JP5847757B2 - Method for producing negative electrode active material for battery - Google Patents

Description

  Embodiments described herein relate generally to a method for producing a negative electrode active material for a battery.

In recent years, titanium oxide having a monoclinic β-type structure has attracted attention as an active material for nonaqueous electrolyte batteries (for example, Patent Documents 1 to 3). Conventionally, spinel-type lithium titanate (Li ₄ Ti ₅ O ₁₂ ) that has been practically used has three lithium ions that can be inserted and removed per unit chemical formula. For this reason, the number of lithium ions that can be inserted / removed per titanium ion was 3/5, and 0.6 was the theoretical maximum. In contrast, a titanium oxide having a monoclinic β-type structure has a maximum number of lithium ions that can be inserted / removed per titanium ion of 1.0, which is a high theory of about 335 mAh / g. Have capacity. Therefore, development of a battery having excellent performance using a titanium oxide having a monoclinic β-type structure is expected.

JP 2008-34368 A JP 2008-117625 A International Publication No. 2009/028553 Pamphlet

R. Marchand, L. Brohan, M. Tournoux, Material Research Bulletin 15, 1129 (1980) “The Journal of the Japan Mining Association” Vol. 81, No. 932, December 1965, pages 1024-1030

  An object is to provide a non-aqueous electrolyte battery having excellent charge / discharge cycle performance, a negative electrode active material for a battery used in the non-aqueous electrolyte battery, and a method for producing the same.

According to the embodiment, it includes primary particles of monoclinic β-type titanium composite oxide having an average primary particle size of 1 nm to 10 μm, an average particle size of 1 μm to 100 μm, and a compressive fracture strength of 20 MPa or more. A method for producing a negative electrode active material for a battery comprising secondary particles,
Producing raw material secondary particles comprising a compound comprising titanium and a compound comprising an alkali cation;
Heat-treating the raw material secondary particles to obtain a secondary particulate proton exchange precursor;
Obtaining a secondary particulate proton exchanger by reacting an acid with the proton exchange precursor to proton exchange an alkali cation;
By providing the proton exchanger with heat treatment, a production method including obtaining a monoclinic β-type titanium composite oxide in the form of secondary particles is provided.

Monoclinic β-type titanium oxide schematic view showing the crystal structure of (TiO ₂ (B)). Sectional drawing which shows the flat type non-aqueous electrolyte battery which concerns on 2nd Embodiment. The expanded sectional view of the A section of FIG. The disassembled perspective view which shows the battery pack which concerns on 3rd Embodiment. The block diagram which shows the electric circuit of the battery pack of FIG. The schematic diagram which shows the series hybrid vehicle which concerns on 4th Embodiment. The schematic diagram which shows the parallel hybrid vehicle which concerns on 4th Embodiment. The schematic diagram which shows the series parallel hybrid vehicle which concerns on 4th Embodiment. The schematic diagram which shows the motor vehicle which concerns on 4th Embodiment. 2 is an X-ray diffraction pattern of the titanium composite oxide synthesized in Example 1. FIG. (A), (b) is the scanning electron micrograph of the electrode surface of Example 1 and Comparative Example 1, respectively.

  Hereinafter, embodiments will be described with reference to the drawings.

(First embodiment)
In the present embodiment, the monoclinic β-type titanium composite oxide refers to a titanium composite oxide having a monoclinic titanium dioxide crystal structure. The crystal structure of monoclinic titanium dioxide is expressed as TiO ₂ (B). TiO ₂ (B) mainly belongs to the space group C2 / m and exhibits a tunnel structure as exemplified in FIG. Non-patent document 1 describes the detailed crystal structure of TiO ₂ (B).

As shown in FIG. 1, TiO ₂ (B) has a structure in which titanium ions 73 and oxide ions 72 constitute a skeleton structure portion 71a, and the skeleton structure portions 71a are alternately arranged. A gap portion 71b is formed between the skeleton structure portions 71a. This void portion 71b can serve as a host site for intercalation (insertion) of different atomic species. TiO ₂ (B) is also said to have host sites capable of occluding and releasing heteroatomic species on the crystal surface. TiO ₂ (B) can reversibly occlude and release lithium ions when lithium ions are inserted into and desorbed from these host sites.

When lithium ions are inserted into the void portion 71b, Ti ⁴⁺ constituting the skeleton is reduced to Ti ³⁺ , thereby maintaining the electrical neutrality of the crystal. Since titanium oxide having TiO ₂ (B) has one Ti ⁴⁺ per chemical formula, it is theoretically possible to insert at most one lithium ion between layers. For this reason, the titanium oxide having TiO ₂ (B) can be expressed by the general formula Li _x TiO ₂ (0 ≦ x ≦ 1). In this case, a theoretical capacity of 335 mAh / g is obtained.

  Since lithium titanate has poor conductivity, it may be used with a reduced particle size in order to improve large current characteristics. However, since finely divided lithium titanate has a large specific surface area, the adhesion strength between the current collector and the active material in the electrode is low, and the resistance at the interface may increase.

  Therefore, the present inventors manufactured secondary particles of monoclinic β-type titanium composite oxide, and manufactured electrodes using this. However, it has been found that such secondary particles are easily collapsed in the electrode manufacturing process and become the shape of primary particles. When the secondary particles collapse to form the primary particles, the binding strength between the active materials decreases, and the active material and the current collector are easily separated.

Furthermore, since a synthetic precursor of a monoclinic β-type titanium composite oxide such as K ₂ Ti ₄ O ₉ is likely to grow into fiber granules, the primary particles are mainly fiber granules. Therefore, in the electrode manufacturing process such as coating and rolling, the fibrous primary particles are aligned in parallel with the substrate serving as the current collector.

  The present inventors have confirmed that the expansion and contraction of the crystal lattice occurs along with the insertion and release of lithium ions, and further, the expansion and contraction greatly occur along a specific crystal axis. When fibrous primary particles are arranged in parallel with the current collector, the expansion and contraction of the electrode volume are repeated in a specific direction, so that the battery thickness changes. Due to this, there are problems that the electrode layer is easily peeled off from the substrate, the battery is swung, the gap between the electrodes is widened, the resistance of the battery is increased, and the battery characteristics are deteriorated.

  Therefore, the present inventors use secondary particles of monoclinic β-type titanium composite oxide with high compressive fracture strength, so that secondary particles do not collapse during electrode manufacturing, and excellent large current performance It was found that an electrode active material that contributes to charge / discharge cycle performance can be provided. Here, the compression fracture strength of the secondary particles can also be referred to as powder strength.

  The active material for a battery in the present embodiment includes secondary particles having an average particle diameter of 1 μm or more and 100 μm or less including primary particles of a monoclinic β-type titanium composite oxide having an average primary particle diameter of 1 nm or more and 10 μm or less. And the compressive fracture strength of the secondary particles is 20 MPa or more.

  By including secondary particles of monoclinic β-type titanium composite oxide in the battery active material, volume change isotropically occurs when lithium ions are occluded and released. It is mitigated and an increase in resistance can be suppressed.

  The secondary particles have an average particle size of 1 μm or more and 100 μm or less. If the average particle size is less than 1 μm, it will be difficult to handle in industrial production, and if it exceeds 100 μm, it will be difficult to make the mass and thickness uniform in the coating film for producing the electrode, Smoothness tends to decrease. The average particle size of the secondary particles is more preferably 3 μm or more and 30 μm or less.

  It can be confirmed by scanning electron microscope (SEM) observation that the monoclinic β-type titanium composite oxide is in the form of secondary particles.

  The measuring method of the average particle diameter of the secondary particles is as follows. Using a laser diffraction distribution analyzer (Shimadzu SALD-300), first add about 0.1 g of the sample, a surfactant, and 1 to 2 mL of distilled water to a beaker, stir well, and then inject into a stirred water tank. The luminous intensity distribution was measured 64 times at intervals of 2 seconds, and the particle size distribution data was analyzed.

  The primary particles constituting the secondary particles have an average primary particle size of 1 nm to 10 μm. When the average primary particle size is less than 1 nm, it is difficult to handle in industrial production, and when it exceeds 10 μm, the diffusion of lithium ions in the solid of the titanium composite oxide is slow. The average primary particle size is more preferably 10 nm or more and 1 μm or less.

  The average primary particle size can be confirmed by observation with a scanning electron microscope (SEM). The average of 10 typical particles extracted from a typical field of view is determined and the average primary particle size is determined.

  The primary particles are preferably fibrous. In the present embodiment, the fibrous particles mean particles having an aspect ratio of 3 or more. When the primary particles are fibrous, the average primary particle size is the fiber diameter. It can be confirmed by scanning electron microscope (SEM) observation that the primary particles are fibrous particles.

  The compressive fracture strength of the secondary particles is 20 MPa or more. When the compressive fracture strength is less than 20 MPa, the particles collapse during the electrode manufacturing process, the binding property of the electrode is lowered, the active material and the current collector are peeled off, and the cycle life is greatly reduced. The compressive fracture strength is preferably 35 MPa or more. The upper limit of the compressive fracture strength is preferably 100 MPa or less. When the compressive fracture strength is 100 MPa or less, the electrode density can be easily increased, and the volume energy density can be increased.

The secondary particles preferably have a specific surface area measured by the BET method of 5 m ² / g or more and 50 m ² / g or less. In the case where the specific surface area is 5 m ² / g or more, it is possible to sufficiently ensure the occlusion / desorption sites of lithium ions. When the specific surface area is 50 m ² / g or less, it becomes easy to handle in industrial production.

(Measurement of compressive fracture strength)
The compressive fracture strength (St [MPa]) is measured by the apparatus shown below, and is determined by the expression of Hiramatsu et al.

Measuring device: Shimadzu micro compression tester MCT-W
<Test conditions>
Test indenter: FLAT50
Measurement mode: Compression test Test force: 20.00 [mN]
Load speed: 0.892405 [mN] / sec]
Calculation formula: St = 2.8 P / πd ² (1) Formula
P: Test force [N], d: Particle diameter (mm)
In the present embodiment, the above-described measurement was performed on five secondary particles having a particle size within ± 3 μm of the average particle size, and the average value of the measured values was taken as the compression fracture strength.

  In the present embodiment, it is preferable that the monoclinic β-type titanium composite oxide further includes at least one element selected from Group 5 and Group 13. The content of the element in the monoclinic β-type titanium composite oxide containing the element is preferably in the range of 0.03% by mass to 15% by mass.

By containing at least one element selected from Group 5 and Group 13 by 0.03% by mass or more, sufficient compressive fracture strength can be obtained, and by containing 15% by mass or less, electric capacity and charge / discharge cycle performance Generation of a heterogeneous phase of TiO ₂ (B), which can be a factor that lowers the temperature, can be prevented. A more preferable content of the element is 1% by mass or more and 10% by mass or less.

  At least one element selected from Group 5 and Group 13 is preferably selected from the group of V, Nb, Ta, Al, Ga and In, and particularly preferably selected from Nb, V and Al. . The at least one element may be added alone, or two or more elements may be added. When two or more elements are added, any combination may be used, but it is particularly preferable to use a combination of Nb and V, Nb and Al, and Nb, V, and Al.

  It is considered that at least one element selected from Group 5 and Group 13 exists in a state where a part of Ti site of the monoclinic β-type titanium composite oxide is substituted or is in a solid solution state. . Increasing the content of at least one element selected from Group 5 and Group 13 can provide higher compressive fracture strength, but since a different phase appears when the solid solubility limit of the element is exceeded, the range of the solid solubility limit It is preferable to add in the inside. By including in the range of 0.03% by mass or more and 15% by mass or less, the compression fracture strength of the secondary particles can be more effectively increased.

  In addition, when adding 2 or more types of elements, it is preferable that content which totaled those elements is 0.03 mass% or more and 15 mass% or less.

  The total content of at least one element selected from Group 5 and Group 13 can be measured by ICP emission spectroscopy. The measurement of the content of the element by ICP emission spectroscopy can be performed by the following method, for example. The battery is disassembled in a discharged state, an electrode (for example, a negative electrode) is taken out, and the negative electrode layer is deactivated in water. Thereafter, the titanium composite oxide in the negative electrode layer is extracted. In the extraction process, for example, when polyvinylidene fluoride is used as the binder, the binder component is removed by washing with N-methyl-2-pyrrolidone or the like, and then the conductive agent is removed with an appropriate mesh. If these components remain slightly, they may be removed by heat treatment in the atmosphere (for example, at 250 ° C. for 30 minutes). After measuring the extracted titanium composite oxide in a container, it is melted by acid or alkali to obtain a measurement solution. The measurement solution is subjected to ICP emission spectroscopy with a measuring device (for example, SPS-1500V, manufactured by SII Nano Technology) to measure the content of the above elements.

When using the active material in this embodiment as a negative electrode active material, you may use independently, but you may use it with another active material. Other active materials include, for example, lithium titanium composite oxides having a spinel structure (such as Li ₄ Ti ₅ O ₁₂ ), titanium composite oxides having anatase or rutile structure (a-TiO ₂ , r-TiO ₂ ), iron can be formed using a composite sulfide (FeS, etc. FeS _2). Moreover, when using the active material in this embodiment as a positive electrode active material, you may use independently, but you may use it with another active material. Other active materials include, for example, lithium titanium composite oxides having a spinel structure (such as Li ₄ Ti ₅ O ₁₂ ), titanium composite oxides having anatase or rutile structure (a-TiO ₂ , r-TiO ₂ ), iron can be formed using a composite sulfide (FeS, etc. FeS _2).

When another active material is also contained in the electrode, the total content of at least one element selected from Group 5 and Group 13 can be measured as follows. The negative electrode active material taken out from the electrode is subjected to TEM-EDX, and the crystal structure of each particle is specified by a limited field diffraction method. Particles having a diffraction pattern attributed to β-type TiO ₂ are selected, and the synthetic content of at least one element selected from Group 5 and Group 13 is measured by EDX analysis.

  When the battery is disassembled and the active material is extracted, it can be performed by the following procedure. First, the battery is discharged to a rated end voltage with a current of 0.1 C in a 25 ° C. environment. The discharged battery is disassembled in an inert atmosphere, and the center part of an electrode (for example, negative electrode) is cut out. The cut-out negative electrode is sufficiently washed with ethyl methyl carbonate to remove the electrolyte component, and then left in the atmosphere for one day, or washed with water and deactivated. Thereafter, the titanium composite oxide in the negative electrode layer is extracted. The extraction treatment can be performed, for example, by removing the conductive agent and the binder in the negative electrode layer by heat treatment at 200 to 300 ° C. for less than 3 hours in the air.

(Production method)
Next, the manufacturing method of the active material for batteries which concerns on embodiment is demonstrated.
The production method of the present embodiment includes producing raw material secondary particles containing a compound containing titanium and a compound containing an alkali cation, and heat-treating the raw material secondary particles to form a secondary particle proton exchange precursor. Obtaining a secondary particulate proton exchanger by reacting an acid with the proton exchange precursor to proton exchange the alkali cation, and heat-treating the proton exchanger, Obtaining a next-particulate monoclinic β-type titanium composite oxide.

  In accordance with the method of the present embodiment, starting materials such as a compound containing titanium and a compound containing alkali cations are formed into secondary particle shapes, and the secondary particles are fired at a high temperature, whereby a single product having a high compression fracture strength is obtained as a final product. Secondary particles of an oblique β-type titanium composite oxide can be obtained.

This will be described in more detail below.
First, secondary particles are produced using starting materials. The secondary particles made of this starting material are called raw material secondary particles. The raw material secondary particles can be produced by mixing the starting raw materials at a predetermined ratio and, for example, spray drying.

As a starting material, a compound containing titanium and a compound containing an alkali cation can be used. For example, TiO ₂ having an anatase structure, K ₂ CO ₃ , Na ₂ CO ₃ , or Cs ₂ CO ₃ is used. be able to.

  Spray drying can be carried out, for example, by dissolving a compound containing an alkali cation in a solvent such as pure water, and dispersing and spraying a compound containing titanium. According to spray drying, droplets in which fine particles are highly dispersed can be instantly dried, so that spherical secondary particles are easily obtained.

Next, the raw material secondary particles are heat-treated to obtain secondary particulate alkali titanate compound used as a proton exchange precursor. The alkali titanate compound is sodium titanate, potassium titanate or cesium titanate, such as, but not limited to, Na ₂ Ti ₃ O ₇ , K ₂ Ti ₄ O ₉ , or Cs ₂ Ti ₅ O _12. It is preferable. The mixing ratio of the starting materials is determined according to the desired alkali titanate compound. The heat treatment is preferably performed in a temperature range of 850 to 1200 ° C. for 1 to 100 hours. By calcining the raw material secondary particles in the above temperature range, the compressive fracture strength of the secondary particles can be increased. The average particle diameter of the primary particles and the secondary particles can be adjusted by changing the temperature and time of the heat treatment.

When the monoclinic β-type titanium composite oxide contains at least one element selected from Group 5 and Group 13, at least one of starting materials, that is, a compound containing titanium and a compound containing alkali cations May contain at least one element selected from Group 5 and Group 13. Alternatively, a compound containing a group 5 or group 13 element such as Nb ₂ O ₅ may be mixed with the starting material.

  Next, the alkali titanate compound is subjected to proton exchange. The obtained secondary particulate alkali titanate compound is sufficiently washed with pure water to remove impurities. Thereafter, the alkali cations are exchanged for protons by treatment with an acid. The acid treatment can be performed, for example, by adding a secondary particulate alkali titanate compound to hydrochloric acid having a concentration of 1 M and stirring. The acid treatment is desirably performed until the proton exchange is sufficiently completed. During proton exchange, an alkaline solution may be added to the solution to adjust the pH. After the proton exchange is completed, it is washed again with pure water. Sodium titanate, potassium titanate and cesium titanate can exchange alkali cations for protons without breaking the crystal structure.

  Next, the secondary particulate product that has undergone proton exchange is washed with water and dried to obtain a secondary particulate proton exchanger that is an intermediate product. By subjecting this proton exchanger to heat treatment, a secondary particulate monoclinic β-type titanium composite oxide as the final product can be obtained. Monoclinic system containing at least one element selected from Group 5 or Group 13 when a compound containing at least one element selected from Group 5 or Group 13 is used in the production process of the raw material secondary particles A β-type titanium composite oxide is obtained.

  The heat treatment of the proton exchanger is preferably performed at 300 ° C to 500 ° C. When the heating temperature is less than 300 ° C., the crystallinity is remarkably lowered, and the electrode capacity, charge / discharge efficiency, and repeatability are lowered. On the other hand, when the heating temperature exceeds 500 ° C., an impurity phase such as an anatase phase is generated, and the capacity may be reduced. A more preferable heating temperature is 350 ° C to 400 ° C. Note that the average particle size of the primary particles and the secondary particles can also be adjusted by changing the temperature and time of the heat treatment in the heat treatment of the proton exchanger.

  In the method of this embodiment, it is possible to perform high-temperature firing in the state of secondary particles by making the starting material into the shape of secondary particles. When fired at a high temperature in the state of secondary particles, the bonding at the interface of the primary particles can be enhanced, whereby secondary particles having a high compression fracture strength can be obtained. The secondary particles of the monoclinic β-type titanium composite oxide obtained by the method of the present embodiment have high compressive fracture strength and do not collapse even in the electrode manufacturing process. Therefore, by using the monoclinic β-type titanium composite oxide, an electrode active material capable of producing a nonaqueous electrolyte battery having excellent charge / discharge cycle performance can be provided.

  In addition, the battery active material according to the present embodiment can be used not only for the negative electrode but also for the positive electrode, and excellent charge / discharge cycle performance can be obtained by applying to any of them. That is, excellent cycle characteristics are the effects obtained by increasing the compressive fracture strength of the secondary particles, and the effects do not change when used for the negative electrode or the positive electrode. Therefore, the battery active material according to the embodiment can be used for both the positive electrode and the negative electrode, and similar effects can be obtained.

  When the battery active material according to the embodiment is used for the positive electrode, the active material of the negative electrode as the counter electrode can be a metallic lithium, a lithium alloy, or a carbon-based material such as graphite or coke.

(Second Embodiment)
Next, the nonaqueous electrolyte battery according to the second embodiment will be described.

  The nonaqueous electrolyte battery according to the embodiment includes an exterior material, a positive electrode accommodated in the exterior material, and an active material that is spatially separated from the positive electrode in the exterior material, for example, via a separator. A negative electrode and a non-aqueous electrolyte filled in the exterior material are provided.

  The battery active material according to the first embodiment is used as the negative electrode active material.

  This will be described in more detail with reference to FIGS. 2 and 3 showing an example of the nonaqueous electrolyte battery 100 according to the embodiment. FIG. 2 is a schematic cross-sectional view of a flat type nonaqueous electrolyte battery 100 in which the outer packaging material 2 is made of a laminate film, and FIG. 3 is an enlarged cross-sectional view of a portion A in FIG. Each figure is a schematic diagram for explanation, and its shape, dimensions, ratio, etc. are different from the actual device, but these are appropriately changed in consideration of the following explanation and known technology. be able to.

  The flat wound electrode group 1 is housed in a bag-shaped exterior material 2 made of a laminate film in which an aluminum foil is 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. As shown in FIG. 3, the outermost negative electrode 3 has a configuration in which a negative electrode layer 3b is formed on one surface on the inner surface side of the negative electrode current collector 3a. The other negative electrode 3 is configured by forming negative electrode layers 3b on both surfaces of a negative electrode current collector 3a. The positive electrode 5 is configured by forming a positive electrode layer 5b on both surfaces of a 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 electrically connected to the negative electrode current collector 3 a of the outermost negative electrode 3, and the positive electrode terminal 7 is electrically connected to the positive electrode current collector 5 a of the inner positive electrode 5. Connected. The negative electrode terminal 6 and the positive electrode terminal 7 are extended to the outside from the opening of the bag-shaped exterior material 2. For example, the liquid non-aqueous electrolyte is injected from the opening of the bag-shaped exterior material 2. The wound electrode group 1 and the liquid nonaqueous electrolyte are completely sealed by heat-sealing the opening of the bag-shaped outer packaging material 2 with the negative electrode terminal 6 and the positive electrode terminal 7 interposed therebetween.

  For the negative electrode terminal, for example, a material having electrical stability and conductivity in a range where the potential with respect to the lithium ion metal is 0.6 V or more and 3 V or less can be used. Specifically, aluminum or an aluminum alloy containing an element such as Mg, Ti, Zn, Mn, Fe, Cu, or Si can be given. The negative electrode terminal 6 is preferably made of the same material as the negative electrode current collector 3a in order to reduce contact resistance with the negative electrode current collector 3a.

  The positive electrode terminal 7 can be made of a material having electrical stability and conductivity in the range of 3 to 5 V with respect to the lithium ion metal. Specifically, aluminum or an aluminum alloy containing an element such as Mg, Ti, Zn, Mn, Fe, Cu, or Si can be given. The positive electrode terminal 7 is preferably made of the same material as the positive electrode current collector 5a in order to reduce the contact resistance with the positive electrode current collector 5a.

  Hereinafter, the exterior material 2, the negative electrode 3, the positive electrode 5, the separator 4 and the non-aqueous electrolyte, which are constituent members of the non-aqueous electrolyte battery 100, will be described in detail.

1) Exterior material The exterior material 2 is formed from a laminate film having a thickness of 1 mm or less. Alternatively, a metal container having a thickness of 3 mm or less is used as the exterior material. The metal container is more preferably 1 mm or less in thickness.

  The shape of the exterior material 2 can be selected from a flat type (thin type), a square type, a cylindrical type, a coin type, and a button type. Examples of the exterior material include, for example, an exterior material for a small battery that is loaded on a portable electronic device or the like, an exterior material for a large battery that is loaded on a two- to four-wheeled vehicle, etc., depending on the battery size.

  As the laminate film, a multilayer film in which a metal layer is interposed between resin layers is used. The metal layer is preferably an aluminum foil or an aluminum alloy foil for weight reduction. For the resin layer, for example, a polymer material such as polypropylene (PP), polyethylene (PE), nylon, polyethylene terephthalate (PET) can be used. The laminate film can be molded into the shape of an exterior material by sealing by heat sealing.

  The metal container is made of aluminum or an aluminum alloy. The aluminum alloy is preferably an alloy containing elements such as magnesium, zinc, and silicon. When transition metals such as iron, copper, nickel, and chromium are included in the alloy, the amount is preferably 100 ppm by mass or less.

2) Negative electrode The negative electrode 3 includes a current collector 3a and a negative electrode layer 3b formed on one or both surfaces of the current collector 3a and including an active material, a conductive agent, and a binder.

  As the active material, the battery active material according to the first embodiment is used.

  The nonaqueous electrolyte battery 100 incorporating the negative electrode 3 including the negative electrode layer 3b containing such an active material can improve large current characteristics and charge / discharge cycle performance.

  The conductive agent improves the current collection performance of the active material and suppresses the contact resistance with the current collector. Examples of the conductive agent include acetylene black, carbon black, and graphite.

  The binder can bind the active material and the conductive agent. Examples of the binder include polytetrafluoroethylene (PTFE), polyvinylidene fluoride (PVdF), fluorine-based rubber, and styrene butadiene rubber.

  The active material, the conductive agent, and the binder in the negative electrode layer 3b may be blended at a ratio of 70% by mass to 96% by mass, 2% by mass to 28% by mass, and 2% by mass to 28% by mass, respectively. preferable. By setting the amount of the conductive agent to 2% by mass or more, the current collecting performance of the negative electrode layer 3b can be improved, and the large current characteristics of the nonaqueous electrolyte battery 100 can be improved. Further, by setting the amount of the binder to 2% by mass or more, the binding property between the negative electrode layer 3b and the current collector 3a can be improved, and the cycle characteristics can be improved. On the other hand, the conductive agent and the binder are each preferably 28% by mass or less in order to increase the capacity.

  The current collector 3a is an aluminum foil that is electrochemically stable in a potential range nobler than 1 V or an aluminum alloy foil containing elements such as Mg, Ti, Zn, Mn, Fe, Cu, and Si. preferable.

  The negative electrode 3 is prepared by, for example, suspending an active material, a conductive agent and a binder in a commonly used solvent to prepare a slurry, applying the slurry to the current collector 3a, drying, and then pressing the slurry. Produced. The negative electrode 3 may also be produced by forming an active material, a conductive agent, and a binder in the form of a pellet to form the negative electrode layer 3b and forming it on the current collector 3a.

3) Positive electrode The positive electrode 5 includes a current collector 5a and a positive electrode layer 5b formed on one or both surfaces of the current collector 5a and containing an active material, a conductive agent, and a binder.

  As the active material, for example, an oxide, a polymer, or the like can be used.

Examples of the oxide include manganese occluded lithium (MnO ₂ ), iron oxide, copper oxide, nickel oxide and lithium manganese composite oxide (for example, Li _x Mn ₂ O ₄ or Li _x MnO ₂ ), lithium nickel composite oxide. (Eg, Li _x NiO ₂ ), lithium cobalt composite oxide (Li _x CoO ₂ ), lithium nickel cobalt composite oxide (eg, LiNi _1-y Co _y O ₂ ), lithium manganese cobalt composite oxide (eg, Li _x Mn _y) Co _{1 -y} O ₂ ), lithium manganese nickel composite oxide having a spinel structure (Li _x Mn _{2 -y} Ni _y O ₄ ), lithium phosphorus oxide having an olivine structure (for example, Li _x FePO ₄ , Li _x Fe _{1) -y Mn y PO 4, Li x} CoPO 4), iron sulfate _{(Fe 2 (SO 4) 3} ), or vanadium oxides (for example, V ₂ O ₅ ) Can be used. Here, x and y are preferably 0 <x ≦ 1 and 0 ≦ y ≦ 1.

  As the polymer, for example, a conductive polymer material such as polyaniline or polypyrrole, or a disulfide polymer material can be used. Sulfur (S) and carbon fluoride can also be used as the active material.

Examples of preferable active materials include lithium manganese composite oxide (Li _x Mn ₂ O ₄ ), lithium nickel composite oxide (Li _x NiO ₂ ), lithium cobalt composite oxide (Li _x CoO ₂ ) having a high positive electrode voltage, Lithium nickel cobalt composite oxide (Li _x Ni _1-y CoyO ₂ ), spinel lithium manganese nickel composite oxide (Li _x Mn _{2 -y} Ni _y O ₄ ), lithium manganese cobalt composite oxide (Li _x Mn _y) Co _1-y O ₂ ), or lithium iron phosphate (Li _x FePO ₄ ). Here, x and y are preferably 0 <x ≦ 1 and 0 ≦ y ≦ 1.

  A more preferable active material is a lithium cobalt composite oxide or a lithium manganese composite oxide. Since these active materials have high ion conductivity, diffusion of lithium ions in the positive electrode active material is unlikely to be a rate-determining step in combination with the negative electrode active material described above. For this reason, the said active material is excellent in compatibility with the lithium titanium complex oxide in the said negative electrode active material.

  The conductive agent improves the current collection performance of the active material and suppresses the contact resistance with the current collector. Examples of the conductive agent include carbonaceous materials such as acetylene black, carbon black, and graphite.

  The binder binds the active material and the conductive agent. Examples of the binder include polytetrafluoroethylene (PTFE), polyvinylidene fluoride (PVdF), and fluorine-based rubber.

  The active material, the conductive agent, and the binder in the positive electrode layer 5b may be blended at a ratio of 80% by mass to 95% by mass, 3% by mass to 18% by mass, and 2% by mass to 17% by mass, respectively. preferable. The conductive agent can exhibit the above-described effects by adjusting the amount to 3% by mass or more. By making the amount of the conductive agent 18% by mass or less, the decomposition of the nonaqueous electrolyte on the surface of the conductive agent under high temperature storage can be reduced. A sufficient positive electrode strength can be obtained by adjusting the amount of the binder to 2% by mass or more. By setting the binder to an amount of 17% by mass 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, for example, an aluminum foil or an aluminum alloy foil containing an element such as Mg, Ti, Zn, Mn, Fe, Cu, or Si.

  The positive electrode 5 is prepared by, for example, preparing a slurry by suspending an active material, a conductive agent and a binder in a commonly used solvent, applying the slurry to the current collector 5a, drying, and then applying a press. Produced. The positive electrode 5 may also be manufactured by forming an active material, a conductive agent, and a binder in the form of a pellet to form the positive electrode layer 5b and forming it on the current collector 5a.

4) Non-aqueous electrolyte As the non-aqueous electrolyte, for example, a liquid non-aqueous electrolyte prepared by dissolving an electrolyte in an organic solvent or a gel-like non-aqueous electrolyte obtained by combining a liquid electrolyte and a polymer material can be used.

  The liquid non-aqueous electrolyte is preferably dissolved in an organic solvent at a concentration of 0.5M to 2.5M.

Examples of electrolytes are lithium perchlorate (LiClO ₄ ), lithium hexafluorophosphate (LiPF ₆ ), lithium tetrafluoroborate (LiBF ₄ ), lithium hexafluoroarsenide (LiAsF ₆ ), trifluorometasulfone Lithium salt of lithium acid (LiCF ₃ SO ₃ ), lithium bistrifluoromethylsulfonylimide [LiN (CF ₃ SO ₂ ) ₂ ], or a mixture thereof. 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 include propylene carbonate (PC), ethylene carbonate (EC), cyclic carbonates such as 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 dietoethane (DEE); or γ-butyrolactone (GBL), acetonitrile ( AN) and sulfolane (SL). These organic solvents can be used alone or in the form of a mixed solvent.

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

  A preferable organic solvent is a mixed solvent in which at least two of the group consisting of propylene carbonate (PC), ethylene carbonate (EC) and diethyl carbonate (DEC) are mixed, or a mixed solvent containing γ-butyrolactone (GBL). is there. By using these mixed solvents, a nonaqueous electrolyte battery having excellent high temperature characteristics can be obtained.

5) Separator As the separator 4, for example, a porous film containing polyethylene, polypropylene, cellulose, or polyvinylidene fluoride (PVdF), or a synthetic resin nonwoven fabric can be used. A preferred porous film is made of polyethylene or polypropylene, and can be melted at a constant temperature to cut off the current, thereby improving safety.

  According to this embodiment described above, a non-aqueous electrolyte battery having excellent charge / discharge cycle performance can be provided.

(Third embodiment)
Next, the battery pack according to the embodiment will be described in detail.

  The battery pack according to the embodiment has one or more nonaqueous electrolyte batteries (that is, single cells) according to the second embodiment. When the battery pack includes a plurality of single cells, the single cells are electrically connected in series, parallel, or connected in series and parallel.

  The battery pack 200 will be specifically described with reference to FIGS. 4 and 5. In the battery pack 200 shown in FIG. 3, the flat type non-aqueous electrolyte battery shown in FIG. 2 is used as the unit cell 21.

  The plurality of single cells 21 are stacked such 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. 5, 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 to detect the temperature of the unit cell 21, and 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. 4 and FIG. 5, a 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 the protective sheets 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.

  4 and 5 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, or a combination of series connection and parallel connection may be used. The assembled battery packs can be further connected in series and in parallel.

  According to this embodiment described above, a battery pack having excellent charge / discharge cycle performance can be provided.

  In addition, the aspect of a battery pack is changed suitably by a use. The battery pack is preferably one that exhibits excellent cycle characteristics when a large current is taken out. Specific examples include a power source for a digital camera, a vehicle for a two- to four-wheel hybrid electric vehicle, a two- to four-wheel electric vehicle, an assist bicycle, and the like. In particular, a battery pack using a nonaqueous electrolyte battery having excellent high temperature characteristics is suitably used for in-vehicle use.

(Fourth embodiment)
The automobile according to the fourth embodiment includes the battery pack according to the third embodiment. Examples of the vehicle herein include a two-wheel to four-wheel hybrid electric vehicle, a two-wheel to four-wheel electric vehicle, and an assist bicycle.

  FIGS. 6 to 8 show a hybrid type automobile using a driving power source by combining an internal combustion engine and a battery-driven electric motor. The driving force of an automobile requires a power source with a wide range of rotation speeds and torques depending on the running conditions. In general, an internal combustion engine has a limited torque and rotational speed that show ideal energy efficiency. Therefore, the energy efficiency decreases under other operating conditions. Hybrid type automobiles generate power by operating an internal combustion engine under optimum conditions, and by driving wheels with a high-efficiency electric motor, or by driving the internal combustion engine and the electric motor together. The overall energy efficiency can be improved. Further, by regenerating the kinetic energy of the vehicle as electric power during deceleration, the travel distance per unit fuel can be dramatically increased compared to a normal internal combustion engine vehicle.

  Hybrid vehicles can be broadly classified into three types depending on the combination of the internal combustion engine and the electric motor.

  FIG. 6 shows a hybrid vehicle 50 that is generally called a series hybrid vehicle. All the power of the internal combustion engine 51 is once converted into electric power by the generator 52, and this electric power is stored in the battery pack 54 through the inverter 53. The battery pack according to the third embodiment is used for the battery pack 54. The electric power of the battery pack 54 is supplied to the electric motor 55 through the inverter 53, and the wheels 56 are driven by the electric motor 55. It is a system in which a generator is combined with an electric vehicle. The internal combustion engine can be operated under highly efficient conditions and can also regenerate power. On the other hand, since driving of the wheels is performed only by the electric motor, a high-output electric motor is required. Also, a battery pack having a relatively large capacity is required. The rated capacity of the battery pack is preferably in the range of 5 to 50 Ah. A more preferable range is 10 to 20 Ah. Here, the rated capacity means a capacity when discharged at a 0.2 C rate.

  FIG. 7 shows a hybrid vehicle 57 called a parallel hybrid vehicle. Reference numeral 58 indicates an electric motor that also serves as a generator. The internal combustion engine 51 mainly drives the wheels 56, and in some cases, a part of the power is converted into electric power by the generator 58, and the battery pack 54 is charged with the electric power. The driving force is assisted by the electric motor 58 at the time of start and acceleration where the load becomes heavy. This is a system based on a normal automobile, which reduces the load fluctuation of the internal combustion engine 51 to improve efficiency and also performs power regeneration. Since the driving of the wheels 56 is mainly performed by the internal combustion engine 51, the output of the electric motor 58 can be arbitrarily determined depending on the necessary auxiliary ratio. The system can also be configured using a relatively small electric motor 58 and battery pack 54. The rated capacity of the battery pack can be in the range of 1-20 Ah. A more preferable range is 5 to 10 Ah.

  FIG. 8 shows a hybrid vehicle 59 called a series / parallel hybrid vehicle. This is a combination of both series and parallel. The power split mechanism 60 splits the output of the internal combustion engine 51 into power generation and wheel drive. The engine load can be controlled more finely than the parallel system, and energy efficiency can be improved.

  The rated capacity of the battery pack is desirably in the range of 1 to 20 Ah. A more preferable range is 5 to 10 Ah.

  The nominal voltage of the battery pack mounted on the hybrid vehicle as shown in FIGS. 6 to 8 is preferably in the range of 200 to 600V.

  The battery pack 54 is preferably arranged in a place that is generally less susceptible to changes in the outside air temperature and is less susceptible to impact during a collision or the like. For example, a sedan type automobile as shown in FIG. 9 can be arranged in the trunk room 62 behind the rear seat 61. Further, it can be placed under or behind the seat 61. When the battery mass is large, it is preferable to arrange the battery under the seat or under the floor in order to lower the center of gravity of the entire vehicle.

  According to this embodiment, by providing the battery pack having excellent cycle characteristics according to the third embodiment, an automobile having excellent performance can be provided.

  As mentioned above, although some embodiment of this invention was described, these embodiment is shown as an example and is not intending limiting the range of 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.

(Example 1)
<Preparation of positive electrode>
A positive electrode was prepared using lithium nickel composite oxide (LiNi _0.8 Co _0.1 Mn _0.1 O ₂ ) as the positive electrode active material and acetylene black and polyvinylidene fluoride (PVdF) as the conductive agent.

First, 90 mass% of lithium nickel composite oxide powder, 5 mass% of acetylene black, and 5 mass% of polyvinylidene fluoride (PVdF) were mixed with N-methylpyrrolidone (NMP) to prepare a slurry. This slurry was applied on both sides of a current collector made of an aluminum foil having a thickness of 15 μm, dried and pressed to produce a positive electrode having an electrode density of 3.15 g / cm ³ .

<Preparation of titanium composite oxide>
Secondary particles were produced by spray drying from potassium carbonate (K ₂ CO ₃ ) and titanium oxide (TiO ₂ ) having an anatase structure. The spray drying was performed by measuring the raw materials at a molar ratio of K: Ti = 2: 4, dispersing them using distilled water as a solvent, and then spray drying using a spray dryer.

Next, the raw material secondary particles were fired at 1000 ° C. for 24 hours to obtain K ₂ Ti ₄ O ₉ secondary particles. The secondary particles of K ₂ Ti ₄ O ₉ were washed with pure water to obtain secondary particles of a proton exchange precursor. The proton exchange precursor secondary particles had an average particle size of about 10 μm. The secondary particles of the proton exchange precursor were put into a 1M hydrochloric acid solution and stirred for 12 hours in an environment at 25 ° C. to perform proton exchange. Thereby, secondary particles of the proton exchanger were obtained.

The secondary particles of the proton exchanger were calcined in the atmosphere at 350 ° C. for 3 hours to obtain secondary particles of titanium composite oxide (TiO ₂ ). The secondary particles were spherical, the average particle size was 9.6 μm, the specific surface area was 10.8 m ² / g, the compression fracture strength was 37 MPa, and the average primary particle size was 0.30 μm. .

<X-ray diffraction analysis of titanium composite oxide>
The obtained titanium composite oxide was packed in a standard glass holder having a diameter of 25 mm and measured by a wide angle X-ray diffraction method. As a result, the X-ray diffraction pattern shown in FIG. 10 was obtained. From this diffraction pattern, it is confirmed that the main material constituting the obtained titanium composite oxide is a monoclinic β-type titanium composite oxide belonging to JCPDS (Joint Committee on Powder Diffraction Standards): 46-1237. It was done. The measuring equipment and conditions are shown below.

(1) X-ray diffractometer: Bruker AXS; D8 ADVANCE (encapsulated tube type)
X-ray source: CuKα ray (using Ni filter)
Output: 40kV, 40mA
Slit system: Div. Slit; 0.3 °
Detector: LynxEye (High-speed detector)
(2) Scan method: 2θ / θ continuous scan (3) Measurement range (2θ): 5 to 100 °
(4) Step width (2θ): 0.01712 °
(5) Counting time: 1 second / step.

<Production of negative electrode>
The obtained titanium composite oxide was used as an active material, and a negative electrode was produced using acetylene black and polyvinylidene fluoride (PVdF) as a conductive agent.

90% by mass of titanium composite oxide powder, 5% by mass of acetylene black, and 5% by mass of polyvinylidene fluoride (PVdF) were mixed with N-methylpyrrolidone (NMP) to prepare a slurry. This slurry was applied to both sides of a current collector made of an aluminum foil having a thickness of 15 μm and dried. Then, the negative electrode whose electrode density is 1.9 g / cm < ³ > was produced by pressing.

<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 spirally wound. This was heated and pressed at 90 ° C. to produce a flat electrode group having a width of 30 mm and a thickness of 1.8 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 has a structure in which a polypropylene layer is formed on both surfaces of an aluminum foil having a thickness of 40 μm, and the total thickness is 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 obtain a mixed solvent. A liquid non-aqueous electrolyte was prepared by dissolving 1 M of LiPF ₆ as an electrolyte in this mixed solvent.

<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 completely sealed by heat sealing to produce a non-aqueous electrolyte secondary battery having a structure shown in FIG. 2 and having a width of 35 mm, a thickness of 2 mm, and a height of 65 mm.

(Examples 2 to 4)
<Preparation of titanium composite oxide>
Secondary particles were produced by spray drying from potassium carbonate (K ₂ CO ₃ ) and titanium oxide (TiO ₂ ) having an anatase structure. The spray drying was performed by measuring the raw materials at a molar ratio of K: Ti = 2: 4, dispersing them using distilled water as a solvent, and then spray drying using a spray dryer. At this time, the spraying conditions were changed to adjust the particle size of the raw material secondary particles. Thereafter, secondary particles of titanium composite oxide (TiO ₂ ) were obtained in the same manner as in Example 1. The secondary particles were spherical, and the average particle diameter, specific surface area, compressive fracture strength, and average primary particle diameter were as shown in Table 1.

  As a result of analyzing the obtained titanium composite oxide by X-ray diffraction, it was confirmed that the main material constituting the titanium composite oxide was a monoclinic β-type titanium composite oxide belonging to JCPDS: 46-1237. It was done.

  Using this titanium composite oxide, a non-aqueous electrolyte secondary battery was manufactured in the same manner as in Example 1.

(Examples 5 to 8)
<Preparation of titanium composite oxide>
Secondary particles were produced by spray drying from potassium carbonate (K ₂ CO ₃ ) and titanium oxide (TiO ₂ ) having an anatase structure. The spray drying was performed by measuring the raw materials at a molar ratio of K: Ti = 2: 4, dispersing them using distilled water as a solvent, and then spray drying using a spray dryer.

Next, the raw material secondary particles were fired for 24 hours at the temperature shown in Table 1 to obtain K ₂ Ti ₄ O ₉ secondary particles. The secondary particles of K ₂ Ti ₄ O ₉ were washed with pure water to obtain secondary particles of a proton exchange precursor. The proton exchange precursor secondary particles had an average particle size of about 10 μm. The secondary particles of the proton exchange precursor were put into a 1M hydrochloric acid solution and stirred for 12 hours in an environment at 25 ° C. to perform proton exchange. Thereby, secondary particles of the proton exchanger were obtained.

Thereafter, secondary particles of titanium composite oxide (TiO ₂ ) were obtained in the same manner as in Example 1. The secondary particles were spherical, and the average particle diameter, specific surface area, compressive fracture strength, and average primary particle diameter were as shown in Table 1.

  As a result of analyzing the obtained titanium composite oxide by X-ray diffraction, it was confirmed that the main material constituting the titanium composite oxide was a monoclinic β-type titanium composite oxide belonging to JCPDS: 46-1237. It was done.

  Using this titanium composite oxide, a non-aqueous electrolyte secondary battery was manufactured in the same manner as in Example 1.

(Examples 9 to 23)
As raw materials, potassium carbonate (K ₂ CO ₃ ) and titanium oxide (TiO ₂ ) having an anatase structure, niobium oxide (Nb ₂ O ₅ ), vanadium oxide (V ₂ O ₅ ), aluminum oxide (Al ₂ O) ₃ ) Titanium oxide (Ta ₂ O ₅ ), gallium oxide (Ga ₂ O ₃ ), or indium oxide (In ₂ O ₃ ) was used, and titanium was prepared in the same manner as in Example 1 except that the compounding ratio was changed. A composite oxide ((Ti, Nb) O ₂ ) was synthesized.

  Table 1 shows the average primary particle size, the average particle size of the secondary particles, the specific surface area, and the compression fracture strength of the obtained titanium composite oxide.

  As a result of analyzing the obtained titanium composite oxide by X-ray diffraction, it was confirmed that the main material constituting the titanium composite oxide was a monoclinic β-type titanium composite oxide belonging to JCPDS: 46-1237. It was done.

  Further, the concentration of Nb, V, Al, Ta, Ga, or In of the obtained titanium composite oxide was measured by ICP emission spectroscopy. The results are shown in Table 1.

  Using the obtained titanium composite oxide, a nonaqueous electrolyte secondary battery was produced in the same manner as in Example 1.

(Comparative Example 1)
<Preparation of titanium composite oxide>
Potassium carbonate (K ₂ CO ₃ ) and titanium oxide having an anatase structure (TiO ₂ ) were mixed by ball milling at 600 rpm for 3 hours using a zirconia container. The mixture was baked at 600 ° C. for 24 hours to synthesize K ₂ Ti ₄ O ₉ . This was washed with pure water to obtain a proton exchange precursor. The obtained proton exchange precursor was put into a 1M hydrochloric acid solution and stirred for 12 hours in an environment at 25 ° C. to obtain a proton exchanger.

By spray-drying the proton exchanger, aggregated particles having an average particle size of about 10 μm were obtained. This was baked in the atmosphere at 350 ° C. for 3 hours to synthesize titanium composite oxide (TiO ₂ ). Table 1 shows the average particle size, specific surface area, compressive fracture strength, and average primary particle size of the synthesized titanium composite oxide.

  As a result of analyzing the obtained titanium composite oxide by X-ray diffraction, it was confirmed that the main material constituting the titanium composite oxide was a monoclinic β-type titanium composite oxide belonging to JCPDS: 46-1237. It was done.

  Using this titanium composite oxide, a non-aqueous electrolyte secondary battery was manufactured in the same manner as in Example 1.

(Comparative Examples 2 and 3)
A titanium composite oxide (TiO ₂ ) was synthesized in the same manner as in Comparative Example 1 except that the firing temperature of the raw material mixture was set as shown in Table 1. As a result of analyzing the obtained titanium composite oxide by X-ray diffraction, it was confirmed that the main material constituting the titanium composite oxide was a monoclinic β-type titanium composite oxide belonging to JCPDS: 46-1237. It was done. Using the obtained titanium composite oxide, a nonaqueous electrolyte secondary battery was produced in the same manner as in Example 1.

(Comparative Example 4)
Titanium composite oxide (TiO ₂ ) as in Comparative Example 1 except that potassium carbonate (K ₂ CO ₃ ), aluminum oxide (Al ₂ O ₃ ), and titanium oxide (TiO ₂ ) having an anatase structure were used as raw materials. ₂ ) was synthesized.

  As a result of analyzing the obtained titanium composite oxide by X-ray diffraction, it was confirmed that the main material constituting the titanium composite oxide was a monoclinic β-type titanium composite oxide belonging to JCPDS: 46-1237. It was done.

  Further, the additive element concentration of the obtained titanium composite oxide was measured by ICP emission spectroscopy. The results are shown in Table 1.

  Using the obtained titanium composite oxide, a nonaqueous electrolyte secondary battery was produced in the same manner as in Example 1.

(Measurement of battery performance)
The resistance values of the obtained secondary batteries of Examples 1 to 23 and Comparative Examples 1 to 4 were measured. Resistance measurement was performed with an AC impedance of 1 kHz. Thereafter, a charge / discharge cycle test was performed. In the charge / discharge cycle test, a charge / discharge cycle of repeating 1C charge / 1C discharge was repeated 100 times. Table 1 shows the ratio of the discharge capacity at the 100th time to the initial discharge capacity, that is, the discharge maintenance ratio (%). For each secondary battery, “resistance value after 100 cycles / resistance value before cycle” was calculated and shown in Table 1 as a resistance increase rate [times]. For the resistance, an AC impedance of 1 kHz was measured.

Moreover, the photograph which image | photographed the electrode surface with the scanning electron microscope was shown in FIG. 11A shows the negative electrode surface of Example 1, and FIG. 11B shows the negative electrode surface of Comparative Example 1. The central part of the negative electrode was cut out and the part in contact with the rolling roller during electrode rolling was photographed.

  The secondary particles of the titanium composite oxide in Examples 1 to 23 had significantly higher compressive fracture strength than the secondary particles of Comparative Examples 1 to 4. The secondary batteries of Examples 1 to 23 using such secondary particles had a smaller resistance increase rate and a higher capacity retention rate than the secondary batteries of Comparative Examples 1 to 4. Therefore, it was shown that the secondary battery using the secondary particles of the titanium composite oxide manufactured according to this embodiment and having a compressive fracture strength of 20 MPa or more has excellent charge / discharge cycle performance.

  It was shown that the secondary batteries of Examples 9 to 23 in which Nb, V, or Al was contained in the monoclinic β-type titanium composite oxide had much better charge / discharge cycle performance.

  Further, it can be seen that the electrode of the battery of Example 1 shown in FIG. 11A has large active material particles, and the shape of the secondary particles is maintained even after the electrode is manufactured. On the other hand, it can be seen that the electrode of the battery of Comparative Example 1 shown in FIG. 11B has small active material particles, and secondary particles are collapsed by the electrode manufacturing process. In the batteries of Comparative Examples 1 to 4, it was shown that the secondary particles of the titanium composite oxide collapsed into the shape of primary particles, thereby increasing the battery resistance and reducing the capacity retention rate. .

  Moreover, the specific surface area of the secondary particle of the titanium composite oxide in Examples 1-23 was remarkably smaller than the secondary particle of Comparative Examples 1-4. This is because the primary particles are melted by firing the raw material secondary particles at a high temperature, and the surface area of the secondary particles is reduced by fusing the interfaces between adjacent primary particles. As shown in Table 1, since the capacity retention ratios of Examples 1 to 23 in which the specific surface area of the secondary particles is small are significantly higher than those in Comparative Examples 1 to 4 having a large specific surface area, good charge / discharge cycle performance is obtained. Therefore, it is considered desirable that the secondary particles have a smaller specific surface area.

Supplementary Note [1] Secondary particles having an average particle size of 1 μm or more and 100 μm or less including primary particles of monoclinic β-type titanium composite oxide having an average primary particle size of 1 nm to 10 μm, The active material for batteries characterized by having a compressive fracture strength of 20 MPa or more.

[2] The monoclinic β-type titanium composite oxide contains at least one element selected from Group 5 and Group 13 in a range of 0.03% by mass to 15% by mass. The active material for batteries as described in 2.

[3] The battery active material according to [1] or [2], wherein the at least one element substitutes a part of a Ti site of the monoclinic β-type titanium composite oxide.

[4] A nonaqueous electrolyte battery comprising: a positive electrode; a negative electrode containing the battery active material according to any one of [1] to [3]; and a nonaqueous electrolyte.

[5] The nonaqueous electrolyte battery according to [4], wherein the positive electrode includes one or more positive electrode active materials selected from a lithium nickel composite oxide and a lithium manganese composite oxide.

[6] The nonaqueous electrolyte battery according to [4] or [5], further comprising an exterior material made of a laminate film.

[7] A battery pack comprising one or more of the nonaqueous electrolyte batteries according to any one of [4] to [6].

[8] The battery pack according to [7], further comprising a protection circuit that includes the plurality of non-aqueous electrolyte batteries that are electrically connected, and that can detect the voltage of each non-aqueous electrolyte battery. .

[9] An automobile comprising the battery pack according to [7] or [8].

  DESCRIPTION OF SYMBOLS 1 ... Winding electrode group, 2 ... Exterior material, 3 ... Negative electrode, 4 ... Separator, 5 ... Positive electrode, 6 ... Negative electrode terminal, 7 ... Positive electrode terminal, 21 ... Single cell, 24 ... Printed wiring board, 25 ... Thermistor, 26 DESCRIPTION OF SYMBOLS ... Protection circuit, 37 ... Storage container, 50, 57, 59 ... Hybrid vehicle, 51, 64 ... Internal combustion engine, 52 ... Generator, 53 ... Inverter, 54 ... Battery pack, 55, 65 ... Electric motor, 56, 66 ... Wheel 58 ... Electric motor also serving as a generator, 60 ... Power split mechanism, 61 ... Rear seat, 62 ... Trunk room, 100 ... Non-aqueous electrolyte secondary battery, 200 ... Battery pack.

Claims (4)

Rights Hitoshitsubu diameter is at 100μm or less than 3.4 .mu.m, compression breaking strength is a method of preparing a negative active material for battery comprising the secondary particles is more than 20 MPa, the secondary particles are average primary particle size 1nm Containing primary particles of monoclinic β-type titanium composite oxide having a thickness of 10 μm or less,
Producing raw material secondary particles comprising a compound comprising titanium and a compound comprising an alkali cation;
Heat-treating the raw material secondary particles at 850 to 1200 ° C. to obtain a secondary particle-like proton exchange precursor;
Obtaining a secondary particulate proton exchanger by reacting an acid with the proton exchange precursor to proton exchange an alkali cation;
A secondary particle monoclinic β-type titanium composite oxide by heat-treating the proton exchanger.   The monoclinic β-type titanium composite oxide contains at least one element selected from Group 5 and Group 13 in a range of 0.03% by mass to 15% by mass. Production method. The manufacturing method according to claim 2 , wherein the at least one element substitutes a part of a Ti site of the monoclinic β-type titanium composite oxide.   The manufacturing method as described in any one of Claims 1-3 whose average particle diameter of the said secondary particle is 3.4 micrometers or more and 28.8 micrometers or less.

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