Negative electrode

Abstract

To provide a solid secondary battery having cycle characteristics, reliability and safety.SOLUTION: A negative electrode includes n (n is an integer equal to or more than 2) negative electrode active material layers and n-1 separation layers on a negative electrode collector. The negative electrode active material layers and separation layers are alternately laminated; the film thickness of the negative electrode active material layer is 20 nm or more and 100 nm or less; the separation layer is a negative electrode including titanium and preferably has titanium (Ti), titanium nitride (TiN) or oxidization titanium nitride (TiOxNy, 0<x<2, 0<y<1); the negative electrode having such a structure can reduce an expansion per one negative electrode active material layer. Therefore, the negative electrode high in capacity and capable of preventing cracks or collapses from occurring is obtained.SELECTED DRAWING: Figure 2

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, an electronic device, or a manufacturing method thereof.

[0002] In this specification, the term "electronic device" refers to any device having a power storage device, and an electro-optical device having a power storage device, an information terminal device having a power storage device, and the like are all classified as electronic devices. [Background technology]

[0003] In recent years, various types of power storage devices, such as lithium ion secondary batteries, lithium ion capacitors, air batteries, all-solid-state batteries, etc. In particular, the demand for high-output, high-capacity lithium ion secondary batteries has rapidly expanded in line with the development of the semiconductor industry, and they have become indispensable in the modern information society as a rechargeable energy source.

[0004] Therefore, improvements in the negative electrodes of lithium ion secondary batteries and the like have been investigated in order to increase the capacity and improve the cycle characteristics.

[0005] Since Si (silicon) has a higher lithium ion absorption capacity per atom than graphite etc., research using Si as a negative electrode active material has been widely conducted. For example, Patent Document 1 describes a lithium ion secondary battery that uses a silicon composite, in which silicon oxide is coated with carbon by thermal CVD, as a negative electrode active material.

[0006] Lithium ion secondary batteries that use liquids such as organic solvents as a medium (hereinafter referred to as electrolyte) for moving lithium ions, which are carrier ions, are widely used. However, secondary batteries that use liquids as electrolytes (hereinafter referred to as electrolyte solution) have problems with the electrolyte decomposition reaction depending on the operating temperature range and operating potential, and leakage to the outside of the secondary battery, because the liquid is used. In addition, secondary batteries that use liquid electrolytes have a risk of ignition due to leakage.

[0007] Furthermore, as a secondary battery that does not use liquid, there is known an electricity storage device called a solid secondary battery that uses a solid electrolyte. For example, Patent Document 2 discloses such a device. [Prior art documents] [Patent documents]

[0008] [Patent Document 1] JP 2004-047404 A [Patent Document 2] U.S. Patent No. 8,404,001 Summary of the Invention [Problem to be solved by the invention]

[0009] As mentioned above, negative electrode active materials having Si coated with carbon have been researched. However, such negative electrode active materials do not fully exhibit the performance required for secondary batteries. It is also known that negative electrode active materials having Si expand in volume when they absorb lithium ions. This expansion may cause cracks or crumble in the negative electrode, adversely affecting the characteristics of the secondary battery.

[0010] In addition, there is still room for improvement in various aspects of solid secondary batteries, such as charge / discharge characteristics, cycle characteristics, reliability, safety, and cost.

[0011] In view of the above, an object of one embodiment of the present invention is to provide a negative electrode having a large charge / discharge capacity. Alternatively, an object of one embodiment of the present invention is to provide a negative electrode having good cycle characteristics. Alternatively, an object of one embodiment of the present invention is to provide a novel negative electrode. Alternatively, an object of one embodiment of the present invention is to provide a solid-state secondary battery having a large charge / discharge capacity. Alternatively, an object of one embodiment of the present invention is to provide a solid-state secondary battery having good cycle characteristics. Alternatively, an object of one embodiment of the present invention is to provide a novel power storage device.

[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 it is possible to extract problems other than these from the description of the specification, drawings, and claims. [Means for solving the problem]

[0013] One embodiment of the present invention is a negative electrode having n negative electrode active material layers (n is an integer of 2 or more) and n-1 separation layers over a negative electrode current collector layer, the negative electrode active material layers and the separation layers being alternately stacked, the thickness of the negative electrode active material layers being 20 nm or more and less than 100 nm, and the separation layers containing a Group 4 element.

[0014] Another embodiment of the present invention is a negative electrode including n negative electrode active material layers (n is an integer of 2 or more) and n-1 separation layers over a negative electrode current collector layer, the negative electrode active material layers and the separation layers being alternately stacked, the thickness of the negative electrode active material layers being 20 nm or more and less than 100 nm, and the separation layers including titanium nitride, titanium oxide, or titanium oxynitride.

[0015] In the above structure, the first negative electrode active material layer is preferably in contact with the negative electrode current collector.

[0016] In the above-mentioned configuration, the separation layer is preferably in contact with the negative electrode active material layer.

[0017] In the above structure, the separation layer preferably has a thickness of 5 nm or more and 40 nm or less.

[0018] In the above configuration, it is preferable that a first layer be provided on the n-th negative electrode active material layer, and it is more preferable that the first layer include Ti.

[0019] In the above structure, the negative electrode active material layer preferably contains Si.

[0020] In the above-mentioned configuration, the separation layer preferably has a laminated structure. Effect of the Invention

[0021] According to one embodiment of the present invention, a negative electrode having a large charge / discharge capacity can be provided. According to one embodiment of the present invention, a negative electrode having good cycle characteristics can be provided. According to one embodiment of the present invention, a novel negative electrode can be provided. According to one embodiment of the present invention, a solid-state secondary battery having a large charge / discharge capacity can be provided. According to one embodiment of the present invention, a solid-state secondary battery having good cycle characteristics can be provided. According to one embodiment of the present invention, a novel power storage device can be provided.

[0022] Furthermore, by increasing the number of layers each consisting of a positive electrode active material layer, a solid electrolyte layer, and a negative electrode active material layer, a thin-film solid secondary battery can be configured as a multi-layer stack connected in series or parallel, thereby increasing the capacity.

[0023] Furthermore, the capacity of a thin-film solid secondary battery can also be increased by increasing its area.

[0024] In addition, by using the peel-and-transpose technique, it is possible to enlarge the area and then fold it to a desired size. [Brief description of the drawings]

[0025] [Figure 1] Fig. 1A is a cross-sectional view of a secondary battery according to one embodiment of the present invention, and Fig. 1B is a cross-sectional view of a conventional negative electrode active material layer. [Diagram 2] 2A to 2D are cross-sectional views showing one embodiment of the present invention. [Diagram 3] 3A to 3D are cross-sectional views showing one embodiment of the present invention. [Figure 4] Fig. 4A is a top view showing one embodiment of the present invention, and Fig. 4B and Fig. 4C are cross-sectional views showing one embodiment of the present invention. [Diagram 5] FIG. 5 is a diagram illustrating a production flow of a solid secondary battery according to one embodiment of the present invention. [Figure 6] 6A and 6B are a top view and a cross-sectional view showing one embodiment of the present invention. [Figure 7] FIG. 7 is a cross-sectional view showing one embodiment of the present invention. [Figure 8] 8A is a perspective view illustrating an example of a battery cell according to one embodiment of the present invention, FIG 8B is a perspective view of a circuit according to one embodiment of the present invention, and FIG 8C is a perspective view illustrating a battery cell and a circuit according to one embodiment of the present invention superimposed on each other. [Figure 9] Fig. 9A is a perspective view showing an example of a battery cell according to one embodiment of the present invention, Fig. 9B is a perspective view of a circuit, and Figs. 9C and 9D are perspective views showing a battery cell according to one embodiment of the present invention and a circuit superimposed thereon. [Figure 10] Fig. 10A is a perspective view of a battery cell, and Fig. 10B is a diagram showing an example of an electronic device. [Figure 11] FIG. 11 illustrates an example of an electronic device according to one embodiment of the present invention. [Figure 12] 12A to 12C are diagrams illustrating examples of electronic devices according to one embodiment of the present invention. [Figure 13] 13A to 13D are diagrams illustrating examples of electronic devices according to one embodiment of the present invention. [Figure 14] Fig. 14A is a schematic diagram of an electronic device according to one embodiment of the present invention, Fig. 14B is a diagram showing a part of a system, and Fig. 14C is an example of a perspective view of a portable data terminal used in the system according to one embodiment of the present invention. [Figure 15] 15A to 15C are diagrams illustrating the structure of a sample according to an embodiment of the present invention. [Figure 16] FIG. 16 is a diagram illustrating cycle characteristics according to the example. [Figure 17]17A and 17B are cross-sectional TEM images according to the embodiment. [Figure 18] 18A and 18B are cross-sectional TEM images according to the embodiment. [Figure 19] FIG. 19 is a diagram illustrating the structure of a sample according to an embodiment of the present invention. [Figure 20] 20A to 20C are diagrams illustrating the state of the sample after charging and discharging according to the example. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0026] Hereinafter, the 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 easily understood by those skilled in the art that the form and details of the present invention can be modified in various ways. Furthermore, the present invention is not to be interpreted as being limited to the description of the embodiments shown below.

[0027] In this specification, the ordinal numbers "first," "second," and "third" are used to avoid confusion of components. Therefore, they do not limit the number of components. Furthermore, they do not limit the order of the components. For example, a component referred to as "first" in one embodiment of this specification may be a component referred to as "second" in another embodiment or in the claims. For example, a component referred to as "first" in one embodiment of this specification may be omitted in another embodiment or in the claims.

[0028] In the drawings, the same elements or elements having similar functions, elements made of the same material, or elements formed simultaneously may be given the same reference numerals, and repeated explanations may be omitted. Furthermore, the same elements or elements having similar functions, elements made of the same material, or elements formed simultaneously may be given the same hatch pattern, and the reference numerals may be omitted.

[0029] In this specification, charging refers to moving conductive ions (lithium ions in the case of a lithium ion secondary battery) from the positive electrode to the negative electrode inside the battery and moving electrons from the negative electrode to the positive electrode in an external circuit. For a positive electrode active material, removing conductive ions is called charging, and for a negative electrode active material, inserting conductive ions is called charging. For a positive electrode active material, inserting conductive ions is called discharging, and for a negative electrode active material, removing conductive ions is called discharging. Hereinafter, the case where the conductive ions are lithium ions will be described.

[0030] (Embodiment 1) A negative electrode and a secondary battery of one embodiment of the present invention will be described with reference to Fig. 1A, Fig. 2A, and Fig. 2B. Note that in this specification, a negative electrode includes at least a negative electrode current collector and a negative electrode active material layer.

[0031] 1A shows a secondary battery 150 according to one embodiment of the present invention, in which a negative electrode current collector layer 200, a negative electrode active material layer 201, a solid electrolyte layer 202, a positive electrode active material layer 203, and a positive electrode current collector layer 205 are stacked in this order on a substrate 101. Note that the order of stacking may be reversed. That is, the positive electrode current collector layer 205, the positive electrode active material layer 203, the solid electrolyte layer 202, the negative electrode active material layer 201, and the negative electrode current collector layer 200 may be stacked in this order on the substrate 101.

[0032] Substrates that can be used for the substrate 101 include ceramic substrates, glass substrates, plastic substrates, silicon substrates, metal substrates, and the like.

[0033] As materials for the negative electrode current collector layer 200 and the positive electrode current collector layer 205, one or more conductive materials selected from Al, Ti, Cu, Au, Cr, W, Mo, Ni, Ag, etc. are used. As the film formation method, a sputtering method, an evaporation method, etc. can be used. Further, in the sputtering method, selective film formation can be achieved by using a metal mask. Also, the conductive film may be patterned by selectively removing it by dry etching or wet etching using a resist mask or the like. Further, the negative electrode current collector layer 200 and the positive electrode current collector layer 205 may be formed by laminating a plurality of materials.

[0034] The positive electrode active material layer 203 is a sputtering target mainly composed of lithium cobalt oxide (for example, LiCoO 2 , LiCo 2 O 4 , Li 1.2 CoO 2 , etc.), a sputtering target mainly composed of lithium manganese oxide (for example, LiMnO 2 , LiMn 2 O 4 , etc.), a sputtering target mainly composed of lithium nickel oxide (for example, Li to O 2 , LiNi 2 O 4 , etc.), and can be formed by sputtering. Also, lithium manganese cobalt oxide (for example, LiMnCoO 4 , Li 2 MnCoO 4 , etc.), a ternary material of nickel cobalt manganese (for example, LiNi 1 / 3 Mn 1 / 3 Co 1 / 3 O 2 : NCM), a ternary material of nickel cobalt aluminum (for example, LiNi 0.8 Co 0.15 Al 0.05 O 2 : NCA), etc. can also be used. The above-mentioned materials desorb lithium ions during charging and accumulate lithium ions during discharging.

[0035] The negative electrode active material layer 201 may be formed by sputtering, CVD, or the like, using a film mainly made of silicon, a film mainly made of carbon, a titanium oxide film, a vanadium oxide film, an indium oxide film, a zinc oxide film, a tin oxide film, a nickel oxide film, or the like. The film mainly made of silicon may be doped with phosphorus or boron by plasma CVD, for example, to form an n+Si film or a p+Si film. Films that alloy with Li, such as tin, gallium, or aluminum, may also be used. Metal oxide films that alloy with these may also be used. A Li metal film may also be used as the negative electrode active material layer 201. Lithium titanium oxide (Li 4 Ti 5 O 12 , LiTi 2 O 4 Among them, a film containing silicon is preferable. The above-mentioned materials store lithium ions during charging and release lithium ions during discharging.

[0036] 1B shows a conventional change in the thickness of the negative electrode active material layer 201 due to charging and discharging. Since lithium ions accumulate in the negative electrode during charging, the thickness of the negative electrode active material layer 201 increases (expands).

[0037] Here, consider the case where silicon is used for the negative electrode active material layer 201. As described above, silicon has a large lithium ion occlusion capacity and can be suitably used as the negative electrode active material. However, silicon expands significantly when it occludes lithium ions, which may cause cracks or collapse in the negative electrode active material layer 201 and deteriorate the battery characteristics, especially the cycle characteristics.

[0038] <Negative electrode configuration example 1> FIG. 2A shows a cross-sectional view of a secondary battery 152 according to one embodiment of the present invention. The inventors have found that, as shown in FIG. 2B, the negative electrode active material layer 201(A) is structured to have n layers (n is an integer of 2 or more) of negative electrode active material layers 201(a) and n-1 layers of separation layers 210, by alternately stacking separation layers 210 and negative electrode active material layers. In this case, the separation layer of the i-th layer (i is an integer of 1 to n) is in contact with the i-th negative electrode active material layer. This structure allows the negative electrode active material layer 201(a) to have a smaller expansion per layer than the negative electrode active material layer 201 shown in FIG. 1B. Therefore, the negative electrode active material layer can have a high capacity and is less likely to crack or collapse. FIG. 2C shows the negative electrode active material layer 201(A) having two negative electrode active material layers 201(a) and one separation layer 210.

[0039] [Negative electrode active material layer 201(A)] 2A to 2C and the negative electrode active material layer 201 shown in FIGS. 1A and 1B preferably have a capacity equal to or greater than the capacity of the lithium ion used in the positive electrode active material layer 203. Therefore, when there is only one negative electrode active material layer, as in the negative electrode active material layer 201 shown in FIG. 1B, the thickness of the negative electrode active material layer may become large in order to ensure the capacity.

[0040] The negative electrode active material layer expands when lithium ions are accumulated. For example, it is known that silicon expands about four times as much when fully charged as when discharged. Therefore, if the thickness of the negative electrode active material layer when discharged is too large, the difference in thickness between when discharged and when charged becomes very large. For example, if the thickness of the negative electrode active material layer when discharged is 200 nm, the thickness of the negative electrode active material layer when fully charged becomes about 800 nm, and the difference in thickness between when fully charged and when discharged is about 600 nm, which is a very large difference, and there is concern about adverse effects such as cracking and crumbling of the negative electrode active material layer 201 as described above. On the other hand, if the thickness of the negative electrode active material layer when discharged is 20 nm, the thickness of the negative electrode active material layer 201 when fully charged is about 80 nm, and the difference in thickness between when fully charged and when discharged is about 60 nm, and it is considered that the possibility of cracking, crumbling, etc. occurring in the negative electrode active material layer 201 is low.

[0041] Furthermore, when silicon is used as the negative electrode active material, the smaller the film thickness, the closer the capacity per weight to the theoretical capacity, i.e., the thinner the film thickness, the greater the capacity per weight of silicon.

[0042] Therefore, it is preferable that the thickness of each negative electrode active material layer is small. For example, when the total thickness of the negative electrode active material layers (in this case, the thickness of silicon) is required to be 200 nm, it is preferable not to obtain a single negative electrode active material layer 201 having a thickness of 200 nm. As shown in FIG. 2B, it is preferable to introduce a separation layer 210 between a plurality of negative electrode active material layers 201(a). In this case, it is preferable that the total thickness of the negative electrode active material layer 201(A) is 200 nm excluding the thickness of the separation layer 210.

[0043] At this time, the thickness of each negative electrode active material layer 201(a) is preferably small, but if it is too thin, the number of layers increases, and the number of steps for producing the negative electrode may increase too much. Therefore, the thickness of each negative electrode active material layer 201(a) is preferably 20 nm or more and less than 100 nm, and more preferably 40 nm or more and 80 nm or less. Furthermore, n is preferably 2 or more and 10 or less, and more preferably 2 or more and 5 or less.

[0044] Furthermore, even if a separation layer 210 is introduced between the negative electrode current collector layer 200 and the first negative electrode active material layer 201(a), the separation layer 210 does not contribute to thinning the negative electrode active material layer 201(a). In addition, there is a risk of a decrease in capacity per volume. For this reason, it is preferable that the negative electrode current collector layer 200 and the first negative electrode active material layer 201(a) are in contact with each other.

[0045] The negative electrode active material layer 201(a) may be crystalline or amorphous. An amorphous film is preferable in terms of high productivity. Also, the negative electrode active material layer 201(a) may have different crystallinities during charging and discharging. For example, it may have crystallinity immediately after film formation without lithium and when lithium is sufficiently released, and may be amorphous during the process of accumulating lithium. Also, when used in a secondary battery having an electrolytic solution, it may become amorphous by reacting with the electrolytic solution. The negative electrode active material layer 201(a) having crystallinity in a state without lithium may be a negative electrode active material layer 201(a) capable of accumulating a large amount of lithium. In the present specification and the like, having crystallinity means being a single crystal, polycrystal or microcrystal.

[0046] [Separator layer 210] If the separator layer 210 reacts with lithium ions, the capacity of the secondary battery will decrease. Therefore, it is preferable that the separator layer 210 is made of a material that is less likely to react with lithium ions. Therefore, it is preferable that the separator layer has a Group 4 element. Examples of the Group 4 element include Ti (titanium), Zr (zirconium), Hf (hafnium), etc. The separator layer 210 preferably has titanium, titanium nitride (TiN), titanium oxide (TiO x . TiO, TiO 2 etc.), and titanium oxynitride (TiOxNy, 0 < x < 2, 0 < y < 1), and more preferably contains titanium or titanium nitride as a main component. Also, when the thickness of titanium, titanium nitride, titanium oxide and titanium oxynitride is 100 nm or less, it does not inhibit the movement of lithium, so the battery capacity does not decrease. That is, titanium, titanium nitride, titanium oxide and titanium oxynitride do not occlude and release lithium ions when the thickness is 100 nm or less. Therefore, since the battery capacity does not decrease even when used for the separator layer 210, titanium, titanium nitride, titanium oxide and titanium oxynitride can be suitably used for the separator layer. Other Group 4 elements are expected to have the same effect as titanium.

[0047] In addition, it is preferable that the separation layer 210 has crystallinity. When the separation layer 210 has crystallinity, the conductivity of lithium ions is improved. In addition, since the separation layer uses a material that is poorly reactive with lithium ions, the crystallinity is unlikely to change before and after charging and discharging.

[0048] The thickness of the separation layer 210 is preferably 5 nm to 100 nm, more preferably 5 nm to 40 nm, and even more preferably 5 nm to 20 nm. If the thickness of the separation layer 210 is large, the charge / discharge capacity per weight of the electrode is reduced, so the thickness of the separation layer 210 is preferably small. On the other hand, if the thickness of the separation layer 210 is too small, for example, the kth layer (k is an integer of 1 to n-1) of the negative electrode active material layer 201(a) and the k+1th layer of the negative electrode active material layer 201(a) may come into contact with each other. Therefore, the separation layer 210 needs to have a thickness that allows it to function sufficiently. In addition, it is preferable that the separation layer 210 and the negative electrode active material layer 201(a) are in contact with each other so that the separation layer 210 can function sufficiently.

[0049] Furthermore, the separation layer 210 may have a laminated structure. For example, when preparing a 20 nm separation layer 210, the separation layer 210 may be formed by laminating a 10 nm layer of titanium nitride on a 10 nm layer of titanium.

[0050] Although the negative electrode active material layer 201(a) and the separation layer 210 are alternately laminated, another layer may be present between them. For example, an alloy layer containing an element contained in the negative electrode active material layer 201(a) and an element contained in the separation layer 210 may be present.

[0051] Furthermore, the elements contained in the layers and films, including the negative electrode active material layer 201(a) and the separation layer 210, do not necessarily have to be distributed uniformly within the film. For example, there may be a concentration gradient for some elements. For example, when the above-mentioned alloy layer is present, the alloy layer may have a concentration gradient for silicon or titanium.

[0052] It can be confirmed that layers, films, etc., including the negative electrode active material layer 201(a) and the separation layer 210 have different compositions from adjacent layers, films, etc., by TEM (transmission electron microscope) images, STEM (scanning transmission electron microscope) images, FFT (fast Fourier transform) analysis, EDX (energy dispersive X-ray analysis), ToF-SIMS (time-of-flight secondary ion mass spectrometry) depth analysis, XPS (X-ray photoelectron spectroscopy), Auger electron spectroscopy, TDS (thermal desorption spectrometry), etc. The thicknesses of the layers, films, etc. can be measured from these results.

[0053] For example, when an alloy layer having a concentration gradient of silicon and titanium is present between anode active material layer 201 having silicon and separation layer 210 having a titanium compound, the concentration gradient can be confirmed by EDX analysis of the cross section of the anode, depth-wise analysis from the surface of the anode by ToF-SIMS, or the like. In this case, a region of the alloy layer having a titanium concentration equal to or more than half the titanium concentration of separation layer 210 may be treated as separation layer 210. Similarly, a region of the alloy layer having a titanium concentration less than half the titanium concentration of separation layer 210 may be treated as anode active material layer 201.

[0054] Furthermore, the negative electrode active material layer 201(a) and the separation layer 210 of one embodiment of the present invention do not necessarily have to be in a film or plate shape. They may have a partially curved surface or may be in a particulate shape. For example, as shown in FIG. 2D , they may be particles having a separation layer 210 between a plurality of negative electrode active material layers 201(a). In this case, the radius and thickness of the negative electrode active material layer 201(a) and the separation layer 210 can be determined by taking into account the film thickness of each layer in this specification and the like.

[0055] <Negative electrode configuration example 2> In the negative electrode active material layer 201(A) according to one embodiment of the present invention, as shown in FIG. 3A, the thickness of each negative electrode active material layer 201(a) may be different from one another. As described above, the thickness of each negative electrode active material layer 201(a) is preferably 20 nm or more and less than 100 nm, and more preferably 40 nm or more and 80 nm or less. The material of each negative electrode active material layer 201(a) may be different from one another. For example, the main component of the k-th negative electrode active material layer 201(a) may be Si, and the main component of the k+1-th negative electrode active material layer 201(a) may be SiO.

[0056] <Negative electrode configuration example 3> In the negative electrode active material layer 201(A) according to one embodiment of the present invention, as shown in FIG. 3B, the thickness of each separation layer 210 may be different. As described above, the thickness of each separation layer 210 is preferably 5 nm or more and 40 nm or less, and more preferably 5 nm or more and 20 nm or less. The material of each separation layer 210 may be different. For example, the kth separation layer may contain titanium, and the k+1th separation layer may contain titanium nitride.

[0057] <Negative Electrode Configuration Example 4> As shown in FIG. 3C, the negative electrode active material layer 201(A) according to one embodiment of the present invention is preferably formed by stacking a layer 212 containing titanium, titanium nitride, or titanium oxynitride on the uppermost negative electrode active material layer 201(a). For example, when silicon is used for the uppermost negative electrode active material layer 201(a), the uppermost negative electrode active material layer 201(a) comes into contact with an electrolyte layer or an electrolyte solution. The electrolyte layer or electrolyte solution may contain oxygen or fluorine. In this case, the silicon in the uppermost negative electrode active material layer 201(a) may react with oxygen or fluorine by the battery reaction, resulting in a decrease in capacity. This reaction can be suppressed by stacking a layer 212 containing titanium, titanium nitride, or titanium oxynitride on the uppermost negative electrode active material layer 201(a), and therefore the decrease in capacity can be suppressed while maintaining electrical conductivity.

[0058] <Negative Electrode Configuration Example 5> 3D , the negative electrode active material layer 201(A) of one embodiment of the present invention may further include a layer 212 containing titanium, titanium nitride, or titanium oxynitride stacked under the lowest negative electrode active material layer 201(a). By providing the layer 212 between the lowest negative electrode active material layer 201(a) and the negative electrode current collector layer 200, the possibility that the negative electrode active material layer 201(a) will crack, collapse, or the like can be further reduced while maintaining conductivity.

[0059] A secondary battery can be made by providing a solid electrolyte and a positive electrode on the negative electrode having the above configuration. Fig. 4A is a top view of the secondary battery, and Fig. 4B is an example of a cross-sectional view taken along the line A-A' in Fig. 4A. In Fig. 4B, the first layer of the negative electrode active material layer 201(A) is shown as 201(1), and the second layer as 201(2). The secondary battery has a negative electrode collector layer 200, a negative electrode active material layer 201(A), a solid electrolyte layer 202, a positive electrode active material layer 203, a positive electrode collector layer 205, and a protective layer 206 on a substrate 101.

[0060] FIG. 4B shows an example in which the secondary battery has one separation layer 210 between the negative electrode active material layer 201(1) and the negative electrode active material layer 201(2) as in FIG. 2C.

[0061] 4C shows an example in which the secondary battery further includes a layer 212 containing titanium, titanium nitride, or titanium oxynitride as shown in FIG 3C. The layer 212 containing titanium, titanium nitride, or titanium oxynitride may be provided only in a region overlapping with the negative electrode active material layer 201(A), or may be provided so as to cover the negative electrode active material layer 201(A) and the negative electrode current collector layer 200 as shown in FIG 4C. By providing the layer 212 containing titanium, titanium nitride, or titanium oxynitride as shown in FIG 4C, the possibility of cracking, crumbling, or the like occurring in the negative electrode active material layer 201(a) may be further reduced.

[0062] This embodiment mode can be implemented in appropriate combination with other embodiment modes.

[0063] (Embodiment 2) In this embodiment, a method for manufacturing the solid-state secondary battery described in Embodiment 1 will be described. An example of a manufacturing flow for obtaining the structures shown in FIGS. 4A and 4B is shown in FIG. 5.

[0064] First, a negative electrode current collector layer 200 is formed on a substrate. As a film formation method, a sputtering method, an evaporation method, or the like can be used. Also, a conductive substrate may be used as the current collector. As the negative electrode current collector layer, the above-described materials can be used. The negative electrode current collector layer 200 preferably has a thickness of 5 μm or more and 100 μm or less, more preferably 5 μm or more and 30 μm.

[0065] Next, the first negative electrode active material layer 201(a) is formed. In the drawings, it is shown as the first negative electrode active material layer 201(1). The negative electrode active material layer 201(a) can be formed using a sputtering method or the like. The materials to be used can be considered in light of the description of the previous embodiment.

[0066] Next, the first separator layer 210 is formed. As a film formation method for the separator layer 210, a sputtering method, an evaporation method, or the like can be used. Also, in the sputtering method, selective film formation can be achieved by using a metal mask. Further, the separator layer 210 may be patterned by selectively removing it by dry etching or wet etching using a resist mask or the like. Also, the separator layer 210 preferably contains titanium (Ti), titanium nitride (TiN), or titanium oxynitride (TiOxNy, 0 < x < 2, 0 < y < 1). When titanium nitride is used as the separator layer 210, for example, titanium nitride can be formed by a reactive sputtering method using a titanium target and nitrogen gas. When titanium oxynitride is used as the separator layer 210, for example, titanium oxynitride can be formed by a reactive sputtering method using a titanium oxide target and nitrogen gas.

[0067] Next, a second negative electrode active material layer 201(a) is formed. In the drawing, this is shown as the first negative electrode active material layer 201(2). The same materials and film formation methods as those for the first negative electrode active material layer 201(a) can be used, but the second negative electrode active material layer may be formed using different materials and film formation methods. The film thickness of the second negative electrode active material layer 201(a) may be the same as or different from that of the first negative electrode active material layer 201(a).

[0068] After the second negative electrode active material layer 201(a), the separation layer 210 and the negative electrode active material layer 201(a) may be alternately laminated according to the number of layers of the negative electrode active material layers required. At this time, there is no particular limit to the thickness and material of each negative electrode active material layer, and each layer may have a different thickness and material, but it is preferable to form each layer with the same material and thickness because it is easy to form each layer. Similarly, there is no particular limit to the thickness and material of each separation layer 210, and each layer may have a different thickness and material, but it is preferable to form each layer with the same material and thickness because it is easy to form each layer. FIG. 4B shows a case where the negative electrode active material layer is two layers of the negative electrode active material layer 201(1) and the negative electrode active material layer 201(2), and the separation layer 210 is one layer.

[0069] After forming the n-th negative electrode active material layer 201(n), the solid electrolyte layer 202 is formed. The material of the solid electrolyte layer is Li 0.35 La 0.55 TiO 3、 La (2 / 3-x) Li (3x) TiO 3 , Li 3 PO 4、 Li x PO (4-y) Ny, LiNb (1-x) Ta (x) WO 6 , Li 7 La 3 Zr 2 O 12 , Li (1+x) Al (x) Ti (2-x) (PO 4 ) 3 , Li (1+x) Al (x) Ge (2-x) (PO4 ) 3 , LiNbO 2 , etc. can be mentioned. As the film formation method, a sputtering method, an evaporation method, etc. can be used. Also, SiO X (0 < X ≤ 2) can also be used as the solid electrolyte layer 202.

[0070] Next, the positive electrode active material layer 203 is formed. A sputtering target mainly composed of lithium cobalt oxide (for example, LiCoO 2 , LiCo 2 O 4 , etc.), a sputtering target mainly composed of lithium manganese oxide (for example, LiMnO 2 , LiMn 2 O 4 , etc.), or a sputtering target mainly composed of lithium nickel oxide (for example, Li to O 2 , LiNi 2 O 4 , etc.) can be used to form a film by the sputtering method. Also, lithium manganese cobalt oxide (for example, LiMnCoO 4 , Li 2 MnCoO 4 , etc.), a ternary material of nickel cobalt manganese (for example, LiNi 1 / 3 Mn 1 / 3 Co 1 / 3 O 2 : NCM), a ternary material of nickel cobalt aluminum (for example, LiNi 0.8 Co 0.15 Al 0.05 O 2 : NCA), etc. can also be used. Also, a film may be formed by the vacuum evaporation method.

[0071] Also, it is preferable to form the positive electrode active material layer 203 at a high temperature (500°C or higher). Or, it is preferable to perform annealing treatment (500°C or higher) after forming the positive electrode active material layer 203. By adopting such a manufacturing method, a positive electrode active material layer 203 with better crystallinity can be manufactured.

[0072] Next, the positive electrode current collector layer 205 is formed. As the material of the positive electrode current collector layer 205, the above-mentioned materials can be used.

[0073] Next, a protective layer 206 is formed. It is preferable to use a silicon nitride film (also called a SiN film) as the protective layer 206. The silicon nitride film can be formed by using a sputtering method.

[0074] In addition, when the negative electrode current collector layer 200 and the positive electrode current collector layer 205 are formed by a sputtering method, it is preferable to form at least one of the positive electrode active material layer 203 and the negative electrode active material layer 201(a) by a sputtering method. The sputtering device can perform continuous film formation in the same chamber or using multiple chambers, and can also be a multi-chamber type manufacturing device or an in-line type manufacturing device. The sputtering method is a manufacturing method suitable for mass production using a chamber and a sputtering target. In addition, the sputtering method can be formed thinly and has excellent film formation characteristics.

[0075] When the negative electrode current collector layer 200 and the negative electrode active material layer 201(a) are formed by sputtering, it is preferable to form them successively. When the positive electrode current collector layer 205 and the positive electrode active material layer 203 are formed by sputtering, it is preferable to form them successively. By forming them successively, contamination of the interface between them can be reduced. Furthermore, the production time can be shortened.

[0076] Furthermore, the layers described in this embodiment are not limited to being formed by sputtering, and gas phase methods (vacuum deposition, thermal spraying, pulsed laser deposition (PLD), ion plating, cold spray, aerosol deposition) can also be used. The aerosol deposition (AD) method is a method for forming a film without heating the substrate. Aerosol refers to fine particles dispersed in a gas. Alternatively, a CVD method or an ALD (Atomic Layer Deposition) method can be used.

[0077] This embodiment mode can be implemented in appropriate combination with other embodiment modes.

[0078] (Embodiment 3) In this embodiment, an example of a material that can be used in a secondary battery having a negative electrode according to one embodiment of the present invention will be described. In this embodiment, a secondary battery in which a positive electrode, a negative electrode according to one embodiment of the present invention, and an electrolyte solution are wrapped in an exterior body will be described as an example.

[0079] [Positive electrode] The positive electrode has a positive electrode active material layer and a positive electrode current collector layer.

[0080] <Cathode active material layer> The positive electrode active material layer can have a positive electrode active material film or positive electrode active material particles as a positive electrode active material. If the positive electrode active material film is included, it can be combined with the negative electrode of one embodiment of the present invention to form a thin-film battery, which is preferable. On the other hand, if the positive electrode active material particles are included, a high-capacity positive electrode can be produced inexpensively, and productivity is good. In addition, if the positive electrode active material particles are included, a so-called core-shell structure in which the composition is different between the surface layer and the inside may improve cycle characteristics, which is more preferable.

[0081] The positive electrode active material layer may also contain a conductive assistant and a binder.

[0082] The material of the positive electrode active material particles may be a composite oxide having an olivine type crystal structure, a layered rock salt type crystal structure, or a spinel type crystal structure. For example, LiFePO 4 , LiFeO 2 , LiCoO 2 , LiNiO 2 , LiMn 2 O 4 , V 2 O 5 , Cr 2 O 5 , MnO 2 Compounds such as the above are included.

[0083] In particular, LiCoO 2 The capacity is large, and LiNiO 2 It is more stable in air than LiNiO 2It is preferable because it is thermally more stable compared to

[0084] In addition, it is preferable to mix a lithium-containing material having a spinel-type crystal structure containing manganese such as LiMn 2 O 4 with lithium nickelate (LiNiO 2 or LiNi 1-x M x O 2 (0 < x < 1) (M = Co, Al, etc.)). By adopting such a configuration, the characteristics of the secondary battery can be improved.

[0085] In addition, as the positive electrode active material, a lithium manganese composite oxide represented by the composition formula Li a Mn b M c O d can be used. Here, the element M is preferably a metal element selected from those other than lithium and manganese, or silicon or phosphorus, and more preferably nickel. When measuring the entire film of the lithium manganese composite oxide, it is preferable to satisfy 0 < a / (b + c) < 2, c > 0, and 0.26 ≤ (b + c) / d < 0.5 during discharge. The composition of metals, silicon, phosphorus, etc. in the entire particle film of the lithium manganese composite oxide can be measured using, for example, ICP-MS (inductively coupled plasma mass spectrometer). Also, the oxygen composition of the entire film of the lithium manganese composite oxide can be measured using, for example, EDX (energy dispersive X-ray analysis method). In addition, it can be obtained by using the valence evaluation of melting gas analysis and XAFS (X-ray absorption fine structure) analysis in combination with ICP-MS analysis. The lithium manganese composite oxide refers to an oxide containing at least lithium and manganese, and may contain at least one element selected from the group consisting of chromium, cobalt, aluminum, nickel, iron, magnesium, molybdenum, zinc, indium, gallium, copper, titanium, niobium, silicon, and phosphorus.

[0086] The conductive assistant may be a carbon material, a metal material, a conductive ceramic material, or the like. A fibrous material may also be used as the conductive assistant. The content of the conductive assistant relative to the total amount of the active material layer is preferably 1 wt% to 10 wt%, more preferably 1 wt% to 5 wt%.

[0087] The conductive assistant can form an electrical conductive network in the positive electrode active material. The conductive assistant can maintain an electrical conductive path between the positive electrode active materials. By adding the conductive assistant to the active material layer, an active material layer having high electrical conductivity can be realized.

[0088] As the conductive assistant, for example, natural graphite, artificial graphite such as mesocarbon microbeads, carbon fiber, etc. can be used. As the carbon fiber, for example, mesophase pitch carbon fiber, isotropic pitch carbon fiber, etc. can be used. As the carbon fiber, carbon nanofiber, carbon nanotube, etc. can be used. Carbon nanotube can be produced by, for example, vapor phase growth method, etc. As the conductive assistant, for example, carbon material such as carbon black (acetylene black (AB) etc.), graphite (graphite) particles, graphene, fullerene, etc. can be used. As the conductive assistant, for example, metal powder or metal fiber such as copper, nickel, aluminum, silver, gold, etc., conductive ceramic material, etc. can be used. These materials may be used in combination.

[0089] In addition, a graphene compound may be used as the conductive assistant.

[0090] Graphene compounds may have excellent electrical properties such as high electrical conductivity, and excellent physical properties such as high flexibility and high mechanical strength. Graphene compounds may also have a sheet-like shape. Graphene compounds may have a curved surface, enabling surface contact with low contact resistance. Graphene compounds may also have very high electrical conductivity even when thin, and can efficiently form a conductive path in an active material layer with a small amount. Therefore, it is preferable to use a graphene compound as a conductive assistant, since it is possible to increase the contact area between the active material and the conductive assistant.

[0091] As the binder, it is preferable to use a rubber material such as styrene-butadiene rubber (SBR), styrene-isoprene-styrene rubber, acrylonitrile-butadiene rubber, butadiene rubber, ethylene-propylene-diene copolymer, etc. Also, as the binder, fluororubber can be used.

[0092] Moreover, it is preferable to use, for example, a water-soluble polymer as the binder. For example, polysaccharides can be used as the water-soluble polymer. For example, cellulose derivatives such as carboxymethyl cellulose (CMC), methyl cellulose, ethyl cellulose, hydroxypropyl cellulose, diacetyl cellulose, and regenerated cellulose, and starch can be used as the polysaccharide. It is even more preferable to use these water-soluble polymers in combination with the above-mentioned rubber material.

[0093] Alternatively, it is preferable to use materials such as polystyrene, polymethyl acrylate, polymethyl methacrylate (PMMA), sodium polyacrylate, polyvinyl alcohol (PVA), polyethylene oxide (PEO), polypropylene oxide, polyimide, polyvinyl chloride, polytetrafluoroethylene, polyethylene, polypropylene, polyisobutylene, polyethylene terephthalate, nylon, polyvinylidene fluoride (PVDF), polyacrylonitrile (PAN), ethylene propylene diene polymer, polyvinyl acetate, and nitrocellulose as the binder.

[0094] The binder may be used in combination of two or more of the above.

[0095] For example, a material having a particularly excellent viscosity adjusting effect may be used in combination with another material. For example, while rubber materials and the like have excellent adhesive strength and elasticity, it may be difficult to adjust the viscosity when mixed with a solvent. In such a case, it is preferable to mix the material with a material having a particularly excellent viscosity adjusting effect. For example, a water-soluble polymer may be used as a material having a particularly excellent viscosity adjusting effect. In addition, as a water-soluble polymer having a particularly excellent viscosity adjusting effect, the above-mentioned polysaccharides, for example, carboxymethylcellulose (CMC), methylcellulose, ethylcellulose, hydroxypropylcellulose, diacetylcellulose, cellulose derivatives such as regenerated cellulose, and starch may be used.

[0096] In addition, the solubility of cellulose derivatives such as carboxymethylcellulose is increased by converting them into salts such as sodium salts and ammonium salts of carboxymethylcellulose, and they are more likely to exhibit their effect as viscosity adjusters. The increased solubility can also increase the dispersibility of the active material and other components when preparing an electrode slurry. In this specification, the cellulose and cellulose derivatives used as electrode binders include their salts.

[0097] Water-soluble polymers stabilize the viscosity by dissolving in water, and can stably disperse active materials and other materials combined as binders, such as styrene-butadiene rubber, in an aqueous solution. In addition, since they have functional groups, they are expected to be easily and stably adsorbed onto the surface of active materials. In addition, many cellulose derivatives, such as carboxymethyl cellulose, have functional groups such as hydroxyl groups and carboxyl groups, and since they have functional groups, the polymers are expected to interact with each other and widely cover the surface of the active material.

[0098] When the binder covers the active material surface or contacts the surface to form a film, it is expected to function as a passive film and suppress the decomposition of the electrolyte. Here, the passive film is a film with no electrical conductivity or a film with extremely low electrical conductivity. For example, when a passive film is formed on the surface of the active material, it can suppress the decomposition of the electrolyte at the battery reaction potential. Moreover, it is more preferable that the passive film suppresses electrical conductivity and can conduct lithium ions.

[0099] [Electrolyte] The electrolytic solution has a solvent and an electrolyte. The solvent of the electrolytic solution is preferably an aprotic organic solvent, and for example, one of ethylene carbonate (EC), propylene carbonate (PC), butylene carbonate, chloroethylene carbonate, vinylene carbonate, γ-butyrolactone, γ-valerolactone, dimethyl carbonate (DMC), diethyl carbonate (DEC), ethyl methyl carbonate (EMC), methyl formate, methyl acetate, ethyl acetate, methyl propionate, ethyl propionate, propyl propionate, methyl butyrate, 1,3-dioxane, 1,4-dioxane, dimethoxyethane (DME), dimethyl sulfoxide, diethyl ether, methyl diglyme, acetonitrile, benzonitrile, tetrahydrofuran, sulfolane, sultone, etc., or two or more of these can be used in any combination and ratio.

[0100] In addition, by using one or more ionic liquids (room-temperature molten salts) that are flame-retardant and non-volatile as a solvent for the electrolyte, even if the internal temperature of the electricity storage device rises due to an internal short circuit or overcharging, the electricity storage device can be prevented from bursting or catching fire. The ionic liquid is composed of a cation and an anion, and includes an organic cation and an anion. Examples of the organic cation used in the electrolyte include aliphatic onium cations such as quaternary ammonium cations, tertiary sulfonium cations, and quaternary phosphonium cations, and aromatic cations such as imidazolium cations and pyridinium cations. Examples of the anion used in the electrolyte include monovalent amide anions, monovalent methide anions, fluorosulfonic acid anions, perfluoroalkylsulfonic acid anions, tetrafluoroborate anions, perfluoroalkylborate anions, hexafluorophosphate anions, and perfluoroalkylphosphate anions.

[0101] The electrolyte to be dissolved in the above-mentioned solvent is, for example, LiPF 6 , LiClO 4 , LiAsF 6 , LiBF 4 , LiAlCl 4 , LiSCN, LiBr, LiI, Li 2 SO 4 , Li 2 B 10 Cl 10 , Li 2 B 12 Cl 12 , LiCF 3 SO 3 , LiC 4 F 9 SO 3 , LiC(CF 3 SO 2 ) 3 , LiC(C 2 F 5 SO 2 ) 3 , LiN(CF 3 SO 2 ) 2 , LiN(C 4 F 9 SO 2 )(CF3 SO 2 ), LiN(C 2 F 5 SO 2 ) 2 or any combination and ratio of two or more of these lithium salts can be used.

[0102] The electrolyte used in the electricity storage device is preferably a highly purified electrolyte with a low content of granular waste and elements other than the constituent elements of the electrolyte (hereinafter, simply referred to as "impurities"). Specifically, the weight ratio of impurities to the electrolyte is preferably 1% or less, more preferably 0.1% or less, and even more preferably 0.01% or less.

[0103] In addition, additives such as vinylene carbonate, propane sultone (PS), tert-butylbenzene (TBB), fluoroethylene carbonate (FEC), lithium bis(oxalate)borate (LiBOB), and dinitrile compounds such as succinonitrile and adiponitrile may be added to the electrolyte. The concentration of the additive may be, for example, 0.1 wt % to 5 wt % of the total solvent.

[0104] Alternatively, a polymer gel electrolyte may be used in which a polymer is swollen with an electrolytic solution.

[0105] The use of a polymer gel electrolyte improves safety against leakage, etc. Also, it is possible to make the secondary battery thinner and lighter.

[0106] Examples of the polymer to be gelled include silicone gel, acrylic gel, acrylonitrile gel, polyethylene oxide gel, polypropylene oxide gel, and fluorine-based polymer gel. For example, polymers having a polyalkylene oxide structure such as polyethylene oxide (PEO), PVDF, polyacrylonitrile, and copolymers containing these can be used. For example, PVDF-HFP, which is a copolymer of PVDF and hexafluoropropylene (HFP), can be used. The polymer to be formed may also have a porous shape.

[0107] Note that in the negative electrode according to one embodiment of the present invention shown in Embodiment 1, the negative electrode active material layer 201(a) and the separation layer 210 may be alternately formed on the negative electrode current collector layer 200 by a coating method. For example, the negative electrode according to one embodiment of the present invention can be manufactured by alternately coating an electrode slurry containing Si and a slurry containing Ti. The coating method is advantageous in terms of increasing the area and reducing costs.

[0108] This embodiment mode can be implemented in appropriate combination with other embodiment modes.

[0109] (Embodiment 4) In order to increase the output voltage of the solid-state secondary battery, the solid-state secondary batteries can be connected in series. In this embodiment, an example of solid-state secondary batteries connected in series is shown.

[0110] Fig. 6A shows a top view of a secondary battery in which a first secondary battery 220(1) and a second secondary battery 220(2) are connected in series. Fig. 6B shows a cross-sectional view taken along line B-B' in Fig. 6A. In Figs. 6A and 6B, the same reference numerals are used for the same parts as in Figs. 4A and 4B shown in the second embodiment.

[0111] 6A has a negative electrode current collector layer 200, a first negative electrode, a first solid electrolyte layer 202, a first positive electrode, and a current collector layer 215 on a substrate 101. A second secondary battery 220(2) has a current collector layer 215, a second negative electrode, a second solid electrolyte layer 211, a second positive electrode, and a current collector layer 213 on a substrate 101.

[0112] The current collector layer 215 functions as both a positive electrode current collector layer for the first secondary battery 220(1) and a negative electrode current collector layer for the second secondary battery 220(2). The first secondary battery 220(1) and the second secondary battery 220(2) are electrically connected by the current collector layer 215. The first negative electrode and the second negative electrode are the negative electrodes described in the previous embodiment.

[0113] This embodiment mode can be implemented in appropriate combination with other embodiment modes.

[0114] (Embodiment 5) In this embodiment, an example of a multi-layer cell is shown. Fig. 7 shows one embodiment of the present invention in the case of a multi-layer cell of a thin-film solid secondary battery.

[0115] FIG. 7 shows an example of a cross section of a three-layer cell.

[0116] A negative electrode current collector layer 200 is formed on a substrate 101, and a negative electrode active material layer 201(A), a solid electrolyte layer 202, a positive electrode active material layer 203, and a positive electrode current collector layer 205 are sequentially formed on the negative electrode current collector layer 200 to constitute a first cell.

[0117] Furthermore, a second positive electrode active material layer, a second solid electrolyte layer, a second negative electrode active material layer, and a second negative electrode current collector layer are sequentially formed on the positive electrode current collector layer 205 to form a second cell.

[0118] Furthermore, a third negative electrode active material layer, a third solid electrolyte layer, a third positive electrode active material layer, and a third positive electrode current collector layer are sequentially formed on the second negative electrode current collector to form a third cell.

[0119] In Fig. 7, a protective layer 206 is formed last. The three-layer laminate shown in Fig. 7 is configured to be connected in series to increase capacity, but it can also be connected in parallel with external wiring. Also, series and parallel or series-parallel can be selected with external wiring.

[0120] It is preferable to use the same material for the first solid electrolyte layer 202, the second solid electrolyte layer, and the third solid electrolyte layer, since this reduces manufacturing costs.

[0121] This embodiment mode can be implemented in appropriate combination with other embodiment modes.

[0122] (Embodiment 6) 8A is an external view of a thin-film solid-state secondary battery having a negative electrode according to one embodiment of the present invention. A secondary battery 913 has a terminal 951 and a terminal 952. The terminal 951 is electrically connected to a positive electrode, and the terminal 952 is electrically connected to a negative electrode.

[0123] 8B is an external view of the battery control circuit. The battery control circuit shown in FIG. 8B includes a substrate 900 and a layer 916. A circuit 912 and an antenna 914 are provided over the substrate 900. The antenna 914 is electrically connected to the circuit 912. A terminal 971 and a terminal 972 are electrically connected to the circuit 912. The circuit 912 is electrically connected to a terminal 911.

[0124] The terminal 911 is connected to, for example, a device to which power from the thin-film solid-state secondary battery is supplied, such as a display device, a sensor, or the like.

[0125] The layer 916 has a function of shielding, for example, an electromagnetic field caused by the secondary battery 913. The layer 916 can be made of, for example, a magnetic material.

[0126] 8C shows an example in which the battery control circuit shown in FIG. 8B is disposed on a secondary battery 913. Terminal 971 is electrically connected to terminal 951, and terminal 972 is electrically connected to terminal 952. Layer 916 is disposed between substrate 900 and secondary battery 913.

[0127] The substrate 900 is preferably a flexible substrate.

[0128] A thin battery control circuit can be realized by using a flexible substrate as the substrate 900. In addition, the battery control circuit can be wound around the secondary battery as shown in Fig. 9D, which will be described later.

[0129] 9A is an external view of a thin-film solid-state secondary battery. The battery control circuit shown in FIG.

[0130] As shown in FIG. 9C, by bending the substrate 900 to fit the shape of a secondary battery 913 and arranging the battery control circuit around the secondary battery, the battery control circuit can be wrapped around the secondary battery as shown in FIG. 9D.

[0131] This embodiment mode can be implemented in appropriate combination with other embodiment modes.

[0132] (Embodiment 7) In this embodiment, examples of electronic devices using a thin-film secondary battery will be described with reference to FIGS. 10A, 10B, and 11. A secondary battery having a negative electrode of one embodiment of the present invention can be prevented from cracking, collapsing, or the like, and therefore can improve cycle characteristics, reliability, or safety of the secondary battery. For this reason, the battery can be suitably used in the following electronic devices. In particular, the battery can be suitably used in electronic devices that require durability.

[0133] 10A is a perspective view of the appearance of a thin-film secondary battery 3001. 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 are sealed with an exterior body such as a laminate film or an insulating film so as to protrude.

[0134] 10B shows an IC card as an example of an application device using the thin-film secondary battery according to the present invention. Electric power obtained by power supply from radio waves 3005 can be charged into thin-film secondary battery 3001. An antenna and 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 attached onto IC card 3000. Signals such as authentication signals can also be transmitted from the antenna using the power charged in thin-film secondary battery 3001.

[0135] Moreover, an active matrix display device may be provided in place of the photograph 3003. Examples of active matrix display devices include reflective liquid crystal display devices, organic EL display devices, and electronic paper. Images (moving or still images) and time can also be displayed on the active matrix display device. Power for the active matrix display device can be supplied from a thin-film secondary battery 3001.

[0136] Since a plastic substrate is used in an IC card, an organic EL display device using a flexible substrate is preferable.

[0137] A solar cell may be provided in place of the photograph 3003. When exposed to external light, the light is absorbed, electricity is generated, and the thin-film secondary battery 3001 can be charged with the electricity.

[0138] 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 mounted on vehicles, as a secondary battery for MEMS devices, and the like.

[0139] Figure 11 shows an example of a wearable device. Wearable devices often use secondary batteries as a power source. In order to improve water resistance in daily life or outdoor use, there is a demand for wearable devices that can be charged wirelessly as well as by wires with exposed connectors.

[0140] For example, the secondary battery of one embodiment of the present invention can be mounted on a glasses-type device 400 as illustrated in FIG. 11. The glasses-type device 400 includes a frame 400a and a display portion 400b. By mounting a secondary battery on temple portions of the curved frame 400a, the glasses-type device 400 can be lightweight, well-balanced in weight, and has a long continuous use time. By including the secondary battery described in the above embodiment, a configuration that can accommodate space saving associated with a miniaturized housing can be realized.

[0141] Furthermore, the secondary battery of one embodiment of the present invention can be mounted on a headset type device 401. The headset type device 401 has at least a microphone unit 401a, a flexible pipe 401b, and an earphone unit 401c. The secondary battery can be provided in the flexible pipe 401b or the earphone unit 401c. By providing the secondary battery described in the above embodiment, a configuration that can accommodate space saving associated with a miniaturized housing can be realized.

[0142] Furthermore, the secondary battery of 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. When the secondary battery described in the above embodiment is provided, a configuration that can accommodate space saving due to miniaturization of the housing can be realized.

[0143] Furthermore, the secondary battery of 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. When the secondary battery described in the above embodiment is provided, a configuration that can accommodate space saving due to miniaturization of the housing can be realized.

[0144] 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. When the belt type device 406 includes the secondary battery described in the above embodiment, a configuration that can accommodate space saving associated with miniaturization of the housing can be realized.

[0145] 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. When the wristwatch device 405 includes the secondary battery described in the above embodiment, a configuration that can accommodate space saving due to miniaturization of the housing can be realized.

[0146] Display unit 405a can display not only the time, but also various other information such as incoming e-mails and phone calls.

[0147] In addition, since the wristwatch type device 405 is a wearable device that is directly wrapped around the arm, it may be equipped with sensors that measure the user's pulse, blood pressure, etc. Data on the user's amount of exercise and health can be accumulated and used to maintain health.

[0148] This embodiment mode can be implemented in appropriate combination with other embodiment modes.

[0149] (Embodiment 8) In this embodiment, electronic devices using a secondary battery having a negative electrode of one embodiment of the present invention will be described with reference to FIGS. 12A to 12C and 13A to 13D. A secondary battery having a negative electrode of one embodiment of the present invention can be prevented from cracking, collapsing, or the like, and therefore can improve cycle characteristics, reliability, or safety of the secondary battery. For this reason, the secondary battery can be suitably used in the following electronic devices. In particular, the secondary battery can be suitably used in electronic devices that require durability.

[0150] 12A shows a perspective view of a wristwatch-type mobile information terminal (also called a smart watch) 700. The 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.

[0151] 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. It is preferable that the display panel 702 is flexible. The display area may be non-rectangular.

[0152] Band 705A and band 705B are connected to housing 701. Clasp 703 is connected to band 705A. Band 705A and housing 701 are connected, for example, via a pin 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.

[0153] 12B and 12C are perspective views of the band 705A and the secondary battery 750, respectively. The band 705A has the secondary battery 750. The secondary battery described in the previous embodiment can be used for the secondary battery 750. 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. 12B). 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. 12C). The pins may 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 that connect the band 705A and the housing 701, respectively. In this way, the configuration at the connection portion between the band 705A and the housing 701 can be simplified.

[0154] The secondary battery 750 is flexible. Therefore, the band 705A can be produced by integrally forming it with the secondary battery 750. For example, the secondary battery 750 is set in a mold that corresponds to the outer shape of the band 705A, and the material of the band 705A is poured into the mold and the material is hardened, thereby producing the band 705A shown in FIG. 12B.

[0155] When a rubber material is used as the material of 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.

[0156] Materials used for the band 705A include fluororubber, silicone rubber, fluorosilicone rubber, and urethane rubber.

[0157] 12A 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 a program or data recorded in a recording medium and displaying it in a display area, etc.

[0158] The housing 701 may also have a speaker, a sensor (including a function of measuring force, displacement, position, speed, 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, or the like inside the housing 701. The portable information terminal 700 can be manufactured by using a light-emitting element for the display panel 702.

[0159] 12A 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.

[0160] 13A 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 surface, a brush 6304, an operation button 6305, various sensors 6306, 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 provided on the bottom surface.

[0161] For example, the cleaning robot 6300 can analyze an image captured by the camera 6303 and determine the presence or absence of an obstacle such as a wall, furniture, or a step. When an object that may become entangled in the brush 6304, such as a wire, is detected by image analysis, the rotation of the brush 6304 can be stopped. The cleaning robot 6300 includes a secondary battery according to one embodiment of the present invention and a semiconductor device or electronic component therein. By using the secondary battery according to one embodiment of the present invention in the cleaning robot 6300, the cleaning robot 6300 can be an electronic device with long operating time and high reliability.

[0162] Fig. 13B shows an example of a robot. The robot 6400 shown in Fig. 13B 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 moving mechanism 6408, a computing device, and the like.

[0163] 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.

[0164] 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 removable information terminal, and by installing it in a fixed position on the robot 6400, charging and data transfer are possible.

[0165] The upper camera 6403 and the lower camera 6406 have a function of capturing images of the surroundings of the robot 6400. In addition, the obstacle sensor 6407 can detect the presence or absence of an obstacle in the moving direction when the robot 6400 moves forward using the moving 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.

[0166] The robot 6400 includes a secondary battery 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.

[0167] Fig. 13C shows an example of an aircraft. An aircraft 6500 shown in Fig. 13C has a propeller 6501, a camera 6502, a secondary battery 6503, and the like, and has a function of flying autonomously.

[0168] 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. The electronic component 6504 can estimate the remaining battery charge from a change in the power storage capacity of the secondary battery 6503. The flying object 6500 includes therein the secondary battery 6503 according to one embodiment of the present invention. 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.

[0169] 13D shows an example of an automobile. The automobile 7160 has a secondary battery 7161, an engine, tires, brakes, a steering device, a camera, and the like. The automobile 7160 is equipped with 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 driving range, a long life, high safety, and high reliability.

[0170] This embodiment mode can be implemented in appropriate combination with other embodiment modes.

[0171] (Embodiment 9) The device described in this embodiment has at least a biosensor and the secondary battery described in the previous embodiment that supplies power to the biosensor, and can obtain various types of bioinformation using infrared light and visible light and store the information in a memory. Such bioinformation can be used for both personal authentication of a user and health care. The secondary battery of one embodiment of the present invention has high discharge capacity and cycle characteristics, and is also highly safe. Therefore, the device can be used for a long period of time.

[0172] A biosensor is a sensor that acquires biological information, and acquires biological information that can be used for healthcare purposes. The biological information includes pulse wave, blood glucose level, oxygen saturation, triglyceride concentration, etc. The data is stored in a memory.

[0173] Furthermore, it is preferable to provide a means for acquiring other biological information in the device described in this embodiment. For example, in addition to internal biological information such as electrocardiogram, blood pressure, and body temperature, there is superficial biological information such as facial expression, complexion, and pupils. Information on the number of steps, exercise intensity, elevation change, and diet (calories ingested, nutrients, etc.) are also important information for health care. Using multiple biological information enables comprehensive health management, which leads not only to daily health management but also to early detection of injuries and illnesses.

[0174] For example, blood pressure can be calculated from an electrocardiogram and the difference in timing between the two beats of a pulse wave (length of pulse wave propagation time). High blood pressure results in a short pulse wave propagation time, and conversely, low blood pressure results in a long pulse wave propagation time. The relationship between heart rate and blood pressure calculated from an electrocardiogram and pulse wave can also be used to estimate the user's physical condition. For example, if both the heart rate and blood pressure are high, it can be estimated that the user is in a state of tension or excitement, and conversely, if both the heart rate and blood pressure are low, it can be estimated that the user is in a relaxed state. Furthermore, if the user continues to have low blood pressure and a high heart rate, this may be a sign of heart disease.

[0175] Users can check their own physical condition estimated based on the biometric information measured by electronic devices at any time, which will improve their health awareness. As a result, they may be prompted to review their daily habits, such as avoiding overeating and drinking, taking appropriate exercise, and managing their physical condition, and may even be prompted to receive a medical examination if necessary.

[0176] Each data may be shared among multiple biosensors. Fig. 14A shows an example in which a biosensor 80a is embedded in a user's body and an example in which a biosensor 80b is attached to the user's wrist. Fig. 14A shows a device having a biosensor 80a capable of measuring an electrocardiogram, for example, and a device having a biosensor 80b capable of measuring a user's heart rate by optically monitoring the pulse of the user's arm. Note that the wearable device of the watch or wristband type shown in Fig. 14A is not limited to measuring a heart rate, and various biosensors can be used.

[0177] 14A is premised on being small, generating almost no heat, and causing no allergic reactions when it comes into contact with the skin. The secondary battery used in the device of one embodiment of the present invention is suitable because it is small, generates almost no heat, and causes no allergic reactions. In addition, it is preferable that the embedded device has a built-in antenna to enable wireless charging.

[0178] The device of the type implanted in a living body shown in FIG. 14A is not limited to a biosensor capable of measuring an electrocardiogram, and a biosensor capable of acquiring other biological data can be used.

[0179] The biosensor 80b built into the device may be temporarily stored in a memory built into the device. Alternatively, the data acquired by the biosensors may be sent wirelessly or via wire to a portable data terminal 85 in FIG. 14B, and the waveform may be detected by the portable data terminal 85. The portable data terminal 85 is a smartphone or the like, and can detect whether a problem such as arrhythmia has occurred from the data acquired from each biosensor. When sending data acquired by multiple biosensors to the portable data terminal 85 via wire, it is preferable to transfer the acquired data acquired before connecting via wire together. Each detected data may be automatically assigned a date and stored in the memory of the portable data terminal 85, and managed personally. Alternatively, the data may be sent to a medical institution 87 such as a hospital via a network (including the Internet) as shown in FIG. 14B. The data is managed by a data server of the hospital, and can be used as test data during treatment. Since the amount of medical data may be huge, a network including Bluetooth (registered trademark) or a frequency band of 2.4 GHz to 2.4835 GHz may be used from the biosensor 80b to the portable data terminal 85, and a fifth-generation (5G) wireless system may be used from the portable data terminal 85 to the portable data terminal 85 for high-speed communication. The fifth-generation (5G) wireless system uses frequencies of 3.7 GHz, 4.5 GHz, and 28 GHz. By using the fifth-generation (5G) wireless system, data can be acquired and transmitted to a medical institution 87 not only at home but also when going out, and data when the user's physical condition is abnormal can be accurately acquired and used for subsequent processing or treatment. The configuration shown in FIG. 14C can be used as the portable data terminal 85.

[0180] 14C shows another example of a portable data terminal 89. The portable data terminal 89 has a speaker, a pair of electrodes 83, a camera 84, and a microphone 86 in addition to a secondary battery.

[0181] A pair of electrodes 83 are provided on a part of the housing 82, sandwiching a display unit 81a therebetween. The display unit 81b is a region having a curved surface. The electrodes 83 function as electrodes for acquiring biological information.

[0182] As shown in FIG. 14C, by arranging a pair of electrodes 83 in the longitudinal direction of housing 82, when using portable data terminal 89 with a landscape screen, biometric information can be acquired without the user being aware of it.

[0183] 1 shows an example of a usage state of a portable data terminal 89. The display unit 81a can display electrocardiogram information 88a acquired by a pair of electrodes 83, heart rate information 88b, and the like.

[0184] This function is unnecessary when biosensor 80a is embedded in the user's body as shown in Fig. 14A, but when biosensor 80a is not embedded, the user can obtain an electrocardiogram by holding a pair of electrodes 83 with both hands. Even when biosensor 80a is embedded in the user's body, portable data terminal 89 shown in Fig. 14C can be used to compare electrocardiogram data with that of other users to check whether biosensor 80a is functioning normally.

[0185] The camera 84 can capture an image of the user's face, etc. From the image of the user's face, biological information such as facial expression, pupils, and complexion can be obtained.

[0186] The microphone 86 can acquire the user's voice. Voiceprint information that can be used for voiceprint authentication can be acquired from the acquired voice information. In addition, voice information can be acquired periodically and changes in voice quality can be monitored for use in health management. Of course, the microphone 86, camera 84, and speaker can also be used to make a videophone call with a doctor at a medical institution 87.

[0187] By using the device shown in FIG. 14A and the portable data terminal 89 shown in FIG. 14C, a remote medical support system can be realized in which information can be sent from a remote location to a doctor in a hospital and the patient can receive medical treatment from the doctor.

[0188] This embodiment mode can be implemented in appropriate combination with other embodiment modes. EXAMPLES

[0189] In this example, a secondary battery having a negative electrode according to one embodiment of the present invention or a comparative negative electrode and its characteristics are described. The structure of the negative electrode prepared in this example is shown in Figs. 15A to 15C and Table 1. Comparative sample 1, which is a comparative example for the present invention, has a structure in which the negative electrode active material layer is one layer. Sample 2, which is one embodiment of the present invention, has two negative electrode active material layers and one separation layer. Sample 3, which is one embodiment of the present invention, has five negative electrode active material layers and four separation layers. Each sample was prepared so that the total thickness of the amorphous silicon (a-Si) layer, which is the negative electrode active material, was 100 nm.

[0190] [Table 1]

[0191] <Preparation of Comparative Sample 1> An amorphous silicon film was formed by sputtering on a titanium (Ti) sheet having a thickness of 100 μm so as to have the structure shown in FIG. 15A and the film thickness shown in Table 1.

[0192] <Preparation of Sample 2 and Sample 3> Amorphous silicon and titanium were alternately formed on a titanium (Ti) sheet having a thickness of 100 μm by sputtering so as to obtain the structure shown in FIG. 15B or FIG. 15C and the film thickness and structure shown in Table 1.

[0193] <Preparation of secondary battery> Next, in order to examine the charge-discharge characteristics of each sample obtained above, a coin-type secondary battery of CR2032 type (diameter 20 mm, height 3.2 mm) was fabricated. The secondary battery had a positive electrode, a negative electrode, a separator, an electrolyte, a positive electrode can electrically connected to the positive electrode, and a negative electrode can electrically connected to the negative electrode.

[0194] The counter electrode was made of lithium metal, and a separator (described later) was sandwiched between the lithium and the negative electrode active material layer.

[0195] The electrolyte contained 1 mol / L lithium hexafluorophosphate (LiPF 6 ) was used, and the electrolyte was a mixture of ethylene carbonate (EC) and diethyl carbonate (DEC) at a volume ratio of EC:DEC = 3:7. For the secondary batteries used to evaluate the charge / discharge characteristics, 10 wt% of FEC (fluoroethylene carbonate) was added to the electrolyte.

[0196] The separator was made of polypropylene having a thickness of 25 μm.

[0197] The positive electrode can and the negative electrode can were made of stainless steel (SUS).

[0198] <Measurement of cycle characteristics> Next, the cycle characteristics of the secondary battery thus prepared were evaluated. First, the battery was discharged at CCCV (0.05C, 4.6V, end current 0.005C) and charged at CC (0.05C, 2.5V) for two cycles at 25°C. The two cycles of charge and discharge were not included in the number of cycle characteristics. Then, the battery was discharged at CCCV (0.2C, 4.6V, end current 0.02C) and charged at CC (0.2C, 2.5V) for repeated charge and discharge at 25°C to evaluate the cycle characteristics. The measurement results after the second cycle are shown in FIG. 16. Since this embodiment is a negative electrode monopolarity evaluation, the insertion of lithium ions into the negative electrode active material layer is called discharging, and the desorption of lithium ions from the negative electrode active material layer is called charging.

[0199] 16, it can be seen that Samples 2 and 3, which are embodiments of the present invention, have larger capacities and better cycle characteristics than Comparative Sample 1. In addition, the charge / discharge efficiency at the 39th cycle was 86.7% for Comparative Sample 1, whereas it was 89.0% for both Samples 2 and 3. It was therefore found that by alternately laminating negative electrode active material layers and separation layers, a secondary battery with large capacity, good cycle characteristics, and high charge / discharge efficiency can be fabricated.

[0200] <Cross-sectional STEM (scanning transmission electron microscope) image> Next, cross-sectional STEM images of Sample 2 before and after charge / discharge are shown in FIG. 17A and FIG. 17B, respectively. Cross-sectional STEM images of Sample 3 before and after charge / discharge are shown in FIG. 18A and FIG. 18B, respectively. It was found from FIG. 17A to FIG. 18B that the film quality of each sample did not change significantly before and after charge / discharge. Thus, according to one embodiment of the present invention, a secondary battery with high cycle characteristics, high reliability, and high safety can be manufactured. EXAMPLES

[0201] This example describes one embodiment of the present invention having a structure different from that of the sample described in Example 1. The structure of the negative electrode (sample 4) produced in this example is shown in FIG. 19 and Table 2. Sample 4 further has a Ti film on the negative electrode active material layer 201(2) of Sample 2.

[0202] [Table 2]

[0203] <Preparation of Sample 4> Amorphous silicon and titanium were alternately formed on a titanium (Ti) sheet having a thickness of 100 μm by sputtering so as to obtain the structure shown in FIG.

[0204] <Battery cell production> Next, in order to examine the charge / discharge characteristics of the sample 4 obtained above, a coin-type secondary battery of CR2032 type (diameter 20 mm, height 3.2 mm) was fabricated in the same manner as in Example 1.

[0205] <Negative electrode before and after charging and discharging> 20A to 20C show the appearances of Comparative Sample 1, Sample 2, and Sample 4, respectively, after 40 cycles of charge and discharge. Note that FIG. 20A shows Comparative Sample 1, FIG. 20B shows Sample 2, and FIG. 20C shows Sample 4. Note that the charge and discharge conditions were the same as those described in Example 1. In the photographs, the negative electrode active material layer appears black. The gray areas are areas where the negative electrode active material layer has peeled off and the titanium sheet is visible.

[0206] It can be seen that the peeling of the negative electrode active material layer is suppressed in FIG. 20B and FIG. 20C compared with FIG. 20A. That is, according to one embodiment of the present invention, the cycle characteristics, reliability, or safety of the secondary battery can be improved. Moreover, when FIG. 20B is compared with FIG. 20C, it can be seen that the peeling of the negative electrode active material layer is further suppressed in FIG. 20C. Therefore, it was found that the cycle characteristics, reliability, or safety of the secondary battery can be improved by introducing a film containing Ti between the negative electrode active material layer and the electrolyte layer or the electrolyte solution. [Explanation of symbols]

[0207] 80a: biosensor, 80b: biosensor, 81a: display unit, 81b: display unit, 82: housing, 83: electrode, 84: camera, 85: portable data terminal, 86: microphone, 87: medical institution, 88a: information, 88b: information, 89: portable data terminal, 101: substrate, 150: secondary battery, 152: secondary battery, 200: negative electrode collector layer, 201: negative electrode active material layer, 202: solid electrolyte layer, 203: positive electrode active material layer, 205: positive electrode collector layer, 206: protective layer, 210: separation layer, 211: solid electrolyte layer, 212: layer, 213: collector layer, 215: collector layer, 220( 1): secondary battery, 220(2): secondary battery, 400: glasses-type device, 400a: frame, 400b: display unit, 401: headset-type device, 401a: microphone unit, 401b: flexible pipe, 401c: earphone unit, 402: device, 402a: housing, 402b: secondary battery, 403: device, 403a: housing, 403b: secondary battery, 405: wristwatch-type device, 405a: display unit, 405b: belt unit, 406: belt-type device, 406a: belt unit, 406b: wireless power supply receiving unit, 511: negative lead electrode, 513 : Positive electrode lead electrode, 700: Portable 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, 900: Substrate, 911: Terminal, 912: Circuit, 913: Secondary battery, 914: Antenna, 916: Layer, 951: Terminal, 952: Terminal, 971: Terminal, 972: Terminal, 3000: IC card, 3001: Thin-film secondary battery, 3002: ID, 3003: Photo, 3004: IC, 300 5: radio waves, 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 parts, 7160: automobile, 7161: secondary battery

Claims

[Claim 1] a negative electrode current collector layer having n negative electrode active material layers (n is an integer of 2 or more) and n-1 separation layers; The negative electrode active material layers and the separation layers are alternately laminated, The thickness of each of the n negative electrode active material layers is 20 nm or more and less than 100 nm, The separation layer comprises a Group 4 element.

Images