JP6657829B2 - Non-aqueous electrolyte storage element - Google Patents

Description

  The present invention relates to a non-aqueous electrolyte storage element.

  In recent years, non-aqueous electrolyte energy storage devices that can increase the energy density have become more widely used due to their improved characteristics as mobile devices have become smaller and more sophisticated. The development of excellent non-aqueous electrolyte energy storage devices has also been progressed, and their use in electric vehicles and the like has begun. As such a non-aqueous electrolyte energy storage device, a lithium ion secondary battery is often used.

  On the other hand, an electric double layer capacitor that can be charged and discharged at high speed without requiring a chemical reaction is used as a power storage element of a hybrid vehicle or the like. However, since the electric double layer capacitor has an energy density of several tens of minutes as compared with the lithium ion secondary battery, a heavy power storage element is required to secure a sufficient discharge capacity, and the electric double layer capacitor is mounted on an automobile. If so, it hindered fuel efficiency improvement.

  As a power storage element having both the high energy density of the lithium ion secondary battery and the high output characteristics of the electric double layer capacitor, a positive electrode containing activated carbon, a negative electrode containing graphite, and lithium ions using lithium ions as carrier ions Capacitors are receiving attention.

In the lithium ion capacitor, a negative electrode material capable of occluding and releasing lithium ions is doped in advance with lithium ions by a chemical method or the like, and by lowering the negative electrode potential, the withstand voltage is improved, and the energy density is increased. It can be significantly higher than a double layer capacitor. Further, it has been proposed to increase the energy density by using a mixed active material of lithium metal oxide particles such as lithium cobalt oxide (LiCoO ₂ ) or lithium iron phosphate (LiFePO ₄ ) and activated carbon particles as a positive electrode. (For example, see Patent Documents 1 and 2).

  An object of the present invention is to provide a non-aqueous electrolyte storage element having a high energy density, a small reduction rate of discharge capacity even when charge and discharge are repeated, and excellent in long-term cycle characteristics.

  The non-aqueous electrolyte energy storage device of the present invention as a means for solving the above problems, a positive electrode including a positive electrode active material capable of occluding and releasing anions, a negative electrode including a negative electrode active material, a non-aqueous electrolyte, Wherein the positive electrode active material contains carbon particles and lithium metal oxide particles, and the carbon particles have a plurality of pores forming a three-dimensional network structure. .

  Advantageous Effects of Invention According to the present invention, it is possible to provide a non-aqueous electrolyte energy storage device having a high energy density, a small decrease in discharge capacity even when charge and discharge are repeated, and excellent long-term cycle characteristics.

FIG. 1 is a schematic sectional view showing an example of the non-aqueous electrolyte energy storage device of the present invention. FIG. 2A is a schematic diagram illustrating an example of carbon particles in the nonaqueous electrolyte storage device of the present invention. FIG. 2B is a schematic diagram illustrating an example of activated carbon particles in a conventional nonaqueous electrolyte storage element. FIG. 3 is a diagram showing a 1C discharge curve in the first cycle, a 10C discharge curve in the second cycle, and a 10C discharge curve in the 1,000th cycle in Example 1. FIG. 4 is a diagram showing a 1C discharge curve in the first cycle, a 10C discharge curve in the second cycle, and a 10C discharge curve in the 1,000th cycle in Comparative Example 1. FIG. 5 is a diagram showing a 1C discharge curve in the first cycle, a 10C discharge curve in the second cycle, and a 10C discharge curve in the 1,000th cycle in Comparative Example 3.

(Non-aqueous electrolyte storage element)
The nonaqueous electrolyte energy storage device of the present invention has a positive electrode, a negative electrode, and a nonaqueous electrolyte, wherein the positive electrode has a positive electrode active material containing carbon particles and lithium metal oxide particles, The carbon particles have a plurality of pores forming a three-dimensional network structure, and further have other members as necessary.

According to the conventional technique, the positive electrode active material contains activated carbon particles having pores only on the surface as shown in FIG. 2B and lithium metal oxide particles, and 4 V (with respect to Li potential) for the purpose of obtaining a high energy density. When charge and discharge are repeated when the voltage is increased to a value close to the vicinity, a strong force acts on the anion in the direction of occlusion and release with respect to the pores of the activated carbon particles. For this reason, the anion having a diameter of 0.5 nm or more and 2 nm or less collides with the pores having a minimum diameter of about 1 nm on average, so that the pores are expanded, and the activated carbon particles are collapsed, thereby causing the collapse of the positive electrode. Would.
In the non-aqueous electrolyte energy storage device of the present invention, when the activated carbon particles are used as the positive electrode active material in the above-described conventional technology, when charge and discharge are repeated at a high voltage, the positive electrode collapses. For this reason, it is based on the finding that it is not possible to combine high energy density and excellent long-term cyclability with a small decrease rate of discharge capacity.
Further, in the non-aqueous electrolyte storage element of the present invention, in the prior art, since the specific surface area of the activated carbon particles is relatively large, when the voltage is high, the decomposition reaction of the electrolyte is further promoted and the electrolyte is deteriorated. It is based on the finding that it is not possible to combine high energy density and excellent long-term cyclability with a small rate of decrease in discharge capacity due to the fact that it is easy to make it easy.

The nonaqueous electrolyte energy storage device of the present invention is a device in which charge and discharge are repeatedly performed at a high voltage for the purpose of obtaining a high energy density, and a force in the direction of occlusion and release in the pores of the carbon particles strongly acts on anions. However, since the minimum diameter of the pores of the carbon particles is 2 nm or more and 50 nm or less in many cases, the anion is unlikely to collide with the pores of the carbon particles. Further, even if the anion collides with the pores of the carbon particles, the other pores relax the force applied to the pores of the carbon particles, so that the carbon particles are less likely to collapse.
Further, the carbon particles are provided with three-dimensionally connected pores extending from the surface toward the inside. However, since the specific surface area is smaller than that of the activated carbon particles, the decomposition reaction of the electrolytic solution is relatively small. Less likely.
Therefore, the high voltage has a high energy density by increasing the voltage, and even when charge and discharge are repeated at a high voltage, the collapse of the positive electrode and the deterioration of the electrolytic solution can be suppressed. It is possible to provide a non-aqueous electrolyte liquid storage element having excellent cyclability.
From the viewpoint of heat generation, in the conventional technology, the occlusion and release of anions with respect to the activated carbon particles accompany heat generation due to a decrease in enthalpy, and when rapid charge and discharge are repeated, lithium metal oxide particles Due to the high resistance, the deterioration of the non-aqueous electrolyte storage element becomes more serious as the temperature rises. On the other hand, in the present invention, since the pores forming the three-dimensional network structure of the carbon particles do not hinder the movement of the anion, even when used in combination with the lithium metal oxide particles, rapid charge and discharge (migration of the anion) generates heat. Hard to do. Therefore, it is possible to provide a non-aqueous electrolyte storage element having a small rate of decrease in discharge capacity even with rapid repetition of charge and discharge, and having excellent long-term cycle characteristics.

<Positive electrode>
The positive electrode is not particularly limited as long as it contains a positive electrode active material, and can be appropriately selected depending on the intended purpose. For example, a positive electrode provided with a positive electrode material containing the positive electrode active material on a positive electrode current collector Is mentioned.
The shape of the positive electrode is not particularly limited and can be appropriately selected depending on the purpose. Examples thereof include a flat plate shape.

<< Positive electrode material >>
The positive electrode material includes the positive electrode active material, and further includes a conductive additive, a binder, a thickener, and the like, as necessary.

−Positive electrode active material−
The positive electrode active material can occlude and release anions and is not particularly limited as long as it contains carbon particles and lithium metal oxide particles, and can be appropriately selected depending on the purpose.

--- Carbon particles ---
The carbon particles are not particularly limited as long as they have a plurality of pores forming a three-dimensional network structure, and can be appropriately selected according to the purpose.
That the carbon particles have "a plurality of pores forming a three-dimensional network structure" means that the carbon particles have a plurality of pores on the surface and the inside of the carbon particles, and adjacent pores are connected to each other to three-dimensionally. It means a state in which a communication hole that is connected and has an opening on the surface is formed.
As a method for confirming that the carbon particles have a plurality of pores forming a three-dimensional network structure, for example, a method of observing using SEM (Scanning Electron Microscope), TEM (Transmission Electron Microscope) or the like can be mentioned. Can be A cross section of the carbon particles having the “plurality of pores forming a three-dimensional network structure” can be shown as a schematic cross-sectional view of FIG. 2A created based on a TEM photograph. When the carbon particles have a plurality of pores forming a three-dimensional network structure, it is advantageous in that anions are easily inserted and released into and from the pores.

The carbon particles may have any of micropores having a minimum diameter of less than 2 nm and “mesopores” having a minimum diameter of 2 nm or more and 50 nm or less. The plurality of pores to be formed are preferably mesopores. When the pores of the carbon particles are mesopores, the diameter of the anion is 0.5 nm or more and 2 nm or less, and the minimum diameter of the mesopores is 2 nm or more and 50 nm or less. This is advantageous in that it is easily moved and occluded.
The direction of the opening of the pores in the carbon particles is not particularly limited and can be appropriately selected depending on the purpose. However, it is preferable that the carbon particles have no anisotropy and have isotropic properties. When the carbon particles have the isotropic property, it is advantageous in that anions can be occluded from various angles.

  The shape of the carbon particles is not particularly limited and may be appropriately selected depending on the purpose, but is preferably spherical.

As the BET specific surface area of the carbon particles is preferably 800 m ² / g or more 1,800 m ² / g or less, 900 meters ² / g or more 1,500 m ² / g or less is more preferable. When the BET specific surface area is within the preferred range, the amount of the pores formed is sufficient, and it is advantageous in that occlusion and release of anions can be sufficiently performed to increase the discharge capacity. Furthermore, as compared with the activated carbon particles, the reaction with the electrolytic solution can be reduced, so that decomposition of the electrolytic solution is less likely to be promoted, and a reduction in discharge capacity due to repeated charge and discharge is advantageous.
The BET specific surface area can be determined by a BET (Brunauer, Emmett, Teller) method from a measurement result of an adsorption isotherm by an automatic specific surface area / pore distribution measuring device (TriStarII3020, manufactured by Shimadzu Corporation), for example. it can.

The pore volume of the carbon particles is preferably from 0.2 mL / g to 2.3 mL / g, and more preferably from 0.5 mL / g to 2.3 mL / g. When the pore volume is 0.2 mL / g or more, the mesopores rarely become independent pores, and a large discharge capacity can be obtained without hindering the movement of anions. On the other hand, if the pore volume of the carbon particles is 2.3 mL / g or less, the carbon structure does not become bulky, the energy density as an electrode is increased, and the discharge capacity per unit volume can be increased. In addition, the carbonaceous wall forming the pores is not thin, and the shape of the carbonaceous wall can be maintained even if occlusion and release of anions are repeated, which is advantageous in that the long-term cycle property is improved. .
The pore volume of the carbon particles can be determined, for example, by using the BJH (Barrett, Joyner, Hallender) method based on the measurement result of the adsorption isotherm by an automatic specific surface area / pore distribution measuring device (TriStarII3020, manufactured by Shimadzu Corporation). You can ask.

  Regarding the crystallinity of the carbon particles, it is not necessary that all of the carbonaceous material has a crystalline structure, and an amorphous structure may partially exist, or even if all of them have an amorphous structure. Good.

  As the carbon particles, appropriately manufactured ones or commercially available ones may be used. Examples of the commercially available products include Knobel (registered trademark) (manufactured by Toyo Tanso Co., Ltd.).

The method for producing the carbon particles is not particularly limited and can be appropriately selected depending on the intended purpose.For example, a reinforcing material having a three-dimensional network structure and an organic material as a carbon material forming source are formed by molding. After carbonization, a method of dissolving the muscle material with an acid or an alkali may, for example, be mentioned. In this case, the trace of the dissolution of the reinforcing material becomes a plurality of mesopores forming a three-dimensional network structure, and can be formed intentionally.
The reinforcing material is not particularly limited and may be appropriately selected depending on the purpose. Examples thereof include metals, metal oxides, metal salts, and metal-containing organic substances. Among them, those soluble in acids or alkalis are preferable.
The organic substance is not particularly limited as long as it can be carbonized, and can be appropriately selected depending on the purpose. In addition, since the organic substance emits a volatile substance at the time of carbonization, a micropore is formed as a trace of release, and it is difficult to produce carbon particles having no micropore.

--- Lithium metal oxide particles--
The lithium metal oxide particles are not particularly limited and may be appropriately selected depending on the purpose. Examples thereof include a lithium-containing transition metal oxide used as a positive electrode material of a lithium ion battery.
Examples of the lithium-containing transition metal oxide include lithium cobaltate (LiCoO ₂ ), lithium nickelate (LiNiO ₂ ), lithium manganate (LiMn ₂ O ₄ ), olivine-type lithium iron phosphate (LiFePO ₄ ), and Li Lithium manganese-cobalt-nickel ternary oxide (e.g., LiNi _1/3 Co _1/3 Mn _1/3 O ₂ ) which can be represented by a composition formula of _p Ni _x Co _y Mn _z O ₂ is exemplified. . These may be used alone or in combination of two or more. Among these, olivine-type lithium iron phosphate and lithium manganese-cobalt-nickel ternary oxide are preferred from the viewpoint of the rate characteristics at the time of rapid charge and discharge and the long-term cyclability with respect to repeated charge and discharge.

The median diameter (D50) according to the volume-based particle size distribution of the positive electrode active material is not particularly limited and may be appropriately selected depending on the purpose. The median diameter is preferably 30 μm or less, more preferably 10 μm or less. It is advantageous that the median diameter of the positive electrode active material is within the above-mentioned preferred range in that a large decrease in the volume density of the electrode can be suppressed.
The median diameter (D50) can be measured, for example, by a laser diffraction scattering particle size distribution measuring method.

  The mass ratio of the carbon particles to the lithium metal oxide particles (the carbon particles / the lithium metal oxide particles) is not particularly limited and may be appropriately selected depending on the intended purpose. / 5 or less, more preferably 60/40 or more and 80/20 or less. When the mass ratio is within the preferable range, it is advantageous in that the long-term cyclability is excellent and a decrease in discharge capacity can be suppressed.

-Conductive aid-
The conductive assistant is not particularly limited and may be appropriately selected depending on the purpose. Examples thereof include a metal material and a carbonaceous material.
Examples of the metal material include copper and aluminum.
Examples of the carbonaceous material include acetylene black and carbon nanotube.
These may be used alone or in combination of two or more.

-Binder and thickener-
The binder and the thickener are not particularly limited as long as they are stable to a solvent used for manufacturing an electrode, an electrolytic solution, and an applied potential, and can be appropriately selected depending on the purpose. , Fluorine-based binder, ethylene-propylene-butadiene rubber (EPBR), styrene-butadiene rubber (SBR), isoprene rubber, acrylate-based latex, carboxymethylcellulose (CMC), methylcellulose, hydroxymethylcellulose, ethylcellulose, polyacrylic acid, polyvinyl alcohol, Alginic acid, oxidized starch, starch phosphate, casein and the like can be mentioned.
Examples of the fluorine-based binder include polyvinylidene fluoride (PVDF) and polytetrafluoroethylene (PTFE).
These may be used alone or in combination of two or more.
Among these, a fluorine-based binder, an acrylate-based latex, and carboxymethyl cellulose (CMC) are preferred.

<< Positive electrode current collector >>
The shape of the positive electrode current collector is not particularly limited, and can be appropriately selected depending on the purpose.
The size of the positive electrode current collector is not particularly limited as long as it can be used for the non-aqueous electrolyte storage device, and can be appropriately selected depending on the purpose.
The material of the positive electrode current collector is formed of a conductive material, and is not particularly limited as long as it is stable to an applied potential, and can be appropriately selected depending on the purpose. Examples include steel, nickel, aluminum, titanium, and tantalum. Among these, stainless steel and aluminum are preferred.

<< Positive electrode manufacturing method >>
The method for producing the positive electrode is not particularly limited and can be appropriately selected depending on the intended purpose.For example, the positive electrode active material includes, as necessary, the binder, the thickener, the conductive agent, and a solvent. And applying a slurry-like positive electrode material onto the positive electrode current collector, followed by drying.
The solvent is not particularly limited and may be appropriately selected depending on the purpose. Examples thereof include an aqueous solvent and an organic solvent.
Examples of the aqueous solvent include water and alcohol.
Examples of the organic solvent include N-methyl-2-pyrrolidone (NMP), toluene and the like.
The positive electrode active material may be roll-formed as it is to form a sheet electrode, or may be formed into a pellet electrode by compression molding.

<Negative electrode>
The negative electrode is not particularly limited as long as it contains a negative electrode active material, and can be appropriately selected depending on the purpose. For example, a negative electrode provided with a negative electrode material containing the negative electrode active material on a negative electrode current collector And the like.
The shape of the negative electrode is not particularly limited and can be appropriately selected depending on the purpose. Examples thereof include a flat plate shape.

<< Negative electrode material >>
The negative electrode material includes the negative electrode active material, and further includes a conductive auxiliary, a binder, a thickener, and the like, as necessary.

-Negative electrode active material-
The negative electrode active material is not particularly limited as long as it can occlude and release cations in a nonaqueous solvent system, and can be appropriately selected depending on the intended purpose.For example, it can occlude and release lithium ions as cations. Examples include a carbonaceous material, a metal oxide, a metal or metal alloy that can be alloyed with lithium, a composite alloy compound of lithium and an alloy containing a metal that can be alloyed with lithium and lithium, and lithium metal nitride.
Examples of the metal oxide include antimony tin oxide and silicon monoxide.
Examples of the metal or metal alloy include lithium, aluminum, tin, silicon, and zinc.
Examples of the composite alloy compound with lithium include lithium titanate.
Examples of the lithium metal nitride include lithium cobalt nitride.
These may be used alone or in combination of two or more. Among these, the carbonaceous material is preferable from the viewpoint of safety and cost.
Note that lithium ions are widely used as the cation.

The carbonaceous material is not particularly limited and may be appropriately selected depending on the intended purpose. Examples thereof include graphite (graphite) and pyrolysates of organic substances under various pyrolysis conditions.
Examples of the graphite (graphite) include coke, artificial graphite, and natural graphite.
Among these, artificial graphite and natural graphite are preferred.

-Conductive aid-
As the conductive auxiliary, the same conductive auxiliary as the positive electrode active material can be used.

-Binder and thickener-
As the binder and the thickener, the same binder and the thickener as in the positive electrode active material can be used.
Among them, a fluorine-based binder, styrene-butadiene rubber (SBR), and carboxymethyl cellulose (CMC) are preferable.

<< Negative electrode current collector >>
The negative electrode current collector is not particularly limited and can be appropriately selected depending on the purpose.
The material of the negative electrode current collector is formed of a conductive material, and is not particularly limited as long as it is stable to an applied potential, and can be appropriately selected depending on the purpose. Examples include stainless steel, nickel, aluminum, and copper. Among these, stainless steel, copper, and aluminum are particularly preferred.
The shape of the current collector is not particularly limited, and can be appropriately selected depending on the purpose.
The size of the current collector is not particularly limited as long as it can be used for the nonaqueous electrolyte storage element, and can be appropriately selected depending on the purpose.

<< Negative electrode production method >>
The method for producing the negative electrode is not particularly limited and can be appropriately selected depending on the intended purpose.For example, the binder, the thickener, the conductive auxiliary agent, and the solvent may be added to the negative electrode active material as necessary. A method of applying a slurry-like negative electrode material onto the negative electrode current collector and drying the same; a method of forming the slurry-like negative electrode material as it is into a roll of a sheet electrode; And a method of forming a thin film of the negative electrode active material on the negative electrode current collector by vapor deposition, sputtering, plating, or the like.
As the solvent, the same solvent as in the method for producing the positive electrode can be used.

<Non-aqueous electrolyte>
The non-aqueous electrolyte is an electrolyte obtained by dissolving an electrolyte salt in a non-aqueous solvent.

<< non-aqueous solvent >>
The non-aqueous solvent is not particularly limited and may be appropriately selected depending on the purpose. Examples thereof include an aprotic organic solvent, an ester organic solvent, and an ether organic solvent. These may be used alone or in combination of two or more. Of these, aprotic organic solvents are preferred.

Examples of the aprotic organic solvent include a carbonate-based organic solvent, and a low-viscosity solvent is preferable.
Examples of the carbonate-based organic solvent include a chain carbonate and a cyclic carbonate.
Among these, a chain carbonate is preferable in that it has a high dissolving power of the electrolyte salt.

Examples of the chain carbonate include dimethyl carbonate (DMC), diethyl carbonate (DEC), and methyl ethyl carbonate (EMC). These may be used alone or in combination of two or more. Among them, dimethyl carbonate (DMC) and methyl ethyl carbonate (EMC) are preferable.
In the case of using a mixed solvent obtained by combining dimethyl carbonate (DMC) and methyl ethyl carbonate (EMC), the mixing ratio of dimethyl carbonate (DMC) and methyl ethyl carbonate (EMC) is not particularly limited, and may be selected depending on the purpose. It can be selected as appropriate.

Examples of the cyclic carbonate include propylene carbonate (PC), ethylene carbonate (EC), butylene carbonate (BC), vinylene carbonate (VC), and fluoroethylene carbonate (FEC). These may be used alone or in combination of two or more. Among these, propylene carbonate (PC) and ethylene carbonate (EC) are preferred.
When a mixed solvent of ethylene carbonate (EC) as the cyclic carbonate and dimethyl carbonate (DMC) as the chain carbonate is used, the mixing ratio of ethylene carbonate (EC) and dimethyl carbonate (DMC) is particularly preferable. There is no limitation, and it can be appropriately selected according to the purpose.

Examples of the ester organic solvent include a cyclic ester and a chain ester.
Examples of the cyclic ester include γ-butyrolactone (γBL), 2-methyl-γ-butyrolactone, acetyl-γ-butyrolactone, and γ-valerolactone.
Examples of the chain ester include alkyl propionate, dialkyl malonate, alkyl acetate, and alkyl formate.
Examples of the alkyl acetate include methyl acetate (MA) and ethyl acetate.
Examples of the alkyl formate include methyl formate (MF) and ethyl formate.

Examples of the ether organic solvent include a cyclic ether and a chain ether.
Examples of the cyclic ether include tetrahydrofuran, alkyltetrahydrofuran, alkoxytetrahydrofuran, dialkoxytetrahydrofuran, 1,3-dioxolan, alkyl-1,3-dioxolan, and 1,4-dioxolan.
Examples of the chain ether include 1,2-dimethoxyethane (DME), diethyl ether, ethylene glycol dialkyl ether, diethylene glycol dialkyl ether, triethylene glycol dialkyl ether, and tetraethylene glycol dialkyl ether.

<< electrolyte salt >>
As the electrolyte salt, a lithium salt is preferable. The lithium salt is not particularly limited as long as it dissolves in the non-aqueous solvent and exhibits high ionic conductivity. For example, lithium hexafluorophosphate (LiPF ₆ ), lithium perchlorate (LiClO ₄ ), Lithium chloride (LiCl), lithium borofluoride (LiBF ₄ ), lithium arsenide hexafluoride (LiAsF ₆ ), lithium trifluorometasulfonate (LiCF ₃ SO ₃ ), lithium bistrifluoromethylsulfonylimide (LiN (C ₂ F ₅ SO ₂ ) ₂ ) and lithium bis (fluoroethylsulfonylimide) (LiN (CF ₂ F ₅ SO ₂ ) ₂ ). These may be used alone or in combination of two or more. Among these, lithium hexafluorophosphate (LiPF ₆ ) and lithium borofluoride (LiBF ₄ ) are preferable from the viewpoint of the amount of occlusion of anions in the carbon electrode.

  The concentration of the electrolyte salt is not particularly limited and may be appropriately selected depending on the intended purpose. However, from the viewpoint of compatibility between the discharge capacity and the output, the concentration in the nonaqueous solvent is 0.5 mol / L to 6 mol / L. L or less is preferable, and 1 mol / L or more and 4 mol / L or less are more preferable.

<Other components>
The other members are not particularly limited and can be appropriately selected depending on the purpose. Examples thereof include a separator.

<< Separator >>
The separator is provided between the positive electrode and the negative electrode to prevent a short circuit between the positive electrode and the negative electrode.
The material, shape, size, and structure of the separator are not particularly limited, and can be appropriately selected depending on the purpose.
Examples of the material of the separator include kraft paper, vinylon-mixed paper, paper such as synthetic pulp-mixed paper, cellophane, polyethylene graft membrane, polyolefin nonwoven fabric such as polypropylene melt-blown nonwoven fabric, polyamide nonwoven fabric, glass fiber nonwoven fabric, and micropore membrane. No. Among them, those having a porosity of 50% or more are preferable from the viewpoint of holding the electrolytic solution.
As the shape of the separator, a nonwoven fabric having a high porosity is more preferable than a thin film type having micropores (micropores). The average thickness of the separator is preferably 20 μm or more from the viewpoint of preventing short circuit and retaining the electrolyte.
The size of the separator is not particularly limited as long as it can be used for the non-aqueous electrolyte storage element, and can be appropriately selected depending on the purpose.
The structure of the separator may be a single layer structure or a laminated structure.

<Non-aqueous electrolyte storage element manufacturing method>
The method for producing the non-aqueous electrolyte storage element of the present invention is not particularly limited and can be appropriately selected depending on the intended purpose. For example, the positive electrode, the negative electrode, and the non-aqueous electrolytic solution may be used as needed. And a method of assembling the used separator into an appropriate shape. Further, if necessary, other components such as an outer can can be used.

  The shape of the non-aqueous electrolyte energy storage device of the present invention is not particularly limited, and can be appropriately selected from various generally employed shapes according to the application. Examples of the shape include a cylinder type in which a sheet electrode and a separator are formed in a spiral shape, a cylinder type having an inside-out structure in which a pellet electrode and a separator are combined, and a coin type in which a pellet electrode and a separator are stacked.

<Application>
The non-aqueous electrolyte storage device of the present invention can be suitably used, for example, as a non-aqueous electrolyte secondary battery, a non-aqueous electrolyte capacitor, and the like.
The use of the non-aqueous electrolyte storage element is not particularly limited and can be used for various purposes, for example, a notebook computer, a pen input computer, a mobile computer, an electronic book player, a mobile phone, a mobile fax, a mobile copy, Portable printers, headphone stereos, video movies, LCD TVs, handy cleaners, portable CDs, minidiscs, transceivers, electronic organizers, calculators, memory cards, portable tape recorders, radios, motors, lighting fixtures, toys, game machines, watches, strobes , A power source for a camera, a backup power source, and the like.

Hereinafter, examples of the present invention will be described, but the present invention is not limited to these examples.
First, the formation state of pores in the carbon particles and the activated carbon particles used in each of Examples and Comparative Examples was confirmed, and the BET specific surface area and the pore volume were measured.

<Formation of pores of carbon particles and activated carbon particles>
In the carbon particles and the activated carbon particles used in each of the examples and comparative examples, the presence or absence of pores forming a three-dimensional network structure was observed by TEM (JEM-2100, manufactured by JEOL Ltd.), and evaluated based on the following criteria. did. The results are shown in Tables 1-1 to 4.
[Evaluation criteria]
：: pores forming a three-dimensional network structure as shown in FIG. 2A could be confirmed. ×: pores as shown in FIG. 2B, not pores forming a three-dimensional network structure as shown in FIG. 2A. It could be confirmed

<Measurement of BET specific surface area and pore volume of carbon particles and activated carbon particles>
The BET specific surface area of the carbon particles and the activated carbon particles used in each of the Examples and Comparative Examples was determined from the measurement results of the adsorption isotherm by an automatic specific surface area / pore distribution measuring device (TriStarII3020, manufactured by Shimadzu Corporation). (Brunauer, Emmett, Teller) method. The results are shown in Tables 1-1 to 4.
The pore volume of the carbon particles and the activated carbon particles was determined by using the BJH (Barrett, Joyner, Hallender) method from the measurement results of the adsorption isotherm used when the BET specific surface area was determined. The results are shown in Tables 1-1 to 4.

(Example 1)
<Preparation of positive electrode>
-Preparation of positive electrode active material-
The lithium metal oxide olivine type lithium iron phosphate as particles (LiFePO _4, manufactured by Hohsen Corporation), using carbon particles A (Kunoberu (registered trademark), manufactured by Toyo Tanso Co., Ltd.) as the carbon particles, olivine-type phosphate The mass ratio of carbon particles A to lithium iron oxide (carbon particles A / olivine-type lithium iron phosphate) was mixed using a planetary mixer (Hibismix 3D-2, manufactured by Primix Corporation) so as to be 70/30. To prepare a positive electrode active material.

-Preparation of positive electrode slurry-
The obtained positive electrode active material, acetylene black (denka black powder, manufactured by Denki Kagaku Kogyo KK) as the conductive aid, acrylate latex (TRD202A, manufactured by JSR Corporation) as the binder, and carboxyl as the thickener Methylcellulose (Daicel 1270, manufactured by Daicel Corporation) was mixed at a solid content of 100: 7.0: 2.9: 7.7, and water was added to adjust the viscosity to an appropriate value. A slurry was obtained.

-Preparation of positive electrode-
Next, the obtained positive electrode slurry was applied to one surface of an aluminum foil having an average thickness of 20 μm as the positive electrode current collector using a doctor blade. The average of the basis weight after drying (the mass of the carbon active material powder in the coated positive electrode) was 3.0 mg / cm ² . This was punched out to a diameter of 16 mm to obtain a positive electrode.

<Separator>
Two separators prepared by punching glass filter paper (GA100, manufactured by ADVANTEC) to a diameter of 16 mm were prepared.

<Preparation of negative electrode>
-Preparation of negative electrode slurry 1-
Artificial graphite (MAGD, manufactured by Hitachi Chemical Co., Ltd.) as the negative electrode active material, acetylene black (Denka black powder, manufactured by Denki Kagaku Kogyo Co., Ltd.) as the conductive aid, and styrene butadiene rubber (EX1215, electrochemical (Manufactured by Kogyo Co., Ltd.) and carboxymethyl cellulose (Daicel 2200, manufactured by Daicel Co., Ltd.) as the thickener so as to be 100: 5.0: 3.0: 2.0 by mass ratio of solid content. And water were added to adjust the viscosity to an appropriate value, and a negative electrode slurry 1 was obtained.

-Preparation of negative electrode-
Next, the obtained negative electrode slurry 1 was applied to one surface of a copper foil having an average thickness of 18 μm as the negative electrode current collector using a doctor blade. The average of the basis weight after drying (the mass of the carbon active material powder in the coated negative electrode) was 3.0 mg / cm ² . This was punched out to a diameter of 16 mm to obtain a negative electrode.

<Non-aqueous electrolyte>
As the non-aqueous electrolyte, propylene carbonate (PC): dimethyl carbonate (DMC): methyl ethyl carbonate (EMC) containing 1.8 mol / L LiPF ₆ electrolyte and 0.2 mol / L LiBF ₄ electrolyte A mixed solution (manufactured by Ube Industries, Ltd.) of 1: 1: 1 (mass ratio) was used.

<Manufacture of non-aqueous electrolyte storage element>
After vacuum drying the positive electrode, the negative electrode, and the separator at 150 ° C. for 4 hours, a 2032-type coin cell as a power storage element was assembled in a glove box in a dry argon atmosphere.
400 μL of the non-aqueous electrolyte was injected into the 2032 type coin cell.
Next, the negative electrode and the positive electrode of the 2032 type coin cell were short-circuited for two days, thereby doping lithium ions to the negative electrode side, thereby producing the non-aqueous electrolyte energy storage device of Example 1.
The obtained non-aqueous electrolyte storage device of Example 1 was subjected to a charge / discharge test as follows.

<Charging / discharging test>
The obtained non-aqueous electrolyte storage element of Example 1 was held in a thermostat at 25 ° C., and an automatic battery evaluation device (1024B-7V0.1A-4, manufactured by Electrofield Co., Ltd.) was used as follows. Was subjected to a charge / discharge test.
The first charge / discharge is performed as an aging process. After a constant current charge up to 4.2 V as a charge end voltage at a charge / discharge rate of 0.2 C as a aging process, the battery is paused for 24 hours, and at a charge / discharge rate of 1 C as a current value. A constant current discharge was performed to 1.8 V as a discharge end voltage. After the aging treatment, the following charge / discharge test was performed.
Note that the 0.2C-converted current value is a current value at which a non-aqueous electrolyte storage element having a capacity of a nominal capacity value is discharged at a constant current and discharge is completed in 5 hours. The 1C-converted current value is a current value at which a non-aqueous electrolyte storage element having a capacity of a nominal capacity value is discharged at a constant current and discharge is completed in one hour.
[1]: Constant current charge up to 4.2 V at a charge / discharge rate 1 C converted current value [2]: Pause for 5 minutes [3]: Constant current discharge up to 1.8 V at a charge / discharge rate 1 C converted current value [4] : Pause for 5 minutes [5]: Constant current charge up to 4.2 V at a charge / discharge rate of 10 C [6]: Pause for 5 minutes [7]: Constant current up to 1.8 V at a charge / discharge rate of 10 C Discharge [8]: Pause for 5 minutes [9]: The above [5] to [8] were defined as one cycle, and charging and discharging were repeated up to the 1,000th cycle.

While repeating the charge / discharge test up to the 1,000th cycle in the above charge / discharge test, the 1C discharge capacity in the first cycle after the aging treatment, the 10C discharge capacity in the rapid charge / discharge in the second cycle, and the 1,000th cycle Was measured at the time of rapid charge and discharge. The discharge capacity is a converted value (mAh / g) per 1 g of the positive electrode active material. FIG. 3 shows a 1C discharge curve in the first cycle, a 10C discharge curve in the second cycle, and a 10C discharge curve in the 1,000th cycle in Example 1.
The capacity retention rate at the time of rapid charge and discharge and the capacity retention rate at the time of 1,000 cycles were obtained from the following formulas. The results are shown in Table 1-1.

(Example 2)
Example 2 was repeated in the same manner as in Example 1 except that the negative electrode slurry 1 was replaced with the negative electrode slurry 2 prepared as described below, and the copper foil of the negative electrode current collector was replaced with an aluminum foil. Was manufactured.

-Preparation of negative electrode slurry 2-
Lithium titanate (LTO, manufactured by Ishihara Sangyo Co., Ltd.) as the negative electrode active material, acetylene black (Denka black powder, manufactured by Denki Kagaku Kogyo Co., Ltd.) as the conductive aid, and styrene butadiene rubber (TRD102A, JSR stock) as the binder Company) and carboxymethylcellulose (Daicel 2200, manufactured by Daicel Co., Ltd.) as the thickener so that the mass ratio of the solid content is 100: 7: 3: 1, and water is added to obtain an appropriate viscosity. And negative electrode slurry 2 was obtained.

  In Example 2, since lithium titanate was used as the negative electrode active material, the charge end voltage under the aging treatment and charge / discharge test conditions was changed from 4.2 V to 2.9 V, and the discharge end voltage was set at 1 Evaluation was performed in the same manner as in Example 1 except that the voltage was changed from 0.8 V to 0.5 V. The results are shown in Table 1-1.

(Comparative Example 1)
The non-aqueous electrolysis of Comparative Example 1 was performed in the same manner as in Example 1 except that the carbon particles A in the positive electrode active material were replaced with activated carbon particles (Bellfine AP, manufactured by AT Electrode Co., Ltd.). A liquid storage element was manufactured and evaluated in the same manner as in Example 1. The results are shown in Table 1-1. FIG. 4 shows a 1C discharge curve at the first cycle, a 10C discharge curve at the second cycle, and a 10C discharge curve at the 1,000th cycle in Comparative Example 1.

(Comparative Example 2)
In Example 2, the non-aqueous electrolysis of Comparative Example 2 was performed in the same manner as in Example 2 except that the carbon particles A in the positive electrode active material were replaced with activated carbon particles (Bellfine AP, manufactured by AT Electrode Co., Ltd.). A liquid storage element was manufactured and evaluated in the same manner as in Example 1. The results are shown in Table 1-1.

(Comparative Example 3)
In Example 1, the non-aqueous electrolyte storage of Comparative Example 3 was carried out in the same manner as in Example 1 except that the positive electrode active material was changed from a combination of carbon particles A and olivine-type lithium iron phosphate to carbon particles A alone. An element was manufactured and evaluated in the same manner as in Example 1. The results are shown in Table 1-2. FIG. 5 shows a 1C discharge curve in the first cycle, a 10C discharge curve in the second cycle, and a 10C discharge curve in the 1,000th cycle in Comparative Example 3.

(Comparative Example 4)
In Example 2, the non-aqueous electrolyte storage of Comparative Example 4 was carried out in the same manner as in Example 2 except that the positive electrode active material was changed from a combination of carbon particles A and olivine-type lithium iron phosphate to carbon particles A alone. An element was manufactured and evaluated in the same manner as in Example 1. The results are shown in Table 1-2.

(Comparative Example 5)
In the same manner as in Example 1, except that the positive electrode active material was changed from a combination of carbon particles A and lithium olivine-type iron phosphate to activated carbon particles alone (Bellfine AP, manufactured by AT Electrode Co., Ltd.). Thus, a non-aqueous electrolyte storage element of Comparative Example 5 was manufactured and evaluated in the same manner as in Example 1. The results are shown in Table 1-2.

(Comparative Example 6)
In Example 2, it carried out similarly to Example 2 except having changed the said positive electrode active material from the combination of the carbon particle A and the olivine type lithium iron phosphate to the activated carbon particle (Bellfine AP, AT Electrode Co., Ltd.) alone. Thus, a non-aqueous electrolyte storage element of Comparative Example 6 was manufactured and evaluated in the same manner as in Example 1. The results are shown in Table 1-2.

From the results of Table 1-1 and Table 1-2, Examples 1 to 2 including carbon particles A having a plurality of pores forming a three-dimensional network structure therein and lithium metal oxide particles in the positive electrode active material are shown. It was found that the sample had higher discharge capacity at 1 C and higher energy density than Comparative Examples 1 to 6. In Comparative Examples 1 and 2, in which the activated carbon particles and the lithium metal oxide particles were included in the positive electrode active material, the capacity retention at 1,000 cycles was less than 80%, whereas in Examples 1 and 2, 80% or more was maintained, and it was found that Examples 1 and 2 were excellent in long-term cycle properties.
3 to 5 show changes in the discharge curves of Example 1, Comparative Example 1, and Comparative Example 3, respectively. From these results, it was found that Example 1 had a higher discharge capacity than Comparative Examples 1 and 3.

(Examples 3 to 11)
In Example 1, the mixing ratio of the carbon particles A in the positive electrode active material and the olivine type lithium iron phosphate was changed as shown in Tables 2-1 and 2-2, and the negative electrode was replaced with a lithium metal foil having an average thickness of 500 μm. Except for the above, the non-aqueous electrolyte storage elements of Examples 3 to 11 were manufactured in the same manner as Example 1.
For the obtained non-aqueous electrolyte energy storage devices of Examples 3 to 11, except that the evaluation of the capacity retention rate at 1,000 cycles was changed to the evaluation of the capacity retention rate at 2,000 cycles. Evaluation was performed in the same manner as in Example 1. The results are shown in Tables 2-1 and 2-2.

(Comparative Example 7)
A non-aqueous electrolyte storage element of Comparative Example 7 was manufactured in the same manner as in Example 3 except that the positive electrode active material was changed from carbon particles A and olivine-type lithium iron phosphate to carbon particles A in Example 3. Then, evaluation was performed in the same manner as in Example 3. The results are shown in Table 2-2.

From the results of Tables 2-1 and 2-2, when the mixing ratio of the carbon particles A to the lithium metal oxide particles in the positive electrode active material is reduced, the discharge capacity increases, but the capacity retention rate at 2,000 cycles is increased. Was found to decrease. When the mass ratio of the carbon particles to the lithium metal oxide particles (carbon particles / lithium metal oxide particles) is less than 50/50, the capacity retention at 2,000 cycles becomes less than 60%, It has been found that the mass ratio of the carbon particles to the lithium metal oxide particles (carbon particles / lithium metal oxide particles) is preferably 50/50 or more.
When the mass ratio between the carbon particles and the lithium metal oxide particles (carbon particles / lithium metal oxide particles) is increased, the capacity retention at 2,000 cycles increases, but the discharge capacity decreases. . If the mass ratio between the carbon particles and the lithium metal oxide particles (carbon particles / lithium metal oxide particles) exceeds 95/5, the discharge capacity will be less than 70 mAh / g. It was found that the mass ratio to the metal oxide particles (carbon particles / lithium metal oxide particles) is preferably 95/5 or less.

(Examples 12 to 19)
In Example 7, carbon particles A in the positive electrode active material were converted into carbon particles B to I (Knovel (registered trademark), manufactured by Toyo Carbon Co., Ltd.) having different specific surface areas as shown in Tables 3-1 and 3-2. Except having changed each, the non-aqueous electrolyte storage element of Examples 12-19 was manufactured like Example 7, and it evaluated similarly to Example 1. The results are shown in Table 3-1 and Table 3-2.

From the results of Tables 3-1 and 3-2, it was found that when the specific surface area of the carbon particles in the positive electrode active material was reduced, the discharge capacity was reduced. When the specific surface area of the carbon particles is less than 800 m ² / g, the discharge capacity is less than 70 mAh / g, so it was found that the specific surface area of the carbon particles is preferably 800 m ² / g or more.
It was also found that when the specific surface area of the carbon particles was increased, the discharge capacity was increased, but the capacity retention at 2,000 cycles was reduced. When the specific surface area of the carbon particles exceeds 1,800 m ² / g, the capacity retention rate at 2,000 cycles is less than 60%, so that the specific surface area of the carbon particles is preferably 1,800 m ² / g or less. I understood.

(Example 20)
In Example 7, olivine-type lithium iron phosphate and manganese in the cathode active material - cobalt - nickel ternary oxide lithium _{(LiNi 1/3 Co 1/3 Mn 1/3 O} 2, Ltd. Toshima Seisakusho) A non-aqueous electrolyte energy storage device of Example 20 was manufactured in the same manner as in Example 7, except for replacing the above. In the same manner as in Example 7, except that the evaluation of the capacity retention rate at 2,000 cycles was changed to the evaluation of the capacity retention rate at 100 cycles for the obtained nonaqueous electrolyte storage element of Example 20, evaluated. The results are shown in Table 4.

(Example 21)
In Example 7, the non-aqueous solution of Example 21 was changed in the same manner as in Example 7 except that lithium olivine-type iron phosphate in the positive electrode active material was changed to lithium cobaltate (LiCoO ₂ , manufactured by Toshima Seisakusho Co., Ltd.). An electrolyte storage element was manufactured and evaluated in the same manner as in Example 20. The results are shown in Table 4.

  From the results in Table 4, the lithium metal oxide contained in the positive electrode active material is preferably olivine-type lithium iron phosphate and lithium manganese-cobalt-nickel ternary oxide in terms of discharge capacity and long-term cyclability. I understood.

  From the above results, according to the nonaqueous electrolyte energy storage device of the present invention, a high energy density was achieved in the nonaqueous electrolyte energy storage device using an electrode of a type that stores anions in the positive electrode, and charge / discharge was repeated. Even in this case, it was found that a non-aqueous electrolyte storage element having a small rate of decrease in discharge capacity and excellent in long-term cycle characteristics could be provided.

Aspects of the present invention are, for example, as follows.
<1> A non-aqueous electrolyte storage element including a positive electrode including a positive electrode active material capable of inserting and extracting an anion, a negative electrode including a negative electrode active material, and a non-aqueous electrolyte, wherein the positive electrode active material includes: A non-aqueous electrolyte liquid storage element containing carbon particles and lithium metal oxide particles, wherein the carbon particles have a plurality of pores forming a three-dimensional network structure.
<2> The BET specific surface area of the carbon particles is 800 m ² / g or more and 1,800 m ² / g or less, and the pore volume of the carbon particles is 0.5 mL / g or more and 2.3 mL / g or less. The non-aqueous electrolyte storage device according to <1>.
<3> The nonaqueous electrolyte storage device according to any one of <1> to <2>, wherein the minimum diameter of the pores is 2 nm or more and 50 nm or less.
<4> Any one of the above items <1> to <3>, wherein a mass ratio of the carbon particles to the lithium metal oxide particles (carbon particles / lithium metal oxide particles) is 50/50 or more and 95/5 or less. 3. The non-aqueous electrolyte storage device according to item 1.
<5> The non-aqueous electrolyte storage element according to any one of <1> to <4>, wherein a median diameter (D50) according to a volume-based particle size distribution of the positive electrode active material is 30 μm or less.
<6> The battery according to any one of <1> to <5>, wherein the lithium metal oxide particles contain at least one of olivine-type lithium iron phosphate and manganese-cobalt-nickel lithium ternary oxide. It is a non-aqueous electrolyte storage element described in the above.
<7> The non-aqueous electrolyte storage element according to any one of <1> to <6>, wherein the non-aqueous electrolyte is obtained by dissolving an electrolyte salt in a non-aqueous solvent.
<8> The non-aqueous electrolyte storage element according to <7>, wherein the non-aqueous solvent is an aprotic organic solvent.
<9> The non-aqueous electrolyte storage element according to <8>, wherein the aprotic organic solvent is a chain carbonate.
<10> The non-aqueous electrolyte storage element according to any one of <7> to <9>, wherein the electrolyte salt contains at least one of LiPF ₆ and LiBF ₄ .
<11> The nonaqueous electrolyte liquid storage element according to any one of <7> to <10>, wherein the concentration of the electrolyte salt is 0.5 mol / L or more and 6 mol / L or less in the nonaqueous solvent. is there.
<12> The non-aqueous electrolyte storage device according to any one of <1> to <11>, wherein the negative electrode active material is at least one of artificial graphite and lithium titanate.

  According to the non-aqueous electrolyte storage element described in any one of <1> to <12>, the above-described problems in the related art can be solved and the object of the present invention can be achieved.

DESCRIPTION OF SYMBOLS 11 Positive electrode 12 Negative electrode 13 Separator 20 Positive electrode collector 21 Positive electrode active material 22 Binder 23 Conductive auxiliary agent 24 Negative electrode collector 25 Negative electrode active material 26 Nonaqueous electrolytic solution 27 Electrolyte salt 31 Carbon particle 32 Mesopore 33 Micropore 41 Activated carbon particle

JP 2012-89825 A JP 2014-127316 A

Claims (7)

A positive electrode including a positive electrode active material capable of storing and releasing anions, a negative electrode including a negative electrode active material, and a non-aqueous electrolyte, a non-aqueous electrolyte storage element having:
The positive electrode active material contains carbon particles and lithium metal oxide particles,
When the non-aqueous electrolyte storage element is charged at a constant current up to a potential of 4.2 V with respect to Li potential as a charge termination voltage, the carbon particles occlude the anion at least when the potential with respect to Li is 4 V.
The non-aqueous electrolyte storage element according to claim 1 , wherein the carbon particles have a plurality of pores forming a three-dimensional network structure. 2. The non-aqueous electrolyte storage element according to claim 1, wherein the capacity retention rate at 1,000 cycles is 80% or less. The BET specific surface area of the carbon particles is 800 m ² / G or more and 1,800m ² The non-aqueous electrolyte storage element according to claim 1, wherein the carbon particles have a pore volume of 0.5 mL / g or more and 2.3 mL / g or less. 4. The nonaqueous electrolysis according to any one of claims 1 to 3, wherein a mass ratio between the carbon particles and the lithium metal oxide particles (carbon particles / lithium metal oxide particles) is 50/50 or more and 95/5 or less. Liquid storage element. The non-aqueous electrolyte according to any one of claims 1 to 4, wherein the lithium metal oxide particles contain at least one of olivine-type lithium iron phosphate and manganese-cobalt-nickel lithium ternary oxide. Storage element. The non-aqueous electrolyte is LiPF ₆ And LiBF ₄ The non-aqueous electrolyte storage device according to any one of claims 1 to 5, comprising at least one of the following. The non-aqueous electrolyte storage device according to claim 1, wherein the negative electrode active material is at least one of artificial graphite and lithium titanate.