Active material, electrode, secondary battery, battery pack, and vehicle

Abstract

To provide an active material which can realize a secondary battery that can show the excellent output characteristics and cycle life characteristics.SOLUTION: There is provided an active material according to one embodiment. The active material includes a primary particle including an Nb10Ti2O29 phase and at least one Nb rich phase selected from a group consisting of an Nb14TiO37 phase and an Nb24TiO64 phase. In the primary particle, a ratio MNb / MTi of a substance quantity of niobium to a substance quantity of titanium satisfies 5.0<MNb / MTi≤24.0. A diffraction chart by a wide-angle X-ray diffraction method that uses a CuKα ray to the active material as an X-ray source includes: a peak A and a peak C which belong to the Nb10Ti2O29 phase; and a peak B in which 2θ appears within a range of 25.5±0.2° and which belongs to the Nb rich phase. The active material satisfies a peak intensity ratio expressed by a formula (1). (1) 0<IB / IA<5.0. A half value width of the peak C is within a range between 0.15° and 0.80°.SELECTED DRAWING: Figure 12

Description

[Technical field]

[0001] FIELD OF THE DISCLOSURE Embodiments of the present invention relate to an active material, an electrode, a secondary battery, a battery pack, and a vehicle.

[0002] In recent years, research and development of secondary batteries such as non-aqueous electrolyte secondary batteries, such as lithium ion secondary batteries, as high energy density batteries, has been actively promoted. Secondary batteries such as non-aqueous electrolyte secondary batteries are expected to be used as power sources for vehicles such as hybrid electric vehicles and electric vehicles, and for uninterruptible power sources for mobile phone base stations. Therefore, in addition to high energy density, secondary batteries are also required to have excellent other performances such as rapid charge and discharge performance and long-term reliability. For example, secondary batteries capable of rapid charge and discharge not only significantly reduce charging time, but also improve the power performance of vehicles such as hybrid electric vehicles and efficiently recover regenerative energy from power.

[0003] In order to enable rapid charging and discharging, it is necessary that electrons and lithium ions can move quickly between the positive and negative electrodes. However, when a battery using a carbon-based negative electrode is repeatedly charged and discharged rapidly, dendrites of metallic lithium are precipitated on the electrode, which may cause heat generation or fire due to an internal short circuit.

[0004] Therefore, batteries that use metal composite oxides instead of carbonaceous materials for the anode have been developed. Among them, batteries that use titanium oxide for the anode are capable of stable rapid charging and discharging and have a longer life than batteries that use carbon-based anodes.

[0005] However, titanium oxide has a higher potential relative to metallic lithium than carbonaceous materials, i.e., it is more noble. Moreover, titanium oxide has a low capacity per weight. Therefore, batteries using titanium oxide in the negative electrode have a problem of low energy density.

[0006] For example, the electrode potential of titanium oxide is about 1.5 V (vs. Li / Li) based on metallic lithium. +), which is higher (more noble) than the potential of a carbon-based negative electrode. The potential of titanium oxide is the potential of Ti when electrochemically inserting and extracting lithium. 3+ and Ti 4+ The charge is electrochemically limited because it is caused by an oxidation-reduction reaction between the two. + It is also true that rapid charging and discharging of lithium ions can be performed stably at high electrode potentials of around 1000 kV. Therefore, it has been difficult to lower the electrode potential in order to improve the energy density.

[0007] On the other hand, in terms of capacity per unit weight, the theoretical capacity of titanium dioxide (anatase structure) is about 165 mAh / g, and Li4Ti5O 12 The theoretical capacity of spinel-type lithium-titanium composite oxides such as those shown in Fig. 1 is about 180 mAh / g. On the other hand, the theoretical capacity of general graphite-based electrode materials is 385 mAh / g or more. Thus, the capacity density of titanium oxides is significantly lower than that of carbon-based negative electrodes. This is because the crystal structure of titanium oxides has few sites for absorbing lithium and lithium is easily stabilized in the structure, resulting in a decrease in the actual capacity.

[0008] In view of the above, new electrode materials containing Ti and Nb are being investigated. Such niobium titanium composite oxide materials are expected to have high charge / discharge capacities. In particular, the composite oxide represented by TiNb2O7 has a high theoretical capacity of more than 380 mAh / g. Therefore, the niobium titanium composite oxide is Li4Ti5O 12 However, there is room for improvement in terms of output characteristics and cycle life characteristics. [Prior art documents] [Patent documents]

[0009] [Patent Document 1] China Patent Application Publication No. 105633456 [Patent Document 2] JP 2019-169343 A [Non-patent literature]

[0010] [Non-Patent Document 1] Chunfu Lin, et. al., Chem. Commun., 2015,51, 8970-8973 , "TiNb6O17: a new electrode material for lithium-ion batteries" Summary of the Invention [Problem to be solved by the invention]

[0011] The object is to provide an active material capable of realizing a secondary battery capable of exhibiting excellent output characteristics and cycle life characteristics, an electrode containing this active material, a secondary battery equipped with this electrode, a battery pack equipped with this secondary battery, and a vehicle equipped with this battery pack. [Means for solving the problem]

[0012] According to an embodiment, an active material is provided. The active material comprises Nb 10 Ti2O 29 Phase and Nb 14 TiO 37 Phase and Nb 24 TiO 64 and at least one Nb-rich phase selected from the group consisting of Nb-rich phases. In the primary particles, the ratio M of the amount of substance of niobium to the amount of substance of titanium is Nb / M Ti is 5.0 <M Nb / M Ti ≦24.0. The diffraction chart of the active material by wide-angle X-ray diffraction method using CuKα radiation as the X-ray source shows 2θ in the range of 24.9±0.2°, and Nb 10 Ti2O 29 Peak A, which is assigned to the Nb-rich phase, appears within a 2θ range of 25.5±0.2°, and peak B, which is assigned to the Nb-rich phase, appears within a 2θ range of 23.7±0.2°. 10 Ti2O 29and peak C assigned to the Fe-phase. The active material satisfies the peak intensity ratio represented by the following formula (1). 0 B / I A <5.0 (1) In formula (1), I A is the peak intensity of the peak A, and I B is the peak intensity of the peak B. The half width of the peak C is in the range of 0.15° to 0.80°.

[0013] According to another embodiment, an electrode is provided that includes an active material according to the embodiment.

[0014] According to another embodiment, there is provided a secondary battery comprising a positive electrode, a negative electrode, and an electrolyte. The negative electrode is an electrode according to the embodiment.

[0015] According to another embodiment, a battery pack including a secondary battery according to the embodiment is provided.

[0016] According to another embodiment, a vehicle equipped with a battery pack according to the embodiment is provided. [Brief description of the drawings]

[0017] [Figure 1] Schematic diagram showing the crystal structure of niobium titanium composite oxide Nb2TiO7. [Diagram 2] Schematic diagram showing the crystal structure of FIG. 1 from another angle. [Diagram 3] FIG. 1 is a cross-sectional view illustrating an example of a secondary battery according to an embodiment. [Figure 4] 4 is an enlarged cross-sectional view of a portion A of the secondary battery shown in FIG. 3. [Diagram 5] FIG. 4 is a partially cutaway perspective view illustrating a schematic diagram of another example of a secondary battery according to an embodiment. [Figure 6] 5 is an enlarged cross-sectional view of part B of the secondary battery shown in FIG. 4. [Figure 7] FIG. 1 is a perspective view illustrating an example of a battery pack according to an embodiment. [Figure 8] FIG. 1 is an exploded perspective view illustrating an example of a battery pack according to an embodiment.​ [Figure 9] 9 is a block diagram showing an example of an electric circuit of the battery pack shown in FIG. 8. [Figure 10] 1 is a cross-sectional view illustrating an example of a vehicle according to an embodiment. [Figure 11] FIG. 13 is a diagram illustrating another example of a vehicle according to an embodiment. [Figure 12] FIG. 5 is a diffraction chart obtained by powder X-ray diffraction measurement in Example 4. [Figure 13] FIG. 13 is a diffraction chart obtained by powder X-ray diffraction measurement in Example 10. [Figure 14] FIG. 13 is a diffraction chart obtained by powder X-ray diffraction measurement in Comparative Example 3. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0018] Hereinafter, the embodiments will be described with reference to the drawings. Note that the same reference numerals are used to designate common components throughout the embodiments, and duplicated descriptions will be omitted. Each figure is a schematic diagram for explaining the embodiments and for facilitating understanding thereof, and the shapes, dimensions, ratios, etc. may differ from those of the actual device, but these can be appropriately modified in design by taking into consideration the following explanation and known techniques.

[0019] (First embodiment) According to a first embodiment, an active material is provided. The active material comprises Nb 10 Ti2O 29 Phase and Nb 14 TiO 37 Phase and Nb 24 TiO 64 and at least one Nb-rich phase selected from the group consisting of Nb-rich phases. In the primary particles, the ratio M of the amount of substance of niobium to the amount of substance of titanium is Nb / M Ti is 5.0 <M Nb / M Ti ≦24.0. The diffraction chart of the active material by wide-angle X-ray diffraction method using CuKα radiation as the X-ray source shows 2θ in the range of 24.9±0.2°, and Nb 10 Ti2O29 Peak A, which is assigned to the Nb-rich phase, appears within a 2θ range of 25.5±0.2°, and peak B, which is assigned to the Nb-rich phase, appears within a 2θ range of 23.7±0.2°. 10 Ti2O 29 and peak C assigned to the Fe-phase. The active material satisfies the peak intensity ratio represented by the following formula (1). 0 B / I A <5.0 (1) In formula (1), I A is the peak intensity of the peak A, and I B is the peak intensity of the peak B. The half width of the peak C is in the range of 0.15° to 0.80°.

[0020] The active material according to the embodiment may be a battery active material. The active material may be, for example, an electrode active material used in an electrode of a secondary battery such as a lithium ion battery or a non-aqueous electrolyte battery. The active material may be, for example, a negative electrode active material used in a negative electrode of the secondary battery.

[0021] Nb 10 Ti2O 29 Phase, Nb 14 TiO 37 Phase and Nb 24 TiO 64 The phase is explained below. 10 Ti2O 29 Phase, Nb 14 TiO 37 Phase and Nb 24 TiO 64 The crystal structure of the monoclinic Nb2TiO7 phase is similar to the crystal structure of niobium titanium composite oxide Nb2TiO7 having a monoclinic crystal structure shown in Figures 1 and 2. Here, the crystal structure of the monoclinic Nb2TiO7 phase will be described with reference to Figures 1 and 2.

[0022] The monoclinic Nb2TiO7 phase may have a crystal structure with space group C2 / m symmetry and atomic coordinates as set forth in Journal of Solid State Chemistry 53, pp144-147 (1984). 10 Ti2O​29 Phase, Nb 14 TiO 37 Phase and Nb 24 TiO 64 Each of the phases, like the Nb2TiO7 phase, may have the symmetry of space group C2 / m and a monoclinic crystal structure.

[0023] As shown in FIG. 1, in the crystal structure of monoclinic Nb2TiO7, metal ions 101 and oxide ions 102 constitute a skeletal structure portion 103. Nb ions and Ti ions are randomly arranged at the positions of the metal ions 101 in a ratio of Nb:Ti=2:1. These skeletal structure portions 103 are arranged alternately in a three-dimensional manner, so that void portions 104 exist between the skeletal structure portions 103. These void portions 104 act as hosts for lithium ions. Lithium ions can be inserted into this crystal structure in an amount of 0 moles to a maximum of 5.0 moles. Therefore, the composition when 0 to 5.0 moles of lithium ions are inserted is Li x It can be expressed as Nb2TiO7(0≦x≦5).

[0024] In FIG. 1, regions 105 and 106 are portions that have two-dimensional channels in the

[0100] and

[0010] directions. As shown in FIG. 2, the crystal structure of monoclinic Nb2TiO7 has a void portion 107 in the

[0001] direction. This void portion 107 has a tunnel structure that is favorable for the conduction of lithium ions, and serves as a conductive path in the

[0001] direction that connects regions 105 and 106. The existence of this conductive path enables lithium ions to travel between regions 105 and 106. In addition, the niobium titanium composite oxide has a low resistance of 1.5 V (vs. Li / Li + Therefore, an electrode containing the niobium titanium composite oxide as an active material can realize a battery capable of stable repeated rapid charging and discharging.

[0025] Furthermore, in the above crystal structure, when lithium ions are inserted into the voids 104, the metal ions 101 constituting the framework are reduced to trivalent, thereby maintaining the electrical neutrality of the crystal. In the niobium titanium composite oxide, not only are Ti ions reduced from tetravalent to trivalent, but Nb ions are reduced from pentavalent to trivalent. Therefore, the reduction valence per active material weight is large. Therefore, even if many lithium ions are inserted, it is possible to maintain the electrical neutrality of the crystal. Therefore, the energy density is higher than that of compounds such as titanium oxide that contain only tetravalent cations.

[0026] As mentioned above, the Nb2TiO7 phase has a high energy density and excellent input characteristics. On the other hand, the ion diffusion speed (output characteristics) when lithium ions are released from the crystal structure is insufficient.

[0027] In the case of using a niobium titanium composite oxide as an active material, the inventors have found that the Nb2TiO7 phase is insufficient in order to improve the output characteristics. 10 Ti2O 29 The Nb phase was adopted. 10 Ti2O 29 The Nb2TiO7 phase has more tunnel structures 107 in its structure than the Nb2TiO7 phase, and has a stable crystal structure due to its high low-temperature stability, so it has a higher lithium ion diffusion rate than the Nb2TiO7 phase. 10 Ti2O 29 By adopting this phase, the output characteristics are improved.

[0028] However, Nb 10 Ti2O 29 The lithium ion phase has a property that the lattice volume expands and contracts greatly when lithium ions are inserted and removed. When the crystal structure expands and contracts, cracks occur in the crystal, which in turn causes the particles themselves to break. When the particles themselves break, for example, the specific surface area increases, shortening the cycle life.

[0029] The present inventors have investigated the effect of suppressing cracking of primary particles by dispersing Nb 10Ti2O 29 Not only the phase, but also Nb 14 TiO 37 Phase and / or Nb 24 TiO 64 We succeeded in making the phases coexist. 14 TiO 37 Phase and / or Nb 24 TiO 64 The phase is Nb 10 Ti2O 29 In the present specification and claims, a niobium titanium composite oxide phase in which the Nb / Ti ratio in the crystal phase is greater than 5 is defined as an "Nb-rich phase." Nb 14 TiO 37 Phase and Nb 24 TiO 64 The primary particles according to the embodiment are all Nb rich phases. 10 Ti2O 29 The Nb-rich phase may be a mixture of the Nb-rich phase and the Nb-rich phase.

[0030] Nb 10 Ti2O 29 In primary particles containing a Nb-rich phase and a Nb-rich phase, the weak points of each crystal phase are dispersed within the active material particles. Therefore, even if a crack occurs in one of the crystal structures, the primary particle as a whole is unlikely to break. Therefore, the cycle life characteristics of the active material containing such primary particles are excellent.

[0031] It is generally known that when multiple types of crystal phases coexist in a primary particle, the diffusibility of lithium ions between these crystal phases decreases. However, the primary particles according to the present embodiment contain two types of crystal phases, i.e., Nb 10 Ti2O 29 Between the Nb-rich phase and the Nb-rich phase, the decrease in diffusivity of lithium ions can be suppressed for the following reason.

[0032] Here, for the sake of understanding, we use the term Nb 24 TiO 64 The phase is described as a typical crystal phase of Nb-rich phase. 10 Ti2O29 Phase and Nb 24 TiO 64 Each phase is formed by an arrangement of blocks containing 12 octahedra (NbO6) each consisting of one Nb atom and six oxygen atoms. The blocks are formed by the above octahedra in a 3x4 arrangement. Nb 10 Ti2O 29 The Nb phase has a structure in which only this block is arranged in a three-dimensional order. 24 TiO 64 In the Nb phase, multiple blocks are arranged in a three-dimensional order. 24 TiO 64 In the phase, NbO4 tetrahedrons are inserted between these blocks at regular intervals. 10 Ti2O 29 Phase and Nb 24 TiO 64 The phases are each mainly composed of blocks of the above octahedrons (NbO6) arranged in a 3 × 4 array. In other words, these crystal phases have similar structures that include a similar number of edge-sharing and corner-sharing, so that the movement of lithium is not easily hindered despite the presence of crystal boundaries, and the entire active material particle (primary particle) can be utilized during charging and discharging.

[0033] Nb 14 TiO 37 Phase also, Nb 24 TiO 64 The primary particles have a crystal structure similar to that of the Nb phase. 10 Ti2O 29 Phase and Nb 14 TiO 37 Phase and Nb 24 TiO 64 When at least one Nb-rich phase selected from the group consisting of Nb-rich phases is present, excellent input / output characteristics can be maintained.

[0034] In addition, Nb 10 Ti2O 29 Phase, Nb 14 TiO 37 Phase and Nb24 TiO 64 In the niobium titanium composite oxides consisting of the Nb2TiO7 phase, the edge sharing between the octahedra consisting of NbO6 is more than that in the Nb2TiO7 phase, which has a low niobium content. In this edge sharing, the amount of oxygen bonded to the metal ion is twice as much as in the case of apex sharing, in which metal ions are bonded to each other by one oxygen. Therefore, the bond is less likely to break during lithium insertion and desorption, and the crystal structure can be stably maintained during charge and discharge cycles. In addition, when there is a lot of edge sharing, the collapse of the crystal structure during charge and discharge, especially at high temperatures, can be suppressed. In other words, niobium titanium composite oxides with an Nb / Ti ratio of 5 or more are excellent not only in cycle life characteristics but also in high-temperature durability.

[0035] As described above, the active material (active material powder) according to the embodiment contains Nb 10 Ti2O 29 Since the primary particles contain a Nb-rich phase and a Nb-rich phase, excellent output characteristics and cycle life characteristics can be achieved.

[0036] In addition, Nb 10 Ti2O 29 When lithium ions are inserted into the phase, the composition is Li x Nb 10 Ti2O 29 (0≦x≦22). Nb 14 TiO 37 When lithium ions are inserted into the phase, the composition is Li x Nb 14 TiO 37 (0≦x≦29). Nb 24 TiO 64 When lithium ions are inserted into the phase, the composition is Li x Nb 24 TiO 64 It can be expressed as (0≦x≦49).

[0037] The active material according to the embodiment has a ratio M of the amount of niobium to the amount of titanium. Nb / M Ti But 5.0 <M Nb / M TiIn the present specification and claims, the term "M Nb " indicates the amount of niobium contained in the particle, and "M Ti " indicates the amount of titanium contained in the particle. Nb / M Ti The average particle diameter may be less than 24.0. <M Nb / M Ti ≦24.0, the primary particles contain Nb 10 Ti2O 29 Phase and Nb 14 TiO 37 Phase and Nb 24 TiO 64 It can be determined that at least one Nb-rich phase selected from the group consisting of Nb-rich phases coexists.

[0038] The active material according to the embodiment is 5.0 <M Nb / M Ti Whether or not the material contains primary particles that satisfy the condition ≦24.0 can be confirmed by scanning electron microscopy-energy dispersive X-ray spectroscopy (SEM-EDX) described later. By using SEM-EDX, the distribution of the crystal phase within each particle can be confirmed.

[0039] Ratio M within the primary particle Nb / M Ti By being within this range, Nb 10 Ti2O 29 It can be said that both the Nb-rich phase and the Nb-rich phase are present in sufficient amounts. Therefore, even if cracks occur in at least a part of the primary particles, the primary particles themselves are not likely to break. In other words, the specific surface area of ​​the active material can be prevented from increasing, thereby achieving excellent cycle life characteristics.

[0040] Ratio M within the primary particle Nb / M Ti When the value is less than 5.0, Nb 10 Ti2O29 The Nb-rich phase and the Nb-rich phase tend to be separated and difficult to exist. If the primary particles are composed of only a single crystal phase, weak parts of the crystal, such as corner-sharing parts, are aligned in one direction during lithium ion insertion and desorption associated with charging and discharging, and the particles are likely to crack along that direction. This is a factor that deteriorates the cycle life.

[0041] Ratio M within the primary particle Nb / M Ti If the cation exchange ratio exceeds 24.0, a titanium-free niobium oxide phase (Nb2O5) may be formed. The niobium oxide phase is undesirable because it has poor lithium ion conductivity and adversely affects battery performance.

[0042] Ratio M Nb / M Ti , 6.5≦M Nb / M Ti It is preferable that the ratio M satisfies ≦12.0. Nb / M Ti If is within this range, Nb 10 Ti2O 29 This includes cases where the ratio of Nb-rich phase to Nb-rich phase is 1:1. 10 Ti2O 29 Phase and Nb 24 TiO 64 The ratio of the phase to the 1:1 phase is M Nb / M Ti is 14.5, and Nb 10 Ti2O 29 Phase and Nb 14 TiO 37 The ratio of the phase to the 1:1 phase is M Nb / M Ti In the primary particles, Nb 10 Ti2O 29 When the ratio of the Nb-rich phase to the Nb-rich phase is 1:1 or close to that ratio, the crystal phases tend to be uniformly separated. Therefore, the effect of easily suppressing particle cracking is obtained. In other words, excellent cycle life characteristics can be achieved.

[0043] In the embodiment, each primary particle contained in the active material preferably has a composition close to the overall Nb / Ti ratio. The overall Nb / Ti ratio is the peak intensity ratio I B / I A The abundance ratio of Nb atoms and Ti atoms can be calculated from the ratio M Nb / M Ti The active material (active material powder) according to the embodiment may be Nb 10 Ti2O 29 In addition to the primary particles that are a mixture of Nb phase and Nb-rich phase, 10 Ti2O 29 It may further contain primary particles consisting of a single Nb-rich phase and / or primary particles consisting of a single Nb-rich phase.

[0044] Furthermore, the active material according to this embodiment satisfies the peak intensity ratio represented by the following formula (1). 0 B / I A <5.0 (1) In formula (1), I A In the diffraction chart by the wide-angle X-ray diffraction method using CuKα radiation as the X-ray source, 2θ appears within the range of 24.9±0.2°, and Nb 10 Ti2O 29 is the peak intensity of the peak assigned to the I phase. B is the peak intensity of a peak that appears within the range of 2θ of 25.5±0.2° in the diffraction chart and is attributed to the Nb-rich phase. The method for carrying out the wide-angle X-ray diffraction method will be described later.

[0045] Peak Intensity I A is Nb 10 Ti2O 29 Peak intensity I is the peak intensity (peak height) of peak A assigned to the phase. Peak A is the peak having the maximum peak intensity within the range of 2θ of 24.9±0.2°. A The larger the Nb content of the entire active material, the 10 Ti2O 29 This means that the weight of the phase is large.

[0046] ​Peak Intensity I B is Nb 14 TiO 37 Phase and Nb 24 TiO 64 Peak intensity I is the peak intensity (peak height) of peak B which is attributed to at least one Nb-rich phase selected from the group consisting of Nb-rich phases. This peak B is a peak having the maximum peak intensity within the range of 2θ of 25.5±0.2°. B A larger value means that the weight of the Nb-rich phase in the entire active material is large.

[0047] The active material is Nb 10 Ti2O 29 In addition to the Nb-rich phase, the peak intensity ratio I B / I A As mentioned above, by increasing the Nb-rich phase in an amount greater than 0, the cycle life characteristics are improved. However, if the Nb-rich phase is increased without limit, the cycle life characteristics are not improved by the amount of increase. This is because B / I A If the peak intensity ratio (I B / I A ) is less than or equal to 5.0.

[0048] Peak intensity ratio I B / I A is preferably 0.01 or more and 1.20 or less, and more preferably 0.01 or more and 0.80 or less. B / I A When the peak intensity ratio I is 1.20 or less, the generation of the niobium oxide phase tends to be sufficiently suppressed. Therefore, when this is satisfied, both the output characteristics and the cycle life characteristics are excellent. B / I A may be in the range of 0.10 or more and 0.80 or less, or in the range of 0.30 or more and 0.80 or less.

[0049] Furthermore, the diffraction chart of the active material according to the embodiment by a wide-angle X-ray diffraction method using CuKα radiation as an X-ray source shows that Nb 10 Ti2O 29 The peak C is assigned to the SiO2 phase and appears within a 2θ range of 23.7±0.2°. The half-width of the peak C is within a range of 0.15° to 0.80°.

[0050] The half-width of peak C is Nb 10 Ti2O 29 The half-width is the width of a peak at half the maximum intensity. The peak intensity of peak C is the peak intensity I C Also called.

[0051] If the half-width of peak C is 0.15° or more, Nb 10 Ti2O 29 This means that the crystals of the Nb phase are small enough. 10 Ti2O 29 Since the crystals of the phase are small and dispersed within the active material particles, particle cracking is suppressed. If the half-width of peak C is less than 0.15°, that is, if peak C is sharp, the crystals are too large and particle cracking is induced, which is not preferable. On the other hand, if the half-width of peak C exceeds 0.80°, the crystals are too small and the crystal arrangement is disturbed, which may inhibit the movement of lithium ions. It is more preferable that the half-width of peak C is in the range of 0.20° to 0.45°.

[0052] As described above, the active material according to the embodiment is Nb 10 Ti2O 29 Phase and Nb 14 TiO 37 Phase and Nb 24 TiO 64 and at least one Nb-rich phase selected from the group consisting of Nb-rich phases, and a ratio M of the amount of niobium to the amount of titanium. Nb / M Ti is 5.0 <M Nb / M Ti In addition, the X-ray diffraction of this active material shows that the peak intensity ratio IB / I A is in the range of 0 to 5.0. 10 Ti2O 29 The half width of peak C assigned to the phase is in the range of 0.15° to 0.80°. Therefore, the active material can realize a secondary battery capable of exhibiting excellent output characteristics and cycle life characteristics.

[0053] It is preferable that the active material according to this embodiment further satisfies the peak intensity ratio represented by the following formula (2). 0≦I D / I A <0.01 (2) In formula (2), I A In the diffraction chart by the wide-angle X-ray diffraction method using CuKα radiation as the X-ray source, 2θ appears within the range of 24.9±0.2°, and Nb 10 Ti2O 29 is the peak intensity of peak A assigned to the I phase. D is the peak intensity of peak D, which appears within the 2θ range of 20.1±0.2° in the diffraction chart and is assigned to the Nb2TiO7 phase.

[0054] Peak Intensity I A As mentioned above, Nb 10 Ti2O 29 is the peak intensity (peak height) of peak A assigned to the phase.

[0055] Peak Intensity I D is the peak intensity (peak height) of peak D, which is attributed to the Nb2TiO7 phase. This peak D is the peak that has the maximum peak intensity within the 2θ range of 20.1±0.2°. D A large value means that the weight of the Nb2TiO7 phase in the entire active material is large.

[0056] As mentioned above, Nb 10 Ti2O 29 Phase, Nb 14 TiO 37 Phase and Nb 24 TiO 64The Nb2TiO7 phase contains many edge-sharing octahedra made of NbO6 in the crystal structure constituting them. Therefore, the active material according to the embodiment shows excellent cycle life characteristics. On the other hand, since the Nb2TiO7 phase has few edge-sharing, the bonds are easily broken during insertion and desorption of lithium ions. Therefore, it is preferable that the active material according to the embodiment does not contain the Nb2TiO7 phase. Specifically, as described above, when the active material satisfies the formula (2), the active material contains little or no Nb2TiO7 phase. As is clear from the formula (2), the diffraction chart may not have peak D. It is preferable that the diffraction chart does not have peak D.

[0057] The active material according to the embodiment may contain one or more additive elements selected from the group consisting of Ta, K, and P. The total amount of additive elements contained in the active material is preferably 5000 ppm or less in molar ratio relative to the niobium titanium composite oxide. A more preferred amount is in the range of 200 ppm or more and 3000 ppm or less. When the active material contains Ta, the stability of the crystal can be improved. When the active material contains at least one element selected from the group consisting of K and P, the melting point can be lowered and the crystallinity can be improved.

[0058] Whether or not the active material contains an additive element can be confirmed by inductively coupled plasma atomic emission spectroscopy (ICP analysis).

[0059] First, an active material from which Li has been completely removed is prepared using the procedure described in the explanation of the powder X-ray diffraction method below. This is subjected to vacuum drying at a temperature of 140°C for 24 hours. Next, the total weight of this active material is measured in a dry atmosphere. This is dissolved in acid and subjected to inductively coupled plasma atomic emission spectroscopy (ICP analysis). ICP allows the type and concentration of added elements contained in the active material to be measured.

[0060] Next, the form, particle size, and specific surface area of the active material according to the embodiment will be described.

[0061] <Form> The form of the active material (niobium-titanium composite oxide) according to the embodiment is not particularly limited. The niobium-titanium composite oxide can take, for example, the form of primary particles or the form of secondary particles formed by aggregation of primary particles. The particles of the niobium-titanium composite oxide may be a mixture of primary particles and secondary particles. Nb 10 Ti2O 29 Primary particles containing a Ti2O phase and an Nb-rich phase can constitute the niobium-titanium composite oxide.

[0062] The particles of the niobium-titanium composite oxide may have a carbon-containing layer on the surface. The carbon-containing layer may adhere to the surface of the primary particles or the surface of the secondary particles. Alternatively, the particles of the niobium-titanium composite oxide may include secondary particles formed by aggregation of primary particles with a carbon-containing layer adhered to the surface. Since carbon exists between such primary particles, such secondary particles can exhibit excellent conductivity. An embodiment including such secondary particles is preferable because the active material-containing layer can exhibit lower resistance.

[0063] <Particle size> The average particle size of the active material particles, which are primary particles or secondary particles of the niobium-titanium composite oxide, is not particularly limited. The average particle size of the active material particles is, for example, in the range of 0.1 μm to 50 μm. The average particle size can be changed according to the required battery characteristics. For example, in order to enhance the rapid charge and discharge performance, it is preferable to set the average particle size to 1.0 μm or less. By doing so, the diffusion distance of lithium ions in the crystal can be reduced, so that the rapid charge and discharge performance can be enhanced. The average particle size can be determined, for example, by the laser diffraction method.

[0064] <BET specific surface area> The BET (Brunauer, Emmett, Teller) specific surface area of ​​the active material according to the embodiment is not particularly limited. However, the BET specific surface area is preferably within 5 m 2 / g or more, 200m 2 It is preferable that the molecular weight is less than 1 / g.

[0065] 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, good discharge rate characteristics can be easily obtained, and the charging time can be shortened. 2 When the molecular weight is less than 1 / g, the reactivity with the electrolyte is not too high, and the life characteristics can be improved. In addition, the coating property of a slurry containing an active material used in the production of an electrode, which will be described later, can be improved.

[0066] Here, the specific surface area is measured by adsorbing molecules with known adsorption occupancy areas onto the powder particle surfaces at liquid nitrogen temperature, and then calculating the specific surface area of ​​the sample from the amount of adsorption. The most commonly used method is the BET method, which uses low-temperature, low-humidity physical adsorption of an inert gas. This is the most famous 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 calculated in this way is called the BET specific surface area.

[0067] <Manufacturing method> The active material according to the embodiment can be produced by the first or second synthesis method described below. Both the first and second synthesis methods are solid-phase synthesis methods.

[0068] (First synthesis method) The first synthesis method is Nb 10 Ti2O 29 Single-phase primary particles and Nb 14 TiO 37 Single-phase primary particles and / or Nb 24 TiO 64 In this method, single-phase primary particles are produced, the particles are appropriately mixed and crushed, and then sintered at a low temperature.

[0069] The mixing ratio of each particle is such that the total Nb / Ti ratio (molar ratio) is in the range of more than 5.0 and 24.0 or less. If the Nb / Ti ratio at the time of mixing is 5.0 or less, In other words, a solid solution is formed in the primary particles. 10 Ti2O 29 In this case, no separation occurs between the I phase and the Nb-rich phase. B / I A will be 0.

[0070] Primary particles of each single crystal phase can be synthesized as follows. First, starting materials Nb2O5 particles and TiO2 particles are mixed in the Nb / Ti ratio of the target phase. This mixture is mixed in a ball mill for 1 to 10 hours, and then fired at a temperature of 900°C to 1400°C for 1 to 12 hours to obtain active material particles consisting of the target single crystal phase.

[0071] Nb 10 Ti2O 29 Single-phase primary particles and Nb 14 TiO 37 Single-phase primary particles and / or Nb 24 TiO 64 After producing the single-phase primary particles, as described above, they are mixed in a weight ratio such that the total Nb / Ti ratio is in the range of more than 5.0 and not more than 24.0. The resulting mixture is then sufficiently crushed and mixed, and then fired at a temperature of 700°C to 1000°C for 15 minutes to 2 hours. In this manner, the active material according to the embodiment can be produced.

[0072] (Second synthesis method) The second synthesis method is a method in which a titanium source and a niobium source are mixed as starting materials so that the molar ratio of niobium to titanium, Nb / Ti, is greater than 5.0 and not greater than 24.0, and then calcined.

[0073] First, the starting materials, Nb2O5 particles and TiO2 particles, are mixed. At this time, the starting materials are mixed so that the molar ratio of the starting materials is a desired Nb / Ti ratio, for example, Nb2O5:TiO2=2.5-12.0:1. If the molar ratio of the starting materials is within this range, a Nb-rich phase is stably formed.

[0074] In order to make the final active material particles (primary particles) less likely to break, as mentioned above, it is advantageous that the crystals constituting the primary particles are not arranged adjacent to each other. In order to produce such primary particles, it is necessary that the microcrystals constituting each crystal phase are not localized but are dispersed within the particles. In other words, it is preferable to grind the raw material particles to have an average particle size of a certain amount or less. By making the raw material particles into microcrystals, the half-width of the above peak C tends to become larger.

[0075] Specifically, when Nb2O5 particles are used as the niobium source, it is preferable to adjust the average particle size of the Nb2O5 particles to within the range of 0.05 μm to 0.6 μm. When TiO2 particles are used as the titanium source, it is preferable to adjust the average particle size of the TiO2 particles to within the range of 0.01 μm to 0.4 μm. Here, the average particle size refers to the particle size at 50% volume frequency (D50). D50 can be measured by a laser diffraction scattering type particle size distribution measuring device. By microparticulating the raw material particles, Nb 10 Ti2O 29 The Nb-rich phase and the Nb-rich phase tend to be sufficiently dispersed.

[0076] In order to suppress the appearance of the Nb2TiO7 phase, which contains a large amount of titanium, it is preferable to make the average particle size of the TiO2 particles smaller than the average particle size of the Nb2O5 particles.

[0077] Next, when synthesizing an active material by the solid phase method, first, the mixture of raw materials is mixed in a ball mill for 1 to 10 hours. Then, pre-firing (first firing) is performed before the main firing. Pre-firing is preferably performed at a temperature of 600°C to 1100°C for 1 to 12 hours. By performing pre-firing, it is possible to remove a small amount of impurity components (e.g., water, organic matter, etc.) adsorbed to the raw material powder. Pre-firing may be omitted.

[0078] The main firing (second firing) is preferably performed at a temperature of 900° C. to 1200° C. for 1 hour to 10 hours, and more preferably at a temperature of 950° C. to 1050° C. for 2.5 hours to 3.5 hours. By setting the firing temperature in the range of 900 to 1200° C. to suppress the reaction between Nb and Ti, it is possible to produce mixed-phase active material particles that satisfy the peak intensity ratio represented by the following formula (1).

[0079] 0 B / I A <5.0 (1) In formula (1), I A In the diffraction chart by the wide-angle X-ray diffraction method using CuKα radiation as the X-ray source, 2θ appears within the range of 24.9±0.2°, and Nb 10 Ti2O 29 is the peak intensity of the peak assigned to the I phase. B is the peak intensity of a peak which appears within the range of 2θ of 25.5±0.2° in the diffraction chart and which is attributed to the Nb-rich phase.

[0080] When mixing the raw materials, an oxide containing at least one selected from the group consisting of Si, Na, K, and P may be added. These elements have the effect of improving the bonding between the crystalline phases dispersed in the active material particles and promoting lithium conduction.

[0081] ​If the sintering is performed at a temperature lower than 900°C, the reaction between Nb and Ti will not proceed easily, and the raw material oxide will remain, which may result in the inclusion of the Nb2TiO7 phase, which has a low niobium content. Also, if the sintering is performed at a temperature higher than 1200°C, the diffusion of Nb and Ti elements will proceed quickly, which will tend to result in a material with a homogeneous composition, and Nb will remain in the primary particles. 10 Ti2O 29 It becomes difficult to form a mixed phase of the Nb-rich phase and the Nb-rich phase.

[0082] Annealing may be performed after the firing. The temperature for the annealing is preferably 350°C to 800°C. By performing annealing in this temperature range, the distortion within the crystals can be alleviated and the interpenetrating parts of the crystal lattice between different crystal phases can be stabilized.

[0083] <Powder X-ray diffraction measurement and peak intensity ratio of active materials I B / I A Calculation of > The powder X-ray diffraction measurement of the active material according to the embodiment can be carried out, for example, as follows. First, the target sample is crushed until the average particle size is about 5 μm. The crushed sample is filled into the holder portion formed on the glass sample plate, with a depth of 0.2 mm. At this time, care is taken to ensure that the sample is filled sufficiently into the holder portion. Also, care is taken to fill the sample with just the right amount so that cracks, voids, etc. do not occur. Next, another glass plate is pressed from the outside to flatten the surface of the sample filled into the holder portion. Care is taken to ensure that the amount of filling is not too much or too little, resulting in unevenness compared to the reference surface of the holder.

[0084] Next, the glass plate filled with the sample is placed in a powder X-ray diffractometer, and a diffraction pattern (XRD pattern; X-Ray Diffraction pattern) is obtained using Cu-Kα radiation.

[0085] In addition, the orientation of the particles may become large depending on the particle shape of the sample. When the orientation of the sample is high, the peak position may shift or the intensity ratio may change depending on how the sample is filled. Samples with extremely high orientation are measured using a glass capillary. Specifically, the sample is inserted into a capillary, and the capillary is placed on a rotating sample stage for measurement. This measurement method can reduce the orientation. As the glass capillary, it is preferable to use a Lindemann glass capillary with a diameter of 1 mm to 6 mmφ.

[0086] When performing powder X-ray diffraction measurement on the active material contained in the electrode, the measurement can be carried out, for example, as follows. First, in order to grasp the crystalline state of the active material, the active material is placed in a state in which lithium ions are completely removed. For example, when the active material is used in a negative electrode, the battery is placed in a completely discharged state. For example, the battery is discharged at a current of 0.1 C in a 25° C. environment until the rated end voltage or the battery voltage reaches 1.0 V, and the current value during discharge is set to 1 / 100 or less of the rated capacity, thereby placing the battery in a discharged state. Residual lithium ions may still be present even in the discharged state.

[0087] Next, the battery is disassembled in a glove box filled with argon, and the electrodes are removed and washed with a suitable solvent. An example of a suitable solvent is ethyl methyl carbonate. If the electrodes are not sufficiently washed, lithium ions remaining in the electrodes may cause impurity phases such as lithium carbonate and lithium fluoride to be mixed in. In that case, it is recommended to use an airtight container in which the measurement atmosphere can be in an inert gas. The washed electrodes are cut to have an area approximately the same as the area of ​​the holder of the powder X-ray diffraction apparatus to prepare the measurement sample. This sample is directly attached to the glass holder and the measurement is performed.

[0088] At this time, the peaks originating from the metal foil, conductive agent, binder, etc., which is the current collector, are measured and understood in advance using XRD. Of course, if these are known in advance, this operation can be omitted. When the peak of the current collector and the peak of the active material overlap, it is desirable to peel off the active material-containing layer from the current collector and measure it. This is to separate the overlapping peaks when quantitatively measuring the peak intensity. The active material-containing layer may be physically peeled off, but it is easier to peel off by applying ultrasonic waves in a solvent. When ultrasonic treatment is performed to peel off the active material-containing layer from the current collector, the electrode body powder (including the active material, conductive agent, and binder) can be recovered by volatilizing the solvent. The recovered electrode body powder can be filled in, for example, a Lindemann glass capillary and measured to perform powder X-ray diffraction measurement of the active material. The electrode body powder recovered by ultrasonic treatment can also be subjected to various analyses other than powder X-ray diffraction measurement.

[0089] As an apparatus for powder X-ray diffraction measurement, for example, SmartLab manufactured by Rigaku Co., Ltd. is used. The measurement conditions are as follows: X-ray source: Cu target Output: 45kV, 200mA Soller slit: 5° for both incidence and reception Step width (2θ): 0.01 deg Scan speed: 2deg / min Semiconductor detector: D / teX Ultra 250 Sample plate holder: Flat glass sample plate holder (thickness 0.5 mm) Measurement range: 5°≦2θ≦90°.

[0090] When using other equipment, perform measurements using standard Si powder for powder X-ray diffraction to find conditions that give measurement results for peak intensity, half-width, and diffraction angle equivalent to those obtained by the above equipment, and then measure the sample under those conditions.

[0091] In addition, in the obtained diffraction chart, Nb having a maximum peak intensity within the range of 2θ of 24.9±0.2° is 10 Ti2O29 Peak intensity of peak A assigned to phase I A In addition, Nb having a maximum peak intensity within the range of 2θ of 25.5±0.2° in the diffraction chart is determined. 14 TiO 37 Phase and Nb 24 TiO 64 Peak intensity I of peak B assigned to at least one Nb-rich phase selected from the group consisting of Nb-rich phases B Then, the peak intensity ratio I B / I A Calculate.

[0092] Scanning electron microscopy-energy dispersive X-ray spectroscopy Nb / M Ti Measurement> Observation using a scanning electron microscope-energy dispersive X-ray spectroscopy (SEM-EDX) revealed that, for example, M Nb / M Ti The ratio can be measured.

[0093] Measurement by SEM-EDX Nb / M Ti The ratio can be measured, for example, as follows. First, the target sample is crushed until the average particle size is about 5 μm. The crushed sample is fixed on a sample stage using carbon tape or the like. In this case, the fixing equipment and sample stage should be free of niobium and titanium.

[0094] Next, the sample stage is introduced into a SEM (Scanning Electron Microscope) and measurements are performed under vacuum. The measurement is performed by specifying the entire active material particle as the measurement range and measuring the average M Nb / M Ti Alternatively, by narrowing the measurement range, the M Nb / M TiThe ratio can be measured.

[0095] The accelerating voltage for the measurement was M Nb / M Ti In order to properly evaluate the ratio, it is desirable to use at least 5 kV or more, and measurement can be performed at, for example, 15 kV.

[0096] When performing SEM-EDX on the active material contained in the electrode, it can be carried out, for example, as follows. First, a cleaned electrode is prepared in the same manner as described in the powder X-ray diffraction measurement above. This is attached to the SEM sample stage to prepare a measurement sample.

[0097] At this time, in order to measure the active material particles, the shapes of the conductive agent and binder, etc. are measured and understood in advance using an SEM. Of course, if these are known in advance, this operation can be omitted. It is effective to use the mapping function of the energy dispersive X-ray spectroscopy analysis to compare titanium and niobium with the part that does not contain them. It is preferable to measure only the active material particles, but even if a small amount of conductive agent and binder are attached to the particles, the measured M Nb / M Ti It does not significantly affect the ratio, so it is measurable.

[0098] According to a first embodiment, an active material is provided. The active material comprises Nb 10 Ti2O 29 Phase and Nb 14 TiO 37 Phase and Nb 24 TiO 64 and at least one Nb-rich phase selected from the group consisting of Nb-rich phases. In the primary particles, the ratio M of the amount of substance of niobium to the amount of substance of titanium is Nb / M Ti is 5.0 <M Nb / M Ti ≦24.0. The diffraction chart of the active material by wide-angle X-ray diffraction method using CuKα radiation as the X-ray source shows 2θ in the range of 24.9±0.2°, and Nb 10Ti2O 29 Peak A, which is assigned to the Nb-rich phase, appears within a 2θ range of 25.5±0.2°, and peak B, which is assigned to the Nb-rich phase, appears within a 2θ range of 23.7±0.2°. 10 Ti2O 29 and peak C assigned to the Fe-phase. The active material satisfies the peak intensity ratio represented by the following formula (1). 0 B / I A <5.0 (1) In formula (1), I A is the peak intensity of the peak A, and I B is the peak intensity of the peak B. The half width of the peak C is in the range of 0.15° to 0.80°.

[0099] This active material can realize a secondary battery that can exhibit excellent output characteristics and cycle life characteristics.

[0100] Second embodiment According to a second embodiment, an electrode is provided.

[0101] The electrode according to the second embodiment includes the active material according to the first embodiment. This electrode can be a battery electrode that includes the active material according to the first embodiment as a battery active material. The electrode as a battery electrode can be, for example, a negative electrode that includes the active material according to the first embodiment as a negative electrode active material.

[0102] The electrode according to the second embodiment 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, and optionally a conductive agent and a binder.

[0103] The active material-containing layer may contain the active material according to the first embodiment alone, or may contain two or more types of the active material according to the first embodiment. Furthermore, it may contain a mixture of one or more types of the active material according to the first embodiment and one or more types of other active materials. The active material according to the first embodiment may be a niobium titanium composite oxide.

[0104] ​ For example, when the active material according to the first embodiment is contained as a negative electrode active material, examples of other active materials include lithium titanate having a ramsdellite structure (e.g., Li 2+y Ti3O7, 0≦y≦3), lithium titanates with spinel structure (e.g., Li 4+x Ti5O 12 , 0≦x≦3), monoclinic titanium dioxide (TiO2), anatase titanium dioxide, rutile titanium dioxide, hollandite titanium composite oxide, and orthorhombic titanium-containing composite oxide.

[0105] As an example of an orthorhombic titanium-containing composite oxide, Li 2+a M(I) 2-b Ti 6-c M(II) d O 14+σ Here, M(I) is at least one selected from the group consisting of Sr, Ba, Ca, Mg, Na, Cs, Rb, and K. M(II) is 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).

[0106] The conductive agent is blended to improve the current collecting performance and to reduce the contact resistance between the active material and the current collector. Examples of the conductive agent include vapor grown carbon fiber (VGCF), carbon black such as acetylene black, and carbonaceous 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. Alternatively, instead of using a conductive agent, a carbon coating or an electronically conductive inorganic material coating may be applied to the surface of the active material particles.

[0107] The binder is blended to fill the gaps between the dispersed active materials and to bind the active materials and the current collector. Examples of the binder include polytetrafluoroethylene (PTFE), polyvinylidene fluoride (PVdF), fluorine-based rubber, styrene butadiene 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 may be used in combination as the binder.

[0108] The mixing ratio of the active material, 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 a negative electrode of a secondary battery, it is preferable to mix the active material (negative electrode active material), conductive agent and binder at a ratio of 68% by mass or more and 96% by mass or less, 2% by mass or more and 30% by mass or less, and 2% by mass or more and 30% by mass or less, respectively. By making the amount of the conductive agent 2% by mass or more, the current collection performance of the active material-containing layer can be improved. In addition, by making the amount of the binder 2% by mass or more, the binding property between the active material-containing layer and the current collector becomes sufficient, and excellent cycle performance can be expected. On the other hand, it is preferable to make the conductive agent and the binder 30% by mass or less, respectively, in order to increase the capacity.

[0109] The current collector is made of a material that is electrochemically stable at the potential at which lithium (Li) is inserted and removed 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, or aluminum, or an aluminum alloy containing one or more elements selected from Mg, Ti, Zn, Mn, Fe, Cu, and Si. 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.

[0110] 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.

[0111] The electrode can be produced, for example, by the following method. First, an active material, a conductive agent, and a binder are suspended in a solvent to prepare a slurry. This slurry is applied to one or both sides of 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, the laminate is pressed. In this manner, an electrode is produced.

[0112] Alternatively, the electrode may be prepared by the following method: first, the active material, the conductive agent, and the binder are mixed to obtain a mixture, then the mixture is formed into pellets, and then the pellets are placed on a current collector to obtain an electrode.

[0113] The electrode according to the second embodiment includes the active material according to the first embodiment, and therefore this electrode can realize a secondary battery that can exhibit excellent output characteristics and cycle life characteristics.

[0114] Third embodiment According to the third embodiment, a secondary battery including a negative electrode, a positive electrode, and an electrolyte is provided. This secondary battery includes the electrode according to the second embodiment as the negative electrode. That is, the secondary battery according to the third embodiment includes an electrode including the active material according to the first embodiment as a battery active material as the negative electrode.

[0115] The secondary battery according to the third embodiment 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 group. The electrolyte may be held in the electrode group.

[0116] Moreover, the secondary battery according to the third embodiment may further include an exterior member that houses the electrode group and the electrolyte.

[0117] Furthermore, the secondary battery according to the third embodiment may further include a negative electrode terminal electrically connected to the negative electrode and a positive electrode terminal electrically connected to the positive electrode.

[0118] The secondary battery according to the third embodiment may be, for example, a lithium ion secondary battery. The secondary battery includes a non-aqueous electrolyte secondary battery that contains a non-aqueous electrolyte.

[0119] The negative electrode, the positive electrode, the electrolyte, the separator, the exterior member, the negative electrode terminal, and the positive electrode terminal will be described in detail below.

[0120] (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 that can be included in the electrode according to the second embodiment, respectively. The negative electrode active material-containing layer includes the active material according to the first embodiment as a negative electrode active material.

[0121] Among the details of the negative electrode, parts that overlap with the details explained in the second embodiment will be omitted.

[0122] The density of the negative electrode active material-containing layer (excluding the current collector) is 1.8 g / cm 3 More than 3.5g / cm 3 The density of the negative electrode active material-containing layer is preferably 2.5 g / cm or less. A negative electrode having a density in this range of the negative electrode active material-containing layer is excellent in energy density and electrolyte retention. 3 More than 2.9g / cm 3 It is more preferable that:

[0123] The negative electrode can be produced, for example, by the same method as that for the electrode according to the second embodiment.

[0124] (2) Positive electrode The positive electrode may include a positive electrode current collector and a positive electrode active material-containing layer. The positive electrode active material-containing layer may be formed on one or both sides of the positive electrode current collector. The positive electrode active material-containing layer may include a positive electrode active material, and optionally a conductive agent and a binder.

[0125] As the positive electrode active material, for example, an oxide or a sulfide can be used. The positive electrode may contain, as the positive electrode active material, one type of compound alone, or may contain a combination of two or more types of compounds. Examples of the oxide and the sulfide include compounds into which Li or Li ions can be inserted and desorbed.

[0126] Examples of such compounds include manganese dioxide (MnO2), iron oxide, copper oxide, nickel oxide, lithium manganese composite oxide (for example, Li x Mn2O4 or Li x MnO2; 0 < x ≦ 1), lithium nickel composite oxide (for example, Li x NiO2; 0 < x ≦ 1), lithium cobalt composite oxide (for example, Li x CoO2; 0 < x ≦ 1), lithium nickel cobalt composite oxide (for example, Li x Ni 1-y Co y O2; 0 < x ≦ 1, 0 < y < 1), lithium manganese cobalt composite oxide (for example, Li x Mn y Co 1-y O2; 0 < x ≦ 1, 0 < y < 1), lithium manganese nickel composite oxide having a spinel structure (for example, Li x Mn 2-y Ni y O4; 0 < x ≦ 1, 0 < y < 2), lithium phosphate having an olivine structure (for example, 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 (for example, 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.

[0127] Among the above, examples of more preferable compounds as the positive electrode active material include lithium manganese composite oxides having a spinel structure (for example, Li x Mn2O4; 0 < x ≦ 1), lithium nickel composite oxides (for example, Li x NiO2; 0 < x ≦ 1), lithium cobalt composite oxides (for example, Li x CoO2; 0 < x ≦ 1), lithium nickel cobalt composite oxides (for example, Li x Ni 1-y Co y O2; 0 < x ≦ 1, 0 < y < 1), lithium manganese nickel composite oxides having a spinel structure (for example, Li x Mn 2-y Ni y O4; 0 < x ≦ 1, 0 < y < 2), lithium manganese cobalt composite oxides (for example, Li x Mn y Co 1-y O2; 0 < x ≦ 1, 0 < y < 1), lithium iron phosphate (for example, Li x FePO4; 0 < x ≦ 1), and lithium nickel cobalt manganese composite oxides (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.

[0128] When a room temperature molten salt is used as the electrolyte of the battery, it is preferable to use a positive electrode active material containing lithium iron phosphate, Li x VPO4F (0 ≦ x ≦ 1), a lithium manganese composite oxide, a lithium nickel composite oxide, a lithium nickel cobalt composite oxide, or a mixture thereof. Since these compounds have low reactivity with the room temperature molten salt, the cycle life can be improved. Details of the room temperature molten salt will be described later.

[0129] The 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 a primary particle size of 100 nm or more is easy to handle in industrial production. A positive electrode active material with a primary particle size of 1 μm or less can smoothly diffuse lithium ions in the solid.

[0130] The specific surface area of ​​the positive electrode active material is 0.1 m 2 / g or more 10m 2 / g or less. 2 A positive electrode active material having 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 ​​100 / g or less is easy to handle in industrial production and can ensure good charge-discharge cycle performance.

[0131] The binder is blended to fill the gaps between the dispersed positive electrode active material 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-based 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 may be used in combination as the binder.

[0132] 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 the conductive agent 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 combined and used as the conductive agent. The conductive agent may also be omitted.

[0133] In the positive electrode active material-containing layer, the positive electrode active material and the binder are preferably mixed in proportions of 80% by mass to 98% by mass and 2% by mass to 20% by mass, respectively.

[0134] By making the amount of binder 2% by mass or more, sufficient electrode strength can be obtained. In addition, the binder can function as an insulator. Therefore, by making the amount of binder 20% by mass or less, the amount of insulator contained in the electrode is reduced, and the internal resistance can be reduced.

[0135] When a conductive agent is added, the positive electrode active material, the binder, and the conductive agent are preferably mixed in proportions of 77% by mass or more and 95% by mass or less, 2% by mass or more and 20% by mass or less, and 3% by mass or more and 15% by mass or less, respectively.

[0136] By setting the amount of the conductive agent to 3% by mass or more, the above-mentioned effects can be achieved. Also, by setting the amount of the conductive agent to 15% by mass or less, the ratio of the conductive agent in contact with the electrolyte can be reduced. If this ratio is low, decomposition of the electrolyte during high-temperature storage can be reduced.

[0137] 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.

[0138] The thickness of the aluminum foil or aluminum alloy foil is preferably 5 μm or more and 20 μm or less, more preferably 15 μm or less. The purity of the aluminum foil is preferably 99 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 mass% or less.

[0139] 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.

[0140] The positive electrode can be produced, for example, by using a positive electrode active material in the same manner as in the electrode according to the second embodiment.

[0141] (3) Electrolyte 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.

[0142] Examples of the electrolyte salt include lithium salts such as lithium perchlorate (LiClO4), lithium hexafluorophosphate (LiPF6), lithium tetrafluoroborate (LiBF4), lithium hexafluoroarsenate (LiAsF6), lithium trifluoromethanesulfonate (LiCF3SO3), and lithium bistrifluoromethylsulfonylimide (LiN(CF3SO2)2), and mixtures thereof. The electrolyte salt is preferably one that is difficult to oxidize even at high potentials, and LiPF6 is most preferred.

[0143] Examples of organic solvents include cyclic carbonates such as propylene carbonate (PC), ethylene carbonate (EC), and vinylene carbonate (VC); chain 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); chain ethers such as dimethoxyethane (DME) and diethoxyethane (DEE); γ-butyrolactone (GBL), acetonitrile (AN), and sulfolane (SL). These organic solvents can be used alone or as a mixed solvent.

[0144] The gelled 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.

[0145] Alternatively, as the nonaqueous electrolyte, 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.

[0146] 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 by themselves, 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. In general, the melting point of room temperature molten salts used in secondary batteries is 25°C or lower. In addition, organic cations generally have a quaternary ammonium skeleton.

[0147] The polymer solid electrolyte is prepared by dissolving an electrolyte salt in a polymer material and solidifying it.

[0148] The inorganic solid electrolyte is a solid material that has Li-ion conductivity.

[0149] (4) Separator The separator is formed, for example, from a porous film containing polyethylene (PE), polypropylene (PP), cellulose, or polyvinylidene fluoride (PVdF), or a synthetic resin nonwoven fabric. From the viewpoint of safety, it is preferable to use a porous film formed from polyethylene or polypropylene. This is because these porous films melt at a certain temperature and are capable of cutting off electric current.

[0150] (5) Exterior materials As the exterior member, for example, a container made of a laminate film or a metal container can be used.

[0151] The thickness of the laminate film is, for example, 0.5 mm or less, preferably 0.2 mm or less.

[0152] The laminate film is a multi-layer film including a plurality of resin layers and a metal layer interposed between the resin layers. The resin layers include polymeric materials such as polypropylene (PP), polyethylene (PE), nylon, and polyethylene terephthalate (PET). The metal layer is preferably made of aluminum foil or aluminum alloy foil for weight reduction. The laminate film can be molded into the shape of the exterior member by sealing it by heat fusion.

[0153] 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.

[0154] The metal container is made of, for example, aluminum or an aluminum alloy. The aluminum alloy preferably contains elements such as magnesium, zinc, and silicon. When the aluminum alloy contains transition metals such as iron, copper, nickel, and chromium, the content of the transition metals is preferably 100 ppm by mass or less.

[0155] 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, or button. The exterior member can be appropriately selected depending on the battery dimensions and the application of the battery.

[0156] (6) Negative terminal The negative electrode terminal can be made of a material that is electrochemically stable at the Li absorption / release potential of the negative electrode active material and has electrical conductivity. Specifically, the material of 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 of 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 the contact resistance with the negative electrode current collector.

[0157] (7) Positive terminal The positive electrode terminal has a potential range of 3.0 V to 5.0 V with respect to the redox potential of lithium (vs. Li / Li + ) and can be formed from a material that is electrically stable and conductive. Examples of the material for the positive electrode terminal include aluminum and an aluminum alloy containing at least one element selected from the group consisting of Mg, Ti, Zn, Mn, Fe, Cu, and Si. The positive electrode terminal is preferably formed from the same material as the positive electrode current collector in order to reduce the contact resistance with the positive electrode current collector.

[0158] Next, the secondary battery according to the third embodiment will be described more specifically with reference to the drawings.

[0159] Fig. 3 is a cross-sectional view showing an example of a secondary battery according to a third embodiment of the present invention, and Fig. 4 is an enlarged cross-sectional view of part A of the secondary battery shown in Fig. 3.

[0160] The secondary battery 100 shown in Figures 3 and 4 includes a bag-shaped exterior member 2 shown in Figures 3 and 4, an electrode group 1 shown in Figure 3, and an electrolyte (not shown). The electrode group 1 and the electrolyte are stored in the bag-shaped exterior member 2. The electrolyte (not shown) is held in the electrode group 1.

[0161] The bag-shaped exterior member 2 is made of a laminate film including two resin layers and a metal layer interposed between them.

[0162] As shown in Fig. 3, the electrode group 1 is a flat wound-type electrode group. As shown in Fig. 4, the flat wound-type 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.

[0163] The negative electrode 3 includes a negative electrode current collector 3a and a negative electrode active material-containing layer 3b. In the negative electrode 3, in a portion located at the outermost shell of the wound-type 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. 4. 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.

[0164] The positive electrode 5 includes a positive electrode current collector 5a and a positive electrode active material-containing layer 5b formed on both sides of the positive electrode current collector 5a.

[0165] As shown in FIG. 3, the negative electrode terminal 6 and the positive electrode terminal 7 are located near the outer peripheral end 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.

[0166] The secondary battery according to the third embodiment is not limited to the secondary battery having the configuration shown in FIGS. 3 and 4, but may be a battery having the configuration shown in FIGS.

[0167] Fig. 5 is a partially cutaway perspective view typically showing another example of the secondary battery according to embodiment 3. Fig. 6 is an enlarged cross-sectional view of part B of the secondary battery shown in Fig. 5.

[0168] The secondary battery 100 shown in Figures 5 and 6 includes an electrode group 1 shown in Figures 5 and 6, an exterior member 2 shown in Figure 5, 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.

[0169] The exterior member 2 is made of a laminate film including two resin layers and a metal layer interposed between them.

[0170] The electrode group 1 is a laminated type electrode group, as shown in Fig. 6. The laminated type electrode group 1 has a structure in which negative electrodes 3 and positive electrodes 5 are alternately laminated with separators 4 interposed therebetween.

[0171] 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.

[0172] The negative electrode current collector 3a of each negative electrode 3 includes a portion 3c on one side of which the negative electrode active material-containing layer 3b is not supported on any surface. This portion 3c serves as a negative electrode current collector tab. As shown in FIG. 6, the portion 3c serving as the negative electrode current collector tab does not overlap with the positive electrode 5. In addition, the multiple negative electrode current collector tabs (portions 3c) are electrically connected to a strip-shaped negative electrode terminal 6. The tip of the strip-shaped negative electrode terminal 6 is pulled out to the outside of the exterior member 2.

[0173] 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 serves as a positive electrode current collector tab. The positive electrode current collector tab does not overlap with the negative electrode 3, similar to the negative electrode current collector tab (portion 3c). The positive electrode current collector tab is located on the opposite side of the electrode group 1 to the negative electrode current collector tab (portion 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 to the negative electrode terminal 6, and is drawn out to the outside of the exterior member 2.

[0174] The secondary battery according to the third embodiment contains, as a negative electrode active material, the active material according to the first embodiment, and therefore the secondary battery can exhibit excellent output characteristics and cycle life characteristics.

[0175] (Fourth embodiment) According to a fourth embodiment, there is provided a battery pack. The battery pack according to the fourth embodiment includes a plurality of secondary batteries according to the third embodiment.

[0176] In the battery pack according to the fourth embodiment, the individual cells may be electrically connected in series or in parallel, or may be connected in a combination of series and parallel.

[0177] Next, an example of a battery pack according to a fourth embodiment will be described with reference to the drawings.

[0178] Fig. 7 is a perspective view showing an example of a battery pack according to the fourth embodiment. The battery pack 200 shown in Fig. 7 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 third embodiment.

[0179] For example, the bus bar 21 connects the negative terminal 6 of one cell 100a to the positive terminal 7 of the adjacent cell 100b. In this manner, the five cells 100 are connected in series by the four bus bars 21. That is, the battery pack 200 in FIG. 7 is a five-series battery pack.

[0180] 7, the positive electrode terminal 7 of the leftmost cell 100a among the five cells 100a to 100e is connected to a positive electrode lead 22 for external connection. Also, the negative electrode terminal 6 of the rightmost cell 100e among the five cells 100a to 100e is connected to a negative electrode lead 23 for external connection.

[0181] The battery pack according to the fourth embodiment includes the secondary battery according to the third embodiment, and therefore this battery pack can exhibit excellent output characteristics and cycle life characteristics.

[0182] Fifth embodiment According to a fifth embodiment, there is provided a battery pack. The battery pack includes the battery assembly according to the fourth embodiment. The battery pack may include a single secondary battery according to the third embodiment, instead of the battery assembly according to the fourth embodiment.

[0183] The battery pack according to the fifth embodiment may further include a protection circuit. The protection circuit has a function of controlling charging and discharging of the secondary battery. Alternatively, a circuit included in a device (e.g., electronic device, automobile, etc.) that uses the battery pack as a power source may be used as the protection circuit for the battery pack.

[0184] The battery pack according to the fifth embodiment may further include an external terminal for current flow. The external terminal for current flow is for outputting current from the secondary battery to the outside and / or for 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 terminal for current flow. When the battery pack is charged, a charging current (including regenerative energy from the power of an automobile or the like) is supplied to the battery pack through the external terminal for current flow.

[0185] Next, an example of a battery pack according to a fifth embodiment will be described with reference to the drawings.

[0186] Fig. 8 is an exploded perspective view showing an example of a battery pack according to the fifth embodiment, Fig. 9 is a block diagram showing an example of an electric circuit of the battery pack shown in Fig. 8.

[0187] The battery pack 300 shown in Figs. 8 and 9 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).

[0188] 8 is a bottomed, square container having a rectangular bottom. The container 31 is configured to be capable of housing 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 container 31 to house the battery pack 200 and the like. Although not shown, the container 31 and the lid 32 are provided with openings or connection terminals for connection to an external device or the like.

[0189] 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.

[0190] The single cell 100 has a structure shown in Figs. 3 and 4. At least one of the multiple single cells 100 is a secondary battery according to the third embodiment. The multiple single cells 100 are stacked in an aligned manner so that the negative electrode terminal 6 and the positive electrode terminal 7 extending outward face the same direction. Each of the multiple single cells 100 is electrically connected in series as shown in Fig. 8. The multiple single cells 100 may be electrically connected in parallel, or may be connected in a combination of series and parallel connections. When the multiple single cells 100 are connected in parallel, the battery capacity is increased compared to when they are connected in series.

[0191] The adhesive tape 24 fastens the plurality of unit cells 100. The plurality of unit cells 100 may be fixed using heat shrink tape instead of the adhesive tape 24. In this case, the protective sheets 33 are disposed on both side surfaces of the battery pack 200, the heat shrink tape is wrapped around the battery pack 200, and the heat shrink tape is then thermally shrunk to bind the plurality of unit cells 100 together.

[0192] One end of the positive electrode lead 22 is connected to the positive electrode terminal 7 of the cell 100 located in the bottom layer in the stack of the cells 100. One end of the negative electrode lead 23 is connected to the negative electrode terminal 6 of the cell 100 located in the top layer in the stack of the cells 100.

[0193] The printed wiring board 34 is disposed along one of the short side surfaces of the inner surface of the container 31. The printed wiring board 34 includes a positive connector 341, a negative connector 342, a thermistor 343, a protection circuit 344, wires 345 and 346, an external terminal 347 for current supply, a positive wire 348a, and a negative wire 348b. One main surface of the printed wiring board 34 faces the surface of the battery pack 200 from which the negative terminal 6 and the positive terminal 7 extend. An insulating plate (not shown) is interposed between the printed wiring board 34 and the battery pack 200.

[0194] The positive electrode side connector 341 has a through hole. The other end of the positive electrode side lead 22 is inserted into this through hole, thereby electrically connecting the positive electrode side connector 341 and the positive electrode side lead 22. The negative electrode side connector 342 has a through hole. The other end of the negative electrode side lead 23 is inserted into this through hole, thereby electrically connecting the negative electrode side connector 342 and the negative electrode side lead 23.

[0195] The thermistor 343 is fixed to one main surface of the printed wiring board 34. The thermistor 343 detects the temperature of each of the cells 100, and transmits a detection signal thereto to the protection circuit 344.

[0196] The external terminal 347 for current supply is fixed to the other main surface of the printed wiring board 34. The external terminal 347 for current supply is electrically connected to a device present outside the battery pack 300.

[0197] The protection circuit 344 is fixed to the other main surface of the printed wiring board 34. The protection circuit 344 is connected to an external terminal 347 for electrical conduction via a positive side wiring 348a. The protection circuit 344 is connected to an external terminal 347 for electrical conduction via a negative side wiring 348b. The protection circuit 344 is also electrically connected to the positive electrode side connector 341 via a wiring 345. The protection circuit 344 is electrically connected to the negative electrode side connector 342 via a wiring 346. Furthermore, the protection circuit 344 is electrically connected to each of the plurality of single cells 100 via the wiring 35.

[0198] The protective sheet 33 is disposed on both inner surfaces in the long side direction of the container 31 and on the inner surface in the short side direction that faces the printed wiring board 34 via the battery pack 200. The protective sheet 33 is made of, for example, resin or rubber.

[0199] The protection circuit 344 controls charging and discharging of the multiple cells 100. In addition, the protection circuit 344 cuts off electrical connection between the protection circuit 344 and an external terminal 347 for supplying electricity to an external device, based on a detection signal transmitted from the thermistor 343, or a detection signal transmitted from each of the cells 100 or the battery pack 200.

[0200] An example of the detection signal transmitted from the thermistor 343 is a signal that detects 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 that detects overcharging, overdischarging, and overcurrent of the cell 100. When detecting overcharging 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.

[0201] The protection circuit 344 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.

[0202] As described above, the battery pack 300 includes the external terminal 347 for current supply. Therefore, the battery pack 300 can output a current from the assembled battery 200 to an external device and input a current from the external device to the assembled battery 200 via the external terminal 347 for current supply. In other words, when the battery pack 300 is used as a power source, the current from the assembled battery 200 is supplied to the external device through the external terminal 347 for current supply. When the battery pack 300 is charged, a charging current from the external device is supplied to the battery pack 300 through the external terminal 347 for current supply. When the battery pack 300 is used as an in-vehicle battery, regenerative energy of the vehicle's power can be used as the charging current from the external device.

[0203] 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 external terminals for current flow.

[0204] Such a battery pack is used in applications that require excellent cycle performance, for example, when a large current is drawn. Specifically, the battery pack is used, for example, as a power source for electronic devices, a stationary battery, or an on-board battery for various vehicles. An example of the electronic device is a digital camera. The battery pack is particularly suitable for use as an on-board battery.

[0205] The battery pack according to the fifth embodiment includes the secondary battery according to the third embodiment or the battery pack according to the fourth embodiment, and therefore this battery pack can exhibit excellent output characteristics and cycle life characteristics.

[0206] Sixth embodiment According to a sixth embodiment, a vehicle is provided. The vehicle is equipped with the battery pack according to the fifth embodiment.

[0207] In the vehicle according to the sixth embodiment, the battery pack, for example, recovers regenerative energy of the vehicle's motive power. The vehicle may include a mechanism for converting the kinetic energy of the vehicle into regenerative energy.

[0208] Examples of the vehicle according to the sixth embodiment include a two-wheeled to four-wheeled hybrid electric vehicle, a two-wheeled to four-wheeled electric vehicle, an electric-assisted bicycle, and a railroad car.

[0209] The mounting position of the battery pack in the vehicle according to the sixth embodiment 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.

[0210] The vehicle according to the sixth embodiment may be equipped with a plurality of battery packs. In this case, the battery packs may be electrically connected in series, electrically connected in parallel, or electrically connected in a combination of series and parallel connections.

[0211] Next, an example of a vehicle according to a sixth embodiment will be described with reference to the drawings.

[0212] FIG. 10 is a cross-sectional view that illustrates an example of a vehicle according to the sixth embodiment.

[0213] A vehicle 400 shown in Fig. 10 includes a vehicle body 40 and a battery pack 300 according to the fifth embodiment. In the example shown in Fig. 10, the vehicle 400 is a four-wheeled automobile.

[0214] The vehicle 400 may be equipped with a plurality of battery packs 300. In this case, the battery packs 300 may be connected in series, in parallel, or in a combination of series and parallel connections.

[0215] 10 illustrates an example in which the battery pack 300 is mounted in an engine room located in the front of the vehicle body 40. As described above, the battery pack 300 may be mounted, for example, in 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 the motive power of the vehicle 400.

[0216] Next, an embodiment of a vehicle according to the sixth embodiment will be described with reference to FIG.

[0217] Fig. 11 is a diagram illustrating an example of a vehicle according to embodiment 6. A vehicle 400 illustrated in Fig. 11 is an electric vehicle.

[0218] The vehicle 400 shown in FIG. 11 comprises a vehicle body 40, a vehicle power supply 41, a vehicle ECU (ECU: Electric Control Unit) 42 which is a higher-level control means for the vehicle power supply 41, an external terminal (a terminal for connecting to an external power supply) 43, an inverter 44, and a drive motor 45.

[0219] The vehicle 400 has a vehicle power supply 41 mounted, for example, in an engine compartment, the rear of the vehicle body, or under a seat. Note that, in the vehicle 400 shown in FIG. 11, the mounting location of the vehicle power supply 41 is shown diagrammatically.

[0220] The vehicle power supply 41 includes a plurality of (eg, three) battery packs 300a, 300b, and 300c, a battery management unit (BMU) 411, and a communication bus 412.

[0221] The three battery packs 300a, 300b, and 300c are electrically connected in series. The battery pack 300a includes an assembled battery 200a and an assembled battery monitoring device 301a (e.g., 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, 300b, and 300c can be removed independently and replaced with other battery packs 300.

[0222] Each of the assembled batteries 200a to 200c includes a plurality of unit cells connected in series. At least one of the plurality of unit cells is the secondary battery according to the third embodiment. The assembled batteries 200a to 200c are charged and discharged via a positive terminal 413 and a negative terminal 414, respectively.

[0223] In order to collect information related to the maintenance of the vehicle power supply 41, the battery management device 411 communicates with the battery pack monitoring devices 301a to 301c and collects information related to the voltage and temperature of the cells 100 included in the battery packs 200a to 200c included in the vehicle power supply 41.

[0224] A communication bus 412 is connected between the battery management device 411 and the assembled battery monitoring devices 301a to 301c. The communication bus 412 is configured so that one set of communication lines is shared by a plurality of nodes (the battery management device and one or more assembled battery monitoring devices). The communication bus 412 is a communication bus configured based on, for example, the CAN (Control Area Network) standard.

[0225] 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 communicated from the battery management device 411. However, the temperature can be measured at only a few points per battery pack, and it is not necessary to measure the temperatures of all the cells.

[0226] The vehicle power supply 41 may also have an electromagnetic contactor (for example, a switch device 415 shown in FIG. 11) for connecting and disconnecting 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 charged, and a main switch (not shown) that is turned on when the battery output is supplied to a load. The pre-charge switch and the main switch include a relay circuit (not shown) that is turned on or off by a signal supplied to a coil arranged near the switch element.

[0227] The inverter 44 converts the input DC voltage into a three-phase AC high voltage for driving the motor. The three-phase output terminals of the inverter 44 are connected to the three-phase input terminals of the drive motor 45. The inverter 44 controls the output voltage based on a control signal from the battery management unit 411 or the vehicle ECU 42 for controlling the operation of the entire vehicle.

[0228] The drive motor 45 rotates by the electric power supplied from the inverter 44. This rotation is transmitted to the axles and drive wheels W via, for example, a differential gear unit.

[0229] Although not shown, the vehicle 400 is also equipped with a regenerative braking mechanism. The regenerative braking mechanism rotates the drive motor 45 when the vehicle 400 is braked, and converts kinetic energy into regenerative energy as electrical energy. The regenerative energy recovered by the regenerative braking mechanism is input to the inverter 44 and converted into a direct current. The direct current is input to the vehicle power supply 41.

[0230] One terminal of a connection line L1 is connected to the negative terminal 414 of the vehicle power supply 41 via a current detection unit (not shown) in the battery management device 411. The other terminal of the connection line L1 is connected to the negative input terminal of the inverter 44.

[0231] One terminal of a connection line L2 is connected to the positive terminal 413 of the vehicle power supply 41 via a switch device 415. The other terminal of the connection line L2 is connected to the positive input terminal of the inverter 44.

[0232] The external terminal 43 is connected to the battery management unit 411. The external terminal 43 can be connected to, for example, an external power source.

[0233] Vehicle ECU 42 responds to operational inputs from the driver or the like and cooperates with other devices to control battery management device 411 to manage the entire vehicle. Data relating to the maintenance of vehicle power supply 41, such as the remaining capacity of vehicle power supply 41, is transferred between battery management device 411 and vehicle ECU 42 via a communication line.

[0234] The vehicle according to the sixth embodiment is equipped with the battery pack according to the fifth embodiment. Therefore, according to this embodiment, it is possible to provide a vehicle equipped with a battery pack that can exhibit excellent output characteristics and cycle life characteristics.

[0235] [Example] The above embodiment will now be described in more detail with reference to examples.

[0236] <Synthesis method> Example 1 The niobium titanium composite oxide was synthesized by the solid phase synthesis method described below. The synthesis method according to Example 1 corresponds to the first synthesis method described in the first embodiment.

[0237] First, Nb2O5 particles with a D50 of 0.6 μm and TiO2 particles with a D50 of 0.5 μm were prepared. 10 Ti2O 29To obtain the Nb2O5 phase, the molar ratio of Nb2O5 particles and TiO2 particles was set to 2.5:1 and mixed in a dry ball mill. The obtained powder was placed in an alumina crucible and pre-fired (first firing) at 800°C for 12 hours. After pre-firing, the obtained powder was placed in a platinum crucible and fired at 1100°C for 12 hours. After firing, the powder was crushed and mixed in an agate mortar, passed through a 25 μm mesh sieve to remove coarse particles, and then sintered to obtain the Nb 10 Ti2O 29 The obtained niobium titanium composite oxide had a Nb 10 Ti2O 29 It contained only single-phase primary particles.

[0238] Next, Nb 24 TiO 64 The above procedure was repeated except that the molar ratio of Nb2O5 particles to TiO2 particles was 12:1 to obtain the Nb phase. 10 Ti2O 29 The solid-phase synthesis method was carried out in the same manner as the synthesis of the phase. The obtained niobium titanium composite oxide was Nb 24 TiO 64 It contained only single-phase primary particles.

[0239] 100 parts by mass of Nb 10 Ti2O 29 75 parts by mass of Nb per primary particle of single phase 24 TiO 64 The single-phase primary particles were mixed and subjected to a dry ball mill. The resulting powder was placed in an alumina crucible and sintered at 800° C. for 1 hour to obtain the active material according to Example 1.

[0240] Example 2 100 parts by mass of Nb 10 Ti2O 29 66 parts by mass of Nb per primary particle of single phase 14 TiO 37 An active material was obtained by the method described in Example 1, except that single-phase primary particles were mixed.

[0241] In addition, Nb 14 TiO 37The single-phase primary particles were the same as those of Example 1 except that the molar ratio of Nb2O5 particles to TiO2 particles was 7:1. 10 Ti2O 29 It was synthesized in the same manner as in the synthesis of the first phase.

[0242] Example 3 100 parts by mass of Nb 10 Ti2O 29 55 parts by mass of Nb per primary particle of single phase 24 TiO 64 The active material was obtained by the method described in Example 1, except that the primary particles of the Nb phase were mixed. 24 TiO 64 As the single-phase primary particles, the same ones as those synthesized in Example 1 were used.

[0243] Example 4 The niobium titanium composite oxide was synthesized by the solid phase synthesis method described below. The synthesis method according to Example 4 corresponds to the second synthesis method described in the first embodiment. First, Nb2O5 particles with a D50 of 0.3 μm and TiO2 particles with a D50 of 0.2 μm were prepared. The molar ratio of Nb2O5 particles and TiO2 particles was set to 7:1 and mixed using a dry ball mill. The obtained powder was placed in an alumina crucible and pre-fired (first firing) at a temperature of 800°C for 12 hours. After pre-firing, the obtained powder was placed in a platinum crucible and pre-fired at 1000°C for 12 hours.

[0244] In this way, by synthesizing Nb as a single phase at an appropriate temperature range not exceeding 1200°C, 14 TiO 37 Suppresses the formation of Nb phases within the primary particles. 24 TiO 64 Phase and Nb 10 Ti2O 29 It is possible to separate the mixture of the two phases.

[0245] The powder obtained after the main firing was pulverized and mixed in an agate mortar, and passed through a 25 μm mesh sieve to remove coarse particles, thereby synthesizing the active material powder according to Example 4.

[0246] Example 5 An active material powder according to Example 5 was synthesized in the same manner as described in Example 4, except that pre-baking was not performed.

[0247] Example 6 An active material powder according to Example 6 was synthesized in the same manner as described in Example 4, except that the time for main baking was set to 2 hours.

[0248] Example 7 An active material powder according to Example 7 was synthesized in the same manner as described in Example 4, except that the time for main baking was set to 10 hours.

[0249] Example 8 The active material powder of Example 8 was synthesized in the same manner as described in Example 5, except that the molar ratio of Nb2O5 particles to TiO2 particles was changed to 7.1:1, and SiO2, Fe2O3, and Ta2O5 were added to the raw materials at 0.1 atm% each relative to Nb element.

[0250] Example 9 The active material powder of Example 9 was synthesized in the same manner as described in Example 5, except that the molar ratio of Nb2O5 particles to TiO2 particles was changed to 8:1, and KCl was added in an amount of 0.5 atm % relative to Nb element, and Na2CO3, P2O5, and SnO2 were each added in an amount of 0.05 atm % relative to Nb element in the raw materials.

[0251] Example 10 An active material powder according to Example 10 was synthesized in the same manner as described in Example 5, except that the molar ratio of Nb2O5 particles to TiO2 particles was changed to 12:1.

[0252] Comparative Example 1 100 parts by mass of Nb 10 Ti2O 29 30 parts by mass of Nb per primary particle of single phase 14 TiO 37An active material powder was obtained by the method described in Example 1, except that single-phase primary particles were mixed.

[0253] Comparative Example 2 An active material powder according to Comparative Example 2 was obtained in the same manner as in Example 5, except that the molar ratio of Nb2O5 particles to TiO2 particles was changed to 1:1.

[0254] Comparative Example 3 Nb obtained in Example 1 10 Ti2O 29 The powder consisting of only single-phase primary particles was used as the active material powder of Comparative Example 3.

[0255] Comparative Example 4 Nb obtained in Example 2 14 TiO 37 The powder consisting of only single-phase primary particles was used as the active material powder of Comparative Example 4.

[0256] Comparative Example 5 Nb obtained in Example 1 24 TiO 64 The powder consisting of only single-phase primary particles was used as the active material powder of Comparative Example 5.

[0257] Comparative Example 6 An active material powder according to Comparative Example 6 was obtained in the same manner as in Example 5, except that Nb2O5 particles with a D50 of 3.2 μm and TiO2 particles with a D50 of 2.2 μm were used as raw material particles.

[0258] Comparative Example 7 An active material powder according to Comparative Example 7 was obtained in the same manner as in Example 5, except that the temperature during main firing was changed to 1400°C.

[0259] Comparative Example 8 Nb 10 Ti2O 29 Single-phase primary particles and Nb 24 TiO 64The single-phase primary particles were mixed in a dry ball mill to obtain an active material powder according to Comparative Example 8.

[0260] <Powder X-ray diffraction measurement and peak intensity ratio I B / I A Calculation of > The active material powders obtained in Examples 1 to 11 and Comparative Examples 1 to 3 were subjected to the powder X-ray diffraction measurement described in the first embodiment under the conditions of a sampling interval of 0.01° and a scan speed of 2° / min. In the obtained diffraction chart, the peak intensity ratio I B / I A was calculated.

[0261] As an example, a diffraction chart obtained by powder X-ray diffraction for the active material according to Example 4 is shown in Fig. 12. A diffraction chart obtained by powder X-ray diffraction for the active material according to Example 10 is shown in Fig. 13. A diffraction chart obtained by powder X-ray diffraction for the active material according to Comparative Example 3 is shown in Fig. 14.

[0262] In the diffraction charts shown in Figs. 12 and 13, the maximum peak appears within the range of 2θ of 24.9±0.2°, and Nb 10 Ti2O 29 In the diffraction charts shown in Figs. 12 and 13, a peak A was observed which was the maximum peak appearing within a 2θ range of 25.5±0.2° and which was assigned to the Nb-rich phase. In the diffraction charts shown in Figs. 12 and 13, a peak B was observed which was the maximum peak appearing within a 2θ range of 23.7±0.2° and which was assigned to the Nb-rich phase. 10 Ti2O 29 Peak C assigned to the phase was observed.

[0263] The peak intensity ratio I from peaks A and B observed in Fig. 12 B / I A The peak intensity ratio I of the active material according to Example 4 was calculated. B / I A The half width of peak C observed in the diffraction chart shown in FIG.

[0264] The peak intensity ratio I B / I A was calculated from the peaks A and B observed in FIG. 13. The peak intensity ratio I B / I A of the active material according to Example 10 was 0.82. The half-width of the peak C observed in the diffraction chart shown in FIG. 13 was 0.35°.

[0265] In the diffraction chart shown in FIG. 14, a peak A, which is the maximum peak appearing within the range of 2θ of 24.9 ± 0.2°, and which is attributed to the Nb 10 Ti2O 29 phase, was observed. Also, in the diffraction chart shown in FIG. 14, a peak C, which is the maximum peak appearing within the range of 2θ of 23.7 ± 0.2°, and which is attributed to the Nb 10 Ti2O 29 phase, was observed. However, in the diffraction chart shown in FIG. 14, a peak B, which is the maximum peak appearing within the range of 2θ of 25.5 ± 0.2° and which is attributed to the Nb-rich phase, was not observed.

[0266] The peak intensity ratio I B / I A was calculated from the peaks A and B observed in FIG. 14. The peak intensity ratio I B / I A of the active material according to Comparative Example 3 was 0. Also, the half-width of the peak C observed in the diffraction chart shown in FIG. 14 was 0.12°.

[0267] <SEM-EDX Observation> The active material powders obtained in Examples 1 to 10 and Comparative Examples 1 to 8 were observed by SEM-EDX, and the ratio M Nb / M Ti of the amount of niobium to the amount of titanium in the primary particles contained in the active material powder was confirmed.

[0268] <Electrochemical Measurement> First, 100% by mass of the niobium titanium composite oxide powder obtained in each example, 10% by mass of acetylene black as a conductive agent, 5% by mass of carbon nanofiber, 10% by mass of polyvinylidene fluoride (PVdF) as a binder, and N-methylpyrrolidone (NMP) were added and mixed to obtain a slurry. This slurry was applied to one side of a current collector made of aluminum foil with a thickness of 12 μm, dried, and pressed to obtain an electrode density of 2.4 g / cm. 3 The electrodes were prepared as follows.

[0269] Next, an electrolyte solution was prepared by dissolving LiPF6 supporting salt at a concentration of 1 mol / L in a mixed solvent of ethylene carbonate (EC) and diethyl carbonate (DEC) in a volume ratio of 1:2.

[0270] The resulting electrode was used as the working electrode, and Li metal was used as the counter electrode and reference electrode. A coin cell was fabricated using an electrolyte to evaluate the electrochemical properties.

[0271] In this embodiment, the coin cell for measurement uses lithium metal as the counter electrode, so that the electrode potentials of the embodiment and comparative example are more noble than the counter electrode and operate as positive electrodes. Therefore, the definitions of charge and discharge are reversed when the electrodes of the embodiment and comparative example are used as negative electrodes. Here, to avoid confusion, in this embodiment, the direction in which lithium ions are inserted into the electrode is unified as charge, and the direction in which they are removed is unified as discharge. The active material of this embodiment operates as a negative electrode when combined with a known positive electrode material.

[0272] The electrochemical measurement cell thus fabricated was charged and discharged in the potential range of 1.0 V to 3.0 V with respect to the metallic lithium electrode. The charge and discharge current value was set to 0.2 C (time discharge rate), and the 0.2 C discharge capacity was confirmed at room temperature. The 0.2 C discharge capacity value is an index of energy density.

[0273] Next, a life test was performed at room temperature on the cells of the examples and comparative examples by repeatedly charging and discharging at 1C in a potential range of 1.0V to 3.0V based on the metallic lithium electrode. Under these conditions, 100 cycles of charging and discharging were repeated (one cycle is one charge and one discharge), and the discharge capacity retention rate after 100 cycles was examined. In addition, in order to evaluate the charge and discharge rate characteristics, the charge or discharge current value was changed between 1C and 5C, and the capacity retention rate at each current was measured.

[0274] The above results are summarized in Tables 1 to 4. In Tables 1 and 2, the column "Raw material molar ratio (Nb2O5:TiO2) when synthesizing single-phase particles" shows the mixed molar ratio of Nb2O5 particles and TiO2 particles used as starting materials when particles having each crystal phase were produced in the first synthesis method. The column "Raw material molar ratio Nb2O5:TiO2" shows the mixed molar ratio of Nb2O5 particles and TiO2 particles used as starting materials in the second synthesis method.

[0275] [Table 1]

[0276] [Table 2]

[0277] [Table 3]

[0278] [Table 4]

[0279] As shown in Examples 1 to 10, Nb 10 Ti2O 29 Phase and Nb 14 TiO 37 Phase and Nb 24 TiO 64and at least one Nb-rich phase selected from the group consisting of Nb-rich phases, and a ratio M of the amount of niobium to the amount of titanium. Nb / M Ti 5.0 <M Nb / M Ti The active material containing primary particles satisfying the relationship ≦24.0, satisfying the above formula (1), and having a half width of peak C in the range of 0.15° or more and 0.80° or less exhibited excellent rate characteristics and cycle life characteristics.

[0280] As shown in Comparative Examples 1 to 3, the peak intensity ratio I B / I A These active materials do not contain an Nb-rich phase when θ is 0. The active material particles according to these examples tend to be more easily cracked than the active material particles according to the examples, and therefore tend to have inferior cycle capacity retention rates.

[0281] As shown in Comparative Examples 4 and 5, the peak intensity ratio I B / I A When the ratio exceeds 5.0, the volume of the active material particles tends to expand significantly and the particles are easily cracked, resulting in poor cycle capacity retention.

[0282] In Comparative Example 6, the particle diameter of the raw material particles was large, so that solid-phase diffusion was insufficient, and a relatively large amount of Nb2TiO7 phase with a small Nb / Ti ratio was generated in the generated particles. The active material according to Comparative Example 6 tended to be inferior in both rate characteristics and cycle life characteristics compared to Examples 1-10.

[0283] When the temperature in the main sintering is relatively high as in Comparative Example 7, Nb and Ti tend to diffuse sufficiently to form a stable crystal phase. 10 Ti2O 29 Phase and Nb 14 TiO 37 Phase and Nb 24 TiO 64In this case, the primary particles tend to be easily cracked by the insertion and removal of lithium ions because weak parts of the crystals, such as corner-sharing parts, are aligned in one direction in each crystal phase. Therefore, the cycle capacity retention rate tends to be poor.

[0284] The active material powder according to Comparative Example 8 contains Nb 10 Ti2O 29 Single-phase primary particles and Nb 24 TiO 64 The single-phase primary particles were simply mixed together. That is, no subsequent sintering was performed. In this active material, the peak intensity ratio I B / I A Although the above formula (1) was satisfied, the active material particles did not contain phase-separated primary particles, and therefore the particles were prone to cracking, and lithium did not tend to move smoothly between the active material particles having different crystal phases.

[0285] According to at least one of the embodiments and examples described above, an active material is provided. The active material comprises Nb 10 Ti2O 29 Phase and Nb 14 TiO 37 Phase and Nb 24 TiO 64 and at least one Nb-rich phase selected from the group consisting of Nb-rich phases. In the primary particles, the ratio M of the amount of substance of niobium to the amount of substance of titanium is Nb / M Ti is 5.0 <M Nb / M Ti ≦24.0. The diffraction chart of the active material by wide-angle X-ray diffraction method using CuKα radiation as the X-ray source shows 2θ in the range of 24.9±0.2°, and Nb 10 Ti2O 29 Peak A, which is assigned to the Nb-rich phase, appears within a 2θ range of 25.5±0.2°, and peak B, which is assigned to the Nb-rich phase, appears within a 2θ range of 23.7±0.2°. 10 Ti2O 29and peak C assigned to the Fe-phase. The active material satisfies the peak intensity ratio represented by the following formula (1). 0 B / I A <5.0 (1) In formula (1), I A is the peak intensity of the peak A, and I B is the peak intensity of the peak B. The half width of the peak C is in the range of 0.15° to 0.80°.

[0286] This active material can realize a secondary battery that can exhibit excellent output characteristics and cycle life characteristics.

[0287] Although some 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 implemented 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 in the scope and spirit of the invention, and are included in the scope of the invention and its equivalents described in the claims. [Explanation of symbols]

[0288] ​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 collector portion, 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, 23...negative electrode side lead, 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...driving motor, 100...secondary battery, 101...metal ion, 102...oxide ion, 103...skeletal structure portion, 104...void portion, 105, 106...area, 2 00... battery pack, 200a... battery pack, 200b... battery pack, 200c... battery pack, 300... battery pack, 300a... battery pack, 300b... battery pack, 300c... battery pack, 301a... battery pack monitoring device, 301b... battery pack monitoring device, 301c... battery pack monitoring device, 341... positive connector, 342... negative connector, 343... thermistor, 344... protection circuit, 345... wiring, 346... wiring, 347... external terminal for energizing, 348a... positive wiring, 348b... negative wiring, 400... vehicle, 411... battery management device, 412... communication bus, 413... positive terminal, 414... negative terminal, 415... switch device, L1... connection line, L2... connection line, W... drive wheel.

Claims

1. Nb 10 Ti 2 O 29 phase and Nb 14 TiO 37 Phase and Nb 24 TiO 64 and at least one Nb-rich phase selected from the group consisting of Nb-rich phases; In the primary particles, the ratio M of the amount of substance of niobium to the amount of substance of titanium Nb / M Ti is 5.0<M Nb / M Ti An active material that satisfies ≦24.0, The diffraction chart of the active material obtained by a wide-angle X-ray diffraction method using CuKα radiation as an X-ray source is as follows: 2θ appears within the range of 24.9±0.2°, and the Nb 10 Ti 2 O 29 Peak A assigned to the phase; Peak B, which appears within the range of 2θ of 25.5 ± 0.2 ° and is assigned to the Nb-rich phase; 2θ appears within the range of 23.7±0.2°, and the Nb 10 Ti 2 O 29 and a peak C assigned to the α-phase; The peak intensity ratio represented by the following formula (1) is satisfied, 0<I B / I A <5.0 (1) In the formula (1), I A is the peak intensity of the peak A, and I B is the peak intensity of the peak B, The half width of the peak C is within a range of 0.15° or more and 0.80° or less.

2. The primary particles are 10 Ti 2 O 29 2. The active material of claim 1, which is a mixed phase of a Nb-rich phase and said at least one Nb-rich phase.

3. The active material according to claim 1 or 2, further satisfying a peak intensity ratio represented by the following formula (2): 0≦I D / I A <0.01 (2) In the formula (2), I A In a diffraction chart by a wide-angle X-ray diffraction method using CuKα radiation as an X-ray source, 2θ appears within the range of 24.9±0.2°, and the Nb 10 Ti 2 O 29 is the peak intensity of the peak A assigned to the I phase. D In the diffraction chart, 2θ appears within the range of 20.1±0.2°, and Nb 2 TiO 7 is the peak intensity of peak D assigned to the phase.

4. The peak intensity ratio I B / I A The active material according to any one of claims 1 to 3, wherein is in the range of 0.01 or more and 1.20 or less.

5. Said ratio M Nb / M Ti Ratio M is 6.5 or less Nb / M Ti 5. The active material according to claim 1, which satisfies ≦12.

0.

6. 6. The active material according to claim 1, wherein the half width of the peak C is within a range of 0.20° or more and 0.45° or less.

7. 7. The active material according to claim 1, further comprising at least one selected from the group consisting of Ta, K and P.

8. An electrode comprising the active material according to any one of claims 1 to 7.

9. The electrode according to claim 8 , wherein the electrode comprises an active material-containing layer that contains the active material.

10. A positive electrode and A negative electrode; and an electrolyte, The negative electrode of the secondary battery is the electrode according to claim 8 or 9.

11. A battery pack comprising the secondary battery according to claim 10.

12. An external terminal for supplying electricity; The battery pack of claim 11, further comprising a protection circuit.

13. 13. The battery pack according to claim 11, comprising a plurality of the secondary batteries, the secondary batteries being electrically connected in series, in parallel, or in a combination of series and parallel.

14. A vehicle equipped with the battery pack according to any one of claims 11 to 13.

15. 15. The vehicle of claim 14, further comprising a mechanism for converting kinetic energy of the vehicle into regenerative energy.

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