current collector may be a film or foil formed of gold, silver, copper, aluminum, nickel or the like, and is formed by, for example, a sputtering method.

固体電解質１４は、リチウムイオン伝導性を有するセラミックスからなる。リチウムイオン伝導性無機固体電解質の好ましい例としては、ガーネット型又はガーネット類似型セラミックス材料、ペロブスカイト型セラミックス材料、ＮＡＳＩＣＯＮ型リン酸系セラミックスないしガラスセラミックス材料、窒化物系セラミックス材料からなる群から選択される少なくとも一種が挙げられる。中でも、ガーネット型、ペロブスカイト型、ＮＡＳＩＣＯＮ型が好ましい。ガーネット系セラミックス材料の例としては、Ｌｉ−Ｌａ−Ｚｒ−Ｏ系材料（具体的には、Ｌｉ７Ｌａ３Ｚｒ２Ｏ１２など）、Ｌｉ−Ｌａ−Ｔａ−Ｏ系材料（具体的には、Ｌｉ７Ｌａ３Ｔａ２Ｏ１２など）、特許文献２〜４に記載されているものも用いることができる。そのなかでも、Ｌｉ７Ｌａ３Ｚｒ２Ｏ１２を主成分とする材料が好ましい。負極としてのリチウム金属と反応せず、高いイオン伝導度が得られるからである。ペロブスカイト系セラミックス材料の例としては、Ｌｉ−Ｌａ−Ｔｉ−Ｏ系材料（具体的には、ＬｉＬａ１−ｘＴｉｘＯ３（０．０４≦ｘ≦０．１４）など）が挙げられる。リン酸系セラミックス材料の例としては、Ｌｉ−Ａｌ−Ｔｉ−Ｐ−Ｏ，Ｌｉ−Ａｌ−Ｇｅ−Ｐ−Ｏ、及びＬｉ−Ａｌ−Ｔｉ−Ｓｉ−Ｐ−Ｏ（具体的には、Ｌｉ１＋ｘ＋ｙＡｌｘＴｉ２−ｘＳｉｙＰ３−ｙＯ１２（０≦ｘ≦０．４、０＜ｙ≦０．６）など）が挙げられる。中でもＬｉ１．５Ａｌ０．５Ｇｅ１．５（ＰＯ４）３がイオン伝導度が高く好ましい。窒化物系セラミックス材料の例としては、Ｌｉ１３Ｎ、ＬｉＰＯＮなどが挙げられる。 The solid electrolyte 14 is made of a ceramic having lithium ion conductivity. Preferred examples of the lithium ion conductive inorganic solid electrolyte are selected from the group consisting of garnet-type or garnet-like ceramic materials, perovskite-type ceramic materials, NASICON-type phosphate ceramics or glass ceramic materials, and nitride-based ceramic materials. There is at least one kind. Of these, garnet type, perovskite type, and NASICON type are preferable. Examples of garnet ceramic material, Li-La-Zr-O-based material (specifically, such as Li 7 La 3 Zr 2 O 12 ), the Li-La-Ta-O-based material (specifically, Li 7 La 3 Ta 2 O 12 ) and those described in Patent Documents 2 to 4 can also be used. Among them, material mainly composed of Li 7 La 3 Zr 2 O 12 is preferable. It is because it does not react with the lithium metal as the negative electrode and high ionic conductivity is obtained. Examples of the perovskite-based ceramic material include Li—La—Ti—O based materials (specifically, LiLa 1-x Ti x O 3 (0.04 ≦ x ≦ 0.14) and the like). Examples of phosphoric acid-based ceramic materials include Li-Al-Ti-PO, Li-Al-Ge-PO, and Li-Al-Ti-Si-PO (specifically, Li 1 + x + y al x Ti 2-x Si y P 3-y O 12 (0 ≦ x ≦ 0.4,0 <y ≦ 0.6) , and the like). Among these, Li 1.5 Al 0.5 Ge 1.5 (PO 4 ) 3 is preferable because of high ion conductivity. Examples of nitride ceramic materials include Li 13 N, LiPON, and the like.

特に好ましい固体電解質１４は、（ｉ）少なくともＬｉ，Ｌａ，Ｚｒ及びＯで構成され、ガーネット型又はガーネット類似結晶構造を有する複合酸化物、（ｉｉ）少なくともＬｉ，Ａｌ，Ｇｅ，Ｐ及びＯで構成され、ＮＡＳＩＣＯＮ型結晶構造を有する複合酸化物、並びに（ｉｉｉ）少なくともＬｉ，Ｌａ，Ｔｉ及びＯで構成され、ペロブスカイト型結晶構造を有する複合酸化物からなる群から選択される。これらの固体電解質は、高いリチウムイオン伝導率を有し、界面層の効果でその材料特性を損なうことなく正極−固体電解質複合体を構成できる。最も好ましい固体電解質は、少なくともＬｉ，Ｌａ，Ｚｒ及びＯで構成され、ガーネット型又はガーネット類似結晶構造を有する複合酸化物であって、添加物としてＡｌ及びＭｇから選ばれる少なくとも一種の元素を含み、かつ、Ｚｒの一部がＴａ及びＮｂから選択される少なくとも一種の元素で置換されている。この組成の固体電解質は、高いリチウムイオン伝導度とともに緻密なセラミックスが得られ、かつ負極との化学的安定性にも優れる。   Particularly preferred solid electrolyte 14 is (i) a composite oxide composed of at least Li, La, Zr and O and has a garnet-type or garnet-like crystal structure, and (ii) composed of at least Li, Al, Ge, P and O. And (iii) selected from the group consisting of a composite oxide having at least Li, La, Ti and O and having a perovskite crystal structure. These solid electrolytes have high lithium ion conductivity, and can constitute a positive electrode-solid electrolyte complex without impairing material properties due to the effect of the interface layer. The most preferable solid electrolyte is a composite oxide composed of at least Li, La, Zr and O, and has a garnet-type or garnet-like crystal structure, and contains at least one element selected from Al and Mg as an additive, A part of Zr is substituted with at least one element selected from Ta and Nb. The solid electrolyte having this composition can provide a dense ceramic with high lithium ion conductivity, and is excellent in chemical stability with the negative electrode.

Ｌｉ，Ｌａ，Ｚｒ及びＯを含んで構成されるガーネット型又はガーネット類似の結晶構造はＬＬＺ結晶構造と呼ばれ、ＣＳＤ（Cambridge Structural Database）のＸ線回折ファイルＮｏ．４２２２５９（Ｌｉ７Ｌａ３Ｚｒ２Ｏ１２）に類似のＸＲＤパターンを有する。なお、Ｎｏ．４２２２５９と比較すると構成元素が異なり、またセラミックス中のＬｉ濃度などが異なる可能性があるため、回折角度や回折強度比が異なる場合もある。Ｌａに対するＬｉのモル数の比Ｌｉ／Ｌａは２．０以上２．５以下であることが好ましく、Ｌａに対するＺｒのモル比Ｚｒ／Ｌａは０．５以上０．６７以下であるのが好ましい。このガーネット型又はガーネット類似型の結晶構造はＮｂ及び／又はＴａをさらに含んで構成されるものであってもよい。すなわち、ＬＬＺのＺｒの一部がＮｂ及びＴａのいずれか一方又は双方で置換されることにより、置換前に比べて伝導率を向上させることができる。ＺｒのＮｂ及び／又はＴａによる置換量（モル比）は、（Ｎｂ十Ｔａ）／Ｌａのモル比が０．０３以上０．２０以下となる量にすることが好ましい。また、このガーネット系酸化物焼結体はＡｌ及び／又はＭｇをさらに含んでいるのが好ましく、これらの元素は結晶格子に存在してもよいし、結晶格子以外に存在していてもよい。Ａｌの添加量は焼結体の０．０１〜１質量％とするのが好ましく、Ｌａに対するＡｌのモル比Ａｌ／Ｌａは、０．００８〜０．１２であるのが好ましい。Ｍｇの添加量は０．０１〜１質量％以上が好ましく、より好ましくは０．０５〜０．３０質量％である。Ｌａに対するＭｇのモル比Ｍｇ／Ｌａは、０．００１６〜０．０７であるのが好ましい。このようなＬＬＺ系セラミックスの製造は、特許文献２〜４に記載されるような公知の手法に従って又はそれを適宜修正することにより行うことができる。 A garnet-type or garnet-like crystal structure including Li, La, Zr, and O is called an LLZ crystal structure, and is an X-ray diffraction file No. of CSD (Cambridge Structural Database). It has an XRD pattern similar to 422259 (Li 7 La 3 Zr 2 O 12 ). In addition, No. Compared to 422259, the constituent elements are different and the Li concentration in the ceramics may be different, so the diffraction angle and the diffraction intensity ratio may be different. The molar ratio Li / La of Li to La is preferably 2.0 or more and 2.5 or less, and the molar ratio Zr / La to La is preferably 0.5 or more and 0.67 or less. This garnet-type or garnet-like type crystal structure may further comprise Nb and / or Ta. That is, by replacing a part of Zr of LLZ with one or both of Nb and Ta, the conductivity can be improved as compared with that before the substitution. The substitution amount (molar ratio) of Zr with Nb and / or Ta is preferably set such that the molar ratio of (Nb + Ta) / La is 0.03 or more and 0.20 or less. The garnet-based oxide sintered body preferably further contains Al and / or Mg, and these elements may exist in the crystal lattice or may exist in other than the crystal lattice. The addition amount of Al is preferably 0.01 to 1% by mass of the sintered body, and the molar ratio Al / La to La is preferably 0.008 to 0.12. The addition amount of Mg is preferably 0.01 to 1% by mass or more, and more preferably 0.05 to 0.30% by mass. It is preferable that the molar ratio Mg / La of Mg to La is 0.0016 to 0.07. Such LLZ-based ceramics can be manufactured according to a known technique as described in Patent Documents 2 to 4, or by appropriately modifying it.

固体電解質１４の形状及び寸法は特に限定されず、例えば板状であってもよく、その厚さは充放電レート特性と機械的強度の観点から、０．００５ｍｍ〜５ｍｍが好ましく、より好ましくは０．００５ｍｍ〜２ｍｍ、さらに好ましくは０．０１〜１ｍｍであり、板面の大きさは充放電容量と機械的強度の観点から、０．２ｍｍ平方〜５００ｍｍ平方が好ましく、より好ましくは０．５ｍｍ平方〜１００ｍｍ平方である。   The shape and dimensions of the solid electrolyte 14 are not particularly limited, and may be, for example, a plate shape. The thickness is preferably 0.005 mm to 5 mm, more preferably 0, from the viewpoint of charge / discharge rate characteristics and mechanical strength. 0.005 mm to 2 mm, more preferably 0.01 to 1 mm, and the size of the plate surface is preferably 0.2 mm square to 500 mm square, more preferably 0.5 mm square from the viewpoint of charge / discharge capacity and mechanical strength. ~ 100 mm square.

製造方法
本発明のセラミック正極−固体電解質複合体は、（ＬａＸＬｉｙ）（Ｎｂ２Ｏ６）の化学式で表されるリチウムイオン伝導性複合酸化物からなる界面層が界面に形成されるように、板状正極を固体電解質と接合させる任意の手法によって製造することができる。 Production Method In the ceramic positive electrode-solid electrolyte composite of the present invention, an interface layer made of a lithium ion conductive composite oxide represented by the chemical formula (La X Li y ) (Nb 2 O 6 ) is formed at the interface. Moreover, it can manufacture by the arbitrary methods of joining a plate-shaped positive electrode with a solid electrolyte.

例えば、界面層の形成は、所望組成のセラミックスのバルク体を作製し、このバルク体をスパッタリングターゲットとして用いてスパッタリングを行うことにより、正極又は固体電解質に上記組成の界面層を成膜することにより好ましく行うことができる。あるいは、Ｌｉ及びＬａを含有する固体電解質上にスパッタリング等でＮｂ金属膜を成膜し、酸化雰囲気下、固体電解質の分解温度以下の温度で熱処理して上記組成の界面層を得る方法によっても界面形成を行うことができ、この場合、固体電解質の表面組成のみが（ＬａＸＬｉｙ）（Ｎｂ２Ｏ６）に変わるため固体電解質の特性を劣化させることはない。 For example, the interface layer is formed by forming a ceramic bulk body having a desired composition and performing sputtering using the bulk body as a sputtering target, thereby forming the interface layer having the above composition on the positive electrode or the solid electrolyte. It can be preferably performed. Alternatively, the interface can also be obtained by forming an Nb metal film on the solid electrolyte containing Li and La by sputtering or the like and heat-treating it in an oxidizing atmosphere at a temperature lower than the decomposition temperature of the solid electrolyte to obtain an interface layer having the above composition. In this case, since only the surface composition of the solid electrolyte is changed to (La X Li y ) (Nb 2 O 6 ), the characteristics of the solid electrolyte are not deteriorated.

板状正極と固体電解質の接合は、正極又は固体電解質に形成された（ＬａＸＬｉｙ）（Ｎｂ２Ｏ６）界面層を挟むように正極及び固体電解質をスタックし、ホットプレス法により接合することにより好ましく行うことができる。通常、界面層を意図的に形成させることなくホットプレス接合を試みると、正極及び固体電解質の構成元素が相互拡散してしまい高抵抗の界面をもたらしてしまうが、本発明による界面層を介在させることにより、それらの望ましくない拡散が抑制され、正極活物質と固体電解質の間に良好な低抵抗な界面が形成される。 The plate-like positive electrode and the solid electrolyte are joined by stacking the positive electrode and the solid electrolyte so as to sandwich the (La X Li y ) (Nb 2 O 6 ) interface layer formed on the positive electrode or the solid electrolyte, and joining them by hot pressing. This can be preferably performed. Normally, when hot press bonding is attempted without intentionally forming the interface layer, the constituent elements of the positive electrode and the solid electrolyte are interdiffused to provide a high resistance interface, but the interface layer according to the present invention is interposed. As a result, these undesirable diffusions are suppressed, and a good low resistance interface is formed between the positive electrode active material and the solid electrolyte.

界面層の形成を板状正極及び固体電解質の接合と同時に行うことも可能である。例えば、板状正極上にＮｂ金属膜を形成し、このＮｂ金属膜を酸化雰囲気で酸化させ、得られたＮｂ酸化膜上にエアロゾルデポジション法、パウダージェットデポジション法、溶射法等の手法によりＬｉ及びＬａを含有する固体電解質の膜をバルク状に形成し、熱処理を行うことで、板状正極を固体電解質と接合しながら（ＬａＸＬｉｙ）（Ｎｂ２Ｏ６）なる組成の界面層を同時に形成することができる。 It is also possible to form the interface layer simultaneously with the joining of the plate-like positive electrode and the solid electrolyte. For example, an Nb metal film is formed on a plate-shaped positive electrode, the Nb metal film is oxidized in an oxidizing atmosphere, and an aerosol deposition method, a powder jet deposition method, a thermal spraying method, or the like is applied to the obtained Nb oxide film. An interface layer having a composition of (La X Li y ) (Nb 2 O 6 ) is formed by joining a plate-like positive electrode to a solid electrolyte by forming a solid electrolyte film containing Li and La in a bulk shape and performing heat treatment. Can be formed simultaneously.

本発明を以下の例によってさらに具体的に説明する。   The present invention is more specifically described by the following examples.

例１：ＮＣＡセラミックス板の作製
本発明において板状正極として用いられるＮＣＡセラミックス板を以下の手順で作製した。 Example 1: Production of NCA ceramic plate An NCA ceramic plate used as a plate-like positive electrode in the present invention was produced by the following procedure.

（１）スラリー調製
Ｎｉ（ＯＨ）２粉末（株式会社高純度化学研究所製）８１．６重量部、Ｃｏ（ＯＨ）２粉末（和光純薬工業株式会社製）１５．０重量部、及びＡｌ２Ｏ３・Ｈ２Ｏ粉末（ＳＡＳＯＬ社製）３．４重量部を秤量して、原料粉末を用意した。次に、純水９７．３重量部、分散剤（日油株式会社製：品番ＡＫＭ−０５２１）０．４重量部、消泡剤としての１−オクタノール（片山化学株式会社製）０．２重量部、及びバインダー（日本酢ビ・ポバール株式会社製：品番ＰＶ３）２．０重量部からなるビヒクルを作製した。こうして得られたビヒクルと原料粉末を湿式で混合及び粉砕することで、スラリーを調製した。この混合及び粉砕は、直径２ｍｍのジルコニアボールを用いたボールミルで２４時間処理した後、直径０．１ｍｍのジルコニアビーズを用いたビーズミルで４０分間処理することによって行った。 (1) Slurry preparation 81.6 parts by weight of Ni (OH) 2 powder (manufactured by Kojundo Chemical Laboratory Co., Ltd.), 15.0 parts by weight of Co (OH) 2 powder (manufactured by Wako Pure Chemical Industries, Ltd.), and Al A raw material powder was prepared by weighing 3.4 parts by weight of 2 O 3 .H 2 O powder (manufactured by SASOL). Next, 97.3 parts by weight of pure water, 0.4 part by weight of a dispersant (manufactured by NOF Corporation: Part No. AKM-0521), 0.2 weight of 1-octanol (made by Katayama Chemical Co., Ltd.) as an antifoaming agent Part and a binder (Nippon Vinegar Poval Co., Ltd. product: PV3) 2.0 parts by weight was produced. The vehicle and raw material powder thus obtained were mixed and pulverized in a wet manner to prepare a slurry. This mixing and pulverization was performed by treating for 24 hours with a ball mill using zirconia balls having a diameter of 2 mm and then treating with a bead mill using zirconia beads having a diameter of 0.1 mm for 40 minutes.

（２）造粒
得られたスラリーを二流体ノズル方式のスプレードライヤーに投入することにより、造粒体を形成した。スプレードライヤーの噴出圧力、ノズル径、循環風量等のパラメータを適宜調整することで、種々の大きさの造粒体を形成することが可能である。 (2) Granulation The obtained slurry was put into a two-fluid nozzle type spray dryer to form a granulated body. By appropriately adjusting parameters such as the spray pressure of the spray dryer, the nozzle diameter, and the circulating air volume, it is possible to form granulated bodies of various sizes.

（３）熱処理（仮焼成）
得られた造粒体を１１００℃で３時間（大気雰囲気）熱処理して、ニッケル、コバルト、及びアルミニウムの複合酸化物（（Ｎｉ０．８，Ｃｏ０．１５，Ａｌ０．０５）Ｏ）の粒子である、正極活物質前駆体粒子を得た。得られた正極活物質前駆体粒子を以下に示されるとおり分析したところ、平均粒径Ｄ５０（体積基準）は２．３μｍであり、比表面積は１２ｍ２／ｇであり、相対タップ密度は０．３であった。
＜平均粒径Ｄ５０＞
水を分散媒として正極活物質前駆体粒子の粉末試料を分散させたものを、レーザ回折／散乱式粒度分布測定装置（株式会社堀場製作所製 型番「ＬＡ−７００」）に投入することで、平均粒径Ｄ５０（体積基準）を測定した。
＜相対タップ密度＞
正極活物質前駆体粒子の粉末試料を入れたメスシリンダを市販のタップ密度測定装置を用いて２００回タッピングした後、（粉末重量）／（粉末のかさ体積）を算出することによって、タップ密度を求めた。その後、得られたタップ密度を理論密度で除することで、相対タップ密度［無次元値］を算出した。 (3) Heat treatment (temporary firing)
The obtained granule was heat-treated at 1100 ° C. for 3 hours (atmospheric atmosphere) to form a composite oxide of nickel, cobalt, and aluminum ((Ni 0.8 , Co 0.15 , Al 0.05 ) O). Positive electrode active material precursor particles, which are particles, were obtained. When the obtained positive electrode active material precursor particles were analyzed as shown below, the average particle diameter D50 (volume basis) was 2.3 μm, the specific surface area was 12 m 2 / g, and the relative tap density was 0.00. 3.
<Average particle diameter D50>
By dispersing a powder sample of positive electrode active material precursor particles using water as a dispersion medium into a laser diffraction / scattering particle size distribution measuring apparatus (model number “LA-700” manufactured by Horiba, Ltd.), an average is obtained. The particle size D50 (volume basis) was measured.
<Relative tap density>
After tapping the measuring cylinder containing the powder sample of the positive electrode active material precursor particles 200 times using a commercially available tap density measuring device, the tap density is calculated by calculating (powder weight) / (powder bulk volume). Asked. Thereafter, the relative tap density [dimensional value] was calculated by dividing the obtained tap density by the theoretical density.

（４）成形
得られた正極活物質前駆体粒子粉末１００重量部、分散媒（キシレン：ブタノール＝１：１）５０重量部、バインダーとしてのポリビニルブチラール（積水化学工業株式会社製：品番ＢＭ−２、）１０重量部、可塑剤としてのＤＯＰ（Ｄｉ（２−ｅｔｈｙｌｈｅｘｙｌ）ｐｈｔｈａｌａｔｅ：黒金化成株式会社製）４．５重量部、及び分散剤（花王株式会社製 製品名「レオドールＳＰＯ−３０」）３重量部を秤量し、乳鉢で予備混練した後、トリロールを用いて混練することで、（ブルックフィールド社製ＬＶＴ型粘度計を用いて測定して）２０００〜３０００ｃＰの粘度を有する成形用スラリーを調製した。こうして得られた成形用スラリーを用いて、ドクターブレード法により、厚さ５０μｍのシートを形成した。乾燥後のシートに対して打ち抜き加工を施すことによって、１ｍｍ平方のグリーンシート成形体を得た。 (4) Molding 100 parts by weight of the obtained positive electrode active material precursor particle powder, 50 parts by weight of a dispersion medium (xylene: butanol = 1: 1), polyvinyl butyral as a binder (manufactured by Sekisui Chemical Co., Ltd .: product number BM-2) )) 10 parts by weight, DOP as a plasticizer (Di (2-ethylhexyl) phthalate: manufactured by Kurokin Kasei Co., Ltd.), and a dispersant (product name “Reodol SPO-30” manufactured by Kao Corporation) 3 parts by weight are weighed, pre-kneaded in a mortar, and then kneaded using a tri-roll to measure a molding slurry having a viscosity of 2000 to 3000 cP (measured using a Brookfield LVT viscometer). Prepared. A sheet having a thickness of 50 μm was formed by the doctor blade method using the molding slurry thus obtained. By punching the dried sheet, a 1 mm square green sheet molded body was obtained.

（５）焼成（リチウム導入）
上述のようにして得られた１ｍｍ平方のグリーンシート成形体を、大気雰囲気中で９００℃にて熱処理することで、成形体の脱脂及び仮焼成を行った。かかる成形体仮焼成の温度は、上述の熱処理（造粒体仮焼成）温度よりも低い。これは、成形体の仮焼成時に内部の粒子間の焼結の進行を抑制することで、後続する本焼成時にリチウムが均一に拡散及び反応するようにするためである。 (5) Firing (Lithium introduction)
The 1 mm square green sheet molded body obtained as described above was heat-treated at 900 ° C. in an air atmosphere, whereby the molded body was degreased and pre-fired. The temperature of the green body preliminary firing is lower than the above-described heat treatment (granulated body preliminary firing) temperature. This is because lithium is uniformly diffused and reacted during the subsequent main firing by suppressing the progress of sintering between the internal particles during the temporary firing of the molded body.

一方、水酸化リチウムのエタノール分散液を以下のようにして調製した。まず、ＬｉＯＨ・Ｈ２Ｏ粉末（和光純薬工業株式会社製）を、ジェットミルを用いて、電子顕微鏡観察による目視粒径で１〜５μｍになるように粉砕した。この粉末をエタノール（片山化学株式会社製）１００重量部に対し１重量部の割合で加えたものを、超音波により、粉末が目視によって確認することができなくなるまで分散させた。 On the other hand, an ethanol dispersion of lithium hydroxide was prepared as follows. First, LiOH.H 2 O powder (manufactured by Wako Pure Chemical Industries, Ltd.) was pulverized using a jet mill so as to have a visual particle diameter of 1 to 5 μm by observation with an electron microscope. What added this powder in the ratio of 1 weight part with respect to 100 weight part of ethanol (made by Katayama Chemical Co., Ltd.) was disperse | distributed until it became impossible to confirm powder visually by an ultrasonic wave.

上記仮焼成成形体の両面に対して、上記水酸化リチウムのエタノール分散液をエアブラシによって所定量スプレーしたものを、７５０℃で１０時間（酸素雰囲気）熱処理することで、Ｌｉ（Ｎｉ０．８，Ｃｏ０．１５，Ａｌ０．０５）Ｏ２の組成を有するＮＣＡセラミックス板を板状正極として得た。得られた板状正極を以下に示される手順で分析したところ、空隙率は１５％、開気孔比率は９５％、回折強度（ピーク強度）の比率［００３］／［１０４］は０．５であった。
＜空隙率＞
空隙率は、相対密度から計算される値（空隙率＝１−相対密度）である。相対密度は、アルキメデス法で求めた嵩密度を、ピクノメータを用いて求めた真密度で除して求めた値である。嵩密度の測定では、空隙中に存在する空気を十分に追い出すために、試料を水中で煮沸処理をした。
＜開気孔比率＞
開気孔比率は、閉気孔率と全気孔率から計算によって求められる値（開気孔比率＝開気孔／全気孔＝開気孔／（開気孔＋閉気孔））である。閉気孔率は、アルキメデス法で測定した見かけ密度より求められる。また、全気孔率は、同じくアルキメデス法で測定した嵩密度より求められる。
＜回折強度（ピーク強度）比率＞
回折強度（ピーク強度）比率の測定は、φ５〜１０ｍｍ程度の大きさに加工した正極活物質層用セラミックス板を、ＸＲＤ測定用の試料フォルダに載せ、ＸＲＤ装置（株式会社リガク製 製品名「ＲＩＮＴ-ＴＴＲIII」）を用いて、板状正極の表面に対してＸ線を照射したときのＸＲＤプロファイルを測定し、（１０４）面による回折強度（ピーク高さ）に対する（００３）面による回折強度（ピーク高さ）の比率を求めることにより行った。この測定方法によれば、板面の結晶面に平行に存在する結晶面、すなわち板面方向に配向する結晶面による回折プロファイルが得られる。 A solution obtained by spraying a predetermined amount of the ethanol dispersion of lithium hydroxide with an airbrush onto both surfaces of the calcined molded body is heat-treated at 750 ° C. for 10 hours (oxygen atmosphere), whereby Li (Ni 0.8 , An NCA ceramic plate having a composition of Co 0.15 , Al 0.05 ) O 2 was obtained as a plate-like positive electrode. When the obtained plate-like positive electrode was analyzed by the procedure shown below, the porosity was 15%, the open pore ratio was 95%, and the diffraction intensity (peak intensity) ratio [003] / [104] was 0.5. there were.
<Porosity>
The porosity is a value calculated from the relative density (porosity = 1−relative density). The relative density is a value obtained by dividing the bulk density obtained by the Archimedes method by the true density obtained using a pycnometer. In the measurement of the bulk density, the sample was boiled in water in order to sufficiently expel the air present in the voids.
<Open pore ratio>
The open pore ratio is a value obtained by calculation from the closed porosity and the total porosity (open pore ratio = open pores / total pores = open pores / (open pores + closed pores)). The closed porosity is obtained from the apparent density measured by the Archimedes method. The total porosity is determined from the bulk density measured by the Archimedes method.
<Diffraction intensity (peak intensity) ratio>
The diffraction intensity (peak intensity) ratio is measured by placing a ceramic plate for a positive electrode active material layer processed to a size of about φ5 to 10 mm in a sample folder for XRD measurement, and an XRD apparatus (product name “RINT, manufactured by Rigaku Corporation”). -TTRIII ") was used to measure the XRD profile when the surface of the plate-shaped positive electrode was irradiated with X-rays, and the diffraction intensity (003) plane relative to the (104) plane diffraction intensity (peak height) ( This was done by determining the ratio of peak height. According to this measuring method, a diffraction profile can be obtained from a crystal plane parallel to the crystal plane of the plate plane, that is, a crystal plane oriented in the plate plane direction.

例２：ＬＬＺセラミックスの作製
本発明において固体電解質として用いられるＬＬＺセラミックスを以下の手順で作製した。 Example 2: Production of LLZ ceramics LLZ ceramics used as a solid electrolyte in the present invention were produced by the following procedure.

焼成用原料調製のための各原料成分として、水酸化リチウム（関東化学株式会社）、水酸化ランタン（信越化学工業株式会社）、酸化ジルコニウム（東ソー株式会社）、酸化タンタルを用意した。これらの粉末をＬｉＯＨ：Ｌａ（ＯＨ）３：ＺｒＯ２：Ｔａ２Ｏ５＝７：３：１．６２５：０．１８７５になるように秤量及び配合し、ライカイ機にて混合して焼成用原料を得た。 Lithium hydroxide (Kanto Chemical Co., Inc.), lanthanum hydroxide (Shin-Etsu Chemical Co., Ltd.), zirconium oxide (Tosoh Corp.), and tantalum oxide were prepared as raw material components for preparing the raw material for firing. These powders are weighed and blended so as to be LiOH: La (OH) 3 : ZrO 2 : Ta 2 O 5 = 7: 3: 1.625: 0.1875, and mixed by a laika machine to be a raw material for firing. Got.

第一の焼成工程として、上記焼成用原料をアルミナ坩堝に入れて大気雰囲気で６００℃／時間にて昇温し９００℃にて６時間保持した。   As the first firing step, the firing raw material was placed in an alumina crucible, heated at 600 ° C./hour in the air atmosphere, and held at 900 ° C. for 6 hours.

第二の焼成工程として、第一の焼成工程で得られた粉末に対しγ−Ａｌ２Ｏ３をＡｌ濃度が０．０８ｗｔ％となるように添加し、この粉末と玉石を混合し振動ミルを用いて３時間粉砕した。この粉砕粉を篩通しした後、得られた粉末を、金型を用いて約１００ＭＰａにてプレス成形してペレット状にした。得られたペレットをマグネシア製のセッター上に乗せ、セッターごとマグネシア製のサヤ内に入れて、Ａｒ雰囲気にて２００℃／時間で昇温し、１０００℃で３６時間保持することにより、３５ｍｍ×１８ｍｍのサイズで厚さ１１ｍｍの焼結体を得て、そこから１０ｍｍ×１０ｍｍのサイズで厚さ１ｍｍのＬＬＺセラミックス板を固体電解質として得た。なお、Ａｒ雰囲気は、事前に容量約３Ｌの炉内を減圧し、純度９９．９９％以上のＡｒガスで置換した後、２Ｌ／分の流量で電気炉内にＡｒを導入することにより作製した。 As a second firing step, γ-Al 2 O 3 is added to the powder obtained in the first firing step so that the Al concentration is 0.08 wt%, and this powder and cobblestone are mixed to form a vibration mill. And milled for 3 hours. After pulverizing this pulverized powder, the obtained powder was press-molded at about 100 MPa using a mold into pellets. The obtained pellets are placed on a magnesia setter, and the whole setter is placed in a magnesia sheath, heated at 200 ° C./hour in an Ar atmosphere, and held at 1000 ° C. for 36 hours to obtain 35 mm × 18 mm. A sintered body having a size of 11 mm and a thickness of 11 mm was obtained, and a LLZ ceramic plate having a size of 10 mm × 10 mm and a thickness of 1 mm was obtained as a solid electrolyte. The Ar atmosphere was prepared by depressurizing the furnace having a capacity of about 3 L in advance and replacing it with Ar gas having a purity of 99.99% or more, and then introducing Ar into the electric furnace at a flow rate of 2 L / min. .

得られた焼結体試料の上下面を研磨した後、以下に示される各種の評価ないし測定を行った。焼結体試料のＸ線回折測定を行ったところ、ＣＳＤ（Cambridge Structural Database）のＸ線回折ファイルＮｏ．４２２２５９（Ｌｉ７Ｌａ３Ｚｒ２Ｏ１２）類似の結晶構造が得られた。このことから、得られた試料がＬＬＺ結晶構造の特徴を有することが確認された。また、焼結体試料のＡｌ及びＭｇ含有量を把握するため、誘導結合プラズマ発光分析（ＩＣＰ分析）により化学分析を行ったところ、Ａｌ含有量は０．０８ｗｔ％、Ｍｇ含有量は０．０７ｗｔ％であった。 After polishing the upper and lower surfaces of the obtained sintered body sample, various evaluations and measurements shown below were performed. When the X-ray diffraction measurement of the sintered body sample was performed, an X-ray diffraction file No. of CSD (Cambridge Structural Database) was obtained. A crystal structure similar to 422259 (Li 7 La 3 Zr 2 O 12 ) was obtained. From this, it was confirmed that the obtained sample has the characteristics of the LLZ crystal structure. Further, in order to grasp the Al and Mg contents of the sintered body sample, when chemical analysis was performed by inductively coupled plasma emission analysis (ICP analysis), the Al content was 0.08 wt% and the Mg content was 0.07 wt. %Met.

例３：界面層の作製
酸化ランタン（関東化学製）、炭酸リチウム（本荘ケミカル製）、酸化ニオブ（関東化学製）粉末を（Ｌａ０．５Ｌｉ０．５）（Ｎｂ２Ｏ６）の組成となるように秤量し、乾式で混合／粉砕した。得られた混合粉末をペレットに成形し、大気雰囲気１０００℃で２時間焼成した。純度と合成度を上げるため、得られたペレット焼結体を再粉砕し、再度ペレットを成形し、大気雰囲気下１１００℃で３６時間焼成して（Ｌａ０．５Ｌｉ０．５）（Ｎｂ２Ｏ６）焼結体を作製した。合成した焼結体をターゲットとして、マグネトロンスパッタリングにより、固体電解質上に０．０５μｍの膜を界面層として形成した。こうして界面層付きＬＬＺセラミックス板（固体電解質）を得た。 Example 3: Preparation of interface layer Composition of lanthanum oxide (manufactured by Kanto Chemical), lithium carbonate (manufactured by Honjo Chemical), niobium oxide (manufactured by Kanto Chemical) and (La 0.5 Li 0.5 ) (Nb 2 O 6 ) And weighed and mixed / pulverized dry. The obtained mixed powder was formed into pellets and fired at 1000 ° C. for 2 hours. In order to increase the purity and the degree of synthesis, the obtained pellet sintered body is reground, formed again, and fired at 1100 ° C. for 36 hours in an air atmosphere (La 0.5 Li 0.5 ) (Nb 2 An O 6 ) sintered body was produced. Using the synthesized sintered body as a target, a 0.05 μm film was formed as an interface layer on the solid electrolyte by magnetron sputtering. Thus, an LLZ ceramic plate (solid electrolyte) with an interface layer was obtained.

例４：ホットプレスによるＮＣＡ／ＬＬＺ複合体の作製
例３で得られた１０ｍｍ平方に加工した厚さ１ｍｍの界面層付きＬＬＺセラミックス板の界面層上に、例１で作製された１ｍｍ平方の厚さ５０μｍのＮＣＡセラミックス板を３行３列となるように９枚配列した。この配列体の上下面を焼成冶具との癒着防止用Ｐｔ箔で挟み、焼成条件７００℃で５時間、２０００ｋｇｆ／ｃｍ２の圧力でホットプレスにより焼成して、ＮＣＡ／ＬＬＺ複合体（界面層あり）を得た。得られた複合体において、ＮＣＡセラミックス板（板状正極）とＬＬＺセラミックス板（固体電解質）との界面には剥がれ等が観察されず、極めて密着性が高いことが確認された。また、ＮＣＡセラミックス板（板状正極）が多数の気孔を有することも確認された。 Example 4: Production of NCA / LLZ composite by hot pressing The thickness of 1 mm square produced in Example 1 was formed on the interface layer of the LLZ ceramic plate with an interface layer having a thickness of 1 mm processed in 10 mm square obtained in Example 3. Nine 50 μm thick NCA ceramic plates were arranged in 3 rows and 3 columns. The upper and lower surfaces of this array are sandwiched between Pt foils for preventing adhesion to a firing jig, fired at 700 ° C. for 5 hours by hot pressing at a pressure of 2000 kgf / cm 2 , and an NCA / LLZ composite (with an interface layer) ) In the obtained composite, peeling or the like was not observed at the interface between the NCA ceramic plate (plate-like positive electrode) and the LLZ ceramic plate (solid electrolyte), and it was confirmed that the adhesion was extremely high. It was also confirmed that the NCA ceramic plate (plate-like positive electrode) has a large number of pores.

また、比較のため、界面層付きＬＬＺセラミックス板の代わりに、例２で作製されたままの界面層を有しないＬＬＺセラミックス板を用いたこと以外は上記同様にして、比較試料としてのＮＣＡ／ＬＬＺ複合体（界面層なし）を作製した。   For comparison, an NCA / LLZ as a comparative sample was used in the same manner as above except that an LLZ ceramic plate having no interface layer as prepared in Example 2 was used instead of the LLZ ceramic plate with an interface layer. A composite (no interfacial layer) was prepared.

例５：コインセルの作製及び内部抵抗の評価
例４において製造されたＮＣＡ／ＬＬＺ複合体のＮＣＡセラミックス板の板面にＡｕ膜をスパッタリングにより形成して正極集電体（厚さ：５００オングストローム）を形成した。次に、Ａｒ雰囲気のグローブボックス内で、ＬＬＺセラミックス板の板面にリチウム金属を２００℃で溶融圧着して負極とした。こうして得られたＡｕ／ＮＣＡ／界面層／ＬＬＺ／Ｌｉ接合体及びＡｕ／ＮＣＡ／ＬＬＺ／Ｌｉ接合体をステンレス製ＣＲ２０３２ケースに組み込み、コインセルとした。 Example 5: Preparation of coin cell and evaluation of internal resistance A positive electrode current collector (thickness: 500 angstroms) was formed by sputtering an Au film on the surface of the NCA ceramic plate of the NCA / LLZ composite produced in Example 4. Formed. Next, in a glove box in an Ar atmosphere, lithium metal was melt bonded to the plate surface of the LLZ ceramic plate at 200 ° C. to obtain a negative electrode. The Au / NCA / interface layer / LLZ / Li joined body and the Au / NCA / LLZ / Li joined body thus obtained were incorporated into a stainless steel CR2032 case to form a coin cell.

抵抗を測定するために、コインセルを大気中に取り出し、電気化学測定システム（ソーラトロン社製、ポテンショ／ガルバノスタッド及び周波数応答アナライザの組合せ）を用い、周波数１ＭＨｚ〜０．０１Ｈｚ、電圧１０ｍＶにて交流インピーダンス測定を行った。得られたインピーダンスカーブの円弧を解析ソフト（Scribner Associates, Inc.社製、Zview2）を用いてフィッティングし、界面抵抗値を算出した。その結果、界面層を有しない比較試料の抵抗値を１００（相対値）とした場合、本発明による（Ｌａ０．５Ｌｉ０．５）（Ｎｂ２Ｏ６）なる組成の界面層を有する試料の界面抵抗値は１（相対値）であった。このように、正極と固体電解質とを単に接合するのではなく、元素拡散を抑制できるリチウムイオン伝導性材料を意図的に界面に形成することにより、内部抵抗の低い正極−固体電解質複合体、更には固体電池を実現することができる。 In order to measure resistance, the coin cell is taken out into the atmosphere and an AC impedance is measured at a frequency of 1 MHz to 0.01 Hz and a voltage of 10 mV using an electrochemical measurement system (combination of potentiometer / galvano stud and frequency response analyzer manufactured by Solartron). Measurements were made. The arc of the obtained impedance curve was fitted using analysis software (Zview 2 manufactured by Scribner Associates, Inc.), and the interface resistance value was calculated. As a result, when the resistance value of the comparative sample having no interface layer is 100 (relative value), the sample having the interface layer having the composition of (La 0.5 Li 0.5 ) (Nb 2 O 6 ) according to the present invention. The interfacial resistance value was 1 (relative value). In this way, a positive electrode-solid electrolyte composite having a low internal resistance is formed by intentionally forming a lithium ion conductive material capable of suppressing element diffusion at the interface, rather than simply joining the positive electrode and the solid electrolyte. Can realize a solid state battery.

Claims (6)

層状岩塩型構造を有する正極活物質を含むセラミックス焼結体からなる板状正極と、
リチウムイオン伝導性を有するセラミックスからなり、ガーネット型又はガーネット類似型セラミックス材料、ペロブスカイト型セラミックス材料、ＮＡＳＩＣＯＮ型リン酸系セラミックスないしガラスセラミックス材料、窒化物系セラミックス材料からなる群から選択される少なくとも一種からなる固体電解質と、
前記板状正極及び前記固体電解質の間に介在し、（ＬａＸＬｉｙ）（Ｎｂ２Ｏ６）（式中、３ｘ＋ｙ＝２、０．４０≦ｘ≦０．５４、及び０．３８≦ｙ≦０．８０である）の化学式で表されるリチウムイオン伝導性複合酸化物からなる界面層と、
を備えた、セラミック正極−固体電解質複合体。 A plate-like positive electrode comprising a ceramic sintered body containing a positive electrode active material having a layered rock salt structure;
Ri Do ceramics with lithium ion conductivity, at least one of a garnet-type or garnet similar ceramics material, perovskite type ceramic material, NASICON type phosphate ceramics or glass ceramic material is selected from the group consisting of nitride-based ceramic material A solid electrolyte comprising:
(La X Li y ) (Nb 2 O 6 ) (where 3x + y = 2, 0.40 ≦ x ≦ 0.54, and 0.38 ≦ y) interposed between the plate-like positive electrode and the solid electrolyte. An interface layer composed of a lithium ion conductive composite oxide represented by a chemical formula of ≦ 0.80;
A ceramic positive electrode-solid electrolyte composite comprising: 前記界面層が、１０ｎｍ〜１００ｎｍの厚さを有する、請求項１に記載のセラミック正極−固体電解質複合体。   The ceramic positive electrode-solid electrolyte composite according to claim 1, wherein the interface layer has a thickness of 10 nm to 100 nm. 前記正極活物質が、コバルト酸リチウム、ニッケル−マンガン−コバルト酸リチウム、ニッケル酸リチウム、及びニッケル−コバルト−アルミニウム酸リチウムからなる群から選択される化合物を主成分として含んでなる、請求項１に記載のセラミック正極−固体電解質複合体。   The positive electrode active material comprises, as a main component, a compound selected from the group consisting of lithium cobaltate, nickel-manganese-lithium cobaltate, lithium nickelate, and nickel-cobalt-lithium aluminum oxide. The ceramic positive electrode-solid electrolyte composite as described. 前記正極活物質が、複数の結晶粒子からなる多結晶体であり、該複数の結晶粒子が配向されてなる、請求項１〜３のいずれか一項に記載のセラミック正極−固体電解質複合体。   The ceramic positive electrode-solid electrolyte composite according to any one of claims 1 to 3, wherein the positive electrode active material is a polycrystal formed of a plurality of crystal particles, and the plurality of crystal particles are oriented. 前記固体電解質が、少なくともＬｉ，Ｌａ，Ｚｒ及びＯで構成され、ガーネット型又はガーネット類似結晶構造を有する複合酸化物、少なくともＬｉ，Ａｌ，Ｇｅ，Ｐ及びＯで構成され、ＮＡＳＩＣＯＮ型結晶構造を有する複合酸化物、並びに少なくともＬｉ，Ｌａ，Ｔｉ及びＯで構成され、ペロブスカイト型結晶構造を有する複合酸化物からなる群から選択される、請求項１〜４のいずれか一項に記載のセラミック正極−固体電解質複合体。   The solid electrolyte is composed of at least Li, La, Zr and O, and is composed of a complex oxide having a garnet type or garnet-like crystal structure, at least Li, Al, Ge, P and O, and has a NASICON type crystal structure. The ceramic positive electrode according to any one of claims 1 to 4, wherein the ceramic positive electrode is selected from the group consisting of a complex oxide and a complex oxide composed of at least Li, La, Ti, and O and having a perovskite crystal structure. Solid electrolyte composite. 前記固体電解質が、少なくともＬｉ，Ｌａ，Ｚｒ及びＯで構成され、ガーネット型又はガーネット類似結晶構造を有する複合酸化物であって、添加物としてＡｌ及びＭｇから選ばれる少なくとも一種の元素を含み、かつ、Ｚｒの一部がＴａ及びＮｂから選択される少なくとも一種の元素で置換されている、請求項１〜５のいずれか一項に記載のセラミック正極−固体電解質複合体。
The solid electrolyte is composed of at least Li, La, Zr and O, and is a complex oxide having a garnet-type or garnet-like crystal structure, containing at least one element selected from Al and Mg as an additive; and The ceramic positive electrode-solid electrolyte composite according to any one of claims 1 to 5, wherein a part of Zr is substituted with at least one element selected from Ta and Nb.
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