JP7707531B2 - Nonaqueous liquid composition for preparing electrochemical element, method for producing electrode, method for producing electrochemical element and electrode - Google Patents

Description

The present invention relates to a liquid composition for producing an electrochemical element, a method for producing an electrode, a method for producing an electrochemical element, and an electrode.

Demand for electrochemical elements, including lithium-ion secondary batteries, is expanding as they are installed in portable devices, hybrid cars, electric cars, and more. In addition, there is a growing need for thin batteries to be installed in various wearable devices and medical patches, and the requirements for electrochemical elements are becoming more diverse.

Conventionally, a method for manufacturing electrodes constituting an electrochemical element is known in which a liquid composition is applied to an electrode substrate using a die coater, comma coater, reverse roll coater, or the like to form an electrode mixture layer on the electrode substrate.

A liquid composition generally contains an active material, a dispersion medium, and a binder, and because the binder is dissolved in the dispersion medium, the viscosity at 25°C is several thousand to several tens of thousands of mPa·s.

On the other hand, a method is known in which an electrode mixture layer is formed on an electrode substrate using a liquid composition that can be discharged by a liquid discharge method (see, for example, Patent Document 1).

The liquid ejection method is a method of ejecting fine droplets of a liquid composition from the ejection holes of a liquid ejection head. Methods for ejecting droplets from a liquid ejection head include the piezo method, thermal method, valve method, etc. Among these, the piezo method can precisely control the amount of liquid composition ejected by controlling the voltage, and since it does not require heating, it is less affected by the usage environment and has high durability.

Liquid compositions that can be ejected by liquid ejection methods generally have a viscosity of several to several hundred mPa·s at 25°C from the viewpoints of storage stability and ejection stability, and therefore need to have a lower viscosity than conventional liquid compositions at 25°C. In particular, when using a piezo-type liquid ejection head, it is necessary to adjust the viscosity and surface tension of the liquid composition to appropriate values in order to improve ejection stability.

One way to reduce the viscosity of the liquid composition is to reduce the binder content.

However, since the binder is added to bind the active material to the electrode substrate and to each other, it is necessary to add a certain amount of binder to the active material. In addition, in obtaining a liquid composition that can be discharged by a liquid discharge method, it is also important to increase the freedom of selection of materials such as the dispersion medium from the viewpoints of reducing the environmental load and optimizing the process.

One aspect of the present invention aims to provide a liquid composition for producing electrochemical elements that has excellent storage stability and ejection stability.

One embodiment of the liquid composition for producing an electrochemical element according to the present invention includes at least one of an active material and an electrolyte, a dispersion medium, and a polymer,
The polymer has the general formula (I)

(In the formula, X is an oxygen atom, or a carbon atom substituted with a hydrogen atom or an alkyl group; R ¹ , R ² , R ³ and R ⁴ each independently is a hydrogen atom, a substituted or unsubstituted alkyl group, or a substituted or unsubstituted cycloalkyl group; and m and n are positive integers.)
and a structural unit containing an amide bond and/or an imide bond.

According to one aspect of the present invention, a liquid composition for producing electrochemical elements having excellent storage stability and ejection stability can be provided.

FIG. 2 is a cross-sectional view showing an example of a negative electrode according to the present embodiment. 3A to 3C are schematic diagrams illustrating an example of a method for producing a negative electrode according to the present embodiment. 5A to 5C are schematic diagrams illustrating another example of the method for producing a negative electrode according to the present embodiment. FIG. 4 is a schematic diagram showing a modification of the liquid ejection device of FIGS. FIG. 2 is a cross-sectional view showing an example of a positive electrode of the present embodiment. FIG. 2 is a cross-sectional view showing an example of an electrode element constituting the electrochemical device of the present embodiment. FIG. 1 is a cross-sectional view showing an example of an electrochemical element according to an embodiment of the present invention. FIG. 1 is a diagram showing the results of Examples 3, 4, and 5 and Comparative Example 2.

Below, a description will be given of an embodiment of the present invention with reference to the drawings. Note that identical components will be given the same reference numerals and descriptions may be omitted.

<Liquid composition for producing electrochemical device>
The liquid composition for producing an electrochemical device of the present embodiment contains at least one of an active material and an electrolyte, a dispersion medium, and a polymer, and may further contain a conductive assistant, a dispersant, etc., as necessary. The liquid composition for producing an electrochemical device of the present embodiment preferably contains an active material, a dispersion medium, and a polymer.

The viscosity of the liquid composition for producing electrochemical elements of this embodiment at 25°C is preferably 200 mPa·s or less, and more preferably 50 mPa·s or less. When the viscosity of the liquid composition for producing electrochemical elements of this embodiment at 25°C is 200 mPa·s or less, the ejection stability of the liquid composition for producing electrochemical elements is improved.

The lower limit of the viscosity of the liquid composition for producing electrochemical elements according to this embodiment at 25°C is not particularly limited, but is typically 10 mPa·s.

The liquid composition for producing an electrochemical element according to this embodiment can be produced by dissolving or dispersing a composition containing at least one of an active material and an electrolyte, and a polymer in a dispersion medium.

Here, the liquid composition for producing an electrochemical element of this embodiment can be used to manufacture electrodes for an electrochemical element.

Electrochemical elements are not particularly limited as long as they are capable of storing electricity, but examples include secondary batteries and capacitors.

[Active material]
As the active material, a positive electrode active material or a negative electrode active material that can be applied to an electrochemical element can be used.

As the positive electrode active material, there are no particular limitations as long as it is capable of reversibly absorbing and releasing alkali metal ions, but an alkali metal-containing transition metal compound can be used.

Examples of alkali metal-containing transition metal compounds include lithium-containing transition metal compounds such as composite oxides containing lithium and one or more elements selected from the group consisting of cobalt, manganese, nickel, chromium, iron, and vanadium.

Examples of lithium-containing transition metal compounds include lithium cobalt oxide, lithium nickel oxide, and lithium manganese oxide.

As the alkali metal-containing transition metal compound, a polyanion-based compound having an _XO4 tetrahedron (X=P, S, As, Mo, W, Si, etc.) in the crystal structure can also be used. Among these, lithium-containing transition metal phosphate compounds such as lithium iron phosphate and lithium vanadium phosphate are preferred in terms of cycle characteristics, and lithium vanadium phosphate is particularly preferred in terms of lithium diffusion coefficient and input/output characteristics of electrochemical elements.

In addition, from the viewpoint of electronic conductivity, it is preferable that the polyanion compound is composited by coating the surface with a conductive assistant such as a carbon material.

There are no particular limitations on the negative electrode active material, so long as it is capable of reversibly absorbing and releasing alkali metal ions, but carbon materials containing graphite having a graphite-type crystal structure can be used.

Examples of carbon materials include natural graphite, artificial graphite, non-graphitizable carbon (hard carbon), and easily graphitizable carbon (soft carbon).

Examples of negative electrode active materials other than carbon materials include lithium titanate and titanium oxide.

In addition, from the viewpoint of the energy density of the electrochemical element, it is preferable to use a high-capacity material such as silicon, tin, a silicon alloy, a tin alloy, silicon oxide, silicon nitride, or tin oxide as the negative electrode active material.

When the active material contains lithium, the dispersion medium is preferably a non-aqueous dispersion medium. In this case, the water content in the liquid composition for producing an electrochemical device of this embodiment is preferably 5% by mass or less, and more preferably 1% by mass or less. When the water content in the liquid composition for producing an electrochemical device of this embodiment is 5% by mass or less, the lithium contained in the active material reacts with water to form a compound such as lithium carbonate, which can prevent a decrease in the discharge capacity of the electrochemical device. In addition, the compound such as lithium carbonate can be prevented from decomposing and generating gas during charging and discharging of the electrochemical device.

The mode diameter of the active material is preferably 3 μm or less, and more preferably 1 μm or less. When the mode diameter of the active material is 3 μm or less, the ejection stability and storage stability of the liquid composition for producing an electrochemical element of this embodiment are improved.

The 10% diameter (D ₁₀ ) of the active material is preferably 0.1 μm or more, and more preferably 0.15 μm or more. When the D ₁₀ of the active material is 0.1 μm or more, the storage stability of the liquid composition for producing an electrochemical device of this embodiment is improved.

The content of the active material in the liquid composition for producing an electrochemical element of this embodiment is preferably 10% by mass or more, and more preferably 15% by mass or more. When the content of the active material in the liquid composition for producing an electrochemical element of this embodiment is 10% by mass or more, the number of printing cycles required to form an electrode mixture layer with a specified basis weight is reduced.

[Electrolyte]
The electrolyte may be an aqueous electrolyte solution or a non-aqueous electrolyte. The electrolyte may be an electrolyte used in an electrochemical element, which will be described later. The electrolyte will be described in detail later.

[Dispersion medium]
The dispersion medium is not particularly limited as long as it is capable of dissolving the polymer and dispersing the active material, and examples of the dispersion medium include ethylene glycol, propylene glycol, N-methyl-2-pyrrolidone, cyclohexanone, acetate, mesitylene, 2-n-butoxymethanol, 2-dimethylethanol, N,N-dimethylacetamide, N,N-dimethylformamide, dimethylsulfoxide, lactate, tetramethylurea, anisole, dibutyl ether, 1,2-diethoxyethane, and the like, and two or more of them may be used in combination.

[Polymer]
The polymer has the following general formula (I):

(In the formula, X is an oxygen atom, or a carbon atom substituted with a hydrogen atom or an alkyl group; R ¹ , R ² , R ³ and R ⁴ each independently is a hydrogen atom, a substituted or unsubstituted alkyl group, or a substituted or unsubstituted cycloalkyl group; and m and n are positive integers.)
and a structural unit containing an amide bond and/or an imide bond.

The polymer has the following general formula (II):

(In the formula, R ¹ , R ² , R ³ and R ⁴ each independently represent a hydrogen atom, a substituted or unsubstituted alkyl group, or a substituted or unsubstituted cycloalkyl group, and n is a positive integer.)
From the viewpoint of improving the solubility of the polymer and the dispersibility of the active material, it is preferable for the polymer to have a structural unit containing a group represented by the following formula:

The substituted or unsubstituted alkyl group for R ¹ , R ² , R ³ and R ⁴ is preferably an alkyl group having 1 to 30 carbon atoms, more preferably an alkyl group having 1 to 18 carbon atoms, from the viewpoint of solubility.

The alkyl group may be either a straight chain or a branched chain.

Examples of alkyl groups having 1 to 30 carbon atoms include methyl, ethyl, propyl, butyl, isopropyl, isobutyl, pentyl, hexyl, heptyl, ethylhexyl, octyl, decyl, dodecyl, 2-butyloctyl, and octadecyl groups.

The substituted or unsubstituted cycloalkyl group for R ¹ , R ² , R ³ and R ⁴ is preferably a cycloalkyl group having 3 to 30 carbon atoms, more preferably a cycloalkyl group having 3 to 18 carbon atoms, from the viewpoint of availability of raw materials.

The cycloalkyl group may be either monocyclic or polycyclic.

Examples of cycloalkyl groups having 3 to 30 carbon atoms include cyclopropyl, cyclobutyl, cyclopentyl, cyclohexyl, and adamantyl groups.

Examples of the substituents in R ¹ , R ² , R ³ and R ⁴ include a halogen atom, a cyano group, a phenyl group, a hydroxyl group, a carboxyl group and the like.

These substituents may have multiple identical groups or multiple different groups.

Other examples of the substituents include alkyl groups having 1 to 12 carbon atoms, cycloalkyl groups having 3 to 12 carbon atoms, and phenyl groups substituted with alkoxy groups having 1 to 12 carbon atoms.

The above polymers can be obtained by reacting diamines with carboxylic acid derivatives such as carboxylic acid chlorides and carboxylic acid anhydrides, or by reacting diisocyanates with carboxylic acids or acid anhydrides. One example is the reaction of trimellitic anhydride chloride with diamines as shown below, and this method can produce polymers having structural units containing amide bonds and/or imide bonds.

Furthermore, in this embodiment, a substituent represented by general formula (I) is introduced into the polymer. The polymer has excellent solubility and functions as a binder with excellent binding properties for active materials, solid electrolytes, etc.

The mass ratio of the polymer to the active material is preferably 1 to 10%, more preferably 1 to 5%, and even more preferably 1 to 3%. When the mass ratio of the polymer to the active material is 1% or more, the binding between the active materials or between the active material and the electrode substrate is improved, and when it is 5% or less, the internal resistance of the electrochemical element is lowered, improving the input/output characteristics of the electrochemical element.

[Conductive assistant]
As the conductive assistant, for example, a carbon material such as conductive carbon black, carbon nanofiber, carbon nanotube, graphene, graphite particles, etc. can be used.

Conductive carbon black can be produced by the furnace method, acetylene method, gasification method, etc.

Other conductive additives that can be used include metal particles such as aluminum and metal fibers.

The mass ratio of the conductive assistant to the active material is preferably 10% or less, and more preferably 8% or less. When the mass ratio of the conductive assistant to the active material is 10% or less, the storage stability of the liquid composition for producing an electrochemical element of this embodiment is improved.

Here, the conductive additive may be composited with the active material as described above.

[Dispersant]
The dispersant is not particularly limited as long as it is capable of improving the dispersibility of the active material and conductive assistant in the dispersion medium. Examples of the dispersant include polymer-type dispersants such as polycarboxylic acid-based dispersants, naphthalenesulfonic acid-formaldehyde condensation-based dispersants, polyethylene glycol-based dispersants, polycarboxylic acid partial alkyl ester-based dispersants, polyether-based dispersants, and polyalkylene polyamine-based dispersants; surfactant-type dispersants such as alkylsulfonic acid-based dispersants, quaternary ammonium salt-based dispersants, higher alcohol alkylene oxide-based dispersants, polyhydric alcohol ester-based dispersants, and alkyl polyamine-based dispersants; and inorganic-type dispersants such as polyphosphate-based dispersants. Two or more of these may be used in combination.

<Electrode manufacturing method>
The method for producing an electrode of the present embodiment includes a step of applying the liquid composition for producing an electrochemical element of the present embodiment onto an electrode substrate, and preferably includes a step of ejecting the liquid composition for producing an electrochemical element of the present embodiment onto the electrode substrate.

There are no particular limitations on the material that constitutes the electrode substrate (current collector), so long as it is conductive and stable with respect to the applied potential.

The electrode manufacturing method of this embodiment preferably further includes a step of pressurizing the electrode substrate onto which the liquid composition has been ejected. This makes it difficult for the components that make up the electrode mixture layer to peel off, improving the reliability of the electrochemical element.

[Negative electrode]
FIG. 1 shows an example of the negative electrode of this embodiment.

The negative electrode 10 has a negative electrode composite layer 12 containing a negative electrode active material and a polymer formed on one side of the negative electrode substrate 11.

The negative electrode composite layer 12 may be formed on both sides of the negative electrode substrate 11.

The shape of the negative electrode 10 is not particularly limited, and may be, for example, a flat plate shape.

Examples of materials that can be used to form the negative electrode substrate 11 include stainless steel, nickel, aluminum, copper, etc.

[Method of manufacturing negative electrode]
FIG. 2 shows an example of a method for producing the negative electrode of this embodiment.

The method for manufacturing the negative electrode 10 includes a step of ejecting liquid composition 12A, which is the liquid composition for producing an electrochemical element according to this embodiment, onto the negative electrode substrate 11 using a liquid ejection device 300.

Here, the liquid composition 12A contains a negative electrode active material, a dispersion medium, and a polymer.

Liquid composition 12A is stored in tank 307 and is supplied from tank 307 to liquid ejection head 306 via tube 308.

The liquid ejection device 300 may also be provided with a mechanism for capping the nozzle to prevent drying when the liquid composition 12A is not being ejected from the liquid ejection head 306.

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 may move, or the liquid ejection head 306 may move.

When heating the liquid composition 12A dispensed onto the negative electrode substrate 11, it may be heated by the stage 400, or it may be heated by a heating mechanism other than the stage 400.

There are no particular limitations on the heating mechanism as long as it does not come into direct contact with the liquid composition 12A, and examples include a resistance heater, an infrared heater, a fan heater, etc.

Note that multiple heating mechanisms may be installed.

There are no particular limitations on the heating temperature as long as it is possible to volatilize the dispersion medium, but from the viewpoint of power consumption, it is preferable that the heating temperature be in the range of 70 to 150°C.

In addition, when heating the liquid composition 12A dispensed onto the negative electrode substrate 11, ultraviolet light may be irradiated.

Figure 3 shows another example of the method for manufacturing the negative electrode of this embodiment.

The method for manufacturing the negative electrode 10 includes a step of ejecting the liquid composition 12A onto the negative electrode substrate 11 using a liquid ejection device 300.

First, prepare an elongated negative electrode substrate 11. Then, wind the negative electrode substrate 11 around a cylindrical core and set it on the feed roller 304 and the take-up roller 305 so that the side on which the negative electrode composite layer 12 is formed is the upper side in the figure. Here, the feed roller 304 and the take-up roller 305 rotate counterclockwise, and the negative electrode substrate 11 is transported from right to left in the figure. Then, from the liquid ejection head 306 installed above the negative electrode substrate 11 between the feed roller 304 and the take-up roller 305, droplets of the liquid composition 12A are ejected onto the transported negative electrode substrate 11. The droplets of the liquid composition 12A are ejected so as to cover at least a part of the negative electrode substrate 11.

In addition, multiple liquid ejection heads 306 may be installed in a direction approximately parallel to or approximately perpendicular to the transport direction of the negative electrode substrate 11.

Next, the negative electrode substrate 11 onto which the liquid composition 12A has been discharged is transported to the heating mechanism 309 by the delivery roller 304 and the take-up roller 305. As a result, the dispersion medium contained in the liquid composition 12A on the negative electrode substrate 11 volatilizes to form the negative electrode composite layer 12, and the negative electrode 10 is obtained. The negative electrode 10 is then cut to the desired size by punching or the like.

There are no particular limitations on the heating mechanism 309, so long as it does not come into direct contact with the liquid composition 12A, and examples of the heating mechanism 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 may be installed.

There are no particular limitations on the heating temperature as long as it is possible to volatilize the dispersion medium, but from the viewpoint of power consumption, it is preferable that the heating temperature be in the range of 70 to 150°C.

In addition, when heating the liquid composition 12A dispensed onto the negative electrode substrate 11, ultraviolet light may be irradiated.

Figure 4 shows a modified example of the liquid ejection device 300.

The liquid ejection device 300' is capable of circulating the liquid composition 12A through the liquid ejection head 306, the tank 307, and the tube 308 by controlling the pump 310 and the valves 311 and 312.

The liquid ejection device 300' is also provided with an external tank 313, and when the liquid composition 12A in the tank 307 decreases, it is possible to supply the liquid composition 12A from the external tank 313 to the tank 307 by controlling the pump 310 and the valves 311, 312, and 314.

The liquid ejection device 300, 300' can be used to eject the liquid composition 12A at a targeted location on the negative electrode substrate 11. The liquid ejection device 300, 300' can also be used to bond the contacting surfaces of the negative electrode substrate 11 and the negative electrode composite layer 12 from above and below. Furthermore, the liquid ejection device 300, 300' can be used to make the thickness of the negative electrode composite layer 12 uniform.

[Positive electrode]
FIG. 5 shows an example of the positive electrode of this embodiment.

The positive electrode 20 has a positive electrode composite layer 22 containing a positive electrode active material and a polymer formed on one side of the positive electrode substrate 21.

The positive electrode composite layer 22 may be formed on both sides of the positive electrode substrate 21.

The shape of the positive electrode 20 is not particularly limited, and may be, for example, flat.

Examples of materials that can be used to form the positive electrode substrate 21 include stainless steel, aluminum, titanium, and tantalum.

[Method of manufacturing positive electrode]
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, and a polymer, and may also contain an electrolyte component.

<Method of Manufacturing Electrochemical Device>
The method for producing an electrochemical device of this embodiment includes a step of producing an electrode using the method for producing an electrode of this embodiment.

[Electrode element]
FIG. 6 shows an example of an electrode element constituting the electrochemical device of this embodiment.

The electrode element 40 is formed by stacking a negative electrode 15 and a positive electrode 25 with a separator 30 in between. Here, the positive electrode 25 is 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.

The negative electrode 15 is similar to the negative electrode 10, except that a negative electrode composite layer 12 is formed on both sides of the negative electrode substrate 11.

The positive electrode 25 is similar to the positive electrode 20, except that a positive electrode composite layer 22 is formed on both sides of the positive electrode substrate 21.

There is no particular limit to the number of layers of the negative electrodes 15 and positive electrodes 25 of the electrode element 40.

In addition, the number of negative electrodes 15 and the number of positive electrodes 25 in the electrode element 40 may be the same or different.

(Separator)
The separator 30 is provided between the negative electrode 15 and the positive electrode 25 to prevent a short circuit between the negative electrode 15 and the positive electrode 25 .

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.

There are no particular limitations on the size of the separator 30, as long as it can be used in an electrochemical element.

The separator 30 may be a single-layer structure or a laminated structure.

If a solid electrolyte is used, the separator 30 can be omitted.

<Electrochemical element>
FIG. 7 shows a secondary battery as an example of the electrochemical device of this embodiment.

In the secondary battery 1, an electrolyte layer 51 is formed by injecting an aqueous electrolyte solution or a non-aqueous electrolyte into the electrode element 40, and the secondary battery 1 is sealed with an exterior 52. In the secondary battery 1, the lead wires 41 and 42 are pulled out to the outside of the exterior 52.

The secondary battery 1 may include other components as necessary.

There are no particular limitations on the secondary battery 1, and examples include a lithium ion secondary battery.

The shape of the secondary battery 1 is not particularly limited, and examples 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 that combines a pellet electrode and a separator, and a coin type in which a pellet electrode and a separator are laminated.

[Electrolyte]
As the electrolyte, an aqueous electrolyte solution or a non-aqueous electrolyte can be used.

(Aqueous electrolyte solution)
Examples of electrolyte salts constituting the aqueous electrolyte solution include sodium hydroxide, potassium hydroxide, sodium chloride, potassium chloride, ammonium chloride, zinc chloride, zinc acetate, zinc bromide, zinc iodide, zinc tartrate, and zinc perchlorate.

(Non-aqueous electrolyte)
As the non-aqueous electrolyte, a non-aqueous electrolytic solution or a solid electrolyte can be used.

((Nonaqueous electrolyte))
The non-aqueous electrolyte is an electrolyte in which an electrolyte salt is dissolved in a non-aqueous solvent.

-Electrolyte salt-
There are no particular limitations on the electrolyte salt, so long as it has high ionic conductivity and is soluble in a non-aqueous solvent.

The electrolyte salt preferably contains a halogen atom.

Examples of cations that make up the electrolyte salt include lithium ions.

Examples of anions constituting the electrolyte salt include BF ₄ ⁻ , PF ₆ ⁻ , AsF ₆ ⁻ , CF ₃ SO ₃ ⁻ , (CF ₃ SO ₂ ) ₂ N ⁻ , (C ₂ F ₅ SO ₂ ) ₂ N ⁻ , and the like.

The lithium salt is not particularly limited and can be appropriately selected depending on the purpose, and examples thereof include lithium hexafluorophosphate (LiPF ₆ ), lithium borofluoride (LiBF ₄ ), lithium arsenic hexafluoride (LiAsF ₆ ), lithium trifluoromethasulfonate (LiCF ₃ SO ₃ ), lithium bis(trifluoromethylsulfonyl)imide (LiN(CF ₃ SO ₂ ) ₂ ), lithium bis(pentafluoroethylsulfonyl)imide (LiN(C ₂ F ₅ SO ₂ ) ₂ ), etc. Among these, LiPF ₆ is preferred from the viewpoint of ionic conductivity, and LiBF ₄ is preferred from the viewpoint of stability.

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

The concentration of the electrolyte salt in the non-aqueous electrolyte can be selected appropriately depending on the purpose, but if the non-aqueous storage element is a swing type, it is preferably 1 mol/L to 2 mol/L, and if the non-aqueous storage element is a reserve type, it is preferably 2 mol/L to 4 mol/L.

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

As the aprotic organic solvent, a carbonate-based organic solvent such as a chain carbonate or a cyclic carbonate can be used. Among these, a chain carbonate is preferred because of its high dissolving power for electrolyte salts.

In addition, it is preferable that the aprotic organic solvent has a low viscosity.

Examples of chain carbonates include dimethyl carbonate (DMC), diethyl carbonate (DEC), and methyl ethyl carbonate (EMC).

The content of the chain carbonate in the non-aqueous solvent is preferably 50% by mass or more. When the content of the chain carbonate in the non-aqueous solvent is 50% by mass or more, the content of the cyclic substance is low 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). Therefore, even if a non-aqueous electrolyte solution with a high concentration of 2M or more is prepared, the viscosity of the non-aqueous electrolyte solution is low, and the non-aqueous electrolyte solution penetrates the electrodes and the ions diffuse well.

Examples of cyclic carbonates include propylene carbonate (PC), ethylene carbonate (EC), butylene carbonate (BC), vinylene carbonate (VC), etc.

In addition, examples of non-aqueous solvents that can be used other than carbonate-based organic solvents include ester-based organic solvents such as cyclic esters and chain esters, and ether-based organic solvents such as cyclic ethers and chain ethers.

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

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).

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

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

((solid electrolyte))
The solid electrolyte has a property of being able to withstand high voltage, has electronic insulation and exhibits ionic conductivity. The material constituting the solid electrolyte layer is not particularly limited as long as it is a solid substance having electronic insulation and ionic conductivity, and any suitable material can be used. As the material constituting the solid electrolyte layer, a sulfide-based solid electrolyte or an oxide-based solid electrolyte is preferable from the viewpoint of having high ionic conductivity.

Examples of sulfide-based solid electrolytes include Li ₁₀ GeP ₂ S ₁₂ and Li ₆ PS ₅ X (X is F, Cl, Br or I) having an argyrodite-type crystal structure.

Examples of oxide-based solid electrolytes include LLZ ( _Li7La3Zr2O12 ) having _a garnet-type crystal structure, LATP ( _{Li1 + xAlxTi20x} ( _PO4 ) ₃ ) (0.1≦X≦0.4) having a NASICON-type crystal structure, LLT ( _{Li0.33La0.55TiO3 )} having a _perovskite -type crystal structure, and _{amorphous LIPON} ( _{Li2.9PO3.3N0.4 )} . These _solid electrolytes may be used alone or in combination of two or _more .

Examples of electrolyte materials that are dissolved or dispersed in liquid to form these solid electrolyte layers include solid electrolyte precursors such as _Li2S , _P2S5 , and LiCl, and solid electrolyte materials such as _Li2S - _{P2S5 - based} glass and _{Li7P3S11 glass} ceramics _.

Also, materials for forming a gel electrolyte layer can be used as the electrolyte.

There are no particular limitations on the gel electrolyte as long as it exhibits ionic conductivity. For example, polymers that make up the network structure of the gel electrolyte include polyethylene oxide, polypropylene oxide, polyacrylonitrile, polymethyl methacrylate, polyvinyl chloride, copolymers of vinylidene fluoride and propylene hexafluoride, and polyethylene carbonate.

Examples of solvent molecules held in the gel electrolyte include ionic liquids. Examples of ionic liquids include methyl-1-propylpyrrolidinium bis(fluorosulfonylimide), 1-butyl-1-methylpyrrolidinium bis(fluorosulfonylimide), 1-methyl-1-propylpiperidinium bis(fluorosulfonylimide), 1-ethyl-3-methylimidazolium bis(fluorosulfonylimide), 1-methyl-3-propylimidazolium bis(fluorosulfonylimide), and N,N-diethyl-N-methyl-N-(2-methoxyethyl)ammonium bis(fluorosulfonyl)imide.

The ionic liquid may be a mixture of a liquid such as tetraglyme, propylene carbonate, fluoroethylene carbonate, ethylene carbonate, or diethyl carbonate with a lithium salt.

The lithium salt is not particularly limited and can be appropriately selected depending on the purpose. Examples of the lithium salt include lithium hexafluorophosphate ( _LiPF6 ), lithium borofluoride ( _LiBF4 ), lithium arsenic hexafluoride (LiAsF6), lithium trifluoromethansulfonate ( _LiCF3SO3 ), lithium bis( _{trifluoromethylsulfonyl} )imide (LiN( _{CF3SO2 ) 2 )} , lithium bis(pentafluoroethylsulfonyl)imide (LiN( _{C2F5SO2 ) 2} ) _, and the like.

The ionic liquid and lithium salt contained in the gel electrolyte may be used alone or in combination of two or more.

To form these gel electrolyte layers, the electrolyte material dissolved or dispersed in the liquid may be a solution in which the above-mentioned polymer compound and an ionic liquid or lithium salt are dissolved. In addition, the electrolyte material dissolved or dispersed in the liquid may be a material that serves as a precursor of the gel electrolyte (for example, a combination of polyethylene oxide or polypropylene oxide, both of which have acrylate groups at both ends, and a solution in which an ionic liquid or lithium salt is dissolved).

When using these solid electrolytes and gel electrolytes, they can be used as liquid compositions together with the active material.

(Applications of electrochemical elements)
Applications of electrochemical elements are not particularly limited, and examples thereof include notebook computers, pen-input computers, mobile computers, electronic book players, mobile phones, mobile fax machines, mobile copiers, mobile printers, headphone stereos, video movie machines, liquid crystal televisions, handheld cleaners, portable CDs, mini discs, transceivers, electronic organizers, calculators, memory cards, portable tape recorders, radios, backup power sources, motors, lighting equipment, toys, game devices, clocks, strobes, cameras, and the like.

The following describes examples of the present invention, but the present invention is not limited to these examples.

The particle size distribution of the active material, and the viscosity and particle size distribution of the liquid composition for producing electrochemical devices were measured by the following methods.

<Particle size distribution of active material>
After dispersing the active material in water, the particle size distribution of the active material was measured at a temperature of 25° C. using a laser diffraction particle size distribution measuring device Mastersizer 3000 (manufactured by Malvern Instruments).

<Viscosity of liquid composition for producing electrochemical device>
The viscosity of the liquid composition for producing an electrochemical device was measured using a Brookfield viscometer (cone-plate viscometer) equipped with a No. CPA-40Z rotor at a rotation speed of 100 rpm and a temperature of 25°C.

<Particle size distribution of liquid composition for producing electrochemical device>
The particle size distribution of the liquid composition for producing an electrochemical device was measured at a temperature of 25° C. using a laser diffraction particle size distribution measuring device Mastersizer 3000 (manufactured by Malvern Instruments).

<Production of Positive Electrode Active Material>
[Production of Positive Electrode Active Material 1]
Vanadium pentoxide, lithium hydroxide, phosphoric acid, sucrose, and water were mixed to generate a precipitate, which was spray-dried using a spray dryer and then pulverized using a jet mill to obtain a precursor of lithium _vanadium phosphate (Li3V2( _PO4 ) ₃ ) particles. Next, the precursor of _the lithium vanadium phosphate particles was fired at 900°C under a nitrogen atmosphere to obtain lithium vanadium phosphate particles having a carbon content of 3% by mass. Next, the lithium vanadium phosphate particles were crushed using a jet mill so that the _D90 was less than 3 μm, to obtain a positive electrode active material 1. The positive electrode active material 1 had a mode diameter of 0.7 μm.

[Production of positive electrode active material 2]
Lithium iron phosphate (LiFePO ₄ ) particles (manufactured by Sigma-Aldrich) were pulverized by a jet mill so that the D ₉₀ was less than 3 μm, to obtain positive electrode active material 2. Positive electrode active material 2 had a mode diameter of 0.6 μm.

[Production of positive electrode active material 3]
Lithium cobalt oxide (LiCoO ₂ ) particles (manufactured by Sigma-Aldrich) were pulverized by a jet mill so that the D ₉₀ was less than 3 μm, to obtain positive electrode active material 3. Positive electrode active material 3 had a mode diameter of 0.9 μm.

[Production of Positive Electrode Active Material 4]
Lithium nickel oxide (LiNi _0.8 Co _0.15 Al _0.05 O ₂ ) particles (manufactured by Sigma-Aldrich) were pulverized by a jet mill so that D ₉₀ was less than 3 μm to obtain positive electrode active material 4. Positive electrode active material 4 had a mode diameter of 1.2 μm.

[Production of Positive Electrode Active Material 5]
Ni-Mn-Co based (LiNi _1/3 Mn _1/3 Co _1/3 O ₂ ) particles (manufactured by Sigma-Aldrich) were pulverized by a jet mill so that D ₉₀ was less than 3 μm, to obtain positive electrode active material 5. Positive electrode active material 5 had a mode diameter of 0.9 μm.

[Production of Positive Electrode Active Material 6]
Lithium manganate (LiMn ₂ O ₄ ) particles (manufactured by Sigma-Aldrich) were pulverized by a jet mill so that the D ₉₀ was less than 3 μm, to obtain the positive electrode active material 6. The positive electrode active material 6 had a mode diameter of 1.2 μm.

<Production of negative electrode active material>
[Production of negative electrode active material 1]
Artificial graphite (manufactured by MT Carbon) was pulverized by a jet mill so that _D90 was less than 3 μm, to obtain negative electrode active material 1. Negative electrode active material 1 had a mode diameter of 1.8 μm.

[Production of negative electrode active material 2]
Lithium titanate (Li ₄ Ti ₅ O ₁₂ ) particles (manufactured by Sigma-Aldrich) were pulverized by a jet mill so that D ₉₀ was less than 3 μm to obtain negative electrode active material 2. Negative electrode active material 2 had a mode diameter of 0.7 μm.

<Production of Polymer>
[Synthesis of Polymer 1]
Polymer 1 was synthesized according to the following scheme.

(Synthesis of Compound 1)
After 4.63 g (28.2 mmol) of triethylene glycol monomethyl ether and 80 ml of tetrahydrofuran were placed in a flask, the system was replaced with nitrogen. Next, the reaction solution was cooled to 0°C, and 5.00 g (21.7 mmol) of 3,5-dinitrobenzoyl chloride was added. Next, 4.60 ml (32.5 mmol) of triethylamine was slowly added dropwise, and the reaction solution was returned to room temperature and stirred overnight. Next, the reaction solution was filtered through Celite, and the solvent was distilled off from the filtrate under reduced pressure. Next, the residue was purified by column chromatography to obtain compound 1.

(Synthesis of Compound 2)
The obtained compound 1, 0.7 g of 10% palladium carbon, and 80 ml of ethyl acetate were placed in a flask, and then stirred in a hydrogen atmosphere until hydrogen consumption ceased. Next, the reaction solution was filtered through Celite, and the filtrate was purified by column chromatography to obtain compound 2 (5.69 g; yield 88%).

(Synthesis of Polymer 1)
Into a flask, 1.50g (5.03mmol) of compound 2, 30ml of DMF and 0.7ml of triethylamine were added, and then the system was replaced with nitrogen. Next, 1.06g (5.03mmol) of trimellitic anhydride chloride was added to the reaction solution, and then the mixture was stirred for 10 hours. Next, water was added to the reaction solution, and the precipitated solid was filtered out. The obtained solid was dried in vacuum to obtain polymer 1 (1.92g; yield 81%).

[Synthesis of Polymer 2]
Polymer 2 was synthesized according to the following scheme. That is, 0.40 g of polymer 1 was weighed into a glass petri dish and then left at 180° C. for 2 hours in the atmosphere to obtain polymer 2 (0.37 g). The polystyrene-equivalent molecular weight measured by GPC was Mw: 4904 and Mn: 2820. Polymer 2 was soluble in solvents such as NMP, DMF, DMA, and DMSO.

[Synthesis of Polymer 3]
Polymer 3 was synthesized according to the following scheme. That is, 0.50 g of polymer 1, 5 ml of DMF, and 5 ml of methanol were added to a flask. Next, a 0.6 M hexane solution of trimethylsilyldiazomethane was added to the reaction solution, and the mixture was stirred at room temperature for 2 hours. Next, the solvent was distilled off from the reaction solution under reduced pressure. Next, the residue was washed with ethyl acetate and then dried in vacuum to obtain polymer 3.

[Synthesis of Polymer 4]
Polymer 4 was synthesized according to the following scheme: That is, Polymer 4 was synthesized in the same manner as Polymer 1, except that tripropylene glycol monomethyl ether was used instead of triethylene glycol monomethyl ether.

[Synthesis of Polymer 5]
Polymer 5 was synthesized according to the following scheme. That is, polymer 5 was synthesized in the same manner as polymer 2, except that polymer 4 was used instead of polymer 1. The polystyrene-equivalent molecular weights measured by GPC were Mw: 8960 and Mn: 4360. Polymer 5 was soluble in solvents such as NMP, DMF, DMA, DMSO, THF, ethyl lactate, acetone, and cyclohexanone.

[Synthesis of Polymer 6]
Polymer 6 was synthesized according to the following scheme. That is, 0.33 g (1.10 mmol) of compound 2, 1.13 g (3.30 mmol) of compound 4, and 30 ml of DMF were placed in a flask, and then the system was replaced with nitrogen. Next, 0.93 g (4.40 mmol) of trimellitic anhydride chloride was added to the reaction solution. Next, 0.61 ml of triethylamine was added dropwise, and the mixture was stirred at room temperature for 10 hours. Next, water was added to the reaction solution, and the precipitated solid was filtered. Next, the obtained solid was vacuum dried to obtain polymer 6 (2.10 g; yield: 100%).

[Synthesis of Polymer 7]
Polymer 7 was synthesized according to the following scheme. That is, polymer 7 was synthesized in the same manner as polymer 2, except that polymer 6 was used instead of polymer 1. The polystyrene-equivalent molecular weights measured by GPC were Mw: 5780 and Mn: 2860. Polymer 7 was soluble in solvents such as NMP, DMF, DMA, DMSO, THF, ethyl lactate, acetone, and cyclohexanone.

[Synthesis of Polymer 8]
Polymer 8 was synthesized according to the following scheme: That is, Polymer 8 was synthesized in the same manner as Polymer 1, except that 3,7-dimethyloctanol was used instead of triethylene glycol monomethyl ether.

[Synthesis of Polymer 9]
Polymer 9 was synthesized according to the following scheme. That is, polymer 9 was synthesized in the same manner as polymer 2, except that polymer 8 was used instead of polymer 1. The polystyrene-equivalent molecular weights measured by GPC were Mw: 3687 and Mn: 1820. Polymer 9 was soluble in solvents such as NMP, DMF, DMA, DMSO, THF, 1,2-diethoxyethane, chloroform, and anisole.

[Synthesis of Polymer 10]
Polymer 10 was synthesized according to the following scheme: That is, polymer 8 was synthesized in the same manner as polymer 1, except that 2-ethylhexanol was used instead of triethylene glycol monomethyl ether.

[Synthesis of Polymer 11]
Polymer 11 was synthesized according to the following scheme. That is, polymer 11 was synthesized in the same manner as polymer 2, except that polymer 10 was used instead of polymer 1. The polystyrene-equivalent molecular weights measured by GPC were Mw: 3820 and Mn: 2100. Polymer 11 was soluble in solvents such as NMP, DMF, DMA, DMSO, 1,2-diethoxyethane, THF, chloroform, and anisole.

[Synthesis of Polymer 12]
Polymer 12 was synthesized according to the following scheme: That is, polymer 12 was synthesized in the same manner as polymer 6, except that compound 6 and compound 7 were used instead of compound 2 and compound 4.

[Synthesis of Polymer 13]
Polymer 13 was synthesized according to the following scheme. Polymer 13 was synthesized in the same manner as in the synthesis of Polymer 2, except that Polymer 12 was heat-treated at 260° C. Polymer 13 was soluble in solvents such as NMP, DMF, DMA, and DMSO.

[Synthesis of Polymer 14]
Polymer 14 was synthesized according to the following scheme: That is, polymer 14 was synthesized in the same manner as polymer 6, except that compound 6 and compound 8 were used instead of compound 2 and compound 4.

[Synthesis of Polymer 15]
Polymer 15 was synthesized according to the following scheme. That is, polymer 15 was synthesized in the same manner as polymer 2, except that polymer 14 was used instead of polymer 1. Polymer 13 was soluble in solvents such as NMP, DMF, DMA, and DMSO.

Example 1
A liquid composition for forming a positive electrode was prepared by adding ethyl lactate to a solid content of 35.8% by mass, which was composed of a positive electrode active material 1 (93.1% by mass), a polyethylene glycol-based dispersant (0.9% by mass), carbon black (3% by mass), and polymer 5 (3% by mass). The liquid composition for forming a positive electrode had a viscosity of 15 mPa·s, a mode diameter of 0.7 μm, and a D ₉₀ of 3.1 μm.

When the particle size distribution of the positive electrode-forming liquid composition was measured again 24 hours after preparation, no change was observed in the particle size distribution, and the positive electrode-forming liquid composition had good storage stability.

Using a liquid ejection device EV2500 (manufactured by Ricoh), the liquid composition for forming a positive electrode was ejected onto aluminum foil as a positive electrode substrate to form a positive electrode. At this time, the liquid composition for forming a positive electrode could be ejected continuously, and the liquid composition for forming a positive electrode had good ejection stability and no ejection failure occurred. In other words, the liquid composition for forming a positive electrode had good printing efficiency.

Example 2
A positive electrode forming liquid composition was prepared in the same manner as in Example 1, except that Polymer 7 was used instead of Polymer 5. The positive electrode forming liquid composition had a viscosity of 13 mPa·s, a mode diameter of 0.7 μm, and a D ₉₀ of 2.9 μm.

When the particle size distribution of the positive electrode-forming liquid composition was measured again 24 hours after preparation, no change was observed in the particle size distribution, and the positive electrode-forming liquid composition had good storage stability.

Using a liquid ejection device EV2500 (manufactured by Ricoh), the liquid composition for forming a positive electrode was ejected onto aluminum foil as a positive electrode substrate. At this time, the liquid composition for forming a positive electrode could be ejected continuously, and the liquid composition for forming a positive electrode had good ejection stability and no ejection failure occurred. In other words, the liquid composition for forming a positive electrode had good printing efficiency.

<Comparative Example 1>
An attempt was made to prepare a liquid composition for forming a positive electrode using polyvinylidene fluoride (PVDF), which is widely used as a binder for batteries, in a manner similar to that of Example 1, but the PVDF did not dissolve and preparation was not possible.

Example 3
[Evaluation of binding ability]
To the solid content consisting of the positive electrode active material 1 (93% by mass) and the polymer 2 (3% by mass), N-methylpyrrolidone was added so that the concentration of the solid content was 50% by mass, and a liquid composition for preparing an electrochemical element was prepared. This dispersion was applied to an aluminum foil with a gap of 100 μm using a doctor blade, and then dried at 120 ° C. for 10 minutes. The peel strength of the electrode mixture layer was measured using an adhesive/film peeling analyzer VPA-3 (manufactured by Kyowa Interface Science Co., Ltd.) for the obtained film (peel strength test method). Specifically, the electrode was cut into a width of 1.8 cm x length of 10 cm, and cellophane tape was attached to the surface of the electrode mixture layer side of the test piece, and the cellophane tape was peeled off 50 mm from one end of the test piece under the conditions of a peel speed of 30 mm / min and a peel angle of 90 °, and the stress at that time was measured. The results are shown in Figure 8.

<Examples 4 and 5>
The binding ability was evaluated using polymer 5 and polymer 7 in the same manner as in Example 3. The results are shown in FIG.

<Comparative Example 2>
The binding property was evaluated using polyvinylidene fluoride (PVDF), which is widely used as a binder for batteries, in the same manner as in Example 3. The results are shown in FIG.

The results in Figure 8 show that the peel strength of the polymers used in Examples 3, 4, and 5 is superior to that of PVDF. In other words, when an electrochemical element is produced using the liquid composition for producing an electrochemical element of this embodiment, an electrochemical element with excellent peel strength and high safety can be provided.

REFERENCE SIGNS LIST 1 secondary battery 10, 15 negative electrode 11 negative electrode substrate 12 negative electrode mixture layer 12A liquid composition 20, 25 positive electrode 21 positive electrode substrate 22 positive electrode mixture layer 30 separator 40 electrode element 41, 42 lead wire 51 electrolyte layer 52 exterior 300, 300' liquid ejection device 306 liquid ejection head

JP 2010-97946 A

Claims (13)

The battery includes at least one of an active material and an electrolyte, a dispersion medium, and a polymer,
The polymer has the general formula (I)
(In the formula, X is an oxygen atom ; R ¹ , R ² , R ³ and R ⁴ each independently represent a hydrogen atom or a substituted or unsubstituted alkyl group having 1 to 18 carbon atoms ; m is 1 and n is 3. )
and a polyamide-imide resin having a group represented by the following formula (1) on a side chain:
The polyamide-imide resin is characterized in that the group represented by the general formula (I) is bonded to the group represented by the general formula (I) by an ester bond via an oxygen atom of the group represented by the general formula (I).
A non-aqueous liquid composition for producing an electrochemical device. The nonaqueous liquid composition for producing an electrochemical device according to claim 1 , comprising the active material . The non-aqueous liquid composition for producing an electrochemical element according to claim 1 or 2, wherein the polymer is dissolved in the dispersion medium. The non-aqueous liquid composition for producing an electrochemical element according to any one of claims 1 to 3, wherein the content of the active material is 10% by mass or more. The non-aqueous liquid composition for producing an electrochemical element according to any one of claims 1 to 4, wherein the active material is at least one selected from the group consisting of a lithium-containing transition metal compound, a lithium-containing transition metal phosphate compound, and a carbon material. Further comprising a conductive assistant,
the active material includes the lithium-containing transition metal phosphate compound,
The lithium-containing transition metal phosphate compound is composited with the conductive assistant,
The nonaqueous liquid composition for producing an electrochemical device according to claim 5 , wherein the conductive assistant is a carbon material. The non-aqueous liquid composition for producing electrochemical elements according to any one of claims 1 to 6, having a viscosity of 200 mPa·s or less at 25°C. The active material includes lithium,
8. The non-aqueous liquid composition for producing an electrochemical device according to claim 1, wherein the dispersion medium is a non-aqueous dispersion medium. A method for manufacturing an electrode, comprising a step of applying the non-aqueous liquid composition for producing an electrochemical element according to any one of claims 1 to 8 onto an electrode substrate. The method for producing an electrode according to claim 9, wherein the non-aqueous liquid composition for producing an electrochemical element is discharged onto an electrode substrate. The method for producing an electrode according to claim 10, further comprising a step of pressurizing the electrode substrate onto which the non-aqueous liquid composition for producing an electrochemical element has been discharged. A method for manufacturing an electrochemical element, comprising a step of manufacturing an electrode using the method for manufacturing an electrode according to any one of claims 9 to 11. An electrode manufactured by the electrode manufacturing method described in any one of claims 9 to 11.