Secondary battery

Abstract

To provide a secondary battery excellent in cycle characteristics.SOLUTION: An all-solid-state battery including a positive electrode current collector layer, a base film, a positive electrode active material layer, a buffer layer, and a solid electrolyte layer, wherein the base film includes titanium nitride, the positive electrode active material layer includes lithium cobalt oxide, the buffer layer includes titanium oxide, and the solid electrolyte layer includes a titanium compound. In addition, by applying titanium oxide to the buffer layer, a side reaction between the positive electrode active material layer and the solid electrolyte layer can be suppressed, and the cycle characteristics can be improved.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] One embodiment of the present invention relates to an object, a method, or a manufacturing method. Alternatively, the present invention relates to a process, a machine, a manufacture, or a composition of matter. One embodiment of the present invention relates to a semiconductor device, a display device, a light-emitting device, a power storage device, a lighting device, or an electronic device, or a manufacturing method thereof. In particular, the present invention relates to a secondary battery using a sputtering method.

[0002] In this specification, the term "electronic device" refers to any device having a power storage device, and includes electro-optical devices having a power storage device, information terminal devices having a power storage device, and the like.

[0003] In this specification, the term "power storage device" refers to elements and devices in general that have a power storage function, including, for example, power storage devices such as lithium ion secondary batteries (also called secondary batteries), lithium ion capacitors, and electric double layer capacitors. [Background technology]

[0004] In recent years, there has been active development of various types of power storage devices, such as lithium-ion secondary batteries, lithium-ion capacitors, and air batteries. Demand for high-power, high-energy-density lithium-ion secondary batteries, in particular, has rapidly expanded alongside the development of the semiconductor industry, and they are now essential to the modern information society as a rechargeable energy source, thanks to their high output and high energy density, and are used in a variety of applications, including mobile phones, smartphones, and laptop computers, as well as portable music players, digital cameras, medical devices, and next-generation clean-energy vehicles, such as hybrid vehicles (EVs), electric vehicles (EVs), and plug-in hybrid vehicles (PHVs).

[0005] In addition, electric vehicles (EVs) are vehicles that are driven solely by electric motors, but there are also hybrid vehicles that have both an internal combustion engine and an electric motor. Multiple secondary batteries used in automobiles are grouped into a single battery pack, and multiple sets of battery packs are placed under the automobile.

[0006] As described above, lithium ion secondary batteries are used in a variety of fields and applications, and among these, the characteristics required of lithium ion secondary batteries include high energy density, high cycle characteristics, and safety in various operating environments.

[0007] Lithium-ion secondary batteries, which use liquids such as organic solvents as a medium for transporting lithium ions (carrier ions), are becoming increasingly common. Many commonly used lithium-ion secondary batteries use a nonaqueous electrolyte (also referred to as a nonaqueous electrolyte or simply an electrolyte) containing an organic solvent, such as ethylene carbonate, propylene carbonate, fluorinated cyclic esters, fluorinated chain esters, fluorinated cyclic ethers, or fluorinated chain ethers, and a lithium salt containing lithium ions. However, secondary batteries using liquids face challenges, such as electrolyte decomposition reactions over a wide operating temperature range and operating potential, as well as leakage problems. For example, organic solvents have volatility and low flash points. Therefore, their use in lithium-ion secondary batteries can lead to internal short circuits, overcharging, or other internal temperature rises, potentially resulting in the battery exploding or catching fire. Furthermore, some organic solvents generate hydrofluoric acid through hydrolysis, which corrodes metals, raising concerns about battery reliability.

[0008] Furthermore, a power storage device called an all-solid-state battery that uses a solid electrolyte is known as a secondary battery that does not use a liquid. Among all-solid-state batteries, a solid battery formed by film formation using a sputtering method is called a thin-film secondary battery. Patent Document 1 describes an example in which a lithium cobalt oxide film is formed on a positive electrode current collector by a sputtering method. [Prior art documents] [Patent documents]

[0009] [Patent Document 1] U.S. Patent No. 8,404,001 Summary of the Invention [Problem to be solved by the invention]

[0010] Secondary batteries have room for improvement in various aspects, such as charge / discharge characteristics, cycle characteristics, reliability, safety, and cost. For example, with regard to cycle characteristics, repeated charge / discharge cycles can cause the crystal structure of the positive electrode active material to collapse, potentially leading to a decrease in charge / discharge capacity. Furthermore, side reactions can occur at the interface between the positive electrode active material and the electrolyte, or the interface between the positive electrode active material and the positive electrode current collector, potentially leading to a decrease in charge / discharge capacity.

[0011] An object of one embodiment of the present invention is to provide a secondary battery in which side reactions are unlikely to occur at an interface between a positive electrode active material layer and a solid electrolyte layer, an interface between a negative electrode active material layer and a solid electrolyte layer, or the like, even after repeated charging and discharging. Another object is to provide a secondary battery with excellent charge-discharge cycle characteristics. Another object is to provide a secondary battery with large charge-discharge capacity. Another object is to provide a secondary battery with high safety or reliability.

[0012] Note that the description of these problems does not preclude the existence of other problems. Note that one embodiment of the present invention does not necessarily solve all of these problems. Note that problems other than these can be extracted from the description of the specification, drawings, and claims. [Means for solving the problem]

[0013] In one embodiment of the present invention, a buffer layer (also referred to as a buffer layer) is provided between the positive electrode active material layer and the solid electrolyte layer in order to make the crystal structure less likely to collapse, suppress side reactions, and improve cycle characteristics.

[0014] The invention disclosed in this specification is a secondary battery having a positive electrode active material layer, a buffer layer on the positive electrode active material layer, and a solid electrolyte layer on the buffer layer, wherein the solid electrolyte layer contains a titanium compound, the positive electrode active material layer contains lithium cobalt oxide, and the buffer layer contains a titanium compound.

[0015] Another invention provides a secondary battery having a base film on a current collector, a positive electrode active material layer on the base film, a buffer layer on the positive electrode active material layer, and a solid electrolyte layer on the buffer layer, wherein the solid electrolyte layer contains a titanium compound, the positive electrode active material layer contains lithium cobalt oxide, the buffer layer contains a titanium compound, and the base film contains a titanium compound.

[0016] In the above configuration, both the crystal structure of the underlayer and the crystal structure of the positive electrode active material layer have a plane in which only anions are arranged. The thickness of the underlayer is preferably 50 nm or more, more preferably 100 nm or more, and even more preferably 200 nm or more. The thickness of the underlayer is preferably 1 μm or less, and more preferably 500 nm or less.

[0017] In each of the above structures, the positive electrode active material layer contains at least one of nickel, aluminum, magnesium, and fluorine.

[0018] In each of the above configurations, the negative electrode active material layer is provided on the solid electrolyte layer.

[0019] In each of the above configurations, the solid electrolyte layer is porous. The porous solid electrolyte layer is a solid having a large number of holes therein, and is preferably formed by adjusting the film formation conditions using a porous target. The porous solid electrolyte layer may also be formed using a vapor deposition method by adjusting the film formation conditions. The shape of the large number of holes is not particularly limited, and may be spherical, ellipsoidal, irregular three-dimensional, or the like. The large number of holes in the solid electrolyte layer can serve as ion conduction paths. The distribution of the holes in the porous solid electrolyte layer may be uniform or non-uniform.

[0020] The materials for the porous solid electrolyte layer include titanium compounds, Li 0.35 La 0.55 TiO3, La (2 / 3-x) Li 3x TiO 3、 Li3PO 4、 LixPO (4-y) Ny, LiNb (1-x) Ta (x) WO6, Li7La3Zr2O 12 ,Li (1+x) Al (x) Ti (2-x) (PO4)3, Li (1+x) Al (x) Ge (2-x) Examples include (PO4)3 and LiNbO2. Note that X>0 and Y>.

[0021] Furthermore, when used in a secondary battery using an electrolytic solution, the porous solid electrolyte layer functions as a separator. Therefore, when a secondary battery using an electrolytic solution is configured to use a porous solid electrolyte layer, it is not necessary to use a separator using an organic resin. The porous solid electrolyte layer is effective in preventing short circuits.

[0022] In each of the above structures, the undercoat film, the positive electrode active material layer, the buffer layer, and the solid electrolyte layer are formed by sputtering.

[0023] In each of the above structures, the thickness of the buffer layer is set to 1 nm or more and 100 nm or less, preferably 5 nm or more and 40 nm or less. [Effects of the Invention]

[0024] It is possible to realize a secondary battery in which side reactions are unlikely to occur at the interface between the positive electrode active material layer and the solid electrolyte layer, or the interface between the negative electrode active material layer and the solid electrolyte layer, even after repeated charging and discharging.

[0025] Furthermore, it is possible to provide a positive electrode for a secondary battery in which the decrease in capacity during charge / discharge cycles is suppressed. It is also possible to provide a secondary battery with excellent charge / discharge cycle characteristics. It is also possible to provide a secondary battery with large charge / discharge capacity. It is also possible to provide a secondary battery with high safety and reliability. [Brief explanation of the drawings]

[0026] [Figure 1] 1A to 1C are perspective views of a positive electrode and a solid electrolyte layer according to one embodiment of the present invention. [Figure 2] 2A and 2B illustrate a crystal structure of a positive electrode of one embodiment of the present invention. [Figure 3] 3A to 3C illustrate a stacked structure of a secondary battery of one embodiment of the present invention. [Figure 4] FIG. 4A is a top view illustrating one embodiment of the present invention, and FIGS. 4B to 4D are cross-sectional views illustrating one embodiment of the present invention. [Figure 5] 5A and 5C are top views showing one embodiment of the present invention, and FIGS. 5B and 5D are cross-sectional views showing one embodiment of the present invention. [Figure 6] FIG. 6 is a diagram illustrating a manufacturing flow of a secondary battery according to one embodiment of the present invention. [Figure 7] 7A and 7B are top views showing one embodiment of the present invention. [Figure 8] FIG. 8 is a cross-sectional view showing one embodiment of the present invention. [Figure 9] FIG. 9 illustrates a manufacturing flow of a secondary battery according to one embodiment of the present invention. [Figure 10] FIG. 10 is a schematic top view of a secondary battery manufacturing apparatus. [Figure 11] FIG. 11 is a cross-sectional view of a part of a secondary battery manufacturing apparatus. [Figure 12] 12A to 12C illustrate a stacked structure of a secondary battery of one embodiment of the present invention. [Figure 13] Fig. 13A is a perspective view of a battery cell, and Fig. 13B is a diagram showing an example of an electronic device. [Figure 14] 14A to 14C are diagrams showing examples of electronic devices. [Figure 15] 15A to 15C are diagrams showing examples of electronic devices. [Figure 16] 16A to 16D are diagrams showing examples of electronic devices. DETAILED DESCRIPTION OF THE INVENTION

[0027] Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. However, the present invention is not limited to the following description, and it will be readily understood by those skilled in the art that various modifications can be made to the embodiments and details. Furthermore, the present invention should not be interpreted as being limited to the description of the embodiments shown below.

[0028] (Embodiment 1) The lamination of a positive electrode for a secondary battery and a solid electrolyte layer according to one embodiment of the present invention will be described with reference to FIG.

[0029] 1A is a perspective view of an example of a stack of a positive electrode 100 for a secondary battery and a solid electrolyte layer according to one embodiment of the present invention. The positive electrode 100 for a secondary battery includes a positive electrode current collector 103, a base film 104, a positive electrode active material layer 101, and a buffer layer 102. A solid electrolyte layer 203 is provided on the buffer layer 102.

[0030] The base film 104 is provided between the positive electrode current collector 103 and the positive electrode active material layer 101. The base film 104 has a function of increasing the conductivity between the positive electrode current collector 103 and the positive electrode active material layer 101, a function of suppressing side reactions such as oxidation of the positive electrode current collector 103 by oxygen contained in the positive electrode active material layer 101, etc., and diffusion of metal atoms, and a function of stabilizing the crystal structure of the positive electrode active material layer 101.

[0031] It is preferable to use a material having electrical conductivity for the underlayer 104. It is also preferable to use a material that is easily inhibited from oxidation. For example, titanium compounds such as titanium oxide, titanium nitride, titanium oxide partially substituted with nitrogen, titanium nitride partially substituted with oxygen, or titanium oxynitride (TiOx N y It is possible to apply (such as 0 < x < 2, 0 < y < 1). Among them, titanium nitride is particularly preferable because it has high conductivity and a high function of suppressing oxidation.

[0032] The buffer layer 102 is provided on the positive electrode active material layer 101. The buffer layer 102 has a function of suppressing side reactions between the positive electrode active material layer 101 and the electrolyte, or has a function of stabilizing the crystal structure of the positive electrode active material layer 101.

[0033] It is preferable to use a titanium compound as the buffer layer 102. For example, titanium oxide, titanium nitride, titanium oxide partially substituted with nitrogen, titanium nitride partially substituted with oxygen, or titanium oxynitride (TiO x N y and having 0 < x < 2, 0 < y < 1). Titanium and oxygen are materials that can be included in the solid electrolyte layer 203. Therefore, titanium oxide is particularly suitable as the buffer layer 102.

[0034] Also, since the buffer layer 102 is formed by sputtering, a mixed layer may be formed at the interface between the positive electrode active material layer 101 and the buffer layer 102. When a mixed layer is formed, the boundary between the buffer layer 102 and the positive electrode active material layer 101 may become unclear.

[0035] As the material of the solid electrolyte layer 203, Li 0.35 La 0.55 TiO3, La (2 / 3-x) Li 3x TiO 3、 Li3PO 4、 LixPO (4-y) Ny, LiNb (1-x) Ta (x) WO6, Li7La3Zr2O 12 ,Li (1+x) Al (x) Ti (2-x) (PO4)3, Li (1+x) Al (x) Ge (2-x)Examples include (PO4)3 and LiNbO2. Note that X>0 and Y>. Film formation methods include sputtering and vapor deposition.

[0036] It is preferable to use a compound containing titanium for the solid electrolyte layer 203. Since the buffer layer 102 contains titanium, if a material containing titanium is also used for the solid electrolyte layer 203, a secondary battery can be easily fabricated.

[0037] The solid electrolyte layer 203 may have a laminated structure. In this case, at least one layer of the laminated layer is made of a material obtained by adding nitrogen to lithium phosphate (Li3PO4) (Li3PO (4-Z) N Z : It is also possible to use LiPON, where Z>0.

[0038] Furthermore, since the solid electrolyte layer 203 is formed by sputtering, a mixed layer may be formed at the interface between the buffer layer 102 and the solid electrolyte layer 203 .

[0039] The positive electrode active material layer 101 contains lithium, a transition metal M, and oxygen. It can also be said that the positive electrode active material layer 101 contains a composite oxide containing lithium and the transition metal M.

[0040] The transition metal M contained in the positive electrode active material layer 101 is preferably a metal capable of forming, together with lithium, a layered rock-salt composite oxide belonging to the space group R-3m. For example, one or more of manganese, cobalt, and nickel can be used as the transition metal M. That is, the transition metal M contained in the positive electrode active material layer 101 may be cobalt alone, nickel alone, a combination of cobalt and manganese, or a combination of cobalt and nickel, or three of cobalt, manganese, and nickel. That is, the positive electrode active material layer 101 may contain a composite oxide containing lithium and the transition metal M, such as lithium cobalt oxide, lithium nickel oxide, lithium cobalt oxide in which some of the cobalt is substituted with manganese, lithium cobalt oxide in which some of the cobalt is substituted with nickel, or nickel-manganese-lithium cobalt oxide.

[0041] Furthermore, the positive electrode active material layer 101 may contain elements other than the transition metal M, such as magnesium, fluorine, and aluminum, in addition to the above. These elements may further stabilize the crystal structure of the positive electrode active material layer 101. That is, the positive electrode active material layer 101 may contain lithium cobalt oxide to which magnesium and fluorine have been added, lithium nickel-cobalt oxide to which magnesium and fluorine have been added, lithium cobalt-aluminate to which magnesium and fluorine have been added, nickel-cobalt-lithium aluminum oxide, nickel-cobalt-lithium aluminum oxide, or nickel-cobalt-lithium aluminum oxide to which magnesium and fluorine have been added.

[0042] When the positive electrode active material layer 101 contains lithium, cobalt, nickel, aluminum, magnesium, oxygen, and fluorine, the atomic ratio of nickel is preferably, for example, 0.05 to 2, more preferably 0.1 to 1.5, and even more preferably 0.1 to 0.9, relative to the atomic ratio of cobalt contained in the positive electrode active material layer 101 taken as 100. The atomic ratio of aluminum is preferably, for example, 0.05 to 2, more preferably 0.1 to 1.5, and even more preferably 0.1 to 0.9, relative to the atomic ratio of cobalt contained in the positive electrode active material layer 101 taken as 100. The atomic ratio of magnesium is preferably, for example, 0.1 to 6, more preferably 0.3 to 3. Furthermore, when the atomic ratio of magnesium contained in the positive electrode active material layer 101 is taken as 1, the atomic ratio of fluorine is preferably, for example, 2 to 3.9.

[0043] By containing nickel, aluminum, and magnesium at the above concentrations, a stable crystal structure can be maintained even with small particle diameters, even after repeated charge and discharge at high voltages, resulting in a positive electrode active material layer 101 with high capacity and excellent charge and discharge cycle characteristics.

[0044] The molar concentrations of cobalt, nickel, aluminum, and magnesium can be determined, for example, by inductively coupled plasma mass spectrometry (ICP-MS). The molar concentration of fluorine can be determined, for example, by glow discharge mass spectrometry (GD-MS).

[0045] <First principles calculation> Here, the results of calculations of the crystal structure at the interface between the positive electrode active material layer 101 and the base film 104 when lithium cobalt oxide is used for the positive electrode active material layer 101 will be described with reference to FIG.

[0046] 2A shows the case where titanium nitride is used as the underlayer 104. Calculations were made assuming that the titanium nitride has a rock-salt crystal structure belonging to the space group Fm-3m, and the lithium cobalt oxide has a layered rock-salt crystal structure belonging to the space group R-3m. The (111) plane of the titanium nitride and the (001) plane of the lithium cobalt oxide are stacked parallel to each other.

[0047] 2B shows the case where titanium oxide is used as the underlayer 104. Calculations were made assuming that the titanium oxide has a rutile-type crystal structure belonging to the space group P42 / mnm, and the lithium cobalt oxide has a layered rock-salt-type crystal structure belonging to the space group R-3m. The (100) plane of the titanium oxide and the (001) plane of the lithium cobalt oxide are stacked parallel to each other.

[0048] Each figure shows an excerpt of the interface between the positive electrode active material layer 101 and the undercoat film 104. Other calculation conditions are shown in Table 1.

[0049] [Table 1]

[0050] In the case of FIG. 2A, where titanium nitride (represented as TiN in the table) was used as the underlayer 104, the Ti-O distance was 2.03 Å, the Ti-N distance was 1.93 Å, the Co-O distance was 2.25 Å, and the Co-N distance was 2.21 Å. -10 m.

[0051] In rock-salt crystal structures belonging to the space group Fm-3m, the planes where only anions are arranged are parallel to the (111) plane. In titanium nitride, only nitrogen atoms are arranged parallel to the (111) plane. In layered rock-salt crystal structures belonging to the space group R-3m, the planes where only anions are arranged are parallel to the (001) plane. In lithium cobalt oxide, only oxygen atoms are arranged parallel to the (001) plane.

[0052] When the (111) plane of titanium nitride and the (001) plane of lithium cobalt oxide are parallel, the planes on which only anions are arranged are parallel, making the crystal structure more stable.

[0053] Furthermore, both the rock-salt crystal structure belonging to the space group Fm-3m and the layered rock-salt crystal structure belonging to the space group R-3m are crystal structures in which cations and anions are arranged alternately. Therefore, when lithium cobalt oxide having a layered rock-salt crystal structure is laminated on titanium nitride having a rock-salt crystal structure, the crystal orientations of underlayer 104 and positive-electrode active material layer 101 tend to roughly match.

[0054] On the other hand, in the case of Figure 2B, where titanium oxide (referred to as TiO2 in the table) was used as the underlayer 104, the Ti-O distance was 2.15 Å and the Co-O distance was 1.91 Å. In titanium oxide with a rutile crystal structure, the oxygen atoms are not arranged on a plane parallel to the (100) plane. Therefore, compared to titanium nitride, it may have a lower ability to stabilize the layered rock-salt crystal structure.

[0055] When lithium cobalt oxide having a layered rock salt type crystal structure is used for the positive electrode active material layer 101 in this way, titanium nitride is particularly suitable for the underlayer 104 .

[0056] FIG. 1B is a perspective view of another example of a stack of a positive electrode 100 for a secondary battery and a solid electrolyte layer 203 according to one embodiment of the present invention. The positive electrode 100 for a secondary battery shown in FIG. 1B includes a positive electrode current collector 103, a positive electrode active material layer 101, and a buffer layer 102. As described above, the positive electrode 100 for a secondary battery does not necessarily include the base film 104. Even if the base film 104 is not included, the presence of the buffer layer 102 may result in a secondary battery with sufficiently improved cycle characteristics.

[0057] 1A and 1B illustrate a positive electrode in which the positive electrode current collector 103 functions both as a current collector and a substrate, but this is not a limitation of one embodiment of the present invention. Fig. 1C is a perspective view of another example of a positive electrode for a secondary battery 100. As shown in Fig. 1C, the positive electrode for a secondary battery 100 may be fabricated by forming the positive electrode current collector 103, an undercoat film 104, a positive electrode active material layer 101, and a buffer layer 102 on a substrate 110.

[0058] This embodiment mode can be implemented in appropriate combination with other embodiment modes.

[0059] (Embodiment 2) In this embodiment, a secondary battery including the stacked positive electrode for secondary battery 100 and the solid electrolyte layer 203 described in Embodiment 1 and a manufacturing method thereof will be described with reference to FIGS.

[0060] [Secondary battery configuration] FIG. 3A is a diagram illustrating an example of a stacked structure of a secondary battery 200 including a positive electrode for a secondary battery 100 according to one embodiment of the present invention.

[0061] The secondary battery 200 is a thin-film battery, and includes the secondary battery positive electrode 100 and solid electrolyte layer 203 described in the previous embodiment, with the negative electrode 212 formed on the solid electrolyte layer 203. The negative electrode 212 includes a negative electrode current collector 205 and a negative electrode active material layer 204. As shown in FIG. 3A , the negative electrode 212 preferably includes an undercoat film 214 and a buffer layer 209.

[0062] The underlayer film 214 is provided between the negative electrode current collector 205 and the negative electrode active material layer 204. The underlayer film 214 has a function of enhancing the conductivity between the negative electrode current collector 205 and the negative electrode active material layer 204. Or it has a function of suppressing excessive expansion of the negative electrode active material layer. Or it has a function of suppressing side reactions between the negative electrode current collector 205 and the negative electrode active material layer 204.

[0063] As the underlayer film 214, it is preferable to use a material having conductivity. It is also preferable to use a material that can suppress excessive expansion of the negative electrode active material layer. It is also preferable to use a material that is easy to suppress side reactions. For example, titanium compounds such as titanium oxide, titanium nitride, titanium oxide partially substituted with nitrogen, titanium nitride partially substituted with oxygen, or titanium oxynitride (TiO x N y , 0 < x < 2, 0 < y < 1) is preferably used. In particular, titanium nitride is highly preferable because it has high conductivity and a high function of suppressing side reactions.

[0064] The buffer layer 209 is provided between the negative electrode active material layer 204 and the solid electrolyte layer 203. It has a function of suppressing side reactions between the negative electrode active material layer 204 and the solid electrolyte layer 203.

[0065] Since the buffer layer 209 is formed by sputtering, there may be a mixed layer at the interface between the solid electrolyte layer 203 and the buffer layer 209.

[0066] As the buffer layer 209, it is preferable to use titanium or a titanium compound. Examples of the titanium compound include titanium oxide, titanium nitride, titanium oxide partially substituted with nitrogen, titanium nitride partially substituted with oxygen, or titanium oxynitride (TiO x N y , 0 < x < 2, 0 < y < 1) is preferably used. Titanium is contained in the solid electrolyte layer 203. Therefore, titanium and titanium compounds are particularly suitable as the buffer layer 209.

[0067] For the negative electrode active material layer 204, silicon, carbon, titanium oxide, vanadium oxide, indium oxide, zinc oxide, tin oxide, nickel oxide, etc. can be used. Also, materials that can be alloyed with Li, such as tin, gallium, and aluminum, can be used. Metal oxides that can be alloyed with these can also be used. Lithium titanium oxide (Li4Ti5O 12 , LiTi2O4, etc.) may be used, among which a material containing silicon and oxygen (also called an SiOx film) is preferable. Furthermore, Li metal may be used as the negative electrode active material layer 204.

[0068] The solid electrolyte layer 203 is provided between the positive electrode 100 for the secondary battery and the negative electrode 212 .

[0069] 3B , a secondary battery 200 may be provided having an anode 212 in which a plurality of anode active material layers 204 and buffer layers 209 are stacked. By stacking a plurality of anode active material layers 204 and buffer layers 209, it is possible to improve capacity while suppressing excessive expansion of the anode 212. In this case, the buffer layer 209 in contact with the solid electrolyte layer 203 and the buffer layer 209 sandwiched between the anode active material layers 204 may be made of the same material or different materials. For example, titanium oxide may be used for the buffer layer 209 in contact with the solid electrolyte layer 203, and titanium nitride may be used for the buffer layer 209 sandwiched between the anode active material layers 204. In the anode 212 in which a plurality of anode active material layers 204 and buffer layers 209 are stacked, the thickness of each buffer layer 209 is set to 5 nm or more and 40 nm or less, and the thickness of each anode active material layer 204 is set to 20 nm or more and 100 nm or less.

[0070] Furthermore, a mixed layer may be formed at the interface between the buffer layer 209 and the negative electrode active material layer 204 .

[0071] Furthermore, as shown in FIG. 3C , a secondary battery 200 may be provided that includes a secondary battery positive electrode 100 in which a plurality of positive electrode active material layers 101 and buffer layers 102 are stacked. By stacking a plurality of positive electrode active material layers 101 and buffer layers 102, it is possible to improve the capacity while suppressing the collapse of the crystalline structure of the positive electrode active material layers 101. In this case, the buffer layer 102 in contact with the solid electrolyte layer 203 and the buffer layer 102 sandwiched between the positive electrode active material layers 101 may be made of the same material or different materials. For example, titanium oxide may be used for the buffer layer 102 in contact with the solid electrolyte layer 203, and titanium nitride may be used for the buffer layer 102 sandwiched between the positive electrode active material layers 101.

[0072] 4A and 4B show a more specific example of a secondary battery 200 according to one embodiment of the present invention. Here, the secondary battery 200 formed over a substrate 110 will be described.

[0073] Fig. 4A is a top view, and Fig. 4B is a cross-sectional view taken along line A-A' in Fig. 4A. Secondary battery 200 is a thin-film battery, and as shown in Fig. 4B, secondary battery positive electrode 100 and solid electrolyte layer 203 described in the previous embodiment are laminated on substrate 110, and negative electrode 210 is formed on solid electrolyte layer 203. Negative electrode 210 has negative electrode current collector 205, base film 214, negative electrode active material layer 204, and buffer layer 209.

[0074] In addition, it is preferable that the secondary battery 200 has a protective layer 206 formed on the positive electrode 100 for secondary batteries, the solid electrolyte layer 203 and the negative electrode 210 .

[0075] The films forming these layers can be formed using a metal mask. The positive electrode current collector 103, the base film 104, the positive electrode active material layer 101, the buffer layer 102, the solid electrolyte layer 203, the buffer layer 209, the negative electrode active material layer 204, the base film 214, and the negative electrode current collector 205 can be selectively formed using a sputtering method. The solid electrolyte layer 203 may also be selectively formed using a metal mask.

[0076] 4A, a portion of the negative electrode current collector 205 is exposed to form a negative electrode terminal. Also, a portion of the positive electrode current collector 103 is exposed to form a positive electrode terminal. The area other than the negative electrode terminal and the positive electrode terminal is covered with a protective layer 206.

[0077] 4A and 4B include the positive electrode current collector 103, the base film 104, the positive electrode active material layer 101, and the buffer layer 102. Although the configuration in which the solid electrolyte layer 203, the negative electrode active material layer 204, and the negative electrode current collector 205 are stacked in this order on the positive electrode for secondary battery 100 has been described, one embodiment of the present invention is not limited thereto.

[0078] 4C , the secondary battery 200 may have a secondary battery positive electrode 100 without an underlayer 104 between the positive electrode current collector 103 and the positive electrode active material layer 101. Alternatively, the secondary battery 200 may have a negative electrode 210 without an underlayer 214 and a buffer layer 209.

[0079] In addition, both the positive electrode and the negative electrode of the secondary battery of one embodiment of the present invention may have a stacked structure of an active material layer and a buffer layer. As shown in FIG. 4D , a secondary battery 200 may have a negative electrode 210 in which a plurality of negative electrode active material layers 204 and a plurality of buffer layers 209 are stacked. Alternatively, the secondary battery may have a positive electrode 100 in which a plurality of positive electrode active material layers 101 and a plurality of buffer layers 102 are stacked.

[0080] 5A and 5B, a secondary battery of one embodiment of the present invention may be a secondary battery 201 including a negative electrode 211 that serves both as a negative electrode current collector layer and a negative electrode active material layer. FIG. 5A is a top view of the secondary battery 201, and FIG. 5B is a cross-sectional view taken along line B-B' in FIG. 5A. By using the negative electrode 211 that serves both as a negative electrode current collector layer and a negative electrode active material layer, a secondary battery can be manufactured with simplified manufacturing processes and high productivity. Furthermore, a secondary battery with high energy density can be manufactured.

[0081] 5C and 5D, the secondary battery of one embodiment of the present invention may be a secondary battery 202 in which a solid electrolyte layer 203 and a secondary battery positive electrode 100 are stacked on a negative electrode 210. FIG. 5C is a top view of the secondary battery 202, and FIG. 5D is a cross-sectional view taken along line CC' in FIG. 5C.

[0082] [Production method] Next, an example of the flow of a method for manufacturing the secondary battery 200 shown in FIGS. 4A and 4B will be described with reference to FIG.

[0083] First, a positive electrode current collector 103 is formed on a substrate 110 (S1). Examples of film formation methods include sputtering and vapor deposition. A conductive substrate may also be used as the current collector. The positive electrode current collector 103 may be made of a highly conductive material, such as gold, platinum, aluminum, titanium, copper, magnesium, iron, cobalt, nickel, zinc, germanium, indium, silver, or palladium, or an alloy thereof. Alternatively, aluminum doped with an element that improves heat resistance, such as silicon, titanium, neodymium, scandium, or molybdenum, may also be used. Alternatively, the positive electrode current collector 103 may be made of a metal element that reacts with silicon to form a silicide. Examples of metal elements that react with silicon to form a silicide include zirconium, titanium, hafnium, vanadium, niobium, tantalum, chromium, molybdenum, tungsten, cobalt, and nickel.

[0084] Furthermore, a ceramic substrate, a glass substrate, a resin substrate, a silicon substrate, a metal substrate, or the like can be used as the substrate 110. If a flexible material is used as the substrate 110, a flexible thin-film secondary battery can be manufactured.

[0085] The positive electrode current collector 103 can function both as a substrate and a positive electrode current collector by using a highly conductive material. In this case, it is preferable to use a metal substrate such as titanium or copper. When the base film 104 is provided, the base film 104 prevents the positive electrode current collector 103 from being oxidized by oxygen contained in the positive electrode active material layer 101 or the like and prevents the diffusion of metal atoms. Therefore, even a material that is easily oxidized or a material that contains easily diffusible metal atoms can be used for the positive electrode current collector 103.

[0086] Next, the base film 104 is formed (S2). The base film 104 can be formed by sputtering, vapor deposition, or the like. For example, when titanium nitride is used as the base film 104, the titanium nitride can be formed by reactive sputtering using a titanium target and nitrogen gas.

[0087] Next, the positive electrode active material layer 101 is formed (S3). The positive electrode active material layer 101 can be formed by sputtering using a sputtering target whose main component is an oxide containing lithium and one or more of manganese, cobalt, and nickel. For example, a sputtering target whose main component is lithium cobalt oxide (LiCoO2, LiCo2O4, etc.), a sputtering target whose main component is lithium manganese oxide (LiMnO2, LiMn2O4, etc.), or a sputtering target whose main component is lithium nickel oxide (LiNiO2, LiNi2O4, etc.) can be used. Alternatively, the positive electrode active material layer 101 may be formed by vacuum deposition. The thickness of the positive electrode active material layer 101 is in the range of 100 nm to 1 μm.

[0088] In addition, in the sputtering method, selective film formation is possible by using a metal mask. Alternatively, the positive electrode active material layer 101 may be patterned by selectively removing the resist mask or the like by dry etching or wet etching.

[0089] Furthermore, in order to form the positive electrode active material layer 101 containing magnesium, fluorine, aluminum, etc., a sputtering target containing magnesium, fluorine, aluminum, etc. in addition to lithium and one or more of manganese, cobalt, and nickel may be used for film formation. Alternatively, after forming a film using a sputtering target containing as its main component an oxide containing lithium and one or more of manganese, cobalt, and nickel, magnesium, fluorine, aluminum, etc. may be deposited by vacuum evaporation and annealed.

[0090] Next, the buffer layer 102 is formed on the positive electrode active material layer 101 (S4). The buffer layer 102 can be formed by sputtering, vapor deposition, or the like. For example, when titanium oxide is used as the buffer layer 102, the titanium oxide can be formed by reactive sputtering using a titanium target and oxygen gas. Alternatively, the buffer layer 102 can be formed by sputtering a titanium oxide target.

[0091] The positive electrode active material layer 101 and the buffer layer 102 are preferably formed at high temperatures (500° C. or higher), which allows the secondary battery positive electrode 100 to be produced with better crystallinity.

[0092] Next, the solid electrolyte layer 203 is formed on the positive electrode active material layer 101 (S5).

[0093] It is preferable to use a titanium-containing compound for the solid electrolyte layer 203. Since the buffer layer 102 contains titanium, if a titanium-containing material is also used for the solid electrolyte layer 203, a secondary battery can be easily fabricated. The film formation method can be a sputtering method, a vapor deposition method, or the like. The film thickness of the solid electrolyte layer 203 is set to 100 nm or more and 5 μm or less.

[0094] Next, the negative electrode active material layer 204 is formed on the solid electrolyte layer 203 (S6). As the film forming method, a sputtering method, a vapor deposition method, or the like can be used.

[0095] Next, the negative electrode current collector 205 is formed on the negative electrode active material layer 204 (S7). The material of the negative electrode current collector 205 is one or more conductive materials selected from Al, Ti, Cu, Au, Cr, W, Mo, Ni, Ag, etc. Sputtering, vapor deposition, etc. can be used as the film formation method. In the sputtering method, a metal mask can be used to selectively form a film. Alternatively, the conductive film may be patterned by selectively removing the film by dry etching or wet etching using a resist mask, etc.

[0096] When the positive electrode current collector 103 or the negative electrode current collector 205 is formed by sputtering, it is preferable to form at least one of the positive electrode active material layer 101 and the negative electrode active material layer 204 by sputtering. The sputtering device can perform continuous film formation in the same chamber or using multiple chambers, and can also be a multi-chamber manufacturing device or an in-line manufacturing device. The sputtering method is a manufacturing method suitable for mass production using a chamber and a sputtering target. Furthermore, the sputtering method allows for thin film formation and has excellent film formation characteristics.

[0097] Next, it is preferable to form a protective layer 206 on the secondary battery positive electrode 100, the solid electrolyte layer 203, and the negative electrode 210 (S8). The protective layer 206 can be made of a metal oxide containing one or more elements selected from hafnium, aluminum, gallium, yttrium, zirconium, tungsten, titanium, tantalum, nickel, germanium, neodymium, lanthanum, magnesium, etc. Silicon nitride oxide or silicon nitride can also be used. The protective layer 206 can be formed by sputtering.

[0098] Furthermore, the layers described in this embodiment are not limited to being formed by sputtering, and gas phase methods (vacuum evaporation, thermal spraying, pulsed laser deposition (PLD), ion plating, cold spray, and aerosol deposition) can also be used. The aerosol deposition (AD) method is a method of forming a film without heating the substrate. Aerosol refers to fine particles dispersed in a gas. Alternatively, CVD or ALD (Atomic Layer Deposition) can also be used.

[0099] Through the above steps, the secondary battery 200 of one embodiment of the present invention can be manufactured.

[0100] This embodiment mode can be implemented in appropriate combination with other embodiment modes.

[0101] (Embodiment 3) In order to increase the output voltage of a thin-film secondary battery, the secondary batteries can be connected in series. While the example of a secondary battery having one cell was shown in the second embodiment, this embodiment shows an example of fabricating a thin-film secondary battery in which a plurality of cells are connected in series.

[0102] Fig. 7A shows a top view of the first secondary battery immediately after its formation, and Fig. 7B shows a top view of two secondary batteries connected in series. Note that in Fig. 7A and Fig. 7B, the same reference numerals are used for the same parts as in Fig. 5A shown in Embodiment 2.

[0103] 7A shows the state immediately after the deposition of negative electrode current collector 205. The shape of the top surface of negative electrode current collector 205 differs from that of FIG. 5A. Negative electrode current collector 205 shown in FIG. 7A is in contact with a part of the side surface of the solid electrolyte layer and also with the insulating surface of the substrate.

[0104] 7B, a second negative electrode active material layer is formed on a region of the negative electrode current collector 205 that does not overlap with the first negative electrode active material layer. Then, a second solid electrolyte layer 213 is formed, and a second positive electrode active material layer and a second positive electrode current collector 215 are formed thereon. Finally, a protective layer 206 is formed.

[0105] FIG. 7B shows a configuration in which two solid-state secondary batteries are arranged on a plane and connected in series.

[0106] This embodiment mode can be implemented in appropriate combination with other embodiment modes.

[0107] (Fourth embodiment) In order to increase the output voltage or discharge capacity of the thin-film secondary battery, a multi-layer secondary battery can be formed in which multiple positive electrodes and multiple negative electrodes are stacked one on top of the other. While the second embodiment shows an example of a secondary battery that is a single-layer cell, the present embodiment shows an example of a thin-film battery that is a multi-layer cell.

[0108] 8 shows an example of a cross section of a three-layer thin-film battery. A positive electrode current collector 103 is formed on a substrate 110, and a base film 104, a positive electrode active material layer 101, a buffer layer 102, a positive electrode active material layer 101, a solid electrolyte layer 203, a negative electrode active material layer 204, and a negative electrode current collector 205 are sequentially formed on the positive electrode current collector 103 to form the first cell.

[0109] Furthermore, a second negative electrode active material layer 204, a solid electrolyte layer, a buffer layer, a positive electrode active material layer, a base film, and a positive electrode current collector layer are sequentially formed on the negative electrode current collector 205 to form a second cell.

[0110] Furthermore, the third cell is constructed by sequentially forming a third layer of base film, a positive electrode active material layer, a buffer layer, a solid electrolyte layer, a negative electrode active material layer, and a negative electrode current collector layer on the second layer of positive electrode current collector.

[0111] In Fig. 8, a protective layer 206 is formed last. The three-layer stack shown in Fig. 8 is configured to be connected in series to increase capacity, but it can also be connected in parallel via external wiring. Also, series and parallel or series-parallel can be selected via external wiring.

[0112] It is preferable to use the same material for solid electrolyte layer 203, the second solid electrolyte layer, and the third solid electrolyte layer, as this reduces manufacturing costs.

[0113] FIG. 9 shows an example of a manufacturing flow for obtaining the structure shown in FIG.

[0114] 9, in order to reduce the number of manufacturing steps, it is preferable to use a lithium cobalt oxide film as the positive electrode active material layer and a titanium film as the positive electrode current collector and the negative electrode current collector (conductive layer). By using a titanium film as the common electrode, a three-layer stacked cell can be realized with a small configuration.

[0115] This embodiment mode can be implemented in appropriate combination with other embodiment modes.

[0116] (Embodiment 5) In this embodiment, an example of a multi-chamber manufacturing apparatus that can fully automate the manufacturing of the positive electrode current collector layer to the negative electrode current collector layer of a secondary battery is shown in FIGS. 10 and 11. The manufacturing apparatus can be suitably used for manufacturing the thin-film secondary battery of one embodiment of the present invention.

[0117] Figure 10 shows an example of a multi-chamber manufacturing apparatus equipped with gates 880, 881, 882, 883, 884, 885, 886, 887, 888, a load lock chamber 870, a mask alignment chamber 891, a first transfer chamber 871, a second transfer chamber 872, a third transfer chamber 873, multiple film formation chambers (first film formation chamber 892, second film formation chamber 874), a heating chamber 893, a second material supply chamber 894, a first material supply chamber 895, and a third material supply chamber 896.

[0118] The mask alignment chamber 891 includes at least a stage 851 and a substrate transport mechanism 852 .

[0119] The first transfer chamber 871 has a substrate cassette lifting mechanism, the second transfer chamber 872 has a substrate transfer mechanism 853, and the third transfer chamber has a substrate transfer mechanism 854.

[0120] The first film formation chamber 892, the second film formation chamber 874, the second material supply chamber 894, the first material supply chamber 895, the third material supply chamber 896, the mask alignment chamber 891, the first transfer chamber 871, the second transfer chamber 872, and the third transfer chamber 873 are each connected to an exhaust mechanism. As the exhaust mechanism, an appropriate exhaust device may be selected depending on the intended use of each chamber, and examples include an exhaust mechanism equipped with a pump having an adsorption means such as a cryopump, a sputter ion pump, or a titanium sublimation pump, and an exhaust mechanism equipped with a turbomolecular pump and a cold trap.

[0121] The procedure for forming a film on a substrate is as follows: a substrate 850 or a substrate cassette is placed in a load lock chamber 870, and then transported to a mask alignment chamber 891 by a substrate transport mechanism 852. In the mask alignment chamber 891, a mask to be used is picked up from a plurality of masks that have been set in advance, and the mask is aligned with the substrate on a stage 851. After alignment is complete, a gate 880 is opened, and the substrate is transported to a first transport chamber 871 by the substrate transport mechanism 852. The substrate is transported to the first transport chamber 871, and the gate 881 is opened, and the substrate is transported to a second transport chamber 872 by a substrate transport mechanism 853.

[0122] The first film formation chamber 892, which is connected to the second transfer chamber 872 via a gate 882, is a sputtering film formation chamber. The sputtering film formation chamber has a mechanism that can switch between an RF power supply and a pulsed DC power supply to apply voltage to the sputtering target. Two or three types of sputtering targets can be set. In this embodiment, a single crystal silicon target, a sputtering target mainly composed of lithium cobalt oxide (LiCoO2), and a titanium target are installed. A substrate heating mechanism is installed in the first film formation chamber 892, and it is also possible to perform film formation while the heater temperature is raised to 700°C.

[0123] The negative electrode active material layer can be formed by sputtering using a single crystal silicon target. Also, SiO2 can be formed as a negative electrode by reactive sputtering using Ar gas and O2 gas. XA film made of titanium can be used as the negative electrode active material layer. A silicon nitride film can also be used as a sealing film by reactive sputtering using Ar gas and N2 gas. A positive electrode active material layer can also be formed by sputtering using a sputtering target whose main component is lithium cobalt oxide (LiCoO2). A conductive film that serves as a current collector can be formed by sputtering using a titanium target. A titanium nitride film can also be formed by reactive sputtering using Ar gas and N2 gas, and used as a buffer layer or base film.

[0124] When forming a positive electrode active material layer, the substrate is transported from the second transport chamber 872 to the first film formation chamber 892 with the mask and the substrate stacked thereon by the substrate transport mechanism 853, and then the gate 882 is closed and film formation is performed by sputtering. After film formation is completed, the gates 882 and 883 are opened, the substrate is transported to the heating chamber 893, and the gate 883 is closed, after which heating can be performed. For the heating treatment in the heating chamber 893, an RTA (Rapid Thermal Anneal) device, a resistance heating furnace, or a microwave heating device can be used. For the RTA device, a GRTA (Gas Rapid Thermal Anneal) device or an LRTA (Lamp Rapid Thermal Anneal) device can be used. The heating treatment in the heating chamber 893 can be performed in an atmosphere of nitrogen, oxygen, a rare gas, or dry air. The heating time is from 1 minute to 24 hours.

[0125] After the film formation or heat treatment is completed, the substrate and mask are returned to the mask alignment chamber 891, and a new mask is aligned. After alignment, the substrate and mask are transferred to the first transfer chamber 871 by the substrate transfer mechanism 852. The substrate is transferred by the lifting mechanism of the first transfer chamber 871, and after the gate 884 is opened, the substrate is transferred to the third transfer chamber 873 by the substrate transfer mechanism 854.

[0126] The second film formation chamber 874, which is connected to the third transfer chamber 873 via a gate 885, performs film formation by evaporation.

[0127] An example of the cross-sectional structure of the second film formation chamber 874 is shown in FIG. 11. FIG. 11 is a schematic cross-sectional view taken along the dotted line in FIG. 10. The second film formation chamber 874 is connected to an exhaust mechanism 849, and the first material supply chamber 895 is connected to an exhaust mechanism 848. The second material supply chamber 894 is connected to an exhaust mechanism 847. The second film formation chamber 874 shown in FIG. 11 is an evaporation chamber that performs evaporation using an evaporation source 856 transferred from the first material supply chamber 895. Evaporation sources can be transferred from multiple material supply chambers, and multiple substances can be simultaneously vaporized and evaporated for evaporation, i.e., co-evaporation can be performed. FIG. 11 also shows an evaporation source having an evaporation boat 858 transferred from the second material supply chamber 894.

[0128] The second film formation chamber 874 is connected to a second material supply chamber 894 via a gate 886. The second film formation chamber 874 is connected to a first material supply chamber 895 via a gate 888. The second film formation chamber 874 is connected to a third material supply chamber 896 via a gate 887. Therefore, the second film formation chamber 874 is capable of three-source co-evaporation.

[0129] In the vapor deposition procedure, first, a substrate is placed on a substrate holder 845. The substrate holder 845 is connected to a rotation mechanism 865. Then, a first vapor deposition material 855 is heated to a certain extent in a first material supply chamber 895, and when the vapor deposition rate becomes stable, a gate 888 is opened, an arm 862 is extended, and a vapor deposition source 856 is moved and stopped at a position below the substrate. The vapor deposition source 856 is composed of the first vapor deposition material 855, a heater 857, and a container for storing the first vapor deposition material 855. Similarly, a second vapor deposition material is heated to a certain extent in a second material supply chamber 894, and when the vapor deposition rate becomes stable, a gate 886 is opened, and an arm 861 is extended, and the vapor deposition source is moved and stopped at a position below the substrate.

[0130] Thereafter, the shutter 868 and the deposition source shutter 869 are opened to perform co-evaporation. During the evaporation, the rotation mechanism 865 is rotated to improve the uniformity of the film thickness. After the evaporation, the substrate is transported to the mask alignment chamber 891 along the same route. When the substrate is to be removed from the manufacturing equipment, it is transported from the mask alignment chamber 891 to the load lock chamber 870 and then removed.

[0131] 11 shows an example in which a substrate 850 and a mask are held by the substrate holder 845. By rotating the substrate 850 (and the mask) using a substrate rotation mechanism, the uniformity of film formation can be improved. The substrate rotation mechanism may also serve as a substrate transport mechanism.

[0132] Furthermore, the second film formation chamber 874 may be provided with an imaging means 863 such as a CCD camera. By providing the imaging means 863, the position of the substrate 850 can be confirmed.

[0133] In the second film formation chamber 874, the thickness of the film formed on the surface of the substrate can be predicted based on the measurement results of the film thickness measurement mechanism 867. The film thickness measurement mechanism 867 may include, for example, a quartz oscillator.

[0134] In order to control the deposition of the vaporized deposition material, a shutter 868 that overlaps with the substrate until the evaporation rate of the deposition material stabilizes, and a deposition source shutter 869 that overlaps with the deposition source 856 and the deposition boat 858 are provided.

[0135] Although an example of a resistance heating type of evaporation source 856 is shown, an EB (Electron Beam) evaporation type may also be used. Furthermore, although a crucible is shown as an example of a container for evaporation source 856, an evaporation boat may also be used. An organic material is placed as first evaporation material 855 in the crucible heated by heater 857. Furthermore, when pellets or particulate SiO or the like are used as the evaporation material, an evaporation boat 858 is used. The evaporation boat 858 consists of three parts, which are stacked on top of each other: a member with a concave surface, an inner lid with two holes, and an upper lid with one hole. Note that the inner lid may be removed during evaporation. The evaporation boat 858 acts as a resistor when electricity is applied, and the evaporation boat itself heats up.

[0136] Furthermore, although the present embodiment has been described as an example of a multi-chamber system, the present invention is not particularly limited thereto, and an in-line type manufacturing apparatus may also be used.

[0137] This embodiment mode can be implemented in appropriate combination with other embodiment modes.

[0138] (Sixth embodiment) In this embodiment, an example in which the solid electrolyte layer is porous is described. Note that the configuration other than the porous solid electrolyte layer is the same as that in Embodiment 1, and therefore detailed description thereof may be omitted here. Fig. 12A illustrates an example of a stacked structure of a secondary battery 200 including a positive electrode for a secondary battery 100 according to one embodiment of the present invention.

[0139] The secondary battery 200 is a thin-film battery, and has the secondary battery positive electrode 100 described in embodiment 1, a porous solid electrolyte layer 203p thereon, and a negative electrode 212 formed on the porous solid electrolyte layer 203p.

[0140] The material of the porous solid electrolyte layer 203p is Li 0.35 La 0.55 TiO3, La (2 / 3-x) Li 3x TiO 3、 Li3PO 4、 LixPO (4-y) Ny, LiNb(1-x) Ta (x) WO6, Li7La3Zr2O 12 ,Li (1+x) Al (x) Ti (2-x) (PO4)3, Li (1+x) Al (x) Ge (2-x) Examples include (PO4)3 and LiNbO2. Note that X>0 and Y>. Porous films can be obtained by sputtering using porous targets made of these materials.

[0141] It is preferable to use a titanium-containing compound for the porous solid electrolyte layer 203p. Because the buffer layer contains titanium, if a titanium-containing material is also used for the porous solid electrolyte layer 203p, a secondary battery can be easily fabricated.

[0142] The porous solid electrolyte layer 203p may have a laminated structure. In this case, at least one layer of the laminated structure is made of a material in which nitrogen is added to lithium phosphate (Li3PO4) (Li3PO (4-Z) N Z : It is also possible to use LiPON, where Z>0.

[0143] Furthermore, since the porous solid electrolyte layer 203p is formed by sputtering, a mixed layer may be formed at the interface between the buffer layer and the porous solid electrolyte layer 203p.

[0144] The negative electrode 212 includes a negative electrode current collector 205 and a negative electrode active material layer 204. Furthermore, the negative electrode 212 preferably includes an undercoat film 214 and a buffer layer 209 as shown in FIG.

[0145] The base film 214 is provided between the negative electrode current collector 205 and the negative electrode active material layer 204. The base film 214 has a function of increasing the electrical conductivity between the negative electrode current collector 205 and the negative electrode active material layer 204, a function of suppressing excessive expansion of the negative electrode active material layer, or a function of suppressing a side reaction between the negative electrode current collector 205 and the negative electrode active material layer 204.

[0146] The buffer layer 209 is provided between the negative electrode active material layer 204 and the porous solid electrolyte layer 203p and has the function of suppressing side reactions between the negative electrode active material layer 204 and the porous solid electrolyte layer 203p.

[0147] Since the buffer layer 209 is formed by sputtering, a mixed layer may be present at the interface between the porous solid electrolyte layer 203p and the buffer layer 209.

[0148] The porous solid electrolyte layer 203p is provided between the positive electrode 100 for the secondary battery and the negative electrode 212.

[0149] 12B , a secondary battery 200 may be provided having an anode 212 in which a plurality of anode active material layers 204 and buffer layers 209 are stacked. By stacking a plurality of anode active material layers 204 and buffer layers 209, it is possible to improve the capacity while suppressing excessive expansion of the anode 212. In this case, the buffer layer 209 in contact with the porous solid electrolyte layer 203p and the buffer layer 209 sandwiched between the anode active material layers 204 may be made of the same material or different materials. For example, titanium oxide may be used for the buffer layer 209 in contact with the porous solid electrolyte layer 203p, and titanium nitride may be used for the buffer layer 209 sandwiched between the anode active material layers 204. In the anode 212 in which a plurality of anode active material layers 204 and buffer layers 209 are stacked, the thickness of each buffer layer 209 is set to 5 nm or more and 40 nm or less, and the thickness of each anode active material layer 204 is set to 20 nm or more and 100 nm or less.

[0150] Furthermore, a mixed layer may be formed at the interface between the buffer layer 209 and the negative electrode active material layer 204 .

[0151] Furthermore, as shown in FIG. 12C , a secondary battery 200 may be provided that includes a secondary battery positive electrode 100 in which a plurality of positive electrode active material layers 101 and buffer layers 102 are stacked. By stacking a plurality of positive electrode active material layers 101 and buffer layers 102, it is possible to improve the capacity while suppressing the collapse of the crystalline structure of the positive electrode active material layers 101. In this case, the buffer layer 102 in contact with the porous solid electrolyte layer 203p and the buffer layer 102 sandwiched between the positive electrode active material layers 101 may be made of the same material or different materials. For example, titanium oxide may be used for the buffer layer 102 in contact with the porous solid electrolyte layer 203p, and titanium nitride may be used for the buffer layer 102 sandwiched between the positive electrode active material layers 101.

[0152] This embodiment mode can be freely combined with other embodiment modes.

[0153] (Embodiment 7) In this embodiment, examples of electronic devices using a thin-film secondary battery will be described with reference to FIGS. 13A, 13B, and 14A to 14C. The secondary battery of one embodiment of the present invention has high discharge capacity, high cycle characteristics, and high safety. Therefore, the electronic devices are highly safe and can be used for a long time.

[0154] 13A is a perspective view of the appearance of a thin-film secondary battery 3001. The battery is sealed with a laminate film or an insulating film so that a positive electrode lead electrode 513 electrically connected to the positive electrode of the solid secondary battery and a negative electrode lead electrode 511 electrically connected to the negative electrode thereof protrude.

[0155] 13B shows an IC card, which is an example of an application device using the thin-film secondary battery according to the present invention. Power obtained by power supply from radio waves 3005 can be charged into thin-film secondary battery 3001. An antenna, IC 3004, and thin-film secondary battery 3001 are arranged inside IC card 3000. ID 3002 and photo 3003 of the worker wearing the management badge are displayed on IC card 3000. The power charged in thin-film secondary battery 3001 can also be used to transmit signals such as authentication signals from the antenna.

[0156] An active matrix display device may be provided to display the ID 3002 and the photo 3003. Examples of active matrix display devices include reflective liquid crystal displays, organic EL displays, and electronic paper. The active matrix display device can also display images (moving or still images) and time. Power for the active matrix display device can be supplied from a thin-film secondary battery 3001.

[0157] Since a plastic substrate is used in an IC card, an organic EL display device using a flexible substrate is preferred.

[0158] A solar cell may be provided in place of the photo 3003. When irradiated with external light, the solar cell absorbs the light, generates electricity, and the electricity can be used to charge the thin-film secondary battery 3001.

[0159] Furthermore, the thin-film secondary battery is not limited to use in IC cards, but can also be used as a power source for wireless sensors used in vehicles, a secondary battery for MEMS devices, and the like.

[0160] Figure 14A shows an example of a wearable device. The wearable device uses a secondary battery as a power source. Furthermore, in order to improve splash-proof, water-resistant, or dust-proof performance when used at home or outdoors, there is a demand for wearable devices that can be charged wirelessly as well as via wired charging with an exposed connector.

[0161] For example, a secondary battery according to one embodiment of the present invention can be mounted on an eyeglasses-type device 400 as shown in FIG. 14A. The eyeglasses-type device 400 includes a frame 400a and a display unit 400b. Mounting a secondary battery on the temples of the curved frame 400a makes it possible to provide an eyeglasses-type device 400 that is lightweight, has a good weight balance, and can be used for a long time. The inclusion of a secondary battery according to one embodiment of the present invention makes it possible to realize a configuration that can accommodate space saving associated with a smaller housing.

[0162] Furthermore, a secondary battery according to one embodiment of the present invention can be mounted on a headset-type device 401. The headset-type device 401 includes at least a microphone unit 401a, a flexible pipe 401b, and an earphone unit 401c. A secondary battery can be provided in the flexible pipe 401b or the earphone unit 401c. By including a secondary battery according to one embodiment of the present invention, a configuration that can accommodate space savings due to a smaller housing can be realized.

[0163] Furthermore, the secondary battery according to one embodiment of the present invention can be mounted on a device 402 that can be directly attached to the body. A secondary battery 402b can be provided in a thin housing 402a of the device 402. By providing the secondary battery according to one embodiment of the present invention, a space-saving configuration can be realized that accompanies a miniaturized housing.

[0164] Furthermore, the secondary battery according to one embodiment of the present invention can be mounted on a device 403 that can be attached to clothing. A secondary battery 403b can be provided in a thin housing 403a of the device 403. By providing the secondary battery according to one embodiment of the present invention, a space-saving configuration can be realized that accompanies a miniaturized housing.

[0165] Furthermore, the secondary battery of one embodiment of the present invention can be mounted on the belt-type device 406. The belt-type device 406 has a belt portion 406a and a wireless power receiving portion 406b, and the secondary battery can be mounted inside the belt portion 406a. By including the secondary battery of one embodiment of the present invention, a configuration that can accommodate space saving due to miniaturization of the housing can be realized.

[0166] Furthermore, the secondary battery of one embodiment of the present invention can be mounted on the wristwatch device 405. The wristwatch device 405 has a display portion 405a and a belt portion 405b, and the secondary battery can be provided on the display portion 405a or the belt portion 405b. By providing the secondary battery of one embodiment of the present invention, a space-saving configuration can be realized that accompanies a miniaturized housing.

[0167] The display unit 405a can display not only the time but also various other information such as incoming emails and phone calls.

[0168] Furthermore, since the wristwatch device 405 is a wearable device that is worn directly on the wrist, it may be equipped with sensors that measure the user's pulse, blood pressure, etc. Data on the user's exercise volume and health can be accumulated to manage the user's health.

[0169] FIG. 14B shows a perspective view of the wristwatch type device 405 removed from the wrist.

[0170] 14C shows a side view of the display portion 405a. FIG. 14C shows that a secondary battery 913 is built in the display portion 405a. The secondary battery 913 is the secondary battery described in Embodiment 5. The secondary battery 913 is provided at a position overlapping with the display portion 405a, and is small and lightweight.

[0171] This embodiment mode can be implemented in appropriate combination with other embodiment modes.

[0172] (Embodiment 8) In this embodiment, electronic devices using a secondary battery including a positive electrode of one embodiment of the present invention will be described with reference to FIGS. 15A to 15C and 16A to 16D. A secondary battery including a positive electrode of one embodiment of the present invention has high discharge capacity, high cycle characteristics, and high safety. Therefore, it can be suitably used in the following electronic devices. It can be suitably used in electronic devices that require durability in particular.

[0173] 15A shows a perspective view of a wristwatch-type mobile information terminal (also called a smart watch (registered trademark)) 700. Mobile information terminal 700 has a housing 701, a display panel 702, a clasp 703, bands 705A and 705B, and operation buttons 711 and 712.

[0174] A display panel 702 mounted on a housing 701 that also serves as a bezel has a rectangular display area. The display area has a curved surface. The display panel 702 is preferably flexible. The display area may also be non-rectangular.

[0175] Band 705A and band 705B are connected to housing 701. Clasp 703 is connected to band 705A. Band 705A and housing 701 are connected via a pin, for example, so that the connection can rotate. The same applies to the connections between band 705B and housing 701, and between band 705A and clasp 703.

[0176] 15B and 15C are perspective views of the band 705A and the secondary battery 750, respectively. The band 705A includes the secondary battery 750. The secondary battery 750 may be, for example, the secondary battery described in the previous embodiment. The secondary battery 750 is embedded inside the band 705A, and a portion of each of the positive electrode lead 751 and the negative electrode lead 752 protrudes from the band 705A (see FIG. 15B). The positive electrode lead 751 and the negative electrode lead 752 are electrically connected to the display panel 702. The surface of the secondary battery 750 is covered with an exterior body 753 (see FIG. 15C). The pins may also function as electrodes. Specifically, the positive electrode lead 751 and the display panel 702, and the negative electrode lead 752 and the display panel 702 may be electrically connected via pins connecting the band 705A to the housing 701, respectively. This simplifies the configuration at the connection between the band 705A and the housing 701.

[0177] Secondary battery 750 is flexible. Therefore, band 705A can be manufactured by integrally forming it with secondary battery 750. For example, secondary battery 750 is placed in a mold that corresponds to the outer shape of band 705A, and material for band 705A is poured into the mold and cured, thereby manufacturing band 705A shown in FIG. 15B.

[0178] When a rubber material is used as the material for the band 705A, the rubber is hardened by heat treatment. For example, when fluororubber is used as the rubber material, it is hardened by heat treatment at 170°C for 10 minutes. When silicone rubber is used as the rubber material, it is hardened by heat treatment at 150°C for 10 minutes.

[0179] Materials used for the band 705A include fluororubber, silicone rubber, fluorosilicone rubber, and urethane rubber.

[0180] 15A can have various functions. For example, it can have a function of displaying various information (still images, videos, text images, etc.) in a display area, a touch panel function, a function of displaying a calendar, date or time, etc., a function of controlling processing by various software (programs), a wireless communication function, a function of connecting to various computer networks using the wireless communication function, a function of transmitting or receiving various data using the wireless communication function, a function of reading out programs or data recorded on a recording medium and displaying them in a display area, etc.

[0181] The housing 701 may also include a speaker, a sensor (including a function of measuring force, displacement, position, velocity, acceleration, angular velocity, rotation speed, distance, light, liquid, magnetism, temperature, chemical substance, sound, time, hardness, electric field, current, voltage, power, radiation, flow rate, humidity, gradient, vibration, odor, or infrared ray), a microphone, etc. The portable information terminal 700 can be manufactured by using a light-emitting element for the display panel 702.

[0182] 15A shows an example in which secondary battery 750 is included in band 705A, secondary battery 750 may be included in band 705B. Band 705B can be made of the same material as band 705A.

[0183] 16A shows an example of a cleaning robot. The cleaning robot 6300 has a display unit 6302 arranged on the top surface of a housing 6301, a plurality of cameras 6303 arranged on the side, a brush 6304, an operation button 6305, various sensors, and the like. Although not shown, the cleaning robot 6300 is provided with tires, a suction port, and the like. The cleaning robot 6300 can move by itself, detect dust 6310, and suck up the dust from a suction port arranged on the bottom surface.

[0184] For example, the cleaning robot 6300 can analyze an image captured by the camera 6303 to determine whether or not there is an obstacle such as a wall, furniture, or a step. Furthermore, when an object that may become entangled in the brush 6304, such as a wire, is detected through image analysis, the cleaning robot 6300 can stop rotation of the brush 6304. The cleaning robot 6300 includes a secondary battery according to one embodiment of the present invention and a semiconductor device or an electronic component. By using the secondary battery according to one embodiment of the present invention in the cleaning robot 6300, the cleaning robot 6300 can be a highly reliable electronic device with a long operating time.

[0185] Fig. 16B shows an example of a robot. A robot 6400 shown in Fig. 16B includes a secondary battery 6409, an illuminance sensor 6401, a microphone 6402, an upper camera 6403, a speaker 6404, a display unit 6405, a lower camera 6406, an obstacle sensor 6407, a movement mechanism 6408, a computing device, etc.

[0186] The microphone 6402 has a function of detecting the user's voice, environmental sounds, etc. The speaker 6404 has a function of emitting sound. The robot 6400 can communicate with the user using the microphone 6402 and the speaker 6404.

[0187] The display unit 6405 has a function of displaying various information. The robot 6400 can display information desired by the user on the display unit 6405. The display unit 6405 may be equipped with a touch panel. The display unit 6405 may also be a detachable information terminal, which can be installed in a fixed position on the robot 6400 to enable charging and data transfer.

[0188] The upper camera 6403 and the lower camera 6406 have the function of capturing images of the surroundings of the robot 6400. In addition, the obstacle sensor 6407 can detect the presence or absence of obstacles in the direction of travel when the robot 6400 moves forward using the movement mechanism 6408. The robot 6400 can recognize the surrounding environment and move safely using the upper camera 6403, the lower camera 6406, and the obstacle sensor 6407.

[0189] The robot 6400 includes a secondary battery 6409 according to one embodiment of the present invention and a semiconductor device or an electronic component inside the robot 6400. By using the secondary battery according to one embodiment of the present invention in the robot 6400, the robot 6400 can be a highly reliable electronic device with a long operating time.

[0190] Fig. 16C shows an example of an aircraft. Aircraft 6500 shown in Fig. 16C has propeller 6501, camera 6502, secondary battery 6503, etc., and has the function of flying autonomously.

[0191] For example, image data captured by the camera 6502 is stored in the electronic component 6504. The electronic component 6504 can analyze the image data and detect the presence or absence of an obstacle when moving. Furthermore, the electronic component 6504 can estimate the remaining battery charge from a change in the storage capacity of the secondary battery 6503. The flying object 6500 includes the secondary battery 6503 according to one embodiment of the present invention therein. By using the secondary battery according to one embodiment of the present invention in the flying object 6500, the flying object 6500 can be an electronic device with a long operating time and high reliability.

[0192] 16D shows an example of an automobile. The automobile 7160 includes a secondary battery 7161, an engine, tires, brakes, a steering device, a camera, and the like. The automobile 7160 includes a secondary battery 7161 according to one embodiment of the present invention inside. By using a secondary battery according to one embodiment of the present invention in the automobile 7160, the automobile 7160 can have a long cruising distance, high safety, and high reliability.

[0193] This embodiment mode can be implemented in appropriate combination with other embodiment modes. [Explanation of symbols]

[0194] 100: positive electrode for secondary battery, 101: positive electrode active material layer, 102: buffer layer, 103: positive electrode current collector, 104: underlayer, 110: substrate, 200: secondary battery, 201: secondary battery, 202: secondary battery, 203: solid electrolyte layer, 203p: porous solid electrolyte layer, 204: negative electrode active material layer, 205: negative electrode current collector, 206: protective layer, 209: buffer layer, 210: negative electrode, 211: negative electrode, 212: negative electrode, 213: solid electrolyte layer, 214: underlayer, 215: positive electrode current collector, 400: eyeglass-type device, 400a: frame, 400b: display unit, 401: headset-type device, 401a: mask jack section, 401b: flexible pipe, 401c: earphone section, 402: device, 402a: housing, 402b: secondary battery, 403: device, 403a: housing, 403b: secondary battery, 405: wristwatch type device, 405a: display section, 405b: belt section, 406: belt type device, 406a: belt section, 406b: wireless power supply receiving section, 511: negative lead electrode, 513: positive lead electrode, 700: mobile information terminal, 701: housing, 702: display panel, 703: clasp, 705A: band, 705B: band, 711: operation button, 712: operation Button, 750: secondary battery, 751: positive electrode lead, 752: negative electrode lead, 753: exterior body, 845: substrate holder, 847: exhaust mechanism, 848: exhaust mechanism, 849: exhaust mechanism, 850: substrate, 851: stage, 852: substrate transport mechanism, 853: substrate transport mechanism, 854: substrate transport mechanism, 855: evaporation material, 856: evaporation source, 857: heater, 858: evaporation boat, 861: arm, 862: arm, 863: imaging means, 865: rotation mechanism, 867: film thickness measurement mechanism, 868: shutter, 869: evaporation source shutter, 870: load lock chamber, 871: transport chamber, 872: Transfer chamber, 873: Transfer chamber, 874: Film formation chamber, 880: Gate, 881: Gate, 882: Gate, 883: Gate, 884: Gate, 885: Gate, 886: Gate, 887: Gate, 888: Gate, 891: Mask alignment chamber, 892: Film formation chamber, 893: Heating chamber, 894: Material supply chamber, 895: Material supply chamber, 896: Material supply chamber, 913: Secondary battery, 3000: IC card, 3001: Thin film secondary battery, 3002: ID, 3003: Photo, 3004: IC, 3005: Radio wave, 6300: Cleaning robot, 6301: Housing, 6302: Display unit,6303: camera, 6304: brush, 6305: operation button, 6310: dust, 6400: robot, 6401: illuminance sensor, 6402: microphone, 6403: upper camera, 6404: speaker, 6405: display unit, 6406: lower camera, 6407: obstacle sensor, 6408: moving mechanism, 6409: secondary battery, 6500: flying object, 6501: propeller, 6502: camera, 6503: secondary battery, 6504: electronic component, 7160: automobile, 7161: secondary battery,

Claims

[Claim 1] a base film on a current collector, a positive electrode active material layer on the base film, a buffer layer on the positive electrode active material layer, and a solid electrolyte layer on the buffer layer; the solid electrolyte layer contains a titanium compound, the positive electrode active material layer contains lithium cobalt oxide, the buffer layer comprises a titanium compound; The secondary battery includes an undercoat film containing a titanium compound.

Images