Electrode

Abstract

To provide a conductive additive agent for forming an active material layer having high electron conductivity with a small amount of the conductive additive agent, provide an electrode for a secondary battery including an active material layer having a high filling amount and a high density with a small amount of the conductive additive agent, and provide a secondary battery having a large capacity per electrode volume.SOLUTION: An electrode comprises: an active material layer having a plurality of particulate active materials and a plurality of fibrous carbon-containing compounds. The carbon-containing compounds are polymer compounds, and a monomer of the polymer compounds is at least one selected from a group consisting of thiophene, benzene, pyrrol, aniline, phenol, phthalocyanine, furan, azulene, and derivatives thereof.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] One aspect of the present invention relates to an article, a method, or a manufacturing method. Alternatively, one aspect of the present invention relates to a process, a machine, a manufacture, or a composition of matter. One aspect of the present invention relates to an active material usable in a secondary battery, an electrode, a positive electrode active material, a negative electrode active material, a positive electrode, a negative electrode, a secondary battery, and an electronic device having a secondary battery. [Background technology]

[0002] With the remarkable spread of portable electronic devices such as mobile phones, smartphones, electronic books (e-books), and portable game consoles in recent years, there is an increasing demand for smaller and larger-capacity secondary batteries, which are the driving power sources for these devices. Secondary batteries, such as lithium-ion secondary batteries, which have advantages such as high energy density and large capacity, are widely used as secondary batteries for portable electronic devices.

[0003] Among secondary batteries, lithium-ion secondary batteries are widely used due to their high energy density. They consist of a positive electrode containing an active material such as lithium cobalt oxide (LiCoO2) or lithium iron phosphate (LiFePO4), a negative electrode made of a carbon material such as graphite that can absorb and release lithium ions, and a non-aqueous electrolyte solution in which an electrolyte made of a lithium salt such as LiBF4 or LiPF6 is dissolved in an organic solvent such as ethylene carbonate or diethyl carbonate. Charging and discharging of lithium-ion secondary batteries is carried out by lithium ions in the secondary battery moving between the positive and negative electrodes via the non-aqueous electrolyte solution, and the lithium ions being inserted into and extracted from the active materials of the positive and negative electrodes.

[0004] A binder is mixed into the positive or negative electrode to bind the active materials together or between the active materials and the current collector. Binders are typically made of insulating polymeric organic compounds such as PVDF (polyvinylidene fluoride), which have extremely low electronic conductivity. Therefore, increasing the ratio of the amount of binder mixed in to the amount of active material reduces the relative amount of active material in the electrode, resulting in a decrease in the discharge capacity of the secondary battery.

[0005] Therefore, by mixing a conductive additive such as acetylene black (AB) or graphite particles, the electronic conductivity between active materials or between the active material and the current collector is improved, which makes it possible to provide a positive electrode active material with high electronic conductivity (see Patent Document 1).

[0006] Patent Document 2 and Non-Patent Document 1 disclose methods for producing composites containing conductive polymers. [Prior art documents] [Patent documents]

[0007] [Patent Document 1] Japanese Patent Application Laid-Open No. 2002-110162 [Patent Document 2] Japanese Patent Application Laid-Open No. 2016-62651 [Non-patent literature]

[0008] [Non-Patent Document 1] Y. Koizumi et al., “Electropolymerzation on wireless electrodes towards conducting polymer microfibre networks”, NATURE COMMUNICATIONS, 7, 10404(2016). Summary of the Invention [Problem to be solved by the invention]

[0009] An object of one embodiment of the present invention is to provide a conductive additive for forming an active material layer with high electronic conductivity using a small amount of conductive additive. Another object is to provide an electrode including an active material layer with a high filling amount and high density using a small amount of conductive additive. Another object is to provide a battery with a large capacity per electrode volume. Another object is to provide a novel substance, active material particles, a battery, a secondary battery, a power storage device, or a manufacturing method thereof. [Means for solving the problem]

[0010] One aspect of the present invention is an electrode having a current collector and an active material layer, the active material layer having a plurality of granular active materials and a plurality of fibrous carbon-containing compounds, each of the plurality of fibrous carbon-containing compounds being a polymer compound, and the monomer of the polymer compound being at least one selected from the group consisting of thiophene, benzene, polyol, aniline, phenol, phthalocyanine, furan, azulene, and derivatives thereof. As the carbon-containing compound of one aspect of the present invention, a polymer having a monomer selected from the group consisting of thiophene, benzene, polyol, aniline, phenol, phthalocyanine, furan, azulene, and derivatives thereof can be used.

[0011] In the above-described configuration, the average diameter of the plurality of fibrous carbon-containing compounds is preferably 0.01 μm or more and 50 μm or less.

[0012] In the above-described configuration, the plurality of fibrous carbon-containing compounds preferably form a network structure that reaches the surface of the active material layer.

[0013] In the above-described structure, it is preferable that a current collector is provided, the active material layer is provided on the current collector, and the network structure is in contact with the surface of the current collector.

[0014] In the above structure, the active material is preferably a lithium-containing composite oxide having an olivine-type crystal structure.

[0015] In the above-mentioned configuration, the average particle size of the primary particles of the active material is preferably 50 nm or more and 500 nm or less.

[0016] Alternatively, one aspect of the present invention is an electrode having a current collector and an active material layer, the active material layer having a plurality of granular active materials and a plurality of fibrous carbon-containing compounds, each of the plurality of fibrous carbon-containing compounds being a polymer compound, the monomer of the polymer compound being at least one selected from the group consisting of thiophene, benzene, polyol, aniline, phenol, phthalocyanine, furan, azulene, and derivatives thereof, and the plurality of fibrous carbon-containing compounds being in contact with each other to form paths penetrating the active material layer.

[0017] In the above-described configuration, the average diameter of the plurality of fibrous carbon-containing compounds is preferably 0.01 μm or more and 50 μm or less.

[0018] In the above structure, the active material is preferably a lithium-containing composite oxide having an olivine-type crystal structure.

[0019] In the above-mentioned configuration, the average particle size of the primary particles of the active material is preferably 50 nm or more and 500 nm or less.

[0020] Alternatively, one aspect of the present invention is an electrode comprising a current collector and an active material layer, wherein the active material layer comprises first aggregates of aggregated active material, second aggregates of aggregated active material, and a plurality of fibrous carbon-containing compounds, wherein the first aggregates and the second aggregates each comprise a plurality of primary particles, and each of the plurality of fibrous carbon-containing compounds is a polymeric compound, and the monomer of the polymeric compound is at least one selected from the group consisting of thiophene, benzene, polyol, aniline, phenol, phthalocyanine, furan, azulene, and derivatives thereof.

[0021] In the above-described configuration, the average diameter of the plurality of fibrous carbon-containing compounds is preferably 0.01 μm or more and 50 μm or less.

[0022] In the above-described configuration, the plurality of fibrous carbon-containing compounds preferably form a network structure that reaches the surface of the active material layer.

[0023] In the above-described structure, it is preferable that the active material layer is provided on a current collector, and the network structure is in contact with the surface of the current collector.

[0024] In the above structure, the active material is preferably a lithium-containing composite oxide having an olivine-type crystal structure.

[0025] In the above-mentioned configuration, the average particle size of the primary particles of the active material is preferably 50 nm or more and 500 nm or less.

[0026] Another embodiment of the present invention is a secondary battery including any one of the above electrodes.

[0027] Another embodiment of the present invention is an electronic device in which any of the above secondary batteries is mounted. [Effects of the Invention]

[0028] According to one embodiment of the present invention, a conductive additive for forming an active material layer with high electronic conductivity with a small amount of conductive additive can be provided. Furthermore, an electrode including an active material layer with a high filling amount and high density can be provided with a small amount of conductive additive. Furthermore, by using the electrode, a battery with a large capacity per electrode volume can be provided. Furthermore, a novel material, active material particles, a battery, a secondary battery, a power storage device, or a manufacturing method thereof can be provided. [Brief explanation of the drawings]

[0029] [Figure 1] Fig. 1A is a perspective view showing an electrode, and Fig. 1B is a cross-sectional view of an active material layer. [Figure 2] 2A and 2B are cross-sectional views of the active material layer. [Figure 3] FIG. 3 shows an example of a carbon-containing compound. [Figure 4] 4A and 4B are cross-sectional views of the active material layer. [Figure 5] 5A and 5B are top views of the active material layer. [Figure 6]6A is a cross-sectional view of an active material layer, and FIGS. 6B and 6C are diagrams illustrating an example of a method for forming an active material layer according to one embodiment of the present invention. [Figure 7] FIG. 7 is a flowchart showing an example of a method for forming an active material layer according to one embodiment of the present invention. [Figure 8] 8A, 8B, and 8C are diagrams showing an example of graphene. [Figure 9] 9A, 9B and 9C are diagrams illustrating the dispersion state in a polar solvent. [Figure 10] 10A and 10B are diagrams illustrating the dispersion state in a polar solvent. [Figure 11] 11A and 11B are diagrams illustrating a coin-type secondary battery. [Figure 12] FIG. 12 is a diagram illustrating a laminated secondary battery. [Figure 13] 13A and 13B are diagrams illustrating a cylindrical secondary battery. [Figure 14] FIG. 14 is a diagram illustrating an electronic device. [Figure 15] 15A, 15B, and 15C are diagrams illustrating electronic devices. [Figure 16] 16A and 16B are diagrams illustrating an electronic device. [Figure 17] FIG. 17 is a diagram illustrating an electronic device. [Figure 18] FIG. 18 is a diagram illustrating an electronic device. DETAILED DESCRIPTION OF THE INVENTION

[0030] Hereinafter, embodiments will be described with reference to the drawings. However, it will be readily understood by those skilled in the art that the embodiments can be implemented in many different ways and that various changes in form and details can be made without departing from the spirit and scope of the present invention. Therefore, the present invention should not be interpreted as being limited to the following description of the embodiments.

[0031] In addition, in each drawing described in this specification, the size of each component, the thickness of a film, or the area may be exaggerated for clarity, and therefore, the drawings are not necessarily limited to the scale.

[0032] (Embodiment 1) In this embodiment, an electrode for a secondary battery according to one embodiment of the present invention will be described.

[0033] FIG. 1A is a perspective view of an electrode 200. While FIG. 1A shows the electrode 200 in the form of a rectangular sheet, the shape of the electrode 200 is not limited to this and any shape can be appropriately selected. The electrode 200 is produced by applying an electrode paste to a current collector 201 and then drying the paste in a reducing atmosphere or under reduced pressure to form an active material layer 202. In FIG. 1A, the active material layer 202 is formed on only one side of the current collector 201, but the active material layer 202 may be formed on both sides of the current collector 201. Furthermore, the active material layer 202 does not need to be formed on the entire surface of the current collector 201; an uncoated region, such as a region for connecting to an electrode tab, may be appropriately provided.

[0034] The current collector 201 can be made of a highly conductive material that does not alloy with carrier ions such as lithium, such as metals such as stainless steel, gold, platinum, zinc, iron, copper, aluminum, and titanium, or alloys thereof. Aluminum alloys containing elements that improve heat resistance, such as silicon, titanium, neodymium, scandium, and molybdenum, can also be used. The current collector 201 can also be made of a metal element that reacts with silicon to form silicide. Examples of metal elements that react with silicon to form silicide include zirconium, titanium, hafnium, vanadium, niobium, tantalum, chromium, molybdenum, tungsten, cobalt, and nickel. The current collector 201 can be in any suitable shape, such as a foil, plate, sheet, mesh, punched metal, or expanded metal. The current collector 201 preferably has a thickness of 10 μm to 30 μm.

[0035] 1B is a schematic diagram showing a vertical cross section of active material layer 202. Active material layer 202 contains granular active material 203, a carbon-containing compound 207 as a conductive additive, and a binding agent (also referred to as a binder, not shown).

[0036] The active material 203 is a granular positive electrode active material composed of secondary particles having an average particle size and particle size distribution, which are obtained by mixing raw material compounds in a predetermined ratio, firing the mixture, and then pulverizing, granulating, and classifying the fired product by an appropriate means. For this reason, although the active material 203 is shown as a sphere in Fig. 1B and other figures, the shape is not limited to this.

[0037] The active material 203 can be a material that can insert and extract lithium ions.

[0038] In addition, when the carrier ions are alkali metal ions or alkaline earth metal ions other than lithium ions, alkali metals (e.g., sodium, potassium, etc.) or alkaline earth metals (e.g., calcium, strontium, barium, beryllium, magnesium, etc.) may be used as the positive electrode active material in place of lithium in the lithium compound and lithium-containing composite oxide described above.

[0039] When the active material 203 is a positive electrode active material, for example, a lithium-containing composite oxide having an olivine-type crystal structure, a layered rock salt-type crystal structure, or a spinel-type crystal structure can be used.

[0040] Examples of lithium-containing composite oxides with an olivine structure include composite oxides represented by the general formula LiMPO4 (where M is one or more of Fe(II), Mn(II), Co(II), and Ni(II)). Representative examples of the general formula LiMPO4 include LiFePO4, LiNiPO4, LiCoPO4, LiMnPO4, and LiFe a Ni b PO4, LiFe a Co b PO4, LiFe a Mn b PO4, LiNi a Co bPO4, LiNi a Mn b PO4 (where a + b ≤ 1, 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 (where c + d + e ≤ 1, 0 < c < 1, 0 < d < 1, 0 < e < 1), LiFe f Ni g Co h Mn i PO4 (where f + g + h + i ≤ 1, 0 < f < 1, 0 < g < 1, 0 < h < 1, 0 < i < 1), etc. can be mentioned.

[0041] In particular, LiFePO4 is preferable because it well balances the requirements for a cathode active material, such as safety, stability, high capacity density, high potential, and the presence of lithium ions that can be extracted during initial oxidation (charging).

[0042] On the other hand, lithium-containing composite oxides with an olivine-type structure may have low electrical conductivity. Therefore, the output characteristics in a secondary battery may be low. By increasing the conductivity of the electrode with a conductive aid, the output characteristics can be improved. Also, for example, by reducing the primary particle size, the output characteristics can be improved.

[0043] According to one aspect of the present invention, excellent output characteristics can be realized in an electrode having a lithium-containing composite oxide with an olivine-type structure.

[0044] Examples of lithium-containing composite oxides having a layered rock salt-type crystal structure include lithium cobalt oxide (LiCoO2), LiNiO2, LiMnO2, Li2MnO3, LiNi 0.8 Co 0.2 O2 and other NiCo-based (general formula: LiNi x Co 1-x O2 (0 < x < 1)), LiNi 0.5 Mn 0.5O2 etc. NiMn system (general formula: LiNi x Mn 1-x O2(0 <x<1))、LiNi 1 / 3 Mn 1 / 3 Co 1 / 3 O2, etc. NiMnCo system (also called NMC. The general formula is LiNi x Mn y Co 1-x-y O2(x>0, y>0, x+y<1)). 0.8 Co 0.15 Al 0.05 )O2, Li2MnO3-LiMO2 (M=Co, Ni, Mn), etc.

[0045] In particular, LiCoO2 is preferable because it has advantages such as a large capacity, being more stable in the air than LiNiO2, and being more thermally stable than LiNiO2.

[0046] Examples of lithium-containing composite oxides having a spinel-type crystal structure include LiMnO, Li 1+x Mn 2-x O4, LiMn 2-x Al x O4, LiMn 1.5 Ni 0.5 Examples include O4.

[0047] Lithium-containing composite oxides with a spinel-type crystal structure containing manganese, such as LiMn2O4, are mixed with a small amount of lithium nickel oxide (LiNiO2 or LiNi 1-x M x Mixing O2 (M=Co, Al, etc.) is preferable because it has the advantages of suppressing the elution of manganese and the decomposition of the electrolyte.

[0048] In addition, the positive electrode active material is a compound of the general formula Li (2-j) A composite oxide represented by MSiO4 (M is one or more of Fe(II), Mn(II), Co(II), and Ni(II), 0≦j≦2) can be used. (2-j) A typical example of MSiO4 is Li (2-j) FeSiO4, Li (2-j) NiSiO4, Li(2-j) CoSiO4, Li (2-j) MnSiO4, Li (2-j) Fe k Ni l SiO4, Li (2-j) Fe k Co l SiO4, Li (2-j) Fe k Mn l SiO4, Li (2-j) Ni k Co l SiO4, Li (2-j) Ni k Mn l SiO4 (where k + l is 1 or less, 0 < k < 1, 0 < l < 1), Li (2-j) Fe m Ni n Co q SiO4, Li (2-j) Fe m Ni n Mn q SiO4, Li (2-j) Ni m Co n Mn q SiO4 (where m + n + q is 1 or less, 0 < m < 1, 0 < n < 1, 0 < q < 1), Li (2-j) Fe r Ni s Co t Mn u SiO4 (where r + s + t + u is 1 or less, 0 < r < 1, 0 < s < 1, 0 < t < 1, 0 < u < 1), etc. can be mentioned.

[0049] Also, as the positive electrode active material, A xNasicon-type compounds represented by the general formula M2(XO4)3 (A = Li, Na, Mg, M = Fe, Mn, Ti, V, Nb, Al, X = S, P, Mo, W, As, Si) can be used. Examples of Nasicon-type compounds include Fe2(MnO4)3, Fe2(SO4)3, and Li3Fe2(PO4)3. Positive electrode active materials include compounds represented by the general formula Li2MPO4F, Li2MP2O7, and Li5MO4 (M = Fe and Mn), perovskite-type fluorides such as FeF3, metal chalcogenides (sulfides, selenides, tellurides) such as TiS2 and MoS2, lithium-containing composite oxides with an inverse spinel crystal structure such as LiMVO4, and vanadium oxides (VO5, VO6). 13 Materials such as manganese oxides, organic sulfur compounds, etc. can be used.

[0050] When the active material 203 is a negative electrode active material, a material capable of dissolving and precipitating lithium or inserting and desorbing lithium ions can be used, such as lithium metal, carbon-based materials, and alloy-based materials.

[0051] Lithium metal has a low redox potential (-3.045 V vs. the standard hydrogen electrode) and a high specific capacity per weight and volume (3860 mAh / g and 2062 mAh / cm, respectively). 3 ) and is therefore preferable.

[0052] Examples of carbon-based materials include graphite, easily graphitizable carbon (soft carbon), non-graphitizable carbon (hard carbon), carbon nanotubes, graphene, and carbon black.

[0053] Examples of graphite include artificial graphite such as mesocarbon microbeads (MCMB), coke-based artificial graphite, and pitch-based artificial graphite, and natural graphite such as spheroidized natural graphite.

[0054] When lithium ions are inserted into graphite (when lithium-graphite intercalation compounds are formed), graphite exhibits a potential as low as that of metallic lithium (0.1 to 0.3 V vs. Li / Li +This allows lithium-ion batteries to exhibit high operating voltages. Graphite is also preferred because it has advantages such as a relatively high capacity per unit volume, small volume expansion, low cost, and higher safety compared to lithium metal.

[0055] As the negative electrode active material, an alloy-based material capable of undergoing charge-discharge reactions through alloying and dealloying reactions with lithium can also be used. When the carrier ion is lithium ion, examples of the alloy-based material include materials containing at least one of Al, Si, Ge, Sn, Pb, Sb, Bi, Ag, Zn, Cd, In, and Ga. These elements have a large capacity relative to carbon, and silicon in particular has a dramatically high theoretical capacity of 4200 mAh / g. For this reason, it is preferable to use silicon as the negative electrode active material. Examples of alloy-based materials using such elements include Mg2Si, Mg2Ge, Mg2Sn, SnS2, V2Sn3, FeSn2, CoSn2, Ni3Sn2, Cu6Sn5, Ag3Sn, Ag3Sb, Ni2MnSb, CeSb3, LaSn3, La3Co2Sn7, CoSb3, InSb, and SbSn.

[0056] In addition, as the negative electrode active material, SiO, 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 (MoO2), and other oxides can be used.

[0057] In addition, the negative electrode active material is a composite nitride of lithium and transition metals, Li3N-type 3-x M x N (M=Co, Ni, Cu) can be used. For example, Li 2.6 Co 0.4 N3 is preferable because it exhibits a large charge / discharge capacity (900 mAh / g).

[0058] When a composite nitride of lithium and a transition metal is used, lithium ions are contained in the negative electrode active material, which is preferable because it can be combined with a material that does not contain lithium ions, such as V2O5 or Cr3O8, as the positive electrode active material. Even when a material containing lithium ions is used as the positive electrode active material, the composite nitride of lithium and a transition metal can be used as the negative electrode active material by first desorbing the lithium ions contained in the positive electrode active material.

[0059] In addition, materials that undergo a conversion reaction can also be used as the negative electrode active material. For example, transition metal oxides that do not undergo an alloying reaction with lithium, such as cobalt oxide (CoO), nickel oxide (NiO), and iron oxide (FeO), can be used as the negative electrode active material. Materials that undergo a conversion reaction include oxides such as Fe2O3, CuO, Cu2O, RuO2, and Cr2O3, and CoS 0.89 This phenomenon also occurs with sulfides such as NiS and CuS, nitrides such as Zn3N2, Cu3N and Ge3N4, phosphides such as NiP2, FeP2 and CoP3, and fluorides such as FeF3 and BiF3. Note that the above fluorides have high potentials and may therefore be used as positive electrode active materials.

[0060] Furthermore, the carbon-containing compound 207 added to the active material layer 202 as a conductive additive is preferably fibrous. Alternatively, the carbon-containing compound 207 is thread-like. Preferably, a plurality of carbon-containing compounds 207 are in contact with each other to form a conductive path. The conductive path formed by the plurality of carbon-containing compounds 207 is in contact with, for example, the active material 203. Preferably, the conductive path formed by the plurality of carbon-containing compounds 207 is electrically connected to the active material 203. Vapor-Grown Carbon Fiber (VGCF (registered trademark)) can be used as the carbon-containing compound 207. Alternatively, the carbon-containing compound 207 may be fibrous graphene, or graphene may be rolled up into a carbon nanofiber. Alternatively, the carbon-containing compound 207 preferably contains a conductive polymer, which will be described later.

[0061] The conductive path formed by one or more carbon-containing compounds 207 preferably contacts the surface of the current collector and reaches the surface of the active material layer 202. When the conductive path reaches from the surface of the current collector to the surface of the active material layer 202, the conductivity of the active material layer 202 in the thickness direction can be increased.

[0062] The conductive paths formed by one or more carbon-containing compounds 207 can branch and be dispersed in the active material layer 202. By increasing the dispersibility of the carbon-containing compounds 207, high conductivity can be achieved with a smaller amount of carbon-containing compounds 207, the weight percentage and volume percentage of the carbon-containing compounds 207 in the active material layer 202 can be reduced, and the weight percentage and volume percentage of the active material 203 in the active material layer 202 can be increased. This allows the energy density of the secondary battery to be increased.

[0063] Furthermore, as shown in FIG. 2A , aggregates 208 may be formed from a plurality of active materials 203. When aggregates 208 are formed from a plurality of active materials 203, the strength of active material layer 202 may be increased, for example. The strength of active material layer 202 refers to, for example, the strength of resistance to a peel test or the suppression of the active material from collapsing from active material layer 202 after charge and discharge. Alternatively, when aggregates 208 are formed from a plurality of active materials 203, the density of active material layer 202 may be easily increased, for example. Increasing the density of active material layer 202 can increase, for example, the energy density of a secondary battery. The aggregates are, for example, aggregates formed by a plurality of active materials.

[0064] When the plurality of active materials 203 form aggregates, it is preferable that the plurality of carbon-containing compounds 207 form a conductive path that envelops the aggregates 208, as shown in FIG. 2B , for example. The carbon-containing compounds 207 enveloping the aggregates 208 may increase the conductivity of the active material layer 202. The carbon-containing compounds 207 enveloping the aggregates 208 may also increase the density of the active material layer 202. The carbon-containing compounds 207 enveloping the aggregates 208 may also increase the strength of the active material layer 202. The carbon-containing compounds 207 enveloping the aggregates 208 also act to buffer distortion due to expansion and contraction of the positive electrode active material that occurs during charge and discharge. This, for example, suppresses collapse of the active material layer, improving the cycle characteristics of the secondary battery.

[0065] Alternatively, the carbon-containing compound 207 is preferably fibrous. When the carbon-containing compound 207 is fibrous, the carbon-containing compound 207 may have branches. For example, the carbon-containing compound 207 has a branched resinous form.

[0066] When the carbon-containing compound 207 is formed by rolling graphene into a carbon nanofiber, for example, three or more carbon nanofibers are linked at the branched portions, and the carbon nanofibers are connected by linking hexagons formed by carbon. In this case, the hexagons formed by carbon may be distorted at the branched portions.

[0067] The carbon-containing compound contained in the active material layer of one embodiment of the present invention can be, for example, a conductive polymer. Examples of conductive polymer monomers include thiophene, benzene, pyrrole, aniline, phenol, phthalocyanine, furan, azulene, and derivatives thereof. More specifically, 3,4-ethylenedioxythiophene, benzoquinone, and the like can be used. As described below, conductive polymers are formed by electrolytic polymerization of monomers. When monomers bond and grow through electrolytic polymerization, the tips of the growth may branch. Branching is thought to occur, for example, when multiple monomers bond to the tips of the growth.

[0068] The average diameter of the carbon-containing compound 207 is not particularly limited, but is preferably smaller than the particle diameter of the active material 203. For example, it is preferably 0.01 μm or more and 1 μm or less. The length of the carbon-containing compound 207 is not particularly limited, but is preferably 1 μm or more and 300 μm or less. When the carbon-containing compound is resinous or fibrous, the diameter of the carbon-containing compound refers to, for example, the diameter of the cross section.

[0069] Fig. 3 shows an example of a carbon-containing compound having a branched resinous form. In Fig. 3, for example, the path length 211 from a branching point P to the next branching point Q is, for example, 1 µm or more and 300 µm or less.

[0070] 4A is a diagram showing an example in which carbon-containing compound 207 does not form a conductive path reaching from the surface of the current collector to the surface of active material layer 202, but is arranged in agglomerates in the intermediate portion of active material layer 202, for example. In addition, in FIG. 4, part of carbon-containing compound 207 is not dispersed, but forms aggregates 209. When VGCF is used as carbon-containing compound 207, for example, carbon-containing compound 207 may be arranged in agglomerates in the intermediate portion of active material layer 202, forming aggregates 209.

[0071] FIG. 4B shows an example in which, in addition to the carbon-containing compound 207 shown in FIG. 4A (referred to as carbon-containing compound 207a in FIG. 4B for clarity), there is also a carbon-containing compound 207b (shown by a thick line for clarity) that forms a conductive path that extends from the surface of the current collector to the surface of the active material layer 202.

[0072] The active material layer of one embodiment of the present invention may include, as the carbon-containing compound, one or more selected from graphene, VGCF, and AB, in addition to the conductive polymer.

[0073] 5A is a schematic diagram showing the upper surface of active material layer 202. In FIG. 5A, carbon-containing compound 207 is disposed so as to cover a plurality of active materials 203.

[0074] As shown in FIG. 5B , the active material layer 202 may contain graphene 204 as a conductive additive in addition to the carbon-containing compound 207. As shown in FIG. 5B , a plurality of active material particles 203 are coated with a plurality of graphene particles 204. The graphene has a shape such as a flat plate or a sheet. Preferably, the graphene has a curved shape. One graphene particle 204 is electrically connected to a plurality of active material particles 203. A plurality of active material particles 203 may form an aggregate. Preferably, the graphene particle 204 is arranged so as to wrap around the aggregate. A single graphene particle 204 is electrically connected to a plurality of active material particles 203 included in the aggregate.

[0075] Fig. 6A is a diagram showing an example of a cross section taken along dashed line AB in Fig. 5B. The curved shape of the graphene 204 allows it to come into surface contact with part of the surface of the active material 203 so as to wrap around it.

[0076] The graphene 204 enables surface contact with low contact resistance, and therefore can improve the electronic conductivity between the granular active material 203 and the graphene 204 without increasing the amount of conductive additive. Furthermore, multiple graphenes 204 may be in surface contact. The graphene 204 does not necessarily overlap with other graphenes only on the surface of the active material layer 202, but a portion of the graphene 204 is provided between multiple active material layers 202. The graphene 204 is an extremely thin film (sheet) composed of a single layer of carbon molecules or a laminate of these molecules, and therefore covers and contacts a portion of the surface of each individual granular active material 203, tracing the surface of the active material 203. The portions not in contact with the active material 203 are bent, wrinkled, or stretched and taut between the multiple granular active material 203.

[0077] The graphene 204 is formed, for example, by performing a reduction treatment on graphene oxide, which has an atomic ratio of oxygen to carbon of 0.405 or more.

[0078] Graphene oxide, which has an oxygen to carbon atomic ratio of 0.405 or more, can be produced using an oxidation method called the Hummers method.

[0079] The Hummers method involves adding a sulfuric acid solution of potassium permanganate, hydrogen peroxide, or other chemicals to graphite powder to induce an oxidation reaction, producing a dispersion containing graphite oxide. Oxidation of the carbon in graphite bonds functional groups such as epoxy groups, carbonyl groups, carboxyl groups, and hydroxyl groups to graphite oxide. This results in a longer interlayer distance between multiple graphene layers than in graphite, facilitating separation and flaking. Next, ultrasonic vibrations are applied to the dispersion containing graphite oxide to cleave the graphite oxide with a long interlayer distance, separating the graphene oxide and producing a dispersion containing graphene oxide. Finally, powdered graphene oxide can be obtained by removing the solvent from the dispersion containing graphene oxide.

[0080] Here, graphene oxide with an oxygen to carbon atomic ratio of 0.405 or more can be produced by appropriately adjusting the amount of an oxidizing agent such as potassium permanganate. That is, the degree of oxidation of graphene oxide (oxygen to carbon atomic ratio) can be increased by increasing the amount of oxidizing agent relative to graphite powder. Therefore, the amount of oxidizing agent relative to the graphite powder used as raw material can be determined according to the amount of graphene oxide to be produced.

[0081] Note that the method for preparing graphene oxide is not limited to the Hummers method using a sulfuric acid solution of potassium permanganate, and for example, a Hummers method using nitric acid, potassium chlorate, sodium nitrate, or the like, or a method for preparing graphene oxide other than the Hummers method may be used as appropriate.

[0082] Furthermore, graphite oxide may be flaked by applying ultrasonic vibration, or by irradiating it with microwaves, radio waves, or thermal plasma, or by applying physical stress.

[0083] The graphene oxide produced contains epoxy groups, carbonyl groups, carboxyl groups, hydroxyl groups, etc. In polar solvents such as NMP, the oxygen in the functional groups of graphene oxide is negatively charged, so it interacts with NMP while repelling different graphene oxides, making it difficult to aggregate. For this reason, graphene oxide is easily dispersed uniformly in polar solvents.

[0084] The length of one side of the graphene oxide (also referred to as flake size) is 50 nm to 100 μm, preferably 800 nm to 20 μm. In particular, when the flake size is smaller than the average particle size of the active material particles 203, it becomes difficult for the graphene particles to come into surface contact with the active material particles 203 and to connect with each other, making it difficult to improve the electronic conductivity of the active material layer 202.

[0085] 8A to 8C are diagrams showing examples of top views of graphene oxide with various shapes.

[0086] Fig. 8A is a diagram showing an example of length 213 of one side of graphene oxide 214. Furthermore, as shown in Fig. 8B, in a top view of graphene oxide 214, the smallest circle including graphene oxide 214 may be created, and its diameter may be set as length 213 of one side. Furthermore, as shown in Fig. 8C, it is preferable that protrusion 212 is not included in length 213 of one side.

[0087] The average particle size of the primary particles of the granular active material 203 is, for example, 10 nm to 100 μm. Furthermore, by reducing the average particle size of the primary particles, the output characteristics of the secondary battery may be improved. The positive electrode active material of one embodiment of the present invention is preferably 500 nm or less, more preferably 50 nm to 500 nm.

[0088] In addition, the binder contained in the active material layer 202 may be a typical polyvinylidene fluoride (PVDF), as well as polyimide, polytetrafluoroethylene, polyvinyl chloride, ethylene propylene diene polymer, styrene-butadiene rubber, acrylonitrile-butadiene rubber, fluororubber, polyvinyl acetate, polymethyl methacrylate, polyethylene, nitrocellulose, etc.

[0089] The active material layer 202 described above preferably contains the active material 203, the conductive additive, and the binder in proportions of 85 wt% to 94 wt%, 1 wt% to 5 wt%, and 1 wt% to 10 wt%, respectively, relative to the total amount of the active material layer 202. When both a conductive polymer and graphene are used as the conductive additive, the proportion of the conductive polymer is preferably greater than the proportion of graphene, for example, preferably 1.5 times or more.

[0090] The density of the active material layer is, for example, preferably 30% or more, more preferably 50% or more, and even more preferably 70% or more of the density of the material used as the active material. When the active material layer of one embodiment of the present invention uses LiFePO4 as the active material, the density of the active material layer is preferably 1.1 g / cm 3 , more preferably 1.8 g / cm3 More preferably, 2.6 g / cm 3 That's all.

[0091] <Example of manufacturing method 1> An example of a method for forming an active material layer according to one embodiment of the present invention is shown in the flowchart of FIG.

[0092] In step S11, the active material 203, the carbon-containing compound monomer 221, the binder 222, and the solvent 223 are prepared, and in step S12, they are mixed to prepare a slurry.

[0093] The solvent may be, for example, one or a mixture of two or more selected from nonpolar solvents, protic polar solvents, aprotic polar solvents, etc. More specifically, for example, water, NMP (also known as N-methylpyrrolidone, 1-methyl-2-pyrrolidone, N-methyl-2-pyrrolidone, etc.), etc. may be used as the solvent. In addition, it is preferable that the solvent has low solubility in the monomer of the carbon-containing compound.

[0094] Next, in step S13, a current collector 201 is prepared, in step S14, the prepared slurry is applied to one surface of the current collector 201, and in step S15, a sample 224 having a first layer on one surface of the current collector 201 is formed.

[0095] Next, in step S16, the solvent contained in the first layer is volatilized by heating, and in step S17, a sample 225 having a layer 231a on one surface of the current collector 201 is formed. Heating may be performed in a reduced pressure atmosphere.

[0096] Furthermore, the slurry may be applied to the other surface of the current collector 201, and the solvent may be evaporated to form a layer 231b on the other surface of the current collector 201 as well.

[0097] Next, in step S18, a solution 226, an electrode 227, and an electrode 228 are prepared.

[0098] The solution 226 includes a supporting electrolyte and a solvent, and may also include a monomer dispersed therein.

[0099] Known supporting electrolytes can be used as the supporting electrolyte contained in the solution 226. Examples of the supporting electrolyte include cations such as alkali metal ions, alkaline earth metal ions, transition metal ions, pyridinium ions, imidazolium ions, and quaternary phosphonium ions. Examples of the supporting electrolyte include anions such as halogen, PF6 ions, ClO4 ions, AsF6 ions, BF4 ions, AlCl4 ions, SCN ions, SO4 ions, and B 10 Cl 10 Ion, B 12 Cl 12 ions, CF3SO3 ions, C4F9SO3 ions, C(CF3SO2)3 ions, C(C2F5SO2)3 ions, N(CF3SO2)2 ions, N(C4F9SO2)(CF3SO2) ions, N(C2F5SO2)2 ions, etc. can be used.

[0100] The solvent of the solution 226 may be, for example, one of water, acetonitrile, nitrobenzene, hexane, toluene, diethyl ether, benzene, ethylene carbonate (EC), propylene carbonate (PC), butylene carbonate, chloroethylene carbonate, vinylene carbonate, γ-butyrolactone, γ-valerolactone, dimethyl carbonate (DMC), diethyl carbonate (DEC), ethyl methyl carbonate (EMC), methyl formate, methyl acetate, ethyl acetate, methyl propionate, ethyl propionate, propyl propionate, methyl butyrate, 1,3-dioxane, 1,4-dioxane, dimethoxyethane (DME), dimethyl sulfoxide, diethyl ether, methyl diglyme, acetonitrile, benzonitrile, tetrahydrofuran, sulfolane, sultone, etc., or two or more of these may be used in any combination and ratio.

[0101] The electrodes 227 and 228 are preferably flat.

[0102] Next, sample 225 is immersed in solution 226. In solution 226, electrodes 227 and 228 are preferably arranged substantially parallel to each other, as shown in an example in FIG. 6B. Furthermore, current collector 201 of sample 225 is preferably arranged substantially parallel to electrodes 227 and 228. Furthermore, electrode 200 may be arranged on insulating mesh 232, as shown in FIG. 6C.

[0103] Next, in step S19, a voltage is applied between electrode 227 and electrode 228. A DC voltage is applied as the voltage. Alternatively, for example, an AC voltage is applied as the voltage. The magnitude of the voltage and the frequency of the AC current may be adjusted as appropriate before applying the voltage. The application of the voltage causes electrolytic polymerization of the carbon-containing compound monomers contained in layers 231a and 231b, forming a polymer. The polymer is preferably formed so that the fibers are oriented in a direction approximately perpendicular to the surface of current collector 201. Furthermore, the polymer preferably forms a conductive path connecting current collector 201 to the metal layer.

[0104] When an AC voltage is applied to electrode 227 and electrode 228, if one of positive and negative polarities (here, for example, a negative voltage) is applied to electrode 227, for example, a monomer contained in layer 231a undergoes electrolytic polymerization to form a polymer, and if one of positive and negative polarity (here, for example, a negative voltage) is applied to electrode 228, for example, a monomer contained in layer 231b undergoes electrolytic polymerization.

[0105] Here, when a plurality of active materials 203 form aggregates 208, as shown in an example in FIG. 2B , there is a possibility that a polymer will grow between the aggregates 208 and the active materials 203 or between the plurality of aggregates 208. In such a case, there is a possibility that the growth of the polymer will be promoted. There is also a possibility that the polymer will grow so as to wrap around the aggregates 208.

[0106] Furthermore, by the above process, in step S20, an electrode 200 can be obtained in which active material layers 202 having a conductive polymer are provided on both sides of current collector 201.

[0107] In step S12 of the above-described fabrication method, graphene oxide may be added as a material serving as a conductive additive in addition to the monomer of the carbon-containing compound. Graphene oxide has functional groups and therefore has high dispersibility in the slurry.

[0108] Graphene oxide can be reduced, for example, by a heating process. For example, graphene oxide may be reduced by heating in step S16. Alternatively, graphene oxide may be reduced by applying a voltage to cause a reduction reaction. For example, graphene oxide may be reduced by applying a voltage in step S15. Alternatively, graphene oxide may be reduced by immersing it in a solution containing a reducing agent. For example, graphene oxide may be reduced by adding ascorbic acid, hydrazine, dimethylhydrazine, hydroquinone, sodium arsenic hydride (NaBH4), LiAlH4, N,N-diethylhydroxylamine, or the like to Solution 1 in step S15.

[0109] This embodiment mode can be implemented in appropriate combination with other embodiment modes.

[0110] (Embodiment 2) In this embodiment, graphene contained in an electrode included in a secondary battery of one embodiment of the present invention will be described.

[0111] Graphene is a carbon material with a crystalline structure in which a hexagonal carbon skeleton is extended into a plane. Graphene is an atomic plane of a graphite crystal, and has astonishing electrical, mechanical, and chemical properties. It has attracted attention for its potential applications in a variety of fields, including high-mobility field-effect transistors, highly sensitive sensors, highly efficient solar cells, and next-generation transparent conductive films.

[0112] In this specification, graphene includes single-layer graphene and multi-layer graphene having 2 to 100 layers. Single-layer graphene refers to a sheet of carbon molecules having one atomic layer with π bonds. Graphene oxide refers to a compound obtained by oxidizing the graphene. When graphene is formed by reducing graphene oxide, not all of the oxygen contained in the graphene oxide is released, and some oxygen remains in the graphene. When graphene contains oxygen, the proportion of oxygen is 2 to 20 atomic % of the entire graphene, preferably 3 to 15 atomic %, as measured by XPS.

[0113] Here, when the graphene is multilayer graphene, the graphene is obtained by reducing graphene oxide, and thus the interlayer distance of the graphene is 0.34 nm to 0.5 nm, preferably 0.38 nm to 0.42 nm, and more preferably 0.39 nm to 0.41 nm. While the interlayer distance of single-layer graphene in ordinary graphite is 0.34 nm, the graphene used in the secondary battery according to one embodiment of the present invention has a longer interlayer distance, which facilitates the movement of carrier ions between layers of the multilayer graphene.

[0114] In the electrode for a secondary battery according to one embodiment of the present invention, graphene is dispersed in an active material layer so as to overlap with and contact a plurality of active material particles. In other words, a network for electron conduction by graphene is formed in the active material layer. This maintains the bonding between the plurality of active material particles, resulting in the formation of an active material layer with high electron conductivity.

[0115] An active material layer containing graphene as a conductive additive can be produced by the following method. First, graphene is dispersed in a dispersion medium (also called a solvent), and then an active material is added and kneaded to produce a mixture. Then, a binding agent (also called a binder) is added to this mixture and kneaded to produce an electrode paste. Finally, the electrode paste is applied to a current collector, and the dispersion medium is volatilized to produce an active material layer containing graphene as a conductive additive.

[0116] Graphene oxide has functional groups compared to graphene, which can improve the dispersibility of graphene oxide in a slurry. Figure 9A shows the structural formula of NMP, a typical dispersion medium. NMP100 is a compound with a five-membered ring structure and is a polar solvent. As shown in Figure 9A, the oxygen in NMP is electrically biased to the negative (-) side, and the carbon double-bonded to the oxygen is electrically biased to the positive (+) side. Graphene, RGO, or graphene oxide is added to a dilute solvent with such polarity.

[0117] As mentioned above, graphene is a carbon crystalline structure with a hexagonal skeleton extended in a planar fashion, and the structure contains substantially no functional groups. Furthermore, RGO is a material in which the original functional groups have been reduced by heat treatment, and the proportion of functional groups in the structure is low, at approximately 10 wt%. Therefore, as shown in Figure 9B, the surface of graphene or RGO101 is hydrophobic because it has no polarity. Therefore, the interaction between the dispersion medium NMP100 and graphene or RGO101 is extremely weak. Rather, it is thought that graphene or RGO101 aggregates due to interactions between graphene or RGO101 particles (see Figure 9C).

[0118] On the other hand, graphene oxide 102 is a polar substance containing functional groups such as epoxy groups, carbonyl groups, carboxyl groups, and hydroxyl groups. Because the oxygen in the functional groups of graphene oxide 102 is negatively charged, different graphene oxides are less likely to aggregate together in a polar solvent, but they have a strong interaction with NMP 100, a polar solvent (see FIG. 10A). Therefore, as shown in FIG. 10B, the functional groups such as epoxy groups possessed by graphene oxide 102 interact with the polar solvent, inhibiting aggregation of graphene oxides. As a result, graphene oxide 102 is uniformly dispersed in the dispersion medium (see FIG. 10B).

[0119] From the above, in order to use graphene as a conductive additive and to construct a network with high electronic conductivity in the active material layer, it is very effective to use highly dispersible graphene oxide in the dispersion medium when preparing the electrode paste. The dispersibility of graphene oxide in the dispersion medium is thought to depend on the amount of oxygen-containing functional groups such as epoxy groups (in other words, the degree of oxidation of graphene oxide).

[0120] Therefore, one embodiment of the present invention is graphene oxide used as a raw material of a conductive additive for an electrode for a secondary battery, in which the atomic ratio of oxygen to carbon is 0.405 or more.

[0121] Here, the atomic ratio of oxygen to carbon is an index showing the degree of oxidation, and is the ratio of the weight of carbon and oxygen among the constituent elements of graphene oxide, based on carbon. The weight of the elements constituting graphene oxide can be measured, for example, by X-ray photoelectron spectroscopy (XPS).

[0122] The atomic ratio of oxygen to carbon in graphene oxide of 0.405 or more means that graphene oxide has high dispersibility in polar solvents, and is a polar substance with sufficient functional groups such as epoxy groups, carbonyl groups, carboxyl groups, and hydroxyl groups bonded to it.

[0123] Therefore, by dispersing and kneading graphene oxide, which has an atomic ratio of oxygen to carbon of 0.405 or more, in a dispersion medium together with an active material and a binder, applying the mixture to a current collector, and heating it, it is possible to form an electrode for a secondary battery that contains graphene that is highly dispersible and has an electron-conducting network.

[0124] The graphene oxide preferably has a side length of 50 nm or more and 100 μm or less, and more preferably 800 nm or more and 20 μm or less.

[0125] Another embodiment of the present invention is an electrode for a secondary battery including, on a current collector, an active material layer including a plurality of granular active material particles, a conductive additive including a plurality of graphenes, and a binder, in which the graphenes are larger than the average particle size of the granular active material particles, the graphenes are dispersed in the active material layer to be in surface-to-surface contact with one or more adjacent graphene particles, and the graphenes are in surface-to-surface contact with each other so as to wrap around part of a surface of the granular active material particles.

[0126] Another embodiment of the present invention is an electrode for a secondary battery including an active material layer over a current collector, the active material layer including a plurality of granular active materials, a conductive additive including a plurality of graphenes, and a binder, in which, with respect to a bonding state of carbon included in the active material layer, a proportion of C═C bonds is 35% or more and a proportion of C═C bonds is 5% or more and 20% or less.

[0127] Another embodiment of the present invention is a method for manufacturing an electrode for a secondary battery, comprising: dispersing graphene oxide having an oxygen to carbon atomic ratio of 0.405 or more in a dispersion medium; adding an active material to the dispersion medium in which the graphene oxide is dispersed and kneading the mixture; adding a binder to the mixture and kneading the mixture to prepare an electrode paste; applying the electrode paste to a current collector; and reducing the graphene oxide after or simultaneously with volatilizing the dispersion medium contained in the applied electrode paste, thereby forming an active material layer containing graphene on the current collector.

[0128] When graphene contains oxygen, the oxygen content is 2 atomic % to 20 atomic % of the entire graphene, preferably 3 atomic % to 15 atomic % as measured by XPS. The lower the oxygen content, the higher the conductivity of graphene, resulting in the formation of a network with high electron conductivity. Furthermore, the higher the oxygen content, the more gaps that serve as ion passages can be formed in graphene.

[0129] This embodiment mode can be implemented in appropriate combination with other embodiment modes.

[0130] (Embodiment 3) In this embodiment, a structure of a secondary battery will be described with reference to FIG.

[0131] FIG. 11A is an external view of a coin-type (single-layer flat) secondary battery, and FIG. 11B is a cross-sectional view thereof.

[0132] In the coin-type secondary battery 300, a positive electrode can 301, which also serves as a positive electrode terminal, and a negative electrode can 302, which also serves as a negative electrode terminal, are insulated and sealed by 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 306 provided in contact with the positive electrode current collector. The negative electrode 307 is formed by a negative electrode current collector 308 and a negative electrode active material layer 309 provided in contact with the negative electrode current collector. A separator 310 and an electrolyte (not shown) are provided between the positive electrode active material layer 306 and the negative electrode active material layer 309.

[0133] At least one of the positive electrode 304 and the negative electrode 307 can be formed using the electrode 200 described in Embodiment 1.

[0134] Separator 310 can be made of an insulating material such as cellulose (paper), or porous polypropylene or polyethylene.

[0135] The electrolytic solution uses a material having carrier ions as an electrolyte. Typical examples of the electrolyte include lithium salts such as LiClO4, LiAsF6, LiBF4, LiPF6, and Li(C2F5SO2)2N. Also, electrolytes having anions exemplified as anions of the supporting electrolyte contained in the solution 226 can be used.

[0136] In addition, when the carrier ions are alkali metal ions or alkaline earth metal ions other than lithium ions, alkali metals (e.g., sodium, potassium, etc.) or alkaline earth metals (e.g., calcium, strontium, barium, beryllium, magnesium) may be used as the electrolyte in place of lithium in the lithium salt.

[0137] The solvent for the electrolyte solution is a material that allows carrier ions to migrate. The solvent for the electrolyte solution is preferably an aprotic organic solvent. Typical examples of aprotic organic solvents include ethylene carbonate (EC), propylene carbonate, dimethyl carbonate, diethyl carbonate (DEC), γ-butyrolactone, acetonitrile, dimethoxyethane, and tetrahydrofuran, and one or more of these can be used. Using a gelatinizable polymer material as the electrolyte solution solvent enhances safety against leakage and other issues. This also enables the secondary battery to be made thinner and lighter. Typical examples of gelatinizable polymer materials include silicone gel, acrylic gel, acrylonitrile gel, polyethylene oxide gel, polypropylene oxide gel, and fluorine-based polymer gel. The use of one or more flame-retardant and non-volatile ionic liquids (room-temperature molten salts) as the electrolyte solution solvent can prevent the secondary battery from exploding or catching fire even if the internal temperature rises due to an internal short circuit or overcharging.

[0138] In addition, instead of an electrolyte solution, a solid electrolyte containing inorganic materials such as sulfides or oxides, or a solid electrolyte containing polymer materials such as polyethylene oxide (PEO) can be used. When a solid electrolyte is used, the installation of a separator or spacer is unnecessary. Furthermore, since the entire battery can be solidified, there is no risk of leakage, dramatically improving safety.

[0139] Metals such as nickel, aluminum, and titanium that are corrosion-resistant to liquids such as electrolytes during charging and discharging of the secondary battery, alloys of these metals, alloys of these metals with other metals (e.g., stainless steel), laminates of these metals, laminates of these metals with the above-mentioned alloys (e.g., stainless steel / aluminum), and laminates of these metals with other metals (e.g., nickel / iron / nickel) can be used for positive electrode can 301 and negative electrode can 302. Positive electrode can 301 is electrically connected to positive electrode 304, and negative electrode can 302 is electrically connected to negative electrode 307.

[0140] These negative electrode 307, positive electrode 304, and separator 310 are impregnated with an electrolyte, and as shown in FIG. 11B, the positive electrode 304, separator 310, negative electrode 307, and negative electrode can 302 are stacked in this order with the positive electrode can 301 facing downwards, and the positive electrode can 301 and the negative electrode can 302 are crimped together via a gasket 303 to produce a coin-type secondary battery 300.

[0141] Next, an example of a laminated secondary battery will be described with reference to FIG.

[0142] 12 includes a positive electrode 503 having a positive electrode current collector 501 and a positive electrode active material layer 502, a negative electrode 506 having a negative electrode current collector 504 and a negative electrode active material layer 505, a separator 507, an electrolyte 508, and an exterior body 509. The separator 507 is disposed between the positive electrode 503 and the negative electrode 506 provided within the exterior body 509. The interior of the exterior body 509 is filled with the electrolyte 508.

[0143] 12, the positive electrode current collector 501 and the negative electrode current collector 504 also serve as terminals for electrical contact with the outside. Therefore, a portion of the positive electrode current collector 501 and a portion of the negative electrode current collector 504 are arranged so as to be exposed to the outside from the exterior body 509.

[0144] In the laminated secondary battery 500, the exterior body 509 can be a three-layer laminate film having a highly flexible metal thin film made of aluminum, stainless steel, copper, nickel, or the like provided on a film made of a material such as polyethylene, polypropylene, polycarbonate, ionomer, or polyamide, and an insulating synthetic resin film made of polyamide resin, polyester resin, or the like provided on the metal thin film as the outer surface of the exterior body. This three-layer structure blocks permeation of electrolyte and gas, ensures insulation, and also provides electrolyte resistance.

[0145] Next, an example of a cylindrical secondary battery will be described with reference to Fig. 13. As shown in Fig. 13A, a cylindrical secondary battery 600 has a positive electrode cap (battery lid) 601 on the top surface, and a battery can (external can) 602 on the side and bottom surfaces. The positive electrode cap and battery can (external can) 602 are insulated by a gasket (insulating packing) 610.

[0146] FIG. 13B is a schematic diagram showing the cross section of a cylindrical secondary battery. Inside a hollow cylindrical battery can 602, a battery element is provided, in which a strip-shaped positive electrode 604 and a negative electrode 606 are wound with a separator 605 sandwiched between them. Although not shown, the battery element is wound around a center pin. One end of the battery can 602 is closed and the other end is open. The battery can 602 can be made of metals such as nickel, aluminum, and titanium, alloys of these metals, alloys of these metals with other metals (e.g., stainless steel), laminates of these metals, laminates of these metals with the aforementioned alloys (e.g., stainless steel / aluminum), or laminates of these metals with other metals (e.g., nickel / iron / nickel), all of which are corrosion-resistant to liquids such as electrolytes during charging and discharging of the secondary battery. Inside the battery can 602, the wound battery element, in which the positive electrode, negative electrode, and separator are wound, is sandwiched between a pair of opposing insulating plates 608 and 609. A non-aqueous electrolyte (not shown) is poured into the battery can 602 in which the battery element is provided. The non-aqueous electrolyte may be the same as that used in coin-type or laminate-type secondary batteries.

[0147] The positive electrode 604 and negative electrode 606 may be manufactured in the same manner as the positive electrode and negative electrode of the coin-type secondary battery described above. However, the positive electrode and negative electrode used in the cylindrical secondary battery are wound, and therefore active material is formed on both sides of the current collector. 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. Both the positive electrode terminal 603 and the negative electrode terminal 607 can be made of a metal material such as aluminum. The positive electrode terminal 603 is resistance-welded to a safety valve mechanism 612, and the negative electrode terminal 607 is resistance-welded to the bottom of the battery can 602. The safety valve mechanism 612 is electrically connected to the positive electrode cap 601 via a PTC (Positive Temperature Coefficient) element 611. The safety valve mechanism 612 cuts off the electrical connection between the positive electrode cap 601 and the positive electrode 604 when the internal pressure of the battery exceeds a predetermined threshold. The PTC element 611 is a thermosensitive resistor whose resistance increases as the temperature rises, and the increased resistance limits the amount of current to prevent abnormal heat generation. Barium titanate (BaTiO3) based semiconductor ceramics or the like can be used for the PTC element.

[0148] In this embodiment, coin-type, laminate-type, and cylindrical-type secondary batteries are shown as the secondary battery, but secondary batteries of various other shapes such as sealed secondary batteries, square secondary batteries, etc. Also, the secondary battery may have a structure in which a plurality of positive electrodes, negative electrodes, and separators are stacked, or a structure in which a positive electrode, negative electrode, and separator are wound.

[0149] The positive electrodes of the secondary batteries 300, 500, and 600 described in this embodiment are formed using the positive electrodes according to one embodiment of the present invention. Therefore, the discharge capacities of the secondary batteries 300, 500, and 600 can be increased.

[0150] This embodiment mode can be implemented in appropriate combination with other embodiment modes.

[0151] (Fourth embodiment) A secondary battery according to one embodiment of the present invention can be used as a power source for various electric devices that are driven by electricity.

[0152] Specific examples of electrical devices using the secondary battery according to one embodiment of the present invention include display devices such as televisions and monitors, lighting devices, desktop or notebook personal computers, word processors, image playback devices that play back still images or videos stored on recording media such as DVDs (Digital Versatile Discs), portable CD players, radios, tape recorders, headphone stereos, stereos, table clocks, wall clocks, cordless telephone handsets, transceivers, mobile phones, car phones, portable game consoles, calculators, personal digital assistants, electronic organizers, e-book readers, electronic translators, voice input devices, video cameras, digital still cameras, toys, high-frequency heating devices such as electric shavers and microwave ovens, air conditioning equipment such as electric rice cookers, electric washing machines, electric vacuum cleaners, water heaters, electric fans, hair dryers, air conditioners, humidifiers, and dehumidifiers, dishwashers, dish dryers, clothes dryers, futon dryers, electric refrigerators, electric freezers, electric refrigerator-freezers, freezers for DNA storage, flashlights, power tools such as chainsaws, smoke detectors, and medical devices such as dialysis machines. Other examples include industrial equipment such as emergency lights, traffic lights, conveyor belts, elevators, escalators, industrial robots, power storage systems, and power storage devices for power leveling and smart grids. Mobile vehicles propelled by electric motors using power from secondary batteries are also included in the category of electrical equipment. Examples of such mobile vehicles include electric vehicles (EVs), hybrid vehicles (HVs) that combine internal combustion engines and electric motors, plug-in hybrid vehicles (PHVs), tracked vehicles in which the tires and wheels of these vehicles have been replaced with tracks, mopeds including electrically assisted bicycles, motorcycles, electric wheelchairs, golf carts, small or large ships, submarines, helicopters, aircraft, rockets, artificial satellites, space probes, planetary probes, and spaceships.

[0153] The electrical device can use the secondary battery according to one embodiment of the present invention as a main power source for covering almost all of its power consumption. Alternatively, the electrical device can use the secondary battery according to one embodiment of the present invention as an uninterruptible power source that can supply power to the electrical device when power supply from the main power source or a commercial power source is stopped. Alternatively, the electrical device can use the secondary battery according to one embodiment of the present invention as an auxiliary power source that supplies power to the electrical device in parallel with power supply from the main power source or a commercial power source to the electrical device.

[0154] FIG. 14 illustrates a specific configuration of the electrical device. In FIG. 14, a display device 700 is an example of an electrical device using a secondary battery 704 according to one embodiment of the present invention. Specifically, the display device 700 corresponds to a display device for receiving TV broadcasts and includes a housing 701, a display unit 702, a speaker unit 703, a secondary battery 704, and the like. The secondary battery 704 according to one embodiment of the present invention is provided inside the housing 701. The display device 700 can be supplied with power from a commercial power source or can use power stored in the secondary battery 704. Therefore, even when power cannot be supplied from the commercial power source due to a power outage or the like, the display device 700 can be used by using the secondary battery 704 according to one embodiment of the present invention as an uninterruptible power source.

[0155] The display unit 702 can be a liquid crystal display device, a light-emitting device in which each pixel has a light-emitting element such as an organic EL element, an electrophoretic display device, a semiconductor display device such as a DMD (Digital Micromirror Device), a PDP (Plasma Display Panel), or an FED (Field Emission Display).

[0156] The display device includes all display devices for displaying information, such as those for receiving TV broadcasts, those for personal computers, and those for displaying advertisements.

[0157] 14 , a stationary lighting device 710 is an example of an electrical device using a secondary battery 713 according to one embodiment of the present invention. Specifically, the lighting device 710 includes a housing 711, a light source 712, a secondary battery 713, and the like. Although FIG. 14 illustrates the case where the secondary battery 713 is provided inside a ceiling 714 on which the housing 711 and the light source 712 are installed, the secondary battery 713 may be provided inside the housing 711. The lighting device 710 can receive power from a commercial power source or can use power stored in the secondary battery 713. Therefore, even when power cannot be supplied from the commercial power source due to a power outage or the like, the lighting device 710 can be used by using the secondary battery 713 according to one embodiment of the present invention as an uninterruptible power supply.

[0158] Note that although FIG. 14 illustrates an example of a stationary lighting device 710 provided on the ceiling 714, the secondary battery of one embodiment of the present invention can also be used in a stationary lighting device provided on a side wall 715, a floor 716, a window 717, or the like other than the ceiling 714, or can also be used in a tabletop lighting device.

[0159] Furthermore, an artificial light source that artificially obtains light using electric power can be used as the light source 712. Specifically, examples of the artificial light source include discharge lamps such as incandescent lamps and fluorescent lamps, and light-emitting elements such as LEDs and organic EL elements.

[0160] In FIG. 14 , an air conditioner including an indoor unit 720 and an outdoor unit 724 is an example of an electrical device using a secondary battery 723 according to one embodiment of the present invention. Specifically, the indoor unit 720 includes a housing 721, an air outlet 722, a secondary battery 723, and the like. Although FIG. 14 illustrates the case where the secondary battery 723 is provided in the indoor unit 720, the secondary battery 723 may be provided in the outdoor unit 724. Alternatively, the secondary battery 723 may be provided in both the indoor unit 720 and the outdoor unit 724. The air conditioner can receive power from a commercial power source or can use power stored in the secondary battery 723. In particular, when the secondary battery 723 is provided in both the indoor unit 720 and the outdoor unit 724, the air conditioner can be used by using the secondary battery 723 according to one embodiment of the present invention as an uninterruptible power source even when power cannot be supplied from the commercial power source due to a power outage or the like.

[0161] Note that although FIG. 14 illustrates an example of a separate-type air conditioner including an indoor unit and an outdoor unit, a secondary battery according to one embodiment of the present invention can also be used in an integrated-type air conditioner that has the functions of both the indoor unit and the outdoor unit in a single housing.

[0162] 14 , an electric refrigerator-freezer 730 is an example of an electrical device using a secondary battery 734 of one embodiment of the present invention. Specifically, the electric refrigerator-freezer 730 includes a housing 731, a refrigerator compartment door 732, a freezer compartment door 733, a secondary battery 734, and the like. In FIG. 14 , the secondary battery 734 is provided inside the housing 731. The electric refrigerator-freezer 730 can receive power from a commercial power source or can use power stored in the secondary battery 734. Therefore, even when power cannot be supplied from the commercial power source due to a power outage or the like, the electric refrigerator-freezer 730 can be used by using the secondary battery 734 of one embodiment of the present invention as an uninterruptible power supply.

[0163] Among the above-mentioned electrical appliances, electrical appliances such as microwave ovens and other high-frequency heating devices, electric rice cookers, etc. require a large amount of power for a short period of time. Therefore, by using a secondary battery according to one embodiment of the present invention as an auxiliary power source for supplementing the power that cannot be supplied by the commercial power source, it is possible to prevent the breaker of the commercial power source from tripping when the electrical appliance is in use.

[0164] Furthermore, by storing power in the secondary battery during time periods when electrical devices are not in use, particularly during time periods when the ratio of the amount of power actually used to the total amount of power that can be supplied by the commercial power supplier (referred to as power usage rate) is low, it is possible to prevent the power usage rate from increasing outside of these time periods. For example, in the case of electric refrigerator-freezer 730, power is stored in secondary battery 734 during the night when the temperature is low and refrigerator compartment door 732 and freezer compartment door 733 are not opened or closed. Then, during the daytime when the temperature rises and refrigerator compartment door 732 and freezer compartment door 733 are opened and closed, secondary battery 734 is used as an auxiliary power source, thereby making it possible to keep the daytime power usage rate low.

[0165] This embodiment mode can be implemented in appropriate combination with other embodiment modes.

[0166] (Embodiment 5) Next, a portable information terminal, which is an example of an electrical device, will be described with reference to FIG.

[0167] 15A and 15B show a foldable tablet terminal 800. Fig. 15A shows the tablet terminal 800 in an open state, and the tablet terminal 800 has a housing 801, a display unit 802a, a display unit 802b, a display mode selector switch 803, a power switch 804, a power saving mode selector switch 805, and an operation switch 807.

[0168] A part of the display unit 802a can be used as a touch panel area 808a, and data can be input by touching the displayed operation keys 809. Note that, as an example, the display unit 802a is configured such that half of the area has a display function and the other half has a touch panel function, but this configuration is not limiting. The entire area of the display unit 802a may also have a touch panel function. For example, the entire surface of the display unit 802a can be used as a touch panel by displaying keyboard buttons, and the display unit 802b can be used as a display screen.

[0169] Similarly to the display unit 802a, a part of the display unit 802b can be used as a touch panel area 808b. By touching the position on the touch panel where the keyboard display switch button 810 is displayed with a finger or a stylus, keyboard buttons can be displayed on the display unit 802b.

[0170] It is also possible to simultaneously perform touch input on the touch panel area 808a and the touch panel area 808b.

[0171] Furthermore, the display mode selector switch 803 can switch the display orientation, such as portrait or landscape, and can select between black and white and color display. The power saving mode selector switch 805 can optimize the display brightness according to the amount of external light during use, as detected by an optical sensor built into the tablet terminal. The tablet terminal may also be equipped with other detection devices, such as a gyroscope, an acceleration sensor, or other sensors that detect tilt, in addition to the optical sensor.

[0172] 15A shows an example in which the display areas of the display units 802b and 802a are the same, but this is not particularly limited, and the sizes of one unit and the other unit may be different, and the display qualities may also be different. For example, one unit may be a display panel that can display at a higher resolution than the other unit.

[0173] 15B shows a tablet terminal 800 in a closed state, which includes a housing 801, a solar cell 811, a charge / discharge control circuit 850, a battery 851, and a DC-DC converter 852. Note that Fig. 15B shows a configuration including the battery 851 and the DC-DC converter 852 as an example of the charge / discharge control circuit 850, and the battery 851 includes the secondary battery described in the above embodiment.

[0174] Since tablet terminal 800 can be folded in half, housing 801 can be closed when not in use. This protects display units 802a and 802b, providing tablet terminal 800 that is highly durable and reliable for long-term use.

[0175] In addition, the tablet terminals shown in Figures 15A and 15B can have functions such as displaying various information (still images, videos, text images, etc.), displaying a calendar, date or time on the display unit, a touch input function for touch input operations or editing information displayed on the display unit, and controlling processing using various software (programs).

[0176] The solar cell 811 attached to the surface of the tablet terminal can supply power to a touch panel, a display unit, a video signal processor, or the like. Note that the solar cell 811 can be provided on one or both surfaces of the housing 801, which is preferable because it allows efficient charging of the battery 851. Note that using a secondary battery according to one embodiment of the present invention as the battery 851 has advantages such as miniaturization.

[0177] The configuration and operation of the charge / discharge control circuit 850 shown in Fig. 15B will be described with reference to a block diagram in Fig. 15C. Fig. 15C shows a solar cell 811, a battery 851, a DC-DC converter 852, a converter 853, switches SW1 to SW3, and a display unit 802. The battery 851, the DC-DC converter 852, the converter 853, and the switches SW1 to SW3 correspond to the charge / discharge control circuit 850 shown in Fig. 15B.

[0178] First, an example of operation when power is generated by the solar cell 811 using external light will be described. The power generated by the solar cell is stepped up or down by the DC-DC converter 852 to a voltage for charging the battery 851. When power from the solar cell 811 is used to operate the display unit 802, the switch SW1 is turned on, and the converter 853 steps up or steps down the voltage to the voltage required for the display unit 802. When no display is to be performed on the display unit 802, SW1 is turned off and SW2 is turned on to charge the battery 851.

[0179] Although the solar cell 811 is shown as an example of a power generating means, it is not particularly limited, and the battery 851 may be charged by other power generating means such as a piezoelectric element (piezo element) or a thermoelectric conversion element (Peltier element). For example, a non-contact power transmission module that transmits and receives power wirelessly (contactlessly) for charging, or a combination of other charging means may be used.

[0180] Furthermore, it goes without saying that the electrical device is not particularly limited to the one shown in FIG. 15, as long as it is equipped with the secondary battery described in the above embodiment.

[0181] This embodiment mode can be implemented in appropriate combination with other embodiment modes.

[0182] (Embodiment 6) Furthermore, an example of a mobile object, which is an example of an electrical device, will be described with reference to FIG.

[0183] The secondary battery described in the previous embodiment can be used as the control battery. The control battery can be charged by external power supply using plug-in technology or wireless power supply. If the moving body is an electric railcar, it can be charged by power supply from overhead wires or conductive rails.

[0184] 16A and 16B show an example of an electric vehicle. An electric vehicle 860 is equipped with a battery 861. The power output of the battery 861 is adjusted by a control circuit 862 and supplied to a drive device 863. The control circuit 862 is controlled by a processing device 864 having a ROM, RAM, CPU, etc. (not shown).

[0185] The drive device 863 is configured by a DC motor or an AC motor alone, or a combination of an electric motor and an internal combustion engine. The processing device 864 outputs a control signal to the control circuit 862 based on input information such as operation information (acceleration, deceleration, stopping, etc.) from the driver of the electric vehicle 860 and information during driving (information such as uphill and downhill slopes, and information on the load on the drive wheels). The control circuit 862 adjusts the electric energy supplied from the battery 861 based on the control signal from the processing device 864 to control the output of the drive device 863. If an AC motor is installed, an inverter that converts DC to AC is also built in, although not shown.

[0186] The battery 861 can be charged by external power supply using plug-in technology. For example, the battery 861 is charged from a commercial power source through a power plug. Charging can be performed by converting the power into a constant DC voltage having a constant voltage value using a conversion device such as an AC / DC converter. By incorporating a secondary battery according to one embodiment of the present invention as the battery 861, it is possible to increase the capacity of the battery, thereby improving convenience. Furthermore, if the battery 861 itself can be made smaller and lighter by improving the characteristics of the battery 861, this contributes to reducing the weight of the vehicle, thereby improving fuel efficiency.

[0187] Note that it goes without saying that the electronic devices are not particularly limited to the above-described electronic devices as long as they include a secondary battery of one embodiment of the present invention.

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

[0189] (Embodiment 7) 17 includes at least a secondary battery, a protection circuit, a charge control circuit, and a neural network unit, and may also include a mechanism for performing wired or wireless communication, a display panel 8702 for displaying an operating state, and the like.

[0190] A power cord 8701 of the uninterruptible power supply 8700 is electrically connected to a system power supply 8703. The uninterruptible power supply 8700 is electrically connected to precision equipment 8704. The precision equipment 8704 refers to, for example, server equipment that should not be subject to power outages. The uninterruptible power supply 8700 has multiple secondary batteries connected in series or in parallel to provide a desired voltage (for example, 80V or higher, 100V or 200V, etc.).

[0191] The secondary battery of one embodiment of the present invention can be used as the secondary battery.

[0192] Deterioration of the uninterruptible power supply 8700 is affected by various factors. When the user installs the uninterruptible power supply 8700 indoors or outdoors, the deterioration is also affected by the size of the room in which it is installed, the temperature of the room, temperature changes in the installation environment, and the like.

[0193] According to this embodiment, deterioration prediction is periodically performed by AI (Artificial Intelligence) on the secondary battery of the uninterruptible power supply 8700, and the user can determine the timing of replacement based on the results.

[0194] Furthermore, by inputting periodically obtained data into the neural network section and carrying out learning, feature quantities are extracted from calculations in neural network processing, and the state of the secondary battery is analyzed more accurately.

[0195] For example, neural network processing can be used to predict and detect abnormal occurrences (specifically, occurrences of micro-short circuits) in secondary batteries.

[0196] FIG. 18 illustrates an example of an aircraft. The aircraft 6500 illustrated in FIG. 18 includes a propeller 6501, a camera 6502, a battery 6503, and the like, and has a function of flying autonomously. The secondary battery of one embodiment of the present invention can be used as the battery 6503. The secondary battery of one embodiment of the present invention has high energy density, and therefore, the traveling distance of the aircraft 6500 can be increased. Furthermore, the secondary battery of one embodiment of the present invention has excellent output characteristics and is therefore suitable for cases where high output characteristics are required, such as when the aircraft 6500 is accelerating.

[0197] For example, image data captured by the camera 6502 is stored in the electronic component 6504. The electronic component 6504 can analyze the image data and detect the presence or absence of obstacles when moving. The camera 6502 may be an imaging device of multiple types.

[0198] This embodiment mode can be implemented in appropriate combination with other embodiment modes. [Explanation of symbols]

[0199] : 100: NMP, 101: RGO, 102: graphene oxide, 200: electrode, 201: current collector, 202: active material layer, 203: active material, 204: graphene, 207: carbon-containing compound, 208: aggregate, 209: aggregate, 211: path length, 212: protrusion, 213: side length, 214: graphene oxide, 221: monomer, 222: binder, 223: solvent, 224: sample, 225: sample, 226: solution, 227: electrode, 228: electrode, 231a: layer, 231b: layer, 300: secondary battery, 301: positive electrode can, 302: negative electrode can, 303: gasket , 304: positive electrode, 305: positive electrode current collector, 306: positive electrode active material layer, 307: negative electrode, 308: negative electrode current collector, 309: negative electrode active material layer, 310: separator, 500: secondary battery, 501: positive electrode current collector, 502: positive electrode active material layer, 503: positive electrode, 504: negative electrode current collector, 505: negative electrode active material layer, 506: negative electrode, 507: separator, 508: electrolyte, 509: exterior body, 600: secondary battery, 601: positive electrode cap, 602: battery can, 603: positive electrode terminal, 604: positive electrode, 605: separator, 606: negative electrode, 607: negative electrode terminal, 608: insulating plate, 609: insulating Plate, 611: PTC element, 612: safety valve mechanism, 700: display device, 701: housing, 702: display unit, 703: speaker unit, 704: secondary battery, 710: lighting device, 711: housing, 712: light source, 713: secondary battery, 714: ceiling, 715: side wall, 716: floor, 717: window, 720: indoor unit, 721: housing, 722: air outlet, 723: secondary battery, 724: outdoor unit, 730: electric refrigerator-freezer, 731: housing, 732: refrigerator compartment door, 733: freezer compartment door, 734: secondary battery, 800: tablet terminal, 801: housing, 802: display unit, 802a : Display unit, 802b: Display unit, 803: Switch, 804: Power switch, 805: Switch, 807: Operation switch, 808a: Area, 808b: Area, 809: Operation key, 810: Button, 811: Solar cell, 850: Charge and discharge control circuit, 851: Battery, 852: DCDC converter, 853: Converter, 860: Electric vehicle, 861: Battery, 862: Control circuit, 863: Drive unit, 864: Processing unit, 8700: Uninterruptible power supply, 8701: Power cord, 8702: Display panel, 8703: System power supply, 8704: Precision equipment,

[0200]

Claims

[Claim 1] A current collector and an active material layer, the active material layer includes a plurality of granular active materials and a plurality of fibrous carbon-containing compounds; each of the plurality of fibrous carbon-containing compounds is a polymer compound; The monomer of the polymer compound is at least one selected from the group consisting of thiophene, benzene, propane, aniline, phenol, phthalocyanine, furan, azulene, and derivatives thereof.

Images