JP2015201438A - Titanium-based structure for power storage devices and manufacturing method thereof, and electrode active material arranged by titanium-based structure, electrode active material layer, electrode, and power storage device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a titanium-based structure which achieves a higher level of safety than that of an existing carbon-based material, has a higher capacity than that of an existing titanium-based material such as lithium titanate, is usable for a power storage device, and which can offer a material exhibiting a high discharge capacity and a superior rate characteristic when adopting such a titanium-based structure for a lithium ion secondary battery, and offer a material showing a high electrostatic capacitance when adopting for an electric double layer capacitor; and a simple method for manufacturing such a titanium-based structure.SOLUTION: A titanium-based structure for power storage devices comprises at least atoms of Group I of the periodic table, Ti atoms and O atoms. The ratio (periodic table I Group atoms/Ti atoms) of the atoms of the periodic table Group I to the Ti atoms is 0.01-0.5(mole ratio). The ratio (O atoms/Ti atoms) of the O atoms to the Ti atoms is 2.005-2.25. The titanium-based structure has an average minimum size of 1-100 nm, and a specific surface area of 10 m/g or larger.

Description

  The present invention relates to a titanium-based structure for an electricity storage device such as a lithium ion secondary battery and a capacitor, a method for producing the same, and an electrode active material, an electrode active material layer, an electrode, and an electricity storage device using the titanium-based structure.

  Carbon-based materials are mainly used as electrode materials (such as negative electrode materials) for power storage devices such as lithium ion secondary batteries and capacitors.

  However, for example, when a carbon material is used as the negative electrode material of a lithium ion secondary battery, lithium (Li) dendrite is generated, although not as much as when lithium metal is used. In addition, it caused thermal runaway, causing abnormal heat generation and fire.

  Because of these problems, when a carbon material is used for the negative electrode material of a lithium ion secondary battery, propylene carbonate that cannot be used at a high temperature (for example, 60 ° C. or higher) and excellent in low temperature characteristics cannot be used (low temperature characteristics are poor). ), And there is a problem that it is necessary to use an expensive separator. In addition, the ionic liquid electrolyte having high heat resistance is decomposed and thus cannot be used, and the performance is deteriorated during rapid charge / discharge.

  It is also known to use titanium oxide as a negative electrode material instead of this carbon material. In the case of titanium oxide, the theoretical discharge capacity is as high as 335 mAh / g. However, since rutile type titanium oxide and anatase type titanium oxide have a closely packed crystal structure, the actual discharge capacity is about 100 mAh / g at most. .

Therefore, in recent years, lithium titanate (LTO: Li ₄ Ti ₅ O ₁₂ ) which does not generate Li dendrite, does not cause thermal runaway, and has excellent cycle characteristics has come to be used as a negative electrode material. Moreover, since specific gravity is high compared with a carbon material, it is anticipated that the capacity | capacitance per volume will be improved. However, LTO (Li ₄ Ti ₅ O ₁₂ ) has the disadvantage that the theoretical discharge capacity is as low as 175 mAh / g and the actual discharge capacity is as low as about 163 to 168 mAh / g (Patent Document 1, Non-Patent Document). 1). The theoretical discharge capacity of the ramsdellite LTO was also 235 mAh / g (Patent Document 2).

  The above problems have been described only for the lithium ion secondary battery, but the same applies to the electric double layer capacitor.

JP 2002-274849 A Japanese Patent Laid-Open No. 10-247496

E. Ferg et al, J. Electrochem. Soc., Vol. 141, No. 11, L147 (1994)

  The present invention provides a titanium-based structure that is safer than existing carbon-based materials, has a higher capacity than existing titanium-based materials such as lithium titanate, and can be used for an electricity storage device, and a simple manufacturing method thereof. With the goal. In addition, when this titanium-based structure is used in a lithium ion secondary battery, it has a high discharge capacity and excellent rate characteristics, and when it is used in an electric double layer capacitor, it is also a material that exhibits a high capacitance. And

  As a result of intensive studies in view of the above-mentioned purpose, a substance having a Ti atom is added to an aqueous alkali solution having a specific concentration, heated to 50 to 450 ° C., and the alkali is replaced with hydrogen as necessary. It has been found that a specific titanium-based structure can be obtained by heating, and that the above-described problems can be solved by employing this titanium-based structure. Thereafter, further research was conducted to complete the present invention.

That is, the present invention includes the following configurations.
Item 1. Including at least group 1 atom of the periodic table, Ti atom and O atom,
The ratio of Periodic Table Group 1 atoms to Ti atoms (Periodic Table Group 1 atoms / Ti atoms) is 0.01 to 0.5 (molar ratio),
The ratio of O atom to Ti atom (O atom / Ti atom) is 2.005 to 2.25,
The average minimum size is 1 to 100 nm, and
A titanium-based structure for an electricity storage device, having a specific surface area of 10 m ² / g or more.
Item 2. Composition formula:
AxTiOy
[Wherein, A is a group 1 atom of the periodic table; x is 0.01 to 0.5; y is 2.005 to 2.25. ]
Item 2. The titanium-based structure for an electricity storage device according to Item 1, which is represented by:
Item 3. Item 4. The titanium-based structure for an electricity storage device according to Item 1, further comprising at least one selected from the group consisting of Nb atoms, B atoms, C atoms, and N atoms.
Item 4. Composition formula:
AxTiOyMz
[Wherein, A is a group 1 atom of the periodic table; M is an Nb atom, B atom, C atom, or N atom; x is 0.01 to 0.5; y is 2.005 to 2.25; z is 0.01 to 0.20. ]
Item 4. The titanium-based structure for an electricity storage device according to Item 3, which is represented by:
Item 5. Item 5. The titanium-based structure for an electricity storage device according to any one of Items 1 to 4, wherein the Group 1 atom of the periodic table contains 80 mol% or more of H atom and 10 mol% or less of Na atom.
Item 6. Item 5. The titanium-based structure for an electricity storage device according to any one of Items 1 to 4, wherein the Group 1 atom of the periodic table contains 50 mol% or more of H atoms and 50 mol% or less of K atoms.
Item 7. Item 7. The titanium-based structure for an electricity storage device according to any one of Items 1 to 6, wherein the Group 1 atom of the periodic table has a total content of Na and K of 1% by weight or less.
Item 8. Item 8. The titanium-based structure for an electricity storage device according to any one of Items 1 to 7, wherein the average minimum size is 1 to 40 nm and the specific surface area is 50 m ² / g or more.
Item 9. Item 9. The titanium structure for an electricity storage device according to any one of Items 1 to 8, wherein the average minimum size is 1 nm or more and less than 5 nm.
Item 10. Item 10. The titanium-based structure for an electricity storage device according to any one of Items 1 to 9, wherein the electricity storage device is a lithium ion secondary battery, an electric double layer capacitor, or a lithium ion capacitor.
Item 11. The method for producing a titanium-based structure for an electricity storage device according to any one of Items 1 to 10,
(1) A production method comprising a step of alkali-treating a material containing at least titanium at 50 to 450 ° C. in an alkaline aqueous solution of 2 to 20 mol / L.
Item 12. Item 12. The method according to Item 11, wherein the alkali contains sodium hydroxide and / or potassium hydroxide.
Item 13. Item 13. The method according to Item 11 or 12, wherein the alkali contains at least 30 mol% of sodium hydroxide.
Item 14. further,
(2) The manufacturing method according to any one of Items 11 to 13, comprising a step of replacing sodium and / or potassium present in the titanium oxide structure obtained in the step (1) with hydrogen and / or lithium.
Item 15. further,
(3) A manufacturing method according to item 14, comprising a step of heat-treating the titanium-based structure obtained in step (2) at 150 to 500 ° C.
Item 16. Item 13. An electrode for an electricity storage device comprising the titanium-based structure for an electricity storage device according to any one of Items 1 to 10, or the titanium-based structure for an electricity storage device obtained by the production method according to any one of Items 11 to 15. Active material.
Item 17. Item 18. An electrode active material layer for an electricity storage device, comprising the electrode active material for an electricity storage device according to Item 16.
Item 18. Furthermore, it contains a conductive material and a binder, and the mixing ratio of the negative electrode active material in the electrode active material layer is 30 to 99% by weight, and the mixing ratio of the conductive material is 1 to 50% by weight. Item 18. An electrode active material layer for an electricity storage device according to Item 17.
Item 19. An electrode for an electricity storage device, comprising the electrode current collector and the negative electrode active material layer for an electricity storage device according to Item 17 or 18.
Item 20. Item 20. An electricity storage device comprising the electrode for an electricity storage device according to Item 19.
Item 21. Item 20. The electricity storage device according to Item 20, which is a lithium ion secondary battery, an electric double layer capacitor, or a lithium ion capacitor.

  According to the present invention, it is possible to provide a titanium-based structure that has a higher capacity than existing titanium-based materials such as lithium titanate and can be applied to an electricity storage device, and a simple manufacturing method thereof. This titanium-based structure exhibits a high discharge capacity and excellent rate characteristics when employed in a lithium ion secondary battery, and exhibits a high capacitance when employed in an electric double layer capacitor. In addition, this titanium-based structure is a material that has high safety compared to existing carbon-based materials because it hardly generates dendrites and does not easily decompose the electrolytic solution.

2 is an electron microscope (TEM) image of the titanium-based structure produced in Example 1. FIG. 10 is an electron microscope (TEM) image of the titanium-based structure produced in Example 8. 10 is an electron microscope (STEM) image of the titanium-based structure produced in Example 8.

1. Titanium-based structure The titanium-based structure for an electricity storage device of the present invention includes at least a periodic table group 1 atom, a Ti atom, and an O atom, and a ratio of the periodic table group 1 atom to a Ti atom (periodic table group 1 Atom / Ti atom) is 0.01 to 0.5 (molar ratio), the ratio of O atom to Ti atom (O atom / Ti atom) is 2.005 to 2.25, and the average minimum size is The structure is 1 to 100 nm and has a specific surface area of 10 m ² / g or more.

In the present invention, the “titanium-based structure” typically means a structure made of a titanium compound typified by titanium oxide. “Titanium oxide” does not refer to only titanium dioxide (TiO ₂ ), which is the most common titanium oxide, but titanium dioxide (Ti ₂ O ₃ ); titanium monoxide (TiO); Ti ₄ O ₇ In addition, a composition in which oxygen is deficient from titanium dioxide typified by Ti ₅ O ₉ is also included. Further, as represented by the terminal OH group, a group other than Ti—O—Ti resulting from the synthesis of titanium oxide may be included. Further, it may contain a Group 1 atom such as Li atom.

<Shape>
The shape of the titanium-based structure of the present invention may be any of a rod shape, a fiber shape, a sheet shape (including a non-planar shape), a particle shape, or a mixture thereof. Further, in the case of a rod shape, a fiber shape, or a sheet shape, it is not always necessary to be linear like a rectangular parallelepiped or a columnar shape, and may be bent. Moreover, it is not necessary to have a perfect plane, and a curved surface may be sufficient. The cross section is not particularly limited, such as a circular shape, an elliptical shape, or a rectangular shape. Moreover, the titanium-based structure of the present invention may have some unevenness. However, cylinders (tubes) and rolls are excluded. From the viewpoint of capacity (particularly discharge capacity), a sheet-like one is preferable.

  The average minimum size of the titanium-based structure of the present invention is 1 to 100 nm, preferably 1 to 40 nm, more preferably 1 nm or more and less than 5 nm. If the average minimum size is less than 1 nm, the titanium-based structure is likely to aggregate, so that isolation is difficult, and it is difficult to obtain a pore size (pore diameter) necessary for the diffusion of the electrolyte. On the other hand, when the average minimum size exceeds 100 nm, the specific surface area becomes small and the rate characteristics and the like deteriorate.

  In the present invention, the “average minimum size” of the titanium-based structure means, for example, in the case of a rod or fiber, the smallest of the average diameter and the average length, and in the case of a sheet Means the smallest of average width, average thickness, and average length. That is, the “average minimum size” of the titanium-based structure means the smallest dimension among the dimensions of the titanium-based structure. When the titanium-based structure of the present invention is rod-shaped or fiber-shaped, the average diameter is preferably the average minimum size, and when it is sheet-shaped, the average thickness is preferably the average minimum size.

  In the present invention, dimensions other than the average minimum size of the titanium-based structure are not particularly limited.

  For example, when the titanium-based structure of the present invention is in the form of a rod or fiber, the average length is from the viewpoint of improving the strength and rate characteristics of the coating film and improving the film properties when applied. 0.5-50 micrometers (especially 1-20 micrometers) are preferable. Further, from the viewpoint of making it easier to obtain physical properties resulting from a high aspect ratio such as high conductivity and high strength, and improving the film properties when applied, the average aspect ratio is 5 to 5000 (particularly 10 to 1000). ) Is preferable.

  Further, when the titanium-based structure of the present invention is in sheet form, the titanium-based structures are less likely to be entangled with each other to suppress aggregation and make isolation easier, and the specific surface area is increased to increase the rate. From the viewpoint of further improving the characteristics, the average thickness is preferably 1 to 50 nm (particularly 2 to 20 nm). In addition, the average width (average of the longest width) is 0.05 to 50 μm (particularly 0.1 to 0.1 μm) from the viewpoint of further improving the strength and rate characteristics of the coating film and improving the film properties when applied. 20 μm) is preferable. Furthermore, the ratio of the average width to the thickness is 5 to 5000 (in particular, from the viewpoint of making it easier to obtain physical properties resulting from a high aspect ratio, such as high conductivity and high strength, and improving the film properties when applied. 10 to 1000).

  The shape (average minimum size, average diameter, average width, average length, and average aspect ratio) of the titanium-based structure is measured, for example, by observation with an electron microscope (SEM or TEM), and the cross section is, for example, FIB (Focused). It shall be observed by TEM after processing by Ion Beam).

The specific surface area of the titanium-based structure of the present invention is 10 m ² / g or more, preferably 15 m ² / g or more, more preferably 50 m ² / g or more. When the specific surface area is less than 10 m ² / g, the contact area with the electrolytic solution is small, the quick reactivity with the electrolytic solution is reduced, and the rate characteristics are deteriorated. On the other hand, further suppressed the shrinkage of the coating film, from the viewpoint of further preventing cracks, the specific surface area is preferably 1000 m ² / g or less, 500 meters ² / g or less is more preferable. The specific surface area is measured by the BET method or the like.

<Composition>
As described above, the titanium-based structure of the present invention includes at least a periodic table group 1 atom, a Ti atom, and an O atom, and the ratio of the periodic table group 1 atom to the Ti atom (periodic group 1 atom / Ti atom) is 0.01 to 0.5 (molar ratio), and the ratio of O atom to Ti atom (O atom / Ti atom) is 2.005 to 2.25.

That is, the main component of the titanium-based nanostructure of the present invention is not TiO ₂ of anatase type, rutile type, brookite type, etc., but these may be mixed, and the content thereof is, for example, about 10% by weight or less. It is. The specific crystal structure of the titanium-based structure of the present invention is not particularly limited, and may include a plurality of crystal forms. The crystal structure of the titanium-based structure is measured by, for example, X-ray diffraction, electron beam diffraction, Raman spectroscopic analysis, or the like.

  Examples of the periodic table Group 1 atoms of the titanium-based structure of the present invention include H atoms, Li atoms, Na atoms, and K atoms. In addition, the content of Na and K in the titanium-based structure of the present invention can improve the charge / discharge capacity and cycle characteristics more preferably, and is preferably 20% by weight or less of the total weight of the titanium-based structure, 10% by weight or less is more preferable.

  In the case where the titanium-based structure of the present invention contains an alkali metal as a group 1 atom of the periodic table, the content of the alkali metal is the alkali metal derived from the raw material when the hydrothermal synthesis method is employed (for example, hydroxylation). (Sodium in sodium, potassium in potassium hydroxide, etc.) is intended, and as described above, the smaller the number, the more the charge / discharge capacity and cycle characteristics can be improved. In addition, when heat resistance is required, it may be preferable to contain alkali metals such as sodium and potassium to some extent. Therefore, the metal content may be appropriately set according to the purpose and the like.

  From such a viewpoint, the periodic table group 1 atom contained in the titanium-based structure of the present invention contains 80 mol% or more (80 to 100 mol%, particularly 90 to 100 mol%) of H atoms, and Na atoms. Including 10 mol% or less (0 to 10 mol%, particularly 0 to 5 mol%) is preferable because it has a higher charge / discharge capacity. The alkali element content is measured by ion chromatography, ICP emission spectroscopy, or the like.

  On the other hand, as another preferred embodiment, when the titanium-based structure of the present invention contains a K atom as a group 1 atom in the periodic table, the H atom is contained in an amount of 50 mol% or more (50 to 100 mol%, particularly 70 to 100 mol%) and 50 atoms% or less (0 to 50 mol%, particularly 0 to 30 mol%) of K atoms are preferable because they have a higher charge / discharge capacity. The content of the alkali metal element is measured by ion chromatography, ICP emission spectroscopy, or the like.

  The content of Li atoms in the titanium-based structure of the present invention has a higher charge / discharge capacity as it is smaller, and has higher cycle characteristics as it is larger. Therefore, it may be appropriately set according to required characteristics. .

  In the titanium-based structure of the present invention, the Group 1 atom of the periodic table preferably has a total content of Na and K of 1% by weight or less. In this case, the charge / discharge capacity can be further increased, and the cycle characteristics can be improved.

In the titanium-based structure of the present invention, the ratio of group 1 atom of the periodic table to Ti atom (period group 1 atom / Ti atom; molar ratio) is 0.01 to 0.5, preferably 0.1 to 0.1. 0.35. If the ratio of group 1 atom of the periodic table to Ti atom is less than 0.01, the chemical structure is close to TiO ₂ and the cycle characteristics may be deteriorated. Moreover, when the ratio of the periodic table group 1 atom to the Ti atom exceeds 0.5, the charge / discharge capacity and the cycle characteristics are deteriorated. Further, the ratio of the group 1 atom of the periodic table to the Ti atom is not necessarily a single substance having an integer ratio, and a mixture of structures having different ratios may be used. The content of alkali metal element is measured by ion chromatography, ICP emission spectroscopic analysis, etc., and the content of Ti atom, O atom, etc. is measured by fluorescent X-ray (WDX), X-ray diffraction (XRD), TG- It shall be measured by DTA or the like.

  In the titanium-based structure of the present invention, the ratio of O atom to Ti atom (O atom / Ti atom; molar ratio) is 2.005 to 2.25, preferably 2.05 to 2.2. When the ratio of O atoms to Ti atoms is less than 2.005, the cycle characteristics may be deteriorated. On the other hand, when the ratio of O atoms to Ti atoms exceeds 2.25, the charge / discharge capacity and the cycle characteristics deteriorate. Content of Ti atoms, O atoms, etc. shall be measured by fluorescent X-ray (WDX), X-ray diffraction (XRD), TG-DTA, etc.

Examples of the titanium-based structure of the present invention that satisfies the above conditions include a composition formula:
AxTiOy
[Wherein, A is a group 1 atom of the periodic table; x is 0.01 to 0.5; y is 2.005 to 2.25. ]
It is preferable to have the composition shown by these.

  The titanium-based structure of the present invention may contain at least one of Nb atom, B atom, C atom, and N atom. By including these elements, effects such as improving the conductivity and suppressing the reaction with the electrolytic solution can be obtained. In particular, when the titanium-based structure of the present invention contains Nb atoms, C atoms, etc., the cycle characteristics can be further improved.

  When the titanium-based structure of the present invention contains Nb atoms, B atoms, etc., it is preferable to dope these elements by a conventional method. Further, C atoms and N atoms may be included when the titanium-based structure of the present invention is produced.

Examples of the titanium-based structure of the present invention that satisfies the above conditions include a composition formula:
AxTiOyMz
[Wherein, A is a group 1 atom of the periodic table; M is an Nb atom, B atom, C atom, or N atom; x is 0.01 to 0.5; y is 2.005 to 2.25; z is 0.01 to 0.20. ]
It is preferable to have the composition shown by these.

  The titanium-based structure of the present invention having such properties has a higher capacity than existing titanium-based materials such as lithium titanate, and has a high discharge capacity and excellent rate characteristics when used in a lithium ion secondary battery. When it is used for an electric double layer capacitor, it shows a high capacitance. In addition, the titanium-based structure of the present invention having such properties is a material with higher safety than existing carbon-based materials because it hardly generates dendrites and hardly decomposes the electrolyte. For this reason, it can be used for electrical storage devices, such as a lithium ion secondary battery, an electric double layer capacitor, and a lithium ion capacitor, for example.

2. Method for producing titanium-based structure <Step (1)>
The production method of the titanium-based structure of the present invention is as follows:
(1) A step of subjecting a material containing at least titanium to an alkali treatment at 50 to 450 ° C. in an alkali aqueous solution of 2 to 20 mol / L.

  In the step (1), although not limited to this, it is preferable that a material containing at least titanium and an aqueous alkali solution of 2 to 20 mol / L are heated to 50 to 450 ° C. and allowed to react.

  Specifically, an alkali metal hydroxide is added to a dispersion of a material containing at least titanium (for example, an aqueous dispersion or an aqueous sol) (particularly, an aqueous dispersion or aqueous sol of titanium oxide or a titanium oxide precursor). It is preferable that the concentration is adjusted to 50 to 450 ° C. and left as it is. The specific method is not limited to this, and a material containing at least titanium (particularly titanium oxide or a titanium oxide precursor), or a dispersion or an aqueous sol thereof (particularly, 2-20 mol / L alkaline aqueous solution). An aqueous dispersion or aqueous sol of titanium oxide or a titanium oxide precursor) may be added and heated to 50 to 450 ° C. and allowed to stand.

  In addition, the reaction temperature is not limited to this, and even if the temperature is high, the reaction time can be shortened (for example, 1 hour. If supercritical water at 400 ° C. is used, several seconds to several tens of seconds). Although it is possible to obtain the titanium-based structure of the invention, when it is reacted for a long time at a high temperature, a substance having a large size and a small specific surface area is generated.

  The aqueous alkaline solution is preferably an aqueous solution in which an alkali, particularly an alkali metal hydroxide (sodium hydroxide, potassium hydroxide, lithium hydroxide, etc.) is dissolved. Especially, it is preferable that sodium hydroxide and / or potassium hydroxide are included.

  As the alkaline aqueous solution, an aqueous solution of an alkali metal hydroxide is preferable from the viewpoint of dissolving the surface of a raw material containing titanium (particularly titanium oxide or a titanium oxide precursor) and promoting the reaction. In addition, it is good also as an aqueous solution containing 2 or more types of alkalis as an alkali, for example, it is also possible to use sodium hydroxide as a main component and to use potassium hydroxide, lithium hydroxide, etc. together. In particular, the alkali is preferably sodium hydroxide and / or potassium hydroxide in order to synthesize a high aspect ratio structure. When sodium hydroxide is used as the main component, a sheet-like structure tends to be generated, and when potassium hydroxide is used as the main component, a fiber-like structure having a small average width is generated. There is a tendency.

  The concentration of the alkaline aqueous solution is 2 to 20 mol / L, preferably about 3 to 20 mol / L, more preferably about 5 to 15 mol / L. When the concentration of the aqueous alkali solution is less than 2 mol / L, the material containing titanium as a raw material is difficult to dissolve and the reaction does not proceed sufficiently, or the reaction rate becomes extremely slow. On the other hand, when the concentration of the aqueous alkali solution exceeds 20 mol / L, there may be a problem in production such as a high viscosity of the reaction solution and a large amount of waste solution generated after synthesis.

  When the alkaline aqueous solution is an alkaline aqueous solution containing sodium hydroxide as a main component, an aqueous solution containing only sodium hydroxide as an alkaline component may be used, but two or more types of alkaline components (sodium hydroxide and other alkalis may be used). An aqueous solution containing the component) may be used. However, from the viewpoint of obtaining a sheet-like titanium structure having a higher aspect ratio, the concentration of sodium hydroxide with respect to the total alkali component is preferably 30 to 100 mol%, more preferably 50 to 100 mol%, and 60 to 100 mol. % Is more preferable.

  When the alkaline aqueous solution is an alkaline aqueous solution containing potassium hydroxide as a main component, an aqueous solution containing only potassium hydroxide as an alkaline component may be used. However, two or more types of alkaline components (potassium hydroxide and other alkalis) may be used. An aqueous solution containing the component) may be used. However, from the viewpoint of obtaining a fiber-like titanium-based structure having a higher aspect ratio, the concentration of potassium hydroxide relative to the total alkali components is preferably 30 to 100 mol%, more preferably 50 to 100 mol%, and 60 to 100 mol. % Is more preferable.

  Although there is no restriction | limiting in particular as a material containing titanium to be used, A titanium oxide or a titanium oxide precursor is preferable. Specifically, known or commercially available titanium oxide fine particles may be used as they are, or titanium hydroxide may be used. In addition, titanium halide, titanium alkoxide, or the like that generates titanium hydroxide by contact with water may be used. These materials containing titanium may be used alone or in combination of two or more.

  When titanium oxide is used, the shape is not particularly limited. Known or commercially available titanium oxide fine particles may be used as they are, or when the particle size is large, they may be used by dry or wet pulverization using a planetary ball mill, paint shaker or the like. Moreover, you may employ | adopt a sol form.

  When titanium oxide is used as the material containing titanium, it is preferable to contain amorphous or anatase type titanium oxide.

  The average particle diameter of titanium oxide is preferably 50 nm or less, and more preferably 35 nm or less from the viewpoint that the surface dissolves rapidly in an alkaline aqueous solution and the titanium-based structure of the present invention can be produced at a lower temperature and in a shorter time. The lower limit of the average particle diameter of the titanium oxide is not particularly limited, but is usually about 1 nm. The average particle diameter of titanium oxide is measured by observation with an electron microscope (SEM or TEM).

  The amount of the material containing titanium to be introduced into the alkaline aqueous solution is not particularly limited, but is preferably about 0.01 to 1 mol / L from the viewpoint of balancing the fluidity and productivity of the reaction solution, About 0.5 mol / L is more preferable.

  Moreover, the form of the material containing titanium is not particularly limited. For example, an aqueous dispersion of a material containing titanium or an aqueous sol of a material containing titanium may be used. Further, a material containing titanium may be put into an alkaline aqueous solution as it is. From the viewpoint of further improving the dispersibility of the product, an aqueous sol of a material containing titanium is preferable.

  The process temperature of a process (1) is 50-450 degreeC, Preferably it is 60-300 degreeC, More preferably, it is 70-160 degreeC. The higher the temperature, the shorter the reaction time, and the average minimum size tends to increase when compared at the same reaction time. Conversely, when the reaction is performed at a low temperature, a titanium-based structure having a large specific surface area and a small average minimum size is likely to be generated.

  There is no restriction | limiting in particular in the time of the said alkali treatment, About 0.5 to 72 hours are preferable. The smaller the raw material containing titanium and the higher the concentration of the alkaline aqueous solution, the shorter the reaction time.

<Step (2)>
In step (2), sodium (Na) and / or potassium (K) present in the titanium-based structure obtained in step (1) is replaced with hydrogen (H) and / or lithium (Li).

  As a method of replacing sodium (Na) and / or potassium (K) with hydrogen (H), it is preferable to contact the titanium-based structure obtained in step (1) with an acidic solution having a pH of 4 or less. Specifically, it is preferable to immerse the titanium-based structure obtained in step (1) in an acidic solution. Specifically, the titanium-based structure may be directly charged into the acidic solution, or a dispersion of the titanium-based structure and the acidic solution may be mixed. From the viewpoint of uniformly dispersing in an acidic solution, it is preferable to prepare a dispersion of a titanium-based structure in advance and mix this with an acidic solution. In addition, in order to promote dispersion | distribution in the case of immersion, time can be shortened if dispersion | distribution operation by stirring, an ultrasonic wave, etc. is performed.

  The pH of the acidic solution is preferably 5 or less, but is preferably −1 to 4.5 from the viewpoint of efficiently removing alkali metals (particularly potassium and the like) and maintaining the shape of the titanium-based structure having a large aspect ratio. 1-4 are more preferable. The acidic solution is preferably an aqueous solution of a protonic acid which can exchange alkali metal ions and protons, has a low molecular weight and can be easily removed later, and is easily volatilized or decomposed. Specific examples include aqueous solutions of common inorganic acids or organic acids such as hydrochloric acid, nitric acid, acetic acid, oxalic acid, sulfuric acid, hydrofluoric acid, and formic acid, and hydrochloric acid, nitric acid, acetic acid, oxalic acid, and the like are more preferable. . These acids may be used individually by 1 type, and may be used in combination of 2 or more type.

  The amount of the titanium-based structure to be added to the acidic solution is not particularly limited, but is preferably about 0.1 to 20% by weight from the viewpoint of sufficiently stirring and enhancing the production efficiency, and about 1 to 10% by weight. Is more preferable.

  In the titanium-based structure obtained in the step (1), metals such as sodium and potassium may remain slightly, particularly when potassium hydroxide is contained in the alkaline aqueous solution in the step (1). Although potassium does not easily desorb from the titanium-based structure, excess alkali components and metals other than titanium contained in the titanium-based structure can be removed by this step.

  However, since an acidic solution is used, it is preferable to wash the titanium-based structure with water after this step to remove the acid and the liberated metal salt.

  The time for contacting with the acidic solution is preferably about 0.1 to 168 hours under atmospheric pressure conditions, and more preferably 1 hour or more when it is necessary to sufficiently remove the alkali metal.

  Further, the method for replacing sodium (Na) and / or potassium (K) with lithium (Li) is not particularly limited, but (1) a method in which a titanium-based structure is brought into contact with an aqueous lithium salt solution, and (2) titanium. Examples thereof include a method of bringing a system structure into contact with a lithium-based molten salt, and (3) a method of heat-treating a titanium-based structure and a lithium salt in a dry state. In the methods (1) and (2), the titanium-based structure may be used as it is or as a dispersion. In any of these methods, sodium (Na) and / or potassium (K) can be directly substituted with lithium (Li), or once substituted with hydrogen (H) and further substituted with lithium (Li). You can also.

In the method (1), for example, the titanium-based structure is preferably contacted by mixing (immersing) with an aqueous solution of LiCl, LiOH, LiNO ₃ or the like.

In the method (2), for example, it is preferable that the mixture is brought into contact, for example, by melting a mixture of two or more of LiOH, LiNO ₃ , LiCl and the like at 250 to 1000 ° C. and mixing (immersing) with a titanium-based structure. .

In the method (3), for example, it is preferable to mix a titanium-based structure with LiCO ₃ , LiOH or the like and perform heat treatment at 400 to 1000 ° C.

<Step (3)>
In the method for producing a titanium-based structure of the present invention, after the above step (2), (3) a step of heat-treating the titanium-based structure obtained in step (2) at 150 to 500 ° C. It is preferable to provide.

  The heat treatment temperature is preferably from 180 to 450 ° C., more preferably from 200 to 400 ° C., from the viewpoint that the Ti—OH group remaining in the titanium-based structure can be dehydrated.

  The heat treatment may be performed in a normal gas phase or in vacuum, but may be performed in a liquid phase.

  In addition, there is no restriction | limiting in particular as atmosphere in the case of heat-processing in a gaseous phase, Air atmosphere, nitrogen atmosphere, argon atmosphere, etc. are preferable. Further, it may be under reduced pressure such as vacuum.

  On the other hand, when performing in a liquid phase, since crystallinity can be raised at low processing temperature, 150-400 degreeC is preferable, 160-350 degreeC is more preferable, 180-300 degreeC is further more preferable.

  The titanium-based structure obtained in this way has the characteristics as described in “1. Titanium oxide structure” above.

3. Electrode active material layer The electrode active material of the present invention contains the titanium-based structure of the present invention. And in this invention, an electrode active material layer contains the electrode active material containing the titanium structure of this invention.

  In the present invention, the negative electrode active material conventionally used in lithium ion secondary batteries, electric double layer capacitors and the like may be used in combination with the electrode active material layer as another negative electrode active material.

Examples of negative electrode active materials that can be used in combination include carbonaceous materials such as graphite, non-graphitizable carbon (hard carbon), and graphitizable carbon (soft carbon); silicon-based materials such as Si and SiO; Al and Si , Pb, Sn, Zn, Cd, and the like and an alloy compound of lithium; tungsten oxide; molybdenum oxide; iron sulfide; titanium sulfide; lithium titanate; In particular, lithium titanate represented by Li _{4 + x} Ti ₅ O ₁₂ (0 ≦ x ≦ 3) and having a spinel structure is preferable. These negative electrode active materials may be used individually by 1 type, and may be used in combination of 2 or more type.

  The ratio between the titanium-based structure of the present invention and the other electrode active material in the electrode active material layer of the present invention is not particularly limited, but from the viewpoint of achieving both safety and charge / discharge capacity, The titanium-based structure of the present invention is preferably 50 to 100% by weight, more preferably 70 to 100% by weight.

  In addition to the above active material, the electrode active material layer may contain a known conductive material, binder, and the like. Examples of the conductive material include acetylene black, ketjen black, carbon black, graphite, carbon nanotubes, carbon nanofibers, graphene, and amorphous carbon obtained by heat treating an organic substance. As the binder, for example, fluorinated resins such as polytetrafluoroethylene (PTFE), polyvinylidene fluoride (PVdF), vinylidene fluoride-hexafluoropropylene copolymer, styrene-butadiene rubber, acrylonitrile butadiene rubber ( NBR), polyacrylonitrile, polyimide, ethylene-vinyl alcohol copolymer resin (EVOH), ethylene-propylene-diene rubber (EPDM), polyurethane, polyacrylic acid, polyamide, polyacrylic acid ester, polyvinyl ether, carboxymethylcellulose sodium Salt, carboxymethylcellulose ammonium, hydroxypropylcellulose, hydroxyethylcellulose, modified cellulose such as methylcellulose and cellulose nanofiber It may also be mentioned.

  The mixing ratio of the electrode active material, the conductive material and the binder in the electrode active material layer is not particularly limited, but the electrode active material is preferably 30 to 99% by weight, and 40 to 95% by weight from the viewpoint of achieving both capacity and conductivity. % Is more preferable. Further, the conductive material is preferably 1 to 50% by weight, and more preferably 2 to 40% by weight. Further, the binder is preferably 1 to 30% by weight, and more preferably 3 to 20% by weight.

  The titanium-based structure of the present invention is a sheet-like, rod-like, or fiber-like material as described above. Other active materials, conductive materials, binders, and the like are particulate or powder materials. Therefore, when these are mixed to form an electrode active material layer paste, it is preferable to mix water or an organic solvent such as acetone, N-methylpyrrolidone, dimethyl sulfoxide, dimethylformamide or the like to make a paste.

  The thickness of the electrode active material layer of the present invention is preferably 5 to 200 μm, more preferably 10 to 150 μm, from the viewpoint of securing sufficient capacity and electrode strength.

  The electrode active material layer of the present invention as described above can be formed by molding and drying the electrode active material layer paste formed as described above.

4). Electrode The electrode for an electricity storage device of the present invention includes the electrode active material layer of the present invention. More specifically, the electrode active material layer of the present invention is preferably provided on the electrode current collector.

  As a material of the electrode current collector, for example, copper, nickel, iron, stainless steel, titanium or the like can be used. Furthermore, the surface of the electrode current collector made of these materials may be treated with carbon, nickel, titanium, silver or the like for the purpose of adhesion, conductivity, and reduction resistance.

  Although the preferable thickness of an electrode electrical power collector can be set arbitrarily, 1-500 micrometers is preferable, for example, and 5-200 micrometers is more preferable.

  The method for forming the electrode active material layer on the electrode current collector is not particularly limited. For example, the electrode active material layer paste may be applied and dried on the electrode current collector, or the electrode active material layer paste may be formed and then dried and adhered to the electrode current collector. A known method may be employed for the application, drying, and adhesion. In addition, about 50-300 degreeC is preferable for drying temperature, and about 70-200 degreeC is more preferable.

  The electrode for an electricity storage device of the present invention can be used for both the negative electrode and the positive electrode, but is preferably used for the negative electrode.

5. Electric storage device The electric storage device of the present invention includes the electrode for an electric storage device of the present invention. Examples of such an electricity storage device include a lithium ion secondary battery, an electric double layer capacitor, and a lithium ion capacitor.

  Further, when the electricity storage device of the present invention is a lithium ion secondary battery or an electric double layer capacitor, a positive electrode and a negative electrode may be further installed via a separator, and a nonaqueous electrolyte solution may be filled between the positive electrode and the negative electrode. preferable. Specifically, it is preferable to install the positive electrode and the negative electrode through a separator impregnated with a nonaqueous electrolytic solution.

  As the positive electrode, the electrode for an electricity storage device of the present invention may be used, and when the electrode for an electricity storage device of the present invention is used as a negative electrode, a known positive electrode may be used.

  When a well-known positive electrode is used as the positive electrode, for example, a positive electrode including a positive electrode active material and a positive electrode active material layer containing a conductive material, a binder, and the like as necessary can be used on the positive electrode current collector.

  As the positive electrode current collector, the same electrode current collector as described above can be used.

The positive electrode active material is not particularly limited and includes various oxides and sulfides. For example, manganese dioxide (MnO ₂ ), iron oxide, copper oxide, nickel oxide, lithium manganese composite oxide (eg, Li _x Mn ₂ O ₄ , Li _x MnO _2, etc.), lithium nickel composite oxide (eg, Li _x NiO _2). Etc.), lithium cobalt composite oxide (eg Li _x CoO ₂ etc.), lithium nickel cobalt composite oxide (eg LiNi _1-y Co _y O ₂ etc.), lithium nickel cobalt manganese composite oxide (eg LiNi _x Co _y Mn) _1-x-y O ₂ etc.), spinel type lithium manganese nickel composite oxide (Li _x Mn _2-y Ni _y O ₄ etc.), lithium phosphorous oxide having an olivine structure (eg Li _x FePO ₄ , Li _x Fe) _{1-y Mn y PO 4,} Li x CoPO 4 , etc.), iron sulfate _(Fe 2 _{(SO 4) 3} , Vanadium oxide (for example, _V 2 _{O 5,} etc.) and the like. In addition, conductive polymer materials such as polyaniline and polypyrrole, disulfide polymer materials, sulfur (S), carbon fluoride, and the like are also included. In particular, a lithium transition metal composite oxide represented by LiMn _x Ni _y Co _z O ₂ (x + y + z = 1; 0 ≦ x ≦ 0.5; 0 ≦ y ≦ 1; 0 ≦ z ≦ 1) is preferable. These positive electrode active materials may be used individually by 1 type, and may be used in combination of 2 or more type.

  As the conductive material and the binder, those described above can be used.

  As the negative electrode, the electrode for an electricity storage device of the present invention may be used, and when the electrode for an electricity storage device of the present invention is used as a positive electrode, a known negative electrode may be used.

  When using a well-known negative electrode as a negative electrode, the negative electrode provided with the negative electrode active material and the negative electrode active material layer containing a electrically conductive material, a binder, etc. as needed on a negative electrode collector can be used, for example.

  As the negative electrode current collector, the same electrode current collector as described above can be used.

Examples of the negative electrode active material include carbonaceous materials such as graphite, non-graphitizable carbon (hard carbon), graphitizable carbon (soft carbon); silicon-based materials such as Si and SiO; Al, Si, Pb, An alloy-based compound of Sn, Zn, Cd, and the like and lithium; tungsten oxide; molybdenum oxide; iron sulfide; titanium sulfide; lithium titanate; In particular, lithium titanate represented by Li _{4 + x} Ti ₅ O ₁₂ (0 ≦ x ≦ 3) and having a spinel structure is preferable. These negative electrode active materials may be used individually by 1 type, and may be used in combination of 2 or more type.

  As the conductive material and the binder, those described above can be used.

  As the non-aqueous electrolyte, an organic electrolyte containing an organic solvent and an electrolyte salt is preferable.

  Examples of the organic solvent for the non-aqueous electrolyte include low-viscosity chain carbonates such as dimethyl carbonate, methyl ethyl carbonate, and diethyl carbonate; cyclic carbonates having a high dielectric constant such as ethylene carbonate, propylene carbonate, butylene carbonate, and vinylene carbonate; 1,2-dimethoxyethane; tetrahydrofuran; 2-methyltetrahydrofuran; 1-3 dioxolane; methyl acetate; methylpropionate; dimethylformamide; sulfolane; triglyme; tetraglyme; it can. Moreover, when seeking heat resistance, you may use various molten salts (ionic liquid), such as an imidazolium salt. Of these, ethylene carbonate, propylene carbonate, dimethyl carbonate, methyl ethyl carbonate, diethyl carbonate and the like are preferable.

As the electrolyte salt is not particularly limited, for _{example, LiClO 4, LiBF 4, LiAsF} 6, LiPF 6, LiCF 3 SO 3, LiN (CF 3 SO 2) 2, LiN (C 2 F 5 SO 2) 2 , LiI, LiAlCl ₄ , a mixture thereof, and the like. Preferably, the lithium salt of LiBF ₄ and / or LiPF ₆ is good.

  As the separator, a microporous membrane made of a polyolefin resin such as polyethylene is used, which is formed by laminating a plurality of microporous membranes having different materials, weight average molecular weights and porosity, and various plastic films on these microporous membranes. It may be one containing an appropriate amount of additives such as an agent, an antioxidant, and a flame retardant. In addition, since the dendrites hardly occur in the titanium-based structure of the present invention, a normal resin mesh or cellulose film can also be used.

  As the shape of the electricity storage device, a wound oval shape, a circular shape, or the like can be used. Other constituent elements of the battery include a terminal, an insulating plate, a battery case, and the like. Conventionally, these components can be used as they are.

  The present invention will be specifically described based on examples, but the present invention is not limited to these examples.

Example 1 (Ti-NS)
To 28.4 g of titanium tetraisopropoxide (0.1 mol: 8.0 g in terms of TiO ₂ ), 12.0 g of acetic acid, water and 1 ml of 65 wt% nitric acid were added and heated at 80 ° C. for 3 hours. After adjusting, 80 g of NaOH was added (NaOH concentration 10 mol / L). This solution was kept at 120 ° C. for 24 hours in a polymethylpentene container immersed in an oil bath.

  The resulting material was added to 2000 g water and filtered. Furthermore, after adding to 1000 g of water and dispersing, 35 wt% HCl aqueous solution was added to adjust to pH 1 and stirred for 24 hours. Thereafter, filtration and dispersion in 1000 g of water were repeated to finally obtain 8.6 g of a white substance.

  This material was heated in vacuum at 200 ° C. for 12 hours and in air at 300 ° C. for 5 hours to give 8.2 g of white material.

When observed by TEM, a sheet-like substance having an average width of 50 nm or more, an average thickness of less than 5 nm, and an average length of 100 nm or more was observed. Moreover, it was 385 m < ² > / g when the BET specific surface area was measured. In addition, the TEM image of the titanium-type structure (before 300 degreeC heat processing in the air) obtained in this Example 1 is shown in FIG.

  In addition, as a result of elemental analysis, the titanium-based structure obtained in Example 1 has a ratio of periodic table group 1 atom to Ti atom (periodic group 1 atom / Ti atom) of 0.01 to 0.00. 5 (molar ratio), and the ratio of O atom to Ti atom (O atom / Ti atom) was in the range of 2.005 to 2.25.

Example 2 (Ti-NS)
An experiment was conducted in the same manner as in Example 1 except that 8 g of titanium oxide nanoparticles having an average particle diameter of 7 nm were used as a titanium source, and 200 g of water and 80 g of NaOH were added to the nanoparticles.

When observed by TEM, a sheet-like substance having an average width of 50 nm or more, an average thickness of less than 5 nm, and an average length of 100 nm or more was observed. Moreover, it was 310 m < ² > / g when the BET specific surface area was measured.

  In addition, as a result of elemental analysis, the titanium-based structure obtained in Example 2 has a ratio of Periodic Table Group 1 atoms to Ti atoms (Periodic Table Group 1 atoms / Ti atoms) of 0.01 to 0.00. 5 (molar ratio), and the ratio of O atom to Ti atom (O atom / Ti atom) was in the range of 2.005 to 2.25.

Example 3 (Ti-NW)
Acetic acid 12.0 g, water and 1 ml of 65 wt% nitric acid were added to 28.4 g of titanium tetraisopropoxide, heated at 80 ° C. for 3 hours, the total weight was adjusted to 200 g, and KOH 124.7 g (purity 90%. 2 mol). The experiment was performed in the same manner as in Example 1 except that the above was mixed.

When observed by TEM, a fiber-like substance having an average width of 7 nm and an average length of 3 μm or more (average aspect ratio of 430 or more) was observed. Moreover, it was 306 m < ² > / g when the BET specific surface area was measured.

  In addition, as a result of elemental analysis, the titanium-based structure obtained in Example 3 has a ratio of Periodic Table Group 1 atoms to Ti atoms (Periodic Table Group 1 atoms / Ti atoms) of 0.01 to 0.00. 5 (molar ratio), and the ratio of O atom to Ti atom (O atom / Ti atom) was in the range of 2.005 to 2.25.

Example 4 (Ti-NW)
The experiment was performed in the same manner as in Example 3 except that the reaction temperature was 250 ° C. instead of 120 ° C., and the reaction was performed in a Hastelloy microreactor.

When observed by SEM, a fiber-like substance having an average width of 11 nm and an average length of 5 μm or more (average aspect ratio of 450 or more) was observed. Moreover, it was 260 m < ² > / g when the BET specific surface area was measured.

  In addition, as a result of elemental analysis, the titanium-based structure obtained in Example 4 has a ratio of Periodic Table Group 1 atoms to Ti atoms (Periodic Table Group 1 atoms / Ti atoms) of 0.01 to 0.00. 5 (molar ratio), and the ratio of O atom to Ti atom (O atom / Ti atom) was in the range of 2.005 to 2.25.

Example 5
The experiment was performed in the same manner as in Example 2 except that the reaction temperature was set to 200 ° C. instead of 120 ° C., and the reaction was performed in a titanium microreactor.

When observed by TEM, a rod-like substance having an average width of 50 nm and an average length of 5 μm or more (average aspect ratio of 100 or more) was observed. Moreover, it was 50 m < ² > / g when the BET specific surface area was measured.

  Further, as a result of elemental analysis, the titanium-based structure obtained in Example 5 has a ratio of periodic table group 1 atoms to Ti atoms (periodic group 1 atoms / Ti atoms) of 0.01 to 0.00. 5 (molar ratio), and the ratio of O atom to Ti atom (O atom / Ti atom) was in the range of 2.005 to 2.25.

Example 6
The experiment was performed in the same manner as in Example 5 except that sodium hydroxide was reduced to 24 g (NaOH concentration 3 mol / L) instead of 80 g.

When observed by TEM, a fiber-like substance having an average width of 20 nm and an average length of 3 μm or more (average aspect ratio of 150 or more) was observed. Moreover, it was 196 m < ² > / g when the BET specific surface area was measured.

  In addition, as a result of elemental analysis, the titanium-based structure obtained in Example 6 has a ratio of periodic table group 1 atoms to Ti atoms (periodic group 1 atoms / Ti atoms) of 0.01 to 0.00. 5 (molar ratio), and the ratio of O atom to Ti atom (O atom / Ti atom) was in the range of 2.005 to 2.25.

Example 7
The experiment was performed in the same manner as in Example 5 except that the reaction was carried out by adding 10 mol% of boric acid to Ti together with NaOH.

When observed by TEM, a fiber-like substance having an average width of 60 nm and an average length of 5 μm or more (average aspect ratio of 83 or more) was observed. Moreover, it was 40 m < ² > / g when the BET specific surface area was measured.

  Further, as a result of elemental analysis, the titanium-based structure obtained in Example 7 had a ratio of periodic table group 1 atoms to Ti atoms (periodic group 1 atoms / Ti atoms) of 0.01 to 0.00. 5 (molar ratio), and the ratio of O atom to Ti atom (O atom / Ti atom) was in the range of 2.005 to 2.25.

Example 8
8 g of titanium oxide nanoparticles having an average particle diameter of 7 nm were used as a titanium source, 200 g of water and 80 g of NaOH were added to the nanoparticles, and this liquid was kept at 80 ° C. for 12 hours in a polymethylpentene container immersed in an oil bath.

  The obtained substance was treated in the same manner as in Example 1 to obtain 8.1 g of a white substance.

In addition, when observed with TEM and STEM (scanning transmission electron microscope), a sheet-like substance having a width of 10 to 50 nm and a thickness of about 2 nm and a length of 100 to 500 nm was observed although it could not be measured accurately. . FIG. 2 shows a TEM image and FIG. 3 shows a STEM image of the titanium-based structure obtained in Example 8 (before heat treatment in air at 300 ° C., specific surface area 383 m ² / g).

  Further, as a result of elemental analysis, the titanium-based structure obtained in Example 8 had a ratio of periodic table group 1 atoms to Ti atoms (periodic group 1 atoms / Ti atoms) of 0.01 to 0.00. 5 (molar ratio), and the ratio of O atom to Ti atom (O atom / Ti atom) was in the range of 2.005 to 2.25.

Example 9
Using 10 g of titanium oxide nanoparticles having an average particle diameter of 16 nm as a titanium source, 200 g of water and 80 g of NaOH were added to the nanoparticles, and this liquid was kept at 110 ° C. for 15 hours in a polymethylpentene container immersed in an oil bath.

  The resulting reaction solution was filtered by adding to 2000 g of water. Further, 100 g of acetic acid and 500 g of water were added and dispersed. As a result, a pH 2.3 dispersion was obtained, and this dispersion was stirred for 60 hours. Thereafter, filtration and dispersion in 1000 g of water were repeated to obtain 10.5 g of a white substance.

This material was treated at 200 ° C. under vacuum for 12 hours and at 300 ° C. for 5 hours to obtain 10.1 g of a white material.
As a result of elemental analysis, the titanium-based structure obtained in Example 9 has a ratio of periodic table group 1 atoms to Ti atoms (periodic group 1 atoms / Ti atoms) of 0.01 to 0.5 ( The ratio of O atoms to Ti atoms (O atoms / Ti atoms) was in the range of 2.005 to 2.25.
Moreover, as a result of measuring Na content of this substance by WDX (fluorescence X ray), it was about 0.1 wt%.

Example 10
When 14.2 g of titanium tetraisopropoxide was used as a titanium source and 200 g of water was added, a large amount of white precipitate was produced. When 80 g of NaOH was further added, a slurry was obtained. At the same time, the temperature rose to 95 ° C. and isopropanol and water volatilized, so the total weight was adjusted to 288 g.

  This solution was kept at 110 ° C. for 12 hours in a polymethylpentene container immersed in an oil bath.

When observed by TEM, a sheet-like substance having an average width of 50 nm or more, an average thickness of less than 5 nm, and an average length of 100 nm or more was observed. Moreover, it was 310 m < ² > / g when the BET specific surface area was measured.

  Further, as a result of elemental analysis, the titanium-based structure obtained in Example 10 has a ratio of periodic table group 1 atoms to Ti atoms (periodic group 1 atoms / Ti atoms) of 0.01 to 0.00. 5 (molar ratio), and the ratio of O atom to Ti atom (O atom / Ti atom) was in the range of 2.005 to 2.25.

Comparative Example 1
300 g of water was added to 10 g of commercially available sodium titanate (Na ₂ Ti ₃ O ₇ ; manufactured by Mitsuwa Chemicals Co., Ltd.), and a 35% aqueous HCl solution was added to adjust the pH to 1. This dispersion was stirred at 80 ° C. for 5 hours and at room temperature for 3 days, and washed with water and filtered until pH 7 was obtained to obtain titanic acid. This material was vacuum dried at 200 ° C. for 12 hours and then heated in air at 300 ° C. for 5 hours to obtain 10.1 g of a white substance.

The BET specific surface area was measured and found to be about 12 m ² / g.

  Moreover, the obtained material was spherical and was not in the form of a sheet or fiber.

Comparative Example 2
Commercially available lithium titanate nanoparticles (Li ₄ Ti ₅ O ₁₂ ; manufactured by Sigma-Aldrich) were vacuum-dried at 200 ° C. and then heated in air at 300 ° C. for 5 hours.

The BET specific surface area was measured and found to be about 16 m ² / g.

  Moreover, the obtained material was spherical and was not in the form of a sheet or fiber.

Experimental example 1
The titanium-based structures synthesized in Examples 1 and 3 to 10 and Comparative Examples 1 and 2, acetylene black, and PTFE powder are mixed at a predetermined weight ratio, kneaded with acetone, and molded with a biaxial roll. Then, drying was performed at 170 ° C. in vacuum. The obtained sheet was bonded to an aluminum foil to produce an electrode. A charge and discharge test was conducted at 0.2 C using LiPF ₆ (EC / PC = 3/7) with Li metal and 1 mol / L electrolyte as a counter electrode. Then, the discharge capacity at the third cycle was measured. The conditions and results are shown in Table 1.

  As a result, it was found that the titanium-based structure of the present invention has a large discharge capacity compared to titanic acid synthesized from the existing material (Comparative Example 1) and lithium titanate (Comparative Example 2) which is an existing material. It was.

  Moreover, about the said "Experimental example 1-10", the charging / discharging test was continued to 50 cycles. As a result, it was found to be 240 mAh / g, and to have excellent cycle characteristics.

Experimental example 2
The titanium-based structure synthesized in Examples 1, 3 and 4, acetylene black, and PTFE powder were mixed at a predetermined weight ratio, kneaded with acetone, molded with a biaxial roll, and dried at 170 ° C. in a vacuum. Went. The obtained sheet was bonded to an aluminum foil to produce an electrode. Mixture of lithium manganate / acetylene black / polyvinylidene fluoride (PVDF) = 89.5 / 5 / 5.5 (weight ratio) at the counter electrode, LiPF ₆ (EC / PC = 3/7) of electrolyte 1 mol / L The charge / discharge test was conducted at 0.2 C, 2 C, 5 C, 10 C, and 20 C (however, the discharge lower limit voltage was 2.0 V). Then, the discharge capacity at the third cycle was measured, the discharge capacity at 0.2C was taken as 100%, and the comparison was made with the discharge capacities at 2C, 5C, 10C, and 20C. The results are shown in Table 2.

  As a result, all the samples maintained a discharge capacity of 80% or more up to 10C, and had excellent rate characteristics. Further, in 20C, there was a difference in the capacity retention rate, and the larger the specific surface area, the better the rate characteristics.

Claims (21)

Including at least group 1 atom of the periodic table, Ti atom and O atom,
The ratio of Periodic Table Group 1 atoms to Ti atoms (Periodic Table Group 1 atoms / Ti atoms) is 0.01 to 0.5 (molar ratio),
The ratio of O atom to Ti atom (O atom / Ti atom) is 2.005 to 2.25,
The average minimum size is 1 to 100 nm, and
A titanium-based structure for an electricity storage device, having a specific surface area of 10 m ² / g or more. Composition formula:
AxTiOy
[Wherein, A is a group 1 atom of the periodic table; x is 0.01 to 0.5; y is 2.005 to 2.25. ]
The titanium structure for electrical storage devices of Claim 1 shown by these. Furthermore, the titanium-type structure for electrical storage devices of Claim 1 containing at least 1 sort (s) chosen from the group which consists of Nb atom, B atom, C atom, and N atom. Composition formula:
AxTiOyMz
[Wherein, A is a group 1 atom of the periodic table; M is an Nb atom, B atom, C atom, or N atom; x is 0.01 to 0.5; y is 2.005 to 2.25; z is 0.01 to 0.20. ]
The titanium-type structure for electrical storage devices of Claim 3 shown by these. 5. The titanium-based structure for an electricity storage device according to claim 1, wherein the Group 1 atom of the periodic table contains 80 mol% or more of H atoms and 10 mol% or less of Na atoms. 5. The titanium-based structure for an electricity storage device according to claim 1, wherein the Group 1 atom of the periodic table contains 50 mol% or more of H atoms and 50 mol% or less of K atoms. The titanium group structure for an electricity storage device according to any one of claims 1 to 6, wherein the group 1 atom of the periodic table has a total content of Na and K of 1% by weight or less. The titanium-based structure for an electricity storage device according to claim 1, wherein the average minimum size is 1 to 40 nm and the specific surface area is 50 m ² / g or more. The titanium-based structure for an electricity storage device according to any one of claims 1 to 8, wherein the average minimum size is 1 nm or more and less than 5 nm. The titanium structure for electrical storage devices in any one of Claims 1-9 whose said electrical storage device is a lithium ion secondary battery, an electrical double layer capacitor, or a lithium ion capacitor. A method for producing a titanium-based structure for an electricity storage device according to any one of claims 1 to 10,
(1) A production method comprising a step of alkali-treating a material containing at least titanium at 50 to 450 ° C. in an alkaline aqueous solution of 2 to 20 mol / L. The manufacturing method of Claim 11 with which the said alkali contains sodium hydroxide and / or potassium hydroxide. The production method according to claim 11 or 12, wherein the alkali contains at least 30 mol% or more of sodium hydroxide. further,
(2) The production method according to any one of claims 11 to 13, comprising a step of replacing sodium and / or potassium present in the titanium oxide structure obtained in step (1) with hydrogen and / or lithium. . further,
(3) The manufacturing method of Claim 14 provided with the process of heat-processing the titanium-type structure obtained at the process (2) at 150-500 degreeC. An electrical storage device comprising the titanium-based structure for an electrical storage device according to any one of claims 1 to 10, or the titanium-based structure for an electrical storage device obtained by the production method according to any one of claims 11 to 15. Electrode active material. The electrode active material layer for electrical storage devices containing the electrode active material for electrical storage devices of Claim 16. Furthermore, it contains a conductive material and a binder, and the mixing ratio of the negative electrode active material in the electrode active material layer is 30 to 99% by weight, and the mixing ratio of the conductive material is 1 to 50% by weight. The electrode active material layer for an electricity storage device according to claim 17. The electrode for electrical storage devices provided with an electrode electrical power collector and the negative electrode active material layer for electrical storage devices of Claim 17 or 18. An electricity storage device comprising the electrode for an electricity storage device according to claim 19. The electricity storage device according to claim 20, which is a lithium ion secondary battery, an electric double layer capacitor, or a lithium ion capacitor.