Lithium ion secondary battery

Abstract

To provide a secondary battery with high capacity and less deterioration. A novel power storage device is provided.SOLUTION: A secondary battery includes a positive electrode and a negative electrode, in which the negative electrode includes a first active material, a second active material, and a graphene compound, at least part of a surface of the first active material includes a region covered with the second active material, a surface of the second active material and at least part of a surface of the first active material include a region covered with the graphene compound, the first active material includes graphite, the second active material includes silicon, and the capacity of the positive electrode is higher than or equal to 50% and lower than 100% of the capacity of the negative electrode.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to an electrode and a method for manufacturing the same, or to an active material contained in the electrode and a method for manufacturing the same. Or, it relates to a secondary battery and a method for manufacturing the same. Or, it relates to a vehicle having a secondary battery. This relates to mobile devices, including portable information terminals, electronic devices, etc.

[0002] One aspect of the present invention relates to an article, a method, or a manufacturing method. , machine, manufacture, or composition of matter One embodiment of the present invention is a semiconductor device, a display device, a light-emitting device, a power storage device, a lighting device, an electronic device, or the like. or a method for producing the same.

[0003] In this specification, the term "electronic device" refers to any device having a power storage device. Electro-optical devices having a power storage device, and information terminal devices having a power storage device are all electronic devices.

[0004] In this specification, the term "power storage device" refers to elements and devices in general that have a power storage function. For example, a storage battery (also called a secondary battery) such as a lithium-ion secondary battery, These include lithium ion capacitors and electric double layer capacitors. [Background technology]

[0005] In recent years, various types of energy storage devices have become available, including lithium-ion secondary batteries, lithium-ion capacitors, and air batteries. The development of lithium-ion batteries, which have high output and high energy density, is particularly active. Secondary batteries are used in portable information terminals such as mobile phones, smartphones, and laptop computers. terminals, portable music players, digital cameras, medical equipment, or hybrid vehicles (HV), electric vehicles Next-generation clean energy vehicles such as electric vehicles (EV) or plug-in hybrid vehicles (PHV) Demand for high-energy vehicles has expanded rapidly along with the development of the semiconductor industry, and It has become an indispensable source of energy in today's information society. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Japanese Patent Application Laid-Open No. 2002-216751 [Patent Document 2] Special Publication No. 2019-522886 Summary of the Invention [Problem to be solved by the invention]

[0007] Secondary batteries used in vehicles such as electric vehicles and hybrid vehicles are designed to extend driving distances. Therefore, capacity needs to be increased.

[0008] In addition, power consumption is increasing in mobile terminals and other devices due to their increasing functionality. The secondary batteries used in mobile terminals are required to be small and lightweight. There is also a demand for higher capacity secondary batteries.

[0009] In addition to its stability, it is important that the secondary battery has a high capacity. Alloy materials such as ZnO-based materials have high capacity and are promising as active materials for secondary batteries. Therefore, alloy materials with high charge / discharge capacity tend to pulverize the active material and cause volume changes during charge / discharge. Problems such as the battery breaking down and falling off occur, and sufficient cycle characteristics are not obtained.

[0010] In order to improve the problems of alloy-based materials as mentioned above, alloy-based materials and graphite or carbonaceous materials are used. In Patent Document 1, silicon-containing particles and carbon-containing particles are bonded together. The paper describes a composite material in which a carbon coating layer is formed on the surface of a porous particle core formed by combining particles. In Patent Document 2, a composite material containing silicon (Si), lithium fluoride (LiF) and a carbon material is used. However, in any of the above documents, the composite particles To fully resolve the problem of active material pulverization and falling off due to the expansion of gold-based materials, We haven't reached that point yet.

[0011] The electrodes of a secondary battery are made up of materials such as an active material, a conductive material, and a binder. The higher the proportion of materials that contribute to capacity, such as active materials, the higher the capacity of the secondary battery. The conductive material in the electrodes increases the conductivity of the electrodes, resulting in excellent output characteristics. Furthermore, the active material repeatedly expands and contracts during charging and discharging of the secondary battery. This can cause the active material to collapse, the conductive path to be interrupted, etc. In such a case, the electrode has a conductive material and a binder, which prevents the active material from collapsing and being conductive. On the other hand, by using a conductive material and a binder, However, the proportion of the active material decreases, which may result in a decrease in the capacity of the secondary battery.

[0012] An object of one aspect of the present invention is to provide an electrode having excellent characteristics. An object of one embodiment of the present invention is to provide an active material having excellent properties. An object of one aspect of the present invention is to provide a novel electrode.

[0013] Another object of one embodiment of the present invention is to provide a mechanically strong negative electrode. An object of one aspect of the present invention is to provide a mechanically strong positive electrode. An object of one embodiment of the present invention is to provide a negative electrode having a high capacity. Another object of the present invention is to provide a positive electrode with high capacity. Another object of the present invention is to provide a negative electrode. The goal is to

[0014] Another object of one embodiment of the present invention is to provide a secondary battery that is less susceptible to deterioration. An object of one embodiment of the present invention is to provide a highly safe secondary battery. According to one embodiment of the present invention, an object is to provide a secondary battery having high energy density. An object of one embodiment of the present invention is to provide a novel secondary battery.

[0015] The description of these problems does not preclude the existence of other problems. It is not necessary for one embodiment to solve all of these problems. It is possible to extract other problems from the claims. [Means for solving the problem]

[0016] One embodiment of the present invention includes a positive electrode and a negative electrode. The negative electrode includes a first active material and a second active material. and a graphene compound, and at least a portion of the surface of the first active material is covered with a second active material. and a surface of the second active material and at least one of the surfaces of the first active material. The portion has a region covered with a graphene compound, the first active material has graphite, and the second active material has The material contains silicon, and the capacity of the positive electrode is 50% or more but less than 100% of the capacity of the negative electrode. It is a secondary battery.

[0017] Another embodiment of the present invention includes a positive electrode and a negative electrode. The negative electrode contains a first active material and a second active material. and a graphene compound, and at least a portion of the surface of the first active material is and a surface of the second active material and a surface of the first active material. The first active material has a region partially covered with a graphene compound, the second active material has graphite, and the third active material has a region partially covered with a graphene compound. The second active material has silicon, and in a fully charged state, the second active material has a Si-Si bond. It is a secondary battery.

[0018] Another embodiment of the present invention is a semiconductor device including a positive electrode, a negative electrode, and an electrolyte. a second active material and a graphene compound, and at least one of the surfaces of the first active material is The portion has a region covered with a second active material, and the surface of the second active material and the surface of the first active material At least a portion of the surface has a region covered with a graphene compound, and the first active material is graphite. The second active material contains silicon, and the capacity of the positive electrode is 50% or more of the capacity of the negative electrode. It is a secondary battery, in which the capacity is less than 100% and the electrolyte has an ionic liquid.

[0019] Another embodiment of the present invention is a semiconductor device including a positive electrode, a negative electrode, and an electrolyte. a second active material and a graphene compound, and at least one of the surfaces of the first active material is The portion has a region covered with a second active material, and the surface of the second active material and the surface of the first active material At least a portion of the surface has a region covered with a graphene compound, and the first active material is graphite. The second active material has silicon, and in a fully charged state, the second active material is Si- This secondary battery has Si bonds and an ionic liquid electrolyte.

[0020] In any one of the secondary batteries described above, the ionic liquid contains 2 mol / L or more of Li It is desirable to have FSI and EMI-FSI.

[0021] In any one of the secondary batteries described above, the positive electrode is made of a material selected from the group consisting of magnesium, fluorine, and aluminum. lithium cobalt oxide having magnesium and nickel, The concentration of one or more selected from the group consisting of nesium, fluorine, and aluminum is the highest. It is desirable that the surface layer has a region where the surface area is large.

[0022] In any one of the secondary batteries described above, the first active material is composed of particles having a particle diameter of 5 μm or more. Preferably, the first active material comprises graphite, and the second active material comprises silicon having a particle size of 250 nm or less. stomach.

[0023] One embodiment of the present invention is a vehicle including any one of the above secondary batteries.

[0024] One embodiment of the present invention is a power storage system including any one of the above secondary batteries.

[0025] One embodiment of the present invention is an electronic device including any one of the above secondary batteries. [Effects of the Invention]

[0026] According to one embodiment of the present invention, an active material having excellent properties can be provided. Furthermore, according to one embodiment of the present invention, a novel electrode having excellent properties can be provided. The poles can be provided.

[0027] Furthermore, according to one embodiment of the present invention, a mechanically strong negative electrode can be provided. According to one embodiment of the present invention, a mechanically strong positive electrode can be provided. In this manner, a negative electrode having a high capacity can be provided. Furthermore, according to one embodiment of the present invention, a negative electrode that is less deteriorated can be provided. According to one embodiment of the present invention, a positive electrode that is less susceptible to deterioration can be provided. Cut.

[0028] According to one embodiment of the present invention, a secondary battery with little deterioration can be provided. According to one embodiment of the present invention, a highly safe secondary battery can be provided. According to one embodiment, a secondary battery with high energy density can be provided. According to one aspect, a novel secondary battery can be provided.

[0029] The description of these effects does not preclude the existence of other effects. An embodiment does not necessarily have to have all of these effects. The above will be made clear from the description, drawings, claims, etc. It is possible to extract other effects from the descriptions in the aspects and claims. [Brief explanation of the drawings]

[0030] [Figure 1] 1A and 1B are diagrams showing an example of a cross section of an electrode, and Fig. 1C is a diagram illustrating the capacity ratio between the positive electrode and the negative electrode. [Figure 2] 2A to 2C are diagrams illustrating the capacity ratio between the positive electrode and the negative electrode, and the voltage of the secondary battery. [Figure 3] Fig. 3A is a diagram showing an example of particles contained in a negative electrode, and Fig. 3B and Fig. 3C are diagrams showing changes in particle shape during charge and discharge. [Figure 4]4A and 4B are diagrams relating to calculations of the negative electrode according to one embodiment of the present invention. [Figure 5] FIG. 5 is a diagram relating to calculations of the negative electrode according to one embodiment of the present invention. [Figure 6] 6A to 6C are diagrams relating to calculations of the negative electrode according to one embodiment of the present invention. [Figure 7] FIG. 7 is a diagram showing an example of a method for producing an electrode. [Figure 8] 8A and 8B are examples of graphene compound models. [Figure 9] FIG. 9 shows a cross-sectional structure of a positive electrode of one embodiment of the present invention. [Figure 10] 10A1 to 10C2 are diagrams showing cross-sectional structures of positive electrode active material composites according to embodiments of the present invention. [Figure 11] FIG. 11A is a top view of the positive electrode active material of one embodiment of the present invention, and FIGS. 11B and 11C are cross-sectional views of the positive electrode active material of one embodiment of the present invention. [Figure 12] FIG. 12 illustrates a crystal structure of a positive electrode active material of one embodiment of the present invention. [Figure 13] FIG. 13 shows the XRD pattern calculated from the crystal structure. [Figure 14] FIG. 14 is a diagram illustrating the crystal structure of a positive electrode active material of a comparative example. [Figure 15] FIG. 15 shows the XRD pattern calculated from the crystal structure. [Figure 16] Figure 16 is an example of a TEM image in which the crystal orientations are roughly consistent. [Figure 17] Figure 17A is an example of a STEM image in which the crystal orientations are roughly consistent, Figure 17B is an FFT of a region of the rock-salt-type crystal RS, and Figure 17C is an FFT of a region of the layered rock-salt-type crystal LRS. [Figure 18] 18A is an exploded perspective view of the coin-type secondary battery, FIG. 18B is a perspective view of the coin-type secondary battery, and FIG. 18C is a cross-sectional perspective view thereof. [Figure 19]Fig. 19A shows an example of a cylindrical secondary battery. Fig. 19B shows an example of a cylindrical secondary battery. Fig. 19C shows an example of multiple cylindrical secondary batteries. Fig. 19D shows an example of a power storage system having multiple cylindrical secondary batteries. [Figure 20] 20A and 20B are diagrams illustrating an example of a secondary battery, and FIG. 20C is a diagram showing the inside of the secondary battery. [Figure 21] 21A to 21C are diagrams illustrating an example of a secondary battery. [Figure 22] 22A and 22B are diagrams showing the external appearance of a secondary battery. [Figure 23] 23A to 23C are diagrams illustrating a method for manufacturing a secondary battery. [Figure 24] 24A to 24C are diagrams showing examples of the configuration of a battery pack. [Figure 25] 25A and 25B are diagrams illustrating an example of a secondary battery. [Figure 26] 26A to 26C are diagrams illustrating an example of a secondary battery. [Figure 27] 27A and 27B are diagrams illustrating an example of a secondary battery. [Figure 28] FIG. 28A is a perspective view of a battery pack showing one embodiment of the present invention, FIG. 28B is a block diagram of the battery pack, and FIG. 28C is a block diagram of a vehicle having a motor. [Figure 29] 29A to 29D are diagrams illustrating an example of a transportation vehicle. [Figure 30] 30A and 30B illustrate a power storage device according to one embodiment of the present invention. [Figure 31] FIG. 31A is a diagram showing an electric bicycle, FIG. 31B is a diagram showing a secondary battery of the electric bicycle, and FIG. 31C is a diagram explaining an electric motorcycle. [Figure 32] 32A to 32D are diagrams illustrating an example of an electronic device. [Figure 33]Fig. 33A shows an example of a wearable device, Fig. 33B shows a perspective view of a wristwatch-type device, Fig. 33C is a diagram illustrating a side view of the wristwatch-type device, and Fig. 33D is a diagram illustrating an example of a wireless earphone. [Figure 34] 34A and 34B are SEM images of the electrodes. [Figure 35] 35A and 35B are graphs showing cycle characteristics. [Figure 36] 36A and 36B are graphs showing cycle characteristics. [Figure 37] 37A and 37B are graphs showing discharge characteristics. DETAILED DESCRIPTION OF THE INVENTION

[0031] Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings. The present invention is not limited to the following description, and it is understood by those skilled in the art that various modifications may be made to the modes and details thereof. The present invention will be easily understood by reading the following description of the embodiments. It is not something that is done.

[0032] In the drawings, the size, thickness of layers, or areas may be exaggerated for clarity. Therefore, it is not necessarily limited to that scale.

[0033] In addition, in this specification, ordinal numbers such as 1st, 2nd, etc. are used for convenience. It does not indicate the order of processes or stacking. For example, "first" may be changed to "second" The term "the" or "third" can be used interchangeably in the description. The ordinal numbers listed may not match the ordinal numbers used to identify an aspect of the present invention. There may be cases where this is the case.

[0034] In this specification, particles are not limited to spherical particles (with a circular cross section), The cross-sectional shape of each particle may be elliptical, rectangular, trapezoidal, triangular, square with rounded corners, or asymmetrical. The individual particles may have any shape, and may also be irregular in shape.

[0035] (Embodiment 1) In this embodiment, an example of a secondary battery of one embodiment of the present invention will be described.

[0036] [Example of secondary battery configuration] A secondary battery having a positive electrode, a negative electrode, and an electrolyte will be described below.

[0037] 1A is a cross-sectional view showing the inside of a secondary battery according to one embodiment of the present invention. The electrode 570a, the positive electrode 570b, and the electrolyte 576 are arranged in a coin-type secondary battery shown in the embodiment described later. The negative electrode 57 can be applied to batteries, cylindrical secondary batteries, laminated secondary batteries, etc. 0a denotes a negative electrode current collector 571a and a negative electrode active material layer 571b formed in contact with the negative electrode current collector 571a. The positive electrode 570b includes at least a positive electrode current collector 571b and a positive electrode current collector 571b 1A. 1C is an enlarged view of the area surrounded by the dashed line A and dashed line B in FIG. 1A. 10 is a diagram illustrating the capacity ratio of the negative electrode 570a to the positive electrode 570b in a region including the secondary battery. The battery may have a separator between the negative electrode 570a and the positive electrode 570b.

[0038] [Capacity ratio of negative electrode to positive electrode] The negative electrode characteristic curve 560a and the positive electrode characteristic curve 560b shown in FIGS. 1C, 2A, 2B, and 2C are The projections 560b are opposed to each other in the areas surrounded by the dashed lines A and B in FIG. 1A. The negative electrode active material layer 572a and the positive electrode active material layer 572b of the negative electrode 570a and the positive electrode 570b having the same area are 10 is a characteristic curve showing the relationship between capacitance and potential of layer 572b.

[0039] In the negative electrode characteristic curve 560a of FIG. 1C, the capacity C1 is the capacity at which the negative electrode 570a can be charged and discharged. The total capacity that the negative electrode 570a can charge and discharge is, for example, the total capacity of the negative electrode 570a and the lithium A half cell containing aluminum metal and Zn was prepared and discharged at a constant current (0.2 C, lower limit voltage 0.01 V). ) followed by constant voltage discharge (lower limit current density 0.02C), then constant current charge (0.2C, upper limit voltage 1V). Also, the positive electrode characteristic curve 560 in Figure 1C In b, the capacity C2 is the capacity of the positive electrode of the secondary battery in a fully charged state. The fully charged state of a secondary battery is, for example, the rated capacity specified in JIS C8711 (2013). This refers to the state of charge at which a certain amount of charge is obtained.

[0040] The capacity ratio of the negative electrode 570a and the positive electrode 570b in the secondary battery is In the case of the negative electrode 570a and the positive electrode 570b, the capacity of the positive electrode 570a is 100%. For example, as shown in FIG. 2A, the capacity of anode 570a is When the capacity of the positive electrode 570b is equal to that of the negative electrode 570a, the capacity ratio of the negative electrode 570a to the positive electrode 570b is 100%. is.

[0041] Next, when the capacity ratio of the negative electrode 570a to the positive electrode 570b is lower than 100%, The case where the capacity ratio is lower than 100% means that the charge / discharge capacity of the negative electrode 570a is This indicates that the total capacity is greater than the charge / discharge capacity of the positive electrode 570b. The capacitance C1 of the negative electrode 570a shown in FIG. 1C is larger than the capacitance C2 of the positive electrode 570b. become.

[0042] In this way, when the capacity ratio is lower than 100%, the capacity C1 of the negative electrode 570a has an excess capacity. Although a large amount of lithium ions is generated, it is believed that this makes it easier to suppress unintended deposition of lithium ions in the negative electrode 570a. In addition, in a secondary battery having the negative electrode 570a according to one embodiment of the present invention, In this case, the capacity is preferably 50% or more and less than 100%, and more preferably 70% or more and less than 90%. In this case, a secondary battery with high charge / discharge capacity and good charge / discharge cycle characteristics can be obtained. be.

[0043] Next, the voltage of the secondary battery will be explained. The voltage of the secondary battery is the difference between the positive electrode potential and the negative electrode potential. For example, when the capacity ratio of the negative electrode 570a to the positive electrode 570b is 100%, The voltage of the secondary battery when the capacity ratio is lower than 100% is shown as ΔVa in FIG. This is shown as ΔVb in FIG. 2B. As shown in FIG. 2B, when the capacity ratio is lower than 100%, In this case, the negative electrode 570a is used in a high potential range, so the voltage of the secondary battery decreases.

[0044] Next, in FIG. 2C, when the capacity ratio of the negative electrode 570a to the positive electrode 570b is lower than 100%, Here, the case where the secondary battery voltage does not decrease even if the voltage is increased is shown. In FIG. 2B, the usable potential range of the positive electrode 570b is the same as that of Vc. The range is the same as the range of potential used for the positive electrode 570b in FIG. 2A. As described above, the voltage ΔVb is smaller than ΔVa. When the available potential range of 70b is expanded to a high potential, the secondary battery voltage ΔVc is It becomes a high value.

[0045] As shown in FIG. 2C, when the capacity ratio of the negative electrode 570a to the positive electrode 570b is lower than 100%, In this case, it is possible to obtain a secondary battery in which the voltage does not decrease even in the case where the positive electrode 57 Since the positive electrode 570b is exposed to a relatively high potential, the positive electrode 570b is The positive electrode active material 100 according to one embodiment of the present invention is required to have high resistance to a high-potential charge state. Since it can have a stable crystal structure in the above atmosphere, it is suitable as an active material for positive electrode 570b. The positive electrode active material 100 will be described in detail later.

[0046] [Negative electrode] FIG. 1B is an enlarged view of the area surrounded by the dashed line C in FIG. 1A. As shown in FIG. 1B, The electrode active material layer 572a is formed of a first active material 581, a second active material 582, and a sheet-like shape. The graphene compound 583 and the electrolyte 576 are included as materials having the graphene compound 583 and the electrolyte 576. The laphene compound 583 forms a second active material 582 located on the surface of the first active material 581. The state of contact with the first active material 581 as if it were covering, wrapping, or clinging to it. The graphene compound 583 included in the negative electrode 570a is, for example, a conductive material In one embodiment of the present invention, the conductive material functions as an active material by hydrogen bonding. Since it can cling to the substrate, it is possible to realize a highly conductive electrode.

[0047] Various materials can be used as the first active material 581 and the second active material 582. The first active material 581 and the second active material 582 are particles of one embodiment of the present invention. particles having oxygen-containing functional groups or fluorine on the surface, When particles having a region terminated by fluorine atoms are used, the first active material 581 and The affinity between the second active material 582 and the graphene compound 583 is improved, and the graphene compound 583 is As shown, the graphene compound 583 is a second active material located on the surface of the first active material 581. The first active material 58 is disposed so as to cover, encase, or cling to the material 582. The graphene compound 583 can contact the first active material 581 and the second active material 582. Since the electrode can be attached to the substrate 582, a highly conductive electrode can be realized. The state of clinging to something is not a point contact, but rather a close contact. It can also be said that the particles are in contact with each other along the particle surface. In other words, the first active material 581 and the second active material 582 are in surface contact with each other. Materials that can be used as the second active material 582 will be described later.

[0048] When an active material with a large volume change during charging and discharging is used as the second active material 582, 3B and 3C. In FIG. 3B, a first active material 581 and a second active material and a graphene compound 583 as a material having a sheet shape. The laphene compound 583 forms a second active material 582 located on the surface of the first active material 581. The state of contact with the first active material 581 as if it were covering, wrapping, or clinging to it. The second active material 582 is a mixture of the first active material 581 and a graphene compound 583. The graphene compound 583 is located between the first active material 581 and the second active material 582. It can also be said that the second active material 582 is in contact with the second active material 582. The graphene compound 58 is shown in Figure 3C. 3 is disposed so as to cover and encase the second active material 582 located on the surface of the first active material 581. Since the first active material 581 is in contact with the first active material 581 in a manner similar to that of a urchin or clinging to the first active material 581, the first active material 581 is not charged or discharged. Even if the volume of the second active material 582 increases due to the charge, the volume of the second active material 58 2 and the first active material 581. It can be suppressed.

[0049] The graphene compound 583 is attached to the active materials such as the first active material 581 and the second active material 582. When the graphene compound 583 is attached to the active material, the contact area between the graphene compound 583 and the active material is large. This improves the conductivity of electrons moving through the graphene compound 583. When the volume of the active material changes significantly due to the change in the temperature, the graphene compound 583 wraps around the active material. By making contact with the active material, it is possible to effectively prevent the active material from falling off. These effects are even more pronounced when the product is applied in close contact with the skin. Here, the graphene compound 583 has pores large enough to pass Li ions, and the number of pores is It is desirable to have a large amount of the graphene compound 583 so as not to impair the electronic conductivity of the graphene compound 583.

[0050] The negative electrode active material layer 572a contains, in addition to the graphene compound 583, carbon black, graphite, The carbon black may be a carbon-based material such as carbon fiber, fullerene, etc. For example, acetylene black (AB) can be used as the graphite. Lead, artificial graphite such as mesocarbon microbeads, etc. can be used. The material has high conductivity and can function as a conductive material in the active material layer. These carbonaceous materials may function as active materials.

[0051] Examples of carbon fibers include mesophase pitch-based carbon fibers and isotropic pitch-based carbon fibers. The carbon fibers may be carbon nanofibers or Carbon nanotubes can be used. Carbon nanotubes can be used in the gas phase, for example. It can be produced by a growth method or the like.

[0052] The active material layer may be made of a conductive material such as copper, nickel, aluminum, silver, or gold powder. Alternatively, it may have metal fibers, conductive ceramic materials, etc.

[0053] The content of the conductive material relative to the total amount of solids in the active material layer is 0.5 wt% or more and 10 wt% or less is preferable, and 0.5 wt% or more and 5 wt% or less is more preferable.

[0054] Unlike granular conductive materials such as carbon black, which make point contact with the active material, graphene compounds Since it allows for surface contact with low contact resistance, it can be used in smaller amounts than ordinary conductive materials. Therefore, the electrical conductivity between the active material and the graphene compound can be improved. The ratio in the material layer can be increased, thereby increasing the discharge capacity of the secondary battery. It can be done.

[0055] Furthermore, the graphene compound of one embodiment of the present invention has excellent lithium permeability, and therefore is suitable for use in secondary batteries. The charge and discharge rate can be increased.

[0056] Particulate carbon-containing compounds such as carbon black and graphite, and carbon nanotubes Fibrous carbon-containing compounds such as cellulose, cellulose acetate, and cellulose acetate tend to enter tiny spaces. It refers to the area between active materials. It is made up of carbon-containing compounds that can easily enter tiny spaces and those that are spread across multiple particles. It is combined with a sheet-like carbon-containing compound such as graphene, which can provide electrical conductivity. By using it in this way, the density of the electrodes can be increased and an excellent conductive path can be formed. In addition, the secondary battery includes the electrolyte 576 of one embodiment of the present invention, and thus the stability of the operation of the secondary battery can be improved. That is, the secondary battery according to one embodiment of the present invention can improve the quality of the energy density. It is possible to achieve both height and stability, making it effective as a secondary battery for vehicles. Increasing the number of ponds and the weight of the vehicle increases the energy required to move it. Therefore, the driving range is also shorter. By using high-density secondary batteries, the secondary batteries installed in the vehicle Even if the weight of the vehicle is the same, that is, even if the total weight of the vehicle is the same, the range can be increased. It is possible.

[0057] In addition, when the capacity of a vehicle's secondary battery increases, more power is required to charge it, so It is desirable to terminate charging at this time. In addition, when braking, temporary power is generated. This is called regenerative charging, and charging is performed under high-rate charging conditions. Therefore, good rate characteristics are required for secondary batteries for vehicles.

[0058] By using the electrolyte 576 according to one embodiment of the present invention, an in-vehicle A secondary battery having the above structure can be obtained.

[0059] Furthermore, the secondary battery of one embodiment of the present invention has high energy density and can be miniaturized. High conductivity allows rapid charging. It is also effective for mobile information terminals.

[0060] The negative electrode active material layer 572a preferably contains a binder (not shown). For example, the binder binds or fixes the electrolyte 576 and the active material. and carbon-based materials, active materials and carbon-based materials, multiple active materials, multiple carbon-based materials, etc. or fixed.

[0061] As binders, polystyrene, polymethyl acrylate, polymethyl methacrylate (poly Poly(dimethyl methacrylate, PMMA), sodium polyacrylate, polyvinyl alcohol (PVA), polyethylene oxide (PEO), polypropylene oxide, polyimide , polyvinyl chloride, polytetrafluoroethylene, polyethylene, polypropylene, poly Isobutylene, polyethylene terephthalate, nylon, polyvinylidene fluoride (PVD F), polyacrylonitrile (PAN), ethylene propylene diene polymer, polyacetic acid It is preferable to use materials such as vinyl and nitrocellulose.

[0062] Polyimide has excellent thermal, mechanical and chemical stability. When polyimide is used as the polymer, a dehydration reaction and a cyclization (imidization) reaction are carried out. These reactions can be carried out by, for example, heat treatment. The graphene compound is graphene having oxygen-containing functional groups, and the binder is polyimide. When a graphene compound is used, the graphene compound can also be reduced by the heat treatment. This allows for simplification of the process. In addition, because of its excellent heat resistance, it can be used at temperatures of, for example, 200°C or higher. Heat treatment can be performed at a temperature of 200°C or higher. This allows the reduction reaction of the graphene compound to proceed sufficiently, further increasing the conductivity of the electrode. It is possible.

[0063] Fluorine-containing polymer materials, specifically polyvinylidene fluoride ( PVDF, etc. can be used. PVDF has a melting point in the range of 134°C to 169°C. It is a resin with excellent thermal stability.

[0064] In addition, styrene-butadiene rubber (SBR), styrene-isoprene Styrene rubber, acrylonitrile-butadiene rubber, butadiene rubber, ethylene-propylene It is preferable to use a rubber material such as a olefin-diene copolymer. Fluorine rubber can be used.

[0065] As the binder, it is preferable to use, for example, a water-soluble polymer. As the molecule, for example, polysaccharides can be used. cellulose (CMC), methylcellulose, ethylcellulose, hydroxypropyl Cellulose, diacetyl cellulose, regenerated cellulose and other cellulose derivatives, or stabilisers These water-soluble polymers can be used in combination with the rubber materials mentioned above. It is more preferable to use it as such.

[0066] The binder may be used in combination with two or more of the above.

[0067] The graphene compound 583 has flexibility, and the first active material 581 and the second active material The first active material 581 and the second active material 582 can be attached to each other like natto. The second active material 582 is made of soybeans, and the graphene compound 583 is made of a sticky component, such as polyglucose. The graphene compound 583 can be compared to anode active material layer 5 72a includes an electrolyte 576, a plurality of active materials, a plurality of carbon-based materials, and the like. By disposing the negative electrode active material layer 572a in this manner, not only is a good conductive path formed in the negative electrode active material layer 572a, but Instead, graphene compounds 583 can be used to constrain or immobilize these materials. For example, a three-dimensional mesh structure, a polygonal arrangement, formed by multiple graphene compounds 583 For example, a honeycomb structure is formed in which hexagons are arranged in a matrix, and electrolyte 5 is placed in the mesh. 76. By arranging materials such as a plurality of active materials and a plurality of carbon-based materials, graphene Compound 583 forms a three-dimensional conductive path, and electrolyte 576 falls off from the current collector. In addition, in the structure in which the polygons are arranged, it is possible to suppress the number of sides from being different. Therefore, the graphene compound 583 can be used for the negative electrode active material. In the material layer 572a, when the material functions as a conductive material and a binder, Graphene compound 583 has holes with nine or more ring members, and even if it covers the active material, Since it does not hinder the movement of Li ions, it is particularly suitable as a conductive material for use in the negative electrode active material layer 572a. preferable.

[0068] [Negative electrode active material] The first active material 581 and the second active material 582 have a rounded shape, a cornered shape, In addition, in the cross section of the electrode, the first active material 581 The second active material 582 may have various cross-sectional shapes such as a circle, an ellipse, a curved figure, a polygon, etc. For example, as shown in FIG. 1B and FIG. 3A, a first active material 581 and The cross section of the first active material 58 and the second active material 582 has a rounded shape. The cross sections of the first and second active materials 582 may have corners. may have corners.

[0069] An example of the negative electrode active material will be described below.

[0070] The negative electrode active material may be silicon. It is preferable to use silicon-containing particles as 82 .

[0071] The negative electrode active material contained in the second active material 582 may include tin, gallium, aluminum, or the like. , germanium, lead, antimony, bismuth, silver, zinc, cadmium, and indium A metal or compound having one or more elements that can be used. Examples of alloy compounds using Mg include Mg2Si, Mg2Ge, Mg2Sn, and SnS. 2, V2Sn3, FeSn2, CoSn2, Ni3Sn2, Cu6Sn5, Ag3Sn, Ag3Sb, Ni2MnSb, CeSb3, LaSn3, La3Co2Sn7, CoSb 3, InSb, SbSn, etc.

[0072] In addition, silicon is doped with impurity elements such as phosphorus, arsenic, boron, aluminum, and gallium. A material with low resistance due to the addition of lithium may also be used. As a pre-doping method, lithium fluoride, lithium carbonate, etc. and silicon The methods include mechanical alloying of lithium metal and silicon, and annealing the mixture with silicon. There is also a method in which a first electrode is formed using silicon as the active material, and then a second electrode such as lithium metal is formed. When combined with an electrode, the silicon in the first electrode is doped with lithium through a charge-discharge reaction. Then, the doped first electrode is used to connect a counter electrode (e.g., a pre-doped negative electrode) to the A secondary battery may be fabricated by combining a positive electrode with a negative electrode.

[0073] For example, nanosilicon particles can be used as the second active material 582. The average diameter of the corn particles is preferably 5 nm or more and less than 1 μm, more preferably 10 nm The thickness is preferably from 10 nm to 100 nm, more preferably from 10 nm to 300 nm.

[0074] The nanosilicon particles may have a spherical shape or a flattened spherical shape. The size of the nanosilicon particles (particle diameter) may be 1 / 2 mm or 1 / 4 mm. ) is, for example, preferably 5 nm or more and 1 μm or less as D50 of laser diffraction particle size distribution measurement. More preferably, the nm is 10 nm or more and 300 nm or less, and even more preferably, the nm is 10 nm or more and 100 nm or less. Here, D50 is the value in the cumulative particle amount curve of the particle size distribution measurement results. The particle size when the cumulative amount of particles is 50% is called the median. The determination is not limited to laser diffraction particle size distribution measurement, but may also be performed by SEM or TEM analysis. The major axis of the particle cross section may be measured by the method described above.

[0075] The nanosilicon particles preferably comprise amorphous silicon. The nanosilicon particles preferably comprise amorphous silicon and polycrystalline silicon. It is preferable that the nanosilicon particles have crystalline silicon. and amorphous regions.

[0076] Examples of silicon-containing materials include SiO x (x is preferably less than 2, more preferably Preferably, a material having a refractive index of 0.5 or more and 1.6 or less can be used.

[0077] For example, a silicon-containing material may be used that has a form in which multiple crystal grains are present within one particle. For example, a form having one or more silicon crystal grains in one particle can be used. The single particle may have silicon oxide around the silicon crystal grain. The silicon oxide may be amorphous. It may also be particles with graphene compound 583 attached.

[0078] Silicon-containing compounds include, for example, Li2SiO3 and Li4SiO4. Li2SiO3 and Li4SiO4 may each be crystalline. , may be amorphous.

[0079] Analysis of silicon-containing compounds is performed using NMR, XRD, Raman spectroscopy, SEM, TEM, E This can be done using DX etc.

[0080] The first active material 581 of the negative electrode 570a preferably contains graphite.

[0081] It is more preferable that the first active material 581 is a material that undergoes little volume change during charging and discharging. It's nice.

[0082] The volume change of the first active material 581 due to charging or discharging is If the minimum volume is 1, the maximum volume during charging or discharging must be 2 or less. It is preferable that the ratio is 1.5 or less, more preferable that the ratio is 1.1 or less. stomach.

[0083] The particle size of the first active material 581 is preferably larger than the particle size of the second active material 582. It's nice.

[0084] For example, in a laser diffraction particle size distribution measurement, the D50 of the first active material 581 is The D50 of the active material 582 is preferably 1.5 times or more and less than 1000 times, and more preferably 2 times or more and 500 times or more. It is more preferable that the D50 is 10 times or more and 100 times or less. The particle diameter when the cumulative amount occupies 50% in the cumulative particle amount curve of the measurement results of the fabric, that is, In other words, it is the median. Note that particle size measurement is limited to laser diffraction particle size distribution measurement. The diameter of the particle cross section may be measured by analysis such as SEM or TEM.

[0085] The first active material 581 may be, for example, graphite or graphitized lead, which has a small volume change during charging and discharging. graphitizable carbon, non-graphitizable carbon, carbon nanotubes, carbon black and graphene Carbon-based materials such as compound 583 can be used.

[0086] The first active material 581 may be, for example, titanium, niobium, tungsten, or molybdenum. An oxide having one or more elements selected from the group consisting of zinc, zinc oxide, zinc fluoride ...

[0087] The first active material 581 may be a combination of the above-described metals, materials, compounds, etc. It is possible.

[0088] The first active material 581 may be, for example, SnO, SnO2, titanium dioxide (TiO2), or lithium. Lithium Titanium Oxide (Li4Ti5O 12 ), lithium-graphite intercalation compound (Li x C6) , niobium pentoxide (Nb2O5), tungsten oxide (WO2), molybdenum oxide (MoO 2) and other oxides can be used.

[0089] Alternatively, a material that causes a conversion reaction can be used as the first active material 581. For example, cobalt oxide (CoO), nickel oxide (NiO), iron oxide (FeO), etc. Alternatively, a transition metal oxide that does not undergo an alloying reaction with lithium may be used as the first active material 581. Further materials that undergo conversion reactions include Fe2O3, CuO, Cu2O, RuO2, Cr2O3, and other oxides, CoS 0.89 , sulfides such as NiS and CuS, Zn3 Nitrides such as N2, Cu3N, and Ge3N4, phosphides such as NiP2, FeP2, and CoP3, Examples of suitable fluorides include FeF3 and BiF3. Note that the potential of the above fluorides is high, so It may also be used as a positive electrode material.

[0090] [Negative electrode calculation 1] In a negative electrode 570a according to one embodiment of the present invention, graphite is used as a first active material 581, and When silicon is used as the active material 582, the first active material 581 and the second active material First-principles calculations were performed on the diffusion coefficient of lithium in the material 582.

[0091] Figure 4A shows graphite (Li 0.25 The crystal structure model used for the calculation of C6) is shown below. Figure 4B shows the silicon (Li 1.25 The crystal structure model used for the calculation of Si is shown below. is doing.

[0092] The calculation was performed using the first-principles electronic structure calculation package VASP. The conditions shown in Table 1 were used.

[0093] [Table 1]

[0094] Regarding the crystal structure model shown in Figures 4A and 4B, after volume relaxation calculations at each temperature, MD (molecular dynamics) calculations were performed under constant volume conditions. The diffusion coefficient was derived from the relationship between the amount of lithium displacement at each step and the elapsed time. I put it out.

[0095] The results of the calculations shown in Figures 4A and 4B and Table 1 are shown in Figure 5. It was shown that the diffusion coefficient of lithium is higher in graphite than in silicon.

[0096] In addition, regarding the relationship between the oxidation-reduction potential of graphite and silicon, graphite is 0.05V (vs. It is known that the oxidation-reduction potential of Si is 0.4V (vs. Li) and that of Si is 0.4V (vs. Li). , which correlates with the voltage at which charging (lithium uptake) begins, and the lithium insertion during charging When considering the priority of the two, lithium is preferentially absorbed into Si, which has a high redox potential. It is thought that...

[0097] These were estimated by combining the calculation results of the diffusion coefficient shown in Figure 5 and the relationship with the redox potential. Then, in the initial stage of charging, lithium is preferentially absorbed into silicon due to the difference in redox potential. However, as charging progresses, the diffusion coefficient gradually decreases due to the difference in the rate of lithium uptake. It is possible that lithium uptake into graphite, which has a high uptake rate, will be prioritized. Therefore, when the capacity of the negative electrode 570a according to one embodiment of the present invention is limited, the first active The graphite of the material 581 absorbs lithium to a level close to the theoretical capacity of the graphite, and the second active material 582 It is presumed that the silicon absorbs the excess lithium. In the case of the negative electrode 570a, when the capacity is limited, the silicon of the second active material 582 The graphite of the first active material 581 is used preferentially for charging and discharging, and the capacity limiting effect is , which may mainly affect the silicon of the second active material 582.

[0098] [Negative electrode calculation 2] FIG. 6A shows lithium-free silicon crystals, while FIGS. 6B and 6C show silicon-filled silicon crystals. FIG. 1 shows the structure in the charged state (alloyed with Li).

[0099] FIG. 6B shows the structure at Li / Si=1.714, and Si-Si bonds are present in the structure. On the other hand, the theoretical capacity limit value, Li / In the crystal structure at Si=4.4, the Li ratio is increased, and Si-Si crystals are formed in the structure. It can be seen that no such phenomenon exists. The crystalline structure of silicon is destroyed by repeated charging and discharging, and It is known that the battery becomes flaky and flakes, but for example, when a secondary battery is fully charged, In the case where the Si-Si bond shown in Figure 6B remains, the charge-discharge cycle is repeated. It is considered that the structure is likely to be maintained to some extent. When used with a lithium ratio (molar ratio) of Si=1.714 or less, good charging It may exhibit discharge cycle characteristics.

[0100] [Capacity limit of negative electrode] The negative electrode 570a of one embodiment of the present invention is a negative electrode composed of a first active material 581 and a second active material 582. It is preferable to use the negative electrode 570a with a smaller capacity than the capacity of the negative electrode 570a. As a limit, for example, the theoretical capacity of the first active material 581 and the second active material 582 is preferably The capacity ratio is 50% or more but less than 100%, and more preferably 70% or more but less than 90%. This is preferable because it allows the production of a secondary battery with high charge / discharge capacity and good charge / discharge cycle characteristics.

[0101] [Method for producing the negative electrode] FIG. 7 is a flowchart illustrating an example of a method for manufacturing the negative electrode 570a of one embodiment of the present invention.

[0102] First, in step S61, silicon-containing particles are used as the second active material 582. The silicon-containing particles are prepared, for example, by using the second active material 582 described above. Particles having such a structure can be used.

[0103] In step S62, a solvent is prepared. Examples of the solvent include water, methanol, and ethanol. alcohol, acetone, tetrahydrofuran (THF), dimethylformamide (DMF), N-methylpyrrolidone (NMP) or dimethyl sulfoxide (DMSO) Alternatively, a mixture of two or more kinds can be used.

[0104] Next, in step S63, the silicon-containing particles prepared in step S61 and The solvent prepared in step S62 is mixed with the mixture, and the mixture is recovered in step S64. In step S65, a mixture E-1 is obtained. A kneader or the like can be used for mixing. As the kneader, for example, a planetary centrifugal mixer can be used.

[0105] Next, in step S72, particles containing graphite are prepared as the first active material 581. As the particles having graphite, for example, the particles described above as the first active material 581 can be used. It can be used.

[0106] Next, in step S73, the mixture E-1 and the graphite-containing mixture prepared in step S72 are mixed. The particles are mixed with the particles to be mixed, and the mixture is collected in step S74. A mixture E-2 is obtained. A kneader or the like can be used for mixing. For example, a kneader A revolving mixer or the like can be used.

[0107] Next, in step S80, a graphene compound 583 is prepared.

[0108] Next, in step S81, the mixture E-2 and the graph prepared in step S80 are The mixture is mixed with the phenyl compound 583, and the mixture is recovered in step S82. It is preferable that the mixture is in a high viscosity state. In step S83, kneading (kneading at high viscosity) can be performed.

[0109] Next, in step S83, the mixture is kneaded. For example, a spatula or the like is used to knead the mixture. By kneading the mixture, the silicon-containing particles and the graphene particles are mixed. A mixture of graphene compound 583 and graphene compound 583 with excellent dispersibility. It can form things.

[0110] Next, in step S84, a solvent is added to the kneaded mixture and mixing is carried out. For example, a kneader or the like can be used. The mixed mixture is circulated in step S85. Consolidate.

[0111] The mixture collected in step S85 is subjected to steps S83 to S85. It is preferable to repeat the process n times, where n is a natural number, for example, between 2 and 10. In addition, in the process of step S83, if the mixture is in a dry state, a solvent is added. On the other hand, if too much solvent is added, the viscosity decreases and the effect of kneading is reduced. Lower.

[0112] After repeating steps S83 to S85 n times, a mixture E-3 is obtained (step P86).

[0113] Next, in step S87, a binder is prepared. It is possible to use a material, and it is particularly preferable to use polyimide. In the method 7, a precursor of a material to be used as a binder may be prepared. For example, An imide precursor is prepared.

[0114] Next, in step S88, the mixture E-3 and the binder prepared in step S87 are mixed. Next, in step S89, the viscosity is adjusted. In step S62, the same type of solvent as that prepared in step S88 is prepared. The viscosity is adjusted to, for example, the desired viscosity in step S97. In some cases, it may be possible to adjust the thickness, density, etc. of the resulting electrode.

[0115] Next, a solvent is added to the mixture whose viscosity has been adjusted in step S89, and step S9 The mixture is mixed in step S90 and collected in step S91 to obtain mixture E-4 (step S9 2) The mixture E-4 obtained in step S92 is called, for example, a slurry.

[0116] Next, in step S93, a current collector is prepared.

[0117] Next, in step S94, the mixture E-4 is applied to the current collector prepared in step S93. The coating method can be slot die, gravure, blade, or a combination of these. A continuous coating machine or the like may also be used for coating.

[0118] Next, in step S95, a first heating is performed. The first heating volatilizes the solvent. The first heating is performed at a temperature of 40°C or higher and 200°C or lower, preferably 50°C or higher and 150°C or lower. The first heating step may be called drying.

[0119] The first heating is performed, for example, at a temperature of 30°C to 70°C for 10 minutes or longer in an air atmosphere. After that, for example, heat treatment is performed on a hot plate at room temperature or above 100°C for 1 hour or more. The heat treatment may be carried out in a reduced pressure environment under the conditions of 100° C. for 1 hour or less.

[0120] Alternatively, the heat treatment may be carried out using a drying oven or the like. When a drying oven is used, for example, Heat treatment may be carried out at a temperature of 30° C. or higher and 120° C. or lower for 30 seconds or longer and 2 hours or shorter.

[0121] Alternatively, the temperature may be increased stepwise. For example, heat treatment at 60°C or less for 10 minutes or less may be performed. After this, a further heat treatment may be carried out at a temperature of 65°C or higher for 1 minute or more.

[0122] Next, in step S96, a second heating is performed. In this case, it is preferable that the cycloaddition reaction of the polyimide occurs by the second heating. In addition, the second heating may cause a dehydration reaction of the polyimide. Heat may cause a dehydration reaction of the polyimide. In the second heating, the cyclization reaction of the graphene compound 583 may occur. It is preferable that a reduction reaction occurs. The second heating is also called an imidization heat treatment or a reduction heat treatment. This is sometimes called thermal reduction treatment.

[0123] By performing a pressing process before the second heating, the electrode density can be increased without deteriorating the battery characteristics. It is preferable to perform the press treatment before step S96, since this can increase the temperature.

[0124] The second heating is performed at a temperature of 150°C or higher and 500°C or lower, preferably 200°C or higher and 450°C or lower. It is best to do this within a certain range.

[0125] The second heating is performed, for example, at 200°C or higher and 450°C or lower for 1 hour or longer and 10 hours or shorter. If it is performed in a reduced pressure environment of 0 Pa or less, or in an inert atmosphere such as nitrogen or argon, good.

[0126] In step S97, negative electrode 570a is obtained, in which an active material layer is provided on a current collector.

[0127] The thickness of the active material layer thus formed is preferably, for example, 5 μm to 300 μm. The thickness of the active material layer is preferably 10 μm or more and 150 μm or less. The mass loading is preferably 2 mg / cm 2 More than 50mg / cm 2 The following is fine.

[0128] The active material layer may be formed on both sides of the current collector, or on only one side. Alternatively, the active material layer may be formed partially on both sides.

[0129] After the solvent is evaporated from the active material layer, the active material layer is compressed by a roll press method or a flat press method. Pressing may be performed by applying heat.

[0130] [Positive electrode] The positive electrode 570b is a positive electrode current collector 571b and a positive electrode formed in contact with the positive electrode current collector 571b. The positive electrode 570b includes at least an active material layer 572b. will be explained.

[0131] [Conductive material] The conductive material is also called a conductive agent or conductive assistant, and is made of a carbon material. By attaching a conductive agent between the active materials, the active materials are electrically connected to each other, thereby increasing the conductivity. Note that "adhesion" only refers to the physical adhesion between the active material and the conductive agent. When covalent bonds are formed, rather than when bonds are formed by van der Waals forces, the surface of the active material When the conductive material covers part of the surface, or when the conductive material is embedded in the surface irregularities of the active material, This concept also includes cases where the device is electrically connected even if it is not.

[0132] Examples of conductive materials include carbon black such as acetylene black and furnace black. Graphite, such as Bomb Black, artificial graphite, and natural graphite, carbon nanofibers, and Carbon fibers such as carbon nanotubes, and graphene compounds 583, either One or more species can be used.

[0133] The positive electrode 570b of the secondary battery is a positive electrode current collector 571b such as a metal foil and an active material. To make the material adhere, a binder (resin) is mixed in. The binder is also called a binding agent. Indium is a polymer material, and when a large amount of binder is included, the activity in the positive electrode active material layer 572b increases. The proportion of the material decreases, and the discharge capacity of the secondary battery decreases. Therefore, the amount of binder is kept to a minimum. It is mixed with

[0134] Graphene has amazing electrical, mechanical and chemical properties, Carbon nanotubes are expected to be used in a variety of fields, including field-effect transistors and solar cells. It is a material.

[0135] Carbon fibers can also be used as the conductive material. For example, mesophase pitch carbon Carbon fibers such as carbon fibers and isotropic pitch-based carbon fibers can be used. , carbon nanofibers, carbon nanotubes, etc. can be used. The carbon nanotubes can be produced by, for example, vapor phase growth.

[0136] [Graphene compounds] In this specification, graphene compound 583 refers to graphene, multi-layer graphene, multi-layer graphene, and graphene-based composites. Zigraphene, graphene oxide, multi-layer graphene oxide, multi-graphene oxide, reduced reduced graphene oxide, reduced multi-layer graphene oxide, reduced multi-graphene oxide, Graphene compounds 583 are carbon-containing, flat, and silicon-based compounds. It has a shape such as a hexagonal ring and a two-dimensional structure formed by six-membered carbon rings. The two-dimensional structure formed by the six-membered rings can be called a carbon sheet. Graphene compound 58 The graphene compound 583 may have a curved shape. It is also preferable that the graphene compound 583 be rolled up into a carbon nanofiber. It may be like this.

[0137] In this specification and the like, graphene oxide refers to, for example, a graphene having carbon and oxygen and having a sheet-like shape. and has a functional group, particularly an epoxy group, a carboxy group, or a hydroxy group. .

[0138] In this specification and the like, reduced graphene oxide refers to, for example, a graphene oxide having carbon and oxygen, It has a two-dimensional structure formed by a six-membered carbon ring. Although a single sheet of reduced graphene oxide can function, stacking multiple sheets The reduced graphene oxide may have a carbon concentration of greater than 80 atomic %. and have a portion where the oxygen concentration is between 2 atomic % and 15 atomic %. By setting the carbon concentration and oxygen concentration in such a range, a conductive material having high conductivity can be obtained even with a small amount. The reduced graphene oxide can function as an electrical material. It is preferable that the intensity ratio G / D of the G band to the D band in the above-mentioned case is 1 or more. Reduced graphene oxide, which has a high strength ratio, functions as a highly conductive material even in small amounts. It is possible.

[0139] By reducing graphene oxide, holes can be created in the reduced graphene oxide. It may be possible.

[0140] In addition, as a graphene compound, a material in which the edges of graphene are terminated with fluorine is used. Good too.

[0141] In the longitudinal section of the active material layer, the inner region of the active material layer is uniformly covered with a sheet-like graphite layer. The graphene compound 583 is dispersed. It is formed so that it covers or adheres to the surface of multiple granular active materials. , are in surface contact with each other.

[0142] Here, a plurality of graphene compounds 583 are bonded to each other to form a mesh-like graphene. A graphene compound sheet (hereinafter referred to as a graphene compound net or graphene net) is formed. When the active material is covered with a graphene net, the graphene net can It can also function as a binder that binds materials together. This allows for a reduction in electrode volume and weight, or even for the absence of electrode material. In other words, the charge / discharge capacity of the secondary battery can be increased. It is possible.

[0143] Here, graphene oxide is used as the graphene compound 583, and is mixed with an active material to form an active material. After forming the layer that will become the porous layer, it is preferable to reduce the graphene oxide. The material layer preferably comprises reduced graphene oxide. When forming the active material layer, graphene oxide, which has extremely high dispersibility in polar solvents, is used. By this, the graphene compound 583 is dispersed almost uniformly in the inner region of the active material layer. It can be done.

[0144] A dispersion liquid in which graphene oxide is dispersed uniformly in a solvent is applied to a current collector, and the solvent is The active material layer was then prepared by reducing the graphene oxide. The graphene compound 583 in the material layer partially overlaps. The graphene oxide is dispersed to the extent that it comes into surface contact with each other, creating a three-dimensional conductive path. The graphene oxide may be reduced by, for example, heat treatment. Alternatively, a reducing agent may be used.

[0145] In addition, by covering the surface of the active material with a graphene compound in advance, a conductive coating is formed on the surface of the active material. The active materials are electrically connected by a graphene compound, creating a conductive path. It can also be formed.

[0146] The graphene compound 583 according to one embodiment of the present invention preferably has holes in some of the carbon sheets. In the graphene compound 583 according to one embodiment of the present invention, lithium is preferably contained in a part of the carbon sheet. By providing holes through which carrier ions such as ions can pass, graphene compounds On the surface of the active material covered with the substance 583, the insertion and desorption of carrier ions becomes easy, and The holes provided in the carbon sheet are voids, These may be called defects or voids.

[0147] The graphene compound 583 according to one embodiment of the present invention includes a plurality of carbon atoms and one or more fluorine atoms. and the carbon atoms are preferably bonded in a ring. Preferably, one or more of the carbon atoms bonded to the ring are bonded to the fluorine atom. It is preferable that the fluorine is terminated. Fluorine has a high electronegativity and is easily negatively charged. When charged lithium ions approach each other, they interact with each other, stabilizing the energy and This lowers the barrier energy for lithium ions to pass through the holes. The pores of the silicon compound 583 contain fluorine, so that lithium ions can be ionized even in small pores. It is possible to realize a graphene compound583 that has excellent conductivity and allows electrons to pass through easily. In addition, one or more of the carbon atoms bonded to the ring may be terminated with hydrogen. That's fine.

[0148] 8A and 8B show an example of the structure of a graphene compound 583 having holes. The graphene compound 583 having holes shown in FIGS. 8A and 8B is a graphene having holes, or It is also called reduced graphene with holes.

[0149] The structure shown in FIG. 8A has a 22-membered ring, and 8 of the carbon atoms constituting the 22-membered ring are In graphene compound 583, the two linked The six-membered ring is removed, and the carbon bonded to the removed six-membered ring is terminated with hydrogen. It can also be said that...

[0150] The structure shown in FIG. 8B has a 22-membered ring, and 8 of the carbon atoms constituting the 22-membered ring are Six carbon atoms are terminated with hydrogen and two carbon atoms are terminated with fluorine. In the phenanthroline compound 583, two connected six-membered rings were removed, and the removed six-membered ring It can also be said that the carbon bonded to the hydroxyl group has been terminated with hydrogen or fluorine.

[0151] Silicon terminated with a hydroxyl group reacts with the hydrogen of the hydroxyl group on the silicon surface. A hydrogen atom contained in the graphene compound 583 or a fluorine atom contained in the graphene compound 583 Hydroxy-terminated silicon can form hydrogen bonds with the atoms, resulting in pores. It is thought that the interaction with the graphene compound 583 having

[0152] The graphene compound 583 has fluorine in addition to hydrogen, which allows the hydroxyl group to be easily converted into an acid. In addition to the hydrogen bonds between the hydrogen atoms of the element and the hydrogen atoms of the graphene compound 583, the Hydrogen bonds are also formed between the hydrogen atoms and the fluorine atoms of the graphene compound 583, bonding the silicon It is thought that the interaction between the particles and the graphene compound 583 becomes stronger and more stable. can be obtained.

[0153] For example, when graphene compound 583 has holes, it can be used for Raman spectroscopy mapping measurements. This may enable us to observe spectra based on the characteristics caused by the holes. It is possible to observe the bonds and functional groups that are involved in the formation of the molecules using ToF-SIMS. This may enable analysis of the vicinity of the hole, the periphery of the hole, etc.

[0154] [Binder] In this specification, the term "binder" refers to a material used solely to bind active materials, conductive materials, etc. onto a current collector. Refers to the polymer compound that is mixed. For example, polyvinylidene fluoride (PVDF), styrene -Butadiene rubber (SBR), styrene-isoprene-styrene rubber, butadiene rubber, Rubber materials such as ethylene-propylene-diene copolymer, fluororubber, polystyrene, Polyvinyl chloride, polytetrafluoroethylene, polyethylene, polypropylene, polyiso This refers to materials such as butylene, ethylene propylene diene polymer, etc.

[0155] Since lithium ion conductive polymers are polymer compounds, they must be mixed thoroughly before use in the active material layer. By using a binder, it is possible to bind the active material and the conductive material onto the current collector. The electrode can be fabricated without using binders. Binders are materials that do not contribute to charge / discharge reactions. Therefore, the less binder there is, the more materials that contribute to charging and discharging, such as active materials and electrolytes, can be used. Therefore, it is possible to provide a secondary battery with improved discharge capacity, cycle characteristics, etc. do.

[0156] The electrolyte 576 is sufficiently organic solvent-free or very organic solvent-free to form an electrolyte layer. It is preferable that the material is dried. In this specification, the material is dried under reduced pressure at 90°C for 1 hour. The electrolyte layer is said to be sufficiently dried if the weight change is within 5%.

[0157] The lithium ion conductive polymer, lithium salt, binder, and To identify materials such as additives, for example, nuclear magnetic resonance (NMR) can be used. Raman spectroscopy, Fourier transform infrared spectroscopy (FT-IR), time-of-flight secondary ion mass spectrometry Time of Flight-SIMS, Gas Chromatography Mass Spectrometry (GC / MS), Pyrolysis Gas Liquid chromatography mass spectrometry (Py-GC / MS), liquid chromatography mass spectrometry ( The results of analysis such as LC / MS may also be used as a basis for judgment. It is preferable to separate the substance from other materials before subjecting it to analysis such as NMR.

[0158] In each of the above configurations, the negative electrode 570a may further contain a solid electrolyte material to provide flame retardancy. It is preferable to use an oxide-based solid electrolyte as the solid electrolyte material. .

[0159] Oxide-based solid electrolytes include LiPON, Li2O, Li2CO3, and Li2MoO4 , Li3PO4, Li3VO4, Li4SiO4, LLT(La 2 / 3-x Li 3x Ti O3), LLZ(Li7La3Zr2O 12 ) and other lithium composite oxides and lithium oxides Examples of such materials include:

[0160] LLZ is a garnet-type oxide containing Li, La, and Zr, and is also may be a compound containing Ta.

[0161] In addition, polymer solid electrolytes such as PEO (polyethylene oxide) formed by coating methods, etc. Such a polymer solid electrolyte can also function as a binder. Therefore, when a polymer solid electrolyte is used, the number of components of the electrode can be reduced, and manufacturing costs can be reduced. It is also possible to reduce

[0162] [Current collector] The positive electrode current collector 571b and the negative electrode current collector 571a may be made of stainless steel, gold, platinum, zinc, Metals such as iron, copper, aluminum, titanium, and their alloys have high electrical conductivity and are Materials that do not alloy with carrier ions, such as silicon, titanium, etc., can be used. Aluminium alloys with added elements that improve heat resistance, such as silicon, neodymium, scandium, and molybdenum. Aluminum alloys can be used, and they react with silicon to form silicides. The metal element may be formed of a metal element. The metal element that reacts with silicon to form silicide is , Zirconium, Titanium, Hafnium, Vanadium, Niobium, Tantalum, Chromium, Molyb The current collectors are available in sheet, mesh, and punched shapes. Shapes such as ring metal shape, expanded metal shape, etc. can be appropriately used. The current collector preferably has a thickness of 10 μm or more and 30 μm or less.

[0163] Note that the negative electrode current collector 571a preferably uses a material that does not alloy with carrier ions such as lithium. It is preferable.

[0164] A titanium compound may be provided by laminating it on the above-described metal element as the current collector. As the titanium compound, for example, titanium nitride, titanium oxide, titanium oxynitride in which a part of nitrogen is replaced by oxygen (TiO x N y , 0 < x < 2, 0 < y < 1), and titanium oxide in which a part of oxygen is replaced by nitrogen, one selected therefrom, or two or more thereof may be mixed or laminated and used. Among them, titanium nitride is particularly preferable because it has high conductivity and a high function of suppressing oxidation. By providing the titanium compound on the surface of the current collector, for example, the reaction between the material of the active material layer formed on the current collector and the metal is suppressed. When the active material layer contains a compound having oxygen, the oxidation reaction between the metal element and oxygen can be suppressed. For example, when aluminum is used as the current collector and the active material layer is formed using graphene oxide described later, there is a concern about the oxidation reaction between the oxygen of graphene oxide and aluminum. In such a case, by providing a titanium compound on aluminum, the oxidation reaction between the current collector and graphene oxide can be suppressed. It can be used. Among them, titanium nitride is particularly preferable because it has high conductivity and a high function of suppressing oxidation. By providing the titanium compound on the surface of the current collector, for example, the reaction between the material of the active material layer formed on the current collector and the metal is suppressed. When the active material layer contains a compound having oxygen, the oxidation reaction between the metal element and oxygen can be suppressed. For example, when aluminum is used as the current collector and the active material layer is formed using graphene oxide described later, there is a concern about the oxidation reaction between the oxygen of graphene oxide and aluminum. In such a case, by providing a titanium compound on aluminum, the oxidation reaction between the current collector and graphene oxide can be suppressed. In such a case, by providing a titanium compound on aluminum, the oxidation reaction between the current collector and graphene oxide can be suppressed. In such a case, by providing a titanium compound on aluminum, the oxidation reaction between the current collector and graphene oxide can be suppressed. It can be suppressed.

[0165] [[ID=?]] [Separator] A separator is disposed between the positive electrode 570b and the negative electrode 570a. As the separator, for example, fibers having cellulose such as paper, non-woven fabric, glass fiber, ceramics, or Nylon (polyamide), Vinylon (polyvinyl alcohol fiber), polyester , acrylic, polyolefin, polyurethane synthetic fibers, etc. The separator is processed into a bag shape and can be used for either the positive electrode 570b or the negative electrode 570a. It is preferable to arrange it so that it wraps around one side.

[0166] The separator has pores with a diameter of about 20 nm, preferably pores with a diameter of 6.5 nm or more. The porous material preferably has pores with a diameter of at least 2 nm. In the case of a semi-solid secondary battery, the separator may be omitted.

[0167] The separator may have a multi-layer structure. For example, the separator may be made of an organic material such as polypropylene or polyethylene. The material film is made of ceramic material, fluorine material, polyamide material, or a combination of these. The ceramic material can be, for example, aluminum oxide. Examples of the fluorine-based material include aluminum particles, silicon oxide particles, etc. For example, PVDF, polytetrafluoroethylene, etc. can be used. For example, nylon, aramid (meta-aramid, para-aramid), etc. can be done.

[0168] Coating with ceramic materials improves oxidation resistance, making it possible to use separators during high-voltage charging and discharging. This suppresses the deterioration of the battery and improves the reliability of the secondary battery. Coating the separator and electrodes makes them adhere more easily, improving output characteristics. Coating polyamide materials, especially aramid, improves heat resistance, making it suitable for secondary batteries. Safety can be improved.

[0169] For example, a mixture of aluminum oxide and aramid is coated on both sides of a polypropylene film. Alternatively, an oxidized aluminum film may be applied to the surface of the polypropylene film that contacts the positive electrode 570b. The surface that comes into contact with the negative electrode 570a is coated with a mixture of aluminum and aramid. It may be coated.

[0170] By using a multilayer separator, the safety of the secondary battery can be maintained even if the overall thickness of the separator is thin. Since the capacity per unit volume of the secondary battery can be increased,

[0171] [Electrolyte] When a liquid electrolyte 576 is used in the secondary battery, for example, ethylene carbonate is used as the electrolyte 576. Carbonate (EC), Propylene Carbonate (PC), Butylene Carbonate, Chloride Ethylene carbonate, vinylene carbonate, gamma-butyrolactone, gamma-valerolactone Dimethyl carbonate (DMC), diethyl carbonate (DEC), ethyl methyl Carbonate (EMC), methyl formate, methyl acetate, ethyl acetate, methyl propionate, Ethyl propionate, propyl propionate, methyl butyrate, 1,3-dioxane, 1,4 -Dioxane, dimethoxyethane (DME), dimethyl sulfoxide, diethyl ether , methyl diglyme, acetonitrile, benzonitrile, tetrahydrofuran, sulfonyl One of the following, or two or more of these in any combination and ratio: It can be used at a rate.

[0172] In addition, a flame-retardant and non-volatile ionic liquid (melting point: room temperature) was used as the solvent for the electrolyte 576. By using one or more of these salts, the internal area of ​​the secondary battery can be short-circuited or overcharged. Even if the temperature of the region rises, the secondary battery can be prevented from exploding or catching fire. The organic cation is composed of a cation and an anion, and includes an organic cation and an anion. quaternary ammonium cations, tertiary sulfonium cations, and quaternary phosphonium cations. Aliphatic onium cations such as thiones, as well as imidazolium cations and pyridinium cations Examples of anions include aromatic cations such as ammonium cations. Anions, monovalent methide anions, fluorosulfonate anions, perfluoroalkanes perfluoroalkyl borate anion, tetrafluoroborate anion, perfluoroalkyl bo ... phosphate anion, hexafluorophosphate anion, or perfluoroalkyl phosphate hydrate anions, etc.

[0173] In particular, in the secondary battery of one embodiment of the present invention, the second active material 582 contained in the negative electrode 570a When silicon is used as the electrolyte, it is preferable to use a liquid electrolyte 576 having an ionic liquid. I wish.

[0174] The secondary battery according to one embodiment of the present invention may contain, for example, lithium ions, sodium ions, and potassium ions. Alkali metal ions such as ammonium ions, as well as calcium ions and strontium ions alkaline earth metals such as ions, barium ions, beryllium ions, and magnesium ions The compound has one or more of the group ions as carrier ions.

[0175] When lithium ions are used as carrier ions, for example, the electrolyte is a lithium salt. Examples of lithium salts include LiPF6, LiClO4, LiAsF6, and LiBF4. , LiAlCl4, LiSCN, LiBr, LiI, Li2SO4, Li2B 10 Cl1 0, Li2B 12 Cl 12 , LiCF3SO3, LiC4F9SO3, LiC(CF3S O2)3, LiC(C2F5SO2)3, LiN(CF3SO2)2, LiN(C4F9 SO2)(CF3SO2), LiN(C2F5SO2)2, etc. can be used.

[0176] The electrolyte preferably contains fluorine. Examples of the fluorine-containing electrolyte include fluorine. An electrolyte containing one or more halogenated cyclic carbonates and lithium ions is used. Fluorinated cyclic carbonates improve non-flammability and are suitable for lithium-ion secondary batteries. The safety of the battery can be improved.

[0177] Fluorinated cyclic carbonates include fluorinated ethylene carbonate, for example, monofluoroethylene carbonate. Fluoroethylene carbonate (fluoroethylene carbonate, FEC, F1EC), difluoroethylene ethylene carbonate (DFEC, F2EC), trifluoroethylene carbonate (F3E C), tetrafluoroethylene carbonate (F4EC), etc. can be used. DFEC has isomers such as cis-4,5 and trans-4,5. and solvating lithium ions using one or more fluorinated cyclic carbonates. Therefore, it is important for the electrode to be transported within the electrolyte during charging and discharging in order to operate at low temperatures. Fluorinated cyclic carbonate is used not as a small amount of additive, but as a lithium By contributing to the transport of ions, operation at low temperatures becomes possible. Ons move in groups of several to several dozen.

[0178] By using fluorinated cyclic carbonate as the electrolyte, the solvent in the electrolyte contained in the electrode The desolvation energy required for solvated lithium ions to enter the active material particles is reduced. If this desolvation energy can be reduced, the lithium ions can be desolvated even at low temperatures. Lithium ions are easily inserted into or removed from the active material particles. Although the molecule may move in the same state, a hopping phenomenon occurs in which the coordinated solvent molecules are swapped. When lithium ions become more easily desolvated, they tend to move by hopping. This may make it easier for lithium ions to move. The decomposition products of the electrolyte adhere to the surface of the active material, causing deterioration of the secondary battery. However, if the electrolyte contains fluorine, the electrolyte is smooth and Therefore, the decomposition products of the electrolyte are less likely to adhere to the surface of the active material. It can be suppressed.

[0179] The solvated lithium ions form clusters in the electrolyte, and the negative electrode a, between the positive electrode 570b and the negative electrode 570a, within the positive electrode 570b, and so on.

[0180] In this specification, the term "electrolyte" is a general term that includes solid, liquid, or semi-solid materials. .

[0181] Deterioration is likely to occur at interfaces present in secondary batteries, for example, at the interface between the active material and the electrolyte. In the secondary battery of one embodiment, the active material and the electrolyte are mixed by using an electrolyte containing fluorine. To prevent deterioration that may occur at the interface with the electrolyte, typically the deterioration of the electrolyte or the increase in the viscosity of the electrolyte. In addition, it is possible to use a binder or graphene compound for the electrolyte containing fluorine. By adopting such a configuration, the electrolytic It is possible to maintain a low viscosity of the electrolyte, in other words, a smooth electrolyte state. This improves the reliability of secondary batteries. F4EC, which has four fluorine atoms bonded, has a higher viscosity than FEC, which has one fluorine atom bonded. Therefore, the viscosity of the active material particles is low and the coordination bond with lithium is weak. It is possible to reduce the adhesion of highly viscous decomposition products to the active material particles. If the particles adhere to or cling to each other, it becomes difficult for lithium ions to move at the interface between the active material particles. Electrolytes containing fluorine solvate to form a fluorine-containing electrolyte on the surface of the active material (positive electrode active material or negative electrode active material). In addition, by using an electrolyte containing fluorine, the generation of decomposition products that adhere to the surface is reduced. By preventing adhesion of substances, the occurrence and growth of dendrites can be prevented.

[0182] Another feature is that the main component is an electrolyte containing fluorine. The electrolyte is 5% by volume or more, 10% by volume or more, preferably 30% by volume or more and 100% by volume or more. % or less.

[0183] In this specification, the main component of the electrolyte is 5% by volume or more of the total electrolyte of the secondary battery. In addition, the term "5% by volume or more of the total electrolyte of the secondary battery" means that the secondary battery This refers to the percentage of the total electrolyte measured during the manufacturing process. In the case of decomposition, the proportion of each of the various electrolytes is quantified. It is difficult to determine whether a single organic compound accounts for more than 5% by volume of the entire electrolyte. It can be determined.

[0184] By using a fluorine-containing electrolyte, a wide temperature range is possible, specifically, from -40°C to 15°C. It is possible to realize a secondary battery that can operate at 0°C or below, preferably between -40°C and 85°C. Cut.

[0185] The electrolyte is vinylene carbonate, propane sultone (PS), tert-butyl Benzene (TBB), lithium bis(oxalato)borate (LiBOB), and sc Additives such as dinitrile compounds such as adiponitrile and adiponitrile may also be added. The concentration of the additive may be, for example, 0.1% by volume or more and less than 5% by volume with respect to the entire electrolyte.

[0186] In addition to the above, the electrolytes include γ-butyrolactone, acetonitrile, dimethoxyethane, It may also comprise one or more aprotic organic solvents such as tetrahydrofuran.

[0187] In addition, the use of a polymer material that gels the electrolyte increases safety against leakage, etc. Typical examples of polymeric materials that can be gelled include silicone gel, acrylic gel, and Lyronitrile gel, polyethylene oxide gel, polypropylene oxide gel, Examples include fluorine-based polymer gels.

[0188] Examples of polymeric materials include polyalkylene oxide (PEO) and the like. Polymers having an oxide structure, such as PVDF and polyacrylonitrile, and the like, For example, a copolymer containing PVDF and hexafluoropropylene can be used. PVDF-HFP, a copolymer of PVDF and HFP, can be used. The polymer may have a porous shape.

[0189] Although the above configuration shows an example of a secondary battery using a liquid electrolyte, the present invention is not limited thereto. For example, semi-solid and all-solid batteries can be fabricated.

[0190] In this specification, the positive electrode The layer disposed between the negative electrode 570a and the negative electrode 570b is called an electrolyte layer. The electrolyte layer can be said to be a layer formed by film deposition, and can be distinguished from a liquid electrolyte layer.

[0191] In this specification, a semi-solid battery is a battery comprising an electrolyte layer, a positive electrode 570b, and a negative electrode 570a. A battery that contains at least one semi-solid material. In this context, semi-solid means a battery that contains a proportion of solid material. It does not mean that the volume is 50%. A semi-solid has the properties of a solid, such as a small change in volume. This means that while it has the properties of a liquid, it also has some of the properties of a liquid, such as flexibility. As long as these properties are met, the material may be a single material or multiple materials. The material may be infiltrated into a porous solid material.

[0192] In this specification and the like, a polymer electrolyte secondary battery is a battery having a positive electrode 570b and a negative electrode 570a. Polymer electrolyte secondary batteries are batteries that have a polymer electrolyte layer between the dry cell and the battery. (or intrinsic) polymer electrolyte batteries, and polymer gel electrolyte batteries.

[0193] The electrolyte 576 comprises a lithium ion conducting polymer and a lithium salt.

[0194] In this specification, the lithium ion conductive polymer is a polymer that conducts cations such as lithium. More specifically, it is a polymer that has a polar group to which a cation can be coordinated. The polar groups are ether groups, ester groups, nitrile groups, carbonyl groups, It is preferable that the resin contains siloxane or the like.

[0195] Examples of lithium ion conductive polymers include polyethylene oxide (PEO), Derivatives with polyethylene oxide as the main chain, polypropylene oxide, polyacrylic Polyacrylate, polymethacrylate, polysiloxane, polyphosphazene, etc. You can be there.

[0196] The lithium ion conductive polymer may be branched or crosslinked. It may be a polymer. The molecular weight is preferably 10,000 or more, and more preferably 100,000 or more. It is more preferable to have one.

[0197] Lithium ion conductive polymers are characterized by the partial motion (also called segmental motion) of the polymer chain. Lithium ions move while changing polar groups that interact more. For example, PEO In this case, the lithium ion moves by changing the oxygen that interacts with it due to the segmental motion of the ether chain. When the temperature is close to or above the melting or softening point of the lithium ion conductive polymer, When the temperature is higher than 1000 K, the crystalline region dissolves and the amorphous region increases, and the movement of the ether chains becomes active. Therefore, PEO is used as a lithium ion conductive polymer. When using a battery, it is preferable to charge and discharge the battery at a temperature of 60°C or higher.

[0198] Shannon's ionic radius (Shannon et al., Acta A 32(19 76) According to 751.), the radius of a monovalent lithium ion is 0.0590 when it is tetracoordinated. nm, 0.076 nm for 6-coordinated, and 0.092 nm for 8-coordinated. The radius of the elementary ion is 0.135 nm for two-coordinated, 0.136 nm for three-coordinated, and 0.136 nm for four-coordinated. 0.138 nm for 6-coordination, 0.140 nm for 8-coordination, and 0.142 nm for 8-coordination. The distance between the polar groups of adjacent lithium ion conductive polymer chains is as described above. The lithium ions and the anions of the polar groups can exist stably while maintaining the ionic radius. It is preferable that the distance is equal to or greater than the distance required for the interaction between the lithium ion and the polar group. However, as mentioned above, segment movement occurs, so It is not necessary to always maintain a constant distance. When lithium ions pass through, That would be good.

[0199] The lithium salt may contain, for example, phosphorus, fluorine, nitrogen, sulfur, oxygen, At least one of chlorine, arsenic, boron, aluminum, bromine, and iodine, Compounds such as LiPF6, LiN(FSO2)2 (lithium bimetallic compounds) can be used. (fluorosulfonyl)imide, LiFSI), LiClO4, LiAsF6, LiB F4, LiAlCl4, LiSCN, LiBr, LiI, Li2SO4, Li2B 10 C l 10 , Li2B 12 Cl 12 , LiCF3SO3, LiC4F9SO3, LiC(CF 3SO2)3, LiC(C2F5SO2)3, LiN(CF3SO2)2(lithium bismuth (trifluoromethanesulfonyl)imide, LiTFSA), LiN(C4F9SO2) (CF3SO2), LiN(C2F5SO2)2, Lithium bis(oxalate)boron One or any combination of two or more of these lithium salts, such as tetrahydrofuran (LiBOB), It can be used in any number and ratio.

[0200] In particular, the use of LiFSI is preferable because it provides good low-temperature properties. TFSA is less reactive with water than LiPF6, etc. Therefore, the electrochemical reaction using LiFSI is This makes it easier to control the dew point when producing the electrode and electrolyte layers. In addition to inert atmospheres such as argon and dry rooms with controlled dew points, It can be handled in a gas atmosphere. This is preferable as it improves productivity. and LiTFSA, which has high dissociation and plasticizing effect, are better suited to ethers. When using lithium conduction due to the segmental motion of the chain, it can be used in a wide temperature range. This is particularly preferred.

[0201] By using no organic solvent or very little of it, the secondary battery is less likely to catch fire or ignite. This is preferable as it improves safety.

[0202] [Exterior body] The exterior body of the secondary battery is made of, for example, a metal material such as aluminum or a resin material. A film-like outer casing can also be used. Examples of suitable materials include polyethylene, polypropylene, polycarbonate, ionomers, and polyamides. A flexible material such as aluminum, stainless steel, copper, or nickel is applied to a film made of a material such as aluminum. A thin metal film made of a polyamide resin or a polyester resin is provided on the thin metal film as the outer surface of the exterior body. A three-layer film with an insulating synthetic resin film such as an ester-based resin can be used. It is also preferable to use a fluororesin film as the film. The polymer has high stability against acids, alkalis, organic solvents, etc., and is resistant to side reactions that occur in secondary batteries. This suppresses reactions, corrosion, etc., and allows for the realization of an excellent secondary battery. PTFE (polytetrafluoroethylene), PFA (perfluoroalkoxyalkane) FE: copolymer of tetrafluoroethylene and perfluoroalkyl vinyl ether P(perfluoroethylene propene copolymer): Tetrafluoroethylene and hexafluoroethylene copolymer of ethylene tetrafluoroethylene), ETFE (ethylene tetrafluoroethylene copolymer; tetrafluoroethylene copolymer) copolymer of tetrafluoroethylene and ethylene).

[0203] This embodiment mode can be implemented in appropriate combination with other embodiment modes.

[0204] (Embodiment 2) In this embodiment, a positive electrode and a positive electrode active material composite according to one embodiment of the present invention will be described.

[0205] An example of a positive electrode 570b of one embodiment of the present invention is shown in FIG. The positive electrode active material layer 572b has a positive electrode active material composite 100 As an example of the positive electrode active material composite 100z, the positive electrode active material composite 100z shown in FIGS. 10A1 and 10A2 may be used. The first active material 100x and the second active material 100x are capable of absorbing and releasing carrier ions in the above manner. In FIG. 9, the conductive material includes a graphene compound 102 and a carbon nanotube. Although the example using Bomb Black 103 is shown, the positive electrode active material composite 100z has sufficient electrons. If the positive electrode active material layer 572b has conductivity, it is not necessary to use a conductive material in the positive electrode active material layer 572b. The type of material is not limited to the examples shown in FIG. 9, and may be a graphene compound, carbon black, Alternatively, only carbon fibers such as carbon nanotubes may be used. Carbon fibers such as cellulose acylate may be used in combination with carbon black. Although not required, the positive electrode active material layer 572b preferably contains a binder. Polymer materials such as polyvinylidene fluoride and molecular crystal electrolytes such as Li(FSI)(SN)2 Quality can be used.

[0206] The positive electrode active material composite 100z is disposed in a state in which electrons can be exchanged with the positive electrode current collector 571b. That is, the positive electrode active material composite 100z is electrically connected to the positive electrode current collector 571b. The positive electrode current collector 571b may be provided with an undercoat layer. The positive electrode active material composite 100z is electrically connected to the positive electrode current collector 571b via the undercoat layer. The positive electrode active material composite 100z is in contact with the positive electrode current collector 571 via a conductive material. It may be configured to be in electrical contact with b.

[0207] The density of the positive electrode active material layer 572b is preferably 3.0 g / cm 3 More than that, more preferable 3.5g / cm 3 More preferably, 3.8 g / cm 3 It is preferable that the above Therefore, a press treatment may be performed to increase the density of the positive electrode active material layer 572b. However, when the pressing process is performed, the first active material 100x and the positive electrode active material composite described later are It is desirable to set the conditions for the press process appropriately so as not to damage the structure of the 100z. .

[0208] [Cathode active material composite] 10A1 to 10C2 are cross-sectional schematic views illustrating a positive electrode active material composite 100z. is.

[0209] 10A1 and 10A2 show a first active material 100x that functions as a positive electrode active material and a second active material 100x that functions as a positive electrode active material. A positive electrode active material composite having a second active material 100y covering at least a part of a first active material 100x. 10A1 is a diagram illustrating a combination 100z. Note that FIG. 10A1 shows one first active material 100x However, the present invention is not limited to this. Alternatively, a configuration may be adopted in which a plurality of first active material particles 100x are covered with a second active material particle 100y. .

[0210] For example, as shown in FIG. 10A2, the first active material 100xa and the first active material 100 At least a part of xb may be covered with the second active material 100y. In the case where the first active material 100xa and the first active material 100xb are at least partially in contact with each other, However, the first active material 100xa and the first active material 100xb are not in direct contact with each other. The particle surface of the particulate first active material 100x that functions as a positive electrode active material may be In a state where at least a part of the surface, preferably substantially the entire surface, is covered with the second active material 100y. As a result, the area of ​​the first active material 100x in direct contact with the electrolyte 576 is reduced, and the high-voltage charging state Therefore, it is possible to prevent the transition metal element and / or oxygen from being released from the first active material 100x. This prevents the capacity from decreasing due to repeated charging and discharging. By covering the second active material 100y, which is electrochemically stable even in the presence of the second active material 100y, The secondary battery using the positive electrode active material composite 100z has improved stability at high temperatures and improved fire resistance. It is possible to obtain effects such as improving the

[0211] 10B1 and 10B2 show a first active material 100x that functions as a positive electrode active material and a second active material 100x that functions as a positive electrode active material. The positive electrode active material composite 10 has glass 101 covering at least a portion of the active material 100x. 10B1 is a diagram illustrating the structure of a first active material 100x. However, the present invention is not limited to this. The active material 100x may be covered with the glass 101.

[0212] For example, as shown in FIG. 10B2, the first active material 100xa and the first active material 100 At least a part of xb may be covered with glass 101. The first active material 100xa and the second active material 100xb are in contact with each other at least partially. However, when the first active material 100xa and the first active material 100xb are not in direct contact with each other, A small amount of the particle surface of the particulate first active material 100x that functions as a positive electrode active material may be In a state where the glass 101 covers at least a part of, and preferably almost the entire, the first active material The area of ​​the first active material 100x in direct contact with the electrolyte 576 is reduced, and the first active material 100x is in a high-voltage charging state. Since the desorption of transition metal elements and / or oxygen from 100x can be suppressed, repeated charge and discharge It is also possible to suppress the capacity decrease caused by repeated charging. By covering the cathode active material composite 100z with the thermally stable glass 101, the cathode active material composite 100z according to one embodiment of the present invention can be obtained. Secondary batteries using this material have the advantages of improved stability at high temperatures and improved fire resistance. This becomes possible.

[0213] 10C1 and 10C2 show a first active material 100x that functions as a positive electrode active material, The first active material 100x is covered with a glass 101 that covers at least a part of the first active material 100x. x and a second active material 100y in contact with the positive electrode active material composite 100z. In addition, in FIG. 10C1, one first active material particle 100x is covered with glass 101. However, the present invention is not limited to this configuration. It may be configured to be covered with glass 101.

[0214] For example, as shown in FIG. 10C2, the first active material 100xa and the first active material 100 At least a part of xb may be covered with glass 101. The first active material 100xa and the second active material 100xb are in contact with each other at least partially. However, when the first active material 100xa and the first active material 100xb are not in direct contact with each other, A small amount of the particle surface of the particulate first active material 100x that functions as a positive electrode active material may be The glass 101 is placed in a state where it covers at least a part of the surface, and preferably almost the entire surface. a positive electrode active material composite having a second active material (100y) in contact with a first active material (100x) via a In 100z, the area where the first active material 100x is in direct contact with the electrolyte 576 is reduced, In a high-voltage charging state, a transition metal element and / or oxygen is released from the first active material 100x. This can suppress the capacity decrease due to repeated charging and discharging. Glass 101 is electrochemically stable even under high voltage conditions, and is stable even under high charging voltage conditions. By being covered with a stable second active material 100y, the positive electrode active material composite 100 of one embodiment of the present invention is formed. Secondary batteries using Z have the advantages of improved stability at high temperatures and improved fire resistance. This makes it possible to

[0215] In the positive electrode active material composite 100z shown in FIGS. 10A1 to 10C2, the first active material Lithium cobalt oxide with magnesium and fluorine, as 100x, magnesium, Lithium cobalt oxide with fluorine, aluminum, and nickel, and nickel: Cobalt:Manganese = 8:1:1, and Nickel:Cobalt:Manganese = 9:0.5: High voltage charge state, such as lithium nickel-cobalt-manganese oxide with a molar ratio of 0.5, By using a material with excellent stability at high voltage, the above-mentioned positive electrode active material composite 100z The durability and stability during charging can be further improved. The heat resistance and / or fire resistance of the secondary battery using the composite 100z can be further improved. Cut.

[0216] In addition, lithium cobalt oxide having magnesium, fluorine, aluminum, and nickel The cathode active material has a large amount of magnesium, fluorine, or aluminum in the surface layer thereof, and the particles Nickel is widely distributed throughout the battery, and the repeated charge / discharge characteristics at high voltages are remarkably excellent. Therefore, it is a particularly preferable material for the first active material 100x. If the material has a lot of magnesium, fluorine, or aluminum, for example, STEM-ED In X-ray analysis, the characteristic X-rays from magnesium, fluorine, or aluminum The number of counts has a maximum value in the surface layer portion. This refers to the region from the surface of the material to about 10 nm. The layer portion has a layer portion, and the addition of magnesium, fluorine, or aluminum in the production of the positive electrode active material The cracks that occurred before the processing step were found to contain a large amount of magnesium, fluorine, or aluminum. It has a surface layer.

[0217] The positive electrode active material composite 100z shown in FIGS. 10A1 and 10A2 includes a first active material 1 00x and the second active material 100y, Examples of the composite treatment include the mechanochemical method, the mechanofusion method, and the ball method. Mechanical energy composite processing such as milling, coprecipitation, hydrothermal, and sol-gel methods Composite processing by liquid phase reaction, barrel sputtering method, ALD (Atomic Layer Deposition, evaporation, and CVD (Chemical Vapor Deposition) and composite processing by gas phase reaction such as the porosity deposition method. In the composite treatment, the above-mentioned composite treatment can be carried out by heating once or multiple times. In this specification, the composite treatment is preferably a surface coating treatment. This is sometimes called a treatment or coating treatment.

[0218] In addition, the positive electrode active material composite 100z shown in FIGS. 10B1 and 10B2 has a first active It is obtained by a composite process using at least the substance 100x and the glass 101. Examples of the composite treatment include the mechanochemical method, the mechanofusion method, and the ball milling method. Composite processing using mechanical energy such as the sol-gel method, co-precipitation method, hydrothermal method, and sol-gel method Composite processing by liquid phase reaction, as well as barrel sputtering, ALD, vapor deposition, and C and composite treatment by gas phase reaction such as VD method. In the composite treatment, it is preferable to carry out heat treatment once or multiple times.

[0219] Furthermore, the positive electrode active material composite 100z shown in FIGS. 10C1 and 10C2 has at least A composite process using the first active material 100x, the second active material 100y, and the glass 101 The composite treatment can be carried out by, for example, mechanochemical method, mechanofusion method, etc. The composite treatment using mechanical energy such as the ball mill method, coprecipitation method, hydrothermal method, and and sol-gel method, as well as barrel sputtering and ALD. compositing by gas phase reaction such as deposition method, vapor deposition method, and CVD method. In the composite treatment, one or more heat treatments can be performed. It is preferable to do so.

[0220] As described above, the positive electrode active material composite 100z of one embodiment of the present invention is a composite of the first active material 100x and the second active material 100x. Since the first active material 100x is not in contact with the electrolyte 576, deterioration of the first active material 100x caused by the electrolyte is prevented. The deterioration may be caused by defects occurring in the first active material 100x, for example. For example, there is a defect called a pit. Pits are formed during charge-discharge cycle testing. , refers to a region where several layers of the main components of the first active material 100x, such as cobalt and oxygen, are missing. For example, cobalt may dissolve into the electrolyte. In the test, the pits may progress toward the inside of the active material. The shape is not circular but has a depth and a groove-like shape. The structure in which the 100x and the 100x do not come into contact with each other suppresses the occurrence and progression of the defects, particularly pits. This can be done.

[0221] The positive electrode active material composite 100z is in contact with the first active material 100x via the glass 101. When the positive electrode active material composite 100z has the second active material 100y, the positive electrode active material composite 100z has a double structure in the surface layer portion. However, the positive electrode active material composite 100z according to one embodiment of the present invention has a glass 1 The present invention is not limited to a case in which the active material 100y and the second active material 100y are combined to form a double structure. Another example of the positive electrode active material composite 100z of one embodiment is a composite of glass 101 and a second active material 10 A glass-active material mixed layer having a thickness of 0y covers at least a portion of the surface of the first active material 100x. The structure may be as follows.

[0222] Furthermore, as a positive electrode active material composite 100z of one embodiment of the present invention, The graphene compound 102 may be present on the surface layer portion or the glass active material mixed layer. Instead of the graphene compound 102, a carbon such as carbon black or carbon nanotubes may be used. Fiber may also be used.

[0223] The glass 101 may be a material having an amorphous portion. Materials include, for example, SiO2, SiO, Al2O3, TiO2, Li4SiO4, Li 3PO4, Li2S, SiS2, B2S3, GeS4, AgI, Ag2O, Li2O, P 2O5, B2O3, and V2O5, etc., and a material having one or more selected from Li7P3S 11 , or Li 1+x+y Al x Ti 2-x Si y P 3-y O 12 (0 <x<2、0<y<3 , ) etc. Materials having amorphous parts can be used in an amorphous state. It is used in the state of partially crystallized glass (also called glass ceramics). It is desirable that the glass 101 has lithium ion conductivity. Lithium ion conductivity means that the material has lithium ion diffusibility and lithium ion penetration. The glass 101 preferably has a melting point of 800° C. or less, and more preferably has a melting point of 500° C. or less. It is more preferable that the glass 101 has electronic conductivity. The glass 101 preferably has a softening point of 800°C or less, for example, Li2 O-B2O3-SiO2 based glass can be used.

[0224] It is desirable that the glass 101 has electronic conductivity. However, if the electronic conductivity of the glass 101 is low, In cases where glass 101 is not used, graphene compounds, carbon black, or carbon By mixing carbon fiber conductive materials such as carbon nanotubes into glass 101, It is possible to impart electronic conductivity.

[0225] At least a portion of the surface of the positive electrode active material composite 100z is covered with a graphene compound. Preferably, the particle surface of the positive electrode active material composite 100z and / or the positive electrode A structure in which 80% or more of the aggregate having the active material composite 100z is covered with the graphene compound is preferred. The graphene compound will be described later.

[0226] In addition, the positive electrode active material composite 100z is preferably covered with a molecular crystalline electrolyte. The molecular crystal electrolyte can function as a binder for the positive electrode active material layer 572b. The molecular crystalline electrolyte is preferably a material with high ionic conductivity, and the Positive electrode active material composite 100z can exchange carrier ions with electrolyte 576.

[0227] [Cathode active material] The first active material 100x is LiM1O2 (M1 is (one or more selected from the group consisting of Fe, Ni, Co, and Mn) can be used. In addition, the first active material 100x is a composite oxide represented by LiM1O2, and the additive element The first active material 100x can be doped with an element X. These include nickel, cobalt, magnesium, calcium, chlorine, fluorine, and aluminum. Aluminum, manganese, titanium, zirconium, yttrium, vanadium, iron, chromium, niobium lanthanum, hafnium, zinc, silicon, sulfur, phosphorus, boron, and arsenic. It is preferable to use the above elements. In other words, the first active material 100x may further stabilize the magnesium and fluorine. Lithium cobalt oxide containing elements, magnesium, fluorine, aluminum, nickel lithium cobalt oxide with magnesium, fluorine and titanium; Lithium nickel-cobalt oxide with magnesium and fluorine, magnesium and fluorine Cobalt-lithium aluminum oxide and nickel-cobalt-lithium aluminum oxide containing Lithium nickel-cobalt-aluminate with lithium, magnesium, and fluorine , lithium nickel-cobalt-manganese oxide containing magnesium and fluorine, etc. The transition metal ratio of nickel-cobalt-lithium manganese oxide is as follows: A high nickel ratio is preferred, for example, nickel:cobalt:manganese=8:1:1, A material with a molar ratio of chromium:cobalt:manganese=9:0.5:0.5 is preferred. The nickel-cobalt-manganese lithium oxide is preferably a nickel-cobalt-manganese lithium oxide having calcium. It is preferred to have lithium baruto-manganate.

[0228] The first active material 100x is LiM1O2 (M1 is Fe, Ni, Co, Mn The secondary particles of a composite oxide represented by the formula (I) are coated with a metal oxide. The metal oxide may be selected from Al, Ti, Nb, Zr, La, and Li. The oxide of one or more metals can be used. For example, LiM1O2 (where M1 is Fe The secondary particles of the composite oxide represented by the formula (I) are aluminum oxide. A metal oxide-coated composite oxide coated with aluminum is used as the first active material 100x. For example, nickel:cobalt:manganese = 8:1:1, nickel:cobalt Nickel-cobalt-lithium manganate with a molar ratio of nickel:manganese=9:0.5:0.5 The secondary particles of the aluminum oxide are coated with a metal oxide-coated composite oxide. Here, the coating layer is preferably thin, for example, 1 nm or more and 200 nm or less. More preferably, it is 1 nm or more and 100 nm or less. Lithium manganese oxide: Lithium nickel-cobalt-manganese oxide with calcium It is preferred that the compound has the following structure:

[0229] As the first active material 100x, the positive electrode active material 100 described in the embodiment described later is used. It is possible.

[0230] As the second active material 100y, one or more of oxides and LiM2P having an olivine-type crystal structure O4 (M2 is one or more selected from Fe, Ni, Co, Mn) can be used. Examples of the oxide include aluminum oxide, zirconium oxide, hafnium oxide, and niobium oxide and the like. Examples of LiM2PO4 include LiFePO4, LiNiP O4, LiCoPO4, LiMnPO4, LiFe O4, LiFe a Ni b PO4, LiFe a Co b P O4, LiFe a Mn b PO4, LiNi a Co b PO4, LiNi a Mn b PO4 (a[[ID=3H]] +b is 1 or less, 0 < a < 1, 0 < b < 1), LiFe c Ni d Co e PO4, LiFe c Ni d Mn e PO4, LiNi c Co d Mn e PO4 (c + d + e is 1 or less, 0 < c < 1 , 0 < d < 1, 0 < e < 1), LiFe f Ni g Co h Mn i PO4 (f + g + h + i is 1 or less, 0 < f < 1, 0 < g < 1, 0 < h < 1, 0 < i < 1), etc. Further, the particle surface of the second active material 100y may have a carbon coating layer.

[0231] Examples of the conductive material include carbon blacks such as acetylene black and furnace black, graphite such as artificial graphite and natural graphite, carbon nanofibers, and the like. Carbon fibers such as carbon nanotubes, and graphene compounds, or Two or more types can be used.

[0232] This embodiment mode can be implemented in appropriate combination with other embodiment modes.

[0233] (Embodiment 3) In this embodiment, a positive electrode active material of one embodiment of the present invention will be described with reference to FIGS. Reveal.

[0234] In this specification, crystal planes and directions are expressed in Miller indices. In crystallography, numbers are usually marked with a superscript bar, but in this specification and other documents, due to limitations on the notation used in the application, numbers are marked with a superscript bar. Instead of putting a bar above the letter, a number may be expressed by putting a - (minus sign) before it. Also, individual orientations that indicate directions within a crystal are [ ], and collective orientations that indicate all equivalent directions are The symbols are < >, individual crystal faces are ( ), and collective faces with equivalent symmetry are {}. Also, the Miller indices of trigonal and hexagonal crystals, including R-3m, are expressed as (h Sometimes (hkil) is used instead of just (kl), where i is -(h+k).

[0235] In the present specification and the like, the layered rock salt type composite oxide containing lithium and a transition metal The crystal structure of has a rock salt type ion arrangement in which cations and anions are arranged alternately, and The metal and lithium are regularly arranged to form a two-dimensional plane, allowing two-dimensional diffusion of lithium. It is possible for defects such as missing cations or anions to exist. Strictly speaking, the layered rock salt crystal structure is a distorted rock salt crystal lattice structure. This may be the case.

[0236] In this specification, a rock salt type crystal structure is a structure in which cations and anions are arranged alternately. It is also possible for a part of the crystal structure to be deficient in cations or anions. good.

[0237] In this specification and the like, the theoretical capacity of the positive electrode active material is the insertion / desorption capacity of the positive electrode active material. This refers to the amount of electricity when all possible lithium is removed. For example, the theoretical capacity of LiFePO4 The theoretical capacity of LiCoO2 is 170mAh / g, the theoretical capacity of LiNiO2 is 274mAh / g, The capacity is 275mAh / g, while the theoretical capacity of LiMn2O4 is 148mAh / g.

[0238] The amount of lithium remaining in the positive electrode active material that can be inserted or removed is determined by the x , for example, Li x x in CoO2, or Li x In this specification, Li x CoO2 is appropriately Li x It can be read as MO2. x can be said to be the occupancy rate. In the case of a positive electrode active material in a secondary battery, x may be expressed as (theoretical capacity - charging capacity) / theoretical capacity. For example, a secondary battery using LiCoO2 as the positive electrode active material was charged at 219.2mAh / g. In the case of Li 0.2 CoO2 or x=0.2. x x in CoO2 is small, for example, 0.1 <x≦0.24をいう。

[0239] When lithium cobalt oxide is approximately stoichiometric, it is LiCoO2 and lithium sulphide. The Li occupancy rate of the site is x = 1. The secondary battery after discharge is also LiCoO2. Therefore, it can be said that x = 1. The discharge is completed when, for example, the current is 100 mA / g. This refers to the state in which the voltage is 2.5V (lithium counter electrode) or less under the current. In the pond, the occupancy rate of lithium on the lithium site is x = 1, and no more lithium can enter. When the voltage drops, the discharge is complete. In a lithium-ion secondary battery using oO2, the discharge voltage reaches 2.5V. Since the voltage drops rapidly, the discharge is considered to have ended under the above conditions.

[0240] In this specification and the like, it is not intended that all of the lithium that can be inserted or removed from the positive electrode active material is inserted. The depth of charge when all the intercalable lithium in the positive electrode active material is deintercalated is 0. The depth of charge is sometimes referred to as 1.

[0241] [Cathode active material] A positive electrode active material of one embodiment of the present invention will be described with reference to FIGS.

[0242] FIG. 11A is a schematic top view of a positive electrode active material 100 according to one embodiment of the present invention. A schematic cross-sectional view taken along line AB is shown in FIG. 11B.

[0243] <Elements and distribution> The positive electrode active material 100 contains lithium, a transition metal, oxygen, and an additive element X. The electrode active material 100 is LiM1O2 (M1 is one or more selected from Fe, Ni, Co, and Mn). It can be said that the additive element X is added to the composite oxide represented by the formula:

[0244] The transition metal contained in the positive electrode active material 100 is a metal that belongs to the space group R-3m together with lithium. It is preferable to use a metal that can form a layered rock salt type composite oxide. At least one of barium and nickel can be used. Cobalt alone may be used as the transition metal, or nickel alone may be used, Two types of cobalt and manganese or two types of cobalt and nickel may be used. In other words, the positive electrode active material 100 may be a cobalt oxide. Lithium, lithium nickel oxide, and lithium cobalt oxide in which some of the cobalt is replaced with manganese Lithium, lithium cobalt oxide in which some of the cobalt is replaced by nickel, nickel-manganese -It can have a composite oxide containing lithium and a transition metal, such as lithium cobalt oxide. When nickel is included in addition to cobalt as a transition metal, the resulting electrolyte is in a charged state at a high voltage. This is preferable because the crystal structure may become more stable.

[0245] The additive element X contained in the positive electrode active material 100 is nickel, cobalt, magnesium, Calcium, chlorine, fluorine, aluminum, manganese, titanium, zirconium, yttrium um, vanadium, iron, chromium, niobium, lanthanum, hafnium, zinc, silicon, sulfur, It is preferable to use one or more elements selected from phosphorus, boron, and arsenic. This may further stabilize the crystal structure of the positive electrode active material 100. lithium cobalt oxide with magnesium and fluorine, magnesium, fluorine and titanium Lithium cobalt oxide with fluorine, nickel-cobalt oxide with magnesium and fluorine Lithium cobalt-aluminate with lithium, magnesium and fluorine, nickel Lithium-cobalt-aluminate, nickel-cobalt with magnesium and fluorine Baltic-Lithium Aluminate, Nickel-Manganese with Magnesium and Fluorine -lithium cobalt oxide, etc. In this specification, etc., the additive element X may be replaced with a term such as a mixture or a part of the raw material.

[0246] As shown in FIG. 11B, the positive electrode active material 100 has a surface layer 100a and an inner layer 100b. It is preferable that the concentration of the additional element X is higher in the surface layer portion 100a than in the inner portion 100b. As shown by the gradation in Figure 11B, the concentration of the added element X increases from the interior to the surface. It is preferable that the surface layer 100a has a concentration gradient. This refers to the area from the surface of 100 to about 10 nm. The surface where the ion implantation occurred can also be called the surface, and as shown in Figure 11C, the area from the surface to about 10 nm The surface layer 100a and the surface layer 100c of the positive electrode active material 100 are called the surface layer 100c. The deeper region is referred to as the interior 100b. The positive electrode active material 100 forms a positive electrode active material composite 100z. When forming the glass 101, it is desirable that the surface where the crack occurs is also covered with the glass 101.

[0247] In the positive electrode active material 100 according to one embodiment of the present invention, lithium is released from the positive electrode active material 100 upon charging. The concentration of the added element X is adjusted so that the layered structure consisting of cobalt and oxygen octahedra is not broken even when the element X is removed. The surface layer 100a with high strength, that is, the outer periphery of the particle, is reinforced.

[0248] The concentration gradient of the additive element X is uniformly present throughout the entire surface layer 100a of the positive electrode active material 100. Even if a part of the surface layer 100a is reinforced, if there is a part that is not reinforced, If the particles are not uniform, stress may be concentrated in the non-uniform area, which is undesirable. When they become concentrated, defects such as cracks may occur, leading to cracking of the positive electrode active material and a decrease in charge / discharge capacity. This could lead to:

[0249] Magnesium is divalent and is more readily accessible to lithium than to the transition metal sites in the layered rocksalt crystal structure. Since magnesium is more stable at the lithium site, it is more likely to enter the lithium site. The presence of an appropriate concentration in the lithium site of the surface layer 100a allows the formation of a layered rock salt type crystal structure. In addition, magnesium has a strong bond with oxygen, so magnesium Magnesium, at an appropriate concentration, can suppress the release of oxygen from the surrounding area. It is preferable because it does not adversely affect the insertion and extraction of lithium during charging. This may adversely affect the insertion and extraction of lithium.

[0250] Aluminum is trivalent and can reside on the transition metal site in the layered rock salt crystal structure. Aluminum can suppress the elution of surrounding cobalt. Because of its strong bonding strength with oxygen, it can suppress the release of oxygen from the surroundings of aluminum. Therefore, if aluminum is added as the additive element X, the crystal structure will not collapse even after repeated charging and discharging. Therefore, the positive electrode active material 100 can be made to be difficult to dissolve.

[0251] Fluorine is a monovalent anion, and part of the oxygen in the surface layer portion 100a is replaced by fluorine. This is because the cobalt content of the SiO2 layer increases with lithium desorption. The change in valence of the ion is from trivalent to tetravalent when there is no fluorine, and from trivalent to tetravalent when there is fluorine. This is because the oxidation-reduction potential changes from divalent to trivalent. In 100a, if some of the oxygen atoms are replaced by fluorine atoms, the lithium ions near the fluorine atoms Therefore, when used in a secondary battery, This is preferable because it improves electrical properties, rate characteristics, etc.

[0252] Titanium oxide is known to have superhydrophilicity. By using a cathode active material 100 containing titanium oxide, the wettability with respect to a highly polar solvent is improved. When a secondary battery is formed, the positive electrode active material 100 and the highly polar electrolyte solution This may improve the contact at the interface and suppress the increase in resistance. Here, the electrolytic solution corresponds to a liquid electrolyte.

[0253] As the charging voltage of the secondary battery increases, the voltage of the positive electrode generally increases. The positive electrode active material has a stable crystal structure even at high voltages. The stable crystalline structure of the material prevents the capacity from decreasing with repeated charging and discharging. This can be done.

[0254] In addition, a short circuit in the secondary battery may cause malfunctions in the charging and / or discharging operations of the secondary battery. This not only causes a malfunction but also may lead to heat generation and fire. For this reason, it is preferable that the short circuit current is suppressed even at a high charging voltage. The positive electrode active material 100 of one embodiment suppresses short-circuit current even at high charging voltages. Therefore, it is possible to provide a secondary battery that is both high in capacity and safe.

[0255] A secondary battery using the positive electrode active material 100 of one embodiment of the present invention preferably has a high capacity and excellent It simultaneously satisfies charge / discharge cycle characteristics and safety.

[0256] The concentration gradient of the added element X can be measured, for example, by energy dispersive X-ray spectroscopy (EDX). y Dispersive X-ray Spectroscopy) EDX measurement involves scanning the area and evaluating it two-dimensionally. This is sometimes called EDX area analysis. Also, data on linear areas can be extracted from EDX area analysis. The evaluation of the distribution of atomic concentrations within the positive electrode active material particles is sometimes called line analysis. .

[0257] By EDX area analysis (for example, element mapping), it was found that the surface layer 100a of the positive electrode active material 100 The concentration of the added element X in the interior 100b and in the vicinity of the grain boundary can be quantitatively analyzed. Furthermore, the concentration distribution of the added element X can be analyzed by EDX ray analysis.

[0258] When EDX analysis was performed on the positive electrode active material 100, the magnesium concentration in the surface layer 100a was The peak of the concentration (the position where the concentration is maximum) was observed from the surface of the positive electrode active material 100 toward the center. It is preferable that the depth is up to 3 nm, and more preferable that the depth is up to 1 nm. It is more preferable that the pores are present to a depth of 0.5 nm.

[0259] In addition, the distribution of fluorine contained in the positive electrode active material 100 may overlap with the distribution of magnesium. Therefore, when EDX analysis is performed, the peak of the fluorine concentration in the surface layer portion 100a (concentration The position where the degree of change is maximum is from the surface of the positive electrode active material 100 to a depth of 3 nm toward the center. Preferably, the pores are present at a depth of up to 1 nm, more preferably at a depth of 0.5 nm. It is more preferred that the thickness is up to nm.

[0260] It is not necessary for all of the additive elements X to have the same concentration distribution. When aluminum is added as the X element, the distribution is slightly different from that of magnesium and fluorine. For example, when EDX analysis is performed, it is preferable that the aluminum of the surface layer portion 100a The magnesium concentration peak (the position where the concentration is maximum) is higher than the magnesium concentration peak (the position where the concentration is maximum). It is preferable that the position where the aluminum concentration peaks is close to the surface. The positive electrode active material 100 has a depth of 0.5 nm or more and 20 nm or less from the surface toward the center. It is preferable that the depth of the pores is 1 nm or more and 5 nm or less.

[0261] In addition, when the positive electrode active material 100 is subjected to line analysis or area analysis, the amount of the additive in the vicinity of the grain boundary is The ratio (X / M1) of the element X to the transition metal M1 is preferably 0.020 or more and 0.50 or less. More preferably, it is 0.025 or more and 0.30 or less. For example, when the additive element X is magnesium and the transition metal M1 is cobalt, The ratio of the number of magnesium and cobalt atoms (Mg / Co) is preferably 0.020 or more and 0.50 or less. It is more preferable that the ratio is 0.025 or more and 0.30 or less. It is even more preferable that the ratio is 0.030 or more and 0. 20 or less is preferable.

[0262] As described above, if the additive element X contained in the positive electrode active material 100 is in excess, the amount of lithium This may adversely affect insertion and removal. In addition, when used as a secondary battery, the resistance may increase and the capacity may decrease. On the other hand, if the amount is insufficient, the surface layer 100a will not be distributed over the entire surface layer 100a, and the crystal structure In this way, the additive element X may not be effective in retaining the positive electrode active material 100. Adjust the concentration to an appropriate level.

[0263] Therefore, for example, the positive electrode active material 100 has a region where the excess additive element X is unevenly distributed. The presence of such a region allows the excess additive element X to be removed from the other regions, The concentration of the additive element X is appropriate in the interior and most of the surface layer of the positive electrode active material 100. The positive electrode active material 100 can have an appropriate concentration of the additive element X in the interior and most of the surface layer thereof. By doing so, it is possible to suppress an increase in resistance and a decrease in capacity when used as a secondary battery. Being able to suppress the increase in resistance of a secondary battery is extremely advantageous, especially during high-rate charging and discharging. This is a desirable characteristic.

[0264] In addition, in the positive electrode active material 100 having a region where the excess additive element X is unevenly distributed, In this case, it is permissible to mix an excess amount of additive element X to some extent. This is preferable as it widens the engine.

[0265] In this specification, uneven distribution means that the concentration of a certain element is different between a certain region A and a certain region B. It refers to segregation, precipitation, non-uniformity, bias, high or low concentration, etc. It is also possible.

[0266] <Crystal structure> Materials with a layered rock-salt crystal structure, such as lithium cobalt oxide (LiCoO2), are It has a high capacitance and is known to be an excellent positive electrode active material for secondary batteries. An example of a material with a crystal structure is LiM1O2 (M1 is composed of Fe, Ni, Co, and Mn). and one or more selected from the group consisting of:

[0267] The Jahn-Teller effect in transition metal compounds depends on the number of electrons in the d orbital of the transition metal: The strength of the effect is known to vary.

[0268] In compounds containing nickel, distortion is likely to occur due to the Jahn-Teller effect. Therefore, when LiNiO2 is charged and discharged at high voltage, In LiCoO2, the Jahn-Teller effect is This suggests that the effect of the ion implantation is small, and the resistance to charging and discharging at high voltages may be superior, which is preferable. It's nice.

[0269] The structure of the positive electrode active material will be described with reference to Figs. The case where cobalt is used as the transition metal in the positive electrode active material will be described.

[0270] <Conventional positive electrode active materials> The positive electrode active material shown in FIG. 14 is lithium cobalt oxide to which no halogen or magnesium is added. The lithium cobalt oxide shown in Figure 14 has a charge depth of 1000 s. Therefore, the crystal structure changes. In other words, when written as LixCoO2, The crystal structure changes depending on the lithium occupancy rate x of the umsite.

[0271] As shown in Figure 14, lithium cobalt oxide in the x=1 state (discharged state) is in the space group It has a region with an R-3m crystal structure, and there are three CoO2 layers in the unit cell. Therefore, this crystal structure is sometimes called an O3 type crystal structure. The structure is an octahedral structure in which oxygen atoms are six-coordinated to the base, and the structure is continuous in the planar direction with edge sharing. Let's say.

[0272] When x = 0, the crystal structure has the space group P-3m1, and CoO2 There is one layer, so this crystal structure is sometimes called the O1-type crystal structure.

[0273] In addition, when x is about 0.12, lithium cobalt oxide has a crystal structure of the space group R-3m. This structure is different from the structure of CoO2 such as P-3m1(O1) and R-3m(O3). The structure of LiCoO2 is like this, and it can be said that it is a structure in which layers are stacked alternately. This structure is sometimes called the H1-3 type crystal structure. Therefore, the H1-3 type crystal structure is experimentally observed from about x = 0.25. Actually, the H1-3 crystal structure has a different number of cobalt atoms per unit cell than other structures. However, in this specification, including Figure 14, in order to make it easier to compare with other structures, Therefore, the c-axis of the H1-3 type crystal structure is shown as half of the unit cell.

[0274] For example, the H1-3 type crystal structure has the coordinates of cobalt and oxygen in the unit cell as C o(0, 0, 0.42150±0.00016), O1(0, 0, 0.27671±0. 00045), O2(0, 0, 0.11535±0.00045). O1 and O2 are oxygen atoms. Thus, the H1-3 crystal structure is On the other hand, as will be described later, the present invention The O3' type crystal structure of one embodiment is preferably a unitary structure using one cobalt and one oxygen. This is expressed by a unit cell in the case of the O3' type crystal structure and the H1-3 type structure. The symmetry between cobalt and oxygen is different, and the O3' type crystal structure is more stable than the H1-3 type structure. This shows that the change from the O3 structure is small in all cases. The choice of whether to use a unit cell for the analysis can be made based on, for example, the readings of the XRD patterns. In the Tobelt analysis, the GOF (goodness of fit) value becomes smaller. You can choose to do so.

[0275] High-voltage charging where the charging voltage is 4.6V or higher based on the oxidation-reduction potential of lithium metal When the battery is repeatedly charged or discharged to a deep depth where x=0.24 or less, Lithium valence oxide has a crystal structure between H1-3 type and R-3m(O3) type in discharge state. This causes repeated changes in the crystal structure (i.e., non-equilibrium phase changes).

[0276] However, these two crystal structures have a large misalignment of the CoO2 layers. As shown by the double arrows, in the H1-3 type crystal structure, the CoO2 layer is Such dynamic structural changes have a negative effect on the stability of the crystal structure. Can be given.

[0277] Furthermore, the difference in volume is large. When comparing the same number of cobalt atoms, the H1-3 type crystal The difference in volume between the structure and the O3-type crystal structure in the discharged state is more than 3.0%.

[0278] In addition, the H1-3 type crystal structure has continuous CoO2 layers such as P-3m1(O1). The resulting structure is likely to be unstable.

[0279] Therefore, repeated high-voltage charging and discharging causes the crystal structure of lithium cobalt oxide to collapse. The breakdown of the crystal structure causes a deterioration in cycle characteristics. , the number of sites where lithium can exist stably decreases, and lithium insertion and desorption becomes difficult. This is thought to be the reason.

[0280] <Positive Electrode Active Material of One Embodiment of the Present Invention> <Internal> The positive electrode active material 100 according to one embodiment of the present invention has a high resistance to CoO2 The layer displacement can be reduced. Furthermore, the volume change can be reduced. Therefore, the positive electrode active material of one embodiment of the present invention can achieve excellent cycle characteristics. In addition, the positive electrode active material of one embodiment of the present invention can have a stable crystal structure in a charged state at a high voltage. Therefore, the positive electrode active material of one embodiment of the present invention has a high resistance to charge when maintained in a charged state at a high voltage. In such cases, safety is improved, so it is preferable to use I wish.

[0281] The positive electrode active material of one embodiment of the present invention has a sufficient discharge state and a high voltage charged state. The change in crystal structure and the difference in volume when compared per the same number of transition metal atoms are small. Sai.

[0282] The crystal structure of the positive electrode active material 100 before and after charge and discharge is shown in FIG. It is a composite oxide containing ammonium as a transition metal, cobalt as a transition metal, and oxygen. It is preferable that the additional element X contains magnesium. The additional element X may also contain fluorine, It is preferred to have a halogen such as chlorine.

[0283] The crystal structure of x=1 (discharged state) in Figure 12 is R-3m(O3), the same as in Figure 14. On the other hand, the positive electrode active material 100 according to one embodiment of the present invention has a charge depth of H1-3 The crystal structure is different from the crystalline structure of the benzophenone-type crystalline structure. This structure is assigned to the space group R-3m, and Ions such as iodine and magnesium ions occupy the 6-coordinated oxygen sites. The symmetry is the same as that of the O3 type. Therefore, this structure is referred to as the O3' type crystal structure in this specification. In the diagram of the O3' type crystal structure shown in Figure 12, the symmetry of the cobalt atom and the acid In order to explain the symmetry of elementary atoms, the lithium is omitted. Between the O2 layers, for example, 20 atomic % or less of lithium is present relative to the cobalt.

[0284] In the O3'-type crystal structure, light elements such as lithium may occupy the oxygen tetracoordination position. Possible.

[0285] The O3' type crystal structure has random lithium between layers, but the CdCl2 type crystal structure It can be said that this crystal structure is similar to the CdCl2 type. The structure is that when lithium nickel oxide is charged to a charge depth of 0.94 (Li 0.06 NiO 2) It has a similar crystal structure to pure lithium cobaltate, or a layered rock containing a large amount of cobalt. It is known that salt-type positive electrode active materials do not usually have this crystal structure.

[0286] In the positive electrode active material 100 of one embodiment of the present invention, a large amount of lithium was released by charging at a high voltage. The change in the crystal structure is suppressed more than in conventional positive electrode active materials. As shown by the dotted lines, there is almost no misalignment of the CoO2 layers in these crystal structures.

[0287] More specifically, the positive electrode active material 100 according to one embodiment of the present invention exhibits a high charge voltage. For example, conventional positive electrode active materials have an H1-3 type crystal structure. Even at a charging voltage of about 4.6V, for example, based on the potential of lithium metal, R-3 There is a region of charging voltage where the crystal structure of m(O3) can be maintained, and there is a region where the charging voltage is further increased. For example, at a voltage of about 4.65 V to 4.7 V based on the potential of lithium metal Furthermore, when the charging voltage is increased, the H In some cases, 1-3 type crystals are observed. When graphite is used, for example, even when the voltage of the secondary battery is between 4.3V and 4.5V, R There is a region of charging voltage where the crystal structure of -3m(O3) can be maintained, and if the charging voltage is further increased, For example, in the region between 4.35V and 4.55V based on the potential of lithium metal There is also a region that can adopt the O3' type crystal structure.

[0288] Therefore, in the positive electrode active material 100 of one embodiment of the present invention, repeated charging and discharging at a high voltage Even if it is heated, the crystal structure is not easily broken.

[0289] In addition, the positive electrode active material 100 has an O3 type crystal structure with x=1 and an O3' type crystal structure with x=0.2. The difference in volume per unit cell of the structure is 2.5% or less, more specifically 2.2% or less.

[0290] In the O3' type crystal structure, the coordinates of cobalt and oxygen in the unit cell are expressed as Co(0, 0,0.5), O(0,0,x), and can be shown within the range of 0.20≦x≦0.25. .

[0291] The additive element X, which exists randomly and dilutely between the CoO2 layers, i.e., at the lithium site, For example, magnesium has the effect of suppressing the displacement of the CoO2 layers. When magnesium is present, it tends to form the O3' type crystal structure. The positive electrode active material 100 according to the present invention is distributed in at least a part of the surface layer thereof, and further It is preferable that magnesium is distributed over the entire surface of the material 100. In order to distribute the positive electrode active material 100 over the entire surface layer of the positive electrode active material 100, In the step, a heat treatment is preferably carried out.

[0292] However, if the heat treatment temperature is too high, cation mixing occurs and the added element X For example, magnesium is more likely to enter the cobalt site. The magnesium contained in the battery is ineffective in maintaining the structure of the R-3m when it is charged at high voltage. If the heat treatment temperature is too high, cobalt will be reduced to divalent, and lithium will There are also concerns about adverse effects such as evaporation.

[0293] Therefore, a heat treatment for distributing magnesium over the entire surface layer of the positive electrode active material 100 is performed. Before this, it is recommended to add a halogen compound such as a fluorine compound to the lithium cobalt oxide. Addition of a halogen compound lowers the melting point of lithium cobalt oxide. By lowering the temperature, magnesium is mixed with the positive electrode active material at a temperature where cation mixing is unlikely to occur. It is easy to distribute the fluorine compound over the entire surface of the substrate. This is expected to improve corrosion resistance against hydrofluoric acid produced by decomposition of the electrolyte.

[0294] If the magnesium concentration is increased above a desired value, the effect on stabilizing the crystal structure is reduced. In addition to the lithium site, magnesium may also be present at the cobalt site. This is thought to be because the magnesium contained in the positive electrode active material of one embodiment of the present invention also enters the matrix. The number of atoms of ammonium is preferably 0.001 to 0.1 times the number of atoms of the transition metal such as cobalt. Preferably, it is greater than 0.01 and less than 0.04, and more preferably about 0.02. The magnesium concentration shown here is determined by, for example, measuring the concentration of magnesium in the positive electrode active material using ICP-MS or the like. The value may be obtained by performing elemental analysis on the entire cathode active material 100, or may be obtained by analyzing the raw materials in the process of producing the cathode active material 100. It may also be based on the value of the ingredient combination.

[0295] Lithium cobalt oxide is added with a metal other than cobalt (hereinafter referred to as additive element X), for example, nickel. one or more metals selected from the group consisting of zinc, aluminum, manganese, titanium, vanadium, and chromium may be added, and it is particularly preferred to add one or more of nickel and aluminum. Manganese, titanium, vanadium, and chromium may be stable in their tetravalent state. The addition of the additive element X can contribute significantly to the structural stability. In some cases, the crystal structure of the positive electrode active material according to one embodiment of the present invention becomes more stable in the charged state. In the material, the added element X is present at a concentration that does not significantly change the crystallinity of lithium cobalt oxide. For example, it is preferable to add the cellulose ester at a concentration that does not cause the above-mentioned Jahn-Teller effect. It is preferable that the amount is .

[0296] Nickel, manganese, and other transition metals, as well as aluminum, are present in the cobalt site. It is preferable that the magnesium is present at the lithium site, but a part of the magnesium may be present at the lithium site. It is preferable that oxygen exists at the lithium site. Even if some oxygen is substituted with fluorine, good.

[0297] As the magnesium concentration of the positive electrode active material of one embodiment of the present invention increases, the volume of the positive electrode active material increases. The amount of magnesium may decrease. For example, this can occur when magnesium enters the lithium site. This may reduce the amount of lithium that contributes to charging and discharging. The positive electrode active material has nickel as an additive element X in addition to magnesium. In addition, the positive electrode active material according to one embodiment of the present invention can have improved charge-discharge cycle characteristics. The substance contains aluminum as an added element X in addition to magnesium, and thus the substance is filled. In some cases, the discharge cycle characteristics can be improved. By using a positive electrode active material of one embodiment of the present invention containing ammonium, nickel, and aluminum, In this case, the charge-discharge cycle characteristics can be improved.

[0298] The following describes the present invention in which the additive element X is magnesium, nickel, or aluminum. The concentrations of elements in the positive electrode active material of one embodiment of the present invention will be examined.

[0299] The number of nickel atoms in the positive electrode active material of one embodiment of the present invention is 10% of the number of cobalt atoms. Preferably, it is 7.5% or less, more preferably 7.5% or less, and even more preferably 0.05% or more and 4% or less. The nickel concentration shown here is preferably 0.1% or more and 2% or less. The value may be a value obtained by performing elemental analysis of the entire positive electrode active material using MS or the like, or may be a value obtained by performing elemental analysis of the positive electrode active material using MS or the like. It may be based on the value of the blend of raw materials in the manufacturing process.

[0300] If the battery is charged at a high voltage for a long period of time, the constituent elements of the positive electrode active material will dissolve into the electrolyte, However, by having nickel in the above ratio, the positive electrode active material It may be possible to suppress the leaching of constituent elements from the material 100.

[0301] The number of aluminum atoms in the positive electrode active material of one embodiment of the present invention is 0.01 to the number of cobalt atoms. The range is preferably 0.05% or more and 4% or less, and more preferably 0.1% or more and 2% or less. The aluminum concentration can be determined by performing elemental analysis of the entire positive electrode active material using, for example, ICP-MS. It may be a value determined by the calculation or may be based on the value of the blending of raw materials in the process of producing the positive electrode active material. stomach.

[0302] In addition, the positive electrode active material having an additional element X according to one embodiment of the present invention uses phosphorus as the additional element X. In addition, the positive electrode active material of one embodiment of the present invention preferably contains a compound containing phosphorus and oxygen. It is more preferable to have

[0303] The positive electrode active material according to one embodiment of the present invention contains a compound containing phosphorus as the additional element X. When a high temperature and high voltage charging state is maintained for a long time, a short circuit is unlikely to occur. There is.

[0304] When the positive electrode active material according to an embodiment of the present invention contains phosphorus as the additional element X, decomposition of the electrolyte The hydrogen fluoride generated by this may react with phosphorus, reducing the hydrogen fluoride concentration in the electrolyte. There is.

[0305] When the electrolyte contains LiPF6 as the lithium salt, hydrogen fluoride is generated by hydrolysis. In addition, the reaction between PVDF, which is used as a component of the positive electrode, and alkali may occur. This can also result in the generation of hydrogen fluoride. This may prevent the current collector from corroding and / or peeling off. This may prevent a decrease in adhesiveness due to gelation and / or insolubilization.

[0306] The positive electrode active material 100 according to one embodiment of the present invention has phosphorus and magnesium as the additional element X. When the additive element X is phosphorus or magnesium, the stability is extremely high in a high voltage charging state. When cobalt is contained, the number of phosphorus atoms is preferably 1% or more and 20% or less of the number of cobalt atoms. It is more preferable that the content is 2% or more and 10% or less, and even more preferable that the content is 3% or more and 8% or less. The number of magnesium atoms is preferably 0.1% or more and 10% or less of the number of cobalt atoms, and 0.5 % or more and 5% or less, and more preferably 0.7% or more and 4% or less. The concentration of magnesium is measured by measuring the total elemental mass of the positive electrode active material 100 using, for example, ICP-MS. It may be a value obtained by elementary analysis, or a value obtained by mixing raw materials in the process of producing the positive electrode active material 100. may be based on the value of

[0307] When the positive electrode active material 100 has cracks, phosphorus, more specifically, for example, phosphorus, is present inside the cracks. The presence of compounds containing fluorine and oxygen may inhibit the progression of cracks.

[0308] In Figure 12, the oxygen atoms in the O3 crystal structure and the O3' crystal structure have slightly different symmetry. Specifically, in the O3 crystal structure, the oxygen atoms are aligned along the dotted line, whereas in the Therefore, the oxygen atoms in the O3' crystal structure are not strictly aligned. As the lithium content decreases, the tetravalent cobalt content increases, the Jahn-Teller strain increases, and the Co This is due to the distortion of the octahedral structure of O6. Also, as lithium decreases, the oxygen atoms in the CoO2 layer become distorted. Another factor that contributed to this was the growing opposition from the samurai.

[0309] <Surface layer 100a> Magnesium is distributed throughout the surface layer of the positive electrode active material 100 according to one embodiment of the present invention. In addition, the magnesium concentration in the surface layer 100a is preferably higher than the overall average. For example, it is preferable that the magnesium concentration of the surface layer portion 100a measured by XPS or the like is It is preferable that the magnesium concentration is higher than the overall average magnesium concentration measured by ICP-MS or the like.

[0310] Furthermore, the positive electrode active material 100 according to one embodiment of the present invention does not contain any element other than cobalt, such as nickel or aluminum. In the case where the composition contains one or more metals selected from aluminum, manganese, iron, and chromium, It is preferable that the concentration of the metal near the particle surface is higher than the overall average. For example, The concentrations of elements other than cobalt in the surface layer 100a measured by XPS etc. are It is preferably higher than the overall average concentration of the element measured.

[0311] The surface layer of the positive electrode active material 100 is, so to speak, entirely made up of crystal defects, and during charging, the surface As lithium is released from the inside, the lithium concentration is likely to be lower than in the inside. Therefore, the magnesium concentration in the surface layer 100a is low and the crystal structure is easily broken. If the surface layer portion 100a has a high crystalline structure, the change in the crystalline structure can be more effectively suppressed. A high magnesium concentration improves corrosion resistance to hydrofluoric acid produced by decomposition of the electrolyte. We can also expect this.

[0312] Furthermore, halogens such as fluorine are also present in the surface layer portion 100a of the positive electrode active material 100 according to one embodiment of the present invention. It is preferable that the concentration in the surface layer 1, which is the region in contact with the electrolyte, is higher than the overall average. The presence of halogen in 00a effectively improves corrosion resistance to hydrofluoric acid. can.

[0313] In this way, the surface layer 100a of the positive electrode active material 100 according to one embodiment of the present invention is thicker than the inner layer 100b. , the concentration of additive elements, such as magnesium and fluorine, is high, and the composition is different from the inside It is also preferable that the composition has a stable crystal structure at room temperature. The surface layer 100a may have a different crystal structure from the inner layer 100b. At least a part of the surface layer 100a of the positive electrode active material 100 of this embodiment has a rock salt type crystal structure. In addition, when the surface layer portion 100a and the inner portion 100b have different crystal structures, It is preferable that the crystal orientation of the surface layer portion 100a and the inner portion 100b be roughly the same.

[0314] Layered rock salt crystals and the anions of rock salt crystals are in a cubic close-packed structure (face-centered cubic lattice structure) ) in the O3'-type crystal, the anions are also estimated to have a cubic close-packed structure. In the specification, the layers A, B, and C each having an anion are arranged in a manner similar to ABCABC. If the structure is stacked with a shift, it is called a cubic close-packed structure. does not have to be a cubic lattice. At the same time, real crystals always have defects, so the analysis results For example, FFT (Fast Fourier Transform) of electron diffraction or TEM images is not necessarily theoretical. In the Fourier transform, the spots may appear at positions slightly different from the theoretical positions. For example, if the orientation with respect to the theoretical position is less than 5 degrees or less than 2.5 degrees, it is a cubic close-packed structure. It can be said that this is the case.

[0315] When layered rock salt crystals come into contact with each other, a cubic close-packed structure consisting of anions is formed. There are crystal faces with aligned structures.

[0316] Alternatively, it can be explained as follows: On the (111) plane of the cubic crystal structure The anions are arranged in a triangular shape. The layered rock salt structure has the space group R-3m, and is rhombohedral. However, to make it easier to understand the structure, it is generally expressed as a composite hexagonal lattice, and the layered rock salt structure The (0001) plane of the cubic crystal has a hexagonal lattice. The triangular lattice of the cubic crystal (111) is similar to that of the layered rock salt type ( The atomic arrangement is similar to that of the hexagonal lattice of the (0001) plane. This means that the orientation of the cubic close-packed structure is aligned.

[0317] However, the space group of the layered rock salt crystal and O3' type crystal is R-3m, and the space group of the rock salt type crystal is The space groups Fm-3m (the common rock salt crystal space group) and Fd-3m (the simplest symmetry Since this is different from the space group of rock salt crystals, the Miller indices of the crystal planes that satisfy the above conditions are is different between layered rock salt crystals and O3'-type crystals and rock salt crystals. In salt-type crystals, O3'-type crystals, and rock salt-type crystals, the cubic maxima composed of anions When the orientation of the close-packed structure is aligned, it is sometimes said that the crystal orientation is roughly the same.

[0318] The crystal orientation of the two regions roughly coincides with each other, as can be seen from TEM (transmission electron microscope) images and STE M (scanning transmission electron microscope) image, HAADF-STEM (high angle annular dark field scanning transmission electron microscope) image microscope) image, ABF-STEM (annular bright-field scanning transmission electron microscope) image, electron diffraction, TEM This can be determined from FFT of images, etc. X-ray diffraction (XRD), neutron diffraction, etc. can also be determined. It can be used as a material for.

[0319] Figure 16 shows a TEM image showing that the orientation of the layered rock salt crystal LRS and the rock salt crystal RS roughly coincides. Examples of TEM, STEM, HAADF-STEM, and ABF-STEM images are shown below. An image that reflects the crystal structure is obtained.

[0320] For example, in high-resolution TEM images, contrast originating from crystal planes can be observed. By the diffraction and interference of the electron beam, for example, the electron beam is perpendicular to the c-axis of the layered rock salt type composite hexagonal lattice. When light is incident, the contrast originating from the (0003) plane appears as a repetition of bright and dark lines. Therefore, repeated bright and dark lines are observed in the TEM image, and the bright lines (for example) For example, the L shown in Figure 16 RS and L LRS ) angle is 5 degrees or less, or 2.5 degrees or less It can be determined that the crystal planes are roughly aligned, i.e., the crystal orientations are roughly aligned. Similarly, if the angle between the dark lines is less than 5 degrees or less than 2.5 degrees, the crystal It can be determined that the orientations are roughly the same.

[0321] In addition, the HAADF-STEM image provides contrast according to the atomic number, For example, the layered rocksalt type koba, which belongs to the space group R-3m, is observed brighter. In the case of lithium cobaltate, cobalt (atomic number 27) has the highest atomic number, so The electron beam is strongly scattered at the positions of the cobalt atoms, and the arrangement of the cobalt atoms appears as bright lines or points of high brightness. Therefore, lithium cobalt oxide with a layered rock salt type crystal structure is observed as an arrangement of When observed perpendicular to the c-axis, the arrangement of cobalt atoms perpendicular to the c-axis appears as a bright line or a strongly luminous line. The arrangement of lithium atoms and oxygen atoms is observed as a dark line or low brightness area. The doping elements of lithium cobalt oxide are fluorine (atomic number 9) and manganese. The same is true when it contains magnesium (atomic number 12).

[0322] Therefore, in the HAADF-STEM image, bright and dark lines appear in two regions with different crystal structures. If the repetition of the above is observed and the angle between the bright lines is less than 5 degrees or less than 2.5 degrees, It can be determined that the arrangement of the molecules is roughly the same, that is, the orientation of the crystals is roughly the same. Similarly, if the angle between the dark lines is less than 5 degrees or less than 2.5 degrees, the crystal It can be determined that the orientations are roughly the same.

[0323] In ABF-STEM, elements with smaller atomic numbers are observed brighter. Similar to HAADF-STEM, the contrast obtained is dependent on the HAADF. The crystal orientation can be determined in the same way as with F-STEM images.

[0324] Figure 17A shows a STEM image of the layered rock salt crystal LRS and the rock salt crystal RS, showing that their orientations are roughly the same. Figure 17B shows an example of an FFT image of the rock salt type crystal RS, and Figure 17C shows an FFT image of the layered rock salt type crystal LRS. The FFT of the region is shown in Figure 17C. The literature values ​​are shown on the left in Figures 17B and 17C, and the measured values ​​are shown on the right. The spot marked with an O is the zeroth diffraction order.

[0325] The spot marked A in Figure 17B is due to the 11-1 reflection of the cubic crystal. The spot marked A in C is derived from the 0003 reflection of the layered rock salt type. It can be seen that the line passing through AO in FIG. 17B and the line passing through AO in FIG. 17C are approximately parallel. 17B and 17C, the 11-1 reflection of the cubic crystal and the layered rock salt It can be seen that the orientation of the 0003 reflection of the model roughly matches. "Approximately parallel" means that the angle is 5 degrees or less, or 2.5 degrees or less.

[0326] Thus, the orientation of the layered rock salt crystals and the rock salt crystals roughly coincides in the FFT and electron diffraction. The layered rock salt type has a <0003> orientation or an equivalent plane orientation, and the rock salt type has a <1 1-1〉 orientation or an equivalent plane orientation. These reciprocal lattice points are preferably spot-like, that is, not continuous with other reciprocal lattice points. The fact that the reciprocal lattice points are spot-like and not continuous with other reciprocal lattice points indicates high crystallinity. means.

[0327] As mentioned above, the 11-1 reflection of the cubic crystal and the 0003 reflection of the layered rock salt crystal are When and are roughly the same, depending on the incident direction of the electron beam, the layered rock salt type 0003 reflection A spot that is not due to the layered rocksalt type 0003 reflection is observed in the reciprocal lattice space, which is different from the orientation of the For example, the spot marked B in Figure 17C is a layered rock salt type 10-14 This is due to the reciprocal lattice point (Figure 17) originating from the 0003 reflection of the layered rock salt type. From the direction of A of C), the angle is between 52° and 56° (i.e., ∠AOB is less than 52°). 56° or less), and d is observed in the area between 0.19 nm and 0.21 nm. Note that this index is just an example and does not necessarily have to match. For example, Reciprocal lattice points equivalent to 0003 and 1014 may also be used.

[0328] Similarly, in a reciprocal lattice space different from the orientation in which cubic 11-1 was observed, cubic 11-1 Spots that are not of the origin may be observed. For example, the spot marked B in Figure 17B is due to the 200 reflection of the cubic crystal. This is due to the 11-1 reflection of the cubic crystal ( From the direction of A in Figure 17B, the angle is between 54° and 56° (i.e., ∠AOB is 5 Diffraction spots may be observed at points where the angle is between 4° and 56°. is just an example and does not necessarily have to match. For example, 11-1 and 200, etc. A valence reciprocal lattice point may also be used.

[0329] In addition, layered rock salt type positive electrode active materials such as lithium cobalt oxide have a (0003) plane. and its equivalent planes, as well as the (10-14) plane and its equivalent planes, appear as crystal planes. Therefore, it is important to carefully observe the shape of the positive electrode active material using an SEM or other device. In order to make it easier to observe the (0003) plane, for example, in a TEM, the electron beam is focused on [1-2 10] It is possible to thin the observation sample using FIB etc. so that the incident light is When you want to judge the coincidence of the orientation of the layered rock salt type, the (0003) plane is easy to observe. It is preferable to thin the film.

[0330] However, the surface layer 100a has a structure in which only MgO is present or in which MgO and CoO(II) are solid-solved. Therefore, the surface layer 100a is at least It also contains cobalt in the discharged state and lithium in the discharged state, providing a pathway for lithium insertion and desorption. It is also preferable that the concentration of cobalt is higher than that of magnesium.

[0331] The additive element X is located in the surface layer portion 100a of the particle of the positive electrode active material 100 according to one embodiment of the present invention. For example, the positive electrode active material 100 according to one embodiment of the present invention has an additive element X. It may be covered with a coating.

[0332] <Grain boundary> The additive element X contained in the positive electrode active material 100 according to one embodiment of the present invention is randomly and dilutely distributed inside the positive electrode active material 100. Although they may be present, it is more preferable that some of them are segregated at the grain boundaries.

[0333] In other words, the additional element X at and near the grain boundaries of the positive electrode active material 100 according to one embodiment of the present invention The concentration of the fluorine-containing compound is also preferably higher than that of the other regions inside the fluorine-containing compound.

[0334] Grain boundaries can be considered as planar defects. Therefore, like the grain surfaces, they are unstable. Therefore, the added elements at the grain boundaries and their vicinity are easily The higher the concentration of X, the more effectively the change in the crystal structure can be suppressed.

[0335] In addition, when the concentration of the additional element X at and near the grain boundary is high, the positive electrode active material according to one embodiment of the present invention Even if a crack occurs along the grain boundary of a particle of material 100, the crack The concentration of the added element X is high near the surface. Therefore, after cracks occur in the positive electrode active material, In addition, the corrosion resistance to hydrofluoric acid can be improved.

[0336] In this specification, the vicinity of the grain boundary refers to the region up to about 10 nm from the grain boundary. We will do so.

[0337] <Particle size> If the particle size of the positive electrode active material 100 of one embodiment of the present invention is too large, it becomes difficult for lithium to diffuse. Or, when the active material layer is applied to the current collector, the surface of the active material layer becomes too rough. On the other hand, if the particle size is too small, it will be difficult to support the active material layer when it is applied to the current collector, and the reaction with the electrolyte will be Therefore, the average particle size (D50: also called the median diameter) ) is preferably 1 μm or more and 100 μm or less, more preferably 2 μm or more and 40 μm or less. It is more preferable that the thickness is 5 μm or more and 30 μm or less, and further more preferable that the thickness is 5 μm or more and 30 μm or less.

[0338] <Analysis method> In one embodiment of the present invention, a positive electrode active material exhibits an O3'-type crystal structure when charged at a high voltage. Whether or not the positive electrode active material 100 is the positive electrode active material 100 can be determined by examining the positive electrode charged at a high voltage using XRD, electron diffraction, neutral By analyzing using sagittal beam diffraction, electron spin resonance (ESR), nuclear magnetic resonance (NMR), etc. In particular, XRD can accurately determine the symmetry of transition metals such as cobalt contained in the positive electrode active material. It is possible to analyze the crystallinity and the orientation of the crystals, and to compare the periodic distortion and the crystal structure. The crystallite size can be analyzed, and sufficient accuracy can be obtained by measuring the positive electrode obtained by disassembling the secondary battery. This is preferable in that it allows you to obtain a high degree of

[0339] As described above, the positive electrode active material 100 according to one embodiment of the present invention is in a state where it is charged at a high voltage. It has the characteristic that the crystal structure changes little when it is charged at a high voltage and when it is discharged. Materials with a crystal structure that exhibits large changes in the charge and discharge states, accounting for 50 wt% or more, are resistant to high-voltage charging and discharging. Furthermore, the desired crystal structure cannot be obtained by simply adding an additional element. It should be noted that there are cases where the cobalt with magnesium and fluorine is not Although they share the common feature of being lithium nitrate, when charged at high voltage, the O3'-type crystal structure When the H1-3 type crystal structure is 60 wt% or more, or when the H1-3 type crystal structure is 50 wt% or more, At a certain voltage, the O3' type crystal structure becomes almost 100 wt %. In some cases, when a certain voltage is applied, the H1-3 type crystal structure is generated. To determine whether the positive electrode active material 100 is the same as the above, it is necessary to analyze the crystal structure using XRD and other methods. Further analysis is needed.

[0340] However, when the positive electrode active material is in a high-voltage charged or discharged state, its crystalline structure changes when it comes into contact with the air. For example, the O3' crystal structure may change to the H1-3 crystal structure. Therefore, all samples should be handled in an inert atmosphere such as argon. It is preferable to perform this process.

[0341] <Charging method> In order to determine whether a certain composite oxide is the positive electrode active material 100 of one embodiment of the present invention, High voltage charging is performed using a coin cell (CR2032 type, 20mm diameter, high) with a lithium counter electrode. It is possible to create a battery (thickness 3.2mm) and charge it.

[0342] More specifically, for the positive electrode, a slurry containing a positive electrode active material, a conductive material, and a binder is mixed. A positive electrode current collector made of aluminum foil coated with the binder can be used.

[0343] Lithium metal can be used for the counter electrode. When the secondary battery is in a charged state, the potential of the secondary battery is different from the potential of the positive electrode. Unless otherwise specified, the potential is that of the positive electrode.

[0344] The electrolyte contained 1 mol / L of lithium hexafluorophosphate (LiPF6). The electrolyte used was ethylene carbonate (EC) and diethyl carbonate (DEC). EC:DEC = 3:7 (volume ratio), vinylene carbonate (VC) was mixed at 2 wt%. The above can be used.

[0345] The separator can be made of polypropylene with a thickness of 25 μm.

[0346] The positive and negative electrode cans can be made of stainless steel (SUS). Cut.

[0347] The coin cell prepared under the above conditions was charged at a constant current of 4.6 V and 0.5 C, and then the current value The battery is charged at a constant voltage until the temperature reaches 0.01C. Here, 1C is 137mA / g. After charging in this way, place the coin cell in a glow By disassembling it in the box and removing the positive electrode, the positive electrode active material charged at high voltage can be obtained. When various analyses are carried out after this, the container is sealed in an argon atmosphere to prevent reactions with external components. For example, XRD can be performed in a sealed container in an argon atmosphere. can.

[0348] <xrd> O3' type crystal structure and H1-3 type crystal structure model, calculated by CuKα1 radiation The ideal powder XRD patterns are shown in Figures 13 and 15. For comparison, the Li Ideal XR calculated from the crystal structure of CoO2(O3) and CoO2(O1) with x=0 The patterns of LiCoO2(O3) and CoO2(O1) are also shown. SD (Inorganic Crystal Structure Database) The model of Materials Studio (BIOVIA) was created from the crystal structure information obtained from Using Reflex Powder Diffraction, one of the modules The range of 2θ was set to 15° to 75°, the step size was 0.01, and the wavelength λ 1=1.540562×10 -10 m, λ2 are not set, Monochromator is The crystal structure pattern of the O3'-type crystal structure is a positive electrode active material according to one embodiment of the present invention. The crystal structure was estimated from the XRD pattern of the material and analyzed using TOPAS ver.3 (Bruker) The XRD patterns were fitted using the crystal structure analysis software (manufactured by Sigma-Aldrich) and analyzed in the same way as the others. Created.

[0349] As shown in Figure 13, in the O3' type crystal structure, 2θ = 19.30 ± 0.20° (19. 10° or more and 19.50° or less), and 2θ=45.55±0.10° (45.45° or more) Diffraction peaks appear at 2θ=19.30±45.65°. 0.10° (19.20° to 19.40°), and 2θ=45.55±0.05° However, a sharp diffraction peak appears at an angle between 45.50° and 45.60°. As shown, in the H1-3 type crystal structure and CoO2 (P-3m1, O1), peaks are formed at these positions. Therefore, when charged at high voltage, 2θ=19.30±0.20°, The appearance of peaks at 2θ=45.55±0.10° indicates the positive electrode activity of one embodiment of the present invention. This can be said to be a characteristic of Substance 100.

[0350] This is because the crystal structure of x=1 and the crystal structure of the high-voltage charged state show XRD diffraction peaks. More specifically, two of the main diffraction peaks of both are close to each other. The difference in the positions at which peaks appear is 2θ=0.7 or more, more preferably three or more. 2θ=0.5° or less, and more preferably 2θ=0.5° or less.

[0351] The positive electrode active material 100 according to one embodiment of the present invention exhibits an O3'-type crystal structure when charged at a high voltage. However, not all of the positive electrode active material 100 has the O3' type crystal structure. However, the XRD pattern may be When Rietveld analysis is performed, it is preferable that the O3' type crystal structure is 50 wt% or more. It is more preferable that the content is 60 wt% or more, and even more preferable that the content is 66 wt% or more. The O3' type crystal structure is preferably 50 wt% or more, more preferably 60 wt% or more, and even more preferably If the content is 66 wt % or more, it is possible to obtain a positive electrode active material with sufficiently excellent cycle characteristics. do.

[0352] In addition, even after more than 100 charge / discharge cycles from the start of measurement, Rietveld analysis was performed. In this case, the O3' type crystal structure is preferably 35 wt% or more, and more preferably 40 wt% or more. It is more preferable that the content is 43 wt % or more, and even more preferable that the content is 43 wt % or more.

[0353] In addition, the crystallite size of the O3'-type crystal structure of the positive electrode active material particles is The charge / discharge ratio is only about 1 / 10 of that of CoO2(O3). Even under the XRD measurement conditions, a clear peak of the O3' type crystal structure was not observed in the high voltage charging state. On the other hand, in simple LiCoO2, some of the structures are similar to the O3' type crystal structure. Even if it is possible, the crystallite size will be small and the peak will be broad and small. The size can be determined from the half-width of the XRD peak.

[0354] As described above, in the positive electrode active material according to one embodiment of the present invention, the influence of the Jahn-Teller effect is small. The positive electrode active material of one embodiment of the present invention has a layered rock salt type crystal structure and is preferably It is preferable that the transition metal is mainly cobalt. In materials where the influence of the Jahn-Teller effect is small, other than cobalt, It may also have the additional element X mentioned above.

[0355] As a result of considering a preferable range of the lattice constant, it was found that the positive electrode active material according to one embodiment of the present invention In this case, the positive state of the battery without charging or discharging, which can be estimated from the XRD pattern, In the layered rock salt type crystal structure of the active material particles, the lattice constant of the a-axis is 2.814 × 10 -10 m, 2.817×10 -10 m and the c-axis lattice constant is 1 4.05×10 -10 m, 14.07 × 10 -10 Preferably smaller than m The state in which no charge and discharge is performed is, for example, the state in which the powder is used before the positive electrode of the secondary battery is produced. It may be in the state of

[0356] Alternatively, the layer structure of the particles of the positive electrode active material in a state where no charge / discharge is performed or in a discharged state may be In a rock salt crystal structure, the lattice constant of the a-axis divided by the lattice constant of the c-axis (a-axis / c-axis) is preferably greater than 0.20000 and less than 0.20049.

[0357] Alternatively, the layer structure of the particles of the positive electrode active material in a state where no charge / discharge is performed or in a discharged state may be In the rock salt crystal structure, when XRD analysis was performed, 2θ was 18.50° or more and 19.30° or less. The first peak is observed at 2θ of 38.00° or less and the second peak is observed at 2θ of 38.80° or less. A peak may be observed.

[0358] The peaks appearing in the powder XRD pattern occupy most of the volume of the positive electrode active material 100. 100a and the like, which reflect the crystal structure of the inner portion 100b of the positive electrode active material 100. The crystal structure can be analyzed by electron diffraction or the like of a cross section of the positive electrode active material 100 .

[0359] <xps> X-ray photoelectron spectroscopy (XPS) measures the surface to a depth of approximately 2 to 8 nm (usually approximately 5 nm). Since it is possible to analyze the region up to about half of the surface layer 100a, the amount of each element can be analyzed. The concentration can be quantitatively analyzed. In addition, narrow scan analysis can be used to analyze the bonding state of elements. The quantitative accuracy of XPS is usually about ±1 atomic percent, and the The limit is about 1 atomic %, depending on the element.

[0360] For example, monochromated aluminum can be used as the X-ray source when performing XPS analysis. The take-off angle may be set to, for example, 45°.

[0361] Furthermore, when the positive electrode active material 100 according to one embodiment of the present invention was analyzed by XPS, it was found that fluorine and other The peak showing the binding energy of the element is preferably 682 eV or more and less than 685 eV. It is more preferable that the bond energy of lithium fluoride is about 684.3 eV. The energy of 685 eV, and the binding energy of magnesium fluoride, 686 eV In other words, the positive electrode active material 100 according to one embodiment of the present invention contains fluorine. If so, it is preferably a bond other than lithium fluoride and magnesium fluoride.

[0362] Furthermore, when the positive electrode active material 100 according to one embodiment of the present invention was analyzed by XPS, magnesium The peak showing the binding energy between uranium and other elements is between 1302 eV and 1304 eV. It is preferable that the energy is about 1303 eV, and more preferably about 1303 eV. This is a different value from the 1305 eV binding energy of magnesium oxide. In other words, the positive electrode active material 100 according to one embodiment of the present invention is When the compound has a magnesium fluoride bond, it is preferably a bond other than magnesium fluoride.

[0363] The additive element X, such as magnesium and aluminum, is preferably present in a large amount in the surface layer portion 100a. The concentration of aluminum measured by XPS etc. is different from that measured by ICP-MS (inductively coupled plasma mass spectrometry). ), or GD-MS (glow discharge mass spectrometry), etc. preferable.

[0364] Magnesium and aluminum are processed to expose their cross sections, and the cross sections are examined by TEM-E When analyzing using DX, the concentration of the surface layer 100a is higher than the concentration of the inside 100b. The processing can be carried out by, for example, FIB.

[0365] In XPS (X-ray photoelectron spectroscopy) analysis, the number of magnesium atoms is On the other hand, the mag- netic acid concentration by ICP-MS analysis is preferably 0.4 to 1.5 times that of the The ratio of the number of neodymium atoms, Mg / Co, is preferably 0.001 or more and 0.06 or less.

[0366] On the other hand, nickel contained in the transition metal is not unevenly distributed in the surface layer portion 100a, but is distributed throughout the positive electrode active material 100. However, there may be areas where the excess added element X is unevenly distributed. This does not apply if there is one.

[0367] <Surface roughness and specific surface area> The positive electrode active material 100 of one embodiment of the present invention preferably has a smooth surface with few irregularities. The fact that the surface is smooth and has few irregularities means that the distribution of the additive element X in the surface layer portion 100a is good. In the process of producing the positive electrode active material 100, Lithium cobalt oxide or lithium nickel-cobalt-manganese oxide before adding additional element X When initial heating was performed on lithium, the repeated charge / discharge characteristics at high voltage were significantly superior. Therefore, it is particularly preferable as the positive electrode active material 100 .

[0368] In addition, the surface of the positive electrode active material 100 is smooth and has few irregularities, so that the positive electrode active material 100 This may improve surface stability and reduce the occurrence of pits.

[0369] The surface is smooth and has few irregularities, for example, when a cross-sectional SEM image of the positive electrode active material 100 or This can be determined from a cross-sectional TEM image, the specific surface area of ​​the positive electrode active material 100, and the like.

[0370] For example, the surface smoothness is quantified from a cross-sectional SEM image of 100 positive electrode active material as shown below. It is possible.

[0371] First, the cathode active material 100 is processed by FIB or the like to expose a cross section. It is preferable to cover the positive electrode active material 100 with a protective agent or the like. An SEM image of the interface is taken. Noise is removed from the SEM image using image processing software. For example, After applying Gaussian blur (σ=2), the image is binarized. Then, the interface is extracted using image processing software. Furthermore, the interface between the protective film and the positive electrode active material 100 is removed using a magic hand tool or the like. Select the option and extract the data into a spreadsheet or similar software. Use the functions of the spreadsheet or similar software to perform regression analysis. Correction is performed from the curve (quadratic regression), and the parameters for calculating roughness are obtained from the data after the slope correction. To calculate the surface roughness, the root mean square (RMS) surface roughness is calculated using the standard deviation. The surface roughness of the positive electrode active material is the surface roughness within at least 400 nm of the outer periphery of the particle.

[0372] On the particle surfaces of the positive electrode active material 100 of this embodiment, the root mean square, which is an index of roughness, The root mean square (RMS) surface roughness is 10 nm or less, less than 3 nm, preferably less than 1 nm, and Preferably, the surface has a root mean square (RMS) surface roughness of less than 0.5 nm. .

[0373] There are no particular restrictions on the image processing software used for noise processing, boundary extraction, etc., but for example, For example, "ImageJ" can be used. There are no particular restrictions on spreadsheet software. However, for example, Microsoft Office Excel can be used. .

[0374] For example, the actual specific surface area A measured by the gas adsorption method using the constant volume method R and the ideal ratio surface area A i The surface smoothness of the positive electrode active material 100 can also be quantified from the ratio of do.

[0375] Ideal specific surface area A i is that all particles have the same diameter as D50 and the same weight. The shape is calculated assuming an ideal sphere.

[0376] The median diameter D50 can be measured using a particle size distribution analyzer that uses the laser diffraction and scattering method. The specific surface area can be measured using a specific surface area measuring device that uses a gas adsorption method based on a constant volume method, for example. Therefore, it can be measured.

[0377] The positive electrode active material 100 according to one embodiment of the present invention has an ideal specific surface area calculated from the median diameter D50. Product A i and the actual specific surface area A R Ratio A R / A i is preferably 1 or more and 2 or less.

[0378] The content of this embodiment mode can be freely combined with the content of other embodiment modes.

[0379] (Fourth embodiment) In this embodiment, a positive electrode or a negative electrode manufactured by the manufacturing method described in the previous embodiment will be described. Examples of various shapes of secondary batteries having a negative electrode will be described.

[0380] [Coin-type secondary battery] An example of a coin-type secondary battery will be described. FIG. 18A shows a coin-type (single-layer flat) secondary battery. 18B is an exploded perspective view of the secondary battery, FIG. 18B is an external view, and FIG. 18C is a cross-sectional view thereof. Coin-type secondary batteries are mainly used in small electronic devices. The type battery includes a button battery.

[0381] In Figure 18A, the overlapping of the components (vertical relationship and positional relationship) is shown clearly for ease of understanding. Therefore, Figures 18A and 18B are not completely identical corresponding figures. Not yet.

[0382] In FIG. 18A, the positive electrode 304, the separator 310, the negative electrode 307, the spacer 322, the washer These are sealed with a negative electrode can 302 and a positive electrode can 301. In Figure 18A, the gasket for sealing is not shown. The ferrule 312 is used to protect the inside of the can or to fix the position inside the can when the positive electrode can 301 and the negative electrode can 302 are crimped together. The spacer 322 and washer 312 are made of stainless steel or Or use insulating materials.

[0383] The positive electrode 304 has a laminated structure in which a positive electrode active material layer 306 is formed on a positive electrode current collector 305. do.

[0384] To prevent short circuits between the positive and negative electrodes, a separator 310 and a ring-shaped insulator 313 are attached to the positive electrode 30. The separator 310 is disposed so as to cover the side and top surfaces of the positive electrode 304. It also has a large planar area.

[0385] FIG. 18B is a perspective view of the completed coin-type secondary battery.

[0386] The coin-type secondary 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. The can 302 is insulated and sealed with a gasket 303 made of polypropylene or the like. The positive electrode 304 is composed of a positive electrode current collector 305 and a positive electrode active material layer 30 provided in contact with the positive electrode current collector 305. The negative electrode 307 is formed by a negative electrode current collector 308 and a negative electrode current collector 308 which is set in contact with the negative electrode current collector 308. The negative electrode 307 is formed by a negative electrode active material layer 309 formed by laminating the negative electrode active material layer 309. Alternatively, a lithium metal foil or a lithium-aluminum alloy foil may be used.

[0387] The positive electrode 304 and the negative electrode 307 used in the coin-type secondary battery 300 are active The material layer only needs to be formed on one side.

[0388] The positive electrode can 301 and the negative electrode can 302 are made of nickel and aluminum, which are corrosion-resistant to the electrolyte. Metals such as aluminum and titanium, or their alloys, and alloys of these with other metals (e.g., steel In addition, nickel is used to prevent corrosion by electrolytes. The positive electrode can 301 is made of a positive electrode 304 and a negative electrode can 305. 302 are electrically connected to the negative electrode 307, respectively.

[0389] The negative electrode 307, the positive electrode 304, and the separator 310 are immersed in an electrolyte solution, and the resulting mixture is then heated to a temperature of 10 ... As shown in the figure, the positive electrode can 301 is placed downward, the positive electrode 304, the separator 310, the negative electrode 307, and the negative electrode can The positive electrode can 301 and the negative electrode can 302 are stacked in this order, and the positive electrode can 301 and the negative electrode can 302 are pressed together with a gasket 303 interposed therebetween. The coin-type secondary battery 300 is manufactured by bonding the two layers together.

[0390] By having the above-mentioned configuration, it is possible to obtain a high capacity, a high charge / discharge capacity, and excellent cycle characteristics. This results in an excellent coin-type secondary battery 300. In the case of a secondary battery having a solid electrolyte layer between the separator 310 and the separator 310, the separator 310 may not be necessary. can.

[0391] [Cylindrical secondary battery] An example of a cylindrical secondary battery will be described with reference to Figs. 19A and 19B. 1 is a diagram showing a cross section of a cylindrical secondary battery. As shown in FIGS. 9A and 19B, the battery has a positive electrode cap (battery cover) 601 on the top surface, and The battery can (external can) 602 is provided on the bottom surface. The container 602 is insulated from the container 602 by a gasket (insulating packing) 610.

[0392] Inside the hollow cylindrical battery can 602, a strip-shaped positive electrode 604 and a negative electrode 606 are placed with a separator. The battery element is wound with the battery 605 sandwiched between them. The battery can 602 is wound around a core shaft. One end is closed and the other end is open. The battery can 602 is made of nickel, aluminum, titanium, or other metals that are resistant to corrosion by the electrolyte. metals, or their alloys, and alloys of these with other metals (e.g., stainless steel, etc.) In addition, nickel and aluminum can be used to prevent corrosion by the electrolyte. It is preferable to coat the battery can 602 with the positive electrode, the negative electrode, etc. The battery element with the separator wound around it is held in place by a pair of opposing insulating plates 608 and 609. The inside of the battery can 602 in which the battery element is provided is filled with a non-aqueous electrolyte (not shown). The non-aqueous electrolyte used can be the same as that used in coin-type secondary batteries. can.

[0393] The positive and negative electrodes used in cylindrical storage batteries are wound, so active material is formed on both sides of the current collector. 19A to 19D, the height of the cylinder is larger than the diameter of the cylinder. Although a large secondary battery 616 is illustrated, this is not limiting. A large secondary battery may also be used. With this configuration, for example, the secondary battery can be made smaller. It is possible.

[0394] By using the negative electrode 570a obtained in the above-described embodiment as the negative electrode 606, high capacity and This results in a cylindrical secondary battery 616 with high charge / discharge capacity and excellent cycle characteristics. In addition, the positive electrode active material composite 100z obtained in the above-described embodiment can be used for the positive electrode 604. This allows for a cylindrical battery with high capacity, high charge / discharge capacity, and excellent cycle characteristics. The battery 616 may be a secondary battery.

[0395] A positive electrode terminal (positive electrode current collecting lead) 603 is connected to the positive electrode 604, and a negative electrode terminal The positive terminal 603 and the negative terminal 607 are connected to The positive terminal 603 is connected to a safety valve mechanism 606. 13, the negative electrode terminals 607 are resistance welded to the bottom of the battery can 602. 3 is a PTC element (Positive Temperature Coefficient The safety valve mechanism 613 is electrically connected to the positive electrode cap 601 via the safety valve mechanism 611. When the internal pressure of the battery exceeds a predetermined threshold, the electric potential between the positive electrode cap 601 and the positive electrode 604 is increased. The PTC element 611 cuts off the electrical connection when the temperature rises. This is a thermal resistor element in which the resistance increases, 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 semiconducting ceramics. etc. can be used.

[0396] 19C shows an example of a power storage system 615. The power storage system 615 includes a plurality of secondary batteries 6 The positive electrode of each secondary battery is connected to a conductor 624 separated by an insulator 625. The conductor 624 is in contact with the control circuit 620 via the wiring 623. The negative electrodes of the secondary batteries are electrically connected to the control terminals 626. The control circuit 620 is electrically connected to the A protection circuit or the like can be applied to prevent this.

[0397] 19D shows an example of a power storage system 615. The power storage system 615 includes a plurality of secondary batteries. 616, and the plurality of secondary batteries 616 are sandwiched between the conductive plate 628 and the conductive plate 614. The plurality of secondary batteries 616 are electrically connected to the conductive plate 628 and the conductive plate 614 by wiring 627. The plurality of secondary batteries 616 may be connected in parallel or in series. By configuring the power storage system 615 with a plurality of secondary batteries 616, It is possible to extract a large amount of power.

[0398] A plurality of secondary batteries 616 may be connected in parallel and then further connected in series.

[0399] A temperature control device may be provided between the plurality of secondary batteries 616. If the secondary battery 616 is too cold, the temperature control device cools it down. Therefore, the performance of the power storage system 615 is not affected by the outside temperature. It will be less susceptible to noise.

[0400] 19D, the power storage system 615 includes a control circuit 620 and a wiring 621. The wiring 621 is electrically connected to a plurality of secondary electrodes via a conductive plate 628. The wiring 622 is connected to the positive terminal of the battery 616 via the conductive plate 614 and to the negative terminal of the secondary batteries 616. , are electrically connected to each other.

[0401] [Other examples of secondary battery structures] An example of the structure of the secondary battery will be described with reference to FIGS. 20 and 21. FIG.

[0402] The secondary battery 913 shown in FIG. 20A has a terminal 951 and a terminal 952 provided inside a housing 930. The winding 950 is immersed in the electrolyte inside the housing 930. The terminal 952 is in contact with the housing 930, and the terminal 951 is in contact with the housing by using an insulating material or the like. 20A, the housing 930 is not in contact with the housing 930. For convenience, the housing 930 is shown separately. However, in reality, the wound body 950 is covered by the housing 930, and the terminals 951 and 952 are not covered by the housing. The housing 930 is made of a metal material (e.g., aluminum, etc.). ) or a resin material can be used.

[0403] As shown in FIG. 20B, the housing 930 shown in FIG. 20A is made of a plurality of materials. For example, the secondary battery 913 shown in FIG. 20B may have a housing 930a and a housing 930b attached thereto. The housings 930a and 930b are joined together, and a wound body 950 is provided in the area surrounded by the housings 930a and 930b. It is being done.

[0404] The housing 930a can be made of an insulating material such as organic resin. By using a material such as organic resin on the surface on which the capacitor is formed, the electric field generated by the secondary battery 913 If the shielding of the electric field by the housing 930a is small, the housing 930a The antenna may be provided inside the housing 930b. For example, a metal material may be used for the housing 930b. can be done.

[0405] Furthermore, the structure of the wound body 950 is shown in FIG. The wound body 950 has a positive electrode 932 and a separator 933. A laminated sheet in which a negative electrode 931 and a positive electrode 932 are sandwiched and stacked is wound. The negative electrode 931, the positive electrode 932, and the separator 933 may be further laminated. Multiple layers may be stacked.

[0406] Also, a secondary battery 913 having a wound body 950a as shown in FIGS. 21A to 21C may be used. The wound body 950a shown in FIG. 21A includes a negative electrode 931, a positive electrode 932, and a separator. The negative electrode 931 has a negative electrode active material layer 931a. The positive electrode 932 has a positive electrode active material layer 933. It has a material layer 932a.

[0407] By using the negative electrode 570a obtained in the above-described embodiment as the negative electrode 606, high capacity and This results in a cylindrical secondary battery 616 with high charge / discharge capacity and excellent cycle characteristics. In addition, the positive electrode active material composite 100z obtained in the above-described embodiment can be used for the positive electrode 932. This allows for a secondary battery with high capacity, high charge / discharge capacity, and excellent cycle characteristics. It can be 13.

[0408] The separator 933 has a width greater than that of the negative electrode active material layer 931a and the positive electrode active material layer 932a. and wound so as to overlap with the negative electrode active material layer 931a and the positive electrode active material layer 932a. In addition, the width of the negative electrode active material layer 931a is wider than that of the positive electrode active material layer 932a, which is important for safety. Furthermore, the wound body 950a having such a shape is preferable in terms of safety and productivity. stomach.

[0409] As shown in FIG. 21B, the negative electrode is electrically connected to terminal 951. Terminal 951 is connected to terminal 9 11a. The positive electrode is electrically connected to terminal 952. Terminal 952 is electrically connected to terminal 911b.

[0410] As shown in FIG. 21C, the wound body 950a and the electrolyte are covered by the housing 930, and the secondary This becomes the battery 913. The housing 930 is preferably provided with a safety valve, an overcurrent protection element, and the like. The safety valve is a valve that opens when the inside of the housing 930 reaches a predetermined internal pressure to prevent the battery from exploding. .

[0411] As shown in FIG. 21B, the secondary battery 913 may have a plurality of wound bodies 950a. By using a number of windings 950a, the secondary battery 913 can have a larger charge / discharge capacity. Other elements of the secondary battery 913 shown in FIGS. 21A and 21B are the same as those shown in FIGS. The description of the secondary battery 913 shown in 20C can be taken into consideration.

[0412] <Laminated secondary battery> Next, an example of an external view of a laminated secondary battery is shown in FIGS. 22A and 22B. 22A and 22B show a positive electrode 503, a negative electrode 506, a separator 507, and an outer casing 508. 09, has a positive electrode lead electrode 510 and a negative electrode lead electrode 511.

[0413] 23A shows an external view of the positive electrode 503 and the negative electrode 506. The positive electrode 503 is a positive electrode current collector 501. The positive electrode active material layer 502 is formed on the surface of the positive electrode current collector 501. The negative electrode 503 has a region where the positive electrode current collector 501 is partially exposed (hereinafter referred to as the tab region). 06 has a negative electrode current collector 504, and a negative electrode active material layer 505 is formed on the surface of the negative electrode current collector 504. The negative electrode 506 has a region where the negative electrode current collector 504 is partially exposed, i.e., a tab region. The area and shape of the tab regions of the positive electrode and negative electrode are not limited to the example shown in FIG. I can't.

[0414] <Method for manufacturing laminated secondary batteries> Here, an example of a method for producing a laminated secondary battery shown in FIG. 22A will be described. 23B and 23C.

[0415] First, the negative electrode 506, the separator 507, and the positive electrode 503 are stacked. The negative electrode 506, separator 507, and positive electrode 503 are shown. Here, five pairs of negative electrodes and four pairs of positive electrodes are shown. This is an example of using a negative electrode, separator, and positive electrode. 03, and joining the positive electrode lead electrode 510 to the tab area of ​​the outermost positive electrode. For example, ultrasonic welding may be used for the joining. Similarly, the tab region of the negative electrode 506 The negative electrode lead electrode 511 is then bonded to the tab region of the negative electrode on the outermost surface.

[0416] Next, the negative electrode 506 , the separator 507 and the positive electrode 503 are placed on the exterior body 509 .

[0417] Next, as shown in Figure 23C, exterior body 509 is folded at the portion indicated by the dashed line. The outer periphery of the exterior body 509 is bonded. For example, thermocompression bonding may be used for bonding. It is joined to a part (or one side) of the exterior body 509 so that an electrolyte can be poured in later. An area where there is no air (hereinafter referred to as an inlet) is provided.

[0418] Next, the electrolyte is introduced into the inside of the exterior body 509 through an inlet provided in the exterior body 509. The introduction of the electrolyte solution is preferably carried out under a reduced pressure atmosphere or an inert atmosphere. Finally, the inlet is joined. In this way, the laminated secondary battery 500 is produced. It is possible.

[0419] By using the negative electrode 570a obtained in the above-described embodiment as the negative electrode 606, high capacity and This results in a cylindrical secondary battery 616 with high charge / discharge capacity and excellent cycle characteristics. In addition, the positive electrode active material composite 100z obtained in the above-described embodiment can be used for the positive electrode 503. This allows for a secondary battery5 with high capacity, high charge / discharge capacity, and excellent cycle characteristics. It can be set to 00.

[0420] [Example of a battery pack] FIG. 1 shows an example of a secondary battery pack according to one embodiment of the present invention that can be wirelessly charged using an antenna. 24A to 24C.

[0421] FIG. 24A is a diagram showing the appearance of secondary battery pack 531, which has a thin rectangular parallelepiped shape (thickness FIG. 24B is a diagram illustrating the configuration of secondary battery pack 531. The secondary battery pack 531 includes a circuit board 540 and a secondary battery 513. A label 529 is attached to the secondary battery 513. The circuit board 540 is attached with a sticker 515. The secondary battery pack 531 also has an antenna 517.

[0422] The inside of the secondary battery 513 may have a structure having a wound body or a structure having a laminated body. You may do so.

[0423] In the secondary battery pack 531, for example, as shown in FIG. 24B, the following is provided on the circuit board 540: The circuit board 540 has a control circuit 590. The circuit board 540 is electrically connected to the terminal 514. The circuit board 540 also includes an antenna 517, a positive lead and a negative lead of the secondary battery 513. One of the leads 551 is electrically connected to the other of the positive and negative leads 552 .

[0424] Alternatively, as shown in FIG. 24C, a circuit system 590 provided on a circuit board 540 a, and a circuit system 590b electrically connected to the circuit board 540 via the terminal 514. , may have.

[0425] The antenna 517 is not limited to a coil shape, but may be, for example, a wire shape or a plate shape. Also, planar antennas, aperture antennas, traveling wave antennas, EH antennas, magnetic field antennas, induction Alternatively, the antenna 517 may be a flat conductor. This flat conductor can function as one of the conductors for electric field coupling. Therefore, the antenna 517 functions as one of the two conductors of the capacitor. This allows power to be exchanged not only in electromagnetic fields and magnetic fields but also in electric fields. can.

[0426] The secondary battery pack 531 has a layer 519 between the antenna 517 and the secondary battery 513. The layer 519 has a function of blocking an electromagnetic field generated by the secondary battery 513, for example. The layer 519 may be made of, for example, a magnetic material.

[0427] The content of this embodiment mode can be freely combined with the content of other embodiment modes.

[0428] (Embodiment 5) In this embodiment, the positive electrode active material composite 100z obtained in the above-described embodiment is used to An example of fabricating a solid-state battery will be shown.

[0429] As shown in FIG. 25A, a secondary battery 400 according to one embodiment of the present invention includes a positive electrode 410, a solid electrolyte layer 420 and a negative electrode 430 .

[0430] The positive electrode 410 includes a positive electrode current collector 413 and a positive electrode active material layer 414. 4 has a positive electrode active material 411 and a solid electrolyte 421. The positive electrode active material 411 contains the above-mentioned The positive electrode active material composite 100z obtained in the embodiment is used. may include a conductive material and a binder.

[0431] The solid electrolyte layer 420 includes a solid electrolyte 421. The solid electrolyte layer 420 includes a positive electrode 410. and the negative electrode 430, and does not have either the positive electrode active material 411 or the negative electrode active material 431. This is a challenging area.

[0432] The negative electrode 430 includes a negative electrode current collector 433 and a negative electrode active material layer 434. The negative electrode active material layer 434 has a negative electrode active material 431 and a solid electrolyte 421. The negative electrode active material 431 may contain metallic lithium. When using a solid electrolyte 421, it is not necessary to make it into particles, so as shown in FIG. 25B, When metallic lithium is used for the negative electrode 430, the secondary battery 40 This is preferable because it can improve the energy density of 0.

[0433] The solid electrolyte 421 of the solid electrolyte layer 420 may be, for example, a sulfide-based solid electrolyte, An oxide-based solid electrolyte, a halide-based solid electrolyte, or the like can be used.

[0434] Sulfide-based solid electrolytes include thiolithium-based (Li 10 GeP2S 12 , Li 3.25 G e 0.25 P 0.75 S4, etc.), sulfide glass (70Li2S・30P2S5, 30Li 2S·26B2S3·44LiI, 63Li2S·36SiS2·1Li3PO4, 57 Li2S・38SiS2・5Li4SiO4, 50Li2S・50GeS2, etc.), sulfides Glass-ceramic (Li7P3S 11 , Li 3.25 P 0.95 S4, etc.) are included. Solid electrolytes based on ZnO have high conductivity, can be synthesized at low temperatures, and are relatively soft. Because it is soft, it has the advantage of easily maintaining conductive paths even after charging and discharging.

[0435] Oxide-based solid electrolytes include materials with a perovskite crystal structure (La 2 / 3-x L i 3x Materials having a NASICON-type crystal structure (such as TiO3), Li 1-Y Al Y Ti2 -Y (PO4)3, etc.), materials having a garnet-type crystal structure (Li7La3Zr2O 12 etc.), materials having a LISICON-type crystal structure (Li 14 ZnGe4O 16 etc.), LLZ O (Li7La3Zr2O 12 ), oxide glasses (Li3PO4-Li4SiO4, 50 Li4SiO4·50Li3BO3, etc.), oxide crystallized glasses (Li 1.07 Al 0.6 9Ti 1.46 (PO4)3, Li 1.5 Al 0.5 Ge 1.5 (PO4)3, etc.) are included. Oxide-based solid electrolytes have the advantage of being stable in air.

[0436] Halide-based solid electrolytes include LiAlCl4, Li3InBr6, LiF, LiC l, LiBr, LiI, etc. Also, composite materials in which these halide-based solid electrolytes are filled in the pores of porous aluminum oxide or porous silica can also be used as solid electrolytes.

[0437] Also, different solid electrolytes may be mixed and used.

[0438] Among them, Li 1-x Al x Ti 2-x (PO4)3 (0 < x < 1) (hereinafter, LATP) contains aluminum and titanium, which are elements that the positive electrode active material used in the secondary battery 400 according to one aspect of the present invention may have, so the cycle characteristics are improved. ​​​This is desirable as it is expected to have a synergistic effect. In addition, productivity can be improved by reducing the number of processes. In this specification and the like, the NASICON type crystal structure is M2(XO4)3 (M: In compounds represented by transition metals (X: S, P, As, Mo, W, etc.), MO6 octahedrons and XO4 refers to a structure in which tetrahedrons are arranged three-dimensionally with their vertices shared.

[0439] [Shapes of exterior body and secondary battery] The exterior body of the secondary battery 400 according to one embodiment of the present invention can be made of various materials and in various shapes. However, it is preferable that the positive electrode, the solid electrolyte layer, and the negative electrode have a function of applying pressure thereto. .

[0440] For example, Figure 26 shows an example of a cell for evaluating materials for all-solid-state batteries.

[0441] FIG. 26A is a cross-sectional view of the test cell. The test cell is made up of a lower member 761 and an upper member 762. 62 and a fixing screw or wing nut 764 that secures them together, and a cap screw 763 By rotating the electrode plate 753, the evaluation material is fixed. An insulator 766 is provided between the lower member 761 and the upper member 762. In addition, an O-ring is provided between the upper member 762 and the holding screw 763 for sealing. 765 is provided.

[0442] The evaluation material is placed on an electrode plate 751, surrounded by an insulating tube 752, and It is pressed by the electrode plate 753. The perspective view is shown in Figure 26B.

[0443] As an example of the evaluation material, a stack of a positive electrode 750a, a solid electrolyte layer 750b, and a negative electrode 750c was used. 26A to 26C, the cross-sectional view is shown in FIG. uses the same sign.

[0444] The electrode plate 751 and the lower member 761 electrically connected to the positive electrode 750a are The electrode plate electrically connected to the negative electrode 750c corresponds to the electrode terminal. The electrode plate 753 and the upper member 762 can be said to correspond to the negative electrode terminal. While applying pressure to the evaluation material via the electrode 751 and the electrode plate 753, It is possible to measure things like:

[0445] In addition, a package with excellent airtightness is used for the exterior body of the secondary battery according to one embodiment of the present invention. For example, a ceramic package or a resin package can be used. In addition, when sealing the exterior body, the outside air is blocked and the device is placed in a sealed environment, for example, in a globe. It is preferable to do this in a box.

[0446] FIG. 27A shows a perspective view of a secondary battery according to one embodiment of the present invention, which has an exterior body and a shape different from those shown in FIG. 26. The secondary battery in FIG. 27A has external electrodes 771 and 772 and is made up of multiple packages. The device is sealed in an exterior body having components.

[0447] An example of a cross section taken along the dashed line in FIG. 27A is shown in FIG. 27B. The laminate having the electrolyte layer 750b and the negative electrode 750c is formed by providing an electrode layer 773a on a flat plate. A package member 770a, a frame-shaped package member 770b, and a flat electrode layer 773b The package member 770c is provided with a sealing member 770b, and the package member 770c is enclosed by the sealing member 770b. The cage members 770a, 770b, and 770c are made of insulating materials, such as resin materials and ceramics. A lock can be used.

[0448] The external electrode 771 is electrically connected to the positive electrode 750a via the electrode layer 773a. The external electrode 772 also functions as an electrode. It is electrically connected to the negative terminal.

[0449] By using the positive electrode active material composite 100z obtained in the above-described embodiment, high energy It is possible to realize an all-solid-state secondary battery with high density and good output characteristics.

[0450] The content of this embodiment mode can be combined with the content of other embodiment modes as appropriate.

[0451] (Embodiment 6) This embodiment is an example different from the cylindrical secondary battery shown in FIG. 19D. An example of applying this to an electric vehicle (EV) is shown.

[0452] The electric vehicle includes first batteries 1301a and 1301b as main driving secondary batteries. 1b and a second battery that supplies power to an inverter 1312 that starts the motor 1304. The second battery 1311 is a cranking battery (starter battery). The second battery 1311 is a high-power, clean battery. The capacity of the second battery 1311 is not so large that it is necessary to have a large capacity. It is smaller than 1301a and 1301b.

[0453] The internal structure of the first battery 1301a is a wound type as shown in FIG. 20A or FIG. 21C. Alternatively, the first barrier may be a laminated type as shown in FIG. 22A or FIG. 22B. The battery 1301a may be the all-solid-state battery of the fifth embodiment. By using the all-solid-state battery of embodiment 5 for 1a, a high capacity can be achieved and safety is improved. This allows for smaller and lighter devices.

[0454] In this embodiment, two first batteries 1301a and 1301b are connected in parallel. However, three or more batteries may be connected in parallel. If sufficient power can be stored in the first battery 1301b, the first battery 1301b may not be necessary. By configuring a battery pack having such a secondary battery, it is possible to extract a large amount of power. The plurality of secondary batteries may be connected in parallel, in series, or in parallel. After being connected, the secondary batteries may be further connected in series. A plurality of secondary batteries is also called a battery pack.

[0455] In addition, in the case of secondary batteries for vehicles, in order to cut off power from multiple secondary batteries, It has a service plug or circuit breaker that can cut off high voltage without using The battery 1301a is provided with a power supply.

[0456] The power of the first batteries 1301a and 1301b is mainly used to rotate the motor 1304. It is used to connect 42V automotive components (electric power) via the DCDC circuit 1306. (power steering) 1307, heater 1308, defogger 1309, etc.) Even when a rear motor 1317 is provided on the rear wheels, the first battery 13 01a is used to rotate the rear motor 1317.

[0457] The second battery 1311 also supplies power to 14V-based in-vehicle components via the DCDC circuit 1310. (Audio 1313, Power Window 1314, Lamps 1315, etc.) Provide.

[0458] The first battery 1301a will be described with reference to FIG. 28A.

[0459] FIG. 28A shows an example in which nine rectangular secondary batteries 1300 are combined into one battery pack 1415. Also, nine square secondary batteries 1300 are connected in series, and one electrode is connected to the insulator. The other electrode is fixed by a fixing part 1414 made of an insulating material. In this embodiment, an example in which the battery is fixed by the fixing parts 1413 and 1414 is shown. The vehicle may be configured to be stored in a storage box (also called a housing). Since it is assumed that vibration or shaking is applied from the fixing parts 1413, 1414 and It is preferable to fix a plurality of secondary batteries in place using a battery housing box or the like. The other electrode is electrically connected to the control circuit section 1320 by a wiring 1421. The electrodes are electrically connected to the control circuit section 1320 by wiring 1422 .

[0460] The control circuit 1320 includes a memory circuit including a transistor using an oxide semiconductor. A charge control circuit having a memory circuit including a transistor using an oxide semiconductor may be used. The road or battery control system is called BTOS (Battery operating system) Battery oxide semiconductor There is a match.

[0461] It is preferable to use a metal oxide that functions as an oxide semiconductor. In-M-Zn oxide (element M is aluminum, gallium, yttrium, copper, barium) sodium, beryllium, boron, titanium, iron, nickel, germanium, zirconium, Molybdenum, lanthanum, cerium, neodymium, hafnium, tantalum, tungsten, or It is preferable to use metal oxides such as one or more selected from the group consisting of magnesium and tungsten. The In-M-Zn oxide that can be used as an oxide is CAAC-OS (C-Axis Al igned Crystal Oxide Semiconductor), CAC-O S(Cloud-Aligned Composite Oxide Semiconductor In addition, the oxide may be an In-Ga oxide, an In-Z The CAAC-OS has multiple crystalline regions, and the multiple crystalline regions may be used as well. The c-axis of the oxide semiconductor is oriented in a specific direction. The thickness direction of the AC-OS film, the normal direction to the surface on which the CAAC-OS film is formed, or the CAAC-O The direction is normal to the surface of the S film. The crystalline region is a region with periodic atomic arrangement. If the atomic arrangement is considered as a lattice arrangement, the crystalline region is also a region where the lattice arrangement is aligned. Furthermore, CAAC-OS has a region where multiple crystalline regions are connected in the ab-plane direction. The region may have distortion. Note that distortion refers to a state where multiple crystalline regions are connected. In the region, the lattice arrangement is changed between a region with a uniform lattice arrangement and another region with a uniform lattice arrangement. In other words, the CAAC-OS has a c-axis orientation and an ab-plane orientation. CAC-OS is an oxide semiconductor that does not have a clear orientation in the direction of crystal orientation. The elements constituting the metal oxide are 0.5 nm or more and 10 nm or less, preferably 1 nm or more. This is a composition of materials unevenly distributed in sizes of 3 nm or less or close to that size. In the metal oxide, one or more metal elements are unevenly distributed, and the region having the metal elements is The size is 0.5 nm or more and 10 nm or less, preferably 1 nm or more and 3 nm or less, or in the vicinity thereof. The state where the colors are mixed in size is also called a mosaic or patch pattern.

[0462] Furthermore, CAC-OS is a material that is separated into a first region and a second region. The first regions are in a shape similar to a cloud, and the first regions are distributed throughout the film (hereinafter also referred to as a cloud shape). ) In other words, the CAC-OS is a mixture of the first area and the second area. It is a composite metal oxide having a structure in which

[0463] Here, the I ratio of the metal elements constituting the CAC-OS in the In-Ga-Zn oxide is The atomic ratios of n, Ga, and Zn are defined as [In], [Ga], and [Zn], respectively. For example, in the CAC-OS of In-Ga-Zn oxide, the first region is the region where [In] is larger than [In] in the composition of the CAC-OS film. The second region is a region where [Ga] is larger than [Ga] in the composition of the CAC-OS film. Or, for example, the first region has [In] higher than the [In] in the second region. In this region, [Ga] is larger than [Ga] in the first region. In addition, the second region has a larger [Ga] than the [Ga] in the first region and a smaller [I [n] is smaller than [In] in the first region.

[0464] Specifically, the first region is mainly composed of indium oxide, indium zinc oxide, etc. The second region is a region containing gallium oxide, gallium zinc oxide, etc. In other words, the first region is called a region in which In is the main component. The second region can be rephrased as a region containing Ga as the main component. It is possible.

[0465] Note that there are cases where a clear boundary between the first region and the second region cannot be observed. .

[0466] For example, in the case of CAC-OS in In-Ga-Zn oxide, energy dispersive X-ray diffraction (EDX) Optical method (EDX:Energy Dispersive X-ray spectrosc) The EDX mapping obtained using the opy revealed a region containing In as the main component (the first region). The structure has a structure in which a first region (a first region) and a region (a second region) mainly composed of Ga are unevenly distributed and mixed. It can be confirmed that this is the case.

[0467] When CAC-OS is used in a transistor, the conductivity due to the first region and the conductivity due to the second region are The insulating properties due to the region act complementary to each other to provide a switching function (On In other words, the CAC-OS and has a conductive function in a part of the material and an insulating function in a part of the material, and By separating the conductive function from the insulating function, Therefore, by using CAC-OS in transistors, This allows for a high on-state current (I on ), high field-effect mobility (μ), and good switching This allows for realizing a switching operation.

[0468] Oxide semiconductors have a variety of structures, each of which has different characteristics. The oxide semiconductors in morphous-like Oxide Semiconductor), CAC-O S, nc-OS(nano crystalline Oxide Semiconductor ctor), and CAAC-OS.

[0469] In addition, the control circuit section 1320 uses an oxide semiconductor so that it can be used in a high-temperature environment. It is preferable to use a transistor. In order to simplify the process, the control circuit section 1 The transistor 320 may be formed using a unipolar transistor. The operating ambient temperature range of the transistor is wider than that of single-crystal silicon transistors, from -40°C to 15°C. 0°C or less, and even if the secondary battery overheats, the change in characteristics is smaller than that of single-crystal Si transistors. The off-state current of a transistor using an oxide semiconductor is below the lower limit of measurement even at 150°C. However, the off-current characteristics of single-crystal Si transistors are highly temperature dependent. At 50°C, the off-current of the single-crystal Si transistor increases and the current on / off ratio becomes large enough. The control circuit unit 1320 can improve safety. The positive electrode active material composite 100z obtained in this embodiment can be combined with a secondary battery using the positive electrode. This provides a synergistic effect on safety.

[0470] The control circuit unit 1320 using a memory circuit including a transistor using an oxide semiconductor is Functions as an automatic control device for secondary batteries to prevent instability such as micro-short circuits Functions that eliminate the causes of instability in secondary batteries include preventing overcharging and overcharging. Current flow prevention, overheat control during charging, cell balancing in battery packs, over-discharge prevention, remaining capacity meter, temperature-dependent Automatic control of charging voltage and current amount according to the degree of deterioration, control of charging current amount according to the degree of deterioration, micro short circuit detection These include normal behavior detection and abnormal prediction of micro-short circuits, among which at least One function is provided by the control circuit section 1320. It is possible.

[0471] Micro-shorts refer to tiny short circuits inside secondary batteries, The positive and negative electrodes of the battery are not short-circuited to the point that they become unable to be charged or discharged, but rather there is a slight short circuit. This refers to the phenomenon where a small amount of short-circuit current flows in a relatively short period of time. Even at this location, large voltage changes can occur, and the abnormal voltage value can affect subsequent estimations. There is a risk of giving

[0472] One of the causes of micro-short circuits is the breakdown of the positive electrode active material due to repeated charge and discharge. The uneven distribution of the current causes localized current concentration in parts of the positive electrode and negative electrode, resulting in the separation Parts of the capacitor may become non-functional, or micro-cracks may occur due to the generation of side reaction products. It is said that a short circuit has occurred.

[0473] In addition to detecting micro-short circuits, the control circuit section 1320 also detects the terminal voltage of the secondary battery. It can also be said that it detects the voltage and manages the charge / discharge state of the secondary battery. Both the output transistor of the charging circuit and the cutoff switch can be turned off almost simultaneously. can.

[0474] FIG. 28B shows an example of a block diagram of the battery pack 1415 shown in FIG. 28A.

[0475] The control circuit section 1320 includes at least a switch for preventing overcharging and a switch for preventing overdischarging. a switch unit 1324 including a switch; and a control circuit 1322 for controlling the switch unit 1324. The control circuit section 1320 includes a voltage measuring section for the first battery 1301a. The upper and lower limits of the secondary battery voltage are set, and the input current from the outside and the The output current of the secondary battery is limited. It is recommended to use the secondary battery within the range of the lower limit voltage and the upper limit voltage. If the voltage is outside the recommended range, the switch 1324 will operate to protect the The control circuit 1320 also controls the switch 1324 to prevent overdischarge. It can also be called a protection circuit because it prevents overcharging and overcharging. When the control circuit 1322 detects this, the switch of the switch unit 1324 is turned off. Furthermore, a PTC element is installed in the charge / discharge path to cut off the current according to the rise in temperature. The control circuit 1320 may be provided with a function to cut off the external terminal 1325 (+I N) and an external terminal 1326 (-IN).

[0476] The switch section 1324 is made up of an n-channel transistor and a p-channel transistor. The switch section 1324 is made of single crystal silicon. The present invention is not limited to switches having Si transistors, but may also include switches using, for example, Ge (germanium), S iGe (silicon germanium), GaAs (gallium arsenide), GaAlAs (gallium Aluminum arsenide), InP (indium phosphide), SiC (silicon carbide), Z nSe (zinc selenide), GaN (gallium nitride), GaO x (Gallium oxide; x is 0 or more The switch section 1324 may be formed by a power transistor having a In addition, memory elements using OS transistors can be mounted on circuits using Si transistors. By stacking, it can be freely arranged, making integration easy. The transistors can be fabricated using the same manufacturing equipment as Si transistors. That is, the switch portion 1324 can be fabricated at low cost by using an OS transistor. The control circuit section 1320 can be stacked and integrated into a single chip. The volume occupied by the circuit section 1320 can be reduced, which allows for miniaturization.

[0477] The first batteries 1301a and 1301b are mainly used to power 42V (high voltage) in-vehicle devices. The second battery 1311 supplies power to the 14V system (low voltage system) in-vehicle equipment. do.

[0478] In this embodiment, both the first battery 1301a and the second battery 1311 have a built-in battery. The second battery 1311 is a lead-acid battery, an all-solid-state battery, or the like. For example, the all-solid-state battery of the fifth embodiment may be By using the all-solid-state battery according to the fifth embodiment as the second battery 1311, a high capacity can be obtained. The amount can be reduced, and the size and weight can be reduced.

[0479] The regenerative energy generated by the rotation of the tire 1316 is transmitted to the motor 1305 via the gear 1305. 304, and the motor controller 1303 and the battery controller 1302 The second battery 1311 is charged from the battery 1311 via the control circuit unit 1321. The controller 1302 charges the first battery 1301a via the control circuit unit 1320. Alternatively, the first battery is supplied from the battery controller 1302 via the control circuit unit 1320. The regenerative energy is charged into the battery 1301b. It is desirable that the batteries 1301a and 1301b be capable of being quickly charged.

[0480] The battery controller 1302 controls the charging voltage of the first batteries 1301a and 1301b. The battery controller 1302 can set the battery voltage, the charging current, etc. Charging conditions can be set according to the charging characteristics of the secondary battery, allowing for rapid charging.

[0481] Although not shown, when connecting to an external charger, the charger's outlet or The charger connection cable is electrically connected to the battery controller 1302. The power supplied from the charger is transferred to the first battery via the battery controller 1302. 1301a and 1301b. In addition, some chargers are equipped with a control circuit. Therefore, the functions of the battery controller 1302 may not be used, but to prevent overcharging, It is preferable to charge the first batteries 1301a and 1301b via the control circuit unit 1320. It is also preferable to use a charger that has a control circuit in the charger outlet or the charger connection cable. The control circuit unit 1320 is an ECU (Electronic Control Unit). The ECU is also called a CAN (Control Unit). CAN is used as an in-vehicle LAN. It is one of the serial communication standards that can be used. The ECU also uses a CPU or GPU.

[0482] External chargers installed at charging stations, etc., can be plugged into 100V or 200V outlets. There are also outlets, 3-phase 200V and 50kW. It can also be charged by receiving power from a charging facility.

[0483] When fast charging, in order to charge in a short time, a secondary battery that can withstand high voltage charging is required. Batteries are desired.

[0484] The secondary battery of the present embodiment described above is also made of the positive electrode active material composite obtained in the above-described embodiment. Furthermore, graphene is used as a conductive material, and the electrode layer is thickened. Even if the loading amount is increased, the capacity decrease is suppressed and high capacity is maintained, which has a synergistic effect that significantly reduces the electric This makes it possible to realize a secondary battery with improved characteristics. This is particularly effective for secondary batteries used in vehicles, and A long driving range without increasing the weight ratio of the secondary battery to the total weight. can provide vehicles with a driving range of over 500km on a single charge.

[0485] In particular, the secondary battery of the present embodiment described above is made of the positive electrode active material composite material described in the above embodiment. By using the body 100z, the operating voltage of the secondary battery can be increased, and the charging voltage can be increased. As a result, the usable capacity can be increased. By using the electrode active material composite 100z as the positive electrode, a secondary battery for vehicles with excellent cycle characteristics can be developed. can be provided.

[0486] Next, an example in which a secondary battery according to one embodiment of the present invention is mounted on a vehicle, typically a transportation vehicle, will be described. and explain.

[0487] In addition, the secondary battery shown in any one of Figs. 19D, 21C, and 28A is mounted on a vehicle. and hybrid vehicles (HV), electric vehicles (EV), or plug-in hybrid vehicles (P This will enable the realization of next-generation clean energy vehicles such as hybrid vehicles (HVs). motorized bicycles including touring bicycles, motorcycles, electric wheelchairs, electric carts, small or large boats Ships, submarines, fixed-wing and rotary-wing aircraft, rockets, satellites, space probes, planets, The secondary battery can also be mounted on transportation vehicles such as star probes and spacecraft. The secondary battery of this embodiment can be a high-capacity secondary battery. is suitable for miniaturization and weight reduction, and can be suitably used in transportation vehicles.

[0488] 29A to 29D, a transportation vehicle is shown as an example of a moving body using one embodiment of the present invention. An automobile 2001 shown in FIG. 29A uses an electric motor as a power source for traveling. Or, an electric vehicle that uses an electric motor and an engine as a power source for running. It is a hybrid vehicle that can be used by selecting the appropriate secondary battery. In this case, the secondary battery shown in the fourth embodiment is installed in one or more locations. The automobile 2001 shown in FIG. 9A has a battery pack 2200. The battery pack includes a plurality of secondary batteries. The battery module is electrically connected to the secondary battery module. It is preferable to have a charging control device that:

[0489] In addition, the automobile 2001 has a secondary battery that is plug-in type and non- It can be charged by receiving power from an external charging facility using a contactless power supply system or the like. When charging, the charging method and connector specifications are specified by CHAdeMO (registered trademark) or The secondary battery can be charged at a charging station provided in a commercial facility. For example, plug-in technology can be used to connect to an external power source. The power storage device mounted on the automobile 2001 can be charged by the power supply from the Power is generated by converting AC power to DC power via a converter such as an AC / DC converter. This can be done.

[0490] 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, the road or exterior wall is equipped with a power transmission device. By incorporating a charging station, charging can be performed not only when the vehicle is stopped but also while the vehicle is moving. Electric power may be transmitted and received between two vehicles using a contactless power supply method. Solar cells may be provided on the exterior of both vehicles to charge the secondary battery when the vehicle is stopped and when the vehicle is running. For such contactless power supply, the electromagnetic induction method or the magnetic resonance method can be used. Cut.

[0491] FIG. 29B shows a large transport vehicle having an electrically controlled motor as an example of a transport vehicle. 2002. The secondary battery module of the transport vehicle 2002 has a nominal voltage of, for example, 3.0 The battery is made up of 48 cells connected in series, with each cell consisting of 4 secondary batteries of 17V or higher and 5.0V or lower. The maximum voltage of the secondary battery constituting the secondary battery module of the battery pack 2201 is 0V. Other than the difference in number, etc., it has the same functions as FIG. 29A, so the explanation will be omitted.

[0492] FIG. 29C shows, as an example, a large transport vehicle 2003 having an electrically controlled motor. The secondary battery module of the transport vehicle 2003 has a nominal voltage of 3.0V or more, for example. The maximum voltage is 600V when more than 100 secondary batteries with a voltage of 0.0V or less are connected in series. By using the negative electrode 570a obtained in the above form as the negative electrode, a high capacity and a high charge / discharge capacity can be obtained. Moreover, the cylindrical secondary battery 616 can be excellent in cycle characteristics. A secondary battery using the positive electrode active material composite 100z described in the embodiment as a positive electrode is used. Therefore, a secondary battery having good rate characteristics and charge / discharge cycle characteristics can be manufactured, and the transportation This can contribute to improving the performance and extending the life of the vehicle 2003. 29A except for the number of secondary batteries constituting the secondary battery module of 02. Since it has the functions, the explanation will be omitted.

[0493] FIG. 29D shows an example aircraft 2004 with a fuel-burning engine. The aircraft 2004 shown in FIG. 29D has wheels for takeoff and landing, making it a type of transport vehicle. In other words, a secondary battery module is constructed by connecting a plurality of secondary batteries. The battery pack 2203 includes a battery and a charging controller.

[0494] The secondary battery module of the aircraft 2004 is, for example, eight 4V secondary batteries connected in series. The maximum voltage is 32 V. The secondary battery that constitutes the secondary battery module of the battery pack 2203 Apart from the difference in the number of items, the functions are the same as those in FIG. 29A, so a description thereof will be omitted.

[0495] The content of this embodiment mode can be combined with the content of other embodiment modes as appropriate.

[0496] (Embodiment 7) In this embodiment, an example in which a secondary battery according to one embodiment of the present invention is mounted in a building is shown in FIG. 0A and FIG. 30B.

[0497] The house in FIG. 30A includes a power storage device 2612 including a secondary battery of one embodiment of the present invention. The solar panel 2610 is provided. The power storage device 2612 is connected to the solar panel 2610 via a wiring. 2611 and the like. The device 2604 may be electrically connected to the solar panel 2610. The power storage device 2612 can be charged. The power stored in the power storage device 2612 can be used as follows: The secondary battery of the vehicle 2603 can be charged via the charging device 2604. The device 2612 is preferably installed in the underfloor space. This allows for more efficient use of the space above the floor. may be installed in

[0498] The power stored in the power storage device 2612 can also be used to supply power to other electronic devices in the home. Therefore, even when power cannot be supplied from the commercial power source due to a power outage or other reason, this invention The power storage device 2612 according to one embodiment of the present invention can be used as an uninterruptible power supply, thereby improving the usability of electronic devices. It becomes possible.

[0499] FIG. 30B illustrates an example of a power storage device according to one embodiment of the present invention. A power storage device 791 according to one embodiment of the present invention is installed in an underfloor space 796 of a building 799. The power storage device 791 may be provided with the control circuit described in Embodiment 6. By using the negative electrode 570a obtained in the above embodiment as a negative electrode, a high capacity and a long charge / discharge capacity can be obtained. The cylindrical secondary battery 616 can have a large capacity and excellent cycle characteristics. In addition, a secondary battery using the positive electrode active material composite 100z obtained in the above-described embodiment as a positive electrode is stored. By using the same in the power storage device 791, the power storage device 791 can have a long life.

[0500] The storage device 791 is provided with a control device 790, which is connected to the storage device 791 by wiring. The distribution board 703, the power storage controller 705 (also called a control device), and the display 706 and a router 709.

[0501] Electric power is sent from a commercial power source 701 to a distribution board 703 via a service line attachment portion 710. In addition, power is supplied to the distribution board 703 from the power storage device 791 and the commercial power source 701. The distribution board 703 distributes the received power to the general loads 707 via an outlet (not shown). and supplies it to the storage load 708.

[0502] The general load 707 is, for example, an electrical appliance such as a television or a personal computer. The power storage load 708 is, for example, an electric appliance such as a microwave oven, a refrigerator, or an air conditioner.

[0503] The power storage controller 705 includes a measurement unit 711, a prediction unit 712, and a planning unit 713. The measurement unit 711 measures the general load 707, the storage battery 708, and the The measuring unit 711 has a function of measuring the amount of power consumed by the system load 708. The power consumption of the device 791 and the power consumption supplied from the commercial power source 701 are measured. The prediction unit 712 may also predict the general load 707 and the power storage load 70 during a day. 8, the general load 707 and the storage load 708 are calculated during the next day based on the amount of power consumed. The planning unit 713 has a function of predicting the amount of power demand consumed by the prediction unit 712. Based on the predicted power demand, the system has a function of planning the charging and discharging of the power storage device 791. .

[0504] The power consumed by the general load 707 and the power storage load 708 measured by the measurement unit 711 is The power can be confirmed by the display 706. Also, the power can be confirmed by the router 709. It can also be checked in electrical equipment such as televisions and personal computers. Furthermore, through the router 709, the data can be transmitted by a mobile electronic terminal such as a smartphone or a tablet. Also, the display 706, the electric device, the portable electronic terminal, The amount of power demand for each time period (or each hour) predicted by the prediction unit 712 can also be confirmed. This can be done.

[0505] The content of this embodiment mode can be combined with the content of other embodiment modes as appropriate.

[0506] (Embodiment 8) In this embodiment, an example in which a power storage device according to one embodiment of the present invention is mounted on a motorcycle or a bicycle will be described. vinegar.

[0507] FIG. 31A illustrates an example of an electric bicycle using the power storage device of one embodiment of the present invention. The power storage device of one embodiment of the present invention can be applied to an electric bicycle 8700 shown in FIG. A power storage device of one embodiment includes, for example, a plurality of storage batteries and a protection circuit.

[0508] The electric bicycle 8700 includes a power storage device 8702. The power storage device 8702 The power storage device 8702 can supply electricity to a motor that operates. FIG. 31B shows the state where the power storage device 8702 is removed from the bicycle. The power storage device of one embodiment of the present invention includes a plurality of built-in storage batteries 8701. The remaining battery charge and other information can be displayed on the display unit 8703. The control circuit 8704 capable of controlling charging or detecting abnormality of the secondary battery, an example of which is shown in the sixth embodiment, The control circuit 8704 is electrically connected to the positive and negative electrodes of the storage battery 8701. In addition, the control circuit 8704 is provided with a small solid secondary battery as shown in FIGS. 27A and 27B. 27A and 27B may be provided in the control circuit 8704. This allows power to be supplied to hold data in the memory circuit of the control circuit 8704 for a long time. The positive electrode active material composite 100z obtained in the above-described embodiment can also be supplied. By combining it with a secondary battery that uses a cathode, a synergistic effect on safety can be obtained. A secondary battery using the positive electrode active material composite 100z obtained in the embodiment as a positive electrode and a control circuit 8 704 can make a significant contribution to eradicating accidents such as fires caused by secondary batteries.

[0509] 31C illustrates an example of a two-wheeled vehicle including a power storage device of one embodiment of the present invention. The scooter 8600 shown in FIG. 1 includes a power storage device 8602, a side mirror 8601, a turn signal light 86 03. The power storage device 8602 can supply electricity to the direction indicator light 8603. In addition, a secondary battery using the positive electrode active material composite 100z obtained in the above-described embodiment as a positive electrode The power storage device 8602 in which a plurality of batteries are stored can have a high capacity and contribute to miniaturization. can.

[0510] In addition, the scooter 8600 shown in FIG. 31C has a storage unit 8604 under the seat and a power storage device 8602. The power storage device 8602 can be stored in a small under-seat storage space 8604. It can be stored in under-seat storage 8604.

[0511] The content of this embodiment mode can be combined with the content of other embodiment modes as appropriate.

[0512] (Embodiment 9) In this embodiment, an example in which a secondary battery according to one embodiment of the present invention is mounted in an electronic device will be described. As an electronic device incorporating a secondary battery, for example, a television device (television or (also called television receivers), computer monitors, digital cameras, digital digital video cameras, digital photo frames, mobile phones (also called mobile phones or mobile phone devices) (c), portable game machines, personal digital assistants, audio playback devices, large game machines such as pachinko machines, etc. Examples of portable information terminals include notebook personal computers and tablet computers. These include terminals, e-book readers, and mobile phones.

[0513] FIG. 32A shows an example of a mobile phone. A mobile phone 2100 has a housing 2101. In addition to the built-in display unit 2102, operation buttons 2103, an external connection port 2104, a speaker The mobile phone 2100 is equipped with a speaker 2105, a microphone 2106, etc. The positive electrode active material composite 100z described in the above embodiment is used as the positive electrode active material composite 100z. By providing the secondary battery 2107 used in the above, it is possible to achieve high capacity, and the size of the housing can be reduced. A configuration that can save space can be realized.

[0514] The mobile phone 2100 is a device that can be used for 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.

[0515] The operation button 2103 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 auto-start, silent mode activation and deactivation, power saving mode activation and deactivation, etc. For example, the operating system built into the mobile phone 2100 can The function of the operation button 2103 can also be freely set using the stem.

[0516] In addition, the mobile phone 2100 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.

[0517] The mobile phone 2100 also has an external connection port 2104, and can be connected to other information terminals via a connector. Data can be exchanged directly via the external connection port 2104. Charging can also be performed wirelessly without going through the external connection port 2104. It may also be done by electricity.

[0518] The mobile phone 2100 preferably has a sensor, such as a fingerprint sensor. sensors, pulse sensors, body temperature sensors, touch sensors, pressure sensors, acceleration sensors , etc. are preferably installed.

[0519] FIG. 32B shows unmanned aerial vehicle 2300 with multiple rotors 2302. 300 is sometimes called a drone. Unmanned aerial vehicle 2300 is an embodiment of the present invention. The unmanned aerial vehicle includes a secondary battery 2301, a camera 2303, and an antenna (not shown). 2300 can be remotely controlled via an antenna. The secondary battery using the electrode active material composite 100z as the positive electrode has a high energy density and is highly safe. Therefore, it can be used safely for a long period of time, and it is suitable for secondary use on the unmanned aerial vehicle 2300. It is suitable as a battery.

[0520] Figure 32C shows an example of a robot. The robot 6400 shown in Figure 32C is a secondary Battery 6409, illuminance sensor 6401, microphone 6402, upper camera 6403, A peaker 6404, a display unit 6405, a lower camera 6406 and an obstacle sensor 6407, It is equipped with a moving mechanism 6408, a computing device, etc.

[0521] The microphone 6402 has the function of detecting the user's voice and environmental sounds. The speaker 6404 has a function of emitting sound. Use the phone 6402 and speaker 6404 to communicate with the user. is possible.

[0522] The display unit 6405 has a function of displaying various information. The display unit 6405 can display information desired by the user. The display unit 6405 may be a detachable information terminal. By placing it in a fixed position on the robot 6400, charging and data transfer can be performed. This makes it possible.

[0523] The upper camera 6403 and the lower camera 6406 capture images of the surroundings of the robot 6400. The obstacle sensor 6407 also detects the obstacles by using the moving mechanism 6408. Robot 6 can detect the presence or absence of obstacles in its path as it moves forward. 400 uses an upper camera 6403, a lower camera 6406, and an obstacle sensor 6407. This allows the robot to recognize its surroundings and move safely.

[0524] The robot 6400 has a secondary battery 6409 according to one embodiment of the present invention and a semiconductor The positive electrode active material composite 100z obtained in the above-described embodiment is provided with a body device or an electronic component. Secondary batteries that use this material in the positive electrode have a high energy density and are highly safe, so they can be used for a long period of time. It can be used safely for a long time and is suitable as a secondary battery 6409 to be installed in a robot 6400. be.

[0525] FIG. 32D shows an example of a cleaning robot. The cleaning robot 6300 is housed in a housing 630 1, a display unit 6302 arranged on the top surface, a plurality of cameras 6303 arranged on the side, and a brush 6 304, an operation button 6305, a secondary battery 6306, various sensors, etc. Although not shown, the cleaning robot 6300 is equipped with tires, a suction nozzle, etc. Bot 6300 moves by itself, detects the dust 6310, and removes it from the suction port on the bottom. can be sucked in.

[0526] For example, the cleaning robot 6300 analyzes the image captured by the camera 6303 and detects the walls, furniture, etc. It can also determine whether there are obstacles such as steps. If an object that is likely to get tangled in the brush 6304 is detected, the rotation of the brush 6304 is stopped. The cleaning robot 6300 has a secondary battery according to one embodiment of the present invention in its internal area. 6306 and a semiconductor device or electronic component. Secondary batteries using the polymer composite 100z as the positive electrode have high energy density and are highly safe. , long-term safe use for a long time, and the secondary battery installed in the cleaning robot 6300 Suitable as 6306.

[0527] FIG. 33A shows an example of a wearable device. The wearable device is In addition, when the user uses the device in his / her daily life or outdoors, the device must be splash-proof. Wired devices with exposed connectors for improved performance, water resistance, or dust resistance There is a demand for wearable devices that can be charged not only by battery but also wirelessly.

[0528] For example, a secondary battery according to one embodiment of the present invention may be applied to a glasses-type device 4000 as shown in FIG. 33A. The eyeglass-type device 4000 includes a frame 4000a and a display unit. A secondary battery is mounted on the temple of the curved frame 4000a. This allows for a lightweight, well-balanced eyeglass-type device that can be used for a long time. The positive electrode active material composite 100z obtained in the above-described embodiment can be set to 000. The secondary battery used in the electrode has high energy density, which allows for space saving due to the miniaturization of the housing. It is possible to realize a configuration in which this is possible.

[0529] In addition, the headset device 4001 may be equipped with a secondary battery according to one embodiment of the present invention. The headset type device 4001 includes at least a microphone unit 4001a and a The flexible pipe 4001b has an earphone section 4001c. A secondary battery can be provided in the earphone unit 4001b or the earphone unit 4001c. A secondary battery using the positive electrode active material composite 100z obtained in the embodiment as a positive electrode has high energy This allows for a configuration that can accommodate space-saving measures that come with a smaller housing. .

[0530] In addition, a secondary battery according to one embodiment of the present invention is installed in a device 4002 that can be directly attached to the body. The device 4002 can be equipped with a secondary battery 40 in a thin housing 4002a. The positive electrode active material composite 100z obtained in the above-described embodiment can be provided with a The secondary battery used for the positive electrode has a high energy density and is suitable for space saving due to the miniaturization of the housing. It is possible to realize a configuration that can respond to such changes.

[0531] In addition, a device 4003 that can be attached to clothing is equipped with a secondary battery according to one embodiment of the present invention. The device 4003 has a thin housing 4003a in which a secondary battery 4003 is disposed. The positive electrode active material composite 100z obtained in the above-described embodiment can be used as a positive electrode active material composite 100z. The secondary battery used has a high energy density and can be used to save space by downsizing the housing. It is possible to realize a configuration in which this is possible.

[0532] In addition, the belt-type device 4006 can be equipped with a secondary battery according to one embodiment of the present invention. The belt-type device 4006 includes a belt part 4006a and a wireless power receiving part 4006b. 006b, and a secondary battery can be mounted in the internal area of ​​the belt portion 4006a. A secondary battery using the positive electrode active material composite 100z obtained in the above-described embodiment as a positive electrode is a high-energy secondary battery. This allows for a high energy density and a configuration that can accommodate space-saving requirements associated with smaller enclosures. can.

[0533] In addition, the secondary battery according to one embodiment of the present invention can be mounted on the wristwatch device 4005. The wristwatch type device 4005 has a display part 4005a and a belt part 4005b. A secondary battery can be provided in the display portion 4005a or the belt portion 4005b. A secondary battery using the positive electrode active material composite 100z obtained in the embodiment as a positive electrode has high energy This allows for a configuration that can accommodate space-saving measures that come with a smaller housing. .

[0534] The display unit 4005a displays not only the time but also various information such as incoming emails and phone calls. It can be shown.

[0535] The wristwatch type device 4005 is a wearable device that can be worn directly on the wrist. Since the device is a mobile device, it may be equipped with sensors to measure the user's pulse, blood pressure, etc. It allows you to accumulate data on your intake and health, and manage your health.

[0536] FIG. 33B shows a perspective view of the wristwatch type device 4005 removed from the wrist.

[0537] A side view is shown in Fig. 33C. In Fig. 33C, a secondary battery 913 is built in the internal area. The secondary battery 913 is the secondary battery described in the fourth embodiment. The pond 913 is provided at a position overlapping the display section 4005a, and is high density and large capacity. It is small and lightweight.

[0538] The wristwatch type device 4005 is required to be small and lightweight. The positive electrode active material composite 100z obtained in the above-described embodiment is used as the positive electrode of the secondary battery 913. This allows the secondary battery 913 to have a high energy density and be small in size.

[0539] FIG. 33D shows an example of a wireless earphone. Here, a pair of main body 4100a and Although the wireless earphones shown in the figure have a pair of earphones and a main body 4100b, they do not necessarily have to be a pair. stomach.

[0540] The main bodies 4100a and 4100b include a driver unit 4101, an antenna 4102, It has a secondary battery 4103. It may have a display unit 4104. In addition, it may have a circuit such as a wireless IC. It is preferable that the device has a circuit board, a charging terminal, etc. It may also have a microphone. .

[0541] The case 4110 has a secondary battery 4111. Also, the case 4110 contains circuits for a wireless IC, a charge control IC, etc. It is preferable that the device has a board on which a circuit is mounted and a charging terminal. It also has a display, buttons, etc. That's fine.

[0542] The main units 4100a and 4100b communicate wirelessly with other electronic devices such as smartphones. This allows the main body 4100a and the main body 4100b to receive sound data and the like sent from other electronic devices. The main units 4100a and 4100b can also play back the recorded audio. If so, the sound picked up by the microphone is sent to another electronic device, and after processing by that electronic device, The sound data can be sent back to the main units 4100a and 4100b and played back. It can also be used as a translation device, for example.

[0543] In addition, the secondary battery 4111 in the case 4110 is connected to the secondary battery in the main body 4100a. The secondary battery 4111 and the secondary battery 4103 can be charged. The coin-type secondary battery, cylindrical secondary battery, etc., of the previous embodiment can be used. The secondary battery obtained in this embodiment has a high energy density, and the secondary battery 4103 and the secondary battery By using Ike 4111, it is possible to save space due to the miniaturization of wireless earphones. A configuration like this can be realized.

[0544] This embodiment mode can be implemented in appropriate combination with other embodiment modes. [Example]

[0545] In this example, a negative electrode according to one embodiment of the present invention was fabricated and evaluated.

[0546] <Preparation of negative electrode> The negative electrode was fabricated according to the flow shown in Figure 7. ALDRI particles were used as the silicon-containing particles. Nano silicon particles manufactured by CH were used. Graphite particles were manufactured by Linyi Gelon. New Battery Materials' artificial graphite particles MCMB-G10 are used. Graphene oxide was used as the graphene compound. Polyimide was manufactured by Toray Industries, Inc. A polyimide precursor manufactured by KOGYO CO., LTD. was used.

[0547] An electrode GS1 was fabricated as a negative electrode. The weight ratio of the materials prepared in S87 was: artificial graphite particles: nanosilicon particles: graphite oxide. The weight ratio of the graphite particles to the polyimide precursor was 82.8:9.2:5:3. The weight ratio of silicon to nanosilicon particles is 9:1.

[0548] Nanosilicon particles and a solvent were prepared and mixed (steps S61 and S62 in FIG. 7). S63). NMP was used as the solvent. Mixing was carried out using a planetary centrifugal mixer (Thinner Mixer, TH The mixture was mixed at 2000 rpm for 3 minutes using a mixer (manufactured by INKY Co., Ltd.), and then collected to obtain mixture E-1 (Figure 1). 7 steps S64 and S65).

[0549] Next, artificial graphite particles were prepared and mixed with the mixture E-1 (steps S72 and S73 in FIG. 7). 3) Mixing was carried out using a planetary centrifugal mixer at 2000 rpm for 3 minutes, and the mixture was collected and named Mixture E. -2 was obtained (steps S74 and S75 in FIG. 7).

[0550] Next, the mixture E-2 and the graphene compound were repeatedly mixed while adding the solvent. Graphene oxide was prepared as a graphene compound and mixed using a planetary mixer. The mixture was mixed at 2000 rpm for 3 minutes and then collected (steps S80, S81, and S82 in FIG. 7). The recovered mixture was then kneaded, NMP was added as needed, and the mixture was mixed using a planetary centrifugal mixer. The mixture was mixed at 2000 rpm for 3 minutes and then collected (steps S83, S84, and S8 in FIG. 7). 5) Steps S83 to S85 were repeated five times to obtain mixture E-3. (Step S86 in Figure 7).

[0551] Next, the mixture E-3 was mixed with a polyimide precursor (step S88 in FIG. 7). The mixture was mixed using a planetary centrifugal mixer at 2000 rpm for 3 minutes. The mixture is then added to adjust the viscosity (step S89 in FIG. 7), and further mixed. (Twice in a planetary centrifugal mixer at 2000 rpm for 3 minutes), and the mixture was collected as a slurry. E-4 was obtained (steps S90, S91, and S92 in FIG. 7).

[0552] Next, a current collector was prepared and coated with the mixture E-4 (steps S93 and S94 in FIG. 7). ) A copper foil with a thickness of 18 μm was prepared as a current collector, and Mixture E-3 was applied to the copper foil with a gap thickness of 100 μm. Mixture E-4 was applied to copper foil using a 10 μm doctor blade.

[0553] Next, the copper foil coated with the mixture E-4 was subjected to a first heating at 50°C for 1 hour (Fig. 7 Then, the second heating is performed at 400° C. for 5 hours under reduced pressure (step S95 in FIG. 7). The electrode was obtained by Step S96. Heating reduced the graphene oxide, decreasing the amount of oxygen. do.

[0554] <sem> The surface of the prepared electrode was observed using an SEM. 800 was used. The accelerating voltage was 5 kV.

[0555] 34A and 34B are observation images of the surface of electrode GS1. The silicon particles show relatively bright contrast.

[0556] Figure 34B is an enlarged image of the surface of electrode GS1. Particles of approximately 5 μm to 15 μm in size On the surface of a graphite particle of about 50 nm to 250 nm, multiple nanosilicon particles exist. These nanosilicon particles are covered with graphene (reduced graphene oxide). In other words, the electrode GS1 is composed of nanosilicon particles and graphene. It can also be said that the mixed layer of and covers the graphite particles.

[0557] <Coin cell fabrication> Next, using the electrode GS1, a CR2032 type (diameter 20 mm, height 3.2 mm) Five coin cells (also called coin-type secondary batteries) were fabricated (GS-C1, GS-C 2, GS-C3, GS-C4, GS-C5).

[0558] Lithium metal was used as the counter electrode, and lithium hexafluorophosphate (LiPF 6) Ethylene carbonate (EC) and diethyl carbonate (DEC) are EC:DE Mixed at a concentration of 1 mol / L compared to a mixture at C=3:7 (volume ratio) was used.

[0559] The separator used was a polypropylene separator with a thickness of 25 μm.

[0560] The positive electrode can and the negative electrode can were made of stainless steel (SUS).

[0561] <Charge / discharge characteristics> The charge-discharge characteristics were evaluated using five coin cells. In the coin cell, electrode GS1 acts as a positive electrode and emits During charging, lithium is absorbed into the electrode, and during charging, lithium is released from the electrode.

[0562] For the five coin cells produced, the first charge / discharge was performed under the following discharge conditions (lithium absorption). ) The conditions were constant current discharge (0.1C, lower limit voltage 0.01V) followed by constant voltage discharge (lower limit current density 0 0.01C), and the charging conditions (lithium release) were constant current charging (0.1C, upper limit voltage 1V). Next, for the second charge / discharge, the discharge conditions (lithium absorption) were constant current discharge (0. 2C, lower limit voltage 0.01V) followed by constant voltage discharge (lower limit current density 0.02C), charging conditions (Lithium release) was performed at a constant current (0.2C, upper voltage 1V). The charge-discharge cycle test was carried out at 5°C. Next, the third and subsequent charge-discharge cycle tests were carried out under the discharge conditions (lithium absorption). The conditions were constant current discharge (0.2C, lower limit voltage 0.01V) followed by constant voltage discharge (lower limit current density 0. The charging conditions (lithium discharge) were constant current charging (0.2C, upper limit voltage 1V). ,Based on the second charging capacity, no capacity limit, 90% capacity limit, 80% capacity limit, capacity limit The discharge and charge were performed under different conditions, with the capacity limit set to 70% and the capacity limit set to 60%. was carried out at 25°C.

[0563] Table 2 shows the maximum charge capacity and 30-cycle retention rate of coin cells GS-C1 to GS-C5. The results of the charge-discharge cycle test are shown in Figures 35A and 35B.

[0564] [Table 2]

[0565] As shown in Figures 35A and 35B, the capacity of the coin cell (GS-C2) was limited. In the case of GS-C5, the charge capacity degradation is suppressed in the charge-discharge cycle test. It was confirmed that the capacity limit was set to 60%, 70, and 80% for GS-C2 to GS-C5. , 90%, and GS No significant differences were observed between GS-C2 and GS-C5.

[0566] Next, regarding the results of this experiment, in embodiment 1, negative electrode calculation 1 and negative electrode calculation 2 We will consider this together with the contents presented above.

[0567] Based on the calculation 1 of the negative electrode in the first embodiment, The alloying ratio of silicon to lithium (Li / Si) was calculated using Equation 1. The calculation results are shown in Table 3.

[0568]

number

[0569] [Table 3]

[0570] As shown in Table 3, GS-C1, which had poor charge-discharge cycle characteristics, had a low Li / Si On the other hand, in GS-C2, which has excellent charge-discharge cycle characteristics, the Li / S i is 1.75, and the structure shown in FIG. 6B (crystal structure at Li / Si=1.714) The structure shown in Figure 6B has Si-Si bonds. Therefore, GS-C2 to GS-C5 can be formed as long as the Si-Si bond is not lost. It is thought that charging and discharging were performed during this time, and the reason for the good charge-discharge cycle efficiency was I can think. [Example]

[0571] In this example, a carp electrode was prepared using the electrode GS1 shown in Example 1 and an ionic liquid. Cancellation was evaluated.

[0572] <Coin cell fabrication> Next, using the electrode GS1, a CR2032 type (diameter 20 mm, height 3.2 mm) A coin cell (also called a coin-type secondary battery) was fabricated (GS-C6).

[0573] The counter electrode was lithium metal, and the electrolyte was LiF at a concentration of 2.15 mol / L. EMI-FSI with SI was used.

[0574] The separator is made of polypropylene with a thickness of 25 μm and glass with a thickness of 260 μm. A separator made of carbon fiber was laminated and used.

[0575] The positive electrode can and the negative electrode can were made of stainless steel (SUS).

[0576] <Charge / discharge characteristics> The charge-discharge characteristics were evaluated using the coin cell GS-C6. Because lithium metal is used, electrode GS1 acts as a positive electrode in the coin cell. During discharge, lithium is absorbed into the electrode, and during charge, lithium is released from the electrode. .

[0577] For the coin cell GS-C6 produced, the first charge / discharge was performed under the following discharge conditions (lithium The conditions for absorption are constant current discharge (0.1C, lower limit voltage 0.01V) followed by constant voltage discharge (lower limit current density The charging conditions (lithium discharge) were constant current charging (0.1C, upper limit voltage 1V ) Next, for the second charge / discharge, the discharge conditions (lithium absorption) were constant current discharge ( After constant voltage discharge (0.2C, lower limit voltage 0.01V), charge The conditions (lithium release) were constant current charging (0.2C, upper limit voltage 1V). The discharge conditions (lithium absorption) of the charge-discharge cycle test were constant current discharge (0.2C, After the lower limit voltage of 0.01V, the battery was discharged at a constant voltage (lower limit current density 0.02C). The battery is charged at a constant current (0.2C, upper limit voltage 1V) and the capacity is controlled based on the second charge capacity. The discharge and charge were performed at 25°C.

[0578] The results of the charge / discharge cycle test for GS-C6 are shown below, along with the results for GS-C2 and GS-C3. The maximum charge capacity was 468 mAh / g, and the retention rate at 30 cycles was 1.0%. The result was 99.99%, which was an extremely excellent characteristic. The calculation result is Li / Si=1.40. The curves of the third discharge (first discharge under capacity-limited conditions) for GS-C3 and GS-C6 are shown. 37B is an enlarged view of a portion of FIG. 37A.

[0579] As shown in Figures 36A and 36B, GS-C6 has excellent charge-discharge cycle characteristics. In the first embodiment, the relationship between the Li / Si ratio and the charge / discharge cycle characteristics is shown. The Li / Si value of C6 is 1.40, which is the same as the Li / Si value of GS-C2 and the Li / Si value of GS-C3. Although the value is between and , in Figure 36B, the charge-discharge cycle degradation is 99. As shown in Figure 37B, GS-C6 showed a remarkable result of 99%. Even at the end of discharge (at the end of Li absorption), the potential is 0.05 V or higher, and Li deposition and It is thought that this may be due to the suppression of reductive decomposition of the electrolyte. A secondary battery having a negative electrode and an ionic liquid was used under a capacity-limited condition. This resulted in a remarkable improvement in characteristics that could not have been easily predicted. [Explanation of symbols]

[0580] 560a: negative electrode characteristic curve, 560b: positive electrode characteristic curve, 570a: negative electrode, 570b: positive electrode Electrode, 571a: Negative electrode current collector, 571b: Positive electrode current collector, 572a: Negative electrode active material layer, 572b : Positive electrode active material layer, 576: Electrolyte, 581: First active material, 582: Second active material, 58 3: Graphene compounds< / sem> < / xps> < / xrd>

Claims

1. A lithium ion secondary battery having a positive electrode, a negative electrode, an electrolyte, and a separator, the negative electrode includes a first negative electrode active material containing silicon particles, a second negative electrode active material containing graphite having a particle size larger than that of the silicon particles, and a graphene compound; the silicon particles are in contact with the graphite, and the graphene compound is in surface contact with the first negative electrode active material and the second negative electrode active material; In the first negative electrode active material, at least a portion of the surface of the silicon particle is terminated with a hydroxy group, The graphene compound has a pore with 9 or more ring members, the graphene compound has a plurality of carbon atoms that form the pores, one or more of the carbon atoms is terminated with a fluorine atom; Lithium-ion secondary battery.

2. In claim 1, the negative electrode has a negative electrode current collector, The negative electrode current collector contains copper. Lithium-ion secondary battery.

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