Lithium ion secondary battery

Abstract

To provide a secondary battery with high capacity and less deterioration, or a novel power storage device.SOLUTION: A secondary battery includes a positive electrode and a negative electrode. The negative electrode includes a first active material, a second active material, and a graphene compound. At least a part of a surface of the first active material includes a region that is covered with a second active material. At least a part of a surface of the second active material and a surface of the first active material includes a region that is covered with the graphene compound. The first active material contains graphite. The second active material contains silicon. The capacity of the positive electrode is 50% or more and less than 100% of the capacity of the negative electrode.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] Relates to an electrode and a method for manufacturing the same. Or, relates to an active material included in the electrode and a method for manufacturing the same. Or, relates to a secondary battery and a method for manufacturing the same. Or, relates to a moving body including a vehicle having the secondary battery, and a portable information terminal, an electronic device, etc. Includes. Relates to a portable information terminal, an electronic device, etc.

[0002] One aspect of the present invention relates to an object, a method, or a manufacturing method. Or, the present invention relates to a process, a machine, a manufacture, or a composition of matter. Relates to a semiconductor device, a display device, a light-emitting device, a power storage device, a lighting device, an electronic device, or a manufacturing method thereof. One aspect of the present invention relates to a semiconductor device, a display device, a light-emitting device, a power storage device, a lighting device, an electronic device, or a manufacturing method thereof. Relates to a semiconductor device, a display device, a light-emitting device, a power storage device, a lighting device, an electronic device, or a manufacturing method thereof.

[0003] In this specification, the electronic device refers to all devices having a power storage device. An electro-optical device having a power storage device, an information terminal device having a power storage device, etc. are all electronic devices. Relates to a semiconductor device, a display device, a light-emitting device, a power storage device, a lighting device, an electronic device, or a manufacturing method thereof.

[0004] In this specification, the power storage device refers to an element and a device having a power storage function in general. For example, it includes a power storage device (also referred to as a secondary battery) such as a lithium-ion secondary battery, a lithium-ion capacitor, and an electric double layer capacitor. Relates to a semiconductor device, a display device, a light-emitting device, a power storage device, a lighting device, an electronic device, or a manufacturing method thereof. Relates to a semiconductor device, a display device, a light-emitting device, a power storage device, a lighting device, an electronic device, or a manufacturing method thereof.

Background Art

[0005] In recent years, various power storage devices such as lithium-ion secondary batteries, lithium-ion capacitors, and air batteries have been actively developed. In particular, lithium-ion secondary batteries with high output and high energy density are used in portable information terminals such as mobile phones, smartphones, or notebook computers, portable music players, digital cameras, medical devices, or hybrid vehicles (HV), electric Relates to a semiconductor device, a display device, a light-emitting device, a power storage device, a lighting device, an electronic device, or a manufacturing method thereof. Relates to a semiconductor device, a display device, a light-emitting device, a power storage device, a lighting device, an electronic device, or a manufacturing method thereof. Relates to a semiconductor device, a display device, a light-emitting device, a power storage device, a lighting device, an electronic device, or a manufacturing method thereof. Next-generation clean energy vehicles such as electric vehicles (EVs) or plug-in hybrid vehicles (PHVs), etc., are rapidly increasing in demand along with the development of the semiconductor industry and are essential in modern information societies as an energy source that can be repeatedly charged. With the development of the semiconductor industry, the demand for next-generation clean energy vehicles such as electric vehicles (EVs), plug-in hybrid vehicles (PHVs), etc., is rapidly expanding and has become indispensable in modern information societies as an energy source that can be repeatedly charged. As an energy source that can be repeatedly charged, it has become indispensable in modern information societies.

Prior Art Documents

Patent Documents

[0006]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0007] Secondary batteries used in mobile bodies such as electric vehicles and hybrid vehicles need to have a higher capacity to increase the driving range. Therefore, it is necessary to increase the capacity.

[0008] In addition, in portable terminals and the like, the power consumption is increasing with the multifunctionalization. Also, secondary batteries used in portable terminals and the like are required to be miniaturized and lightweight. Therefore, there is also a demand for higher capacity in secondary batteries used in portable terminals. In addition, in portable terminals and the like, the power consumption is increasing with the multifunctionalization. Also, secondary batteries used in portable terminals and the like are required to be miniaturized and lightweight. Therefore, there is also a demand for higher capacity in secondary batteries used in portable terminals. Therefore, there is also a demand for higher capacity in secondary batteries used in portable terminals.

[0009] In addition to its stability, it is important for a secondary battery to have a high capacity. Alloy-based materials such as silicon-based materials have a high capacity and are promising as active materials for secondary batteries. However, alloy-based materials with a high charge-discharge capacity have problems such as pulverization and shedding of the active material due to volume changes during charge and discharge, and sufficient cycle characteristics have not been obtained. However, alloy-based materials with a high charge-discharge capacity have problems such as pulverization and shedding of the active material due to volume changes during charge and discharge, and sufficient cycle characteristics have not been obtained. Therefore, problems such as pulverization and shedding of the active material occur, and sufficient cycle characteristics have not been obtained.

[0010] To improve the problems of alloy-based materials as described above, an alloy-based material and graphite or a carbonaceous material Composite with materials is under consideration. In Patent Document 1, a composite material is described in which a coating layer made of carbon is formed on the surface of a porous particle nucleus formed by combining silicon-containing particles and carbon-containing particles. In Patent Document 2, composite particles containing silicon (Si), lithium fluoride (LiF), and a carbon material are described. However, in any of the above documents, the problems such as pulverization and shedding of the active material accompanying the expansion of the alloy-based material during charge and discharge have not been fully solved.

[0011] The electrode of a secondary battery is composed of materials such as an active material, a conductive material, and a binder, for example. The higher the proportion of the material contributing to the charge and discharge capacity, such as the active material, the higher the capacity of the secondary battery can be increased. By having a conductive material in the electrode, the conductivity of the electrode can be increased and excellent output characteristics can be obtained. Also, during charge and discharge of the secondary battery, the active material repeatedly expands and contracts, and as a result, in the electrode, the collapse of the active material, the interruption of the conductive path, etc. may occur. In such a case, by having a conductive material and a binder in the electrode, the collapse of the active material and the interruption of the conductive path can be suppressed. On the other hand, by using a conductive material and a binder, the proportion of the active material decreases, and thus the capacity of the secondary battery may decrease.

[0012] One aspect of the present invention aims to provide an electrode having excellent characteristics. Or, one aspect of the present invention aims to provide an active material having excellent characteristics. Or, one aspect of the present invention aims to provide a novel electrode.

[0013] Or, one aspect of the present invention aims to provide a mechanically strong negative electrode. Or , one aspect of the present invention aims to provide a mechanically robust positive electrode. Or, one aspect of the present invention aims to provide a negative electrode with high capacity. Or, one aspect of the present invention is to provide a positive electrode with high capacity. Or, one aspect of the present invention is to provide a negative electrode with little degradation. Or, one aspect of the present invention is to provide a positive electrode with little degradation.

[0014] Or, one aspect of the present invention aims to provide a secondary battery with little degradation. Also one aspect of the present invention aims to provide a highly safe secondary battery. Or, one aspect of the present invention aims to provide a secondary battery with high energy density. Or, one aspect of the present invention aims to provide a novel secondary battery.

[0015] Note that the description of these problems does not prevent the existence of other problems. Note that one aspect of the present invention is not required to solve all of these problems. Note that it is possible to extract other problems from the descriptions in the specification, drawings, and claims.

Means for Solving the Problems

[0016] One aspect of the present invention has a positive electrode and a negative electrode. The negative electrode has a first active material, a second active material and a graphene compound. At least a part of the surface of the first active material has a region covered by the second active material. The surface of the second active material and at least a part of the surface of the first active material have regions covered by the graphene compound. The first active material has graphite, and the second active material has silicon. The capacity of the positive electrode is 50% or more and less than 100% of the capacity of the negative electrode . It is a secondary battery.

[0017] Also, one aspect of the present invention has a positive electrode and a negative electrode. The negative electrode has a first active material, a second active material, and a graphene compound. At least a part of the surface of the first active material has a region covered by the second active material. The surface of the second active material and at least a part of the surface of the first active material have a region covered by the graphene compound. The first active material has graphite, and the second active material has silicon. In a fully charged state, the second active material has Si-Si bonds, and it is a secondary battery.

[0018] Also, one aspect of the present invention has a positive electrode, a negative electrode, and an electrolyte. The negative electrode has a first active material a second active material, and a graphene compound. At least a part of the surface of the first active material has a region covered by the second active material. The surface of the second active material and at least a part of the surface of the first active material have a region covered by the graphene compound. The first active material has graphite, and the second active material has silicon. The capacity of the positive electrode is 50% or more and less than 100% of the capacity of the negative electrode, and the electrolyte has an ionic liquid, and it is a secondary battery.

[0019] Also, one aspect of the present invention has a positive electrode, a negative electrode, and an electrolyte. The negative electrode has a first active material a second active material, and a graphene compound. At least a part of the surface of the first active material has a region covered by the second active material. The surface of the second active material and at least a part of the surface of the first active material have a region covered by the graphene compound. The first active material has graphite, and the second active material has silicon. In a fully charged state, the second active material has Si- Si bonds, and the electrolyte has an ionic liquid, and it is a secondary battery.

[0020] ​​​​​ In the secondary battery according to any one of the above, it is desirable that the ionic liquid has LiFSI and EMI-FSI at 2 mol / L or more.

[0021] In the secondary battery according to any one of the above, the positive electrode has lithium cobaltate containing magnesium, fluorine, aluminum, and nickel, and in the lithium cobaltate, it is desirable that the surface layer portion has a region where the concentration of any one or more selected from magnesium, fluorine, and aluminum is maximized.

[0022] In the secondary battery according to any one of the above, it is desirable that the first active material has graphite with a particle diameter of 5 μm or more, and the second active material has silicon with a particle diameter of 250 nm or less.

[0023] One aspect of the present invention is a vehicle having the secondary battery according to any one of the above.

[0024] One aspect of the present invention is a power storage system having the secondary battery according to any one of the above.

[0025] One aspect of the present invention is an electronic device having the secondary battery according to any one of the above.

Advantages of the Invention

[0026] According to one aspect of the present invention, an active material having excellent characteristics can be provided. In addition, an electrode having excellent characteristics can be provided. Further, according to one aspect of the present invention, a novel electrode can be provided.

[0027] In addition, according to one aspect of the present invention, a mechanically strong negative electrode can be provided. According to one aspect of the invention, a mechanically robust positive electrode can be provided. Also, according to one aspect of the present invention, a negative electrode with high capacity can be provided. Also, according to one aspect of the present invention, a positive electrode with high capacity can be provided. Also, according to one aspect of the present invention, a negative electrode with less deterioration can be provided. Also, according to one aspect of the present invention, a positive electrode with less deterioration can be provided. Also, according to one aspect of the present invention, a secondary battery with less deterioration can be provided. Also, according to one aspect of the present invention, a highly safe secondary battery can be provided. Also, according to one aspect of the present invention, a secondary battery with high energy density can be provided. Also, according to one aspect of the present invention, a novel secondary battery can be provided. It should be noted that the description of these effects does not prevent the existence of other effects. It should be noted that one aspect of the present invention does not necessarily have all of these effects. It should be noted that other effects will be obvious from the description in the specification, drawings, claims, etc., and it is possible to extract these other effects from the description in the specification, drawings, claims, etc.

[0028]

[0029]

Brief Description of the Drawings

[0030]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Figure 8

Figure 9

Figure 10

Figure 11

Figure 12

Figure 13

Figure 14

Figure 15

Figure 16

Figure 17

Figure 18

Figure 19

Figure 20

Figure 21

Figure 22

Figure 23

Figure 24

Figure 25

Figure 26

Figure 27

Figure 28

Figure 29

Figure 30

Figure 31

Figure 32

Figure 33

Figure 34

Figure 35

Figure 36

Figure 37

DETAILED DESCRIPTION OF THE INVENTION

[0031] Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. However, the present invention is not limited to the following description, and it will be easily understood by those skilled in the art that its form and details can be variously changed. Also, the present invention is not construed as being limited to the description of the embodiments shown below.

[0032] Also, in the drawings, the size, layer thickness, or area may be exaggerated for clarity purposes. Therefore, it is not necessarily limited to that scale.

[0033] Also, in this specification and the like, ordinal numbers such as first, second, etc. are used for convenience and do not indicate the process order or lamination order. Therefore, for example, "first" can be appropriately replaced with "second" or "third" etc. for explanation. Also, the ordinal numbers described in this specification and the like may not match the ordinal numbers used to identify an aspect of the present invention.

[0034] ​In addition, in this specification and the like, the particles are not limited to referring only to spherical shapes (circular cross-sectional shapes), and the cross-sectional shapes of the individual particles may be elliptical, rectangular, trapezoidal, triangular, rounded quadrilateral, asymmetric shapes, etc., and furthermore, the individual particles may be amorphous.

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

[0036] [Configuration example of secondary battery] Hereinafter, a secondary battery having a positive electrode, a negative electrode, and an electrolyte will be described.

[0037] FIG. 1A is a schematic cross-sectional view showing the inside of a secondary battery according to one aspect of the present invention. The negative electrode 570a, positive electrode 570b, and electrolyte 576 shown in FIG. 1A can be applied to a coin-type secondary battery, a cylindrical secondary battery, a laminate-type secondary battery, etc. shown in the embodiments described later. The negative electrode 57 0a includes at least a negative electrode current collector 571a and a negative electrode active material layer 5 72a 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 active material layer 572b formed in contact with the positive electrode current collector 571b . FIG. 1B is an enlarged view of the region surrounded by the dashed line C in FIG. 1A. FIG. 1C is a diagram for explaining the capacity ratio of the negative electrode 570a and the positive electrode 570b in the region surrounded by the dashed lines A and B in FIG. 1A. The secondary battery may have a separator between the negative electrode 570a and the positive electrode 570b.

[0038] [Capacity ratio of negative electrode and positive electrode] The negative electrode characteristic curve 560a and the positive electrode characteristic curve 560b shown in FIGS. 1C, 2A, 2B, and 2C face each other in the region surrounded by the dashed lines A and B in FIG. 1A and are the same as each other . 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 13 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 0.01 V 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 charging (0.2C, upper limit voltage 1V). Also, the positive electrode characteristic curve 560 in FIG. 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 defined in JIS C8711 (2013). This refers to the state of charge at which a certain amount of charge can be 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 taken as 100%. For example, as shown in FIG. 2A, the capacity of negative electrode 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%. It is.

[0041] Next, in the case where 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 shows that the total capacity is greater than the capacity that the positive electrode 570b can charge and discharge. In FIG. 1C, the capacitance C1 of the negative electrode 570a is larger than the capacitance C2 of the positive electrode 570b. It becomes.

[0042] Thus, when the capacity ratio is lower than 100%, an excess capacity is generated in the capacity C1 of the negative electrode 570a, but there is an advantage that unintended lithium ion precipitation in the negative electrode 570a is easily suppressed. In addition, in the secondary battery having the negative electrode 570a according to one aspect of the present invention described later, preferably when the capacity ratio is 50% or more and less than 100%, more preferably 70% or more and less than 90%, a secondary battery having a high charge and discharge capacity and good charge and discharge cycle characteristics can be obtained. Next, the voltage of the secondary battery will be described. The voltage of the secondary battery can be considered as the difference between the positive electrode potential and the negative electrode potential. For example, the voltage of the secondary battery when the capacity ratio of the negative electrode 570a and the positive electrode 570b is 100% is shown as ΔVa in FIG. 2A. In addition, the case where the capacity ratio is lower than 100% is shown as ΔVb in FIG. 2B.

[0043] As shown in FIG. 2B, when the capacity ratio is lower than 100%, since the utilization potential range of the negative electrode 570a is used in a high region, the voltage of the secondary battery decreases.

[0044] Next, FIG. 2C shows an example in which the secondary battery voltage does not decrease even when the capacity ratio of the negative electrode 570a and the positive electrode 570b is lower than 100%. Here, it is shown that ΔVa and ΔVc shown in FIG. 2C have the same voltage value. In FIG. 2B, the utilization potential range of the positive electrode 570b is the same as the utilization potential range of the positive electrode 570b in FIG. 2A, and the secondary battery voltage ΔVb in this case is smaller than ΔVa as described above. Here, as shown in FIG. 2C, when the utilization potential range of the positive electrode 570b is expanded to a high potential, the secondary battery voltage ΔVc becomes as high as ΔVa. ​​​​​​​​​

[0045] As shown in FIG. 2C, even in a case where the capacity ratio of the negative electrode 570a to the positive electrode 570b is lower than 100%, it is possible to obtain a secondary battery in which the voltage does not decrease. In this case, since the positive electrode 57 0b is exposed to a relatively high potential, the positive electrode 570b needs to have high resistance to charge and discharge at a high potential. The positive electrode active material 100 shown in one aspect of the present invention is suitable as the active material included in the positive electrode 570b because it can have a stable crystal structure in a charged state at a high potential. Details of the positive electrode active material 100 will be described later.

[0046] [Negative Electrode] FIG. 1B is an enlarged view of a region surrounded by a dashed line C in FIG. 1A. As shown in FIG. 1B, the negative electrode active material layer 572a includes a first active material 581, a second active material 582, a graphene compound 583 as a material having a sheet-like shape, and an electrolyte 576. FIG. 3A is a schematic diagram showing a state in which the graphene compound 583 contacts the first active material 581 so as to cover, wrap, or surround the second active material 582 located on the surface of the first active material 581. The graphene compound 583 included in the negative electrode 570a preferably functions as a conductive material, for example. In one aspect of the present invention, since the conductive material can be wrapped around the active material by hydrogen bonds, an electrode having high conductivity can be realized.

[0047] Various materials can be used as the first active material 581 and the second active material 582. As the first active material 581 and the second active material 582, particles in a surface layer portion which are particles of one aspect of the present invention, particles having a functional group containing oxygen or fluorine, or a surface having a functional group containing oxygen or ​​​​​​​​​​​When using particles having a region terminated by fluorine atoms, the affinity between the first active material 581 and the second active material 582 and the graphene compound 583 is improved, and as shown in FIGS. 1B and 3A, the graphene compound 583 can be positioned on the surface of the first active material 581 to cover, wrap, or adhere to the second active material 582 in contact with the first active material 581. Since the graphene compound 583 can adhere to the first active material 581 and the second active material 582, an electrode with high conductivity can be realized. The state of adhering can also be described as being in close contact rather than in point contact. It can also be described as being in contact along the particle surface. It can also be described as being in surface contact with a plurality of particles. Materials that can be used as the first active material 581 and the second active material 582 will be described later.

[0048] Regarding the case of using an active material with a large volume change during charge and discharge as the second active material 582, FIGS. 3B and 3C will be used for explanation. FIG. 3B shows the first active material 581, the second active material 582, and the graphene compound 583 as a material having a sheet-like shape, and the graphene compound 583 is in contact with the first active material 581 to cover, wrap, or adhere to the second active material 582 located on the surface of the first active material 581. The second active material 582 is located between the first active material 581 and the graphene compound 583, and it can also be said that the graphene compound 583 is in contact with the first active material 581 and the second active material 582. The volume of the second active material 582 shown in The case where it expands significantly due to charging or discharging is shown in FIG. 3C. The graphene compound 58 3 covers, wraps around, or is in contact with the first active material 581 so as to cover the second active material 582 located on the surface of the first active material 581. Therefore, even when the volume of the second active material 582 increases due to charging or discharging, the electrical contact between the second active material 582 and the first active material 581 can be maintained. Also, the collapse of the electrode can be suppressed. Since it is in contact with the first active material 581 so as to cover, wrap around, or cling to it, even when the volume of the second active material 582 increases due to charging or discharging, the electrical contact between the second active material 582 and the first active material 581 can be maintained. Also, the collapse of the electrode can be suppressed. 2 and the first active material 581 can be maintained. Also, the collapse of the electrode can be suppressed. 2 and the first active material 581 can be maintained. Also, the collapse of the electrode can be suppressed. Suppression can be achieved.

[0049] When the graphene compound 583 is in contact with active materials such as the first active material 581 and the second active material 582 so as to cling to them, the contact area between the graphene compound 583 and the active materials becomes large, and the conductivity of electrons moving through the graphene compound 583 is improved. Also, when the volume of the active materials changes significantly due to charge and discharge, the graphene compound 583 clings to the active materials, so that it is possible to effectively prevent the active materials from falling off. These effects can be further enhanced when in close contact so as to cling to each other. Here, the graphene compound 583 has pores of a size that allows Li ions to pass through, and it is desirable to have a large number of pores to such an extent that they do not interfere with the electron conductivity of the graphene compound 583. When the graphene compound 583 is in contact with active materials such as the first active material 581 and the second active material 582 so as to cling to them, the contact area between the graphene compound 583 and the active materials becomes large, and the conductivity of electrons moving through the graphene compound 583 is improved. Also, when the volume of the active materials changes significantly due to charge and discharge, the graphene compound 583 clings to the active materials, so that it is possible to effectively prevent the active materials from falling off. These effects can be further enhanced when in close contact so as to cling to each other. Here, the graphene compound 583 has pores of a size that allows Li ions to pass through, and it is desirable to have a large number of pores to such an extent that they do not interfere with the electron conductivity of the graphene compound 583. When the graphene compound 583 is in contact with active materials such as the first active material 581 and the second active material 582 so as to cling to them, the contact area between the graphene compound 583 and the active materials becomes large, and the conductivity of electrons moving through the graphene compound 583 is improved. Also, when the volume of the active materials changes significantly due to charge and discharge, the graphene compound 583 clings to the active materials, so that it is possible to effectively prevent the active materials from falling off. These effects can be further enhanced when in close contact so as to cling to each other. Here, the graphene compound 583 has pores of a size that allows Li ions to pass through, and it is desirable to have a large number of pores to such an extent that they do not interfere with the electron conductivity of the graphene compound 583. When the volume of the active materials changes significantly due to charge and discharge, the graphene compound 583 clings to the active materials, so that it is possible to effectively prevent the active materials from falling off. These effects can be further enhanced when in close contact so as to cling to each other. Here, the graphene compound 583 has pores of a size that allows Li ions to pass through, and it is desirable to have a large number of pores to such an extent that they do not interfere with the electron conductivity of the graphene compound 583. When the volume of the active materials changes significantly due to charge and discharge, the graphene compound 583 clings to the active materials, so that it is possible to effectively prevent the active materials from falling off. These effects can be further enhanced when in close contact so as to cling to each other. Here, the graphene compound 583 has pores of a size that allows Li ions to pass through, and it is desirable to have a large number of pores to such an extent that they do not interfere with the electron conductivity of the graphene compound 583. When in close contact so as to cling to each other, these effects can be further enhanced. Here, the graphene compound 583 has pores of a size that allows Li ions to pass through, and it is desirable to have a large number of pores to such an extent that they do not interfere with the electron conductivity of the graphene compound 583. Here, the graphene compound 583 has pores of a size that allows Li ions to pass through, and it is desirable to have a large number of pores to such an extent that they do not interfere with the electron conductivity of the graphene compound 583. Here, the graphene compound 583 has pores of a size that allows Li ions to pass through, and it is desirable to have a large number of pores to such an extent that they do not interfere with the electron conductivity of the graphene compound 583.

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

[0051] As the carbon fiber, for example, mesophase pitch-based carbon fiber, isotropic pitch-based carbon fiber, etc. of carbon fiber can be used. Also, as the carbon fiber, carbon nanofiber or carbon nanotube, etc. can be used. Carbon nanotubes can be produced, for example, by a vapor growth method or the like.

[0052] Also, the active material layer may contain metal powders such as copper, nickel, aluminum, silver, gold, etc., or metal fibers, conductive ceramic materials, etc.

[0053] The content of the conductive material with respect to the total amount of the solid content of the active material layer is preferably 0.5 wt% or more and 10 wt% or less and more preferably 0.5 wt% or more and 5 wt% or less.

[0054] Unlike granular conductive materials such as carbon black that make point contact with the active material, graphene compounds enable surface contact with low contact resistance, so that the electrical conductivity between the granular active material and the graphene compound can be improved with a smaller amount than ordinary conductive materials. Therefore, the ratio of the active material in the active material layer can be increased. As a result, the discharge capacity of the secondary battery can be increased thereby.

[0055] Also, since the graphene compound of one aspect of the present invention has excellent lithium permeability, the charge and discharge rate of the secondary battery can be increased.

[0056] Particulate carbon-containing compounds such as carbon black and graphite, and carbon nanotubes Fibrous carbon-containing compounds such as can easily enter into minute spaces. The minute spaces refer to, for example, the regions between a plurality of active materials. By combining a carbon-containing compound that can easily enter into minute spaces with a sheet-like carbon-containing compound such as graphene that can impart conductivity to a plurality of particles, it is possible to increase the density of the electrodes and form excellent conductive paths. Further, since the secondary battery has the electrolyte 576 of one aspect of the present invention, the operating stability of the secondary battery can be enhanced. That is, the secondary battery of one aspect of the present invention can have both a high energy density and stability, and is effective as an in-vehicle secondary battery. When the number of secondary batteries is increased and the weight of the vehicle increases, the energy

[0057] required to move the vehicle also increases, so the cruising range becomes shorter. By using a high-density secondary battery, even if the weight of the secondary battery mounted on the vehicle is the same, that is, even if the total weight of the vehicle is the same, the cruising range can be extended.

[0058] By using the electrolyte 576 of one aspect of the present invention, an in-vehicle secondary battery having a wide operating temperature range can be obtained.

[0059] Further, since the secondary battery of one aspect of the present invention has a high energy density, it can be miniaturized, and since it has high conductivity, It is also effective in a belt information terminal.

[0060] The negative electrode active material layer 572a preferably has a binder (not shown). The binder binds or fixes, for example, the electrolyte 576 and the active material. The binder also binds the electrolyte 576 and the carbon-based material, the active material and the carbon-based material, a plurality of active materials, a plurality of carbon-based materials, etc. or can fix them.

[0061] As the binder, polystyrene, methyl polyacrylate, polymethyl methacrylate (poly methyl methacrylate, PMMA), sodium polyacrylate, polyvinyl alcohol (PVA), polyethylene oxide (PEO), polypropylene oxide, polyimide imide, polyvinyl chloride, polytetrafluoroethylene, polyethylene, polypropylene, poly isobutylene, polyethylene terephthalate, nylon, polyvinylidene fluoride (PVD F), polyacrylonitrile (PAN), ethylene propylene diene polymer, polyvinyl acetate vinyl, nitrocellulose and other materials are preferably used.

[0062] Polyimide has very excellent thermal, mechanical, and chemical stability properties. Also, when polyimide is used as the binder a dehydration reaction and a cyclization (imidation) reaction are carried out. These reactions can be carried out, for example, by heat treatment. In the electrode of one aspect of the present invention when graphene having a functional group containing oxygen as a graphene compound and polyimide as a binder are used the reduction of the graphene compound can also be carried out by the heat treatment, and the process can be simplified. Also, since it has excellent heat resistance, for example, a heating temperature of 200 °C or higher Heat treatment can be performed at a temperature. By performing heat treatment at a heating temperature of 200 °C or higher, the reduction reaction of the graphene compound can be sufficiently carried out, and the conductivity of the electrode can be further increased.

[0063] A fluoropolymer, which is a polymer material having fluorine, specifically polyvinylidene fluoride ( PVDF), etc. can be used. PVDF is a resin having a melting point in the range of 134 °C or higher and 169 °C or lower, and is a material with excellent thermal stability.

[0064] Also, as the binder, rubber materials such as styrene-butadiene rubber (SBR), styrene-isoprene- styrene rubber, acrylonitrile-butadiene rubber, butadiene rubber, ethylene-propylene- diene copolymer, etc. are preferably used. Also, as the binder, fluorine rubber can be used.

[0065] Also, as the binder, it is preferable to use, for example, a water-soluble polymer. As the water-soluble polymer, for example, polysaccharides can be used. As the polysaccharides, carboxymethyl cellulose (CMC), methyl cellulose, ethyl cellulose, hydroxypropyl cellulose, diacetyl cellulose, cellulose derivatives such as regenerated cellulose, or starch, etc. can be used. Also, using these water-soluble polymers in combination with the aforementioned rubber materials is even more preferable.

[0066] The binder may be used in combination of a plurality of the above.

[0067] Also, the graphene compound 583 has flexibility, and the first active material 581 and the second active ​​​​​The mass 582 can wrap around like natto. Also, for example, the first active substance 581 and the second active substance 582 can be exemplified in soybeans, and the graphene compound 583 can be exemplified in a sticky component, for example, polyglutamic acid. By disposing the graphene compound 583 between the electrolyte 576, the plurality of active substances, the plurality of carbon-based materials, and other materials included in the negative electrode active material layer 572a, not only a good conductive path can be formed in the negative electrode active material layer 572a, but also these materials can be bound or fixed using the graphene compound 583. Also, for example, a three-dimensional network structure, a structure in which polygons are arranged, for example, a honeycomb structure in which hexagons are arranged in a matrix shape is formed by a plurality of graphene compounds 583, and the electrolyte 576, a plurality of active substances, a plurality of carbon-based materials, and other materials are disposed in the network, so that the graphene compound 583 forms a three-dimensional conductive path and suppresses the dropout of the electrolyte 576 from the current collector. In the structure in which the above-mentioned polygons are arranged, polygons having different numbers of sides may be mixed and arranged. Therefore, the graphene compound 583 sometimes functions as a conductive material and sometimes functions as a binder in the negative electrode active material layer 572a. The graphene compound 583 has holes of 9-membered rings or more and does not inhibit the movement of Li ions even when covering the active substance, so it is particularly preferable as a conductive material used for the negative electrode active material layer 572a.

[0068] [Negative Electrode Active Material] The first active substance 581 and the second active substance 582 can have various shapes, such as a rounded shape and a shape having corners. Also, in the cross-section of the electrode, the first active substance 581 ​​​​And the second active material 582 can have various cross-sectional shapes such as a circle, an ellipse, a figure having a curve, a polygon, etc. For example, as an example in FIGS. 1B and 3A, an example is shown in which the cross-sections of the first active material 581 and the second active material 582 have a rounded shape, but the cross-sections of the first active material 58 1 and the second active material 582 may have corners. Also, a part may be rounded and a part may have corners.

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

[0070] As the negative electrode active material, silicon can be used. The negative electrode 570a preferably uses particles having silicon as the second active material 5 82.

[0071] Also, as the negative electrode active material included in the second active material 582, a metal or a compound having one or more elements selected from tin, gallium, aluminum , germanium, lead, antimony, bismuth, silver, zinc, cadmium, indium can be used. As alloy-based compounds using such elements , for example, Mg2Si, Mg2Ge, Mg2Sn, SnS 2, V2Sn3, FeSn2, CoSn2, Ni3Sn2, Cu6Sn5, Ag3Sn, Ag3Sb, Ni2MnSb, CeSb3, LaSn3, La3Co2Sn7, CoSb 3, InSb, SbSn, etc. can be mentioned.

[0072] Also, materials with reduced resistance by adding phosphorus, arsenic, boron, aluminum, gallium, etc. as impurity elements to silicon may be used. Also, a silicon material predoped with lithium may be used. As the predoping method, lithium fluoride, lithium carbonate, etc. and silicon can be used. There are methods such as mechanical alloying of lithium metal and silicon, followed by annealing after mixing them. Also, after forming a first electrode using silicon as the active material, a second electrode such as lithium metal is combined with it, and lithium is doped into the silicon contained in the first electrode through a charge-discharge reaction. Then, an electrode serving as a counter electrode (for example, a positive electrode with respect to a pre-doped

[0073] negative electrode) may be combined using the doped first electrode to fabricate a secondary battery. For example, nanosilicon particles can be used as the second active material 582. The

[0074] average diameter of the nanosilicon particles is preferably, for example, 5 nm or more and less than 1 μm, more preferably 10 nm or more and 300 nm or less, and even more preferably 10 nm or more and 100 nm or less. The nanosilicon particles may have a spherical shape, a flattened spherical shape, or a rectangular parallelepiped shape with rounded corners. The size (particle diameter) of the nanosilicon particles is preferably, for example, 5 nm or more and 1 μm or less as the D50 of laser diffraction particle size distribution measurement, more preferably 10 nm or more and 300 nm or less, and even more preferably 10 nm or more and 100

[0075] nm or less. Here, D50 is the particle diameter at which the integrated amount occupies 50% in the integrated particle amount curve of the particle size distribution measurement Preferably, it has crystalline silicon. Further, the nanosilicon particles may have a crystalline region and an amorphous region.

[0076] As a material having silicon, for example, SiO x (x is preferably less than 2, more preferably 0.5 or more and 1.6 or less) can be used.

[0077] As a material having silicon, for example, a form having a plurality of crystal grains in one particle can be used For example, a form having one or more silicon crystal grains in one particle can be used Further, the one particle may have silicon oxide around the silicon crystal grains The silicon oxide may be amorphous. The secondary particles of silicon may be particles wrapped with the graphene compound 583.

[0078] Further, the compound having silicon can have, for example, Li2SiO3 and Li4SiO4 Li2SiO3 and Li4SiO4 may each have crystallinity , or may be amorphous.

[0079] Analysis of the compound having silicon can be performed using NMR, XRD, Raman spectroscopy, SEM, TEM, E DX, etc.

[0080] The first active material 581 included in the negative electrode 570a preferably has graphite.

[0081] The first active material 581 is more preferably a material with a small volume change associated with charge and discharge.

[0082] As the volume change of the first active material 581 associated with charging or discharging, in charging or discharging When the minimum volume is set to 1, the maximum volume during charging or discharging is preferably 2 or less, more preferably 1.5 or less, and even more preferably 1.1 or less.

[0083] It is desirable that the particle size of the first active material 581 is larger than that of the second active material 582.

[0084] For example, in laser diffraction particle size distribution measurement, the D50 of the first active material 581 is preferably more than 1.5 times and less than 1000 times the D50 of the second active material 582, more preferably more than 2 times and less than 500 times, and even more preferably more than 10 times and less than 100 times. Here, D50 refers to the particle size when the integrated amount occupies 50% in the integrated particle amount curve of the particle size distribution measurement result, that is, the median. Note that the measurement of the particle size is not limited to laser diffraction particle size distribution measurement, and the diameter of the particle cross-section may be measured by analysis such as SEM or TEM.

[0085] Also, as the first active material 581, for example, carbon-based materials such as graphite, easily graphitizable carbon, difficultly graphitizable carbon, carbon nanotubes, carbon black, and graphene compound 583, which have a small volume change accompanying charge and discharge, can be used.

[0086] Also, as the first active material 581, for example, oxides having one or more elements selected from titanium, niobium, tungsten, and molybdenum can be used.

[0087] As the first active material 581, a plurality of the above-mentioned metals, materials, compounds, etc. can be combined and used.

[0088] ​​​​​​​As the first active material 581, for example, oxides such as SnO, SnO2, titanium dioxide (TiO2), lithium titanium oxide (Li4Ti5O 12 ), lithium-graphite intercalation compound (Li x C6) , niobium pentoxide (Nb2O5), tungsten oxide (WO2), molybdenum oxide (MoO 2), etc. can be used.

[0089] In addition, a material that causes a conversion reaction can also be used as the first active material 581 . For example, transition metal oxides such as cobalt oxide (CoO), nickel oxide (NiO), iron oxide (FeO), etc. that do not undergo an alloying reaction with lithium may be used as the first active material 581 . Materials that cause a conversion reaction further include oxides such as Fe2O3, CuO, Cu2O, RuO2, Cr2O3, sulfides such as CoS 0.89 , NiS, CuS, nitrides such as Zn3 N2, Cu3N, Ge3N4, phosphides such as NiP2, FeP2, CoP3, fluorides such as FeF3, BiF3. Since the potential of the above fluorides is high, they may be used as a positive electrode material.

[0090] [Calculation of negative electrode 1] Regarding the case where graphite is used as the first active material 581 and silicon is used as the second active material 582 for the negative electrode 570a of one aspect of the present invention, first-principles calculations were performed on the lithium diffusion coefficients in the first active material 581 and the second active

[0091] Figure 4A shows a model of the crystal structure used for the calculation of graphite (Li 0.25 C6), and Figure 4B shows a model of the crystal structure used for the calculation of silicon (Li Si) 1.25 . are shown.

[0092] For the calculations, the first-principles electronic state calculation package VASP was used. Regarding the specific calculation conditions, the conditions shown in Table 1 were used.

[0093]

Table 1

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

[0095] The results of the calculations shown in FIGS. 4A, 4B, and Table 1 are shown in FIG. 5. As a result of the calculations, it was shown that the diffusion coefficient of lithium is higher in graphite than in silicon.

[0096] Also, regarding the relationship between the redox potentials of graphite and silicon, it is known that graphite is 0.05 V (vs. Li) and Si is 0.4 V (vs. Li). The redox potential is correlated with the voltage at which charging (lithium uptake) starts. Considering the priority of lithium insertion during charging, it is considered that lithium is preferentially taken up by Si with a higher redox potential.

[0097] Combining these, the calculation results of the diffusion coefficient shown in FIG. 5 and the relationship of the redox potential, and inferring it is considered that lithium is preferentially taken up by silicon due to the difference in redox potential at the initial stage of charging, but as the charging progresses, due to the difference in the lithium uptake rate, the diffusion coefficient gradually becomes larger. ​​​It is possible that the uptake of lithium 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 nearly the theoretical capacity of the graphite, and the second active material 582 It is presumed that the silicon in the silicon layer takes in 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 effect of capacity limitation 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 a charged state (alloyed with Li).

[0099] FIG. 6B shows the structure at Li / Si=1.714, and there are Si-Si bonds in the structure. On the other hand, the theoretical capacity limit Li / In the crystal structure at Si=4.4, the Li ratio is increased, and Si-Si bonds are formed in the structure. It can be seen that no combination exists. The crystal structure of silicon breaks down as it is repeatedly charged and discharged, and amorphization occurs. It is known that the battery becomes lumpy and flaky when fully charged. In the case where the Si-Si bond shown in FIG. 6B remains, the charge-discharge cycle is repeated. It is considered that the structure is likely to be maintained to a certain extent. When used with a lithium ratio (molar ratio) of Si=1.714 or less, it has good charging properties. There is a possibility that discharge cycle characteristics may be exhibited.

[0100] [Negative electrode capacity limitation] The negative electrode 570a of one embodiment of the present invention preferably has a capacity less than the theoretical capacities of the first active material 581 and the second active material 582 and is used as a secondary battery. The capacity limitation of the negative electrode 570a is, for example, preferably 50% or more and less than 100% of the theoretical capacities of the first active material 581 and the second active material 582, more preferably 70% or more and less than 90% of the capacity ratio. In this case, a secondary battery with a high charge-discharge capacity and good charge-discharge

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

[0102] the present invention. First, in step S61, particles containing silicon are prepared as the second active material 582. As the particles containing silicon, for example, the particles described as the second active material 582 above can be used.

[0103] In step S62, a solvent is prepared. As the solvent, for example, any one of water, methanol, ethanol, acetone, tetrahydrofuran (THF), dimethylformamide (DMF), N-methylpyrrolidone (NMP), and dimethyl sulfoxide (DMSO), or a mixture of two or more thereof can be used.

[0104] Next, in step S63, the particles containing silicon prepared in step S61 and the solvent prepared in step S62 are mixed, and in step S64, the mixture is recovered to obtain a mixture E-1 in step S65. A kneader or the like can be used for mixing. As the kneader, for example, a rotation-revolution mixer or the like can be used.

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

[0106] Next, in step S73, the mixture E-1 and the particles containing graphite prepared in step S72 are mixed, the mixture is recovered in step S74, and in step S75, mixture E-2 is obtained. For mixing, a kneader or the like can be used. As the kneader, for example, a tilting mixer 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 graphene compound 583 prepared in step S80 are mixed, and the mixture is recovered in step S82. The recovered mixture is preferably in a high-viscosity state. Due to the high viscosity of the mixture, in the next step S83, solid kneading (kneading at high viscosity) can be performed.

[0109] Next, in step S83, solid kneading is performed. Solid kneading can be performed using, for example, a spatula. By performing solid kneading, particles containing silicon and the graphene compound 583 are well mixed, and a mixture with excellent dispersibility of the graphene compound 583 can be formed.

[0110] Next, in step S84, a solvent is added to the solid-kneaded mixture and mixed. For mixing, for example, a kneader or the like can be used. The mixed mixture is recovered in step S85.​​​​​ Collect it.

[0111] For the mixture recovered in step S85, the steps of steps S83 to S85 It is preferable to repeat the process n times. n is a natural number of, for example, 2 or more and 10 or less. Also in the process of step S83, when the mixture is in a dry state, it is preferable to add a solvent However, if too much solvent is added, the viscosity decreases and the effect of kneading becomes low down.

[0112] After repeating steps S83 to S85 n times, mixture E-3 is obtained (step S86).

[0113] Next, in step S87, a binder is prepared. As the binder, the materials described above can be used, and it is particularly preferable to use polyimide. In step S8 7, there may be a case where a precursor of the material used as the binder is prepared. For example, poly imide precursor is prepared.

[0114] Next, in step S88, mixture E-3 and the binder prepared in step S87 are mixed. Next, in step S89, the viscosity is adjusted. Specifically, for example , a solvent of the same type as the solvent prepared in step S62 is prepared and added to the mixture obtained in step S88 . By adjusting the viscosity, for example, the thickness, density, etc. of the electrode obtained in step S97 can be adjusted in some cases.

[0115] Next, a solvent is added to the mixture whose viscosity was adjusted in step S89, mixed in step S9 0, recovered in step S91, and mixture E-4 is obtained (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 onto the current collector prepared in step S93. Coating methods include the slot die method, gravure method, blade method, and a combination of these. A continuous coater or the like may be used for coating.

[0118] Next, in step S95, a first heating is performed. The first heating causes the solvent to volatilize. 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 step is, for example, a heating step in an air atmosphere at a temperature of 30° C. to 70° C. for 10 minutes or more. Then, for example, heat treatment is performed on a hot plate at room temperature or above 100°C for 1 hour or more. Heat treatment may be carried out in a reduced pressure environment for the following time.

[0120] Alternatively, the heat treatment may be performed using a drying oven or the like. When a drying oven is used, for example, Heat treatment may be performed 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 that, 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 the case of [a certain situation], it is preferable that a cyclization addition reaction of the polyimide occurs due to the second heating. Also, in some cases, a dehydration reaction of the polyimide may occur due to the second heating. Alternatively, a dehydration reaction of the polyimide may occur due to the first heating. In addition, in the first heating, a cyclization reaction of the polyimide may occur. Also, in the second heating, it is preferable that a reduction reaction of the graphene compound 583 occurs. Note that the second heating may be referred to as imidization heat treatment, reduction heat treatment, or thermal reduction treatment.

[0123] By performing a pressing process before the second heating, it becomes possible to increase the electrode density without degrading the battery characteristics. Therefore, it is preferable to perform a pressing process before step S96.

[0124] The second heating is preferably carried out in a temperature range of 150°C or higher and 500°C or lower, more preferably 200°C or higher and 450°C or lower.

[0125] The second heating can be carried out, for example, under a reduced pressure environment of 10 Pa or lower, or in an inert atmosphere such as nitrogen or argon, under the conditions of 200°C or higher and 450°C or lower, and 1 hour or longer and 10 hours or shorter.

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

[0127] The thickness of the thus formed active material layer is, for example, preferably 5 μm or more and 300 μm or less, more preferably 10 μm or more and 150 μm or less. Also, the active material loading amount of the active material layer is, for example, preferably 2 mg / cm² or more and 50 mg / cm² or less. 2 2

[0128] ​​​​​​​​​​​The active material layer may be formed on both sides of the current collector or on only one side. Or, it may partially have regions where the active material layer is formed on both sides.

[0129] After volatilizing the solvent from the active material layer, compression methods such as the roll pressing method or the flat pressing method may be used for pressing. Heat may be applied during pressing.

[0130] [Positive Electrode] The positive electrode 570b includes at least a positive electrode current collector 571b and a positive electrode active material layer 572b formed in contact with the positive electrode current collector 571b. Details of the positive electrode 570b will be described in the following embodiments.

[0131] [Conductive Material] The conductive material, also called a conductivity-imparting agent or a conductive auxiliary agent, is a carbon material. By attaching a conductive agent between a plurality of active materials, the plurality of active materials are electrically connected to each other, enhancing conductivity. Note that "attachment" only refers to the physical adhesion between the active material and the conductive agent. Therefore, it does not include cases where a covalent bond occurs, cases where bonding occurs by van der Waals forces, cases where a part of the surface of the active material is covered by the conductive agent, cases where the conductive agent fits into the surface irregularities of the active material, and cases where they are electrically connected even if they are not in contact with each other. It is defined as a concept including such cases.

[0132] As the conductive material, for example, any one or two or more of acetylene black, furnace black, etc. carbon black, graphite such as artificial graphite and natural graphite, carbon fibers such as carbon nanofibers, and carbon nanotubes, and graphene compound 583 can be used.

[0133] ​​​​As the positive electrode 570b of the secondary battery, a positive electrode current collector 571b such as a metal foil and an active material are fixed by mixing a binder (resin). The binder is also called a binding agent. The b inder is a polymer material. If a large amount of the binder is included, the proportion of the active material in the positive electrode active material layer 572b decreases, and the discharge capacity of the secondary battery becomes small. Therefore, the amount of the binder is mixed to the minimum .

[0134] Since graphene has electrically, mechanically or chemically amazing properties, applications in various fields such as field effect transistors and solar cells using graphene are expected. It is a carbon material.

[0135] In addition, carbon fibers can be used as a conductive material. For example, carbon fibers such as mesophase pitch-based carbon fibers and isotropic pitch-based carbon fibers can be used. Also, as the carbon fibers , carbon nanofibers or carbon nanotubes can be used. Carbon nanotubes can be produced, for example, by a vapor phase growth method.

[0136] [Graphene Compound] In this specification and the like, the graphene compound 583 includes graphene, multi-layer graphene, multi -layer graphene, oxidized graphene, multi-layer oxidized graphene, multi-oxidized graphene, reduced oxidized graphene, reduced multi-layer oxidized graphene, reduced multi-oxidized graphene, graphene quantum dots, etc. The graphene compound 583 has carbon, has a flat plate shape, a sheet -like shape, etc., and has a two-dimensional structure formed by carbon six-membered rings. The carbon two-dimensional structure formed by the six-membered rings may be referred to as a carbon sheet. The graphene compound 58 3 may have a functional group containing oxygen. Further, the graphene compound 583 preferably has a bent shape. Also, the graphene compound 583 may be rounded like a carbon nanofiber. In the present specification and the like, graphene oxide refers to, for example, a material having carbon, oxygen, a sheet-like shape, and having a functional group, particularly an epoxy group, a carboxy group or a hydroxy group.

[0137] In the present specification and the like, reduced graphene oxide refers to, for example, a material having carbon, oxygen, a sheet-like shape, and having a two-dimensional structure formed of carbon six-membered rings. It may be referred to as a carbon sheet. Reduced graphene oxide functions even when it is a single sheet, but a plurality of sheets may be stacked. Reduced graphene oxide preferably has a portion where the carbon concentration is greater than 80 atomic% and the oxygen concentration is 2 atomic% or more and 15 atomic% or less. By setting such a carbon concentration and oxygen concentration, it can function as a highly conductive conductive material even in a small amount. Also, reduced graphene oxide preferably has an intensity ratio G / D of the G band and the D band in the Raman spectrum of 1 or more. Reduced graphene oxide having such an intensity ratio can function as a highly conductive conductive material even in a small amount.

[0138] By reducing graphene oxide, pores may be provided in the reduced graphene oxide. Also, as the graphene compound, a material in which the ends of graphene are terminated with fluorine may be used.

[0139]

[0140] ​​​​​​​​​​​​

[0141] In the longitudinal section of the active material layer, sheet-like graphene compound 583 is dispersed approximately uniformly in the internal region of the active material layer. A plurality of graphene compounds are formed so as to cover a part of the plurality of granular active materials or to adhere onto the surfaces of the plurality of granular active materials, and thus are in surface contact with each other. Here, by bonding the plurality of graphene compounds 583 to each other, a network-like graphene compound sheet (hereinafter referred to as a graphene compound net or a graphene net) can be formed. When the active material is covered with the graphene net, the graphene net can also function as a binder that binds the active materials to each other. Therefore, the amount of the binder can be reduced or the binder can be dispensed with, and thus the ratio of the active material in the electrode volume and the electrode weight can be improved. That is, the charge and discharge capacity of the secondary battery can be increased.

[0142] compound sheet (hereinafter referred to as a graphene compound net or a graphene net) can be formed. When the active material is covered with the graphene net, the graphene net can also function as a binder that binds the active materials to each other. Therefore, the amount of the binder can be reduced or the binder can be dispensed with, and thus the ratio of the active material in the electrode volume and the electrode weight can be improved. That is, the charge and discharge capacity of the secondary battery can be increased. compound sheet (hereinafter referred to as a graphene compound net or a graphene net) can be formed. When the active material is covered with the graphene net, the graphene net can also function as a binder that binds the active materials to each other. Therefore, the amount of the binder can be reduced or the binder can be dispensed with, and thus the ratio of the active material in the electrode volume and the electrode weight can be improved. That is, the charge and discharge capacity of the secondary battery can be increased. Here, it is preferable to use graphene oxide as the graphene compound 583, mix it with the active material to form a layer serving as the active material layer, and then reduce the graphene oxide. That is, it is preferable that the completed active material layer has reduced graphene oxide. When forming the active material layer having the graphene compound 583, by using graphene oxide having extremely high dispersibility in a polar solvent, the graphene compound 583 can be dispersed approximately uniformly in the internal region of the active material layer. Here, it is preferable to use graphene oxide as the graphene compound 583, mix it with the active material to form a layer serving as the active material layer, and then reduce the graphene oxide. That is, it is preferable that the completed active material layer has reduced graphene oxide. When forming the active material layer having the graphene compound 583, by using graphene oxide having extremely high dispersibility in a polar solvent, the graphene compound 583 can be dispersed approximately uniformly in the internal region of the active material layer. Here, it is preferable to use graphene oxide as the graphene compound 583, mix it with the active material to form a layer serving as the active material layer, and then reduce the graphene oxide. That is, it is preferable that the completed active material layer has reduced graphene oxide. When forming the active material layer having the graphene compound 583, by using graphene oxide having extremely high dispersibility in a polar solvent, the graphene compound 583 can be dispersed approximately uniformly in the internal region of the active material layer. Here, it is preferable to use graphene oxide as the graphene compound 583, mix it with the active material to form a layer serving as the active material layer, and then reduce the graphene oxide. That is, it is preferable that the completed active material layer has reduced graphene oxide. When forming the active material layer having the graphene compound 583, by using graphene oxide having extremely high dispersibility in a polar solvent, the graphene compound 583 can be dispersed approximately uniformly in the internal region of the active material layer.

[0143] Here, it is preferable to use graphene oxide as the graphene compound 583, mix it with the active material to form a layer serving as the active material layer, and then reduce the graphene oxide. That is, it is preferable that the completed active material layer has reduced graphene oxide. When forming the active material layer having the graphene compound 583, by using graphene oxide having extremely high dispersibility in a polar solvent, the graphene compound 583 can be dispersed approximately uniformly in the internal region of the active material layer. Here, it is preferable to use graphene oxide as the graphene compound 583, mix it with the active material to form a layer serving as the active material layer, and then reduce the graphene oxide. That is, it is preferable that the completed active material layer has reduced graphene oxide. When forming the active material layer having the graphene compound 583, by using graphene oxide having extremely high dispersibility in a polar solvent, the graphene compound 583 can be dispersed approximately uniformly in the internal region of the active material layer. Here, it is preferable to use graphene oxide as the graphene compound 583, mix it with the active material to form a layer serving as the active material layer, and then reduce the graphene oxide. That is, it is preferable that the completed active material layer has reduced graphene oxide. When forming the active material layer having the graphene compound 583, by using graphene oxide having extremely high dispersibility in a polar solvent, the graphene compound 583 can be dispersed approximately uniformly in the internal region of the active material layer. Here, it is preferable to use graphene oxide as the graphene compound 583, mix it with the active material to form a layer serving as the active material layer, and then reduce the graphene oxide. That is, it is preferable that the completed active material layer has reduced graphene oxide. When forming the active material layer having the graphene compound 583, by using graphene oxide having extremely high dispersibility in a polar solvent, the graphene compound 583 can be dispersed approximately uniformly in the internal region of the active material layer. Here, it is preferable to use graphene oxide as the graphene compound 583, mix it with the active material to form a layer serving as the active material layer, and then reduce the graphene oxide. That is, it is preferable that the completed active material layer has reduced graphene oxide. When forming the active material layer having the graphene compound 583, by using graphene oxide having extremely high dispersibility in a polar solvent, the graphene compound 583 can be dispersed approximately uniformly in the internal region of the active material layer.

[0144] Apply a dispersion liquid in which graphene oxide is dispersed approximately uniformly in a solvent onto a current collector, and remove the solvent. In the active material layer produced by volatilizing and then reducing graphene oxide, the graphene compounds 583 included in the active material layer partially overlap. Thus, the reduced graphene oxides are dispersed to such an extent that they are in surface contact with each other, so that a three-dimensional conductive path can be formed. Note that the reduction of graphene oxide may be performed, for example, by heat treatment or

[0145] using a reducing agent. Further, by previously covering the surface of the active material with a graphene compound, a conductive film is formed on the surface of the active material, and by

[0146] electrically connecting the active materials with the graphene compound, a conductive path can also be formed. It is preferable that the graphene compound 583 according to one embodiment of the present invention has pores in a part of the carbon sheet. In the graphene compound 583 according to one embodiment of the present invention, by providing pores through which carrier ions such as lithium ions can pass in a part of the carbon sheet,

[0147] insertion and extraction of carrier ions become easy on the surface of the active material covered with the graphene compound 583, and the rate characteristics of the secondary battery can be improved. The pores provided in a part of the carbon sheet may be called voids, defects or gaps. It is preferable that the graphene compound 583 according to one embodiment of the This lowers the barrier energy for lithium ions to pass through the holes. The pores of the fluorine-containing compound 583 allow lithium ions to be sorbed even in the small pores. It was found that the graphene compound 583, which is easy for ions to pass through and has excellent electrical conductivity, was realized. In addition, one or more of the carbon atoms bonded to the ring may be terminated with hydrogen. This is also 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 FIG. 8A and FIG. 8B is a graphene having holes, It is also called reduced graphene with holes.

[0149] The structure shown in FIG. 8A has a 22-membered ring, and 8 of the carbons constituting the 22-membered ring are Each of the graphene compounds is terminated with hydrogen. 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 Of these, six carbons are terminated with hydrogen and two carbons are terminated with fluorine. In the laphene compound 583, the two connected 6-membered rings were removed, and the removed 6-membered ring It can also be said that the carbon bonded to the aryl group has a structure in which the carbon atom has been terminated with hydrogen or fluorine.

[0151] Silicon terminated with a hydroxyl group is a silicon surface that is bonded to the hydrogen of the hydroxyl group. A hydrogen atom contained in the graphene compound 583 or a fluorine atom contained in the graphene compound 583 Since a hydrogen bond is formed between the atoms, silicon terminated with a hydroxy group is considered to have a large interaction with the graphene compound 583 having pores.

[0152] Since the graphene compound 583 has fluorine in addition to hydrogen, in addition to the hydrogen bond between the oxygen atom of the hydroxy group and the hydrogen atom of the graphene compound 583, the hydrogen bond between the hydrogen atom of the hydroxy group and the fluorine atom of the graphene compound 583 is also formed, and the interaction between the particle having silicon and the graphene compound 583 is considered to become stronger and more stable.

[0153] When the graphene compound 583 has pores, for example, it may be possible to observe a spectrum based on the characteristics caused by the pores by Raman spectroscopy mapping measurement. In addition, it may be possible to observe the bonds, functional groups, etc. constituting the pores by ToF-SIMS. Further, it may be possible to analyze the vicinity of the pores, the periphery of the pores, etc. by TEM observation.

[0154] [Binder] In this specification and the like, the binder refers to a polymer compound that is mixed only for binding an active material, a conductive material, etc. onto a current collector. 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, polyisobutylene, ethylene propylene diene polymer and other materials.

[0155] Since the lithium ion conductive polymer is a polymer compound, it is often mixed and used for the active material layer. By being present, it becomes possible to bind the active material and the conductive material onto the current collector. Therefore, an electrode can be fabricated without using a binder. A binder is a material that does not contribute to the charge-discharge reaction. Therefore, the smaller the amount of the binder, the more materials that contribute to the charge-discharge of the active material, electrolyte, etc. can be increased. Therefore, it is possible to obtain a secondary battery with improved discharge capacity, cycle characteristics, etc. For the electrolyte 576, it is preferably sufficiently dried to form an electrolyte layer without or with very little organic solvent. In this specification, etc., when the weight change of the electrolyte layer dried under reduced pressure at 90 °C for 1 hour is within 5%, it is considered to be sufficiently dried.

[0156]

[0157] For the identification of materials such as the lithium ion conductive polymer, lithium salt, binder, and additive contained in the secondary battery, for example, nuclear magnetic resonance (NMR) can be used. Also, the analysis results of Raman spectroscopy, Fourier transform infrared spectroscopy (FT-IR), time-of-flight secondary ion mass spectrometry (TOF-SIMS), gas chromatography mass spectrometry (GC / MS), pyrolysis gas chromatography mass spectrometry (Py-GC / MS), liquid chromatography mass spectrometry (LC / MS), etc. may be used as materials for judgment. It is preferable to suspend the active material layer in a solvent, separate the active material and other materials, and then subject them to analysis such as NMR.

[0158] Also, in each of the above configurations, a solid electrolyte material may be further included in the negative electrode 570a to improve the flame retardancy. It is preferable to use an oxide-based solid electrolyte as the solid electrolyte material.

[0159] As the oxide-based solid electrolyte, LiPON, Li2O, Li2CO3, Li2MoO4 , Li3PO4, Li3VO4, Li4SiO4, LLT (La 2 / 3-x Li 3x Ti O3), LLZ (Li7La3Zr2O 12 ), etc., lithium composite oxides and lithium oxide materials can be mentioned.

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

[0161] Also, a polymer-based solid electrolyte such as PEO (polyethylene oxide) formed by a coating method or the like may be used. Since such a polymer-based solid electrolyte can also function as a binder, when using a polymer-based solid electrolyte, the components of the electrode can be reduced, and the manufacturing cost can also be reduced.

[0162] [Current collector] As the positive electrode current collector 571b and the negative electrode current collector 571a, metals such as stainless steel, gold, platinum, zinc, iron, copper, aluminum, titanium, etc., and alloys thereof, which have high conductivity and do not alloy with carrier ions such as lithium , can be used. Also, an aluminum alloy added with an element for improving heat resistance such as silicon, titanium, neodymium, scandium, molybdenum, etc. can be used. Also, it may be formed of a metal element that reacts with silicon to form a silicide. As the metal element that reacts with silicon to form a silicide, there are zirconium, titanium, hafnium, vanadium, niobium, tantalum, chromium, molyb denum, tungsten, cobalt, nickel, etc. The current collector may be in the form of a sheet, a net, a punched Ring metal shape, expanded metal shape, etc. can be appropriately used. The current collector has a thickness It is advisable to use one with a thickness of 10 μm or more and 30 μm or less.

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

[0164] A titanium compound may be provided by laminating on the above-mentioned metal element as the current collector. For example, as the titanium compound, titanium nitride, titanium oxide, titanium oxynitride in which part of nitrogen is replaced by oxygen (TiO x N y , 0 < x < 2, 0 < y < 1), and titanium oxide in which part of oxygen is replaced by nitrogen One selected from, or two or more mixed or laminated and used, can be used. Among them, titanium nitride is particularly preferable because it has high conductivity and a high function of suppressing oxidation. By providing a 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 concern about the oxidation reaction between the oxygen contained in 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.

[0165] [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 ​​​Or nylon (polyamide), vinylon (polyvinyl alcohol-based fiber), polyester , synthetic fibers made of acrylic, polyolefin, polyurethane, etc. can be used . The separator can be processed into a bag shape and is preferably arranged to wrap either the positive electrode 570b or the negative electrode 570a .

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

[0167] The separator may have a multilayer structure. For example, an organic material film such as polypropylene or polyethylene can be coated with a ceramic-based material, a fluorine-based material, a polyamide-based material, or a mixture thereof . As the ceramic-based material, for example, aluminum oxide particles, silicon oxide particles, etc. can be used . As the fluorine-based material, for example, PVDF, polytetrafluoroethylene, etc. can be used . As the polyamide-based material , for example, nylon, aramid (meta-aramid, para-aramid), etc. can be used .

[0168] Coating with a ceramic-based material improves oxidation resistance, so it can suppress the deterioration of the separator during high-voltage charge and discharge and improve the reliability of the secondary battery . Also, coating with a fluorine-based material makes it easier for the separator and the electrode to adhere, and can improve the output characteristics . Coating with a polyamide-based material, especially aramid, improves heat resistance, so it can improve the safety of the secondary battery . .

[0169] For example, a mixed material of aluminum oxide and aramid may be coated on both sides of a polypropylene film. Also, a mixed material of aluminum oxide and aramid may be coated on the surface of the polypropylene film that contacts the positive electrode 570b, and a fluorine-based material may be coated on the surface that contacts the negative electrode 570a.

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

[0171] [Electrolyte] When using a liquid electrolyte 576 in a secondary battery, for example, as the electrolyte 576, ethylene carbonate (EC), propylene carbonate (PC), butylene carbonate, chloroethylene carbonate, vinylene carbonate, γ-butyrolactone, γ-valerolactone, dimethyl carbonate (DMC), diethyl carbonate (DEC), ethyl methyl carbonate (EMC), methyl formate, methyl acetate, ethyl acetate, methyl propionate, ethyl propionate, propyl propionate, methyl butyrate, 1,3-dioxane, 1,4-dioxane, dimethoxyethane (DME), dimethyl sulfoxide, diethyl ether, methyl diglyme, acetonitrile, benzonitrile, tetrahydrofuran, sulfolane, sultone, etc., one kind, or any combination and ratio of two or more of these can be used.

[0172] In addition, by using one or more ionic liquids (room temperature molten salts) that are flame-retardant and hardly volatile as the solvent of the electrolyte 576, internal short circuits or overcharging in the secondary battery can cause internal ​ Even if the temperature of the region rises, rupture or ignition of the secondary battery can be prevented. Ionic liquid consists of a cation and an anion, and includes an organic cation and an anion. As the organic cation are mentioned aliphatic onium cations such as quaternary ammonium cation, tertiary sulfonium cation, and quaternary phosphonium ca tion, as well as imidazolium cation and aromatic cations such as pyridinium cation . Also, as the anion, monovalent amide-based anion, monovalent methide-based anion, fluorosulfonic acid anion, perfluoroalkyl sulfonic acid anion, tetrafluoroborate anion, perfluoroalkylborate anion, hexafluorophosphate anion, or perfluoroalkylphosphate anion etc. are mentioned.

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

[0174] The secondary battery of one aspect of the present invention has, for example, any one or two or more of alkali metal ions such as lithium ion, sodium ion, and potassium ion as well as alkaline earth metal ions such as calcium ion, strontium ion , barium ion, beryllium ion, and magnesium ion as carrier ions.

[0175] When lithium ion is used as the carrier ion, for example, the electrolyte contains a lithium salt . As the lithium salt, for example, LiPF6, LiClO4, LiAsF6, 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 electrolyte containing fluorine include fluorine. The electrolyte contains one or more halogenated cyclic carbonates and lithium ions. Fluorinated cyclic carbonates improve non-flammability and are suitable for lithium-ion secondary batteries. The safety of the battery can be improved.

[0177] As the fluorinated cyclic carbonate, fluorinated ethylene carbonate, for example, monofluoro 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 with one or more fluorinated cyclic carbonates. In order to operate at low temperatures, it is important to transport the electrolyte contained in the electrodes during charging and discharging. The fluorinated cyclic carbonate is not used 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 clumps of several to several dozen.

[0178] By using a fluorinated cyclic carbonate as an electrolyte, the energy for desolvation required when lithium ions coordinated with the solvent in the electrolyte enter the active material particles is reduced. If the desolvation energy can be reduced, lithium ions can be more easily inserted into or detached from the active material particles even in the low temperature range. Although lithium ions may move while being solvated, a hopping phenomenon may occur where the coordinating solvent molecules are replaced. When lithium ions can be easily desolvated, movement by the hopping phenomenon becomes easier, and the movement of lithium ions may become easier. There is a concern that decomposition products of the electrolyte during charge and discharge of the secondary battery may adhere to the surface of the active material, causing deterioration of the secondary battery. However, when the electrolyte contains fluorine, the electrolyte is more slippery, and the decomposition products of the electrolyte are less likely to adhere to the surface of the active material. Therefore, deterioration of the secondary battery can be suppressed. Solvated lithium ions may form clusters of multiple ions in the electrolyte and move within the negative electrode 570a, between the positive electrode 570b and the negative electrode 570a, within the positive electrode 570b, etc. In this specification, an electrolyte is a general term including solid, liquid, or semi-solid materials, etc. Interfaces existing in the secondary battery, such as the interface between the active material and the electrolyte, are likely to deteriorate. In the secondary battery according to one aspect of the present invention, by having an electrolyte containing fluorine, deterioration that may occur at the interface between the active material and the electrolyte, typically alteration of the electrolyte or increase in the viscosity of the electrolyte, is prevented.

[0179]

[0180]

[0181] can be achieved. Also, for an electrolyte having fluorine, it may be configured to entangle or hold a binder or a graphene compound, etc. By adopting such a configuration, it is possible to maintain the state where the viscosity of the electrolyte is reduced, in other words, the electrolyte is in a free-flowing state, and the reliability of the secondary battery can be improved. DFEC in which two fluorine atoms are bonded and F4EC in which four fluorine atoms are bonded have a lower viscosity and are more free-flowing than FEC in which one fluorine atom is bonded, and the coordination bond with lithium becomes weaker. Therefore, it is possible to reduce the adhesion of a decomposition product having a high viscosity to the active material particles. When a decomposition product having a high viscosity adheres to or entangles the active material particles, it becomes difficult for lithium ions to move at the interface of the active material particles. The electrolyte having fluorine alleviates the generation of decomposition products adhering to the surface of the active material (positive electrode active material or negative electrode active material) by solvation. Also, by using an electrolyte having fluorine, it is possible to prevent the generation and growth of dendrites by preventing the adhesion of decomposition products. Also, using an electrolyte having fluorine as a main component is also one of the features. The electrolyte having fluorine is 5% by volume or more, 10% by volume or more, preferably 30% by volume or more and 100% by volume or less. In this specification, the main component of the electrolyte means that it is 5% by volume or more of the entire electrolyte of the secondary battery. Also, 5% by volume or more of the entire electrolyte of the secondary battery referred to here means the ratio occupied by the entire electrolyte measured during the manufacture of the secondary battery. Also, when the secondary battery decomposes after being manufactured, it is necessary to quantify the proportion of each of the plurality of types of electrolytes.

[0182]

[0183] Although it is difficult, it can be determined whether a certain type of organic compound is 5% by volume or more of the entire electrolyte.

[0184] By using an electrolyte containing fluorine, it is possible to realize a secondary battery that can operate in a wide temperature range, specifically, -40°C or higher and 150°C or lower, preferably -40°C or higher and 85°C or lower.

[0185] In addition, additives such as vinylene carbonate, propane sultone (PS), tert-butylbenzene (TBB), lithium bis(oxalate) borate (LiBOB), and dinitrile compounds such as succinonitrile and adiponitrile may be added to the electrolyte. The concentration of the additive may be, for example, 0.1% by volume or more and less than 5% by volume based on the entire electrolyte.

[0186] In addition to the above, the electrolyte may also contain one or more aprotic organic solvents such as γ-butyrolactone, acetonitrile, dimethoxyethane, and tetrahydrofuran.

[0187] In addition, by having a polymer material that gels the electrolyte, the safety against leakage and the like is enhanced. Representative examples of the polymer material that gels include silicone gel, acrylic gel, acrylonitrile gel, polyethylene oxide-based gel, polypropylene oxide-based gel, and gels of fluorine-based polymers.

[0188] As the polymer material, for example, polymers having a polyalkylene oxide structure such as polyethylene oxide (PEO), PVDF, polyacrylonitrile, and copolymers containing them can be used. For example, copolymers of PVDF and hexafluoropropylene ​​​​​​​​​​​​PVDF-HFP, which is a copolymer of (HFP), can be used. Also, the formed polymer may have a porous shape.

[0189] Also, the above configuration shows an example of a secondary battery using a liquid electrolyte, but is not particularly limited. For example, semi-solid batteries and all-solid batteries can also be manufactured.

[0190] In the case of a secondary battery using a liquid electrolyte and in the case of a semi-solid battery in this specification and the like, the layer disposed between the positive electrode 570b and the negative electrode 570a shall be referred to as the electrolyte layer. The electrolyte layer of the semi-solid battery can be said to be a layer formed by film formation and can be distinguished from a liquid electrolyte layer.

[0191] Also, in this specification and the like, a semi-solid battery refers to a battery having a semi-solid material in at least one of the electrolyte layer, the positive electrode 570b, and the negative electrode 570a. Here, the semi-solid does not mean that the ratio of the solid material is 50%. The semi-solid means having the properties of a solid such as small volume change while also having some properties similar to a liquid such as flexibility. If these properties are satisfied, it may be a single material or a plurality of materials. For example, it may be a material obtained by infiltrating a liquid material into a porous solid material.

[0192] Also, in this specification and the like, a polymer electrolyte secondary battery refers to a secondary battery having a polymer in the electrolyte layer between the positive electrode 570b and the negative electrode 570a. The polymer electrolyte secondary battery includes dry (or true) polymer electrolyte batteries and polymer gel electrolyte batteries. (or true) polymer electrolyte batteries, and polymer gel electrolyte batteries.

[0193] The electrolyte 576 has a lithium ion conductive polymer and a lithium salt.

[0194] ​In this specification and the like, the lithium ion conductive polymer is a polymer having conductivity of cations such as lithium. More specifically, it is a polymer compound having a polar group capable of coordinating cations. As the polar group, it preferably has an ether group, an ester group, a nitrile group, a carbonyl group, a siloxane, or the like.

[0195] Examples of the lithium ion conductive polymer include polyethylene oxide (PEO), a derivative having polyethylene oxide as the main chain, polypropylene oxide, polyacrylate ester, polymethacrylate ester, polysiloxane, polyphosphazene, and the like can be used.

[0196] The lithium ion conductive polymer may be branched or crosslinked. It may also be a copolymer. The molecular weight is preferably, for example, 10,000 or more, and more preferably 100,000 or more.

[0197] In the lithium ion conductive polymer, lithium ions move while changing polar groups that interact more with the segmental motion (also called segment motion) of the polymer chain. For example, in the case of PEO, lithium ions move while changing oxygen that interacts with the segmental motion of the ether chain. When the temperature is close to or higher than the melting point or softening point of the lithium ion conductive polymer, the crystal region dissolves and the amorphous region increases, and the motion of the ether chain becomes active, so the ionic conductivity increases. Therefore, when using PEO as the lithium ion conductive polymer, it is preferable to perform charge and discharge at 60 °C or higher.

[0198] According to the Shannon ionic radius (Shannon et al., Acta A 32(1 76) 751.), the radius of the monovalent lithium ion is 0.0590 nm in the case of 4 coordination, 0.076 nm in the case of 6 coordination, and 0.092 nm in the case of 8 coordination. Also, the radius of the divalent oxygen ion is 0.135 nm in the case of 2 coordination, 0.136 nm in the case of 3 coordination, 0.138 nm in the case of 4 coordination , 0.140 nm in the case of 6 coordination, and 0.142 nm in the case of 8 coordination . The distance between the polar groups of adjacent lithium ion-conductive polymer chains is preferably greater than the distance at which lithium ions and the anions of the polar groups can stably exist while maintaining the ionic radius as described above . And it is preferably a distance at which sufficient interaction occurs between the lithium ions and the polar groups. However, as described above, due to the occurrence of segmental motion , it is not necessary to always maintain a constant distance. It is sufficient if there is an appropriate distance when the lithium ions pass through .

[0199] Also, as the lithium salt, for example, a compound having at least one or more of phosphorus, fluorine, nitrogen, sulfur, oxygen , chlorine, arsenic, boron, aluminum, bromine, iodine together with lithium can be used . For example, LiPF6, LiN(FSO2)2 (lithium bis (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 bis ​​(Trifluoromethanesulfonyl)imide, LiTFSA, LiN(C4F9SO2) (CF3SO2), LiN(C2F5SO2)2, lithium bis(oxalate) borate One kind of lithium salts such as LiBOB, or two or more of these can be used in any combination and ratio.

[0200] In particular, when using LiFSI, the low-temperature characteristics are good, which is preferable. Also, LiFSI and Li TFSA are less likely to react with water compared to LiPF6 etc. Therefore, when fabricating the electrode and the electrolyte layer using LiFSI, it becomes easier to control the dew point. For example, not only in an inert atmosphere such as argon with water removed as much as possible, and a dry room with controlled dew point, but also it can be handled in a normal atmosphere. Therefore, the productivity is improved, which is preferable. Also, when using highly dissociative and plasticizing-effect Li salts such as LiFSI and LiTFSA, when using lithium conduction utilizing the segmental motion of the ether chain, it can be used in a wide temperature range, so it is particularly preferable.

[0201] By having no or very little organic solvent, a secondary battery that is less likely to catch fire or ignite can be formed, and the safety is improved, which is preferable.

[0202] [Outer package] As the outer package of the secondary battery, for example, metal materials such as aluminum and resin materials can be used. Also, a film-shaped outer package can be used. As the film, for example, on a film made of materials such as polyethylene, polypropylene, polycarbonate, ionomer, polyamide, etc., aluminum, stainless steel, copper, nickel etc. with excellent flexibility A metal thin film is provided, and further, an insulating synthetic resin film such as a polyamide resin or a polyester resin is provided as the outer surface of the exterior body on the metal thin film. A three-layer film can be used. Moreover, it is preferable to use a fluororesin film as the film. The fluororesin film has high stability against acids, alkalis, organic solvents, etc., suppresses side reactions, corrosion, etc. associated with the reaction of the secondary battery, etc., and can realize an excellent secondary battery. Examples of the fluororesin film include PTFE (polytetrafluoroethylene), PFA (perfluoroalkoxyalkane: copolymer of tetrafluoroethylene and perfluoroalkyl vinyl ether), FEP (perfluoroethylene propene copolymer: copolymer of tetrafluoroethylene and hexafluoropropylene), ETFE (ethylene tetrafluoroethylene copolymer: copolymer of tetrafluoroethylene and ethylene), etc. This embodiment can be used in appropriate combination with other embodiments. (Embodiment 2) In this embodiment, the positive electrode and the positive electrode active material composite of one aspect of the present invention will be described. An example of the positive electrode 570b of one aspect of the present invention is shown in FIG. 9. The positive electrode 570b has a positive electrode current collector 571b and a positive electrode active material layer 572b. The positive electrode active material layer 572b has a positive electrode active material composite 100z. As the positive electrode active material composite 100z, for example, as shown in FIGS. 10A1 and 10A2, it has a first active material 100x and a second active material 100y capable of occluding and releasing carrier ions. In FIG. 9, as the conductive material, a graphene compound 102 and carbon are used.

[0203]

[0204]

[0205] Although an example using acetylene black 103 is shown, when the positive electrode active material composite 100z has sufficient electron conductivity, it is not necessary to use a conductive material in the positive electrode active material layer 572b. Also, the type of conductive material is not limited to the example shown in FIG. 9, and only carbon fibers such as graphene compounds, carbon black, or carbon nanotubes may be used, or carbon fibers such as carbon nanotubes and carbon black may be used in combination. Although not shown in FIG. 9, the positive electrode active material layer 572b preferably has a binder. As the binder, polymer materials such as polyvinylidene fluoride and molecular crystal electrolytes such as Li(FSI)(SN)2 can be used.

[0206] Also, the positive electrode active material composite 100z is arranged in a state where electron transfer with the positive electrode current collector 571b is possible. That is, the positive electrode active material composite 100z has a configuration in electrical contact with the positive electrode current collector 571b. An undercoat layer may be provided on the positive electrode current collector 571b. In this case, the positive electrode active material composite 100z has a configuration in electrical contact with the positive electrode current collector 571b via the undercoat layer. Also, the positive electrode active material composite 100z may have a configuration in electrical contact with the positive electrode current collector 571 b via a conductive material. b.

[0207] Note that the density of the positive electrode active material layer 572b is preferably 3.0 g / cm 3 or more, more preferably 3.5 g / cm 3 or more, and even more preferably 3.8 g / cm 3 or more. Therefore, in order to increase the density of the positive electrode active material layer 572b, pressing treatment may be performed. However, when performing pressing treatment, the first active material 100x and the positive electrode active material composite described later ​​​​​It is desirable to set the pressing conditions appropriately so as not to damage the structure of the 100z. .

[0208] [Cathode active material composite] 10A1 to 10C2 are schematic cross-sectional views illustrating a positive electrode active material composite 100z. It 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. FIG. 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 configuration. Alternatively, a configuration in which a plurality of first active materials 100x are covered with a second active material 100y may be used. .

[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 functioning as the positive electrode active material may be In a state where at least a portion of the surface, preferably substantially the entire surface, is covered with the second active material 100y. In this case, 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 suppress the transition metal element and / or oxygen from being released from the first active material 100x. This suppresses the capacity loss caused by repeated charging and discharging. Even when covered with the second electrochemically stable active material 100y, the positive electrode active material composite 100z of one aspect of the present invention used in a secondary battery has effects such as improved stability at high temperatures and improved fire resistance. It becomes possible to obtain effects such as the above.

[0211] Figures 10B1 and 10B2 are diagrams for explaining a positive electrode active material composite 100z having a first active material 100x that functions as a positive electrode active material and a glass 101 that covers at least a part of the first active material 100x. In Figure 10B1, a configuration in which one first active material 100x is covered with glass 101 is shown, but the present invention is not limited to this, and a configuration in which a plurality of first active materials 100x are covered with glass 101 may be used. 100x and a glass 101 that covers at least a part of the first active material 100x. In Figure 10B1, a configuration in which one first active material 100x is covered with glass 101 is shown, but the present invention is not limited to this, and a configuration in which a plurality of first active materials 100x are covered with glass 101 may be used. 0z. In Figure 10B1, a configuration in which one first active material 100x is covered with glass 101 is shown, but the present invention is not limited to this, and a configuration in which a plurality of first active materials 100x are covered with glass 101 may be used. active materials 100x may be covered with glass 101. active materials 100x may be covered with glass 101.

[0212] For example, as shown in Figure 10B2, at least a part of the first active material 100xa and the first active material 100xb may be covered with glass 101. In Figure 10B2, a case where at least a part of the first active material 100xa and the first active material 100xb are in contact is shown, but the first active material 100xa and the first active material 100xb may not be in direct contact. When at least a part, preferably substantially the whole, of the particle surface of the particulate first active material 100x that functions as a positive electrode active material is covered with glass 101, the region where the first active material 100x is in direct contact with the electrolyte 576 decreases, and it is possible to suppress the desorption of transition metal elements and / or oxygen from the first active material 100x in a high voltage charged state. Therefore, it is possible to suppress the capacity reduction due to repeated charge and discharge. Also, even in a high temperature and high voltage charged state, by being covered with the electrochemically stable glass 101, the positive electrode active material composite 100z of one aspect of the present invention 0z. In Figure 10B2, a case where at least a part of the first active material 100xa and the first active material 100xb are in contact is shown, but the first active material 100xa and the first active material 100xb may not be in direct contact. When at least a part, preferably substantially the whole, of the particle surface of the particulate first active material 100x that functions as a positive electrode active material is covered with glass 101, the region where the first active material 100x is in direct contact with the electrolyte 576 decreases, and it is possible to suppress the desorption of transition metal elements and / or oxygen from the first active material 100x in a high voltage charged state. Therefore, it is possible to suppress the capacity reduction due to repeated charge and discharge. Also, even in a high temperature and high voltage charged state, by being covered with the electrochemically stable glass 101, the positive electrode active material composite 100z of one aspect of the present invention 0z. In Figure 10B2, a case where at least a part of the first active material 100xa and the first active material 100xb are in contact is shown, but the first active material 100xa and the first active material 100xb may not be in direct contact. When at least a part, preferably substantially the whole, of the particle surface of the particulate first active material 100x that functions as a positive electrode active material is covered with glass 101, the region where the first active material 100x is in direct contact with the electrolyte 576 decreases, and it is possible to suppress the desorption of transition metal elements and / or oxygen from the first active material 100x in a high voltage charged state. Therefore, it is possible to suppress the capacity reduction due to repeated charge and discharge. Also, even in a high temperature and high voltage charged state, by being covered with the electrochemically stable glass 101, the positive electrode active material composite 100z of one aspect of the present invention 0z. In Figure 10B2, a case where at least a part of the first active material 100xa and the first active material 100xb are in contact is shown, but the first active material 100xa and the first active material 100xb may not be in direct contact. When at least a part, preferably substantially the whole, of the particle surface of the particulate first active material 100x that functions as a positive electrode active material is covered with glass 101, the region where the first active material 100x is in direct contact with the electrolyte 576 decreases, and it is possible to suppress the desorption of transition metal elements and / or oxygen from the first active material 100x in a high voltage charged state. Therefore, it is possible to suppress the capacity reduction due to repeated charge and discharge. Also, even in a high temperature and high voltage charged state, by being covered with the electrochemically stable glass 101, the positive electrode active material composite 100z of one aspect of the present invention 0z. In Figure 10B2, a case where at least a part of the first active material 100xa and the first active material 100xb are in contact is shown, but the first active material 100xa and the first active material 100xb may not be in direct contact. When at least a part, preferably substantially the whole, of the particle surface of the particulate first active material 100x that functions as a positive electrode active material is covered with glass 101, the region where the first active material 100x is in direct contact with the electrolyte 576 decreases, and it is possible to suppress the desorption of transition metal elements and / or oxygen from the first active material 100x in a high voltage charged state. Therefore, it is possible to suppress the capacity reduction due to repeated charge and discharge. Also, even in a high temperature and high voltage charged state, by being covered with the electrochemically stable glass 101, the positive electrode active material composite 100z of one aspect of the present invention 0z. In Figure 10B2, a case where at least a part of the first active material 100xa and the first active material 100xb are in contact is shown, but the first active material 100xa and the first active material 100xb may not be in direct contact. When at least a part, preferably substantially the whole, of the particle surface of the particulate first active material 100x that functions as a positive electrode active material is covered with glass 101, the region where the first active material 100x is in direct contact with the electrolyte 576 decreases, and it is possible to suppress the desorption of transition metal elements and / or oxygen from the first active material 100x in a high voltage charged state. Therefore, it is possible to suppress the capacity reduction due to repeated charge and discharge. Also, even in a high temperature and high voltage charged state, by being covered with the electrochemically stable glass 101, the positive electrode active material composite 100z of one aspect of the present invention 0z. In Figure 10B2, a case where at least a part of the first active material 100xa and the first active material 100xb are in contact is shown, but the first active material 100xa and the first active material 100xb may not be in direct contact. When at least a part, preferably substantially the whole, of the particle surface of the particulate first active material 100x that functions as a positive electrode active material is covered with glass 101, the region where the first active material 100x is in direct contact with the electrolyte 576 decreases, and it is possible to suppress the desorption of transition metal elements and / or oxygen from the first active material 100x in a high voltage charged state. Therefore, it is possible to suppress the capacity reduction due to repeated charge and discharge. Also, even in a high temperature and high voltage charged state, by being covered with the electrochemically stable glass 101, the positive electrode active material composite 100z of one aspect of the present invention 0z. In Figure 10B2, a case where at least a part of the first active material 100xa and the first active material 100xb are in contact is shown, but the first active material 100xa and the first active material 100xb may not be in direct contact. When at least a part, preferably substantially the whole, of the particle surface of the particulate first active material 100x that functions as a positive electrode active material is covered with glass 101, the region where the first active material 100x is in direct contact with the electrolyte 576 decreases, and it is possible to suppress the desorption of transition metal elements and / or oxygen from the first active material 100x in a high voltage charged state. Therefore, it is possible to suppress the capacity reduction due to repeated charge and discharge. Also, even in a high temperature and high voltage charged state, by being covered with the electrochemically stable glass 101, the positive electrode active material composite 100z of one aspect of the present invention 0z. In Figure 10B2, a case where at least a part of the first active material 100xa and the first active material 100xb are in contact is shown, but the first active material 100xa and the first active material 100xb may not be in direct contact. When at least a part, preferably substantially the whole, of the particle surface of the particulate first active material 100x that functions as a positive electrode active material is covered with glass 101, the region where the first active material 100x is in direct contact with the electrolyte 576 decreases, and it is possible to suppress the desorption of transition metal elements and / or oxygen from the first active material 100x in a high voltage charged state. Therefore, it is possible to suppress the capacity reduction due to repeated charge and discharge. Also, even in a high temperature and high voltage charged state, by being covered with the electrochemically stable glass 101, the positive electrode active material composite 100z of one aspect of the present invention 0z. In Figure 10B2, a case where at least a part of the first active material 100xa and the first active material 100xb are in contact is shown, but the first active material 100xa and the first active material 100xb may not be in direct contact. When at least a part, preferably substantially the whole, of the particle surface of the particulate first active material 100x that functions as a positive electrode active material is covered with glass 101, the region where the first active material 100x is in direct contact with the electrolyte 576 decreases, and it is possible to suppress the desorption of transition metal elements and / or oxygen from the first active material 100x in a high voltage charged state. Therefore, it is possible to suppress the capacity reduction due to repeated charge and discharge. Also, even in a high temperature and high voltage charged state, by being covered with the electrochemically stable glass 101, the positive electrode active material composite 100z of one aspect of the present invention The secondary battery using this can achieve effects such as improved stability at high temperatures and improved fire resistance. This becomes possible.

[0213] FIG. 10C1 and FIG. 10C2 are diagrams for explaining a positive electrode active material composite 100z having a first active material 100x that functions as a positive electrode active material and a second active material 100y that is in contact with the first active material 100x via a glass 101 that covers at least a part of the first active material 100x. The first active material 100x and the second active material 100y in contact with the first active material 100x via the glass 101 that covers at least a part of the first active material 100x. x. Note that in FIG. 10C1, a configuration in which one first active material 100x is covered with the glass 101 is shown, but the present invention is not limited to this, and a configuration in which a plurality of first active materials 100x are covered with the glass 101 may be used. For example, as shown in FIG. 10C2, at least a part of the first active material 100xa and the first active material 100xb may be covered with the glass 101. In FIG. 10C2, a case where at least a part of the first active material 100xa and the first active material 100xb are in contact is shown, but the first active material 100xa and the first active material 100xb may not be in direct contact. In the positive electrode active material composite 100z having the second active material 100y in contact with the first active material 100x via the glass 101 in a state where at least a part, preferably substantially the whole, of the particle surface of the particulate first active material 100x that functions as a positive electrode active material is covered with the glass 101, the region where the first active material 100x is in direct contact with the electrolyte 576 is reduced. Therefore, it is possible to suppress the desorption of transition metal elements and / or oxygen from the first active material 100x in a high voltage charging state, and thus it is possible to suppress the capacity reduction due to repeated charge and discharge. Also, the glass 101 that is electrochemically stable even in a high temperature and high voltage state and the second active material 100y that is stable even in a high charging voltage state.

[0214] For example, as shown in FIG. 10C2, at least a part of the first active material 100xa and the first active material 100xb may be covered with the glass 101. In FIG. 10C2, a case where at least a part of the first active material 100xa and the first active material 100xb are in contact is shown, but the first active material 100xa and the first active material 100xb may not be in direct contact. For example, as shown in FIG. 10C2, at least a part of the first active material 100xa and the first active material 100xb may be covered with the glass 101. In FIG. 10C2, a case where at least a part of the first active material 100xa and the first active material 100xb are in contact is shown, but the first active material 100xa and the first active material 100xb may not be in direct contact. In the positive electrode active material composite 100z having the second active material 100y in contact with the first active material 100x via the glass 101 in a state where at least a part, preferably substantially the whole, of the particle surface of the particulate first active material 100x that functions as a positive electrode active material is covered with the glass 101, the region where the first active material 100x is in direct contact with the electrolyte 576 is reduced. Therefore, it is possible to suppress the desorption of transition metal elements and / or oxygen from the first active material 100x in a high voltage charging state, and thus it is possible to suppress the capacity reduction due to repeated charge and discharge. Also, the glass 101 that is electrochemically stable even in a high temperature and high voltage state and the second active material 100y that is stable even in a high charging voltage state. In the positive electrode active material composite 100z having the second active material 100y in contact with the first active material 100x via the glass 101 in a state where at least a part, preferably substantially the whole, of the particle surface of the particulate first active material 100x that functions as a positive electrode active material is covered with the glass 101, the region where the first active material 100x is in direct contact with the electrolyte 576 is reduced. Therefore, it is possible to suppress the desorption of transition metal elements and / or oxygen from the first active material 100x in a high voltage charging state, and thus it is possible to suppress the capacity reduction due to repeated charge and discharge. Also, the glass 101 that is electrochemically stable even in a high temperature and high voltage state and the second active material 100y that is stable even in a high charging voltage state. In the positive electrode active material composite 100z having the second active material 100y in contact with the first active material 100x via the glass 101 in a state where at least a part, preferably substantially the whole, of the particle surface of the particulate first active material 100x that functions as a positive electrode active material is covered with the glass 101, the region where the first active material 100x is in direct contact with the electrolyte 576 is reduced. Therefore, it is possible to suppress the desorption of transition metal elements and / or oxygen from the first active material 100x in a high voltage charging state, and thus it is possible to suppress the capacity reduction due to repeated charge and discharge. Also, the glass 101 that is electrochemically stable even in a high temperature and high voltage state and the second active material 100y that is stable even in a high charging voltage state. Therefore, it is possible to suppress the desorption of transition metal elements and / or oxygen from the first active material 100x in a high voltage charging state, and thus it is possible to suppress the capacity reduction due to repeated charge and discharge. Also, the glass 101 that is electrochemically stable even in a high temperature and high voltage state and the second active material 100y that is stable even in a high charging voltage state. Therefore, it is possible to suppress the desorption of transition metal elements and / or oxygen from the first active material 100x in a high voltage charging state, and thus it is possible to suppress the capacity reduction due to repeated charge and discharge. Also, the glass 101 that is electrochemically stable even in a high temperature and high voltage state and the second active material 100y that is stable even in a high charging voltage state. In the positive electrode active material composite 100z having the second active material 100y in contact with the first active material 100x via the glass 101 in a state where at least a part, preferably substantially the whole, of the particle surface of the particulate first active material 100x that functions as a positive electrode active material is covered with the glass 101, the region where the first active material 100x is in direct contact with the electrolyte 576 is reduced. By being covered with the fixed second active material 100y, the positive electrode active material composite 100 of one aspect of the present invention The secondary battery using z can obtain effects such as improved stability at high temperatures and improved fire resistance It becomes possible.

[0215] In the positive electrode active material composite 100z shown in FIGS. 10A1 to 10C2, as the first active material 100x, lithium cobaltate having magnesium and fluorine, magnesium, Lithium cobaltate having fluorine, aluminum, and nickel, and nickel: Cobalt:Manganese = 8:1:1, and nickel:cobalt:manganese = 9:0.5: Lithium nickel-cobalt-manganese oxide such as 0.5 and other molar ratios, etc., by using a material excellent in stability in a high voltage charged state The durability and stability of the above-mentioned positive electrode active material composite 100z during high voltage charging can be further improved. In addition, the heat resistance and / or fire resistance of the secondary battery using the above-mentioned positive electrode active material Composite 100z can be further improved. Composite 100z can be further improved. It can be done.

[0216] Incidentally, lithium cobaltate having magnesium, fluorine, aluminum, and nickel M has a lot of magnesium, fluorine, or aluminum in the surface layer portion of the positive electrode active material, and particles As a whole, nickel is widely distributed, and the charge and discharge repetition characteristics at high voltage are remarkably excellent Therefore, it is a particularly preferable material as the first active material 100x. When the surface layer portion of the positive electrode active material has a lot of magnesium, fluorine, or aluminum For example, in STEM-ED In X-ray analysis, the characteristic X-ray count number derived from magnesium, fluorine, or aluminum has a maximum value at the surface layer portion. Here, the surface layer portion refers to the positive electrode active Substance It refers to the region up to about 10 nm from the surface of the mass. In addition, the crack part of the positive electrode active material also has a surface layer part, and the crack part generated before the addition process of magnesium, fluorine, or aluminum in the production of the positive electrode active material has a surface layer part rich in magnesium, fluorine, or aluminum. The positive electrode active material composite 100z as shown in FIGS. 10A1 and 10A2 is obtained by a composite treatment using at least the first active material 100x and the second active material 100y. As the composite treatment, for example, a composite treatment by mechanical energy such as a mechanochemical method, a mechanofusion method, and a ball mill method, a composite treatment by a liquid phase reaction such as a coprecipitation method, a hydrothermal method, and a sol-gel method, and a composite treatment by a gas phase reaction such as a barrel sputtering method, an ALD (Atomic Layer Deposition) method, a vapor deposition method, and a CVD (Chemical Vapor Deposition) method can be used alone or in combination. In addition, in the composite treatment, it is preferable to perform one or more heating treatments. In this specification, the composite treatment may be referred to as a surface coating treatment or a coating treatment.

[0217] The positive electrode active material composite 100z as shown in FIGS. 10A1 and 10A2 is obtained by a composite treatment using at least the first active material 100x and the second active material 100y. As the composite treatment, for example, a composite treatment by mechanical energy such as a mechanochemical method, a mechanofusion method, and a ball mill method, a composite treatment by a liquid phase reaction such as a coprecipitation method, a hydrothermal method, and a sol-gel method, and a composite treatment by a gas phase reaction such as a barrel sputtering method, an ALD (Atomic Layer Deposition) method, a vapor deposition method, and a CVD (Chemical Vapor Deposition) method can be used alone or in combination. In addition, in the composite treatment, it is preferable to perform one or more heating treatments. In this specification, the composite treatment may be referred to as a surface coating treatment or a coating treatment. The positive electrode active material composite 100z as shown in FIGS. 10B1 and 10B2 is obtained by a composite treatment using at least the first active material 100x and the glass 101. As the composite treatment, for example, a composite treatment by mechanical energy such as a mechanochemical method, a mechanofusion method, and a ball mill method, a composite treatment by a liquid phase reaction such as a coprecipitation method, a hydrothermal method, and a sol-gel method, and a composite treatment by a gas phase reaction such as a barrel sputtering method, an ALD method, a vapor deposition method, and a CVD (Chemical Vapor Deposition) method can be used alone or in combination. In addition, in the composite treatment, it is preferable to perform one or more heating treatments. In this specification, the composite treatment may be referred to as a surface coating treatment or a coating treatment. The positive electrode active material composite 100z as shown in FIGS. 10B1 and 10B2 is obtained by a composite treatment using at least the first active material 100x and the glass 101. As the composite treatment, for example, a composite treatment by mechanical energy such as a mechanochemical method, a mechanofusion method, and a ball mill method, a composite treatment by a liquid phase reaction such as a coprecipitation method, a hydrothermal method, and a sol-gel method, and a composite treatment by a gas phase reaction such as a barrel sputtering method, an ALD method, a vapor deposition method, and a CVD (Chemical Vapor Deposition) method can be used alone or in combination.

[0218] The positive electrode active material composite 100z as shown in FIGS. 10B1 and 10B2 is obtained by a composite treatment using at least the first active material 100x and the glass 101. As the composite treatment, for example, a composite treatment by mechanical energy such as a mechanochemical method, a mechanofusion method, and a ball mill method, a composite treatment by a liquid phase reaction such as a coprecipitation method, a hydrothermal method, and a sol-gel method, and a composite treatment by a gas phase reaction such as a barrel sputtering method, an ALD method, a vapor deposition method, and a CVD (Chemical Vapor Deposition) method can be used alone or in combination. In addition, in the composite treatment, it is preferable to perform one or more heating treatments. In this specification, the composite treatment may be referred to as a surface coating treatment or a coating treatment. (Chemical Vapor Deposition) method can be used alone or in combination. It is possible to use one or more of the composite treatment methods such as vapor-phase reaction methods such as the VD method. In the composite treatment, it is preferable to perform heat treatment once or multiple times.

[0219] In addition, as shown in FIGS. 10C1 and 10C2, the positive electrode active material composite 100z is obtained by a composite treatment using at least the first active material 100x, the second active material 100y, and glass 101. Examples of the composite treatment include composite treatment methods using mechanical energy such as the mechanochemical method, the mechanofusion method, and the ball milling method, coprecipitation methods, hydrothermal methods, and composite treatment methods using liquid-phase reactions such as the sol-gel method, and composite treatment methods using vapor-phase reactions such as the barrel sputtering method, the ALD method, the vapor deposition method, and the CVD method. One or more of these composite treatment methods can be used. In the composite treatment, it is preferable to perform heat treatment once or multiple times.

[0220] As described above, in the positive electrode active material composite 100z according to one aspect of the present invention, the first active material 100x and the electrolyte 576 are not in contact with each other, so that the deterioration of the first active material 100x caused by the electrolyte is suppressed. The deterioration may be caused by defects generated in the first active material 100x. For example, there are defects called pits. Pits refer to regions where several layers of the main components of the first active material 100x, such as cobalt and oxygen, are missing in the charge-discharge cycle test. For example, cobalt may elute into the electrolyte. Pits may progress in the charge-discharge cycle test, and the pits may progress inwardly in the active material. The opening shape of the pits is not circular but has a shape like a groove with depth. The electrolyte 576 and the first active material The structure in which the 100x does not come into contact with the 100x can suppress the occurrence and progression of the above 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 structure of glass 1. The present invention is not limited to a case in which the active material 100 and the second active material 100y are formed as a double structure. As another example of the positive electrode active material composite 100z according to one embodiment, a positive electrode active material composite 100z having a 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] As another embodiment of the positive electrode active material composite 100z of the present invention, The graphene compound 102 may be present on the surface portion or the glass active material mixed layer. Instead of the graphene compound 102, carbon such as carbon black or carbon nanotubes may be used. Natural fibers 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, V2O5, etc., and a material having one or more selected from Li7P3S 11 , or Li 1+x+y Al x Ti 2-x S y P 3-y O 12 (0 <x<2、0<y<3 , etc. can be used. The material having an amorphous part can be used in an entirely amorphous state or in a state of crystallized glass (also referred to as glass ceramics) in which a part is crystallized. It is desirable that the glass 101 has lithium ion conductivity. Lithium ion conductivity means having lithium ion diffusivity and lithium ion penetrability. Also, the glass 101 preferably has a melting point of 800 °C or lower, more preferably 500 °C or lower. Also, it is preferable that the glass 101 has electronic conductivity. Also, the glass 101 preferably has a softening point of 800 °C or lower. For example, Li2 O - B2O3 - SiO2 - based glass can be used.

[0224] Although it is desirable that the glass 101 has electronic conductivity, when the electronic conductivity of the glass 101 is low, a carbon fiber conductive material such as a graphene compound, carbon black, or carbon nanotubes is mixed with the glass 101 to impart electronic conductivity to the glass 101.

[0225] Note that at least a part of the surface of the positive electrode active material composite 100z may have a structure covered with a graphene compound. Preferably, a structure in which 80% or more of the particle surface of the positive electrode active material composite 100z and / or the aggregate having the positive electrode active material composite 100z is covered with a graphene compound is preferable. The graphene compound will be described later.

[0226] Also, the positive electrode active material composite 100z preferably has a configuration covered with a molecular crystal electrolyte. The molecular crystal electrolyte can function as a binder for the positive electrode active material layer 572b. It is preferable that the molecular crystal electrolyte is a material having high ionic conductivity and is covered with the molecular crystal electrolyte. The positive electrode active material composite 100z can exchange carriers and ions with the electrolyte 576.

[0227] [Positive Electrode Active Material] As the first active material 100x, a composite oxide represented by LiM1O2 (M1 is one or more selected from Fe, Ni, Co, Mn) having a layered rock salt type crystal structure can be used. Further, as the first active material 100x, a composite oxide represented by LiM1O2 added with an additive element X can be used. The additive element X included in the first active material 100x is preferably one or more selected from nickel, cobalt, magnesium, calcium, chlorine, fluorine, aluminum, manganese, titanium, zirconium, yttrium, vanadium, iron, chromium, niobium, lanthanum, hafnium, zinc, silicon, sulfur, phosphorus, boron, and arsenic. These elements may further stabilize the crystal structure of the first active material 100x. That is, the first active material 100x can include lithium cobaltate having magnesium and fluorine, lithium cobaltate having magnesium, fluorine, aluminum, and nickel, lithium cobaltate having magnesium, fluorine, and titanium, lithium nickel-cobaltate having magnesium and fluorine, lithium cobalt-aluminate having magnesium and fluorine, lithium nickel-cobalt-aluminate, lithium nickel-cobalt-aluminate having magnesium and fluorine, lithium nickel-cobalt-manganate having magnesium and fluorine, etc. Note that the transition metal ratio of lithium nickel-cobalt-manganate is ​​​​​​​​​​​​​​A high nickel ratio is preferred. For example, materials with a molar ratio of nickel:cobalt:manganese = 8:1:1, nickel:cobalt:manganese = 9:0.5:0.5 are preferred. Also, as the above-mentioned lithium nickel-cobalt-manganese oxide, it preferably has lithium nickel-cobalt-manganese oxide containing calcium. In addition, as the first active material 100x, secondary particles of a composite oxide represented by LiM1O2 (M1 is one or more selected from Fe, Ni, Co, Mn) coated with a metal oxide may be used. As the metal oxide, one or more metal oxides selected from Al, Ti, Nb, Zr, La, and Li can be used. For example, secondary particles of a composite oxide represented by LiM1O2 (M1 is one or more selected from Fe, Ni, Co, Mn) coated with aluminum oxide, a metal oxide-coated composite oxide can be used as the first active material 100x. For example, secondary particles of nickel-cobalt-manganese oxide with a molar ratio of nickel:cobalt:manganese = 8:1:1, nickel:cobalt:manganese = 9:0.5:0.5 coated with aluminum oxide, a metal oxide-coated composite oxide can be used. Here, the coating layer is preferably thin, for example, 1 nm or more and 200 nm or less, more preferably 1 nm or more and 100 nm or less. Also, as the above-mentioned lithium nickel-cobalt-manganese oxide, it preferably has lithium nickel-cobalt-manganese oxide containing calcium. As the first active material 100x, the positive electrode active material 100 described in the following embodiments can be used.

[0228] In addition, as the first active material 100x, secondary particles of a composite oxide represented by LiM1O2 (M1 is one or more selected from Fe, Ni, Co, Mn) coated with a metal oxide may be used. As the metal oxide, one or more metal oxides selected from Al, Ti, Nb, Zr, La, and Li can be used. For example, secondary particles of a composite oxide represented by LiM1O2 (M1 is one or more selected from Fe, Ni, Co, Mn) coated with aluminum oxide, a metal oxide-coated composite oxide can be used as the first active material 100x. For example, nickel:cobalt:manganese = 8:1:1, nickel:cobalt:manganese = 9:0.5:0.5 molar ratio of nickel-cobalt-manganese oxide secondary particles coated with aluminum oxide, a metal oxide-coated composite oxide can be used. Here, the coating layer is preferably thin, for example, 1 nm or more and 200 nm or less, more preferably 1 nm or more and 100 nm or less. Also, as the above-mentioned lithium nickel-cobalt-manganese oxide, it preferably has lithium nickel-cobalt-manganese oxide containing calcium. For example, nickel:cobalt:manganese = 8:1:1, nickel:cobalt:manganese = 9:0.5:0.5 molar ratio of nickel-cobalt-manganese oxide secondary particles coated with aluminum oxide, a metal oxide-coated composite oxide can be used. Here, the coating layer is preferably thin, for example, 1 nm or more and 200 nm or less, more preferably 1 nm or more and 100 nm or less. Also, as the above-mentioned lithium nickel-cobalt-manganese oxide, it preferably has lithium nickel-cobalt-manganese oxide containing calcium. Here, the coating layer is preferably thin, for example, 1 nm or more and 200 nm or less, more preferably 1 nm or more and 100 nm or less. Also, as the above-mentioned lithium nickel-cobalt-manganese oxide, it preferably has lithium nickel-cobalt-manganese oxide containing calcium. In addition, as the first active material 100x, the positive electrode active material 100 described in the following embodiments can be used. As the above-mentioned lithium nickel-cobalt-manganese oxide, it preferably has lithium nickel-cobalt-manganese oxide containing calcium. As the first active material 100x, the positive electrode active material 100 described in the following embodiments can be used.

[0229] As the first active material 100x, the positive electrode active material 100 described in the following embodiments can be used. As the first active material 100x, the positive electrode active material 100 described in the following embodiments can be used.

[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 +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 surface of the particles 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, graphites such as artificial graphite and natural graphite, carbon nanofibers, and the like. Either one or two or more of carbon fibers such as carbon nanotubes and graphene compounds can be used.

[0232] This embodiment can be used in appropriate combination with other embodiments.

[0233] (Embodiment 3) In this embodiment, one aspect of the positive electrode active material of the present invention will be described with reference to FIGS. 11 to 17. Explanation.

[0234] In addition, in this specification and the like, crystal planes and directions are indicated by Miller indices. The notation of crystal planes and directions is, in crystallography, a bar is placed above the number, but in this specification and the like, due to the constraints of the application notation, instead of placing a bar above the number, a -(minus sign) may be placed in front of the number in some cases. In addition, individual orientations indicating directions within a crystal are represented by [ ], set orientations indicating all equivalent directions are represented by < >, individual planes indicating crystal planes are represented by ( ), and set planes having equivalent symmetries are represented by {}, respectively. For the Miller indices of trigonal and hexagonal crystals including R-3m, (h kl) may be used in addition to (hkil). Here, i is -(h + k). In addition, in this specification and the like, the layered rock salt-type crystal structure of a composite oxide containing lithium and a transition metal has a rock salt-type ion arrangement in which cations and anions are alternately arranged, and the transition metal and lithium are regularly arranged to form a two-dimensional plane, so that the two-dimensional diffusion of lithium is possible. A crystal structure is meant. Note that there may be defects such as deficiencies of cations or anions. In addition, strictly speaking, the layered rock salt-type crystal structure may be a structure in which the lattice of the rock salt-type crystal is distorted. In addition, in this specification and the like, the layered rock salt-type crystal structure means a crystal structure having a rock salt-type ion arrangement in which cations and anions are alternately arranged, and a two-dimensional plane is formed by the regular arrangement of transition metals and lithium, so that two-dimensional diffusion of lithium is possible. Note that there may be defects such as deficiencies of cations or anions.

[0235] In addition, in this specification and the like, the layered rock salt-type crystal structure of a composite oxide containing lithium and a transition metal has a rock salt-type ion arrangement in which cations and anions are alternately arranged, and the transition metal and lithium are regularly arranged to form a two-dimensional plane, so that the two-dimensional diffusion of lithium is possible. A crystal structure is meant. Note that there may be defects such as deficiencies of cations or anions. metal and lithium are regularly arranged to form a two-dimensional plane, so that the two-dimensional diffusion of lithium is possible. A crystal structure is meant. Note that there may be defects such as deficiencies of cations or anions. metal and lithium are regularly arranged to form a two-dimensional plane, so that the two-dimensional diffusion of lithium is possible. A crystal structure is meant. Note that there may be defects such as deficiencies of cations or anions. In addition, strictly speaking, the layered rock salt-type crystal structure may be a structure in which the lattice of the rock salt-type crystal is distorted. In some cases.

[0236] In addition, in this specification and the like, the rock salt-type crystal structure refers to a structure in which cations and anions are alternately arranged. Even if there are defects in cations or anions in a part of the crystal structure, it is acceptable. That is, it is a structure in which cations and anions are alternately arranged. Even if there are defects in cations or anions in a part of the crystal structure, it is acceptable. It is acceptable.

[0237] In addition, in this specification and the like, the theoretical capacity of the positive electrode active material refers to the amount of electricity when all the lithium that can be inserted and extracted from the positive electrode active material has been extracted. For example, the theoretical capacity of LiFePO4 is 170 mAh / g, the theoretical capacity of LiCoO2 is 274 mAh / g, the theoretical capacity of LiNiO2 is 275 mAh / g, and the theoretical capacity of LiMn2O4 is 148 mAh / g. That is, it refers to the amount of electricity when all the lithium that can be inserted and extracted from the positive electrode active material has been extracted. For example, the theoretical capacity of LiFePO4 is 170 mAh / g, the theoretical capacity of LiCoO2 is 274 mAh / g, the theoretical capacity of LiNiO2 is 275 mAh / g, and the theoretical capacity of LiMn2O4 is 148 mAh / g. is 170 mAh / g, the theoretical capacity of LiCoO2 is 274 mAh / g, the theoretical capacity of LiNiO2 is 275 mAh / g, and the theoretical capacity of LiMn2O4 is 148 mAh / g. It is 148 mAh / g.

[0238] In addition, the degree to which lithium that can be inserted and extracted remains in the positive electrode active material is indicated by x in the composition formula. For example, x in LiCoO2, or x in LiMO2. LiCoO2 in this specification can be appropriately read as LiMO2. x can be called the occupancy rate. In the case of the positive electrode active material in the secondary battery, x = (theoretical capacity - charged capacity) / theoretical capacity may be used. For example, when a secondary battery using LiCoO2 as the positive electrode active material is charged at 219.2 mAh / g, it can be said that LiCoO2 or x = 0.2. When x in LiCoO2 is small, for example, it means 0.1 < x ≤ 0.24. For example, x in LiCoO2, or x in LiMO2. x CoO2, or x in LiMO2. x MO2. x CoO2 can be appropriately read as LiMO2. x MO2. x can be called the occupancy rate. In the case of the positive electrode active material in the secondary battery, x = (theoretical capacity - charged capacity) / theoretical capacity may be used. For example, when a secondary battery using LiCoO2 as the positive electrode active material is charged at 219.2 mAh / g, it can be said that LiCoO2 or x = 0.2. 0.2 CoO2 or x = 0.2. x When x in LiCoO2 is small, for example, it means 0.1 < x ≤ 0.24.

[0239] When lithium cobaltate approximately satisfies the stoichiometric ratio, it is LiCoO2, and the occupancy rate of Li in lithium cobaltate is x = 1. Also, a secondary battery after discharge is also LiCoO2, and it can be said that x = 1. Here, when it is said that the discharge is completed, for example, it means a current of 100 mA / g. That is, when lithium cobaltate approximately satisfies the stoichiometric ratio, it is LiCoO2, and the occupancy rate of Li in lithium cobaltate is x = 1. Also, a secondary battery after discharge is also LiCoO2, and it can be said that x = 1. Here, when it is said that the discharge is completed, for example, it means a current of 100 mA / g. it can be said that x = 1. Here, when it is said that the discharge is completed, for example, it means a current of 100 mA / g. The term "flow" refers to a state where the voltage becomes 2.5 V (versus lithium metal) or less. In a lithium-ion secondary battery, when the occupancy rate of lithium in the lithium sites reaches x = 1 and no more lithium can enter, the voltage drops rapidly. At this time, it can be said that discharging has ended. Generally, in a lithium-ion secondary battery using LiCoO2, since the discharge voltage drops rapidly until it reaches 2.5 V, it is assumed that discharging has ended under the above conditions. In a lithium-ion secondary battery, when the occupancy rate of lithium in the lithium sites reaches x = 1 and no more lithium can enter, the voltage drops rapidly. At this time, it can be said that discharging has ended. Generally, in a lithium-ion secondary battery using LiCoO2, since the discharge voltage drops rapidly until it reaches 2.5 V, it is assumed that discharging has ended under the above conditions. In a lithium-ion secondary battery using LiCoO2, since the discharge voltage drops rapidly until it reaches 2.5 V, it is assumed that discharging has ended under the above conditions. At this time, it can be said that discharging has ended. Generally, in a lithium-ion secondary battery using LiCoO2, since the discharge voltage drops rapidly until it reaches 2.5 V, it is assumed that discharging has ended under the above conditions.

[0240] Also, in this specification and the like, the state where all the lithium that can be inserted and removed from the positive electrode active material is inserted is defined as a state of charge (SOC) of 0, and the state where all the lithium that can be inserted and removed from the positive electrode active material has been removed is defined as a state of charge (SOC) of 1. Also, in this specification and the like, the state where all the lithium that can be inserted and removed from the positive electrode active material is inserted is defined as a state of charge (SOC) of 0, and the state where all the lithium that can be inserted and removed from the positive electrode active material has been removed is defined as a state of charge (SOC) of 1. Also, in this specification and the like, the state where all the lithium that can be inserted and removed from the positive electrode active material is inserted is defined as a state of charge (SOC) of 0, and the state where all the lithium that can be inserted and removed from the positive electrode active material has been removed is defined as a state of charge (SOC) of 1.

[0241] [Positive Electrode Active Material] A positive electrode active material according to one embodiment of the present invention will be described with reference to FIGS. 11 to 15.

[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 A-B in FIG. 11A is shown in FIG. 11B. A schematic cross-sectional view taken along line A-B in FIG. 11A is shown in FIG. 11B.

[0243] [Contained Elements and Distribution] The positive electrode active material 100 contains lithium, a transition metal, oxygen, and an additive element X. The positive electrode active material 100 may be a composite oxide represented by LiM1O2 (where M1 is one or more selected from Fe, Ni, Co, and Mn) to which the additive element X is added. The positive electrode active material 100 contains lithium, a transition metal, oxygen, and an additive element X. The positive electrode active material 100 may be a composite oxide represented by LiM1O2 (where M1 is one or more selected from Fe, Ni, Co, and Mn) to which the additive element X is added. The positive electrode active material 100 contains lithium, a transition metal, oxygen, and an additive element X. The positive electrode active material 100 may be a composite oxide represented by LiM1O2 (where M1 is one or more selected from Fe, Ni, Co, and Mn) to which the additive element X is added.

[0244] As the transition metal contained in the positive electrode active material 100, it is preferable to use a metal that can form a layered rock salt-type composite oxide belonging to the space group R-3m together with lithium. For example, at least one of manganese, cobalt, and nickel can be used. That is, the positive electrode active material 100 As the transition metal contained in the positive electrode active material 100, it is preferable to use a metal that can form a layered rock salt-type composite oxide belonging to the space group R-3m together with lithium. For example, at least one of manganese, cobalt, and nickel can be used. That is, the positive electrode active material 100 As the transition metal contained in the positive electrode active material 100, it is preferable to use a metal that can form a layered rock salt-type composite oxide belonging to the space group R-3m together with lithium. For example, at least one of manganese, cobalt, and nickel can be used. That is, the positive electrode active material 100 Cobalt alone may be used as the transition metal having the above structure, or nickel alone may be used. Two types of metals, cobalt and manganese, or cobalt and nickel, may be used. In other words, the positive electrode active material 100 may be made of three types of cobalt oxide. Lithium, lithium nickel oxide, lithium cobalt oxide in which some of the cobalt is replaced by 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 can be charged at a high voltage. This is preferable since 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 the present specification, etc., the additive element X It may be referred to by replacing it with a mixture, a part of the raw material, etc.

[0246] As shown in FIG. 11B, the positive electrode active material 100 has a surface layer portion 100a and an interior 100b. It is preferable that the concentration of the additive element X in the surface layer portion 100a is higher than that in the interior 100b. Also, As shown by gradation in FIG. 11B, the additive element X preferably has a concentration gradient that increases from the interior toward the surface. In this specification, etc., the surface layer portion 100a refers to a region from the surface of the positive electrode active material 100 up to about 10 nm. A surface generated by a crack and / or a fissure may also be referred to as the surface, and as shown in FIG. 11C, the region from the surface up to about 10 nm is referred to as the surface layer portion 100c. Also, a region deeper than the surface layer portion 100a and the surface layer portion 100c of the positive electrode active material 100 is defined as the interior 100b. When the positive electrode active material 100 forms the positive electrode active material composite 100z, it is desirable that the surface generated by a crack is also covered with the glass 101.

[0247] In the positive electrode active material 100 according to one aspect of the present invention, even when lithium is removed from the positive electrode active material 100 upon charging, the layered structure composed of octahedra of cobalt and oxygen is not broken, and thus the surface layer portion 100a with a high concentration of the additive element X, that is, the outer peripheral portion of the particles, is reinforced.

[0248] Also, it is preferable that the concentration gradient of the additive element X is uniformly present throughout the surface layer portion 100a of the positive electrode active material 100. This is because if there is a non-reinforced portion even when a part of the surface layer portion 100a is reinforced, stress may concentrate on the non-reinforced portion, which is not preferable. When stress concentrates on a part of the particles, defects such as cracks may occur therefrom, leading to cracking of the positive electrode active material and a decrease in the charge / discharge capacity.

[0249] Magnesium is divalent and more likely to enter the lithium site than the transition metal site in the layered rock salt crystal structure, so it easily enters the lithium site. When magnesium exists at an appropriate concentration in the lithium site of the surface layer portion 100a, it is easy to maintain the layered rock salt crystal structure. Also, since magnesium has a strong binding force with oxygen, it can suppress the detachment of oxygen around magnesium. Magnesium is preferable as long as it is at an appropriate concentration and does not adversely affect the insertion and extraction of lithium during charge and discharge. However, if it is excessive, it may have an adverse effect on the insertion and extraction of lithium.

[0250] Aluminum is trivalent and can exist in the transition metal site in the layered rock salt crystal structure. Aluminum can suppress the elution of surrounding cobalt. Also, since aluminum has a strong binding force with oxygen, it can suppress the detachment of oxygen around aluminum. Therefore, when having aluminum as the additive element X, the positive electrode active material 100 can be obtained in which the crystal structure is not easily broken even when charge and discharge are repeated.

[0251] Fluorine is a monovalent anion. When part of the oxygen is replaced by fluorine in the surface layer portion 100a, the lithium detachment energy becomes smaller. This is because the change in the valence of cobalt ions accompanying lithium desorption is different in the case without fluorine (from trivalent to tetravalent) and in the case with fluorine (from divalent to trivalent), resulting in different redox potentials. Therefore, when part of the oxygen is replaced by fluorine in the surface layer portion 100a of the positive electrode active material 100, it can be said that the detachment and insertion of lithium ions near fluorine occur smoothly. Therefore, when used in a secondary battery, it is preferable as charge and discharge characteristics, rate characteristics, etc. are improved. ​

[0252] Titanium oxides are known to have super hydrophilicity. Therefore, by using the positive electrode active material 100 having a titanium oxide in the surface layer portion 100a, the wettability with respect to a highly polar solvent may be improved. When a secondary battery is used, the contact between the positive electrode active material 100 and a highly polar electrolytic solution may be improved, and an increase in resistance may be suppressed. In the present specification and the like, 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 according to one aspect of the present invention has a stable crystal structure even at a high voltage. Since the crystal structure of the positive electrode active material is stable in the charged state, a decrease in capacity due to repeated charge and discharge can be suppressed.

[0254] In addition, a short circuit of the secondary battery not only causes a malfunction in the charging operation and / or the discharging operation of the secondary battery, but also may cause heat generation and ignition. In order to realize a safe secondary battery, it is preferable that the short circuit current is suppressed even at a high charging voltage. The positive electrode active material 100 according to one aspect of the present invention suppresses the short circuit current even at a high charging voltage. Therefore, a secondary battery having both high capacity and safety can be obtained.

[0255] The secondary battery using the positive electrode active material 100 according to one aspect of the present invention preferably satisfies high capacity, excellent charge and discharge cycle characteristics, and safety at the same time.

[0256] The concentration gradient of the additive element X can be evaluated, for example, by using energy dispersive X-ray spectroscopy (EDX: Energy Dispersive X-ray Spectroscopy). In EDX measurement, measurement is performed while scanning within the region, and two-dimensional evaluation within the region is sometimes referred to as EDX surface analysis. Also, from the surface analysis of EDX, data of a linear region is extracted and evaluation of the distribution of the atomic concentration within the positive electrode active material particles is sometimes referred to as line analysis .

[0257] By EDX surface analysis (for example, element mapping), the concentration of the additive element X in the surface layer portion 100a, inside 100b, near the grain boundaries, etc. of the positive electrode active material 100 can be quantitatively analyzed. Also, by EDX line analysis, the distribution of the concentration of the additive element X can be analyzed.

[0258] When EDX line analysis is performed on the positive electrode active material 100, the peak of the magnesium concentration (the position where the concentration is the maximum value) in the surface layer portion 100a is preferably present within a depth of 3 nm from the surface of the positive electrode active material 100 toward the center, more preferably present within a depth of 1 nm, and even more preferably present within a depth of 0.5 nm.

[0259] Also, the distribution of fluorine in the positive electrode active material 100 preferably overlaps with the distribution of magnesium. Therefore, when EDX line analysis is performed, the peak of the fluorine concentration (the position where the concentration is the maximum value) in the surface layer portion 100a is preferably present within a depth of 3 nm from the surface of the positive electrode active material 100 toward the center, more preferably present within a depth of 1 nm, and even more preferably present within a depth of 0.5 nm.

[0260] Note that not all the additive elements X need to have the same concentration distribution. For example, when the positive electrode active material 100 has aluminum as the additive element X, it has a slightly different distribution from magnesium and fluorine It is preferably as follows. For example, when performing EDX analysis, the peak of the magnesium concentration (the position where the concentration becomes the maximum value) is closer to the surface than the peak of the aluminum concentration (the position where the concentration becomes the maximum value) in the surface layer portion 100a. For example, it is preferable that the peak of the magnesium concentration (the position where the concentration becomes the maximum value) is closer to the surface than the peak of the aluminum concentration (the position where the concentration becomes the maximum value). For example, the peak of the aluminum concentration is preferably present at a depth of 0.5 nm or more and 20 nm or less from the surface of the positive electrode active material 100 toward the center, and more preferably present at a depth of 1 nm or more and 5 nm or less.

[0261] When performing line analysis or surface analysis on the positive electrode active material 100, the ratio (X / M1) of the additive element X to the transition metal M1 in the vicinity of the grain boundary is preferably 0.020 or more and 0.50 or less. Furthermore, it is preferably 0.025 or more and 0.30 or less. Furthermore, it is preferably 0.030 or more and 0.20 or less. For example, when the additive element X is magnesium and the transition metal M1 is cobalt, the ratio (Mg / Co) of the number of atoms of magnesium to cobalt is preferably 0.020 or more and 0.50 or less. Furthermore, it is preferably 0.025 or more and 0.30 or less. Furthermore, it is preferably 0.030 or more and 0.20 or less. For example, when the additive element X is magnesium and the transition metal M1 is cobalt, the ratio (Mg / Co) of the number of atoms of magnesium to cobalt is preferably 0.020 or more and 0.50 or less. Furthermore, it is preferably 0.025 or more and 0.30 or less. Furthermore, it is preferably 0.030 or more and 0.20 or less. is preferably 0.20 or less.

[0262] As described above, if the additive element X contained in the positive electrode active material 100 is excessive, it may have an adverse effect on the insertion and extraction of lithium. There is also a risk of an increase in resistance and a decrease in capacity when used as a secondary battery. On the other hand, if it is insufficient, it may not be distributed throughout the surface layer portion 100a, and the effect of maintaining the crystal structure may become insufficient. Thus, the additive element X is adjusted to an appropriate concentration in the positive electrode active material 100. Therefore, for example, the positive electrode active material 100 has a region where the excessive additive element X is unevenly distributed.

[0263] Therefore, for example, the positive electrode active material 100 has a region where the excessive additive element X is unevenly distributed. This is also possible. Due to the existence of such a region, excessive additive element X is removed from other regions, to achieve an appropriate concentration of additive element X in most of the interior and surface layer of the positive electrode active material 100 This can be achieved. By setting an appropriate concentration of additive element X in most of the interior and surface layer of the positive electrode active material 100 it is possible to suppress an increase in resistance, a decrease in capacity, etc. when the battery is used as a secondary battery . The ability to suppress an increase in the resistance of the secondary battery is an extremely favorable characteristic, especially in high-rate charge and discharge.

[0264] In addition, in the positive electrode active material 100 having a region where excessive additive element X is unevenly distributed, it is allowed to mix additive element X excessively to a certain extent in the manufacturing process. Therefore, the margin in production becomes wider, which is preferable.

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

[0266] <Crystal structure> Materials having a layered rock salt-type crystal structure such as lithium cobalt oxide (LiCoO2) are known to have a high discharge capacity and be excellent as the positive electrode active material of a secondary battery. Examples of materials having a layered rock salt-type crystal structure include composite oxides represented by LiM1O2 (M1 is one or more selected from Fe, Ni, Co, Mn).

[0267] In transition metal compounds, the Jahn-Teller effect is known to have different strengths depending on the number of electrons in the d orbitals of the transition metal.

[0268] In the case of a compound having nickel, distortion is likely to occur due to the Jahn-Teller effect. Therefore, when charging and discharging at a high voltage in LiNiO2, there is a concern that the crystal structure may collapse due to distortion. In LiCoO2, it is suggested that the influence of the Jahn-Teller effect is small, and it may be more resistant to charging and discharging at a high voltage, which is preferable.

[0269] The structure of the positive electrode active material will be described with reference to FIGS. 12 to 17. FIGS. 12 to 17 describe the case where cobalt is used as the transition metal included in the positive electrode active material.

[0270] <Conventional positive electrode active material> The positive electrode active material shown in FIG. 14 is lithium cobalt oxide (LiCoO2, LCO) to which halogen and magnesium are not added. The lithium cobalt oxide shown in FIG. 14 has a crystal structure that changes depending on the depth of charge. In other words, when expressed as LixCoO2, the crystal structure changes according to the occupancy x of lithium in the lithium site.

[0271] As shown in FIG. 14, lithium cobalt oxide in the state of x = 1 (discharged state) has a region having a crystal structure of space group R-3m, and there are three CoO2 layers in the unit cell. Therefore, this crystal structure may be referred to as an O3-type crystal structure. The CoO2 layer refers to a structure in which an octahedral structure in which oxygen is six-coordinated to cobalt is continuous in the plane direction in a state of sharing edges.

[0272] When x = 0, it has a crystal structure of space group P-3m1, and there is one CoO2 layer in the unit cell. Therefore, this crystal structure may be referred to as an O1-type crystal structure.

[0273] Lithium cobaltate when x is about 0.12 has a crystal structure of space group R-3m This structure can also be said to be a structure in which the structure of CoO2 such as P-3m1 (O1) and the structure of LiCoO2 such as R-3m (O3) are alternately stacked. Therefore, this crystal structure is sometimes called the H1-3 type crystal structure. Note that since unevenness can occur in the actual insertion and extraction of lithium, the H1-3 type crystal structure is experimentally observed from about x = 0.25. In addition in reality, in the H1-3 type crystal structure, the number of cobalt atoms per unit cell is twice that of other structures. However, in this specification including FIG. 14, in order to make it easier to compare with other structures it is shown in a figure in which the c-axis of the H1-3 type crystal structure is made 1 / 2 of the unit cell. As an example, the H1-3 type crystal structure can represent the coordinates of cobalt and oxygen in the unit cell as Co(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 respectively. Thus, the H1-3 type crystal structure is represented by a unit cell using one cobalt and two oxygens. On the other hand, as will be described later, the O3' type crystal structure of one aspect of the present invention is preferably represented by a unit cell using one cobalt and one oxygen. This indicates that in the case of the O3' type crystal structure and the H1-3 type structure

[0274] the symmetry between cobalt and oxygen is different, and the change from the O3 structure in the O3' type crystal structure is smaller than that in the H1-3 type structure. Whether it is more preferable to represent the crystal structure of the positive electrode active material using any unit cell is selected, for example, from the Rietveld analysis of the XRD pattern of the XRD pattern. ​​​​​​​​In the to - belt analysis, it may be selected so that the value of GOF (goodness of fit) becomes smaller.

[0275] When high - voltage charging such that the charging voltage becomes 4.6 V or more based on the redox potential of lithium metal, or deep - depth charging such that x = 0.24 or less, and discharging are repeated, lithium cobaltate repeats a change in crystal structure (that is, a non - equilibrium phase change) between the H1 - 3 type crystal structure and the R - 3m (O3) structure in the discharged state. However, the shift of the CoO2 layer between these two crystal structures is large. As shown by the dotted line and double - headed arrows in FIG. 14, in the H1 - 3 type crystal structure, the CoO2 layer is largely shifted from R - 3m (O3). Such dynamic structural changes can have an adverse effect on the stability of the crystal structure.

[0276] Moreover, the volume difference is also large. When compared per the same number of cobalt atoms, the volume difference between the H1 - 3 type crystal structure and the O3 type crystal structure in the discharged state is 3.0% or more.

[0277] In addition, the structure in which the CoO2 layer, such as P - 3m1 (O1), of the H1 - 3 type crystal structure is continuous is likely to be unstable.

[0278] Therefore, when high - voltage charge - discharge is repeated, the crystal structure of lithium cobaltate collapses.

[0279] The collapse of the crystal structure causes deterioration of the cycle characteristics. This is presumably because when the crystal structure collapses, the sites where lithium can exist stably decrease, and the insertion and desorption of lithium become difficult.

[0280] <The positive electrode active material of one aspect of the present invention> ​​​​​​​​​​​<Internal> The cathode active material 100 of one embodiment of the present invention can reduce the layer shift of CoO2 during repeated high-voltage charge and discharge. Furthermore, the volume change can be reduced. Thus, the cathode active material of one embodiment of the present invention can achieve excellent cycle characteristics. Also, the cathode active material of one embodiment of the present invention can have a stable crystal structure in a high-voltage charged state. Therefore, when the cathode active material of one embodiment of the present invention maintains a high-voltage charged state, short circuits may be less likely to occur. In such cases, since safety is further improved, it is preferable. In the cathode active material of one embodiment of the present invention, the change in crystal structure and the volume difference per the same number of transition metal atoms in a fully discharged state and a state charged at a high voltage are small. The crystal structures of the cathode active material 100 before and after charge and discharge are shown in FIG. 12. The cathode active material 100 is a composite oxide having lithium, cobalt as a transition metal, and oxygen. In addition to the above, it is preferable to have magnesium as the additive element X. It is also preferable to have a halogen such as fluorine or chlorine as the additive element X. The crystal structure of x = 1 (discharged state) in FIG. 12 is the same R-3m (O3) as FIG. 14. On the other hand, the cathode active material 100 of one embodiment of the present invention has crystals with a structure different from the H1-3 type crystal structure when fully charged to a depth of charge. This structure belongs to the space group R-3m, and ions such as cobalt and magnesium occupy the oxygen six-coordinate positions. Also, the symmetry of the CoO2 layer of this structure is the same as that of the O3 type. Therefore, this structure is referred to as an O3'-type crystal structure in this specification and the like. Therefore, when the cathode active material of one embodiment of the present invention maintains a high-voltage charged state, short circuits may be less likely to occur. In such cases, since safety is further improved, it is preferable. In the cathode active material of one embodiment of the present invention, the change in crystal structure and the volume difference per the same number of transition metal atoms in a fully discharged state and a state charged at a high voltage are small. It is preferable.

[0281] In the cathode active material of one embodiment of the present invention, the change in crystal structure and the volume difference per the same number of transition metal atoms in a fully discharged state and a state charged at a high voltage are small. In the cathode active material of one embodiment of the present invention, the change in crystal structure and the volume difference per the same number of transition metal atoms in a fully discharged state and a state charged at a high voltage are small. It is small.

[0282] The crystal structures of the cathode active material 100 before and after charge and discharge are shown in FIG. 12. The cathode active material 100 is a composite oxide having lithium, cobalt as a transition metal, and oxygen. In addition to the above, it is preferable to have magnesium as the additive element X. It is also preferable to have a halogen such as fluorine or chlorine as the additive element X. The crystal structure of x = 1 (discharged state) in FIG. 12 is the same R-3m (O3) as FIG. 14. On the other hand, the cathode active material 100 of one embodiment of the present invention has crystals with a structure different from the H1-3 type crystal structure when fully charged to a depth of charge. This structure belongs to the space group R-3m, and ions such as cobalt and magnesium occupy the oxygen six-coordinate positions. Also, the symmetry of the CoO2 layer of this structure is the same as that of the O3 type. Therefore, this structure is referred to as an O3'-type crystal structure in this specification and the like. The crystal structure of x = 1 (discharged state) in FIG. 12 is the same R-3m (O3) as FIG. 14. On the other hand, the cathode active material 100 of one embodiment of the present invention has crystals with a structure different from the H1-3 type crystal structure when fully charged to a depth of charge. This structure belongs to the space group R-3m, and ions such as cobalt and magnesium occupy the oxygen six-coordinate positions. Also, the symmetry of the CoO2 layer of this structure is the same as that of the O3 type. Therefore, this structure is referred to as an O3'-type crystal structure in this specification and the like. It is preferable to have a halogen such as fluorine or chlorine as the additive element X.

[0283] The crystal structure of x = 1 (discharged state) in FIG. 12 is the same R-3m (O3) as FIG. 14. On the other hand, the cathode active material 100 of one embodiment of the present invention has crystals with a structure different from the H1-3 type crystal structure when fully charged to a depth of charge. This structure belongs to the space group R-3m, and ions such as cobalt and magnesium occupy the oxygen six-coordinate positions. Also, the symmetry of the CoO2 layer of this structure is the same as that of the O3 type. Therefore, this structure is referred to as an O3'-type crystal structure in this specification and the like. On the other hand, the cathode active material 100 of one embodiment of the present invention has crystals with a structure different from the H1-3 type crystal structure when fully charged to a depth of charge. This structure belongs to the space group R-3m, and ions such as cobalt and magnesium occupy the oxygen six-coordinate positions. Also, the symmetry of the CoO2 layer of this structure is the same as that of the O3 type. Therefore, this structure is referred to as an O3'-type crystal structure in this specification and the like. This structure belongs to the space group R-3m, and ions such as cobalt and magnesium occupy the oxygen six-coordinate positions. Also, the symmetry of the CoO2 layer of this structure is the same as that of the O3 type. Therefore, this structure is referred to as an O3'-type crystal structure in this specification and the like. This structure belongs to the space group R-3m, and ions such as cobalt and magnesium occupy the oxygen six-coordinate positions. Also, the symmetry of the CoO2 layer of this structure is the same as that of the O3 type. Therefore, this structure is referred to as an O3'-type crystal structure in this specification and the like. Therefore, this structure is referred to as an O3'-type crystal structure in this specification and the like. In addition, 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' 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 bonds It can be said that the crystal structure is similar to that of 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 cobalt oxide, 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 compared to 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 has a high charging voltage. For example, conventional positive electrode active materials have an H1-3 type crystal structure. Even at a charging voltage of about 4.6V based on the potential of lithium metal, for example, R-3 There exists 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. In a region, for example, at a voltage of about 4.65 V to 4.7 V with reference to the potential of lithium metal there exists a region where an O3' type crystal structure can be adopted. Further, when the charging voltage is increased, finally, a H1-3 type crystal may be observed. In a secondary battery, for example, when using graphite as the negative electrode active material, there exists a region of charging voltage where an R-3m(O3) crystal structure can be retained even when the voltage of the secondary battery is 4.3 V or more and 4.5 V or less. Further, in a region where the charging voltage is increased, for example, at 4.35 V or more and 4.55 V or less with reference to the potential of lithium metal, there exists a region where an O3' type crystal structure can be adopted.

[0288] Therefore, in the positive electrode active material 100 of one aspect of the present invention, the crystal structure is less likely to collapse even when charge and discharge are repeated at a high voltage.

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

[0290] The O3' type crystal structure can be represented by the coordinates of cobalt and oxygen in the unit cell as Co(0, 0, 0.5), O(0, 0, x), within the range of 0.20 ≤ x ≤ 0.25.

[0291] An additive element X, for example, magnesium, which is randomly and thinly present in the CoO2 layer, that is, in the lithium site, has an effect of suppressing the displacement of the CoO2 layer. Therefore, when magnesium exists between the CoO2 layers, an O3' type crystal structure is likely to be formed. Therefore, magnesium is distributed in at least a part of the surface layer of the positive electrode active material 100 of one aspect of the present invention, and further, the positive electrode active material It is preferably distributed throughout the surface layer portion of the active material 100. Further, in order to distribute magnesium throughout the surface layer portion of the positive electrode active material 100, it is preferable to perform heat treatment in the process of manufacturing the positive electrode active material 100 according to one aspect of the present invention. However, if the temperature of the heat treatment is too high, cation mixing may occur and the added element X, for example magnesium, may be more likely to enter the cobalt site. Magnesium present in the cobalt site has no effect of maintaining the R-3m structure in the high voltage charged state. Furthermore, if the temperature of the heat treatment is too high, there are concerns about adverse effects such as cobalt being reduced to divalent and lithium evaporating.

[0292] Therefore, it is preferable to add a halogen compound such as a fluorine compound to lithium cobaltate before the heat treatment for distributing magnesium throughout the surface layer portion of the positive electrode active material 100. Adding the halogen compound causes a decrease in the melting point of lithium cobaltate. By lowering the melting point, it becomes easier to distribute magnesium throughout the surface layer portion of the positive electrode active material 100 at a temperature at which cation mixing is less likely to occur. Furthermore, if a fluorine compound is present, it can be expected that the corrosion resistance against hydrofluoric acid generated by the decomposition of the electrolytic solution will be improved. In addition, if the magnesium concentration is increased to a value equal to or higher than a desired value, the effect on the stabilization of the crystal structure may become small. This is presumably because magnesium enters not only the lithium site but also the cobalt site. The number of magnesium atoms in the positive electrode active material according to one aspect of the present invention is preferably 0.001 times or more and 0.1 times or less the number of atoms of transition metals such as cobalt. It is preferably distributed throughout the surface layer portion of the active material 100. Further, in order to distribute magnesium throughout the surface layer portion of the positive electrode active material 100, it is preferable to perform heat treatment in the process of manufacturing the positive electrode active material 100 according to one aspect of the present invention. However, if the temperature of the heat treatment is too high, cation mixing may occur and the added element X, for example magnesium, may be more likely to enter the cobalt site. Magnesium present in the cobalt site has no effect of maintaining the R-3m structure in the high voltage charged state. Furthermore, if the temperature of the heat treatment is too high, there are concerns about adverse effects such as cobalt being reduced to divalent and lithium evaporating.

[0293] Therefore, it is preferable to add a halogen compound such as a fluorine compound to lithium cobaltate before the heat treatment for distributing magnesium throughout the surface layer portion of the positive electrode active material 100. Adding the halogen compound causes a decrease in the melting point of lithium cobaltate. By lowering the melting point, it becomes easier to distribute magnesium throughout the surface layer portion of the positive electrode active material 100 at a temperature at which cation mixing is less likely to occur. Furthermore, if a fluorine compound is present, it can be expected that the corrosion resistance against hydrofluoric acid generated by the decomposition of the electrolytic solution will be improved. In addition, if the magnesium concentration is increased to a value equal to or higher than a desired value, the effect on the stabilization of the crystal structure may become small. This is presumably because magnesium enters not only the lithium site but also the cobalt site. The number of magnesium atoms in the positive electrode active material according to one aspect of the present invention is preferably 0.001 times or more and 0.1 times or less the number of atoms of transition metals such as cobalt. It is preferably distributed throughout the surface layer portion of the active material 100. Further, in order to distribute magnesium throughout the surface layer portion of the positive electrode active material 100, it is preferable to perform heat treatment in the process of manufacturing the positive electrode active material 100 according to one aspect of the present invention. However, if the temperature of the heat treatment is too high, cation mixing may occur and the added element X, for example magnesium, may be more likely to enter the cobalt site. Magnesium present in the cobalt site has no effect of maintaining the R-3m structure in the high voltage charged state. Furthermore, if the temperature of the heat treatment is too high, there are concerns about adverse effects such as cobalt being reduced to divalent and lithium evaporating. Therefore, it is preferable to add a halogen compound such as a fluorine compound to lithium cobaltate before the heat treatment for distributing magnesium throughout the surface layer portion of the positive electrode active material 100. Adding the halogen compound causes a decrease in the melting point of lithium cobaltate. By lowering the melting point, it becomes easier to distribute magnesium throughout the surface layer portion of the positive electrode active material 100 at a temperature at which cation mixing is less likely to occur. Furthermore, if a fluorine compound is present, it can be expected that the corrosion resistance against hydrofluoric acid generated by the decomposition of the electrolytic solution will be improved.

[0294] In addition, if the magnesium concentration is increased to a value equal to or higher than a desired value, the effect on the stabilization of the crystal structure may become small. This is presumably because magnesium enters not only the lithium site but also the cobalt site. The number of magnesium atoms in the positive electrode active material according to one aspect of the present invention is preferably 0.001 times or more and 0.1 times or less the number of atoms of transition metals such as cobalt. In addition, if the magnesium concentration is increased to a value equal to or higher than a desired value, the effect on the stabilization of the crystal structure may become small. This is presumably because magnesium enters not only the lithium site but also the cobalt site. The number of magnesium atoms in the positive electrode active material according to one aspect of the present invention is preferably 0.001 times or more and 0.1 times or less the number of atoms of transition metals such as cobalt. In addition, if the magnesium concentration is increased to a value equal to or higher than a desired value, the effect on the stabilization of the crystal structure may become small. This is presumably because magnesium enters not only the lithium site but also the cobalt site. The number of magnesium atoms in the positive electrode active material according to one aspect of the present invention is preferably 0.001 times or more and 0.1 times or less the number of atoms of transition metals such as cobalt. In addition, if the magnesium concentration is increased to a value equal to or higher than a desired value, the effect on the stabilization of the crystal structure may become small. This is presumably because magnesium enters not only the lithium site but also the cobalt site. The number of magnesium atoms in the positive electrode active material according to one aspect of the present invention is preferably 0.001 times or more and 0.1 times or less the number of atoms of transition metals such as cobalt. Preferably, it is more than 0.01 times and less than 0.04 times, and about 0.02 times is even more preferred. The concentration of magnesium shown here may be, for example, a value obtained by performing elemental analysis of the entire positive electrode active material using ICP-MS or the like, or may be based on the value of the raw material formulation in the process of producing 100 of the positive electrode active material.

[0295] One or more metals selected from, for example, nickel, aluminum, manganese, titanium, vanadium, and chromium may be added to lithium cobaltate as a metal other than cobalt (hereinafter, additive element X). In particular, it is preferable to add one or more of nickel and aluminum. Manganese, titanium, vanadium, and chromium may be stable in the tetravalent state and may contribute highly to structural stability. By adding additive element X, the crystal structure may become more stable in the fully charged state at high voltage. Here, in the positive electrode active material of one aspect of the present invention, additive element X is preferably added at a concentration that does not significantly change the crystallinity of lithium cobaltate. For example, it is preferably an amount that does not exhibit the Jahn-Teller effect or the like described above.

[0296] Transition metals such as nickel and manganese and aluminum preferably exist at the cobalt site, but a part may exist at the lithium site. Magnesium preferably exists at the lithium site. A part of oxygen may be substituted with fluorine.

[0297] As the magnesium concentration of the positive electrode active material of one aspect of the present invention increases, the capacity of the positive electrode active material may decrease. For example, as a factor, magnesium may enter the lithium site. ​​​​​​​​​​​​​As a result, it is conceivable that the amount of lithium contributing to charge and discharge may decrease. One aspect of the present invention When a cathode active material of a certain aspect has nickel in addition to magnesium as the additive element X, the charge-discharge cycle characteristics may be improved in some cases. Also, when a cathode active material of one aspect of the present invention has aluminum in addition to magnesium as the additive element X, the charge-discharge cycle characteristics may be improved in some cases. Further, by using a cathode active material of one aspect of the present invention having magnesium, nickel, and aluminum as the additive element X, the charge-discharge cycle characteristics may be improved in some cases.

[0298] Hereinafter, the concentration of the elements of the cathode active material of one aspect of the present invention having magnesium, nickel, and aluminum as the additive element X will be examined.

[0299] The number of nickel atoms in the cathode active material of one aspect of the present invention is preferably 10% or less of the number of cobalt atoms, more preferably 7.5% or less, still more preferably 0.05% or more and 4% or less, and particularly preferably 0.1% or more and 2% or less. The nickel concentration shown here may be, for example, a value obtained by performing elemental analysis of the entire cathode active material using ICP-MS or the like, or may be based on the value of the raw material formulation in the process of producing the cathode active

[0300] When the state of being charged at a high voltage is maintained for a long time, the constituent elements of the cathode active material may elute into the electrolyte, and there is a risk that the crystal structure may collapse. However, by having nickel in the above ratio, elution of the constituent elements from 100 of the cathode active material may be suppressed.

[0301] The number of aluminum atoms in the cathode active material of one aspect of the present invention is 0 of the number Preferably, it is more than 0.05% and not more than 4%, and more preferably more than 0.1% and not more than 2%. The aluminum concentration shown here may be a value obtained by performing elemental analysis of the entire positive electrode active material using, for example, ICP-MS or the like, or may be based on the blending value of the raw materials in the process of producing the positive electrode active material. The aluminum concentration shown here may be a value obtained by performing elemental analysis of the entire positive electrode active material using, for example, ICP-MS or the like, or may be based on the blending value of the raw materials in the process of producing the positive electrode active material. The aluminum concentration shown here may be a value obtained by performing elemental analysis of the entire positive electrode active material using, for example, ICP-MS or the like, or may be based on the blending value of the raw materials in the process of producing the positive electrode active material. Preferably, it is more than 0.05% and not more than 4%, and more preferably more than 0.1% and not more than 2%. The aluminum concentration shown here may be a value obtained by performing elemental analysis of the entire positive electrode active material using, for example, ICP-MS or the like, or may be based on the blending value of the raw materials in the process of producing the positive electrode active material.

[0302] Further, the positive electrode active material having the additive element X according to one aspect of the present invention preferably uses phosphorus as the additive element X. Further, the positive electrode active material according to one aspect of the present invention more preferably contains a compound containing phosphorus and oxygen. Further, the positive electrode active material having the additive element X according to one aspect of the present invention preferably uses phosphorus as the additive element X. Further, the positive electrode active material according to one aspect of the present invention more preferably contains a compound containing phosphorus and oxygen. Further, the positive electrode active material having the additive element X according to one aspect of the present invention preferably uses phosphorus as the additive element X. Further, the positive electrode active material according to one aspect of the present invention more preferably contains a compound containing phosphorus and oxygen.

[0303] When the positive electrode active material according to one aspect of the present invention has a compound containing phosphorus as the additive element X, short circuits are less likely to occur when a charged state of high temperature and high voltage is maintained for a long time. When the positive electrode active material according to one aspect of the present invention has a compound containing phosphorus as the additive element X, short circuits are less likely to occur when a charged state of high temperature and high voltage is maintained for a long time. When the positive electrode active material according to one aspect of the present invention has a compound containing phosphorus as the additive element X, short circuits are less likely to occur when a charged state of high temperature and high voltage is maintained for a long time.

[0304] When the positive electrode active material according to one aspect of the present invention has phosphorus as the additive element X, hydrogen fluoride generated by the decomposition of the electrolytic solution may react with phosphorus, and the hydrogen fluoride concentration in the electrolytic solution may decrease. When the positive electrode active material according to one aspect of the present invention has phosphorus as the additive element X, hydrogen fluoride generated by the decomposition of the electrolytic solution may react with phosphorus, and the hydrogen fluoride concentration in the electrolytic solution may decrease. When the positive electrode active material according to one aspect of the present invention has phosphorus as the additive element X, hydrogen fluoride generated by the decomposition of the electrolytic solution may react with phosphorus, and the hydrogen fluoride concentration in the electrolytic solution may decrease.

[0305] When the electrolytic solution has LiPF6 as a lithium salt, hydrogen fluoride may be generated by hydrolysis. Further, hydrogen fluoride may be generated by the reaction of PVDF used as a component of the positive electrode with an alkali. By reducing the hydrogen fluoride concentration in the electrolytic solution, corrosion of the current collector and / or peeling of the film may be suppressed. Further, a decrease in adhesiveness due to gelation and / or insolubilization of PVDF may be suppressed. When the electrolytic solution has LiPF6 as a lithium salt, hydrogen fluoride may be generated by hydrolysis. Further, hydrogen fluoride may be generated by the reaction of PVDF used as a component of the positive electrode with an alkali. By reducing the hydrogen fluoride concentration in the electrolytic solution, corrosion of the current collector and / or peeling of the film may be suppressed. Further, a decrease in adhesiveness due to gelation and / or insolubilization of PVDF may be suppressed. When the electrolytic solution has LiPF6 as a lithium salt, hydrogen fluoride may be generated by hydrolysis. Further, hydrogen fluoride may be generated by the reaction of PVDF used as a component of the positive electrode with an alkali. By reducing the hydrogen fluoride concentration in the electrolytic solution, corrosion of the current collector and / or peeling of the film may be suppressed. Further, a decrease in adhesiveness due to gelation and / or insolubilization of PVDF may be suppressed. When the electrolytic solution has LiPF6 as a lithium salt, hydrogen fluoride may be generated by hydrolysis. Further, hydrogen fluoride may be generated by the reaction of PVDF used as a component of the positive electrode with an alkali. By reducing the hydrogen fluoride concentration in the electrolytic solution, corrosion of the current collector and / or peeling of the film may be suppressed. Further, a decrease in adhesiveness due to gelation and / or insolubilization of PVDF may be suppressed. When the electrolytic solution has LiPF6 as a lithium salt, hydrogen fluoride may be generated by hydrolysis. Further, hydrogen fluoride may be generated by the reaction of PVDF used as a component of the positive electrode with an alkali. By reducing the hydrogen fluoride concentration in the electrolytic solution, corrosion of the current collector and / or peeling of the film may be suppressed. Further, a decrease in adhesiveness due to gelation and / or insolubilization of PVDF may be suppressed.

[0306] The positive electrode active material 100 according to one aspect of the present invention has phosphorus and magnesium as the additive element X. In this case, the stability in the high-voltage charged state is extremely high. When phosphorus and magnesium are used as the additive element X, the number of phosphorus atoms is preferably 1% or more and 20% or less of the number of cobalt atoms, more preferably 2% or more and 10% or less, still more preferably 3% or more and 8% or less. In addition, the number of magnesium atoms is preferably 0.1% or more and 10% or less of the number of cobalt atoms, more preferably 0.5% or more and 5% or less, and still more preferably 0.7% or more and 4% or less. The concentrations of phosphorus and magnesium shown here may be, for example, values obtained by performing elemental analysis of the entire positive electrode active material 100 using ICP-MS or the like, or may be based on the compounding values of the raw materials in the process of producing the positive electrode active material 100. When having, the number of phosphorus atoms is preferably 1% or more and 20% or less of the number of cobalt atoms, more preferably 2% or more and 10% or less, still more preferably 3% or more and 8% or less. In addition, the number of magnesium atoms is preferably 0.1% or more and 10% or less of the number of cobalt atoms, 0.5 % or more and 5% or less is more preferable, and 0.7% or more and 4% or less is more preferable. The phosphorus and magnesium concentrations shown here are, for example, values obtained by performing elemental analysis of the entire positive electrode active material 100 using ICP-MS or the like, or may be based on the compounding values of the raw materials in the process of producing the positive electrode active material 100.

[0307] When the positive electrode active material 100 has cracks, the progress of the cracks may be suppressed by the presence of phosphorus, more specifically, a compound containing, for example, phosphorus and oxygen, inside thereof.

[0308] In FIG. 12, the symmetry of oxygen atoms is clearly different between the O3-type crystal structure and the O3'-type crystal structure. Specifically, in the O3-type crystal structure, oxygen atoms are aligned along the dotted line, whereas in the O3'-type crystal structure, the oxygen atoms are not strictly aligned. This is due to the increase in tetravalent cobalt with the decrease in lithium, resulting in a large Jahn-Teller distortion and the distortion of the octahedral structure of CoO6. In addition, the increase in the repulsion between oxygen atoms in the CoO2 layer with the decrease in lithium also has an impact. With the decrease in lithium, tetravalent cobalt increases, the Jahn-Teller distortion becomes large, and the octahedral structure of Co O6 is distorted. In addition, the increase in the repulsion between oxygen atoms in the CoO2 layer with the decrease in lithium also has an impact.

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

[0310] Further, when the positive electrode active material 100 of one embodiment of the present invention has one or more metals selected from elements other than cobalt, such as nickel, aluminum, manganese, iron, and chromium, it is preferable that the concentration in the vicinity of the particle surface of the metal is higher than the overall average. For example, the concentration of the element other than cobalt in the surface layer portion 100a measured by XPS or the like is preferably higher than the concentration of the element in the overall average measured by ICP-MS or the like.

[0311] The surface layer portion of the positive electrode active material 100 is, so to speak, entirely crystal defects, and during charging, lithium escapes from the surface, so it is a portion where the lithium concentration tends to be lower than that inside. Therefore, it tends to become unstable and the crystal structure tends to collapse. If the magnesium concentration in the surface layer portion 100a is high, the change in the crystal structure can be more effectively suppressed. Also, when the magnesium concentration in the surface layer portion 100a is high, it can be expected that the corrosion resistance against hydrofluoric acid generated by the decomposition of the electrolytic solution is improved.

[0312] Also, the concentration of a halogen such as fluorine in the surface layer portion 100a of the positive electrode active material 100 of one embodiment of the present invention is preferably higher than the overall average. The presence of halogen in the surface layer portion 100a, which is the region in contact with the electrolytic solution, can effectively improve the corrosion resistance against hydrofluoric acid.

[0313] Thus, the surface layer portion 100a of the positive electrode active material 100 of one embodiment of the present invention is more than the interior 100b ​​​​​​​​​​​, it is preferable that the added element, for example, magnesium and fluorine have a high concentration and a composition different from that of the interior. It is also preferable that the composition has a crystal structure that is stable at normal temperature. Therefore, , the surface layer portion 100a may have a crystal structure different from that of the interior 100b. For example, in one aspect of the present invention, at least a part of the surface layer portion 100a of the positive electrode active material 100 may have a rock-salt type crystal structure. When the surface layer portion 100a and the interior 100b have different crystal structures, it is preferable that the crystal orientations of the surface layer portion 100a and the interior 100b are substantially the same.

[0314] The anions of the layered rock-salt type crystal and the rock-salt type crystal take a cubic close-packed structure (face-centered cubic lattice structure ). It is also estimated that the O3' type crystal has a cubic close-packed structure for the anions. In the present specification, etc., when the A layer, B layer, and C layer having anions are stacked so as to be shifted from each other like ABCABC, it will be called a cubic close-packed structure. Therefore, the anions do not necessarily have to be strictly cubic lattices. At the same time, since real crystals always have defects, the analysis results do not necessarily have to be as theoretical. For example, in electron diffraction or FFT (fast Fourier transform) of a TEM image, etc., spots may appear at positions slightly different from the theoretical positions. For example, if the orientation with respect to the theoretical position is 5 degrees or less, or 2.5 degrees or less, it can be said that the cubic close-packed structure is taken.

[0315] When the layered rock-salt type crystal and the rock-salt type crystal are in contact, there is a crystal plane where the orientations of the cubic close-packed structures composed of anions are aligned.

[0316] Alternatively, it can also be explained as follows. On the (111) plane of the crystal structure of the cubic crystal, ​​The anions have a triangular arrangement. The layered rock salt type has a space group of R-3m and a rhombohedral structure, but is generally represented by a composite hexagonal lattice for ease of understanding of the structure. The (0001) plane of the layered rock salt type has a hexagonal lattice. The triangular lattice of the cubic (111) has the same atomic arrangement as the hexagonal lattice of the ( 0001) plane of the layered rock salt type. It can be said that the orientations of the two lattices are aligned when the cubic close-packed structure is in the same orientation.

[0317] However, since the space groups of the layered rock salt type crystal and the O3’ type crystal are R-3m, which are different from the space group Fm-3m (the space group of a general rock salt type crystal) and Fd-3m (the space group of a rock salt type crystal with the simplest symmetry ) of the rock salt type crystal, the Miller indices of the crystal planes that satisfy the above conditions are different between the layered rock salt type crystal and the O3’ type crystal and the rock salt type crystal. In this specification, in the layered rock salt type crystal, the O3’ type crystal, and the rock salt type crystal, when the orientations of the cubic close- packed structures composed of anions are aligned, it may be said that the crystal orientations are generally in agreement.

[0318] The approximate agreement of the crystal orientations in two regions can be determined from TEM (transmission electron microscope) images, STEM (scanning transmission electron microscope) images, HAADF-STEM (high-angle annular dark-field scanning transmission electron microscope) images, ABF-STEM (annular bright-field scanning transmission electron microscope) images, electron diffraction, FFT of TEM images, etc. X-ray diffraction (XRD), neutron diffraction, etc. can also be used as materials for determination.

[0319] Fig. 16 shows an example of a TEM image in which the orientations of the layered rock salt type crystal LRS and the rock salt type crystal RS are generally in agreement. TEM images, STEM images, HAADF-STEM images, ABF-STEM images, etc. can obtain images that reflect the crystal structure. ​

[0320] For example, in high-resolution images of TEM, contrast derived from crystal planes can be obtained. Electrons By diffraction and interference of electron beams, for example, when an electron beam is incident perpendicular to the c-axis of a layered rock-salt type composite hexagonal lattice Contrast derived from the (0003) plane is obtained as a repetition of bright and dark lines. Therefore, a repetition of bright and dark lines is observed in the TEM image. When the angle between bright lines (for example, L and L RS shown in Fig. 16 LRS ) is 5 degrees or less, or 2.5 degrees or less, it can be determined that the crystal planes are approximately aligned, that is, the crystal orientations are approximately aligned. Similarly, when the angle between dark lines is 5 degrees or less, or 2.5 degrees or less, it can also be determined that the crystal orientations are approximately aligned.

[0321] In the HAADF-STEM image, contrast according to the atomic number is obtained, and elements with a larger atomic number are observed brighter. For example, in the case of layered rock-salt type lithium cobaltate belonging to the space group R-3m, since cobalt (atomic number 27) has the largest atomic number, the electron beam is strongly scattered at the position of cobalt atoms, and the arrangement of cobalt atoms is observed as an arrangement of bright lines or points with strong brightness. Therefore, when observing lithium cobaltate having a layered rock-salt type crystal structure perpendicular to the c-axis, the arrangement of cobalt atoms perpendicular to the c-axis is observed as an arrangement of bright lines or points with strong brightness, and the arrangements of lithium atoms and oxygen atoms are observed as dark lines or regions with low brightness. The same applies when fluorine (atomic number 9) and magnesium (atomic number 12) are used as additive elements of lithium cobaltate.

[0322] ​​​​​​​Therefore, in the HAADF-STEM image, bright and dark lines are repeated in two regions with different crystal structures. When the angle between the bright lines is 5 degrees or less, or 2.5 degrees or less, it can be determined that the atomic arrangement is roughly consistent, that is, the crystal orientations are roughly consistent. Similarly, when the angle between the dark lines is 5 degrees or less, or 2.5 degrees or less, it can also be determined that the crystal orientations are roughly consistent.

[0323] In ABF-STEM, elements with smaller atomic numbers are observed brighter, but since it is the same as HAADF-STEM in terms of obtaining contrast according to the atomic number, the crystal orientation can be judged in the same way as in the HAADF-STEM image.

[0324] Fig. 17A shows an example of a STEM image in which the orientations of the layered rock salt-type crystal LRS and the rock salt-type crystal RS are roughly consistent. The FFT of the region of the rock salt-type crystal RS is shown in Fig. 17B, and the FFT of the region of the layered rock salt-type crystal LRS is shown in Fig. 17C. Literature values are shown on the left and measured values are shown on the right in Figs. 17B and 17C. The spots marked with O are the 0th order diffraction.

[0325] The spot marked with A in Fig. 17B is derived from the 11-1 reflection of the cubic crystal. The spot marked with A in Fig. 17C is derived from the 0003 reflection of the layered rock salt type. Here, it can be seen that the straight line passing through AO in Fig. 17B and the straight line passing through AO in Fig. 17C are roughly parallel. That is, it can be seen from Figs. 17B and 17C that the orientation of the 11-1 reflection of the cubic crystal and the orientation of the 0003 reflection of the layered rock salt type are roughly consistent. The so-called rough consistency and rough parallelism here mean that the angle is 5 degrees or less, or 2.5 degrees or less.

[0326] ​​​​​​​​​​​​​​In this way, in FFT and electron diffraction, when the orientations of the layered rock salt type crystal and the rock salt type crystal are generally consistent with each other, the <0003> orientation of the layered rock salt type or an equivalent plane orientation, and the <1 1-1> orientation of the rock salt type or an equivalent plane orientation may be generally consistent. At this time, it is preferred that these reciprocal lattice points are spot-shaped, that is, not continuous with other reciprocal lattice points. The fact that the reciprocal lattice points are spot-shaped and not continuous with other reciprocal lattice points means high crystallinity.

[0327] Also, as described above, when the orientation of the 11-1 reflection of the cubic crystal and the orientation of the 0003 reflection of the layered rock salt type are generally consistent, depending on the incident orientation of the electron beam, spots that are not derived from the 0003 reflection of the layered rock salt type may be observed in a reciprocal lattice space different from the orientation of the 0003 reflection of the layered rock salt type. For example, the spot labeled B in Fig. 17C is derived from the 10-14 reflection of the layered rock salt type. This is at an angle of 52° or more and 56° or less from the orientation of the reciprocal lattice point (A in Fig. 17C) derived from the 0003 reflection of the layered rock salt type (that is, ∠AOB is 52° or more and 56° or less), and may be observed at a location where d is 0.19 nm or more and 0.21 nm or less. Note that this index is an example and does not necessarily have to match this. For example, reciprocal lattice points equivalent to 0003 and 1014 may also be acceptable.

[0328] Similarly, spots that are not derived from the 11-1 of the cubic crystal may be observed in a reciprocal lattice space different from the orientation where the 11-1 of the cubic crystal was observed. For example, the spot labeled B in Fig. 17B is derived from the 200 reflection of the cubic crystal. This is at an angle of 54° or more and 56° or less from the orientation of the reflection (A in Fig. 17B) derived from the 11-1 of the cubic crystal (that is, ∠AOB is 5 ​ Diffraction spots may be observed at locations where the temperature is 4° or higher and 56° or lower. Note that this index is just an example and does not necessarily have to match this. For example, reciprocal lattice points such as 11-1 and 200 may also be acceptable.

[0329] Note that layered rock-salt type cathode active materials such as lithium cobaltate have (0003) planes and equivalent planes, as well as (10-14) planes and equivalent planes, which are likely to appear as crystal planes. Therefore, when observing the shape of the cathode active material well with SEM or the like it is possible to thin the observation sample with FIB or the like so that the (0003) plane is easy to observe, for example, in TEM or the like, such that the electron beam is incident at [1-2 10]. When it is desired to judge the coincidence of crystal orientation, it is preferable to thin the sample so that the (0003) plane of the layered rock-salt type is easy to observe. 10]. When it is desired to judge the coincidence of crystal orientation, it is preferable to thin the sample so that the (0003) plane of the layered rock-salt type is easy to observe. it is preferable to thin the sample so that the (0003) plane of the layered rock-salt type is easy to observe. it is preferable to thin the sample so that the (0003) plane of the layered rock-salt type is easy to observe.

[0330] However, in the case where the surface layer portion 100a is only MgO or has a structure in which MgO and CoO(II) are solid-solved, the insertion and extraction of lithium become difficult. Therefore, the surface layer portion 100a should have at least cobalt and also have lithium in the discharged state and have a path for the insertion and extraction of lithium. Also, it is preferable that the concentration of cobalt is higher than that of magnesium.

[0331] Also, the additive element X is preferably located in the surface layer portion 100a of the particles of the cathode active material 100 according to one aspect of the present invention. For example, the cathode active material 100 according to one aspect of the present invention may be covered with a film having the additive element X. may be covered with a film having the additive element X.

[0332] <Grain boundary> The additive element X included in the cathode active material 100 according to one aspect of the present invention is randomly and thinly distributed inside It may exist, but it is more preferable that a part of it segregates at grain boundaries.

[0333] In other words, the concentration of the additive element X in and near the crystal grain boundaries of the positive electrode active material 100 according to one aspect of the present invention is also preferably higher than that in other regions inside.

[0334] The crystal grain boundaries can be considered as plane defects. Therefore, similar to the particle surface, they tend to become unstable and the change in the crystal structure easily starts. Therefore, if the concentration of the additive element X in and near the crystal grain boundaries is high, the change in the crystal structure can be more effectively suppressed.

[0335] Also, when the concentration of the additive element X in and near the crystal grain boundaries is high, even if cracks occur along the crystal grain boundaries of the particles of the positive electrode active material 100 according to one aspect of the present invention, the concentration of the additive element X becomes high near the surface generated by the cracks. Therefore, the corrosion resistance of the positive electrode active material after the occurrence of cracks can be enhanced. against hydrofluoric acid.

[0336] In this specification and the like, the vicinity of the crystal grain boundaries means a region up to about 10 nm from the grain boundaries. shall be as such.

[0337] <Particle diameter> If the particle diameter of the positive electrode active material 100 according to one aspect of the present invention is too large, the diffusion of lithium becomes difficult or there are problems such as the surface of the active material layer becoming too rough when coated on the current collector. On the other hand, if it is too small, it becomes difficult to support the active material layer during coating on the current collector, and problems such as an excessive reaction with the electrolytic solution occur. Therefore, the average particle diameter (also referred to as the median diameter, D50) is preferably 1 μm or more and 100 μm or less, more preferably 2 μm or more and 40 μm or less, and even more preferably 5 μm or more and 30 μm or less.

[0338] <Analysis method> Whether a certain positive electrode active material is the positive electrode active material 100 of one aspect of the present invention, which shows an O3'-type crystal structure when charged at a high voltage, can be determined by analyzing the positive electrode charged at a high voltage using XRD, electron diffraction, neutron beam diffraction, electron spin resonance (ESR), nuclear magnetic resonance (NMR), etc. In particular, XRD can analyze the symmetry of transition metals such as cobalt in the positive electrode active material with high resolution, compare the high crystallinity and crystal orientation, analyze the periodic lattice strain and crystal grain size, and sufficient accuracy can be obtained even by directly measuring the positive electrode obtained by disassembling the secondary battery. These points are preferable.

[0339] The positive electrode active material 100 of one aspect of the present invention has the characteristic that the change in crystal structure is small between the charged state at a high voltage and the discharged state as described above. In the charged state at a high voltage, a material in which a crystal structure with a large change from the discharged state occupies 50 wt% or more is not preferable because it cannot withstand the charge and discharge at a high voltage. And it should be noted that the target crystal structure may not be obtained only by adding an additive element. For example, even though lithium cobaltate having magnesium and fluorine is common in this regard, there are cases where the O3'-type crystal structure becomes 60 wt% or more in the charged state at a high voltage and cases where the H1-3 type crystal structure occupies 50 wt% or more. Also, at a predetermined voltage, the O3'-type crystal structure becomes almost 100 wt%, and when the predetermined voltage is further increased, the H1-3 type crystal structure may occur. Therefore, in order to determine whether it is the positive electrode active material 100 of one aspect of the present invention, analysis of the crystal structure including XRD is necessary.

[0340] ​​​​​​​​​​​​​ However, the positive electrode active material in a charged state or a discharged state at a high voltage may undergo a change in crystal structure when exposed to the atmosphere. For example, it may change from an O3'-type crystal structure to an H1-3 type crystal structure. Therefore, it is preferable to handle all samples in an inert atmosphere such as an argon atmosphere.

[0341] <Charging method> To determine whether a certain composite oxide is the positive electrode active material 100 of one aspect of the present invention, high-voltage charging can be performed, for example, by fabricating a coin cell (CR2032 type, diameter 20 mm, height 3.2 mm) with a counter electrode lithium and charging it.

[0342] More specifically, for the positive electrode, a slurry obtained by mixing a positive electrode active material, a conductive material, and a binder can be used by coating it on a positive electrode current collector made of aluminum foil.

[0343] Lithium metal can be used for the counter electrode. When a material other than lithium metal is used for the counter electrode, the potential of the secondary battery is different from the potential of the positive electrode. The voltage and potential in this specification, etc. are the potential of the positive electrode unless otherwise specified.

[0344] For the electrolyte contained in the electrolyte solution, 1 mol / L of lithium hexafluorophosphate (LiPF6) is used, and for the electrolyte solution, ethylene carbonate (EC) and diethyl carbonate (DEC) are mixed at EC:DEC = 3:7 (volume ratio) and vinylene carbonate (VC) is 2 wt%.

[0345] A polypropylene with a thickness of 25 μm can be used for the separator.

[0346] ​​​​​​​​​​​For the positive electrode can and the negative electrode can, those made of stainless steel (SUS) can be used. It is possible.

[0347] The coin cell fabricated under the above conditions is charged at a constant current of 4.6 V and 0.5 C, and then charged at a constant voltage until the current value becomes 0.01 C. Here, 1 C is taken as 137 mA / g. The temperature is 25 °C. After charging in this way, if the coin cell is disassembled in a glove box under an argon atmosphere to take out the positive electrode, a positive electrode active material charged at a high voltage can be obtained. When performing various analyses thereafter, in order to suppress the reaction with external components, it is preferably sealed in an argon atmosphere. For example, XRD can be performed by enclosing it in a sealed container under an argon atmosphere. After charging in this way, if the coin cell is disassembled in a glove box under an argon atmosphere to take out the positive electrode, a positive electrode active material charged at a high voltage can be obtained. After charging in this way, if the coin cell is disassembled in a glove box under an argon atmosphere to take out the positive electrode, a positive electrode active material charged at a high voltage can be obtained. When performing various analyses thereafter, in order to suppress the reaction with external components, it is preferably sealed in an argon atmosphere. For example, XRD can be performed by enclosing it in a sealed container under an argon atmosphere. It can be done.

[0348] <xrd> The ideal powder XRD patterns calculated from the O3’-type crystal structure and the H1-3-type crystal structure for CuKα1 radiation are shown in Figs. 13 and 15. For comparison, the ideal XRD patterns calculated from the crystal structures of LiCoO2 (O3) with x = 1 and CoO2 (O1) with x = 0 are also shown. The patterns of LiCoO2 (O3) and CoO2 (O1) were created using Reflex Powder Diffraction, one of the modules in Materials Studio (BIOVIA), from the crystal structure information obtained from the Inorganic Crystal Structure Database (ICSD). The range of 2θ was from 15° to 75°, the step size was 0.01, the wavelength λ1 was 1.540562×10 m, λ2 was not set, and the monochromator was single. The pattern of the crystal structure of the O3’-type crystal structure was estimated from the XRD pattern of the cathode active material of one embodiment of the present invention and fitted using TOPAS ver. 3 (crystal structure analysis software manufactured by Bruker), and the XRD pattern was created in the same manner as others. As shown in Fig. 13, in the O3’-type crystal structure, diffraction peaks appear at 2θ = 19.30 ± 0.20° (19.10° or more and 19.50° or less) and 2θ = 45.55 ± 0.10° (45.45° or more and 45.65° or less). More specifically, sharp diffraction peaks appear at 2θ = 19.30 ± 0.10° (19.20° or more and 19.40° or less) and 2θ = 45.55 ± 0.05° (45.50° or more and 45.60° or less). However, as shown in Fig. 15, from the crystal structure information obtained from the ICSD, using Reflex Powder Diffraction, one of the modules in Materials Studio (BIOVIA). The range of 2θ was from 15° to 75°, the step size was 0.01, the wavelength λ1 was 1.540562×10 m, λ2 was not set, and the monochromator was single. The pattern of the crystal structure of the O3’-type crystal structure was estimated from the XRD pattern of the cathode active material of one embodiment of the present invention and fitted using TOPAS ver. 3 (crystal structure analysis software manufactured by Bruker), and the XRD pattern was created in the same manner as others. As shown in Fig. 13, in the O3’-type crystal structure, diffraction peaks appear at 2θ = 19.30 ± 0.20° (19.10° or more and 19.50° or less) and 2θ = 45.55 ± 0.10° (45.45° or more and 45.65° or less). More specifically, sharp diffraction peaks appear at 2θ = 19.30 ± 0.10° (19.20° or more and 19.40° or less) and 2θ = 45.55 ± 0.05° -10 (45.50° or more and 45.60° or less). However, as shown in Fig. 15, In the O3’-type crystal structure, diffraction peaks appear at 2θ = 19.30 ± 0.20° (19.10° or more and 19.50° or less), and 2θ = 45.55 ± 0.10° (45.45° or more and 45.65° or less). More specifically, sharp diffraction peaks appear at 2θ = 19.30 ± 0.10° (19.20° or more and 19.40° or less), and 2θ = 45.55 ± 0.05° (45.50° or more and 45.60° or less). However, as shown in Fig. 15, from the XRD pattern of the cathode active material of one embodiment of the present invention, the crystal structure was estimated, and using TOPAS ver. 3 (crystal structure analysis software manufactured by Bruker), fitting was performed, and the XRD pattern was created in the same manner as others. As shown in Fig. 13, in the O3’-type crystal structure, diffraction peaks appear at 2θ = 19.30 ± 0.20° (19.10° or more and 19.50° or less), and 2θ = 45.55 ± 0.10° (45.45° or more and 45.65° or less). More specifically, sharp diffraction peaks appear at 2θ = 19.30 ± 0.10° (19.20° or more and 19.40° or less), and 2θ = 45.55 ± 0.05° (45.50° or more and 45.60° or less). However, as shown in Fig. 15, The ideal powder XRD patterns calculated from the O3’-type crystal structure and the H1-3-type crystal structure for CuKα1 radiation are shown in Figs. 13 and 15. For comparison, the ideal XRD patterns calculated from the crystal structures of LiCoO2 (O3) with x = 1 and CoO2 (O1) with x = 0 are also shown. The patterns of LiCoO2 (O3) and CoO2 (O1) were created using Reflex Powder Diffraction, one of the modules in Materials Studio (BIOVIA), from the crystal structure information obtained from the Inorganic Crystal Structure Database (ICSD). The range of 2θ was from 15° to 75°, the step size was 0.01, the wavelength λ1 was 1.540562×10

[0349] As shown in Fig. 13, in the O3’-type crystal structure, diffraction peaks appear at 2θ = 19.30 ± 0.20° (19.10° or more and 19.50° or less), and 2θ = 45.55 ± 0.10° (45.45° or more and 45.65° or less). More specifically, sharp diffraction peaks appear at 2θ = 19.30 ± 0.10° (19.20° or more and 19.40° or less), and 2θ = 45.55 ± 0.05° (45.50° or more and 45.60° or less). However, as shown in Fig. 15, As shown in Fig. 13, in the O3’-type crystal structure, diffraction peaks appear at 2θ = 19.30 ± 0.20° (19.10° or more and 19.50° or less), and 2θ = 45.55 ± 0.10° (45.45° or more and 45.65° or less). More specifically, sharp diffraction peaks appear at 2θ = 19.30 ± 0.10° (19.20° or more and 19.40° or less), and 2θ = 45.55 ± 0.05° (45.50° or more and 45.60° or less). However, as shown in Fig. 15, As shown in Fig. 13, in the O3’-type crystal structure, diffraction peaks appear at 2θ = 19.30 ± 0.20° (19.10° or more and 19.50° or less), and 2θ = 45.55 ± 0.10° (45.45° or more and 45.65° or less). More specifically, sharp diffraction peaks appear at 2θ = 19.30 ± 0.10° (19.20° or more and 19.40° or less), and 2θ = 45.55 ± 0.05° (45.50° or more and 45.60° or less). However, as shown in Fig. 15, As shown in Fig. 13, in the O3’-type crystal structure, diffraction peaks appear at 2θ = 19.30 ± 0.20° (19.10° or more and 19.50° or less), and 2θ = 45.55 ± 0.10° (45.45° or more and 45.65° or less). More specifically, sharp diffraction peaks appear at 2θ = 19.30 ± 0.10° (19.20° or more and 19.40° or less), and 2θ = 45.55 ± 0.05° (45.50° or more and 45.60° or less). However, as shown in Fig. 15, As shown in Fig. 13, in the O3’-type crystal structure, diffraction peaks appear at 2θ = 19.30 ± 0.20° (19.10° or more and 19.50° or less), and 2θ = 45.55 ± 0.10° (45.45° or more and 45.65° or less). More specifically, sharp diffraction peaks appear at 2θ = 19.30 ± 0.10° (19.20° or more and 19.40° or less), and 2θ = 45.55 ± 0.05° (45.50° or more and 45.60° or less). However, as shown in Fig. 15, In the H1-3 type crystal structure and CoO2 (P-3m1, O1), peaks do not appear at these positions. Therefore, the appearance of peaks at 2θ = 19.30 ± 0.20° and 2θ = 45.55 ± 0.10° in the state charged at a high voltage can be said to be a characteristic of the positive electrode active material 100 of one aspect of the present invention. This can also mean that in the crystal structure with x = 1 and the crystal structure in the high-voltage charged state, the positions where the diffraction peaks of XRD appear are close. More specifically, it can be said that in two or more, more preferably three or more of the main diffraction peaks of both, the difference in the positions where the peaks appear is 2θ = 0.7° or less, more preferably 2θ = 0.5° or less. And the appearance of peaks at 2θ = 45.55 ± 0.10° can be said to be a characteristic of the positive electrode active material 100 of one aspect of the present invention. Substance 100.

[0350] This can also mean that in the crystal structure with x = 1 and the crystal structure in the high-voltage charged state, the positions where the diffraction peaks of XRD appear are close. More specifically, it can be said that in two or more, more preferably three or more of the main diffraction peaks of both, the difference in the positions where the peaks appear is 2θ = 0.7° or less, more preferably 2θ = 0.5° or less. In two or more, more preferably three or more of the main diffraction peaks of both, the difference in the positions where the peaks appear is 2θ = 0.7° or less, more preferably 2θ = 0.5° or less. ° or less, more preferably 2θ = 0.5° or less.

[0351] The positive electrode active material 100 of one aspect of the present invention has an O3' type crystal structure when charged at a high voltage, but not all of the positive electrode active material 100 needs to have an O3' type crystal structure. It may contain other crystal structures or a part thereof may be amorphous. However, when performing Rietveld analysis on the XRD pattern, it is preferable that the O3' type crystal structure is 50 wt% or more, more preferably 60 wt% or more, and even more preferably 66 wt% or more. If the O3' type crystal structure is 50 wt% or more, more preferably 60 wt% or more, and even more preferably 66 wt% or more, a positive electrode active material with excellent cycle characteristics can be obtained. It may contain other crystal structures or a part thereof may be amorphous. However, when performing Rietveld analysis on the XRD pattern, it is preferable that the O3' type crystal structure is 50 wt% or more, more preferably 60 wt% or more, and even more preferably 66 wt% or more. When performing Rietveld analysis on the XRD pattern, it is preferable that the O3' type crystal structure is 50 wt% or more, more preferably 60 wt% or more, and even more preferably 66 wt% or more. Preferably, it is 60 wt% or more, more preferably 66 wt% or more. Preferably, it is 60 wt% or more, more preferably 66 wt% or more. If the O3' type crystal structure is 50 wt% or more, more preferably 60 wt% or more, and even more preferably 66 wt% or more, a positive electrode active material with excellent cycle characteristics can be obtained. Can be.

[0352] Also, even after 100 or more charge and discharge cycles from the start of measurement, when performing Rietveld analysis, it is preferable that the O3' type crystal structure is 35 wt% or more, more preferably 40 wt% or more, and even more preferably 43 wt% or more. When performing Rietveld analysis, it is preferable that the O3' type crystal structure is 35 wt% or more, more preferably 40 wt% or more, and even more preferably 43 wt% or more. Preferably, it is 40 wt% or more, more preferably 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 current is reduced to only about 1 / 10 of that of CoO2(O3). Even under the XRD measurement conditions, no clear peak of the O3' type crystal structure was 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 according to one embodiment of the present invention has a layered rock salt type crystal structure and has a transition 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 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 has In the case of the positive charge / discharge state or the positive discharge state, which can be estimated from the XRD pattern, The layered rock-salt crystal structure of the active material particles has a lattice constant of 2.814× 10 -10 m or larger, 2.817×10 -10 m and the c-axis lattice constant is 1 4.05×10 -10 m or larger, 14.07×10 -10 Preferably smaller than m The state in which no charge and discharge takes place is, for example, the state in which the powder is not yet fabricated into a positive electrode for a secondary battery. The state may be as follows.

[0356] Alternatively, in the layered rock salt-type crystal structure of the particles of the positive electrode active material in a state where charge and discharge are not performed or in a discharged state, the value obtained by dividing the lattice constant of the a-axis 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, in the layered rock salt-type crystal structure of the particles of the positive electrode active material in a state where charge and discharge are not performed or in a discharged state, when XRD analysis is performed, the first peak may be observed at 2θ of 18.50° or more and 19.30 ° or less, and the second peak may be observed at 2θ of 38.00° or more and 38.80° or less.

[0358] Note that the peaks appearing in the powder XRD pattern reflect the crystal structure of the interior 100b of the positive electrode active material 100, which occupies the majority of the volume of the positive electrode active material 100. The crystal structure of the surface layer portion 100a, etc. can be analyzed by electron diffraction of the cross section of the positive electrode active material 100 or the like.

[0359] <xps> In X-ray photoelectron spectroscopy (XPS), since analysis of a region with a depth of about 2 to 8 nm (usually about 5 nm) from the surface is possible, for about half of the region of the surface layer portion 100a, the concentration of each element can be quantitatively analyzed. Further, if narrow scan analysis is performed, the bonding state of the element can be analyzed. The quantitative accuracy of XPS is often about ±1 atomic %, and the detection limit is about 1 atomic % depending on the element. When performing XPS analysis, for example, monochromatic aluminum can be used as the X-ray source. Also, the take-off angle can be, for example, 45°. When XPS analysis is performed on the positive electrode active material 100 of one aspect of the present invention, the peak indicating the binding energy between fluorine and other elements is preferably 682 eV or more and less than 685 eV, and more preferably about 684.3 eV. This is a value different from both 685 eV, which is the binding energy of lithium fluoride, and 686 eV, which is the binding energy of magnesium fluoride. That is, when the positive electrode active material 100 of one aspect of the present invention contains fluorine, it is preferably a bond other than lithium fluoride and magnesium fluoride. Furthermore, when XPS analysis is performed on the positive electrode active material 100 of one aspect of the present invention, the peak indicating the binding energy between magnesium and other elements is preferably 1302 eV or more and less than 1304 eV, and more preferably about 1303 eV. This is a value different from 1305 eV, which is the binding energy of magnesium fluoride, and is a value close to the binding energy of magnesium oxide. That is, when the positive electrode active material 100 of one aspect of the present invention contains magnesium, it is preferably a bond other than magnesium fluoride.

[0360] When performing XPS analysis, for example, monochromatic aluminum can be used as the X-ray source. Also, the take-off angle can be, for example, 45°. When performing XPS analysis, for example, monochromatic aluminum can be used as the X-ray source. Also, the take-off angle can be, for example, 45°.

[0361] When XPS analysis is performed on the positive electrode active material 100 of one aspect of the present invention, the peak indicating the binding energy between fluorine and other elements is preferably 682 eV or more and less than 685 eV, and more preferably about 684.3 eV. This is a value different from both 685 eV, which is the binding energy of lithium fluoride, and 686 eV, which is the binding energy of magnesium fluoride. That is, when the positive electrode active material 100 of one aspect of the present invention contains fluorine, it is preferably a bond other than lithium fluoride and magnesium fluoride. When XPS analysis is performed on the positive electrode active material 100 of one aspect of the present invention, the peak indicating the binding energy between fluorine and other elements is preferably 682 eV or more and less than 685 eV, and more preferably about 684.3 eV. This is a value different from both 685 eV, which is the binding energy of lithium fluoride, and 686 eV, which is the binding energy of magnesium fluoride. That is, when the positive electrode active material 100 of one aspect of the present invention contains fluorine, it is preferably a bond other than lithium fluoride and magnesium fluoride. When XPS analysis is performed on the positive electrode active material 100 of one aspect of the present invention, the peak indicating the binding energy between fluorine and other elements is preferably 682 eV or more and less than 685 eV, and more preferably about 684.3 eV. This is a value different from both 685 eV, which is the binding energy of lithium fluoride, and 686 eV, which is the binding energy of magnesium fluoride. That is, when the positive electrode active material 100 of one aspect of the present invention contains fluorine, it is preferably a bond other than lithium fluoride and magnesium fluoride. When XPS analysis is performed on the positive electrode active material 100 of one aspect of the present invention, the peak indicating the binding energy between fluorine and other elements is preferably 682 eV or more and less than 685 eV, and more preferably about 684.3 eV. This is a value different from both 685 eV, which is the binding energy of lithium fluoride, and 686 eV, which is the binding energy of magnesium fluoride. That is, when the positive electrode active material 100 of one aspect of the present invention contains fluorine, it is preferably a bond other than lithium fluoride and magnesium fluoride. When XPS analysis is performed on the positive electrode active material 100 of one aspect of the present invention, the peak indicating the binding energy between fluorine and other elements is preferably 682 eV or more and less than 685 eV, and more preferably about 684.3 eV. This is a value different from both 685 eV, which is the binding energy of lithium fluoride, and 686 eV, which is the binding energy of magnesium fluoride. That is, when the positive electrode active material 100 of one aspect of the present invention contains fluorine, it is preferably a bond other than lithium fluoride and magnesium fluoride. When XPS analysis is performed on the positive electrode active material 100 of one aspect of the present invention, the peak indicating the binding energy between fluorine and other elements is preferably 682 eV or more and less than 685 eV, and more preferably about 684.3 eV. This is a value different from both 685 eV, which is the binding energy of lithium fluoride, and 686 eV, which is the binding energy of magnesium fluoride. That is, when the positive electrode active material 100 of one aspect of the present invention contains fluorine, it is preferably a bond other than lithium fluoride and magnesium fluoride.

[0362] Furthermore, when XPS analysis is performed on the positive electrode active material 100 of one aspect of the present invention, the peak indicating the binding energy between magnesium and other elements is preferably 1302 eV or more and less than 1304 eV, and more preferably about 1303 eV. This is a value different from 1305 eV, which is the binding energy of magnesium fluoride, and is a value close to the binding energy of magnesium oxide. That is, when the positive electrode active material 100 of one aspect of the present invention contains magnesium, Furthermore, when XPS analysis is performed on the positive electrode active material 100 of one aspect of the present invention, the peak indicating the binding energy between magnesium and other elements is preferably 1302 eV or more and less than 1304 eV, and more preferably about 1303 eV. This is a value different from 1305 eV, which is the binding energy of magnesium fluoride, and is a value close to the binding energy of magnesium oxide. That is, when the positive electrode active material 100 of one aspect of the present invention contains magnesium, Furthermore, when XPS analysis is performed on the positive electrode active material 100 of one aspect of the present invention, the peak indicating the binding energy between magnesium and other elements is preferably 1302 eV or more and less than 1304 eV, and more preferably about 1303 eV. This is a value different from 1305 eV, which is the binding energy of magnesium fluoride, and is a value close to the binding energy of magnesium oxide. That is, when the positive electrode active material 100 of one aspect of the present invention contains magnesium, Furthermore, when XPS analysis is performed on the positive electrode active material 100 of one aspect of the present invention, the peak indicating the binding energy between magnesium and other elements is preferably 1302 eV or more and less than 1304 eV, and more preferably about 1303 eV. This is a value different from 1305 eV, which is the binding energy of magnesium fluoride, and is a value close to the binding energy of magnesium oxide. That is, when the positive electrode active material 100 of one aspect of the present invention contains magnesium, Furthermore, when XPS analysis is performed on the positive electrode active material 100 of one aspect of the present invention, the peak indicating the binding energy between magnesium and other elements is preferably 1302 eV or more and less than 1304 eV, and more preferably about 1303 eV. This is a value different from 1305 eV, which is the binding energy of magnesium fluoride, and is a value close to the binding energy of magnesium oxide. That is, when the positive electrode active material 100 of one aspect of the present invention contains magnesium, When having a bond, it is preferably a bond other than magnesium fluoride.

[0363] The additive element X, such as magnesium and al uminum, which is preferably present in a large amount in the surface layer portion 100a, has a concentration measured by XPS or the like higher than the concentration measured by ICP-MS (inductively coupled plasma mass spectrometry ), or GD-MS (glow discharge mass spectrometry) or the like. Preferably.

[0364] When magnesium and aluminum expose their cross sections by processing and analyze the cross section using TEM-EDX, it is preferable that the concentration of the surface layer portion 100a is higher than the concentration of the interior 100b. The processing can be performed, for example, by FIB.

[0365] In the analysis of XPS (X-ray photoelectron spectroscopy), the atomic number of magnesium is preferably 0.4 times or more and 1.5 times or less the atomic number of cobalt. On the other hand, the ratio Mg / Co of the atomic number of magnesium by the analysis of ICP-MS is preferably 0.001 or more and 0.06 or less.

[0366] On the other hand, nickel contained in the transition metal is preferably not unevenly distributed in the surface layer portion 100a but is distributed throughout the entire positive electrode active material 100. However, this is not the case when there is a region where the above-mentioned excessive additive element X is unevenly distributed.

[0367] <Surface roughness and specific surface area> The positive electrode active material 100 according to one aspect of the present invention preferably has a smooth surface and few irregularities. The fact that the surface is smooth and has few irregularities is one factor indicating that the distribution of the additive element X in the surface layer portion 100a is good. In the production process of the positive electrode active material 100, add ​​​​​​​Lithium cobaltate or lithium nickel-cobalt-manganese oxide before adding element X, when initially heated, has significantly superior charge-discharge cycle characteristics at high voltage, so it is particularly preferred as the positive electrode active material 100. Also, since the surface of the positive electrode active material 100 is smooth and has few irregularities, the stability of the positive electrode active material 100 on the surface can be improved, and the generation of pits may be suppressed.

[0368]

[0369]

[0370]

[0371]

[0372] ​​​​​​​​​​​​​​​​ On the particle surface of the positive electrode active material 100 of the present embodiment, the root mean square (RMS) surface roughness, which is an index of roughness, is 10 nm or less, less than 3 nm, preferably less than 1 nm, and more preferably less than 0.5 nm in root mean square (RMS) surface roughness. .

[0373] Note that the image processing software for performing noise processing, interface extraction, etc. is not particularly limited, but for example, "ImageJ" can be used. Also, the spreadsheet software etc. is not particularly limited, but for example, Microsoft Office Excel can be used. .

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

[0375] The ideal specific surface area A i is calculated and obtained on the assumption that the diameter of all particles is the same as D50, the weight is the same, and the shape is an ideal sphere.

[0376] The median diameter D50 can be measured by a particle size distribution meter using the laser diffraction / scattering method or the like. The specific surface area can be measured by, for example, a specific surface area measuring device using the gas adsorption method by the constant volume method.

[0377] For the positive electrode active material 100 according to one aspect of the present invention, the ratio A / A i between the ideal specific surface area A R obtained from the median diameter D50 and the actual specific surface area A R is preferably 1 or more and 2 or less. i ​

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

[0379] (Embodiment 4) In this embodiment, a positive electrode or 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 type) secondary battery. 18B is an external view of the battery, and FIG. 18C is a cross-sectional view of the battery. Coin-type secondary batteries are mainly used in small electronic devices. The type battery includes a button battery.

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

[0382] In FIG. 18A, a positive electrode 304, a separator 310, a negative electrode 307, a spacer 322, a washer These are sealed with a negative electrode can 302 and a positive electrode can 301. In FIG. 18A, the gasket for sealing is not shown. The ferrite 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 use insulating materials.

[0383] A laminated structure in which a positive electrode active material layer 306 is formed on a positive electrode current collector 305 is used as a positive electrode 304. It is.

[0384] To prevent short - circuiting between the positive electrode and the negative electrode, a separator 310 and a ring - shaped insulator 313 are respectively arranged so as to cover the side surface and the upper surface of the positive electrode 30 4. The separator 310 has a larger planar area than the positive electrode 304. It has a wider planar area.

[0385] Fig. 18B is a perspective view of a 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, which are insulated and sealed with a gasket 303 made of polypropylene or the like. The positive electrode 304 is formed by a positive electrode current collector 305 and a positive electrode active material layer 30 6 provided in contact therewith. Also, the negative electrode 307 is formed by a negative electrode current collector 308 and a negative electrode active material layer 309 provided in contact therewith. Further, the negative electrode 307 is not limited to a laminated structure, and a lithium metal foil or an alloy foil of lithium and aluminum may be used. It is formed by a negative electrode current collector 308 and a negative electrode active material layer 309 provided in contact therewith. Also, the negative electrode 307 is not limited to a laminated structure, and a lithium metal foil or an alloy foil of lithium and aluminum may be used. It is formed by a negative electrode current collector 308 and a negative electrode active material layer 309 provided in contact therewith. Also, the negative electrode 307 is not limited to a laminated structure, and a lithium metal foil or an alloy foil of lithium and aluminum may be used. It is not limited to a laminated structure, and a lithium metal foil or an alloy foil of lithium and aluminum may be used.

[0387] Note that for the positive electrode 304 and the negative electrode 307 used in the coin - type secondary battery 300, the active material layers may be formed on only one side. The active material layers may be formed on only one side.

[0388] For the positive electrode can 301 and the negative electrode can 302, metals such as nickel, aluminum, titanium, etc., which are corrosion - resistant to the electrolyte, or alloys thereof, and alloys of these with other metals (e.g., stainless steel, etc.) can be used. Also, to prevent corrosion by the electrolyte, etc., it is preferable to coat with nickel and aluminum, etc. The positive electrode can 301 is electrically connected to the positive electrode 304, and the negative electrode can 302 is electrically connected to the negative electrode 307 respectively. 302 is electrically connected to the negative electrode 307 respectively. 302 is electrically connected to the negative electrode 307 respectively. 302 is electrically connected to the negative electrode 307 respectively.

[0389] These negative electrode 307, positive electrode 304, and separator 310 are immersed in an electrolytic solution as shown in Fig. 18C. With the positive electrode can 301 facing downwards as shown, the positive electrode 304, separator 310, negative electrode 307, and negative electrode can 302 are stacked in this order, and the positive electrode can 301 and the negative electrode can 302 are pressed against each other via a gasket 303 to manufacture a coin-shaped secondary battery 300.

[0390] By having the above configuration, a coin-shaped secondary battery 300 with high capacity, high charge / discharge capacity, and excellent cycle characteristics can be obtained. Note that when making a secondary battery having a solid electrolyte layer between the negative electrode 307 and the positive electrode 304, the separator 310 can be dispensed with.

[0391] [Cylindrical Secondary Battery] An example of a cylindrical secondary battery will be described with reference to Figs. 19A and 19B. Fig. 19B is a diagram schematically showing a cross section of the cylindrical secondary battery. As shown in Figs. 1 9A and 19B, the cylindrical secondary battery 616 has a positive electrode cap (battery lid) 601 on the upper surface and a battery can (outer can) 602 on the side surface and the bottom surface. The positive electrode cap 601 and the battery can (outer can) 602 are insulated from each other by a gasket (insulating packing) 610.

[0392] Inside the hollow cylindrical battery can 602, a battery element in which a strip-shaped positive electrode 604 and a negative electrode 606 are wound with a separator 605 interposed therebetween is provided. Although not shown, the battery element is wound around a central axis. One end of the battery can 602 is closed and the other end is open. The battery can 602 is made of a metal such as nickel, aluminum, titanium, etc. that is corrosion-resistant to the electrolytic solution, or an alloy thereof, and an alloy of these with other metals (for example, stainless steel, etc.). It can be used. Also, in order to prevent corrosion by the electrolytic solution, nickel and aluminum etc. are preferably coated on the battery can 602. Inside the battery can 602, a battery element in which a positive electrode, a negative electrode and a separator are wound is sandwiched between a pair of opposing insulating plates 608 and 609. Also, the inside of the battery can 602 where the battery element is provided is filled with a non-aqueous electrolytic solution (not shown ). As the non-aqueous electrolytic solution, the same one as that used in a coin-type secondary battery can be used.

[0393] Since the positive electrode and the negative electrode used in the cylindrical storage battery are wound, it is preferable to form active materials on both sides of the current collector. In FIGS. 19A to 19D, a secondary battery 616 in which the height of the cylinder is larger than the diameter of the cylinder is illustrated, but it is not limited thereto. A secondary battery in which the diameter of the cylinder is larger than the height of the cylinder may also be used. With such a configuration, for example, miniaturization of the secondary battery can be achieved.

[0394] By using the negative electrode 570a obtained in the above-described embodiment as the negative electrode 606, a cylindrical secondary battery 616 having a high capacity, a high charge / discharge capacity, and excellent cycle characteristics can be obtained. By using the positive electrode active material composite 100z obtained in the above-described embodiment as the positive electrode 604, a cylindrical secondary battery 616 having a high capacity, a high charge / discharge capacity, and excellent cycle characteristics can be obtained.

[0395] A positive electrode terminal (positive electrode current collector lead) 603 is connected to the positive electrode 604, and a negative electrode terminal (negative electrode current collector lead) 607 is connected to the negative electrode 606. The positive electrode terminal 603 and the negative electrode terminal 607 can both be made of a metal material such as aluminum. The positive electrode terminal 603 is a safety valve mechanism 6 ​​​​​​​​​At 13, the negative terminal 607 is resistance welded to the bottom of the battery can 602 respectively. The safety valve mechanism 61 3 is electrically connected to the positive cap 601 via a PTC element (Positive Temperature Coefficient t) 611. The safety valve mechanism 613 is configured to disconnect the electrical connection between the positive cap 601 and the positive electrode 604 when the internal pressure of the battery rises beyond a predetermined threshold value. Also, the PTC element 611 is a thermal resistance element whose resistance increases when the temperature rises, and it prevents abnormal heat generation by restricting the current amount due to the increase in resistance . For the PTC element, barium titanate (BaTiO3)-based semiconductor ceramics etc. can be used.

[0396] FIG. 19C shows an example of the power storage system 615. The power storage system 615 has a plurality of secondary batteries 6 16. The positive electrodes of the respective secondary batteries are in contact with and electrically connected to a conductor 624 separated by an insulator 625 . The conductor 624 is electrically connected to a control circuit 620 via a wiring 623 . Also, the negative electrodes of the respective secondary batteries are electrically connected to the control circuit 620 via a wiring 626 . As the control circuit 620, a protection circuit or the like that prevents overcharging or over-discharging can be applied .

[0397] FIG. 19D shows an example of the power storage system 615. The power storage system 615 has a plurality of secondary batteries 616, and the plurality of secondary batteries 616 are sandwiched between a conductive plate 628 and a conductive plate 614 . The plurality of secondary batteries 616 are electrically connected to the conductive plate 628 and the conductive plate 614 by a wiring 627 . The plurality of secondary batteries 616 may be connected in parallel or in series . By configuring the power storage system 615 having a plurality of secondary batteries 616, large​​ Kinetic power can be extracted.

[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. When the secondary battery 616 overheats, it is cooled by the temperature control device, and when the secondary battery 616 is too cold, it can be heated by the temperature control device. Therefore, the performance of the power storage system 615 is less affected by the outside air temperature.

[0400] Also, in FIG. 19D, the power storage system 615 is electrically connected to the control circuit 620 via the wiring 621 and the wiring 622. The wiring 621 is electrically connected to the positive electrodes of the plurality of secondary batteries 616 via the conductive plate 628, and the wiring 622 is electrically connected to the negative electrodes of the plurality of secondary batteries 616 via the conductive plate 614 , respectively.

[0401] [Other Structural Examples of Secondary Batteries] Structural examples of secondary batteries will be described with reference to FIGS. 20 and 21.

[0402] The secondary battery 913 shown in FIG. 20A has a wound body 950 in which a terminal 951 and a terminal 952 are provided inside the housing 930. The wound body 950 is immersed in the electrolytic solution inside the housing 930 . The terminal 952 is in contact with the housing 930, and the terminal 951 is not in contact with the housing 930 by using an insulating material or the like. In FIG. 20A, for the sake of convenience, the housing 930 is shown separated , but actually, the wound body 950 is covered by the housing 930, and the terminals 951 and 952 extend outside the housing 930. As the housing 930, a metal material (such as aluminum, etc. ) or a resin material can be used. ​

[0403] Note that, as shown in FIG. 20B, the housing 930 shown in FIG. 20A may be formed of a plurality of materials. For example, in the secondary battery 913 shown in FIG. 20B, a housing 930a and a housing 930b are bonded to each other, and a wound body 950 is provided in a region surrounded by the housing 930a and the housing 930b.

[0404] As the housing 930a, an insulating material such as an organic resin can be used. In particular, by using a material such as an organic resin on the surface where the antenna is formed, shielding of the electric field by the secondary battery 913 can be suppressed. If the shielding of the electric field by the housing 930a is small, an antenna may be provided inside the housing 930a. As the housing 930b, for example, a metal material can be used.

[0405] Furthermore, the structure of the wound body 950 is shown in FIG. 20C. The wound body 950 includes a negative electrode 931, a positive electrode 932, and a separator 933. The wound body 950 is a wound body obtained by winding a laminated sheet in which the negative electrode 931 and the positive electrode 932 overlap each other with the separator 933 interposed therebetween. Note that a plurality of laminations of the negative electrode 931, the positive electrode 932, and the separator 933 may be further 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 933. The negative electrode 931 has a negative electrode active material layer 931a. The positive electrode 932 has a positive electrode active material layer 932a.

[0407] By using the negative electrode 570a obtained in the above-described embodiment as the negative electrode 606, high capacity and ​​​​​​​​​​​, a cylindrical secondary battery 616 having a high charge-discharge capacity and excellent cycle characteristics can be obtained. Further, by using the positive electrode active material composite 100z obtained in the above-described embodiment for the positive electrode 932, a secondary battery 9 13 having a high capacity, a high charge-discharge capacity, and excellent cycle characteristics can be obtained.

[0408] The separator 933 has a width wider than that of the negative electrode active material layer 931a and the positive electrode active material layer 932a, and is wound so as to overlap with the negative electrode active material layer 931a and the positive electrode active material layer 932a. Also, it is preferable in terms of safety that the width of the negative electrode active material layer 931a is wider than that of the positive electrode active material layer 932a. Further, the wound body 950a having such a shape is preferable in terms of safety and productivity.

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

[0410] As shown in FIG. 21C, the wound body 950a and the electrolytic solution are covered with the housing 930 to form a secondary battery 913. It is preferable to provide a safety valve, an overcurrent protection element, etc. in the housing 930. The safety valve is a valve that opens when the inside of the housing 930 reaches a predetermined internal pressure to prevent battery rupture.

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

[0412] <Laminated secondary battery> Next, regarding an example of a laminated secondary battery, an example of an external view is shown in FIGS. 22A and 22B. FIGS. 22A and 22B have a positive electrode 503, a negative electrode 506, a separator 507, an exterior body 5 09, a positive electrode lead electrode 510, and a negative electrode lead electrode 511.

[0413] FIG. 23A shows an external view of the positive electrode 503 and the negative electrode 506. The positive electrode 503 has a positive electrode current collector 501 , and the positive electrode active material layer 502 is formed on the surface of the positive electrode current collector 501. Also, the positive electrode 5 03 has a region where the positive electrode current collector 501 is partially exposed (hereinafter referred to as a tab region). The negative electrode 5 06 has a negative electrode current collector 504, and the negative electrode active material layer 505 is formed on the surface of the negative electrode current collector 504 . Also, the negative electrode 506 has a region where the negative electrode current collector 504 is partially exposed, that is, a tab region . The area and shape of the tab regions of the positive electrode and the negative electrode are not limited to the example shown in FIG. 23A.

[0414] <Manufacturing method of laminated secondary battery> Here, an example of the manufacturing method of the laminated secondary battery whose external view is shown in FIG. 22A will be described with reference to FIGS. 23B and 23C.

[0415] First, the negative electrode 506, the separator 507, and the positive electrode 503 are laminated. FIG. 23B shows the laminated negative electrode 506, separator 507, and positive electrode 503. Here, an example of using 5 sets of negative electrodes and 4 sets of positive electrodes is shown. It can also be called a laminate composed of a negative electrode, a separator, and a positive electrode. Next, the joining of the tab regions of the positive electrode 5 03 to each other and the joining of the positive electrode lead electrode 510 to the tab region of the outermost positive electrode Perform the operation. For joining, for example, ultrasonic welding or the like may be used. Similarly, the tab regions of the negative electrode 506 are joined to each other, and the negative electrode lead electrode 511 is joined to the tab region of the outermost negative electrode.

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

[0417] Next, as shown in FIG. 23C, the exterior body 509 is bent at the portion indicated by the broken line. Then , the outer peripheral portion of the exterior body 509 is joined. For joining, for example, thermocompression bonding or the like may be used. At this time, a region (hereinafter referred to as an introduction port) that is not joined to a part (or one side) of the exterior body 509 is provided so that an electrolytic solution can be introduced later.

[0418] Next, the electrolytic solution is introduced into the interior of the exterior body 509 through the introduction port provided in the exterior body 509. The introduction of the electrolytic solution is preferably performed under a reduced-pressure atmosphere or an inert atmosphere. And finally, the introduction port is joined. In this way, the laminated secondary battery 500 can be manufactured.

[0419] By using the negative electrode 570a obtained in the above-described embodiment as the negative electrode 606, a cylindrical secondary battery 616 having a high capacity, a high charge / discharge capacity, and excellent cycle characteristics can be obtained. Also, by using the positive electrode active material composite 100z obtained in the above-described embodiment as the positive electrode 503, a secondary battery 500 having a high capacity, a high charge / discharge capacity, and excellent cycle characteristics can be obtained.

[0420] [Example of Battery Pack] An example of a secondary battery pack according to one aspect of the present invention capable of wireless charging using an antenna will be described with reference to FIGS. 24A to 24C.

[0421] FIG. 24A is a view showing the appearance of the secondary battery pack 531, which has a thin rectangular parallelepiped shape (which can also be called a flat plate shape with a certain thickness). FIG. 24B is a view for explaining the configuration of the secondary battery pack 531. The secondary battery pack 531 has a circuit board 540 and a secondary battery 513. A label 529 is attached to the secondary battery 513. The circuit board 540 is fixed by a seal 515. Also, the secondary battery pack 531 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 laminate.

[0423] In the secondary battery pack 531, for example, as shown in FIG. 24B, a control circuit 590 is provided on the circuit board 540. Also, the circuit board 540 is electrically connected to a terminal 514. Also, the circuit board 540 is electrically connected to the antenna 517, one of the positive electrode lead and the negative electrode lead of the secondary battery 513, and the other of the positive electrode lead and the negative electrode lead 552.

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

[0425] Note that the antenna 517 is not limited to a coil shape, and may be, for example, linear or plate-shaped. Also, an antenna such as a planar antenna, an aperture antenna, a traveling wave antenna, an EH antenna, a magnetic field antenna, or an induced electric body antenna may be used. Or, the antenna 517 may be a flat plate-shaped conductor. This flat plate-shaped conductor can function as one of the conductors for electric field coupling. That is, ​​​​​​​​​​​​ As one of the two conductors of the capacitor, the antenna 517 may function. Thereby, not only electromagnetic fields and magnetic fields, but also power exchange can be performed by electric fields. It is possible.

[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 shielding, for example, the electromagnetic field generated by the secondary battery 513. As the layer 519, for example, a magnetic material can be used.

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

[0428] (Embodiment 5) In this embodiment, an example of manufacturing an all-solid-state battery using the positive electrode active material composite 100z obtained in the above-described embodiment is shown. It shows an example of manufacturing an all-solid-state battery.

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

[0430] The positive electrode 410 includes a positive electrode current collector 413 and a positive electrode active material layer 414. The positive electrode active material layer 41 4 includes a positive electrode active material 411 and a solid electrolyte 421. The positive electrode active material 411 uses the positive electrode active material composite 100z obtained in the above-described embodiment. Further, the positive electrode active material layer 414 may include a conductive material and a binder.

[0431] The solid electrolyte layer 420 includes a solid electrolyte 421. The solid electrolyte layer 420 is located between the positive electrode 410 and the negative electrode 430, and is a region that does not include either the positive electrode active material 411 or the negative electrode active material 431. It is.

[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 is a conductive layer. The negative electrode active material 431 may include a conductive material and a binder. 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 that the conductive path is easily maintained 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 the atmosphere.

[0436] Halide-based solid electrolytes i...

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 including silicon particles, a second negative electrode active material including graphite having a particle size larger than that of the silicon, and a graphene compound; the silicon particles are in contact with the graphite, and the graphene or graphene compound is in surface-to-surface contact with the first negative electrode active material and the second negative electrode active material; The silicon particles include silicon oxide. Lithium-ion secondary battery.

2. 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 including a compound having silicon, a second negative electrode active material including graphite having a particle size larger than that of the compound having silicon, and graphene or a graphene compound; the silicon-containing compound is in contact with the graphite, and the graphene or graphene compound is in surface-to-surface contact with the first negative electrode active material and the second negative electrode active material. Lithium-ion secondary battery.

3. A lithium ion secondary battery having a positive electrode, a negative electrode, an electrolyte, and a separator, The negative electrode has a first negative electrode active material including SiOx (x is smaller than 2), a second negative electrode active material including graphite having a particle size larger than that of the SiOx, and graphene or a graphene compound; the SiOx is in contact with the graphite, and the graphene or graphene compound is in surface-to-surface contact with the first negative electrode active material and the second negative electrode active material; Lithium-ion secondary battery.

4. 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 including silicon particles, a second negative electrode active material including graphite having a particle size larger than that of the silicon particles, and a conductive assistant; The silicon particles are in contact with the graphite. The silicon particles include silicon oxide. Lithium-ion secondary battery.

5. 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 including a compound having silicon, a second negative electrode active material including graphite having a particle size larger than that of the compound having silicon, and a conductive assistant; The silicon-containing compound is in contact with the graphite. Lithium-ion secondary battery.

6. A lithium ion secondary battery having a positive electrode, a negative electrode, an electrolyte, and a separator, The negative electrode has a first negative electrode active material containing SiOx (x is smaller than 2), a second negative electrode active material containing graphite having a particle size larger than that of the SiOx, and a conductive assistant; The SiOx is in contact with the graphite. Lithium-ion secondary battery.

7. In claim 2 or claim 4, The silicon-containing compound is Li ２ SiO ３ , or Li ４ SiO ４ have Lithium-ion secondary battery.

8. In claim 1 or claim 4, The silicon oxide has an amorphous structure. Lithium-ion secondary battery.

9. In any one of claims 1 to 8, The first active material has a particle size of 5 μm or more, The second active material has a particle size of 250 nm or less. Lithium-ion secondary battery.

10. In any one of claims 1 to 9, The negative electrode has a negative electrode current collector, The negative electrode current collector contains copper. Lithium-ion secondary battery.

11. In any one of claims 1 to 10, The first negative electrode active material is in contact with the second negative electrode active material so as to cover, wrap, or cling to the second negative electrode active material. Lithium-ion secondary battery.

12. In any one of claims 1 to 3, The graphene or graphene compound is in contact with the first negative electrode active material and the second negative electrode active material so as to cover, wrap, or cling to the first negative electrode active material and the second negative electrode active material. Lithium-ion secondary battery.

Images