Active material, electrode, secondary battery, battery pack, vehicle, and method for manufacturing active material

Abstract

To provide an active material and an electrode capable of realizing a secondary battery having a high energy density and a long life, a secondary battery and a battery pack having a high energy density and a long life, a vehicle equipped with the battery pack, and a method for manufacturing the active material.SOLUTION: An active material according to an embodiment includes a composite metal oxide containing tetravalent Mo, Nb, and at least one element M selected from the group consisting of Ti, V, Ta, Fe, Co, Mn, Ni, Bi, Sb, As, P, Cr, W, B, Na, K, Mg, Al, Ca, Y, and Si. The crystalline structure of the composite metal oxide has an aperiodic crystalline structure.SELECTED DRAWING: Figure 1

Description

[Technical Field]

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

[0002] In recent years, research and development of high-energy density secondary batteries, such as lithium-ion secondary batteries and nonaqueous electrolyte secondary batteries, has been actively promoted. Secondary batteries are expected to be used as power sources for vehicles such as hybrid vehicles and electric vehicles, and as uninterruptible power sources for mobile phone base stations. Therefore, in addition to energy density, secondary batteries are also required to have excellent performance characteristics such as rapid charge / discharge performance and long-term reliability.

[0003] A typical negative electrode in a lithium-ion battery is a carbon-based negative electrode, which uses a carbonaceous material such as graphite as the active material. Repeated rapid charging and discharging of a battery using a carbon-based negative electrode can cause metallic lithium dendrites to precipitate on the electrode, which can lead to internal short circuits and the risk of heat generation or fire. Therefore, batteries have been developed that use metal composite oxides instead of carbonaceous materials for the negative electrode, thereby increasing the negative electrode operating potential. For example, spinel-type lithium-titanium composite oxide Li4Ti5O 12 The battery using as the negative electrode has an average operating potential of 1.55V (vs. Li / Li + ), the precipitation of Li dendrites does not progress, allowing stable rapid charging and discharging, and the battery operates at a potential where reduction side reactions of the electrolyte are unlikely to occur, resulting in a longer lifespan compared to batteries using carbon-based anodes. 12 In batteries using this material for the anode, the theoretical capacity of the active material was low at 175 mAh / g, and the energy density was lower than that of batteries with carbon-based anodes.

[0004] Therefore, monoclinic niobium titanium oxide TiNb2O7 is being investigated. +) while exhibiting high capacity. Therefore, it is expected that the volumetric energy density will exceed that of carbon-based anodes. However, in order to fully popularize electric vehicles, it is desirable to further increase the energy density of lithium-ion secondary batteries in order to improve driving range, and it is also desirable to develop high-capacity, fast-charging batteries. Of course, it is undesirable for other battery performance characteristics, such as lifespan, to deteriorate as capacity increases. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Laid-Open No. 2012-99287 [Patent Document 2] Patent Publication No. 2021-61223 [Patent Document 3] International Publication No. 2019 / 234248 [Patent Document 4] Japanese Patent Publication No. 2022-176525 [Patent Document 5] Japanese Patent Publication No. 2022-145421 [Non-patent literature]

[0006] [Non-Patent Document 1] J. Mater. Chem. A, 2019, 7, 6522-6532 [Non-patent document 2] International Tables for Crystallography (2006). 1st online ed. Chester: International Union of Crystallography. [Non-patent document 3] "Practice of Powder X-ray Analysis" First Edition (2002) Edited by the X-ray Analysis Research Forum of the Japan Society for Analytical Chemistry, edited by Izumi Nakai and Fujio Izumi (Asakura Shoten) Summary of the Invention [Problem to be solved by the invention]

[0007] An object of the embodiments is to provide an active material and an electrode that can realize a secondary battery with high energy density and long life, a secondary battery and a battery pack with high energy density and long life, a vehicle equipped with the battery pack, and a method for manufacturing the active material. [Means for solving the problem]

[0008] According to an embodiment, there is provided an active material comprising a composite metal oxide containing tetravalent Mo, Nb, and at least one element M selected from the group consisting of Ti, V, Ta, Fe, Co, Mn, Ni, Bi, Sb, As, P, Cr, W, B, Na, K, Mg, Al, Ca, Y, and Si. The crystalline structure of the composite metal oxide has an aperiodic crystalline structure.

[0009] According to another embodiment, an electrode is provided that includes the active material described above.

[0010] According to yet another embodiment, there is provided a secondary battery comprising a positive electrode, a negative electrode, and an electrolyte. The positive electrode or the negative electrode is the electrode described above.

[0011] According to another embodiment, there is provided a battery pack including the above secondary battery.

[0012] According to an embodiment, a vehicle including the battery pack is provided.

[0013] Additionally, according to an embodiment, there is provided a method for producing the active material. The method includes preparing a precursor composite metal oxide and mixing the precursor composite metal oxide with hydrogen or an organic substance and firing the mixture in an oxygen-free atmosphere at 700°C or less. The precursor composite metal oxide contains hexavalent Mo, Nb, and at least one element M selected from the group consisting of Ti, V, Ta, Fe, Co, Mn, Ni, Bi, Sb, As, P, Cr, W, B, Na, K, Mg, Al, Ca, Y, and Si. [Brief explanation of the drawings]

[0014] [Figure 1] 1 is a schematic diagram showing an example of a crystal structure contained in a composite metal oxide contained in an active material according to an embodiment. [Figure 2] 1A and 1B are schematic diagrams showing examples of crystal structures that may be contained in a composite metal oxide contained in an active material according to an embodiment. [Figure 3] 1 is a cross-sectional view schematically illustrating an example of a secondary battery according to an embodiment. [Figure 4] FIG. 4 is an enlarged cross-sectional view of part A of the secondary battery shown in FIG. [Figure 5] FIG. 10 is a partially cutaway perspective view schematically showing another example of a secondary battery according to an embodiment. [Figure 6] FIG. 6 is an enlarged cross-sectional view of part B of the secondary battery shown in FIG. 5. [Figure 7] FIG. 1 is a perspective view schematically illustrating an example of a battery pack according to an embodiment. [Figure 8] FIG. 1 is an exploded perspective view schematically showing an example of a battery pack according to an embodiment. [Figure 9] FIG. 9 is a block diagram showing an example of an electrical circuit of the battery pack shown in FIG. 8. [Figure 10] 1 is a partially see-through view schematically illustrating an example of a vehicle according to an embodiment. [Figure 11] 1 is a diagram illustrating an example of a control system for an electrical system in a vehicle according to an embodiment; [Figure 12] Graph showing X-ray diffraction spectra of the active material powders obtained in Example 1 and Comparative Example 1. [Figure 13] 13 is a graph showing an enlarged portion of the spectrum shown in FIG. 12. [Figure 14] 1 is a graph showing initial charge-discharge curves of beaker cells using the active material powders obtained in Example 1 and Comparative Example 1. [Figure 15] 1 is a graph showing dQ / dV curves versus potential for beaker cells using the active material powders obtained in Example 1 and Comparative Example 1. DETAILED DESCRIPTION OF THE INVENTION

[0015] In order to obtain a high-capacity material, it is desirable to select a material with a large charge compensation amount during the insertion of carrier ions (e.g., lithium ions). For this purpose, as a higher-capacity compound, for example, a composite oxide containing a molybdenum element (Mo), which is an element with a normal valence of up to hexavalent, can be adopted.

[0016] Hereinafter, embodiments will be described with reference to the drawings. In the following description, components that exhibit the same or similar functions are given the same reference numerals throughout all the drawings, and duplicate descriptions are omitted. Each drawing is a schematic diagram for facilitating the explanation of the embodiments and their understanding. Although the shape, dimensions, ratio, etc. are different from those of the actual device, these can be appropriately designed and changed in consideration of the following description and known techniques.

[0017] (First Embodiment) According to the first embodiment, an active material containing a composite metal oxide having an aperiodic crystal structure is provided. The composite metal oxide contains a Mo element, a Nb element, and an element M. The element M is at least one selected from the group consisting of Ti, V, Ta, Fe, Co, Mn, Ni, Bi, Sb, As, P, Cr, W, B, Na, K, Mg, Al, Ca, Y, and Si. The valence of the Mo element is tetravalent.

[0018] The above composite metal oxide is, for example, of the general formula M x NbMo y O z It may be a compound represented by. In the general formula, M is at least one of the above element M and is selected from the group consisting of Ti, V, Ta, Fe, Co, Mn, Ni, Bi, Sb, As, P, Cr, W, B, Na, K, Mg, Al, Ca, Y, and Si. Each subscript in the formula satisfies respectively 0.1 < x ≦ 0.6, 0.1 < y ≦ 0.6, and 2.5 < z ≦ 5.2.

[0019] Such an active material can be an active material for a battery. The active material can be, for example, an electrode active material used for an electrode of a secondary battery such as a lithium-ion battery or a non-aqueous electrolyte battery. More specifically, the active material can be, for example, a negative electrode active material used for the negative electrode of a secondary battery.

[0020] By using a composite metal oxide having a non-periodic crystal structure composed of substantially tetravalent Mo, Nb, and at least one of the above elements M as an electrode active material, a secondary battery with high energy density and long life can be realized. The composite metal oxide in which Mo is substantially tetravalent here refers to a composite metal oxide in which the majority of Mo contained in the crystal structure is tetravalent, and even if some Mo element has a valence other than tetravalent, the valence of Mo is judged to be tetravalent when viewed as a composite metal oxide as a whole. Of course, there may be cases in which all Mo elements are tetravalent.

[0021] <Crystal structure> The composite metal oxide contained in the active material according to the first embodiment corresponds to a part of an oxide material having a Wadsley-Roth phase structure, which is a crystalline phase in an oxide material containing niobium. The Wadsley-Roth phase has a ratio of oxygen O to metal element Me in the composition, where the number of oxygen atoms and the number of metal element atoms are A and B, respectively. O and A Me As such, 2.33≦A O / A Me It has been reported that TiNb2O7 has a crystal structure in the range of A ≦2.65. O / A Me =2.33, resulting in a reduced crystal structure.

[0022] Here, "reduced" means that the proportion of oxygen in the structure is low. In the Wadsley-Roth phase, the corner-sharing structure of oxygen-metal octahedra forms a rhenium oxide-type block structure, and the blocks share the rhombuses of the octahedra, or tetrahedra interpose and share the corners, forming a crystal structure in which the rhenium oxide-type blocks (ReO3-type blocks) are connected in two dimensions. The reduced-side crystal structure has a structure in which the rhenium oxide-type blocks are small in size. Although the rhenium oxide-type crystal structure has voids that can accommodate a large amount of Li, due to its highly symmetrical crystal structure, it is difficult to change the bond length between the metal element and the oxygen element to eliminate the charge repulsion when Li is inserted. For this reason, the rhenium oxide-type crystal structure can be said to be a structure in which Li insertion is restricted by the charge repulsion that occurs when Li is inserted. Here, the reduced-side crystal structure is A O / A Me As the size of the rhenium oxide-type block decreases, the number of oxygen atoms in the structure decreases, resulting in a smaller size of the rhenium oxide-type block. As a result, when Li is inserted, a crystal structure can be formed in which volume expansion is possible due to a change in the bond length between the metal element and the oxygen element. Therefore, by including a rhenium oxide-type crystal structure, there is a large gap, but there are no restrictions on the structural change when Li is inserted, so a large amount of Li insertion can be achieved.

[0023] The composite metal oxide contained in the active material according to the first embodiment also has a reduction-side crystal structure, such as TiNb2O7, which allows for the insertion of more lithium (Li) into the crystal structure, resulting in a crystal structure with a large reversible capacity. In other words, the crystal structure of this composite metal oxide is a reduction-side crystal structure belonging to the Wadsley-Roth phase, which is composed of three elements: niobium, molybdenum, and element M. It is known that the Wadsley-Roth phase containing molybdenum has a high (noble) operating potential. Comparing oxides containing titanium and niobium, for example, the titanium-niobium-molybdenum composite oxide according to the first embodiment has a crystal structure containing a high concentration of molybdenum, thereby enabling the operating potential to be higher than that of TiNb2O7. This allows the operating potential to fall within a potential range where the reduction side reaction of the electrolyte is minimal, thereby enabling the oxide to exhibit a long service life.

[0024] FIG. 1 shows a schematic diagram of an example of a crystal structure that such a composite metal oxide may contain. The crystal structure 10 contains octahedra 10a and tetrahedra 10b, each composed of a metal element 18 and an oxygen element 19. The octahedra 10a are connected to each other by corner-sharing to form rhenium oxide blocks (ReO3 blocks). FIG. 1 shows the crystal structure 10 as viewed from the stacking direction of the ReO3 blocks. The ReO3 blocks enclosed by thick lines (e.g., block 15a) and the ReO3 blocks indicated only by thin lines (e.g., block 15d) have different planes on which the metal elements 18 are arranged. This example is characterized by the absence of structural periodicity. Blocks of different sizes are connected and exist according to the arrangement pattern of the Wadsley-Roth phase. The smallest blocks have two sides and the largest have six sides. For example, block 15a consists of 3 x 3 octahedrons 10a, block 15b consists of 2 x 3 octahedrons 10a, block 15c consists of 2 x 4 octahedrons 10a, block 15d consists of 2 x 2 octahedrons 10a, block 15e consists of 3 x 6 octahedrons 10a, block 15f consists of 5 x 3 octahedrons 10a, and block 15g consists of 4 x 4 octahedrons 10a. These sizes can be freely adjusted depending on the metal / oxygen ratio due to the mixed state of Nb, Mo, and element M, and are not limited thereto. Most are connected by octahedral edge sharing 17, but some may also include tetrahedral vertex sharing by tetrahedrons 10b.

[0025] Another example of the crystal structure that can be included in such a composite metal oxide is shown in FIG. 2. In this example, the number of atoms A of the metal element Me included as a constituent element is 1. Me A is the number of oxygen atoms O The ratio of A O / A Me = 2.50. This crystal structure has periodicity. Figure 2 shows the unit cell of the crystal structure in the

[0001] direction as viewed along the c-axis direction. The space group notation of the crystal structure is I -It belongs to the space group 4 and is assigned the space group number 82. The space group referred to here corresponds to the International Tables for Crystallography (Non-Patent Document 2), specifically, the contents of Vol. A: Space-group symmetry of the said material (2nd online edition (2016); ISBN: 978-0-470-97423-0, doi: 10.1107 / 97809553602060000114). However, the space groups are P4 (space group number 75), I4 (space group number 79), P - 4 (space group number 81), P42 / n (space group number 86), I4 / m (space group number 87), P4nc (space group number 104), P - 421c (space group number 114), P - 4n2 (space group number 118) - This can also be explained by the assignment of a simple cubic lattice with a fourfold symmetry axis or a fourfold anti-axis similar to 4 (space group number 82). However, this may change if the stoichiometric composition is deviated by adjusting the composition ratio or if the structure is distorted due to the presence of other phases. Crystal structure 11 contains octahedra 11a and tetrahedra 11b, each composed of metal element 18 and oxygen element 19. The octahedra 11a are connected to each other by corner-sharing to form rhenium oxide-type blocks (ReO3-type blocks). The size of the blocks is 3 x 3 = 9 octahedra 11a. The nine-unit rhenium oxide-type blocks form planes in the a-axis and b-axis directions by sharing the edges of the octahedra 11a or the vertices of the tetrahedra 11b. The crystal structure is formed by multiple planes containing these nine octahedra 11a connected along the c-axis by octahedral edge-sharing or tetrahedral corner-sharing.

[0026] Comparing the crystal structure 10 shown in Figure 1 with the crystal structure 11 shown in Figure 2, Figure 1 has fewer tetrahedra than Figure 2, and the replacement of tetrahedral vertex connections with octahedral edge connections results in a larger number of octahedral edge-sharing structures, resulting in increased octahedral lattice distortion. Therefore, in the crystal structure 10 shown in Figure 1, the large octahedral lattice distortion facilitates structural relaxation due to changes in bond length during Li insertion, enabling increased Li insertion. Furthermore, because the octahedral edge-sharing structures in the crystal structure 10 shown in Figure 1 are not periodic, the framework asymmetry is maintained even with increased Li insertion. Therefore, the reversible capacity of the crystal structure 10 shown in Figure 1 is even greater than that of the crystal structure 11 shown in Figure 2. Therefore, incorporating the aperiodic crystal structure shown in Figure 1 into an active material can improve capacity.

[0027] In the above non-periodic crystal structure, the metal / oxygen ratio, which changes with the composition ratio, can be adjusted by changing the size of the ReO3-type block and the number of octahedral edge-sharing or tetrahedral vertex-sharing connections. Therefore, the oxygen / metal ratio can be changed by the composition ratio and can be freely adjusted.

[0028] In the active material according to the first embodiment, Mo is in a tetravalent state. The composite metal oxides having the above-described aperiodic crystal structure include those in which molybdenum (Mo) is incorporated into the crystal structure not only in a tetravalent state but also in a pentavalent or hexavalent state. The valence of Mo is determined by adjusting the charge balance depending on the amount of niobium and element M present and the amount of oxygen in the crystal structure shown in FIG. 1 or 2. In the active material according to the first embodiment, Mo is substantially tetravalent, and compared with composite metal oxides containing pentavalent or hexavalent Mo, the charge / discharge efficiency and cycle life of the battery when used as an active material for a battery are improved. Therefore, the use of the active material according to the first embodiment allows for the production of a battery with improved energy density and life performance.

[0029] In an electrode using the active material according to the first embodiment, which includes a composite metal oxide having an aperiodic crystal structure in which Mo is substantially tetravalent, the discharge curve changes to a shape suitable for a negative electrode, compared to an electrode using a composite metal oxide having a similar aperiodic crystal structure but containing pentavalent or hexavalent Mo as the active material. Therefore, the electrode using the active material according to the first embodiment exhibits improved charge / discharge efficiency and energy density. When Mo is tetravalent, the composite metal oxide becomes a conductive oxide, thereby improving cycle life.

[0030] The change in the discharge curve will be explained in detail. The discharge curve of an electrode using a composite metal oxide as the active material was measured using the electrode potential (V vs. Li / Li + ) versus the differential capacitance dQ / dV, the capacitance is 2.2 V (vs. Li / Li + ) to 3.5 V (vs. Li / Li + ) range. This peak is due to charge compensation by pentavalent Mo and hexavalent Mo. In batteries using such composite metal oxides as electrode active materials, it is difficult to utilize the discharge capacity that appears as the Mo pentavalent / hexavalent charge compensation peak. In the case of composite metal oxides containing substantially tetravalent Mo, no peak such as the Mo pentavalent / hexavalent charge compensation peak appears in the dQ / dV plot. Because the unusable discharge capacity is reduced, the charge / discharge efficiency and energy density of the Mo tetravalent composite metal oxide are improved compared to those of the Mo pentavalent and Mo hexavalent composite metal oxides.

[0031] Tetravalent Mo in the crystal structure has a larger ionic radius than pentavalent or hexavalent Mo. Therefore, in a non-periodic crystal structure in which Mo is substantially tetravalent, the lattice expands in the stacking direction due to the increase in the Mo ionic radius while maintaining the same non-periodic crystal structure with variable block size in the planar direction as a non-periodic crystal structure containing pentavalent or hexavalent Mo as a constituent element. Based on this lattice expansion in the stacking direction, X-ray diffraction (XRD) measurement can be used to confirm whether Mo in the crystal structure is substantially tetravalent. The XRD spectrum obtained for a non-periodic crystal structure in which the valence of Mo as a constituent element is tetravalent includes, for example, a peak whose top is located within the range of 2θ = 47.2 ± 0.4°. Details will be described later.

[0032] In such an active material, oxygen vacancies can be formed by reducing the amount of Mo element from the ideal composition. The formation of oxygen vacancies improves the electronic conductivity of the active material, thereby improving battery performance. However, excessive oxygen vacancies can cause charge repulsion of Li. Therefore, excessive oxygen vacancies are undesirable because they inhibit Li migration.

[0033] The non-periodic crystal structure shown in FIG. 1 can be confirmed by observation using a scanning transmission electron microscope with a high-angle annular dark-field method, which will be described later.

[0034] This composite metal oxide contains at least one of the aforementioned elements M in addition to Nb and Mo as metal elements. In the aperiodic crystal structure shown in Figure 1, the structure can be maintained by changing the size of the ReO3-type blocks and the octahedral edge-sharing and tetrahedral vertex-sharing at the connecting portions as the oxygen / metal composition ratio changes due to charge compensation. The Mo element is contained in the structure in a substantially tetravalent state. Furthermore, as described above, this active material easily creates oxygen vacancies and cation vacancies within the structure. This allows for a high degree of freedom in adjusting the charge balance within the structure, allowing for the free selection of element M. Element M can be at least one selected from the group consisting of Ti, V, Ta, Fe, Co, Mn, Ni, Bi, Sb, As, P, Cr, W, B, Na, K, Mg, Al, Ca, Y, and Si.

[0035] The element M can be contained in the crystal structure as a metal element constituting the tetrahedron or octahedron described above, or can be present in the active material in a form that is not contained in the crystal structure of the composite metal oxide.

[0036] For example, vanadium (V) and phosphorus (P) can be incorporated into the crystal structure as pentavalent elements. Titanium (Ti), zirconia (Zr), and silicon (Si) can be incorporated into the structure as tetravalent elements. Iron (Fe), chromium (Cr), aluminum (Al), bismuth (Bi), antimony (Sb), boron (B), arsenic (As), cobalt (Co), manganese (Mn), nickel (Ni), and yttrium (Y) can be incorporated into the crystal structure as trivalent elements. Magnesium (Mg) and calcium (Ca) can be incorporated into the crystal structure as divalent elements. Potassium (K) and sodium (Na) can be incorporated into the crystal structure as monovalent elements. Of these elements, tetravalent elements are preferred because they have a higher charge than elements with a valence of less than three, allowing for greater inclusion without decreasing the oxygen / metal ratio in the structure and increasing the Mo ratio in the structure. In particular, titanium (Ti) is the most preferable element among the M elements because it is the element that can be contained in the largest amount in the structure and has an ionic radius close to that of pentavalent Nb, making it easy to incorporate into the structure.

[0037] Tantalum (Ta) is a pentavalent element that can replace Nb. Ta and Nb are in the same group on the periodic table, and therefore have similar physical and chemical properties. Therefore, it is possible to obtain equivalent battery performance by substituting Ta for Nb.

[0038] Tungsten (W) is a hexavalent element that can partially replace Mo. Generally, Wadsley-Roth phases containing W have high rate performance due to the fast Li diffusion rate within the solid. Therefore, the inclusion of W can further improve the rate performance of the active material.

[0039] <Active material particles> The active material according to the first embodiment may be in the form of particles, for example, and may be made of secondary particles of a composite metal oxide containing Mo, Nb, and the element M and having a non-periodic crystal structure.

[0040] The active material can also be composed of secondary particles containing a composite metal oxide and a carbon material. Although the tetravalent Mo composite metal oxide itself exhibits electrical conductivity, the inclusion of a carbon material within the secondary particles can form a conductive path between the primary particles of the composite metal oxide. To establish a conductive path, a high carbon content is desirable; for example, the active material secondary particles can contain 0.5 to 5 wt% carbon. Furthermore, the presence of carbon between the primary particles maintains voids between the particles. This prevents destruction of the active material due to volume expansion and contraction during Li insertion and desorption. Additionally, carbon reacts with the electrolyte to form a favorable solid-electrolyte interface (SEI) coating. These findings suggest that the battery life can be further improved by forming an active material in the form of secondary particles containing carbon together with a composite metal oxide.

[0041] The average primary particle size of the composite metal oxide is preferably 10 nm or more and 300 nm or less. From the viewpoint of the appropriate range of Li diffusivity and diffusion distance of the material in the embodiment, by adjusting the primary particle size within the above range, it is possible to operate the battery with low resistance and stability. Furthermore, it is possible to suppress cracking of the primary particles due to volume expansion and contraction of the composite metal oxide during insertion and desorption of Li.

[0042] The average secondary particle diameter of the spherical particles is preferably 1 μm or more and 10 μm or less. On the one hand, if the secondary particle diameter is moderately large, particle contact points can be reduced, making it easier to establish good conductive paths between particles. On the other hand, since the secondary particle diameter is not unnecessarily large, it is easier to ensure conductive paths within the particles. By adjusting the secondary particle diameter within the above range, it is possible to maintain stable conductive paths between particles within the electrode and improve life performance. This average secondary particle diameter refers to the particle size at which the volume cumulative value reaches 50% in the particle size distribution determined using a laser diffraction particle size distribution analyzer.

[0043] <Manufacturing method> The active material according to the first embodiment can be manufactured by the following manufacturing method. The manufacturing method of the active material includes preparing a precursor composite metal oxide, and mixing the precursor composite metal oxide with hydrogen or an organic substance and firing the resulting mixture in an oxygen-free atmosphere at 700°C or less. The precursor composite metal oxide contains hexavalent Mo, Nb, and at least one element M selected from the group consisting of Ti, V, Ta, Fe, Co, Mn, Ni, Bi, Sb, As, P, Cr, W, B, Na, K, Mg, Al, Ca, Y, and Si.

[0044] (liquid phase synthesis) The method for producing the precursor composite metal oxide is not particularly limited, but it can be synthesized by, for example, a solid-state reaction method, a sol-gel method, a hydrothermal synthesis method, etc. As an example, a method for producing a titanium-niobium-molybdenum composite oxide (i.e., element M=Ti) using the sol-gel method will be described.

[0045] Starting materials include titanium compounds, niobium compounds, and molybdenum compounds. Examples of titanium compounds include titanium tetraisopropoxide, titanyl sulfate, titanium chloride, ammonium titanium oxalate and its hydrates, titanium hydroxide, and titanium oxide. Examples of niobium compounds include niobium chloride, ammonium niobium oxalate and its hydrates, niobium hydroxide, and niobium oxide. Examples of molybdenum compounds include molybdenum chloride, ammonium molybdate and its hydrates, molybdenum hydroxide, and molybdenum oxide. When an element other than Ti is selected as element M, or when another element is selected together with Ti, the titanium compound is appropriately replaced with or used in combination with a compound containing the selected element M.

[0046] It is preferable to dissolve the starting materials in pure water or acid beforehand to prepare a solution. By dissolving them in solution, it is possible to obtain a dry gel in which each element is homogeneously mixed, thereby increasing reactivity. If the starting materials cannot be dissolved in pure water, they are dissolved using acid.

[0047] Examples of acids used to dissolve the raw materials include citric acid and oxalic acid, but oxalic acid is preferred from the viewpoint of solubility. For example, when using oxalic acid, the concentration is preferably 0.5 M or more and 1 M or less. When dissolving, it is preferred to use a temperature of 70° C. or more to shorten the reaction time.

[0048] If it is difficult to dissolve the raw materials, the reaction can also proceed as a dispersion. In this case, the average particle size of the raw materials contained in the dispersion should be 3 μm or less, more preferably 1 μm. After preparing a solution (or dispersion) with the specified composition ratio of each compound, the solution is heated and stirred while being neutralized with an aqueous ammonia solution to adjust the pH. A gel solution is obtained by adjusting the pH. By setting the pH to between 5 and 8, it is possible to form a gel that uniformly contains each raw material, which allows for the production of a dry gel that has good reactivity when fired.

[0049] Next, the gel solution is heated to near its boiling point to evaporate the water and promote gelation. After gelation, the water is further evaporated and the solution is dried to obtain a dry gel. During gelation and drying, for example, the entire solution can be evaporated and concentrated to obtain a dry gel. The dry gel produced by evaporating and concentrating the entire solution is preferably pulverized before firing to reduce the average particle size to 10 μm or less, more preferably 5 μm or less. This reduces the particle size after firing. The obtained dry gel is then fired.

[0050] It is more preferable to use a spray dryer in the process of evaporating the solvent to gel and obtain a dried gel. By spraying, it is possible to form minute droplets of the sol solution. By drying in the form of minute droplets, it is possible to prevent particle aggregation that occurs during solvent drying, thereby making it possible to reduce the particle size after drying and to reduce the number of coarse particles. This increases the homogeneity of the reaction during the firing of the precursor and also makes it possible to suppress particle aggregation during firing. The drying temperature during spray drying is preferably 100°C or higher and 200°C or lower.

[0051] The dried gel is pre-baked at 200°C to 500°C for 1 hour to 10 hours. This process burns off excess organic components, increasing the reactivity during the main baking.

[0052] The firing is preferably carried out at a temperature of 600° C. to 800° C. for a time of 1 hour to 10 hours. By performing firing within this temperature range, it is possible to obtain the target phase while suppressing the sublimation of molybdenum.

[0053] In the sintered powder, secondary particles, in which particles aggregate into irregular shapes, may be formed. When constructing an electrode using the active material, it is desirable to break down the irregular aggregates in order to maintain good conductive paths between particles. For example, coarse particles can be pulverized by dry dispersion, or agglomerations can be broken down by wet dispersion. It is preferable to prepare a slurry containing the sintered powder and then use the slurry to break down the aggregated particles to the vicinity of primary particles using a wet bead mill. Alternatively, when performing a reduction treatment using an organic substance, as described below, a slurry containing the organic substance is prepared together with the sintered powder, and then mixed and dispersed, so that the prior break-down of the irregular particles can be omitted. For the slurry containing the sintered powder, it is preferable to select water as the solvent and include a dispersant in a mass ratio of 5 or less relative to the mass of the active material.

[0054] Examples of dispersants that can be used include surfactants, polyacrylic acid, polyethylene glycol, polyethyleneimine, polyvinylpyrrolidone, styrene-maleic acid polymers, ethylene-maleic acid polymers, hydroxyethyl cellulose, carboxymethyl cellulose, ethyl cellulose, and polyvinyl alcohol. The diameter of the bead mill media is selected to be 1 mm or less, preferably 0.2 mm or less, from the viewpoint of dispersing particles to the vicinity of the primary particle size mentioned above. Zirconia is preferred as the media material from the viewpoint of preventing contamination. Using small-diameter beads increases the frequency of contact between particles. This allows for good progress in fine particle dispersion, making it possible to disperse particles in the liquid to the vicinity of the primary particle size mentioned above.

[0055] (reduction treatment) Under the liquid-phase synthesis conditions described above, a precursor composite metal oxide powder in which the valence of Mo element is hexavalent is usually obtained. To reduce Mo from hexavalent to tetravalent, a reduction treatment is carried out in which the mixture is calcined in an oxygen-free atmosphere at 700°C or less with hydrogen or an organic substance mixed in. This reduction treatment can change the valence of Mo to a lower valence while maintaining the aperiodic crystal structure, resulting in a composite metal oxide containing Mo that is essentially tetravalent.

[0056] In the hydrogen reduction treatment, the precursor composite metal oxide is calcined using a mixture of an inert gas (e.g., nitrogen (N), argon (Ar), carbon dioxide (CO)) and hydrogen (H) while controlling the calcination atmosphere. Hydrogen acts as a reducing agent to reduce Mo to a tetravalent state. The hydrogen concentration in the mixed gas should be 1% by volume or more. There is no particular upper limit to the hydrogen concentration, but from the viewpoint of production, it is preferable to set the concentration below the explosion limit. The calcination temperature is 400°C to 600°C, more preferably 450°C to 550°C. The calcination time is 1 hour to 12 hours, more preferably 2 hours to 6 hours.

[0057] When an organic substance is mixed and fired, the carbon material obtained by carbonizing the organic substance through firing acts as a reducing agent. Therefore, the reduction process using mixed organic substances can be called a carbonization reduction process. The organic substance is not particularly limited, but sugars, celluloses, synthetic resins, etc. can be used. From the viewpoint of uniform coating with the carbonized material, it is preferable to use polyvinyl alcohol (PVA). The amount of organic raw material is preferably adjusted so that the carbon remaining after carbonization is 0.5% by weight or more and 5% by weight or less. The residual carbon can function as a carbon material that forms a conductive path within the secondary particles of the active material.

[0058] A solution containing an organic substance is prepared, and the precursor composite metal oxide is mixed and dispersed in it by a wet method. The resulting slurry is spray-dried to remove the solvent and then calcined in an atmosphere controlled by an inert gas or a hydrogen / inert gas mixture. This reduction process allows the synthesis of a composite metal oxide containing substantially tetravalent Mo. When calcined in an inert gas that does not contain hydrogen, the calcination temperature is 500°C to 650°C, preferably 450°C to 650°C. The calcination time is 1 hour to 12 hours, more preferably 2 hours to 6 hours. It is also possible to calcinate the mixture with hydrogen. In this case, the recommended calcination temperature and conditions are the same as those for the hydrogen-mixed calcination described above (400°C to 600°C, more preferably 450°C to 550°C; 1 hour to 12 hours, more preferably 2 hours to 6 hours). Hydrogen reduction improves the crystallinity of the coated carbon, thereby enabling better life performance.

[0059] <Various measurement methods> The method for measuring the active material will be described below, specifically, the method for confirming the composite metal oxide.

[0060] When the active material contained in a battery electrode is used as a sample, the measurement sample is prepared by pre-treating it using the following method. First, the battery is fully discharged. Next, the battery is disassembled in a glove box under an argon atmosphere, and the electrodes are removed. The removed electrodes are then washed using a solvent such as ethyl methyl carbonate. Further processing is performed for each measurement to prepare a sample in an appropriate form.

[0061] The crystal structure of the active material can be confirmed by combining high-angle annular dark-field (HAADF) and wide-angle X-ray diffraction (XRD). The active material contains a composite metal oxide containing Mo, Nb, and at least one of the elements M. The valence of the elements can be measured, for example, by X-ray photoelectron spectroscopy (XPS) using characteristic X-rays.

[0062] The structure in Figure 1 is difficult to analyze by XRD measurement because it lacks structural periodicity. To confirm the structure in Figure 1, it is preferable to directly observe the microstructure. Observation can be performed using a scanning transmission electron microscope (STEM) with the high-angle annular dark-field (HAADF) method. To improve measurement resolution, spherical aberration correction is preferable. The structure can be confirmed by acquiring an atomic image (10 nm × 10 nm) perpendicular to the ReO3 block and confirming the relative positions of the metal elements that make up the ReO3 block.

[0063] In the non-periodic crystal structure shown in Figure 1, as mentioned above, when Mo in the crystal structure is substantially tetravalent, an increase in the Mo ionic radius causes lattice expansion in the stacking direction. Therefore, the increase in interplanar spacing associated with lattice expansion can be confirmed from the peaks derived from lattice planes containing the stacking direction in the XRD spectrum. In particular, the peak near 2θ = 48° does not include the axis in the planar direction, clearly indicating a change in interplanar spacing. For a non-periodic crystal structure in which the valence of Mo as a constituent element is tetravalent, the peak top position of this peak shifts, for example, to within the range of 2θ = 47.2 ± 0.4°.

[0064] XRD measurement is performed as follows. First, the active material is pulverized as necessary to obtain a powdered sample. The average particle size of the powdered sample is preferably 20 μm or less. This average particle size can be determined using a laser diffraction particle size distribution analyzer.

[0065] Next, the powdered sample is filled into the holder portion of a glass sample plate, and the surface is flattened. For example, the glass sample plate may have a holder portion with a depth of 0.2 mm.

[0066] Next, the glass sample plate is placed in a powder X-ray diffractometer, and the XRD spectrum is measured using Cu-Kα radiation. Specific measurement conditions are, for example, as follows: X-ray diffraction equipment: Rigaku Corporation SmartLab X-ray source: CuKα ray Output: 40kV, 200mA Package measurement name: General purpose measurement (concentration method) Incident parallel slit aperture angle: 5° Incident length limiting slit length: 10 mm Photosensitive PSA: None Receiving parallel slit aperture angle: 5° Monochromatization method: Kβ filter method Measurement mode: Continuous Entrance slit width: 0.5° Receiving slit width: 20 mm Measurement range (2θ): 5 to 70° Sampling width (2θ): 0.01° Scan speed: 1° ~ 20° / min.

[0067] In this way, an XRD spectrum of the active material is obtained. In this XRD spectrum, the horizontal axis represents the angle of incidence (2θ) and the vertical axis represents the diffraction intensity (cps). The scan speed can be adjusted so that the count number of the main peak in the XRD spectrum is between 50,000 and 150,000.

[0068] When the active material contained in a battery electrode is used as a sample, the electrode after cleaning obtained by the above-mentioned pretreatment is cut into a piece having an area approximately equal to the area of ​​the glass sample plate holder to be used as a measurement sample.

[0069] Next, the obtained measurement sample is directly attached to a glass holder and subjected to XRD measurement. Next, materials other than the active material that may be contained in the electrode, such as the current collector, conductive agent, and binder, are measured using XRD to determine the XRD patterns derived from these. Next, if there are peaks in the measurement sample that overlap with peaks derived from the active material and peaks derived from other materials, the peaks derived from the materials other than the active material are separated. In this way, an XRD spectrum of the active material is obtained.

[0070] To more precisely confirm whether the measured sample contains a crystal structure that can be attributed to the tetragonal crystal structure shown in Figure 2, the Rietveld method is used. For example, RIETAN-FP is used as an analysis program, and the reliability factor R wpThis can be confirmed by confirming that the value is at least 20% or less, more preferably 15% or less. At this time, if there is a peak containing impurities and it overlaps with the phase to be analyzed, the accuracy of the analysis may be deteriorated. In this case, it is preferable to perform an analysis in which the areas that clearly overlap with the peaks derived from impurities are excluded from the analysis range. However, this does not apply when the sample contains materials other than the active material according to the first embodiment, when the sample has a significantly high orientation, or when coarse particles are mixed in, as the intensity ratio changes. The structure can be confirmed by confirming that there are no inconsistencies in the positions and relative intensities of all peaks attributed to the crystal structure. Furthermore, when the spectral intensity is low and the background intensity is low, R wp The reliability factor may be small, and its absolute value is not significant, but rather it is meaningful to judge the relative quality of the fit under certain measurement conditions.

[0071] The analytical method using RIETAN-FP is explained in detail, for example, in Chapter 9, "Let's try using RIETAN-FP," of Non-Patent Document 3 ("Practicalities of Powder X-Ray Analysis," First Edition (2002), edited by the X-Ray Analysis Research Forum of the Japan Society for Analytical Chemistry, edited by Nakai Izumi and Izumi Fujio (Asakura Publishing)).

[0072] RIETAN-FP is a Rietveld analysis program that was distributed free of charge on its developer's internet webpage (closed in 2022). As of February 2024, the program is available from the following web archive: http: / / web.archive.org / web / 20220209014122fw_ / http: / / fujioizumi.verse.jp / download / download.html The content of each element in the active material particles contained in the sample can be confirmed by ICP atomic emission spectrometry for metal elements, and although the O element can be quantified by inert gas dissolution-infrared absorption spectroscopy or other methods, precise quantification is difficult.

[0073] After the above-described pretreatment, the active material particles contained in the electrode are further subjected to the following treatment. After the cleaning, a member containing the active material (e.g., the active material-containing layer described in the second embodiment) is peeled off from the electrode's current collector, for example. The part peeled off from the electrode is heated in the atmosphere for a short time (at 500°C for about 1 hour) to burn off unnecessary parts such as binder components and carbon. The content of each element can then be quantified by ICP emission spectrometry or the like.

[0074] Measurement of the valence of metal elements contained in composite metal oxides using the XPS method can be carried out as follows. It is preferable to use hard X-rays for the measurement, as they have a deep detection depth and can measure a state closer to the bulk. Spectroscopic techniques using hard X-rays are also called HAXPES. The valence can be determined by checking the position of the binding energy in the narrow spectrum of each element. For example, for the Ti element, Ti2p 3 / 2 A tetravalent peak due to Mo is observed at 459.0±0.4 eV. For Mo element, a tetravalent peak due to Mo3d is observed at 229.4±0.4 eV. For hexavalent Mo element, 5 / 2 For pentavalent Mo, a peak due to Mo~ is observed at 231.0±0.4 eV. For Nb, a peak due to Nb3d is observed at 232.2±0.4 eV. 5 / 2 A peak due to the pentavalent element is observed at 207.5±0.4 eV. If a low-valence element is included, it can be identified by detecting a peak at a lower energy position than the previous valence.

[0075] Sample measurements are performed nondestructively to prevent changes in element valence. Therefore, when measuring composite metal oxides contained in electrodes, the electrode is used as the sample without material extraction. Care must be taken to ensure that charge-up during sample measurement does not affect the peak position. To prevent peak shifts due to charge-up, it is preferable to measure the electrode in a fully discharged state. Charge-up can be reduced if the electrode contains a conductive agent. Care must be taken, as prolonged X-ray irradiation can damage the sample and change element valence. Furthermore, when materials with different structures are mixed, peak shifts may occur due to changes in bonding state, so care must be taken not to confuse this with changes in valence. When elements with different valences are mixed, i.e., when the spectrum contains multiple peaks, the spectrum can be separated using least-squares fitting, and the mixing ratio can be estimated from the area ratio of the separated peaks.

[0076] As a result of combining the above measurements, it was found that the compound has a non-periodic crystal structure and is, for example, represented by the above general formula M x NbMo y O z It can be confirmed that the active material contains a composite metal oxide represented by the general formula M (element M and each subscript are as described above; hereinafter omitted). x NbMo y O z represents a composition in a state that does not contain charge carriers such as Li ions. Depending on the state of charge of an electrode in which the composite metal oxide is used as an active material, the composite metal oxide may contain charge carriers such as Li. For example, in a composite metal oxide contained in the negative electrode of a lithium-ion battery, Li is inserted as the battery is charged and Li is desorbed as the battery is discharged. Therefore, the above general formula represents the state in which the composite metal oxide is used as a battery active material in an uncharged or fully discharged state. In such an active material, the valence of Mo contained in the composite metal oxide is 4 in this uncharged or fully discharged state. The subscript z reflects the amount of oxygen vacancies.

[0077] (Measurement of average particle size) The average primary particle size of the active material can be determined by observation using a scanning electron microscope (SEM). Specifically, the average primary particle size determined by SEM observation can be calculated by the following method.

[0078] First, the length of the longest axis and the length of the shortest axis of the primary particles contained in the SEM image of the secondary particles obtained by SEM observation are measured, and the arithmetic mean of these is taken as the primary particle diameter. This measurement of the primary particle diameter is performed on 100 randomly selected particles, and the mean value of these is taken as the average primary particle diameter.

[0079] The average secondary particle diameter of the active material can be determined from the particle size distribution measured using a laser diffraction particle size distribution analyzer. The sample used for this particle size distribution measurement is a dispersion diluted with N-methyl-2-pyrrolidone to a concentration of 0.1% to 1% by mass of the active material. The particle diameter at which the volumetric cumulative value reaches 50% in the obtained particle size distribution is defined as the average secondary particle diameter.

[0080] The active material according to the first embodiment includes a composite metal oxide containing Mo, Nb, and at least one of the elements M described above. The composite metal oxide has a non-periodic crystal structure. The Mo element is tetravalent. An electrode using the composite metal oxide as an electrode active material has high energy density and life performance. Furthermore, a secondary battery and a battery pack using the composite metal oxide as an electrode active material have high energy density and life performance. That is, the active material exhibits high capacity and long life.

[0081] (Second embodiment) According to a second embodiment, an electrode is provided.

[0082] The electrode according to the second embodiment includes the active material according to the first embodiment. This electrode may be a battery electrode containing the active material according to the first embodiment as a battery active material. The electrode as a battery electrode may be, for example, a negative electrode containing the active material according to the first embodiment as a negative electrode active material. Alternatively, the electrode may be a positive electrode containing the active material according to the first embodiment as a positive electrode active material.

[0083] Such an electrode may include a current collector and an active material-containing layer. The active material-containing layer may be formed on one or both sides of the current collector. The active material-containing layer may include an active material and, optionally, a conductive agent and a binder.

[0084] The active material-containing layer may contain the active material according to the first embodiment alone, or may contain two or more types of active materials according to the first embodiment. Furthermore, the active material-containing layer may contain a mixture of one or more active materials according to the first embodiment and one or more other active materials. It is desirable that the content of the active material according to the first embodiment relative to the total mass of the active material according to the first embodiment and the other active materials be 10% by mass or more and 100% by mass or less.

[0085] For example, when the active material according to the first embodiment is contained as a negative electrode active material, examples of other active materials include lithium titanate having a ramsdellite structure (e.g., Li 2+x Ti3O7, 0≦x≦3), lithium titanates with spinel structure (e.g., Li 4+x Ti5O 12 , 0≦x≦3), titanium dioxide (TiO2), anatase type titanium dioxide, rutile type titanium dioxide, niobium pentoxide (Nb2O5), hollandite type titanium composite oxide, orthorhombic titanium composite oxide, and monoclinic type niobium titanium oxide, niobium oxide, niobium titanium oxide, niobium molybdenum composite oxide, and niobium tungsten composite oxide.

[0086] As an example of the above orthorhombic titanium-containing composite oxide, Li 2+e M I 2-f Ti 6-g MII h O 14+σ In this case, M I is at least one selected from the group consisting of Sr, Ba, Ca, Mg, Na, Cs, Rb and K. II is at least one selected from the group consisting of Zr, Sn, V, Nb, Ta, Mo, W, Y, Fe, Co, Cr, Mn, Ni, and Al. The subscripts in the composition formula are 0≦e≦6, 0≦f<2, 0≦g<6, 0≦h<6, and -0.5≦σ≦0.5. Specific examples of orthorhombic titanium-containing composite oxides include Li 2+e Na2Ti6O 14 (0≦e≦6).

[0087] As an example of the monoclinic niobium titanium oxide, Li x Ti 1-y M1 y Nb 2-z M2 z O 7+δ Here, M1 is at least one selected from the group consisting of Zr, Si, and Sn. M2 is at least one selected from the group consisting of V, Ta, and Bi. The subscripts in the composition formula are 0≦x≦5, 0≦y<1, 0≦z<2, and −0.3≦δ≦0.3. Specific examples of monoclinic niobium titanium oxide include Li x Examples include Nb2TiO7 (0≦x≦5).

[0088] Another example of monoclinic niobium titanium oxide is Li x Ti 1-y M3 y+z Nb 2-z O 7-δ Here, M3 is at least one selected from the group consisting of Mg, Fe, Ni, Co, W, Ta, and Mo. The subscripts in the composition formula are 0≦x≦5, 0≦y<1, 0≦z<2, and −0.3≦δ≦0.3.

[0089] The conductive agent is blended to improve current collection performance and reduce contact resistance between the active material and the current collector. Examples of conductive agents include carbonaceous materials such as vapor-grown carbon fiber (VGCF), carbon black such as acetylene black, graphite, carbon nanotubes, and carbon nanofibers. One of these may be used as the conductive agent, or two or more may be used in combination. Alternatively, instead of using a conductive agent, the surfaces of the active material particles may be coated with carbon or an electronically conductive inorganic material. Furthermore, the current collection performance of the active material-containing layer can be improved by using a conductive agent and coating the active material surface with carbon or a conductive material.

[0090] The binder is blended to fill gaps between the dispersed active materials and to bind the active materials and the current collector. Examples of binders include polytetrafluoroethylene (PTFE), polyvinylidene fluoride (PVdF), fluorine-containing rubber, styrene-butadiene rubber, polyacrylic acid compounds, imide compounds, carboxymethyl cellulose (CMC), and CMC salts. One of these may be used as the binder, or two or more may be used in combination as the binder.

[0091] The blending ratios of the active material, conductive agent, and binder in the active material-containing layer can be appropriately changed depending on the application of the electrode. For example, when the electrode is used as the negative electrode of a secondary battery, the active material (negative electrode active material), conductive agent, and binder are preferably blended in proportions of 68% by mass to 96% by mass, 2% by mass to 30% by mass, and 2% by mass to 30% by mass, respectively. By setting the amount of conductive agent to 2% by mass or more, the current collection performance of the active material-containing layer can be improved. Furthermore, by setting the amount of binder to 2% by mass or more, sufficient binding between the active material-containing layer and the current collector can be achieved, and excellent cycle performance can be expected. On the other hand, it is preferable to set the amount of conductive agent and binder to 30% by mass or less, respectively, in order to achieve high capacity.

[0092] When the surface of the active material is coated with carbon or a conductive material, the amount of coating material can be considered to be included in the amount of conductive agent. Furthermore, when the carbonization reduction treatment described in the first embodiment is performed, the amount of carbon remaining after the carbonization of the organic material can also be considered to be included in the amount of conductive agent. The amount of carbon or conductive material that coats the active material or is contained within the active material secondary particles is preferably 0.5% by mass or more and 5% by mass or less. A carbon amount within this range can improve current collection performance and electrode density.

[0093] The current collector is made of a material that is electrochemically stable at the potential at which lithium (Li) is inserted into and extracted from the active material. For example, when the active material is used as a negative electrode active material, the current collector is preferably made of copper, nickel, stainless steel, aluminum, or an aluminum alloy containing one or more elements selected from the group consisting of Mg, Ti, Zn, Mn, Fe, Cu, and Si. The thickness of the current collector is preferably 5 μm or more and 20 μm or less. A current collector having such a thickness can balance the strength and weight of the electrode.

[0094] The current collector may also include a portion on the surface of which no active material-containing layer is formed, and this portion can function as a current collecting tab.

[0095] The electrode can be produced, for example, by the following method. First, an active material, a conductive agent, and a binder are suspended in a solvent to prepare a slurry. This slurry is applied to one or both sides of a current collector. Next, the applied slurry is dried to obtain a laminate of an active material-containing layer and a current collector. After that, this laminate is pressed. In this manner, the electrode is produced.

[0096] Alternatively, the electrode may be fabricated by the following method: First, the active material, the conductive agent, and the binder are mixed to obtain a mixture, and then the mixture is formed into pellets. The pellets are then placed on a current collector to obtain an electrode.

[0097] The electrode according to the second embodiment contains the active material according to the first embodiment, and therefore the electrode according to the second embodiment can realize a secondary battery with high energy density and long life performance.

[0098] (Third embodiment) According to a third embodiment, a secondary battery is provided that includes a negative electrode, a positive electrode, and an electrolyte. This secondary battery includes the electrode according to the second embodiment as the negative electrode or the positive electrode. That is, the secondary battery according to the third embodiment includes, as a battery electrode, an electrode that includes the active material according to the first embodiment as a battery active material. A secondary battery according to a desirable aspect includes, as a negative electrode, an electrode according to the second embodiment. That is, a secondary battery according to a desirable aspect includes, as a negative electrode, an electrode that includes the active material according to the first embodiment as a battery active material. Desired aspects will be described below.

[0099] The secondary battery may further include a separator disposed between the positive electrode and the negative electrode. The negative electrode, the positive electrode, and the separator may constitute an electrode assembly. The electrolyte may be held in the electrode assembly.

[0100] Moreover, such a secondary battery can further include an exterior member that houses the electrode group and the electrolyte.

[0101] Furthermore, such a secondary battery may further include a negative electrode terminal electrically connected to the negative electrode and a positive electrode terminal electrically connected to the positive electrode.

[0102] The secondary battery according to the third embodiment may be, for example, a lithium secondary battery, and includes a non-aqueous electrolyte secondary battery containing a non-aqueous electrolyte.

[0103] The negative electrode, positive electrode, electrolyte, separator, exterior member, negative electrode terminal, and positive electrode terminal will be described in detail below.

[0104] 1) Negative electrode The negative electrode may include a negative electrode current collector and a negative electrode active material-containing layer. The negative electrode current collector and the negative electrode active material-containing layer may be the current collector and the active material-containing layer, respectively, that can be included in the electrode according to the second embodiment. The negative electrode active material-containing layer contains the active material according to the first embodiment as the negative electrode active material.

[0105] Details of the negative electrode that overlap with those described in the second embodiment will be omitted.

[0106] The density of the negative electrode active material-containing layer (excluding the current collector) is 1.8 g / cm 3 More than 2.8g / cm 3 A negative electrode having a negative electrode active material-containing layer with a density within this range is excellent in energy density and electrolyte retention. The density of the negative electrode active material-containing layer is preferably 2.1 g / cm or less. 3 More than 2.6g / cm 3 More preferably, it is:

[0107] The negative electrode can be produced, for example, by the same method as that for the electrode according to the second embodiment.

[0108] 2) Positive electrode The positive electrode may include a positive electrode current collector and a positive electrode active material-containing layer. The positive electrode active material-containing layer may be formed on one or both sides of the positive electrode current collector. The positive electrode active material-containing layer may include a positive electrode active material and, optionally, a conductive agent and a binder.

[0109] The positive electrode active material may be, for example, an oxide or a sulfide. The positive electrode may contain one type of compound alone or two or more types of compounds in combination as the positive electrode active material. Examples of oxides and sulfides include compounds that can insert and extract Li or Li ions.

[0110] Examples of such compounds include manganese dioxide (MnO2), iron oxide, copper oxide, nickel oxide, and lithium manganese composite oxides (e.g., Li x Mn2O4 or Li xMnO2; 0 < x ≤ 1), lithium nickel composite oxide (e.g., Li x NiO2; 0 < x ≤ 1), lithium cobalt composite oxide (e.g., Li x CoO2; 0 < x ≤ 1), lithium nickel cobalt composite oxide (e.g., Li x Ni 1-y Co y O2; 0 < x ≤ 1, 0 < y < 1), lithium manganese cobalt composite oxide (e.g., Li x Mn y Co 1-y O2; 0 < x ≤ 1, 0 < y < 1), lithium manganese nickel composite oxide having a spinel structure (e.g., Li x Mn 2-y Ni y O4; 0 < x ≤ 1, 0 < y < 2), lithium phosphate having an olivine structure (e.g., Li x FePO4; 0 < x ≤ 1, Li x Fe 1-y Mn y PO4; 0 < x ≤ 1, 0 < y ≤ 1, Li x CoPO4; 0 < x ≤ 1), iron sulfate (Fe2(SO4)3), vanadium oxide (e.g., V2O5), and lithium nickel cobalt manganese composite oxide (Li x Ni 1-y-z Co y Mn z O2; 0 < x ≤ 1, 0 < y < 1, 0 < z < 1, y + z < 1) are included.

[0111] Among the above, examples of more preferable compounds as the positive electrode active material include lithium manganese composite oxide having a spinel structure (e.g., Li x Mn2O4; 0 < x ≤ 1), lithium nickel composite oxide (e.g., Li x NiO2; 0 < x ≤ 1), lithium cobalt composite oxide (e.g., Li x CoO2; 0 < x ≤ 1), lithium nickel cobalt composite oxide (e.g., Li x Ni 1-y Co y O2; 0 < x ≤ 1, 0 < y < 1), lithium manganese nickel composite oxide having a spinel structure (e.g., Li x Mn 2-y Niy O4; where 0 < x ≤ 1, 0 < y < 2), lithium manganese cobalt composite oxide (e.g., Li x Mn y Co 1-y O2; where 0 < x ≤ 1, 0 < y < 1), lithium iron phosphate (e.g., Li x FePO4; where 0 < x ≤ 1), and lithium nickel cobalt manganese composite oxide (Li[[ID=IO]] x Ni 1-y-z Co y Mn z O2; where 0 < x ≤ 1, 0 < y < 1, 0 < z < 1, y + z < 1) are included. When these compounds are used as the positive electrode active material, the positive electrode potential can be increased.

[0112] 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. Since these compounds have low reactivity with the room temperature molten salt, the cycle life can be improved. Details of the room temperature molten salt will be described later.

[0113] t The primary particle size of the positive electrode active material is preferably 100 nm or more and 1 μm or less. A positive electrode active material with a primary particle size of 100 nm or more is easy to handle in industrial production. A positive electrode active material with a primary particle size of 1 μm or less can smoothly progress the solid-state diffusion of lithium ions.

[0114] <00OO604>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. A positive electrode active material having a specific surface area of 0.1 m 2 / g or more can sufficiently secure the insertion / desorption sites of Li ions. A positive electrode active material having a specific surface area of 10 m 2 / g or less is easy to handle in industrial production and can ensure good charge / discharge cycle performance. <OO00606> The binder is blended to fill gaps between the dispersed positive electrode active material and to bind the positive electrode active material and the positive electrode current collector. Examples of binders include polytetrafluoroethylene (PTFE), polyvinylidene fluoride (PVdF), fluorine-containing rubber, polyacrylic acid compounds, imide compounds, carboxymethyl cellulose (CMC), and CMC salts. One of these may be used as the binder, or two or more may be used in combination as the binder.

[0116] The conductive agent is blended to improve current collection performance and reduce contact resistance between the positive electrode active material and the positive electrode current collector. Examples of conductive agents include vapor-grown carbon fiber (VGCF), carbon black such as acetylene black, and carbonaceous materials such as graphite. One of these may be used as the conductive agent, or two or more may be used in combination as the conductive agent. The conductive agent may also be omitted.

[0117] In the positive electrode active material-containing layer, the positive electrode active material and the binder are preferably mixed in proportions of 80% by mass to 98% by mass and 2% by mass to 20% by mass, respectively.

[0118] By using a binder amount of 2% by mass or more, sufficient electrode strength can be obtained. Furthermore, the binder can function as an insulator. Therefore, by using a binder amount of 20% by mass or less, the amount of insulator contained in the electrode is reduced, thereby reducing internal resistance.

[0119] When a conductive agent is added, the positive electrode active material, binder, and conductive agent are preferably mixed in proportions of 77% by mass or more and 95% by mass or less, 2% by mass or more and 20% by mass or less, and 3% by mass or more and 15% by mass or less, respectively.

[0120] By setting the amount of conductive agent to 3% by mass or more, the above-mentioned effects can be achieved. Furthermore, by setting the amount of conductive agent to 15% by mass or less, the proportion of conductive agent in contact with the electrolyte can be reduced. This low proportion can reduce decomposition of the electrolyte during high-temperature storage.

[0121] The positive electrode current collector is preferably an aluminum foil or an aluminum alloy foil containing one or more elements selected from the group consisting of Mg, Ti, Zn, Ni, Cr, Mn, Fe, Cu, and Si.

[0122] The thickness of the aluminum foil or aluminum alloy foil is preferably 5 μm or more and 20 μm or less, more preferably 15 μm or less. The purity of the aluminum foil is preferably 99% by mass or more. The content of transition metals such as iron, copper, nickel, and chromium contained in the aluminum foil or aluminum alloy foil is preferably 1% by mass or less.

[0123] The positive electrode current collector may also include a portion on the surface of which the positive electrode active material-containing layer is not formed, and this portion can function as a positive electrode current collecting tab.

[0124] The positive electrode can be produced, for example, using a positive electrode active material by the same method as that for the electrode according to the second embodiment.

[0125] 3) Electrolytes The electrolyte may be, for example, a liquid nonaqueous electrolyte or a gel nonaqueous electrolyte. The liquid nonaqueous electrolyte is prepared by dissolving an electrolyte salt as a solute in an organic solvent. The concentration of the electrolyte salt is preferably 0.5 mol / L or more and 2.5 mol / L or less.

[0126] Examples of electrolyte salts include lithium perchlorate (LiClO), lithium hexafluorophosphate (LiPF), lithium tetrafluoroborate (LiBF), lithium hexafluoride (LiAsF), lithium trifluoromethanesulfonate (LiCFSO), and lithium salts such as lithium bistrifluoromethylsulfonylimide (LiN(CFSO)), lithium bis(fluorosulfonyl)imide (LiN(SOF); LiFSI), and mixtures thereof. The electrolyte salt is preferably one that is difficult to oxidize even at high potentials, and LiPF is most preferred.

[0127] Examples of organic solvents include cyclic carbonates such as propylene carbonate (PC), ethylene carbonate (EC), and vinylene carbonate (VC); linear carbonates such as diethyl carbonate (DEC), dimethyl carbonate (DMC), and methyl ethyl carbonate (MEC); cyclic ethers such as tetrahydrofuran (THF), 2-methyl tetrahydrofuran (2MeTHF), and dioxolane (DOX); linear ethers such as dimethoxyethane (DME) and diethoxyethane (DEE); γ-butyrolactone (GBL), acetonitrile (AN), and sulfolane (SL). These organic solvents can be used alone or in combination.

[0128] The gel-like non-aqueous electrolyte is prepared by combining a liquid non-aqueous electrolyte with a polymeric material, such as polyvinylidene fluoride (PVdF), polyacrylonitrile (PAN), polyethylene oxide (PEO), or a mixture thereof.

[0129] Alternatively, in addition to liquid nonaqueous electrolytes and gel nonaqueous electrolytes, room temperature molten salts containing lithium ions (ionic melts), polymer solid electrolytes, inorganic solid electrolytes, and the like may be used as the nonaqueous electrolyte.

[0130] Room-temperature molten salts (ionic melts) refer to organic salts consisting of a combination of organic cations and anions that can exist as a liquid at room temperature (15°C or higher and 25°C or lower). Room-temperature molten salts include room-temperature molten salts that exist as a liquid on their own, room-temperature molten salts that become liquid when mixed with an electrolyte salt, room-temperature molten salts that become liquid when dissolved in an organic solvent, and mixtures of these. Generally, the melting point of room-temperature molten salts used in secondary batteries is 25°C or lower. Furthermore, organic cations generally have a quaternary ammonium skeleton.

[0131] The solid polymer electrolyte is prepared by dissolving an electrolyte salt in a polymer material and solidifying it.

[0132] The inorganic solid electrolyte is a solid substance that has Li-ion conductivity. Here, "having Li-ion conductivity" means that the Li-ion conductivity is 1×10 at 25°C. -6 This refers to a material that exhibits a lithium ion conductivity of 1000 S / cm or more. Examples of inorganic solid electrolytes include oxide-based solid electrolytes and sulfide-based solid electrolytes. Specific examples of inorganic solid electrolytes are as follows:

[0133] The oxide-based solid electrolyte has a NASICON (Sodium (Na) Super Ionic Conductor) type structure and is represented by the general formula Li 1+xIt is preferable to use a lithium phosphate solid electrolyte represented by Mα2(PO4)3. Mα in the above general formula is, for example, one or more selected from the group consisting of titanium (Ti), germanium (Ge), strontium (Sr), zirconium (Zr), tin (Sn), aluminum (Al), and calcium (Ca). The subscript x is within the range of 0 ≦ x ≦ 2.

[0134] Specific examples of the lithium phosphate solid electrolyte having a NASICON-type structure include LATP compounds represented by Li 1+x Al x Ti 2-x (PO4)3 with 0.1 ≦ x ≦ 0.5; compounds represented by Li 1+x Al y Mβ 2-y (PO4)3 where Mβ is one or more selected from the group consisting of Ti, Ge, Sr, Zr, Sn, and Ca and 0 ≦ x ≦ 1 and 0 ≦ y ≦ 1; compounds represented by Li 1+x Al x Ge 2-x (PO4)3 with 0 ≦ x ≦ 2; and compounds represented by Li 1+x Al x Zr 2-x (PO4)3 with 0 ≦ x ≦ 2; compounds represented by Li 1+x+y Al x Mγ 2-x Si y P 3-y O 12 where Mγ is one or more selected from the group consisting of Ti and Ge and 0 < x ≦ 2, 0 ≦ y < 3; compounds represented by Li 1+2x Zr 1-x Ca x (PO4)3 with 0 ≦ x < 1 can be mentioned.

[0135] In addition, as the oxide-based solid electrolyte, in addition to the above lithium phosphate solid electrolyte, there is also an amorphous LIPON compound represented by Li x PO y N z where 2.6 ≦ x ≦ 3.5, 1.9 ≦ y ≦ 3.8, and 0.1 ≦ z ≦ 1.3 (for example, Li 2.9 PO 3.3 N 0.46);La with garnet structure 5+ xA x La 3-x MδO 12 A is at least one selected from the group consisting of Ca, Sr, and Ba, Mδ is at least one selected from the group consisting of Nb and Ta, and 0≦x≦0.5; Li3Mδ 2-x L2O 12 wherein Mδ is at least one selected from the group consisting of Nb and Ta, L may contain Zr, and 0≦x≦0.5; Li 7-3x Al x La3Zr3O 12 and 0≦x≦0.5; Li 5+x La3Mδ 2-x Zr x O 12 where Mδ is at least one selected from the group consisting of Nb and Ta, and 0≦x≦2. LLZ compounds (e.g., Li7La3Zr2O 12 ); and La 2 / 3-x Li x Examples include compounds represented by TiO3 where x is 0.3≦x≦0.7.

[0136] One or more of the above compounds can be used as the solid electrolyte, and two or more of the above solid electrolytes can also be used.

[0137] Alternatively, instead of a non-aqueous electrolyte, a liquid aqueous electrolyte or a gel aqueous electrolyte can be used as the electrolyte. The liquid aqueous electrolyte is prepared by dissolving, for example, the above-mentioned electrolyte salt as a solute in an aqueous solvent. The gel aqueous electrolyte is prepared by compounding the liquid aqueous electrolyte with the above-mentioned polymer material. A solution containing water can be used as the aqueous solvent. The solution containing water may be pure water or a mixed solvent of water and an organic solvent.

[0138] 4) Separator The separator is formed from, for example, a porous film containing polyethylene (PE), polypropylene (PP), cellulose, or polyvinylidene fluoride (PVdF), or a synthetic resin nonwoven fabric. From the viewpoint of safety, it is preferable to use a porous film formed from polyethylene or polypropylene, because these porous films melt at a certain temperature and can interrupt current.

[0139] 5) Exterior materials The exterior member may be, for example, a container made of a laminate film or a metal container.

[0140] The thickness of the laminate film is, for example, 0.5 mm or less, preferably 0.2 mm or less.

[0141] The laminate film is a multilayer film containing multiple resin layers and metal layers interposed between the resin layers. The resin layers include polymeric materials such as polypropylene (PP), polyethylene (PE), nylon, and polyethylene terephthalate (PET). The metal layers are preferably made of aluminum foil or aluminum alloy foil to reduce weight. The laminate film can be molded into the shape of the exterior component by sealing it by heat fusion.

[0142] The thickness of the wall of the metal container is, for example, 1 mm or less, more preferably 0.5 mm or less, and even more preferably 0.2 mm or less.

[0143] The metal container is made of, for example, aluminum or an aluminum alloy. The aluminum alloy preferably contains elements such as magnesium, zinc, and silicon. If the aluminum alloy contains transition metals such as iron, copper, nickel, and chromium, the content of these metals is preferably 1% by mass or less.

[0144] The shape of the exterior member is not particularly limited. The shape of the exterior member may be, for example, flat (thin), rectangular, cylindrical, coin-shaped, or button-shaped. The exterior member can be appropriately selected depending on the battery dimensions and the intended use of the battery.

[0145] 6) Negative terminal The negative electrode terminal can be formed from a material that is electrochemically stable at the Li insertion / extraction potential of the above-mentioned negative electrode active material and has electrical conductivity. Specifically, the material for the negative electrode terminal can be copper, nickel, stainless steel, aluminum, or an aluminum alloy containing at least one element selected from the group consisting of Mg, Ti, Zn, Mn, Fe, Cu, and Si. Aluminum or an aluminum alloy is preferably used as the material for the negative electrode terminal. The negative electrode terminal is preferably made of the same material as the negative electrode current collector in order to reduce contact resistance with the negative electrode current collector.

[0146] 7) Positive terminal The positive electrode terminal has a potential range of 3V to 4.5V relative to the redox potential of lithium (vs. Li / Li + ) and can be formed from a material that is electrically stable and conductive. Examples of materials for the positive electrode terminal include aluminum and aluminum alloys containing at least one element selected from the group consisting of Mg, Ti, Zn, Mn, Fe, Cu, and Si. The positive electrode terminal is preferably formed from the same material as the positive electrode current collector in order to reduce contact resistance with the positive electrode current collector.

[0147] Above, we have described an aspect in which the electrode according to the second embodiment is included as a negative electrode. Among the aspects of the secondary battery according to the third embodiment, in an aspect in which the electrode according to the second embodiment is included as a positive electrode, the negative electrode, which is the counter electrode, can be, for example, the following counter electrodes. At least one electrode selected from lithium metal, lithium metal alloy, graphite, silicon, silicon oxide, tin oxide, silicon, tin, and other alloys can be used as a negative electrode. A material that does not contain Li in the active material can be used as a negative electrode by pre-doping it with Li element.

[0148] In the aspect in which the electrode according to the second embodiment is included as a positive electrode, the details of the positive electrode are the same as those explained in the second embodiment, and therefore will be omitted.

[0149] Next, the secondary battery according to the third embodiment will be described in more detail with reference to the drawings.

[0150] Fig. 3 is a cross-sectional view schematically showing an example of a secondary battery, and Fig. 4 is an enlarged cross-sectional view of part A of the secondary battery shown in Fig. 3.

[0151] 3 and 4 includes an electrode group 1 shown in Fig. 3, a bag-shaped exterior member 2 shown in Fig. 3 and 4, and an electrolyte (not shown). The electrode group 1 and the electrolyte are housed in the bag-shaped exterior member 2. The electrolyte (not shown) is held in the electrode group 1.

[0152] The bag-shaped exterior member 2 is made of a laminate film including two resin layers and a metal layer interposed between them.

[0153] As shown in Fig. 3, the electrode group 1 is a flat wound electrode group. As shown in Fig. 4, the flat wound electrode group 1 includes a negative electrode 3, a separator 4, and a positive electrode 5. The separator 4 is interposed between the negative electrode 3 and the positive electrode 5.

[0154] The negative electrode 3 includes a negative electrode current collector 3a and a negative electrode active material-containing layer 3b. In the portion of the negative electrode 3 located at the outermost shell of the wound-type electrode group 1, the negative electrode active material-containing layer 3b is formed only on the inner surface side of the negative electrode current collector 3a, as shown in Fig. 4. In the other portions of the negative electrode 3, the negative electrode active material-containing layer 3b is formed on both sides of the negative electrode current collector 3a.

[0155] The positive electrode 5 includes a positive electrode current collector 5a and positive electrode active material-containing layers 5b formed on both sides of the positive electrode current collector 5a.

[0156] As shown in FIG. 3, the negative electrode terminal 6 and the positive electrode terminal 7 are located near the outer peripheral edge of the wound electrode group 1. The negative electrode terminal 6 is connected to a portion located at the outermost shell of the negative electrode current collector 3a. The positive electrode terminal 7 is connected to a portion located at the outermost shell of the positive electrode current collector 5a. The negative electrode terminal 6 and the positive electrode terminal 7 extend to the outside from an opening of the bag-shaped exterior member 2. A thermoplastic resin layer is provided on the inner surface of the bag-shaped exterior member 2, and the opening is closed by heat sealing the thermoplastic resin layer.

[0157] The secondary battery according to the embodiment is not limited to the secondary battery having the configuration shown in FIGS. 3 and 4, but may also be a battery having the configuration shown in FIGS. 5 and 6, for example.

[0158] Fig. 5 is a partially cutaway perspective view schematically showing another example of a secondary battery, and Fig. 6 is an enlarged cross-sectional view of part B of the secondary battery shown in Fig. 5.

[0159] 5 and 6 includes an electrode group 1 shown in Fig. 5 and 6, an exterior member 2 shown in Fig. 5, and an electrolyte (not shown). The electrode group 1 and the electrolyte are housed in the exterior member 2. The electrolyte is held in the electrode group 1.

[0160] The exterior member 2 is made of a laminate film including two resin layers and a metal layer interposed between them.

[0161] The electrode group 1 is a laminated electrode group, as shown in Fig. 6. The laminated electrode group 1 has a structure in which negative electrodes 3 and positive electrodes 5 are alternately laminated with separators 4 interposed therebetween.

[0162] The electrode group 1 includes a plurality of negative electrodes 3. Each of the plurality of negative electrodes 3 includes a negative electrode current collector 3a and a negative electrode active material-containing layer 3b supported on both sides of the negative electrode current collector 3a. The electrode group 1 also includes a plurality of positive electrodes 5. Each of the plurality of positive electrodes 5 includes a positive electrode current collector 5a and a positive electrode active material-containing layer 5b supported on both sides of the positive electrode current collector 5a.

[0163] The negative electrode current collector 3a of each negative electrode 3 includes a portion on one side where no negative electrode active material-containing layer 3b is supported on any surface. This portion serves as a negative electrode current collector tab 3c. As shown in FIG. 6 , the negative electrode current collector tab 3c does not overlap with the positive electrode 5. The multiple negative electrode current collector tabs 3c are electrically connected to a strip-shaped negative electrode terminal 6. The tip of the strip-shaped negative electrode terminal 6 is extended to the outside of the exterior member 2.

[0164] Although not shown, the positive electrode current collector 5a of each positive electrode 5 includes a portion on one side where the positive electrode active material-containing layer 5b is not supported on any surface. This portion functions as a positive electrode current collector tab. Like the negative electrode current collector tab 3c, the positive electrode current collector tab does not overlap with the negative electrode 3. The positive electrode current collector tab is located on the opposite side of the electrode group 1 from the negative electrode current collector tab 3c. The positive electrode current collector tab is electrically connected to a strip-shaped positive electrode terminal 7. The tip of the strip-shaped positive electrode terminal 7 is located on the opposite side from the negative electrode terminal 6 and is drawn out to the outside of the exterior member 2.

[0165] 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 the electrode containing the active material according to the first embodiment. Therefore, the secondary battery according to the third embodiment has high energy density and long life performance.

[0166] (Fourth embodiment) According to a fourth embodiment, there is provided a battery pack, which includes a plurality of secondary batteries according to the third embodiment.

[0167] In such a battery pack, the individual cells may be electrically connected in series or in parallel, or may be connected in a combination of series and parallel.

[0168] Next, an example of a battery pack according to a fourth embodiment will be described with reference to the drawings.

[0169] Fig. 7 is a perspective view schematically showing an example of a battery pack. The battery pack 200 shown in Fig. 7 includes five cells 100a to 100e, four bus bars 21, a positive electrode lead 22, and a negative electrode lead 23. Each of the five cells 100a to 100e is a secondary battery according to the third embodiment.

[0170] The bus bar 21 connects, for example, the negative electrode terminal 6 of one cell 100a to the positive electrode terminal 7 of the adjacent cell 100b. In this way, the five cells 100 are connected in series by four bus bars 21. That is, the battery pack 200 in FIG. 7 is a five-series battery pack. Although an example is not shown, in a battery pack including a plurality of cells electrically connected in parallel, the plurality of cells can be electrically connected by, for example, connecting the negative electrode terminals to each other by a bus bar and connecting the positive electrode terminals to each other by a bus bar.

[0171] The positive electrode terminal 7 of at least one of the five cells 100a to 100e is electrically connected to a positive electrode lead 22 for external connection. Also, the negative electrode terminal 6 of at least one of the five cells 100a to 100e is electrically connected to a negative electrode lead 23 for external connection.

[0172] The battery pack according to the fourth embodiment includes the secondary battery according to the third embodiment, and therefore has high energy density and long life performance.

[0173] (Fifth embodiment) According to a fifth embodiment, there is provided a battery pack. This battery pack includes the battery assembly according to the fourth embodiment. This battery pack may include a single secondary battery according to the third embodiment instead of the battery assembly according to the fourth embodiment.

[0174] Such a battery pack may further include a protection circuit. The protection circuit has a function of controlling the charging and discharging of the secondary battery. Alternatively, a circuit included in a device that uses the battery pack as a power source (e.g., electronic equipment, automobile, etc.) may be used as the protection circuit for the battery pack.

[0175] The battery pack may further include external terminals for current flow. The external terminals for current flow are for outputting current from the secondary battery to the outside and / or inputting current from the outside to the secondary battery. In other words, when the battery pack is used as a power source, current is supplied to the outside through the external terminals for current flow. When the battery pack is charged, charging current (including regenerative energy from the power of an automobile or the like) is supplied to the battery pack through the external terminals for current flow.

[0176] Next, an example of a battery pack according to an embodiment will be described with reference to the drawings.

[0177] Fig. 8 is an exploded perspective view schematically showing an example of a battery pack, and Fig. 9 is a block diagram showing an example of an electric circuit of the battery pack shown in Fig. 8.

[0178] The battery pack 300 shown in FIGS. 8 and 9 includes a container 31, a lid 32, a protective sheet 33, a battery pack 200, a printed wiring board 34, wiring 35, and an insulating plate (not shown).

[0179] The storage container 31 shown in Fig. 8 is a bottomed, square container having a rectangular bottom. The storage container 31 is configured to be able to accommodate a protective sheet 33, a battery pack 200, a printed wiring board 34, and wiring 35. The lid 32 has a rectangular shape. The lid 32 covers the storage container 31 to accommodate the battery pack 200 and other components. Although not shown, the storage container 31 and the lid 32 are provided with openings or connection terminals for connection to external devices and the like.

[0180] The battery pack 200 includes a plurality of cells 100, a positive electrode lead 22, a negative electrode lead 23, and an adhesive tape 24.

[0181] At least one of the plurality of cells 100 is a secondary battery according to the third embodiment. The plurality of cells 100 are electrically connected in series as shown in FIG. 9. The plurality of cells 100 may be electrically connected in parallel, or may be connected in a combination of series and parallel connections. When the plurality of cells 100 are connected in parallel, the battery capacity increases compared to when they are connected in series.

[0182] The adhesive tape 24 fastens the plurality of cells 100 together. Heat-shrinkable tape may be used to secure the plurality of cells 100 together instead of the adhesive tape 24. In this case, protective sheets 33 are placed on both side surfaces of the battery pack 200, and the heat-shrinkable tape is wrapped around the cells 100, and the heat-shrinkable tape is then thermally shrunk to bind the plurality of cells 100 together.

[0183] One end of the positive electrode lead 22 is connected to the battery pack 200. One end of the positive electrode lead 22 is electrically connected to the positive electrode of one or more cells 100. One end of the negative electrode lead 23 is connected to the battery pack 200. One end of the negative electrode lead 23 is electrically connected to the negative electrode of one or more cells 100.

[0184] The printed wiring board 34 is installed along one of the shorter sides of the inner surface of the container 31. The printed wiring board 34 includes a positive connector 342, a negative connector 343, a thermistor 345, a protection circuit 346, wires 342a and 343a, an external terminal 350 for supplying current, a positive wire (positive wire) 348a, and a negative wire (negative wire) 348b. One main surface of the printed wiring board 34 faces one side of the battery pack 200. An insulating plate (not shown) is interposed between the printed wiring board 34 and the battery pack 200.

[0185] The other end 22a of the positive electrode lead 22 is electrically connected to the positive electrode connector 342. The other end 23a of the negative electrode lead 23 is electrically connected to the negative electrode connector 343.

[0186] The thermistor 345 is fixed to one main surface of the printed wiring board 34. The thermistor 345 detects the temperature of each of the cells 100 and transmits the detection signal to the protection circuit 346.

[0187] The external terminals 350 for applying current are fixed to the other main surface of the printed wiring board 34. The external terminals 350 for applying current are electrically connected to devices located outside the battery pack 300. The external terminals 350 for applying current include a positive terminal 352 and a negative terminal 353.

[0188] The protection circuit 346 is fixed to the other main surface of the printed wiring board 34. The protection circuit 346 is connected to the positive terminal 352 via a positive wiring 348a. The protection circuit 346 is connected to the negative terminal 353 via a negative wiring 348b. The protection circuit 346 is also electrically connected to the positive connector 342 via a wiring 342a. The protection circuit 346 is electrically connected to the negative connector 343 via a wiring 343a. The protection circuit 346 is also electrically connected to each of the plurality of single cells 100 via wiring 35.

[0189] The protective sheet 33 is disposed on both inner surfaces of the long sides of the container 31 and on the inner surface of the short side that faces the printed wiring board 34 across the battery pack 200. The protective sheet 33 is made of, for example, resin or rubber.

[0190] The protection circuit 346 controls charging and discharging of the plurality of cells 100. Furthermore, the protection circuit 346 cuts off the electrical connection between the protection circuit 346 and external terminals 350 (positive terminal 352, negative terminal 353) for supplying electricity to an external device, based on a detection signal transmitted from the thermistor 345 or a detection signal transmitted from each cell 100 or the battery pack 200.

[0191] An example of the detection signal transmitted from the thermistor 345 is a signal indicating that the temperature of the cell 100 is equal to or higher than a predetermined temperature. An example of the detection signal transmitted from each cell 100 or the battery pack 200 is a signal indicating that overcharge, overdischarge, or overcurrent of the cell 100 is detected. When detecting overcharge or the like for each cell 100, the battery voltage may be detected, or the positive electrode potential or the negative electrode potential may be detected. In the latter case, a lithium electrode used as a reference electrode is inserted into each cell 100.

[0192] The protection circuit 346 may be a circuit included in a device (such as an electronic device or an automobile) that uses the battery pack 300 as a power source.

[0193] As described above, the battery pack 300 is also provided with the external terminals 350 for current application. Therefore, the battery pack 300 can output current from the battery assembly 200 to an external device and input current from the external device to the battery assembly 200 via the external terminals 350 for current application. In other words, when the battery pack 300 is used as a power source, the current from the battery assembly 200 is supplied to the external device via the external terminals 350 for current application. When the battery pack 300 is charged, a charging current from the external device is supplied to the battery pack 300 via the external terminals 350 for current application. When the battery pack 300 is used as an in-vehicle battery, regenerative energy from the vehicle's power can be used as the charging current from the external device.

[0194] The battery pack 300 may include a plurality of assembled batteries 200. In this case, the assembled batteries 200 may be connected in series, in parallel, or in a combination of series and parallel connections. The printed wiring board 34 and the wiring 35 may be omitted. In this case, the positive electrode lead 22 and the negative electrode lead 23 may be used as a positive terminal 352 and a negative terminal 353, respectively, of the external terminal 350 for supplying current.

[0195] Such a battery pack is used in applications requiring excellent cycle performance when drawing a large current, for example. Specifically, this battery pack is used, for example, as a power source for electronic devices, a stationary battery, or an on-board battery for various vehicles. Examples of electronic devices include digital cameras. This battery pack is particularly suitable for use as an on-board battery.

[0196] The battery pack according to the fifth embodiment includes the secondary battery according to the third embodiment or the battery pack according to the fourth embodiment, and therefore has high energy density and long life performance.

[0197] (Sixth embodiment) According to a sixth embodiment, a vehicle is provided, which is equipped with the battery pack according to the fifth embodiment.

[0198] In such a vehicle, the battery pack recovers, for example, regenerative energy for powering the vehicle, and the vehicle may include a mechanism (regenerator) for converting the kinetic energy of the vehicle into regenerative energy.

[0199] Examples of vehicles include two- to four-wheel hybrid electric vehicles, two- to four-wheel electric vehicles, power-assisted bicycles, and rail vehicles.

[0200] The mounting position of the battery pack in a vehicle is not particularly limited. For example, when the battery pack is mounted in an automobile, the battery pack can be mounted in the engine compartment, the rear of the vehicle body, or under the seat of the vehicle.

[0201] A vehicle may be equipped with multiple battery packs. In this case, the batteries included in each battery pack may be electrically connected in series, in parallel, or a combination of series and parallel connections. For example, if each battery pack includes a battery pack, the battery packs may be electrically connected in series, in parallel, or a combination of series and parallel connections. Alternatively, if each battery pack includes a single battery, the batteries may be electrically connected in series, in parallel, or a combination of series and parallel connections.

[0202] Next, an example of a vehicle according to an embodiment will be described with reference to the drawings.

[0203] FIG. 10 is a partially transparent view that schematically illustrates an example of a vehicle.

[0204] A vehicle 400 shown in Fig. 10 includes a vehicle body 40 and a battery pack 300 according to the fifth embodiment. In the example shown in Fig. 10, the vehicle 400 is a four-wheeled automobile.

[0205] The vehicle 400 may be equipped with a plurality of battery packs 300. In this case, the batteries (for example, single cells or assembled batteries) included in the battery packs 300 may be connected in series, in parallel, or in a combination of series and parallel connections.

[0206] 10 illustrates an example in which the battery pack 300 is mounted in an engine compartment located in the front of the vehicle body 40. As described above, the battery pack 300 may be mounted, for example, at the rear of the vehicle body 40 or under a seat. This battery pack 300 can be used as a power source for the vehicle 400. In addition, this battery pack 300 can recover regenerative energy for powering the vehicle 400.

[0207] Next, an embodiment of a vehicle according to the present invention will be described with reference to FIG.

[0208] Fig. 11 is a diagram that schematically illustrates an example of a control system for an electrical system in a vehicle. The vehicle 400 shown in Fig. 11 is an electric vehicle.

[0209] The vehicle 400 shown in FIG. 11 comprises a vehicle body 40, a vehicle power supply 41, a vehicle ECU (ECU: Electric Control Unit) 42 which is a higher-level control device of the vehicle power supply 41, an external terminal (terminal for connecting to an external power supply) 43, an inverter 44, and a drive motor 45.

[0210] Vehicle 400 has vehicle power supply 41 mounted, for example, in the engine compartment, the rear of the vehicle body, or under the seat. Note that in vehicle 400 shown in Fig. 11, the mounting location of vehicle power supply 41 is shown schematically.

[0211] The vehicle power supply 41 includes a plurality of (for example, three) battery packs 300a, 300b, and 300c, a battery management unit (BMU) 411, and a communication bus 412.

[0212] The battery pack 300a includes an assembled battery 200a and an assembled battery monitoring device 301a (for example, VTM: Voltage Temperature Monitoring). The battery pack 300b includes an assembled battery 200b and an assembled battery monitoring device 301b. The battery pack 300c includes an assembled battery 200c and an assembled battery monitoring device 301c. The battery packs 300a to 300c are the same as the battery pack 300 described above, and the assembled batteries 200a to 200c are the same as the assembled battery 200 described above. The assembled batteries 200a to 200c are electrically connected in series. The battery packs 300a, 300b, and 300c can each be removed independently and replaced with another battery pack 300.

[0213] Each of the assembled batteries 200a to 200c includes a plurality of unit cells connected in series. At least one of the plurality of unit cells is the secondary battery according to the third embodiment. Each of the assembled batteries 200a to 200c is charged and discharged via a positive terminal 413 and a negative terminal 414.

[0214] The battery management device 411 communicates with the assembled battery monitoring devices 301a to 301c and collects information on the voltage, temperature, etc. of each of the cells 100 included in the assembled batteries 200a to 200c included in the vehicle power supply 41. In this way, the battery management device 411 collects information on the maintenance of the vehicle power supply 41.

[0215] The battery management unit 411 and the assembled battery monitoring units 301a to 301c are connected via a communication bus 412. In the communication bus 412, one set of communication lines is shared by multiple nodes (the battery management unit 411 and one or more assembled battery monitoring units 301a to 301c). The communication bus 412 is a communication bus configured based on, for example, the CAN (Control Area Network) standard.

[0216] The battery pack monitoring devices 301a to 301c measure the voltage and temperature of each of the cells constituting the battery packs 200a to 200c based on commands received through communication from the battery management device 411. However, the temperature can be measured at only a few locations per battery pack, and it is not necessary to measure the temperature of all the cells.

[0217] The vehicle power supply 41 may also have an electromagnetic contactor (for example, a switch device 415 shown in FIG. 11) that switches between electrical connection and disconnection between the positive terminal 413 and the negative terminal 414. The switch device 415 includes a pre-charge switch (not shown) that is turned on when the assembled batteries 200a-200c are being charged, and a main switch (not shown) that is turned on when the output from the assembled batteries 200a-200c is being supplied to a load. Each of the pre-charge switch and the main switch includes a relay circuit (not shown) that is switched on or off by a signal supplied to a coil disposed near the switch element. Electromagnetic contactors such as the switch device 415 are controlled based on a control signal from the battery management device 411 or the vehicle ECU 42 that controls the operation of the entire vehicle 400.

[0218] The inverter 44 converts the input DC voltage into a three-phase alternating current (AC) high voltage for driving the motor. The three-phase output terminals of the inverter 44 are connected to the three-phase input terminals of the drive motor 45. The inverter 44 is controlled based on control signals from the battery management unit 411 or the vehicle ECU 42, which controls the operation of the entire vehicle. By controlling the inverter 44, the output voltage from the inverter 44 is adjusted.

[0219] The drive motor 45 is rotated by the electric power supplied from the inverter 44. The drive force generated by the rotation of the drive motor 45 is transmitted to the axles and drive wheels W via, for example, a differential gear unit.

[0220] Although not shown, vehicle 400 also includes a regenerative braking mechanism (regenerator). When vehicle 400 is braked, regenerative braking mechanism rotates drive motor 45 and converts kinetic energy into regenerative energy as electrical energy. The regenerative energy recovered by the regenerative braking mechanism is input to inverter 44 and converted into direct current. The converted direct current is input to vehicle power supply 41.

[0221] One terminal of a connection line L1 is connected to the negative terminal 414 of the vehicle power supply 41. The other terminal of the connection line L1 is connected to a negative input terminal 417 of the inverter 44. A current detection unit (current detection circuit) 416 in the battery management device 411 is provided on the connection line L1 between the negative terminal 414 and the negative input terminal 417.

[0222] One terminal of a connection line L2 is connected to the positive terminal 413 of the vehicle power supply 41. The other terminal of the connection line L2 is connected to a positive input terminal 418 of the inverter 44. A switch device 415 is provided on the connection line L2 between the positive terminal 413 and the positive input terminal 418.

[0223] The external terminal 43 is connected to the battery management device 411. The external terminal 43 can be connected to, for example, an external power source.

[0224] In response to operational inputs from the driver or the like, the vehicle ECU 42 coordinates with other management devices and control devices including the battery management device 411 to control the vehicle power supply 41, the switch device 415, the inverter 44, etc. Through the coordinated control of the vehicle ECU 42, etc., the output of power from the vehicle power supply 41 and the charging of the vehicle power supply 41 are controlled, thereby managing the entire vehicle 400. Data relating to the maintenance of the vehicle power supply 41, such as the remaining capacity of the vehicle power supply 41, is transferred between the battery management device 411 and the vehicle ECU 42 via a communication line.

[0225] The vehicle according to the sixth embodiment is equipped with the battery pack according to the fifth embodiment. Because the battery pack has a high energy density, it is possible to provide a high-performance vehicle. In addition, because the battery pack has a long lifespan, it is possible to provide a highly reliable vehicle. [Example]

[0226] The above-described embodiment will be described in more detail below based on examples, but the present invention is not limited to the examples listed below.

[0227] <Synthesis> Example 1 A titanium-niobium-molybdenum composite oxide was synthesized as follows.

[0228] Niobium ammonium oxalate, ammonium molybdate, and titanium tetraisopropoxide were prepared as raw materials. These raw materials were weighed according to the specified composition ratio. Solution A was prepared by dissolving niobium ammonium oxalate and ammonium molybdate in pure water. Next, titanium tetraisopropoxide was added to a 1M aqueous oxalic acid solution and dissolved by heating and stirring to prepare Solution B. Solutions A and B were mixed, and then an ammonia solution was added while heating and stirring to adjust the pH to 7, yielding a sol. The sol was spray-dried at 160°C to evaporate the solvent, yielding a white precursor powder. The precursor powder was placed in an alumina crucible and fired in air at 650°C for 4 hours (first firing), forming amorphous particles composed of a titanium-niobium-molybdenum composite oxide phase, which served as the base material prior to carbonization and reduction. ICP emission spectroscopy of the obtained base material confirmed the composition shown in Table 1 below.

[0229] Next, a carbonization-reduction treatment was carried out. Polyvinyl alcohol (PVA) was selected as the organic raw material, and a solution of this was dissolved in pure water. The amorphous particles composed of the titanium-niobium-molybdenum composite oxide phase synthesized as described above were then added to the solution to form a slurry. The amount of organic raw material was 1 wt% relative to the base material, as shown in Table 1 below. The resulting slurry was subjected to a wet bead mill to crush and disperse the particles. The slurry was then spray-dried at 140°C to evaporate the solvent, yielding a powder composite of the base material and organic raw material. This composite powder was then calcined at 650°C for 4 hours (second calcination) under an argon gas atmosphere. This carbonization resulted in the formation of low-crystalline carbon, while simultaneously performing a carbonization-reduction calcination of elemental molybdenum using the formed carbon as a reducing agent. The amount of carbon remaining after calcination was determined by thermogravimetry (TG) analysis to be 0.5 wt%. In this manner, an active material powder was obtained.

[0230] Examples 2 and 3 First, amorphous particles (base material before carbonization and reduction) were formed by the same method as in Example 1. An active material powder was obtained by carrying out the same carbonization and reduction treatment as in Example 1, except that the amount of organic raw material was changed as shown in Table 1 below.

[0231] Example 4 First, amorphous particles (base material before carbonization reduction) were formed using the same method as in Example 1. Then, coarse particles were pulverized using a dry ball mill. Next, hydrogen reduction was performed instead of carbonization reduction treatment. The base material was subjected to hydrogen reduction treatment by firing (second firing) at 650°C for 4 hours while flowing a hydrogen / argon mixed gas, in which 3% by volume of hydrogen was mixed with argon gas, into a tubular furnace, to obtain an active material powder.

[0232] Example 5 Active material powder was obtained in the same manner as in Example 4, except that the baking temperature in the hydrogen reduction treatment was changed to 500° C. as shown in Table 1 below.

[0233] Example 6 First, amorphous particles (base material before carbonization reduction) were formed using the same method as in Example 1. Next, a combined treatment of hydrogen reduction and carbonization reduction was carried out. Except for changing the amount of organic raw material to 5 wt%, the same procedure as the carbonization reduction treatment in Example 1 was followed, up to the acquisition of composite powder by spray drying. This powder was subjected to a hydrogen reduction treatment by firing (second firing) at 650°C for 4 hours while flowing a hydrogen / argon mixed gas, in which 3 volume % of hydrogen was mixed with argon gas, in a tubular furnace, to obtain an active material powder.

[0234] Examples 7 to 9 The proportions of the raw materials were adjusted so as to obtain a base material having the composition shown in Table 1. In addition, the amount of organic raw materials used in the carbonization reduction treatment was changed to 5 wt %. Except for these points, an active material powder was obtained in the same manner as in Example 1.

[0235] (Comparative Example 1) First, irregular particles (base material before carbonization and reduction) were formed in the same manner as in Example 1, except that the temperature during the first firing was changed to 600°C. Then, coarse particles were pulverized using a dry ball mill. The reduction treatment was omitted. In this manner, an active material powder was obtained.

[0236] <Measurement> The powders obtained in each of the above examples and comparative examples were observed using a scanning transmission electron microscope. Specifically, as described above in detail, the microstructure was observed using a 10 nm × 10 nm image using a spherical aberration-corrected STEM-HAADF image. Measurements were also performed using wide-angle X-ray diffraction (XRD). The measurements were performed in accordance with the details described above. Crystal structure analysis was performed using the Rietveld method on the obtained spectra.

[0237] The microstructure of the composite metal oxides obtained in Examples 1 to 9 and Comparative Example 1 was observed using STEM-HAADF images, and it was confirmed that the size of the ReO3 blocks within the field of view was different and that the crystal structure was non-periodic and connected by octahedral edge-sharing. From this, the crystal structure was identified as shown in Figure 1.

[0238] As specific examples of XRD measurement, XRD spectra measured for the powders obtained in Example 1 and Comparative Example 1 are shown in Figures 12 and 13. Figure 13 is an enlarged view of the range near 2θ = 48° of the spectrum shown in Figure 12. The dashed line 48 in Figure 12 indicates the position of 2θ = 48°. In both figures, the upper curve 50 represents the spectrum of Example 1, and the lower curve 51 represents the spectrum of Comparative Example 1. As can be seen from the spectra in each figure, the peak near 2θ = 48° in Example 1 is shifted to a lower angle compared to that in Comparative Example 1. From the position of this peak, it can be determined that molybdenum (Mo) in the composite metal oxide in Example 1 is substantially tetravalent.

[0239] Table 1 shows the composition of the base material obtained by the first calcination before reduction (carbonization reduction or hydrogen reduction), the reduction conditions, the amount of carbon remaining after carbonization of the organic solvent, and the peak top position of the peak near 2θ = 48° in the XRD spectrum. The reduction conditions include whether carbonization reduction or hydrogen reduction was performed, the organic raw material used in the carbonization reduction and its amount, and the temperature of the reduction calcination (second calcination).

[0240] [Table 1]

[0241] As shown in Table 1, in Examples 1 to 9, in which reduction treatment was performed, the peak near 2θ=48° in the XRD spectrum of the obtained active material powder shifted to within the range of 47.2±0.4°, indicating that Mo in the composite metal oxide was substantially reduced to a tetravalent state. In contrast, in Comparative Example 1, in which reduction treatment was not performed, the corresponding peak remained at about 48°, indicating that Mo in the composite metal oxide did not become tetravalent.

[0242] <Battery performance evaluation> Using the active material powders obtained in the above Examples and Comparative Examples, electrodes were fabricated as follows.

[0243] First, 100 parts by mass of active material, 6 parts by mass of conductive agent, and 4 parts by mass of binder were dispersed in a solvent to prepare a slurry. The composite material powders obtained by the above-mentioned method were used as the active material. A mixture of acetylene black, carbon nanotubes, and graphite was used as the conductive agent. A mixture of carboxymethyl cellulose (CMC) and styrene butadiene rubber (SBR) was used as the binder. Pure water was used as the solvent.

[0244] The resulting slurry was then applied to one side of a current collector, and the coating was dried to form an active material-containing layer. An aluminum foil with a thickness of 12 μm was used as the current collector. The current collector and the active material-containing layer were then pressed together to obtain an electrode. The electrode had a basis weight of 60 g / m. 2 It was.

[0245] A non-aqueous electrolyte was prepared as follows. An electrolyte salt was dissolved in an organic solvent to obtain a liquid non-aqueous electrolyte. LiPF6 was used as the electrolyte salt. The molar concentration of LiPF6 in the non-aqueous electrolyte was 1 mol / L. A mixed solvent of ethylene carbonate (EC) and diethyl carbonate (DEC) was used as the organic solvent. The volume ratio of EC to DEC was 1:2.

[0246] A three-electrode beaker cell was fabricated using the electrode obtained by the above method as a working electrode, metallic lithium foil as a counter electrode and a reference electrode, and the nonaqueous electrolyte prepared by the above method.

[0247] The initial charge-discharge performance and cycle life performance of each cell were evaluated. Specifically, the evaluation temperature was 25°C, and the potential range was the lower limit potential of 0.4 V (vs. Li / Li) from the lithium reference potential. + ), upper limit potential 3.2V (vs. Li / Li + ) and charge / discharge were carried out. Charging was carried out in constant current / constant voltage mode, and discharging was carried out in constant current mode. The current value for the initial charge / discharge was 0.2 C. The lower limit potential was 0.4 V (vs. Li / Li +) was measured to determine the initial charge capacity. In a battery using the above electrode as the negative electrode in combination with the positive electrode active material described in the third embodiment, the cutoff potential of the negative electrode was assumed to be 2.50 V (vs. Li / Li), and the capacity during discharge until this potential was reached was measured to determine the initial discharge capacity. The initial discharge capacity was divided by the initial charge capacity to determine the initial charge / discharge efficiency (initial charge / discharge efficiency (%) = [initial discharge capacity / initial charge capacity] × 100%). The average operating potential during discharge to the 2.50 V (vs. Li / Li) cutoff potential was also calculated. Furthermore, a plot of dQ / dV versus the potential (vs. Li / Li) during discharge was obtained, and it was confirmed whether or not there was a peak at 2.35 V (vs. Li / Li).

[0248] 14 shows initial charge / discharge curves for beaker cells using the active material powders of Example 1 and Comparative Example 1. Solid charge curve 60 and discharge curve 70 respectively represent the initial charge / discharge for the beaker cell of Example 1. Dashed charge curve 61 and discharge curve 71 respectively represent the initial charge / discharge for the beaker cell of Comparative Example 1. The straight dashed line 25 indicates the 2.50 V (vs. Li / Li) cutoff potential.

[0249] 15 shows dQ / dV plots at the time of the first discharge of the beaker cells according to Example 1 and Comparative Example 1. A solid line 80 indicates the plot for Example 1, and a dotted line 81 indicates the plot for Comparative Example 1.

[0250] After the initial discharge, the cycle life was evaluated by repeatedly charging and discharging at a current of 1 C and calculating the retention rate of the discharge capacity at the 30th cycle relative to the discharge capacity at the 1st cycle (cycle capacity retention rate (%) = [discharge capacity at the 30th cycle / discharge capacity at the 1st cycle] × 100%).

[0251] The evaluation results of the battery performance are summarized in Table 2. Specifically, the initial charge capacity, initial discharge capacity, initial charge / discharge efficiency, dQ / dV value at 2.35 V (vs. Li / Li), average working potential at the initial discharge, and cycle capacity retention are shown.

[0252] [Table 2]

[0253] As shown in Table 2, the beaker cells using the active material powders of Examples 1 to 9 exhibited better initial charge-discharge efficiency and cycle capacity retention rate than the beaker cell using the active material powder of Comparative Example 1. Furthermore, the dQ / dV plot (dotted line 81) of the beaker cell according to Comparative Example 1 was 2.35 V (vs. Li / Li) as shown in FIG. + ) around 2.35 V (vs. Li / Li + ) showed a high dQ / dV of 146.9 mAh / g V. In contrast, the dQ / dV of the beaker cells according to Examples 1 to 9 was 2.35 V (vs. Li / Li + ) had low dQ / dV values ​​as shown in Table 2, and there was no pentavalent / hexavalent charge compensation peak of Mo, as seen in the dQ / dV plot (solid line 80) of Example 1 shown in Figure 15. That is, in the active materials of Examples 1 to 9, the Mo element was essentially tetravalent, and there was no change in valence related to the pentavalent / hexavalent state of Mo, which makes it difficult to use it as electricity. Therefore, the charge / discharge efficiency and cycle capacity retention rate were improved compared to Comparative Example 1.

[0254] According to one or more of the embodiments and examples described above, an active material containing a composite metal oxide is provided. The composite metal oxide contains Mo, Nb, and at least one element M. The element M is selected from the group consisting of Ti, V, Ta, Fe, Co, Mn, Ni, Bi, Sb, As, P, Cr, W, B, Na, K, Mg, Al, Ca, Y, and Si. The crystalline structure of the composite metal oxide is aperiodic. The valence of the Mo element is tetravalent. This active material can provide an electrode that can realize a secondary battery with high energy density and long life, a secondary battery and battery pack with high energy density and long life, and a vehicle equipped with the battery pack.

[0255] Several embodiments of the present invention will be described below. [1] An active material containing a composite metal oxide containing a tetravalent Mo element and at least one element M selected from the group consisting of Nb element, Ti, V, Ta, Fe, Co, Mn, Ni, Bi, Sb, As, P, Cr, W, B, Na, K, Mg, Al, Ca, Y and Si, and the crystal structure of the composite metal oxide has an aperiodic crystal structure. [2] The composite metal oxide is M x NbMo y O z represented by, and satisfying 0.1 < x ≦ 0.6, 0.1 < y ≦ 0.6, and 2.5 < z ≦ 5.2, the active material according to [1]. [3] The active material according to [1] or [2], including a peak whose peak top is located within the range of 2θ = 47.2 ± 0.4° in the X-ray diffraction spectrum of the composite metal oxide. [4] An electrode containing the active material according to any one of [1] to [3]. [5] The electrode according to [4], including an active material-containing layer containing the active material. [6] A positive electrode, a negative electrode, and an electrolyte A secondary battery comprising, wherein the positive electrode or the negative electrode is the electrode according to [4] or [5]. [7] A battery pack comprising the secondary battery according to [6]. [8] An external terminal for energization, and a protection circuit The battery pack according to [7], further comprising. [9] Comprising a plurality of the secondary batteries, [[ID=3,6]]wherein 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 [7] to [9].

[11] The vehicle according to

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

[12] Preparing a precursor composite metal oxide containing hexavalent Mo, Nb, and at least one element M selected from the group consisting of Ti, V, Ta, Fe, Co, Mn, Ni, Bi, Sb, As, P, Cr, W, B, Na, K, Mg, Al, Ca, Y, and Si; The precursor composite metal oxide is mixed with hydrogen or an organic substance and fired in an oxygen-free atmosphere at 700°C or less. Including, A method for producing an active material comprising a composite metal oxide containing tetravalent Mo element, Nb element, and the element M, wherein the composite metal oxide has a non-periodic crystal structure.

[0256] Although several embodiments of the present invention have been described, these embodiments are presented as examples and are not intended to limit the scope of the invention. These novel embodiments can be embodied in various other forms, and various omissions, substitutions, and modifications can be made without departing from the spirit of the invention. These embodiments and their modifications are included within the scope and spirit of the invention, and are also included in the scope of the invention and its equivalents as defined in the claims. [Explanation of symbols]

[0257] 1... Electrode group, 2... Exterior member, 3... Negative electrode, 3a... Negative electrode current collector, 3b... Negative electrode active material containing layer, 3c... Negative electrode current collecting tab, 4... Separator, 5... Positive electrode, 5a... Positive electrode current collector, 5b... Positive electrode active material containing layer. Layered, 6... Negative electrode terminal, 7... Positive electrode terminal, 10... Crystal structure, 10a... Octahedron, 10b... Tetrahedron, 11... Crystal structure, 11a... Octahedron, 11b... Tetrahedron, 18... Metal element, 19... Oxygen element, 21...bus bar, 22...positive electrode lead, 23...negative electrode lead, 24...adhesive tape, 31...container, 32...lid, 33...protective sheet, 34...printed wiring board, 35...wiring, 40...vehicle body, 41...vehicle power supply, 42...electrical control device, 43...external terminal, 44...inverter, 45...drive motor, 100...secondary battery, 200...battery assembly, 200a...battery assembly, 200b... Battery pack, 200c... battery pack, 300... battery pack, 300a... battery pack, 300b... battery pack, 300c... battery pack, 301a... battery pack monitoring device, 301b... battery pack monitoring device, 301c... battery pack monitoring device, 342... positive electrode connector, 343... negative electrode connector, 345... thermistor, 346... protection circuit, 342a... wiring, 343a... wiring, 350... for energizing External terminals, 352...positive terminal, 353...negative terminal, 348a...positive wiring, 348b...negative wiring, 400...vehicle, 411...battery management device, 412...communication bus, 413...positive terminal, 414...negative terminal, 415...switch device, 416...current detection unit, 417...negative input terminal, 418...positive input terminal, L1...connection line, L2...connection line, W...drive wheel.

Claims

1. An active material comprising a composite metal oxide containing tetravalent Mo, Nb, and at least one element M selected from the group consisting of Ti, V, Ta, Fe, Co, Mn, Ni, Bi, Sb, As, P, Cr, W, B, Na, K, Mg, Al, Ca, Y, and Si, wherein the crystalline structure of the composite metal oxide has a non-periodic crystalline structure.

2. The composite metal oxide is M x NbMo y O z 2. The active material according to claim 1, wherein x is represented by the following formula: and 0.1<x≦0.6, 0.1<y≦0.6, and 2.5<z≦5.2 are satisfied.

3. 3. The active material according to claim 1, wherein the X-ray diffraction spectrum of the composite metal oxide contains a peak whose top is located within a range of 2θ=47.2±0.4°.

4. An electrode comprising the active material according to claim 1 or 2.

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

6. A positive electrode and a negative electrode; Electrolytes and A secondary battery comprising: The secondary battery, wherein the positive electrode or the negative electrode is the electrode according to claim 4 .

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

8. An external terminal for applying current; Protection circuit and The battery pack of claim 7 further comprising:

9. A battery includes a plurality of the secondary batteries, The battery pack according to claim 7 , wherein 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 claim 7.

11. The vehicle of claim 10, further comprising a mechanism for converting kinetic energy of the vehicle into regenerative energy.

12. preparing a precursor composite metal oxide containing hexavalent Mo, Nb, and at least one element M selected from the group consisting of Ti, V, Ta, Fe, Co, Mn, Ni, Bi, Sb, As, P, Cr, W, B, Na, K, Mg, Al, Ca, Y, and Si; The precursor composite metal oxide is mixed with hydrogen or an organic substance and then fired in an oxygen-free atmosphere at 700°C or less. Including, A method for producing an active material comprising a composite metal oxide containing tetravalent Mo, Nb, and the element M, wherein the composite metal oxide has a non-periodic crystal structure.

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