Electrode, secondary battery, battery pack and vehicle

Abstract

To provide an electrode having excellent cycle performance, a secondary battery including the electrode, a battery pack including the secondary battery, and a vehicle including the battery pack.SOLUTION: According to one embodiment, an electrode is provided. The electrode includes an active material and a titanium-containing solid electrolyte. The active material includes a transition metal oxide. In an X-ray absorption fine structure spectrum, a first X-ray absorption amount I at a first incident X-ray energy for the electrode in a discharged state satisfies 0.2≤I≤0.6. A second X-ray absorption amount at a second incident X-ray energy for anatase titanium dioxide is equal to the first X-ray absorption amount I. The first incident X-ray energy is higher than the second incident X-ray energy.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] FIELD Embodiments of the present invention relate to an electrode, a secondary battery, a battery pack, and a vehicle. [Background technology]

[0002] In non-aqueous electrolyte batteries such as lithium ion secondary batteries, there is a problem that the discharge capacity of the electrodes decreases with the charge-discharge cycle. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] International Publication No. 2019-239890 [Patent Document 2] Japanese Patent Application Laid-Open No. 2009-140910 Summary of the Invention [Problem to be solved by the invention]

[0004] An object of the embodiments is to provide an electrode having excellent cycle performance, a secondary battery including the electrode, a battery pack including the secondary battery, and a vehicle including the battery pack. [Means for solving the problem]

[0005] According to an embodiment, an electrode is provided. The electrode includes an active material and a titanium-containing solid electrolyte. The active material includes a transition metal oxide.

[0006] In an X-ray absorption fine structure spectrum at the Ti-K absorption edge for an electrode in a discharged state, when the X-ray absorption amount is 1 when the incident X-ray energy is 5500 eV, the first X-ray absorption amount I at a first incident X-ray energy in the incident X-ray energy range of 4930 eV to 5000 eV satisfies 0.2≦I≦0.6.

[0007] In an X-ray absorption fine structure spectrum at the Ti-K absorption edge of anatase titanium dioxide, when the X-ray absorption amount when the incident X-ray energy is 5500 eV is set to 1, the second X-ray absorption amount at a second incident X-ray energy in the range of incident X-ray energy 4930 eV to 5000 eV is equal to the first X-ray absorption amount I. The first incident X-ray energy is higher than the second incident X-ray energy.

[0008] According to another embodiment, a secondary battery including the electrode of the embodiment is provided.

[0009] According to another embodiment, a battery pack including the secondary battery of the embodiment is provided.

[0010] According to another embodiment, a vehicle including the battery pack of the embodiment is provided. [Brief explanation of the drawings]

[0011] [Figure 1] 1 is a cross-sectional view schematically illustrating an example of a secondary battery according to an embodiment. [Figure 2] FIG. 2 is an enlarged cross-sectional view of part A of the secondary battery shown in FIG. [Figure 3] FIG. 10 is a partially cutaway perspective view schematically showing another example of a secondary battery according to an embodiment. [Figure 4] FIG. 4 is an enlarged cross-sectional view of part B of the secondary battery shown in FIG. [Figure 5] FIG. 1 is a perspective view schematically illustrating an example of a battery pack according to an embodiment. [Figure 6] FIG. 1 is an exploded perspective view schematically showing an example of a battery pack according to an embodiment. [Figure 7] FIG. 7 is a block diagram showing an example of an electrical circuit of the battery pack shown in FIG. 6. [Figure 8] 1 is a partially see-through view schematically illustrating an example of a vehicle according to an embodiment. [Figure 9] 1 is a diagram illustrating an example of a control system for an electrical system in a vehicle according to an embodiment; [Figure 10] X-ray absorption fine structure spectrum showing an example of a titanium-containing solid electrolyte. [Figure 11] X-ray absorption fine structure spectra showing other examples of titanium-containing solid electrolytes. DETAILED DESCRIPTION OF THE INVENTION

[0012] The following describes the embodiments with reference to the drawings as appropriate. Note that common components throughout the embodiments are designated by the same reference numerals, and redundant explanations will be omitted. The drawings are schematic diagrams for explaining and facilitating understanding of the embodiments, and the shapes, dimensions, ratios, etc. may differ from those of actual devices. However, these can be appropriately modified in design, taking into consideration the following explanation and known techniques.

[0013] (First embodiment) One of the reasons for the decrease in the discharge capacity of an electrode with repeated charge-discharge cycles is the deterioration of the active material in the electrode, which can occur, for example, when hydrofluoric acid produced by a side reaction comes into contact with the active material.

[0014] Based on this result, the inventors conducted further research and achieved the electrode according to the first embodiment.

[0015] The electrode according to the first embodiment includes an active material and a titanium-containing solid electrolyte. The active material includes a transition metal oxide.

[0016] In an X-ray absorption fine structure spectrum at the Ti-K absorption edge for an electrode in a discharged state, when the X-ray absorption amount is 1 when the incident X-ray energy is 5500 eV, the first X-ray absorption amount I at a first incident X-ray energy in the incident X-ray energy range of 4930 eV to 5000 eV satisfies 0.2≦I≦0.6.

[0017] In an X-ray absorption fine structure spectrum at the Ti-K absorption edge of anatase titanium dioxide, when the X-ray absorption amount when the incident X-ray energy is 5500 eV is set to 1, the second X-ray absorption amount at a second incident X-ray energy in the range of incident X-ray energy 4930 eV to 5000 eV is equal to the first X-ray absorption amount I. The first incident X-ray energy is higher than the second incident X-ray energy.

[0018] The titanium-containing solid electrolyte can capture (trap) hydrofluoric acid, thereby preventing the hydrofluoric acid generated by a side reaction from coming into contact with the active material, thereby preventing the active material from deteriorating.

[0019] The first X-ray absorption amount is a relative value when the X-ray absorption amount when the incident X-ray energy is 5500 eV in an X-ray absorption fine structure (XAFS) spectrum of the electrode in a discharged state is set to 1. The second X-ray absorption amount is a relative value when the X-ray absorption amount when the incident X-ray energy is 5500 eV in an XAFS spectrum of anatase titanium dioxide is set to 1.

[0020] In the XAFS spectrum of the Ti-K absorption edge, the range of incident X-ray energy from 4930 eV to 5000 eV is the X-ray Absorption Near Edge Structure (XANES) region. In the XANES region, the first X-ray absorption amount at the first incident X-ray energy is equal to the second X-ray absorption amount at the second incident X-ray energy, and the first incident X-ray energy is higher than the second incident X-ray energy. This means that the electrode in a discharged state contains a material with a higher valence than anatase titanium dioxide. The valence of anatase titanium dioxide is, for example, tetravalent.

[0021] Note that the first incident X-ray energy may be higher than the second incident X-ray energy at all points in the XANES region where the first X-ray absorption amount at the first incident X-ray energy and the second X-ray absorption amount at the second incident X-ray energy are equal. The first incident X-ray energy may be higher than the second incident X-ray energy at at least one point among points in the XANES region where the first X-ray absorption amount at the first incident X-ray energy and the second X-ray absorption amount at the second incident X-ray energy are equal.

[0022] Examples of materials with a higher valence than anatase titanium dioxide include titanium-containing solid electrolytes. Titanium-containing solid electrolytes with a higher valence than anatase titanium dioxide have a larger surface area, as described below. This allows them to efficiently capture hydrofluoric acid, thereby improving cycle performance.

[0023] Hereinafter, electrodes according to embodiments will be described in detail with reference to the drawings.

[0024] Such an electrode may be used, for example, in a nonaqueous electrolyte battery. The nonaqueous electrolyte battery may be, for example, a nonaqueous electrolyte battery using alkali metal ions as carrier ions. For example, it may be a lithium battery (lithium ion battery). Such an electrode may be used, for example, in a secondary battery.

[0025] In the manufacturing process of a non-aqueous electrolyte battery, water is likely to be mixed in as an inevitable impurity. When a non-aqueous electrolyte containing fluorine atoms is used as the non-aqueous electrolyte to be combined with an electrode, a side reaction occurs between water and the non-aqueous electrolyte, and hydrofluoric acid (hydrogen fluoride, HF) may be generated as a decomposition product of the non-aqueous electrolyte. Details of non-aqueous electrolytes will be described later.

[0026] When hydrofluoric acid comes into contact with materials contained in an electrode, it may dissolve, for example, transition metals. The dissolved transition metals may deposit, for example, on the electrode. In addition, when an electrode is combined with an electrolyte, hydrofluoric acid may react with the electrolyte to form lithium fluoride. The lithium fluoride may deposit, for example, on the electrode. These substances deposited on the electrode may cause an increase in resistance.

[0027] The electrode contains a titanium-containing solid electrolyte, which can suppress the elution of transition metals and the formation of lithium fluoride, thereby improving the output performance of the electrode.

[0028] The titanium-containing solid electrolyte is a solid substance that has Li-ion conductivity. Here, "having Li-ion conductivity" means that the Li-ion conductivity is 1×10 at 25°C. -6 The titanium-containing solid electrolyte may be, for example, in the form of particles. At least a portion of the surface of the titanium-containing solid electrolyte particles may be amorphous.

[0029] If the titanium-containing solid electrolyte is completely amorphous, i.e., an amorphous solid electrolyte, when combined with a non-aqueous electrolyte, there is a possibility that side reactions with the non-aqueous electrolyte may increase. Therefore, it is preferable that at least a portion of the titanium-containing solid electrolyte is crystalline.

[0030] The titanium-containing solid electrolyte preferably contains a titanium-containing composite oxide. The titanium-containing composite oxide may be, for example, a titanium-containing lithium phosphate composite oxide. Examples of titanium-containing lithium phosphate composite oxides include those having a NASICON (Sodium (Na) Super Ionic Conductor) structure and represented by the general formula Li 1+xExamples include lithium phosphate solid electrolytes represented by Mα2(PO4)3. Mα in the above general formula contains titanium (Ti). Mα may consist only of titanium (Ti), or may contain Ti and one or more selected from the group consisting of, for example, germanium (Ge), strontium (Sr), zirconium (Zr), tin (Sn), aluminum (Al), and calcium (Ca). The subscript x is within the range of 0 ≦ x ≦ 2.

[0031] Specific examples of the lithium phosphate solid electrolyte having a NASICON-type structure include Li 1+x Al x Ti 2-x (PO4)3, the LATP compound where 0.1 ≦ x ≦ 0.5; Li 1+x Al y Mβ 2-y (PO4)3, where Mβ is one or more selected from the group consisting of Ti, Ge, Sr, Zr, Sn, and Ca, and among the compounds where 0 ≦ x ≦ 1 and 0 ≦ y ≦ 1, the compounds containing Ti in the composition; and, Li 1+x+y Al x Mγ 2-x Si y P 3-y O 12 represented by, where Mγ is one or more selected from the group consisting of Ti and Ge, and among the compounds where 0 < x ≦ 2 and 0 ≦ y < 3, the compounds containing Ti in the composition can be mentioned.

[0032] The types of titanium-containing solid electrolytes can be one or more than two.

[0033] The content of the lithium phosphate composite oxide in the titanium-containing solid electrolyte is preferably more than 98% by mass. When the titanium-containing solid electrolyte contains more than 98% by mass of the lithium phosphate composite oxide, the fluoric acid capture effect can be easily obtained, so the cycle performance and output performance can be improved. The ratio of the lithium phosphate composite oxide in the titanium-containing solid electrolyte can be 100% by mass.

[0034] 10 shows X-ray absorption fine structure spectra of an example of a titanium-containing solid electrolyte that can be included in an electrode according to an embodiment. The horizontal axis represents incident X-ray energy, and the vertical axis represents the relative value of X-ray absorption. The relative value of X-ray absorption is the value of X-ray absorption normalized to 1 when the incident X-ray energy is 5500 eV. Spectrum 10 is an XAFS spectrum of anatase titanium dioxide. Spectrum 11 is an XAFS spectrum of an example of a titanium-containing solid electrolyte. Spectra 10 and 11 are normalized to 1 when the incident X-ray energy is 5500 eV.

[0035] In spectrum 11, an incident X-ray energy in the range of 4930 eV to 5000 eV is defined as a first incident X-ray energy a, and the X-ray absorption amount for the first incident X-ray energy a is defined as a first X-ray absorption amount I. The first X-ray absorption amount I satisfies 0.2≦I≦0.6.

[0036] Furthermore, in spectrum 10, an incident X-ray energy in the range of 4930 eV to 5000 eV is defined as second incident X-ray energy b, and the X-ray absorption amount for second incident X-ray energy b is defined as second X-ray absorption amount. The second X-ray absorption amount is set to be equal to the first X-ray absorption amount I.

[0037] By doing so, it is possible to obtain a point a on spectrum 11 of the titanium-containing solid electrolyte where the first incident X-ray energy is higher than the second incident X-ray energy. Therefore, an electrode including the titanium-containing solid electrolyte according to spectrum 11 can have a first incident X-ray energy higher than the second incident X-ray energy. In other words, the XAFS spectrum of the electrode can be shifted to the higher energy side compared to the XAFS spectrum of anatase titanium dioxide.

[0038] The titanium-containing solid electrolyte according to the example shown in Spectrum 11 can be prepared, for example, by surface-treating a titanium-containing solid electrolyte as follows. A crystalline titanium-containing solid electrolyte can be used for the surface treatment. The surface treatment can be carried out, for example, by an acid treatment as follows.

[0039] The acid treatment can be carried out, for example, by adding the titanium-containing solid electrolyte to an aqueous hydrofluoric acid solution and stirring it. The concentration of the aqueous hydrofluoric acid solution is preferably 1% by mass or more and 5% by mass or less. The stirring temperature is preferably in the range of 25°C or more and 45°C or less. The stirring time is preferably in the range of 1 hour or more and 80 hours or less.

[0040] The acid treatment can amorphize the surfaces of titanium-containing solid electrolyte particles. When the concentration of the hydrofluoric acid solution is 1% by mass or more, the amorphization of the surface can be efficiently promoted. When the concentration of the hydrofluoric acid solution is 5% by mass or less, the amorphization can be prevented from progressing excessively. Therefore, the crystalline structure inside the titanium-containing solid electrolyte particles can be easily maintained. Therefore, titanium-containing solid electrolyte particles whose particle surfaces are amorphous and at least a portion of the particles is crystalline can be easily obtained. Such titanium-containing solid electrolyte particles are preferred because they have a stable amorphization state.

[0041] The acid treatment can also be performed by immersing the titanium-containing solid electrolyte in a liquid obtained by adding water to a liquid electrolyte containing fluorine atoms. Details of the liquid electrolyte will be described later. Examples of liquid electrolytes containing fluorine atoms include liquid electrolytes containing lithium hexafluorophosphate (LiPF), lithium tetrafluoroborate (LiBF), lithium hexafluoroarsenic (LiAsF), lithium trifluoromethanesulfonate (LiCFSO), or lithium bistrifluoromethylsulfonylimide (LiN(CFSO)). The liquid electrolyte may contain one or more electrolyte salts. The water concentration in the liquid is preferably 0.1% by mass or more and 1% by mass or less. By setting the water concentration in the liquid to 0.1% by mass or more, the acid treatment can be performed efficiently. By setting the water concentration in the liquid to 1% by mass or less, excessive amorphization can be suppressed.

[0042] The surface treatment can increase the valence of the titanium-containing solid electrolyte, and therefore, the first incident X-ray energy of an electrode including the surface-treated titanium-containing solid electrolyte can be higher than the second incident X-ray energy.

[0043] Furthermore, the surface area of ​​titanium-containing solid electrolyte particles can be increased by performing the surface treatment. This is because the particle surface becomes amorphous by the surface treatment. Titanium-containing solid electrolyte particles with amorphous surfaces can efficiently capture hydrofluoric acid.

[0044] This is thought to be due to the following mechanism. Titanium-containing solid electrolytes have functional groups on their surfaces that can capture hydrofluoric acid. When the surfaces of titanium-containing solid electrolyte particles are made amorphous by the above-mentioned surface treatment, the surface area of ​​the particles increases. Therefore, the number of functional groups that can capture hydrofluoric acid increases, and the amount of hydrofluoric acid that the titanium-containing solid electrolyte particles can capture increases.

[0045] Therefore, in an electrode in which the first incident X-ray energy is higher than the second incident X-ray energy, the titanium-containing solid electrolyte has a high hydrofluoric acid trapping ability, which can improve cycle performance and output performance.

[0046] The difference (shift amount) between the first incident X-ray energy and the second incident X-ray energy is preferably within the range of 1 eV to 4 eV, and more preferably within the range of 3 eV to 3.5 eV.

[0047] When the difference between the first incident X-ray energy and the second incident X-ray energy is large, the titanium-containing solid electrolyte tends to have a large amount of amorphous portions.

[0048] If the difference between the first incident X-ray energy and the second incident X-ray energy is too large, the titanium-containing solid electrolyte may be amorphous to the inside. If the titanium-containing solid electrolyte is amorphous to the inside, the hydrofluoric acid trapping ability of the titanium-containing solid electrolyte may be reduced. The difference between the first incident X-ray energy and the second incident X-ray energy is preferably 4.0 eV or less, and more preferably 3.5 eV or less.

[0049] Furthermore, if the difference between the first incident X-ray energy and the second incident X-ray energy is too small, the effect of improving the hydrofluoric acid trapping ability due to at least a portion of the surface of the titanium-containing solid electrolyte being amorphous may be reduced. The difference between the first incident X-ray energy and the second incident X-ray energy is preferably 1.0 eV or more, and more preferably 3.0 eV or more.

[0050] 11 shows X-ray absorption fine structure spectra of another example of a titanium-containing solid electrolyte. The horizontal axis represents incident X-ray energy, and the vertical axis represents the relative value of the X-ray absorption amount. Spectrum 12 is an XAFS spectrum of another example of a titanium-containing solid electrolyte. This example of a titanium-containing solid electrolyte is similar to the titanium-containing solid electrolyte shown in Spectrum 11 described above, except that the surface treatment described above was not performed.

[0051] Spectra 10 and 12 are normalized such that the X-ray absorption amount when the incident X-ray energy in each spectrum is 5500 eV is set to 1.

[0052] In spectrum 12, for an incident X-ray energy within the range of 4930 eV or more and 5000 eV or less, a certain incident X-ray energy is defined as the first incident X-ray energy c, and the X-ray absorption amount for the first incident X-ray energy c is defined as the first X-ray absorption amount. The first X-ray absorption amount I is made to satisfy 0.2 ≤ I ≤ 0.6.

[0053] Furthermore, in spectrum 10, for an incident X-ray energy within the range of 4930 eV or more and 5000 eV or less, a certain incident X-ray energy is defined as the second incident X-ray energy d, and the X-ray absorption amount for the second incident X-ray energy d is defined as the second X-ray absorption amount. The second X-ray absorption amount is made equal to the first X-ray absorption amount I.

[0054] On spectrum 12, there is no point c where the first incident X-ray energy is higher than the second incident X-ray energy. Therefore, when the electrode includes a titanium-containing solid electrolyte related to spectrum 12, the first incident X-ray energy cannot be higher than the second incident X-ray energy.

[0055] The X-ray absorption fine structure spectrum can be obtained as follows.

[0056] <X-ray absorption fine structure analysis> (Preparation of measurement sample) When analyzing substances such as anatase-type titanium dioxide and titanium-containing solid electrolytes, the powder of the substance to be analyzed is subjected to X-ray absorption fine structure (XAFS) analysis. As the anatase-type titanium dioxide, those with a purity of 99.5% or more among commercially available anatase-type titanium dioxide powders can be used.

[0057] When analyzing an electrode, as described below, an electrochemical measurement cell is prepared using the measurement electrode, and then the electrode is placed in a discharged state by discharging the electrochemical measurement cell.

[0058] If the electrode to be measured is incorporated into a battery, the electrode to be measured is removed from the battery, washed, and dried as follows before being used to prepare an electrochemical measurement cell. First, the battery containing the electrode is disassembled in a glove box filled with argon. The electrode to be measured is removed from the disassembled battery. This electrode is washed with an appropriate solvent. For example, methyl ethyl carbonate can be used as the solvent for washing. The washed electrode is then dried under vacuum. In this way, the electrode for measurement is obtained.

[0059] Next, an electrochemical measurement cell is fabricated using the measurement electrode. The electrochemical measurement cell can be fabricated using the measurement electrode, a lithium metal foil as a counter electrode, and a non-aqueous electrolyte. The non-aqueous electrolyte is prepared by dissolving lithium hexafluorophosphate (LiPF) at a concentration of 1 M in a mixed solvent of ethylene carbonate and diethyl carbonate (volume ratio 1:1).

[0060] The prepared electrochemical measurement cell is discharged at 0.05 C, and the potential of the measurement electrode is adjusted to 3.0 V relative to metallic lithium. In this way, the electrode is put into a discharged state.

[0061] The discharged electrode is subjected to X-ray absorption fine structure (XAFS) analysis.

[0062] (XAFS analysis) XAFS analysis can be performed using a synchrotron radiation facility such as the large synchrotron radiation facility SPring-8.

[0063] The conditions for the Ti K-edge XAFS measurements are as follows: ·Spectrometer: Si(111) double crystal spectrometer Higher order light rejection: Rh coated mirror 6mrad Incident X-ray size: 1mm length x 1mm width ·Measurement method: transmission method Detector: Ion chamber Under the above conditions, the incident light intensity I0 and transmitted light intensity I1 are measured in the incident X-ray energy range of 4600 eV to 6000 eV. The X-ray absorption amount for each incident X-ray energy is calculated from I0 and I1 using the following formula. μt in the formula represents the X-ray absorption amount.

[0064]

number

[0065] An XAFS spectrum can be obtained by plotting the incident X-ray energy on the x-axis and the X-ray absorption (μt) on the y-axis. The Victoreen equation, which represents the intensity change due to X-ray scattering, is used to approximate the data before the absorption edge using the least-squares method, and the background is subtracted. This removes the background from the XAFS spectrum.

[0066] In the XAFS spectrum from which the background has been removed, the X-ray absorption amount is normalized by setting the X-ray absorption amount when the incident X-ray energy is 5500 eV as 1. In this way, a normalized spectrum can be obtained.

[0067] By performing XAFS analysis after discharging the electrode, it is possible to determine, for example, that the Ti atoms contained in the active material in the electrode are tetravalent, which allows the valence of Ti to be the same between the anatase titanium dioxide used as a comparison standard and the electrode being measured.

[0068] The electrodes according to the embodiment will be described in further detail.

[0069] Such an electrode may include a current collector and an active material-containing layer. The active material-containing layer may be formed on one or both sides of the current collector. The active material-containing layer may include an active material, a titanium-containing solid electrolyte, and optionally a conductive agent and a binder. The active material includes a transition metal oxide.

[0070] The active material-containing layer may contain, as the active material, one type of transition metal oxide alone or a combination of two or more types of transition metal oxides, or the active material may contain a combination of a transition metal oxide and another compound.

[0071] The form of the active material is not particularly limited. The active material can be, for example, in the form of primary particles or in the form of secondary particles formed by aggregation of primary particles. The active material may be a mixture of primary particles and secondary particles. The active material may be in the form of granules or chunks having dimensions larger than the size of what is called a particle.

[0072] The active material may be in the form of a powder consisting of aggregates of primary particles and secondary particles. The average particle size of the active material powder may be in the range of 0.1 μm to 30 μm. The average particle size of the active material powder is preferably in the range of 0.5 μm to 30 μm.

[0073] The average particle size can be measured by laser diffraction scattering. The particle size at which the cumulative volume distribution in a particle size distribution chart obtained by laser diffraction scattering is 50% is defined as the average particle size (D50).

[0074] The specific surface area of ​​the active material is not particularly limited, but is preferably 0.1 m 2 / g or more 200m 2 The specific surface area can be in the range of less than 5 m 2 / g or more 200m 2 It is preferable that the SiO2 content is less than 1 / g.

[0075] Specific surface area is 5m 2 If the specific surface area is 200 m / g or more, the contact area with the electrolyte can be secured, which makes it easier to obtain good discharge rate characteristics and shortens the charging time. 2 If the slurries are less than 1 / g, the reactivity with the electrolyte is not too high, thereby improving the life characteristics. Also, the coating properties of the slurry containing the active material can be improved. The slurry will be described later.

[0076] Here, specific surface area is measured by adsorbing molecules with known adsorption areas onto the powder particle surfaces at liquid nitrogen temperature, and then determining the specific surface area of ​​the sample from the amount of adsorption. The most commonly used method is the Brunauer, Emmett, Teller (BET) method, which uses low-temperature, low-humidity physical adsorption of an inert gas. This is the most well-known method for calculating specific surface area, and extends the Langmuir theory, which is a theory of monolayer adsorption, to multilayer adsorption. The specific surface area determined in this way is called the BET specific surface area.

[0077] The following description will be made separately for the case where the electrode is a negative electrode and the case where the electrode is a positive electrode.

[0078] 1) Negative electrode First, a case where the electrode according to the embodiment is a negative electrode will be described.

[0079] When the electrode according to the first embodiment is used as a negative electrode, examples of the transition metal oxide contained in the active material include lithium titanate having a ramsdellite structure (for example, Li 2+y Ti3O7, 0≦y≦3), lithium titanates with spinel structure (e.g., Li 4+x Ti5O 12 , 0≦x≦3), titanium dioxide (TiO2), anatase type titanium dioxide, rutile type titanium dioxide, niobium pentoxide (Nb2O5), hollandite type titanium composite oxide, orthorhombic titanium-containing composite oxide, and monoclinic type niobium titanium oxide.

[0080] As an example of the above orthorhombic titanium-containing composite oxide, Li 2+a M I 2-b Ti 6-c M II d O 14+σ In this case, M I is at least one selected from the group consisting of Sr, Ba, Ca, Mg, Na, Cs, Rb and K. IIis at least one selected from the group consisting of Zr, Sn, V, Nb, Ta, Mo, W, Y, Fe, Co, Cr, Mn, Ni, and Al. The subscripts in the composition formula are 0≦a≦6, 0≦b<2, 0≦c<6, 0≦d<6, and -0.5≦σ≦0.5. Specific examples of orthorhombic titanium-containing composite oxides include Li 2+a Na2Ti6O 14 (0≦a≦6).

[0081] As an example of the monoclinic niobium titanium oxide, Li x Ti 1-y M1 y Nb 2-z M2 z O 7+δ Here, M1 is at least one selected from the group consisting of Zr, Si, and Sn. M2 is at least one selected from the group consisting of V, Ta, and Bi. The subscripts in the composition formula are 0≦x≦5, 0≦y<1, 0≦z<2, and -0.3≦δ≦0.3. Specific examples of monoclinic niobium titanium oxides include Li x Examples include Nb2TiO7 (0≦x≦5).

[0082] Another example of monoclinic niobium titanium oxide is Li x Ti 1-y M3 y+z Nb 2-z O 7-δ Here, M3 is at least one selected from Mg, Fe, Ni, Co, W, Ta, and Mo. The subscripts in the composition formula are 0≦x≦5, 0≦y<1, 0≦z<2, and −0.3≦δ≦0.3.

[0083] The conductive agent is blended to improve current collection performance and reduce contact resistance between the active material and the current collector. Examples of conductive agents include carbonaceous materials such as vapor-grown carbon fiber (VGCF), carbon black such as acetylene black, graphite, carbon nanotubes, and carbon nanofibers. One of these may be used as the conductive agent, or two or more may be used in combination. Alternatively, instead of using a conductive agent, the surfaces of the active material particles may be coated with carbon or an electronically conductive inorganic material.

[0084] The binder is blended to fill gaps between the dispersed active materials and to bind the active materials and the current collector. Examples of binders include polytetrafluoroethylene (PTFE), polyvinylidene fluoride (PVdF), fluorine-based rubber, styrene-butadiene rubber (SBR), polyacrylic acid compounds, imide compounds, carboxymethyl cellulose (CMC), and CMC salts. These may be used alone or in combination.

[0085] The blending ratios of the active material, titanium-containing solid electrolyte, conductive agent, and binder in the active material-containing layer can be appropriately changed depending on the application of the electrode. For example, when the electrode is used as the negative electrode of a secondary battery, the active material (negative electrode active material) is preferably blended in at a ratio of 68% by mass to 96% by mass. The titanium-containing solid electrolyte is preferably blended in at a ratio of 0.05% by mass to 30% by mass. The conductive agent is preferably blended in at a ratio of 2% by mass to 30% by mass. The binder is preferably blended in at a ratio of 2% by mass to 30% by mass.

[0086] The total blending ratio of the negative electrode active material, titanium-containing solid electrolyte, conductive agent, and binder can be 100% by mass. In this case, the blending ratio of each material may be any value regardless of the above ratio. For example, when the negative electrode active material is blended in the above ratio, the blending ratio of the titanium-containing solid electrolyte, conductive agent, and binder can be set to any value, thereby adjusting the total blending ratio of the negative electrode active material, titanium-containing solid electrolyte, conductive agent, and binder to 100% by mass. The blending ratio of the conductive agent or binder may be 0% by mass.

[0087] It is particularly preferable that the blending proportions of the negative electrode active material, titanium-containing solid electrolyte, conductive agent, and binder are all within the above numerical ranges, and that the total blending proportions is 100 mass %.

[0088] By setting the amount of titanium-containing solid electrolyte to 0.05% by mass or more, output performance can be further improved. By setting the amount of conductive agent to 2% by mass or more, the current collection performance of the active material-containing layer can be improved. Furthermore, by setting the amount of binder to 2% by mass or more, sufficient binding between the active material-containing layer and the current collector can be achieved, and excellent cycle performance can be expected. On the other hand, in order to achieve high capacity, it is preferable that the amount of conductive agent and binder be 30% by mass or less. In order to improve energy density, it is preferable that the amount of titanium-containing solid electrolyte be 30% by mass or less.

[0089] The current collector is made of a material that is electrochemically stable at the potential at which lithium (Li) is inserted into and extracted from the active material. For example, when the active material is used as a negative electrode active material, the current collector is preferably made of copper, nickel, stainless steel, aluminum, or an aluminum alloy containing one or more elements selected from Mg, Ti, Zn, Mn, Fe, Cu, and Si. The current collector may be, for example, a metal foil containing the above-mentioned material. The thickness of the current collector is preferably 5 μm or more and 20 μm or less. A current collector having such a thickness can balance the strength and weight of the electrode.

[0090] The current collector may also include a portion on the surface of which the negative electrode active material-containing layer is not formed, and this portion can function as a negative electrode current collecting tab.

[0091] The negative electrode can be fabricated, for example, by the following method. First, an active material, a titanium-containing solid electrolyte, a conductive agent, and a binder are suspended in a solvent to prepare a slurry. This slurry is then applied to one or both sides of a current collector. Next, the applied slurry is dried to obtain a laminate of an active material-containing layer and a current collector. After that, this laminate is pressed. In this manner, the negative electrode is fabricated.

[0092] In producing the negative electrode, for example, water can be used as the solvent for the slurry.

[0093] Alternatively, the negative electrode may be fabricated by the following method: First, an active material, a titanium-containing solid electrolyte, a conductive agent, and a binder are mixed to obtain a mixture. Then, the mixture is formed into pellets. Then, the pellets are placed on a current collector to obtain a negative electrode.

[0094] 2) Positive electrode Next, a case where the electrode according to the embodiment is a positive electrode will be described.

[0095] For example, when the electrode according to the first embodiment is used as a positive electrode, examples of the active material include oxides and sulfides. Examples of oxides and sulfides include compounds capable of inserting and desorbing Li or Li ions. The oxide may be a transition metal oxide. The transition metal oxide may be a compound containing a transition metal and oxygen. The type of transition metal may be one or more types. The transition metal oxide may be a compound consisting of a transition metal and oxygen, or may be a compound containing an element other than a transition metal and oxygen. Examples of transition metal oxides include polyanion compounds such as phosphates, sulfates, and silicates. An example of a phosphate is lithium phosphate having an olivine structure. An example of a sulfate is iron sulfate.

[0096] Specific examples of the transition metal oxide include, for example, manganese dioxide (MnO2), iron oxide, copper oxide, nickel oxide, lithium manganese composite oxide (e.g., Li x Mn2O4 or Li x MnO2; 0 < x ≦ 1), lithium nickel composite oxide (e.g., Li x NiO2; 0 < x ≦ 1), lithium cobalt composite oxide (e.g., Li x CoO2; 0 < x ≦ 1), lithium nickel cobalt composite oxide (e.g., Li x Ni 1-y Co y O2; 0 < x ≦ 1, 0 < y < 1), lithium manganese cobalt composite oxide (e.g., Li x Mn y Co 1-y O2; 0 < x ≦ 1, 0 < y < 1), lithium manganese nickel composite oxide having a spinel structure (e.g., Li x Mn 2-y Ni y O4; 0 < x ≦ 1, 0 < y < ₂), lithium phosphate having an olivine structure (e.g., Li x FePO4; 0 < x ≦ 1, Li x Fe 1-y Mn y PO4; 0 < x ≦ 1, 0 < y ≦ 1, Li x CoPO4; 0 < x ≦ 1), iron sulfate (Fe2(SO4)3), vanadium oxide (e.g., V2O5), and lithium nickel cobalt manganese composite oxide (Li x Ni 1-y-z Co y Mn z O2; 0 < x ≦ 1, 0 < y < 1, 0 < z < 1, y + z < 1) are included.

[0097] Among the above, examples of more preferable compounds as the positive electrode active material include lithium manganese composite oxide having a spinel structure (e.g., Li x Mn2O4; 0 < x ≦ 1), lithium nickel composite oxide (e.g., Li x NiO2; 0 < x ≦ 1), lithium cobalt composite oxide (e.g., Li xCoO₂ (0 < x ≤ 1), lithium nickel cobalt composite oxide (e.g., Li x Ni 1-y Co y O₂; 0 < x ≤ 1, 0 < y < 1), lithium manganese nickel composite oxide having a spinel structure (e.g., Li x Mn 2-y Ni y O₄; 0 < x ≤ 1, 0 < y < 2), lithium manganese cobalt composite oxide (e.g., Li x Mn y Co 1-y O₂; 0 < x ≤ 1, 0 < y < 1), lithium iron phosphate (e.g., Li x FePO₄; 0 < x ≤ 1), and lithium nickel cobalt manganese composite oxide (Li x Ni 1-y-z Co y Mn z O₂; 0 < x ≤ 1, 0 < y < 1, 0 < z < 1, y + z < 1) are included. When these compounds are used as the positive electrode active material, the positive electrode potential can be increased.

[0098] The binder is blended to fill the gaps between the dispersed positive electrode active materials and to 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 compounds, imide compounds, carboxymethyl cellulose (CMC), and salts of CMC. One of these may be used as the binder, or two or more of them may be combined and used as the binder.

[0099] The conductive agent is blended to improve current collection performance and reduce contact resistance between the positive electrode active material and the positive electrode current collector. Examples of conductive agents include vapor-grown carbon fiber (VGCF), carbon black such as acetylene black, and carbonaceous materials such as graphite. One of these may be used as the conductive agent, or two or more may be used in combination as the conductive agent. The conductive agent may also be omitted.

[0100] In the positive electrode active material-containing layer, the positive electrode active material is preferably blended in a proportion of 80% by mass to 98% by mass, the titanium-containing solid electrolyte is preferably blended in a proportion of 0.05% by mass to 30% by mass, and the binder is preferably blended in a proportion of 2% by mass to 20% by mass.

[0101] The total blending ratio of the positive electrode active material, titanium-containing solid electrolyte, and binder can be 100% by mass. In this case, the blending ratio of each material may be any value regardless of the above ratio. For example, when the positive electrode active material is blended in the above ratio, the blending ratio of the titanium-containing solid electrolyte and binder can be set to any value, so that the total blending ratio of the positive electrode active material, titanium-containing solid electrolyte, and binder can be adjusted to 100% by mass. The blending ratio of the binder may be 0% by mass.

[0102] It is particularly preferable that the blending proportions of the positive electrode active material, titanium-containing solid electrolyte, and binder are all within the above numerical ranges, and that the total blending proportions is 100 mass %.

[0103] By using a binder amount of 2% by mass or more, sufficient electrode strength can be obtained. Furthermore, the binder can function as an insulator. Therefore, by using a binder amount of 20% by mass or less, the amount of insulator contained in the electrode is reduced, thereby reducing internal resistance.

[0104] When a conductive agent is added, the positive electrode active material is preferably blended in a proportion of 77% by mass to 95% by mass. The titanium-containing solid electrolyte is preferably blended in a proportion of 0.05% by mass to 30% by mass. The binder is preferably blended in a proportion of 2% by mass to 20% by mass. The conductive agent is preferably blended in a proportion of 3% by mass to 15% by mass.

[0105] The total blending ratio of the positive electrode active material, titanium-containing solid electrolyte, conductive agent, and binder can be 100% by mass. In this case, the blending ratio of each material may be any value regardless of the above ratio. For example, when the positive electrode active material is blended in the above ratio, the blending ratio of the titanium-containing solid electrolyte, conductive agent, and binder can be adjusted to any value, so that the total blending ratio of the positive electrode active material, titanium-containing solid electrolyte, conductive agent, and binder is 100% by mass. The blending ratio of the binder may be 0% by mass.

[0106] It is particularly preferable that the blending proportions of the positive electrode active material, titanium-containing solid electrolyte, conductive agent, and binder are all within the above numerical ranges, and that the total blending proportions is 100 mass %.

[0107] By setting the amount of conductive agent to 3% by mass or more, the above-mentioned effects can be achieved. Furthermore, by setting the amount of conductive agent to 15% by mass or less, when the electrode is used in combination with an electrolyte, the proportion of conductive agent in contact with the electrolyte can be reduced. This low proportion can reduce decomposition of the electrolyte during high-temperature storage.

[0108] 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 mass 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 mass or less.

[0109] The positive electrode current collector may also include a portion on the surface of which the positive electrode active material-containing layer is not formed, and this portion can function as a positive electrode current collecting tab.

[0110] The positive electrode can be produced, for example, by the following method. First, an active material, a titanium-containing solid electrolyte, a conductive agent, and a binder are suspended in a solvent to prepare a slurry. This slurry is applied to one or both sides of a current collector. Next, the applied slurry is dried to obtain a laminate of an active material-containing layer and a current collector. After that, this laminate is pressed. In this way, a positive electrode is produced. In producing the positive electrode, for example, N-methylpyrrolidone (NMP) can be used as the solvent for the slurry.

[0111] Alternatively, the positive electrode may be prepared by the following method: First, an active material, a titanium-containing solid electrolyte, a conductive agent, and a binder are mixed to obtain a mixture. Then, the mixture is formed into pellets. Then, the pellets are placed on a current collector to obtain a positive electrode.

[0112] The electrode according to the first embodiment includes an active material and a titanium-containing solid electrolyte. The active material includes a transition metal oxide.

[0113] In an X-ray absorption fine structure spectrum at the Ti-K absorption edge for an electrode in a discharged state, when the X-ray absorption amount is 1 when the incident X-ray energy is 5500 eV, the first X-ray absorption amount I at a first incident X-ray energy in the incident X-ray energy range of 4930 eV to 5000 eV satisfies 0.2≦I≦0.6.

[0114] In an X-ray absorption fine structure spectrum at the Ti-K absorption edge of anatase titanium dioxide, when the X-ray absorption amount when the incident X-ray energy is 5500 eV is set to 1, the second X-ray absorption amount at a second incident X-ray energy in the range of 4930 eV to 5000 eV is equal to the first X-ray absorption amount I. The first incident X-ray energy is higher than the second incident X-ray energy. Therefore, such an electrode can improve cycle performance.

[0115] (Second embodiment) According to the second embodiment, a secondary battery is provided that includes a negative electrode, a positive electrode, and an electrolyte. At least one of the positive electrode and the negative electrode is the electrode according to the first embodiment. That is, the secondary battery includes the electrode according to the first embodiment.

[0116] The secondary battery may further include a separator disposed between the positive electrode and the negative electrode. The negative electrode, the positive electrode, and the separator may constitute an electrode assembly. The electrolyte may be held in the electrode assembly.

[0117] Moreover, such a secondary battery can further include an exterior member that houses the electrode group and the electrolyte.

[0118] Furthermore, such a 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.

[0119] Such a secondary battery may be, for example, a lithium secondary battery. The secondary battery also includes a non-aqueous electrolyte secondary battery containing a non-aqueous electrolyte.

[0120] The negative electrode, positive electrode, electrolyte, separator, exterior member, negative electrode terminal, and positive electrode terminal will be described in detail below.

[0121] 1) Negative electrode The negative electrode may include a negative electrode current collector and a negative electrode active material-containing layer. The negative electrode current collector and the negative electrode active material-containing layer may be the current collector and the active material-containing layer, respectively, that may be included in the electrode according to the first embodiment. When the electrode according to the first embodiment is included as the positive electrode, the negative electrode may not be the electrode according to the first embodiment. For example, the negative electrode may not include the titanium-containing solid electrolyte described in the first embodiment.

[0122] Details of the negative electrode that overlap with those described in the first embodiment will be omitted.

[0123] The density of the negative electrode active material-containing layer (excluding the current collector) is 1.8 g / cm 3 More than 2.8g / cm 3 A negative electrode having a negative electrode active material-containing layer with a density within this range is excellent in energy density and electrolyte retention. The density of the negative electrode active material-containing layer is preferably 2.1 g / cm or less. 3 More than 2.6g / cm 3 More preferably, it is:

[0124] The negative electrode can be produced, for example, by the same method as that for the electrode according to the first embodiment.

[0125] 2) Positive electrode The positive electrode may include a positive electrode current collector and a positive electrode active material-containing layer. The positive electrode current collector and the positive electrode active material-containing layer may be the current collector and active material-containing layer, respectively, that may be included in the electrode according to the first embodiment. When the electrode according to the first embodiment is included as the negative electrode, the positive electrode does not have to be the electrode according to the first embodiment. For example, the positive electrode does not have to include the titanium-containing solid electrolyte described in the first embodiment. Details of the positive electrode that overlap with those described in the first embodiment will be omitted.

[0126] When room temperature molten salt is used as the electrolyte of the battery, lithium iron phosphate, Li x It is preferable to use a positive electrode active material containing VPO4F (0≦x≦1), lithium manganese composite oxide, lithium nickel composite oxide, lithium nickel cobalt composite oxide, or a mixture thereof. These compounds have low reactivity with room-temperature molten salts, which can improve cycle life. Details of room-temperature molten salts will be described later.

[0127] The average primary particle size of the positive electrode active material is preferably 100 nm or more and 1 μm or less. A positive electrode active material with an average primary particle size of 100 nm or more is easy to handle in industrial production. A positive electrode active material with an average primary particle size of 1 μm or less allows smooth diffusion of lithium ions within the solid.

[0128] The specific surface area of ​​the positive electrode active material is 0.1 m 2 / g or more 10m 2 / g or less is preferable. 2 A positive electrode active material with a specific surface area of ​​10m / g or more can secure sufficient sites for absorbing and releasing Li ions. 2 A positive electrode active material having a specific surface area of ​​0.15g / g or less is easy to handle in industrial production and can ensure good charge-discharge cycle performance.

[0129] The positive electrode can be produced, for example, by the same method as that for the electrode according to the first embodiment.

[0130] 3) Electrolytes The electrolyte may be, for example, a liquid nonaqueous electrolyte or a gel nonaqueous electrolyte. The liquid nonaqueous 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.

[0131] Examples of electrolyte salts include lithium salts such as lithium perchlorate (LiClO), lithium hexafluorophosphate (LiPF), lithium tetrafluoroborate (LiBF), lithium hexafluoride (LiAsF), lithium trifluoromethanesulfonate (LiCFSO), and lithium bistrifluoromethylsulfonylimide (LiN(CFSO)), and mixtures thereof. The electrolyte salt is preferably one that is difficult to oxidize even at high potentials, and LiPF is most preferred.

[0132] Examples of organic solvents include cyclic carbonates such as propylene carbonate (PC), ethylene carbonate (EC), and vinylene carbonate (VC); linear carbonates such as diethyl carbonate (DEC), dimethyl carbonate (DMC), and methyl ethyl carbonate (MEC); cyclic ethers such as tetrahydrofuran (THF), 2-methyl tetrahydrofuran (2MeTHF), and dioxolane (DOX); linear ethers such as dimethoxyethane (DME) and diethoxyethane (DEE); γ-butyrolactone (GBL), acetonitrile (AN), and sulfolane (SL). These organic solvents can be used alone or in combination.

[0133] The gel-like non-aqueous electrolyte is prepared by combining a liquid non-aqueous electrolyte with a polymeric material, such as polyvinylidene fluoride (PVdF), polyacrylonitrile (PAN), polyethylene oxide (PEO), or a mixture thereof.

[0134] Alternatively, in addition to liquid nonaqueous electrolytes and gel nonaqueous electrolytes, room temperature molten salts containing lithium ions (ionic melts), polymer solid electrolytes, inorganic solid electrolytes, and the like may be used as the nonaqueous electrolyte.

[0135] Room-temperature molten salts (ionic melts) refer to organic salts consisting of a combination of organic cations and anions that can exist as a liquid at room temperature (15°C or higher and 25°C or lower). Room-temperature molten salts include room-temperature molten salts that exist as a liquid on their own, room-temperature molten salts that become liquid when mixed with an electrolyte salt, room-temperature molten salts that become liquid when dissolved in an organic solvent, and mixtures of these. Generally, the melting point of room-temperature molten salts used in secondary batteries is 25°C or lower. Furthermore, organic cations generally have a quaternary ammonium skeleton.

[0136] The solid polymer electrolyte is prepared by dissolving an electrolyte salt in a polymer material and solidifying it.

[0137] The inorganic solid electrolyte is a solid substance that has Li-ion conductivity. Here, "having Li-ion conductivity" means that the Li-ion conductivity is 1×10 at 25°C. -6 This refers to a material that exhibits a lithium ion conductivity of 1000 S / cm or more. Examples of inorganic solid electrolytes include oxide-based solid electrolytes and sulfide-based solid electrolytes. Specific examples of inorganic solid electrolytes are as follows:

[0138] The oxide-based solid electrolyte has a NASICON (Sodium (Na) Super Ionic Conductor) type structure and is represented by the general formula Li 1+xIt is preferable to use a lithium phosphate solid electrolyte represented by Mα2(PO4)3. Mα in the above general formula is, for example, one or more selected from the group consisting of titanium (Ti), germanium (Ge), strontium (Sr), zirconium (Zr), tin (Sn), aluminum (Al), and calcium (Ca). The subscript x is within the range of 0 ≦ x ≦ 2.

[0139] Specific examples of the lithium phosphate solid electrolyte having a NASICON-type structure include LATP compounds represented by Li 1+x Al x Ti 2-x (PO4)3 with 0.1 ≦ x ≦ 0.5; Li 1+x Al y Mβ 2-y (PO4)3 where Mβ is one or more selected from the group consisting of Ti, Ge, Sr, Zr, Sn, and Ca and 0 ≦ x ≦ 1 and 0 ≦ y ≦ 1; Li 1+x Al x Ge 2-x (PO4)3 with 0 ≦ x ≦ 2; and Li 1+x Al x Zr 2-x (PO4)3 with 0 ≦ x ≦ 2; Li 1+x+y Al x Mγ 2-x [[ID=​​​​​​​​​​​​​​​​​​​​​​​​​​​);La with garnet structure 5+x A x La 3-x MδO 12 A is at least one selected from the group consisting of Ca, Sr, and Ba, Mδ is at least one selected from the group consisting of Nb and Ta, and 0≦x≦0.5; Li3Mδ 2-x L2O 12 wherein Mδ is at least one selected from the group consisting of Nb and Ta, L may contain Zr, and 0≦x≦0.5; Li 7-3x Al x La3Zr3O 12 and 0≦x≦0.5; Li 5+x La3Mδ 2-x Zr x O 12 where Mδ is at least one selected from the group consisting of Nb and Ta, and 0≦x≦2. LLZ compounds (e.g., Li7La3Zr2O 12 ); and La 2 / 3-x Li x Examples include compounds represented by TiO3 where x is 0.3≦x≦0.7.

[0141] One or more of the above compounds can be used as the solid electrolyte, and two or more of the above solid electrolytes can also be used.

[0142] 4) Separator The separator is formed from, 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, because these porous films melt at a certain temperature and can interrupt current.

[0143] 5) Exterior materials The exterior member may be, for example, a container made of a laminate film or a metal container.

[0144] The thickness of the laminate film is, for example, 0.5 mm or less, preferably 0.2 mm or less.

[0145] The laminate film is a multilayer film containing multiple resin layers and metal layers interposed between the resin layers. The resin layers include polymeric materials such as polypropylene (PP), polyethylene (PE), nylon, and polyethylene terephthalate (PET). The metal layers are preferably made of aluminum foil or aluminum alloy foil to reduce weight. The laminate film can be molded into the shape of the exterior component by sealing it by heat fusion.

[0146] The thickness of the wall of the metal container is, for example, 1 mm or less, more preferably 0.5 mm or less, and even more preferably 0.2 mm or less.

[0147] 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. If the aluminum alloy contains transition metals such as iron, copper, nickel, and chromium, the content of these metals is preferably 100 mass ppm or less.

[0148] The shape of the exterior member is not particularly limited. The shape of the exterior member may be, for example, flat (thin), rectangular, cylindrical, coin-shaped, or button-shaped. The exterior member can be appropriately selected depending on the battery dimensions and the intended use of the battery.

[0149] 6) Negative terminal The negative electrode terminal has a potential range of 1V to 3V relative to the redox potential of lithium (vs. Li / Li +) and can be formed from a material that is electrically stable and conductive. Specifically, the material for the negative electrode terminal can be copper, nickel, stainless steel, 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 material for the negative electrode terminal is preferably aluminum or an aluminum alloy. The negative electrode terminal is preferably made of the same material as the negative electrode current collector in order to reduce contact resistance with the negative electrode current collector.

[0150] 7) Positive terminal The positive electrode terminal has a potential range of 3V to 4.5V relative to the redox potential of lithium (vs. Li / Li + ) and can be formed from a material that is electrically stable and conductive. Examples of materials for the positive electrode terminal include aluminum and aluminum alloys 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 from the same material as the positive electrode current collector in order to reduce contact resistance with the positive electrode current collector.

[0151] Next, the secondary battery according to the embodiment will be described in more detail with reference to the drawings.

[0152] Fig. 1 is a cross-sectional view schematically showing an example of a secondary battery, and Fig. 2 is an enlarged cross-sectional view of part A of the secondary battery shown in Fig. 1.

[0153] 1 and 2 includes a bag-shaped exterior member 2 shown in Fig. 1, an electrode group 1 shown in Fig. 1 and 2, and an electrolyte (not shown). The electrode group 1 and the electrolyte are housed in the bag-shaped exterior member 2. The electrolyte (not shown) is held in the electrode group 1.

[0154] The bag-shaped exterior member 2 is made of a laminate film including two resin layers and a metal layer interposed between them.

[0155] As shown in Fig. 1, the electrode group 1 is a flat wound electrode group. As shown in Fig. 2, the flat 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.

[0156] The negative electrode 3 includes a negative electrode current collector 3a and a negative electrode active material-containing layer 3b. In the portion of the negative electrode 3 located at the outermost shell of the wound electrode group 1, the negative electrode active material-containing layer 3b is formed only on the inner surface side of the negative electrode current collector 3a, as shown in Fig. 2. In the other portions of the negative electrode 3, the negative electrode active material-containing layer 3b is formed on both sides of the negative electrode current collector 3a.

[0157] The positive electrode 5 includes a positive electrode current collector 5a and positive electrode active material-containing layers 5b formed on both sides of the positive electrode current collector 5a.

[0158] As shown in FIG. 1, the negative electrode terminal 6 and the positive electrode terminal 7 are located near the outer peripheral edge of the wound electrode group 1. The negative electrode terminal 6 is connected to a portion located at the outermost shell of the negative electrode current collector 3a. The positive electrode terminal 7 is connected to a portion located at the outermost shell of the positive electrode current collector 5a. The negative electrode terminal 6 and the positive electrode terminal 7 extend to the outside from an 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 this.

[0159] The secondary battery according to the embodiment is not limited to the secondary battery having the configuration shown in FIGS. 1 and 2, but may also be a battery having the configuration shown in FIGS. 3 and 4, for example.

[0160] Fig. 3 is a partially cutaway perspective view schematically showing another example of a secondary battery, and Fig. 4 is an enlarged cross-sectional view of part B of the secondary battery shown in Fig. 3.

[0161] 3 and 4 includes an electrode group 1 shown in Fig. 3 and 4, an 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.

[0162] The exterior member 2 is made of a laminate film including two resin layers and a metal layer interposed between them.

[0163] The electrode group 1 is a laminated electrode group, as shown in Fig. 4. The laminated electrode group 1 has a structure in which negative electrodes 3 and positive electrodes 5 are alternately laminated with separators 4 interposed therebetween.

[0164] 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 sides of the negative electrode current collector 3a. The electrode group 1 also 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 sides of the positive electrode current collector 5a.

[0165] The negative electrode current collector 3a of each negative electrode 3 includes a portion on one side where no negative electrode active material-containing layer 3b is supported on any surface. This portion serves as a negative electrode current collector tab 3c. As shown in FIG. 4, the negative electrode current collector tab 3c does not overlap with the positive electrode 5. The multiple negative electrode current collector tabs 3c are electrically connected to a strip-shaped negative electrode terminal 6. The tip of the strip-shaped negative electrode terminal 6 is extended to the outside of the exterior member 2.

[0166] Although not shown, the positive electrode current collector 5a of each positive electrode 5 includes a portion on one side where the positive electrode active material-containing layer 5b is not supported on any surface. This portion functions as a positive electrode current collector tab. Like the negative electrode current collector tab 3c, the positive electrode current collector tab does not overlap with the negative electrode 3. The positive electrode current collector tab is located on the opposite side of the electrode group 1 from the negative electrode current collector tab 3c. The positive electrode current collector tab is electrically connected to a strip-shaped positive electrode terminal 7. The tip of the strip-shaped positive electrode terminal 7 is located on the opposite side from the negative electrode terminal 6 and is drawn out to the outside of the exterior member 2.

[0167] The secondary battery according to the second embodiment includes the electrode according to the first embodiment, and therefore, the cycle performance of the secondary battery can be improved.

[0168] (Third embodiment) According to a third embodiment, there is provided a battery pack, which includes a plurality of secondary batteries according to the second embodiment.

[0169] In such a battery pack, the individual cells may be electrically connected in series or in parallel, or may be connected in a combination of series and parallel.

[0170] Next, an example of a battery pack according to an embodiment will be described with reference to the drawings.

[0171] Fig. 5 is a perspective view schematically showing an example of a battery pack. The battery pack 200 shown in Fig. 5 includes five cells 100a to 100e, four bus bars 21, a positive electrode lead 22, and a negative electrode lead 23. Each of the five cells 100a to 100e is a secondary battery according to the second embodiment.

[0172] The bus bar 21 connects, for example, the negative electrode terminal 6 of one cell 100a to the positive electrode terminal 7 of the adjacent cell 100b. In this way, the five cells 100 are connected in series by four bus bars 21. That is, the battery pack 200 in FIG. 5 is a five-series battery pack. Although an example is not shown, in a battery pack including a plurality of cells electrically connected in parallel, the plurality of cells can be electrically connected by, for example, connecting the negative electrode terminals to each other by a bus bar and connecting the positive electrode terminals to each other by a bus bar.

[0173] The positive electrode terminal 7 of at least one of the five cells 100a to 100e is electrically connected to a positive electrode lead 22 for external connection. Also, the negative electrode terminal 6 of at least one of the five cells 100a to 100e is electrically connected to a negative electrode lead 23 for external connection.

[0174] The battery pack according to the third embodiment includes the secondary battery according to the second embodiment, and therefore can achieve excellent cycle performance.

[0175] (Fourth embodiment) According to a fourth embodiment, there is provided a battery pack. This battery pack includes the battery assembly according to the third embodiment. This battery pack may include a single secondary battery according to the second embodiment instead of the battery assembly according to the third embodiment.

[0176] Such a battery pack may further include a protection circuit. The protection circuit has a function of controlling the charging and discharging of the secondary battery. Alternatively, a circuit included in a device that uses the battery pack as a power source (e.g., electronic equipment, automobile, etc.) may be used as the protection circuit for the battery pack.

[0177] The battery pack may further include external terminals for current flow. The external terminals for current flow are for outputting current from the secondary battery to the outside and / or inputting 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 terminals for current flow. When the battery pack is charged, charging current (including regenerative energy from the power of an automobile or the like) is supplied to the battery pack through the external terminals for current flow.

[0178] Next, an example of a battery pack according to an embodiment will be described with reference to the drawings.

[0179] Fig. 6 is an exploded perspective view schematically showing an example of a battery pack, and Fig. 7 is a block diagram showing an example of an electric circuit of the battery pack shown in Fig. 6.

[0180] The battery pack 300 shown in FIGS. 6 and 7 includes a container 31, a lid 32, a protective sheet 33, a battery pack 200, a printed wiring board 34, wiring 35, and an insulating plate (not shown).

[0181] The storage container 31 shown in Fig. 6 is a bottomed, prismatic container having a rectangular bottom. The storage container 31 is configured to be able to accommodate a protective sheet 33, a battery pack 200, a printed wiring board 34, and wiring 35. The lid 32 has a rectangular shape. The lid 32 covers the storage container 31 to accommodate the battery pack 200 and other components. Although not shown, the storage container 31 and the lid 32 are provided with openings or connection terminals for connection to external devices and the like.

[0182] The battery pack 200 includes a plurality of cells 100, a positive electrode lead 22, a negative electrode lead 23, and an adhesive tape 24.

[0183] At least one of the plurality of cells 100 is a secondary battery according to the second embodiment. The plurality of cells 100 are electrically connected in series as shown in FIG. 7. The plurality of cells 100 may be electrically connected in parallel, or may be connected in a combination of series and parallel connections. When the plurality of cells 100 are connected in parallel, the battery capacity increases compared to when they are connected in series.

[0184] The adhesive tape 24 fastens the plurality of cells 100 together. Heat-shrinkable tape may be used to secure the plurality of cells 100 together instead of the adhesive tape 24. In this case, protective sheets 33 are placed on both side surfaces of the battery pack 200, and the heat-shrinkable tape is wrapped around the cells 100, and the heat-shrinkable tape is then thermally shrunk to bind the plurality of cells 100 together.

[0185] One end of the positive electrode lead 22 is connected to the battery pack 200. One end of the positive electrode lead 22 is electrically connected to the positive electrode of one or more cells 100. One end of the negative electrode lead 23 is connected to the battery pack 200. One end of the negative electrode lead 23 is electrically connected to the negative electrode of one or more cells 100.

[0186] The printed wiring board 34 is installed along one of the shorter sides of the inner surface of the container 31. The printed wiring board 34 includes a positive connector 342, a negative connector 343, a thermistor 345, a protection circuit 346, wires 342a and 343a, an external terminal 350 for supplying current, a positive wire (positive wire) 348a, and a negative wire (negative wire) 348b. One main surface of the printed wiring board 34 faces one side of the battery pack 200. An insulating plate (not shown) is interposed between the printed wiring board 34 and the battery pack 200.

[0187] The other end 22a of the positive electrode lead 22 is electrically connected to the positive electrode connector 342. The other end 23a of the negative electrode lead 23 is electrically connected to the negative electrode connector 343.

[0188] The thermistor 345 is fixed to one main surface of the printed wiring board 34. The thermistor 345 detects the temperature of each of the cells 100 and transmits the detection signal to the protection circuit 346.

[0189] The external terminals 350 for applying current are fixed to the other main surface of the printed wiring board 34. The external terminals 350 for applying current are electrically connected to devices located outside the battery pack 300. The external terminals 350 for applying current include a positive terminal 352 and a negative terminal 353.

[0190] The protection circuit 346 is fixed to the other main surface of the printed wiring board 34. The protection circuit 346 is connected to the positive terminal 352 via a positive wiring 348a. The protection circuit 346 is connected to the negative terminal 353 via a negative wiring 348b. The protection circuit 346 is also electrically connected to the positive connector 342 via a wiring 342a. The protection circuit 346 is electrically connected to the negative connector 343 via a wiring 343a. The protection circuit 346 is also electrically connected to each of the plurality of single cells 100 via wiring 35.

[0191] The protective sheet 33 is disposed on both inner surfaces of the long sides of the container 31 and on the inner surface of the short side that faces the printed wiring board 34 across the battery pack 200. The protective sheet 33 is made of, for example, resin or rubber.

[0192] The protection circuit 346 controls charging and discharging of the plurality of cells 100. Furthermore, the protection circuit 346 cuts off the electrical connection between the protection circuit 346 and external terminals 350 (positive terminal 352, negative terminal 353) for supplying electricity to an external device, based on a detection signal transmitted from the thermistor 345 or a detection signal transmitted from each cell 100 or the battery pack 200.

[0193] An example of the detection signal transmitted from the thermistor 345 is a signal indicating that the temperature of the cell 100 is equal to or higher than a predetermined temperature. An example of the detection signal transmitted from each cell 100 or the battery pack 200 is a signal indicating that overcharge, overdischarge, or overcurrent of the cell 100 is detected. When detecting overcharge or the like for each 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 cell 100.

[0194] The protection circuit 346 may be a circuit included in a device (such as an electronic device or an automobile) that uses the battery pack 300 as a power source.

[0195] As described above, the battery pack 300 is also provided with the external terminals 350 for current application. Therefore, the battery pack 300 can output current from the battery assembly 200 to an external device and input current from the external device to the battery assembly 200 via the external terminals 350 for current application. In other words, when the battery pack 300 is used as a power source, the current from the battery assembly 200 is supplied to the external device via the external terminals 350 for current application. When the battery pack 300 is charged, a charging current from the external device is supplied to the battery pack 300 via the external terminals 350 for current application. When the battery pack 300 is used as an in-vehicle battery, regenerative energy from the vehicle's power can be used as the charging current from the external device.

[0196] The battery pack 300 may include a plurality of assembled batteries 200. In this case, the assembled batteries 200 may be connected in series, in parallel, or in a combination of series and parallel connections. The printed wiring board 34 and the wiring 35 may be omitted. In this case, the positive electrode lead 22 and the negative electrode lead 23 may be used as a positive terminal 352 and a negative terminal 353, respectively, of the external terminal 350 for supplying current.

[0197] Such a battery pack is used in applications requiring excellent cycle performance when drawing a large current, for example. Specifically, this battery pack is used, for example, as a power source for electronic devices, a stationary battery, or an on-board battery for various vehicles. Examples of electronic devices include digital cameras. This battery pack is particularly suitable for use as an on-board battery.

[0198] The battery pack according to the fourth embodiment includes the secondary battery according to the second embodiment or the battery pack according to the third embodiment, and therefore the battery pack can achieve excellent cycle performance.

[0199] (Fifth embodiment) According to a fifth embodiment, a vehicle is provided, which is equipped with the battery pack according to the fourth embodiment.

[0200] In such a vehicle, the battery pack recovers, for example, regenerative energy for powering the vehicle, and the vehicle may include a mechanism (regenerator) for converting the kinetic energy of the vehicle into regenerative energy.

[0201] Examples of vehicles include two- to four-wheel hybrid electric vehicles, two- to four-wheel electric vehicles, power-assisted bicycles, and rail vehicles.

[0202] The mounting position of the battery pack in a vehicle is not particularly limited. For example, when the battery pack is mounted in an automobile, the battery pack can be mounted in the engine compartment, the rear of the vehicle body, or under the seat of the vehicle.

[0203] A vehicle may be equipped with multiple battery packs. In this case, the batteries included in each battery pack may be electrically connected in series, in parallel, or a combination of series and parallel connections. For example, if each battery pack includes a battery pack, the battery packs may be electrically connected in series, in parallel, or a combination of series and parallel connections. Alternatively, if each battery pack includes a single battery, the batteries may be electrically connected in series, in parallel, or a combination of series and parallel connections.

[0204] Next, an example of a vehicle according to an embodiment will be described with reference to the drawings.

[0205] FIG. 8 is a partial perspective view that schematically illustrates an example of a vehicle.

[0206] A vehicle 400 shown in Fig. 8 includes a vehicle 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.

[0207] The vehicle 400 may be equipped with a plurality of battery packs 300. In this case, the batteries (for example, single cells or assembled batteries) included in the battery packs 300 may be connected in series, in parallel, or in a combination of series and parallel connections.

[0208] 8 illustrates an example in which the battery pack 300 is mounted in an engine compartment located in the front of the vehicle body 40. As described above, the battery pack 300 may be mounted, for example, at the rear of the vehicle body 40 or under a seat. This battery pack 300 can be used as a power source for the vehicle 400. In addition, this battery pack 300 can recover regenerative energy for powering the vehicle 400.

[0209] Next, an embodiment of the vehicle according to the embodiment will be described with reference to FIG.

[0210] 9 is a diagram illustrating an example of a control system for an electrical system in a vehicle. The vehicle 400 shown in FIG. 9 is an electric vehicle.

[0211] The vehicle 400 shown in Figure 9 includes a vehicle body 40, a vehicle power supply 41, a vehicle ECU (ECU: Electric Control Unit) 42 which is a higher-level control device of the vehicle power supply 41, an external terminal (terminal for connecting to an external power supply) 43, an inverter 44, and a drive motor 45.

[0212] Vehicle 400 has vehicle power supply 41 mounted, for example, in the engine compartment, the rear of the vehicle body, or under the seat. Note that in vehicle 400 shown in Fig. 9, the mounting location of vehicle power supply 41 is shown schematically.

[0213] 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.

[0214] 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 300a to 300c are the same as the battery pack 300 described above, and the assembled batteries 200a to 200c are the same as the assembled battery 200 described above. The assembled batteries 200a to 200c are electrically connected in series. The battery packs 300a, 300b, and 300c can each be removed independently and replaced with another battery pack 300.

[0215] Each of the battery packs 200a to 200c includes a plurality of unit cells connected in series. At least one of the unit cells is the secondary battery according to the second embodiment. Each of the battery packs 200a to 200c is charged and discharged via a positive terminal 413 and a negative terminal 414.

[0216] The battery management device 411 communicates with the assembled battery monitoring devices 301a to 301c and collects information on the voltage, temperature, etc. of each of the cells 100 included in the assembled batteries 200a to 200c included in the vehicle power supply 41. In this way, the battery management device 411 collects information on the maintenance of the vehicle power supply 41.

[0217] The battery management unit 411 and the assembled battery monitoring units 301a to 301c are connected via a communication bus 412. In the communication bus 412, one set of communication lines is shared by multiple nodes (the battery management unit 411 and one or more assembled battery monitoring units 301a to 301c). The communication bus 412 is a communication bus configured based on, for example, the CAN (Control Area Network) standard.

[0218] The battery pack monitoring devices 301a to 301c measure the voltage and temperature of each of the cells constituting the battery packs 200a to 200c based on commands received through communication from the battery management device 411. However, the temperature can be measured at only a few locations per battery pack, and it is not necessary to measure the temperature of all the cells.

[0219] The vehicle power supply 41 may also have an electromagnetic contactor (for example, a switch device 415 shown in FIG. 9) that switches between electrical connection and disconnection between the positive terminal 413 and the negative terminal 414. The switch device 415 includes a pre-charge switch (not shown) that is turned on when the assembled batteries 200a-200c are being charged, and a main switch (not shown) that is turned on when the output from the assembled batteries 200a-200c is being supplied to a load. Each of the pre-charge switch and the main switch includes a relay circuit (not shown) that is switched on or off by a signal supplied to a coil disposed near the switch element. Electromagnetic contactors such as the switch device 415 are controlled based on a control signal from the battery management device 411 or the vehicle ECU 42 that controls the operation of the entire vehicle 400.

[0220] 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 is controlled based on control signals from the battery management unit 411 or the vehicle ECU 42, which controls the operation of the entire vehicle. By controlling the inverter 44, the output voltage from the inverter 44 is adjusted.

[0221] The drive motor 45 is rotated by the electric power supplied from the inverter 44. The drive force generated by the rotation of the drive motor 45 is transmitted to the axles and drive wheels W via, for example, a differential gear unit.

[0222] Although not shown, vehicle 400 also includes a regenerative braking mechanism (regenerator). When vehicle 400 is braked, regenerative braking mechanism rotates drive motor 45 and converts kinetic energy into regenerative energy as electrical energy. The regenerative energy recovered by the regenerative braking mechanism is input to inverter 44 and converted into direct current. The converted direct current is input to vehicle power supply 41.

[0223] One terminal of a connection line L1 is connected to the negative terminal 414 of the vehicle power supply 41. The other terminal of the connection line L1 is connected to a negative input terminal 417 of the inverter 44. A current detection unit (current detection circuit) 416 in the battery management device 411 is provided on the connection line L1 between the negative terminal 414 and the negative input terminal 417.

[0224] One terminal of a connection line L2 is connected to the positive terminal 413 of the vehicle power supply 41. The other terminal of the connection line L2 is connected to a positive input terminal 418 of the inverter 44. A switch device 415 is provided on the connection line L2 between the positive terminal 413 and the positive input terminal 418.

[0225] The external terminal 43 is connected to the battery management device 411. The external terminal 43 can be connected to, for example, an external power source.

[0226] In response to operational inputs from the driver or the like, the vehicle ECU 42 coordinates with other management devices and control devices including the battery management device 411 to control the vehicle power supply 41, the switch device 415, the inverter 44, etc. Through the coordinated control of the vehicle ECU 42, etc., the output of power from the vehicle power supply 41 and the charging of the vehicle power supply 41 are controlled, thereby managing the entire vehicle 400. Data relating to the maintenance of the vehicle power supply 41, such as the remaining capacity of the vehicle power supply 41, is transferred between the battery management device 411 and the vehicle ECU 42 via a communication line.

[0227] The vehicle according to the fifth embodiment is equipped with the battery pack according to the fourth embodiment. Therefore, since the cycle performance of the battery pack is high, the reliability of the vehicle is high.

Example

[0228] Examples will be described below, but the embodiments are not limited to the examples described below.

[0229] (Example 1) <Surface treatment of LATP> As LATP particles, particles of Li 1.3 Al 0.3 Ti 1.7 (PO4)3 were prepared. The surface treatment of the LATP particles was performed as follows. A 2 mass% hydrofluoric acid aqueous solution was placed in a beaker made of polytetrafluoroethylene (PTFE), and the LATP particles were added. Stirring was performed at 45 °C for 80 hours. After stirring, the LATP particles were taken out and washed with water. Thus, surface-treated LATP particles were obtained.

[0230] <Preparation of negative electrode> As the negative electrode active material, monoclinic niobium titanate (Nb2TiO7) powder was prepared. The average secondary particle diameter of the niobium titanate powder was 7.5 μm. The specific surface area of the niobium titanate powder was 4.0 m 2 / g. Also, acetylene black was prepared as a conductive agent, and CMC and SBR were prepared as binders. As the titanium-containing solid electrolyte, the surface-treated LATP particles described above were prepared. Next, the negative electrode active material, conductive agent, CMC, SBR, and titanium-containing solid electrolyte were added to water as a solvent at a ratio of 88 mass%: 5 mass%: 2 mass%: 2 mass%: 3 mass% and mixed to prepare a negative electrode slurry. This negative electrode slurry was applied to both sides of a current collector made of an aluminum foil having a thickness of 15 μm. Then, the coating film was dried in a constant temperature bath at 120 °C to form a negative electrode active material-containing layer. The negative electrode active material-containing layer was pressed to obtain a negative electrode.

[0231] (Examples 2 to 9) A negative electrode was produced in the same manner as in Example 1, except that the hydrofluoric acid concentration, stirring temperature, and stirring time in the surface treatment of LATP were changed as shown in Table 1.

[0232] (Comparative Example 1) A negative electrode was prepared in the same manner as in Example 1, except that, instead of the surface-treated LATP particles, non-surface-treated LATP particles were used as the titanium-containing solid electrolyte. Note that, since the surface treatment of LATP was not performed in Comparative Example 1, the columns for the hydrofluoric acid concentration, stirring temperature, and stirring time of Comparative Example 1 in Table 1 are indicated by "-".

[0233] Example 10 The surface treatment of LATP was carried out in the same manner as in Example 1. <Preparation of positive electrode> The positive electrode active material is lithium nickel cobalt manganese composite oxide (LiNi 0.5 Co 0.2 Mn 0.3 O2) powder was prepared. Acetylene black was prepared as a conductive agent. Polyvinylidene fluoride (PVdF) was prepared as a binder. The surface-treated LATP particles described above were prepared as a titanium-containing solid electrolyte. Next, the positive electrode active material, conductive agent, binder, and titanium-containing solid electrolyte were added to N-methylpyrrolidone (NMP) as a solvent in a ratio of 87% by mass:5% by mass:5% by mass:3% by mass and mixed to prepare a positive electrode slurry. This positive electrode slurry was applied to both sides of a current collector made of aluminum foil with a thickness of 15 μm. Next, the coating was dried in a thermostatic oven at 120°C to form a positive electrode active material-containing layer. The positive electrode active material-containing layer was pressed to obtain a positive electrode.

[0234] Examples 11 to 18 Positive electrodes were produced in the same manner as in Example 10, except that the hydrofluoric acid concentration, stirring temperature, and stirring time in the surface treatment of LATP were changed as shown in Table 2.

[0235] (Comparative Example 2) A positive electrode was produced in the same manner as in Example 10, except that in the preparation of the positive electrode slurry, the surface-treated LATP particles were changed to LATP particles that had not been subjected to a surface treatment. Note that, since the surface treatment of LATP was not performed in Comparative Example 2, the columns for the hydrofluoric acid concentration, stirring temperature, and stirring time of Comparative Example 2 in Table 2 are indicated by "-".

[0236] <Preparation of electrochemical measurement cell> An electrochemical measurement cell was fabricated using a measurement electrode, a lithium metal foil as a counter electrode, and a non-aqueous electrolyte. The electrodes fabricated in each example and comparative example were used as the measurement electrode. The non-aqueous electrolyte was prepared by dissolving lithium hexafluorophosphate (LiPF6) at a concentration of 1 M in a mixed solvent of ethylene carbonate and diethyl carbonate (volume ratio 1:1).

[0237] <0.2C discharge capacity measurement> (Examples 1 to 9, Comparative Example 1) The electrochemical measurement cell was tested in the potential range of 1.0 V to 3.0 V with respect to the metallic lithium electrode. The battery was charged and discharged at room temperature. The current value during charging and discharging was 0.2 C (hourly discharge rate). The capacity during discharge was measured and designated as the 0.2 C discharge capacity (initial discharge capacity).

[0238] (Examples 10 to 18, Comparative Example 2) The discharge capacity was measured in the same manner as in Examples 1 to 9 and Comparative Example 1, except that the charge / discharge potential range of the electrochemical measurement cell was changed to 3.0 V to 4.2 V relative to the metallic lithium electrode, and this was taken as the 0.2 C discharge capacity (initial discharge capacity).

[0239] <10C / 0.2C discharge capacity ratio measurement> The electrochemical measurement cell was charged and discharged in the same manner as in the measurement of the 0.2 C discharge capacity performed for each Example and Comparative Example, except that the current value during discharge was changed to 10 C. The capacity during discharge was measured and defined as the 10 C discharge capacity. The ratio of the 10 C discharge capacity to the initial discharge capacity was calculated.

[0240] <Charge / discharge cycle test> (Examples 1 - 9, Comparative Example 1) The electrochemical measurement cell was charged and discharged at room temperature within a potential range of 1.0 V to 3.0 V with reference to the metallic lithium electrode. The current value during charging and discharging was set to 1C.

[0241] The above charging and discharging were regarded as one charge - discharge cycle. This charge - discharge cycle was repeated 100 times at room temperature.

[0242] For the electrochemical measurement cell after repeating the charge - discharge 100 cycles, the 0.2C discharge capacity was measured in the same manner as described above. The discharge capacity at this time was defined as the discharge capacity after 100 cycles. The capacity retention rate (%) was calculated by dividing the discharge capacity after 100 cycles by the initial discharge capacity and multiplying by 100, assuming the initial discharge capacity as 100%.

[0243] (Examples 10 - 18, Comparative Example 2)[[ID=—16]] A charge - discharge cycle test was conducted and the capacity retention rate (%) was calculated in the same manner as in Examples 1 - 9 and Comparative Example 1, except that the potential range of charge - discharge of the electrochemical measurement cell was changed to 3.0 V to 4.2 V with reference to the metallic lithium electrode.

[0244] [Preparation of Samples for Measurement]< As samples for measurement, commercially available anatase - type titanium dioxide powder with a purity of 99.5% was prepared. Also, the electrodes of the examples and comparative examples were made into a discharged state and used as samples for measurement as follows.

[0245] The electrochemical measurement cell was discharged at 0.05C, and the potential of the electrodes of the examples and comparative examples was adjusted to 3.0 V with reference to the metallic lithium. In this way, the electrodes were put into a discharged state.

[0246] Inside an argon box, the discharged electrodes were taken out from the electrochemical measurement cell and washed with methyl ethyl carbonate (MEC). The washed electrodes were vacuum - dried and used as samples for measurement.

[0247] [XAFS Analysis]< The electrodes of the examples and comparative examples and the anatase titanium dioxide measurement sample were subjected to XAFS analysis in the same manner as described above. The XAFS analysis was carried out using BL16B2 at SPring-8.

[0248] The normalized spectrum for the electrodes of each of the Examples and Comparative Examples was compared with the normalized spectrum for anatase titanium dioxide in the following manner, and the amount of shift was calculated.

[0249] From the normalized spectra of the electrodes of each Example and Comparative Example, a point was taken where the first X-ray absorption amount was 0.2 at a first incident X-ray energy in the range of 4930 eV to 5000 eV inclusive.From the normalized spectrum of anatase titanium dioxide, a point was taken where the second X-ray absorption amount was 0.2 at a second incident X-ray energy in the range of 4930 eV to 5000 eV inclusive.

[0250] The difference between the first incident X-ray energy (eV) and the second incident X-ray energy (eV) for each point was calculated and determined as "shift amount (eV) from TiO2 I = 0.2."

[0251] In the same manner as above, the point where the first X-ray absorption amount was 0.5 and the point where the second X-ray absorption amount was 0.5 were taken from each spectrum. The difference between the first incident X-ray energy (eV) and the second incident X-ray energy (eV) for each point was calculated and defined as the "shift amount (eV) from TiO2 = 0.5."

[0252] The measurement results of each of the examples and comparative examples are shown in Tables 1 and 2.

[0253] [Table 1]

[0254] [Table 2]

[0255] The capacity retention rate is an index of cycle performance, and the 10C / 0.2C discharge capacity ratio is an index of output performance.

[0256] In all of the electrodes of the examples, the "shift amount from TiO2 (eV)I = 0.2" and "shift amount from TiO2 (eV)I = 0.5" were positive values. That is, when the first X-ray absorption amount and the second X-ray absorption amount were equal at 0.2 and equal at 0.5, the first incident X-ray energy was higher than the second incident X-ray energy. This is thought to be because all of the electrodes of the examples contain surface-treated LATP particles as the titanium-containing solid electrolyte. The surface-treated LATP particles have a large valence, which is thought to be why the first incident X-ray energy was higher than the second incident X-ray energy.

[0257] Although the electrodes of the comparative examples were electrodes containing a titanium-containing solid electrolyte in the active material-containing layer, the "shift amount from TiO2 (eV)I = 0.2" and "shift amount from TiO2 (eV)I = 0.5" were both 0. That is, when the first X-ray absorption amount and the second X-ray absorption amount were equal at 0.2 and 0.5, the first incident X-ray energy was not higher than the second incident X-ray energy. This is thought to be because the LATP particles contained in the electrodes of the comparative examples were not surface-treated, and therefore the valence of LATP did not change.

[0258] The electrodes of the Examples all had higher 10 C / 0.2 C discharge capacity ratios and higher capacity retention rates than the electrodes of the Comparative Examples, demonstrating that the electrodes of the Examples were superior in output performance and cycle performance.

[0259] Furthermore, Examples 2 to 9 and 11 to 18, in which the "shift amount from TiO2 (eV)I = 0.2" and the "shift amount from TiO2 (eV)I = 0.5" were within the ranges of 1.0 to 4.0, exhibited particularly high 10C / 0.2C discharge capacity ratios and capacity retention rates. Examples 2, 3, 5 to 9, 11, 12, and 14 to 18, in which the "shift amount from TiO2 (eV)I = 0.2" and the "shift amount from TiO2 (eV)I = 0.5" were within the ranges of 3.0 to 3.5, exhibited even higher 10C / 0.2C discharge capacity ratios and capacity retention rates. Therefore, it was revealed that an electrode in which the difference between the first incident X-ray energy and the second incident X-ray energy was 1 eV to 4 eV exhibited particularly excellent output performance and cycle performance, and an electrode in which the difference was 3 eV to 3.5 eV exhibited even better output performance and cycle performance.

[0260] According to at least one embodiment described above, there is provided an electrode. The electrode includes an active material and a titanium-containing solid electrolyte. The active material includes a transition metal oxide.

[0261] In an X-ray absorption fine structure spectrum at the Ti-K absorption edge for an electrode in a discharged state, when the X-ray absorption amount is 1 when the incident X-ray energy is 5500 eV, the first X-ray absorption amount I at a first incident X-ray energy in the incident X-ray energy range of 4930 eV to 5000 eV satisfies 0.2≦I≦0.6.

[0262] In an X-ray absorption fine structure spectrum at the Ti-K absorption edge of anatase titanium dioxide, when the X-ray absorption amount when the incident X-ray energy is 5500 eV is set to 1, the second X-ray absorption amount at a second incident X-ray energy in the range of 4930 eV to 5000 eV is equal to the first X-ray absorption amount I. The first incident X-ray energy is higher than the second incident X-ray energy. Therefore, such an electrode can improve cycle performance.

[0263] The invention according to the embodiment will be described below.

[0264] [1] An electrode comprising an active material and a titanium-containing solid electrolyte, the active material comprises a transition metal oxide; In the X-ray absorption fine structure spectrum at the Ti-K absorption edge for the electrode in a discharged state, When the incident X-ray energy is 5500 eV, the X-ray absorption amount is set to 1. The first X-ray absorption amount I at the first incident X-ray energy in the range of 4930 eV or more and 5000 eV or less satisfies 0.2≦I≦0.6, and In the X-ray absorption fine structure spectrum of anatase titanium dioxide at the Ti-K absorption edge, When the incident X-ray energy is 5500 eV, the X-ray absorption amount is set to 1. a second X-ray absorption amount at a second incident X-ray energy in the range of 4930 eV or more and 5000 eV or less is equal to the first X-ray absorption amount I; The electrode, wherein the first incident X-ray energy is higher than the second incident X-ray energy.

[0265] [2] The electrode according to [1], wherein the titanium-containing solid electrolyte contains a titanium-containing lithium phosphate composite oxide.

[0266] [3] The electrode according to [1] or [2], wherein the difference between the first incident X-ray energy and the second incident X-ray energy is 1 eV or more and 4 eV or less.

[0267] [4] The electrode according to any one of [1] to [3], wherein the transition metal oxide comprises at least one selected from the group consisting of lithium titanate having a ramsdellite structure, lithium titanate having a spinel structure, niobium pentoxide, hollandite-type titanium composite oxide, orthorhombic titanium composite oxide, and monoclinic niobium titanium oxide.

[0268] [5] The electrode according to any one of [1] to [4], wherein the transition metal oxide comprises at least one selected from the group consisting of manganese dioxide, iron oxide, copper oxide, nickel oxide, lithium manganese composite oxide, lithium nickel composite oxide, lithium cobalt composite oxide, lithium nickel cobalt composite oxide, lithium manganese cobalt composite oxide, lithium manganese nickel composite oxide having a spinel structure, lithium phosphate oxide having an olivine structure, iron sulfate, vanadium oxide, and lithium nickel cobalt manganese composite oxide.

[0269] [6] a positive electrode; a negative electrode; Electrolytes and A secondary battery comprising: A secondary battery in which at least one selected from the group consisting of the positive electrode and the negative electrode is the electrode according to any one of [1] to [5].

[0270] [7] The secondary battery according to [6], wherein the electrolyte contains fluorine atoms.

[0271] [8] A battery pack including the secondary battery according to [6] or [7].

[0272] [9] An external terminal for applying current; Protection circuit and The battery pack according to [8], further comprising:

[0273]

[10] A battery comprising a plurality of the secondary batteries, The battery pack according to [8] or [9], wherein the secondary batteries are electrically connected in series, in parallel, or in a combination of series and parallel.

[0274]

[11] A vehicle including the battery pack according to any one of [8] to

[10] .

[0275]

[12] The vehicle according to

[11] , including a mechanism for converting the kinetic energy of the vehicle into regenerative energy.

[0276] Although several embodiments of the present invention have been described, these embodiments are presented as examples and are not intended to limit the scope of the invention. These novel embodiments can be embodied in various other forms, and various omissions, substitutions, and modifications can be made without departing from the spirit of the invention. These embodiments and their modifications are included within the scope and spirit of the invention, and are also included in the scope of the invention and its equivalents as defined in the claims. [Explanation of symbols]

[0277] 1...electrode group, 2...exterior member, 3...negative electrode, 3a...negative electrode current collector, 3b...negative electrode active material-containing layer, 3c...negative electrode current collecting tab, 4...separator, 5...positive electrode, 5a...positive electrode current collector, 5b...positive electrode active material-containing layer, 6...negative electrode terminal, 7...positive electrode terminal, 21...bus bar, 22...positive electrode side lead, 22a...other end, 23...negative electrode side lead, 23a...other end, 24...adhesive tape, 31...container, 32...lid, 33...protective sheet, 34...printed wiring board, 35...wiring, 40...vehicle body, 41...vehicle power source, 42...electrical control device, 43...external terminal, 44...inverter, 45...drive motor, 100...secondary battery, 200...battery pack, 200a...battery pack, 200b...battery pack, 200c...battery pack, 300...battery pack, 30 0a...battery pack, 300b...battery pack, 300c...battery pack, 301a...assembled battery monitoring device, 301b...assembled battery monitoring device, 301c...assembled battery monitoring device, 342...positive side connector, 343...negative side connector, 345...thermistor, 346...protection circuit, 342a...wiring, 343a...wiring, 350...external terminal for supplying current, 352...positive side terminal, 353...negative side terminal, 348a...positive side wiring, 348b...negative side wiring, 400...vehicle, 411...battery management device, 412...communication bus, 413...positive side terminal, 414...negative side terminal, 415...switch device, 416...current detection unit, 417...negative side input terminal, 418...positive side input terminal, L1...connection line, L2...connection line, W...drive wheel.

Claims

1. An electrode comprising an active material and a titanium-containing solid electrolyte, the active material comprises a transition metal oxide; In the X-ray absorption fine structure spectrum at the Ti-K absorption edge for the electrode in a discharged state, When the X-ray absorption amount is 1 when the incident X-ray energy is 5500 eV, a first X-ray absorption amount I at a first incident X-ray energy in the range of 4930 eV or more and 5000 eV or less satisfies 0.2≦I≦0.6, and In the X-ray absorption fine structure spectrum of anatase titanium dioxide at the Ti-K absorption edge, When the X-ray absorption amount is 1 when the incident X-ray energy is 5500 eV, a second X-ray absorption amount at a second incident X-ray energy in the range of 4930 eV to 5000 eV is equal to the first X-ray absorption amount I; The first incident x-ray energy is greater than the second incident x-ray energy.

2. The electrode according to claim 1 , wherein the titanium-containing solid electrolyte comprises a titanium-containing lithium phosphate composite oxide.

3. 3. The electrode according to claim 1, wherein a difference between the first incident X-ray energy and the second incident X-ray energy is 1 eV or more and 4 eV or less.

4. 3. The electrode according to claim 1, wherein the transition metal oxide comprises at least one selected from the group consisting of lithium titanate having a ramsdellite structure, lithium titanate having a spinel structure, niobium pentoxide, hollandite-type titanium composite oxide, orthorhombic titanium composite oxide, and monoclinic niobium titanium oxide.

5. 3. The electrode according to claim 1 or 2, wherein the transition metal oxide comprises at least one selected from the group consisting of manganese dioxide, iron oxide, copper oxide, nickel oxide, lithium manganese composite oxide, lithium nickel composite oxide, lithium cobalt composite oxide, lithium nickel cobalt composite oxide, lithium manganese cobalt composite oxide, lithium manganese nickel composite oxide having a spinel structure, lithium phosphate oxide having an olivine structure, iron sulfate, vanadium oxide, and lithium nickel cobalt manganese composite oxide.

6. A positive electrode and a negative electrode; Electrolytes and A secondary battery comprising: A secondary battery, wherein at least one selected from the group consisting of the positive electrode and the negative electrode is the electrode according to claim 1 or 2.

7. The secondary battery according to claim 6 , wherein the electrolyte contains fluorine atoms.

8. A battery pack comprising the secondary battery according to claim 6.

9. An external terminal for applying current; Protection circuit and The battery pack of claim 8 further comprising:

10. a plurality of the secondary batteries; The battery pack according to claim 8 , wherein the secondary batteries are electrically connected in series, in parallel, or in a combination of series and parallel.

11. A vehicle including the battery pack of claim 8.

12. The vehicle according to claim 11, further comprising a mechanism for converting kinetic energy of the vehicle into regenerative energy.

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