Active materials, electrodes, secondary batteries, battery packs, vehicles, and stationary power supplies

Abstract

To provide an active material and an electrode capable of realizing a secondary battery that achieves both high reversible capacity and high cycle capacity retention rate, a secondary battery and a battery pack that achieve both high reversible capacity and high cycle capacity retention rate, and a vehicle and a stationary power source equipped with the battery pack.SOLUTION: An active material according to an embodiment is represented by a general formula of LixNb10Ti2O29 (0≤x≤5), includes orthorhombic particles having a unit cell volume of 2230 Å3 or more, and has a half-width of a maximum peak appearing at 24.5°≤2θ≤25.0° in a powder X-ray diffraction spectrum of 0.09° or less.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] Embodiments of the present invention relate to active materials, electrodes, secondary batteries, battery packs, vehicles, and stationary power supplies. [Background technology]

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

[0003] A common negative electrode in lithium-ion batteries is a carbon-based negative electrode that uses carbonaceous materials such as graphite as the active material. However, batteries using carbon-based negative electrodes were susceptible to internal short circuits, heat generation, and fire due to the deposition of metallic lithium dendrites on the electrode after repeated rapid charging and discharging. Therefore, batteries were 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 A battery using Li as the negative electrode has an average operating potential of 1.55V (vs. Li / Li + Because of its high potential, Li dendrite deposition does not progress, enabling stable rapid charging and discharging, and because it operates at a potential where reduction side reactions of the electrolyte are less likely to occur, it has a longer lifespan compared to batteries using carbon-based negative electrodes. However, Li4Ti5O 12 The theoretical capacity of the active material using this as the negative electrode is low at 175 mAh / g, and there was a problem with its lower energy density compared to batteries equipped with a carbon-based negative electrode.

[0004] Therefore, monoclinic titanium niobium oxide (TiNb2O7) is being investigated. Using the oxidation-reduction potential of lithium as a reference, 1V (vs.Li / Li) is considered. +This active material exhibits high capacity while having an operating potential in the vicinity of the 2000 ohm. For this reason, it is expected to achieve an energy density exceeding that of carbon-based anodes in terms of volumetric energy density. However, in order to fully popularize electric vehicles, it is desirable to further increase the energy density of lithium-ion secondary batteries from the perspective of improving driving range, and the development of even higher-capacity rapid-charging batteries is desired. [Prior art documents] [Non-patent literature]

[0005] [Non-Patent Document 1] RJ Cava et al., J. Electrochem. Soc., 130 (1983) 2345. [Non-Patent Document 2] Nakai, Izumi et al. (eds.): "Practical Aspects of Powder X-ray Diffraction," 1st edition, Asakura Shoten, February 10, 2002, pp. 97-115. [Overview of the Initiative] [Problems that the invention aims to solve]

[0006] The problem that this invention aims to solve is to provide an active material and electrodes that can realize a secondary battery that achieves both high reversible capacity and high cycle capacity retention rate, a secondary battery and battery pack that achieve both high reversible capacity and high cycle capacity retention rate, and a vehicle and stationary power supply equipped with the battery pack. [Means for solving the problem]

[0007] According to the embodiment, the general formula Li x Nb 10 Ti2O 29 It is represented as (0≦x≦5) and has a unit cell volume of 2230 Å. 3 An active material is provided which contains orthorhombic particles as described above, and in the powder X-ray diffraction spectrum, the full width at half maximum of the largest peak appearing at 24.5°≦2θ≦25.0° is 0.09° or less. [Brief explanation of the drawing]

[0008] [Figure 1] Cross-sectional view schematically showing an example of a secondary battery according to an embodiment. [Figure 2] Enlarged cross-sectional view of part A of the secondary battery shown in FIG. 1. [Figure 3] Partial cutaway perspective view schematically showing another example of a secondary battery according to an embodiment. [Figure 4] Enlarged cross-sectional view of part B of the secondary battery shown in FIG. 3. [Figure 5] Perspective view schematically showing an example of a battery pack according to an embodiment. [Figure 6] Exploded perspective view schematically showing an example of a battery pack according to an embodiment. [Figure 7] Block diagram showing an example of an electrical circuit of the battery pack shown in FIG. 6. [Figure 8] Partial transparent view schematically showing an example of a vehicle according to an embodiment. [Figure 9] Diagram schematically showing an example of a control system for an electrical system in a vehicle according to an embodiment. [Figure 10] Block diagram showing an example of a system including a stationary power supply according to an embodiment. [Figure 11] Graph showing spectra obtained by powder X-ray diffraction measurement of active materials in each example. [Embodiments for Carrying Out the Invention]

[0009] Hereinafter, embodiments will be described with reference to the drawings. In the following description, components that exhibit the same or similar functions are given the same reference numerals throughout all the drawings, and redundant descriptions are omitted. Each drawing is a schematic diagram for facilitating the description of the embodiments and their understanding, and there are differences in its shape, dimensions, ratio, etc. from the actual device, but these can be appropriately designed and changed in consideration of the following description and known techniques.

[0010] [First Embodiment] According to the first embodiment, the general formula Li x Nb 10Ti2O 29 An active material is provided that is represented by (0≦x≦5). In this active material, the unit cell volume is 2230 Å. 3 The particles contain orthorhombic crystals as described above, and the full width at half maximum of the largest peak appearing in the powder X-ray diffraction spectrum at 24.5° ≤ 2θ ≤ 25.0° is 0.09° or less.

[0011] The active material in question is, for example, an electrode active material and may be included in the electrodes of secondary batteries such as lithium-ion batteries and non-aqueous electrolyte batteries. The electrode comprises an active material-containing layer containing the active material. More specifically, the electrode may be, for example, the negative electrode of a secondary battery.

[0012] The above general formula Li x Nb 10 Ti2O 29 Represented by this, by using an active material containing orthorhombic particles as the electrode active material, a high-power and long-life secondary battery can be realized.

[0013] Generally, active materials that exhibit small volume changes due to charging and discharging of secondary batteries can achieve excellent cycle capacity retention. This is because Li ions are inserted into and removed from the active material during charging and discharging of secondary batteries. For example, an active material with a large unit cell volume, such as one with voids equal to or greater than the diameter of a Li ion, can minimize the volume change of the active material due to charging and discharging of the secondary battery. By minimizing the volume change of the active material, distortion of the electrode layer can be reduced, thereby improving the cycle capacity retention of the secondary battery.

[0014] In particular, when the crystal structure is a Wadsley-Roth phase, the void volume is almost proportional to the unit cell volume, so the effect of increasing the unit cell volume to improve the cycle capacity maintenance rate is even more pronounced.

[0015] The cycle capacity retention rate mentioned above can also be improved by the high crystallinity of the active material. This is because high crystallinity means that there are few lattice defects, the lattice volume is uniform, and the crystal is stable, making it less likely for the active material to undergo structural changes due to charging and discharging of the secondary battery. As mentioned above, by making it less likely for the active material to undergo structural changes, it is possible to reduce distortion in the electrode layer and improve the cycle capacity retention rate of the secondary battery.

[0016] Generally, there is a trade-off between the reversible capacity and cycle capacity retention rate of an active material. This is because the higher the reversible capacity, the greater the number of Li ions (per unit weight of the active material) inserted into and removed from the active material during charging and discharging of the secondary battery, which tends to lead to larger volume changes in the active material. However, if the active material has a large unit cell volume with voids equal to or greater than the diameter of the Li ions, the volume change of the active material can be kept small even if a large number of Li ions are inserted into and removed from the active material during charging and discharging of the secondary battery. Furthermore, in active materials with a large unit cell volume, the movement of Li ions within the active material is promoted, improving Li ion conductivity and thus improving the reversible capacity. Therefore, in a secondary battery using the active material according to this embodiment, it is possible to achieve both high reversible capacity and high cycle capacity retention rate.

[0017] To obtain high crystallinity, the above general formula Li x Nb 10 Ti2O 29 This requires firing at a relatively high temperature. However, firing the active material at a high temperature causes the primary particles to grow significantly, and the crystal structure (crystal system) of some of the active material changes from monoclinic to orthorhombic, which has a relatively small unit cell volume.

[0018] In contrast, the active material according to this embodiment has the general formula Li x Nb 10 Ti2O 29 Represented as such, the inclusion of orthorhombic particles with high crystallinity and large unit cell volume enables the realization of high reversible capacity and cycle capacity retention.

[0019] The active material according to this embodiment is Li x Nb 10 Ti2O 29 It is represented as (0≦x≦5) and has a unit cell volume of 2230 Å. 3 The particles contain orthorhombic crystals as described above, and the full width at half maximum of the largest peak appearing in the powder X-ray diffraction spectrum at 24.5° ≤ 2θ ≤ 25.0° is 0.09° or less.

[0020] Next, the unit cell volume and powder X-ray diffraction (XRD) spectrum of the active material in question will be described.

[0021] The active material in question contains orthorhombic particles, and the full width at half maximum (FWHM) of the largest peak appearing in the powder XRD spectrum between 24.5° and 2θ between 25.0° is 0.09° or less. The fact that the FWHM of the largest peak appearing in the range of 24.5° between 2θ between 25.0° in the powder XRD spectrum is 0.09° or less indicates that the crystal structure of the measured active material is uniform and that it has good crystallinity. The preferred FWHM of the peak appearing in the aforementioned range is between 0.05° and 0.09°. Being 0.05° or more suppresses the enlargement of the primary particle size due to significant grain growth of the crystals of the active material. By suppressing the enlargement of the primary particles, it is possible to prevent the electrode film from being formed with large particles and resulting in insufficient conductive paths in the film, thereby suppressing a decrease in reversible capacitance.

[0022] <Measurement using powder XRD> The powder XRD of the active material can be obtained, for example, by the following method.

[0023] First, if the active material is contained within the secondary battery, the secondary battery is discharged, then disassembled to remove the electrodes. This disassembly is performed in a glove box under an inert gas atmosphere such as argon. The discharged state refers to the state in which the battery's charge level is discharged to 0%. The removed electrodes are immersed in a solvent for 3 minutes, and then dried in a glove box under an inert gas atmosphere. Diethyl carbonate, for example, is used as the solvent.

[0024] Next, the active material powder is extracted. The active material powder can be extracted, for example, as follows: First, the electrode containing the binder is dispersed in a solvent. The solvent used at this time is, for example, N-methylpyrrolidone if the binder is an organic solvent-based binder, or pure water if the binder is an aqueous binder (for example, a water-soluble binder). The electrode is dispersed by irradiating the solvent with ultrasound for 30 minutes or more. This dissolves the binder and separates the electrode material from the current collector as a powder. Next, the solvent containing the electrode material powder is placed in a centrifuge to separate it into conductive agent and active material particles, which are then recovered by freeze-drying.

[0025] The extracted active material is washed with an organic solvent such as diethyl carbonate to dissolve and remove the lithium salt, and then dried. After drying, the active material is thoroughly washed with water in air to remove residual lithium ions, and this is the material to be measured.

[0026] Powder XRD measurement is performed as follows. First, the active material obtained by the method described above is thoroughly pulverized to obtain a powder sample. The average particle size of the powder sample is preferably 20 μm or less. This average particle size can be determined using a laser diffraction particle size distribution analyzer.

[0027] Next, the powdered sample is filled into the holder portion of the glass sample plate, and its surface is made flat. For example, a glass sample plate with a holder portion depth of 0.2 mm can be used.

[0028] Next, the glass sample plate is placed in a powder X-ray diffractometer, and the XRD spectrum is measured using Cu-Kα rays. Specific measurement conditions are, for example, as follows: X-ray diffractometer: SmartLab manufactured by Rigaku Corporation X-ray source: CuKα ray Output: 40kV, 200mA Package measurement name: General-purpose measurement (concentrated method) Incident parallel slit opening angle: 5° Incident longitudinal limiting slit length: 10 mm Photodetector PSA: None Light-receiving parallel slit aperture angle: 5° Monochromatic method: Kβ filter method Measurement mode: Continuous Entrance slit width: 0.5° Light-receiving slit width: 20mm Measurement range (2θ): 5~70° Sampling width (2θ): 0.01° Scan speed: 1°~20° / min.

[0029] In this way, an XRD spectrum relating to 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 within a range such that the count of the main peak in the XRD spectrum is between 50,000 and 150,000 counts. In the XRD spectrum obtained by the method described above, the full width at half maximum (FWHM) of the maximum peak in the range of 24.5° ≤ 2θ ≤ 25.0° can be obtained. The FWHM refers to the width (FWHM total width) between two points where the intensity of a given peak is 50% of the peak value.

[0030] Next, we will explain the unit cell volume of the active material.

[0031] The unit cell volume of the orthorhombic particles contained in the active material is 2230 Å. 3 This concludes the explanation. This makes it possible to reduce the volume change of the active material due to charging and discharging of the secondary battery, thereby realizing a secondary battery with excellent cycle capacity retention. The preferred unit cell volume of the active material is 2230 Å. 3 The above 2245Å 3 The following is the result: 2245 Å 3 The following conditions make it possible to suppress the insertion of multiple Li ions into a single void during the charging and discharging of secondary batteries, as well as the destruction of the crystal structure due to the movement of Ti and Nb ions.

[0032] <Measurement of Unit Cell Volume> The unit cell volume of orthorhombic particles contained in the active material can be obtained, for example, by the following method.

[0033] The unit cell volume of orthorhombic particles contained in the active material is measured using the XRD spectrum obtained by the method described in <Measurement of Powder XRD> above. The XRD pattern obtained in this way is analyzed by the Rietveld method. In the Rietveld method, the diffraction pattern is calculated from a pre-estimated crystal structure model. By fitting all of these calculated values ​​with the measured values, parameters related to the crystal structure (lattice constants, atomic coordinates, occupancy, etc.) can be precisely analyzed. This allows for the investigation of the characteristics of the crystal structure of the synthesized compound.

[0034] Furthermore, it is possible to examine the occupancy rate of each constituent element within each site. A fitting parameter S is used as a measure to estimate the degree of agreement between observed and calculated intensities in Rietveld analysis. The analysis must be performed so that S is less than 1.8. Additionally, the standard deviation σj must be taken into consideration when determining the occupancy rate of each site. The fitting parameter S and standard deviation σj defined here shall be estimated using the formulas described in Non-Patent Document 2.

[0035] Furthermore, if the active material being measured contains crystals with different space groups, the content of those space groups can be quantified using Rietveld analysis. Specifically, crystal structure information is input for each different crystal phase, and these are fitted to the measured XRD pattern to determine the mass fraction from the intensity information of each phase. More details can be obtained using the method described in Chapter 10, Section 5, "Calculation of Phase Mass Fractions," of Non-Patent Literature 2.

[0036] By the above method, information regarding the crystal structure of the active material to be measured can be obtained. For example, when the active material according to the first embodiment is measured as described above, it can be found that the active material to be measured has a composite oxide having a monoclinic crystal structure. Further, by measuring as described above, the symmetry of the crystal structure to be measured, such as the space group Amma, can be examined. Furthermore, the degree of growth from the crystal orientation parameter to a specific plane index can be examined. For example, when the peak intensity of the (001) plane is higher than the peak intensity assumed from the crystal structure, it can be considered that there is crystal growth in the

[0010] direction.

[0037] <Active material particles> The active material according to the first embodiment can take, for example, the form of particles. That is, such an active material has the general formula Li x Nb 10 Ti2O 29 and contains orthorhombic particles. Further, in addition to the composite oxide, such an active material can be composed of particles in which the above-described traceable additive elements are mixed. The active material can be a single primary particle, secondary particles formed by aggregation of a plurality of primary particles, or a mixture thereof. The active material can contain the above elements, for example, on the surface of the primary particles of the composite oxide or between the primary particles of the composite oxide.

[0038] The active material according to the first embodiment can further contain an M element, and can be represented by the general formula Li x Nb 10+0.5y Ti 2-y M 0.5y O 29 (0 ≦ x ≦ 5, 0 < y ≦ 1). M is at least one element selected from the group consisting of Ta, Sc, Y, V, Cr, Fe, Co, Mn, Al, and Ga.

[0039] In the first embodiment, the average primary particle diameter 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 diameter of the active material is small, the diffusion distance of lithium ions within the primary particles is short, which tends to increase lithium ion diffusivity. Also, when the average primary particle diameter 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 and deinsertion reaction.

[0040] In the first embodiment, 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 manufacturing can be improved, and a battery with good performance can be obtained. This average secondary particle diameter refers to the particle size at which the integrated volume value in the particle size distribution determined by a laser diffraction particle size distribution analyzer becomes 50%.

[0041] <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 obtained by SEM observation can be calculated using the following method.

[0042] First, the lengths of the longest and shortest axes of the primary particles in the SEM images obtained by SEM observation are measured, and the arithmetic mean of these lengths is defined as the primary particle diameter. This primary particle diameter measurement is performed on 100 randomly selected particles, and the average of these measurements is defined as the average primary particle diameter.

[0043] 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. For this particle size distribution measurement, a dispersion of the active material diluted with N-methyl-2-pyrrolidone to a concentration of 0.1% to 1% by mass is used as the sample. The particle size at which the integrated volume value in the obtained particle size distribution reaches 50% is defined as the average secondary particle diameter.

[0044] The BET specific surface area of the active material is 3.0 m 2 / g or more and 120 m 2 / g or less, preferably 4.0 m 2 / g or more and 110 m 2 / g or less. Using an active material with a high specific surface area can increase the reversible capacity of the battery. Also, using an active material with a low specific surface area can improve the life performance of the battery, and in the electrode manufacturing process described later in the second embodiment, the coating property of the slurry containing the active material can be made good.

[0045] The BET specific surface area means 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 is as follows.

[0046] <Measurement of BET Specific Surface Area> The BET specific surface area of the active material particles can be determined by the following method.

[0047] First, 4 g of the active material is taken as a sample. Next, the evaluation cell of the measuring device is dried under reduced pressure at a temperature of 100 °C or higher for 15 hours to perform a degassing treatment. As the evaluation cell, for example, a 1 / 2-inch one can be used. Next, the sample is installed in the measuring device. As the measuring device, for example, TriStar II 3020 manufactured by Shimadzu Corporation - Micromeritics can be used. Next, in nitrogen gas at 77 K (the boiling point of nitrogen), while gradually increasing the pressure P (mmHg) of nitrogen gas, the nitrogen gas adsorption amount (mL / g) of the sample is measured for each pressure P. Next, the value obtained by dividing the pressure P (mmHg) by the saturated vapor pressure P0 (mmHg) of nitrogen gas is taken as the relative pressure P / P0, and an adsorption isotherm is obtained by plotting the nitrogen gas adsorption amount for each relative pressure P / P0. Next, a BET plot is calculated from this nitrogen adsorption isotherm and the BET equation, and the specific surface area is obtained using this BET plot.

[0048] Note that the BET multipoint method is used for the calculation of the BET plot.

[0049] <Manufacturing method> The active material according to the first embodiment can be manufactured as follows.

[0050] A precursor is obtained by dissolving a titanium source and a niobium source in an acidic solution as starting materials, then neutralizing the solution and drying the resulting gel. A niobium-titanium oxide is obtained by heat treatment of the precursor.

[0051] Examples of titanium sources include titanium tetraisopropoxide (C 12 H 28 O4Ti can be used. As a niobium source, for example, ammonium niobium oxalate hydrate (C4H4NNbO9·xH2O) can be used. As an acidic solution to dissolve these Ti and Nb sources, for example, an aqueous oxalic acid solution can be used. For neutralization, for example, aqueous ammonia can be used. For drying the gel after neutralization, for example, heating in air or spray drying can be applied.

[0052] When obtaining an oxide by heat treatment of the precursor, the precursor is densely packed into a container with an appropriate opening. By increasing the density in this way, sufficient oxidation of the precursor is promoted while suppressing the volatilization of the metal. In the heat treatment, pre-calcination (first calcination) is performed before the main calcination. Pre-calcination is preferably performed at a temperature of 200°C to 400°C for 1 to 12 hours. Pre-calcination removes trace amounts of impurities (e.g., water and organic matter) adsorbed on the precursor. Pre-calcination may be omitted. The main calcination (second calcination) is preferably performed at a temperature of 900°C to 1500°C for 1 to 40 hours. After that, cooling is performed to 100°C at a rate setting of -2°C / min to -0.05°C / min. By cooling under the above conditions after the main calcination, an active material according to the embodiment can be obtained with a large unit cell volume and high crystallinity. This is because sufficient time is spent during the cooling process, when the active material returns to room temperature from the firing temperature, for the atoms to rearrange themselves. As described above, a slow cooling rate makes it easier for the atoms of the active material to form a regular arrangement, thereby improving crystallinity. Furthermore, a sufficiently long time for the atoms of the active material to rearrange themselves reduces the likelihood of lattice defects, including oxygen vacancies, being formed, thus allowing for a larger unit cell volume.

[0053] In addition to the liquid-phase synthesis method described above, the active material according to the embodiment can also be obtained by a general solid-phase reaction method, for example. Specifically, the active material related to the embodiment can be obtained by mixing titanium dioxide (TiO2) and niobium oxide (Nb2O5, or NbO2) in a mortar or ball mill and firing them in the air.

[0054] The active material according to the first embodiment is Li x Nb 10 Ti2O 29 It is represented as (0≦x≦5) and has a unit cell volume of 2230 Å. 3The particle contains orthorhombic particles as described above, and the full width at half maximum of the maximum peak appearing at 24.5° ≤ 2θ ≤ 25.0° in the powder X-ray diffraction spectrum is 0.09° or less. This enables the realization of a secondary battery that exhibits high output and excellent cycle capacity retention.

[0055] [Second Embodiment] According to the second embodiment, an electrode is provided that comprises an active material-containing layer containing the active material described in the first embodiment.

[0056] The electrode according to the second embodiment includes the active material according to the first embodiment. This electrode may be an electrode containing the active material according to the first embodiment as an electrode active material. The 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.

[0057] The electrode according to the second embodiment may include a current collector and an active material-containing layer. The active material-containing layer may be formed on one or both sides of the current collector. The active material-containing layer may include an active material and optionally a conductive agent and a binder.

[0058] The active material-containing layer may contain the active material according to the first embodiment alone, or it may contain two or more types of active materials according to the first embodiment. Furthermore, it may contain a mixture of one or more types of active materials according to the first embodiment and one or more other active materials. It is desirable that the content ratio of the active material according to the first embodiment 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.

[0059] For example, if the active material according to the first embodiment is included as the negative electrode active material, other examples of active materials include lithium titanate having a ramsdelite structure (e.g., Li 2+x Ti3O7 (-1≦x≦3)), lithium titanate having a spinel structure (for example, Li 4+x Ti5O 12Examples include monoclinic titanium dioxide (TiO2), anatase titanium dioxide, rutile titanium dioxide, hollandite titanium composite oxide, orthorhombic titanium composite oxide, and monoclinic niobium titanium composite oxide, niobium oxide, niobium titanium oxide, niobium molybdenum composite oxide, and niobium tungsten composite oxide.

[0060] 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 A compound represented by the formula is shown below. 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. A specific example of an orthorhombic titanium-containing composite oxide is Li 2+e Na2Li6O 14 (0 ≤ e ≤ 6) is one example.

[0061] As an example of the above monoclinic niobium-titanium composite oxide, Li x Ti 1-y M4 y Nb 2-z M5 z O 7+δ Examples of compounds represented by are: 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 compositional formula are 0≦x≦5, 0≦y<1, 0≦z<2, and -0.3≦δ≦0.3. A specific example of a monoclinic niobium titanium composite oxide is Li x Nb2TiO7 (0≦x≦5) is one example.

[0062] Another example of monoclinic niobium-titanium composite oxides is Li x Ti 1-y M6y+z Nb 2-z O 7-δ A compound represented by the formula is shown below. Here, M6 is at least one selected from the group consisting of Mg, Fe, Ni, Co, W, Ta, and Mo. The subscripts in the empirical formula represent 0≦x<5, 0≦y<1, 0≦z<2, and -0.3≦δ≦0.3.

[0063] Conductive agents are added to enhance 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 a conductive agent, or two or more may be used in combination. Alternatively, instead of using a conductive agent, a carbon coating or an electronically conductive inorganic material coating may be applied to the surface of the active material particles. Furthermore, the current collection performance of the active material-containing layer can be improved by using a conductive agent and coating the surface of the active material with carbon or a conductive material.

[0064] A binder is added to fill the gaps between dispersed active materials and to bond the active materials to the current collector. Examples of binders include polytetrafluoroethylene (PTFE), polyvinylidene fluoride (PVdF), fluororubber, styrene-butadiene rubber, polyacrylic acid compounds, imide compounds, carboxymethyl cellulose (CMC), and salts of CMC. One of these may be used as a binder, or two or more may be used in combination.

[0065] The mixing 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, it is preferable to mix the active material (negative electrode active material), conductive agent, and binder in the following proportions: 68% to 96% by mass, 2% to 30% by mass, and 2% 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 bonding 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 each in order to achieve high capacity.

[0066] When the surface of the active material is coated with carbon or a conductive material, the amount of coating material can be considered as being included in the amount of conductive agent. The amount of carbon or conductive material coating is preferably 0.5% by mass or more and 5% by mass or less. Within this range of coating amounts, current collection performance and electrode density can be improved.

[0067] The current collector is made of a material that is electrochemically stable at the potential at which lithium (Li) is inserted into and removed from the active material. For example, when the active material is used as the negative electrode active material, the current collector is preferably made of copper, nickel, stainless steel, or aluminum, or an aluminum alloy containing one or more elements selected from the group consisting of Mg, Ti, Zn, Mn, Fe, Cu, and Si. The thickness of the current collector is preferably 5 μm to 20 μm. A current collector with such a thickness can balance electrode strength and weight reduction.

[0068] Furthermore, the current collector may include portions on its surface where the active material-containing layer is not formed. These portions can function as current-collecting tabs.

[0069] Electrodes can be manufactured, 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 the active material-containing layer and the current collector. After that, this laminate is pressed. In this way, electrodes are manufactured.

[0070] Alternatively, electrodes may be manufactured by the following method: First, an active material, a conductive agent, and a binder are mixed to obtain a mixture. Next, this mixture is formed into pellets. Then, electrodes can be obtained by placing these pellets on a current collector.

[0071] The electrode according to the second embodiment comprises an active material-containing layer containing the active material according to the first embodiment. Therefore, the electrode according to the second embodiment can realize a secondary battery that exhibits high output and excellent cycle capacity retention.

[0072] [Third Embodiment] According to the third embodiment, a secondary battery is provided that comprises a positive electrode, a negative electrode, and an electrolyte. This secondary battery includes an electrode according to the second embodiment as either the negative electrode or the positive electrode. That is, the secondary battery according to the third embodiment includes the active material according to the first embodiment as the electrode active material. A preferred embodiment of the secondary battery includes an electrode according to the second embodiment as the negative electrode. That is, the preferred embodiment of the secondary battery includes an electrode as the negative electrode that comprises an active material-containing layer containing the active material according to the first embodiment. Preferred embodiments will be described below.

[0073] The secondary battery may further include a separator positioned between the positive and negative electrodes. The negative electrode, positive electrode, and separator can constitute an electrode group. The electrolyte can be held within the electrode group.

[0074] Furthermore, the secondary battery may further comprise an outer casing that houses the electrode group and the electrolyte.

[0075] Furthermore, the secondary battery may further include a negative terminal electrically connected to the negative electrode and a positive terminal electrically connected to the positive electrode.

[0076] The secondary battery according to the third embodiment may be, for example, a lithium secondary battery. The secondary battery also includes a non-aqueous electrolyte secondary battery containing a non-aqueous electrolyte.

[0077] The following provides a detailed explanation of the negative electrode, positive electrode, electrolyte, separator, outer casing, negative electrode terminal, and positive electrode terminal.

[0078] 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 a current collector and an active material-containing layer that can be included in the electrode according to the second embodiment, respectively. The negative electrode active material-containing layer contains the active material according to the first embodiment as the negative electrode active material.

[0079] Details of the negative electrode that overlap with the details described in the second embodiment will be omitted.

[0080] The density of the negative electrode active material layer (excluding the current collector) is 1.8 g / cm³. 3 More than 2.8g / cm 3 The following is preferable. A negative electrode with a density of the negative electrode active material-containing layer within this range exhibits excellent energy density and electrolyte retention. The density of the negative electrode active material-containing layer is 2.1 g / cm³. 3 More than 2.6g / cm 3 The following is more preferable:

[0081] The negative electrode can be manufactured, for example, by the same method as the electrode according to the second embodiment.

[0082] 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 optionally include a positive electrode active material and a conductive agent and a binder.

[0083] 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.

[0084] Examples of such compounds include manganese dioxide (MnO2), iron oxide, copper oxide, nickel oxide, lithium manganese composite oxide (e.g., Li x Mn2O4 or Li x MnO2; 0 < x ≦ 1), lithium nickel composite oxide (e.g., Li x NiO2; 0 < x ≦ 1), lithium cobalt composite oxide (e.g., Li x CoO2; 0 < x ≦ 1), lithium nickel cobalt composite oxide (e.g., Li x Ni 1-y Co y O2; 0 < x ≦ 1, 0 < y < 1), lithium manganese cobalt composite oxide (e.g., Li x Mn y Co 1-y O2; 0 < x ≦ 1, 0 < y < 1), lithium manganese nickel composite oxide having a spinel structure (e.g., Li x Mn 2-y Ni y O4; 0 < x ≦ 1, 0 < y < 2), lithium phosphate having an olivine structure (e.g., Li x FePO4; 0 < x ≦ 1, Li x Fe 1-y Mn y PO4; 0 < x ≦ 1, 0 < y ≦ 1, Li x [[ID=四十一]]CoPO4; 0 < x ≦ 1), iron sulfate (Fe2(SO4)3), vanadium oxide (e.g., V2O5), and lithium nickel cobalt manganese composite oxide (Li x Ni 1-y-z Co y Mn z O2; 0 < x ≦ 1, 0 < y < 1, 0 < z < 1, y + z < 1) are included.

[0085] Among the above, examples of more preferable compounds as the positive electrode active material include lithium manganese composite oxides having a spinel structure (e.g., Li x Mn2O4; 0 < x ≦ 1), lithium nickel composite oxides (e.g., Li x NiO2; 0 < x ≦ 1), lithium cobalt composite oxides (e.g., Li x CoO2; 0 < x ≦ 1), lithium nickel cobalt composite oxides (e.g., Li x Ni 1-y Co y O2; 0 < x ≦ 1, 0 < y < 1), lithium manganese nickel composite oxides having a spinel structure (e.g., Li x Mn 2-y Ni y O4; 0 < x ≦ 1, 0 < y < 2), lithium manganese cobalt composite oxides (e.g., Li x Mn y Co 1-y O2; 0 < x ≦ 1, 0 < y < 1), lithium iron phosphate (e.g., 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.

[0086] When a room temperature molten salt is used as the electrolyte of the battery, it is preferable to use a positive electrode active material containing lithium iron phosphate, Li x VPO4F (0 ≦ x ≦1), a lithium manganese composite oxide, a lithium nickel composite oxide, a lithium nickel cobalt composite oxide, or a mixture thereof. Since these compounds have low reactivity with the room temperature molten salt, the cycle life can be improved. Details of the room temperature molten salt will be described later.

[0087] The primary particle size of the positive electrode active material is preferably between 100 nm and 1 μm. Positive electrode active material with a primary particle size of 100 nm or more is easy to handle in industrial production. Positive electrode active material with a primary particle size of 1 μm or less allows for smooth diffusion of lithium ions within the solid.

[0088] The specific surface area of ​​the positive electrode active material is 0.1 m². 2 / g or more 10m 2 It is preferable that it is less than or equal to / g. 0.1m 2 A positive electrode active material having a specific surface area of ​​10m or more can adequately secure Li ion insertion and deinsertion sites. 2 Positive electrode active materials with a specific surface area of ​​less than / g are easy to handle in industrial production and can ensure good charge-discharge cycle performance.

[0089] A binder is added to fill the gaps between the dispersed positive electrode active material and to bond the positive electrode active material to the positive electrode current collector. Examples of binders include PTFE, PVdF, fluororubber, polyacrylic acid compounds, imide compounds, CMC, and salts of CMC. One of these may be used as a binder, or two or more may be used in combination.

[0090] Conductive agents are added to enhance current collection performance and reduce contact resistance between the positive electrode active material and the positive electrode current collector. Examples of conductive agents include carbon black such as VGCF and acetylene black, and carbonaceous materials such as graphite. One of these may be used as a conductive agent, or two or more may be used in combination. Conductive agents can also be omitted.

[0091] In the positive electrode active material-containing layer, it is preferable that the positive electrode active material and the binder are blended in proportions of 80% to 98% by mass and 2% to 20% by mass, respectively.

[0092] Sufficient electrode strength can be obtained by using a binder amount of 2% by mass or more. Furthermore, the binder can function as an insulator. Therefore, reducing the binder amount to 20% by mass or less reduces the amount of insulator contained in the electrode, thereby reducing internal resistance.

[0093] When a conductive agent is added, it is preferable that the positive electrode active material, binder, and conductive agent are blended in proportions of 77% to 95% by mass, 2% to 20% by mass, and 3% to 15% by mass, respectively.

[0094] The above-mentioned effects can be achieved by increasing the amount of conductive agent to 3% by mass or more. Furthermore, by reducing 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 lower proportion reduces the decomposition of the electrolyte under high-temperature storage conditions.

[0095] The positive electrode current collector is preferably an aluminum foil, or an aluminum alloy foil containing one or more elements selected from the group consisting of Mg, Ti, Zn, Ni, Cr, Mn, Fe, Cu, and Si.

[0096] The thickness of the aluminum foil or aluminum alloy foil is preferably 5 μm or more and 20 μm or less, and more preferably 15 μm or less. The purity of the aluminum foil is preferably 99% by mass or more. The content of transition metals such as iron, copper, nickel, and chromium in the aluminum foil or aluminum alloy foil is preferably 1% by mass or less.

[0097] Furthermore, the positive electrode current collector may include portions on its surface where the positive electrode active material-containing layer is not formed. These portions can function as positive electrode current collector tabs.

[0098] The positive electrode can be manufactured, for example, using a positive electrode active material in the same manner as the electrode according to the second embodiment.

[0099] 3) Electrolytes As the electrolyte, for example, a liquid non-aqueous electrolyte or a gel-type non-aqueous electrolyte can be used. A liquid non-aqueous 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.

[0100] Examples of electrolyte salts include lithium perchlorate (LiClO4), lithium hexafluoride phosphate (LiPF6), lithium tetrafluoroborate (LiBF4), lithium arsenide hexafluoride (LiAsF6), lithium trifluoromethanesulfonate (LiCF3SO3), and lithium salts such as bistrifluoromethylsulfonylimide lithium (LiN(CF3SO2)2), lithium bis(fluorosulfonyl)imide (LiN(SO2F)2; LiFSI), and mixtures thereof. The electrolyte salt is preferably resistant to oxidation even at high potentials, with LiPF6 being the most preferred.

[0101] 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); and γ-butyrolactone (GBL), acetonitrile (AN), and sulfolane (SL). These organic solvents can be used alone or as mixed solvents.

[0102] Gel-like non-aqueous electrolytes are prepared by compounding a liquid non-aqueous electrolyte with a polymer material. Examples of polymer materials include PVdF, polyacrylonitrile (PAN), polyethylene oxide (PEO), or mixtures thereof.

[0103] Alternatively, in addition to liquid nonaqueous electrolytes and gel-type nonaqueous electrolytes, room-temperature molten salts (ionic melts) containing lithium ions, polymer solid electrolytes, and inorganic solid electrolytes may be used as nonaqueous electrolytes.

[0104] Room temperature molten salts (ionic melts) refer to organic salts consisting of a combination of organic cations and anions that can exist as liquids at room temperature (15°C to 25°C). Room temperature molten salts include room temperature molten salts that exist as liquids 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, or mixtures thereof. Generally, the melting point of room temperature molten salts used in secondary batteries is 25°C or lower. Also, organic cations generally have a quaternary ammonium skeleton.

[0105] Polymeric solid electrolytes are prepared by dissolving an electrolyte salt in a polymer material and then solidifying it.

[0106] Inorganic solid electrolytes are solid materials that have lithium ion conductivity. Here, "having lithium ion conductivity" means that at 25°C, they have a conductivity of 1 × 10⁻⁶. -6 This refers to exhibiting a lithium ion conductivity of S / cm or higher. Examples of inorganic solid electrolytes include oxide-based solid electrolytes and sulfide-based solid electrolytes. Specific examples of inorganic solid electrolytes are as follows.

[0107] As an oxide-based solid electrolyte, it has a NASICON (Sodium (Na) Super Ionic Conductor) type structure, and its general formula is Li 1+xIt is preferable to use a lithium phosphate solid electrolyte represented by Mα2(PO4)3. Mα in the above general formula is, for example, one or more selected from the group consisting of titanium (Ti), germanium (Ge), strontium (Sr), zirconium (Zr), tin (Sn), aluminum (Al), and calcium (Ca). The subscript x is within the range of 0 ≦ x ≦ 2.

[0108] Specific examples of the lithium phosphate solid electrolyte having a NASICON-type structure include LATP compounds represented by Li 1+x Al x Ti 2-x (PO4)3 with 0.1≦ x ≦ 0.5; compounds represented by Li 1+x Al y Mβ 2-y (PO4)3 where Mβ is one or more selected from the group consisting of Ti, Ge, Sr, Zr, Sn, and Ca and 0 ≦ x ≦ 1 and 0 ≦ y ≦ 1; compounds represented by Li 1+x Al x Ge 2-x (PO4)3 with 0 ≦ x ≦ 2; and compounds represented by Li 1+x Al x Zr 2-x (PO4)3 with 0 ≦ x ≦ 2; compounds represented by Li 1+x+y Al x Mγ 2-x Si y P 3-y O 12 where Mγ is one or more selected from the group consisting of Ti and Ge and 0 < x ≦ 2, 0 ≦ y < 3; compounds represented by Li 1+2x Zr 1-x Ca x (PO4)3 with 0 ≦ x < 1 can be mentioned.

[0109] In addition, as the oxide-based solid electrolyte, in addition to the above lithium phosphate solid electrolyte, there is also an amorphous LIPON compound represented by Li x PO y N z where 2.6 ≦ x ≦ 3.5, 1.9 ≦ y ≦ 3.8, and 0.1 ≦ z ≦ 1.3 (for example, Li 2.9 PO 3.3 N 0.46); Garnet-type structure La 5+x A x La 3-x Mδ2O 12 A compound represented as follows: A is one or more selected from the group consisting of Ca, Sr, and Ba, and 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 1 or more selected from the group consisting of Nb and Ta, and L may contain Zr, with 0 ≤ x ≤ 0.5; Li 7-3x Al x La3Zr3O 12 Compounds represented by 0 ≤ x ≤ 0.5; Li 5+x La3MCSR 2-x Zr x O 12 Represented as such, Mδ is 1 or more selected from the group consisting of Nb and Ta, and 0 ≤ x ≤ 2, and is an LLZ compound (e.g., Li7La3Zr2O 12 ); and having a perovskite-type structure La 2 / 3-x Li x Examples include compounds represented as TiO3 where 0.3 ≤ x ≤ 0.7.

[0110] One or more of the above compounds can be used as a solid electrolyte. Two or more of the above solid electrolytes may also be used.

[0111] Alternatively, a liquid aqueous electrolyte or a gel-type aqueous electrolyte can be used as the electrolyte instead of a non-aqueous electrolyte. A liquid aqueous electrolyte is prepared by dissolving, for example, the electrolyte salt in an aqueous solvent as the solute. A gel-type aqueous electrolyte is prepared by compounding a liquid aqueous electrolyte with the polymer material. As the aqueous solvent, a solution containing water may be used. The solution containing water may be pure water or a mixed solvent of water and an organic solvent.

[0112] 3) Separator The separator can be any material as long as it can electrically insulate the positive and negative electrodes. For example, it can be formed from a porous film containing polyethylene (PE), polypropylene (PP), cellulose, or PVdF, or from a nonwoven fabric made of synthetic resin. From a safety standpoint, it is preferable to use a porous film made of polyethylene or polypropylene, because these porous films can melt at a certain temperature and interrupt the electric current.

[0113] 4) Exterior components For example, the outer packaging material can be a container made of laminate film or a metal outer can.

[0114] The thickness of the laminating film is, for example, 0.5 mm or less, and preferably 0.2 mm or less.

[0115] As the laminate film, a multilayer film is used that includes multiple resin layers and a metal layer interposed between these resin layers. The resin layers include polymer materials such as polypropylene (PP), polyethylene (PE), nylon, and polyethylene terephthalate (PET). The metal layer is preferably made of aluminum foil or aluminum alloy foil for weight reduction. The laminate film can be molded into the shape of an exterior component by sealing it by heat fusion.

[0116] The thickness of the outer can wall is, for example, 1 mm or less, more preferably 0.5 mm or less, and even more preferably 0.2 mm or less.

[0117] The outer container is made from, 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 transition metals is preferably 1% by mass or less.

[0118] The shape of the exterior components is not particularly limited. For example, the exterior components may be flat (thin), rectangular, cylindrical, coin-shaped, or button-shaped. The exterior components can be appropriately selected according to the battery dimensions and intended use.

[0119] 5) Negative terminal The negative terminal has a potential range of 0.8V to 3V relative to the oxidation-reduction potential of lithium (vs.Li / Li + The negative electrode terminal can be formed from a material that is electrochemically stable and conductive in the field. Specifically, examples of materials for the negative electrode terminal include copper, nickel, stainless steel, or aluminum, or an aluminum alloy containing at least one element selected from the group consisting of Mg, Ti, Zn, Mn, Fe, Cu, and Si. It is preferable to use aluminum or an aluminum alloy as the material for the negative electrode terminal. It is preferable that the negative electrode terminal be made of the same material as the negative electrode current collector in order to reduce contact resistance with the negative electrode current collector.

[0120] 6) Positive terminal The positive terminal has a potential range of 3V to 4.5V relative to the oxidation-reduction potential of lithium (vs.Li / Li + The positive electrode terminal can be formed from an electrically stable and conductive material. Examples of positive electrode terminal materials include aluminum, or an aluminum alloy containing at least one element selected from the group consisting of Mg, Ti, Zn, Mn, Fe, Cu, and Si. It is preferable that the positive electrode terminal be formed from the same material as the positive electrode current collector in order to reduce contact resistance with the positive electrode current collector.

[0121] The above describes an embodiment of the secondary battery in which the electrode according to the second embodiment is used as the negative electrode. In the embodiment of the secondary battery according to the third embodiment in which the electrode according to the second embodiment is used as the positive electrode, for example, the following types of counter electrodes can be used as the negative electrode. At least one electrode selected from lithium metal, lithium metal alloy, graphite, silicon, silicon oxide, tin oxide, silicon, tin, and other alloys can be used as the negative electrode. Materials that do not contain Li in the active material can be used as the negative electrode by pre-doping with the element Li.

[0122] In an embodiment that includes the electrode according to the second embodiment as the positive electrode, the details of the positive electrode are omitted because they overlap with those described in the second embodiment.

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

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

[0125] The secondary battery 100 shown in Figures 1 and 2 comprises an electrode group 1 shown in Figure 1, a bag-shaped outer casing member 2 shown in Figures 1 and 2, and an electrolyte (not shown). The electrode group 1 and the electrolyte are housed within the bag-shaped outer casing member 2. The electrolyte (not shown) is held by the electrode group 1.

[0126] The bag-shaped outer packaging member 2 consists of a laminate film comprising two resin layers and a metal layer interposed between them.

[0127] As shown in Figure 1, electrode group 1 is a flat, wound electrode group. As shown in Figure 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 in 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 Figure 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 thereof.

[0130] As shown in Figure 1, the negative electrode terminal 6 and the positive electrode terminal 7 are located near the outer edge of the wound electrode group 1. The negative electrode terminal 6 is connected to the outermost part of the negative electrode current collector 3a. The positive electrode terminal 7 is connected to the outermost part of the positive electrode current collector 5a. These negative electrode terminals 6 and positive electrode terminals 7 extend outward from the opening of the bag-shaped outer casing member 2. A thermoplastic resin layer is installed on the inner surface of the bag-shaped outer casing member 2, and the opening is closed by heat fusion of this layer.

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

[0132] Figure 3 is a schematic partially cutaway perspective view showing another example of a secondary battery according to the third embodiment. Figure 4 is an enlarged cross-sectional view of part B of the secondary battery shown in Figure 3.

[0133] The secondary battery 100 shown in Figures 3 and 4 comprises an electrode group 1 shown in Figures 3 and 4, an outer casing member 2 shown in Figure 3, and an electrolyte (not shown). The electrode group 1 and the electrolyte are housed within the outer casing member 2. The electrolyte is held within the electrode group 1.

[0134] The exterior component 2 consists of a laminate film comprising two resin layers and a metal layer interposed between them.

[0135] As shown in Figure 4, electrode group 1 is a stacked electrode group. The stacked electrode group 1 has a structure in which negative electrodes 3 and positive electrodes 5 are alternately stacked with separators 4 interposed between them.

[0136] The electrode group 1 includes a plurality of negative electrodes 3. Each of the plurality of negative electrodes 3 comprises 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 comprises 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] Each negative electrode 3's negative electrode current collector 3a includes a portion 3c on one side where the negative electrode active material-containing layer 3b is not supported on any surface. This portion 3c functions as a negative electrode current collector tab. As shown in Figure 4, the portion 3c acting as a negative electrode current collector tab does not overlap with the positive electrode 5. Furthermore, multiple negative electrode current collector tabs (portions 3c) are electrically connected to a strip-shaped negative electrode terminal 6. The tip of the strip-shaped negative electrode terminal 6 is extended to the outside of the outer casing member 2.

[0138] Although not shown in the diagram, 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. The positive electrode current collector tab, like the negative electrode current collector tab (part 3c), does not overlap with the negative electrode 3. Furthermore, the positive electrode current collector tab is located on the opposite side of the electrode group 1 from the negative electrode current collector tab (part 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 extended to the outside of the outer casing member 2.

[0139] The secondary battery according to the third embodiment comprises the electrode according to the second embodiment. In other words, the secondary battery according to the third embodiment includes an electrode comprising an active material-containing layer containing the active material according to the first embodiment. Therefore, the secondary battery according to the third embodiment exhibits high output and excellent cycle capacity retention.

[0140] [Fourth Embodiment] According to the fourth embodiment, a battery pack is provided. The battery pack according to the fourth embodiment comprises a plurality of secondary batteries according to the third embodiment.

[0141] In the battery pack according to the fourth embodiment, each individual cell may be arranged in series or parallel connections, or a combination of series and parallel connections.

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

[0143] Figure 5 is a schematic perspective view showing an example of a battery pack according to the fourth embodiment. The battery pack 200 shown in Figure 5 comprises five single cells 100a to 100e, four busbars 21, a positive electrode lead 22, and a negative electrode lead 23. Each of the five single cells 100a to 100e is a secondary battery according to the third embodiment.

[0144] The busbar 21 connects, for example, the negative terminal 6 of one cell 100a to the positive terminal 7 of the adjacent cell 100b. In this way, the five cells 100 are connected in series by four busbars 21. That is, the battery pack 200 in Figure 5 is a battery pack with five cells in series. Although not illustrated, in a battery pack containing multiple cells that are electrically connected in parallel, the multiple cells can be electrically connected, for example, by connecting multiple negative terminals to each other and multiple positive terminals to each other by busbars.

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

[0146] The battery pack according to the fourth embodiment comprises a secondary battery according to the third embodiment. Therefore, this battery pack exhibits high output and excellent cycle capacity retention.

[0147] [Fifth Embodiment] According to a fourth embodiment, a battery pack is provided. This battery pack may comprise a single secondary battery according to a third embodiment instead of the battery pack according to the fourth embodiment.

[0148] The battery pack according to this embodiment may further include a protection circuit. The protection circuit has the 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., an electronic device, an automobile, etc.) may be used as the protection circuit for the battery pack.

[0149] Furthermore, the battery pack according to this embodiment may also have external terminals for power supply. These external terminals are for outputting current from the secondary battery to the outside and / or for inputting current from the outside to the secondary battery. In other words, when the battery pack is used as a power source, current is supplied to the outside through the external terminals. Also, when charging the battery pack, the charging current (including regenerative energy from the power of an automobile, etc.) is supplied to the battery pack through the external terminals.

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

[0151] Figure 6 is an exploded perspective view schematically showing an example of a battery pack according to the embodiment. Figure 7 is a block diagram showing an example of the electrical circuit of the battery pack shown in Figure 6.

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

[0153] The container 31 shown in Figure 6 is a rectangular-bottomed rectangular container. The container 31 is configured to accommodate a protective sheet 33, a battery pack 200, a printed circuit board 34, and wiring 35. The lid 32 has a rectangular shape. The lid 32 covers the container 31, thereby housing the battery pack 200 and the other components. The container 31 and the lid 32 are provided with openings or connection terminals for connecting to external devices, etc., although these are not shown in the figures.

[0154] The battery pack 200 comprises multiple individual cells 100, a positive electrode lead 22, a negative electrode lead 23, and an adhesive tape 24.

[0155] The single cell 100 has the structure shown in Figures 4 and 5. At least one of the multiple single cells 100 is a secondary battery according to the third embodiment. The multiple single cells 100 are stacked so that the negative terminal 6 and positive terminal 7 extending to the outside are facing the same direction. Each of the multiple single cells 100 is electrically connected in series as shown in Figure 7. The multiple single cells 100 may also be electrically connected in parallel, or a combination of series and parallel connections may be used. When the multiple single cells 100 are connected in parallel, the battery capacity increases compared to when they are connected in series.

[0156] The adhesive tape 24 fastens multiple single cells 100 together. Alternatively, heat-shrinkable tape may be used to secure the multiple single cells 100 instead of the adhesive tape 24. In this case, protective sheets 33 are placed on both sides of the battery pack 200, the heat-shrinkable tape is wrapped around it, and then the heat-shrinkable tape is heat-shrinked to bundle the multiple single cells 100 together.

[0157] One end of the positive lead 22 is connected to the positive terminal 7 of the bottommost cell 100 in the stack of cell 100s. One end of the negative lead 23 is connected to the negative terminal 6 of the topmost cell 100 in the stack of cell 100s.

[0158] The printed circuit board 34 is installed along one of the shorter sides of the inner surface of the housing container 31. The printed circuit board 34 includes a positive terminal connector 341, a negative terminal connector 342, a thermistor 343, a protection circuit 344, wiring 345 and 346, an external terminal 347 for energization, a positive terminal wiring 348a, and a negative terminal wiring 348b. One main surface of the printed circuit board 34 faces the surface from which the negative terminal 6 and positive terminal 7 extend in the battery pack 200. An insulating plate (not shown) is interposed between the printed circuit board 34 and the battery pack 200.

[0159] The positive terminal connector 341 is provided with a through-hole. The other end of the positive terminal lead 22 is inserted into this through-hole, thereby electrically connecting the positive terminal connector 341 and the positive terminal lead 22. The negative terminal connector 342 is provided with a through-hole. The other end of the negative terminal lead 23 is inserted into this through-hole, thereby electrically connecting the negative terminal connector 342 and the negative terminal lead 23.

[0160] The thermistor 343 is fixed to one main surface of the printed circuit board 34. The thermistor 343 detects the temperature of each of the single cells 100 and transmits the detection signal to the protection circuit 344.

[0161] The external terminal 347 for power supply is fixed to the other main surface of the printed circuit board 34. The external terminal 347 for power supply is electrically connected to equipment located outside the battery pack 300.

[0162] The protection circuit 344 is fixed to the other main surface of the printed circuit board 34. The protection circuit 344 is connected to the external terminal 347 for power supply via the positive side wiring 348a. The protection circuit 344 is connected to the external terminal 347 for power supply via the negative side wiring 348b. The protection circuit 344 is also electrically connected to the positive side connector 341 via wiring 345. The protection circuit 344 is also electrically connected to the negative side connector 342 via wiring 346. Furthermore, the protection circuit 344 is electrically connected to each of the multiple single cells 100 via wiring 35.

[0163] The protective sheet 33 is positioned on both inner surfaces in the long-side direction of the housing container 31 and on the inner surface in the short-side direction facing the printed circuit board 34 via the battery pack 200. The protective sheet 33 is made of, for example, resin or rubber.

[0164] The protection circuit 344 controls the charging and discharging of multiple single cells 100. The protection circuit 344 also disconnects the electrical connection between the protection circuit 344 and the external terminal 347 for power supply based on a detection signal transmitted from the thermistor 343 or a detection signal transmitted from an individual single cell 100 or a battery pack 200.

[0165] An example of a detection signal transmitted from the thermistor 343 is a signal indicating that the temperature of a single cell 100 is above a predetermined temperature. An example of a detection signal transmitted from an individual single cell 100 or a battery pack 200 is a signal indicating that overcharging, over-discharging, or overcurrent has been detected in a single cell 100. When detecting overcharging, etc., in an individual single cell 100, the battery voltage may be detected, or the positive electrode potential or negative electrode potential may be detected. In the latter case, a lithium electrode to be used as a reference electrode is inserted into each individual single cell 100. The protection circuit 344 may be a circuit included in a device that uses the battery pack 300 as a power source (e.g., electronic equipment, automobile, etc.).

[0166] Furthermore, as described above, the battery pack 300 is equipped with an external terminal 347 for power supply. Therefore, the battery pack 300 can output current from the battery pack 200 to an external device and input current from an external device to the battery pack 200 via the external terminal 347. In other words, when the battery pack 300 is used as a power source, current from the battery pack 200 is supplied to the external device through the external terminal 347. Also, when charging the battery pack 300, charging current from an external device is supplied to the battery pack 300 through the external terminal 347. When this battery pack 300 is used as an on-board battery, the regenerative energy of the vehicle's power can be used as the charging current from the external device.

[0167] The battery pack 300 may comprise multiple battery packs 200. In this case, the multiple battery packs 200 may be connected in series, in parallel, or in a combination of series and parallel connections. The printed circuit board 34 and wiring 35 may be omitted. In this case, the positive lead 22 and the negative lead 23 may be used as external terminals for energization.

[0168] Such battery packs are used in applications where excellent cycle performance is required when drawing high currents. Specifically, these battery packs are used as power supplies for electronic devices, stationary batteries, and on-board batteries for various vehicles. Examples of electronic devices include digital cameras. These battery packs are particularly suitable for use as on-board batteries.

[0169] The battery pack according to the fifth embodiment comprises a secondary battery according to the third embodiment or a battery pack according to the fourth embodiment. Therefore, this battery pack exhibits high output and excellent cycle capacity retention.

[0170] [Sixth Embodiment] According to the sixth embodiment, a vehicle is provided, which is equipped with a battery pack according to the fifth embodiment.

[0171] In the vehicle according to the sixth embodiment, the battery pack, for example, recovers regenerative energy from the vehicle's power. The vehicle may also include a mechanism (regenerator) that converts the vehicle's kinetic energy into regenerative energy.

[0172] Examples of vehicles according to the sixth embodiment include, for example, two-wheeled to four-wheeled hybrid electric vehicles, two-wheeled to four-wheeled electric vehicles, electric assist bicycles, and railway vehicles.

[0173] The mounting location of the battery pack in the vehicle according to the sixth embodiment is not particularly limited. For example, when the battery pack is mounted in an automobile, it can be mounted in the engine compartment, at the rear of the vehicle, or under the seats.

[0174] The vehicle according to the sixth embodiment may be equipped with multiple battery packs. In this case, the batteries contained in each battery pack may be electrically connected in series, electrically connected in parallel, or electrically connected in a combination of series and parallel connections. For example, if each battery pack contains a battery pack, the battery packs may be electrically connected in series, electrically connected in parallel, or electrically connected in a combination of series and parallel connections. Alternatively, if each battery pack contains a single battery, the batteries may be electrically connected in series, electrically connected in parallel, or electrically connected in a combination of series and parallel connections.

[0175] Next, an example of a vehicle according to the sixth embodiment will be described with reference to the drawings.

[0176] Figure 8 is a schematic partial transparency diagram showing an example of a vehicle according to the sixth embodiment. The vehicle 400 shown in Figure 8 includes a vehicle body 40 and a battery pack 300 according to the fourth embodiment. In the example shown in Figure 8, the vehicle 400 is a four-wheeled automobile.

[0177] This vehicle 400 may be equipped with multiple battery packs 300. In this case, the batteries contained in the battery pack 300 (for example, single cells or battery packs) may be connected in series, in parallel, or in a combination of series and parallel connections.

[0178] Figure 8 illustrates an example in which the battery pack 300 is mounted in the engine compartment located in front of the vehicle body 40. As described above, the battery pack 300 may also be mounted, for example, in the rear of the vehicle body 400 or under the seats. 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 from the vehicle 400's power.

[0179] Next, an embodiment of the vehicle according to the sixth embodiment will be described with reference to Figure 9. Figure 9 is a schematic diagram showing an example of a control system for the electrical system in the vehicle according to the sixth embodiment. The vehicle 400 shown in Figure 9 is an electric vehicle.

[0180] The vehicle 400 shown in Figure 9 comprises a vehicle body 40, a vehicle power supply 41, a vehicle ECU (ECU: Electric Control Unit) 42 which is a higher-level control device for 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.

[0181] Vehicle 400 has its vehicle power supply 41 mounted, for example, in the engine compartment, at the rear of the vehicle body, or under the seats. Note that in the vehicle 400 shown in Figure 9, the mounting location of the vehicle power supply 41 is shown in a schematic manner.

[0182] The vehicle power supply 41 comprises a plurality (for example, three) of battery packs 300a, 300b, and 300c, a battery management unit (BMU) 411, and a communication bus 412.

[0183] Battery pack 300a comprises a battery pack 200a and a battery pack monitoring device 310a (e.g., VTM: Voltage Temperature Monitoring). Battery pack 300b comprises a battery pack 200b and a battery pack monitoring device 310b. Battery pack 300c comprises a battery pack 200c and a battery pack monitoring device 310c. Battery packs 300a to 300c are similar to the aforementioned battery pack 300, and battery packs 200a to 200c are similar to the aforementioned battery pack 200. Battery packs 200a to 200c are electrically connected in series. Battery packs 300a, 300b, and 300c can each be independently removed and replaced with another battery pack 300.

[0184] Each of the battery packs 200a to 200c comprises multiple single cells connected in series. At least one of the multiple single cells is a secondary battery according to the first embodiment. Each of the battery packs 200a to 200c is charged and discharged through a positive terminal 413 and a negative terminal 414.

[0185] The battery management device 411 communicates with the battery pack monitoring devices 310a to 310c and collects information such as voltage and temperature for each of the single cells 100 included in the battery packs 200a to 200c included in the vehicle power supply 41. In this way, the battery management device 411 collects information related to the maintenance of the vehicle power supply 41.

[0186] The battery management device 411 and the battery pack monitoring devices 310a to 310c are connected via a communication bus 412. On the communication bus 412, one set of communication lines is shared by multiple nodes (the battery management device 411 and one or more battery pack monitoring devices 310a to 310c). The communication bus 412 is a communication bus configured, for example, based on the CAN (Control Area Network) standard.

[0187] The battery pack monitoring devices 310a to 310c measure the voltage and temperature of each individual cell constituting the battery packs 200a to 200c based on commands communicated from the battery management device 411. However, temperature can be measured at only a few locations per battery pack, and it is not necessary to measure the temperature of all individual cells.

[0188] The vehicle power supply 41 may also have an electromagnetic contactor (for example, a switch device 415 shown in Figure 9) that switches the presence or absence of an electrical connection between the positive terminal 413 and the negative terminal 414. The switch device 415 includes a pre-charge switch (not shown) that turns on when charging is performed on the battery packs 200a to 200c, and a main switch (not shown) that turns on when the output from the battery packs 200a to 200c is supplied to the 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 located 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.

[0189] The inverter 44 converts the input DC voltage into a high voltage of three-phase alternating current (AC) for motor drive. 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 device 411 or the vehicle ECU 42 for controlling the operation of the entire vehicle. By controlling the inverter 44, the output voltage from the inverter 44 is adjusted.

[0190] The drive motor 45 rotates using power supplied from the inverter 44. The driving force generated by the rotation of the drive motor 45 is transmitted to the axle and drive wheels W, for example, via a differential gear unit.

[0191] Although not shown in the diagram, vehicle 400 is also equipped with a regenerative braking mechanism (regenerator). The regenerative braking mechanism rotates the drive motor 45 when vehicle 400 is braked, converting kinetic energy into regenerative energy as electrical energy. The regenerative energy recovered by the regenerative braking mechanism is input to the inverter 44 and converted into a DC current. The converted DC current is input to the vehicle power supply 41.

[0192] One terminal of connection line L1 is connected to the negative terminal 414 of the vehicle power supply 41. The other terminal of connection line L1 is connected to the negative input terminal 417 of the inverter 44. A current detection unit (current detection circuit) 416 within the battery management device 411 is provided on connection line L1 between the negative terminal 414 and the negative input terminal 417.

[0193] One terminal of connection line L2 is connected to the positive terminal 413 of the vehicle power supply 41. The other terminal of connection line L2 is connected to the positive input terminal 418 of the inverter 44. A switch device 415 is provided between the positive terminal 413 and the positive input terminal 418 of connection line L2.

[0194] External terminal 43 is connected to battery management device 411. External terminal 43 can be connected to an external power supply, for example.

[0195] The vehicle ECU 42, in response to operational inputs from the driver and others, coordinates control of the vehicle power supply 41, switch device 415, inverter 44, etc., together with other management and control devices, including the battery management device 411. 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, and the entire vehicle 400 is managed. Data related 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.

[0196] The vehicle according to the sixth embodiment is equipped with a battery pack according to the fifth embodiment. Since the battery pack achieves high output and excellent cycle capacity retention, it is possible to provide a highly reliable vehicle.

[0197] [Seventh Embodiment] According to the seventh embodiment, a stationary power supply including a battery pack according to the fifth embodiment is provided.

[0198] The stationary power supply may be equipped with a secondary battery according to the third embodiment or a battery pack according to the fourth embodiment instead of the battery pack according to the fifth embodiment. The stationary power supply according to the embodiment can achieve a long lifespan.

[0199] Figure 10 is a block diagram showing an example of a system including a stationary power supply according to the seventh embodiment. Figure 10 is a diagram showing an example of the application of the battery packs 300A and 300B according to the embodiment to stationary power supplies 112 and 123. In the example shown in Figure 10, a system 110 is shown in which stationary power supplies 112 and 123 are used. The system 110 comprises a power plant 111, a stationary power supply 112, a consumer-side power grid 113, and an energy management system (EMS) 115. A power grid 116 and a communication network 117 are also formed in the system 110, and the power plant 111, the stationary power supply 112, the consumer-side power grid 113, and the EMS 115 are connected via the power grid 116 and the communication network 117. The EMS 115 utilizes the power grid 116 and the communication network 117 to perform control to stabilize the entire system 110.

[0200] Power plant 111 generates a large amount of electricity using fuel sources such as thermal and nuclear power. Electricity is supplied from power plant 111 through the power grid 116, etc. A battery pack 300A is installed in stationary power supply 112. The battery pack 300A can store electricity supplied from power plant 111, etc. The stationary power supply 112 can also supply the electricity stored in the battery pack 300A through the power grid 116, etc. System 110 is equipped with a power converter 118. The power converter 118 includes a converter, inverter, and transformer, etc. Therefore, the power converter 118 can perform conversion between DC and AC, conversion between ACs with different frequencies relative to each other, and voltage transformation (boost and step down). For this reason, the power converter 118 can convert the electricity from power plant 111 into electricity that can be stored in the battery pack 300A.

[0201] The consumer-side power system 113 includes power systems for factories, buildings, and households. The consumer-side power system 113 is equipped with a consumer-side EMS 121, a power converter 122, and a stationary power supply 123. The stationary power supply 123 is fitted with a battery pack 300B. The consumer-side EMS 121 performs control to stabilize the consumer-side power system 113.

[0202] The consumer-side power grid 113 is supplied with power from the power plant 111 and power from the battery pack 300A via the power grid 116. The battery pack 300B can store the power supplied to the consumer-side power grid 113. The power converter 122, like the power converter 118, includes a converter, inverter, and transformer. Therefore, the power converter 122 can perform conversions between DC and AC, conversions between ACs with different frequencies, and voltage transformations (boost and step down). Thus, the power converter 122 can convert the power supplied to the consumer-side power grid 113 into power that can be stored in the battery pack 300B.

[0203] The electricity stored in the battery pack 300B can be used, for example, to charge vehicles such as electric cars. Furthermore, the system 110 may be equipped with a renewable energy source. In this case, the renewable energy source generates electricity using natural energy sources such as wind and solar power. Electricity is then supplied from both the power plant 111 and the renewable energy source through the power grid 116.

[0204] The stationary power supply according to the seventh embodiment includes the battery pack according to the fifth embodiment. Therefore, it is possible to realize a stationary power supply that achieves high output and excellent cycle capacity retention rate.

[0205] [Examples] The embodiments described above will be further explained below based on the examples. However, the present invention is not limited to the examples listed below.

[0206] (Example 1) <Fabrication of negative electrode active material> Niobium-titanium oxides were synthesized as follows.

[0207] Oxalic acid was dissolved in water to prepare a 1M oxalic acid aqueous solution. Titanium tetraisopropoxide (C) was added to this oxalic acid aqueous solution. 12 H 28 O4Ti) was dissolved, and niobium ammonium oxalate hydrate (C4H4NNbO9·xH2O) was dissolved in it. These Ti sources (C 12 H 28 The proportions of O4Ti) and Nb source (C4H4NNbO9·xH2O) were 11.5% by mass and 88.5% by mass, respectively. Subsequently, the solution was neutralized by adding ammonia water dropwise to obtain a white gel. This gel was dried using a spray dryer to obtain a precursor. This precursor was placed up to the top of a cylindrical alumina crucible with an aspect ratio of approximately 1 and densely packed by tapping. The active material of Example 1 was obtained by sequentially performing calcination at 300°C for 1 hour in air and heat treatment at 1400°C for 36 hours using an electric furnace, followed by cooling to 100°C. Cooling from 1400°C to 100°C was carried out at a rate setting of -0.6°C / min.

[0208] <Fabrication of Negative Electrode> First, 100% by mass of the active material powder obtained in the above <Fabrication of Negative Electrode Active Material>, 10% by mass of acetylene black as a conductive agent, 5% by mass of carbon nanofibers, and 10% by mass of PVdF as a binder were mixed with N-methylpyrrolidone (NMP) added thereto to obtain a slurry. This slurry was applied to one side of a current collector made of an aluminum foil with a thickness of 15 μm, and after drying, it was pressed to fabricate an electrode.

[0209] <Adjustment of Electrolyte> PC and DEC were mixed at a volume ratio of PC:DEC = 1:2 to obtain a mixed solvent. 1.0 M of lithium hexafluorophosphate (LiPF6) was dissolved in the mixed solvent to prepare a liquid non-aqueous electrolyte.

[0210] <Fabrication of Electrochemical Measurement Cell> Using the electrode obtained in <Fabrication of Negative Electrode> as the working electrode, Li metal as the counter electrode and reference electrode, and the electrolyte adjusted in <Adjustment of Electrolyte>, an evaluation glass cell was fabricated.

[0211] (Example 2) Synthesis was carried out in the same manner as in Example 1 except that the heat treatment temperature was changed to 1300 °C, and the active material of Example 2 was obtained.

[0212] (Example 3) Synthesis was carried out in the same manner as in Example 1 except that the heat treatment temperature was changed to 1350 °C, and the active material of Example 3 was obtained. <​​​​​​​​​​​​ (Comparative Example 3) The synthesis was carried out in the same manner as in Comparative Example 1, except that the heat treatment temperature was changed to 1100°C, to obtain the active material of Comparative Example 3.

[0216] (Comparative Example 4) The active material for Comparative Example 4 was obtained by synthesis in the same manner as for Comparative Example 1, except that the heat treatment temperature was changed to 1200°C. From the powder XRD measurements described later, it was found that the active material for Comparative Example 4 contained a large amount of monoclinic particles in addition to orthorhombic particles.

[0217] (Comparative Example 5) The synthesis was carried out in the same manner as in Comparative Example 1, except that the heat treatment temperature was changed to 1300°C, to obtain the active material of Comparative Example 5.

[0218] In this embodiment, since lithium metal is used as the counter electrode in this measuring glass cell, the electrode potential of the embodiment and comparative example becomes nobler than that of the counter electrode and therefore functions as the positive electrode. For this reason, the definition of charge and discharge is reversed when the electrodes of the embodiment and comparative example are used as the negative electrode. To avoid confusion, in this embodiment, the direction in which lithium ions are inserted into the electrode is called charging, and the direction in which they are removed is called discharging. The active material of this embodiment functions as the negative electrode when combined with a known positive electrode material.

[0219] <Measurement of reversible capacity> The fabricated electrochemical measurement cell was charged and discharged within a potential range of 0.7V to 3.0V relative to the metallic lithium electrode. The charge / discharge current was set to 0.2C (time discharge rate), and the 0.2C reversible capacity was confirmed at room temperature of 25°C. The 0.2C reversible capacity value serves as an indicator of energy density.

[0220] <Measurement of cycle capacity maintenance rate> Next, each example cell underwent a life test at room temperature of 25°C, involving repeated 1C charge-discharge cycles within a potential range of 0.7V to 3.0V relative to the metallic lithium electrode. Under these conditions, 100 charge-discharge cycles were performed (one cycle consisted of charging and discharging), and the 0.2C reversible capacity was measured again. The cycle capacity retention rate was calculated by dividing the reversible capacity after 100 cycles by the reversible capacity before the cycle (Cycle capacity retention rate = (0.2C reversible capacity after 100 cycles / 0.2C reversible capacity before 100 cycles) × 100%).

[0221] <Battery pretreatment> Before measuring the powder XRD of the active material contained in each of the batteries prepared in the above-described examples, the batteries were pre-treated using the following method.

[0222] First, the secondary battery was discharged, then disassembled to remove the electrodes. This disassembly was carried out in a glove box under an argon gas atmosphere. Discharge refers to the state in which the battery's charge level is discharged to 0%. The removed electrodes were immersed in a solvent for 3 minutes, and then dried in a glove box under an argon gas atmosphere. Diethyl carbonate was used as the solvent.

[0223] Next, the active material powder was extracted as follows. First, the electrodes containing the binder were dispersed in a solvent. N-methylpyrrolidone was used as the solvent. The electrodes were dispersed by irradiating the solvent with ultrasound for more than 30 minutes. This dissolved the binder and separated the electrode material from the current collector as a powder. Next, the solvent containing the electrode material powder was placed in a centrifuge to separate it into conductive agent and active material particles, which were then recovered by freeze-drying.

[0224] The extracted active material was washed with diethyl carbonate solvent to dissolve and remove the lithium salt, and then dried. After drying, the active material was thoroughly washed with water in air to remove residual lithium ions, and this was used for measurement.

[0225] <Measurement using powder XRD> The active material obtained in the above <pre-treatment of battery> was sufficiently pulverized to obtain a powdery sample. The average particle size of the powdery sample was set to 20 μm or less. This average particle size was determined by a laser diffraction particle size distribution measuring device. The measurement method of powder XRD was performed as described above in the section <Measurement of powder XRD> of [First Embodiment].

[0226] In this way, an XRD spectrum related to the active material was obtained. FIG. 11 is a graph showing the spectra obtained by powder X-ray diffraction measurement of the active material in each example. In FIG. 11, ◆ is orthorhombic Ti2Nb 10 O 29 , ◇ is monoclinic Ti2Nb 10 O 29 of the JCPDS card data. In this XRD spectrum, the horizontal axis indicates the incident angle (2θ), and the vertical axis indicates the normalized intensity. The scan speed was adjusted within a range such that the count number of the main peak of the XRD spectrum was 50,000 counts or more and 150,000 counts or less.

[0227] By comparison with these card data, in Example 1, Example 2, and Comparative Example 5, it can be seen that the peak that coincides with the position of the peak of orthorhombic Ti2Nb 10 O 29 appearing at 24.5° ≤ 2θ ≤ 25.0° is very large. Also, in Example 1, Example 2, and Comparative Example 5, it can be seen that the peak that coincides with the peak position of monoclinic Ti2Nb 10 O 29 at an incident angle smaller than the aforementioned peak is very small. From this, it was found that in Example 1, Example 2, and Comparative Example 5, more orthorhombic form is contained. In addition, in Example 1 and Example 2, since the full width at half maximum of the peak appearing at 24.5° ≤ 2θ ≤ 25.0° is 0.09° or less, it was found that the crystallinity is good.

[0228] <Measurement of unit cell volume> The unit cell volume of the active material was measured using the XRD spectrum (graph in Figure 11) obtained by the method described in <Measurement of Powder XRD> above. The analysis method was carried out as described above in the <Measurement of Unit Cell Volume> section of [First Embodiment], and information regarding the crystal structure of the active material to be measured was obtained.

[0229] The measurement results are summarized in Table 1. Specifically, the full width at half maximum of the peak appearing in the XRD spectrum at 24.5°≦2θ≦25.0°, the unit cell volume of the active material, the 0.2C reversible capacity, and the cycle capacity retention rate after 100 charge-discharge cycles are shown for each example.

[0230] [Table 1]

[0231] A comparison of Examples 1-3 and Comparative Examples 1-5 shows that the unit cell volume of the active material is 2230 Å. 3 As described above, the full width at half maximum of the peak appearing at 24.5°≦2θ≦25.0° in the XRD spectrum is 0.09° or less, indicating that Examples 1-3 achieve both high reversible capacity and high cycle capacity retention. This is thought to be because, in the preparation of the negative electrode active material in Examples 1-3, the cooling rate after the main firing was sufficiently slowed, allowing the atomic arrangement of the active material to be rearranged regularly over a sufficient period of time, resulting in improved crystallinity. This good crystallinity of the active material leads to stability as a crystal. Furthermore, the aforementioned methods for preparing the negative electrode active material in Examples 1-3 also increase the unit cell volume of the active material, making structural changes in the active material less likely due to charging and discharging of the secondary battery, thus resulting in high cycle capacity retention for the secondary batteries in Examples 1-3. Therefore, it can be seen that Examples 1-3 achieved both high reversible capacity and high cycle capacity retention.

[0232] The active material according to this embodiment is Li x Nb 10 Ti2O 29 It is represented as (0≦x≦5) and has a unit cell volume of 2230 Å. 3It contains orthorhombic particles as described above, and the full width at half maximum of the peak appearing at 24.5° ≤ 2θ ≤ 25.0° in the powder X-ray diffraction spectrum is 0.09° or less. As a result, an active material and an electrode capable of realizing a secondary battery that achieves both a high reversible capacity and a high cycle capacity retention rate, a secondary battery and a battery pack that achieve both a high reversible capacity and a high cycle capacity retention rate, and a vehicle and a stationary power source equipped with the battery pack can be realized.

[0233] 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 implemented in various other forms, and various omissions, replacements, and changes can be made without departing from the gist of the invention. These embodiments and their modifications are included in the scope and gist of the invention, and are included in the invention described in the claims and its equivalent scope.

[0234] The invention according to the embodiment is appended below.

[0235] [1] General formula Li x Nb 10 Ti2O 29 (0 ≤ x ≤ 5), and an active material containing orthorhombic particles having a unit cell volume of 2230 Å 3 or more, and the full width at half maximum of the maximum peak appearing at 24.5° ≤ 2θ ≤ 25.0° in the powder X-ray diffraction spectrum is 0.09° or less.

[0236] [2] It further contains at least one M element selected from the group consisting of Ta, Sc, Y, V, Cr, Fe, Co, Mn, Al, and Ga, and the general formula Li x Nb 10+0.5y Ti 2-y M 0.5y O[[ID=3९]] 29 (0 ≤ x ≤ 5, 0 < y ≤ 1), the active material according to [1].

[0237] [3] An electrode comprising an active material-containing layer containing the active material described in [1] or [2].

[0238] [4] Positive electrode and, The negative electrode and, A secondary battery comprising an electrolyte, The negative electrode is a secondary battery having the electrode described in [3].

[0239] [5] A battery pack comprising the rechargeable battery described in [4].

[0240] [6] External terminals for power supply, The battery pack described in [5] further comprises a protection circuit.

[0241] [7] The device comprises multiple secondary batteries, The battery pack according to [5] or [6], wherein the secondary batteries are electrically connected in series, parallel, or a combination of series and parallel.

[0242] [8] A vehicle equipped with a battery pack as described in any one of items [5] to [7].

[0243] [9] The vehicle according to [8], comprising a mechanism for converting the kinetic energy of the vehicle into regenerative energy.

[0244]

[10] A stationary power supply comprising a battery pack as described in any one of items [5] to [7]. [Explanation of Symbols]

[0245] 1…Electrode group, 2…Outer casing, 3…Negative electrode, 3a…Negative electrode current collector, 3b…Negative electrode active material containing layer, 4…Separator, 5…Positive electrode, 5a…Positive electrode current collector, 5b…Positive electrode active material containing layer, 6…Negative electrode terminal, 7…Positive electrode terminal, 21…Bus bar, 22…Positive electrode side lead, 23…Negative electrode side lead, 24…Adhesive tape, 31…Housing container, 32…Lid, 33…Protective sheet, 34…Printed wiring board, 35…Wiring, 40…Vehicle body, 41…Vehicle power supply, 42…Electrical control device, 43…External terminal, 44…Inverter, 45…Drive motor, 100…Secondary battery, 200…Battery pack, 200a…Battery pack, 200b…Battery pack, 200c…Battery pack, 300…Battery pack, 300a…Battery pack, 300 b...Battery pack, 300c...Battery pack, 301a...Battery pack monitoring device, 301b...Battery pack monitoring device, 301c...Battery pack monitoring device, 342...Positive side connector, 343...Negative side connector, 345...Thermistor, 346...Protection circuit, 342a...Wiring, 343a...Wiring, 350...External terminal for power supply, 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 terminal, 414...Negative terminal, 415...Switching device, 416...Current detection unit, 417...Negative input terminal, 418...Positive input terminal, L1...Connection line, L2...Connection line, W...Drive wheel.

Claims

1. General formula Li ｘ Nb １０ Ti ２ O ２９ It is expressed as (0 ≤ x ≤ 5), The unit cell volume is 2230 Å. ３ An active material containing orthorhombic particles as described above, wherein the full width at half maximum of the largest peak appearing at 24.5° ≤ 2θ ≤ 25.0° in the powder X-ray diffraction spectrum is 0.09° or less.

2. Further comprising at least one M element selected from the group consisting of Ta, Sc, Y, V, Cr, Fe, Co, Mn, Al and Ga, and the general formula Li ｘ Nb １０＋０．５ｙ Ti ２－ｙ M ０．５ｙ O ２９ The active material according to claim 1, represented by (0 ≦ x ≦ 5, 0 < y ≦ 1).

3. An electrode comprising an active material-containing layer containing the active material described in claim 1 or claim 2.

4. Positive electrode and, The negative electrode and, A secondary battery comprising an electrolyte, The secondary battery wherein the negative electrode is the electrode described in claim 3.

5. A battery pack comprising the secondary battery described in claim 4.

6. External terminals for power supply, The battery pack according to claim 5, further comprising a protection circuit.

7. The device comprises multiple secondary batteries, The battery pack according to claim 5, wherein the secondary batteries are electrically connected in series, parallel, or a combination of series and parallel.

8. A vehicle comprising the battery pack described in claim 5.

9. The vehicle according to claim 8, comprising a mechanism for converting the kinetic energy of the vehicle into regenerative energy.

10. A stationary power supply comprising the battery pack described in claim 5.

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