WO2018179167A1

WO2018179167A1 - Material for lithium ion secondary batteries, positive electrode mixed material, positive electrode for lithium ion secondary batteries, and lithium ion secondary battery

Info

Publication number: WO2018179167A1
Application number: PCT/JP2017/013010
Authority: WO
Inventors: 馨今野; 紘揮三國
Original assignee: 日立化成株式会社
Priority date: 2017-03-29
Filing date: 2017-03-29
Publication date: 2018-10-04
Also published as: JP6883230B2; JPWO2018179167A1

Abstract

A material for lithium ion secondary batteries, which is an aluminum silicate compound complex containing an aluminum silicate compound and carbon and having a total pore volume of 0.05 cm3/g or more as measured by a nitrogen adsorption method.

Description

Material for lithium ion secondary battery, positive electrode mixture, positive electrode for lithium ion secondary battery, and lithium ion secondary battery

The present invention relates to a material for a lithium ion secondary battery, a positive electrode mixture, a positive electrode for a lithium ion secondary battery, and a lithium ion secondary battery.

Lithium ion secondary batteries are high energy density secondary batteries, and are widely used as power sources for electronic devices such as notebook personal computers and portable information terminals such as smartphones by taking advantage of their characteristics.
In recent years, especially with the enhancement of functionality of portable information terminals, development of lithium ion secondary batteries having excellent capacity retention after charge / discharge cycles has been strongly demanded.

In order to suppress a decrease in capacity retention rate, (1) a method using a fluorine-containing salt and a phosphonoacetate compound as an electrolyte and a zirconium-containing lithium cobalt composite oxide as a positive electrode active material (see, for example, Patent Document 1), (2) A method using a fluorinated cyclic carbonate and a fluorinated chain ester as an electrolytic solution (see, for example, Patent Document 2), (3) Lithium cobaltate in which a rare earth compound is fixed to a part of the surface as a positive electrode active material There has been proposed a method (for example, refer to Patent Document 3) using the method.

JP 2014-127256 A JP 2014-110122 A JP 2013-179095 A

However, even by the methods described in Patent Documents 1 to 3, it has been clarified by the present inventors that it is difficult to sufficiently suppress the decrease in capacity retention rate when used at a high voltage. As the cause, for example, the following two are conceivable. First, due to hydrogen fluoride (HF) generated when water contained in the lithium ion secondary battery reacts with a fluorine-containing electrolyte such as lithium hexafluorophosphate (LiPF ₆ ), the positive electrode active material It is conceivable that metal ions such as cobalt are eluted. Secondly, it is conceivable that the metal ions such as the eluted cobalt reprecipitate on the negative electrode or the like.

The present invention has been made in view of the above circumstances, and is a material for a lithium ion secondary battery and a positive electrode composite material excellent in metal precipitation suppression ability, and a positive electrode for a lithium ion secondary battery produced using these materials and An object is to provide a lithium ion secondary battery.

Specific means for solving the above problems include the following embodiments.
<1> An aluminum silicate compound complex containing an aluminum silicate compound and carbon and having a total pore volume measured by a nitrogen adsorption method of 0.05 cm ³ / g or more, for a lithium ion secondary battery material.
Is calculated by the following equation from <2> and the peak area A of the oxidation point in the vicinity of 1490cm ^-1, which derived from pyridine adsorption IR spectrum of the aluminum silicate compound complex, the peak area B of the hydrogen bonds in the vicinity of 1446cm ^-1 The material for a lithium ion secondary battery according to <1>, wherein the oxidation point ratio (RA) is less than 25%.
RA (%) = A / B × 100
<3> The lithium ion secondary battery according to <1> or <2>, wherein an element molar ratio (Si / Al) of silicon to aluminum in the aluminum silicate compound composite is 1.0 to 5.0 material.
<4> The mass reduction rate between 350 ° C. and 850 ° C. measured by differential thermal-thermogravimetric analysis (TG-DTA) of the aluminum silicate compound composite is 0.5% to 30%. <1>-<3> The material for a lithium ion secondary battery according to any one of <1> to <3>.
<5> The volume average particle diameter measured by a laser diffraction particle size distribution analyzer of the aluminum silicate compound composite is 0.1 μm to 50 μm, according to any one of <1> to <4>. Materials for lithium ion secondary batteries.
<6> The lithium according to any one of <1> to <5>, wherein an element molar ratio (Si / Al) of silicon to aluminum of the aluminum silicate compound composite is 1.5 to 3.0 Material for ion secondary battery.
<7> A positive electrode mixture comprising the lithium ion secondary battery material according to any one of <1> to <6> and a positive electrode active material.
<8> The positive electrode mixture according to <7>, wherein the content of the lithium ion secondary battery material is 0.01% by mass to 10% by mass with respect to the total amount of the positive electrode mixture.
<9> A positive electrode for a lithium ion secondary battery comprising the material for a lithium ion secondary battery according to any one of <1> to <6>.
<10> A lithium ion secondary battery comprising the positive electrode for a lithium ion secondary battery according to <9>.

ADVANTAGE OF THE INVENTION According to this invention, the lithium ion secondary battery material and positive electrode compound material which are excellent in metal precipitation suppression capability, and the positive electrode and lithium ion secondary battery which are manufactured using these are provided. With the goal.
Since the lithium ion secondary battery material of the present invention is excellent in the ability to suppress the precipitation of metal, the lithium ion secondary battery using the lithium ion secondary battery material of the present invention has a reduced capacity retention rate. There is a tendency.

It is a perspective view which shows roughly the internal structure of an example (cylindrical type) of a lithium ion secondary battery. It is a graph which shows the relationship between the adsorption amount of Co ion of the produced aluminum silicate compound composite, and Si / Al ratio. It is a graph which shows the relationship between the adsorption amount of hydrogen fluoride of the produced aluminum silicate compound composite, and Si / Al ratio.

Hereinafter, embodiments for carrying out the present invention will be described in detail. However, the present invention is not limited to the following embodiments. In the following embodiments, the components (including element steps and the like) are not essential unless otherwise specified. The same applies to numerical values and ranges thereof, and the present invention is not limited thereto.

In this specification, the term “process” includes a process that is independent of other processes and includes the process if the purpose of the process is achieved even if it cannot be clearly distinguished from the other processes. It is.
In the present specification, numerical values indicated by using “to” include numerical values described before and after “to” as the minimum value and the maximum value, respectively.
In the numerical ranges described stepwise in this specification, the upper limit value or the lower limit value described in one numerical range may be replaced with the upper limit value or the lower limit value of another numerical range. Good. Further, in the numerical ranges described in this specification, the upper limit value or the lower limit value of the numerical range may be replaced with the values shown in the examples.
In the present specification, the content rate or content of each component in the composition is such that when there are a plurality of substances corresponding to each component in the composition, the plurality of kinds present in the composition unless otherwise specified. It means the total content or content of substances.
In the present specification, the particle diameter of each component in the composition is a mixture of the plurality of types of particles present in the composition unless there is a specific indication when there are a plurality of types of particles corresponding to each component in the composition. Means the value of.
In this specification, the term “layer” or “film” refers to a part of the region in addition to the case where the layer or the film is formed when the region where the layer or film exists is observed. It is also included when it is formed only.
In this specification, the term “lamination” indicates that layers are stacked, and two or more layers may be combined, or two or more layers may be detachable.

<Materials for lithium ion secondary batteries>
The material for a lithium ion secondary battery of the present embodiment includes an aluminum silicate compound and a carbon, and an aluminum silicate compound composite having a total pore volume of 0.05 cm ³ / g or more measured by a nitrogen adsorption method Is the body.

The material for a lithium ion secondary battery according to the present embodiment is excellent in metal precipitation suppression ability. Therefore, in the lithium ion secondary battery manufactured using the lithium ion secondary battery material of the present embodiment, a decrease in capacity maintenance rate is suppressed. The reason is not necessarily clear, but the metal in the negative electrode or the like is absorbed by the aluminum silicate compound complex by adsorbing metal ions such as cobalt eluted from the positive electrode active material due to hydrogen fluoride generated in the electrolyte. It is presumed that the reprecipitation of ions is suppressed. In addition, it is estimated that elution of metal ions such as cobalt from the positive electrode active material is suppressed by adsorbing the hydrogen fluoride generated in the electrolytic solution to the aluminum silicate compound complex.

Furthermore, as a result of the study by the present inventors, when the total pore volume measured by the nitrogen adsorption method of the aluminum silicate compound complex is 0.05 cm ³ / g or more, a lithium ion secondary produced using this The battery was found to be superior in cycle characteristics and storage characteristics. The reason is not necessarily clear, but when the total pore volume measured by the nitrogen adsorption method of the aluminum silicate compound complex is 0.05 cm ³ / g or more, the adsorption ability of hydrogen fluoride and metal ions is more excellent. It is presumed that.

From the viewpoint of suppressing a fine short circuit due to metal deposition on the negative electrode, the total pore volume measured by the nitrogen adsorption method of the aluminum silicate compound composite is preferably 0.08 cm ³ / g or more.

The total pore volume measured by the nitrogen adsorption method of the aluminum silicate compound complex is measured from the nitrogen adsorption ability at 77K according to JIS Z 8830: 2001. As an evaluation apparatus, a nitrogen adsorption measuring apparatus (for example, BELSORP-miniII manufactured by Nippon Bell Co., Ltd.) or the like can be used.

When measuring the total pore volume, it is considered that the moisture adsorbed on the sample surface and in the structure affects the gas adsorption capacity. Therefore, pretreatment for removing moisture by heating is first performed. In the pretreatment, the measurement cell into which the measurement sample has been placed is kept under vacuum at 250 ° C. for 2 hours, and then naturally cooled to room temperature (25 ° C.) while maintaining the reduced pressure. After performing this pretreatment, the evaluation temperature is 77K, and the evaluation pressure range is measured as a relative pressure (equilibrium pressure with respect to saturated vapor pressure) of less than 1. The total pore volume is determined from the amount of adsorption when the relative pressure is 0.990.

The state of the aluminum silicate compound and carbon (arrangement relationship, etc.) in the aluminum silicate compound composite is not particularly limited. For example, it is preferable to provide carbon on an aluminum silicate compound, and it is more preferable to provide carbon on the surface of the aluminum silicate compound. Carbon may be provided in a part or all of the aluminum silicate compound.
Examples of the aluminum silicate compound composite include those in which all or part of the surface of the particulate aluminum silicate compound is coated with carbon.
The presence or absence of carbon in the aluminum silicate compound complex can be confirmed by, for example, laser Raman spectroscopy measurement with an excitation wavelength of 532 nm.

Examples of the aluminum silicate compound in the aluminum silicate compound composite include allophane, kaolin, zeolite, saponite and imogolite which are aluminum silicates. Among these, from the viewpoint of improving the cycle characteristics, an amorphous aluminum silicate compound whose specific surface area can be easily adjusted is preferable.

The amorphous aluminum silicate compound is an aluminum silicate having an element molar ratio Si / Al in the range of 0.3 to 5.0. The amorphous aluminum silicate compounds, _{_{_{_{e.g., nSiO 2 · Al 2 O 3}}}} · mH 2 O [n = 0.6 ~ 10.0, m = 0 or] include those having a composition represented by.

The amorphous aluminum silicate compound has a broad peak in the vicinity of 2θ = 10 ° to 30 ° in the powder X-ray diffraction spectrum using CuKα ray as the X-ray source, with no clear peak showing a mullite structure being observed. . As the X-ray diffractometer, for example, Geigerflex RAD-2X (manufactured by Rigaku Corporation) can be used. Specific measurement conditions are as follows.
-Measurement condition-
Divergence slit: 1 °
Scattering slit: 1 °
Receiving slit: 0.30mm
X-ray output: 40 kV, 40 mA

The amorphous aluminum silicate compound may be synthesized or a commercially available product may be used. When an amorphous aluminum silicate compound is synthesized, a step of mixing a solution containing silicate ions and a solution containing aluminum ions to obtain a reaction product, and the reaction product in an aqueous medium in the presence of an acid A step of heat treatment, and may include other steps as necessary. From the viewpoint of the yield of the reaction product obtained and structure formation, etc., a washing step for performing desalting and solid separation at least after the heat treatment step, preferably both before and after the heat treatment step. It is preferable to have.

After removing coexisting ions from the solution containing the reaction product by desalting, heat treatment is performed in the presence of an acid, so that an amorphous aluminum silicate compound having excellent adsorption ability for metal ions and hydrogen fluoride can be efficiently obtained. Can be manufactured. Examples of the coexisting ions include sodium ions, chloride ions, perchlorate ions, nitrate ions, sulfate ions and the like.

The method for providing carbon to the amorphous aluminum silicate compound is not particularly limited. For example, a method of coating an amorphous aluminum silicate compound with an organic compound (carbon precursor) that changes to a carbonaceous material by heat treatment and changing the carbon precursor to a carbonaceous material can be mentioned.

As a method of coating an amorphous aluminum silicate compound with a carbon precursor, a wet method in which an amorphous aluminum silicate compound is added to a carbon precursor dissolved or dispersed in a solvent and then the solvent is removed by heating or the like. Examples thereof include a dry method in which a mixture obtained by mixing a carbon precursor and an amorphous aluminum silicate compound with solids is kneaded while applying a shearing force, and a gas phase method such as a CVD method. From the viewpoint of cost and production process reduction, a dry method or a gas phase method without using a solvent is preferable.

The type of carbon precursor is not particularly limited. Examples thereof include ethylene heavy end pitch, crude oil pitch, coal tar pitch, asphalt cracking pitch, pitch generated by thermal decomposition of polyvinyl chloride and the like, and synthetic pitch obtained by polymerizing naphthalene or the like in the presence of a super strong acid. Moreover, polyvinyl chloride, polyvinyl alcohol, polyvinyl acetate, polyvinyl butyral, etc. can be used as a thermoplastic carbon precursor, and a phenol resin, a furan resin, etc. can be used as a thermosetting carbon precursor.

As a method for changing the carbon precursor to carbonaceous, there is a method of heating in an inert atmosphere. The heating conditions in this case are not particularly limited and can be determined in consideration of the carbonization rate of the carbon precursor. For example, it is preferable to heat in the range of 800 ° C. to 1300 ° C. in an inert atmosphere. When the heating temperature is 800 ° C. or higher, carbonization of the carbon precursor proceeds sufficiently, the specific surface area of the aluminum silicate compound composite does not become too large, and the initial irreversible capacity tends not to increase. When the heating temperature is 1300 ° C. or lower, the specific surface area does not become too small, and the resistance does not easily increase. Examples of the inert atmosphere include nitrogen, argon, helium, and mixed gases thereof.

In the aluminum silicate compound composite, the element molar ratio of silicon to aluminum (Si / Al ratio) is preferably 1.0 to 5.0, and more preferably 1.5 to 3.0.

The Si / Al ratio of the aluminum silicate compound composite can be calculated from the values obtained for silicon and aluminum by conducting elemental analysis of the measurement sample. Elemental analysis can be performed by inductively coupled plasma (ICP) emission spectroscopy.

As an apparatus used for elemental analysis by ICP emission spectroscopic analysis, for example, “P-4010” of Hitachi, Ltd. may be mentioned.

The aluminum silicate compound complex preferably has a chlorine ratio (RCl) of 1% or less, more preferably 0.1% or less, and even more preferably less than 0.1%. When the chlorine ratio (RCl) is 1% or less, there is a tendency that a decrease in life due to deterioration (elution, film formation, etc.) of the positive electrode active material caused by a chlorine-derived compound (hydrogen chloride or the like) tends to be suppressed. Further, when the chlorine ratio (RCl) is less than 0.1%, the expansion of the battery due to the gas generated by the reaction between chlorine and the electrolytic solution tends to be suppressed.

In the present specification, the chlorine ratio (RCl) means the ratio (%) of the Cl content to the total content of Al and Si in the aluminum silicate compound composite. Specifically, it is a value calculated by the following equation (1) from values obtained for each element by performing elemental analysis in the measurement sample. Elemental analysis can be measured using the same method and apparatus as the Si / Al ratio.

RCl (%) = (Cl ratio (mass%)) / (Al ratio (mass%) + Si ratio (mass%)) × 100 (1)

Aluminum silicate compound complex is calculated and the peak area A of the oxidation point in the vicinity of 1490cm ^-1, which derived from pyridine adsorption IR spectrum, the following equation from the peak area B of the hydrogen bonds in the vicinity of 1446cm ^-1 (2) The oxidation point ratio (RA) is preferably less than 25%, and more preferably less than 20%.
RA (%) = A / B × 100 (2)

When the ratio (RA) of the oxidation point of the aluminum silicate compound complex is less than 25%, it becomes difficult to adsorb water, and the lifetime tends to be suppressed. In addition, when the oxidation point ratio (RA) is less than 20%, the expansion of the battery caused by the reaction between the functional group of the aluminum silicate compound complex and the electrolytic solution tends to be suppressed.

The oxidation point of the aluminum silicate compound complex can be measured from a pyridine adsorption IR spectrum obtained by infrared spectroscopy. The pyridine adsorption IR spectrum can be obtained using, for example, a Fourier transform infrared spectrophotometer (for example, “Cary670” manufactured by Agilent Technologies).

Specifically, the oxidation point of the aluminum silicate compound complex is measured as follows.
The cell filled with the sample is evacuated at 500 ° C. for 1 hour and then cooled to 30 ° C. Next, pyridine gas is introduced into the cell while being heated to 100 ° C., and is adsorbed for 5 minutes. Then, the physisorbed pyridine is removed by heating to 150 ° C. and exhausting for 60 minutes. Subsequently, it cools to 30 degreeC and measures an IR spectrum.

From the obtained IR spectrum, the peak area A of the oxidation point and the peak area B of the hydrogen bond are calculated by the following method, and the values calculated by the equation (2) using the calculated peak areas are the oxidation points. The ratio (RA).

(Calculation of peak area A of oxidation point)
A baseline is drawn with a straight line in the region of IR spectrum from 1485 cm ⁻¹ to 1500 cm ⁻¹ . The maximum peak in the vicinity of 1490 cm ^{−1 is} separated using a Gaussian function, and the area of the portion surrounded by the baseline is obtained.
(Calculation of hydrogen bond peak area B)
Subtracting a baseline in a straight line from 1430 cm ^-1 of the IR spectrum in the region of 1460 cm ^-1. The maximum peak near 1446 cm ^{−1 in the} meantime is separated using a Gaussian function, and the area of the portion surrounded by the baseline is obtained.

From the viewpoints of input / output characteristics and cycle characteristics, the mass reduction rate between 350 ° C. and 850 ° C. measured using differential thermal-thermogravimetric analysis (TG-DTA) of the aluminum silicate compound composite is 0. 5% to 30% is preferable, 2% to 25% is more preferable, and 5% to 20% is still more preferable. When the mass reduction rate of 350 ° C. to 850 ° C. is within the above range, the resistance increase due to the reaction between the surface of the aluminum silicate compound composite and the electrolyte tends to be suppressed, and hydrogen fluoride and metal ions It tends to be more excellent in adsorbing ability.

The mass reduction rate of 350 ° C. to 850 ° C. of the aluminum silicate compound composite is the value obtained by the following formula (3).

Mass reduction rate (%) = {(W1-W2) / W1} × 100 (3)

In Formula (3), W1 is the mass (g) of the measurement target after being heated from 25 ° C. to 350 ° C. at a rate of temperature increase of 10 ° C./min under a circulation of dry air and held at 350 ° C. for 20 minutes. , W2 is the mass (g) of the object to be measured after raising the temperature from 350 ° C. to 850 ° C. at a rate of temperature rise of 10 ° C./min under a circulation of dry air and holding at 850 ° C. for 20 minutes.

Examples of the apparatus used for analysis by TG-DTA include “TG-DTA-6200 type” manufactured by SII NanoTechnology Co., Ltd.

When the aluminum silicate compound composite is a particle, the volume average particle diameter (D50) measured by the laser diffraction particle size distribution analyzer is selected according to the desired size of the aluminum silicate compound composite, and 0 It is preferably 1 μm to 50 μm, more preferably 0.2 μm to 20 μm, and even more preferably 0.5 μm to 10 μm.

If the volume average particle diameter (D50) of the aluminum silicate compound composite is 0.1 μm or more, the viscosity of the positive electrode mixture does not become too high when a positive electrode is prepared using the positive electrode mixture described later, Tend to be well maintained. When the volume average particle diameter (D50) of the aluminum silicate compound composite is 50 μm or less, streaks tend not to be drawn when the positive electrode mixture is applied onto the current collector.

The volume average particle diameter (D50) of the aluminum silicate compound composite is preferably 0.5 μm or more from the viewpoint of cost reduction required for grinding, and from the viewpoint of the efficiency of adsorption of hydrogen fluoride and metal ions. It is preferable that it is 10 micrometers or less.

The volume average particle diameter (D50) of the aluminum silicate compound composite is measured using a laser diffraction method. The measurement by the laser diffraction method can be performed using, for example, a laser diffraction particle size distribution measuring apparatus (SALD3000J, Shimadzu Corporation). Specifically, an aluminum silicate compound complex is dispersed in a dispersion medium such as water to prepare a dispersion, and a volume cumulative distribution curve is measured from the small diameter side from the small diameter side of this dispersion using a laser diffraction particle size distribution analyzer. When drawn, the particle diameter (D50) when the cumulative volume is 50% is determined as the volume average particle diameter.

The BET specific surface area of the aluminum silicate compound composite is preferably 80 m ² / g or less, more preferably 40 m ² / g or less, and 20 m ² / g or less from the viewpoint of cycle characteristics and storage characteristics. More preferably it is. The lower limit of the BET specific surface area is not particularly limited, but is preferably 1 m ² / g or more and more preferably 2 m ² / g or more from the viewpoint of improving the adsorption ability for hydrogen fluoride and metal ions. , even more preferably ^3m 2 / g or more.

The BET specific surface area of the aluminum silicate compound composite is measured from the nitrogen adsorption capacity according to JIS Z 8830 (2001). As the evaluation device, for example, a nitrogen adsorption measuring device (AUTOSORB-1, QUANTACHROME) or the like can be used. When measuring the BET specific surface area, it is assumed that the moisture adsorbed on the sample surface and structure affects the gas adsorption capacity. Therefore, first, pretreatment for removing moisture by heating is performed. .

In the pretreatment, a measurement cell charged with 0.05 g of a measurement sample is depressurized to 10 Pa or less with a vacuum pump and then heated at 110 ° C. After maintaining in this state for 3 hours or longer, the product is naturally cooled to room temperature (25 ° C.) while maintaining the reduced pressure state. After performing this pretreatment, the evaluation temperature is 77K, and the evaluation pressure range is measured as a relative pressure (equilibrium pressure with respect to saturated vapor pressure) of less than 1.

<Positive electrode mixture>
The positive electrode mixture of the present embodiment contains the lithium ion secondary battery material of the present embodiment and the positive electrode active material. In a lithium ion secondary battery having a positive electrode formed using the positive electrode mixture of the present embodiment, a decrease in capacity maintenance rate is suppressed.

Details and preferred aspects of the lithium ion secondary battery material contained in the positive electrode mixture are the same as those described for the lithium ion secondary battery material of the present embodiment. The details and preferred embodiments of the positive electrode active material contained in the positive electrode mixture are the same as those described for the lithium ion secondary battery described later. The positive electrode mixture may include other materials such as a conductive material, a binder, a thickener, and a dispersion solvent as necessary. Details and preferred embodiments of the other materials are the same as those described for the lithium ion secondary battery described later.

The content of the lithium ion secondary battery material in the positive electrode mixture may be, for example, 0.01% by mass to 10% by mass with respect to the total amount of the positive electrode mixture, and 0.05% by mass to 5% by mass. It is preferable that Further, the mass ratio of the lithium ion secondary battery material and the positive electrode active material in the positive electrode mixture (lithium ion secondary battery material / positive electrode active material) may be, for example, 0.009 to 9.8, It is preferably 0.045 to 4.9.

<Positive electrode for lithium ion secondary battery>
The positive electrode for a lithium ion secondary battery of the present embodiment contains the material for a lithium ion secondary battery of the present embodiment. The positive electrode for lithium ion secondary batteries can be manufactured by a well-known method using the positive electrode compound material of this embodiment, for example.

<Lithium ion secondary battery>
The lithium ion secondary battery of this embodiment is provided with the positive electrode for lithium ion secondary batteries of this embodiment. In the lithium ion secondary battery of the present embodiment, the capacity maintenance rate is prevented from decreasing.

First, an outline of the lithium ion secondary battery of this embodiment will be briefly described. A lithium ion secondary battery has a positive electrode and a negative electrode, and a separator through which lithium ions can pass is usually disposed between the positive electrode and the negative electrode.

When charging a lithium ion secondary battery, a charger is connected between the positive electrode and the negative electrode. At the time of charging, lithium ions inserted into the positive electrode active material of the positive electrode are desorbed and released into the electrolytic solution. The lithium ions released into the electrolytic solution move through the electrolytic solution, pass through the separator, and reach the negative electrode. The lithium ions that have reached the negative electrode are inserted into the negative electrode active material of the negative electrode.

When discharging a lithium ion secondary battery, an external load is connected between the positive electrode and the negative electrode. At the time of discharge, lithium ions inserted into the negative electrode active material of the negative electrode are desorbed and released into the electrolyte. At this time, electrons are emitted from the negative electrode. The lithium ions released into the electrolytic solution move in the electrolytic solution, pass through the separator, and reach the positive electrode. The lithium ions that have reached the positive electrode are inserted into the positive electrode active material of the positive electrode. When lithium ions are inserted into the positive electrode active material, electrons flow into the positive electrode. In this way, discharge is performed by the movement of electrons from the negative electrode to the positive electrode.

As described above, charging / discharging is performed by inserting or desorbing lithium ions between the positive electrode active material and the negative electrode active material. A configuration example of an actual lithium ion secondary battery will be described later (see, for example, FIG. 1). Hereinafter, the positive electrode, negative electrode, electrolytic solution, separator, and other components of the lithium ion secondary battery will be described.

1. Positive electrode The positive electrode includes the lithium ion secondary battery material of the present embodiment and a positive electrode active material. Specifically, for example, the positive electrode has a current collector and a positive electrode mixture layer provided on both sides or one side of the current collector, and the positive electrode mixture layer is for the lithium ion secondary battery of the present embodiment. A material and a positive electrode active material. The positive electrode mixture layer may include other materials such as a conductive material, a binder, a thickener, and a dispersion solvent as necessary.

(Positive electrode active material)
Only one type or two or more types of positive electrode active materials included in the positive electrode may be used. From the viewpoint of improving the energy density, it is preferable to include a lithium-containing composite metal oxide or a lithium-containing phosphate compound. The lithium-containing composite metal oxide or lithium-containing phosphate compound is a metal oxide or phosphate compound containing lithium and a metal other than lithium. The metal other than lithium contained in the lithium-containing composite metal oxide or the lithium-containing phosphate compound may be only one kind or two or more kinds.

The lithium-containing composite metal oxide is preferably a metal oxide containing lithium and at least one transition metal selected from Co, Ni, and Mn. In the metal oxide containing lithium and a transition metal, part of the transition metal may be substituted with an element (heterogeneous element) different from the transition metal. Specific examples of the different elements include Na, Mg, Sc, Y, Mn, Fe, Co, Ni, Cu, Zn, Al, Cr, Pb, Sb, and B. Mn, Al, Co, Ni, and the like At least one selected from the group consisting of Mg is preferred.

Examples of the lithium-containing composite metal oxide include Li _x CoO ₂ , Li _x NiO ₂ , Li _x MnO ₂ , Li _x Co _y Ni _1-y O ₂ , and Li _x Co _y M ¹ _1-y O _z (Li _{In x} Co _y M ¹ _1-y O _z , M ¹ is at least one selected from the group consisting of Na, Mg, Sc, Y, Mn, Fe, Cu, Zn, Al, Cr, Pb, Sb, V, and B Li _x Ni _1-y M ² _y O _z (in Li _x Ni _1-y M ² _y O _z , M ² is Na, Mg, Sc, Y, Mn, Fe, Cu, Represents at least one element selected from the group consisting of Zn, Al, Cr, Pb, Sb, V and B.), Li _x Mn ₂ O ₄ and Li _x Mn _2-y M ³ _y O ₄ (Li _x In Mn _2-y M ³ _y O ₄ , M ³ is Na, Mg, Sc, Y, Fe, Co, Cu, Zn, Al, Cr, Pb, Sb, at least one element selected from the group consisting of V and B.). Here, x is in the range of 0 <x ≦ 1.2, y is in the range of 0 to 0.9, and z is in the range of 2.0 to 2.3. Further, the x value indicating the molar ratio of lithium increases or decreases due to charge / discharge.

Examples of the lithium-containing phosphate compound include LiMPO ₄ and Li ₂ MPO ₄ F (in the above formulas, M is Na, Mg, Sc, Y, Mn, Fe, Co, Ni, Cu, Zn, Al, Cr, And at least one element selected from the group consisting of Pb, Sb, V and B.). As the lithium-containing phosphate compound, an olivine type lithium salt is preferable, and LiFePO ₄ is more preferable.

The positive electrode active material may contain a compound other than the lithium-containing composite metal oxide or the lithium-containing phosphate compound. Examples of such compounds include chalcogen compounds and manganese dioxide. Examples of the chalcogen compound include titanium disulfide and molybdenum disulfide.

The positive electrode active material may be in the form of particles, and is preferably in a state of secondary particles formed by aggregation of primary particles. When the positive electrode active material is in the state of secondary particles, expansion and contraction of the positive electrode active material due to charge / discharge are alleviated compared to the case where the positive electrode active material is only primary particles, and positive electrode active due to stress caused by expansion and contraction is reduced. There is a tendency that deterioration such as destruction of a substance and cutting of a conductive path hardly occurs.

When the positive electrode active material is in the form of particles, the shape is not particularly limited, and examples thereof include a lump shape, a polyhedron shape, a spherical shape, an elliptical spherical shape, a flake shape, a needle shape, and a column shape. Of these, spherical or elliptical spheres are preferred. When the shape of the positive electrode active material is spherical or elliptical, the degree of orientation of the positive electrode active material in the electrode is smaller than when the plate has a large aspect ratio, such as a plate shape, and the expansion of the electrode during charge / discharge Shrinkage tends to be suppressed. Further, when preparing the positive electrode mixture, it tends to be easily mixed with other materials such as a conductive material. For the definition of the shape when the positive electrode active material is particulate, the definition of the shape when the conductive material described later is particulate can be referred to.

The positive electrode active material is preferably in the form of secondary particles formed by aggregation of primary particles, and the shape of the secondary particles is preferably spherical or elliptical.

The volume average particle diameter (D50) measured with a laser diffraction particle size distribution analyzer of the positive electrode active material is not particularly limited. From the viewpoint of easily obtaining a desired tap density, the volume average particle diameter (D50) of the positive electrode active material may be 0.1 μm or more, preferably 0.5 μm or more, and more preferably 1 μm or more. Preferably, it is 3 μm or more. From the viewpoint of improving electrode formability and battery performance, the volume average particle diameter (D50) of the positive electrode active material may be 20 μm or less, preferably 18 μm or less, more preferably 16 μm or less, and more preferably 15 μm. More preferably, it is as follows.

The volume average particle diameter (D50) of the positive electrode active material means the volume average particle diameter (D50) of the secondary particles when the positive electrode active material is in the state of secondary particles. The volume average particle diameter (D50) of the positive electrode active material is measured in the same manner as the volume average particle diameter (D50) of the lithium ion secondary battery material (aluminum silicate compound composite) of the present embodiment.

When the positive electrode active material is in a secondary particle state, the average particle diameter of the primary particles forming the secondary particles is not particularly limited. From the viewpoint of improving the reversibility of charge and discharge, the average particle diameter of the primary particles may be 0.01 μm or more, preferably 0.05 μm or more, more preferably 0.08 μm or more, 0 More preferably, it is 1 μm or more. From the viewpoint of improving battery performance such as output characteristics, the average particle size of the primary particles may be 3 μm or less, preferably 2 μm or less, more preferably 1 μm or less, and 0.6 μm or less. More preferably.

The average particle diameter of the primary particles when the positive electrode active material is in the state of secondary particles is, for example, scanning electron microscope / energy dispersive X-ray spectroscopy (SEM-EDX), transmission electron microscope / energy dispersive X It can be measured by line spectroscopy (TEM-EDX) or the like.

The BET specific surface area of the positive electrode active material is not particularly limited. From the viewpoint of improving battery performance, the BET specific surface area of the positive electrode active material is preferably 0.1 m ² / g or more, more preferably 0.2 m ² / g or more, and 0.3 m ² / g. More preferably, it is the above. From the viewpoint of electrode formability, the BET specific surface area of the positive electrode active material is preferably 4.0 m ² / g or less, more preferably 2.5 m ² / g or less, and 1.5 m ² / g or less. More preferably.

The BET specific surface area of the positive electrode active material is measured by the same method as the method for measuring the BET specific surface area of the aluminum silicate compound composite described above.

(Conductive material)
The positive electrode preferably contains a conductive material from the viewpoint of improving battery performance. Examples of the conductive material include natural graphite, artificial graphite, graphite such as fibrous graphite, carbon black, and the like. Among the carbon blacks, acetylene black is preferable from the viewpoint of improving input / output characteristics.

When carbon black is used as the conductive material, from the viewpoint of dispersibility in the positive electrode mixture and input / output characteristics of the battery, the carbon black is preferably particles having an average particle diameter of 20 nm to 100 nm, and the average particle diameter is More preferred are particles of 30 nm to 80 nm, and even more preferred are particles having an average particle size of 40 nm to 60 nm.

When graphite is included as the conductive material, the graphite is preferably particles having an average particle diameter of 1 μm to 10 μm. Further, the graphite preferably has a carbon network plane interlayer (d002) in the X-ray wide angle diffraction method of 0.3354 nm to 0.337 nm.

The average particle diameter of the conductive material is an arithmetic average value of values measured for all particle images in the image taken with a scanning electron microscope taken at 200,000 times.

When the conductive material is particles, the shape is not particularly limited, and examples thereof include particles, flakes, spheres, columns, irregular shapes, and the like. Here, “particulate” is not an irregular shape but a shape having substantially the same dimensions (JIS Z2500: 2000). The flake shape (strip shape) is a plate-like shape (JIS Z2500: 2000) and is also referred to as a scaly shape because it is thin like a scale. In this embodiment, a scanning electron microscope is used. Analysis is performed from the observation results of the above, and particles having an aspect ratio (particle diameter a / average thickness t) in the range of 2 to 100 are formed into flakes. The particle diameter a here is defined as the value of the square root of the area S when the flaky particles are viewed in plan. “Spherical” means a shape almost similar to a sphere (see JIS Z2500: 2000). Further, the shape does not necessarily need to be spherical, and the ratio of the major axis (DL) to the minor axis (DS) of the particle (DL) / (DS) (sometimes referred to as spherical coefficient or sphericity) is 1. Those in the range of 0.0 to 1.2 are included in “spherical”. When the particles are spherical, the major axis (DL) is taken as the particle size. Examples of the columnar shape include a substantially circular column and a substantially polygonal column. When the particles are columnar, the height of the column is the particle size.

When using a conductive material, the content is preferably 0.1% by mass or more, more preferably 0.2% by mass or more, and more preferably 0.5% by mass or more with respect to the total amount of the positive electrode mixture. More preferably. The upper limit of the content of the conductive material is preferably 30% by mass or less, more preferably 20% by mass or less, and further preferably 10% by mass or less. When the content of the conductive material is within the above range, the battery capacity and input / output characteristics tend to be more excellent.

(Binder)
The positive electrode preferably includes a binder from the viewpoint of obtaining adhesion between the positive electrode mixture, the current collector, and the positive electrode active material. The kind of binder is not particularly limited. Specific examples include resin polymers such as polyethylene, polypropylene, polyethylene terephthalate, polymethyl methacrylate, polyimide, aromatic polyamide, cellulose, and nitrocellulose; SBR (styrene-butadiene rubber), NBR (acrylonitrile-butadiene rubber), fluorine Rubbery polymers such as rubber, isoprene rubber, butadiene rubber, ethylene-propylene rubber; styrene / butadiene / styrene block copolymer or its hydrogenated product, EPDM (ethylene / propylene / diene terpolymer), styrene / Thermoplastic elastomeric polymers such as ethylene / butadiene / ethylene copolymers, styrene / isoprene / styrene block copolymers or hydrogenated products thereof; syndiotactic-1,2-polybutadiene, polyvinyl acetate , Ethylene / vinyl acetate copolymer, propylene / α-olefin copolymer and other soft resinous polymers; polyvinylidene fluoride (PVdF), polytetrafluoroethylene, fluorinated polyvinylidene fluoride, polytetrafluoroethylene / ethylene copolymer Examples thereof include fluorine polymers such as polymers and polytetrafluoroethylene / vinylidene fluoride copolymers; polymer compositions having ion conductivity of alkali metal ions (particularly lithium ions).

The binder may be used alone or in combination of two or more. From the viewpoint of the stability of the positive electrode, it is preferable to use a fluorine-based polymer such as polyvinylidene fluoride (PVdF) or a polytetrafluoroethylene / vinylidene fluoride copolymer. When the positive electrode mixture layer is formed on the current collector by a wet method, it is preferable to select a binder having good solubility or dispersibility in the dispersion solvent contained in the positive electrode mixture.

When the positive electrode mixture includes a binder, the content is preferably 0.5% by mass or more, more preferably 1% by mass or more, and more preferably 2% by mass with respect to the total amount of the positive electrode mixture. More preferably, it is the above. The upper limit of the binder content is preferably 50% by mass or less, more preferably 40% by mass or less, further preferably 30% by mass or less, and preferably 10% by mass or less. Particularly preferred. By making the content rate of a binder into the said range, it exists in the tendency which is excellent by battery performance, such as cycling characteristics.

(Dispersion solvent)
When the positive electrode mixture is in a slurry state, a dispersion solvent may be included.
The dispersion solvent is not particularly limited as long as it can dissolve or disperse the material contained in the positive electrode mixture, and may be an aqueous solvent or an organic solvent.
Examples of the aqueous solvent include water, a mixed solvent of alcohol and water, and examples of the organic solvent include N-methyl-2-pyrrolidone (NMP), dimethylformamide, dimethylacetamide, methyl ethyl ketone, cyclohexanone, methyl acetate, and acrylic. Methyl acid, diethyltriamine, N, N-dimethylaminopropylamine, tetrahydrofuran (THF), toluene, acetone, diethyl ether, dimethylacetamide, hexamethylphosphalamide, dimethyl sulfoxide, benzene, xylene, quinoline, pyridine, methyl Naphthalene, hexane, etc. are mentioned.

When the positive electrode mixture is in a slurry state, a thickener may be included to adjust the viscosity. The thickener is not particularly limited, and examples thereof include polymer compounds such as carboxymethyl cellulose, methyl cellulose, hydroxymethyl cellulose, ethyl cellulose, polyvinyl alcohol, oxidized starch, phosphorylated starch, and casein, and salts of these polymer compounds. A thickener may be used individually by 1 type, or may be used in combination of 2 or more type.

When the positive electrode mixture contains a thickener, the content is not particularly limited. From the viewpoint of applicability of the positive electrode mixture, it is preferably 0.1% by mass or more, more preferably 0.2% by mass or more, and more preferably 0.5% by mass or more with respect to the total amount of the positive electrode mixture. More preferably. From the viewpoint of suppressing a decrease in battery capacity or an increase in resistance between the positive electrode active materials, the content of the thickener is preferably 5% by mass or less with respect to the total amount of the positive electrode mixture, and 3% by mass or less. More preferably, it is more preferably 2% by mass or less.

(Current collector)
The material of the current collector is not particularly limited, and examples thereof include metal materials such as aluminum, stainless steel, nickel-plated steel, titanium, and tantalum, and carbonaceous materials such as carbon cloth and carbon paper. Of these, metal materials are preferable, and aluminum is more preferable.

The shape of the current collector is not particularly limited, and materials processed into various shapes can be used. Examples of the shape when the current collector is a metal material include metal foil, metal cylinder, metal coil, metal plate, metal thin film, expanded metal, punch metal, and foam metal. Examples of the shape when the current collector is a carbonaceous material include a carbon plate, a carbon thin film, and a carbon cylinder. Among these, a metal thin film is preferable. The thin film may be mesh.

When the shape of the current collector is a thin film, the thickness is not particularly limited. From the viewpoint of obtaining sufficient strength as a current collector, the thickness of the current collector may be 1 μm or more, preferably 3 μm or more, and more preferably 5 μm or more. From the viewpoint of obtaining sufficient flexibility and workability, the thickness of the current collector may be 1 mm or less, preferably 100 μm or less, and more preferably 50 μm or less.

As a method of forming a positive electrode mixture layer using a positive electrode mixture on a current collector, a method of forming the positive electrode mixture into a sheet shape and press-bonding it to the current collector (dry method), a slurry-like positive electrode Examples thereof include a method (wet method) in which a composite material is applied to a current collector and dried.

The positive electrode mixture layer formed on the current collector is preferably consolidated by a hand press, a roller press or the like in order to improve the packing density of the positive electrode active material.

From the viewpoint of input / output characteristics, the density of the positive electrode mixture layer is preferably 3.0 g / cm ³ to 4.0 g / cm ³ . Further, the single-side coating amount on the current collector (in the case of a wet method, the single-side coating amount after drying) is preferably 100 g / m ² to 300 g / m ² .

2. Negative electrode The negative electrode contains a negative electrode active material. Specifically, for example, the negative electrode includes a current collector and a negative electrode mixture layer provided on both sides or one side of the current collector, and the negative electrode mixture layer includes a negative electrode active material. The negative electrode may include other materials such as a conductive material, a binder, a thickener, and a dispersion solvent as necessary.

(Negative electrode active material)
The negative electrode active material is not particularly limited as long as it is a material that can occlude and release lithium ions. For example, carbonaceous materials, metal composite oxides, oxides or nitrides of Group 4 elements such as tin, germanium, and silicon, lithium alone, lithium alloys such as lithium aluminum alloys, and alloys with lithium such as Sn and Si Possible substances are listed. From the viewpoint of safety, at least one selected from the group consisting of a carbonaceous material and a metal composite oxide is preferable. A negative electrode active material may be used individually by 1 type, and may be used in combination of 2 or more type. The negative electrode active material may be in the form of particles, for example.

Examples of carbonaceous materials include amorphous carbon materials, natural graphite, composite carbonaceous materials in which a film of amorphous carbon material is formed on natural graphite, artificial graphite (resin raw materials such as epoxy resins and phenol resins, or petroleum, And obtained by firing a pitch-based raw material obtained from coal or the like.

From the viewpoint of charge / discharge characteristics at a high current density, the metal composite oxide preferably contains one or both of titanium and lithium, and more preferably contains lithium.

Among the negative electrode active materials, carbonaceous materials have high conductivity and are particularly excellent in low temperature characteristics and cycle stability. Among the carbonaceous materials, graphite is preferable from the viewpoint of increasing the capacity. Graphite preferably has a carbon network plane interlayer (d002) of less than 0.34 nm in the X-ray wide angle diffraction method, more preferably 0.3354 nm or more and 0.337 nm or less. A carbonaceous material that satisfies such conditions may be referred to as pseudo-anisotropic carbon.

(Conductive material)
The negative electrode mixture containing the negative electrode active material may further contain a conductive material. As the conductive material, a highly conductive carbonaceous material such as graphitic carbon material, amorphous carbon material, activated carbon, or the like can be used. Specific examples include graphite (graphite) such as natural graphite and artificial graphite, carbon black such as acetylene black, and amorphous carbon material such as needle coke. A conductive material may be used individually by 1 type, and may be used in combination of 2 or more type. When the negative electrode mixture contains a conductive material, effects such as reduction of the resistance of the electrode tend to be obtained.

When a carbonaceous material is used as the negative electrode active material and a carbonaceous material is used as the conductive material, the conductive material is a carbonaceous material having different properties from the carbonaceous material (first carbonaceous material) used as the negative electrode active material ( The second carbonaceous material) is preferable. Examples of the properties include X-ray diffraction parameters, median diameter, aspect ratio, BET specific surface area, orientation ratio, Raman R value, tap density, true density, pore distribution, circularity, and ash content. Exhibit one or more characteristics.

When the negative electrode composite contains a conductive material, the content is not particularly limited. From the viewpoint of improving the conductivity, the content of the conductive material may be 1% by mass or more, preferably 2% by mass or more, and preferably 3% by mass or more with respect to the total amount of the negative electrode mixture. Is more preferable. From the viewpoint of suppressing an increase in initial irreversible capacity, the content of the conductive material may be 45% by mass or less, and preferably 40% by mass or less, with respect to the total amount of the negative electrode mixture.

(Binder)
The negative electrode mixture may contain a binder. The binder is not particularly limited, and examples thereof include those exemplified as the binder that may be included in the positive electrode mixture. A binder may be used individually by 1 type, and may be used in combination of 2 or more type.

When the negative electrode mixture contains a binder, the content is not particularly limited. From the viewpoint of suppressing a decrease in the strength of the negative electrode composite material, the content of the binder is preferably 0.1% by mass or more and 0.2% by mass or more with respect to the total amount of the negative electrode composite material. It is more preferable that the content is 0.5% by mass or more. From the viewpoint of suppressing a decrease in battery capacity due to an increase in the ratio of the binder that does not contribute to the battery capacity, the content of the binder is 20% by mass or less with respect to the total amount of the negative electrode mixture. It is preferably 15% by mass or less, more preferably 10% by mass or less, and further preferably 8% by mass or less.

When a rubbery polymer represented by styrene-butadiene rubber (SBR) is used as the main component of the binder, the content of the binder is 0.1% by mass or more based on the total amount of the negative electrode mixture. It may be 0.2% by mass or more, and more preferably 0.5% by mass or more. Moreover, it may be 5 mass% or less with respect to the total amount of negative electrode compound materials, it is preferable that it is 3 mass% or less, and it is more preferable that it is 2 mass% or less.

When a fluorine-based polymer typified by polyvinylidene fluoride is used as the main component of the binder, the content of the binder may be 1% by mass or more based on the total amount of the negative electrode mixture, and 2% by mass. Preferably, it is preferably 3% by mass or more. Moreover, it may be 15 mass% or less with respect to the total amount of negative electrode compound materials, it is preferable that it is 10 mass% or less, and it is more preferable that it is 8 mass% or less.

(Thickener)
The negative electrode mixture may contain a thickener in order to adjust the viscosity. The thickener is not particularly limited, and examples thereof include carboxymethyl cellulose, methyl cellulose, hydroxymethyl cellulose, ethyl cellulose, polyvinyl alcohol, oxidized starch, phosphorylated starch, casein, and salts thereof. A thickener may be used individually by 1 type, or may be used in combination of 2 or more type.

When the negative electrode mixture contains a thickener, the content is not particularly limited. From the viewpoint of the applicability of the negative electrode mixture, the content of the thickener may be 0.1% by mass or more, preferably 0.2% by mass or more, and more preferably 0.5% by mass or more. Is more preferable. From the viewpoint of suppressing a decrease in battery capacity or an increase in resistance between the negative electrode active materials, the content of the thickener may be 5% by mass or less, preferably 3% by mass or less, and preferably 2% by mass or less. It is more preferable that

(Current collector)
The material of the current collector used for the negative electrode is not particularly limited, and examples thereof include metal materials such as copper, nickel, stainless steel, and nickel-plated steel. Among these, copper is preferable from the viewpoint of ease of processing and cost.

The shape of the current collector is not particularly limited, and materials processed into various shapes can be used. Specific examples include metal foil, metal cylinder, metal coil, metal plate, metal thin film, expanded metal, punch metal, and foam metal. Among these, a metal thin film is preferable, and a copper foil is more preferable. The copper foil includes a rolled copper foil formed by a rolling method and an electrolytic copper foil formed by an electrolytic method, both of which are suitably used as a current collector.

The thickness of the current collector is not particularly limited, but when the thickness is less than 25 μm, it is stronger to use a strong copper alloy (phosphor bronze, titanium copper, Corson alloy, Cu—Cr—Zr alloy, etc.) than pure copper. From the viewpoint of

A method for producing a negative electrode by using a negative electrode mixture and a current collector is not particularly formed. For example, it can be produced by forming a negative electrode mixture layer on a current collector using a negative electrode mixture in the same manner as the positive electrode described above.

3. Electrolytic Solution The electrolytic solution includes an electrolyte and a non-aqueous solvent that dissolves the electrolyte. The electrolytic solution may contain an additive as necessary. An electrolyte may be used individually by 1 type, or may be used in combination of 2 or more type. Moreover, as electrolyte solution, what contains a fluorine-containing electrolyte is preferable.

The electrolyte preferably contains a lithium salt, and more preferably contains lithium hexafluorophosphate (LiPF ₆ ). When the electrolyte comprises a LiPF _6, even using only LiPF _6, it may be used in combination of a lithium salt other than LiPF _6.

The lithium salt other than _{_{_{LiPF 6, LiBF 4, LiAsF 6}}} , LiSbF ₆ such as inorganic fluoride _salts; inorganic chloride salts such as _{_{LiAlCl 4;; LiClO 4, LiBrO}} 4, perhalogenate of LiIO ₄ such LiCF ₃ Perfluoroalkane sulfonates such as SO ₃ ; perfluoro such as LiN (CF ₃ SO ₂ ) ₂ , LiN (CF ₃ CF ₂ SO ₂ ) ₂ , LiN (CF ₃ SO ₂ ) (C ₄ F ₉ SO ₉ ) Alkanesulfonylimide salt; Perfluoroalkanesulfonylmethide salt such as LiC (CF ₃ SO ₂ ) ₃ ; Li [PF ₅ (CF ₂ CF ₂ CF ₃ )], Li [PF ₄ (CF ₂ CF ₂ CF ₃ ) ₂ ], Li [PF ₃ (CF ₂ CF ₂ CF ₃ ) ₃ ], Li [PF ₅ (CF ₂ CF ₂ CF ₂ CF ₃ )], L fluoroalkyl fluorophosphates such as i [PF ₄ (CF ₂ CF ₂ CF ₂ CF ₃ ) ₂ ], Li [PF ₃ (CF ₂ CF ₂ CF ₂ CF ₃ ) ₃ ]; lithium bis (oxalato) borate, Examples include lithium difluorooxalatoborate.

When the electrolyte contains LiPF ₆ and a lithium salt other than this, the content of LiPF ₆ is preferably 10% by mass or more, and preferably 50% by mass or more of the entire lithium salt from the viewpoint of battery performance. More preferred.

The concentration of the electrolyte in the electrolytic solution is not particularly limited. From the viewpoint of sufficiently obtaining the electric conductivity of the electrolytic solution, it may be 0.5 mol / L or more, preferably 0.6 mol / L or more, and more preferably 0.7 mol / L or more. From the viewpoint of suppressing a decrease in electrical conductivity due to an increase in the viscosity of the electrolytic solution, it may be 2 mol / L or less, preferably 1.8 mol / L or less, and more preferably 1.7 mol / L or less. preferable.

The non-aqueous solvent is not particularly limited as long as it can be used as an electrolyte solvent for a lithium ion secondary battery. Specific examples include cyclic carbonates, chain carbonates, chain esters, cyclic ethers, chain ethers and the like.

As the cyclic carbonate, an alkylene group constituting the cyclic carbonate preferably has 2 to 6 carbon atoms, and more preferably 2 to 4 carbon atoms. Specific examples include ethylene carbonate, propylene carbonate, butylene carbonate, and the like. Of these, ethylene carbonate and propylene carbonate are preferable.

As the chain carbonate, a dialkyl carbonate is preferable, and the number of carbon atoms of the two alkyl groups is preferably 1 to 5, and more preferably 1 to 4, respectively. Specifically, symmetrical chain carbonates such as dimethyl carbonate, diethyl carbonate, and di-n-propyl carbonate, asymmetric chain carbonates such as methyl ethyl carbonate, methyl-n-propyl carbonate, and ethyl-n-propyl carbonate Is mentioned. Of these, dimethyl carbonate, diethyl carbonate, and methyl ethyl carbonate are preferable.

Examples of chain esters include methyl acetate, ethyl acetate, propyl acetate, and methyl propionate. Among these, methyl acetate is preferable from the viewpoint of improving low temperature characteristics.

Examples of the cyclic ether include tetrahydrofuran, 2-methyltetrahydrofuran, tetrahydropyran and the like. Among these, tetrahydrofuran is preferable from the viewpoint of improving input / output characteristics.

Examples of chain ethers include dimethoxyethane and dimethoxymethane.

The non-aqueous solvent may be used alone or in combination of two or more. Examples of the combination of two or more types include a combination of a high dielectric constant solvent such as cyclic carbonate and a low viscosity solvent such as chain carbonate and chain ester. One of the preferable combinations is a combination mainly composed of a cyclic carbonate and a chain carbonate. In this case, the total of the cyclic carbonate and the chain carbonate in the entire non-aqueous solvent may be 80% by volume or more, preferably 85% by volume or more, and more preferably 90% by volume or more. Moreover, the volume of the cyclic carbonate relative to the total of the cyclic carbonate and the chain carbonate may be 5% by volume or more, preferably 10% by volume or more, and more preferably 15% by volume or more. The volume of the cyclic carbonate relative to the total of the cyclic carbonate and the chain carbonate may be 50% by volume or less, preferably 35% by volume or less, and more preferably 30% by volume or less. By using such a combination of non-aqueous solvents, the cycle characteristics and storage characteristics of the battery tend to be further improved.

Specific examples of preferred combinations of cyclic carbonates and chain carbonates include ethylene carbonate and dimethyl carbonate, ethylene carbonate and diethyl carbonate, ethylene carbonate and methyl ethyl carbonate, ethylene carbonate and dimethyl carbonate and diethyl carbonate, ethylene carbonate and dimethyl carbonate And methyl ethyl carbonate, ethylene carbonate, diethyl carbonate and methyl ethyl carbonate, ethylene carbonate, dimethyl carbonate, diethyl carbonate and methyl ethyl carbonate.

The additive is not particularly limited as long as it is an additive for a non-aqueous electrolyte solution of a lithium ion secondary battery. For example, a heterocyclic compound containing at least one of nitrogen and sulfur, a cyclic carboxylic acid ester, a cyclic carbonate having a double bond in the molecule such as vinylene carbonate, a cyclic carbonate containing a halogen atom such as fluoroethylene carbonate, etc. .
In addition to the above additives, other additives such as an overcharge preventing material, a negative electrode film forming material, a positive electrode protective material, and a high input / output material may be used depending on the required function.

From the viewpoint of cycle characteristics, it is preferable to contain vinylene carbonate as an additive. When the electrolytic solution contains vinylene carbonate, the content is preferably 0.3% by mass to 2.0% by mass with respect to the entire electrolytic solution. When the content of vinylene carbonate is 0.3% by mass or more, a coating film can be sufficiently formed on the negative electrode, and decomposition of the electrolytic solution tends to be suppressed. When the content of vinylene carbonate is 2.0% by mass or less, an increase in internal pressure at high temperatures and high voltages tends to be suppressed. The content of vinylene carbonate is more preferably 0.5% by mass to 1.5% by mass with respect to the entire electrolytic solution. When the content of vinylene carbonate is 0.5% by mass or more, vinylene carbonate tends to be suppressed from being consumed by decomposition and depletion. When the content of vinylene carbonate is 1.5% by mass or less, the decomposition of vinylene carbonate and the generation of gas during high-temperature storage tend to be suppressed.

4). Separator A separator is particularly suitable if it has ion permeability while electrically insulating between the positive electrode and the negative electrode, and has sufficient resistance to oxidation on the positive electrode side and reducibility on the negative electrode side. Not limited. Examples of the material (material) of the separator that satisfies such characteristics include resins, inorganic substances, and glass fibers.

Examples of the resin include olefin polymers, fluorine polymers, cellulose polymers, polyimide, nylon, and the like. Specifically, it is preferable to select from materials that are stable with respect to the non-aqueous electrolyte and have excellent liquid retention properties, and more preferable are porous sheets made of polyolefin such as polyethylene and polypropylene, and nonwoven fabrics.

Examples of the inorganic substance include oxides such as alumina and silicon dioxide, nitrides such as aluminum nitride and silicon nitride, and sulfates such as barium sulfate and calcium sulfate. Examples of the separator using an inorganic material include a material in which a fiber-shaped or particle-shaped inorganic material is attached to a thin film-shaped substrate such as a nonwoven fabric, a woven fabric, or a microporous film. As the thin film-shaped substrate, those having a pore diameter of 0.01 μm to 1 μm and a thickness of 5 μm to 50 μm are preferably used. Another example includes a composite porous layer made of a fiber-shaped or particle-shaped inorganic substance using a binder such as a resin. Furthermore, what formed this composite porous layer in the surface of the positive electrode or the negative electrode is good also as a separator. For example, a composite porous layer in which alumina particles having a 90% particle size of less than 1 μm are bound using a fluororesin as a binder may be formed on the surface of the positive electrode to form a separator.

5). Other components The lithium ion secondary battery may be provided with a cleavage valve as another component. By opening the cleavage valve, it is possible to suppress an increase in pressure inside the battery and to improve safety.

Moreover, you may provide the structure part which discharge | releases an inert gas (for example, carbon dioxide) with a temperature rise. By providing such a component, when the temperature inside the battery rises, the cleavage valve can be opened quickly due to the generation of inert gas, and safety can be improved. Examples of the material used for the above components include lithium carbonate and polyalkylene carbonate resin.

(Lithium ion secondary battery)
First, an example of an embodiment when the lithium ion secondary battery is a laminate type will be described. A laminate-type lithium ion secondary battery can be manufactured, for example, as follows. First, the positive electrode and the negative electrode are cut into squares, and tabs are welded to the respective electrodes to produce positive and negative electrode terminals. Next, a positive electrode, a separator (insulating layer), and a negative electrode are laminated in this order to produce a laminate, which is accommodated in a laminate pack, and the positive and negative electrode terminals are taken out of the laminate pack. Next, a non-aqueous electrolyte is poured into the laminate pack, and the opening of the laminate pack is sealed. Examples of the material of the laminate pack include aluminum.

Next, an example of an embodiment in the case where the lithium ion secondary battery has a 18650 type cylindrical shape will be described with reference to the drawings. As shown in FIG. 1, the lithium ion secondary battery 1 has a bottomed cylindrical battery container 6 made of steel plated with nickel. The battery container 6 accommodates an electrode group 5 produced by winding a belt-like positive electrode plate 2 and a negative electrode plate 3 with a separator 4 interposed therebetween. The separator 4 may be a polyethylene porous sheet, for example, and may have a width of 58 mm and a thickness of 30 μm. On the upper end surface of the electrode group 5, a ribbon-like positive electrode tab terminal made of aluminum and having one end fixed to the positive electrode plate 2 is led out. The other end of the positive electrode tab terminal is disposed on the upper side of the electrode group 5 and is joined to the lower surface of a disk-shaped battery lid serving as a positive electrode external terminal by ultrasonic welding. On the other hand, a negative electrode tab terminal made of copper and having one end fixed to the negative electrode plate 3 is led out on the lower end surface of the electrode group 5. The other end of the negative electrode tab terminal is joined to the inner bottom of the battery container 6 by resistance welding. Therefore, the positive electrode tab terminal and the negative electrode tab terminal are respectively led to both end faces of the electrode group 5. In addition, the insulation coating which abbreviate | omitted illustration is given to the outer peripheral surface whole periphery of the electrode group 5. FIG. The battery lid is caulked and fixed to the upper part of the battery container 6 via an insulating resin gasket. For this reason, the inside of the lithium ion secondary battery 1 is sealed. In addition, a non-aqueous electrolyte (not shown) is injected into the battery container 6.

In the present embodiment, the capacity ratio of the negative electrode to the positive electrode (negative electrode capacity / positive electrode capacity) is preferably 1.03 to 1.8, and preferably 1.05 to 1.4 from the viewpoint of safety and energy density. It is more preferable.
Here, the negative electrode capacity indicates [negative electrode discharge capacity], and the positive electrode capacity indicates [positive charge capacity of positive electrode minus negative electrode or positive electrode, whichever is greater, irreversible capacity]. Here, the “negative electrode discharge capacity” is defined to be calculated by the charge / discharge device when the lithium ions inserted into the negative electrode active material are desorbed. Further, the “initial charge capacity of the positive electrode” is defined as that calculated by the charge / discharge device when lithium ions are desorbed from the positive electrode active material.
The capacity ratio between the negative electrode and the positive electrode can be calculated from, for example, “discharge capacity of the lithium ion secondary battery / discharge capacity of the negative electrode”. The discharge capacity of the lithium ion battery is, for example, 4.4 V, 0.1 C to 0.5 C, 0.1 C to 0 after performing constant current and constant voltage (CCCV) charging with an end time of 2 to 15 hours. It can be measured under the conditions when a constant current (CC) is discharged to 2.5V at 5C.
The discharge capacity of the negative electrode was prepared by cutting a negative electrode having a measured discharge capacity of the lithium ion secondary battery into a predetermined area, using lithium metal as a counter electrode, and preparing a single electrode cell through a separator impregnated with an electrolyte. Then, after performing constant current and constant voltage (CCCV) charging at 0 V, 0.1 C to 0.5 C, and a termination current of 0.01 C, the constant current (CC) was discharged to 1.5 V at 0.1 C to 0.5 C. It can be calculated by measuring the discharge capacity per predetermined area under the conditions of time and converting this to the total area when used as the negative electrode of the lithium ion battery. In this single electrode cell, the direction in which lithium ions are inserted into the negative electrode active material is defined as charging, and the direction in which the lithium ions inserted into the negative electrode active material are desorbed is defined as discharging.
C means “current value (A) / battery discharge capacity (Ah)”.

<Aluminum silicate compound composite>
The aluminum silicate compound composite of this embodiment contains an aluminum silicate compound and carbon, and the total pore volume measured by the nitrogen adsorption method is 0.05 cm ³ / g or more.
The details and preferred aspects of the aluminum silicate compound composite of the present embodiment are the same as the details and preferred aspects of the aluminum silicate compound composite used as the material for the lithium ion secondary battery described above.

The aluminum silicate compound composite of the present embodiment is preferably used as a material for a lithium ion secondary battery, and is used as a material for a lithium ion secondary battery of a lithium ion secondary battery containing a fluorine-containing electrolyte in an electrolytic solution. It is more preferable.
The use of the aluminum silicate compound composite of the present embodiment is not limited to a material for a lithium ion secondary battery, and expresses an excellent adsorbing ability for metal ions, for example, for example, an air purification filter, It can be used as a component of water treatment materials, light absorption films, electromagnetic wave shielding films, organic solvents, non-aqueous solvent ion exchange filters, semiconductor encapsulants, and electronic materials.

Hereinafter, the present embodiment will be described in more detail based on examples. In addition, this embodiment is not limited by the following examples.

[Production Example 1]
To an aluminum sulfate aqueous solution (500 mL) with an Al concentration of 1 mol / L, water glass (sodium silicate No. 3, Na ₂ O.nSiO ₂ .mH ₂ O) (500 mL) with an Si concentration of 2 mol / L is added and stirred for 30 minutes. did. A 1 mol / L sodium hydroxide aqueous solution was added to this solution to adjust the pH to 7. The solution with adjusted pH was stirred for 30 minutes, and then desalted by pressure filtration. To the precipitate after the desalting treatment, 1 mol / L sulfuric acid was added to adjust the pH to 4, followed by stirring for 30 minutes. The solution was then placed in a dryer and heated at 98 ° C. for 48 hours. A 1 mol / L sodium hydroxide aqueous solution was added to the heated solution to adjust the pH to 9. The salt in the solution was aggregated by adjusting the pH, the aggregate was precipitated by the same pressure filtration as described above, and then the supernatant was discharged to perform desalting. The precipitate obtained after the desalting treatment was dried at 110 ° C. for 16 hours to collect the particle mass. The recovered particle lump was pulverized with a jet mill to obtain a particulate aluminum silicate compound having a volume average particle diameter of about 3.5 μm.
Next, the obtained aluminum silicate compound and polyvinyl alcohol powder (Wako Pure Chemical Industries, Ltd.) were mixed at a mass ratio of 100: 70 and fired (carbonized) at 1000 ° C. for 1 hour in a nitrogen atmosphere. A particulate aluminum silicate compound composite comprising carbon derived from polyvinyl alcohol on an aluminum silicate compound was prepared.

[Production Example 2]
Water glass (sodium silicate No. 3, Na ₂ O.nSiO ₂ .mH ₂ O) (429 mL) with an Si concentration of 2 mol / L is added to an aluminum sulfate aqueous solution (571 mL) with an Al concentration of 1 mol / L, and stirred for 30 minutes. did. Then, operation similar to manufacture example 1 was performed and the particulate aluminum silicate compound was obtained. Next, in the same manner as in Production Example 1, a particulate aluminum silicate compound composite was produced.

[Production Example 3]
Water glass (sodium silicate No. 3, Na ₂ O.nSiO ₂ .mH ₂ O) (600 mL) with an Si concentration of 2 mol / L is added to an aluminum sulfate aqueous solution (400 mL) with an Al concentration of 1 mol / L and stirred for 30 minutes. did. Then, operation similar to manufacture example 1 was performed and the particulate aluminum silicate compound was obtained. Next, in the same manner as in Production Example 1, a particulate aluminum silicate compound composite was produced.

[Production Example 4]
Water glass (sodium silicate No. 3, Na ₂ O.nSiO ₂ .mH ₂ O) (333 mL) with an Si concentration of 2 mol / L was added to an aluminum sulfate aqueous solution (667 mL) with an Al concentration of 1 mol / L, and stirred for 30 minutes. did. Then, operation similar to manufacture example 1 was performed and the particulate aluminum silicate compound was obtained. Next, in the same manner as in Production Example 1, a particulate aluminum silicate compound composite was produced.

[Production Example 5]
Al concentration in 1 mol / L aqueous solution of aluminum sulfate of (286 mL), Si concentration: 2 mol / L of water glass (sodium silicate No. _{_{_{3, Na 2 O · nSiO 2 ·}}} mH 2 O) a (714 ml) was added, stirred for 30 minutes did. Then, operation similar to manufacture example 1 was performed and the particulate aluminum silicate compound was obtained. Next, in the same manner as in Production Example 1, a particulate aluminum silicate compound composite was produced.

[Production Example 6]
A particulate aluminum silicate compound composite was produced in the same manner as in Production Example 1 except that the firing conditions for carbonization were set at 900 ° C. for 1 hour.

[Production Example 7]
A particulate aluminum silicate compound composite was produced in the same manner as in Production Example 1 except that the firing conditions for carbonization were 1 hour at 850 ° C.

[Production Example 8]
A particulate aluminum silicate compound composite was produced in the same manner as in Production Example 1 except that the aluminum silicate compound described in Production Example 1 and polyvinyl alcohol powder were mixed at a mass ratio of 100: 45.

[Production Example 9]
A particulate aluminum silicate compound composite was produced in the same manner as in Production Example 1 except that the aluminum silicate compound described in Production Example 1 and polyvinyl alcohol powder were mixed at a mass ratio of 100: 100.

[Production Example 10]
A particulate aluminum silicate compound having a volume average particle diameter of about 1.5 μm was obtained by pulverizing a particle lump of the aluminum silicate compound obtained in the same manner as in Production Example 1 with a jet mill. A particulate aluminum silicate compound composite was prepared in the same manner as in Example 1 except that this aluminum silicate compound and polyvinyl alcohol powder were mixed at a mass ratio of 100: 70.

[Production Example 11]
Water glass (sodium silicate No. 3, Na ₂ O.nSiO ₂ .mH ₂ O) (91 mL) with an Si concentration of 2 mol / L was added to an aluminum sulfate aqueous solution (909 mL) with an Al concentration of 1 mol / L, and stirred for 30 minutes. did. Then, operation similar to manufacture example 1 was performed and the particulate aluminum silicate compound was obtained. Next, in the same manner as in Production Example 1, a particulate aluminum silicate compound composite was produced.

[Production Example 12]
Water glass (sodium silicate No. 3, Na ₂ O.nSiO ₂ .mH ₂ O) (833 mL) with an Si concentration of 2 mol / L was added to an aluminum sulfate aqueous solution (167 mL) with an Al concentration of 1 mol / L and stirred for 30 minutes. did. Then, operation similar to manufacture example 1 was performed and the particulate aluminum silicate compound was obtained. Next, in the same manner as in Production Example 1, a particulate aluminum silicate compound composite was produced.

[Production Example 13]
To an aluminum chloride aqueous solution (500 mL) having an Al concentration of 700 mmol / L, an aqueous sodium orthosilicate solution (500 mL) having an Si concentration of 350 mmol / L was added and stirred for 30 minutes. To this solution, 330 mL of a 1 mol / L aqueous sodium hydroxide solution was added to adjust the pH to 6.1. After the pH-adjusted solution is stirred for 30 minutes, it is centrifuged for 5 minutes at a rotational speed of 3,000 rpm using a centrifuge (Tomy Seiko Co., Ltd .: Suprema23 and Standard Rotor NA-16). went. After centrifugation, the supernatant solution was discharged, the gel precipitate was redispersed in pure water, and returned to the volume before centrifugation. Such desalting treatment by centrifugation was performed three times.

135 mg of 1 mol / L hydrochloric acid was added to the gel-like precipitate obtained after the supernatant was discharged for the third time in the desalting treatment, and the pH was adjusted to 3.5, followed by stirring for 30 minutes. The solution was then placed in a dryer and heated at 98 ° C. for 48 hours. 188 mL of 1 mol / L sodium hydroxide aqueous solution was added to the heated solution (salt concentration 47 g / L) to adjust the pH to 9.1. The salt in the solution was aggregated by adjusting the pH, the aggregate was precipitated by the same centrifugation as described above, and then the supernatant was discharged. The desalting process of adding pure water to the precipitate after discharging the supernatant and returning to the volume before centrifugation was performed three times. A gel-like precipitate obtained after the third desalting of the desalting treatment was dried at 60 ° C. for 16 hours to recover 30 g of a particle lump. The particle lump was pulverized with a jet mill to produce a particulate aluminum silicate compound.

Next, the particulate aluminum silicate compound and polyvinyl alcohol powder (Wako Pure Chemical Industries, Ltd.) were mixed at a mass ratio of 100: 70 (aluminum oxide: polyvinyl alcohol powder), and 1 at 850 ° C. in a nitrogen atmosphere. By firing for a time, a particulate aluminum silicate compound composite in which carbon derived from polyvinyl alcohol was provided on an aluminum silicate compound was produced.

[Measurement of total pore volume]
The total pore volume of the aluminum silicate compound composites obtained in Production Examples 1 to 13 was measured by the method described above. The results are shown in Table 1.

[Calculation of Si / Al ratio]
With respect to the aluminum silicate compound composites obtained in Production Examples 1 to 13, the element molar ratio of Si and Al was measured by a conventional ICP emission spectroscopic analysis (ICP emission spectrophotometer: P-4010 (Hitachi Ltd.)). (Si / Al) was determined. The results are shown in Table 1.

[Evaluation of crystal structure]
The crystal structures of the aluminum silicate compound composites obtained in Production Examples 1 to 13 were evaluated using the X-ray diffractometer (Geigerflex RAD-2X, manufactured by Rigaku Corporation) under the measurement conditions described above. As a result of the measurement, it was confirmed that the aluminum silicate compound composites obtained in Production Examples 1 to 13 were amorphous aluminum silicate compounds.

[Evaluation of metal ion adsorption capacity]
With respect to the aluminum silicate compound composites obtained in Production Examples 1 to 5 and Production Examples 11 to 13, the metal ion adsorption ability was evaluated as follows.
An electrolyte solution containing 1M LiPF ₆ (volume ratio of ethylene carbonate: dimethyl carbonate: diethyl carbonate is 1: 1: 1) is prepared, and Co (BF ₄ ) ₂ is dissolved therein to prepare a 500 ppm Co solution. did. To this Co solution (5 g), 0.05 g of each aluminum silicate compound complex was added and stirred for 30 minutes, and then allowed to stand overnight at room temperature.
The Co solution before the addition of the aluminum silicate compound complex and the supernatant of the Co solution after standing were filtered using a filter having a pore size of 0.45 μm, and the Co ion concentration (ppm) was measured using an ICP emission spectrometer. ) Were measured respectively.
The difference between the Co ion concentration (500 ppm) of the Co solution at the initial stage (before addition of the aluminum silicate compound complex) and the Co ion concentration (ppm) of the supernatant after adsorption (after standing) was determined. The Co adsorption capacity (mg / g) was calculated by multiplying the difference value by the amount of Co solution (5 g) and dividing by the mass (0.05 g) of the aluminum silicate compound complex. FIG. 2 shows the relationship between the measurement results and the Si / Al ratio of the aluminum silicate compound composite.

[Evaluation of hydrogen fluoride adsorption capacity]
The aluminum silicate compound composites obtained in Production Examples 1 to 5 and Production Example 13 were evaluated for hydrogen fluoride adsorption ability as follows.
First, 1 mol / L of lithium hexafluorophosphate (LiPF ₆ ) and 0.5% by mass of vinylene carbonate (VC) with respect to a mixed solvent of ethylene carbonate (EC): ethyl methyl carbonate (EMC) volume ratio 3: 7. A dissolved electrolyte solution (40 g) was prepared. Thereafter, an aluminum silicate compound composite (0.4 g) vacuum-dried at 120 ° C. for 10 hours was added to the electrolytic solution and stirred for 10 minutes, and then allowed to stand at room temperature for 3 hours.
About the electrolyte solution before the addition of the aluminum silicate compound complex and the supernatant of the electrolyte solution after standing, the hydrogen fluoride concentration (ppm) was measured using ion chromatography (ICS-2000, manufactured by Thermo Fisher SCIENTIFIC). It was measured.
The difference between the hydrogen fluoride concentration of the electrolyte solution at the initial stage (before addition of the aluminum silicate compound complex) and the hydrogen fluoride concentration (ppm) of the supernatant after adsorption (after standing) was determined. The hydrogen fluoride adsorption capacity (mg / g) was calculated by multiplying the difference value by the amount of the electrolytic solution (40 g) and dividing by the mass of the aluminum silicate compound complex (0.4 g). FIG. 3 shows the relationship between the measurement results and the Si / Al ratio of the aluminum silicate compound composite.

[Calculation of oxidation point ratio (RA)]
The oxidation point ratio (RA) of the aluminum silicate compound composites obtained in Production Examples 1 to 13 was calculated by the method described above. The results are shown in Table 1.

[Calculation of mass reduction rate]
The mass reduction rate of 350 ° C. to 850 ° C. of the aluminum silicate compound composites obtained in Production Examples 1 to 13 was calculated by the method described above. The results are shown in Table 1.

Example 1
[Production of positive electrode]
Lithium cobaltate (94% by mass) as a positive electrode active material, fibrous graphite (1% by mass) and acetylene black (AB) (1% by mass) as conductive materials, and the aluminum silicate compound produced in Production Example 1 The composite (1% by mass) and polyvinylidene fluoride (PVDF) (3% by mass) as a binder were sequentially added and mixed. The composition of the mixture is shown in Table 1. The content of the conductive material in Table 1 is the total of fibrous graphite (1% by mass) and acetylene black (1% by mass).
A slurry-like positive electrode mixture was prepared by adding N-methyl-2-pyrrolidone (NMP) as a dispersion solvent to the above mixture and kneading. This positive electrode mixture was applied substantially uniformly and uniformly to an aluminum foil having a thickness of 20 μm, which is a current collector for the positive electrode. Then, the drying process was performed and it consolidated by the press to the predetermined density. The density of the positive electrode mixture after drying was 3.6 g / cm ^3, and the coating amount on one side of the positive electrode mixture after drying was 202 g / m ² .

[Production of negative electrode]
SBR (styrene butadiene rubber) as a binder and carboxymethylcellulose (trade name: CMC # 2200, manufactured by Daicel Finechem Co., Ltd.) as a thickener on artificial graphite having an average particle size of 22 μm as a negative electrode active material Added. These mass ratios were negative electrode active material: binder: thickening material = 98: 1: 1. To this was added water as a dispersion solvent and kneaded to prepare a slurry-like negative electrode mixture. A predetermined amount of this negative electrode mixture was applied substantially uniformly and uniformly to both surfaces of a rolled copper foil having a thickness of 10 μm, which is a negative electrode current collector. The density of the negative electrode mixture after drying was 1.65 g / cm ^3, and the coating amount on one side of the negative electrode mixture after drying was 113 g / m ² .

[Production of lithium ion secondary battery]
A positive electrode cut into a 13.5 cm ² square is sandwiched between polyethylene porous sheets (trade name: Hypore, manufactured by Asahi Kasei Co., Ltd., thickness 30 μm, “Hypore” is a registered trademark), and further 14.3 cm. A negative electrode cut into ^two squares was superposed to produce a laminate. This laminate is placed in an aluminum laminate container (trade name: aluminum laminate film, manufactured by Dai Nippon Printing Co., Ltd.), 1 mL of electrolyte is added, the laminate container is heat-welded, and a lithium ion secondary battery for evaluation is prepared. Produced. As the electrolytic solution, one obtained by adding 1% by mass of vinylene carbonate (VC) to a mixed solution of ethylene carbonate, dimethyl carbonate and diethyl carbonate containing 1 mol / L LiPF ₆ with respect to the total amount of the mixed solution was used.

(Examples 2 to 11)
Instead of the aluminum silicate compound composite obtained in Production Example 1, the same procedure as in Example 1 was conducted except that the aluminum silicate compound composite obtained in Production Example shown in Table 1 was added to the positive electrode mixture. Thus, a lithium ion secondary battery for evaluation was produced.

(Comparative Example 1)
Example 1 except that the ratio of lithium cobaltate as the positive electrode active material was 95% by mass, the aluminum silicate compound composite was not added, and the coating amount on one side of the positive electrode mixture was changed to 200 g / m ^2. Thus, a lithium ion secondary battery for evaluation was produced.

(Comparative Examples 2 to 4)
Instead of the aluminum silicate compound composite obtained in Production Example 1, the aluminum silicate compound composite obtained in Production Examples 11 to 13 was added to the positive electrode mixture, respectively, in the same manner as in Example 1. A lithium ion secondary battery for evaluation was produced.

[Evaluation of output characteristics]
The output characteristics of the produced lithium ion secondary battery were evaluated by the following methods.
First, constant current charging was performed up to an upper limit voltage of 4.4 V at a current value of 0.1 C under an environment of 25 ° C., and then constant voltage charging was performed at 4.4 V. The charge termination condition was a current value of 0.01C. Thereafter, constant current discharge with a final voltage of 2.5 V was performed at a current value of 0.1 C. This charge / discharge cycle was repeated three times. “C” used as a unit of current value means “current value (A) / battery capacity (Ah)”. Further, constant current charging at 0.2 C was performed up to the upper limit voltage of 4.4 V, and then constant voltage charging was performed at 4.4 V. The charge termination condition was a current value of 0.02C. Thereafter, constant current discharge with a final voltage of 2.5 V was performed at a current value of 0.2 C, and the capacity at the time of discharge was defined as the discharge capacity at a current value of 0.2 C. Next, a constant current charge of 0.2 C is performed up to the upper limit voltage of 4.4 V, and then a constant voltage charge is performed at 4.4 V (the charge termination condition is set to a current value of 0.02 C). A constant current discharge with a final voltage of 2.5 V was performed at a current value, and the capacity at the time of discharge was defined as the discharge capacity at a current value of 3C. Next, output characteristics were calculated by the following formula. The results are shown in Table 1.

Output characteristics (%) = (discharge capacity at current value 3C / discharge capacity at current value 0.2C) × 100

[Evaluation of cycle characteristics]
After evaluating the output characteristics under the conditions shown above, a cycle test in which charging and discharging are repeated was performed to evaluate the cycle characteristics. As for the charging pattern, each lithium battery was subjected to constant current charging at an electric current value of 1 C up to an upper limit voltage of 4.4 V in an environment of 45 ° C., followed by constant voltage charging at 4.4 V. The charge termination condition was a current value of 0.1C. Discharge was performed at a constant current of 1C up to 2.5V. The cycle characteristics were calculated by the following formula. The results are shown in Table 1.

Cycle characteristics (%) = (discharge capacity after 200 cycles at current value 1C / discharge capacity after one cycle at current value 1C) × 100

[Evaluation of high-temperature storage characteristics]
High-temperature storage characteristics (battery expansion coefficient) were calculated as follows.
After evaluating the output characteristics under the above conditions, the volume of the lithium ion secondary battery was measured with a high-precision electronic hydrometer (MDS-300, manufactured by Alpha Mirage Co., Ltd.). Thereafter, constant current charging was performed at 25 ° C. with a current value of 0.1 C up to an upper limit voltage of 4.4 V, and then constant voltage charging was performed at 4.4 V. The charge termination condition was a current value of 0.01C. In the charged state, the lithium ion secondary battery was left in a constant temperature bath at 80 ° C. for 48 hours, and a high temperature storage test was performed. After the test, the lithium ion secondary battery was taken out from the thermostat, the volume after cooling to 25 ° C. was measured with a high-precision electronic hydrometer, and the expansion coefficient of the lithium ion secondary battery was calculated from the following formula. The results are shown in Table 1.

Battery expansion rate (%) = (volume of lithium battery after high-temperature storage test / volume of lithium battery before high-temperature storage test) × 100

[Evaluation of Co precipitation amount]
The lithium ion secondary battery after the cycle test was disassembled, and the negative electrode was washed with dimethyl carbonate and dried. Thereafter, the negative electrode mixture layer is peeled off from the copper foil as the current collector, and the amount of cobalt precipitated (mass basis, ppm) in the negative electrode mixture layer is analyzed by ICP emission spectroscopy (ICP emission spectrometer: P-4010 (Hitachi Co., Ltd.). From the manufacturing plant)). The results are shown in Table 1.

As shown in the results of Table 1, the lithium ion secondary batteries of Examples 1 to 11 manufactured using the aluminum silicate compound composite having a total pore volume of 0.05 cm ³ / g or more are aluminum silicate. The lithium ion secondary battery of Comparative Example 1 manufactured without using the compound composite and the Comparative Examples 2 to 4 manufactured using the aluminum silicate compound composite having a total pore volume of less than 0.05 cm ³ / g As compared with the lithium ion secondary battery, the evaluation of the output characteristics and the cycle characteristics was good. Moreover, the precipitation of cobalt was also suppressed as compared with the lithium ion secondary battery of the comparative example. From these results, in the lithium ion secondary batteries of Examples 1 to 11, it was considered that the suppression of the precipitation of cobalt on the negative electrode was related to the suppression of the deterioration of the output characteristics and the cycle characteristics.

The reason why the precipitation of cobalt in the lithium ion secondary batteries of Examples 1 to 11 was suppressed was that cobalt ions eluted from the positive electrode active material due to hydrogen fluoride generated in the electrolyte were converted to aluminum silica. It is considered that the reprecipitation of cobalt ions was suppressed by the adsorption of the acid compound complex. Further, it is considered that elution of cobalt ions from the positive electrode active material was suppressed by adsorbing the hydrogen fluoride generated in the electrolytic solution to the aluminum silicate compound complex.
From this, the aluminum silicate compound composite of this embodiment can be suitably used as an adsorbent such as metal ions and hydrogen fluoride, and is not particularly limited. For example, a lithium ion secondary battery It is preferably used for a positive electrode of a lithium ion secondary battery.

Among the examples 1 to 11, the lithium ion secondary batteries of the examples 1 to 10 were suppressed in expansion of the battery as compared with the lithium ion secondary battery of the example 11. The reason for this is not necessarily clear, but since the oxidation point ratio (RA) of the aluminum silicate compound composite used in Examples 1 to 10 is lower than that in Example 11, gas generation due to reaction with the electrolytic solution is small, It is conceivable that gas such as carbon dioxide generated by the reaction between hydrogen fluoride and lithium carbonate on the electrode was less generated due to the adsorption of hydrogen fluoride in the electrolytic solution.

DESCRIPTION OF SYMBOLS 1 Lithium ion secondary battery 2 Positive electrode plate 3 Negative electrode plate 4 Separator 5 Electrode group
6 Battery container

Claims

A material for a lithium ion secondary battery, which is an aluminum silicate compound composite containing an aluminum silicate compound and carbon and having a total pore volume measured by a nitrogen adsorption method of 0.05 cm 3 / g or more.
And the peak area A of the oxidation point in the vicinity of 1490cm -1, which derived from pyridine adsorption IR spectrum of the aluminum silicate compound complex, the oxidation point which is calculated by the following equation from the peak area B of the hydrogen bonds in the vicinity of 1446cm -1 The material for lithium ion secondary batteries according to claim 1, wherein the ratio (RA) is less than 25%.
RA (%) = A / B × 100
The material for a lithium ion secondary battery according to claim 1 or 2, wherein an element molar ratio (Si / Al) of silicon to aluminum in the aluminum silicate compound composite is 1.0 to 5.0.
The mass reduction rate between 350 ° C and 850 ° C as measured using differential thermal-thermogravimetric analysis (TG-DTA) of the aluminum silicate compound composite is 0.5% to 30%. The material for a lithium ion secondary battery according to any one of claims 1 to 3.
The lithium ion secondary particle according to any one of claims 1 to 4, wherein the volume average particle diameter of the aluminum silicate compound composite measured by a laser diffraction particle size distribution analyzer is 0.1 μm to 50 μm. Secondary battery material.
The lithium ion secondary according to any one of claims 1 to 5, wherein an element molar ratio (Si / Al) of silicon to aluminum in the aluminum silicate compound composite is 1.5 to 3.0. Battery material.
A positive electrode mixture comprising the lithium ion secondary battery material according to any one of claims 1 to 6 and a positive electrode active material.
The positive electrode mixture according to claim 7, wherein the content of the lithium ion secondary battery material is 0.01 mass% to 10 mass% with respect to the total amount of the positive electrode mixture.
A positive electrode for a lithium ion secondary battery comprising the material for a lithium ion secondary battery according to any one of claims 1 to 6.
A lithium ion secondary battery comprising the positive electrode for a lithium ion secondary battery according to claim 9.