JP2017134972A - Method for producing negative electrode active material for secondary battery - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for producing a negative electrode active material for a secondary battery which can effectively shorten a heat treatment time even in a production method by a solid phase method.SOLUTION: The method for producing a negative electrode active material for a secondary battery by a solid phase method includes: a steps (I) in which, after adding a niobium compound to a titanium compound aqueous solution to obtain a suspension, the resulting suspension is heated and stirred to obtain a suspension containing a composite having a titanium oxide sol film formed on a surface of the niobium compound; and a step (II) of obtaining a titanium niobium oxide by solid-liquid separating the obtained suspension to obtain a complex as a solid content and then calcining the obtained complex.SELECTED DRAWING: None

Description

  The present invention relates to a method for producing a negative electrode active material for a secondary battery by a solid phase method including a step of obtaining a titanium niobium oxide.

  Conventionally, the use of graphite as a negative electrode for lithium ion batteries has been widespread. Such graphite has an operating potential in the vicinity of 0.1 to 0.3 V on the basis of lithium, and plays a large role in realizing higher voltage and higher energy density of the lithium ion battery.

  On the other hand, since the operating potential of such graphite is also near the deposition potential of metallic lithium, when the battery is overcharged, metallic lithium leaking from the immobile film on the graphite surface crystallizes toward the counter electrode and dendrites are generated. End up. Further, in the discharge process, the dendrite root part elutes and the tip part separates from the graphite surface and remains in the battery. The metallic lithium that remains in the electrolyte and floats is also called dead lithium, and it becomes very active micro metallic lithium, which not only lowers the charge / discharge efficiency but also causes internal short circuits and heat generation in the battery. There is also a risk of causing this.

Where To avoid the occurrence of generation or dead lithium dendrites, the material working potential of the negative electrode is more than 1V relative to lithium is required, for example, Non-Patent Document 1, Chitan'niobu oxide (TiNb ₂ O _7, Ti ₂ Nb ₁₀ O ₂₉ ) has been reported to show a high capacity of 250 to 280 mAh / g in a potential range of 1 V or more based on lithium. Such a titanium niobium oxide operates at a potential equivalent to that of lithium titanate (Li ₄ Ti ₅ O ₁₂ ) having a spinel structure, and exhibits a higher capacity than lithium titanate, so that it can be used for future lithium ion secondary batteries. The development is being promoted as a promising material to carry the negative electrode active material.

  By the way, titanium niobium oxide has a problem that charge / discharge characteristics (rate characteristics) under a high current density are low because all titanium in the crystal structure is +4 valent and does not have 3d electrons responsible for electrical conduction. . For this reason, it is also known that it is effective to refine the titanium niobium oxide in enhancing the charge / discharge characteristics. Such titanium niobium oxide production methods are roughly classified into those using hydrothermal methods, those using solid phase methods, and those using complex polymerization methods. Since it is simple, a production method by a solid phase method is widely adopted.

For example, in Patent Document 1, monoclinic TiNb ₂ O ₇ and Ti ₂ Nb ₁₀ O ₂₉ obtained by a solid phase method are heat-treated at 1000 to 1400 ° C. for 24 hours in an air atmosphere, then pulverized, and again A method of performing heat treatment at the same temperature for 24 hours is disclosed. Patent Document 2 discloses a method for producing TiNb ₂ O ₇ which is heat-treated at 1000 ° C. for 12 hours in an air atmosphere, then pulverized and heat-treated at 1100 ° C. for 12 hours.

JP 2010-287496 A JP, 2015-84321, A

Jian-Tao Han et al, “New Anode Framework for Rechargeable Lithium Batteries”, CHEMISTRY OF MATERIALS, 2011, Vol. 23, p2027-2029.

  However, in any of the production methods described in the literature, long-term heat treatment that repeats the firing step and the pulverization or mixing step is unavoidable, thus ensuring good performance as a negative electrode active material for secondary batteries. However, it is still difficult to reduce the heat treatment time even though the manufacturing method is based on the solid phase method.

  Therefore, the subject of this invention is providing the manufacturing method of the negative electrode active material for secondary batteries which can aim at shortening of heat processing time effectively even if it is the manufacturing method by a solid-phase method.

  Therefore, the present inventors have made various studies. After adding the niobium source as an aqueous solution to the titanium source, through the step of heating and stirring this, even if the solid phase method is used, the firing step and the pulverization and mixing are performed. The heat treatment time can be shortened without repeating the steps, and a negative electrode active material for a secondary battery that can exhibit equivalent or better performance than a negative electrode active material obtained by a conventional manufacturing method can be obtained. As a result, the present invention has been completed.

That is, the present invention provides a composite in which a niobium compound is added to an aqueous titanium compound solution to obtain a suspension, and then the obtained suspension is heated and stirred to form a titanium oxide sol film on the surface of the niobium compound. Obtaining a suspension comprising: (I),
Step of obtaining the titanium niobium oxide by solid-liquid separation of the obtained suspension to obtain a composite as a solid content and then firing the obtained composite (II)
The manufacturing method of the negative electrode active material for secondary batteries by a solid-phase method is provided.

  According to the production method of the present invention, even in a method for producing a negative electrode active material for a secondary battery by a solid phase method including a step of obtaining a titanium niobium oxide, the heat treatment can be effectively shortened and the operation is simplified. Thus, good performance can be secured in the obtained battery.

Hereinafter, the present invention will be described in detail.
In the method for producing a negative electrode active material for a secondary battery according to the present invention, a niobium compound is added to an aqueous titanium compound solution to obtain a suspension, and the resulting suspension is heated and stirred to obtain niobium. The step (I) of obtaining a suspension containing a complex in which a titanium oxide sol film is formed on the surface of the compound, and the obtained suspension are subjected to solid-liquid separation to obtain a complex as a solid content. A step of obtaining a titanium niobium oxide by firing the composite (II),
Is provided.

  Step (I) is a composite in which a niobium compound is added to an aqueous titanium compound solution to obtain a suspension, and then the resulting suspension is heated and stirred to form a titanium oxide sol film on the surface of the niobium compound. Is a step of obtaining a suspension containing Thus, in the present invention, the titanium compound is used as an aqueous solution. Such a titanium compound is a titanium source for obtaining a titanium niobium oxide in a later step. Further, in the composite contained in the obtained suspension, the titanium oxide sol coating formed on the surface of the niobium compound is converted into an anatase type titanium oxide sol. Is a compound that can be produced as

Examples of the titanium compound that can be used include one or more selected from titanium alkoxide (titanium isopropoxide, etc.), titanium salt (titanium sulfate, titanium nitrate, etc.), and titanium chloride (titanium tetrachloride, etc.). It is done. Of these, titanyl sulfate is preferable from the viewpoint of effectively shortening the reactivity, operability, and heat treatment.
The content of the titanium compound may vary depending on the type of the titanium compound, but is preferably 1 to 80% by mass, more preferably 10 to 70% by mass in the titanium compound aqueous solution used in the step (I). is there.

  In addition, such a titanium compound is inevitably mixed, and a part thereof is a different metal M other than titanium and niobium (M is Zr, Hf, V, Ta, Fe, Bi, Sb, As, P, Cr). And at least one selected from the group consisting of Mo, W, B, Na, Mg, Al, and Si. The content of the foreign metal (M) is preferably 33% by mass or less, more preferably 15% by mass or less, and further preferably 7% by mass in the titanium compound from the viewpoint of securing better battery physical properties. % Or less.

  The content of water in the titanium compound aqueous solution used in the step (I) is required from the viewpoint of ensuring dispersibility and reactivity in the suspension of the niobium compound added later and other components used as necessary. In a titanium compound aqueous solution, Preferably it is 20-99 mass%, More preferably, it is 30-90 mass%.

  The niobium compound added to the titanium compound aqueous solution is a niobium source for obtaining a titanium niobium oxide in a later step, and is a compound capable of forming a titanium oxide sol film on the surface of the niobium compound in step (I). In step (I), by adding the niobium compound to the titanium compound aqueous solution in this manner, a titanium oxide sol film can be favorably formed on the surface of the niobium compound, and shortening of the heat treatment can be promoted.

Examples of niobium compounds that can be used include niobium hydroxide (Nb (OH) ₅ , Nb (OH) ₂ , Nb (OH) ₄ ), niobium oxide (Nb ₂ O ₅ , NbO ₂ , Nb ₂ O ₃ , NbO, etc.) 1 or 2 selected from niobium pentachloride, niobium ammonium oxalate, niobium oxychloride, niobium bromide, niobium fluoride, and niobium oxide sol. Among these, niobium oxide (V) (Nb ₂ O ₅ ) is preferable from the viewpoint of effectively shortening the reactivity, operability, and heat treatment.

  The amount of the niobium compound added is preferably a molar ratio of niobium to titanium (Nb / Ti) in the suspension obtained in step (I), preferably 1.2 to 5.8, more preferably 1 .3 to 5.6, and more preferably 1.5 to 5.5. More specifically, when the titanium niobium oxide obtained in the present invention is represented by the formula (1) described later, the amount of niobium compound added is niobium relative to titanium in the suspension obtained in step (I). The molar ratio (Nb / Ti) is preferably 1.2 to 2.4, more preferably 1.3 to 2.3, and still more preferably 1.5 to 2.1. When the titanium niobium oxide obtained in the present invention is represented by the formula (2) described later, the amount of niobium compound added is the molar amount of niobium with respect to titanium in the suspension obtained in step (I). The ratio (Nb / Ti) is 4.5 to 5.8, more preferably 4.7 to 5.6, and still more preferably 4.8 to 5.5. What is necessary is just to add a niobium compound to a titanium compound aqueous solution so that it may become such an amount in the said suspension liquid.

  The pH of the suspension in the step (I) is preferably 0 to 4 and more preferably 0 to 4 from the viewpoint of obtaining a desired titanium niobium oxide as a target product through the step (II) described later. 2. In addition, you may use a pH adjuster suitably.

Next, in step (I), the obtained suspension is heated and stirred. Thereby, the titanium compound can be thermally hydrolyzed satisfactorily, and a titanium oxide sol film can be effectively formed on the surface of the niobium compound. From the viewpoint of effectively promoting the hydrolysis of the titanium compound, the heating and stirring temperature is preferably 30 to 100 ° C, more preferably 40 to 100 ° C. Moreover, from the same viewpoint, the stirring speed in the heating and stirring is preferably 200 to 800 rpm, more preferably 400 to 800 rpm. Furthermore, from the same viewpoint, the heating and stirring time is preferably 0.2 to 18 hours, and more preferably 0.5 to 14 hours. For heating and stirring, for example, an ordinary stirring device capable of mixing the suspension, such as a device equipped with a magnetic stirrer or a rotary blade, can be used.
As described above, in the step (I), a composite in which a titanium oxide sol film is formed on the surface of the niobium compound can be obtained as a suspension containing this by subjecting the suspension to heating and stirring.

  Step (II) is a step of solid-liquid separation of the suspension obtained in step (I) to obtain a composite as a solid content, and then firing the obtained composite to obtain a titanium niobium oxide. . Examples of the apparatus used for solid-liquid separation include a vacuum filter, a filter press, and a centrifugal filter. Especially, it is preferable to use a vacuum filter from a viewpoint of obtaining solid content efficiently.

  Moreover, the composite which is the separated solid content is 8 to 60 mass parts in advance with respect to 1 mass part of the dry mass of the composite before firing from the viewpoint of effectively removing impurities such as anion components. It is preferable to wash with parts by mass of washing water. The amount of washing water is more preferably 10 to 50 parts by mass, and still more preferably 10 to 40 parts by mass with respect to 1 part by mass of the dry mass of the composite. The temperature of the washing water is preferably 10 to 80 ° C., more preferably 10 to 70 ° C., from the viewpoint of effectively increasing the discharge capacity of a battery using the obtained titanium niobium oxide as a negative electrode material.

  When the composite is washed, it is preferably dried in advance before firing. Examples of the drying means include constant temperature drying and vacuum drying. Of these, isothermal drying is preferred from the viewpoint of ease of operation and the need for special equipment. When performing such constant temperature drying, various conditions that can be usually employed may be appropriately selected. From the viewpoint of effectively shortening the drying time, the drying temperature is preferably 100 to 200 ° C., more preferably. 150-200 ° C. The drying time is preferably 15 to 120 minutes, more preferably 30 to 60 minutes.

  Next, in the step (II), the composite obtained as the solid content is fired. Thereby, a titanium niobium oxide having high crystallinity and having a crystallite diameter controlled within an appropriate range can be obtained. The firing temperature is preferably 600 to 1250 ° C., more preferably 600 to 1200 ° C. from the viewpoint of obtaining a titanium niobium oxide having an appropriate range of crystallite diameters while increasing the crystallinity of the obtained titanium niobium oxide. Yes, more preferably 700 to 1200 ° C. Moreover, from the same viewpoint, the firing time is preferably 0.3 to 7 hours, and more preferably 0.5 to 6 hours. Note that the firing atmosphere needs to be fired in an oxidizing atmosphere in order to set the valence of titanium to +4, and firing in an air atmosphere is most preferable from the viewpoint of simplicity and economy.

The titanium niobium oxide obtained by the present invention is specifically a compound represented by the following formula (1) or (2) and having a monoclinic structure.
Ti _1-x M _x Nb ₂ O ₇ (1)
(In formula (1), M is at least one selected from the group consisting of Zr, Hf, V, Ta, Fe, Bi, Sb, As, P, Cr, Mo, W, B, Na, Mg, Al, and Si. X represents a number satisfying 0 ≦ x <0.1.)
_{Ti 2-y M y Nb 10} O 29 ··· (2)
(In the formula (2), M is at least one selected from the group consisting of Zr, Hf, V, Ta, Fe, Bi, Sb, As, P, Cr, Mo, W, B, Na, Mg, Al and Si. Y represents a number satisfying 0 ≦ y <0.2.)
The titanium niobium oxide may contain a mixed phase of Ti ₂ Nb ₁₀ O ₂₉ and / or TiO ₂ when represented by the formula (1) within a range that does not impair the effects of the present invention. When represented by (2), a mixed phase of TiNb ₂ O ₇ and / or TiO ₂ may be included. The content of these contaminated phases is preferably 5% by mass or less, more preferably 4% by mass or less, and further preferably 3% by mass in the titanium niobium oxide from the viewpoint of exhibiting excellent charge / discharge characteristics. It is as follows. In addition, the content rate of this contaminating phase means the quantitative value calculated | required about the obtained titanium niobium oxide by applying the X-ray diffraction-Riet belt method.

Chitan'niobu oxide obtained by the present invention, from the viewpoint of charge and discharge efficiency and the battery capacity to obtain a high battery, the BET specific surface area, is preferably 1.0 m ² / g or more, more preferably 1.2 m ² / g or more, more preferably 1.5 m ² / g or more. The upper limit of the BET specific surface area is not particularly limited, but is usually 10 m ² / g or less, preferably 7 m ² / g or less, more preferably 5 m ² / g or less.

The titanium niobium oxide obtained by the present invention has a crystallite diameter of preferably 25 to 250 nm, more preferably 25 to 220 nm, and high crystallinity. Moreover, the average particle diameter of a titanium niobium oxide is 50-900 nm, More preferably, it is 50-800 nm. The crystallite diameter of the titanium niobium oxide means a value obtained by applying Scherrer's equation for an X-ray diffraction profile having a diffraction angle 2θ range of 10 ° to 80 ° by Cu-kα rays. Here, when the obtained titanium niobium oxide is expressed by, for example, the above formula (1) and contains a contaminating phase such as TiO ₂ , those contaminating phases calculated based on the crystal structure parameter (ICDD database) The value obtained by applying Scherrer's equation to the X-ray diffraction profile of TiNb ₂ O ₇ obtained by subtracting the X-ray diffraction profile from the X-ray diffraction profile of the obtained titanium niobium oxide mixture is meant.

The titanium niobium oxide can be used as a negative electrode active material for a secondary battery as it is, but carbon is supported on the surface of the titanium niobium oxide to ensure more sufficient electron conductivity and excellent battery characteristics. From the viewpoint of expression, it is preferable to add a carbon source such as glucose, saccharose, fructose, dextrin, starch, polyethylene glycol, polyvinyl alcohol, carboxymethyl cellulose, carbon black, fibrous carbon, and the like, and calcinate. Under the present circumstances, the addition amount of a carbon source is a carbon atom conversion amount, and is 0.5-10 mass% in a negative electrode active material for secondary batteries, More preferably, it is 1-8 mass%.
The firing conditions are preferably performed under an inert gas atmosphere or under reducing conditions, and the firing temperature is preferably 500 to 800 ° C, more preferably 550 to 750 ° C, and further preferably 600 to 750. ° C. The firing time is preferably 10 minutes to 5 hours, more preferably 30 minutes to 4 hours.
In addition, the carbon amount which exists in the negative electrode active material for secondary batteries can be confirmed as a carbon amount measured using the carbon and sulfur analyzer.

  A method for producing a secondary battery using the obtained titanium niobium oxide as a negative electrode active material is not particularly limited, and any known method can be used. For example, the negative electrode active material is mixed with additives such as a binder and a solvent to obtain a coating liquid. At this time, if necessary, a conductive additive may be further added and mixed. The binder is not particularly limited, and any known agent can be used. Specific examples include polytetrafluoroethylene, polyvinylidene fluoride, polyvinyl chloride, and ethylene propylene diene polymer. Moreover, it does not specifically limit as this conductive support agent, Any well-known agents other than graphite can be used. Specific examples include acetylene black, ketjen black, and fibrous carbon. Subsequently, this coating liquid is apply | coated on negative electrode collectors, such as copper foil, and it is made to dry and is set as a negative electrode.

  The obtained negative electrode active material for a secondary battery is useful in that it exhibits a very excellent discharge capacity and cycle specification as a negative electrode for a secondary battery such as a lithium ion battery or a sodium ion battery. A secondary battery to which such a negative electrode can be applied is not particularly limited as long as it has a positive electrode, a negative electrode, an electrolytic solution, and a separator as essential components.

  Here, the positive electrode is not particularly limited in its material configuration as long as it can release a predetermined metal ion such as lithium ion or sodium ion at the time of charging and can be occluded at the time of discharging. Things can be used. For example, it is preferable to suitably use various olivine compounds obtained by hydrothermal reaction of the raw materials.

  The electrolytic solution is obtained by dissolving a supporting salt in an organic solvent. The organic solvent is not particularly limited as long as it is an organic solvent that is usually used for an electrolyte of a secondary battery such as a lithium ion battery or a sodium ion battery. For example, carbonates, halogenated hydrocarbons, ethers, ketones , Nitriles, lactones, oxolane compounds and the like can be used.

The type of the supporting salt is not particularly limited. For example, in the case of a lithium ion secondary battery, an inorganic salt selected from LiPF ₆ , LiBF ₄ , LiClO ₄ , LiAsF ₆ , a derivative of the inorganic salt, LiSO ₃ CF ₃ , LiC (SO ₃ CF ₃ ) ₂ , LiN (SO ₃ CF ₃ ) ₂ , LiN (SO ₂ C ₂ F ₅ ) ₂ and LiN (SO ₂ CF ₃ ) (SO ₂ C ₄ F ₉ ) It is preferably at least one of an organic salt and a derivative of the organic salt. In the case of a sodium ion secondary battery, for example, an inorganic salt selected from NaPF ₆ , NaBF ₄ , NaClO ₄ and NaAsF ₆ , a derivative of the inorganic salt, NaSO ₃ CF ₃ , NaC (SO ₃ CF ₃ ) ₂ and NaN ( At least one organic salt selected from SO ₃ CF ₃ ) ₂ , NaN (SO ₂ C ₂ F ₅ ) ₂ and NaN (SO ₂ CF ₃ ) (SO ₂ C ₄ F ₉ ), and a derivative of the organic salt Preferably there is.

  The separator plays a role of electrically insulating the positive electrode and the negative electrode and holding the electrolytic solution. For example, a porous synthetic resin film, particularly a polyolefin polymer (polyethylene, polypropylene) porous film may be used.

  EXAMPLES Hereinafter, although this invention is demonstrated concretely based on an Example, this invention is not limited to these Examples.

<Identification of the formation phase in the composite and measurement of the content, and evaluation of the crystallite size of the titanium niobium oxide>
Described later, examples and compositions obtained in Comparative Example for (Chitan'niobu oxide) constituent phases of Chitan'niobu compound by X-ray diffraction analysis _{(TiNb 2 O 7, Ti 2} Nb 10 O 29, TiO 2 and amorphous ) And the content of each constituent phase was determined by applying the X-ray diffraction-Rietbelt method. The amorphous content was determined by subtracting the total content (% by mass) of the crystal phase from 100% by mass.
Next, by applying the Scherrer formula to the crystallite diameter of TiNb ₂ O ₇ or Ti ₂ Nb ₁₀ O ₂₉ , respectively, to the X-ray diffraction profile (full angle) (based on JIS K 0131 “X-ray diffraction analysis general rules”) Asked. In the evaluation of the crystallite diameter, when there are a plurality of constituent phases of the titanium niobium oxide, TiNb obtained by subtracting the X-ray diffraction profile of the impurity phase other than the main phase from the X-ray diffraction profile of the obtained titanium niobium oxide. X-ray diffraction profiles of ₂ O ₇ single phase or Ti ₂ Nb ₁₀ O ₂₉ single phase were used. Note that the X-ray diffraction profile of the contaminating phase used for the calculation of the content ratio and the crystallite size was obtained by calculation using the crystal structure parameters of the ICDD database. The obtained results are shown in Tables 1 and 2.
Sample preparation: Pressed at a pressure of 70 kg with a powder sample molding machine (TK-750 manufactured by Tokyo Kagaku) X-ray: Cu-kα (tube voltage-current = 35 kV-350 mA)
Scanning method: Step scan (step size 0.023 °, 0.13 sec / step)
Measurement range (2θ): 10 ° -80 °
Measuring device: D8 Advance (Bruker AXS Co., Ltd.)
Analysis software: DIFFRAC ^plus TOPAS (ver. 3) (Bruker AXS Co., Ltd.)

<< Measurement of BET specific surface area of titanium niobium oxide >>
Using a specific surface area measuring apparatus (FlowSorbIII 2305, manufactured by Shimadzu Corporation), the BET specific surface area of the titanium niobium oxide obtained in Examples and Comparative Examples was measured by a nitrogen adsorption method. The obtained results are shown in Tables 1 and 2.

<< Manufacture of Negative Electrode Active Material for Secondary Battery with TiNb ₂ O ₇ as Main Phase >>
[Example 1]
10 mL of water was put into a beaker, and 7.50 g of TiOSO ₄ (purity 32.9%, manufactured by Teika Co., Ltd.) was dissolved therein (TiOSO ₄ / water mass ratio corresponding to 0.75) to obtain an aqueous solution A1. . After adding 8.219 g (Nb / Ti molar ratio corresponding to 2.0) of Nb ₂ O ₅ (manufactured by Kanto Chemical Co., Inc., purity 99.95%) to the obtained aqueous solution A1, a hot stirrer (AS ONE RSH-4DN) was used, the stirrer in the beaker was rotated at 500 rpm, and stirred at 100 ° C. for 1 hour to obtain a suspension A1.
Subsequently, the suspension A1 was subjected to suction filtration to obtain a complex A. After washing 1 part by mass of the complex A1 with 10 parts by mass of water, the complex A1 was dried at 150 ° C. for 30 minutes using a constant temperature dryer.

The composite A1 after drying was fired at 1150 ° C. for 4 hours in an air atmosphere to obtain a titanium niobium oxide (TiNb ₂ O ₇ ) represented by the above formula (1).
Then, to 3 g of the obtained titanium niobium oxide, 0.240 g of glucose (corresponding to 3% by mass in terms of carbon atom in the negative electrode active material), 2 g of water, and 8 ml of ethanol were added, and a ball mill (planet type, Fritsch Japan ( After mixing for 15 minutes with P-5) manufactured by Co., Ltd., firing was performed at 750 ° C. for 1 hour in a nitrogen atmosphere, and the negative electrode active material A1 for secondary battery (TiNb ₂ O ₇ / Ti ₂ Nb ₁₀ O ₂₉ = 98 mass) % / 2% by mass, amount of carbon = 2.9% by mass).

[Example 2]
The negative electrode active material B1 for secondary battery (TiNb ₂ O ₇ = 100% by mass, in the same manner as in Example 1 except that the stirring condition in the hot stirrer (RSH-4DN) was stirred at 40 ° C. for 12 hours. Amount = 3.0% by mass).

[Example 3]
The negative electrode active material C1 for secondary battery C1 (TiNb ₂ O ₇ = 100% by mass), except that the stirring condition in the hot stirrer (RSH-4DN) was stirred at 40 ° C. for 2 hours, as in Example 1. Amount = 3.1% by mass).

[Example 4]
The Nb ₂ O ₅ added to the aqueous solution A1 was 6.572 g (Nb / Ti molar ratio corresponding to 1.6), and the stirring conditions with a hot stirrer (RSH-4DN) were set at 40 ° C. for 2 hours. In the same manner as in Example 1, the negative electrode active material D1 for secondary battery (TiNb ₂ O ₇ / Ti ₂ Nb ₁₀ O ₂₉ / TiO ₂ = 92 mass% / 4 mass% / 4 mass%, the amount of carbon = 3. 0% by mass) was obtained.

[Example 5]
Anode active material E1 for secondary battery (TiNb ₂ O ₇ = 100 mass%) in the same manner as in Example 1 except that the amount of water used in the aqueous solution A1 was 750 mL (TiOSO ₄ / water mass ratio corresponds to 0.01). , Carbon amount = 3.1 mass%).

[Example 6]
The stirring conditions with a hot stirrer (RSH-4DN) were stirring at 40 ° C. for 12 hours, and the dried composite F1 was the same as in Example 1 except that it was fired at 800 ° C. for 4 hours in an air atmosphere. for the next battery negative electrode active material F1 (TiNb ₂ O ₇ = 100 wt%, weight = 3.0% by weight of carbon) was obtained.

[Comparative Example 1]
24.324 g of TiO ₂ (powder, manufactured by Kanto Chemical Co., Inc., grade 18.5% purity), Nb (OH) ₅ (powder, HC Starck, purity 92.4%) 115.552 g, and 100 g of water Was put into a beaker and then mixed for 30 minutes with a magnetic stirrer to obtain a mixed solution G1. The obtained mixed solution G1 was wet-mixed at 25 ° C. for 18 hours in a ball mill (rotation speed 120 rpm, inner diameter 7.6 cm, medium φ1 mm ZrO ₂ ball, medium filling rate 70%) to obtain a mixture G1.
The obtained mixture G1 was spray-dried by a spray drying method (spray dryer: MDL-050M manufactured by Fujisaki Electric Co., Ltd.), and the obtained powder was calcined at 1200 ° C. for 12 hours in an air atmosphere to obtain titanium niobium oxide ( TiNb ₂ O ₇ ) G1 was obtained.
Then, 0.237 g of glucose (corresponding to 3% by mass in terms of carbon atom in the negative electrode active material), 2 g of water, and 8 ml of ethanol were added to 3 g of the titanium niobium oxide G1, and a ball mill (planet type, Fritsch) was added. After mixing for 60 minutes in Japan Co., Ltd. P-5), it was fired at 700 ° C. for 1 hour in a nitrogen atmosphere, and the secondary battery negative electrode active material G1 (TiNb ₂ O ₇ = 100 mass%, amount of carbon) = 3.1% by mass).

[Comparative Example 2]
The negative electrode active material for secondary batteries H1 (TiNb ₂ O ₇ / Ti ₂ Nb ₁₀ O ₂₉₎ was used in the same manner as in Example 1 except that the stirring conditions in the hot stirrer (RSH-4DN) were changed to 20 ° C. for 12 hours. / TiO ₂ / amorphous = 59% by mass / 4% by mass / 8% by mass / 29% by mass, and the amount of carbon = 2.9% by mass).

[Comparative Example 3]
The negative electrode active material I1 for secondary battery I1 (TiNb ₂ O ₇ / Ti ₂ Nb ₁₀₎ was used in the same manner as in Example 1 except that the stirring condition in the hot stirrer (RSH-4DN) was 0.1 hour at 40 ° C. O ₂₉ / TiO ₂ / amorphous = 3 mass% / 3 mass% / 4 mass% / 90 mass%, carbon amount = 3.0 mass%).

[Comparative Example 4]
The Nb ₂ O ₅ added to the aqueous solution A1 was 4.124 g (Nb / Ti molar ratio was equivalent to 1.0), and the stirring conditions with a hot stirrer (RSH-4DN) were set at 40 ° C. for 2 hours. In the same manner as in Example 1, the negative electrode active material J1 for secondary battery (TiNb ₂ O ₇ / Ti ₂ Nb ₁₀ O ₂₉ / TiO ₂ / amorphous = 67 mass% / 3 mass% / 3 mass% / 27 mass) %, Amount of carbon = 3.1% by mass).

[Comparative Example 5]
The negative electrode active material K1 for secondary batteries (TiNb ₂ O ₇ / Ti ₂ Nb) was used in the same manner as in Example 1 except that the amount of water used for the aqueous solution A1 was 7500 mL (TiOSO ₄ / water mass ratio was equivalent to 0.001). ₁₀ O ₂₉ / TiO ₂ / amorphous = 56 mass% / 6 mass% / 5 mass% / 33 mass%, carbon amount = 3.0 mass%).

[Comparative Example 6]
The stirring condition with a hot stirrer (RSH-4DN) was 12 hours at 40 ° C., and the dried composite L1 was calcined at 750 ° C. for 4 hours in an air atmosphere. Secondary battery negative electrode active material L1 (TiNb ₂ O ₇ / Ti ₂ Nb ₁₀ O ₂₉ / TiO ₂ / amorphous = 59 mass% / 10 mass% / 12 mass% / 19 mass%, amount of carbon = 3.0 Mass%).

_"Ti 2 Nb10O29 preparation of the negative electrode active material for a secondary battery as a main phase an"
[Example 7]
10 mL of water was put into a beaker, and 7.50 g of TiOSO ₄ was dissolved therein (corresponding to a TiOSO ₄ / water mass ratio of 0.75) to obtain an aqueous solution A2. After adding 20.542 g of Nb ₂ O ₅ (corresponding to Nb / Ti molar ratio equal to 5.0) to the obtained aqueous solution A2, the stirrer in the beaker was rotated at 500 rpm using a hot stirrer (RSH-4DN). And stirred at 100 ° C. for 1 hour to obtain a suspension A2.
Subsequently, the suspension A2 was subjected to suction filtration to obtain a complex A2. After washing 1 part by mass of the complex A2 with 10 parts by mass of water, the complex A2 was dried at 150 ° C. for 30 minutes using a constant temperature dryer.

The dried composite A2 was fired at 1150 ° C. for 4 hours in an air atmosphere to obtain titanium niobium oxide A2 (Ti ₂ Nb ₁₀ O ₂₉ ) represented by the above formula (2).
Then, 0.240 g of glucose (corresponding to 3% by mass in terms of carbon atom in the negative electrode active material), 2 g of water, and 8 ml of ethanol were added to 3 g of the obtained titanium niobium oxide A2, and a ball mill (planet type, Fritsch Japan) was added. After mixing for 15 minutes with P-5 manufactured by Co., Ltd., the mixture was baked at 700 ° C. for 1 hour in a nitrogen atmosphere, and the secondary battery negative electrode active material A2 (Ti ₂ Nb ₁₀ O ₂₉ / TiNb ₂ O ₇ = 99). Mass% / 1 mass%, amount of carbon = 3.0 mass%).

[Example 8]
The secondary battery negative electrode active material B2 (Ti ₂ Nb ₁₀ O ₂₉ = 100% by mass) was the same as in Example 7 except that the stirring condition with the hot stirrer (RSH-4DN) was 12 hours at 40 ° C. Carbon amount = 2.9% by mass).

[Example 9]
The negative electrode active material for secondary battery C2 (Ti ₂ Nb ₁₀ O ₂₉ = 100% by mass) was the same as in Example 7 except that the stirring condition with the hot stirrer (RSH-4DN) was changed to 40 ° C. for 2 hours. Carbon amount = 3.0% by mass).

[Example 10]
The Nb ₂ O ₅ added to the aqueous solution A2 was 22.192 g (Nb / Ti molar ratio was equivalent to 5.4), and the stirring conditions with a hot stirrer (RSH-4DN) were set at 40 ° C. for 2 hours. Then, a negative electrode active material D2 for secondary battery (Ti ₂ Nb ₁₀ O ₂₉ / TiO ₂ = 96 mass% / 4 mass%, carbon amount = 3.1 mass%) was obtained in the same manner as in Example 7.

[Example 11]
Anode active material E2 for secondary battery (Ti ₂ Nb ₁₀ O ₂₉ = 100) in the same manner as in Example 7, except that the amount of water used for the aqueous solution A2 was changed to 750 mL (TiOSO ₄ / water mass ratio corresponding to 0.01). Mass%, amount of carbon = 3.0 mass%).

[Example 12]
The stirring conditions with a hot stirrer (RSH-4DN) were stirring at 40 ° C. for 12 hours, and the dried composite F2 was the same as in Example 7 except that it was fired at 800 ° C. for 4 hours in an air atmosphere. The negative electrode active material F2 for secondary batteries (Ti ₂ Nb ₁₀ O ₂₉ = 100% by mass, the amount of carbon = 3.0% by mass) was obtained.

[Comparative Example 7]
24.324 g of TiO ₂ (powder, manufactured by Kanto Chemical Co., Inc., grade 18.5% purity), Nb (OH) ₅ (powder, HC Starck, purity 92.4%) 115.552 g, and 100 g of water Was put into a beaker and mixed with a magnetic stirrer for 30 minutes to obtain a mixed solution G2. The obtained mixed solution G2 was wet-mixed at 25 ° C. for 18 hours in a ball mill (rotation speed 120 rpm, inner diameter 7.6 cm, medium φ1 mm ZrO ₂ ball, medium filling rate 70%) to obtain a mixture G2.
The obtained mixture G2 was spray-dried by a spray drying method (spray dryer: MDL-050M manufactured by Fujisaki Electric Co., Ltd.), and the obtained powder was calcined at 1200 ° C. for 12 hours in an air atmosphere to obtain titanium niobium oxide ( to obtain a _{Ti 2 Nb 10 O 29) G2} .
Then, 0.237 g of glucose (corresponding to 3% by mass in terms of carbon atom in the negative electrode active material), 2 g of water, and 8 ml of ethanol were added to 3 g of the titanium niobium oxide G2, and a ball mill (planet type, Fritsch) was added. After mixing for 60 minutes in Japan Co., Ltd. P-5), it was fired at 700 ° C. for 1 hour in a nitrogen atmosphere, and the secondary battery negative electrode active material G2 (Ti ₂ Nb ₁₀ O ₂₉ = 100 mass%, carbon Obtained) was obtained.

[Comparative Example 8]
The negative electrode active material for secondary batteries H2 (Ti ₂ Nb ₁₀ O ₂₉ / TiO ₂ / Non) was used in the same manner as in Example 7 except that the stirring conditions in the hot stirrer (RSH-4DN) were set at 20 ° C. for 12 hours. Crystalline = 66% by mass / 8% by mass / 26% by mass, amount of carbon = 2.9% by mass).

[Comparative Example 9]
The negative electrode active material for secondary battery I2 (Ti ₂ Nb ₁₀ O ₂₉ / TiO ₂₎ was used in the same manner as in Example 7 except that the stirring condition in the hot stirrer (RSH-4DN) was 0.1 hour at 40 ° C. / Amorphous = 4 mass% / 3 mass% / 93 mass%, carbon amount = 2.9 mass%).

[Comparative Example 10]
The Nb ₂ O ₅ added to the aqueous solution A2 was 24.666 g (Nb / Ti molar ratio was equivalent to 6.0), and the stirring conditions with a hot stirrer (RSH-4DN) were set at 40 ° C. for 2 hours. In the same manner as in Example 7, the negative electrode active material for secondary battery J2 (Ti ₂ Nb ₁₀ O ₂₉ / TiO ₂ / amorphous = 71% by mass / 19% by mass / 10% by mass, the amount of carbon = 2.9 Mass%).

[Comparative Example 11]
Anode active material K2 for secondary battery (Ti ₂ Nb ₁₀ O ₂₉ / TiO ₂ ) in the same manner as in Example 7, except that the amount of water used for the aqueous solution A2 was 7500 mL (TiOSO ₄ / water mass ratio corresponds to 0.001). ₂ / amorphous = 64% by mass / 9% by mass / 27% by mass, amount of carbon = 2.9% by mass).

[Example 12]
The stirring conditions with a hot stirrer (RSH-4DN) were stirring at 40 ° C. for 12 hours, and the dried complex L2 was calcined at 750 ° C. for 4 hours in an air atmosphere. A secondary battery negative electrode active material L2 (Ti ₂ Nb ₁₀ O ₂₉ / TiO ₂ / amorphous = 73% by mass / 11% by mass / 16% by mass, amount of carbon = 3.1% by mass) was obtained.

<Evaluation of charge / discharge characteristics>
The negative electrode active materials for secondary batteries obtained in the examples and comparative examples, ketjen black (conductive agent), and polyvinylidene fluoride (binding agent) were mixed at a mass ratio of 85: 10: 5. N-methyl-2-pyrrolidone was added and sufficiently kneaded to prepare a negative electrode slurry.
The obtained negative electrode slurry was applied to a current collector made of a copper foil having a thickness of 20 μm using a coating machine, and vacuum dried at 80 ° C. for 12 hours. Thereafter, it was punched into a disk shape of φ14 mm and pressed at 16 MPa for 2 minutes using a hand press to obtain a negative electrode.
Next, a Li foil punched to φ15 mm was used as the counter electrode, and LiPF ₆ dissolved at a concentration of 1 mol / L in a mixed solvent in which ethylene carbonate and ethyl methyl carbonate were mixed at a volume ratio of 3: 7 was used as the electrolyte. Using a polymer porous film (made of polypropylene) as a separator, the separator was incorporated and housed in an ordinary manner in an atmosphere having a dew point of −50 ° C. or lower to produce a coin-type lithium secondary battery (CR-2032).
For each lithium secondary battery created, the charging condition was a constant current charge of 1 CA (387 mA / g) and a voltage of 3 V under a temperature of 30 ° C., the discharge condition was a constant current of 1 CA (387 mA / g) and a final voltage of 1 V. As constant voltage discharge, discharge capacities at 0.2 CA and 3 CA were measured (measuring device: HJ-1001SD8 manufactured by Hokuto Denko Co., Ltd.).
The results are shown in Tables 1 and 2.

Claims (7)

After a niobium compound is added to an aqueous titanium compound solution to obtain a suspension, the resulting suspension is heated and stirred to obtain a suspension containing a composite in which a titanium oxide sol film is formed on the surface of the niobium compound. Step (I) and solid-liquid separation of the obtained suspension to obtain a composite as a solid content, and then firing the obtained composite to obtain titanium niobium oxide (II)
A method for producing a negative electrode active material for a secondary battery by a solid phase method.   The manufacturing method of the negative electrode active material for secondary batteries of Claim 1 whose content of the water of the titanium compound aqueous solution in process (I) is 20-99 mass%.   The method for producing a negative electrode active material for a secondary battery according to claim 1 or 2, wherein the heating and stirring of the suspension in the step (I) is a treatment of stirring at a temperature of 30 to 100 ° C for 0.2 to 18 hours. .   The manufacturing method of the negative electrode active material for secondary batteries of any one of Claims 1-3 whose pH of the suspension liquid in process (I) is 0-4.   The secondary battery according to any one of claims 1 to 4, wherein a molar ratio of niobium to titanium (Nb / Ti) in the suspension in step (I) is 1.2 to 5.8. For producing a negative electrode active material.   In process (II), before baking the obtained composite_body | complex, it wash | cleans with 8-60 mass parts wash water previously with respect to 1 mass part dry mass of a composite_body | complex. The manufacturing method of the negative electrode active material for secondary batteries as described in an item.   The manufacturing method of the negative electrode active material for secondary batteries of any one of Claims 1-6 whose calcination temperature in process (II) is 600-1250 degreeC.