JP2010287496A - Negative electrode material for nonaqueous electrolyte secondary battery, negative electrode for nonaqueous electrolyte secondary battery, and nonaqueous electrolyte secondary battery using it - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a negative electrode material for nonaqueous electrolyte secondary battery capable of supplying a nonaqueous electrolyte secondary battery having a high discharge capacity and a high charge and discharge efficiency and with superior rate characteristics, and a negative electrode for nonaqueous electrolyte secondary battery using the same, and a nonaqueous secondary battery using these. <P>SOLUTION: The negative electrode material for nonaqueous electrolyte secondary battery is a negative electrode material containing a compound oxide with titanium (Ti) and niobium (Nb) contained and the specific surface area by BET method is 0.18 m<SP>2</SP>/g or more. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a negative electrode material for a nonaqueous electrolyte secondary battery, a negative electrode for a nonaqueous electrolyte secondary battery, and a nonaqueous electrolyte secondary battery using the same.

In recent years, there has been a demand for large-sized secondary batteries as power sources for electric vehicles and road labeling, and in particular, non-aqueous solvent lithium secondary batteries with higher energy density compared to nickel-cadmium and nickel-hydrogen batteries. Has attracted attention.
As a negative electrode material for a lithium secondary battery, graphite and the like have been studied so far. Graphite has been used because of its excellent cycle characteristics, small electrode expansion, and low cost. However, the negative electrode material made of graphite has a problem of low high input / output characteristics, which is one of the important characteristics of large secondary batteries. Therefore, in recent years, lithium titanate having a spinel structure excellent in input / output characteristics (hereinafter sometimes abbreviated as “Li ₄ Ti ₅ O ₁₂ ”, etc.) has been studied in place of the graphite negative electrode. In particular, lithium titanate is excellent in rate characteristics (input / output characteristics) and cycle characteristics, and therefore, many studies as a negative electrode have been made. However, the theoretical capacity of lithium titanate is 175 mAh / g, which is smaller than the theoretical capacity of 372 mAh / g of the current graphite negative electrode, and development of a titanium oxide negative electrode material with higher capacity and higher input / output is desired. Yes.
Under these circumstances, Patent Document 1 discloses that Ti ₂ Nb ₁₀ O ₂₉ and TiNb ₂₄ O ₆₂ synthesized by solid-phase reaction are used as positive electrode powders, and the initial discharge capacity up to 1.5 V based on the Li electrode is Li / (Ti
It is described that the + Nb) molar ratio is 0.46 (= 99 mAh / g) and 0.72 (= 147 mAh / g), respectively.

In Non-Patent Document 1, TiNb ₂ O ₇ , Ti ₂ Nb ₁₀ O ₂₉ , and TiNb ₂₄ O ₆₂ synthesized by solid-phase reaction are used as positive electrode powders, and the initial discharge capacity up to 1.4 V on the basis of the Li electrode is disclosed. It is described that the Li / (Ti + Nb) molar ratio is 0.89 (= 207 mAh / g), 0.83 (= 179 mAh / g), and 0.80 (= 164 mAh / g), respectively.

Also after the ion exchange the KTiNbO ₅ synthesized in solid phase reactions in Non-Patent Document 2 with an acid, to obtain a _Ti 2 _Nb 2 _{O 9} was dehydrated by firing at 330 ° C.. It is described that this is a positive electrode material powder, and the initial discharge capacity up to 1.0 V on the basis of the Li electrode with a low rate of C / 100 is 1 (= 251 mAh / g) as the Li / (Ti + Nb) molar ratio. Yes.
Furthermore, Non-Patent Document 3 discloses that a part of Nb is obtained by charging / discharging PNb ₉ O ₂₅ , H—Nb ₂ O ₅ , GeNb ₁₈ O ₄₇ , VNb ₉ O ₂₅ synthesized by solid phase reaction to 1.0 V. It is described that the initial discharge capacity is about 225 mAh / g at the maximum by oxidation-reduction from V valence to III valence.

No. 6-66141

R. J. et al. Cava, D.C. W. Murphy, S.M. M.M. Zahurak, Journal of The Electrochemical Society, 130 (1983) 2345-2351. J. et al. -F. Colin, V.M. Pralong, M.M. Hervieu, V.M. Caignaert, B.A. Raveau, Chemistry of Materials 20 (2008) 1534-1540 Sebastian Patux, Mickel Doll, Gwenaelle Rousse, and Christian Masquerier, Journal of The Electrochemical Society, 149 (2002) A391-A400.

  As described above, with the need for higher input / output in recent years, it is desired to use a titanium oxide-based negative electrode material having a high capacity and capable of high input / output. The titanium oxide negative electrode material having a simple layered structure has a problem that the developed capacity is smaller than the theoretical capacity, and the cycle characteristics are liable to deteriorate. Therefore, for example, in order to further increase the capacity of lithium secondary batteries, improve cycle characteristics, etc., polyvalent ions are introduced into titanium oxide, and there is a strong demand for improvements in the insertion sites of lithium ions and the efficiency of migration. ing.

  However, in the case of the positive electrode material powder of titanium-niobium composite oxide disclosed in Patent Document 1 and Non-Patent Document 1, only 1.5 V and 1.4 V are discharged based on the oxidation-reduction potential of lithium, respectively. Is reduced only to the IV value, and thus the expression capacity is small. In these documents, only 1.5V or 1.4V was discharged because these composite oxides were considered as positive electrodes, and when the battery was charged and discharged at as high a potential as possible, This is because a larger potential can be obtained and is advantageous.

  Further, in the case of the positive electrode powder of titanium niobium composite oxide disclosed in Non-Patent Document 2, discharge is performed to 1.0 V with reference to the oxidation-reduction potential of lithium, but there are actually few sites where Li + can be inserted. For this reason, even at a very low rate of C / 100, Nb is reduced only to the IV value and the initial irreversible capacity is large, so the reversible capacity after 30 cycles is as small as 125 mAh / g.

Further, Non-Patent Document 3 discloses that PNb ₉ O ₂₅ , H—Nb ₂ O ₅ , GeNb ₁₈ O ₄₇ , and VNb ₉ O ₂₅ are discharged to 1.0 V on the basis of the oxidation-reduction potential of lithium, so that Nb The maximum initial discharge capacity is as low as 225 mAh / g at a low rate of C / 10, and there is no description of high rate characteristics. TiNb ₂
Although there is a description that O ₇ was synthesized by solid phase reaction at 1400 ° C., there is no description about the evaluation result as an electrode. In addition, TiNb ₂ O ₇ produced by the method described in Non-Patent Document 3 has a too small non-surface area by the BET method, as in Comparative Example 1 of the present invention described later. For this reason, it is expected that the reversible capacity is small and the rate characteristics are inferior.

The present invention has been made in view of the above problems.
That is, the present invention provides a nonaqueous electrolyte secondary battery having a high discharge capacity and excellent rate characteristics, a negative electrode material for a nonaqueous secondary battery, a negative electrode for a nonaqueous electrolyte secondary battery, and a nonaqueous electrolyte using these An object is to provide a secondary battery.

As a result of intensive studies in view of the above problems, the present inventors have found a titanium niobium composite oxide having good charge / discharge efficiency, discharge capacity, and rate characteristics by increasing the specific surface area of the titanium niobium composite oxide. Completed.
That is, the gist of the present invention is as follows.
(1) A non-aqueous electrolyte comprising a composite oxide containing titanium (Ti) and niobium (Nb), and having a specific surface area of 0.18 m ² / g or more according to the BET method Secondary battery negative electrode material.
(2) It has a peak a at the position of binding energy = 204.3 ± 1 eV in XPS analysis in which the 3d 5/2 peak of Nb (+ V valence) is 207.5 eV in the charged state (1) A negative electrode material for a non-aqueous electrolyte secondary battery according to 1.
(3) The composite oxide containing titanium (Ti) and niobium (Nb) has the same structure as at least one of TiNb ₂ O ₇ , Ti ₂ Nb ₁₀ O ₂₉ and TiNb ₂₄ O ₆₂ ( The negative electrode material for nonaqueous electrolyte secondary batteries according to 1) or (2).
(4) A negative electrode for a non-aqueous electrolyte secondary battery comprising the negative electrode material according to any one of claims (1) to (3) as a negative electrode active material.
(5) A nonaqueous electrolyte secondary battery comprising a positive electrode and a negative electrode capable of inserting and extracting lithium ions, and an electrolyte, wherein the negative electrode is a negative electrode for a nonaqueous electrolyte secondary battery according to (4), Non-aqueous electrolyte secondary battery.

  According to the present invention, it is possible to stably and efficiently realize a high-performance nonaqueous electrolyte secondary battery having a high discharge capacity, high initial discharge efficiency during cycles and high cycle characteristics, and excellent cycle characteristics.

Is a diagram showing the XPS analysis results of NbO _2. FIG. 3 is a diagram showing the XPS analysis result of the negative electrode material obtained in Example 1.

Hereinafter, the present invention will be described in detail, but the present invention is not limited to the following description, and can be arbitrarily modified and implemented without departing from the gist of the present invention.
[1] Anode material for non-aqueous electrolyte secondary battery
The negative electrode material for a non-aqueous secondary battery of the present invention is a negative electrode material containing a composite oxide containing titanium (Ti) and niobium (Nb), and has a specific surface area of 0.18 m ² / g or more by the BET method. It is characterized by being.

<Composite oxide containing titanium (Ti) and niobium (Nb)>
In the present invention, “a composite oxide containing titanium (Ti) and niobium (Nb)” is not particularly limited as long as the main constituent element is a composite oxide containing titanium and niobium.
1A group elements such as Li, Na, K, and Cs may be contained, and a part of titanium and niobium may be substituted with VA group and VIA group elements such as V, Ta, Cr, Mo, and W. good. Specifically, compounds such as TiNb ₂ O ₇ , Ti ₂ Nb ₁₀ O ₂₉ , TiNb ₂₄ O ₆₂ , K ₄ Ti ₁₀ Nb ₂ O ₂₇ having a tunnel and layered structure, and NaTi ₅ NbO ₁₃ , which are called wadsley phases, are mentioned. .

  The reason why the above complex oxide exhibits the effects of the present invention is presumed as follows. That is, when the above compound is used as a negative electrode, charging to a low potential causes reduction of Ti from IV value to III value and simultaneously reduction of Nb from V value to III value, resulting in charging efficiency and discharge capacity. It is presumed that the rate characteristic becomes higher. In the case where the constituent elements contain Ti and Nb, unlike the case where the composite oxide is composed of other elements, the atomic weight is relatively small, so that the charge / discharge capacity per mass is increased and the redox is reversible. Because of its good properties, it has the above characteristics.

<BET specific surface area>
The negative electrode material of the present invention has a BET specific surface area of 0.18 m ² / g or more. Among them, preferably 0.19 m ² / g or more, more preferably ^2m 2 / g or more, with respect to the upper limit is not particularly limited, usually 300 meters ² / g or less, preferably 280 meters ² / g, further Preferably it is the range of 260 m < ² > / g or less. If the value of the BET specific surface area is in this range, it is preferable because the charge / discharge efficiency and discharge capacity of the battery are high, lithium is quickly taken in and out in high-speed charge / discharge, and the rate characteristics are excellent. The measurement conditions are as shown in the examples described later.
<XPS analysis>
In addition, the above complex oxide preferably has a peak a at the position of binding energy = 204.3 ± 1 eV in XPS analysis in which the 3d 5/2 peak of Nb (+ V valence) is 207.5 eV in a charged state. .

Here, the binding energy of XPS analysis of the composite oxide in the present invention will be described.
In the composite oxide of the present invention, the 3d 5/2 peak of Nb (+ V valence) is 207.5 eV.
The PS analysis is characterized by having a peak a at a position of binding energy = 204.3 ± 1 eV. When lithium ions are inserted into a composite oxide containing titanium and niobium, a composite oxide that does not show peak a can only be used to reduce Nb from the V valence to the IV valence. The capacity is also reduced. Therefore, it is preferable from the viewpoint of reversibility that peak a appears when lithium ions are inserted and peak a disappears when lithium ions are desorbed.

Here, the peak a indicates the peak having the maximum intensity among the peaks appearing at the position of binding energy = 204.3 ± 1 eV. Moreover, when it overlaps with another peak, it is necessary to obtain a peak position by separation analysis.
Here, the peak a is a peak derived from a lower valence state than the IV valence because the binding energy derived from the IV valence observed in NbO ₂ shown in FIG. 1 is on the lower energy side than 205.7 eV. is there. The measurement conditions are as shown in the examples described later.

In addition, in the titanium and niobium-containing composite oxide, whether or not Nb is used after being oxidized / reduced to a lower valence than the IV value depends on the IV value of all Ti contained in the composite oxide for convenience. Compared with the capacity obtained when it is assumed that the valence and the IV valence of all Nb are used, it can be confirmed that the capacity actually expressed is larger than that. Specifically, in TiNb ₂ O ₇ , Ti ₂ Nb ₁₀ O ₂₉ , and TiNb ₂₄ O ₆₂ , 232 mAh / g and 215 m, respectively.
When the expression capacity is larger than Ah / g and 204 mAh / g, it can be considered that Nb is oxidized / reduced to a valence lower than the IV value, and when Nb is a valence lower than the IV value, the above XPS analysis A peak a is observed in FIG. The expression capacity here is a value obtained at a low rate sufficient to oxidize and reduce titanium and niobium contained in the composite oxide. As a specific example of the low rate, the conditions described in the discharge capacity evaluation in the examples described later can be given.

  The negative electrode material of the present invention is extremely useful as a negative electrode active material in a non-aqueous electrolyte secondary battery such as a positive and negative electrodes capable of occluding and releasing lithium ions, and a lithium secondary battery equipped with an electrolyte. For example, a non-aqueous electrolyte secondary battery using a negative electrode material of the present invention as a negative electrode and combining a commonly used metal chalcogenide positive electrode for lithium secondary batteries and an organic electrolyte mainly composed of a carbonate solvent is It has a large capacity, excellent cycle characteristics, and is extremely excellent as a large battery or a vehicle battery.

For example, the peak position a can be obtained by XPS under the conditions described above.
In the following, the “negative electrode” is the one in which the negative electrode material of the present invention is used as an active material and a layer containing the active material is provided on a current collector.
<X-ray diffraction measurement>
As the X-ray diffraction measurement, for example, a negative electrode material powder sample is packed in a glass sample holder and set on an irradiation surface, and measurement can be performed using a powder X-ray diffraction apparatus (for example, “PW1700” manufactured by Panalical). The conditions are as shown in the examples described later.

<Volume standard average particle size>
The volume-based average particle diameter of the negative electrode material of the present invention is not particularly limited, but is usually 0.1 μm or more, preferably 1 μm or more, more preferably 3 μm or more, and usually 60 μm or less, preferably 55 μm or less, more preferably 50 μm or less. It is. If the volume-based average particle size of the negative electrode material is below this range, the particle size is too small, and it is difficult to take a conductive path between the negative electrode material powder and a conductive path between the negative electrode material powder and a conductive agent described later. In some cases, the cycle characteristics may deteriorate. On the other hand, if it exceeds this range, unevenness may easily occur when the negative electrode active material layer is produced on the current collector by coating as described later.
The volume-based average particle size is measured by mixing a 2% by volume aqueous solution (about 1 mL) of polyoxyethylene (20) sorbitan monolaurate, which is a surfactant, and laser diffraction particle size distribution using ion-exchanged water as a dispersion medium. A value obtained by measuring a volume-based average particle diameter (median diameter) with a meter (for example, “LA-920” manufactured by Horiba, Ltd.) is used.

<Average particle size of primary particles>
The average particle size of the primary particles of the negative electrode material of the present invention is not particularly limited, but is usually 5 nm or more, preferably 10 nm or more, more preferably 20 nm or more, and usually 20 μm or less, preferably 15 μm or less, more preferably The range is 10 μm or less. If the value of the average particle diameter of the primary particles is within this range, it is preferable because lithium can be taken in and out quickly and the rate characteristics are excellent in high-speed charge / discharge of the battery.
The average particle diameter of the primary particles is obtained by observing three or more different views of the negative electrode material with an SEM, and obtaining the average particle diameter of the primary particles from the average value. The fiber diameter direction is used as the average particle diameter when the primary particles are fibrous, and the minor axis direction is used as the average particle diameter when the primary particles are elliptical.

<Tap density>
The tap density of the negative electrode material of the present invention is not particularly limited, but is usually 0.1 g / cm ³ or more, preferably 0.4 g / cm ³ or more, more preferably 0.7 g / cm ³ or more, and usually 4. The range is 0 g / cm ³ or less, preferably 3.0 g / cm ³ or less. If the tap density is within this range, it is easy to increase the packing density of the negative electrode active material layer, and it is easy to obtain a high-capacity battery excellent in rate characteristics.

The tap density is measured using a sieve having a mesh size of 300 μm, dropping the negative electrode material into a 20 cm ³ tapping cell to fill the cell, and then using a powder density measuring device (for example, a tap denser manufactured by Seishin Enterprise Co., Ltd.). Then, tapping with a stroke length of 10 mm is performed 1000 times, and a value obtained by measuring the tapping density at that time is used.
[Production method]
Although there is no restriction | limiting in particular in the manufacturing method of the negative electrode material used for the negative electrode of this invention, For example, it can manufacture by the manufacturing method etc. which are mentioned below.

<Raw material>
Among the raw materials for the negative electrode material (hereinafter sometimes referred to as “raw material” as appropriate), examples of the Ti raw material include titanium metal, titanium oxide (anatase type, rutile type, etc.), titanium complex (titanium glycolate complex, citric acid). Titanium complex etc.), titanium alkoxide (titanium isopropoxide etc.), titanium salt (titanium sulfate etc.), titanium chloride (titanium tetrachloride etc.), titania sol etc. can be used. Examples of the Nb raw material include metal niobium, niobium oxide (Nb ₂ O ₅ ,
NbO ₂ , Nb ₂ O ₃ , NbO, etc.), niobium ammonium oxalate, niobium hydroxide, niobium pentachloride, niobium oxychloride, niobium bromide, niobium fluoride, niobium alkoxide (pentamethoxyniobium, pentaethoxyniobium, penta- i-propoxyniobium, penta-n-
Propoxyniobium, penta-i-ptoxyniobium, penta-n-ptoxyniobium, penta-sec-ptoxyniobium, etc.), niobium oxide sol, and the like can be used.

As an oxygen source, oxygen-containing gas (air, oxygen, etc.), Ti, oxygen in oxide as element M source, oxygen in carbonate, etc. can be used.
As a raw material for Ti, Nb, and oxygen, a single compound (or element) combining Ti, Nb, and oxygen may be used, or a plurality of compounds may be used.
Moreover, the form of these Ti, Nb, and oxygen raw material can be used as a powder form, a granular form, a pellet form, a lump shape, a plate shape, etc., for example.

<Method>
As a manufacturing method of the negative electrode material,
(1) Method using hydrothermal synthesis treatment
(2) Method using solid-phase reaction treatment
(3) Method using complex polymerization reaction treatment
Etc.

Below, the manufacturing method of (1), (2), (3) is demonstrated.
(1) Method using hydrothermal synthesis treatment
(Hydrothermal synthesis)
Hydrothermal synthesis is carried out by placing an aqueous starting material in a pressure vessel and maintaining it at a predetermined temperature under stirring or without stirring under self-generated pressure or under pressure of a gas that does not inhibit crystallization. The hydrothermal synthesis treatment in the present invention is a step of reacting the above mixed solution composed of the Ti raw material and the Nb raw material at a temperature of 100 ° C. or higher in a pressure-resistant vessel such as an autoclave.

You may adjust pH of the said mixed aqueous solution as needed. For pH adjustment, an acidic aqueous solution such as sulfuric acid or an alkaline aqueous solution such as ammonia water can be used.
The temperature of the hydrothermal synthesis can be appropriately set according to the negative electrode material to be synthesized, but is preferably 100 to 300 ° C. and 150 to 250 ° C. from the viewpoint of ease of synthesis. In addition, the hydrothermal synthesis pressure is, for example, about 0.1 MPa to 1.6 MPa, and the hydrothermal synthesis time is, for example, about 1 hour to 10 days. Moreover, stirring may be performed during the hydrothermal synthesis process, or the stationary state may be maintained. After hydrothermal synthesis, the product is separated, washed with water, and dried to obtain the titanium-niobium-containing composite oxide. Baking may be performed in order to remove attached organic substances or to increase crystallinity. For example, baking is held at a temperature of 500 to 1300 ° C. for about 0.5 hour to 1 day. The atmosphere during firing is preferably an air atmosphere in order to stably produce the titanium-niobium composite oxide. The apparatus used for firing is not particularly limited, and examples include a shuttle furnace, a tunnel furnace, an electric furnace, a lead hammer furnace, and a rotary kiln.

(Other processing)
After the baking treatment, further pulverization and classification treatment may be performed as necessary. The apparatus used for pulverization is not particularly limited. For example, examples of the coarse pulverizer include a jaw crusher, an impact crusher, and a cone crusher. Examples of the intermediate pulverizer include a roll crusher and a hammer mill. Examples of the pulverizer include a ball mill, a vibration mill, a pin mill, a stirring mill, and a jet mill.

There are no particular restrictions on the apparatus used for the classification process. For example, in the case of dry sieving: rotary sieving, oscillating sieving, rotating sieving, vibrating sieving, etc. can be used. Cases: Gravity classifiers, inertial classifiers, centrifugal classifiers (classifiers, cyclones, etc.) can be used. In the case of wet sieving: mechanical wet classifiers, hydraulic classifiers, sedimentation classifiers A centrifugal wet classifier or the like can be used.

(2) Method using solid-phase reaction treatment
(Solid-phase reaction treatment)
The solid-phase reaction generally refers to a chemical reaction that occurs in a solid or between solids. The solid-phase reaction treatment in the present invention is a process in which the Ti raw material and the Nb raw material are mixed, heat-treated and reacted. That is.

The heat treatment temperature of the solid phase reaction treatment is maintained at a temperature of about 600 to 1400 ° C. for about 1 to 48 hours to obtain a solid phase reacted powder. The atmosphere during the heat treatment is preferably an air atmosphere in order to stably produce the titanium-niobium composite oxide.
(Other processing)
A method similar to the other processing described above can be used.

(3) Method using complex polymerization reaction treatment
(Complex polymerization reaction treatment)
The complex polymerization reaction is a chemical reaction that first stabilizes a constituent metal element as a metal complex, and secondly fixes it in an organic polymer network to prevent decomposition or precipitation of the metal complex. The complex polymerization reaction treatment in the present invention means that the above-mentioned Ti raw material and Nb raw material are dissolved in a glycol (ethylene glycol, propylene glycol, etc.) solution containing an excessive amount of oxycarboxylic acid such as citric acid as a complex forming agent. After forming the metal oxycarboxylic acid complex, the polyester polymer gel is heated to a temperature of about 120 to 200 ° C. and subjected to a chain dehydration ester reaction between the carboxyl group of the oxycarboxylic acid and the hydroxyl group of the glycol. Get.

Furthermore, it carbonizes by adding heat processing at about 300-350 degreeC. Further, it is a step of decrystallization by heat treatment at about 500 ° C., and further crystallization by applying heat treatment at a temperature of about 600 to 1100 ° C. for about 1 to 48 hours. The atmosphere during the heat treatment is preferably an air atmosphere in order to stably produce the titanium-niobium composite oxide.
(Other processing)
A method similar to the other processing described above can be used.

[2] Negative electrode for nonaqueous electrolyte secondary battery
The negative electrode for a non-aqueous electrolyte secondary battery of the present invention uses the negative electrode material of the present invention as a negative electrode active material, and generally includes a negative electrode active material layer containing the negative electrode material of the present invention on a current collector. Is provided so as to ensure conductivity.
Such a negative electrode of the present invention is extremely useful as a negative electrode in a non-aqueous electrolyte secondary battery such as a positive and negative electrodes capable of inserting and extracting lithium ions, and a lithium secondary battery including an electrolyte. In particular, the non-aqueous electrolyte secondary battery comprising the negative electrode of the present invention in combination with a metal chalcogenide-based positive electrode for a lithium secondary battery that is normally used and an organic electrolyte mainly composed of a carbonate-based solvent has a discharge capacity, charge capacity, and the like. The discharge efficiency is large, the rate characteristic is good, and it is extremely excellent.

[Negative electrode active material]
As the negative electrode active material of the present invention, the negative electrode material of the present invention is used. As long as the effects of the present invention are not hindered, the negative electrode material is a negative electrode material other than the negative electrode material of the present invention (hereinafter referred to as “negative electrode material A”). May be used in combination. When the negative electrode material A is used, the negative electrode material A may be anything as long as it can charge and discharge lithium ions. For example, as the negative electrode material A, natural graphite (flaky graphite, spheroidized graphite, etc.), artificial graphite (mesocarbon microbeads, etc.), amorphous carbon obtained by firing pitch, resin, etc., graphite and amorphous Materials composed of carbonaceous composites, metals such as aluminum and tin, Si
Examples thereof include oxides such as O ₂ . These may be used individually by 1 type and may be used in combination of 2 or more type.
The addition amount of the negative electrode material A is not particularly limited, but is usually 1% by mass or more, preferably 5% by mass or more, more preferably 20% by mass or more, and usually 80% by mass or less with respect to the negative electrode material of the present invention. Preferably, it is 70 mass% or less, More preferably, it is 60 mass% or less.

[Current collector]
As the current collector, for example, a metal cylinder, a metal coil, a metal plate, a metal foil film, a carbon plate, a carbon thin film, a carbon cylinder, or the like is used. Among these, a metal foil film is particularly preferable because it is currently used in industrialized products. The metal thin film may be used in a suitable mesh shape.

The thickness of the metal foil film is not particularly limited, but is usually 1 μm or more, preferably 5 μm or more, more preferably 10 μm or more, and usually 100 μm or less, preferably 50 μm or less, more preferably 20 μm or less. In the case of a metal foil film thinner than the above range, the strength required as a current collector may be insufficient.
Specific examples of the metal used for the current collector include copper, nickel, stainless steel, iron, titanium, aluminum, and an aluminum alloy.

[Physical properties]
<Filling density>
The packing density of the negative electrode is not particularly limited, but is usually 0.1 g / cm ³ or more, preferably 0.5 g / cm ³ or more, and usually 5.0 g / cm ³ or less, preferably 4.0 g / cm ³ or less. is there. When the packing density of the negative electrode is below this range, it may be difficult to obtain a high-capacity battery. On the other hand, if it exceeds this range, the amount of pores in the negative electrode may be reduced, and it may be difficult to obtain favorable battery characteristics. As the packing density of the negative electrode, a value obtained by dividing the negative electrode weight excluding the current collector by the negative electrode area and the negative electrode thickness is used.

<Porosity>
The porosity of the negative electrode is not particularly limited, but is usually 10% or more, preferably 20% or more, and usually 50% or less, preferably 40% or less. When the porosity of the negative electrode is less than this range, there are few pores in the negative electrode, and the electrolyte does not easily penetrate, and it may be difficult to obtain preferable battery characteristics. On the other hand, if it exceeds this range, there may be many pores in the negative electrode and the negative electrode strength becomes too weak, making it difficult to obtain favorable battery characteristics. As the porosity of the negative electrode, a percentage of a value obtained by dividing the total pore volume obtained by measuring the pore distribution with a mercury porosimeter of the negative electrode by the apparent volume of the negative electrode active material layer excluding the current collector is used.

<Conductive agent>
The negative electrode active material layer may include a conductive agent. The conductive agent may be any electronic conductive material that does not cause a chemical change at the charge / discharge potential of the negative electrode active material to be used. For example, carbon blacks such as acetylene black, ketjen black, channel black, furnace black, lamp black and thermal black, carbon fibers, vapor grown carbon fibers (VGCF), conductive fibers such as metal fibers, fluorine Metal powders such as carbonized carbon and copper can be contained alone or as a mixture thereof. Of these conductive agents, acetylene black and VGCF are particularly preferable. These may be used individually by 1 type and may be used in combination of 2 or more type. Although the addition amount of a electrically conductive agent is not specifically limited, 1-30 mass% is preferable with respect to a negative electrode active material, and 1-15 mass% is especially preferable.

<Binder>
As the binder, a polymer that is stable against a liquid solvent described later is preferable. For example, resin polymers such as polyethylene, polypropylene, polyethylene terephthalate, aromatic polyamide, cellulose, rubbery polymers such as styrene / butadiene rubber, isoprene rubber, butadiene rubber or ethylene / propylene rubber, styrene / butadiene / styrene block Polymers, hydrogenated products thereof, styrene / ethylene / butadiene / styrene copolymers, styrene / isoprene / styrene block copolymers and thermoplastic elastomeric polymers such as hydrogenated products, syndiotactic 1,2-polybutadiene , Ethylene / vinyl acetate copolymer, or soft resinous polymer such as propylene / α-olefin (carbon number 2 to 12) copolymer, polyvinylidene fluoride, polytetrafluoroethylene, or polytetrafluoroethylene / ethylene The fluoropolymer of the polymer such as, a polymer composition or the like having an ionic conductivity of alkali metal ions (especially lithium ions) can be mentioned. These may be used individually by 1 type and may be used in combination of 2 or more type.

  Examples of the polymer composition having ion conductivity include polyether polymer compounds such as polyethylene oxide and polypropylene oxide, crosslinked polymers of polyether compounds, polyepichlorohydrin, polyphosphazene, polysiloxane, and polyvinylpyrrolidone. , A polymer in which a lithium salt or an alkali metal salt mainly composed of lithium is combined with a polymer compound such as polyvinylidene carbonate or polyacrylonitrile, or a high dielectric such as propylene carbonate, ethylene carbonate, or γ-butyrolactone. A polymer in which an organic compound having a rate or an ion-dipole interaction force is blended can be used.

  Specifically, resin polymers such as polyethylene, polypropylene, polyethylene terephthalate, aromatic polyamide, or cellulose and derivatives thereof (for example, carboxymethylcellulose), styrene / butadiene rubber, isoprene rubber, butadiene rubber, or ethylene / propylene are usually used. Rubber-like polymers such as rubber, fluoropolymers such as polyvinylidene fluoride, polytetrafluoroethylene, or polytetrafluoroethylene / ethylene copolymers, polyether polymer compounds such as polyethylene oxide and polypropylene oxide, polyethers Examples include crosslinked polymers of the compound, preferably polyethylene, polypropylene, styrene / butadiene rubber, polyvinylidene fluoride, polytetrafluoroethylene, or polyethylene oxide. Is, more preferably, polyethylene, styrene-butadiene, polyvinylidene fluoride, or polytetrafluoroethylene. These are currently used industrially and are suitable because they are easy to handle.

The structure of this negative electrode is that the negative electrode material of the present invention, the negative electrode material A and / or a conductive agent, and a slurry in which a binder is dispersed in a dispersion liquid are thinly applied and dried on a current collector substrate. Followed by a pressing step of compacting to a predetermined thickness and density.
An aqueous solvent or an organic solvent is used as a dispersion medium for preparing a negative electrode active material slurry when a negative electrode active material, a conductive agent and a binder used as necessary are mixed and applied onto a current collector. As the aqueous solvent, water is usually used, and additives such as alcohols such as ethanol and cyclic amides such as N-methylpyrrolidone may be added to water up to about 30% by mass or less. it can.

  As the organic solvent, usually, cyclic amides such as N-methylpyrrolidone, linear amides such as N, N-dimethylformamide and N, N-dimethylacetamide, and aromatic carbonization such as anisole, toluene and xylene Examples thereof include alcohols such as hydrogens, butanol and cyclohexanol, among which cyclic amides such as N-methylpyrrolidone, linear amides such as N, N-dimethylformamide and N, N-dimethylacetamide are preferable. .

A negative electrode active material, a binder, and a conductive agent blended as necessary are mixed with these solvents to prepare a negative electrode active material slurry, and this is applied to the negative electrode current collector substrate so as to have a predetermined thickness. Thus, the negative electrode active material layer is formed. The upper limit of the concentration of the negative electrode active material in the negative electrode active material slurry is usually 70% by mass or less, preferably 55% by mass or less, and the lower limit is usually 30% by mass or more. , Preferably it is 40 mass% or more. When the concentration of the negative electrode active material exceeds this upper limit, the negative electrode active material in the negative electrode active material slurry tends to aggregate, and when the concentration is lower than the lower limit, the negative electrode active material tends to settle during storage of the negative electrode active material slurry.

The upper limit of the binder concentration in the negative electrode active material slurry is usually 30% by mass or less, preferably 10% by mass or less, and the lower limit is usually 0.1% by mass or more, preferably 0.5% or more. . When the concentration of the binder exceeds this upper limit, the internal resistance of the negative electrode obtained increases, and when the concentration is lower than the lower limit, the binding property of the negative electrode active material layer becomes poor.
[3] Non-aqueous electrolyte secondary battery
The nonaqueous electrolyte secondary battery of the present invention is a nonaqueous electrolyte secondary battery comprising a positive electrode and a negative electrode capable of inserting and extracting lithium ions, and an electrolyte, and the negative electrode material of the present invention is used for the negative electrode.

There is no particular limitation on the selection of members other than the negative electrode necessary for the battery configuration such as the positive electrode and the electrolyte constituting the nonaqueous electrolyte secondary battery of the present invention. In the following, materials of members other than the negative electrode constituting the nonaqueous electrolyte secondary battery when the negative electrode material of the present invention is used as a negative electrode will be exemplified, but usable materials are limited to these specific examples. is not.
[Positive electrode]
The positive electrode is formed by forming a positive electrode active material and an active material layer containing an organic substance (binder) having a binding and thickening effect on a current collector substrate. Usually, the positive electrode active material and the binder are used. The slurry is dispersed in water or an organic solvent, and is applied by a thin coating and drying process on a current collector substrate, followed by a pressing process for compacting to a predetermined thickness and density.

<Positive electrode active material>
The positive electrode active material is not particularly limited as long as it has a function capable of inserting and extracting lithium. For example, lithium transition metal composite oxide materials such as lithium cobalt oxide, lithium nickel oxide, and lithium manganese oxide Transition metal oxide materials such as manganese dioxide; carbonaceous materials such as graphite fluoride can be used. Specifically, LiFeO ₂ , LiCoO ₂ , LiNiO ₂ , LiMn ₂ O ₄ and their non-stoichiometric compounds, MnO ₂ , TiS ₂ , FeS ₂ , Nb ₃ S ₄ , Mo ₃ S ₄ , CoS ₂ , V ₂ O ₅ , P ₂ O ₅ , CrO ₃ , V ₃ O ₃ , TeO ₂ , GeO _2, LiFePO ₄ , LiMnPO ₄ , LiNi _0.5 Mn _1.5 O _{4 and the} like can be used. These may be used individually by 1 type and may be used in combination of 2 or more type.

<Conductive agent>
A positive electrode conductive agent can be used for the positive electrode active material layer. The positive electrode conductive agent may be any electron conductive material that does not cause a chemical change at the charge / discharge potential of the positive electrode active material used. For example, graphite such as natural graphite (flaky graphite etc.), artificial graphite, etc .; carbon blacks such as acetylene black, ketjen black, channel black, furnace black, lamp black, thermal black; carbon fiber, metal fiber, etc. Conductive fibers of: carbon fluorides; metal powders such as aluminum; conductive whiskers such as zinc oxide and potassium titanate; conductive metal oxides such as titanium oxide; organic conductive materials such as polyphenylene derivatives; Etc. can be included alone or as a mixture thereof. Among these conductive agents, artificial graphite, acetylene black and the like are particularly preferable. These may be used individually by 1 type and may be used in combination of 2 or more type.

Although the addition amount of a electrically conductive agent is not specifically limited, 1-50 mass% is preferable with respect to a positive electrode active material, and 1-30 mass% is especially preferable. In the case of carbon or graphite, 2 to 15% by mass is particularly preferable.
<Binder>
There is no restriction | limiting in particular as a binder used for formation of a positive electrode active material layer, Any of a thermoplastic resin and a thermosetting resin may be sufficient. For example, polyethylene, polypropylene, polytetrafluoroethylene (PTFE), polyvinylidene fluoride (PVDF), styrene butadiene rubber, tetrafluoroethylene-hexafluoroethylene copolymer, tetrafluoroethylene-hexafluoropropylene copolymer (FEP), Tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer (PFA), vinylidene fluoride-hexafluoropropylene copolymer, vinylidene fluoride-chlorotrifluoroethylene copolymer, ethylene-tetrafluoroethylene copolymer (ETFE resin) , Polychlorotrifluoroethylene (PCTFE), vinylidene fluoride-pentafluoropropylene copolymer, propylene-tetrafluoroethylene copolymer, ethylene-chlorotrif Oroethylene copolymer (ECTFE), vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene copolymer, vinylidene fluoride-perfluoromethyl vinyl ether-tetrafluoroethylene copolymer, ethylene-acrylic acid copolymer or (Na ⁺ ) ion crosslinked product, ethylene-methacrylic acid copolymer or (Na ⁺ ) ion crosslinked product of the material, ethylene-methyl acrylate copolymer, or (Na ⁺ ) ion crosslinked product of the material, ethylene-methacrylic acid Examples thereof include an acid methyl copolymer or a (Na ⁺ ) ion-crosslinked product of the above materials, and these materials can be used alone or as a mixture. Among these materials, more preferable materials are polyvinylidene fluoride (PVDF) and polytetrafluoroethylene (PTFE).

<Other additives>
In addition to the conductive agent described above, the positive electrode active material layer may further contain a filler, a dispersant, an ionic conductor, a pressure enhancer, and other various additives. Any filler can be used as long as it is a fibrous material that does not cause a chemical change in the constructed battery. Usually, olefin polymers such as polypropylene and polyethylene, and fibers such as glass and carbon are used. Although the addition amount of a filler is not specifically limited, 0-30 mass% is preferable as content in an active material layer.

<Solvent>
In preparing the positive electrode active material slurry, an aqueous solvent or an organic solvent is used as a dispersion medium. As the aqueous solvent, water is usually used, and additives such as alcohols such as ethanol and cyclic amides such as N-methylpyrrolidone may be added to water up to about 30% by mass or less. it can. As the organic solvent, usually, cyclic amides such as N-methylpyrrolidone, linear amides such as N, N-dimethylformamide and N, N-dimethylacetamide, and aromatic carbonization such as anisole, toluene and xylene Examples thereof include alcohols such as hydrogens, butanol and cyclohexanol, among which cyclic amides such as N-methylpyrrolidone, linear amides such as N, N-dimethylformamide and N, N-dimethylacetamide are preferable. .

A positive electrode active material, a binder as a binder, an organic substance having a thickening effect, a positive electrode conductive agent blended as necessary, and other fillers are mixed in these solvents to prepare a positive electrode active material slurry, The positive electrode active material layer is formed by applying this to the positive electrode current collector substrate so as to have a predetermined thickness.
The upper limit of the concentration of the positive electrode active material in the positive electrode active material slurry is usually 70% by mass or less, preferably 55% by mass or less, and the lower limit is usually 30% by mass or more, preferably 40% by mass or more. If the concentration of the positive electrode active material exceeds this upper limit, the positive electrode active material in the positive electrode active material slurry tends to aggregate, and if it falls below the lower limit, the positive electrode active material tends to settle during storage of the positive electrode active material slurry.

  Further, the upper limit of the concentration of the binder in the positive electrode active material slurry is usually 30% by mass or less, preferably 10% by mass or less, and the lower limit is usually 0.1% by mass or more, preferably 0.5% or more. . When the concentration of the binder exceeds this upper limit, the internal resistance of the positive electrode obtained increases, and when it falls below the lower limit, the binding property of the positive electrode active material layer may be inferior.

<Current collector>
As the positive electrode current collector, for example, it is preferable to use a valve metal or an alloy thereof that forms a passive film on the surface by anodic oxidation in an electrolytic solution. Examples of the valve metal include metals belonging to Groups 4, 5, and 13 of the periodic table and alloys thereof. Specifically, Al, Ti, Zr, Hf, Nb, Ta and alloys containing these metals can be exemplified, and Al, Ti, Ta and alloys containing these metals can be preferably used. . In particular, Al and its alloys are desirable because of their light weight and high energy density. The thickness of the positive electrode current collector is not particularly limited, but is usually about 1 to 50 μm.

[Electrolytes]
Any electrolyte such as an electrolytic solution or a solid electrolyte can be used as the electrolyte. Here, the electrolyte refers to all ionic conductors, and both the electrolytic solution and the solid electrolyte are included in the electrolyte.
As the electrolytic solution, for example, a solution obtained by dissolving a solute in a non-aqueous solvent can be used. As the solute, an alkali metal salt, a quaternary ammonium salt, or the like can be used. Specifically, LiClO ₄ , LiPF ₆ , LiBF ₄ , LiCF ₃ SO ₃ , LiN (CF ₃ SO ₂ ) ₂ , LiN (CF ₃ CF ₂ SO ₂ ) ₂ , LiN (CF ₃ SO ₂ ) (C ₄ F ₉ SO ₂ ), LiC (CF ₃ SO ₂ ) _{3 and the} like are preferably used. One kind of these solutes may be selected and used, or two or more kinds may be mixed and used. The content of these solutes in the electrolytic solution is preferably 0.2 mol / L or more, particularly 0.5 mol / L or more, and 2 mol / L or less, particularly 1.5 mol / L or less.

Examples of the non-aqueous solvent include cyclic carbonates such as ethylene carbonate, propylene carbonate, butylene carbonate and vinylene carbonate, cyclic ester compounds such as γ-butyrolactone; chain ethers such as 1,2-dimethoxyethane; crown ethers, 2- Cyclic ethers such as methyltetrahydrofuran, 1,2-dimethyltetrahydrofuran, 1,3-dioxolane, and tetrahydrofuran; chain carbonates such as diethyl carbonate, ethyl methyl carbonate, and dimethyl carbonate can be used. Among these, a nonaqueous solvent containing a cyclic carbonate and a chain carbonate is preferable.
One type of these solvents may be selected and used, or two or more types may be mixed and used.

The nonaqueous electrolytic solution according to the present invention may contain various auxiliary agents such as a cyclic carbonate having an unsaturated bond in the molecule, a conventionally known overcharge inhibitor, a deoxidizer, and a dehydrator.
Examples of the cyclic carbonate having an unsaturated bond in the molecule include vinylene carbonate compounds, vinyl ethylene carbonate compounds, methylene ethylene carbonate compounds, and the like.

Examples of the vinylene carbonate compounds include vinylene carbonate, methyl vinylene carbonate, ethyl vinylene carbonate, 4,5-dimethyl vinylene carbonate, 4,5-diethyl vinylene carbonate, fluoro vinylene carbonate, trifluoromethyl vinylene carbonate, and the like.
Examples of the vinyl ethylene carbonate compound include vinyl ethylene carbonate, 4-methyl-4-vinyl ethylene carbonate, 4-ethyl-4-vinyl ethylene carbonate, 4-n-propyl-4-vinyl ethylene carbonate, 5-methyl- Examples include 4-vinylethylene carbonate, 4,4-divinylethylene carbonate, 4,5-divinylethylene carbonate, and the like.

Examples of the methylene ethylene carbonate compound include methylene ethylene carbonate, 4,4-dimethyl-5-methylene ethylene carbonate, 4,4-diethyl-5-methylene ethylene carbonate, and the like.
Of these, vinylene carbonate and vinyl ethylene carbonate are preferable, and vinylene carbonate is particularly preferable.

These may be used individually by 1 type, or may use 2 or more types together.
When the non-aqueous electrolyte contains a cyclic carbonate compound having an unsaturated bond in the molecule, the proportion in the non-aqueous electrolyte is usually 0.01% by mass or more, preferably 0.1% by mass or more, particularly Preferably it is 0.3 mass% or more, Most preferably, it is 0.5 mass% or more, Usually 8 mass% or less, Preferably it is 4 mass% or less, Most preferably, it is 3 mass% or less.

  By including in the electrolyte a cyclic carbonate having an unsaturated bond in the molecule, the cycle characteristics of the battery can be improved. Although the reason is not clear, it is presumed that a stable protective film can be formed on the surface of the negative electrode. However, when the content is small, this property is not sufficiently improved. However, if the content is too large, the gas generation amount tends to increase during high-temperature storage, so the content in the electrolyte is preferably in the above range.

Examples of the overcharge inhibitor include aromatic compounds such as biphenyl, alkylbiphenyl, terphenyl, partially hydrogenated terphenyl, cyclohexylbenzene, t-butylbenzene, t-amylbenzene, diphenyl ether, and dibenzofuran; 2-fluoro Partially fluorinated products of the above aromatic compounds such as biphenyl, o-cyclohexylfluorobenzene, p-cyclohexylfluorobenzene; fluorine-containing compounds such as 2,4-difluoroanisole and 2,5-difluoroanisole; Anisole compounds and the like can be mentioned.
These may be used alone or in combination of two or more.
The ratio of the overcharge inhibitor in the non-aqueous electrolyte is usually 0.1 to 5% by mass. By containing an overcharge preventing agent, rupture / ignition of the battery can be suppressed during overcharge or the like.

Other auxiliary agents include, for example, carbonate compounds such as fluoroethylene carbonate, trifluoropropylene carbonate, phenylethylene carbonate, erythritan carbonate, spiro-bis-dimethylene carbonate, methoxyethyl-methyl carbonate; succinic anhydride, anhydrous glutar Carboxylic acid anhydrides such as acid, maleic anhydride, citraconic anhydride, glutaconic anhydride, itaconic anhydride, diglycolic anhydride, cyclohexanedicarboxylic anhydride, cyclopentanetetracarboxylic dianhydride, phenylsuccinic anhydride; Ethylene sulfite, 1,3-propane sultone, 1,4-butane sultone, methyl methanesulfonate, busulfan, sulfolane, sulfolene, dimethyl sulfone, tetramethylthiuram monosulfide Sulfur-containing compounds such as N, N-dimethylmethanesulfonamide and N, N-diethylmethanesulfonamide; 1-methyl-2-pyrrolidinone, 1-methyl-2-piperidone, 3-methyl-2-oxazolidinone, 1,3 -Nitrogen-containing compounds such as dimethyl-2-imidazolidinone and N-methylsuccinimide; hydrocarbon compounds such as heptane, octane and cycloheptane; fluorine-containing compounds such as fluorobenzene, difluorobenzene, hexafluorobenzene and benzotrifluoride An aromatic compound etc. are mentioned.
These may be used alone or in combination of two or more.
The ratio of these auxiliaries in the nonaqueous electrolytic solution is usually 0.1 to 5% by mass. By containing these auxiliaries, capacity maintenance characteristics and cycle characteristics after high-temperature storage can be improved.

  Further, the non-aqueous electrolyte solution may include an organic polymer compound in the electrolyte solution, and may be a solid electrolyte such as a gel, rubber, or solid sheet. In this case, specific examples of the organic polymer compound include polyether polymer compounds such as polyethylene oxide and polypropylene oxide; crosslinked polymers of polyether polymer compounds; vinyl alcohol polymers such as polyvinyl alcohol and polyvinyl butyral. Compound; insolubilized product of vinyl alcohol polymer; polyepichlorohydrin; polyphosphazene; polysiloxane; vinyl polymer such as polyvinylpyrrolidone, polyvinylidene carbonate, polyacrylonitrile; poly (ω-methoxyoligooxyethylene methacrylate), Examples thereof include polymer copolymers such as poly (ω-methoxyoligooxyethylene methacrylate-co-methyl methacrylate).

[Other components]
In addition to the electrolyte, the negative electrode, and the positive electrode, an outer can, a separator, a gasket, a sealing plate, a cell case, and the like can be used for the non-aqueous electrolyte secondary battery as necessary.
The material and shape of the separator are not particularly limited. The separator is separated so that the positive electrode and the negative electrode do not come into physical contact with each other, and preferably has high ion permeability and low electrical resistance. The separator is preferably selected from materials that are stable with respect to the electrolyte and excellent in liquid retention. Specific examples include porous sheets or nonwoven fabrics made from polyolefins such as polyethylene and polypropylene.

[Shape of non-aqueous electrolyte secondary battery]
The shape of the nonaqueous electrolyte secondary battery of the present invention is not particularly limited. For example, a cylinder type in which a sheet electrode and a separator are spiral, a cylinder type having an inside-out structure in which a pellet electrode and a separator are combined, a pellet electrode and a separator It can be made into the coin type etc. which were laminated | stacked.

[Method for producing non-aqueous electrolyte secondary battery]
The method for producing the nonaqueous electrolyte secondary battery of the present invention having at least an electrolyte, a negative electrode, and a positive electrode is not particularly limited, and can be appropriately selected from commonly employed methods. An example of the method for producing the nonaqueous electrolyte secondary battery of the present invention is as follows: a negative electrode is placed on an outer can, an electrolytic solution and a separator are provided thereon, and a positive electrode is placed so as to face the negative electrode; A method of assembling the battery by caulking with a sealing plate is mentioned.

EXAMPLES Next, although an Example demonstrates this invention further in detail, this invention is not limited at all by these Examples, unless the summary is exceeded.
[Example 1]
(Solid phase reaction)
Titanium oxide powder (“Titanium (IV) oxide, anatase type” manufactured by Wako Pure Chemical Industries, Ltd.) and niobium pentoxide powder (“Nb ₂ O ₅ , Ceramic Grade” manufactured by HC Starck) in molar ratio Weighed the mixture to a ratio of 1: 1, added an appropriate amount of ethanol in a mortar, wet-mixed, placed in an alumina crucible, and heat-treated in an air oven at 1000 ° C. for 24 hours. Then, the mixture was pulverized and mixed again in a mortar, and heat-treated at 1000 ° C. for 24 hours, the XRD peak coincided with TiNb ₂ O _7. The specific surface area by the BET method by N ₂ adsorption was 1.77 m ² / g. Met.

<XRD measurement conditions>
X-ray source: Cu-Kα ray (λ = 1.5405Å),
Output setting: 40 kV, 30 mA
Optical conditions during measurement:
Divergent slit = 1 °
Scattering slit = 1 °
Receiving slit = 0.2mm
Diffraction peak position 2θ (Diffraction angle)
Measurement range 2θ = 5 to 60 degrees Scan speed: 0.05 degrees (2θ) / sec
Continuous scan <BET specific surface area measurement conditions>
The BET specific surface area was 150 ° C. under reduced pressure (degree of vacuum 5 × 10 ⁻⁴ Torr or less) with respect to the negative electrode material powder using a specific surface area measuring device “NOVA1200” (manufactured by Yuasa Ionics Co., Ltd.)
High-purity nitrogen gas adjusted so that the relative pressure of nitrogen with respect to atmospheric pressure is 0.01, 0.02, 0.04, 0.07, 0.10 (5N8) was used, and the value measured by the nitrogen adsorption BET 5-point method was used.

<Method for producing negative electrode for lithium secondary battery>
20 mg of carbon black (“Denka Black Powder” manufactured by Denki Kagaku Kogyo Co., Ltd.) as a conductive auxiliary agent was added to 70 mg of the negative electrode material powder produced by the above method, and mixed in a mortar. To this mixture, 10 mg of PTFE (“6-J” manufactured by Mitsui DuPont Fluorochemical Co., Ltd.) as a binder was further added and further mixed in a mortar. The obtained mixture containing the binder was stretched, punched out to a diameter of 9 mmφ, and further pressure-bonded to a stainless steel mesh at a pressure of 10 kN to obtain a negative electrode. Here, the weight of the negative electrode was adjusted so that the weight (excluding the stainless steel mesh) was in the range of 6.5 to 7.5 mg when punched to 9 mmφ.
This negative electrode was vacuum-dried at 110 ° C. for a whole day and night to obtain a negative electrode for evaluation.

<Production method of lithium secondary battery>
The obtained negative electrode was transferred to a glove box under an argon atmosphere, and 1 mol / L-LiPF ₆ using a mixed solution of ethylene carbonate (EC) / ethyl methyl carbonate (EMC) = 3/7 (weight ratio) as a solvent as an electrolytic solution. A coin battery (lithium secondary battery) was manufactured using the electrolytic solution, a polyethylene separator as a separator, and a lithium metal counter electrode as a counter electrode.

<Discharge capacity evaluation>
Charge to a lithium counter electrode to 1.0 V at a current density of 0.15 mA / cm ² , and
Charging / discharging at a constant voltage of 10 mV until the current value reaches 0.02 mA, doping lithium into the negative electrode, and then discharging to 2.5 V with respect to the lithium counter electrode at a current density of 0.15 mA / cm ² The cycle was repeated 5 cycles, and the average value of the discharge at the 3rd to 5th cycles was defined as the discharge capacity. Further, when the discharge capacity per weight was determined, the weight of the active material was obtained by subtracting the weight of the conductive additive, the binder, and the stainless mesh from the weight of the negative electrode, and calculated according to the following.

Discharge capacity (mAh / g)
= 3-5th cycle average discharge capacity (mAh) / active material weight (g)
Active material weight (g) = Negative electrode weight (g) − (Binder weight (g) + Conductive auxiliary agent weight (g)
+ Stainless steel mesh weight (g)

<Evaluation of charge / discharge efficiency>
When measuring the discharge capacity, it was calculated according to the following.
Charge / discharge efficiency (%) = {3rd discharge capacity (mAh) / 3rd charge capacity (mAh)} × 1
00

<Rate characteristic evaluation>
Charge to a lithium counter electrode to 1.0 V at a current density of 0.15 mA / cm ² , and
The battery was charged at a constant voltage of 10 mV until the current value reached 0.02 mA, doped with lithium in the negative electrode, and then discharged to 2.5 V with respect to the lithium counter electrode at a rate of 5 C to obtain a discharge capacity.
Table 1 shows the physical properties and battery evaluation results of the negative electrode material powder.

<XPS measurement conditions>
For XPS analysis (X-ray photoelectron spectroscopy), an ESCA manufactured by ULVAC-PHI is used, an Al Kα ray is used as an X-ray source, an output is 14 kV, 350 W, and the extraction angle is 65 ° by multiplex measurement. . The measurement sample is a battery with a current density of 0.15 mA / cm ² .
After charging to 0V and further charging until the current value reaches 0.02mA at a constant voltage of 10mV, the battery is disassembled in a glove box filled with argon gas, the negative electrode is cut out, and the XPS device is exposed to the atmosphere Set. The XPS spectrum obtained by the measurement is Nb (+ V
The 3d5 / 2 peak of (valence) was set to 207.5 eV, and the charge correction was performed. For peak analysis, baseline correction was performed in the range of 202 eV to 215 eV using analysis software (multipak) attached to the apparatus, and curve fitting was performed with four peaks. The result is shown in FIG. Peak a is located at 204.3 eV.

[Example 2]
(Solid phase reaction)
In Example 1, the same operation was performed except that heat treatment was performed at 1100 ° C. The XRD peak was consistent with TiNb ₂ O ₇ . The specific surface area according to the BET method by N ₂ adsorption was 1.13 m ² / g. Using this powder, the negative electrode and coin battery were prepared and evaluated in the same manner as in Example 1, and the results are shown in Table 1.

[Example 3]
(Solid phase reaction)
In Example 1, the same operation was performed except that the crucible was heat-treated at 1300 ° C. on platinum. The XRD peak was consistent with TiNb ₂ O ₇ . The specific surface area according to the BET method by N ₂ adsorption was 0.43 m ² / g. Using this powder, the negative electrode and coin battery were prepared and evaluated in the same manner as in Example 1, and the results are shown in Table 1.

[Comparative Example 1]
(Solid phase reaction)
In Example 3, the same operation was performed except that heat treatment was performed at 1400 ° C. for 24 hours. The XRD peak was consistent with TiNb ₂ O ₇ . Specific surface area of BET method by N ₂ adsorption is 0.17
m ² / g. Using this powder, the negative electrode and coin battery were prepared and evaluated in the same manner as in Example 1, and the results are shown in Table 1.

[Example 4]
(Solid phase reaction)
In Example 1, the same operation was performed except that the molar ratio of the titanium oxide powder to the niobium pentoxide powder was 2: 5 and the heat treatment temperature was 1100 ° C. The XRD peak was consistent with Ti ₂ Nb ₁₀ O ₂₉ . The specific surface area according to the BET method by N ₂ adsorption was 0.69 m ² / g. Using this powder, the negative electrode and coin battery were prepared and evaluated in the same manner as in Example 1, and the results are shown in Table 1.

[Example 5]
(Solid phase reaction)
In Example 4, the same operation was performed except that the crucible was heat-treated on platinum at 1300 ° C. for 24 hours. The XRD peak was consistent with Ti ₂ Nb ₁₀ O ₂₉ . The specific surface area according to the BET method by N ₂ adsorption was 0.75 m ² / g. Using this powder, the negative electrode and coin battery were prepared and evaluated in the same manner as in Example 1, and the results are shown in Table 1.

[Example 6]
(Solid phase reaction)
In Example 5, the same operation was performed except that the heat treatment temperature was 1400 ° C. The XRD peak was consistent with Ti ₂ Nb ₁₀ O ₂₉ . The specific surface area according to the BET method by N ₂ adsorption was 0.34 m ² / g. Using this powder, the negative electrode and coin battery were prepared and evaluated in the same manner as in Example 1, and the results are shown in Table 1.

[Example 7]
(Solid phase reaction)
In Example 1, the same operation was performed except that the crucible was made of platinum and the molar ratio of the titanium oxide powder to the niobium pentoxide powder was heat-treated at 1:12, 1300 ° C. for 24 hours. The XRD peak was consistent with TiNb ₂₄ O ₆₂ . The specific surface area according to the BET method by N ₂ adsorption was 0.20 m ² / g. Using this powder, the negative electrode and coin battery were prepared and evaluated in the same manner as in Example 1, and the results are shown in Table 1.

[Example 8]
(Solid phase reaction)
In Example 1, the same operation was performed except that the crucible was made of platinum and the molar ratio of titanium oxide powder to niobium pentoxide powder was heat-treated at 1: 7, 1400 ° C. for 24 hours. The XRD peak was consistent with TiNb ₂₄ O ₆₂ . The specific surface area according to the BET method by N ₂ adsorption was 0.66 m ² / g. Using this powder, the negative electrode and coin battery were prepared and evaluated in the same manner as in Example 1, and the results are shown in Table 1.

[Comparative Example 2]
(Solid phase reaction)
In Comparative Example 1, the same operation was performed except that the molar ratio of the titanium oxide powder and the niobium pentoxide powder was 1:12. The XRD peak was consistent with TiNb ₂₄ O ₆₂ . The specific surface area according to the BET method by N ₂ adsorption was 0.16 m ² / g. Using this powder, the negative electrode and coin battery were prepared and evaluated in the same manner as in Example 1, and the results are shown in Table 1.

Table 1 shows the following.
The negative electrode material powders of Comparative Examples 1 and 2 are composite oxides containing titanium and niobium whose specific surface area by the BET method is smaller than that of the present invention. These discharge capacities and charge / discharge efficiencies of 3rd were low, and the rate characteristics were also poor.
On the other hand, the negative electrode material powders of the present invention of Examples 1 to 8 are composite oxide negative electrode materials containing titanium and niobium whose specific surface area by the BET method is within the specified range of the present invention. It satisfies the range. When such a negative electrode material powder is used, a high-performance battery having high discharge capacity, 3rd charge / discharge efficiency, and excellent rate characteristics can be obtained.

  By using the negative electrode material of the present invention, it is possible to realize a non-aqueous electrolyte secondary battery having high discharge capacity, high charge / discharge efficiency, and excellent rate characteristics. Therefore, the negative electrode for a non-aqueous electrolyte secondary battery of the present invention and The non-aqueous electrolyte secondary battery can be suitably used in a field where a non-aqueous electrolyte secondary battery requiring a large and high input / output characteristic is applied.

Claims (5)

A non-aqueous electrolyte secondary battery comprising a composite oxide containing titanium (Ti) and niobium (Nb), wherein the specific surface area by the BET method is 0.18 m ² / g or more Negative electrode material. XP in which the 3d 5/2 peak of Nb (+ V valence) is 207.5 eV in the charged state
2. The negative electrode material for a non-aqueous electrolyte secondary battery according to claim 1, which has a peak a at a position of binding energy = 204.3 ± 1 eV in S analysis. The composite oxide containing titanium (Ti) and niobium (Nb) has the same structure as at least one of TiNb ₂ O ₇ , Ti ₂ Nb ₁₀ O _29, and TiNb ₂₄ O ₆₂ , 2. The negative electrode material for a nonaqueous electrolyte secondary battery according to 2.   A negative electrode for a nonaqueous electrolyte secondary battery comprising the negative electrode material according to any one of claims 1 to 3 as a negative electrode active material. A nonaqueous electrolyte secondary battery comprising a positive electrode and a negative electrode capable of inserting and extracting lithium ions, and an electrolyte, wherein the negative electrode is a negative electrode for a nonaqueous electrolyte secondary battery according to claim 4. Electrolyte secondary battery.

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