JP7042589B2 - Negative electrode - Google Patents

Description

The present invention relates to a negative electrode.

In recent years, from the viewpoint of energy conservation and effective use of energy aiming at conservation of global environment, power smoothing system or midnight power storage system for wind power generation, distributed power storage system for home use based on solar power generation technology, power storage for electric vehicles Systems and the like are attracting attention.
The first requirement of the batteries used in these power storage systems is high energy density. Lithium-ion batteries are being energetically developed as promising candidates for high-energy density batteries that can meet such demands.
The second requirement is that the output characteristics are high. For example, in a combination of a high-efficiency engine and a power storage system (for example, a hybrid electric vehicle) or a combination of a fuel cell and a power storage system (for example, a fuel cell electric vehicle), a power storage system that exhibits high output discharge characteristics during acceleration is required. Has been done.
Currently, electric double layer capacitors, nickel-metal hydride batteries, and the like are being developed as high-output power storage devices.

Among the electric double layer capacitors, those using activated carbon for the electrodes have an output characteristic of about 0.5 to 1 kW / L. This electric double layer capacitor has not only high output characteristics but also high durability (cycle characteristics and high temperature storage characteristics), and has been considered to be the most suitable device in the above-mentioned field where high output is required. However, its energy density is only about 1 to 5 Wh / L. Therefore, it is necessary to further improve the energy density.
On the other hand, the nickel-metal hydride battery generally used in hybrid electric vehicles at present has a high output equivalent to that of an electric double layer capacitor and an energy density of about 160 Wh / L. However, research is being vigorously pursued to further enhance its energy density and output characteristics, as well as to enhance its durability (particularly, stability at high temperatures).
In addition, research is underway to increase the output of 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 (that is, a ratio (%) of a discharge amount to a discharge capacity of a power storage element) of 50%. However, the energy density is 100 Wh / L or less, and the design is such that the high energy density, which is the greatest feature of the lithium ion battery, is intentionally suppressed. Moreover, its durability (cycle characteristics and high temperature storage characteristics) is inferior to that of electric double layer capacitors. Therefore, such lithium-ion batteries are used in a range narrower than the range of 0 to 100% in the discharge depth in order to have practical durability. Since the capacity that can actually be used becomes smaller, research is being vigorously pursued to further improve durability.

As described above, there is a strong demand for practical use of a power storage element having high energy density, high output characteristics, and high durability. However, each of the existing power storage elements described above has advantages and disadvantages. Therefore, there is a demand for a new power storage element that satisfies these technical requirements. As a promising candidate, a power storage element called a lithium ion capacitor has attracted attention and is being actively developed.
A lithium ion capacitor is a type of storage element (hereinafter, also referred to as "non-aqueous lithium type storage element") that uses a non-aqueous electrolyte solution containing a lithium salt, and is an electric double layer capacitor with a positive voltage of about 3 V or higher. It is a power storage element that charges and discharges by a non-Faraday reaction by adsorption and desorption of anions similar to the above, and by a Faraday reaction by storage and release of lithium ions similar to lithium ion batteries in the negative electrode.
To summarize the electrode materials generally used for the above energy storage elements and their characteristics, generally, a material such as activated carbon is used for the electrodes, and charging and discharging are performed by adsorption and desorption (non-Faraday reaction) of ions on the surface of activated carbon. If this is done, high output and high durability will be obtained, but the energy density will be low (for example, 1 times). On the other hand, when an oxide or carbon material is used for the electrode and charging / discharging is performed by a Faraday reaction, the energy density becomes high (for example, 10 times that of a non-Faraday reaction using activated carbon), but the durability and output are increased. There is a problem with the characteristics.

As a combination of these electrode materials, the electric double layer capacitor is characterized by using activated carbon (energy density 1 times) for the positive and negative electrodes and charging and discharging both the positive and negative electrodes by a non-Faraday reaction, and thus has high output and high durability. Although it has properties, it is characterized by a low energy density (1x positive electrode x 1x negative electrode = 1).
Lithium-ion secondary batteries are characterized by using a lithium transition metal oxide (energy density 10 times) for the positive electrode and a carbon material (energy density 10 times) for the negative electrode, and charging and discharging both the positive and negative electrodes by a Faraday reaction. It has a high energy density (positive electrode 10 times x negative electrode 10 times = 100), but has problems in output characteristics and durability. Further, in order to satisfy the high durability required for a hybrid electric vehicle or the like, the discharge depth must be limited, and a lithium ion secondary battery can use only 10 to 50% of its energy.
Lithium-ion capacitors are characterized by using activated carbon (1x energy density) for the positive electrode and carbon material (10x energy density) for the negative electrode, and charging and discharging by a non-Faraday reaction at the positive electrode and a Faraday reaction at the negative electrode. It is an asymmetric capacitor that combines the characteristics of an electric double-layer capacitor and a lithium-ion secondary battery. The lithium-ion capacitor has a high energy density (1x positive electrode x 10x negative electrode = 10) while having high output and high durability, and it is not necessary to limit the discharge depth unlike a lithium ion secondary battery. Is a feature.

Examples of applications in which lithium ion capacitors are used include storage applications in railways, construction machinery, automobiles, and the like. In these applications, the operating environment is harsh, so the capacitors used are required to simultaneously achieve excellent input / output characteristics, excellent high-temperature durability, and excellent charge / discharge cycle characteristics under high load. To.
As a countermeasure technique for such a requirement, Patent Document 1 describes a lithium ion secondary battery having excellent input / output characteristics, capacity, and cycle characteristics by changing the content of crystalline carbon and amorphous carbon. The technology that can provide the above is disclosed. However, Patent Document 1 does not consider the characteristics during high-temperature storage.
In Patent Document 2, lithium precipitation is caused by using a negative electrode in which the degree of graphitization of the graphite particles distributed on the surface side of the negative electrode active material layer is lower than the degree of graphitization of the graphite particles distributed on the negative electrode current collector side. Disclosed is a technique capable of providing a lithium ion secondary battery that suppresses, improves cycle characteristics, and obtains good charge / discharge characteristics.
However, both of Patent Documents 1 and 2 assume a lithium ion secondary battery, and improvement of cycle characteristics in a high load charge / discharge cycle of about 100 C rate such as a lithium ion capacitor is taken. No consideration is given to storage characteristics at high temperatures.

Japanese Unexamined Patent Publication No. 2012-15501 Japanese Unexamined Patent Publication No. 2010-267540

E. P. Barrett, L. et al. G. Joiner and P. Hallenda, J. et al. Am. Chem. Soc. , 73,373 (1951) B. C. Lippens, J. Mol. H. de Boer, J.M. Catalysis, 4319 (1965) R. S. Mikhair, S.M. Brunar, E. et al. E. Border, J.M. Colloid Interface Sci. , 26,45 (1968)

In view of the above situation, the problems to be solved by the present invention are the charge / discharge cycle characteristics at low resistance and high load in the negative electrode having the negative electrode active material layer containing the negative electrode active material capable of storing and releasing lithium ions. It is an object of the present invention to provide a negative electrode which is excellent in high temperature storage durability and in which the loss of a negative electrode active material during cell assembly is suppressed.

The above problems are solved by the following technical means.
That is, the present invention is as follows:
[1] A negative electrode having a negative electrode current collector and a negative electrode active material layer containing a negative electrode active material made of a carbon material capable of storing and releasing lithium ions on one or both sides of the negative electrode current collector.
The following (i) to (iii):
(I) The negative electrode active material layer contains a first negative electrode active material made of a carbon material and a second negative electrode active material made of a carbon material and different from the first negative electrode active material.
(Ii) The specific surface area of the negative electrode active material layer calculated by the BET method based on the mass of the negative electrode active material is 4 m ² / g or more and 75 m ² / g or less, and
(Iii) In the Raman mapping of the surface of the negative electrode active material layer obtained by Raman spectroscopy, the peak intensity ID of the _D band appearing at 1350 ± 15 cm ^-1 and the peak intensity IG of the _G band appearing at 1585 ± 15 cm ^-1 . The ratio A1 of the mapping area having an I _D / _IG of 0.5 or more and 1.3 or less to the total mapping area is 50% or more and 95% or less.
The negative electrode is characterized by satisfying all of the above.
[2] The negative electrode according to [1], wherein the A1 is 60% or more and 90% or less.
[3] The ratio A2 of the mapping area having the _ID / _IG of 1.0 or more and 1.3 or less to the total mapping area is 3% or more and 70% or less, according to [1] or [2]. Negative electrode.
[4] The negative electrode active material layer has a pore size of V _m1 (cc / g) and a diameter of 20 nm derived from pores having a diameter of 2 nm or more and 50 nm or less calculated by the BJH method based on the mass of the negative electrode active material. When the amount of pores derived from the pores of 50 nm or less is V _m2 (cc / g), 0.6 ≦ V _m1 / (V _m1 + V _m2 ) ≦ 0.8 is satisfied, [1] to [3]. ] The negative electrode according to any one of the items.
[5] The negative electrode active material layer has at least one peak in a region having a diameter of 20 nm or more and 50 nm or less in a pore distribution curve obtained by analyzing an isotherm at the time of nitrogen desorption by the BJH method [1] to. The negative electrode according to any one of [4].
[6] The negative electrode according to any one of [1] to [5], wherein the peel strength of the negative electrode active material layer is 0.40 N / cm or more and 2.00 N / cm or less.
[7] The first negative electrode active material is
It is a graphite-based composite material in which a base material made of (i) a graphite-based material or (ii) a graphite-based material and a carbonaceous material precursor are composited.
The second negative electrode active material is
(I) An amorphous carbon composite material in which a base material made of an amorphous carbon material or (ii) an amorphous carbon material and a carbonaceous material precursor are composited.
The negative electrode according to any one of [1] to [6].
[8] The ratio of the mass of the first negative electrode active material to the negative electrode active material layer is M ₁ (mass%), and the ratio of the mass of the second negative electrode active material to the negative electrode active material layer is M. 2. The negative electrode according to [7], wherein M ₂ / (M ₁ + M ₂ ) is 0.01 or more and 0.75 or less when ₂ (mass%) is used.
[9] The negative electrode according to any one of [1] to [8], wherein the negative electrode active material layer has a bulk density of 0.6 g / cc or more and 1.6 g / cc or less.
[10] The negative electrode according to any one of [1] to [9], wherein the negative electrode active material layer has a thickness of 10 μm or more and 50 μm or less per surface.
[11] The negative electrode according to any one of [1] to [10], wherein the negative electrode current collector is a perforated copper foil.
[12] The negative electrode according to any one of [1] to [10], which is a non-perforated copper foil whose surface is roughened on the surface of the negative electrode current collector.
[13] The negative electrode according to any one of [1] to [12], wherein the negative electrode active material layer contains an alloy-based material that forms an alloy with lithium.
[14] The negative electrode according to any one of [1] to [13], wherein the negative electrode active material layer contains lithium titanate.
[15] A step of applying a negative electrode coating liquid onto the negative electrode current collector to form a negative electrode active material layer is included.
The negative electrode coating liquid contains the first negative electrode active material, the second negative electrode active material, a solvent, and a binder, and has the mass of all the components in the negative electrode coating liquid excluding the solvent. The method for manufacturing a negative electrode according to any one of [1] to [14], wherein the ratio _WT (mass%) of the negative electrode coating liquid to the total mass is 10 ≦ _WT ≦ 70.
[16] The binder is at least one of latex, styrene-butadiene copolymer, fluororubber, acrylic copolymer, polyvinylidene fluoride, polytetrafluoroethylene, and polyimide, [15]. The method described.
[17] The method according to [15] or [16], wherein the negative electrode coating liquid is multi-stripped on the negative electrode current collector to form the negative electrode active material layer.
[18] The method according to any one of [15] to [17], wherein the negative electrode coating liquid is intermittently applied onto the negative electrode current collector to form the negative electrode active material layer.
[19] The method according to any one of [15] to [18], further comprising a step of applying the negative electrode coating liquid on the negative electrode current collector, then slitting, and then pressing. ..
[20] The item according to any one of [15] to [19], further comprising a step of applying the negative electrode coating liquid on the negative electrode current collector and then drying using far infrared rays or near infrared rays. the method of.
[21] The item according to any one of [15] to [19], further comprising a step of applying the negative electrode coating liquid on the negative electrode current collector and then drying using hot air at 80 ° C. or higher. the method of.
[22] An electrode body including the negative electrode according to any one of [1] to [14], and a positive electrode and a separator.
[23] The negative electrode according to any one of [1] to [14], and the non-aqueous electrolyte solution containing the positive electrode, the separator, and the lithium ion are stored in the exterior body, and the non-aqueous lithium storage is stored. element.
[24] The non-aqueous lithium-type power storage element according to [23], wherein the exterior body is made of a metal can or a laminated film.
[25] A power storage module including the non-aqueous lithium power storage element according to [23] or [24].
[26] A power regeneration assist system including the non-aqueous lithium power storage element according to [23] or [24].
[27] A power load leveling system comprising the non-aqueous lithium storage element according to [23] or [24].
[28] An uninterruptible power supply system including the non-aqueous lithium power storage element according to [23] or [24].
[29] A non-contact power feeding system including the non-aqueous lithium power storage element according to [23] or [24].
[30] An energy harvesting system comprising the non-aqueous lithium storage element according to [23] or [24].
[31] A power storage system including the non-aqueous lithium power storage element according to [23] or [24].
[32] The power storage system according to [31], wherein the non-aqueous lithium power storage element and a lead battery, a nickel hydrogen battery, a lithium ion secondary battery, or a fuel cell are connected in series or in parallel.
[33] A photovoltaic power storage system including the non-aqueous lithium power storage element according to [23] or [24].
[34] An electric power steering system including the non-aqueous lithium power storage element according to [23] or [24].
[35] An emergency power supply system including the non-aqueous lithium power storage element according to [23] or [24].
[36] An in-wheel motor system comprising the non-aqueous lithium storage element according to [23] or [24].
[37] An idling stop system including the non-aqueous lithium storage element according to [23] or [24].
[38] A fast charging system comprising the non-aqueous lithium storage element according to [23] or [24].
[39] A smart grid system comprising the non-aqueous lithium storage element according to [23] or [24].
[40] A vehicle comprising the non-aqueous lithium storage element according to [23] or [24].
[41] The vehicle according to [40], which is an electric vehicle, a plug-in hybrid vehicle, a hybrid vehicle, or an electric motorcycle.

INDUSTRIAL APPLICABILITY According to the present invention, in a negative electrode having a negative electrode active material layer containing a negative electrode active material capable of storing and releasing lithium ions, a negative electrode having low resistance, charge / discharge cycle characteristics under high load, and excellent high temperature storage durability is provided. To.

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

<Negative electrode>
The negative electrode in the present embodiment has a negative electrode current collector and a negative electrode active material layer containing a negative electrode active material made of a carbon material capable of storing and releasing lithium ions on one or both sides of the negative electrode current collector.

[Negative electrode active material layer]
In the present embodiment, the negative electrode active material made of a carbon material capable of storing and releasing lithium ions is made of a first negative electrode active material made of a carbon material and a carbon material, and is different from the first negative electrode active material. Contains negative electrode active material.
The negative electrode active material layer in the present embodiment may contain optional components such as a conductive filler, a binder, and a dispersion stabilizer, if necessary, in addition to the first negative electrode active material and the second negative electrode active material. ..

In the present embodiment, the negative electrode active material layer has a specific surface area of 4 m ² / g or more and 75 m ² / g or less calculated by the BET method based on the mass of the negative electrode active material. The lower limit of the specific surface area calculated by the BET method is preferably 5 m ² / g or more, more preferably 6 m ² / g or more, and particularly preferably 7 m ² / g or more. The upper limit of the specific surface area calculated by the BET method is 60 m ² / g or less, more preferably 40 m ² / g or less, and particularly preferably 30 m ² / g or less.
In the present embodiment, the negative electrode active material layer appears at the peak intensity ID of the _D band appearing at 1350 ± 15 cm ^-1 and 1585 ± 15 cm ^-1 in the Raman mapping of the negative electrode active material layer obtained by Raman spectroscopy. The ratio A1 of the mapping area having the ratio _ID / _IG to the peak intensity IG of the _G band to 0.5 or more and 1.3 or less with respect to the total mapping area is 50% or more and 95% or less. The lower limit of A1 is preferably 60% or more, more preferably 65% or more. The upper limit of A1 is preferably 90% or less and 85% or less.

In the negative electrode of the present embodiment, the specific surface area calculated by the BET method for the negative electrode active material layer and the ratio A1 in the Raman mapping obtained by the Raman spectroscopy on the surface of the negative electrode active material layer are adjusted to a specific range. Excellent high load charge / discharge cycle characteristics and excellent high temperature storage characteristics at high voltage can be obtained. The principle is not clear and is not limited to theory, but it is inferred as follows.
If the specific surface area calculated by the BET method is 4 m ² / g or more and A1 is 60% or more, it is considered that the high load charge / discharge cycle is improved. The principle is not always clear, but by setting these values in the above range, the surface area of the negative electrode active material layer that receives lithium when charging with a large current is large, and the crystallinity of the carbon material is low. .. Therefore, it is considered that the diffusion of lithium ions becomes faster during charging and discharging, and the acceptability of lithium ions is improved. As a result, it is considered that lithium precipitation when charging with a large current is suppressed and the high load charge / discharge cycle characteristics are improved. In particular, when the positive electrode precursor contains a lithium compound, decomposition products of the lithium compound are deposited on the surface of the negative electrode and the acceptability of lithium is lowered, so that lithium is likely to be deposited, but the specific surface area of the negative electrode active material layer and It is considered that the precipitation of lithium can be suppressed by setting AI in the above range.

On the other hand, if the specific surface area calculated by the BET method is 75 m ² / g or less and A1 is 95% or less, it is considered that excellent high-temperature storage characteristics at high voltage are exhibited. Although the principle is not always clear, it is considered that by setting these values in the above range, the decomposition reaction of the electrolytic solution on the surface of the negative electrode can be suppressed, so that excellent high temperature storage characteristics at high voltage can be exhibited. In particular, when the positive electrode precursor contains a lithium compound, the lithium compound is decomposed by applying a high voltage, the film on the surface of the negative electrode is destroyed, and gas is easily generated at a high temperature, but the specific surface area of the negative electrode active material layer is increased. By setting A1 and A1 in the above range, the decomposition of the lithium compound is suppressed, and as a result, excellent high voltage and high temperature storage characteristics can be exhibited.
Further, if A1 is 60% or more and 95% or less, it means that the two carbon materials can be uniformly mixed, and the resistance distribution in the negative electrode active material layer is small, so that the high load charge / discharge cycle characteristics are exhibited. It is thought to improve.

In the negative electrode of the present embodiment, the ratio A2 of the mapping area in which the _ID / _IG of the negative electrode active material layer is 1.0 or more and 1.3 or less to the total mapping area is 3% or more and 70% or less. preferable. The lower limit of A2 is more preferably 4% or more, still more preferably 5% or more. The upper limit of A2 is more preferably 50% or less, still more preferably 30% or less. When A2 is 3% or more, the resistance at room temperature is excellent, and when A2 is 70% or less, the energy density is excellent.

In the present specification, the specific surface area of the negative electrode active material layer calculated by the BET method uses an adsorption / desorption isotherm measured using the negative electrode active material layer as a sample and nitrogen or argon as an adsorbent according to the method described later. It is a value calculated by the BET multipoint method or the BET1 point method.

(Raman mapping)
Raman mapping of the negative electrode active material layer can be obtained, for example, as follows.
First, prepare the negative electrode to be measured. The negative electrode is preferably a negative electrode before use before being incorporated into the non-aqueous power storage element, but may be a negative electrode after use taken out by disassembling the non-aqueous power storage element in an inert atmosphere. When the negative electrode is used as a sample after use, the sample is obtained by washing with a solvent such as ethyl methyl carbonate to remove the lithium salt adhering to the negative electrode. The washed sample is dried under reduced pressure to completely remove the washing solvent.

An example of a sample measurement method by micro-Raman spectroscopy will be described below.
In micro-Raman spectroscopy, a 40 μm × 40 μm field of view is mapped and measured in 1 μm steps using a laser having a wavelength of 532 nm. The excitation light intensity at the sample position is about 0.1 mW, the objective lens magnification is 100 times, the diffraction grating is 1,800 gr / mm, the mapping method is point scanning, the exposure time per point is 5 seconds, and the number of integrations is 1. It can be measured under the conditions of times. If spike noise is observed for each of the measured 1,600 Raman spectra, the spike noise is removed. To remove the noise component, after performing the principal component analysis, the spectrum is reconstructed up to about 12 components having a large score. A straight baseline is set at 1,000 to 1,800 cm ^-1 for 1,600 points in the reconstructed spectrum, and the peak height of the D band appearing at 1,350 ± 15 cm ^-1 at each measurement point. ( _ID ) and the peak height (IG) of the _G band appearing at 1585 ± 15 cm ^-1 are calculated. Then, _ID / _IG is calculated at each measurement point.
From the above, the mapping data of _ID / _IG can be obtained from the measurement result of Raman spectroscopy.

The negative electrode active material layer in the negative electrode of the present embodiment has a diameter of V m1 (cc / g) and a diameter of V _m1 (cc / g) derived from pores having a diameter of 2 nm or more and 50 nm or less calculated by the BJH method based on the mass of the negative electrode active material. When the amount of pores derived from pores of 20 nm or more and 50 nm or less is V _m2 (cc / g), it is preferable to satisfy 0.6 ≦ V _m1 / (V _m1 + V _m2 ) ≦ 0.8. The lower limit of V _m1 / (V _m1 + V _m2 ) is more preferably 0.63 or more. The upper limit of V _m1 / (V _m1 + V _m2 ) is more preferably 0.75 or less. When V _m1 / (V _m1 + V _m2 ) is 0.6 or more, the resistance at low temperature is excellent, and when V _m1 / (V _m1 + V _m2 ) is 0.7 or less, the energy density is excellent.
The negative electrode active material layer in the negative electrode of the present embodiment preferably has at least one peak in a region having a diameter of 20 nm or more and 50 nm or less in the pore distribution curve obtained by analyzing the isotherms at the time of nitrogen desorption by the BJH method. .. Having at least one peak in a region having a diameter of 20 nm or more and 50 nm or less provides excellent resistance at low temperatures.

(Calculation of BET specific surface area, and calculation of pore distribution curve and pore amount by BJH method)
In the present specification, the BET specific surface area, the pore distribution curve, and the amount of pores per mass of the negative electrode active material layer are obtained by the following methods.
As the sample used for the measurement, a negative electrode before use may be used, or a negative electrode after use may be used.
When the negative electrode after use is used for the measurement sample, it is preferable to perform, for example, the following steps as the pretreatment of the measurement sample. First, the non-aqueous lithium-type power storage element is disassembled under an inert atmosphere such as argon, and the negative electrode (negative electrode after use) is taken out. After use, the negative electrode taken out is immersed in a chain carbonate (for example, methyl ethyl carbonate, dimethyl carbonate, etc.) to remove a non-aqueous electrolyte solution, a lithium salt, etc., and then air-dried. Then, for example, it is preferable to carry out the following steps 1), 2) or 3).

1) After use, the negative electrode taken out is immersed in a mixed solvent consisting of methanol and isopropanol to inactivate the lithium ions occluded in the negative electrode active material and air-dried. Then, a measurement sample can be obtained by removing the chain carbonate, the organic solvent and the like contained in the negative electrode after use by vacuum drying or the like.
2) In an inert atmosphere such as argon, after use, the negative electrode is used as the working electrode, and metallic lithium is used as the counter electrode and the reference electrode, and these are immersed in a non-aqueous electrolyte solution to prepare an electrochemical cell. The obtained electrochemical cell is adjusted so that the negative electrode potential (vs. Li / Li ⁺ ) is in the range of 1.5 V to 3.5 V using a charger / discharger or the like. Next, the negative electrode is taken out from the electrochemical cell under an inert atmosphere such as argon, immersed in a chain carbonate, the non-aqueous electrolyte solution, the lithium salt and the like are removed, and the mixture is air-dried. Then, a measurement sample can be obtained by removing the chain carbonate and the like contained in the obtained negative electrode by vacuum drying or the like.
3) The taken-out negative electrode after use can be used as it is as a measurement sample.

The negative electrode before use or the negative electrode after use obtained above is prepared, and the negative electrode active material layer is scraped from the current collector with a spatula or the like as a measurement sample. The mass _MA (g) of the measurement sample is measured. For the measurement sample, the isotherms of adsorption and desorption are measured using nitrogen or argon as an adsorbent. Using the isotherms on the adsorption side obtained here, the BET surface area can be calculated by the BET multipoint method or the BET single point method, and the pore amount can be calculated by the BJH method. The BJH method is a calculation method generally used for analysis of mesopores, and has been proposed by Barrett, Joiner, Hallenda et al. (Non-Patent Document 1).
By dividing the obtained BET surface area and pore amount values by the mass _MA of the measurement sample, the BET specific surface area per mass of the negative electrode active material layer and the pore amount can be calculated. Further, the obtained isotherm on the adsorption side can be analyzed by the BJH method to obtain a pore distribution curve, and by using this pore distribution curve, the presence or absence of a peak in a region having a diameter of 20 nm or more and 50 nm or less can be determined. It can be judged.

(Peeling strength)
The peel strength of the negative electrode active material layer in the negative electrode of the present embodiment is 0.40 N / cm or more and 2.00 N / cm or less. When the peel strength is 0.40 N / cm or more, it is possible to suppress the loss of the negative electrode active material layer and suppress a slight short circuit. When the peel strength is 2.00 N / cm or less, it means that there is no excessive binder or the like in the negative electrode active material layer, so that the diffusibility of the electrolytic solution can be improved and the resistance can be lowered.
The peel strength of the negative electrode active material layer of the present invention is a value measured after pressing when pressing is performed when the negative electrode is manufactured. When pressing multiple times, it is a value measured after the final pressing. In the case of a negative electrode that is not pressed, it is a value measured in an unpressed state.
The peel strength of the present invention can be measured by a known method. For example, a peeling test based on JIS Z0237 (2009) "Adhesive Tape / Adhesive Sheet Test Method" may be used. Alternatively, the test method used in the examples described later may be used.

[Negative electrode active material]
In the present embodiment, the negative electrode active material layer contains a first negative electrode active material made of a carbon material and a second negative electrode active material made of a carbon material and different from the first negative electrode active material.
Examples of the carbon material include refractory carbon materials; easily graphitizable carbon materials; carbon black; carbon nanoparticles; activated carbon; artificial graphite; natural graphite; graphitized mesophase carbon spherules; graphite whiskers; high specific surface area. Graphite; Amorphous carbonaceous material such as polyacene-based material; Carbonaceous material precursor such as petroleum-based pitch, coal-based pitch, mesocarbon microbeads, coke, synthetic resin (for example, phenol resin, etc.), obtained by heat treatment. Carbonaceous materials; thermal decomposition products of full frill alcohol resin or novolak resin; fullerene; carbon nanophones; and composite carbon materials composed of two or more of these can be mentioned.

In the present embodiment, the first negative electrode active material is a graphite-based composite material in which a base material made of (i) a graphite-based material or (ii) a graphite-based material and a carbonaceous material precursor are composited.
The second negative electrode active material may be an amorphous carbon composite material in which a base material made of (i) an amorphous carbon material or (ii) an amorphous carbon material and a carbonaceous material precursor are composited. preferable.
By using the above-mentioned first negative electrode active material and second negative electrode active material, it is possible to achieve both high energy density, low resistance and high durability.

(1st negative electrode active material)
The graphite-based material used for the first negative electrode active material is not particularly limited, and for example, artificial graphite, natural graphite, graphitized mesophase carbon microspheres, graphite whiskers, high specific surface area graphite and the like can be used. ..
The average particle size of the graphite material is preferably 1 μm or more and 10 μm or less, and more preferably 2 μm or more and 8 μm or less.
As the first negative electrode active material, the above-mentioned graphite-based material may be used as it is, but from the viewpoint of lowering the resistance, a substrate made of the graphite-based material and a carbonaceous material precursor will be used as described later. A graphite-based composite material that has undergone various composite treatments is more suitable.

The carbonaceous material precursor used in the first negative electrode active material is a solid, liquid, or liquid, which can be heat-treated together with a graphite-based material to obtain a graphite-based composite material in which a graphite material and a carbonaceous material are composited. Alternatively, it is an organic material that can be dissolved in a solvent. The carbonaceous material precursor is not particularly limited as long as it is composited with a graphite-based material by heat treatment, and examples thereof include pitch, mesocarbon microbeads, coke, and synthetic resin (for example, phenol resin). be able to. Among these carbonaceous material precursors, it is preferable to use an inexpensive pitch in terms of manufacturing cost. Pitches are roughly divided into petroleum-based pitches and coal-based pitches. Examples of petroleum-based pitches include distillation residue of crude oil, fluid contact decomposition residue (decant oil, etc.), bottom oil derived from thermal crackers, ethylene tar obtained during naphtha cracking, and the like.

The amount of the carbonaceous material precursor used is preferably 10 parts by mass or more and 100 parts by mass or less, and more preferably 20 parts by mass or more and 80 parts by mass or less with respect to 100 parts by mass of the base material made of a graphite-based material. More preferably, it is 30% by mass or more and 60% by mass or less.

The graphite material and the carbonaceous material precursor are mixed and then heat-treated. The base material and the carbonaceous material precursor may be mixed at a temperature equal to or lower than the melting point of the carbonic material precursor, or may be carried out at a temperature higher than the melting point of the carbonic material precursor.
The heat treatment temperature may be any temperature as long as the component generated by volatilization or thermal decomposition of the carbonaceous material precursor to be used becomes the carbonaceous material. The heat treatment temperature is preferably 400 ° C. or higher and 2,500 ° C. or lower, more preferably 500 ° C. or higher and 2,000 ° C. or lower, and further preferably 550 ° C. or higher and 1,500 ° C. or lower. The atmosphere in which the heat treatment is performed is not particularly limited, but a non-oxidizing atmosphere is preferable.

(Second negative electrode active material)
The amorphous carbon material used for the second negative electrode active material is not particularly limited, but for example, activated carbon, hard carbon, soft carbon, carbon black and the like are preferably used.
The carbonaceous material precursor used for the second negative electrode active material is heat-treated together with the amorphous carbon material to obtain an amorphous carbon composite material in which the amorphous carbon material and the carbonaceous material are composited. It is an organic material that can be dissolved in a solid, liquid, or solvent. The carbonaceous material precursor is not particularly limited as long as it is composited with the amorphous carbon material by heat treatment, and is, for example, the above-mentioned carbonaceous material precursor used for synthesizing the first negative electrode active material. Can be appropriately selected and used from those exemplified in.

The amount of the carbonaceous material precursor used is preferably 10 parts by mass or more and 200 parts by mass or less, and more preferably 20 parts by mass or more and 1600 parts by mass or less with respect to 100 parts by mass of the base material made of an amorphous carbon material. It is more preferably 30% by mass or more and 120% by mass or less.
Then, the amorphous carbon material and the carbonaceous material precursor are mixed and then heat-treated.
The mixing and heat treatment may be carried out in the same manner as the synthesis of the graphite-based composite material of the first negative electrode active material after replacing "graphite material" with "amorphous carbon material".

(Mass ratio between the first negative electrode active material and the second negative electrode active material)
In the present embodiment, the ratio of the mass of the first negative electrode active material to the total mass of the negative electrode active material layer is M ₁ (mass%), and the ratio of the mass of the second negative negative active material to the total mass of the negative electrode active material layer. When it is M ₂ (mass%), it is preferable that M ₂ / (M ₁ + M ₂ ) is 0.01 or more and 0.75 or less. The lower limit of M ₂ / (M ₁ + M ₂ ) is more preferably 0.02 or more, and particularly preferably 0.05 or more. The upper limit of M ₂ / (M ₁ + M ₂ ) is more preferably 0.6 or less, and particularly preferably 0.4 or less. When M ₂ / (M ₁ + M ₂ ) is 0.01 or more, low resistance characteristics can be obtained, and when M 2 / (M 1 + M 2) is 0.75 or less, high energy density can be obtained.

(Optional negative electrode active material)
The negative electrode active material in the present embodiment may contain, in addition to the first negative electrode active material and the second negative electrode active material, an alloy-based material forming an alloy with lithium or lithium titanate (third negative electrode active material). ..
The alloy-based material that forms an alloy with lithium in the third negative electrode active material is preferably a base material selected from silicon, a silicon compound, tin, and a tin compound, and these base materials and a carbon or carbonaceous material. It preferably contains at least one selected from the group consisting of composite materials.
As the base material of the third negative electrode active material, a silicon compound or a silicon oxide is preferable, and SiO _x (0.01 ≦ x ≦ 1) is more preferable.
When the third negative electrode active material is a composite material, at least one base material preferably selected from the group consisting of silicon, a silicon compound, tin, and a tin compound, and a non-graphitizable carbon material; easily graphitizable. Carbon material; Carbon black; Carbon nanoparticles; Activated carbon; Artificial graphite; Natural graphite; Graphitized mesophase carbon globules; Graphite whiskers; Amorphous carbonaceous materials such as polyacene-based materials; Petroleum-based pitch, coal-based pitch, mesocarbon It consists of a carbonaceous material obtained by heat-treating a carbonaceous material precursor such as microbeads, coke, synthetic resin (for example, phenol resin, etc.); a thermal decomposition product of furfuryl alcohol resin or novolak resin; fullerene; carbon nanophone; It is preferable that the material is a composite of at least one carbon or carbonaceous material selected from the group by heat treatment or the like.

Lithium titanate among the third negative electrode active materials is represented by the chemical formula Li ₄ Ti ₅ O ₁₂ .
Since lithium titanate has a small expansion and contraction due to charge and discharge, the inclusion of lithium titanate further improves the high load charge / discharge cycle characteristics.

When the negative electrode active material in the present embodiment contains, in addition to the first negative electrode active material and the second negative electrode active material, an alloy-based material forming an alloy with lithium or lithium titanate (third negative electrode active material), the negative electrode activity The lower limit of the total content of the first negative electrode active material and the second negative electrode active material with respect to the total amount of the material is preferably 20% by mass or more, more preferably 50% by mass or more. The upper limit of the total content of the first negative electrode active material and the second negative electrode active material may be 100% by mass or less, preferably 90% by mass or less, and more preferably 80% by mass or less. You may. The upper and lower limits of the range of the total content of the first negative electrode active material and the second negative electrode active material can be arbitrarily combined.

[Arbitrary component of negative electrode active material layer]
The negative electrode active material layer in the present invention may contain an optional component such as a binder, a conductive filler, and a dispersion stabilizer, in addition to the negative electrode active material, if necessary.

(Binder)
As the binder, for example, polyvinylidene fluoride (PVdF), polytetrafluoroethylene (PTFE), fluororubber, latex, styrene-butadiene copolymer, acrylic polymer, polyimide and the like can be used. The amount of the binder used in the negative electrode active material layer is preferably 1 part by mass or more and 30 parts by mass or less, more preferably 2 parts by mass or more and 27 parts by mass or less, and further preferably 3 with respect to 100 parts by mass of the negative electrode active material. It is 5 parts by mass or more and 25 parts by mass or less. When the amount of the binder used is 1 part by mass or more, sufficient electrode strength is exhibited. When the amount of the binder used is 30 parts by mass or less, high input / output characteristics are exhibited without inhibiting the entry and exit of lithium ions into the negative electrode active material.

(Conductive filler)
The type of the conductive filler is not particularly limited, but it is preferably made of a conductive carbonaceous material having higher conductivity than the negative electrode active material. As such a conductive filler, for example, Ketjen black, acetylene black, vapor phase grown carbon fiber, graphite, carbon nanotube, a mixture of two or more of these, and the like are preferable.
The mixing amount of the conductive filler is preferably 20 parts by mass or less, and more preferably 1 to 15 parts by mass with respect to 100 parts by mass of the negative electrode active material. It is preferable to mix the conductive filler from the viewpoint of high input, but when the mixing amount is more than 20 parts by mass, the content of the negative electrode active material in the negative electrode active material layer is reduced, so that the energy density per volume is reduced. Is not preferable because it decreases.

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

(Thickness of negative electrode active material layer)
The thickness of the negative electrode active material layer is preferably 10 μm or more and 70 μm or less, and more preferably 20 μm or more and 60 μm or less per one side. When this thickness is 10 μm or more, good charge / discharge capacity can be exhibited. On the other hand, if this thickness is 70 μm or less, the cell volume can be reduced and the energy density can be increased. When the negative electrode current collector has holes, the thickness of the active material layer of the negative electrode means the average value of the thickness per side of the portion of the negative electrode current collector that does not have holes.

(Bulk density of negative electrode active material layer)
The bulk density of the negative electrode active material layer in the present embodiment is preferably 0.6 g / cc or more and 1.6 g / cc or less. More preferably, it is 0.7 g / cc or more and 1.2 g / cc or less.
When the bulk density is 0.60 g / cm ³ or more, the negative electrode can maintain sufficient strength and can exhibit sufficient conductivity between the negative electrode active materials. On the other hand, if it is 1.6 g / cm ³ or less, it is possible to secure pores in which ions can be sufficiently diffused in the negative electrode active material layer.

(Moisture content of negative electrode active material layer)
The water content in the negative electrode active material layer is preferably 0.1% by mass or more and 10% by mass or less when the mass of the negative electrode active material layer is 100% by mass. When the water content is 0.1% by mass or more, deterioration of the binder due to excessive drying can be suppressed and the resistance can be lowered. When the water content is 10% by mass or less, the deactivation of lithium ions in the non-aqueous lithium-type power storage element can be suppressed and the capacity can be increased.
The water content contained in the negative electrode can be measured by, for example, the Karl Fischer titration method (JIS 0068 (2001) “Method for measuring water content of chemical products”).

(Solvent content of negative electrode active material layer)
When N-methyl-2-pyrrolidone (NMP) was used to prepare the coating liquid, the content of NMP in the negative electrode active material layer after drying was determined when the mass of the negative electrode active material layer was 100% by mass. It is preferably 0.1% by mass or more and 10% by mass or less. When NMP is 0.1% by mass or more, deterioration of the binder due to excessive drying can be suppressed and resistance can be reduced. When the NMP is 10% by mass or less, the self-discharge characteristics of the non-aqueous lithium storage element can be improved.
The NMP contained in the negative electrode active material layer is obtained by impregnating the negative electrode with ethanol having a mass of 50 to 100 times that of the negative electrode active material layer for 24 hours in an environment of 25 ° C. to extract GC / MS of the extract. It can be measured and quantified based on a calibration curve prepared in advance.

(Existence mode of the negative electrode active material layer)
The negative electrode active material layer in the present embodiment may be uniformly present on one or both sides of the negative electrode current collector described later on the entire surface of each surface, or the negative electrode active material layer on each surface. There may be a region where is present and a region where is not present. In the latter case, the negative electrode material layer may be, for example, striped, lattice-shaped, or the like, or may be a case where a plurality of negative electrode active material layers having an arbitrary shape are independently scattered.

[Negative electrode current collector]
The material constituting the negative electrode current collector in the present invention is preferably a metal foil having high electron conductivity and not deteriorated by elution into an electrolytic solution and reaction with an electrolyte or ions. Such metal foil is not particularly limited, and examples thereof include aluminum foil, copper foil, nickel foil, and stainless steel foil. Copper foil is preferable as the negative electrode current collector in the negative electrode of the present embodiment. The copper foil may be a normal non-perforated copper foil having no irregularities, through holes, etc. and having a smooth surface, or may be a perforated copper foil having through holes such as expanded metal, punching metal, and etching foil. A non-perforated copper foil having irregularities subjected to roughening treatment such as embossing, chemical etching, electrolytic precipitation, and blasting may be used.
The thickness of the negative electrode current collector is not particularly limited as long as the shape and strength of the negative electrode can be sufficiently maintained, but is preferably 1 to 100 μm, for example. When the negative electrode current collector has through holes or irregularities, the thickness of the negative electrode current collector shall be measured based on the portion where the through holes or irregularities do not exist.

<Manufacturing method of negative electrode>
The negative electrode has a negative electrode active material layer on one side or both sides of the negative electrode current collector. In a typical embodiment, the negative electrode active material layer is fixed to the negative electrode current collector.
The negative electrode can be manufactured by a technique for manufacturing electrodes in known lithium ion batteries, electric double layer capacitors and the like.
The negative electrode of this embodiment is, for example,
It includes a step of applying a negative electrode coating liquid on a negative electrode current collector to form a negative electrode active material layer.
The negative electrode coating liquid contains a first negative electrode active material, a second negative electrode active material, a solvent, and a binder, and is a negative electrode coating liquid having a mass of all components excluding the solvent in the negative electrode coating liquid. It can be manufactured by a method for manufacturing a negative electrode in which the ratio _WT (% by mass) to the total mass is 10 ≦ _WT ≦ 70.
As another method for manufacturing the negative electrode, various materials including the negative electrode active material are mixed in a dry manner without using a solvent, the obtained mixture is press-molded, and then attached to the negative electrode current collector using a conductive adhesive. It is also possible to attach it.
Hereinafter, a method for manufacturing a negative electrode using a negative electrode coating liquid will be described.

[Negative electrode coating liquid]
The negative electrode coating liquid contains a first negative electrode active material, a second negative electrode active material, a solvent, and a binder.
The negative electrode coating solution may be prepared, for example, by dry-blending all the materials including the negative electrode active material and then adding water or an organic solvent;
After dry-blending a part of the material containing the negative electrode active material and adding water or an organic solvent, prepare by adding a solution or slurry in which the remaining material including the binder, dispersion stabilizer, etc. is dissolved or dispersed. May; or
The remaining material including the negative electrode active material may be added to the solution or slurry in which a binder, a dispersion stabilizer or the like is dissolved or dispersed in water or an organic solvent.

The method for dissolving or dispersing the material powder in water or an organic solvent is not particularly limited, but is preferably a disperser such as a homodisper, a multi-axis disperser, a planetary mixer, or a thin film swirl type high-speed mixer. Etc. can be used. In order to obtain a negative electrode coating liquid in a good dispersed state, it is preferable to disperse at a peripheral speed of 1 m / s or more and 50 m / s or less. When the peripheral speed is 1 m / s or more, it is preferable because various material powders are satisfactorily dissolved or dispersed. When the peripheral speed is 50 m / s or less, various materials are not easily destroyed by heat due to dispersion, shearing force, etc., and reaggregation is reduced, which is preferable.
Further, it is particularly preferable to disperse the negative electrode coating liquid while cooling. Due to the heat generated during dispersion, a part of various materials (for example, binder, dispersant, etc.) may be destroyed. Then, the two types of negative electrode active materials are not uniformly dispersed, one active material is aggregated and settled to obtain a uniform electrode, and only the other negative electrode active material is present on the surface. In this regard, by dispersing the negative electrode coating liquid while cooling, the destruction of various materials is significantly suppressed, so that two types of negative electrode active materials can be uniformly dispersed, and two types of negative electrodes can be uniformly dispersed on the negative electrode surface. A homogeneous negative electrode in which the active material is present is obtained, which is preferable.
The dispersion temperature is, for example, preferably 20 ° C. or lower, and may be −10 ° C. or higher and 15 ° C. or lower, or 0 ° C. or higher and 10 ° C. or lower.

The negative electrode coating liquid is preferably defoamed after dispersion. The defoaming method is not particularly limited, but for example, a method of stirring the negative electrode coating liquid at a low speed in a reduced pressure environment, a method of allowing the negative electrode coating liquid to stand still, a method of stirring at a low speed using a rotation / revolution mixer, and the like. Can be mentioned.
After the negative electrode coating liquid is dispersed, it is preferable to remove agglomerates with a filter or the like. By removing agglomerates having a large particle size, an electrode having a uniform distribution in the thickness direction can be obtained.

The ratio _WT (mass%) of the mass of all the components in the negative electrode coating liquid excluding the solvent to the total mass of the negative electrode coating liquid is preferably 10 ≤ _WT ≤ 70, and 15 ≤ _WT ≤ 65. Is more preferable, and 20 ≦ _WT ≦ 60 is even more preferable.
The viscosity (ηb) of the negative electrode coating liquid is preferably 1,000 mPa · s or more and 20,000 mPa · s or less, more preferably 1,500 mPa · s or more and 10,000 mPa · s or less, and further preferably 1,700 mPa · s. It is 5,000 mPa · s or less. When the viscosity (ηb) of the negative electrode coating liquid is 1,000 mPa · s or more, liquid dripping during coating film formation is suppressed, and the coating film width and thickness can be satisfactorily controlled. When the viscosity (ηb) of the negative electrode coating liquid is 20,000 mPa · s or less, the pressure loss in the flow path of the coating liquid when using the coating machine is small and stable coating can be performed, and the desired coating film can be applied. It can be controlled to the thickness.
The TI value (thixotropy index value) of the negative electrode coating liquid is preferably 1.1 or more, more preferably 1.2 or more, and further preferably 1.5 or more. When the TI value of the negative electrode coating liquid is 1.1 or more, the coating film width and thickness can be satisfactorily controlled.

(Coating method)
The method for forming the coating film of the negative electrode is not particularly limited, but a coating machine such as a die coater, a comma coater, a knife coater, and a gravure coating machine can be preferably used. The coating film may be formed by a single-layer coating or a multi-layer coating. The coating speed is preferably 0.1 m / min or more and 100 m / min or less, more preferably 0.5 m / min or more and 70 m / min or less, and further preferably 1 m / min or more and 50 m / min or less. If the coating speed is 0.1 m / min or more, stable coating can be performed, and if it is 100 m / min or less, coating accuracy can be sufficiently ensured.
The coating film may be formed by a single-layer coating or a multi-layer coating. In the case of multi-layer coating, the content of the negative electrode active material in each layer of the coating film may be the same, or the composition of the negative electrode coating liquid is different so that the content of the negative electrode active material in each layer of the coating film is different. May be adjusted.
Further, when coating on both sides of the negative electrode current collector, one side of the negative electrode current collector may be coated and dried, and then the other surface may be sequentially coated and dried, or the negative electrode may be applied. Both sides of the current collector may be simultaneously coated with the negative electrode coating liquid and dried.
When the coating film is applied to the negative electrode current collector, it may be applied in multiple rows, intermittently, or intermittently.

(Drying of coating film)
The method for drying the coating film obtained by applying the negative electrode coating liquid is not particularly limited, but a drying method such as hot air drying or infrared (IR) drying can be preferably used. As the infrared rays, either far infrared rays or near infrared rays may be used.
The coating film may be dried at a single temperature, or may be dried at different temperatures in a multi-step or gradual manner. Further, a plurality of drying methods may be combined and dried.
The drying temperature is preferably 25 ° C. or higher and 200 ° C. or lower, more preferably 40 ° C. or higher and 180 ° C. or lower, and further preferably 50 ° C. or higher and 160 ° C. or lower. When the drying temperature is 25 ° C. or higher, the solvent in the coating film can be sufficiently volatilized. When the drying temperature is 200 ° C. or lower, it is possible to suppress cracking of the coating film due to rapid volatilization of the solvent, uneven distribution of the binder due to migration, and oxidation of the negative electrode current collector and the negative electrode active material layer.
The drying time may be appropriately set within a range in which the amount of water and the amount of solvent in the formed negative electrode active material layer reach the above-mentioned preferable range and do not fall below the above-mentioned preferable range.

(press)
Further, the obtained negative electrode may be pressed to adjust the film thickness, bulk density and the like of the negative electrode active material layer.
The negative electrode may be slit (cut) prior to the press, or a slit step may be provided after the press. When the negative electrode is multi-row coated, it is preferable to slit it before pressing. When the multi-row coated positive electrode precursor is pressed without slitting, stress may be applied to the region of the negative electrode current collector where the negative electrode active material layer is not applied, and wrinkles may be formed. After slitting and pressing, the negative electrode can be slit again.

The method of pressing the negative electrode is not particularly limited, but a press machine such as a hydraulic press machine, a vacuum press machine, or a roll press machine can be preferably used. The film thickness, bulk density, and electrode strength of the negative electrode active material layer can be adjusted by the press pressure, the gap, the surface temperature of the press portion, and the like.
The press pressure is preferably 0.5 kN / cm or more and 20 kN / cm or less, more preferably 1 kN / cm or more and 10 kN / cm or less, and further preferably 2 kN / cm or more and 7 kN / cm or less. When the press pressure is 0.5 kN / cm or more, the electrode strength can be sufficiently increased. When the press pressure is 20 kN / cm or less, the negative electrode is less likely to bend and wrinkle, and the negative electrode active material layer can be easily adjusted to a desired film thickness and bulk density.
When a roll press machine is used as the press machine, the gap between the press rolls can be set to an arbitrary value according to the negative electrode film thickness after drying so as to have a desired film thickness and bulk density of the negative electrode active material layer. .. The press speed can be set to any speed so as to reduce the bending and wrinkles of the negative electrode.

The surface temperature of the pressed portion may be room temperature or may be heated if necessary. The lower limit of the surface temperature of the pressed portion when heating is preferably the melting point of the binder used at minus 60 ° C. or higher, more preferably the melting point of the binder at minus 45 ° C. or higher, and further preferably the melting point of the binder at minus 30 ° C. It is above ° C. The upper limit of the surface temperature of the pressed portion during heating is preferably the melting point of the binder used plus 50 ° C. or lower, more preferably the melting point of the binder plus 30 ° C. or lower, and even more preferably the melting point of the binder plus 20 ° C. It is below ° C. For example, when PVdF (polyvinylidene fluoride: melting point 150 ° C.) is used as the binder, it is preferably heated to 90 ° C. or higher and 200 ° C. or lower, more preferably 105 ° C. or higher and 180 ° C. or lower, and further preferably 120 ° C. or higher and 170 ° C. or lower. do. When a styrene-butadiene copolymer (melting point 100 ° C.) is used as the binder, the temperature is preferably 40 ° C. or higher and 150 ° C. or lower, more preferably 55 ° C. or higher and 130 ° C. or lower, and further preferably 70 ° C. or higher and 120 ° C. or lower. Warm up.
The melting point of the binder can be determined from the endothermic peak position of DSC (Differential Scanning Calorimetry). For example, using a differential scanning calorimeter "DSC7" manufactured by PerkinElmer, 10 mg of sample resin is set in a measurement cell, and the temperature rises from 30 ° C. to 250 ° C. at a heating rate of 10 ° C./min in a nitrogen gas atmosphere. The temperature rises, and the heat absorption peak temperature in the temperature rise process becomes the melting point.

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

<< Non-aqueous lithium-type power storage element >>
The non-aqueous lithium storage element of the present embodiment has a negative electrode, a positive electrode, a separator, and an electrolytic solution as main components, and preferably these are housed in an appropriate exterior body.
As the negative electrode, the negative electrode of the present embodiment described above is used.

<Positive electrode>
The positive electrode has a positive electrode current collector and a positive electrode active material layer existing on one side or both sides thereof.
The positive electrode active material layer contains a positive electrode active material, and preferably contains a lithium compound. As will be described later, in the present embodiment, the lithium compound in the positive electrode active material functions as a pre-doped source of lithium ions for the negative electrode in the assembly process of the non-aqueous lithium storage element.
In the present specification, the positive electrode containing a predetermined lithium compound before the lithium doping step is referred to as a “positive electrode precursor”, and the positive electrode after the lithium doping step is referred to as a “positive electrode”.

[Positive electrode active material layer]
The positive electrode active material layer preferably contains a positive electrode active material containing a carbon material, and may also contain optional components such as a conductive filler, a binder, and a dispersion stabilizer, if necessary. Further, it is preferable to contain a lithium compound in the positive electrode active material layer or on the surface of the positive electrode active material layer. It is most preferable that the positive electrode active material further contains a lithium transition metal oxide together with the carbon material.

(Positive electrode active material)
A carbon material is preferable as the positive electrode active material. As the carbon material, it is more preferable to use a carbon nanotube, a conductive polymer, or a porous carbon material, and more preferably activated carbon.
The content of the carbon material with respect to the total amount of the positive electrode active material is preferably 50% by mass or more, more preferably 70% by mass or more. The content of the carbon material with respect to the total amount of the positive electrode active material can be 100% by mass, but from the viewpoint of obtaining a good effect by the combined use of other materials, for example, it is 90% by mass or less or 80% by mass or less. Is preferable.

When activated carbon is used as the positive electrode active material, there are no particular restrictions on the type of activated carbon and its raw material. However, it is preferable to optimally control the pores of the activated carbon in order to achieve both high input / output characteristics and high energy density. Specifically, the amount of mesopores derived from pores with a diameter of 20 Å or more and 500 Å or less calculated by the BJH method is V ₁ (cc / g), and the amount of micropores derived from pores with a diameter of less than 20 Å calculated by the MP method. When is V ₂ (cc / g),
(1) For high input / output characteristics, 0.3 <V ₁ ≤ 0.8 and 0.5 ≤ V ₂ ≤ 1.0 are satisfied, and the specific surface area measured by the BET method is 1. Activated carbon having a temperature of 500 m ² / g or more and 3,000 m ² / g or less (hereinafter, also referred to as activated carbon 1) is preferable.
(2) In order to obtain a high energy density, 0.8 <V ₁ ≤ 2.5 and 0.8 <V ₂ ≤ 3.0 are satisfied, and the specific surface area measured by the BET method is 2, Activated carbon having a thickness of 300 m ² / g or more and 4,000 m ² / g or less (hereinafter, also referred to as activated carbon 2) is preferable.

The BET specific surface area, mesopore amount, micropore amount, and average pore diameter of the active material in the present invention are values obtained by the following methods, respectively. The sample is vacuum-dried at 200 ° C. for a whole day and night, and the isotherms of adsorption and desorption are measured using nitrogen as an adsorbent. Using the isotherms on the adsorption side obtained here, the BET specific surface area is calculated by the BET multipoint method or the BET single point method, the mesopore amount is calculated by the BJH method, and the micropore amount is calculated by the MP method.
The BJH method is a calculation method generally used for analysis of mesopores, and has been proposed by Barrett, Joiner, Hallenda et al. (Non-Patent Document 1).
The MP method means a method for obtaining the micropore volume, the micropore area, and the distribution of micropores by using the "t-plot method" (Non-Patent Document 2). S. It is a method devised by Mikhair, Brunauer, and Bodor (Non-Patent Document 3).
The average pore diameter is obtained by dividing the total pore volume per mass of the sample obtained by measuring each equilibrium adsorption amount of nitrogen gas under each relative pressure under the liquid nitrogen temperature by the BET specific surface area. Refers to the thing.
Hereinafter, (1) activated carbon 1 and (2) activated carbon 2 will be described individually in sequence.

(Activated carbon 1)
The mesopore amount V1 of the activated carbon ₁ is preferably a value larger than 0.3 cc / g in terms of increasing the input / output characteristics when the positive electrode material is incorporated into the power storage element. On the other hand, it is preferably 0.8 cc / g or less from the viewpoint of suppressing a decrease in the bulk density of the positive electrode. The V ₁ is more preferably 0.35 cc / g or more and 0.7 cc / g or less, and further preferably 0.4 cc / g or more and 0.6 cc / g or less.
The micropore amount V2 of the activated carbon ₁ is preferably 0.5 cc / g or more in order to increase the specific surface area and the capacity of the activated carbon. On the other hand, it is preferably 1.0 cc / g or less from the viewpoint of suppressing the bulk of the activated carbon, increasing the density as an electrode, and increasing the capacity per unit volume. The V ₂ is more preferably 0.6 cc / g or more and 1.0 cc / g or less, and further preferably 0.8 cc / g or more and 1.0 cc / g or less.
The ratio of the mesopore amount V ₁ to the micropore amount V ₂ (V ₁ / V ₂ ) is preferably in the range of 0.3 ≤ V ₁ / V ₂ ≤ 0.9. That is, V ₁ / V ₂ should be 0.3 or more from the viewpoint of increasing the ratio of the mesopore amount to the micropore amount to the extent that the deterioration of the output characteristics can be suppressed while maintaining the high capacity. preferable. On the other hand, V ₁ / V ₂ should be 0.9 or less from the viewpoint of increasing the ratio of the amount of micropores to the amount of mesopores to the extent that the decrease in capacitance can be suppressed while maintaining high output characteristics. Is preferable. The more preferred range of V ₁ / V ₂ is 0.4 ≤ V ₁ / V ₂ ≤ 0.7, and the more preferred range of V ₁ / V ₂ is 0.55 ≤ V ₁ / V ₂ ≤ 0.7.

The average pore diameter of the activated carbon 1 is preferably 17 Å or more, more preferably 18 Å or more, and most preferably 20 Å or more from the viewpoint of maximizing the output of the obtained power storage element. Further, from the viewpoint of maximizing the capacity, the average pore diameter of the activated carbon 1 is preferably 25 Å or less.
The BET specific surface area of the activated carbon 1 is preferably 1,500 m ² / g or more and 3,000 m ² / g or less, and more preferably 1,500 m ² / g or more and 2,500 m ² / g or less. When the BET specific surface area is 1,500 m ² / g or more, good energy density is likely to be obtained, while when the BET specific surface area is 3,000 m ² / g or less, in order to maintain the strength of the electrode. Since it is not necessary to add a large amount of binder, the performance per electrode volume is improved.

The average particle size of the activated carbon 1 is preferably 2 to 20 μm.
When the average particle size is 2 μm or more, the capacity per electrode volume tends to be high due to the high density of the active material layer. Here, if the average particle size is small, the durability may be low, but if the average particle size is 2 μm or more, such a defect is unlikely to occur. On the other hand, when the average particle size is 20 μm or less, it tends to be easy to adapt to high-speed charging / discharging. The average particle size is more preferably 2 to 15 μm, still more preferably 3 to 10 μm.

[Activated carbon 2]
The mesopore amount V1 of the activated carbon ₂ is preferably a value larger than 0.8 cc / g from the viewpoint of increasing the output characteristics when the positive electrode material is incorporated into the power storage element, while reducing the capacity of the power storage element. From the viewpoint of suppressing, it is preferably 2.5 cc / g or less. The V ₁ is more preferably 1.00 cc / g or more and 2.0 cc / g or less, and further preferably 1.2 cc / g or more and 1.8 cc / g or less.
On the other hand, the micropore amount V2 of the activated carbon ₂ is preferably a value larger than 0.8 cc / g in order to increase the specific surface area and the capacity of the activated carbon, while increasing the density of the activated carbon as an electrode. It is preferably 3.0 cc / g or less from the viewpoint of increasing the capacity per unit volume. The V ₂ is more preferably larger than 1.0 cc / g and 2.5 cc / g or less, and further preferably 1.5 cc / g or more and 2.5 cc / g or less.

The activated carbon 2 having the above-mentioned mesopore amount and micropore amount has a higher BET specific surface area than the activated carbon used for a conventional electric double layer capacitor or a lithium ion capacitor. The specific value of the BET specific surface area of the activated carbon 2 is preferably 3,000 m ² / g or more and 4,000 m ² / g or less, and 3,200 m ² / g or more and 3,800 m ² / g or less. Is more preferable. When the BET specific surface area is 3,000 m ² / g or more, good energy density is likely to be obtained, while when the BET specific surface area is 4,000 m ² / g or less, in order to maintain the strength of the electrode. Since it is not necessary to add a large amount of binder, the performance per electrode volume is improved.
The average particle size of the activated carbon 2 is preferably 2 μm or more and 20 μm or less. More preferably, it is 3 μm or more and 10 μm or less.

[Usage of activated carbon]
Activated carbons 1 and 2 may be one type of activated carbon, respectively, or may be a mixture of two or more types of activated carbon, and each of the above-mentioned characteristic values may be shown as a whole mixture.
The activated carbons 1 and 2 may be used by selecting one of them, or a mixture of the two may be used.
The positive electrode active material is a material other than activated carbons 1 and 2 (for example, activated carbon without the specific V ₁ and / or V ₂ or a material other than activated carbon (for example, a composite oxide of lithium and a transition metal family). It may also contain (also referred to as "lithium transition metal oxide"), a conductive polymer, etc.).

Examples of the lithium transition metal oxide include Li _x CoO ₂ , Li _x NiO ₂ , Li _x Ny M _{(1-y) O 2} (M is a group consisting of Co, Mn, Al, Fe, Mg, and Ti). At least one element selected from the above, y satisfies 0.2 <y <0.97), Li _x Ni _1/3 Co _1/3 Mn _1/3 O ₂ , Li _x MnO ₂ , α. -Li _x FeO ₂ , Li _x VO ₂ , Li _x CrO ₂ , Li _x FePO ₄ , Li _z V ₂ (PO ₄ ) ₃ , Li _x Mn ₂ O ₄ , Li _x My Mn (2- _{y )} O ₄ (M is at least one element selected from the group consisting of Co, Mn, Al, Fe, Mg, and Ti, and y satisfies 0.2 <y <0.97.), Li _x Ni _a Co. _b Al _(1-ab) O ₂ (a and b satisfy 0.2 <a <0.97, 0.2 <b <0.97), Li _x Ni _c Co _d Mn _(1- ). _cd) O ₂ (c and d satisfy 0.2 <c <0.97, 0.2 <d <0.97.) (X satisfies 0 ≦ x ≦ 1, z satisfies 0 ≦ z. ≤ 3) and the like.

In an exemplary embodiment, the content of activated carbon 1, the content of activated carbon 2, or the total content of activated carbons 1 and 2 is preferably more than 50% by mass, and 70% by mass or more, respectively, of the total positive electrode active material. More preferably, 90% by mass or more is further preferable, and 100% by mass is most preferable.
The content ratio of the positive electrode active material in the positive electrode active material layer is preferably 35% by mass or more and 95% by mass or less based on the total mass of the positive electrode active material layer in the positive electrode precursor. The upper limit of the content ratio of the positive electrode active material is more preferably 45% by mass or more, further preferably 55% by mass or more. On the other hand, the lower limit of the content ratio of the positive electrode active material is more preferably 90% by mass or less, further preferably 80% by mass or less. By setting the content ratio in this range, suitable charge / discharge characteristics are exhibited.

[Lithium compound]
The positive electrode active material layer of the positive electrode precursor of the present embodiment preferably contains a lithium compound in addition to the positive electrode active material. Further, the positive electrode active material layer of the positive electrode of the present embodiment contains a lithium compound other than the positive electrode active material.
The lithium compound can be decomposed at the positive electrode in the lithium doping step described later to release lithium ions, and from the viewpoint that it can release lithium ions, lithium carbonate, lithium oxide, lithium hydroxide, lithium fluoride, lithium chloride, and sucrose. One or more selected from the group consisting of lithium, lithium iodide, lithium hydroxide, lithium oxalate, and lithium acetate are preferably used. Among them, one or more selected from the group consisting of lithium carbonate, lithium oxide, and lithium hydroxide is more preferable, and lithium carbonate is further preferable from the viewpoint that it can be handled in the air and has low hygroscopicity. preferable. Such a lithium compound decomposes when a voltage is applied, functions as a dopant source for lithium doping to the negative electrode, and forms pores in the positive electrode active material layer, so that the electrolytic solution has excellent retention and ionic conductivity. It is possible to form an excellent positive electrode.

[Lithium compound of positive electrode precursor]
The lithium compound in the positive electrode active material layer of the positive electrode precursor is preferably in the form of particles. The average particle size of the lithium compound contained in the positive electrode active material layer of the positive electrode precursor is preferably 0.1 μm or more and 100 μm or less. The upper limit of the average particle size of this lithium compound is more preferably 50 μm or less, further preferably 20 μm or less, and most preferably 10 μm or less. On the other hand, the lower limit of the average particle size of this lithium compound is more preferably more than 0.1 μm, further preferably 0.5 μm or more. When the average particle size of the lithium compound is 0.1 μm or more, the pores remaining after the oxidation reaction of the lithium compound in the positive electrode have a sufficient volume to hold the electrolytic solution, so that the high load charge / discharge characteristics are exhibited. improves. When the average particle size of the lithium compound is 100 μm or less, the surface area of the lithium compound does not become excessively small, so that the rate of the oxidation reaction of the lithium compound can be ensured.

The content ratio of the lithium compound in the positive electrode active material layer of the positive electrode precursor is preferably 5% by mass or more and 60% by mass or less based on the total mass of the positive electrode active material layer in the positive electrode precursor, and is preferably 10% by mass or more and 50% by mass. It is more preferably mass% or less. By setting the content ratio in this range, it is possible to exert a suitable function as a dopant source for the negative electrode, to impart an appropriate degree of porosity to the positive electrode, and to combine both of them with high load charge / discharge efficiency. It is possible to provide an excellent power storage element. The upper and lower limits of this content ratio range can be arbitrarily combined.

[Lithium compound of positive electrode]
When the average particle size of the lithium compound in the positive electrode active material layer of the positive electrode is X ₁ , it is preferably 0.1 μm ≤ X ₁ ≤ 10 μm, and more preferably 0.5 μm ≤ X ₁ ≤ 5 μm. When X ₁ is 0.1 μm or more, the high load charge / discharge cycle characteristics are improved by adsorbing the fluorine ions generated in the high load charge / discharge cycle. When X ₁ is 10 μm or less, the reaction area with the fluorine ions generated in the high load charge / discharge cycle increases, so that the adsorption of the fluorine ions can be efficiently performed.
The amount of the lithium compound in the positive electrode active material layer of the positive electrode is preferably 1% by mass or more and 50% by mass or less, and 2.5% by mass or more and 25% by mass or less, based on the total mass of the positive electrode active material layer in the positive electrode. Is more preferable. When the amount of the lithium compound is 1% by mass or more, lithium carbonate suppresses the decomposition reaction of the electrolytic solution solvent on the positive electrode in a high temperature environment, so that the high temperature durability is improved, and the amount is 2.5% by mass or more. , The effect becomes remarkable. Further, when the amount of the lithium compound is 50% by mass or less, the electron conductivity between the positive electrode active materials is relatively small to be hindered by the lithium compound, so that high input / output characteristics are exhibited, and the amount is 25% by mass or less. , High input / output characteristics become remarkable.

(Other components of the positive electrode active material layer)
In the positive electrode active material layer of the positive electrode and the positive electrode precursor of the present embodiment, in addition to the positive electrode active material and the lithium compound, for example, a conductive filler, a binder, a dispersion stabilizer, a pH adjuster, etc. It may contain any component of.

(Thickness of positive electrode active material layer)
The thickness of the positive electrode active material layer is preferably 10 μm or more and 200 μm or less per one side of the positive electrode current collector. The thickness of the positive electrode active material layer is more preferably 20 μm or more and 100 μm or less, and further preferably 30 μm or more and 80 μm or less per one side. When this thickness is 10 μm or more, a sufficient charge / discharge capacity can be developed. On the other hand, when this thickness is 200 μm or less, the ion diffusion resistance in the electrode can be kept low. Therefore, sufficient output characteristics can be obtained, the cell volume can be reduced, and therefore the energy density can be increased. The thickness of the positive electrode active material layer when the current collector has through holes or irregularities means the average value of the thickness per surface of the portion of the current collector that does not have through holes or irregularities.

(Bulk density of positive electrode active material layer)
The bulk density of the positive electrode active material layer in the positive electrode after the lithium doping step described later is preferably 0.25 g / cm ³ or more, more preferably 0.30 g / cm ³ or more and 1.3 g / cm ³ or less. Is. When the bulk density of the positive electrode active material layer is 0.25 g / cm ³ or more, a high energy density can be exhibited and the miniaturization of the power storage element can be achieved. On the other hand, when the bulk density is 1.3 g / cm ³ or less, the electrolytic solution is sufficiently diffused in the pores in the positive electrode active material layer, and high output characteristics can be obtained.

[Positive current collector]
The material constituting the positive electrode current collector in the present embodiment is not particularly limited as long as it has high electron conductivity and does not deteriorate due to elution into the electrolytic solution and reaction with the electrolyte or ions, but is not particularly limited. Foil is preferred. Aluminum foil is particularly preferable as the positive electrode current collector in the non-aqueous lithium power storage device of the present embodiment.
This metal foil may be a normal metal foil having no irregularities, through holes, etc., or a metal foil having irregularities subjected to embossing, chemical etching, electrolytic precipitation, blasting, etc., or expanded metal, A metal foil having through holes such as punching metal and etching foil may be used.
From the viewpoint of ease of electrode production and high electron conductivity, the positive electrode current collector in this embodiment is preferably non-porous. Here, it is sufficient if at least the region where the positive electrode active material layer is present in the positive electrode current collector is non-porous, and there are holes in the surplus portion of the positive electrode current collector where the positive electrode active material layer is not coated. It may or may not be present.
The thickness of the positive electrode current collector is not particularly limited as long as the shape and strength of the positive electrode can be sufficiently maintained, but is preferably 1 to 100 μm, for example.

It is preferable to provide an anchor layer containing a conductive material such as graphite, scaly graphite, carbon nanotube, graphene, Ketjen black, acetylene black, and vapor-grown carbon fiber on the surface of the metal foil. By providing the anchor layer, the electrical conduction between the positive electrode current collector and the positive electrode active material layer is improved, and the resistance can be lowered. The thickness of the anchor layer is preferably 0.1 μm or more and 5 μm or less per one side of the positive electrode current collector.

[Separator]
The positive electrode precursor and the negative electrode are laminated via a separator to form an electrode laminate having a positive electrode precursor, a negative electrode and a separator, or are laminated via a separator and then wound to form a positive electrode precursor, a negative electrode and a negative electrode. And an electrode winding body having a separator is formed.
As the separator, a polyethylene microporous film used for a lithium ion secondary battery, a polypropylene microporous film, a cellulose non-woven paper used for an electric double layer capacitor, or the like can be used. A film made of organic or inorganic fine particles may be laminated on one side or both sides of these separators. Further, organic or inorganic fine particles may be contained inside the separator.
The thickness of the separator is preferably 5 μm or more and 35 μm or less. A thickness of 5 μm or more is preferable because self-discharge due to internal microshorts tends to be small. On the other hand, it is preferable to set the thickness to 35 μm or less because the output characteristics of the power storage element tend to be high.
The thickness of the film made of organic or inorganic fine particles is preferably 1 μm or more and 10 μm or less. When the thickness of this film is 1 μm or more, self-discharge due to micro short circuit inside the separator tends to be small, which is preferable. On the other hand, when the thickness is 10 μm or less, the output characteristics of the power storage element tend to be high, which is preferable.

[Electrolytic solution]
The electrolytic solution in the non-aqueous lithium-type power storage element of the present embodiment is a non-aqueous electrolytic solution containing lithium ions. That is, this non-aqueous electrolyte solution contains a lithium salt that gives lithium ions and a non-aqueous solvent, and may further contain other additives.

(Lithium salt)
Examples of the lithium salt contained in the non-aqueous electrolyte solution in the present embodiment include (LiN (SO ₂ F) ₂ ), LiN (SO ₂ CF ₃ ) ₂ , LiN (SO ₂ C ₂ F ₅ ) ₂ , and LiN ( SO ₂ CF ₃ ) (SO ₂ C ₂ F ₅ ), LiN (SO ₂ CF ₃ ) (SO ₂ C ₂ F ₄ H), LiC (SO ₂ F) ₃ , LiC (SO ₂ CF ₃ ) ₃ , LiC ( SO ₂ C ₂ F ₅ ) ₃ , LiCF ₃ SO ₃ , LiC ₄ F ₉ SO ₃ , LiPF ₆ , LiBF ₄ and the like can be mentioned. These can be used alone or in combination of two or more. It is preferable that the lithium salt contains at least one selected from LiPF ₆ and LiN (SO ₂ F) ₂ because it can exhibit high conductivity.
The lithium salt concentration in the non-aqueous electrolyte solution is preferably 0.5 mol / L or more, more preferably 0.5 to 2.0 mol / L. When the lithium salt concentration is 0.5 mol / L or more, anions are sufficiently present, so that the capacity of the non-aqueous lithium storage element can be sufficiently increased. When the lithium salt concentration is 2.0 mol / L or less, it is possible to prevent undissolved lithium salt from precipitating in the non-aqueous electrolyte solution and the viscosity of the non-aqueous electrolyte solution from becoming too high, resulting in a decrease in conductivity. It is preferable because it is difficult to do and the output characteristics are not easily deteriorated.

(Non-aqueous solvent)
The non-aqueous electrolyte solution in the present embodiment preferably contains a cyclic carbonate and a chain carbonate as the non-aqueous solvent. It is advantageous that the non-aqueous electrolyte solution contains a cyclic carbonate and a chain carbonate in that it dissolves a lithium salt having a desired concentration and that it exhibits high lithium ion conductivity.
Examples of the cyclic carbonate include alkylene carbonate compounds typified by ethylene carbonate, propylene carbonate, butylene carbonate and the like. The alkylene carbonate compound is typically unsubstituted.
Examples of the chain carbonate include dialkyl carbonate compounds typified by dimethyl carbonate, diethyl carbonate, methyl ethyl carbonate, dipropyl carbonate, dibutyl carbonate and the like. Dialkyl carbonate compounds are typically unsubstituted.
The total content of the cyclic carbonate and the chain carbonate is preferably 50% by mass or more, more preferably 65% by mass or more, preferably 95% by mass or less, more preferably more preferably, based on the total mass of the non-aqueous electrolyte solution. It is 90% by mass or less. When the total content of the cyclic carbonate and the chain carbonate is 50% by mass or more, it is possible to dissolve a lithium salt having a desired concentration, and high lithium ion conductivity can be exhibited. When the total concentration of the cyclic carbonate and the chain carbonate is 95% by mass or less, the non-aqueous electrolytic solution can further contain the additive described later.

(Additive)
The non-aqueous electrolytic solution in the present embodiment may further contain an additive. The additive is not particularly limited, and examples thereof include sultone compounds, cyclic phosphazene, acyclic fluorinated ether, fluorinated cyclic carbonate, cyclic carbonate ester, cyclic carboxylic acid ester, and cyclic acid anhydride. These can be used alone, or two or more kinds may be mixed and used.

Examples of the sultone compound include sultone compounds represented by the following general formulas (1) to (3). These sultone compounds may be used alone or in combination of two or more.

｛式（１）中、Ｒ^１１～Ｒ^１６は、水素原子、ハロゲン原子、炭素数１～１２のアルキル基又は炭素数１～１２のハロゲン化アルキル基を表し、互いに同一であっても異なっていてもよく；そしてｎは０～３の整数である。｝

｛式（２）中、Ｒ^１１～Ｒ^１４は、水素原子、ハロゲン原子、炭素数１～１２のアルキル基又は炭素数１～１２のハロゲン化アルキル基を表し、互いに同一であっても異なっていてもよく；そしてｎは０～３の整数である。｝

｛式（７）中、Ｒ^１１～Ｒ^１６は、水素原子、ハロゲン原子、炭素数１～１２のアルキル基又は炭素数１～１２のハロゲン化アルキル基を表し、互いに同一であっても異なっていてもよい。｝

{In the formula (1), R ¹¹ to R ¹⁶ represent a hydrogen atom, a halogen atom, an alkyl group having 1 to 12 carbon atoms or an alkyl halide group having 1 to 12 carbon atoms, and are different even if they are the same as each other. May; and n is an integer from 0 to 3. }

{In formula (2), R ¹¹ to R ¹⁴ represent a hydrogen atom, a halogen atom, an alkyl group having 1 to 12 carbon atoms or an alkyl halide group having 1 to 12 carbon atoms, and are different even if they are the same as each other. May; and n is an integer from 0 to 3. }

{In formula (7), R ¹¹ to R ¹⁶ represent a hydrogen atom, a halogen atom, an alkyl group having 1 to 12 carbon atoms or an alkyl halide group having 1 to 12 carbon atoms, and are different even if they are the same as each other. You may. }

In the present embodiment, the sultone compound represented by the formula (1) is preferably 1. Examples thereof include 3-propane sultone, 2,4-butane sultone, 1,4-butane sultone, 1,3-butane sultone, and 2,4-pentane sultone; the sultone compound represented by the formula (2) is preferably preferred. Examples thereof include 1,3-propen sultone and 1,4-buten sultone; the sultone compound represented by the formula (3) is preferably 1,5,2,4-dioxadithiepan 2,2. Examples include 4,4-tetraoxide; other sultone compounds are preferably methylenebis (benzenesulfonic acid), methylenebis (phenylmethanesulfonic acid), methylenebis (ethanesulfonic acid), methylenebis (2,4,6). Trimethylbenzene sulfonic acid) and methylenebis (2-trifluoromethylbenzene sulfonic acid), and at least one selected from these groups is more preferable.
The total content of the sulton compound contained in the non-aqueous electrolyte solution of the non-aqueous lithium-type power storage element in the present embodiment shall be 0.5% by mass to 15% by mass based on the total mass of the non-aqueous electrolyte solution. Is more preferable, and more preferably 1% by mass or more and 10% by mass or less, and further preferably 3% by mass or more and 8% by mass or less.

Examples of the cyclic phosphazene include ethoxypentafluorocyclotriphosphazene, diethoxytetrafluorocyclotriphosphazene, and phenoxypentafluorocyclotriphosphazene, and at least one selected from these groups is preferable.
The content of cyclic phosphazene in the non-aqueous electrolyte solution is preferably 0.5% by mass to 20% by mass, more preferably 2% by mass or more and 15% by mass or less, based on the total mass of the non-aqueous electrolyte solution. Yes, more preferably 4% by mass or more and 12% by mass or less.
Examples of the acyclic fluorine-containing ether include HCF ₂ CF ₂ OCH ₂ CF ₂ CF ₂ H, CF ₃ CFHCF ₂ OCH ₂ CF ₂ CF ₂ H, HCF ₂ CF ₂ CH ₂ OCH ₂ CF ₂ CF ₂ H, and CF ₃ CFHCF ₂ OCH ₂ CF ₂ CFHCF ₃ and the like can be mentioned, and among these, HCF ₂ CF ₂ OCH ₂ CF ₂ CF ₂ H is preferable from the viewpoint of electrochemical stability.
The content of the acyclic fluorine-containing ether is preferably 0.5% by mass or more and 15% by mass or less, and more preferably 1% by mass or more and 10% by mass or less, based on the total mass of the non-aqueous electrolyte solution.

As the fluorine-containing cyclic carbonate, at least one selected from the group consisting of fluoroethylene carbonate (FEC) and difluoroethylene carbonate (dFEC) is preferable from the viewpoint of compatibility with other non-aqueous solvents.
The content of the fluorine-containing cyclic carbonate is preferably 0.5% by mass or more and 10% by mass or less, and more preferably 1% by mass or more and 5% by mass or less, based on the total mass of the non-aqueous electrolytic solution.
As the cyclic carbonate, vinylene carbonate is preferable. The content of the cyclic carbonate is preferably 0.5% by mass or more and 10% by mass or less, and more preferably 1% by mass or more and 5% by mass or less, based on the total mass of the non-aqueous electrolyte solution.
Examples of the cyclic carboxylic acid ester include gamma-butyrolactone, gamma-valerolactone, gamma caprolactone, and epsilon caprolactone, and it is preferable to use at least one selected from these groups. Among them, gamma-butyrolactone is particularly preferable in that it improves the battery characteristics derived from the improvement of the degree of lithium ion dissociation.
The content of the cyclic carboxylic acid ester is preferably 0.5% by mass or more and 15% by mass or less, and more preferably 1% by mass or more and 5% by mass or less, based on the total mass of the non-aqueous electrolyte solution.

As the cyclic acid anhydride, at least one selected from the group consisting of succinic anhydride, maleic anhydride, citraconic anhydride, and itaconic anhydride is preferable. Among them, it is preferable to select from succinic anhydride and maleic anhydride because the production cost of the non-aqueous electrolyte solution can be suppressed due to the industrial availability and the solubility in the non-aqueous electrolyte solution is easy.
The content of the cyclic acid anhydride is preferably 0.5% by mass or more and 15% by mass or less, and more preferably 1% by mass or more and 10% by mass or less, based on the total mass of the non-aqueous electrolyte solution. When the content of cyclic acid anhydride is 0.5% by mass or more, a high-quality film can be formed on the negative electrode, and by suppressing the reductive decomposition of the non-aqueous electrolyte solution on the negative electrode, it is durable at high temperatures. A non-aqueous lithium-type power storage element having high properties can be obtained. When the content of the cyclic acid anhydride is 10% by mass or less, the solubility of the electrolyte salt can be kept good, and the ionic conductivity of the non-aqueous electrolyte solution can be kept high, and therefore high input / output characteristics can be obtained. It becomes possible to express.

[Exterior body]
As the exterior body, a metal can, a laminated film, or the like can be used.
The metal can is preferably made of aluminum.
As the laminated film, a film in which a metal foil and a resin film are laminated is preferable, and a film having a three-layer structure composed of an outer layer resin film / a metal foil / an 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 preferably used. The metal foil is for preventing the permeation of moisture and gas, and a foil of copper, aluminum, stainless steel or the like can be preferably used. Further, the interior resin film is for protecting the metal foil from the electrolytic solution stored inside and for melting and sealing the exterior body at the time of heat sealing, and polyolefins, acid-modified polyolefins and the like can be preferably used.

<Manufacturing method of non-aqueous lithium-type power storage element>
[Assembly process: Fabrication of electrode body]
In the present specification, the electrode body is an electrode laminate including at least one structure in which a positive electrode precursor, a separator, and a negative electrode are laminated in this order, or a positive electrode precursor, a separator, and a negative electrode are laminated in this order and rolled up. It means a rotated electrode winding body.
In the assembly process of a certain embodiment, for example, an electrode laminate is formed by connecting a positive electrode terminal and a negative electrode terminal to a laminate obtained by laminating a positive electrode precursor and a negative electrode cut into a single-wafer shape via a separator. The electrode body is manufactured. In another embodiment, an electrode body which is an electrode winding body is manufactured by connecting a positive electrode terminal and a negative electrode terminal to a winding body in which a positive electrode precursor and a negative electrode are laminated and wound via a separator. .. The shape of the electrode winding body may be cylindrical or flat.
The method of connecting the positive electrode terminal and the negative electrode terminal is not particularly limited, but a method such as resistance welding or ultrasonic welding can be used.

It is preferable to further dry the electrode body (electrode laminated body or electrode winding body) to which the terminals are connected to remove the residual solvent. The drying method is not limited, but it can be carried out by vacuum drying or the like. The residual solvent is preferably 1.5% by mass or less based on the total mass of the positive electrode active material layer or the negative electrode active material layer. If the residual solvent is more than 1.5% by mass, the solvent remains in the system and the self-discharge characteristics are deteriorated, which is not preferable.
The dried electrode body is housed in an exterior body typified by a metal can or a laminated film, preferably in a dry environment with a dew point of -40 ° C. or lower, and an opening for injecting a non-aqueous electrolytic solution is provided. It is preferable to seal by leaving only one side. If the dew point is higher than -40 ° C, water adheres to the electrode body, water remains in the system, and the self-discharge characteristics are deteriorated, which is not preferable. The method for sealing the exterior body is not particularly limited, but a method such as heat sealing or impulse sealing can be used.

The non-aqueous lithium-type power storage element according to the present embodiment can be typically manufactured by sequentially performing the following liquid injection, impregnation sealing step, lithium doping step, and aging step. After the aging step, a degassing step may be further performed.

[Liquid injection, impregnation, and sealing process]
After the assembly process, a non-aqueous electrolyte solution is injected into the exterior body in which the electrode body is housed.
After pouring, it is desirable to further impregnate and sufficiently immerse the positive electrode, negative electrode, and separator with a non-aqueous electrolyte solution. When the electrolytic solution is not immersed in at least a part of the positive electrode, the negative electrode, and the separator, the lithium doping proceeds non-uniformly in the lithium doping step described later, so that the resistance of the obtained non-aqueous lithium storage element increases. However, inconveniences such as deterioration of durability may occur. The method of impregnation is not particularly limited, but for example, the electrode body after injection is installed in a decompression chamber with the outer body open, the inside of the chamber is decompressed using a vacuum pump, and the atmospheric pressure is again reduced. It is possible to use a method of returning to.
After pouring, preferably after impregnation, the outer body can be sealed by sealing the electrode body with the outer body open while reducing the pressure.

[Lithium dope process]
In the lithium doping step, a voltage is applied between the positive electrode precursor and the negative electrode to decompose the lithium compound in the positive electrode precursor to release lithium ions, and the lithium ions are reduced at the negative electrode to reduce the negative electrode active material. This is a step of pre-doping the layer with lithium ions.
In the lithium doping step, gas such as CO ₂ is generated due to the decomposition of the lithium compound in the positive electrode precursor. Therefore, when applying a voltage, it is preferable to take measures to release the generated gas to the outside of the exterior body. As this means, for example, a method of applying a voltage with a part of the exterior body opened; with an appropriate gas discharge means such as a gas vent valve and a gas permeable film installed in the part of the exterior body in advance. A method of applying a voltage; etc. can be mentioned.

[Aging process]
It is preferable to perform an aging step after the lithium doping step. In the aging step, the solvent in the electrolytic solution is decomposed at the negative electrode, and a lithium ion-permeable solid polymer film is formed on the surface of the negative electrode. This solid polymer coating is considered to function as SEI (Solid Electrolyte Interphase).
The aging method is not particularly limited, but for example, a method of reacting the solvent in the electrolytic solution in a high temperature environment or the like can be used.

[Degassing process]
After the aging step, it is preferable to further degas to surely remove the gas remaining in the electrolytic solution, the positive electrode, and the negative electrode. In a state where gas remains in at least a part of the electrolytic solution, the positive electrode, and the negative electrode, ion conduction is inhibited, so that the resistance of the obtained non-aqueous lithium storage element increases.
The method of degassing is not particularly limited, but for example, a method of installing the electrode laminate in the decompression chamber with the exterior body open and depressurizing the inside of the chamber using a vacuum pump can be used. .. After degassing, the exterior body is sealed to seal the exterior body, and a non-aqueous lithium power storage element can be manufactured.

[Characteristics of non-aqueous lithium-type power storage element]
The non-aqueous lithium storage element of the present embodiment has low internal resistance at both normal temperature and high temperature, has a high capacity retention rate when the charge / discharge cycle is repeated, and suppresses lithium precipitation. Furthermore, the amount of gas generated when stored in a high-temperature environment for a long period of time in a highly charged state is small, and the rate of increase in internal resistance is suppressed.

<Applications for non-aqueous lithium-type power storage elements>
A plurality of non-aqueous lithium-type power storage elements according to the present embodiment can be connected in series or in parallel to form a power storage module. Further, since the non-aqueous lithium type power storage element and the power storage module of the present embodiment can achieve both high input / output characteristics and safety at high temperature, a power regeneration assist system, a power load leveling system, and a power failure-free power supply can be achieved. It can be used in systems, contactless power supply systems, energy harvest systems, power storage systems, electric power steering systems, emergency power supply systems, in-wheel motor systems, idling stop systems, quick charging systems, smart grid systems and the like.

The power storage system is preferably used for natural power generation such as solar power generation or wind power generation, the power load leveling system is preferably used for microgrids, etc., and the power failure-free power supply system is preferably used for production equipment in factories. In the non-contact power supply system, the non-aqueous lithium energy storage element is used for leveling voltage fluctuations such as microwave power transmission or electric field resonance and for storing energy. In the energy harvest system, the non-aqueous lithium energy storage element is used for vibration power generation. In order to use the electric power generated by the above, each is suitably used.

In a power storage system, a plurality of non-aqueous lithium-type power storage elements are connected in series or in parallel as a cell stack, or a non-water-based lithium power storage element and a lead battery, a nickel hydrogen battery, a lithium ion secondary battery, etc. Alternatively, the fuel cell is connected in series or in parallel.
Further, the non-aqueous lithium power storage element according to the present embodiment can achieve both high input / output characteristics and safety at high temperatures, and therefore, for example, an electric vehicle, a plug-in hybrid vehicle, a hybrid vehicle, an electric motorcycle, etc. Can be mounted on vehicles. The power regeneration assist system, the electric power steering system, the emergency power supply system, the in-wheel motor system, the idling stop system, or a combination thereof described above are suitably mounted on the vehicle.

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

<Negative electrode active material>
(1) Preparation of 1st negative electrode active material (1-1) Carbon material 1-1 Stainless steel containing 200 g of commercially available artificial graphite in a cage made of stainless steel mesh and 80 g of coal-based pitch (softening point: 80 ° C.). They were placed on a stainless steel bat and both were installed in an electric furnace (effective size in the furnace 300 mm × 300 mm × 300 mm). This was heated to 1,100 ° C. in a nitrogen atmosphere in 8 hours and kept at the same temperature for 4 hours for thermal reaction. Then, after cooling to 60 ° C. by natural cooling, the carbon material 1-1 was obtained by taking it out from the electric furnace.
(1-2) Carbon material 1-2
Commercially available high specific surface area graphite was used as carbon material 1-2.
(1-3) Preparation of carbon material 1-3 200 g of commercially available natural graphite was placed in a stainless steel mesh cage and placed on a stainless steel bat containing 80 g of coal-based pitch (softening point: 80 ° C.), and both were placed. Was installed in an electric furnace (effective size in the furnace 300 mm × 300 mm × 300 mm). This was heated to 1100 ° C. in a nitrogen atmosphere in 8 hours and kept at the same temperature for 4 hours for thermal reaction. Then, after cooling to 60 ° C. by natural cooling, the carbon material 1-3 was obtained by taking it out from the electric furnace.
(1-4) Carbon material 1-4
Commercially available natural graphite was used as carbon material 1-4.
(1-5) Carbon material 1-5
Commercially available artificial graphite was used as carbon material 1-5.

(2) Preparation of second negative electrode active material (2-1) carbon material 2-1 Stainless steel containing 200 g of commercially available carbon black in a cage made of stainless steel mesh and 200 g of coal-based pitch (softening point: 80 ° C.). They were placed on a stainless steel bat and both were installed in an electric furnace (effective size in the furnace 300 mm × 300 mm × 300 mm). This was heated to 900 ° C. in a nitrogen atmosphere in 8 hours and kept at the same temperature for 4 hours for thermal reaction. Then, after cooling to 60 ° C. by natural cooling, the carbon material 2-1 was obtained by taking it out from an electric furnace.
(2-2) Preparation of carbon material 2-2 200 g of commercially available hard carbon is placed in a stainless steel mesh cage and placed on a stainless steel bat containing 80 g of coal-based pitch (softening point: 80 ° C.), and both are placed. Was installed in an electric furnace (effective size in the furnace 300 mm × 300 mm × 300 mm). This was heated to 900 ° C. in a nitrogen atmosphere in 8 hours and kept at the same temperature for 4 hours for thermal reaction. Then, after cooling to 60 ° C. by natural cooling, the carbon material 2-2 was obtained by taking it out from the electric furnace.

(2-3) Carbon material 2-3
Commercially available soft carbon was used as carbon material 2-3.
(2-4) Preparation of carbon material 2-4 200 g of commercially available coconut shell activated carbon is placed in a stainless steel mesh cage, and placed on a stainless steel bat containing 200 g of coal-based pitch (softening point: 80 ° C.). Both were installed in an electric furnace (effective size in the furnace 300 mm × 300 mm × 300 mm). This was heated to 660 ° C. in a nitrogen atmosphere in 8 hours and kept at the same temperature for 4 hours for thermal reaction. Then, after cooling to 60 ° C. by natural cooling, the carbon material 2-4 was obtained by taking it out from the electric furnace.
(2-5) Carbon material 2-5
Commercially available hard carbon was used as carbon material 2-5.

(3) Third Negative Electrode Active Material (3-1) Preparation of Silicon Composite Material 3-1 Commercially available silicon with an average particle diameter of 0.9 μm was placed in a 100 g stainless steel mesh cage, and a coal-based pitch (softening point: 50) was placed. It was placed on a stainless steel bat containing 30 g (° C.), and both were installed in an electric furnace (effective size in the furnace 300 mm × 300 mm × 300 mm). This was heated to 1,000 ° C. in a nitrogen atmosphere in 15 hours and kept at the same temperature for 6 hours for thermal reaction. Then, after cooling to 60 ° C. by natural cooling, it was taken out from an electric furnace to obtain a silicon composite material 3-1.

The negative electrode active materials obtained above are summarized in Table 1 below.

<Manufacturing of positive electrode precursor>
(1) Preparation of positive electrode active material The crushed coconut shell carbide was placed in a small carbonization furnace and carbonized at 500 ° C. for 3 hours in a nitrogen atmosphere to obtain carbonized material. The obtained carbide was put into an activation furnace, steam heated in the preheating furnace was introduced into the activation furnace at 1 kg / h, and the temperature was raised to 900 ° C. over 8 hours for activation. The activated carbonized material was taken out and cooled in a nitrogen atmosphere to obtain activated activated carbon. The obtained activated activated carbon was washed with water for 10 hours, drained, dried in an electric dryer maintained at 115 ° C. for 10 hours, and then pulverized with a ball mill for 1 hour to obtain activated carbon 1.
(2) Crushing of lithium carbonate 200 g of lithium carbonate having an average particle diameter of 53 μm was cooled to -196 ° C. with liquid nitrogen using a crusher (liquid nitrogen bead mill LNM) manufactured by IMEX, and then dry ice beads were used. The mixture was crushed at a peripheral speed of 10.0 m / s for 9 minutes.
By the above operation, lithium carbonate was pulverized by brittle fracture while preventing thermal denaturation at -196 ° C.
The average particle size of the pulverized lithium carbonate was measured and found to be 2.0 μm.

(3) Preparation of Positive Electrode Coating Liquid A positive electrode coating liquid was produced by the following method using the activated carbon 1 obtained above as the positive electrode active material and the lithium carbonate obtained above as the lithium compound.
59.5 parts by mass of activated carbon 1, 28.0 parts by mass of lithium carbonate, 3.0 parts by mass of Ketjen Black as a conductive filler, 1.5 parts by mass of PVP (polyvinylpyrrolidone) as a binder, and PVDF. (Polyfluoride vinylidene) is mixed with 8.0 parts by mass and NMP (N-methylpyrrolidone) as a solvent, and a thin film swirl type high-speed mixer fill mix manufactured by PRIMIX is used, and the peripheral speed is 17.0 m / s. A positive coating solution was obtained by dispersing in.
(4) Preparation of positive electrode precursor The above positive electrode coating solution was applied to both sides of an aluminum foil having a thickness of 15 μm using a die coater manufactured by Toray Engineering Co., Ltd. at a coating speed of 1 m / s, and a drying temperature of 100 was applied. After drying at ° C., a positive electrode precursor was obtained by pressing with a roll press machine under the conditions of a pressure of 4 kN / cm and a surface temperature of the pressed portion of 25 ° C.

<Example 1>
(1) Preparation of Negative Electrode Coating Liquid 99 parts by mass of carbon material 1-1 as the first negative electrode active material, 1 part by mass of carbon material 2-1 as the second negative electrode active material, and 12 parts by mass of acetylene black as the conductive filler. 8 parts by mass of PVdF (polyvinylidene fluoride) as a binder and NMP (N-methyl-2-pyrrolidone) as a solvent were mixed so that the mass ratio of the solid content was 23.0%. The obtained mixture was mixed with a thin film swirl type high-speed mixer "Fillmix (registered trademark)" manufactured by PRIMIX Co., Ltd. for 5 minutes under the condition of a peripheral speed of 15 m / s while keeping the inside of the stirring vessel at about 5 ° C. with cooling water. By dispersing, a negative electrode coating liquid was obtained.
The viscosity (ηb) and TI value of the obtained negative electrode coating liquid were measured using an E-type viscometer TVE-35H manufactured by Toki Sangyo Co., Ltd. As a result, the viscosity (ηb) was 2,300 mPa · s, and the TI value was 4.2.

(2) Manufacture of negative electrode Using a die coater manufactured by Toray Engineering Co., Ltd., a negative electrode coating liquid was applied to both sides of an electrolytic copper foil having a thickness of 10 μm at a coating speed of 1 m / s, and a drying temperature of 120 ° C. It was dried in. Next, a negative electrode was manufactured by pressing with a roll press machine under the conditions of a pressure of 5 kN / cm and a surface temperature of the pressed portion of 25 ° C. The total thickness of the obtained negative electrode after pressing was measured at any 10 points on the negative electrode using a film thickness meter Linear Gauge Sensor GS-551 manufactured by Ono Keiki Co., Ltd., and an average value was obtained. The bulk density of the negative electrode active material layer of the negative electrode calculated from the obtained average thickness and mass was 1.02 g / cc.

(3) Measurement of peel strength The negative electrode was cut into a width of 25 mm and a length of 120 mm (100 mm is the negative electrode active material layer, and the remaining 20 mm is the uncoated part to which the negative electrode active material layer is not applied). A cellophane tape (registered trademark) having a width of 24 mm (manufactured by Nichiban, CT405AP-24, adhesive strength (JIS Z 0237: 2009) 3.93N / 10 mm) was cut to a length of 100 mm and attached to the negative electrode active material layer. Using Tencilon (STB-1225S manufactured by A & D Co., Ltd.), sandwich the uncoated part of the negative electrode current collector on the lower clip jaw (jaw) side and the end of the cellophane tape on the upper clip jaw side, and peel strength (peeling strength (under the following conditions). 180 ° peeling force) was measured. The measurement of the peel strength was started within 3 minutes after the cellophane tape was attached to the negative electrode active material layer.
Environmental temperature: 25 ° C
Stroke: 100 mm
Speed: 50mm / min
Data acquisition: When the integrated average load measurement of 25 to 65 mm was performed with a total of 3 samples, the average value was 1.88 N / cm.

(4) Analysis of Pore Distribution of Negative Electrode The negative electrode active material layer of the negative electrode obtained above was scraped from the current collector with a spatula and used as a measurement sample, and the mass Ma of the negative electrode active material layer was measured.
The pore distribution of the negative electrode active material layer 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 4.3 m ² / g based on the mass of the negative electrode active material. Further, when analyzed by the BJH method, it was found that V _m1 / (V _m1 + V _m2 ) = 0.55, and one peak was found in a region having a diameter of 20 nm or more and 50 nm or less.

(5) Raman mapping on the surface of the negative electrode active material layer _ID / _IG mapping was performed using a micro-Raman spectroscope in Via Reflex manufactured by Renishaw. The wavelength of the laser of the excitation light was 532 nm, and the light was focused using a 100x objective lens so as to have a power of about 0.1 mW at the sample position.
On the surface of the negative electrode active material layer, a range of 40 μm × 40 μm was point-scanned at 1 μm intervals to obtain Raman spectra at each measurement point.
For the spike noise reduction, Cosmic ray remote attached to WiRE, which is Renishaw's analysis software, was used. For the principal component analysis for noise removal, the Noise filter attached to WiRE, which is the analysis software of Renishaw, was used, and the spectrum was reconstructed up to 12 components having a large score.
A straight line baseline is drawn from 1,000 cm ^-1 to 1,800 cm ^-1 in the Raman spectrum, and the peak height (ID) of the _D band observed at 1,350 ± 15 cm ^-1 and 1,585 ± 15 cm. The peak height (IG) of the _G band appearing at ^-1 was calculated, and 1,600 points of _ID / _IG mapping data were obtained.
(5-1) Calculation of A1 A1 (Raman mapping of the surface of the negative electrode active material layer obtained by Raman spectroscopy, the peak intensity ID of the _D band appearing at 1,350 ± 15 cm ^-1 , and 1,585 ± 15 cm. The ratio of the mapping area in which the ratio _ID / _IG to the peak intensity IG of the _G band appearing in ^-1 is 0.5 or more and 1.3 or less with respect to the total mapping area) is 1 obtained at each measurement position. , 600 points of _ID / _IG , calculated by counting the points of 0.5 or more and 1.3 or less and dividing by 1,600, which is the total number of measurement points. The A1 in the negative electrode active material of Example 1 was 53%.
(5-2) Calculation of A2 A2 (In Raman mapping of the surface of the negative electrode active material layer obtained by Raman spectroscopy, the peak intensity ID of the _D band appearing at 1,350 ± 15 cm ^-1 and 1,585 ± 15 cm. The ratio of the _G band appearing in ^-1 to the peak intensity IG and the ratio of the mapping area where the _ID / _IG is 1.0 or more and 1.3 or less to the total mapping area) is 1, which is obtained at each measurement position. It was calculated by counting the points of 1.0 or more and 1.3 or less out of 600 points of _ID / _IG and dividing by 1,600 which is the total number of measurement points. The A2 in the negative electrode active material of Example 1 was 3.2%.

(6) Preparation of Electrolyte A mixed solvent of ethylene carbonate (EC): ethylmethyl carbonate (EMC) = 33: 67 (volume ratio) was used as an organic solvent so that the concentration of LiPF ₆ was 1.2 mol / L. An electrolyte salt was dissolved in the solution to obtain a non-aqueous electrolyte solution.
(7) Preparation of Non-Aqueous Lithium Storage Element The obtained double-sided positive electrode precursor was cut out into 20 sheets so that the positive electrode active material layer had a size of 10.0 cm × 10.0 cm (100 cm ² ). Subsequently, 21 double-sided negative electrodes were cut out so that the negative electrode active material layer had a size of 10.1 cm × 10.1 cm (102 cm ² ). In addition, 40 polyethylene separators (manufactured by Asahi Kasei, thickness 10 μm) of 10.3 cm × 10.3 cm (106 cm ² ) were prepared. Regarding these, the negative electrode was arranged on the outermost layer, and the positive electrode precursor, the separator, the negative electrode, and the separator were laminated in this order so that the positive electrode active material layer and the negative electrode active material layer faced each other with the separator interposed therebetween to obtain an electrode body. .. The positive electrode terminal and the negative electrode terminal were ultrasonically welded to the obtained electrode body, placed in a container made of an aluminum laminated packaging material, and the three sides including the electrode terminal portion were sealed by heat sealing.
Approximately 70 g of a non-aqueous electrolyte solution was injected into the electrode body housed in the aluminum laminated packaging material under atmospheric pressure, a temperature of 25 ° C., and a dry air environment with a dew point of −40 ° C. or lower. Subsequently, the aluminum laminate packaging material containing the electrode laminate and the non-aqueous electrolyte solution was placed in a decompression chamber, the pressure was reduced from atmospheric pressure to −87 kPa, the pressure was returned to atmospheric pressure, and the mixture was allowed to stand for 5 minutes. Then, the packaging material in the chamber was depressurized from atmospheric pressure to −87 kPa, the process of returning to atmospheric pressure was repeated 4 times, and then the mixture was allowed to stand for 15 minutes. Further, the packaging material in the chamber was depressurized from atmospheric pressure to −91 kPa, and then returned to atmospheric pressure. Similarly, the process of depressurizing the packaging material and returning it to atmospheric pressure was repeated a total of 7 times (reduced pressure from atmospheric pressure to -95, -96, -97, -81, -97, -97, -97 kPa, respectively). By the above steps, the electrode laminate was impregnated with the non-aqueous electrolyte solution.
After that, the electrode laminate impregnated with the non-aqueous electrolyte solution was placed in a vacuum sealing machine, and the aluminum laminate packaging material was sealed by sealing at 180 ° C. for 10 seconds at a pressure of 0.1 MPa with the pressure reduced to -95 kPa. I stopped.

(8) Lithium Dope Step The electrode body obtained after sealing was placed in a dry box having a temperature of 40 ° C. and a dew point of −40 ° C. or lower. Initially, the surplus part of the aluminum laminate packaging material is cut and opened, and constant current charging is performed until the voltage reaches 4.5V at a current value of 500mA, and then 4.5V constant voltage charging is continued for 10 hours. Charging was performed and the negative electrode was lithium-doped. After the lithium doping was completed, the aluminum laminate was sealed using a heat sealing machine (FA-300) manufactured by Fuji Impulse.
(9) Aging step The electrode body after lithium doping is taken out from the dry box, and a constant current discharge is performed at 100 mA at 100 mA until the voltage reaches 3.8 V, and then a constant current discharge at 3.8 V is performed. The voltage was adjusted to 3.8V by the time. Subsequently, the electrode body was stored in a constant temperature bath at 60 ° C. for 48 hours.
(10) Degassing Step The aging electrode body was partially opened in a dry air environment with a temperature of 25 ° C and a dew point of −40 ° C. Subsequently, the electrode body was placed in the decompression chamber, the pressure was reduced from atmospheric pressure to −80 kPa for 3 minutes using a diaphragm pump, and then the pressure was returned to atmospheric pressure over 3 minutes, and the process was repeated a total of 3 times. After that, the electrode body was placed in a vacuum sealing machine, the pressure was reduced to -90 kPa, and then the aluminum laminated packaging material was sealed by sealing at 200 ° C. for 10 seconds at a pressure of 0.1 MPa to form a non-aqueous lithium-type power storage element. Made.

(11) Evaluation of non-aqueous lithium-type power storage element (11-1) Energy density With respect to the obtained power storage element, a charging / discharging device (5V, 360A) manufactured by Fujitsu Telecom Networks Co., Ltd. is placed in a constant temperature bath set at 25 ° C. ) Was used to perform constant current charging until the current value of 20C reached 3.8V, and then constant voltage charging to which a constant voltage of 3.8V was applied was performed for a total of 30 minutes. Capacitance Fa calculated by F = Q / (3.8-2.2) was calculated, where Q was the capacitance when constant current discharge was performed with a current value of 2C up to 2.2V.
The obtained power storage element is disassembled, the electrode laminate housed inside is taken out, and the outer dimensions of the region where the positive electrode active material layer and the negative electrode active material layer exist (the region excluding the unpainted portion of the positive electrode and the negative electrode). Energy density (Wh / L) = using V ₁ (= l ₁ × w ₁ × t ₁ ) obtained from the length (l ₁ ), the outer dimension width (w ₁ ), and the thickness (t ₁ ). When F × (3.8 ² -2.2 ² ) / 7200 / V ₁ was calculated, it was calculated as 16.1 Wh / L.
Here, the current discharge rate (also referred to as "C rate") is the relative ratio of the current at the time of discharge to the discharge capacity, and generally, when performing constant current discharge from the upper limit voltage to the lower limit voltage, it takes 1 hour. The current value at which the discharge is completed is called 1C. In the present specification, 1C is a current value at which discharge is completed in 1 hour when constant current discharge is performed from an upper limit voltage of 4.0 V to a lower limit voltage of 2.2 V.

(11-2) Measurement of room temperature internal resistance Ra For a non-aqueous lithium-type power storage element, use a charging / discharging device (5V, 360A) manufactured by Fujitsu Telecom Networks Limited in a constant temperature bath set at 25 ° C. Constant current charging was performed until 3.8V was reached at a current value of 20C, and then constant voltage charging was performed for a total of 30 minutes by applying a constant voltage of 3.8V. Subsequently, the sampling interval was set to 0.05 seconds, and constant current discharge was performed up to 2.2 V at a current value of 20 C to obtain a discharge curve (time-voltage). In this discharge curve, the voltage drop ΔE = 4.0 when the voltage at the discharge time = 0 second obtained by extrapolating from the voltage values at the time points of the discharge time of 1 second and 2 seconds is taken as Eo. When the room temperature internal resistance Ra calculated as Ra = ΔE / (current value of 20C) was obtained from −Eo, it was 0.98 mΩ.

(11-3) Measurement of low-temperature internal resistance Rb After allowing the non-aqueous lithium-type power storage element to stand in a constant temperature bath set at -30 ° C for 2 hours, Fujitsu Telecom keeps the constant temperature bath temperature at -30 ° C. Using a charging / discharging device (5V, 360A) manufactured by Networks Fukushima Co., Ltd., constant current charging is performed with a current value of 1.0C until 3.8V is reached, and then a constant voltage of 3.8V is applied. Voltage charging was performed for a total of 2 hours. Subsequently, a constant current discharge was performed up to 2.2 V with a current value of 10 C to obtain a discharge curve (time-voltage). In this discharge curve, the voltage drop ΔE = 4.0-, where Eo is the voltage at the discharge time = 0 seconds obtained by extrapolating from the voltage values at the discharge times of 2 seconds and 4 seconds. When the low-temperature internal resistance Rb calculated as Rb = ΔE / (10C (current value A)) was obtained from Eo, it was 28.3 mΩ.

(11-3) High-load charge / discharge cycle test For a non-aqueous lithium power storage element, use a charge / discharge device (5V, 360A) manufactured by Fujitsu Telecom Networks Fukushima Co., Ltd. in a constant temperature bath set at 25 ° C. The charging / discharging operation of constant current charging until reaching 4.2 V at a current value of 200 C and then constant current discharging until reaching 2.2 V at a current value of 200 C was repeated 60,000 times without interruption. When the capacitance before the start of the test was Fa (F) and the internal resistance after the end of the test was Fc (F), Fc / Fa = 0.81.
After adjusting the voltage of the non-aqueous lithium storage element after the high load charge / discharge cycle test to 2.2V, disassemble it in the argon box, take out the negative electrode, observe it with a loupe, and check the lithium precipitation according to the following criteria. As a result of the judgment, it was a "B" judgment.
(Criteria for judging lithium precipitation after high load charge / discharge cycle test) When the metallic gloss of the precipitated lithium is not confirmed: "A" judgment, good The metallic gloss of the precipitated lithium is confirmed, but the deposited area of lithium is the area of the negative electrode. If it is 50% or less: "B" judgment, possible If the metallic luster of the deposited lithium is confirmed and the deposited area of lithium exceeds 50% of the area of the negative electrode: "C" judgment, defective

(11-4) High-temperature and high-voltage storage test For non-aqueous lithium-type power storage elements, the amount of gas generated when stored for 2 months at a cell voltage of 4.2 V and an environmental temperature of 60 ° C. and the rate of increase in internal resistance at room temperature are as follows. Obtained by the method of.
(11-4-1) Amount of gas generated after high-temperature and high-voltage storage test First, in a constant temperature bath in which the non-aqueous lithium storage element is set to 25 ° C, a constant current is reached at a current value of 100 C until it reaches 4.2 V. Charging was performed, and then constant voltage charging was performed for 10 minutes by applying a constant voltage of 4.2 V. After that, the power storage element is stored in a 60 ° C environment, taken out from the 60 ° C environment every two weeks, charged to 4.2 V in the cell voltage in the same charging process as described above, and then the cell is placed in the 60 ° C environment again. Saved in. By repeating this step, the power storage element was stored for 2 months at a cell voltage of 4.2 V and an environmental temperature of 60 ° C.
After that, using the cell volume Va before the start of storage measured by the Archimedes method, the cell volume Vb after storage for 2 months, and the capacitance Fa, the amount of gas generated by (Vb-Va) / Fa was calculated. It was 4.91 × 10 ^-3 cc / F.
(11-4-2) Rate of increase in internal resistance at room temperature after high-temperature and high-voltage storage test (11-2) Internal resistance at room temperature of the power storage element after storage at a cell voltage of 4.2 V and an environmental temperature of 60 ° C for 2 months. When the resistance value obtained by using the same measurement method as the above measurement is the normal temperature internal resistance Rd after the high temperature storage test, the rate of increase of this Rd with respect to the normal temperature internal resistance Ra before the high temperature high voltage storage test is calculated by Rd / Ra. As a result of calculation, it was 1.81.

<Examples 2 to 34 and Comparative Examples 1 to 10>
Negative electrode coating was performed in the same manner as in Example 1, except that the types and amounts of the first negative electrode active material and the second negative electrode active material, and the dispersion temperature at the time of preparing the negative electrode coating liquid were changed as shown in Table 2, respectively. A working solution was prepared, and a negative electrode and a non-aqueous lithium-type power storage element were manufactured using the solution, and various evaluations were performed.
In Comparative Example 5, the second negative electrode active material was not used, and in Comparative Example 8, the second negative electrode active material was not used.
The evaluation results are shown in Tables 3 and 4.
<Example 35>
A negative electrode coating solution was prepared in the same manner as in Example 1 except that the first negative electrode active material was not used and the two types and amounts of the second negative electrode active material shown in Table 2 were used. Negative electrodes and non-aqueous lithium-type power storage elements were manufactured using the materials, and various evaluations were performed.
The evaluation results are shown in Tables 3 and 4.
<Examples 36 and 37>
The same as in Example 1 except that the type and amount of the first negative electrode active material and the second negative electrode active material shown in Table 2 and the third negative electrode active material of the type and amount shown in Table 2 were further used. A negative electrode coating liquid was prepared, and a negative electrode and a non-aqueous lithium-type power storage element were manufactured using the negative electrode coating liquid, and various evaluations were performed.
The evaluation results are shown in Tables 3 and 4.

<Example 38>
A negative electrode coating liquid was prepared in the same manner as in Example 1 except that the first negative electrode active material and the second negative electrode active material shown in Table 2 were used, and a negative electrode was manufactured using the negative electrode coating liquid. Using this negative electrode, a non-aqueous lithium storage element having a flat electrode winder was produced by the following method, and various evaluations were performed. The results are shown in Tables 3 and 4.
The evaluation was based on the method in Example 1, but when the energy density was calculated, the volume of the flat electrode winding body was used as shown below.

(1) Fabrication of non-aqueous lithium-type power storage element One positive electrode precursor for double-sided coating is cut into a size of 12.0 cm × 210.0 cm (the size of the positive electrode active material layer is 10.0 cm × 210.0 cm). The uncoated portion of the positive electrode where the positive electrode active material layer is not coated on the positive electrode current collector is 2.0 cm × 210.0 cm.), The negative electrode of double-sided coating is 12.1 × 220.0 cm in size. One sheet is cut (the size of the negative electrode active material layer is 10.1 cm × 220.0 cm, and the negative electrode uncoated part where the negative electrode active material layer is not coated on the negative electrode current collector is 2.0 cm × 220. (0 cm), the cut-out positive electrode precursor and the negative electrode are coated on both sides via two polyethylene separators (manufactured by Asahi Kasei Co., Ltd., cut into a size of 10 μm, 12.4 cm × 225 cm). The positive electrode precursor of the work, the separator, the negative electrode of the double-sided coating, and the separator were wound in this order to prepare a flat electrode winder.
The terminal was connected to the obtained electrode winding body, inserted into a metal square can made of aluminum, and sealed. An electrolytic solution was injected through the opening of the metal square can, and then a removable check valve was attached. The obtained element is placed in a dry box having a temperature of 40 ° C. and a dew point of -40 ° C. or lower, and under pressure of 100 kPa, constant current charging is performed at a current value of 500 mA until the voltage reaches 4.5 V. After that, the initial charge was continuously performed by a method of continuing 4.5 V constant voltage charging for 10 hours, and the negative electrode was lithium-doped.
Subsequently, an aging step is performed under the same conditions as in Example 1, a degassing step is performed under the same conditions as in Example 1 after removing the check valve, and the opening is closed to store non-aqueous lithium-type electricity. The element was manufactured.

(2) Energy density With respect to the obtained power storage element, a charging / discharging device (5V, 360A) manufactured by Fujitsu Telecom Networks Limited was used in a constant temperature bath set at 25 ° C., and the current value was 3.8V at 20C. The constant current charge was performed until the value reached, and then the constant voltage charge of applying a constant voltage of 3.8 V was performed for a total of 30 minutes. Capacitance Fa calculated by F = Q / (3.8-2.2) was calculated, where Q was the capacitance when constant current discharge was performed with a current value of 2C up to 2.2V.
The obtained power storage element is disassembled, the flat electrode winding body housed inside is taken out, and the region where the positive electrode active material layer and the negative electrode active material layer exist (the region excluding the uncoated portion of the positive electrode and the negative electrode). ), V ₁ (= l ₁ × w ₁ × t ₁ ) obtained from the outer dimension length (l ₁ ), outer dimension width (w ₁ ), and thickness (t ₁ ), and energy density (Wh). / L) = F × (3.8 ² -2.2 ² ) / 7200 / V ₁ was calculated and calculated as 20.4 Wh / L.

<Examples 39 and 40>
A negative electrode coating liquid was prepared in the same manner as in Example 1 except that the types and amounts of the first negative electrode active material and the second negative electrode active material were changed as shown in Table 2, respectively, and carried out using this. A negative electrode and a non-aqueous lithium storage element were manufactured in the same manner as in Example 38, and various evaluations were performed.
The evaluation results are shown in Tables 3 and 4.

From the above examples, it was verified that the negative electrode of the present embodiment can provide a non-aqueous lithium-type power storage element having low resistance, charge / discharge cycle characteristics at high load, and excellent high temperature storage durability.

The negative electrode of the present invention can be suitably used for a non-aqueous lithium-type power storage element, for example, in an application for assisting an instantaneous power peak in a hybrid drive system of an automobile.
The negative electrode of the present invention can be suitably applied to, for example, a lithium ion capacitor or a lithium ion secondary battery. The negative electrode of the present invention is particularly preferable because the effect of the present invention is maximized when applied to a lithium ion capacitor.

Claims (41)

A negative electrode having a negative electrode current collector and a negative electrode active material layer containing a negative electrode active material made of a carbon material capable of storing and releasing lithium ions on one or both sides of the negative electrode current collector.
The following (i) to ( iv ):
(I) The negative electrode active material layer contains a first negative electrode active material made of a carbon material and a second negative electrode active material made of a carbon material and different from the first negative electrode active material.
(Ii) The specific surface area of the negative electrode active material layer calculated by the BET method based on the mass of the negative electrode active material is 4 m ² / g or more and 75 m ² / g or less .
(Iii) In the Raman mapping of the surface of the negative electrode active material layer obtained by Raman spectroscopy, the peak intensity ID of the _D band appearing at 1350 ± 15 cm ^-1 and the peak intensity IG of the _G band appearing at 1585 ± 15 cm ^-1 . The ratio A1 of the mapping area having the ratio _ID / _IG of 0.5 or more and 1.3 or less to the total mapping area is 50% or more and 95% or less , and
(Iv) The ratio A2 of the mapping area having the ID / IG of 1.0 or more and 1.3 or less to the total mapping area is 3% or more and 70% _or less _.
The negative electrode is characterized by satisfying all of the above. The negative electrode according to claim 1, wherein the A1 is 60% or more and 90% or less. The negative electrode according to claim 1 or 2, wherein the ratio A2 of the mapping area having an _ID / _IG of 1.0 or more and 1.3 or less to the total mapping area is 4 % or more and 50 % or less. In the negative electrode active material layer, the amount of pores derived from pores having a diameter of 2 nm or more and 50 nm or less calculated by the BJH method based on the mass of the negative electrode active material is V _m1 (cc / g), and the diameter is 20 nm or more and 50 nm or less. 1 of any one of claims 1 to 3 _satisfying 0.6 ≦ V _m1 / (V _m1 + V _m2 ) ≦ 0.8 when the amount of pores derived from the pores of Negative electrode as described in the section. Any of claims 1 to 4, wherein the negative electrode active material layer has at least one peak in a region having a diameter of 20 nm or more and 50 nm or less in a pore distribution curve obtained by analyzing an isotherm at the time of nitrogen desorption by the BJH method. The negative electrode according to item 1. The negative electrode according to any one of claims 1 to 5, wherein the peel strength of the negative electrode active material layer is 0.40 N / cm or more and 2.00 N / cm or less. The first negative electrode active material is
It is a graphite-based composite material in which a base material made of (i) a graphite-based material or (ii) a graphite-based material and a carbonaceous material precursor are composited.
The second negative electrode active material is
(I) An amorphous carbon composite material in which a base material made of an amorphous carbon material or (ii) an amorphous carbon material and a carbonaceous material precursor are composited.
The negative electrode according to any one of claims 1 to 6. The ratio of the mass of the first negative electrode active material to the negative electrode active material layer is M ₁ (mass%), and the ratio of the mass of the second negative electrode active material to the negative electrode active material layer is M ₂ (mass). %), The negative electrode according to claim 7, wherein M ₂ / (M ₁ + M ₂ ) is 0.01 or more and 0.75 or less. The negative electrode according to any one of claims 1 to 8, wherein the bulk density of the negative electrode active material layer is 0.6 g / cc or more and 1.6 g / cc or less. The negative electrode according to any one of claims 1 to 9, wherein the negative electrode active material layer has a thickness of 10 μm or more and 50 μm or less per surface. The negative electrode according to any one of claims 1 to 10, wherein the negative electrode current collector is a perforated copper foil. The negative electrode according to any one of claims 1 to 10, wherein the surface of the negative electrode current collector is a non-perforated copper foil whose surface has been roughened. The negative electrode according to any one of claims 1 to 12, wherein the negative electrode active material layer contains an alloy-based material that forms an alloy with lithium. The negative electrode according to any one of claims 1 to 13, wherein the negative electrode active material layer contains lithium titanate. A step of applying a negative electrode coating liquid onto the negative electrode current collector to form a negative electrode active material layer is included.
The negative electrode coating liquid contains the first negative electrode active material, the second negative electrode active material, a solvent, and a binder, and has the mass of all the components in the negative electrode coating liquid excluding the solvent. The method for manufacturing a negative electrode according to any one of claims 1 to 14, wherein the ratio _WT (mass%) of the negative electrode coating liquid to the total mass is 10 ≦ _WT ≦ 70. The method according to claim 15, wherein the binder is at least one of latex, styrene-butadiene copolymer, fluororubber, acrylic copolymer, polyvinylidene fluoride, polytetrafluoroethylene, and polyimide. .. The method according to claim 15 or 16, wherein the negative electrode coating liquid is multi-stripped on the negative electrode current collector to form the negative electrode active material layer. The method according to any one of claims 15 to 17, wherein the negative electrode coating liquid is intermittently applied onto the negative electrode current collector to form the negative electrode active material layer. The method according to any one of claims 15 to 18, further comprising a step of applying the negative electrode coating liquid onto the negative electrode current collector, then slitting, and then pressing. The method according to any one of claims 15 to 19, further comprising a step of applying the negative electrode coating liquid on the negative electrode current collector and then drying using far infrared rays or near infrared rays. The method according to any one of claims 15 to 19, further comprising a step of applying the negative electrode coating liquid onto the negative electrode current collector and then drying using hot air at 80 ° C. or higher. An electrode body comprising the negative electrode according to any one of claims 1 to 14, as well as a positive electrode and a separator. A non-aqueous lithium-type power storage element in which the negative electrode according to any one of claims 1 to 14, and the non-aqueous electrolyte solution containing the positive electrode, the separator, and lithium ions are stored and stored in the exterior body. The non-aqueous lithium power storage element according to claim 23, wherein the exterior body is made of a metal can or a laminated film. A power storage module comprising the non-aqueous lithium power storage element according to claim 23 or 24. A power regeneration assist system comprising the non-aqueous lithium storage element according to claim 23 or 24. A power load leveling system comprising the non-aqueous lithium storage element according to claim 23 or 24. An uninterruptible power supply system comprising the non-aqueous lithium power storage element according to claim 23 or 24. A non-contact power feeding system comprising the non-aqueous lithium power storage element according to claim 23 or 24. An energy harvesting system comprising the non-aqueous lithium storage element according to claim 23 or 24. A power storage system comprising the non-aqueous lithium power storage element according to claim 23 or 24. The power storage system according to claim 31, wherein the non-aqueous lithium power storage element and a lead battery, a nickel hydrogen battery, a lithium ion secondary battery, or a fuel cell are connected in series or in parallel. A photovoltaic power storage system comprising the non-aqueous lithium power storage element according to claim 23 or 24. An electric power steering system comprising the non-aqueous lithium storage element according to claim 23 or 24. An emergency power supply system comprising the non-aqueous lithium storage element according to claim 23 or 24. An in-wheel motor system comprising the non-aqueous lithium storage element according to claim 23 or 24. An idling stop system comprising the non-aqueous lithium storage element according to claim 23 or 24. A fast charging system comprising the non-aqueous lithium storage element according to claim 23 or 24. A smart grid system comprising the non-aqueous lithium storage element according to claim 23 or 24. A vehicle comprising the non-aqueous lithium storage element according to claim 23 or 24. The vehicle according to claim 40, which is an electric vehicle, a plug-in hybrid vehicle, a hybrid vehicle, or an electric motorcycle.