Active materials, electrodes, secondary batteries, battery packs, and vehicles

Abstract

Embodiments of the present invention relate to active materials, electrodes, secondary batteries, battery packs, and vehicles. Provided are active materials and electrodes capable of achieving high-capacity secondary batteries, high-capacity secondary batteries and battery packs, and vehicles equipped with the battery packs. According to an embodiment, an active material containing a composite oxide having a tetragonal crystal structure can be provided. The composite oxide can be represented by the general formula Li a Ti b Nb 2‑2d M c+2d O 2b+5+3c Here, M is any one selected from W and Mo, and 0≤a≤b+4+3c, 0<b<2-2d, and 0<c<2-4d.

Description

Technical Field

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

[0002] In recent years, research and development of high-energy-density secondary batteries, such as lithium-ion secondary batteries and non-aqueous electrolyte secondary batteries, has been extensive. These batteries are expected to be used as power sources for vehicles like hybrid electric vehicles and electric vehicles, as well as for uninterruptible power supplies in mobile phone base stations. Therefore, in addition to energy density, secondary batteries are required to exhibit excellent performance, such as rapid charge and discharge capabilities and long-term reliability.

[0003] As the negative electrode of a common lithium-ion battery, a carbon-based negative electrode using carbonaceous materials such as graphite as an active material can be cited. If a battery using a carbon-based negative electrode is repeatedly charged and discharged rapidly, dendrites of metallic lithium will be generated on the electrode, and there is a concern of heat and fire caused by internal short circuits. Therefore, a battery has been developed that uses metal composite oxides instead of carbonaceous materials in the negative electrode to increase the negative electrode working potential. For example, spinel-type lithium titanium composite oxide Li4Ti5O is used in the negative electrode. 12 The average working potential of the battery is as high as 1.55V (vs.Li / Li + ), so there is no precipitation of Li dendrites, so stable and rapid charge and discharge can be performed, and it works at a potential where the reduction side reaction of the electrolyte is difficult to occur, so the life is longer than that of batteries using carbon-based negative electrodes. However, using Li4Ti5O in the negative electrode 12 In batteries with carbon-based negative electrodes, the theoretical capacity of the active material is as low as 175 mAh / g, which results in a lower energy density than batteries with carbon-based negative electrodes.

[0004] Therefore, the monoclinic niobium-titanium composite oxide TiNb2O7 was studied. Although the lithium oxidation-reduction potential is 1V (vs.Li / Li + ) while exhibiting high capacity. Therefore, in terms of volumetric energy density, it is expected to exceed that of carbon-based negative electrodes. However, to truly popularize electric vehicles, from the perspective of increasing cruising range, it is expected that the energy density of lithium-ion secondary batteries will be further increased in the future, and high-capacity fast-charging batteries will also be developed. Summary of the Invention

[0005] An object of the embodiment is to provide an active material and an electrode capable of realizing a high-capacity secondary battery, a high-capacity secondary battery and a battery pack, and a vehicle equipped with the battery pack.

[0006] According to an embodiment, an active material containing a composite oxide having a tetragonal crystal structure can be provided. The composite oxide can be represented by the general formula Li a Ti b Nb 2-2d M c+2d O 2b+5+3c Here, M is any one selected from W and Mo, and 0≤a≤b+4+3c, 0<b<2-2d, and 0<c<2-4d.

[0007] According to another embodiment, an electrode containing the above-mentioned active material is provided.

[0008] According to another embodiment, a secondary battery including a positive electrode, a negative electrode, and an electrolyte is provided. The negative electrode is the electrode described above.

[0009] According to still another embodiment, a battery pack including the above-mentioned secondary battery is provided.

[0010] Furthermore, according to an embodiment, a vehicle including the above-described battery pack can be provided.

[0011] The active material can realize a high-capacity secondary battery. In addition, the active material can provide an electrode for a high-capacity secondary battery, a high-capacity secondary battery and a battery pack, and a vehicle equipped with the battery pack. BRIEF DESCRIPTION OF THE DRAWINGS

[0012] Figure 1 It is a schematic diagram showing the crystal structure of an example of a complex oxide contained in the active material according to the embodiment.

[0013] Figure 2 This is a schematic diagram showing the crystal structure of another example of the complex oxide contained in the active material according to the embodiment.

[0014] Figure 3 This is a schematic diagram showing the crystal structure of another example of the complex oxide contained in the active material according to the embodiment.

[0015] Figure 4 It is a cross-sectional view schematically showing an example of a secondary battery according to an embodiment.

[0016] Figure 5 yes Figure 4 An enlarged cross-sectional view of portion A of the secondary battery shown.

[0017] Figure 6 It is a partially cutaway perspective view schematically showing another example of the secondary battery according to the embodiment.

[0018] Figure 7 yes Figure 6An enlarged cross-sectional view of portion B of the secondary battery shown.

[0019] Figure 8 It is a perspective view schematically showing an example of a battery pack according to an embodiment.

[0020] Figure 9 This is an exploded perspective view schematically showing an example of a battery pack according to an embodiment.

[0021] Figure 10 Yes Figure 9 A block diagram of an example of a battery pack circuit is shown.

[0022] Figure 11 This is a partial perspective view schematically showing an example of a vehicle according to the embodiment.

[0023] Figure 12 This is a diagram schematically showing an example of a control system related to an electrical system in a vehicle according to an embodiment.

[0024] Figure 13 This is a graph showing the spectrum of the active material composite oxide in Example 1 obtained by wide-angle X-ray scattering measurement.

[0025] Figure 14 This is a graph showing the spectrum of the active material composite oxide in Example 2 obtained by wide-angle X-ray scattering measurement.

[0026] Figure 15 This is a graph showing the spectrum of the active material composite oxide in Example 3 obtained by wide-angle X-ray scattering measurement.

[0027] Figure 16 This is a graph showing the spectrum of the active material composite oxide in Comparative Example 1 obtained by wide-angle X-ray scattering measurement.

[0028] Figure 17 This is a graph showing the initial charge and discharge curves in Example 1 and Comparative Example 1.

[0029] Figure 18 It is a graph showing the initial charge and discharge curves in Example 2 and Comparative Example 1.

[0030] Figure 19 It is a graph showing the initial charge and discharge curves in Example 3 and Comparative Example 1.

[0031] Explanation of symbols

[0032] 1-Electrode group, 2-Outer packaging member, 3-Negative electrode, 3a-Negative electrode current collector, 3b-Negative electrode active material layer, 4-Separator, 5-Positive electrode, 5a-Positive electrode current collector, 5b-Positive electrode active material layer, 6-Negative electrode terminal, 7-Positive electrode terminal, 10-Crystal structure, 10a-Octahedron, 10b-Tetrahedron, 11-Crystal structure, 11a-Octahedron, 12-Crystal structure, 12a-Octahedron, 12b-Tetrahedron, 2 1 - Busbar, 22 - Positive Lead, 23 - Negative Lead, 24 - Adhesive Tape, 31 - Storage Container, 32 - Lid, 33 - Protective Sheet, 34 - Printed Circuit Board, 35 - Wiring, 40 - Vehicle Body, 41 - Vehicle Power Supply, 42 - Electric Control Device, 43 - External Terminal, 44 - Converter, 45 - Drive Motor, 100 - Secondary Battery, 200 - Battery Pack, 200a - Battery Pack, 200b - Battery Pack Battery, 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 side connector, 343 - negative side connector, 345 - thermistor, 346 - protection circuit, 342a - wiring, 343a - wiring, 350 - for power supply External terminal, 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 - Switching device, 416 - Current detection unit, 417 - Negative input terminal, 418 - Positive input terminal, L1 - Connecting line, L2 - Connecting line, W - Drive wheel. DETAILED DESCRIPTION

[0033] In order to obtain a high-capacity material, it is preferable to select a material that has a large charge compensation amount when carrier ions (such as lithium ions) are inserted. Therefore, as a compound with higher capacity, for example, a composite oxide containing a hexavalent element, tungsten (W) or molybdenum (Mo) can be used. As a tungsten-niobium composite oxide material, for example, a composition with a high W ratio has a composition with Nb 18 W8O 69 and Nb 16 W5O 55 Compounds with crystal structures such as those shown in Figure 1 and Figure 2 have been reported. However, the reported reversible lithium insertion and extraction capacities for such materials do not exceed 250 mAh / g. Furthermore, there are no reports of battery materials with high niobium content as molybdenum-niobium composite oxide materials.

[0034] The following describes the embodiments with reference to the accompanying drawings. In the following description, components that perform the same or similar functions are denoted by the same reference numerals throughout the drawings, and duplicate descriptions are omitted. Furthermore, the figures are schematic diagrams to facilitate the description and understanding of the embodiments. While their shapes, dimensions, and proportions may differ from those of the actual device, appropriate design modifications can be made by referring to the following description and known techniques.

[0035] [First embodiment]

[0036] According to the first embodiment, an active material containing a composite oxide having a tetragonal crystal structure can be provided. The composite oxide can be represented by the general formula Li a Ti b Nb 2-2d M c+2d O 2b+5+3c Indicated. In the general formula, M is any one selected from W and Mo. The subscripts in the formula respectively satisfy 0≤a≤b+4+3c, 0<b<2-2d, and 0<c<2-4d. Such an active material may contain a trace amount of an additive element as described later. The method of containing such a trace additive element as a substitution element in the composite oxide is also included in the first embodiment. However, in the above general formula, a composition in which such a trace amount of substitution element is omitted is represented.

[0037] Such an active material may be a battery active material. For example, the active material may be an electrode active material used in electrodes of secondary batteries such as lithium-ion batteries and non-aqueous electrolyte batteries. More specifically, the active material may be a negative electrode active material used in the negative electrode of a secondary battery.

[0038] By using the above general formula Li a Ti b Nb 2-2d M c+2d O 2b+5+3c A composite oxide having a tetragonal crystal structure represented by (M is W or Mo, 0≤a≤b+4+3c, 0<b<2-2d, and 0<c<2-4d) can realize a high-capacity secondary battery as an electrode active material.

[0039] <Crystal Structure>

[0040] The tetragonal composite oxide contained in the active material according to the first embodiment corresponds to a portion of the oxide material having a Wadsley-Roth phase, a crystal phase, in the niobium-containing oxide material. Regarding the ratio of oxygen O and the metal element M in the Wadsley-Roth phase, it is reported that the ratio of oxygen O and the metal element M in the composition is obtained by setting the number of oxygen atoms and the number of metal atoms to A, B, C, and D, respectively. O and A M, can be calculated as 2.33≤A O / A M The crystal structure is obtained in the range of ≤2.65. For example, in TiNb2O7, it is A O / A M =2.33 on the reduced side of the crystal structure.

[0041] Here, the so-called reduction means that the proportion of oxygen in the structure is low. In the Wadsley-Roth phase, the vertex sharing structure of the oxygen-metal octahedron forms a rhenium oxide type block structure, and the block shares the rhombus of the octahedron, or the tetrahedron enters the middle and shares the vertex, thereby taking a crystal structure in which the rhenium oxide type block (ReO3 type block) is connected in a two-dimensional direction. The crystal structure on the reduction side takes a structure in which the size of the rhenium oxide type block is smaller. Although the rhenium oxide type crystal structure has voids that can be embedded in a large amount of Li, it is a crystal structure with high symmetry and eliminates charge repulsion when embedding Li, so the bond length between the metal element and the oxygen element is difficult to change. Therefore, the rhenium oxide type crystal structure can be said to be a structure that restricts Li embedding by charge repulsion when Li is embedded. Here, it is set as the crystal structure on the reduction side because A O / A M As the number of oxygen atoms decreases, the size of the rhenium oxide-type block decreases due to the reduction in the number of oxygen atoms in the structure. This results in a crystal structure that can potentially expand in volume due to changes in the bond length between the metal element and oxygen when Li is incorporated. Therefore, the inclusion of a rhenium oxide-type crystal structure provides wide voids and unrestricted structural changes during Li insertion, enabling the insertion of large amounts of Li.

[0042] The composite oxide contained in the active material according to the first embodiment can also incorporate more lithium (Li) into the crystal structure by adopting a reduction-side crystal structure like TiNb2O7, resulting in a crystal structure with a high reversible capacity. Specifically, the crystal structure of such a composite oxide is a reduction-side crystal structure belonging to a Wadsley-Roth phase composed of ternary elements including tetravalent titanium, a low-valent element.

[0043] In the above general formula Li a Ti b Nb 2-2d M c+2d O 2b+5+3c In the tetragonal composite oxide represented by (M is W or Mo; a, b, c, d are values ​​satisfying 0≤a≤b+4+3c, 0<b<2-2d and 0<c<2-4d), the compound oxide having M=W and the general formula Li a Ti b Nb2W c O 2b+5+3cThe tetragonal titanium-niobium-tungsten composite oxide represented by the general formula Li a Ti b Nb 2- 2d Mo c+2d O 2b+5+3c Represents a tetragonal titanium-niobium-molybdenum composite oxide.

[0044] In the general formula Li a Ti b Nb 2-2d M c+2d O 2b+5+3c In the formula, subscripts b, c, and d may be within the ranges of 0<b<2, 0<c<2, and 0≤d<0.5, respectively. a Ti b Nb2W c O 2b+5+3c , preferably, the subscripts b and c are in the range of 0.4≤b≤1.6 and 0.4≤c≤1.6, respectively. a Ti b Nb 2-2d Mo c+2d O 2b+5+3c , preferably, the subscripts b, c and d are in the ranges of 0.3≤b≤1.6, 0.3≤c<1.6 and 0≤d<0.4, respectively.

[0045] As the general formula Li a Ti b Nb2M c O 2b+5+3c An example of a tetragonal titanium-niobium-tungsten composite oxide is shown. Figure 1 Ti2Nb 10 W5O 44 Schematic diagram of the crystal structure. Figure 1 In FIG, the unit cell of the crystal structure in the

[001] direction along the c-axis is shown. Furthermore, the stoichiometric ratio in the composite oxide is expressed as Ti2Nb 10 W5O 44 , but the composition is the same as Ti 0.4 Nb2WO 8.8 The space group symbol of the crystal structure belongs to I -4, space group number 82. The space group mentioned here corresponds to the International Tables for Crystallography, specifically, to the contents of Vol. A: Space-group symmetry (2nd online edition (2016); ISBN: 978-0-470-97423-0, doi: 10.1107 / 97809553602060000114). However, it is also possible to use space groups P4 (space group number 75), I4 (space group number 79), P - 4 (space group number 81), P42 / n (space group number 86), P4nc (space group number 104), P - 421c (space group number 114), P - 4n2 (space group number 118) and others have similarities to I - 4 (space group number 82) similar to the simple cubic lattice of the fourth symmetry axis or the fourth anti-axis. It may change when the structure is deformed by adjusting the composition ratio to deviate from the stoichiometric composition ratio or when there is a mixture with a different phase. 10 W5O 44 The number of atoms of oxygen O is A O Atomic number A relative to the metal element M (including Ti, Nb, and W) M The ratio is A O / A M =2.59. The crystal structure 10 includes 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 sharing vertices, forming a rhenium oxide-type block (ReO3-type block). Regarding the size of the block, the number of octahedra is 4 × 4 = 16. The rhenium oxide-type blocks share the edges of the octahedron 10a or the vertices of the tetrahedron 10b, forming planes in the a-axis and b-axis directions. The planes containing the 16 octahedra 10a are also connected to each other on the c-axis side by sharing the edges of the octahedrons or the vertices of the tetrahedrons, thereby forming a crystal structure.

[0046] Generally speaking, tungsten-niobium composite oxides have a crystal structure with a relatively high tungsten composition, and this crystal structure includes a block structure with a block size of 4 × 5 = 20 or 5 × 5 = 25. The titanium-niobium-tungsten composite oxide of one embodiment of the first embodiment is based on the discovery that by containing titanium, a low-valent element, i.e., a tetravalent element, the block structure can be reduced even in a state with a relatively high tungsten composition. By reducing the block size, the amount of lithium embedded can be increased. In addition, since tungsten belongs to the sixth period, it is a heavier element than titanium and niobium, and thus a material with a higher true density than conventional TiNb2O7 can be obtained. As a result, the capacity per unit volume can be increased.

[0047] In the crystal structure, since the ionic radii of hexavalent tungsten, tetravalent titanium, and pentavalent niobium are close to each other, they can share equivalent sites. Niobium (Nb), titanium (Ti), and tungsten (W) are arranged at the 8g site (the central site of the octahedral structure), which is the metal site in the octahedron, and the 2c site (the central site of the tetrahedral structure), which is the metal site in the tetrahedron, in the form of adjusting the charge balance within the crystal structure. The occupancy ratio is different at each site, and it can exist unevenly. By adopting a crystal structure in which atoms are unevenly present, the charge balance can be maintained even when multiple elements are contained in the crystal structure, and the skeleton structure can be maintained. In addition, it can be expected that the solid diffusion of Li can be improved in a crystal structure containing tetrahedral sites.

[0048] As the general formula Li a Ti b Nb2W c O 2b+5+3c Other examples of titanium-niobium-tungsten composite oxides are shown, Figure 2 TiNb2WO is shown in 10 Schematic diagram of the crystal structure of . Figure 2 , also shows the unit cell of the

[001] direction of the crystal structure along the c-axis direction. Figure 1 Differently, the vertex-sharing structure formed by the tetrahedrons connecting the blocks of rhenium oxide is changed to the edge-sharing structure of the octahedrons 11a between the blocks of rhenium oxide. The space group symbol of the crystal structure can be expressed as I - 4 (space group number 82) or P4 (space group number 75), I4 (space group number 79), P - 4 (space group number 81), P42 / n (space group number 86), P4nc (space group number 104), P - 421c (space group number 114), P - 4n2 (space group number 118) and others have similarities to I -4 (space group number 82) similar to the simple cubic lattice with a fourth-order symmetry axis or fourth-order anti-axis. This may sometimes change when the structure is deformed by adjusting the composition ratio to deviate from the stoichiometric composition ratio or when there is a mixture with a different phase. 10 The number of oxygen atoms (A O ) relative to the number of atoms of the metal element M (A M = the number of Ti atoms + the number of Nb atoms + the number of W atoms) is A O / A M =2.50. By increasing the Ti composition ratio in the crystal structure, A is reduced. O / A M Compared with Figure 2 By replacing the tetrahedral vertex connection with the octahedral edge connection, the amount of voids caused by Li insertion is increased, and it is easy to use the change in bond length when Li is inserted to relax the structure. Therefore, in TiNb2WO 10 ( Figure 2 ) with Ti2Nb 10 W5O 44 ( Figure 1 ) can further improve the reversible capacity compared with the conventional method.

[0049] Regarding the active material according to the first embodiment, in the general formula Li a Ti b Nb 2-2d M c+2d O 2b+5+3c In the embodiment where the element M is tungsten (W), the titanium-niobium-tungsten composite oxide as the active material can be represented by the general formula Li a Ti b Nb2W c O 2b+5+3c The crystal structure of the composite oxide can be, for example, Figure 1 The crystal structure exemplified in Figure 2 The crystal structure exemplified in the above formula or the crystal structure in which both are mixed. a Ti b Nb2W c O 2b+5+3c The composition range represented by the subscripts in the relevant formula can be within the ranges of 0≤a≤b+4+3c, 0<b<2, and 0<c<2. Within any of these ranges, a high-capacity active material can be obtained, allowing the composition to be selected according to the battery design.

[0050] Generally speaking, tungsten (W) and titanium (Ti) are elements that readily incorporate into the Wadsley-Roth phase, a polymorphic structure with varying composition ratios. Therefore, niobium (Nb) is more readily substituted than other elements. Therefore, by combining these elements, the composition ratio within the crystal structure can be adjusted.

[0051] As the general formula Li a Ti b Nb 2-2d Mo c+2d O 2b+5+3c An example of a tetragonal titanium-niobium-molybdenum composite oxide is represented by Figure 3 TiNb5Mo2O 20 Schematic diagram of the crystal structure. Figure 3 In FIG, the unit lattice of the crystal structure in the

[001] direction along the c-axis is shown. Furthermore, the stoichiometric ratio in the composite oxide is expressed as TiNb5Mo2O 20 , but the composition is called Ti 1 / 3 Nb 5 / 3 Mo 2 / 3 O 20 / 3 The space group symbol of the crystal structure belongs to I - 4, the space group number is 82. However, the space group can also be P4 (space group number 75), I4 (space group number 79), P - 4 (space group number 81), P42 / n (space group number 86), P4nc (space group number 104), P - 421c (space group number 114), P - 4n2 (space group number 118) and others have similarities to I - 4 (space group number 82) similar to the simple cubic lattice of the fourth symmetry axis or fourth anti-axis, and may sometimes change when the structure is deformed by deviating from the stoichiometric composition ratio by adjusting the composition ratio or when there is a mixture with a different phase. 20 The ratio of the number of atoms of oxygen O to the number of atoms of the metal element M (including Ti, Nb, and Mo) is A O / A M = 2.50. Crystal structure 12 includes octahedra 12a and tetrahedra 12b, composed of metal element 18 and oxygen element 19. Octahedrons 12a are connected by shared vertices, forming a rhenium oxide-type block. The block size corresponds to a structure with 3 x 3 = 9 octahedra 12a arranged.

[0052] Molybdenum (Mo) can enter the crystal structure not only in a 6-valent state but also in a 5-valent state. Among the 6-valent elements, since the charge compensation when embedding Li with the Ti element is a 3-electron reaction, the theoretical capacity of the Li that can be embedded can be increased. The 5-valent element exists in the form of replacing the Nb element. The Mo element in the 5-valent state exists in the crystal structure in the form of supplying electrons to the d band of the Mo element. Therefore, by containing the 5-valent Mo element and changing the conductivity, the battery capacity can be increased. It is known that the working potential of the Wadsley-Roth phase containing molybdenum is high (expensive). In one embodiment of the present invention, the titanium-niobium-molybdenum composite oxide has a crystal structure containing molybdenum elements at a high concentration, and the working potential can be increased compared to TiNb2O7. As a result, since the working potential is a potential region with few reduction side reactions of the electrolyte, high life performance can be achieved. In addition, since the shape of the potential curve changes more steeply than that of TiNb2O7, the secondary battery using the composite oxide in the negative electrode can be expected to further improve the input and output performance.

[0053] Furthermore, the general formula Li a Ti b Nb 2-2d Mo c+2d O 2b+5+3c The subscript c in the formula represents the stoichiometric ratio of the hexavalent Mo element. The subscript d is proportional to the stoichiometric ratio of the pentavalent Mo element, and "2d" represents the stoichiometric ratio of the pentavalent Mo element. However, regarding the titanium-niobium-tungsten composite oxide described above, since the W element does not enter the crystal structure in a pentavalent state, the general formula Li a Ti b Nb2Wo c O 2b+5+3c The subscript d is not included (in other words, d=0).

[0054] In the diffraction pattern (diffraction spectrum) of powder X-ray diffraction of the above-mentioned composite oxide having a tetragonal crystal structure using a Cu-Kα radiation source, the peak intensity I1 of the peak with the highest intensity appearing in the range of 2θ = 25.1 ± 0.5° and the peak intensity I2 of the peak appearing in the range of 2θ = 23.8 ± 0.5° preferably satisfy the relationship of 0.1 ≤ I2 / I1 ≤ 1.0, and more preferably satisfy the relationship of 0.1 ≤ I2 / I1 ≤ 0.8. The main peak corresponding to the peak intensity I1 appearing in the range of 2θ = 25.1 ± 0.5° in the X-ray diffraction pattern is attributed to a plane that does not contain the c-axis in the crystal structure. The peak corresponding to the peak intensity I2 appearing in the range of 2θ = 23.8 ± 0.5° in the X-ray diffraction pattern is attributed to the direction of a plane containing the c-axis.

[0055] The crystal structure of the composite oxide of such an active material has wide gaps in the c-axis direction. Therefore, Li in the crystal structure mainly diffuses in the c-axis direction. The above-mentioned peak intensity ratio I2 / I1 is in the range of 0.1≤I2 / I1≤1.0 and 0.1≤I2 / I1≤0.8, which involves reducing the diffusion distance of Li. That is, in the composite oxide with an I2 / I1 ratio in the range of 0.1≤I2 / I1≤1.0 and in the range of 0.1≤I2 / I1≤0.8, the orientation in the c-axis direction in the crystal structure is suppressed. Therefore, by satisfying such an intensity ratio, the battery performance can be improved. The peak intensity ratio I2 / I1 is preferably in the range of 0.1≤I2 / I1≤0.9, and more preferably in the range of 0.1≤I2 / I1≤0.65.

[0056] The above peak intensity ratio conditions can be achieved by adjusting the Ti / Nb ratio or M / Nb ratio (M=W or Mo) in the stoichiometric composition and suppressing the crystal growth rate during sintering during the synthesis of the composite oxide. In other words, by adjusting the element ratios in the composite oxide, the orientation of the c-axis in the crystal structure can be controlled. Such composite oxides have a wide composition range because they can change the crystal structure while maintaining the structure by adjusting the Ti / Nb ratio and the M / Nb ratio. Therefore, there is room for controlling the orientation by adjusting the composition ratio.

[0057] <Trace added elements>

[0058] In such an active material, the performance can be further improved by adding elements to the composite oxide. That is, in the active material according to the first embodiment, in addition to the above-mentioned general formula Li a Ti b Nb 2-2d M c+2d O 2b+5+3c In addition to the tetragonal composite oxides shown above, trace amounts of additional elements may be contained. Examples of these elements include Ti, V, Ta, Fe, Bi, Sb, As, P, Cr, Mo, W, B, Na, K, Mg, Al, Ca, Y, Zr, and Si.

[0059] The above-mentioned additional elements can be contained in the structure in a manner that replaces a part of the constituent elements of the composite oxide. That is, the active material involved in the first embodiment can also contain the above-mentioned general formula Li a Ti b Nb 2-2d M c+2d O 2b+5+3c The above-mentioned additional elements may be present in the active material in a manner not contained in the crystal structure of the composite oxide.

[0060] For example, vanadium (V) and phosphorus (P) can be incorporated into the crystal structure as pentavalent elements. By partially replacing the tetravalent Ti element contained as a basic constituent element with pentavalent elements, the electronic conductivity of the active material can be improved. This can improve the rate performance and life performance of the active material. In addition, regarding titanium-niobium-molybdenum composite oxide, since its skeleton structure is similar to Nb9VO 25 、Nb9PO 25 The same crystal structure makes it particularly easy for V and P to substitute into the structure. 25 and Nb9PO 25 The working potential of titanium-niobium-molybdenum composite oxide is lower (cheaper) than that of titanium-niobium-molybdenum composite oxide, but by introducing V and / or P, the working potential of titanium-niobium-molybdenum composite oxide can be made close to that of Nb9VO 25 、Nb9PO 25 Therefore, by replacing the elements with V and / or P, the shape of the battery curve can be adjusted.

[0061] The element selected from Mo, W and V, potassium (K), boron (B), and sodium (Na) can bring about the effect of a sintering aid due to the low melting point of the composite oxide. Here, W as an added element refers to the niobium-titanium-molybdenum composite oxide (Li a Ti b Nb 2-2d Mo c+2d O 2b+5+3c ). Similarly, Mo as an additive element refers to the niobium-titanium-tungsten composite oxide (Li a Ti b Nb2W c O 2b+5+3c ). V, K, B, and Na can be used in both composite oxides. Adding trace amounts of these elements can lower the sintering temperature during composite oxide synthesis and improve crystallinity. Improving crystallinity can improve the rate performance and cycle performance of the active material. Furthermore, Mo and W, the fundamental constituent elements of the niobium-titanium-molybdenum composite oxide and the niobium-titanium-tungsten composite oxide, respectively, easily evaporate during sintering. However, lowering the sintering temperature can suppress evaporation during sintering.

[0062] Titanium (Ti) can partially substitute for Nb as a tetravalent element. This can increase the amount of hexavalent elements substituted in the structure to adjust the charge, thereby improving battery performance.

[0063] Tantalum (Ta) can be used as a pentavalent element to replace Nb. Since Ta and Nb are elements in the same group on the periodic table, their physical and chemical properties are similar. Therefore, even if Ta is used to replace Nb, equivalent battery performance can be achieved.

[0064] Elements selected from iron (Fe), chromium (Cr), aluminum (Al), bismuth (Bi), antimony (Sb), and arsenic (As) can be incorporated into the crystal structure as trivalent elements. Magnesium (Mg) can be incorporated into the crystal structure as a divalent element. By partially replacing the Ti element with a trivalent or divalent element, the composition ratio of the hexavalent W element or Mo element can be increased to maintain electrical neutrality within the structure. This can increase the theoretical capacity of the battery and further increase the amount of Li intercalated into the active material.

[0065] Elements such as calcium (Ca), zirconium (Zr), yttrium (Y), and silicon (Si) are elements whose oxides can stably exist under the firing conditions used in the synthesis of such composite oxides, and are elements that are not replaced within the crystal structure. The presence of these elements in trace amounts can function as grain growth inhibitors that suppress grain growth during firing. This can adjust the shape of the particle size distribution and further suppress fluctuations in the particle size distribution.

[0066] It is preferable that at least one element selected from the group consisting of Ti, V, Ta, Fe, Bi, Sb, As, P, Cr, Mo, W, B, Na, K, Mg, Al, Ca, Y, Zr and Si is added in a trace amount. a Ti b Nb 2-2d M c+2d O 2b+5+3c , preferably fixed in the range of 10 ppm or more and 10000 ppm or less in mass unit, more preferably fixed in the range of 3000 ppm or less. a Ti b Nb 2-2d M c+2d O 2b+5+3c The composition of the composite oxide is not limited to substitution composite oxides containing trace elements incorporated into the crystal structure. Of course, although trace elements not incorporated into the crystal structure of the composite oxide are not marked in the above general formula, the active material according to the first embodiment also includes a form containing the above elements in addition to the composite oxide. The active material according to the first embodiment may also be a non-substituted Li-ion composite oxide that does not contain the above trace elements. a Ti b Nb 2-2d M c+2d O 2b+5+3c Composite oxides.

[0067] <Active Material Particles>

[0068] The active material according to the first embodiment may be in the form of particles, for example.a Ti b Nb 2-2d M c+2d O 2b+5+3c The active material may be composed of particles of a composite oxide having a tetragonal crystal structure (regardless of the presence or absence of trace substitution elements). Furthermore, such an active material may be composed of particles mixed with the aforementioned traceable elements in addition to the composite oxide. The active material may be a single primary particle, a secondary particle formed by agglomeration of multiple primary particles, or a mixture thereof. For example, the active material may contain the aforementioned elements on the surface of the composite oxide primary particles or between the composite oxide primary particles.

[0069] The average primary particle size of the active material involved in the first embodiment is preferably 10 μm or less, more preferably 5 μm or less, and even more preferably 3 μm or less. If the average primary particle size of the active material is small, the diffusion distance of lithium ions within the primary particles is short, thereby tending to improve the diffusivity of lithium ions. In addition, if the average primary particle size of the active material is small, the reaction area increases, thereby tending to improve the reactivity of the active material and lithium ions and enhance the lithium ion insertion and deinsertion reaction.

[0070] The average secondary particle size of the active material in the first embodiment is preferably 1 μm or more and 50 μm or less. By setting the average secondary particle size of the active material within this range, productivity during electrode production can be improved, while also providing a high-performance battery. This average secondary particle size represents the particle size at which the cumulative volume value reaches 50% in the particle size distribution determined using a laser diffraction particle size analyzer.

[0071] The BET specific surface area of ​​the active material is preferably 3.0 m 2 / g or above and 120m 2 / g or less, more preferably 4.0m 2 / g or above and 110m 2 / g or less. If an active material with a high specific surface area is used, the discharge rate performance of the battery can be improved. In addition, if an active material with a low specific surface area is used, the battery life performance can be improved, and in the electrode manufacturing process described later in the second embodiment, the coating properties of the slurry containing the active material can be improved.

[0072] The BET specific surface area means the specific surface area determined by the nitrogen BET (Brunauer-Emmet-Teller) method. The method for determining the specific surface area by the nitrogen BET method will be described in detail later.

[0073] <Manufacturing method>

[0074] The active material according to the first embodiment can be produced as follows. aTi b Nb 2-2d M c+2d O 2b+5+3c Herein, regarding an embodiment of a titanium-niobium-tungsten composite oxide in which the element M is W and an embodiment of a titanium-niobium-molybdenum composite oxide in which the element M is Mo, the production methods are described respectively.

[0075] (Synthesis of Titanium-Niobium-Tungsten Composite Oxide)

[0076] The production of titanium-niobium-tungsten composite oxide is not particularly limited and can be synthesized, for example, by solid-phase reaction, sol-gel method, hydrothermal synthesis, etc. The solid-phase reaction method is described as an example. The solid-phase reaction method is a simple and inexpensive production method because it does not use a liquid phase.

[0077] As starting materials, titanium compounds, niobium compounds, and tungsten compounds are used. Examples of titanium compounds include titanium hydroxide, anatase-type titanium oxide, and rutile-type titanium oxide. Examples of niobium compounds include niobium hydroxide and niobium oxide. Examples of tungsten compounds include ammonium paratungstate and its hydrates, ammonium tungstate and its hydrates, tungsten hydroxide, and tungsten oxide.

[0078] When producing a substituted composite oxide obtained by substituting a portion of titanium, niobium, or tungsten in the crystal structure with the aforementioned trace elements (trace additive elements), for example, the starting material may further contain an oxide of the element introduced as the substituting element.

[0079] As the starting material, for example, a particulate material is used. The average particle size of the starting material is preferably set to 5 μm or less, more preferably set to 2 μm or less. Since the solid phase reaction method reacts at the contact points between the particles, reducing the particle size can increase reactivity and easily obtain the target phase.

[0080] After weighing the starting materials to the specified composition ratio, the materials are thoroughly mixed. Mixing can be done by either a wet or dry method. After the raw materials are mixed, they are calcined.

[0081] During firing, a temporary firing may be performed before the main firing. The temporary firing is preferably performed at a firing temperature of 800°C to 1100°C for a time of 5 hours to 20 hours. Within this firing temperature and firing time range, a solid-phase reaction can proceed. By including the temporary firing before the main firing, the reaction can be pre-processed, thereby improving reactivity.

[0082] The main calcination temperature is preferably set to 1000° C. to 1200° C. and the calcination time is preferably set to 5 hours to 20 hours. Within this range of calcination temperature and calcination time, a solid phase reaction can proceed and the target crystal phase can be obtained.

[0083] After calcination, the raw materials are crushed using a pulverizer until the particles reach a predetermined average particle size. During calcination, mechanical impact may reduce the crystallinity of the active material. In such cases, it is preferable to restore the crystallinity by performing annealing again. Annealing is preferably performed at a temperature of 800°C to 1000°C and for a time of 1 hour to 5 hours.

[0084] (Synthesis of Titanium-Niobium-Molybdenum Composite Oxide)

[0085] The production of the titanium-niobium-molybdenum composite oxide is not particularly limited, but can be synthesized by, for example, a solid phase reaction method, a sol-gel method, a hydrothermal synthesis method, etc. As an example thereof, a production method using the sol-gel method will be described.

[0086] As starting materials, titanium compounds, niobium compounds, and molybdenum compounds are used. Examples of titanium compounds include tetraisopropoxytitanium, titanyl sulfate, titanium chloride, ammonium titanium oxalate and its hydrates, and titanium hydroxide. Examples of niobium compounds include niobium chloride, ammonium niobium oxalate and its hydrates, and niobium hydroxide. Examples of molybdenum compounds include molybdenum chloride, ammonium molybdate and its hydrates, and molybdenum hydroxide.

[0087] It is preferred to pre-dissolve the starting materials in pure water or an acid to form a solution. This solubilization yields a dry gel in which all elements are homogeneously mixed, thereby improving reactivity. If the starting materials cannot be dissolved in pure water, dissolution can be performed using an acid.

[0088] Examples of the acid used to dissolve the raw materials include citric acid and oxalic acid, but oxalic acid is preferred from the perspective of solubility. For example, when oxalic acid is used, the concentration is preferably set to 0.5 M or higher and 1 M or lower. During dissolution, a temperature of 70°C or higher is preferably used to shorten the reaction time.

[0089] When the raw materials are difficult to dissolve, the reaction can also be carried out in a dispersion. The average particle size of the raw materials contained in the dispersion at this time is preferably 3 μm or less, more preferably 1 μm. After modulating a solution (or dispersion) in which each compound is adjusted to a specified composition ratio, the solution is heated and stirred while being neutralized with an aqueous ammonia solution to adjust the pH. A gel solution is obtained by pH adjustment. By setting the pH to 5 or more and 8 or less, a gel containing each raw material in a homogeneous manner can be formed, thereby obtaining a dry gel with good reactivity during firing.

[0090] Next, the gel solution is heated to near its boiling point to evaporate the water, causing gelation. After gelation, the water is further evaporated and dried to produce a dried gel. While evaporating and concentrating the total amount of the solution during gelation and drying can also produce a dried gel, using a spray dryer is more preferred because it can further reduce the particle size after drying. The dried gel produced by evaporating and concentrating the total amount of the solution is preferably pulverized to reduce the average particle size to less than 10 μm, more preferably less than 5 μm, before calcination. This reduces the particle size after calcination. The resulting dried gel is then calcined.

[0091] When calcining the dried gel, temporary calcination is performed at 200°C to 500°C for 1 to 10 hours to eliminate excess organic components and improve reactivity during the main calcination.

[0092] Main calcination is preferably performed at a calcination temperature of 700° C. to 900° C. for 1 to 10 hours. Calcination within this temperature range can achieve the desired phase while suppressing molybdenum sublimation.

[0093] The powder after firing may form aggregates and thus have a large average particle size. In such a case, it is preferable to adjust the average particle size to a predetermined value by pulverizing.

[0094] When adding the aforementioned trace elements to an active material containing a composite oxide synthesized by the sol-gel method, for example, the oxide of the element to be added can be mixed with a powder sample obtained by pulverizing a dried gel before firing. Firing in a mixed oxide state can yield an active material containing the element along with the composite oxide, or an active material containing a substituted composite oxide in which the element has been introduced into the crystal structure of the composite oxide. Furthermore, when an oxide of an element that can function as a sintering aid is added, the firing temperature can be lowered.

[0095] <Various Measurement Methods>

[0096] The following describes the measurement method of the active material, specifically, the identification of the composite oxide, the measurement of the average particle size of the active material particles, and the measurement of the specific surface area of ​​the active material.

[0097] When using active materials contained in battery electrodes as samples, pretreatment is performed using the following method to prepare the sample for measurement. 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 cleaned with a solvent such as ethyl methyl carbonate. Further processing is performed for each measurement to prepare the sample in the appropriate form.

[0098] (Confirmation of composite oxides)

[0099] The active material has the above-mentioned tetragonal crystal structure and contains the general formula Li a Ti b Nb 2-2d M c+ 2d O 2b+5+3c The composite oxides shown can be identified by combining wide-angle X-ray diffraction (XRD), inductively coupled plasma (ICP) emission spectrometry, and inert gas dissolution-infrared absorption spectroscopy. Wide-angle XRD can reveal the crystal structure, while ICP emission spectrometry and inert gas dissolution-infrared absorption spectroscopy can reveal the elemental composition.

[0100] XRD measurement is performed as follows. First, the active material particles are thoroughly crushed to obtain a powdered sample. The average particle size of the powdered sample is preferably set to 20 μm or less. This average particle size can be determined using a laser diffraction particle size distribution analyzer.

[0101] Next, the powdered sample is filled in the holder portion of a glass sample plate to make the surface flat. For example, a glass sample plate having a holder portion with a depth of 0.2 mm can be used.

[0102] Next, the glass sample plate is placed on a powder X-ray diffraction apparatus and an XRD spectrum is measured using Cu-Kα radiation. Specific measurement conditions are, for example, as follows:

[0103] X-ray diffraction device: SmartLab manufactured by Rigaku Co., Ltd.

[0104] X-ray source: CuKα rays

[0105] Power: 40kV, 200mA

[0106] Package Assay Name: Universal Assay (Centralized Method)

[0107] Incident parallel slit opening angle: 5°

[0108] Incident length limit slit length: 10mm

[0109] Light-receiving PSA: None

[0110] Light receiving parallel slit opening angle: 5°

[0111] Monochromatization method: Kβ filter method

[0112] Measurement mode: continuous

[0113] Entrance slit width: 0.5°

[0114] Light receiving slit width: 20mm

[0115] Measuring range (2θ): 5 to 70°

[0116] Sampling width (2θ): 0.01°

[0117] Scanning speed: 1°~20° / min.

[0118] In this way, an XRD spectrum of the active material is obtained. In this XRD spectrum, the horizontal axis represents the incident angle (2θ) and the vertical axis represents the diffraction intensity (cps). The scanning speed can be adjusted so that the number of counts of the main peak of the XRD spectrum is within the range of 50,000 counts or more and 150,000 counts or less.

[0119] When the active material contained in the battery electrode is used as a sample, the cleaned electrode obtained by the above-mentioned pretreatment is cut into an area substantially the same as that of the holder of the glass sample plate to prepare a measurement sample.

[0120] Next, the obtained measurement sample is directly attached to a glass holder and subjected to XRD measurement. XRD is then used to measure materials other than the active material that may be contained in the electrode, such as the current collector, conductive agent, and binder, to identify the XRD patterns derived from these materials. Next, if peaks thought to be derived from the active material overlap with peaks from other materials in the measurement sample, the peaks from materials other than the active material are separated. This yields the XRD spectrum of the active material.

[0121] In order to confirm whether the crystal structure of the sample to be measured belongs to the above-mentioned tetragonal crystal structure, the Rietveld method is used. As an analysis program, for example, RIETAN-FP is used. wp The value can be determined by confirming that it is at least 20% or less, more preferably 15% or less. At this time, when there are peaks containing impurities that overlap with the peaks that are the target of analysis, the accuracy of analysis is sometimes deteriorated. In this case, it is preferable to adopt a method that can perform analysis outside the analysis range for places where the overlap with the peaks originating from impurities is clear. However, when the sample contains materials other than the active material involved in the first embodiment, when the orientation of the sample is significantly high, or when coarse particles are mixed, the structure can be determined by confirming that there is no contradiction in the positions and relative intensities of all peaks that are not in the range due to changes in the intensity ratio and that belong to the crystal structure. In addition, if the background intensity is low due to low spectral intensity, sometimes R wp The reliability factor has no meaning for its absolute value, but it is meaningful for judging the goodness of fit relatively under certain measurement conditions.

[0122] The analysis method using RIETAN-FP is described in detail in Chapter 9, "Trying to Use RIETAN-FP," of the first edition (2002) of "The Reality of Powder X-ray Analysis," edited by the X-ray Analysis Research Council of the Japan Society of Analytical Chemistry and written by Izumi Nakai and Fujio Izumi (Asakura Shoten).

[0123] RIETAN-FP is a Rietveld analysis program that was released free of charge (actually available as of February 2021) on the developer's website on the Internet (http: / / fujioizumi.verse.jp / ).

[0124] The content of each element in the active material particles in the sample can be determined by ICP emission spectrometry for metal elements and by inert gas dissolution-infrared absorption spectroscopy for O, but precise quantification is difficult.

[0125] After the above-mentioned pretreatment, the active material particles contained in the electrode are further subjected to the following treatment. From the cleaned electrode, for example, from the electrode's current collector, the component containing the active material (e.g., the active material-containing layer described in the second embodiment) is peeled off. The portion peeled from the electrode is heated in the atmosphere for a short time (about 1 hour at 500°C) to burn off unnecessary parts such as the binder component and carbon. The content of each element can then be quantified by performing ICP emission analysis or the like.

[0126] (Measurement of average particle size)

[0127] 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 based on SEM observation can be calculated as follows.

[0128] First, the lengths of the longest axis and the shortest axis of the primary particles in the SEM image obtained by SEM observation are measured, and the arithmetic average of these is taken as the primary particle size. This primary particle size measurement is performed on 100 randomly selected particles, and the average of these is taken as the average primary particle size.

[0129] The average secondary particle size of the active material can be determined from a particle size distribution measured using a laser diffraction particle size analyzer. A dispersion diluted with N-methyl-2-pyrrolidone to a concentration of 0.1% to 1% by mass of the active material is used as the sample for this particle size distribution measurement. The particle size at which the cumulative volume value reaches 50% in the obtained particle size distribution is defined as the average secondary particle size.

[0130] (Measurement of BET specific surface area)

[0131] The BET specific surface area of ​​the active material particles can be determined by the following method.

[0132] First, 4 g of active material is collected as a sample. Next, the evaluation cell of the measuring device is dried under reduced pressure at a temperature above 100°C for 15 hours to perform a degassing treatment. As an evaluation cell, a 1 / 2-inch cell can be used, for example. Next, the sample is placed in the measuring device. As a measuring device, for example, the TriStar II3020 manufactured by Shimadzu Corporation-Micromeritic can be used. Next, in nitrogen at 77K (the boiling point of nitrogen), while slowly increasing the nitrogen pressure P (mmHg), the nitrogen adsorption amount (mL / g) of the sample is measured at each pressure P. Next, the pressure P (mmHg) is divided by the saturated vapor pressure P0 (mmHg) of nitrogen, and the resulting value is taken as the relative pressure P / P0. By plotting the nitrogen adsorption amount relative to each relative pressure P / P0, an adsorption isotherm is obtained. Next, a BET diagram is calculated from the nitrogen adsorption isotherm and the BET formula, and the specific surface area is obtained using the BET diagram. Furthermore, the BET diagram is calculated using the BET multi-point method.

[0133] The active material according to the first embodiment has a tetragonal crystal structure and contains a compound represented by the general formula Li a Ti b Nb 2- 2d M c+2d O 2b+5+3c A composite oxide represented by . In the above general formula, M is any one selected from W and Mo. The subscripts a, b, c, and d are numbers that satisfy 0≤a≤b+4+3c, 0<b<2-2d, and 0<c<2-4d. The capacity per unit volume of an electrode using the above composite oxide as an electrode active material is high. In addition, the capacity per unit volume of a secondary battery and a battery pack using the above composite oxide as an electrode active material is high. That is, such an active material shows a high capacity.

[0134] [Second embodiment]

[0135] According to the second embodiment, an electrode can be provided.

[0136] The electrode according to the second embodiment contains 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. For example, the electrode used as a battery electrode may be 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.

[0137] The electrode according to the second embodiment may include a current collector and an active material-containing layer. The active material-containing layer may be formed on one or both surfaces of the current collector. The active material-containing layer may include an active material and optionally a conductive agent and a binder.

[0138] The active material-containing layer may contain the active material according to the first embodiment alone, or may contain two or more active materials according to the first embodiment. Furthermore, it may contain a mixture of one or more active materials according to the first embodiment and one or more other active materials. The content ratio 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 is preferably 10% by mass or more and 100% by mass or less.

[0139] For example, when the active material according to the first embodiment is contained as the negative electrode active material, examples of other active materials include lithium titanate having a ramsdellite structure (e.g., Li 2+y Ti3O7, 0≤y≤3), lithium titanate with spinel structure (such as Li 4+x Ti5O 12 , 0≤x≤3), monoclinic titanium dioxide (TiO2), anatase titanium dioxide, rutile titanium dioxide, alkali-pyrolusite titanium composite oxide, orthorhombic titanium composite oxide and monoclinic niobium titanium composite oxide, niobium oxide, niobium titanium oxide, niobium-molybdenum composite oxide, niobium-tungsten composite oxide.

[0140] Examples of the orthorhombic titanium-containing composite oxide include Li 2+e M2 2-f Ti 6-g M3 h O 14+σ Here, M2 is at least one selected from Sr, Ba, Ca, Mg, Na, Cs, Rb and K. M3 is at least one selected from 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, -0.5≤σ≤0.5. As a specific example of the orthorhombic titanium-containing composite oxide, Li 2+ e Na2Ti6O 14 (0≤e≤6).

[0141] Examples of the monoclinic niobium titanium composite oxide include Li x Ti 1-y M4 y Nb 2-z M5z O 7+δ Here, M4 is at least one selected from Zr, Si and Sn. M5 is at least one selected from V, Ta and Bi. The subscripts in the composition formula are 0≤x≤5, 0≤y<1, 0≤z<2, -0.3≤δ≤0.3. As a specific example of monoclinic niobium titanium composite oxide, Li x Nb2TiO7(0≤x≤5).

[0142] Other examples of monoclinic niobium titanium composite oxides include Li x Ti 1-y M6 y+z Nb 2-z O 7-δ Here, M6 is at least one selected from Mg, Fe, Ni, Co, W, Ta, and Mo. The subscripts in the composition formula are 0≤x<5, 0≤y<1, 0≤z<2, and -0.3≤δ≤0.3.

[0143] The conductive agent is formulated to improve the current collection performance and suppress the contact resistance between the active material and the current collector. Examples of conductive agents include carbon black such as vapor grown carbon fiber (VGCF), acetylene black, graphite, carbon nanotubes, and carbon nanofibers. One of these can be used as the conductive agent, or two or more can be used in combination. Alternatively, instead of using a conductive agent, the surface of the active material particles can be coated with carbon and an electronically conductive inorganic material. In addition, by coating the surface of the active material with carbon and a conductive material while using a conductive agent, the current collection performance of the active material layer can also be improved.

[0144] Binders are added to fill gaps between dispersed active materials and bond the active materials to the current collector. Examples include polytetrafluoroethylene (PTFE), polyvinylidene fluoride (PVdF), fluororubber, styrene-butadiene rubber, polyacrylic acid compounds, imide compounds, carboxymethyl cellulose (CMC), and CMC salts. A single binder may be used, or a combination of two or more may be used.

[0145] The proportion of active material, conductive agent and binder in the active material layer can be changed appropriately according to the purpose of the electrode. For example, when the electrode is used as the negative electrode of a secondary battery, it is preferred to mix the active material (negative electrode active material), conductive agent and binder in a ratio of 68% by mass or more and 96% by mass or less, 2% by mass or more and 30% by mass or less, and 2% by mass or more and 30% by mass or less. By setting the amount of conductive agent to 2% by mass or more, the current collection performance of the active material layer can be improved. In addition, by setting the amount of binder to 2% by mass or more, the binding property of the active material layer and the current collector can be made sufficient, and excellent cycle performance can be expected. On the other hand, it is preferred that the conductive agent and binder are set to 30% by mass or less, respectively, in order to achieve high capacity.

[0146] When coating the active material surface with carbon or a conductive material, the coating material can be considered as part of the conductive material amount. The coating amount of carbon or conductive material is preferably 0.5% by mass or greater and 5% by mass or less. Within this range, current collection performance and electrode density can be improved.

[0147] As the current collector, a material that is electrochemically stable at the potential at which lithium (Li) is inserted and removed from the active material can be used. For example, when the active material is used as the negative electrode active material, the current collector is preferably made of copper, nickel, stainless steel, or aluminum, or an aluminum alloy containing one or more elements selected from Mg, Ti, Zn, Mn, Fe, Cu, and Si. The thickness of the current collector is preferably not less than 5 μm and not more than 20 μm. A current collector having such a thickness can achieve a balance between electrode strength and lightweight.

[0148] Furthermore, the current collector may include a portion on its surface where the active material-containing layer is not formed. This portion can function as a current collector tab.

[0149] Electrodes 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 then applied to one or both surfaces of a current collector. The applied slurry is then dried to form a laminate containing the active material layer and the current collector. This laminate is then pressurized. This produces an electrode.

[0150] Alternatively, the electrode can be made by the following method. First, the active material, conductive agent, and binder are mixed to obtain a mixture. Next, the mixture is formed into particles. Then, these particles are arranged on a current collector to obtain an electrode.

[0151] The electrode according to the second embodiment contains the active material according to the first embodiment. Therefore, the electrode according to the second embodiment can realize a secondary battery having a high capacity per unit volume.

[0152] [Third embodiment]

[0153] According to the third embodiment, a secondary battery including a negative electrode, a positive electrode, and an electrolyte can be provided. The secondary battery includes the electrode involved in the second embodiment as a negative electrode, a positive electrode, or both a negative electrode and a positive electrode. In other words, the secondary battery involved in the third embodiment includes an electrode containing the active material involved in the first embodiment as a battery active material as a battery electrode. The secondary battery of a preferred embodiment includes the electrode involved in the second embodiment as a negative electrode. In other words, the secondary battery of a preferred embodiment includes the electrode containing the active material involved in the first embodiment as a battery active material as a negative electrode. The preferred embodiment is described below.

[0154] The secondary battery according to the third embodiment may further include a separator disposed between the positive electrode and the negative electrode. The negative electrode, the positive electrode, and the separator may constitute an electrode assembly. The electrolyte may be retained in the electrode assembly.

[0155] Furthermore, the secondary battery according to the third embodiment may further include an outer packaging member for housing the electrode group and the electrolyte.

[0156] In addition, the secondary battery according to the third embodiment may further include a negative electrode terminal electrically connected to the negative electrode and a positive electrode terminal electrically connected to the positive electrode.

[0157] The secondary battery according to the third embodiment may be, for example, a lithium secondary battery. The secondary battery includes a non-aqueous electrolyte secondary battery containing a non-aqueous electrolyte.

[0158] Hereinafter, the negative electrode, the positive electrode, the electrolyte, the separator, the outer casing, the negative electrode terminal, and the positive electrode terminal will be described in detail.

[0159] 1) Negative electrode

[0160] The negative electrode may include a negative electrode current collector and a layer containing a negative electrode active material. The negative electrode current collector and the layer containing a negative electrode active material may be the current collector and the layer containing an active material, respectively, that can be included in the electrode according to the second embodiment. The layer containing a negative electrode active material contains the active material according to the first embodiment as the negative electrode active material.

[0161] The details of the negative electrode that overlap with those described in the second embodiment are omitted.

[0162] The density of the negative electrode active material layer (excluding the current collector) is preferably 1.8 g / cm 3 Above and 2.8g / cm 3 The negative electrode energy density and electrolyte retention are excellent when the density of the negative electrode active material layer is within this range. The density of the negative electrode active material layer is more preferably 2.1 g / cm 3 Above and 2.6g / cm 3 the following.

[0163] The negative electrode can be produced, for example, by the same method as that of the electrode according to the second embodiment.

[0164] 2) Positive electrode

[0165] 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 surfaces of the positive electrode current collector. The positive electrode active material-containing layer may include the positive electrode active material and any conductive agent and binder.

[0166] As the positive electrode active material, for example, an oxide or a sulfide can be used. The positive electrode can contain a single compound as the positive electrode active material, or it can contain a combination of two or more compounds. Examples of oxides and sulfides include compounds that can intercalate and deintercalate Li or Li ions.

[0167] Examples of such compounds include manganese dioxide (MnO2), iron oxide, copper oxide, nickel oxide, lithium manganese composite oxide (e.g., Li x Mn2O4 or Li x MnO2, 0<x≤1), lithium nickel composite oxide (such as Li x NiO2, 0<x≤1), lithium cobalt composite oxide (such as Li x CoO2, 0<x≤1), lithium nickel cobalt composite oxide (such as Li x Ni 1-y Co y O2, 0<x≤1, 0<y<1), lithium manganese cobalt composite oxide (such as Li x Mn y Co 1-y O2, 0<x≤1, 0<y<1), lithium manganese nickel composite oxide with spinel structure (such as Li x Mn 2-y Ni y O4, 0<x≤1, 0<y<2), lithium phosphate with olivine structure (such as 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 (such as 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).

[0168] Among the above, examples of more preferred compounds as positive electrode active materials include: lithium manganese composite oxides having a spinel structure (e.g., Li x Mn2O4, 0<x≤1), lithium nickel composite oxide (such as Li x NiO2, 0<x≤1), lithium cobalt composite oxide (such as Li x CoO2, 0<x≤1), lithium nickel cobalt composite oxide (such as Li x Ni 1-y Co y O2, 0<x≤1, 0<y<1), lithium manganese nickel composite oxide with spinel structure (such as Li x Mn 2-y Ni y O4, 0<x≤1, 0<y<2), lithium manganese cobalt composite oxide (such as Li x Mn y Co 1-y O2, 0<x≤1, 0<y<1), lithium iron phosphate (such as Li x FePO4, 0<x≤1) and lithium nickel cobalt manganese composite oxide (Li x Ni 1-y-z Co y Mn z O2, 0<x≤1, 0<y<1, 0<z<1, y+z<1). If these compounds are used in the positive electrode active material, the positive electrode potential can be increased.

[0169] When using room temperature molten salt as the electrolyte of the battery, it is preferable to use a x Positive electrode active materials include VPO4F (0≤x≤1), lithium-manganese composite oxides, lithium-nickel composite oxides, lithium-nickel-cobalt composite oxides, or mixtures thereof. These compounds have low reactivity with room-temperature molten salts, which can improve cycle life. Details of room-temperature molten salts will be discussed later.

[0170] The primary particle size of the positive electrode active material is preferably 100 nm or larger and 1 μm or smaller. Positive electrode active materials with a primary particle size of 100 nm or larger are easy to handle in industrial production. Positive electrode active materials with a primary particle size of 1 μm or smaller facilitate the diffusion of lithium ions within the solid.

[0171] The specific surface area of ​​the positive electrode active material is preferably 0.1 m 2 / g or more and 10m 2 / g or less. With 0.1m 2 / g or more of the positive electrode active material can fully ensure the insertion and extraction sites of Li ions. 2A positive electrode active material having a specific surface area of ​​1000 Å / g or less is easy to handle in industrial production and can ensure good charge-discharge cycle performance.

[0172] The binder is added to fill the gaps between the dispersed positive electrode active material and to bond the positive electrode active material to the positive electrode current collector. Examples of binders include polytetrafluoroethylene (PTFE), polyvinylidene fluoride (PVdF), fluororubber, polyacrylic acid compounds, imide compounds, carboxymethyl cellulose (CMC), and CMC salts. A single binder may be used, or a combination of two or more may be used.

[0173] Conductive agents are added 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. A single conductive agent may be used, or a combination of two or more may be used. Furthermore, the conductive agent may be omitted.

[0174] In the positive electrode active material-containing layer, the positive electrode active material and the binder are preferably blended in a ratio of 80 mass % to 98 mass % and 2 mass % to 20 mass %, respectively.

[0175] By setting the binder content to 2% by mass or more, sufficient electrode strength can be achieved. Furthermore, the binder can function as an insulator. Therefore, if the binder content is set to 20% by mass or less, the amount of insulator contained in the electrode is reduced, thereby reducing internal resistance.

[0176] When a conductive agent is added, the positive electrode active material, binder, and conductive agent are preferably blended in proportions of 77% to 95% by mass, 2% to 20% by mass, and 3% to 15% by mass, respectively.

[0177] By setting the amount of the conductive agent to 3% by mass or more, the above-mentioned effects can be achieved. Furthermore, by setting the amount of the conductive agent to 15% by mass or less, the proportion of the conductive agent in contact with the electrolyte can be reduced. A low proportion can reduce electrolyte decomposition during high-temperature storage.

[0178] The positive electrode current collector is preferably aluminum foil or aluminum alloy foil containing one or more elements selected from Mg, Ti, Zn, Ni, Cr, Mn, Fe, Cu, and Si.

[0179] 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 in the aluminum foil or aluminum alloy foil is preferably 1% by mass or less.

[0180] Furthermore, the positive electrode current collector may include a portion on its surface where the positive electrode active material layer is not formed. This portion may function as a positive electrode current collector tab.

[0181] The positive electrode can be produced, for example, by using a positive electrode active material and by the same method as that of the electrode according to the second embodiment.

[0182] 3) Electrolytes

[0183] As the electrolyte, for example, a liquid nonaqueous electrolyte or a gel nonaqueous electrolyte can be used. The liquid nonaqueous electrolyte can be prepared by dissolving an electrolyte salt as a solute in an organic solvent. The concentration of the electrolyte salt is preferably 0.5 mol / L or more and 2.5 mol / L or less.

[0184] Examples of electrolyte salts include lithium perchlorate (LiClO4), lithium hexafluorophosphate (LiPF6), lithium tetrafluoroborate (LiBF4), lithium hexafluoroarsenate (LiAsF6), lithium trifluoromethanesulfonate (LiCF3SO3), lithium bis(trifluoromethanesulfonyl imide) (LiN(CF3SO2)2), lithium bis(fluorosulfonyl imide) (LiN(SO2F)2:LiFSI), and mixtures thereof. Electrolyte salts that are difficult to oxidize even at high potentials are preferred, with LiPF6 being the most preferred.

[0185] Examples of organic solvents include cyclic carbonates such as propylene carbonate (PC), ethylene carbonate (EC), and vinylene carbonate (VC); chain carbonates such as diethyl carbonate (DEC), dimethyl carbonate (DMC), and methylethyl carbonate (MEC); cyclic ethers such as tetrahydrofuran (THF), 2-methyltetrahydrofuran (2MeTHF), and dioxolane (DOX); chain ethers such as dimethoxyethane (DME) and diethoxyethane (DEE); and gamma-butyrolactone (GBL), acetonitrile (AN), and sulfolane (SL). These organic solvents can be used alone or as a mixture.

[0186] The gel nonaqueous electrolyte can be prepared by compounding a liquid nonaqueous electrolyte with a polymer material. Examples of the polymer material include polyvinylidene fluoride (PVdF), polyacrylonitrile (PAN), polyethylene oxide (PEO), or a mixture thereof.

[0187] Alternatively, as the nonaqueous electrolyte, besides liquid nonaqueous electrolytes and gel nonaqueous electrolytes, room-temperature molten salts (ionic melts) containing lithium ions, polymer solid electrolytes, inorganic solid electrolytes, and the like may be used.

[0188] As a room temperature molten salt (ionic melt), it refers to a compound that can exist as a liquid at room temperature (15°C to 25°C) in an organic salt formed by a combination of organic cations and anions. Room temperature molten salts include room temperature molten salts that exist as liquids in the form of monomers, room temperature molten salts that become liquids by mixing with electrolyte salts, room temperature molten salts that become liquids by dissolving in organic solvents, or mixtures of these room temperature molten salts. Generally speaking, the melting point of the room temperature molten salts used in secondary batteries is below 25°C. In addition, the organic cation usually has a quaternary ammonium skeleton.

[0189] A polymer solid electrolyte can be prepared by dissolving an electrolyte salt in a polymer material and solidifying it.

[0190] The inorganic solid electrolyte is a solid substance having Li ion conductivity.

[0191] Alternatively, a liquid aqueous electrolyte or a gel aqueous electrolyte can be used as the electrolyte instead of the non-aqueous electrolyte. The liquid aqueous electrolyte can be prepared, for example, by dissolving the above-mentioned electrolyte salt as a solute in an aqueous solvent. The gel aqueous electrolyte can be prepared by compounding the liquid aqueous electrolyte with the above-mentioned polymer material. As the aqueous solvent, a solution containing water can be used. The so-called solution containing water can be pure water or a mixed solvent of water and an organic solvent.

[0192] 4) Diaphragm

[0193] The separator can be formed from a porous film or synthetic resin nonwoven fabric made of, for example, polyethylene (PE), polypropylene (PP), cellulose, or polyvinylidene fluoride (PVdF). From a safety perspective, porous films made of polyethylene or polypropylene are preferred. This is because these porous films melt at a certain temperature, interrupting the current flow.

[0194] 5) Outer packaging components

[0195] As the outer packaging member, for example, a container formed of a laminated film or a metal container can be used.

[0196] The thickness of the laminate film is, for example, 0.5 mm or less, and preferably 0.2 mm or less.

[0197] Laminated films can be multilayer films comprising multiple resin layers and a metal layer sandwiched between these resin layers. Resin layers can be made of polymers such as polypropylene (PP), polyethylene (PE), nylon, and polyethylene terephthalate (PET). For lightweighting, the metal layer is preferably made of aluminum foil or aluminum alloy foil. Laminated films can be sealed by thermal fusion bonding and molded into the shape of an outer packaging member.

[0198] The thickness of the metal container is, for example, preferably 1 mm or less, more preferably 0.5 mm or less, and even more preferably 0.2 mm or less.

[0199] The metal container can be made of, for example, aluminum or an aluminum alloy. Preferably, the aluminum alloy contains elements such as magnesium, zinc, and silicon. When the aluminum alloy contains transition metals such as iron, copper, nickel, and chromium, the content thereof is preferably 1% by mass or less.

[0200] The shape of the outer packaging member is not particularly limited. For example, the shape of the outer packaging member may be flat (thin), square, cylindrical, coin-shaped, or button-shaped. The outer packaging member can be appropriately selected according to the size of the battery and the application of the battery.

[0201] 6) Negative terminal

[0202] The negative terminal can be formed from a material that is electrochemically stable and conductive at the Li insertion and deinsertion potential of the above-mentioned negative electrode active material. Specifically, examples of the material for the negative terminal include copper, nickel, stainless steel, aluminum, or an aluminum alloy containing at least one element selected from Mg, Ti, Zn, Mn, Fe, Cu, and Si. Aluminum or an aluminum alloy is preferably used as the material for the negative terminal. The negative terminal is preferably formed from the same material as the negative electrode current collector in order to reduce contact resistance with the negative electrode current collector.

[0203] 7) Positive terminal

[0204] The positive terminal can be formed by a potential range of 3V or more and 5V or less relative to the redox potential of lithium (vs.Li / Li + ) is formed of a material that is electrically stable and conductive. Examples of materials for the positive terminal include aluminum or an aluminum alloy containing at least one element selected from Mg, Ti, Zn, Mn, Fe, Cu, and Si. The positive terminal is preferably formed of the same material as the positive electrode current collector to reduce contact resistance with the positive electrode current collector.

[0205] The above describes a method for including the electrode involved in the second embodiment as a negative electrode. In the method of the secondary battery involved in the third embodiment, in the method including the electrode involved in the second embodiment as a positive electrode, as its counter electrode, i.e., the negative electrode, for example, the following counter electrode can be used. At least one electrode selected from lithium metal, lithium metal alloy, graphite, silicon, silicon oxide, tin oxide, tin, and other alloys can be used as the negative electrode. Materials that do not contain Li in the active material can be used as the negative electrode by pre-doping with the Li element.

[0206] In the embodiment including the electrode according to the second embodiment as a positive electrode, the detailed configuration of the positive electrode is omitted because it overlaps with the configuration described in the second embodiment.

[0207] Next, a secondary battery according to a third embodiment will be described in more detail with reference to the drawings.

[0208] Figure 4It is a cross-sectional view schematically showing an example of a secondary battery according to a third embodiment. Figure 5 yes Figure 4 An enlarged cross-sectional view of portion A of the secondary battery shown.

[0209] Figure 4 and Figure 5 The secondary battery 100 shown includes: Figure 4 The electrode group 1 shown Figure 4 and Figure 5 The electrode group 1 and the electrolyte are contained in the bag-shaped outer packaging member 2. The electrolyte (not shown) is retained in the electrode group 1.

[0210] The bag-like outer package member 2 is formed of a laminated film including two resin layers and a metal layer sandwiched therebetween.

[0211] like Figure 4 As shown, the electrode group 1 is a flat wound electrode group. Figure 5 As shown, 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.

[0212] The negative electrode 3 includes a negative electrode current collector 3a and a negative electrode active material layer 3b. Figure 5 As shown, the negative electrode active material containing layer 3b is formed only on the inner surface of the negative electrode current collector 3a. In the other parts of the negative electrode 3, the negative electrode active material containing layer 3b is formed on both surfaces of the negative electrode current collector 3a.

[0213] The positive electrode 5 includes a positive electrode current collector 5 a and positive electrode active material-containing layers 5 b formed on both surfaces thereof.

[0214] like Figure 4 As shown, a negative terminal 6 and a positive terminal 7 are located near the outer edges of the wound electrode assembly 1. The negative terminal 6 is connected to the outermost portion of the negative electrode current collector 3a. Furthermore, the positive terminal 7 is connected to the outermost portion of the positive electrode current collector 5a. These negative and positive terminals 6 and 7 extend to the outside through the opening of the bag-like outer packaging member 2. A thermoplastic resin layer is provided on the inner surface of the bag-like outer packaging member 2, and the opening is sealed by heat-melting.

[0215] The secondary battery according to the third embodiment is not limited to Figure 4 and Figure 5 The secondary battery of the structure shown can also be, for example Figure 6 and Figure 7 A battery having the structure shown.

[0216] Figure 6 It is a partially cutaway perspective view schematically showing another example of the secondary battery according to the third embodiment. Figure 7 yes Figure 6 An enlarged cross-sectional view of portion B of the secondary battery shown.

[0217] Figure 6 and Figure 7 The secondary battery 100 shown has Figure 6 and Figure 7 The electrode group 1 shown Figure 6 The outer packaging member 2 is shown, and the electrolyte is not shown. The electrode group 1 and the electrolyte are housed in the outer packaging member 2. The electrolyte is retained in the electrode group 1.

[0218] The outer package member 2 is formed of a laminate film including two resin layers and a metal layer sandwiched therebetween.

[0219] Electrode group 1 Figure 7 The stacked electrode group 1 has a structure in which negative electrodes 3 and positive electrodes 5 are alternately stacked with separators 4 interposed therebetween.

[0220] The electrode assembly 1 includes a plurality of negative electrodes 3. Each of the negative electrodes 3 includes a negative electrode current collector 3a and a negative electrode active material-containing layer 3b supported on both surfaces of the negative electrode current collector 3a. Furthermore, the electrode assembly 1 includes a plurality of positive electrodes 5. Each of the positive electrodes 5 includes a positive electrode current collector 5a and a positive electrode active material-containing layer 5b supported on both surfaces of the positive electrode current collector 5a.

[0221] The negative electrode current collector 3a of each negative electrode 3 has a portion 3c on one side thereof where no negative electrode active material layer 3b is supported on any surface. This portion 3c functions as a negative electrode current collector tab. Figure 7 As shown, portion 3c, which functions as a negative electrode collector tab, does not overlap with positive electrode 5. Furthermore, the plurality of negative electrode collector tabs (portion 3c) are electrically connected to a strip-shaped negative electrode terminal 6. The tip of strip-shaped negative electrode terminal 6 is led outside of outer casing 2.

[0222] In addition, although not shown, the positive electrode current collector 5a of each positive electrode 5 has a portion on one side thereof that does not carry the positive electrode active material layer 5b on any surface. This portion functions as a positive electrode collector tab. The positive electrode collector tab, like the negative electrode collector tab (portion 3c), does not overlap with the negative electrode 3. In addition, the positive electrode collector tab is located on the opposite side of the electrode group 1 relative to the negative electrode collector tab (portion 3c). The positive electrode collector tab is electrically connected to the strip-shaped positive terminal 7. The front end of the strip-shaped positive terminal 7 is located on the opposite side of the negative terminal 6 and is led to the outside of the outer packaging member 2.

[0223] The secondary battery according to the third embodiment includes the electrode according to the second embodiment. In other words, 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 a high capacity per unit volume.

[0224] [Fourth embodiment]

[0225] According to a fourth embodiment, a battery pack is provided. The battery pack according to the fourth embodiment includes a plurality of secondary batteries according to the third embodiment.

[0226] In the assembled battery according to the fourth embodiment, the individual cells may be arranged by being electrically connected in series or in parallel, or may be arranged by combining series connection and parallel connection.

[0227] Next, an example of a battery pack according to a fourth embodiment will be described with reference to the drawings.

[0228] Figure 8 It is a perspective view schematically showing an example of a battery assembly according to a fourth embodiment. Figure 8 The illustrated assembled battery 200 includes five cells 100 a to 100 e , four bus bars 21 , a positive electrode lead 22 , and a negative electrode lead 23 . The five cells 100 a to 100 e are each a secondary battery according to the third embodiment.

[0229] The busbar 21 connects, for example, the negative terminal 6 of one cell 100a and the positive terminal 7 of the adjacent cell 100b. In this way, five cells 100 are connected in series via four busbars 21. Figure 8 The battery pack 200 is a battery pack consisting of five cells connected in series. Although not shown in the figure, 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 plurality of negative terminals with a bus bar and simultaneously connecting the plurality of positive terminals with a bus bar.

[0230] The positive electrode terminal 7 of at least one of the five cells 100a to 100e is electrically connected to the positive electrode lead 22 for external connection. The negative electrode terminal 6 of at least one of the five cells 100a to 100e is electrically connected to the negative electrode lead 23 for external connection.

[0231] The battery pack according to the fourth embodiment includes the secondary battery according to the third embodiment. Therefore, the capacity per unit volume of such a battery pack is high.

[0232] [Fifth embodiment]

[0233] According to a fifth embodiment, a battery pack is provided. The battery pack includes the battery assembly according to the fourth embodiment. The battery pack may include a single secondary battery according to the third embodiment instead of the battery assembly according to the fourth embodiment.

[0234] The battery pack according to the fifth embodiment may further include a protection circuit. The protection circuit has the function of controlling the charge and discharge of the secondary battery. Alternatively, a circuit included in a device that uses the battery pack as a power source (e.g., an electronic device, an automobile, etc.) may be used as the battery pack protection circuit.

[0235] In addition, the battery pack according to the fifth embodiment may further include external terminals for power supply. The external terminals for power supply are used to output current from the secondary battery to the outside and / or input 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 power supply. Furthermore, when charging the battery pack, the charging current (including regenerative energy from the power of a vehicle, etc.) is supplied to the battery pack through the external terminals for power supply.

[0236] Next, an example of a battery pack according to a fifth embodiment will be described with reference to the drawings.

[0237] Figure 9 This is an exploded perspective view schematically showing an example of a battery pack according to a fifth embodiment. Figure 10 Yes Figure 9 A block diagram of an example of a battery pack circuit is shown.

[0238] Figure 9 and Figure 10 The battery pack 300 shown includes a storage container 31 , a cover 32 , a protective sheet 33 , a battery assembly 200 , a printed wiring board 34 , wiring 35 , and an insulating plate (not shown).

[0239] Figure 9 The illustrated storage container 31 is a square container with a rectangular bottom. The storage container 31 is configured to accommodate a protective sheet 33, a battery assembly 200, a printed wiring board 34, and wiring 35. The lid 32 has a rectangular shape. The lid 32 covers the storage container 31, thereby housing the battery assembly 200 and other components. Although not shown, the storage container 31 and lid 32 also have openings and connection terminals for connecting to external devices.

[0240] The assembled battery 200 includes a plurality of cells 100 , a positive electrode lead 22 , a negative electrode lead 23 , and an adhesive tape 24 .

[0241] At least one of the plurality of cells 100 is a secondary battery according to the third embodiment. Figure 10As shown, the cells 100 are electrically connected in series. Multiple cells 100 may also be electrically connected in parallel, or a combination of series and parallel connections. Connecting multiple cells 100 in parallel increases the battery capacity compared to connecting them in series.

[0242] Adhesive tape 24 is used to bundle the multiple cells 100. Heat shrink tape can also be used instead of adhesive tape 24 to secure the multiple cells 100. In this case, protective sheets 33 are placed on both sides of the battery pack 200, and after wrapping the heat shrink tape around them, the heat shrink tape is thermally shrunk to bundle the multiple cells 100.

[0243] One end of the positive electrode lead 22 is connected to the assembled battery 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 assembled battery 200. One end of the negative electrode lead 23 is electrically connected to the negative electrode of one or more cells 100.

[0244] The printed wiring board 34 is provided along one of the short sides of the inner surface of the storage container 31. The printed wiring board 34 includes a positive-side connector 342, a negative-side connector 343, a thermistor 345, a protective circuit 346, wirings 342a and 343a, external terminals 350 for power supply, positive-side wiring (positive-side wiring) 348a, and negative-side wiring (negative-side wiring) 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.

[0245] The other end 22 a of the positive electrode lead 22 is electrically connected to the positive electrode connector 342 . The other end 23 a of the negative electrode lead 23 is electrically connected to the negative electrode connector 343 .

[0246] The thermistor 345 is fixed to one main surface of the printed wiring board 34 . The thermistor 345 detects the temperature of each cell 100 and sends the detection signal to the protection circuit 346 .

[0247] The external terminals 350 for power supply are fixed to the other main surface of the printed wiring board 34. The external terminals 350 for power supply are electrically connected to devices outside the battery pack 300. The external terminals 350 for power supply include a positive terminal 352 and a negative terminal 353.

[0248] 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 the positive-side wiring 348a. The protection circuit 346 is connected to the negative terminal 353 via the negative-side wiring 348b. Furthermore, the protection circuit 346 is electrically connected to the positive-side connector 342 via the wiring 342a. The protection circuit 346 is electrically connected to the negative-side connector 343 via the wiring 343a. Furthermore, the protection circuit 346 is electrically connected to each of the plurality of cells 100 via the wiring 35.

[0249] The protective sheet 33 is disposed on both inner side surfaces in the longitudinal direction of the storage container 31 and on the inner side surface in the transverse direction facing the printed wiring board 34 via the battery module 200. The protective sheet 33 is formed of, for example, resin or rubber.

[0250] The protection circuit 346 controls the charge and discharge of the plurality of battery cells 100. Furthermore, based on a detection signal transmitted from the thermistor 345 or a detection signal transmitted from each battery cell 100 or the assembled battery 200, the protection circuit 346 blocks the electrical connection between the protection circuit 346 and the external terminals 350 (positive terminal 352 and negative terminal 353) for supplying power to external devices.

[0251] Examples of detection signals sent from the thermistor 345 include signals detecting that the temperature of the cell 100 has reached or exceeded a predetermined temperature. Examples of detection signals sent from individual cells 100 or assembled batteries 200 include signals detecting overcharge, overdischarge, and overcurrent in the cell 100. To detect overcharge, etc. in individual cells 100, the cell voltage, positive electrode potential, or negative electrode potential can be detected. In the latter case, a lithium electrode serving as a reference electrode is inserted into each cell 100.

[0252] Alternatively, as the protection circuit 346 , a circuit included in a device (eg, electronic equipment, automobile, etc.) that uses the battery pack 300 as a power source may be used.

[0253] As mentioned above, the battery pack 300 is equipped with external terminals 350 for power supply. Therefore, the battery pack 300 can output current from the assembled battery 200 to an external device via the external terminals 350 for power supply, and can also input current from the external device into the assembled battery 200. In other words, when the battery pack 300 is used as a power source, current from the assembled battery 200 can be supplied to the external device via the external terminals 350 for power supply. Furthermore, when charging the battery pack 300, charging current from the external device can be supplied to the battery pack 300 via the external terminals 350 for power supply. 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.

[0254] Alternatively, the battery pack 300 may include multiple battery assemblies 200. In this case, the multiple battery assemblies 200 may be connected in series, in parallel, or in a combination of series and parallel connections. Furthermore, the printed wiring board 34 and wiring 35 may be omitted. In this case, the positive electrode lead 22 and the negative electrode lead 23 may serve as the positive terminal 352 and negative terminal 353 of the external terminals 350 for current flow, respectively.

[0255] Such battery packs can be used, for example, in applications requiring excellent cycling performance when drawing high currents. Specifically, they can be used as power sources for electronic devices, stationary batteries, and onboard batteries for various vehicles. Examples of electronic devices include digital cameras. These battery packs are particularly suitable for use as onboard batteries.

[0256] The battery pack according to the fifth embodiment includes the secondary battery according to the third embodiment or the assembled battery according to the fourth embodiment. Therefore, such a battery pack has a high capacity per unit volume.

[0257] [Sixth embodiment]

[0258] According to a sixth embodiment, a vehicle is provided. The vehicle is equipped with the battery pack according to the fifth embodiment.

[0259] In the vehicle according to the sixth embodiment, the battery pack can recover regenerative energy of the vehicle's kinetic energy, for example. The vehicle may also include a mechanism (regenerator) that converts the vehicle's kinetic energy into regenerative energy.

[0260] Examples of the vehicle according to the sixth embodiment include a two-wheeled to four-wheeled hybrid electric vehicle, a two-wheeled to four-wheeled electric vehicle, an assist bicycle, and a railway vehicle.

[0261] The mounting position of the battery pack in the vehicle according to the sixth embodiment is not particularly limited. For example, when the battery pack is mounted in an automobile, the battery pack may be mounted in the engine compartment, behind the vehicle body, or under a seat.

[0262] The vehicle according to the sixth embodiment may also be equipped with multiple battery packs. In this case, the batteries contained in each battery pack may be electrically connected in series, in parallel, or in a combination of series and parallel connections. For example, when each battery pack includes a battery pack, the battery packs may be electrically connected in series, in parallel, or in a combination of series and parallel connections. Alternatively, when each battery pack includes a single battery cell, the batteries may be electrically connected in series, in parallel, or in a combination of series and parallel connections.

[0263] Next, an example of a vehicle according to a sixth embodiment will be described with reference to the drawings.

[0264] Figure 11 This is a partial perspective view schematically showing an example of a vehicle according to the sixth embodiment.

[0265] Figure 11 The vehicle 400 shown includes a vehicle body 40 and a battery pack 300 according to the fifth embodiment. Figure 11 In the example shown, the vehicle 400 is a four-wheeled automobile.

[0266] The vehicle 400 may also be equipped with multiple battery packs 300. In this case, the batteries (e.g., single cells or battery packs) included in the battery pack 300 may be connected in series, in parallel, or in a combination of series and parallel connections.

[0267] Figure 11 The middle figure shows an example where the battery pack 300 is mounted in the engine compartment located in front of the vehicle body 40. As mentioned above, the battery pack 300 can also be mounted, for example, behind the vehicle body 40 or under a seat. This battery pack 300 can serve as a power source for the vehicle 400. Furthermore, this battery pack 300 can recover regenerative energy from the vehicle 400's power.

[0268] Next, refer to Figure 12 An embodiment of a vehicle according to a sixth embodiment will be described.

[0269] Figure 12 This is a diagram schematically showing an example of a control system related to an electrical system in a vehicle according to the sixth embodiment. Figure 12 The illustrated vehicle 400 is an electric vehicle.

[0270] Figure 12The vehicle 400 shown includes a vehicle body 40 , a vehicle power supply 41 , a vehicle ECU (Electric Control Unit) 42 which is a higher-level control device for the vehicle power supply 41 , external terminals (terminals for connecting to an external power supply) 43 , a converter 44 , and a drive motor 45 .

[0271] The vehicle 400 has a vehicle power supply 41 mounted in, for example, the engine room, the rear of the vehicle body, or under a seat. Figure 12 In the illustrated vehicle 400 , the mounting location of the vehicle power supply 41 is schematically shown.

[0272] The vehicle power supply 41 includes a plurality of (eg, three) battery packs 300 a , 300 b , and 300 c , a battery management unit (BMU) 411 , and a communication bus 412 .

[0273] Battery pack 300a includes a battery pack 200a and a battery pack monitoring device 301a (e.g., VTM: Voltage Temperature Monitoring). Battery pack 300b includes a battery pack 200b and a battery pack monitoring device 301b. Battery pack 300c includes a battery pack 200c and a battery pack monitoring device 301c. Battery packs 300a-300c are similar to battery pack 300 described above, and battery packs 200a-200c are similar to battery pack 200 described above. Battery packs 200a-200c are electrically connected in series. Battery packs 300a, 300b, and 300c are each independently removable and interchangeable with another battery pack 300.

[0274] Each of the assembled batteries 200a to 200c includes a plurality of cells connected in series. At least one of the plurality of cells is a secondary battery according to the third embodiment. Each of the assembled batteries 200a to 200c is charged and discharged via a positive electrode terminal 413 and a negative electrode terminal 414.

[0275] The battery management device 411 communicates with the assembled battery monitoring devices 301a to 301c to collect information on the voltage and temperature of each cell 100 included in the assembled batteries 200a to 200c of the vehicle power supply 41. Thus, the battery management device 411 collects information related to the maintenance of the vehicle power supply 41.

[0276] 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, a single set of communication lines is shared among multiple nodes (the battery management unit 411 and one or more assembled battery monitoring units 301a to 301c). The communication bus 412 is, for example, a communication bus constructed in accordance with the CAN (Control Area Network) standard.

[0277] The assembled battery monitoring devices 301a to 301c measure the voltage and temperature of each cell constituting the assembled batteries 200a to 200c based on a communication command from the battery management device 411. However, the temperature may be measured at only a few locations in one assembled battery, or not at all cells.

[0278] The vehicle power supply 41 may further include an electromagnetic contactor (eg, Figure 12 The switching device 415 is shown. The switching device 415 includes a pre-charge switch (not shown) that is turned on when charging the assembled batteries 200a-200c, and a main switch (not shown) that is turned on when the output from the assembled batteries 200a-200c is supplied to a load. The pre-charge switch and the main switch each include a relay circuit (not shown) that switches on and off based on a signal supplied to a coil located near the switching element. The electromagnetic contactor, such as the switching device 415, is controlled by a control signal from the vehicle ECU 42, which controls the operation of the battery management unit 411 and the entire vehicle 400.

[0279] Converter 44 converts the input DC voltage into a high three-phase alternating current (AC) voltage for driving the motor. The three-phase output terminals of converter 44 are connected to the three-phase input terminals of drive motor 45. Converter 44 is controlled based on control signals from vehicle ECU 42, which controls battery management unit 411 or overall vehicle operation. Control of converter 44 regulates the output voltage from converter 44.

[0280] The drive motor 45 is rotated by the electric power supplied from the converter 44. The driving force generated by the rotation of the drive motor 45 is transmitted to the axles and the drive wheels W via, for example, a differential gear unit.

[0281] Although not shown, vehicle 400 is equipped with a regenerative braking mechanism (regenerator). When braking vehicle 400, the regenerative braking mechanism rotates drive motor 45, converting kinetic energy into regenerative energy as electrical energy. The regenerative energy recovered by the regenerative braking mechanism is input to converter 44 and converted into direct current. The converted direct current is then input to vehicle power supply 41.

[0282] One terminal of connection line L1 is connected to negative terminal 414 of vehicle power supply 41. The other terminal of connection line L1 is connected to negative input terminal 417 of converter 44. Current detection unit (current detection circuit) 416 within battery management unit 411 is provided on connection line L1 between negative terminal 414 and negative input terminal 417.

[0283] One terminal of connection line L2 is connected to positive terminal 413 of vehicle power supply 41. The other terminal of connection line L2 is connected to positive input terminal 418 of converter 44. Switch device 415 is provided on connection line L2 between positive terminal 413 and positive input terminal 418.

[0284] The external terminal 43 is connected to the battery management device 411. The external terminal 43 can be connected to an external power source, for example.

[0285] In response to input from the driver and others, the vehicle ECU 42 coordinates with other management and control devices, including the battery management unit 411, to control the vehicle power supply 41, the switching device 415, the inverter 44, and other components. Through coordinated control by the vehicle ECU 42 and other components, the vehicle 400 is managed as a whole, controlling the output of power from the vehicle power supply 41 and the charging of the vehicle power supply 41. Data related to the maintenance of the vehicle power supply 41, such as the remaining capacity of the vehicle power supply 41, is transmitted between the battery management unit 411 and the vehicle ECU 42 via a communication line.

[0286] The vehicle according to the sixth embodiment is equipped with the battery pack according to the fifth embodiment. The high capacity per unit volume of the battery pack allows for greater freedom in vehicle design, allowing for a variety of vehicle styles without sacrificing vehicle performance.

[0287] [Example]

[0288] Hereinafter, the above-mentioned embodiment will be described in more detail based on examples. However, the present invention is not limited to the examples described below.

[0289] <Synthesis>

[0290] (Example 1)

[0291] The synthesis of Ti2Nb 10 W5O 44 and TiNb2WO 10 Represents the composition of titanium-niobium-tungsten composite oxide.

[0292] Titanium oxide, niobium oxide, and tungsten oxide are prepared as raw materials. These raw materials are mixed in a predetermined composition ratio and dry-ground and mixed. The resulting mixture is then placed in an alumina crucible and calcined in an atmosphere at 1200°C for 12 hours, followed by furnace cooling. The calcined product is dry-ground and then classified to adjust the particle size. Oxide powder is obtained in this manner.

[0293] (Example 2)

[0294] The synthesis of Ti2Nb 10 W5O 44 and TiNb2WO 10 Represents the composition of titanium-niobium-tungsten composite oxide.

[0295] An oxide powder was synthesized in the same manner as in Example 1 except that the composition ratio of titanium oxide, niobium oxide, and tungsten oxide was changed according to the target composition and the sintering temperature was changed to 1150°C.

[0296] (Example 3)

[0297] The synthesis of TiNb5Mo2O 20 The composition represents the composition of the titanium-niobium-molybdenum composite oxide.

[0298] As raw materials, ammonium niobium oxalate, ammonium molybdate, and tetraisopropoxytitanium are prepared. These raw materials are weighed according to the specified composition ratio. Solution A is prepared by dissolving ammonium niobium oxalate and ammonium molybdate in pure water. Next, tetraisopropoxytitanium is added to a 1M aqueous oxalic acid solution and dissolved by heating and stirring to prepare solution B. After mixing solution A and solution B, ammonia solution is added while heating and stirring to adjust the pH to 7, thereby obtaining a sol. After pH adjustment, the solvent is evaporated while heating and stirring to obtain a gel. The gel is then placed in a drying furnace at 100°C for drying. After drying, the obtained solid is pulverized to obtain a white precursor powder. The precursor powder is placed in an alumina crucible, covered to suppress molybdenum evaporation, and calcined at 800°C for 4 hours. The calcined product is then dry-pulverized and the pulverized product is classified to adjust the particle size. Active material powder is obtained as described above.

[0299] (Example 4)

[0300] The same steps as in Example 3 are carried out until the pulverization treatment after drying of the gel to obtain a white precursor powder. Potassium oxide (K2O) is added to the precursor powder in an amount such that the K addition amount reaches 10,000 ppm relative to the expected synthesis amount obtained after sintering the active material powder, and dry mixing and pulverization are carried out. The precursor powder is placed in an alumina crucible, covered with a lid to suppress molybdenum evaporation, and sintered at 750°C for 4 hours. Then, the sintered product is dry-pulverized and the pulverized product is classified to adjust the particle size. Active material powder is obtained as described above.

[0301] (Example 5)

[0302] The raw materials were mixed in the same mixing ratio as in Example 2, and iron oxide (Fe2O3) was added to the mixture so that the Fe addition amount reached 2000 ppm relative to the expected synthesis amount of the active material powder after calcination. The material was then prepared under the same production conditions as in Example 2 to obtain active material powder.

[0303] (Example 6)

[0304] The same steps as in Example 3 were followed until the gel was dried and pulverized, yielding a white precursor powder. Phosphorus oxide (P2O5) was added to the precursor powder in an amount such that the phosphorus content reached 2000 ppm relative to the expected synthesis amount after calcination of the active material powder. Dry mixing and pulverization were then performed. Subsequent steps were performed under the same conditions as in Example 3 to synthesize the material and obtain the active material powder.

[0305] (Example 7)

[0306] The raw materials were mixed in the same mixing ratio as in Example 2, and molybdenum oxide (MoO3) was added to the mixture so that the Mo addition amount would be 8000 ppm relative to the expected synthesis amount of the active material powder after sintering. The materials were then synthesized under the same conditions as in Example 2, except that the sintering temperature was changed to 1100°C, to obtain the active material powder.

[0307] (Example 8)

[0308] The raw materials were mixed in the same mixing ratio as in Example 1, and zirconium oxide (ZrO2) was added to the mixture so that the Zr addition amount would be 2000 ppm relative to the expected synthesis amount obtained after sintering the active material powder. Then, the materials were synthesized under the same conditions as in Example 1 to obtain the active material powder.

[0309] (Comparative Example 1)

[0310] A titanium-niobium composite oxide having a composition represented by TiNb2O7 was synthesized as follows.

[0311] Titanium oxide and niobium oxide were prepared as raw materials. These raw materials were mixed in a predetermined composition ratio, and the mixture was dry-pulverized and mixed. The resulting mixed powder was then placed in an alumina crucible and calcined at 1100°C for 12 hours in an air atmosphere, followed by furnace cooling. The calcined product was dry-pulverized and classified to adjust the particle size. Oxide powder was obtained in the above manner.

[0312] (Examples 9-12)

[0313] The same steps as in Example 3 were performed except that the composition ratio of the raw materials was changed to synthesize Ti4Nb 10 Mo4O 45 、Ti2Nb 10 Mo2O 35 、Ti5Nb 10 Mo7O 55 and Ti7Nb 10 Mo7O 60 The titanium-niobium-molybdenum composite oxide having the composition shown in FIG.

[0314] <Measurement>

[0315] The powders obtained in each of the above examples and comparative examples were subjected to wide-angle X-ray scattering measurements. The measurements were performed according to the detailed procedures described above. The resulting spectra were analyzed using the Rietveld method for crystal structure analysis.

[0316] Figure 13-16 Part of each obtained spectrum is shown in . Figure 13 The spectrum of the composite oxide obtained in Example 1 is shown. Figure 14 The spectrum of the composite oxide obtained in Example 2 is shown. Figure 15 The spectrum of the composite oxide obtained in Example 3 is shown. Figure 16 The spectrum of the composite oxide obtained in Comparative Example 1 is shown.

[0317] The composite oxide obtained in Example 1 was analyzed based on the results of structural analysis. Figure 1 and Figure 2 The two mixed crystal structures of the phases of the crystal structures similar to the crystal structures shown respectively were identified. Specifically, the space group was assigned to I -4 (space group number: 82), that is, the block structure of rhenium oxide type containing a tetrahedral vertex-sharing structure is set to 4×4=16, and the ratio of the number of oxygen to the number of metal elements in the unit cell is set to A O / A M =2.59, and is assigned to the space group I - 4 (space group number: 82), that is, the block structure of rhenium oxide type without tetrahedral structure is set to 4×4=16, and the ratio of the number of oxygen to the number of metal elements in the unit cell is set to A O / A M = 2.50 as the inferred model. When such a crystal structure is used as the inferred model, the reliability factor of the Rietveld method, i.e., R, is obtained by performing the Rietveld method on all peaks except the heterogeneous phases appearing at 5° to 70°. wp The fitting value reached 9.86%, and the peak positions and relative intensities were confirmed to be consistent, so the structure was identified as the above-mentioned crystal structure.

[0318] The composition of each phase was determined to be Ti2Nb 10 W5O 44 and TiNb2WO 10 , and their respective components are contained in a composition ratio of 2:1.

[0319] The composite oxide obtained in Example 2 was analyzed based on the results of structural analysis. Figure 1 and Figure 2 The two mixed crystal structures of the phases of the crystal structures similar to the crystal structures shown respectively were identified. Specifically, the space group was assigned to I - 4 (space group number: 82), that is, the block structure of rhenium oxide type containing a tetrahedral vertex-sharing structure is set to 4×4=16, and the ratio of the number of oxygen to the number of metal elements in the unit cell is set to A O / A M = 2.59, and is assigned to P according to the space group label. - The crystal structure of 4n2 (space group number: 82), that is, the block structure of rhenium oxide type without tetrahedral structure is set to 4×4=16, and the ratio of the number of oxygen and the number of metal elements in the unit cell is set to A O / A M = 2.50 as the inferred model. When such a crystal structure is used as the inferred model, the reliability factor of the Rietveld method, i.e., R, is obtained by performing the Rietveld method on all peaks except the heterogeneous phases appearing at 5° to 70°. wp The fitting value reached 13.78%, and it was confirmed that the peak position and relative intensity were consistent, so it was identified as the above-mentioned crystal structure.

[0320] The composition of each phase was determined to be Ti2Nb 10 W5O 44 and TiNb2WO 10 , and their respective components are contained in a composition ratio of 1:9.

[0321] The composite oxide obtained in Example 3 was analyzed based on the results of structural analysis. Figure 3 The crystal structure similar to the crystal structure shown in Figure 1 was identified. Specifically, the space group label is assigned to I - 4 (space group number: 82), that is, the block structure of rhenium oxide type containing a tetrahedral vertex-sharing structure is set to 3×3=9, and the ratio of the number of oxygen to the number of metal elements in the unit cell is set to A O / A M = 2.56 as the inferred model. When such a crystal structure is used as the inferred model, the reliability factor of the Rietveld method, i.e., R, is obtained by performing the Rietveld method on all peaks except the heterogeneous phases appearing at 5° to 70°. wp The fitting value reached 9.92%, and the peak positions and relative intensities were confirmed to be consistent, so the structure was identified as the above-mentioned crystal structure.

[0322] The composite oxide obtained in Comparative Example 1 was identified as having a monoclinic crystal structure based on the results of structural analysis. Specifically, the composite oxide was assigned a space group notation of C2 / m (space group number: 12), i.e., a vertex-sharing structure without tetrahedrons, a block structure of rhenium oxide type with 3×3=9 elements, and a ratio of the number of oxygen to the number of metal elements in the unit cell of A. O / A M = 2.33 as the inferred model. When such a crystal structure is used as the inferred model, the reliability factor of the Rietveld method, i.e., R, is calculated for all peaks except for the heterogeneous phases appearing at 5° to 70°. wp The fitting value was 4.36%, and it was confirmed that there was no contradiction between the peak position and relative intensity, so it was identified as the above-mentioned crystal structure.

[0323] <Evaluation of Battery Performance>

[0324] Using the composite oxide powders obtained in the above-mentioned Examples and Comparative Examples as active materials, electrodes were prepared as follows.

[0325] First, 100 parts by mass of an active material, 6 parts by mass of a conductive agent, and 4 parts by mass of a binder were dispersed in a solvent to prepare a slurry. The active material used was a composite material powder obtained by the above method. 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.

[0326] Next, the obtained slurry is applied to one side of the current collector, and the coating is dried to form an active material layer. A 12 μm thick aluminum foil is used as the current collector. Next, the current collector and the active material layer are pressed to obtain an electrode. The unit area weight of the electrode is 60 g / m 2 .

[0327] Prepare a non-aqueous electrolyte as follows. Dissolve an electrolyte salt in an organic solvent to obtain a liquid non-aqueous electrolyte. Use LiPF6 as the electrolyte salt. Set the molar concentration of LiPF6 in the non-aqueous electrolyte to 1 mol / L. Use a mixed solvent of ethylene carbonate (EC) and diethyl carbonate (DEC) as the organic solvent. The volume ratio of EC to DEC is 1:2.

[0328] The electrode obtained by the above method is used as a working electrode, metal lithium foil is used as a counter electrode and a reference electrode, and the non-aqueous electrolyte prepared by the above method is used to prepare a three-electrode beaker cell.

[0329] The cycle performance of each battery produced was evaluated. Specifically, first, at a temperature of 25°C, the battery was charged at a charging current of 0.2C until the battery voltage reached 0.7V. Then, the battery was discharged at a discharge current of 0.2C until the battery voltage reached 3.0V. The charge and discharge capacity at this time was measured, and the capacity value per unit volume (excluding the collector) of the electrode containing the active material layer was calculated for charging and discharging respectively. In addition, the charge and discharge efficiency in the above-mentioned initial charge and discharge was calculated (initial charge and discharge efficiency = [(initial discharge capacity / initial charge capacity) × 100%]).

[0330] Figure 17-Figure 19 , a graph showing the initial charge and discharge curves of some beaker batteries is shown. Figure 17 The charge and discharge curves of the battery using the composite oxide obtained in Example 1 are shown by solid lines (charge curve 51 and discharge curve 61). Figure 17 The charge and discharge curves of the battery using the composite oxide obtained in Comparative Example 1 are also shown by dashed lines (charge curve 50 and discharge curve 60). Figure 18 The charge and discharge curves of the battery using the composite oxide obtained in Example 2 are shown by solid lines (charge curve 52 and discharge curve 62). Figure 19The charge and discharge curves of the battery using the composite oxide obtained in Example 3 are shown by solid lines (charge curve 53 and discharge curve 63). Figure 18 and Figure 19 In addition, the charge and discharge curves of the battery using the composite oxide obtained in Comparative Example 1 are shown by dashed lines (charge curve 50 and discharge curve 60).

[0331] The following Tables 1 and 2 summarize the composition and crystal structure details of the composite oxides synthesized in each Example and Comparative Example, as well as their performance as battery active materials. Specifically, the composite oxide composition, crystal structure, the number of rhenium oxide-type blocks per unit cell in the crystal structure, the number of oxygen per unit cell (A), and the like are shown as detailed in the composite oxide. O ) and the number of metal elements (A M ) than (A O / A M Ratio), peak intensity ratio I2 / I1 in the X-ray diffraction spectrum, and the type of added element. In addition, when no element is added, it is marked as "(none)" in the item of added element. As the performance of the battery active material, the charge capacity and discharge capacity per unit volume and the initial charge and discharge efficiency are shown. In addition, for Comparative Example 1, as shown in FIG. Figure 16 As shown, no peak was obtained in the range of 2θ=25.1±0.5° in the spectrum, and the I2 / I1 ratio could not be calculated. Therefore, "-" (not equivalent) was marked in the term of the I2 / I1 ratio.

[0332] The compositions of the composite oxides shown in Table 1 are obtained by multiplying the chemical formula by a certain coefficient so that the numerical value representing the stoichiometric ratio of the constituent elements is an integer. For example, in Examples 1 and 2, the composition of one phase is represented as Ti2Nb 10 W5O 44 , but this formula will be called Ti 0.4 Nb2WO 8.8 The chemical formula of is equal to the formula obtained by multiplying the chemical formula by a coefficient of 5. That is, the composite oxides synthesized in Examples 1 and 2 contain the same amount of available Li a Ti b Nb 2-2d M c+2d O 2b+5+3c The phase corresponding to the compound where M is W, a=0, b=0.4, c=1, and d=0 is shown. The composition of the other phase is TiNb2WO 10 , when the coefficient is 1 and no conversion is performed, it is the same as the general formula Li a Ti b Nb 2-2d M c+2d O 2b+5+3c Corresponding. Regarding TiNb5Mo2O in Example 320 , and will be called Ti 1 / 3 Nb 5 / 3 Mo 2 / 3 O 20 / 3 The chemical formula of is equal to the formula obtained by multiplying the coefficient 3. That is, the composite oxide synthesized in Example 3 is equal to the available Li a Ti b Nb 2-2d M c+2d O 2b+5+3c = 0, b = 1 / 3, c = 1 / 3 and d = 1 / 6. a Ti b Nb 2-2d M c+2d O 2b+5+3c Corresponding. Regarding Example 4-8, the composition without trace additive elements and substitution elements is shown. The composition of the composite oxide of Example 4-8 is the same as the composition of any composite oxide in Example 1-3, and is consistent with the general formula Li a Ti b Nb 2-2d M c+2d O 2b+5+3c correspond.

[0333]

[0334] The compositions of the composite oxides shown in Table 2 are also shown as formulas obtained by multiplying the chemical formula by a certain coefficient. 10 Mo4O 45 , corresponds to a compound with a coefficient of 5, M being Mo, a=0, b=0.8, c=0.8, and d=0. 10 Mo2O 35 , corresponds to a compound with a coefficient of 5, M being Mo, a=0, b=0.4, c=0.4, and d=0. 10 Mo7O 55 , corresponds to a compound with a coefficient of 6, M being Mo, a=0, b=5 / 6, c=5 / 6, and d=1 / 6. 10 Mo7O 60 , which corresponds to a compound having a coefficient of 5, M being Mo, a=0, b=7 / 5, c=7 / 5, and d=0.

[0335]

[0336] The active material obtained in Example 1-12 contains the composite oxide and the above-mentioned general formula Lia Ti b Nb 2- 2d M c+2d O 2b+5+3c (M = W, Mo, 0 ≤ a ≤ b + 4 + 3 c, 0 < b < 2-2 d, 0 < c < 2-4 d, regardless of the presence or absence of added elements). In contrast, the composite oxide obtained in Comparative Example 1 does not satisfy this general formula. As shown in Tables 1 and 2, the active materials of Examples 1-12 exhibit higher charge and discharge capacities than the composite oxide of Comparative Example 1. Furthermore, the initial charge and discharge efficiencies achieved with the active materials of Examples 1-12 are comparable to those achieved with the active material of Comparative Example 1.

[0337] Therefore, it is known that: it has a tetragonal crystal structure and can be used with the above general formula Li a Ti b Nb 2-2d M c+2d O 2b+5+3c The composite oxide represented by (M is W or Mo; 0≤a≤b+4+3c, 0<b<2-2d, 0<c<2-4d) shows good initial charge and discharge efficiency as an electrode active material and has a high charge and discharge capacity per unit volume.

[0338] According to one or more embodiments and examples described above, an active material containing a composite oxide can be provided. The composite oxide has a tetragonal crystal structure and can be represented by the general formula Li a Ti b Nb 2-2d M c+2d O 2b+5+3c Indicated. Here, M in the formula is any one selected from W and Mo. The subscripts in the formula satisfy the relationships 0≤a≤b+4+3c, 0<b<2-2d, and 0<c<2-4d. Such an active material can provide electrodes for high-capacity secondary batteries, high-capacity secondary batteries and battery packs, and vehicles equipped with such battery packs.

[0339] In addition, the above-mentioned embodiments can be summarized into the following technical solutions.

[0340] (Technical Solution 1)

[0341] An active material comprising a tetragonal crystal structure and a general formula Li a Ti b Nb 2-2d M c+2d O 2b+5+3c The composite oxide represented by , wherein M is any one selected from W and Mo, and 0≤a≤b+4+3c, 0<b<2-2d, and 0<c<2-4d.

[0342] (Technical Solution 2)

[0343] According to the above-mentioned technical solution 1, wherein M in the above-mentioned general formula is W, the above-mentioned composite oxide has the following crystal structure: an octahedral structure composed of oxygen and metal elements, and a rhenium oxide-type bulk structure composed of 16 of the above-mentioned octahedral structures in a vertex-sharing manner.

[0344] (Technical Solution 3)

[0345] According to the above-mentioned technical solution 1, wherein M in the above-mentioned general formula is Mo, the above-mentioned composite oxide has the following crystal structure: an octahedral structure composed of oxygen and metal elements, and a rhenium oxide-type bulk structure composed of 9 above-mentioned octahedral structures in a vertex-sharing manner.

[0346] (Technical Solution 4)

[0347] According to any one of the above-mentioned technical solutions 1 to 3, it further contains one or more elements selected from Ti, V, Ta, Fe, Bi, Sb, As, P, Cr, Mo, W, B, Na, K, Mg, Al, Ca, Y, Zr and Si.

[0348] (Technical Solution 5)

[0349] According to any one of the above-mentioned technical solutions 1 to 4, in the diffraction spectrum of powder X-ray diffraction using a Cu-Kα ray source, the peak intensity I1 of the highest intensity peak appearing in the range of 2θ=25.1±0.5° and the peak intensity I2 of the peak appearing in the range of 2θ=23.8±0.5° satisfy the relationship of 0.1≤I2 / I1≤1.0.

[0350] (Technical Solution 6)

[0351] An electrode comprising the active material according to any one of technical solutions 1 to 5.

[0352] (Technical Solution 7)

[0353] According to the above-mentioned technical solution 6, it includes an active material-containing layer containing the above-mentioned active material.

[0354] (Technical Solution 8)

[0355] A secondary battery comprising a positive electrode, a negative electrode, and an electrolyte, wherein the negative electrode is the electrode according to claim 6 or 7.

[0356] (Technical Solution 9)

[0357] A secondary battery comprising a positive electrode, a negative electrode, and an electrolyte, wherein the positive electrode is the electrode according to claim 6 or 7.

[0358] (Technical Solution 10)

[0359] A battery pack comprising the secondary battery described in technical solution 8 or 9 above.

[0360] (Technical Solution 11)

[0361] According to the above technical solution 10, an external terminal for conducting electricity and a protection circuit are further provided.

[0362] (Technical Solution 12)

[0363] According to the technical solution 10 or 11, a plurality of the secondary batteries are provided, and the secondary batteries are electrically connected in series, in parallel, or in a combination of series and parallel.

[0364] (Technical Solution 13)

[0365] A vehicle comprises the battery pack according to any one of technical solutions 10 to 12.

[0366] (Technical Solution 14)

[0367] According to the above technical solution 13, it includes a mechanism for converting the kinetic energy of the above vehicle into regenerative energy.

[0368] While 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 may be implemented in various other forms, and various omissions, substitutions, and modifications may be made without departing from the spirit of the invention. These embodiments and their variations are intended to be included within the scope and spirit of the invention, as well as within the invention set forth in the claims and their equivalents.

Claims

1. An active material comprising a Ti b Nb 2-2d M c+2d O 2b+5+3c The composite oxide represented by is any one selected from W and Mo, and 0≤a≤b+4+3c, 0<b<2-2d, and 0<c<2-4d, and the composite oxide has a tetragonal crystal structure.

2. The active material according to claim 1, wherein In the general formula, M is W, and the composite oxide has a crystal structure including an octahedral structure composed of oxygen and a metal element, and a rhenium oxide-type bulk structure in which 16 of the octahedral structures share vertices.

3. The active material according to claim 1, wherein In the general formula, M is Mo, and the composite oxide has a crystal structure including an octahedral structure composed of oxygen and a metal element, and a rhenium oxide-type bulk structure in which nine octahedral structures share vertices.

4. The active material according to any one of claims 1 to 3, wherein It further contains one or more elements selected from Ti, V, Ta, Fe, Bi, Sb, As, P, Cr, Mo, W, B, Na, K, Mg, Al, Ca, Y, Zr and Si, and the amount of the one or more elements is greater than 10 ppm and less than 10000 ppm in mass units.

5. The active material according to any one of claims 1 to 3, wherein In the diffraction spectrum obtained by powder X-ray diffraction using a Cu-Kα ray source, the peak intensity I1 of the highest peak appearing in the range of 2θ=25.1±0.5° and the peak intensity I2 of the peak appearing in the range of 2θ=23.8±0.5° satisfy the relationship 0.1≤I2 / I1≤1.

0.

6. An active material comprising a Ti b Nb 2-2d M c+2d O 2b+5+3c A substituted oxide obtained by replacing a part of the constituent elements of the represented composite oxide with one or more elements selected from Ti, V, Ta, Fe, Bi, Sb, As, P, Cr, Mo, W, B, Na, K, Mg, Al, Ca, Y, Zr and Si, M is any one selected from W and Mo, and 0≤a≤b+4+3c, 0<b<2-2d, 0<c<2-4d, and the composite oxide has a tetragonal crystal structure.

7. The active material according to claim 6, wherein The amount of the one or more elements is 10 ppm or more and 10,000 ppm or less in mass units. 8 . An electrode comprising the active material according to claim 1 .

9. The electrode according to claim 8, wherein The active substance-containing layer includes the active substance.

10. A secondary battery comprising a positive electrode, a negative electrode and an electrolyte, wherein: The negative electrode is the electrode according to claim 8 or 9.

11. A secondary battery comprising a positive electrode, a negative electrode and an electrolyte, wherein: The positive electrode is the electrode according to claim 8 or 9. 12 . A battery pack comprising the secondary battery according to claim 10 .

13. The battery pack according to claim 12, wherein: Further possess: External terminals for power supply, and Protection circuit.

14. The battery pack according to claim 12 or 13, wherein: A plurality of the secondary batteries are provided. The secondary batteries are electrically connected in series, in parallel, or in a combination of series and parallel. 15 . A vehicle comprising the battery pack according to claim 12 .

16. The vehicle of claim 15, wherein: Includes a mechanism for converting the kinetic energy of the vehicle into regenerative energy.

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