JP6096984B2 - Negative electrode active material, non-aqueous electrolyte battery, battery pack and vehicle - Google Patents

Description

  The present embodiment relates to an active material, a manufacturing method thereof, a nonaqueous electrolyte battery, and a battery pack.

  Non-aqueous electrolyte batteries using titanium oxide as a negative electrode generate lithium dendride compared to batteries using carbonaceous materials because the lithium storage and release potential of titanium oxide is higher than that of carbonaceous materials. Is less likely to do. In addition, since the oxide of titanium is ceramic, it is difficult to cause thermal runaway. Therefore, a non-aqueous electrolyte battery using a titanium oxide for the negative electrode has high safety.

  However, titanium oxide has a higher reactivity with non-aqueous electrolyte than a commonly used graphite negative electrode. When the oxide of titanium reacts with the nonaqueous electrolyte, for example, there is a problem that the impedance increases due to decomposition products of the nonaqueous electrolyte, or gas is generated and the battery swells. For this reason, the battery using the oxide of titanium sometimes has a short cycle life. In particular, a titanium oxide having a monoclinic titanium dioxide crystal structure has a problem in that the cycle life is remarkably reduced.

JP 2010-534915 A JP 2013-69532 A JP 2010-118330 A

R. Marchand, L. Brohan, M. Tournoux, Material Research Bulletin 15, 1129 (1980).

  Provided are a nonaqueous electrolyte battery with improved cycle life, an active material used in the battery, a method for producing the same, and a battery pack.

According to the embodiment, a negative electrode active comprising: titanium oxide particles having a TiO ₂ (B) structure; and a layer containing a Si component and an organic component present on at least a part of the surface of the titanium oxide particles. Substance is provided. In the negative electrode active material, the C / Si molar ratio is 0.4 or more and 2 or less.

  In addition, according to the embodiment, a nonaqueous electrolyte battery including the negative electrode including the active material, the positive electrode, and a nonaqueous electrolyte is provided.

According to another embodiment, a battery pack including the nonaqueous electrolyte battery is provided. Moreover, according to other embodiment, the vehicle containing the battery pack which concerns on embodiment is provided.

It is sectional drawing which shows the flat type nonaqueous electrolyte battery of embodiment. It is an expanded sectional view of the A section of FIG. It is a partial notch perspective view which shows typically the other flat type nonaqueous electrolyte battery which concerns on embodiment. It is an expanded sectional view of the B section of FIG. It is a disassembled perspective view of the battery pack which concerns on embodiment. It is a block diagram which shows the electric circuit of the battery pack of FIG.

  Each embodiment will be described below with reference to the drawings. In addition, the same code | symbol shall be attached | subjected to a common structure through embodiment and the overlapping description is abbreviate | omitted. Each figure is a schematic diagram for promoting explanation and understanding of the invention, and its shape, dimensions, ratio, and the like are different from those of an actual device. However, these are in consideration of the following explanation and known techniques. The design can be changed as appropriate.

(First embodiment)
The negative electrode active material of the first embodiment includes titanium oxide particles and a layer that exists on the surface of the titanium oxide particles and includes a Si component and an organic component. C / Si molar ratio is 0.4 or more and 2 or less.

  Since the oxide of titanium has a solid acid point or a hydroxyl group on the surface, the reactivity with the non-aqueous electrolyte is high. Therefore, in a battery using a titanium oxide as a negative electrode active material, an excessive inorganic film or organic film is formed on the negative electrode with charge and discharge, the resistance increases, and the output characteristics deteriorate. As a result, the electrode performance decreases, the battery internal resistance increases, the nonaqueous electrolyte deteriorates, and the like, and the cycle life of the battery decreases due to these factors.

  In particular, titanium oxide having a monoclinic titanium dioxide crystal structure is a solid acid, and therefore has high reactivity with a non-aqueous electrolyte. Since a titanium oxide having a monoclinic titanium dioxide crystal structure has a high theoretical capacity, it is expected to increase the battery capacity when used as an active material. However, for the reasons described above, there is a problem that the cycle life is significantly reduced.

The crystal structure of monoclinic titanium dioxide mainly belongs to the space group C2 / m and exhibits a tunnel structure. Here, such a crystal structure is referred to as a TiO ₂ (B) crystal structure. A titanium oxide having a monoclinic titanium dioxide crystal structure is referred to as a titanium oxide having a TiO ₂ (B) crystal structure. The detailed crystal structure of TiO ₂ (B) is described in Non-Patent Document 1. The composition of the oxide of titanium having a TiO ₂ (B) structure can be represented by the general formula Li _x TiO ₂ (0 ≦ x ≦ 1). Here, x in the above equation varies in the range of 0 to 1 depending on the charge / discharge reaction.

In a battery using a carbonaceous material or spinel structure lithium titanate as the negative electrode active material, it is possible to suppress the reaction between the negative electrode and the nonaqueous electrolyte by adding vinylene carbonate to the nonaqueous electrolyte. In such a battery, vinylene carbonate is reduced and decomposed on the negative electrode to form a stable film on the negative electrode, whereby excessive film formation can be suppressed. However, in a battery in which a titanium oxide having a solid acid point or a hydroxyl group on the surface, such as a titanium oxide having a TiO ₂ (B) structure, is used as a negative electrode active material, even if vinylene carbonate is added. The reaction with the nonaqueous electrolyte is not suppressed, and a film is continuously formed on the negative electrode. Therefore, there exists a problem that resistance increases and a cycle life falls.

  However, according to the present embodiment, it includes a titanium oxide particle and a layer that exists on the surface of the titanium oxide particle and includes a Si component and an organic component, and the C / Si molar ratio is 0.4 or more and 2 By using the following negative electrode active material, it is possible to suppress an increase in the resistance of the nonaqueous electrolyte battery and improve the cycle life.

Particles of oxides of titanium, has long as it has Lewis acid point (solid acid point), for example, oxides of titanium TiO ₂ (B) crystalline structure, TiO 2 having an anatase _structure, rutile structure TiO ₂ etc. can be mentioned.

  Titanium oxide particles may be those in which primary particles exist alone, secondary particles in which primary particles are aggregated, or particles in which primary particles and secondary particles are mixed.

Examples of organic components include those containing C, specifically organic solvents dispersible in metal alkoxides (for example, CH ₃ group, C ₂ H ₅ group, C ₃ H ₇ group, C ₄ H ₉ group, etc. Organic components), other organic solvents, or part of these organic solvents. The type of organic component can be one type or two or more types. The organic component remaining in the coating layer is presumed to be entangled in the SiO ₂ network covering the active material surface generated by the polymerization reaction.

Examples of the Si component include inorganic oxides containing Si, such as silicon oxide (for example, SiO ₂ ).

On the surface of the titanium oxide particles, a layer containing SiO ₂ and C can be formed on the entire surface or a part of the surface. The reason why the C / Si molar ratio is in the range of 0.4 to 2 is as follows. When the C / Si molar ratio is less than 0.4, the reductive decomposition reaction of the nonaqueous electrolyte proceeds and the cycle life is shortened. When the C / Si molar ratio exceeds 2, the Li occlusion and release of the negative electrode active material is inhibited and the cycle life is shortened.

  A more preferable range of the C / Si molar ratio is 0.4 or more and 1.2 or less.

  In order to form a coating layer containing an inorganic oxide containing Si and an organic component, for example, a metal alkoxide is used to coat the surface of the inorganic oxide containing Si, and further, the oxide is contained in the oxide. In order to allow the organic component to coexist, adjustment of drying conditions and use of an organic substance having a high boiling point together with a metal alkoxide can be mentioned.

  Examples of the metal alkoxide include monomers such as methyl silicate or ethyl silicate, and condensation polymers such as methyl polysilicate and ethyl polysilicate. The kind of metal alkoxide to be used can be one kind or two or more kinds.

  A method for forming a coating layer containing Si on the surface of titanium oxide particles will be described below. A solution obtained by diluting a metal alkoxide with a solvent such as ethanol and titanium oxide particles are mixed, and the obtained mixture is dried. Next, a coating layer is formed by a sol-gel reaction (hydrolysis / polymerization reaction). Inorganic components containing Si on the surface of titanium oxide particles do not contribute to charge and discharge, so the water necessary for the sol-gel reaction is added as liquid water to uniformly coat the thin inorganic oxide on the particles. It is desirable not to.

  In order to leave the organic component inside the inorganic coating layer, the drying temperature is preferably 0 to 50 ° C., more preferably 10 to 40 ° C. If the temperature is low, the time required for the hydrolysis / polymerization reaction or drying of the diluting solvent becomes long. On the other hand, if the drying temperature is high, hydrolysis / polymerization reaction and volatilization of the diluting solvent occur quickly, so that the inorganic organic film is formed unevenly or the residual organic components are reduced due to rapid volatilization of the solvent. This is not desirable.

Further, the drying process is performed in an environment with low humidity so that excess moisture is not taken into the particle surface. The dew point under desirable drying conditions is 0 ° C. or less, more desirably −20 ° C., and even more desirably −40 ° C. or less. When dried in an environment having a dew point of −40 ° C. or lower, a coating layer containing Si can be formed without taking in excess moisture. For example, compared with a general laboratory environment (temperature is 25 ° C., humidity is 25 to 70%), according to the manufacturing conditions of the embodiment, the drying speed is slowed down, but is thereby taken into the coating layer during formation. By reducing the amount of water, an inorganic coating layer containing Si is uniformly formed on the particle surface, and an organic component (for example, a residual organic component derived from a metal alkoxide) can be taken into the inorganic coating layer. The amount of the organic component incorporated into the inorganic coating layer can be adjusted by methods other than the drying conditions. For example, when mixing metal alkoxide, titanium oxide particles and a diluting solvent (ethanol or the like), it can also be adjusted by adding an organic solvent having a high boiling point.

  In addition to adjusting the dew point in the drying step, for example, a mixture of metal alkoxide and titanium oxide particles and a diluting solvent (such as ethanol) was replaced with a drying gas (such as nitrogen or argon). The amount of organic components taken into the inorganic coating layer can also be adjusted by drying in the bath.

Further, Si amount in terms of SiO ₂ in the coating layer is preferably 0.5 to 20% by weight relative to the weight of the oxides of titanium calculated as TiO _2. By reducing the amount of Si in terms of SiO ₂ in the coating layer to 20% by weight or less, a decrease in battery capacity can be suppressed. On the other hand, the reaction between titanium oxide and the nonaqueous electrolyte can be suppressed by setting the Si content to 0.5 wt% or more. A more preferable range is 0.5 to 15% by weight, and a further preferable range is 1 to 10% by weight.

The C / Si molar ratio, the weight of titanium oxide in terms of TiO ₂ , and the amount of Si in terms of SiO ₂ are measured by wet analysis such as ICP (inductively coupled plasma). The First, in the case of a negative electrode in a battery, a portion containing an active material is taken out, and a polymer material or a conductive agent mixed in the active material is used in combination with a Soxhlet extraction method (detailed method will be described later) and heat treatment. To remove the active material. The active material is eluted in an acid solvent, and the total composition amount of particles mainly composed of titanium oxide and the constituent components of the coating layer mainly composed of Si is calculated by an ICP emission analyzer. Next, the sample was cut by embedding the same active material in an epoxy resin, etc., and observed by SEM (scanning electron microscope) -EDX (energy-dispersive X-ray analysis). In addition to confirming the material covering the surface, the elemental analysis of the particles and the coating material is performed with the attached EDX. By the combined use of the above ICP analysis and SEM-EDX, the weight of each component of the particles and the coating layer can be calculated. TEM (Transmission Electron Microscope)-When conducting elemental analysis with EDX, the active material after coating treatment is pretreated for TEM observation, and elemental analysis is performed by EDX from the center of the particle toward the edge. In this way, it is observed that the Si peak increases from the center toward the end with respect to the Ti peak. The C / Si molar ratio is measured by the following method. The amount of C is determined by measuring the total amount of carbon in the active material by a method such as an infrared absorption method. Further, the total amount of Si in the active material measured by ICP analysis is measured. The C / Si ratio is calculated from the obtained C amount and Si amount. At that time, it is confirmed in advance by a scanning electron microscope (SEM) or a transmission electron microscope (TEM) that Si and C are not present inside the active material.

(Method for confirming inorganic coating layer containing Si element)
A method for confirming the presence of the inorganic coating layer containing Si on the titanium oxide particles is performed by the following method. The presence of an inorganic compound containing Si is confirmed by dissolving the active material in a 1N aqueous sulfuric acid solution and examining the Si component in the solution using an analysis technique such as ICP emission analysis. After confirming the presence, pyridine is adsorbed on the active material powder, and the infrared absorption spectrum of the powder is observed to confirm that the inorganic coating layer containing Si is present on the titanium oxide particle surface. can do. For example, a case where titanium oxide particles such as TiO ₂ (B) are coated with an inorganic coating layer containing Si will be described. With a solid acid such as TiO ₂ (B), the red of the powder after pyridine adsorption. When the external absorption spectrum is acquired, B acid points and L acid points appear. When the infrared spectrum is examined by adsorbing pyridine on each of the TiO ₂ (B) particle surface formed with the Si element-containing coating layer using the method of the embodiment and uncoated TiO ₂ (B) particles, how peaks of the L acid sites only (e.g. 1608 cm ^-1) is selectively reduced as compared to the peak of B acid sites (e.g. 1540 cm ^-1) are observed in the active material of the embodiment.

Moreover, it can confirm directly that the inorganic type coating layer containing Si exists in the particle | grain surface of the oxide of titanium by TEM-EDX observation of the active material of embodiment. Since the inorganic coating layer is very thin, it may not be possible to confirm the state in which a film is formed on the surface of the titanium oxide particles in a region where the amount of Si in terms of SiO ₂ is small. In this case, if the EDX beam is measured while shifting from the particle center to the end (particle surface side), the peak intensity of Si increases with respect to the peak intensity of Ti of the active material component as it moves to the end. A relatively increasing state is observed.

(Infrared diffuse reflectance spectroscopy)
A method for measuring the infrared diffuse reflection spectrum will be described.
First, an active material to be used for measurement is put in a sample cup and installed in a diffuse reflection measuring device. While flowing nitrogen gas at 50 mL / min, the temperature is raised to 500 ° C. and held for 1 hour. Thereafter, the temperature is lowered to room temperature, and the temperature is raised to 100 ° C. again. Next, the inside of the cell in which the sample cup is installed is decompressed, pyridine vapor is introduced into the cell, and is adsorbed for 30 minutes.

  Next, while flowing nitrogen gas at 100 mL / min, it is held at 100 ° C. for 1 hour, and then heated to 150 ° C. and held for 1 hour. As a result, pyridine physically adsorbed or hydrogen bonded to the active material is eliminated. Thereafter, infrared diffuse reflection measurement is performed.

  In the obtained spectrum, the background is excluded and the peak area is obtained. The peak area is obtained by subtracting the baseline from both ends of the peak.

  According to such infrared diffuse reflection spectroscopy, the functional group present in the sample is known, and therefore the configuration of the measurement sample can be clarified.

(Soxhlet extraction method)
In the Soxhlet extraction method, the polymer material can be removed from the electrode by using N-methylpyrrolidone (NMP) as a solvent. Only the active material can be extracted by oxidizing the conductive agent with oxygen or ozone and removing it as carbon dioxide from the mixture of the active material and the conductive agent (for example, carbon material) obtained by the Soxhlet extraction method.

The titanium oxide as the active material in the embodiment preferably includes a titanium oxide having a TiO ₂ (B) structure. Since the titanium oxide having the TiO ₂ (B) structure has high reactivity with the non-aqueous electrolyte, the configuration of the embodiment can be expected to greatly improve the cycle life of the battery.

The fact that the oxide of titanium has a crystal structure of TiO ₂ (B) can be measured by powder X-ray diffraction using Cu—Kα as a radiation source. The powder X-ray diffraction measurement can be performed as follows. First, the target sample is pulverized until the average particle size becomes about 5 μm. The average particle diameter can be determined by a laser diffraction method. The crushed sample is filled in a holder portion having a depth of 0.2 mm formed on a glass sample plate. At this time, care should be taken so that the sample is sufficiently filled in the holder portion. Also, be careful that there are no cracks or voids due to insufficient filling of the sample. Next, using another glass plate from the outside, it is sufficiently pressed and smoothed. Be careful not to cause unevenness from the reference surface of the holder due to excessive or insufficient filling amount. Next, the glass plate filled with the sample is placed in a powder X-ray diffractometer, and a diffraction pattern is obtained using Cu-Kα rays. In general, TiO ₂ (B) has low crystallinity, so that depending on the sample, the peak intensity of the X-ray diffraction pattern is weak in powder X-ray measurement, and it is difficult to observe the intensity of any peak. The diffraction spectrum of the titanium oxide obtained by the powder X-ray diffraction method shows that the Si amount in the coating layer in terms of SiO ₂ is 0.5 to 20 with respect to the weight of the titanium oxide in terms of TiO _2. When the content is% by weight, it can be measured with little influence on the coating layer. Further, the titanium oxide having such a TiO ₂ (B) structure may contain a different element. As the different element, at least one element selected from Zr, Nb, Mo, Ta, Y, P, and B can be used. By including the different elements, the influence of Lewis acid sites on the surface of the titanium oxide is suppressed.

  The foreign element is preferably contained in a range of 0.01 to 8% by weight with respect to the total weight of the titanium oxide containing the foreign element. By containing 0.01% by weight or more of a different element, the influence of Lewis acid sites can be reduced. From the viewpoint of the solid solubility limit of different elements, it is preferably contained in the range of 8% by weight or less. More preferably, the different elements are contained in the range of 0.05 to 3% by weight. In the titanium oxide containing a different element, the content of the different element can be measured by inductively coupled plasma (ICP) emission spectroscopy.

  The active material of the first embodiment described above includes titanium oxide particles and a layer that is present on the surface of the titanium oxide particles and contains a Si component and an organic component. / Si molar ratio is 0.4 or more and 2 or less. The nonaqueous electrolyte battery using this active material can suppress increase in resistance and improve cycle life.

(Second Embodiment)
Next, the manufacturing method of the active material which concerns on 1st Embodiment is demonstrated. According to this embodiment, the surface physical properties of titanium oxide can be modified by forming a coating layer containing a metal oxide containing Si element and a residual organic component on the surface of titanium oxide particles. The active material according to the first embodiment can be manufactured.

  Examples of a method for forming a coating layer containing a metal oxide containing Si element on the surface of titanium oxide include the following two methods.

(First method)
In the first method, titanium oxide particle powder is mixed with a metal alkoxide containing Si element to obtain a mixture, and by drying the mixture, Si is deposited on the surface of titanium oxide particles. Forming a coating layer containing the contained metal oxide.

  Forming a metal oxide precursor on the surface of titanium oxide particles by mixing titanium oxide particle powder with a metal alkoxide containing Si element and a dilute organic solvent (such as ethanol). Can do. Next, by subjecting this powder to a drying treatment, the metal oxide precursor can be polymerized to form a metal oxide coating layer. Such a method is called a sol-gel method. In order not to form an excessive metal oxide precursor or a non-uniform coating layer on the surface of the active material, it is desirable not to add water required for hydrolysis / polymerization reaction from the outside as liquid water.

  The drying treatment is preferably performed at a low temperature. In order to leave the organic component inside the inorganic coating layer, the drying temperature is preferably 0 to 50 ° C., more preferably 10 to 40 ° C. If the temperature is low, the time required for the hydrolysis / polymerization reaction or drying of the diluting solvent becomes long. On the other hand, if the drying temperature is high, hydrolysis / polymerization reaction and volatilization of the diluting solvent occur quickly, so that the inorganic organic film is formed unevenly or the residual organic components are reduced due to rapid volatilization of the solvent. This is not desirable. When drying is performed at a high temperature, the metal oxide precursor and the organic matter separated by the polymerization reaction are evaporated. As a result, the surface of the titanium oxide particles may not be uniformly coated, and the coating layer may be present in spots. In addition, residual organic components are reduced and cycle characteristics are deteriorated. On the other hand, if the drying temperature is too low, it takes a long time to complete the drying. Therefore, the drying treatment is desirably performed at 0 to 50 ° C. or less, and more desirably performed at a temperature of 10 to 40 ° C.

  Also, in the metal alkoxide, it is desirable to use a polycondensation polymer such as polymethyl silicate or polyethyl silicate rather than a monomer such as methyl silicate or ethyl silicate because the residual organic component can be efficiently left in the inorganic coating. .

  Furthermore, the drying process is performed in an environment with low humidity so that excess water is not taken into the surface of the titanium oxide particles. For the same reason as described in the first embodiment, the dew point under desirable drying conditions is 0 ° C. or lower, more desirably −20 ° C., and further desirably −40 ° C. or lower.

Such a sol-gel method is particularly suitable when the titanium oxide is a titanium oxide having a TiO ₂ (B) structure. The titanium oxide having a TiO ₂ (B) structure has an advantage that no catalyst needs to be added because the catalytic action promotes the polymerization reaction of the alkoxide.

(Second method)
The second method includes Si in which residual organic components are mixed on the surface of titanium oxide particles by drying in a room temperature air atmosphere having a relatively high dew point instead of the low dew point drying environment in the first method. This is a method for producing an inorganic coating. In the first method, water necessary for hydrolysis and polymerization reaction is added as liquid water in order to suppress non-uniform formation of inorganic coating layers due to excessive moisture in the dry environment and volatilization of residual organic components. Without drying, perform the drying process in a low dew point environment. Since the room temperature air environment used in the second method has a relatively high dew point, the hydrolysis / polymerization reaction is likely to proceed, and the organic components may be volatilized. In order to secure the residual organic component and form a thin inorganic coating layer uniformly, the contact between the moisture and the raw material in the dry environment is suppressed, and the residual organic component amount is ensured. As the method, for example, a method using an organic solvent having a high boiling point as a part of a diluting solvent (for example, ethanol) used when mixing metal alkoxide and titanium oxide particles can be mentioned. By using this method, even when the drying process is performed in an environment with a relatively high dew point, the progress of hydrolysis and polymerization reaction can be suppressed and the remaining organic components can be secured. Examples of the high boiling point organic solvent include alcohols such as propanol and butanol, dimethylformamide ((CH ₃ ) ₂ NCHO: boiling point 153 ° C.) and formamide (NH ₂ CHO: boiling point 210) used as a drying inhibitor in the sol-gel method. ° C) and the like. This method can also be applied to the first method, and can be used as a method of adjusting the amount of residual organic components.

(First synthesis method of titanium oxide having TiO ₂ (B) structure)
The titanium oxide used in the present embodiment may be obtained by synthesis from raw materials, or may be commercially available. Hereinafter, a method of synthesizing a titanium oxide having a TiO ₂ (B) structure will be described as a synthesis example of titanium oxide.

A method for synthesizing a titanium oxide having a TiO ₂ (B) structure includes a step of synthesizing an alkali titanate compound by mixing and heating a compound containing Ti and a compound containing an alkali element, and titanium. It includes a step of reacting an acid-alkali compound with an acid to exchange an alkali cation with a proton to obtain a titanate proton compound, and a step of heat-treating the titanate proton compound at least twice.

  First, as a starting material, a compound containing Ti and a compound containing an alkali element are used. These starting materials are mixed at a predetermined stoichiometric ratio and heated to synthesize an alkali titanate compound. The crystal shape of the alkali titanate compound synthesized here may be any shape. The heat treatment can be performed at 800 to 1100 ° C.

Among the starting materials, for the compound containing Ti, one or more compounds selected from anatase TiO ₂ , rutile TiO ₂ , and TiCl ₄ can be used. As the compound containing an alkali element, a compound containing Na, K, or Cs can be used. For example, one or more compounds selected from carbonates, hydroxides, and chlorides can be used.

  Next, proton exchange by acid treatment is performed. First, the alkali titanate compound is thoroughly washed with distilled water to remove impurities. Then, the titanate proton compound can be obtained by acid-treating the alkali titanate compound and exchanging the alkali cation of the alkali titanate compound with protons. Alkali titanate compounds such as sodium titanate, potassium titanate and cesium titanate can exchange their alkali cations with protons without breaking the crystal structure.

  The acid treatment can be performed by adding an acid to the powder of the alkali titanate compound and stirring. As the acid, an acid selected from hydrochloric acid, nitric acid and sulfuric acid having a concentration of 0.5 to 2M can be used. The acid treatment is preferably continued until the alkali cations are sufficiently exchanged for protons. The time for the acid treatment is not particularly limited, but it is preferably 24 hours or more at room temperature around 25 ° C., more preferably about 1 to 2 weeks. Furthermore, it is more preferable to replace the acid solution with a new one every 24 hours. The conditions for the acid treatment can be, for example, 24 hours at room temperature using 1M sulfuric acid.

  For example, by performing an acid treatment while applying vibration such as ultrasonic waves, proton exchange can be performed more smoothly, and a titanate proton compound in a suitable state can be obtained.

In order to perform proton exchange more efficiently, it is also preferable to pulverize the alkali titanate compound in advance with a ball mill or the like. The pulverization can be performed, for example, by rotating a zirconia ball for about 1 to 3 hours at a rotation speed of 600 to 1000 rpm using a zirconia ball having a diameter of about 10 to 15 mm per 100 cm ² container. By performing pulverization for 1 hour or longer, the alkali titanate compound can be sufficiently pulverized. By setting the pulverization time to 3 hours or less, it is possible to prevent a compound different from the target product from being generated by a mechanochemical reaction.

  After the proton exchange is complete, optionally an alkaline solution such as an aqueous lithium hydroxide solution is added to neutralize the remaining acid. The obtained titanate proton compound is washed with distilled water and then dried. It is preferable that the titanate proton compound is sufficiently washed with water until the pH of the wash water falls within the range of 6-8. On the other hand, it is possible to proceed to the next step without neutralizing, washing and drying the acid remaining after the acid treatment.

  Next, the titanate proton compound is heat-treated at least twice. The first heat treatment is performed at a temperature in the range of 350 to 500 ° C. for 1 to 3 hours. Next, the obtained titanium oxide is subjected to a second heat treatment. The second heat treatment is performed at a temperature in the range of 200 to 300 ° C. for 1 to 24 hours. Further, the further heat treatment may be repeated at a temperature in the range of 200 to 300 ° C.

By the above method, a titanium oxide having a TiO ₂ (B) structure can be synthesized. The titanium oxide having a TiO ₂ (B) structure obtained by such a method may contain Li in advance by using a compound containing Li as a starting material. May be occluded.

(Second method for synthesizing titanium oxide containing TiO ₂ (B) structure containing different elements)
Next, a method for synthesizing a titanium oxide having a TiO ₂ (B) structure containing a different element will be described.

  The method includes a step of synthesizing an alkali titanate compound containing a different element by mixing and heating a compound containing Ti, a compound containing an alkaline element, and a compound containing a different element, A process of obtaining a titanate proton compound containing a different element by reacting an alkali titanate compound containing an element with an acid to exchange an alkali cation with a proton, and heating the titanate proton compound containing a different element And a step of producing an oxide of titanium having a monoclinic titanium dioxide crystal structure and containing a different element.

  First, as a starting material, a compound containing Ti, a compound containing an alkali element, and a compound containing a different element are used. These starting materials are mixed at a predetermined stoichiometric ratio and heated to synthesize an alkali titanate compound containing a different element. The crystal shape of the alkali titanate compound synthesized here may be any shape. Although heat processing is not limited to this, It can carry out at 800-1100 degreeC.

  Among the starting materials, compounds described in the first synthesis method can be used as the compound containing Ti and the compound containing an alkali element.

  As the compound containing a different element, a compound containing at least one element selected from Zr, Nb, Mo, Ta, Y, P and B can be used, for example, from carbonate, hydroxide, and the like. One or more selected compounds can be used.

  Examples of alkali titanate compounds containing different elements include, but are not limited to, sodium titanate, potassium titanate and cesium titanate containing different elements.

  Next, proton exchange by acid treatment is performed. First, an alkali titanate compound containing a different element is thoroughly washed with distilled water to remove impurities. Then, the titanate proton compound containing a different element can be obtained by acid-treating the alkali titanate compound and exchanging the alkali cation of the alkali titanate compound with a proton. Alkali titanate compounds such as sodium titanate, potassium titanate and cesium titanate are capable of exchanging their alkali cations with protons without breaking the crystal structure and containing different elements Is the same.

  The acid treatment can be performed by adding an acid to the powder of the alkali titanate compound and stirring. As the acid, an acid selected from hydrochloric acid, nitric acid and sulfuric acid having a concentration of 0.5 to 2M can be used. The acid treatment is preferably continued until the alkali cations are sufficiently exchanged for protons. The time for the acid treatment is not particularly limited, but when hydrochloric acid having a concentration of about 1M is used at around room temperature of 25 ° C., it is preferably performed for 24 hours or more, and more preferably for about 1 to 2 weeks. Furthermore, it is more preferable to replace the acid solution with a new one every 24 hours. As described in the first synthesis method, acid treatment may be performed while applying vibration such as ultrasonic waves. In order to perform proton exchange more efficiently, it is also preferable to pulverize the alkali titanate compound in advance with a ball mill or the like.

  After the proton exchange is complete, optionally an alkaline solution such as an aqueous lithium hydroxide solution is added to neutralize the remaining acid. The obtained titanate proton compound containing a different element is washed with distilled water and then dried. It is preferable that the titanate proton compound is sufficiently washed with water until the pH of the wash water falls within the range of 6-8. On the other hand, it is possible to proceed to the next step without neutralizing, washing and drying the acid remaining after the acid treatment.

Next, by subjecting the titanate proton compound containing the different element to heat treatment, an oxide of titanium having a TiO ₂ (B) structure containing the different element can be obtained.

The heat treatment temperature is appropriately determined depending on the titanate proton compound because the optimum temperature differs depending on the conditions such as the composition, particle diameter, and crystal shape of the titanate proton compound body, but is in the range of 250 to 500 ° C. It is preferable that When it is 250 ° C. or higher, the crystallinity is good, the generation of an impurity phase of H ₂ Ti ₈ O ₁₇ is suppressed, and the electrode capacity, charge / discharge efficiency, and repeatability are also good. On the other hand, when the temperature is 500 ° C. or lower, the generation of impurity phases of H ₂ Ti ₈ O _{17 and} anatase TiO ₂ is suppressed, so that a reduction in electrode capacity can be prevented. A more preferable heat treatment temperature is 300 to 400 ° C.

  The heating time can be set in a range of 30 minutes to 24 hours depending on the temperature. For example, in the case of a temperature of 300 ° C. or higher and 400 ° C. or lower, the temperature can be 1 hour or longer and 3 hours or shorter.

By the above method, a titanium oxide having a TiO ₂ (B) structure containing a different element can be synthesized. The titanium oxide having a TiO ₂ (B) structure obtained by such a method may contain Li in advance by using a compound containing Li as a starting material. May be occluded.

An inorganic system containing Si on the surface of the TiO ₂ (B) particles by the method shown in the first method and the second method for the TiO ₂ (B) particles obtained by the first or second synthesis method described above. By producing the coating layer, titanium oxide particles having a coating layer having a C / Si molar ratio of 0.4 or more and 2 or less can be produced. By using such an active material, it is possible to realize a nonaqueous electrolyte battery in which increase in resistance is suppressed and cycle life is improved.

(Third embodiment)
The nonaqueous electrolyte battery of the third embodiment includes a negative electrode including the active material of the first embodiment, a positive electrode, and a nonaqueous electrolyte.

  The nonaqueous electrolyte battery according to the third embodiment will be described more specifically with reference to the drawings. FIG. 1 is a cross-sectional view of a flat type nonaqueous electrolyte battery. FIG. 2 is an enlarged cross-sectional view of a portion A in FIG. Each figure is a schematic diagram for facilitating the explanation and understanding of the invention, and its shape, dimensions, ratio, etc. are different from the actual device, but these are considered in consideration of the following explanation and known techniques. The design can be changed as appropriate.

  The flat wound electrode group 1 is housed in a bag-shaped exterior member 2 made of a laminate film having a metal layer interposed between two resin layers. The flat wound electrode group 1 is formed by winding a laminate of the negative electrode 3, the separator 4, the positive electrode 5, and the separator 4 in this order from the outside in a spiral shape and press-molding.

  The negative electrode 3 includes a negative electrode current collector 3a and a negative electrode active material-containing layer 3b. As shown in FIG. 2, the outermost negative electrode 3 has a configuration in which a negative electrode active material-containing layer 3b is formed on one surface on the inner surface side of the negative electrode current collector 3a. In the other negative electrode 3, negative electrode active material-containing layers 3b are formed on both surfaces of the negative electrode current collector 3a.

  In the positive electrode 5, positive electrode active material-containing layers 5b are formed on both surfaces of the positive electrode current collector 5a.

  In the vicinity of the outer peripheral end of the wound electrode group 1, the negative electrode terminal 6 is connected to the negative electrode current collector 3 a of the outermost negative electrode 3, and the positive electrode terminal 7 is connected to the positive electrode current collector 5 a of the inner positive electrode 5. The negative electrode terminal 6 and the positive electrode terminal 7 are extended to the outside from the opening of the bag-shaped exterior member 2. For example, the liquid nonaqueous electrolyte is injected from the opening of the bag-shaped exterior member 2. The wound electrode group 1 and the liquid nonaqueous electrolyte are sealed in the exterior member by heat-sealing the opening of the bag-shaped exterior member 2 with the negative electrode terminal 6 and the positive electrode terminal 7 interposed therebetween.

  Hereinafter, the negative electrode, the positive electrode, the nonaqueous electrolyte, the separator, the exterior member, the positive electrode terminal, and the negative electrode terminal used in the nonaqueous electrolyte battery of the embodiment will be described in detail.

(Negative electrode)
The negative electrode includes a negative electrode current collector and a negative electrode active material-containing layer. The negative electrode active material-containing layer includes a negative electrode active material, a conductive agent, and a binder. The negative electrode active material-containing layer is formed on one side or both sides of the negative electrode current collector.

  As the active material, the active material of the first embodiment is used. Such an active material can be manufactured, for example, by the method of the second embodiment. Such an active material is one in which an increase in resistance is suppressed as described above. Therefore, the cycle life of the nonaqueous electrolyte battery can be improved by using a negative electrode containing such an active material.

Note that a titanium oxide other than TiO ₂ (B) may be included as an active material. Examples of other active materials include lithium titanate having a spinel structure (for example, Li _{4 + x} Ti ₅ O ₁₂ (0 ≦ x ≦ 3), Li ₂ Ti ₃ O ₇ having a Ramsdellite structure, LiTiNbO ₅ , LiTi ₃ P ₃ O ₁₂ , TiO ₂ having a rutile structure, TiO ₂ —P ₂ O ₅ (such as TiP ₂ O ₇ ), TiO ₂ —V ₂ O ₅ , TiO ₂ —Nb ₂ O ₅ , MgTi ₂ O ₅ , TiNb ₂ O ₇ , TiO ₂ —SnO ₂ , TiO ₂ —P ₂ O ₅ —MeO (Me is at least one element selected from Cu, Ni, Fe and Co) based compounds. There can be more than one type.

  The conductive agent improves current collection performance and suppresses contact resistance between the active material and the current collector. Examples of the conductive agent include acetylene black, carbon black, graphite, carbon nanofiber, and carbon nanotube. The type of conductive agent can be one type or two or more types.

  The binder binds the active material, the conductive agent, and the current collector. Examples of the binder include polytetrafluoroethylene (PTFE), polyvinylidene fluoride (PVdF), a water-soluble cellulose-based polymer (such as carboxymethyl cellulose (CMC)), a fluorine-based rubber, and a styrene butadiene rubber. . The type of the binder can be one type or two or more types.

  The active material, the conductive agent, and the binder in the negative electrode active material-containing layer are blended in proportions of 70% to 96% by weight, 2% to 28% by weight, and 2% to 28% by weight, respectively. It is preferable to do. By setting the amount of the conductive agent to 2% by weight or more, the current collecting performance of the negative electrode active material-containing layer can be improved. Moreover, the binding property of a negative electrode active material content layer and a collector can be improved by making the quantity of a binder into 2 weight% or more. On the other hand, the conductive agent and the binder are each preferably 28% by weight or less in order to increase the capacity.

The negative electrode current collector is desirably formed of a material that is electrochemically stable in a potential range nobler than 1 V (vsLi ⁺ / Li). Examples of such materials include aluminum foil, aluminum alloy foil containing at least one element selected from the group consisting of Mg, Ti, Zn, Mn, Fe, Cu, and Si.

  The negative electrode can be produced, for example, by the following method. First, a negative electrode active material, a conductive agent, and a binder are suspended in a solvent to prepare a slurry. This slurry is applied to one or both sides of the negative electrode current collector and dried to form a negative electrode active material-containing layer. Then press. Alternatively, the negative electrode active material, the conductive agent, and the binder can be formed into a pellet and used as the negative electrode active material-containing layer.

(Positive electrode)
The positive electrode includes a positive electrode current collector and a positive electrode active material-containing layer. The positive electrode active material-containing layer includes a positive electrode active material, a conductive agent, and a binder. The positive electrode active material-containing layer is formed on one side or both sides of the positive electrode current collector.

For example, an oxide or a polymer can be used as the active material. The type of active material can be one type or two or more types.
Examples of oxides include manganese dioxide (MnO ₂ ), iron oxide, copper oxide or nickel oxide capable of occluding and releasing lithium; lithium manganese composite oxides (eg, Li _x Mn ₂ O ₄ or Li _x MnO ₂ (0 <x ≦ 1); lithium nickel composite oxide (for example, Li _x NiO ₂ (0 <x ≦ 1)); lithium cobalt composite oxide (for example, Li _x CoO ₂ (0 <x ≦ 1)) ; lithium-nickel-cobalt composite oxide _{(e.g., Li x Ni 1-y Co} y O 2 (0 <x ≦ 1,0 <y <1)); lithium-manganese-cobalt composite oxide (e.g., Li _x Mn _y Co _{1 -y} O ₂ (0 <x ≦ 1, 0 <y <1)); lithium nickel cobalt manganese composite oxide (for example, LiNi _1-yz Co _y Mn _z O ₂ (0 <1-yz <1, 0 <y <1, 0 <z <1)); lithium nickel cobalt aluminum composite oxide (for example, LiNi _1-yz Co _y Al _z O ₂ (0 <1-yz <1, 0 <y <1, 0 <z <1)); lithium manganese nickel composite oxide having a spinel structure (for example, Li _x Mn _2-y Ni _{y O 4 (0 <x ≦} 1,0 <y <2)); lithium phosphates having an olivine structure _{(e.g., Li x FePO 4, Li x} Fe 1-y Mn y PO 4, Li x CoPO 4 ( 0 <x ≦ 1, 0 <y <1)); iron sulfate (Fe ₂ (SO ₄ ) ₃ ); and vanadium oxide (eg, V ₂ O ₅ ). They may be used alone or in combination with a plurality of compounds.

  Examples of the polymer include conductive polymer materials such as polyaniline and polypyrrole, and disulfide-based polymer materials.

  Also, sulfur (S) or carbon fluoride can be used as an active material.

Examples of more preferable active materials include a lithium manganese composite oxide (Li _x Mn ₂ O ₄ (0 <x ≦ 1)) having a high positive electrode voltage and a lithium manganese nickel composite oxide having a spinel structure (Li _x Mn _{2 − y} Ni _y O ₄ (0 <x ≦ 1, 0 <y <2)), lithium nickel composite oxide (Li _x NiO ₂ (0 <x ≦ 1)), lithium cobalt composite oxide (Li _x CoO ₂ ( 0 <x ≦ 1)), a lithium nickel cobalt composite oxide _{(Li x Ni 1-y coyO} 2 (0 <x ≦ 1,0 <y <1)), lithium manganese cobalt composite oxide (Li _x Mn _y Co _{1-y O 2 (0 <} x ≦ 1,0 <y <1)), a lithium nickel cobalt manganese complex oxide (e.g., _{LiNi 1-yz Co y Mn z} O 2 (0 <1-yz <1, 0 <y <1, 0 <z <1)) and lithium iron phosphate (Li _x FePO ₄ (0 <x ≦ 1)).

  The conductive agent improves the current collecting performance and suppresses the contact resistance between the active material and the current collector. Examples of the conductive agent include carbonaceous materials such as acetylene black, carbon black, graphite, carbon nanofiber, and carbon nanotube. The type of conductive agent can be one type or two or more types.

  The binder binds the active material, the conductive agent, and the current collector. Examples of the binder include polytetrafluoroethylene (PTFE), polyvinylidene fluoride (PVdF), and fluorine-based rubber. The type of the binder can be one type or two or more types.

  The active material, the conductive agent, and the binder in the positive electrode active material-containing layer are blended at a ratio of 80% to 95% by weight, 3% to 18% by weight, and 2% to 17% by weight, respectively. It is preferable to do. The conductive agent can exert the above-described effects by setting the amount to 3% by weight or more. By making the amount of the conductive agent 18% by weight or less, decomposition of the non-aqueous electrolyte on the surface of the conductive agent under high temperature storage can be reduced. Sufficient positive electrode strength can be obtained by setting the binder to an amount of 2% by weight or more. By setting the amount of the binder to 17% by weight or less, the amount of the binder, which is an insulating material in the positive electrode, can be reduced, and the internal resistance can be reduced.

  The current collector is preferably formed from an aluminum foil or an aluminum alloy foil containing one or more elements selected from Mg, Ti, Zn, Mn, Fe, Cu, and Si.

  The positive electrode can be produced, for example, by the following method. First, a positive electrode active material, a conductive agent, and a binder are suspended in a solvent to prepare a slurry. This slurry is applied to one or both sides of the positive electrode current collector and dried to form a positive electrode active material-containing layer. Then press. Alternatively, the positive electrode active material, the conductive agent, and the binder can be formed into a pellet and used as the positive electrode active material-containing layer.

(Nonaqueous electrolyte)
As the non-aqueous electrolyte, a liquid non-aqueous electrolyte or a gel non-aqueous electrolyte can be used. The liquid non-aqueous electrolyte is prepared by dissolving the electrolyte in an organic solvent. The concentration of the electrolyte is preferably in the range of 0.5 to 2.5 mol / l. The gel-like nonaqueous electrolyte is prepared by combining a liquid electrolyte and a polymer material.

Examples of electrolytes include lithium perchlorate (LiClO ₄ ), lithium hexafluorophosphate (LiPF ₆ ), lithium tetrafluoroborate (LiBF ₄ ), lithium hexafluoroarsenate (LiAsF ₆ ), trifluorometa Lithium salts such as lithium sulfonate (LiCF ₃ SO ₃ ) and lithium bistrifluoromethylsulfonylimide [LiN (CF ₃ SO ₂ ) ₂ ] and mixtures thereof are included. The electrolyte is preferably one that is not easily oxidized even at a high potential, and LiPF ₆ is most preferred.

  Examples of organic solvents are cyclic carbonates such as propylene carbonate (PC), ethylene carbonate (EC), vinylene carbonate; chain carbonates such as diethyl carbonate (DEC), dimethyl carbonate (DMC), and methyl ethyl carbonate (MEC). Cyclic ethers such as tetrahydrofuran (THF), 2-methyltetrahydrofuran (2MeTHF), dioxolane (DOX); chain ethers such as dimethoxyethane (DME) and diethoxyethane (DEE); or γ-butyrolactone (GBL), Contains acetonitrile (AN) and sulfolane (SL). These organic solvents can be used alone or in combination of two or more.

  Examples of more preferable organic solvents include at least two or more of the group consisting of propylene carbonate (PC), ethylene carbonate (EC), diethyl carbonate (DEC), dimethyl carbonate (DMC), and methyl ethyl carbonate (MEC). And a mixed solvent containing γ-butyrolactone (GBL). By using such a mixed solvent, a nonaqueous electrolyte battery having excellent low temperature characteristics can be obtained.

  Examples of the polymer material include polyvinylidene fluoride (PVdF), polyacrylonitrile (PAN), and polyethylene oxide (PEO).

(Separator)
For the separator, for example, a porous film, a synthetic resin nonwoven fabric, or the like can be used. Examples of the material constituting the separator include polyolefin resins (for example, polyethylene and polypropylene), cellulose, and polyvinylidene fluoride (PVdF). The type of material can be one type or two or more types. Especially, the porous film which consists of polyolefin resin, such as polyethylene or a polypropylene, can melt | dissolve at fixed temperature and can interrupt | block an electric current and is preferable from a viewpoint of a safety improvement.

(Exterior material)
As the exterior member, a laminated film bag-like container or a metal container is used.

  Examples of the shape include a flat type, a square type, a cylindrical type, a coin type, a button type, a sheet type, and a laminated type. Of course, in addition to a small battery mounted on a portable electronic device or the like, a large battery mounted on a two-wheel to four-wheel automobile or the like may be used.

  As the laminate film, a multilayer film in which a metal layer is interposed between resin films is used. The metal layer is preferably an aluminum foil or an aluminum alloy foil for weight reduction. For the resin film, for example, one or more polymer materials such as polypropylene (PP), polyethylene (PE), nylon, and polyethylene terephthalate (PET) can be used. The laminate film can be formed into the shape of an exterior member by sealing by heat sealing. The laminate film preferably has a thickness of 0.2 mm or less.

  The metallic container can be formed from aluminum or an aluminum alloy. The aluminum alloy preferably contains at least one element such as magnesium, zinc and silicon. On the other hand, the content of one or more transition metals such as iron, copper, nickel and chromium is preferably 100 ppm by weight or less. Thereby, it becomes possible to dramatically improve long-term reliability and heat dissipation in a high temperature environment. The metal container preferably has a thickness of 0.5 mm or less, and more preferably has a thickness of 0.2 mm or less.

(Positive terminal)
The positive terminal is electrically stable at 3.0V (vsLi ⁺ / Li) or 4.25V (vsLi ⁺ / Li) following range with respect to Li potential, is formed from a material and having conductivity. It is preferably formed from aluminum or an aluminum alloy containing one or more elements such as Mg, Ti, Zn, Mn, Fe, Cu and Si. The positive electrode terminal is preferably formed of the same material as the positive electrode current collector in order to reduce contact resistance with the positive electrode current collector.

(Negative terminal)
The negative terminal is electrically stable at 1.0V (vsLi ⁺ / Li) or 3.0V (vsLi ⁺ / Li) following range with respect to Li potential, and is formed of a conductive material. It is preferably formed from aluminum or an aluminum alloy containing one or more elements such as Mg, Ti, Zn, Mn, Fe, Cu, and Si. The negative electrode terminal is preferably formed from the same material as the negative electrode current collector in order to reduce the contact resistance with the negative electrode current collector.

  The nonaqueous electrolyte battery according to the third embodiment is not limited to the one shown in FIGS. 1 and 2, and may be a battery shown in FIGS. 3 and 4, for example. FIG. 3 is a partially cutaway perspective view schematically showing another flat type nonaqueous electrolyte secondary battery according to the third embodiment, and FIG. 4 is an enlarged cross-sectional view of a portion B in FIG.

  The laminated electrode group 11 is housed in an exterior member 12 made of a laminate film in which a metal layer is interposed between two resin films. As shown in FIG. 4, the stacked electrode group 11 has a structure in which positive electrodes 13 and negative electrodes 14 are alternately stacked with separators 15 interposed therebetween. There are a plurality of positive electrodes 13, each of which includes a current collector 13 a and a positive electrode active material-containing layer 13 b supported on both surfaces of the current collector 13 a. There are a plurality of negative electrodes 14, each including a negative electrode current collector 14 a and a negative electrode active material-containing layer 14 b supported on both surfaces of the negative electrode current collector 14 a. One side of the negative electrode current collector 14 a of each negative electrode 14 protrudes from the negative electrode 14. The protruding negative electrode current collector 14 a is electrically connected to the strip-shaped negative electrode terminal 16. The tip of the strip-shaped negative electrode terminal 16 is drawn out from the exterior member 11 to the outside. Although not shown, the positive electrode current collector 13a of the positive electrode 13 has a side protruding from the positive electrode 13 on the side opposite to the protruding side of the negative electrode current collector 14a. The positive electrode current collector 13 a protruding from the positive electrode 13 is electrically connected to the belt-like positive electrode terminal 17. The tip of the belt-like positive electrode terminal 17 is located on the opposite side to the negative electrode terminal 16 and is drawn out from the side of the exterior member 11 to the outside.

  According to the third embodiment described above, since the active material of the first embodiment is contained in the negative electrode, it is possible to provide a nonaqueous electrolyte battery in which increase in resistance is suppressed and cycle life is improved. .

(Fourth embodiment)
A battery pack according to a fourth embodiment will be described with reference to the drawings. The battery pack includes one or more nonaqueous electrolyte batteries (unit cells) according to the third embodiment. When a plurality of unit cells are included, each unit cell is electrically connected in series or in parallel.

  5 and 6 show an example of a battery pack including a plurality of the flat batteries shown in FIG. FIG. 5 is an exploded perspective view of the battery pack. FIG. 6 is a block diagram showing an electric circuit of the battery pack of FIG.

  The plurality of unit cells 21 are laminated so that the negative electrode terminal 6 and the positive electrode terminal 7 extending to the outside are aligned in the same direction, and are fastened with an adhesive tape 22 to constitute an assembled battery 23. These unit cells 21 are electrically connected to each other in series as shown in FIG.

  The printed wiring board 24 is disposed to face the side surface of the unit cell 21 from which the negative electrode terminal 6 and the positive electrode terminal 7 extend. As shown in FIG. 6, a thermistor 25, a protection circuit 26, and a terminal 27 for energizing external devices are mounted on the printed wiring board 24. An insulating plate (not shown) is attached to the surface of the protection circuit board 24 facing the assembled battery 23 in order to avoid unnecessary connection with the wiring of the assembled battery 23.

  The positive electrode side lead 28 is connected to the positive electrode terminal 7 positioned at the lowermost layer of the assembled battery 23, and the tip thereof is inserted into the positive electrode side connector 29 of the printed wiring board 24 and electrically connected thereto. The negative electrode side lead 30 is connected to the negative electrode terminal 6 located in the uppermost layer of the assembled battery 23, and the tip thereof is inserted into the negative electrode side connector 31 of the printed wiring board 24 and electrically connected thereto. These connectors 29 and 31 are connected to the protection circuit 26 through wirings 32 and 33 formed on the printed wiring board 24.

  The thermistor 25 is used for detecting the temperature of the unit cell 21. The detection signal is transmitted to the protection circuit 26. The protection circuit 26 can cut off the plus side wiring 34a and the minus side wiring 34b between the protection circuit 26 and the energization terminal 27 to the external device under a predetermined condition. The predetermined condition is, for example, when the temperature detected by the thermistor 25 is equal to or higher than a predetermined temperature. The predetermined condition is when the overcharge, overdischarge, overcurrent, etc. of the cell 21 are detected. This detection of overcharge or the like is performed for each single cell 21 or the entire single cell 21. When detecting each single cell 21, the battery voltage may be detected, or the positive electrode potential or the negative electrode potential may be detected. In the latter case, a lithium electrode used as a reference electrode is inserted into each unit cell 21. In the case of FIG. 5 and FIG. 6, wiring 35 for voltage detection is connected to each single cell 21, and a detection signal is transmitted to the protection circuit 26 through these wirings 35.

  Protective sheets 36 made of rubber or resin are disposed on the three side surfaces of the assembled battery 23 excluding the side surfaces from which the positive electrode terminal 7 and the negative electrode terminal 6 protrude.

  The assembled battery 23 is stored in a storage container 37 together with each protective sheet 36 and the printed wiring board 24. That is, the protective sheet 36 is disposed on each of the inner side surface in the long side direction and the inner side surface in the short side direction of the storage container 37, and the printed wiring board 24 is disposed on the inner side surface on the opposite side in the short side direction. The assembled battery 23 is located in a space surrounded by the protective sheet 36 and the printed wiring board 24. The lid 38 is attached to the upper surface of the storage container 37.

  In addition, instead of the adhesive tape 22, a heat shrink tape may be used for fixing the assembled battery 23. In this case, protective sheets are arranged on both side surfaces of the assembled battery, the heat shrinkable tape is circulated, and then the heat shrinkable tape is heat shrunk to bind the assembled battery.

  5 and 6 show the configuration in which the unit cells 21 are connected in series, but in order to increase the battery capacity, they may be connected in parallel. Alternatively, series connection and parallel connection may be combined. The assembled battery packs can be further connected in series or in parallel.

  Moreover, the aspect of a battery pack is changed suitably by a use. The battery pack according to the embodiment is suitably used for applications that require excellent cycle characteristics when a large current is taken out. Specifically, it is used as a power source for a digital camera, or as an in-vehicle battery for, for example, a two-wheel to four-wheel hybrid electric vehicle, a two-wheel to four-wheel electric vehicle, and an assist bicycle. In particular, it is suitably used as a vehicle-mounted battery.

  According to the battery pack of the fourth embodiment described above, since the nonaqueous electrolyte battery including the negative electrode including the active material of the first embodiment is provided, high input / output performance can be obtained even in a low SOC region, and A battery pack having excellent charge / discharge cycle performance can be realized.

Example 1
<Synthesis of TiO ₂ (B) structure titanium oxide>
As starting materials, potassium carbonate (K ₂ CO ₃ ) and anatase-type titanium dioxide (TiO ₂ ) were used. The starting materials were mixed and fired at 1000 ° C. for 24 hours to synthesize a potassium titanate compound (K ₂ Ti ₄ O ₉ ). The potassium titanate compound was dry pulverized with zirconia beads to adjust the particle size, and then washed with distilled water to obtain a proton exchange precursor. This proton exchange precursor was put into a 1M hydrochloric acid solution and subjected to ultrasonic stirring at 25 ° C. for 1 hour. This operation was repeated 12 times while exchanging the hydrochloric acid solution. After completion of the acid treatment, the titanate proton compound was obtained by washing with distilled water. This titanate proton compound was calcined in the atmosphere at 350 ° C. for 3 hours to obtain TiO ₂ having a TiO ₂ (B) structure.

<Preparation of negative electrode active material>
Were synthesized as described above, with respect to _{TiO 2} (B) TiO ₂ 15g of structure, polymethyl silicate _{(Si n O (n-1} ) (OCH 3) 2 (n + 1); n = 3~5 ( average) ; 50 to 53% as silica) 0.8 g and 2 g of ethanol are added, and a drying treatment is performed in a room temperature environment (temperature is 25 ° C., dew point −40 ° C., nitrogen gas flow). It was confirmed that the weight increased by 5%. When the surface of this powder was observed with a TEM, it was confirmed that a Si oxide coating layer was formed on the surface of the titanium dioxide particles. TiO ₂ particles having this coating layer and having a TiO ₂ (B) structure were used as the negative electrode active material.

<Production of negative electrode>
NMP was added to 90% by weight of the negative electrode active material powder, 5% by weight of acetylene black, and 5% by weight of polyvinylidene fluoride (PVdF) to prepare a slurry. This slurry was applied to both surfaces of a current collector made of an aluminum foil having a thickness of 15 μm, dried, and pressed to prepare a negative electrode having an electrode density of 2.0 g / cm ³ .

<Preparation of positive electrode>
Lithium nickel cobalt aluminum composite oxide (LiNi _0.82 Co _0.15 Al _0.03 O ₂ ) was used as the positive electrode active material, and acetylene black and polyvinylidene fluoride (PVdF) were used as the conductive agent. A slurry was prepared by adding 90% by weight of lithium nickel cobalt aluminum composite oxide powder, 5% by weight of acetylene black and 5% by weight of polyvinylidene fluoride (PVdF) in addition to NMP and mixing them. This slurry was applied to both surfaces of a current collector made of an aluminum foil having a thickness of 15 μm, dried, and pressed to prepare a positive electrode having an electrode density of 3.15 g / cm ³ .

<Production of electrode group>
A positive electrode, a separator made of a polyethylene porous film having a thickness of 25 μm, a negative electrode, and a separator were laminated in this order, and then wound in a spiral shape. This was heated and pressed at 90 ° C. to produce a flat electrode group having a width of 30 mm and a thickness of 3.0 mm. The obtained electrode group was housed in a pack made of a laminate film and vacuum dried at 80 ° C. for 24 hours. The laminate film was constituted by forming a polypropylene layer on both sides of an aluminum foil having a thickness of 40 μm, and the overall thickness was 0.1 mm.

<Preparation of liquid nonaqueous electrolyte>
Ethylene carbonate (EC) and ethyl methyl carbonate (EMC) were mixed at a volume ratio of 1: 2 to prepare a mixed solvent. 1M LiPF ₆ was dissolved as an electrolyte in this mixed solvent to prepare a liquid non-aqueous electrolyte.

<Manufacture of non-aqueous electrolyte secondary batteries>
A liquid non-aqueous electrolyte was poured into a laminate film pack containing the electrode group. Thereafter, the pack was sealed by heat sealing to produce a nonaqueous electrolyte secondary battery having a structure as shown in FIG. 1, having a width of 35 mm, a thickness of 3.2 mm, and a height of 65 mm.

(Example 2)
<Synthesis of titanium oxide with Nb-containing TiO ₂ (B) structure>
As starting materials, potassium carbonate (K ₂ CO ₃ ), anatase type titanium dioxide (TiO ₂ ), and niobium hydroxide (Nb ₂ O ₅ .nH ₂ O) were used. The starting materials were mixed and baked at 1000 ° C. for 24 hours to synthesize an alkali titanate compound (K—Ti—Nb—O compound) containing Nb. The K—Ti—Nb—O compound was dry-pulverized with zirconia beads to adjust the particle size, and then washed with distilled water to obtain a proton exchange precursor. This proton exchange precursor was put into a 1M hydrochloric acid solution and subjected to ultrasonic stirring at 25 ° C. for 1 hour. This operation was repeated 12 times while exchanging the hydrochloric acid solution. After the completion of the acid treatment, it was washed with distilled water to obtain a titanate proton compound containing Nb. This Nb-containing titanate proton compound was calcined in the atmosphere at 350 ° C. for 3 hours to obtain an oxide of titanium having a TiO ₂ (B) structure containing Nb.

As a result of measuring the obtained titanium oxide by ICP emission spectrometry, the Nb content (in terms of Nb ₂ O ₅ ) was 8% by weight with respect to the total weight of the titanium oxide containing Nb. .

<Preparation of negative electrode active material>
To 15 g of titanium oxide having a TiO ₂ (B) structure containing Nb synthesized as described above, 0.6 g of polymethyl silicate and 2 g of ethanol are added, and the room temperature environment (temperature is 25 ° C., nitrogen flow) The dew point was dried at -20 ° C., and it was confirmed that the weight after drying was increased by 9% with respect to the weight before addition, and the surface of this powder was observed with TEM-EDX. It was confirmed that a Si oxide coating layer was formed on the surface of the titanium oxide particles with a TiO ₂ (B) structure containing Nb, and the titanium oxide having this coating layer was used as the negative electrode active material. It was.

<Manufacture of non-aqueous electrolyte secondary batteries>
A nonaqueous electrolyte secondary battery was produced in the same manner as in Example 1 using the above negative electrode active material.

(Example 3)
3 g of polymethyl silicate and 2 g of ethanol are added to 15 g of titanium oxide having a TiO ₂ (B) structure containing Nb synthesized in Example 2, and a room temperature environment (temperature is 25 ° C., nitrogen flow, dew point) A drying treatment was performed at −40 ° C., and it was confirmed that the weight after drying increased by 9% with respect to the weight before addition, and TiO ₂ (B) containing Nb was observed by surface observation with TEM-EDX. It was confirmed that an oxide coating layer composed mainly of Si was present on the surface of the titanium oxide particles having the structure, and the titanium oxide having this coating layer was used as the negative electrode active material.

  A non-aqueous electrolyte battery was produced in the same manner as in Example 1 using the negative electrode active material obtained as described above.

Example 4
To 15 g of titanium oxide having a TiO ₂ (B) structure containing Nb synthesized in Example 2, 0.7 g of polymethyl silicate, 1 g of ethanol, and 2 g of 1-propanol were added, and the room temperature environment (25 ° C. , Nitrogen flow, dew point: −30 ° C.), and it was confirmed that the weight after drying was increased by 3% with respect to the weight before addition. Surface observation by TEM-EDX confirmed that an oxide coating layer mainly composed of Si was present on the surface of the titanium oxide having a TiO ₂ (B) structure containing Nb. A titanium oxide having this coating layer was used as a negative electrode active material.

  A non-aqueous electrolyte battery was produced in the same manner as in Example 1 using the negative electrode active material obtained as described above.

(Example 5)
With respect to 15 g of titanium oxide having a TiO ₂ (B) structure containing Nb synthesized in Example 2, 0.45 g of polymethyl silicate, 1 g of ethanol, and 2 g of 1-propanol, a dew point of −40 ° C. A nonaqueous electrolyte battery was produced in the same manner as in Example 2 except that it was dried in the environment.

(Example 6)
With respect to 15 g of titanium oxide having a TiO ₂ (B) structure containing Nb synthesized in Example 2, 0.6 g of polyethyl silicate, 2 g of ethanol, and 2 g of 1-butanol were used, and the dew point was −40 ° C. Except for drying in the environment, it was produced under the same conditions as in Example 2, and a weight increase of 2.8% was confirmed. Furthermore, a non-aqueous electrolyte battery was manufactured in the same manner.

(Example 7)
With respect to 15 g of titanium oxide having a TiO ₂ (B) structure containing Nb synthesized in Example 2, 1 g of polyethyl silicate, 2 g of ethanol, 1 g of 1-propanol, and 1 g of 1-butanol were used as dew points— Except that it was dried in an environment of 40 ° C., it was produced under the same conditions as in Example 2, and a weight increase of 3.8% was confirmed. Furthermore, a non-aqueous electrolyte battery was manufactured in the same manner.

(Example 8)
Using 15 g of titanium oxide having a TiO ₂ (B) structure containing Nb synthesized in Example 2, 1.6 g of methyl silicate and 2 g of ethanol were used to dry in an argon flow environment at a dew point of −40 ° C. Except for the above, it was produced under the same conditions as in Example 2, and a weight increase of 3.1% was confirmed. Furthermore, a non-aqueous electrolyte battery was manufactured in the same manner.

Example 9
Argon flow environment using 1 g of methyl silicate, 2 g of ethanol, 1 g of 1-propanol, and 1 g of 1-butanol with respect to 15 g of titanium oxide of TiO ₂ (B) structure containing Nb synthesized in Example 2. The sample was prepared under the same conditions as in Example 2 except that it was dried in an environment having a dew point of −40 ° C., and a weight increase of 2.1% was confirmed. Furthermore, a non-aqueous electrolyte battery was manufactured in the same manner.

(Example 10)
Using 15 g of titanium oxide having a TiO ₂ (B) structure containing Nb and synthesized in Example 2, 1.3 g of ethyl silicate and 2 g of ethanol were used for drying in an argon flow environment with a dew point of −40 ° C. Except that, it was produced under the same conditions as in Example 2, and a weight increase of 1.9% was confirmed. Furthermore, a non-aqueous electrolyte battery was manufactured in the same manner.

Example 11
Using 15 g of titanium oxide having a TiO ₂ (B) structure containing Nb synthesized in Example 2, 0.8 g of polymethyl silicate, 2 g of ethanol, and 2 g of 1-butanol as a high boiling point organic solvent, A drying treatment was performed in an atmosphere (25 ° C., humidity 50%), and a weight increase of 2.8% was confirmed. Thereafter, a nonaqueous electrolyte battery was produced in the same manner as in Example 2.

(Example 12)
For 15 g of titanium oxide having a TiO ₂ (B) structure containing Nb synthesized in Example 2, 0.6 g of polymethyl silicate, 1 g of 1-propanol and 2 g of 1-butanol as a high boiling point organic solvent were used. Then, a drying process was performed in an atmosphere of air atmosphere (25 ° C., humidity 40%), and a weight increase of 1.8% was confirmed. Thereafter, a nonaqueous electrolyte battery was produced in the same manner as in Example 2.

(Example 13)
For 15 g of titanium oxide having a TiO ₂ (B) structure containing Nb synthesized in Example 2, 3 g of polymethyl silicate, 2 g of ethanol, 2 g of 1-propanol and 1 g of 1-butanol as a high boiling point organic solvent. Using this, a drying treatment was performed in an atmosphere of air atmosphere (25 ° C., humidity 25%), and a weight increase of 8.9% was confirmed. Thereafter, a nonaqueous electrolyte battery was produced in the same manner as in Example 2.

(Example 14)
For 15 g of titanium oxide having a TiO ₂ (B) structure containing Nb synthesized in Example 2, 0.7 g of polymethyl silicate, 1 g of ethanol, 2 g of 1-propanol and 1-butanol as a high boiling point organic solvent Using 1 g, a drying treatment was performed in an atmosphere of air atmosphere (25 ° C., humidity 30%), and a weight increase of 2.9% was confirmed. Thereafter, a nonaqueous electrolyte battery was produced in the same manner as in Example 2.

(Comparative Example 1)
A non-aqueous electrolyte battery similar to that of Example 1 was prepared by using the titanium oxide having a TiO ₂ (B) structure containing Nb synthesized in Example 2 as a negative electrode active material (not coated with SiO ₂ or the like). Manufactured.

(Comparative Example 2)
Using 15 g of titanium oxide having a TiO ₂ (B) structure containing Nb synthesized in Example 2, 0.8 g of polymethyl silicate and 2 g of ethanol were used, and air atmosphere (25 ° C., humidity 50%) The drying process was performed in an environment of 2.5% and a weight increase of 2.5% was confirmed. Thereafter, a nonaqueous electrolyte battery was produced in the same manner as in Example 2.

(Comparative Example 3)
Using 15 g of titanium oxide having a TiO ₂ (B) structure containing Nb synthesized in Example 2, 0.6 g of polymethyl silicate and 2 g of ethanol were used, and air atmosphere (25 ° C., humidity 40%) The drying process was performed in an environment of 2 to confirm a weight increase of 2.0%. Thereafter, a nonaqueous electrolyte battery was produced in the same manner as in Example 2.

(Comparative Example 4)
Using 15 g of titanium oxide having a TiO ₂ (B) structure containing Nb synthesized in Example 2, 3 g of polymethyl silicate and 2 g of ethanol were used, and the atmosphere was an atmosphere (25 ° C., humidity 70%). A drying treatment was carried out at 7.7 to confirm a weight increase of 7.7%. Thereafter, a nonaqueous electrolyte battery was produced in the same manner as in Example 2.

(Comparative Example 5)
Using 15 g of titanium oxide having a TiO ₂ (B) structure containing Nb synthesized in Example 2, 0.7 g of polymethyl silicate and 2 g of ethanol were used, and the air atmosphere (25 ° C., humidity 30%) The drying process was performed in an environment of 2.2, and a weight increase of 2.2% was confirmed. Thereafter, a nonaqueous electrolyte battery was produced in the same manner as in Example 2.

(Charge / discharge cycle test)
Tripolar cells were prepared from the negative electrodes of Examples 1 to 14 and Comparative Examples 1 to 5, respectively. Li metal was used for the counter electrode and the reference electrode of the triode cell, and a glass filter was used for the separator. Further, LiPF ₆ was dissolved as a supporting salt in a solvent in which ethylene carbonate (EC) and diethyl carbonate (DEC) were mixed at a ratio of 1: 2, to prepare an electrolytic solution. Each tripolar cell was subjected to a single electrode charge / discharge cycle test in a 45 ° C. environment, and the capacity retention rate was measured.

The charge / discharge conditions were 1C rate in a 45 ° C. environment. Charging was performed at a constant current and a constant voltage of 1.4 V, and the charging time was 3 hours. A constant current discharge was performed with a discharge cutoff voltage of 3.0V. Charging / discharging is repeated 50 cycles (one cycle is charge / discharge). The ratio of the discharge capacity at the 50th cycle to the discharge capacity at the 1st cycle is calculated. Show. Tables 2 and 4 show the weight (wt%) of titanium oxide in terms of TiO ₂ for the negative electrode active material and the amount of Si in terms of SiO ₂ in the coating layer (in the table, the amount of SiO ₂ (wt%)). ), C amount (wt%), and C / Si ratio (molar ratio).

  As is clear from Tables 1 to 4, the batteries of Examples 1 to 14 having a C / Si molar ratio in the range of 0.4 to 2 have a high capacity retention rate of 85% or more at the 50th cycle.

In contrast, the batteries of Comparative Example 1 in which the coating layer was not formed and Comparative Examples 2 to 5 having a C / Si molar ratio of less than 0.4 were 66% even when the capacity retention ratio at the 50th cycle was high. It was. In Comparative Examples 2, 3, and 5, since the raw material does not contain an organic solvent having a boiling point higher than ethanol such as 1-propanol and 1-butanol, the organic component remaining in the coating layer is small, and the C / Si molar ratio is It became less than 0.4. On the other hand, in Comparative Example 4, since the humidity is as high as 70%, the volatilization of the organic component and the sol-gel reaction proceed quickly, and the organic component cannot remain in the SiO ₂ network covering the active material surface generated by the polymerization reaction. The C / Si molar ratio was less than 0.4.

In the above examples, titanium dioxide having a TiO ₂ (B) structure was used as the titanium oxide. However, the present invention is not limited to this, and titanium oxide having a solid acid point or a hydroxyl group on the particle surface and titanic acid composite oxidation. It is also effective for those using particles of the product as the negative electrode active material.

  According to the active material of at least one of the embodiments and examples described above, the surface of titanium oxide particles includes a layer containing a Si component and an organic component, and the C / Si molar ratio is 0.4. Since it is 2 or less, a nonaqueous electrolyte battery capable of suppressing an increase in resistance and improving the cycle life can be realized.

Although several embodiments of the present invention have been described, these embodiments are presented by way of example and are not intended to limit the scope of the invention. These novel embodiments can be implemented in various other forms, and various omissions, replacements, and changes can be made without departing from the scope of the invention. These embodiments and modifications thereof are included in the scope and gist of the invention, and are included in the invention described in the claims and the equivalents thereof.
Hereinafter, the invention described in the scope of claims of the present application will be appended.
[1] A titanium oxide particle and a layer that is present on at least a part of the surface of the titanium oxide particle and includes a Si component and an organic component, and a C / Si molar ratio is 0.4 or more and 2 or less A negative electrode active material.
[2] The negative electrode active material according to [1], wherein the Si component is an oxide of silicon.
[3] The negative electrode active material according to [1] or [2], wherein the organic component includes a component derived from a metal alkoxide.
[4] A negative electrode comprising the negative electrode active material according to any one of [1] to [3],
A positive electrode;
A non-aqueous electrolyte,
Including non-aqueous electrolyte battery.
[5] A battery pack including the nonaqueous electrolyte battery according to [4].

  DESCRIPTION OF SYMBOLS 1,11 ... Electrode group, 2,12 ... Exterior member, 3,13 ... Positive electrode, 3a, 13a ... Positive electrode collector, 3b, 13b ... Positive electrode active material containing layer, 4,15 ... Separator, 5,14 ... Negative electrode 5a, 14a ... negative electrode current collector, 5b, 14b ... negative electrode active material containing layer, 6, 16 ... negative electrode terminal, 7, 17 ... positive electrode terminal, 20 ... battery pack, 21 ... single cell, 22 ... adhesive tape, 23 ... assembled battery, 24 ... printed wiring board, 28 ... positive side wiring, 29 ... positive side connector, 30 ... negative side wiring, 31 ... negative side connector, 37 ... storage container, 38 ... lid.

Claims (8)

A titanium oxide particle having a TiO ₂ (B) structure; and a layer that is present on at least a part of the surface of the titanium oxide particle and includes a Si component and an organic component, and the C / Si molar ratio is 0. Negative electrode active material that is 4 or more and 2 or less.   The negative electrode active material according to claim 1, wherein the Si component is an oxide of silicon.   The negative electrode active material according to claim 1, wherein the organic component includes a component derived from a metal alkoxide. A negative electrode comprising the negative electrode active material according to claim 1;
A positive electrode;
A non-aqueous electrolyte,
Including non-aqueous electrolyte battery.   A battery pack comprising the nonaqueous electrolyte battery according to claim 4. The battery pack according to claim 5, further comprising an external terminal for energization and a protection circuit. The battery pack according to claim 5 or 6, comprising a plurality of the non-aqueous electrolyte batteries, wherein the plurality of non-aqueous electrolyte batteries are connected in series, parallel, or a combination of series and parallel. A vehicle comprising the battery pack according to claim 5.

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