JP6851928B2 - Positive electrode slurry - Google Patents

Description

The present invention relates to a slurry for producing a positive electrode of a non-aqueous hybrid capacitor.

In recent years, from the viewpoint of effective use of energy aiming at conservation of the global environment and resource saving, power smoothing system or midnight power storage system for wind power generation, distributed power storage system for home use based on solar power generation technology, power storage for electric vehicles Systems and the like are attracting attention.

The first requirement of the batteries used in these power storage systems is high energy density. Lithium-ion batteries are being energetically developed as promising candidates for high-energy density batteries that can meet such demands.

The second requirement is high output characteristics. For example, in a combination of a high-efficiency engine and a power storage system (for example, a hybrid electric vehicle) or a combination of a fuel cell and a power storage system (for example, a fuel cell electric vehicle), high output discharge characteristics in the power storage system are required at the time of acceleration. There is.

Currently, electric double layer capacitors, nickel-metal hydride batteries, and the like are being developed as high-power power storage devices.

Among the electric double layer capacitors, those using activated carbon for the electrodes have an output characteristic of about 0.5 to 1 kW / L. This electric double layer capacitor has high durability (cycle characteristics and high temperature storage characteristics), and has been considered to be the most suitable device in the field where high output is required. However, its energy density is only about 1 to 5 Wh / L. Therefore, the electric double layer capacitor needs to be further improved in energy density.

On the other hand, the nickel-metal hydride battery currently used in hybrid electric vehicles has a high output equivalent to that of an electric double layer capacitor and an energy density of about 160 Wh / L. However, research is being vigorously pursued to further increase its energy density and output and to improve its durability.

In addition, research is underway to increase the output of lithium-ion batteries. For example, a lithium ion battery has been developed in which a high output exceeding 3 kW / L can be obtained at a discharge depth (a value indicating what percentage of the discharge capacity of the power storage element is discharged) of 50%. However, its energy density is 100 Wh / L or less, and the design is such that the high energy density, which is the greatest feature of the lithium ion battery, is intentionally suppressed. Its durability (cycle characteristics and high temperature storage characteristics) is inferior to that of electric double layer capacitors. Therefore, in order to give the lithium ion battery practical durability, it is used in a range where the discharge depth is narrower than the range of 0 to 100%. Since the capacity of the lithium-ion battery that can be actually used becomes smaller, research for further improving the durability of the lithium-ion battery is being vigorously pursued.

As described above, there is a strong demand for practical use of a power storage element having high energy density, high output characteristics, and durability. However, each of the existing power storage elements described above has advantages and disadvantages. Therefore, there is a demand for a new power storage element that satisfies these technical requirements. As a promising candidate, a power storage element called a lithium ion capacitor has attracted attention and is being actively developed.

The energy of the capacitor is represented by 1/2 · C · V ² (in the equation, C is the capacitance and V is the voltage).

A lithium ion capacitor is a type of power storage element (non-aqueous hybrid capacitor) that uses a non-aqueous electrolyte solution containing a lithium salt, and at a positive electrode of about 3 V or more, adsorption and desorption of anions similar to those of an electric double layer capacitor. In the negative electrode, it is a power storage element that charges and discharges by a Faraday reaction by storing and releasing lithium ions, which is similar to that of a lithium ion battery.

To summarize the above-mentioned electrode materials and their characteristics, high output and high durability are achieved when a material such as activated carbon is used for the electrodes and charging and discharging are performed by adsorption and desorption (non-Faraday reaction) of ions on the surface of activated carbon. However, the energy density becomes low (for example, it is multiplied by 1). When an oxide or carbon material is used for the electrode and charging / discharging is performed by the Faraday reaction, the energy density becomes high (for example, 10 times that of the non-Faraday reaction using activated carbon), but there are problems in durability and output characteristics. There is.

As a combination of these electrode materials, the electric double layer capacitor is characterized by using activated carbon (energy density 1 times) for the positive electrode and the negative electrode and charging / discharging both the positive electrode and the negative electrode by a non-Faraday reaction, and has high output and high durability. However, it is characterized by low energy density (1x positive electrode x 1x negative electrode = 1).

The lithium ion secondary battery is characterized by using a lithium transition metal oxide (energy density 10 times) for the positive electrode and a carbon material (energy density 10 times) for the negative electrode, and charging and discharging both the positive electrode and the negative electrode by a Faraday reaction. Although the energy density is 10 times the positive electrode x 10 times the negative electrode = 100, there are problems in output characteristics and durability. In order to satisfy the high durability required for hybrid electric vehicles and the like, the depth of discharge must be limited, and a lithium ion secondary battery can use only 10 to 50% of its energy.

Lithium-ion capacitors use activated carbon (1x energy density) for the positive electrode and carbon material (10x energy density) for the negative electrode, and are characterized by performing charging and discharging by a non-Faraday reaction at the positive electrode and a Faraday reaction at the negative electrode. It is a new asymmetric capacitor that combines the characteristics of a multi-layer capacitor and a lithium-ion secondary battery. Lithium-ion capacitors have high energy density (1x positive electrode x 10x negative electrode = 10) while having high output and high durability, and there is no need to limit the discharge depth as in lithium-ion secondary batteries. Is a feature.

Various studies have been conducted on the positive electrode of the power storage element (particularly the lithium ion secondary battery) described above.

For example, Patent Document 1 proposes a lithium ion secondary battery that uses a positive electrode containing lithium carbonate in the positive electrode and has a current cutoff mechanism that operates in response to an increase in battery internal pressure. Patent Document 2 proposes a lithium ion secondary battery in which a lithium composite oxide such as lithium manganic acid is used as a positive electrode and lithium carbonate is contained in the positive electrode to suppress elution of manganese. Patent Document 3 proposes a method of oxidizing various lithium compounds as oxides at a positive electrode to recover the capacity of a deteriorated power storage element. Patent Document 4 proposes a method in which a carbonate, a hydroxide, or a silicate is contained in an activated carbon positive electrode as an antacid.

Japanese Unexamined Patent Publication No. 4-328278 Japanese Unexamined Patent Publication No. 2001-167767 Japanese Unexamined Patent Publication No. 2012-174437 Japanese Unexamined Patent Publication No. 2006-261516

The methods described in Patent Documents 1 to 4 do not consider pre-doping the negative electrode in the non-aqueous hybrid capacitor at all, and further improve the efficiency of pre-doping and increase the energy density and the resistance of the non-aqueous hybrid capacitor. There was room for improvement. Further, Patent Documents 1 to 4 do not mention at all the properties of the slurry used for forming the positive electrode of the non-aqueous hybrid capacitor.

Therefore, the problem to be solved by the present invention is for a non-aqueous hybrid capacitor that can pre-dope the negative electrode uniformly in a short time, has high energy density and high input / output, and has excellent high temperature durability. It is to provide a positive electrode slurry.

The present inventors diligently studied and repeated experiments in order to solve the above problems. As a result, the present inventors set the weight ratio of all solid components, the weight ratio of alkali metal carbonate, and the slurry viscosity in a specific state in the positive electrode slurry for a non-aqueous hybrid capacitor containing activated carbon and alkali metal carbonate. By controlling to, it becomes possible to suppress the precipitation of alkali metal carbonate in the slurry and enhance the dispersion uniformity, and when the slurry is coated to form a positive electrode precursor, it is contained in the positive electrode active material layer. The alkali metal carbonate can be uniformly distributed without being localized, and when the positive electrode precursor is incorporated for a non-aqueous hybrid capacitor, the alkali metal carbonate is uniformly decomposed and the predoping to the negative electrode is shortened. The present invention has been completed by finding that it can be carried out uniformly in the negative electrode over time, high energy density and high input / output can be obtained, and it is also excellent in high temperature durability. That is, the present invention is as follows.
[1]
A slurry containing a positive electrode active material containing activated carbon, an alkali metal carbonate other than the positive electrode active material, a binder, and a solvent.
Based on the total weight of the slurry, the weight ratio of the total solid content excluding the solvent when the W _T mass%, a 10 ≦ W _T ≦ 50,
Based on the total weight of the total solid components of the slurry, when said mass ratio of the alkali metal carbonate and W _A mass%, 5 ≦ W is _A ≦ 50, and left stirring after 7 days in a container When the total mass of the slurry in the above state is divided into three in the height direction and the viscosities of the uppermost layer liquid and the lowermost layer liquid are η _U (mPa · s) and η _L (mPa · s), respectively, it is 0. .50 ≤ η _U / η _L ≤ 1.00 slurry.
[2]
The densities of the top layer liquid and the bottom layer liquid when the total volume of the slurry was divided into three in the height direction in a state of being allowed to stand for 7 days after stirring in the container were ρ _U (g / mL) and ρ _{L, respectively.} The slurry according to [1], wherein (g / mL) is 0.60 ≤ ρ _U / ρ _{L ≤ 1.00.}
[3]
When the average particle size of the alkali metal carbonate is X ₁ , 0.1 μm ≤ X ₁ ≤ 10 μm, and when the average particle size of the positive electrode active material is Y ₁ , 2 μm ≤ Y ₁ ≤ 20 μm. , [1] or [2].
[4]
The slurry according to [3], wherein X ₁ <Y ₁ in the average particle size X ₁ of the alkali metal carbonate and the average particle size Y _{1 of the positive electrode active material.}
[5]
The slurry according to any one of [1] to [4], wherein the alkali metal carbonate is at least one selected from the group consisting of lithium carbonate, sodium carbonate, potassium carbonate, rubidium carbonate, and cesium carbonate. ..
[6]
The slurry according to any one of [1] to [5], which contains 10% by mass or more of lithium carbonate in the alkali metal carbonate.
[7]
_{The activated carbon has a mesopore amount of V 1} (cc / g) derived from pores having a diameter of 20 Å or more and 500 Å or less calculated by the BJH method, and a micropore amount derived from pores having a diameter of less than 20 Å calculated by the MP method. When V ₂ (cc / g), 0.3 <V ₁ ≤ 0.8 and 0.5 ≤ V ₂ ≤ 1.0 are satisfied, and the specific surface area measured by the BET method is 1,500 m ² The slurry according to any one of [1] to [6], which is not less than / g and 3,000 m ^{2 / g.}
[8]
_{The activated carbon has a mesopore amount V 1} (cc / g) derived from pores having a diameter of 20 Å or more and 500 Å or less calculated by the BJH method _{satisfying 0.8 <V 1} ≤ 2.5, and a diameter calculated by the MP method. _{The amount of micropores V 2} (cc / g) derived from pores less than 20 Å _{satisfies 0.8 <V 2} ≤ 3.0, and the specific surface area measured by the BET method is 2,300 m ² / g or more 4 The slurry according to any one of [1] to [6], which is 000 m ^{2 / g or less.}
[9]
The slurry according to any one of [1] to [8], wherein the binder contains a fluorine-containing substance, and the weight average molecular weight of the binder is 500,000 or more and 1,800,000 or less.
[10]
The slurry according to [9], wherein the fluorine-containing material contains polyvinylidene fluoride.
[11]
The slurry according to any one of [1] to [10], wherein the binder contains a rubber-based polymer.
[12]
The slurry according to any one of [1] to [11], wherein the binder contains an acrylic polymer.
[13]
The slurry according to any one of [1] to [12], which contains 50% by mass or more of N-methylpyrrolidone in the solvent.
[14]
The slurry according to any one of [1] to [12], which contains 50% by mass or more of water in the solvent.
[15]
The slurry according to any one of [1] to [14], which is used for producing a positive electrode of a non-aqueous hybrid capacitor.

According to the present invention, it is possible to manufacture a positive electrode of a non-aqueous hybrid capacitor which can be pre-doped into a negative electrode in a short time and uniformly, has a high energy density, high input / output, and is excellent in high temperature durability, and a positive electrode thereof. It is possible to provide a slurry capable of producing.

Hereinafter, embodiments of the present invention (hereinafter referred to as “the present embodiment”) will be described in detail, but the present invention is not limited to the present embodiment. The upper limit value and the lower limit value in each numerical range of the present embodiment can be arbitrarily combined to form an arbitrary numerical range.

<< Non-aqueous hybrid capacitor >>
A non-aqueous hybrid capacitor generally has a positive electrode, a negative electrode, a separator, and an electrolytic solution as main components. As the electrolytic solution, an organic solvent in which an electrolyte such as an alkali metal salt is dissolved (hereinafter referred to as "non-aqueous electrolytic solution") is used.

In the present specification, the positive electrode state before pre-doping is defined as “positive electrode precursor”, and the positive electrode state after pre-doping is defined as “positive electrode”. In the present specification, a slurry for producing a positive electrode precursor or a positive electrode is referred to as a “positive electrode slurry”. The positive electrode slurry may include not only the form of a known slurry but also the form of a known suspension, dispersion, emulsion, composition or mixture. The positive electrode slurry according to the present embodiment may be simply referred to as a coating liquid, a coating liquid, or the like.

The positive electrode slurry in the present embodiment is, for example, coated on one or both sides of a positive electrode current collector to form a coating film, which is dried to form a positive electrode precursor which is a positive electrode of a non-aqueous hybrid capacitor. can do.
The positive electrode slurry of the present embodiment contains an alkali metal carbonate other than the positive electrode active material, and the processed positive electrode precursor also contains the alkali metal carbonate. In the present embodiment, when assembling a non-aqueous hybrid capacitor, it is preferable to pre-dope the negative electrode with alkali metal ions. As a pre-doping method, after assembling a non-aqueous hybrid capacitor using a positive electrode precursor containing an alkali metal carbonate, a negative electrode, a separator, and a non-aqueous electrolyte solution, a voltage is applied between the positive electrode precursor and the negative electrode. It is preferable to apply.

<Positive electrode slurry>
The positive electrode slurry in the present embodiment contains a positive electrode active material containing activated carbon, an alkali metal carbonate other than the positive electrode active material, a binder, and a solvent. Based on the total weight of the positive electrode slurry, when the mass ratio of the total solid content excluding the solvent and W _T%, W _T is 10 ≦ W _T ≦ 50, the total mass of the total solid content of the positive electrode slurry as a reference, when the mass ratio of alkali metal carbonate and _{W a} mass%, _{W a} is a 5 ≦ _{W a} ≦ 50. The viscosities of the uppermost layer liquid and the lowermost layer liquid when the total volume of the positive electrode slurry was divided into three in the height direction in a state where the positive electrode slurry was allowed to stand for 7 days after being stirred in the container were η _U and η _L (mPa ·, respectively. When s), 0.50 ≤ η _U / η _L ≤ 1.00. The pre-doping of the negative electrode quickly and uniformly carried out, a high energy density and high output, the configuration of the positive electrode slurry for nonaqueous hybrid capacitor excellent in high-temperature durability, W _T, W _A and eta _U / It is specified by the entire numerical range of η _L.

The positive electrode slurry in the present embodiment may contain optional components such as a conductive filler, a dispersion stabilizer, and a pH adjuster in addition to the above-mentioned positive electrode active material, alkali metal carbonate, binder, and solvent. ..

[Positive electrode active material]
The positive electrode active material according to this embodiment contains activated carbon. As the positive electrode active material, activated carbon may be used alone, one or more types of carbon materials other than activated carbon may be mixed and used, or materials other than carbon materials (for example, composite oxidation of an alkali metal and a transition metal) may be used. Things, etc.) may be included. Examples of carbon materials other than activated carbon include carbon nanotubes, conductive polymers, and porous carbon materials.

The type of activated carbon and its raw material are not particularly limited. However, it is preferable to optimally control the pores of the activated carbon in order to achieve both high input / output characteristics and high energy density when incorporated into a non-aqueous hybrid capacitor. Specifically, the amount of mesopores derived from pores with a diameter of 20 Å or more and 500 Å or less calculated by the BJH method is V ₁ (cc / g), and the amount of micropores derived from pores with a diameter of less than 20 Å calculated by the MP method. When is V ₂ (cc / g),
(1) In order to obtain high input / output characteristics, 0.3 <V ₁ ≤ 0.8 and 0.5 ≤ V ₂ ≤ 1.0 are satisfied, and the specific surface area measured by the BET method is 1. , 500 m ² / g or more and 3,000 m ² / g or less of activated carbon (hereinafter, also referred to as “activated carbon 1”) is preferable.
(2) In order to obtain a high energy density, 0.8 <V ₁ ≤ 2.5 and 0.8 <V ₂ ≤ 3.0 are satisfied, and the specific surface area measured by the BET method is 2, Activated carbon having a thickness of 300 m ² / g or more and 4,000 m ² / g or less (hereinafter, also referred to as “activated carbon 2”) is preferable.

Hereinafter, the above-mentioned (1) activated carbon 1 and the above-mentioned (2) activated carbon 2 will be described individually in sequence.

(Activated carbon 1)
Meso Anaryou V ₁ of the activated carbon 1, with a view to increasing the output characteristics when incorporated into non-aqueous hybrid capacitor, it is preferable that 0.3 cc / g greater than. On the other hand, from the viewpoint of suppressing a decrease in the bulk density of the positive electrode, it is preferably 0.8 cc / g or less. The above V ₁ is more preferably 0.35 cc / g or more and 0.7 cc / g or less, and further preferably 0.4 cc / g or more and 0.6 cc / g or less.

The micropore amount V ₂ of the activated carbon 1 is preferably 0.5 cc / g or more in order to increase the specific surface area and the capacity of the activated carbon. On the other hand, from the viewpoint of suppressing the bulk of the activated carbon, increasing the density as an electrode, and increasing the capacity per unit volume, it is preferably 1.0 cc / g or less. The above V ₂ is more preferably 0.6 cc / g or more and 1.0 cc / g or less, and further preferably 0.8 cc / g or more and 1.0 cc / g or less.

The ratio of meso Anaryou _{V 1} relative to the micropore volume _{V 2} of activated carbon 1 _(V 1 / V ₂₎ is preferably in the range of _{0.3 ≦ V 1 / V 2 ≦} 0.9. _{That is, V 1} / V ₂ is 0.3 or more from the viewpoint of increasing the ratio of the mesopore amount to the micropore amount to the extent that the deterioration of the input / output characteristics can be suppressed while maintaining the high capacity. Is preferable. _{On the other hand, V 1} / V ₂ is preferably 0.9 from the viewpoint of increasing the ratio of the amount of micropores to the amount of mesopores to the extent that the decrease in capacitance can be suppressed while maintaining high input / output characteristics. Hereinafter, it is more preferably 0.4 ≦ V ₁ / V ₂ ≦ 0.7, _{and even more preferably 0.55 ≦ V 1} / V ₂ ≦ 0.7.

_{For V 1} , V ₂ and V ₁ / V ₂ of activated carbon 1, the upper and lower limits of the suitable ranges described above can be arbitrarily combined.

The average pore diameter of the activated carbon 1 is preferably 17 Å or more, more preferably 18 Å or more, and further preferably 20 Å or more, from the viewpoint of increasing the input / output of the obtained non-aqueous hybrid capacitor. Further, from the viewpoint of increasing the capacity, the average pore diameter of the activated carbon 1 is preferably 25 Å or less.

BET specific surface area of the activated carbon 1 is preferably from 1,500 m ² / g or more 3,000 m ² / g, more preferably not more than 1,500 m ² / g or more 2,500 m ² / g. When the BET specific surface area is 1,500 m ² / g or more, a good energy density can be easily obtained, while when the BET specific surface area is 3,000 m ² / g or less, in order to maintain the strength of the electrode. Since it is not necessary to add a large amount of binder, the performance per electrode volume is improved. The upper and lower limits of the BET specific surface area range can be arbitrarily combined.

Activated carbon 1 having the above characteristics can be obtained, for example, by using the raw materials and the treatment method described below.

In the present embodiment, the carbon source used as the raw material of the activated carbon 1 is not particularly limited. For example, plant-based raw materials such as wood, wood flour, coconut shells, by-products during pulp production, bagas, waste sugar honey; peat, sub-charcoal, brown charcoal, bituminous charcoal, smokeless charcoal, petroleum distillation residue components, petroleum pitch, coke, coal tar, etc. Fossil raw materials; various synthetic resins such as phenol resin, vinyl chloride resin, vinyl acetate resin, melamine resin, urea resin, resorcinol resin, celluloid, epoxy resin, polyurethane resin, polyester resin, polyamide resin; polybutylene, polybutadiene, polychloroprene, etc. Synthetic rubber; other synthetic wood, synthetic pulp, etc., and carbonized products thereof. Among these raw materials, plant-based raw materials such as coconut shells and wood flour and their carbides are preferable, and coconut shell carbides are particularly preferable, from the viewpoint of mass production and cost.

As a carbonization and activation method for obtaining the activated carbon 1 from these raw materials, for example, known methods such as a fixed bed method, a moving bed method, a fluidized bed method, a slurry method, and a rotary kiln method can be adopted.

Examples of the carbonization method for these raw materials include inert gases such as nitrogen, carbon dioxide, helium, argon, xenone, neon, carbon monoxide, and combustion exhaust gas, or other gases containing these inert gases as main components. Examples thereof include a method of firing at 400 to 700 ° C., preferably 450 to 600 ° C. for about 30 minutes to 10 hours using a mixed gas.

As a method for activating the carbide obtained by the above carbonization method, a gas activation method in which the carbide is fired using an activation gas such as steam, carbon dioxide, or oxygen is preferably used. Of these, a method using water vapor or carbon dioxide as the activating gas is preferable.

In this activation method, the above-mentioned carbide is preferably supplied for 3 to 12 hours while supplying the activation gas at a ratio of preferably 0.5 to 3.0 kg / h, more preferably 0.7 to 2.0 kg / h. It is more preferable to activate by raising the temperature to 800 to 1,000 ° C. over 5 to 11 hours, more preferably 6 to 10 hours.

Prior to the activation treatment of the carbide, the carbide may be first activated in advance. In this primary activation, a method in which a carbon material is usually calcined at a temperature of less than 900 ° C. using an activation gas such as steam, carbon dioxide, or oxygen to activate the gas is preferable.

Activated carbon 1 having the above characteristics can be produced by appropriately combining the firing temperature and firing time in the carbonization method with the amount of activated gas supplied, the rate of temperature rise, and the maximum activation temperature in the activation method.

(Activated carbon 2)
Meso Anaryou V ₁ of the activated carbon 2, from the viewpoint of increasing the output characteristics when incorporated into non-aqueous hybrid capacitor, it is preferable that 0.8 cc / g greater than. V ₁ is preferably 2.5 cc / g or less from the viewpoint of suppressing a decrease in the capacity of the non-aqueous hybrid capacitor. The above V ₁ is more preferably 1.0 cc / g or more and 2.0 cc / g or less, and further preferably 1.2 cc / g or more and 1.8 cc / g or less.

On the other hand, the micropore amount V ₂ of the activated carbon 2 is preferably a value larger than 0.8 cc / g in order to increase the specific surface area and the capacity of the activated carbon. V ₂ is preferably 3.0 cc / g or less from the viewpoint of increasing the density of activated carbon as an electrode and increasing the capacity per unit volume. The above V ₂ is more preferably larger than 1.0 cc / g and 2.5 cc / g or less, and further preferably 1.5 cc / g or more and 2.5 cc / g or less.

The activated carbon 2 having the above-mentioned meso-pore amount and micro-pore amount has a higher BET specific surface area than the activated carbon used for conventional electric double layer capacitors or lithium ion capacitors. The specific value of the BET specific surface area of the activated carbon 2 ^{is preferably 2,300 m 2} / g or more and 4,000 m ² / g or less. The lower limit of the BET specific surface area ^{is more preferably 3,000 m 2} / g or more, and further preferably 3,200 m ² / g or more. The upper limit of the BET specific surface area ^{is more preferably 3,800 m 2} / g or less. When the BET specific surface area is 2,300 m ² / g or more, a good energy density can be easily obtained, while when the BET specific surface area is 4,000 m ² / g or less, in order to maintain the strength of the electrode. Since it is not necessary to add a large amount of binder, the performance per electrode volume is improved.

_{For the V 1} , V ₂ and BET specific surface areas of the activated carbon 2, the upper and lower limits of the suitable ranges described above can be arbitrarily combined.

Activated carbon 2 having the above characteristics can be obtained by using, for example, the raw materials and treatment methods described below.

The carbon source used as a raw material for activated carbon 2 is not particularly limited as long as it is a carbon source normally used as a raw material for activated carbon. For example, plant-based raw materials such as wood, wood flour, and coconut shell; petroleum pitch, coke. Fossil-based raw materials such as, and various synthetic resins such as phenol resin, furan resin, vinyl chloride resin, vinyl acetate resin, melamine resin, urea resin, resorcinol resin and the like can be mentioned. Among these raw materials, phenol resin and furan resin are particularly preferable because they are suitable for producing activated carbon having a high specific surface area.

Examples of the method of carbonizing these raw materials or the heating method at the time of activation treatment include known methods such as a fixed bed method, a moving bed method, a fluidized bed method, a slurry method, and a rotary kiln method. As the atmosphere at the time of heating, an inert gas such as nitrogen, carbon dioxide, helium, or argon, or a gas containing these inert gases as a main component and mixed with other gases is used. The carbonization temperature is preferably 400 to 700 ° C., the lower limit is preferably 450 ° C. or higher, further preferably 500 ° C. or higher, the upper limit is preferably 650 ° C. or lower, and the firing time is preferably about 0.5 to 10 hours. is there.

Examples of the method for activating the carbide after the carbonization treatment include a gas activation method in which the carbide is fired using an activation gas such as steam, carbon dioxide, and oxygen, and an alkali metal activation method in which heat treatment is performed after mixing with an alkali metal compound. An alkali metal activation method is preferable for producing activated carbon having a high specific surface area.

In this activation method, the mass ratio of the carbide to the alkali metal compound such as potassium hydroxide (KOH) and sodium hydroxide (NaOH) is 1: 1 or more (the amount of the alkali metal compound is equal to or less than the amount of the carbide). After mixing to a large amount), heating is carried out in an inert gas atmosphere, preferably in the range of 600 to 900 ° C., more preferably 650 ° C. to 850 ° C. for 0.5 to 5 hours. Then, the alkali metal compound is washed and removed with acid and water, and further dried.

The mass ratio of the carbide to the alkali metal compound (= carbide: alkali metal compound) is preferably 1: 1 or more, and the amount of mesopores increases as the amount of the alkali metal compound increases, and the mass ratio is around 1: 3.5. Since the amount of pores tends to increase rapidly at the boundary, the mass ratio of the carbide to the alkali metal compound is preferably 1: 3 or more. The mass ratio of the carbide to the alkali metal compound increases as the amount of the alkali metal compound increases, but it is preferably 1: 5.5 or less in consideration of the treatment efficiency such as subsequent cleaning.

In order to increase the amount of micropores and not increase the amount of mesopores, it is advisable to increase the amount of carbides at the time of activation and mix with KOH. In order to increase both the amount of micropores and the amount of mesopores, it is advisable to use a large amount of KOH. Mainly, in order to increase the amount of mesopores, it is preferable to perform steam activation after performing alkali activation treatment.

(Usage mode of activated carbon)
As the activated carbon used for the positive electrode active material, the activated carbons 1 and 2 may be one kind of activated carbon, respectively, or a mixture of two or more kinds of activated carbons, and each of the above-mentioned characteristic values is used as the whole mixture. It may be shown.

As the activated carbons 1 and 2 described above, either one of them may be selected and used, or both may be mixed and used.

The positive electrode active material is a material other than activated carbons 1 and 2 (for example, _{activated carbon that does not have the specific V 1} and / or V ₂ described above, or a carbon material other than the activated carbon described above, or a material other than the carbon material (for example, alkali). It may contain a composite oxide of a metal and a transition metal, etc.)). The content of activated carbon 1, the content of activated carbon 2, or the total content of activated carbons 1 and 2, is preferably 50% by mass or more, more preferably 70% by mass or more, respectively, with respect to the total mass of the positive electrode active material. Or may be 100% by mass. From the viewpoint of obtaining a good effect when used in combination with other materials, for example, the content of activated carbon is preferably 90% by mass or less, or 80% by mass or less, based on the total mass of the positive electrode active material. May be good.

The content ratio of the positive electrode active material in the positive electrode slurry is preferably 35% by mass or more and 95% by mass or less based on the total mass of all solid components of the positive electrode slurry. The upper limit of the content ratio of the positive electrode active material is more preferably 40% by mass or more, further preferably 50% by mass or more. The lower limit of the content ratio of the positive electrode active material is more preferably 90% by mass or less, and further preferably 80% by mass or less. By setting the content ratio in this range, suitable charge / discharge characteristics are exhibited.

[Alkali metal carbonate]
The positive electrode slurry of the present embodiment contains an alkali metal carbonate other than the positive electrode active material. A positive electrode precursor containing an alkali metal carbonate can be prepared using the positive electrode slurry. In the present embodiment, when assembling a non-aqueous hybrid capacitor, it is preferable to pre-dope the negative electrode with alkali metal ions. As a pre-doping method, after assembling a non-aqueous hybrid capacitor using a positive electrode precursor containing an alkali metal carbonate, a negative electrode, a separator, and a non-aqueous electrolyte solution, a voltage is applied between the positive electrode precursor and the negative electrode. It is preferable to apply.

As the alkali metal carbonate in the present embodiment, a carbonate compound capable of decomposing in the positive electrode precursor to release alkali metal ions is used. As the alkali metal carbonate, at least one selected from the group consisting of lithium carbonate, sodium carbonate, potassium carbonate, rubidium carbonate, and cesium carbonate is preferably used, and among them, from the viewpoint of high capacity per unit weight. Lithium carbonate is more preferably used. The alkali metal carbonate contained in the positive electrode slurry may be one kind or two or more kinds. When two or more kinds of alkali metal carbonates are contained in the positive electrode slurry, the alkali metal carbonates preferably contain 10% by mass or more of lithium carbonate based on the total mass of the alkali metal carbonates contained in the positive electrode slurry. More preferably, it contains 12% by mass or more and 90% by mass or less of lithium carbonate.

Further, the positive electrode slurry of the present embodiment may contain at least one kind of alkali metal carbonate, and in addition to the alkali metal carbonate, M may be one or more selected from Li, Na, K, Rb and Cs. as, oxides such as _{M 2} O, hydroxides MOH such as a halide such as MF or _{MCl, M 2 (CO 2)} 2 and the like oxalates, RCOOM (R is H, an alkyl group, an aryl group), It may contain one or more carbonates of. Also, the positive electrode _{slurry, BeCO 3, MgCO 3, CaCO} 3, SrCO 3, or alkaline earth metal carbonate selected from BaCO _3, or alkaline earth metal oxides, alkaline earth metal hydroxides, alkaline earth It may contain one or more metal halides, alkaline earth metal oxalates, or alkaline earth metal carboxylates.

In the present embodiment, based on the total weight of all solid components of the positive electrode slurry, when the mass ratio of the alkali metal carbonate and W _A mass% is 5 ≦ W _A ≦ 50, preferably 10 ≦ W _A ≦ 45, more preferably 15 ≦ _{W a} ≦ 40.

If W _A is 5 or more, with alkali metal ions pre-doped into the negative electrode is sufficiently ensured, the positive electrode can be given a suitable degree of porosity, increased input-output characteristic of the non-aqueous hybrid capacitor. If W _A is 50 or less, by the decomposition of alkali metal carbonate in the electron conductivity of the positive electrode precursor is increased is promoted, together with the pre-doping time can be shortened, high-energy density non-aqueous hybrid capacitor Is obtained.

When the positive electrode slurry contains the above alkali metal compound or alkaline earth metal compound in addition to the alkali metal carbonate, the total mass of the alkali metal carbonate and the alkali metal compound or the alkaline earth metal compound is the positive electrode slurry. It is preferable to prepare the positive electrode slurry so that it is contained in a proportion of 5% by mass or more and 50% by mass or less based on the total mass of all solid components.

The quantification of alkali metal elements and alkaline earth metals can be calculated by ICP-AES, atomic absorption spectrometry, fluorescent X-ray analysis, neutron activation analysis, ICP-MS and the like.

The alkali metal carbonate, alkali metal compound and alkaline earth metal compound are preferably in the form of particles. Various methods can be used for micronization. For example, a crusher such as a ball mill, a bead mill, a ring mill, a jet mill, or a rod mill can be used.

(Average particle size of alkali metal carbonate and positive electrode active material)
In the positive electrode slurry of the present embodiment, when the average particle size of the alkali metal carbonate is X ₁ , it is preferable that 0.1 μm ≦ X _{1 ≦ 10 μm.} The lower limit of X ₁ is more preferably 0.3 μm or more, further preferably 0.5 μm or more, and _{the upper limit of X 1} is more preferably 5 μm or less, further preferably 3 μm or less. The upper limit and the lower limit of _{X 1 can be arbitrarily combined.}

When X ₁ is 0.1 μm or more, the dispersion uniformity of the alkali metal carbonate in the positive electrode slurry and the positive electrode precursor is excellent. When X ₁ is 10 μm or less, the precipitation of the alkali metal carbonate in the positive electrode slurry can be suppressed, and the surface area of the alkali metal carbonate increases, so that the positive electrode precursor is decomposed when incorporated for a non-aqueous hybrid capacitor. The reaction proceeds efficiently.

Further, in the positive electrode slurry of the present embodiment, when the average particle size of the positive electrode active material is Y ₁ , it is preferable that 2 μm ≦ Y _{1 ≦ 20 μm.} The lower limit of Y ₁ is more preferably 2.5 μm or more, and further preferably 3 μm or more. The upper limit of Y ₁ is more preferably 15 μm or less, further preferably 10 μm or less. The upper limit and the lower limit of _{Y 1 can be arbitrarily combined.}

When Y ₁ is 2 μm or more, the electrode density can be maintained high when the positive electrode precursor is formed, so that a high energy density can be obtained. When Y ₁ is 20 μm or less, high input / output characteristics can be exhibited because the reaction area with the electrolyte ion increases.

Further, in the positive electrode slurry of the present embodiment, the relationship between the average particle size of the alkali metal carbonate and the positive electrode active material is preferably _{X 1} <Y _1. When X ₁ <Y ₁ , the dispersion uniformity of the alkali metal carbonate and the positive electrode active material in the positive electrode slurry and the positive electrode precursor is excellent, and the alkali metal carbonate is formed in the gap between the positive electrode active materials inside the positive electrode precursor. Since the salt is filled, the energy density can be increased while ensuring the electron conductivity between the positive electrode active materials.

[Binder]
The positive electrode slurry of the present embodiment contains a binder. The type of the binder is not particularly limited, and examples thereof include a fluorine-containing substance, a rubber-based polymer, and a polyimide. The positive electrode slurry contains a fluorine-containing substance and / or a rubber-based polymer as the binder. Is preferable. As the binder contained in the positive electrode slurry, one type may be used alone, or two or more types may be used in combination.

(Fluorine-containing material)
When a fluorine-containing substance is contained as the binder of the positive electrode slurry of the present embodiment, the fluorine-containing substances are preferably PVdF (polyvinylidene fluoride) and PTFE (polytetra-tetra) from the viewpoint of oxidation resistance and high peel strength. Fluoroethylene), and PVdF (polyvinylidene fluoride) is more preferable from the viewpoint of easy thinning of the positive electrode precursor and high input / output when incorporated into a non-aqueous hybrid capacitor.

The weight average molecular weight of the binder contained in the positive electrode slurry of the present embodiment is preferably 500,000 or more and 1,800,000 or less. The upper limit of the weight average molecular weight of the binder is preferably 1,600,000 or less, more preferably 1,450,000 or less, further preferably 1,300,000 or less, and the lower limit is 600,000 or more. Is preferable, 700,000 or more is more preferable, and 800,000 or more is further preferable. The upper and lower limits of the weight average molecular weight of the binder can be arbitrarily combined.

When the weight average molecular weight of the binder contained in the positive electrode slurry is 500,000 or more, the sedimentation of the solid content in the positive electrode slurry can be suppressed and the binder does not easily enter the pores of the positive electrode active material. When the positive electrode precursor is formed, the added binder can efficiently bind the constituent members of the positive electrode precursor to each other. Further, even if the pores remaining after the alkali metal carbonate is removed after predoping are formed in the electrode, the molecular chain of the binder is long, so that high peel strength can be ensured. If the weight average molecular weight of the binder is 1,800,000 or less, the insulating binder does not inhibit the ingress and egress and diffusion of ions into the positive electrode active material when incorporated into a non-aqueous hybrid capacitor. , High input / output characteristics are expressed. In addition, pre-doping is promoted because the diffusion of alkali metal ions derived from the oxidative decomposition of alkali metal carbonate is promoted during pre-doping.

Since the positive electrode slurry in the present embodiment contains an alkali metal carbonate, the positive electrode slurry may be alkaline due to the alkali metal carbonate. If the positive electrode slurry is alkaline, the binder may crosslink, gel, or the like, and the molecular weight of the binder may decrease. Therefore, in the present specification, the weight average molecular weight of the binder in the positive electrode slurry means the weight average molecular weight of the binder contained in the produced positive electrode slurry. As the binder, it is preferable that the binder has strong alkali resistance, that is, it does not denature even when added to an alkaline solution (for example, the molecular weight does not decrease).

(Rubber polymer)
When a rubber-based polymer is contained as the binder of the positive electrode slurry of the present embodiment, examples of the rubber-based polymer include a diene-based polymer, an acrylic-based polymer, and a fluororubber. A diene polymer or an acrylic polymer is preferable from the viewpoint of high binding property and excellent electrode strength or flexibility. Among them, an acrylic polymer is more preferable from the viewpoint that it does not contain an unsaturated bond in the main chain of the polymer and has high electrochemical stability. The acrylic polymer is not particularly limited, but is preferably a polymer of an acrylic acid ester and / or a methacrylic acid ester, or a copolymer of a monomer copolymerizable with these.

As the binder of the positive electrode slurry of the present embodiment, the rubber-based polymer may contain fluorine, the fluorine-containing material and the rubber-based polymer may be used in combination, and the fluorine-containing material and the above-mentioned fluorine-containing material may be used in combination. It may be a composite particle of the rubber-based polymer.

The amount of the binder used in the positive electrode slurry is preferably 1% by mass or more and 30% by mass or less, more preferably 3% by mass or more and 27% by mass or less, still more preferably 5% by mass, based on 100% by mass of the positive electrode active material. It is 25% by mass or less. When the amount of the binder used is 1% by mass or more, sufficient electrode strength is exhibited. When the amount of the binder used is 30% by mass or less, it does not hinder the entry and exit and diffusion of ions into the positive electrode active material, exhibits high input / output characteristics, and is derived from oxidative decomposition of alkali metal carbonate during predoping. Pre-doping is also promoted because the diffusion of alkali metal ions is promoted.

[solvent]
The positive electrode slurry of this embodiment contains a solvent. The type of the solvent is not particularly limited, and an organic solvent-based medium and / or an aqueous medium is used, and the solvent is used properly according to the type of the binder.

(Organic solvent-based medium)
When an organic solvent-based medium is contained as the solvent of the positive electrode slurry of the present embodiment, N-methylpyrrolidone (NMP) is preferably contained in an amount of 50% by mass or more, preferably 70% by mass, based on the total mass of the solvent in the positive electrode slurry. It is more preferably contained in an amount of 90% by mass or more, and further preferably contained in an amount of 95% by mass or more.
When an organic solvent-based medium is included as the solvent, a liquid medium other than NMP may be contained. Examples of the liquid medium other than NMP include amide compounds, sulfoxides, ketones, ethers, esters, lactones, cyclic or chain carbonates, and the like, such as dimethylformamide, dimethylacetamide, dimethylsulfoxide, acetone, methylethylketone, and methylisobutylketone. , Cyclohexanone, tetrahydrofuran, 1,4-dioxane, ethyl acetate, butyl acetate and the like.

(Aqueous medium)
When an aqueous medium is contained as the solvent of the positive electrode slurry of the present embodiment, water is preferably contained in an amount of 50% by mass or more, more preferably 70% by mass or more, based on the total mass of the solvent in the positive electrode slurry. It is more preferably contained in an amount of 90% by mass or more, further preferably contained in an amount of 95% by mass or more, and most preferably 100% by mass. If the water content is 50% by mass or more, the solid content in the positive electrode slurry is unlikely to settle. The water used as the solvent for the positive electrode slurry is preferably ion-exchanged water or ultrapure water treated with an ion-exchange resin or a reverse osmosis membrane water purification system.

When an aqueous medium is included as the solvent, a non-aqueous liquid medium other than water may be contained. Examples of the non-aqueous liquid medium include amide compounds, hydrocarbons, alcohols, ketones, esters, amine compounds, lactones, sulfoxides, sulfone compounds and the like, preferably methanol, ethanol, propanol, isopropanol, n-butanol, and the like. It is an alcohol such as t-butanol, and one or more selected from these can be used.

[Arbitrary component of positive electrode slurry]
The positive electrode slurry in the present embodiment contains, if necessary, optional components such as a conductive filler, a dispersion stabilizer, and a pH adjuster in addition to a positive electrode active material, an alkali metal carbonate, a binder, and a solvent. May be good.

(Conductive filler)
The conductive filler is not particularly limited, and for example, acetylene black, ketjen black, vapor-grown carbon fibers, graphite, carbon nanotubes, and a mixture thereof can be used. The amount of the conductive filler used in the positive electrode slurry is preferably more than 0% by mass and 30% by mass or less, more preferably 0.01% by mass or more and 20% by mass or less, still more preferably 1 with respect to 100% by mass of the positive electrode active material. It is mass% or more and 15 mass% or less. The conductive filler promotes oxidative decomposition at the time of pre-doping by contacting with an alkali metal carbonate, and from the viewpoint of high input / output characteristics, the positive electrode slurry preferably contains the conductive filler. When the amount of the conductive filler used is 30% by mass or less, the content ratio of the positive electrode active material increases, so that the energy density per volume of the non-aqueous hybrid capacitor can be secured.

(Dispersion stabilizer)
The dispersion stabilizer is not particularly limited, and PVP (polyvinylpyrrolidone), PVA (polyvinyl alcohol), a cellulose derivative and the like can be used, and they are used properly according to the type of solvent. Examples of the cellulosic derivative include a cellulosic polymer or salts such as an ammonium salt or an alkali metal salt of the cellulosic polymer, and carboxymethyl cellulose is preferably used. The amount of the dispersion stabilizer used is preferably more than 0% by mass or 0.1% by mass or more and 10% by mass or less with respect to 100% by mass of the positive electrode active material. When the amount of the dispersion stabilizer used is 10% by mass or less, the solid content in the positive electrode slurry does not settle and the dispersion stability is excellent, and the input / output and diffusion of ions into the positive electrode active material are not hindered and the content is high. Output characteristics are expressed.

(PH regulator)
The positive electrode slurry in the present embodiment may exhibit alkalinity as described above, but under the condition that the positive electrode slurry exhibits strong alkalinity when the positive electrode precursor is produced as well as the decrease in the molecular weight of the binder, the positive electrode collection It is considered that the corrosion of the electric body is promoted and the life of the non-aqueous hybrid capacitor is shortened. Therefore, when the positive electrode slurry is alkaline, it is preferable to add a pH adjuster. The type of pH adjuster is not particularly limited, but either a strong acid or a weak acid can be used. The strong acid or weak acid may be an inorganic acid or an organic acid.

For example, examples of the inorganic acid include hydrochloric acid, nitric acid, sulfuric acid, phosphoric acid, carbonic acid and the like, and examples of the organic acid include acetic acid, oxalic acid and citric acid. Among them, it is preferable that the positive electrode precursor and / or the non-aqueous hybrid capacitor is decomposed or volatilized in the manufacturing process, and acetic acid, hydrochloric acid and the like can be mentioned. The amount of the pH adjuster used in the positive electrode slurry is preferably more than 0% by mass or 0.1% by mass or more and 1% by mass or less based on the total mass of the total solid content in the positive electrode slurry. When the amount of the pH adjuster used is 1% by mass or less, the residual pH adjuster is suppressed.

[Manufacturing of positive electrode slurry]
In the present embodiment, the positive electrode slurry for a non-aqueous hybrid capacitor can be produced by a technique for producing an electrode slurry in a known lithium ion battery, electric double layer capacitor, or the like. For example, a positive electrode active material, an alkali metal carbonate, and a binder, and other optional components used as necessary are dispersed or dissolved in a solvent to prepare a positive electrode slurry.

The positive electrode slurry may be a dry blend of some or all of various material powders containing the positive electrode active material, and then a solvent may be added, and / or a liquid in which a binder or a dispersion stabilizer is dissolved or dispersed. Alternatively, a slurry-like substance may be added to prepare the mixture. Alternatively, a positive electrode slurry may be prepared by adding various material powders containing a positive electrode active material to a liquid or slurry-like substance in which a binder or a dispersion stabilizer is dissolved or dispersed in a solvent. .. As a method of dry blending, for example, a positive electrode active material and an alkali metal carbonate are premixed using a ball mill or the like, and if necessary, a conductive filler is premixed, and the low conductive alkali metal carbonate is coated with the conductive filler. Premixing may be allowed. Premixing facilitates the decomposition of alkali metal carbonates in the positive electrode precursor in the predoping described below. When the positive electrode slurry becomes alkaline by adding an alkali metal carbonate, a pH adjuster is added as necessary.

The method for dispersing the positive electrode slurry is not particularly limited, and a homodisper or a multi-axis disperser, a planetary mixer, a disperser such as a thin film swirl type high-speed mixer, or the like can be preferably used. In order to obtain a positive electrode slurry in a good dispersed state, it is preferable to disperse at a peripheral speed of 1 m / s or more and 50 m / s or less. When the peripheral speed is 1 m / s or more, various materials are preferably dissolved or dispersed. When the peripheral speed is 50 m / s or less, various materials are less likely to be destroyed by heat or shearing force due to dispersion, and reaggregation is less likely to occur, which is preferable.

In the present embodiment, as described later, after assembling a non-aqueous hybrid capacitor, an alkali metal carbonate of the positive electrode precursor is applied by applying a voltage between the positive electrode precursor containing the alkali metal carbonate and the negative electrode. Is decomposed, and it is preferable that the negative electrode is pre-doped with alkali metal ions. At this time, it is very important that the alkali metal carbonate is uniformly decomposed in the positive electrode precursor. That is, the negative electrode potential spots are suppressed by the uniform progress of the pre-doping in the negative electrode, and the residue of the alkali metal carbonate that could not be completely decomposed in the positive electrode after the pre-doping is also suppressed, so that it is durable at high temperature. A non-aqueous hybrid capacitor having excellent properties can be obtained. Further, since the alkali metal carbonate is an insulator, if it exists as a residue in the positive electrode after predoping, it hinders the electron conduction of the positive electrode and causes a factor of lowering the input / output characteristics. Therefore, the alkali metal is contained in the positive electrode precursor. It is important that the carbonates are not localized and are evenly distributed. Here, in order to improve the uniformity in the positive electrode precursor, it is required that the solid content, particularly the alkali metal carbonate, is hard to settle even in the positive electrode slurry, and the dispersion uniformity is high.

The positive electrode slurry of this embodiment, based on the total weight of the positive electrode slurry, when the mass ratio of the total solid components except solvent and W _T% by weight, and 10 ≦ W _T ≦ 50. Preferably 45 or less as the upper limit of W _T, more preferably 40 or less, more preferably 35 or less. On the other hand, preferably 12.5 or more as the lower limit of the _{W T,} more preferably 15 or more. Upper and lower limits of the W _T can be combined arbitrarily.

If W _T is 10 or more, the freedom of movement of the particles or the polymer is a solid of the positive electrode slurry is suppressed, precipitation is suppressed, it can be maintained uniform dispersion. In addition, the process load of drying the coating film at the time of forming the positive electrode precursor and removing the solvent at the time of assembling the non-aqueous hybrid capacitor is reduced, so that the productivity can be maintained. On the other hand, if the W _T is 50 or less, it is possible controlled below a desired coating film thickness at the time of the positive electrode precursor formation, since the basis weight unevenness of the coating film surface can be suppressed, even when the non-aqueous hybrid capacitor built, alkali metal carbonate The decomposition uniformity of the salt is maintained, and the high temperature storage characteristics are excellent.

Further, in the positive electrode slurry of the present embodiment, the viscosities of the uppermost layer liquid and the lowermost layer liquid when the total volume of the positive electrode slurry in a state of being allowed to stand for 7 days after stirring in a container is divided into three in the height direction, respectively. When η _U and η _L (mPa · s), 0.50 ≦ η _U / η _L ≦ 1.00. The upper limit of η _U / η _L may be 0.98 or less or 0.95 or less, and _{the lower limit of η U} / η _L is preferably 0.60 or more, more preferably 0.70 or more. 0.80 or more is more preferable, and 0.85 or more is even more preferable. The upper and lower limits of _{η U} / η _{L can be arbitrarily combined.}

When η _U / η _L is 0.50 or more, the dispersion stability of the positive electrode slurry is high, the handling during storage becomes easy, and the constituent material of the positive electrode active material layer is used when forming the coating film of the positive electrode precursor. It can be evenly distributed in the thickness direction of the coating film, and is excellent in high input / output characteristics and high temperature storage characteristics when incorporated into a non-aqueous hybrid capacitor. On the other hand, when η _U / η _L is 1.00 or less, the solid content in the positive electrode slurry is sufficiently dispersed, and when the positive electrode precursor is incorporated into the non-aqueous hybrid capacitor, the alkali metal carbonate is sufficient by predoping. It is decomposed into high energy density and excellent high temperature storage characteristics.

_{The positive electrode slurry has ρ U} and ρ _L , respectively, when the total volume of the positive electrode slurry is divided into three in the height direction in a state where the positive electrode slurry is allowed to stand for 7 days after being stirred in a container. When (g / mL), it is preferable that _{0.60 ≤ ρ U} / ρ _{L ≤ 1.00, and the upper limit of ρ U} / ρ _L is 0.98 or less or 0.95 or less. Also, _{as the lower limit of ρ U} / ρ _L , 0.70 or more is more preferable, 0.80 or more is further preferable, and 0.85 or more is further preferable. The upper and lower limits of _{ρ U} / ρ _{L can be arbitrarily combined.}

When ρ _U / ρ _L is 0.60 or more, it is difficult for the dense alkali metal carbonate to settle in the positive electrode slurry, and the alkali metal carbonate is in the vicinity of the positive electrode current collector even when the coating film of the positive electrode precursor is formed. A non-aqueous hybrid capacitor that is not unevenly distributed and has both high input / output characteristics and excellent high-temperature storage characteristics can be obtained. On the other hand, when ρ _U / ρ _L is 1.00 or less, the solid content in the positive electrode slurry is sufficiently dispersed, the coating stability at the time of forming the positive electrode precursor is excellent, and the negative electrode is at the time of assembling the non-aqueous hybrid capacitor. Pre-doping of alkali metal ions to the electrode proceeds uniformly.

The viscosity (ηb) of the positive electrode slurry is preferably 1,000 mPa · s or more and 20,000 mPa · s or less, more preferably 1,500 mPa · s or more and 10,000 mPa · s or less, and further preferably 1,700 mPa · s or more. It is 5,000 mPa · s or less. When the viscosity (ηb) is 1,000 mPa · s or more, liquid dripping during coating film formation is suppressed, and the coating film width and thickness can be satisfactorily controlled. When the viscosity (ηb) is 20,000 mPa · s or less, the pressure loss in the flow path of the positive electrode slurry when using the coating machine is small and stable coating can be performed, and the coating film thickness can be controlled to be less than the desired thickness.

The TI value (thixotropy index value) of the positive electrode slurry is preferably 1.1 or more, more preferably 1.2 or more, and further preferably 1.5 or more. When the TI value is 1.1 or more, the coating film width and thickness can be satisfactorily controlled.

The dispersity of the positive electrode slurry is preferably such that the particle size measured by the grain gauge is 0.1 μm or more and 100 μm or less. The upper limit of the dispersity is more preferably a particle size of 80 μm or less, and further preferably a particle size of 50 μm or less. If the particle size is less than 0.1 μm, the size is equal to or smaller than the particle size of various material powders containing the positive electrode active material, and the material is crushed during the production of the positive electrode slurry, which is not preferable. When the particle size is 100 μm or less, the dispersion uniformity of the positive electrode slurry can be maintained, and clogging or streaks of the coating film are less likely to occur when the positive electrode slurry is discharged, so that stable coating can be performed.

<Positive electrode precursor>
The positive electrode precursor according to the present embodiment may be simply referred to as an electrode before pre-doping, a one-sided electrode before pre-doping, a half cell, a coating electrode, a dry electrode, or the like, depending on the desired configuration of the non-aqueous hybrid capacitor.
The positive electrode slurry in the present embodiment is applied to, for example, one or both sides of the positive electrode current collector to form a coating film, which is dried to form a positive electrode active material layer on one or both sides of the positive electrode current collector. A positive electrode precursor having the above can be prepared.

[Positive electrode active material layer]
The positive electrode active material layer contained in the positive electrode precursor is composed of the total solid content excluding the solvent of the positive electrode slurry. That is, the positive electrode active material layer contains a positive electrode active material containing activated carbon, an alkali metal carbonate other than the positive electrode active material, and a binder, and other optional components such as a conductive filler, a dispersion stabilizer, and a pH adjuster. May include.

[Positive current collector]
The material constituting the positive electrode current collector in the present embodiment is not particularly limited as long as it is a material having high electron conductivity and is unlikely to deteriorate due to elution into an electrolytic solution and reaction with an electrolyte or ions, and is not particularly limited. Is preferable. As the metal foil as the positive electrode current collector, an aluminum foil is particularly preferable.

The positive electrode current collector may be a metal foil having no irregularities or through holes, a metal foil having irregularities subjected to embossing, chemical etching, electrolytic precipitation, blasting, etc., and expanded metal, punching metal, etc. A metal foil having through holes such as an etching foil may be used.
Among them, the positive electrode current collector is preferably a metal foil having no through hole. If there is no through hole, the manufacturing cost is low, the thin film can be easily formed, which contributes to high energy density, and the current collecting resistance can be lowered, so that high input / output characteristics can be obtained.

The thickness of the positive electrode current collector is not particularly limited as long as the shape and strength of the positive electrode can be sufficiently maintained, and is preferably 1 to 100 μm, for example.

[Manufacturing of positive electrode precursor]
In the present embodiment, the positive electrode precursor for a non-aqueous hybrid capacitor can be manufactured by a known electrode manufacturing technique in a lithium ion battery, an electric double layer capacitor, or the like. For example, a positive electrode precursor can be obtained by applying the positive electrode slurry on one side or both sides of a positive electrode current collector to form a coating film and drying the coating film. The obtained positive electrode precursor may be pressed to adjust the thickness or bulk density of the positive electrode active material layer.

The method for forming the coating film of the positive electrode precursor is not particularly limited, and a coating machine such as a die coater or a comma coater, a knife coater, or a gravure coating machine can be preferably used. The coating film may be formed by a single-layer coating or a multi-layer coating. In the case of multi-layer coating, the positive electrode slurry composition may be adjusted so that the content of the alkali metal carbonate in each layer of the coating film is different. The coating speed is preferably 0.1 m / min or more and 100 m / min or less, more preferably 0.5 m / min or more and 70 m / min or less, and further preferably 1 m / min or more and 50 m / min or less. If the coating speed is 0.1 m / min or more, stable coating can be performed. If the coating speed is 100 m / min or less, sufficient coating accuracy can be ensured.

The method for drying the coating film of the positive electrode precursor is not particularly limited, and a drying method such as hot air drying or infrared (IR) drying can be preferably used. The coating film may be dried at a single temperature, or may be dried at different temperatures in multiple stages. The coating film may be dried by combining a plurality of drying methods. The drying temperature is preferably 25 ° C. or higher and 200 ° C. or lower, more preferably 40 ° C. or higher and 180 ° C. or lower, and further preferably 50 ° C. or higher and 160 ° C. or lower. When the drying temperature is 25 ° C. or higher, the solvent in the coating film can be sufficiently volatilized. When the drying temperature is 200 ° C. or lower, it is possible to suppress cracking of the coating film due to rapid volatilization of the solvent or uneven distribution of the binder due to migration, and oxidation of the positive electrode current collector or the positive electrode active material layer.

The method for pressing the positive electrode precursor is not particularly limited, and a press machine such as a hydraulic press machine or a vacuum press machine can be preferably used. The thickness, bulk density and electrode strength of the positive electrode active material layer can be adjusted by the press pressure, the gap, and the surface temperature of the press portion, which will be described later.

The press pressure is preferably 0.5 kN / cm or more and 20 kN / cm or less, more preferably 1 kN / cm or more and 10 kN / cm or less, and further preferably 2 kN / cm or more and 7 kN / cm or less. When the press pressure is 0.5 kN / cm or more, the electrode strength can be sufficiently increased. When the press pressure is 20 kN / cm or less, the positive electrode precursor does not bend or wrinkle, and the desired positive electrode active material layer thickness or bulk density can be adjusted.

A person skilled in the art can set an arbitrary value for the gap between the press rolls according to the thickness of the positive electrode precursor after drying so as to have a desired thickness or bulk density of the positive electrode active material layer. Those skilled in the art can set the press speed to any speed at which the positive electrode precursor is unlikely to bend or wrinkle.

The surface temperature of the pressed portion may be room temperature, or the pressed portion may be heated if necessary. The lower limit of the surface temperature of the pressed portion at the time of heating is preferably a melting point of minus 60 ° C. or higher, more preferably minus 45 ° C. or higher, and even more preferably minus 30 ° C. or higher of the melting point of the binder to be used. The upper limit of the surface temperature of the pressed portion when heating is preferably the melting point of the binder used plus 50 ° C. or lower, more preferably the melting point plus 30 ° C. or lower, and further preferably the melting point plus 20 ° C. or lower. For example, when PVdF (polyvinylidene fluoride: melting point 150 ° C.) is used as the binder, the surface temperature of the pressed portion is preferably 90 ° C. or higher and 200 ° C. or lower, more preferably 105 ° C. or higher and 180 ° C. or lower, and further preferably 120 ° C. It is ℃ or more and 170 ℃ or less. When a styrene-butadiene copolymer (melting point 100 ° C.) is used as the binder, the surface temperature of the pressed portion is preferably 40 ° C. or higher and 150 ° C. or lower, more preferably 55 ° C. or higher and 130 ° C. or lower, and further preferably 70 ° C. It is ℃ or more and 120 ℃ or less.

The melting point of the binder can be determined from the endothermic peak position of DSC (Differential Scanning Calorimetry, differential scanning calorimetry). For example, using a differential scanning calorimeter "DSC7" manufactured by PerkinElmer, 10 mg of sample resin is set in a measurement cell, and the temperature rises from 30 ° C. to 250 ° C. at a heating rate of 10 ° C./min in a nitrogen gas atmosphere. The temperature is raised, and the endothermic peak temperature in the temperature raising process becomes the melting point.

The press may be performed a plurality of times while changing the conditions of the press pressure, the gap, the speed, and the surface temperature of the press portion.

The thickness of the positive electrode active material layer is preferably 20 μm or more and 200 μm or less, more preferably 25 μm or more and 100 μm or less, and further preferably 30 μm or more and 80 μm or less per one side of the positive electrode current collector. When the thickness of the positive electrode active material layer is 20 μm or more, sufficient charge / discharge capacity can be exhibited. When the thickness of the positive electrode active material layer is 200 μm or less, the ion diffusion resistance in the electrode can be kept low. Therefore, sufficient input / output characteristics can be obtained, the cell volume can be reduced, and therefore the energy density can be increased. The upper and lower limits of the thickness range of the positive electrode active material layer can be arbitrarily combined. In the present specification, the thickness of the positive electrode active material layer when the current collector has through holes or irregularities means the average value of the thickness per side of the portion of the current collector that does not have through holes or irregularities. ..

<Negative electrode>
The negative electrode generally has a negative electrode current collector and a negative electrode active material layer existing on one side or both sides of the negative electrode current collector.

[Negative electrode active material layer]
The negative electrode active material layer preferably contains a negative electrode active material capable of occluding and releasing alkali metal ions. The negative electrode active material layer may contain an optional component such as a conductive filler, a binder, and a dispersion stabilizer, if necessary, in addition to the negative electrode active material.

-Negative electrode active material-
As the negative electrode active material, a substance capable of occluding and releasing alkali metal ions can be used. Specific examples of the negative electrode active material include carbon materials, titanium oxides, silicon, silicon oxides, silicon alloys, silicon compounds, tin and tin compounds. The content of the carbon material with respect to the total mass of the negative electrode active material may be preferably 50% by mass or more, more preferably 70% by mass or more, or 100% by mass. From the viewpoint of obtaining a good effect when used in combination with other materials, the content of the carbon material is preferably, for example, 90% by mass or less, and may be 80% by mass or less. The upper and lower limits of the carbon material content range can be arbitrarily combined.

Examples of the carbon material include non-graphitizable carbon materials; easily graphitizable carbon materials; carbon black; carbon nanoparticles; activated carbon; artificial graphite; natural graphite; graphitized mesophase carbon globules; graphite whiskers; polyacene-based substances. Amorphous carbonaceous materials such as; carbonaceous materials obtained by heat-treating a carbonaceous material precursor; thermal decomposition products of furfuryl alcohol resin or novolak resin; fullerene; carbon nanophones; and composite carbon materials thereof. it can. The carbonaceous material precursor is not particularly limited as long as it becomes a carbonic material by heat treatment, and is, for example, petroleum-based pitch, coal-based pitch, mesocarbon microbeads, coke, and synthetic resin (for example, phenol). Resin, etc.).

-Arbitrary component of negative electrode active material layer-
If necessary, the negative electrode active material layer may contain an optional component such as a conductive filler, a binder, and a dispersion stabilizer in addition to the negative electrode active material.

The type of the conductive filler is not particularly limited, and examples thereof include acetylene black, ketjen black, and vapor-grown carbon fiber. The amount of the conductive filler used is preferably more than 0 parts by mass and 30 parts by mass or less, more preferably 0.01 parts by mass or more and 20 parts by mass or less, and further preferably 0.1 parts by mass with respect to 100 parts by mass of the negative electrode active material. More than 15 parts by mass or less.

The binder is not particularly limited, and for example, PVdF (polyvinylidene fluoride), PTFE (polytetrafluoroethylene), polyimide, latex, styrene-butadiene copolymer, fluororubber, acrylic polymer and the like can be used. it can. The amount of the binder used is preferably 1 part by mass or more and 30 parts by mass or less, more preferably 2 parts by mass or more and 27 parts by mass or less, and further preferably 3 parts by mass or more and 25 parts by mass with respect to 100 parts by mass of the negative electrode active material. It is less than a part. When the amount of the binder used is 1 part by mass or more, sufficient electrode strength is exhibited. On the other hand, when the amount of the binder used is 30 parts by mass or less, high input / output characteristics are exhibited without inhibiting the entry and exit of alkali metal ions into the negative electrode active material.

The dispersion stabilizer is not particularly limited, but for example, PVP (polyvinylpyrrolidone), PVA (polyvinyl alcohol), a cellulose derivative and the like can be used. The amount of the dispersion stabilizer used is preferably more than 0 parts by mass or 0.1 parts by mass or more and 10 parts by mass or less with respect to 100 parts by mass of the negative electrode active material. When the amount of the dispersion stabilizer used is 10 parts by mass or less, high input / output characteristics are exhibited without inhibiting the entry and exit of alkali metal ions into the negative electrode active material.

[Negative electrode current collector]
The material constituting the negative electrode current collector is preferably a metal foil having high electron conductivity and less likely to be deteriorated due to elution into an electrolytic solution and reaction with an electrolyte or ions. Such metal foil is not particularly limited, and examples thereof include aluminum foil, copper foil, nickel foil, and stainless steel foil. Copper foil is preferable as the negative electrode current collector in the non-aqueous hybrid capacitor.

The metal foil may be a metal foil having no irregularities or through holes, a metal foil having irregularities subjected to embossing, chemical etching, electrolytic precipitation, blasting, etc., expanded metal, punching metal, etching, etc. A metal foil having a through hole such as a foil may be used.
Among them, the negative electrode current collector is preferably a metal foil having no through hole. If there is no through hole, the manufacturing cost is low, the thin film can be easily formed, which contributes to high energy density, and the current collecting resistance can be lowered, so that high input / output characteristics can be obtained.

The thickness of the negative electrode current collector is not particularly limited as long as the shape and strength of the negative electrode can be sufficiently maintained, but is preferably 1 to 100 μm, for example.

[Manufacturing of negative electrode]
The negative electrode has a negative electrode active material layer on one side or both sides of the negative electrode current collector. In a typical embodiment, the negative electrode active material layer is fixed to the negative electrode current collector.

The negative electrode can be manufactured by a known electrode manufacturing technique in a lithium ion battery, an electric double layer capacitor, or the like. For example, various materials including a negative electrode active material are dispersed or dissolved in water or an organic solvent to prepare a slurry coating liquid, and this coating liquid is applied to one or both sides of a negative electrode current collector. A negative electrode can be obtained by forming a coating film and drying it. Further, the obtained negative electrode may be pressed to adjust the film thickness or bulk density of the negative electrode active material layer.

The thickness of the negative electrode active material layer is preferably 5 μm or more and 100 μm or less per side. When this thickness is 5 μm or more, no streaks or the like are generated when the negative electrode active material layer is applied, and the coatability is excellent. When this thickness is 100 μm or less, high energy density can be developed by reducing the cell volume. The upper and lower limits of the thickness range of the negative electrode active material layer can be arbitrarily combined. The thickness of the negative electrode active material layer when the current collector has through holes or irregularities means the average value of the thickness per side of the portion of the current collector that does not have through holes or irregularities.

The bulk density of the negative electrode active material layer is preferably 0.30 g / cm ³ or more and 1.8 g / cm ³ or less. When the bulk density is 0.30 g / cm ³ or more, sufficient strength can be maintained and sufficient conductivity between the negative electrode active materials can be exhibited. When the bulk density is 1.8 g / cm ³ or less, pores capable of sufficiently diffusing ions can be secured in the negative electrode active material layer.

<Separator>
The positive electrode precursor and the negative electrode can be laminated, laminated and wound through a separator to form an electrode laminate or an electrode wound body having a positive electrode precursor, a separator, and a negative electrode.

As the separator, a polyethylene microporous membrane or polypropylene microporous membrane used in a lithium ion secondary battery, a cellulose non-woven paper used in an electric double layer capacitor, or the like can be used. A film composed of organic or inorganic fine particles may be laminated on one side or both sides of these separators. Organic or inorganic fine particles may be contained inside the separator.

The thickness of the separator is preferably 5 μm or more and 35 μm or less. A thickness of 5 μm or more is preferable because self-discharge due to internal microshorts tends to be small. A thickness of 35 μm or less is preferable because the input / output characteristics of the non-aqueous hybrid capacitor tend to be high.

The thickness of the film composed of organic or inorganic fine particles is preferably 1 μm or more and 10 μm or less. A thickness of 1 μm or more is preferable because self-discharge due to internal microshorts tends to be small. A thickness of 10 μm or less is preferable because the input / output characteristics of the non-aqueous hybrid capacitor tend to be high.

<Exterior body>
As the exterior body, a metal can, a laminated film, or the like can be used. The metal can is preferably made of aluminum. As the laminated film, a film in which a metal foil and a resin film are laminated is preferable, and a three-layer structure composed of an outer layer resin film / metal foil / inner layer resin film is exemplified. The outer layer resin film is for preventing the metal foil from being damaged by contact or the like, and a resin such as nylon or polyester can be preferably used. The metal foil is for preventing the permeation of moisture and gas, and a foil of copper, aluminum, stainless steel or the like can be preferably used. The inner layer resin film protects the metal foil from the electrolytic solution stored inside and melts and seals the outer body at the time of heat sealing, and polyolefins, acid-modified polyolefins and the like can be preferably used.

<Non-aqueous electrolyte solution>
The electrolytic solution used for the non-aqueous hybrid capacitor is preferably a non-aqueous electrolytic solution. That is, the electrolytic solution contains a non-aqueous solvent. The non-aqueous electrolyte solution contains an alkali metal salt of 0.5 mol / L or more based on the total amount of the non-aqueous electrolyte solution. That is, the non-aqueous electrolyte solution contains an alkali metal salt as an electrolyte. Examples of the non-aqueous solvent contained in the non-aqueous electrolyte solution include cyclic carbonates typified by ethylene carbonate and propylene carbonate, and chain carbonates typified by dimethyl carbonate, diethyl carbonate, ethyl methyl carbonate and the like.

<< Manufacturing method of non-aqueous hybrid capacitor >>
<Assembly>
Typically, the positive electrode precursor and the negative electrode cut into a single-wafer shape are laminated via a separator to obtain an electrode laminate, and the positive electrode terminal and the negative electrode terminal are connected to the electrode laminate. Alternatively, the positive electrode precursor and the negative electrode are laminated and wound via a separator to obtain an electrode wound body, and the positive electrode terminal and the negative electrode terminal are connected to the electrode wound body. The shape of the electrode winding body may be cylindrical or flat.

The method of connecting the positive electrode terminal and the negative electrode terminal is not particularly limited, and a method such as resistance welding or ultrasonic welding can be used.

It is preferable that the electrode laminate or the electrode wound body to which the terminals are connected is dried to remove the residual solvent. It is not limited to the drying method, and is dried by vacuum drying or the like. The residual solvent is preferably 1.5% by mass or less per weight of the positive electrode active material layer or the negative electrode active material layer. If the residual solvent is more than 1.5% by mass, the solvent remains in the system and the self-discharge characteristics are deteriorated, which is not preferable.

The dried electrode laminate or electrode wound body is preferably stored in an exterior body typified by a metal can or a laminate film in a dry environment with a dew point of −40 ° C. or lower, leaving only one opening. It is preferable to seal it in a fresh state. If the dew point is higher than −40 ° C., water may adhere to the electrode laminate or the electrode winding body, and water may remain in the system, deteriorating the self-discharge characteristics. The sealing method of the outer body is not particularly limited, and a method such as heat sealing or impulse sealing can be used.

<Liquid injection, impregnation, sealing>
After assembly, the non-aqueous electrolyte solution is injected into the electrode laminate or electrode winding body housed in the exterior body. After pouring, it is desirable to sufficiently impregnate the positive electrode precursor, negative electrode, and separator with a non-aqueous electrolytic solution. When the electrolytic solution is not immersed in at least a part of the positive electrode precursor, the negative electrode, and the separator, the doping proceeds non-uniformly in the pre-doping described later, so that the resistance of the obtained non-aqueous hybrid capacitor increases or the resistance of the obtained non-aqueous hybrid capacitor increases. Durability is reduced. The impregnation method is not particularly limited. For example, a non-aqueous hybrid capacitor after injection is installed in a decompression chamber with the exterior body open, and the inside of the chamber is decompressed using a vacuum pump. A method of returning to atmospheric pressure or the like can be used. After impregnation, the non-aqueous hybrid capacitor with the outer body open is sealed while reducing the pressure.

<Pre-dope>
As a preferable predoping method, a voltage is applied between the positive electrode precursor and the negative electrode to decompose the alkali metal carbonate in the positive electrode precursor to release alkali metal ions, and the alkali metal ions are reduced at the negative electrode. As a result, a method of pre-doping the negative electrode active material layer with alkali metal ions can be mentioned.

_{In pre-doping, gas such as CO 2} is generated due to oxidative decomposition of alkali metal carbonate in the positive electrode precursor. Therefore, when applying a voltage, it is preferable to take measures to release the generated gas to the outside of the exterior body. As this means, for example, a method of applying a voltage with a part of the exterior body opened; a state in which an appropriate gas release means such as a gas vent valve or a gas permeable film is installed in advance on a part of the exterior body. A method of applying a voltage; etc. can be mentioned.

<Aging>
After completion of pre-doping, it is preferable to age the non-aqueous hybrid capacitor. During aging, the solvent in the electrolytic solution is decomposed at the negative electrode, and an alkali gold ion permeable solid polymer film is formed on the surface of the negative electrode.

The aging method is not particularly limited, but for example, a method of reacting a solvent in an electrolytic solution in a high temperature environment or the like can be used.

<Degassing>
After the aging is completed, it is preferable to further degas to surely remove the gas remaining in the electrolytic solution, the positive electrode, and the negative electrode. In a state where gas remains in at least a part of the electrolytic solution, the positive electrode, and the negative electrode, ionic conduction is inhibited, so that the resistance of the obtained non-aqueous hybrid capacitor increases.

The degassing method is not particularly limited, and for example, a method of installing a non-aqueous hybrid capacitor in a decompression chamber with the exterior body open and depressurizing the inside of the chamber using a vacuum pump is used. be able to.

<Characteristic evaluation of power storage element>
(Capacitance)
In the present specification, the capacitance F (F) is a value obtained by the following method.
First, in a constant temperature bath in which the cell corresponding to the non-aqueous hybrid capacitor is set to 25 ° C., constant current charging is performed until the current value of 2C reaches 3.8V, and then a constant voltage of 3.8V is applied. Constant voltage charging is performed for a total of 30 minutes. After that, let Q be the capacitance when constant current discharge is performed with a current value of 2C up to 2.2V. It means a value calculated by F = Q / (3.8-2.2) using the Q obtained here.

Here, the C rate of the current is the current value at which the discharge is completed in one hour when the constant current discharge is performed from the upper limit voltage to the lower limit voltage, which is referred to as 1C. In the present specification, 1C is the current value at which the discharge is completed in 1 hour when the constant current discharge is performed from the upper limit voltage of 3.8 V to the lower limit voltage of 2.2 V.

(Internal resistance)
In the present specification, the internal resistance Ra (Ω) is a value obtained by the following method.
First, a non-aqueous hybrid capacitor is charged with a constant current in a constant temperature bath set at 25 ° C. until it reaches 3.8 V with a current value of 20 C, and then a constant voltage charge with a constant voltage of 3.8 V is applied. For 30 minutes. Subsequently, a constant current discharge is performed up to 2.2 V with a current value of 20 C to obtain a discharge curve (time-voltage). In this discharge curve, when the voltage at the discharge time = 0 second obtained by extrapolating from the voltage values at the discharge times of 2 seconds and 4 seconds is set to Vo, the voltage drop ΔV = 3.8-. It is a value calculated by Vo and Ra = ΔV / (current value of 20C).

(Electric energy)
In the present specification, the electric energy E (Wh) is a value obtained by the following method.
Using the capacitance F (F) calculated by the method described above,
It refers to the value calculated by F × (3.8 ² -2.2 ^{2) / 2/3600.}

(volume)
The volume V (L) of the power storage element refers to the volume of the portion of the electrode laminate or the electrode wound body in which the positive electrode active material layer and the negative electrode active material layer are stacked and is housed by the exterior body.

For example, in the case of an electrode laminate or an electrode wound body housed by a laminate film, a region of the electrode laminate or the electrode wound body in which the positive electrode active material layer and the negative electrode active material layer are present is cup-molded. Although it is housed in the laminated film, the volume (V _x ) of this power storage element is the outer dimension length (l _x ) and outer dimension width (w _x ) of the cup-molded portion, and the storage including the laminated film. It is calculated by V _x = l _x x w _x x t _{x according} to the thickness of the element (t _x).

In the case of an electrode laminate or an electrode winding body housed in a square metal can, the volume of the power storage element is simply the volume of the outer dimension of the metal can. That is, the volume of the storage element _{(V y),} the outer dimensions length of the square of the metal can _{(l y)} to the outer dimension width _(w y), the outer dimensions thickness _{(t y), V y =} l y It is calculated by × w _y × t _y.

Even in the case of an electrode winding body housed in a cylindrical metal can, the volume of the power storage element in the outer dimension of the metal can is used. That is, the volume (V _z ) of this power storage element depends on the outer dimension radius (r) and the outer dimension length (l _z ) of the bottom surface or the upper surface of the cylindrical metal can, and V _z = 3.14 × r × r. It is calculated by × l _z.

[High temperature storage test]
In the present specification, the amount of gas generated during the high temperature storage test and the rate of increase in internal resistance at room temperature after the high temperature storage test are measured by the following methods:
First, the cell corresponding to the non-aqueous hybrid capacitor is charged with a constant current at a current value of 100 C until it reaches 4.0 V in a constant temperature bath set at 25 ° C., and then a constant voltage of 4.0 V is applied. Voltage charging is performed for 10 minutes. Then, the cell is stored in a 60 ° C environment, taken out from the 60 ° C environment every two weeks, charged to 4.0 V in the cell voltage in the above-mentioned charging step, and then the cell is stored again in the 60 ° C environment. .. This step is repeated, and the cell volume Va before the start of storage and the cell volume Vb 3 months after the storage test are measured by the Archimedes method. Let Vb-V be the amount of gas generated when stored for 3 months at a cell voltage of 4.0 V and an environmental temperature of 60 ° C.
When the resistance value obtained by using the same measurement method as the normal temperature internal resistance for the cell after the high temperature storage test is the normal temperature internal resistance Rb after the high temperature storage test, the normal temperature internal resistance before the start of the high temperature storage test The rate of increase in internal resistance at room temperature after the high-temperature storage test for Ra is calculated by Rb / Ra.

"Measuring method"
<BET specific surface area, mesopore amount, micropore amount, average pore diameter>
The BET specific surface area, the amount of mesopores, the amount of micropores, and the average pore diameter in the present embodiment are values obtained by the following methods, respectively. The sample is vacuum-dried at 200 ° C. for 24 hours, and the isotherms of adsorption and desorption are measured using nitrogen as an adsorbent. Using the isotherms on the adsorption side obtained here, the BET specific surface area is calculated by the BET multipoint method or the BET1 point method, the mesopore amount is calculated by the BJH method, and the micropore amount is calculated by the MP method.

The BJH method is a calculation method generally used for analysis of mesopores and was proposed by Barrett, Joiner, Hallenda et al. (E.P. Barrett, L.G. Joiner and P. Hallenda, J. Am. Chem. Soc., 73, 373 (1951)).

The MP method is a micropore volume, a micropore area, and a micropore using the "t-plot method" (BC Lippens, JH de Boer, J. Catalysis, 4319 (1965)). It means a method for obtaining the distribution of R. S. It is a method devised by Mikhair, Brunauer, and Bodor (RS Mikhair, S. Brunauer, EE Bodor, J. Colloid Interface Sci., 26, 45 (1968)).

The average pore diameter is obtained by dividing the total pore volume per mass of a sample obtained by measuring each equilibrium adsorption amount of nitrogen gas under each relative pressure under the liquid nitrogen temperature by the BET specific surface area. Refers to the thing.

<Viscosity and TI value>
The viscosity (ηb) and TI value in this embodiment are values obtained by the following methods, respectively. First, a stable viscosity (ηa) is obtained after measuring for 2 minutes or more under the conditions of a temperature of 25 ° C. and a shear rate of 2s- ^{1 using an E-type viscometer.} The viscosity (ηb) measured under the same conditions as above is obtained except that the shear rate is ^{changed to 20s -1.} Using the viscosity value obtained above, the TI value is calculated by the formula TI value = ηa / ηb. When increasing the shear rate from 2s ^-1 to 20s ^-1 , the shear rate may be increased in one step, or the shear rate may be increased in multiple steps within the above range, and the shear rate may be increased while appropriately acquiring the viscosity at the shear rate. You may let me.

<Viscosity ratio, density ratio>
The viscosity ratio η _U / η _L and the density ratio ρ _U / ρ _L in the present embodiment are values obtained by the following methods, respectively. Here, in the present invention, each of η _U , η _L , ρ _U , and ρ _L is obtained when the total volume of the positive electrode slurry in a state of being left to stand for 7 days after stirring in a container is divided into three in the height direction. It refers to the viscosity of the top layer liquid, the viscosity of the bottom layer liquid, the density of the top layer liquid, and the density of the bottom layer liquid.
To prepare the measurement slurry sample, first, the container is filled with the slurry sample. At this time, the volume and shape of the container used for the measurement are particularly limited as long as the slurry can be uniformly agitated, can be allowed to stand stably, and the entire volume of the slurry can be divided into three without being mixed. Not done. For example, the volume of the container is preferably 50 mL or more and 100 L or less, the shape of the container is preferably substantially tubular, and more preferably cylindrical. The amount of slurry to be filled in the container is preferably 50% by volume or more and 90% by volume or less based on the total volume of the container.
Next, the slurry sample filled in the container is stirred using a stirrer in an environment of 25 ° C. so that the constituent materials in the slurry are uniformly dispersed. At this time, the stirring method is not particularly limited as long as the constituent materials in the slurry can be stirred uniformly without precipitation. For example, using the product name "Awatori Rentaro" manufactured by Shinky Co., Ltd. as a stirrer, the rotation speed is 1000 rpm for 2 minutes. Stir. After stirring, the slurry sample is allowed to stand in an environment of 25 ° C. for 7 days. After standing, the entire volume of the slurry sample is divided into three in the height direction and separated into the uppermost layer liquid, the intermediate layer liquid and the lowermost layer liquid. At this time, the dividing method is not particularly limited as long as the liquids of the divided layers can be separated without being mixed with each other.
The stable viscosities of the obtained top layer liquid and bottom layer liquid after being measured for 2 minutes or more under the conditions of a temperature of 25 ° C. and a shear rate of 20 s ^-1 _{using an E-type viscometer were measured as η U} and η U, respectively. Let η _L.

The densities of the obtained top layer liquid and bottom layer liquid are determined by the density measurement method using a specific gravity bottle specified in JIS Z8804. That is, a standard substance such as water is filled in the specific gravity bottle, and the mass B _{1 [g] of the empty specific gravity bottle at room temperature (temperature t ° C.) and the mass B 2} [g] of the specific gravity bottle containing the standard substance are measured. By doing so, the internal volume of the specific gravity bottle is first calibrated. Next, the specific gravity bottle is filled with the sample liquid, and the mass B ₃ [g] of the specific gravity bottle containing the sample liquid at room temperature (temperature t ° C.) is measured. At this time, it is preferable to defoam by a depressurization operation, a vibration operation, or the like so that bubbles do not enter the sample liquid in the specific gravity bottle. _{The density ρ t} [g / mL] of the sample liquid at the temperature t ° C. can be obtained by using the following formula (1).
ρ _t = (B _3- B ₁ ) / (B _2- B ₁ ) × (ρ _s −ρ _air ) + ρ _air equation (1)
{Here, ρ _s ; the density of the standard substance at a temperature of t ° C. [g / mL], ρ _air ; the density of air in the measurement environment [g / mL]. }
Using the obtained top layer liquid and bottom layer liquid as sample liquids and using the above-mentioned density measurement method, ρ _U and ρ _L can be obtained, respectively.

<Dispersity>
The degree of dispersion in this embodiment is a value obtained by a degree of dispersion evaluation test using a grain gauge specified in JIS K5600. That is, a sufficient amount of sample is poured into the tip of the deeper groove of the grain gauge having a groove having a desired depth according to the size of the grain, and the sample is slightly overflowed from the groove. Place the scraper so that the long side of the scraper is parallel to the width direction of the gauge and the cutting edge is in contact with the deep tip of the groove of the grain gauge, and hold the scraper so that it is on the surface of the gauge, with respect to the long side direction of the groove. At right angles, pull the gauge surface at a uniform speed for 1 to 2 seconds to a groove depth of 0, and within 3 seconds after the end of pulling, shine light at an angle of 20 ° or more and 30 ° or less to observe. , Read the depth at which the grain appears in the groove of the grain gauge.

<Weight ratio of all solid components excluding solvent in slurry>
Method of measuring the weight ratio W _T of the total solid components except solvent in the slurry in this embodiment is not particularly limited, can be measured, for example, the following method. First, a slurry sample is prepared, and the total mass W ₁ [g] of the sample is measured. Next, the slurry sample is dried, the solvent is volatilized to obtain only the solid component, and the mass W ₂ [g] of all the solid components excluding the solvent is measured. The drying method and conditions are not particularly limited, but it is preferable that the drying is performed in multiple stages by combining air drying, vacuum drying, etc., the drying temperature is in the range of 60 to 200 ° C., and the residual solvent amount is 1% by mass or less. The condition of 0.5% by mass or less is more preferable. The amount of residual solvent can be quantified by using GC / MS (gas chromatograph mass spectrometry) when the solvent is an organic solvent-based medium, or by the Karl Fischer method when the solvent is an aqueous medium. By the above method, using the following equation (2), we can calculate the weight ratio W _T of the total solid components except solvent in the slurry.
W _T = W ₂ / W ₁ x 100 formula (2)

<Method of identifying alkali metal carbonates>
The method for identifying the alkali metal carbonate contained in the positive electrode slurry is not particularly limited. For example, in the state of the positive electrode precursor having a coating film formed on the positive electrode current collector, the following scanning electron microscope-energy dispersive X-ray analysis It can be identified by (SEM-EDX), micro Raman spectroscopy, and X-ray photoelectron spectroscopy (XPS). For the identification of the alkali metal carbonate, it is preferable to identify by combining a plurality of analysis methods described below.

In ion chromatography, anions can be identified by analyzing the water after washing the positive electrode precursor with distilled water.

If alkali metal carbonate cannot be identified by the above analysis method, other analysis methods include ⁷ Li-solid NMR, XRD (X-ray diffraction), TOF-SIMS (time-of-flight secondary ion mass spectrometry), and AES. Alkali metal carbonates can also be identified by using (Auger electron spectroscopy), TPD / MS (heat generation gas mass spectrometry), DSC (differential scanning calorific value analysis) and the like.

(SEM-EDX)
The alkali metal carbonate and the positive electrode active material can be identified by oxygen mapping using an SEM-EDX image on the surface of the positive electrode precursor measured at an observation magnification of 1000 to 4000 times. As a measurement example of the SEM-EDX image, the acceleration voltage is 10 kV, the emission current is 1 μA, the number of measurement pixels is 256 × 256 pixels, and the number of integrations is 50. In order to prevent the sample from being charged, gold, platinum, osmium or the like can be surface-treated by a method such as vacuum deposition or sputtering. As the measurement conditions of the SEM-EDX image, it is preferable to adjust the brightness and the contrast so that the brightness does not reach the maximum brightness and the average value of the brightness is in the range of 40% to 60%. Particles containing 50% or more of bright areas binarized with respect to the obtained oxygen mapping based on the average value of brightness are designated as alkali metal carbonates.

(Microscopic Raman spectroscopy)
The alkali metal carbonate and the positive electrode active material can be discriminated by Raman imaging of carbonate ions on the surface of the positive electrode precursor measured at an observation magnification of 1000 to 4000 times. As an example of measurement conditions, the excitation light is 532 nm, the excitation light intensity is 1%, the long operation of the objective lens is 50 times, the diffraction grating is 1800 gr / mm, the mapping method is point scanning (slit 65 mm, binning 5 fix), 1 mm step, The exposure time per point can be measured for 3 seconds, the number of integrations can be measured once, and the measurement can be performed under the condition of having a noise filter. For the measured Raman spectrum ^{, a straight baseline is set in the range of 1071-1104 cm -1} , the area is calculated with a positive value from the baseline as the peak of carbonate ion, and the frequency is integrated. At this time, the noise component is added. The frequency for the bicarbonate peak area approximated by the Gaussian function is subtracted from the above frequency distribution of bicarbonate.

(XPS)
By analyzing the electronic state of the positive electrode precursor by XPS, the bonding state of the compound contained in the positive electrode precursor can be determined.

As an example of measurement conditions, the X-ray source is monochromatic AlKα, the X-ray beam diameter is 100 μmφ (25 W, 15 kV), the path energy is narrow scan: 58.70 eV, there is charge neutralization, and the number of sweeps is narrow scan: 10 times. (Carbon, oxygen) 20 times (fluorine) 30 times (phosphorus) 40 times (alkali metal) 50 times (silicon), energy steps can be measured under the conditions of narrow scan: 0.25 eV.

It is preferable to clean the surface of the positive electrode precursor by sputtering before measuring XPS. As the sputtering conditions, for example, the surface of the positive electrode precursor can be cleaned under the condition of an acceleration voltage of 1.0 kV, 2 mm × 2 mm for 1 minute ( _{1.25 nm / min in terms of SiO 2).}

About the obtained XPS spectrum
The peak of the binding energy of Li1s of 50 to 54 eV is LiO ₂ or Li-C bond,
Peaks of 55-60 eV are LiF, Li ₂ CO ₃ ,
Li _x PO _y F _z (in the formula, x, y, z are integers 1 to 6),
The peak of the binding energy of 285 eV of C1s is CC-bonded,
286eV peak is CO-bonded,
COO at the peak of 288eV,
The peak of 290 to 292 eV is CO ₃ ^2- , CF bond,
The peak of the binding energy of O1s of 527 to 530 eV is set to O ^2- (Li ₂ O),
Peaks of 531 to 532 eV are CO, CO ₃ , OH, PO _x (in the formula, x is an integer of 1 to 4), SiO _x (in the formula, x is an integer of 1 to 4),
The peak of 533 eV is CO, SiO _x (in the formula, x is an integer of 1 to 4),
The peak of the binding energy of F1s of 685 eV is LiF.
The peak of 687 eV C-F _bond, Li x _PO y _{F z} (wherein, x, y, z are an integer of 1 to 6), PF ₆ ^-,
Furthermore, regarding the binding energy of P2p,
The peak of 133 eV is PO _x (in the formula, x is an integer of 1 to 4),
Peaks of 134 to 136 eV are PF _x (in the formula, x is an integer of 1 to 6),
The peak of the binding energy 99eV of Si2p is Si, Silicide,
Peaks of 101-107 eV are Si _x O _y (in the formula, x and y are arbitrary integers)
Can be attributed as.

When the peaks of the obtained spectrum overlap, it is preferable to separate the peaks assuming a Gaussian function or a Lorentz function and assign the spectra. The existing alkali metal carbonate can be identified from the measurement result of the electronic state and the result of the existing element ratio obtained above.

(Ion chromatography)
By analyzing the distilled water washing solution of the positive electrode precursor by ion chromatography, the anion species eluted in water can be identified. As the column to be used, an ion exchange type, an ion exclusion type, and a reverse phase ion pair type can be used. As the detector, an electric conductivity detector, an ultraviolet-visible absorptiometric detector, an electrochemical detector, etc. can be used, and a suppressor method in which a suppressor is installed in front of the detector, or electricity without a suppressor. A non-suppressor method using a solution having low conductivity as an eluent can be used. Mass spectrometers and charged particle detectors can also be used in combination with detectors for measurement.

The retention time of the sample is constant for each ionic species component if conditions such as the column to be used and the eluent are determined, and the magnitude of the peak response differs for each ionic species but is proportional to the concentration. By measuring in advance a standard solution having a known concentration that ensures traceability, it is possible to qualitatively and quantify the ionic species components.

<Calculation of quantitative methods W _A alkali metal carbonates>
The method for quantifying the alkali metal carbonate contained in the positive electrode slurry is described below. In this embodiment, the weight ratio W _A alkali metal carbonate in the slurry, based on the total weight of all solid components except solvent. As a method of calculating the W _A from the solid components of the slurry, following water immersion method or combustion method is used, the water immersion method depending on the characteristics of the material other than an alkali metal carbonate contained in the solid component and / or The combustion method can be selected and may be used in combination. For example, if the binder and / or the dispersion stabilizer is water-insoluble, the water immersion method is preferably used, and if it is water-soluble, the combustion method is preferably used.

(Water immersion method)
The solid component of the positive electrode slurry is immersed in distilled water, and the alkali metal carbonate can be quantified from the weight change before and after the immersion. That is, in the same manner as the measuring method of the above-mentioned W _T, a slurry sample was dried, to evaporate the solvent to obtain only the solid component, measuring the mass W _{2 [g]} of the total solid components except solvent. Subsequently, in an environment of 25 ° C., the solid component is sufficiently immersed in distilled water 100 times the weight of the positive electrode slurry solid component (100 W ₂ [g]) for 3 days or more, and the alkali metal carbonate is eluted in the water. At this time, it is preferable to take measures such as covering the container so that the distilled water does not volatilize. After soaking for 3 days or more, the solid component is taken out from distilled water and vacuum dried. As the conditions for vacuum drying, for example, it is preferable that the residual water content in the solid component is 1% by mass or less in the range of temperature: 100 to 200 ° C., pressure: 0 to 10 kPa, and time: 5 to 20 hours. The residual amount of water can be quantified by the Karl Fischer method. The weight of the solid component after vacuum drying and W _{3 [g],} the weight ratio W _A alkali metal carbonate contained in the positive electrode slurry solids _[wt%] can be calculated by the following equation (3).
_{W A = (W 2 -W 3} ) / W 2 × 100 Equation (3)

(Combustion method)
The solid component of the positive electrode slurry is burned, and the alkali metal carbonate can be quantified from the weight change before and after combustion. That is, in the same manner as the measuring method of the above-mentioned W _T, a slurry sample was dried to obtain only the solid component to volatilize the solvent. Subsequently, this solid component is placed in a sample pan made of platinum, and a TG curve is obtained under the following conditions with a TG measuring device.
・ Gas: Atmospheric atmosphere or compressed air ・ Temperature rise rate: 0.5 ° C / min or less ・ Temperature range: 25 ° C to 500 ° C or more Melting point of alkali metal carbonate minus 50 ° C temperature or less 25 of the obtained TG curve The mass at ° C. is W ₂ [g] (mass of all solid components excluding the solvent), and _{the initial temperature at which the mass reduction rate becomes W 2} × 0.01 [g / min] or less at a temperature of 500 ° C. or higher. Let W ₄ [g] be the mass in.
All components other than alkali metal carbonates such as activated carbon, binder, and dispersion stabilizer contained in the positive electrode active material are oxidized and burned by heating at a temperature of 500 ° C or lower in an oxygen-containing atmosphere (for example, atmospheric atmosphere). To do. On the other hand, the mass of the alkali metal carbonate does not decrease up to the melting point of the alkali metal carbonate minus 50 ° C. even in an oxygen-containing atmosphere. Therefore, the weight ratio W _A alkali metal carbonate contained in the positive electrode slurry solids _[wt%] can be calculated by the following equation (4).
_{W A = W 4 / W 2} × 100 Equation (4)

<Method for quantifying alkali metal elements ICP-MS>
The solid component of the positive electrode slurry is acid-decomposed with a strong acid such as concentrated nitric acid, concentrated hydrochloric acid, and aqua regia, and the obtained solution is diluted with pure water so as to have an acid concentration of 2% to 3%. As for acid decomposition, it can be decomposed by heating and pressurizing as appropriate. The obtained diluted solution is analyzed by ICP-MS, and it is preferable to add a known amount of elements as an internal standard at this time. When the alkali metal element to be measured exceeds the upper limit concentration for measurement, it is preferable to further dilute the diluted solution while maintaining the acid concentration. With respect to the obtained measurement results, each element can be quantified based on a calibration curve prepared in advance using a standard solution for chemical analysis.

<Average particle size of alkali metal carbonate and positive electrode active material X ₁ and Y ₁ >
No particular limitation is imposed on the average measurement method of particle size X ₁ and Y ₁ of alkali metal carbonate and a positive electrode active material in the positive electrode slurry, for example in the state of the positive electrode precursors coating formed on the positive electrode current collector, the positive electrode It can be calculated from an image of a cross section of the precursor by a scanning electron microscope (SEM) and an image by a scanning electron microscope / energy dispersive X-ray spectroscopy (SEM-EDX). As a method for forming the positive electrode cross section, for example, BIB (Broad Ion Beam) processing for irradiating an Ar beam from the upper part of the positive electrode precursor to prepare a smooth cross section along the edge of the shielding plate installed directly above the sample can be used. it can. It is also possible to determine the distribution of carbonate ions by measuring Raman imaging of the cross section of the positive electrode precursor.

(Method of distinguishing between alkali metal carbonate and positive electrode active material)
The alkali metal carbonate and the positive electrode active material can be identified by oxygen mapping using an SEM-EDX image of a cross section of the positive electrode precursor measured at an observation magnification of 1000 to 4000 times. As for the measurement method conditions of the SEM-EDX image, it is preferable to adjust the brightness and the contrast so that the brightness does not reach the maximum brightness and the average value of the brightness is in the range of 40% to 60%. With respect to the obtained oxygen mapping, particles containing 50% or more of bright areas binarized based on the average value of brightness can be discriminated as alkali metal carbonates.

(Calculation method of _{X 1} and Y ₁₎
X ₁ and Y ₁ can be obtained by image analysis of images obtained from the cross section SEM-EDX measured in the same field of view as the positive electrode precursor cross section SEM. The alkali metal carbonate particles X and the other particles identified in the SEM image of the cross section of the positive electrode precursor are designated as the particles Y of the positive electrode active material, and all the particles of X and Y observed in the cross section SEM image are all. The cross-sectional area S is obtained, and the particle diameter d calculated by the following formula (5) is obtained.
d = 2 × (S / π) ^1/2 equation (5)
{In the formula, let the pi be π. }

Using the obtained particle size d, the volume average particle size X ₀ and Y ₀ are obtained in the following formula (6).
X ₀ (Y ₀ ) = Σ [4 / 3π × (d / 2)] ³ × d] / Σ [4 / 3π × (d / 2)] ³ ] Equation (6)

The field of view of the cross section of the positive electrode precursor is changed, and 5 or more points are measured, _{and the average value of X 0} and Y ₀ , respectively, is taken as the average particle size X ₁ and Y ₁ .

<Method of identifying binder>
The method for identifying the binder contained in the positive electrode slurry is not particularly limited. Examples of the method for identifying fluorine-containing substances include FT-IR (Fourier Transform Infrared Spectroscopy) measurement. Fluorine-containing substances can be identified by observing the CF absorption of the obtained IR spectrum. Other analytical ^methods, 19 F- by using a solid ^NMR, 19 F- solution NMR, etc., may also be used to identify binding agent. Further, as a method for identifying the rubber-based polymer, for example, Py-GC / MS (pyrolysis gas chromatograph mass spectrometry) measurement can be mentioned. For identification of the binder, it is preferable to identify by combining a plurality of analysis methods.

<Method of quantifying binder>
The method for quantifying the binder contained in the positive electrode slurry is not particularly limited, and can be measured by, for example, TG (thermogravimetric analysis). An example of a method for quantifying a binder when TG is used. The positive electrode slurry is air-dried and / or vacuum-dried to volatilize the solvent and obtain only the solid content. The obtained solid content can be scraped off into a platinum pan and heated at 2 to 10 ° C./min in an atmospheric atmosphere to quantify the binder contained in the positive electrode slurry solid content from the amount of weight loss. For example, in the case of PVdF, it can be judged by the amount of weight loss that decomposes in the region of 400 to 500 ° C. or lower in the atmospheric atmosphere.

If it is a method for quantifying a fluorine-containing substance, for example, the solid content obtained by volatilizing a solvent from a positive electrode slurry can be quantified from the amount of fluorinated ions by combustion ion chromatography by a tubular combustion method in the same manner as described above. For example, in the case of PVdF, the amount of PVdF can be calculated from the measured amount of fluorinated ion × 64 (CH ₂ CF _{2) / 38 (2F).}

Further, in the case of a method for quantifying a rubber-based polymer, for example, the solid content obtained by volatilizing the solvent from the positive electrode slurry is quantified by using Py-GC / MS (pyrolysis gas chromatograph mass spectrometry) measurement as described above. it can.
For the quantification of the binder, it is preferable to quantify by combining a plurality of analysis methods.

<Weight average molecular weight of binder>
The method for measuring the weight average molecular weight of the binder contained in the positive electrode slurry is not particularly limited, but it can be measured by, for example, GPC (gel permeation chromatography). A method for measuring the weight average molecular weight of the binder when GPC is used will be illustrated.

The positive electrode slurry is adjusted to a polymer concentration of about 1 mg / ml with an eluent such as DMF, then filtered through a filter, and the filtrate is used as a GPC measurement sample. If necessary, heating and pressurization may be performed to promote the dissolution of the binder.

The column used for GPC measurement is not particularly limited as long as the sample components can be efficiently separated. The detector is not particularly limited as long as the molecular weight of the sample can be measured with high sensitivity, but the average of the contained polymers is obtained by detecting the change in the refractive index due to the change in the solute component using an RI (differential refractometer) detector. Information on molecular weight or molecular weight distribution can be obtained. The weight average molecular weight of the polymer, which is a binder, is calculated by processing the data with the device.

In addition to the binder, another polymer such as a dispersion stabilizer may be mixed in the positive electrode slurry. It may be detected separately from the binder in the GPC measurement data, but even if it is difficult to separate from the binder, the weight average molecular weight of the binder and the dispersion stabilizer combined in the positive electrode slurry is the above-mentioned value. Is preferable.

Hereinafter, embodiments of the present invention will be specifically described with reference to Examples and Comparative Examples, however, the present invention is not limited to the following Examples and Comparative Examples.

<Preparation of positive electrode active material>
[Preparation of activated carbon 1]
The crushed coconut shell carbide was carbonized in nitrogen at 500 ° C. for 3 hours in a small carbonization furnace to obtain carbonized material. The obtained carbide was put into an activation furnace, and 1 kg / h of steam was introduced into the above-mentioned activation furnace in a state of being heated by the preheating furnace, and the temperature was raised to 900 ° C. for 8 hours for activation. The activated carbon was taken out and cooled in a nitrogen atmosphere to obtain activated activated carbon. The obtained activated carbon was washed with water for 10 hours and then drained. Activated carbon 1 was obtained by drying in an electric dryer maintained at 115 ° C. for 10 hours and then pulverizing with a ball mill for 1 hour.

The average particle size of this activated carbon 1 was 4.2 μm as a result of measuring the average particle size using a laser diffraction type particle size distribution measuring device (SALD-2000J) manufactured by Shimadzu Corporation. The pore distribution was measured using a pore distribution measuring device (AUTOSORB-1 AS-1-MP) manufactured by Yuasa Ionics. As a result, the BET specific surface area was 2360 m ² / g, the mesopore amount (V ₁ ) was 0.52 cc / g, the micro hole amount (V ₂ ) was 0.88 cc / g, and V ₁ / V ₂ = 0.59. there were.

[Preparation of activated carbon 2]
The crushed coconut shell carbide was carbonized in nitrogen at 550 ° C. for 3 hours in a small carbonization furnace to obtain carbonized material. The obtained carbide was put into an activation furnace, and 1 kg / h of steam was introduced into the above-mentioned activation furnace in a state of being heated in the preheating furnace, and the temperature was raised to 800 ° C. for 6 hours for activation. The activated carbon was taken out and cooled in a nitrogen atmosphere to obtain activated activated carbon. The obtained activated carbon was washed with water for 10 hours and then drained. Activated carbon 2 was obtained by drying in an electric dryer maintained at 115 ° C. for 10 hours and then pulverizing with a ball mill for 1 hour.

The average particle size of this activated carbon 2 was 8.8 μm as a result of measuring the average particle size using a laser diffraction type particle size distribution measuring device (SALD-2000J) manufactured by Shimadzu Corporation. The pore distribution was measured using a pore distribution measuring device (AUTOSORB-1 AS-1-MP) manufactured by Yuasa Ionics. As a result, the BET specific surface area was 1880 m ² / g, the mesopore amount (V ₁ ) was 0.33 cc / g, the micro hole amount (V ₂ ) was 0.80 cc / g, and V ₁ / V ₂ = 0.41. there were.

[Preparation of activated carbon 3]
The phenol resin was carbonized in a firing furnace at 600 ° C. for 2 hours in a nitrogen atmosphere, then pulverized with a ball mill and classified to obtain a carbide having an average particle size of 3.5 μm. This carbide and KOH were mixed at a mass ratio of 1: 4 and activated by heating in a firing furnace at 800 ° C. for 1 hour in a nitrogen atmosphere to obtain activated activated carbon. The obtained activated carbon was washed with stirring in dilute hydrochloric acid adjusted to a concentration of 2 mol / L for 1 hour, then boiled and washed with distilled water until it became stable at pH 5 to 6, and dried to obtain activated carbon 3. ..

The average particle size of this activated carbon 3 was measured using a laser diffraction type particle size distribution measuring device (SALD-2000J) manufactured by Shimadzu Corporation and found to be 3.4 μm. The pore distribution was measured using a pore distribution measuring device (AUTOSORB-1 AS-1-MP) manufactured by Yuasa Ionics. As a result, the BET specific surface area was 2612 m ² / g, the mesopore amount (V ₁ ) was 0.94 cc / g, the micro hole amount (V ₂ ) was 1.41 cc / g, and V ₁ / V ₂ = 0.67. there were.

[Preparation of activated carbon 4]
The phenol resin was carbonized in a firing furnace at 600 ° C. for 2 hours in a nitrogen atmosphere, then pulverized with a ball mill and classified to obtain a carbide having an average particle size of 7.0 μm. This carbide and KOH were mixed at a mass ratio of 1: 5 and activated by heating in a firing furnace at 800 ° C. for 1 hour in a nitrogen atmosphere to obtain activated activated carbon. The obtained activated carbon was washed with stirring in dilute hydrochloric acid adjusted to a concentration of 2 mol / L for 1 hour, then boiled and washed with distilled water until it became stable at pH 5 to 6, and dried to obtain activated carbon 4. ..

The average particle size of this activated carbon 4 was measured using a laser diffraction type particle size distribution measuring device (SALD-2000J) manufactured by Shimadzu Corporation and found to be 7.1 μm. The pore distribution was measured using a pore distribution measuring device (AUTOSORB-1 AS-1-MP) manufactured by Yuasa Ionics. As a result, the BET specific surface area was 3627 m ² / g, the mesopore amount (V ₁ ) was 1.50 cc / g, the micro hole amount (V ₂ ) was 2.28 cc / g, and V ₁ / V ₂ = 0.66. there were.

[Preparation of activated carbon 5]
The phenol resin was carbonized in a firing furnace at 600 ° C. for 2 hours in a nitrogen atmosphere, then pulverized with a ball mill and classified to obtain a carbide having an average particle size of 17.5 μm. This carbide and KOH were mixed at a mass ratio of 1: 4.5 and activated by heating in a firing furnace at 800 ° C. for 1 hour in a nitrogen atmosphere to obtain activated activated carbon. The obtained activated carbon was washed with stirring in dilute hydrochloric acid adjusted to a concentration of 2 mol / L for 1 hour, then boiled and washed with distilled water until it became stable at pH 5 to 6, and dried to obtain activated carbon 5. ..

The average particle size of the activated carbon 5 was measured using a laser diffraction type particle size distribution measuring device (SALD-2000J) manufactured by Shimadzu Corporation and found to be 17.7 μm. The pore distribution was measured using a pore distribution measuring device (AUTOSORB-1 AS-1-MP) manufactured by Yuasa Ionics. As a result, the BET specific surface area was 3130 m ² / g, the mesopore amount (V ₁ ) was 1.26 cc / g, the micro hole amount (V ₂ ) was 2.07 cc / g, and V ₁ / V ₂ = 0.61. there were.

<Manufacturing of positive electrode slurry>

[Manufacturing of positive electrode slurry (composition a)]
Using any one of the activated carbons 1 to 5 obtained above as the positive electrode active material, a positive electrode slurry (composition a) was produced by the following method.

Either one of the activated charcoal 1 or 2 is 55.5 parts by mass and the alkali metal carbonate is used, and lithium carbonate having the average molecular weight shown in Table 1 is 32.0 parts by mass or the compounding ratio shown in Table 1 is lithium carbonate. A total of 32.0 parts by mass of a mixture of sodium carbonate or potassium carbonate, 3.0 parts by mass of Ketjenblack, 1.5 parts by mass of PVP (polypolypyrrolidone), and either PVdF (polyvinylidene fluoride) 1 or 2. (PVdF1: Weight average molecular weight of raw material alone 1.18 million, PVdF2: Weight average molecular weight of raw material alone 1.92 million) is 8.0 parts by mass, and NMP (N-methylpyrrolidone) is the charged solid content weight ratio shown in Table 1. The mixture was mixed in an appropriate amount as described above, and the mixture was dispersed under the condition of a peripheral speed of 17.0 m / s using a thin film swirl type high-speed mixer fill mix manufactured by PRIMIX to obtain a positive electrode slurry (composition a).

[Manufacturing of positive electrode slurry (composition b)]
Any one of activated carbon 3 or 4 is 64.4 parts by mass, lithium carbonate is 21.1 parts by mass, Ketjen Black is 3.5 parts by mass, PVP is 1.7 parts by mass, and PVdF1 is 9.3 parts by mass. A positive electrode slurry (composition b) was obtained in the same manner as in the positive electrode slurry (composition a) except for the portion.

[Manufacturing of positive electrode slurry (composition c)]
Any one of activated carbon 3 or 5 is 71.7 parts by mass, lithium carbonate is 12.2 parts by mass, Ketjen Black is 3.9 parts by mass, PVP is 1.9 parts by mass, and PVdF1 is 10.3 parts by mass. A positive electrode slurry (composition c) was obtained in the same manner as in the positive electrode slurry (composition a) except for the portion.

[Manufacturing of positive electrode slurry (composition d)]
Positive electrode except that activated carbon 1 was 75.4 parts by mass, lithium carbonate was 7.6 parts by mass, Ketjen Black was 4.0 parts by mass, PVP was 2.0 parts by mass, and PVdF1 was 11.0 parts by mass. A positive electrode slurry (composition d) was obtained in the same manner as the slurry (composition a).

[Manufacturing of positive electrode slurry (composition e)]
Any one of activated carbon 2 or 3 is 43.1 parts by mass, lithium carbonate is 47.2 parts by mass, Ketjen Black is 2.3 parts by mass, PVP is 1.2 parts by mass, and PVdF1 is 6.2 parts by mass. A positive electrode slurry (composition e) was obtained in the same manner as in the positive electrode slurry (composition a) except for the portion.

[Manufacturing of positive electrode slurry (composition f)]
Positive electrode except that activated carbon 5 is 78.5 parts by mass, lithium carbonate is 3.9 parts by mass, Ketjen Black is 4.2 parts by mass, PVP is 2.1 parts by mass, and PVdF1 is 11.3 parts by mass. A positive electrode slurry (composition f) was obtained in the same manner as the slurry (composition a).

[Manufacturing of positive electrode slurry (composition g)]
Positive electrode except that activated carbon 2 is 30.8 parts by mass, lithium carbonate is 62.3 parts by mass, Ketjen Black is 1.7 parts by mass, PVP is 0.8 parts by mass, and PVdF1 is 4.4 parts by mass. A positive electrode slurry (composition g) was obtained in the same manner as the slurry (composition a).

[Manufacturing of positive electrode slurry (composition h)]
Using the activated carbon 1 obtained above as the positive electrode active material, a positive electrode slurry (composition h) was produced by the following method.

Activated carbon 1 is 61.2 parts by mass, alkali metal carbonate, lithium carbonate having an average particle size shown in Table 1 is 27.9 parts by mass, Ketjen black is 4.3 parts by mass, and CMC (carboxymethyl cellulose) is 3 parts. .3 parts by mass (added as an aqueous solution having a solid content equivalent value of 2% by mass in concentration) was mixed, and the mixture was kneaded using a kneader Hibismix manufactured by PRIMIX under the condition of 60 rpm. After that, either of the acrylic polymer 1 or 2 (acrylic polymer 1: average particle diameter 200 nm, acrylic polymer 2: average particle diameter 100 nm) was added to 3.3 parts by mass (solid content conversion value, concentration 40 mass). %), Acrylic and water were added in appropriate amounts so as to have the charged solid content weight ratio shown in Table 1, and kneaded under the condition of 20 rpm to obtain a positive electrode slurry (composition h).

[Manufacturing of positive electrode slurry (composition i)]
Activated carbon 5 was 73.8 parts by mass, lithium carbonate was 14.6 parts by mass, Ketjen Black was 4.8 parts by mass, CMC was 3.6 parts by mass, and acrylic polymer 1 was 3.2 parts by mass. A positive electrode slurry (composition i) was obtained in the same manner as the positive electrode slurry (composition h) except for the above.

[Manufacturing of positive electrode slurry (composition j)]
Activated carbon 5 was 82.6 parts by mass, lithium carbonate was 4.4 parts by mass, Ketjen Black was 5.4 parts by mass, CMC was 4.0 parts by mass, and acrylic polymer 1 was 3.6 parts by mass. A positive electrode slurry (composition j) was obtained in the same manner as the positive electrode slurry (composition h) except for the above.

[Manufacturing of positive electrode slurry (composition k)]
Activated carbon 1 was 39.7 parts by mass, lithium carbonate was 53.2 parts by mass, Ketjenblack was 2.7 parts by mass, CMC was 2.2 parts by mass, and acrylic polymer 1 was 2.2 parts by mass. A positive electrode slurry (composition k) was obtained in the same manner as the positive electrode slurry (composition h) except for the above.

<< Example 1 >>
<Manufacturing of positive electrode slurry>
Using activated carbon 1 and PVdF1, a positive electrode slurry 1 was obtained with the above composition a.

<Calculation of _{η U} / η _L and ρ _U / ρ _L>
A part of the positive electrode slurry 1 was taken in a container (volume 150 mL, cylindrical) in 100 mL, and stirred for 2 minutes at a rotation speed of 1000 rpm using the product name “Awatori Rentaro” manufactured by Shinky Co., Ltd. as a stirrer. After stirring, the slurry sample was allowed to stand in an environment of 25 ° C. for 7 days. After standing, the entire volume of the slurry sample was divided into three in the height direction and separated into the uppermost layer liquid 1, the intermediate layer liquid 1 and the lowermost layer liquid 1. The obtained top layer liquid 1 and bottom layer liquid 1 were measured using an E-type viscometer under the conditions of a temperature of 25 ° C. and a shear rate of 20 s ^-1 , and from the viscosities after 3 minutes, η _U and η _L. Asked. _{Further, with respect to the obtained upper layer liquid 1 and the lowermost layer liquid 1, the mass B 1} [g] of an empty specific gravity bottle was used at a temperature of 25 ° C. and pure water was used as a standard substance by the above-mentioned measurement method using a specific gravity bottle. _{And the mass B 2} [g] of the specific gravity bottle containing pure water was measured. Further placed sample liquid in the pycnometer, after vacuum degassing, by measuring the mass B _{3 [g]} of the specific gravity bottle containing a sample liquid, or more B _1, B ₂ and B ₃ from the above equation in accordance with (1) [rho _U and ρ _L were calculated. From the above η _U , η _L , ρ _U and ρ _L , η _U / η _L and ρ _U / ρ _L were calculated. The results obtained are shown in Table 1.

<Calculation of _{W T>}
A part of the positive electrode slurry 1 was weighed in a metal container, and the total mass W ₁ [g] of the slurry sample 1 was measured. Next, this metal container is placed in a hot air dryer, the slurry sample 1 is dried at 120 ° C. until the liquid surface gloss disappears, and further vacuum dried at 180 ° C. for 15 hours to obtain the slurry solid component sample 1. Was obtained, and the mass W ₂ [g] of all solid components excluding the solvent was measured. From _{W 1} and _{W 2} above was calculated _{W T} according to the above formula (2). The results obtained are shown in Table 1.

<Calculation of _{W A>}
(Water immersion method)
By impregnating the slurry solid component sample 1 with _{distilled water having a mass of 100 × W 2} [g] and maintaining it in an environment of 25 ° C. for 3 days, lithium carbonate in the slurry solid component sample 1 is made into distilled water. It was eluted in. The slurry solid component sample 1 was taken out and vacuum dried at 150 ° C. and 3 kPa for 12 hours. The weight W ₃ [g] at this time was measured. Was calculated _{W A} according to the above formula (3) from the above _{W 2} and _{W 3,} was 31.3 wt%. The results obtained by the water immersion method are shown in Table 1.

(Combustion method)
Using the above slurry solid component sample 1, TG measurement was carried out under the following conditions to obtain a TG curve.
・ Equipment: Hitachi High-Tech Science TG / DTA6200
-Gas: Compressed air (100 mL / min)
・ Temperature rise rate: 0.5 ° C / min
-Temperature range: 25 ° C to 550 ° C (melting point of lithium carbonate: 723 ° C)
_{W 2} and W ₄ were obtained from the obtained TG curve by the method described above. Was calculated _{W A} according to the above formula (4) from the above _{W 2} and _{W 4,} was 30.9 wt%.

<Calculation of weight average molecular weight of binder>
A part of the positive electrode slurry 1 is filtered through a filter, and DMF (5 mmol / L LiBr) is further added as an eluent to the obtained filtrate to adjust the polymer concentration to 1 mg / ml, and at 50 ° C. After heating for 7 hours, the mixture was allowed to stand overnight, and then filtered through a 0.2 μm filter, and a filtrate was used as a sample.

GPC measurement was performed on the obtained sample. The measurement conditions are described below.
(GPC measurement conditions)
-Measuring device: HLC-8220GPC manufactured by Tosoh (data processing: GPC-8020)
-Column: Shodex KF-606M, KF-601
・ Detector: RI
-Sample: 50 μl
・ Oven temperature: 40 ℃
-Calibration curve: PMMA
When the weight average molecular weight was calculated from the data obtained by the above measurement, it was 1.01 million.

<Manufacturing of positive electrode precursor>
The positive electrode slurry 1 is applied to one side and both sides of an aluminum foil having a thickness of 15 μm using a die coater manufactured by Toray Engineering Co., Ltd. at a coating speed of 1 m / s, dried at a drying temperature of 100 ° C., and then rolled pressed. Pressing was carried out using a machine under the conditions of a pressure of 4 kN / cm and a surface temperature of the press portion of 25 ° C. to obtain a double-sided positive electrode precursor 1 and a single-sided positive electrode precursor 1. The thickness of the positive electrode active material layer of the obtained double-sided and single-sided positive electrode precursor 1 was measured at any 10 locations of the double-sided and single-sided positive electrode precursor 1 using a film thickness meter Liner Gauge Sensor GS-551 manufactured by Ono Keiki Co., Ltd. It was obtained by subtracting the thickness of the aluminum foil from the average value of the thickness. As a result, the thickness of the positive electrode active material layer of the double-sided and single-sided positive electrode precursor 1 was 60 μm per one side.

<Calculation of _{X 1} and Y _1>
A small piece of 1 cm × 1 cm was cut out from the double-sided positive electrode precursor 1, and using SM-09020CP manufactured by JEOL Ltd., using argon gas, in the plane direction of the positive electrode precursor sample under the conditions of an acceleration voltage of 4 kV and a beam diameter of 500 μm. A vertical cross section was made. Gold was coated on the cross section by sputtering in a vacuum of 10 Pa. Subsequently, under the conditions shown below, SEM-EDX in the cross section of the positive electrode was measured under atmospheric exposure.
(SEM-EDX measurement conditions)
-Measuring device: Field emission scanning electron microscope FE-SEM S-4700 manufactured by Hitachi High-Technology
・ Acceleration voltage: 10kV
・ Emission current: 1 μA
・ Measurement magnification: 2000 times ・ Electron beam incident angle: 90 °
・ X-ray extraction angle: 30 °
・ Dead time: 15%
-Mapping elements: C, O, F
-Number of measurement pixels: 256 x 256 pixels-Measurement time: 60 sec.
-Number of integrations: 50 times-The brightness and contrast were adjusted so that there were no pixels that reached the maximum brightness and the average value of the brightness was within the range of 40% to 60%.
(Analysis of SEM-EDX)
_{X 1} and Y ₁ were calculated by analyzing the image obtained from the measured SEM-EDX of the positive electrode cross section by the method described above using image analysis software (ImageJ). The results are shown in Table 1.

<Preparation of negative electrode active material>
Made of stainless steel containing 150 g of commercially available artificial graphite with a BET specific surface area of 3.1 m ² / g and an average particle size of 4.8 μm in a stainless steel mesh cage and 15 g of carboniferous pitch (softening point: 50 ° C.). They were placed on a bat and both were installed in an electric furnace (effective dimensions in the furnace 300 mm × 300 mm × 300 mm). The temperature was raised to 1000 ° C. over 8 hours under a nitrogen atmosphere, and the temperature was maintained at the same temperature for 4 hours to cause a thermal reaction between the two to obtain a composite carbon material 1. Subsequently, after cooling to 60 ° C. by natural cooling, the composite carbon material 1 was taken out from the furnace.

The average particle size and BET specific surface area of the obtained composite carbon material 1 were measured by the same method as described above. As a result, the average particle size was 4.9 μm and the BET specific surface area was 6.1 m ² / g. The mass ratio of the carbonaceous material derived from coal-based pitch to artificial graphite was 2%.

<Manufacturing of negative electrode>
Using the composite carbon material 1 as the negative electrode active material, the negative electrode 1 was manufactured as follows.
80 parts by mass of composite carbon material 1, 8 parts by mass of acetylene black, 12 parts by mass of PVdF (polyvinylidene fluoride), and NMP (N-methylpyrrolidone) are mixed, and the mixture is a thin film swirl type manufactured by PRIMIX Corporation. A coating liquid was obtained by dispersing under the condition of a peripheral speed of 15 m / s using a high-speed mixer fill mix. The viscosity (ηb) and TI value of the obtained coating liquid were measured using an E-type viscometer TVE-35H manufactured by Toki Sangyo Co., Ltd. As a result, the viscosity (ηb) was 2,798 mPa · s, and the TI value was 2.7. The above coating liquid was applied to both sides of an electrolytic copper foil having a thickness of 10 μm using a die coater manufactured by Toray Engineering Co., Ltd. at a coating speed of 1 m / s, dried at a drying temperature of 85 ° C., and double-sided negative electrode 1 Got The obtained negative electrode 1 was pressed using a roll press machine under the conditions of a pressure of 4 kN / cm and a surface temperature of the pressed portion of 25 ° C. The thickness of the negative electrode active material layer of the negative electrode 1 obtained above was measured from the average value of the thickness measured at any 10 locations of the negative electrode 1 using a film thickness meter Linear Gauge Sensor GS-551 manufactured by Ono Keiki Co., Ltd., and copper was used. It was calculated by subtracting the thickness of the foil. As a result, the thickness of the negative electrode active material layer of the negative electrode 1 was 30 μm per one side.

<Preparation of non-aqueous electrolyte solution>
As the organic solvent, a mixed solvent of ethylene carbonate (EC): methyl ethyl carbonate (EMC) = 33: 67 (volume ratio) was used, and LiN (SO ₂ F) ₂ and LiPF ₆ were added to the obtained non-aqueous electrolyte solution. Each electrolyte salt is dissolved in a mixed solvent so that the concentration ratio is 75:25 (molar ratio) and _{the sum of the concentrations of LiN (SO 2} F) ₂ and LiPF _{6 is 1.2 mol / L.} A non-aqueous electrolyte solution was obtained.

_{The concentrations of LiN (SO 2} F) ₂ and LiPF _{6 in} the obtained non-aqueous electrolyte solution were 0.9 mol / L and 0.3 mol / L, respectively.

<Manufacturing of non-aqueous hybrid capacitors>
[Assembly and drying of power storage element]
The obtained double-sided positive electrode precursor 1, double-sided negative electrode 1, and single-sided positive electrode precursor 1 were cut into ^{10 cm × 10 cm (100 cm 2).} A single-sided positive electrode precursor 1 is used for the uppermost surface and the lowermost surface, 21 double-sided negative electrode 1s and 20 double-sided positive electrode precursors 1 are used, and a microporous film having a thickness of 15 μm is used between the negative electrode and the positive electrode precursor. Laminated with a separator in between. The negative electrode terminal and the positive electrode terminal were connected to the negative electrode and the positive electrode precursor by ultrasonic welding, respectively, to form an electrode laminate. This electrode laminate was vacuum dried at a temperature of 80 ° C. and a pressure of 50 Pa under the conditions of a drying time of 60 hr. The dried electrode laminate is housed in an exterior body made of aluminum laminate packaging material in a dry environment with a dew point of −45 ° C., and the electrode terminals and the bottom exterior body are placed at a temperature of 180 ° C. and a sealing time. Heat sealing was performed under the conditions of 20 sec and a sealing pressure of 1.0 MPa.

[Liquid injection, impregnation, sealing of power storage elements]
Approximately 80 g of the non-aqueous electrolyte solution is injected under atmospheric pressure into the electrode laminate housed in the aluminum laminate packaging material in a dry air environment with a temperature of 25 ° C and a dew point of -40 ° C or less, and pre-doped treatment is performed. The previous non-aqueous hybrid capacitor was formed. Subsequently, the non-aqueous hybrid capacitor was placed in the decompression chamber, the pressure was reduced from normal pressure to −87 kPa, the pressure was returned to atmospheric pressure, and the mixture was allowed to stand for 5 minutes. After reducing the pressure from normal pressure to −87 kPa, the operation of returning to atmospheric pressure was repeated four times, and then the power storage element was allowed to stand for 15 minutes. After reducing the pressure from normal pressure to -91 kPa, the pressure was returned to atmospheric pressure. Similarly, the operation of reducing the pressure and returning to the atmospheric pressure was repeated 7 times in total (the pressure was reduced from normal pressure to -95, -96, -97, -81, -97, -97, and -97 kPa, respectively). By the above procedure, the electrode laminate was impregnated with the non-aqueous electrolyte solution.

The exterior body containing the electrode laminate impregnated with the non-aqueous electrolyte solution was placed in a decompression sealing machine, and the pressure was reduced to -95 kPa, and the aluminum laminate was sealed at 180 ° C. for 10 seconds at a pressure of 0.1 MPa. The packaging material was sealed to obtain a non-aqueous hybrid capacitor.

[Pre-dope]
The obtained non-aqueous hybrid capacitor is constantly charged using a charging / discharging device (TOSCAT-3100U) manufactured by Toyo Systems Co., Ltd. in a 25 ° C environment at a current value of 0.5 A until a voltage of 4.5 V is reached. After that, the initial charge was continuously performed by a method of continuing 4.5 V constant voltage charging for 2 hours, and the negative electrode was pre-doped.

[aging]
After pre-doping the non-aqueous hybrid capacitor in a 25 ° C environment, constant current discharge is performed at 0.5 A until the voltage reaches 3.0 V, and then 3.0 V constant current discharge is performed for 1 hour to increase the voltage to 3.0 V. Adjusted to. Subsequently, the non-aqueous hybrid capacitor was stored in a constant temperature bath at 60 ° C. for 12 hours.

[gas releasing]
A part of the aluminum laminate packaging material of the non-aqueous hybrid capacitor after aging was opened in a dry air environment at a temperature of 25 ° C. and a dew point of −40 ° C. Subsequently, the non-aqueous hybrid capacitor was placed in the decompression chamber, and the pressure was reduced from atmospheric pressure to -80 kPa using a diaphragm pump (N816.3KT.45.18) manufactured by KNF for 3 minutes. The operation of multiplying and returning to atmospheric pressure was repeated a total of three times. A non-aqueous hybrid capacitor was placed in a vacuum sealing machine, the pressure was reduced to −90 kPa, and then the aluminum laminate packaging material was sealed by sealing at 200 ° C. for 10 seconds at a pressure of 0.1 MPa.

Through the above procedure, a non-aqueous hybrid capacitor was completed.

<Evaluation of non-aqueous hybrid capacitors>
[Measurement of capacitance and Ra / F]
With respect to the obtained non-aqueous hybrid capacitor, the capacitance F and 25 were obtained by the above-mentioned method using a charging / discharging device (5V, 360A) manufactured by Fujitsu Telecom Networks Limited in a constant temperature bath set at 25 ° C. The internal resistance Ra at ° C. was calculated, and Ra · F and energy density E / V were obtained. The results obtained are shown in Table 1.

[Gas generated after high temperature storage test]
The non-aqueous hybrid capacitor obtained in the above step was 4.0V at a current value of 100C using a charging / discharging device (5V, 360A) manufactured by Fujitsu Telecom Networks Limited in a constant temperature bath set at 25 ° C. It was charged with a constant current until it reached the above, and then a constant voltage charge of applying a constant voltage of 4.0 V was performed for a total of 10 minutes. After that, the non-aqueous hybrid capacitor is stored in a 60 ° C environment, taken out from the 60 ° C environment every two weeks, charged to 4.0 V in the cell voltage in the same charging process, and then the cell is placed in the 60 ° C environment again. Saved in. This step was repeated for 3 months, the cell volume Va before the start of the storage test and the cell volume Vb 3 months after the storage test were measured by the Archimedes method, and the amount of gas generated was determined by Vb-Va. The results obtained are shown in Table 1.

[Calculation of Rb / Ra]
For the non-aqueous hybrid capacitor after the high temperature storage test, the normal temperature internal resistance Rb after the high temperature storage test was calculated in the same manner as the above calculation of Ra and F. Rb / Ra was calculated by dividing this Rb (Ω) by the internal resistance Ra (Ω) before the high temperature storage test obtained by calculating Ra and F. The results obtained are shown in Table 1.

<< Examples 2 to 21 and Comparative Examples 1 to 3 >>
Examples were the same as in Example 1 except that the positive electrode active material of the positive electrode slurry, the type of alkali metal carbonate, the compounding ratio and the average particle size thereof, the composition, and the charged solid content weight ratio were set as shown in Table 1, respectively. Positive electrode slurries and non-aqueous hybrid capacitors of Comparative Examples 1 to 3 as well as 2 to 21 were prepared and evaluated in various ways. The obtained evaluation results are shown in Table 1.

<< Example 22 >>
The positive electrode slurry and the non-aqueous hybrid capacitor of Example 22 were prepared in the same manner as in Example 1 except that the binder of the positive electrode slurry was PVdF2, and various evaluations were performed. The obtained evaluation results are shown in Table 1. The weight average molecular weight of the binder contained in the positive electrode slurry was 1.7 million.

<< Example 23 >>
<Manufacturing of positive electrode slurry>
Using activated carbon 1 and an acrylic polymer 1, a positive electrode slurry 2 was obtained with the above composition h.

<Calculation of _{W A>}
(Combustion method)
A part of the positive electrode slurry 2 is weighed in a metal container, the metal container is placed in a hot air dryer, the slurry sample 1 is dried at 120 ° C. until the liquid surface gloss disappears, and vacuum is further applied at 180 ° C. for 15 hours. Using the slurry solid component sample 2 obtained by carrying out drying, TG measurement was carried out under the following conditions to obtain a TG curve.
・ Equipment: Hitachi High-Tech Science TG / DTA6200
-Gas: Compressed air (100 mL / min)
・ Temperature rise rate: 0.5 ° C / min
-Temperature range: 25 ° C to 550 ° C (melting point of lithium carbonate: 723 ° C)
_{W 2} and W ₄ were obtained from the obtained TG curve by the method described above. Was calculated _{W A} according to the above formula (4) from the above _{W 2} and _{W 4.} The results obtained by the combustion method are shown in Table 1.

The positive electrode slurry 2 of η _{U /} η _L, calculation of ρ _{U /} ρ _L and W _T in the same manner as in Example 1 was subjected to various evaluations. The obtained evaluation results are shown in Table 1.

<Manufacturing and evaluation of positive electrode precursors and non-aqueous hybrid capacitors>
The positive electrode precursor and the non-aqueous hybrid capacitor of Example 23 were prepared in the same manner as in Example 1 except that the drying temperature at the time of coating was set to 80 ° C. using the positive electrode slurry 2, and various evaluations were made. Was done. The obtained evaluation results are shown in Table 1.

<< Examples 24 to 27 and Comparative Examples 4 to 5 >>
Examples 24 to 24 are the same as in Example 23, except that the positive electrode active material of the positive electrode slurry, the average particle size of the alkali metal carbonate, the binder, the composition, and the charged solid content weight ratio are as shown in Table 1, respectively. The positive electrode slurry and the non-aqueous hybrid capacitor of Comparative Examples 4 to 5 of 27 and Comparative Examples 4 to 5 were prepared, respectively, and various evaluations were performed. The obtained evaluation results are shown in Table 1.

<< Comparative Example 6 >>
<Manufacturing of positive electrode slurry (composition l) and positive electrode precursor>
87.5 parts by mass of activated carbon 2, 3.0 parts by mass of Ketjen black, 1.5 parts by mass of PVP (polyvinylpyrrolidone), 8.0 parts by mass of PVdF1, and NMP (N-methylpyrrolidone). An appropriate amount is mixed so as to have the charged solid content weight ratio shown in 1, and the mixture is dispersed under the condition of a peripheral speed of 17 m / s using a thin film swirl type high-speed mixer fill mix manufactured by PRIMIX Co., Ltd. I got 3. The positive electrode slurry 3 is coated on one or both sides of an aluminum foil having a thickness of 15 μm using a die coater manufactured by Toray Engineering Co., Ltd. under a coating speed of 1 m / s, dried at a drying temperature of 100 ° C., and the positive electrode precursor 3 Got The obtained positive electrode precursor 3 was pressed using a roll press machine under the conditions of a pressure of 4 kN / cm and a surface temperature of the pressed portion of 25 ° C. The obtained positive electrode slurry 3 and positive electrode precursor 3 were evaluated in the same manner as in Example 1. The results are shown in Table 1.

<Manufacturing and evaluation of non-aqueous hybrid capacitors>
The same as in Example 1 except that the obtained positive electrode precursor 3 and a negative electrode in which a metallic lithium foil corresponding to 211 mAh / g per unit mass of the negative electrode active material is attached to the surface of the negative electrode active material layer of the negative electrode 1 are used. The non-aqueous hybrid capacitor was assembled, injected, impregnated, and sealed.

Next, as a pre-dope, the non-aqueous hybrid capacitor obtained above was stored in a constant temperature bath at an ambient temperature of 45 ° C. for 72 hours, and metallic lithium was ionized to dope the negative electrode 1. The obtained non-aqueous hybrid capacitor was aged and degassed in the same manner as in Example 1 to produce a non-aqueous hybrid capacitor, which was evaluated. The results are shown in Table 1.

<< Comparative Example 7 >>
<Manufacturing of positive electrode slurry (composition m) and positive electrode precursor>
88.4 parts by mass of activated carbon 5, 4.8 parts by mass of Ketjen black, and 3.6 parts by mass of CMC (added as an aqueous solution with a solid content equivalent value of 2% by mass), and the mixture was mixed by PRIMIX Corporation. The mixture was kneaded under the condition of 60 rpm using the kneader Hibismix manufactured by the same company. After that, 3.2 parts by mass of the acrylic polymer 1 (added as an aqueous dispersion having a solid content equivalent value of 40% by mass), and acetic acid and water were appropriately added so as to have the solid content weight ratio shown in Table 1. In addition, kneading was performed under the condition of 20 rpm to obtain a positive electrode slurry 4 having a composition m. The positive electrode slurry 4 is coated on one or both sides of an aluminum foil having a thickness of 15 μm using a die coater manufactured by Toray Engineering Co., Ltd. under a coating speed of 1 m / s, dried at a drying temperature of 80 ° C., and the positive electrode precursor 4 Got The obtained positive electrode precursor 4 was pressed using a roll press machine under the conditions of a pressure of 4 kN / cm and a surface temperature of the pressed portion of 25 ° C. The obtained positive electrode slurry 4 and positive electrode precursor 4 were evaluated in the same manner as in Example 23. The results are shown in Table 1.

<Manufacturing and evaluation of non-aqueous hybrid capacitors>
The same as in Example 23 except that the obtained positive electrode precursor 4 and a negative electrode in which a metallic lithium foil corresponding to 211 mAh / g per unit mass of the negative electrode active material is attached to the surface of the negative electrode active material layer of the negative electrode 1 are used. The non-aqueous hybrid capacitor was assembled, injected, impregnated, and sealed.

Next, as a pre-dope, the non-aqueous hybrid capacitor obtained above was stored in a constant temperature bath at an ambient temperature of 45 ° C. for 72 hours, and metallic lithium was ionized to dope the negative electrode 1. The obtained non-aqueous hybrid capacitor was aged and degassed in the same manner as in Example 23 to produce a non-aqueous hybrid capacitor, which was evaluated. The results are shown in Table 1.

In Examples 18 to 21 in Table 1, a mixture of lithium carbonate and sodium carbonate or a mixture of lithium carbonate and potassium carbonate was used as the alkali metal carbonate, and lithium carbonate and carbonic acid used in Examples 18 to 21 were used. Both sodium and potassium carbonate had an average particle size of 0.8 μm.

Further, in Table 1, the item "average particle size (μm)" is the average particle size at the time of preparation (that is, before dispersion), and the item "X ₁ (μm)" is after the slurry is completed (that is, dispersion). After and after the completion of the positive electrode precursor), the average particle size.

As described above, the alkali metal carbonate contained in the positive electrode slurry and the positive electrode precursor is decomposed, and the alkali metal ions that can participate in charging and discharging are pre-doped into the negative electrode or released into the electrolytic solution. Charging and discharging of non-aqueous hybrid capacitors will proceed.

As can be seen from the comparison of Examples 1 to 27 and Comparative Examples 1 to 7, a weight ratio W _{T (wt%)} is 10 ≦ W _T ≦ 50 of the total solid components except solvent of positive electrode slurry, the positive electrode slurry alkaline the weight ratio of metal carbonate W _{a (%} by weight) and is 5 ≦ W _a ≦ 50, when the 3 dividing the total volume of the positive electrode slurry in the height direction in a state allowing to stand after stirring for 7 days, the top layer solution And when the viscosity η _U and η _L (mPa · s) of _{the bottom layer liquid are 0.50 ≦ η U} / η _L ≦ 1.00, the positive electrode precursor in which the positive electrode slurry is coated on the positive electrode current collector is formed. Ra ・ F is small (internal resistance is low, that is, input / output characteristics are high), energy density E / V is high, and gas generation amount and Rb / Ra after high temperature storage test are small. It can be seen that a non-aqueous hybrid capacitor having low (excellent high-temperature storage characteristics) characteristics can be obtained.

Without being bound by theory, these are, if W _A is 5 or more, alkali metal ions capable of participating in the charge and discharge is sufficiently secured when incorporating the positive electrode precursor was coated film formed from the positive electrode slurry to a non-aqueous hybrid capacitor Therefore, it is considered that a non-aqueous hybrid capacitor having a high capacitance F and a high energy density can be obtained. Further, it is considered that a non-aqueous hybrid capacitor exhibiting high input / output characteristics can be obtained by forming appropriate pores remaining in the positive electrode after the alkali metal carbonate is oxidatively decomposed. If W _A is 50 or less, with pre-doping by the decomposition of alkali metal carbonate in the electron conductivity of the positive electrode precursor is increased is accelerated sufficiently proceeds, the positive electrode active material ratio in the positive electrode sufficient Therefore, it is considered that a non-aqueous hybrid capacitor with high energy density can be obtained.

If W _T is 10 or more, the precipitation of the particles or the polymer is a solid of the positive electrode slurry is suppressed, alkali metal carbonates are uniformly distributed without aggregation or segregation in the positive electrode precursor body, the positive electrode It is considered that a non-aqueous hybrid capacitor with high input / output can be obtained by ensuring the electron conductivity inside. Further, it is considered that a non-aqueous hybrid capacitor having a high energy density can be obtained because the alkali metal carbonate is efficiently decomposed, the predoping to the negative electrode proceeds sufficiently, and the negative electrode potential is sufficiently lowered. If W _T is 50 or less, because the basis weight plaques in the coating film surface when the cathode precursor formation can be suppressed, can remaining alkali metal carbonate after pre-doping or potential plaque suppression of negative electrode in the surface of the negative electrode, a high temperature It is considered that a non-aqueous hybrid capacitor having excellent storage characteristics can be obtained.

When η _U / η _L is 0.50 or more, the dispersion stability of the positive electrode slurry is high, and the constituent materials of the positive electrode active material layer are uniformly distributed in the coating film thickness direction when forming the coating film of the positive electrode precursor. It is considered that a non-aqueous hybrid capacitor exhibiting high input / output characteristics and excellent high temperature storage characteristics can be obtained. When η _U / η _L is 1.00 or less, the solid content in the positive electrode slurry is sufficiently dispersed, and when incorporated into a non-aqueous hybrid capacitor, the alkali metal carbonate is sufficiently decomposed by predoping, resulting in high energy. It is considered that a non-aqueous hybrid capacitor exhibiting high density and excellent high temperature storage characteristics can be obtained.

The positive electrode slurry of the present invention can be suitably used as a positive electrode slurry for a non-aqueous hybrid capacitor in, for example, in the field of hybrid drive systems for automobiles, assist applications for instantaneous power peaks, and the like. The non-aqueous hybrid capacitor of the present invention is preferable because the effect of the present invention is maximized when applied as a lithium ion capacitor.

Claims (15)

A slurry containing a positive electrode active material containing activated carbon, an alkali metal carbonate other than the positive electrode active material, a binder, and a solvent.
Based on the total weight of the slurry, the weight ratio of the total solid content excluding the solvent when the W _T mass%, a 10 ≦ W _T ≦ 50,
Based on the total weight of the total solid components of the slurry, when said mass ratio of the alkali metal carbonate and W _A mass%, 5 ≦ W is _A ≦ 50, and left stirring after 7 days in a container When the total mass of the slurry in the above state is divided into three in the height direction and the viscosities of the uppermost layer liquid and the lowermost layer liquid are η _U (mPa · s) and η _L (mPa · s), respectively, it is 0. .50 ≤ η _U / η _L ≤ 1.00 slurry. The densities of the top layer liquid and the bottom layer liquid when the total volume of the slurry was divided into three in the height direction in a state of being allowed to stand for 7 days after stirring in the container were ρ _U (g / mL) and ρ _{L, respectively.} The slurry according to claim 1, wherein when (g / mL) is set to (g / mL), 0.60 ≤ ρ _U / ρ _{L ≤ 1.00.} When the average particle size of the alkali metal carbonate is X ₁ , 0.1 μm ≤ X ₁ ≤ 10 μm, and when the average particle size of the positive electrode active material is Y ₁ , 2 μm ≤ Y ₁ ≤ 20 μm. , The slurry according to claim 1 or 2. The slurry according to claim 3, wherein X ₁ <Y ₁ in the average particle size X ₁ of the alkali metal carbonate and the average particle size Y _{1 of the positive electrode active material.} The slurry according to any one of claims 1 to 4, wherein the alkali metal carbonate is at least one selected from the group consisting of lithium carbonate, sodium carbonate, potassium carbonate, rubidium carbonate, and cesium carbonate. The slurry according to any one of claims 1 to 5, wherein the alkali metal carbonate contains 10% by mass or more of lithium carbonate. _{The activated carbon has a mesopore amount of V 1} (cc / g) derived from pores having a diameter of 20 Å or more and 500 Å or less calculated by the BJH method, and a micropore amount derived from pores having a diameter of less than 20 Å calculated by the MP method. When V ₂ (cc / g), 0.3 <V ₁ ≤ 0.8 and 0.5 ≤ V ₂ ≤ 1.0 are satisfied, and the specific surface area measured by the BET method is 1,500 m ² The slurry according to any one of claims 1 to 6, wherein the slurry is at least / g and at least 3,000 m ^{2 / g.} _{The activated carbon has a mesopore amount V 1} (cc / g) derived from pores having a diameter of 20 Å or more and 500 Å or less calculated by the BJH method _{satisfying 0.8 <V 1} ≤ 2.5, and a diameter calculated by the MP method. _{The amount of micropores V 2} (cc / g) derived from pores less than 20 Å _{satisfies 0.8 <V 2} ≤ 3.0, and the specific surface area measured by the BET method is 2,300 m ² / g or more 4 The slurry according to any one of claims 1 to 6, which is 000 m ^{2 / g or less.} The slurry according to any one of claims 1 to 8, wherein the binder contains a fluorine-containing substance, and the weight average molecular weight of the binder is 500,000 or more and 1,800,000 or less. The slurry according to claim 9, wherein the fluorine-containing material contains polyvinylidene fluoride. The slurry according to any one of claims 1 to 10, wherein the binder contains a rubber-based polymer. The slurry according to any one of claims 1 to 11, wherein the binder contains an acrylic polymer. The slurry according to any one of claims 1 to 12, which contains 50% by mass or more of N-methylpyrrolidone in the solvent. The slurry according to any one of claims 1 to 12, which contains 50% by mass or more of water in the solvent. The slurry according to any one of claims 1 to 14, which is used for manufacturing a positive electrode of a non-aqueous hybrid capacitor.