JP2017010798A - Non-aqueous electrolyte storage element - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a non-aqueous electrolyte storage element capable of maintaining a high capacity even when charging and discharging are repeated and suppressing a volume change of a positive electrode due to charging and discharging. (1) A positive electrode including a positive electrode active material capable of inserting and releasing anions, a negative electrode, and a non-aqueous electrolyte, wherein the positive electrode active material has crystallinity and a BET specific surface area. A non-aqueous electrolyte storage element using a carbonaceous material that has been activated to 23 to 100 m2/g. (2) The nonaqueous electrolyte storage element according to (1), wherein the negative electrode contains a negative electrode active material capable of inserting and releasing cations. [Selection diagram] None

Description

  The present invention relates to a non-aqueous electrolyte storage element in which an anion is inserted into or removed from a positive electrode and a cation is inserted or removed from a negative electrode.

In recent years, with the downsizing and higher performance of portable devices, the characteristics of non-aqueous electrolyte storage elements with high energy density have improved and become widespread. Non-aqueous electrolyte storage elements with higher capacity and superior safety Development is also underway, and installation in electric vehicles has begun. As such a non-aqueous electrolyte storage element, a lithium ion secondary battery is often used.
On the other hand, electric double layer capacitors that can be charged and discharged at high speed without requiring a chemical reaction are used as power storage elements such as hybrid automobiles. However, compared with lithium ion storage elements, the energy density is a few tenths, and heavy storage elements are necessary to secure sufficient capacity, which hinders improvement in fuel consumption when mounted on automobiles. It was.

また、アニオンを吸蔵・放出する活物質として黒鉛が知られており、正極活物質として黒鉛を用い、充電終止電圧をリチウム参照極に対して５．３〜５．６Ｖ（対Ｌｉ電位）とすることにより、高い容量が得られる二次電池が提案されている（特許文献３参照）。 As an energy storage device having high energy density and suitable for high-speed charge / discharge, a conductive polymer material, a carbon material or the like is used as a positive electrode, and a negative electrode such as carbon and a nonaqueous electrolytic solution in which a lithium salt is dissolved in a nonaqueous solvent, Various proposals have been made on so-called dual intercalation type non-aqueous electrolyte storage elements (see, for example, Patent Documents 1 and 2).
When LiPF ₆ is used as the lithium salt, as shown in the following reaction formula, charging is performed by inserting PF ₆ ⁻ into the positive electrode and inserting Li ⁺ into the negative electrode from the non-aqueous electrolyte, Discharge occurs when PF ₆ ^{− from} the positive electrode and Li ⁺ from the negative electrode are desorbed into the non-aqueous electrolyte.

In addition, graphite is known as an active material that absorbs and releases anions, and graphite is used as a positive electrode active material, and a charge end voltage is set to 5.3 to 5.6 V (vs. Li potential) with respect to a lithium reference electrode. Thus, a secondary battery capable of obtaining a high capacity has been proposed (see Patent Document 3).

However, the dual carbon electricity storage element is used in a voltage region where the maximum voltage is 1 V or more higher than 4.2 V of the lithium ion secondary battery, which is higher than the decomposition potential of a general non-aqueous electrolyte. It is an area. As a result, generation of gas inside the electricity storage device due to decomposition of the non-aqueous electrolyte and excessive deposition of fluoride on the negative electrode surface occur, so that reversible occlusion or release of ions during repeated charge / discharge is performed. There is a possibility that the possible capacity is greatly reduced and the life of the electricity storage device is shortened.
Also, in an anion intercalation battery, the electrode expands or contracts greatly due to charge and discharge, and the thickness of the electrode film changes, so that a compressive stress or tensile stress is generated in the battery depending on the amount of change in the electrode film thickness. Arise. As a result, cracking of the electrode material with the progress of the cycle, peeling of the electrode material from the current collector, crushing of the electrode material and the separator, drainage of the electrolyte due to generation of a gap between the positive electrode or the negative electrode and the separator, etc. Inhibits battery reaction. That is, the volume change rate of the electrode film affects the battery life.

  The present invention solves the above-described conventional problems, and can maintain a high capacity even when charging and discharging are repeated, and a non-aqueous electrolyte storage element in which volume change of the positive electrode accompanying charging and discharging is suppressed. For the purpose of provision.

The above problem is solved by the following invention 1).
1) It has a positive electrode containing a positive electrode active material capable of inserting and releasing anions, a negative electrode, and a non-aqueous electrolyte. The positive electrode active material has crystallinity and a BET specific surface area of 23 to 100 m ² / A nonaqueous electrolyte storage element using the carbonaceous material subjected to activation treatment of g.

  ADVANTAGE OF THE INVENTION According to this invention, even when charging / discharging is repeated, a high capacity | capacitance can be maintained and the nonaqueous electrolyte storage element by which the volume change of the positive electrode accompanying charging / discharging was suppressed can be provided.

The charging / discharging curve of the 1st cycle of the comparative example 1 and Examples 1-2. Schematic which shows an example of a non-aqueous electrolyte electrical storage element.

Hereinafter, the present invention 1) will be described in detail, but the following 2) to 7) are also included in the embodiment, and these will also be described together.
2) The nonaqueous electrolyte storage element according to 1), wherein the negative electrode includes a negative electrode active material capable of inserting and removing cations.
3) In the X-ray diffraction spectrum of the carbonaceous material, the peak derived from the inter-plane distance d (002) corresponding to the interlayer distance of the carbonaceous material is between 20.0 and 26.0 degrees with a Bragg angle 2θ. The non-aqueous electrolyte storage element according to 1) or 2), which is located in 1).
4) The nonaqueous electrolyte storage element according to any one of 1) to 3), wherein the carbonaceous material is graphitizable carbon.
5) The nonaqueous electrolyte storage element according to any one of 1) to 3), wherein the carbonaceous material is natural graphite or artificial graphite.
6) The nonaqueous electrolyte storage element according to any one of 1) to 5), wherein the activation treatment is an alkali activation treatment.
7) The non-aqueous electrolyte storage element according to any one of 1) to 6), wherein the non-aqueous electrolyte includes LiPF ₆ as an electrolyte salt.

<< Nonaqueous Electrolyte Storage Element >>
The non-aqueous electrolyte storage element of the present invention includes a positive electrode, a negative electrode, and a non-aqueous electrolyte, and further includes other members as necessary.
FIG. 2 shows an example of a non-aqueous electrolyte storage element. This non-aqueous electrolyte storage element 10 has a positive electrode 1, a negative electrode 2, and a separator 3 containing the non-aqueous electrolyte contained in an outer can 4, and provided with a negative electrode lead wire 5 and a positive electrode lead wire 6. It is.
Examples of the non-aqueous electrolyte storage element include a non-aqueous electrolyte secondary battery and a non-aqueous electrolyte capacitor.

As a result of intensive studies on the carbon species and structure of the carbon active material used for the positive electrode in the non-aqueous electrolyte storage element using the type of electrode that stores anions on the positive electrode, the present inventors have found that the carbon having activated crystallinity has been obtained. It is found that the use of a porous material facilitates ion intercalation due to the presence of pores formed on the carbon surface, so that a relatively high capacity can be obtained even in a voltage range of 5 V (vs. Li potential) or less. It was.
Moreover, since the pores formed by the alkali activation treatment relieve the volume expansion of the particles themselves, it is possible to suppress a change in the volume of the electrode accompanying charge / discharge.

A component of the nonaqueous electrolyte storage element of the present invention and a manufacturing method thereof will be described.
1. The positive electrode is not particularly limited as long as it contains a positive electrode active material into which anions can be inserted and desorbed, and can be appropriately selected according to the purpose. For example, a positive electrode having a positive electrode active material on a positive electrode current collector Examples include a positive electrode provided with a material.
There is no restriction | limiting in particular in the shape of a positive electrode, According to the objective, it can select suitably, For example, flat form etc. are mentioned.

1-1. Positive electrode material There is no restriction | limiting in particular in a positive electrode material, According to the objective, it can select suitably, For example, a positive electrode active material is included at least, Furthermore, a binder, a thickener, a conductive support agent, etc. are included as needed.

(1) Positive electrode active material As a positive electrode active material, what activated carbon material is used.
Examples of the carbonaceous material include artificial graphite, graphite such as natural graphite (graphite), graphitizable carbon, and pyrolysis products of organic substances under various pyrolysis conditions.
Examples of the graphitizable carbon include pitches such as petroleum pitch, coal pitch, and mesophase pitch; easy to obtain from petroleum needle cocos, coal needle coke, anthracene, polyvinyl chloride, polyacrylonitrile, and the like. Examples include pyrolysates such as graphitizable coke.

Examples of the activation treatment include potassium hydroxide (KOH), sodium hydroxide (NaOH), lithium hydroxide (LiOH), cesium hydroxide (CsOH), rubidium hydroxide (RbOH), and sodium phosphate (Na ₃ PO). ₄ ), calcium chloride (CaCl ₂ ), potassium sulfide (K ₂ S), potassium carbonate (K ₂ CO ₃ ), sodium carbonate (Na ₂ CO ₃ ), sodium sulfate (Na ₂ SO ₄ ), potassium sulfate (K ₂₎ SO ₄ ), alkali activation treatment using calcium carbonate (CaCO ₃ ) or the like as an activator; gas activation treatment using carbon dioxide (CO ₂ ), air or the like as an activator; water vapor using water vapor (H ₂ O) as an activator An activation process etc. are mentioned.
Among these, an alkali activation treatment is preferable, and an alkali activation treatment using potassium hydroxide (KOH) is more preferable.

The activation process is performed as follows.
For example, in the case of activation with KOH, for example, KOH is impregnated uniformly into a carbonaceous material, and then fired at 700 ° C. to 1000 ° C., for example, in an inert gas atmosphere such as argon or nitrogen. Next, the activated carbonaceous material (activated charcoal) is obtained by washing with water or an acid such as hydrochloric acid or sulfuric acid to remove the chemicals and drying. The amount of KOH used is, for example, 1 to 5 parts by mass with respect to 1 part by mass of the carbonaceous material.

As the activated charcoal, one having a BET specific surface area of 23 to 100 m ² / g is used. If it is less than 23 m < ² > / g, development of a pore will become inadequate and a high capacity | capacitance will not be obtained. On the other hand, if it exceeds 100 m ² / g, the reaction area between the active material and the electrolytic solution becomes wide, so that the decomposition reaction of the electrolytic solution is promoted and the cycle characteristics may be deteriorated.
Moreover, it is preferable that the said activated carbon has a peak in Bragg angle 2 (theta) in 20.0-26.0 degree | times in the X-ray-diffraction spectrum. If there is a peak at a lower angle than 20.0 degrees, the average distance between the hexagonal mesh planes constituting the graphite crystal exceeds 4 mm, so the van der Waals force between the hexagonal mesh planes becomes weak, and the anion is inserted. -Cleavage may occur when desorption is repeated, and the crystal structure may be destroyed, leading to deterioration of cycle characteristics. In addition, if there is a peak at a higher angle than 26 degrees, the average distance between the hexagonal mesh planes is narrower than 3.4 mm and extremely narrow with respect to the size of the anion to be inserted, so that anion insertion is suppressed. There is a risk that high capacity cannot be obtained.

(2) Binder and thickener The binder and thickener are not particularly limited as long as they are materials that are stable with respect to the solvent and electrolyte used during electrode production and the applied potential, and are appropriately selected according to the purpose. can do. Examples thereof include fluorine-based binders such as polyvinylidene fluoride (PVDF) and polytetrafluoroethylene (PTFE), ethylene-propylene-butadiene rubber (EPBR), styrene-butadiene rubber (SBR), isoprene rubber, acrylate latex, Examples thereof include carboxymethylcellulose (CMC), methylcellulose, hydroxymethylcellulose, ethylcellulose, polyacrylic acid, polyvinyl alcohol, alginic acid, oxidized starch, phosphate starch, and casein. These may be used alone or in combination of two or more. Among these, fluorine-based binders such as PVDF and PTFE, acrylate latex, and CMC are preferable.

(3) Conductive aid Examples of the conductive aid include metal materials such as copper and aluminum, and carbonaceous materials such as carbon black, acetylene black, and carbon nanotube. These may be used alone or in combination of two or more.

1-2. Positive electrode current collector The material of the positive electrode current collector is not particularly limited as long as it is formed of a conductive material and is stable with respect to the applied potential, and can be appropriately selected according to the purpose. For example, stainless steel, nickel , Aluminum, titanium, tantalum, and the like. Among these, stainless steel and aluminum are particularly preferable.
There is no restriction | limiting in particular in the shape and structure of a positive electrode electrical power collector, According to the objective, it can select suitably.
The size of the positive electrode current collector is not particularly limited as long as it is a size that can be used for the nonaqueous electrolyte storage element, and can be appropriately selected according to the purpose.

1-3. Method for Producing Positive Electrode The positive electrode is produced by applying a positive electrode material in a slurry form by adding a binder, a thickener, a conductive agent, a solvent, etc. to the positive electrode active material as necessary, and drying it. can do. There is no restriction | limiting in particular in the said solvent, According to the objective, it can select suitably, For example, an aqueous solvent, an organic solvent, etc. are mentioned. Examples of the aqueous solvent include water, alcohol, and the like. Examples of the organic solvent include N-methyl-2-pyrrolidone (NMP) and toluene.
In addition, the positive electrode active material can be roll-formed as it is to obtain a sheet electrode, or a pellet electrode can be obtained by compression molding.

2. The negative electrode is not particularly limited as long as it contains a negative electrode active material, and can be appropriately selected according to the purpose. For example, a negative electrode including a negative electrode material having a negative electrode active material on a negative electrode current collector, and the like. Can be mentioned.
There is no restriction | limiting in particular in the shape of a negative electrode, According to the objective, it can select suitably, For example, flat form etc. are mentioned.

2-1. Negative electrode material The negative electrode material contains at least a negative electrode storage material (negative electrode active material or the like), and includes a binder, a thickener, a conductive aid, and the like as necessary.

(1) Negative electrode active material The negative electrode active material is not particularly limited as long as it is a substance capable of inserting and removing cations in a non-aqueous solvent system. Lithium ions are widely used as cations. Corresponding negative electrode active materials include carbonaceous materials, antimony tin oxide, metal oxides that can occlude and release lithium such as silicon monoxide, and metals that can be alloyed with lithium such as aluminum, tin, silicon, and zinc. Alternatively, a metal alloy, a metal alloyable with lithium, a composite alloy compound of an alloy containing the metal and lithium, lithium metal nitride such as cobalt lithium nitride, and the like can be given. These may be used alone or in combination of two or more. Among these, carbonaceous materials are particularly preferable from the viewpoint of safety and cost.
Examples of the carbonaceous material include graphite (graphite) such as coke, artificial graphite and natural graphite, and organic pyrolysis products under various pyrolysis conditions. Among these, artificial graphite and natural graphite are particularly preferable.

(2) Binder and thickener The binder and thickener are not particularly limited as long as they are materials that are stable with respect to the solvent and electrolyte used during electrode production and the applied potential, and are appropriately selected according to the purpose. can do. Examples thereof include the same as those of the positive electrode described above, and one of these may be used alone or two or more of them may be used in combination. Among these, fluorine binders such as PVDF and PTFE, SBR, and CMC are preferable.

(3) Conductive auxiliary agent Examples of the conductive auxiliary agent are the same as those of the positive electrode described above, and one of these may be used alone or two or more of them may be used in combination.

2-2. Negative electrode current collector The material of the negative electrode current collector is not particularly limited as long as it is formed of a conductive material and is stable with respect to the applied potential, and can be appropriately selected according to the purpose, for example, stainless steel, Nickel, aluminum, copper, etc. are mentioned. Among these, stainless steel, copper, and aluminum are particularly preferable.
There is no restriction | limiting in particular in the shape and structure of a negative electrode collector, According to the objective, it can select suitably.
The size of the negative electrode current collector is not particularly limited as long as it is a size that can be used for the nonaqueous electrolyte storage element, and can be appropriately selected according to the purpose.

2-3. Preparation method of negative electrode The negative electrode is prepared by applying a negative electrode material in the form of a slurry by adding a binder, a thickener, a conductive agent, a solvent, etc. to the negative electrode active material as necessary, and drying it. can do. As the solvent, the same solvent as in the method for producing the positive electrode can be used.
In addition, a negative electrode active material added with a binder, a thickener, a conductive agent, etc., is roll-formed as it is to form a sheet electrode, a pellet electrode by compression molding, or a negative electrode current collector by techniques such as vapor deposition, sputtering, and plating. A thin film of a negative electrode active material can also be formed on the body.

3. Nonaqueous Electrolytic Solution The nonaqueous electrolytic solution is an electrolytic solution in which an electrolyte salt is dissolved in a nonaqueous solvent.

3-1. Nonaqueous solvent There is no restriction | limiting in particular in a nonaqueous solvent, Although it can select suitably according to the objective, An aprotic organic solvent is suitable.
Examples of the aprotic organic solvent include carbonate-based organic solvents such as chain carbonates and cyclic carbonates, but those having a low viscosity are preferable. Among these, a chain carbonate is particularly preferable from the viewpoint that the dissolving power of the electrolyte salt is high.
Examples of the chain carbonate include dimethyl carbonate (DMC), diethyl carbonate (DEC), and ethyl methyl carbonate (EMC). Among these, DMC is preferable.

  There is no restriction | limiting in particular in content of the said DMC, Although it can select suitably according to the objective, 70 mass% or more is preferable with respect to a nonaqueous solvent, and 83 mass% or more is more preferable. When the content is 70% by mass or more, even when the remaining solvent is a cyclic substance (cyclic carbonate, cyclic ester, etc.) having a high dielectric constant, a high concentration non-aqueous electrolyte of 3M or more is produced. The viscosity does not become too high, and the non-aqueous electrolyte does not permeate into the electrode or cause problems in terms of ion diffusion.

Examples of the cyclic carbonate include propylene carbonate (PC), ethylene carbonate (EC), butylene carbonate (BC), vinylene carbonate (VC), and fluoroethylene carbonate (FEC).
Moreover, when using the mixed solvent which combined EC of the said cyclic carbonate and DMC of the said chain carbonate, there is no restriction | limiting in particular in the mixing ratio of EC and DMC, According to the objective, it can select suitably.

In addition, as said non-aqueous solvent, ester type organic solvents, such as cyclic ester and chain ester, ether type organic solvents, such as cyclic ether and chain ether, etc. can be used as needed.
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 propionic acid alkyl ester, malonic acid dialkyl ester, acetic acid alkyl ester [methyl acetate (MA), ethyl acetate, etc.], formic acid alkyl ester [methyl formate (MF), ethyl formate, etc.], etc. Is mentioned.
Examples of the cyclic ether include tetrahydrofuran, alkyltetrahydrofuran, alkoxytetrahydrofuran, dialkoxytetrahydrofuran, 1,3-dioxolane, alkyl-1,3-dioxolane, 1,4-dioxolane, and the like.
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.

3-2. Electrolyte salt The electrolyte salt is preferably a lithium salt, and is not particularly limited as long as it is dissolved in a non-aqueous solvent and exhibits high ionic conductivity. Examples thereof include lithium hexafluorophosphate (LiPF ₆ ), lithium perchlorate (LiClO ₄ ), lithium chloride (LiCl), lithium borofluoride (LiBF ₄ ), lithium arsenic hexafluoride (LiAsF ₆ ), tri Lithium fluorometasulfonate (LiCF ₃ SO ₃ ), lithium bistrifluoromethylsulfonylimide [LiN (CF ₃ SO ₂ ) ₂ ], lithium bisperfluoroethylsulfonylimide [LiN (C ₂ F ₅ SO ₂ ) ₂ ], etc. Is mentioned. These may be used alone or in combination of two or more. Among these, LiPF ₆ is particularly 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 can be appropriately selected according to the purpose. However, it is preferably 0.5 to 6 mol / L in the non-aqueous solvent, and 2 to 4 mol in terms of both battery capacity and output. / L is more preferable.

4). Separator In the nonaqueous electrolyte storage element of the present invention, a separator is provided between the positive electrode and the negative electrode as necessary in order to prevent a short circuit between the positive electrode and the negative electrode.
There is no restriction | limiting in particular in the material of a separator, a shape, a magnitude | size, and a structure, According to the objective, it can select suitably.
Examples of the material of the separator include paper such as kraft paper, vinylon mixed paper, 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. Can be mentioned. Among these, those having a porosity of 50% or more are preferable from the viewpoint of electrolyte solution retention.
The shape of the separator is preferably a non-woven fabric system having a higher porosity than the thin film type having micropores. The thickness of the separator is preferably 20 μm or more from the viewpoint of short circuit prevention and electrolyte solution retention.
The magnitude | size of a separator should just be a magnitude | size which can be used for a non-aqueous-electrolyte electrical storage element.
The structure of the separator may be a single layer structure or a laminated structure.

5). Method for Manufacturing Nonaqueous Electrolyte Storage Element The nonaqueous electrolyte storage element of the present invention can be manufactured by assembling a positive electrode, a negative electrode, a nonaqueous electrolyte, and a separator used as necessary into an appropriate shape. Furthermore, other constituent members such as a battery outer can can be used as necessary.
There is no restriction | limiting in particular in the method of assembling a nonaqueous electrolyte electrical storage element, What is necessary is just to select suitably from the methods generally employ | adopted.

There is no restriction | limiting in particular in the shape of the non-aqueous-electrolyte electrical storage element of this invention, According to the use, it can select suitably from the various shapes generally employ | adopted.
Examples thereof include a cylinder type in which the sheet electrode and the separator are spiral, a cylinder type having an inside-out structure in which the pellet electrode and the separator are combined, a coin type in which the pellet electrode and the separator are stacked, and the like.

6). Applications The nonaqueous electrolyte storage element of the present invention can be used for various applications without particular limitation. Examples include notebook computers, pen input computers, mobile computers, electronic book players, mobile phones, mobile faxes, mobile copy, mobile printers, headphone stereos, video movies, LCD TVs, handy cleaners, portable CDs, minidiscs, and transceivers. Electronic notebooks, calculators, memory cards, portable tape recorders, radios, backup power supplies, motors, lighting equipment, toys, game machines, watches, strobes, cameras, etc.

  EXAMPLES Hereinafter, although an Example and a comparative example are shown and this invention is demonstrated further more concretely, this invention is not limited at all by these Examples.

Example 1
<Preparation of positive electrode active material>
The pulverized raw coke was fired at 1200 ° C. in an argon atmosphere to obtain graphitizable carbon. Subsequently, it baked at 700 degreeC for 5 hours with 2.5 mass parts potassium hydroxide (KOH) with respect to 1 mass part of this graphitizable carbon in argon atmosphere, and performed the alkali activation process. Subsequently, the graphitizable carbon subjected to the alkali activation treatment was washed with ultrapure water, filtered, and dried at 120 ° C. in a dryer to obtain a positive electrode active material (graphitizable carbon A).

<Preparation of positive electrode>
Easily graphitizable carbon A as a positive electrode active material, acetylene black (Denka black powder: manufactured by Denki Kagaku Kogyo Co., Ltd.) as a conductive auxiliary, acrylate latex (TRD202A: manufactured by JSR) as a binder, and carboxymethyl cellulose (as a thickener) Daicel 2200: manufactured by Dial Chemical Co., Ltd.) is mixed so that the mass ratio of the solid content is 100: 7.5: 3.8: 3.0, and water is added to adjust the slurry to an appropriate viscosity. Obtained. This slurry was applied on one side of an aluminum foil having a thickness of 20 μm using a doctor blade, and then punched out to φ16 mm to obtain a positive electrode. The average basis weight of the positive electrode active material after drying was 3.0 mg / cm ² .

<Preparation of nonaqueous electrolyte storage element>
Using the positive electrode, a negative electrode made of lithium metal foil having a diameter of 16 mm, two separators, and an electrolytic solution, a nonaqueous electrolytic solution storage element was produced. As the separator, a glass filter paper (GA100: manufactured by ADVANTEC) punched to φ16 mm was used. 400 μL of EC: DMC: FEC = 2: 96: 2 (mass%) mixed solution (Kishida Chemical Co., Ltd.) containing 2 mol / L LiPF ₆ electrolyte was used as the electrolyte.
First, the positive electrode and the separator were vacuum-dried at 150 ° C. for 4 hours, and then a 2032 type coin cell was assembled using each of the above members in a dry argon glove box.

(Example 2)
A positive electrode active material (graphitizable carbon B) subjected to alkali activation treatment in the same manner as in Example 1 except that the firing conditions of graphitizable carbon and potassium hydroxide (KOH) were set at 900 ° C. for 2 hours. )
Except for using this graphitizable carbon B as the positive electrode active material, a positive electrode and a nonaqueous electrolyte storage element were produced in the same manner as in Example 1.

(Example 3)
A positive electrode active material (graphitizable carbon C) subjected to alkali activation treatment in the same manner as in Example 1 except that the firing conditions of graphitizable carbon and potassium hydroxide (KOH) were set at 900 ° C. for 5 hours. )
Except for using this graphitizable carbon C as a positive electrode active material, a positive electrode and a nonaqueous electrolyte storage element were produced in the same manner as in Example 1.

Example 4
A positive electrode active material (graphitizable carbon D) subjected to alkali activation treatment in the same manner as in Example 1 except that the firing conditions of graphitizable carbon and potassium hydroxide (KOH) were set at 900 ° C. for 10 hours. )
Except for using this graphitizable carbon D as a positive electrode active material, a positive electrode and a nonaqueous electrolyte storage element were produced in the same manner as in Example 1.

(Example 5)
A positive electrode active material (graphitizable carbon E) subjected to alkali activation treatment in the same manner as in Example 1 except that the baking conditions of graphitizable carbon and potassium hydroxide (KOH) were set at 1000 ° C. for 2 hours. )
Except for using this graphitizable carbon E as a positive electrode active material, a positive electrode and a nonaqueous electrolyte storage element were produced in the same manner as in Example 1.

(Example 6)
A positive electrode active material (graphitizable carbon F) subjected to alkali activation treatment in the same manner as in Example 1 except that the baking conditions of graphitizable carbon and potassium hydroxide (KOH) were set at 1000 ° C. for 5 hours. )
Except for using this graphitizable carbon F as the positive electrode active material, a positive electrode and a nonaqueous electrolyte storage element were produced in the same manner as in Example 1.

(Comparative Example 1)
The positive electrode and non-aqueous electrolysis were performed in the same manner as in Example 1 except that graphitizable carbon (graphitizable carbon G) obtained by firing the raw coke pulverized in Example 1 was used as the positive electrode active material. A liquid storage element was produced.

(Comparative Example 2)
A positive electrode active material (graphitizable carbon) subjected to alkali activation treatment in the same manner as in Example 1 except that the baking conditions of graphitizable carbon and potassium hydroxide (KOH) were set to 700 ° C. for 2 hours. H) was obtained.
Except for using this graphitizable carbon H as a positive electrode active material, a positive electrode and a nonaqueous electrolyte storage element were produced in the same manner as in Example 1.

(Comparative Example 3)
A positive electrode active material (graphitizable carbon I) subjected to an alkali activation treatment in the same manner as in Example 1 except that the firing conditions of graphitizable carbon and potassium hydroxide (KOH) were set at 1000 ° C. for 10 hours. Got.
Except for using this graphitizable carbon I as the positive electrode active material, a positive electrode and a nonaqueous electrolyte storage element were produced in the same manner as in Example 1.

<Measurement of physical properties of positive electrode active material>
The physical properties of each positive electrode active material of Examples 1 to 6 and Comparative Examples 1 to 3 were measured. The results are shown in Table 1.
The BET specific surface area was calculated using the BET method from the results of adsorption isotherms by TriStar 3020 (manufactured by Shimadzu Corporation).
The peak position of the spectrum derived from the inter-plane distance d (002) corresponding to the interlayer distance of graphite was determined by X-ray diffraction measurement using X'Part Pro (manufactured by Philip).

<Charge / discharge test of nonaqueous electrolyte storage element>
A charge / discharge test was performed on each of the nonaqueous electrolyte storage elements of Examples 1 to 6 and Comparative Examples 1 to 3, and the discharge capacity at the first cycle and the discharge capacity at the 100th cycle after the pretreatment were measured. The discharge capacity is a converted value per 1 g of the positive electrode active material (mAh / g), and the capacity retention rate (%) is the ratio of the discharge capacity at the 100th cycle to the discharge capacity at the first cycle.
The results are shown in Table 1.

[Method of conducting charge / discharge test]
Each non-aqueous electrolyte storage element was held in a constant temperature bath at 25 ° C., and a charge / discharge test was performed using an automatic battery evaluation device (1024B-7V0.1A-4: manufactured by Electrofield).
The first charge and discharge is pre-processed by setting the reference current value to 1.0 mA, performing a constant current charge to 4.7 V, maintaining 4.7 V for 5 hours, and performing an electric field activation process to perform a constant current discharge to 3.0 V. did. In the electric field activation treatment, an overvoltage is applied during the initial voltage application to generate a high electric field in the electrode, and the pores are expanded by allowing electrolyte ions to enter the pores below the micropores formed by the activation treatment. effective. After this pretreatment, a charge / discharge test assuming the following normal use state was performed 100 cycles.
[1]: Constant current charge up to 4.6 V at the reference current value [2]: Pause for 5 minutes [3]: Constant current discharge up to 3.0 V at the reference current value [4]: Pause for 5 minutes [5]: [1 ] To [4] are defined as one cycle, and charging and discharging are repeated.

<Measurement of volume change rate>
The volume change rate of the positive electrode film thickness after charge / discharge relative to the positive electrode film thickness before charge / discharge was measured. The results are shown in Table 1.
The volume change rate is the rate of change (%) in the thickness of the positive electrode after 100 cycles with respect to the thickness of the positive electrode before charging / discharging, as expressed by the following equation. Become.

As can be seen from the results in Table 1, in Examples 1 to 6 in which carbon materials having a BET specific surface area of 23 m ² / g or more by alkali activation treatment of graphitizable carbon were used as positive electrode active materials, Comparative Examples 1 to 6 were used. Compared to 2, the discharge capacity was improved and the volume change rate was reduced. In Comparative Example 3 using a positive electrode active material having a BET specific surface area exceeding 100 m ² / g, although the discharge capacity was increased, the capacity retention rate (cycle characteristics) after 100 cycles was significantly reduced.
Moreover, about the crystallinity of the carbonaceous material which carried out the alkali activation process of graphitizable carbon, the position of the peak of d (002) from which discharge capacity becomes large seeing from Examples 1-5 and Comparative Examples 1-2, Those of 26.0 degrees or less are preferable. However, in Example 6 where the peak position was 19.9, the capacity retention rate was slightly lowered, and therefore the peak position is preferably 20.0 degrees or more.
Moreover, although the charging / discharging curve of the 1st cycle of Examples 1-2 and the comparative example 1 is shown in FIG. 1, the direction of Examples 1-2 is compared with the comparative example 1 whose BET specific surface area is less than 23 m < ² > / g. It can be seen that both the charge capacity and the discharge capacity are large.

(Examples 7 to 12)
Except for using natural graphite (manufactured by Nippon Graphite Co., Ltd .: Special CP) instead of the graphitizable carbon obtained by firing the raw coke crushed in Example 1, the same as in Examples 1 to 6, A positive electrode active material (natural graphite A to F) subjected to alkali activation treatment was obtained.
Except that this natural graphite A to F was used as a positive electrode active material, each positive electrode and nonaqueous electrolyte storage element of Examples 7 to 12 was produced in the same manner as Examples 1 to 6.

(Comparative Example 4)
Instead of graphitizable carbon obtained by firing the raw coke pulverized in Example 1, natural graphite (Nippon Graphite Co., Ltd .: special CP, natural graphite G) not subjected to alkali activation treatment is used as the positive electrode active material. A positive electrode and a nonaqueous electrolyte storage element were produced in the same manner as in Example 1 except for the points used as.

(Comparative Examples 5-6)
Except for using natural graphite (manufactured by Nippon Graphite Co., Ltd .: Special CP) instead of the graphitizable carbon obtained by firing the raw coke pulverized in Example 1, the same as in Comparative Examples 2-3, A positive electrode active material (natural graphite H to I) subjected to alkali activation treatment was obtained.
Except that this natural graphite H to I was used as a positive electrode active material, each positive electrode and nonaqueous electrolyte storage element of Comparative Examples 5 to 6 was produced in the same manner as Comparative Examples 2 to 3.

The physical properties of each positive electrode active material of Examples 7 to 12 and Comparative Examples 4 to 6 and the charge / discharge characteristics of each nonaqueous electrolyte storage element were measured in the same manner as in Example 1. The results are shown in Table 2.

(Examples 13 to 18)
Alkaline in the same manner as in Examples 1 to 6 except that artificial graphite (manufactured by Timcal: KS-6) was used instead of the graphitizable carbon obtained by firing the raw coke pulverized in Example 1. The positive electrode active material (artificial graphite AF) which performed the activation process was obtained.
Except that this artificial graphite A to F was used as a positive electrode active material, each positive electrode and nonaqueous electrolyte storage element of Examples 13 to 18 were produced in the same manner as Examples 1 to 6.

(Comparative Example 7)
Instead of graphitizable carbon obtained by firing the raw coke pulverized in Example 1, artificial graphite not subjected to alkali activation treatment (manufactured by Timcal: KS-6, artificial graphite G) is used as the positive electrode active material A positive electrode and a nonaqueous electrolyte storage element were produced in the same manner as in Example 1 except for the points used as.

(Comparative Examples 8-9)
Alkaline in the same manner as in Comparative Examples 2 to 3 except that artificial graphite (manufactured by Timcal: KS-6) was used instead of the graphitizable carbon obtained by firing the raw coke pulverized in Example 1. A positive electrode active material (artificial graphite H to I) subjected to activation treatment was obtained.
Except that this artificial graphite H to I was used as a positive electrode active material, the positive electrodes and nonaqueous electrolyte storage elements of Comparative Examples 8 to 9 were produced in the same manner as Comparative Examples 2 to 3.

The physical properties of each positive electrode active material in Examples 13 to 18 and Comparative Examples 7 to 9 and the charge / discharge characteristics of each nonaqueous electrolyte storage element were measured in the same manner as in Example 1. The results are shown in Table 3.

As can be seen from the results in Tables 2 and 3, Examples 7 to 12 and 13 to 18 (carbon materials having a BET specific surface area of 23 m ² / g or more by alkali-activating natural graphite or artificial graphite as a positive electrode active material) In use), the discharge capacity was improved and the volume change rate was reduced as compared with Comparative Examples 4 to 5 and 7 to 8. In Comparative Examples 6 and 9 using a positive electrode active material having a BET specific surface area exceeding 100 m ² / g, although the discharge capacity increased, the capacity retention rate (cycle characteristics) after 100 cycles significantly decreased.
Moreover, about the crystallinity of the carbonaceous material which carried out the alkali activation process of the natural graphite or artificial graphite, when it sees from Examples 8-12, 14-18, and Comparative Examples 4-5, 7-8, d becomes large discharge capacity. The (002) peak position is preferably 26.0 degrees or less. However, in Comparative Examples 6 and 9 in which the peak positions were 24.9 and 24.8, the capacity retention rate was slightly reduced. Therefore, for these carbonaceous materials, the peak position was 25.0 degrees or more. preferable.

(Example 19)
<Positive electrode activation of Example 1 except that the conditions for the activation treatment were changed to firing at 1000 ° C. for 5 hours with 2.5 parts by mass of cesium hydroxide (CsOH) with respect to 1 part by mass of graphitizable carbon. A positive electrode active material (graphitizable carbon J) subjected to an alkali activation treatment was obtained in the same manner as in the case of preparation of material>.
Except for using this graphitizable carbon J as a positive electrode active material, a positive electrode and a nonaqueous electrolyte storage element were produced in the same manner as in Example 1.

(Example 20)
Except that the activation treatment conditions were changed to firing at 1000 ° C. for 5 hours with 2.5 parts by mass of sodium hydroxide (NaOH) with respect to 1 part by mass of graphitizable carbon, <Cathode active> A positive electrode active material (graphitizable carbon K) subjected to an alkali activation treatment was obtained in the same manner as in the case of preparation of material>.
Except for using this graphitizable carbon K as the positive electrode active material, a positive electrode and a nonaqueous electrolyte storage element were produced in the same manner as in Example 1.

The physical properties of each positive electrode active material of Examples 19 and 20 and the charge / discharge characteristics of each non-aqueous electrolyte storage element were measured in the same manner as in Example 1. The results are shown in Table 4.

  As can be seen from the results in Table 4, the discharge capacity and the volume change rate were higher in Examples 6, 19 and 20 using the positive electrode active material subjected to the alkali activation treatment than in Comparative Example 1 where the activation treatment was not performed. Is excellent. Of the alkali activators, potassium hydroxide (KOH) is the best.

(Example 21)
<Production of negative electrode>
Artificial graphite (manufactured by Hitachi Chemical Co., Ltd .: MAGD) as the negative electrode active material, acetylene black (denka black powder: manufactured by Denki Kagaku Kogyo Co., Ltd.) as the conductive additive, and SBR-based material (EX1215: manufactured by Denki Kagaku Kogyo Co., Ltd.) Carboxymethyl cellulose (Daicel 2200: manufactured by Dial Chemical Co., Ltd.) as a thickener is mixed so that the mass ratio of the solid content is 100: 5.0: 3.0: 2.0, and water is added appropriately. The slurry was adjusted to a suitable viscosity. This slurry was applied to one side of a 18 μm thick copper foil using a doctor blade, and then punched out to φ16 mm to form a negative electrode. The average basis weight of the negative electrode active material after drying was 3.0 mg / cm ² .

<Preparation of nonaqueous electrolyte storage element>
A 2032 type coin cell was assembled in the same manner as in Example 1 except that the positive electrode was changed to the same one as in Example 2 and the negative electrode was changed from the lithium metal foil to the above one.

(Example 22)
<Production of negative electrode>
Lithium titanate [Li ₄ Ti ₅ O ₁₂ (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 additive, and styrene butadiene rubber (TRD102A) as the binder : Manufactured by JSR), carboxymethyl cellulose (Daicel 2200: manufactured by Daicel Chemical Industries, Ltd.) as a thickener is mixed so that the mass ratio of the solid content is 100: 7: 3: 1, and water is added appropriately. The slurry was adjusted to the viscosity. This slurry was applied to one side of an 18 μm thick aluminum foil using a doctor blade, and then punched out to a diameter of 16 mm to form a negative electrode. The average basis weight of the negative electrode active material after drying was 3.0 mg / cm ² .

<Preparation of nonaqueous electrolyte storage element>
A 2032 type coin cell was assembled in the same manner as in Example 1 except that the positive electrode was changed to the same one as in Example 2 and the negative electrode was changed from the lithium metal foil to the above one.

(Example 23)
A 2032 type coin cell was assembled in the same manner as in Example 1 except that the same positive electrode as in Example 8 and the same negative electrode as in Example 21 were used.

(Example 24)
A 2032 type coin cell was assembled in the same manner as in Example 1 except that the same positive electrode as in Example 8 and the same negative electrode as in Example 22 were used.

(Example 25)
A 2032 type coin cell was assembled in the same manner as in Example 1 except that the same positive electrode as in Example 14 and the same negative electrode as in Example 21 were used.

(Example 26)
A 2032 type coin cell was assembled in the same manner as in Example 1 except that the same positive electrode as in Example 14 and the same negative electrode as in Example 22 were used.

(Comparative Example 10)
A 2032 type coin cell was assembled in the same manner as in Example 1 except that the same positive electrode as in Comparative Example 1 and the same negative electrode as in Example 21 were used.

(Comparative Example 11)
A 2032 type coin cell was assembled in the same manner as in Example 1 except that the same positive electrode as in Comparative Example 1 and the same negative electrode as in Example 22 were used.

(Comparative Example 12)
A 2032 type coin cell was assembled in the same manner as in Example 1 except that the same positive electrode as in Comparative Example 4 and the same negative electrode as in Example 21 were used.

(Comparative Example 13)
A 2032 type coin cell was assembled in the same manner as in Example 1 except that the same positive electrode as in Comparative Example 4 and the same negative electrode as in Example 22 were used.

(Comparative Example 14)
A 2032 type coin cell was assembled in the same manner as in Example 1 except that the same positive electrode as in Comparative Example 7 and the same negative electrode as in Example 21 were used.

(Comparative Example 15)
A 2032 type coin cell was assembled in the same manner as in Example 1 except that the same positive electrode as in Comparative Example 7 and the same negative electrode as in Example 22 were used.

The BET specific surface area of each positive electrode active material of Examples 21 to 26 and Comparative Examples 10 to 15, and the discharge capacity and volume change rate of each non-aqueous electrolyte storage element were measured in the same manner as in Example 1. The results are shown in Table 5.

  As can be seen from the results in Table 5, even when graphite or lithium titanate (LTO) was used for the negative electrode, Examples 21 to 26 had better discharge capacity and volume change rate than Comparative Examples 10 to 15. ing.

DESCRIPTION OF SYMBOLS 1 Positive electrode 2 Negative electrode 3 Separator 4 Battery outer can 5 Negative electrode lead wire 6 Positive electrode lead wire 10 Nonaqueous electrolyte storage element

JP2013-058442A JP 2014-112524 A Japanese Patent No. 4569126

Claims (7)

It has a positive electrode containing a positive electrode active material capable of inserting and removing anions, a negative electrode, and a non-aqueous electrolyte. The positive electrode active material has crystallinity and a BET specific surface area of 23 to 100 m ² / g. A non-aqueous electrolyte storage element using an activated carbonaceous material.   The non-aqueous electrolyte storage element according to claim 1, wherein the negative electrode includes a negative electrode active material capable of inserting and removing cations.   In the X-ray diffraction spectrum of the carbonaceous material, the peak derived from the inter-plane distance d (002) corresponding to the interlayer distance of the carbonaceous material is located between 20.0 to 26.0 degrees of the Bragg angle 2θ. The non-aqueous electrolyte storage element according to claim 1 or 2.   The non-aqueous electrolyte storage element according to claim 1, wherein the carbonaceous material is graphitizable carbon.   The non-aqueous electrolyte storage element according to claim 1, wherein the carbonaceous material is natural graphite or artificial graphite.   The non-aqueous electrolyte storage element according to claim 1, wherein the activation process is an alkali activation process. The non-aqueous electrolyte storage element according to claim 1, wherein the non-aqueous electrolyte includes LiPF ₆ as an electrolyte salt.

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