JP2016173938A - Nonaqueous electrolyte power storage device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a nonaqueous electrolyte secondary battery arranged so that the delamination of a negative electrode can be prevented, which enables the increase in energy density.SOLUTION: A nonaqueous electrolyte power storage device comprises: a positive electrode; a negative electrode; and a nonaqueous electrolyte. The positive electrode allows at least an anion to go thereinto and to go out thereof. The negative electrode includes: a lithium titanate compound; and a (co)polymer consisting of at least one selected from a group consisting of an acrylic acid, a methacrylic acid, an acrylic acid ester, a methacrylic acid ester and an acrylonitrile.SELECTED DRAWING: None

Description

  The present invention relates to a non-aqueous electrolyte storage element that contains lithium titanate in a negative electrode and into which lithium ions are inserted or desorbed.

Various configurations have been proposed so far for power storage devices mainly composed of a positive electrode, a negative electrode, and a non-aqueous electrolyte, and have been put into practical use as power sources for mobile devices, power storage systems for regeneration, backup power sources for personal computers, etc. ing.
Above all, electric double layer capacitors using graphite as the positive electrode material and carbonaceous material as the negative electrode material are superior in electric capacity and withstand voltage compared to conventional power storage devices using activated carbon as the electrode (patent) Reference 1).

On the other hand, as a negative electrode material, there is a case in which titanium oxide is contained and a high capacity is achieved (see Patent Document 2). Further, Patent Document 3 describes that a copolymer is added to the positive electrode of the battery.
In the above technical background, vigorous studies have been conducted using graphite for the positive electrode and lithium titanate for the negative electrode. (See Patent Documents 4 to 10)

It has been confirmed that when the negative electrode weight is changed, the capacity increases, particularly when the thickness of the electrode of the negative electrode is 50 μm or more. However, when the thickness of the lithium titanate-containing electrode is increased, problems such as peeling occur.
An object of this invention is to provide the non-aqueous-electrolyte secondary battery which can solve the subject that said peeling generate | occur | produces etc. and can improve an energy density.

This invention for solving the said subject concerns the non-aqueous-electrolyte electrical storage element as described in following (1).
(1) A non-aqueous electrolyte storage element having a positive electrode, a negative electrode, and a non-aqueous electrolyte,
The positive electrode is capable of at least inserting and removing anions;
The negative electrode contains a lithium titanate compound and a (co) polymer composed of at least one selected from the group consisting of acrylic acid, methacrylic acid, acrylic acid ester, methacrylic acid ester and acrylonitrile. Non-aqueous electrolyte storage element.

  ADVANTAGE OF THE INVENTION According to this invention, the film thickness of the negative electrode containing lithium titanate can be achieved, and a high capacity | capacitance nonaqueous electrolyte secondary battery is provided.

It is the schematic of an example of the non-aqueous-electrolyte electrical storage element of embodiment of this invention. It is a figure which shows the peeling apparatus used for the peeling test in an Example. It is a figure which shows the result of a peeling test. It is a figure which shows a mode that it pushed for 5 second at 500 gf using the peeling apparatus, and was peeled off at 10 m / s after that. It is a figure which shows the charging / discharging curve of the half cell produced in the Example. It is a figure which shows the carbon coating apparatus used in order to manufacture a graphite-carbon composite particle. It is a figure which shows the relationship between the weight ratio of the positive electrode of a battery produced in the Example, and a negative electrode, and the charge capacity of the 1st time. It is a figure which shows the relationship between the film thickness of a negative electrode when the film thickness of a positive electrode is made constant, and the film thickness of a negative electrode is changed. It is a figure which shows a charging / discharging curve.

  DESCRIPTION OF EMBODIMENTS Hereinafter, embodiments of the present invention will be described in detail. However, the description of the constituent elements described below is an example (representative example) of an embodiment of the present invention. It is not specified in the contents of.

The nonaqueous electrolyte storage element of the present invention includes a positive electrode, a negative electrode, and a nonaqueous electrolyte, and further includes other members as necessary.
FIG. 1 shows an example of a nonaqueous electrolyte storage element. A non-aqueous electrolyte storage element 10 shown in FIG. 1 accommodates a positive electrode 1, a negative electrode 2, and a separator 3 containing the non-aqueous electrolyte in an outer can 4, and a negative electrode lead wire 5 and a positive electrode lead wire 6. Is provided.
Examples of the non-aqueous electrolyte storage element include a non-aqueous electrolyte secondary battery and a non-aqueous electrolyte capacitor.
Next, members constituting the nonaqueous electrolyte storage element will be described.

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

<< Positive electrode material >>
The positive electrode material is not particularly limited and may be appropriately selected depending on the purpose. For example, the positive electrode material includes at least a positive electrode active material, and optionally includes a conductive agent, a binder, a thickener, and the like. Become.

-Positive electrode active material-
The positive electrode active material is not particularly limited as long as it is a substance capable of inserting or removing anions, and can be appropriately selected according to the purpose. Examples thereof include a carbonaceous material and a conductive polymer. Among these, a carbonaceous material is particularly preferable because of its high energy density.
Examples of the conductive polymer include polyaniline, polypyrrole, polyparaphenylene, and the like.
Examples of the carbonaceous material include graphite (graphite) such as coke, artificial graphite, and natural graphite, and pyrolysis products of organic substances under various pyrolysis conditions. Among these, artificial graphite and natural graphite are particularly preferable.

The carbonaceous material is preferably a carbonaceous material having high crystallinity. This crystallinity can be evaluated by X-ray diffraction, Raman analysis, and the like. For example, in a powder X-ray diffraction pattern using CuKα rays, diffraction peak intensity I _{2θ = 22.3} at 2θ = 22.3 °, it is preferable intensity ratio _{I 2θ = 22.3 / I 2θ =} 26.4 in the diffraction peak intensity _{I 2 [Theta] = 26.4} at 2 [Theta] = 26.4 ° is 0.4 or less.
The BET specific surface area by nitrogen adsorption of the carbonaceous material is preferably 1 m ² / g or more and 100 m ² / g or less, and the average particle size (median diameter) obtained by the laser diffraction / scattering method is 0.1 μm or more and 100 μm or less. preferable.

In the present invention, it is preferable to use graphite-carbon composite particles as the carbonaceous material of the positive electrode.
The graphite-carbon composite particles are composite particles in which a carbon coating layer is formed on the surface of the graphite particles.
When this graphite-carbon composite particle is used for a positive electrode, the charge / discharge rate is remarkably improved.
In the polarizable electrode, the electrolyte is adsorbed on the surface of the carbonaceous material and the electrostatic capacity is developed.
Therefore, it is considered that an increase in the surface area of the carbonaceous material is effective for improving the capacitance.
This concept applies not only to activated carbon, which is inherently porous, but also to non-porous carbon having microcrystalline carbon similar to graphite.

It is after irreversible expansion | swelling by the first charge (electric field activation) that nonporous carbon expresses an electrostatic capacity.
This is because, as a result of the electrolyte ions and the solvent breaking open between the layers by this initial charge, the nonporous carbon is theoretically made porous.
On the other hand, graphite has a very small specific surface area and high crystallinity compared to activated carbon and non-porous carbon.
In addition, graphite exhibits a capacitance from the initial charge, and the expansion at the time of charge is reversible and the expansion rate is low.
As a result, graphite inherently has a small specific surface area and exhibits a behavior that is not made porous even by electric field activation. In other words, graphite is a material that is theoretically very disadvantageous for expressing a capacitance.

Carbon coated on the surface of the graphite particles may be non-crystalline, low-crystalline, or crystalline.
A material in which the surface of graphite particles is coated with amorphous carbon or low crystalline carbon is known. For example, a composite material in which graphite is coated with low crystalline carbon using a chemical vapor deposition method, and graphite has an average interplanar spacing d002. Examples thereof include a composite material coated with carbon of 0.337 nm or more, and a composite material coated with graphite with amorphous carbon.

However, it is particularly preferable that the carbon coated on the surface of the graphite particles is crystalline, because an advantage of improving the adsorption / desorption rate of ions can be obtained.
As a method for coating the surface of graphite particles with crystalline carbon, chemical vapor deposition using a fluidized bed reactor is excellent.
Examples of the organic substance used as the carbon source for the chemical vapor deposition treatment include aromatic hydrocarbons such as benzene, toluene, xylene, and styrene, and aliphatic hydrocarbons such as methane, ethane, and propane.

These organic substances are introduced into the fluidized bed reactor mixed with an inert gas such as nitrogen.
As a density | concentration of the organic substance in mixed gas, 2-50 mol% is preferable and 5-33 mol% is more preferable.
As chemical vapor deposition processing temperature, 850-1200 degreeC is preferable and 950-1150 degreeC is more preferable.
By performing chemical vapor deposition under such conditions, the surface of the graphite particles can be uniformly and completely covered with the AB surface (that is, the basal surface) of crystalline carbon.

The amount of carbon necessary for forming the coating layer varies depending on the particle size and shape of the graphite particles, but the amount of coated carbon in the composite material is preferably 0.1 to 10% by mass, and 0.5 to 7% by mass. More preferably, 0.8-5 mass% is further preferable.
If the amount is less than 0.1% by mass, the effect of coating cannot be obtained. Conversely, if the amount of coated carbon is too large, the proportion of graphite is reduced, resulting in inconveniences such as a reduction in charge / discharge amount.

The graphite particles used for the raw material may be natural or artificial.
Preferred graphite for use has a specific surface area of 10 m ² / g or less, preferably 7 m ² / g or less, more preferably 5 m ² / g or less.
The specific surface area can be determined by a BET method using N ₂ or CO ₂ as an adsorbent.
Preferred graphite is highly crystalline.
For example, the crystal lattice constant C0 of the 002 plane may be 0.67 to 0.68 nm, preferably 0.671 to 0.674.
Furthermore, the half width of the 002 peak in the X-ray crystal diffraction spectrum using CuKα rays is less than 0.5, preferably 0.1 to 0.4, more preferably 0.2 to 0.3.

When the crystallinity of graphite is low, the irreversible capacity of the electric double layer capacitor tends to increase.
It is preferable that the graphite is moderately disturbed in the graphite layer, and the ratio of the basal surface to the edge surface falls within a certain range.
The disorder of the graphite layer appears in the result of Raman spectroscopic analysis, for example.
Preferable graphite has a ratio (hereinafter referred to as “I”) of a peak intensity of 1360 cm ⁻¹ (hereinafter referred to as “I (1360)”) and a peak intensity of 1580 cm ⁻¹ (hereinafter referred to as “I (1580)”) in a Raman spectrum. (1360) / I (1580) ") is 0.02 to 0.5, preferably 0.05 to 0.25, more preferably 0.1 to 0.2, still more preferably about 0.16 ( For example, 0.13 to 0.17).
When the CVD process is performed, the approximate intensity ratio is not established, and a value of 2.5 or more is shown. This appears to be because the coated carbon is less crystalline than the substrate.

Moreover, preferable graphite can also be specified by the result of an X-ray crystal analysis.
That is, the ratio (hereinafter referred to as “IB / IA”) of the rhombohedral peak intensity (hereinafter referred to as “IB”) and the hexagonal peak intensity (hereinafter referred to as “IA”) in the X-ray crystal diffraction spectrum. The graphite is 0.3 or more, preferably 0.35 to 1.3.
The shape and dimensions of the graphite particles are not particularly limited as long as the obtained graphite-carbon composite particles can be formed into a polarizable electrode.
For example, flaky graphite particles, consolidated graphite particles, and spheroidized graphite particles can be used.
The properties and production methods of these graphite particles are known.

The flaky graphite particles generally have a thickness of 1 μm or less, preferably 0.1 μm or less, and the maximum particle length is 100 μm or less, preferably 50 μm or less.
Flaky graphite particles can be obtained by pulverizing natural graphite or artificial graphite by a chemical or physical method.
For example, artificial graphite materials such as natural graphite, quiche graphite, and highly crystalline pyrolytic graphite are treated with a mixed acid of sulfuric acid and nitric acid, heated to obtain expanded graphite, and exfoliated graphite is pulverized by an ultrasonic method or the like. A graphite-sulfuric acid intercalation compound obtained by electrochemically oxidizing graphite in sulfuric acid, or a graphite-organic intercalation compound such as graphite-tetrahydrofuran in an externally heated or internally heated furnace, It can be produced according to a known method such as rapid heating treatment by laser heating or the like to expand and pulverize.
Alternatively, natural graphite or artificial graphite can be obtained by mechanically pulverizing with, for example, a jet mill.

The flaky graphite particles can be obtained, for example, by flaking and granulating natural graphite or artificial graphite.
As a method for thinning and granulating, for example, there is a method of mechanically or physically pulverizing these using ultrasonic waves or various pulverizers.
For example, graphite particles obtained by pulverizing natural graphite and artificial graphite with a pulverizer that does not apply a share such as a jet mill are particularly referred to as scaly graphite particles.
On the other hand, graphite particles obtained by pulverizing and flaking expanded graphite using ultrasonic waves or the like are particularly referred to as flake graphite.

The flaky graphite particles may be annealed in an inert atmosphere at 2000 ° C. to 2800 ° C. for about 0.1 to 10 hours to further enhance crystallinity.
The consolidated graphite particles are graphite particles having a high bulk density, and generally have a tap density of 0.7 to 1.3 g / cm ³ .
Consolidated graphite particles are defined herein as containing 10 vol% or more of spindle-shaped graphite particles having an aspect ratio of 1 to 5 or containing 50 vol% or more of disk-shaped graphite particles having an aspect ratio of 1 to 10 To do.
The consolidated graphite particles can be produced by consolidating the raw graphite particles.

As raw material graphite particles, either natural graphite or artificial graphite may be used, but natural graphite is preferred because of its high crystallinity and availability.
Graphite can be pulverized as it is to obtain raw graphite particles, but the above-mentioned flaky graphite particles may be used as raw graphite particles.

The consolidation process is performed by applying an impact to the raw graphite particles.
Consolidation treatment using a vibration mill is particularly preferable because it can increase the consolidation.
Examples of the vibration mill include a vibration ball mill, a vibration disk mill, and a vibration rod mill.
When scaly raw graphite particles with a large aspect ratio are consolidated, the raw graphite particles are converted into secondary particles while being laminated mainly on the graphite basal plane (base surface), and the edges of the simultaneously laminated secondary particles are rounded. It is cut into a thick disk shape with an aspect ratio of 1 to 10 or a spindle shape with an aspect ratio of 1 to 5, and converted into graphite particles with a small aspect ratio.

As a result of converting the graphite particles into those having a small aspect ratio in this way, graphite particles having excellent isotropic properties and high tap density can be obtained despite the high crystallinity of the graphite particles.
Therefore, when the obtained graphite-carbon composite particles are molded into a polarizable electrode, the graphite concentration in the graphite slurry can be increased, and the density of the molded electrode becomes high.

The spheroidized graphite particles are obtained by collecting the flakes and compressing them into a spherical shape while pulverizing the highly crystalline graphite with an impact pulverizer having a relatively small crushing force.
For example, a hammer mill or a pin mill can be used as the impact pulverizer.
The outer peripheral linear velocity of the rotating hammer or pin is preferably about 50 to 200 m / sec.
Moreover, it is preferable to perform supply and discharge | emission of graphite with respect to these grinders by making it accompany airflow, such as air.

The degree of spheroidization of the graphite particles can be expressed by the ratio of the major axis to the minor axis (major axis / minor axis) of the particle. That is, in an arbitrary cross section of the graphite particle, when the axis having the longest / shortest axis ratio is selected among the axes orthogonal to the center of gravity, the longer the long / short axis ratio is, the closer to 1 is true. It will be close to a sphere.
By the spheroidizing treatment, the ratio of major axis / minor axis can be easily set to 4 or less (1 to 4). Further, if the spheroidization treatment is sufficiently performed, the ratio of the major axis / minor axis can be set to 2 or less (1-2).

Highly crystalline graphite is obtained by increasing the thickness by growing a large number of AB planes in which carbon particles form a network structure and spread on a plane, and grow in a lump.
The bonding force between the laminated AB surfaces (bonding force in the C-axis direction) is much smaller than the bonding force of the AB surface. Tends to be scaly.
When a cross section perpendicular to the AB plane of the graphite crystal is observed with an electron microscope, a streak-like line indicating a laminated structure can be observed.
The internal structure of scaly graphite is simple, and when a cross section perpendicular to the AB plane is observed, the streaky line indicating the laminated structure is always linear, and is a flat laminated structure.
On the other hand, as for the internal structure of the spheroidized graphite particles, the streaky lines indicating the laminated structure are often curved, and many voids are seen, resulting in a remarkably complicated structure.
That is, it is spheroidized as if scaly (plate-like) particles were folded or rolled up.
Thus, it is said that the layered structure that was originally linear changes into a curved shape due to compressive force or the like as a “folding”.

What is more characteristic about the spheroidized graphite particles is that, even with a randomly selected cross section, the vicinity of the surface of the particle has a curved laminated structure along the roundness of the surface.
That is, the surface of the spheroidized graphite particles is generally covered with a curved laminated structure, and the outer surface is an AB plane (ie, a basal plane) of graphite crystals.

-Binder-
The binder is not particularly limited as long as it is a material that is stable with respect to the solvent and electrolyte used in electrode production, and can be appropriately selected according to the purpose. For example, polyvinylidene fluoride (PVDF), Examples thereof include fluorine-based binders such as polytetrafluoroethylene (PTFE), styrene-butadiene rubber (SBR), and isoprene rubber. These may be used individually by 1 type and may use 2 or more types together.

-Thickener-
Examples of the thickener include carboxymethyl cellulose, methyl cellulose, hydroxymethyl cellulose, ethyl cellulose, polyvinyl alcohol, oxidized starch, phosphate starch, and casein. These may be used individually by 1 type and may use 2 or more types together.

-Conductive agent-
Examples of the conductive agent include metal materials such as copper and aluminum, and carbonaceous materials such as carbon black and acetylene black. These may be used individually by 1 type and may use 2 or more types together.

<< Positive electrode current collector >>
There is no restriction | limiting in particular as a material, a shape, a magnitude | size, and a structure of the said positive electrode electrical power collector, According to the objective, it can select suitably.
The material of the positive electrode current collector is not particularly limited as long as it is formed of a conductive material, and can be appropriately selected according to the purpose. For example, stainless steel, nickel, aluminum, copper, titanium, Examples include tantalum. Among these, stainless steel and aluminum are particularly preferable.
There is no restriction | limiting in particular as a shape of the said positive electrode electrical power collector, Although it can select suitably according to the objective, It is a sheet form, a mesh form, etc.
The size of the positive electrode current collector is not particularly limited as long as it is a size that can be used for a non-aqueous electrolyte secondary battery, and can be appropriately selected according to the purpose.

-Method for producing positive electrode-
The positive electrode is coated with a positive electrode material made into a slurry by adding a binder, a thickener, a conductive agent, a solvent, etc. to the positive electrode active material as necessary, and dried. Can be manufactured. There is no restriction | limiting in particular as said solvent, According to the objective, it can select suitably, An aqueous solvent or an organic solvent may be sufficient. Examples of the aqueous solvent include water and alcohol. Examples of the organic solvent include N-methylpyrrolidone (NMP) and toluene.
In addition, the positive electrode active material can be roll-formed as it is to form a sheet electrode, or a pellet electrode by compression molding.

The positive electrode containing graphite-carbon composite particles can be produced by a method similar to the conventional method using graphite-carbon composite particles as a carbonaceous material.
For example, in order to produce a sheet-like polarizable electrode, after adjusting the particle size of the above-mentioned graphite-carbon composite particles, if necessary, a conductive auxiliary agent for imparting conductivity to the graphite-carbon composite particles For example, carbon black and a binder such as polyvinylidene fluoride (PVDF) are added and kneaded, and then formed into a sheet shape by pressure drawing.
As the conductive auxiliary agent, acetylene black or the like can be used in addition to carbon black, and as the binder, PTFE, PE, PP or the like can be used in addition to PVDF.
At this time, the blending ratio of the nonporous carbon, the conductive auxiliary agent (carbon black), and the binder (PVDF) is generally about 10 to 1: 0.5 to 10: 0.5 to 0.25. is there.

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

<< Anode Material >>
The negative electrode material may contain only a negative electrode active material, and may contain a binder, a conductive agent, and the like as necessary in addition to the negative electrode active material.

-Negative electrode active material-
The negative electrode active material is a substance that can insert and desorb at least one of lithium metal and lithium ions. For example, a metal that can insert and desorb lithium such as a carbonaceous material, antimony tin oxide, and silicon monoxide. Metals or metal alloys that can be alloyed with lithium, such as oxides, aluminum, tin, silicon, zinc, etc., composite alloys of lithium-alloyable metal and alloys containing the metal and lithium, cobalt lithium nitride, etc. Examples thereof include lithium metal nitride. These may be used individually by 1 type and may use 2 or more types together. Among these, carbonaceous materials are particularly preferable from the viewpoint of safety and cost.
Examples of the carbonaceous material include graphite (graphite) such as coke, artificial graphite, and natural graphite, and pyrolysis products of organic substances under various pyrolysis conditions. Among these, artificial graphite and natural graphite are particularly preferable.
The BET specific surface area of carbonaceous materials such as graphite materials used as the negative electrode material is usually 0.5 m ² / g or more and 25.0 m ² / g or less, and the median diameter determined by the laser diffraction / scattering method is Usually, it is preferably 1 μm or more and 100 μm or less.

-Binder-
The present invention comprises a lithium titanate compound having a negative electrode and a (co) polymer comprising at least one selected from the group consisting of acrylic acid, methacrylic acid, acrylic acid ester, methacrylic acid ester and acrylonitrile, which are binder components. Contains. Then, by combining the lithium titanate compound and the specific (co) polymer, the negative electrode can be thickened to obtain a high capacity non-aqueous electrolyte secondary battery.
In the present specification, “(co) polymer” is a concept encompassing both a homopolymer obtained by polymerizing one kind of monomer and a copolymer obtained by polymerizing two or more kinds of monomers.
The (co) polymer will be described below.

<(Co) polymer>
The (co) polymer used in the present invention is a (co) polymer comprising at least one of acrylic acid, methacrylic acid, acrylic acid ester, methacrylic acid ester, and acrylonitrile.
The (co) polymer contains a vinyl monomer having an acid component.
Acrylic acid, methacrylic acid, acrylic acid ester, and methacrylic acid ester are represented by the following general formula (1), R ₁ represents a hydrogen atom or an alkyl group having 3 to 16 carbon atoms, and R ₂ represents a hydrogen atom or Represents a methyl group.

Examples of acrylic acid or methacrylic acid esters include butyl methacrylate, pentyl methacrylate, hexyl methacrylate, heptyl methacrylate, octyl methacrylate, nonyl methacrylate, decyl methacrylate, propyl acrylate, n-butyl acrylate, isobutyl acrylate, t-butyl acrylate, pentyl Acrylate, hexyl acrylate, heptyl acrylate, octyl acrylate, 2-ethylhexyl acrylate, nonyl acrylate, decyl acrylate, etc., preferably heptyl acrylate, octyl acrylate, 2-ethylhexyl acrylate, nonyl acrylate, more preferably nonyl acrylate, 2-ethylhexyl acrylate.
Vinyl monomers having an acid component are acrylic acid, methacrylic acid and maleic acid, preferably acrylic acid and methacrylic acid.

The preferred composition of each component of the (co) polymer in the present invention is 50 mol% or more and 95 mol% or less of acrylic acid or methacrylic acid ester (referred to as component A), and 3 mol% or more and 40 of acrylonitrile (component B). The vinyl monomer having an acid component (component C) is 1 mol% or more and 25 mol% or less.
More preferably, A is 60 mol% to 90 mol%, B is 5 mol% to 30 mol%, and C is 3 mol% to 20 mol%.

The (co) polymer in the present invention may contain other repeating units in addition to the above components A, B and C.
Other repeating units are repeating units derived from other vinyl monomers, such as monofunctional monomers such as styrene, α-methylstyrene, chlorostyrene, acrylamide, vinylbenzyl alcohol, styrenesulfinate, styrenesulfonate, And bifunctional monomers such as divinylbenzene, ethylene glycol dimethacrylate, isopropylene glycol diacrylate, and tetramethylene glycol dimethacrylate.

The (co) polymer in the present invention is preferably latex. When making latex, you may use said bifunctional monomer as a crosslinking agent.
These crosslinking agents can be used at 15 mol% or less, preferably 10 mol% or less.
The (co) polymer of the present invention is preferably used as an aqueous dispersion, and the form thereof may be an emulsion-dispersed polymer or a latex.
The latex may be crosslinked or non-crosslinked.

The polymerization method of the (co) polymer in the present invention may be any of solution polymerization, emulsion polymerization, suspension polymerization and gas phase polymerization, and the structure of the polymer is any of random type, graft type or block type. Also good.
The aqueous dispersion of the (co) polymer in the present invention can contain anionic and nonionic surfactants, but these are preferably used in combination.
The amount of these surfactants used is 0.01% or more and 3% or less, preferably 0.1% or more and 2% or less, and most preferably 0.5% or more and 1.5%, based on the mass of the (co) polymer. % Or less.

Although the preferable composition of the (co) polymer in this invention is shown below, this invention is not limited to these.
The solid content in the aqueous dispersion was adjusted to 50% by mass.
P-1: 2-ethylhexyl acrylate, an aqueous dispersion of a copolymer of acrylic acid and acrylonitrile (copolymerization ratio 80: 5: 15)
P-2: aqueous dispersion of copolymer of nonyl acrylate, acrylic acid, acrylonitrile and styrene (copolymerization ratio 82: 3: 10: 5)
P-3: An aqueous dispersion of a copolymer of 2-ethylhexyl acrylate, acrylic acid, acrylonitrile and divinylbenzene (copolymerization ratio 80: 5: 10: 5)
P-4: Water dispersion of copolymer of butyl acrylate, acrylic acid and acrylonitrile (copolymerization ratio 90: 3: 7)
P-5: Aqueous dispersion of copolymer of butyl acrylate, acrylic acid, acrylonitrile and divinylbenzene (copolymerization ratio 80: 5: 10: 5)
P-6: 2-ethylhexyl acrylate, maleic acid / acrylonitrile copolymer aqueous dispersion (copolymerization ratio 80: 5: 15)
P-7: An aqueous dispersion of a copolymer of 2-ethylhexyl acrylate, methacrylic acid and acrylonitrile (copolymerization ratio 80: 5: 15)
P-8: An aqueous dispersion of 2-ethylhexyl acrylate, a copolymer of acrylic acid and acrylonitrile (copolymerization ratio 60:15:25)
P-9: 2-ethylhexyl acrylate, copolymer of acrylic acid and acrylonitrile (copolymerization ratio 80: 5: 15)
P-10: Copolymer of butyl acrylate, acrylic acid and acrylonitrile (copolymerization ratio 90: 3: 7)
P-11: Aqueous dispersion of copolymer of ethyl acrylate, acrylic acid and acrylonitrile (copolymerization ratio 80: 5: 15) P12: Aqueous dispersion of copolymer of 2-ethylhexyl acrylate, acrylic acid and acrylonitrile (co-polymer) (Polymerization ratio 50:20:30)

Other binders that can be used in conjunction with the (co) polymer (binder) in the present invention include starch, polyvinyl alcohol, carboxymethyl cellulose, hydroxypropyl cellulose, regenerated cellulose, diacetyl cellulose, polyvinyl chloride, polyvinyl Pyrrolidone, polytetrafluoroethylene, polyvinylidene fluoride, polyethylene, polypropylene, ethylene-propylene-diene terpolymer (EPDM), sulfonated EPDM, styrene butadiene rubber, polybutadiene, fluoro rubber, polyethylene oxide and other polysaccharides, thermoplastic resin In addition, one or a mixture of polymers having rubber elasticity can be used.
Moreover, when using the compound containing a functional group which reacts with lithium like a polysaccharide, it is preferable to add the compound like an isocyanate group and to deactivate the functional group, for example.
Of these binders, fluororesin and carboxymethyl cellulose are particularly preferred.

  Examples of the fluororesin that can be used in combination with the (co) polymer in the present invention include polytetrafluoroethylene (PTFE), tetrafluoroethylene / hexafluoropropylene copolymer (FEP), and tetrafluoroethylene / perfluoroalkyl. Vinyl ether copolymer (PFA), polychlorotrifluoroethylene (PCTFE), polyvinylidene fluoride (PVDF), polyvinyl fluoride, ethylene / tetrafluoroethylene copolymer (ETFE resin), ethylene / chlorotrifluoroethylene copolymer (ECTFE).

The molecular weight of the carboxymethyl cellulose that can be used in combination with the (co) polymer in the present invention is preferably from 200,000 to 5,000,000, more preferably from 500,000 to 2,000,000. The degree of etherification is preferably from 0.5 to 1.0, more preferably from 0.6 to 0.8.
The negative electrode preferably contains 1% by mass or more and 4% by mass or less of carboxymethyl cellulose (CMC) with respect to the active material.

The addition amount of the (co) polymer in the present invention is preferably 16% by mass or less, more preferably 2% by mass or more and 3% by mass or less with respect to the mass of all the electrode materials.
When the (co) polymer in the present invention is used in combination with other binders (for example, fluororesin, carboxymethyl cellulose, etc.), the proportion of the (co) polymer is 30% or more, preferably 50% or more. .
The total amount of the binder used in the present invention is 1% to 40% by mass of the electrode mixture, and preferably 2% to 30% by mass.
The proportion of the (co) polymer in the present invention in the binder is 10% by mass or more, preferably 20% by mass to 90% by mass, and particularly preferably 30% by mass to 80% by mass.

-Conductive agent-
Examples of the conductive agent include metal materials such as copper and aluminum, and carbonaceous materials such as carbon black and acetylene black. These may be used individually by 1 type and may use 2 or more types together.

<< Negative electrode current collector >>
There is no restriction | limiting in particular as a material, a shape, a magnitude | size, and a structure of the said negative electrode collector, According to the objective, it can select suitably.
The material of the negative electrode current collector is not particularly limited as long as it is formed of a conductive material, and can be appropriately selected according to the purpose. Examples thereof include stainless steel, nickel, aluminum, and copper. It is done. Among these, stainless steel and copper are particularly preferable.
There is no restriction | limiting in particular as a shape of the said electrical power collector, Although it can select suitably according to the objective, It is a sheet form, a mesh form, etc.
The size of the current collector is not particularly limited as long as it is a size that can be used for a non-aqueous electrolyte secondary battery, and can be appropriately selected according to the purpose.

-Negative electrode manufacturing method-
The negative electrode can be produced by applying a negative electrode material in a slurry form by adding a binder, a conductive agent, a solvent, or the like to the negative electrode active material, if necessary, and drying the negative electrode current collector. . As the solvent, the same solvent as that for the positive electrode can be used.
In addition, a material obtained by adding a binder, a conductive agent, etc. to the negative electrode active material as it is is formed into a sheet electrode, formed into a pellet electrode by compression molding, or deposited on the negative electrode current collector by techniques such as vapor deposition, sputtering, or plating. A thin film of a negative electrode active material can also be formed.
The film thickness of the negative electrode is preferably 50 μm or more and 240 μm or less.

As the negative electrode material (negative electrode active material), a material capable of inserting and removing metallic lithium or lithium ions is used.
For example, the metal lithium carbonaceous material and the metal and metal compound which can insert and desorb lithium ion are mentioned.
Of these, specific examples of metals and metal compounds capable of inserting and removing lithium ions include the following.
・ Metal oxide capable of inserting and removing lithium such as tin oxide, antimony tin oxide, silicon monoxide, vanadium oxide, etc. ・ Aluminum, silicon, tin, antimony, lead, arsenic, zinc, bismuth, copper, cadmium, silver, Metals that can be alloyed with lithium such as gold, platinum, palladium, magnesium, sodium, potassium, etc.-Alloys containing the above metals (including intermetallic compounds)
・ Metal that can be alloyed with lithium and composite alloy compound of lithium and alloy containing the metal ・ Lithium metal lithium such as cobalt lithium nitride These negative electrode materials may be used alone or in combination of two or more. You may do it.

A method for producing a negative electrode using such a negative electrode material is not particularly limited.
For example, a negative electrode can be produced by adding a binder, a thickener, a conductive material, a solvent, and the like to the negative electrode material as necessary to form a slurry, which is applied to a substrate of a current collector and dried. it can.
In this case, it can be manufactured in the same manner as the positive electrode manufacturing method described above.
In addition, the negative electrode material added with a binder or a conductive material is roll-formed as it is to form a sheet electrode, a pellet electrode by compression molding, or deposition, sputtering, plating, etc. on the current collector A thin film of negative electrode material can also be formed.

As the material for the current collector for the negative electrode, metals such as copper, nickel, stainless steel, and aluminum are used, and copper foil is preferred from the viewpoint of easy processing into a thin film and cost.
Furthermore, lithium titanate can also be used as a negative electrode material (negative electrode active material). Lithium titanate is represented by the general formula LixTi _y O ₄ (0.8 ≦ x ≦ 1.4, 1.6 ≦ y ≦ 2.2), and X-ray diffraction was performed using Cu as a target. In this case, the peak positions are at least 4.84Å, 2.53Å, 2.09Å, and 1.48Å (each ± 0.02Å). The peak intensity ratio is preferably 4.84 ピ ー ク peak intensity: 1.48 ピ ー ク peak intensity (each ± 0.02 Å) = 100: 30 (± 10).
More preferably, in the general formula LixTi _y O ₄ , x = 1, y = 2 Further preferably, in the general formula LixTi yO ₄ , x = 1.33, y = 1.66, In the general formula LixTiyO ₄ , x = 0.8 and y = 2.2.

Further, when rutile titanium oxide is mixed with the lithium titanate, the peak positions of X-ray diffraction are 3.25Å, 2.49Å, 2.19Å, 1. The peak at 69Å (each ± 0.02Å) increases.
Preferably, the peak intensity ratio is 3.25 to peak intensity: 2.49 to peak intensity: 1.69 to peak intensity = 100: 50 (± 10): 60 (± 10).
More preferably, in the general formula LixTi _y O ₄ , x = 1 and y = 2.
Preferably, in the general formula Li _x Ti _y O ₄ , x = 1.33, y = 1.66, and more preferably in the general formula Li _x Ti _y O ₄ , x = 0.8, y = 2. .2.

On the other hand, the method for producing a negative electrode of a lithium secondary battery using the above lithium titanate includes a step of mixing a lithium compound and titanium oxide, and heat-treating the mixture at a temperature of 800 ° C. to 1600 ° C. Lithium calcination or lithium carbonate is used for the lithium compound which has the process of baking lithium and is a starting material of baking.
The heat treatment is more preferably performed under a temperature condition of 800 ° C. or higher and 1100 ° C. or lower.

<Non-aqueous electrolyte>
The non-aqueous electrolyte is an electrolyte obtained by dissolving an electrolyte salt in a non-aqueous solvent.
-Non-aqueous solvent-
The non-aqueous solvent is an aprotic organic solvent, and examples thereof include carbonate-based organic solvents such as chain carbonates. A low-viscosity solvent is preferable, and as the cyclic carbonate, for example, propylene carbonate (PC), ethylene carbonate (EC), butylene carbonate (BC), vinylene carbonate (VC) and the like are preferably less than 10 wt% of the chain carbonate.
Examples of the chain carbonate include dimethyl carbonate (DMC), diethyl carbonate (DEC), and methyl ethyl carbonate.
Examples of the cyclic carbonate include propylene carbonate (PC), ethylene carbonate (EC), butylene carbonate (BC), vinylene carbonate (VC), and the like.

In addition, ether solvents are also included.
Examples of the chain ether include 1,2-dimethoxyethane (DME), diethyl ether, ethylene glycol dialkyl ether, diethylene glycol dialkyl ether, triethylene glycol dialkyl ether, and tetraethylene glycol dialkyl ether.
Examples of the cyclic ester include γ-butyrolactone (γBL), 2-methyl-γ-butyrolactone, acetyl-γ-butyrolactone, and γ-valerolactone.
Examples of the chain ester include propionic acid alkyl ester, malonic acid dialkyl ester, and acetic acid alkyl ester.
Examples of the cyclic ether include tetrahydrofuran, alkyltetrahydrofuran, alkoxytetrahydrofuran, dialkoxytetrahydrofuran, 1,3-dioxolane, alkyl-1,3-dioxolane, 1,4-dioxolane, and the like.
Among these, what contains 90 mass% or more which has propylene carbonate (PC) as a main component is preferable.

-Electrolyte salt-
As the electrolyte salt, one that dissolves in a non-aqueous solvent and exhibits high ionic conductivity is used.
A combination of the following cations and anions can be used, but various electrolyte salts that can be dissolved in the nonaqueous solvent to be used can be used.
Examples of the cation include alkali metal ions, alkaline earth metal ions, tetraalkylammonium ions, and spiro quaternary ammonium ions.
As anions, Cl ⁻ , Br ⁻ , I ⁻ , SCN ⁻ , ClO ₄ ⁻ , BF ₄ ⁻ , PF ₆ ⁻ , SbF ₆ ⁻ , CF ₃ SO ₃ ⁻ , (CF ₃ SO ₂ ) ₂ N ⁻ , (C _{2 ^{F 5 SO 2) 2 N -}} , (C 6 H 5) 4 B - can be exemplified.
In terms of improving the capacity, a lithium salt having a Li cation as a cationic species is preferable.

The lithium salt is not particularly limited and may be appropriately selected depending on the purpose. For example, lithium hexafluorophosphate (LiPF ₆ ), lithium perchlorate (LiClO ₄ ), lithium chloride (LiCl), borofluoride Lithium fluoride (LiBF ₄ ), LiB (C ₆ H ₅ ) ₄ , lithium arsenic hexafluoride (LiAsF ₆ ), lithium trifluorometasulfonate (LiCF ₃ SO ₃ ), lithium bistrifluoromethylsulfonylimide (LiN (C ₂₎ F ₅ SO _{2) 2),} lithium bis fur fluoroethyl imide _{(LiN (CF 2 F 5 SO} 2) 2) , and the like.
These may be used individually by 1 type and may use 2 or more types together. Among these, LiPF ₆ or LiBF _{4 is} particularly preferable.

  There is no restriction | limiting in particular as a density | concentration of the said lithium salt, Although it can select suitably according to the objective, 0.5 mol / L-6 mol / L is preferable in the said organic solvent, 2-4 mol / L fixed The latter is particularly preferable from the viewpoint of both battery capacity and output.

<Separator>
The separator is provided between the positive electrode and the negative electrode in order to prevent a short circuit between the positive electrode and the negative electrode.
There is no restriction | limiting in particular as a material of the said separator, a shape, a magnitude | size, and a structure, According to the objective, it can select suitably.
Examples of the material of the separator include paper such as kraft paper, vinylon mixed paper, synthetic pulp mixed paper, cellophane, polyethylene graft film, polyolefin nonwoven fabric such as polypropylene melt blown nonwoven fabric, polyamide nonwoven fabric, and glass fiber nonwoven fabric.
Examples of the shape of the separator include a sheet shape.
There is no restriction | limiting in particular as long as the magnitude | size of the said separator is a magnitude | size which can be used for a nonaqueous electrolyte secondary battery, According to the objective, it can select suitably.
The separator may have a single layer structure or a laminated structure.

<Method for Manufacturing Nonaqueous Electrolyte Storage Element>
The non-aqueous electrolyte storage element of the present invention is manufactured by assembling the positive electrode, the negative electrode, and the non-aqueous electrolyte and a separator used as necessary into an appropriate shape. Furthermore, other constituent members such as a battery outer can can be used as necessary. There is no restriction | limiting in particular as a method of assembling a battery, It can select suitably from the methods normally employ | adopted.

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

When the solute concentration in the electrolytic solution is reduced by charging and the solute concentration becomes 0, charging cannot be performed any more. Therefore, it is necessary to contain an amount of solute corresponding to the capacity of the positive electrode and the negative electrode in the electrolytic solution.
When the solute concentration is low, a large amount of electrolyte solution is required in the battery. Therefore, it is preferable that the solute concentration in the electrolyte solution is high.
In some cases, the solute can be deposited in the solvent in the discharged state.

From such points, the lower limit of the concentration of the lithium salt in the non-aqueous electrolyte is usually 0.05 mol / L or more, preferably 0.5 mol / L or more, particularly preferably 1 mol / L or more, and the upper limit is usually 5 mol / L. L or less, preferably 4 mol / L or less, particularly preferably 3 mol / L or less.
Below this lower limit, the conductivity decreases, or a large amount of electrolyte is required to secure a solute suitable for the capacity of the positive and negative electrodes, so the energy density per mass or volume of the battery tends to decrease. .
On the other hand, when the upper limit is exceeded, there is a possibility that a solute precipitates or the conductivity decreases.

The shape of the nonaqueous electrolyte storage element of the present invention is not particularly limited, and can be appropriately selected from various shapes generally employed according to the application.
Examples of the shape include a cylinder type in which a sheet electrode and a separator are spiral, a cylinder type having an inside-out structure in which a pellet electrode and a separator are combined, a coin type in which a pellet electrode and a separator are stacked, and the like.
The nonaqueous electrolyte storage element may be assembled by a known method in accordance with the shape of the target storage element.

<Aging method of nonaqueous electrolyte storage element>
The nonaqueous electrolyte storage element of the present invention may be aged. In this method, charging / discharging is performed an arbitrary number of times so as to obtain an arbitrarily set SOC of 100% or more.
In addition, in the case of charging to a storage element composed of a positive electrode and a negative electrode, the charge end voltage is changed depending on the type of the negative electrode, the charge end voltage when the lithium to the positive electrode is used as a reference electrode is a predetermined voltage, A similar effect can be obtained by defining a charging method for changing the state of charge of the positive electrode to a predetermined state.

If the charging rate (rate) is too high, the battery reaches the charge end voltage before the positive electrode and the negative electrode are sufficiently charged, so that a sufficient capacity cannot be obtained.
For this reason, when charging with a constant current, it is preferable to charge at a charging rate of 1C or less (1C is a current value for discharging a rated capacity with a discharge capacity of 1 hour in 1 hour) or less.
However, if the charging speed is excessively slow, it takes a long time for charging. Therefore, in the case of constant current charging, it is preferably 0.01C or more.
It is also possible to charge the battery while maintaining a constant voltage after reaching the end-of-charge voltage.
At the time of charging, if the battery temperature is excessively high, the non-aqueous electrolyte is likely to be decomposed. If the temperature is low, charging to the positive electrode and the negative electrode is likely to be insufficient. .

  The discharge method of the secondary battery of the present invention obtained by charging in this way varies depending on the discharge rate and the negative electrode used, but usually a value of about 2 to 3 V at a discharge rate of 1 C or less from the charged state. By using it as a discharge end voltage, a nearly rated discharge capacity can be obtained. For example, a high discharge capacity of 60 mAh / g or more, particularly about 80 to 120 mAh / g can be obtained in terms of discharge capacity per positive electrode active material.

<Application>
The use of the nonaqueous electrolyte storage element of the present invention is not particularly limited, and can be used for various known uses.
Specific examples include notebook computers, pen input computers, mobile computers, electronic book players, mobile phones, mobile faxes, mobile copy, mobile printers, headphone stereos, video movies, LCD TVs, handy cleaners, portable CDs, minidiscs, and transceivers. Electronic notebooks, calculators, memory cards, portable tape recorders, radios, cars, backup power supplies, motors, lighting equipment, toys, game machines, watches, aircraft, strobes, cameras, etc.
In particular, the non-aqueous electrolyte storage element of the present invention that secures an overcharge region is excellent in safety.

EXAMPLES Next, although an Example demonstrates this invention further more concretely, this invention is not limited to description of a following example, unless the summary is exceeded.
Hereinafter, the charge end voltage of the positive electrode using lithium as a reference electrode is referred to as “charge end voltage (vs. Li)”.
Further, in the examples, the amount represented by “part” or “%” is based on mass unless otherwise specified.

[Example 1]
(Manufacture of (co) polymer (binder))
In polymerization can A, 10.75 parts of 2-ethylhexyl acrylate, 1.25 parts of acrylonitrile which is an α, β-unsaturated nitrile monomer, 0.12 parts of sodium lauryl sulfate which is a surfactant, and 79 of ion-exchanged water Then, 0.2 parts of ammonium persulfate as a polymerization initiator and 10 parts of ion-exchanged water were added, heated to 60 ° C. and stirred for 90 minutes.

Next, in a polymerization can B different from the polymerization can A, 67 parts of 2-ethylhexyl acrylate, 19 parts of acrylonitrile, 2.0 parts of methacrylic acid which is a vinyl monomer having an acid component, 0.7 parts of sodium lauryl sulfate Then, 46 parts of ion exchange water was added and stirred to prepare an emulsion.
The emulsion was sequentially added from the polymerization vessel B to the polymerization vessel A over about 180 minutes, and then stirred for about 120 minutes. When the consumption of the monomer reached 95%, the reaction was terminated by cooling.
Thereafter, the pH was adjusted with a 4% NaOH aqueous solution to obtain an aqueous dispersion of an aqueous acrylic polymer.
The obtained acrylic polymer aqueous dispersion had a pH of 10.5 and a dispersed particle size of 0.10 μm, and the glass transition temperature of the acrylic polymer was −32 ° C. The obtained acrylic polymer is a binder.
When the composition of this acrylic polymer was measured by ¹ H-NMR, it was 77.75% by mass of 2-ethylhexyl acrylate units, 20.25% by mass of acrylonitrile units, and 2% by mass of methacrylic acid units.

(Manufacture of negative electrode)
As a negative electrode active material negative electrode material, 3 g of LTO (Li ₄ Ti ₅ O ₁₂ ) (manufactured by Titanium Industry) and 4 g of an acetylene black solution (solution obtained by diluting AB made by Gokoku Dye Co., Ltd. 5 times: 5% AB-H ₂ O) The mixture was kneaded at 1000 rpm for 15 minutes with a non-bubble kneader NBK1 (Nippon Seiki Seisakusho).
Furthermore, 1-3 g of CMC 3% aqueous solution was added to adjust conductivity and viscosity.
Further, the above binder was added in various amounts, and the kneaded product was formed on an 18 μm aluminum sheet using a film forming apparatus to obtain a negative electrode.
(Evaluation)
Adhesiveness of the obtained electrode was evaluated using a peeling apparatus shown in FIG. The result is shown in FIG.
In FIG. 3, ◯ indicates no peeling and X indicates peeling.
A representative example of the measurement result is shown in FIG. FIG. 4 shows a state where 500 gf is pressed for 5 seconds and then peeled off at 10 m / s.
As can be seen from FIG. 3, the adhesiveness was greatly improved by adding 2 wt% of the binder to the total amount of the slurry. Further, by adding 3 wt%, peeling could be prevented at a film thickness of 300 μm or less.

(Determine the upper limit of addition amount)
Next, the upper limit of the addition amount is determined.
A slurry was prepared according to the above method, a half cell having a counter electrode of Li was prepared, and charging / discharging was performed. The charge / discharge curve at a film thickness of 100 μm is shown in FIG.
FIG. 5 shows the state of charge and discharge when a binder is added at 17% and 16%.
In FIG. 5, ◇ indicates a case where 16% by mass is added, and X indicates a case where 17% by mass is added.
As can be seen from FIG. 5, in order to maintain the charge / discharge capacity of 169 mAh / g, the addition amount of the binder was preferably 16%. That is, when 17% was added, the capacity decreased.
This phenomenon was the same in the film thickness range of 70 μm to 300 μm.

(Determination of film thickness)
Here, as a representative example, 3% of a binder is added, and the influence of the film thickness is examined.
The following graphite particles were prepared. The graphite particles are artificial graphite, and are spherical graphitized particles obtained by graphitizing mesophase carbon by baking at 2800 ° C.
The graphite particles were analyzed by the following method.

(1) The BET specific surface area was determined by a specific surface area measuring device (“Gemini 2375” manufactured by Shimadzu Corporation). Nitrogen was used as the adsorbent and the adsorption temperature was 77K.
(2) X-ray crystallographic analysis of the graphite particles was performed using an X-ray diffractometer (“RINT-UltimaIII” manufactured by Rigaku Corporation). The obtained X-ray diffraction spectrum was analyzed, and the (002) plane crystal lattice constant [C0 (002)], the average interplanar spacing d002, and the (002) peak (peak near 2θ = 26.5 °) The half width of was determined.
The target was CuKα, and measurement was performed at 40 kV and 200 mA.
The peak position of the rhombohedral crystal (101-R) is in the vicinity of 2θ = 43.3 °, and the peak intensity is IB. The peak position of hexagonal crystal (101-H) is in the vicinity of 2θ = 44.5 °, and the peak intensity is IA.
And the ratio IB / IA of the rhombohedral crystal structure which exists in crystal structure was calculated | required.
(3) Raman spectroscopy Raman spectrometer using (manufactured by JASCO Corporation "laser Raman spectrophotometer NRS-3100"), the ratio of the peak intensity of the peak intensity and 1580 cm ^-1 in 1360 cm ^-1 in the Raman spectrum, I (1360 ) / I (1580).
(4) It observed using the electron microscope by JEOL Ltd., and confirmed the external shape.
(5) The sample was put into a 10 mL glass graduated cylinder and tapped. When the sample volume stopped changing, the sample volume was measured, and the value obtained by dividing the sample mass by the sample volume was taken as the tap density.
The graphite particles have a BET surface area of 10 to 300 m ² / g, a rhombohedral peak intensity ratio (IB / IA) of 0.3 or more by X-ray diffraction method, a peak intensity ratio by Raman spectroscopy of (1360) ) / I (1580) was 0.11 to 0.30.

Graphite-carbon composite particles were manufactured by the following method using a carbon coating apparatus (CVD = chemical vapor deposition method) schematically shown in FIG.
Graphite particles were allowed to stand in a quartz cuvette in a furnace heated to 1100 ° C., and toluene vapor was introduced into this using argon gas as a carrier to precipitate and carbonize toluene on the graphite. The precipitation carbonization treatment was performed for 3600 seconds. The resulting coated graphite was analyzed, having peaks peak and 1580 cm ^-1 in 1360 cm ^-1 in the Raman spectrum of 0.02 to 0.30. The peak intensity ratio was 0.16 for I (1360) / I (1580).

(1) Production of positive electrode Non-bubble kneader 3 g of graphite-carbon composite particles produced by the above method and 4 g of acetylene black solution (solution obtained by diluting AB of Gokoku Dye Co., Ltd. 5 times: 5% AB-H ₂ O) The mixture was kneaded at 1000 rpm for 15 minutes with NBK1 (Nippon Seiki Seisakusho).
Furthermore, 1-3 g of CMC 3% aqueous solution was added to adjust conductivity and viscosity.
Using a film forming apparatus, the kneaded product was formed on an 18 μm aluminum sheet to obtain a positive electrode.

(2) Production of negative electrode As a negative electrode material, 3 g of LTO (manufactured by Titanium Industry) and 4 g of acetylene black solution (a solution obtained by diluting AB made by Gokoku Dye Co., Ltd. 5 times: 5% AB-H2O) Kneading at 1000 rpm for 15 minutes.
Furthermore, 1-3 g of CMC 3% aqueous solution was added to adjust conductivity and viscosity.
Using a film forming apparatus, the kneaded product was formed on an 18 μm aluminum sheet to obtain a negative electrode.

<Electrolyte>
As an electrolytic solution, 0.3 mL of EC / PC = 1: 1 solution (manufactured by Kishida Chemical Co., Ltd.) in which LiBF ₄ was dissolved was prepared.

<Separator>
An experimental filter paper (ADVANTEC GA-100 GLASS FIBER FILTER) was prepared as a separator.

<Production of electricity storage element>
A coin-type non-aqueous electrolyte storage element was manufactured by placing a separator between a positive electrode and a negative electrode that were manufactured in an argon dry box and punched out to 16 mm, and placed adjacent to each other.

<Charge / discharge characteristics>
When this battery was charged at a constant current of 0.57 mA / cm ² up to a charge end voltage of 4.5 V at room temperature, the first charge capacity per positive electrode active material was 50− due to the mass ratio of the positive electrode to the negative electrode. 340 mAh / g was obtained.
After the first charge, the discharge capacity per positive electrode active material when discharged to 2.5 V at a constant current of 0.57 mA was 60-100 mAh / g depending on the mass ratio of the positive electrode to the negative electrode.
FIG. 7 shows the relationship between the mass ratio of the positive electrode to the negative electrode and the first charge capacity.
On the other hand, FIG. 8 shows the relationship between the capacities when the film thickness of the positive electrode is fixed at 130 μm and the film thickness of the negative electrode is changed based on the result of FIG.

On the other hand, FIG. 9 shows an example of a charge / discharge curve.
As can be seen from FIG. 9, in this case, the capacity of the positive electrode graphite is about 280 mAh / g.
In consideration of the capacity 370 of the first stage BF ₄ C6 and the capacity of about 180 mAh / g of the second stage BF ₄ C12, BF ₄ ions are inserted up to the first stage in charging the positive electrode.
However, in order to be completely in the first stage, the voltage is insufficient and 4.5 V or more is necessary.
The charging potential of about 4.4 V is the first and second stage charging curves.
As can be seen from FIG. 9, it is possible to increase the thickness of the negative electrode by adding a binder, and it is desirable to obtain an electrode with a thickness of preferably 50-300 μm, more preferably 70-240 μm, and even more preferably 120-240 μm. Thus, a capacity of 170 to 280 mAh / g can be obtained, and troubles such as ignition can be prevented even when overcharging is performed due to a circuit failure or the like.

DESCRIPTION OF SYMBOLS 1 Positive electrode 2 Negative electrode 3 Separator 4 Battery outer can 5 Negative electrode lead wire 6 Positive electrode lead wire

JP 2005-294780 A JP 2008-1224012 A Japanese Patent No. 3539448 Japanese Patent No. 3920310 JP 4081125 A Japanese Patent No. 4194052 JP 2006-332627 A JP 2006-332626 A JP 2006-332625 A JP 2008-042182 A

Claims (10)

A non-aqueous electrolyte storage element having a positive electrode, a negative electrode, and a non-aqueous electrolyte,
The positive electrode is capable of at least inserting and removing anions;
The negative electrode contains a lithium titanate compound and a (co) polymer composed of at least one selected from the group consisting of acrylic acid, methacrylic acid, acrylic acid ester, methacrylic acid ester and acrylonitrile. Non-aqueous electrolyte storage element.   The non-aqueous electrolyte storage element according to claim 1, wherein the (co) polymer contains a vinyl monomer having an acid component. The non-aqueous electrolyte storage element according to claim 1, wherein the acrylic acid or methacrylic acid ester is represented by the following general formula (1). :
General formula (1)
Here, R ₁ represents a hydrogen atom or an alkyl group having 3 to 16 carbon atoms, and R ₂ represents a hydrogen atom or a methyl group.   The non-aqueous electrolyte storage element according to claim 1, wherein the vinyl monomer having an acid component is acrylic acid, methacrylic acid, or maleic acid.   5. The non-aqueous electrolyte storage element according to claim 1, wherein the addition amount of the (co) polymer is 16% by mass or less based on the mass of all electrode materials. .   6. The non-aqueous solution according to claim 1, wherein the addition amount of the (co) polymer is 2% by mass or more and 3% by mass or less with respect to the mass of all the electrode materials. Electrolyte storage element.   The film thickness of the said negative electrode is 50 micrometers or more and 240 micrometers or less, The nonaqueous electrolyte storage element of any one of Claims 1-6 characterized by the above-mentioned.   The non-aqueous solution according to any one of claims 1 to 7, wherein the negative electrode contains 1% by mass or more and 4% by mass or less of carboxymethyl cellulose (CMC) with respect to the active material. Electrolyte storage element.   9. The electrode according to claim 1, wherein the positive electrode is an electrode including graphite-carbon composite particles comprising graphite particles and a carbon layer made of crystalline carbon covering the graphite particles. The nonaqueous electrolyte storage element described. The positive electrode contains graphite-carbon composite particles composed of graphite particles and a carbon layer made of crystalline carbon covering the graphite particles;
The non-aqueous electrolyte storage element according to claim 1, wherein the negative electrode has a thickness of 70 μm or more and 240 μm or less.