Niobium-containing oxide powder, electrodes using same, and power storage devices

Abstract

A niobium-containing oxide powder that satisfies the following formula (I), wherein, in the following formula (I), when x=0 and y=0, the specific surface area of ​​the niobium-containing oxide powder is 2.3 m 2 / g or more 10m 2 / g or less. A a Ti 2-x M 1 x Nb 14-y M 2 y O 39±z (I) [During the ceremony, A is at least one element selected from the group consisting of Li and Na; M 1 is M IV , (M III 0.5+v M V 0.5-v ), (M V 0.67+v M II 0.33-v ), (M III 0.67+v M VI 0.33-v ), and (M II 0.5+v M VI 0.5-v ) selected from the group consisting of M 2 is M V , (M IV 0.5+w M VI 0.5-w ), (M VI 0.67+w M III 0.33-w ), and (M VI 0.75+w M II 0.25-w ) selected from the group consisting of M II are each independently at least one divalent metallic element, M III are each independently at least one trivalent metallic element; M IVare each independently at least one tetravalent metallic element; M V are each independently at least one pentavalent metallic element; M VI are each independently at least one hexavalent metallic element; 0≦a≦6, -0.05≦v≦0.05, -0.05≦w≦0.05, 0≦x<2, 0≦y<14, 0≦z≦1.

Description

[Technical field]

[0001] The present invention relates to a niobium-containing oxide powder suitable as an electrode material for an electricity storage device, an electrode using the same, and an electricity storage device. [Background technology]

[0002] Electrical storage devices for electric vehicles require high energy density in order to improve fuel efficiency or power consumption, and lithium-ion batteries in particular are widely used as power sources for electric vehicles and power storage. Various materials have been researched as electrode materials for lithium-ion batteries, and although lithium titanate has excellent input / output characteristics, its energy density remains at 175mAh / g, and there are still challenges to be overcome in order to further increase its energy. Therefore, as an alternative candidate, there is a movement to use niobium-containing oxides, mainly niobium titanate, which has a high energy density of 380mAh / g, as negative electrode materials.

[0003] In addition, lithium-ion batteries currently on the market use electrolytes that contain flammable organic solvents, so they require the installation of safety devices to suppress temperature rises in the event of a short circuit and structures to prevent short circuits. Under these circumstances, all-solid-state secondary batteries that use inorganic solid electrolytes instead of organic electrolytes have attracted attention. Since the positive and negative electrodes and electrolytes of all-solid-state secondary batteries are all solid, there is a possibility that they can significantly improve the safety and reliability issues that are problems with batteries that use organic electrolytes. In addition, since safety devices can be simplified, high energy density can be achieved, so they are expected to be applied to electric vehicles, large storage batteries, etc.

[0004] Non-Patent Documents 1 and 2 describe porous Ti nanoparticles composed of primary particles with particle sizes in the range of 20 to 200 nm, which are produced by a solvothermal method. 2 Nb 14 O 39 When applied as an electrode material for a lithium-ion battery using an electrolyte solution, Ti prepared by a solid-phase method 2 Nb 14 O 39It has been reported that it has better rate characteristics than

[0005] Patent Document 1 describes TiNb 2 O 7 Or Ti 2 Nb 10 O 29 It has been reported that when such a niobium-titanium composite oxide is used as an electrode material for an electricity storage device, it can provide an electricity storage device with high capacity and excellent rate performance. 2 O 7 , TiNb 10 O 29 have been disclosed, which have been reported to have lower capacity loss with cycling than oxides that do not contain trivalent metals. [Prior art documents] [Non-patent literature]

[0006] [Non-Patent Document 1] Small 2017, 13, 1702903 [Non-Patent Document 2] Journal of Colloid and Interface Science 608 (2022) 90-102 [Patent documents]

[0007] [Patent Document 1] JP 2010-287496 A [Patent Document 2] International Publication No. 2014 / 122376 Summary of the Invention [Problem to be solved by the invention]

[0008] However, the porous Ti of Non-Patent Document 1, which is composed of primary particles of 20 to 200 nm, 2 Nb 14 O 39When used as an anode material, it contains a large amount of conductive additive in order to ensure conductivity even inside the secondary particles. As a result, the ratio of active material in the anode mixture becomes small, which causes a problem of a small energy density per anode. In addition, since the specific surface area is very large, there is also a problem of a large drop in initial efficiency. Furthermore, when such porous particles are applied to an all-solid-state battery, the inside of the secondary particles cannot come into contact with the solid electrolyte, and therefore capacity cannot be obtained. In addition, Ti prepared by the solid-phase method shown in Non-Patent Document 1 2 Nb 14 O 39 However, when the negative electrode mixture is evaluated with a higher ratio of active material and a lower ratio of conductive additive, the rate characteristics and cycle capacity retention rate are reduced. 2 O 7 Or Ti 2 Nb 10 O 29 , TiNb containing trivalent metals 2 O 7 Or Ti 2 Nb 10 O 29 Although the initial capacity of batteries using TiNb is good, there is a problem that the capacity of the battery decreases significantly with cycling. 2 O 7 , Ti 2 Nb 10 O 29 , TiNb containing trivalent metals 2 O 7 Or Ti 2 Nb 10 O 29 It was found that the change in electrode thickness during charging and discharging was large, resulting in a decrease in cycle life. The benefits of increasing battery capacity include an increase in energy density per unit weight or unit area (unit volume), which can lead to an extension of the driving range of electric vehicles and the creation of more space for storage batteries.

[0009] For the reasons mentioned above, the energy density, discharge rate characteristics, cycle performance, and change in electrode thickness during charging and discharging of electricity storage devices using the negative electrode active materials of Non-Patent Document 1, Non-Patent Document 2, Patent Document 1, and Patent Document 2 are not fully satisfactory, and further improvements are necessary.

[0010] Therefore, an object of the present invention is to provide a niobium-containing oxide powder that can be used as an electrode material for a non-aqueous electrolyte electricity storage device, and that in a liquid lithium ion secondary battery, has excellent discharge rate characteristics while maintaining an initial discharge capacity, has a small rate of change in electrode thickness due to charge and discharge, and has excellent cycle characteristics, and also has excellent initial discharge capacity and rate characteristics in an all-solid-state battery, an electrode for an electricity storage device using the same, and an electricity storage device. [Means for solving the problem]

[0011] As a result of various investigations aimed at achieving the above object, the present inventors have found that Ti 2 Nb 14 O 39 By subjecting niobium-containing oxide powder such as Ti to a particle size control process, the specific surface area and particle size distribution can be controlled within a certain range. 2 Nb 14 O 39 It has been found that a remarkable effect can be obtained by applying a niobium-containing oxide powder in which Ti and / or Nb in a niobium-containing oxide such as niobium-containing oxides are partially replaced with a different element as an electrode material. In a liquid-based lithium-ion secondary battery, an electricity storage device in which the niobium-containing oxide powder is applied as an electrode material has excellent discharge rate characteristics while maintaining an initial discharge capacity, and has a small change rate in the thickness of the electrode due to charging and discharging. This has been found to provide excellent cycle characteristics and to exhibit the performance of the initial discharge capacity and rate characteristics even in an all-solid-state battery, and the present invention has been completed. Such an effect, particularly the effect of being able to reduce the change in electrode thickness due to charging and discharging, is not described or suggested at all in the above Non-Patent Documents 1 and 2 and Patent Documents 1 and 2. That is, the present invention relates to the following matters.

[0012] (1) A niobium-containing oxide powder that satisfies the following formula (I), wherein, in the following formula (I), when x = 0 and y = 0, the specific surface area of ​​the niobium-containing oxide powder is 2.3 m 2 / g or more 10m 2 / g or less of the niobium-containing oxide powder. A a Ti 2-x M 1 x Nb 14-y M 2 y O 39±z (I) [During the ceremony, A is at least one element selected from the group consisting of Li and Na; M 1 is M IV , (M III 0.5+v M V 0.5-v ), (M V 0.67+v M II 0.33-v ), (M III 0.67+v M VI 0.33-v ), and (M II 0.5+v M VI 0.5-v ) selected from the group consisting of M 2 is M V , (M IV 0.5+w M VI 0.5-w ), (M VI 0.67+w M III 0.33-w ), and (M VI 0.75+w M II 0.25-w ) selected from the group consisting of M II are each independently at least one divalent metallic element; M III are each independently at least one trivalent metallic element; M IVare each independently at least one tetravalent metallic element; M V are each independently at least one pentavalent metallic element; M VI are each independently at least one hexavalent metallic element; 0≦a≦6, -0.05≦v≦0.05, -0.05≦w≦0.05, 0≦x<2, 0≦y<14, 0≦z≦1. (2) In the formula (I), in any case where 0≦x<2 and 0≦y<14, the specific surface area of ​​the niobium-containing oxide powder is 2.3 m 2 / g or more 10m 2 The niobium-containing oxide powder according to (1), wherein the niobium-containing oxide powder has a molecular weight of 1.0 to 1.0 kg / g or less. (3) The niobium-containing oxide powder satisfies the following formula (II), and the specific surface area of ​​the niobium-containing oxide powder is 2.3 m 2 / g or more 10m 2 The niobium-containing oxide powder according to (1), wherein the niobium content is 1 / g or less. A a Ti 2-x M 1a x Nb 14-y M 2a y O 39±z (II) [During the ceremony, A is the same as in formula (I), M 1a is at least one tetravalent metallic element selected from the group consisting of Zr, Si, Ge and Sn; M 2a is at least one pentavalent metallic element selected from the group consisting of V and Ta; a, x, y, and z are the same as in formula (I). (4) The niobium-containing oxide powder according to (1), which satisfies any one of the following formulae (III) to (IX): A a Ti 2-x (M III 0.5+v M V 0.5-v )x Nb 14 O 39±z (III) A a Ti 2-x (M V 0.67+v M II 0.33-v ) x Nb 14 O 39±z (IV) A a Ti 2-x (M III 0.67+v M VI 0.33-v ) x Nb 14 O 39±z (V) A a Ti 2-x (M II 0.5+v M VI 0.5-v ) x Nb 14 O 39±z (VI) A a Ti 2 Nb 14-y (M IV 0.5+w M VI 0.5-w ) y O 39±z (VII) A a Ti 2 Nb 14-y (M VI 0.67+w M III 0.33-w ) y O 39±z (VIII) A a Ti 2 Nb 14-y (M VI 0.75+w M II 0.25-w ) y O 39±z (IX) 〔wherein, A, M II 、M III 、M IV 、M V, and M. VI is the same as in formula (I), a, v, w, and z are the same as in formula (I); 0 <x<2、0<y<14である。〕 (5) M II are each independently at least one divalent metallic element selected from the group consisting of Mg, Ca, Cu, and Zn; M III are each independently at least one trivalent metallic element selected from the group consisting of Al, Ga, Fe, and Cr; M IV are each independently at least one tetravalent metallic element selected from the group consisting of Zr, Si, Ge, and Sn; M V are each independently at least one pentavalent metallic element selected from the group consisting of Nb, V, and Ta; M VI The niobium-containing oxide powder according to (1) or (4), wherein is at least one hexavalent metallic element selected from the group consisting of Mo and W. (6) The specific surface area of ​​the niobium-containing oxide powder is 2.3 m 2 / g or more 10m 2 The niobium-containing oxide powder according to (4) or (5), wherein the niobium content is 1 / g or less. (7) The niobium-containing oxide powder according to any one of (1) to (6), characterized in that the D50 of primary particles corresponding to a volume cumulative 50% in a volume-based particle size distribution measured by a laser diffraction scattering method of the niobium-containing oxide powder is 0.25 μm or more and 4.5 μm or less. (8) The niobium-containing oxide powder according to any one of (1) to (7), characterized in that the D90 of primary particles corresponding to 90% of the volume cumulative in a volume-based particle size distribution of the niobium-containing oxide powder measured by a laser diffraction scattering method is 20 μm or less. (9) The niobium-containing oxide powder according to any one of (1) to (8), characterized in that at least one metal element selected from Mo and Ce is localized and present on the surface of the niobium-containing oxide particle. (10) The niobium-containing oxide powder according to (9), characterized in that the content (mass%) of at least one metal element selected from Mo and Ce present on the particle surface as determined by X-ray fluorescence analysis (XRF) is 0.01 to 1.5. (11) An electrode for an electricity storage device, comprising the niobium-containing oxide powder according to any one of (1) to (10) as an active material. (12) A negative electrode active material composition for a non-aqueous electrolyte storage device, comprising the niobium-containing oxide powder according to any one of (1) to (10) above and an inorganic solid electrolyte. (13) A non-aqueous electrolyte electricity storage device comprising the electrode according to (11). (14) An all-solid-state secondary battery comprising a positive electrode layer, a negative electrode layer, and a solid electrolyte layer, the negative electrode layer being a layer containing the negative electrode active material composition according to (12). Effect of the Invention

[0013] According to the present invention, it is possible to provide a niobium-containing oxide powder which, in a liquid lithium ion secondary battery of a nonaqueous electrolyte electricity storage device, has excellent discharge rate characteristics while maintaining an initial discharge capacity, has a small rate of change in electrode thickness due to charging and discharging, and has excellent cycle characteristics, and further has excellent initial discharge capacity and rate characteristics even in an all-solid-state battery, an electrode for an electricity storage device using the same, and an electricity storage device. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0014] [Niobium-containing oxide powder of the present invention] The niobium-containing oxide powder of the present invention is preferably used for electrodes of non-aqueous electrolyte storage devices. That is, the niobium-containing oxide powder of the present invention is preferably used as a niobium-containing oxide powder for electrodes of non-aqueous electrolyte storage devices. The non-aqueous electrolyte may be any electrolyte other than an aqueous electrolyte, and is not particularly limited, but may include, for example, a non-aqueous electrolyte solution or a solid electrolyte.

[0015] <Niobium-containing oxide powder represented by general formula (I)> The niobium-containing oxide powder of the present invention preferably contains a niobium-containing oxide powder that satisfies the following general formula (I): In the case where x=0 and y=0 in the following general formula (I), the niobium-containing oxide powder has a specific surface area of ​​2.3 m 2 / g or more 10m 2 It is preferable that the molecular weight is not more than 1 / g. A a Ti 2-x M 1 x Nb 14-y M 2 y O 39±z (I) [During the ceremony, A is at least one element selected from the group consisting of Li and Na; M 1 is M IV , (M III 0.5+v M V 0.5-v ), (M V 0.67+v M II 0.33-v ), (M III 0.67+v M VI 0.33-v ), and (M II 0.5+v M VI 0.5-v ) selected from the group consisting of M 2 is M V , (M IV 0.5+w M VI 0.5-w ), (M VI 0.67+w M III 0.33-w ), and (M VI 0.75+w M II 0.25-w ) selected from the group consisting of M II are each independently at least one divalent metallic element; M III are each independently at least one trivalent metallic element; MIV are each independently at least one tetravalent metallic element; M V are each independently at least one pentavalent metallic element; M VI are each independently at least one hexavalent metallic element; 0≦a≦6, -0.05≦v≦0.05, -0.05≦w≦0.05, 0≦x<2, 0≦y<14, 0≦z≦1.

[0016] <Niobium-containing oxide powder represented by general formula (II)> The niobium-containing oxide powder of the present invention more preferably contains a niobium-containing oxide powder represented by general formula (II). A a Ti 2-x M 1a x Nb 14-y M 2a y O 39±z (II) [During the ceremony, A is at least one element selected from the group consisting of Li and Na; M 1a is at least one tetravalent metallic element selected from the group consisting of Zr, Si, Ge, and Sn; M 2a is at least one pentavalent metallic element selected from the group consisting of V and Ta; 0≦a≦6, 0≦x<2, 0≦y<14, 0≦z≦1. A specific example of the compound is a niobium titanium composite oxide, Ti 2 Nb 14 O 39 Niobium titanium composite oxides contain titanium oxide phases derived from the synthesis raw materials (e.g., rutile type TiO 2, TiO, etc.) In the case of the niobium titanium composite oxide, the ratio of the number of moles of Nb to the number of moles of Ti (Nb / Ti ratio) is preferably in the range of 6.0 to 8.0, more preferably in the range of 6.5 to 7.5. Within this range, the electronic conductivity of the niobium titanium composite oxide is improved, and the rate characteristics are excellent. The niobium-containing oxide powder represented by the general formula (II) can provide a liquid lithium ion secondary battery in a nonaqueous electrolyte storage device with excellent discharge rate characteristics while maintaining an initial discharge capacity, a small rate of change in electrode thickness during charging and discharging, and excellent cycle characteristics, and can also provide an all-solid-state battery with excellent initial discharge capacity and rate characteristics.

[0017] The aforementioned A is not particularly limited as long as it is at least one element selected from Li and Na, but is preferably Li. Said M 1a is not particularly limited as long as it is at least one tetravalent metal element selected from the group consisting of Zr, Si, Ge, and Sn. 2a is not particularly limited as long as it is at least one pentavalent metal element selected from the group consisting of V and Ta. The reason why the above element group is preferable is not clear, but is thought to be as follows. Ti 2 Nb 14 O 39 In the case of elemental substitution of Ti or Nb, if the ionic radius of the substitution element is too large or too small relative to the size of the Ti site or Nb site, the elemental substitution is thought to not proceed. Therefore, it is thought that the above-mentioned element group close to Ti and Nb in the periodic table is suitable as the substitution element.

[0018] In the general formula (II), 0≦a≦6, preferably 0≦a≦2, more preferably 0≦a≦0.5, and even more preferably a=0. Also, 0≦x<2, preferably 0≦x≦1, more preferably 0≦x≦0.5, and even more preferably x=0. Also, 0≦y<14, preferably 0≦y≦7, more preferably 0≦y≦2, and even more preferably y=0. Also, 0≦z≦1, preferably 0≦z≦0.5, more preferably 0≦z≦0.2, and even more preferably z=0. That is, Ti 2 Nb 14 O 39 It is particularly preferred that:

[0019] <Niobium-containing oxide powder represented by general formulas (III) to (IX)> The niobium-containing oxide powder of the present invention more preferably contains niobium-containing oxide powder represented by any one of the general formulae (III) to (IX). A a Ti 2-x (M III 0.5+v M V 0.5-v ) x Nb 14 O 39±z (III) A a Ti 2-x (M V 0.67+v M II 0.33-v ) x Nb 14 O 39±z (IV) A a Ti 2-x (M III 0.67+v M VI 0.33-v ) x Nb 14 O 39±z (V) A a Ti 2-x (M II 0.5+v M VI 0.5-v ) x Nb14 O 39±z (VI) A a Ti 2 Nb 14-y (M IV 0.5+w M VI 0.5-w ) y O 39±z (VII) A a Ti 2 Nb 14-y (M VI 0.67+w M III 0.33-w ) y O 39±z (VIII) A a Ti 2 Nb 14-y (M VI 0.75+w M II 0.25-w ) y O 39±z (IX) [During the ceremony, A is at least one element selected from the group consisting of Li and Na; M II are each independently at least one divalent metallic element; M III are each independently at least one trivalent metallic element; M IV are each independently at least one tetravalent metallic element; M V are each independently at least one pentavalent metallic element; M VI are each independently at least one hexavalent metallic element; 0≦a≦6, -0.05≦v≦0.05, -0.05≦w≦0.05, 0 <x<2、0<y<14、0≦z≦1である。〕 The niobium-containing oxide powder represented by any one of the general formulae (III) to (IX) can provide a liquid lithium ion secondary battery in a nonaqueous electrolyte storage device with excellent charge / discharge rate characteristics and a small rate of change in electrode thickness during charge / discharge while maintaining an initial discharge capacity, thereby providing excellent cycle characteristics. Furthermore, the powder can provide an all-solid-state battery with excellent initial discharge capacity and rate characteristics.

[0020] The A is preferably Li. Said M III are each independently preferably Al, Ga, Fe and Cr, more preferably Al, Fe and Cr, even more preferably Al and Fe, and most preferably Al.

[0021] Said M V are each independently preferably Nb, Ta, or V, and more preferably Nb.

[0022] Said M II are each independently preferably Mg, Ca, Cu, and Zn, more preferably Mg, Cu, and Zn, and even more preferably Cu and Mg.

[0023] Said M VI are each independently preferably Mo and W.

[0024] Said M IV are each independently Zr, Si, Ge, and Sn.

[0025] In general formulas (III) to (IX), a is preferably 0 ≦ a ≦ 2, more preferably 0 ≦ a ≦ 0.5, and even more preferably a = 0. Also, v is preferably -0.01 ≦ v ≦ 0.01, and more preferably v = 0. Also, w is preferably -0.01 ≦ w ≦ 0.01, and more preferably w = 0. Also, x is preferably 0 < x ≦ 1.3, more preferably 0 < x ≦ 1, even more preferably 0 < x ≦ 0.9, and even more preferably 0 < x ≦ 0.5. Also, y is preferably 0 < y ≦ 5, more preferably 0 < y ≦ 3, and even more preferably 0 < y ≦ 2. Also, z is preferably 0 ≦ z ≦ 0.5, more preferably 0 ≦ z ≦ 0.2, and even more preferably z = 0. In general formula (IV), M V and M II The ratio of is M V :M II = 0.67 + v:0.33 - v, but M V :M II = 2 / 3 + w:1 / 3 - w may also be used. That is, in this case, when w = 0, M V :M II = 2 / 3:1 / 3 (that is, A a Ti 2-y (M V 2 / 3 M II 1 / 3 ) y Nb 14 O 39±z ) is obtained. The same applies to general formulas (V) and (VIII) (that is, in general formula (V), M III :M VI = 2 / 3 + w:1 / 3 - w may also be used, and in general formula (VIII), M VI :M III = 2 / 3 + w:1 / 3 - w may also be used.).

[0026] <Content of at least one metal element selected from the group consisting of Mo and Ce> The niobium-containing oxide powder of the present invention may contain at least one metal element selected from the group consisting of Mo and Ce. The term "containing at least one metal element selected from the group consisting of Mo and Ce" means that the metal element is present in a localized manner on the surface of the niobium-containing oxide particles constituting the powder, and more specifically, that at least one metal element selected from the group consisting of Mo and Ce is present in a localized manner in a larger amount in the surface region than in the internal region of the niobium-containing oxide particles. In addition, the term "containing at least one metal element selected from the group consisting of Mo and Ce" means that at least one metal element selected from the group consisting of Mo and Ce is detected in the inductively coupled plasma atomic emission spectrometry (ICP-AES) or X-ray fluorescence spectrometry (XRF) of the niobium oxide powder of the present invention. The lower limit of the amount detected by inductively coupled plasma atomic emission spectrometry is usually 0.001% by mass. The particle surface of the niobium-containing oxide powder may contain two types of Mo and Ce. From the viewpoint of improving the initial discharge capacity and rate characteristics, it is preferable to contain Mo.

[0027] The content (mass%) of at least one metal element selected from the group consisting of Mo and Ce in the niobium-containing oxide powder of the present invention determined by X-ray fluorescence analysis (XRF) may be 0.01 to 2.0. If the content of at least one metal element selected from the group consisting of the metal elements Mo and Ce is within this range, a secondary battery excellent in initial discharge capacity and rate characteristics can be obtained. It is preferably 0.01 to 1.7, and from the viewpoint of further improving the charge rate characteristics, it is more preferably 0.015 to 1.5, even more preferably 0.04 to 1.3, even more preferably 0.07 to 1.25, and particularly preferably 0.2 to 1.1. However, when Mo and Ce are simultaneously contained on the particle surface of the niobium-containing oxide powder, the above content (mass%) is the total content of the two metal elements.

[0028] As an example, in the cross-sectional analysis of the niobium-containing oxide particles using a scanning transmission electron microscope, it is sufficient that at least one metal element selected from the group consisting of Mo and Ce is contained in a large amount in the so-called near-surface region from the surface of the niobium-containing oxide particles to a depth of about 20 nm measured by energy dispersive X-ray spectroscopy, and it is preferable that at least one metal element selected from the group consisting of Mo and Ce is detected at a depth position of 20 nm from the surface of the niobium-containing oxide particles, while Mo and Ce are not detected at a depth position of 100 nm from the surface, and in such a state, it can be determined that at least one metal element selected from the group consisting of Mo and Ce is localized on the surface of the niobium-containing oxide particles. That is, when measured by energy dispersive X-ray spectroscopy, it means that it is below the amount detected by the measurement, and the lower limit of the amount detected by the measurement by energy dispersive X-ray spectroscopy varies depending on the element and state to be measured, but is usually 0.5 atm%. Other surface analysis techniques include X-ray photoelectron spectroscopy (XPS) and Auger electron spectroscopy (AES). In the present invention, the form of the at least one metal element selected from the group consisting of Mo and Ce that is localized on the surface of the niobium-containing oxide particle is not particularly limited, and it is sufficient that at least one metal element selected from the group consisting of Mo element and Ce element is localized on the surface, and it may be in a metallic state or in the form of a metal compound such as a metal oxide.

[0029] The niobium-containing oxide powder of the present invention may contain fibrous carbon such as single-walled carbon nanotubes (SWCNTs) and multi-walled carbon nanotubes (MWCNTs). The fibrous carbon is preferably localized on the surface of the niobium-containing oxide powder to enhance electronic conductivity, and it is more preferable to contain single-walled carbon nanotubes (SWCNTs). The content (mass%) of the fibrous carbon is calculated from measurements by thermogravimetric analysis, and the content may be 0.001 to 2.0. If the content of the fibrous carbon is within this range, a secondary battery excellent in initial discharge capacity and rate characteristics can be obtained. It is preferably 0.01 to 1.8, and from the viewpoint of further improving the charge rate characteristics, it is more preferably 0.05 to 1.5, and particularly preferably 0.1 to 1.0.

[0030] <Specific surface area> The specific surface area of ​​the niobium-containing oxide powder of the present invention is the surface area per unit mass when nitrogen is used as an adsorption gas. The measuring method will be described in the examples below.

[0031] The niobium-containing oxide powder of the present invention has a specific surface area of ​​10 m 2 / g or less, and 2 / g or less is preferable, and 6.5m 2 / g or less is more preferable, and 6m 2 On the other hand, the lower limit of the specific surface area is 2.0 m / g or less in the case of a niobium-containing oxide powder satisfying the formulas (I) to (II). 2 / g or more, 2.3m 2 / g or more is preferable, and 2.5m 2 / g or more is more preferable, and 2.9m 2 / g or more is more preferable, and 3.4m 2 On the other hand, in the case of formulas (III) to (IX), the specific surface area is preferably 1.5 m 2 / g or more, 2.0m 2 / g or more is preferable, and 2.1m 2 / g or more is more preferable, and 2.3m 2 / g or more is more preferable, and 2.4m 2 / g or more is even more preferable, and 3.0m 2 Within the above range, in a liquid lithium ion secondary battery as a nonaqueous electrolyte storage device, it is possible to obtain an electricity storage device having excellent initial discharge capacity and rate characteristics, a small rate of change in electrode thickness during charging and discharging, and excellent cycle characteristics, and further, in an all-solid-state battery, it is possible to obtain an electricity storage device having excellent initial discharge capacity and rate characteristics.

[0032] <d50> D50 of the niobium-containing oxide powder of the present invention is an index of the volume median particle size. It means the particle size at which the cumulative volume frequency calculated from the volume fraction determined by laser diffraction / scattering particle size distribution measurement is 50% when calculated from the smallest particle size. The measurement method will be described in the examples below.

[0033] The niobium-containing oxide powder of the present invention may be a primary particle or a secondary particle formed by agglomeration of the primary particles. When the primary particles made of niobium-containing oxide particles contain secondary particles formed by agglomeration, a part of the secondary particles may not form secondary particles and may be in the form of the primary particles themselves.

[0034] When the niobium-containing oxide powder of the present invention is a secondary particle, the lower limit of the D50 of the secondary particle is preferably 5 μm or more, more preferably 7 μm or more, and even more preferably 9 μm or more, from the viewpoint of improving the electrode density. Furthermore, the upper limit of the D50 of the secondary particle is preferably 20 μm or less, more preferably 18 μm or less, and even more preferably 14 μm or less.

[0035] In the present invention, the primary particle D50 of the niobium-containing oxide powder is preferably 0.25 μm or more, more preferably 0.4 μm or more, and even more preferably 0.6 μm or more, from the viewpoint of improving the rate characteristics in the liquid lithium ion secondary battery of the nonaqueous electrolyte storage device, further improving the initial discharge capacity and rate characteristics in the all-solid-state battery, in addition to improving the rate characteristics, and the lower limit of the D50 of the primary particle is preferably 0.25 μm or more, more preferably 0.4 μm or more, and even more preferably 0.6 μm or more. In addition, in the case of the niobium-containing oxide powder satisfying the formula (II), the upper limit of the D50 of the primary particle is preferably 4.5 μm or less, more preferably 3 μm or less, even more preferably 2 μm or less, even more preferably 1.8 μm or less, and particularly preferably 1.1 μm or less. On the other hand, in the case of the formulas (III) to (IX), it is preferably 4.5 μm or less, more preferably 4 μm or less, more preferably 3 μm or less, even more preferably 2 μm or less, and especially preferably 1.8 μm or less. The niobium-containing oxide powder may contain primary particles having a size of less than 0.4 μm, or may contain primary particles having a size of more than 4.5 μm.

[0036] <d90> In the present invention, the D90 of the primary particles of the niobium-containing oxide powder is preferably 0.8 μm or more, more preferably 1.0 μm or more, and even more preferably 1.2 μm or more, from the viewpoint of improving the rate characteristics in the liquid lithium ion secondary battery of the nonaqueous electrolyte storage device, further improving the cycle characteristics, and further improving the initial discharge capacity and rate characteristics in the all-solid-state battery. In addition, the D90 of the primary particles is preferably 20 μm or less, more preferably 15 μm or less, even more preferably 10 μm or less, even more preferably 5 μm or less, and particularly preferably 3 μm or less. The D90 of the primary particles of the niobium-containing oxide powder means the particle size at which the cumulative volume frequency calculated from the volume fraction obtained by laser diffraction / scattering particle size distribution measurement is 90% when calculated from the smallest particle size. The measurement method will be described in the examples described later.

[0037] <d10> In the present invention, the D10 of the primary particles of the niobium-containing oxide powder is preferably 0.05 μm or more, more preferably 0.1 μm or more, and even more preferably 0.2 μm or more, from the viewpoint of improving the discharge rate characteristics in a liquid lithium ion secondary battery of a nonaqueous electrolyte storage device, further improving the cycle characteristics, and further improving the initial discharge capacity and rate characteristics in an all-solid-state battery. The lower limit of the D10 of the primary particles is preferably 0.05 μm or more, more preferably 0.1 μm or more, and even more preferably 0.2 μm or more. The upper limit of the D10 of the primary particles is preferably 0.9 μm or less, more preferably 0.8 μm or less, even more preferably 0.7 μm or less, and even more preferably 0.6 μm or less. The D10 of the primary particles of the niobium-containing oxide powder means a particle size at which the cumulative volume frequency calculated from the volume fraction obtained by laser diffraction / scattering particle size distribution measurement is 10% when calculated from the smallest particle size. The measurement method will be described in the examples described later.

[0038] Ti 2 Nb 14 O 39 The reason why a remarkable effect was observed by controlling the specific surface area of ​​the primary particles of the niobium-containing oxide powder such as Ti, etc., within a certain range (preferably, by controlling the particle size distribution of the primary particles within a certain range) is not clear, but is thought to be as follows. 2 Nb 14 O 39 A negative electrode active material such as niobium-containing oxide powder exhibits capacity by absorbing and releasing lithium ions through an electrolyte or solid electrolyte. Therefore, the contact area between the non-aqueous electrolyte such as an electrolyte or solid electrolyte and the negative electrode active material, the diffusion of lithium ions in the active material particles, and the diffusion of electrons are very important. In the case of particles with a small specific surface area described in Non-Patent Document 1, the contact with the non-aqueous electrolyte is insufficient, and satisfactory battery characteristics cannot be obtained. In addition, when D50 or D90 is large, since it contains a large number of primary particles with a large particle size, the diffusion within the particles is not sufficient, and satisfactory battery characteristics are often not obtained. On the other hand, when the specific surface area of ​​the active material is too large, although it is in sufficient contact with the non-aqueous electrolyte, the reactivity with the non-aqueous electrolyte is also high, and the decomposition of the non-aqueous electrolyte at the interface progresses considerably, and a satisfactory battery capacity cannot be obtained. In addition, in the case of porous particles composed of nano-sized primary particles such as Non-Patent Documents 1 and 2, especially when applied to an all-solid-state battery using a solid electrolyte, the solid electrolyte cannot contact the inside of the secondary particles, and satisfactory battery characteristics cannot be obtained.

[0039] Furthermore, in an electrode using a niobium oxide active material with low electronic conductivity, the contact with the conductive additive gradually disappears due to the volume change accompanying the charge and discharge of the active material in the negative electrode mixture layer, and the cycle characteristics are significantly reduced. The niobium oxide of the present invention is a Ti oxide in which a part of all the cation sites is vacant. 2 Nb 14 O 39 The unique crystal structure of Ti reduces the volume change during charging and discharging. 2 Nb 14 O 39 It is believed that the good battery characteristics were obtained because the contact between the niobium-containing oxide powder such as TiNb and the non-aqueous electrolyte and conductive additive was maintained for a long period of time. 2 O 7 , Ti 2 Nb 10 O 29 , TiNb with trivalent metal 2 O 7 Or Ti 2 Nb 10 O 29 It is considered that favorable battery characteristics could not be obtained because the volume change during charging and discharging was large.

[0040] [Method of producing the niobium-containing oxide powder of the present invention] An example of the method for producing the niobium-containing oxide powder of the present invention will be described below, divided into a raw material preparation step and a firing step, but the method for producing the niobium-containing oxide powder of the present invention is not limited thereto.

[0041] <Raw material preparation process> First, the starting materials are mixed. In particular, in the case of niobium titanium composite oxide, an oxide or salt containing Ti and Nb is used as the starting material. In addition, in the case of containing other additive elements of niobium titanium composite oxide, in addition to an oxide containing Ti and Nb, an oxide or salt containing at least one element selected from the group consisting of Zr, Si, Ge, Sn, V, Ta, Al, Ga, Fe, Cr, Mg, Ca, Cu, Zn, Bi, Mo, and W is used as the starting material, and mixed in a stoichiometric ratio to obtain the target composition of the present invention. The salt used is preferably a salt that decomposes at a relatively low melting point to produce an oxide, such as a hydroxide salt, carbonate salt, or nitrate salt. In addition, in order to reduce the primary particle size, it is preferable to use a powder having an average primary particle size of 2 μm or less, preferably an average primary particle size of 0.5 μm or less, as the starting material.

[0042] The method for mixing the raw materials is not particularly limited, and either wet mixing or dry mixing may be used. For example, a Henschel mixer, an ultrasonic dispersing device, a homomixer, a mortar, a ball mill, a centrifugal ball mill, a planetary ball mill, a vibration ball mill, an attritor type high speed ball mill, a bead mill, a roll mill, etc. may be used.

[0043] <Firing process> Next, the mixture obtained above is fired. The firing is preferably performed at a temperature range of 500°C or more and 1200°C or less, more preferably at a temperature range of 700°C or more and 1150°C or less, and even more preferably at a temperature range of 900°C or more and 1150°C or less. By performing the firing temperature at 1200°C or less, general-purpose equipment can be used. When the mixture is fired for a short period of time, it is preferable to prepare the mixed powder constituting the mixture before firing so that D95 in the particle size distribution curve measured by a laser diffraction / scattering type particle size distribution measuring device is 5 μm or less. Here, D95 refers to the particle size at which the cumulative volume frequency calculated by volume fraction is 95% when integrated from the smallest particle size.

[0044] The calcination method is not particularly limited as long as it can be performed under the above conditions. Examples of calcination methods that can be used include fixed bed calcination furnaces, roller hearth calcination furnaces, mesh belt calcination furnaces, fluidized bed calcination furnaces, and rotary kiln calcination furnaces. However, in the case of performing efficient calcination in a short time, roller hearth calcination furnaces, mesh belt calcination furnaces, and rotary kiln calcination furnaces are preferred. In particular, the rotary kiln calcination furnace is a particularly preferred calcination furnace for producing the niobium-containing oxide powder of the present invention, since it does not require a container to accommodate the mixture, it can be calcined while continuously feeding the mixture, the thermal history of the calcined material is uniform, and a homogeneous oxide can be obtained.

[0045] <Surface treatment process> The niobium-containing oxide obtained above may be subjected to a surface treatment. At least one metal element selected from the group consisting of Mo and Ce and fibrous carbon such as single-walled carbon nanotubes (SWCNT) and multi-walled carbon nanotubes (MWCNT) are present locally on the surface of the particles constituting the niobium-containing oxide powder of the present invention, and when applied as a negative electrode material of a battery, a dense negative electrode layer can be formed and excellent charge rate characteristics can be imparted. In the firing step, a compound containing at least one metal element selected from the group consisting of Mo and Ce (hereinafter, sometimes referred to as a treatment agent) or fibrous carbon can be added to produce the niobium-containing oxide powder of the present invention that has been surface-treated, but it is more preferable to produce the niobium-containing oxide powder of the present invention that has been surface-treated by the following surface treatment step or the like. In particular, by adopting the following surface treatment step, it is possible to appropriately and relatively simply make the surface of the niobium-containing oxide particles have at least one metal element selected from the group consisting of Mo and Ce and fibrous carbon present.

[0046] There is no particular limitation on the method of mixing the base niobium-containing oxide powder with the compound containing at least one metal element selected from the group consisting of Mo and Ce and the fibrous carbon, and either wet mixing or dry mixing can be used. However, it is preferable to uniformly disperse the compound containing at least one metal element selected from the group consisting of Mo and Ce and the fibrous carbon on the surfaces of the particles constituting the base niobium-containing oxide powder, and in this respect, wet mixing is preferred.

[0047] In the wet mixing, the treatment agent and the niobium-containing oxide powder of the substrate are put into a water or alcohol solvent and mixed in a slurry state. As the alcohol solvent, those with a boiling point of 100°C or less, such as methanol, ethanol, and isopropyl alcohol, are preferred because they are easy to remove. In addition, from an industrial perspective, water solvents are preferred because they are easy to recover and dispose of.

[0048] Compounds (treatment agents) containing at least one metal element selected from the group consisting of Mo and Ce are not particularly limited, and examples thereof include oxides, phosphoric oxides, hydroxides, sulfate compounds, nitrate compounds, fluorides, chlorides, organic compounds, and metal salt compounds such as ammonium salts and phosphates. Specifically, compounds of Mo include molybdenum oxide, molybdenum trioxide, molybdenum trioxide hydrate, molybdenum boride, molybdophosphoric acid, molybdenum disilicide, molybdenum chloride, molybdenum sulfide, molybdosilicic acid hydrate, sodium molybdenum oxide, molybdenum carbide, molybdenum acetate dimer, lithium molybdate, sodium molybdate, potassium molybdate, calcium molybdate, magnesium molybdate, manganese molybdate, and ammonium molybdate, and among these, molybdenum trioxide, molybdenum trioxide hydrate, molybdenum chloride, molybdenum sulfide, and lithium molybdate are preferred. Examples of Ce compounds include cerium oxide, cerium hydroxide, cerium fluoride, cerium sulfate, cerium nitrate, cerium carbonate, cerium acetate, cerium oxalate, cerium chloride, cerium boride, and cerium phosphate. Of these, cerium sulfate and its hydrates are preferred.

[0049] The amount of the compound containing at least one metal element selected from the group consisting of Mo and Ce may be any amount as long as the amount of the at least one metal element selected from the group consisting of Mo and Ce in the niobium-containing oxide falls within the range of the present invention, but it may be added at a rate of 0.03 mass% or more relative to the niobium-containing oxide powder of the substrate, and it is preferable to add it at a rate of 0.05 mass% or more. In addition, it may be added at a rate of 12 mass% or less relative to the niobium-containing oxide powder of the substrate, preferably at a rate of 10 mass% or less, and more preferably at a rate of 8 mass% or less. In addition, the amount of the fibrous carbon may be any amount as long as the amount of the fibrous carbon in the niobium-containing oxide falls within the range of the present invention, but it may be added at a rate of 0.001 mass% or more relative to the niobium-containing oxide powder of the substrate, and it is preferable to add it at a rate of 0.05 mass% or more. In addition, it may be added at a rate of 2 mass% or less relative to the niobium-containing oxide powder of the substrate, and it is preferable to add it at a rate of 1.5 mass% or less, and more preferably at a rate of 1 mass% or less.

[0050] When at least one metal element selected from the group consisting of Mo and Ce is contained, it is preferable to carry out heat treatment after carrying out the surface treatment. The heat treatment temperature is a temperature at which the at least one metal element selected from the group consisting of Mo and Ce diffuses into at least the surface region of the niobium-containing oxide particles constituting the niobium-containing oxide powder of the base material, and is a temperature at which the specific surface area does not decrease significantly due to sintering of the niobium-containing oxide of the base material. The upper limit of the heat treatment temperature is preferably 700°C or less, more preferably 600°C or less. The lower limit of the heat treatment temperature is preferably 300°C or more, more preferably 400°C or more. The heat treatment time is preferably 0.1 hours to 8 hours, more preferably 0.5 hours to 5 hours. The temperature and time at which the at least one metal element selected from the group consisting of Mo and Ce diffuses into at least the surface region of the niobium-containing oxide powder of the base material differ in reactivity depending on the compound containing at least one metal element selected from the group consisting of Mo and Ce, so they should be appropriately set. In addition, the heating method in the heat treatment is not particularly limited. Examples of heat treatment furnaces that can be used include fixed bed furnaces, roller hearth furnaces, mesh belt furnaces, fluidized bed furnaces, and rotary kiln furnaces. The atmosphere during the heat treatment may be either an air atmosphere or an inert atmosphere such as a nitrogen atmosphere. In particular, when a metal salt compound is used for the surface treatment, an air atmosphere is preferred because anion species are easily removed from the particle surface.

[0051] It is preferable to perform a crushing process on the niobium-containing oxide powder obtained after the heat treatment as described above, if necessary, in order to set the specific surface area within the above range. The crushing process can be performed, for example, using a ball mill, and the conditions for the crushing process are not particularly limited as long as they are conditions that allow the specific surface area to be within the above range. In addition to the crushing process, classification may be performed.

[0052] The niobium-containing oxide powder of the present invention may be granulated and heat-treated to form a powder containing secondary particles formed by aggregation of primary particles. Any method for granulation may be used as long as secondary particles can be formed, but a spray dryer is preferred because it can process a large amount of the powder.

[0053] In order to reduce the amount of moisture contained in the niobium-containing oxide powder of the present invention, dew point control may be performed in the heat treatment process. If the heat-treated powder is exposed to the air as it is, moisture in the air will be adsorbed by the powder, so it is preferable to handle the powder in a dew point controlled environment during cooling in the heat treatment furnace and after the heat treatment. The heat-treated powder may be classified as necessary to make the particles within the desired maximum particle size range. When dew point control is performed in the heat treatment process, it is preferable to seal the niobium-containing oxide powder of the present invention in an aluminum laminate bag or the like and then place it in an environment outside of dew point control. Even under dew point control, if the heat-treated niobium-containing oxide powder is pulverized, moisture will be easily absorbed from the crushed surface, and the amount of moisture contained in the powder will increase, so it is preferable not to pulverize the powder after heat treatment. As for the heat treatment conditions, the temperature and holding time in a specific range greatly affect the secondary particle morphology and the surface treatment process. The heat treatment temperature is preferably 450°C or higher, and preferably less than 550°C. This is because if the heat treatment temperature exceeds 550°C, the specific surface area will be significantly reduced, and the battery performance, especially the rate characteristics, will be significantly reduced. Furthermore, the holding time is preferably one hour or more, because if the holding time is short, not only will the amount of moisture in the powder increase, but it is also thought to affect the surface condition of the particles.

[0054] [Active material] The active material of the present invention contains the niobium-containing oxide powder of the present invention. It may contain one or more substances other than the niobium-containing oxide powder of the present invention. Examples of other substances include carbon materials (pyrolytic carbons, cokes, graphites (artificial graphite, natural graphite, etc.), organic polymer compound combustion bodies, carbon fibers), tin and tin compounds, silicon and silicon compounds, and metal oxides containing lithium. In particular, the metal oxides containing lithium include Li 4 Ti 5 O 12 Lithium titanate having the main component is exemplified.

[0055] [Electricity storage device] The electricity storage device of the present invention is a device that includes an electrode containing the active substance material of the present invention and stores and releases energy by utilizing the intercalation and deintercalation of lithium ions into such an electrode, and examples of such a device include a hybrid capacitor and a lithium battery.

[0056] [Hybrid capacitor] The hybrid capacitor is a device that uses an active material such as activated carbon, which forms a capacitance by physical adsorption similar to the electrode material of an electric double layer capacitor, an active material such as graphite, which forms a capacitance by physical adsorption and intercalation / deintercalation, or an active material such as a conductive polymer, which forms a capacitance by redox, in the positive electrode, and the active material of the present invention in the negative electrode. The active material of the present invention is usually used in the form of an electrode sheet of the hybrid capacitor.

[0057] [Lithium battery] The lithium battery of the present invention is a general term for lithium primary batteries and lithium secondary batteries. In this specification, the term lithium secondary battery is used as a concept including so-called lithium ion secondary batteries and all-solid-state lithium ion secondary batteries.

[0058] The lithium battery is composed of a positive electrode, a negative electrode, and a non-aqueous electrolyte in which an electrolyte salt is dissolved in a non-aqueous solvent, or a solid electrolyte, and the active material of the present invention can be used as an electrode material. The active material of the present invention is usually used in the form of an electrode sheet for the lithium battery. This active material may be used as either a positive electrode active material or a negative electrode active material, but the following description will be given of the case where it is used as a negative electrode active material.

[0059] <Negative electrode> The negative electrode has a negative electrode layer containing a negative electrode active material (the active material of the present invention), a conductive agent, and a binder on one or both sides of a negative electrode current collector. This negative electrode layer is usually in the form of an electrode sheet. In the case of a negative electrode current collector having pores such as a porous body, the negative electrode layer contains a negative electrode active material (the active material of the present invention), a conductive agent, and a binder in the pores.

[0060] The conductive agent for the negative electrode is not particularly limited as long as it is an electron conductive material that does not undergo chemical change. For example, graphites such as natural graphite (e.g., flake graphite) and artificial graphite, carbon blacks such as acetylene black, ketjen black, channel black, furnace black, lamp black, and thermal black, carbon nanotubes such as single-walled carbon nanotubes, multi-walled carbon nanotubes (graphite layers are multi-layered concentric cylinders) (non-fishbone-shaped), cup-stacked carbon nanotubes (fishbone-shaped), nodular carbon nanofibers (non-fishbone structure), and platelet-shaped carbon nanofibers (playing cards).

[0061] The amount of conductive agent added should be optimized because it varies depending on the specific surface area of ​​the active material and the type and combination of conductive agents. It is preferably 0.1% by mass to 10% by mass, more preferably 0.5% by mass to 5% by mass in the negative electrode layer. If it is less than 0.1% by mass, the conductivity of the negative electrode layer cannot be ensured, and if it exceeds 10% by mass, the active material ratio decreases, and the discharge capacity of the power storage device per unit mass and unit volume of the negative electrode layer becomes insufficient, so it is not suitable for increasing the capacity. The conductive agent may be added when the electrode is prepared, or may be coated on the active material itself. This is because the conductivity of the negative electrode layer can be further improved by coating with a conductive agent such as carbon fiber.

[0062] Examples of the binder for the negative electrode include polytetrafluoroethylene (PTFE), polyvinylidene fluoride (PVDF), polyvinylpyrrolidone (PVP), styrene-butadiene copolymer (SBR), acrylonitrile-butadiene copolymer (NBR), and carboxymethyl cellulose (CMC).

[0063] The amount of binder added should be optimized since it varies depending on the specific surface area of ​​the active material and the type and combination of the conductive agent, but is preferably 0.2% by mass to 15% by mass in the negative electrode layer. From the viewpoint of increasing the binding property and ensuring the strength of the negative electrode layer, it is preferably 0.5% by mass or more, more preferably 1% by mass or more, and even more preferably 2% by mass or more. From the viewpoint of preventing a decrease in the active material ratio and a decrease in the discharge capacity of the power storage device per unit mass and unit volume of the negative electrode layer, it is preferably 10% by mass or less, and more preferably 5% by mass or less.

[0064] Examples of the negative electrode current collector include aluminum, stainless steel, nickel, copper, titanium, baked carbon, and those having their surfaces coated with carbon, nickel, titanium, silver, etc. The surface of these materials may be oxidized, or the surface of the negative electrode current collector may be roughened by surface treatment.

[0065] The negative electrode can be produced by uniformly mixing the negative electrode active material (including the active material of the present invention), the conductive agent, and the binder in a solvent to prepare a paint, which is then applied to the negative electrode current collector, dried, and compressed. In the case of a negative electrode current collector having pores, such as a porous body, the paint is pressed into the pores of the current collector to fill the pores, or the current collector having pores is immersed in the paint to diffuse the pores, and then dried and compressed.

[0066] As a method for uniformly mixing the negative electrode active material (the active material of the present invention), the conductive agent, and the binder in a solvent to prepare a paint, for example, a kneader of the type in which a stirring rod revolves while rotating in a kneading vessel such as a planetary mixer, a twin-screw extrusion type kneader, a planetary stirring defoamer, a bead mill, a high-speed rotating type mixer, a powder suction continuous dissolution and dispersion device, etc. Also, as a manufacturing process, the process may be divided according to the solid content concentration, and these devices may be used separately.

[0067] In order to mix the negative electrode active material (the active material of the present invention), the conductive agent and the binder uniformly in the solvent, the specific surface area of ​​the active material, the type of conductive agent, the type of binder and the combination of these should be optimized. However, when using a kneader in which the stirring rod revolves while rotating in a kneading container such as a planetary mixer, a twin-screw extrusion type kneader, a planetary stirring degassing device or the like, it is preferable to divide the process according to the solid content concentration in the manufacturing process, knead the mixture in a state where the solid content concentration is high, and then gradually reduce the solid content concentration to adjust the viscosity of the paint. The high solid content concentration is preferably 60% by mass to 90% by mass. If it is 60% by mass or more, it is preferable because shear force can be obtained, if it is 90% by mass or less, it is preferable because the load on the device is reduced, and if it is 80% by mass or less, it is more preferable.

[0068] The mixing procedure is not particularly limited, but examples thereof include a method of simultaneously mixing the negative electrode active material, the conductive agent, and the binder in a solvent, a method of previously mixing the conductive agent and the binder in a solvent and then adding and mixing the negative electrode active material, a method of previously preparing a negative electrode active material slurry, a conductive agent slurry, and a binder solution, and then mixing each of them, etc. Among these, in order to disperse them uniformly, a method of previously mixing the conductive agent and the binder in a solvent and then adding and mixing the negative electrode active material, and a method of previously preparing a negative electrode active material slurry, a conductive agent slurry, and a binder solution, and then mixing each of them are preferred.

[0069] As the solvent, an organic solvent can be used. Examples of the organic solvent include aprotic organic solvents such as 1-methyl-2-pyrrolidone, dimethylacetamide, and dimethylformamide, which may be used alone or in combination of two or more kinds, and preferably 1-methyl-2-pyrrolidone.

[0070] When an organic solvent is used as the solvent, it is preferable to dissolve the binder in the organic solvent before use.

[0071] <Positive electrode> The positive electrode has a positive electrode layer containing a positive electrode active material, a conductive agent, and a binder on one or both sides of a positive electrode current collector.

[0072] As the positive electrode active material, a material capable of absorbing and releasing lithium is used. For example, the active material may be a composite metal oxide containing lithium and containing cobalt, manganese, or nickel, or a lithium-containing olivine-type phosphate. These positive electrode active materials may be used alone or in combination of two or more. Examples of such composite metal oxides include LiCoO 2 , LiMn 2 O 4 , LiNiO 2 , LiCo 1-x Ni x O 2 (0.01 <x<1)、LiCo 1 / 3 Ni 1 / 3 Mn 1 / 3 O 2 , LiNi 1 / 2 Mn 3 / 2 O 4 These lithium composite oxides may be partially substituted with other elements, such as by substituting a portion of the cobalt, manganese, or nickel with at least one element such as B, Nb, Sn, Mg, Fe, Ti, Al, Zr, Cr, V, Ga, Zn, Cu, Bi, Mo, or La, or by substituting a portion of the O with S or F, or by coating with a compound containing these other elements. Examples of lithium-containing olivine-type phosphates include LiFePO 4 , LiCoPO 4 , LiNiPO 4 , LiMnPO 4 , Life 1-x MxPO 4 (M is at least one selected from Co, Ni, Mn, Cu, Zn, and Cd, and x is 0≦x≦0.5.)

[0073] The conductive agent and binder for the positive electrode may be the same as those for the negative electrode. The positive electrode current collector may be, for example, aluminum, stainless steel, nickel, titanium, baked carbon, or aluminum or stainless steel surface-treated with carbon, nickel, titanium, or silver. The surface of these materials may be oxidized, or the positive electrode current collector surface may be roughened by surface treatment.

[0074] <Nonaqueous electrolyte> The non-aqueous electrolyte is a non-aqueous solvent having an electrolyte salt dissolved therein. There are no particular limitations on the type of non-aqueous electrolyte, and various types can be used.

[0075] The electrolyte salt used is one that dissolves in a non-aqueous electrolyte, such as LiPF 6 , LiBF 4 , LiPO 2 F 2 , LiN(SO 2 F) 2 , LiClO 4 Inorganic lithium salts such as LiN(SO 2 CF 3 ) 2 , LiN(SO 2 C 2 F 5 ) 2 , LiCF 3 SO 3 , LiC(SO 2 CF 3 ) 3 , LiPF 4 (CF 3 ) 2 , LiPF 3 (C 2 F 5 ) 3 , LiPF 3 (CF 3 ) 3 , LiPF 3 (iso-C 3 F 7 ) 3 , LiPF 5 (iso-C 3 F 7 Lithium salts containing chain-shaped fluorinated alkyl groups such as (CF 2 ) 2 (SO 2 ) 2 NLi, (CF 2 ) 3 (SO 2 ) 2 Examples of the electrolyte salt include lithium salts containing a cyclic fluorinated alkylene chain such as NLi, and lithium salts having an oxalate complex as the anion such as lithium bis[oxalate-O,O']borate and lithium difluoro[oxalate-O,O']borate. Among these, a particularly preferred electrolyte salt is LiPF 6 , LiBF 4 , LiPO 2 F 2 , and LiN(SO 2 F) 2 and the most preferred electrolyte salt is LiPF 6 These electrolyte salts can be used alone or in combination of two or more.

[0076] The concentration of all of these electrolyte salts dissolved in the nonaqueous solvent is usually preferably 0.3 M or more, more preferably 0.5 M or more, and even more preferably 0.7 M or more. The upper limit is preferably 2.5 M or less, more preferably 2.0 M or less, and even more preferably 1.5 M or less.

[0077] On the other hand, the non-aqueous solvent may be a cyclic carbonate, a chain carbonate, a chain ester, an ether, an amide, a phosphoric acid ester, a sulfone, a lactone, a nitrile, an S=O bond-containing compound, etc., and preferably contains a cyclic carbonate. The term "chain ester" is used as a concept including a chain carbonate and a chain carboxylate ester.

[0078] Examples of cyclic carbonates include ethylene carbonate (EC), propylene carbonate (PC), 1,2-butylene carbonate, 2,3-butylene carbonate, 4-fluoro-1,3-dioxolan-2-one (FEC), trans or cis-4,5-difluoro-1,3-dioxolan-2-one (hereinafter, both are collectively referred to as "DFEC"), vinylene carbonate (VC), vinyl ethylene carbonate (VEC), and 4-ethynyl-1,3-dioxolane. Examples of suitable cyclic carbonates include one or more selected from EC, PC, 1,2-butylene carbonate, 2,3-butylene carbonate, FEC and EEC, and more preferably from the viewpoints of improving the charge rate characteristics of the electricity storage device and suppressing the amount of gas generation during high temperature operation. Further preferably, one or more cyclic carbonates having an alkylene chain selected from propylene carbonate, 1,2-butylene carbonate and 2,3-butylene carbonate are further preferably used.

[0079] In particular, the total electrolyte salt concentration is 0.5M to 2.0M, and the electrolyte salt contains at least LiPF 6 and 0.001M to 1M LiBF 4 , LiPO 2 F 2 , and LiN(SO 2 F) 2 It is preferable to use a non-aqueous electrolyte containing at least one lithium salt selected from LiPF 6 When the proportion of lithium salts other than the lithium salt in the non-aqueous solvent is 0.001 M or more, the effect of improving the charge rate characteristics of the electricity storage device and suppressing the amount of gas generation during high-temperature operation is easily achieved, and when the proportion is 1.0 M or less, there is little concern that the effect of improving the charge rate characteristics of the electricity storage device and the effect of suppressing the amount of gas generation during high-temperature operation will be reduced, which is preferable.

[0080] In addition, the non-aqueous solvent is preferably used in a mixed state in order to achieve appropriate physical properties. Examples of the combination include a combination of a cyclic carbonate and a chain carbonate, a combination of a cyclic carbonate, a chain carbonate and a lactone, a combination of a cyclic carbonate, a chain carbonate and an ether, a combination of a cyclic carbonate, a chain carbonate and a chain ester, a combination of a cyclic carbonate, a chain carbonate and a nitrile, and a combination of a cyclic carbonate, a chain carbonate and a compound containing an S=O bond.

[0081] Suitable examples of the chain ester include one or more asymmetric chain carbonates selected from methyl ethyl carbonate (MEC), methyl propyl carbonate (MPC), methyl isopropyl carbonate (MIPC), methyl butyl carbonate, and ethyl propyl carbonate; one or more symmetric chain carbonates selected from dimethyl carbonate (DMC), diethyl carbonate (DEC), dipropyl carbonate, and dibutyl carbonate; pivalic acid esters such as methyl pivalate, ethyl pivalate, and propyl pivalate; and one or more chain carboxylate esters selected from methyl propionate, ethyl propionate, propyl propionate, methyl acetate, and ethyl acetate (EA).

[0082] <The structure of a lithium battery> The structure of the lithium battery of the present invention is not particularly limited, and examples include a coin battery having a positive electrode, a negative electrode, and a single-layer or multi-layer separator, and further, a cylindrical battery or a square battery having a positive electrode, a negative electrode, and a roll-shaped separator.

[0083] The separator is an insulating thin film having a large ion permeability and a certain mechanical strength. Examples of the separator include polyethylene, polypropylene, cellulose paper, glass fiber paper, polyethylene terephthalate, and polyimide microporous membranes, and multi-layer membranes made by combining two or more of them can also be used. The surface of these separators can also be coated with resins such as PVDF, silicone resins, and rubber-based resins, or particles of metal oxides such as aluminum oxide, silicon dioxide, and magnesium oxide.

[0084] [Negative electrode active material composition] The negative electrode active material composition of the present invention is a negative electrode active material composition containing the niobium-containing oxide powder of the present invention and an inorganic solid electrolyte having conductivity of metal ions belonging to Group 1 of the periodic table. The content of the inorganic solid electrolyte is not particularly limited, but may be 1% by mass or more in the active material composition, preferably 5% by mass or more, more preferably 20% by mass or more, and even more preferably 30% by mass or more. The higher the content of the inorganic solid electrolyte, the easier it is to obtain contact between the niobium-containing oxide powder and the solid electrolyte, which is preferable. In addition, if the content of the inorganic solid electrolyte is too high, the battery capacity of the all-solid-state secondary battery becomes small, so the content may be 70% by mass or less, preferably 60% by mass or less. In general, in order to increase the battery capacity of the all-solid-state secondary battery, it is preferable that the content of the inorganic solid electrolyte is small, but if the content is small, it becomes difficult to obtain contact between the niobium-containing oxide powder and the solid electrolyte. By using the niobium-containing oxide powder used in the negative electrode active material composition of the present invention, a satisfactory contact between the niobium-containing oxide powder and the solid electrolyte can be obtained even when the content of the inorganic solid electrolyte is small. The niobium-containing oxide powder and inorganic solid electrolyte of the present invention may contain one or more substances other than the inorganic solid electrolyte. Examples of the other substances include carbon materials (pyrolytic carbons, cokes, graphites (artificial graphite, natural graphite, etc.), organic polymer compound combustion bodies, carbon fibers), tin and tin compounds, silicon and silicon compounds, and metal oxides containing lithium. In particular, the lithium-containing metal oxides include Li 4 Ti 5 O 12 Lithium titanate having the main component is exemplified.

[0085] <Periodic table> The periodic table in this specification refers to a long-form periodic table of elements based on the provisions of IUPAC (International Union of Pure and Applied Chemistry).

[0086] <Solid electrolyte> A solid electrolyte is a solid electrolyte that allows ions to move inside. In particular, inorganic solid electrolytes are solid in a stationary state, and therefore are not usually dissociated or liberated into cations and anions. There are no particular limitations on the inorganic solid electrolyte as long as it has the conductivity of metal ions belonging to Group 1 of the periodic table, and it is common for inorganic solid electrolytes to have almost no electronic conductivity. Representative examples of inorganic solid electrolytes include (A) sulfide inorganic solid electrolytes, (B) oxide inorganic solid electrolytes, and (C) chloride inorganic solid electrolytes. In particular, sulfide inorganic solid electrolytes are preferably used because they have high ionic conductivity and can be formed into a dense molded body with few grain boundaries by simply applying pressure at room temperature.

[0087] The sulfide inorganic solid electrolyte may be a non-crystalline glass, a crystallized glass, or a crystalline material. Specific examples of the sulfide inorganic solid electrolyte include, but are not limited to, the following combinations. Li 2 SP 2 S 5 , Li 2 SP 2 S 5 -Al 2 S 3 , Li 2 S-GeS 2 , Li 2 S-Ga 2 S 3 , Li 2 S-GeS 2 -Ga 2 S 3 , Li 2 S-GeS 2 -P 2 S 5 , Li 2 S-GeS 2 -Sb 2 S 5 , Li 2 S-GeS 2 -Al 2 S 3 , Li 2 S-SiS 2 , Li 2 S-Al 2 S 3 , Li 2 S-SiS 2 -Al 2 S 3 , Li 2 S-SiS 2 -P 2 S 5 , Li 10 GeP 2 S 12 .

[0088] Among the above combinations, Li 2 SP 2 S 5 The LPS glass and LPS glass ceramics manufactured by combining the above are preferred. In addition, as sulfide inorganic solid electrolytes other than those mentioned above, Li 6 P.S. 5 Cl and Li 6 P.S. 5 Suitable examples of the solid electrolyte include argerodite-type solid electrolytes such as Br.

[0089] The oxide inorganic solid electrolyte contains oxygen atoms and is a metal iridium that belongs to Group 1 of the periodic table. It is preferable that the material has both on-conductivity and electronic insulation properties.

[0090] As the oxide inorganic solid electrolyte, for example, Li having a LISICON (Lithium super ionic conductor) type crystal structure is used. 3.5 Zinc 0.25 GeO 4 , La with perovskite crystal structure 0.55 Li 0.35 TiO 3 LiTi with NASICON (sodium super ionic conductor) type crystal structure 2 P 3 O 12 and Li having a garnet-type crystal structure 7 La 3 Zr 2 O 12 (LLZ), lithium phosphate (Li 3 PO 4 ), LiPON in which part of the oxygen of lithium phosphate is substituted with nitrogen, Li 3 BO 3 -Li 2 SO 4 , Li 2 O-B 2 O 3 -P 2 O 5 , Li 2 O-SiO 2 , and Li 6 BaLa 2 Ta 2 O 12 etc. are preferably mentioned.

[0091] As the chloride inorganic solid electrolyte, Li 3 ScCl 6 , LiAlCl 4 , Ln 1-X A X OCl 1-X (wherein, Ln represents any rare earth element, A represents an alkaline earth metal, and X satisfies 0 < X < 1) etc. are preferably mentioned.

[0092] The volume average particle diameter of the inorganic solid electrolyte is not particularly limited, but it is preferably 0.01 μm or more, more preferably 0.1 μm or more. As the upper limit, it is preferably 100 μm or less, more preferably 50 μm or less.

Examples

[0093] Next, examples and comparative examples will be given for more specific description, but the present invention is not limited to the following examples, and includes various combinations that can be easily inferred from the gist of the invention.

[0094] (Liquid-based lithium ion secondary battery) [Example 1-1] <Raw material preparation process> Nb 2 O 5 (average particle size 0.2 μm) and anatase type TiO 2 (Specific surface area 10m 2 The two materials (1,2-dinitrophenyl niobium, 1,3-trimethylanilinoic acid, 1,2-dinitrophenyl niobium, 1,3-trimethylanilinoic acid, 1,3-dinitrophenyl niobium ... 2 Nb 14 O 39 ) was confirmed.

[0095] <Crushing process> Zirconia beads having a diameter of 2.0 mm were added to the obtained fired powder sample, and the mixture was crushed in a ball mill to produce the niobium-containing oxide powder according to Example 1-1, in which the particle size distribution of the primary particles was adjusted.

[0096] [Examples 1-2 to 1-5] The same procedure as in Example 1-1 was carried out except that in the raw material preparation step, the firing temperature was changed to 950° C. to 1100° C. as shown in Table 1, to produce niobium-containing oxide powders according to Examples 1-2 to 1-5.

[0097] [Examples 1-6 to 1-9] The niobium-containing oxide powders according to Examples 1-6 to 1-9 were produced in the same manner as in Example 1-1, except that the raw materials and mixing ratios were changed in the raw material preparation step so as to satisfy the composition formula shown in Table 1.

[0098] [Comparative Example 1-1] Nb 2 O 5 and anatase TiO 2 They were weighed and mixed so that the molar ratio was 7:2. Niobium-containing oxide powder according to Comparative Example 1-1 was produced by only subjecting this mixed powder to a firing treatment at 1100°C for 12 hours, without performing a crushing treatment step as in Non-Patent Document 1.

[0099] [Comparative Example 1-2] Nb 2 O 5 and anatase-type TiO 2 Niobium-containing oxide powder according to Comparative Example 1-2 was produced in the same manner as in Example 1-3, except that the molar ratio was changed to 1:1.

[0100] [Comparative Example 1-3] Nb 2 O 5 and anatase-type TiO 2 Niobium-containing oxide powder according to Comparative Example 1-3 was produced in the same manner as in Example 1-5, except that the molar ratio was changed to 5:2.

[0101] [Measurement of Powder Physical Properties] Various physical properties of the niobium-containing oxide powders of each example and comparative example were measured as follows.

[0102] [Measurement of Specific Surface Area] The specific surface area (m 2 / g) of the niobium-containing oxide powders of each example and each comparative example was measured using a fully automatic BET specific surface area measuring device (manufactured by Mountech Co., Ltd., trade name "Macsorb HM model-1208"), with nitrogen gas used as the adsorption gas. 0.5 g of the measurement sample powder was weighed, placed in a φ12 standard cell (HM1201-031), degassed under vacuum at 100°C for 0.5 hours, and then measured by the BET single-point method.

[0103] [Calculation of D10, D50, D90: Dry Laser Diffraction Scattering Method] The D50 of the niobium-containing oxide powder in each Example and Comparative Example was calculated from a particle size distribution curve measured using a laser diffraction / scattering type particle size distribution measuring instrument (Microtrac MT3300EXII, manufactured by Nikkiso Co., Ltd.). 50 mg of a sample was placed in a container containing 50 ml of ion-exchanged water as a measurement solvent, and the measurement solvent was added until the transmittance of the slurry was within the appropriate range (the range displayed by the green bar of the instrument), and particle size distribution measurement was performed. The D10, D50, and D90 of the powder were calculated from the obtained particle size distribution curve.

[0104] [Evaluation of battery characteristics] The niobium-containing oxide powders of the Examples and Comparative Examples were used to fabricate coin-type batteries, and the battery characteristics were evaluated. The evaluation results are shown in Table 1.

[0105] <Preparation of negative electrode sheet> The negative electrode sheet was prepared as follows in a room controlled at a room temperature of 25°C and a dew point of -20°C or less. The niobium-containing oxide powder of each Example and Comparative Example was taken out of the aluminum laminated bag in a room controlled at a temperature of 25°C and a dew point of -20°C or less. The niobium-containing oxide powder of each Example and Comparative Example taken out was mixed in a ratio of 85 mass% as an active material, 10 mass% as acetylene black as a conductive agent, and 5 mass% as polyvinylidene fluoride as a binder to prepare a paint. The obtained paint was applied to an aluminum foil and dried to prepare a negative electrode single-sided sheet to be used in a coin battery described later.

[0106] <Preparation of electrolyte> The electrolyte used in the battery for characteristic evaluation was prepared as follows. In an argon glove box controlled at a temperature of 25°C and a dew point of -70°C or less, a non-aqueous solvent of ethylene carbonate: dimethyl carbonate = 1:2 (volume ratio) was prepared, and LiPF 6 was dissolved to a concentration of 1 M to prepare an electrolyte for a coin battery, which will be described later.

[0107] <Preparation of coin battery> The negative electrode sheet prepared by the above method was punched into a circle with a diameter of 14 mm and a thickness of 2 t / cm 2 The electrode was pressed at a pressure of 1000 MPa and then vacuum dried at 120° C. for 5 hours to prepare an electrode for evaluation. The electrode for evaluation and metallic lithium (formed into a circle with a thickness of 0.5 mm and a diameter of 16 mm) were placed opposite each other via glass filters (one each of ADVANTEC GA-100 and Whatman GF / C), and the nonaqueous electrolyte prepared by the method described above in <Preparation of electrolyte> was added and sealed to prepare a 2032-type coin battery.

[0108] <Initial battery characteristics: initial discharge capacity, initial efficiency> The coin-type battery prepared by the method described in the above <Preparation of Coin Battery> was placed in a thermostatic chamber at 25°C and charged at 0.2 mA / cm in the direction in which Li was absorbed in the evaluation electrode. 2 The battery was charged to 1 V at a current density of 0.05 mA / cm at 1 V. 2 After constant current and constant voltage charging, the battery was charged to a current density of 0.2 mA / cm 2 A constant current discharge was performed at a current density of 0.01 V to 2 V. The initial discharge capacity (mAh / g) was calculated by dividing the obtained discharge capacity (mAh) by the mass of the niobium-containing oxide, and the initial efficiency (%) was calculated by dividing the discharge capacity (mAh) by the charge capacity (mAh).

[0109] <Measurement of 10C discharge rate characteristics> The battery was charged to 1V at a current equivalent to 10C of the initial discharge capacity, and then constant-current constant-voltage charging was performed at 1V until the charging current reached a current density of 0.05C. The battery was then discharged at a constant current of 10C to 3V. The 10C rate discharge rate (%) was calculated by dividing the capacity obtained by the 10C constant-current discharge by the initial discharge capacity. If the 10C rate discharge rate of niobium-containing oxide is high, it is expected that the discharge rate characteristics of the battery will be improved when it is used as an electrode material for a battery storage device. The C in 1C represents the current value when charging and discharging. For example, 1C refers to the current value at which the theoretical capacity can be fully discharged (or fully charged) in 1 / 1 hour, and 0.1C refers to the current value at which the theoretical capacity can be fully discharged (or fully charged) in 1 / 0.1 hour.

[0110] <Cycle characteristics: cycle capacity retention rate> A cycle test was carried out in a thermostatic chamber at 25°C using the coin-type battery prepared by the method described above in <Preparation of Coin Battery>. The direction in which Li is absorbed in the evaluation electrode was set as charging, and charging was performed up to 0.8V at a current value equivalent to 0.5C of the initial discharge capacity, followed by constant-current constant-voltage charging at 0.8V until the charging current reached a current value equivalent to 0.05C, and then constant-current discharging was performed up to 2V at a current value equivalent to 0.5C of the initial discharge capacity, which constituted one cycle. A total of 20 cycles were repeated. The discharge capacity after 20 cycles was divided by the initial discharge capacity to obtain the cycle capacity retention rate (%).

[0111] [Table 1]

[0112] <Evaluation Results> It was found that the electrodes using the niobium-containing oxide powders of Examples 1-1 to 1-5, in which the BET specific surface area and the D50 and D90 of the primary particles were controlled within a certain range, and Examples 1-6 to 1-9, in which a portion of the Ti and Nb was replaced with a metal element, had superior cycle capacity retention and discharge rate characteristics to the electrode using the niobium-containing oxide powder of Comparative Example 1-1, in which the BET specific surface area was not controlled, and the electrodes using the niobium-containing oxide powders with different Nb / Ti ratios of Comparative Examples 1-2 and 1-3.

[0113] [Examples 1-10] <Surface treatment process> The niobium-containing oxide of Example 1-4 was mixed with ion-exchanged water so that the solid content of the slurry was 30 mass %, and the mixture was stirred to disintegrate the slurry. Lithium molybdate (Li 2 MoO 4 ) was added to 100 g of the crushed fired powder in an amount of 0.8% by mass to prepare a mixed slurry. This mixed slurry was mixed for 3 hours using a paint shaker, dried at a temperature of 100°C, and then heat-treated for 1 hour at 500°C using a muffle furnace to produce a niobium-containing oxide powder according to Example 1-10. A secondary battery according to Example 1-10 was produced in the same manner as in Example 1-1, except that the obtained niobium-containing oxide was used.

[0114] [Examples 1-11] The niobium-containing oxide of Example 1-4 was crushed by adding ion-exchanged water to the slurry so that the solid content concentration of the slurry was 30 mass%, and the mixture was stirred. Multi-walled carbon nanotubes (MWCNTs) were added as a treatment agent at 1 mass% per 100 g of the crushed fired powder to prepare a mixed slurry. The mixed slurry was mixed with a paint shaker for 3 hours, and then dried at a temperature of 100°C to produce the niobium-containing oxide powder of Example 1-11. A secondary battery of Example 1-11 was produced in the same manner as in Example 1-1, except that the obtained niobium-containing oxide was used.

[0115] [Examples 1-12] Niobium-containing oxide powder according to Example 1-12 was produced in the same manner as in Example 1-11 except that in the surface treatment step, the treatment agent (single-walled carbon nanotube (SWCNT)) and the content were changed as shown in Table 2. A secondary battery according to Example 1-12 was produced in the same manner as in Example 1-1 except that the obtained niobium-containing oxide was used.

[0116] The battery characteristics of the secondary batteries according to Examples 1-10 to 1-12 were evaluated. The results are shown in Table 2.

[0117] [Table 2]

[0118] <Evaluation Results> It was also found that the electrodes using the surface-treated niobium-containing oxide powders of Examples 1-10, 1-11, and 1-12 had better cycle capacity retention and discharge rate characteristics than the electrodes using the niobium-containing oxide powder of Comparative Example 1-1 and the electrodes of Comparative Examples 1-2 and 1-3.

[0119] (All-solid-state secondary battery) [Example 2-1] In a glove box under an argon atmosphere, the niobium-containing oxide and sulfide solid electrolyte of Example 1-1, Li 6 P.S. 5 Cl powder (volume average particle size measured using a laser diffraction / scattering type particle size distribution analyzer: 6 μm) and a conductive agent, niobium-containing oxide: Li 6 P.S. 5 The materials were weighed out so that the mass ratio of Cl:conductive agent was 60:40:6, and mixed by stirring in an agate mortar and a planetary ball mill to obtain a negative electrode active material composition of Example 2-1. The obtained negative electrode active material composition was pressed (360 MPa) at room temperature for 10 minutes to produce pellets (molded bodies) with a diameter of 10 mm and a thickness of about 0.7 mm. A pellet-shaped electrode containing this negative electrode active material composition and a pellet-shaped solid electrolyte layer (Li 2 S:P 2 S 5 A lithium-indium alloy foil was sandwiched between stainless steel current collectors to produce an all-solid-state secondary battery.

[0120] [Example 2-2] An all-solid-state secondary battery according to Example 2-2 was produced in the same manner as in Example 2-1, except that the niobium-containing oxide was changed to that of Example 1-4.

[0121] [Example 2-3] An all-solid-state secondary battery according to Example 2-3 was produced in the same manner as in Example 2-1, except that the niobium-containing oxide was changed to that of Example 1-10.

[0122] [Example 2-4] In the surface treatment process, lithium molybdate (Li 2 MoO 4 The same procedure as in Example 2-1 was carried out except that the amounts of added ) were as shown in Table 2, to produce a niobium-containing oxide powder according to Example 2-4.

[0123] [Comparative Example 2-1] Except for using the niobium-containing oxide of Comparative Example 1-1, the negative electrode active material composition of Comparative Example 2-1 was obtained in the same manner as in Example 2-1, and then an all-solid-state secondary battery was produced.

[0124] [Comparative Example 2-2] Except for using the niobium-containing oxide of Comparative Example 1-2, the negative electrode active material composition of Comparative Example 2-2 was obtained in the same manner as in Example 2-1, and then an all-solid-state secondary battery was produced.

[0125] [Comparative Example 2-3] Except for using the niobium-containing oxide of Comparative Example 1-3, the negative electrode active material composition of Comparative Example 2-3 was obtained in the same manner as in Example 2-1, and then an all-solid-state secondary battery was produced.

[0126] The battery characteristics of the all-solid-state secondary batteries according to Examples 2-1 to 2-4 and Comparative Examples 2-1 to 2-3 were evaluated. The evaluation results are shown in Table 3.

[0127] <Measurement of 0.4C charge / discharge rate characteristics> In a thermostatic chamber at 25°C, the all-solid-state secondary battery prepared by the above-mentioned method was charged to 0.5V with a current equivalent to 0.05C of the theoretical capacity of the niobium-containing oxide, with the direction of Li absorption in the evaluation electrode being the charging direction, and further constant current constant voltage charging was performed in which charging was performed at 0.5V until the charging current became a current equivalent to 0.01C, and the charging capacity (mAh) was divided by the mass of the niobium-containing oxide to obtain the initial charging capacity (mAh / g). Then, constant current discharging was performed to 2V with a current equivalent to 0.05C. The discharge capacity (mAh) was divided by the mass of the niobium-containing oxide to obtain the initial discharging capacity (mAh / g). Next, charging was performed to 0.5V with a current equivalent to 0.4C of the theoretical capacity of the niobium-containing oxide, and the 0.4C charging capacity was obtained. The 0.4C charging capacity was divided by the initial charging capacity to calculate the 0.4C rate charging rate (%). Thereafter, the battery was discharged to 2 V at a current equivalent to 0.4 C of the theoretical capacity of the niobium-containing oxide, and the 0.4 C discharge capacity was calculated. The 0.4 C discharge capacity was divided by the initial discharge capacity to calculate the 0.4 C rate discharge ratio (%).

[0128] [Table 3]

[0129] <Evaluation Results> In the all-solid-state battery, the electrodes using the niobium-containing oxide powders of Examples 2-1 and 2-2, in which the BET specific surface area and the D50 and D90 of the primary particles were controlled within a certain range, and the electrodes using the niobium-containing oxide powders of Examples 2-3 and 2-4, which were surface-treated, were found to have excellent initial discharge capacity and 0.4C rate characteristics. It was also found that the 0.4C rate characteristics were further improved by performing the surface treatment.

[0130] (Lithium-ion secondary battery) [Example 3-1] <Raw material preparation process> Nb 2 O 5 (average particle size 0.2μm), anatase type TiO 2 (Specific surface area 10m 2 / g) and Al 2 O 3 were weighed out and mixed in a molar ratio of 78.5:21.2:0.3. This mixed powder was subjected to a calcination treatment at 1050°C for 12 hours. Powder X-ray diffraction measurement was performed on the obtained calcined powder sample under conditions of a sampling interval of 0.01° and a scan speed of 2° / min. No peaks derived from the starting materials were confirmed, and it was confirmed that the reaction had progressed completely. From the results of crystal structure analysis of the synthesized sample and X-ray fluorescence analysis (XRF) using an X-ray fluorescence spectrometer (manufactured by SII Technology Inc., product name "SPS5100"), it was confirmed that the synthesized sample was the target niobium-containing oxide (Ti 1.9 Nb 14.05 Al 0.05 O 39 ) was confirmed.

[0131] <Crushing process> Zirconia beads having a diameter of 2.0 mm were added to the obtained fired powder sample, and the mixture was subjected to a crushing treatment using a ball mill, thereby producing the niobium-containing oxide powder according to Example 3-1 in which the particle size distribution of the primary particles was adjusted.

[0132] [Examples 3-2 to 3-36] Niobium-containing oxide powders according to Examples 3-2 to 3-36 were produced in the same manner as in Example 3-1, except that in the raw material preparation step, the raw materials and mixing ratios were changed so as to obtain the composition formulas shown in Tables 4 to 7.

[0133] [Measurement of powder properties] Various physical properties of the niobium-containing oxide powder of each of the Examples, Comparative Examples, and Reference Examples were measured in the same manner as in Example 1-1.

[0134] [Evaluation of battery characteristics] Coin-type batteries according to Examples 3-1 to 3-36 were produced in the same manner as in Example 1-1, except that the niobium-containing oxide powders of Examples 3-1 to 3-36 were used, and their battery characteristics were evaluated. The evaluation results are shown in Tables 4 to 7.

[0135] <Measurement of 10C charge / discharge rate characteristics> The battery was charged to 1V at a current equivalent to 10C of the initial discharge capacity, and then constant-current constant-voltage charging was performed at 1V until the charging current reached a current density of 0.05C, after which constant-current discharging was performed at a current of 10C to 3V. The 10C rate charge rate (%) was calculated by dividing the capacity obtained by the 10C constant-current charging by the initial discharge capacity, and the 10C rate discharge rate (%) was calculated by dividing the capacity obtained by the 10C constant-current discharging by the initial discharge capacity. If the niobium-containing oxide has high 10C rate characteristics, it is expected that the discharge rate characteristics of the energy storage device will be improved when it is used as an electrode material for the energy storage device.

[0136] [Table 4]

[0137] [Table 5]

[0138] [Table 6]

[0139] [Table 7]

[0140] [Example 3-37] <Surface treatment process> The niobium-containing oxide of Example 3-1 was mixed with ion-exchanged water so that the solid content of the slurry was 30 mass %, and the mixture was stirred to disintegrate the slurry. Lithium molybdate (Li 2 MoO 4 ) was added to 100 g of the crushed fired powder in an amount of 0.8% by mass to prepare a mixed slurry. This mixed slurry was mixed for 3 hours using a paint shaker, dried at a temperature of 100°C, and then heat-treated for 1 hour at 500°C using a muffle furnace to produce a niobium-containing oxide powder according to Example 3-37. A secondary battery according to Example 3-37 was prepared in the same manner as in Example 3-1, except that the obtained niobium-containing oxide was used.

[0141] [Example 3-38] A secondary battery according to Example 3-38 was produced in the same manner as in Example 3-37, except that the niobium-containing oxide was changed to that of Example 3-3.

[0142] [Example 3-39] A secondary battery according to Example 3-39 was produced in the same manner as in Example 3-37, except that the niobium-containing oxide was changed to that of Example 3-13.

[0143] The battery characteristics of the secondary batteries according to Examples 3-37 to 3-39 were evaluated. The evaluation results are shown in Table 8.

[0144] [Table 8]

[0145] <Evaluation Results> It was found that the electrodes using the niobium-containing oxide powders of Examples 3-1 to 3-39 had good 10C charge rate and 10C discharge rate, and were excellent in rate characteristics.

[0146] <Measurement of electrode thickness change rate due to charging and discharging> The coin-type battery prepared by the method described in the above <Preparation of Coin Battery> was placed in a thermostatic chamber at 25°C and charged at 0.2 mA / cm in the direction in which Li was absorbed in the evaluation electrode. 2 The battery was charged to 0.8 V at a current density of 0.05 mA / cm at 0.8 V. 2 After constant current and constant voltage charging, the battery was charged to a current density of 0.2 mA / cm 2 The battery was discharged to 2 V at a current density of 0.2 mA / cm. 2 The battery was charged to 0.8 V at a current density of 0.05 mA / cm at 0.8 V. 2 After constant-current constant-voltage charging was performed until the current density reached 0.8 V, the coin battery was disassembled, the negative electrode sheet in the charged state was taken out, and its thickness was measured. The thickness of the negative electrode sheet after charging to 0.8 V was divided by the thickness of the negative electrode sheet before the coin battery was made to calculate the rate of change in electrode thickness due to charging and discharging.

[0147] <Evaluation Results> The electrode thickness change rate with charge and discharge of the electrode using the niobium-containing oxide powder of Example 1-4 was 10.9%, that of Example 1-6 was 9.5%, the electrode thickness change rate of the electrode using the powder of Example 3-1 was 10.5%, that of Example 3-18 was 9.2%, that of Example 3-24 was 10.1%, and that of Example 3-30 was 10.1%. 2 Nb 10 O 29 The thickness change rate of the electrode using the niobium-containing oxide powder of the present invention with charging was 13.4%, and it was found that the electrode using the niobium-containing oxide powder of the present invention has a smaller thickness change with charging and discharging than the electrode using the niobium-containing oxide powder described in Patent Document 1. This effect is not described at all in Non-Patent Document 1, Non-Patent Document 2, and Patent Document 1. In addition, from the results of Example 1-4 and Example 1-6, it is considered that the effect of suppressing the electrode thickness change rate with charging and discharging of the electrode can be obtained similarly in Examples 1-1 to 1-3 and Examples 1-5 to 1-13 other than Example 1-4, and further, from the results of Example 3-1, Example 3-18, and Example 3-24, it is considered that the effect of suppressing the electrode thickness change rate with charging and discharging of the electrode can be obtained similarly in Examples 3-2 to 3-39 other than Example 3-1.

[0148] (All-solid-state secondary battery) [Example 4-1] In a glove box under an argon atmosphere, the niobium-containing oxide and sulfide solid electrolyte of Example 3-3, Li 6 P.S. 5 Cl powder (volume average particle size measured using a laser diffraction / scattering type particle size distribution analyzer: 6 μm) and a conductive agent, niobium-containing oxide: Li 6 P.S. 5 The materials were weighed out so that the mass ratio of Cl:conductive agent was 60:40:6, and mixed by stirring in an agate mortar and a planetary ball mill to obtain the negative electrode active material composition of Example 4-1. The obtained negative electrode active material composition was pressed (360 MPa) at room temperature for 10 minutes to produce pellets (molded bodies) with a diameter of 10 mm and a thickness of about 0.7 mm. A pellet-shaped electrode containing this negative electrode active material composition and a pellet-shaped solid electrolyte layer (Li 2 S:P 2 S 5 A lithium-indium alloy foil was laminated in this order as a counter electrode and a lithium-indium alloy foil was sandwiched between stainless steel current collectors to prepare an all-solid-state secondary battery. The evaluation results are shown in Table 9.

[0149] [Example 4-2] An all-solid-state secondary battery according to Example 4-2 was produced in the same manner as in Example 4-1, except that the niobium-containing oxide was changed to that of Example 3-13.

[0150] [Example 4-3] An all-solid-state secondary battery according to Example 4-3 was produced in the same manner as in Example 4-1, except that the niobium-containing oxide was changed to that of Example 3-38.

[0151] [Example 4-4] An all-solid-state secondary battery according to Example 4-4 was produced in the same manner as in Example 4-1, except that the niobium-containing oxide was changed to that of Example 3-39.

[0152] [Comparative Example 4-1] Except for using the niobium-containing oxide of Comparative Example 1-1, the negative electrode active material composition of Comparative Example 4-1 was obtained in the same manner as in Example 4-1, and then an all-solid-state secondary battery was produced.

[0153] The battery characteristics of the all-solid-state secondary batteries according to Examples 4-1 to 4-4 and Comparative Example 4-1 were evaluated. The evaluation results are shown in Table 9.

[0154] <Measurement of 1C charge / discharge rate characteristics> In a thermostatic chamber at 25°C, the all-solid-state secondary battery prepared by the above-mentioned method was charged to 0.5V with a current equivalent to 0.05C of the theoretical capacity of the niobium-containing oxide, with the direction in which Li was absorbed in the evaluation electrode being the charging direction, and further constant current constant voltage charging was performed in which charging was performed at 0.5V until the charging current became a current equivalent to 0.01C, and the charging capacity (mAh) was divided by the mass of the niobium-containing oxide to obtain the initial charging capacity (mAh / g). Then, constant current discharging was performed to discharge to 2V with a current equivalent to 0.05C. The discharge capacity (mAh) was divided by the mass of the niobium-containing oxide to obtain the initial discharging capacity (mAh / g). Next, charging was performed to 0.5V with a current equivalent to 1C of the theoretical capacity of the niobium-containing oxide, and the 1C charging capacity was obtained. The 1C rate charging rate (%) was calculated by dividing the 0.4C charging capacity by the initial charging capacity. Thereafter, the battery was discharged to 2 V at a current equivalent to 1 C of the theoretical capacity of the niobium-containing oxide, and the 1 C discharge capacity was calculated. The 1 C discharge capacity was divided by the initial discharge capacity to calculate the 1 C rate discharge ratio (%).

[0155] [Table 9]

[0156] <Evaluation Results> It was found that the electrodes using the niobium-containing oxide powder of the present invention in all-solid-state batteries also have excellent initial discharge capacity and 1C charge / discharge rate characteristics. It was also found that the 1C charge / discharge rate characteristics were further improved in Examples 4-3 and 4-4, which were surface-treated with lithium molybdate. It can be said that the niobium-containing oxides surface-treated with lithium molybdate according to Examples 4-3 and 4-4 have Mo localized on the surface due to their manufacturing method.

[0157] In Examples 3-1 to 3-39 and Examples 4-1 to 4-4, which used the niobium-containing oxide powder of the present invention in which a portion of Ti and / or Nb was replaced with a different element, the effect of improving the rate characteristics was observed regardless of the type of electricity storage device.

[0158] The niobium-containing oxide powder obtained by the present invention can improve the cycle capacity retention rate and discharge rate characteristics, so it is useful as an electrode active material for lithium-ion batteries, and can also improve the rate characteristics of all-solid-state batteries, so it is also useful as an electrode active material for all-solid-state secondary batteries. An electricity storage device using this niobium-containing oxide powder as an electrode active material is useful as a secondary battery for driving or backing up various devices such as automobiles and electronic devices, and for storing power at night in homes and offices. By providing electrode materials for lithium-ion batteries, such as non-aqueous electrolyte secondary batteries, to society, it can contribute to the achievement of Goal 12 (ensure sustainable consumption and production patterns), Goal 3 (ensure healthy lives and promote well-being for all at all ages), Goal 7 (ensure access to affordable, reliable, sustainable and modern energy for all), and Goal 11 (make cities and human settlements inclusive, safe, resilient and sustainable), out of the 17 goals of the Sustainable Development Goals (SDGs) established by the United Nations.

Claims

1. A niobium-containing oxide powder that satisfies the following formula (I), wherein the specific surface area of ​​the niobium-containing oxide powder is 2.3 m ２ / g or more 10m ２ / g or less of the niobium-containing oxide powder. A ａ Ti ２－ｘ M １ ｘ Nb １４－ｙ M ２ ｙ O ３９±ｚ (I) [During the ceremony, A is at least one element selected from the group consisting of Li and Na; M １ M ＩV , (M ＩＩＩ ０．５＋ｖ M Ｖ ０．５－ｖ ), (M Ｖ ０．６７＋ｖ M ＩＩ ０．３３－ｖ ), (M ＩＩＩ ０．６７＋ｖ M ＶＩ ０．３３－ｖ ), and (M ＩＩ ０．５＋ｖ M ＶＩ ０．５－ｖ ) selected from the group consisting of M ２ M Ｖ , (M ＩV ０．５＋ｗ M ＶＩ ０．５－ｗ ), (M ＶＩ ０．６７＋ｗ M ＩＩＩ ０．３３－ｗ ), and (M ＶＩ ０．７５＋ｗ M ＩＩ ０．２５－ｗ ) selected from the group consisting of M ＩＩ are each independently at least one divalent metal element; M ＩＩＩ are each independently at least one trivalent metallic element; M ＩV are each independently at least one tetravalent metallic element; M Ｖ are each independently at least one pentavalent metallic element; M ＶＩ are each independently at least one hexavalent metallic element; 0≦a≦6, −0.05≦v≦0.05, −0.05≦w≦0.05, 0≦x<2, 0≦y<14, 0≦z≦1.

2. The niobium-containing oxide powder according to claim 1, wherein the niobium-containing oxide powder satisfies the following formula (II): A ａ Till ２－ｘ M １ａ ｘ N﹂ １４－ｙ M ２ａ ｙ Oh ３９±ｚ (II) [During the ceremony, A is the same as in formula (I), M １ａ is at least one tetravalent metallic element selected from the group consisting of Zr, Si, Ge, and Sn; M ２ａ is at least one pentavalent metallic element selected from the group consisting of V and Ta; a, x, y, and z are the same as those in formula (I).

3. The niobium-containing oxide powder according to claim 1, wherein the niobium-containing oxide powder satisfies any one of the following formulas (III) to (IX). A ａ Ti ２－ｘ (M ＩＩＩ ０．５＋ｖ M Ｖ ０．５－ｖ ) ｘ Nb １４ O ３９±ｚ (III) A ａ Ti ２－ｘ (M Ｖ ０．６７＋ｖ M ＩＩ ０．３３－ｖ ) ｘ Nb １４ O ３９±ｚ (IV) A ａ Ti ２－ｘ (M) ＩＩＩ ０．６７＋ｖ M ＶＩ ０．３３－ｖ ) ｘ Nb １４ O ３９±ｚ (V) A ａ Till ２－ｘ (M) ＩＩ ０．５＋ｖ M ＶＩ ０．５－ｖ ) ｘ N﹂ １４ Oh ３９±ｚ (VI) A ａ Ti ２ Nｺ １４-y (M) ＩV ０．５＋ｗ M ＶＩ ０．５－ｗ ) y O ３９±ｚ (VII) _ ａ () ２ b １４-y (* ＶＩ ０．６７＋ｗ * ＩＩＩ ０．３３－ｗ ) ｙ . ３９±ｚ (().|) A ａ Ti ２ Nb １４-y (M ＶＩ ０．７５＋ｗ M ＩＩ ０．２５－ｗ ) ｙ O ３９±ｚ (IX) [During the ceremony, A, M ＩＩ , M. ＩＩＩ , M. ＩV , M. Ｖ , and M ＶＩ is the same as in formula (I), a, v, w, and z are the same as in formula (I); 0<x<2, 0<y<14.

4. M ＩＩ are each independently at least one divalent metallic element selected from the group consisting of Mg, Ca, Cu, and Zn; M ＩＩＩ are each independently at least one trivalent metallic element selected from the group consisting of Al, Ga, Fe, and Cr; M ＩV are each independently at least one tetravalent metallic element selected from the group consisting of Zr, Si, Ge, and Sn; M Ｖ are each independently at least one pentavalent metallic element selected from the group consisting of Nb, V, and Ta; M ＶＩ The niobium-containing oxide powder according to claim 1 or 3, wherein is at least one hexavalent metallic element selected from the group consisting of Mo and W.

5. The niobium-containing oxide powder according to any one of claims 1 to 3, characterized in that the D50 of primary particles corresponding to a volume cumulative of 50% in a volume-based particle size distribution by a laser diffraction scattering method is 0.25 μm or more and 4.5 μm or less. The niobium-containing oxide powder.

6. The niobium-containing oxide powder according to any one of claims 1 to 3, characterized in that the D90 of primary particles corresponding to 90% of the volume cumulative in the volume-based particle size distribution by the laser diffraction scattering method of the niobium-containing oxide powder is 20 μm or less. The niobium-containing oxide powder.

7. The niobium-containing oxide powder according to any one of claims 1 to 3, characterized in that at least one metal element selected from Mo and Ce is localized and present on the surface of the niobium-containing oxide particle.

8. The niobium-containing oxide powder according to claim 7, characterized in that the content (mass%) of at least one metal element selected from Mo and Ce present on the particle surface as determined by X-ray fluorescence analysis (XRF) is 0.01 to 1.

5.

9. An electrode for an electricity storage device, comprising the niobium-containing oxide powder according to any one of claims 1 to 3 as an active material.

10. A negative electrode active material composition for a non-aqueous electrolyte storage device, comprising the niobium-containing oxide powder according to any one of claims 1 to 3 and an inorganic solid electrolyte.

11. A non-aqueous electrolyte electricity storage device comprising the electrode according to claim 9.

12. 11. An all-solid-state secondary battery comprising a positive electrode layer, a negative electrode layer, and a solid electrolyte layer, the negative electrode layer being a layer containing the negative electrode active material composition according to claim 10.

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