JP2019169400A - Active material composite, electrode, secondary battery, battery pack and vehicle - Google Patents

Abstract

To provide an active material composite which enables the materialization of a secondary battery superior in input/output performance and energy density, an electrode containing the active material composite, a secondary battery, a battery pack and a vehicle.SOLUTION: An active material composite comprising: particles of a niobium titanium composite oxide; and a carbon-containing layer covering at least a part of the surface of each niobium titanium composite oxide particle is provided according to an embodiment. The carbon-containing layer satisfies the following expression (1): 1.2<I/I≤5 (1), where Iis a peak intensity of D band arising in a range of 1280-1400 cmin Raman spectra according to Raman spectroscopy with a light source of 532 nm, and Iis a peak intensity of G band arising in a range of 1530-1650 cmin the Raman spectra.SELECTED DRAWING: Figure 10

Description

  Embodiments described herein relate generally to an active material composite, an electrode, a secondary battery, a battery pack, and a vehicle.

  In recent years, research and development of non-aqueous electrolyte batteries such as lithium ion secondary batteries have been actively promoted as high energy density batteries. Non-aqueous electrolyte batteries are expected as a power source for uninterruptible power supplies of hybrid vehicles, electric vehicles, and mobile phone base stations. In particular, a battery having a higher energy density is required as a vehicle-mounted battery.

Therefore, a new electrode material containing titanium and niobium has been studied. In particular, in the monoclinic niobium titanium composite oxide represented by TiNb ₂ O ₇ , when lithium ions are inserted, tetravalent titanium ions are reduced to trivalent titanium ions, and pentavalent niobium ions are reduced to three. Reduced to valent niobium ions. Therefore, this monoclinic niobium titanium composite oxide can maintain the electrical neutrality of the crystal structure even when many lithium ions are inserted as compared with other titanium oxides. As a result, the theoretical capacity of the monoclinic Nb—Ti composite oxide represented by TiNb ₂ O ₇ is as high as 387 mAh / g.

JP, 2015-84321, A

M. Gasperin, Journal of Solid State Chemistry 53, pp144-147 (1984) Yuji Yoshimura, Shoji Ogawa (1993). A simple method for quantifying the particle shape of sandy granular materials. Journal of Japan Society of Civil Engineers, No.463 / III-22, pp.95-103 Dr. Michael et al., Image Processing with ImageJ, Reprinted from the July 2004 issue of Biophotonics International copyrighted by Laurin Publishing Co. INC. Book by Izumi Nakai and Fujio Izumi, “Practice of X-ray powder analysis”, Japan Society for Analytical Chemistry, X-ray Analysis Research Roundtable (Asakura Shoten) Published July 10, 2009, pages 97-115

  The present invention has been made in view of the above circumstances, and provides an active material composite capable of realizing a secondary battery excellent in input / output performance and energy density, an electrode including the active material composite, a secondary battery, a battery pack, and a vehicle. For the purpose.

According to the embodiment, an active material composite including particles of niobium titanium composite oxide and a carbon-containing layer that covers at least a part of the surface of the niobium titanium composite oxide particles is provided. The carbon-containing layer satisfies the following formula (1).
1.2 < _IG / _ID ≦ 5 (1)
However, _{I D} is the peak intensity of D band appearing in 1280～1400Cm ^-1 in the Raman spectrum by Raman spectroscopy using a light source of 532 nm, G band _{I G} appearing at 1530～1650Cm ^-1 in the Raman spectrum of the above The peak intensity.
According to an embodiment, an electrode is provided. This electrode includes the active material composite according to the embodiment.

  According to the embodiment, a secondary battery is provided. This secondary battery includes the electrode according to the embodiment.

  According to an embodiment, a battery pack is provided. This battery pack includes the secondary battery according to the embodiment.

  According to an embodiment, a vehicle is provided. This vehicle includes the battery pack according to the embodiment.

Sectional drawing which shows schematically an example of the secondary battery which concerns on embodiment. Sectional drawing which expanded the A section of the secondary battery shown in FIG. The partial notch perspective view which shows the other example of the secondary battery which concerns on embodiment typically. Sectional drawing which expanded the B section of the secondary battery shown in FIG. The perspective view which shows roughly an example of the assembled battery which concerns on embodiment. The perspective view which shows roughly an example of the battery pack which concerns on embodiment. The block diagram which shows an example of the electric circuit of the battery pack shown in FIG. 1 is a cross-sectional view schematically showing an example of a vehicle according to an embodiment. The figure which showed schematically the other example of the vehicle which concerns on embodiment. The figure which shows the Raman spectrum by the Raman spectroscopy about the active material composite_body | complex of an Example and a comparative example. Schematic view showing the crystal structure of the niobium titanium composite oxide Nb ₂ TiO _7. The schematic diagram which shows the crystal structure of FIG. 11 from another direction. The figure which shows an example of the SEM (Scanning Electron Microscope) image of the active material particle which concerns on embodiment. The figure which shows the other example of the SEM image of the active material particle which concerns on embodiment.

  Hereinafter, embodiments will be described with reference to the drawings as appropriate. 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 embodiment, and its shape, dimensions, ratio, etc. are different from the actual device, but these are the following explanations and known techniques. The design can be changed as appropriate.

(First embodiment)
According to the first embodiment, an active material composite including niobium titanium composite oxide particles and a carbon-containing layer is provided. The carbon-containing layer covers a part or all of the surface of the niobium titanium composite oxide particles. The carbon-containing layer satisfies the following formula (1).

1.2 < _IG / _ID ≦ 5 (1)
However, _ID is the peak intensity of the D band appearing at 1280 to 1400 cm ⁻¹ in the Raman spectrum by Raman spectroscopy using a light source of 532 nm. I _G is the peak intensity of G-band appearing at 1530～1650Cm ^-1 in the Raman spectrum.

The G band is a peak derived from the graphite structure and exhibits high electrical conductivity. On the other hand, the D band is a peak derived from the defect structure or metastable form of carbon, and shows a high intensity with sp3 hybrid orbitals. When the peak intensity ratio I _G / _ID is 1.2 or less, carbon defects in the carbon-containing layer increase. As a result, the side reaction between the carbon-containing layer and the electrolyte is promoted, which adversely affects output performance or life performance. On the other hand, when the peak intensity ratio I _G / _ID is larger than 5, the metastable form in the carbon-containing layer is extremely reduced, so that the carbon-containing layer cannot maintain sufficient strength, and the particle surface of the niobium titanium composite oxide The deviation of the distribution of the carbon-containing layer in is increased. A more preferable range of the peak intensity ratio I _G / _ID is 1.5 ≦ I _G / _ID ≦ 4.

  According to the active material composite of the embodiment, the particle surface of the niobium titanium composite oxide can be uniformly coated with the highly crystalline carbon-containing layer. Therefore, when this active material composite is used for an electrode, the niobium titanium composite oxide is filled in the electrode at a high density. In addition, since the crystallinity of the carbon-containing layer is high, an electrode having a high active material filling density and excellent conductivity can be realized. As a result, a secondary battery and a battery pack having high energy density and excellent input / output performance can be provided. In addition, since the adhesion between the particle surface of the niobium titanium composite oxide and the carbon-containing layer is excellent, it is possible to suppress the separation of the carbon-containing layer due to the expansion and contraction of the niobium titanium composite oxide particles accompanying the charge / discharge reaction. it can. Therefore, the durability of the active material composite can be increased, and the life of the electrode and the secondary battery can be improved.

  The thickness of the carbon-containing layer can be 0.1 nm or more and 10 nm or less.

  The coating amount of the carbon-containing layer is desirably 0.1 parts by weight or more and 3 parts by weight or less with respect to 100 parts by weight of the niobium titanium composite oxide particles. When the coating amount by the carbon-containing layer is small, it is difficult to improve the conductive path between the niobium titanium composite oxide particles. On the other hand, when the coating amount is large, due to the bulkiness of the carbon-containing layer, the compactability in the pressing process during electrode production is poor, and the electrode density is difficult to increase even when pressing is performed at a high pressing pressure. Therefore, high energy density cannot be achieved.

  The carbon-containing layer is allowed to contain inevitable impurities such as hydrogen atoms and oxygen atoms. Further, the carbon-containing layer may be layered, granular, or have a mixed form of layered and granular.

  The particles of the niobium titanium composite oxide may be primary particles, secondary particles, or a mixed form of primary particles and secondary particles. Secondary particles are aggregates of primary particles in which primary particles are aggregated. The primary particles are single primary particles that do not take the form of secondary particles.

  The content of the niobium titanium composite oxide particles in the active material composite is preferably in the range of 75 wt% to 100 wt%.

The niobium titanium composite oxide is represented by, for example, Nb ₂ TiO ₇ as a representative composition. Niobium titanium composite oxide is not limited to this, but has a symmetry of space group C2 / m and a crystal structure having atomic coordinates described in Non-Patent Document 1 (Journal of Solid State Chemistry 53, pp144-147 (1984)). Is preferably at least partially.

The niobium titanium composite oxide mainly has a monoclinic crystal structure. As an example, schematic diagrams of the crystal structure of monoclinic Nb ₂ TiO ₇ are shown in FIGS.

As shown in FIG. 11, in the crystal structure of monoclinic Nb ₂ TiO ₇ , metal ions 101 and oxide ions 102 constitute a skeleton structure portion 103. At the position of the metal ion 101, Nb ions and Ti ions are randomly arranged at a ratio of Nb: Ti = 2: 1. The skeletal structure portions 103 are alternately arranged three-dimensionally, so that void portions 104 exist between the skeleton structure portions 103. The void 104 serves as a lithium ion host. Lithium ions can be inserted into this crystal structure from 0 moles up to 5.0 moles. The composition in which 5.0 mol of lithium ions are inserted can be expressed as Li ₅ Nb ₂ TiO ₇ .

In FIG. 11, a region 105 and a region 106 are portions having two-dimensional channels in the [100] direction and the [010] direction. As shown in FIG. 12, the monoclinic Nb ₂ TiO ₇ crystal structure has a void portion 107 in the [001] direction. This void portion 107 has a tunnel structure that is advantageous for conducting lithium ions, and serves as a conductive path in the [001] direction that connects the region 105 and the region 106. The presence of this conductive path enables lithium ions to move between the region 105 and the region 106.

Further, in the above crystal structure, when lithium ions are inserted into the gap portion 104, the metal ions 101 constituting the skeleton are reduced to trivalent, thereby maintaining the electrical neutrality of the crystals. In the niobium titanium composite oxide, not only Ti ions are reduced from tetravalent to trivalent, but Nb ions are reduced from pentavalent to trivalent. For this reason, the reduction valence per active material weight is large. Therefore, even if many lithium ions are inserted, the electrical neutrality of the crystal can be maintained. For this reason, compared with a compound such as titanium oxide containing only tetravalent cations, the energy density is high. The niobium titanium composite oxide has a lithium occlusion potential of about 1.5 V (vs. Li / Li ⁺ ). Therefore, an electrode including niobium titanium composite oxide as an active material can realize a battery that can be stably and repeatedly rapidly charged and discharged.

The niobium titanium composite oxide includes, for example, at least one selected from the group consisting of Nb ₂ TiO ₇ , Nb ₂ Ti ₂ O ₉ , Nb ₁₀ Ti ₂ O ₂₉ , Nb ₁₄ TiO ₃₇ and Nb ₂₄ TiO ₆₂ . The niobium titanium composite oxide may be a substituted niobium titanium composite oxide in which at least a part of Nb and / or Ti is substituted with a different element. Examples of substitution elements are Na, K, Ca, Co, Ni, Si, P, V, Cr, Mo, Ta, Zr, Mn, Fe, Mg, B, Pb, and Al. The substituted niobium titanium composite oxide may contain one type of substitution element or may contain two or more types of substitution elements. The active material particles may contain one type of niobium titanium composite oxide or may contain a plurality of types of niobium titanium composite oxide. The niobium titanium composite oxide preferably contains a monoclinic niobium titanium composite oxide Nb ₂ TiO ₇ . Thereby, the active material composite which can achieve the electrode and secondary battery excellent in energy density and input-output performance can be obtained.

The monoclinic niobium titanium composite oxide may contain Li. Li can be included in the monoclinic niobium titanium composite oxide by synthesis, but can also be contained in the monoclinic niobium titanium composite oxide by a charge / discharge reaction. The amount of Li in the monoclinic niobium titanium composite oxide containing Li can vary due to the influence of the charge / discharge reaction.
As an example of the monoclinic niobium titanium complex oxide, a compound represented by Li _a Ti _1-x M1 _x Nb _2-y M2 _y O ₇ can be given. Here, 0 ≦ a ≦ 5, 0 ≦ x <1, 0 ≦ y <1, M1 is Nb, V, Ta, Fe, Bi, Sb, As, P, Cr, Mo, W, B, Na, Mg And at least one element selected from the group consisting of Al and Si, and M2 is V, Ta, Fe, Ti, Bi, Sb, As, P, Cr, Mo, W, B, Na, Mg, Al And at least one element selected from the group consisting of Si. M1 and M2 may be the same or different from each other.

Another example of the monoclinic niobium titanium composite oxide is a compound represented by Li _a Ti _1-x M _x Nb ₂ O ₇ . Here, 0 ≦ a ≦ 5, 0 ≦ x <1, M is Nb, V, Ta, Bi, Sb, As, P, Cr, Mo, W, B, Na, Mg, Al, and Si. At least one selected. The use of monoclinic niobium titanium composite oxide particles having this composition can improve the input / output performance of the active material.

The active material composite may contain other active materials other than the niobium titanium composite oxide. Examples of other active materials include lithium titanate having a ramsdellite structure (for example, Li _{2 + y} Ti ₃ O ₇ , 0 ≦ y ≦ 3), lithium titanate having a spinel structure (for example, Li _{4 + x} Ti ₅ O ₁₂ , 0 ≦ x ≦ 3), monoclinic titanium dioxide (TiO ₂ (B)), anatase-type titanium dioxide, rutile-type titanium dioxide, hollandite-type titanium composite oxide, and orthorhombic-type titanium A composite oxide can be mentioned.

The BET specific surface area of the niobium titanium composite oxide particles is not particularly limited, but is preferably 0.1 m ² / g or more and less than 100 m ² / g. When the specific surface area is 0.1 m ² / g or more, the contact area with the electrolyte can be secured, good discharge rate characteristics can be easily obtained, and the charging time can be shortened. On the other hand, when the specific surface area is less than 100 m ² / g, the reactivity with the electrolyte does not become too high, and the life characteristics can be improved. Moreover, when the specific surface area is less than 100 m ² / g, it is possible to improve the coatability of the slurry containing the active material used for manufacturing the electrode described later.

  The niobium titanium composite oxide particles preferably include primary particles of the niobium titanium composite oxide. The primary particles are those in which the average value (FUave) of the uneven shape factor FU shown in the following formula (2) for 100 particles satisfies 0.7 or more, and the 100 primary particles are laser diffraction scattering method. It is desirable to have a particle diameter of 0.2 to 4 times the average particle diameter (D50) of primary particles.

  In the formula (2), l is the outer peripheral length of the primary particle in the projected cross section, and a is the cross sectional area of the primary particle in the projected cross section. π represents the pi and is assumed to be 3.14.

  Specifically, first, the average particle diameter (D50) of the primary particles is calculated from the particle size distribution chart for the niobium titanium composite oxide particles, and the particle diameter (diameter) is 0.2 to 4 times the value of D50. 100 primary particles are extracted from among a plurality of primary particles having). Next, for each of these particles, the value of the concavo-convex shape factor FU is calculated according to Equation (2). A specific method for extracting 100 primary particles will be described later.

  Since the primary particles of the niobium titanium composite oxide satisfying the above formula (2) are not obtained by a strong pulverization treatment, the primary particles have high crystallinity. Further, the niobium titanium composite oxide particles contain many primary particles having a smooth surface. Therefore, the surface of the niobium titanium composite oxide particles can be thinly and uniformly covered with the carbon-containing layer satisfying the formula (1). As a result, the compactibility of the active material composite can be greatly improved, so that the adhesion between the niobium titanium composite oxide particles is increased and the conductive path between the niobium titanium composite oxide particles can be improved. . The average value FUave of the uneven shape factor FU is preferably in the range of 0.7 to 1, and more preferably in the range of 0.7 to 0.85.

The average particle diameter (D50) of the primary particles of the niobium titanium composite oxide is preferably in the range of 0.5 μm to 5 μm, and more preferably in the range of 0.5 μm to 2 μm. If the average particle diameter (D50) of the primary particles is less than 0.5 μm, it is difficult to increase the electrode density because the specific surface area is high and voids are increased in the electrode. As a result, the contact between the active material particles in the electrode and the contact between the active material particles and the conductive agent are deteriorated, and the life performance tends to be lowered. Moreover, since the reactivity with an electrolyte becomes high because the specific surface area is high, and resistance increases due to the formation of a film on the electrode surface, the rapid charge / discharge performance tends to decrease. On the other hand, when the average particle diameter (D50) of the primary particles is larger than 50 μm, the Li ion diffusion distance in the solid becomes long and the rapid charge / discharge performance tends to be lowered. A method for determining the average particle diameter (D50) of the plurality of primary particles contained as the active material will be described later.
<Manufacturing method>
The method for synthesizing the niobium titanium composite oxide particles is not particularly limited, and for example, a solid phase method, a hydrothermal method, a sol-gel method, a coprecipitation method, or the like can be employed.

  The niobium titanium composite oxide particles satisfying the formula (2) can be produced, for example, by the following method.

  First, the starting materials are mixed. As a starting material for the niobium titanium composite oxide, an oxide or salt containing Li, Ti, and Nb is used. The salt used as the starting material is preferably a salt that decomposes at a relatively low temperature to form an oxide, such as carbonates and nitrates. The particle diameter of these starting materials is preferably in the range of 0.1 μm to 10 μm, more preferably in the range of 0.1 μm to 5 μm. This is because if it is smaller than 0.1 μm, it tends to float in the atmosphere during mixing, causing a composition shift, and if it is larger than 10 μm, an unreacted product is generated.

  When mixing the starting materials, they are mixed at a molar ratio such that the Nb source and Ti source do not have the target composition. For example, when the ratio of Nb and Ti in the target composition is not 1: 1, mixing is performed at a molar ratio of 1: 1 so that the Nb source and Ti source as raw materials are equimolar. The mixed raw material is subjected to provisional baking at a temperature in the range of 500 ° C. to 1000 ° C. for about 2 hours to 5 hours. Next, the starting materials are additionally mixed with the powder after the pre-baking in an amount so as to obtain the target composition. By this addition, the element ratio of the entire starting material used matches the target composition. The mixture after the addition of the raw material is further subjected to firing. The main baking is performed at a temperature of 1000 ° C. to 1450 ° C. and divided into two or more bakings for a total of 10 hours to 40 hours. After the main baking, it is preferable to further carry out an annealing process at a temperature equal to or lower than the temperature during the main baking. The annealing treatment is performed by heat treatment at a temperature of 350 ° C. to 800 ° C. for 1 hour to 5 hours. By performing the annealing treatment, the oxygen deficiency of the niobium titanium composite oxide can be repaired, so that high capacity and excellent life performance can be achieved.

  The powder after firing is quickly removed from the electric furnace and cooled to room temperature. This cooling is preferably performed under the condition that the temperature of the fired product becomes 100 ° C. or less within 1 hour from the temperature at the time of firing.

  In this way, the starting material is not mixed and fired at the desired composition ratio from the beginning, but the composition ratio of the raw material mixed at the time of temporary firing is different from the composition ratio of the raw material mixed at the time of main firing. In addition, the growth of primary particles can be suppressed by performing the firing in two or more times. Because firing from the beginning at the mixing ratio of the target composition proceeds from particle necking to particle growth in the sintering reaction all at once, but under the mixing ratio different from the target composition, the raw material becomes excessive or insufficient. This is because raw material particles remain between the reaction particles, and particle growth can be suppressed.

  The surfaces of the plurality of active material particles in which the growth of the primary particles is suppressed are smooth. That is, according to such a production method, niobium titanium composite oxide particles satisfying the formula (2) can be produced.

  Note that lithium ions may be inserted into the niobium titanium composite oxide synthesized by the above method by charging the battery. Or as above-mentioned, you may synthesize | combine as a complex oxide containing lithium by using the compound containing lithium like lithium carbonate as a starting material.

  The niobium titanium composite oxide particles are mixed with a solution in which a carbon source is dispersed using, for example, a ball mill, and then dried to obtain a phase containing niobium titanium composite oxide particles and a carbon-containing compound covering at least a part of the surface. To obtain a composite comprising By subjecting the obtained composite to reduction firing in an inert atmosphere such as a nitrogen atmosphere, a carbon-containing layer is formed on the particle surface of the niobium titanium composite oxide.

  Examples of the carbon source include water-soluble saccharides, water-soluble alcohols, water-soluble polymers, acrylic resins, and the like. Examples of the water-soluble saccharide include sucrose, glucose, maltose, and sodium alginate. Examples of water-soluble alcohols include polyvinyl alcohol (PVA). Examples of the water-soluble polymer include carboxymethyl cellulose (CMC). Examples of the acrylic resin include acrylic acid ester, methacrylic acid ester, and polymethyl methacrylate. The acrylic resin has high adsorptivity to the particle surface of the niobium titanium composite oxide. Therefore, it is useful for the synthesis of the active material complex of the embodiment.

  The addition amount of the carbon source is desirably 1 to 20 parts by weight with respect to 100 parts by weight of the niobium titanium composite oxide particles.

  Examples of the solvent in which the carbon source is dispersed include water, alcohol and the like. Examples of the alcohol include ethanol and ethylene glycol. The solvent is preferably a mixed solvent containing water and alcohol. When this mixed solvent is used and the drying temperature is 50 ° C. or higher and 90 ° C. or lower, the amount of solvent remaining on the particle surface can be reduced while the solvent evaporates little by little. And can be uniformly attached.

  The viscosity μ of the solution in which the carbon source is dispersed is desirably in the range of 0.1 Pa · s to 100 Pa · s. If the viscosity is small, the fluidity of the solution is high, so that it is difficult to uniformly attach the solution to the particle surface. On the other hand, if the viscosity is large, the carbon-containing layer becomes thick. A preferable range is 5 Pa · s or more and 80 Pa · s or less.

  Niobium titanium composite oxide particles, carbon source, and solvent are mixed in place of a ball mill by introducing them into an autoclave and subjecting them to hydrothermal treatment at 80 to 200 ° C. for 0.5 to 10 hours. May be performed.

  The drying temperature is desirably 50 ° C. or higher and 90 ° C. or lower. By setting the drying temperature within this range, the solvent can be slowly evaporated, so that the carbon source can be thinly and uniformly attached to the particle surface.

  The conditions for the reduction firing include, for example, performing at a temperature in the range of 500 ° C. to 1,000 ° C., preferably 600 ° C. to 900 ° C. for 0.1 to 40 hours. When the firing temperature is low or the firing time is short, the crystallinity of the carbon-containing layer is lowered. On the other hand, when the firing temperature is high or the firing time is long, oxygen vacancies are likely to occur in the niobium titanium composite oxide, and the performance of the niobium titanium composite oxide deteriorates.

  The carbon-containing layer satisfying the formula (1) can be obtained, for example, by thinly and uniformly attaching a carbon source to the particle surface of the niobium titanium composite oxide and then reducing and firing under the above conditions. By adjusting conditions such as the combination of the carbon source and the solvent, the viscosity of the solution in which the carbon source is dispersed, and the drying temperature of the solution, the carbon source can be deposited thinly and uniformly on the particle surface of the niobium titanium composite oxide. It becomes possible.

<Measurement by Raman spectroscopy>
A micro-Raman spectrometer is used. As the measuring device, for example, Nicolet Almega (registered trademark) manufactured by Thermo Fisher Scientific or a device having an equivalent function can be used. The measurement conditions are a wavelength of 532 nm, a slit size of 25 μm, a laser intensity of 10%, an exposure time of 10 s, and an integration count of 10 times. The obtained Raman spectrum to perform a fitting according to Lorentzian function, 1350 cm and D band having a peak top at around ^-1, 1580 cm each peak intensity of G-band having a peak top at around ^-1 _(I D, I The ratio I _G / _ID of _G ) is calculated.

<State and thickness of carbon-containing layer>
The state and thickness of the carbon-containing layer can be confirmed by observation with a transmission electron microscope (TEM). Specifically, first, ruthenium is adsorbed on the surface of the active material composite by vapor deposition. Next, the active material composite is embedded in the resin and thinned by ion milling using DualMill 600 manufactured by GATAN or an apparatus having an equivalent function. Next, TEM observation is performed on the primary particles of any active material complex. This observation makes it possible to grasp the dispersibility of the carbon-containing layer on the particles. This observation is performed on 10 or more particles, and the average value of the thickness of the carbon-containing layer is calculated to obtain the thickness of the carbon-containing layer. As the TEM device, for example, H-9000UHR III manufactured by Hitachi, Ltd. or a device having an equivalent function can be used. In this measurement, the acceleration voltage is set to 300 kV and the magnification of the image is set to 2000000 times.

<Determination of average value FU _ave of uneven shape factor FU>
A method for determining the average value FU _ave of the uneven shape factor FU for a plurality of primary particles containing niobium titanium composite oxide will be described.

  When the active material particles contained in the battery are to be measured, the active material is removed from the battery by the following procedure.

  First, the battery is completely discharged. By discharging the battery to a rated end voltage with a current of 0.1 C in a 25 ° C. environment, the battery can be put into a discharged state.

  Next, the battery is disassembled in a glove box filled with argon, and the electrode body (or electrode group) is taken out. This electrode body is washed with an appropriate solvent and dried under reduced pressure at 60 ° C. for 12 hours. As the cleaning solvent, for example, ethyl methyl carbonate can be used. Thus, the organic electrolyte contained in the electrode body can be removed. Next, the electrode is cut to obtain two electrode pieces. One of the cut electrode pieces is immersed in a solvent (preferably an organic solvent such as alcohol or NMP), and ultrasonic waves are applied. Thereby, a collector and the electrode constituent material contained in an electrode body can be isolate | separated. Next, the dispersion solvent in which the electrode constituent material is dispersed is applied to a centrifugal separator to separate only the active material particles from the powder of the electrode body containing a conductive agent such as carbon.

  Then, the measuring method of the particle size distribution of the several active material particle prepared as mentioned above is demonstrated.

  By subjecting the active material powder to particle size distribution measurement by a laser diffraction scattering method, the average particle diameter (D50) of the primary particles can be determined from the cumulative frequency curve of the active material particles. As the laser diffractometer, for example, MT3000II manufactured by Microtrack Bell Co., Ltd. can be used.

  However, when the active material particles to be measured mainly contain secondary particles, it is difficult to measure the average particle diameter (D50) of the primary particles using a laser diffractometer. Therefore, in this case, it is necessary to estimate the average particle diameter (D50) of the primary particles by observing a scanning electron microscope (SEM) image. In addition, it is judged by observing by SEM whether the active material particle made into a measurement object mainly contains a secondary particle. The active material powder is affixed on the SEM stage with carbon tape, and the particles are observed at a magnification of, for example, 5000 to 20000 times so that the boundary line of the outer periphery (contour) of the primary particles can be clearly recognized. For any 100 particles in this SEM image, the particle diameter is determined by the following procedure. A circle having the smallest diameter (referred to as a minimum circumscribed circle) is drawn out of circles (ie, circumscribed circles) enclosing the target particles, and the diameter of this circle is defined as the particle diameter. The average value of the particle diameters determined for any 100 particles is used as a substitute value for the average particle diameter (D50) of the primary particles.

  Next, the uneven shape factor FU is determined for each of the plurality of primary particles. This procedure will be described with reference to FIGS. FIG. 13 is a diagram illustrating an example of an SEM image (20,000 times) of particles of a niobium titanium composite oxide. FIG. 14 is a diagram showing another example of an SEM image (20,000 times) of particles of niobium titanium composite oxide. Regarding the specific definition of the uneven shape factor FU, the contents of Non-Patent Document 2 are cited by reference.

  The other of the previously prepared electrode pieces is affixed with a carbon tape on the SEM stage. At this time, it is pasted so that the layer can be observed from the perpendicular direction of the active material-containing layer. Then, a total of 100 central portions in the short direction of the electrode are observed at regular intervals from the end of the electrode in the longitudinal direction. At each observation point, one primary particle satisfying the following condition is selected from particles whose boundary line of the outer periphery (contour) of the primary particle is clearly visible. Thus, a total of 100 primary particles are measured. Note that the observation magnification is a particle magnification at which the boundary line of the outer periphery (contour) of the primary particles can be clearly recognized, for example, 5000 times to 20000 times.

  First, the center of gravity is obtained from the projected area of the primary particles. Here, a circle having a radius of the value of D50 determined previously is defined as a circle X. A circle having a radius of a value obtained by multiplying the value of D50 by 0.1 is defined as a circle Y. As shown in FIG. 13, when the centers of the circle X and the circle Y are overlapped with the center of gravity of the primary particle 10 to be measured, the outer periphery L of the primary particle 10 is larger than the circle Y and smaller than the circle X. Such primary particles are determined at each observation point.

For these 100 primary particle images, an outer peripheral length l of the outer periphery L of the target particle 10 and a cross-sectional area a of the target particle 10 are obtained using an image analysis tool. As an image analysis tool, for example, ImageJ shown in Non-Patent Document 3 can be used. From the obtained outer peripheral length l and the cross-sectional area a, the concavo-convex shape factor FU is calculated for each of the selected 100 primary particles according to the following formula (2). Further, an average value FU _ave of the calculated 100 uneven shape factors FU is calculated.

  When measuring the outer peripheral length l of the target particle 10 and the cross-sectional area a of the target particle 10, the fine particles 11 having a particle diameter smaller than the circle Y on the surface and / or outer periphery of the primary particle 10 to be measured. Is attached, the outer circumference including the fine particles 11 is regarded as the outer circumference L of the primary particle 10 and measured. The cross-sectional area of the fine particles 11 is also measured in addition to the cross-sectional area a of the target particle 10. The SEM image shown in FIG. 14 shows an example when fine particles 11 having a particle diameter smaller than the circle Y are attached to the surface and / or outer periphery of the primary particles 10 to be measured. 14 that the particle diameter of the fine particles 11 is smaller than the circle Y. The reason for considering the outer peripheral length and cross-sectional area of the fine particles 11 in addition to the outer peripheral length and cross-sectional area of the primary particles 10 to be measured is that such fine particles 11 are attached to the surface of the primary particles 10. This is to reflect the loss of the smoothness of the particle surface in the value of the uneven shape factor FU.

<Confirmation of crystal structure of active material>
The crystal structure of the active material can be confirmed by combining, for example, powder X-ray diffraction measurement (XRD) and analysis by the Rietveld method.

The powder X-ray diffraction measurement of the active material can be performed, for example, as follows.
First, the active material is pulverized as necessary to prepare a sample having an average particle size of less than about 5 μm. The average particle diameter can be determined by a laser diffraction method. The obtained sample is filled in a holder portion having a depth of 0.2 mm formed on a glass sample plate. Next, another glass plate is pressed from the outside to flatten the surface of the filled sample. Care should be taken to fill the sample with a sufficient amount so that there are no cracks, voids, irregularities, etc. in the sample. Care should be taken to press the glass plate with sufficient pressure. Next, the glass plate filled with the sample is placed in a powder X-ray diffractometer, and an XRD pattern is obtained using Cu-Kα rays.

  In addition, when the orientation of the sample is high, the position of the peak may be shifted or the peak intensity ratio may be changed depending on how the sample is filled. Such a sample with extremely high orientation is measured using a capillary. Specifically, a sample is inserted into a capillary, and this capillary is placed on a rotary sample table for measurement. The orientation can be relaxed by such a measuring method. A capillary made of Lindeman glass is used.

  The active material contained in the battery as the electrode material can be measured as follows. First, lithium ions are completely separated from the active material (for example, niobium titanium composite oxide) in the electrode material. For example, when this active material is used for the negative electrode, the battery is completely discharged. Thereby, the crystalline state of the active material can be observed. There may be residual lithium ions even in a discharged state. Due to the influence of lithium ions remaining in the electrode, an impurity phase such as lithium carbonate or lithium fluoride may be mixed in the powder X-ray diffraction measurement result. Mixing of the impurity phase can be prevented, for example, by setting the measurement atmosphere to an inert gas atmosphere or cleaning the electrode surface. Even if there is an impurity phase, it is possible to analyze by ignoring these phases.

  Next, the battery is disassembled in a glove box filled with argon, and the electrode is taken out. The removed electrode is washed with an appropriate solvent. For example, ethyl methyl carbonate can be used. The cleaned electrode is cut into an area substantially the same as the area of the holder of the powder X-ray diffractometer to obtain a measurement sample.

  The cut sample (electrode) is directly attached to a glass holder and measured. At this time, the position of a peak derived from an electrode substrate such as a metal foil is measured in advance. In addition, the peaks of other components such as a conductive agent and a binder are also measured in advance. When the peak of the substrate and the peak of the active material overlap, it is desirable to peel off a layer containing the active material (for example, an active material-containing layer described later) from the substrate for measurement. This is for separating overlapping peaks when quantitatively measuring the peak intensity. For example, the active material layer can be peeled off by irradiating the electrode substrate with ultrasonic waves in a solvent. The active material layer is sealed in a capillary and placed on a rotary sample table for measurement. By such a method, the XRD pattern of the active material can be obtained while reducing the influence of orientation. The XRD pattern acquired at this time must be applicable to Rietveld analysis. In order to collect the data for the Rietveld, the step width is set to 1/3 to 1/5 of the minimum half width of the diffraction peak, and the intensity at the peak position of the maximum intensity reflection is 5000 to 10,000 counts. The measurement time and / or X-ray intensity is adjusted as appropriate.

  The obtained XRD pattern is analyzed by the Rietveld method. In the Rietveld method, a diffraction pattern is calculated from a crystal structure model estimated in advance. By fitting all of the calculated values and the actually measured values, parameters (lattice constant, atomic coordinates, occupancy, etc.) relating to the crystal structure can be analyzed precisely. Thereby, the characteristics of the crystal structure of the synthesized oxide can be examined. Moreover, it is possible to investigate the occupation rate in each site of a constituent element.

The fitting parameter S is used as a scale for estimating the degree of coincidence between the observed intensity and the calculated intensity in Rietveld analysis. It is necessary to perform an analysis so that S is smaller than 1.8. Also, the standard deviation σ _j must be taken into account when determining the occupancy of each site. The fitting parameter S and the standard deviation σ _j defined here are estimated by mathematical formulas described in Non-Patent Document 4 (pages 97 to 115). In this method, in the monoclinic niobium titanium composite oxide having the symmetry of the space group C2 / m of the embodiment, each cation is evenly occupied in each metal cation occupying site of 2a or 4i in the crystal structure. The case where the fitting is performed assuming that the cation is present, and the case where the fitting is performed by setting individual occupancy for each element on the assumption that each cation is unevenly distributed are tried. As a result, it can be determined that the smaller the convergence value of the fitting parameter S, that is, the better the fitting, is closer to the actual occupied state. Thereby, it can be determined whether or not each cation is randomly arranged.

<Method for confirming composition of active material>
The composition of the active material can be analyzed using, for example, inductively coupled plasma (ICP) emission spectroscopy. At this time, the abundance ratio (molar ratio) of each element depends on the sensitivity of the analyzer to be used. Therefore, the measured molar ratio may deviate from the actual molar ratio by the error of the measuring device. However, even if the numerical value deviates within the error range of the analyzer, the performance of the electrode according to the embodiment can be sufficiently exhibited.

  In order to measure the composition of the active material incorporated in the battery by ICP emission spectroscopy, specifically, the following procedure is used.

  First, according to the procedure described in the section of powder X-ray diffraction, an electrode containing an active material to be measured is taken out from the secondary battery and washed. A portion containing the electrode active material such as the active material-containing layer is peeled off from the cleaned electrode. For example, the portion containing the electrode active material can be peeled off by irradiating ultrasonic waves. As a specific example, for example, an active material-containing layer containing an electrode active material can be peeled from an electrode current collector by placing an electrode in ethyl methyl carbonate placed in a glass beaker and vibrating in an ultrasonic cleaner. it can.

  Next, the peeled portion is heated in the atmosphere for a short time (for example, at 500 ° C. for about 1 hour) to burn away unnecessary components such as a binder component and carbon. By dissolving the residue with an acid, a liquid sample containing an active material can be prepared. At this time, hydrochloric acid, nitric acid, sulfuric acid, hydrogen fluoride and the like can be used as the acid. By subjecting this liquid sample to ICP analysis, the composition in the active material can be known.

<Measurement method of specific surface area of active material particles>
The measurement of the specific surface area of the active material particles can be carried out by a method in which molecules having a known adsorption occupation area are adsorbed on the surface of the powder particles at the temperature of liquid nitrogen and the specific surface area of the sample is obtained from the amount. The BET method based on low-temperature and low-humidity physical adsorption of inert gas is the most widely used theory, which is the most famous theory for calculating specific surface area, which is an extension of the monolayer adsorption theory Langmuir theory to multi-layer adsorption. is there. The specific surface area determined in this way is referred to as the BET specific surface area.

The active material composite according to the first embodiment described above covers at least part of the surfaces of the niobium titanium composite oxide particles and the niobium titanium composite oxide particles, and 1.2 <I in formula (1). _{And a} carbon-containing layer satisfying _{G 1} / _ID ≦ 5. Since this active material composite is excellent in conductivity and compactibility (press moldability), it is possible to realize an electrode and a secondary battery having high energy density and excellent input / output performance.

(Second Embodiment)
According to the second embodiment, an electrode including the active material complex of the first embodiment can be provided. The electrode includes an active material-containing layer containing an active material composite. The electrode can further include a current collector. The active material-containing layer can be formed on one side or both sides of the current collector. The active material-containing layer can optionally contain a conductive agent and a binder in addition to the active material composite. The electrode is, for example, a battery electrode or a secondary battery electrode. The electrode can function as a positive electrode or a negative electrode depending on the potential of the counterpart electrode.

  The conductive agent is blended in order to improve current collection performance and suppress contact resistance between the active material and the current collector. Examples of the conductive agent include vapor grown carbon fiber (VGCF), carbon black such as acetylene black, and carbonaceous material such as graphite. One of these may be used as a conductive agent, or a combination of two or more may be used as a conductive agent. In addition, since the active material composite of 1st Embodiment is excellent in electroconductivity, a electrically conductive agent is not necessarily required.

  The binder is blended to fill a gap between the dispersed active materials and bind the active material and the current collector. Examples of the binder include polytetrafluoroethylene (PTFE), polyvinylidene fluoride (PVdF), fluorine rubber, styrene butadiene rubber, polyacrylic acid compound, imide compound, carboxymethyl cellulose (carboxymethyl). cellulose; CMC), and salts of CMC. One of these may be used as a binder, or a combination of two or more may be used as a binder.

  As the current collector, a material that is electrochemically stable at a potential at which lithium (Li) is inserted into and extracted from the active material is used. For example, when the electrode is used as a negative electrode, the current collector includes one or more elements selected from copper, nickel, stainless steel, or aluminum, or Mg, Ti, Zn, Mn, Fe, Cu, and Si. Preferably it is made from an aluminum alloy. The thickness of the current collector is preferably 5 μm or more and 20 μm or less. The current collector having such a thickness can balance the strength and weight reduction of the electrode.

  In addition, the current collector can include a portion where the active material-containing layer is not formed on the surface thereof. This part can act as a current collecting tab.

(Excluding the current collector) density of the active material-containing layer is preferably in the range of ^{2.4g / cm 3 ~3g / cm 3} . The density of the active material-containing layer can also be referred to as an electrode density. When the electrode density is within this range, the active material particles and the conductive agent are in close contact with each other, so that the balance between the formation of the electronic conductive path in the electrode and the electrolyte permeability is good, and rapid charge / discharge performance and life performance are improved. improves.

  The active material composite, the conductive agent, and the binder in the active material-containing layer are in a ratio of 68% to 96% by weight, 2% to 30% by weight, and 2% to 30% by weight, respectively. It is preferable to mix.

  For example, an electrode is produced by the following method. First, a slurry is prepared by suspending an active material composite, a conductive agent, and a binder in a solvent. This slurry is applied to one side or both sides of the current collector. Next, the applied slurry is dried to obtain a laminate of the active material-containing layer and the current collector. Thereafter, the laminate is pressed. In this way, an electrode is produced.

  Or you may produce an electrode with the following method. First, an active material composite, a conductive agent, and a binder are mixed to obtain a mixture. The mixture is then formed into pellets. Subsequently, an electrode can be obtained by arranging these pellets on a current collector.

  According to a second embodiment, an electrode is provided. Since this electrode contains the first active material composite, a secondary battery having high energy density and excellent input / output performance can be realized.

(Third embodiment)
According to the second embodiment, a secondary battery including a negative electrode, a positive electrode, and an electrolyte is provided. At least one of the negative electrode and the positive electrode is an electrode according to the first embodiment.

  The secondary battery may further include a separator disposed between the positive electrode and the negative electrode. A negative electrode, a positive electrode, and a separator can comprise an electrode group. The electrolyte can be held on the electrode group. The secondary battery may further include an exterior member that accommodates the electrode group and the electrolyte. The secondary battery may further include a negative electrode terminal electrically connected to the negative electrode and a positive electrode terminal electrically connected to the positive electrode.

  The secondary battery can be, for example, a lithium ion secondary battery. The secondary battery includes a non-aqueous electrolyte secondary battery including a non-aqueous electrolyte.

  Hereinafter, the negative electrode, the positive electrode, the electrolyte, the separator, the exterior member, the negative electrode terminal, and the positive electrode terminal will be described in detail.

(1) Negative Electrode The negative electrode included in the secondary battery according to the embodiment can be, for example, the electrode described in the second embodiment.

(2) Positive Electrode The positive electrode included in the secondary battery according to the embodiment can be, for example, the electrode described in the second embodiment. When the negative electrode is an electrode corresponding to the second embodiment, the positive electrode may be an electrode described below.

  The positive electrode can include a positive electrode current collector and a positive electrode active material-containing layer. The positive electrode active material-containing layer can be formed on one side or both sides of the positive electrode current collector. The positive electrode active material-containing layer includes a positive electrode active material. The positive electrode active material-containing layer can optionally contain a conductive agent and a binder.

  As the positive electrode active material, for example, an oxide or a sulfide can be used. The positive electrode may contain one kind of compound alone as a positive electrode active material, or may contain two or more kinds of compounds in combination. Examples of oxides and sulfides include compounds that can insert and desorb Li or Li ions.

As such a compound, for example, manganese dioxide (MnO ₂ ), iron oxide, copper oxide, nickel oxide, lithium manganese composite oxide (for example, 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 (for example, 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) a 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), a lithium phosphorous oxide having an olivine structure (for example, Li _x FePO _4; 0 _{x ≦ 1, Li x Fe 1} -y Mn y PO 4; 0 <x ≦ 1,0 <y <1, Li x CoPO 4; 0 <x ≦ 1), ferrous sulfate _{(Fe 2 (SO 4) 3} ) , Vanadium oxide (for example, V ₂ O ₅ ), and lithium nickel cobalt manganese composite oxide (Li _x Ni _1-yz Co _y Mn _z O ₂ ; 0 <x ≦ 1, 0 <y <1, 0 <z <1, y + z <1).

Among the above, examples of compounds more preferable as the positive electrode active material include lithium manganese composite oxide having a spinel structure (for example, Li _x Mn ₂ O ₄ ; 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 (for example, Li _x Ni _1-y Co _y O ₂ ; 0 < x ≦ 1, 0 <y <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 manganese cobalt composite oxides (e.g., _{Li x Mn y Co 1-y} O 2; 0 <x ≦ 1,0 <y <1), lithium iron phosphate (e.g. _{Li x FePO 4; 0 <x} ≦ 1), and lithium Nickel cobalt manganese composite Oxide _{(Li x Ni 1-yz Co} y Mn z O 2; 0 <x ≦ 1,0 <y <1,0 <z <1, y + z <1) are included. When these compounds are used for the positive electrode active material, the positive electrode potential can be increased.

When room temperature molten salt is used as the battery electrolyte, lithium iron phosphate, Li _x VPO ₄ F (0 ≦ x ≦ 1), lithium manganese composite oxide, lithium nickel composite oxide, lithium nickel cobalt composite oxide, or these It is preferable to use a positive electrode active material containing a mixture of the above. Since these compounds have low reactivity with room temperature molten salts, the cycle life can be improved. Details of the room temperature molten salt will be described later.

  The positive electrode active material particles may be in the form of primary particles, for example, or may be in the form of secondary particles formed by agglomeration of primary particles. The positive electrode active material particles may be a mixture of primary particles and secondary particles.

  The average primary particle diameter of the positive electrode active material is preferably 100 nm or more and 2 μm or less. A positive electrode active material having a primary particle size of 100 nm or more is easy to handle in industrial production. A positive electrode active material having a primary particle size of 2 μm or less can smoothly diffuse lithium ions in a solid.

The BET specific surface area of the positive electrode active material is preferably 0.1 m ² / g or more and 10 m ² / g or less. The positive electrode active material having a specific surface area of 0.1 m ² / g or more can sufficiently ensure the storage / release sites of Li ions. The positive electrode active material having a specific surface area of 10 m ² / g or less is easy to handle in industrial production and can ensure good charge / discharge cycle performance.

  The conductive agent is blended in order to improve current collecting performance and suppress contact resistance between the positive electrode active material and the positive electrode current collector. Examples of the conductive agent include vapor grown carbon fiber (VGCF), carbon black such as acetylene black, and carbonaceous material such as graphite. One of these may be used as a conductive agent, or a combination of two or more may be used as a conductive agent. Further, the conductive agent can be omitted.

  The binder is blended to fill a gap between the dispersed positive electrode active materials and bind the positive electrode active material and the positive electrode current collector. Examples of the binder include polytetrafluoroethylene (PTFE), polyvinylidene fluoride (PVdF), fluorine rubber, polyacrylic acid compound, imide compound, carboxymethyl cellulose (CMC). , And salts of CMC. One of these may be used as a binder, or a combination of two or more may be used as a binder.

  In the positive electrode active material-containing layer, the positive electrode active material and the binder are preferably blended in proportions of 80% by weight to 98% by weight and 2% by weight to 20% by weight, respectively. When a conductive agent is added, the positive electrode active material, the binder, and the conductive agent are 77 wt% or more and 95 wt% or less, 2 wt% or more and 20 wt% or less, and 3 wt% or more and 15 wt% or less, respectively. It is preferable to mix | blend in a ratio.

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

  The thickness of the aluminum foil or aluminum alloy foil is preferably 5 μm or more and 20 μm or less, and more preferably 15 μm or less. The purity of the aluminum foil is preferably 99% by weight or more. The content of transition metals such as iron, copper, nickel, and chromium contained in the aluminum foil or aluminum alloy foil is preferably 1% by weight or less.

  Moreover, the positive electrode current collector can include a portion where the positive electrode active material-containing layer is not formed on the surface thereof. This part can serve as a positive current collecting tab.

(3) Electrolyte As the electrolyte, for example, a liquid nonaqueous electrolyte or a gelled nonaqueous electrolyte can be used. The liquid non-aqueous electrolyte is prepared by dissolving an electrolyte salt as a solute in an organic solvent. The concentration of the electrolyte salt is preferably 0.5 mol / L or more and 2.5 mol / L or less.

Examples of electrolyte salts include lithium perchlorate (LiClO ₄ ), lithium hexafluorophosphate (LiPF ₆ ), lithium tetrafluoroborate (LiBF ₄ ), lithium arsenic hexafluoride (LiAsF ₆ ), trifluoromethane 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 salt is preferably one that is difficult to oxidize even at a high potential, and LiPF ₆ is most preferred.

  Examples of the organic solvent include cyclic carbonates such as propylene carbonate (PC), ethylene carbonate (EC), and vinylene carbonate (VC); diethyl carbonate (DEC) and dimethyl carbonate. (Dimethyl carbonate; DMC), chain carbonates such as methyl ethyl carbonate (MEC); tetrahydrofuran (tetrahydrofuran; THF); Cyclic ethers such as: dimethoxyethane (DME), chain ethers such as diethoxyethane (DEE); γ-butyrolactone (GBL), acetonitrile (acetonitrile) AN), and sulfolane (Sulfolane; include SL). These organic solvents can be used alone or as a mixed solvent.

  The gel nonaqueous electrolyte is prepared by combining a liquid nonaqueous electrolyte and a polymer material. Examples of the polymer material include polyvinylidene fluoride (PVdF), polyacrylonitrile (PAN), polyethylene oxide (PEO), or a mixture thereof.

  Alternatively, as the non-aqueous electrolyte, in addition to the liquid non-aqueous electrolyte and the gel-like non-aqueous electrolyte, a room temperature molten salt (ionic melt) containing lithium ions, a polymer solid electrolyte, an inorganic solid electrolyte, and the like are used. Also good.

  A room temperature molten salt (ionic melt) refers to a compound that can exist as a liquid at room temperature (15 ° C. or more and 25 ° C. or less) among organic salts formed by a combination of an organic cation and an anion. Room temperature molten salt includes room temperature molten salt that exists as a liquid alone, room temperature molten salt that becomes liquid when mixed with electrolyte salt, room temperature molten salt that becomes liquid when dissolved in organic solvent, or a mixture thereof It is. Generally, the melting point of the room temperature molten salt used for the secondary battery is 25 ° C. or less. The organic cation generally has a quaternary ammonium skeleton.

  The polymer solid electrolyte is prepared by dissolving an electrolyte salt in a polymer material and solidifying it.

  The inorganic solid electrolyte is a solid material having Li ion conductivity.

(4) Separator The separator is formed of, for example, a porous film containing polyethylene (PE), polypropylene (PP), cellulose, or polyvinylidene fluoride (PVdF), or a synthetic resin nonwoven fabric. . From the viewpoint of safety, it is preferable to use a porous film formed from polyethylene or polypropylene. This is because these porous films can be melted at a constant temperature to interrupt the current.

(5) Exterior Member As the exterior member, for example, a container made of a laminate film or a metal container can be used.

  The thickness of the laminate film is, for example, 0.5 mm or less, and preferably 0.2 mm or less.

  As the laminate film, a multilayer film including a plurality of resin layers and a metal layer interposed between these resin layers is used. The resin layer contains, for example, a polymer material such as polypropylene (PP), polyethylene (PE), nylon, and polyethylene terephthalate (PET). It is preferable that a metal layer consists of aluminum foil or aluminum alloy foil for weight reduction. The laminate film can be formed into the shape of the exterior member by sealing by heat sealing.

  The thickness of the wall of the metal container is, for example, 1 mm or less, more preferably 0.5 mm or less, and still more preferably 0.2 mm or less.

  The metal container is made of, for example, aluminum or an aluminum alloy. The aluminum alloy preferably contains elements such as magnesium, zinc, and silicon. When an aluminum alloy contains transition metals, such as iron, copper, nickel, and chromium, it is preferable that the content is 100 weight ppm or less.

  The shape of the exterior member is not particularly limited. The shape of the exterior member may be, for example, a flat type (thin type), a square type, a cylindrical type, a coin type, or a button type. The exterior member can be appropriately selected according to the battery size and the application of the battery.

(6) Negative electrode terminal A negative electrode terminal can be formed from the material which is electrochemically stable in the above-mentioned negative electrode active material Li occlusion discharge potential, and has electroconductivity. Specifically, the negative electrode terminal material includes copper, nickel, stainless steel, or aluminum, or at least one element selected from the group consisting of Mg, Ti, Zn, Mn, Fe, Cu, and Si. An aluminum alloy is mentioned. As a material for the negative electrode terminal, aluminum or an aluminum alloy is preferably used. In order to reduce the contact resistance with the negative electrode current collector, the negative electrode terminal is preferably made of the same material as the negative electrode current collector.

(7) Positive electrode terminal The positive electrode terminal may be formed of a material that is electrically stable and has conductivity in a potential range (vs. Li ^/ Li ⁺ ) of 3 V to 5 V with respect to the oxidation-reduction potential of lithium. it can. Examples of the material of the positive electrode terminal include aluminum or an aluminum alloy containing at least one element selected from the group consisting of 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.

  Next, the secondary battery according to the embodiment will be described more specifically with reference to the drawings. FIG. 1 is a cross-sectional view schematically illustrating an example of the secondary battery according to the embodiment. 2 is an enlarged cross-sectional view of a portion A of the secondary battery shown in FIG.

  A secondary battery 100 shown in FIGS. 1 and 2 includes the bag-shaped exterior member 2 shown in FIG. 1, the electrode group 1 shown in FIGS. 1 and 2, and an electrolyte (not shown). The electrode group 1 and the electrolyte are housed in a bag-shaped exterior member 2. An electrolyte (not shown) is held by the electrode group 1.

  The bag-shaped exterior member 2 is made of a laminate film including two resin layers and a metal layer interposed therebetween.

  As shown in FIG. 1, the electrode group 1 is a flat wound electrode group. As shown in FIG. 2, the flat and wound electrode group 1 includes a negative electrode 3, a separator 4, and a positive electrode 5. The separator 4 is interposed between the negative electrode 3 and the positive electrode 5.

  The negative electrode 3 includes a negative electrode current collector 3a and a negative electrode active material-containing layer 3b. In the negative electrode 3, the portion located in the outermost shell of the wound electrode group 1 has the negative electrode active material containing layer 3 b formed only on the inner surface side of the negative electrode current collector 3 a as shown in FIG. 2. In other portions of the negative electrode 3, negative electrode active material-containing layers 3b are formed on both surfaces of the negative electrode current collector 3a.

  The positive electrode 5 includes a positive electrode current collector 5a and positive electrode active material-containing layers 5b formed on both surfaces thereof.

  As shown in FIG. 1, the negative electrode terminal 6 and the positive electrode terminal 7 are located in the vicinity of the outer peripheral end of the wound electrode group 1. The negative electrode terminal 6 is connected to a portion located in the outermost shell of the negative electrode current collector 3a. Moreover, the positive electrode terminal 7 is connected to the part located in the outermost shell of the positive electrode collector 5a. 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. A thermoplastic resin layer is provided on the inner surface of the bag-shaped exterior member 2, and the opening is closed by heat-sealing it.

  The secondary battery according to the embodiment is not limited to the secondary battery having the configuration shown in FIGS. 1 and 2, and may be a battery having the configuration shown in FIGS. 3 and 4, for example.

  FIG. 3 is a partially cutaway perspective view schematically showing another example of the secondary battery according to the embodiment. 4 is an enlarged cross-sectional view of part B of the secondary battery shown in FIG.

  The secondary battery 100 shown in FIGS. 3 and 4 includes the electrode group 1 shown in FIGS. 3 and 4, the exterior member 2 shown in FIG. 3, and an electrolyte (not shown). The electrode group 1 and the electrolyte are housed in the exterior member 2. The electrolyte is held in the electrode group 1.

  The exterior member 2 is made of a laminate film including two resin layers and a metal layer interposed therebetween.

  The electrode group 1 is a stacked electrode group as shown in FIG. The stacked electrode group 1 has a structure in which negative electrodes 3 and positive electrodes 5 are alternately stacked with a separator 4 interposed therebetween.

  The electrode group 1 includes a plurality of negative electrodes 3. Each of the plurality of negative electrodes 3 includes a negative electrode current collector 3a and a negative electrode active material-containing layer 3b supported on both surfaces of the negative electrode current collector 3a. The electrode group 1 includes a plurality of positive electrodes 5. Each of the plurality of positive electrodes 5 includes a positive electrode current collector 5a and a positive electrode active material-containing layer 5b supported on both surfaces of the positive electrode current collector 5a.

  The negative electrode current collector 3a of each negative electrode 3 includes, on one side thereof, a portion 3c where the negative electrode active material-containing layer 3b is not supported on any surface. This portion 3c serves as a negative electrode current collecting tab. As shown in FIG. 4, the portion 3 c serving as the negative electrode current collecting tab does not overlap the positive electrode 5. The plurality of negative electrode current collecting tabs (part 3 c) are electrically connected to the strip-shaped negative electrode terminal 6. The tip of the strip-like negative electrode terminal 6 is drawn out of the exterior member 2.

  Moreover, although not shown in figure, the positive electrode collector 5a of each positive electrode 5 contains the part by which the positive electrode active material content layer 5b is not carry | supported on either surface in the one side. This portion serves as a positive electrode current collecting tab. The positive electrode current collecting tab does not overlap the negative electrode 3, similarly to the negative electrode current collecting tab (part 3 c). Further, the positive electrode current collecting tab is located on the opposite side of the electrode group 1 with respect to the negative electrode current collecting tab (part 3c). The positive electrode current collecting tab is electrically connected to the belt-like positive electrode terminal 7. The front end of the strip-like positive electrode terminal 7 is located on the opposite side of the negative electrode terminal 6 and is drawn out of the exterior member 2.

  The secondary battery according to the embodiment may constitute an assembled battery. The assembled battery includes a plurality of secondary batteries according to the embodiment.

  In the assembled battery according to the embodiment, each unit cell may be arranged by being electrically connected in series or in parallel, or may be arranged by combining series connection and parallel connection.

  An example of the assembled battery according to the embodiment will be described with reference to the drawings.

  FIG. 5 is a perspective view schematically showing an example of the assembled battery according to the embodiment. The assembled battery 200 shown in FIG. 5 includes five unit cells 100 a to 100 e, four bus bars 21, a positive electrode side lead 22, and a negative electrode side lead 23. Each of the five single cells 100a to 100e is a secondary battery according to the embodiment.

  The bus bar 21 connects, for example, the negative electrode terminal 6 of one single cell 100a and the positive electrode terminal 7 of the single cell 100b located next to the single cell 100a. In this way, the five unit cells 100 are connected in series by the four bus bars 21. That is, the assembled battery 200 of FIG. 5 is a 5-series assembled battery.

  As shown in FIG. 5, the positive electrode terminal 7 of the single cell 100 a located at the left end among the five single cells 100 a to 100 e is connected to the positive electrode side lead 22 for external connection. Moreover, the negative electrode terminal 6 of the unit cell 100e located at the right end among the five unit cells 100a to 100e is connected to the negative electrode side lead 23 for external connection.

  The secondary battery according to the third embodiment includes a negative electrode, a positive electrode, and an electrolyte. At least one of the negative electrode and the positive electrode is an electrode according to the second embodiment. Therefore, this secondary battery is excellent in input / output performance and energy density.

(Fourth embodiment)
According to the fourth embodiment, a battery pack is provided. This battery pack includes the secondary battery according to the third embodiment. This battery pack may include one secondary battery according to the third embodiment, or may include an assembled battery including a plurality of secondary batteries.

  The battery pack according to the embodiment may further include a protection circuit. The protection circuit has a function of controlling charging / discharging of the secondary battery. Or you may use the circuit contained in the apparatus (for example, electronic device, a motor vehicle, etc.) which uses a battery pack as a power supply as a protection circuit of a battery pack.

  The battery pack according to the embodiment can further include an external terminal for energization. The external terminal for energization is for outputting a current from the secondary battery to the outside and / or for inputting a current from the outside to the secondary battery. In other words, when the battery pack is used as a power source, current is supplied to the outside through the external terminal for energization. Further, when charging the battery pack, a charging current (including regenerative energy of motive power of an automobile or the like) is supplied to the battery pack through an external terminal for energization.

  Next, an example of the battery pack according to the embodiment will be described with reference to the drawings.

  FIG. 6 is an exploded perspective view schematically showing an example of the battery pack according to the embodiment. FIG. 7 is a block diagram showing an example of an electric circuit of the battery pack shown in FIG.

  The battery pack 300 shown in FIG.6 and FIG.7 is equipped with the storage container 31, the lid | cover 32, the protection sheet 33, the assembled battery 200, the printed wiring board 34, the wiring 35, and the insulating board which is not shown in figure. .

  The storage container 31 shown in FIG. 6 is a bottomed rectangular container having a rectangular bottom surface. The container 31 is configured to accommodate the protective sheet 33, the assembled battery 200, the printed wiring board 34, and the wiring 35. The lid 32 has a rectangular shape. The lid 32 houses the assembled battery 200 and the like by covering the housing container 31. Although not shown, the storage container 31 and the lid 32 are provided with an opening or a connection terminal for connection to an external device or the like.

  The assembled battery 200 includes a plurality of single cells 100, a positive electrode side lead 22, a negative electrode side lead 23, and an adhesive tape 24.

  The unit cell 100 has the structure shown in FIGS. At least one of the plurality of unit cells 100 is the secondary battery according to the embodiment. The plurality of single cells 100 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. Each of the plurality of unit cells 100 is electrically connected in series as shown in FIG. The plurality of single cells 100 may be electrically connected in parallel, or may be connected in combination of series connection and parallel connection. When the plurality of single cells 100 are connected in parallel, the battery capacity is increased as compared to the case where they are connected in series.

  The adhesive tape 24 fastens a plurality of unit cells 100. Instead of the adhesive tape 24, a plurality of single cells 100 may be fixed using a heat shrink tape. In this case, the protective sheets 33 are arranged on both side surfaces of the assembled battery 200, the heat shrink tape is circulated, and then the heat shrink tape is heat shrunk to bind the plurality of unit cells 100 together.

  One end of the positive electrode side lead 22 is connected to the positive electrode terminal 7 of the unit cell 100 located in the lowermost layer in the stacked body of the unit cells 100. One end of the negative electrode side lead 23 is connected to the negative electrode terminal 6 of the unit cell 100 located in the uppermost layer in the stacked body of the unit cells 100.

  The printed wiring board 34 is installed along one short side surface of the inner surface of the container 31. The printed wiring board 34 includes a positive connector 341, a negative connector 342, a thermistor 343, a protection circuit 344, wirings 345 and 346, an external terminal 347 for energization, a positive wiring 348a, and a negative wiring. 348b. One main surface of the printed wiring board 34 faces the surface of the assembled battery 200 from which the negative electrode terminal 6 and the positive electrode terminal 7 extend. An insulating plate (not shown) is interposed between the printed wiring board 34 and the assembled battery 200.

  The positive connector 341 is provided with a through hole. By inserting the other end of the positive electrode side lead 22 into this through hole, the positive electrode side connector 341 and the positive electrode side lead 22 are electrically connected. The negative electrode side connector 342 is provided with a through hole. By inserting the other end of the negative electrode side lead 23 into this through hole, the negative electrode side connector 342 and the negative electrode side lead 23 are electrically connected.

  The thermistor 343 is fixed to one main surface of the printed wiring board 34. The thermistor 343 detects the temperature of each unit cell 100 and transmits the detection signal to the protection circuit 344.

  The external terminal 347 for energization is fixed to the other main surface of the printed wiring board 34. The external terminal 347 for energization is electrically connected to a device existing outside the battery pack 300.

  The protection circuit 344 is fixed to the other main surface of the printed wiring board 34. The protection circuit 344 is connected to the external terminal 347 for energization through the plus side wiring 348a. The protection circuit 344 is connected to the external terminal 347 for energization via the minus side wiring 348b. Further, the protection circuit 344 is electrically connected to the positive connector 341 via the wiring 345. The protection circuit 344 is electrically connected to the negative connector 342 through the wiring 346. Further, the protection circuit 344 is electrically connected to each of the plurality of single cells 100 via the wiring 35.

  The protective sheet 33 is disposed on both inner side surfaces of the storage container 31 in the long side direction and on the inner side surface in the short side direction facing the printed wiring board 34 via the assembled battery 200. The protective sheet 33 is made of, for example, resin or rubber.

  The protection circuit 344 controls charging / discharging of the plurality of single cells 100. In addition, the protection circuit 344 performs electrical connection between the protection circuit 344 and the energization external terminal 347 based on the detection signal transmitted from the thermistor 343 or the detection signal transmitted from each individual battery 100 or the assembled battery 200. Block connections.

  As a detection signal transmitted from the thermistor 343, for example, a signal detected that the temperature of the unit cell 100 is equal to or higher than a predetermined temperature can be cited. As a detection signal transmitted from each unit cell 100 or the assembled battery 200, for example, a signal that detects overcharge, overdischarge, and overcurrent of the unit cell 100 can be cited. When detecting an overcharge or the like for each unit cell 100, 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 100.

  Note that as the protection circuit 344, a circuit included in a device (for example, an electronic device, an automobile, or the like) that uses the battery pack 300 as a power source may be used.

  Further, the battery pack 300 includes the external terminals 347 for energization as described above. Accordingly, the battery pack 300 can output the current from the assembled battery 200 to the external device and the current from the external device to the assembled battery 200 via the external terminal 347 for energization. In other words, when the battery pack 300 is used as a power source, the current from the assembled battery 200 is supplied to the external device through the external terminal 347 for energization. When charging the battery pack 300, charging current from an external device is supplied to the battery pack 300 through the external terminal 347 for energization. When this battery pack 300 is used as a vehicle-mounted battery, regenerative energy of vehicle power can be used as a charging current from an external device.

  The battery pack 300 may include a plurality of assembled batteries 200. In this case, the plurality of assembled batteries 200 may be connected in series, may be connected in parallel, or may be connected by combining series connection and parallel connection. Further, the printed wiring board 34 and the wiring 35 may be omitted. In this case, the positive electrode side lead 22 and the negative electrode side lead 23 may be used as external terminals for energization.

  Such a battery pack is used, for example, in applications that require excellent cycle performance when a large current is taken out. Specifically, this battery pack is used, for example, as a power source for electronic devices, a stationary battery, and an in-vehicle battery for various vehicles. An example of the electronic device is a digital camera. This battery pack is particularly preferably used as an in-vehicle battery.

  The battery pack according to the fourth embodiment includes the secondary battery according to the third embodiment. Therefore, this battery pack is excellent in input / output performance and energy density.

(Fifth embodiment)
According to a fifth embodiment, a vehicle is provided. This vehicle is equipped with the battery pack according to the fourth embodiment.

  In the vehicle according to the embodiment, the battery pack collects, for example, regenerative energy of the power of the vehicle. The vehicle may include a mechanism that converts the kinetic energy of the vehicle into regenerative energy.

  Examples of the vehicle include a two-wheel to four-wheel hybrid electric vehicle, a two-wheel to four-wheel electric vehicle, an assist bicycle, and a railway vehicle.

  The mounting position of the battery pack in the vehicle is not particularly limited. For example, when the battery pack is mounted on an automobile, the battery pack can be mounted on the engine room of the vehicle, behind the vehicle body, or under the seat.

  The vehicle may be equipped with a plurality of battery packs. In this case, the battery packs may be electrically connected in series, electrically connected in parallel, or may be electrically connected by combining series connection and parallel connection.

An example of a vehicle according to an embodiment will be described with reference to the drawings.
FIG. 8 is a cross-sectional view schematically illustrating an example of a vehicle according to the embodiment.

  A vehicle 400 shown in FIG. 8 includes a vehicle main body 40 and a battery pack 300 according to the fourth embodiment. In the example shown in FIG. 8, the vehicle 400 is a four-wheeled automobile.

  This vehicle 400 may be equipped with a plurality of battery packs 300. In this case, the battery pack 300 may be connected in series, may be connected in parallel, or may be connected by a combination of series connection and parallel connection.

  FIG. 8 illustrates an example in which the battery pack 300 is mounted in an engine room located in front of the vehicle main body 40. As described above, the battery pack 300 may be mounted, for example, behind the vehicle body 40 or under the seat. The battery pack 300 can be used as a power source for the vehicle 400. In addition, the battery pack 300 can recover the regenerative energy of the power of the vehicle 400.

  Next, an embodiment of the vehicle according to the embodiment will be described with reference to FIG.

  FIG. 9 is a diagram schematically illustrating an example of a vehicle according to the embodiment. A vehicle 400 shown in FIG. 9 is an electric vehicle.

  A vehicle 400 shown in FIG. 9 includes a vehicle main body 40, a vehicle power supply 41, a vehicle ECU (ECU: Electric Control Unit) 42, which is a higher-level control means of the vehicle power supply 41, and an external terminal (external power supply). Terminal 43), an inverter 44, and a drive motor 45.

  The vehicle 400 has a vehicle power supply 41 mounted, for example, in an engine room, behind a vehicle body or under a seat. In addition, in the vehicle 400 shown in FIG. 9, the mounting location of the vehicle power supply 41 is schematically shown.

  The vehicle power supply 41 includes a plurality of (for example, three) battery packs 300a, 300b, and 300c, a battery management unit (BMU) 411, and a communication bus 412.

  The three battery packs 300a, 300b, and 300c are electrically connected in series. The battery pack 300a includes an assembled battery 200a and an assembled battery monitoring device 301a (for example, VTM: Voltage Temperature Monitoring). The battery pack 300b includes an assembled battery 200b and an assembled battery monitoring device 301b. The battery pack 300c includes an assembled battery 200c and an assembled battery monitoring device 301c. The battery packs 300 a, 300 b, and 300 c can be detached independently and can be replaced with another battery pack 300.

  Each of the assembled batteries 200a to 200c includes a plurality of single cells connected in series. At least one of the plurality of unit cells is the secondary battery according to the embodiment. The assembled batteries 200a to 200c are charged and discharged through the positive terminal 413 and the negative terminal 414, respectively.

  The battery management device 411 communicates with the assembled battery monitoring devices 301a to 301c in order to collect information related to the maintenance of the vehicle power supply 41, and the battery management device 411 includes the single batteries included in the assembled batteries 200a to 200c included in the vehicle power supply 41. Information on the voltage and temperature of the battery 100 is collected.

  A communication bus 412 is connected between the battery management device 411 and the assembled battery monitoring devices 301a to 301c. The communication bus 412 is configured to share a set of communication lines with a plurality of nodes (battery management device and one or more assembled battery monitoring devices). The communication bus 412 is a communication bus configured based on, for example, a CAN (Control Area Network) standard.

  The assembled battery monitoring devices 301a to 301c measure the voltage and temperature of individual cells constituting the assembled batteries 200a to 200c based on a command from the battery management device 411 through communication. However, the temperature can be measured at only a few locations per assembled battery, and the temperature of all the cells need not be measured.

  The vehicle power supply 41 can also include an electromagnetic contactor (for example, a switch device 415 shown in FIG. 9) for turning on and off the connection between the positive terminal 413 and the negative terminal 414. The switch device 415 includes a precharge switch (not shown) that is turned on when the assembled batteries 200a to 200c are charged, and a main switch (not shown) that is turned on when the battery output is supplied to the load. Is included. The precharge switch and the main switch include a relay circuit (not shown) that is turned on or off by a signal supplied to a coil disposed in the vicinity of the switch element.

  The inverter 44 converts the input DC voltage into a three-phase alternating current (AC) high voltage for driving the motor. The three-phase output terminals of the inverter 44 are connected to the three-phase input terminals of the drive motor 45. The inverter 44 controls the output voltage based on a control signal from the battery management device 411 or the vehicle ECU 42 for controlling the operation of the entire vehicle.

  The drive motor 45 is rotated by electric power supplied from the inverter 44. This rotation is transmitted to the axle and the drive wheels W via, for example, a differential gear unit.

  Although not shown, the vehicle 400 includes a regenerative brake mechanism. The regenerative brake mechanism rotates the drive motor 45 when the vehicle 400 is braked, and converts the kinetic energy into regenerative energy as electric energy. The regenerative energy recovered by the regenerative brake mechanism is input to the inverter 44 and converted into a direct current. The direct current is input to, for example, a battery pack included in the vehicle power supply 41.

  One terminal of the connection line L1 is connected to the negative terminal 414 of the vehicle power supply 41 via a current detection unit (not shown) in the battery management device 411. The other terminal of the connection line L <b> 1 is connected to the negative input terminal of the inverter 44.

  One terminal of the connection line L <b> 2 is connected to the positive terminal 413 of the vehicle power supply 41 via the switch device 415. The other terminal of the connection line L2 is connected to the positive input terminal of the inverter 44.

  The external terminal 43 is connected to the battery management device 411. The external terminal 43 can be connected to an external power source, for example.

  The vehicle ECU 42 manages the entire vehicle by cooperatively controlling the battery management device 411 together with other devices in response to an operation input from the driver or the like. Between the battery management device 411 and the vehicle ECU 42, data transfer relating to maintenance of the vehicle power source 41 such as the remaining capacity of the vehicle power source 41 is performed via a communication line.

  The vehicle according to the fifth embodiment includes the battery pack according to the fourth embodiment. Therefore, according to the present embodiment, it is possible to provide a vehicle equipped with a battery pack excellent in input / output performance and energy density.

[Example]
Examples will be described below, but the embodiments are not limited to the examples described below.

Example 1
First, commercially available oxide reagents Nb ₂ O ₅ and TiO ₂ were prepared. These powders were weighed so that the Nb / Ti molar ratio was 1.0. These were mixed for 1 hour using a ball mill. The obtained mixture was put into an electric furnace and subjected to calcination at a temperature of 1000 ° C. for 12 hours. The powder after calcination was put again into a ball mill, and TiO ₂ powder was added and mixed for 3 hours so that the final Nb / Ti molar ratio was 0.5. The mixture was put into the electric furnace again, and the first firing was performed at a temperature of 1100 ° C. for 5 hours. After cooling to room temperature, grinding with a ball mill was performed for 1 hour, and the second main firing was performed at a temperature of 1100 ° C. for 5 hours. Thereafter, annealing was performed at a temperature of 500 ° C. for 2 hours. The annealed powder was lightly pulverized using an agate mortar to deagglomerate the particles. Thus, monoclinic niobium titanium composite oxide particles represented by Nb ₂ TiO ₇ were obtained as active material particles. The BET specific surface area of the monoclinic niobium titanium composite oxide particles was 1.2 m ² / g.

The obtained active material particles according to the method described in the embodiment, to determine the average particle size of the primary particles (D50), was determined further to average FU _ave uneven shape factor FU. The results are shown in Table 1.

  5 parts by weight of maltose was prepared with respect to 100 parts by weight of the active material particles. Maltose was dispersed in a mixed solvent containing ethanol and pure water at a volume ratio of 1: 3 to prepare a solution having a viscosity μ of 10 Pa · s. Active material particles were charged into this solution and mixed with a ball mill. After mixing, the mixture was dried with a heater at 60 ° C. to completely remove moisture. A composite comprising active material particles and a phase containing a carbon-containing compound covering at least a part of the surface was obtained. The obtained composite was subjected to reduction firing at 700 ° C. for 3 hours in a nitrogen atmosphere. By this firing, the active material composite of Example 1 was obtained.

(Examples 2 to 4)
As described in Example 1, except that the amount of TiO ₂ or Nb ₂ O ₅ added after calcination was changed and the final Nb / Ti molar ratio was changed as shown in Table 3. Active material particles were synthesized in the same manner. That is, Nb ₂ O ₅ and TiO ₂ , which are commercially available oxide reagents, are prepared, and these powders are weighed and mixed so that the Nb / Ti molar ratio is 1.0, and then pre-baked. This is the same procedure as in the first embodiment.
An active material composite was synthesized by forming a carbon-containing layer in the same manner as in Example 1 except that the firing conditions were changed as shown in Table 2 for the active material particles synthesized by the above method.

(Comparative Example 1)
As described in Example 1, except that the amount of TiO ₂ or Nb ₂ O ₅ added after calcination was changed and the final Nb / Ti molar ratio was changed as shown in Table 3. Active material particles were synthesized in the same manner.
A maltose aqueous solution was prepared in the same manner as in Example 1 except that pure water was used instead of the mixed solvent of ethanol and pure water. The viscosity of the aqueous maltose solution was 5 Pa · s. Active material particles were charged into this solution and mixed with a ball mill. After mixing, the mixture was dried with a heater at 60 ° C. to completely remove moisture. A composite comprising active material particles and a phase containing a carbon-containing compound covering at least a part of the surface was obtained. The obtained composite was subjected to reduction firing under the conditions shown in Table 2. By this firing, an active material composite of Comparative Example 1 was obtained.

(Comparative Example 2)
As described in Example 1, except that the amount of TiO ₂ or Nb ₂ O ₅ added after calcination was changed and the final Nb / Ti molar ratio was changed as shown in Table 3. Active material particles were synthesized in the same manner.
An active material composite was synthesized by forming a carbon-containing layer in the same manner as in Comparative Example 1 except that the firing conditions were changed as shown in Table 2 for the active material particles synthesized by the above method.

(Example 5)
As described in Example 1, except that the amount of TiO ₂ or Nb ₂ O ₅ added after calcination was changed and the final Nb / Ti molar ratio was changed as shown in Table 3. Active material particles were synthesized in the same manner.
A maltose solution was prepared in the same manner as in Example 1 except that a mixed solvent of acrylic acid ester, ethanol and pure water (volume ratio 1: 1: 3) was used instead of the mixed solvent of ethanol and pure water. . The viscosity of the maltose solution was 20 Pa · s. Active material particles were charged into this solution to obtain an active material composite of Example 5 in the same manner as in Example 1.

(Example 6)
As described in Example 1, except that the amount of TiO ₂ or Nb ₂ O ₅ added after calcination was changed and the final Nb / Ti molar ratio was changed as shown in Table 3. Active material particles were synthesized in the same manner.
A maltose solution was prepared in the same manner as in Example 1 except that a mixed solvent of ethylene glycol, ethanol, and pure water (volume ratio 1: 1: 3) was used instead of the mixed solvent of ethanol and pure water. The viscosity of the maltose solution was 15 Pa · s. Active material particles were charged into this solution to obtain an active material composite of Example 6 in the same manner as in Example 1.

(Example 7)
As described in Example 1, except that the amount of TiO ₂ or Nb ₂ O ₅ added after calcination was changed and the final Nb / Ti molar ratio was changed as shown in Table 3. Active material particles were synthesized in the same manner.
10 parts by weight of polyvinyl alcohol (PVA) was prepared with respect to 100 parts by weight of the active material particles. PVA was dispersed in a mixed solvent containing ethanol and pure water at a volume ratio of 1: 3 to prepare a solution having a viscosity μ of 25 Pa · s. Active material particles synthesized in the same manner as in Example 1 were put into this solution, and these were mixed by a ball mill. After mixing, the mixture was dried with a heater at 60 ° C. to completely remove moisture. A composite comprising active material particles and a phase containing a carbon-containing compound covering at least a part of the surface was obtained. The obtained composite was subjected to reduction firing under the conditions shown in Table 2. By this firing, an active material composite of Example 7 was obtained.
(Example 8)
Commercially available oxide reagents Nb ₂ O ₅ and TiO ₂ were prepared. These powders were weighed so that the Nb / Ti molar ratio was 2.0, which is the target composition. These were mixed for 1 hour using a ball mill. The obtained mixture was put into an electric furnace and subjected to firing at a temperature of 1200 ° C. for 12 hours. After carrying out the strong grinding | pulverization using a hammer mill and a roller compactor with respect to the obtained baked material, in order to make the average particle diameter (D50) of a primary particle into the value of 50 micrometers or less, active material powder is used using a planetary ball mill. Crushed.
The obtained active material particles according to the method described in the embodiment, to determine the average particle size of the primary particles (D50), was determined further to average FU _ave uneven shape factor FU. The results are shown in Table 1.
Subsequently, a carbon-containing layer was formed in the same manner as in Example 7 to synthesize an active material composite.

(Examples 9 to 13)
As described in Example 1, except that the amount of TiO ₂ or Nb ₂ O ₅ added after calcination was changed and the final Nb / Ti molar ratio was changed as shown in Table 3. Active material particles were synthesized in the same manner.
An active material composite was synthesized by forming a carbon-containing layer in the same manner as in Example 7 except that the firing conditions were changed as shown in Table 2 for the active material particles synthesized by the above method.

(Comparative Example 3)
As described in Example 1, except that the amount of TiO ₂ or Nb ₂ O ₅ added after calcination was changed and the final Nb / Ti molar ratio was changed as shown in Table 3. Active material particles were synthesized in the same manner.
A PVA aqueous solution was prepared in the same manner as in Example 7 except that pure water was used instead of the mixed solvent of ethanol and pure water. The viscosity of the PVA aqueous solution was 2 Pa · s. Active material particles were charged into this solution and mixed with a ball mill. After mixing, the mixture was dried with a heater at 60 ° C. to completely remove moisture. A composite comprising active material particles and a phase containing a carbon-containing compound covering at least a part of the surface was obtained. The obtained composite was subjected to reduction firing under the conditions shown in Table 2. By this firing, an active material composite of Comparative Example 3 was obtained.

(Example 14)
As described in Example 1, except that the amount of TiO ₂ or Nb ₂ O ₅ added after calcination was changed and the final Nb / Ti molar ratio was changed as shown in Table 3. Active material particles were synthesized in the same manner.
5 parts by weight of carboxymethyl cellulose (CMC) was prepared with respect to 100 parts by weight of the active material particles. CMC was dispersed in a mixed solvent containing ethanol and pure water at a volume ratio of 1: 3 to prepare a solution having a viscosity μ of 40 Pa · s. Active material particles synthesized in the same manner as in Example 1 were put into this solution, and these were mixed by a ball mill. After mixing, the mixture was dried with a heater at 60 ° C. to completely remove moisture. A composite comprising active material particles and a phase containing a carbon-containing compound covering at least a part of the surface was obtained. The obtained composite was subjected to reduction firing under the conditions shown in Table 2. By this firing, an active material composite of Example 14 was obtained.

(Comparative Example 4)
As described in Example 1, except that the amount of TiO ₂ or Nb ₂ O ₅ added after calcination was changed and the final Nb / Ti molar ratio was changed as shown in Table 3. Active material particles were synthesized in the same manner.
A CMC aqueous solution was prepared in the same manner as in Example 14 except that pure water was used instead of the mixed solvent of ethanol and pure water. The viscosity of the CMC aqueous solution was 40 Pa · s. Active material particles were charged into this solution and mixed with a ball mill. After mixing, the mixture was dried with a heater at 60 ° C. to completely remove moisture. A composite comprising active material particles and a phase containing a carbon-containing compound covering at least a part of the surface was obtained. The obtained composite was subjected to reduction firing under the conditions shown in Table 2. By this firing, an active material composite of Comparative Example 4 was obtained.

(Example 15)
As described in Example 1, except that the amount of TiO ₂ or Nb ₂ O ₅ added after calcination was changed and the final Nb / Ti molar ratio was changed as shown in Table 3. Active material particles were synthesized in the same manner.
10 parts by weight of sodium alginate was prepared with respect to 100 parts by weight of the active material particles. Sodium alginate was dispersed in a mixed solvent containing ethanol and pure water in a volume ratio of 1: 3 to prepare a solution having a viscosity μ of 20 Pa · s. Active material particles synthesized in the same manner as in Example 1 were put into this solution, and these were mixed by a ball mill. After mixing, the mixture was dried with a heater at 60 ° C. to completely remove moisture. A composite comprising active material particles and a phase containing a carbon-containing compound covering at least a part of the surface was obtained. The obtained composite was subjected to reduction firing under the conditions shown in Table 2. By this firing, an active material composite of Example 15 was obtained.

For the active material complexes of the above Examples and Comparative Examples, the peak intensity (I _D , I _G ) ratio I _G / _ID was determined by Raman spectroscopy under the conditions described above, and the results are shown in Table 1. In FIG. 10, the Raman spectrum about the active material composite_body | complex of Example 1 and Comparative Example 1 is shown. Example 1 and Comparative Example 1 each Raman spectrum, a D band having a peak top at around 1350 cm ^-1, and the G band having a peak top at around 1580 cm ^-1 appeared. The intensity of each peak top of the D band and G band of Example 1 was smaller than the intensity of each peak top of the D band and G band of Comparative Example 1.
For the active material composites of the above examples and comparative examples, the thickness of the carbon-containing layer and the coating amount of the carbon-containing layer (the niobium titanium composite oxide particles are 100 parts by weight) are measured by the above-described methods, The results are shown in Table 1.

<Negative electrode production>
A negative electrode was produced by the following method using the active material composites of the above Examples and Comparative Examples.

  100% by weight of the active material composite, 4% by weight of acetylene black and 3% by weight of graphite as the conductive agent, and 3% by weight of polyvinylidene fluoride (PVdF) as the binder, and N-methylpyrrolidone (NMP). In addition, a slurry was prepared by mixing. This slurry was applied to both surfaces of a current collector made of an aluminum foil having a thickness of 12 μm and dried. By pressing after drying, negative electrodes having electrode densities shown in Table 3 were produced.

<Preparation of positive electrode>
As the positive electrode active material, LiNi _0.5 Co _0.2 Mn _0.3 O ₂ composite oxide particles having an average primary particle diameter of 2 μm, graphite powder as a conductive agent, and polyvinylidene fluoride (PVdF) as a binder were prepared. The positive electrode active material, the conductive agent, and the binder were respectively blended in a proportion of 90% by weight of the positive electrode active material, 6% by weight of the conductive agent, and 4% by weight of the binder with the positive electrode active material-containing layer being 100% by weight. A slurry was prepared by dispersing in -methyl-2-pyrrolidone (NMP) solvent. This slurry was applied to both surfaces of a 15 μm thick aluminum alloy foil (purity 99%), and the coating film was dried to obtain a laminate composed of a current collector and an active material-containing layer. This laminate was pressed to produce a positive electrode having an electrode density of 3.2 g / cm ³ .

<Preparation of electrolyte>
Propylene carbonate and diethyl carbonate were mixed at a volume ratio of 1: 2 to prepare a mixed solvent. In this mixed solvent, LiPF ₆ was dissolved at a concentration of 1.2 M to prepare a nonaqueous electrolyte.

<Production of secondary battery>
A separator made of a polyethylene porous film having a thickness of 12 μm was placed between the positive electrode and the negative electrode obtained above, and the electrode group was prepared by winding in a spiral shape so that the negative electrode was located on the outermost periphery. This was heated and pressed at 90 ° C. to produce a flat electrode group. The obtained electrode group was stored in a thin metal can made of stainless steel having a thickness of 0.25 mm. After pouring electrolyte into this metal can, the secondary battery was produced by sealing.

<Rate performance evaluation and discharge capacity evaluation>
Each battery produced in the examples and comparative examples was subjected to a rate test in a 25 ° C. environment. In charging / discharging, first, the battery was charged to 3.0V at 1C, then discharged to 1.7V at 1C to check the capacity of the battery, and then the discharge current was discharged at 20C to check the capacity of the battery.

  Table 4 shows the discharge capacity at 1 C discharge and the discharge capacity at 20 C discharge when the discharge capacity at 1 C discharge is 100%. In Table 4, the electrode densities of the negative electrodes of the examples and comparative examples are also shown.

In Tables 1 to 4, by comparing Examples 1 to 6 and Comparative Examples 1 and 2 using maltose as a carbon source, Examples 1 to 6 are compared with Comparative Examples 1 and 2 in terms of electrode density and rate performance. It turns out that it is superior.
Moreover, by comparing Examples 7 to 13 and Comparative Example 3 using PVA as a carbon source, it can be seen that Examples 7 to 13 are superior in electrode density and rate performance to Comparative Example 3. .
On the other hand, by comparing Example 14 using CMC as a carbon source and Comparative Example 4, it can be seen that Example 14 is superior in electrode density and rate performance to Comparative Example 4.
Furthermore, in Example 15 using sodium alginate as the carbon source, the electrode density and rate performance equivalent to those in Example 1 were obtained.
As described above, according to the active material composites of Examples 1 to 15, an electrode and a secondary battery with high energy density and excellent rate performance can be obtained.
In each of Comparative Examples 1 to 4, water is used as the solvent in the carbon-containing layer precursor. Therefore, in the step of drying the solvent in which the carbon source is dispersed, water as a solvent remains on the particle surface. As a result, the bias of the carbon source distribution on the particle surface increases. Under the firing conditions of Comparative Examples 1, 3, and 4, sufficient oxygen could not be obtained during the carbonization treatment, and thus I _G / _ID was less than 1.2. On the other hand, in Comparative Example 2, since the firing temperature exceeded 1000 ° C., the crystallinity of the carbon-containing layer became too high, and I _G / _ID exceeded 5.

The active material composite according to at least one embodiment and example described above covers at least a part of the surface of the niobium titanium composite oxide particles, and the formula (1): 1.2 <I _G / I _D ≦ 5 is included, an electrode and a secondary battery excellent in input / output performance and energy density can be provided.

  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 embodiments can be implemented in various other forms, and various omissions, replacements, and changes can be made without departing from the spirit of the invention. These embodiments and modifications thereof are included in the scope and gist of the invention and are also included in the invention described in the claims and the equivalents thereof.

  DESCRIPTION OF SYMBOLS 1 ... Electrode group, 2 ... Exterior member, 3 ... Negative electrode, 3a ... Negative electrode collector, 3b ... Negative electrode active material content layer, 3c ... Negative electrode current collection tab, 4 ... Separator, 5 ... Positive electrode, 5a ... Positive electrode collector 5 ... Positive electrode active material containing layer, 6 ... Negative electrode terminal, 7 ... Positive electrode terminal, 21 ... Bus bar, 22 ... Positive electrode side lead, 23 ... Negative electrode side lead, 24 ... Adhesive tape, 31 ... Container, 32 ... Cover, 33 DESCRIPTION OF SYMBOLS ... Protective sheet, 34 ... Printed wiring board, 35 ... Wiring, 40 ... Vehicle main body, 41 ... Vehicle power supply, 42 ... Electric control device, 43 ... External terminal, 44 ... Inverter, 45 ... Drive motor, 100 ... Secondary battery 200 ... assembled battery, 200a ... assembled battery, 200b ... assembled battery, 200c ... assembled battery, 300 ... battery pack, 300a ... battery pack, 300b ... battery pack, 300c ... battery pack, 301a ... assembled battery monitoring device, 301b ... set Pond monitoring device, 301c ... assembled battery monitoring device, 341 ... positive electrode side connector, 342 ... negative electrode side connector, 343 ... thermistor, 344 ... protection circuit, 345 ... wiring, 346 ... wiring, 347 ... external terminal for energization, 348a ... Positive side wiring, 348b ... negative side wiring, 400 ... vehicle, 411 ... battery management device, 412 ... communication bus, 413 ... positive terminal, 414 ... negative terminal, 415 ... switch device, L1 ... connection line, L2 ... connection line, W: Drive wheel.

Claims (11)

Niobium titanium composite oxide particles,
An active material composite comprising a carbon-containing layer that covers at least a part of the surface of the particles of the niobium titanium composite oxide and satisfies the following formula (1):
1.2 < _IG / _ID ≦ 5 (1)
However, the _{I D} is the peak intensity of the D band appearing in 1280～1400Cm ^-1 in the Raman spectrum by Raman spectroscopy using a light source of 532 nm, the _{I G} appears at 1530～1650Cm ^-1 in the Raman spectrum G It is the peak intensity of the band. The niobium titanium composite oxide is Li _a Ti _1-x M1 _x Nb _2-y M2 _y O ₇ (where 0 ≦ a ≦ 5, 0 ≦ x <1, 0 ≦ y <1, M1 is Nb, V , Ta, Fe, Bi, Sb, As, P, Cr, Mo, W, B, Na, Mg, Al, and Si, and M2 is V, Ta, Fe , Ti, Bi, Sb, As, P, Cr, Mo, W, B, Na, Mg, Al and Si, and at least one element selected from the group consisting of M1 and M2. The active material composite according to claim 1, which may be present or may be different from each other. The niobium titanium composite oxide is Li _a Ti _1-x M _x Nb ₂ O ₇ (where 0 ≦ a ≦ 5, 0 ≦ x <1, where M is Nb, V, Ta, Bi, Sb, As, The active material composite according to claim 1, wherein the active material composite is represented by: at least one selected from the group consisting of P, Cr, Mo, W, B, Na, Mg, Al, and Si. The particles of the niobium titanium composite oxide include primary particles of the niobium titanium composite oxide, and the average value (FUave) of the concavo-convex shape factor FU shown in the following formula (2) for 100 of the primary particles. The 100 primary particles satisfy 0.7 or more and have a particle size of 0.2 to 4 times the average particle size (D50) of the primary particles of the niobium titanium composite oxide. The active material complex according to any one of claims 1 to 3:
In the formula (2), l is the outer peripheral length of the primary particle in the projected cross section, and a is the cross sectional area of the primary particle in the projected cross section.   The electrode containing the active material composite_body | complex of any one of Claims 1-4. A secondary battery comprising a positive electrode, a negative electrode, and an electrolyte,
The secondary battery according to claim 5, wherein at least one of the positive electrode and the negative electrode is the electrode according to claim 5.   A battery pack comprising the secondary battery according to claim 6. An external terminal for energization,
The battery pack according to claim 7, further comprising a protection circuit. A plurality of the secondary batteries,
The battery pack according to claim 7 or 8, wherein the secondary batteries are electrically connected in series, parallel, or a combination of series and parallel.   A vehicle equipped with the battery pack according to any one of claims 7 to 9.   The vehicle according to claim 10, comprising a mechanism that converts kinetic energy of the vehicle into regenerative energy.