Negative electrode for power storage device

Abstract

To provide a power storage device with high capacity, a power storage device with an excellent cycle characteristic, a power storage device with high charge-discharge efficiency, or a power storage device including a negative electrode with low resistance.SOLUTION: A negative electrode for a power storage device includes a number of composite bodies with a particulate shape. The composite body includes a negative electrode active material, a first functional material, and a compound. The compound includes a constituent element of a negative electrode active material, and a constituent element of the first functional material. The negative electrode active material includes a region in contact with at least one of the first functional material and the compound.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present invention relates to an article, a method, or a manufacturing method. Alternatively, the present invention relates to a process, a machine, relating to the manufacture or composition of matter, especially One embodiment of the present invention is a semiconductor device, a display device, a light-emitting device, a power storage device, a driving method thereof, In particular, one embodiment of the present invention relates to an electrode for a power storage device and a manufacturing method thereof. Regarding the manufacturing method. [Background technology]

[0002] In recent years, portable devices such as mobile phones, smartphones, electronic books (e-books), and portable game consoles have become increasingly popular. Electronic devices are becoming widespread. As a result, the lithium-ion secondary battery that drives these devices is becoming increasingly popular. In addition, there are growing research and development efforts into energy storage devices, such as solar power plants. With the growing interest in the issue of hybrid and electric vehicles, Electrical storage devices are becoming increasingly important in applications.

[0003] Among energy storage devices, lithium-ion secondary batteries are widely used due to their high energy density. The battery is made of lithium cobalt oxide (LiCoO2) or lithium iron phosphate (LiFePO4). The positive electrode contains the active material and the negative electrode is made of a carbon material such as graphite that can absorb and release lithium. and LiBF4 and Li in organic solvents such as ethylene carbonate and diethyl carbonate. It is composed of an electrolyte solution in which an electrolyte made of lithium salt such as PF6 is dissolved. Charging and discharging of lithium-ion secondary batteries is carried out by transferring lithium ions in the secondary battery through the electrolyte. Lithium ions move between the positive and negative electrodes, and are inserted into and removed from the positive and negative electrode active materials. This is done by:

[0004] On the other hand, lithium-ion secondary batteries are widely used as power sources for portable electronic devices and electric vehicles. Therefore, there is a strong demand for smaller and larger capacity lithium ion secondary batteries.

[0005] Therefore, instead of carbon materials such as graphite that have been used in conventional negative electrode active materials, There is active development in forming electrodes using alloy materials such as silicon and tin. The negative electrode used in the secondary battery is formed by forming an active material on at least one surface of a current collector. Conventionally, negative electrode active materials have been produced using carrier ions (hereinafter referred to as carrier ions). Graphite, which is a material capable of absorbing and releasing hydrogen, has been used as the negative electrode active material. Graphite, carbon black as a conductive additive, and resin as a binder are kneaded to form a slurry. The negative electrode was manufactured by forming a film, applying it onto a current collector, and drying it.

[0006] In contrast, silicon, a material that undergoes alloying and dealloying reactions with lithium, is used as the negative electrode active material. When used, the capacity can be increased compared to carbon. Theoretical capacity of carbon (graphite) anode The theoretical capacity of the silicon anode is 4200mAh / g, which is significantly higher than the 372mAh / g. Therefore, it is the optimal material for increasing the capacity of lithium-ion secondary batteries.

[0007] However, materials that alloy with lithium, such as silicon, tend to absorb more carrier ions. The expansion and contraction caused by the absorption and release of carrier ions during charge and discharge cycles is large, so the active This can lead to poor contact between the material and the conductive additive, between the active materials themselves, or between the active material and the current collector, resulting in poor conductivity. The electrical path may be damaged. This damage to the electrical path may cause problems during the charge / discharge cycle. Furthermore, in some cases, the silicon may deform or collapse, causing the current collector to By peeling off or pulverizing the material, the function of the lithium-ion secondary battery is maintained. It becomes difficult.

[0008] In Patent Document 1, a silicon layer is formed on a current collector, and a conductive layer is formed on the silicon layer. This allows the silicon to repeatedly expand and contract, causing the silicon layer to separate from the current collector. Even if the battery is peeled off, current can be collected via the conductive layer, so deterioration of battery characteristics is reduced. In addition, impurities such as phosphorus and boron are added to the silicon layer to form a conductive layer. The use of a layer containing a fluorine-containing compound is also disclosed. [Prior art documents] [Patent documents]

[0009] [Patent Document 1] Japanese Patent Application Laid-Open No. 2012-009429 Summary of the Invention [Problem to be solved by the invention]

[0010] An object of one embodiment of the present invention is to provide a power storage device with high capacity. An object of one embodiment of the present invention is to provide a power storage device with excellent cycle characteristics. An object of one embodiment of the present invention is to provide a power storage device with high charge and discharge efficiency. An object of one embodiment of the present invention is to provide a novel power storage device or the like.

[0011] The description of these problems does not preclude the existence of other problems. It is not necessary for the present invention to solve all of these problems. The above will be made clear from the description, drawings, claims, etc. It is possible to extract other issues from the descriptions in the patent, claims, etc. [Means for solving the problem]

[0012] One aspect of the present invention is a composite material having a large number of particles, the composite material comprising a negative electrode active material and a first functional material. a negative electrode active material having a region in contact with the first functional material; be.

[0013] The composite also includes a large number of particulate composites, and the composites include a negative electrode active material, a first functional material, and a compound. and a compound containing a constituent element of the negative electrode active material and a constituent element of the functional material, The active material is a negative electrode for a power storage device having a region in contact with at least one of a functional material and a compound. The poles are also an aspect of the present invention.

[0014] The composite has a large number of particles, and the composite has the negative electrode active material and a first functional material. and a composite having the negative electrode active material, the first functional material, and the compound. A negative electrode for a power storage device is also one embodiment of the present invention.

[0015] In addition, the first functional material has a higher Young's modulus than the negative electrode active material. This is one aspect of the invention.

[0016] The above-described negative electrode for a power storage device in which the negative electrode active material contains silicon is also one embodiment of the present invention.

[0017] The above-described negative electrode for a power storage device in which the first functional material contains titanium is also one embodiment of the present invention.

[0018] In addition, the atomic ratio of silicon to titanium is 2 to 8 times the aforementioned material for use in an electricity storage device. The negative electrode is also an aspect of the present invention.

[0019] The present invention also provides the above-mentioned negative electrode for a power storage device, in which the particle size of the composite is 0.1 μm or more and 20 μm or less. This is one aspect of the invention.

[0020] The present invention also provides the above-mentioned negative electrode for an electricity storage device, in which the surface of the composite is coated with a second functional material. This is one aspect of clarity.

[0021] In one aspect of the present invention, the film thickness of the second functional material is 10 nm or more and 200 nm or less. , the negative electrode for the electricity storage device.

[0022] In one aspect of the present invention, the second functional material contains a common constituent element with the first functional material. This is the aforementioned negative electrode for the electricity storage device.

[0023] A power storage device including the above-described negative electrode for a power storage device is also one embodiment of the present invention.

[0024] Further, an electric device equipped with the above-described power storage device is also one embodiment of the present invention. [Effects of the Invention]

[0025] According to one embodiment of the present invention, a power storage device with high capacity can be provided. According to one embodiment, a power storage device with excellent cycle characteristics can be provided. According to one embodiment of the present invention, a power storage device with high charge and discharge efficiency can be provided. In this way, it is possible to provide an electricity storage device using a negative electrode with low resistance. According to one embodiment, a novel power storage device or the like can be provided.

[0026] The description of these effects does not preclude the existence of other effects. The embodiment does not necessarily have to have all of these effects. , the specification, drawings, claims, etc., and It is possible to extract other effects from the claims and other descriptions. [Brief explanation of the drawings]

[0027] [Figure 1] FIG. [Figure 2] FIG. 3 is a diagram illustrating a composite particle contained in a negative electrode active material layer. [Figure 3] FIG. 3 is a diagram illustrating a composite particle contained in a negative electrode active material layer. [Figure 4] FIG. 3 is a diagram illustrating a composite particle contained in a negative electrode active material layer. [Figure 5] FIG. [Figure 6] FIG. 1 is a diagram illustrating a coin-type storage battery. [Figure 7] FIG. 1 is a diagram illustrating a cylindrical storage battery. [Figure 8] FIG. 1 is a diagram illustrating a thin storage battery. [Figure 9] 1A and 1B are diagrams illustrating a thin, flexible storage battery. [Figure 10] FIG. 1 is a diagram illustrating a thin storage battery. [Figure 11] FIG. 1 is a diagram illustrating a thin storage battery. [Figure 12] 1A and 1B illustrate examples of power storage devices. [Figure 13] 1A and 1B illustrate examples of power storage devices. [Figure 14] 1A and 1B illustrate examples of power storage devices. [Figure 15] 1A and 1B illustrate examples of power storage devices. [Figure 16] 1A and 1B illustrate examples of power storage devices. [Figure 17] 1A and 1B illustrate examples of power storage devices. [Figure 18] 10A and 10B are diagrams showing application examples of a power storage device. [Figure 19] 1 is a cross-sectional STEM image of electrode A according to Example 1. [Figure 20] 1 shows the results of STEM-EDX analysis of electrode A according to Example 1. [Figure 21] 10 is a cross-sectional STEM image of electrode B according to Example 1. [Figure 22] 1 shows a connection configuration of half cells according to the first embodiment. [Figure 23] 1 shows a connection configuration of half cells according to the first embodiment. [Figure 24] 1 shows a connection configuration of half cells according to the first embodiment. [Figure 25] 1 shows a connection configuration of half cells according to the first embodiment. [Figure 26] 4 is a graph showing the change in capacity retention rate of each half-cell according to Example 1. [Figure 27] 10 shows the initial charge-discharge characteristics of each sample according to Example 2. [Figure 28] 10 is a graph showing the change in capacity retention rate of each sample according to Example 2. [Figure 29] 10 is a graph showing the change in capacity retention rate of each sample according to Example 3. [Figure 30] 10A to 10C are cross-sectional images of each sample after charge and discharge according to Example 3. DETAILED DESCRIPTION OF THE INVENTION

[0028] Hereinafter, embodiments will be described with reference to the drawings. It is possible to implement the present invention in various ways without departing from the spirit and scope of the present invention. It will be readily apparent to those skilled in the art that various modifications may be made to the details of the present invention. However, the present invention should not be construed as being limited to the description of the following embodiments.

[0029] (Embodiment 1) In this embodiment, a negative electrode used in a power storage device according to one embodiment of the present invention will be described. A method for producing the negative electrode will now be described.

[0030] [Negative electrode structure 1] FIG. 1(A) is a bird's-eye view of the negative electrode, and FIG. 1(B) is an enlarged view of the cross section enclosed by the dashed line in FIG. 1(A). The negative electrode 100 is provided with a negative electrode active material layer 102 in contact with a negative electrode current collector 101. In the figure, negative electrode active material layers 102 are provided on both sides of a negative electrode current collector 101. However, the negative electrode active material layer 102 may be provided on only one surface of the negative electrode current collector 101 .

[0031] The negative electrode active material layer 102 includes a large number of particulate composites. The negative electrode for an electric device includes a composite. The composite includes a negative electrode active material and a functional material. The specific structure of the body will be described later.

[0032] The active material refers to a material involved in the insertion and desorption of ions, which are carriers. When manufacturing the negative electrode, the active material is mixed with conductive additives, binders, solvents, etc. The mixture of these materials is formed on the current collector as an active material layer. are distinguished.

[0033] The negative electrode current collector 101 is made of a metal such as gold, platinum, zinc, iron, copper, titanium, tantalum, or manganese. and their alloys (such as stainless steel), which have high conductivity and are suitable for carrying lithium ions, etc. Materials that do not alloy with silicon can be used. The metal may be a metal element that reacts with silicon to form a silicide. The elements include zirconium, titanium, hafnium, vanadium, niobium, tantalum, Examples of the material include chromium, molybdenum, tungsten, cobalt, and nickel. Foil, plate (sheet), mesh, cylinder, coil, punched metal, expanded The negative electrode current collector 101 may have a thickness of, for example, 5 μm. The thickness is preferably 8 μm or more and 15 μm or less. The negative electrode current collector 101 may have a thickness of 5 μm or more over the entire area, for example. The thickness is preferably 30 μm or less, and more preferably 8 μm or more and 15 μm or less. However, one aspect of the embodiment of the present invention is not limited to this. For example, the negative electrode current collector 101 At least in part, the thickness is 5 μm or more and 30 μm or less, more preferably Alternatively, the negative electrode current collector 101 may have a region having a diameter of 8 μm or more and 15 μm or less. Preferably, the thickness is 5 μm or more and 30 μm or less in 50% or more of the area of ​​the negative electrode current collector 101. More preferably, the thickness of the region is 8 μm or more and 15 μm or less.

[0034] The negative electrode active material undergoes charge and discharge reactions through alloying and dealloying reactions with carrier ions. The carrier ions are lithium ions and their compounds. In this case, the metal may be, for example, Mg, Ca, Al, Si, Ge, Sn, Pb, or As. , Sb, Bi, Ag, Au, Zn, Cd, Hg, etc. can be used. has a larger capacity than graphite, and Si (silicon) in particular has a theoretical capacity of 4200mAh / g. Therefore, it is preferable to use silicon as the negative electrode active material. Examples of compound materials using elements include SiO, Mg2Si, Mg2Ge, SnO, and S nO2, Mg2Sn, SnS2, V2Sn3, FeSn2, CoSn2, Ni3Sn2, Cu6Sn5, Ag3Sn, Ag3Sb, Ni2MnSb, CeSb3, LaSn3, L Examples include a3Co2Sn7, CoSb3, InSb, and SbSn.

[0035] In addition, titanium dioxide (TiO2) and lithium titanium oxide (Li4T i5O 12 ), niobium pentoxide (Nb2O5), tungsten oxide (WO2), molyb oxide The negative electrode active material can be an oxide such as lithium-ion (MoO2). Graphite intercalation compound (Li x C6) may also be used.

[0036] In addition, the negative electrode active material is a nitride of lithium and transition metals, which has a Li3N structure. i 3-x M x N (M=Co, Ni, Cu) can be used. For example, Li 2.6 C o 0.4 N3 is preferable because it exhibits a large charge / discharge capacity (900 mAh / g).

[0037] When a nitride of lithium and a transition metal is used, the negative electrode active material contains lithium ions, so the positive electrode Combine with materials such as V2O5 and Cr3O8 that do not contain lithium ions as electrode active materials Even when a material containing lithium ions is used as the positive electrode active material, By first removing the lithium ions contained in the positive electrode active material, the negative electrode active material Nitrides of lithium and transition metals can be used as the lithium-containing oxide.

[0038] In a negative electrode for a power storage device according to one embodiment of the present invention, silicon is used as a negative electrode active material. Amorphous silicon, microcrystalline silicon, polycrystalline silicon, or a combination thereof Generally, the higher the crystallinity, the higher the electrical conductivity of silicon. Highly crystalline silicon can be used as an electrode with high conductivity in an energy storage device. When silicon is amorphous, more ions such as lithium ions are trapped in it than in crystalline silicon. Since carrier ions can be absorbed, the discharge capacity can be increased.

[0039] In addition, by increasing the conductivity of silicon by adding impurities, the unevenness of the battery reaction in the electrode can be reduced. As the impurity to be added, for example, as an impurity to give n-type The impurities that give p-type conductivity include phosphorus (P) and arsenic (As), and boron (B), aluminum (Al), gallium (Ga), etc. The resistivity of the silicon is preferably 10 -4 [Ω·cm] or more and 50 [Ω·cm] or less, more preferable Preferably 10 -3 [Ω·cm] or more and 20 [Ω·cm] or less.

[0040] The composite includes a functional material. The functional material is formed in contact with the negative electrode active material. For example, at the interface between the functional material and the negative electrode active material, A chemical bond such as a metallic bond or a covalent bond may be formed between the constituent atoms of both. Even if a compound such as an alloy of the functional material and the negative electrode active material is formed near the interface between them, good.

[0041] The functional material is formed in contact with the negative electrode active material, which prevents deformation and shrinkage due to the expansion and contraction of the negative electrode active material. Therefore, it is preferable that the Young's modulus is high for a functional material. Specifically, it is preferable that the functional material has a higher Young's modulus than the negative electrode active material. The functional material is designed to absorb and release carrier ions so that the material can absorb and release carrier ions even when it is covered with the functional material. It is preferable that the material does not form an alloy with rear ions and has high permeability to carrier ions. Preferably, the functional material has high electrical conductivity.

[0042] The Young's modulus of the negative electrode active material may change depending on the charge / discharge state of the power storage device. For example, when silicon is used as the negative electrode active material, the active material contains almost no lithium. The Young's modulus is higher in the charged state than in the charged state where lithium is contained in the active material. It is preferable that the Young's modulus is higher than that of the active material in the discharged state.

[0043] As the functional material, it is preferable to use a material containing titanium. Specifically, titanium, Titanium silicides such as Ti3Si, Ti5Si3, TiSi, and TiSi2, and titanium-containing Titanium oxide (TiO x ), titanium nitride (TiN x ), titanium-containing oxynitride (T iO x N y ), lithium titanate (L4Ti5O 12 (also written as LTO) Titanium has a high Young's modulus and is highly permeable to lithium ions, Materials containing tungsten can be suitably used as functional materials. Alternatively, titanium, aluminum oxide, etc. may be used.

[0044] The negative electrode for a power storage device according to one embodiment of the present invention includes a functional material such as titanium or TiN. x or TiO x for There are.

[0045] The negative electrode active material layer 102 preferably contains a conductive additive. The presence of the auxiliary improves the electronic conductivity of the negative electrode active material layer 102. , acetylene black particles, Ketjenblack (registered trademark) particles, carbon nanofiber Various conductive additives can be used, such as carbon particles such as bars, graphene, etc.

[0046] The negative electrode active material layer 102 may also contain a binder. By using the above, the binding property between the negative electrode active material and the conductive additive, etc., and the binding property between the negative electrode active material and the current collector can be improved. The binder is typically polyvinylidene fluoride (PVDF). ), as well as polyimide, polytetrafluoroethylene, polyvinyl chloride, ethylene polypropylene Propylene diene polymer, butadiene rubber, styrene-butadiene rubber, butyl rubber, Crylonitrile-butadiene rubber, fluororubber, polyvinyl acetate, polymethyl methacrylate Polyethylene, polypropylene, nitrocellulose, etc. can be used. When silicon or the like, which undergoes significant volume changes during charging and discharging, is used as the negative electrode active material, the binding property is excellent. By using polyimide, it is possible to bond the negative electrode active materials together, the negative electrode active material and the conductive additive, and the negative electrode active material and the conductive additive. This can improve the bonding strength between the current collector and the graphene. This can prevent the negative electrode active material from peeling off or pulverizing, thereby achieving good charge-discharge cycle characteristics.

[0047] Next, with reference to FIGS. 2 to 4, the cross-sectional structure of a particulate composite that can be used for the negative electrode active material layer 102 will be described. 2 to 4 show an example of the structure of the complex. FIG. 1 is a cross-sectional view corresponding to a cutting plane passing through the vicinity of the heart.

[0048] <Example 1 of cross-sectional structure of composite particle> The composite 110 shown in FIG. 2(A) includes a negative electrode active material 115, a functional material 116, a compound 117, and Compounds 117 and 118 are negative electrode active material 115 and functional material 11. That is, compounds 117 and 118 are compounds of the negative electrode active material 115 and and the constituent elements of the functional material 116.

[0049] The functional material 116 has a function of alleviating stress caused by the expansion and contraction of the composite 110. In addition, the compounds 117 and 118, which contain the elements that make up the functional material 116, also relieve the stress. In the structure shown in FIG. 2(A), the ability to relieve the stress is The order of highest is Material 116, Compound 117, and Compound 118.

[0050] Compounds 117 and 118 are compounds of the elements constituting the negative electrode active material 115. The weight ratio of the functional material 116 is different from that of the compound 117. In comparison, the compound 118 has a larger weight ratio of the elements that make up the negative electrode active material 115 .

[0051] The negative electrode active material 115 is in contact with one or more of the functional material 116, the compound 117, and the compound 118. By adopting such a structure, cracks occurring on the surface of the negative electrode active material 115 can be prevented. Therefore, the power storage device of one embodiment of the present invention can have excellent cycle characteristics. In addition, the surface of the negative electrode active material 115 can be formed by the functional material 116 and the compound 117. , 118, the surface of the negative electrode active material 115 is covered with the The functional material 116 has a function of transmitting carrier ions. Therefore, the negative electrode active material 115 is one or more of the functional material 116, the compound 117, and the compound 118. In Figure 2(A), the negative electrode An example is shown in which an active material 115 is covered with a functional material 116 and a compound 117 .

[0052] Negative electrode active material 115 and compounds 117 and 118, and functional material 116 and compounds 117 and 11 8 have common constituent atoms, so there are chemical bonds (e.g., metal The formation of a bond) is facilitated by the use of compound 117 and / or compound 118. This can improve the adhesion between the negative electrode active material 115 and the functional material 116 .

[0053] The negative electrode active material 115 has a function of absorbing and releasing carrier ions. Since compounds 117 and 118 contain elements that make up 115, they also absorb and release carrier ions. In the configuration shown in FIG. 2(A), the ability to absorb and release carrier ions is The negative electrode active material 115 has the highest conductivity, followed by compound 118 and compound 117.

[0054] The greater the weight ratio of the functional material 116, compounds 117, and 118 in the composite 110, the Therefore, the capacity of the power storage device including the negative electrode active material layer 102 is reduced. By making the weight ratio of the compounds 117 and 118 as small as possible, the battery of one embodiment of the present invention can be The weight ratio can be set to 1 / 200 of the total weight of the battery. The cycle time can be determined depending on the cycle characteristics required.

[0055] In this embodiment, the negative electrode active material 115 and the functional material 116 are silicon and silicon dioxide, respectively. In this case, compounds 117 and 118 are titanium silicides. There is no limitation on the composition of the silicon silicide, but for example, Ti:Si=1:2, 1:3, 1:4, etc. Examples include:

[0056] In addition, the vicinity of the boundaries of the negative electrode active material 115, the functional material 116, and the compounds 117 and 118 In this region, the elements constituting the negative electrode active material 115 and / or the functional material 116 are Therefore, the weight ratio of the elements may change continuously. It may be difficult to clearly determine the boundaries of compounds 116, 117, and 118. do.

[0057] In addition, the complex 110 may not have the compound 117 or the compound 118. The composite 110 is a composite of elements constituting the negative electrode active material 115 and elements constituting the functional material 116. The negative electrode active material may contain one or more compounds whose amount ratio is different from that of the compounds 117 and 118. A portion of the substance 115 or / and functional material 116 is not covered by the compound 117, and The combined body 110 may be exposed on the surface.

[0058] The surface of the composite 110 may be covered with a thin film of functional material 116A (FIG. 2(B)). By adopting such a structure, the stress on the surface of the composite 110A is further reduced. This can further improve the cycle characteristics of the power storage device of one embodiment of the present invention. 116A may be a different material than functional material 116, but is preferably a similar material. It is preferable that the functional material 116A and the functional material 116 have common constituent elements. When the body 110A has a region where the functional material 116 and the functional material 116A are in contact with each other, This can improve the adhesion between the material 116 and the functional material 116A.

[0059] <Example 2 of cross-sectional structure of composite particle> The composite 111 shown in FIG. 3(A) includes a negative electrode active material 115 and a functional material 116. Alternatively, The composite 111 includes one or more masses of negative electrode active material 115 and one or more functional materials 116. The negative electrode active material 115 has a region in contact with the functional material 116.

[0060] Since the composite 111 does not contain the compound 117, the negative electrode active material 115 in the composite 111 Therefore, the power storage device of one embodiment of the present invention can have a higher capacity. It can be made into something like this.

[0061] The functional material 116 is formed in contact with the negative electrode active material 115, and the negative electrode active material 115 expands. The negative electrode active material 115 and the functional material 116 can be used to relieve stress caused by the shrinkage. At the interface with 116, it is preferable that a chemical bond is formed between the constituent atoms of both. stomach.

[0062] The greater the weight ratio of the functional material 116 in the composite 111, the greater the amount of the negative electrode active material layer 102. The weight ratio of the functional material 116 should be as small as possible because this reduces the capacity of the resulting power storage device. The weight ratio can be determined depending on the cycle characteristics required for the electricity storage device. do.

[0063] A thin film of functional material 116A may be provided on the surface of the composite 111 (FIG. 3(B) )). By adopting such a configuration, the stress applied to the surface of the composite 111A is alleviated and accumulated. The functional material 116A can further improve the cycle characteristics of the battery. The functional material 11 may be a different material from that of the functional material 116, but is preferably a similar material. 6A and the functional material 116 have common constituent elements, The adhesion of 116A can be improved.

[0064] <Example 3 of cross-sectional structure of composite particle> The composite 112 shown in FIG. 4 includes a negative electrode active material 115 and a functional material 116B. The negative electrode active material 115 has a region in contact with the functional material 116B. is covered with functional material 116B.

[0065] The functional material 116B is formed in contact with the negative electrode active material 115, and the expansion of the negative electrode active material 115 is suppressed. The negative electrode active material 115 and the functional material 116 can be used to relieve stress caused by tension and contraction. At the interface with the material 116B, it is preferable that a chemical bond is formed between the constituent atoms of both. Desirable.

[0066] The cracks and peeling caused by the absorption and release of carrier ions in the negative electrode active material 115 are caused by the negative electrode active material 11 Therefore, it is important to cover only the area where the cracks start. By providing the functional material 116B in the composite 112, the power storage device of one embodiment of the present invention can be realized. , and can be made even higher capacity.

[0067] The functional material 116B is the same as the functional material 116 or the functional material 116A. It is possible.

[0068] The above negative electrode can be used in the power storage device of one embodiment of the present invention.

[0069] [Method of manufacturing negative electrode structure 1] In this embodiment, silicon is used as the negative electrode active material 115, and titanium is used as the functional material 116. A method for producing the above-mentioned negative electrode 100 will be described below.

[0070] First, granular silicon and granular titanium are prepared, weighed, and mechanically mixed. The silicon content should be more than 2 times and less than 8 times that of titanium (for example, the molar ratio should be between 2 and 8 times). Specifically, the mechanical mixing is carried out by mixing the weighed materials in a metal container with the A number of metal balls are placed in the container and the container is rotated. The amount of balls is determined by, for example, the total weight of each material. The amount should be at least 10 times the amount of the mixture. Adjust the rotation speed of the container, the number of balls, the processing time of the mechanical mixing, etc. By doing so, it is possible to obtain the composite 110 and / or composite 111 having an appropriate particle size. That is, fine particles of a mixture or compound of an active material and a functional material having an appropriate particle size, or and mixtures of active and functional materials, and fine particles made of compounds of active and functional materials. It can be generated.

[0071] In addition, barrels are formed on the surface of the composite 110 and / or composite 111 obtained as described above. The composite 110A and / or the composite 110B are formed by depositing the functional material 116A by sputtering. Alternatively, the surface of the granular silicon may be subjected to barrel sputtering. By forming a film of the functional material 116B by the above method, the composite 112 can be obtained. Sputtering is a process in which a target is fixed in a container with a polygonal or circular cross section, and a film is formed on the target. A film formation method in which particulate samples are placed in a rotating container in a vacuum and sputtered. Barrel sputtering allows the target's constituent elements to be deposited on the surface of each particle. The thickness of the functional material 116A formed by barrel sputtering is is preferably 10 nm or more and 200 nm or less.

[0072] Alternatively, a functional material may be formed on the surface of the composite 110 and / or the composite 111 by a sol-gel method. 116A may be formed.

[0073] The complexes referred to below are complexes 110, 111, 110A, 111A, and 112. It shall include at least one.

[0074] Here, the particle size of the composite will be described. If the composite particles are large compared to the conductive additive, the conductive additive It may be difficult to mix uniformly with the agent, and a good conductive path may not be formed. In addition, when the particle size is large, the surface area is small relative to the volume expansion, so stress occurs on the surface. On the other hand, the particle size of the composite may become large, which may cause cracks to occur in the particles. If the value is too small, the surface area of ​​the composite increases, and the decomposition reaction of the electrolyte increases, resulting in a decrease in the charge / discharge efficiency. Therefore, the particle size of the composite has an optimum value. For example, the particle size of the complex is preferably 0.001 μm or more and 20 μm or less, more preferably 0.001 μm or more and 20 μm or less. The thickness is preferably 0.1 μm or more and 20 μm or less, and more preferably 0.5 μm or more and 5 μm or less. It is good.

[0075] The silicon to be prepared to obtain the composite having the above particle size is, for example, a granular silicon wafer. It can be obtained by crushing silicon that is not of a large particle size. The silicon may be crushed to obtain silicon of a desired particle size. Examples of methods include grinding the material in a ball mill or grinding it in a mortar. After crushing, the powder may be crushed using a ball mill. A solvent is added to one or more weighed raw materials, and the raw materials are mixed with a metal or ceramic material. The mixture is rotated using balls made of a material called a mill. At the same time as mixing the materials, the raw materials can be atomized, and the electrode material after production can be In addition, by using a ball mill, the raw materials can be homogenized. They can be mixed together.

[0076] The conductive additive, the particulate complex, and the binder are added to a solvent and mixed in the following ratio: The amount may be adjusted appropriately depending on the desired battery characteristics.

[0077] The solvent may be a liquid in which the raw material does not dissolve but in which the raw material disperses. The solvent is preferably a polar solvent, for example, water, methanol, ethanol, acetone, tetrahydrofuran, etc. Tetrahydrofuran (THF), dimethylformamide (DMF), N-methyl-2-pyrrolidone One or more of NMP and DMSO A mixture can be used.

[0078] In addition, a binder with high heat resistance, such as polyimide, is used as the binder. The material mixed in the mixing step is a polyimide precursor, and the precursor is then heated in the subsequent heating step. The precursor is imidized to form a polyimide.

[0079] The above-mentioned compounds may be mixed, for example, using a kneader. The aggregate and a solvent are combined and stirred using a kneader to prepare a slurry (mixture).

[0080] Next, the slurry is applied onto the negative electrode current collector 101, and the negative electrode current collector on which the slurry is applied is The solvent is removed by drying. The drying step is carried out, for example, at room temperature in a dry atmosphere. It is possible to remove the solvent by a subsequent heating step. In this case, the drying step is not necessarily required.

[0081] Next, the negative electrode current collector coated with the slurry is heated to a heating temperature of 200°C or higher for 40 minutes. The temperature is set to 0°C or lower, preferably about 300°C, and the temperature is maintained at this temperature for 1 hour to 2 hours, preferably about The heating is carried out for 1 hour. The slurry is baked by the heating, and the polyimide precursor is imidized. This results in polyimide.

[0082] In this embodiment, the heating step for firing the slurry is performed at a temperature at which the binder is not decomposed, e.g. The temperature is preferably 200°C or higher and 400°C or lower, and more preferably 300°C. Decomposition can be prevented, and a decrease in the reliability of the power storage device can be prevented.

[0083] By the above-described manufacturing process, a negative electrode 102 having a negative electrode active material layer 102 on a negative electrode current collector 101 is obtained. 00 can be manufactured.

[0084] [Negative electrode structure 2] Next, a negative electrode current collector is applied to the negative electrode of the electricity storage device, and the particulate composite is applied to the negative electrode current collector. A negative electrode active material layer including graphene and a binder will be described.

[0085] Graphene functions as a conductive additive that forms an electron conduction path between the composite and the current collector. In this specification, graphene refers to a single layer of graphene or a layer of graphene having 2 to 100 layers. It includes multi-layer graphene. Single-layer graphene is a single atomic layer of carbon with π bonds. Graphene is a sheet of molecules. When this graphene is formed by reducing graphene oxide, In this case, not all of the oxygen contained in the graphene oxide is released, and some of the oxygen remains in the graphene. When graphene contains oxygen, the oxygen ratio can be determined by XPS (X-ray photoelectron spectroscopy). When measured by the method, for example, the content is 2 atomic % or more and 20 atomic % or less of the entire graphene, preferably The content is 3 atomic % or more and 15 atomic % or less. Note that graphene oxide is a material in which the graphene is oxidized. This refers to a compound that has been

[0086] Furthermore, the binder may be the same as the materials mentioned above. In particular, the negative electrode active material that makes up the composite is made of silicon, which undergoes significant volume changes during charging and discharging. In this case, by using polyimide with excellent binding properties, the particle-shaped composites can be easily bonded to each other and to the particle-shaped composites. The adhesion between the particle and graphene, between the particle composite and the current collector, and between the graphene and the current collector was investigated. This can prevent the composite from peeling off or pulverizing, resulting in good charge / discharge characteristics. You can obtain cycle characteristics.

[0087] In this way, when a negative electrode active material layer including a particulate composite, graphene, and a binder is used, The graphene sheets come into two-dimensional contact with the alloy material particles, enveloping them. The graphenes are in two-dimensional contact with each other, so that they overlap, forming giant nanoparticles in the negative electrode active material layer. A large three-dimensional network of electron conduction paths is constructed. Particulate acetylene black (AB) and ketjen black ( When using a negative electrode active material with high electronic conductivity, electrical contact occurs at a point. A layer of solid can be formed.

[0088] In addition, graphene is bonded to itself to form a mesh-like graphene (hereafter referred to as graphene network). When the composite is covered with a graphene net, Fennet can also function as a binder to bind particles together. This allows the amount of binder to be reduced or even eliminated, making it possible to The ratio of the composite to the volume and the weight of the electrode can be improved. The capacity can be increased.

[0089] FIG. 5(A) is a bird's-eye view of the negative electrode, and FIG. 5(B) is an enlarged view of the cross section enclosed by the dashed line in FIG. 5(A). The negative electrode 200 has a structure in which a negative electrode active material layer 202 is provided on a negative electrode current collector 201. In the figure, the negative electrode active material layer 202 is provided on both sides of the negative electrode current collector 201. Alternatively, the negative electrode active material layer 202 may be provided on only one surface of the negative electrode current collector 201 .

[0090] The negative electrode current collector 201 can be the same as the negative electrode current collector 101 .

[0091] FIG. 5(C) shows the composite 203 and the sheet-like graphene 2 covering the composite 203. 1 is a top view of a negative electrode active material layer 202 having a plurality of composite particles 204 and a binder (not shown). The surface of the composite 203 is covered with different graphenes 204. The complex 203 may be the complex 110 or / and the complex 110 described above. The combined total is 111.

[0092] Graphene 204 is a thin film of carbon molecules having a thickness of a single layer or multiple layers. The granules 204 are arranged to surround or cover the granular composite 203, or Since they are formed so as to be attached to the surface of the composite 203, they are in surface contact with each other. In addition, the graphenes 204 are in surface contact with each other, so that the plurality of graphenes 204 This forms a three-dimensional electrical conduction network.

[0093] As will be described later, the formation of graphene 204 requires the use of an acid that is highly dispersible in polar solvents. This is because graphene oxide is used. The solvent is removed by evaporation, and the graphene oxide is reduced to form graphene. The graphene 204 remaining on the substrate 2 is dispersed to the extent that it partially overlaps with and is in surface contact with each other. This creates a pathway for electrical conduction.

[0094] Therefore, unlike conventional granular conductive additives such as acetylene black, which come into point contact with the active material, Since Rafen 204 enables surface contact with low contact resistance, the amount of conductive additive is increased. The electrical conductivity between the granular composite 203 and the graphene 204 is improved without adding any additives. Therefore, the ratio of the composite 203 in the negative electrode active material layer 202 can be increased. This allows the capacity of the power storage device to be increased. The weight of the graphene 204 used is preferably, for example, 30% or less of the weight of the composite 203. The graphene oxide is preferably reduced to 15% or less, more preferably 3% or less. After that, the weight of the graphene is almost halved.

[0095] As described above, in order to improve the characteristics of the electron conduction path in the negative electrode active material layer 202, a conductive additive is used. The negative electrode active material layer 202 contains graphene, and in addition, acetylene black particles, ketjen black particles, carbon particles such as carbon nanofibers, etc. It may contain various conductive additives.

[0096] The complex 203 is at least one of the complexes 110, 111, 110A, and 111A. Includes one.

[0097] FIG. 5(D) is a cross-sectional view of a part of the negative electrode active material layer 202. The composite 203 is covered with graphene 204. The graphene 204 is The multiple composites 203 are observed as lines. The graphene 204 is sandwiched between the graphene 204. In some cases, the nanoparticles are not covered with graphene 204, and contain multiple complexes 203. Some of the complexes 203 may be exposed.

[0098] The graphene 204 forms a three-dimensional network. In addition, the graphene network is a complex that can absorb and release carrier ions. 203. Therefore, it can also serve as a binder. Therefore, the amount of the binder used can be reduced, and the amount of the composite 2 per negative electrode active material layer 202 can be reduced. It is possible to increase the proportion of 03, thereby increasing the discharge capacity of the power storage device.

[0099] In addition, in the composite 203 whose volume expands due to the absorption of carrier ions, the negative electrode The active material layer 202 may become brittle, causing part of the negative electrode active material layer 202 to collapse. If a part of the negative electrode active material layer 202 collapses, the reliability of the power storage device will decrease. However, even if the volume of the composite 203 increases or decreases due to charging or discharging, the graphene 204 covers the periphery of the composite 203. Therefore, the graphene 204 prevents the dispersion of the composite 203 and the collapse of the negative electrode active material layer 202. That is, the graphene 204 increases the volume of the composite 203 with charging and discharging. Even if the amount of the complex 203 increases or decreases, the complex 203 has a function of maintaining the bond between the complexes 203.

[0100] In addition, when applied to flexible display devices and electronic devices, flexible parts (such as housings) A storage device such as a secondary battery is provided in the whole or part of the Even in this case, repeated bending or other deformation of the electricity storage device can cause the negative electrode current collector inside the electricity storage device to There is a risk that peeling may occur between the body 201 and the composite 203, accelerating the deterioration of the electricity storage device. .

[0101] Here, the graphenes are in surface contact with each other, forming a plurality of graphenes. Graphene forms a three-dimensional electrical conduction network. It has the advantage of being strong and the network is resistant to deformation such as bending. Therefore, a good conductive path can be maintained even after repeated deformation. If the envelope is bag-shaped and contains the complex 203, the complex 203 may be detached due to bending. The electrode layer is less likely to collapse.

[0102] The above negative electrode can be used in the power storage device of one embodiment of the present invention.

[0103] [Method of manufacturing negative electrode structure 2] The negative electrode active material layer 202 in the negative electrode 200 according to one embodiment of the present invention is made of graphite as described above. Graphene includes, for example, graphene oxide, which is the raw material of graphene, and The aggregate 203 can be obtained by kneading the aggregate 203 with a binder and then subjecting it to thermal reduction. An example of a method for producing such a negative electrode will be described.

[0104] First, graphene oxide, the raw material for graphene, is produced. Various synthesis methods, such as the Hummers method, the modified Hummers method, or oxidation of graphite It can be prepared using the method.

[0105] For example, the Hummers method involves oxidizing graphite such as flake graphite to produce oxidized graphite. This is a method to form graphite. The graphite oxide formed is In fact, functional groups such as carbonyl groups, carboxyl groups, and hydroxyl groups are oxidized. The crystallinity of graphite is impaired and the distance between layers is increased. Therefore, the layers can be easily separated by ultrasonic treatment to obtain graphene oxide. The length of one side of the graphene oxide (also called the flake size) is several μm. It is preferable that the thickness is not less than several tens of μm.

[0106] Next, the graphene oxide obtained by the above method or the like and the particulate composite 203 are bonded. The mixing ratio of these is adjusted appropriately depending on the desired battery characteristics. For example, the ratio of the particulate negative electrode active material, graphene oxide, and binder to be added may be , and can be weighed out to give a weight ratio of 80:5:15.

[0107] The solvent may be a liquid in which the raw material does not dissolve but in which the raw material disperses. The solvent is preferably a polar solvent, for example, water, methanol, ethanol, acetone, tetrahydrofuran, etc. Tetrahydrofuran (THF), dimethylformamide (DMF), N-methyl-2-pyrrolidone One or more of NMP and DMSO A mixture can be used.

[0108] In addition, a binder with high heat resistance, such as polyimide, is used as the binder. The material mixed in the mixing step is a polyimide precursor, and the precursor is then heated in the subsequent heating step. The precursor is imidized to form a polyimide.

[0109] In a polar solution, the functional groups of graphene oxide As a result, different graphene oxides are less likely to aggregate together. In polar liquids, graphene oxide tends to be dispersed uniformly. By adding the compound to the solvent and mixing it, especially at the beginning of the mixing process, the compound will be more uniformly dispersed in the solvent. As a result, graphene is uniformly dispersed in the negative electrode active material, improving electrical conductivity. Therefore, a highly conductive negative electrode active material can be produced.

[0110] The above-mentioned compounds may be mixed using, for example, a kneader. For example, a planetary mixer can be used. The binder, the active material, and the solvent are mixed together and kneaded in the mixer. Stir using a stirring device to create a slurry (mixture).

[0111] Here, the order of adding graphene oxide, particulate composite 203, and binder to the solvent is as follows: For example, the particulate composite 203 is added to a solvent and mixed. After mixing, graphene oxide is added and mixed, and then a binder is added and mixed. In each mixing step, a solvent may be added as needed to adjust the viscosity of the mixture. stomach.

[0112] An example of the mixing method will be described. First, a solvent is added to the composite 203 and mixed in a kneader. For example, NMP may be used as the solvent. Next, graphene oxide is added and kneaded. Kneading is a process of kneading with high viscosity, and by kneading the graphene oxide, it is possible to aggregate it. This allows the aggregation of the composite 203 and graphene oxide to be dispersed more uniformly. A solvent may be added during the kneading process. It is preferable that the amount of the electrolyte is, for example, 0.46 ml or more and 0.80 ml or less per 1 g of the active material. Next, a binder is added and mixed in a kneader. A solvent is then added and the mixture is mixed in a kneader.

[0113] Through the above steps, the particulate composite 203, graphene oxide, binder, and solvent are mixed. A slurry (mixture) is formed.

[0114] Next, the slurry is applied onto the negative electrode current collector 201, and the negative electrode current collector on which the slurry is applied is The solvent is removed by drying. The drying step is carried out, for example, at room temperature in a dry atmosphere. It is possible to remove the solvent by a subsequent heating step. In this case, the drying step is not necessarily required.

[0115] Next, the negative electrode current collector coated with the slurry is heated to a heating temperature of 200°C or higher for 40 minutes. The temperature is set to 0°C or lower, preferably about 300°C, and the temperature is maintained at this temperature for 1 hour to 2 hours, preferably about The heating is carried out for 1 hour. The slurry is baked by the heating, and the polyimide precursor is imidized. At the same time, the graphene oxide is reduced to form graphene. In this way, both the heating for slurry baking and the heating for graphene oxide reduction can be achieved by a single heating. Therefore, it is not necessary to perform the heating step twice. This makes it possible to reduce the number of steps required to manufacture the negative electrode.

[0116] In this embodiment, the heating steps for firing the slurry and reducing the graphene oxide are performed in a manner that the binder is The reaction is carried out at a temperature at which decomposition does not occur, for example, at a temperature of 200°C or higher and 400°C or lower, preferably at 300°C. This makes it possible to prevent the binder from being decomposed, and to prevent a decrease in the reliability of the electricity storage device. The weight of graphene oxide can be reduced by almost half through reduction treatment.

[0117] In addition, the reduced graphene oxide has poor dispersibility due to the loss of functional groups, and the composite 20 3) and binder. If the composite 203 is used, the composite 203 and the like will not be mixed uniformly, resulting in an electricity storage device with poor electrical properties. This is because graphene oxide has oxygen-containing functional groups on its surface. The graphene oxide particles are negatively charged by bonding together, and are dispersed by repulsion with each other and with polar solvents. In contrast, reduced graphene loses many of these functional groups upon reduction. This is because the dispersibility of the particles is reduced due to the fact that the particles are made of a material that has been mixed with other particles.

[0118] Therefore, after mixing the graphene oxide and the composite 203, the mixture was heated to form In the negative electrode active material layer, graphene oxide was dispersed before the functional groups were reduced by reduction. Therefore, the graphene after reduction is uniformly dispersed in the negative electrode active material layer. Therefore, by dispersing graphene oxide and then carrying out a reduction process, it is possible to create a highly electrically conductive battery. You can get a position.

[0119] By the above-described manufacturing process, a negative electrode 202 having a negative electrode active material layer 202 on a negative electrode current collector 201 is obtained. 00 can be manufactured.

[0120] Note that various power storage devices can be configured using the above negative electrode. Examples of such batteries include batteries, secondary batteries, and lithium-ion secondary batteries. As another example of the device, the electrode of one aspect of the present invention can be applied to a capacitor. The material is used as the negative electrode, and this is combined with an electric double layer positive electrode to form a lithium-ion capacitor. It is also possible to configure a capacitor such as a capacitor.

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

[0122] (Embodiment 2) In this embodiment, a power storage device using a negative electrode manufactured by the manufacturing method described in Embodiment 1 will be described. The structure of the storage battery will be described with reference to FIGS. 6 to 9. 10 to 14 will be used to explain this. In addition, an example of an electrical device will be explained with reference to FIG. 15. This will be explained using:

[0123] [Coin-type battery] FIG. 6(A) is an external view of a coin-type (single-layer flat) storage battery, and FIG. 6(B) is a cross-sectional view of the battery. FIG.

[0124] The coin-type storage battery 300 has a positive electrode can 301 that also serves as a positive electrode terminal and a negative electrode can 302 that also serves as a negative electrode terminal. 02 are insulated and sealed by a gasket 303 made of polypropylene or the like. Here, the negative electrode for a power storage device described in Embodiment 1 is used as the negative electrode 307.

[0125] The positive electrode 304 is composed of a positive electrode current collector 305 and a positive electrode active material layer 306 provided in contact with the positive electrode current collector 305. The positive electrode active material layer 306 is formed by the following: and a conductive additive for increasing the conductivity of the positive electrode active material layer. As a conductive additive, a material with a large specific surface area is desirable. Carbon black (AB) and the like can be used. Carbon nanotubes, graphene Carbon materials such as fluorene and fullerene can also be used.

[0126] The negative electrode 307 includes a negative electrode current collector 308 and a negative electrode active material layer provided in contact with the negative electrode current collector. The negative electrode 307 is formed using the negative electrode for a power storage device described in Embodiment 1. .

[0127] Between the positive electrode active material layer 306 and the negative electrode active material layer 309, a separator 310 and an electrolyte (see FIG. (not shown).

[0128] The separator 310 may be made of cellulose (paper), or porous polypropylene, polypropylene, or An insulator such as ethylene can be used.

[0129] The electrolyte solution uses a material having carrier ions as an electrolyte. Typical examples of electrolytes Examples include LiPF6, LiClO4, LiAsF6, LiBF4, LiCF3SO3, Lithium salts include Li(CF3SO2)2N and Li(C2F5SO2)2N. The electrolytes may be used alone or in any combination and ratio of two or more. Good too.

[0130] In addition, the carrier ions are alkali metal ions other than lithium ions, alkaline earth metal ions, etc. In the case of metal ions, the electrolyte is an alkali metal ion instead of lithium in the above lithium salt. alkali metals (e.g., sodium and potassium), alkaline earth metals (e.g., calcium, Strontium, barium, beryllium, magnesium, etc.) may also be used.

[0131] As the solvent for the electrolyte, a material that allows the movement of carrier ions is used. The solvent is preferably an aprotic organic solvent. Typical examples of the aprotic organic solvent include: , ethylene carbonate (EC), propylene carbonate, dimethyl carbonate, di Ethyl carbonate (DEC), γ-butyrolactone, acetonitrile, dimethoxyethanol One or more of these can be used. By using a polymer material that gels as a solvent for the electrolyte, safety against leakage etc. is improved. In addition, it is possible to make the storage battery thinner and lighter. Examples include silicone gel, acrylic gel, acrylonitrile gel, and polyethylene glycol. Examples include oxide-based gels, polypropylene oxide-based gels, and fluorine-based polymer gels.

[0132] In addition, a flame-retardant and non-volatile ionic liquid (room-temperature molten salt) was used as the solvent for the electrolyte. By using multiple batteries, even if the internal temperature rises due to an internal short circuit or overcharging, This can prevent the battery from exploding or catching fire. Ionic liquids are made up of cations and anions. The organic cations used in the electrolyte include quaternary anions. ammonium cations, tertiary sulfonium cations, and quaternary phosphonium cations aromatic onium cations, imidazolium cations, and pyridinium cations Examples of anions used in the electrolyte include monovalent amide anions, Monovalent methide anions, fluorosulfonate anions, perfluoroalkyl sulfones Acid anion, tetrafluoroborate anion, perfluoroalkylborate anion , hexafluorophosphate anion, or perfluoroalkylphosphate anion On and others.

[0133] In particular, when an aliphatic quaternary ammonium cation is used, the resistance to reduction is high, so that it is possible to Therefore, the effect of suppressing the decomposition of the electrolyte during charging and discharging is particularly high. This can reduce the capacity of the power storage device, resulting in good cycle characteristics. It can be increased.

[0134] In addition, instead of the electrolyte solution, solid electrolytes containing inorganic materials such as sulfides and oxides, and P A solid electrolyte containing a polymer material such as EO (polyethylene oxide) can be used. When a solid electrolyte is used, there is no need to install a separator or spacer. Since the entire pond can be solidified, there is no risk of leakage, dramatically improving safety.

[0135] The positive electrode can 301 and the negative electrode can 302 are made of nickel and aluminum, which are resistant to corrosion by the electrolyte. Metals such as aluminum and titanium, or alloys of these and other metals (e.g., stainless steel) In addition, nickel or aluminum can be used to prevent corrosion by the electrolyte. The positive electrode can 301 is preferably covered with a positive electrode 304, and the negative electrode can 302 is preferably covered with a negative electrode 303. 07 and electrically connect to each other.

[0136] The negative electrode 307, the positive electrode 304, and the separator 310 are impregnated with an electrolyte, and as shown in FIG. As shown, the positive electrode can 301 is placed downwards, and the positive electrode 304, separator 310, negative electrode 307, and negative electrode The cans 302 are stacked in this order, and the positive electrode can 301 and the negative electrode can 302 are secured together with a gasket 303 interposed therebetween. The coin-shaped storage battery 300 is manufactured by crimping.

[0137] Here, the flow of current when charging the power storage device will be described with reference to FIG. When the secondary battery used is considered as a closed circuit, the movement of lithium ions and the flow of current are the same. In secondary batteries using lithium ions, the anode (positive electrode) ) and the cathode (negative electrode) are switched, and the oxidation reaction and reduction reaction are switched. The electrode with a high reaction potential is called the positive electrode, and the electrode with a low reaction potential is called the negative electrode. In the specification, it is stated that the reverse pulse current is applied whether during charging or discharging. Even when a charging current is flowing, the positive pole is called the "positive pole" or "+ pole (plus pole)." The negative electrode is called the "negative electrode" or "-electrode (minus electrode)." The terms anode (positive electrode) and cathode (negative electrode) related to the reaction are used to distinguish between charging and discharging. When the current is applied, the anode is turned on and off, which can cause confusion. The terms cathode and cathode are not used in this specification. When using the terms anode and cathode, specify whether they are being used during charging or discharging. In addition, it is also necessary to indicate whether it corresponds to a positive electrode (plus pole) or a negative electrode (minus pole). do.

[0138] A charger is connected to the two terminals shown in Figure 6(C) to charge the storage battery 400. As the charging of the battery 400 progresses, the potential difference between the electrodes increases. It flows from the external terminal to the positive electrode 402, and then flows from the positive electrode 402 to the negative electrode 402 inside the storage battery 400. The direction of the current flowing from the negative electrode to the external terminal of the storage battery 400 is called positive. In other words, the direction of the current is the same as the direction of the charging current.

[0139] [Cylindrical storage battery] Next, an example of a cylindrical storage battery will be described with reference to FIG. 7. As shown in FIG. 7(A), the battery has a positive electrode cap (battery lid) 601 on the top surface, and The positive electrode cap and the battery can (external can) 602 are are insulated from each other by a gasket (insulating packing) 610.

[0140] FIG. 7(B) is a schematic diagram showing a cross section of a cylindrical storage battery. Inside the 02, a strip-shaped positive electrode 604 and a negative electrode 606 are wound with a separator 605 sandwiched between them. Although not shown, the battery element is wound around a center pin. The battery can 602 is closed at one end and open at the other end. Metals such as nickel, aluminum, titanium, etc. that are corrosion-resistant to the electrolyte, or Alloys and alloys of these with other metals (e.g., stainless steel, etc.) can be used. In addition, it is preferable to coat the electrode with nickel, aluminum, etc. to prevent corrosion by the electrolyte. Inside the battery can 602, the battery element in which the positive electrode, the negative electrode, and the separator are wound is The battery element is sandwiched between a pair of insulating plates 608 and 609. The inside of the battery can 602 is filled with a non-aqueous electrolyte (not shown). A similar type of storage battery can be used.

[0141] The negative electrode for a power storage device described in Embodiment 1 is used for the negative electrode 606. 06 can be manufactured in the same way as the positive and negative electrodes of the coin-type storage battery described above, but The positive and negative electrodes used in the storage battery are wound, so active materials are formed on both sides of the current collector. The positive electrode 604 is connected to a positive electrode terminal (positive electrode current collecting lead) 603, and the negative electrode 606 is connected to a A negative electrode terminal (negative electrode current collecting lead) 607 is connected to the positive electrode terminal 603 and the negative electrode terminal 607. The positive terminal 603 is a safety valve. The negative terminals 607 are resistance welded to the bottom of the battery can 602 by the mechanism 612. The structure 612 is a PTC element (Positive Temperature Coefficient The positive electrode cap 601 is electrically connected to the positive electrode cap 601 via the safety valve mechanism 611. 12, when the internal pressure of the battery exceeds a predetermined threshold, the positive electrode cap 601 and the positive electrode 604 In addition, the PTC element 611 cuts off the electrical connection between the It is a thermal resistor element whose resistance increases over time, and the increase in resistance limits the amount of current to prevent abnormal heat generation. The PTC element is made of barium titanate (BaTiO3) based semiconductor ceramic. A binder such as a binder may be used.

[0142] [Thin storage battery] Next, an example of a thin storage battery will be described with reference to FIG. 8. The thin storage battery is flexible. If the structure has such a configuration, when the device is mounted in an electronic device having at least a part with flexibility, This allows the storage battery to bend in accordance with the deformation of the electronic device.

[0143] FIG. 8 shows an external view of a thin storage battery 500. Also, FIGS. 9(A) and 9(B) show the external view of the thin storage battery 500. The thin storage battery 500 is shown in cross section A1-A2 and cross section B1-B2 indicated by dashed lines. A positive electrode 503 having a positive electrode current collector 501 and a positive electrode active material layer 502, a negative electrode current collector 504 and a a negative electrode 506 having a negative electrode active material layer 505; a separator 507; and an electrolyte solution 508. and an outer casing 509. Between the positive electrode 503 and the negative electrode 506 provided in the outer casing 509 A separator 507 is placed between the outer casing 509 and the battery. The inside of the outer casing 509 is filled with an electrolyte 508. The negative electrode for a power storage device described in Embodiment 1 is used as the negative electrode 506.

[0144] The separator 507 is processed into a bag shape and is wrapped around either the positive electrode 503 or the negative electrode 506. For example, as shown in FIG. 10(A), the positive electrode 503 is sandwiched between the positive electrode 503 and the positive electrode 503. The separator 507 is folded in half as shown in FIG. 1, and the sealing portion 51 is formed outside the area overlapping with the positive electrode 503. By sealing with 4, the positive electrode 503 can be reliably supported within the separator 507. Then, as shown in FIG. 10(B), the positive electrode 503 and the negative electrode 504 are wrapped in a separator 507. 506 are alternately stacked and placed inside an exterior body 509 to form a thin storage battery 500 It is advisable to form a

[0145] 11(B) shows an example in which a current collector is welded to a lead electrode. For example, a positive electrode current collector 501 The positive electrode current collector 501 is welded to the positive electrode lead electrode 510 by ultrasonic welding or the like. The positive electrode current collector 501 is welded to the positive electrode lead electrode 510 in a welding region 512. By providing the curved portion 513 shown in FIG. 11(B), it is possible to prevent external force from being applied after the storage battery 500 is fabricated. This can alleviate stress caused by the application of heat, thereby improving the reliability of the storage battery 500. Cut.

[0146] In the thin storage battery 500 shown in FIGS. 8 and 9, the positive electrode lead electrode 510 is a positive electrode current collector. 501 and the negative electrode lead electrode 511 are ultrasonically bonded to the negative electrode current collector 504. The positive electrode current collector 501 and the negative electrode current collector 504 serve as terminals for electrical contact with the outside. In this case, the positive electrode current collector 501 and the negative electrode current collector 502 can be connected without using a lead electrode. The electric body 504 may be arranged so that a part of the electric body 504 is exposed to the outside from the exterior body 509 .

[0147] In the thin storage battery 500, the exterior body 509 is made of, for example, polyethylene or polypropylene. , polycarbonate, ionomer, polyamide, etc., on a film made of a material such as aluminum A thin metal film made of a material with excellent flexibility, such as stainless steel, copper, or nickel, is then formed on the thin metal film. The outer surface of the exterior body is provided with an insulating synthetic resin film such as polyamide resin or polyester resin. A film having a three-layer structure can be used.

[0148] In addition, in FIG. 8, the number of electrode layers is set to three as an example, but the number of electrode layers is of course not limited to three. The number of electrode layers may be large or small. Furthermore, when the number of electrode layers is small, the battery can be made thin and flexible. This can be an excellent storage battery.

[0149] In this embodiment, the storage batteries are coin-type, cylindrical, and thin storage batteries. However, other types of batteries such as sealed batteries and rectangular batteries can also be used. In addition, a structure in which a positive electrode, a negative electrode, and a separator are stacked in multiple layers, a structure in which a positive electrode, a negative electrode, and a separator are stacked in multiple layers, It may also have a wound structure.

[0150] The negative electrodes of the storage batteries 300, 500, and 600 shown in this embodiment are Therefore, the negative electrode active material layer according to the embodiment is used. The discharge capacity of the battery 600 can be increased, or the cycle characteristics can be improved. Cut.

[0151] The thin storage battery is not limited to that shown in FIG. 8. Another example of a thin storage battery is shown in FIG. 12. The wound body 993 shown in FIG. 9 has a negative electrode 994, a positive electrode 995, and a separator 996. .

[0152] The wound body 993 is made up of a negative electrode 994 and a positive electrode 995 stacked together with a separator 996 sandwiched therebetween. The laminated sheet is then wound. This wound body 993 is used to form a square sealed container or the like. A square secondary battery is produced by covering the battery with a material such as aluminum.

[0153] The number of layers of the negative electrode 994, the positive electrode 995, and the separator 996 is determined based on the required capacity. The negative electrode 994 may be designed appropriately depending on the amount and volume of the element. The positive electrode 995 is connected to a negative electrode current collector (not shown) via one of the electrodes 998. 97 and the other of the lead electrodes 998 are connected to a positive electrode current collector (not shown).

[0154] The power storage device 980 shown in FIGS. 12B and 12C includes a film 981 and a filter having a recess. The above-mentioned wound body 993 is placed in the space formed by bonding the film 982 and the film 982 together by thermocompression bonding or the like. The wound body 993 has a lead electrode 997 and a lead electrode 998. The interiors of film 981 and film 982 having recesses are impregnated with an electrolyte.

[0155] The film 981 and the film 982 having the recesses are made of a metal material such as aluminum. The film 981 and the film 982 having the recesses can be made of a material such as a resin material. If a resin material is used as the material, when an external force is applied, the film 981 and the recessed portion are effectively bonded. The film 982 can be deformed, and a flexible storage battery can be produced. Cut.

[0156] In addition, although two films are used in FIGS. 12(B) and (C), one film may be used. A space is formed by folding the film, and the above-mentioned wound body 993 is housed in the space. You may do so.

[0157] In addition, the exterior body of the power storage device and the sealing container are made of a resin material, etc., to provide flexibility. However, when the outer casing or the sealing container is made of a resin material, The parts that are connected to the outside are made of conductive material.

[0158] For example, an example of a flexible rectangular storage battery is shown in FIG. 13. The wound body 993 in FIG. 13(A) is , is the same as that shown in FIG. 12(A), so detailed description will be omitted.

[0159] The electricity storage device 990 shown in FIGS. 13B and 13C includes an outer casing 991 and the above-described wound body. The winding body 993 houses the lead electrodes 997 and 998. The exterior bodies 991 and 992 are impregnated with an electrolyte solution inside. For example, a metal material such as aluminum or a resin material can be used. If a resin material is used as the material for 92, the outer casings 991 and 99 2 can be deformed to produce a flexible rectangular storage battery.

[0160] In addition, structural examples of the electricity storage device (electricity storage body) will be described with reference to FIGS. 14, 15, and 16. .

[0161] 14A and 14B are diagrams showing the appearance of a power storage device. The device includes a substrate 900 and a power storage unit 913. A label 910 is attached to the power storage unit 913. Furthermore, as shown in FIG. 14B, the power storage device has a terminal 951, a terminal 952, and It has an antenna 914 and an antenna 915.

[0162] The circuit board 900 has a terminal 911 and a circuit 912. The terminal 911 is connected to a terminal 951. , terminal 952, antenna 914, antenna 915, and circuit 912. A plurality of terminals 911 are provided, and each of the plurality of terminals 911 is used as a control signal input terminal, a power supply terminal, etc. may also be used.

[0163] The circuit 912 may be provided on the back surface of the circuit board 900. The antenna 915 is not limited to a coil shape, but may be, for example, a wire shape or a plate shape. Planar antenna, aperture antenna, traveling wave antenna, EH antenna, magnetic field antenna, dielectric Alternatively, antenna 914 or antenna 915 may be used. The flat conductor may function as one of the conductors for electric field coupling. In other words, the capacitor has two conductors, one of which is an annulus. The antenna 914 or the antenna 915 may be activated. Instead, power can be exchanged using an electric field.

[0164] The line width of antenna 914 is preferably larger than the line width of antenna 915. This allows the amount of power received by the antenna 914 to be increased.

[0165] The power storage device has a layer 916 between the antenna 914 and the power storage body 913 and between the antenna 915 and the power storage body 913. The layer 916 has a function of shielding an electromagnetic field generated by the power storage unit 913, for example. The layer 916 may be made of, for example, a magnetic material.

[0166] The structure of the power storage device is not limited to that shown in FIG.

[0167] For example, as shown in FIGS. 15(A-1) and 15(A-2), In the power storage unit 913 shown in (B), an antenna may be provided on each of a pair of opposing surfaces. FIG. 15(A-1) is an external view seen from one side of the pair of surfaces. 14(A) and 14(B) are external views seen from the other side of the pair of surfaces. 14(A) and 14(B) are the same as those in the power storage device shown in FIG. The description of the power storage device can be used as appropriate.

[0168] As shown in FIG. 15(A-1), a layer 916 is sandwiched between one of a pair of surfaces of a power storage unit 913. 15(A-2), a tenon 914 is provided on the other of the pair of surfaces of the power storage unit 913. An antenna 915 is provided between the power storage unit 913 and the layer 917. The layer 917 has a function of shielding the electromagnetic field. It is possible.

[0169] By adopting the above structure, the size of both the antenna 914 and the antenna 915 can be increased. It is possible.

[0170] Alternatively, as shown in Figs. 15(B-1) and 15(B-2), In the case of the power storage unit 913 shown in B), a separate antenna may be provided on each of a pair of opposing surfaces. FIG. 15(B-1) is an external view seen from one side of the pair of surfaces. 14(A) and 14(B) are external views seen from the other side of the pair of surfaces. The same parts as those of the power storage device shown in FIG. 14B are shown in FIGS. 14A and 14B. The description of the electricity storage device can be used as appropriate.

[0171] As shown in FIG. 15(B-1), a layer 916 is sandwiched between one of a pair of surfaces of a power storage unit 913. 15B-2, a capacitor 91 An antenna 918 is provided on the other of the pair of surfaces of the substrate 3, sandwiching a layer 917 therebetween. For example, the antenna 918 has a function of performing data communication with an external device. For example, antennas having shapes applicable to the antennas 914 and 915 can be applied. As a communication method between the power storage device and other devices via antenna 918, NFC is available. It is possible to apply a response method that can be used between the power storage device and other devices, such as do.

[0172] 16A, the power storage unit 913 shown in FIGS. 14A and 14B A display device 920 may be provided. The display device 920 is connected to the terminal 911 via the terminal 919. The label 910 is not necessarily provided in the area where the display device 920 is provided. Note that the same parts as those of the power storage device shown in FIGS. The description of the power storage device shown in FIGS. 14(A) and 14(B) can be used as appropriate.

[0173] The display device 920 displays, for example, an image indicating whether charging is in progress or not, an image indicating the amount of stored power, etc. The display device 920 may be, for example, an electronic paper, a liquid crystal display, an electrophotographic display, or the like. For example, an electroluminescence (EL) display device can be used. By using the par, the power consumption of the display device 920 can be reduced.

[0174] 16B, the power storage unit 913 shown in FIGS. 14A and 14B may be A sensor 921 may be provided. The sensor 921 is electrically connected to the terminal 911 via a terminal 922. 14(A) and 14(B) are connected to the same parts as those of the power storage device shown in FIG. The description of the power storage device in FIGS. 14A and 14B can be used as appropriate.

[0175] The sensor 921 may be, for example, a sensor for detecting force, displacement, position, velocity, acceleration, angular velocity, rotation speed, distance, etc. , light, liquid, magnetism, temperature, chemicals, sound, time, hardness, electric field, current, voltage, power, radiation The equipment may include functions to measure flow rate, humidity, gradient, vibration, odor, or infrared rays. By providing the sensor 921, for example, it is possible to detect the environment in which the power storage device is placed. Data (such as temperature) can also be sensed and stored in memory within the circuit 912 .

[0176] In addition, examples in which the flexible storage battery shown in FIGS. 8, 12, and 13 is mounted in an electronic device are shown. The flexible storage device is shown in FIG. For example, television equipment (also called television or television receiver), computer equipment, etc. Any monitor, digital camera, digital video camera, digital photo frame, mobile phone Mobile phones (also called mobile phones or mobile phone devices), portable game consoles, portable information terminals, sound reproduction equipment Examples include large gaming machines such as pachinko machines.

[0177] In addition, the flexible energy storage device can be mounted on the inner or outer wall of a house or building, or on the inside or outside of a car. It is also possible to incorporate it along the curved surface of the interior or exterior of the vehicle.

[0178] FIG. 17A shows an example of a mobile phone. The mobile phone 7400 has a housing 7401. In addition to the display unit 7402 incorporated in the The mobile phone 7400 is equipped with a speaker 7405, a microphone 7406, and the like. It has device 7407.

[0179] FIG. 17B shows the mobile phone 7400 in a bent state. When the entire device is deformed by an external force and curved, the power storage device installed inside 7407 is also bent. At this time, the bent state of the power storage device 7407 is shown in FIG. The power storage device 7407 is a thin storage battery. The power storage device 7407 is fixed by a lead wire electrically connected to the current collector 7409. For example, the current collector 7409 is made of copper foil, and is partially mixed with gallium. The adhesion between the current collector 7409 and the active material layer in contact therewith is improved, and the power storage device 7407 This configuration is highly reliable even when bent.

[0180] FIG. 17(D) shows an example of a bangle-type display device. The portable display device 7100 includes: The device includes a housing 7101, a display portion 7102, operation buttons 7103, and a power storage device 7104. FIG. 17E shows the bent state of the power storage device 7104. When the device is worn on the user's arm in a buckled state, the housing may deform and cause damage to part of the power storage device 7104 or The total curvature changes. The degree of curvature at any point on the curve is expressed as the radius of the corresponding circle. The value expressed is the radius of curvature, and the reciprocal of the radius of curvature is called the curvature. Specifically, the radius of curvature is A part of the main surface of the housing or the power storage device 7104 within the range of R of 40 mm or more and 150 mm or less Or the entire surface of the power storage device 7104 changes. High reliability can be maintained within the range of 50 mm or less. The lead electrode 7105 is electrically connected to the current collector 7106. 06 is copper foil, and is partially alloyed with gallium to form a layer of the active material in contact with the current collector 7106. The adhesiveness is improved, and the power storage device 7104 has high reliability even when the curvature is changed and the device is bent many times. It is designed to maintain reliability.

[0181] FIG. 17(F) shows an example of a wristwatch-type portable information terminal. The portable information terminal 7200 is , a housing 7201, a display unit 7202, a band 7203, a buckle 7204, and an operation button 72 05, input / output terminal 7206, etc.

[0182] The portable information terminal 7200 is capable of carrying out mobile phone calls, e-mails, viewing and creating documents, playing music, and internet access. - It can run various applications such as internet communication and computer games. do.

[0183] The display surface of the display unit 7202 is curved, and the display is performed along the curved display surface. The display portion 7202 is provided with a touch sensor, and can be touched with a finger or a stylus. For example, the icon 72 displayed on the display unit 7202 can be operated by touching it. You can launch the application by touching 07.

[0184] The operation button 7205 is used to set the time, turn the power on and off, and turn wireless communication on and off. It has various functions such as operation, silent mode activation and deactivation, power saving mode activation and deactivation, etc. For example, an operating system installed in the portable information terminal 7200 can The function of the operation button 7205 can also be freely set using the stem.

[0185] In addition, the mobile information terminal 7200 is capable of performing standardized short-range wireless communication. For example, by communicating with a wireless headset, hands-free operation is possible. You can also make calls.

[0186] The portable information terminal 7200 also has an input / output terminal 7206, and can be connected to other information terminals via a connector. It is also possible to charge the battery via the input / output terminal 7206. The charging operation can be performed by wireless power supply without going through the input / output terminal 7206. That's fine.

[0187] The display portion 7202 of the portable information terminal 7200 includes a power storage device including the electrode member of one embodiment of the present invention. For example, the power storage device 7104 in FIG. 17E is included in a housing 7201. It can be installed in a curved state in the part or in a curved state inside the band 7203. Cut.

[0188] [Example of electrical equipment: installed in a vehicle] Next, we will show an example of installing a storage battery in a vehicle. Hybrid electric vehicles (HEV), electric vehicles (EV), plug-in hybrid vehicles (PHEV), etc. This will make next-generation clean energy vehicles a reality.

[0189] 18A and 18B show examples of vehicles using one embodiment of the present invention. 100 is an electric vehicle that uses an electric motor as a power source for running. A hybrid vehicle that can select between an electric motor and an engine as a power source for driving. By using one aspect of the present invention, a vehicle with a long driving range can be realized. The automobile 8100 also has a power storage device. The power storage device can be used to power the electric motor 8 In addition to driving the 106, it also drives the headlights 8101 and room lights (not shown). The light emitting device can be supplied with power.

[0190] In addition, the power storage device may be used for displaying information such as a speedometer and a tachometer of the automobile 8100. The power storage device can supply power to the navigation system of the automobile 8100. The present invention can provide power to semiconductor devices such as distribution systems.

[0191] The automobile 8100 shown in FIG. 18B is a power storage device of the automobile 8100. It can be charged by receiving power from an external charging facility using a contactless power supply system or other methods. FIG. 18(B) shows the charging of electricity from a ground-mounted charging device 8021 to a storage battery mounted on an automobile 8100. The figure shows a state in which the charging device is being charged via a cable 8022. The power supply method and connector standards are determined as appropriate using the specified methods such as CHAdeMO (registered trademark) and Combo. The charging device 8021 may be a charging station provided in a commercial facility, or For example, plug-in technology allows the system to be connected to an external power supply. The power storage device mounted on the automobile 8100 can be charged by the AC / DC converter. This can be done by converting AC power into DC power via a conversion device such as an inverter.

[0192] Although not shown, a power receiving device is mounted on the vehicle and power is supplied contactlessly from a power transmitting device on the ground. In this case, a power transmission device is installed on the road or exterior wall. By incorporating this technology, charging can be carried out not only when the vehicle is stopped but also while the vehicle is moving. This method may be used to transmit and receive power between vehicles. A solar cell may be provided to charge the power storage device while the vehicle is stopped or running. The power can be supplied by an electromagnetic induction method or a magnetic resonance method.

[0193] According to one embodiment of the present invention, the cycle characteristics of a power storage device can be improved, and the reliability can be improved. Furthermore, according to one embodiment of the present invention, the characteristics of the power storage device can be improved. Therefore, the size and weight of the power storage device itself can be reduced. This contributes to reducing the vehicle's weight, thereby improving the vehicle's cruising range. The power storage device can also be used as a power supply source for other purposes than vehicles. It is possible to avoid using commercial power during peak hours.

[0194] This embodiment mode can be implemented in appropriate combination with other embodiment modes. [Example]

[0195] In the following examples, a half cell was fabricated using the negative electrode shown in Embodiment 1, and cycle characteristics were evaluated. Sexuality was assessed.

[0196] (Preparation of the complex) The composite particles were prepared by first preparing titanium powder with a particle size of 45 μm and silicon powder with a particle size of 5 μm. Weigh out silicon powder so that the molar ratio of Ti:Si=1:2 and the total weight is about 20 g. The grinding container (C) attached to the planetary rotation type ball mill grinder (LP-4, manufactured by Ito Seisakusho) Weighed titanium powder, silicon powder and media are placed in a 500ml container (manufactured by ROM). The media is chrome steel balls with a diameter of 10 mm, and the amount is 1 / 3 of the crushing container. The crushing container was filled with Ar atmosphere and the rotation speed was 200. A composite of sample A was prepared by rotating and revolving the mixture at rpm. The rotation speed was changed to 250 rpm and further rotation / revolution stirring was performed, whereby the composites of samples B to D were obtained. For each of Samples B to D, the processing time of the stirring at a rotation speed of 250 rpm was That is, sample B was stirred for 18 hours, sample C for 38 hours, and sample D for 50 hours. Table 1 shows the results of the composites prepared, namely, the powders of Samples A to D. Processing conditions by the crusher, and the average particle size and The particle size was measured using a laser diffraction particle size distribution analyzer (SALD-2200, Shima The particle size was measured using a laser diffraction and scattering method. Although the average particle size and D90 of sample A were not measured, they are thought to be larger than those of sample B. can be.

[0197] [Table 1]

[0198] (Preparation of negative electrode) Using the obtained samples A to D and comparative sample E, negative electrodes were prepared by the following method. That is, a 10 μm thick stainless steel foil with nickel coated on the surface was used as the negative electrode current collector. The composite particles or Si particles, acetylene black, and polyimide ( More precisely, the mixing ratio of the polyimide precursor was 80:5:15 (wt%). The mixture was mixed using a planetary mixer to prepare a slurry. First, a solvent was added to the composite particles or Si particles, and the mixture was mixed in a kneader. Cetylene black and NMP were added and the mixture was kneaded. Finally, NMP was added again and mixed in the kneader. The kneading conditions were a rotation speed of 2000 rpm and 5 minutes, including hard kneading. The slurry was then applied to the current collector using the blade method. The operation speed was 10 mm / sec. The NMP was evaporated by drying in air at 50°C for 1 hour. In order to imidize the polyimide precursor, it was heated at 400°C for 5 hours in a N2 atmosphere. Heat treatment was carried out.

[0199] The negative electrodes prepared using Samples A to D and Comparative Sample E in the above manner were designated as negative electrode A. to negative electrode D, and comparative negative electrode E.

[0200] Figure 19 shows a cross section of electrode A fabricated using sample A, photographed by STEM (Scanning Transform). The results are from observations using Transmission Electron Microscopy (TEM). The sample A in FIG. 19 contains the composite 111. Also, the sample A was prepared using the composite 111 in FIG. STEM-EDX (Energy Dispersive X-ray Spectroscopy) of electrode A Fig. 20(A) shows the results of elemental analysis by spectroscopy. 20(B) is a STEM image of the Ti layer, and FIG. 20(C) is a mapping image of the Ti layer. 19 and 20, the composite 111 is a silicon The negative electrode active material 115 contains titanium, and the functional material 116 contains titanium. 5 is in contact with the functional material 116 .

[0201] Figure 21 shows the results of STEM observation of the cross section of electrode B fabricated using sample B. The composite 110 shown in FIG. 1 includes a silicon-containing negative electrode active material 115 and a titanium-containing functional material 116. , Compound 117 containing titanium silicide, Compound 118. The substrate 115 is in contact with at least one of the functional material 116, the compound 117, and the compound 118. The weight ratio of silicon to titanium in compound 118 is higher than that in compound 117. The weight ratio of silicon and titanium in Compound 117 and Compound 118 is It is not constant within 111.

[0202] (Cell preparation) Next, negative electrodes A to D (hereinafter collectively referred to as composite electrodes) prepared as described above were used. A half cell was prepared using the negative electrode E for comparison (hereinafter also referred to as the silicon electrode). The characteristics were evaluated using a CR2032 type (diameter 20 mm, height 3.2 mm) coin-type battery. The counter electrode was made of metallic lithium, and the separator was made of polypropylene. The solution contained 1Mol / L LiPF6 as the solute and EC (ethylene carbonate) as the solvent. A mixture of ethyl acetate (ETA) and diethyl carbonate (DEC) in a volume ratio of 3:7 was used. The half cells prepared using negative electrodes A to D are designated as cells A to D, respectively, and comparative negative electrodes are designated as cells A to D. The half cell made using pole E is called cell E.

[0203] Here, the charge and discharge of the half-cell using the composite electrode or the silicon electrode is calculated using the formula: Figure 22 shows a half cell using a composite electrode or a silicon electrode and a Li counter electrode. 1 shows a connection configuration between half-cell 121A and load 122 when discharging. When discharging the Fusel 121A, the reaction of formula (1) occurs at the composite electrode or silicon electrode. happen.

[0204] Si + xLi + + xe - → SiLi x (1)

[0205] Furthermore, the reaction shown in formula (2) occurs at the Li electrode.

[0206] xLi → xLi + + xe - (2)

[0207] Figure 23 shows the case of charging a half-cell using a composite electrode or a silicon electrode and a Li counter electrode. 1 shows a connection configuration between half cell 121A and charger 123 in the half cell 121. When A is charged, the reaction of formula (3) occurs at the composite electrode or silicon electrode.

[0208] SiLi x → Si + xLi + + xe - (3)

[0209] Furthermore, the reaction of formula (4) occurs at the Li electrode.

[0210] xLi + + xe - → xLi (4)

[0211] Here, in the formulas (1) to (4), x satisfies x≦4.4.

[0212] As shown in equations (1) to (4), Li is inserted into silicon during discharge and released from silicon during charging. Li is released from the

[0213] In the composite electrode, if a part of the titanium contained in the composite particles is oxidized, the oxidation Titanium dioxide may also contribute to charging and discharging. The following reaction may occur. When discharging a half cell using a composite electrode with titanium dioxide and a Li counter electrode, The figure shows the connection configuration between the half cell 121B and the load 122. In this case, the reaction of equation (5) occurs at the composite electrode.

[0214] Si + TiO2+ (x+y)Li + + (x+y)e - → SiLi x + Li y TiO2(5)

[0215] Furthermore, the reaction of formula (6) occurs at the Li electrode.

[0216] (x+y)Li → (x+y)Li + + (x+y)e - (6)

[0217] Figure 25 shows the case where a half-cell using a composite electrode containing titanium oxide and a Li counter electrode is charged. 1 shows a connection configuration between half cell 121B and charger 123 in the half cell 121. When B is charged, the reaction of formula (7) occurs at the composite electrode.

[0218] SiLi x + Li y TiO2 → Si + TiO2+ (x+y)Li + + (x+y)e - (7)

[0219] Furthermore, the reaction of formula (8) occurs at the Li electrode.

[0220] (x+y)Li + + (x+y)e - → (x+y)Li (8)

[0221] In the formulas (5) to (8), x satisfies x≦4.4, and y satisfies y<0.7. Add.

[0222] As shown in formulas (5) to (8), Li is inserted into silicon and titanium oxide by discharge. Lithium is released from silicon and titanium oxide upon charging.

[0223] (Cell measurement) Next, the measurement results of the charge / discharge characteristics and cycle characteristics of cells A to E prepared as described above were reported. The results are shown below.

[0224] The measurement conditions for the half-cell are explained below. The charge / discharge method is a constant current at a rate of 0.2C. The battery was charged at a constant voltage and discharged at a constant current of 0.2 C. The upper limit of the charge / discharge voltage was 1.5 V. The lower limit voltage was set to 0.01 V. The measurement temperature was 25°C. The calculation is based on the theoretical capacity of 4200mAh / g.

[0225] Table 2 shows the initial discharge capacities obtained as a result of charging and discharging cells A to E, and the ratio of the initial discharge capacities to the initial discharge capacities. The capacity retention rate after 10 cycles and the capacity after 20 cycles relative to the initial discharge capacity Figure 26 shows the change in capacity retention rate when the initial discharge capacity is set to 100%. The results of cell A are shown as a solid line, the results of cell B as a dashed line, the results of cell C as a dashed line, and the results of cell The results for cell D are shown by the dashed double-dashed line, and the results for cell E are shown by the dotted line. The amount maintenance rate is not listed as it is still being measured.

[0226] [Table 2]

[0227] As shown in Table 2 and FIG. 26, the composites used as the negative electrode active materials for the negative electrodes of power storage devices according to one embodiment of the present invention Cells A to D using silicon particles were found to have a higher negative electrode active material than Cell E using silicon particles. This is because the titanium is in contact with the silicon in the composite particles. The presence of silicon dioxide relieves the stress that occurs when silicon expands and contracts during charging and discharging. This is thought to be because cracks and peeling of the silicon are suppressed.

[0228] In addition, the longer the stirring time in the preparation of the composite microparticles, the lower the initial volume tends to be. This is because the amount of titanium silicide formed in the composite particles varies depending on the stirring time. This is thought to be because the amount of silicon, which mainly contributes to the absorption and release of lithium ions, increases and the amount of silicon decreases. On the other hand, there is no simple proportional relationship between the stirring time and the cell capacity maintenance rate. Therefore, in order to obtain a high-capacity electricity storage device with excellent cycle characteristics, the stirring time is It is preferable to determine it appropriately. [Example]

[0229] In this example, a power storage device was fabricated to confirm the performance of a negative electrode for a power storage device according to one embodiment of the present invention. The results of evaluating the characteristics are explained below.

[0230] The power storage device manufactured in this example is a coin-type battery (coin cell), and Sample F, Sample There are four samples in total: Sample G, Sample H, and Comparative Sample I. Each sample has an electrode, a counter electrode, an electrolyte, and a separator. The structure other than the electrodes is common to all samples. The method for fabricating the electrodes will be explained below. The electrodes used for Sample F, Sample G, Sample H, and Comparative Sample I are referred to as Electrode F and Electrode G, respectively. , electrode H, and electrode I.

[0231] (Electrode manufacturing method) An active material layer and a functional layer are formed on a titanium substrate, which serves as a current collector, using a sputtering device. The silicon target used to form the active material layer was common to electrodes F to I. The titanium target used for forming the functional layer is common to electrodes F to H. be.

[0232] Electrode F is a titanium substrate with a silicon film of 90 nm and titanium nitride (TiN x ) film to 30 nm The deposition conditions for the titanium nitride film were an Ar gas flow rate of 9 sccm and an N2 gas flow rate of 1 s It was set to ccm.

[0233] Electrode G is a titanium substrate with a 90 nm silicon film and titanium oxide (TiO x ) film to 30 nm The deposition conditions for the titanium oxide film were an Ar gas flow rate of 9 sccm and an O2 gas flow rate of 1 s It was set to ccm.

[0234] Electrode H was made by depositing a 90 nm silicon film and a 30 nm titanium film on a titanium substrate. The film was formed under conditions of an Ar gas flow rate of 9 sccm.

[0235] Electrode I was made by depositing a silicon film to a thickness of 90 nm on a titanium substrate.

[0236] The nitrogen content of the titanium nitride film of electrode F is about 18 atomic % and the oxygen content is The oxide content of electrode G was approximately 0.1 atomic % to 0.3 atomic %. The oxygen content of the titanium film is approximately 40 atomic % and the nitrogen content is approximately 0.3 atomic %. The titanium nitride film and titanium oxide film were For quantitative analysis of titanium films, secondary ion mass spectrometry (SIMS) was used. Mass Spectrometry was used.

[0237] (Sample preparation) In Samples F to H and Comparative Sample I, a Li foil with a thickness of 600 μm was used as the counter electrode. The electrolyte solution was a mixture of EC and DEC in a volume ratio of 3:7 as the solvent, and LiPF6 was used, and polypropylene with a thickness of 25 μm was used as the separator.

[0238] In this manner, each sample was prepared.

[0239] (Sample Measurement) Next, the initial charge-discharge characteristics of each sample of this example at 25°C were evaluated. The measurement was carried out using a voltage measuring instrument (manufactured by Toyo Systems Co., Ltd.). Constant current charging was carried out with an upper limit of 1.5 V. The charge / discharge rate was 0.2 C, and the lower limit was 0.01 V. The rate is calculated based on the theoretical capacity of silicon, 4200mAh / g.

[0240] Fig. 27(A) shows the results of sample F, Fig. 27(B) shows the results of sample G, Fig. 27(C) shows the results of sample H, and Fig. 27( Fig. 27 shows the initial charge / discharge curve of comparative sample I. The horizontal axis is capacity (mAh / g). The vertical axis is voltage (V). The servings are different.

[0241] The initial discharge capacity obtained was 2645mAh / g for sample F and 2955mAh / g for sample G. The sample H had a capacity of 2158mAh / g, and the comparative sample I had a capacity of 4518mAh / g. The initial charge-discharge efficiency of sample F was 84.8%, and the initial charge-discharge efficiency of sample G was 79.9%.

[0242] Next, the cycle characteristics of each sample of this example at 25°C were evaluated. The charging conditions were the same as those used in the initial evaluation of the charge-discharge characteristics.

[0243] Figure 28 shows the change in capacity retention rate when the initial discharge capacity is set to 1. Figure 28(A) shows the change in capacity retention rate when the initial discharge capacity is set to 1. 28(B) is a graph showing the capacity retention rates of sample G, sample H, and comparative sample I. 28(C) and (D) are graphs in which the capacity retention rates of sample H and comparative sample I are superimposed. are graphs in which the vertical axes of Figures 28(A) and 28(B) are enlarged. ), samples F and G are shown by thick solid lines, sample H is shown by a thin solid line, and comparative sample I is shown by a thin dashed line. The capacity retention rate for samples F and G up to 20 cycles is shown. H and comparative sample I show a capacity retention rate up to 50 cycles.

[0244] From Figure 28, it can be seen that Samples F and G exhibit good cycle characteristics, similar to Sample H. Therefore, titanium nitride and titanium oxide, as well as titanium, are also suitable for use in one embodiment of the present invention. It has been shown to be suitable as a functional material contained in composite particles in negative electrodes for energy storage devices. . [Example]

[0245] In this example, a negative electrode for a power storage device according to one embodiment of the present invention was prepared. A power storage device was manufactured and its characteristics were evaluated. The results are described below.

[0246] The power storage device manufactured in this example is a coin-type battery (coin cell), and Sample J, Each sample contains an electrode, a counter electrode, an electrolyte, and a separator. The structure is common to all samples. The method for fabricating the electrodes is explained below. The electrodes used for the comparative sample K are referred to as electrode J and electrode K, respectively.

[0247] (Electrode manufacturing method) An active material layer and a functional layer are formed on a titanium substrate, which serves as a current collector, using a sputtering device. The silicon target used to form the active material layer was the same for both electrodes J and K. It is common.

[0248] Electrode J was made by depositing a 70 nm silicon film and a 30 nm titanium film on a titanium substrate. The deposition conditions for the titanium film were an Ar gas flow rate of 9 sccm.

[0249] The electrode K was made by depositing a silicon film with a thickness of 70 nm on a titanium substrate.

[0250] (Sample preparation) A half cell was fabricated using electrode J and electrode K. The characteristics were evaluated using a CR2032 type. A coin-type power storage device (20 mm in diameter, 3.2 mm in height) was used. The separator was made of polypropylene. The electrolyte contained EC and DEC as solvents. The mixture was mixed in a volume ratio of 3:7 and LiPF6 was used as the solute. This was dissolved to prepare an electrolyte solution with a LiPF6 concentration of 1.0 mol / L.

[0251] In this manner, each sample was prepared.

[0252] (Sample Measurement) Next, the cycle characteristics of each sample of this example at 25°C were evaluated. The test was performed using a constant current / constant voltage charger (manufactured by Toyo Systems Co., Ltd.). The charge / discharge rate was 0.2 C, and the lower limit was 0.01 V. The theoretical capacity of the active material, including silicon and titanium, is 4190mAh / g. The calculation is based on the relationship between any one charge / discharge cycle and the next charge / discharge cycle. There was a 30-minute or 2-hour break between sessions.

[0253] Figure 29 shows the change in capacity of each sample during cycle evaluation. The dashed line shows the capacity change of sample J, and the dashed line shows the capacity change of comparative sample K. 2122mAh / g, and comparative sample K has 3814mAh / g.

[0254] From Figure 29, it can be seen that sample J exhibits better cycle characteristics than comparative sample K. Light.

[0255] (Cross-section observation of sample) FIG. 30 shows the results of STEM observation of cross sections of Sample J and Comparative Sample K after charge and discharge. Figure 30(A) shows the results of a sample prepared under the same conditions as sample J after 10 charge-discharge cycles. Fig. 30(B) shows the cross-sectional image of the sample fabricated under the same conditions as comparative sample K after 10 cycles. The cross-sectional images are of the cell after charging and discharging.

[0256] In the comparative sample K, protrusions and depressions occurred in the silicon film 715 on the titanium substrate 705, On the other hand, the surface roughness is large (see FIG. 30(B)). In the sample J in which the silicon film 715 is covered with the titanium film 716, the silicon No large irregularities were observed on the titanium film 715 (see FIG. 30(A)). It was confirmed that this material is suitable as a functional material that can suppress deformation caused by silicon expansion and contraction. . [Explanation of symbols]

[0257] 100 negative electrode 101 Negative electrode current collector 102 Negative electrode active material layer 110 Complex 110A complex 111 Complex 111A complex 112 Complex 115 Anode active material 116 Functional Materials 116A Functional materials 116B Functional materials 117 Compound 118 compounds 121A Half Cell 121B Half Cell 122 Load 123 Charger 200 negative electrode 201 Negative electrode current collector 202 Negative electrode active material layer 203 Complex 204 Graphene 300 storage battery 301 Positive electrode can 302 Anode can 303 Gasket 304 Positive electrode 305 Positive electrode current collector 306 Positive electrode active material layer 307 Negative electrode 308 Negative electrode current collector 309 Negative electrode active material layer 310 Separator 372mAh theoretical capacity 400 storage battery 402 Positive electrode 404 Negative electrode 500 battery 501 Positive electrode current collector 502 Positive electrode active material layer 503 Positive electrode 504 Negative electrode current collector 505 Negative electrode active material layer 506 negative electrode 507 Separator 508 Electrolyte 509 Exterior body 510 Positive lead electrode 511 Negative lead electrode 512 Welding Area 513 Curved section 514 Sealing part 600 storage battery 601 Positive electrode cap 602 Battery can 603 Positive terminal 604 Positive electrode 605 Separator 606 negative electrode 607 Negative terminal 608 Insulating plate 609 Insulating board 611 PTC element 612 Safety valve mechanism 705 titanium substrate 715 Silicone membrane 716 Titanium Film 900 Circuit Board 910 Label 911 terminal 912 circuits 913 Electricity storage unit 914 Antenna 915 Antenna 916 layers 917 layers 918 Antenna 919 terminal 920 Display device 921 Sensor 922 terminal 951 terminal 952 terminals 981 Film 982 Film 990 Power storage device 991 Exterior body 992 exterior body 993 Wound body 994 negative electrode 995 positive electrode 996 Separator 997 Lead Electrode 998 Lead electrode 7100 Portable display devices 7101 Housing 7102 Display section 7103 Operation button 7104 Energy storage devices 7105 Lead electrode 7106 Current collector 7200 Personal Digital Assistant 7201 Case 7202 Display section 7203 Band 7204 Buckle 7205 Operation button 7206 Input / output terminal 7207 Icon 7400 mobile phone 7401 Housing 7402 Display section 7403 Operation button 7404 External connection port 7405 Speaker 7406 Microphone 7407 Electricity storage devices 7408 Lead electrode 7409 Current collector 8021 Charging device 8022 cable 8100 Automobiles 8101 Headlight 8106 Electric motor

Claims

1. a negative electrode active material layer including a particulate composite, a conductive additive, and a binder, disposed on a current collector; the composite has an active material containing silicon, a material containing titanium, a first compound containing silicon and titanium, and a second compound containing silicon and titanium; the second compound has a higher weight ratio of silicon to titanium than the first compound; The negative electrode for an electricity storage device contains a particulate conductive additive.

2. a negative electrode active material layer including a particulate composite, a conductive additive, and a binder, disposed on a current collector; the composite has an active material containing silicon, a material containing titanium, a first compound containing silicon and titanium, and a second compound containing silicon and titanium; the second compound has a higher weight ratio of silicon to titanium than the first compound; The conductive additive is a sheet-like conductive additive.

3. a negative electrode active material layer including a particulate composite, a conductive additive, and a binder, disposed on a current collector; the composite has an active material containing silicon, a material containing titanium, a first compound containing silicon and titanium, and a second compound containing silicon and titanium; the second compound has a higher weight ratio of silicon to titanium than the first compound; the active material has a region in contact with at least one of the material, the first compound, and the second compound; The negative electrode for an electricity storage device contains a particulate conductive additive.

4. a negative electrode active material layer including a particulate composite, a conductive additive, and a binder, disposed on a current collector; the composite has an active material containing silicon, a material containing titanium, a first compound containing silicon and titanium, and a second compound containing silicon and titanium; the second compound has a higher weight ratio of silicon to titanium than the first compound; the active material has a region in contact with at least one of the material, the first compound, and the second compound; The conductive additive is a sheet-like conductive additive.

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