JP2017134914A - Positive electrode material for lithium ion secondary battery, positive electrode mixture for lithium ion secondary battery, positive electrode for lithium ion secondary battery, and lithium ion secondary battery - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide: a positive electrode material for lithium ion secondary batteries, with which a lithium ion secondary battery can be obtained, the lithium ion secondary battery being excellent in output characteristics and being suppressed in capacity decrease after charge/discharge cycles at high voltages (for example, a charge voltage of 4.35 V); a positive electrode mixture for lithium ion secondary batteries, in which the positive electrode material is used; a positive electrode for lithium ion secondary batteries; and a lithium ion secondary battery.SOLUTION: A positive electrode material for lithium ion secondary batteries is used for a positive electrode mixture layer of a lithium ion secondary battery that includes a positive electrode having a current collector and the positive electrode mixture layer, a negative electrode, a separator, and an electrolytic solution containing a fluorine-containing lithium salt electrolyte. The positive electrode material for lithium ion secondary batteries includes an oxygen-containing aluminum compound composite in which carbon is arranged on at least a part of a surface of an oxygen-containing aluminum compound particle.SELECTED DRAWING: None

Description

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

  A lithium ion secondary battery is a high energy density secondary battery, and is used as a power source for portable devices such as notebook PCs (Personal Computers) and mobile phones by taking advantage of its characteristics. As a shape of the lithium ion secondary battery, there are various shapes such as a cylindrical shape, a laminate shape, and a square shape. Among them, the cylindrical lithium ion secondary battery employs a wound structure of a positive electrode, a negative electrode, and a separator. A cylindrical lithium ion secondary battery is manufactured as follows, for example. First, a positive electrode mixture and a negative electrode mixture are respectively applied to two strip-shaped metal foils to produce a positive electrode and a negative electrode. Next, a separator is sandwiched between the positive electrode and the negative electrode, and these laminated bodies are wound in a spiral shape to form a wound group. The wound group is accommodated in a cylindrical battery can serving as a battery container, and after injecting an electrolytic solution, sealing is performed to manufacture a cylindrical lithium ion secondary battery.

  As the cylindrical lithium ion secondary battery, an 18650 type lithium ion secondary battery is widely used as a consumer lithium ion secondary battery. The outer diameter of the 18650 type lithium ion secondary battery is a small size having a diameter of 18 mm and a height of about 65 mm. As the positive electrode active material of the 18650 type lithium ion secondary battery, lithium cobaltate having a high capacity and a long life is mainly used. The battery capacity of the 18650 type lithium ion secondary battery is about 1.0 Ah to 2.0 Ah (3.7 Wh to 7.4 Wh).

  In recent years, with the enhancement of functions of portable information terminals such as smartphones and tablet PCs, further increase in capacity is strongly demanded for consumer lithium-ion secondary batteries. As measures for achieving a higher capacity of the battery, it is conceivable to increase the capacity of the active material, improve the energy density, increase the voltage of the battery, and the like. However, increasing the voltage of the battery has a problem that the reaction between the constituent materials inside the battery is promoted, and the capacity of the lithium ion secondary battery after the charge / discharge cycle is greatly reduced.

  Conventionally, as a method for suppressing the capacity reduction of a lithium ion secondary battery, (1) a fluorine-containing lithium salt electrolyte and a specific phosphonoacetate compound are used as an electrolyte, and a zirconium-containing lithium cobalt composite is used as a positive electrode active material. A method using an oxide (for example, see Patent Document 1), (2) a method using a fluorinated cyclic carbonate and a fluorinated chain ester as an electrolytic solution (for example, see Patent Document 2), and (3) a positive electrode active A method of fixing a rare earth compound to a part of the surface of lithium cobaltate which is a substance (for example, see Patent Document 3) has been proposed.

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

However, it is difficult to sufficiently suppress a decrease in the capacity of the lithium ion secondary battery after a charge / discharge cycle at a high voltage (for example, a charge voltage of 4 V or more) even by the methods described in Patent Documents 1 to 3 above. . This is caused by hydrogen fluoride (HF) generated when water contained in the lithium ion secondary battery reacts with a fluorine-containing lithium salt electrolyte such as lithium hexafluorophosphate (LiPF ₆ ). From this, it is estimated that a capacity drop occurs when a metal such as cobalt is eluted and the eluted metal such as cobalt is reprecipitated at the negative electrode or the like.

  The present invention has been made in view of the above circumstances, and is a lithium ion secondary excellent in output characteristics and suppressed in capacity reduction after a charge / discharge cycle at a high voltage (for example, a charge voltage of 4.35 V). Provided are a positive electrode material for a lithium ion secondary battery capable of obtaining a battery, a positive electrode mixture for a lithium ion secondary battery using the positive electrode material, a positive electrode for a lithium ion secondary battery, and a lithium ion secondary battery. This is the issue.

Specific means for solving the above problems include the following embodiments.
<1> Used for the positive electrode mixture layer of a lithium ion secondary battery comprising a positive electrode having a current collector and a positive electrode mixture layer, a negative electrode, a separator, and an electrolyte solution containing a fluorine-containing lithium salt electrolyte. A positive electrode material for a lithium ion secondary battery,
A positive electrode material for a lithium ion secondary battery comprising an oxygen-containing aluminum compound composite in which carbon is disposed on at least a part of the surface of oxygen-containing aluminum compound particles.

<2> The weight loss rate in the range of 350 ° C. to 850 ° C. measured using a differential thermal-thermogravimetric analyzer (TG-DTA) of the oxygen-containing aluminum compound composite is 0.5% to 30%. The positive electrode material for a lithium ion secondary battery according to a certain <1>.

<3> The weight reduction rate in the range of 25 ° C. to 350 ° C. measured using a differential thermal-thermogravimetric analyzer (TG-DTA) of the oxygen-containing aluminum compound composite is less than 5% <1> Or the positive electrode material for lithium ion secondary batteries as described in <2>.

<4> lithium according to any one of the oxygen specific surface area determined from nitrogen adsorption measurements at 77K containing aluminum compound complex is ^{1m 2 / g~80m 2 / g <} 1> ~ <3> Positive electrode material for ion secondary battery.

<5> The lithium ion according to any one of <1> to <4>, wherein the volume average particle diameter of the oxygen-containing aluminum compound composite measured by a laser diffraction particle size distribution analyzer is 0.1 μm to 50 μm. Positive electrode material for secondary battery.

<6> The lithium ion secondary battery according to any one of <1> to <5>, wherein an R value obtained from a Raman spectrum analysis of the oxygen-containing aluminum compound composite is 0.1 to 5.0. Positive electrode material.

<7> For forming the positive electrode mixture layer of a lithium ion secondary battery comprising a positive electrode having a current collector and a positive electrode mixture layer, a negative electrode, a separator, and an electrolyte solution containing a fluorine-containing lithium salt electrolyte. A lithium-ion secondary battery positive electrode mixture used,
A positive electrode mixture for a lithium ion secondary battery, comprising: a positive electrode active material; and the positive electrode material for a lithium ion secondary battery according to any one of <1> to <6>.

<8> A positive electrode for a lithium ion secondary battery used in a lithium ion secondary battery comprising a positive electrode, a negative electrode, a separator, and an electrolytic solution containing a fluorine-containing lithium salt electrolyte,
A current collector, and a positive electrode mixture layer formed on the current collector,
A positive electrode for a lithium ion secondary battery, wherein the positive electrode mixture layer contains a positive electrode active material and the positive electrode material for a lithium ion secondary battery according to any one of <1> to <6>.

<9> A lithium ion secondary battery comprising the positive electrode for a lithium ion secondary battery according to <8>, a negative electrode, a separator, and an electrolytic solution containing a fluorine-containing lithium salt electrolyte.

  According to the present invention, a lithium ion secondary battery capable of obtaining a lithium ion secondary battery that has excellent output characteristics and suppresses a decrease in capacity after a charge / discharge cycle at a high voltage (for example, a charge voltage of 4.35 V). A positive electrode material for a secondary battery, a positive electrode mixture for a lithium ion secondary battery using the positive electrode material, a positive electrode for a lithium ion secondary battery, and a lithium ion secondary battery can be provided.

It is a schematic sectional drawing which shows an example of the oxygen containing aluminum compound composite body of this embodiment. It is a schematic sectional drawing which shows the other example of the oxygen containing aluminum compound composite body of this embodiment. It is a schematic sectional drawing which shows the other example of the oxygen containing aluminum compound composite body of this embodiment. It is a schematic sectional drawing which shows the other example of the oxygen containing aluminum compound composite body of this embodiment. It is a schematic sectional drawing which shows the other example of the oxygen containing aluminum compound composite body of this embodiment. It is a perspective sectional view showing an example of a lithium ion secondary battery of this embodiment.

  Hereinafter, referring to the drawings, examples of embodiments of a positive electrode material for a lithium ion secondary battery, a positive electrode mixture for a lithium ion secondary battery, a positive electrode for a lithium ion secondary battery, and a lithium ion secondary battery to which the present invention is applied will be described. The details will be described. 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. Moreover, the magnitude | size of the member in each figure is notional, The relative relationship of the magnitude | size between members is not limited to this.

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, the numerical ranges indicated by using “to” include numerical values described before and after “to” as the minimum value and the maximum value, respectively.
In the present specification, the content of each component in the composition is the sum of the plurality of substances present in the composition unless there is a specific indication when there are a plurality of substances corresponding to each component in the composition. It means the content rate of.
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” refers to the case where the layer is formed only in a part of the region in addition to the case where the layer is formed over the entire region. Is also included.

<Positive electrode material for lithium ion secondary battery>
The positive electrode material for a lithium ion secondary battery of the present embodiment (hereinafter also simply referred to as “positive electrode material”) is an oxygen-containing aluminum compound composite in which carbon is disposed on at least a part of the surface of oxygen-containing aluminum compound particles. Including.

  The positive electrode material of the present embodiment is a positive electrode mixture in a lithium ion secondary battery comprising a positive electrode having a current collector and a positive electrode mixture layer, a negative electrode, a separator, and an electrolyte solution containing a fluorine-containing lithium salt electrolyte. Used for layers. By using the positive electrode material of this embodiment for the positive electrode mixture layer of the lithium ion secondary battery having the above-described configuration, the output characteristics are excellent, and the charge / discharge cycle at a high voltage (for example, a charge voltage of 4.35 V) is performed. It is possible to obtain a lithium ion secondary battery in which subsequent capacity reduction is suppressed. The reason is not clear, but can be considered as follows, for example.

Since it is difficult to completely remove the water in the lithium ion secondary battery, the water inevitably mixed with the fluorine-containing lithium salt electrolyte such as lithium hexafluorophosphate (LiPF ₆ ) reacts with hydrogen fluoride. It is known to generate (HF). This hydrogen fluoride (HF) elutes metal ions such as cobalt ions from the positive electrode active material, and the eluted metal ions are reprecipitated at the negative electrode and the like, causing a decrease in capacity.
The oxygen-containing aluminum compound composite contained in the positive electrode mixture layer of the lithium ion secondary battery has the ability to adsorb hydrogen fluoride (HF) and metal ions, and other ions such as cobalt ions than lithium ions. Since it exhibits the property of easily adsorbing metal ions, it is considered that capacity reduction after charge / discharge cycles at high voltage is suppressed. Further, since the oxygen-containing aluminum compound composite has high conductivity, it is considered that the output characteristics of the lithium ion secondary battery are improved. The effect of improving the output characteristics by the oxygen-containing aluminum compound composite is particularly remarkable when lithium hexafluorophosphate (LiPF ₆ ) is used among the fluorine-containing lithium salt electrolytes.

  Examples of the oxygen-containing aluminum compound include activated alumina; aluminum silicates such as allophane, kaolin, zeolite, saponite, imogolite, and amorphous aluminum silicate. Among these, from the viewpoint of improving the cycle characteristics of the lithium ion secondary battery, the oxygen-containing aluminum compound is preferably an amorphous aluminum silicate whose specific surface area can be easily adjusted.

When amorphous aluminum silicate is used as the oxygen-containing aluminum compound, the element molar ratio Si / Al is preferably 0.1 to 50, more preferably 0.2 to 30, and 0.3 to 10 More preferably. Such amorphous aluminum silicates, for _{example, nSiO 2 · Al 2 O 3} · mH 2 O [n = 0.2~100, m = 0 or] include those having a composition represented by.

In addition, amorphous aluminum silicate has no broad peak in the powder X-ray diffraction spectrum using CuKα ray as an X-ray source, and has broad peaks around 2θ = 25 ° and 41 °. . As an X-ray diffraction apparatus, for example, Geigerflex RAD-2X (trade name) manufactured by Rigaku Corporation can be used. Specific measurement conditions are as follows.
Divergence slit: 1 °
Scattering slit: 1 °
Receiving slit: 0.30mm
X-ray output: 40 kV, 40 mA

  In addition, from the viewpoint of storage characteristics, it is preferable that the amorphous aluminum silicate does not have a tubular product having a length of 50 nm or more when observed with a transmission electron microscope (TEM) at a magnification of 100,000. The amorphous aluminum silicate is observed with a transmission electron microscope at an acceleration voltage of 100 kV.

The oxygen-containing aluminum compound particles may be synthesized, or a commercially available product may be purchased and used.
When synthesizing the oxygen-containing aluminum compound particles, for example, the oxygen-containing aluminum compound particles can be synthesized according to a method described in JP-A-2015-18800. Specifically, the method for producing oxygen-containing aluminum compound particles includes a reaction step of mixing a solution containing silicate ions and a solution containing aluminum ions to obtain a reaction product, and the reaction product is mixed with an acid in an aqueous medium. A heat treatment step of performing heat treatment in the presence, and may have other steps as necessary.

  From the viewpoint of the yield of the obtained oxygen-containing aluminum compound particles, structure formation, etc., it is preferable to have a washing step for performing desalting and solid separation at least after the heat treatment step, preferably before and after the heat treatment step. . After desalting the coexisting ions from the solution containing the reaction product, heat treatment is performed in the presence of an acid to efficiently produce oxygen-containing aluminum compound particles having excellent adsorption ability for hydrogen fluoride (HF) and metal ions. be able to. This is thought to be because oxygen-containing aluminum compound particles having a regular structure can be obtained by heat-treating the reaction product from which coexisting ions that inhibit the formation of the regular structure are removed in the presence of an acid. . Examples of the coexisting ions include sodium ions, chloride ions, perchlorate ions, nitrate ions, sulfate ions, and the like.

  In the oxygen-containing aluminum compound composite, carbon is arranged on at least a part of the surface of the oxygen-containing aluminum compound particles.

  Carbon may be disposed on the surface of the oxygen-containing aluminum compound particles. The structural example of an oxygen containing aluminum compound composite is shown in the schematic sectional drawing of FIGS. In FIG. 1, carbon 40 covers the entire surface of oxygen-containing aluminum compound particles 50. In FIG. 2, the carbon 40 covers the entire surface of the oxygen-containing aluminum compound particles 50, but the thickness of the carbon 40 varies. In FIG. 3, the carbon 40 is partially present on the surface of the oxygen-containing aluminum compound particle 50, and the surface of the oxygen-containing aluminum compound particle 50 has a portion that is not covered with the carbon 40. In FIG. 4, carbon 40 particles having a particle size smaller than that of the oxygen-containing aluminum compound particles 50 are present on the surface of the oxygen-containing aluminum compound particles 50. FIG. 5 is a modification of FIG. 4, and the shape of the carbon 40 is scaly. 1 to 5, the shape of the oxygen-containing aluminum compound particles 50 is schematically represented as a sphere (a circle as a cross-sectional shape), but a spherical shape, a block shape, a scale shape, or a cross-sectional shape is a polygon. Any of the shapes (cornered shapes) may be used.

  There is no restriction | limiting in particular as a method of arrange | positioning carbon on the surface of an oxygen-containing aluminum compound particle. Examples of the method for arranging carbon on the surface of the oxygen-containing aluminum compound particles include a wet coating method, a dry coating method, and a vapor phase coating method such as CVD (Chemical Vapor Deposition). Among these methods, a dry coating method or a vapor phase coating method that does not use a solvent is preferable from the viewpoints of cost and manufacturing process reduction.

In the case of the wet coating method, for example, after adding oxygen-containing aluminum compound particles as a nucleus to a mixed solution in which an organic compound is dissolved or dispersed in a solvent, the solvent is removed as necessary, and then the organic compound is subjected to heat treatment. By carbonizing the carbon, carbon can be arranged on the surface of the oxygen-containing aluminum compound particles.
The content of the organic compound in the mixed solution is preferably 0.01% by mass to 30% by mass and more preferably 0.05% by mass to 20% by mass from the viewpoint of ease of dispersion. Preferably, it is 0.1 mass%-10 mass%. As a mixing ratio of oxygen-containing aluminum compound particles and organic compound (oxygen-containing aluminum compound particles: organic compound), from the viewpoint of coexistence of hydrogen fluoride (HF) and metal ion adsorption ability and conductivity, It is preferable that it is 100: 1-100: 500, and it is more preferable that it is 100: 5-100: 300.

In the case of the dry coating method, for example, the surface of the oxygen-containing aluminum compound particles is obtained by mixing the oxygen-containing aluminum compound particles and the organic compound together to form a mixture, and heat-treating the mixture to carbonize the carbon source. Carbon can be placed on the surface. In addition, when mixing an oxygen-containing aluminum compound particle and an organic compound, you may perform the process (for example, mechanochemical process) which adds mechanical energy.
As a mixing ratio of oxygen-containing aluminum compound particles and organic compound (oxygen-containing aluminum compound particles: organic compound) when mixing oxygen-containing aluminum compound particles and organic compound as solids, hydrogen fluoride (HF) and metal From the viewpoint of achieving both ion adsorption capacity and conductivity, the mass ratio is preferably 100: 1 to 100: 500, and more preferably 100: 5 to 100: 300.

  In the case of the vapor phase coating method, for example, carbon can be arranged on the surface of the oxygen-containing aluminum compound particles by heat-treating the oxygen-containing aluminum compound particles in an atmosphere containing a gas obtained by vaporizing an organic compound.

  When carbon is arranged on the surface of oxygen-containing aluminum compound particles by a wet coating method or a dry coating method, the organic compound may be a compound that can leave carbon by heat treatment. Specifically, as organic compounds, ethylene heavy end pitch, crude oil pitch, coal tar pitch, asphalt cracking pitch, pitch generated by pyrolyzing polyvinyl chloride, naphthalene, etc. are polymerized in the presence of a super strong acid. Pitches such as synthetic pitch; thermoplastic materials such as polyvinyl chloride, polyvinyl alcohol, polyvinyl acetate, and polyvinyl butyral; thermosetting materials such as phenol resin and furan resin. These organic compounds may be used individually by 1 type, and may be used in combination of 2 or more type.

  When carbon is arranged on the surface of the oxygen-containing aluminum compound particles by a vapor phase coating method, the organic compound is not particularly limited, and is preferably a gas or a compound that can be easily gasified. Specifically, examples of the organic compound include hydrocarbons such as methane, ethane, propane, toluene, benzene, xylene, styrene, naphthalene, and anthracene; and hydrocarbon derivatives such as cresol. These organic compounds may be used individually by 1 type, and may be used in combination of 2 or more type.

  The heat treatment conditions for carbonizing the organic compound disposed on the surface of the oxygen-containing aluminum compound particles may be appropriately determined in consideration of the carbonization rate of the organic compound, and there is no particular limitation. For example, heat treatment is preferably performed at 800 ° C. to 1300 ° C. in an inert atmosphere. By setting the heat treatment temperature to 800 ° C. or higher, the carbonization of the organic compound becomes sufficient, and when used for the positive electrode mixture layer of the lithium ion secondary battery, the increase in the first irreversible capacity tends to be suppressed. . Moreover, it exists in the tendency which can suppress the raise of a resistivity by making heat processing temperature into 1300 degrees C or less. Examples of the inert atmosphere include nitrogen, argon, helium and the like.

The BET specific surface area of the oxygen-containing aluminum compound composite is, for example, preferably 80 m ² / g or less, and from the viewpoint of improving storage characteristics and cycle characteristics of the lithium ion secondary battery, it is 60 m ² / g or less. Is more preferable, and it is still more preferable that it is 40 m < ² > / g or less. Further, the BET specific surface area of the oxygen-containing aluminum compound composite is, for example, preferably 1 m ² / g or more, from the viewpoint of improving the adsorption ability of hydrogen fluoride (HF) and metal ions, and is 2 m ² / g or more. It is more preferable that it is 3 m ² / g or more. That, BET specific surface area of the oxygen-containing aluminum compound complex ^is preferably 1m ² / g~80m 2 / ^g, more preferably ^{2m 2 / g~60m 2 / g,} 3m 2 / g~ More preferably, it is 40 m ² / g.

The BET specific surface area of the oxygen-containing aluminum compound composite is measured from the nitrogen adsorption ability at 77K according to JIS Z 8830 (2001). As an evaluation apparatus, a nitrogen adsorption measuring apparatus (AUTOSORB-1, manufactured by 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 the structure affects the gas adsorption capacity. Therefore, pretreatment for removing moisture by heating is first 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, heated at 110 ° C. and held for 3 hours or more, and then kept at a normal temperature ( Cool to 25 ° C). 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.

  From the viewpoint of improving the input / output characteristics and cycle characteristics of the lithium ion secondary battery, the oxygen-containing aluminum compound composite has a temperature of 350 ° C. to 850 ° C. measured using a differential thermal-thermogravimetric analyzer (TG-DTA). The weight reduction rate in the range is, for example, preferably 0.5% to 30%, more preferably 2% to 25%, and still more preferably 5% to 20%. When the weight loss rate in the range of 350 ° C. to 850 ° C. is 0.5% to 30%, an increase in resistance due to the reaction between the oxygen-containing aluminum compound composite and the electrolytic solution can be suppressed, and hydrogen fluoride (HF) and metal ion adsorption ability tend to be improved.

  In addition, the oxygen-containing aluminum compound composite increases the capacity of the lithium ion secondary battery and improves the cycle characteristics, so that the oxygen-containing aluminum compound composite is in a range of 25 ° C. to 350 ° C. measured using a differential thermal-thermogravimetric analyzer. For example, the weight reduction rate is preferably less than 5%, more preferably less than 4%, and still more preferably less than 3%. From the practical viewpoint, the weight reduction rate in the range of 25 ° C. to 350 ° C. is preferably 0.01% or more, for example.

A differential thermal-thermogravimetric analyzer (TG-DTA-6200, manufactured by Hitachi High-Tech Science Co., Ltd.) or the like can be used for measuring the weight reduction rate.
The weight reduction rate is measured by raising the temperature from 25 ° C. at a rate of temperature increase of 10 ° C./min and holding at 850 ° C. for 20 minutes under a dry air flow. The weight reduction rate is expressed by the following formula (1) with respect to the mass at 25 ° C. (W0), the mass at 350 ° C. (W1), and the mass at 850 ° C. (W2) measured with a differential thermal-thermogravimetric analyzer. ) And the value obtained in (2).
Weight reduction rate in the range of 25 ° C. to 350 ° C. (D1) (%) = {(W0−W1) / W0} × 100 (1)
Weight reduction rate in the range between 350 ° C. and 850 ° C. (D2) (%) = {(W1-W2) / W1} × 100 (2)

  The volume average particle diameter of the oxygen-containing aluminum compound composite is, for example, preferably 0.1 μm to 50 μm, more preferably 0.5 μm to 20 μm, in accordance with the final desired size. When the volume average particle diameter is 0.1 μm or more, there is a tendency that it is possible to suppress deterioration in workability due to an increase in slurry viscosity when an electrode is produced. In addition, by setting the volume average particle diameter to 50 μm or less, streaking tends to be suppressed when the electrode mixture is applied. The volume average particle diameter of the oxygen-containing aluminum compound composite is more preferably 1 μm to 10 μm. By setting the volume average particle diameter to 1 μm or more, it is possible to reduce the load and cost for pulverizing the particles, and by setting the volume average particle diameter to 10 μm or less, the adsorption ability of hydrogen fluoride (HF) and metal ions. Tend to improve.

  The volume average particle diameter of the oxygen-containing aluminum compound composite is measured using a laser diffraction method. The laser diffraction method can be measured, for example, using a laser diffraction particle size distribution measuring device (SALD3000J, manufactured by Shimadzu Corporation). Specifically, an oxygen-containing aluminum compound composite is dispersed in a dispersion medium such as water to prepare a dispersion. For this dispersion, when a volume cumulative distribution curve is drawn from the small diameter side using a laser diffraction particle size distribution measuring device, the particle diameter (D50) that is 50% cumulative is determined as the volume average particle diameter.

  The oxygen-containing aluminum compound composite preferably has an R value obtained from Raman spectrum analysis of, for example, 0.1 to 5.0. By setting the R value to 0.1 or more, the surface coating effect by amorphous carbon tends to be excellent. Moreover, it exists in the tendency which can prevent that surface coating carbon amount becomes excess because R value shall be 5.0 or less. For example, the R value is more preferably 0.3 to 3.0, and still more preferably 0.5 to 1.5.

R value of the oxygen-containing aluminum compound complexes in the Raman spectrum obtained by laser Raman spectroscopy of the excitation wavelength 532 nm, the intensity of the peak appearing in the vicinity of 1360 cm ^-1 and Id, the intensity of the peak appearing near 1580 cm ^-1 Is calculated as the intensity ratio Id / Ig (D / G) of the two peaks. The peak appearing in the vicinity of 1360 cm ⁻¹ is usually a peak identified as corresponding to the amorphous structure of carbon, for example, a peak observed at 1300 cm ^{−1 to} 1400 cm ⁻¹ . Also, the peak appearing near 1580 cm ^-1, generally a peak identified as corresponding to the crystal structure of the carbon, for ^example, refers to peaks observed at 1530cm ^-1 ~1630cm -1.
The R value of the oxygen-containing aluminum compound composite is baselined over the entire measurement range (830 cm ^{−1 to} 1940 cm ⁻¹ ) using a Raman spectrum measurement device (NSR-1000 type, manufactured by JASCO Corporation, excitation wavelength 532 nm). Can be obtained from Raman spectrum analysis.

<Positive electrode mixture for lithium ion secondary battery>
The positive electrode mixture for lithium ion secondary batteries of the present embodiment (hereinafter also simply referred to as “positive electrode mixture”) contains the positive electrode active material and the positive electrode material described above.

  The positive electrode mixture of the present embodiment is a positive electrode composite in a lithium ion secondary battery comprising a positive electrode having a current collector and a positive electrode mixture layer, a negative electrode, a separator, and an electrolyte solution containing a fluorine-containing lithium salt electrolyte. Used to form material layers. By using the positive electrode mixture of the present embodiment for forming the positive electrode mixture layer of the lithium ion secondary battery having the above-described configuration, the output characteristics are excellent and the voltage is high (for example, the charging voltage is 4.35 V). A lithium ion secondary battery in which a decrease in capacity after the charge / discharge cycle is suppressed can be obtained.

(Positive electrode active material)
The positive electrode active material is not particularly limited, and examples thereof include lithium-containing composite metal oxides, olivine-type lithium salts, chalcogen compounds, and manganese dioxide. A positive electrode active material may be used individually by 1 type, and may be used in combination of 2 or more type. Among these positive electrode active materials, it is preferable to include a lithium-containing composite metal oxide.

The lithium-containing composite metal oxide is a metal oxide containing lithium and a transition metal, or a metal oxide in which a part of the transition metal in the metal oxide is substituted with a different element. Here, examples of the different elements include Na, Mg, Sc, Y, Mn, Fe, Co, Ni, Cu, Zn, Al, Cr, Pb, Sb, V, and B. Mn, Al, Co, Ni, Mg and the like are preferable. The heterogeneous element may be one type or two or more types.
Examples of the lithium-containing composite metal oxide include Li _x CoO ₂ , Li _x NiO ₂ , Li _x Co _y Ni _1-y O ₂ , Li _x Co _y M ¹ _1-y O _z (wherein M ¹ is Na And at least one element selected from the group consisting of Mg, Sc, Y, Mn, Fe, Ni, Cu, Zn, Al, Cr, Pb, Sb, V, and B.), Li _x Ni _{1− y} M ² _y O _z (wherein M ² is selected from the group consisting of Na, Mg, Sc, Y, Mn, Fe, Co, Cu, Zn, Al, Cr, Pb, Sb, V, and B) Represents at least one element), LiM ³ PO ₄ (wherein M ³ is Na, Mg, Sc, Y, Mn, Fe, Co, Ni, Cu, Zn, Al, Cr, Pb, Sb, At least one element selected from the group consisting of V and B). i in ₂ M ³ PO ₄ F (wherein, ^{M 3} is, Na, Mg, Sc, Y , Mn, Fe, Co, Ni, Cu, Zn, Al, Cr, Pb, Sb, V, and the group consisting of B And at least one element selected from the above. Here, in each formula, x is 0 to 1.2, y is 0 to 0.9, and z is 2.0 to 2.3. The x value indicating the molar ratio of lithium is increased or decreased by charging and discharging.

Examples of the olivine type lithium salt include LiFePO ₄ .
Examples of the chalcogen compound include titanium disulfide and molybdenum disulfide.

  The positive electrode active material is generally in the form of particles, and examples of the shape of the particles include lumps, polyhedrons, spheres, ellipsoids, plates, needles, and columns. As the positive electrode active material, it is preferable that primary particles aggregate to form secondary particles, and the shape of the secondary particles is spherical or elliptical.

  In an electrochemical element such as a battery, the active material in the electrode expands and contracts as it is charged and discharged, and the stress tends to cause degradation such as destruction of the active material and disconnection of the conductive path. Therefore, as the positive electrode active material, rather than using the material present as the primary particles, it is preferable to use the material present by agglomerating the primary particles to form the secondary particles, which reduces the stress of expansion and contraction. Can be prevented. In addition, it is preferable to use spherical or oval spherical particles rather than plate-like particles having axial orientation, since the orientation in the electrode is reduced, so that the expansion and contraction of the electrode during charge / discharge is reduced. Further, it is preferable because other materials such as a conductive material are easily mixed uniformly when forming the electrode.

From the viewpoint of obtaining a desired tap density, the volume average particle diameter of the positive electrode active material (when the primary particles aggregate to form secondary particles, the volume average particle diameter of the secondary particles, the same shall apply hereinafter), for example, The thickness is preferably 0.1 μm or more, more preferably 0.5 μm or more, still more preferably 1 μm or more, and particularly preferably 3 μm or more. Further, the volume average particle diameter of the positive electrode active material is, for example, preferably 20 μm or less, more preferably 18 μm or less, and further preferably 16 μm or less, from the viewpoint of improving electrode formability and battery performance. The thickness is preferably 15 μm or less. Here, as the positive electrode active material, the tap density (fillability) may be improved by mixing two or more types having different volume average particle diameters.
The volume average particle diameter of the positive electrode active material is measured using a laser diffraction method in the same manner as the volume average particle diameter of the oxygen-containing aluminum compound composite.

  When the positive electrode active material is formed by agglomerating primary particles to form secondary particles, the average particle diameter of the primary particles is, for example, 0.01 μm or more from the viewpoint of good reversibility of charge and discharge. Is preferably 0.05 μm or more, more preferably 0.08 μm or more, and particularly preferably 0.1 μm or more. The average particle diameter of the primary particles is, for example, preferably 3 μm or less, more preferably 2 μm or less, and even more preferably 1 μm or less, from the viewpoint of improving battery performance such as output characteristics. Particularly preferably, it is 0.6 μm or less.

From the viewpoint of improving battery performance, the BET specific surface area of the positive electrode active material is, for example, preferably 0.1 m ² / g or more, more preferably 0.2 m ² / g or more, and 0.3 m ^2. / G or more is more preferable. In addition, 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, from the viewpoint of enhancing the electrode formability, and 1.5 m ^2. / G or less is more preferable.
Similar to the BET specific surface area of the oxygen-containing aluminum compound composite, the BET specific surface area of the positive electrode active material is measured from the nitrogen adsorption ability at 77 K according to JIS Z 8830 (2001).

(Positive electrode material)
The positive electrode mixture of the present embodiment contains the positive electrode material described above. Since the positive electrode material has been described above, a detailed description thereof will be omitted.

  The content rate of the oxygen-containing aluminum compound composite with respect to the total amount of the positive electrode mixture is, for example, from 0.1% by mass to 30% by mass from the viewpoint of suppressing a decrease in capacity after a charge / discharge cycle at a high voltage and improving output characteristics. %, And more preferably 0.2% by mass to 20% by mass.

(Conductive material)
The positive electrode mixture may contain a conductive material in order to improve battery performance. The conductive material is not particularly limited, and examples thereof include graphite (graphite) such as natural graphite, artificial graphite, and fibrous graphite; carbon black such as acetylene black. Among carbon blacks, acetylene black is particularly preferable. A conductive material may be used individually by 1 type, and may be used in combination of 2 or more type.

In the case of containing carbon black as the conductive material, from the viewpoint of improving the dispersibility of the positive electrode mixture and the input / output characteristics of the battery, the carbon black is preferably particles having an average particle diameter of 20 nm to 100 nm, for example. Are more preferably particles having an average particle size of 40 nm to 60 nm.
Examples of the shape of the particles include granular shapes, flake shapes (flaky shapes), spherical shapes, columnar shapes, irregular shapes, and the like.
“Granular” is not an irregular shape but a shape having substantially the same dimensions (see JIS Z2500: 2000).
“Flake shape (strip shape)” is a plate-like shape (see JIS Z2500: 2000), and is also referred to as a scale-like shape because it is a thin plate shape like a scale. In this specification, it analyzes from the result observed with the scanning electron microscope (SEM), and makes the range whose aspect ratio (particle diameter a / average thickness t) 2-100 into a piece. The particle diameter a here is defined as the square root of the area S when the flaky particles are viewed in plan, and this is the particle diameter of the flaky particles.
“Spherical” means a shape that is almost 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) (also referred to as spherical coefficient or sphericity) is 1. It shall be in the range of 0-1.2, and a particle diameter shall point out a long diameter (DL).
“Columnar” refers to a shape such as a substantially cylindrical column or a substantially polygonal column, and the particle diameter refers to the height of the column.

  When graphite is contained as the conductive material, the average particle size of graphite is preferably 1 μm to 10 μm. Moreover, it is preferable that the carbon network surface interlayer (d002) in a X-ray wide angle diffraction method is 0.3354 nm-0.337 nm.

  In the case where both carbon black and graphite are contained as the conductive material, the mass ratio (A1 / (A1 + A2)) when the content of carbon black is A1 and the content of graphite is A2, is the charge / discharge of the battery. From the viewpoint of characteristics, for example, it is preferably 0.1 to 0.9, and more preferably 0.4 to 0.85.

  Note that the average particle diameter of the conductive material is an arithmetic average particle diameter obtained by photographing with a scanning electron microscope photographed at a magnification of 200,000 and measuring all the diameters of the in-image particle images.

  When the positive electrode mixture contains a conductive material, the content of the conductive material is, for example, preferably 0.1% by mass or more and 0.2% by mass or more with respect to the total amount of the positive electrode mixture. Is more preferable, and it is still more preferable that it is 0.5 mass% or more. Further, the content of the conductive material is, for example, preferably 30% by mass or less, more preferably 20% by mass or less, and further preferably 10% by mass or less, with respect to the total amount of the positive electrode mixture. preferable. Within the above range, the battery capacity and input / output characteristics tend to be excellent.

  Moreover, when carbon black is contained as a conductive material, the content of carbon black is, for example, 0.1% by mass to 15% by mass with respect to the total amount of the positive electrode mixture from the viewpoint of conductivity and high capacity. It is preferable that it is 0.2 mass%-10 mass%, and it is still more preferable that it is 0.5 mass%-5 mass%. Within the above range, the battery capacity and input / output characteristics tend to be excellent.

(Binder)
The positive electrode mixture may contain a binder in order to improve the adhesion between the positive electrode mixture and the current collector and the adhesion between the positive electrode active materials.
The binding material is not particularly limited. When the positive electrode mixture layer is formed by a wet method, a material having good dispersibility in the dispersion solvent is preferable. Specific examples of the binder 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), fluoropolymer, isoprene rubber, butadiene rubber, ethylene-propylene rubber, and other rubbery polymers; styrene / butadiene / styrene block copolymers or hydrogenated products thereof, EPDM (ethylene / propylene / diene terpolymers) ), Thermoplastic elastomeric polymers such as styrene / ethylene / butadiene / ethylene copolymers, styrene / isoprene / styrene block copolymers or hydrogenated products thereof; syndiotactic-1,2-polybutadiene, poly Soft resin polymers such as vinyl acid, ethylene / vinyl acetate copolymer, propylene / α-olefin copolymer; polyvinylidene fluoride (PVdF), polytetrafluoroethylene, fluorinated polyvinylidene fluoride, polytetrafluoroethylene Fluorine polymers such as ethylene copolymers and polytetrafluoroethylene / vinylidene fluoride copolymers; polymer compositions having ion conductivity of alkali metal ions (particularly lithium ions), and the like. A binder may be used individually by 1 type and may be used in combination of 2 or more type.
From the viewpoint of the stability of the positive electrode, it is preferable to use a fluorine-based polymer such as polyvinylidene fluoride (PVdF), polytetrafluoroethylene / vinylidene fluoride copolymer, among the binders.

  When the positive electrode mixture contains a binder, the content of the binder is, for example, preferably 0.5% by mass or more with respect to the total amount of the positive electrode mixture, and is 1% by mass or more. Is more preferable, and it is still more preferable that it is 2 mass% or more. The content of the binder is, for example, preferably 50% by mass or less, more preferably 40% by mass or less, and preferably 30% by mass or less with respect to the total amount of the positive electrode mixture. More preferred is 10% by mass or less. Within the above range, battery performance such as cycle characteristics tends to be improved.

<Positive electrode for lithium ion secondary battery>
The positive electrode for a lithium ion secondary battery of the present embodiment (hereinafter also simply referred to as “positive electrode”) includes a current collector and a positive electrode mixture layer formed on the current collector. The layer contains a positive electrode active material and the positive electrode material described above.

  The positive electrode of this embodiment is used for a lithium ion secondary battery including a positive electrode, a negative electrode, a separator, and an electrolytic solution containing a fluorine-containing lithium salt electrolyte. By using the positive electrode of the present embodiment for a lithium ion secondary battery having the above-described configuration, the output characteristics are excellent, and capacity reduction after a charge / discharge cycle at a high voltage (for example, a charge voltage of 4.35 V) is suppressed. The obtained lithium ion secondary battery can be obtained.

  The material of the current collector is not particularly limited. Examples of the material of the current collector 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 in the case of using a metal material include a metal foil, a metal cylinder, a metal coil, a metal plate, a metal thin film, an expanded metal, a punch metal, a foam metal, and the shape in the case of using a carbonaceous material. A board, a carbon thin film, a carbon cylinder, etc. are mentioned. Among these, a metal thin film is preferably used as the current collector. The metal thin film may be formed in a mesh shape as necessary. The thickness of the metal thin film is arbitrary, for example, preferably 1 μm or more, more preferably 3 μm or more, and still more preferably 5 μm or more. Further, the thickness of the metal thin film is preferably 1 mm or less, more preferably 100 μm or less, and further preferably 50 μm or less. By setting the thickness of the metal thin film to 1 μm or more, the strength required for the current collector tends to be obtained. Further, when the thickness of the metal thin film is 1 mm or less, sufficient flexibility is obtained and the workability tends to be good.

  The positive electrode mixture layer contains the positive electrode active material and the positive electrode material described above, and is formed on the current collector. For example, the positive electrode mixture described above can be used to form the positive electrode mixture layer. In the case of using a current collector on a thin film or plate, the positive electrode mixture layer may be formed on one side of the current collector or on both sides of the current collector.

  The method for forming the positive electrode mixture layer is not particularly limited, and examples thereof include a dry method and a wet method. In the dry method, the positive electrode active material, the above-described positive electrode material, and other materials such as a conductive material and a binder used as necessary are dry mixed to form a sheet, which is pressure-bonded to a current collector. In the wet method, the positive electrode active material, the positive electrode material described above, and other materials such as a conductive material and a binder used as necessary are dissolved or dispersed in a dispersion solvent to form a slurry, which is used as a current collector. Apply to and dry.

  The dispersion solvent for preparing the slurry may be a solvent that can dissolve or disperse the positive electrode active material, the positive electrode material described above, and other materials such as a conductive material and a binder used as necessary. For example, the type is not limited, and either an aqueous solvent or an organic solvent may be used. Examples of the aqueous solvent include water, a mixed solvent of alcohol and water, and the like. Examples of organic solvents include N-methylpyrrolidone (NMP), dimethylformamide, dimethylacetamide, methyl ethyl ketone, cyclohexanone, methyl acetate, methyl acrylate, diethyltriamine, N, N-dimethylaminopropylamine, tetrahydrofuran (THF), toluene, Acetone, diethyl ether, dimethylacetamide, hexamethylphosphalamide, dimethyl sulfoxide, benzene, xylene, quinoline, pyridine, methylnaphthalene, hexane and the like can be mentioned. Dispersion solvents may be used alone or in combination of two or more.

  When an aqueous solvent is used as a dispersion solvent for preparing the slurry, the slurry preferably contains a thickener. The thickener is not particularly limited. Specific examples of the thickener 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, and may be used in combination of 2 or more type.

  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.

Positive electrode composite material layer is preferably a density of ^{3.0g / cm 3 ~4.0g / cm 3} . When the density of the positive electrode mixture layer is within the above range, the input / output characteristics tend to be improved. From such a viewpoint, the amount of one surface applied to the current collector is preferably 100 g / m ^{2 to} 300 g / m ² or less, more preferably 150 g / m ^{2 to} 250 g / m ² , and 185 g / m ^2. it is more preferably ^{m 2} ~220g / m ^2.

<Lithium ion secondary battery>
The lithium ion secondary battery of the present embodiment includes the above-described positive electrode, negative electrode, separator, and an electrolytic solution containing a fluorine-containing lithium salt electrolyte.
The lithium ion secondary battery of the present embodiment has excellent output characteristics and suppresses a decrease in capacity after a charge / discharge cycle at a high voltage (for example, a charge voltage of 4.35 V).

  When charging the 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 are desorbed and released into the electrolytic solution. The lithium ions released into the electrolytic solution move in 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 constituting the negative electrode.

  When discharging the lithium ion secondary battery, an external load is connected between the positive electrode and the negative electrode. At the time of discharging, the lithium ions inserted into the negative electrode active material are desorbed and released into the electrolytic solution. 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 reaching the positive electrode are inserted into the positive electrode active material constituting the positive electrode. At this time, 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.

  Thus, the lithium ion secondary battery can be charged and discharged by inserting and 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.

  Since the positive electrode of the lithium ion secondary battery of this embodiment is as described above, the following description will be made on the negative electrode, electrolyte, separator, and other components of the lithium ion secondary battery of this embodiment.

1. Negative Electrode The negative electrode (negative electrode plate) of the present embodiment has a current collector and a negative electrode mixture layer formed on the current collector. The negative electrode mixture layer may be formed on one side of the current collector or on both sides of the current collector. The negative electrode mixture layer contains a negative electrode active material capable of electrochemically inserting and extracting lithium ions. The negative electrode mixture layer may contain a conductive material, a binder, and the like as necessary.

  The material of the current collector is not particularly limited. Examples of the material of the current collector 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. 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 suitable as a current collector.

  The thickness of the current collector is not particularly limited. When the thickness of the current collector is less than 25 μm, the strength of the current collector is improved by using a stronger copper alloy (phosphor bronze, titanium copper, Corson alloy, Cu—Cr—Zr alloy, etc.) than pure copper. Can do.

  The negative electrode active material contained in the negative electrode mixture layer includes carbonaceous materials; metal oxides such as tin oxide and silicon oxide; metal composite oxides; lithium simple substance; lithium alloys such as lithium aluminum alloys; Sn, Si, Ge Examples thereof include metal oxides or nitrides capable of forming an alloy with lithium. A negative electrode active material may be used individually by 1 type, and may be used in combination of 2 or more type.

  The metal composite oxide is not particularly limited as long as it can occlude and release lithium. Among metal complex oxides, Ti (titanium), Li (lithium), or one containing both Ti and Li is preferable from the viewpoint of high current density charge / discharge characteristics.

  Examples of carbonaceous materials include amorphous carbon; natural graphite; composite carbonaceous material in which a film formed on natural graphite by a dry CVD method or a wet spray method; a resin material such as an epoxy compound or a phenol compound; or Examples thereof include artificial graphite obtained by firing a pitch material obtained from petroleum or coal as a raw material.

  The carbonaceous material is highly conductive and is an excellent material in terms of low temperature characteristics and cycle stability. Among the carbonaceous materials, a material (amorphous carbon) having a wide carbon network interlayer (d002) is preferable from the viewpoint of high input / output characteristics. However, since a material having a wide carbon network surface layer (d002) may have low capacity or charge / discharge efficiency at the initial stage of charging, the carbon network layer (d002) is a carbonaceous material from the viewpoint of battery characteristics. It is preferable to select a material of 0.39 nm or less. Such a carbonaceous material is sometimes referred to as pseudo-anisotropic carbon.

  Examples of the material (amorphous carbon) having a wide carbon network surface layer (d002) include hard carbon and soft carbon, and soft carbon is preferable from the viewpoint of cycle characteristics. The soft carbon preferably has a carbon network plane interlayer (d002) in the X-ray wide angle diffraction method of, for example, 0.34 nm to 0.36 nm, more preferably 0.341 nm to 0.355 nm, and More preferably, it is 342 nm-0.35 nm.

As the carbonaceous material, graphite is preferable from the viewpoint of increasing the capacity. Graphite preferably has a carbon network plane interlayer (d002) of, for example, less than 0.34 nm and more preferably 0.3354 nm to 0.337 nm in the X-ray wide angle diffraction method.
Further, as the negative electrode active material, a carbonaceous material having high conductivity such as graphite, amorphous, activated carbon or the like may be mixed and used.

  The negative electrode mixture layer may contain a second carbonaceous material having a different property from the first carbonaceous material used as the negative electrode active material as a conductive material. The above properties consist of X-ray diffraction parameters, median diameter, aspect ratio, BET specific surface area, orientation ratio, R value obtained from Raman spectrum analysis, tap density, true density, pore distribution, circularity, and ash content. At least one characteristic selected from the group; When the negative electrode mixture layer contains the second carbonaceous material (conductive material), the resistance of the electrode tends to be reduced.

  As the second carbonaceous material (conductive material), a highly conductive carbonaceous material such as graphite, amorphous, activated carbon or the like can be used. Specifically, graphite (graphite) such as natural graphite and artificial graphite, carbon black such as acetylene black, and amorphous carbon such as needle coke can be used. A 2nd carbonaceous material (electrically conductive material) may be used individually by 1 type, and may be used in combination of 2 or more type.

  The content of the second carbonaceous material (conductive material) with respect to the mass of the negative electrode mixture layer is, for example, preferably 1% by mass or more, more preferably 2% by mass or more, and 3% by mass or more. More preferably. Moreover, it is preferable that the content rate of the 2nd carbonaceous material (electrically conductive material) with respect to the mass of a negative electrode compound material layer is 45 mass% or less, for example, and it is more preferable that it is 40 mass% or less. By making the content rate of the second carbonaceous material (conductive material) with respect to the mass of the negative electrode composite material layer 1% by mass or more, an effect of improving conductivity is obtained, and the second carbonaceous material with respect to the mass of the negative electrode composite material layer is obtained. By setting the content of (conductive material) to 45% by mass or less, an increase in initial irreversible capacity tends to be suppressed.

  The negative electrode mixture layer may contain a binder in order to improve the adhesion between the positive electrode mixture and the current collector and the adhesion between the positive electrode active materials. The binder is not particularly limited, and for example, those exemplified as the binder used for the positive electrode mixture can be used.

  When the negative electrode mixture layer contains a binder, the content of the binder is preferably 0.1% by mass or more, for example, 0.2% by mass with respect to the total amount of the negative electrode mixture layer. More preferably, it is more preferably 0.5% by mass or more. The content of the binder is, for example, preferably 20% by mass or less, more preferably 15% by mass or less, and preferably 10% by mass or less, with respect to the total amount of the negative electrode mixture layer. Is more preferable, and it is especially preferable that it is 8 mass% or less. By setting the content of the binder to 0.1% by mass or more, the strength of the negative electrode mixture layer tends to be increased. Moreover, it exists in the tendency which can suppress the fall of battery capacity by making the content rate of a binder into 20 mass% or less.

  In particular, when a rubbery polymer such as SBR is used as the binder, the content of the binder is preferably, for example, 0.1% by mass or more with respect to the total amount of the negative electrode mixture layer. It is more preferably 2% by mass or more, and further preferably 0.5% by mass or more. In addition, the content of the binder is, for example, preferably 5% by mass or less, more preferably 3% by mass or less, and more preferably 2% by mass or less with respect to the total amount of the negative electrode mixture layer. Is more preferable.

  When a fluorine-based polymer such as polyvinylidene fluoride is used as the binder, the content of the binder is preferably 1% by mass or more with respect to the total amount of the negative electrode mixture layer. The content is more preferably at least 3% by mass, and still more preferably at least 3% by mass. Further, the content of the binder is, for example, preferably 15% by mass or less, more preferably 10% by mass or less, and 8% by mass or less, with respect to the total amount of the negative electrode mixture layer. Is more preferable.

  The negative electrode mixture layer is formed on the current collector. The method for forming the negative electrode mixture layer is not limited, and it can be formed by a dry method or a wet method in the same manner as the positive electrode mixture layer.

  When the negative electrode mixture layer is formed by a wet method, the dispersion solvent for preparing the slurry is not particularly limited, and for example, those exemplified as the dispersion solvent used for forming the positive electrode mixture layer can be used.

  When an aqueous solvent is used as a dispersion solvent for preparing the slurry, the slurry preferably contains a thickener. It does not restrict | limit especially as a thickener, For example, what was illustrated as a thickener used for formation of a positive mix layer can be used.

  When the slurry contains a thickener, the content of the thickener is, for example, preferably 0.1% by mass or more and more preferably 0.2% by mass or more with respect to the total amount of the slurry. Preferably, it is 0.5 mass% or more. The content of the thickener is, for example, preferably 5% by mass or less, more preferably 3% by mass or less, and still more preferably 2% by mass or less with respect to the total amount of the slurry. . By setting the content of the thickener to 0.1% by mass or more, the coating property of the slurry tends to be improved. Moreover, it exists in the tendency which can suppress the fall of battery capacity and the raise of the resistance between negative electrode active materials by making the content rate of a thickener into 5 mass% or less.

2. Electrolytic Solution The electrolytic solution includes a fluorine-containing lithium salt electrolyte and a nonaqueous solvent that dissolves the same. The electrolytic solution may contain an additive as necessary.

From the viewpoint of output characteristics, the fluorine-containing lithium salt electrolyte preferably contains lithium hexafluorophosphate (LiPF ₆ ). If necessary, a fluorine-containing lithium salt electrolyte other than lithium hexafluorophosphate (LiPF ₆ ) may be used. May be included.

The lithium hexafluorophosphate (LiPF ₆₎ other than a fluorine-containing lithium salt _electrolyte, LiBF _4, LiAsF _6, LiSbF ₆ such as inorganic fluoride _salts; LiClO _4, LiBrO _4, perhalogenate of LiIO ₄ like; LiAlCl Inorganic chloride salts such as ₄ ; perfluoroalkane sulfonates such as LiCF ₃ SO ₃ ; LiN (CF ₃ SO ₂ ) ₂ , LiN (CF ₃ CF ₂ SO ₂ ) ₂ , LiN (CF ₃ SO ₂ ) (C Perfluoroalkanesulfonylimide salts such as ₄ F ₉ SO ₂ ); perfluoroalkanesulfonylmethide salts 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)], Li [PF 4 (CF 2 CF 2 CF 2 CF 3) 2], Li [PF 3 (CF 2 CF 2 CF 2 CF 3) 3] such as Examples thereof include fluoroalkyl fluorophosphates; oxalate borates such as lithium bis (oxalato) borate and lithium difluorooxalatoborate. Fluorine-containing lithium salt electrolytes other than lithium hexafluorophosphate (LiPF ₆ ) may be used singly or in combination of two or more.
From the viewpoint of battery performance, the content of lithium hexafluorophosphate (LiPF ₆ ) is preferably 10% by mass or more and more preferably 50% by mass or more based on the total amount of the fluorine-containing lithium salt electrolyte. preferable.

  The concentration of the fluorine-containing lithium salt electrolyte in the nonaqueous electrolytic solution is not particularly limited. The concentration of the fluorine-containing lithium salt electrolyte in the nonaqueous electrolytic solution is, for example, preferably 0.5 mol / L or more, more preferably 0.6 mol / L or more, and 0.7 mol / L or more. More preferably. The concentration of the fluorine-containing lithium salt electrolyte in the non-aqueous electrolyte is, for example, preferably 2 mol / L or less, more preferably 1.8 mol / L or less, and 1.7 mol / L or less. More preferably. By setting the concentration of the fluorine-containing lithium salt electrolyte to 0.5 mol / L or more, the electric conductivity of the electrolytic solution tends to be sufficiently secured. Further, by setting the concentration of the fluorine-containing lithium salt electrolyte to 2 mol / L or less, an increase in the viscosity of the electrolytic solution is suppressed, and a decrease in electrical conductivity tends to be suppressed. In addition, when the electrical conductivity of electrolyte solution falls, there exists a possibility that the performance of a lithium ion secondary battery may fall.

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

  As the cyclic carbonate, those having 2 to 6 carbon atoms of the alkylene group constituting the cyclic carbonate are preferable, and those having 2 to 4 are more preferable. Specific examples include ethylene carbonate, propylene carbonate, butylene carbonate, and the like. Of these, ethylene carbonate and propylene carbonate are preferable. In addition, as the cyclic carbonate, a cyclic carbonate having a double bond in the molecule such as vinylene carbonate or a cyclic carbonate containing a halogen atom such as fluoroethylene carbonate can also be used. When a carbonaceous material is used as the negative electrode active material, the non-aqueous solvent preferably contains vinylene carbonate from the viewpoint of cycle characteristics.

  As the chain carbonate, dialkyl carbonate is preferable, and those having two alkyl groups each having 1 to 5 carbon atoms are preferable, and those having 1 to 4 carbon atoms are more preferable. Specific examples include symmetric chain carbonates such as dimethyl carbonate, diethyl carbonate, and di-n-propyl carbonate; and asymmetric chain carbonates such as methyl ethyl carbonate, methyl-n-propyl carbonate, and ethyl-n-propyl carbonate. It is done. 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, it is preferable to use methyl acetate 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 preferably used from the viewpoint of improving input / output characteristics.
Examples of chain ethers include dimethoxyethane and dimethoxymethane.

  A non-aqueous solvent may be used individually by 1 type, and may be used in combination of 2 or more type. As the non-aqueous solvent, it is preferable to use a mixed solvent in which two or more kinds of non-aqueous solvents are mixed. For example, a high dielectric constant solvent such as cyclic carbonate and a low viscosity solvent such as chain carbonate or chain ester are preferably used in combination. One of the preferable combinations is a combination mainly composed of a cyclic carbonate and a chain carbonate. Among them, the total of the cyclic carbonate and the chain carbonate in the nonaqueous solvent is, for example, preferably 80% by volume or more, more preferably 85% by volume or more, and further preferably 90% by volume or more. preferable. At this time, the ratio of the cyclic carbonate to the total of the cyclic carbonate and the chain carbonate is, for example, preferably 5% by volume or more, more preferably 10% by volume or more, and 15% by volume or more. Further preferred. Further, the ratio of the cyclic carbonate to the total of the cyclic carbonate and the chain carbonate is, for example, preferably 50% by volume or less, more preferably 35% by volume or less, and further preferably 30% by volume or less. preferable. By using such a combination of non-aqueous solvents, the cycle characteristics and storage characteristics of the lithium ion secondary battery tend to be improved.

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

  Among these combinations, those containing both a symmetric chain carbonate and an asymmetric chain carbonate are preferable as the chain carbonate. Specific examples include a combination of ethylene carbonate, dimethyl carbonate and methyl ethyl carbonate, ethylene carbonate, diethyl carbonate and methyl ethyl carbonate, ethylene carbonate, dimethyl carbonate, diethyl carbonate and methyl ethyl carbonate. Such a combination of cyclic carbonate, symmetric chain carbonate and asymmetric chain carbonate can improve cycle characteristics and input / output characteristics. Among these, a combination in which the asymmetric chain carbonate is methyl ethyl carbonate is preferable. Moreover, the combination whose symmetrical chain carbonate is dialkyl carbonate whose carbon number of an alkyl group is 1-2 is preferable.

  The additive is not particularly limited as long as it is an additive used for a non-aqueous electrolyte of a lithium ion secondary battery. Examples of the additive include nitrogen, sulfur, or a heterocyclic compound containing nitrogen and sulfur, a cyclic carboxylic acid ester, a fluorine-containing cyclic carbonate, and other compounds having an unsaturated bond in the molecule. 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.

3. Separator The separator is not particularly limited as long as it has ion permeability while electronically insulating the positive electrode and the negative electrode, and has resistance to oxidation on the positive electrode side and reducibility on the negative electrode side. As a material (material) of the separator that satisfies such characteristics, a resin, an inorganic substance, or the like is used.

  Examples of the resin include olefin resin, fluororesin, cellulose resin, polyimide resin, and nylon resin. Among these, it is preferable to select from materials that are stable with respect to the non-aqueous electrolyte and have excellent liquid retention properties, and it is preferable to use a porous sheet made of polyolefin such as polyethylene and polypropylene, a nonwoven fabric, and the like.

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

The lithium ion secondary battery of this embodiment may be provided with other components other than a positive electrode, a negative electrode, electrolyte solution, and a separator as needed.
For example, the lithium ion secondary battery of this embodiment may include a cleavage valve in order to suppress an increase in pressure inside the battery. By opening the cleavage valve, it is possible to suppress an increase in pressure inside the battery and to improve safety.

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

4). Configuration of Lithium Ion Secondary Battery The shape of the lithium ion secondary battery of the present embodiment is not particularly limited, and may be any of a laminate type, a cylindrical shape, a rectangular shape, and the like.

  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. A laminated body in which the positive electrode, the separator, and the negative electrode are laminated in this order is prepared, and accommodated in an aluminum laminate pack in this state, and the positive and negative electrode terminals are taken out of the laminate pack and sealed. Next, a nonaqueous electrolytic solution is poured into the laminate pack, and the opening of the laminate pack is sealed. Thereby, a lithium ion secondary battery is obtained.

Next, the configuration of a 18650-type cylindrical lithium ion secondary battery will be described with reference to the drawings. Note that “upper” and “lower” in the description indicate “upper” and “lower” in the figure, and do not limit “upper” and “lower” of the lithium ion secondary battery.
As shown in FIG. 6, the lithium ion secondary battery 1 has a bottomed cylindrical battery container 6 made of steel plated with nickel. The battery case 6 accommodates an electrode group 5 in which a strip-like positive electrode plate 2 and a negative electrode plate 3 are wound in a spiral shape with a separator 4 interposed therebetween. In the electrode group 5, the positive electrode plate 2 and the negative electrode plate 3 are wound in a spiral shape in cross section via a separator 4 made of a polyethylene porous sheet. For example, the separator 4 has a width of 58 mm and a thickness of 30 μm. A ribbon-like positive electrode tab terminal made of aluminum and having one end fixed to the positive electrode plate 2 is led out on the upper end surface of the electrode group 5. 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 ribbon-like negative electrode tab terminal made of copper with 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 out to the opposite sides of the both end surfaces 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. 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.

(Capacity ratio between the negative electrode and the positive electrode of a lithium ion secondary battery)
In the present embodiment, the capacity ratio between the negative electrode and the positive electrode (negative electrode capacity / positive electrode capacity) is preferably 1.03 to 1.8, for example, from the viewpoint of safety and energy density, and 1.05 to 1 .4 is more preferable.
Here, the negative electrode capacity indicates “negative electrode discharge capacity”, and the positive electrode capacity indicates “positive electrode initial charge capacity−negative electrode or positive electrode, whichever is greater,”. The “negative electrode discharge capacity” is defined as calculated by the charge / discharge device when lithium ions inserted into the negative electrode active material are desorbed. The “initial charge capacity of the positive electrode” is defined as 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 lithium ion secondary battery / discharge capacity of negative electrode”. The discharge capacity of the lithium ion secondary battery is, for example, 4.35 V, 0.1 C to 0.5 C, 0.1 C after performing constant current constant voltage (CCCV) charging with an end time of 2 hours to 15 hours. It can be measured under conditions when a constant current (CC) discharge is performed up to 2.5V at 0.5C. The discharge capacity of the negative electrode is obtained by cutting a negative electrode whose discharge capacity of a lithium ion secondary battery is measured into a predetermined area, using lithium metal as a counter electrode, and producing a single electrode cell through a separator impregnated with an electrolyte, After constant current constant voltage (CCCV) charge at 0V, 0.1C to 0.5C, end current 0.01C, and then at constant current (CC) discharge to 1.5V at 0.1C to 0.5C It can be calculated by measuring the discharge capacity per predetermined area under the conditions and converting this to the total area used as the negative electrode of the lithium ion secondary 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 lithium ions inserted into the negative electrode active material are desorbed is defined as discharging. C means “current value (A) / battery discharge capacity (Ah)”.

  Hereinafter, the present embodiment will be described in more detail based on examples. The present invention is not limited to the following examples.

[Production Example 1]
<Production of oxygen-containing aluminum compound particles>
A concentration: 350 mmol / L sodium orthosilicate aqueous solution (500 mL) was added to a 700 mmol / L aluminum chloride aqueous solution (500 mL), and the mixture was stirred for 30 minutes. To this solution, 330 mL of a 1 mol / L sodium hydroxide aqueous solution was added to adjust the pH to 6.1.
After the pH-adjusted solution was stirred for 30 minutes, centrifugal separation was carried out for 5 minutes at a rotational speed of 3000 revolutions / minute, using Tommy Seiko Co., Ltd .: Suprema23 and standard rotor NA-16 as a centrifugal separator. 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 four times.

  135 mL of hydrochloric acid having a concentration of 1 mol / L was added to the gel-like precipitate obtained after discharging the supernatant in the fourth 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 (2 days). To the solution after heating (salt concentration 47 g / L), 188 mL of a 1 mol / L sodium hydroxide aqueous solution was added to adjust the pH to 9.1. By adjusting the pH, the salt in the solution was aggregated, 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 four times. The gel-like precipitate obtained after the fourth desalting of the desalting treatment was dried at 60 ° C. for 16 hours to recover 30 g of a particle lump. The particle mass was pulverized with a jet mill to obtain oxygen-containing aluminum compound particles.

As a result of analyzing the obtained particles using an ICP emission spectrometer (P-4010, manufactured by Hitachi, Ltd.), it was confirmed that the obtained particles were an oxygen-containing aluminum compound having an element molar ratio Si / Al of 0.5. It was done. Further, as a result of powder X-ray diffraction measurement, no peak indicating a mullite structure was observed, and broad peaks were observed around 2θ = 25 ° and 2θ = 41 °. The compound particles were confirmed to be amorphous aluminum silicate.
Moreover, it observed at 100000 times with the acceleration voltage of 100 kV using the transmission electron microscope (TEM) (Hitachi High-Tech Science Co., Ltd. make, H-7100FA type | mold). A sample for TEM observation was prepared as follows. In other words, a solution after heating (salt concentration 47 g / L) 10 times diluted with pure water and subjected to ultrasonic irradiation treatment for 5 minutes before the final desalting treatment step is used for preparing a TEM observation sample. It was prepared by dropping on the body and then drying naturally to form a thin film. As a result of TEM observation, a tubular product having a length of 50 nm or more was not observed.

<Carbon coating>
The above oxygen-containing aluminum compound particles and polyvinyl alcohol powder (manufactured by Wako Pure Chemical Industries, Ltd.) are mixed at a mass ratio of 100: 70, and heat-treated at 850 ° C. for 1 hour in a nitrogen atmosphere to obtain an oxygen-containing aluminum compound. An oxygen-containing aluminum compound composite in which carbon is arranged on at least a part of the particle surface was obtained. In addition, the R value of the obtained oxygen-containing aluminum compound composite was measured using a Raman spectrum measuring device (NSR-1000 type, manufactured by JASCO Corporation, excitation wavelength 532 nm), and the measurement range (830 cm ^{−1 to} 1940 cm ⁻¹ ). When the whole was calculated as a baseline, it was 1.0.

[Production Example 2]
<Production of oxygen-containing aluminum compound particles>
To an aluminum sulfate aqueous solution (800 mL) with an Al concentration of 1 mol / L, water glass (sodium silicate No. 3, Na ₂ O.nSiO ₂ .mH ₂ O) (200 mL) with an Si concentration of 2 mol / L is added and stirred for 30 minutes. did. To this solution, 1900 mL of a 1 mol / L sodium hydroxide aqueous solution was added to adjust the pH to 7. After the pH-adjusted solution was stirred for 30 minutes, desalting was performed by pressure filtration. To the precipitate after the desalting treatment, 90 mL of sulfuric acid having a concentration of 1 mol / L 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 (2 days). To the heated solution, 330 mL of a 1 mol / L sodium hydroxide aqueous solution was added 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 particle mass was pulverized with a jet mill to obtain oxygen-containing aluminum compound particles.

The obtained particles were analyzed using an ICP emission spectrometer (P-4010 (manufactured by Hitachi, Ltd.)) and confirmed to be an oxygen-containing aluminum compound having an element molar ratio Si / Al of 0.5. As a result of powder X-ray diffraction measurement, no peak indicating a mullite structure was observed, and broad peaks were observed around 2θ = 25 ° and 2θ = 41 °. It was confirmed that the oxygen-containing aluminum compound particles were amorphous aluminum silicate.
Further, as a result of TEM observation under the same conditions as in Production Example 1, a tubular product having a length of 50 nm or more was not observed.

<Carbon coating>
Carbon coating was performed in the same manner as described in Production Example 1 to obtain an oxygen-containing aluminum compound composite. The R value of the obtained oxygen-containing aluminum compound composite was calculated under the same conditions as in Production Example 1, and was 1.0.

[Production Example 3]
<Production of oxygen-containing aluminum compound particles>
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. To this solution, 890 mL of a 1 mol / L sodium hydroxide aqueous solution was added to adjust the pH to 7. After the pH-adjusted solution was stirred for 30 minutes, desalting was performed by pressure filtration. To the precipitate after the desalting treatment, 100 mL of sulfuric acid having a concentration of 1 mol / L 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 (2 days). To the heated solution, 235 mL of a sodium hydroxide aqueous solution having a concentration of 1 mol / L was added 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 particle mass was pulverized with a jet mill to obtain oxygen-containing aluminum compound particles.

As a result of analyzing the obtained particles using an ICP emission spectrometer (P-4010 (manufactured by Hitachi, Ltd.)), it was confirmed that it was an oxygen-containing aluminum compound having an element molar ratio Si / Al of 2.0. As a result of powder X-ray diffraction measurement, no peak indicating a mullite structure was observed, and broad peaks were observed around 2θ = 25 ° and 2θ = 41 °. It was confirmed that the oxygen-containing aluminum compound particles were amorphous aluminum silicate.
Further, as a result of TEM observation under the same conditions as in Production Example 1, a tubular product having a length of 50 nm or more was not observed.

<Carbon coating>
Carbon coating was performed in the same manner as described in Production Example 1 to obtain an oxygen-containing aluminum compound composite. The R value of the obtained oxygen-containing aluminum compound composite was calculated under the same conditions as in Production Example 1, and was 1.0.

[Production Example 4]
<Production of oxygen-containing aluminum compound particles>
A commercially available saponite (Smecton SA, manufactured by Kunimine Industry Co., Ltd.) was used as the core material. Saponite was pulverized with a jet mill to obtain oxygen-containing aluminum compound particles.

<Carbon coating>
Carbon coating was performed in the same manner as described in Production Example 1 to obtain an oxygen-containing aluminum compound composite. Further, the R value of the obtained oxygen-containing aluminum compound particles was measured under the same conditions as in Production Example 1, and was 1.0.

[Evaluation of physical properties of oxygen-containing aluminum compound composite]
<Weight reduction rate measurement>
The weight reduction rate of the oxygen-containing aluminum compound composite produced in Production Examples 1 to 4 was measured and calculated using a differential thermal-thermogravimetric analyzer (TG-DTA-6200, manufactured by Hitachi High-Tech Science Co., Ltd.). . The weight reduction rate was measured by raising the temperature from 25 ° C. at a rate of temperature increase of 10 ° C./min and maintaining at 850 ° C. for 20 minutes in a dry air flow. The weight reduction rate is expressed by the following formula (1) with respect to the mass at 25 ° C. (W0), the mass at 350 ° C. (W1), and the mass at 850 ° C. (W2) measured with a differential thermal-thermogravimetric analyzer. ) And (2). The results are shown in Table 1.
Weight reduction rate in the range of 25 ° C. to 350 ° C. (D1) (%) = {(W0−W1) / W0} × 100 (1)
Weight reduction rate in the range between 350 ° C. and 850 ° C. (D2) (%) = {(W1-W2) / W1} × 100 (2)

<Specific surface area measurement>
The BET specific surface area of the oxygen-containing aluminum compound composite produced in Production Examples 1 to 4 was measured from the nitrogen adsorption ability at 77K according to JIS Z 8830 (2001). As an evaluation apparatus, a nitrogen adsorption measuring apparatus (AUTOSORB-1, QUANTACHROME) was used.
When measuring the BET specific surface area, it is assumed that moisture adsorbed on the sample surface and in the structure affects the gas adsorption capacity. Therefore, pretreatment for removing moisture by heating was first 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, heated at 110 ° C. and held for 3 hours or more, and then kept at a normal temperature ( (25 ° C). After performing this pretreatment, the measurement was performed at an evaluation temperature of 77K and an evaluation pressure range of less than 1 in relative pressure (equilibrium pressure with respect to saturated vapor pressure). The results are shown in Table 1.

<Average particle size measurement>
The volume average particle diameter of the oxygen-containing aluminum compound composites produced in Production Examples 1 to 4 was measured using a laser diffraction particle size distribution measuring device (SALD3000J, manufactured by Shimadzu Corporation). Specifically, an oxygen-containing aluminum compound composite was dispersed in a dispersion medium such as water to prepare a dispersion. With respect to this dispersion, when a volume cumulative distribution curve was drawn from the small diameter side using a laser diffraction particle size distribution measuring device, the particle diameter (D50) at which accumulation was 50% was determined as the volume average particle diameter. The results are shown in Table 1.

Example 1
[Production of positive electrode]
The positive electrode plate was produced as follows. 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 oxygen-containing aluminum compound produced in Production Example 1 A composite (1% by mass) and polyvinylidene fluoride (PVDF) (3% by mass) as a binder were sequentially added and mixed to obtain a positive electrode mixture.
Furthermore, a slurry was prepared by adding N-methyl-2-pyrrolidone (NMP) as a dispersion solvent to the positive electrode mixture and kneading. This slurry was applied substantially uniformly and uniformly on both surfaces of a 20 μm thick aluminum foil as a positive electrode current collector. Then, the drying process was performed and it consolidated by the press to the predetermined density. The density of the positive electrode mixture layer was 3.6 g / cm ^3, and the single-sided applied amount of the positive electrode mixture layer was 202 g / m ² .

[Production of negative electrode]
The negative electrode plate was produced as follows. Artificial graphite having an average particle size of 22 μm was used as the negative electrode active material. To this negative electrode active material, SBR (styrene butadiene rubber) was added as a binder, and carboxymethylcellulose (CMC # 2200, manufactured by Daicel Finechem Co., Ltd.) was added as a thickener. 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. A predetermined amount of this slurry was applied substantially uniformly and uniformly on both surfaces of a rolled copper foil having a thickness of 10 μm, which is a current collector for a negative electrode. The density of the negative electrode mixture layer was 1.65 g / cm ^3, and the single-side applied amount of the negative electrode mixture layer was 113 g / m ² .

[Production of laminated battery]
A positive electrode cut into a square of 13.5 cm ² was sandwiched between polyethylene porous sheet separators (Hypore (registered trademark), manufactured by Asahi Kasei Co., Ltd., thickness: 30 μm), and further negative electrode cut into a 14.3 cm ² square Were stacked to produce a laminate. This laminate is put in an aluminum laminate container (aluminum laminate film, manufactured by Dai Nippon Printing Co., Ltd.), and a non-aqueous electrolyte (ethylene carbonate / dimethyl carbonate / diethyl carbonate = 2 containing 1.0 mol / L LiPF _6). 1 mL of 1.0% by mass of vinylene carbonate (produced by Ube Industries, Ltd.) with respect to the total amount of the mixed solution was added to a mixed solution of 5/6 / 1.5 (volume ratio), and aluminum A laminate container was thermally welded to produce a battery for electrode evaluation.

  The composition of the positive electrode mixture layer and the fluorine-containing lithium salt electrolyte in Example 1 is shown in Table 1. In Table 1, as the conductive material, the total amount of fibrous graphite (1% by mass) and acetylene black (1% by mass) is described. In Table 1, “-” in the composition of the fluorine-containing lithium salt electrolyte means that the component is not added.

(Example 2)
The proportion of lithium cobaltate, which is the positive electrode active material described in Example 1, is 90% by mass, the proportion of the oxygen-containing aluminum compound composite prepared in Production Example 1 is 5% by mass, and the amount of one-sided coating of the positive electrode mixture layer is 211 g. A positive electrode and a battery were produced in the same process as in Example 1 except that the voltage was changed to / m ² . Table 1 shows the composition of the positive electrode mixture layer and the fluorine-containing lithium salt electrolyte in Example 2.

(Example 3)
The proportion of lithium cobaltate, which is the positive electrode active material described in Example 1, is 90% by mass, the proportion of the oxygen-containing aluminum compound composite prepared in Production Example 1 is 5% by mass, and the amount of one-sided coating of the positive electrode mixture layer is 211 g. change to / ^{m 2,} the non-aqueous except that the fluorine-containing lithium salt electrolyte in the electrolyte solution was two and LiBF ₄ of LiPF ₆ and 0.4 mol / L of 0.6 mol / L, as in example 1 A positive electrode and a battery were produced in the same process. The composition of the positive electrode mixture layer and the fluorine-containing lithium salt electrolyte in Example 3 is shown in Table 1.

Example 4
A positive electrode and a battery were produced in the same process as in Example 1 except that the oxygen-containing aluminum compound composite produced in Production Example 2 was used instead of the oxygen-containing aluminum compound composite produced in Production Example 1. The composition of the positive electrode mixture layer and the fluorine-containing lithium salt electrolyte in Example 4 is shown in Table 1.

(Example 5)
A positive electrode and a battery were produced in the same process as in Example 1 except that the oxygen-containing aluminum compound composite produced in Production Example 3 was used instead of the oxygen-containing aluminum compound composite produced in Production Example 1. The composition of the positive electrode mixture layer and the fluorine-containing lithium salt electrolyte in Example 5 is shown in Table 1.

(Example 6)
A positive electrode and a battery were produced in the same process as in Example 1, except that the oxygen-containing aluminum compound composite produced in Production Example 4 was used instead of the oxygen-containing aluminum compound composite produced in Production Example 1. The composition of the positive electrode mixture layer and the fluorine-containing lithium salt electrolyte in Example 6 is shown in Table 1.

(Comparative Example 1)
The ratio of lithium cobaltate, which is the positive electrode active material described in Example 1, was 95% by mass, the oxygen-containing aluminum compound composite was not added, and the single-side applied amount of the positive electrode mixture layer was changed to 200 g / m ^2. Except for the above, a positive electrode and a battery were produced in the same process as in Example 1. The composition of the positive electrode mixture layer and the fluorine-containing lithium salt electrolyte in Comparative Example 1 is shown in Table 1. In Comparative Example 1, since no oxygen-containing aluminum compound composite is used, the column of oxygen-containing aluminum compound composite in Table 1 is marked with “-”.

(Evaluation of battery characteristics)
The battery characteristics of the lithium ion secondary batteries produced in Examples 1 to 6 and Comparative Example 1 were evaluated by the methods shown below.

[Evaluation of battery capacity]
The battery capacity was measured as follows.
First, constant current charging was performed up to an upper limit voltage of 4.35 V at a current value of 0.1 C under an environment of 25 ° C., and then constant voltage charging was performed at 4.35 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. Furthermore, constant current charging at 0.2 C was performed up to the upper limit voltage of 4.35 V, and then constant voltage charging was performed at 4.35 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 battery capacity.

[Evaluation of output characteristics]
The output characteristics were calculated as follows.
After measuring the battery capacity, constant current charging at 0.2 C was performed up to the upper limit voltage of 4.35 V, and then constant voltage charging was performed at 4.35 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, constant current charging at 0.2 C was performed up to the upper limit voltage of 4.35 V, and then constant voltage charging was performed at 4.35 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 3 C, the capacity at the time of discharge was defined as the discharge capacity at a current value of 3 C, and the output characteristics were calculated by the following formula. The output characteristics of the batteries of Examples 1 to 6 and Comparative Example 1 are shown in Table 1.
Output characteristics (%) = (discharge capacity at current value 3 C / discharge capacity at current value 0.2 C) × 100

[Evaluation of cycle characteristics]
The cycle characteristics were calculated as follows.
After evaluating the output characteristics under the above conditions, the cycle characteristics were evaluated by a cycle test in which charge and discharge were repeated. As for the charging pattern, each battery was subjected to constant current charging at a current value of 1 C up to an upper limit voltage of 4.35 V in an environment of 50 ° C., and then constant voltage charging at 4.35 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. Table 1 shows the cycle characteristics of the batteries of Examples 1 to 6 and Comparative Example 1.
Cycle characteristics (%) = (discharge capacity after 200 cycles at a current value of 1C / discharge capacity after one cycle at a current value of 1C) × 100

  As shown in Examples 1 and 2 in Table 1, the positive electrode mixture layer contains 1% by mass or 5% by mass of the oxygen-containing aluminum compound composite produced in Production Example 1, and thus compared with Comparative Example 1. It can be confirmed that the output characteristics and cycle characteristics are improved. This is because the oxygen-containing aluminum compound composite has high conductivity, so that the output characteristics are improved, and metal ions such as hydrogen fluoride (HF) in the electrolytic solution or cobalt eluted from the positive electrode active material can be converted into oxygen-containing aluminum. Since the compound complex was adsorbed, it is presumed that the capacity decrease after the charge / discharge cycle was suppressed.

Further, as shown in Example 3, in the system to which the positive electrode mixture layer containing the oxygen-containing aluminum compound composite produced in Production Example 1 and a fluorine-containing lithium salt electrolyte mixed with LiPF ₆ and LiBF ₄ were applied, Compared with Comparative Example 1, the output characteristics are almost the same, but it can be confirmed that the cycle characteristics are greatly improved. This is presumed that the decrease in capacity after the charge / discharge cycle was suppressed because the oxygen-containing aluminum compound composite adsorbed metal ions such as cobalt eluted from hydrogen fluoride (HF) or the positive electrode active material in the electrolytic solution. .

  In addition, in Examples 4 to 6 to which an oxygen-containing aluminum compound composite produced by a production method different from Production Example 1 was added as shown in Production Examples 2 to 4, the output characteristics were the same as in Comparative Example 1. Thus, it can be confirmed that the cycle characteristics are improved. It is presumed that the capacity reduction is suppressed for the same reason as above.

DESCRIPTION OF SYMBOLS 1 Lithium ion secondary battery 2 Positive electrode plate 3 Negative electrode plate 4 Separator 5 Electrode group 6 Battery container 40 Carbon 50 Oxygen-containing aluminum compound particle

Claims (9)

A lithium ion secondary battery used for the positive electrode mixture layer of a lithium ion secondary battery comprising a positive electrode having a current collector and a positive electrode mixture layer, a negative electrode, a separator, and an electrolyte solution containing a fluorine-containing lithium salt electrolyte. A positive electrode material for a secondary battery,
A positive electrode material for a lithium ion secondary battery comprising an oxygen-containing aluminum compound composite in which carbon is disposed on at least a part of the surface of oxygen-containing aluminum compound particles.   The weight loss rate in the range of 350 ° C to 850 ° C measured using a differential thermal-thermogravimetric analyzer (TG-DTA) of the oxygen-containing aluminum compound composite is 0.5% to 30%. The positive electrode material for lithium ion secondary batteries according to 1.   The weight reduction rate in the range of 25 ° C to 350 ° C measured by using a differential thermal-thermogravimetric analyzer (TG-DTA) of the oxygen-containing aluminum compound composite is less than 5%. 2. The positive electrode material for a lithium ion secondary battery according to 2. It said oxygen-containing aluminum compound lithium ion secondary according to specific surface area determined from nitrogen adsorption measurements at 77K of the complex of any one of claims 1 to 3 is a 1m 2 ^/ g~80m 2 ^{/ g} Positive electrode material for batteries.   The lithium ion secondary battery according to any one of claims 1 to 4, wherein the oxygen-containing aluminum compound composite has a volume average particle diameter measured by a laser diffraction particle size distribution measuring device of 0.1 µm to 50 µm. Positive electrode material.   The R value obtained from the Raman spectrum analysis of the oxygen-containing aluminum compound composite is 0.1 to 5.0. The positive electrode material for a lithium ion secondary battery according to any one of claims 1 to 5. Lithium used for forming the positive electrode mixture layer of a lithium ion secondary battery comprising a positive electrode having a current collector and a positive electrode mixture layer, a negative electrode, a separator, and an electrolyte solution containing a fluorine-containing lithium salt electrolyte A positive electrode mixture for an ion secondary battery,
The positive electrode compound material for lithium ion secondary batteries containing a positive electrode active material and the positive electrode material for lithium ion secondary batteries of any one of Claims 1-6. A positive electrode for a lithium ion secondary battery used in a lithium ion secondary battery comprising a positive electrode, a negative electrode, a separator, and an electrolytic solution containing a fluorine-containing lithium salt electrolyte;
A current collector, and a positive electrode mixture layer formed on the current collector,
The positive electrode for lithium ion secondary batteries in which the positive electrode mixture layer contains a positive electrode active material and the positive electrode material for lithium ion secondary batteries 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 8; a negative electrode; a separator; and an electrolytic solution containing a fluorine-containing lithium salt electrolyte.