JP2014131080A - Nonaqueous lithium type storage element - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a nonaqueous lithium type storage element combining a small time constant and less self-discharge.SOLUTION: The main component of a negative electrode active material composing a negative electrode active material layer is a composite porous carbon material having a carbonaceous material on the surface of active carbon, and the main component of a positive electrode active material composing a positive electrode active material layer is active carbon. The ratio of the total length L(cm) of the outline in the plan view to the plane area S(cm) of the negative electrode active material layer, i.e., the edge ratio (L/S), satisfies a relation 0.30≤L/S<1.00. A storage module including a plurality of storage elements where six storage elements 10 are arranged in the same rectangular prism in the height direction thereof (a) has the edge ratio smaller than that of a storage module where six storage elements 11 are arranged in the bottom of a rectangular prism (b), and thereby self-discharge can be reduced.

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 achieve 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 is designed to deliberately suppress the high energy density, which is the greatest feature of lithium ion batteries. 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 development of a power storage element called a lithium ion capacitor has been actively developed as a promising candidate.
A lithium ion capacitor is a power storage element (nonaqueous lithium type power storage element) that uses a non-aqueous electrolyte containing a lithium salt as an electrolyte, and the positive electrode is non-desorbed by anion adsorption / desorption similar to an electric double layer capacitor. The Faraday reaction is a storage element that charges and discharges by a Faraday reaction by insertion and extraction of lithium ions similar to a lithium ion battery in a negative electrode.

  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. as a negative electrode active material A power storage element using the above has been proposed (see Patent Document 1). 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 Documents 2 and 3).

Moreover, hydrogen / carbon different from normal activated carbon as a positive electrode active material is 0.05 to 0.5, BET specific surface area is 300 to 2000 m ² / g, and mesopore volume by BJH method is 0.02 to 0.3 ml / g. , Using a hydrocarbon material having a pore structure with a total pore volume of 0.3 to 1.0 ml / g by the MP method, and using a material obtained by activating an optically anisotropic carbon substance excluding graphite as a negative electrode An element has been proposed (see Patent Document 4).

Further, activated carbon or a polyacene organic semiconductor having a polyacene skeleton structure with a hydrogen atom / carbon atom ratio of 0.05 to 0.50 is used as the positive electrode active material, and hydrogen atoms / carbon atom atoms are used as the negative electrode material. An electric storage element using non-graphitizable carbon having a number ratio of 0 or more and less than 0.05 has been proposed (see Patent Document 5).
In addition, an electric storage element using activated carbon as a positive electrode active material and a carbon material composed of graphitizable carbon and non-graphitizable carbon as a negative electrode active material has been proposed (see Patent Document 6).

  In addition, a power storage element using a specific negative electrode material and a specific positive electrode material has been proposed (see Patent Document 7). The negative electrode material is a composite porous carbon material having a carbonaceous material on the surface of activated carbon, and the amount of mesopores derived from pores having a diameter of 2 nm (20 mm) or more and 50 nm (500 mm) or less calculated by the BJH method is Vm1. (Cc / g), when the amount of micropores derived from pores having a diameter of less than 20 mm calculated by the MP method is Vm2 (cc / g), 0.01 ≦ Vm1 <0.10 and 0.01 ≦ Vm2 < It is made of a carbon material that is 0.30.

The positive electrode material has a mesopore amount derived from pores having a diameter of 2 nm (20 cm) or more and 50 nm (500 cm) or less calculated by the BJH method, V1 (cc / g), and a diameter less than 2 nm (20 cm) calculated by the MP method. When the amount of micropores derived from the pores 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 It consists 1500 m ² / g or more 3000 m ² / g or less is activated carbon.

Japanese Patent Laid-Open No. 8-1007048 JP-A-9-283383 JP 2008-252013 A JP 2005-93778 A JP 2007-115721 A JP 2008-235169A International Publication No. 2009/063966 Pamphlet

The lithium ion capacitor, which is a power storage device having high output density, high energy density, and durability as described above, has the following two additional characteristics. First, in order to reduce the amount of heat generated when modularized, the time constant (value represented by the product of the internal resistance of the storage element and the cell capacity) is small, and second, under irregular usage conditions There is little self-discharge so that
The power storage elements described in Patent Documents 1 to 6 have a problem that the time constant is large, although self-discharge is relatively small. In addition, the power storage device described in Patent Document 7 is excellent in output characteristics and has a relatively small time constant, but because the internal resistance is small, the self-discharge speed is fast (the amount of self-discharge per unit time is large). There is room for further improvement.
An object of the present invention is to provide a non-aqueous lithium storage element that has both a small time constant and a low self-discharge.

In order to solve the above problems, the non-aqueous lithium storage element of the present invention includes a negative electrode body in which a negative electrode active material layer is formed on one or both surfaces of a negative electrode current collector, and a positive electrode on one or both surfaces of a positive electrode current collector. A positive electrode body in which an active material layer is formed; an electrode stack in which separators are stacked; a non-aqueous electrolyte containing a lithium salt as an electrolyte; and an outer package that houses the electrode stack and the non-aqueous electrolyte; A negative electrode active material comprising a negative electrode active material, the main component of the negative electrode active material is a composite porous carbon material having a carbonaceous material on the surface of activated carbon, and the positive electrode active material The main component of the positive electrode active material constituting the layer is activated carbon, and the ratio of the total length L (cm) of the outline in a plan view of the negative electrode active material layer to the plane area S (cm ² ) of the negative electrode active material layer A certain edge ratio (L / S) Meets 0.30 ≦ L / S <1.00, include LiPF ₆ as the lithium salt, the capacity is 50～5000F.

In the non-aqueous lithium storage device of the present invention, the main component of the negative electrode active material is a composite porous carbon material having a carbonaceous material on the surface of the activated carbon, and the main component of the positive electrode active material is activated carbon. When the constant becomes smaller and the edge ratio (L / S) of the negative electrode active material layer satisfies 0.30 ≦ L / S <1.00, the self-discharge is reduced, so that the time constant is small and the self-discharge There are few things that are combined.
As a non-aqueous lithium storage element for solving the above problems, a negative electrode body in which a negative electrode active material layer is formed on one or both surfaces of a negative electrode current collector, and a positive electrode active material layer on one or both surfaces of a positive electrode current collector A non-aqueous electrolyte comprising: a formed positive electrode body; an electrode laminate in which separators are laminated; a non-aqueous electrolyte solution including a lithium salt as an electrolyte; and an outer package housing the electrode laminate and the non-aqueous electrolyte solution. A water-based lithium storage element, wherein the main component of the negative electrode active material constituting the negative electrode active material layer is a composite porous carbon material or a non-graphitizable carbon material having a carbonaceous material on the surface of activated carbon, and the positive electrode The main component of the positive electrode active material constituting the active material layer is activated carbon, and the total length L (cm) of the outline in a plan view of the negative electrode active material layer with respect to the planar area S (cm ² ) of the negative electrode active material layer The ratio is Rate (L / S) is, there is a non-aqueous lithium-type storage element that satisfies 0.10 <L / S <1.00.
In this non-aqueous lithium storage element, the main component of the negative electrode active material constituting the negative electrode active material layer is a composite porous carbon material or a non-graphitizable carbon material having a carbonaceous material on the surface of activated carbon, When the main component of the material is activated carbon, the time constant is reduced, and the edge ratio (L / S) of the negative electrode active material layer satisfies 0.10 <L / S <1.00, so that self-discharge is prevented. Therefore, the time constant is small and the self-discharge is small.

In the non-aqueous lithium-type energy storage device of the present invention, the main component of the negative electrode active material is a composite porous carbon material having a carbonaceous material on the surface of the activated carbon, and the composite porous carbon material has the following condition (1): Satisfies (4).
(1) The amount of mesopores (the amount of pores having a diameter of 2 nm to 50 nm) Vm1 (cc / g) calculated by the BJH method is 0.01 ≦ Vm1 <0.10.
(2) The amount of micropores (amount of pores having a diameter of less than 2 nm) Vm2 (cc / g) calculated by the MP method is 0.01 ≦ Vm2 <0.30.
(3) The BET specific surface area is 10 m ² / g or more and less than 1000 m ² / g.
(4) The average particle size is 1.5 to 25 μm.

In the non-aqueous lithium-type energy storage device of the present invention, the activated carbon that is the main component of the positive electrode active material preferably satisfies the following conditions (1) to (3).
(1) Mesopore amount (amount of pores having a diameter of 2 nm to 50 nm) V1 (cc / g) calculated by the BJH method is 0.3 <V1 ≦ 0.8.
(2) The amount of micropores (the amount of pores having a diameter of less than 2 nm) V2 calculated by the MP method is 0.5 ≦ V2 <1.0.
(3) The specific surface area measured by the BET method is 1500 m ² / g or more and 3000 m ² / g or less.
In the non-aqueous lithium storage element of the present invention, the capacity per unit area of the negative electrode body is preferably in the range of 0.25 to 0.75 (F / cm ² ).
The power storage module of the present invention includes a plurality of non-aqueous lithium-type power storage elements of the present invention.

The method for producing a power storage module of the present invention is the nonaqueous lithium power storage element of the present invention, wherein the capacity per unit area of the negative electrode body is in the range of 0.25 to 0.75 (F / cm ² ). When manufacturing a power storage module by arranging the non-aqueous lithium-type power storage element in a predetermined space, the edge rate is minimized in a range satisfying 0.30 ≦ L / S <1.0. It is characterized in that the number of the bottom surface on which the negative electrode active material layers in the predetermined space are arranged in parallel and the number of the negative electrode active material layers arranged in the bottom surface are determined. As a result, the power storage element has the least self-discharge compared to the power storage element that is arranged in the same predetermined space in another arrangement within the range where the edge rate satisfies 0.30 ≦ L / S <1.0. A module is obtained.
The method of using the non-aqueous lithium storage element of the present invention is a non-aqueous lithium storage element having a capacity per unit area of the negative electrode body in the range of 0.25 to 0.75 (F / cm ² ). The negative electrode active material layer is arranged so as to be the smallest in a range satisfying 0.30 ≦ L / S <1.0, and is used by being arranged in a predetermined space.

The non-aqueous lithium storage element of the present invention has both a small time constant and a low self-discharge. Therefore, the non-aqueous lithium storage element of the present invention can be suitably used in automobiles, in the field of hybrid drive systems that combine an internal combustion engine or a fuel cell, a motor, and a storage element, and for assisting instantaneous power peaks. .
According to the method for manufacturing a power storage module of the present invention, a power storage module having the same size and the least self-discharge can be obtained as compared to a power storage module obtained by arranging power storage elements in the same predetermined space by another method. .

In the method of designing a power storage module by arranging power storage elements in the same rectangular parallelepiped space, when a power storage element having a negative electrode active material layer having substantially the same plane as the bottom surface is used (a), and a flat negative electrode having a bottom surface divided into six It is a figure explaining the difference in the number of the negative electrode active material layers arrange | positioned in the same bottom face by the case where the electrical storage element which has an active material layer is used (b). FIG. 4 is a diagram illustrating the difference in the arrangement method of the storage elements constituting the storage module due to the difference between FIGS. 1A and 1B in the method of designing the storage module by arranging the storage elements in the same rectangular parallelepiped space. is there. It is a fragmentary top view which shows an example of the negative electrode body which provided the ear | edge part in the negative electrode collector.

Embodiments of the present invention will be described below.
[Negative electrode active material]
First, the negative electrode active material constituting the non-aqueous lithium storage element of the present invention will be described.
In a general non-aqueous lithium storage element, as a negative electrode active material, graphite, a graphitizable carbon material, a non-graphitizable carbon material, activated carbon, a composite having a carbonaceous material on the surface of activated carbon (attached) Porous materials, amorphous carbonaceous materials such as polyacenic materials, carbon blacks such as ketjen black and acetylene black, carbonaceous materials such as carbon nanotubes, fullerenes, carbon nanophones, fibrous carbonaceous materials, lithium titanium composite oxides, A material that occludes and releases lithium ions, such as a conductive polymer, can be used.

  In the non-aqueous lithium storage element of the present invention, a composite porous carbon material or a non-graphite having a carbonaceous material on the surface of activated carbon as a main component of the negative electrode active material (a component present in an amount of more than 50% of the total mass) Use carbonizable carbon materials. Thereby, the time constant of a non-aqueous lithium-type electrical storage element can be made small compared with the case where the above-mentioned other material is used as the main component of the negative electrode active material.

  In terms of reducing the time constant of the non-aqueous lithium storage element, use a composite porous carbon material having a carbonaceous material on the surface of activated carbon rather than a non-graphitizable carbon material as the main component of the negative electrode active material. Is preferred. In terms of reducing self-discharge, it is preferable to use a non-graphitizable carbon material as a main component of the negative electrode active material, rather than a composite porous carbon material having a carbonaceous material on the surface of activated carbon.

Composite porous carbon material with carbonaceous material on the surface of activated carbon is generated by applying a carbonaceous material precursor dissolved in a solvent to activated carbon and baking it, or by heating the carbonaceous material precursor. And the like, which are obtained by adsorbing a hydrocarbon-containing gas on activated carbon and calcining it. At this time, it is preferable to use a composite porous carbon material satisfying the following conditions (1) and (2) by controlling the amount of the carbon material to be combined with the activated carbon.
(1) The amount of mesopores (the amount of pores having a diameter of 2 nm to 50 nm) Vm1 (cc / g) calculated by the BJH method is 0.01 ≦ Vm1 <0.10.
(2) The amount of micropores (amount of pores having a diameter of less than 2 nm) Vm2 (cc / g) calculated by the MP method is 0.01 ≦ Vm2 <0.30.

When the amount of each pore is not less than each upper limit value, the charge / discharge efficiency with respect to lithium is lowered, and when it is less than the lower limit value, it is difficult to obtain output characteristics.
The micropore volume and mesopore volume are values determined by the following method. That is, the sample is vacuum-dried at 500 ° C. all 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 is based on the “t-plot method” (BC Lippens, JH deBoer, J. Catalysis, 4319 (1965)), and the micropore volume, the micropore area, and the micropore size. Means a method for obtaining the distribution; This is a method devised by Mikhal, Brunauer, Bodor (RS Mikhal, S. Brunauer, EE Bodor, J. Colloid Interface Sci., 26, 45 (1968)).

The BJH method is a calculation method generally used for analysis of mesopores, and was proposed by Barrett, Joyner, Halenda et al. (EP Barrett, LG Joyner and P. Halenda, J. et al. Amer. Chem. Soc., 73, 373 (1951)).
The composite porous carbon material can be obtained, for example, by heat treatment in a state where activated carbon and a carbonaceous material precursor coexist.

  The activated carbon used as a raw material is not particularly limited as long as the obtained composite porous carbon material exhibits desired characteristics, and there are no particular restrictions on the raw material before the activated carbon, and various types such as petroleum-based, coal-based, plant-based, polymer-based, etc. A commercially available product obtained from the above raw materials can be used, and those having an average particle size of 1 to 50 μm are preferred, and those having an average particle size of 1 to 30 μm are more preferred. 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 carbonaceous material precursor is an organic material capable of depositing a carbonaceous material on activated carbon by heat treatment. Examples thereof include synthetic resins such as pitch, mesocarbon microbeads, coke, and phenol resin. it can. Among these carbonaceous material precursors, it is preferable in terms of production cost to use an inexpensive pitch. Pitch is roughly divided into petroleum pitch and coal pitch. Examples of petroleum pitches include crude oil distillation residue, fluid catalytic cracking residue (decant oil, etc.), bottom oil from thermal cracker, ethylene tar obtained during naphtha cracking, and the like.

  When the pitch is used, the composite porous carbon material can be obtained by depositing a carbonaceous material on the activated carbon by thermally reacting the volatile component or thermal decomposition component of the pitch on the surface of the activated carbon. In this case, the deposition of the volatile component of the pitch or the pyrolysis component into the activated carbon pores proceeds at a temperature of about 200 to 500 ° C., and the deposition component becomes a carbonaceous material at 400 ° C. or higher. Progresses.

  The peak temperature during the heat treatment is appropriately determined according to the characteristics of the composite porous material to be obtained, the thermal reaction pattern, the thermal reaction atmosphere, etc., but is preferably 400 ° C. or higher, more preferably 450 ° C. to 1000 ° C. In particular, a peak temperature of about 500 to 800 ° C. is preferable. The time for maintaining the peak temperature during the heat treatment may be 30 minutes to 10 hours, preferably 1 hour to 7 hours, and more preferably 2 hours to 5 hours. When the heat treatment is performed at a peak temperature of about 500 to 800 ° C. for 2 to 5 hours, the carbonaceous material deposited on the activated carbon surface is considered to be a polycyclic aromatic hydrocarbon.

  In the composite porous carbon material, the atomic ratio of hydrogen atoms / carbon atoms (hereinafter referred to as H / C) is preferably 0.05 or more and 0.35 or less, and 0.05 or more and 0.15 or less. It is more preferable that When H / C exceeds the upper limit value, the carbonaceous material polycyclic aromatic conjugated structure adhering to the activated carbon surface is not sufficiently developed. When the value is below, carbonization proceeds excessively, and a sufficient capacity may not be obtained.

  The composite porous carbon material is obtained by depositing a carbonaceous material on the surface of the activated carbon. In particular, the pore distribution after the carbonaceous material is deposited inside the pores of the activated carbon is important. It can be defined by the amount of micropores and mesopores of the composite porous material after the carbonaceous material is deposited thereon. Even if the composite porous carbon material has a similar BET specific surface area, if the distribution of the micropore amount and the mesopore amount is different, the efficiency of the electricity storage device using the composite porous carbon material as an active material is greatly increased. May be different. That is, it is difficult to optimize efficiency by defining the BET specific surface area. On the other hand, the micropore amount and mesopore amount specified in the present invention can be selected to be efficient by selecting a specific range.

  However, optimization by the BET specific surface area is important in order to obtain a power storage device that has both a small time constant, which is an effect of the present invention, and a small self-discharge. The reason is not clear, but for example, it is considered that when the BET specific surface area is improved, the contact area with the electrolytic solution is also improved, thereby increasing the leakage current and the self-discharge. For the internal resistance, it is important to optimize the solvated ionic radius and the pore size of the active material. As described above, this is largely due to the distribution of micropores and mesopores. As the surface area increases, the output characteristics improve and the internal resistance tends to decrease.

Therefore, BET specific surface area of the composite porous carbon material of the present invention is preferably less than 10 m ² / g or more 1000 m ² / g, more preferably those which are ^{20~500m 2 / g, 30~400m 2 /} g Is more preferred.
In addition, in the composite porous carbon material produced by the heat treatment method described above, unlike the general surface coating, there is no aggregation even after the carbonaceous material is deposited on the surface of the activated carbon, and the average particle diameter of the activated carbon is reduced. Characterized by almost no change. Because of this and the reduction in pores and the specific surface area, in the present invention, most of the volatile components such as pitch or the pyrolysis component used as the raw material for the carbonaceous material to be deposited are: It can be inferred that the reaction in which the deposited components are deposited in the pores of the activated carbon and the deposited component becomes a carbonaceous material has progressed.

  In order to realize the above-mentioned pore structure (a formula that the micro amount and meso pore amount should satisfy), generally, the mass ratio of carbonaceous material / activated carbon (hereinafter referred to as composite ratio) is about 0.25 to 1.00. It becomes. When importance is attached to the capacity, the composite ratio is preferably in the range of 0.25 to 0.45. When importance is placed on the efficiency, the composite ratio is preferably in the range of 0.55 to 1.00. However, even if the composite ratio is within this range, the expected effect cannot be obtained if the pore structure is not within the range. This composite ratio can be controlled by manufacturing conditions, for example, a carbonaceous material precursor that is a raw material for the carbonaceous material to be deposited with activated carbon, for example, the charging ratio of the pitch, the softening point of the pitch, and the like.

The composite porous carbon material has an amorphous structure derived from activated carbon, but at the same time has a crystal structure mainly derived from the deposited carbonaceous material. According to X-ray wide angle diffraction method, a composite porous material (002) plane face spacing d ₀₀₂ of not more than 4.00Å than 3.60A, c-axis of the crystallites obtained from the half width of the peak The size Lc is preferably 8.0 to 20.0 and preferably d ₀₀₂ is 3.60 to 3.75 and the crystallite size Lc in the c-axis direction obtained from the half width of this peak is 11 More preferably, it is not less than 0.01 and not more than 16.0.

The average particle size of the composite porous carbon material used in the present invention is preferably 1 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).
If the average particle size is less than 1 μm, the density of the active material layer is lowered, and the capacity per volume is undesirably lowered. Furthermore, the small average particle diameter can exhibit the characteristic that the time constant is small, but has the disadvantages that self-discharge tends to be large and the durability is lowered. On the contrary, if the average particle size is larger than 30 μm, it is not suitable for high-speed charge / discharge. Accordingly, the thickness is preferably 1.5 to 25 μm, more preferably 2 to 20 μm.

These composite porous carbon materials can be used alone or in combination of two or more.
The non-graphitizable carbon material is not particularly limited, but the following can be exemplified as preferable ones. Low molecular organic compounds such as naphthalene and anthracene; resins such as phenolic resin, furan resin, furfural resin, and cellulose resin; pitch materials such as coal tar pitch, oxygen-crosslinked petroleum pitch, petroleum or coal pitch, etc. Examples thereof include non-graphitizable carbon materials obtained by heating or baking. The method of heating or baking mentioned here may follow a known method. For example, it can be obtained by carbonizing the raw material in a temperature range of about 500 to 1200 degrees in an inert gas atmosphere such as nitrogen.

Further, the non-graphitizable carbon material used in the present invention includes a polyacene-based substance. A polyacene-type substance means the substance which has a polyacene structure obtained by carbonizing a phenol resin etc., for example.
What was heated or baked as mentioned above may be used as it is, and further, what increased the pore volume by treatment such as activation may be used. Moreover, you may use what was grind | pulverized using known grinders, such as a ball mill, as needed.

These non-graphitizable carbon materials can be used alone or in combination of two or more.
The specific surface area of the non-graphitizable carbon material used in the present invention, preferably a specific surface area as measured by BET method is less than 1 m ² / g or more 1000 m ² / g, those that are 3~100m ² / g More preferable is 4 to ²⁰ m ² / g.
When the BET specific surface area is 1 m ² / g or more, a sufficient energy density can be obtained. On the other hand, it was found that when the BET specific surface area is less than 1000 m ² / g, the durability is excellent.
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.

The crystal structure of the non-graphitizable carbon material used in the present invention is obtained by X-ray wide angle diffraction method (002) plane of the surface interval (hereinafter referred to as d ₀₀₂₎ is less than 0.390nm than 0.341nm It is preferable. D ₀₀₂ here is calculated from the peak position of a non-graphitizable carbon material measured on the (002) plane using CuKα rays as X-rays and using high-purity silicon as a standard substance. It is.

When d ₀₀₂ is less than 0.341Nm, crystallinity is improved, no longer a non-graphitizable carbon material. When the crystallinity is improved, the entry / exit of lithium ions at the time of charging / discharging is delayed and the output characteristics are deteriorated. On the other hand, if the thickness is larger than 0.390 nm, the durability characteristics are deteriorated along with the significant decrease in crystallinity. Therefore, it is preferably 0.350 nm or more and 0.385 nm or less, and more preferably 0.360 nm or more and 0.380 nm or less.

  The pore structure of the graphitizable carbon material used in the present invention is not particularly limited, but the mesopore volume Vm1 and the micropore volume Vm2 are. The carbon material is preferably 001 ≦ Vm1 <0.01 and 0.001 ≦ Vm2 <0.01. The mesopore volume Vm1 and the micropore volume Vm2 here are the same as the definitions made in the description regarding the above-mentioned “composite porous carbon material having a carbonaceous material on the surface of activated carbon”.

  When both Vm1 and Vm2 are 0.01 or more, the output characteristics improve as the pores increase, but the density of the active material layer cannot be increased greatly, leading to a decrease in capacity per volume, As the contact area with the liquid is improved, an increase in leakage current is likely to cause a decrease in durability. Therefore, Vm1 <0.0095 and Vm2 <0.0070 are preferable, and Vm1 <0.0085 and Vm2 <0.0050 are more preferable.

The average particle size of the non-graphitizable carbon material used 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).
When the average particle size is less than 5 μm, the density of the active material layer is lowered, and the capacity per volume is lowered, which is not preferable. Furthermore, having a small average particle size has the disadvantage that durability is reduced. On the contrary, if the average particle size is larger than 30 μm, it is not suitable for high-speed charge / discharge. Accordingly, the thickness is preferably 6 to 25 μm, and more preferably 7 to 20 μm.

  The negative electrode active material used in the present invention has a main component (50% by mass or more of the whole) as “a composite porous carbon material or a non-graphitizable carbon material having a carbonaceous material on the surface of activated carbon”. Yes, with the main component as a central material and other materials coated (composite), other materials as the central material with the main components coated (composite), and the main components with other materials It may be a mixture (mixture).

  Other materials include graphite, graphitizable carbon material, non-graphitizable carbon material, composite porous material with activated carbon surface coated with carbonaceous material, amorphous carbonaceous material such as polyacene, kettle Carbon black, carbon nanotubes such as chain black and acetylene black, carbon nanotubes, fullerenes, carbon nanophones, fibrous carbonaceous materials, etc., carbonaceous materials that do not fit into the preferred carbon materials, lithium titanium composite oxides, conductive polymers, etc. It shows a known negative electrode material for lithium ion secondary batteries.

[Positive electrode active material]
Next, the positive electrode active material that constitutes the non-aqueous lithium storage element of the present invention will be described.
For the positive electrode active material of a general non-aqueous lithium-type storage element, amorphous carbonaceous materials such as activated carbon and polyacenic materials, carbon blacks such as ketjen black and acetylene black, carbonaceous materials such as carbon nanotubes and carbon aerogels are used. can do.
In the non-aqueous lithium storage element of the present invention, activated carbon is used as the main component of the positive electrode active material. As a result, the time constant of the non-aqueous lithium storage element can be reduced, the electron conductivity is increased, and the ion diffusibility is increased.

  The carbonaceous material used as a raw material for activated carbon is not particularly limited as long as it is generally used as a raw material for activated carbon. For example, (a) plant raw materials such as wood, wood flour, coconut shell, pulp by-products, bacas, molasses, (b) peat, lignite, lignite, bituminous coal, anthracite, petroleum distillation residue components, petroleum pitch, Fossil raw materials such as coke and coal tar, (c) Various syntheses such as phenol resin, vinyl chloride resin, vinyl acetate resin, melamine resin, urea resin, resorcinol resin, celluloid, epoxy resin, polyurethane resin, polyester resin, polyamide resin, etc. Examples thereof include resins, (d) synthetic rubbers such as polybutylene, polybutadiene, and polychloroprene, other synthetic wood, synthetic pulp, and their carbides. 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 carbonization and activation methods for using these raw materials as 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.
As a carbonization method of these raw materials, nitrogen, carbon dioxide, helium, argon, xenon, neon, carbon monoxide, an exhaust gas such as 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.

As a method for activating the carbide obtained by the carbonization method, a gas activation method in which firing is performed using an activation gas such as water vapor, carbon dioxide, or oxygen is used. 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.
Activated carbon 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.

<Preferred form of activated carbon>
In the non-aqueous lithium-type energy storage device of the present invention, the activated carbon that is the main component of the positive electrode active material preferably satisfies the following conditions (1) to (3).
(1) Mesopore amount (amount of pores having a diameter of 2 nm to 50 nm) V1 (cc / g) calculated by the BJH method is 0.3 <V1 ≦ 0.8.
(2) The amount of micropores (the amount of pores having a diameter of less than 2 nm) V2 calculated by the MP method is 0.5 ≦ V2 <0.30.
(3) The specific surface area measured by the BET method is 1500 m ² / g or more and 3000 m ² / g or less.

The mesopore volume V1 is preferably a value larger than 0.3 cc / g from the viewpoint of increasing the output characteristics of the storage element, and is 0.8 cc / g or less from the viewpoint of suppressing a reduction in the capacity of the storage element. Preferably there is. More preferably, it is 0.35 cc / g or more and 0.7 cc / g or less, More preferably, it is 0.4 cc / g or more and 0.6 cc / g or less.
On the other hand, the micropore volume V2 is preferably 0.5 cc / g 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 cc / g or less. Moreover, More preferably, they are 0.6 cc / g or more and 1.0 cc / g or less, More preferably, they are 0.8 cc / g or more and 1.0 cc / g or less.

  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 addition, the average pore diameter of the activated carbon used as the positive electrode active material is preferably 1.7 nm or more, more preferably 1.8 nm or more, and more preferably 2.0 nm or more from the viewpoint of maximizing the output. Most preferably it is. Moreover, it is preferable that it is 2.5 nm or less from the point which maximizes a capacity | capacitance. The average pore diameter is obtained by dividing the total pore volume per mass by the BET specific surface area obtained by measuring each equilibrium adsorption amount of nitrogen gas under each relative pressure at liquid nitrogen temperature. Indicates.

Furthermore, the activated carbon used as the positive electrode active material preferably has a BET specific surface area of 1500 m ² / g or more and 3000 m ² / g or less. More preferably, 1500 m ² / g or more, or less 2500 m ² / g. When the BET specific surface area is less than 1500 m ² / g, a sufficient energy density cannot be obtained. On the other hand, when the BET specific surface area exceeds 3000 m ² / g, a sufficient amount of binder must be added without adding a large amount of binder. Since the strength cannot be maintained, the performance per volume decreases.
The positive electrode active material used in the present invention has activated carbon as the main component (50% by mass or more of the whole). From the viewpoint of improving the energy density of the storage element, the positive electrode of the lithium ion secondary battery. A metal oxide that occludes and releases known lithium ions as an active material, for example, lithium cobaltate may be added in an amount of less than 50% by mass.

[Edge rate of negative electrode active material layer]
The non-aqueous lithium storage element of the present invention has an edge ratio (L) that is the ratio of the total length L (cm) of the outline in a plan view of the negative electrode active material layer to the flat area S (cm ² ) of the negative electrode active material layer. / S) satisfies 0.30 ≦ L / S <1.00. Thereby, the self-discharge can be reduced while maintaining the effect of reducing the time constant obtained by using the specific carbon material described above as the negative electrode active material.

  It is considered that charge concentration tends to occur at the edge portion of the negative electrode active material layer, and charge leakage is severe. Therefore, self-discharge can be suppressed as the ratio of the edge portion in a plan view of the negative electrode active material layer is smaller. However, if L / S is less than 1.00, the edge rate of the negative electrode active material layer is sufficiently small and self-discharge is prevented. It is considered that the suppressing effect is remarkably obtained. When L / S is greater than 0.10, the shape (the longest length in the case of portrait and landscape) and the area of the negative electrode active material layer in a plan view are within a preferable range in terms of the design of the storage element. The edge ratio (L / S) of the negative electrode active material layer is preferably 0.10 <L / S <0.80, and more preferably 0.10 <L / S <0.75. The edge ratio (L / S) of the negative electrode active material layer is preferably 0.30 ≦ L / S <0.80, and more preferably 0.30 ≦ L / S <0.75.

The total length (hereinafter referred to as “peripheral length”) L of the outer line in plan view of the negative electrode active material layer is, for example, that the negative electrode active material layer is applied in a rectangular shape on the negative electrode current collector in plan view. If it is, it is the sum of the lengths of the four sides of the rectangle.
In the case where the negative electrode active material layers are formed on both surfaces of the negative electrode current collector, the average values of the peripheral length and the flat area of both negative electrode active material layers are set as the peripheral length and the flat area of each negative electrode active material layer. Further, in the case where an ear for connecting the negative electrode external lead to the negative electrode current collector is provided, the negative electrode active material layer is not formed in that portion. In the example of FIG. 3, the rectangular shape of the negative electrode active material layer 3 is rectangular because the rectangular negative electrode current collector 1 has the rectangular ear 2, but the negative electrode active material layer 3 has a rectangular planar shape. In some cases, a part of the shape is missing. It is necessary to calculate the plane area S and the circumference L based on the planar shape of the negative electrode active material layer.

[About time constants]
In the non-aqueous lithium storage element of the present invention, the time constant according to the following definition is preferably 3.0 or less, more preferably 2.0 or less, and further preferably 1.5 or less. This time constant is defined by the internal resistance value R (Ω) when the storage element is discharged at a discharge current of 500 C at 25 ° C. and the cell capacity C (when the discharge is discharged at a discharge current of 1 C at 25 ° C. F) and the product RC (Ω · F).
When the time constant is larger than 3.0, the output characteristics of the cell are lowered, and particularly when a large current is used, the Joule heat generation amount of the cell becomes larger. This is not preferable when considering a module in which a large number of cells are connected in series, because the larger the heat generated from the module system, the greater the equipment and cost required for the cooling system.

The internal resistance R (Ω) is calculated based on a discharge curve at a discharge rate of 500C. Specifically, first, in a discharge curve showing the relationship between voltage and discharge capacity at a discharge rate of 500 C, a curve having a linear tendency in the first half of discharge is fitted to a linear function. Next, a voltage drop: ΔE ₁ (V) = E ₀ −E is calculated from the voltage value E which is an intercept of the straight line (intersection with the voltage axis) and the initial voltage E ₀ . From the ΔE ₁ and the discharge current value I (A), the internal resistance R (Ω) is calculated from R = ΔE ₁ / I.

The cell capacity C (F) is a cell capacity when discharged with a discharge current having a discharge rate of 1C. Specifically, the cell capacity C (F) is calculated from C = As / ΔE ₂ from the voltage difference ΔE ₂ (V) when discharged under the above conditions and the discharge amount As (Q).
In an electrode stack in which a plurality of the same electrode bodies are stacked, the electrode bodies are connected in parallel. Therefore, if the number of stacked layers is doubled, the internal resistance R is halved and the cell capacitance C is doubled. Accordingly, since the time constant does not change even when the number of stacked layers is increased or decreased, the storage element can be evaluated without being affected by the difference in the number of stacked layers by using the time constant.

[Other elements]
Next, other elements constituting 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, such as elution or reaction, when used as a power storage element, and examples thereof include copper foil and aluminum foil. In the non-aqueous lithium storage element 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.
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 mass and volume of the electricity storage device become too large. 1 to 100 μm is preferable.

  In addition to the positive electrode active material and the negative electrode active material described above, known components contained in the active material layer in known lithium ion batteries, capacitors, and the like can be used for the active material layer. For example, a binder, a conductive filler, and / or a thickener can be included, and the type thereof is not particularly limited. Hereinafter, the details of the components of the active material layer in the non-aqueous lithium storage element will be described.

  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. However, if it is more than 30% by mass, the proportion of the active material in the electrode layer is lowered, and the power density per volume is lowered.

  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, and ions enter and exit slowly, so that a high output density cannot 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 (negative electrode body and positive electrode body) constituting the electricity storage device of the present invention may have an active material layer formed only on the upper surface (one surface) of the current collector, or on the upper and lower surfaces (both surfaces). It may be formed.
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 active material to the entire power storage element is reduced, and the energy density is reduced. Furthermore, although the reason is not clear, since the amount of ions adsorbed in the electrode is small, the rate of ion emission in the storage state is large, so that the change in electrode potential is large and self-discharge is large.
On the contrary, when the thickness of the active material layer is larger than 200 μm, the self-discharge is reduced as described above, but the resistance inside the electrode is increased and the output density is lowered.

  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 constituting the active material layer are slurried with water or an organic solvent to collect current. It is obtained by applying on the body, drying, and pressing as necessary. In addition, various materials constituting the active material layer can be dry-mixed without using a solvent, the active material can be press-molded, and then attached to the current collector using a conductive adhesive. .

The molded positive electrode body and negative electrode body are laminated via a separator and inserted into an exterior body formed from a laminate 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 circuit 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.

  The laminate film used for the exterior body is preferably a film in which a metal foil and a resin film are laminated, and an example of a three-layer structure comprising an outer layer resin film / metal foil / interior resin film is exemplified. The outer layer resin film is for preventing the metal foil from being damaged by contact or the like, and a resin such as nylon or polyester can be 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 solution used in the non-aqueous lithium storage element of the present invention include ethylene carbonate (EC), cyclic carbonate represented by propylene carbonate (PC), diethyl carbonate (DEC), dimethyl carbonate (DMC). ), Chain carbonates typified by ethyl methyl carbonate (MEC), lactones such as γ-butyrolactone (γBL), and mixed solvents thereof.

Furthermore, in order to reduce the time constant and reduce self-discharge of the electricity storage device of the present invention, a clear reason is not clear, but the balance of the viscosity, dissociation degree, and mobility of the electrolytic solution is important. Therefore, it is preferable to use a mixed solvent of a chain carbonate having a low viscosity and a cyclic carbonate having a high degree of dissociation. In this case, the ratio of the chain carbonate to the total solvent is 50% by volume to 90% by volume. % Is preferred.
The electrolyte dissolved in these solvents needs to be a lithium salt. For example, 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) and mixed salts thereof.

Furthermore, LiPF ₆ is preferably used as the electrolyte in order to reduce the time constant of the electricity storage device of the present invention and reduce self-discharge. The obvious reason for this is not clear, but LiPF ₆ has a high ionic conductivity and a relatively small anion size. That is, it is important to select anion species that are adsorbed and released from the positive electrode active material layer. For example, it can be considered that a smaller solvated anion size can be adsorbed inside the positive electrode active material pores as much as possible, so that it is difficult for ions to be released in a stored state and self-discharge can be reduced.

In addition to the lithium salt as an electrolyte, an additive can be added to the electrolytic solution as necessary. As the additive, those capable of forming a good solid electrolyte interface (SEI) film on the electrode surface are preferable from the viewpoint of preventing leakage current as much as possible and reducing self-discharge, and examples thereof include vinylidene carbonate.
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. descend.

  The negative electrode body can be doped with lithium ions in advance. 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 a negative electrode active material layer of a negative electrode current collector and putting it in a non-aqueous electrolyte can be used. By doping with lithium ions, the capacity and operating voltage of the power storage element can be controlled.

In order to reduce the self-discharge of the electricity storage device of the present invention, it is important to make the doping amount appropriate. Although the working potential of the negative electrode can be lowered by increasing the doping amount, there is a possibility that Li may be electrodeposited and the safety may be hindered.
In the case of using a composite porous material in which a carbonaceous material is deposited on the surface of activated carbon as the negative electrode active material, the amount is preferably more than 700 mAh / g per mass of the composite porous material, and is 750 mAh / g or more. More preferably. About an upper limit, it is 1500 mAh / g or less, and when precipitation of lithium metal is considered, it is preferable that it is 1300 mAh / g or less. When the doping amount is 700 mAh / g or less, high energy density and high output are obtained, but sufficient durability cannot be obtained.

By pre-doping with lithium ions, the negative electrode potential is lowered, the cell voltage is increased when combined with the positive electrode, and the utilization capacity of the positive electrode is increased, so that the capacity is increased and a high energy density is obtained. Further, in the case of an amount exceeding 700 mAh / g, lithium ions are also doped into an irreversible site that is difficult to desorb once inserted, so that high output characteristics can be exhibited and a low internal resistance cell is obtained. Further, in the case of an amount exceeding 700 mAh / g, the negative electrode potential is sufficiently low, so that the potential change during self-discharge is small, resulting in a cell with little self-discharge.
The same applies to the case of using a non-graphitizable carbon material or other materials as the negative electrode active material, and it is preferable to appropriately select a doping amount in a range where the negative electrode potential is sufficiently low and Li is not electrodeposited.

[Regarding the capacity of the storage element and the number of laminated negative electrode bodies constituting the electrode laminate]
In the electricity storage device of the present invention, the capacity per unit area of the electrode body to be used is preferably large from the viewpoint of high energy density, and is preferably somewhat below from the viewpoint of high output density. Therefore, from the balance between the two, the capacity per unit area of the electrode body is preferably in the range of 0.25 to 0.75 (F / cm ² ). The capacity per unit area of the electrode body can be controlled by the type of the active material, the content in the active material layer, and the thickness of the active material layer. Moreover, since the effect of this invention is high when the capacity | capacitance as an electrical storage element of this invention is about 50-5000F, it is preferable.

In the electricity storage device of the present invention, a specific design example of the electrode laminate will be described below when the capacity per unit area of the electrode body and the capacity as the electricity storage device are within the above ranges. In the calculation, for simplification, it is assumed that the capacity per unit area of the electrode body is 0.5 (F / cm ² ), and the shape of the electrode body and the active material layer is the same square.
When the capacity of the storage element is 50 F, the total electrode area of the electrode stack is 100 cm ² . Therefore, when the negative electrode body constituting the electrode laminate is made into one layer, the flat area S of the negative electrode active material layer is 100 cm ² , the peripheral length L is 40 cm, and the edge rate is 0.40. Similarly, when the negative electrode body constituting the electrode laminate is made into two layers, the negative electrode active material layer has a flat area S of 50 cm ² , a peripheral length L of 28.3 cm, and an edge rate of 0.57. In the same manner, when the negative electrode body constituting the electrode laminate is formed in three layers, the negative electrode active material layer has a plane area S of 33.3 cm ² , a peripheral length L of 23.1 cm, and an edge ratio of 0.69. Become.

In the case where the negative electrode body constituting the electrode laminate has four layers, the flat area S of the negative electrode active material layer is 25 cm ² , the peripheral length L is 20 cm, and the edge rate is 0.80. When the negative electrode body constituting the electrode laminate is composed of five layers, the negative electrode active material layer has a plane area S of 20 cm ² , a peripheral length L of 17.9 cm, and an edge rate of 0.89. When the negative electrode body constituting the electrode laminate is composed of six layers, the negative electrode active material layer has a plane area S of 16.7 cm ² , a peripheral length L of 16.3 cm, and an edge rate of 0.98. When the negative electrode body constituting the electrode laminate is composed of seven layers, the negative electrode active material layer has a flat area S of 14.3 cm ² , a peripheral length L of 15.1 cm, and an edge ratio of 1.06.

Accordingly, in the case of a power storage element having a capacity per unit area of 0.5 (F / cm ² ) and a negative electrode body having a square planar shape and a capacity of 50 F, the edge ratio of the negative electrode active material layer is 0.1. The number of laminated negative electrode bodies constituting the electrode laminated body corresponding to .about.1.0 is 1-6. Similarly, the number of laminated negative electrode bodies corresponding to an edge rate of 0.10 to 0.80 is 1 to 4, and the number of laminated negative electrode bodies corresponding to an edge rate of 0.10 to 0.75 is 1 to 3. It is.

Similarly, in the case of a power storage element having a capacity of 50 F with a capacity per unit area of 0.25 (F / cm ² ) and a square negative electrode body, the edge ratio of the negative electrode active material layer is 0. The number of laminated negative electrode bodies constituting the electrode laminated body corresponding to 1 to 1.0 is 1 to 12. Similarly, the number of laminated negative electrode bodies corresponding to an edge rate of 0.10 to 0.80 is 1 to 8, and the number of laminated negative electrode bodies corresponding to an edge rate of 0.10 to 0.75 is 1 to 7. It is.

Similarly, in the case of a power storage element having a capacity of 50 F with a capacity per unit area of 0.75 (F / cm ² ) and a square negative electrode body, the edge ratio of the negative electrode active material layer is 0. The number of laminated negative electrode bodies constituting the electrode laminated body corresponding to 1 to 1.0 is 1 to 4. Similarly, the number of laminated negative electrode bodies corresponding to an edge rate of 0.10 to 0.80 is 1 to 2, and the number of laminated negative electrode bodies corresponding to an edge rate of 0.10 to 0.75 is 1 to 2. It is.

When the shape of the electrode body (negative electrode active material layer) is rectangular, the edge ratio is higher than that of a square of the same area, but if the ratio of the long side to the short side is close to 1: 1, the case of a square Therefore, it is preferable that the ratio of long side: short side is in the range of 1: 1 to 2: 1. For example, the edge ratio of an electrode body having a planar area of 100 cm ² and a planar shape of square is 0.40, whereas the planar area is about 100 cm ² and the planar shape has a long side of 11.5 cm and a short side of 8 The edge ratio of an electrode body having a rectangular shape of 0.7 cm (long side: short side≈4: 3) is 0.404. The edge ratio of the electrode body is 0.42 when the plane area is about 100 cm ² and the planar shape is a rectangle having a long side of 14.1 cm and a short side of 7.1 cm (long side: short side≈2: 1). is there. The edge ratio of an electrode body having a plane area of about 100 cm ² and a rectangular shape having a long side of 17.3 cm and a short side of 5.8 cm (long side: short side≈3: 1) is 0.46.

Needless to say, even when the capacity of the power storage element is larger than 50F, it can be calculated in the same manner as in the case of 50F.
As described above, the specific edge rate is set by setting the number of stacked electrode laminates within a specific range from the capacity required for the storage element and the capacity density (capacity per unit area) of the electrode bodies to be used. It is possible to manufacture a power storage element that satisfies the sufficient self-discharge. In addition, when a power storage element having a specific capacity is required, it is possible to select and use a power storage element with less self-discharge.

[About storage module]
In order to obtain a required capacity and voltage, a plurality of the power storage elements of the present invention can be used as a power storage module in combination. The power storage module includes a power storage element, an exterior body, and electrode terminals, and may include additional devices such as a control circuit, a safety device, and a cooling device as necessary. When there are a plurality of power storage elements used in the power storage module, it is preferable that at least half or more of them are the power storage elements of the present invention, and it is more preferable that all of them are the power storage elements of the present invention.

Further, when the power storage element of the present invention is disposed in a predetermined space to manufacture a power storage module, the power storage element is disposed in a layout in which the edge ratio of the negative electrode active material layer is smaller, thereby reducing the self-discharge. Modules can be manufactured.
When the predetermined space is, for example, a rectangular parallelepiped having a 6 × 12 cm rectangle as a bottom surface, when a power storage element in which the negative electrode active material layer has a rectangular shape of 6 × 12 cm is used, as shown in FIG. In addition, the number of negative electrode active material layers in the bottom surface of the rectangular parallelepiped is one. On the other hand, in order to obtain almost the same capacity as a power storage module in the same space using a power storage element in which the planar shape of the negative electrode active material layer is a rectangle of 3 × 4 cm, as shown in FIG. The number of negative electrode active material layers in the bottom surface of the rectangular parallelepiped needs to be 6 (= 2 × 3).

The edge ratio (L / S) of the negative electrode active material layer whose plane shape is a rectangle of 6 × 12 cm is 0.50 (= 36/72), but the negative electrode active material whose plane shape is a rectangle of 3 × 4 cm The edge rate (L / S) of the layer is 1.16 (= 14/12).
Here, a plurality of the above-described storage elements are arranged in a rectangular parallelepiped space corresponding to the thickness of an electrode laminate having a bottom surface of a 6 × 12 cm rectangle and a height of 6 pairs of positive and negative electrode active material layers. An example of the power storage module obtained in this way is shown in FIG. As shown in FIG. 2A, a storage element 10 having an electrode stack in which a pair of negative electrode active material layers and positive electrode active material layers having an edge ratio of 0.50 is stacked in a height direction of a rectangular parallelepiped. The one arranged in 6 is defined as the first module. Further, as shown in FIG. 2 (b), the storage element 11 having an electrode laminate in which six pairs of the negative electrode active material layer and the positive electrode active material layer having the edge ratio of 1.16 are stacked is formed on the bottom surface of the rectangular parallelepiped. A module in which six modules are arranged in a second module is referred to as a second module.

Comparing the first module and the second module, the volume as the size of the module and the capacity as the power storage device are almost the same in both, but the first module is more than the second module, Since the edge rate of the negative electrode active material layer is small, self-discharge is reduced, so that the power storage module is more preferable.
On the other hand, when the predetermined space is, for example, a 6 × 12 × 3 cm rectangular parallelepiped, the bottom surface (surface on which the negative electrode active material layer is arranged in parallel) is 3 × 12 cm in addition to the 6 × 12 cm rectangle described above. A rectangle of 3 × 6 cm can also be used.

  Then, assuming that the space to be arranged is a rectangular parallelepiped, and assuming that the negative electrode active material layer is fully arranged in the bottom surface in order to obtain almost the same capacity as the power storage module in the same space, the largest area of the rectangular parallelepiped An arrangement in which only one negative electrode active material layer is formed with the large surface as the bottom surface (hereinafter, this arrangement is referred to as “maximum one bottom surface arrangement”) is “an arrangement in which the edge ratio is minimized”. In addition, since the power storage element of the present invention has an “edge ratio satisfying 0.30 ≦ L / S <1.0”, it is necessary to arrange the storage element to satisfy this range.

  Therefore, in the method for manufacturing a power storage module of the present invention, when the power storage element of the present invention is arranged in a predetermined space to manufacture the power storage module, the edge rate satisfies 0.30 ≦ L / S <1.0. And determining the number of the negative electrode active material layers disposed in parallel in the predetermined space and the number of negative electrode active material layers disposed in the bottom surface (in principle, fully). Yes. An electricity storage module manufactured in this arrangement is substantially the same size as an electricity storage module in which the edge ratio is 0.30 ≦ L / S <1.0 in the same predetermined space as compared to an electricity storage module in which other arrangement is made. Self-discharge can be minimized while having a large capacity.

Note that “the arrangement where the edge ratio is the minimum within the range satisfying 0.30 ≦ L / S <1.0” is the maximum arrangement of one bottom surface if the edge ratio of the single maximum bottom surface arrangement is larger than 0.10. Corresponds to this. When the edge ratio of the maximum single bottom surface arrangement is 0.10 or less, the other arrangement corresponds to “the arrangement where the edge ratio is the minimum within a range satisfying 0.30 ≦ L / S <1.0”. Examples of other arrangements include an arrangement in which only the negative electrode active material layer is formed with the second largest surface of the rectangular parallelepiped as the bottom surface, or two negative electrode active material layers with the largest surface area of the rectangular parallelepiped as the bottom surface. Arrangement etc. are mentioned.
Further, the “arrangement that minimizes the edge rate” is determined by which surface of the predetermined space is selected as the bottom surface and the number of negative electrode active material layers disposed in the bottom surface. In the case where the arrangement shown in FIG. 4 is “an arrangement in which the edge ratio is minimized”, those that differ only in that the dimensions of the negative electrode active material layer are slightly smaller than 6 × 12 cm are included in this “arrangement in which the edge ratio is minimized”. It is.

Hereinafter, the present invention will be specifically described with reference to Examples and Comparative Examples, but the present invention is not limited thereto.
[Example 1]
<Preparation of positive electrode body>
The crushed palm shell carbide was placed in a small carbonization furnace and carbonized in nitrogen at 500 ° C. for 3 hours. The carbide after the carbonization treatment was put into an activation furnace, and steam heated in a preheating furnace was introduced into the activation furnace at 1 kg / h, and the temperature in the activation furnace was increased to 900 ° C. over 8 hours. Then, activated carbon was obtained by cooling the carbide taken out from the activation furnace under a nitrogen atmosphere. The obtained activated carbon was washed with water for 10 hours and then drained. Next, the activated carbon was dried in an electric dryer maintained at 115 ° C. for 10 hours and then pulverized with a ball mill for 1 hour.

The pore distribution of the pulverized activated carbon 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 2360 m ² / g, the mesopore volume (V1) was 0.52 cc / g, and the micropore volume (V2) was 0.88 cc / g. This activated carbon is referred to as “activated carbon 1”.
A solvent containing 80.8 parts by mass of activated carbon 1, 6.2 parts by mass of ketjen black, 10 parts by mass of PVDF (polyvinylidene fluoride) and 3.0 parts by mass of PVP (polyvinylpyrrolidone) As a result, NMP (N-methylpyrrolidone) was mixed to obtain a slurry. The obtained slurry was applied to both sides of an aluminum foil having a thickness of 15 μm, dried and pressed.
As a result, a positive electrode body in which a positive electrode active material layer mainly composed of activated carbon 1 was formed on both surfaces of a positive electrode current collector made of aluminum foil with a thickness of 55 μm was obtained.

<Preparation of negative electrode body>
150 g of commercially available activated carbon (specific surface area by BET method 1955 m ² / g) was placed in a stainless steel mesh basket, and this basket was placed on a stainless steel bat containing 300 g of coal-based pitch. The bat was placed in an electric furnace (effective size in the furnace 300 mm × 300 mm × 300 mm), and heat treatment was performed to bind the carbonaceous material to the surface of the activated carbon to obtain a composite porous carbon material. This heat treatment was performed by raising the temperature to 670 ° C. in 4 hours, holding the same temperature for 4 hours, and then cooling to 60 ° C. by natural cooling in a nitrogen atmosphere.
Thereafter, the bat was taken out from the electric furnace, and the pore distribution of the obtained composite porous carbon material was examined with the above-mentioned measuring apparatus. As a result, the BET specific surface area was 255 m ² / g and the mesopore amount (Vm1) was 0.00. 0580 cc / g, the amount of micropores (Vm2) was 0.0854 cc / g, and the average particle size was 2.9 μm.

The resultant composite porous carbon material was blended at a ratio of 83.4 parts by mass, acetylene black at 8.30 parts by mass, and PVDF (polyvinylidene fluoride) at a ratio of 8.30 parts by mass, and NMP (N- (Methylpyrrolidone) was mixed to obtain a slurry. The obtained slurry was applied to both sides of a copper foil having a thickness of 20 μm, dried and pressed to form a negative electrode active material layer having an edge ratio (L / S) of 0.67.
As a result, a negative electrode body in which a negative electrode active material layer mainly composed of the composite porous carbon material having the pore distribution was formed on both surfaces of a negative electrode current collector made of copper foil with a thickness of 60 μm was obtained. .

<Preparation of electrode laminate>
A lithium metal foil having the same area as the negative electrode active material layer of the negative electrode body and a thickness of 30 μm is brought into contact with the negative electrode active material layer and pressure-bonded, and a thickness of 30 μm is interposed between the positive electrode body and the negative electrode body. The electrode laminated body was produced by arrange | positioning a cellulose-type separator.
<Assembly of storage element>
One end of the positive electrode terminal lead tab made of aluminum and one end of the negative electrode terminal lead tab made of nickel are ultrasonically welded to the ears of the positive electrode body and the negative electrode body of the electrode laminate, respectively. Produced. The obtained electrode assembly with a tab was inserted into an exterior body made of a laminate film, and an electrolyte was injected to seal the exterior body to assemble a non-aqueous lithium storage element. As the electrolytic solution, a solution in which LiPF ₆ was dissolved at a concentration of 1 mol / l in a solvent in which ethylene carbonate and methyl ethyl carbonate were mixed at a mass ratio of 1: 4 was used.

<Characteristic evaluation of storage element>
The following characteristic evaluation was performed at 25 ° C.
The assembled storage element was charged to 4.0 V with a current amount of 1 C, and then constant current and constant voltage charging was performed by applying a constant voltage of 4.0 V. Subsequently, the battery was discharged to 2.0 V with a constant current amount of 1C. It was confirmed that a stable capacity could be obtained by setting this as one cycle and repeating charging and discharging. Thereafter, the discharge capacity at a current amount of 1 C was obtained as the cell capacity of the electricity storage device of this example.

Subsequently, discharge was performed at a current amount of 500 C, a discharge curve showing the relationship between voltage and discharge capacity was created, and a curve having a linear tendency in the first half of discharge was fitted to a linear function. The internal resistance was calculated using the voltage drop obtained from the voltage value that is the intercept of the straight line (intersection with the voltage axis).
From the product of the above measured cell capacity and internal resistance, the time constant of the electricity storage device was 1.40 ΩF. The capacity per unit area was 0.25 (F / cm ² ).

  After this storage element was charged to 4.0 V, constant current and constant voltage charging for applying a constant voltage of 4.0 V was performed for 2 hours. Next, this electricity storage device is left in a room at 25 ° C., the change in voltage over time is measured, and the number of days required to reach 80% voltage (3.2 V) of the initial voltage 4.0 V is examined. It was. The longer the number of days, the better the self-discharge characteristics (the less self-discharge). In the case of this electricity storage element, it was 105 days.

[Example 2]
Commercially available activated carbon (Max Soap MSP20: manufactured by Kansai Thermochemical Co., Ltd.) was prepared as the positive electrode active material. The pore distribution of this activated carbon was performed in the same manner as in Example 1. As a result, the BET specific surface area was 2305 m ² / g, the mesopore volume (V1) was 0.112 cc / g, and the micropore volume (V2) was 0.948 cc / g. This activated carbon is referred to as “activated carbon 2”. A positive electrode body was produced in the same manner as in Example 1 except that this activated carbon 2 was used instead of activated carbon 1.

Using the obtained positive electrode body and the negative electrode body produced in the same manner as in Example 1, an electrode laminate was produced in the same manner as in Example 1, and an electricity storage device was produced in the same manner as in Example 1 using this. Assembled. The characteristics evaluation of this electricity storage device was performed in the same manner as in Example 1, and the cell capacity and internal resistance were obtained. The time constant calculated from these values was 1.82 ΩF, and the capacity per unit area was 0.32 (F / cm ² ). The number of days required to reach 80% of the initial voltage of 4.0V (3.2V) was 91 days.

[Reference Example 3]
As a negative electrode active material, a non-graphitizable carbon material (Carbotron P: manufactured by Kureha Chemical Industry Co., Ltd.) is prepared, and X-ray wide angle diffraction measurement is performed using CuKα rays as X-rays. The diffraction peak on the (002) plane was measured using the mark. As a result, d ₀₀₂ was 0.372. Further, the pore distribution was measured using a pore distribution measuring device (AUTOSORB-1 AS-1-MP) manufactured by Yuasa Ionics. As a result, the BET specific surface area was 5.2 m ² / g, and the pore distribution was mesopore volume (Vm1) of 0.0085 cc / g and micropore volume (Vm2) of 0.0017 cc / g.

NMP (N- (N−)) was added as a solvent to this non-graphitizable carbon material in a ratio of 83.4 parts by mass, acetylene black at 8.30 parts by mass, and PVDF (polyvinylidene fluoride) at a ratio of 8.30 parts by mass. (Methylpyrrolidone) was mixed to obtain a slurry. The obtained slurry was applied to both sides of a copper foil having a thickness of 20 μm, dried and pressed to obtain an edge ratio (L / S
) Formed a negative electrode active material layer of 0.67.

As a result, a negative electrode body in which a negative electrode active material layer mainly composed of the non-graphitizable carbon material having the pore distribution is formed on both surfaces of a negative electrode current collector made of copper foil with a thickness of 60 μm is obtained. It was.
Using the thus obtained negative electrode body and the positive electrode body produced in the same manner as in Example 2, an electrode laminate was produced in the same manner as in Example 1, and the same as in Example 1 using this. The electric storage element was assembled by the method. The characteristics evaluation of this electricity storage device was performed in the same manner as in Example 1, and the cell capacity and internal resistance were obtained. The time constant calculated from these values was 1.99 ΩF, and the capacity per unit area was 0.35 (F / cm ² ). The number of days required to reach 80% of the initial voltage of 4.0V (3.2V) was 229 days.

[Example 4]
Example except that the obtained slurry was applied on both sides of a copper foil (negative electrode current collector) having a thickness of 20 μm so that the edge ratio (L / S) of the negative electrode active material layer was 0.30. As in Example 1, a negative electrode body was produced.
Using the obtained negative electrode body and the positive electrode body prepared in the same manner as in Example 1, an electrode laminate was prepared in the same manner as in Example 1. Using this electrode laminate, a power storage device was assembled in the same manner as in Example 1. The characteristics evaluation of this electricity storage device was performed in the same manner as in Example 1, and the cell capacity and internal resistance were obtained. The time constant calculated from these values was 1.30 ΩF, and the capacity per unit area was 0.50 (F / cm ² ). The number of days required to reach 80% of the initial voltage of 4.0 V (3.2 V) was 202 days.

[Example 5]
An electrode laminate was produced in the same manner as in Example 1, using a positive electrode produced in the same manner as in Example 2 and a negative electrode produced in the same manner as in Example 4. Using this electrode laminate, a power storage device was assembled in the same manner as in Example 1. The characteristics evaluation of this electricity storage device was performed in the same manner as in Example 1, and the cell capacity and internal resistance were obtained. The time constant calculated from these values was 1.85 ΩF, and the capacity per unit area was 0.64 (F / cm ² ). The number of days required to reach 80% of the initial voltage of 4.0 V (3.2 V) was 185 days.

[Reference Example 6]
Example except that the obtained slurry was applied on both sides of a copper foil (negative electrode current collector) having a thickness of 20 μm so that the edge ratio (L / S) of the negative electrode active material layer was 0.30. A negative electrode body was prepared in the same manner as in FIG.
Using this negative electrode body and a positive electrode body manufactured in the same manner as in Example 2, an electrode laminate was prepared in the same manner as in Example 1. Using this electrode laminate, a power storage device was assembled in the same manner as in Example 1. The characteristics evaluation of this electricity storage device was performed in the same manner as in Example 1, and the cell capacity and internal resistance were obtained. The time constant calculated from these values was 1.98 ΩF, and the capacity per unit area was 0.70 (F / cm ² ). The number of days required to reach 80% of the initial voltage of 4.0V (3.2V) was 461 days.

[Comparative Example 1]
Example except that the obtained slurry was applied to both sides of a 20 μm thick copper foil (negative electrode current collector) so that the edge ratio (L / S) of the negative electrode active material layer was 2.43 As in Example 1, a negative electrode body was produced.
Using this negative electrode body and a positive electrode body manufactured in the same manner as in Example 1, an electrode laminate was prepared in the same manner as in Example 1. Using this electrode laminate, a power storage device was assembled in the same manner as in Example 1. The characteristics evaluation of this electricity storage device was performed in the same manner as in Example 1, and the cell capacity and internal resistance were obtained. The time constant calculated from these values was 1.21 ΩF, and the capacity per unit area was 0.25 (F / cm ² ). The number of days required to reach 80% of the initial voltage of 4.0 V (3.2 V) was 35 days.

[Comparative Example 2]
An electrode laminate was produced in the same manner as in Example 1, using a negative electrode produced in the same manner as in Comparative Example 1 and a positive electrode produced in the same manner as in Example 2. Using this electrode laminate, a power storage device was assembled in the same manner as in Example 1. The characteristics evaluation of this electricity storage device was performed in the same manner as in Example 1, and the cell capacity and internal resistance were obtained. The time constant calculated from these values was 1.72 ΩF, and the capacity per unit area was 0.32 (F / cm ² ). The number of days required to reach 80% of the initial voltage of 4.0V (3.2V) was 30 days.

[Comparative Example 3]
Example except that the obtained slurry was applied to both sides of a 20 μm thick copper foil (negative electrode current collector) so that the edge ratio (L / S) of the negative electrode active material layer was 2.43 A negative electrode body was prepared in the same manner as in FIG.
Using this negative electrode body and a positive electrode body manufactured in the same manner as in Example 2, an electrode laminate was produced in the same manner as in Example 1, and using this electrode laminate, electricity was stored in the same manner as in Example 1. The element was assembled. The characteristics evaluation of this electricity storage device was performed in the same manner as in Example 1, and the cell capacity and internal resistance were obtained. The time constant calculated from these values was 1.98 ΩF, and the capacity per unit area was 0.35 (F / cm ² ). The number of days required to reach 80% of the initial voltage of 4.0V (3.2V) was 75 days.

[Comparative Example 4]
Example except that the obtained slurry was applied to both surfaces of a copper foil (negative electrode current collector) having a thickness of 20 μm so that the edge ratio (L / S) of the negative electrode active material layer was 1.77. As in Example 1, a negative electrode body was produced.
Using this negative electrode body and the positive electrode body manufactured in the same manner as in Example 1, an electrode laminate was prepared in the same manner as in Example 1, and using this electrode laminate, the electricity was stored in the same manner as in Example 1. The element was assembled. The characteristics evaluation of this electricity storage device was performed in the same manner as in Example 1, and the cell capacity and internal resistance were obtained. The time constant calculated from these values was 1.31 ΩF, and the capacity per unit area was 0.25 (F / cm ² ). The number of days required to reach 80% of the initial voltage of 4.0V (3.2V) was 45 days.

[Comparative Example 5]
Graphite (MCMB: manufactured by Osaka Gas Co., Ltd.) was prepared as a negative electrode active material. The graphite has a BET specific surface area of 3.0 m ² / g.
NMP (N-methylpyrrolidone) as a solvent is mixed with 3.0 parts by mass of graphite, 2.0 parts by mass of acetylene black, and 5.0 parts by mass of PVDF (polyvinylidene fluoride). Thus, a slurry was obtained. The obtained slurry was applied to both sides of a 20 μm-thick perforated copper foil, dried, and pressed to form a negative electrode active material layer having an edge ratio (L / S) of 0.67.

As a result, a negative electrode body was obtained in which a negative electrode active material layer mainly composed of graphite was formed on both sides of a negative electrode current collector made of perforated copper foil with a thickness of 60 μm.
Using this negative electrode body and a positive electrode body manufactured in the same manner as in Example 2, an electrode laminate was produced in the same manner as in Example 1, and using this electrode laminate, electricity was stored in the same manner as in Example 1. The element was assembled. The characteristics evaluation of this electricity storage device was performed in the same manner as in Example 1, and the cell capacity and internal resistance were obtained. The time constant calculated from these values was 3.51 ΩF, and the capacity per unit area was 0.33 (F / cm ² ). The number of days required to reach 80% of the initial voltage of 4.0V (3.2V) was 251 days.

[Comparative Example 6]
Comparison was made except that the obtained slurry was applied to both sides of a 20 μm-thick perforated copper foil (negative electrode current collector) so that the edge ratio (L / S) of the negative electrode active material layer was 2.43. A negative electrode body was produced in the same manner as in Example 5.
Using this negative electrode body and a positive electrode body manufactured in the same manner as in Example 2, an electrode laminate was produced in the same manner as in Example 1, and using this electrode laminate, electricity was stored in the same manner as in Example 1. The element was assembled. The characteristics evaluation of this electricity storage device was performed in the same manner as in Example 1, and the cell capacity and internal resistance were obtained. The time constant calculated from these values was 3.44 ΩF, and the capacity per unit area was 0.33 (F / cm ² ). The number of days required to reach 80% of the initial voltage of 4.0V (3.2V) was 83 days.
The above results are summarized in Table 1 below.

  From the results of Table 1, the power storage elements of Examples 1, 2, 4, 5 and Reference Example 6 have a smaller time constant and less self-discharge (self-discharge) than the power storage elements of Comparative Examples 1-6. It can be seen that they have performance that also has a good characteristic). The power storage elements of Comparative Examples 1 to 4 had a small time constant, but had poor self-discharge characteristics. The electricity storage device of Comparative Example 5 had good self-discharge characteristics but a large time constant. Comparative Example 6 also had a large time constant and poor self-discharge characteristics.

  The electricity storage devices of Example 1, Example 4, Comparative Example 1, and Comparative Example 4 have configurations that differ only in the edge rate of the negative electrode active material layer. The time constants (ΩF) of these power storage elements are almost the same as 1.40, 1.30, 1.21, and 1.31, but there is a difference in self-discharge characteristics. The self-discharge characteristics of each storage element were the best in Example 4 with an edge rate of 0.30 at 202 days, and the example 1 with an edge rate of 0.67 was good at 105 days. Comparative Example 4 with an edge rate of 1.77 was worse than half of Example 1 at 45 days, and Comparative Example 1 with an edge rate of 2.43 was worst at 35 days.

  The power storage elements of Example 2, Reference Example 3, and Comparative Example 5 have configurations that differ only in the main component of the negative electrode active material. Among these power storage devices, Comparative Example 5 in which the main component of the negative electrode active material is graphite has the best self-discharge characteristics of 251 days, but has the largest time constant (ΩF) of 3.51. In contrast, the power storage elements of Examples 2 and 3 are well-balanced power storage elements with a small time constant and little self-discharge.

  Examples 1 and 2, Examples 4 and 5, and Comparative Examples 1 and 2 are storage elements that differ only in whether the main component of the positive electrode active material is activated carbon 1 or activated carbon 2, respectively. The activated carbon 1 satisfies all of the conditions (1) to (3), which are preferable as the main component of the positive electrode active material, but the activated carbon 2 does not satisfy the condition (2). And the electrical storage element (Examples 1 and 4, Comparative Example 1) using activated carbon 1 as a main component of a positive electrode active material is more than the electrical storage element (Examples 2 and 5, Comparative Example 2) using activated carbon 2. However, the time constant is small.

  In Example 2 and Reference Example 3, Example 5 and Reference Example 6, and Comparative Examples 2 and 3, the main component of the negative electrode active material is a composite porous carbon material or a non-graphitizable carbon material, respectively. Only the different storage elements. And the electrical storage element using the non-graphitizable carbon material as the main component of the negative electrode active material (Reference Examples 3 and 6, Comparative Example 3) is the electrical storage element using the composite porous carbon material (Examples 2 and 5). The self-discharge characteristic is better than that of Comparative Example 2), but the time constant is larger.

DESCRIPTION OF SYMBOLS 1 Negative electrode collector 2 Ear part 3 Negative electrode active material layer 10 Power storage element 11 Power storage element

Claims (6)

A negative electrode body in which a negative electrode active material layer is formed on one or both surfaces of a negative electrode current collector, a positive electrode body in which a positive electrode active material layer is formed on one or both surfaces of a positive electrode current collector, and an electrode stack in which separators are stacked Body,
A non-aqueous electrolyte containing a lithium salt as an electrolyte;
An exterior body that houses the electrode laminate and the non-aqueous electrolyte; and
A non-aqueous lithium storage element comprising:
The main component of the negative electrode active material constituting the negative electrode active material layer is a composite porous carbon material having a carbonaceous material on the surface of the activated carbon, and the composite porous carbon material has the following conditions (1) to (4) The filling,
The main component of the positive electrode active material constituting the positive electrode active material layer is activated carbon,
The edge ratio (L / S), which is the ratio of the total length L (cm) of the outline in a plan view of the negative electrode active material layer to the plane area S (cm ² ) of the negative electrode active material layer, is 0.30 ≦ L /S<1.00,
LiPF ₆ is included as the lithium salt,
A non-aqueous lithium storage element having a capacity of 50 to 5000F.
(1) Mesopore volume (amount of pores having a diameter of 2 nm to 50 nm) Vm1 (cc / g) calculated by the BJH method is 0.01 ≦ Vm1 <0.10.
(2) The amount of micropores (amount of pores having a diameter of less than 2 nm) Vm2 (cc / g) calculated by the MP method is 0.01 ≦ Vm2 <0.30.
(3) The BET specific surface area is 10 m ² / g or more and less than 1000 m ² / g.
(4) The average particle size is 1.5 to 25 μm. The non-aqueous lithium storage element according to claim 1, wherein activated carbon that is a main component of the positive electrode active material satisfies the following conditions (1) to (3).
(1) Mesopore amount (amount of pores having a diameter of 2 nm to 50 nm) V1 (cc / g) calculated by the BJH method is 0.3 <V1 ≦ 0.8.
(2) The amount of micropores (the amount of pores having a diameter of less than 2 nm) V2 calculated by the MP method is 0.5 ≦ V2 <1.0.
(3) The specific surface area measured by the BET method is 1500 m ² / g or more and 3000 m ² / g or less. 3. The non-aqueous lithium storage element according to claim 1, wherein a capacity per unit area of the negative electrode body is in a range of 0.25 to 0.75 (F / cm ² ).   The electrical storage module containing two or more non-aqueous lithium-type electrical storage elements of any one of Claims 1-3. When the nonaqueous lithium electricity storage element according to claim 3 is arranged in a predetermined space to produce an electricity storage module,
A bottom surface on which the negative electrode active material layers in the predetermined space are arranged in parallel so that the edge rate is minimized within a range satisfying 0.30 ≦ L / S <1.0, and a negative electrode arranged in the bottom surface A method for manufacturing a power storage module, wherein the number of active material layers is determined.   The non-aqueous lithium storage element according to claim 3 is used by being arranged in a predetermined space with an arrangement in which the edge ratio of the negative electrode active material layer is minimized within a range satisfying 0.30 ≦ L / S <1.0. To use a non-aqueous lithium storage element.

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