WO2020137617A1 - Sputtering target - Google Patents

Sputtering target Download PDF

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Publication number
WO2020137617A1
WO2020137617A1 PCT/JP2019/048929 JP2019048929W WO2020137617A1 WO 2020137617 A1 WO2020137617 A1 WO 2020137617A1 JP 2019048929 W JP2019048929 W JP 2019048929W WO 2020137617 A1 WO2020137617 A1 WO 2020137617A1
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Prior art keywords
positive electrode
electrode layer
lithium
sputtering
sputtering target
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PCT/JP2019/048929
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French (fr)
Japanese (ja)
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坂脇 彰
晴章 内田
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昭和電工株式会社
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    • CCHEMISTRY; METALLURGY
    • C04CEMENTS; CONCRETE; ARTIFICIAL STONE; CERAMICS; REFRACTORIES
    • C04BLIME, MAGNESIA; SLAG; CEMENTS; COMPOSITIONS THEREOF, e.g. MORTARS, CONCRETE OR LIKE BUILDING MATERIALS; ARTIFICIAL STONE; CERAMICS; REFRACTORIES; TREATMENT OF NATURAL STONE
    • C04B35/00Shaped ceramic products characterised by their composition; Ceramics compositions; Processing powders of inorganic compounds preparatory to the manufacturing of ceramic products
    • C04B35/01Shaped ceramic products characterised by their composition; Ceramics compositions; Processing powders of inorganic compounds preparatory to the manufacturing of ceramic products based on oxide ceramics
    • CCHEMISTRY; METALLURGY
    • C23COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
    • C23CCOATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
    • C23C14/00Coating by vacuum evaporation, by sputtering or by ion implantation of the coating forming material
    • C23C14/22Coating by vacuum evaporation, by sputtering or by ion implantation of the coating forming material characterised by the process of coating
    • C23C14/34Sputtering
    • HELECTRICITY
    • H01ELECTRIC ELEMENTS
    • H01MPROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00Electrodes
    • H01M4/02Electrodes composed of, or comprising, active material
    • H01M4/36Selection of substances as active materials, active masses, active liquids
    • H01M4/48Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides
    • H01M4/50Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides of manganese
    • H01M4/505Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides of manganese of mixed oxides or hydroxides containing manganese for inserting or intercalating light metals, e.g. LiMn2O4 or LiMn2OxFy
    • YGENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02EREDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E60/00Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
    • Y02E60/10Energy storage using batteries

Definitions

  • the present invention relates to a sputtering target.
  • a lithium ion secondary battery is known as a secondary battery satisfying such requirements.
  • a lithium ion secondary battery has a positive electrode containing a positive electrode active material, a negative electrode containing a negative electrode active material, and an electrolyte exhibiting lithium ion conductivity and arranged between the positive electrode and the negative electrode.
  • Patent Document 1 a positive electrode made of a lithium manganate film is formed on a positive electrode current collector layer made of a titanium thin film by a RF magnetron sputtering method (RF sputtering) using a sintered body target of LiMn 2 O 4. It is described that an active material layer is formed.
  • RF sputtering RF magnetron sputtering method
  • An object of the present invention is to provide a sputtering target capable of suppressing a decrease in film formation rate and improving discharge capacity when a positive electrode layer made of lithium manganate is formed by sputtering.
  • the present invention is a sputtering target used for forming a positive electrode layer in a lithium ion secondary battery, which contains lithium, manganese, and oxygen, and the molar ratio of these lithium, manganese, and oxygen does not satisfy the stoichiometric composition. It is composed of a sintered body set as described above. Such a sputtering target can be characterized by containing lithium in a molar ratio larger than that of manganese.
  • the sintered body may be characterized by having a composition of Li x Mn 2 O 4 (2 ⁇ x). Further, it can be characterized in that it contains lithium in a molar ratio smaller than that of manganese. Further, the sintered body may be characterized by having a composition of Li x Mn 2 O 4 (1 ⁇ x ⁇ 2).
  • a positive electrode layer made of lithium manganate is formed by sputtering, it is possible to provide a sputtering target capable of suppressing a decrease in film formation rate and improving discharge capacity.
  • FIG. 3 is a flowchart for explaining the method for manufacturing the lithium-ion secondary battery according to the embodiment. It is a figure which shows the structure of the sputtering target used in the positive electrode layer formation process.
  • FIG. 1 is a diagram showing a cross-sectional structure of a lithium ion secondary battery 1 of the present embodiment.
  • the lithium ion secondary battery 1 shown in FIG. 1 includes a substrate 10, a positive electrode layer 20 stacked on the substrate 10, a solid electrolyte layer 30 stacked on the positive electrode layer 20, and a solid electrolyte layer 30. And a negative electrode current collector layer 50 laminated on the negative electrode layer 40.
  • the substrate 10 serves as a base for laminating the positive electrode layer 20 to the negative electrode current collector layer 50 by a film forming process.
  • the material forming the substrate 10 is not particularly limited, and various materials such as metal, glass, ceramics, and resin can be adopted.
  • the substrate 10 is made of a metal plate material having electronic conductivity.
  • the substrate 10 functions as a positive electrode current collector layer that collects current to the positive electrode layer 20.
  • a stainless steel foil (plate) having higher mechanical strength than copper or aluminum is used as the substrate 10.
  • a metal foil plated with a conductive metal such as tin, copper or chromium may be used as the substrate 10.
  • the thickness of the substrate 10 can be, for example, 20 ⁇ m or more and 2000 ⁇ m or less. If the thickness of the substrate 10 is less than 20 ⁇ m, the strength of the lithium ion secondary battery 1 may be insufficient. On the other hand, when the thickness of the substrate 10 exceeds 2000 ⁇ m, the volume energy density and the weight energy density decrease due to the increase in the battery thickness and weight.
  • the positive electrode layer 20 is a solid thin film and contains a positive electrode active material that releases lithium ions during charging and occludes lithium ions during discharging.
  • the positive electrode layer 20 of the present embodiment has a positive electrode active material containing lithium (Li), manganese (Mn) and oxygen (O). More specifically, the positive electrode layer 20 of the present embodiment is composed of lithium manganate (Li a Mn b O c ). In the following description, various lithium manganates may be referred to as “Li—Mn—O”.
  • a known film forming method such as various PVD (physical vapor deposition) and various CVD (chemical vapor deposition) may be used, but from the viewpoint of production efficiency, the sputtering method is used. It is desirable to use (sputtering). Further, among various sputtering methods, it is preferable to use the DC sputtering method because it is easy to improve the film forming rate as compared with the RF sputtering method.
  • the positive electrode layer 20 is laminated directly on the substrate 10.
  • a positive electrode current collector layer (not shown) having electron conductivity is laminated on the substrate 10 and the positive electrode layer 20 is formed on the positive electrode current collector layer. Will be formed.
  • the thickness of the solid electrolyte layer 30 can be, for example, 10 nm or more and 10 ⁇ m or less.
  • the thickness of the solid electrolyte layer 30 is less than 10 nm, in the obtained lithium ion secondary battery 1, current leakage between the positive electrode layer 20 and the negative electrode layer 40 is likely to occur.
  • the thickness of the solid electrolyte layer 30 exceeds 10 ⁇ m, the internal resistance of the battery becomes high, which is disadvantageous for high-speed charging/discharging.
  • the solid electrolyte layer 30 may have a crystal structure or an amorphous structure having no crystal structure, but the expansion and contraction due to absorption and desorption of lithium ions is more isotropic.
  • the amorphous structure is preferable in that
  • a known film forming method such as various PVD or various CVD may be used, but from the viewpoint of production efficiency, the sputtering method is preferable.
  • the negative electrode layer 40 is a solid thin film and contains a negative electrode active material that occludes lithium ions during charging and releases lithium ions during discharging.
  • a negative electrode active material for example, carbon or silicon can be used. Further, various dopants may be added to the negative electrode layer 40.
  • the thickness of the negative electrode layer 40 can be, for example, 10 nm or more and 40 ⁇ m or less. If the thickness of the negative electrode layer 40 is less than 10 nm, the capacity of the obtained lithium ion secondary battery 1 becomes too small, which is not practical. On the other hand, when the thickness of the negative electrode layer 40 exceeds 40 ⁇ m, it takes too long to form the layer, and the productivity is reduced. However, when the battery capacity required for the lithium ion secondary battery 1 is large, the thickness of the negative electrode layer 40 may be more than 40 ⁇ m.
  • the negative electrode layer 40 may have a crystal structure or an amorphous structure having no crystal structure, but the expansion and contraction due to the absorption and desorption of lithium ions is more isotropic.
  • the amorphous structure is preferable in that
  • a known film forming method such as various PVD or various CVD may be used, but from the viewpoint of production efficiency, the sputtering method is preferable.
  • the thickness of the negative electrode current collector layer 50 can be, for example, 5 nm or more and 50 ⁇ m or less. If the thickness of the negative electrode current collector layer 50 is less than 5 nm, the corrosion resistance and the current collecting function are deteriorated, which is not practical. On the other hand, when the thickness of the negative electrode current collector layer 50 exceeds 50 ⁇ m, the internal resistance of the battery increases, which is disadvantageous for high-speed charging/discharging.
  • the negative electrode current collector layer 50 As a method of manufacturing the negative electrode current collector layer 50, a known film forming method such as various PVD or various CVD may be used, but from the viewpoint of production efficiency, the sputtering method is preferable.
  • the substrate 10 also serving as the positive electrode current collector layer has a load positive electrode, and the negative electrode current collector layer 50 has a negative electrode load. Connected. Then, the lithium ions contained in the negative electrode active material in the negative electrode layer 40 move to the positive electrode layer 20 through the solid electrolyte layer 30, and the positive electrode layer 20 constitutes the positive electrode active material. Along with this, DC current is supplied to the load.
  • a substrate 10 is prepared and a preparation step of mounting it on a sputtering device (not shown) is executed (step 10). More specifically, in the preparation step, the sputtering target used for forming the positive electrode layer 20 is attached to the sputtering apparatus, and the stacking surface of each layer of the substrate 10 described above faces the sputtering target. Next, a positive electrode layer forming step of forming the positive electrode layer 20 on the substrate 10 is executed by the above sputtering apparatus (step 20).
  • a negative electrode current collector layer forming step of forming the negative electrode current collector layer 50 on the negative electrode layer 40 is executed by the above sputtering apparatus (step 50). Then, the extraction process of extracting the lithium ion secondary battery 1 in which the positive electrode layer 20, the solid electrolyte layer 30, the negative electrode layer 40, and the negative electrode current collector layer 50 are laminated on the substrate 10 from the sputtering device is executed (step. 60).
  • FIG. 3 is a diagram showing the configuration of the sputtering target 100 used in the positive electrode layer forming step of step 20.
  • the sputtering target 100 shown in FIG. 3 is composed of a sintered body obtained by sintering powder as a raw material.
  • the sputtering target 100 has a rectangular and plate shape.
  • the sputtering target 100 has a plurality of particles 110 each containing a positive electrode active material.
  • the particle size of the particles 110 is, for example, 0.2 ⁇ m to 5.0 ⁇ m, and the center is 0.5 ⁇ m to 1.0 ⁇ m.
  • the sputtering target 100 of the present embodiment is made of a sintered body that contains lithium (Li), manganese (Mn), and oxygen (O), and the composition ratio of which does not satisfy the stoichiometric composition.
  • Li—Mn—O-based oxide for example, LiMn 2 O 4 and Li 2 Mn 2 O 4 are known, but the sputtering target 100 of the present embodiment has such a composition ratio. Does not have. However, it is considered that the Li—Mn—O-based oxide that constitutes the sputtering target 100 is crystallized, and that each particle 110 contains LiMn 2 O 4 or Li 2 Mn 2 O 4. ..
  • each particle 110 may include a lithium-free manganese oxide or a manganese-free lithium oxide.
  • the sputtering target 100 can be manufactured by mixing various lithium compounds and various manganese compounds and then firing the mixture.
  • the lithium compound can be exemplified by lithium carbonate (for example, Li 2 CO 3 )
  • the manganese compound can be exemplified by manganese oxide (for example, Mn 2 O 3 ).
  • the sputtering target 100 may include inevitable impurities contained in the raw material.
  • the sputtering target 100 has a rectangular shape in the present embodiment, the present invention is not limited to this and may have another shape (for example, a circular shape).
  • the positive electrode layer 20, the solid electrolyte layer 30, the negative electrode layer 40, and the negative electrode current collector layer 50 are stacked in this order on the substrate 10 by the sputtering method, whereby the lithium ion ion The next battery 1 was manufactured.
  • the present invention is not limited to this, and the negative electrode layer 40, the solid electrolyte layer 30, and the positive electrode layer 20 may be laminated in this order on the substrate 10 by a sputtering method.
  • the positive electrode layer 20 is formed on the solid electrolyte layer 30 by using the sputtering target 100.
  • a positive electrode current collector layer having electronic conductivity may be further laminated on the positive electrode layer 20.
  • the negative electrode layer 40 was formed by using the sputtering method (DC sputtering method).
  • silicon (Si) to which boron (B) was added was used as the negative electrode layer 40 (in the table, described as “Si(B)”).
  • the thickness of the negative electrode layer 40 was 200 nm.
  • Comparative Example 1 the sputtering target 100 used for forming the positive electrode layer 20 has a composition of LiMn 2 O 4 (in Table 2, referred to as “Li 1.0 Mn 2 O 4 ”), that is, a stoichiometric composition. The one satisfying the condition was used.
  • the sputtering target 100 used in the positive electrode layer forming step of Comparative Example 1 may be referred to as “1-2-4 target”.
  • This "1-2-4 target” was obtained by mixing Li 2 CO 3 and Mn 2 O 3 at a ratio of 0.6:1 (molar ratio) and then sintering the mixture.
  • the resistance value of this "1-2-4 target” was 5 M ⁇ .
  • Table 3 shows the relationship between the target composition of the sputtering target 100 used for forming the positive electrode layer 20 and the discharge capacity in the lithium ion secondary batteries 1 of Examples 1 and 2 and Comparative Examples 1 and 2. ..
  • Example 1 In Example 1 in which the “1.5-2-4 target” that does not satisfy the stoichiometric composition was used for forming the positive electrode layer 20, the discharge capacity value was 850 ( ⁇ Ah/cm 3 ). Further, in Example 2 in which “2.1-2-4 target” which does not satisfy the stoichiometric composition was used for forming the positive electrode layer 20, the value of the discharge capacity was about twice that of Example 1. Was 1700 ( ⁇ Ah/cm 3 ).
  • SYMBOLS 1 Lithium ion secondary battery, 10... Substrate, 20... Positive electrode layer, 30... Solid electrolyte layer, 40... Negative electrode layer, 50... Negative electrode collector layer, 100... Sputtering target, 110... Particles

Abstract

This sputtering target 100 used to deposit a positive electrode layer in a lithium ion secondary battery is composed of a sintered body of a plurality of particles 110. Said sputtering target 100 contains lithium (Li), manganese (Mn) and oxygen (O), and the molar ratio of lithium, manganese and oxygen is set to a non-stoichiometric relationship.

Description

スパッタリングターゲットSputtering target
 本発明は、スパッタリングターゲットに関する。 The present invention relates to a sputtering target.
 携帯電話やノート型パソコンなどの携帯電子機器の普及に伴い、高いエネルギー密度を有する、小型で軽量な二次電池の開発が強く望まれている。このような要求を満たす二次電池として、リチウムイオン二次電池が知られている。リチウムイオン二次電池は、正極活物質を含む正極と、負極活物質を含む負極と、リチウムイオン伝導性を示し且つ正極および負極の間に配置される電解質とを有している。 With the spread of mobile electronic devices such as mobile phones and laptop computers, there is a strong demand for the development of small, lightweight secondary batteries with high energy density. A lithium ion secondary battery is known as a secondary battery satisfying such requirements. A lithium ion secondary battery has a positive electrode containing a positive electrode active material, a negative electrode containing a negative electrode active material, and an electrolyte exhibiting lithium ion conductivity and arranged between the positive electrode and the negative electrode.
 また、リチウムイオン二次電池を薄膜の積層体で構成することが検討されており、薄膜の形成方法としてスパッタ法が注目されている。
 ここで、特許文献1には、チタン薄膜からなる正極集電体層上に、LiMn24の焼結体ターゲットを用い、RFマグネトロンスパッタリング法(RFスパッタ)によって、マンガン酸リチウム膜からなる正極活物質層を成膜することが記載されている。
Further, it is being studied to construct a lithium ion secondary battery with a laminated body of thin films, and a sputtering method is drawing attention as a method for forming the thin films.
Here, in Patent Document 1, a positive electrode made of a lithium manganate film is formed on a positive electrode current collector layer made of a titanium thin film by a RF magnetron sputtering method (RF sputtering) using a sintered body target of LiMn 2 O 4. It is described that an active material layer is formed.
特開2010-182643号公報JP, 2010-182643, A
 ここで、リチウム、マンガンおよび酸素を含むマンガン酸リチウムをスパッタリングターゲットとして用いる場合、スパッタリングターゲットの電気的な抵抗値が高くなりやすいため、RFスパッタによる成膜を行わざるを得ないことが多い。そして、RFスパッタによる成膜を行う場合、一般に、DCスパッタによる成膜を行う場合と比べて、成膜レートが低下しやすくなり、その分、生産効率が低下することになってしまう。
 本発明は、マンガン酸リチウムからなる正極層をスパッタで形成する場合に、成膜レートの低下を抑制するとともに放電容量を向上させることが可能なスパッタリングターゲットを提供することを目的とする。
Here, when lithium manganate containing lithium, manganese, and oxygen is used as a sputtering target, the electric resistance of the sputtering target is likely to be high, so that film formation by RF sputtering is unavoidable in many cases. In addition, in the case of forming a film by RF sputtering, generally, compared with the case of forming a film by DC sputtering, the film forming rate tends to decrease, and the production efficiency decreases correspondingly.
An object of the present invention is to provide a sputtering target capable of suppressing a decrease in film formation rate and improving discharge capacity when a positive electrode layer made of lithium manganate is formed by sputtering.
 本発明は、リチウムイオン二次電池における正極層の形成に用いられるスパッタリングターゲットであって、リチウム、マンガンおよび酸素を含むとともに、これらリチウム、マンガンおよび酸素のモル比が、化学量論組成を満たさないように設定された焼結体で構成されている。
 このようなスパッタリングターゲットにおいて、リチウムを、モル比で、マンガンよりも多く含んでいることを特徴とすることができる。
 また、前記焼結体が、LixMn24(2<x)なる組成を有していることを特徴とすることができる。
 また、リチウムを、モル比で、マンガンよりも少なく含んでいることを特徴とすることができる。
 また、前記焼結体が、LixMn24(1<x<2)なる組成を有していることを特徴とすることができる。
The present invention is a sputtering target used for forming a positive electrode layer in a lithium ion secondary battery, which contains lithium, manganese, and oxygen, and the molar ratio of these lithium, manganese, and oxygen does not satisfy the stoichiometric composition. It is composed of a sintered body set as described above.
Such a sputtering target can be characterized by containing lithium in a molar ratio larger than that of manganese.
The sintered body may be characterized by having a composition of Li x Mn 2 O 4 (2<x).
Further, it can be characterized in that it contains lithium in a molar ratio smaller than that of manganese.
Further, the sintered body may be characterized by having a composition of Li x Mn 2 O 4 (1<x<2).
 本発明によれば、マンガン酸リチウムからなる正極層をスパッタで形成する場合に、成膜レートの低下を抑制するとともに放電容量を向上させることが可能なスパッタリングターゲットを提供することができる。 According to the present invention, when a positive electrode layer made of lithium manganate is formed by sputtering, it is possible to provide a sputtering target capable of suppressing a decrease in film formation rate and improving discharge capacity.
実施の形態のリチウムイオン二次電池の断面構成を示す図である。It is a figure which shows the cross-sectional structure of the lithium ion secondary battery of embodiment. 実施の形態のリチウムイオン二次電池の製造方法を説明するためのフローチャートである。3 is a flowchart for explaining the method for manufacturing the lithium-ion secondary battery according to the embodiment. 正極層形成工程で用いたスパッタリングターゲットの構成を示す図である。It is a figure which shows the structure of the sputtering target used in the positive electrode layer formation process.
 以下、添付図面を参照して、本発明の実施の形態について詳細に説明する。なお、以下の説明で参照する図面における各部の大きさや厚さ等は、実際の寸法とは異なっている場合がある。 Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings. The size, thickness, etc. of each part in the drawings referred to in the following description may be different from the actual size.
[リチウムイオン二次電池の構成]
 図1は、本実施の形態のリチウムイオン二次電池1の断面構成を示す図である。
 図1に示すリチウムイオン二次電池1は、基板10と、基板10上に積層される正極層20と、正極層20上に積層される固体電解質層30と、固体電解質層30上に積層される負極層40と、負極層40上に積層される負極集電体層50とを備えている。
[Configuration of lithium-ion secondary battery]
FIG. 1 is a diagram showing a cross-sectional structure of a lithium ion secondary battery 1 of the present embodiment.
The lithium ion secondary battery 1 shown in FIG. 1 includes a substrate 10, a positive electrode layer 20 stacked on the substrate 10, a solid electrolyte layer 30 stacked on the positive electrode layer 20, and a solid electrolyte layer 30. And a negative electrode current collector layer 50 laminated on the negative electrode layer 40.
 次に、上記リチウムイオン二次電池1の各構成要素について、より詳細な説明を行う。
(基板)
 基板10は、正極層20~負極集電体層50を、成膜プロセスによって積層するための土台となるものである。
 基板10を構成する材料は、特に限定されるものではなく、金属、ガラス、セラミックス、樹脂など、各種材料を採用することができる。
Next, each component of the lithium ion secondary battery 1 will be described in more detail.
(substrate)
The substrate 10 serves as a base for laminating the positive electrode layer 20 to the negative electrode current collector layer 50 by a film forming process.
The material forming the substrate 10 is not particularly limited, and various materials such as metal, glass, ceramics, and resin can be adopted.
 ここで、本実施の形態では、基板10を、電子伝導性を有する金属製の板材で構成している。これにより、本実施の形態では、基板10を、正極層20への集電を行う正極集電体層として機能させるようになっている。より具体的に説明すると、本実施の形態では、基板10として、銅やアルミニウム等と比較して機械的強度が高いステンレス箔(板)を用いている。また、基板10として、錫、銅、クロム等の導電性金属でめっきした金属箔を用いてもよい。 Here, in the present embodiment, the substrate 10 is made of a metal plate material having electronic conductivity. As a result, in the present embodiment, the substrate 10 functions as a positive electrode current collector layer that collects current to the positive electrode layer 20. More specifically, in the present embodiment, as the substrate 10, a stainless steel foil (plate) having higher mechanical strength than copper or aluminum is used. Further, as the substrate 10, a metal foil plated with a conductive metal such as tin, copper or chromium may be used.
 基板10の厚さは、例えば20μm以上2000μm以下とすることができる。基板10の厚さが20μm未満であると、リチウムイオン二次電池1の強度が不足するおそれがある。一方、基板10の厚さが2000μmを超えると、電池の厚さおよび重量の増加により体積エネルギー密度および重量エネルギー密度が低下する。 The thickness of the substrate 10 can be, for example, 20 μm or more and 2000 μm or less. If the thickness of the substrate 10 is less than 20 μm, the strength of the lithium ion secondary battery 1 may be insufficient. On the other hand, when the thickness of the substrate 10 exceeds 2000 μm, the volume energy density and the weight energy density decrease due to the increase in the battery thickness and weight.
(正極層)
 正極層20は、固体薄膜であって、充電時にはリチウムイオンを放出するとともに放電時にはリチウムイオンを吸蔵する正極活物質を含むものである。
 ここで、本実施の形態の正極層20は、リチウム(Li)、マンガン(Mn)および酸素(O)を含む正極活物質を有している。より具体的に説明すると、本実施の形態の正極層20は、マンガン酸リチウム(LiaMnbc)で構成されている。なお、以下の説明においては、各種マンガン酸リチウムのことを、「Li-Mn-O」と表記することがある。
(Positive layer)
The positive electrode layer 20 is a solid thin film and contains a positive electrode active material that releases lithium ions during charging and occludes lithium ions during discharging.
Here, the positive electrode layer 20 of the present embodiment has a positive electrode active material containing lithium (Li), manganese (Mn) and oxygen (O). More specifically, the positive electrode layer 20 of the present embodiment is composed of lithium manganate (Li a Mn b O c ). In the following description, various lithium manganates may be referred to as “Li—Mn—O”.
 正極層20の厚さは、例えば100nm以上40μm以下とすることが望ましい。正極層20の厚さが100nm未満であると、得られるリチウムイオン二次電池1の容量が小さくなりすぎ、実用的ではなくなる。一方、正極層20の厚さが40μmを超えると、層形成に時間がかかりすぎるようになってしまい、生産性が低下する。ただし、リチウムイオン二次電池1に要求される電池容量が大きい場合には、正極層20の厚さを40μm超としてもかまわない。 The thickness of the positive electrode layer 20 is preferably 100 nm or more and 40 μm or less, for example. If the thickness of the positive electrode layer 20 is less than 100 nm, the capacity of the obtained lithium ion secondary battery 1 becomes too small, which is not practical. On the other hand, when the thickness of the positive electrode layer 20 exceeds 40 μm, it takes too long to form the layer, and the productivity is reduced. However, when the battery capacity required for the lithium-ion secondary battery 1 is large, the thickness of the positive electrode layer 20 may exceed 40 μm.
 また、正極層20は、結晶構造を持つものであっても、結晶構造を持たない非晶質構造であってもかまわないが、リチウムイオンの吸蔵および放出に伴う膨張および収縮がより等方的になるという点で、非晶質構造であることが好ましい。 Further, the positive electrode layer 20 may have a crystal structure or an amorphous structure having no crystal structure, but the expansion and contraction due to the absorption and desorption of lithium ions is more isotropic. The amorphous structure is preferable in that
 さらに、正極層20の製造方法としては、各種PVD(物理的蒸着)や各種CVD(化学的蒸着)など、公知の成膜手法を用いてかまわないが、生産効率の観点からすれば、スパッタ法(スパッタリング)を用いることが望ましい。また、各種スパッタ法の中でも、RFスパッタ法と比べて成膜レートを向上させやすい、DCスパッタ法を用いることが好ましい。 Further, as a method for manufacturing the positive electrode layer 20, a known film forming method such as various PVD (physical vapor deposition) and various CVD (chemical vapor deposition) may be used, but from the viewpoint of production efficiency, the sputtering method is used. It is desirable to use (sputtering). Further, among various sputtering methods, it is preferable to use the DC sputtering method because it is easy to improve the film forming rate as compared with the RF sputtering method.
 なお、本実施の形態では、上述したように、基板10が正極集電体層を兼ねる構成となっているため、基板10上に直接、正極層20を積層している。ただし、絶縁体で構成された基板10を用いる場合には、基板10上に電子伝導性を有する正極集電体層(図示せず)を積層するとともに、正極集電体層上に正極層20を形成することになる。 Note that, in the present embodiment, as described above, since the substrate 10 also serves as the positive electrode current collector layer, the positive electrode layer 20 is laminated directly on the substrate 10. However, when the substrate 10 made of an insulator is used, a positive electrode current collector layer (not shown) having electron conductivity is laminated on the substrate 10 and the positive electrode layer 20 is formed on the positive electrode current collector layer. Will be formed.
(固体電解質層)
 固体電解質層30は、固体薄膜であって、外部から加えられた電場によってリチウムイオンを移動させることのできる固体電解質(この例では無機固体電解質)を含むものである。
 ここで、固体電解質層30を構成する無機固体電解質については、リチウムイオン伝導性を示すものであれば、特に限定されるものではなく、酸化物、窒化物、硫化物など、各種材料で構成されたものを用いることができる。
(Solid electrolyte layer)
The solid electrolyte layer 30 is a solid thin film and contains a solid electrolyte (in this example, an inorganic solid electrolyte) capable of moving lithium ions by an electric field applied from the outside.
Here, the inorganic solid electrolyte that constitutes the solid electrolyte layer 30 is not particularly limited as long as it exhibits lithium ion conductivity, and is composed of various materials such as oxides, nitrides, and sulfides. It can be used.
 固体電解質層30の厚さは、例えば10nm以上10μm以下とすることができる。固体電解質層30の厚さが10nm未満であると、得られたリチウムイオン二次電池1において、正極層20と負極層40との間での電流の漏れ(リーク)が生じやすくなる。一方、固体電解質層30の厚さが10μmを超えると、電池の内部抵抗が高くなり、高速での充放電には不利である。 The thickness of the solid electrolyte layer 30 can be, for example, 10 nm or more and 10 μm or less. When the thickness of the solid electrolyte layer 30 is less than 10 nm, in the obtained lithium ion secondary battery 1, current leakage between the positive electrode layer 20 and the negative electrode layer 40 is likely to occur. On the other hand, if the thickness of the solid electrolyte layer 30 exceeds 10 μm, the internal resistance of the battery becomes high, which is disadvantageous for high-speed charging/discharging.
 また、固体電解質層30は、結晶構造を持つものであっても、結晶構造を持たない非晶質構造であってもかまわないが、リチウムイオンの吸蔵および放出に伴う膨張および収縮がより等方的になるという点で、非晶質構造であることが好ましい。 Further, the solid electrolyte layer 30 may have a crystal structure or an amorphous structure having no crystal structure, but the expansion and contraction due to absorption and desorption of lithium ions is more isotropic. The amorphous structure is preferable in that
 さらに、固体電解質層30の製造方法としては、各種PVDや各種CVDなど、公知の成膜手法を用いてかまわないが、生産効率の観点からすれば、スパッタ法を用いることが望ましい。 Further, as a method for manufacturing the solid electrolyte layer 30, a known film forming method such as various PVD or various CVD may be used, but from the viewpoint of production efficiency, the sputtering method is preferable.
(負極層)
 負極層40は、固体薄膜であって、充電時にはリチウムイオンを吸蔵するとともに放電時にはリチウムイオンを放出する負極活物質を含むものである。
 ここで、負極層40を構成する負極活物質としては、例えば、炭素やシリコンを用いることができる。また、負極層40には、各種ドーパントを添加してもよい。
(Negative electrode layer)
The negative electrode layer 40 is a solid thin film and contains a negative electrode active material that occludes lithium ions during charging and releases lithium ions during discharging.
Here, as the negative electrode active material forming the negative electrode layer 40, for example, carbon or silicon can be used. Further, various dopants may be added to the negative electrode layer 40.
 負極層40の厚さは、例えば10nm以上40μm以下とすることができる。負極層40の厚さが10nm未満であると、得られるリチウムイオン二次電池1の容量が小さくなりすぎ、実用的ではなくなる。一方、負極層40の厚さが40μmを超えると、層形成に時間がかかりすぎるようになってしまい、生産性が低下する。ただし、リチウムイオン二次電池1に要求される電池容量が大きい場合には、負極層40の厚さを40μm超としてもかまわない。 The thickness of the negative electrode layer 40 can be, for example, 10 nm or more and 40 μm or less. If the thickness of the negative electrode layer 40 is less than 10 nm, the capacity of the obtained lithium ion secondary battery 1 becomes too small, which is not practical. On the other hand, when the thickness of the negative electrode layer 40 exceeds 40 μm, it takes too long to form the layer, and the productivity is reduced. However, when the battery capacity required for the lithium ion secondary battery 1 is large, the thickness of the negative electrode layer 40 may be more than 40 μm.
 また、負極層40は、結晶構造を持つものであっても、結晶構造を持たない非晶質構造であってもかまわないが、リチウムイオンの吸蔵および放出に伴う膨張および収縮がより等方的になるという点で、非晶質構造であることが好ましい。 The negative electrode layer 40 may have a crystal structure or an amorphous structure having no crystal structure, but the expansion and contraction due to the absorption and desorption of lithium ions is more isotropic. The amorphous structure is preferable in that
 さらに、負極層40の製造方法としては、各種PVDや各種CVDなど、公知の成膜手法を用いてかまわないが、生産効率の観点からすれば、スパッタ法を用いることが望ましい。 Further, as a method for manufacturing the negative electrode layer 40, a known film forming method such as various PVD or various CVD may be used, but from the viewpoint of production efficiency, the sputtering method is preferable.
(負極集電体層)
 負極集電体層50は、電子伝導性を有する固体薄膜であって、負極層40への集電を行うものである。ここで、負極集電体層50を構成する材料は、電子伝導性を有するものであれば、特に限定されるものではなく、各種金属や、各種金属の合金を含む導電性材料を用いることができる。
(Negative electrode current collector layer)
The negative electrode current collector layer 50 is a solid thin film having electronic conductivity and collects current to the negative electrode layer 40. Here, the material forming the negative electrode current collector layer 50 is not particularly limited as long as it has electronic conductivity, and a conductive material including various metals or alloys of various metals can be used. it can.
 負極集電体層50の厚さは、例えば5nm以上50μm以下とすることができる。負極集電体層50の厚さが5nm未満であると、耐腐食性および集電機能が低下し、実用的ではなくなる。一方、負極集電体層50の厚さが50μmを超えると、電池の内部抵抗が高くなり、高速での充放電には不利である。 The thickness of the negative electrode current collector layer 50 can be, for example, 5 nm or more and 50 μm or less. If the thickness of the negative electrode current collector layer 50 is less than 5 nm, the corrosion resistance and the current collecting function are deteriorated, which is not practical. On the other hand, when the thickness of the negative electrode current collector layer 50 exceeds 50 μm, the internal resistance of the battery increases, which is disadvantageous for high-speed charging/discharging.
 また、負極集電体層50の製造方法としては、各種PVDや各種CVDなど、公知の成膜手法を用いてかまわないが、生産効率の観点からすれば、スパッタ法を用いることが望ましい。 As a method of manufacturing the negative electrode current collector layer 50, a known film forming method such as various PVD or various CVD may be used, but from the viewpoint of production efficiency, the sputtering method is preferable.
[リチウムイオン二次電池の動作]
 続いて、図1に示すリチウムイオン二次電池1の動作(充電動作および放電動作)について説明を行う。
[Operation of lithium-ion secondary battery]
Next, the operation (charging operation and discharging operation) of the lithium ion secondary battery 1 shown in FIG. 1 will be described.
(充電動作)
 放電状態にあるリチウムイオン二次電池1を充電する場合、正極集電体層を兼ねる基板10には直流電源の正極が、負極集電体層50には直流電源の負極が、それぞれ接続される。そして、正極層20で正極活物質を構成するリチウムイオンが、固体電解質層30を介して負極層40へと移動し、負極層40で負極活物質に収容される。
(Charging operation)
When charging the lithium-ion secondary battery 1 in a discharged state, the positive electrode of the DC power source is connected to the substrate 10 also serving as the positive electrode current collector layer, and the negative electrode of the DC power source is connected to the negative electrode current collector layer 50. .. Then, the lithium ions forming the positive electrode active material in the positive electrode layer 20 move to the negative electrode layer 40 through the solid electrolyte layer 30, and are stored in the negative electrode active material in the negative electrode layer 40.
(放電動作)
 また、充電状態にあるリチウムイオン二次電池1を使用(放電)する場合、正極集電体層を兼ねる基板10には負荷の正極が、負極集電体層50には負荷の負極が、それぞれ接続される。そして、負極層40で負極活物質に収容されるリチウムイオンが、固体電解質層30を介して正極層20へと移動し、正極層20で正極活物質を構成する。これに伴い、負荷には直流電流が供給される。
(Discharge operation)
When the lithium ion secondary battery 1 in a charged state is used (discharged), the substrate 10 also serving as the positive electrode current collector layer has a load positive electrode, and the negative electrode current collector layer 50 has a negative electrode load. Connected. Then, the lithium ions contained in the negative electrode active material in the negative electrode layer 40 move to the positive electrode layer 20 through the solid electrolyte layer 30, and the positive electrode layer 20 constitutes the positive electrode active material. Along with this, DC current is supplied to the load.
[リチウムイオン二次電池の製造方法]
 次に、図1に示すリチウムイオン二次電池1の製造方法について説明を行う。
 図2は、本実施の形態のリチウムイオン二次電池1の製造方法を説明するためのフローチャートである。
[Method for manufacturing lithium-ion secondary battery]
Next, a method for manufacturing the lithium ion secondary battery 1 shown in FIG. 1 will be described.
FIG. 2 is a flowchart for explaining the method of manufacturing the lithium ion secondary battery 1 of the present embodiment.
 まず、リチウムイオン二次電池1の製造に先立ち、基板10を準備するとともに図示しないスパッタ装置に装着する準備工程を実行する(ステップ10)。より具体的に説明すると、準備工程では、スパッタ装置に、正極層20の形成に用いられるスパッタリングターゲットを取り付けておくとともに、上述した基板10における各層の積層面を、このスパッタリングターゲットに対峙させる。
 次に、上記スパッタ装置にて、基板10上に、正極層20を形成する正極層形成工程を実行する(ステップ20)。ここで、本実施の形態の正極層形成工程では、化学量論組成を満たさないマンガン酸リチウムをスパッタリングターゲットとして用い、DCスパッタにて、正極層20の形成(成膜)を行う。
 続いて、上記スパッタ装置にて、正極層20上に、固体電解質層30を形成する固体電解質層形成工程を実行する(ステップ30)。
 次いで、上記スパッタ装置にて、固体電解質層30上に、負極層40を形成する負極層形成工程を実行する(ステップ40)。
 それから、上記スパッタ装置にて、負極層40上に、負極集電体層50を形成する負極集電体層形成工程を実行する(ステップ50)。
 そして、基板10上に、正極層20、固体電解質層30、負極層40および負極集電体層50を積層してなるリチウムイオン二次電池1を、スパッタ装置から取り出す取出工程を実行する(ステップ60)。
First, prior to manufacturing the lithium ion secondary battery 1, a substrate 10 is prepared and a preparation step of mounting it on a sputtering device (not shown) is executed (step 10). More specifically, in the preparation step, the sputtering target used for forming the positive electrode layer 20 is attached to the sputtering apparatus, and the stacking surface of each layer of the substrate 10 described above faces the sputtering target.
Next, a positive electrode layer forming step of forming the positive electrode layer 20 on the substrate 10 is executed by the above sputtering apparatus (step 20). Here, in the positive electrode layer forming step of the present embodiment, the positive electrode layer 20 is formed (formed) by DC sputtering using lithium manganate that does not satisfy the stoichiometric composition as a sputtering target.
Then, the solid electrolyte layer forming process of forming the solid electrolyte layer 30 on the positive electrode layer 20 is performed by the above-mentioned sputtering device (step 30).
Then, a negative electrode layer forming step of forming the negative electrode layer 40 on the solid electrolyte layer 30 is executed by the above-mentioned sputtering apparatus (step 40).
Then, a negative electrode current collector layer forming step of forming the negative electrode current collector layer 50 on the negative electrode layer 40 is executed by the above sputtering apparatus (step 50).
Then, the extraction process of extracting the lithium ion secondary battery 1 in which the positive electrode layer 20, the solid electrolyte layer 30, the negative electrode layer 40, and the negative electrode current collector layer 50 are laminated on the substrate 10 from the sputtering device is executed (step. 60).
 なお、このようにして得られたリチウムイオン二次電池1の具体的な構造や特性等については、後段の実施例で説明する。 The specific structure, characteristics, etc. of the lithium-ion secondary battery 1 obtained in this way will be described in the later-described examples.
[正極層形成工程で用いたスパッタリングターゲットの構成]
 図3は、ステップ20の正極層形成工程で用いたスパッタリングターゲット100の構成を示す図である。
 図3に示すスパッタリングターゲット100は、原料となる粉体を焼結してなる焼結体で構成されている。この例において、スパッタリングターゲット100は、長方形状且つ板状の形状を有している。このスパッタリングターゲット100は、それぞれが正極活物質を含む複数の粒子110を有している。ここで、粒子110の粒径は、例えば0.2μm~5.0μmであり、0.5μm~1.0μmが中心である。
[Structure of the sputtering target used in the positive electrode layer forming step]
FIG. 3 is a diagram showing the configuration of the sputtering target 100 used in the positive electrode layer forming step of step 20.
The sputtering target 100 shown in FIG. 3 is composed of a sintered body obtained by sintering powder as a raw material. In this example, the sputtering target 100 has a rectangular and plate shape. The sputtering target 100 has a plurality of particles 110 each containing a positive electrode active material. Here, the particle size of the particles 110 is, for example, 0.2 μm to 5.0 μm, and the center is 0.5 μm to 1.0 μm.
 また、本実施の形態のスパッタリングターゲット100は、リチウム(Li)、マンガン(Mn)および酸素(O)を含むとともに、その組成比が化学量論組成を満たさない焼結体で構成されている。ここで、Li-Mn-O系の酸化物としては、例えばLiMn24やLi2Mn24等が知られているが、本実施の形態のスパッタリングターゲット100は、このような組成比を有していない。ただし、スパッタリングターゲット100を構成するLi-Mn-O系の酸化物は結晶化しており、各々の粒子110にはLiMn24やLi2Mn24等が含まれているものと考えられる。また、各々の粒子110には、リチウムを含まないマンガン酸化物や、マンガンを含まないリチウム酸化物が含まれている場合も有り得る。 The sputtering target 100 of the present embodiment is made of a sintered body that contains lithium (Li), manganese (Mn), and oxygen (O), and the composition ratio of which does not satisfy the stoichiometric composition. Here, as the Li—Mn—O-based oxide, for example, LiMn 2 O 4 and Li 2 Mn 2 O 4 are known, but the sputtering target 100 of the present embodiment has such a composition ratio. Does not have. However, it is considered that the Li—Mn—O-based oxide that constitutes the sputtering target 100 is crystallized, and that each particle 110 contains LiMn 2 O 4 or Li 2 Mn 2 O 4. .. In addition, each particle 110 may include a lithium-free manganese oxide or a manganese-free lithium oxide.
 そして、このスパッタリングターゲット100は、各種リチウム化合物と各種マンガン化合物とを混合した後に焼成することで製造することができる。ここで、リチウム化合物としては炭酸リチウム(例えばLi2CO3)を例示することができ、また、マンガン化合物としては酸化マンガン(例えばMn23)を例示することができる。さらに、スパッタリングターゲット100は、原料に含まれる不可避不純物を含んでいてもよい。 The sputtering target 100 can be manufactured by mixing various lithium compounds and various manganese compounds and then firing the mixture. Here, the lithium compound can be exemplified by lithium carbonate (for example, Li 2 CO 3 ), and the manganese compound can be exemplified by manganese oxide (for example, Mn 2 O 3 ). Further, the sputtering target 100 may include inevitable impurities contained in the raw material.
[その他]
 なお、本実施の形態では、スパッタリングターゲット100を長方形状としていたが、これに限られるものではなく、他の形状(例えば円形状)としてもかまわない。
[Other]
Although the sputtering target 100 has a rectangular shape in the present embodiment, the present invention is not limited to this and may have another shape (for example, a circular shape).
 また、本実施の形態では、基板10上に、スパッタ法を用いて、正極層20、固体電解質層30、負極層40および負極集電体層50を、この順に積層することで、リチウムイオン二次電池1を製造していた。ただし、これに限られるものではなく、基板10上に、スパッタ法を用いて、負極層40、固体電解質層30および正極層20を、この順に積層するようにしてもよい。この場合には、固体電解質層30上に、スパッタリングターゲット100を用いて、正極層20が形成されることになる。なお、この場合は、正極層20の上に、電子伝導性を有する正極集電体層をさらに積層するとよい。 In addition, in the present embodiment, the positive electrode layer 20, the solid electrolyte layer 30, the negative electrode layer 40, and the negative electrode current collector layer 50 are stacked in this order on the substrate 10 by the sputtering method, whereby the lithium ion ion The next battery 1 was manufactured. However, the present invention is not limited to this, and the negative electrode layer 40, the solid electrolyte layer 30, and the positive electrode layer 20 may be laminated in this order on the substrate 10 by a sputtering method. In this case, the positive electrode layer 20 is formed on the solid electrolyte layer 30 by using the sputtering target 100. In this case, a positive electrode current collector layer having electronic conductivity may be further laminated on the positive electrode layer 20.
 以下、実施例に基づいて本発明をさらに詳細に説明する。ただし、本発明は、その要旨を超えない限り、以下の実施例に限定されるものではない。 Hereinafter, the present invention will be described in more detail based on examples. However, the present invention is not limited to the following examples unless it exceeds the gist.
 本発明者は、正極層20の形成に用いるスパッタリングターゲット100の構成を異ならせて、複数のリチウムイオン二次電池1を製造し、得られた各リチウムイオン二次電池1に関する評価を行った。 The present inventor manufactured a plurality of lithium ion secondary batteries 1 with different configurations of the sputtering target 100 used for forming the positive electrode layer 20, and evaluated the obtained lithium ion secondary batteries 1.
[リチウムイオン二次電池の構成]
 表1は、実施例1、2および比較例1、2のリチウムイオン二次電池1における各層の構成を示している。
[Configuration of lithium-ion secondary battery]
Table 1 shows the configuration of each layer in the lithium ion secondary batteries 1 of Examples 1 and 2 and Comparative Examples 1 and 2.
Figure JPOXMLDOC01-appb-T000001
Figure JPOXMLDOC01-appb-T000001
 各実施例および各比較例では、基板10として、ステンレスの一種であるSUS316Lを用いた。そして、基板10の厚さは1mmとした。 In each example and each comparative example, SUS316L, which is a kind of stainless steel, was used as the substrate 10. The substrate 10 has a thickness of 1 mm.
 各実施例および各比較例では、スパッタ法(DCスパッタ法またはRFスパッタ法)を用いて、正極層20の形成を行った。ここで、各実施例および各比較例では、正極層20として、Li-Mn-O系の酸化物(マンガン酸リチウム)を用いた。ただし、各実施例および各比較例では、正極層20の形成に使用するスパッタリングターゲット100やスパッタ条件等が異なるため、得られた正極層20におけるリチウム、マンガンおよび酸素の組成比は、異なるものとなった。そして、正極層20の厚さは600nmとした。 In each example and each comparative example, the positive electrode layer 20 was formed by using the sputtering method (DC sputtering method or RF sputtering method). Here, in each of the examples and the comparative examples, a Li—Mn—O-based oxide (lithium manganate) was used as the positive electrode layer 20. However, since the sputtering target 100 used for forming the positive electrode layer 20, the sputtering conditions, and the like are different in each example and each comparative example, the composition ratio of lithium, manganese, and oxygen in the obtained positive electrode layer 20 is different. became. The thickness of the positive electrode layer 20 was 600 nm.
 各実施例および各比較例では、スパッタ法(DCスパッタ法)を用いて、固体電解質層30の形成を行った。ここで、各実施例および比較例では、固体電解質層30として、リン酸リチウム(Li3PO4)における酸素の一部を窒素に置き換えたLiPON(LiaPObc)を用いた。そして、固体電解質層30の厚さは600nmとした。 In each example and each comparative example, the solid electrolyte layer 30 was formed by using the sputtering method (DC sputtering method). Here, in each of the examples and comparative examples, LiPON (Li a PO b N c ) in which a part of oxygen in lithium phosphate (Li 3 PO 4 ) was replaced with nitrogen was used as the solid electrolyte layer 30. The thickness of the solid electrolyte layer 30 was 600 nm.
 各実施例および各比較例では、スパッタ法(DCスパッタ法)を用いて、負極層40の形成を行った。ここで、各実施例および各比較例では、負極層40として、ホウ素(B)が添加されたシリコン(Si)を用いた(表には、「Si(B)」と記載)。そして、負極層40の厚さは200nmとした。 In each example and each comparative example, the negative electrode layer 40 was formed by using the sputtering method (DC sputtering method). Here, in each example and each comparative example, silicon (Si) to which boron (B) was added was used as the negative electrode layer 40 (in the table, described as “Si(B)”). The thickness of the negative electrode layer 40 was 200 nm.
 各実施例および各比較例では、スパッタ法(DCスパッタ法)を用いて、負極集電体層50の形成を行った。ここで、各実施例および各比較例では、負極集電体層50として、チタン(Ti)を用いた。そして、負極集電体層50の厚さは300nmとした。 In each example and each comparative example, the negative electrode current collector layer 50 was formed by using the sputtering method (DC sputtering method). Here, in each example and each comparative example, titanium (Ti) was used as the negative electrode current collector layer 50. The thickness of the negative electrode current collector layer 50 was 300 nm.
[正極層の成膜条件]
 表2は、実施例1、2および比較例1、2のリチウムイオン二次電池1における、正極層20の成膜条件を示している。より具体的に説明すると、表2は、各実施例および各比較例のそれぞれの正極層形成工程(ステップ20)で用いた、スパッタリングターゲット100の組成および抵抗値と、スパッタ電力の供給形態(DCあるいはRF)と、正極層20の成膜レート(nm/sec)との関係を示している。ここで、スパッタリングターゲット100の抵抗値は、JOHN FLUKE MFG. CO. INC.社製のFLUKE 77を用いて測定した。なお、FLUKE 77で測定できる抵抗値の上限は50MΩである。
[Deposition conditions for positive electrode layer]
Table 2 shows the film forming conditions of the positive electrode layer 20 in the lithium ion secondary batteries 1 of Examples 1 and 2 and Comparative Examples 1 and 2. More specifically, Table 2 shows the composition and resistance value of the sputtering target 100 used in each positive electrode layer forming step (step 20) of each example and each comparative example, and the supply mode of the sputtering power (DC). Alternatively, the relationship between RF) and the film formation rate (nm/sec) of the positive electrode layer 20 is shown. Here, the resistance value of the sputtering target 100 was measured using FLUKE 77 manufactured by JOHN FLUKE MFG. CO. INC. The upper limit of resistance that can be measured with FLUKE 77 is 50 MΩ.
Figure JPOXMLDOC01-appb-T000002
Figure JPOXMLDOC01-appb-T000002
(実施例1)
 実施例1では、正極層20の成膜に用いるスパッタリングターゲット100として、Li1.5Mn24なる組成を有するもの、すなわち、化学量論組成を満たさないものを用いた。以下では、実施例1の正極層形成工程で用いたスパッタリングターゲット100を、「1.5-2-4ターゲット」と称することがある。この「1.5-2-4ターゲット」は、Li2CO3とMn23とを、0.9:1(モル比)で混合した後に焼結することで得た。この「1.5-2-4ターゲット」の抵抗値は、0.5MΩであった。
(Example 1)
In Example 1, the sputtering target 100 used for forming the positive electrode layer 20 has a composition of Li 1.5 Mn 2 O 4 , that is, a sputtering target 100 that does not satisfy the stoichiometric composition. Hereinafter, the sputtering target 100 used in the positive electrode layer forming step of Example 1 may be referred to as a “1.5-2-4 target”. This “1.5-2-4 target” was obtained by mixing Li 2 CO 3 and Mn 2 O 3 at 0.9:1 (molar ratio) and then sintering. The resistance value of this “1.5-2-4 target” was 0.5 MΩ.
 また、実施例1では、「1.5-2-4ターゲット」の抵抗値が0.5MΩと比較的低いことから、DCスパッタによる正極層20の成膜を行うことが可能であった。そして、実施例1における正極層20の成膜レート(DCスパッタ)は0.41(nm/sec)であった。 In addition, in Example 1, since the resistance value of the “1.5-2-4 target” was relatively low at 0.5 MΩ, it was possible to form the positive electrode layer 20 by DC sputtering. The film forming rate (DC sputtering) of the positive electrode layer 20 in Example 1 was 0.41 (nm/sec).
(実施例2)
 実施例2では、正極層20の成膜に用いるスパッタリングターゲット100として、Li2.1Mn24なる組成を有するもの、すなわち、化学量論組成を満たさないものを用いた。以下では、実施例2の正極層形成工程で用いたスパッタリングターゲット100を、「2.1-2-4ターゲット」と称することがある。この「2.1-2-4ターゲット」は、Li2CO3とMn23とを、1.3:1(モル比)で混合した後に焼結することで得た。この「2.1-2-4ターゲット」の抵抗値は、20MΩであった。
(Example 2)
In Example 2, as the sputtering target 100 used for forming the positive electrode layer 20, a sputtering target having a composition of Li 2.1 Mn 2 O 4 , that is, a sputtering target not satisfying the stoichiometric composition was used. Hereinafter, the sputtering target 100 used in the positive electrode layer forming step of Example 2 may be referred to as a “2.1-2-4 target”. This "2.1-2-4 target" was obtained by mixing Li 2 CO 3 and Mn 2 O 3 at 1.3:1 (molar ratio) and then sintering. The resistance value of this “2.1-2-4 target” was 20 MΩ.
 また、実施例2では、「2.1-2-4ターゲット」の抵抗値が20MΩと比較的低いことから、DCスパッタによる正極層20の成膜を行うことが可能であった。そして、実施例2における正極層20の成膜レート(DCスパッタ)は0.74(nm/sec)であり、実施例1よりも高かった。 In addition, in Example 2, since the resistance value of the “2.1-2-4 target” was relatively low at 20 MΩ, it was possible to form the positive electrode layer 20 by DC sputtering. The film forming rate (DC sputtering) of the positive electrode layer 20 in Example 2 was 0.74 (nm/sec), which was higher than that in Example 1.
(比較例1)
 比較例1では、正極層20の成膜に用いるスパッタリングターゲット100として、LiMn24なる組成(表2には「Li1.0Mn24」と表記)を有するもの、すなわち、化学量論組成を満たすものを用いた。以下では、比較例1の正極層形成工程で用いたスパッタリングターゲット100を、「1-2-4ターゲット」と称することがある。この「1-2-4ターゲット」は、Li2CO3とMn23とを、0.6:1(モル比)で混合した後に焼結することで得た。この「1-2-4ターゲット」の抵抗値は、5MΩであった。
(Comparative Example 1)
In Comparative Example 1, the sputtering target 100 used for forming the positive electrode layer 20 has a composition of LiMn 2 O 4 (in Table 2, referred to as “Li 1.0 Mn 2 O 4 ”), that is, a stoichiometric composition. The one satisfying the condition was used. Hereinafter, the sputtering target 100 used in the positive electrode layer forming step of Comparative Example 1 may be referred to as “1-2-4 target”. This "1-2-4 target" was obtained by mixing Li 2 CO 3 and Mn 2 O 3 at a ratio of 0.6:1 (molar ratio) and then sintering the mixture. The resistance value of this "1-2-4 target" was 5 MΩ.
 また、比較例1では、「1-2-4ターゲット」の抵抗値が5MΩと比較的低いことから、DCスパッタによる正極層20の成膜を行うことが可能であった。そして、比較例1における正極層20の成膜レート(DCスパッタ)は1.01(nm/sec)であり、実施例1、2よりも高かった。 Further, in Comparative Example 1, since the resistance value of “1-2-4 target” was relatively low at 5 MΩ, it was possible to form the positive electrode layer 20 by DC sputtering. The film forming rate (DC sputtering) of the positive electrode layer 20 in Comparative Example 1 was 1.01 (nm/sec), which was higher than those in Examples 1 and 2.
(比較例2)
 比較例2では、正極層20の成膜に用いるスパッタリングターゲット100として、Li2Mn24なる組成(表2には「Li2.0Mn24」と表記)を有するもの、すなわち、化学量論組成を満たすものを用いた。以下では、比較例2の正極層形成工程で用いたスパッタリングターゲット100を、「2-2-4ターゲット」と称することがある。この「2-2-4ターゲット」は、Li2CO3とMn23とを、1.2:1(モル比)で混合した後に焼結することで得た。この「2-2-4ターゲット」の抵抗値は50MΩ以上であり、実施例1、2および比較例1よりも高かった。
(Comparative example 2)
In Comparative Example 2, as the sputtering target 100 used for forming the positive electrode layer 20, a sputtering target 100 having a composition of Li 2 Mn 2 O 4 (referred to as “Li 2.0 Mn 2 O 4 ”in Table 2), that is, a stoichiometric amount The one satisfying the theoretical composition was used. Hereinafter, the sputtering target 100 used in the positive electrode layer forming step of Comparative Example 2 may be referred to as “2-2-4 target”. This “2-2-4 target” was obtained by mixing Li 2 CO 3 and Mn 2 O 3 at a ratio of 1.2:1 (molar ratio) and then sintering the mixture. The resistance value of this “2-2-4 target” was 50 MΩ or more, which was higher than those of Examples 1 and 2 and Comparative Example 1.
 また、比較例2では、「2-2-4ターゲット」の抵抗値が50MΩ以上と比較的高いことから、DCスパッタによる正極層20の成膜を行うことが不可能であった。このため、比較例2では、実施例1、2および比較例1とは異なり、RFスパッタによる正極層20の成膜を行わざるを得なかった。そして、比較例2における正極層20の成膜レート(RFスパッタ)は0.07(nm/sec)であり、実施例1、2および比較例1よりも著しく低かった。 Further, in Comparative Example 2, the resistance value of the “2-2-4 target” was relatively high at 50 MΩ or more, and therefore it was impossible to form the positive electrode layer 20 by DC sputtering. Therefore, in Comparative Example 2, unlike Examples 1 and 2 and Comparative Example 1, the positive electrode layer 20 had to be formed by RF sputtering. The film forming rate (RF sputtering) of the positive electrode layer 20 in Comparative Example 2 was 0.07 (nm/sec), which was significantly lower than that in Examples 1 and 2 and Comparative Example 1.
[リチウムイオン二次電池の評価]
 ここでは、実施例1、2および比較例1、2のリチウムイオン二次電池1を評価するための尺度として、リチウムイオン二次電池1の結晶構造と、リチウムイオン二次電池1の放電容量とを用いた。ここで、リチウムイオン二次電池1の結晶構造の解析には、X線回折(XRD)を用いた。また、リチウムイオン二次電池1の放電容量の測定には、北斗電工株式会社製 充放電装置HJ1020mSD8を用いた。放電容量の測定においては、電流密度を4μA/cm2に設定した。そして、得られた測定結果より、各リチウムイオン二次電池1における正極層20の単位体積あたりの放電容量(μAh/cm3)を求めた。
[Evaluation of lithium-ion secondary battery]
Here, as a scale for evaluating the lithium ion secondary batteries 1 of Examples 1 and 2 and Comparative Examples 1 and 2, the crystal structure of the lithium ion secondary battery 1 and the discharge capacity of the lithium ion secondary battery 1 were used. Was used. Here, X-ray diffraction (XRD) was used to analyze the crystal structure of the lithium-ion secondary battery 1. Further, a charge/discharge device HJ1020mSD8 manufactured by Hokuto Denko Co., Ltd. was used to measure the discharge capacity of the lithium ion secondary battery 1. In measuring the discharge capacity, the current density was set to 4 μA/cm 2 . Then, the discharge capacity (μAh/cm 3 ) per unit volume of the positive electrode layer 20 in each lithium ion secondary battery 1 was obtained from the obtained measurement results.
(結晶構造)
 各実施例および各比較例のリチウムイオン二次電池1において、基板10および負極集電体層50は結晶化していたが、正極層20、固体電解質層30および負極層40は非晶質化していた。
(Crystal structure)
In the lithium-ion secondary batteries 1 of Examples and Comparative Examples, the substrate 10 and the negative electrode current collector layer 50 were crystallized, but the positive electrode layer 20, the solid electrolyte layer 30, and the negative electrode layer 40 were amorphized. It was
(放電容量)
 表3は、実施例1、2および比較例1、2のリチウムイオン二次電池1における、正極層20の成膜に用いたスパッタリングターゲット100のターゲット組成と、放電容量との関係を示している。
(Discharge capacity)
Table 3 shows the relationship between the target composition of the sputtering target 100 used for forming the positive electrode layer 20 and the discharge capacity in the lithium ion secondary batteries 1 of Examples 1 and 2 and Comparative Examples 1 and 2. ..
Figure JPOXMLDOC01-appb-T000003
Figure JPOXMLDOC01-appb-T000003
 正極層20の成膜に、化学量論組成を満たさない「1.5-2-4ターゲット」を用いた実施例1では、放電容量の値が850(μAh/cm3)であった。また、正極層20の成膜に、同じく化学量論組成を満たさない「2.1-2-4ターゲット」を用いた実施例2では、放電容量の値が、実施例1の約2倍となる1700(μAh/cm3)であった。 In Example 1 in which the “1.5-2-4 target” that does not satisfy the stoichiometric composition was used for forming the positive electrode layer 20, the discharge capacity value was 850 (μAh/cm 3 ). Further, in Example 2 in which “2.1-2-4 target” which does not satisfy the stoichiometric composition was used for forming the positive electrode layer 20, the value of the discharge capacity was about twice that of Example 1. Was 1700 (μAh/cm 3 ).
 これに対し、正極層20の成膜に、化学量論組成を満たす「1-2-4ターゲット」を用いた比較例1では、放電容量の値が、実施例1の3分の1以下(実施例2の6分の1以下)となる252(μAh/cm3)であった。また、正極層20の成膜に、化学量論組成を満たす「2-2-4ターゲット」を用いた比較例2では、放電容量の値が、実施例1と同等となる850(μAh/cm3)であった。 On the other hand, in Comparative Example 1 in which “1-2-4 target” satisfying the stoichiometric composition was used for forming the positive electrode layer 20, the value of the discharge capacity was 1/3 or less of that in Example 1 ( It was 252 (μAh/cm 3 ) which was 1/6 or less of Example 2. Further, in Comparative Example 2 in which “2-2-4 target” satisfying the stoichiometric composition was used for forming the positive electrode layer 20, the value of the discharge capacity was 850 (μAh/cm 2) which is the same as that of Example 1. 3 ) was.
 以上の結果から、比較例1は、成膜レートに関しては、実施例1に近いレベルを確保できているものの、放電容量に関しては、実施例1、2に対し著しく低下してしまうことがわかる。また、比較例2は、放電容量に関しては、実施例1と同等のレベルを確保できているものの、成膜レートに関しては、実施例1、2に対し著しく低下してしまうことがわかる。これは、比較例2では、「2-2-4ターゲット」の抵抗値が高いために、DCスパッタではなくRFスパッタを採用せざるを得ないことに起因するものと考えられる。したがって、実施例1、2は、比較例1、2と比べて、成膜レートが高く、且つ、放電容量も大きいことが理解される。さらに、実施例2は、成膜レートに関しては、実施例1よりも高いレベルを確保でき、放電容量に関しても、実施例1よりも高いレベルを確保できていることがわかる。 From the above results, it is understood that in Comparative Example 1, the film formation rate can be secured at a level close to that of Example 1, but the discharge capacity is significantly reduced as compared with Examples 1 and 2. Further, in Comparative Example 2, although it is possible to secure the same level of discharge capacity as that of Example 1, the film formation rate is significantly lower than that of Examples 1 and 2. It is considered that this is because in Comparative Example 2, since the resistance value of the “2-2-4 target” is high, the RF sputtering has to be adopted instead of the DC sputtering. Therefore, it is understood that Examples 1 and 2 have a higher film forming rate and a larger discharge capacity than Comparative Examples 1 and 2. Further, it can be seen that the film forming rate of the second embodiment can be kept higher than that of the first embodiment, and the discharge capacity can be kept higher than that of the first embodiment.
 なお、本発明者が、実施例1のリチウムイオン二次電池1における正極層20に対し、ICP-AES(Inductively coupled plasma atomic emission spectroscopy:誘導結合プラズマ発光分析)を用いて、リチウム(Li)およびマンガン(Mn)を測定し、これらのモル比を算出したところ、Li:Mn比は2.1:2.0(1回目)、および、1.9:2.0(2回目)であった。すなわち、実施例1のリチウムイオン二次電池1における正極層20では、マンガンに対するリチウムのモル比が、スパッタリングターゲット100よりも増加していた。 In addition, the present inventor uses ICP-AES (Inductively coupled plasma atomic emission spectrum) for the positive electrode layer 20 in the lithium ion secondary battery 1 of Example 1 to obtain lithium (Li) and When manganese (Mn) was measured and the molar ratio thereof was calculated, the Li:Mn ratio was 2.1:2.0 (first time) and 1.9:2.0 (second time). .. That is, in the positive electrode layer 20 of the lithium ion secondary battery 1 of Example 1, the molar ratio of lithium to manganese was higher than that of the sputtering target 100.
1…リチウムイオン二次電池、10…基板、20…正極層、30…固体電解質層、40…負極層、50…負極集電体層、100…スパッタリングターゲット、110…粒子 DESCRIPTION OF SYMBOLS 1... Lithium ion secondary battery, 10... Substrate, 20... Positive electrode layer, 30... Solid electrolyte layer, 40... Negative electrode layer, 50... Negative electrode collector layer, 100... Sputtering target, 110... Particles

Claims (5)

  1.  リチウムイオン二次電池における正極層の形成に用いられるスパッタリングターゲットであって、
     リチウム、マンガンおよび酸素を含むとともに、これらリチウム、マンガンおよび酸素のモル比が、化学量論組成を満たさないように設定された焼結体で構成されているスパッタリングターゲット。
    A sputtering target used for forming a positive electrode layer in a lithium ion secondary battery,
    A sputtering target including a sintered body containing lithium, manganese, and oxygen, and the molar ratio of the lithium, manganese, and oxygen being set so as not to satisfy the stoichiometric composition.
  2.  リチウムを、モル比で、マンガンよりも多く含んでいることを特徴とする請求項1記載のスパッタリングターゲット。 The sputtering target according to claim 1, wherein the sputtering target contains more lithium than manganese in a molar ratio.
  3.  前記焼結体が、LixMn24(2<x)なる組成を有していることを特徴とする請求項2記載のスパッタリングターゲット。 The sputtering target according to claim 2, wherein the sintered body has a composition of Li x Mn 2 O 4 (2<x).
  4.  リチウムを、モル比で、マンガンよりも少なく含んでいることを特徴とする請求項1記載のスパッタリングターゲット。 The sputtering target according to claim 1, wherein the sputtering target contains less lithium than manganese in a molar ratio.
  5.  前記焼結体が、LixMn24(1<x<2)なる組成を有していることを特徴とする請求項4記載のスパッタリングターゲット。 The sputtering target according to claim 4, wherein the sintered body has a composition of Li x Mn 2 O 4 (1<x<2).
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* Cited by examiner, † Cited by third party
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WO2012176604A1 (en) * 2011-06-20 2012-12-27 ナミックス株式会社 Lithium ion secondary battery
JP2018116892A (en) * 2017-01-20 2018-07-26 昭和電工株式会社 Lithium ion secondary battery and positive electrode active material
JP2018181636A (en) * 2017-04-14 2018-11-15 昭和電工株式会社 Lithium ion secondary battery and method for manufacturing lithium ion secondary battery

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* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2012176604A1 (en) * 2011-06-20 2012-12-27 ナミックス株式会社 Lithium ion secondary battery
JP2018116892A (en) * 2017-01-20 2018-07-26 昭和電工株式会社 Lithium ion secondary battery and positive electrode active material
JP2018181636A (en) * 2017-04-14 2018-11-15 昭和電工株式会社 Lithium ion secondary battery and method for manufacturing lithium ion secondary battery

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