Liquid composition, functional material, electricity storage device, method for manufacturing electrode, and method for manufacturing electricity storage device

Abstract

To provide a liquid composition that can be easily redispersed even if inorganic particles in the liquid composition settle under their own weight.SOLUTION: A liquid composition contains first inorganic particles with a median diameter of 200 nm to less than 1000 nm, second inorganic particles with an average diameter of less than 30 nm, a dispersing agent, and a solvent.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a liquid composition, a functional material, and an electricity storage device. , electrode manufacturing method, and electricity storage device manufacturing method Regarding. [Background technology]

[0002] Conventionally, in electricity storage devices such as lithium ion secondary batteries, electric double layer capacitors, lithium ion capacitors, and redox capacitors, paper, nonwoven fabric, and porous film have been used as separators to prevent short circuits between the positive and negative electrodes.

[0003] In recent years, separator-integrated electrodes have been used, in which an electrode mixture layer and a particle layer are sequentially formed on an electrode substrate (see, for example, Patent Document 1). Separator-integrated electrodes are generally manufactured by applying a liquid composition containing particles to an electrode mixture layer in a thickness of 10 μm or less. This liquid composition is ejected from a liquid ejection head to form a uniform particle layer on the electrode substrate (see, for example, Patent Document 2).

[0004] A liquid composition is generally prepared by uniformly dispersing inorganic particles and a dispersant as solid components in a solvent. In order to produce such a uniform particle layer, attempts have been made to add a dispersant such as a surfactant to the liquid composition and disperse the particles using a dispersing device such as a bead mill, thereby deagglomerating the primary particles of the inorganic particles as much as possible and uniformly dispersing the independent primary particles in the solvent. Summary of the Invention [Problem to be solved by the invention]

[0005] However, in such liquid compositions, since the specific gravity of the inorganic particles is larger than that of the solvent, which is the dispersion medium, even if the inorganic particles are dispersed, they will settle due to their own weight when stored still (hereinafter referred to as "settling by own weight"). For example, even if particles with a large specific gravity, such as alumina, are dispersed in an organic solvent using a dispersant, it is difficult to redisperse the particles once they have settled using conventional liquid compositions.

[0006] Furthermore, if the redispersion of inorganic particles in the liquid composition is insufficient, the physical properties of the liquid composition change, for example, aggregates are generated in the liquid composition, causing a change in particle size distribution, or the viscosity or thixotropy of the liquid composition changes. As a result, for example, when a functional film is formed on a substrate using the liquid composition, ejection defects may occur when the liquid composition is ejected using an inkjet, which may lead to uneven coating.

[0007] An object of the present invention is to provide a liquid composition that can easily redisperse inorganic particles in the liquid composition even if they settle due to their own weight. [Means for solving the problem]

[0008] One aspect of the present invention is a coating composition containing first inorganic particles having a median diameter of 200 nm or more and less than 1000 nm, second inorganic particles having an average diameter of less than 30 nm, a dispersant, and a solvent. and a dispersant for forming a particle layer on an electrode, wherein the dispersant is a nonionic surfactant. It is a liquid composition. [Effects of the Invention]

[0009] According to one aspect of the present invention, it is possible to provide a liquid composition that allows inorganic particles in the liquid composition to be easily redispersed even if they settle due to their own weight. [Brief explanation of the drawings]

[0010] [Figure 1] FIG. 1 is a schematic diagram of an inorganic particle. [Figure 2] This is the interaction potential energy curve between particles. [Figure 3] FIG. 2 is a cross-sectional view showing an example of a negative electrode. [Figure 4] 3A to 3C are schematic diagrams illustrating an example of a method for producing a negative electrode. [Figure 5] 5A to 5C are schematic diagrams illustrating another example of a method for producing a negative electrode. [Figure 6] FIG. 6 is a schematic diagram showing a modified example of the liquid ejection device of FIGS. [Figure 7] FIG. 2 is a cross-sectional view showing an example of a positive electrode. [Figure 8] FIG. 2 is a cross-sectional view showing an example of an electrode element that constitutes an electricity storage device. [Figure 9] FIG. 1 is a cross-sectional view illustrating an example of an electricity storage device. [Figure 10] 1 is a schematic perspective view showing an example of an inkjet printing apparatus. [Figure 11] FIG. 2 is a schematic diagram showing an example of a separator-integrated electrode. [Figure 12] FIG. 12 is a cross-sectional view taken along line AA in FIG. DETAILED DESCRIPTION OF THE INVENTION

[0011] Hereinafter, an embodiment of the present invention will be described.

[0012] <Liquid composition> The liquid composition according to this embodiment contains first inorganic particles, second inorganic particles, a dispersant, and a solvent. Here, the inorganic particles refer to particles of an inorganic compound such as a metal or metal oxide. The liquid composition according to this embodiment may optionally contain a cosolvent, a binder, or other additives.

[0013] [First inorganic particle] The first inorganic particles (hereinafter sometimes referred to as inorganic particles A) are inorganic particles having a median diameter of 200 nm or more and less than 1000 nm.

[0014] In this specification, the median diameter refers to the particle diameter at which the cumulative frequency based on the number of particles is 50% (hereinafter referred to as D50). Note that if the median diameter is 1000 nm or more, coating unevenness is likely to occur when coating to obtain a film thickness in the μm range, and if the median diameter is less than 200 nm, it becomes difficult to maintain a uniform dispersion state.

[0015] The material constituting the first inorganic particles (inorganic particles A) is not particularly limited, but examples thereof include aluminum oxide, silica, calcium carbonate, titanium oxide, calcium phosphate, titanium oxide, silicon oxide, zirconium oxide, etc. These first inorganic particles may be used alone or in combination of two or more types.

[0016] Among these first inorganic particles, inorganic oxides such as aluminum oxide (alumina) are preferred when used to manufacture a separator-integrated electrode, which will be described later, because they have high insulating properties and heat resistance.

[0017] The type of alumina used as the first inorganic particles is not particularly limited, and examples thereof include α-alumina, γ-alumina, β-alumina, fumed alumina, etc. Among these, α-alumina is preferred from the viewpoints of insulation properties and abrasion resistance.

[0018] These aluminas may be used alone or in combination of two or more. When two or more aluminas are used, it is preferable that the main component of the alumina is α-alumina from the viewpoint of insulation properties and abrasion resistance.

[0019] Here, the phrase "the main component is α-alumina" means that the content of α-alumina in the total alumina is 50 mass% or more, preferably 60 mass% or more, and more preferably 70 mass% or more. By setting the content in this range, it is possible to form a particle layer with excellent insulation properties and abrasion resistance.

[0020] The alumina contained in the liquid composition of this embodiment may correspond to the solid content in the liquid composition, and the proportion of the solid content in the liquid composition is 20% by mass or more and 50% by mass or less, and preferably 35% by mass or more and 45% by mass or less.

[0021] Such an alumina content indicates a high solids concentration compared to that of a liquid composition such as a general ink, etc. By setting the alumina content within this range, unevenness in the coating film thickness after the liquid composition is applied and dried can be suppressed.

[0022] [Second inorganic particles] The second inorganic particles (hereinafter sometimes referred to as fine inorganic particles or fine inorganic particles B) are inorganic particles having an average diameter of less than 30 nm.

[0023] In this specification, the average diameter refers to the average value of the long diameter of particles measured by observation with, for example, a transmission electron microscope (TEM). If the average diameter is 30 nm or more, it may be impossible to sufficiently reduce the energy barrier in the interaction potential energy between particles described below.

[0024] Here, the fine inorganic particles B having an average diameter of less than 30 nm can be separated from other particles and recovered, for example, by centrifuging the particles and extracting the supernatant.

[0025] For example, the particle density is 3.95 g / cm according to the Stokes equation below. 3 Alumina has a liquid viscosity of 10 kg / m s and a liquid density of 1.03 g / cm 3 The mixture is centrifuged for 20 minutes at a rotation speed of 3000 rpm and a rotation radius of 10 cm in the solvent prepared in the above. As a result, the particle diameter that settles to 1.8 cm is calculated to be 30 nm or larger, and by collecting the supernatant, it is possible to recover minute inorganic particles less than 30 nm in size.

[0026]

number

[0027] No. 2 nothing The material constituting the organic particles (fine inorganic particles B) is not particularly limited, but examples thereof include aluminum oxide, silica, calcium carbonate, titanium oxide, calcium phosphate, titanium oxide, silicon oxide, zirconium oxide, etc. These second inorganic particles may be used alone or in combination of two or more types.

[0028] Among these second inorganic particles, inorganic oxides such as aluminum oxide (alumina) are preferred when used to manufacture a separator-integrated electrode, which will be described later, because they have high insulating properties and heat resistance.

[0029] The type of alumina used as the second inorganic particles is not particularly limited, and examples thereof include α-alumina, γ-alumina, β-alumina, fumed alumina, etc. Among these, α-alumina is preferred from the viewpoints of insulation properties and abrasion resistance.

[0030] The material constituting the fine inorganic particles B may be the same as or different from the material constituting the inorganic particles A described above.

[0031] The content of the second inorganic particles (fine inorganic particles B) is not particularly limited, but is preferably 1% by mass or more and 5% by mass or less relative to the total mass of the first inorganic particles (inorganic particles A).

[0032] In this embodiment, the liquid composition may contain first inorganic particles and second inorganic particles, but this is not limited to this. Fig. 1 is a schematic diagram of inorganic particles contained in the liquid composition according to this embodiment. In this embodiment, first inorganic particles 1 and second inorganic particles (not shown) are mixed in the liquid composition.

[0033] [Dispersant] A dispersant is a compound that adsorbs or bonds to the surface of particles and has the function of suppressing aggregation of particles by electrostatic repulsion due to Coulomb force or steric hindrance due to molecular chains.

[0034] The number average molecular weight of the dispersant is not particularly limited, but is usually 1,000 to 100,000, and is preferably 1,000 to 10,000, and more preferably 1,000 to 5,000, from the viewpoint of suppressing an increase in viscosity of the liquid composition.

[0035] The dispersant preferably has a dispersing group. When the liquid composition is used as a functional material for a lithium ion battery, for example, the dispersing group is preferably a nonionic group from the viewpoint of ionic conductivity. Here, "nonionic" refers to a group that does not have ionicity, and "nonionic group" refers to a substituent that does not have ionicity. Note that a dispersant having a nonionic group as a dispersing group corresponds to a nonionic surfactant.

[0036] The dispersing group may have any structure that allows solubility in the solvent and auxiliary solvent described below, but when used in a lithium ion secondary battery, an oligoether group is preferred from the viewpoint of ionic conductivity. Here, the oligoether group refers to a group obtained by removing a hydroxyl group from the end of an ethylene glycol or propylene glycol polymer.

[0037] The molecular weight of the ethylene glycol or propylene glycol polymer is preferably 100 to 10,000, and more preferably 100 to 5,000. When the molecular weight of the ethylene glycol or propylene glycol polymer is 100 or more, the dispersibility of inorganic particles (e.g., alumina particles) in the liquid composition is improved, and when it is 10,000 or less, an increase in the viscosity of the liquid composition can be suppressed.

[0038] The terminal on the side where the oligoether group is not bonded may be a hydroxyl group, or a methoxy group, an ethoxy group, a propoxy group, etc. When a dispersant having an oligoether group is used, the dispersibility of inorganic particles can be improved even when a highly polar solvent is used as the solvent.

[0039] When the first inorganic particles are alumina particles, the dispersant is preferably a polymer dispersant having, as an adsorptive group, an ionic group of opposite polarity to the polarity to which the alumina particles are charged, in terms of the adsorption strength with the alumina particles.

[0040] Examples of polymer dispersants include commercially available products such as DISPERBYK (registered trademark)-103, DISPERBYK-118, DISPERBYK-2155 (all manufactured by BIGC-Chemie), NOPCOSPERSE (registered trademark)-092, SN-SPERSE-2190, SN-DISPERSANT-9228 (all manufactured by San Nopco), S-LEAM (registered trademark) AD-3172M, S-LEAM 2093, MARIALYM (registered trademark) AKM-0513, MARIALYM HKM-50A, MARIALYM HKM-150A, MARIALYM SC-0505K, MARIALYM SC-1015F, and MARIALYM SC-0708A (all manufactured by NOF Corporation).

[0041] These polymer dispersants may be used alone or in combination of two or more. The content of the polymer dispersant relative to the inorganic particles is not particularly limited, but is usually 0.01% by mass to 10% by mass, and further taking into consideration the dispersibility of the inorganic particles, it is preferably 0.1% by mass to 10% by mass.

[0042] [Binder] The liquid composition of the present embodiment may optionally contain a binder. By applying a liquid composition containing a binder to a substrate described below, the strength of a functional film produced using the liquid composition can be improved.

[0043] The binder is not particularly limited, but examples thereof include polyvinylidene fluoride, styrene butadiene rubber, and acrylic resin. These binders may be used alone or in combination of two or more. The binder may be dissolved or dispersed in the liquid composition.

[0044] Instead of the binder, a binder precursor may be used. Examples of binder precursors include monomers. A liquid composition containing such a monomer and, if necessary, a polymerization initiator is applied to an absorption medium (hereinafter, sometimes referred to as a substrate), and then the coating is heated or irradiated with light, whereby the monomer is polymerized, thereby improving the strength of the functional film.

[0045] [solvent] The solvent (hereinafter referred to as solvent A) can disperse inorganic particles in the liquid composition. The content of solvent A is arbitrary. The component of solvent A is not particularly limited, and it is an aqueous solvent or a non-aqueous solvent.

[0046] The aqueous solvent is not particularly limited, and examples thereof include water and a mixture of water and a polar solvent.

[0047] Examples of polar solvents include methanol, ethanol, propanol, butanol, pentanol, hexanol, ethylene glycol, hexylene glycol, N-methyl-2-pyrrolidone (NMP), dimethyl sulfoxide (DMSO), N,N-dimethylformamide (DMF), acetone, tetrahydrofuran (THF), etc. The polar solvents may be used alone or in combination of two or more.

[0048] The non-aqueous dispersion medium is not particularly limited, and examples thereof include lactams, alcohols, sulfoxides, esters, and ketones.

[0049] Examples of lactams include 1-methyl-2-pyrrolidone and 2-pyrrolidone.

[0050] Examples of alcohols include isopropyl alcohol, butanol, and diacetone alcohol.

[0051] The sulfoxide includes, for example, dimethyl sulfoxide.

[0052] Examples of esters include ethyl acetate, butyl acetate, ethyl lactate, and ethylene glycol diacetate.

[0053] Examples of ketones include diisobutyl ketone, 2-butanone, 2-pentanone, and diacetone alcohol.

[0054] These non-aqueous solvents may be used alone or in combination of two or more.

[0055] Solvent A is preferably a solvent that has affinity with inorganic particles (for example, alumina particles), and is more preferably a non-aqueous solvent.

[0056] [Co-solvent] The co-solvent (hereinafter referred to as solvent B) is a solvent different from solvent A. Solvent B can be optionally blended in order to compensate for the lack of functionality of solvent A.

[0057] Examples of solvent B include solvents that have the function of dispersing inorganic particles (e.g., alumina particles), solvents with high boiling points intended to prevent the nozzle of the liquid ejection head from drying out, solvents intended to adjust the viscosity and surface tension to an appropriate level when ejecting from the liquid ejection head, and solvents intended to suppress the absorption of alumina particles into the electrode composite layer.

[0058] The component of solvent B is not particularly limited, and may be an aqueous solvent or a non-aqueous solvent.

[0059] The aqueous solvent is not particularly limited, and examples thereof include water and mixtures of water and polar solvents. Examples of polar solvents include methanol, ethanol, propanol, butanol, pentanol, hexanol, ethylene glycol, hexylene glycol, NMP, DMSO, DMF, acetone, and THF. The polar solvents may be used alone or in combination of two or more.

[0060] The non-aqueous dispersion medium is not particularly limited, and examples thereof include ethers, glycols, esters, alcohols, and lactams.

[0061] An example of the ether is propylene glycol monopropyl ether.

[0062] Examples of glycols include propylene glycol, ethylene glycol, triethylene glycol, and hexylene glycol.

[0063] Examples of the ester include ethyl lactate, ethylene carbonate, and ethylene glycol diacetate.

[0064] Examples of alcohols include cyclohexanol, propylene glycol monopropyl ether, etc. Examples of lactams include 2-pyrrolidone, etc.

[0065] These non-aqueous solvents may be used alone or in combination of two or more.

[0066] Solvent B is more preferably a solvent having affinity with inorganic particles such as alumina, and is more preferably a non-aqueous solvent.

[0067] [Other additives] The liquid composition of this embodiment may further contain other components depending on the purpose, such as adjusting viscosity, adjusting surface tension, controlling solvent evaporation, improving the solubility of additives, improving the dispersibility of alumina particles, sterilization, etc. Examples of other components include surfactants, pH adjusters, rust inhibitors, preservatives, antifungal agents, antioxidants, antireducing agents, evaporation accelerators, and chelating agents.

[0068] [Method of producing liquid composition] The method for producing the liquid composition of the present embodiment is not particularly limited, but the liquid composition can be produced by adding first inorganic particles (inorganic particles A), second inorganic particles (fine inorganic particles B), a dispersant, and solvent A, and optionally adding a binder and solvent B, and dispersing the mixture.

[0069] The method for dispersing the liquid composition is not particularly limited, and for example, a known dispersing device can be used. Specific examples of the dispersing device include a stirrer, a ball mill, a bead mill, a ring mill, a high-pressure dispersing device, a rotary high-speed shearing device, and an ultrasonic dispersing device.

[0070] The effects obtained by the liquid composition according to this embodiment can be explained by the DLVO theory, which describes the dispersion and aggregation states acting between particles. The DLVO theory explains that particle dispersion and aggregation phenomena can be predicted by the balance of interparticle attractive forces, which are the sum of the osmotic repulsive force and the London-van der Waals force resulting from the electric double layer between particles.

[0071] Figure 2 shows the potential energy curve for particle interactions based on the DLVO theory. In the graph in Figure 2, H on the horizontal axis represents the interparticle distance, V on the vertical axis represents the potential energy, A represents the London-van der Waals attractive force, B represents the electric double layer repulsive force, C represents the potential energy due to the total interaction of attractive and repulsive forces, C1 represents the minimum point of primary aggregation, C2 represents the maximum point of the energy barrier, and C3 represents the minimum point of secondary aggregation.

[0072] According to the DLVO theory, in order to return the aggregated particles to a dispersed state, it is necessary to overcome the energy barrier (C2) of the potential energy due to the total interaction (C) of the attractive force (A) and the repulsive force (B). Therefore, in order to improve the redispersibility of a liquid composition, it is necessary to reduce the energy barrier (C2) of the potential energy acting between such particles.

[0073] The present inventors have found that when a certain amount of fine inorganic particles defined by an average diameter is added to inorganic particles defined by a median diameter, the London-van der Waals force (A) increases and the potential energy barrier (C2) decreases. The effect of the liquid composition according to this embodiment is believed to be achieved by this mechanism, and is that the redispersibility of the liquid composition containing inorganic particles can be improved.

[0074] That is, as described above, the liquid composition according to this embodiment contains first inorganic particles having a median diameter of 200 nm or more but less than 1000 nm, second inorganic particles having an average diameter of less than 30 nm, a dispersant, and a solvent. This reduces the potential energy barrier acting between the inorganic particles in the liquid composition. Therefore, the dispersibility of the liquid composition can be improved even when the liquid composition contains inorganic particles with a high specific gravity relative to the solvent.

[0075] Furthermore, in this embodiment, as described above, the energy barrier of the potential energy acting between inorganic particles in the liquid composition is reduced, so that even if inorganic particles having a large specific gravity relative to the solvent settle out of the liquid composition due to their own weight, the liquid composition can be easily redispersed. Therefore, according to this embodiment, a liquid composition with excellent storage stability during storage, transportation, etc. can be provided.

[0076] Furthermore, in this embodiment, even if inorganic particles in the liquid composition settle due to their own weight, they can be easily redispersed, so that when the liquid composition is used after being stored or preserved, a large-scale stirring operation is not required, thereby improving redispersion efficiency and reducing product costs. Furthermore, when a functional film is formed on a substrate using the liquid composition, for example, uneven coating can be suppressed when the liquid composition is ejected using an inkjet.

[0077] In the liquid composition according to this embodiment, as described above, the content of the second inorganic particles is 1% by mass or more and 5% by mass or less relative to the total mass of the first inorganic particles, thereby further reducing the potential energy barrier acting between inorganic particles in the liquid composition, thereby improving the redispersibility of inorganic particles having a high specific gravity relative to the solvent after settling under their own weight in the liquid composition.

[0078] In the liquid composition according to this embodiment, as described above, by using α-alumina as the first inorganic particles, the potential energy barrier acting between inorganic particles in the liquid composition can be further reduced, thereby further improving the redispersibility of inorganic particles having a high specific gravity relative to the solvent after settling under their own weight in the liquid composition.

[0079] In the liquid composition according to this embodiment, as described above, by setting the solid content to 20% by mass or more and 50% by mass or less, coating unevenness can be suppressed when the liquid composition is applied to form a coating film.

[0080] In the liquid composition according to this embodiment, as described above, the use of a non-aqueous solvent as the solvent can enhance the affinity between inorganic particles such as alumina and the solvent. This can improve both the dispersibility of the inorganic particles in the liquid composition during production and the redispersibility after sedimentation under its own weight. Furthermore, since the non-aqueous solvent has a higher boiling point than the aqueous solvent, drying is facilitated when the liquid composition is applied to form a coating film.

[0081] As described above, the liquid composition according to this embodiment uses a nonionic surfactant as a dispersant, thereby increasing ionic conductivity when used as a functional material for a lithium ion battery. Therefore, according to this embodiment, when the liquid composition is used in a lithium ion secondary battery, the battery characteristics of the lithium ion battery can be improved.

[0082] In the liquid composition according to this embodiment, as described above, the use of a dispersant having an oligoether group can further increase the ionic conductivity when the liquid composition is used as a functional material for a lithium ion battery. Therefore, according to this embodiment, when the liquid composition is used in a lithium ion secondary battery, the battery characteristics of the lithium ion battery can be further improved.

[0083] <Functional Materials> The functional material according to this embodiment includes the materials contained in the liquid composition described above. That is, the materials contained in the liquid composition described above can be used for the functional material according to this embodiment. Specifically, by applying the liquid composition described above as the functional material to a substrate described below, a functional film can be formed on the substrate.

[0084] [Method for applying liquid composition] The method for applying the liquid composition is not particularly limited, but it is preferable to apply the above-mentioned liquid composition onto the substrate using a liquid ejection method such as an inkjet ejection method, because this allows control of the ejection position.

[0085] Examples of the method for ejecting the liquid composition in the liquid ejection method include a method of applying mechanical energy to the liquid composition, a method of applying thermal energy to the liquid composition, etc. Among these, the method of applying mechanical energy to the liquid composition is preferred in terms of dispersion stability.

[0086] When a liquid ejection method is used, a technique using the liquid ejection principle of a known liquid ejection device may be applied. In this case, it is preferable to use solvents that are resistant to the flow paths and nozzles of the liquid ejection head installed in the liquid ejection device as the solvents A and B contained in the liquid composition.

[0087] [Electrode manufacturing method] The liquid composition described above can be used to manufacture an electrode having a functional film. The method for manufacturing such an electrode includes a step of discharging the liquid composition described above onto an electrode substrate.

[0088] The material constituting the electrode substrate (for example, a current collector, an electrode having a current collector and an active material layer, etc.) is not particularly limited as long as it is conductive and stable against an applied potential.

[0089] The method for manufacturing an electrode using the liquid composition preferably further includes a step of pressurizing the electrode substrate onto which the liquid composition has been ejected, thereby making it difficult for the electrode components to peel off and improving the reliability of devices formed using the functional material.

[0090] The electrode in which the above-mentioned liquid composition is used has a negative electrode and a positive electrode.

[0091] [Negative electrode] An example of a negative electrode is shown in Fig. 3. In negative electrode 10, a negative electrode composite layer 12 containing a negative electrode active material and a polymer is formed on one side of a negative electrode substrate 11. Note that negative electrode composite layer 12 may be formed on both sides of negative electrode substrate 11.

[0092] The shape of the negative electrode 10 is not particularly limited, and may be, for example, a flat plate. Examples of materials constituting the negative electrode substrate 11 include stainless steel, nickel, aluminum, and copper.

[0093] [Method of manufacturing negative electrode] An example of a method for manufacturing a negative electrode is shown in Figure 4. The method for manufacturing a negative electrode 10 includes a step of discharging a liquid composition 12A onto a negative electrode substrate 11 using a liquid discharge device 300.

[0094] Here, the liquid composition 12A contains a negative electrode active material, a dispersion medium (solvent), and a polymer. The liquid composition 12A is stored in a tank 307 and is supplied from the tank 307 to a liquid ejection head 306 via a tube 308.

[0095] The liquid ejection device 300 may also be provided with a mechanism for capping the nozzle (not shown) of the liquid ejection head 306 to prevent the liquid composition 12A from drying out when it is not being ejected from the liquid ejection head 306.

[0096] When manufacturing the negative electrode 10, the negative electrode substrate 11 is placed on a heatable stage 400, droplets of the liquid composition 12A are ejected onto the negative electrode substrate 11, and then the negative electrode substrate 11 is heated. At this time, the stage 400 or the liquid ejection head 306 may be moved.

[0097] Furthermore, when the liquid composition 12A discharged onto the negative electrode substrate 11 is heated, it may be heated by the stage 400 or by a heating mechanism other than the stage 400.

[0098] The heating mechanism is not particularly limited as long as it does not come into direct contact with the liquid composition 12A, and examples thereof include a resistance heater, an infrared heater, a fan heater, etc. Note that a plurality of heating mechanisms may be installed.

[0099] The heating temperature is not particularly limited as long as it is a temperature at which the dispersion medium can be volatilized, and is preferably in the range of 70 to 150°C from the viewpoint of power consumption.

[0100] Furthermore, when the liquid composition 12A discharged onto the negative electrode substrate 11 is heated, ultraviolet light may be irradiated thereto.

[0101] Another example of a method for producing a negative electrode is shown in Fig. 6. In Fig. 6, parts common to those in Fig. 4 are given the same reference numerals as in Fig. 4, and descriptions thereof may be omitted.

[0102] The method for producing the negative electrode 10 includes a step of discharging the liquid composition 12A onto the negative electrode substrate 11 using the liquid discharge device 300.

[0103] First, an elongated negative electrode substrate 11 is prepared. Then, negative electrode substrate 11 is wound around a cylindrical core and set on delivery roller 304 and take-up roller 305 so that the side on which negative electrode composite layer 12 is to be formed faces upward in FIG. 6. Here, delivery roller 304 and take-up roller 305 each rotate counterclockwise (in the direction of the arrow in FIG. 6), and negative electrode substrate 11 is transported from right to left in FIG. 6.

[0104] Then, droplets of liquid composition 12A are ejected onto the conveyed negative electrode substrate 11 from a liquid ejection head 306 installed above the negative electrode substrate 11 between a delivery roller 304 and a take-up roller 305. The droplets of liquid composition 12A are ejected so as to cover at least a portion of the negative electrode substrate 11.

[0105] A plurality of liquid ejection heads 306 may be installed in a direction substantially parallel to or substantially perpendicular to the direction in which the negative electrode substrate 11 is transported.

[0106] Next, negative electrode substrate 11 onto which liquid composition 12A has been ejected is transported to heating mechanism 309 by delivery roller 304 and take-up roller 305. As a result, the dispersion medium (solvent) contained in liquid composition 12A on negative electrode substrate 11 volatilizes, forming negative electrode composite layer 12 and obtaining negative electrode 10. Thereafter, negative electrode 10 is cut to a desired size by punching or the like.

[0107] The heating mechanism 309 is not particularly limited as long as it does not come into direct contact with the liquid composition 12A, and examples thereof include a resistance heater, an infrared heater, a fan heater, etc. The heating mechanism 309 may be installed either above or below the negative electrode substrate 11, or multiple heating mechanisms 309 may be installed.

[0108] The heating temperature is not particularly limited as long as it is a temperature at which the dispersion medium can be volatilized, and is preferably in the range of 70 to 150°C from the viewpoint of power consumption.

[0109] Furthermore, when the liquid composition 12A discharged onto the negative electrode substrate 11 is heated, ultraviolet light may be irradiated thereto.

[0110] Figure 6 shows a modified example of the liquid ejection device 300 of Figures 4 and 5. In Figure 6, parts that are common to those in Figure 5 are given the same reference numerals as in Figure 5, and descriptions thereof may be omitted.

[0111] In the liquid ejection device 300 ′ shown in FIG. 6, the liquid composition 12 A can be circulated through the liquid ejection head 306 , the tank 307 and the tube 308 by controlling the pump 310 and the valves 311 and 312 .

[0112] The liquid ejection device 300′ is also provided with an external tank 314. In the liquid ejection device 300′, when the liquid composition 12A in the tank 307 decreases, the liquid composition 12A can be supplied from the external tank 314 to the tank 307 by controlling the pump 310 and the valves 311, 312, and 313.

[0113] Use of liquid ejection devices 300 and 300' makes it possible to eject liquid composition 12A onto a targeted location on negative electrode substrate 11. Use of liquid ejection devices 300 and 300' also makes it possible to bond the contacting surfaces of negative electrode substrate 11 and negative electrode composite layer 12 together. Use of liquid ejection devices 300 and 300' also makes it possible to make negative electrode composite layer 12 have a uniform thickness.

[0114] [Positive electrode] An example of a positive electrode is shown in Fig. 7. In positive electrode 20, positive electrode composite layer 22 containing a positive electrode active material and a polymer is formed on one surface of positive electrode substrate 21. Note that positive electrode composite layer 22 may be formed on both surfaces of positive electrode substrate 21.

[0115] The shape of the positive electrode 20 is not particularly limited, and may be, for example, a flat plate shape. Examples of materials that form the positive electrode substrate 21 include stainless steel, aluminum, titanium, and tantalum.

[0116] [Cathode manufacturing method] The method for producing the positive electrode 20 is the same as the method for producing the negative electrode 10, except that the liquid composition is discharged onto the positive electrode substrate 21. Here, the liquid composition contains a positive electrode active material, a dispersion medium (solvent), and a polymer.

[0117] <Electricity storage device> The electricity storage device according to this embodiment can be formed using the functional material described above. That is, the functional material containing the liquid composition described above is used to form the electricity storage device according to this embodiment. Specifically, the functional material containing the liquid composition described above can be used to form an electrochemical element such as a secondary battery.

[0118] [Method of manufacturing electrochemical element] A method for manufacturing an electrochemical element (electricity storage device) includes a step of manufacturing an electrode using the above-described method for manufacturing an electrode.

[0119] [Electrode element] 8 shows an example of an electrode element constituting the electricity storage device (electrochemical element) of this embodiment. In an electrode element 40, a negative electrode 15 and a positive electrode 25 are stacked with a separator 30 interposed therebetween. Here, the positive electrodes 25 are stacked on both sides of the negative electrode 15. In addition, a lead wire 41 is connected to the negative electrode substrate 11, and a lead wire 42 is connected to the positive electrode substrate 21.

[0120] Negative electrode 15 is similar to negative electrode 10 described above, except that negative electrode mixture layer 12 is formed on both sides of negative electrode substrate 11 .

[0121] Positive electrode 25 is similar to positive electrode 20 described above, except that positive electrode mixture layers 22 are formed on both sides of positive electrode substrate 21 .

[0122] There is no particular limitation on the number of stacked negative electrodes 15 and positive electrodes 25 of the electrode element 40. The number of negative electrodes 15 and the number of positive electrodes 25 of the electrode element 40 may be the same or different.

[0123] [Separator] The separator 30 is provided between the negative electrode 15 and the positive electrode 25 to prevent short-circuiting between the negative electrode 15 and the positive electrode 25 .

[0124] The separator 30 is not particularly limited and can be appropriately selected depending on the purpose. Examples of the separator 30 include paper such as kraft paper, vinylon-mixed paper, and synthetic pulp-mixed paper, cellophane, polyethylene graft membrane, polyolefin nonwoven fabric such as polypropylene melt-blown nonwoven fabric, polyamide nonwoven fabric, glass fiber nonwoven fabric, and micropore membrane.

[0125] The size of the separator 30 is not particularly limited as long as it can be used in an electrochemical element.

[0126] The separator 30 may have a single layer structure or a laminated structure.

[0127] When a solid electrolyte is used, the separator 30 can be omitted.

[0128] Fig. 9 shows a secondary battery as an example of the electricity storage device (electrochemical element) of this embodiment. In Fig. 9, parts common to those in Fig. 8 are given the same reference numerals as in Fig. 8, and descriptions thereof may be omitted.

[0129] 8, an electrolyte layer 81 is formed by injecting an electrolyte aqueous solution or a non-aqueous electrolyte into the electrode element 40, and the secondary battery 100 is sealed with an exterior case 82. In the secondary battery 100, the lead wires 41 and 42 are drawn out to the outside of the exterior case 82.

[0130] The secondary battery 100 may include other components as necessary. The secondary battery 100 is not particularly limited, and examples thereof include a lithium ion secondary battery.

[0131] The shape of the secondary battery 100 is not particularly limited and can be appropriately selected depending on the purpose. Examples of the shape of the secondary battery 100 include a laminate type, a cylinder type in which a sheet electrode and a separator are spirally wound, a cylinder type with an inside-out structure in which a pellet electrode and a separator are combined, and a coin type in which a pellet electrode and a separator are stacked.

[0132] [Aqueous electrolyte solution] The electrolyte salt constituting the aqueous electrolyte solution is not particularly limited, and examples thereof include sodium hydroxide, potassium hydroxide, sodium chloride, potassium chloride, ammonium chloride, zinc chloride, zinc acetate, zinc bromide, zinc iodide, zinc tartrate, and zinc perchlorate.

[0133] [Non-aqueous electrolyte] The non-aqueous electrolyte may be a solid electrolyte or a non-aqueous electrolyte solution, which is an electrolyte solution in which an electrolyte salt is dissolved in a non-aqueous solvent.

[0134] [Non-aqueous solvent] The non-aqueous solvent is not particularly limited, and it is preferable to use, for example, an aprotic organic solvent.

[0135] As the aprotic organic solvent, carbonate-based organic solvents such as chain carbonates and cyclic carbonates can be used. Among these, chain carbonates are preferred because of their high dissolving power for electrolyte salts. Furthermore, it is preferable that the aprotic organic solvent has low viscosity.

[0136] Examples of the chain carbonate include dimethyl carbonate (DMC), diethyl carbonate (DEC), and methyl ethyl carbonate (EMC).

[0137] The content of the chain carbonate in the non-aqueous solvent is not particularly limited, but is preferably 50% by mass or more.

[0138] When the content of the chain carbonate in the non-aqueous solvent is 50% by mass or more, even if the non-aqueous solvent other than the chain carbonate is a cyclic substance with a high dielectric constant (e.g., a cyclic carbonate or a cyclic ester), the content of the cyclic substance is low. Therefore, even if a non-aqueous electrolyte solution with a high concentration of 2 M or more is prepared, the viscosity of the non-aqueous electrolyte solution is low, and the non-aqueous electrolyte solution penetrates into the electrodes and ions diffuse well.

[0139] Examples of cyclic carbonates include propylene carbonate (PC), ethylene carbonate (EC), butylene carbonate (BC), and vinylene carbonate (VC).

[0140] As non-aqueous solvents other than carbonate-based organic solvents, for example, ester-based organic solvents such as cyclic esters and chain esters, and ether-based organic solvents such as cyclic ethers and chain ethers can be used.

[0141] Examples of cyclic esters include γ-butyrolactone (γBL), 2-methyl-γ-butyrolactone, acetyl-γ-butyrolactone, and γ-valerolactone.

[0142] Examples of chain esters include alkyl propionates, dialkyl malonates, alkyl acetates (e.g., methyl acetate (MA), ethyl acetate), and alkyl formates (e.g., methyl formate (MF), ethyl formate).

[0143] Examples of cyclic ethers include tetrahydrofuran, alkyltetrahydrofuran, alkoxytetrahydrofuran, dialkoxytetrahydrofuran, 1,3-dioxolane, alkyl-1,3-dioxolane, and 1,4-dioxolane.

[0144] Examples of the chain ether include 1,2-dimethoxyethane (DME), diethyl ether, ethylene glycol dialkyl ether, diethylene glycol dialkyl ether, triethylene glycol dialkyl ether, and tetraethylene glycol dialkyl ether.

[0145] [Electrolyte salt] The electrolyte salt is not particularly limited as long as it has high ionic conductivity and is soluble in a non-aqueous solvent.

[0146] The electrolyte salt preferably contains a halogen atom.

[0147] The electrolyte salt can be composed of a cation or an anion.

[0148] Examples of cations that constitute the electrolyte salt include lithium ions (lithium salts).

[0149] Examples of anions that constitute the electrolyte salt include BF4 - , PF6 - , AsF6 - , CF3SO3 - , (CF3SO2)2N - , (C2F5SO2)2N - Examples include:

[0150] The lithium salt is not particularly limited and can be appropriately selected depending on the purpose.

[0151] Examples of lithium salts include lithium hexafluorophosphate (LiPF), lithium borofluoride (LiBF), lithium arsenic hexafluoride (LiAsF), lithium trifluoromethansulfonate (LiCFSO), lithium bis(trifluoromethylsulfonyl)imide (LiN(CFSO)), and lithium bis(pentafluoroethylsulfonyl)imide (LiN(CFSO)).

[0152] Among these, LiPF6 is preferred from the viewpoint of ionic conductivity, and LiBF4 is preferred from the viewpoint of stability.

[0153] The electrolyte salts may be used alone or in combination of two or more.

[0154] The concentration of the electrolyte salt in the nonaqueous electrolyte solution is not particularly limited and can be appropriately selected depending on the purpose. For example, when the nonaqueous storage element is a swing type, the concentration of the electrolyte salt in the nonaqueous electrolyte solution is preferably 1 mol / L to 2 mol / L, and when the nonaqueous storage element is a reserve type, the concentration is preferably 2 mol / L to 4 mol / L.

[0155] [Liquid discharge device] 10 shows an example of an inkjet printing apparatus as the liquid ejection apparatus described above. The inkjet printing apparatus 50 includes a main body 51, a carriage 52, guide shafts 53 and 54, a timing belt 55, a platen 56, a main scanning motor 57, a sub-scanning motor 58, and a gear mechanism 59.

[0156] The inkjet printing device 50 is further equipped with a cartridge 60. The cartridge 60 contains the liquid composition described above. The cartridge 60 is housed in a carriage 52 inside a main body housing 51. In this state, the liquid composition is supplied from the cartridge 60 to a recording head 52A mounted on the carriage 52. The recording head 52A is capable of ejecting the liquid composition.

[0157] A recording head 52A mounted on a carriage 52 is guided by guide shafts 53 and 54 and moves along a timing belt 55 driven by a main scanning motor 57. Meanwhile, an absorption medium (substrate) is positioned by a platen 56 to face the recording head 52A.

[0158] [Method of using the liquid composition] The liquid composition can be used, for example, by applying the liquid composition onto a substrate using the inkjet printing device 50 described above.

[0159] The substrate is preferably a medium capable of absorbing the liquid composition. Specific examples of substrates capable of absorbing the liquid composition include porous membranes.

[0160] The porous membrane is not particularly limited and can be appropriately selected depending on the purpose. For example, when an electrode substrate having an electrode mixture layer (negative electrode mixture layer, positive electrode mixture layer) containing particulate electrode active materials (negative electrode active material, positive electrode active material) formed using the liquid composition is used as the porous membrane, a separator-integrated electrode described below can be produced.

[0161] The negative electrode active material is not particularly limited and can be appropriately selected depending on the purpose. Examples of the negative electrode active material include metal lithium, lithium alloys, carbon materials such as carbon and graphite that can release (desorb) or insert (occlude) lithium ions, and conductive polymers doped with lithium ions.

[0162] The positive electrode active material is not particularly limited and can be appropriately selected depending on the purpose. Examples of the positive electrode active material include graphite fluoride represented by the general formula (CFx)n, metal oxides such as CoLiO2, MnO2, V2O5, CuO, Ag2CrO4, and TiO2, and metal sulfides such as CuS.

[0163] The electrode substrate is not particularly limited and can be appropriately selected depending on the purpose. Examples of the electrode substrate include copper foil and aluminum foil.

[0164] The substrate other than the above is not particularly limited and can be appropriately selected depending on the purpose. Examples of the substrate other than the above include a base used in a reflective display element and an electrode layer used in printed electronics.

[0165] [Separator-integrated electrode] The liquid composition according to this embodiment is used to form a separator-integrated electrode. That is, a separator-integrated electrode can be formed using a functional material containing the liquid composition.

[0166] Fig. 11 is a schematic diagram showing an example of a separator-integrated electrode, and Fig. 12 is a cross-sectional view taken along line AA in Fig. 11. The separator-integrated electrode is an electrode in which an electrode mixture layer and a particle layer serving as a functional layer are sequentially formed on an electrode substrate. The separator-integrated electrode can be formed by applying the liquid composition of this embodiment.

[0167] The separator-integrated electrode 70 has an electrode mixture layer 72 and a particle layer 73 formed in this order on an electrode substrate 71, and the liquid composition of this embodiment is used to form the particle layer 73.

[0168] Use of the separator-integrated electrode 70 eliminates the need for the process of separately unwinding the electrode and separator and winding or stacking them when manufacturing an electrochemical element, which is expected to significantly improve the manufacturing efficiency of the electrochemical element and also to prevent misalignment between the electrode and separator during the winding and stacking processes, thereby improving the reliability of the electrochemical element.

[0169] The electricity storage device (electrochemical element) using the separator-integrated electrode is not particularly limited and can be appropriately selected depending on the purpose. Examples of such electricity storage devices (electrochemical elements) include lithium ion secondary batteries, magnesium ion secondary batteries, sodium ion secondary batteries, and sodium secondary batteries.

[0170] Such power storage devices can be applied to, for example, vehicles equipped with on-board batteries, smartphones, notebook computers, pen-input computers, mobile computers, e-book players, mobile phones, mobile fax machines, mobile copiers, mobile printers, headphone stereos, video movie players, LCD televisions, handheld vacuum cleaners, portable CD players, mini-discs, transceivers, electronic organizers, calculators, memory cards, portable tape recorders, radios, backup power supplies, motors, lighting equipment, toys, game devices, clocks, strobe lights, cameras, and the like.

[0171] [Formation of particle layer] An example of a functional film produced by applying a liquid composition to a substrate is a particle layer that provides an insulating function to an electrode-integrated separator to prevent short-circuiting between the positive and negative electrodes of an electrochemical device. In this case, the thickness of the particle layer is preferably 1 μm or more and 10 μm or less. If the thickness is less than 1 μm, it is difficult to obtain the required insulating function, and if the thickness is more than 10 μm, there is a concern that the characteristics of the electrochemical device may deteriorate.

[0172] The functional material according to this embodiment contains the liquid composition described above, thereby achieving the effects of the liquid composition. Specifically, even if inorganic particles in the liquid composition settle due to their own weight after the liquid composition used to form the functional material is stored, they can be easily redispersed. This prevents uneven coating when the liquid composition is applied to a substrate. This improves the performance of devices obtained using the functional material according to this embodiment.

[0173] As described above, the functional material according to this embodiment can be used to form a separator-integrated electrode, thereby achieving the effects of the functional material described above. Specifically, a separator-integrated electrode is formed using a functional material containing the liquid composition described above, and the liquid composition, which is easily redispersible even after storage, is applied to a substrate, thereby preventing uneven coating. Therefore, the performance of the separator-integrated electrode obtained using the functional material according to this embodiment can be improved.

[0174] The electricity storage device according to this embodiment is formed using the functional material described above, thereby achieving the effects of the functional material described above. Specifically, since the electricity storage device is formed using a functional material containing the liquid composition described above, the liquid composition, which is easily redispersible even after storage, is applied to the substrate, thereby suppressing the occurrence of coating unevenness. Therefore, according to this embodiment, the performance of the electricity storage device obtained using the functional material described above can be improved. [Example]

[0175] The present embodiment will be further described below using examples. Various tests and evaluations were performed according to the following methods. Note that "parts" and "%" are by mass unless otherwise specified.

[0176] Example 1 [Preparing mixed ink] 46.7 parts of ethyl lactate was mixed with 11.28 parts of hexylene glycol to prepare a mixed solvent, to which 2 parts of a surfactant (NOF Corporation, Marialim (registered trademark) AKM-0513) and 40 parts of α-alumina (α-alumina prepared so that the D50 after dispersion was 202 nm and the proportion of second inorganic particles to the total amount of first inorganic particles was 2.5%) were added and stirred. Both the first inorganic particles and the second inorganic particles were α-alumina.

[0177] Then, 12 parts of 0.2 mm diameter zirconia beads were added, and the mixture was stirred using a stirring device (Thinky Corporation, Rotation / Revolution Nano Crusher NP-100) at 1500 rpm and -20°C for 1 minute.The mixture was then passed through a 25 μm filter (Clever Corporation, Nylon mesh #419) to remove the zirconia beads, and mixed ink (1) was prepared.

[0178] [Extraction of supernatant residue by centrifugation] 12 mL of the prepared mixed ink (1) was placed in a 15 mL centrifuge tube and centrifuged at 3000 rpm for 20 minutes using a centrifuge (Kokusan Co., Ltd., H-103N), and 5 g of the supernatant was collected. This procedure was repeated twice to produce 10 g of centrifuged residue (1).

[0179] [Measurement of solid content] A heat-drying moisture meter (ML50, manufactured by A&D) was used to measure the solid content of the residual liquid (1). After gently stirring the residual liquid (1), approximately 1.5 g was sampled using a dropper and measured. In addition, since the solid content contained 2% surfactant in addition to the inorganic particles, the solid content of the inorganic particles (solid content concentration) was calculated by subtracting 2 from the measured value. The solid content concentration was 42%.

[0180] [Evaluation of redispersibility] 400 mL of the prepared mixed ink (1) was placed in an i-boy, the lid was closed, and the mixture was left to stand at room temperature for 30 days. After that, the mixture was stirred for a predetermined time using a stirring device (SKH-40SA, manufactured by Misugi Co., Ltd.), and 10 mL of the supernatant liquid from the mixed ink (1) was collected and used as redispersion liquid (1). The solid content and particle size of the redispersion liquid (1) were evaluated according to the following criteria to determine the redispersibility.

[0181] [Solid content of redispersion liquid] The solid content of the redispersion liquid (1) was measured using a heat-drying moisture meter (ML50, manufactured by A&D Co., Ltd.). After gently stirring the supernatant liquid (1), approximately 1.0 g was sampled using a dropper and measured. The solid content was evaluated based on the stirring time required for the solid content of the supernatant liquid of the stirred liquid composition to return to within ±3% of the solid content of the liquid composition before static storage, as set as follows: Evaluation criteria A, B, and C indicate practically acceptable levels.

[0182] [Evaluation criteria] A: Mixing time is less than 60 minutes B: Mixing time is 60 minutes or more but less than 90 minutes C: Mixing time is 90 minutes or more but less than 120 minutes D: Mixing time is 120 minutes or more

[0183] [Particle size of redispersed liquid] The redispersion liquid (1) was diluted to a solid content of 10% by mass or less, and the median diameter D50 of the liquid composition was measured using a concentrated particle size analyzer (FPAR-1000, manufactured by Otsuka Electronics Co., Ltd.). The rate of change (particle size) from the particle size of the liquid composition before storage was evaluated. The evaluation criteria A, B, and C represent practically acceptable levels.

[0184] [Evaluation criteria] A: Change in particle size is less than ±5% B: Change in particle size is between ±5% and ±10% C: Change in particle size is between ±10% and ±15% D: Particle size change of ±15% or more

[0185] [Dischargeability of redispersed liquid] The ejection properties of the redispersion liquid (1) were evaluated using an inkjet head (manufactured by Ricoh Co., Ltd., MH2420).

[0186] [Evaluation criteria] Good: Continuous discharge from all 384 nozzles for 10 minutes Unacceptable: Poor ejection occurs in some nozzles

[0187] Example 2 In Example 1, except that α-alumina (α-alumina prepared so that D50 after dispersion was 397 nm, and the proportion of second inorganic particles in the total amount of first inorganic particles was 2.2%) was used, mixed ink (2) was prepared in the same manner as in Example 1 and evaluated in the same manner.

[0188] Example 3 In Example 1, except that α-alumina (α-alumina prepared so that D50 after dispersion: 500 nm, proportion of second inorganic particles to the total amount of first inorganic particles: 1.9%) and surfactant (DISPERBYK (registered trademark)-2155, manufactured by BYK-Chemie) were used instead, mixed ink (3) was prepared in the same manner as in Example 1 and evaluated in the same manner.

[0189] Example 4 In Example 3, except that alpha alumina was used (alpha alumina prepared so that D50 after dispersion was 613 nm, and the proportion of second inorganic particles to the total amount of first inorganic particles was 1.8%), mixed ink (4) was prepared in the same manner as in Example 3 and evaluated in the same manner.

[0190] Example 5 A mixed ink (5) was prepared in the same manner as in Example 1, except that in Example 1, alpha alumina (alpha alumina prepared so that D50 after dispersion was 997 nm, and the proportion of second inorganic particles in the total amount of first inorganic particles was 1.8%) and surfactant (NOF Corporation, Marialim (registered trademark) SC0708A) were used instead, and the mixed ink (5) was evaluated in the same manner.

[0191] Example 6 In Example 1, except that the solvent was changed to 58 parts of ethyl lactate alone and to alpha alumina (alpha alumina prepared so that D50 after dispersion was 202 nm, and the proportion of second inorganic particles to the total amount of first inorganic particles was 2.5%), mixed ink (6) was prepared in the same manner as in Example 1 and evaluated in the same manner.

[0192] Example 7 In Example 6, except that alpha alumina was used (alpha alumina prepared so that D50 after dispersion was 397 nm, and the proportion of second inorganic particles to the total amount of first inorganic particles was 2.2%), mixed ink (7) was prepared in the same manner as in Example 6 and evaluated in the same manner.

[0193] Example 8 In Example 1, ethyl lactate was replaced with 46.72 parts of dimethyl sulfoxide (DMSO), and the alpha alumina (alpha alumina prepared so that the D50 after dispersion was 202 nm and the proportion of second inorganic particles to the total amount of first inorganic particles was 3.0%) and surfactant (NOF Corporation, Marialim (registered trademark) HKM-150A) were used. A mixed ink (8) was prepared in the same manner as in Example 1 and evaluated in the same manner.

[0194] Example 9 In Example 8, dimethyl sulfoxide (DMSO) was changed to methyl ethyl ketone (MEK), and alpha alumina (alpha alumina prepared so that D50 after dispersion was 202 nm, and the proportion of second inorganic particles to the total amount of first inorganic particles was 3.2%) was used. A mixed ink (9) was prepared in the same manner as in Example 8, and evaluated in the same manner.

[0195] Example 10 A mixed ink (10) was prepared in the same manner as in Example 9, except that methyl ethyl ketone (MEK) was replaced with isopropyl alcohol (IPA), and the mixed ink (10) was evaluated in the same manner.

[0196] Example 11 A mixed ink (11) was prepared in the same manner as in Example 8, except that dimethyl sulfoxide (DMSO) was changed to ethanol, and was evaluated in the same manner.

[0197] Example 12 In Example 8, dimethyl sulfoxide (DMSO) was changed to diisobutyl ketone (DIBK), and α-alumina (α-alumina prepared so that D50 after dispersion was 202 nm, and the proportion of second inorganic particles to the total amount of first inorganic particles was 2.8%) was used. A mixed ink (12) was prepared in the same manner as in Example 8, and evaluated in the same manner.

[0198] Example 13 In Example 3, hexylene glycol was changed to ethylene glycol, and alpha alumina (alpha alumina prepared so that D50 after dispersion was 613 nm, and the proportion of second inorganic particles to the total amount of first inorganic particles was 4.0%) was used. A mixed ink (13) was prepared in the same manner as in Example 3, and evaluated in the same manner.

[0199] Example 14 A mixed ink (14) was prepared in the same manner as in Example 13, except that ethylene glycol was changed to propylene glycol, and was evaluated in the same manner.

[0200] Example 15 In Example 1, the solvent was changed to 58 parts of pure water only, and the mixture was changed to alpha alumina (alpha alumina prepared so that D50 after dispersion was 500 nm, and the proportion of second inorganic particles to the total amount of first inorganic particles was 3.2%) and surfactant (Dispersant 5023, manufactured by San Nopco Co., Ltd.). A mixed ink (15) was prepared in the same manner as in Example 1 and evaluated in the same manner.

[0201] Example 16 In Example 15, a mixed ink (16) was prepared in the same manner as in Example 15, except that acetone was replaced with α-alumina (α-alumina prepared so that D50 after dispersion was 500 nm, and the proportion of second inorganic particles to the total amount of first inorganic particles was 3.6%) and a surfactant (Nopcosperse (registered trademark) 092, manufactured by San Nopco Ltd.) was used instead of pure water, and the mixed ink (16) was evaluated in the same manner.

[0202] Example 17 A mixed ink (17) was prepared in the same manner as in Example 16, except that the surfactant used in Example 16 was changed to SN Sparce (manufactured by NOF Corporation), and was evaluated in the same manner.

[0203] Example 18 In Example 5, except that α-alumina was replaced with γ-alumina (γ-alumina prepared so that D50 after dispersion was 803 nm, and the proportion of second inorganic particles in the total amount of first inorganic particles was 3.2%), mixed ink (18) was prepared in the same manner as in Example 5 and evaluated in the same manner.

[0204] Example 19 In Example 5, except that α-alumina was replaced with silica (silica prepared so that D50 after dispersion was 486 nm, and the proportion of second inorganic particles to the total amount of first inorganic particles was 2.8%), mixed ink (19) was prepared in the same manner as in Example 5 and evaluated in the same manner.

[0205] Example 20 In Example 5, except that alpha alumina was replaced with aluminum hydroxide (aluminum hydroxide prepared so that D50 after dispersion was 912 nm, and the proportion of second inorganic particles to the total amount of first inorganic particles was 2.0%), mixed ink (20) was prepared in the same manner as in Example 5 and evaluated in the same manner.

[0206] Example 21 In Example 5, except that α-alumina was replaced with titanium oxide (titanium oxide prepared so that D50 after dispersion was 294 nm, and the proportion of second inorganic particles to the total amount of first inorganic particles was 2.8%), mixed ink (21) was prepared in the same manner as in Example 5 and evaluated in the same manner.

[0207] Example 22 [Preparation of inorganic microparticles] 100 g of residual liquid (21) was prepared by centrifuging the mixed ink (21) in the same manner as in Example 1, and concentrated to a solid content of 50% using a rotary evaporator (ARE-V1200, manufactured by AS ONE Corporation) to prepare a fine particle liquid (22).

[0208] [Preparing mixed ink] A mixed solvent was prepared by adding 11.28 parts of propylene glycol to 46.72 parts of ethyl lactate, and then 2 parts of a surfactant (DISPERBYK-2155, manufactured by BYK-Chemie), 40 parts of α-alumina (α-alumina prepared so that D50 after dispersion is 500 nm), and 0.6 parts of the fine particle liquid (22) were added and stirred. The first inorganic particles correspond to α-alumina, and the second inorganic particles correspond to α-alumina in the fine particle liquid (22) (the proportion of the second inorganic particles to the total amount of the first inorganic particles: 0.8).

[0209] Next, 12 parts of 0.2 mm diameter zirconia beads were added, and the mixture was stirred using a stirring device (Thinky Corporation, Rotation-Revolution Nano-Puller NP-100) at 1500 rpm and -20°C for 1 minute. The mixture was then passed through a 25 μm filter (Clever Corporation, Nylon Mesh #419) to remove the zirconia beads, thereby preparing mixed ink (22). The resulting mixed ink (22) was evaluated in the same manner as in Example 1.

[0210] Example 23 In Example 22, except that the second inorganic particles were changed (proportion of the second inorganic particles to the total amount of the first inorganic particles: 1.0%), mixed ink (23) was prepared in the same manner as in Example 22 and evaluated in the same manner.

[0211] Example 24 In Example 22, except that the second inorganic particles were changed (proportion of the second inorganic particles to the total amount of the first inorganic particles: 3.0%), mixed ink (24) was prepared in the same manner as in Example 22 and evaluated in the same manner.

[0212] Example 25 In Example 22, except that the second inorganic particles were changed (proportion of the second inorganic particles to the total amount of the first inorganic particles: 5.0%), a mixed ink (25) was prepared in the same manner as in Example 22 and evaluated in the same manner.

[0213] Example 26 A mixed ink (26) was prepared in the same manner as in Example 22, except that the second inorganic particles (ratio to the total amount of the first inorganic particles: 5.5%) were used, and evaluated in the same manner.

[0214] Example 27 A mixed ink (27) was prepared in the same manner as in Example 14, except that the amount of α-alumina (α-alumina prepared so that D50 after dispersion was 397 nm and the proportion of second inorganic particles to the total amount of first inorganic particles was 3.0%) was changed to 13 parts, and a surfactant (manufactured by NOF Corporation, S-Leam (registered trademark) AD-3172M) was used, and the mixed ink (27) was evaluated in the same manner. The solid content concentration was 15%.

[0215] Example 28 A mixed ink (28) was prepared in the same manner as in Example 27, except that the amount of α-alumina was changed to 18 parts, and evaluated in the same manner. The solid content was 20%.

[0216] Example 29 A mixed ink (29) was prepared in the same manner as in Example 27, except that the amount of α-alumina was changed to 28 parts, and evaluated in the same manner. The solid content was 30%.

[0217] Example 30 A mixed ink (30) was prepared in the same manner as in Example 27, except that the amount of α-alumina was changed to 48 parts, and evaluated in the same manner. The solid content was 50%.

[0218] Example 31 A mixed ink (31) was prepared in the same manner as in Example 27, except that the amount of α-alumina was changed to 53 parts, and evaluated in the same manner. The solid content was 55%.

[0219] (Comparative Example 1) A mixed ink (32) was prepared in the same manner as in Example 1, except that α-alumina (α-alumina prepared so that D50 after dispersion was 397 nm and the proportion of the second inorganic particles to the total amount of the first inorganic particles was 0.0%) was used in Example 1, and was evaluated in the same manner. The solid content was 42%.

[0220] (Comparative Example 2) A mixed ink (33) was prepared in the same manner as in Comparative Example 1, except that the amount of α-alumina was changed to 13 parts, and evaluated in the same manner. The solid content was 15%.

[0221] (Comparative Example 3) A mixed ink (34) was prepared in the same manner as in Comparative Example 1, except that the amount of α-alumina was changed to 18 parts, and evaluated in the same manner. The solid content was 20%.

[0222] Comparative Example 4 A mixed ink (35) was prepared in the same manner as in Comparative Example 1, except that the amount of α-alumina was changed to 28 parts, and evaluated in the same manner. The solid content was 30%.

[0223] (Comparative Example 5) A mixed ink (36) was prepared in the same manner as in Comparative Example 1, except that the amount of α-alumina was changed to 48 parts, and evaluated in the same manner. The solid content was 50%.

[0224] (Comparative Example 6) A mixed ink (37) was prepared in the same manner as in Comparative Example 1, except that the amount of α-alumina was changed to 53 parts, and evaluated in the same manner. The solid content was 55%.

[0225] (Comparative Example 7) A mixed ink (38) was prepared in the same manner as in Comparative Example 1, except that α-alumina (α-alumina prepared so that D50 after dispersion was 202 nm and the proportion of second inorganic particles to the total amount of first inorganic particles was 0.0%) was used instead of Comparative Example 1, and was evaluated in the same manner. The solid content was 42%.

[0226] (Comparative Example 8) A mixed ink (39) was prepared in the same manner as in Comparative Example 1, except that α-alumina (α-alumina prepared so that D50 after dispersion was 1000 nm and the proportion of second inorganic particles to the total amount of first inorganic particles was 0.0%) was used instead of Comparative Example 1, and was evaluated in the same manner. The solid content was 42%.

[0227] Comparative Example 9 A mixed ink (40) was prepared in the same manner as in Comparative Example 1, except that α-alumina was replaced with titanium oxide (titanium oxide prepared so that D50 after dispersion was 408 nm, and the proportion of second inorganic particles to the total amount of first inorganic particles was 0.0%), and evaluated in the same manner. The solid content was 42%.

[0228] (Comparative Example 10) [Preparing mixed ink] 46.72 parts of ethyl lactate was mixed with 11.28 parts of hexylene glycol to prepare a mixed solvent, to which 2 parts of a surfactant (NOF Corporation, Esleem (registered trademark) AD-3172M) and 40 parts of α-alumina (α-alumina prepared so that D50 after dispersion was 397 nm and the proportion of second inorganic particles to the total amount of first inorganic particles was 0.0%) were added and stirred. The solid content was 42%.

[0229] Then, 12 parts of zirconia beads with a diameter of 0.2 mm were added, and the mixture was stirred using a stirring device (Thinky Corporation, Rotation-Revolution Nano-Grinder NP-100) at 1500 rpm and −20° C. for 1 minute. The mixture was then passed through a 25 μm filter (Clever Corporation, Nylon mesh #419) to remove the zirconia beads, and mixed ink (41) was prepared.

[0230] [Extraction of supernatant residue by centrifugation] 12 mL of the prepared mixed ink (41) was placed in a 15 mL centrifuge tube and centrifuged at 3000 rpm for 7.5 minutes using a centrifuge (H-103N, manufactured by Kokusan Co., Ltd.), and 5 g of the supernatant was collected. This procedure was repeated three times to produce 15 g of centrifuged residue (41).

[0231] In addition, 12 mL of the residual liquid (41) was prepared in a 15 mL centrifuge tube and centrifuged at 3000 rpm for 7.5 minutes and 30 minutes using a centrifugal separator (H-103N, manufactured by Kokusan Co., Ltd.), and 5 g of the supernatant was removed to prepare 10 g of the residual liquid (41). The mixed ink (41) from which the residual liquid (41) was obtained was evaluated in the same manner as in Example 1.

[0232] The results for Examples 1 to 31 and Comparative Examples 1 to 10 are shown in Table 1.

[0233] [Table 1]

[0234] As can be seen from Table 1, in Examples 1 to 31, the solid content after redispersion, particle size, and ejectability were all good.

[0235] In contrast to this, in Comparative Examples 1 to 10, both the solid content after redispersion and the ejection properties were poor, and among these, Comparative Examples 1, 2, and 6 to 9 also had poor particle diameters after redispersion.

[0236] Although the embodiments of the present invention have been described above, the present invention is not limited to the specific embodiments, and various modifications and changes are possible within the scope of the invention described in the claims. [Explanation of symbols]

[0237] 1 First inorganic particle H interparticle distance V potential energy A London-van der Waals gravitational force B Electric double layer repulsion (repulsive force) C Primary aggregation minimum C1 Potential energy due to all interactions of attractive and repulsive forces C2 Maximum of energy barrier C3 Secondary aggregation minimum 10 negative electrode 11 Negative electrode substrate 12 Negative electrode composite layer 12A Liquid composition 20 positive electrode 21 Positive electrode substrate 22 Positive electrode mixture layer 100 Secondary battery 15 negative electrode 25 Positive electrode 30 Separator 40 Electrode element 41, 42 Lead wire 81 Electrolyte layer 82 Exterior 300, 300´ liquid discharge device 304 Feed roller 305 Winding roller 306 Liquid ejection head 307 Tank 308 Tube 309 Heating mechanism 310 Pump 311, 312, 313 valves 314 External Tank 400 stages 50 Inkjet printing device 51 Main body housing 52 Carriage 52A recording head 53, 54, guide shaft 55 Timing belt 56 Platen 57 Main scanning motor 58 Sub-scanning motor 59 Gear mechanism 60 cartridges 70 Separator-integrated electrode 71 Electrode base 72 Electrode composite layer 73 Particle layer [Prior art documents] [Patent documents]

[0238] [Patent Document 1] Japanese Patent Application Laid-Open No. 2000-277386 [Patent Document 2] Japanese Patent Application Laid-Open No. 2006-173001

Claims

1. First inorganic particles having a median diameter of 200 nm or more and less than 1000 nm; second inorganic particles having an average diameter of less than 30 nm; a dispersant; and a solvent; The dispersant is a nonionic surfactant. A liquid composition for forming a particle layer on an electrode.

2. The content of the second inorganic particles is 1% by mass or more and 5% by mass or less with respect to the total mass of the first inorganic particles. The liquid composition of claim 1 .

3. the first inorganic particles are alpha alumina; The liquid composition according to claim 1 or 2.

4. The solid content is 20% by mass or more and 50% by mass or less. The liquid composition according to any one of claims 1 to 3.

5. The solvent is a non-aqueous solvent. The liquid composition according to any one of claims 1 to 4.

6. The dispersant has an oligoether group. The liquid composition according to any one of claims 1 to 5.

7. The dispersant, wherein the terminal on the side not bonded to the oligoether group is a hydroxyl group. The liquid composition of claim 6.

8. The particle layer is a separator. The liquid composition according to any one of claims 1 to 7.

9. A liquid composition comprising the liquid composition according to any one of claims 1 to 8. Functional materials.

10. Used to form separator-integrated electrodes, The functional material according to claim 9.

11. Formed using the functional material according to claim 9 or 10. Energy storage device.

12. A coating step of coating a liquid composition onto an electrode active material layer, The liquid composition comprises: First inorganic particles having a median diameter of 200 nm or more and less than 1000 nm; second inorganic particles having an average diameter of less than 30 nm; a dispersant; and a solvent; The dispersant is a nonionic surfactant. Electrode manufacturing method.

13. The coating process is a liquid ejection method. The method for manufacturing the electrode according to claim 12.

14. The liquid ejection method is an inkjet ejection method. The method for manufacturing the electrode according to claim 13.

15. A method for producing an electrode according to any one of claims 12 to 14, A method for manufacturing an electricity storage device.

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