JP2010205846A - Nonaqueous lithium type electricity storage element - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a nonaqueous lithium type electricity storage element which has high durability in addition to high energy density and high output density. <P>SOLUTION: The nonaqueous lithium type electricity storage element is constituted by storing, in a housing, an electrode stack, constituted by stacking a negative electrode body formed by providing a negative electrode active material layer to a negative electrode collector, a positive electrode body formed by providing a positive electrode active material layer to a positive electrode collector, and a separator, and a nonaqueous lithium electrolyte containing an electrolyte containing lithium ions. The positive electrode active material contains activated carbon as a principal component, and the activated carbon satisfies 0.3<V1≤0.8 and 0.5≤V2≤1.0, where V1 is a mesopore amount (cc/g) originating from pores of 20 to 500 Å in diameter and V2 is a micropore amount (cc/g) originating from pores of <20 Å in diameter, and has a specific surface area of 1.500 to 3,000 m<SP>2</SP>/g. The negative electrode active material contains graphitized material as a principal component. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

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

In recent years, midnight power storage systems, home-use distributed power storage systems based on solar power generation technology, and power storage systems for electric vehicles have attracted attention from the viewpoint of the effective use of energy aimed at preserving the global environment and conserving resources. Yes.
The first requirement in these power storage systems is that the energy density of the power storage elements used is high. As a promising candidate for a high energy density battery capable of meeting such demands, development of a lithium ion battery has been vigorously advanced.

The second requirement is high output characteristics. For example, a combination of a high-efficiency engine and a power storage system (for example, a hybrid electric vehicle) or a combination of a fuel cell and a power storage system (for example, a fuel cell electric vehicle) requires high output discharge characteristics in the power storage system during acceleration. ing.
Currently, an electric double layer capacitor using activated carbon as an electrode (hereinafter also simply referred to as a “capacitor”) has been developed as a high-power storage element, and has high durability (cycle characteristics and high-temperature storage characteristics). It has an output characteristic of about 5 to 1 kW / L. These electric double layer capacitors have been considered as the most suitable power storage elements in the field where the above high output is required, but the energy density is only about 1 to 5 Wh / L, and the output duration time is not practical. It is a footpad.

On the other hand, nickel-metal hydride batteries currently used in hybrid electric vehicles realize high output equivalent to electric double layer capacitors and have an energy density of about 160 Wh / L. However, research is underway energetically to further increase the energy density and output, further improve the stability at high temperatures, and enhance the durability.
In addition, research for higher output is also being conducted in lithium ion batteries. For example, a lithium ion battery has been developed that can obtain a high output exceeding 3 kW / L at a discharge depth (a value representing what percentage of the device discharge capacity is discharged) 50%, and its energy density is 100 Wh. / L or less, and a design that dares to suppress the high energy density, which is the greatest feature of the lithium ion battery. Further, its durability (cycle characteristics, high temperature storage characteristics) is inferior to that of an electric double layer capacitor. Therefore, in order to give practical durability, the depth of discharge can be used only in a range narrower than the range of 0 to 100%. For this reason, the capacity that can be actually used is further reduced, and research for further improving the durability is being actively pursued.

  As described above, there is a strong demand for practical use of a power storage device having high output density, high energy density, and durability. However, the existing power storage device described above has advantages and disadvantages. Therefore, a new power storage element that satisfies these technical requirements has been demanded, and the development of a power storage element called a lithium ion capacitor has become active in recent years as a promising candidate.

  A lithium ion capacitor is a storage element that uses a non-aqueous electrolyte containing an electrolyte containing lithium ions (non-aqueous lithium type storage element), and the positive electrode adsorbs and desorbs the same as an electric double layer capacitor at the positive electrode. It is a power storage element that charges and discharges by a non-Faraday reaction caused by Faraday reaction and a Faraday reaction caused by insertion and extraction of lithium ions in the negative electrode similar to a lithium ion battery. As described above, an electric double layer capacitor that charges and discharges by a non-Faraday reaction in both the positive electrode and the negative electrode has excellent output characteristics but low energy density. On the other hand, a secondary battery that charges and discharges by a Faraday reaction in both the positive electrode and the negative electrode is excellent in energy density but inferior in output characteristics. The lithium ion capacitor is a new power storage element that aims to achieve both excellent output characteristics and high energy density by performing charge and discharge by a non-Faraday reaction at the positive electrode and a Faraday reaction at the negative electrode.

  As such a lithium ion capacitor, activated carbon is used as a positive electrode active material, natural graphite or artificial graphite, graphitized mesophase carbon microspheres, graphitized mesophase carbon fiber, graphite whisker, graphitized carbon fiber, etc. A power storage element using the above has been proposed (see Patent Document 1 below). In addition, a power storage element using activated carbon as a positive electrode active material and non-graphitizable carbon or graphite as a negative electrode active material has been proposed (see Patent Document 2 below).

Moreover, hydrogen / carbon different from normal activated carbon as the positive electrode active material is 0.05 to 0.5, the BET specific surface area is 300 to 2,000 m ² / g, and the mesopore volume by the BJH method is 0. A hydrocarbon material having a pore structure of 0.02 to 0.3 ml / g and a total pore volume by the MP method of 0.3 to 1.0 ml / g is used, while graphite is removed as a negative electrode active material An electric storage element using a material obtained by activating an optically anisotropic carbon substance has been proposed (see Patent Document 3 below).

  Moreover, activated non-porous charcoal obtained by activating the graphitized charcoal as a positive electrode active material is used, while natural graphite, artificial graphite, mesophase carbon microbeads, mesophase carbon fiber, coke, An electric storage element using vapor-grown carbon fiber, non-graphitizable carbon, or the like has been proposed (see Patent Document 4 below).

  The negative electrode material of the lithium ion capacitor is a carbonaceous material obtained by depositing a carbonaceous material on the surface of activated carbon, and the amount of mesopores derived from pores having a diameter of 20 mm or more and 500 mm or less is Vm1 (cc / g ), When the amount of micropores derived from pores having a diameter of less than 20 mm is Vm2 (cc / g), the electric storage satisfying 0.01 ≦ Vm1 ≦ 0.20 and 0.01 ≦ Vm2 ≦ 0.40 A negative electrode material for an element has been proposed (see Patent Document 5 below). The negative electrode material has high charge / discharge efficiency for lithium ions and is excellent in output characteristics.

Japanese Patent Laid-Open No. 8-1007048 JP-A-9-283383 JP 2005-93778 A JP 2007-294539 A JP 2003-346801 A

As a result of investigations by the present inventors, it has been found that the power storage element described in Patent Document 3 has a problem that the output characteristics are not sufficient although the energy density is large. Moreover, since the electrical storage element described in the above-mentioned patent document 4 uses the non-porous charcoal as a positive electrode material, it turned out that it has the subject that output characteristics are not enough. The power storage device described in Patent Document 5 described above has high charge / discharge efficiency and excellent output characteristics, but it has been found that there is room for further improvement in applications in which durability is important.
Accordingly, an object of the present invention is to provide a power storage element that has both high energy density and high output density, as well as high durability.

  As a result of intensive studies to solve the above problems, the present inventors have used activated carbon having a specific pore structure as a positive electrode active material in a non-aqueous lithium storage element, and further used a graphitized product as a negative electrode active material. As a result, the present inventors have unexpectedly found that the durability can be dramatically improved while maintaining the high energy density and output density of the non-aqueous lithium storage element, and the present invention has been completed.

That is, the present invention is as follows.
[1] A negative electrode body in which a negative electrode active material layer is provided on a negative electrode current collector, a positive electrode body in which a positive electrode current collector is provided with a positive electrode active material layer, an electrode laminate formed by laminating a separator, and lithium ions A non-aqueous lithium-type electricity storage element in which a non-aqueous electrolyte solution containing a contained electrolyte is housed in an exterior body, wherein the positive electrode active material contains activated carbon as a main component, where the activated carbon is calculated by the BJH method When the amount of mesopores derived from pores having a diameter of 20 to 500 mm is V1 (cc / g) and the amount of micropores derived from pores of less than 20 mm calculated by the MP method is V2 (cc / g) 0.3 <V1 ≦ 0.8 and 0.5 ≦ V2 ≦ 1.0, and the specific surface area measured by the BET method is 1,500 m ² / g or more and 3,000 m ² / g. And the negative electrode active material is graphitized As a main component, the non-aqueous lithium storage element.

[2] Ratio (I ₁₃₆₀ / I ₁₅₈₀ ) of peak intensity (I ₁₃₆₀ ) of ₁₃₆₀ cm ⁻¹ and peak intensity (I ₁₅₈₀ ) of ₁₅₈₀ cm ⁻¹ of the graphitized material measured in a Raman spectrum using a laser having a wavelength of 532 nm The non-aqueous lithium storage element according to [1], in which is 0.05 or more and less than 0.90.

  [3] The non-aqueous lithium-type electricity storage according to [1] or [2], wherein the (002) plane spacing of the graphitized product obtained by the X-ray wide angle diffraction method is 0.335 nm or more and less than 0.340 nm. element.

[4] The non-aqueous lithium storage element according to any one of [1] to [3], wherein a specific surface area of the graphitized material measured by a BET method is 1 m ² / g or more and less than 20 m ² / g.

  [5] The non-aqueous lithium storage element according to any one of [1] to [4], wherein the graphitized material has an average particle size of 5 to 30 μm.

  [6] The nonaqueous lithium storage element according to any one of [1] to [5], wherein the graphitized material is mesocarbon microsphere graphitized material.

  According to the present invention, there is provided a non-aqueous lithium storage element that has both high energy density and high output density, as well as high durability.

Hereinafter, embodiments of the present invention will be described in detail.
The present invention relates to a negative electrode body in which a negative electrode active material layer is provided on a negative electrode current collector, a positive electrode body in which a positive electrode current collector is provided with a positive electrode active material layer, an electrode laminate in which a separator is laminated, and lithium ions A non-aqueous lithium storage element containing a non-aqueous electrolyte solution containing an electrolyte containing the active material, wherein the positive electrode active material contains activated carbon as a main component, and the activated carbon has a diameter of 20 to 500 mm When the amount of mesopores derived from the pores is V1 (cc / g) and the amount of micropores derived from the pores having a diameter of less than 20 mm is V2 (cc / g), 0.3 <V1 ≦ 0.8, and 0.5 ≦ V2 ≦ 1.0, the specific surface area measured by the BET method is 1,500 m ² / g or more and 3,000 m ² / g or less, and the negative electrode active material is mainly graphitized. It is characterized by being a component.

First, the positive electrode active material in the electricity storage device of the present invention will be described.
In the present invention, the positive electrode active material contains activated carbon as a main component, where the activated carbon has a mesopore amount derived from pores having a diameter of 20 mm or more and 500 mm or less calculated by the BJH method as V1 (cc / g), MP. Satisfying 0.3 <V1 ≦ 0.8 and 0.5 ≦ V2 ≦ 1.0 when the amount of micropores derived from pores having a diameter of less than 20 mm calculated by the method is V2 (cc / g) In addition, the specific surface area measured by the BET method is 1,500 m ² / g or more and 3,000 m ² / g or less. Here, including as a main component means including more than 50% when the total weight of the positive electrode active material is 100%.

  The carbonaceous material used as a raw material for the activated carbon is not particularly limited as long as it is a carbon source that is usually used as a raw material for activated carbon. For example, wood, wood flour, coconut shell, by-product during pulp production, bacus, Plant raw materials such as waste molasses; Fossil raw materials such as peat, lignite, lignite, bituminous coal, anthracite, petroleum distillation residue components, petroleum pitch, coke, coal tar; phenol resin, vinyl chloride resin, vinyl acetate resin, melamine resin, Various synthetic resins such as urea resin, resorcinol resin, celluloid, epoxy resin, polyurethane resin, polyester resin, polyamide resin; synthetic rubber such as polybutylene, polybutadiene, polychloroprene; other synthetic wood, synthetic pulp, or their carbides It is done. Among these raw materials, plant raw materials such as coconut shells and wood flour, or carbides thereof are preferable, and coconut shell carbides are particularly preferable.

As a carbonization and activation method for using these raw materials as the activated carbon, known methods such as a fixed bed method, a moving bed method, a fluidized bed method, a slurry method, and a rotary kiln method can be employed.
Carbonization methods for these raw materials include inert gases such as nitrogen, carbon dioxide, helium, argon, xenon, neon, carbon monoxide and combustion exhaust gas, or other gases mainly composed of these inert gases. The method of baking for about 30 minutes to about 10 hours at about 400-700 degreeC (especially 450-600 degreeC) using mixed gas is mentioned.
Examples of a method for activating the carbide obtained by the carbonization method include a gas activation method in which firing is performed using an activation gas such as water vapor, carbon dioxide, and oxygen. Among these, a method using water vapor or carbon dioxide as the activation gas is preferable.

In this activation method, the carbide is supplied for 3 to 12 hours (preferably 5 to 11 hours) while supplying the activation gas at a rate of 0.5 to 3.0 kg / h (particularly 0.7 to 2.0 kg / h). Furthermore, it is preferable to activate by heating to 800 to 1000 ° C. over 6 to 10 hours).
Furthermore, prior to the activation treatment of the carbide, the carbide may be activated in advance. In this primary activation, the carbonaceous material is usually fired at a temperature of less than 900 ° C. using an activation gas such as water vapor, carbon dioxide, oxygen, etc. to activate the gas.
The activated carbon of the present invention having the following characteristics can be produced by appropriately combining the firing temperature / time in the carbonization method and the activation gas supply amount / temperature increase rate / maximum activation temperature in the activation method.

The activated carbon thus obtained preferably has the following characteristics in the present invention.
That is, the amount of mesopores derived from pores having a diameter of 20 to 500 mm calculated by the BJH method of activated carbon is V1 (cc / g), and the amount of micropores derived from pores having a diameter of less than 20 mm calculated by the MP method is V2. (Cc / g), 0.3 <V1 ≦ 0.8 and 0.5 ≦ V2 ≦ 1.0 are satisfied.
The mesopore amount V1 is preferably a value larger than 0.3 g / cc from the viewpoint of increasing the output characteristics when incorporated in the storage element, and from the viewpoint of suppressing a decrease in the capacity of the storage element. Or less, more preferably 0.35 g / cc or more and 0.7 g / cc or less, and still more preferably 0.4 g / cc or more and 0.6 g / cc or less.

  On the other hand, the micropore volume V2 is preferably 0.5 g / cc or more in order to increase the specific surface area of the activated carbon and increase the capacity, and also suppresses the bulk of the activated carbon and increases the density as an electrode. From the viewpoint of increasing the capacity per unit volume, it is preferably 1.0 g / cc or less, more preferably 0.6 g / cc or more and 1.0 g / cc or less, and still more preferably 0.8 g / cc. cc to 1.0 g / cc.

  The mesopore volume V1 and the micropore volume V2 are preferably in the range of 0.3 ≦ V1 / V2 ≦ 0.9. This is because the amount of mesopores is larger than the amount of micropores, and it is preferable that V1 / V2 is 0.3 or more from the viewpoint of suppressing the decrease in output characteristics while obtaining the capacity. Compared to the fact that the amount of micropores is larger than that of the above, and the output characteristics are obtained while suppressing the decrease in capacity, V1 / V2 is preferably 0.9 or less. A more preferable range is 0.4 ≦ V1 / V2 ≦ 0.7, and a further preferable range is 0.55 ≦ V1 / V2 ≦ 0.7.

In the present invention, the micropore volume and mesopore volume are values determined by the following method. That is, the sample is vacuum-dried at 500 ° C. for a whole day and night, and adsorption and desorption isotherms are measured using nitrogen as an adsorbate. Using the isotherm on the desorption side at this time, the micropore volume was calculated by the MP method, and the mesopore volume was calculated by the BJH method.
The MP method uses a “t-plot method” (BC Lippens, JH de Boer, J. Catalysis, 4319 (1965)), and uses a micropore volume, a micropore area, and a micropore. Is a method for obtaining the distribution of M.M. It is a method devised by Mikhail, Brunauer, Bodor (R.S. Mikhal, S. Brunauer, EE Bodor, J. Colloid Interface Sci., 26, 45 (1968)). The BJH method is a calculation method generally used for analyzing mesopores and proposed by BarrEtt, Joyner, Halenda et al. (EP Barrett, LG Joyner and P. Halenda, J Amer. Chem. Soc., 73, 373 (1951)).

  The average pore diameter of the activated carbon used as the positive electrode active material is preferably 17 mm or more, more preferably 18 mm or more, and further preferably 20 mm or more, from the viewpoint of maximizing the output. Further, from the point of maximizing the capacity, it is preferably 25 mm or less. The average pore diameter referred to in the present invention is obtained by dividing the total pore volume per weight obtained by measuring each equilibrium adsorption amount of nitrogen gas under each relative pressure at the liquid nitrogen temperature by the BET specific surface area. Show what you asked for.

The activated carbon used as the positive electrode active material preferably has a BET specific surface area of 1,500 m ² / g or more and 3,000 m ² / g or less. More preferably not more than 1,500 m ² / g or more 2,500 m ² / g. When the BET specific surface area is less than 1,500 m ² / g, sufficient energy density cannot be obtained. On the other hand, when the BET specific surface area exceeds 3,000 m ² / g, a large amount of binder must be added. A sufficient electrode strength cannot be maintained, and the performance per volume is lowered.

  In addition, from the viewpoint of improving the energy density of the electricity storage element, the positive electrode active material includes, in addition to the activated carbon, a metal oxide that occludes and releases lithium ions known as a positive electrode active material of a lithium ion secondary battery, for example, It is also preferable to add lithium cobaltate. When the positive electrode active material is a mixture of activated carbon and a metal oxide that occludes and releases lithium ions, the ratio of activated carbon to the total positive electrode active material is preferably 50% by weight or more.

Next, the negative electrode active material in the electricity storage device of the present invention will be described.
The negative electrode active material includes a graphitized material as a main component. Here, including as a main component means including more than 50% when the total weight of the negative electrode active material is 100%. The power storage device of the present invention using activated carbon having a specific pore structure as described above as the positive electrode active material and further using graphitized material as the negative electrode active material uses activated carbon as the positive electrode active material and the surface of the activated carbon as the negative electrode active material. As compared with the electric storage element described in Patent Document 5 using a composite porous material in which a carbonaceous material is deposited on the substrate, durability is dramatically improved while maintaining a high energy density and an output density.

Although the said reason is not certain, it is thought that it is because the self-discharge or leakage current in a negative electrode can be prevented suitably by using a graphitized material for a negative electrode active material, for example.
Artificial graphite and / or natural graphite can be used for the graphitized material in the present invention, and there is no particular limitation, but the following can be exemplified as preferable ones. Graphitizing carbon (eg, bulk mesophase, mesophase globules, etc.) obtained by heating or firing petroleum or coal-based pitch and a polymer compound (eg, phenol resin, furan resin, furfural resin, cellulose resin, etc.) Examples thereof include graphite obtained by graphitizing the obtained graphite and coke (for example, coal tar pitch, oxygen-crosslinked petroleum pitch, etc.). These graphites can be used alone or in combination of two or more.

The graphite fluoride in the present invention, the ratio of the peak intensity of 1360cm peak intensity of ^-1 _{(I 1360)} and 1580 cm ^-1 as measured in the Raman spectrum using laser with a wavelength of _{532nm (I 1580) (I 1360} / I 1580 ) Is preferably 0.05 or more and less than 0.90. Of the nine types of lattice vibration based on the graphite structure, the Raman spectrum near 1580 cm ⁻¹ corresponding to the E2g type vibration corresponding to the in-plane lattice vibration, and the crystal structure such as crystal defects mainly in the surface layer and stacking irregularities A Raman spectrum in the vicinity of 1360 cm ⁻¹ reflecting the disturbance is measured with a laser Raman spectrometer (NRS-3200, manufactured by JASCO Corporation) using a laser with a wavelength of 532 nm. The intensity ratio (I ₁₃₆₀ / I ₁₅₈₀ ) is calculated from the peak intensity of each Raman spectrum, and the higher the intensity ratio, the lower the surface crystallinity.

When the intensity ratio (I ₁₃₆₀ / I ₁₅₈₀ ) is 0.05 or more, the irreversible capacity increases due to the progress of the decomposition reaction of the electrolytic solution, which occurs because the crystallinity of the surface layer proceeds excessively, and the lithium ion intercalation increases. There is little decrease in output characteristics due to slow curlation / deintercalation. Further, when the intensity ratio (I ₁₃₆₀ / I ₁₅₈₀ ) is less than 0.90, an increase in leakage current and an increase in self-discharge due to a significant decrease in crystallinity are unlikely to occur. Therefore, it is preferably 0.05 or more and less than 0.90, more preferably 0.15 or more and less than 0.50.

The crystalline structure of the graphite product according to the present invention, obtained by X-ray wide angle diffraction method (002) plane of the surface interval _(hereinafter referred to as _{d 002)} are those preferably less than 0.340nm than 0.335 nm. The d ₀₀₂ here is calculated from the peak position of the (002) plane of the graphitized product measured using CuKα rays as X-rays and high-purity silicon as a standard substance.
When d ₀₀₂ is 0.340 nm or more, the degree of graphitization is lowered and is not suitable. Therefore, it is preferably 0.337 nm or less, and more preferably 0.3365 nm or less.

The specific surface area of the graphite product in the present invention is preferably a specific surface area as measured by BET method is less than ^{1 m} 2 / g or more ^{20 m} 2 / g.
When the BET specific surface area of the graphitized material is 1 m ² / g or more, a sufficient energy density is easily obtained. On the other hand, if it is less than 20 m < ² > / g, durability will not fall easily. The reason for this is not clear, but it is considered that, for example, an increase in the contact area with the electrolyte accompanying an increase in the BET specific surface area tends to cause an increase in leakage current and an increase in self-discharge. Therefore, preferably 2 to 15 m ² / g, more preferably 3 to 10 m ² / g.

The average particle size of the graphitized material in the present invention is preferably 5 to 30 μm. The average particle size referred to here is the particle size at which the cumulative curve becomes 50% when the cumulative curve is determined with the total volume being 100% when the particle size distribution is measured using a particle size distribution measuring device. % Diameter, and refers to the 50% diameter (Median diameter).
The average particle size of 5 μm or more is preferable because the density of the active material layer can be increased and the capacity per volume can be increased. Furthermore, a large average particle size contributes to an improvement in durability. An average particle size of 30 μm or less is suitable for high-speed charge / discharge. Accordingly, the thickness is preferably 6 to 25 μm, and more preferably 7 to 20 μm.

  Among the graphitized materials having the above physical properties, mesocarbon microsphere graphitized materials are preferable. Mesocarbon microsphere graphitized material has crystallites oriented in a lamellar shape in spherical particles, so that lithium ion intercalation / deintercalation can proceed smoothly during charge / discharge, rapid charge / discharge and durability It is suitable for combining both sexes.

In addition, the negative electrode active material in the present invention includes those obtained by coating other materials with the above graphitized material as a central carbon material, and those obtained by mixing other materials with the above graphitized material. For example, a multilayer (core-shell) structure (composite) in which the surface of the graphitized material is coated with a carbonaceous material having a low graphitization degree, or a combination of the graphitized material and a carbonaceous material having a low graphitization degree (mixture) ).
Low-graphitizable carbonaceous materials include graphitizable carbon materials, non-graphitizable carbon materials, composite porous materials with a carbonaceous material deposited on the surface of activated carbon, and amorphous carbonaceous materials such as polyacene substances. And carbon black materials such as ketjen black and acetylene black, carbon nanotubes, fullerenes, carbon nanophones, fibrous carbonaceous materials, and the like, and carbonaceous materials that do not fall within the range defined as preferred physical properties in the graphitized material.
The negative electrode active material in the present invention may be a composite or mixture of the above graphitized material and a known negative electrode material for lithium ion secondary batteries such as lithium titanium composite oxide and conductive polymer. As mentioned above, when setting it as a composite or a mixture, it is preferable that the ratio with respect to all the negative electrode active materials of a graphitized material shall be 50 weight% or more.

Next, the non-aqueous lithium storage element of the present invention will be described.
The material of the current collector is not particularly limited as long as it is a metal foil that does not deteriorate due to elution or reaction when it is used as a power storage element, and examples thereof include copper foil and aluminum foil. In the electricity storage device of the present invention, the positive electrode current collector is preferably an aluminum foil and the negative electrode current collector is preferably a copper foil.
Further, the current collector may be a normal metal foil having no through hole or a metal foil having a through hole. The thickness of the current collector is not particularly limited, but if it is smaller than 1 μm, the shape and strength of the electrode body cannot be sufficiently maintained, and if it is larger than 100 μm, the weight and volume of the electricity storage device become too large. Since performance will be inferior, 1-100 micrometers is preferable.

  As the active material layer, a known component contained in the active material layer of a known lithium ion battery, a capacitor, or the like can be used. In addition to the positive electrode active material and the negative electrode active material described above, the active material layer can contain known components, for example, a binder, a conductive filler, and a thickener, and the type thereof is not particularly limited.

Hereinafter, the components of the active material layer in the non-aqueous lithium storage element will be described in detail.
If necessary, a conductive filler may be added to the active material layer, and examples thereof include carbon black. 0-30 mass% is preferable with respect to 100 mass% of active materials, and, as for the addition amount, 1-20 mass% is more preferable. The conductive filler is preferably mixed from the viewpoint of high power density, but if it exceeds 30% by mass, the proportion of the active material in the electrode layer decreases and the power density per volume decreases, so depending on the application. Set as appropriate.

In order to fix the above-mentioned active material, and further optionally added conductive filler on the current collector as an active material layer, as a binder, polyvinylidene fluoride (PVdF), polytetrafluoroethylene (PTFE), Fluororubber, styrene butadiene copolymer, cellulose derivative and the like can be used, and the addition amount thereof is preferably in the range of 3 to 20% by mass, more preferably in the range of 5 to 15% by mass with respect to 100% by mass of the active material. . When the added amount of the binder is more than 20% by mass, the surface of the active material is covered with the binder, so that the entry and exit of ions may be delayed and a high output density may not be obtained. Further, when the added amount of the binder is less than 3% by mass, it is difficult to fix the active material layer on the current collector.
The electrode body in the present invention may be one in which the active material layer is formed only on the upper surface (one surface) of the current collector, or may be formed on the upper and lower surfaces (both surfaces).

In the electrode body in which the active material layer is fixed to the current collector, the thickness of the active material layer is usually preferably about 30 to 200 μm. When the thickness of the active material layer is less than 30 μm, the ratio of the amount of the active material to the entire power storage element decreases, and the energy density decreases. On the other hand, when the thickness of the active material layer is larger than 200 μm, the resistance inside the electrode increases, and the output density decreases.
The electrode body can be manufactured by electrode manufacturing technology such as a known lithium ion battery or an electric double layer capacitor. For example, various materials are slurried with water or an organic solvent, and the active material layer is placed on the current collector. It is obtained by applying to the substrate, drying, and pressing as necessary. Further, without using a solvent, it is also possible to mix by a dry method and press-mold the active material, and then affix using a binder or the like.

The formed positive electrode body and negative electrode body are laminated or wound around via a separator, and inserted into an outer package formed from a metal can or a laminated film. As the separator, a polyethylene microporous film or a polypropylene microporous film used in a lithium ion secondary battery, or a cellulose non-woven paper used in an electric double layer capacitor can be used.
The thickness of the separator is preferably 10 μm or more and 50 μm or less. A thickness of less than 10 μm is not preferable because self-discharge due to an internal micro-short increases. On the other hand, when the thickness is larger than 50 μm, not only the energy density of the electricity storage device is reduced but also the output characteristics are deteriorated, which is not preferable.

  As a metal can used for an exterior body, the thing made from aluminum is preferable. Moreover, as a laminated film used for an exterior body, the film which laminated | stacked metal foil and the resin film is preferable, and the thing of the 3 layer structure which consists of an outer layer resin film / metal foil / interior resin film is illustrated. The outer layer resin film is for preventing the metal foil from being damaged by contact or the like, and a resin such as nylon or polyester can be suitably used. The metal foil is for preventing the permeation of moisture and gas, and foils of copper, aluminum, stainless steel, etc. can be suitably used. The interior resin film protects the metal foil from the electrolyte contained therein and melts and seals it during heat sealing, and polyolefins and acid-modified polyolefins can be suitably used.

Examples of the solvent for the non-aqueous electrolyte used in the electricity storage device of the present invention include cyclic carbonates represented by ethylene carbonate (EC) and propylene carbonate (PC), diethyl carbonate (DEC), dimethyl carbonate (DMC), and ethyl carbonate. A chain carbonate typified by methyl (MEC), a lactone such as γ-butyrolactone (γBL), or a mixed solvent thereof can be used.
The electrolyte dissolved in these solvents must be a lithium salt, and preferred lithium salts include LiBF ₄ , LiPF ₆ , LiN (SO ₂ C ₂ F ₅ ) ₂ , LiN (SO ₂ CF ₃ ) (SO ₂ C ₂ ). F ₅ ), LiN (SO ₂ CF ₃ ) (SO ₂ C ₂ F ₄ H), or a mixed salt thereof.

The electrolyte concentration in the non-aqueous electrolyte is preferably in the range of 0.5 to 2.0 mol / L. If it is less than 0.5 mol / L, anions are insufficient and the capacity of the electricity storage device is reduced. On the other hand, if it exceeds 2.0 mol / L, undissolved salt precipitates in the electrolyte solution, or the viscosity of the electrolyte solution becomes too high, which conversely decreases the conductivity and decreases the output characteristics. To do.
In the electricity storage device of the present invention, the negative electrode body can be pre-doped with lithium ions. As a method for doping, a known method, for example, a method of assembling an electrode body in a state where a lithium metal foil is laminated on the negative electrode active material layer of the negative electrode body and putting it in a non-aqueous electrolyte can be used. By preliminarily doping with lithium ions, it is possible to control the capacity and operating voltage of the power storage element.

Hereinafter, the present invention will be specifically described with reference to Examples and Comparative Examples, but the present invention is not limited thereto.
First, a method for producing a negative electrode material (graphitized material) used in Examples and Comparative Examples is shown below.
The coal tar is heat-treated at 450 ° C. for 1 hour to produce a graphitized precursor in the pitch matrix. Next, in order to take out the graphitized material precursor from the above mixture, tar heavy oil was used as an extraction solvent, and graphitized material was obtained from the pitch matrix. The obtained graphitized material was sintered once at 500 ° C. for 3 hours in a nitrogen stream, cooled to room temperature, put in a graphite container, and subjected to high-temperature heat treatment at 3,000 ° C. for 3 hours in a nitrogen stream. Graphitized product 4 used in Examples 4 and 8 was obtained.
In the above production method, graphitized product 2 used in Examples 2 and 6 was obtained by shortening the high-temperature heat treatment time of 3,000 ° C.
The graphitized product 2 was mechanochemically treated with a hybridization system (manufactured by Nara Machinery Co., Ltd.) at a peripheral speed of 40 m / s and a treatment time of 5 minutes, so that Examples 1 and 5, Comparative Example 1 and Graphitized product 1 used in No. 4 was obtained.
The graphitized product 1 used in Examples 3 and 7 was obtained by subjecting the graphitized product 1 to mechanochemical treatment under the same conditions again.

<Example 1>
[Preparation of positive electrode body]
The crushed palm shell carbide was carbonized in nitrogen in a small carbonization furnace at 500 ° C. for 3 hours. The treated carbide is placed in an activation furnace, 1 kg / h of steam is heated in a preheating furnace, and the temperature is raised to 900 ° C. over 8 hours. To obtain activated carbon. The obtained activated carbon was washed with water for 10 hours and then drained. Then, after drying for 10 hours in an electric dryer maintained at 115 ° C., pulverization was performed for 1 hour by a ball mill to obtain activated carbon 1 as a positive electrode material.
The pore distribution of this activated carbon 1 was measured with a pore distribution measuring device (AUTOSORB-1 AS-1-MP) manufactured by Yuasa Ionics. As a result, the BET specific surface area was 2,360 m ² / g, the mesopore volume (V1) was 0.52 cc / g, and the micropore volume (V2) was 0.88 cc / g. Using the activated carbon 1 as a positive electrode active material, the activated carbon 1 is 80.8 parts by weight, ketjen black 6.20 parts by weight, PVDF (polyvinylidene fluoride) 10.0 parts by weight, and PVP (polyvinylpyrrolidone) 3.00 parts by weight. And NMP (N-methylpyrrolidone) were mixed to obtain a slurry. Next, the obtained slurry was applied to one side of an aluminum foil having a thickness of 15 μm, dried, and pressed to obtain a positive electrode body having an active material layer thickness of 55 μm.

[Preparation of negative electrode body]
The physical properties of the graphitized material 1 produced by the method described above were evaluated. The intensity ratio (I ₁₃₆₀ / I ₁₅₈₀ ) at a laser wavelength of 532 nm was measured using a laser Raman spectrometer (NRS-3200, manufactured by JASCO Corporation), and as a result, it was 0.30. Next, as a result of measuring the BET specific surface area using a pore distribution measuring device (AUTOSORB-1 AS-1-MP) manufactured by Yuasa Ionics, it was 7.4 m ² / g. Moreover, it was 7.5 micrometers as a result of measuring an average particle diameter using the Shimadzu Corporation laser diffraction type particle size distribution analyzer (SALD-2000J). Further, X-ray wide-angle diffraction measurement (RINT-2500, manufactured by Rigaku Corporation) was performed using CuKα rays as X-rays, and the diffraction peak on the (002) plane was measured using high-purity Si as an internal standard. ₀₀₂ was 0.336.
93.0 parts by weight of the graphitized product 1, 2.0 parts by weight of acetylene black, 5.0 parts by weight of PVDF (polyvinylidene fluoride) and NMP (N-methylpyrrolidone) were mixed to obtain a slurry. Next, the obtained slurry was applied to one side of a 15 μm thick copper foil, dried and pressed to obtain a negative electrode body having an active material layer thickness of 60 μm. This electrode body was electrochemically doped with lithium ions corresponding to 290 mAh / g per unit weight of graphitized material using a lithium metal foil.

[Assembly and performance of storage element]
A polyethylene separator (thickness 30 μm) is laminated between the obtained negative electrode body and the positive electrode body, inserted into an outer package formed from a laminate film, and an electrolyte is injected to seal the outer package. Then, a non-aqueous lithium storage element was assembled. A solution obtained by dissolving LiN (SO ₂ C ₂ F ₅ ) ₂ at a concentration of 1 mol / l in a solvent in which ethylene carbonate and methyl ethyl carbonate were mixed at a weight ratio of 1: 4 was used as an electrolytic solution.
The assembled power storage element was charged to 4.0 V with a current of 0.5 mA, and then constant current and constant voltage charging in which a constant voltage of 4.0 V was applied was performed for 2 hours. Subsequently, the battery was discharged to 2.5 V with a constant current of 0.5 mA. This was defined as one cycle, and charging / discharging was repeated up to 13 cycles. When the discharge capacity at the thirteenth cycle was defined as the capacity of the power storage element, the capacity of the power storage element was 44 mAh / g.
Moreover, the produced electrical storage element was charged to 4.0V with the electric current of 1 mA, and the constant current constant voltage charge which applies a constant voltage of 4.0V was performed for 2 hours after that. Next, the battery was discharged to 2.5 V with a constant current of 1 mA. The discharge capacity was 0.333 mAh. Next, when the same charge was performed and the battery was discharged at 250 mA to 2.5 V, a capacity of 0.150 mAh was obtained. That is, the ratio of the discharge capacity at 250 mA to the discharge capacity at 1 mA (hereinafter also referred to as “output characteristics”) was 0.450.
Furthermore, the durability test of the assembled electrical storage element was performed under the conditions of 60 ° C. and 3.8 V application. The resistance magnification was measured at the start of the test (0 h) and after 1000 h had elapsed. The resistance magnification here is a numerical value represented by (resistance value at 0.1 Hz after elapse of 1000 h) / (resistance value at 0.1 Hz at 0 h). The resistance magnification after 1000 hours was 1.05.

<Example 2>
[Preparation of positive electrode body]
The same one as in Example 1 was used.
[Preparation of negative electrode body]
The physical properties of the graphitized product 2 produced by the method described above were evaluated by the same method as in Example 1. The intensity ratio I ₁₃₆₀ / I ₁₅₈₀ was 0.15, the BET specific surface area was 3.1 m ² / g, the average particle size was 15 μm, and d ₀₀₂ was 0.336.
Thereafter, an electrode body was produced in the same manner as in Example 1.
[Assembly and performance of storage element]
Hereinafter, in the same manner as in Example 1, a non-aqueous lithium storage element was assembled and evaluated. The capacity of this power storage element was 45 mAh / g. Also. The output characteristic was 0.453. Furthermore, the durability test of the assembled electrical storage element was performed under the conditions of 60 ° C. and 3.8 V application. After 1000 hours, the resistance magnification was 1.10.

<Example 3>
[Preparation of positive electrode body]
The same one as in Example 1 was used.
[Preparation of negative electrode body]
The physical properties of the graphitized product 3 produced by the method described above were evaluated by the same method as in Example 1. The intensity ratio I ₁₃₆₀ / I ₁₅₈₀ was 1.1, the BET specific surface area was 13 m ² / g, the average particle size was 5.0 μm, and d ₀₀₂ was 0.339.
Thereafter, an electrode body was produced in the same manner as in Example 1.
[Assembly and performance of storage element]
Hereinafter, in the same manner as in Example 1, a non-aqueous lithium storage element was assembled and evaluated. The capacity of this power storage element was 43 mAh / g. Also. The output characteristic was 0.460. Furthermore, the durability test of the assembled electrical storage element was performed under the conditions of 60 ° C. and 3.8 V application. After 1000 hours, the resistance magnification was 1.55.

<Example 4>
[Preparation of positive electrode body]
The same one as in Example 1 was used.
[Preparation of negative electrode body]
The physical properties of the graphitized product 4 produced by the method described above were evaluated by the same method as in Example 1. The intensity ratio I ₁₃₆₀ / I ₁₅₈₀ was 0.03, the BET specific surface area was 0.55 m ² / g, the average particle size was 25 μm, and d ₀₀₂ was 0.335.
Thereafter, an electrode body was produced in the same manner as in Example 1.
[Assembly and performance of storage element]
Hereinafter, in the same manner as in Example 1, a non-aqueous lithium storage element was assembled and evaluated. The capacity of this power storage element was 40 mAh / g. Also. The output characteristic was 0.385. Furthermore, the durability test of the assembled electrical storage element was performed under the conditions of 60 ° C. and 3.8 V application. After 1000 hours, the resistance magnification was 1.08.

<Comparative Example 1>
[Preparation of positive electrode body]
Commercially available activated carbon 2 was used as the active material, and physical properties of this activated carbon 2 were evaluated in the same manner as in Example 1. As a result, the BET specific surface area was 1,620 m ² / g, the mesopore volume (V1) was 0.18 cc / g, and the micropore volume (V2) was 0.67 cc / g.
Thereafter, an electrode body was produced in the same manner as in Example 1.
[Preparation of negative electrode body]
The same one as in Example 1 was used.
[Assembly and performance of storage element]
Hereinafter, in the same manner as in Example 1, a non-aqueous lithium storage element was assembled and evaluated. The capacity of this power storage element was 38 mAh / g. Also. The output characteristic was 0.302. Furthermore, the durability test of the assembled electrical storage element was performed under the conditions of 60 ° C. and 3.8 V application. After 1000 hours, the resistance magnification was 1.80.

<Comparative example 2>
[Preparation of positive electrode body]
The same one as in Example 1 was used.
[Preparation of negative electrode body]
150 g of commercially available activated carbon 3 (specific surface area by BET method is 1,955 m ² / g) is placed in a stainless steel mesh jar and placed on a stainless steel bat containing 300 g of coal-based pitch. It installed in the dimension 300mmx300mmx300mm), and the thermal reaction was performed. In the heat treatment, the temperature was raised to 670 ° C. in 4 hours in a nitrogen atmosphere, held at the same temperature for 4 hours, then cooled to 60 ° C. by natural cooling, and then taken out from the furnace to obtain composite porous material 1 .
The physical properties of the obtained composite porous material 1 were measured in the same manner as in Example 1. The intensity ratio I ₁₃₆₀ / I ₁₅₈₀ was 1.0, the BET specific surface area was 255 m ² / g, the average particle size was 2.9 μm, and d ₀₀₂ was 0.369.
Next, 83.4 parts by weight of the composite porous material obtained above, 8.30 parts by weight of acetylene black, 8.30 parts by weight of polyvinylidene fluoride (PVdF), and N-methylpyrrolidone (NMP) were mixed to obtain a slurry. It was. Next, the obtained slurry was applied to one side of a copper foil having a thickness of 15 μm, dried and pressed to obtain a negative electrode body having an active material layer thickness of 60 μm. This electrode body was electrochemically doped with lithium ions corresponding to 760 mAh / g of composite porous material using a lithium metal foil.
[Assembly and performance of storage element]
Hereinafter, in the same manner as in Example 1, a non-aqueous lithium storage element was assembled and evaluated. The capacity of this power storage element was 42 mAh / g. Also. The output characteristic was 0.491. Furthermore, the durability test of the assembled electrical storage element was performed under the conditions of 60 ° C. and 3.8 V application. After 1000 hours, the resistance magnification was 1.70.

<Comparative Example 3>
[Preparation of positive electrode body]
The thing similar to the comparative example 1 was used.
[Preparation of negative electrode body]
The thing similar to the comparative example 2 was used.
[Assembly and performance of storage element]
Hereinafter, in the same manner as in Example 1, a non-aqueous lithium storage element was assembled and evaluated. The capacity of this power storage element was 41 mAh / g. Also. The output characteristic was 0.354. Furthermore, the durability test of the assembled electrical storage element was performed under the conditions of 60 ° C. and 3.8 V application. After 1000 hours, the resistance magnification was 2.02.

<Example 5>
[Preparation of positive electrode body]
The same one as in Example 1 was used.
[Preparation of negative electrode body]
The same one as in Example 1 was used.
[Assembly and performance of storage element]
A polyethylene separator (thickness 30 μm) was laminated between the obtained negative electrode body and positive electrode body to assemble a non-aqueous lithium storage element. A solution obtained by dissolving LiPF ₆ at a concentration of 1 mol / l in a solvent in which ethylene carbonate and methyl ethyl carbonate were mixed at a weight ratio of 1: 4 was used as an electrolytic solution.
Hereinafter, as in Example 1, the assembly and performance evaluation of the electricity storage element were performed. The capacity of this power storage element was 40 mAh / g. Also. The output characteristic was 0.443. Furthermore, the durability test of the assembled electrical storage element was performed under the conditions of 60 ° C. and 3.8 V application. After 1000 hours, the resistance magnification was 1.03.

<Example 6>
[Preparation of positive electrode body]
The same one as in Example 2 was used.
[Preparation of negative electrode body]
The same one as in Example 2 was used.
[Assembly and performance of storage element]
As in Example 5, a nonaqueous lithium storage element was assembled and evaluated. The capacity of this power storage element was 42 mAh / g. Also. The output characteristic was 0.432. Furthermore, the durability test of the assembled electrical storage element was performed under the conditions of 60 ° C. and 3.8 V application. After 1000 hours, the resistance magnification was 1.08.

<Example 7>
[Preparation of positive electrode body]
The same one as in Example 3 was used.
[Preparation of negative electrode body]
The same one as in Example 3 was used.
[Assembly and performance of storage element]
As in Example 5, a nonaqueous lithium storage element was assembled and evaluated. The capacity of this power storage element was 40 mAh / g. Also. The output characteristic was 0.458. Furthermore, the durability test of the assembled electrical storage element was performed under the conditions of 60 ° C. and 3.8 V application. After 1000 hours, the resistance magnification was 1.51.

<Example 8>
[Preparation of positive electrode body]
The same one as in Example 4 was used.
[Preparation of negative electrode body]
The same one as in Example 4 was used.
[Assembly and performance of storage element]
As in Example 5, a nonaqueous lithium storage element was assembled and evaluated. The capacity of this power storage element was 38 mAh / g. Also. The output characteristic was 0.388. Furthermore, the durability test of the assembled electrical storage element was performed under the conditions of 60 ° C. and 3.8 V application. After 1000 hours, the resistance magnification was 1.12.

<Comparative example 4>
[Preparation of positive electrode body]
The thing similar to the comparative example 1 was used.
[Preparation of negative electrode body]
The thing similar to the comparative example 1 was used.
[Assembly and performance of storage element]
As in Example 5, a nonaqueous lithium storage element was assembled and evaluated. The capacity of this power storage element was 35 mAh / g. Also. The output characteristic was 0.303. Furthermore, the durability test of the assembled electrical storage element was performed under the conditions of 60 ° C. and 3.8 V application. After 1000 hours, the resistance magnification was 2.52.

<Comparative Example 5>
[Preparation of positive electrode body]
The thing similar to the comparative example 2 was used.
[Preparation of negative electrode body]
The thing similar to the comparative example 2 was used.
[Assembly and performance of storage element]
As in Example 5, a nonaqueous lithium storage element was assembled and evaluated. The capacity of this power storage element was 45 mAh / g. Also. The output characteristic was 0.636. Furthermore, the durability test of the assembled electrical storage element was performed under the conditions of 60 ° C. and 3.8 V application. After 1000 hours, the resistance magnification was 2.33.

<Comparative Example 6>
[Preparation of positive electrode body]
The same one as in Comparative Example 3 was used.
[Preparation of negative electrode body]
The same one as in Comparative Example 3 was used.
[Assembly and performance of storage element]
As in Example 5, a nonaqueous lithium storage element was assembled and evaluated. The capacity of this power storage element was 42 mAh / g. Also. The output characteristic was 0.401. Furthermore, the durability test of the assembled electrical storage element was performed under the conditions of 60 ° C. and 3.8 V application. After 1000 hours, the resistance magnification was 3.02.

  As mentioned above, it turns out that the electrical storage element which concerns on this invention is the characteristic which combined high durability in addition to high energy density and high output density.

  The power storage device of the present invention can be suitably used in automobiles, in the field of a hybrid drive system that combines an internal combustion engine or a fuel cell, a motor, and a power storage device, and for assisting instantaneous power peaks.

Claims (6)

A negative electrode body in which a negative electrode active material layer is provided on a negative electrode current collector, a positive electrode body in which a positive electrode current collector is provided with a positive electrode active material layer, an electrode laminate formed by laminating a separator, and an electrolyte containing lithium ions A non-aqueous lithium-type electricity storage element in which a non-aqueous electrolyte solution containing a non-aqueous electrolyte solution is housed in an exterior body, wherein the positive electrode active material contains activated carbon as a main component, where the activated carbon has a diameter of 20 mm calculated by the BJH method. When the amount of mesopores derived from pores having a diameter of 500 mm or less is V1 (cc / g) and the amount of micropores derived from pores having a diameter of less than 20 mm calculated by the MP method is V2 (cc / g). 3 <V1 ≦ 0.8 and 0.5 ≦ V2 ≦ 1.0 are satisfied, and the specific surface area measured by the BET method is 1,500 m ² / g or more and 3,000 m ² / g or less. And the negative electrode active material is mainly composed of graphitized material. The non-aqueous lithium-type electricity storage element, which is included as a fraction. The ratio of the peak intensity of the peak intensity _{(I 1360)} and 1580 cm ^-1 of the graphite product of 1360 cm ^-1 as measured in the Raman spectrum using laser with a wavelength of _{532nm (I 1580) (I 1360} / I 1580) is 0. The non-aqueous lithium-type energy storage device according to claim 1, which is 05 or more and less than 0.90.   3. The non-aqueous lithium storage element according to claim 1, wherein an interval between (002) planes of the graphitized material obtained by an X-ray wide angle diffraction method is 0.335 nm or more and less than 0.340 nm. The non-aqueous lithium storage element according to any one of claims 1 to 3, wherein a specific surface area of the graphitized material measured by a BET method is 1 m ² / g or more and less than 20 m ² / g.   The non-aqueous lithium storage element according to claim 1, wherein the graphitized material has an average particle diameter of 5 to 30 μm.   The non-aqueous lithium storage element according to claim 1, wherein the graphitized material is a mesocarbon microsphere graphitized material.