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

Abstract

Embodiments of the present invention relate to an active material, an electrode, a secondary battery, a battery pack, and a vehicle. The present invention provides an active material and an electrode for a secondary battery that can maintain a high energy density while having balanced input / output performance and excellent cycle life performance; a secondary battery and a battery pack having a high energy density, balanced input / output performance, and excellent cycle life performance; and a vehicle equipped with the battery pack. According to an embodiment, there is provided an active material containing crystal grains including a niobium-titanium composite oxide. The Nb content ratio A Nb in the crystal grains relative to the Ti content ratio A Ti has a ratio A Nb / A Ti satisfying 2.3 ≤ A Nb / A Ti ≤ 4.0. Further, in the powder X-ray diffraction spectrum of the crystal grains using Cu-Kα radiation, the peak intensity I α of peak α appearing at 8.5° ≤ 2θ ≤ 9.0° and the peak intensity I β of peak β appearing at 12.5° ≤ 2θ ≤ 13.0° have an intensity ratio I β / I α in the range of 0.1 < I β / I α ≤ 2.0.

Description

Technical Field

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

[0002] In recent years, as high energy density batteries, research and development of secondary batteries such as non-aqueous electrolyte batteries like lithium ion secondary batteries have been widely carried out. Secondary batteries such as non-aqueous electrolyte secondary batteries are expected as power sources for vehicles such as hybrid electric vehicles and electric vehicles, and for uninterruptible power supplies for mobile phone base stations. Therefore, in addition to high energy density, secondary batteries are required to have excellent other performances such as fast charge and discharge performance and long-term reliability. For example, a secondary battery capable of fast charge and discharge can not only significantly shorten the charging time, but also improve the power performance of vehicles such as hybrid electric vehicles and effectively recover the regenerative energy of power.

[0003] Fast charge and discharge can be achieved by rapidly moving electrons and lithium ions between the positive electrode and the negative electrode. However, in a battery using a carbon-based negative electrode, if fast charge and discharge are repeated, dendritic precipitation of metallic lithium occurs on the electrode, and there is a concern of heat generation or ignition due to internal short circuit.

[0004] Thus, a battery using a metal composite oxide instead of a carbonaceous material in the negative electrode has been developed. In particular, a battery using titanium oxide for the negative electrode has characteristics of being able to achieve stable fast charge and discharge and having a longer life than a battery using a carbon-based negative electrode.

[0005] However, compared with a carbonaceous material, titanium oxide has a higher potential (is more noble) with respect to metallic lithium. Moreover, the capacity per unit mass of titanium oxide is low. Therefore, a battery using titanium oxide for the negative electrode has a problem of low energy density.

[0006] For example, the electrode potential of titanium oxide is about 1.5 V (vs. Li / Li + ), which is higher (more noble) than the potential of a carbon-based negative electrode. The potential of titanium oxide is due to the redox reaction between Ti 3+ and Ti 4+ when lithium is electrochemically inserted and extracted, so it is electrochemically restricted. In addition, there is a fact that fast charge and discharge of lithium ions can be stably performed at a high electrode potential of about 1.5 V (vs. Li / Li + ). Therefore, it has been difficult to lower the electrode potential to improve the energy density.

[0007] On the other hand, regarding the capacity per unit weight, the theoretical capacity of titanium dioxide (anatase structure) is about 165 mAh / g, and Li4Ti5O 12The theoretical capacity of a spinel-type lithium-titanium composite oxide is also about 180 mAh / g. On the other hand, the theoretical capacity of a general graphite-based electrode material is 385 mAh / g or more. Thus, the capacity density of titanium oxide is significantly lower than that of a carbon-based negative electrode. This is because, in the crystal structure of titanium oxide, there are few sites for embedding lithium and lithium is easily stabilized in the structure, resulting in a substantial decrease in capacity.

[0008] In view of the above, a new electrode material containing Ti and Nb is being studied. It is expected that such a niobium-titanium composite oxide material has a high charge-discharge capacity. In particular, the composite oxide represented by TiNb2O7 has a relatively high theoretical capacity exceeding 380 mAh / g. Therefore, the niobium-titanium composite oxide is expected as a high-capacity material to replace Li4Ti5O 12 However, the niobium-titanium composite oxide shows excellent input performance but relatively low output performance, so the poor balance of input-output performance becomes a problem. Summary of the Invention

[0009] According to an embodiment, an active material containing crystal grains including a niobium-titanium composite oxide can be provided. The ratio A of the Nb presence ratio in the crystal grains Nb relative to the Ti presence ratio A Ti of the ratio A Nb / A Ti satisfies 2.3 ≤ A Nb / A Ti ≤ 4.0. Moreover, in the powder X-ray diffraction spectrum of the crystal grains using Cu-Kα radiation, the peak intensity I of peak α that appears at 8.5° ≤ 2θ ≤ 9.0° α and the peak intensity I of peak β that appears at 12.5° ≤ 2θ ≤ 13.0° β of the intensity ratio I β / I α is in the range of 0.1 < I β / I α ≤ 2.0.

[0010] According to another embodiment, an electrode containing the above active material can be provided.

[0011] According to still another embodiment, a secondary battery including a negative electrode, a positive electrode, and an electrolyte can be provided. The negative electrode includes the above electrode.

[0012] According to yet another embodiment, a battery pack including the above secondary battery can be provided.

[0013] In addition, according to an embodiment, a vehicle including the above battery pack can be provided.

[0014] According to the above configuration, it is possible to provide an active material and an electrode for a secondary battery that can achieve a high energy density while maintaining a balanced input-output performance and exhibiting excellent cycle life performance; a secondary battery and a battery pack with a high energy density, a balanced input-output performance, and excellent cycle life performance; and a vehicle equipped with the battery pack. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1 It is a schematic diagram showing the crystal structure of niobium titanium composite oxide Nb2TiO7.

[0016] Figure 2 It is a schematic diagram showing the crystal structure when viewed from another direction Figure 1 of.

[0017] Figure 3 It is a plan view schematically showing the particles to be measured in the observation by a transmission electron microscope (TEM).

[0018] Figure 4 It is a cross-sectional view schematically showing an example of a secondary battery according to an embodiment.

[0019] Figure 5 is Figure 4 an enlarged cross-sectional view of part A of the secondary battery shown.

[0020] Figure 6 It is a partially cutaway perspective view schematically showing another example of a secondary battery according to an embodiment.

[0021] Figure 7 is Figure 6 an enlarged cross-sectional view of part B of the secondary battery shown.

[0022] Figure 8 It is a perspective view schematically showing an example of a battery module according to an embodiment.

[0023] Figure 9 It is an exploded perspective view schematically showing an example of a battery pack according to an embodiment.

[0024] Figure 10 is showing Figure 9 a block diagram of an example of the circuit of the battery pack shown.

[0025] Figure 11 It is a partial perspective view schematically showing an example of a vehicle according to an embodiment.

[0026] Figure 12This is a diagram schematically showing an example of a control system for an electrical system in a vehicle related to an embodiment.

[0027] Symbol Explanation

[0028] 1 - Electrode group, 2 - Outer packaging member, 3 - Negative electrode, 3a - Negative electrode current collector, 3b - Negative electrode active material layer-containing, 4 - Separator, 5 - Positive electrode, 5a - Positive electrode current collector, 5b - Positive electrode active material layer-containing, 6 - Negative terminal, 7 - Positive terminal, 21 - Bus bar, 22 - Positive electrode side lead wire, 23 - Negative electrode side lead wire, 24 - Adhesive tape, 31 - Storage container, 32 - Cover, 33 - Protective sheet, 34 - Printed circuit wiring board, 35 - Wiring, 40 - Vehicle body, 41 - Vehicle power source, 42 - Electric control device, 43 - External terminal, 44 - Inverter, 45 - Drive motor, 100 - Secondary battery, 101 - Metal ion, 102 - Oxide ion, 103 - Skeletal structure part, 104 - Void part, 107 - Void part, 200 - Battery group, 200a - Battery group, 200b - Battery group, 200c - Battery group, 300 - Battery pack, 300a - Battery pack, 300b - Battery pack, 300c - Battery pack, 301a - Battery group monitoring device, 301b - Battery group monitoring device, 301c - Battery group monitoring device, 342 - Positive electrode side connector, 343 - Negative electrode side connector, 345 - Thermistor, 346 - Protection circuit, 342a - Wiring, 343a - Wiring, 350 - External terminal for energization, 352 - Positive side terminal, 353 - Negative side terminal, 348a - Positive electrode side wiring, 348b - Negative electrode side wiring, 400 - Vehicle, 411 - Battery management device, 412 - Communication bus, 413 - Positive terminal, 414 - Negative terminal, 415 - Switch device, 416 - Current detection part, 417 - Negative electrode input terminal, 418 - Positive electrode input terminal, L1 - Connection line, L2 - Connection line, W - Driving wheel. Detailed Embodiment

[0029] Hereinafter, the embodiment will be described with reference to the drawings. Furthermore, in the following description, for components having the same or similar functions, the same reference numerals are assigned in all the drawings, and repeated descriptions are omitted. In addition, each drawing is a schematic diagram for facilitating the description and understanding of the embodiment, and its shape, size, ratio, etc. are different from those of the actual device, but they can be appropriately designed and changed with reference to the following description and known techniques.

[0030] [First Embodiment]

[0031] According to the first embodiment, an active material can be provided. The active material contains crystal grains containing niobium-titanium composite oxide. The Nb content ratio A in the crystal grains Nb relative to the Ti content ratio ATi Ratio to A Nb / A Ti Satisfies 2.3 ≤ A Nb / A Ti ≤ 4.0. Moreover, in the powder X-ray diffraction spectrum of the crystal grains using Cu-Kα rays, the peak appearing in the range of 8.5° ≤ 2θ ≤ 9.0° is defined as peak α, and the peak appearing in the range of 12.5° ≤ 2θ ≤ 13.0° is defined as peak β. The peak intensity I α of peak α and the peak intensity I β of peak β, the intensity ratio I β / I α is in the range of 0.1 < I β / I α ≤ 2.0.

[0032] The active material may be an active material for a battery. For example, the active material may be an electrode active material used in electrodes of secondary batteries such as lithium-ion batteries and non-aqueous electrolyte batteries. More specifically, the active material may be a negative electrode active material used in the negative electrode of a secondary battery.

[0033] The above-mentioned active material can realize a secondary battery that maintains a relatively high energy density similar to that of a battery using a composite oxide represented by Nb2TiO7 as the electrode material, has input-output performance with a balanced state, and can exhibit excellent cycle life performance. The reasons are explained below.

[0034] The active material contains a Nb2TiO7-type crystal phase and a Nb 10 Ti2O 29 -type crystal phase. Hereinafter, the former Nb2TiO7-type crystal phase may sometimes be referred to as a type A niobium-titanium composite oxide phase, and the latter Nb 10 Ti2O 29 -type crystal phase may be referred to as a type B niobium-titanium composite oxide phase. The active material satisfies the existence ratios of Nb element and Ti element represented by the following formula (1), and satisfies the peak intensity ratio represented by the following formula (2):

[0035] 2.3 ≤ A Nb / A Ti ≤ 4.0 (1)

[0036] 0.1 < I β / I α ≤ 2.0 (2)

[0037] In formula (1), A Nb represents the Nb existence ratio, and A Ti represents the Ti existence ratio.

[0038] In formula (2), Iα represents the peak intensity of peak α that appears in the diffraction spectrum according to the wide-angle X-ray diffraction method using Cu-Kα rays as the X-ray source, which is the maximum intensity within the range of 8.5° ≤ 2θ ≤ 9.0° for 2θ, I β represents the peak intensity of peak β that appears in the above diffraction spectrum within the range of 12.5° ≤ 2θ ≤ 13.0° for 2θ.

[0039] Peak α in the X-ray diffraction spectrum of the active material can be attributed to the A-type niobium titanium composite oxide phase (crystalline phase A of the Nb2TiO7 type). Peak β in the spectrum can be attributed to the B-type niobium titanium composite oxide phase (Nb 10 Ti2O 29 type crystalline phase B).

[0040] In the active material, the A-type niobium titanium composite oxide phase and the B-type niobium titanium composite oxide phase are mixed and present in each crystal grain. The mixing ratio of the A-type niobium titanium composite oxide phase and the B-type niobium titanium composite oxide phase in the crystal grains preferably satisfies the following formula (3).

[0041] 0.5 ≤ M A / M B ≤ 2.5 (3)

[0042] In formula (3), M A represents the mass ratio of the A-type niobium titanium composite oxide phase in the crystal grains, and M B represents the mass ratio of the B-type niobium titanium composite oxide phase in the crystal grains.

[0043] The crystalline phase of the Nb2TiO7 type, that is, the A-type niobium titanium composite oxide phase, will be described.

[0044] As a representative composition of the A-type niobium titanium composite oxide phase contained in the active material according to the embodiment, Nb2TiO7 can be cited. The composition of the niobium titanium composite oxide is not limited thereto, but preferably has a crystal structure with a symmetry of space group C2 / m and atomic coordinates described in Non-Patent Document 1, Journal of Solid State Chemistry 53, pp144-147 (1984).

[0045] The niobium titanium composite oxide mainly shows a monoclinic crystal structure. As an example thereof, Figure 1 and Figure 2 show a schematic diagram of the crystal structure of monoclinic Nb2TiO7.

[0046] As Figure 1As shown, in the crystal structure of monoclinic Nb2TiO7, metal ions 101 and oxide ions 102 form a framework structure portion 103. At the positions of the metal ions 101, Nb ions and Ti ions are randomly arranged in a ratio of Nb∶Ti = 2∶1. By three-dimensionally arranging the framework structure portion 103 alternately, void portions 104 exist between the framework structure portions 103. The void portion 104 serves as a host for lithium ions. Lithium ions can be intercalated from 0 mole to a maximum of 5.0 moles in this crystal structure. Therefore, the composition when 0 to 5.0 moles of lithium ions are intercalated can be expressed as Li x xNb2TiO7 (0 ≤ x ≤ 5).

[0047] Figure 1 In , regions 105 and 106 are parts having two-dimensional channels in the

[100] direction and the

[010] direction. As Figure 2 shown, in the crystal structure of monoclinic Nb2TiO7, a void portion 107 exists in the

[001] direction. The void portion 107 has a tunnel structure favorable for the conduction of lithium ions and serves as a conduction path in the

[001] direction connecting regions 105 and 106. Due to the existence of this conduction path, lithium ions can travel back and forth between regions 105 and 106. In addition, the niobium-titanium composite oxide has a lithium intercalation potential of about 1.5 V (relative to Li / Li + +). Therefore, an electrode containing the niobium-titanium composite oxide as an active material can achieve a battery that can stably and repeatedly perform rapid charge and discharge.

[0048] In addition, when lithium ions are intercalated into the void portion 104 in the above crystal structure, 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 can Ti ions be reduced from tetravalent to trivalent, but also Nb ions can be reduced from pentavalent to trivalent. Therefore, the reduction valence number per unit weight of the active material is large. Thus, even when many lithium ions are intercalated, the electrical neutrality of the crystal can be maintained. Therefore, compared with compounds such as titanium oxide containing only tetravalent cations, the energy density is higher. In addition, the A-type niobium-titanium composite oxide phase (Nb2TiO7-type phase) is superior in weight energy density compared with the B-type niobium-titanium composite oxide phase (Nb 10 Ti2O 29 -type phase) described later. This is because the number of Nb atoms per 1 mole contained in the crystal phase of the Nb 10 Ti2O 29 -type is larger, that is, the weight per 1 mole is larger.

[0049] Next, the Nb 10 Ti2O 29 -type crystal phase, that is, the B-type niobium-titanium composite oxide phase, will be described.

[0050] The basic framework structure of the B-type niobium-titanium composite oxide phase is similar to the crystal structure of monoclinic Nb2TiO7 shown in Figure 1 and Figure 2 . When lithium ions are embedded in the interstitial part 104, the metal ions 101 that make up the framework are reduced to trivalent, thereby maintaining the electrical neutrality of the crystal. When lithium ions are embedded in the Nb 10 Ti2O 29 -type crystal phase, the composition can be expressed as Li y Nb 10 Ti2O 29 (0 ≤ y ≤ 22).

[0051] When comparing the Nb 10 Ti2O 29 -type crystal phase with a relatively high niobium content with the Nb2TiO7-type crystal phase, the amount of Nb ions reduced from pentavalent to trivalent increases. Therefore, the reduction valence number per mole of the active material is relatively large. Therefore, even if a large number of lithium ions are embedded, the electrical neutrality of the crystal can be maintained. Therefore, compared with the A-type niobium-titanium composite oxide phase, the B-type niobium-titanium composite oxide phase can maintain the crystal structure more stably even when lithium ions are embedded. As a result, the diffusion of lithium ions is fast, and even if rapid charge and discharge are repeated, the life can be extended. That is to say, the input-output performance and cycle life performance are excellent.

[0052] On the other hand, compared with the Nb2TiO7-type crystal phase, the reduction valence number per unit weight of the active material of the Nb 10 Ti2O 29 -type crystal phase is relatively small. That is, the weight per mole of the B-type niobium-titanium composite oxide phase is relatively large, so the weight energy density is inferior to that of the A-type niobium-titanium composite oxide phase.

[0053] Therefore, the B-type niobium-titanium composite oxide phase (Nb 10 Ti2O 29 -type phase) can accelerate the movement of lithium ions in the crystal, and the A-type niobium-titanium composite oxide phase (Nb2TiO7-type phase) can improve the weight energy density. Therefore, by uniformly distributing the B-type niobium-titanium composite oxide phase and the A-type niobium-titanium composite oxide phase in the same particle respectively, these performances can be taken into account.

[0054] The uniform distribution of the two phases mentioned here means a state where no boundary lines between the respective phases are found within the primary particles of the active material. For any crystal phase, in the uniformly distributed grains, each phase within the particle can be in a state of averaging at the molecular level or atomic level. When there is Nb 10 Ti2O 29Boundary points such as the interpenetration points of the crystalline phases of the B-type and Nb2TiO7-type, i.e., when the crystalline phases are unbalanced, the transfer of lithium ions between different crystalline phases becomes the rate-limiting factor. In particular, during lithium deintercalation (discharge), due to the change in lattice volume, it is easy to generate an offset in the lattice matching, which easily hinders the movement of lithium ions.

[0055] As described above, the crystal grains of the niobium-titanium composite oxide contained in the active material according to the embodiment satisfy the presence ratios of Nb element and Ti element represented by the above formula (1): 2.3 ≤ A Nb / A Ti ≤ 4.0, and satisfy the X-ray diffraction spectrum of the peak intensity ratio represented by the formula (2): 0.1 < I β / I α ≤ 2.0. The active material may be a batch containing a plurality of the above crystal grains, for example, a powdery active material, but each crystal grain satisfies the above formula (1) and formula (2) respectively.

[0056] The symbol A Nb / A Ti in the formula (1) is the molar ratio of the Nb presence ratio A Nb contained in the crystal grain to the Ti presence ratio A Ti . An A Nb / A Ti ratio of 2.3 or more indicates the stable formation of the B-type niobium-titanium composite oxide phase (Nb 10 Ti2O 29 type of crystalline phase). By stably forming the Nb 10 Ti2O 29 type of crystalline phase, high input-output performance can be shown. An A Nb / A Ti ratio of 4.0 or less indicates the stable formation of the A-type niobium-titanium composite oxide phase (Nb2TiO7-type crystalline phase). By stably forming the Nb2TiO7-type crystalline phase, a relatively high energy density can be shown.

[0057] The peak intensity I α is the peak intensity (peak height) of the peak α attributed to the A-type niobium-titanium composite oxide phase (Nb2TiO7-type) in the X-ray diffraction spectrum. The so-called peak α is the peak with the maximum peak intensity in the spectrum measured by the wide-angle X-ray diffraction method described later in the range of 8.5° ≤ 2θ ≤ 9.0° for 2θ.

[0058] The peak intensity I β is the peak intensity in the X-ray diffraction spectrum attributed to the (Nb 10 Ti2O 29The peak intensity (peak height) of peak β of the B-type niobium-titanium composite oxide phase of the () B type. The so-called peak β is the peak having the maximum peak intensity in the spectrum measured by the wide-angle X-ray diffraction method described later in the range of 12.5° ≤ 2θ ≤ 13.0° for 2θ.

[0059] As described above, by uniformly distributing the A-type niobium-titanium composite oxide phase and the B-type niobium-titanium composite oxide phase in the crystal grains of the active material, the active material exhibits improved input-output performance and cycle performance. A peak intensity ratio I exceeding 0.1 β / I α means that the crystallinity of the B-type niobium-titanium composite oxide phase is good. When the peak intensity ratio I β / I α is 0.1 or less, it means that the crystallinity of the Nb 10 Ti2O 29 type phase is very low. In addition, in the range where the peak intensity ratio I is more than 0.1 and 2.0 or less β / I α implies the coexistence of the A-type and B-type (Nb2TiO7 type and Nb 10 Ti2O 29 type) niobium-titanium composite oxide phases and uniform distribution within the particles. In contrast, when the peak intensity ratio I β / I α is greater than 2.0, it implies that the A-type and B-type phases in the active material particles are not uniformly distributed within the particles. This is because when there are distinct boundaries and non-uniformities of each phase in the particles, the influence of particle orientation appears in the wide-angle X-ray diffraction method described later, and the obtained spectrum exceeds the range of the aforementioned peak intensity ratio.

[0060] The active material preferably further satisfies the above formula (3): 0.5 ≤ M A / M B ≤ 2.5. If the mass ratio M A / M B is 0.5 or more, the relative amount of the A-type niobium-titanium composite oxide phase with excellent capacity density contained in the active material is large. Therefore, the capacity of the active material increases, and it is easy to obtain a high energy density. If the mass ratio M A / M B stays below 2.5, since the relative amount of the B-type niobium-titanium composite oxide phase with excellent diffusion of lithium ions contained in the active material is large, it is easy to obtain excellent input-output performance. In addition, when the mass ratio M A / M B is 0.5 or more and 2.5 or less, non-uniformity in the distribution of each phase within the particles is difficult to occur.

[0061] As described above, the active material according to the embodiment contains a crystalline phase A of the Nb2TiO7 type and Nb10 Ti2O 29 Crystalline phase B of type, the Nb element and Ti element in the crystal grains have a ratio of 2.3 ≤ A Nb / A Ti ≤ 4.0, and according to X-ray diffraction, the peak intensity ratio satisfies 0.1 < I β / I α ≤ 2.0, so a secondary battery capable of maintaining a high energy density while having balanced input and output performance and excellent cycle life performance can be achieved. Moreover, in the mass ratio M A / M B is 0.5 ≤ M A / M B ≤ 2.5, a more stable and uniform crystalline phase can be obtained.

[0062] The active material according to the embodiment may also contain one or more additive elements selected from Ta, K, and P. The total amount of the additive elements contained in the active material is preferably 5000 ppm or less in terms of molar ratio with respect to the niobium-titanium composite oxide. A more preferable addition 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 of K and P, the melting point can be lowered and the crystallinity can be improved.

[0063] Next, the morphology, particle size, and specific surface area of the active material according to the embodiment will be described.

[0064] <Morphology>

[0065] The morphology of the active material (niobium-titanium composite oxide) according to the embodiment is not particularly limited. The niobium-titanium composite oxide can be in the form of primary particles, for example, or in the form of secondary particles aggregated from primary particles. The particles of the niobium-titanium composite oxide can also be a mixture of primary particles and secondary particles.

[0066] The particles of the niobium-titanium composite oxide can also have a carbon-containing layer on the surface. The carbon-containing layer can be attached to the surface of the primary particles or the surface of the secondary particles. Or the particles of the niobium-titanium composite oxide can also contain secondary particles aggregated from primary particles with a carbon-containing layer attached to the surface. In such secondary particles, carbon exists between the primary particles, so excellent conductivity can be shown. The mode containing such secondary particles can make the active material-containing layer show a lower resistance, so it is preferred.

[0067] The active material can be a material containing particles and powders of the above-mentioned niobium-titanium composite oxide. The niobium-titanium composite oxide preferably accounts for 50% by mass or more and 100% by mass or less of the active material.

[0068] <Particle size>

[0069] There is no particular limitation on the average particle size of the primary particles or secondary particles of the niobium-titanium composite oxide, i.e., the active material particles. The average particle size of the active material particles is, for example, in the range of 0.1 μm or more and 50 μm or less. The average particle size can vary according to the required battery performance. For example, in order to improve the fast charge-discharge performance, it is preferable to set the average particle size to 1.0 μm or less. In this way, the diffusion distance of lithium ions in the crystal can be shortened, and thus the fast charge-discharge performance can be improved. The average particle size can be obtained, for example, by the laser diffraction method.

[0070] <BET specific surface area>

[0071] There is no particular limitation on the BET (Brunauer, Emmett, Teller) specific surface area of the active material according to the embodiment. However, the BET specific surface area is preferably 2.5 m 2 / g or more and less than 200 m 2 / g.

[0072] As long as the specific surface area is 2.5 m 2 / g or more, the contact area with the electrolyte can be ensured, and it is easy to obtain good discharge rate performance and the charging time can be shortened. On the other hand, as long as the specific surface area is less than 200 m 2 / g, the reactivity with the electrolyte will not increase too much, and the life performance can be improved. In addition, the coatability of the slurry containing the active material used for electrode manufacturing described later can be made good.

[0073] Here, in the measurement of the specific surface area, a method is adopted in which molecules with a known adsorption occupation area are adsorbed on the surface of the powder particles at the temperature of liquid nitrogen, and the specific surface area of the sample is obtained from the amount. The most commonly used is the BET method of low-temperature and low-humidity physical adsorption using an inert gas. This BET method is a method based on the BET theory, which is the most well-known theory as a calculation method of the specific surface area, and expands the Langmuir theory of the monolayer adsorption theory to the multilayer adsorption. The specific surface area obtained in this way is called the BET specific surface area.

[0074] <Manufacturing method>

[0075] The active material according to this embodiment can be manufactured by the following method.

[0076] As the starting materials, Nb2O5 particles and TiO2 particles are prepared. When adding the above-mentioned additive elements Ta, K and / or P, oxides of these additive elements are further prepared, for example, Ta2O5 particles, K2CO3 particles and / or H3PO4 particles.

[0077] Mix the initial raw materials, i.e., oxide particles. At this time, mix them in such a way that the molar ratio in the mixed initial raw materials is rich in Nb compared to Nb2O5∶TiO2 = 1∶1. Specifically, the molar ratio of Nb2O5 and TiO2 in the initial raw materials is preferably in the range of Nb2O5∶TiO2 = 1.15∶1 or more and 2.0∶1 or less. This is because if the molar ratio in the initial raw materials is within this range, in the resulting active material, the ratio A Nb of the presence ratio A of Nb in the crystal grains Ti relative to the presence ratio A of Ti Nb / A Ti expressed by satisfies 2.3 ≤ A Nb / A Ti ≤ 4.0, so that each crystal phase can be stably formed.

[0078] Perform synthesis using the mixed initial raw materials by the solid-phase method. When performing synthesis by the solid-phase method, first, mix the mixture of raw materials with a ball mill for 1 hour or more and 10 hours or less. Then, perform preliminary firing (first firing) before the main firing. Preferably, the preliminary firing is performed at a temperature of 600°C or more and 1100°C or less for 1 hour or more and 12 hours or less. By performing the preliminary firing, trace impurity components (such as water and organic substances) adsorbed on the raw material powder can be removed. The preliminary firing can also be omitted.

[0079] Preferably, the main firing (second firing) is performed at a temperature of 900°C or more and 1200°C or less for 1 hour or more and 10 hours or less. More preferably, it is fired at a temperature of 950°C or more and 1050°C or less for 2.5 hours or more and 3.5 hours or less. By making the firing temperature in the range of 900°C or more and 1200°C or less, the reaction of Nb and Ti is suppressed, thereby separating and generating crystal phases that become the nuclei of the Nb2TiO7 type phase and the Nb 10 Ti2O 29 type phase. Through this firing, the crystallinity in each crystal phase can be improved, but at this stage, for example, similar to Japanese Patent Publication No. 2019-169343, there are boundary points such as interpenetration points between the Nb 10 Ti2O 29 type phase and the Nb2TiO7 type phase in the same particle, that is, non-uniformity of the crystal phase.

[0080] After the main firing, high-temperature heat treatment is carried out. In the high-temperature heat treatment (the third firing), it is preferably heat-treated at a temperature of 1425 °C or higher and 1500 °C or lower for 0.5 hours or more and 2 hours or less. More preferably, it is heat-treated at a temperature of 1450 °C or higher and 1475 °C or lower for 0.5 hours or more and 1 hour or less. After the heat treatment, rapid cooling is carried out. By setting the heat treatment temperature in the range of 1425 °C or higher and 1500 °C or lower, Nb with a low melting point in the active material particles 10 Ti2O 29 type phase liquefies first and enters the interstitial sites of the Nb2TiO7 type phase, thereby eliminating the non-uniformity of the crystalline phase. Similarly, the Nb2TiO7 type phase also promotes the dispersion within the particles through thermal vibration, causing the disappearance of clear boundary points such as the interpenetration points, and each crystalline phase is uniformly dispersed within the particles. As a result, the obtained active material contains a crystalline phase A of the Nb2TiO7 type and Nb 10 Ti2O 29 type crystalline phase B, satisfying the ratio of the presence of Nb element and Ti element represented by the above formula (1): 2.3 ≤ A Nb / A Ti ≤ 4.0, and its X-ray powder spectrum satisfies the peak intensity ratio represented by the above formula (2): 0.1 < I β / I α ≤ 2.0.

[0081] In addition, in the crystal grains contained in the obtained active material, the mass ratio of the crystalline phase A of the Nb2TiO7 type and Nb 10 Ti2O 29 type crystalline phase B can satisfy the above formula (3): 0.5 ≤ M A / M B ≤ 2.5.

[0082] When the main firing is carried out at a temperature lower than 900 °C, the reaction between Nb and Ti is difficult to proceed, and raw material oxides remain. In addition, if the main firing is carried out at a temperature exceeding 1200 °C, since the diffusion of Nb element and Ti element proceeds relatively fast, a mixed phase of Nb2TiO7 type phase and Nb 10 Ti2O 29 type phase cannot be formed within the primary particles, and impurity phases other than the target are likely to be generated.

[0083] When the high-temperature heat treatment is carried out at a temperature lower than 1425 °C, the melting state of the Nb 10 Ti2O 29 type phase and the movement caused by thermal vibration are insufficient, and a crystalline phase with a uniform distribution within the particles cannot be obtained. In addition, when the high-temperature heat treatment is carried out at a temperature higher than 1500 °C, the Nb2TiO7 type phase and Nb 10 Ti2O29 Both the type A and type B phases liquefy simultaneously. As a result, the diffusion of Nb and Ti elements occurs significantly, and thus a mixed phase of the type A niobium-titanium composite oxide phase (crystalline phase of the Nb2TiO7 type) and the type B niobium-titanium composite oxide phase (crystalline phase of the Nb 10 Ti2O 29 type) cannot be formed within the primary particles, and impurity phases other than the target are likely to be generated.

[0084] <Measurement Method>

[0085] Hereinafter, the measurement method of the active material will be described. Specifically, powder X-ray diffraction measurement and observation using transmission electron microscopy-energy dispersive X-ray spectroscopy will be described.

[0086] When the battery contains the active material to be measured, for example, the measurement sample is taken out of the battery by the method described below.

[0087] First, in order to grasp the crystalline state of the active material, a state in which lithium ions are completely detached from the active material is formed. For example, when the active material is used for the negative electrode, the battery is brought into a fully discharged state. For example, by discharging the battery at a current of 0.1C in a 25°C environment to the rated end voltage or until the battery voltage reaches 1.0V, and repeating this multiple times until the current value during discharge reaches 1 / 100 or less of the rated capacity, the battery can be brought into a discharged state. Even in the discharged state, there may sometimes be residual lithium ions.

[0088] Next, the battery is disassembled in a glove box filled with argon, and the electrode is taken out. Then, the taken-out electrode is washed with an appropriate solvent. As the washing solvent, for example, ethylene methyl carbonate can be used. If the electrode is not washed sufficiently, impurity phases such as lithium carbonate and lithium fluoride may be mixed due to the influence of residual lithium ions in the electrode. In such a case, it is preferable to use an airtight container in which the measurement atmosphere can be in an inert gas.

[0089] <Powder X-Ray Diffraction Measurement>

[0090] The powder X-ray diffraction (XRD) measurement of the active material can be carried out as follows, for example.

[0091] First, the object sample is pulverized until the average particle size reaches about 5 μm. The average particle size can be determined by the laser diffraction method. The pulverized sample is filled into the holder part with a depth of 0.2 mm formed on the glass sample plate. At this time, attention should be paid to filling the sample sufficiently in the holder part. In addition, attention should be paid not to have cracks and voids due to insufficient sample filling. Then, it is smoothed by pressing sufficiently from the outside with another glass plate. At this time, attention should be paid not to have unevenness relative to the reference surface of the holder due to excessive or insufficient filling amount. Then, the glass plate filled with the sample is set on the powder X-ray diffractometer, and an X-ray diffraction (XRD) pattern is obtained using Cu-Kα rays.

[0092] In addition, in this measurement, the orientation of the particles is increased by the particle shape of the sample, and the dispersion state of the crystalline phase in the particles is confirmed. Therefore, the measurement using a rotary sample stage and various corrections of the crystal orientation are not performed. The rotary sample stage uses a glass capillary or the like that is known to mitigate the influence of the orientation. If such a measurement is performed, the information regarding the crystal orientation is removed, and the peak intensity ratio related to the above formula (2) cannot be obtained.

[0093] When measuring the active material contained in the electrode taken out from the battery, the cleaned electrode is cut into an area equivalent to that of the holder of the powder X-ray diffractometer as the measurement sample. This sample is directly pasted on the glass holder for measurement.

[0094] At this time, the positions of the peaks from the electrode substrate such as the metal foil are measured in advance. In addition, the peaks of other components such as the conductive agent and the binder are also measured in advance. When the peaks of the substrate and the active material overlap, it is preferable to peel off the layer containing the active material (for example, the active material-containing layer described later) from the substrate and then perform the measurement. This is to separate the overlapping peaks when quantitatively measuring the peak intensity. The layer containing the active material can also be physically peeled off, but it is easier to peel off by applying ultrasonic waves in a solvent. When performing ultrasonic treatment, the electrode material powder (including the active material, the conductive agent, and the binder) can be recovered by evaporating the solvent. By filling the recovered electrode material powder into, for example, a Lindemann glass capillary for measurement, the powder X-ray diffraction measurement of the active material can be performed. In addition, the electrode material powder recovered by ultrasonic treatment can also be used for various analyses other than the powder X-ray diffraction measurement.

[0095] As the device for powder X-ray diffraction measurement, for example, SmartLab manufactured by Rigaku Corporation is used. The measurement conditions are specified as follows:

[0096] X-ray source: Cu target

[0097] Power: 45 kV 200 mA

[0098] Soller slit: Both incident and received light are at 5°

[0099] Step size (2θ): 0.01 deg

[0100] Scanning speed: 2 deg / minute

[0101] Semiconductor detector: D / teX Ultra 250

[0102] Specimen holder: Flat glass specimen holder (thickness 0.5 mm)

[0103] Measurement range: 5° ≤ 2θ ≤ 90°.

[0104] When using other devices, perform measurements using standard Si powder for powder X-ray diffraction, find conditions that can obtain measurement results of peak intensity, full width at half maximum, and diffraction angle equivalent to those obtained by the above device, and perform specimen measurements under these conditions.

[0105] Set the conditions for XRD measurement to conditions that can obtain an XRD pattern applicable to Rietveld analysis. To collect data for Rietveld analysis, specifically, adjust the measurement time or X-ray intensity in such a way that the step size reaches 1 / 3 to 1 / 5 of the minimum full width at half maximum of the diffraction peak and the intensity at the peak position of the strongest reflection reaches 5000 cps or more.

[0106] By performing Rietveld analysis using the obtained diffraction pattern, the mass mixing ratio M of the two crystal phases can be determined A / M B .

[0107] In addition, among the obtained diffraction peaks, the peak with the maximum peak intensity in the range of 8.5° ≤ 2θ ≤ 9.0° for 2θ is defined as peak α, and this peak intensity I is determined α . In addition, the peak with the maximum peak intensity in the range of 12.5° ≤ 2θ ≤ 13.0° for 2θ in this diffraction peak is defined as peak β, and this peak intensity I is determined β . Then, the peak intensity ratio I β / I α .

[0108] <Observation using transmission electron microscope - energy dispersive X-ray spectroscopy>

[0109] Based on observations using transmission electron microscopy - energy dispersive X-ray spectroscopy (TEM-EDS), the distribution of the crystalline phases within each particle in a material with a mixed phase can be confirmed.

[0110] During transmission electron microscopy observation, it is preferable to embed the sample powder to be observed in a resin or the like, and cut out the interior of the specimen by mechanical polishing and ion milling or the like. In addition, the same treatment can be performed even if the sample to be observed is an electrode body. For example, it is also possible to embed the electrode as it is in a resin, observe the desired part, and it is also possible to peel off the current collector (metal foil) from the electrode and observe the electrode powder present as a conductive agent and an adhesive mixture. In this way, how the two crystalline phases are distributed within the particles can be understood.

[0111] The following refers to Figure 3 Specific examples will be described. Figure 3 It is a plan view schematically showing the particle to be measured. First, the center of gravity point of the particle to be measured is regarded as the center of the particle. Next, five measurement points are set at equal intervals on a straight line connecting the center of the particle and an arbitrary point on the particle surface. The multi-wave interference images of the particle parts at three points in the region orthogonal to each measurement point are investigated, and the electron beam diffraction pattern is observed. Through this observation, the crystal structure contained in this measurement point can be known. For example, by pre-simulating the electron beam diffraction pattern, it is possible to easily grasp the distributions of the Nb2TiO7-type phase and the Nb 10 Ti2O 29 type phase and other phases. In addition, the additive elements contained in the crystal can be detected by EDS analysis. By drawing an element distribution map on the TEM image, its distribution state can also be confirmed. For example, when the Nb2TiO7-type phase and the Nb 10 Ti2O 29 type phase that are separately arranged in different regions in the particle can be distinguished, or when unevenness is found in the distribution of at least any one of the crystalline phases, it is determined that a uniform distribution has not been obtained. In contrast, when a uniform distribution of the Nb2TiO7-type phase is observed in the particle, and at the same time a uniform distribution of the Nb 10 Ti2O 29 type phase is also observed, and no boundary lines such as interpenetration points and phase non-uniformity are confirmed, it can be determined that both the A-type niobium-titanium composite oxide phase and the B-type niobium-titanium composite oxide phase are uniformly distributed within the crystal grains.

[0112] The active material according to the first embodiment contains crystal grains including a niobium-titanium composite oxide. The Nb content ratio A in the crystal grains Nb relative to the Ti content ratio ATi Ratio to A Nb / A Ti Satisfies 2.3 ≤ A Nb / A Ti ≤ 4.0, and the peak intensity I of peak α that appears in the powder X-ray diffraction spectrum of the crystal grains using Cu-Kα rays in the range of 8.5° ≤ 2θ ≤ 9.0° α And the peak intensity I of peak β that appears in the range of 12.5° ≤ 2θ ≤ 13.0° β The intensity ratio I β / I α Is in the range of 0.1 < I β / I α ≤ 2.0.

[0113] This active material can realize a secondary battery that exhibits excellent weight energy density, good balance of input / output performance, and high cycle life performance.

[0114] [Second Embodiment]

[0115] According to the second embodiment, an electrode can be provided. This electrode contains the active material related to the first embodiment.

[0116] This electrode can be a battery electrode that contains the active material related to the first embodiment as an active material for the battery. As an electrode as a battery electrode, for example, it can be a negative electrode that contains the active material related to the first embodiment as a negative electrode active material.

[0117] The electrode may include a current collector and an active material-containing layer. The active material-containing layer can be formed on one or both sides of the current collector. The active material related to the first embodiment can be contained in the active material-containing layer, for example. The active material-containing layer can optionally contain a conductive agent and a binder in addition to the active material.

[0118] The active material-containing layer can also contain the powder and particles of the active material related to the first embodiment alone, or can contain the powder and particles of two or more active materials related to the first embodiment. In addition, it can also contain a mixture formed by mixing one kind of powder and particles of the active material related to the first embodiment or two or more kinds of powder and particles with one kind or two or more kinds of powder and particles of other active materials. The content ratio of the active material related to the first embodiment is preferably 50% by mass or more and 100% by mass or less with respect to the total mass of the active material related to the first embodiment and other active materials.

[0119] For example, when the active material related to the first embodiment is contained as a negative electrode active material, as an example of other active materials, lithium titanate having an orthorhombic manganese ore structure (for example, Li 2+zTi3O7, where 0 ≤ z ≤ 3), lithium titanate with a spinel structure (e.g., Li 4+z Ti5O 12 , where 0 ≤ z ≤ 3), powders and particles of monoclinic titanium dioxide (TiO2), anatase titanium dioxide, rutile titanium dioxide, todorokite-type titanium composite oxide, and orthorhombic titanium composite oxide. In addition, as other active materials, powders and particles of monoclinic niobium-titanium composite oxide with a single crystal phase inside the particles can be used.

[0120] As an example of the above orthorhombic titanium-containing composite oxide, compounds represented by Li 2+a M1 2-b Ti 6-c M2 d O 14+σ can be cited. Here, M1 is at least one selected from Sr, Ba, Ca, Mg, Na, Cs, Rb, and K. M2 is at least one selected from Zr, Sn, V, Nb, Ta, Mo, W, Y, Fe, Co, Cr, Mn, Ni, and Al. Each subscript in the composition formula is 0 ≤ a ≤ 6, 0 ≤ b < 2, 0 ≤ c < 6, 0 ≤ d < 6, -0.5 ≤ σ ≤ 0.5. As a specific example of the orthorhombic titanium-containing composite oxide, Li 2+ a Na2Ti6O 14 (0 ≤ a ≤ 6).

[0121] As an example of the particles of the above single-phase, i.e., monoclinic niobium-titanium composite oxide, single-phase particles of compounds represented by Li e Ti 1- f M3 f Nb 2-g M4 g O 7+δ can be cited. Here, M3 is at least one selected from Zr, Si, and Sn. M4 is at least one selected from V, Ta, and Bi. Each subscript in the composition formula is 0 ≤ e ≤ 5, 0 ≤ f < 1, 0 ≤ g < 2, -0.3 ≤ δ ≤ 0.3. As a specific example of the monoclinic niobium-titanium composite oxide, Li e Nb2TiO7(0 ≤ e ≤ 5).

[0122] As another example of the particles of the single-phase, i.e., monoclinic niobium-titanium composite oxide, compounds represented by Li e Ti 1-f M5 f+ g Nb 2-g O 7-δSingle-phase particles of the represented compound. Here, M5 is at least one selected from Mg, Fe, Ni, Co, W, Ta, and Mo. Each subscript in the compositional formula is 0 ≤ e ≤ 5, 0 ≤ f < 1, 0 ≤ g < 2, and -0.3 ≤ δ ≤ 0.3.

[0123] The conductive agent is incorporated to improve the current collection performance and suppress the contact resistance between the active material and the current collector. Examples of the conductive agent include carbon blacks such as vapor grown carbon fiber (VGCF) and acetylene black, and carbonaceous materials such as graphite, carbon nanotubes, and carbon nanofibers. One of them can be used as the conductive agent, or two or more of them can be used in combination as the conductive agent. Alternatively, instead of using the conductive agent, a carbon-containing layer can be provided on the surface of the active material particles, or an electron-conductive inorganic material can be coated. In addition, by coating the surface of the active material with carbon and a conductive material while using the conductive agent, the current collection performance of the active material-containing layer can be further improved.

[0124] The binder is incorporated to fill the gaps between the dispersed active materials and bond the active material 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 them can be used as the binder, or two or more of them can be used in combination as the binder.

[0125] The mixing ratios of the active material, conductive agent, and binder in the active material-containing layer can be appropriately changed according to the use of the electrode. For example, when the electrode is used as the negative electrode of a secondary battery, it is preferable to mix the active material (negative electrode active material), conductive agent, and binder at ratios 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 setting the amount of the conductive agent to 2% by mass or more, the current collection performance of the active material-containing layer can be improved. In addition, by setting the amount of the binder to 2% by mass or more, the adhesion between the active material-containing layer and the current collector is sufficient, and excellent cycle performance can be expected. On the other hand, it is preferable to set the conductive agent and the binder to 30% by mass or less each in order to increase the capacity.

[0126] When the surface of the active material is coated with carbon and a conductive material, the coating amount can be regarded as the amount contained in the conductive agent amount. The coating amount of carbon or the conductive material is preferably 0.5% by mass or more and 5% by mass or less. As long as the coating amount is within this range, the current collection performance and the electrode density can be improved.

[0127] As the current collector, a material that is electrochemically stable at the potential of intercalating and deintercalating lithium (Li) into and from the active material can be used. For example, when using the active material as the 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 achieve a balance between the strength and light weight of the electrode.

[0128] In addition, the current collector can include a portion where no negative electrode active material-containing layer is formed on its surface. This portion can function as a current collector tab.

[0129] The electrode can be manufactured, for example, by the following method. First, a slurry is prepared by suspending the active material, the conductive agent, and the binder in a solvent. The slurry is coated on one or both surfaces of the current collector. Then, the coated slurry is dried to obtain a laminate including the active material-containing layer and the current collector. Then, the laminate is pressed. Thus, the electrode is manufactured.

[0130] Alternatively, the electrode can also be manufactured 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 granular form. Then, by arranging these granules on the current collector, the electrode can be obtained.

[0131] The electrode according to the second embodiment contains the active material according to the first embodiment. Therefore, the electrode according to the second embodiment can realize a secondary battery having a high energy density, achieving a balance between the input performance and the output performance, and showing excellent cycle life performance.

[0132] [Third Embodiment]

[0133] According to the third embodiment, a secondary battery including a negative electrode, a positive electrode, and an electrolyte can be provided. The negative electrode of this secondary battery contains the electrode according to the second embodiment. That is, the negative electrode of the secondary battery according to the third embodiment includes an electrode containing the active material according to the first embodiment as the battery active material.

[0134] The secondary battery according to the third embodiment can further include a separator disposed between the positive electrode and the negative electrode. The negative electrode, the positive electrode, and the separator can form an electrode assembly. The electrolyte can be held in the electrode assembly.

[0135] In addition, the secondary battery according to the third embodiment can further include an outer packaging member for housing the electrode assembly and the electrolyte.

[0136] In addition, 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.

[0137] The secondary battery according to the third embodiment may be, for example, a lithium ion secondary battery. In addition, the secondary battery includes a non-aqueous electrolyte secondary battery containing a non-aqueous electrolyte.

[0138] Hereinafter, the negative electrode, positive electrode, electrolyte, separator, outer packaging member, negative electrode terminal, and positive electrode terminal will be described in detail.

[0139] 1) Negative electrode

[0140] The negative electrode may include a negative electrode current collector and a negative electrode active material layer-containing layer. The negative electrode current collector and the negative electrode active material layer-containing layer may be the current collector and the active material layer-containing layer that the electrode according to the second embodiment may include, respectively. The negative electrode active material layer-containing layer contains the active material according to the first embodiment as a negative electrode active material.

[0141] Parts of the details of the negative electrode that overlap with the details described in the second embodiment are omitted.

[0142] The density of the negative electrode active material layer-containing layer (excluding the current collector) is preferably 1.8 g / cm 3 or more and 3.5 g / cm 3 or less. The negative electrode having the density of the negative electrode active material layer-containing layer within this range has excellent energy density and electrolyte retention. The density of the negative electrode active material layer-containing layer is more preferably 2.5 g / cm 3 or more and 2.9 g / cm 3 or less.

[0143] The negative electrode can be produced, for example, by the same method as the electrode according to the second embodiment.

[0144] 2) Positive electrode

[0145] The positive electrode may include a positive electrode current collector and a positive electrode active material layer-containing layer. The positive electrode active material layer-containing layer may be formed on one or both surfaces of the positive electrode current collector. The positive electrode active material layer-containing layer may contain a positive electrode active material and an optional conductive agent and binder.

[0146] As the positive electrode active material, for example, an oxide or a sulfide can be used. The positive electrode may contain one compound alone as the positive electrode active material, or may contain two or more compounds in combination. Examples of the oxide and sulfide include compounds capable of intercalating and deintercalating Li or Li ions.

[0147] Examples of such compounds include: manganese dioxide (MnO2), iron oxide, copper oxide, nickel oxide, lithium manganese composite oxide (e.g., Li x Mn2O4 or Lix MnO2, where 0 < x ≤ 1), lithium nickel composite oxides (such as Li x NiO2, where 0 < x ≤ 1), lithium cobalt composite oxides (such as Li x CoO2, where 0 < x ≤ 1), lithium nickel cobalt composite oxides (such as Li x Ni 1-y Co y O2, where 0 < x ≤ 1, 0 < y < 1), lithium manganese cobalt composite oxides (such as Li x Mn y Co 1-y O2, where 0 < x ≤ 1, 0 < y < 1), lithium manganese nickel composite oxides with spinel structure (such as Li x Mn 2-y Ni y O4, where 0 < x ≤ 1, 0 < y < 2), lithium phosphates with olivine structure (such as Li x FePO4, where 0 < x ≤ 1, Li x Fe 1-y Mn y PO4, where 0 < x ≤ 1, 0 < y ≤ 1, Li x CoPO4, where 0 < x ≤ 1), iron sulfate (Fe2(SO4)3), vanadium oxides (such as V2O5) and lithium nickel cobalt manganese composite oxides (Li x Ni 1-y-z Co y Mn z O2, where 0 < x ≤ 1, 0 < y < 1, 0 < z < 1, y + z < 1).

[0148] Among the above, examples of preferred compounds as the positive electrode active material include: lithium manganese composite oxides with spinel structure (such as Li x Mn2O4, where 0 < x ≤ 1), lithium nickel composite oxides (such as Li x NiO2, where 0 < x ≤ 1), lithium cobalt composite oxides (such as Li x CoO2, where 0 < x ≤ 1), lithium nickel cobalt composite oxides (such as Li x Ni 1-y Co y O2, where 0 < x ≤ 1, 0 < y < 1), lithium manganese nickel composite oxides with spinel structure (such as Li x Mn 2-y Ni y O4, where 0 < x ≤ 1, 0 < y < 2), lithium manganese cobalt composite oxides (such as Li x Mn y Co 1-y O2, where 0 < x ≤ 1, 0 < y < 1), lithium iron phosphate (such as Li xFePO4, where 0 < x ≤ 1) and lithium nickel cobalt manganese composite oxide (Li x Ni 1-y-z Co y Mn z O2, where 0 < x ≤ 1, 0 < y < 1, 0 < z < 1, and y + z < 1). If these compounds are used in the positive electrode active material, the positive electrode potential can be increased.

[0149] 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), lithium manganese composite oxide, lithium nickel composite oxide, lithium nickel cobalt composite oxide, or a mixture thereof. These compounds can improve the cycle life because of their low reactivity with the room temperature molten salt. Details of the room temperature molten salt will be described later.

[0150] The primary particle size of the positive electrode active material is preferably 100 nm or more and 1 μm or less. The positive electrode active material with a primary particle size of 100 nm or more is easy to handle in industrial production. The positive electrode active material with a primary particle size of 1 μm or less allows smooth solid-state diffusion of lithium ions.

[0151] The specific surface area of the positive electrode active material is preferably 0.1 m 2 / g or more and 10 m 2 / g or less. The positive electrode active material with a specific surface area of 0.1 m 2 / g or more can sufficiently ensure the insertion and extraction sites of Li ions. The positive electrode active material with a specific surface area of 10 m 2 / g or less is easy to handle in industrial production and can ensure good charge-discharge cycle performance.

[0152] The binder is added to fill the gaps between the dispersed positive electrode active materials and to bond 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 them can be used as the binder, or two or more of them can be combined and used as the binder.

[0153] The conductive agent is incorporated to improve the current collection performance and suppress the contact resistance between the positive electrode active material and the positive electrode current collector. Examples of the conductive agent include carbonaceous materials such as vapor grown carbon fiber (VGCF), acetylene black, and graphite. One of them can be used as the conductive agent, or two or more of them can be used in combination as the conductive agent. In addition, the conductive agent can be omitted.

[0154] In the positive electrode active material-containing layer, the positive electrode active material and the binder are preferably incorporated at ratios of 80% by mass or more and 98% by mass or less, and 2% by mass or more and 20% by mass or less, respectively.

[0155] By making the amount of the binder 2% by mass or more, sufficient electrode strength can be obtained. In addition, the binder can function as an insulator. Therefore, if the amount of the binder is 20% by mass or less, the amount of the insulator contained in the electrode is reduced, and the internal resistance can be lowered.

[0156] When a conductive agent is added, the positive electrode active material, the binder, and the conductive agent are preferably incorporated at ratios 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.

[0157] By making the amount of the conductive agent 3% by mass or more, the above-described effects can be exhibited. In addition, by making the amount of the conductive agent 15% by mass or less, the ratio of the conductive agent in contact with the electrolyte can be reduced. If this ratio is low, the decomposition of the electrolyte can be reduced during high-temperature storage.

[0158] 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.

[0159] The thickness of the aluminum foil or the 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% by mass or more. The content of transition metals such as iron, copper, nickel, and chromium contained in the aluminum foil or the aluminum alloy foil is preferably 1% by mass or less.

[0160] In addition, the positive electrode current collector may include a portion where the positive electrode active material-containing layer is not formed on its surface. This portion can function as a positive electrode current collector tab.

[0161] The positive electrode can be produced, for example, by using the positive electrode active material and the same method as the electrode according to the second embodiment.

[0162] 3) Electrolyte

[0163] As the electrolyte, for example, a liquid non-aqueous electrolyte or a gel non-aqueous electrolyte can be used. The liquid non-aqueous electrolyte can be 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.

[0164] 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), lithium bis(trifluoromethanesulfonyl)imide (LiN(CF3SO2)2), and lithium bis[fluorosulfonyl]imide (LiN(SO2F)2: LiFSI), and mixtures thereof. The electrolyte salt is preferably difficult to oxidize even at a high potential, and most preferably LiPF6.

[0165] Examples of the organic solvent 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-methyltetrahydrofuran (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.

[0166] The gel non-aqueous electrolyte can be prepared by complexing a liquid non-aqueous electrolyte with a polymer material. Examples of the polymer material include polyvinylidene fluoride (PVdF), polyacrylonitrile (PAN), polyethylene oxide (PEO), or mixtures thereof.

[0167] Alternatively, as the non-aqueous electrolyte, in addition to the liquid non-aqueous electrolyte and the gel non-aqueous electrolyte, a room temperature molten salt (ionic melt) containing lithium ions, a polymer solid electrolyte, an inorganic solid electrolyte, etc. can also be used.

[0168] The room temperature molten salt (ionic melt) refers to a compound that can exist as a liquid at room temperature (above 15°C and below 25°C) in an organic salt composed of a combination of an organic cation and an anion. The room temperature molten salt includes a room temperature molten salt in which the monomer exists as a liquid, a room temperature molten salt that becomes liquid by mixing with an electrolyte salt, a room temperature molten salt that becomes liquid by dissolving in an organic solvent, or a mixture thereof. Generally speaking, the melting point of the room temperature molten salt used in secondary batteries is 25°C or lower. In addition, the organic cation generally has a quaternary ammonium skeleton.

[0169] The polymer solid electrolyte can be prepared by dissolving an electrolyte salt in a polymer material and solidifying it.

[0170] The inorganic solid electrolyte is a solid substance having Li ion conductivity.

[0171] Alternatively, a liquid aqueous electrolyte or a gel aqueous electrolyte can be used to replace the non-aqueous electrolyte as the electrolyte. The liquid aqueous electrolyte can be prepared, for example, by dissolving the following electrolyte salt in an aqueous solvent. The gel aqueous electrolyte can be prepared by complexing the liquid aqueous electrolyte and the above polymer material. As the aqueous solvent, an aqueous solution can be used. The so-called aqueous solution can be pure water or a mixed solvent of water and an organic solvent.

[0172] As the electrolyte salt that can be used in the aqueous electrolyte, for example, lithium salts, sodium salts, or a mixture thereof can be cited.

[0173] As the lithium salt, for example, lithium chloride (LiCl), lithium bromide (LiBr), lithium hydroxide (LiOH), lithium sulfate (Li2SO4), lithium nitrate (LiNO3), lithium acetate (CH3COOLi), lithium oxalate (Li2C2O4), lithium carbonate (Li2CO3), bis[trifluoromethanesulfonyl]imide lithium (LiTFSI: LiN(SO2CF 3)2 )2), bis[fluorosulfonyl]imide lithium (LiFSI: LiN(SO2F)2), and lithium bis(oxalato)borate (LiBOB: LiB[(OCO)2]2), etc. can be used.

[0174] As the sodium salt, sodium chloride (NaCl), sodium sulfate (Na2SO4), sodium hydroxide (NaOH), sodium nitrate (NaNO3), sodium trifluoromethanesulfonamide (NaTFSA), etc. can be used.

[0175] The molar concentration of lithium ions or sodium ions in the aqueous electrolyte is preferably 3 mol / L or more, more preferably 6 mol / L or more, and still more preferably 12 mol / L or more. In the case of using an aqueous electrolyte, an electrolysis reaction of the aqueous solvent occurs in the negative electrode, which may cause self-discharge and hydrogen generation. If the concentration of lithium ions or sodium ions in the aqueous electrolyte is high, there is a tendency to easily suppress the electrolysis of the aqueous solvent in the negative electrode and reduce hydrogen generation from the negative electrode.

[0176] In addition, in addition to lithium salts and sodium salts, zinc salts such as zinc chloride and zinc sulfate can also be added to the aqueous electrolyte. By adding such compounds to the aqueous electrolyte, in a battery using the active material according to the first embodiment for the negative electrode, a zinc-containing coating layer and / or an oxidized zinc-containing region can be formed in the negative electrode. The members containing these zincs can exhibit the effect of suppressing hydrogen generation in the negative electrode having these structures.

[0177] 4) Separator

[0178] The separator can be formed, for example, from a porous film or a non-woven fabric made of synthetic resin containing polyethylene (PE), polypropylene (PP), cellulose, or polyvinylidene fluoride (PVdF). From the viewpoint of safety, it is preferable to use a porous film made of polyethylene or polypropylene. Because these porous films melt at a certain temperature and can cut off the current.

[0179] 5) Outer packaging member

[0180] As the outer packaging member, for example, a container made of a laminated film or a metal container can be used.

[0181] The thickness of the laminated film is, for example, 0.5 mm or less, preferably 0.2 mm or less.

[0182] As the laminated film, a multilayer film including a plurality of resin layers and a metal layer sandwiched between these resin layers can be used. The resin layer contains, for example, high molecular materials such as polypropylene (PP), polyethylene (PE), nylon, and polyethylene terephthalate (PET). The metal layer is preferably formed of aluminum foil or aluminum alloy foil for weight reduction. The laminated film can be sealed by heat melting and formed into the shape of the outer packaging member.

[0183] The wall thickness of the metal container is, for example, preferably 1 mm or less, more preferably 0.5 mm or less, and still more preferably 0.2 mm or less.

[0184] The metal container can be made of, for example, aluminum or an aluminum alloy. Preferably, the aluminum alloy contains elements such as magnesium, zinc, and silicon. When the aluminum alloy contains transition metals such as iron, copper, nickel, and chromium, the content is preferably 100 mass ppm or less.

[0185] The shape of the outer packaging member is not particularly limited. The shape of the outer packaging member can also be, for example, a flat type (thin type), a square type, a cylindrical type, a coin type, or a button type, etc. The outer packaging member can be appropriately selected according to the battery size and the use of the battery.

[0186] 6) Negative terminal

[0187] The negative terminal can be formed of a material that is electrochemically stable at the Li insertion / extraction potential of the above-mentioned negative electrode active material and has conductivity. Specifically, as the material of the negative terminal, copper, nickel, stainless steel, or aluminum, or an aluminum alloy containing at least one element selected from Mg, Ti, Zn, Mn, Fe, Cu, and Si can be cited. As the material of the negative terminal, aluminum or an aluminum alloy is preferably used. The negative terminal is preferably formed of the same material as the negative electrode current collector in order to reduce the contact resistance with the negative electrode current collector.

[0188] 7) Positive terminal

[0189] The positive terminal can be formed of a material that is electrochemically stable within a potential range of 3 V or more and 5 V or less with respect to the redox potential of lithium (vs. Li / Li + ) and has conductivity. As the material of the positive terminal, aluminum or an aluminum alloy containing at least one element selected from Mg, Ti, Zn, Mn, Fe, Cu, and Si can be cited. The positive terminal is preferably formed of the same material as the positive electrode current collector in order to reduce the contact resistance with the positive electrode current collector.

[0190] Next, the secondary battery according to the third embodiment will be described more specifically with reference to the drawings.

[0191] Figure 4 is a cross-sectional view schematically showing an example of the secondary battery according to the third embodiment. Figure 5 is Figure 4 an enlarged cross-sectional view of part A of the secondary battery shown.

[0192] Figure 4 and Figure 5 The secondary battery 100 shown includes: Figure 4 the electrode group 1 shown in Figure 4 and Figure 5 the bag-shaped outer packaging member 2 shown and an electrolyte (not shown). The electrode group 1 and the electrolyte are housed in the bag-shaped outer packaging member 2. The electrolyte (not shown) is held in the electrode group 1.

[0193] The bag-shaped outer packaging member 2 is made of a laminated film including two resin layers and a metal layer sandwiched between the two resin layers.

[0194] As Figure 4 shown, the electrode group 1 is a flat wound-type electrode group. The flat wound-type electrode group 1, as Figure 5 shown, 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.

[0195] The negative electrode 3 includes a negative electrode current collector 3a and a negative electrode active material layer 3b. In the negative electrode 3, the portion located at the outermost shell of the wound-type electrode group 1 has the negative electrode active material layer 3b formed only on the inner surface side of the negative electrode current collector 3a, as Figure 5 shown. In other portions of the negative electrode 3, the negative electrode active material layer 3b is formed on both surfaces of the negative electrode current collector 3a.

[0196] The positive electrode 5 includes a positive electrode current collector 5a and positive electrode active material layers 5b formed on both of its surfaces.

[0197] As Figure 4 shown, the negative terminal 6 and the positive terminal 7 are located near the outer peripheral end of the wound-type electrode group 1. The negative terminal 6 is connected to the portion located at the outermost shell of the negative electrode current collector 3a. In addition, the positive terminal 7 is connected to the portion located at the outermost layer of the positive electrode current collector 5a. These negative terminal 6 and positive terminal 7 extend out of the opening of the bag-shaped outer packaging member 2 to the outside. A thermoplastic resin layer is provided on the inner surface of the bag-shaped outer packaging member 2, and the opening is closed by thermally melting and bonding it.

[0198] The secondary battery according to the third embodiment is not limited to Figure 4 and Figure 5 the secondary battery having the configuration shown, and for example, it may also be a battery having the configuration shown in Figure 6 and Figure 7 shown.

[0199] Figure 6 is a partial cutaway perspective view schematically showing another example of the secondary battery according to the third embodiment. Figure 7 is Figure 6 an enlarged cross-sectional view of part B of the secondary battery shown.

[0200] Figure 6 and Figure 7 shown, the secondary battery 100 includes Figure 6 and Figure 7 shown electrode group 1, Figure 6 shown outer packaging member 2, and an electrolyte (not shown). The electrode group 1 and the electrolyte are housed in the outer packaging member 2. The electrolyte is held in the electrode group 1.

[0201] The outer packaging member 2 is composed of a laminated film including two resin layers and a metal layer sandwiched between the two resin layers.

[0202] As Figure 7 shown, the electrode group 1 is a stacked electrode group. The stacked electrode group 1 has a structure in which a separator 4 is sandwiched between a negative electrode 3 and a positive electrode 5 and they are alternately stacked.

[0203] 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 negative electrode active material layers 3b supported on both surfaces of the negative electrode current collector 3a. In addition, the electrode group 1 includes a plurality of positive electrodes 5. Each of the plurality of positive electrodes 5 includes a positive electrode current collector 5a and positive electrode active material layers 5b supported on both surfaces of the positive electrode current collector 5a.

[0204] One side of the negative electrode current collector 3a of each negative electrode 3 has a portion 3c on which no negative electrode active material layer 3b is supported on either surface. This portion 3c functions as a negative electrode current collector tab. As Figure 7 shown, the portion 3c functioning as a negative electrode current collector tab does not overlap with the positive electrode 5. In addition, a plurality of negative electrode current collector tabs (portions 3c) are electrically connected to a strip-shaped negative terminal 6. The front end of the strip-shaped negative terminal 6 is led out to the outside of the outer packaging member 2.

[0205] In addition, although not shown, one side of the positive electrode current collector 5a of each positive electrode 5 also includes a portion on which no positive electrode active material layer 5b is supported on either surface. This portion functions as a positive electrode current collector tab. The positive electrode current collector tab does not overlap with the negative electrode 3 in the same way as the negative electrode current collector tab (portion 3c). In addition, the positive electrode current collector tab is located on the opposite side of the electrode group 1 with respect to the negative electrode current collector tab (portion 3c). The positive electrode current collector tab is electrically connected to a strip-shaped positive terminal 7. The front end of the strip-shaped positive terminal 7 is located on the opposite side of the negative terminal 6 and is led out to the outside of the outer packaging member 2.

[0206] The secondary battery according to the third embodiment includes the electrode according to the second embodiment. That is, the secondary battery according to the third embodiment includes an electrode containing the active material according to the first embodiment. Therefore, the secondary battery according to the third embodiment has a high energy density, achieves a balance between input performance and output performance, and can exhibit excellent cycle life performance.

[0207] [Fourth Embodiment]

[0208] According to the fourth embodiment, a battery pack can be provided. The battery pack according to the fourth embodiment includes a plurality of secondary batteries according to the third embodiment.

[0209] In the battery pack according to the fourth embodiment, each single battery can be configured by being electrically connected in series or in parallel, or can also be configured by combining series connection and parallel connection.

[0210] Next, an example of the battery pack according to the fourth embodiment will be described with reference to the drawings.

[0211] Figure 8 It is a perspective view schematically showing an example of the battery pack according to the fourth embodiment. Figure 8 The shown battery pack 200 includes five single batteries 100a to 100e, four bus bars 21, a positive electrode side lead 22, and a negative electrode side lead 23. The five single batteries 100a to 100e are respectively secondary batteries according to the third embodiment.

[0212] The bus bar 21 connects, for example, the negative electrode terminal 6 of one single battery 100a and the positive electrode terminal 7 of the adjacent single battery 100b. In this way, the five single batteries 100 are connected in series by the four bus bars 21. That is, Figure 8 the battery pack 200 is a battery pack of five in series. Although not shown as an example, in a battery pack including a plurality of single batteries electrically connected in parallel, for example, a plurality of negative electrode terminals are connected to each other through a bus bar, and at the same time, a plurality of positive electrode terminals are connected to each other through a bus bar, whereby a plurality of single batteries can be electrically connected.

[0213] The positive electrode terminal 7 of at least one battery among the five single batteries 100a to 100e is electrically connected to the positive electrode side lead 22 for external connection. In addition, the negative electrode terminal 6 of at least one battery among the five single batteries 100a to 100e is electrically connected to the negative electrode side lead 23 for external connection.

[0214] The battery pack according to the fourth embodiment includes the secondary battery according to the third embodiment. Therefore, it has a high energy density, achieves a balance between input performance and output performance, and can exhibit excellent cycle life performance.

[0215] [Fifth Embodiment]

[0216] According to the fifth embodiment, a battery pack can be provided. This battery pack includes the battery pack according to the fourth embodiment. This battery pack may also include a single secondary battery according to the third embodiment instead of the battery pack according to the fourth embodiment.

[0217] The battery pack according to the fifth embodiment can further include a protection circuit. The protection circuit has a function of controlling the charge and discharge of the secondary battery. Alternatively, a circuit included in a device (such as an electronic device, an automobile, etc.) that uses the battery pack as a power source can also be used as the protection circuit of the battery pack.

[0218] In addition, the battery pack according to the fifth embodiment may further include an external terminal for power conduction. The external terminal for power conduction is used to output the current from the secondary battery to the outside and / or input the current from the outside to the secondary battery. In other words, when the battery pack is used as a power source, the current can be supplied to the outside through the external terminal for power conduction. In addition, when the battery pack is charged, the charging current (including the regenerative energy of the power of an automobile or the like) can be supplied to the battery pack through the external terminal for power conduction.

[0219] Next, an example of the battery pack according to the fifth embodiment will be described with reference to the accompanying drawings.

[0220] Figure 9 FIG. is an exploded perspective view schematically showing an example of the battery pack according to the fifth embodiment. Figure 10 It shows Figure 9 FIG. is a block diagram showing an example of the circuit of the battery pack shown.

[0221] Figure 9 and Figure 10 The battery pack 300 shown includes a storage container 31, a lid 32, a protective sheet 33, a battery pack 200, a printed circuit wiring board 34, wiring 35, and an insulating board (not shown).

[0222] Figure 9 The storage container 31 shown is a bottomed square container having a rectangular bottom surface. The storage container 31 is configured to be able to store the protective sheet 33, the battery pack 200, the printed circuit wiring board 34, and the wiring 35. The lid 32 has a rectangular shape. The lid 32 covers the storage container 31 to store the battery pack 200 and the like. Openings or connection terminals for connecting to external devices or the like are provided on the storage container 31 and the lid 32, although not shown.

[0223] The battery pack 200 includes a plurality of single cells 100, a positive electrode side lead 22, a negative electrode side lead 23, and an adhesive tape 24.

[0224] At least one of the plurality of single cells 100 is the secondary battery according to the third embodiment. The plurality of single cells 100 are electrically connected in series as shown in Figure 10 FIG. The plurality of single cells 100 may also be electrically connected in parallel, or may be connected in a combination of series connection and parallel connection. If the plurality of single cells 100 are connected in parallel, the battery capacity increases compared to when they are connected in series.

[0225] The adhesive tape 24 bundles multiple single cells 100. A heat shrinkable tape may also be used instead of the adhesive tape 24 to fix multiple single cells 100. In this case, protective sheets 33 are arranged on both side surfaces of the battery pack 200, and after the heat shrinkable tape is wound around, multiple single cells 100 are bundled by heat shrinking the heat shrinkable tape.

[0226] One end of the positive electrode side lead 22 is connected to the battery pack 200. One end of the positive electrode side lead 22 is electrically connected to the positive electrodes of one or more single cells 100. One end of the negative electrode side lead 23 is connected to the battery pack 200. One end of the negative electrode side lead 23 is electrically connected to the negative electrodes of one or more single cells 100.

[0227] The printed circuit wiring board 34 is provided on the surface along one short side direction in the inner side surface of the storage container 31. The printed circuit wiring board 34 includes a positive electrode side connector 342, a negative electrode side connector 343, a thermistor 345, a protection circuit 346, wirings 342a and 343a, external terminals 350 for energization, a positive electrode side wiring (positive side wiring) 348a, and a negative electrode side wiring (negative side wiring) 348b. One main surface of the printed circuit wiring board 34 faces one side surface of the battery pack 200. An insulating board (not shown) is sandwiched between the printed circuit wiring board 34 and the battery pack 200.

[0228] The other end 22a of the positive electrode side lead 22 is electrically connected to the positive electrode side connector 342. The other end 23a of the negative electrode side lead 23 is electrically connected to the negative electrode side connector 343.

[0229] The thermistor 345 is fixed on one main surface of the printed circuit wiring board 34. The thermistor 345 detects the temperature of each single cell 100 and sends its detection signal to the protection circuit 346.

[0230] The external terminals 350 for energization are fixed on the other main surface of the printed circuit wiring board 34. The external terminals 350 for energization are electrically connected to the devices existing outside the battery pack 300. The external terminals 350 for energization include a positive side terminal 352 and a negative side terminal 353.

[0231] The protection circuit 346 is fixed on the other main surface of the printed circuit wiring board 34. The protection circuit 346 is connected to the positive side terminal 352 through the positive electrode side wiring 348a. The protection circuit 346 is connected to the negative side terminal 353 through the negative electrode side wiring 348b. In addition, the protection circuit 346 is electrically connected to the positive electrode side connector 342 through the wiring 342a. The protection circuit 346 is electrically connected to the negative electrode side connector 343 through the wiring 343a. Further, the protection circuit 346 is electrically connected to multiple single cells 100 through the wiring 35 respectively.

[0232] The protective sheet 33 is disposed on the inner sides of both ends in the long side direction of the storage container 31 and on the inner sides of both ends in the short side direction opposite to the printed circuit wiring board 34 via the battery pack 200. The protective sheet 33 is formed of, for example, resin or rubber.

[0233] The protection circuit 346 controls the charging and discharging of the plurality of single cells 100. Further, the protection circuit 346 blocks the electrical connection between the protection circuit 346 and the external terminals 350 (positive electrode side terminal 352, negative electrode side terminal 353) for energizing an external device based on a detection signal sent from the thermistor 345 or a detection signal sent from each single cell 100 or the battery pack 200.

[0234] As the detection signal sent from the thermistor 345, for example, a signal indicating that the temperature of the single cell 100 has reached a predetermined temperature or higher can be cited. As the detection signal sent from each single cell 100 or the battery pack 200, for example, a signal indicating overcharge, overdischarge, and overcurrent of the single cell 100 can be cited. When detecting overcharge or the like in each single cell 100, the battery voltage can be detected, or the positive electrode potential or the negative electrode potential can be detected. In the latter case, a lithium electrode used as a reference electrode is inserted into each single cell 100.

[0235] Further, as the protection circuit 346, a circuit included in a device (for example, an electronic device, an automobile, etc.) that uses the battery pack 300 as a power source can also be used.

[0236] Further, as described above, the battery pack 300 includes the external terminals 350 for energization. Therefore, the battery pack 300 can output the current from the battery pack 200 to an external device via the external terminals 350 for energization, and at the same time, can input the current from the external device to the battery pack 200. In other words, when using the battery pack 300 as a power source, the current from the battery pack 200 can be supplied to an external device through the external terminals 350 for energization. Further, when charging the battery pack 300, the charging current from the external device can be supplied to the battery pack 300 through the external terminals 350 for energization. When using the battery pack 300 as an in-vehicle battery, the regenerative energy of the vehicle power can be used as the charging current from the external device.

[0237] Further, the battery pack 300 may include a plurality of battery packs 200. In this case, the plurality of battery packs 200 can be connected in series, in parallel, or in a combination of series connection and parallel connection. Further, the printed circuit wiring board 34 and the wiring 35 may be omitted. In this case, the positive electrode side lead 22 and the negative electrode side lead 23 can be used as the positive side terminal 352 and the negative side terminal 353 of the external terminals 350 for energization, respectively.

[0238] Such a battery pack can be used, for example, in applications that require excellent cycle performance when drawing a large current. Specifically, the battery pack can be used, for example, as a power source for electronic devices, a stationary battery, or a vehicle-mounted battery for various vehicles. As an electronic device, a digital camera can be cited, for example. The battery pack is particularly suitable for use as a vehicle-mounted battery.

[0239] The battery pack according to the fifth embodiment includes the secondary battery according to the third embodiment or the battery group according to the fourth embodiment. Therefore, it has a high energy density, achieves a balance between input performance and output performance, and can exhibit excellent cycle life performance.

[0240] [Sixth Embodiment]

[0241] According to the sixth embodiment, a vehicle can be provided. The vehicle is equipped with the battery pack according to the fifth embodiment.

[0242] In the vehicle according to the sixth embodiment, the battery pack can recover, for example, the regenerative energy of the vehicle's power. The vehicle may also include a mechanism (Regenerator) that converts the vehicle's kinetic energy into regenerative energy.

[0243] As an example of the vehicle according to the sixth embodiment, two-wheeled to four-wheeled hybrid electric vehicles, two-wheeled to four-wheeled electric vehicles, assist bicycles, and railway vehicles can be cited, for example.

[0244] The mounting position of the battery pack in the vehicle according to the sixth embodiment is not particularly limited. For example, when mounting the battery pack in an automobile, the battery pack can be mounted in the engine room of the vehicle, behind the vehicle body, or under the seat.

[0245] The vehicle according to the sixth embodiment can also be equipped with multiple battery packs. In this case, the batteries included in each battery pack can be electrically connected in series with each other, in parallel with each other, or in a combined series and parallel connection manner. For example, when each battery pack includes a battery group, the battery groups can be electrically connected in series with each other, in parallel with each other, or in a combined series and parallel connection manner. Or, when each battery pack includes a single battery, the batteries can be electrically connected in series with each other, in parallel with each other, or in a combined series and parallel connection manner.

[0246] Next, an example of the vehicle according to the sixth embodiment will be described with reference to the drawings.

[0247] Figure 11 It is a partial perspective view schematically showing an example of the vehicle according to the sixth embodiment.

[0248] Figure 11 The illustrated vehicle 400 includes a vehicle body 40 and a battery pack 300 according to the fifth embodiment. In Figure 11 the illustrated example, the vehicle 400 is a four-wheel automobile.

[0249] The vehicle 400 may also be equipped with a plurality of battery packs 300. In this case, the batteries (such as single cells or battery groups) included in the battery pack 300 may be connected in series, in parallel, or in a combination of series and parallel connections.

[0250] Figure 11 An example of mounting the battery pack 300 in the engine room in front of the vehicle body 40 is illustrated. As described above, the battery pack 300 may also be mounted, for example, behind the vehicle body 40 or under the seat. The battery pack 300 can be used as a power source for the vehicle 400. In addition, the battery pack 300 can recover the regenerative energy of the power of the vehicle 400.

[0251] Next, refer to Figure 12 to describe an embodiment of a vehicle according to the sixth embodiment.

[0252] Figure 12 is a diagram schematically showing an example of a control system related to the electrical system in a vehicle according to the sixth embodiment. Figure 12 The illustrated vehicle 400 is an electric vehicle.

[0253] Figure 12 The illustrated vehicle 400 includes a vehicle body 40, a vehicle power source 41, a host control device of the vehicle power source 41, that is, a vehicle ECU (ECU: Electric Control Unit) 42, an external terminal (a terminal for connecting to an external power source) 43, an inverter 44, and a drive motor 45.

[0254] The vehicle 400 mounts the vehicle power source 41, for example, in the engine room, behind the vehicle body, or under the seat. Furthermore, in Figure 12 the illustrated vehicle 400, the mounting position of the vehicle power source 41 is schematically shown.

[0255] The vehicle power source 41 includes a plurality of (for example, three) battery packs 300a, 300b, and 300c, a battery management device (BMU: Battery Management Unit) 411, and a communication bus 412.

[0256] The battery pack 300a includes a battery module 200a and a battery module monitoring device 301a (e.g., VTM: Voltage Temperature Monitoring). The battery pack 300b includes a battery module 200b and a battery module monitoring device 301b. The battery pack 300c includes a battery module 200c and a battery module monitoring device 301c. The battery packs 300a to 300c are the same as the above-mentioned battery pack 300, and the battery modules 200a to 200c are the same as the above-mentioned battery module 200. The battery modules 200a to 200c are electrically connected in series. The battery packs 300a, 300b, and 300c can be independently detached and exchanged with other battery packs 300.

[0257] Each of the battery modules 200a to 200c includes a plurality of single cells connected in series. At least one of the plurality of single cells is a secondary battery according to the third embodiment. Each of the battery modules 200a to 200c is charged and discharged through a positive terminal 413 and a negative terminal 414.

[0258] The battery management device 411 communicates between the battery module monitoring devices 301a to 301c, and collects information on voltage, temperature, etc. for each single cell 100 included in the battery modules 200a to 200c of the vehicle power supply 41. Thus, the battery management device 411 collects information on the maintenance of the vehicle power supply 41.

[0259] The battery management device 411 and the battery module monitoring devices 301a to 301c are connected via a communication bus 412. In the communication bus 412, a set of communication lines is shared among a plurality of nodes (the battery management device 411 and one or more battery module monitoring devices 301a to 301c). The communication bus 412 is, for example, a communication bus configured based on the CAN (Control Area Network) standard.

[0260] The battery module monitoring devices 301a to 301c measure the voltage and temperature of each single cell constituting the battery modules 200a to 200c based on a communication instruction from the battery management device 411. However, the temperature can be measured at only a few locations for one battery module, and the temperature of all single cells may not be measured.

[0261] The vehicle power supply 41 may further include an electromagnetic contactor (e.g., Figure 12The switch device 415) shown. The switch device 415 includes a pre-charge switch (not shown) that is turned on when charging the battery packs 200a to 200c, and a main switch (not shown) that is turned on when supplying the output from the battery packs 200a to 200c to the load. The pre-charge switch and the main switch each have a relay circuit (not shown), which is turned on or off based on a signal supplied to a coil disposed near the switching element. Based on a control signal from the vehicle ECU 42 that controls the operation of the battery management device 411 or the vehicle 400 as a whole, electromagnetic contactors such as the switch device 415 are controlled.

[0262] The inverter 44 converts the input DC voltage into a high voltage three-phase alternating current (AC) for driving the motor. The three-phase output terminals of the inverter 44 are connected to the respective three-phase input terminals of the drive motor 45. Based on a control signal from the vehicle ECU 42 that controls the battery management device 411 or the overall operation of the vehicle, the inverter 44 is controlled. The output voltage from the inverter 44 is adjusted by controlling the inverter 44.

[0263] The drive motor 45 rotates by the power supplied by the inverter 44. The driving force generated by the rotation of the drive motor 45 is transmitted to the axle and the drive wheels W through, for example, a differential gear unit.

[0264] In addition, although not shown, the vehicle 400 is equipped with a regenerative braking mechanism (regenerator), which rotates the drive motor 45 when braking the vehicle 400 and converts the 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 converted direct current is input to the vehicle power supply 41.

[0265] One terminal of the connection line L1 is connected to the negative terminal 414 of the vehicle power supply 41. The other terminal of the connection line L1 is connected to the negative input terminal 417 of the inverter 44. In the connection line L1, a current detection unit (current detection circuit) 416 within the battery management device 411 is provided between the negative terminal 414 and the negative input terminal 417.

[0266] One terminal of the connection line L2 is connected to the positive terminal 413 of the vehicle power supply 41. The other terminal of the connection line L2 is connected to the positive input terminal 418 of the inverter 44. In the connection line L2, the switch device 415 is provided between the positive terminal 413 and the positive input terminal 418.

[0267] The external terminal 43 is connected to the battery management device 411. The external terminal 43 can be connected to an external power supply, for example.

[0268] The vehicle ECU 42 coordinates and controls the vehicle power supply 41, the switching device 415, the inverter 44, etc. in response to operation inputs from the driver or the like, together with other management devices and control devices including the battery management device 411. Through the coordinated control by the vehicle ECU 42 and the like, the output of the power from the vehicle power supply 41, the charging of the vehicle power supply 41, etc. are controlled, and the overall management of the vehicle 400 is carried out. Between the battery management device 411 and the vehicle ECU 42, data transmission regarding the maintenance of the vehicle power supply 41 such as the remaining capacity of the vehicle power supply 41 is performed through a communication line.

[0269] The vehicle according to the sixth embodiment is equipped with the battery pack according to the fifth embodiment. Therefore, a vehicle with high performance and high reliability can be provided.

[0270] [Examples]

[0271] Hereinafter, the above-described embodiments will be described in more detail based on examples.

[0272] <Synthesis method>

[0273] (Example 1)

[0274] The niobium-titanium composite oxide is synthesized by the solid-phase synthesis method described below.

[0275] First, Nb2O5 particles and TiO2 particles are prepared. In order to obtain the target crystal phase, each particle is weighed so that the molar ratio of Nb2O5 to TiO2 reaches 1.7:1, and they are mixed with a dry ball mill for 1 hour. The obtained powder is put into an alumina crucible and subjected to a preliminary firing (the first firing) at a temperature of 800 °C for 12 hours. After the preliminary firing, the obtained powder is put into a platinum crucible and subjected to a main firing (the second firing) at 1050 °C for 3 hours. After the main firing, the powder is again pulverized with a dry ball mill for 3 hours and then subjected to a high-temperature heat treatment (the third firing) at a temperature of 1475 °C for 1 hour. Then, it is pulverized again with a dry ball mill for 1 hour to obtain the active material of Example 1.

[0276] (Examples 2 to 5)

[0277] Except for mixing the raw materials in the specified proportions shown in Table 1 regarding the molar ratio of the Nb2O5 particles and TiO2 particles as the raw materials, the active materials of Examples 2 to 5 are obtained by the same synthesis as the method described in Example 1.

[0278] (Example 6)

[0279] Except for the molar ratio of Nb2O5 particles and TiO2 particles with respect to the raw materials, the raw materials were mixed at the specified ratios described in Table 1, and the conditions for high-temperature heat treatment (third firing) were changed to 1500 °C for 2 hours. The active material of Example 6 was obtained by the same synthesis method as described in Example 1.

[0280] (Examples 7 - 8)

[0281] Except for the molar ratio of Nb2O5 particles and TiO2 particles with respect to the raw materials, the raw materials were mixed at the specified ratios described in Table 1. The active materials of Examples 7 - 8 were obtained by the same synthesis method as described in Example 1.

[0282] (Example 9)

[0283] Nb2O5 particles and TiO2 particles were prepared. In order to obtain the target crystal phase, each particle was weighed so that the molar ratio of Nb2O5 and TiO2 reached 1.5:1, and they were mixed with a dry ball mill for 30 minutes. Then, Ta2O5 particles were added so that the Ta element reached 200 ppm (molar ratio) with respect to the total amount of the obtained powder, and they were mixed again with a dry ball mill for 30 minutes. The obtained powder was put into an alumina crucible and pre-fired (first firing) at a temperature of 800 °C for 12 hours. After the pre-firing, the obtained powder was put into a platinum crucible and main-fired (second firing) at 1050 °C for 3 hours. After the main-firing, the powder was pulverized with a dry ball mill for 3 hours again, and then high-temperature heat treatment (third firing) was carried out at a temperature of 1475 °C for 1 hour. Then, it was pulverized with a dry ball mill for 1 hour again to obtain the active material of Example 9.

[0284] (Examples 10 - 12)

[0285] Except for mixing the additive particles (Ta2O5, K2CO3, H3PO4) with the raw materials so that the amounts of Ta element, K element, and P element reached the specified ratios described in Table 1, the active materials of Examples 10 - 12 were obtained by the same synthesis method as described in Example 9.

[0286] (Comparative Example 1)

[0287] The niobium-titanium composite oxide was synthesized by the solid-phase synthesis method described below.

[0288] First, Nb2O5 particles and TiO2 particles are prepared to obtain Nb2TiO7. To obtain the target crystalline phase, each particle is weighed so that the molar ratio of Nb2O5 to TiO2 reaches 1:1, and they are mixed using a dry ball mill. The obtained powder is placed in an alumina crucible and subjected to a preliminary firing (the first firing) at a temperature of 800 °C for 12 hours. After the preliminary firing, the obtained powder is placed in a platinum crucible and subjected to a main firing (the second firing) at 1200 °C for 5 hours. After the main firing, the powder is pulverized and mixed using an agate mortar, and coarse particles are removed through a sieve with a mesh size of 25 μm to obtain the Nb2TiO7 phase. The obtained niobium-titanium composite oxide contains only primary particles of the single-phase Nb2TiO7 phase.

[0289] Next, except that the molar ratio of Nb2O5 particles to TiO2 particles is set to 2.5:1 to obtain the 10 Ti2O 29 phase, solid-phase synthesis is carried out in the same manner as the synthesis of the above Nb2TiO7 phase. The obtained niobium-titanium composite oxide contains only primary particles of the single-phase 10 Ti2O 29 phase.

[0290] Primary particles of the single-phase Nb2TiO7 phase are mixed at a weight ratio of 0.5 wt% with primary particles of the 10 Ti2O 29 phase to obtain the active material related to Comparative Example 1.

[0291] (Comparative Example 2)

[0292] Primary particles of the single-phase Nb2TiO7 phase and primary particles of the 10 Ti2O 29 phase are synthesized by the method described in Comparative Example 1. Primary particles of the 10 Ti2O 29 phase are mixed at a weight ratio of 50 wt% with primary particles of the single-phase Nb2TiO7 phase to obtain the active material related to Comparative Example 2.

[0293] (Comparative Example 3)

[0294] Prepare Nb2O5 particles with an average particle size of 25 μm and TiO2 particles with an average particle size of 1.0 μm as starting materials. Weigh each particle such that the molar ratio of Nb2O5 to TiO2 reaches 1.5:1, and mix them using a dry ball mill. Put the obtained powder into an alumina crucible and conduct a preliminary firing (the first firing) at a temperature of 800 °C for 12 hours. After the preliminary firing, put the obtained powder into a platinum crucible and conduct a main firing (the second firing) at 1000 °C for 5 hours. After the main firing, crush and mix the powder using an agate mortar, and remove coarse particles through a sieve with a mesh size of 25 μm to synthesize the mixed-phase active material particles related to Comparative Example 3.

[0295] (Comparative Example 4)

[0296] Synthesize niobium-titanium composite oxide by the solid-phase synthesis method described below.

[0297] First, prepare Nb2O5 particles and TiO2 particles. To obtain the target crystal phase, weigh each particle such that the molar ratio of Nb2O5 to TiO2 reaches 1.25:1, and mix them using a dry ball mill for 1 hour. Put the obtained powder into an alumina crucible and conduct a preliminary firing (the first firing) at a temperature of 800 °C for 12 hours. After the preliminary firing, put the obtained powder into a platinum crucible and conduct a main firing (the second firing) at 1050 °C for 3 hours. After the main firing, crush the powder using a dry ball mill again for 3 hours, then conduct a high-temperature heat treatment (the third firing) at a temperature of 1600 °C for 2 hours, and crush it using a dry ball mill again for 1 hour to obtain the active material of Comparative Example 4.

[0298] (Comparative Example 5)

[0299] Except for changing the mixing ratio of the starting Nb2O5 particles and TiO2 particles such that the molar ratio of Nb2O5 to TiO2 reaches 2.2:1, synthesize the active material of Comparative Example 5 by the same synthesis method as described in Example 1.

[0300] <Powder X-ray diffraction measurement and calculation of peak intensity ratio I β / I α Calculation>

[0301] For the active material powders obtained in Examples 1 to 12 and Comparative Examples 1 to 5, conduct the powder X-ray diffraction measurement described in the first embodiment under the conditions of a sampling interval of 0.01° and a scanning speed of 2° / min. For peaks α and β observed in the obtained diffraction spectra, calculate the peak intensity ratio I β / I α corresponding to the above formula (2): 0.1 < I β / I α .

[0302] <TEM-EDS Observation>

[0303] Through TEM-EDS, the active material powders obtained in Examples 1 to 12 and Comparative Examples 1 to 5 were observed, and the distribution of each crystal in the single-phase or mixed-phase materials in the primary particles was confirmed.

[0304] The synthesis conditions of niobium-titanium composite oxides and various measurement results in each example are summarized in Table 1 below.

[0305] As the synthesis conditions, the mixing ratio (molar ratio) of the raw materials (Nb2O5 and TiO2) and the firing temperature and firing time in the high-temperature heat treatment (the third firing) are shown. In Examples 9 to 12, in addition to Nb2O5 and TiO2, one or more of Ta2O5, K2CO3, and H3PO4 were added, but they were omitted in Table 1 because of the small amount. In addition, in Comparative Examples 1 to 2, since the particles of single-phase Nb2TiO7 and the particles of single-phase Nb 10 Ti2O 29 were synthesized individually, the mixing ratio of the raw materials is expressed in two groups. It shows the synthesis of particles of Nb2TiO7 phase in the upper section and the synthesis of particles of Nb 10 Ti2O 29 phase in the lower section, respectively, showing the raw material ratio at the time of synthesis.

[0306] As the measurement results, the crystal phase obtained by powder X-ray diffraction measurement, the ratio of the crystal phase (mass ratio), the ratio of the Nb existence ratio to the Ti existence ratio calculated based on the crystal phase (A Nb / A Ti ), and the peak intensity ratio I β / I α calculated by Equation (2) and the distribution of each crystal confirmed by TEM-EDS observation are shown. Regarding the crystal phase, the A-type niobium-titanium composite oxide phase is labeled as "Nb2TiO7", and the B-type niobium-titanium composite oxide phase is labeled as "Nb 10 Ti2O 29 ". In addition, the ratio of these phases in the powder is represented by the mass ratio M A / M B relative to the mass ratio marked as a percentage. Regarding Examples 9 to 12, the addition amounts of Ta, K, and P added are further shown.

[0307] Table 1

[0308]

[0309] As shown in Table 1, in any of the active material powders in Examples 1 to 12, both the A-type niobium-titanium composite oxide phase (Nb2TiO7 type phase) and the B-type niobium-titanium composite oxide phase (Nb 10 Ti2O 29 type phase) coexist in each primary particle, satisfying the above formula (1): 2.3 ≤ A Nb / A Ti ≤ 4.0 and formula (2): 0.1 < I β / I α ≤ 2.0. In addition, in Examples 1 to 7 and 9 to 12 among these examples, the above formula (3): 0.5 ≤ M A / M B ≤ 2.5 is also satisfied. Moreover, in Examples 1 to 12, any of the crystalline phases of the A-type niobium-titanium composite oxide phase and the B-type niobium-titanium composite oxide phase are uniformly distributed in each primary particle.

[0310] In contrast, the active material powders of Comparative Examples 1 to 5 do not satisfy at least one of formula (1) and (2). Additionally, in Comparative Examples 1 and 2, only the single phase of the Nb2TiO7 phase or the single phase of the Nb 10 Ti2O 29 phase is contained in any primary particle. Therefore, as the active material powder as a whole, it can be said to be in a state of being separated into these two phases. In Comparative Example 3, through TEM-EDS, it was confirmed that the Nb2TiO7 phase was concentrated on the center side of the primary particle, and the Nb 10 Ti2O 29 phase was present in a non-uniform distribution with a higher amount on the particle surface side. Regarding the active material powder of Comparative Example 4, an X-ray diffraction spectrum with a smaller value of the peak intensity ratio I β / I α was observed, and thus a lower crystallinity was confirmed. In Comparative Example 5, the proportion (mass ratio) of the B-type niobium-titanium composite oxide phase was too high.

[0311] <Electrochemical measurement>

[0312] First, 100 parts by mass of the niobium-titanium composite oxide powder obtained in each example, 10 parts by mass of acetylene black as a conductive agent, 5 parts by mass of carbon nanofibers, and 10 parts by mass of polyvinylidene fluoride (PVdF) as a binder were added to N-methylpyrrolidone (NMP) and mixed to obtain a slurry. The slurry was coated on one side of a current collector formed of an aluminum foil with a thickness of 12 μm, and after drying, it was pressed to fabricate an electrode with an electrode density (the density of the active material-containing layer excluding the current collector) of 2.4 g / cm 3 .

[0313] Next, an electrolytic solution was prepared by dissolving a LiPF6 supporting salt at a concentration of 1 mol / L in a mixed solvent obtained by mixing ethylene carbonate (EC) and diethyl carbonate (DEC) in a volume ratio of 1:2.

[0314] The obtained electrode was used as the working electrode, and Li metal was used as the counter electrode and reference electrode to fabricate a three-electrode beaker cell using the electrolytic solution, and the electrochemical performance was evaluated.

[0315] In this electrochemical measurement, in the three-electrode beaker cell used for the measurement, since Li metal was used as the counter electrode, the potential of the electrode using the active materials of the examples and comparative examples was higher than that of the counter electrode. Therefore, each working electrode operates as a positive electrode. That is, the definition of charge and discharge is opposite to that when the electrodes of the examples and comparative examples are used as the negative electrode. Here, to avoid confusion, in this electrochemical measurement, the direction of lithium ion insertion into the electrode is uniformly referred to as charging, and the direction of deintercalation is referred to as discharging. In addition, the active material of the present embodiment operates as a negative electrode by being combined with a known positive electrode material.

[0316] The fabricated electrochemical measurement cell was charged and discharged in a potential range of 1.0 V to 3.0 V (vs. Li / Li + ) based on the lithium metal electrode. The charge and discharge current value was set to 0.2 C (hourly discharge rate), and the 0.2 C discharge capacity was confirmed at room temperature. The value of the 0.2 C discharge capacity is an index of the energy density.

[0317] Next, in order to investigate the input / output performance and cycle life performance of the battery, non-aqueous electrolyte batteries (rated capacity 1000 mAh) were fabricated using the active material powders obtained in Examples 1 to 12 and Comparative Examples 1 to 5 according to the steps described below.

[0318] (Fabrication of the negative electrode)

[0319] 100 parts by mass of the active material powders obtained in Examples 1 to 12 and Comparative Examples 1 to 5, 10 parts by mass of acetylene black as a conductive agent, 5 parts by mass of carbon nanofibers, and 10 parts by mass of PVdF as a binder were added to NMP and mixed to obtain a slurry. The slurry was coated on both sides of a current collector formed of an aluminum foil with a thickness of 12 μm and dried in a vacuum at 130°C for 12 hours to obtain a laminate. Then, the laminate was calendered so that the density of the active material layer (excluding the current collector) reached 2.4 g / cm 3 to obtain a negative electrode.

[0320] (Fabrication of the positive electrode)

[0321] In commercially available lithium cobalt oxide (LiCoO₂), acetylene black as a conductive agent was mixed at a ratio of 5% by mass to obtain a mixture. Next, the mixture was dispersed in NMP to obtain a dispersion. In this dispersion, PVdF as a binder was mixed at a ratio of 5% by mass with respect to lithium cobalt oxide to prepare a positive electrode paste. The paste was coated on both sides of a current collector formed of 12-μm aluminum foil using a doctor blade. It was dried under vacuum at 130 °C for 12 hours to obtain a laminate. Then, the laminate was calendered so that the density of the active material layer (excluding the current collector) reached 2.2 g / cm 3 to obtain a positive electrode.

[0322] (Fabrication of the electrode assembly)

[0323] The positive electrode and negative electrode fabricated as above were laminated in such a way that a polyethylene separator was sandwiched between them to obtain a laminate. Then, the laminate was wound and further pressed to obtain a flat wound-type electrode assembly. A positive terminal and a negative terminal were connected to the electrode assembly.

[0324] (Preparation of the non-aqueous electrolyte)

[0325] As a mixed solvent, a mixed solvent of EC and DEC (volume ratio 1:1) was prepared. Lithium hexafluorophosphate (LiPF₆) was dissolved in this solvent at a concentration of 1 M. Thus, a non-aqueous electrolyte was prepared.

[0326] (Assembly of the non-aqueous electrolyte battery)

[0327] The electrode fabricated as above was assembled into a battery outer packaging member made of an aluminum-containing laminated film. After injecting the non-aqueous electrolyte into the outer packaging member, it was sealed by heat sealing to fabricate a non-aqueous electrolyte battery.

[0328] (Charge-discharge test)

[0329] An input-output test was conducted using the obtained laminated battery. After charging the battery's state of charge to half of the rated capacity to reach SOC 50%, the pulse input-output performance at a 10C rate for 10 seconds was measured in the range of 1.5 V to 3.0 V of the battery voltage. Regarding the input value (W) and output value (W) obtained at this time, the balance of the input-output performance was calculated by dividing the output value by the input value. It can be said that the closer this value is to 1.0, the more ideal the battery is for achieving the balance of the input-output performance.

[0330] Next, an accelerated life test was conducted at 45 °C. During the life test, within the potential range of 1.5 V to 3.0 V of the battery voltage, the charge-discharge current value was set to 0.2 C (hourly discharge rate), and repeated charge-discharge was performed for 300 cycles (regarding charging and discharging as one cycle), and the discharge capacity retention rate after 300 cycles was investigated. By dividing the discharge capacity after 300 cycles by the initial discharge capacity and multiplying by 100, the cycle capacity retention rate (%) was calculated with the initial discharge capacity set to 100%.

[0331] The results of the electrochemical measurements are summarized in Table 2 below. Specifically, the 0.2 C discharge capacity values of the three-electrode beaker cell using the working electrode made of the active material powder involved in each example, and the results of the input-output test and life test of the non-aqueous electrolyte battery using the negative electrode made of each active material powder are shown. That is to say, the results of the input-output test and life test are the balance of input-output performance (output / input performance ratio) and the capacity retention rate after 300 cycles (= [discharge capacity after 300 cycles / initial discharge capacity] × 100%).

[0332] Table 2

[0333]

[0334] As shown in Table 2, the results of the electrochemical measurements (0.2 C discharge capacity, output / input performance ratio, and cycle capacity retention rate) of the active material powders according to Examples 1 to 12 were all good. From these results, it was found that the active material powders according to Examples 1 to 12 had a high energy density, achieved a balance of input-output performance, and had excellent cycle life performance. Specifically, in Examples 1 to 12, while maintaining an energy density (0.2 C discharge capacity) equal to or higher than that of Comparative Examples 1 to 5, the balance of input-output performance (output / input performance ratio) was better, and the cycle life performance (cycle capacity retention rate) was more excellent.

[0335] According to at least one of the embodiments and examples described above, an active material can be provided. The active material contains a niobium-titanium composite oxide. In this active material, the Nb content ratio A Nb relative to the Ti content ratio A Ti of the ratio A Nb / A Ti satisfies 2.3 ≤ A Nb / A Ti ≤ 4.0, and in the powder X-ray diffraction spectrum using Cu-Kα rays, the peak intensity I of peak α that appears at 8.5° ≤ 2θ ≤ 9.0° α and the peak intensity I of peak β that appears at 12.5° ≤ 2θ ≤ 13.0° β of the intensity ratio Iβ / I α In the range of 0.1 < I β / I α ≤ 2.0. The active material can achieve a secondary battery that maintains a high energy density while having balanced input-output performance and can exhibit excellent cycle life performance. In addition, through the active material, it is possible to provide an electrode for a secondary battery that can achieve such performance, a secondary battery and a battery pack that exhibit such performance, and a vehicle equipped with the battery pack.

[0336] Several embodiments of the present invention have been described, but 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 ways, and various omissions, substitutions, and changes can be made without departing from the gist of the invention. These embodiments and their modifications are included in the scope and gist of the invention, and at the same time are included in the invention described in the claims and its equivalents.

[0337] Furthermore, the above embodiments can be summarized into the following technical solutions.

[0338] (Technical solution 1)

[0339] An active material containing crystal grains comprising a niobium-titanium composite oxide, wherein the Nb presence ratio A Nb relative to the Ti presence ratio A Ti of the ratio A Nb / A Ti satisfies 2.3 ≤ A Nb / A Ti ≤ 4.0, and in the powder X-ray diffraction spectrum of the crystal grains using Cu-Kα radiation, the peak intensity I of peak α that appears at 8.5° ≤ 2θ ≤ 9.0° α and the peak intensity I of peak β that appears at 12.5° ≤ 2θ ≤ 13.0° β of the intensity ratio I β / I α is in the range of 0.1 < I β / I α ≤ 2.0.

[0340] (Technical solution 2)

[0341] According to the above technical solution 1, wherein the crystal grains contain an A-type niobium-titanium composite oxide phase to which the above peak α belongs and a B-type niobium-titanium composite oxide phase to which the above peak β belongs, and the mass ratio M of the mass proportion M A of the A-type niobium-titanium composite oxide phase relative to the mass proportion M B of the B-type niobium-titanium composite oxide phase A / MB In the range of 0.5 ≤ M A / M B ≤ 2.5

[0342] (Technical solution 3)

[0343] According to the above technical solution 1 or 2, wherein the niobium-titanium composite oxide contains one or more selected from Ta, K, and P.

[0344] (Technical solution 4)

[0345] An electrode containing any one of the active materials in the above technical solutions 1 to 3.

[0346] (Technical solution 5)

[0347] According to the above technical solution 4, wherein it includes an active material-containing layer containing the above active material.

[0348] (Technical solution 6)

[0349] A secondary battery having a negative electrode, a positive electrode, and an electrolyte, wherein the negative electrode includes the electrode of the above technical solution 4 or 5.

[0350] (Technical solution 7)

[0351] A battery pack having the secondary battery of the above technical solution 6.

[0352] (Technical solution 8)

[0353] According to the above technical solution 7, wherein it further includes an external terminal for power conduction and a protection circuit.

[0354] (Technical solution 9)

[0355] According to the above technical solution 7 or 8, wherein it has a plurality of the above secondary batteries, and the secondary batteries are electrically connected in series, in parallel, or in a combination of series and parallel.

[0356] (Technical solution 10)

[0357] A vehicle having any one of the battery packs in the above technical solutions 7 to 9.

[0358] (Technical solution 11)

[0359] According to the above technical solution 10, wherein it includes a mechanism for converting the kinetic energy of the vehicle into regenerative energy.

Claims

1. An active substance containing crystal grains comprising a niobium-titanium composite oxide, wherein the ratio A of the presence of Nb in the crystal grains Nb relative to the presence ratio A of Ti Ti of A Nb / A Ti satisfies 2.3 ≤ A Nb / A Ti ≤ 4.0, and in the powder X-ray diffraction spectrum of the crystal grains using Cu-Kα rays, the peak intensity I of peak α appearing at 8.5° ≤ 2θ ≤ 9.0° α and the peak intensity I of peak β appearing at 12.5° ≤ 2θ ≤ 13.0° β of the intensity ratio I β / I α is in the range of 0.1 < I β / I α ≤ 2.

0. The crystal grains contain an A-type niobium-titanium composite oxide phase to which the peak α belongs and a B-type niobium-titanium composite oxide phase to which the peak β belongs. In the primary particles of the active material, the A-type niobium-titanium composite oxide phase and the B-type niobium-titanium composite oxide phase are uniformly distributed in a state where no boundary line between the respective phases is found within the primary particles.

2. The active substance according to claim 1, wherein The mass ratio M of the A-type niobium-titanium composite oxide phase A Relative to the mass ratio M of the B-type niobium-titanium composite oxide phase B The mass ratio M A / M B In the range of 0.5 ≤ M A / M B ≤ 2.

5.

3. The active substance according to claim 1 or 2, wherein The niobium-titanium composite oxide contains one or more selected from Ta, K, and P.

4. An electrode comprising the active material according to any one of claims 1 to 3.

5. The electrode according to claim 4, wherein, Comprising an active material-containing layer containing the active material.

6. A secondary battery, which is a secondary battery including a negative electrode, a positive electrode, and an electrolyte, wherein the negative electrode includes the electrode according to claim 4 or 5.

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

8. The battery pack according to claim 7, wherein, Further comprising: an external terminal for energization, and a protection circuit.

9. The battery pack according to claim 7 or 8, wherein a plurality of the secondary batteries are provided, and the secondary batteries are electrically connected in series, in parallel, or in a combination of series and parallel.

10. A vehicle comprising the battery pack according to any one of claims 7 to 9.

11. The vehicle according to claim 10, wherein, Comprising a mechanism for converting the kinetic energy of the vehicle into regenerative energy.

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