Active material, electrode, secondary battery, battery pack, vehicle, and stationary power source

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] FIELD OF THE DISCLOSURE The present invention relates to an active material, an electrode, a secondary battery, a battery pack, a vehicle, and a stationary power source. [Background technology]

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

[0003] A typical negative electrode in a lithium-ion battery is a carbon-based negative electrode that uses carbonaceous materials such as graphite as the active material. When a battery using a carbon-based negative electrode is repeatedly charged and discharged rapidly, dendrites of metallic lithium are deposited on the electrode, which may cause an internal short circuit and lead to heat generation or fire. Therefore, a battery has been developed that uses a metal composite oxide instead of a carbonaceous material for the negative electrode, thereby increasing the negative electrode operating potential. For example, the spinel-type lithium titanium composite oxide Li 4 Ti 5 O 12 The battery using this as the negative electrode has an average operating potential of 1.55 V (vs. Li / Li + ) is high, which means that the precipitation of Li dendrites does not progress, making stable rapid charging and discharging possible, and since it operates at a potential where reduction side reactions of the electrolyte are unlikely to occur, it has a longer life than batteries using carbon-based anodes. 4 Ti 5 O 12 The theoretical capacity of the active material used in the negative electrode was low at 175 mAh / g, and there was an issue that the energy density was lower than that of batteries with carbon-based negative electrodes.

[0004] Therefore, monoclinic niobium titanium oxide TiNb 2 O 7is being considered. Based on the oxidation-reduction potential of lithium, 1V (vs. Li / Li + ) while exhibiting high capacity. For this reason, it is expected that the volumetric energy density will exceed that of carbon-based anodes. However, in order to fully popularize electric vehicles, it is desirable to further increase the energy density of lithium-ion secondary batteries from the viewpoint of improving driving range, and it is therefore desirable to develop a high-capacity rapid charging battery. [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] Edited by Izumi Nakai et al.: "Practical Application of Powder X-ray Diffraction", First Edition, Asakura Publishing, February 10, 2002, p.97-115 Summary of the Invention [Problem to be solved by the invention]

[0006] The problem to be solved by the present invention is 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. [Means for solving the problem]

[0007] According to an embodiment, the general formula Li x Nb 10 Ti 2 O 29 (0≦x≦5) and the unit cell volume is 2230Å 3or more, and has a half-width of the maximum peak appearing at 24.5°≦2θ≦25.0° in a powder X-ray diffraction spectrum of 0.09° or less. [Brief description of the drawings]

[0008] [Figure 1] FIG. 1 is a cross-sectional view illustrating an example of a secondary battery according to an embodiment. [Diagram 2] 2 is an enlarged cross-sectional view of a portion A of the secondary battery shown in FIG. 1. [Diagram 3] FIG. 4 is a partially cutaway perspective view illustrating a schematic diagram of another example of a secondary battery according to an embodiment. [Figure 4] 4 is an enlarged cross-sectional view of part B of the secondary battery shown in FIG. 3. [Diagram 5] FIG. 1 is a perspective view illustrating an example of a battery pack according to an embodiment. [Figure 6] FIG. 1 is an exploded perspective view illustrating an example of a battery pack according to an embodiment. [Figure 7] 7 is a block diagram showing an example of an electric circuit of the battery pack shown in FIG. 6. [Figure 8] 1 is a partially see-through view illustrating an example of a vehicle according to an embodiment. [Figure 9] 1 is a diagram illustrating an example of a control system for an electrical system in a vehicle according to an embodiment. [Figure 10] FIG. 1 is a block diagram showing an example of a system including a stationary power supply according to an embodiment. [Figure 11] 3 is a graph showing spectra obtained by powder X-ray diffraction measurement of the active materials in each example. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0009] Hereinafter, the embodiments will be described with reference to the drawings. In the following description, components that perform the same or similar functions are given the same reference numerals throughout the drawings, and duplicated descriptions will be omitted. Note that each figure is a schematic diagram for explaining the embodiment and facilitating understanding thereof, and the shapes, dimensions, ratios, etc. may differ from the actual device, but these can be appropriately modified in design by taking into consideration the following description and known techniques.

[0010] [First embodiment] According to a first embodiment, the general formula Li x Nb 10 Ti 2 O 29 (0≦x≦5) is provided. In the active material, the unit cell volume is 2230 Å. 3 or more, and the half-width of the maximum peak appearing at 24.5°≦2θ≦25.0° in the powder X-ray diffraction spectrum is 0.09° or less.

[0011] The active material may be, for example, an electrode active material, and may be included in an electrode of a secondary battery such as a lithium ion battery or a nonaqueous electrolyte battery. The electrode includes an active material-containing layer that contains the active material. More specifically, the electrode may be, for example, a negative electrode of the secondary battery.

[0012] The above general formula Li x Nb 10 Ti 2 O 29 By using an active material containing orthorhombic particles as an electrode active material, a secondary battery with high output and long life can be realized.

[0013] In general, an active material with small volume change due to charging and discharging of a secondary battery can achieve an excellent cycle capacity retention rate. This is because Li ions are inserted into and removed from the active material due to charging and discharging of the secondary battery, so that an active material with a large unit lattice volume, for example, having voids equal to or larger than the diameter of the Li ions, can reduce the volume change of the active material due to charging and discharging of the secondary battery. By reducing the volume change of the active material, it is possible to make it difficult for the electrode layer to become distorted, and it is possible to improve the cycle capacity retention rate of the secondary battery.

[0014] In particular, when the crystal structure is the Wadsley-Roth phase, the void volume is nearly proportional to the unit cell volume, and therefore the effect of improving the cycle capacity retention rate by increasing the unit cell volume is more remarkable.

[0015] The cycle capacity retention rate described above is also improved by the high crystallinity of the active material. This is because high crystallinity means, in other words, fewer lattice defects, a uniform lattice volume, and stable crystals, and the active material is less likely to undergo structural changes due to charging and discharging of the secondary battery. As described above, the active material is less likely to undergo structural changes, which makes it difficult for distortion to occur in the electrode layer, and thus makes it possible to improve the cycle capacity retention rate of the secondary battery.

[0016] In general, there is a trade-off between the reversible capacity and the 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) that are inserted into and removed from the active material by charging and discharging the secondary battery, and the greater the volume change of the active material. However, if the active material has a large unit lattice volume that has voids equal to or greater than the diameter of the Li ions, the volume change of the active material can be suppressed to a small value even if the number of Li ions that are inserted into and removed from the active material by charging and discharging the secondary battery is large. Furthermore, an active material with a large unit lattice volume promotes the movement of Li ions within the active material, improving Li ion conductivity, and therefore improving the reversible capacity. Therefore, a secondary battery using the active material according to this embodiment can achieve both a high reversible capacity and a high cycle capacity retention rate.

[0017] In order to obtain high crystallinity, the above general formula Li x Nb 10 Ti 2 O 29 However, firing the active material at a high temperature causes the primary particles to grow larger, and the crystal structure (crystal system) of part 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 Ti 2 O 29 By containing orthorhombic particles having high crystallinity and a large unit cell volume, it is possible to realize a high reversible capacity and a high cycle capacity retention rate.

[0019] The active material according to this embodiment has the general formula Li x Nb 10 Ti 2 O 29 (0≦x≦5) and the unit cell volume is 2230Å 3 or more, and the half-width of the maximum peak appearing at 24.5°≦2θ≦25.0° in the powder X-ray diffraction spectrum is 0.09° or less.

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

[0021] The active material contains orthorhombic particles, and the half-width of the maximum peak appearing at 24.5°≦2θ≦25.0° in the powder XRD spectrum is 0.09° or less. The half-width of the maximum peak appearing in the range of 24.5°≦2θ≦25.0° in the powder XRD spectrum is 0.09° or less, which indicates that the measured crystal structure of the active material is uniform and has good crystallinity. The half-width of the peak appearing in the preferred range is 0.05° or more and 0.09° or less. By being 0.05° or more, it is possible to suppress the enlargement of the primary particle size due to the significant grain growth of the crystals of the active material. By suppressing the enlargement of the primary particles, it is possible to suppress the electrode film being formed of giant particles, which prevents the conductive path in the film from being insufficient, and suppress the decrease in reversible capacity.

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

[0023] First, when the active material is contained in the secondary battery, the secondary battery is put into a discharged state, and then disassembled to remove the electrodes. This disassembly is carried out in a glove box under an inert gas atmosphere such as argon. The discharged state refers to a state in which the battery is discharged until the charge rate reaches 0%. The removed electrodes are immersed in a solvent for 3 minutes, and then dried in a glove box under an inert gas atmosphere. For example, diethyl carbonate 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 a water-based binder (for example, a water-soluble binder). The solvent is irradiated with ultrasonic waves for 30 minutes or more to disperse the electrode. This dissolves the binder and allows the electrode material to be separated as a powder from the current collector. Next, the solvent containing the electrode material powder is placed in a centrifuge, and the conductive agent and active material particles are separated, and then recovered by freeze-drying.

[0025] The removed 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 the active material is then used for measurement.

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

[0027] Next, the powdered sample is filled into the holder of a glass sample plate, and the surface is made flat. For example, the glass sample plate may have a holder depth of 0.2 mm.

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

[0029] In this way, the XRD spectrum of the active material is obtained. In this XRD spectrum, the horizontal axis indicates the angle of incidence (2θ) and the vertical axis indicates the diffraction intensity (cps). The scan speed can be adjusted in a range such that the count number of the main peak of the XRD spectrum is 50,000 counts or more and 150,000 counts or less. In the XRD spectrum obtained by the above-mentioned method, the half-width of the maximum peak in the range of 24.5°≦2θ≦25.0° can be obtained. The half-width refers to the width between two points (full width at half maximum) where the intensity of a certain peak is 50% of the peak value.

[0030] Next, the unit lattice volume of the active material will be described.

[0031] The unit cell volume of the orthorhombic particles contained in this active material is 2230 Å. 3 This makes it possible to reduce the volume change of the active material caused by charging and discharging the secondary battery, and to realize a secondary battery having an excellent cycle capacity retention rate. The unit lattice volume of the preferred active material is 2230 Å or less. 3 More than 2245Å 3 It is below. 2245Å 3 By keeping the density below 1.0%, it is possible to suppress the insertion of multiple Li ions into one void during charging and discharging of the secondary battery, and the destruction of the crystal structure due to the movement of Ti and Nb ions, etc.

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

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

[0034] It is also possible to investigate the occupancy rate of each site of the constituent elements. The fitting parameter S is used as a measure for estimating the degree of agreement between the observed intensity and the calculated intensity in the Rietveld analysis. The analysis must be performed so that this S is smaller than 1.8. In addition, when determining the occupancy rate of each site, the standard deviation σj must be taken into consideration. The fitting parameter S and standard deviation σj defined here are estimated by the formula described in Non-Patent Document 2.

[0035] In addition, when the active material to be measured contains crystals having different space groups, the content of the space groups can be quantified by Rietveld analysis. Specifically, crystal structure information for each different crystal phase is input, and the mass fraction is calculated from the intensity information of each phase by fitting them to the measured XRD pattern. More specifically, the mass fraction can be calculated by the method described in Chapter 10, Section 5, "Calculation of Mass Fraction of Phases" in Non-Patent Document 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 space group Amma, can be examined. Furthermore, the degree of growth from the crystal orientation parameter to the 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, for example, take the form of particles. That is, such an active material has the general formula Li x Nb 10 Ti 2 O 29 and contains orthorhombic particles. Further, such an active material can be composed of particles in which, in addition to the composite oxide, the above-described trace-added elements are mixed. The active material can be single primary particles, 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 also 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] The average primary particle size of the active material according to the first embodiment is preferably 10 μm or less, more preferably 5 μm or less, and even more preferably 3 μm or less. When the average primary particle size of the active material is small, the diffusion distance of lithium ions in the primary particles is short, so that the lithium ion diffusibility tends to be increased. In addition, when the average primary particle size of the active material is small, the reaction area increases, so that the reactivity between the active material and lithium ions increases, and the lithium ion insertion / extraction reaction tends to be improved.

[0040] The average secondary particle diameter of the active material according to the first embodiment 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, it is possible to improve the productivity during electrode production and obtain a battery with good performance. This average secondary particle diameter means the particle diameter at which the volume cumulative value is 50% in the particle size distribution determined by a laser diffraction type particle size distribution measuring device.

[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 determined by SEM observation can be calculated by the following method.

[0042] First, the length of the longest axis and the length of the shortest axis are measured for the primary particles in the SEM image obtained by SEM observation, and the arithmetic mean value of these is taken as the primary particle diameter. This measurement of the primary particle diameter is performed for 100 randomly selected particles, and the average value of these is taken 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 measuring device. A dispersion diluted with N-methyl-2-pyrrolidone so that the concentration of the active material is 0.1% by mass to 1% by mass is used as a sample for measuring the particle size distribution. The particle diameter at which the volumetric integrated value is 50% in the obtained particle size distribution 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 manufacturing process of the electrode described later in the second embodiment, the coatability 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 obtaining 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 collected 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 77K (the boiling point of nitrogen), while gradually increasing the pressure P (mmHg) of the 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 P 0 (mmHg) of the nitrogen gas is taken as the relative pressure P / P 0 , and an adsorption isotherm is obtained by plotting the nitrogen gas adsorption amount for each relative pressure P / P 0 . 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] The BET plot is calculated using the BET multipoint method.

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

[0050] The starting materials, titanium and niobium sources, are dissolved in an acidic solution, the solution is neutralized, and the resulting gel is dried to obtain a precursor, which is then heat-treated to obtain a niobium-titanium oxide.

[0051] The titanium source may be, for example, titanium tetraisopropoxide (C 12 H 28 O 4 As a niobium source, for example, ammonium niobium oxalate hydrate (C 4 H 4 NNbO 9 xH 2 O) can be used. As the acidic solution for dissolving the Ti source and Nb source, for example, an aqueous solution of oxalic acid can be used. For example, ammonia water can be used for the neutralization treatment. For example, a heating method in air, a spray drying method, etc. can be applied for drying the gel after neutralization.

[0052] When the precursor is heat-treated to obtain an oxide, the precursor is densely packed in a container having an appropriate opening. By increasing the density in this way, the precursor is sufficiently oxidized while suppressing the volatilization of metal. In the heat treatment, pre-baking (first baking) is performed before the main baking. The pre-baking is preferably performed at a temperature of 200°C to 400°C for 1 hour to 12 hours. By performing the pre-baking, it is possible to remove a small amount of impurity components (e.g., water, organic matter, etc.) adsorbed on the precursor. The pre-baking may be omitted. The main baking (second baking) is preferably performed at a temperature of 900°C to 1500°C for 1 hour to 40 hours. Thereafter, the material is cooled to 100°C at a rate set to -2°C / min to -0.05°C / min. By cooling under the above-mentioned conditions after the main baking, the unit cell volume is increased and an active material having high crystallinity according to the embodiment can be obtained. This is because the atoms of the active material are allowed a sufficient amount of time to rearrange during the cooling process from the firing temperature back to room temperature. The slow cooling rate under the above cooling conditions allows the atoms of the active material to be arranged in a regular atomic arrangement, which improves the crystallinity. In addition, the sufficient time for the atoms of the active material to rearrange makes it difficult for lattice defects such as oxygen defects to occur, which allows the unit lattice volume to be increased.

[0053] In addition to the above-mentioned liquid phase synthesis method, the active material according to the embodiment can be obtained by, for example, a general solid phase reaction method. 2 ) and niobium oxide (Nb 2 O 5 , or NbO 2 Alternatively, the active material according to the present embodiment can be obtained by mixing the above ingredients in a mortar or ball mill and firing the mixture in air.

[0054] The active material according to the first embodiment has the general formula Li x Nb 10 Ti 2 O 29 (0≦x≦5) and the unit cell volume is 2230Å 3or more, and the half-width of the maximum peak appearing at 24.5°≦2θ≦25.0° in the powder X-ray diffraction spectrum is 0.09° or less. This makes it possible to realize a secondary battery that exhibits high output and excellent cycle capacity retention rate.

[0055] [Second embodiment] According to a second embodiment, there is provided an electrode comprising an active material-containing layer that contains 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 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 types of 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 is 10 mass % or more and 100 mass % or less.

[0059] For example, when the active material according to the first embodiment is contained as a negative electrode active material, examples of other active materials include lithium titanate having a ramsdellite structure (e.g., Li 2+x Ti 3 O 7 (-1≦x≦3)), lithium titanate having a spinel structure (for example, lithium having the general formula Li 4+x Ti 5 O12 (x is -1≦x≦3)), monoclinic titanium dioxide (TiO 2 ), anatase type titanium dioxide, rutile type titanium dioxide, hollandite type titanium composite oxide, orthorhombic titanium composite oxide, and monoclinic type 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-mentioned orthorhombic titanium-containing composite oxide, Li 2+e M2 2-f Ti 6-g M3 h O 14+σ Here, M2 is at least one selected from the group consisting of Sr, Ba, Ca, Mg, Na, Cs, Rb, and K. M3 is at least one selected from the group consisting of Zr, Sn, V, Nb, Ta, Mo, W, Y, Fe, Co, Cr, Mn, Ni, and Al. The subscripts in the composition formula are 0≦e≦6, 0≦f<2, 0≦g<6, 0≦h<6, and -0.5≦σ≦0.5. Specific examples of orthorhombic titanium-containing composite oxides include Li 2+e Na 2 Ti 6 O 14 (0≦e≦6).

[0061] As an example of the monoclinic niobium titanium composite oxide, Li x Ti 1-y M4 y Nb 2-z M5 z O 7+δ Here, M4 is at least one selected from the group consisting of Zr, Si, and Sn. M5 is at least one selected from the group consisting of V, Ta, and Bi. The subscripts in the composition formula are 0≦x≦5, 0≦y<1, 0≦z<2, and -0.3≦δ≦0.3. Specific examples of monoclinic niobium titanium composite oxides include Li x Nb 2 TiO 7 (0≦x≦5).

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

[0063] The conductive agent is blended to improve the current collecting performance and to suppress the contact resistance between the active material and the current collector. Examples of the conductive agent include carbonaceous materials such as vapor grown carbon fiber (VGCF), carbon black such as acetylene black, graphite, carbon nanotubes and carbon nanofibers. One of these may be used as the conductive agent, or two or more may be used in combination as the conductive agent. Alternatively, instead of using the conductive agent, a carbon coat or an electronically conductive inorganic material coat may be applied to the surface of the active material particles. In addition, the current collecting performance of the active material-containing layer can be improved by using the conductive agent and coating the active material surface with carbon or a conductive material.

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

[0065] The mixing ratio 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 a negative electrode of a secondary battery, it is preferable to mix the active material (negative electrode active material), conductive agent and binder at a ratio of 68% by mass or more and 96% by mass or less, 2% by mass or more and 30% by mass or less, and 2% by mass or more and 30% by mass or less, respectively. By making the amount of the conductive agent 2% by mass or more, the current collection performance of the active material-containing layer can be improved. In addition, by making the amount of the binder 2% by mass or more, the binding property between the active material-containing layer and the current collector becomes sufficient, and excellent cycle performance can be expected. On the other hand, it is preferable to make the conductive agent and the binder 30% by mass or less, respectively, in order to increase the capacity.

[0066] When the surface of the active material is coated with carbon or a conductive material, the amount of the coating material can be considered to be included in the amount of conductive material. The amount of carbon or conductive material coated is preferably 0.5% by mass or more and 5% by mass or less. If the amount of coating is within this range, the 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 and removed from the active material. For example, when the active material is used as a negative electrode active material, the current collector is preferably made of copper, nickel, stainless steel, 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 or more and 20 μm or less. A current collector having such a thickness can balance the strength and weight of the electrode.

[0068] The current collector may also include a portion on the surface of which no active material-containing layer is formed, and this portion can function as a current collecting tab.

[0069] The electrode can be produced, for example, by the following method. First, an active material, a conductive agent, and a binder are suspended in a solvent to prepare a slurry. This slurry is applied to one or both sides of a current collector. Next, the applied slurry is dried to obtain a laminate of an active material-containing layer and a current collector. After that, the laminate is pressed. In this manner, an electrode is produced.

[0070] Alternatively, the electrode may be prepared by the following method: first, the active material, the conductive agent, and the binder are mixed to obtain a mixture, then the mixture is formed into pellets, and then the pellets are placed on a current collector to obtain an electrode.

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

[0072] [Third embodiment] According to the third embodiment, a secondary battery is provided that includes a positive electrode, a negative electrode, and an electrolyte. This secondary battery includes the electrode according to the second embodiment as the negative electrode or the positive electrode. That is, the secondary battery according to the third embodiment includes the active material according to the first embodiment as an electrode active material. A secondary battery according to a desirable aspect includes the electrode according to the second embodiment as the negative electrode. That is, the secondary battery according to a desirable aspect includes an electrode having an active material-containing layer containing the active material according to the first embodiment as the negative electrode. The desirable aspects will be described below.

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

[0074] Moreover, such a secondary battery can further include an exterior member that houses the electrode group and the electrolyte.

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

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

[0077] The negative electrode, the positive electrode, the electrolyte, the separator, the exterior member, the negative electrode terminal, and the positive electrode terminal will be described in detail below.

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

[0079] Among the details of the negative electrode, those parts that overlap with the details explained in the second embodiment will be omitted.

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

[0081] The negative electrode can be produced, for example, by the same method as that for 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 include a positive electrode active material, and optionally 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 desorbed.

[0084] Such compounds include, for example, manganese dioxide (MnO 2 ), iron oxide, copper oxide, nickel oxide, lithium manganese composite oxide (for example, Li x Mn 2 O 4 or Li x MnO 2 ; 0 < x ≦ 1), lithium nickel composite oxide (for example, Li x NiO 2 ; 0 < x ≦ 1), lithium cobalt composite oxide (for example, Li x CoO 2 ; 0 < x ≦ 1), lithium nickel cobalt composite oxide (for example, Li x Ni 1-y Co y O 2 ; 0 < x ≦ 1, 0 < y < 1), lithium manganese cobalt composite oxide (for example, Li x Mn y Co 1-y O 2 ; 0 < x ≦ 1, 0 < y < 1), lithium manganese nickel composite oxide having a spinel structure (for example, Li x Mn 2-y Ni y O 4 ; 0 < x ≦ 1, 0 < y < 2), lithium phosphate having an olivine structure (for example, Li x FePO 4 ; 0 < x ≦ 1, Li x Fe 1-y Mn y PO 4 ; 0 < x ≦ 1, 0 < y ≦ 1, Li x CoPO 4 ; 0 < x ≦ 1), iron sulfate (Fe 2 (SO 4 ) 3 ), vanadium oxide (for example, V2 O 5 ) and lithium nickel cobalt manganese composite oxide (Li x Ni 1-y-z Co y Mn z O 2 ; 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 oxide having a spinel structure (for example, Li x Mn 2 O 4 ; 0 < x ≤ 1), lithium nickel composite oxide (for example, Li x NiO 2 ; 0 < x ≤ 1), lithium cobalt composite oxide (for example, Li x CoO 2 ; 0 < x ≤ 1), lithium nickel cobalt composite oxide (for example, Li x Ni 1-y Co y O 2 ; 0 < x ≤ 1, 0 < y < 1), lithium manganese nickel composite oxide having a spinel structure (for example, Li x Mn 2-y Ni y O 4 ; 0 < x ≤ 1, 0 < y < 2), lithium manganese cobalt composite oxide (for example, Li x Mn y Co 1-y O 2 ; 0 < x ≤ 1, 0 < y < 1), lithium iron phosphate (for example, Li x FePO 4 ; 0 < x ≤ 1), and lithium nickel cobalt manganese composite oxide (Li x Ni 1-y-z Co y Mn z O 2 ; 0 < x ≤ 1, 0 < y < 1, 0 < z < 1, y + z < 1) are included. Using these compounds as the positive electrode active material can increase the positive electrode potential.

[0086] When using a room temperature molten salt as the electrolyte of the battery, lithium iron phosphate, Lix VPO 4 It is preferable to use a positive electrode active material containing F(0≦x≦1), lithium manganese composite oxide, lithium nickel composite oxide, lithium nickel cobalt composite oxide, or a mixture thereof. These compounds have low reactivity with room temperature molten salts, so that 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 100 nm or more and 1 μm or less. A positive electrode active material with a primary particle size of 100 nm or more is easy to handle in industrial production. A positive electrode active material with a primary particle size of 1 μm or less can smoothly diffuse lithium ions in the solid.

[0088] The specific surface area of ​​the positive electrode active material is 0.1 m 2 / g or more 10m 2 / g or less. 2 A positive electrode active material with a specific surface area of ​​10m / g or more can secure sufficient sites for insertion and desorption of Li ions. 2 A positive electrode active material having a specific surface area of ​​100 / g or less is easy to handle in industrial production and can ensure good charge-discharge cycle performance.

[0089] The binder is blended to fill the gaps between the dispersed positive electrode active material and to bind the positive electrode active material and the positive electrode current collector. Examples of the binder include PTFE, PVdF, fluorine-based rubber, polyacrylic acid compounds, imide compounds, CMC, and salts of CMC. One of these may be used as the binder, or two or more may be used in combination as the binder.

[0090] The conductive agent is blended to improve current collection performance and reduce contact resistance between the positive electrode active material and the positive electrode current collector. Examples of the conductive agent include carbon black such as VGCF and acetylene black, and carbonaceous materials such as graphite. One of these may be used as the conductive agent, or two or more may be combined and used as the conductive agent. The conductive agent may also be omitted.

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

[0092] By making the amount of binder 2% by mass or more, sufficient electrode strength can be obtained. In addition, the binder can function as an insulator. Therefore, by making the amount of binder 20% by mass or less, the amount of insulator contained in the electrode is reduced, and the internal resistance can be reduced.

[0093] When a conductive agent is added, the positive electrode active material, the binder, and the conductive agent are preferably mixed in proportions of 77% by mass or more and 95% by mass or less, 2% by mass or more and 20% by mass or less, and 3% by mass or more and 15% by mass or less, respectively.

[0094] By setting the amount of the conductive agent to 3% by mass or more, the above-mentioned effects can be achieved. Also, by setting the amount of the conductive agent to 15% by mass or less, the ratio of the conductive agent in contact with the electrolyte can be reduced. If this ratio is low, decomposition of the electrolyte during high-temperature storage can be reduced.

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

[0097] The positive electrode current collector may also include a portion on the surface of which the positive electrode active material-containing layer is not formed, and this portion can function as a positive electrode current collecting tab.

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

[0099] 3) Electrolytes The electrolyte may be, for example, a liquid nonaqueous electrolyte or a gel nonaqueous electrolyte. The liquid nonaqueous electrolyte is prepared by dissolving an electrolyte salt as a solute in an organic solvent. The concentration of the electrolyte salt is preferably 0.5 mol / L or more and 2.5 mol / L or less.

[0100] Examples of electrolyte salts include lithium perchlorate (LiClO 4 ), lithium hexafluorophosphate (LiPF 6 ), lithium tetrafluoroborate (LiBF 4 ), lithium arsenic hexafluoride (LiAsF 6 ), lithium trifluoromethanesulfonate (LiCF 3 SO 3 ), and lithium bistrifluoromethylsulfonylimide (LiN(CF 3 SO 2 ) 2 ), lithium bis(fluorosulfonyl)imide (LiN(SO 2 F) 2 The electrolyte salt is preferably one that is not easily oxidized even at high potential, and LiPF 6 is most preferred.

[0101] Examples of organic solvents include cyclic carbonates such as propylene carbonate (PC), ethylene carbonate (EC), and vinylene carbonate (VC); chain carbonates such as diethyl carbonate (DEC), dimethyl carbonate (DMC), and methyl ethyl carbonate (MEC); cyclic ethers such as tetrahydrofuran (THF), 2-methyl tetrahydrofuran (2MeTHF), and dioxolane (DOX); chain ethers such as dimethoxyethane (DME) and diethoxyethane (DEE); γ-butyrolactone (GBL), acetonitrile (AN), and sulfolane (SL). These organic solvents can be used alone or as a mixed solvent.

[0102] The gelled non-aqueous electrolyte is prepared by combining a liquid non-aqueous electrolyte with a polymeric material, such as PVdF, polyacrylonitrile (PAN), polyethylene oxide (PEO), or a mixture thereof.

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

[0104] Room temperature molten salts (ionic melts) refer to organic salts consisting of a combination of organic cations and anions that can exist as a liquid at room temperature (15°C or higher and 25°C or lower). Room temperature molten salts include room temperature molten salts that exist as a liquid by themselves, room temperature molten salts that become liquid when mixed with an electrolyte salt, room temperature molten salts that become liquid when dissolved in an organic solvent, and mixtures of these. In general, the melting point of room temperature molten salts used in secondary batteries is 25°C or lower. In addition, organic cations generally have a quaternary ammonium skeleton.

[0105] The polymer solid electrolyte is prepared by dissolving an electrolyte salt in a polymer material and solidifying it.

[0106] The inorganic solid electrolyte is a solid substance that has Li-ion conductivity. Here, Li-ion conductivity is defined as having a Li-ion conductivity of 1×10 at 25°C. -6 It means that the inorganic solid electrolyte has a lithium ion conductivity of 1.0 S / cm or more. Examples of the inorganic solid electrolyte include oxide-based solid electrolytes and sulfide-based solid electrolytes. Specific examples of the inorganic solid electrolyte are as follows.

[0107] The oxide-based solid electrolyte has a NASICON (Sodium (Na) Super Ionic Conductor) type structure and is represented by the general formula Li 1+x Mα 2 (PO 4 ) 3 It is preferable to use a lithium phosphate solid electrolyte represented by the following general formula: Mα in the above 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] A specific example of a lithium phosphate solid electrolyte having a NASICON structure is Li 1+x Al x Ti 2-x (PO 4 ) 3An LATP compound represented by and 0.1 ≦ x ≦ 0.5; Li 1+x Al y Mβ 2-y (PO 4 ) 3 A compound represented by 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; Li 1+x Al x Ge 2-x (PO 4 ) 3 A compound represented by and 0 ≦ x ≦ 2; and, Li 1+x Al x Zr 2-x (PO 4 ) 3 A compound represented by and 0 ≦ x ≦ 2; Li 1+x+y Al x Mγ 2-x Si y P 3-y O 12 A compound represented by where Mγ is one or more selected from the group consisting of Ti and Ge and 0 < x ≦ 2, 0 ≦ y < 3; Li 1+2x Zr 1-x Ca x (PO 4 ) 3 Compounds represented by and 0 ≦ x < 1 can be exemplified.

[0109] In addition, as the oxide-based solid electrolyte, in addition to the above lithium phosphate solid electrolyte, Li x PO y N z An amorphous LIPON compound represented by 2.6 ≦ x ≦ 3.5, 1.9 ≦ y ≦ 3.8, and 0.1 ≦ z ≦ 1.3 (for example, Li 2.9 PO 3.3 N 0.46 ); La with a garnet-type structure 5+x A x La 3-x Mδ 2 O 12 A compound represented by where 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; Li 3 Mδ 2-x L2 O 12 wherein Mδ is at least one selected from the group consisting of Nb and Ta, and L may contain Zr, and 0≦x≦0.5; Li 7-3x Al x La 3 Zr 3 O 12 and 0≦x≦0.5; Li 5+x La 3 Mδ 2-x Zr x O 12 where Mδ is 1 or more selected from the group consisting of Nb and Ta, and 0≦x≦2. 7 La 3 Zr 2 O 12 ); and La 2 / 3-x Li x TiO 3 and 0.3≦x≦0.7.

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

[0111] Alternatively, instead of the non-aqueous electrolyte, a liquid aqueous electrolyte or a gel aqueous electrolyte can be used as the electrolyte. The liquid aqueous electrolyte is prepared by dissolving, for example, the above-mentioned electrolyte salt as a solute in an aqueous solvent. The gel aqueous electrolyte is prepared by compounding the liquid aqueous electrolyte with the above-mentioned polymer material. As the aqueous solvent, a solution containing water can 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 is not particularly limited as long as it can electrically insulate the positive and negative electrodes. For example, it is formed from a porous film containing polyethylene (PE), polypropylene (PP), cellulose, or PVdF, or a synthetic resin nonwoven fabric. From the viewpoint of safety, it is preferable to use a porous film formed from polyethylene or polypropylene. This is because these porous films melt at a certain temperature and can cut off the current.

[0113] 4) Exterior materials As the exterior member, for example, a container made of a laminate film or a metal exterior can can be used.

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

[0115] The laminate film is a multi-layer film including a plurality of resin layers and a metal layer interposed between the resin layers. The resin layers include polymeric 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 the exterior member by sealing it by heat fusion.

[0116] The wall thickness of the outer can 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 exterior can is made of, for example, aluminum or an aluminum alloy. The aluminum alloy preferably contains elements such as magnesium, zinc, and silicon. When the aluminum alloy contains a transition metal such as iron, copper, nickel, or chromium, the content of the transition metal is preferably 1 mass % or less.

[0118] The shape of the exterior member is not particularly limited. The shape of the exterior member may be, for example, flat (thin), rectangular, cylindrical, coin, or button. The exterior member can be appropriately selected depending on the battery dimensions and the application of the battery.

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

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

[0121] Above, the embodiment including the electrode according to the second embodiment as the negative electrode has been described. In the embodiment of the secondary battery according to the third embodiment including the electrode according to the second embodiment as the positive electrode, the negative electrode which is the counter electrode thereof can be, for example, the following counter 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. A material that does not contain Li in the active material can be used as the negative electrode by pre-doping with Li element.

[0122] In an embodiment including the electrode according to the second embodiment as a positive electrode, details of the positive electrode overlap with those described in the second embodiment, and therefore will be omitted.

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

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

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

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

[0127] As shown in Fig. 1, the electrode group 1 is a flat wound-type electrode group. As shown in Fig. 2, the flat wound-type 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 negative electrode 3, in a portion located at the outermost shell of the wound-type electrode group 1, the negative electrode active material-containing layer 3b is formed only on the inner surface side of the negative electrode current collector 3a as shown in Fig. 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 a positive electrode active material-containing layer 5b formed on both sides of the positive electrode current collector 5a.

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

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

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

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

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

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

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

[0137] The negative electrode current collector 3a of each negative electrode 3 includes a portion 3c on one side of which the negative electrode active material-containing layer 3b is not supported on any surface. This portion 3c serves as a negative electrode current collector tab. As shown in FIG. 4, the portion 3c serving as the negative electrode current collector tab does not overlap with the positive electrode 5. In addition, the 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 pulled out to the outside of the exterior member 2.

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

[0139] The secondary battery according to the third embodiment includes the electrode according to the second embodiment. That is, the secondary battery according to the third embodiment includes an electrode having an active material-containing layer that contains 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 rate.

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

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

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

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

[0144] The bus bar 21 connects, for example, the negative electrode terminal 6 of one cell 100a and the positive electrode terminal 7 of the adjacent cell 100b. In this way, the five cells 100 are connected in series by the four bus bars 21. That is, the battery pack 200 in FIG. 5 is a five-series battery pack. Although no example is shown, in a battery pack including a plurality of cells electrically connected in parallel, for example, the plurality of negative electrode terminals are connected to each other by a bus bar and the plurality of positive electrode terminals are connected to each other by a bus bar, so that the plurality of cells are electrically connected to each other.

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

[0146] The battery pack according to the fourth embodiment includes the secondary battery according to the third embodiment, and therefore exhibits high output and excellent cycle capacity retention rate.

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

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

[0149] The battery pack according to this embodiment may further include an external terminal for current flow. The external terminal for current flow is 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 terminal for current flow. When the battery pack is charged, a charging current (including regenerative energy from the power of an automobile or the like) is supplied to the battery pack through the external terminal for current flow.

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

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

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

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

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

[0155] The single cell 100 has a structure shown in Figs. 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 in a manner that aligns the negative electrode terminal 6 and the positive electrode terminal 7 extending outwardly in the same direction. Each of the multiple single cells 100 is electrically connected in series as shown in Fig. 7. The multiple single cells 100 may be electrically connected in parallel, or may be connected in a combination of series and parallel connections. When the multiple single cells 100 are connected in parallel, the battery capacity is increased compared to when they are connected in series.

[0156] The adhesive tape 24 fastens the plurality of unit cells 100. The plurality of unit cells 100 may be fixed using heat shrink tape instead of the adhesive tape 24. In this case, the protective sheets 33 are disposed on both side surfaces of the battery pack 200, the heat shrink tape is wrapped around the battery pack 200, and the heat shrink tape is then thermally shrunk to bind the plurality of unit cells 100 together.

[0157] One end of the positive electrode lead 22 is connected to the positive electrode terminal 7 of the cell 100 located in the bottom layer in the stack of the cells 100. One end of the negative electrode lead 23 is connected to the negative electrode terminal 6 of the cell 100 located in the top layer in the stack of the cells 100.

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

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

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

[0161] The external terminal 347 for current supply is fixed to the other main surface of the printed wiring board 34. The external terminal 347 for current supply is electrically connected to a device present outside the battery pack 300.

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

[0163] The protective sheet 33 is disposed on both inner surfaces in the long side direction of the container 31 and on the inner surface in the short side direction that faces the printed wiring 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 charging and discharging of the multiple cells 100. The protection circuit 344 also cuts off electrical connection between the protection circuit 344 and an external terminal 347 for current flow, based on a detection signal transmitted from the thermistor 343, or a detection signal transmitted from each of the cells 100 or the battery pack 200.

[0165] An example of the detection signal transmitted from the thermistor 343 may be a signal that detects that the temperature of the cell 100 is equal to or higher than a predetermined temperature. An example of the detection signal transmitted from each cell 100 or the battery pack 200 may be a signal that detects overcharging, overdischarging, and overcurrent of the cell 100. When detecting overcharging or the like for each cell 100, the battery voltage may be detected, or the positive electrode potential or the negative electrode potential may be detected. In the latter case, a lithium electrode used as a reference electrode is inserted into each cell 100. Note that the protection circuit 344 may be a circuit included in a device (e.g., electronic device, automobile, etc.) that uses the battery pack 300 as a power source.

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

[0167] The battery pack 300 may include a plurality of assembled batteries 200. In this case, the assembled batteries 200 may be connected in series, in parallel, or in a combination of series and parallel connections. The printed wiring board 34 and the wiring 35 may be omitted. In this case, the positive electrode lead 22 and the negative electrode lead 23 may be used as external terminals for current flow.

[0168] Such a battery pack is used, for example, in applications that require excellent cycle performance when a large current is drawn. Specifically, the battery pack is used, for example, as a power source for electronic devices, a stationary battery, or an on-board battery for various vehicles. An example of the electronic device is a digital camera. The battery pack is particularly suitable for use as an on-board battery.

[0169] The battery pack according to the fifth embodiment includes the secondary battery according to the third embodiment or the battery pack according to the fourth embodiment, and therefore exhibits high output and excellent cycle capacity retention rate.

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

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

[0172] Examples of the vehicle according to the sixth embodiment include two- to four-wheel hybrid electric vehicles, two- to four-wheel electric vehicles, power-assisted bicycles, and railcars.

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

[0174] The vehicle according to the sixth embodiment may be equipped with a plurality of battery packs. In this case, the batteries included 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, when each battery pack includes 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, when each battery pack includes 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 a sixth embodiment will be described with reference to the drawings.

[0176] Fig. 8 is a partial perspective view that shows a schematic example of a vehicle according to the sixth embodiment. The vehicle 400 shown in Fig. 8 includes a vehicle body 40 and the battery pack 300 according to the fourth embodiment. In the example shown in Fig. 8, the vehicle 400 is a four-wheeled automobile.

[0177] The vehicle 400 may be equipped with a plurality of battery packs 300. In this case, the batteries (e.g., single cells or assembled batteries) included in the battery pack 300 may be connected in series, in parallel, or in a combination of series and parallel connections.

[0178] 8 illustrates an example in which the battery pack 300 is mounted in an engine room located in the front of the vehicle body 40. As described above, the battery pack 300 may be mounted, for example, at the rear of the vehicle body 400 or under a seat. This battery pack 300 can be used as a power source for the vehicle 400. In addition, this battery pack 300 can recover regenerative energy for the motive power of the vehicle 400.

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

[0180] The vehicle 400 shown in FIG. 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 of the vehicle power supply 41, an external terminal (terminal for connecting to an external power supply) 43, an inverter 44, and a drive motor 45.

[0181] The vehicle 400 has a vehicle power supply 41 mounted, for example, in an engine compartment, the rear of the vehicle body, or under a seat. Note that in the vehicle 400 shown in Fig. 9, the mounting location of the vehicle power supply 41 is shown diagrammatically.

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

[0183] The battery pack 300a includes an assembled battery 200a and an assembled battery monitoring device 310a (for example, VTM: Voltage Temperature Monitoring). The battery pack 300b includes an assembled battery 200b and an assembled battery monitoring device 310b. The battery pack 300c includes an assembled battery 200c and an assembled battery monitoring device 310c. The battery packs 300a to 300c are battery packs similar to the above-mentioned battery pack 300, and the assembled batteries 200a to 200c are assembled batteries similar to the above-mentioned battery pack 200. The assembled batteries 200a to 200c are electrically connected in series. The battery packs 300a, 300b, and 300c can be removed independently and replaced with another battery pack 300.

[0184] Each of the assembled batteries 200a to 200c includes a plurality of unit cells connected in series. At least one of the plurality of unit cells is the secondary battery according to the first embodiment. Each of the assembled batteries 200a to 200c is charged and discharged via a positive terminal 413 and a negative terminal 414.

[0185] The battery management device 411 communicates with the assembled battery monitoring devices 310a-310c and collects information on the voltage, temperature, and the like for each of the cells 100 included in the assembled batteries 200a-200c included in the vehicle power supply 41. In this way, the battery management device 411 collects information on the maintenance of the vehicle power supply 41.

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

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

[0188] The vehicle power supply 41 may also have an electromagnetic contactor (for example, a switch device 415 shown in FIG. 9) that switches between the presence and 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 is turned on when the assembled batteries 200a-200c are charged, and a main switch (not shown) that is turned on when the output from the assembled batteries 200a-200c is supplied to a load. Each of the pre-charge switch and the main switch includes a relay circuit (not shown) that is switched on or off by a signal supplied to a coil disposed in the vicinity of the switch element. The electromagnetic contactor such as the switch device 415 is 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 three-phase alternating current (AC) high voltage for driving the motor. The three-phase output terminals of the inverter 44 are connected to the three-phase input terminals of the drive motor 45. The inverter 44 is controlled based on a control signal 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 by electric power supplied from the inverter 44. A driving force generated by the rotation of the drive motor 45 is transmitted to the axles and drive wheels W via, for example, a differential gear unit.

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

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

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

[0194] The external terminal 43 is connected to the battery management unit 411. The external terminal 43 can be connected to, for example, an external power source.

[0195] In response to operational inputs from the driver or the like, the vehicle ECU 42 coordinates with other management devices and control devices including the battery management device 411 to control the vehicle power supply 41, the switch device 415, the inverter 44, etc. Through the coordinated control of the vehicle ECU 42, etc., the output of power from the vehicle power supply 41 and the charging of the vehicle power supply 41 are controlled, and the entire vehicle 400 is managed. Data relating to the maintenance of the vehicle power supply 41, such as the remaining capacity of the vehicle power supply 41, is transferred between the battery management device 411 and the vehicle ECU 42 via a communication line.

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

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

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

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

[0200] The power plant 111 generates a large amount of power using fuel sources such as thermal power and atomic power. Power is supplied from the power plant 111 through a power grid 116 or the like. A battery pack 300A is mounted on the stationary power source 112. The battery pack 300A can store the power supplied from the power plant 111. The stationary power source 112 can supply the power stored in the battery pack 300A through the power grid 116 or the like. The system 110 is provided with a power conversion device 118. The power conversion device 118 includes a converter, an inverter, a transformer, and the like. Thus, the power conversion device 118 can perform conversion between direct current and alternating current, conversion between alternating currents having different frequencies, and voltage transformation (boosting and bucking), and the like. Thus, the power conversion device 118 can convert the power from the power plant 111 into power that can be stored in the battery pack 300A.

[0201] The consumer-side power system 113 includes a power system for a factory, a power system for a building, a power system for a home, etc. The consumer-side power system 113 includes a consumer-side EMS 121, a power conversion device 122, and a stationary power source 123. The stationary power source 123 is equipped 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 system 113 is supplied with power from the power plant 111 and power from the battery pack 300A through the power grid 116. The battery pack 300B can store the power supplied to the consumer-side power system 113. Similarly to the power conversion device 118, the power conversion device 122 includes a converter, an inverter, a transformer, and the like. Therefore, the power conversion device 122 can perform conversion between DC and AC, conversion between ACs with different frequencies, and voltage transformation (boost and step-down), etc. Therefore, the power conversion device 122 can convert the power supplied to the consumer-side power system 113 into power that can be stored in the battery pack 300B.

[0203] The power stored in the battery pack 300B can be used, for example, to charge a vehicle such as an electric car. The system 110 may also be provided with a natural energy source. In this case, the natural energy source generates power using natural energy such as wind power and solar power. Power is supplied from the natural energy source in addition to the power plant 111 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 an excellent cycle capacity maintenance rate.

[0205] [Example] The above-mentioned embodiment will be described in more detail below based on examples, but the present invention is not limited to the examples listed below.

[0206] Example 1 <Preparation of negative electrode active material> The niobium titanium-based oxide was synthesized as follows.

[0207] Oxalic acid was dissolved in water to prepare a 1M oxalic acid solution. Titanium tetraisopropoxide (C 12 H 28 O 4 Ti) was dissolved in the solution, and ammonium niobium oxalate hydrate (C 4 H 4 NNbO 9 xH 2 These Ti sources (C 12 H 28 O 4 Ti) and Nb source (C 4 H 4 NNbO 9 xH 2O) were 11.5% by mass and 88.5% by mass, respectively. The solution was then neutralized by dripping aqueous ammonia into it to obtain a white gel. This gel was dried using a spray dryer to obtain a precursor. This precursor was placed in a cylindrical alumina crucible with an aspect ratio of about 1 up to the top, and densely packed by tapping. Using an electric furnace, calcination was performed in air at 300°C for 1 h and heat treatment was performed at 1400°C for 36 h in succession, followed by cooling to 100°C to obtain the active material of Example 1. Cooling from 1400°C to 100°C was performed at a rate of -0.6°C / min.

[0208] <Preparation of negative electrode> First, 100% by mass of the active material powder obtained in the above <Preparation of negative electrode active material>, 10% by mass of acetylene black as a conductive agent, 5% by mass of carbon nanofiber, 10% by mass of PVdF as a binder, and N-methylpyrrolidone (NMP) were added and mixed to obtain a slurry. This slurry was applied to one side of a current collector made of aluminum foil with a thickness of 15 μm, dried, and pressed to prepare an electrode.

[0209] <Electrolyte adjustment> PC and DEC were mixed in a volume ratio of PC:DEC = 1:2 to obtain a mixed solvent. Lithium hexafluorophosphate (LiPF 6 ) was dissolved in a concentration of 1.0 M to prepare a liquid non-aqueous electrolyte.

[0210] <Preparation of electrochemical measurement cell> <Preparation of negative electrode> The obtained electrode was used as a working electrode, a counter electrode and a reference electrode were made of Li metal, and the electrolyte prepared in <Preparation of electrolyte> was used to prepare a glass cell for evaluation.

[0211] Example 2 The active material of Example 2 was obtained by carrying out synthesis in the same manner as in Example 1, except that the temperature of the heat treatment was changed to 1300°C.

[0212] Example 3 The active material of Example 3 was obtained by carrying out synthesis in the same manner as in Example 1, except that the temperature of the heat treatment was changed to 1350°C.

[0213] Comparative Example 1 The active material of Comparative Example 1 was obtained by synthesizing in the same manner as in Example 1, except that the heat treatment conditions were changed to 900° C. for 4 hours and the cooling rate to 100° C. was set to −10° C. / min.

[0214] Comparative Example 2 The active material of Comparative Example 2 was obtained by carrying out synthesis in the same manner as in Comparative Example 1, except that the temperature of the heat treatment was changed to 1000°C.

[0215] Comparative Example 3 The active material of Comparative Example 3 was obtained by carrying out synthesis in the same manner as in Comparative Example 1, except that the temperature of the heat treatment was changed to 1100°C.

[0216] Comparative Example 4 Except for changing the heat treatment temperature to 1200° C., synthesis was performed in the same manner as in Comparative Example 1 to obtain the active material of Comparative Example 4. In the active material of Comparative Example 4, it was found from the powder XRD measurement described later that many monoclinic particles were mixed in addition to orthorhombic particles.

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

[0218] In this embodiment, the glass cell for measurement uses lithium metal as the counter electrode, so that the electrode potentials of the embodiment and comparative example are nobler than the counter electrode and operate as positive electrodes. Therefore, the definitions of charge and discharge are reversed when the electrodes of the embodiment and comparative example are used as negative electrodes. Here, to avoid confusion, in this embodiment, the direction in which lithium ions are inserted into the electrode is unified as charge, and the direction in which they are removed is unified as discharge. The active material of this embodiment operates as a negative electrode when combined with a known positive electrode material.

[0219] <Measurement of reversible capacity> The electrochemical measurement cell thus fabricated was charged and discharged in the potential range of 0.7 V to 3.0 V based on the metallic lithium electrode. The charge and discharge current value was set to 0.2 C (time discharge rate), and the 0.2 C reversible capacity was confirmed at room temperature of 25°C. The 0.2 C reversible capacity value is an index of energy density.

[0220] <Measurement of cycle capacity retention rate> Next, a life test was performed on each cell at room temperature (25° C.) by repeatedly charging and discharging at 1C in a potential range of 0.7V to 3.0V based on the metallic lithium electrode. 100 cycles of charging and discharging were repeated under these conditions (one cycle is defined as 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 cycles (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 the batteries of each of the examples prepared above, the batteries were pretreated by the following method.

[0222] First, the secondary battery was put into a discharged state, and then disassembled to remove the electrodes. This disassembly was carried out in a glove box under an argon gas atmosphere. The discharged state refers to a state in which the battery is discharged until the charge rate reaches 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 electrode containing the binder was dispersed in a solvent. N-methylpyrrolidone was used as the solvent. The electrode was dispersed by irradiating the solvent with ultrasonic waves for 30 minutes or more. This dissolved the binder and separated the electrode material as a powder from the current collector. Next, the solvent containing the electrode material powder was placed in a centrifuge, and the conductive agent and active material particles were separated, and then collected by freeze-drying.

[0224] The removed 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 used as the measurement subject.

[0225] <Powder XRD Measurement> The active material obtained in the above <battery pretreatment> was thoroughly pulverized to obtain a powdered sample. The average particle size of the powdered sample was 20 μm or less. This average particle size was determined using a laser diffraction particle size distribution analyzer. The powder XRD measurement method was performed as described above in the section <Powder XRD Measurement> of [First embodiment].

[0226] In this manner, the XRD spectrum of the active material was obtained. Figure 11 is a graph showing the spectrum obtained by powder X-ray diffraction measurement of the active material in each example. In Figure 11, the diamonds represent orthorhombic Ti 2 Nb 10 O 29 , ◇ is monoclinic Ti 2 Nb 10 O 29 This is 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 so that the count number of the main peak of the XRD spectrum was in the range of 50,000 counts or more and 150,000 counts or less.

[0227] By comparing these card data, in Examples 1, 2 and Comparative Example 5, the orthorhombic Ti crystals appearing at 24.5°≦2θ≦25.0° are 2 Nb 10 O 29 In addition, in Examples 1 and 2 and Comparative Example 5, the monoclinic Ti crystals at angles of incidence smaller than the above-mentioned peaks are very large. 2 Nb 10 O 29It can be seen that the peak coincident with the peak position of is very small. From this, it was found that in Example 1, Example 2 and Comparative Example 5, the orthorhombic crystals are contained in a larger amount. In addition, in Example 1 and Example 2, the half-width of the peak appearing at 24.5°≦2θ≦25.0° is 0.09° or less, which shows 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 FIG. 11) obtained by the method described above in <Measurement of Powder XRD>. The analysis was performed as described above in the section <Measurement of Unit Cell Volume> of [First Embodiment], and information on the crystal structure of the active material to be measured was obtained.

[0229] The above measurement results are summarized in Table 1. Specifically, the half-width of the peak appearing at 24.5°≦2θ≦25.0° in the XRD spectrum of each example, 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.

[0230] [Table 1]

[0231] Comparing Examples 1 to 3 with Comparative Examples 1 to 5, the unit lattice volume of the active material is 2230 Å 3As described above, it can be seen that in Examples 1 to 3, a high reversible capacity and a high cycle capacity retention rate are both achieved because the half-width of the peak appearing at 24.5°≦2θ≦25.0° in the XRD spectrum is 0.09° or less. This is thought to be because, in the preparation of the negative electrode active material of Examples 1 to 3, the cooling speed after the main baking is sufficiently slowed down, so that the atomic arrangement of the active material is regularly rearranged over a sufficient amount of time, and the crystallinity is improved. In this way, the crystallinity of the active material is stable. In addition, the unit lattice volume of the active material is also large by the above-mentioned method for preparing the negative electrode active material of Examples 1 to 3, and the structure of the active material is unlikely to change due to the charge and discharge of the secondary battery, so that the cycle capacity retention rate of the secondary battery in Examples 1 to 3 is high. Therefore, it can be seen that in Examples 1 to 3, a high reversible capacity and a high cycle capacity retention rate can be both achieved.

[0232] The active material according to this embodiment has the general formula Li x Nb 10 Ti 2 O 29 (0≦x≦5) and the unit cell volume is 2230Å 3 or more, and the half-width of a peak appearing at 24.5°≦2θ≦25.0° in a powder X-ray diffraction spectrum is 0.09° or less. This makes it possible to realize an active material and electrode that can realize a secondary battery that achieves both a high reversible capacity and a high cycle capacity retention rate, a secondary battery and battery pack that achieve both a high reversible capacity and a high cycle capacity retention rate, and a vehicle and stationary power source equipped with the battery pack.

[0233] Although some 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, substitutions, and modifications can be made without departing from the spirit of the invention. These embodiments and their modifications are included in the scope and spirit of the invention, and are included in the scope of the invention and its equivalents described in the claims.

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

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

[0236] [2] Further containing 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 (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 according to [1] or [2].

[0238] [4] A positive electrode, A negative electrode, An electrolyte, a secondary battery comprising: The negative electrode is the electrode according to [3].

[0239] [5] A battery pack comprising the secondary battery according to [4].

[0240] [6] An external terminal for energization, A protection circuit, further comprising the battery pack according to [5].

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

[0242] [8] A vehicle equipped with a battery pack according to any one of [5] to [7].

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

[0244]

[10] A stationary power source comprising a battery pack according to any one of [5] to [7]. [Explanation of symbols]

[0245] 1...electrode group, 2...exterior member, 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...container, 32...lid, 33...protective sheet, 34...printed wiring board, 35...wiring, 40...vehicle body, 41...vehicle power source, 42...electrical control device, 43...external terminal, 44...inverter, 45...driving motor, 100...secondary battery, 200...assembled battery, 200a...assembled battery, 200b...assembled battery, 200c...assembled battery, 300...battery pack, 300a...battery pack, 300 b...battery pack, 300c...battery pack, 301a...assembled battery monitoring device, 301b...assembled battery monitoring device, 301c...assembled battery monitoring device, 342...positive connector, 343...negative connector, 345...thermistor, 346...protection circuit, 342a...wiring, 343a...wiring, 350...external terminal for energizing, 352...positive terminal, 353...negative terminal, 348a...positive wiring, 348b...negative wiring, 400...vehicle, 411...battery management device, 412...communication bus, 413...positive terminal, 414...negative terminal, 415...switch device, 416...current detection unit, 417...negative input terminal, 418...positive input terminal, L1...connection line, L2...connection line, W...drive wheel.

Claims

1. General formula Li ｘ Nb １０ Ti ２ O ２９ (0≦x≦5), The unit cell volume is 2230 Å ３ or more, and the half-width of the maximum peak appearing at 24.5°≦2θ≦25.0° in a powder X-ray diffraction spectrum is 0.09° or less.

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

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

4. A positive electrode and A negative electrode; An electrolyte. The secondary battery, wherein the negative electrode is the electrode according to claim 3 .

5. A battery pack comprising the secondary battery according to claim 4.

6. An external terminal for supplying electricity; The battery pack of claim 5 , further comprising a protection circuit.

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

8. A vehicle comprising the battery pack according to claim 5.

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

10. A stationary power source comprising the battery pack according to claim 5.

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