JP2014091654A - Method of producing b-type titanium dioxide, and negative electrode active material and nonaqueous electrolyte secondary battery including the titanium dioxide - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide B-type titanium dioxide having improved the stability of a crystal structure and the tap density.SOLUTION: MTiO(M=group I element, n=an integer of 3 or more) that is crushed to be 0.01 μm or more and 0.5 or less in average particle diameter is subjected to ion exchange and dehydration in order to produce B-type titanium dioxide.

Description

  The present invention relates to a method for producing B-type titanium dioxide, a negative electrode active material containing the titanium dioxide, and a nonaqueous electrolyte secondary battery produced from the negative electrode active material.

In recent years, non-aqueous electrolyte secondary batteries have been actively researched and developed for portable devices, hybrid vehicles, electric vehicles, and household power storage applications. Non-aqueous electrolyte secondary batteries used in these fields are required to have high safety. In order to satisfy the demand, batteries using a titanium-based material as a negative electrode active material have been developed. Among the titanium-based materials, B-type titanium dioxide (TiO ₂ (B), sometimes referred to as bronze-type titanium dioxide) having a large capacity has attracted attention.

However, since B-type titanium dioxide has a small tap density (tap bulk density), there is a problem that the energy density of the battery is small. In order to solve this problem, M ₂ Ti _n O _{2n + 1} (M = group ₁ element, n = an integer greater than or equal to 3), which is a precursor for producing B-type titanium dioxide, is crushed and ion-exchanged. A method for producing B-type titanium dioxide by dehydration is described in Examples of Patent Documents 1 to 3.

International Publication No. 2009/028530 Pamphlet JP 2008-117625 A JP2012-30989A

However, Patent Documents 1 and 2 do not mention a specific size or particle size of the pulverized precursor.
Patent Document 3 specifies the specific particle size of the precursor used in the production of B-type titanium dioxide. That is, in Example 1, titanium dioxide (rutile type) and sodium hydroxide were mixed, dried and crushed, then transferred to a crucible and baked, and the fired product thus obtained was crushed in an alumina mortar. Thus, Na ₂ Ti ₃ O ₇ is obtained. There is a description that the average particle diameter of the obtained Na ₂ Ti ₃ O ₇ is 1.0 μm using the X-ray diffraction method (paragraphs [0107] to [0108]). As described above, in Patent Document 3, the average particle size is specified. To obtain a powder having this average particle size, the particle size value of a specific size can be obtained simply by “pulverized in an alumina mortar”. The basis for whether or not it was manufactured aiming at is not clear, and the effect based on the particle size value is also unknown. Therefore, the invention described in Patent Document 3 cannot be said to produce B-type titanium dioxide by optimally controlling the particle size of the precursor.

  According to the test results of the present inventors, when the particle size of the precursor is not controlled differently, the crystal structure easily changes from the bronze type to the anatase type, and the irreversible capacity increases. Moreover, the problem that B type titanium dioxide with a low tap density produced | generated also generate | occur | produced. On the other hand, a method of pulverizing after producing B-type titanium dioxide was also tried, but in this case, there was a problem that the capacity hardly developed (see [Example] described later).

  In view of such circumstances, the present invention intends to provide a method for producing B-type titanium dioxide having improved crystal structure stability and tap density, a negative electrode active material containing the titanium dioxide, and a non-aqueous electrolyte secondary battery. Is.

In view of the above circumstances, as a result of repeated investigations by the present inventors, M ₂ Ti _n O _{2n + 1} (M = first group element, n = 3 or more) pulverized to an average particle size of 0.01 μm or more and 0.5 μm or less. By using (integer), it has been found that B-type titanium dioxide having improved crystal structure stability and tap density can be produced, and the present invention has been completed.
That is, the present invention produces a powder of M ₂ Ti _n O _{2n + 1} (M = first group element, n = an integer of 3 or more) having an average particle diameter of 0.01 μm or more and 0.5 μm or less. This relates to a method for producing B-type titanium dioxide using

It is preferable to pass through the manufacturing process of following (1)-(4) at least the manufacturing method of this B type titanium dioxide. (1) A step of producing M ₂ Ti _n O _{2n + 1} (M = Group ₁ element, n = an integer of 3 or more) by mixing and firing a Group 1 elemental carbonate and titanium dioxide, (2) A step of producing a powder having an average particle diameter of 0.01 μm or more and 0.5 μm or less by pulverizing M ₂ Ti _n O _{2n + 1} (M = group ₁ element, n = an integer of 3 or more), (3 ) M ₂ Ti _n O _{2n + 1} (M = Group ₁ element, n = an integer greater than or equal to 3) obtained in the step (2) is ion-exchanged to obtain H ₂ Ti _n O _{2n + 1} (n = a greater than or equal to 3). (4) A step of producing B-type titanium dioxide by dehydrating the H ₂ Ti _n O _{2n + 1} (n = an integer of 3 or more).

The M may be K or Cs, and the n may be 4 or 5.
The B-type titanium dioxide of the present invention is B-type titanium dioxide produced by the production method described above.
The negative electrode for nonaqueous electrolyte secondary batteries of this invention can be manufactured using the said B type titanium dioxide. A non-aqueous electrolyte secondary battery can be manufactured using the negative electrode.

  The B-type titanium dioxide of the present invention has a higher tap density than conventional ones. As a result, the non-aqueous electrolyte secondary battery manufactured using the B-type titanium dioxide has a large battery capacity.

In the half battery created based on Example 1 of this invention, it is the graph which plotted the charging / discharging curve of the 5th time by making voltage on a vertical axis | shaft and capacity | capacitance on the horizontal axis. In the half-cell created based on Example 2 of this invention, it is the graph which plotted the charging / discharging curve of the 5th time by making voltage on a vertical axis | shaft and capacity | capacitance on the horizontal axis. In the half-cell created based on the comparative example 3 of this invention, it is the graph which plotted the charging / discharging curve of the 5th time by making voltage on a vertical axis | shaft and capacity | capacitance on the horizontal axis.

Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings.
The scope of the present invention is defined by the terms of the claims, and is intended to include any modifications within the scope and meaning equivalent to the terms of the claims.
<1. B-type titanium dioxide>
B-type titanium dioxide (TiO ₂ (B)) used for the negative electrode active material used in the nonaqueous electrolyte secondary battery of the present invention is produced through at least the following steps (1) to (4).

(1) A step of producing M ₂ Ti _n O _{2n + 1} (M = first group element, n = an integer of 3 or more) by mixing and firing a group 1 element carbonate and titanium dioxide.
(2) A step of obtaining a powder having an average particle diameter of 0.01 μm or more and 0.5 μm or less by pulverizing the M ₂ Ti _n O _{2n + 1} (M = Group ₁ element, n = an integer of 3 or more).
(3) A step of producing H ₂ Ti _n O _{2n + 1} (n = an integer greater than or equal to 3) by ion exchange of the M ₂ Ti _n O _{2n + 1} (M = Group ₁ element, n = an integer greater than or equal to 3). .

(4) A step of producing B-type titanium dioxide by dehydrating the H ₂ Ti _n O _{2n + 1} (n = an integer of 3 or more).
First of the above (1), “M ₂ Ti _n O _{2n + 1} (M = Group ₁ element, n = integer greater than or equal to 3) is produced by mixing and firing the group 1 element carbonate and titanium dioxide”. The process will be described.

Examples of the carbonate of the first group element (1) include sodium carbonate, potassium carbonate, and cesium carbonate. These mixing ratios for the desired _{M 2 Ti n O 2n + 1} (M = the family element, n = 3 or more integer) may be a ratio capable of forming, for example, carbonates 1mol of the first element, Titanium dioxide is preferably in a ratio of n (n is an integer of 3 or more) mol or more.

The above-mentioned (1) group 1 element titanium dioxide has only to have a crystal structure other than the bronze type, and examples include anatase type, rutile type, and Brookkite type.
The "mixing of group 1 element carbonate and titanium dioxide" in (1) is not particularly limited as long as the group 1 element carbonate and titanium dioxide are uniformly mixed. Therefore, it is preferable to use a ball mill, a bead mill, a jet mill, a crusher, an automatic mortar, or the like.

The mixing method may be dry or wet. In the case of dry mixing, it is mixed with a carbonate of a group 1 element and titanium dioxide. Then, when it is made into a pellet, handling becomes easy.
When the shape is made into a pellet, the shape can be made into a pellet by pressurizing the mixed group 1 element carbonate and titanium dioxide with a pellet die and a hydraulic pump.

  Although the shape of a pellet is not specifically limited, Since a pellet can be stacked in a baking container, it is preferable that it is cylindrical. Moreover, although the dimension of a pellet is not specifically limited, When it is a column shape, it is preferable that height is 1 mm or more and 50 mm or less. When the height is 1 mm or less, it takes time to produce a large number of pellets, and when the height is 50 mm or more, it becomes difficult to pulverize the pellets. The diameter of the pellet is preferably 5 mm or more. When the diameter is 5 mm or less, it takes time to produce a large number of pellets, and when the diameter is larger than 50 mm, it becomes difficult to pulverize the pellets.

It is preferable that the pressure at the time of pelletization is 5 MPa or more and 100 MPa or less. When the pressure is 5 MPa or less, there is a possibility that a by-product may be generated in addition to M ₂ Ti _n O _{2n + 1} when the mixed group 1 element carbonate and titanium dioxide are fired. It becomes difficult to pulverize the pellets.
On the other hand, in the wet mixing, a liquid such as methanol, ethanol, propanol and water is further added to and mixed with the carbonate of the first group element and titanium dioxide.

The firing of (1) may be a general firing furnace, and examples include an electric furnace, an IR furnace, and a rotary kiln.
The firing temperature (1) is preferably 600 ° C. or more and 1200 ° C. or less. Below 600 ° C., all of the mixture may not react with M ₂ Ti _n O _{2n + 1} (M = Group ₁ element, n = an integer greater than or equal to 3), and when it is higher than 1200 ° C., the product decomposes. There is a fear. It is particularly preferable to carry out the reaction at 800 ° C. or higher and 1000 ° C. or lower because of excellent reaction efficiency.

The firing time (1) is preferably performed in the range of 600 ° C. to 1200 ° C. for 1 hour to 50 hours. If it is less than 1 hour, all of the mixture may not react with M ₂ Ti _n O _{2n + 1} (M = Group ₁ element, n = an integer greater than or equal to 3). Therefore, it is not preferable because the cost increases.
In order to dope metals other than M and Ti as will be described later, it is preferable that the titanium dioxide is doped with a metal other than M and Ti in advance. The method of doping the titanium dioxide with a metal other than M and Ti can be obtained by mixing the titanium dioxide and an oxide or carbonate of a metal other than M and Ti, followed by firing treatment.

The firing conditions are preferably in the range of 900 ° C. or higher and 1600 ° C. or lower and 1 hour or longer and 50 hours or shorter.
The amount of oxides and carbonates of metals other than M and Ti can be added arbitrarily so that metals other than M and Ti are contained in an amount of 0.01 mol% or more and 0.2 mol% or less with respect to 1 mol of Ti. That's fine. The metal other than M and Ti is preferably Nb because stability and tap density (tap bulk density) are improved.

Next, by pulverizing “M ₂ Ti _n O _{2n + 1} (M = first group element, n = an integer of 3 or more)” in (2), the average particle diameter is 0.01 μm or more and 0.5 μm or less. The process will be described.
In the method of pulverizing “M ₂ Ti _n O _{2n + 1} (M = group ₁ element, n = an integer of 3 or more)” in (2), the average particle diameter may be 0.01 μm or more and 0.5 μm or less. Examples include a method of crushing with a hammer, a ball mill, a bead mill, a jet mill, a crusher, and an automatic mortar. Among these methods, a method of pulverizing with a ball mill is particularly preferable because a desired average particle diameter can be easily obtained.
The ball material used for the ball mill is not limited as long as the average particle diameter of M ₂ Ti _n O _{2n + 1} (M = group ₁ element, n = an integer of 3 or more) can be pulverized to 0.01 μm or more and 0.5 μm or less. Alumina, zirconia, stainless steel, chrome steel and tungsten carbide are preferred. Among these materials, agate, alumina, and zirconia are particularly preferable because they do not greatly affect the battery reaction even if fragments are mixed.

The size of the ball used in the ball mill is preferably 1 mm or more and 50 mm or less in diameter. If the ball size is less than 1 mm in diameter, the gap between the balls is small, so the average particle size of M ₂ Ti _n O _{2n + 1} (M = first group element, n = an integer greater than or equal to 3) is pulverized to less than 0.01 μm. On the other hand, when the ball size is larger than 50 mm in diameter, the gap between the balls becomes large, so that M ₂ Ti _n O _{2n + 1} (M = first group element, n = integer of 3 or more) There is a possibility that the average particle size cannot be pulverized to 0.5 μm or less.

The number of balls used in the ball mill is preferably 5 or more and less than 100 with respect to 1 g of M ₂ Ti _n O _{2n + 1} (M = first group element, n = an integer of 3 or more). If it is less than 5, the average particle diameter of M ₂ Ti _n O _{2n + 1} (M = Group ₁ element, n = an integer of 3 or more) may not be pulverized to 0.5 μm or less. On the other hand, when the number is more than 100, it may be difficult to recover M ₂ Ti _n O _{2n + 1} (M = first group element, n = an integer of 3 or more) after pulverization.

The process at the time of pulverization may be dry or wet. In the case of a wet type, a solvent such as methanol, ethanol, propanol, isopropanol, or water is added before pulverization and pulverization is performed later. In the case of wet, it is preferable to add 0.1 g or more and 10 g or less of solvent to 1 g of M ₂ Ti _n O _{2n + 1} (M = group ₁ element, n = an integer of 3 or more). If it is less than 0.1 g, M ₂ Ti _n O _{2n + 1} (M = first group element, n = integer of 3 or more) after pulverization may fly at the time of recovery. On the other hand, when the amount is more than 10 g, it may be difficult to recover M ₂ Ti _n O _{2n + 1} (M = first group element, n = an integer of 3 or more) after pulverization.

The rotation speed of the ball mill is preferably 100 rpm or more and 1000 rpm or less. If it is less than 100 rpm, the average particle diameter of M ₂ Ti _n O _{2n + 1} (M = group ₁ element, n = integer of 3 or more) cannot be pulverized to 0.01 μm or more and 0.5 μm or less, and when it is faster than 1000 rpm, The average particle diameter of M ₂ Ti _n O _{2n + 1} (M = first group element, n = an integer of 3 or more) may be less than 0.01 μm.

  The operation time of the ball mill is preferably between 0.1 and 24 hours. When the time is less than 0.5 hours, the average particle size cannot be pulverized to 0.01 μm or more and 0.5 μm or less. When the time is longer than 24 hours, the average particle size may be less than 0.01 μm. The ball milling time may be performed continuously, or a rotation stop time of 1 minute or more and 1 hour or less may be sandwiched in the middle.

When the average particle diameter of M ₂ Ti _n O _{2n + 1} (M = Group ₁ element, n = integer of 3 or more) of (2) is less than 0.01 μm, an anatase phase may be generated, and as a result, Battery performance may be reduced. On the other hand, if the thickness is larger than 0.5 μm, the crystal grows by a process described later, so that the tap density may not be improved.
The average particle diameter can be calculated by observing particles with SEM. Observation with an SEM is preferably performed at a magnification of 10,000 times or more and 50,000 times or less. If it is less than 10,000 times, observation of 0.01 μm particles may be difficult, and if it is more than 50,000 times, observation of 0.5 μm particles becomes difficult. Since observation of particles of 0.01 μm or more and 0.5 μm or less is easy, 20,000 times or more and 30,000 times or less are more preferable, and observation at 25,000 times is particularly preferable.

In order to calculate the average particle diameter, it is preferable to observe 10 or more arbitrary particles by the SEM observation.
The process at the time of pulverization may be dry or wet. In the case of a wet type, a liquid such as methanol, ethanol, propanol or water is added before pulverization and then pulverized later.
Next, (3) “M ₂ Ti _n O _{2n + 1} (M = first group element, n = an integer of 3 or more) is ion-exchanged to produce H ₂ Ti _n O _{2n + 1} (n = an integer of 3 or more). Will be described.

The ion exchange (3) is a step of exchanging M (M = group 1 element) with hydrogen. Examples of the ion exchange method include a method of treating with a general acid.
The acid used for ion exchange may be an aqueous solution containing hydrogen ions. For example, sulfuric acid, hydrochloric acid, oxalic acid, nitric acid, hydrofluoric acid and the like are exemplified, but hydrochloric acid and sulfuric acid are particularly preferable because of easy ion exchange. At this time, the number of hydrogen atoms is preferably larger than the number of M atoms to be ion-exchanged, but the number of hydrogen atoms is preferably 1 to 500 times the number of M atoms. If it is less than 1 time, there is a possibility that ion exchange cannot be performed, and if it is 500 times or more, the amount of acid used for ion exchange is too large, so the cost increases.

The temperature during ion exchange is preferably 5 ° C. or higher and 80 ° C. or lower. If it is less than 5 degreeC, there exists a possibility that ion exchange may not advance, and when higher than 80 degreeC, the water which is a solvent volatilizes.
The ion exchange time is preferably 0.1 hours or more and 200 hours or less. If the time is less than 0.1 hours, ion exchange may not proceed. If the time is longer than 200 hours, the cost increases due to an increase in utility costs, which is not preferable.

After ion exchange, in order to remove unreacted acid, it is washed with deionized water. Thereafter, by _{drying, H 2 Ti n O 2n +} 1 (n = 3 or more integer) can be produced.
The average particle diameter of H ₂ Ti _n O _{2n + 1} (n = an integer of 3 or more) after ion exchange is preferably 0.01 μm or more and 1.0 μm or less. When the average particle diameter is less than 0.01 μm, an anatase phase may be generated, and as a result, battery performance may be deteriorated. On the other hand, if it is larger than 1.0 μm, the tap density may not be improved.

Next, a step of producing B-type titanium dioxide by dehydrating (4) H ₂ Ti _n O _{2n + 1} (n = an integer of 3 or more) will be described.
The dehydration step is a step of producing B-type titanium dioxide by removing H ₂ O from H ₂ Ti _n O _{2n + 1} . As the dehydrating method, a method of removing by heating is preferable because B-type titanium dioxide can be produced stably.

The heating temperature should be such that the dehydration reaction proceeds, and is 300 ° C. or higher and 700 ° C. or lower, more preferably 400 ° C. or higher and 600 ° C. or lower. Above, 550 degrees C or less is especially preferable. If it is lower than 300 ° C., it cannot be dehydrated, and if it is higher than 700 ° C., it may become anatase.
The heating time is preferably in the range of 300 ° C. or more and 700 ° C. or less and 0.1 hours or more and 15 hours or less. If the time is less than 0.1 hour, ion exchange may not proceed. If the time is longer than 15 hours, the cost increases due to an increase in utility costs, which is not preferable.

  The average particle size of B-type titanium dioxide produced by the production method of the present invention is preferably 0.01 μm or more and 1.0 μm or less. When the average particle diameter is less than 0.01 μm, an anatase phase may be generated, and as a result, battery performance may be deteriorated. On the other hand, if it is larger than 1.0 μm, the tap density may not be improved. Here, the calculation method of the “average particle diameter” is not limited, but when the powder is divided into two based on a certain particle diameter, a median diameter (d50) diameter in which the large side and the small side are equal is adopted. May be. In addition, a mode diameter which is a particle diameter having the largest appearance ratio may be employed, or an arithmetic average diameter may be employed.

The presence of B-type titanium dioxide can be confirmed by confirming the crystal structure by XRD (X-ray Diffraction).
The tap density is preferably 0.2 g / cm ³ or more and 1.0 g / cm ³ or less. When it is less than 0.2 g / cm ³ , the energy density of the battery is low, and when it is higher than 1.0 g / cm ^3, it becomes difficult to produce a negative electrode described later.

  The tap density may be measured using a commercially available tap density measurement tester based on the USP Method or ASTM standard, and if there is no measuring device, put a measuring object of 3 g or more in a graduated cylinder (10 mL). Can be measured by tapping manually until is constant. When performing manually, the number of taps is preferably 100 times or more and 5000 times or less. If it is less than 100 times, the volume may not be constant, and if it is more than 5000 times, it takes a lot of time.

The B-type titanium dioxide of the present invention may be doped with a different metal other than Li and Ti. The amount of the dissimilar metal is preferably 1.0 mol% or more and 20.0 mol% or less with respect to 1 mol of Ti. When it is less than 1.0 mol%, the effect of doping is small, and when it is more than 20.0 mol%, the capacity of B-type titanium dioxide is small.
The amount of the different metal can be controlled by including an oxide or carbonate of a metal other than M and Ti at the time of mixing (1). The metal other than Ti is preferably Nb because stability and tap density are improved.

<2. Negative electrode>
The negative electrode of the present invention contains at least the negative electrode active material.
The negative electrode of the present invention may further contain a conductive additive. Although it does not specifically limit as a conductive support material, A metal material and a carbon material are preferable. Examples of the metal material include copper and nickel, and examples of the carbon material include natural graphite, artificial graphite, vapor grown carbon fiber, carbon nanotube, acetylene black, ketjen black, and furnace black. These conductive aids may be used alone or in combination of two or more.

In the present invention, the amount of the conductive additive contained in the negative electrode is preferably 1 part by weight or more and 30 parts by weight or less, more preferably 2 parts by weight or more and 15 parts by weight or less with respect to 100 parts by weight of the negative electrode active material. If it is the said range, the electroconductivity of a negative electrode will be ensured. Moreover, adhesiveness with the below-mentioned binder is maintained, and adhesiveness with a collector can fully be obtained.
In the present invention, a binder may be used for the negative electrode in order to bind the active material to the current collector. The binder is not particularly limited, and for example, at least one selected from the group consisting of polyvinylidene fluoride (PVdF), polytetrafluoroethylene (PTFE), styrene-butadiene rubber, polyimide, acrylic resin, and derivatives thereof is used. be able to. The binder is preferably dissolved or dispersed in a non-aqueous solvent or water from the viewpoint of easy production of the negative electrode. The non-aqueous solvent is not particularly limited, and examples thereof include N-methyl-2-pyrrolidone (NMP), dimethylformamide, dimethylacetamide, methyl ethyl ketone, methyl acetate, ethyl acetate, and tetrahydrofuran. You may add a dispersing agent and a thickener to these.

In the present invention, the amount of the binder contained in the negative electrode is preferably 1 part by weight or more and 30 parts by weight or less, more preferably 2 parts by weight or more and 15 parts by weight or less with respect to 100 parts by weight of the negative electrode active material. If it is the said range, the adhesiveness of a negative electrode active material and a conductive support material will be maintained, and adhesiveness with a collector can fully be acquired.
In the present invention, a preferable negative electrode is manufactured by forming a mixture of a negative electrode active material, a conductive additive, and a binder on a current collector. From the ease of the manufacturing method, the mixture and the solvent are used as a slurry. A method of producing a negative electrode by removing the solvent after coating the obtained slurry on a current collector is preferred.

The current collector that can be used in the negative electrode of the present invention is preferably copper, SUS, nickel, titanium, aluminum, or an alloy thereof.
As the current collector, a metal material (copper, SUS, nickel, titanium, and alloys thereof) coated with a metal that does not react with the potential of the negative electrode can be used.
<3. Positive electrode>
The positive electrode active material contained in the positive electrode used in the nonaqueous electrolyte secondary battery of the present invention is not particularly limited, and may be a lithium transition metal compound, such as a lithium cobalt compound, a lithium nickel compound, a lithium manganese compound, and a lithium iron compound. Is exemplified. Moreover, a transition metal is not limited to one type, Two or more types may be sufficient. For example, a lithium cobalt nickel manganese compound, a lithium nickel manganese compound, etc. are illustrated. Moreover, since the effect which improves the stability of a lithium transition metal compound is high, elements, such as aluminum, magnesium, titanium, may be contained in trace amounts, for example.

The surface of the positive electrode active material of the present invention may be covered with a carbon material, a metal oxide, a polymer, or the like in order to improve conductivity or stability.
The positive electrode of the present invention may contain a conductive additive. Although it does not specifically limit as a conductive support material, A carbon material is preferable. Examples thereof include natural graphite, artificial graphite, vapor grown carbon fiber, carbon nanotube, acetylene black, ketjen black, and furnace black. These carbon materials may be used alone or in combination of two or more.

The amount of the conductive additive contained in the positive electrode of the present invention is preferably 1 part by weight or more and 30 parts by weight or less, more preferably 2 parts by weight or more and 15 parts by weight or less with respect to 100 parts by weight of the positive electrode active material. If it is the said range, the electroconductivity of a positive electrode will be ensured. Moreover, adhesiveness with the below-mentioned binder is maintained, and adhesiveness with a collector can fully be obtained.
The positive electrode of the present invention may contain a binder. The binder is not particularly limited, and for example, at least one selected from the group consisting of polyvinylidene fluoride (PVdF), polytetrafluoroethylene (PTFE), styrene-butadiene rubber, polyimide, acrylic resin, and derivatives thereof is used. be able to. The binder is preferably dissolved or dispersed in a non-aqueous solvent or water from the viewpoint of easy production of the positive electrode. The non-aqueous solvent is not particularly limited, and examples thereof include N-methyl-2-pyrrolidone (NMP), dimethylformamide, dimethylacetamide, methyl ethyl ketone, methyl acetate, ethyl acetate, and tetrahydrofuran. You may add a dispersing agent and a thickener to these.

The amount of the binder contained in the positive electrode of the present invention is preferably 1 part by weight or more and 30 parts by weight or less, more preferably 2 parts by weight or more and 15 parts by weight or less with respect to 100 parts by weight of the positive electrode active material. If it is the said range, the adhesiveness of a positive electrode active material and a conductive support material will be maintained, and adhesiveness with a collector can fully be acquired.
Examples of the method for producing a positive electrode of the present invention include a method for producing a positive electrode active material, a conductive additive, and a binder by coating a current collector on the current collector. And the method of manufacturing a positive electrode by removing a solvent after manufacturing slurry with a solvent and applying the obtained slurry on a current collector is preferred.

The current collector used for the positive electrode of the present invention is preferably aluminum and its alloys. The aluminum is not particularly limited because it is stable in a positive electrode reaction atmosphere, but is preferably high-purity aluminum represented by JIS standards 1030, 1050, 1085, 1N90, 1N99 and the like.
Note that the current collector may be a metal whose surface is covered with aluminum other than aluminum (copper, SUS, nickel, titanium, and alloys thereof).

<4. Separator>
The separator used for the non-aqueous electrolyte secondary battery of the present invention may be any material that is installed between the positive electrode and the negative electrode and has no electronic conductivity and lithium ion conductivity. For example, nylon, cellulose, Examples include polysulfone, polyethylene, polypropylene, polybutene, polyacrylonitrile, polyimide, polyamide, and woven fabrics, nonwoven fabrics, and microporous membranes of two or more of them. The separator may include various plasticizers, antioxidants, flame retardants, and may be coated with a metal oxide or the like.

The thickness of the separator is preferably 10 μm or more and 100 μm or less. When the thickness is less than 10 μm, the positive electrode and the negative electrode may be in contact with each other. When the thickness is greater than 100 μm, the resistance of the battery may be increased. From the viewpoint of economy and handling, it is more preferably 15 μm or more and 50 μm or less.
<5. Non-aqueous electrolyte>
The non-aqueous electrolyte used in the non-aqueous electrolyte secondary battery of the present invention is not particularly limited, but a polymer is impregnated with an electrolytic solution in which a solute is dissolved in a non-aqueous solvent, or an electrolytic solution in which a solute is dissolved in a non-aqueous solvent. A gel electrolyte or the like can be used.

The non-aqueous solvent preferably includes a cyclic aprotic solvent and / or a chain aprotic solvent. Examples of the cyclic aprotic solvent include cyclic carbonates, cyclic esters, cyclic sulfones and cyclic ethers. Examples of the chain aprotic solvent include chain carbonates, chain carboxylic acid esters and chain ethers.
In addition to the above, a solvent generally used as a solvent for nonaqueous electrolytes such as acetonitrile may be used. More specifically, dimethyl carbonate, methyl ethyl carbonate, diethyl carbonate, dipropyl carbonate, methyl propyl carbonate, ethylene carbonate, propylene carbonate, butylene carbonate, γ-butyl lactone, 1,2-dimethoxyethane, sulfolane, dioxolane, propion For example, methyl acid can be used. These solvents may be used alone or as a mixture of two or more. However, in view of the ease of dissolving the solute described below and the high conductivity of lithium ions, a mixture of two or more of these solvents. Is preferably used. A gel electrolyte in which an electrolyte is impregnated in a polymer can also be used.

The solute is not particularly limited. For example, LiClO ₄ , LiBF ₄ , LiPF ₆ , LiAsF ₆ , LiCF ₃ SO ₃ , LiBOB (Lithium Bis (Oxalato) Borate), LiN (SO ₂ CF ₃ ) _2, etc. are dissolved in the solvent. It is preferable because it is easy to do. The concentration of the solute contained in the electrolytic solution is preferably 0.5 mol / L or more and 2.0 mol / L or less. If it is less than 0.5 mol / L, the desired lithium ion conductivity may not be expressed. On the other hand, if it is higher than 2.0 mol / L, the solute may not be dissolved any more. The non-aqueous electrolyte may contain a trace amount of additives such as a flame retardant and a stabilizer.

<6. Non-aqueous electrolyte secondary battery>
The positive electrode and the negative electrode of the nonaqueous electrolyte secondary battery of the present invention may be in the form in which the same electrode is formed on both sides of the current collector, and the positive electrode is formed on one side of the current collector and the negative electrode is formed on one side. Alternatively, it may be a bipolar electrode.
The nonaqueous electrolyte secondary battery of the present invention may be one obtained by winding or laminating a separator disposed between the positive electrode side and the negative electrode side. The positive electrode, the negative electrode, and the separator contain a nonaqueous electrolyte that is responsible for lithium ion conduction.

The amount of the nonaqueous electrolyte used in the nonaqueous electrolyte secondary battery of the present invention is not particularly limited, but is preferably 0.1 mL or more per 1 Ah of battery capacity. If it is less than 0.1 mL, the conduction of lithium ions accompanying the electrode reaction may not catch up, and the desired battery performance may not be exhibited.
The nonaqueous electrolyte may be added to the positive electrode, the negative electrode, and the separator in advance, or may be added after winding or laminating a separator disposed between the positive electrode side and the negative electrode side.

  The non-aqueous electrolyte secondary battery of the present invention may be wound or laminated with a laminate film after the laminate is wound, or may be rectangular, elliptical, cylindrical, coin-shaped, button-shaped, or sheet-shaped. It may be packaged with a metal can. The exterior may be provided with a mechanism for releasing the generated gas. The number of stacked layers can be stacked until a desired voltage value and battery capacity are exhibited.

  The nonaqueous electrolyte secondary battery of the present invention can be formed into an assembled battery by connecting a plurality of the nonaqueous electrolyte secondary batteries. The assembled battery of this invention can be manufactured by connecting in series and parallel suitably according to desired magnitude | size, a capacity | capacitance, and a voltage. Moreover, it is preferable that a control circuit is attached to the assembled battery in order to confirm the state of charge of each battery and improve safety.

EXAMPLES Hereinafter, although an Example demonstrates this invention further more concretely, this invention is not limited at all by these Examples, In the range which does not change the summary, it can change suitably.
<Example 1>
B-type titanium dioxide was produced as follows. First, 20 g of titanium dioxide (325 mesh, anatase) and 9.0 g of potassium carbonate (special grade, potassium carbonate (anhydrous)) were mixed using a uniaxial ball mill. The ball mill conditions were as follows: 25 15 mm zirconia balls were placed in a 200 mL plastic container and mixed at 180 rpm. This mixture of titanium dioxide and potassium carbonate is heat-treated at 900 ° C. for 24 hours at 2 ° C./min under the conditions of temperature rise and fall using a muffle furnace, so that the precursor K ₂ Ti ₄ before pulverization is obtained. O ₉ was produced. The milled precursor before _K 2 _Ti 4 _{O 9} electron microscope (Hitachi High-Technologies Corporation, S-4800) result of observation, the average particle size of the precursor _K 2 _Ti 4 _{O 9} before pulverization is 0. It was 91 μm.

The average particle diameter was calculated by observing the precursor K ₂ Ti ₄ O ₉ before pulverization at 25,000 times, measuring the size of 20 arbitrary particles, and then arithmetically averaging the values. The precursor K ₂ Ti ₄ O ₉ before pulverization was pulverized using a planetary ball mill. The ball mill was pulverized at 600 rpm for 12 hours after adding 30 pieces of 5 mm zirconia balls, 3 g of precursor K ₂ Ti ₄ O ₉ and 2 mL of methanol to the zirconia container. As a result of observing the pulverized precursor K ₂ Ti ₄ O ₉ with an electron microscope (S-4800, manufactured by Hitachi High-Technologies Corporation), the average particle size of the pulverized precursor K ₂ Ti ₄ O ₉ was 0.00. It was 21 μm. The average particle diameter was calculated by observing the precursor K ₂ Ti ₄ O ₉ before pulverization at 25,000 times, measuring the size of 20 arbitrary particles, and then arithmetically averaging the values. H ₂ Ti ₄ O ₉ was produced by ion exchange of the subsequent precursor K ₂ Ti ₄ O ₉ . The ion exchange was performed by adding 200 mL of 1M hydrochloric acid aqueous solution per 1 g of the precursor and stirring at 25 ° C. for 72 hours, and then filtering the powder and washing with 5 mL deionized water four times.

Finally, H ₂ Ti ₄ O ₉ is heat-treated at 500 ° C. for 30 minutes at 2 ° C./minute using a muffle furnace under the conditions of increasing and decreasing temperatures to produce B-type titanium dioxide of Example 1. did. It was confirmed by XRD (X-ray Diffraction) that it was B-type titanium dioxide.
<Example 2> Cs-based precursor and pulverized product Instead of 9.0 g of potassium carbonate (Wako special grade, potassium carbonate (anhydrous)), 16.3 g of cesium carbonate (first grade of Wako, cesium carbonate (anhydrous)) was used. Except for the above, B-type titanium dioxide was produced in the same manner as in Example 1. The precursor in Example 2 was Cs ₂ Ti ₅ O ₁₁ , and the average particle sizes before and after pulverization were 1.14 μm and 0.18 μm, respectively.

The measurement method was the same as in Example 1. Further, it was confirmed by XRD (X-ray Diffraction) that it was B-type titanium dioxide.
Except that no pulverizing the <Comparative Example 1> K system without precursor crushed precursor K ₂ Ti ₄ O ₉ was prepared a B-type titanium dioxide similarly to Example 1 and Comparative Example 1. The average particle diameter of the unpulverized K ₂ Ti ₄ O ₉ was 0.91 μm as described above.

Except that no pulverizing the <Comparative Example 2> Cs system without precursor crushed precursor _Cs 2 _Ti 5 _{O 11,} was prepared B-type titanium dioxide similarly Comparative Example 2 and Example 2. The average particle diameter of Cs ₂ Ti ₅ O ₁₁ which was not pulverized was 1.14 μm as described above.
<Comparative Example 3> Grinding with TiO ₂ (B) B-type titanium dioxide was produced as follows. First, 20 g of titanium dioxide (325 mesh, anatase) and 9.0 g of potassium carbonate (special grade, potassium carbonate (anhydrous)) were mixed using a uniaxial ball mill. The ball mill conditions were as follows: 25 15 mm zirconia balls were placed in a 200 mL plastic container and mixed at 180 rpm. This mixture of titanium dioxide and potassium carbonate is heat-treated at 900 ° C. for 24 hours at 2 ° C./min under the conditions of temperature rise and fall using a muffle furnace, so that the precursor K ₂ Ti ₄ before pulverization is obtained. O ₉ was produced. As a result of observing the precursor K ₂ Ti ₄ O ₉ before pulverization with an electron microscope (S-4800, manufactured by Hitachi High-Technologies Corporation), the average particle size of the precursor K ₂ Ti ₄ O ₉ was 0.91 μm. It was.

Next, this K ₂ Ti ₄ O ₉ was ion-exchanged to produce H ₂ Ti ₄ O ₉ . The ion exchange was performed by adding 200 mL of 1M hydrochloric acid aqueous solution per 1 g of the precursor and stirring at 25 ° C. for 72 hours, and then filtering the powder and washing with 5 mL deionized water four times.
Finally, H ₂ Ti ₄ O ₉ was heat-treated using a muffle furnace at 500 ° C. for 30 minutes at 2 ° C./min. .

  This unground B-type titanium dioxide was pulverized using a planetary ball mill. The condition of the ball mill was that 30 mm of zirconia balls, 3 g of unmilled B-type titanium dioxide and 2 mL of methanol were added to a zirconia container, and then pulverized at 600 rpm for 12 hours. Type titanium dioxide was produced. As a result of observing the B-type titanium dioxide of Comparative Example 3 with an electron microscope (S-4800, manufactured by Hitachi High-Technologies Corporation), the average particle size was 0.18 μm. The average particle size was calculated in the same manner as in Example 1.

<Measurement of tap density>
The tap density of Example 1, Example 2, Comparative Example 1 and Comparative Example 2 was calculated by placing 3 g of B-type titanium dioxide in a 10 mL graduated cylinder, tapping manually 4000 times, and measuring the volume. The results are shown in Table 1. In Example 1 and Example 2 of the present invention, it was confirmed that the tap density was improved as compared with Comparative Examples 1 and 2, respectively.

Here, in Comparative Example 3, the precursor that is not pulverized is ion-exchanged to produce H ₂ Ti ₄ O ₉ , heat-treated, and then pulverized to produce B-type titanium dioxide. The tap density is smaller than B-type titanium dioxide produced by ion-exchange of H to produce H ₂ Ti ₄ O ₉ and heat treatment. The reason for this is speculation, but it is thought that corners were removed by grinding because B-type titanium dioxide was softer than the precursor.

<Measurement of charge / discharge characteristics>
A half cell was prepared using the B-type titanium dioxide of Example 1, Example 2, and Comparative Example 3, and the charge / discharge characteristics were measured. Production of half-cells and charge / discharge characteristics were performed as follows.
A slurry was prepared by mixing 80 parts by weight of B-type titanium dioxide, 10 parts by weight of a conductive additive (Ketjen Black), and 10 parts by weight of a binder (solid content concentration 12 wt%, NMP solution). The slurry was applied to a copper foil (50 μm) and then vacuum-dried at 80 ° C., and then punched out to 16 mmΦ to produce an electrode for measuring charge / discharge characteristics.

This electrode was used as a working electrode, and Li metal was punched out to 16 mmΦ as a counter electrode. Using these electrodes, a working electrode (single-sided coating) / separator / Li metal was laminated in this order in a test cell (HS cell, manufactured by Hosen Co., Ltd.), and a non-aqueous electrolyte (ethylene carbonate / dimethyl carbonate = 3/7 vol). %, LiPF ₆ 1 mol / L) was added to prepare a half cell. The half-cell was allowed to stand at 25 ° C. for one day, and then connected to a charge / discharge test apparatus (HJ1005SD8, manufactured by Hokuto Denko). This half-cell was repeatedly subjected to constant current discharge (end voltage: 1.4 V) and constant current charge (end voltage: 3.0 V) at 25 ° C. and 0.05 mA five times.

  The charge / discharge curves for the second time are shown in FIG. 1, FIG. 2 and FIG. Since the value on the horizontal axis of these charge / discharge curves is time, that is, constant current, it indicates the capacity of B-type titanium dioxide, and the larger the better. From these figures, it was confirmed that the B-type titanium dioxide of Examples 1 and 2 had a sufficient capacity as a negative electrode active material for a non-aqueous electrolyte secondary battery. On the other hand, the B-type titanium dioxide of Comparative Example 3 has a very small capacity as compared with Example 1 and Example 2, and was found to be difficult to use for a non-aqueous electrolyte secondary battery.

Claims (7)

A powder of M ₂ Ti _n O _{2n + 1} (M = first group element, n = an integer of 3 or more) having an average particle size of 0.01 μm or more and 0.5 μm or less is prepared, and B type is used using the powder. A method for producing B-type titanium dioxide, which produces titanium dioxide. The manufacturing method of the B type titanium dioxide of Claim 1 which passes through the manufacturing process of following (1)-(4) at least.
(1) A step of producing a M ₂ Ti _n O _{2n + 1} (M = Group ₁ element, n = an integer greater than or equal to 3) by mixing and firing a Group 1 element carbonate and titanium dioxide,
(2) A step of producing a powder having an average particle diameter of 0.01 μm or more and 0.5 μm or less by pulverizing the M ₂ Ti _n O _{2n + 1} (M = group ₁ element, n = an integer of 3 or more). ,
(3) M ₂ Ti _n O _{2n + 1} (M = group ₁ element, n = an integer greater than or equal to 3) obtained in the step (2) is ion-exchanged to obtain H ₂ Ti _n O _{2n + 1} (n = 3 A step of producing an integer above),
(4) A step of producing B-type titanium dioxide by dehydrating the H ₂ Ti _n O _{2n + 1} (n = an integer of 3 or more).   The method for producing B-type titanium dioxide according to claim 1 or 2, wherein M is K or Cs, and n is 4 or 5.   B-type titanium dioxide manufactured by the manufacturing method of any one of Claims 1-3.   The negative electrode for nonaqueous electrolyte secondary batteries containing the B-type titanium dioxide of Claim 4.   A nonaqueous electrolyte secondary battery using the negative electrode according to claim 5.   A secondary battery module in which a plurality of the nonaqueous electrolyte secondary batteries according to claim 6 are connected.

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