JP6974099B2 - Secondary battery - Google Patents

Description

The present disclosure relates to a secondary battery.

Trioxotriangulene is an organic radical compound having a condensed polycyclic structure. Although this organic radical compound has an open-shell electronic structure, the electron spin is delocalized in the entire 25π conjugated system, and it is stable enough to be handled at room temperature or in the air. Therefore, trioxotriangulene and its derivatives are one of the compounds expected to be applied to electronic devices due to their unique electrochemical properties.
For example, Patent Document 1 _{discloses a technique for using (COONa) 3-} trioxotriangulene or (COOLi) _3- trioxotriangulene as an active material for a sodium ion battery or an active material for a lithium ion battery. There is.

Japanese Unexamined Patent Publication No. 2015-230830

In the examples disclosed in Patent Document 1, acetylene black is used as the conductive material and polyvinylidene fluoride (PVdF) is used as the binder in the electrode layer. However, since the proportion of the active material in the electrode layer is reduced by the amount containing these additives, there is a problem that the energy density is low.
The present disclosure has been accomplished in view of the above circumstances, and an object of the present disclosure is to provide a secondary battery capable of charging and discharging using an electrode layer containing only an active material containing no additives.

The secondary battery of the present disclosure is a secondary battery including a laminate including a positive electrode, an electrolyte layer and a negative electrode, and at least one of the positive electrode and the negative electrode is a trioxo represented by the following formula (1). The trioxotriangulene neutral radical compound is characterized by including, as an active material layer, a thin film having an orientation in which the π plane of the trioxotriangulene neutral radical compound is perpendicular to the stacking direction of the laminate. ..

（上記式（１）中、Ｘは水素、ハロゲンまたは１価の有機基から選ばれ、互いに同一でも異なっていても良い。また、上記式（１）中、実線及び破線からなる二重線は非局在化した二重結合を表しており、黒丸で示される不対電子は、この非局在化した二重結合中に存在する。）

(In the above formula (1), X is selected from hydrogen, halogen or a monovalent organic group, and may be the same or different from each other. Further, in the above formula (1), the double line consisting of a solid line and a broken line is used. It represents a delocalized double bond, and the unpaired electron indicated by the black circle is present in this delocalized double bond.)

According to the present disclosure, since the active material layer contains a thin film having an orientation in which the π plane of the trioxotriangulene neutral radical compound is perpendicular to the stacking direction of the laminated body, the active material does not contain additives. A secondary battery that can be charged and discharged can be obtained by using only the electrode layer.

It is a figure which shows an example of the layer structure of the secondary battery of this disclosure, and is the figure which schematically shows the cross section cut in the stacking direction. It is a scanning electron microscope (SEM) cross-sectional image of a trioxotriangulene (hereinafter, _{may be referred to as “H 3 TOT”) neutral radical thin film according to Production Example 1.} It is an Out-of-Plane XRD spectrum of the _{H 3} TOT neutral radical thin film according to Production Example 1. It is an In-Plane XRD spectrum of the _{H 3} TOT neutral radical thin film which concerns on Production Example 1. FIG. It is a graph which showed the charge / discharge curve of the secondary battery of Example 1 superimposed. FIG. 3 is a schematic cross-sectional view of a secondary battery in which the π plane of a trioxotriangulene neutral radical compound (hereinafter, may be referred to as “TOT compound”) is parallel to the stacking direction of the laminated body. It is a scanning electron microscope (SEM) cross-sectional image of the _{H 3} TOT neutral radical thin film which concerns on Comparative Production Example 1. FIG. It is an Out-of-Plane XRD spectrum of the _{H 3} TOT neutral radical thin film according to Comparative Production Example 1. It is an In-Plane XRD spectrum of the _{H 3} TOT neutral radical thin film which concerns on Comparative Production Example 1. FIG. It is the graph which showed the charge / discharge curve of the secondary battery of the comparative example 1 superimposed.

The secondary battery of the present disclosure is a secondary battery including a laminate including a positive electrode, an electrolyte layer and a negative electrode, and at least one of the positive electrode and the negative electrode is a trioxo represented by the following formula (1). The trioxotriangulene neutral radical compound is characterized by including, as an active material layer, a thin film having an orientation in which the π plane of the trioxotriangulene neutral radical compound is perpendicular to the stacking direction of the laminate. ..

（上記式（１）中、Ｘは水素、ハロゲンまたは１価の有機基から選ばれ、互いに同一でも異なっていても良い。また、上記式（１）中、実線及び破線からなる二重線は非局在化した二重結合を表しており、黒丸で示される不対電子は、この非局在化した二重結合中に存在する。）

(In the above formula (1), X is selected from hydrogen, halogen or a monovalent organic group, and may be the same or different from each other. Further, in the above formula (1), the double line consisting of a solid line and a broken line is used. It represents a delocalized double bond, and the unpaired electron indicated by the black circle is present in this delocalized double bond.)

FIG. 1 is a diagram showing an example of the layer structure of the secondary battery of the present disclosure, and is a diagram schematically showing a cross section cut in the stacking direction. The secondary battery according to the embodiment of the present disclosure includes a laminate 10 including a negative electrode 1, a positive electrode 2, and an electrolyte layer 3. As shown in FIG. 1, the negative electrode 1 is present on one surface of the electrolyte layer 3, and the positive electrode 2 is present on the other surface of the electrolyte layer 3. Further, in the laminated body 10, the positive electrode 2 includes a positive electrode active material layer 2A and a positive electrode current collector 2B. The positive electrode active material layer 2A contains the TOT compound 2a. The secondary battery of the present disclosure is not necessarily limited to this example.

1. 1. Positive Electrode In the present disclosure, a thin film of the TOT compound represented by the following formula (1) is included in the electrode layer (at least one of a positive electrode and a negative electrode). The thin film of the TOT compound may be contained as an active material layer on the positive electrode side (positive electrode active material layer), or may be contained as an active material layer on the negative electrode side (negative electrode active material layer) as described later. good.

上記式（１）中、Ｘは水素、ハロゲンまたは１価の有機基から選ばれ、互いに同一でも異なっていても良い。また、上記式（１）中、実線及び破線からなる二重線は非局在化した二重結合を表しており、黒丸（●）で示される不対電子は、この非局在化した二重結合中に存在する。

In the above formula (1), X is selected from hydrogen, halogen or a monovalent organic group, and may be the same as or different from each other. Further, in the above equation (1), the double line consisting of the solid line and the broken line represents the delocalized double bond, and the unpaired electron indicated by the black circle (●) is the delocalized two. Present in a double bond.

The TOT compound represented by the above formula (1) may be a commercially available product or a pre-synthesized product. As a method for synthesizing a TOT compound, for example, the method for synthesizing a trioxotriangulene derivative described in Patent Document 1 can be applied, and publicly known techniques can be appropriately referred to.

A substrate may be used in the present disclosure. Here, the base material is a member that can support the TOT compound thin film at least during film formation. The TOT compound thin film may be formed as a result of the TOT compound depositing on at least one surface of the substrate.
The base material may have a plane direction perpendicular to the stacking direction of the laminated body, that is, the direction in which the positive electrode, the electrolyte layer, and the negative electrode are stacked. In this case, the film thickness direction of the TOT compound thin film formed on the substrate is parallel to the laminating direction of the laminated body.
Only one base material may be contained in one secondary battery, or two or more base materials may be contained in one secondary battery. When two or more base materials are contained in the secondary battery, it is preferable that the plane directions of these base materials are the same or parallel. Further, the base material may be contained in only one member in the secondary battery, or may be contained in different members in the secondary battery.

FIG. 1 shows a state in which the positive electrode 2 is provided with the positive electrode current collector 2B as a base material, and the positive electrode active material layer 2A containing the TOT compound 2a is formed on one surface of the positive electrode current collector 2B. Examples of the material of the positive electrode current collector include stainless steel, aluminum, copper, nickel, iron, titanium and carbon.
Examples other than the embodiment shown in FIG. 1 include an example in which a solid electrolyte layer is used as a base material and a positive electrode active material layer containing a TOT compound is formed on at least one surface of the solid electrolyte layer.

Hereinafter, the orientation direction of the TOT compound will be considered.
FIG. 4 is a schematic cross-sectional view of a secondary battery in which the π plane of the TOT compound is parallel to the stacking direction. The laminate 20 in FIG. 4 has the same configuration as the laminate 10 in FIG. 1 except for the orientation of the TOT compound 2a. In FIGS. 1 and 4, the major axis direction of the ellipse showing the TOT compound 2a means the π plane direction, and the minor axis direction of the ellipse means the direction perpendicular to the π plane. In FIG. 4, the major axis direction of the ellipse is parallel to the direction in which the positive electrode 2', the electrolyte layer 3 and the negative electrode 1 are stacked (stacking direction), in which the π plane of the TOT compound 2a is the stacking direction of the laminate 20. It means that it is parallel to.
The laminate 20 contains the TOT compound 2a in the positive electrode active material layer 2A'so that the π plane is parallel to the lamination direction. This means that the π plane of the TOT compound 2a is oriented perpendicular to the plane direction of the base material (positive electrode current collector 2B, etc.). Such orientation with respect to the substrate is hereinafter referred to as edge-on orientation.
As shown in Examples described later, the thin film of TOT compound 2a having such an edge-on orientation is inferior in rate characteristics and has a low energy density (Comparative Example 1). The reason is as follows. The TOT compound is excellent in conductivity in the direction of the molecular stack perpendicular to its π plane, while it is inferior in conductivity in the direction parallel to its π plane. Therefore, the TOT compound thin film having the edge-on orientation is inferior in the conductivity parallel to the laminating direction of the laminated body, and thus inferior in the rate characteristics. Further, it is difficult to increase the energy density of the TOT compound thin film as a result of being unable to increase the film thickness of the TOT compound thin film due to its low conductivity.

On the other hand, FIG. 1 is a schematic cross-sectional view of a secondary battery in which the π plane of the TOT compound is perpendicular to the stacking direction. In FIG. 1, the major axis direction of the ellipse showing the TOT compound 2a is parallel to the direction in which the positive electrode 2, the electrolyte layer 3 and the negative electrode 1 are stacked (stacking direction), in which the π plane of the TOT compound 2a is the laminated body 10. It means that it is perpendicular to the stacking direction of. It should be noted that FIG. 1 shows only one of the embodiments of the present disclosure, and the present disclosure is not limited to this embodiment. For example, the size of the TOT compound 2a and the thickness of the positive electrode active material layer 2A are not limited to the embodiments shown in FIG.
The laminate 10 contains the TOT compound 2a in the positive electrode active material layer 2A so that the π plane is perpendicular to the lamination direction. This means that the π plane of the TOT compound 2a is oriented parallel to the plane direction of the substrate (positive electrode current collector 2B or the like). Such orientation with respect to the substrate is hereinafter referred to as face-on orientation.
As shown in Examples described later, the thin film of TOT compound 2a having such face-on orientation has excellent rate characteristics and high energy density (Example 1). Although the details of the reason are not clear, it is probably excellent in the positive electrode active material layer 2A by smoothly conducting electrons and ions by utilizing the overlap (π-π stacking) between the π planes of the TOT compound. It is presumed that this is because both ionic conductivity and conductivity are compatible.

As described above, Patent Document 1 discloses a technique for using a trioxotriangulene derivative as an active material for a battery. However, there is no description or suggestion in the document that the thin film of the trioxotriangulene derivative is used as the electrode active material layer. This is because, at the level of the prior art, the thin film of the trioxotriangulene derivative has low conductivity because it does not contain a conductive material such as carbon or a binder, and as a result, there is a problem in the rate characteristics of the obtained battery. Because it was thought to be.
In order to improve the rate characteristics in the secondary battery, it is necessary to achieve both ionic conductivity and conductivity in the active material layer. Generally, in a thin film containing an aromatic compound, when the aromatic compound is oriented so that the π plane is parallel to the plane direction of the thin film, the thin film is considered to be inferior in ionic conductivity in the film thickness direction. Has been done. However, contrary to such conventional conventional wisdom, the present researchers use a thin film having an orientation in which the π plane of the TOT compound represented by the above formula (1) is perpendicular to the stacking direction of the laminated body. It has been found that by using it as a layer, it is possible to achieve both excellent ionic conductivity and conductivity.

The method for depositing a thin film of the TOT compound on the surface of the substrate is not particularly limited, and examples thereof include a vacuum vapor deposition method.
The method for controlling the π plane of the TOT compound to be perpendicular to the stacking direction of the laminated body is not particularly limited. For example, when a thin film of a TOT compound is formed on the surface of a base material by a vacuum vapor deposition method, the π plane is face-based on the base material by selecting a base material that easily interacts with the π plane of the TOT compound. Can be oriented on.
Here, as a base material that easily interacts with the π plane of the TOT compound, for example, a graphite sheet can be mentioned. In the initial stage of vacuum deposition, a part of the carbon hexagonal network surface of the graphite sheet causes π-π interaction with the π plane of the TOT compound, so that the orientation of the π plane is parallel to the plane direction of the graphite sheet. One molecule of TOT compound is deposited. As a result of vapor deposition of TOT compound molecules one after another from the top of the one molecule, the obtained thin film is formed by stacking TOT compounds so that the π plane is perpendicular to the stacking direction of the laminated body.
Examples of the base material other than the graphite sheet include a graphene film, a multilayer graphene film, a polymer film having a graphene film or a multilayer graphene film formed on the surface, a metal foil having a graphene film or a multilayer graphene film formed on the surface, and the like. Be done.

Specific examples of the method of depositing a thin film of the TOT compound on the surface of the substrate are as follows. First, the TOT compound is added to the container and set in the vacuum vapor deposition machine. Next, a substrate of appropriate thickness is placed so that its surface faces the container. At this time, it is preferable to arrange the base material horizontally so that the amount of the TOT compound deposited is uniform. Subsequently, the inside of the vacuum vapor deposition machine is depressurized and the container is further heated, so that a thin film of the TOT compound can be deposited on the surface of the substrate.

The orientation of the thin film of the TOT compound can be confirmed, for example, by the Out-of-Plane measurement and the In-Plane measurement of the XRD analysis. Here, the Out-of-Plane measurement of the XRD analysis is a measurement for evaluating a crystal lattice plane parallel to the plane direction of the substrate. On the other hand, the In-Plane measurement of the XRD analysis is a measurement for evaluating a crystal lattice plane perpendicular to the plane direction of the substrate.

The face-on orientation of the TOT compound is (a) a peak derived from the stacking of the π planes of the TOT compound formed by π-π stacking in the Out-of-Plane XRD spectrum (hereinafter, this peak is referred to as peak A). ) Is observed, and (b) in the packing of the one-dimensional column structure formed by π-π stacking of the TOT compound in the In-Plane XRD spectrum, substantially with respect to the stretching direction of the one-dimensional column structure. It can be confirmed by observing a peak derived from the periodic structure in the vertical direction (hereinafter, this peak is referred to as peak B). It is sufficient that at least one of these (a) and (b) can be confirmed, and it is preferable that both (a) and (b) can be confirmed. For example, peak A is observed in FIG. 2B, which will be described later, and peak B is observed in FIG. 2C.
On the other hand, the edge-on orientation of the TOT compound can be confirmed by (c) observation of peak A in the In-Plane XRD spectrum. For example, in FIG. 5C (In-Plane XRD spectrum) described later, peak A is observed. However, in the H ₃ TOT neutral radical thin film (Comparative Production Example 1) described later, no peak is observed in the Out-of-Plane XRD spectrum (see FIG. 5B). Therefore, it is considered that the periodicity (crystallinity) in the stacking direction of the thin film is low. Moreover, no unified view has been obtained regarding the face-on orientation and the edge-on orientation of the TOT compound. When _{the interaction between the H 3} TOT and the substrate is weak, the obtained H ₃ TOT neutral radical thin film tends to have an edge-on orientation, so that the H ₃ TOT neutral radical thin film is face-on. It is thought that it tends to be difficult to orient.

When the TOT compound is a negative electrode active material described later, a general active material can be used as the positive electrode active material. Examples of such positive electrode active materials include rock salt layered active materials _{such as LiCoO 2} , LiMnO ₂ , LiNiO ₂ , LiVO ₂ , LiNi _1/3 Co _1/3 Mn _1/3 O _{2 , and LiMn 2} O ₄ . Examples thereof include spinel-type active materials such as Li (Ni _0.5 Mn _1.5 ) O ₄ and olivine-type active materials such as _{LiFePO 4} , LiMnPO ₄ , LiNiPO ₄ , and LiCoPO _4.

The positive electrode active material layer may contain at least one of materials other than the positive electrode active material, for example, a conductive material, a binder and a solid electrolyte material. However, when the positive electrode active material layer contains a thin film of the TOT compound, it is preferable that the positive electrode active material layer does not contain any material other than the positive electrode active material.
The material of the conductive material is not particularly limited as long as it has a desired conductivity, and examples thereof include a carbon material. Further, specific examples of the carbon material include acetylene black, ketjen black, carbon black, coke, carbon fiber, graphite, and carbon nanotubes.
The material of the binder is not particularly limited as long as it is chemically and electrically stable, but for example, a fluorine-based binder such as polyvinylidene fluoride (PVDF) and polytetrafluoroethylene (PTFE). In addition, rubber-based binders such as styrene-butadiene rubber can be mentioned.
The solid electrolyte material is not particularly limited as long as it has desired ionic conductivity, and examples thereof include an oxide solid electrolyte material and a sulfide solid electrolyte material. As a specific example of the solid electrolyte material, the material described in "3. Electrolyte layer" described later can be adopted.

The content of the positive electrode active material in the positive electrode active material layer is preferably large from the viewpoint of volume, and is, for example, in the range of 60% by mass to 100% by mass, particularly in the range of 70% by mass to 100% by mass. preferable. The thickness of the positive electrode active material layer varies greatly depending on the battery configuration, but is preferably in the range of, for example, 0.1 μm to 1000 μm.

2. 2. Negative electrode In the present disclosure, the thin film of the TOT compound may be the negative electrode active material layer. In this case, the characteristics of the thin film of the TOT compound and its orientation are the same as when the positive electrode active material is the TOT compound. The negative electrode current collector may be a base material, and a thin film of the TOT compound may be deposited on at least one surface of the negative electrode current collector. Examples of the material of the negative electrode current collector include stainless steel, aluminum, copper, nickel, iron, titanium and carbon. Further, the solid electrolyte layer may be used as a base material, and a thin film of the TOT compound may be deposited on at least one surface of the solid electrolyte layer.
On the other hand, when the TOT compound is a positive electrode active material, a general active material can be used as the negative electrode active material. In this case, as the negative electrode active material, it is necessary to use an active material having a lower potential than the above-mentioned TOT compound or positive electrode active material. As the negative electrode active material, a lithium metal, a lithium alloy, a metal oxide containing a lithium element, a metal sulfide containing a lithium element, a metal nitride containing a lithium element, and a carbon material doped with lithium ions can be used. preferable.

The content of the negative electrode active material in the negative electrode active material layer is preferably large from the viewpoint of capacity, and is, for example, in the range of 60% by mass to 100% by mass, particularly in the range of 70% by mass to 100% by mass. preferable. The thickness of the negative electrode active material layer varies greatly depending on the battery configuration, but is preferably in the range of, for example, 0.1 μm to 1,000 μm.

3. 3. Electrolyte layer The electrolyte layer in the present disclosure is a layer existing between a positive electrode and a negative electrode. Ion conduction between the positive electrode active material and the negative electrode active material proceeds through the electrolyte contained in the electrolyte layer.
The electrolyte layer may itself be a base material or may be provided with a base material. An example in which the electrolyte layer itself is a base material is a solid electrolyte layer in which a thin film of the TOT compound is formed on one surface. In this case, the thin film functions as a positive electrode active material layer or a negative electrode active material layer.
The form of the electrolyte layer is not particularly limited, and examples thereof include a liquid electrolyte layer, a gel electrolyte layer, and a solid electrolyte layer.

The liquid electrolyte layer is usually a layer made of a non-aqueous electrolyte solution. The non-aqueous electrolyte usually contains a lithium salt and a non-aqueous solvent. Examples of the lithium salt include inorganic lithium salts such as _{LiPF 6} , LiBF ₄ , LiClO ₄ , and LiAsF _{6 , LiCF 3} SO ₃ , LiN (CF ₃ SO ₂ ) ₂ , LiN (C ₂ F ₅ SO ₂ ) ₂ , and LiC. (CF ₃ SO ₂ ) Organic lithium salts such as _{3 and the like can be mentioned.} Examples of the non-aqueous solvent include ethylene carbonate (EC), propylene carbonate (PC), dimethyl carbonate (DMC), diethyl carbonate (DEC), ethylmethyl carbonate (EMC), butylene carbonate (BC), γ-butyrolactone, sulfolane, and the like. Examples thereof include acetonitrile, 1,2-dimethoxymethane, 1,3-dimethoxypropane, diethyl ether, tetrahydrofuran, 2-methyltetrahydrofuran and mixtures thereof. The concentration of the lithium salt in the non-aqueous electrolytic solution is, for example, in the range of 0.5 mol / L to 3 mol / L.

The gel electrolyte layer can be obtained, for example, by adding a polymer to a non-aqueous electrolytic solution and gelling. Specifically, gelation can be performed by adding a polymer such as polyethylene oxide (PEO), polyacrylic nitrile (PAN) or polymethyl methacrylate (PMMA) to the non-aqueous electrolytic solution.

The solid electrolyte layer is a layer made of a solid electrolyte material. The solid electrolyte material may be amorphous or crystalline. Examples of the solid electrolyte material include an oxide solid electrolyte material and a sulfide solid electrolyte material. Examples of the oxide solid electrolyte material having Li ion conductivity include Li _{1 + x} Al _x Ge _2-x (PO ₄ ) ₃ (0 ≦ x ≦ 2) and Li _{1 + x} Al _x Ti _2-x (PO ₄ ) _3. (0 ≦ x ≦ 2), LiLaTIO (eg, Li _0.34 La _0.51 TiO ₃ ), LiPON (eg, Li _2.9 PO _3.3 N _0.46 ), LiLaZrO (eg, Li ₇ La _3). Zr ₂ O ₁₂ ) and the like can be mentioned. On the other hand, the sulfide solid electrolyte material having Li ion conductivity, for _example, can be cited Li 2 _S-P 2 _{S 5 compound,} Li 2 S-SiS _{2 compound,} a Li 2 S-GeS ₂ compounds.

The thickness of the electrolyte layer varies greatly depending on the type of electrolyte and the configuration of the battery, but is preferably in the range of, for example, 0.1 μm to 1000 μm, particularly preferably in the range of 0.1 μm to 300 μm.

4. Others The secondary battery of the present disclosure may include a separator between the positive electrode and the negative electrode. This is because a safer battery can be obtained.
Examples of the shape of the secondary battery of the present disclosure include a coin type, a laminated type, a cylindrical type, a square type, and the like. The method for manufacturing the secondary battery is not particularly limited, and is the same as the manufacturing method for a general secondary battery.

1. 1. Fabrication of H ₃ TOT Neutral Radical Thin Film [Production Example 1]
(1) Synthesis of trioxotriangulene neutral radical 2,3-dichloro-5,6-dicyano-p-benzoquinone (1.61 g) and dichloromethane (120 mL) as a solvent were added to the container. Further, a solution prepared by dissolving tetrabutylammonium salt (2.00 g) of trioxotriangulene _{(H 3} TOT) in dichloromethane (120 mL) was added dropwise to this container, and the mixture was stirred at room temperature for 1 hour. The precipitate in the container was suction-filtered, and the obtained solid was washed with methylene chloride and tetrahydrofuran and then vacuum-dried. As a result, all of the trioxotriangulene neutral radicals (X in the above formula (1)) A radical that is hydrogen) was obtained (yield: 1.00 g). Hereinafter, this neutral radical may be referred to as an H ₃ TOT neutral radical.

(2) Preparation of thin film by vacuum deposition A graphite sheet (thickness: 25 μm) was attached to a glass plate with polyimide tape, and this graphite sheet was used as a base material.
The above H ₃ TOT neutral radical (109 mg) was placed in an alumina crucible having a diameter of 10 mm, and the alumina crucible was set in a vacuum vapor deposition machine. Further, the graphite sheet base material was installed so that the graphite surface faced the alumina crucible and the graphite surface was horizontal. Then, the inside of the vacuum vapor deposition machine ^{was depressurized to 2 × 10 -3} Pa, and the alumina crucible was heated by resistance heating _{to vacuum-deposit a thin film of H 3} TOT neutral radicals on the surface of the graphite sheet substrate.

FIG. 2A is a scanning electron microscope (SEM) cross-sectional image of the _{H 3 TOT neutral radical thin film according to Production Example 1.} The lower part of FIG. 2A shows graphite as a base material, and the upper part shows all H ₃ TOT neutral radical thin films. From FIG. 2A, _{the average film thickness of the H 3} TOT neutral radical thin film is 800 nm.

[Comparative Manufacturing Example 1]
_{The H 3} TOT neutral radical was synthesized in the same manner as in Production Example 1 above.
Indium tin oxide (ITO) was sputtered on the surface of the aluminum foil to a film thickness of 100 nm. This ITO thin film was used as a base material.
The above H ₃ TOT neutral radical (101 mg) was placed in an alumina crucible having a diameter of 10 mm, and the alumina crucible was set in a vacuum vapor deposition machine. The ITO base material was installed so that the ITO surface faced the alumina crucible and the ITO surface was horizontal. Then, the inside of the vacuum vapor deposition machine ^{was depressurized to 2 × 10 -3} Pa, and the alumina crucible was heated by resistance heating _{to vacuum-deposit a thin film of H 3} TOT neutral radicals on the surface of the ITO substrate.

FIG. 5A is a scanning electron microscope (SEM) cross-sectional image of the _{H 3} TOT neutral radical thin film according to Comparative Production Example 1. The lower part of FIG. 5A shows ITO as a base material, and the upper part shows all H ₃ TOT neutral radical thin films. From FIG. 5A, _{the average film thickness of the H 3} TOT neutral radical thin film is 800 nm.

[Reference manufacturing example 1]
_{The H 3} TOT neutral radical (0.66 mg) synthesized in Production Example 1 was placed in an alumina crucible having a diameter of 10 mm, and the alumina crucible was set in a vacuum vapor deposition machine. Further, the glass substrate as a base material was installed so that the glass substrate surface faced the alumina crucible and the glass substrate surface was horizontal. Then, the inside of the vacuum vapor deposition machine ^{was depressurized to 2 × 10 -3} Pa, and the alumina crucible was heated by resistance heating _{to vacuum-deposit a thin film of H 3} TOT neutral radicals on the surface of the glass substrate.
It was clarified from the XRD measurement that this H ₃ TOT neutral radical thin film had an edge-on orientation. That is, _{the microcrystals of H 3} TOT form an aggregate on the substrate so that the π plane of _{H 3 TOT is perpendicular to the substrate.}
Further, _{gold was vacuum-deposited on the H 3} TOT neutral radical thin film to form a comb-shaped pattern of gold electrodes, and then annealing was performed at 150 ° C. for 5 hours. _{The film thickness of the H 3} TOT neutral radical thin film measured by a step meter was 237 nm. When the electric conductivity of the thin film was measured with a comb-shaped electrode, it was 2.5 × 10 ^-2 S / cm.

[Reference manufacturing example 2]
_{The H 3} TOT neutral radical (6.6 mg) synthesized in Production Example 1 was placed in an alumina crucible having a diameter of 10 mm, and the alumina crucible was set in a vacuum vapor deposition machine. Further, a glass substrate (base material) in which ITO was patterned with a width of 0.2 mm was installed so that the glass substrate surface faced the alumina crucible and the glass substrate surface was horizontal. Then, the inside of the vacuum vapor deposition machine ^{was depressurized to 2 × 10 -3} Pa, and the alumina crucible was heated by resistance heating _{to vacuum-deposit a thin film of H 3} TOT neutral radicals on the surface of the glass substrate.
It was clarified from the XRD measurement that this H ₃ TOT neutral radical thin film had an edge-on orientation.
Further, _{gold was vacuum-deposited on the H 3} TOT neutral radical thin film with a width of 0.2 mm so as to be perpendicular to ITO, and then annealed at 150 ° C. for 5 hours. _{The film thickness of the H 3} TOT neutral radical thin film measured by a step meter was 2.15 μm. The electrical conductivity between the ITO-Au electrodes was measured with a comb-shaped electrode and found to be 6.0 × 10 ^-5 S / cm.

2. 2. For _H 3 TOT neutral radicals thin film according to XRD analysis Production Example 1 and Comparative Preparation Example 1 of a thin film, Out-of-Plane measurement, and performs the XRD analysis by In-Plane measured to examine the orientation of the film.
The detailed measurement conditions are as follows.
X-ray diffraction measuring device SmartLab (manufactured by Rigaku)
Measuring range 2θ = 2-60 °
Measurement interval 0.02 °
Scanning speed 1 ° / min
Measured voltage 45kV
Measurement current 200mA

FIG. 2B is an Out-of-Plane XRD spectrum of the _{H 3 TOT neutral radical thin film according to Production Example 1.} In FIG. 2B, peaks appear at 2θ = 26.6 ° and 27.2 °, respectively. Of these, the peak at 2θ = 27.2 ° is a peak _{derived from the stacking of H 3} TOT neutral radicals in the π plane. Further, the large peak of 2θ = 26.6 ° is derived from the graphite sheet (0001) surface of the base material. In FIG. 2B, almost no peak appears near 2θ = 9.5 °.
FIG. 2C is an In-Plane XRD spectrum of the _{H 3 TOT neutral radical thin film according to Production Example 1.} In FIG. 2C, peaks appear at 2θ = 9.8 °, 17.0 °, 19.5 ° and 26.0 °, respectively. All of these peaks have a periodic structure in a direction substantially perpendicular to the stretching direction of the one-dimensional column structure in the packing of the one-dimensional column structure formed by π-π stacking of _{H 3 TOT neutral radicals.} It is the peak from which it is derived. In FIG. 2C, a peak of 2θ = 27.2 ° is also slightly observed, but its intensity is extremely small.
From the above discussion, it can be seen that in the thin film according to Production Example 1, the π plane of the TOT neutral radical has a horizontal orientation (face-on orientation) with respect to the plane direction of the graphite sheet substrate.

FIG. 5B is an Out-of-Plane XRD spectrum of the _{H 3} TOT neutral radical thin film according to Comparative Production Example 1. Almost no peak appears in FIG. 5B.
FIG. 5C is an In-Plane XRD spectrum of the _{H 3} TOT neutral radical thin film according to Comparative Production Example 1. In FIG. 5C, peaks appear at 2θ = 9.8 °, 17.0 °, 19.5 °, 26.0 ° and 27.2 °, respectively. Of these, the peak at 2θ = 27.2 ° is a peak _{derived from the stacking of H 3} TOT neutral radicals in the π plane. The peaks of 2θ = 9.8 °, 17.0 °, 19.5 ° and 26.0 ° are all one-dimensional column structures formed by π-π stacking of _{H 3 TOT neutral radicals.} It is a peak derived from a periodic structure in the packing in a direction substantially perpendicular to the stretching direction of the one-dimensional column structure.
From the above discussion, it can be seen that in the thin film according to Comparative Production Example 1, the π plane of the TOT neutral radical has an orientation (edge-on orientation) perpendicular to the plane direction of the ITO substrate.

3. 3. Measurement of electrical conductivity of thin film The electrical conductivity of the H ₃ TOT neutral radical thin film according to Reference Manufacturing Example 1 and the electrical conductivity between the ITO-Au electrodes of the _{H 3 TOT neutral radical thin film according to Reference Manufacturing Example 2 are measured.} It was measured.
The electrical conductivity was determined by measuring the current when a voltage from -1V to 1V was swept between the terminals by the two-terminal method. A picoammeter (model number 6487, manufactured by Keithley Instruments) was used to measure the electrical conductivity.

The electrical conductivity between the ITO and Au electrodes according to Reference Production Example 2 is 6.0 × 10 ⁻⁵ S / cm. On the other hand, _{the electric conductivity of the H 3} TOT neutral radical thin film according ^{to Reference Production Example 1 is 2.5 × 10 −2} S / cm. Therefore, the electric conductivity of the thin film according to Reference Production Example 1 is 420 times the electric conductivity of the thin film according to Reference Production Example 2.
Here, in the electrical conduction path of Reference Production Example 1, it is considered that not only the one-dimensional column structure existing parallel to the substrate but also many grain boundaries serving as resistance exist. It is considered that such grain boundaries _{do not exist in the H 3} TOT neutral radical thin film of Production Example 1. Therefore, the electrical conductivity of Production Example 1 is expected to be higher than that of Reference Production Example 1.
From the above, it can be said that the face-on oriented thin film (Production Example 1) is at least 420 times more conductive than the edge-on oriented thin film (Comparative Production Example 1).

The following can be seen from the XRD analysis results and the electrical conductivity measurement results.
The thin film according to Production Example 1 uses a graphite sheet as a base material. _{Therefore, it is considered that the film grows while the π plane of the H 3} TOT neutral radical is horizontally oriented on the π plane of the graphite sheet, that is, the (0001) plane, and as a result, the obtained thin film is face-on oriented.
On the other hand, the thin film according to Comparative Production Example 1 uses ITO as a base material. Therefore, it is considered that the obtained thin film has edge-on orientation as a result of the absence of the interaction that causes face-on orientation between the thin film and the base material. Other possible reasons are as follows. Metal atom in the ITO substrate (indium or tin) is, by causing the oxygen interaction in H 3 _TOT neutral radicals relative to ITO substrate surface π plane H ₃ TOT neutral radicals rising vertically _{Since the film growth starts from the H 3} TOT neutral radical in that state, it is considered that the obtained thin film has an edge-on orientation.
As described above, by appropriately selecting the base material for vacuum vapor deposition, it is considered that the orientation of the obtained thin film can be controlled, and as a result, the conductivity in the film thickness direction can be dramatically improved.

4. Manufacture of secondary battery [Example 1]
A secondary battery was manufactured using the following materials.
Positive electrode: H ₃ TOT neutral radical thin film (face-on orientation, average film thickness: 800 nm) according to Production Example 1.
Negative electrode: Li metal Electrolyte: 1M LiPF ₆ , EC / DMC / EMC electrolyte Separator: Polyolefin-based (PP / PE / PP) porous film Evaluation cell: CR2032 type coin battery

[Comparative Example 1]
_{A secondary battery was used using the same material as in Example 1 except that the positive electrode was replaced with the H 3} TOT neutral radical thin film (edge-on orientation, average film thickness: 800 nm) according to Comparative Production Example 1. Manufactured.

5. Charge / Discharge Measurement With respect to the secondary batteries of Example 1 and Comparative Example 1, charge / discharge measurement was performed under the following conditions, and the battery characteristics were evaluated. Charging and discharging were repeated 3 times for each current density.
Upper and lower voltage: 4.0V-1.0V
Evaluation temperature: 25 ° C
Current density: 10 μA / cm ² and 100 μA / cm ²

FIG. 3 is a graph showing the charge / discharge curves of the secondary battery of Example 1 superimposed. Further, FIG. 6 is a graph showing the charge / discharge curves of the secondary battery of Comparative Example 1 superimposed.
First, a case where the current density is 10 μA / cm ² will be examined. As can be seen from FIG. 3, when the current density is 10 μA / cm ² , the secondary battery of Example 1 has both a charge capacity and a discharge capacity of around 50 μAh. On the other hand, as can be seen from FIG. 6, when the current density is 10 μA / cm ² , the discharge capacity of the secondary battery of Comparative Example 1 is about 10 μAh higher than the charge capacity. FIG. 6 means the following results. _{The H 3} TOT neutral radical thin film (edge-on orientation) according to Comparative Production Example 1 _{has a small conductivity in the stacking direction of the H 3} TOT neutral radicals, and therefore has a large overvoltage during charging / discharging. Therefore, the secondary battery of Comparative Example 1 including the thin film reaches the upper limit voltage of 4.0 V early, so that the charge capacity becomes smaller than the discharge capacity.

Next, the case where the current density is 100 μA / cm ² will be examined. As can be seen from FIG. 3, when the current density is 100 μA / cm ² , the secondary battery of Example 1 has both a charge capacity and a discharge capacity of around 15 μAh. On the other hand, as can be seen from FIG. 6, when the current density is 100 μA / cm ² , neither the charge capacity nor the discharge capacity of the secondary battery of Comparative Example 1 can be confirmed. These results indicate _{that the face-on orientation of the H 3} TOT neutral radicals provides a secondary battery with excellent rate characteristics.

Further, from FIG. 3, it can be seen that the energy density of the secondary battery of Example 1 is 330 mAh / g. On the other hand, from FIG. 6, it can be seen that the energy density of the secondary battery of Comparative Example 1 is 280 mAh / g.

6. Conclusion From the above results, _{for a secondary battery containing an H 3} TOT neutral radical thin film as a positive electrode active material layer, when the H ₃ TOT neutral radicals are face-on oriented with _{respect to the substrate (that is, in H 3} TOT). In the case where the π plane of the sex radical is oriented perpendicular to the stacking direction of the laminate. In Example 1), the H ₃ TOT neutral radical is oriented in edge-on with _{respect to the substrate (that is, H 3).} When the π plane of the TOT neutral radical is oriented parallel to the stacking direction of the laminated body, it was demonstrated that the rate characteristics are excellent as compared with Comparative Example 1). _{Further, the conductivity of the H 3} TOT neutral radical thin film having face-on orientation in the film thickness direction is superior to that of the _{H 3} TOT neutral radical thin film having edge-on orientation in the film thickness direction. It was proved that it was the reason for the improvement of the rate characteristics.
Furthermore, a secondary battery containing a face-on oriented H ₃ TOT neutral radical thin film (Example 1) was demonstrated to have a higher energy density than a conventional secondary battery containing a TOT compound. This is a cathode active material layer is made of H ₃ TOT neutral radicals thin, because without the conductive material and binder.
As described above, _{by including the thin film having the orientation in which the π plane of the H 3} TOT neutral radical is perpendicular to the stacking direction of the laminated body as the active material layer, the electrode layer containing only the active material without additives is used. It was demonstrated that a rechargeable secondary battery can be obtained.

1 Negative electrode 2, 2'Positive electrode 2A, 2A'Positive electrode active material layer 2a Trioxotriangulene neutral radical compound 2B Positive electrode current collector 3 Electrolyte layer 10,20 Laminate

Claims (1)

A secondary battery including a laminate including a positive electrode, an electrolyte layer, and a negative electrode.
At least one of the positive electrode and the negative electrode is a trioxotriangulene neutral radical compound represented by the following formula (1), and the π plane of the trioxotriangulene neutral radical compound is the laminate. A secondary battery characterized by containing a thin film having an orientation perpendicular to the stacking direction as an active material layer.

(In the above formula (1), X is selected from hydrogen, halogen or a monovalent organic group, and may be the same or different from each other. Further, in the above formula (1), the double line consisting of a solid line and a broken line is used. It represents a delocalized double bond, and the unpaired electron indicated by the black circle is present in this delocalized double bond.)

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