WO2021200587A1

WO2021200587A1 - Electrode for power storage device, composite particles for power storage device, and power storage device

Info

Publication number: WO2021200587A1
Application number: PCT/JP2021/012682
Authority: WO
Inventors: 千里後藤; 弘義武
Original assignee: 日東電工株式会社
Priority date: 2020-03-31
Filing date: 2021-03-25
Publication date: 2021-10-07
Also published as: JPWO2021200587A1

Abstract

An electrode 1 for a power storage device comprises: an active material 10; and a porous material 20. The porous material 20 comprises a structure in which metal particles and an atomic group comprising non-metal particles are bonded. The non-metal particles include at least an atom other than an oxygen atom. The ratio of the amount of the porous material 20 relative to the sum of the amount of the active material 10 and the amount of the porous material 20 is 0.1-10 mass%.

Description

Electrodes for power storage devices, composite particles for power storage devices, and power storage devices

The present invention relates to an electrode for a power storage device, a composite particle for a power storage device, and a power storage device.

Patent Document 1 describes a power storage system that can further reduce the internal resistance of the power storage device. In this power storage device, an organic skeleton layer containing an aromatic dicarboxylic acid anion having an aromatic ring structure and an alkali metal element layer in which an alkali metal element is coordinated with oxygen contained in the carboxylic acid of the organic skeleton layer to form a skeleton. It has a layered structure containing and as a negative electrode active material.

Japanese Unexamined Patent Publication No. 2020-9846

The technique described in Patent Document 1 has room for reexamination from the viewpoint of reducing the internal resistance of the electrode for the power storage device while providing a negative electrode active material different from the above-mentioned layered structure in charging and discharging the power storage device. Therefore, the present invention provides an advantageous technique for reducing the internal resistance of the electrode for the power storage device in charging and discharging the power storage device.

The present invention
With active material
A porous material containing a structure in which a metal atom and an atomic group containing a non-metal atom are bonded is provided.
The non-metal atom contains at least an atom other than an oxygen atom and contains.
The ratio of the content of the porous material to the sum of the content of the active material and the content of the porous material is 0.1% by mass to 10% by mass.
Provided is an electrode for a power storage device.

In addition, the present invention
Negative electrode active material and
A porous material containing a structure in which a metal atom and an atomic group containing a non-metal atom are bonded and coating the negative electrode active material is provided.
The non-metal atom contains at least an atom other than an oxygen atom and contains.
The ratio of the content of the porous material to the sum of the content of the negative electrode active material and the content of the porous material is 0.1% by mass to 5% by mass.
Provided are composite particles for a power storage device.

In addition, the present invention
Provided is a power storage device provided with the above-mentioned electrode for the power storage device.

According to the present invention, it is possible to provide an electrode for a power storage device which is advantageous for reducing internal resistance in charging and discharging the power storage device.

FIG. 1 is a cross-sectional view schematically showing an electrode for a power storage device according to the present embodiment. FIG. 2 is a cross-sectional view schematically showing a power storage device according to the present embodiment. FIG. 3 is a diagram showing an equivalent circuit for fitting the measurement result of the internal resistance of the electrode for the power storage device according to the examples and the comparative examples.

In a secondary battery such as a lithium ion battery, since the negative electrode has a high reducing power, the electrolytic solution is decomposed by charging and discharging, and a film is formed on the surface of the negative electrode. This coating prevents further reductive decomposition of the electrolyte and provides a place for desorption and / or insertion of lithium ions at the interface between the negative electrode and the electrolyte. This coating is also called a Solid Electrolyte Interface (SEI) coating.

When the power storage device is charged and discharged, an irreversible capacity is generated due to the formation of the SEI film. Since the SEI coating is generally non-conductive, the formation of the SEI coating can increase the internal resistance of the power storage device.

It is important that ions such as lithium can be efficiently diffused into the active material in order to suppress the increase in internal resistance during charging and discharging of the power storage device. As a result of diligent studies, the present inventors have found that by adding a specific porous material to the negative electrode active material, a power storage device whose internal resistance does not easily increase can be obtained. Porous materials are generally non-conductors and are therefore considered to have increased resistance. However, according to the studies by the present inventors, it has been found that when the content of the porous material is within a predetermined range, an electrode for a power storage device whose internal resistance does not easily increase during charging / discharging of the power storage device can be obtained. rice field.

Hereinafter, embodiments of the present invention will be described with reference to the drawings. The present invention is not limited to the following embodiments.

<Electrodes for power storage devices>
As shown in FIG. 1, the electrode 1 for a power storage device includes an active material 10 and a porous material 20. The ratio R of the content of the porous material 20 to the sum of the content of the active material 10 and the content of the porous material 20 is 0.1% by mass to 10% by mass. As a result, the internal resistance of the electrode 1 for the power storage device is unlikely to increase during charging / discharging of the power storage device.

The ratio R may be 0.12% by mass to 7% by mass, or 0.13% by mass to 5% by mass.

The porous material 20 includes, for example, a structure in which a metal atom and an atomic group containing a non-metal atom are bonded. Non-metal atoms include at least atoms other than oxygen atoms. In the porous material 20, for example, atomic groups are arranged between metal atoms in the porous material 20. The atomic group contains, for example, a carbon atom. The atomic group may contain an oxygen atom. The atomic group containing the non-metal atom may be an organic ligand. Atomic groups containing non-metal atoms may further contain functional groups. The type of functional group is not limited to a specific type. Examples of functional groups are amino groups, hydroxy groups, aldehyde groups, carbonyl groups, nitro groups, sulfo groups, and ether groups. The compound forming an atomic group containing a non-metal atom may contain these functional groups, particularly an amino group. The compound forming an atomic group containing a non-metal atom may contain a heterocycle.

The porous material 20 has, for example, a metal ion and an organic ligand. The porous material 20 can be formed, for example, by coordinating an organic ligand containing a non-metal atom to a metal ion. According to such a configuration, it is possible to provide the electrode 1 for a power storage device in which the internal resistance is less likely to increase in the charging / discharging of the power storage device. The internal resistance of the electrode 1 for a power storage device can be measured by, for example, the electrochemical impedance method (EIS). The porous material 20 can also be synthesized by using a solution method, a hydrothermal synthesis method, an atomic layer deposition method (ALD), a solid phase mixing method, an ultrasonic irradiation method, and a microwave irradiation method.

The porous material 20 is, for example, an organic metal-organic framework (MOF). The organic metal structure is also called a porous coordination polymer (PCP). The organic metal structure has a network structure formed by the interaction between a metal ion and an organic ligand. The organic metal structure has a high specific surface area. The porous material 20 has, for example, angstrom-order pores. The porous material 20 may have holes on the order of nanometers.

The size of the pores of the porous material 20 is not limited to a specific value. Its size may be 0.8 angstroms (Å) or greater and 1.0 Å or greater. The pore size of the porous material 20 can be measured, for example, by powder X-ray diffraction (PXRD). The pore size of the porous material 20 can also be determined by using, for example, an X-ray diffraction simulation program such as PowerCell.

In the electrode 1 for a power storage device, the size of the pores of the porous material 20 is preferably larger than the diameter of ^{Li +, for example.} The shape of the pores of the porous material 20 is not limited to a specific shape. Examples of its shape are bottleneck type, straight tube type, and horn type. The pores of the porous material 20 may have flexibility.

The Brunauer-Emmett-Teller (BET) specific surface area of the porous material 20 may be 500 m ² / g or more, 1000 m ² / g or more, or 1500 m ² / g or more. The BET specific surface area is a specific surface area obtained by the BET method by adsorbing nitrogen gas.

The metal atoms contained in the porous material 20 are Zn, Co, Cu, Al, Mg, Ca, Sr, Ba, Sc, Y, Ti, Zr, Hf, V, Nb, Ta, Cr, Mo, W, Mn. , Re, Fe, Ni, Pd, Pt, Ag, Cd, Hg, Au, Be, Ga, In, Tl, Sn, Rh, Ru and even if it contains at least one metal atom selected from the group consisting of Pb. good. The metal atom may contain at least one selected from metal atoms belonging to any of Group 2, Group 3, and Group 5 to Group 14 of the periodic table. The metal atom is specifically selected from at least one metal atom selected from the group consisting of Zn, Co, Cu, Al, Mg, Fe, and Ni, particularly at least selected from the group consisting of Zn, Co, Cu, and Al. It may contain one metal atom. The metal atom may be at least one metal atom selected from the group consisting of Zn, Co, Cu, and Al. Examples of metal salts containing metal atoms are nitrates, sulfates, fluorides, chlorides, bromides, iodides, carbonates, phosphates, sulfides, and hydroxides.

The organic ligand can form a coordinate bond with a metal atom. As the organic ligand, a polydentate ligand having two or more coordination sites for coordinating metal ions can be used. The organic ligand may include at least one organic ligand selected from the group consisting of imidazoles, dipyridines, triazines, pyrazines, salins, and aromatic dicarboxylic acids. Imidazoles are heterocyclic compounds containing one or more N's. Examples of imidazoles are 2-methylimidazole and benzimidazole. Examples of aromatic dicarboxylic acids are phthalic acids, isophthalic acids, terephthalic acids, 2,6-naphthalenedicarboxylic acids, 1,4-naphthalenedicarboxylic acids, biphenylenedicarboxylic acids, 1,2,3-benzenetricarboxylic acids, 1,3. , 5-Benzene tricarboxylic acid, 1,2,3,4-benzenetetracarboxylic acid, 1,2,4,5-benzenetetracarboxylic acid, cyclobutyl-1,4-benzenedicarboxylate, 2-amino-1, 4-Benzene dicarboxylate, tetrahydropyrene-2,7-dicarboxylate, terphenyldicarboxylate, 2,6-naphthalenedicarboxylate, pyrene-2,7-dicarboxylate, and biphenyldicarboxylate. .. The organic ligand may include at least one organic ligand selected from the group consisting of 2-methylimidazole, benzimidazole, terephthalic acid, and benzenetricarboxylic acid. The organic ligand may be at least one organic ligand selected from the group consisting of 2-methylimidazole, benzimidazole, terephthalic acid, and benzenetricarboxylic acid. In some cases, the organic ligand may be at least one organic ligand selected from the group consisting of 2-methylimidazole, benzimidazole, and benzenetricarboxylic acid. When the porous material 20 has such an organic ligand, it is possible to provide an electrode 1 for a power storage device in which the internal resistance is less likely to increase during charging / discharging of the power storage device.

The organic ligand may contain another substituent in the backbone, if desired. Examples of other substituents are hydroxy group, amino group, imino group, amide group, sulfonic acid group, methanedithioic acid group, pyridine group, pyrazine group, methoxy group, methyl group, nitro group, methylamino group, dimethylamino group. , Cyano group, fluoro group, chloro group, and bromo group. By including another substituent in the organic ligand, the porous material 20 ^{can make Li +} more stable. As a result, the electrode 1 for a power storage device whose internal resistance is less likely to increase can be provided.

Examples of the porous material 20 are Zeolitic imidazolate framework-8 (ZIF-8), ZIF-7, ZIF-9, ZIF-67, MIL-53 (Al), and HKUST-1. The porous material 20 may contain at least one selected from the group consisting of ZIF-8, ZIF-67, MIL-53 (Al), and HKUST-1. As the porous material 20, at least one selected from the group consisting of ZIF-8, ZIF-67, MIL-53 (Al), and HKUST-1 may be used, or a plurality of types may be mixed and used. .. In some cases, the porous material 20 may contain at least one selected from the group consisting of ZIF-8, ZIF-67, and HKUST-1. In some cases, as the porous material 20, at least one selected from the group consisting of ZIF-8, ZIF-67, and HKUST-1 may be used, or a plurality of types may be mixed and used. ZIF-8 has Zn and 2-methylimidazole. ZIF-7 has Zn and benzimidazole. ZIF-9 has Co and benzimidazole. ZIF-67 has Co and 2-methylimidazole. MIL-53 (Al) has Al and terephthalic acid. HKUST-1 has Cu and a benzenetricarboxylic acid.

For reducing the internal resistance in the low temperature range, for example, the use of an organic ligand containing an amino group and / or a heterocycle is suitable.

The average particle size of the porous material 20 is not limited to a specific value. The value may be 1 nm to 10 μm or 100 nm to 5 μm. By appropriately adjusting the average particle size of the porous material 20, the porous material 20 tends to exist in a desired state in the electrode 1 for a power storage device. As a result, the electrode 1 for the power storage device can further suppress the increase in internal resistance. In the present specification, the "average particle size" can be determined using, for example, a scanning electron microscope (SEM). The average particle size can be determined by observing the cross section of the electrode 1 for a power storage device by SEM. Specifically, the average particle size is determined by measuring the maximum and minimum diameters of any 50 porous materials 20 capable of observing the entire porous material 20 and setting the average value as the grains of each porous material 20. It can be obtained by using the diameter as the diameter and calculating the average value thereof. The average particle size can also be determined using a transmission electron microscope (TEM).

The active material 10 is, for example, a negative electrode active material. Examples of negative electrode active materials are artificial graphite, natural graphite, mesophase carbon, soft carbon, pitch coated graphite, and hard carbon (HC).

The content of the active substance 10 is not limited to a specific value. The value may be 85% by mass to 99% by mass or 90% by mass to 98% by mass with respect to the total mass of the electrode 1 for the power storage device.

The electrode 1 for the power storage device further includes a binder 30. The binder 30 binds the active material. Examples of the binder 30 are fluororesin, thermoplastic resin, carboxymethyl cellulose, ethylene propylene diene monomer (EPDM) rubber, sulfonated EPDM rubber, natural butyl rubber (NBR), and styrene butadiene rubber (SBR). Examples of fluororesins are polytetrafluoroethylene (PTFE), polyvinylidene fluoride (PVdF), and fluororubber. Examples of thermoplastics are polypropylene and polyethylene. As the binder 30, only one kind selected from these may be used, or a plurality of kinds may be mixed and used.

The content of the binder 30 is not limited to a specific value. The value may be 0.5% by mass to 15% by mass or 1% by mass to 5% by mass with respect to the total mass of the electrode 1 for the power storage device.

At least a part of the porous material 20 may be dispersed in the binder 30. According to such a configuration, it is considered that a portion through which ions easily pass is formed inside the electrode 1 for a power storage device. As a result, it is possible to provide the electrode 1 for a power storage device whose internal resistance is less likely to increase during charging / discharging of the power storage device.

Substantially all of the porous material 20 may be dispersed in the binder 30. As a result, it is possible to provide the electrode 1 for a power storage device in which the internal resistance is less likely to increase during charging and discharging. By "substantially all" is meant to be 85% or more, even 90% or more, especially 95% or more on a mass basis. The dispersed state of the porous material 20 in the electrode 1 for the power storage device can be confirmed by, for example, a transmission electron microscope (TEM).

At least a part of the porous material 20 may be coated with the active material 10. In addition, in this specification, "covering" does not need to cover the entire surface, but is used in the sense of including a mode of covering a part. The interaction between the porous material 20 and the surface of the active material 10 is not limited to the mode in which the active material 10 covers the entire surface. The porous material 20 may be present on the surface of the active material 10 by physical adsorption, or may be present on the surface of the active material 10 by chemical bonding. Examples of chemical bonds are hydrogen bonds, covalent bonds, ionic bonds, coordination bonds, and van der Waals forces. In charging and discharging the power storage device, the active material 10 generally expands and contracts. According to such a configuration, the porous material 20 is difficult to separate from the active material 10 even when the power storage device is charged and discharged. As described above, composite particles including the active material 10 and the porous material 20 can be provided.

Substantially all of the porous material 20 may be coated with the active material 10. As a result, it is possible to provide the electrode 1 for a power storage device whose internal resistance is less likely to increase during charging / discharging of the power storage device.

The fact that the surface of the active material 10 is covered with the porous material 20 can be confirmed by, for example, a powder X-ray diffraction measurement (XRD) method and / or a transmission electron microscope (TEM).

The porous material 20 dispersed in the binder 30 may or may not be coated with the active material 10. At least a part of the porous material 20 dispersed in the binder 30 does not have to be coated with the active material 10. Such an uncoated porous material 20 can be obtained by mixing the preformed porous material 20 with the active material 10.

In the composite particle, the porous material coating the active material 10 with respect to the sum (M ₁₀ + M ₂₀ _{) of the content M 10} of the active material 10 and the content M _{20 of the porous material 20 coating the active material 10} The ratio P ₀ (= 100 × M ₂₀ / (M ₁₀ + M ₂₀ )) of the content M ₂₀ of the material 20 is not limited to a specific value. The ratio P ₀ is 0.05% by mass to 10% by mass, preferably 0.1% by mass to 5% by mass, more preferably 0.1% by mass to 3% by mass, and further preferably 0.15% by mass. ~ 3% by mass. By appropriately adjusting the ratio P ₀ , it is possible to provide an electrode 1 for a power storage device whose internal resistance is less likely to increase during charging / discharging of the power storage device.

_{The ratio P 0} in the composite particle can be obtained, for example, as follows. When the BET specific surface area of the active material 10 is defined as a, the BET specific surface area of the porous material 20 is defined as b, and the BET specific surface area of the composite particle is defined as c, the ratio P ₀ [mass%] is as follows. It is determined by the formula (1).
P ₀ [mass%] = 100 × (ca) / (ba) ・・・ (1)

In the composite particles, at least a part of the porous material 20 may be coated with the negative electrode active material. _{The ratio P 1} of the content of the porous material 20 coated with the negative electrode active material to the sum of the content of the negative electrode active material and the content of the porous material 20 coating the negative electrode active material is a specific value. Not limited to. The ratio P ₁ is 0.05% by mass to 10% by mass, preferably 0.1% by mass to 5% by mass, and particularly 0.15% by mass to 3% by mass. By appropriately adjusting the ratio P ₁ , it is possible to provide an electrode 1 for a power storage device whose internal resistance is less likely to increase during charging / discharging of the power storage device.

The electrode 1 for a power storage device may contain other optional components as long as the effects of the present invention are not impaired.

The electrode 1 for the power storage device may contain a conductive auxiliary agent. The conductive auxiliary agent is typically made of a conductive material having properties that do not change with the voltage applied for charging and discharging the power storage device. The conductive auxiliary agent can be a conductive carbon material or a metallic material. The conductive carbon material is, for example, conductive carbon black such as acetylene black and Ketjen black, or fibrous carbon material such as carbon fiber and carbon nanotube. The conductive carbon material is preferably conductive carbon black.

In order to disperse the active material 10 and the porous material 20 satisfactorily, the electrode 1 for the power storage device may contain a dispersant. Dispersants are, for example, anionic surfactants, cationic surfactants, amphoteric surfactants, and nonionic surfactants. Among them, sulfonic acid-type surfactants such as alkylbenzene sulfonic acid, oil-soluble alkylbenzene sulfonic acid, α-olefin sulfonic acid, sodium alkylbenzene sulfonic acid, oil-soluble alkylbenzene sulfonic acid, and α-olefin sulfonic acid are used as dispersants. It is preferably used. Cellulose derivatives such as carboxymethyl cellulose can also be used.

<Power storage device>
As shown in FIG. 2, it is possible to provide a power storage device 2 provided with an electrode 1 for a power storage device. In the power storage device 2, the power storage device electrode 1 functions as, for example, a negative electrode.

The power storage device 2 includes, for example, a negative electrode current collector 40, an electrode 1 for the power storage device, an electrolyte layer 50, a positive electrode 60, and a positive electrode current collector 70. The electrolyte layer 50 is arranged between the storage device electrode 1 and the positive electrode 60. The electrode 1 for the power storage device is arranged in the negative electrode current collector 40. Specifically, the electrode 1 for a power storage device is arranged between the electrolyte layer 50 and the negative electrode current collector 40. The positive electrode 60 is arranged on the positive electrode current collector 70. Specifically, the positive electrode 60 is arranged between the electrolyte layer 50 and the positive electrode current collector 70.

As the storage device electrode 1, the power storage device electrode 1 described above can be used. The thickness of the electrode 1 for the power storage device is not limited to a specific value. The value is, for example, 0.1 μm to 1000 μm.

The electrolyte layer 50 contains, for example, an electrolyte and a solvent. The electrolyte is, for example, a combination of a metal ion such as lithium ion and a predetermined counter ion for the metal ion. Counterions include, for example, sulfonic acid ion, perchlorate ion, tetrafluoroborate ion, hexafluorophosphate ion, hexafluoroarsenide ion, bis (trifluoromethanesulfonyl) imide ion, bis (pentafluoroethanesulfonyl) imide ion, bis. (Fluorosulfonyl) imide or halogen ion. Specific examples of electrolytes include LiCF ₃ SO ₃ , LiClO ₄ , LiBF ₄ , LiPF ₆ , LiAsF ₆ , LiN (SO ₂ F) ₂ , LiN (SO ₂ CF ₃ ) ₂ , LiN (SO ₂ C ₂ F ₅ ), And LiCl.

An example of a solvent is at least one non-aqueous solvent selected from the group consisting of carbonates, nitriles, amides, and ethers. Specific examples of non-aqueous solvents include ethylene carbonate, propylene carbonate, butylene carbonate, dimethyl carbonate, diethyl carbonate, ethylmethyl carbonate, acetonitrile, propyronitrile, N, N'-dimethylacetamide, N-methyl-2-pyrrolidone, and dimethoxy. Ethane, diethoxyethane, and γ-butyrolactone. As the solvent, one kind of solvent may be used alone, or two or more kinds of solvents may be used in combination. A solution in which an electrolyte is dissolved in the above solvent may be referred to as an "electrolyte solution".

The electrolytic solution may further contain additives. Examples of additives are vinylene carbonate (VC) and fluoroethylene carbonate. The concentration of the additive in the electrolytic solution is, for example, 0.1% by mass to 15% by mass.

The positive electrode 60 is preferably formed by using a positive electrode active material capable of inserting and removing metal or ions. The positive electrode 60 may contain a positive electrode active material as a main component. The principal component means the component contained most in the positive electrode 60 on a mass basis. The positive electrode 60 is not limited to a specific material as long as it contains a positive electrode active material. The positive electrode 60 may be a layer composed of a mixture of the positive electrode active material and other additive materials. As other additive materials, solid electrolytes, conductive auxiliaries, binders and the like can be used.

The thickness of the positive electrode 60 is not limited to a specific value. The value is, for example, 0.1 μm to 1000 μm.

An example of the negative electrode current collector 40 is a foil or mesh made of a metal material such as nickel, aluminum, stainless steel, and copper. The thickness of the negative electrode current collector 40 is, for example, 3 μm to 500 μm.

The material of the positive electrode current collector 70 may be the same as the material of the negative electrode current collector 40. The thickness of the positive electrode current collector 70 is, for example, 3 μm to 500 μm.

The power storage device 2 may further include a conductive layer in order to improve the conductivity between the power storage device electrode 1 and the negative electrode current collector 40. The power storage device 2 may further include an adhesive layer in order to improve the adhesiveness between the power storage device electrode 1 and the negative electrode current collector 40.

The power storage device 2 may further include a conductive layer in order to improve the conductivity between the positive electrode 60 and the positive electrode current collector 70. The power storage device 2 may include an adhesive layer in order to improve the adhesiveness between the positive electrode 60 and the positive electrode current collector 70.

<Method of manufacturing electrodes for power storage devices>
The electrode 1 for a power storage device is obtained by applying an electrode slurry to a current collector. Examples of the method for preparing the slurry for electrodes include a method of preparing the active material 10 and the porous material 20 by mixing them with other components, and a method of synthesizing the porous material 20 on the surface of the active material 10, that is, in situ. There is a method of preparing the composite particles obtained by mixing the composite particles with other components. These methods may be used together.

For example, the active material 10, the porous material 20, and the binder 30 are mixed, and an appropriate solvent is added to prepare a slurry for electrodes. The electrode 1 for a power storage device can be obtained by applying this electrode slurry to the surface of a current collector and drying it. The electrode 1 for a power storage device may be formed by compression, if necessary, in order to increase the electrode density.

According to this method, in the electrode 1 for the power storage device, the porous material 20 is dispersed in the binder 30.

As another method, for example, first, a solution A containing a part of the raw material of the porous material 20 and the active material 10 is prepared. Some of the raw materials of the porous material 20 include, for example, the organic ligand of the porous material 20. Separately, solution B is prepared. Solution B is, for example, an aqueous solution of a metal salt that provides metal ions contained in the porous material 20. Next, solution B is added to solution A, and a mixture is prepared by stirring. As a result, the porous material 20 is synthesized in the mixed solution. Specifically, the porous material 20 is synthesized on the surface of the active material 10. The solid component is then obtained by filtering the mixture. By washing the solid components and vacuum drying, composite particles in which the active material 10 is coated with the porous material 20 can be obtained.

A binder and an appropriate solvent are added to the obtained composite particles to prepare a slurry for electrodes. The electrode 1 for a power storage device can be obtained by applying this electrode slurry to the surface of a current collector and drying it. The electrode 1 for a power storage device may be formed by compression, if necessary, in order to increase the electrode density.

According to this method, the porous material 20 can be coated on the surface of the active material 10. In addition, according to this method, since the cleaning operation is included, the porous material 20 is not substantially dispersed in the binder 30 in the electrode 1 for the power storage device. "Substantially not dispersed" means that a small amount of the porous material 20 is allowed to be mixed in the binder 30, and the amount of the porous material 20 dispersed in the binder 30 is less than 2% by mass, or even 1% by mass. It is less than%, and in particular, it means that it is contained in less than 0.5% by mass.

In addition, according to this method, a part of the porous material 20 is bound to the surface of the active material 10. As a result, when the secondary battery using the electrode 1 for the power storage device is charged and discharged, a side reaction is unlikely to occur between the active material 10 and the porous material 20, and the porous material 20 is separated from the active material 10. Hard to separate.

The method of applying the electrode slurry to the current collector is not limited to a specific method. Examples of such methods are spin coating, dip coating, bar coating, level coating, and spray coating.

Hereinafter, the present invention will be described in more detail with reference to Examples. The present invention is not limited to the following examples.

(Example 1)
Solution A was prepared by adding 25 g of Pitch Coat Graphite SCMG-AF-C® (registered trademark) (average particle size: 10 μm) and 1.9 g of 2-methylimidazole manufactured by Showa Denko Corporation to pure water. Separately, a solution B, 6.9 mass% of Zn (NO ₃₎ was prepared ₂ · 6H ₂ O aqueous solution. 1.08 g of Solution B was added to Solution A, the mixture was stirred for 2 hours, and the obtained mixed solution was filtered. The obtained solid was washed twice with pure water and then twice with methanol. After washing, the solid was vacuum dried at 40 ° C. for 15 hours to obtain composite particles according to Example 1, which is a negative electrode active material coated with ZIF-8.

By mixing 96% by mass of the composite particles according to Example 1, 2% by mass of styrene-butadiene rubber (SBR), and 2% by mass of carboxymethyl cellulose (CMC), the slurry for the storage device electrode according to Examples 1 to 5. Was prepared. By applying this slurry to a Cu substrate and drying it, a negative electrode for a power storage device according to Example 1 was obtained.

Inside the glove box kept in an environment with a dew point of -60 ° C or less and an oxygen concentration of 1 ppm or less, a separator (manufactured by Nippon Kodoshi Kogyo Co., Ltd.) was attached to the negative electrode for the power storage device according to Example 1 to which the current collector tab was attached. , Product name: TF40-50). Next, an electrode having a metal lithium foil attached to a stainless steel mesh to which a current collector tab was attached was placed on the separator. At this time, the metallic lithium foil was brought into contact with the separator. This laminate was placed inside a bag-shaped package made of an aluminum laminate film. In this package, the three sides of the pair of square aluminum laminate films were sealed, and the other sides were separated from each other to form an opening. _{Next, a LiPF 6} carbonate solution having a concentration of ^{1.2 M (mol / dm 3} ) was injected into the inside of this package as an electrolytic solution. This carbonate solution contained ethylene carbonate (EC), ethyl methyl carbonate (EMC), and dimethyl carbonate (DMC) as carbonates. Next, the opening of the package was sealed with the current collector tab protruding from the opening of the package. In this way, a laminated cell for adjusting the state of charge (SOC) was obtained. Next, this laminated cell is taken out from the glove box, and inside a constant temperature bath kept at 25 ° C., in a potential range of 1.5 V to 0.01 V, it corresponds to 0.1 C with respect to the capacity of the graphite negative electrode sheet. Charging and discharging were carried out for 3 cycles with the current value to be applied, and finally, a reaction was carried out in which lithium ions were inserted into graphite up to 40% of SOC with respect to the capacity of the graphite negative electrode sheet. In this way, two laminated cells containing the electrode sheet for the power storage device according to Example 1 in which the SOC was adjusted to 40% were produced.

The laminated cell containing the electrode sheet for the power storage device according to Example 1 in which the SOC was charged to 40% was reinserted into the glove box. The sealed portion of the laminate cell was cut off, and the electrode sheet for the power storage device according to Example 1 was taken out. Next, these were stacked so that the separator was located between the two electrode sheets for the power storage device according to the first embodiment. A non-woven fabric (manufactured by Nippon Kodoshi Kogyo Co., Ltd., product name: TF40-50) was used as the separator. Next, the electrode sheet and separator for the power storage device according to Example 1 and the laminate of the electrode sheet for the power storage device according to Example 1 were placed inside a bag-shaped package made of an aluminum laminate film. In this package, the three sides of the pair of square aluminum laminate films were sealed, and the other sides were separated from each other to form an opening. _{Next, a LiPF 6} carbonate solution having a concentration of 1.2 M (mol / dm ^{3) was injected into the package as an electrolytic solution.} This carbonate solution contained ethylene carbonate (EC), ethyl methyl carbonate (EMC), and dimethyl carbonate (DMC) as carbonates. 1% by mass of vinylene carbonate (VC) was further added to the electrolytic solution. Next, the opening of the package was sealed with the current collector tab of the electrode sheet for the power storage device according to the first embodiment protruding from the opening of the package. In this way, a symmetric cell for electrochemical impedance measurement (EIS) according to Example 1 was produced.

(Examples 2 to 5)
Symmetrical cells for EIS according to Examples 2 to 5 were obtained in the same manner as in Example 1 except that the composite particles were prepared so that the ratio P _{0 was the value shown in Table 1.} _{“P 0} ” in Table 1 indicates “the ratio of the content of the porous material covering the active material to the sum of the content of the active material and the content of the porous material coating the active material”. Means.

(Comparative Example 1)
Comparison was performed in the same manner as in Example 1 except that pitch-coated graphite SCMG-AF-C (average particle size: 10 μm) not coated with a porous material was used instead of the composite particles according to Example 1. A symmetric cell for EIS according to Example 1 was obtained.

(Example 6)
As the active material, 25 g of natural graphite CGB-10 (average particle size: 10 μm) manufactured by Nippon Graphite Industry Co., Ltd. and 7.6 g of 2-methylimidazole were used, and 6.9% by mass of Zn (NO ₃ ) _2. A symmetric cell for EIS according to Example 6 was obtained in the same manner as in Example 1 except that 4.3 g of a _{6H 2 O aqueous solution was used.}

(Example 7)
Symmetrical cells for EIS according to Example 7 were obtained in the same manner as in Example 6 except that vinylene carbonate was not used.

(Example 8)
As an active material, 25 g of natural graphite CGB-10 (average particle size: 10 μm) manufactured by Nippon Graphite Industry Co., Ltd. and 15.2 g of 2-methylimidazole were used, and 6.9% by mass of Zn (NO ₃ ) _2. A symmetric cell for EIS according to Example 8 was obtained in the same manner as in Example 1 except that 8.6 g of a _{6H 2 O aqueous solution was used.}

(Example 9)
Symmetrical cells for EIS according to Example 9 were obtained in the same manner as in Example 8 except that vinylene carbonate was not used.

(Example 10)
As the active material, 25 g of natural graphite CGB-10 (average particle size: 10 μm) manufactured by Nippon Graphite Industry Co., Ltd. and 22.8 g of 2-methylimidazole were used, and 6.7% by mass of Zn (NO ₃ ) _2. A symmetric cell for EIS according to Example 10 was obtained in the same manner as in Example 1 except that 12.9 g of a _{6H 2 O aqueous solution was used.}

(Example 11)
Symmetrical cells for EIS according to Example 11 were obtained in the same manner as in Example 10 except that vinylene carbonate was not used.

(Example 12)
Example 12 in the same manner as in Example 1 except that natural graphite CGB-10 was used as the active material and a 6.7% by mass Co (NO ₃ ) _{2 aqueous solution was used as the solution B.} The composite particles according to the above were obtained. In this composite particle, natural graphite was coated with ZIF-67. An EIS symmetric cell according to Example 12 was obtained in the same manner as in Example 1 except that the composite particle according to Example 12 was used instead of the composite particle according to Example 1.

(Example 13)
A symmetric cell for EIS according to Example 13 was obtained in the same manner as in Example 12 except that vinylene carbonate was not used.

(Example 14)
Composite particles according to Example 14 were obtained in the same manner as in Example 6 except that benzimidazole was used instead of 2-methylimidazole. In this composite particle, natural graphite was coated with ZIF-7. An EIS symmetric cell according to Example 14 was obtained in the same manner as in Example 1 except that the composite particle according to Example 14 was used instead of the composite particle according to Example 1.

(Example 15)
Symmetrical cells for EIS according to Example 15 were obtained in the same manner as in Example 14 except that vinylene carbonate was not used.

(Example 16)
Composite particles according to Example 16 were obtained in the same manner as in Example 12, except that benzimidazole was used instead of 2-methylimidazole. In this composite particle, natural graphite was coated with ZIF-9. An EIS symmetric cell according to Example 16 was obtained in the same manner as in Example 1 except that the composite particle according to Example 16 was used instead of the composite particle according to Example 1.

(Example 17)
Symmetrical cells for EIS according to Example 17 were obtained in the same manner as in Example 16 except that vinylene carbonate was not used.

(Comparative Example 2)
A symmetric cell for EIS according to Comparative Example 2 was obtained in the same manner as in Example 6 except that natural graphite CGB-10 not coated with a porous material was used as an electrode for a power storage device.

(Comparative Example 3)
A symmetric cell for EIS according to Comparative Example 3 was obtained in the same manner as in Comparative Example 2 except that vinylene carbonate was not added.

(Examples 18 to 22)
ZIF-8 Basolite Z1200 and natural graphite CGB-10 manufactured by Aldrich were added in the amounts shown in Table 4. Further, 2% by mass of styrene-butadiene rubber (SBR) and 2% by mass of carboxymethyl cellulose (CMC) were mixed to prepare a slurry for a power storage device electrode according to Examples 18 to 22. By applying this slurry to a Cu substrate and drying it, electrodes for a power storage device according to Examples 18 to 22 were obtained. Then, in the same manner as in Example 1, symmetrical cells for EIS according to Examples 18 to 22 were obtained. The "content R of the porous material" in Table 4 means "the ratio of the content of the porous material to the sum of the content of the negative electrode active material and the content of the porous material".

(Examples 23 to 28)
Instead of ZIF-8, ZIF-67 PL-MOF-ZIF67 manufactured by PlasmaChem, MIL-53 (Al) Basolite A100 manufactured by Aldrich, and HKUST-1 Basolite C300 manufactured by Aldrich were used. Symmetrical cells for EIS according to Examples 23, 25, and 27 were obtained in the same manner as in Example 18, except that the porous material of No. 1 was added in the amount shown in Table 5. Except for the use of ZIF-67, MIL-53 (Al), and HKUST-1 instead of ZIF-8 and the addition of these porous materials in the amounts shown in Table 5. , EIS symmetric cells according to Examples 24, 26, and 28 were obtained in the same manner as in Example 19.

(Examples 29 and 30)
Composite particles were obtained in the same manner as in Example 6. Examples 18 and 19 except that the composite particles, ZIF-8 Basolite Z1200 manufactured by Aldrich, and natural graphite CGB-10 were added to the slurry for the power storage device electrode in the amounts shown in Table 6. Similarly, symmetrical cells for EIS according to Examples 29 and 30, respectively, were obtained.

(Examples 31 to 35)
Implemented except that instead of pitch-coated graphite, mesophase carbon CMS-10 manufactured by Shanghai Sugisugi, hard carbon LN-0010 manufactured by ATEC, or soft carbon NED-270ZJ manufactured by Nippon Steel Chemical Co., Ltd. was used. Similar to Example 4, EIS symmetric cells according to Examples 31, 34, and 35 were obtained. Symmetrical cells for EIS according to Examples 32 and 33 were obtained in the same manner as in Example 4 except that vinylene carbonate was not used.

(Comparative Examples 4 to 8)
2-methylimidazole and Zn (NO ₃₎ except that not using a ₂ · 6H ₂ O aqueous solution, in the same manner as in Example 31-35 to give respectively the EIS for symmetric cell according to Comparative Example 4-8 ..

(Comparative Examples 9 and 10)
In the preparation of the electrode for the power storage device, only natural graphite CGB-10 was added to pure water, stirred for 2 hours, and the obtained mixed solution was filtered. The obtained solid was washed twice with pure water and then twice with methanol. After washing, the solid was vacuum dried at 40 ° C. for 15 hours to obtain negative electrode active material particles according to Comparative Example 9. A symmetrical cell for EIS according to Comparative Example 9 was obtained in the same manner as in Example 4 except that the negative electrode active material particles were used. Further, a symmetric cell for EIS according to Comparative Example 10 was obtained in the same manner as in Example 4 except that the negative electrode active material particles were used and vinylene carbonate was not added.

(Comparative Examples 11 and 12)
A symmetric cell for EIS according to Comparative Example 11 was obtained in the same manner as in Example 4 except that zinc nitrate hexahydrate was not added to Solution A. A symmetric cell for EIS according to Comparative Example 12 was obtained in the same manner as in Example 4 except that zinc nitrate hexahydrate was not added to the solution A and vinylene carbonate was not added.

(Comparative Examples 13 and 14)
A symmetric cell for EIS according to Comparative Example 13 was obtained in the same manner as in Example 4 except that Solution B was not added. A symmetric cell for EIS according to Comparative Example 14 was obtained in the same manner as in Example 4 except that solution B was not added and vinylene carbonate was not added.

[Electrochemical impedance measurement]
The internal resistance of the electrode for the power storage device according to the examples and the comparative examples was measured by the electrochemical impedance method (EIS). The electrochemical impedance of the EIS symmetric cell according to the examples and comparative examples was measured by using the AC impedance device Solartron SI 1287 manufactured by Toyo Corporation equipped with the frequency characteristic analyzer Solartron SI 1260 manufactured by Toyo Corporation. The frequency range was 0.1 Hz to 1 MHz. The amplitude voltage was 10 mV. The measurement temperature was −20 ° C., −10 ° C., 0 ° C., 10 ° C., 25 ° C., 40 ° C., or 60 ° C. Examples and comparative examples are obtained by plotting the measurement results on a complex plane (Nyquist diagram), fitting the arc components appearing on the low frequency side using the equivalent circuit shown in FIG. 3, and calculating the value of R2. The internal resistance of the EIS symmetric cell according to the above was calculated. The measurement results are shown in Tables 8 to 13.

[Calculation of content of porous material]
The content M of the porous material coating the active material with respect to the sum (M ₁₀ + M ₂₀ _{) of the content M 10} of the active material in the composite particle and the content M ₂₀ of the porous material coating the active material. The ratio of ₂₀ _{P 0} = 100 × M ₂₀ / (M ₁₀ + M ₂₀ ) was obtained as follows. First, the BET specific surface area of SCMG-AF-C, the BET specific surface area of CGB-10, the BET specific surface area of ZIF-8, and the BET specific surface area of the composite particles according to Examples 1 to 11 are determined by Microtrac Bell. The measurement was performed using the BET measuring device BELSORP-mini X. _{Then, the ratio P 0} was calculated according to the above formula (1). The BET specific surface area of SCMG-AF-C was 1.96 m ² / g. The BET specific surface area of CGB-10 was 6.7 m ² / g. The BET specific surface area of LN-0010 was 8 m ² / g. The BET specific surface area of NED-270ZJ was 1.7 m ² / g. The BET specific surface area of ZIF-8 was 1692 m ² / g. The BET specific surface area of ZIF-7 was 501 m ² / g. The BET specific surface area of ZIF-67 was 1595 m ² / g. Tables 1 and 2 show the measurement results of the BET specific surface area of the composite particles according to Examples 1 to 11 and _{the calculation results of the ratio P 0 of the composite particles according to Examples 1 to 11.} _{Similarly, the calculation results of the ratio P 0} of the composite particles according to Examples 12 to 15 and 26 to 32 are shown in Tables 3, 5 and 6. For Examples 1 to 15 and 31 to 33, P ₀ corresponds to R.

In the EIS symmetric cells according to Examples 1 to 5, the internal resistance was reduced as compared with the EIS symmetric cells according to Comparative Example 1 regardless of the temperature at which the battery was charged. By using electrodes for power storage devices in which pitch-coated graphite is coated with a porous material, the internal resistance during charging and discharging of the secondary battery is reduced. In addition, the _{smaller the ratio P 0} , the greater the rate of reduction in internal resistance.

In the EIS symmetric cells according to Examples 6 to 17, the internal resistance was lower than the internal resistance of the EIS symmetric cells according to Comparative Examples 2 or 3 regardless of the temperature at which the battery was charged. By using electrodes for power storage devices in which natural graphite is coated with a porous material, the internal resistance during charging and discharging of the secondary battery has been reduced. In addition, even when the negative electrode active material was coated with ZIF-67, ZIF-7, or ZIF-9, the internal resistance during charging and discharging of the secondary battery was reduced.

In the EIS symmetric cells according to Examples 18 to 28, the internal resistance was lower than the internal resistance of the EIS symmetric cells according to Comparative Examples 2 or 3 regardless of the temperature at which the battery was charged. The internal resistance was reduced even when the porous material was dispersed in the binder. In addition, even when ZIF-8, ZIF-67, MIL-53 (Al), or HKUST-1 was used as the porous material, the internal resistance was reduced. It is considered that the inclusion of the porous material in the binder formed a portion inside the binder through which ions could easily pass.

In the EIS symmetric cell according to Examples 29 and 30, the internal resistance was lower than the internal resistance of the EIS symmetric cell according to Comparative Example 2 or 3 regardless of the temperature at which the battery was charged. In addition, in the EIS symmetric cells according to Examples 26 and 27, the internal resistance was reduced as compared with the EIS symmetric cells according to Examples 18 to 28. The EIS symmetric cells according to Examples 29 and 30 include the use of a negative electrode active material coated with a porous material and the dispersion of the porous material in a binder. As a result, in the symmetric cells for EIS according to Examples 29 and 30, the rate of reduction of the internal resistance was larger than that when the symmetric cells for EIS in which the porous material was dispersed in the binder were used.

The internal resistance of the EIS symmetric cells according to Examples 31 to 35 was lower than the internal resistance of the EIS symmetric cells according to Comparative Examples 4 to 8 regardless of the temperature at which the battery was charged. As a result, even when various negative electrode active materials are used, it is possible to reduce the internal resistance by coating the negative electrode active material with the porous material.

The values of the internal resistances of the symmetrical cells for EIS according to Comparative Examples 2 and 9 to 14 were about the same. Therefore, it is considered that the influence of the method of manufacturing the electrode for the power storage device on the value of the internal resistance is small.

Claims

With active material
A porous material containing a structure in which a metal atom and an atomic group containing a non-metal atom are bonded is provided.
The non-metal atom contains at least an atom other than an oxygen atom and contains.
The ratio of the content of the porous material to the sum of the content of the active material and the content of the porous material is 0.1% by mass to 10% by mass.
Electrodes for power storage devices.
Further provided with a binder for binding the active material,
The electrode for a power storage device according to claim 1, wherein at least a part of the porous material is dispersed in the binder.
The electrode for a power storage device according to claim 2, wherein at least a part of the porous material dispersed in the binder is not coated with the active material.
The electrode for a power storage device according to any one of claims 1 to 3, wherein at least a part of the porous material is coated with the active material.
The ratio of the content of the porous material coating the active material to the sum of the content of the active material and the content of the porous material coating the active material is 0.1% by mass. The electrode for a power storage device according to claim 4, which is ~ 5% by mass.
According to any one of claims 1 to 5, the metal atom contains at least one metal atom selected from metal atoms belonging to any of Group 2, Group 3, and Group 5 to Group 14. The electrode for a power storage device described.
The electrode for a power storage device according to claim 6, wherein the metal atom contains at least one metal atom selected from the group consisting of Zn, Co, Cu, and Al.
The electrode for a power storage device according to any one of claims 1 to 7, wherein the compound forming the atomic group contains an amino group.
The electrode for a power storage device according to any one of claims 1 to 8, wherein the compound forming the atomic group contains a heterocycle.
The energy storage device according to any one of claims 1 to 7, wherein the compound forming the atomic group is at least one selected from the group consisting of 2-methylimidazole, benzimidazole, terephthalic acid, and benzenetricarboxylic acid. Electrode.
Claim that the porous material comprises at least one porous material selected from the group consisting of ZIF-8, ZIF-7, ZIF-9, ZIF-67, MIL-53 (Al), and HKUST-1. The electrode for a power storage device according to any one of 1 to 7.
The electrode for a power storage device according to any one of claims 1 to 11, wherein the active material is a negative electrode active material.
Negative electrode active material and
A porous material containing a structure in which a metal atom and an atomic group containing a non-metal atom are bonded and coating the negative electrode active material is provided.
The non-metal atom contains at least an atom other than an oxygen atom and contains.
The ratio of the content of the porous material to the sum of the content of the negative electrode active material and the content of the porous material is 0.1% by mass to 5% by mass.
Composite particles for power storage devices.
A power storage device comprising the electrode for the power storage device according to any one of claims 1 to 12.