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

Abstract

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.SOLUTION: According to an embodiment, an active material is provided that includes a composite oxide having a monoclinic crystal structure. The composite oxide is represented by the general formula LixNb16-y-zMzW5+yO55-u, where M includes at least one element selected from the group consisting of Ta, Ti, Zr, Al, and Fe, and 0≤x≤5, -0.5≤y≤2, 0≤z≤2, and 4≤u≤9 are satisfied.SELECTED DRAWING: Figure 1

Description

[Technical Field]

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

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

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

[0004] Therefore, monoclinic niobium-titanium composite oxide TiNb2O7 is being investigated. +) while exhibiting high capacity. For this reason, it is expected that the volumetric energy density will exceed that of carbon-based anodes. However, in order to fully popularize electric vehicles, it is desirable to further increase the energy density of lithium-ion secondary batteries in order to improve driving range, and it is therefore desirable to develop even higher-capacity, fast-charging batteries. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Publication No. 2022-145421 [Patent Document 2] Japanese Patent Application Publication No. 2023-133954 [Patent Document 3] Special Publication No. 2023-501077 [Patent Document 4] Special Publication No. 2023-501778 [Patent Document 5] Special Publication No. 2023-501888 [Non-patent literature]

[0006] [Non-Patent Document 1] "Practice of Powder X-ray Analysis" First Edition (2002) Edited by the X-ray Analysis Research Forum of the Japan Society for Analytical Chemistry, edited by Izumi Nakai and Fujio Izumi (Asakura Shoten) Summary of the Invention [Problem to be solved by the invention]

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

[0008] According to an embodiment, an active material is provided that includes a composite oxide having a monoclinic crystal structure. The composite oxide has the general formula Li x Nb 16-y-z M z W 5+y O 55-u where M includes at least one selected from the group consisting of Ta, Ti, Zr, Al, and Fe, and 0≦x≦5, −0.5≦y≦2, 0≦z≦2, and 4≦u≦9.

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

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

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

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

[0013] [Figure 1] 1 is a cross-sectional view schematically illustrating an example of a secondary battery according to an embodiment. [Figure 2] FIG. 2 is an enlarged cross-sectional view of part A of the secondary battery shown in FIG. [Figure 3] FIG. 10 is a partially cutaway perspective view schematically showing another example of a secondary battery according to an embodiment. [Figure 4] FIG. 4 is an enlarged cross-sectional view of part B of the secondary battery shown in FIG. [Figure 5] FIG. 1 is a perspective view schematically illustrating an example of a battery pack according to an embodiment. [Figure 6] FIG. 1 is an exploded perspective view schematically showing an example of a battery pack according to an embodiment. [Figure 7] FIG. 7 is a block diagram showing an example of an electrical circuit of the battery pack shown in FIG. 6. [Figure 8] 1 is a partially see-through view schematically illustrating an example of a vehicle according to an embodiment. [Figure 9] 1 is a diagram illustrating an example of a control system for an electrical system in a vehicle according to an embodiment; [Figure 10] 2 is a graph showing a spectrum obtained by wide-angle X-ray scattering measurement of the active material composite oxide in Example 1. [Figure 11] 4 is a graph showing a spectrum obtained by wide-angle X-ray scattering measurement of the active material composite oxide in Example 2. [Figure 12] 10 is a graph showing a spectrum obtained by wide-angle X-ray scattering measurement of the active material composite oxide in Example 3. [Figure 13] 10 is a graph showing a spectrum obtained by wide-angle X-ray scattering measurement of the active material composite oxide in Example 4. [Figure 14] 10 is a graph showing a spectrum obtained by wide-angle X-ray scattering measurement of the active material composite oxide in Example 5. [Figure 15] 10 is a graph showing a spectrum obtained by wide-angle X-ray scattering measurement of the active material composite oxide in Example 6. [Figure 16] 10 is a graph showing a spectrum obtained by wide-angle X-ray scattering measurement of the active material composite oxide in Example 7. [Figure 17] 10 is a graph showing a spectrum obtained by wide-angle X-ray scattering measurement of the active material composite oxide in Example 8. [Figure 18] 10 is a graph showing a spectrum obtained by wide-angle X-ray scattering measurement of the active material composite oxide in Example 9. [Figure 19] 10 is a graph showing a spectrum obtained by wide-angle X-ray scattering measurement of the active material composite oxide in Example 10. [Figure 20] 10 is a graph showing a spectrum obtained by wide-angle X-ray scattering measurement of the active material composite oxide in Example 11. [Figure 21] 1 is a graph showing a spectrum obtained by wide-angle X-ray scattering measurement of the active material composite oxide in Comparative Example 1. DETAILED DESCRIPTION OF THE INVENTION

[0014] To obtain a high-capacity material, it is desirable to select a material that has a large amount of charge compensation when carrier ions (e.g., lithium ions) are inserted. For this purpose, a composite oxide containing tungsten (W), a hexavalent element, can be used as a compound with even higher capacity. For example, WNb is a tungsten-niobium composite oxide material with a high W ratio. 18 O 69 and W5Nb 16 O 55 There are compounds having a crystal structure represented by the formula:

[0015] Hereinafter, embodiments will be described with reference to the drawings. In the following description, components that perform the same or similar functions are designated by the same reference numerals throughout the drawings, and duplicate descriptions will be omitted. Each drawing is a schematic diagram for explaining and facilitating understanding of the embodiments, and the shapes, dimensions, ratios, etc. may differ from those of an actual device. However, these may be appropriately modified in design, taking into consideration the following description and known techniques.

[0016] (First embodiment) According to a first embodiment, an active material is provided that includes a composite oxide having a monoclinic crystal structure. The composite oxide has the general formula Li x Nb 16-y-z M z W 5+y O 55-u In the general formula, M includes at least one selected from the group consisting of Ta, Ti, Zr, Al, and Fe. The subscripts in the formula satisfy the following conditions: 0≦x≦5, −0.5≦y≦2, 0≦z≦2, 4≦u≦9. As will be described later, this active material can contain trace amounts of other elements, and the first embodiment also includes a form in which these trace elements are contained in the composite oxide as substitution elements. However, the general formula above represents a composition in which such minor substitution elements are omitted.

[0017] The active material may be a battery active material. For example, the active material may be an electrode active material used in an electrode of a secondary battery such as a lithium ion battery or a non-aqueous electrolyte battery. More specifically, the active material may be a negative electrode active material used in a negative electrode of a secondary battery.

[0018] The above general formula Li x Nb 16-y-z M z W 5+y O 55-u (M is at least one of Ta, Ti, Zr, Al, and Fe; 0≦x≦5, −0.5≦y≦2, 0≦z≦2, 4≦u≦9; hereafter omitted), and by using a composite oxide with a monoclinic crystal structure as an electrode active material, a high-capacity secondary battery can be realized.

[0019] <Active material> The monoclinic composite oxide contained in the active material according to the first embodiment corresponds to a part of oxide materials having a Wadsley-Roth phase structure, which is a crystalline phase in oxide materials containing niobium. The Wadsley-Roth phase has a crystal structure in which a vertex-sharing structure of oxygen-metal octahedra forms a rhenium oxide-type block structure, and the rhenium oxide-type blocks (ReO3-type blocks) are connected in a three-dimensional direction by sharing the edges of the octahedra or by vertex-sharing between tetrahedra.

[0020] W5Nb is reported as an example of a tungsten-niobium composite oxide with a Wadsley-Roth phase structure. 16 O 55 It is expected that W3Nb will have a high capacity due to its high atomic weight and high valence of W. When attempting to synthesize this oxide by normal firing, W is easily evaporated during firing, so W3Nb 14 O 44 Such a material with a reduced W content results in a lower capacity.

[0021] As a result of improving the capacity by improving the synthesis process of tungsten-niobium composite oxide, the active material according to the first embodiment was discovered. Specifically, this active material achieves improved capacity through a highly airtight sintering process. By performing sintering under conditions that enhance airtightness, it is possible to suppress W volatilization and increase oxygen defects in the resulting oxide. By suppressing W volatilization, W3Nb 14 O 44 This can suppress the formation of low-capacity heterophases such as those described above. Increasing the oxygen vacancies can improve the conductivity of the oxide. Therefore, if the concentration of oxygen vacancies in the oxide is high (for example, 4≦u≦9), an active material with excellent reversible capacity can be obtained. For these reasons, niobium-tungsten composite oxides with improved capacity can be obtained by synthesizing them using a highly sealed firing process.

[0022] In the powder X-ray diffraction spectrum of the active material, the peak intensity I of the most intense peak appearing within the range of 2θ = 24.2 ± 0.3° 24 and the peak intensity I of the peak appearing within the range of 2θ = 24.8 ± 0.3° 25 Intensity ratio I between 24 / I 25 However, 0.5≦I 24 / I 25 In addition, in the diffraction spectrum of the active material by powder X-ray diffraction, the peak intensity I of the most intense peak appearing in the range of 2θ=19.7±0.5° is preferably in the range of ≦1.5. 20 and the peak intensity I of the peak appearing within the range of 2θ = 24.8 ± 0.3° 25 Intensity ratio I between 20 / I 25 However, 0.1≦I 20 / I 25 It is preferable that the ratio is in the range of ≦0.5.

[0023] Peak intensity I of the most intense peak at 2θ = 24.2 ± 0.3° 24 The higher the W5Nb 16 O 55Similarly, the peak intensity I of the most intense peak at 2θ=19.7±0.5° is 20 The high peak intensity I also indicates that there is a large amount of high-capacity crystalline phase in the active material. 24 and I 20 is W3Nb 14 O 44 Therefore, the intensity ratio I 24 / I 25 The active material having an intensity ratio I 20 / I 25 In an active material having a valence of 0.05 to 0.15, a high-capacity crystalline phase is abundant and a low-capacity heterophase is scarce, making it possible to realize a high-capacity secondary battery.

[0024] General formula Li x Nb 16-y-z M z W 5+y O 55-u As shown in the figure, the niobium-tungsten composite oxide can contain, in addition to niobium and tungsten, a metal element M as a third metal element. Among Ta, Ti, Zr, Al, and Fe, it is preferable to contain Ta (tantalum) or Ti (titanium) as the metal element M. In a composite oxide in which M is Ta, the cycle performance of the battery is further improved. In a composite oxide in which M is Ti, the rapid discharge performance (discharge rate performance) of the battery is further improved.

[0025] In addition to the metal element M (Ta, Ti, Zr, Al, Fe), the active material may further contain at least one element selected from the group consisting of Sc, Y, V, Cr, Co, Mn, and Ga. The content of one or more elements selected from the group consisting of Sc, Y, V, Cr, Co, Mn, and Ga is preferably small. Specifically, the active material may contain at least one element selected from the group consisting of Sc, Y, V, Cr, Co, Mn, and Ga, represented by the general formula Li x Nb 16-y-z M z W 5+y O 55-uThe active material according to the first embodiment has a composite oxide composition represented by the general formula Li x Nb 16-y-z M z W 5+y O 55-u Although the general formula is expressed as follows, it does not exclude substituted composite oxides containing minor substitution elements incorporated into their crystal structure. Naturally, trace elements not incorporated into the crystal structure of the composite oxide are not expressed in the general formula above, but the active material according to the first embodiment also includes forms containing the above elements Sc, Y, V, Cr, Co, Mn or Ga in addition to the composite oxide. The active material according to the first embodiment is an unsubstituted Li oxide that does not contain the above minor substitution elements. x Nb 16-y-z M z W 5+y O 55-u It may also be a composite oxide.

[0026] The active material according to the first embodiment may be in the form of particles. That is, the active material may be composed of particles of a composite oxide represented by the general formula and having a monoclinic crystal structure. The active material may be a single primary particle, a secondary particle formed by agglomeration of multiple primary particles, or a mixture thereof.

[0027] The average primary particle size of the active material is preferably 10 μm or less, more preferably 5 μm or less, and even more preferably 3 μm or less. When the average primary particle size of the active material is small, the diffusion distance of lithium ions within the primary particles is short, which tends to increase lithium ion diffusibility. Furthermore, when the average primary particle size of the active material is small, the reaction area increases, which increases the reactivity between the active material and lithium ions and tends to improve the lithium ion insertion / extraction reaction.

[0028] The average secondary particle diameter of the active material is preferably 1 μm or more and 50 μm or less. By setting the average secondary particle diameter of the active material within this range, productivity during electrode production can be improved and batteries with good performance can be obtained. This average secondary particle diameter refers to the particle size at which the volume cumulative value is 50% in the particle size distribution determined by a laser diffraction particle size distribution analyzer.

[0029] The BET specific surface area of ​​the active material is 3.0 m 2 / g or more 120m 2 / g or less is desirable, and 4.0m 2 / g or more 110m 2 / g or less is more preferable. Using an active material with a high specific surface area can improve the discharge rate performance of the battery. Furthermore, using an active material with a low specific surface area can improve the life performance of the battery and can improve the coatability of a slurry containing the active material in the electrode manufacturing process described later in the second embodiment.

[0030] The BET specific surface area refers to the specific surface area determined by the nitrogen BET (Brunauer, Emmet and Teller) method. The method for determining the specific surface area based on this nitrogen BET method will be described in detail later.

[0031] <Manufacturing method> The active material according to the first embodiment can be produced as follows.

[0032] For example, a composite oxide can be synthesized by a solid-state reaction, but firing is carried out under tightly sealed conditions to suppress the volatilization of tungsten (W) and increase oxygen vacancies.

[0033] Niobium compounds, tungsten compounds, and compounds of metal elements M (Ta, Ti, Zr, Al, Fe) are used as starting materials. Examples of niobium compounds include niobium hydroxide and niobium oxide. Examples of tungsten compounds include ammonium paratungstate and its hydrate, ammonium tungstate and its hydrate, tungsten hydroxide, and tungsten oxide. Examples of compounds of metal elements M include hydroxides and oxides of the corresponding metals.

[0034] For example, powdered materials are used as starting materials. After weighing out the starting materials in a predetermined composition ratio, the materials are thoroughly mixed. Mixing can be done by either a wet method or a dry method. If wet mixing is performed, the materials are thoroughly dried after mixing. After mixing the materials, they are press-molded into, for example, pellets. The resulting molded product is wrapped in foil made of a heat-resistant material such as platinum (Pt), and then stored in an airtight container to enhance its airtightness and then fired.

[0035] The calcination can include pre-calcination before the main calcination. The calcination is preferably carried out at a temperature of 600°C or higher and 800°C or lower for a calcination time of 5 hours to 20 hours. This range of calcination temperature and calcination time allows the solid-state reaction to proceed. By allowing the reaction to proceed in advance through pre-calcination before the main calcination, it is possible to increase reactivity.

[0036] The firing temperature is preferably 1100°C or higher and 1400°C or lower, and the firing time is preferably 5 hours or higher and 20 hours or lower. Within this firing temperature and firing time range, it is possible to proceed with a solid-state reaction and obtain the desired crystalline phase.

[0037] After firing, the fired product is pulverized in a pulverizer until it has a predetermined average particle size, thereby obtaining an active material in the form of particles or powder, for example.

[0038] <Various measurement methods> The measurement methods for the active material will be described below. Specifically, the confirmation 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 will be described.

[0039] When the active material contained in a battery electrode is used as a sample, the measurement sample is prepared by pre-treating it using the following method. First, the battery is fully discharged. Next, the battery is disassembled in a glove box under an argon atmosphere, and the electrodes are removed. The removed electrodes are then washed using a solvent such as ethyl methyl carbonate. Further processing is performed for each measurement to prepare a sample in an appropriate form.

[0040] (Confirmation of complex oxides) The active material has the above-mentioned monoclinic crystal structure and has the general formula Li x Nb 16-y-z M z W 5+y O 55-u The presence of a complex oxide represented by the formula (I) can be confirmed by combining wide-angle X-ray diffraction (XRD), inductively coupled plasma (ICP) optical emission spectroscopy, and inert gas dissolution-infrared absorption spectroscopy. The crystal structure can be determined by wide-angle XRD, and the elemental composition can be determined by ICP optical emission spectroscopy and inert gas dissolution-infrared absorption spectroscopy.

[0041] XRD measurement is performed as follows. First, the active material particles are thoroughly pulverized to obtain a powdered sample. The average particle size of the powdered sample is preferably 20 μm or less. This average particle size can be determined using a laser diffraction particle size distribution analyzer.

[0042] Next, the powdered sample is filled into the holder portion of a glass sample plate, and the surface is flattened. For example, the glass sample plate may have a holder portion with a depth of 0.2 mm.

[0043] Next, the glass sample plate is placed in a powder X-ray diffractometer, and the XRD spectrum is measured using Cu-Kα radiation. Specific measurement conditions are, for example, as follows: X-ray diffraction equipment: Rigaku Corporation SmartLab X-ray source: CuKα ray Output: 40kV, 200mA Package measurement name: General purpose measurement (concentration method) Incident parallel slit aperture angle: 5° Incident length limiting slit length: 10 mm Photosensitive PSA: None Receiving parallel slit aperture angle: 5° Monochromatization method: Kβ filter method Measurement mode: Continuous Entrance slit width: 0.5° Receiving slit width: 20 mm Measurement range (2θ): 5° to 70° Sampling width (2θ): 0.01° Scan speed: 1° ~ 20° / min.

[0044] In this way, an XRD spectrum of the active material is obtained. In this XRD spectrum, the horizontal axis represents the angle of incidence (2θ) and the vertical axis represents the diffraction intensity (cps). The scan speed can be adjusted so that the count number of the main peak in the XRD spectrum is between 50,000 and 150,000.

[0045] When the active material contained in a battery electrode is used as a sample, the electrode after cleaning obtained by the above-mentioned pretreatment is cut into a piece having an area approximately equal to the area of ​​the glass sample plate holder to be used as a measurement sample.

[0046] Next, the obtained measurement sample is directly attached to a glass holder and subjected to XRD measurement. Next, materials other than the active material that may be contained in the electrode, such as the current collector, conductive agent, and binder, are measured using XRD to determine the XRD patterns derived from these. Next, if there are peaks in the measurement sample that overlap with peaks derived from the active material and peaks derived from other materials, the peaks derived from the materials other than the active material are separated. In this way, an XRD spectrum of the active material is obtained.

[0047] To confirm whether the crystal structure of the measured sample belongs to the monoclinic crystal structure described above, the Rietveld method is used. For example, RIETAN-FP is used as an analysis program, and the reliability factor R wp This can be confirmed by confirming that the value is at least 20% or less, more preferably 15% or less. At this time, if there are peaks containing impurities and they overlap with the phase to be analyzed, the accuracy of the analysis may be deteriorated. In this case, it is preferable to perform an analysis in which the areas that clearly overlap with the peaks derived from impurities are excluded from the analysis range. However, this does not apply when the sample contains materials other than the active material according to the first embodiment, when the sample has a significantly high orientation, or when coarse particles are mixed in, as the intensity ratio changes. The structure can be confirmed by confirming that there are no inconsistencies in the positions and relative intensities of all peaks attributed to the crystal structure. Furthermore, when the spectral intensity is low and the background intensity is low, R wp The reliability factor may be small, and its absolute value is not significant, but rather it is meaningful to judge the relative quality of the fit under certain measurement conditions.

[0048] The analytical method using RIETAN-FP is explained in detail, for example, in Chapter 9, "Let's try using RIETAN-FP," of Non-Patent Document 1 ("Practicalities of Powder X-Ray Analysis," First Edition (2002), edited by the X-Ray Analysis Research Forum of the Japan Society for Analytical Chemistry, edited by Nakai Izumi and Izumi Fujio (Asakura Publishing)).

[0049] RIETAN-FP is a Rietveld analysis program that is distributed free of charge (as of February 2024) on its developer's online webpage (http: / / fujioizumi.verse.jp / ).

[0050] The content of each element in the active material particles contained in the sample can be confirmed by ICP atomic emission spectrometry for metal elements, and quantification of the O element can be performed by inert gas dissolution-infrared absorption spectroscopy, but precise quantification is difficult.

[0051] After the above-described pretreatment, the active material particles contained in the electrode are further subjected to the following treatment. After the cleaning, a member containing the active material (e.g., the active material-containing layer described in the second embodiment) is peeled off from the electrode's current collector, for example. The part peeled off from the electrode is heated in the atmosphere for a short time (at 500°C for about 1 hour) to burn off unnecessary parts such as binder components and carbon. The content of each element can then be quantified by ICP emission spectrometry or the like.

[0052] (Measurement of average particle size) The average primary particle size of the active material can be determined by observation using a scanning electron microscope (SEM). Specifically, the average primary particle size determined by SEM observation can be calculated by the following method.

[0053] First, the length of the longest axis and the length of the shortest axis of the primary particles in the SEM image obtained by SEM observation are measured, and the arithmetic mean of these is taken as the primary particle diameter. This measurement of the primary particle diameter is performed on 100 randomly selected particles, and the mean value of these is taken as the average primary particle diameter.

[0054] The average secondary particle diameter of the active material can be determined from the particle size distribution measured using a laser diffraction particle size distribution analyzer. The sample used for this particle size distribution measurement is a dispersion diluted with N-methyl-2-pyrrolidone to a concentration of 0.1% to 1% by mass of the active material. The particle diameter at which the volumetric cumulative value reaches 50% in the obtained particle size distribution is defined as the average secondary particle diameter.

[0055] (BET specific surface area measurement) The BET specific surface area of ​​the active material particles can be determined by the following method.

[0056] First, 4 g of active material is collected as a sample. Next, a test cell for the measurement device is degassed by drying under reduced pressure at a temperature of 100°C or higher for 15 hours. A 1 / 2-inch test cell can be used as the test cell. The sample is then placed in the measurement device. For example, a Shimadzu Micromeritics Tristar II 3020 can be used as the test device. Next, the nitrogen gas pressure P (mmHg) is gradually increased in nitrogen gas at 77 K (the boiling point of nitrogen), and the nitrogen gas 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 P (mmHg) of nitrogen gas, P / P. The relative pressure P / P is calculated as P / P. The nitrogen gas adsorption amount is plotted against each relative pressure P / P to obtain an adsorption isotherm. A BET plot is then calculated from the nitrogen adsorption isotherm and the BET equation, and the specific surface area is calculated using this BET plot. The BET plot is calculated using the BET multipoint method.

[0057] The active material according to the first embodiment has a monoclinic crystal structure and is represented by the general formula Li x Nb 16-y-z M z W 5+y O 55-uIn the above general formula, M includes at least one selected from the group consisting of Ta, Ti, Zr, Al, and Fe. The subscripts x, y, z, and u are numbers that satisfy the following conditions: 0≦x≦5, −0.5≦y≦2, 0≦z≦2, and 4≦u≦9. An electrode using the above composite oxide as an electrode active material has a high capacity per volume. Furthermore, a secondary battery and a battery pack using the above composite oxide as an electrode active material have a high capacity per volume. In other words, such an active material exhibits a high capacity.

[0058] (Second embodiment) According to a second embodiment, an electrode is provided.

[0059] The electrode according to the second embodiment includes the active material according to the first embodiment. This electrode may be a battery electrode containing the active material according to the first embodiment as a battery active material. The electrode as a battery electrode may be, for example, a negative electrode containing the active material according to the first embodiment as a negative electrode active material. Alternatively, the electrode may be a positive electrode containing the active material according to the first embodiment as a positive electrode active material.

[0060] The electrode according to the second embodiment can include a current collector and an active material-containing layer. The active material-containing layer can be formed on one or both sides of the current collector. The active material-containing layer can include an active material and, optionally, a conductive agent and a binder.

[0061] The active material-containing layer may contain the active material according to the first embodiment alone, or may contain two or more types of active materials according to the first embodiment. Furthermore, the active material-containing layer may contain a mixture of one or more active materials according to the first embodiment and one or more other active materials. It is desirable that the content of the active material according to the first embodiment relative to the total mass of the active material according to the first embodiment and the other active materials be 10% by mass or more and 100% by mass or less.

[0062] For example, when the active material according to the first embodiment is contained as a negative electrode active material, examples of other active materials include lithium titanate having a ramsdellite structure (e.g., Li 2+xTi3O7, 0≦x≦3), lithium titanates with spinel structure (e.g., Li 4+x Ti5O 12 , 0≦x≦3), monoclinic titanium dioxide (TiO2), anatase titanium dioxide, rutile titanium dioxide, hollandite titanium composite oxide, orthorhombic titanium composite oxide, monoclinic niobium titanium composite oxide, niobium oxide, niobium titanium oxide, and niobium molybdenum composite oxide.

[0063] As an example of the above orthorhombic titanium-containing composite oxide, Li 2+e M2 2-f Ti 6-g M3 h O 14+σ Here, M2 is at least one selected from the group consisting of Sr, Ba, Ca, Mg, Na, Cs, Rb, and K. M3 is at least one selected from the group consisting of Zr, Sn, V, Nb, Ta, Mo, W, Y, Fe, Co, Cr, Mn, Ni, and Al. The subscripts in the composition formula are 0≦e≦6, 0≦f<2, 0≦g<6, 0≦h<6, and -0.5≦σ≦0.5. Specific examples of orthorhombic titanium-containing composite oxides include Li 2+e Na2Ti6O 14 (0≦e≦6).

[0064] As an example of the monoclinic niobium titanium composite oxide, Li x Ti 1-y M4 y Nb 2-z M5 z O 7+δ Here, M4 is at least one selected from the group consisting of Zr, Si, and Sn. M5 is at least one selected from the group consisting of V, Ta, and Bi. The subscripts in the composition formula are 0≦x≦5, 0≦y<1, 0≦z<2, and −0.3≦δ≦0.3. Specific examples of monoclinic niobium titanium composite oxides include Li x Examples include Nb2TiO7 (0≦x≦5).

[0065] Another example of monoclinic niobium titanium composite oxide is Li x Ti 1-y M6 y+z Nb 2-z O 7-δ Here, M6 is at least one selected from the group consisting of Mg, Fe, Ni, Co, W, Ta, and Mo. The subscripts in the composition formula are 0≦x<5, 0≦y<1, 0≦z<2, and −0.3≦δ≦0.3.

[0066] The conductive agent is blended to improve current collection performance and reduce contact resistance between the active material and the current collector. Examples of conductive agents include carbonaceous materials such as vapor-grown carbon fiber (VGCF), carbon black such as acetylene black, graphite, carbon nanotubes, and carbon nanofibers. One of these may be used as the conductive agent, or two or more may be used in combination. Alternatively, instead of using a conductive agent, the surfaces of the active material particles may be coated with carbon or an electronically conductive inorganic material. Furthermore, the current collection performance of the active material-containing layer can be improved by using a conductive agent and coating the active material surface with carbon or a conductive material.

[0067] The binder is blended to fill gaps between the dispersed active materials and to bind the active materials and the current collector. Examples of binders include polytetrafluoroethylene (PTFE), polyvinylidene fluoride (PVdF), fluorine-containing rubber, styrene-butadiene rubber, polyacrylic acid compounds, imide compounds, carboxymethyl cellulose (CMC), and CMC salts. One of these may be used as the binder, or two or more may be used in combination as the binder.

[0068] The blending ratios of the active material, conductive agent, and binder in the active material-containing layer can be appropriately changed depending on the application of the electrode. For example, when the electrode is used as the negative electrode of a secondary battery, the active material (negative electrode active material), conductive agent, and binder are preferably blended in proportions of 68% by mass to 96% by mass, 2% by mass to 30% by mass, and 2% by mass to 30% by mass, respectively. By setting the amount of conductive agent to 2% by mass or more, the current collection performance of the active material-containing layer can be improved. Furthermore, by setting the amount of binder to 2% by mass or more, sufficient binding between the active material-containing layer and the current collector can be achieved, and excellent cycle performance can be expected. On the other hand, it is preferable to set the amount of conductive agent and binder to 30% by mass or less, respectively, in order to achieve high capacity.

[0069] When the surface of the active material is coated with carbon or a conductive material, the amount of the coating material can be considered to be included in the amount of conductive material. The amount of carbon or conductive material coated is preferably 0.5% by mass or more and 5% by mass or less. A coating amount within this range can improve current collection performance and electrode density.

[0070] The current collector is made of a material that is electrochemically stable at the potential at which lithium (Li) is inserted into and extracted from the active material. For example, when the active material is used as a negative electrode active material, the current collector is preferably made of copper, nickel, stainless steel, aluminum, or an aluminum alloy containing one or more elements selected from the group consisting of Mg, Ti, Zn, Mn, Fe, Cu, and Si. The thickness of the current collector is preferably 5 μm or more and 20 μm or less. A current collector having such a thickness can balance the strength and weight of the electrode.

[0071] The current collector may also include a portion on the surface of which no active material-containing layer is formed, and this portion can function as a current collecting tab.

[0072] The electrode can be produced, for example, by the following method. First, an active material, a conductive agent, and a binder are suspended in a solvent to prepare a slurry. This slurry is applied to one or both sides of a current collector. Next, the applied slurry is dried to obtain a laminate of an active material-containing layer and a current collector. After that, this laminate is pressed. In this manner, the electrode is produced.

[0073] Alternatively, the electrode may be fabricated by the following method: First, the active material, the conductive agent, and the binder are mixed to obtain a mixture, and then the mixture is formed into pellets. The pellets are then placed on a current collector to obtain an electrode.

[0074] The electrode according to the second embodiment contains the active material according to the first embodiment, and therefore the electrode according to the second embodiment can realize a secondary battery with a high capacity per volume.

[0075] (Third embodiment) According to a third embodiment, a secondary battery is provided that includes a negative electrode, a positive electrode, and an electrolyte. This secondary battery includes the electrode according to the second embodiment as the negative electrode, the positive electrode, or both the negative electrode and the positive electrode. That is, the secondary battery according to the third embodiment includes, as a battery electrode, an electrode that includes the active material according to the first embodiment as a battery active material. A secondary battery according to a desirable aspect includes, as a negative electrode, an electrode according to the second embodiment. That is, a secondary battery according to a desirable aspect includes, as a negative electrode, an electrode that includes the active material according to the first embodiment as a battery active material. Desired aspects will be described below.

[0076] The secondary battery may further include a separator disposed between the positive electrode and the negative electrode. The negative electrode, the positive electrode, and the separator may constitute an electrode assembly. The electrolyte may be held in the electrode assembly.

[0077] Moreover, such a secondary battery can further include an exterior member that houses the electrode group and the electrolyte.

[0078] Furthermore, such a secondary battery may further include a negative electrode terminal electrically connected to the negative electrode and a positive electrode terminal electrically connected to the positive electrode.

[0079] Such a secondary battery may be, for example, a lithium secondary battery. The secondary battery also includes a non-aqueous electrolyte secondary battery containing a non-aqueous electrolyte.

[0080] The negative electrode, positive electrode, electrolyte, separator, exterior member, negative electrode terminal, and positive electrode terminal will be described in detail below.

[0081] 1) Negative electrode The negative electrode may include a negative electrode current collector and a negative electrode active material-containing layer. The negative electrode current collector and the negative electrode active material-containing layer may be the current collector and the active material-containing layer, respectively, that can be included in the electrode according to the second embodiment. The negative electrode active material-containing layer contains the active material according to the first embodiment as the negative electrode active material.

[0082] Details of the negative electrode that overlap with those described in the second embodiment will be omitted.

[0083] The density of the negative electrode active material-containing layer (excluding the current collector) is 1.8 g / cm 3 More than 2.8g / cm 3 A negative electrode having a negative electrode active material-containing layer with a density within this range is excellent in energy density and electrolyte retention. The density of the negative electrode active material-containing layer is preferably 2.1 g / cm or less. 3 More than 2.6g / cm 3 More preferably, it is:

[0084] The negative electrode can be produced, for example, by the same method as that for the electrode according to the second embodiment.

[0085] 2) Positive electrode The positive electrode may include a positive electrode current collector and a positive electrode active material-containing layer. The positive electrode active material-containing layer may be formed on one or both sides of the positive electrode current collector. The positive electrode active material-containing layer may include a positive electrode active material and, optionally, a conductive agent and a binder.

[0086] As the positive electrode active material, for example, an oxide or a sulfide can be used. The positive electrode may contain, as the positive electrode active material, one type of compound alone, or may contain a combination of two or more types of compounds. Examples of the oxide and the sulfide include compounds into which Li or Li ions can be inserted and extracted.

[0087] Examples of such compounds include, for example, manganese dioxide (MnO2), iron oxide, copper oxide, nickel oxide, lithium manganese composite oxide (e.g., Li x Mn2O4 or Li x MnO2; 0 < x ≦ 1), lithium nickel composite oxide (e.g., Li x NiO2; 0 < x ≦ 1), lithium cobalt composite oxide (e.g., Li x CoO2; 0 < x ≦ 1), lithium nickel cobalt composite oxide (e.g., Li x Ni 1-y Co y O2; 0 < x ≦ 1, 0 < y < 1), lithium manganese cobalt composite oxide (e.g., Li x Mn y Co 1-y [[ID=​​​​​​​​​​​​​​​​​​​​​​​​​​​Among the above, examples of more preferable compounds as the positive electrode active material include lithium manganese composite oxides having a spinel structure (for example, Li x Mn2O4; 0 < x ≦ 1), lithium nickel composite oxides (for example, Li x NiO2; 0 < x ≦ 1), lithium cobalt composite oxides (for example, Li x CoO2; 0 < x ≦ 1), lithium nickel cobalt composite oxides (for example, Li x Ni 1-y Co y O2; 0 < x ≦ 1, 0 < y < 1), lithium manganese nickel composite oxides having a spinel structure (for example, Li x Mn 2-y Ni y O4; 0 < x ≦ 1, 0 < y < 2), lithium manganese cobalt composite oxides (for example, Li x Mn y Co 1-y O2; 0 < x ≦ 1, 0 < y < 1), lithium iron phosphate (for example, Li x FePO4; 0 < x ≦ 1), and lithium nickel cobalt manganese composite oxides (Li x Ni 1-y-z Co y Mn z O2; 0 < x ≦ 1, 0 < y < 1, 0 < z < 1, y + z < 1) are included. When these compounds are used as the positive electrode active material, the positive electrode potential can be increased.

[0089] When a room temperature molten salt is used as the electrolyte of the battery, it is preferable to use a positive electrode active material containing lithium iron phosphate, Li x 0]VPO4F (0 ≦ x ≦ 1), a lithium manganese composite oxide, a lithium nickel composite oxide, a lithium nickel cobalt composite oxide, or a mixture thereof. Since these compounds have low reactivity with the room temperature molten salt, the cycle life can be improved. Details of the room temperature molten salt will be described later.

[0090] The primary particle size of the positive electrode active material is preferably 100 nm or more and 1 μm or less. A positive electrode active material with a primary particle size of 100 nm or more is easy to handle in industrial production. A positive electrode active material with a primary particle size of 1 μm or less allows lithium ions to diffuse smoothly within the solid.

[0091] The specific surface area of ​​the positive electrode active material is 0.1 m 2 / g or more 10m 2 / g or less is preferable. 2 A positive electrode active material with a specific surface area of ​​10m / g or more can secure sufficient sites for absorbing and releasing Li ions. 2 A positive electrode active material having a specific surface area of ​​0.15g / g or less is easy to handle in industrial production and can ensure good charge-discharge cycle performance.

[0092] The binder is blended to fill gaps between the dispersed positive electrode active material and to bind the positive electrode active material and the positive electrode current collector. Examples of binders include polytetrafluoroethylene (PTFE), polyvinylidene fluoride (PVdF), fluorine-containing rubber, polyacrylic acid compounds, imide compounds, carboxymethyl cellulose (CMC), and CMC salts. One of these may be used as the binder, or two or more may be used in combination as the binder.

[0093] The conductive agent is blended to improve current collection performance and reduce contact resistance between the positive electrode active material and the positive electrode current collector. Examples of conductive agents include vapor-grown carbon fiber (VGCF), carbon black such as acetylene black, and carbonaceous materials such as graphite. One of these may be used as the conductive agent, or two or more may be used in combination as the conductive agent. The conductive agent may also be omitted.

[0094] In the positive electrode active material-containing layer, the positive electrode active material and the binder are preferably mixed in proportions of 80% by mass to 98% by mass and 2% by mass to 20% by mass, respectively.

[0095] By using a binder amount of 2% by mass or more, sufficient electrode strength can be obtained. Furthermore, the binder can function as an insulator. Therefore, by using a binder amount of 20% by mass or less, the amount of insulator contained in the electrode is reduced, thereby reducing internal resistance.

[0096] When a conductive agent is added, the positive electrode active material, binder, and conductive agent are preferably mixed in proportions of 77% by mass or more and 95% by mass or less, 2% by mass or more and 20% by mass or less, and 3% by mass or more and 15% by mass or less, respectively.

[0097] By setting the amount of conductive agent to 3% by mass or more, the above-mentioned effects can be achieved. Furthermore, by setting the amount of conductive agent to 15% by mass or less, the proportion of conductive agent in contact with the electrolyte can be reduced. This low proportion can reduce decomposition of the electrolyte during high-temperature storage.

[0098] The positive electrode current collector is preferably an aluminum foil or an aluminum alloy foil containing one or more elements selected from Mg, Ti, Zn, Ni, Cr, Mn, Fe, Cu, and Si.

[0099] The thickness of the aluminum foil or aluminum alloy foil is preferably 5 μm or more and 20 μm or less, more preferably 15 μm or less. The purity of the aluminum foil is preferably 99% by mass or more. The content of transition metals such as iron, copper, nickel, and chromium contained in the aluminum foil or aluminum alloy foil is preferably 1% by mass or less.

[0100] The positive electrode current collector may also include a portion on the surface of which the positive electrode active material-containing layer is not formed, and this portion can function as a positive electrode current collecting tab.

[0101] The positive electrode can be produced, for example, using a positive electrode active material by the same method as that for the electrode according to the second embodiment.

[0102] 3) Electrolytes The electrolyte may be, for example, a liquid nonaqueous electrolyte or a gel nonaqueous electrolyte. The liquid nonaqueous electrolyte is prepared by dissolving an electrolyte salt as a solute in an organic solvent. The concentration of the electrolyte salt is preferably 0.5 mol / L or more and 2.5 mol / L or less.

[0103] Examples of electrolyte salts include lithium salts such as lithium perchlorate (LiClO), lithium hexafluorophosphate (LiPF), lithium tetrafluoroborate (LiBF), lithium hexafluoride (LiAsF), lithium trifluoromethanesulfonate (LiCFSO), and lithium bistrifluoromethylsulfonylimide (LiN(CFSO)), and mixtures thereof. The electrolyte salt is preferably one that is difficult to oxidize even at high potentials, and LiPF is most preferred.

[0104] Examples of organic solvents include cyclic carbonates such as propylene carbonate (PC), ethylene carbonate (EC), and vinylene carbonate (VC); linear carbonates such as diethyl carbonate (DEC), dimethyl carbonate (DMC), and methyl ethyl carbonate (MEC); cyclic ethers such as tetrahydrofuran (THF), 2-methyl tetrahydrofuran (2MeTHF), and dioxolane (DOX); linear ethers such as dimethoxyethane (DME) and diethoxyethane (DEE); γ-butyrolactone (GBL), acetonitrile (AN), and sulfolane (SL). These organic solvents can be used alone or in combination.

[0105] The gel-like non-aqueous electrolyte is prepared by combining a liquid non-aqueous electrolyte with a polymeric material, such as polyvinylidene fluoride (PVdF), polyacrylonitrile (PAN), polyethylene oxide (PEO), or a mixture thereof.

[0106] Alternatively, in addition to liquid nonaqueous electrolytes and gel nonaqueous electrolytes, room temperature molten salts containing lithium ions (ionic melts), polymer solid electrolytes, inorganic solid electrolytes, and the like may be used as the nonaqueous electrolyte.

[0107] Room-temperature molten salts (ionic melts) refer to organic salts consisting of a combination of organic cations and anions that can exist as a liquid at room temperature (15°C or higher and 25°C or lower). Room-temperature molten salts include room-temperature molten salts that exist as a liquid on their own, room-temperature molten salts that become liquid when mixed with an electrolyte salt, room-temperature molten salts that become liquid when dissolved in an organic solvent, and mixtures of these. Generally, the melting point of room-temperature molten salts used in secondary batteries is 25°C or lower. Furthermore, organic cations generally have a quaternary ammonium skeleton.

[0108] The solid polymer electrolyte is prepared by dissolving an electrolyte salt in a polymer material and solidifying the solution.

[0109] The inorganic solid electrolyte is a solid substance that has Li-ion conductivity. Here, Li-ion conductivity is defined as 1×10 -6 This refers to a material that exhibits a lithium ion conductivity of 1000 S / cm or more. Examples of inorganic solid electrolytes include oxide-based solid electrolytes and sulfide-based solid electrolytes. Specific examples of inorganic solid electrolytes are as follows:

[0110] The oxide-based solid electrolyte has a NASICON (Sodium (Na) Super Ionic Conductor) type structure and is represented by the general formula Li 1+x It is preferable to use a lithium phosphate solid electrolyte represented by Mα2(PO4)3. In the general formula, Mα is, for example, one or more elements selected from the group consisting of titanium (Ti), germanium (Ge), strontium (Sr), zirconium (Zr), tin (Sn), aluminum (Al), and calcium (Ca). The subscript x is within the range of 0≦x≦2.

[0111] Specific examples of lithium phosphate solid electrolytes with NASICON structure include Li 1+x Al x Ti 2-x LATP compounds represented by (PO4)3, where 0.1≦x≦0.5; Li 1+x Al y Mβ 2-yA compound represented by (PO4)3, where Mβ is one or more selected from the group consisting of Ti, Ge, Sr, Zr, Sn, and Ca, 0 ≦ x ≦ 1, and 0 ≦ y ≦ 1; Li 1+x Al x Ge 2-x A compound represented by (PO4)3, where 0 ≦ x ≦ 2; and, Li 1+x Al x Zr 2-x A compound represented by (PO4)3, where 0 ≦ x ≦ 2; Li 1+x+y Al x Mγ 2-x Si y P 3-y O 12 A compound represented by, where Mγ is one or more selected from the group consisting of Ti and Ge, 0 < x ≦ 2, and 0 ≦ y < 3; Li 1+2x Zr 1-x Ca x Examples thereof include a compound represented by (PO4)3, where 0 ≦ x < 1.

[0112] In addition to the above lithium phosphate solid electrolyte, examples of the oxide-based solid electrolyte also include an amorphous LIPON compound represented by LixPOyNz, where 2.6 ≦ x ≦ 3.5, 1.9 ≦ y ≦ 3.8, and 0.1 ≦ z ≦ 1.3 (for example, Li 2.9 PO 3.3 N 0.46 ); A garnet-type structure La 5+x A x La 3-x Mδ2O 12 A compound represented by, where A is one or more selected from the group consisting of Ca, Sr, and Ba, Mδ is one or more selected from the group consisting of Nb and Ta, and 0 ≦ x ≦ 0.5; Li3Mδ 2-x L2O 12 A compound represented by, where Mδ is one or more selected from the group consisting of Nb and Ta, L may contain Zr, and 0 ≦ x ≦ 0.; Li 7-3x Al x A compound represented by La3Zr3O 12 where 0 ≦ x ≦ 0.5; Li 5+x La3Mδ 2-x Zr x O 12where Mδ is at least one selected from the group consisting of Nb and Ta, and 0≦x≦2. LLZ compounds (e.g., Li7La3Zr2O 12 ); and La 2 / 3-x Li x Examples include compounds represented by TiO3 where x is 0.3≦x≦0.7.

[0113] One or more of the above compounds can be used as the solid electrolyte, and two or more of the above solid electrolytes can also be used.

[0114] 4) Separator The separator is formed from, for example, a porous film containing polyethylene (PE), polypropylene (PP), cellulose, or polyvinylidene fluoride (PVdF), or a synthetic resin nonwoven fabric. From the viewpoint of safety, it is preferable to use a porous film formed from polyethylene or polypropylene, because these porous films melt at a certain temperature and can interrupt current.

[0115] 5) Exterior materials The exterior member may be, for example, a container made of a laminate film or a metal container.

[0116] The thickness of the laminate film is, for example, 0.5 mm or less, preferably 0.2 mm or less.

[0117] The laminate film is a multilayer film containing multiple resin layers and metal layers interposed between the resin layers. The resin layers include polymeric materials such as polypropylene (PP), polyethylene (PE), nylon, and polyethylene terephthalate (PET). The metal layers are preferably made of aluminum foil or aluminum alloy foil to reduce weight. The laminate film can be molded into the shape of the exterior component by sealing it by heat fusion.

[0118] The thickness of the wall of the metal container is, for example, 1 mm or less, more preferably 0.5 mm or less, and even more preferably 0.2 mm or less.

[0119] The metal container is made of, for example, aluminum or an aluminum alloy. The aluminum alloy preferably contains elements such as magnesium, zinc, and silicon. If the aluminum alloy contains transition metals such as iron, copper, nickel, and chromium, the content of these metals is preferably 100 mass ppm or less.

[0120] The shape of the exterior member is not particularly limited. The shape of the exterior member may be, for example, flat (thin), rectangular, cylindrical, coin-shaped, or button-shaped. The exterior member can be appropriately selected depending on the battery dimensions and the intended use of the battery.

[0121] 6) Negative terminal The negative electrode terminal can be formed from a material that is electrochemically stable at the Li absorption / desorption potential of the above-mentioned negative electrode active material and has electrical conductivity. Specifically, the material for the negative electrode terminal can be copper, nickel, stainless steel, aluminum, or an aluminum alloy containing at least one element selected from the group consisting of Mg, Ti, Zn, Mn, Fe, Cu, and Si. Aluminum or an aluminum alloy is preferably used as the material for the negative electrode terminal. The negative electrode terminal is preferably made of the same material as the negative electrode current collector in order to reduce contact resistance with the negative electrode current collector.

[0122] 7) Positive terminal The positive electrode terminal has a potential range of 3V to 4.5V relative to the redox potential of lithium (vs. Li / Li + ) and can be formed from a material that is electrically stable and conductive. Examples of materials for the positive electrode terminal include aluminum and aluminum alloys containing at least one element selected from the group consisting of Mg, Ti, Zn, Mn, Fe, Cu, and Si. The positive electrode terminal is preferably formed from the same material as the positive electrode current collector in order to reduce contact resistance with the positive electrode current collector.

[0123] Next, the secondary battery according to the embodiment will be described in more detail with reference to the drawings.

[0124] Fig. 1 is a cross-sectional view schematically showing an example of a secondary battery, and Fig. 2 is an enlarged cross-sectional view of part A of the secondary battery shown in Fig. 1.

[0125] 1 and 2 includes a bag-shaped exterior member 2 shown in Fig. 1, an electrode group 1 shown in Fig. 1 and 2, and an electrolyte (not shown). The electrode group 1 and the electrolyte are housed in the bag-shaped exterior member 2. The electrolyte (not shown) is held in the electrode group 1.

[0126] The bag-shaped exterior member 2 is made of a laminate film including two resin layers and a metal layer interposed between them.

[0127] As shown in Fig. 1, the electrode group 1 is a flat wound electrode group. As shown in Fig. 2, the flat wound electrode group 1 includes a negative electrode 3, a separator 4, and a positive electrode 5. The separator 4 is interposed between the negative electrode 3 and the positive electrode 5.

[0128] The negative electrode 3 includes a negative electrode current collector 3a and a negative electrode active material-containing layer 3b. In the portion of the negative electrode 3 located at the outermost shell of the wound electrode group 1, the negative electrode active material-containing layer 3b is formed only on the inner surface side of the negative electrode current collector 3a, as shown in Fig. 2. In the other portions of the negative electrode 3, the negative electrode active material-containing layer 3b is formed on both sides of the negative electrode current collector 3a.

[0129] The positive electrode 5 includes a positive electrode current collector 5a and positive electrode active material-containing layers 5b formed on both sides of the positive electrode current collector 5a.

[0130] As shown in FIG. 1, the negative electrode terminal 6 and the positive electrode terminal 7 are located near the outer peripheral edge of the wound electrode group 1. The negative electrode terminal 6 is connected to a portion located at the outermost shell of the negative electrode current collector 3a. The positive electrode terminal 7 is connected to a portion located at the outermost shell of the positive electrode current collector 5a. The negative electrode terminal 6 and the positive electrode terminal 7 extend to the outside from an opening of the bag-shaped exterior member 2. A thermoplastic resin layer is provided on the inner surface of the bag-shaped exterior member 2, and the opening is closed by heat sealing this.

[0131] The secondary battery according to the embodiment is not limited to the secondary battery having the configuration shown in FIGS. 1 and 2, but may also be a battery having the configuration shown in FIGS. 3 and 4, for example.

[0132] Fig. 3 is a partially cutaway perspective view schematically showing another example of a secondary battery, and Fig. 4 is an enlarged cross-sectional view of part B of the secondary battery shown in Fig. 3.

[0133] 3 and 4 includes an electrode group 1 shown in Fig. 3 and 4, an exterior member 2 shown in Fig. 3, and an electrolyte (not shown). The electrode group 1 and the electrolyte are housed in the exterior member 2. The electrolyte is held in the electrode group 1.

[0134] The exterior member 2 is made of a laminate film including two resin layers and a metal layer interposed between them.

[0135] The electrode group 1 is a laminated electrode group, as shown in Fig. 4. The laminated electrode group 1 has a structure in which negative electrodes 3 and positive electrodes 5 are alternately laminated with separators 4 interposed therebetween.

[0136] The electrode group 1 includes a plurality of negative electrodes 3. Each of the plurality of negative electrodes 3 includes a negative electrode current collector 3a and a negative electrode active material-containing layer 3b supported on both sides of the negative electrode current collector 3a. The electrode group 1 also includes a plurality of positive electrodes 5. Each of the plurality of positive electrodes 5 includes a positive electrode current collector 5a and a positive electrode active material-containing layer 5b supported on both sides of the positive electrode current collector 5a.

[0137] The negative electrode current collector 3a of each negative electrode 3 includes a portion on one side where no negative electrode active material-containing layer 3b is supported on any surface. This portion serves as a negative electrode current collector tab 3c. As shown in FIG. 4, the negative electrode current collector tab 3c does not overlap with the positive electrode 5. The multiple negative electrode current collector tabs 3c are electrically connected to a strip-shaped negative electrode terminal 6. The tip of the strip-shaped negative electrode terminal 6 is extended to the outside of the exterior member 2.

[0138] Although not shown, the positive electrode current collector 5a of each positive electrode 5 includes a portion on one side where the positive electrode active material-containing layer 5b is not supported on any surface. This portion functions as a positive electrode current collector tab. Like the negative electrode current collector tab 3c, the positive electrode current collector tab does not overlap with the negative electrode 3. The positive electrode current collector tab is located on the opposite side of the electrode group 1 from the negative electrode current collector tab 3c. The positive electrode current collector tab is electrically connected to a strip-shaped positive electrode terminal 7. The tip of the strip-shaped positive electrode terminal 7 is located on the opposite side from the negative electrode terminal 6 and is drawn out to the outside of the exterior member 2.

[0139] The secondary battery according to the third embodiment includes the electrode according to the first embodiment, and therefore, the secondary battery can exhibit a high capacity.

[0140] (Fourth embodiment) According to a fourth embodiment, there is provided a battery pack, which includes a plurality of secondary batteries according to the third embodiment.

[0141] In such a battery pack, the individual cells may be electrically connected in series or in parallel, or may be connected in a combination of series and parallel.

[0142] Next, an example of a battery pack according to an embodiment will be described with reference to the drawings.

[0143] Fig. 5 is a perspective view schematically showing an example of a battery pack. The battery pack 200 shown in Fig. 5 includes five cells 100a to 100e, four bus bars 21, a positive electrode lead 22, and a negative electrode lead 23. Each of the five cells 100a to 100e is a secondary battery according to the third embodiment.

[0144] The bus bar 21 connects, for example, the negative electrode terminal 6 of one cell 100a to the positive electrode terminal 7 of the adjacent cell 100b. In this way, the five cells 100 are connected in series by four bus bars 21. That is, the battery pack 200 in FIG. 5 is a five-series battery pack. Although an example is not shown, in a battery pack including a plurality of cells electrically connected in parallel, the plurality of cells can be electrically connected by, for example, connecting the negative electrode terminals to each other by a bus bar and connecting the positive electrode terminals to each other by a bus bar.

[0145] The positive electrode terminal 7 of at least one of the five cells 100a to 100e is electrically connected to a positive electrode lead 22 for external connection. Also, the negative electrode terminal 6 of at least one of the five cells 100a to 100e is electrically connected to a negative electrode lead 23 for external connection.

[0146] The battery pack according to the fourth embodiment includes the secondary battery according to the third embodiment, and therefore can exhibit high capacity.

[0147] (Fifth embodiment) According to a fifth embodiment, there is provided a battery pack. This battery pack includes the battery assembly according to the fourth embodiment. This battery pack may include a single secondary battery according to the third embodiment instead of the battery assembly according to the fourth embodiment.

[0148] Such a battery pack may further include a protection circuit. The protection circuit has a function of controlling the charging and discharging of the secondary battery. Alternatively, a circuit included in a device that uses the battery pack as a power source (e.g., electronic equipment, automobile, etc.) may be used as the protection circuit for the battery pack.

[0149] The battery pack may further include external terminals for current flow. The external terminals for current flow are for outputting current from the secondary battery to the outside and / or inputting current from the outside to the secondary battery. In other words, when the battery pack is used as a power source, current is supplied to the outside through the external terminals for current flow. When the battery pack is charged, charging current (including regenerative energy from the power of an automobile or the like) is supplied to the battery pack through the external terminals for current flow.

[0150] Next, an example of a battery pack according to an embodiment will be described with reference to the drawings.

[0151] Fig. 6 is an exploded perspective view schematically showing an example of a battery pack, and Fig. 7 is a block diagram showing an example of an electric circuit of the battery pack shown in Fig. 6.

[0152] The battery pack 300 shown in FIGS. 6 and 7 includes a container 31, a lid 32, a protective sheet 33, a battery pack 200, a printed wiring board 34, wiring 35, and an insulating plate (not shown).

[0153] The storage container 31 shown in Fig. 6 is a bottomed, prismatic container having a rectangular bottom. The storage container 31 is configured to be able to accommodate a protective sheet 33, a battery pack 200, a printed wiring board 34, and wiring 35. The lid 32 has a rectangular shape. The lid 32 covers the storage container 31 to accommodate the battery pack 200 and other components. Although not shown, the storage container 31 and the lid 32 are provided with openings or connection terminals for connection to external devices and the like.

[0154] The battery pack 200 includes a plurality of cells 100, a positive electrode lead 22, a negative electrode lead 23, and an adhesive tape 24.

[0155] At least one of the plurality of cells 100 is a secondary battery according to the third embodiment. The plurality of cells 100 are electrically connected in series as shown in FIG. 7. The plurality of cells 100 may be electrically connected in parallel, or may be connected in a combination of series and parallel connections. When the plurality of cells 100 are connected in parallel, the battery capacity increases compared to when they are connected in series.

[0156] The adhesive tape 24 fastens the plurality of cells 100 together. Heat-shrinkable tape may be used to secure the plurality of cells 100 together instead of the adhesive tape 24. In this case, protective sheets 33 are placed on both side surfaces of the battery pack 200, and the heat-shrinkable tape is wrapped around the cells 100, and the heat-shrinkable tape is then thermally shrunk to bind the plurality of cells 100 together.

[0157] One end of the positive electrode lead 22 is connected to the battery pack 200. One end of the positive electrode lead 22 is electrically connected to the positive electrode of one or more cells 100. One end of the negative electrode lead 23 is connected to the battery pack 200. One end of the negative electrode lead 23 is electrically connected to the negative electrode of one or more cells 100.

[0158] The printed wiring board 34 is installed along one of the shorter sides of the inner surface of the container 31. The printed wiring board 34 includes a positive connector 342, a negative connector 343, a thermistor 345, a protection circuit 346, wires 342a and 343a, an external terminal 350 for supplying current, a positive wire (positive wire) 348a, and a negative wire (negative wire) 348b. One main surface of the printed wiring board 34 faces one side of the battery pack 200. An insulating plate (not shown) is interposed between the printed wiring board 34 and the battery pack 200.

[0159] The other end 22a of the positive electrode lead 22 is electrically connected to the positive electrode connector 342. The other end 23a of the negative electrode lead 23 is electrically connected to the negative electrode connector 343.

[0160] The thermistor 345 is fixed to one main surface of the printed wiring board 34. The thermistor 345 detects the temperature of each of the cells 100 and transmits the detection signal to the protection circuit 346.

[0161] The external terminals 350 for applying current are fixed to the other main surface of the printed wiring board 34. The external terminals 350 for applying current are electrically connected to devices located outside the battery pack 300. The external terminals 350 for applying current include a positive terminal 352 and a negative terminal 353.

[0162] The protection circuit 346 is fixed to the other main surface of the printed wiring board 34. The protection circuit 346 is connected to the positive terminal 352 via a positive wiring 348a. The protection circuit 346 is connected to the negative terminal 353 via a negative wiring 348b. The protection circuit 346 is also electrically connected to the positive connector 342 via a wiring 342a. The protection circuit 346 is electrically connected to the negative connector 343 via a wiring 343a. The protection circuit 346 is also electrically connected to each of the plurality of single cells 100 via wiring 35.

[0163] The protective sheet 33 is disposed on both inner surfaces of the long sides of the container 31 and on the inner surface of the short side that faces the printed wiring board 34 across the battery pack 200. The protective sheet 33 is made of, for example, resin or rubber.

[0164] The protection circuit 346 controls charging and discharging of the plurality of cells 100. Furthermore, the protection circuit 346 cuts off the electrical connection between the protection circuit 346 and external terminals 350 (positive terminal 352, negative terminal 353) for supplying electricity to an external device, based on a detection signal transmitted from the thermistor 345 or a detection signal transmitted from each cell 100 or the battery pack 200.

[0165] An example of the detection signal transmitted from the thermistor 345 is a signal indicating that the temperature of the cell 100 is equal to or higher than a predetermined temperature. An example of the detection signal transmitted from each cell 100 or the battery pack 200 is a signal indicating that overcharge, overdischarge, or overcurrent of the cell 100 is detected. When detecting overcharge or the like for each cell 100, the battery voltage may be detected, or the positive electrode potential or the negative electrode potential may be detected. In the latter case, a lithium electrode used as a reference electrode is inserted into each cell 100.

[0166] The protection circuit 346 may be a circuit included in a device (such as an electronic device or an automobile) that uses the battery pack 300 as a power source.

[0167] As described above, the battery pack 300 is also provided with the external terminals 350 for current application. Therefore, the battery pack 300 can output current from the battery assembly 200 to an external device and input current from the external device to the battery assembly 200 via the external terminals 350 for current application. In other words, when the battery pack 300 is used as a power source, the current from the battery assembly 200 is supplied to the external device via the external terminals 350 for current application. When the battery pack 300 is charged, a charging current from the external device is supplied to the battery pack 300 via the external terminals 350 for current application. When the battery pack 300 is used as an in-vehicle battery, regenerative energy from the vehicle's power can be used as the charging current from the external device.

[0168] The battery pack 300 may include a plurality of assembled batteries 200. In this case, the assembled batteries 200 may be connected in series, in parallel, or in a combination of series and parallel connections. The printed wiring board 34 and the wiring 35 may be omitted. In this case, the positive electrode lead 22 and the negative electrode lead 23 may be used as a positive terminal 352 and a negative terminal 353, respectively, of the external terminal 350 for supplying current.

[0169] Such a battery pack is used in applications requiring excellent cycle performance when drawing a large current, for example. Specifically, this battery pack is used, for example, as a power source for electronic devices, a stationary battery, or an on-board battery for various vehicles. Examples of electronic devices include digital cameras. This battery pack is particularly suitable for use as an on-board battery.

[0170] The battery pack according to the fifth embodiment includes the secondary battery according to the third embodiment or the battery pack according to the fourth embodiment, and therefore can exhibit high capacity.

[0171] (Sixth embodiment) According to a sixth embodiment, a vehicle is provided, which is equipped with the battery pack according to the fifth embodiment.

[0172] In such a vehicle, the battery pack recovers, for example, regenerative energy for powering the vehicle, and the vehicle may include a mechanism (regenerator) for converting the kinetic energy of the vehicle into regenerative energy.

[0173] Examples of vehicles include two- to four-wheel hybrid electric vehicles, two- to four-wheel electric vehicles, power-assisted bicycles, and rail vehicles.

[0174] The mounting position of the battery pack in a vehicle is not particularly limited. For example, when the battery pack is mounted in an automobile, the battery pack can be mounted in the engine compartment, the rear of the vehicle body, or under the seat of the vehicle.

[0175] A vehicle may be equipped with multiple battery packs. In this case, the batteries included in each battery pack may be electrically connected in series, in parallel, or a combination of series and parallel connections. For example, if each battery pack includes a battery pack, the battery packs may be electrically connected in series, in parallel, or a combination of series and parallel connections. Alternatively, if each battery pack includes a single battery, the batteries may be electrically connected in series, in parallel, or a combination of series and parallel connections.

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

[0177] FIG. 8 is a partial perspective view that schematically illustrates an example of a vehicle.

[0178] A vehicle 400 shown in Fig. 8 includes a vehicle body 40 and a battery pack 300 according to the fifth embodiment. In the example shown in Fig. 8, the vehicle 400 is a four-wheeled automobile.

[0179] The vehicle 400 may be equipped with a plurality of battery packs 300. In this case, the batteries (for example, single cells or assembled batteries) included in the battery packs 300 may be connected in series, in parallel, or in a combination of series and parallel connections.

[0180] 8 illustrates an example in which the battery pack 300 is mounted in an engine compartment located in the front of the vehicle body 40. As described above, the battery pack 300 may be mounted, for example, at the rear of the vehicle body 40 or under a seat. This battery pack 300 can be used as a power source for the vehicle 400. In addition, this battery pack 300 can recover regenerative energy for powering the vehicle 400.

[0181] Next, an embodiment of the vehicle according to the embodiment will be described with reference to FIG.

[0182] 9 is a diagram illustrating an example of a control system for an electrical system in a vehicle. The vehicle 400 shown in FIG. 9 is an electric vehicle.

[0183] The vehicle 400 shown in Figure 9 includes a vehicle body 40, a vehicle power supply 41, a vehicle ECU (ECU: Electric Control Unit) 42 which is a higher-level control device of the vehicle power supply 41, an external terminal (terminal for connecting to an external power supply) 43, an inverter 44, and a drive motor 45.

[0184] Vehicle 400 has vehicle power supply 41 mounted, for example, in the engine compartment, the rear of the vehicle body, or under the seat. Note that in vehicle 400 shown in Fig. 9, the mounting location of vehicle power supply 41 is shown schematically.

[0185] The vehicle power supply 41 includes a plurality of (for example, three) battery packs 300a, 300b, and 300c, a battery management unit (BMU) 411, and a communication bus 412.

[0186] The battery pack 300a includes an assembled battery 200a and an assembled battery monitoring device 301a (for example, VTM: Voltage Temperature Monitoring). The battery pack 300b includes an assembled battery 200b and an assembled battery monitoring device 301b. The battery pack 300c includes an assembled battery 200c and an assembled battery monitoring device 301c. The battery packs 300a to 300c are the same as the battery pack 300 described above, and the assembled batteries 200a to 200c are the same as the assembled battery 200 described above. The assembled batteries 200a to 200c are electrically connected in series. The battery packs 300a, 300b, and 300c can each be removed independently and replaced with another battery pack 300.

[0187] Each of the assembled batteries 200a to 200c includes a plurality of unit cells connected in series. At least one of the plurality of unit cells is the secondary battery according to the third embodiment. Each of the assembled batteries 200a to 200c is charged and discharged via a positive terminal 413 and a negative terminal 414.

[0188] The battery management device 411 communicates with the assembled battery monitoring devices 301a to 301c and collects information on the voltage, temperature, etc. of each of the cells 100 included in the assembled batteries 200a to 200c included in the vehicle power supply 41. In this way, the battery management device 411 collects information on the maintenance of the vehicle power supply 41.

[0189] The battery management unit 411 and the assembled battery monitoring units 301a to 301c are connected via a communication bus 412. In the communication bus 412, one set of communication lines is shared by multiple nodes (the battery management unit 411 and one or more assembled battery monitoring units 301a to 301c). The communication bus 412 is a communication bus configured based on, for example, the CAN (Control Area Network) standard.

[0190] The battery pack monitoring devices 301a to 301c measure the voltage and temperature of each of the cells constituting the battery packs 200a to 200c based on commands received through communication from the battery management device 411. However, the temperature can be measured at only a few locations per battery pack, and it is not necessary to measure the temperature of all the cells.

[0191] The vehicle power supply 41 may also have an electromagnetic contactor (for example, a switch device 415 shown in FIG. 9) that switches between electrical connection and disconnection between the positive terminal 413 and the negative terminal 414. The switch device 415 includes a pre-charge switch (not shown) that is turned on when the assembled batteries 200a-200c are being charged, and a main switch (not shown) that is turned on when the output from the assembled batteries 200a-200c is being supplied to a load. Each of the pre-charge switch and the main switch includes a relay circuit (not shown) that is switched on or off by a signal supplied to a coil disposed near the switch element. Electromagnetic contactors such as the switch device 415 are controlled based on a control signal from the battery management device 411 or the vehicle ECU 42 that controls the operation of the entire vehicle 400.

[0192] The inverter 44 converts the input DC voltage into a three-phase alternating current (AC) high voltage for driving the motor. The three-phase output terminals of the inverter 44 are connected to the three-phase input terminals of the drive motor 45. The inverter 44 is controlled based on control signals from the battery management unit 411 or the vehicle ECU 42, which controls the operation of the entire vehicle. By controlling the inverter 44, the output voltage from the inverter 44 is adjusted.

[0193] The drive motor 45 is rotated by the electric power supplied from the inverter 44. The drive force generated by the rotation of the drive motor 45 is transmitted to the axles and drive wheels W via, for example, a differential gear unit.

[0194] Although not shown, vehicle 400 also includes a regenerative braking mechanism (regenerator). When vehicle 400 is braked, regenerative braking mechanism rotates drive motor 45 and converts kinetic energy into regenerative energy as electrical energy. The regenerative energy recovered by the regenerative braking mechanism is input to inverter 44 and converted into direct current. The converted direct current is input to vehicle power supply 41.

[0195] One terminal of a connection line L1 is connected to the negative terminal 414 of the vehicle power supply 41. The other terminal of the connection line L1 is connected to a negative input terminal 417 of the inverter 44. A current detection unit (current detection circuit) 416 in the battery management device 411 is provided on the connection line L1 between the negative terminal 414 and the negative input terminal 417.

[0196] One terminal of a connection line L2 is connected to the positive terminal 413 of the vehicle power supply 41. The other terminal of the connection line L2 is connected to a positive input terminal 418 of the inverter 44. A switch device 415 is provided on the connection line L2 between the positive terminal 413 and the positive input terminal 418.

[0197] The external terminal 43 is connected to the battery management device 411. The external terminal 43 can be connected to, for example, an external power source.

[0198] In response to operational inputs from the driver or the like, the vehicle ECU 42 coordinates with other management devices and control devices including the battery management device 411 to control the vehicle power supply 41, the switch device 415, the inverter 44, etc. Through the coordinated control of the vehicle ECU 42, etc., the output of power from the vehicle power supply 41 and the charging of the vehicle power supply 41 are controlled, thereby managing the entire vehicle 400. Data relating to the maintenance of the vehicle power supply 41, such as the remaining capacity of the vehicle power supply 41, is transferred between the battery management device 411 and the vehicle ECU 42 via a communication line.

[0199] The vehicle according to the sixth embodiment is equipped with the battery pack according to the fifth embodiment, and therefore, a high-performance vehicle can be provided. [Example]

[0200] The above-described embodiment will be described in more detail below based on examples, but the present invention is not limited to the examples listed below.

[0201] <Synthesis> Example 1 2.921 g of niobium oxide Nb2O5 and 1.739 g of tungsten trioxide WO3 were weighed and mixed for 30 minutes using an agate mortar and agate pestle while adding an appropriate amount of ethanol (C2H5OH) dropwise. The mixture was dried in air at 80°C for 6 hours, then 2 g was loaded into a 15 mm diameter mold and uniaxially pressed at 15 MPa to form a 15 mm diameter pellet. The resulting pellet was tightly wrapped in 100 μm thick Pt foil. The wrapped pellet was placed in a Pt crucible, covered, and subjected to air-conditioning at 700°C for 12 hours and firing at 1200°C for 6 hours. The resulting fired product was crushed and powdered to obtain the active material of Example 1.

[0202] Example 2 The active material of Example 2 was synthesized in the same manner as in Example 1, except that the firing temperature in the 6-hour firing following the pre-firing was changed to 1300°C.

[0203] Example 3 The active material of Example 3 was synthesized in the same manner as in Example 1, except that the firing temperature in the 6-hour firing following the pre-firing was changed to 1350°C.

[0204] Example 4 The active material of Example 4 was synthesized in the same manner as in Example 1, except that the firing temperature in the 6-hour firing following the pre-firing was changed to 1400°C.

[0205] Example 5 The active material of Example 5 was obtained in the same manner as in Example 1, except that the raw materials were changed to 2.977 g of niobium oxide Nb2O5, 0.128 g of titanium oxide TiO2, and 2.226 g of tungsten trioxide WO3.

[0206] Example 6 The active material of Example 6 was synthesized in the same manner as in Example 5, except that the firing temperature in the 6-hour firing following the pre-firing was changed to 1300°C.

[0207] Example 7 The active material of Example 7 was obtained in the same manner as in Example 1, except that the raw materials were changed to 2.472 g of niobium oxide Nb2O5, 0.248 g of titanium oxide TiO2, and 2.515 g of tungsten trioxide WO3.

[0208] Example 8 The active material of Example 8 was synthesized in the same manner as in Example 7, except that the firing temperature in the 6-hour firing following the pre-firing was changed to 1300°C.

[0209] Example 9 The active material of Example 9 was obtained in the same manner as in Example 1, except that the raw materials were changed to 2.871 g of niobium oxide Nb2O5, 0.530 g of tantalum oxide Ta2O5, and 1.739 g of tungsten trioxide WO3.

[0210] Example 10 The active material of Example 10 was obtained in the same manner as in Example 1, except that the raw materials were changed to 2.921 g of niobium oxide Nb2O5, 0.193 g of zirconium oxide ZrO2, and 2.184 g of tungsten trioxide WO3.

[0211] Example 11 An active material of Example 11 was obtained in the same manner as in Example 10, except that the firing temperature in the 6-hour firing following the pre-firing was changed to 1300°C.

[0212] (Comparative Example 1) 2.921 g of niobium oxide Nb2O5 and 1.739 g of tungsten trioxide WO3 were weighed out and mixed for 30 minutes using an agate mortar and pestle while adding an appropriate amount of ethanol C2H5OH dropwise. The mixture was dried in air at 80°C for 6 hours, then poured into an alumina crucible without a lid and calcined in air at 700°C for 12 hours and then fired at 1200°C for 6 hours, yielding the active material of Comparative Example 1.

[0213] <Analysis of composition> The powders obtained in Examples 1 to 11 and Comparative Example 1 were analyzed for contained elements by the method described above to determine the composition of the composite oxide. The compositions determined by the analysis are summarized in Table 1. The analyzed compositions shown in Table 1 are stoichiometric ratios normalized with the sum of the content ratios of the metal elements set to 21. Table 1 also shows the composition of the composite oxides of the general formula Li x Nb 16-y-z M z W 5+y O 55-u The values ​​of the subscripts y, z, and u when fitted to

[0214] [Table 1]

[0215] As shown in Table 1, in Examples 1 to 11, in which the raw material powder mixture was sintered in a sealed state, the general formula Li x Nb 16-y-z M z W 5+y O 55-u A composite oxide having a composition in which the subscripts y, z, and u satisfy the following conditions was obtained: 0≦x≦5, −0.5≦y≦2, 0≦z≦2, and 4≦u≦9. In contrast, in Comparative Example 1, although the same raw materials as in Example 1 were used, the subscripts y and u were below the above ranges. In Comparative Example 1, the raw materials were not sealed during firing, and as a result, W volatilized, and the target composition could not be obtained, as can be seen from the low value of the subscript y. Furthermore, in Comparative Example 1, it can be seen from the low value of the subscript u that not many oxygen vacancies could be introduced.

[0216] <Wide-angle X-ray scattering measurement> Wide-angle X-ray scattering measurements were performed on the powders obtained in each of Examples 1 to 11 and Comparative Example 1. The measurements were performed in accordance with the details described above. Crystal structure analysis was performed on the obtained spectra using the Rietveld method.

[0217] The obtained spectra are shown in Figures 10 to 21. The peak intensity I of the peak at 2θ=24.2±0.3° in each spectrum is24 and the peak intensity I of the peak within the range of 2θ = 24.8 ± 0.3° 25 Intensity ratio I between 24 / I 25 and the peak intensity I of the peak within the range of 2θ=19.7±0.5° 20 and peak intensity I 25 Intensity ratio I between 20 / I 25 Summarize.

[0218] [Table 2]

[0219] <Electrochemical measurements> First, 100% by mass of the active material powder obtained in each example, 10% by mass of acetylene black as a conductive agent, 5% by mass of carbon nanofiber, and 10% by mass of polyvinylidene fluoride (PVdF) as a binder were mixed with N-methylpyrrolidone (NMP) to obtain a slurry. This slurry was applied to one side of a 15 μm thick aluminum foil current collector, dried, and pressed to prepare an electrode.

[0220] Next, an electrolyte solution was prepared by dissolving LiPF6 supporting salt at a concentration of 1 mol / L in a mixed solvent of ethylene carbonate (EC), diethyl carbonate (DEC), and ethyl methyl carbonate (EMC) in a volume ratio of 1:1:1.

[0221] The resulting electrode was used as a working electrode, and Li metal was used as a counter electrode and a reference electrode. A coin cell was fabricated using the above electrolyte, and the electrochemical performance was evaluated.

[0222] In this example, the coin cell used for measurement uses lithium metal as the counter electrode, so the electrode potential of each example is more noble than the counter electrode, and therefore operates as a positive electrode. Therefore, the definitions of charge and discharge are reversed when the electrode in each example is used as a negative electrode. To avoid confusion, in this example, the direction in which lithium ions are inserted into the electrode is referred to as charge, and the direction in which they are removed is referred to as discharge. Note that the active material according to the first embodiment can be used as a negative electrode active material when combined with a known positive electrode material.

[0223] The fabricated electrochemical measurement cell was measured at 1.0 V to 3.0 V (vs. Li / Li) based on the metallic lithium electrode. + The battery was charged and discharged within a potential range of 1000 kJ / s. The charge / discharge current was set to 1 C (time-discharge rate), and the charge and discharge capacities were measured at room temperature. The discharge capacity obtained in this initial charge / discharge was divided by the charge capacity to calculate the initial charge / discharge efficiency: Initial charge / discharge efficiency (%) = [initial discharge capacity / initial charge capacity] × 100%.

[0224] The evaluation results of the electrochemical performance of each example are shown in Table 3. Specifically, the charge capacity, discharge capacity, and charge / discharge efficiency in the initial charge / discharge cycle are shown.

[0225] [Table 3]

[0226] As shown in Table 3, the coin cells using the active material powders obtained in Examples 1 to 11 had high charge and discharge capacities, and active materials capable of realizing high-capacity batteries were obtained. When the active material powder obtained in Comparative Example 1 was used, the charge and discharge efficiency was similar to that of Examples 1 to 11, but lower values ​​were obtained for both the charge and discharge capacities.

[0227] As shown, the general formula Li x Nb 16-y-z M z W 5+y O 55-u A battery containing, as an active material, a composite oxide having a monoclinic crystal structure represented by the formula (I) can exhibit a high capacity.

[0228] Although several embodiments of the present invention have been described, these embodiments are presented as examples and are not intended to limit the scope of the invention. These novel embodiments can be embodied in various other forms, and various omissions, substitutions, and modifications can be made without departing from the spirit of the invention. These embodiments and their modifications are included within the scope and spirit of the invention, and are also included in the scope of the invention and its equivalents as defined in the claims.

[0229] Several embodiments of the present invention will be described below. [1] It has a monoclinic crystal structure and has the general formula Li x Nb 16-y-z M z W 5+y O 55-u wherein M includes at least one selected from the group consisting of Ta, Ti, Zr, Al, and Fe, and 0≦x≦5, −0.5≦y≦2, 0≦z≦2, and 4≦u≦9. [2] The peak intensity I of the most intense peak appearing within the range of 2θ=24.2±0.3° in the powder X-ray diffraction spectrum 24 and the peak intensity I of the peak appearing within the range of 2θ = 24.8 ± 0.3° 25 Intensity ratio I between 24 / I 25 is 0.5≦I 24 / I 25 ≦1.5. [3] The peak intensity I of the most intense peak appearing within the range of 2θ=19.7±0.5° in the powder X-ray diffraction spectrum 20 and the peak intensity I of the peak appearing within the range of 2θ = 24.8 ± 0.3° 25 Intensity ratio I between 20 / I 25 is 0.1≦I 20 / I 25 ≦0.5. [4] The active material according to any one of [1] to [3], wherein M in the general formula is either Ta or Ti. [5] The active material according to any one of [1] to [4], further comprising at least one selected from the group consisting of Sc, Y, V, Cr, Co, Mn, and Ga. [6] An electrode comprising the active material according to any one of [1] to [5]. [7] The electrode according to [6], wherein the electrode includes an active material-containing layer containing the active material. [8] a positive electrode; a negative electrode; Electrolytes and A secondary battery comprising: The secondary battery, wherein the negative electrode is the electrode according to [6] or [7].

[0230] [9] A battery pack including the secondary battery according to [8].

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

[11] A battery comprising a plurality of the secondary batteries, The battery pack according to [9] or

[10] , wherein the secondary batteries are electrically connected in series, in parallel, or in a combination of series and parallel.

[12] A vehicle equipped with a battery pack described in any one of [9] to

[11] .

[13] The vehicle according to

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

[0231] 1...electrode group, 2...exterior member, 3...negative electrode, 3a...negative electrode current collector, 3b...negative electrode active material-containing layer, 3c...negative electrode current collecting tab, 4...separator, 5...positive electrode, 5a...positive electrode current collector, 5b...positive electrode active material-containing layer, 6...negative electrode terminal, 7...positive electrode terminal, 21...bus bar, 22...positive electrode side lead, 22a...other end, 23...negative electrode side lead, 23a...other end, 24...adhesive tape, 31...container, 32...lid, 33...protective sheet, 34...printed wiring board, 35...wiring, 40...vehicle body, 41...vehicle power source, 42...electrical control device, 43...external terminal, 44...inverter, 45...drive motor, 100...secondary battery, 200...battery pack, 200a...battery pack, 200b...battery pack, 200c...battery pack, 300...battery pack, 30 0a...battery pack, 300b...battery pack, 300c...battery pack, 301a...assembled battery monitoring device, 301b...assembled battery monitoring device, 301c...assembled battery monitoring device, 342...positive side connector, 343...negative side connector, 345...thermistor, 346...protection circuit, 342a...wiring, 343a...wiring, 350...external terminal for supplying current, 352...positive side terminal, 353...negative side terminal, 348a...positive side wiring, 348b...negative side wiring, 400...vehicle, 411...battery management device, 412...communication bus, 413...positive side terminal, 414...negative side terminal, 415...switch device, 416...current detection unit, 417...negative side input terminal, 418...positive side input terminal, L1...connection line, L2...connection line, W...drive wheel.

Claims

1. It has a monoclinic crystal structure and has the general formula Li x Nb 16-y-z M z W 5+y O 55-u wherein M includes at least one selected from the group consisting of Ta, Ti, Zr, Al, and Fe, and 0≦x≦5, −0.5≦y≦2, 0≦z≦2, and 4≦u≦9.

2. In the diffraction spectrum obtained by powder X-ray diffraction, the peak intensity I of the most intense peak appearing within the range of 2θ = 24.2 ± 0.3° 24 and the peak intensity I of the peak appearing within the range of 2θ = 24.8 ± 0.3° 25 Intensity ratio I between 24 / I 25 is 0.5≦I 24 / I 25 10. The active material of claim 1, wherein the ρ is in the range of ≦1.

5.

3. In the diffraction spectrum by powder X-ray diffraction, the peak intensity I of the most intense peak appearing within the range of 2θ = 19.7 ± 0.5° 20 and the peak intensity I of the peak appearing within the range of 2θ = 24.8 ± 0.3° 25 Intensity ratio I between 20 / I 25 is 0.1≦I 20 / I 25 3. The active material according to claim 1, wherein the ρ is in the range of ≦0.

5.

4. 3. The active material according to claim 1, wherein M in the general formula is either Ta or Ti.

5. 3. The active material according to claim 1, further comprising at least one selected from the group consisting of Sc, Y, V, Cr, Co, Mn, and Ga.

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

7. The electrode according to claim 6 , wherein the electrode comprises an active material-containing layer containing the active material.

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

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

10. An external terminal for applying current; Protection circuit and The battery pack according to claim 9, further comprising:

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

12. A vehicle equipped with the battery pack according to claim 9.

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

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