Electrodes, secondary batteries, battery packs, and vehicles

Abstract

To provide an electrode, a secondary battery, a battery pack, and a vehicle, having excellent high-temperature cyclic performance.SOLUTION: According to an embodiment, an electrode is provided. The electrode includes an active material-containing layer. The active material-containing layer includes an active material and carbon fiber. The active material includes a titanium-containing composite oxide. The active material-containing layer has a peak indicating a maximum logarithmic differential pore volume, in a logarithmic differential pore volume distribution curve by a mercury intrusion method. A pore diameter PD at the peak is greater than 0.1 μm and 0.3 μm or less. According to another embodiment, a secondary battery includes a positive electrode, a negative electrode, and an electrolyte. At least one of the positive electrode and the negative electrode is the electrode according to the one embodiment. According to still another embodiment, a battery pack is provided. This battery pack includes the secondary battery according to the other embodiment. According to yet another embodiment, a vehicle is provided. This vehicle includes the battery pack according to the still other embodiment.SELECTED DRAWING: Figure 1

Description

[Technical Field]

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

[0002] Lithium-ion secondary batteries, such as non-aqueous electrolyte secondary batteries, are rechargeable batteries that charge and discharge by the movement of lithium ions between the positive and negative electrodes. The positive and negative electrodes hold a non-aqueous electrolyte containing lithium ions. In addition to their use as power sources for small electronic devices, non-aqueous electrolyte secondary batteries are also expected to be used as medium to large-scale power sources for automotive and stationary applications, and therefore require improved high-temperature cycle performance. [Prior art documents] [Patent Documents]

[0003] [Patent Document 1] Japanese Patent Publication No. 2021-44221 [Overview of the project] [Problems that the invention aims to solve]

[0004] The problem that this invention aims to solve is to provide electrodes, secondary batteries, battery packs, and vehicles with excellent high-temperature cycling performance. [Means for solving the problem]

[0005] An electrode is provided according to the embodiment. The electrode includes an active material-containing layer. The active material-containing layer includes an active material and carbon fibers. The active material includes a titanium-containing composite oxide. The active material-containing layer shows a peak indicating the maximum logarithmic differential pore volume in the logarithmic differential pore volume distribution curve obtained by the mercury intrusion method. The pore diameter PD of the peak is greater than 0.1 μm and less than or equal to 0.3 μm. The relationship between the total pore surface area TA of the active material-containing layer and the pore diameter PD of the peak obtained by the mercury intrusion method is given by TA = a × PD + b (where a = -17 and b = 7 ≤ b ≤ 10.6). ru. Titanium-containing composite oxides are A x TiM y Nb 2-y O7±z (0≦x≦5, 0≦y≦0.5, -0.3≦z≦0.3, M is at least one metallic element other than Ti and Nb, A is at least one of Li and Na), Li 2+a Na 2 Ti 6 O 14 (0≦a≦6), Li x TiO 2 (0≦x≦1), Li 2+a M(I) 2-b Ti 6-c M(II)dO 14+σ (M(I) is at least one element selected from the group consisting of Sr, Ba, Ca, Mg, Na, Cs, Rb, and K; M(II) is at least one element selected from the group consisting of Zr, Sn, V, Nb, Ta, Mo, W, Y, Fe, Co, Cr, Mn, Ni, and Al; 0≦a≦6, 0≦b<2, 0≦c<6, 0≦d<6, -0.5≦σ≦0.5), Li x Ti 1-y M1 y Nb 2-z M2 z O 7+δ (M1 is at least one element selected from the group consisting of Zr, Si, and Sn; M2 is at least one element selected from the group consisting of V, Ta, and Bi; 0≦x≦5, 0≦y<1, 0≦z<2, -0.3≦δ≦0.3), and Li x Ti 1-y M3 y+z Nb 2-zO7-δ (M3 is at least one compound represented by a general formula selected from the group consisting of at least one element selected from Mg, Fe, Ni, Co, W, Ta, and Mo, with 0≦x<5, 0≦y<1, 0≦z<2, -0.3≦δ≦0.3). The electrode is in a battery using at least one non-aqueous electrolyte or non-aqueous electrolyte solution as the electrolyte. Furthermore, an electrode is provided according to the embodiment. The electrode includes an active material-containing layer. The active material-containing layer includes an active material and carbon fibers. The active material includes a titanium-containing composite oxide. The active material-containing layer shows a peak indicating the maximum logarithmic differential pore volume in the logarithmic differential pore volume distribution curve obtained by the mercury intrusion method. The pore diameter PD of the peak is greater than 0.1 μm and less than or equal to 0.3 μm. The titanium-containing composite oxide is A x TiM y Nb 2-y O 7±z (0≦x≦5, 0≦y≦0.5, -0.3≦z≦0.3, M is at least one metallic element other than Ti and Nb, A is at least one of Li and Na), Li 2+a Na 2 Ti 6 O 14 (0≦a≦6), Li x TiO 2 (0≦x≦1), Li 2+a M(I) 2-b Ti 6-c M(II)dO 14+σ (M(I) is at least one element selected from the group consisting of Sr, Ba, Ca, Mg, Na, Cs, Rb, and K; M(II) is at least one element selected from the group consisting of Zr, Sn, V, Nb, Ta, Mo, W, Y, Fe, Co, Cr, Mn, Ni, and Al; 0≦a≦6, 0≦b<2, 0≦c<6, 0≦d<6, -0.5≦σ≦0.5), Li x Ti 1-y M1 y Nb 2-z M2 z O7+δ (M1 is at least one element selected from the group consisting of Zr, Si, and Sn; M2 is at least one element selected from the group consisting of V, Ta, and Bi; 0≦x≦5, 0≦y<1, 0≦z<2, -0.3≦δ≦0.3), and Li x Ti 1-y M3 y+z Nb 2-zO7-δ (M3 is at least one compound represented by a general formula selected from the group consisting of at least one element selected from Mg, Fe, Ni, Co, W, Ta, and Mo, with 0≦x<5, 0≦y<1, 0≦z<2, and -0.3≦δ≦0.3). The value MD-PD, obtained by subtracting the peak pore size PD from the median diameter MD of the active material-containing layer by the mercury intrusion method, is between -0.02 μm and 0.02 μm, and the electrode is in a battery using at least one of a non-aqueous electrolyte or non-aqueous electrolyte solution as the electrolyte.

[0006] According to another embodiment, the secondary battery comprises a positive electrode, a negative electrode, and an electrolyte. At least one of the positive electrode and the negative electrode is an electrode according to the embodiment.

[0007] According to another embodiment, a battery pack is provided, which comprises a secondary battery according to the embodiment.

[0008] According to another embodiment, a vehicle is provided, which comprises a battery pack according to the embodiment. [Brief explanation of the drawing]

[0009] [Figure 1] An example of an electrode's active material-containing layer. [Figure 2] An example of a logarithmic differential pore volume distribution curve obtained by the mercury intrusion method in an active material-containing layer. [Figure 3] An example of a rechargeable battery. [Figure 4] Figure 3 shows an enlarged cross-sectional view of section A of the secondary battery. [Figure 5] A partially cutaway perspective view schematically showing another example of a secondary battery. [Figure 6] Figure 5 shows an enlarged cross-sectional view of section B of the secondary battery. [Figure 7] A schematic perspective view showing an example of a battery pack. [Figure 8] An exploded perspective view illustrating an example of a battery pack. [Figure 9] A block diagram showing an example of the electrical circuit of a battery pack. [Figure 10] A partial transparency diagram illustrating an example of a vehicle. [Figure 11] A schematic diagram illustrating an example of a control system for the electrical system in a vehicle. [Figure 12] Relationship between peak pore size (PD) and total pore volume (TA). [Modes for carrying out the invention]

[0010] (First Embodiment) According to this embodiment, an electrode is provided. The electrode includes an active material-containing layer. The active material-containing layer includes an active material and carbon fibers. The active material includes a titanium-containing composite oxide.

[0011] In the active material-containing layer of the electrode according to this embodiment, the active material and carbon fibers are mixed together. The carbon fibers can form conductive paths over longer distances compared to granular carbon. Therefore, even if the volume of the active material changes, the conductive paths between the active materials in the active material-containing layer of the electrode according to this embodiment are less likely to be destroyed.

[0012] Furthermore, the electrode according to the embodiment has an active material-containing layer in which the pore diameter PD of the peak showing the maximum height, i.e., the mode diameter, is large enough to hold the electrolyte, and the full width at half maximum of the peak is relatively small. Therefore, it can be said that this active material-containing layer has a pore distribution in which pores large enough to hold the electrolyte are distributed relatively uniformly. Thus, it can be said that the electrolyte is uniformly held in this active material-containing layer.

[0013] From the above, the electrode according to the embodiment can achieve excellent cycle performance even in high-temperature environments. Hereinafter, in this specification, cycle performance in high-temperature environments may be expressed as "high-temperature cycle performance".

[0014] Figure 1 is a schematic diagram showing an example of an active material-containing layer of an electrode according to an embodiment. The active material-containing layer shown in Figure 1 includes active material particles 50, carbon fibers 51, and granular carbon 52. The active material particles 50 and granular carbon 52 are in contact with elongated, string-like carbon fibers 51. The carbon fibers 51 and granular carbon 52 form conductive paths. The granular carbon 52 is present between the active material particles 50. The carbon fibers 51 can be present between active material particles 50 that are at a distance from each other. An electrolyte (not shown) may be impregnated into the gaps between the active material particles 50 and the granular carbon 52. Note that the granular carbon 52 may be omitted. In the active material-containing layer shown in Figure 1, the conductive paths formed by the carbon fibers 51 are maintained even when the granular carbon 52 is omitted.

[0015] Figure 2 is a graph showing an example of a logarithmic differential pore volume distribution curve obtained by the mercury intrusion method for the active material-containing layer of the electrode according to this embodiment. In the graph of Figure 2, the vertical axis represents the logarithmic differential pore volume, and the horizontal axis represents the pore diameter. The active material-containing layer of the electrode according to this embodiment shows a peak indicating the maximum logarithmic differential pore volume in the logarithmic differential pore volume distribution curve obtained by the mercury intrusion method. The pore diameter PD at the peak is greater than 0.1 μm and less than or equal to 0.3 μm. The pore diameter PD at the peak, i.e., the mode diameter, is the size of the pore diameter with the highest abundance among the multiple pores provided in the active material-containing layer. When PD is within this range, sufficient electrolyte can be retained in the active material-containing layer. When PD is sufficiently large, the electrolyte can easily penetrate the electrode even under high-temperature conditions, and electrolyte depletion during high-temperature cycling can be suppressed. On the other hand, if PD is too large, the strength of the electrode weakens, and the cycling performance deteriorates. Therefore, it is preferable that PD is greater than 0.1 μm and less than or equal to 0.3 μm. The logarithmic differential pore volume distribution curve of the active material-containing layer was obtained by the method described later. The graph shown in Figure 2 relates to Example 1, which will be described later. In the graph in Figure 2, the PD is 0.12 μm.

[0016] The peak's full width at half maximum (FMAX) is 0.1 μm or less. A small peak FMAX indicates that the pores within the active material-containing layer are uniform in size. When the pores within the active material-containing layer are uniform in size, the electrolyte is uniformly maintained within the layer, and the reaction between the active material and the electrolyte is more likely to occur uniformly. There is no particular lower limit for the peak's FMAX, but one example suggests it is 0.01 μm or more. The peak's FMAX is preferably 0.06 μm or less, and more preferably 0.05 μm or less. In the graph in Figure 2, the FMAX is 0.04 μm.

[0017] The logarithmic differential pore volume distribution curve and the integrated pore volume distribution curve of the active material-containing layer obtained by the mercury intrusion method can be obtained, for example, by the following method. First, if the electrodes are contained within a secondary battery, the secondary battery is discharged, then disassembled and the electrodes are removed. This disassembly is performed in a glove box under an inert gas atmosphere such as argon. The discharged state refers to the state in which the battery is discharged until its charge level reaches 0%. The removed electrodes are washed with a solvent and then dried. For example, ethyl methyl carbonate is used as the solvent. After drying, the electrodes are cut to obtain multiple test pieces. The size of the test pieces is, for example, a strip with a short side of 1.25 cm and a long side of 2.5 cm.

[0018] Next, multiple test specimens are placed in the measuring cell of the measuring device, and mercury is introduced into the pores of the test specimens. The number of test specimens is, for example, between 16 and 32. As the measuring cell, for example, a 5cc cell for large specimens with a stem volume of 0.4cc is used. As the measuring device, for example, a Shimadzu Autopore 9520 (Autopore 9520 model manufactured by Shimadzu Corporation) is used. For the measurement, for example, the initial pressure is set to 7kPa and the final pressure to 414MPa. 7kPa corresponds to 1.0 psia (pounds per square inch absolute pressure), which corresponds to a pore with a diameter of approximately 180μm. Also, 414MPa corresponds to approximately 6 psia, which corresponds to a pore with a diameter of approximately 0.003μm. The mercury contact angle is set to 130 degrees, and the mercury surface tension is set to 485 dynes / cm. By processing the obtained data, the logarithmic differential pore volume distribution curve, integrated pore volume distribution curve, total pore surface area, and total pore volume of the active material-containing layer can be obtained.

[0019] The total pore surface area TA of the active material-containing layer obtained by the mercury intrusion method is 4 m². 2 It is preferable that the TA is 1 / g or more. A large TA indicates that multiple fine pores are present within the active material-containing layer. There is no particular upper limit to the size of TA, but for example, 8m 2 It is less than / g. TA is 5m 2 It is preferable that it is 6m or more per g. 2 It is more preferable that the amount be 1 / g or more.

[0020] The total pore volume TV of the active material-containing layer produced by the mercury intrusion method is preferably 0.15 mL / g or less. A smaller TV indicates fewer voids within the active material-containing layer. Using electrodes with such an active material-containing layer can increase the energy density of the secondary battery. On the other hand, from the viewpoint of increasing the amount of electrolyte held by the active material-containing layer, a TV of 0.04 mL / g or more is preferable. A TV of 0.05 mL / g or more and 0.15 mL / g or less is more preferable in terms of achieving both high energy density and sufficient electrolyte retention.

[0021] The value MD-PD, obtained by subtracting the peak pore diameter PD from the median diameter MD of the active material-containing layer produced by the mercury intrusion method, is preferably between -0.02 μm and 0.02 μm. The MD of the active material-containing layer is the pore diameter when the cumulative volume is 50% in the cumulative pore volume distribution curve of the active material-containing layer produced by the mercury intrusion method. If the value MD-PD is within this range, it can be said that PD and MD are approximately equal. Such an active material-containing layer can be said to have more uniform pore diameters. It is more preferable that the value MD-PD is between -0.01 μm and 0.01 μm.

[0022] The relationship between the total pore surface area TA and the peak pore diameter PD of the active material-containing layer formed by the mercury intrusion method is preferably expressed by the following formula (1). TA = a × PD + b (1) Here, in the equation, a = -17 and b = 7 ≤ b ≤ 10.6. Active material-containing layers in which the relationship between TA and PD falls within this range are less prone to degradation due to side reactions. A larger TA improves the electrolyte retention of the electrode, making electrolyte depletion less likely during high-temperature cycling. However, if the size of TA exceeds the threshold, side reactions such as gas generation may occur, potentially reducing cycle performance. As PD decreases, the number of pores increases, and therefore the threshold for TA increases. Thus, there is a negative correlation between PD and TA, so a is a negative value. It is more preferable that b used in equation (1) is 8 ≤ b ≤ 10.6.

[0023] The electrode according to this embodiment can be used as either a positive electrode or a negative electrode, but it is preferable to use it as a negative electrode.

[0024] The details of the electrode according to the embodiment will be described below.

[0025] The electrode may include an active material-containing layer and a current collector. The active material-containing layer is supported on at least one side of the current collector. The active material-containing layer may be supported on one side of the current collector or on both sides. In addition to the active material and fibrous carbon, the active material-containing layer may further contain granular carbon and a binder.

[0026] The active material contains a titanium-containing composite oxide. The titanium-containing composite oxide is A x TiM y Nb 2-y O 7±z (0≦x≦5, 0≦y≦0.5, -0.3≦z≦0.3, M is at least one metallic element other than Ti and Nb, A is at least one of Li and Na), Li 2+a Na2Li6O 14 (0≦a≦6), and Li x It is preferable that the compound contains at least one compound represented by a general formula selected from the group consisting of TiO2 (0 ≤ x ≤ 1).

[0027] Furthermore, titanium-containing composite oxides include lithium titanate (e.g., Li) which has a ramsdelite structure. 2+y Li3O7 (0≦y≦3), lithium titanate having a spinel structure (e.g., Li 4+x Ti5O 12 The material may contain at least one compound selected from the group consisting of monoclinic titanium dioxide (TiO2), anatase titanium dioxide, rutile titanium dioxide, hollandite titanium composite oxide, orthorhombic titanium composite oxide, and monoclinic niobium titanium composite oxide.

[0028] As an example of the above orthorhombic titanium-containing composite oxide, Li 2+a M(I) 2-b Ti 6-c M(II)dO 14+σA compound represented by the formula is shown below. Here, M(I) is at least one selected from the group consisting of Sr, Ba, Ca, Mg, Na, Cs, Rb, and K. M(II) is at least one selected from the group consisting of Zr, Sn, V, Nb, Ta, Mo, W, Y, Fe, Co, Cr, Mn, Ni, and Al. The subscripts in the composition formula are 0≦a≦6, 0≦b<2, 0≦c<6, 0≦d<6, and -0.5≦σ≦0.5. A specific example of an orthorhombic titanium-containing composite oxide is Li 2+a Na2Li6O 14 (0 ≤ a ≤ 6) is one example.

[0029] As an example of the above monoclinic niobium-titanium composite oxide, Li x Ti 1-y M1 y Nb 2-z M2 z O 7+δ Examples of compounds represented by the formula are: Here, M1 is at least one selected from the group consisting of Zr, Si, and Sn. M2 is at least one selected from the group consisting of V, Ta, and Bi. The subscripts in the compositional formula are 0≦x≦5, 0≦y<1, 0≦z<2, and -0.3≦δ≦0.3. A specific example of a monoclinic niobium titanium composite oxide is Li x Nb2TiO7 (0≦x≦5) is one example, and another example of a monoclinic niobium-titanium composite oxide is Li x Ti 1-y M3 y+z Nb 2-zO7-δ A compound represented by the formula is shown below. Here, M3 is at least one selected from Mg, Fe, Ni, Co, W, Ta, and Mo. In the compositional formula, each subscript has the following properties: 0≦x<5, 0≦y<1, 0≦z<2, -0.3≦δ≦0.3.

[0030] Carbon fibers and granular carbon are incorporated as conductive agents to enhance current collection performance and reduce contact resistance between the active material and the current collector.

[0031] Carbon fibers are fibrous carbon fibers in which the ratio L1 / S1 of the length in the longitudinal direction to the diameter of the cross-section perpendicular to the longitudinal direction, i.e., the thickness S1, is 50 or more. The ratio L1 / S1 is preferably between 150 and 10000. The diameter of the cross-section perpendicular to the longitudinal direction of the carbon fiber, i.e., the thickness, is preferably between 1 nm and 200 nm (0.001 μm and 0.2 μm). The length of the carbon fiber is preferably between 5 μm and 50 μm. Examples of carbon fibers include vapor-grown carbon fiber (VGCF). Examples of vapor-grown carbon fiber include carbon nanotubes (CNT) and carbon nanofibers (CNF). One of these may be used as a carbon fiber, or two or more may be combined to form a carbon fiber.

[0032] In the active material-containing layer, the amount of carbon fiber per 100 parts by mass of active material is preferably 0.01 parts by mass or more and 10 parts by mass or less, and more preferably 0.1 parts by mass or more and 5 parts by mass or less. A larger amount of carbon fiber can increase the electronic conductivity of the active material-containing layer. On the other hand, an excessively large amount of carbon fiber may decrease the energy density.

[0033] Granular carbon is granular carbon in which the ratio L2 / S2 (the ratio of the length of the long axis L2 to the length of the short axis S2) is less than 50. Flake carbon is also included in granular carbon. Examples of granular carbon include carbon black such as acetylene black and carbonaceous materials such as graphite. One of these may be used as granular carbon, or two or more may be combined to form granular carbon.

[0034] In the active material-containing layer, the amount of granular carbon per 100 parts by mass of active material is preferably 0 to 10 parts by mass, and more preferably 1 to 5 parts by mass. A larger amount of granular carbon can increase the electronic conductivity of the active material-containing layer. On the other hand, an excessive amount of granular fibers may reduce the energy density.

[0035] A binder is added to fill the gaps between dispersed active materials and to bond the active materials to the negative electrode current collector. Examples of binders include polytetrafluoroethylene (PTFE), polyvinylidene fluoride (PVdF), fluororubber, styrene-butadiene rubber, polyacrylic acid compounds, imide compounds, carboxymethyl cellulose (CMC), and salts of CMC. One of these may be used as a binder, or two or more may be used in combination.

[0036] In the active material-containing layer, the amount of binder per 100 parts by mass of active material is preferably 0 to 10 parts by mass, and more preferably 1 to 5 parts by mass. A larger amount of binder ensures sufficient bonding between the active material-containing layer and the current collector, leading to excellent cycle performance. On the other hand, an excessively large amount of binder may reduce energy density.

[0037] The current collector is made of a material that is electrochemically stable at the potential at which lithium (Li) is inserted into and removed from the active material. For example, the current collector is preferably made of copper, nickel, stainless steel, or aluminum, or an aluminum alloy containing one or more elements selected from Mg, Ti, Zn, Mn, Fe, Cu, and Si. The thickness of the current collector is preferably 5 μm to 20 μm. A current collector with such a thickness can balance electrode strength and weight reduction.

[0038] Furthermore, the current collector may include portions on its surface where the active material-containing layer is not formed. These portions can function as current-collecting tabs.

[0039] The density of the active material-containing layer is 2.3 g / cm³. 3 More than 3g / cm 3 Preferably, it is 2.5 g / cm³. 3More than 2.8g / cm 3 The following is more preferable:

[0040] Next, a method for manufacturing electrodes according to an embodiment will be described.

[0041] First, carbon fibers, a binder, and pure water were mixed and stirred using a planetary mixer. The binder used here is referred to as the first binder. In addition to pure water, other solvents such as N-methyl-2-pyrrolidone may be used as a solvent. The stirring speed was set to, for example, 10 rpm to 60 rpm, and the stirring time was set to 5 minutes to 2 hours. After that, the active material and granular carbon were added to this mixture and stirred further using a planetary mixer. During stirring, the stirring speed was set to 40 rpm and the stirring time was set to 30 minutes. Further stirring was performed using a bead mill. Further stirring with a bead mill improves the dispersibility of the mixture. As a bead mill, for example, the continuous horizontal ready mill RMH-03 manufactured by AIMEX Co., Ltd. was used. The flow rate of the bead mill was set to, for example, 10 mL / min to 50 mL / min. The rotation speed of the bead mill was set to 500 rpm to 2500 rpm. After that, the second binder was added and stirred using a planetary mixer to prepare a dispersed slurry.

[0042] Next, this dispersed slurry was applied to one or both sides of the current collector, and the coating was dried to obtain a laminate of the active material-containing layer and the current collector. By pressing this laminate, electrodes could be obtained.

[0043] The electrode according to the first embodiment described above comprises an active material and an active material-containing layer containing carbon fibers. In the logarithmic differential pore volume distribution curve of the active material-containing layer obtained by the mercury intrusion method, the pore diameter PD of the peak indicating the maximum logarithmic differential pore volume is greater than 0.1 μm and less than or equal to 0.3 μm. The full width at half maximum of the peak is 0.1 μm or less. Using this electrode, a secondary battery with excellent cycle performance can be realized even in high-temperature environments of 60°C or higher. This secondary battery exhibits particularly excellent cycle performance in high-temperature environments of 70°C or higher.

[0044] (Second embodiment) According to the second embodiment, a secondary battery is provided that includes a negative electrode, a positive electrode, and an electrolyte. At least one of the negative electrode and the positive electrode is an electrode according to the first embodiment. When either the negative electrode or the positive electrode is an electrode according to the first embodiment, the counter electrode may have a different configuration from that of the first embodiment.

[0045] The secondary battery according to the second embodiment may further include a separator disposed between the positive electrode and the negative electrode. The negative electrode, positive electrode, and separator can constitute an electrode group. The electrolyte can be held in the electrode group.

[0046] Furthermore, the secondary battery according to the second embodiment may further comprise an outer casing that houses the electrode group and the electrolyte.

[0047] Furthermore, the secondary battery according to the second embodiment may further include a negative terminal electrically connected to the negative electrode and a positive terminal electrically connected to the positive electrode.

[0048] The secondary battery according to the second embodiment may be, for example, a lithium-ion secondary battery. The secondary battery also includes a non-aqueous electrolyte secondary battery containing a non-aqueous electrolyte.

[0049] Figure 3 is a schematic cross-sectional view showing an example of a secondary battery according to the second embodiment. Figure 4 is an enlarged cross-sectional view of part A of the secondary battery shown in Figure 3.

[0050] The secondary battery 100 shown in Figures 3 and 4 comprises a bag-shaped outer casing member 2 shown in Figures 3 and 4, an electrode group 1 shown in Figure 3, and an electrolyte (not shown). The electrode group 1 and the electrolyte are housed within the bag-shaped outer casing member 2. The electrolyte (not shown) is held by the electrode group 1.

[0051] The bag-shaped outer packaging member 2 consists of a laminate film comprising two resin layers and a metal layer interposed between them.

[0052] As shown in Figure 3, electrode group 1 is a flat, wound electrode group. As shown in Figure 4, the flat, wound electrode group 1 includes a negative electrode 3, a separator 4, and a positive electrode 5. The separator 4 is interposed between the negative electrode 3 and the positive electrode 5.

[0053] The negative electrode 3 includes a negative electrode current collector 3a and a negative electrode active material containing layer 3b. In the portion of the negative electrode 3 located in the outermost shell of the wound electrode group 1, the negative electrode active material containing layer 3b is formed only on the inner surface side of the negative electrode current collector 3a, as shown in Figure 4. In the other portions of the negative electrode 3, the negative electrode active material containing layer 3b is formed on both sides of the negative electrode current collector 3a.

[0054] The positive electrode 5 includes a positive electrode current collector 5a and positive electrode active material-containing layers 5b formed on both sides thereof.

[0055] As shown in Figure 3, the negative electrode terminal 6 and the positive electrode terminal 7 are located near the outer edge of the wound electrode group 1. The negative electrode terminal 6 is connected to the outermost part of the negative electrode current collector 3a. The positive electrode terminal 7 is connected to the outermost part of the positive electrode current collector 5a. These negative electrode terminals 6 and positive electrode terminals 7 extend outward from the opening of the bag-shaped outer casing member 2. A thermoplastic resin layer is installed on the inner surface of the bag-shaped outer casing member 2, and the opening is closed by heat-sealing this layer.

[0056] The secondary battery according to the second embodiment is not limited to the secondary battery with the configuration shown in Figures 3 and 4, but may also be a battery with the configuration shown in Figures 5 and 6, for example.

[0057] Figure 5 is a schematic partially cutaway perspective view showing another example of a secondary battery according to the second embodiment. Figure 6 is an enlarged cross-sectional view of part B of the secondary battery shown in Figure 5.

[0058] The secondary battery 100 shown in Figures 5 and 6 comprises an electrode group 1 shown in Figures 5 and 6, an outer casing member 2 shown in Figure 5, and an electrolyte (not shown). The electrode group 1 and the electrolyte are housed within the outer casing member 2. The electrolyte is held within the electrode group 1.

[0059] The exterior component 2 consists of a laminate film comprising two resin layers and a metal layer interposed between them.

[0060] As shown in Figure 6, electrode group 1 is a stacked electrode group. The stacked electrode group 1 has a structure in which negative electrodes 3 and positive electrodes 5 are stacked alternately with a separator 4 interposed between them.

[0061] The electrode group 1 includes a plurality of negative electrodes 3. Each of the plurality of negative electrodes 3 comprises a negative electrode current collector 3a and a negative electrode active material-containing layer 3b supported on both sides of the negative electrode current collector 3a. The electrode group 1 also includes a plurality of positive electrodes 5. Each of the plurality of positive electrodes 5 comprises a positive electrode current collector 5a and a positive electrode active material-containing layer 5b supported on both sides of the positive electrode current collector 5a.

[0062] Each negative electrode 3's negative electrode current collector 3a includes a portion 3c on one side where the negative electrode active material-containing layer 3b is not supported on any surface. This portion 3c functions as a negative electrode current collector tab. As shown in Figure 6, the portion 3c acting as a negative electrode current collector tab does not overlap with the positive electrode 5. Furthermore, multiple negative electrode current collector tabs (portions 3c) are electrically connected to a strip-shaped negative electrode terminal 6. The tip of the strip-shaped negative electrode terminal 6 is extended to the outside of the outer casing member 2.

[0063] Although not shown in the diagram, the positive electrode current collector 5a of each positive electrode 5 includes a portion on one side where the positive electrode active material-containing layer 5b is not supported on any surface. This portion functions as a positive electrode current collector tab. The positive electrode current collector tab, like the negative electrode current collector tab (part 3c), does not overlap with the negative electrode 3. Furthermore, the positive electrode current collector tab is located on the opposite side of the electrode group 1 from the negative electrode current collector tab (part 3c). The positive electrode current collector tab is electrically connected to a strip-shaped positive electrode terminal 7. The tip of the strip-shaped positive electrode terminal 7 is located on the opposite side from the negative electrode terminal 6 and is extended to the outside of the outer casing member 2.

[0064] The counter electrode, electrolyte, separator, outer casing, negative electrode terminal, and positive electrode terminal will be described in detail below.

[0065] 1) Counter electrode The counter electrode may comprise an active material-containing layer and a current collector. The active material-containing layer may be supported on one surface of the current collector, or may be supported on both surfaces of the current collector. The active material-containing layer may comprise an active material, a conductive agent, and a binder. The active material-containing layer may or may not comprise fibrous carbon. The counter electrode is a negative electrode when the electrode according to the embodiment is a positive electrode, and is a positive electrode when the electrode according to the embodiment is a negative electrode. The counter electrode is preferably a positive electrode. Description will be made here on the assumption that the counter electrode is a positive electrode.

[0066] As the positive electrode active material, for example, an oxide or a sulfide can be used. The positive electrode may contain one type of compound alone as the positive electrode active material, or may contain two or more types of compounds in combination as the positive electrode active material. Examples of the oxide and sulfide include compounds capable of inserting and desorbing Li or Li ions.

[0067] Examples of such compounds include manganese dioxide (MnO2), iron oxide, copper oxide, nickel oxide, lithium manganese composite oxide (for example, Li x Mn2O4 or Li x MnO2; 0 < x ≦ 1), lithium nickel composite oxide (for example, Li x NiO2; 0 < x ≦ 1), lithium cobalt composite oxide (for example, Li x CoO2; 0 < x ≦ 1), lithium nickel cobalt composite oxide (for example, Li x Ni 1-y Co y O2; 0 < x ≦ 1, 0 < y < 1), lithium manganese cobalt composite oxide (for example, Li x Mn y Co 1-y O2; 0 < x ≦ 1, 0 < y < 1), lithium manganese nickel composite oxide having a spinel structure (for example, Li x Mn 2-y Ni y O4; 0 < x ≦ 1, 0 < y < 2), lithium phosphate oxide having an olivine structure (for example, Li x FePO4; 0 < x ≦ 1, Li x Fe 1-y Mny PO4; 0 < x ≦ 1, 0 < y < 1, Li x CoPO4; 0 < x ≦ 1), iron(III) sulfate (Fe2(SO4)3), vanadium oxide (for example, V2O5), and lithium nickel cobalt manganese composite oxide (Li x Ni 1-y-z Co y Mn z O2; 0 < x ≦ 1, 0 < y < 1, 0 < z < 1, y+z < 1).

[0068] 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 Mn2O4; 0 < x ≦ 1), lithium nickel composite oxide (for example, Li x NiO2; 0 < x ≦ 1), lithium cobalt composite oxide (for example, Li x CoO2; 0 < x ≦ 1), lithium nickel cobalt composite oxide (for example, Li x Ni 1-y Co y O2; 0 < x ≦ 1, 0 < y < 1), lithium manganese nickel composite oxide having a spinel structure (for example, Li x Mn 2-y Ni y O4; 0 < x ≦ 1, 0 < y < 2), lithium manganese cobalt composite oxide (for example, Li x Mn y Co 1-y O2; 0 < x ≦ 1, 0 < y < 1), lithium iron phosphate (for example, Li x FePO4; 0 < x ≦ 1), and lithium nickel cobalt manganese composite oxide (Li x Ni 1-y-z Co y Mn z O2; 0 < x ≦ 1, 0 < y < 1, 0 < z < 1, y+z < 1). When these compounds are used as the positive electrode active material, the positive electrode potential can be increased.

[0069] When a room-temperature molten salt is used as the electrolyte of the battery, lithium iron phosphate, Li xIt is preferable to use a positive electrode active material containing VPO4F (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, thus improving cycle life. Details of room-temperature molten salts will be described later.

[0070] The primary particle size of the positive electrode active material is preferably between 100 nm and 1 μm. Positive electrode active material with a primary particle size of 100 nm or more is easy to handle in industrial production. Positive electrode active material with a primary particle size of 1 μm or less allows for smooth diffusion of lithium ions within the solid.

[0071] The specific surface area of ​​the positive electrode active material is 0.1 m². 2 / g or more 10m 2 It is preferable that it is less than or equal to / g. 0.1m 2 A positive electrode active material with a specific surface area of ​​10m or more can adequately secure sites for Li ion intercalation and release. 2 Positive electrode active materials with a specific surface area of ​​less than / g are easy to handle in industrial production and can ensure good charge-discharge cycle performance.

[0072] A binder is added to fill the gaps between dispersed positive electrode active materials and to bond the positive electrode active materials to the positive electrode current collector. Examples of binders include polytetrafluoroethylene (PTFE), polyvinylidene fluoride (PVdF), fluororubber, polyacrylic acid compounds, imide compounds, carboxymethyl cellulose (CMC), and salts of CMC. One of these may be used as a binder, or two or more may be used in combination.

[0073] Conductive agents are added to enhance current collection performance and reduce contact resistance between the positive electrode active material and the positive electrode current collector. Examples of conductive agents include vapor-grown carbon fiber (VGCF), carbon black such as acetylene black, and carbonaceous materials such as graphite. One of these may be used as a conductive agent, or two or more may be used in combination. Conductive agents may also be omitted.

[0074] In the positive electrode active material-containing layer, it is preferable that the positive electrode active material and the binder are blended in proportions of 80% to 98% by mass and 2% to 20% by mass, respectively.

[0075] Sufficient electrode strength can be obtained by using a binder amount of 2% by mass or more. Furthermore, the binder can function as an insulator. Therefore, reducing the binder amount to 20% by mass or less reduces the amount of insulator contained in the electrode, thereby reducing internal resistance.

[0076] When a conductive agent is added, it is preferable that the positive electrode active material, binder, and conductive agent are blended in proportions of 77% to 95% by mass, 2% to 20% by mass, and 3% to 15% by mass, respectively.

[0077] The above-mentioned effects can be achieved by increasing the amount of conductive agent to 3% by mass or more. Furthermore, by reducing the amount of conductive agent to 15% by mass or less, the proportion of conductive agent in contact with the electrolyte can be reduced. This lower proportion reduces the decomposition of the electrolyte under high-temperature storage conditions.

[0078] The positive electrode current collector is preferably an aluminum foil, or an aluminum alloy foil containing one or more elements selected from Mg, Ti, Zn, Ni, Cr, Mn, Fe, Cu, and Si.

[0079] The thickness of the aluminum foil or aluminum alloy foil is preferably 5 μm or more and 20 μm or less, and more preferably 15 μm or less. The purity of the aluminum foil is preferably 99% by mass or more. The content of transition metals such as iron, copper, nickel, and chromium in the aluminum foil or aluminum alloy foil is preferably 1% by mass or less.

[0080] Furthermore, the positive electrode current collector may include portions on its surface where the positive electrode active material-containing layer is not formed. These portions can function as positive electrode current collector tabs.

[0081] Electrodes can be manufactured, for example, by the following method. First, an active material, a conductive agent, and a binder are suspended in a solvent to prepare a slurry. This slurry is applied to one or both sides of a current collector. Next, the applied slurry is dried to obtain a laminate of the active material-containing layer and the current collector. After that, this laminate is pressed. In this way, electrodes are manufactured. The materials are mixed to obtain a mixture. This mixture is then formed into pellets. These pellets are then placed on a current collector to obtain electrodes.

[0082] 2) Electrolyte As the electrolyte, for example, a liquid non-aqueous electrolyte or a gel-type non-aqueous electrolyte can be used. A liquid non-aqueous electrolyte is prepared by dissolving an electrolyte salt as a solute in an organic solvent. The concentration of the electrolyte salt is preferably 0.5 mol / L or more and 2.5 mol / L or less.

[0083] Examples of electrolyte salts include lithium salts such as lithium perchlorate (LiClO4), lithium hexafluoride phosphate (LiPF6), lithium tetrafluoroborate (LiBF4), lithium arsenide hexafluoride (LiAsF6), lithium trifluoromethanesulfonate (LiCF3SO3), and lithium bistrifluoromethylsulfonylimide (LiN(CF3SO2)2), as well as mixtures thereof. The electrolyte salt is preferably resistant to oxidation even at high potentials, with LiPF6 being the most preferred.

[0084] Examples of organic solvents include cyclic carbonates such as propylene carbonate (PC), ethylene carbonate (EC), and vinylene carbonate (VC); linear carbonates such as diethyl carbonate (DEC), dimethyl carbonate (DMC), and methyl ethyl carbonate (MEC); cyclic ethers such as tetrahydrofuran (THF), 2-methyl tetrahydrofuran (2MeTHF), and dioxolane (DOX); linear ethers such as dimethoxyethane (DME) and diethoxyethane (DEE); and γ-butyrolactone (GBL), acetonitrile (AN), and sulfolane (SL). These organic solvents can be used alone or as mixed solvents.

[0085] Gel-like non-aqueous electrolytes are prepared by compounding a liquid non-aqueous electrolyte with a polymer material. Examples of polymer materials include polyvinylidene fluoride (PVdF), polyacrylonitrile (PAN), polyethylene oxide (PEO), or mixtures thereof.

[0086] Alternatively, in addition to liquid nonaqueous electrolytes and gel-type nonaqueous electrolytes, room-temperature molten salts (ionic melts) containing lithium ions, polymer solid electrolytes, and inorganic solid electrolytes may be used as nonaqueous electrolytes.

[0087] Room temperature molten salts (ionic melts) refer to organic salts consisting of a combination of organic cations and anions that can exist as liquids at room temperature (15°C to 25°C). Room temperature molten salts include room temperature molten salts that exist as liquids on their own, room temperature molten salts that become liquid when mixed with an electrolyte salt, room temperature molten salts that become liquid when dissolved in an organic solvent, or mixtures thereof. Generally, the melting point of room temperature molten salts used in secondary batteries is 25°C or lower. Also, organic cations generally have a quaternary ammonium skeleton.

[0088] Polymeric solid electrolytes are prepared by dissolving an electrolyte salt in a polymer material and then solidifying it.

[0089] 3) Separator The separator is formed from a porous film containing, for example, polyethylene (PE), polypropylene (PP), cellulose, or polyvinylidene fluoride (PVdF), or from a synthetic resin nonwoven fabric. From a safety standpoint, it is preferable to use a porous film made of polyethylene or polypropylene. This is because these porous films can melt at a certain temperature and interrupt the electric current.

[0090] 4) Exterior components For example, the outer packaging material can be a container made of laminate film or a metal container.

[0091] The thickness of the laminating film is, for example, 0.5 mm or less, and preferably 0.2 mm or less.

[0092] As the laminate film, a multilayer film is used that includes multiple resin layers and a metal layer interposed between these resin layers. The resin layers include polymer materials such as polypropylene (PP), polyethylene (PE), nylon, and polyethylene terephthalate (PET). The metal layer is preferably made of aluminum foil or aluminum alloy foil for weight reduction. The laminate film can be molded into the shape of an exterior component by sealing it by heat fusion.

[0093] The thickness of the metal container wall is, for example, 1 mm or less, more preferably 0.5 mm or less, and even more preferably 0.2 mm or less.

[0094] Metal containers are made from, for example, aluminum or aluminum alloys. Aluminum alloys preferably contain elements such as magnesium, zinc, and silicon. If aluminum alloys contain transition metals such as iron, copper, nickel, and chromium, their content is preferably 100 ppm by mass or less.

[0095] The shape of the exterior components is not particularly limited. For example, the exterior components may be flat (thin), rectangular, cylindrical, coin-shaped, or button-shaped. The exterior components can be appropriately selected according to the battery dimensions and intended use.

[0096] 5) Negative terminal The negative electrode terminal can be formed from a material that is electrochemically stable at the Li absorption / release potential of the negative electrode active material described above, and is also conductive. Specifically, the material for the negative electrode terminal can be copper, nickel, stainless steel, or aluminum, or an aluminum alloy containing at least one element selected from the group consisting of Mg, Ti, Zn, Mn, Fe, Cu, and Si. It is preferable to use aluminum or an aluminum alloy as the material for the negative electrode terminal. It is preferable that the negative electrode terminal be made of the same material as the negative electrode current collector in order to reduce contact resistance with the negative electrode current collector.

[0097] 6) Positive terminal The positive electrode terminal can be formed from a material that is electrically stable and conductive in a potential range of 3V to 4.5V (vs. Li / Li+) relative to the oxidation-reduction potential of lithium. Examples of positive electrode terminal materials include aluminum, or an aluminum alloy containing at least one element selected from the group consisting of Mg, Ti, Zn, Mn, Fe, Cu, and Si. It is preferable that the positive electrode terminal be formed from the same material as the positive electrode current collector to reduce contact resistance with the positive electrode current collector.

[0098] Next, a secondary battery according to the second embodiment will be described in more detail with reference to the drawings.

[0099] The secondary battery according to the second embodiment includes the electrodes according to the first embodiment. Therefore, the secondary battery according to the second embodiment has excellent high-temperature cycling performance.

[0100] (Third embodiment) A third embodiment provides a battery pack. The battery pack according to the third embodiment comprises a plurality of secondary batteries according to the second embodiment. In the battery pack according to the third embodiment, each individual cell may be arranged in series or parallel connections, or a combination of series and parallel connections.

[0101] Figure 7 is a schematic perspective view showing an example of a battery pack according to the third embodiment. The battery pack 200 shown in Figure 7 comprises five single cells 100a to 100e, four busbars 21, a positive electrode lead 22, and a negative electrode lead 23. Each of the five single cells 100a to 100e is a secondary battery according to the second embodiment.

[0102] The busbar 21 connects, for example, the negative terminal 6 of one cell 100a to the positive terminal 7 of the adjacent cell 100b. In this way, the five cells 100 are connected in series by four busbars 21. That is, the battery pack 200 in Figure 7 is a battery pack with five cells in series. Although not illustrated, in a battery pack containing multiple cells that are electrically connected in parallel, the multiple cells can be electrically connected, for example, by connecting multiple negative terminals to each other and multiple positive terminals to each other by busbars.

[0103] The positive terminal 7 of at least one of the five single cells 100a to 100e is electrically connected to the positive lead 22 for external connection. In addition, the negative terminal 6 of at least one of the five single cells 100a to 100e is electrically connected to the negative lead 23 for external connection.

[0104] The battery pack according to the third embodiment comprises the secondary battery according to the second embodiment. Therefore, the battery pack according to the third embodiment has excellent high-temperature cycle performance.

[0105] (Fourth embodiment) According to the fourth embodiment, a battery pack is provided. This battery pack comprises a battery pack according to the third embodiment. This battery pack may also comprise a single secondary battery according to the second embodiment instead of the battery pack according to the third embodiment.

[0106] Figure 8 is an exploded perspective view schematically showing an example of a battery pack according to the fourth embodiment. Figure 9 is a block diagram showing an example of the electrical circuit of the battery pack shown in Figure 8. The battery pack 300 shown in Figures 8 and 9 comprises a housing container 31, a lid 32, a protective sheet 33, a battery pack 200, a printed circuit board 34, wiring 35, and an insulating plate (not shown).

[0107] The container 31 shown in Figure 8 is a rectangular-bottomed rectangular container. The container 31 is configured to accommodate a protective sheet 33, a battery pack 200, a printed circuit board 34, and wiring 35. The lid 32 has a rectangular shape. The lid 32 covers the container 31, thereby housing the battery pack 200 and the other components. The container 31 and the lid 32 are provided with openings or connection terminals for connecting to external devices, etc., although these are not shown in the figures.

[0108] The battery pack 200 comprises multiple individual cells 100, a positive electrode lead 22, a negative electrode lead 23, and an adhesive tape 24.

[0109] At least one of the multiple single cells 100 is a secondary battery according to the second embodiment. Each of the multiple single cells 100 is electrically connected in series as shown in Figure 9. The multiple single cells 100 may also be electrically connected in parallel, or they may be connected in a combination of series and parallel connections. When the multiple single cells 100 are connected in parallel, the battery capacity increases compared to when they are connected in series.

[0110] The adhesive tape 24 fastens multiple single cells 100 together. Alternatively, heat-shrinkable tape may be used to secure the multiple single cells 100 instead of the adhesive tape 24. In this case, protective sheets 33 are placed on both sides of the battery pack 200, the heat-shrinkable tape is wrapped around it, and then the heat-shrinkable tape is heat-shrinked to bundle the multiple single cells 100 together.

[0111] One end of the positive lead 22 is connected to the battery pack 200. One end of the positive lead 22 is electrically connected to the positive terminal of one or more single cells 100. One end of the negative lead 23 is connected to the battery pack 200. One end of the negative lead 23 is electrically connected to the negative terminal of one or more single cells 100.

[0112] The printed circuit board 34 includes a positive terminal connector 342, a negative terminal connector 343, a thermistor 345, a protection circuit 346, wiring 342a and 343a, an external terminal 350 for energizing, a positive side wiring (positive wiring) 348a, and a negative side wiring (negative wiring) 348b. One main surface of the printed circuit board 34 faces one side of the battery pack 200. An insulating plate (not shown) is interposed between the printed circuit board 34 and the battery pack 200.

[0113] The other end 22a of the positive lead 22 is electrically connected to the positive connector 342. The other end 23a of the negative lead 23 is electrically connected to the negative connector 343.

[0114] The thermistor 345 is fixed to one main surface of the printed circuit board 34. The thermistor 345 detects the temperature of each cell 100 and transmits the detection signal to the protection circuit 346. The external power supply terminal 350 is fixed to the other main surface of the printed circuit board 34. The external power supply terminal 350 is electrically connected to equipment located outside the battery pack 300. The external power supply terminal 350 includes a positive terminal 352 and a negative terminal 353. The external power supply terminal 350 is for outputting current from the secondary battery to the outside and / or inputting current from an 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 power supply terminal. Also, when charging the battery pack, the charging current (including regenerative energy from power sources such as automobiles) is supplied to the battery pack through the external power supply terminal.

[0115] The protection circuit 346 is fixed to the other main surface of the printed circuit board 34. The protection circuit 346 is connected to the positive terminal 352 via the positive wiring 348a. The protection circuit 346 is connected to the negative terminal 353 via the negative wiring 348b. The protection circuit 346 is also electrically connected to the positive connector 342 via wiring 342a. The protection circuit 346 is also electrically connected to the negative connector 343 via wiring 343a. Furthermore, the protection circuit 346 is electrically connected to each of the multiple single cells 100 via wiring 35. The protective sheet 33 is placed on both inner surfaces in the long direction of the housing container 31 and on the inner surface in the short direction facing the printed circuit board 34 via the battery pack 200. The protective sheet 33 is made of, for example, resin or rubber.

[0116] The protection circuit 346 controls the charging and discharging of the multiple single cells 100. The protection circuit 346 also disconnects the electrical connection between the protection circuit 346 and the external terminals 350 (positive terminal 352, negative terminal 353) for supplying power to external devices, based on detection signals transmitted from the thermistor 345 or from individual single cells 100 or the battery pack 200. The protection circuit 346 may also be a circuit included in a device that uses the battery pack as a power source (e.g., electronic equipment, automobiles, etc.) and used as the protection circuit for the battery pack.

[0117] An example of a detection signal transmitted from the thermistor 345 is a signal indicating that the temperature of a single cell 100 is above a predetermined temperature. An example of a detection signal transmitted from an individual single cell 100 or a battery pack 200 is a signal indicating that overcharging, over-discharging, or overcurrent has been detected in a single cell 100. When detecting overcharging, etc., in an individual single cell 100, the battery voltage may be detected, or the positive electrode potential or negative electrode potential may be detected. In the latter case, a lithium electrode to be used as a reference electrode is inserted into each individual single cell 100.

[0118] Furthermore, the protection circuit 346 may be a circuit included in a device that uses the battery pack 300 as a power source (for example, an electronic device, an automobile, etc.).

[0119] Furthermore, as described above, the battery pack 300 is equipped with an external terminal 350 for power supply. Therefore, the battery pack 300 can output current from the battery pack 200 to an external device and input current from an external device to the battery pack 200 via the external terminal 350. In other words, when the battery pack 300 is used as a power source, current from the battery pack 200 is supplied to the external device through the external terminal 350. Also, when charging the battery pack 300, charging current from an external device is supplied to the battery pack 300 through the external terminal 350. When this battery pack 300 is used as an on-board battery, the regenerative energy of the vehicle's power can be used as the charging current from the external device.

[0120] The battery pack 300 may comprise multiple battery packs 200. In this case, the multiple battery packs 200 may be connected in series, in parallel, or in a combination of series and parallel connections. The printed circuit board 34 and wiring 35 may also be omitted. In this case, the positive lead 22 and the negative lead 23 may be used as the positive and negative terminals of the external terminals for energization, respectively.

[0121] Such battery packs are used in applications where excellent cycle performance is required, for example, when drawing high currents in high-temperature environments. Specifically, these battery packs are used as stationary batteries and on-board batteries for various vehicles. These battery packs are particularly suitable for use as on-board batteries.

[0122] The battery pack according to the fourth embodiment comprises a secondary battery according to the second embodiment or a battery pack according to the third embodiment. Therefore, the battery pack according to the fourth embodiment has excellent high-temperature cycle performance.

[0123] (Fifth embodiment) According to the fifth embodiment, a vehicle is provided, which is equipped with a battery pack according to the fourth embodiment. Examples of vehicles according to the fifth embodiment include, for example, two-wheeled or four-wheeled hybrid electric vehicles, two-wheeled or four-wheeled electric vehicles, electric assist bicycles, and railway vehicles.

[0124] Figure 10 is a schematic partial transparency diagram showing an example of a vehicle according to the embodiment. The vehicle 400 shown in Figure 10 includes a vehicle body 40 and a battery pack 300 according to the fourth embodiment. In the example shown in Figure 10, the vehicle 400 is a four-wheeled automobile. This vehicle 400 may be equipped with multiple battery packs 300. In this case, the batteries (e.g., single cells or battery packs) included in the battery pack 300 may be connected in series, in parallel, or a combination of series and parallel connections.

[0125] Figure 10 illustrates an example in which the battery pack 300 is mounted in the engine compartment located at the front of the vehicle body 40, but the mounting location of the battery pack 300 is not particularly limited. For example, when the battery pack is installed in a car, it can be mounted in the engine compartment of the vehicle body 40, at the rear of the vehicle, or under the seats.

[0126] This battery pack 300 can be used as a power source for the vehicle 400. Furthermore, this battery pack 300 can recover regenerative energy from the vehicle 400's power.

[0127] The vehicle according to the fifth embodiment may be equipped with a plurality of battery packs 300. In this case, the batteries contained in each battery pack 300 may be electrically connected in series, electrically connected in parallel, or electrically connected in a combination of series and parallel connections. For example, if each battery pack 300 contains a battery pack, the battery packs may be electrically connected in series, electrically connected in parallel, or electrically connected in a combination of series and parallel connections. Alternatively, if each battery pack 300 contains a single battery, the batteries may be electrically connected in series, electrically connected in parallel, or electrically connected in a combination of series and parallel connections.

[0128] Figure 11 is a schematic diagram showing an example of a control system for the electrical system in a vehicle according to an embodiment. The vehicle 400 shown in Figure 11 is an electric vehicle. The vehicle 400 comprises a vehicle body 40, a vehicle power supply 41, a vehicle ECU (ECU: Electric Control Unit) 42 which is a higher-level control device for the vehicle power supply 41, an external terminal (terminal for connecting to an external power supply) 43, an inverter 44, and a drive motor 45. The vehicle power supply 41 is mounted in the vehicle 400, for example, in the engine compartment, at the rear of the vehicle body, or under the seats. Note that the mounting location of the vehicle power supply 41 in the vehicle 400 shown in Figure 11 is schematic.

[0129] The vehicle power supply 41 comprises a plurality (for example, three) of battery packs 300a, 300b, and 300c, a battery management unit (BMU) 411, and a communication bus 412.

[0130] Battery pack 300a comprises a battery pack 200a and a battery pack monitoring device 301a (e.g., VTM: Voltage Temperature Monitoring). Battery pack 300b comprises a battery pack 200b and a battery pack monitoring device 301b. Battery pack 300c comprises a battery pack 200c and a battery pack monitoring device 301c. Battery packs 300a to 300c are similar to the aforementioned battery pack 300, and battery packs 200a to 200c are similar to the aforementioned battery pack 200. Battery packs 200a to 200c are electrically connected in series. Battery packs 300a, 300b, and 300c can each be independently removed and replaced with another battery pack 300.

[0131] Each of the battery packs 200a to 200c comprises multiple single cells connected in series. At least one of the multiple single cells is a secondary battery according to the second embodiment. Each of the battery packs 200a to 200c is charged and discharged through a positive terminal 413 and a negative terminal 414.

[0132] The battery management device 411 communicates with the battery pack monitoring devices 301a to 301c and collects information such as voltage and temperature for each of the single cells 100 included in the battery packs 200a to 200c included in the vehicle power supply 41. In this way, the battery management device 411 collects information related to the maintenance of the vehicle power supply 41.

[0133] The battery management device 411 and the battery pack monitoring devices 301a to 301c are connected via a communication bus 412. On the communication bus 412, one set of communication lines is shared by multiple nodes (the battery management device 411 and one or more battery pack monitoring devices 301a to 301c). The communication bus 412 is a communication bus configured, for example, based on the CAN (Control Area Network) standard.

[0134] The battery pack monitoring devices 301a to 301c measure the voltage and temperature of each individual cell constituting the battery packs 200a to 200c based on commands communicated from the battery management device 411. However, temperature can be measured at only a few locations per battery pack, and it is not necessary to measure the temperature of all individual cells.

[0135] The vehicle power supply 41 may also have an electromagnetic contactor (for example, a switch device 415 shown in Figure 11) that switches the presence or absence of an electrical connection between the positive terminal 413 and the negative terminal 414. The switch device 415 includes a pre-charge switch (not shown) that turns on when charging is performed on the battery packs 200a to 200c, and a main switch (not shown) that turns on when the output from the battery packs 200a to 200c is supplied to the load. Each of the pre-charge switch and the main switch includes a relay circuit (not shown) that is switched on or off by a signal supplied to a coil located near the switch element. Electromagnetic contactors such as the switch device 415 are controlled based on a control signal from the battery management device 411 or the vehicle ECU 42 that controls the operation of the entire vehicle 400.

[0136] The inverter 44 converts the input DC voltage into a high voltage of three-phase alternating current (AC) for motor drive. The three-phase output terminals of the inverter 44 are connected to the three-phase input terminals of the drive motor 45. The inverter 44 is controlled based on control signals from the battery management device 411 or the vehicle ECU 42 for controlling the operation of the entire vehicle. By controlling the inverter 44, the output voltage from the inverter 44 is adjusted.

[0137] The drive motor 45 rotates using power supplied from the inverter 44. The driving force generated by the rotation of the drive motor 45 is transmitted to the axle and drive wheels W, for example, via a differential gear unit.

[0138] In the vehicle according to the fifth embodiment, the battery pack, for example, recovers regenerative energy from the vehicle's power. The vehicle may also include a mechanism (Regenerator) that converts the vehicle's kinetic energy into regenerative energy. The regenerative braking mechanism rotates the drive motor 45 when the vehicle 400 is braked, converting the kinetic energy into regenerative energy as electrical energy. The regenerative energy recovered by the regenerative braking mechanism is input to the inverter 44 and converted into a DC current. The converted DC current is input to the vehicle power supply 41.

[0139] One terminal of connection line L1 is connected to the negative terminal 414 of the vehicle power supply 41. The other terminal of connection line L1 is connected to the negative input terminal 417 of the inverter 44. A current detection unit (current detection circuit) 416 within the battery management device 411 is provided on connection line L1 between the negative terminal 414 and the negative input terminal 417.

[0140] One terminal of connection line L2 is connected to the positive terminal 413 of the vehicle power supply 41. The other terminal of connection line L2 is connected to the positive input terminal 418 of the inverter 44. A switch device 415 is provided between the positive terminal 413 and the positive input terminal 418 of connection line L2.

[0141] External terminal 43 is connected to battery management device 411. External terminal 43 can be connected to an external power supply, for example.

[0142] The vehicle ECU 42, in response to operational inputs from the driver and others, coordinates control of the vehicle power supply 41, switch device 415, inverter 44, etc., together with other management and control devices, including the battery management device 411. Through the coordinated control of the vehicle ECU 42, etc., the output of power from the vehicle power supply 41 and the charging of the vehicle power supply 41 are controlled, and the entire vehicle 400 is managed. Data related to the maintenance of the vehicle power supply 41, such as the remaining capacity of the vehicle power supply 41, is transferred between the battery management device 411 and the vehicle ECU 42 via a communication line.

[0143] The vehicle according to the fifth embodiment is equipped with the battery pack according to the fourth embodiment. Therefore, the vehicle according to the fifth embodiment has superior driving range and driving performance. [Examples]

[0144] (Example 1) First, carbon fibers, a first binder, and pure water were mixed and stirred using a planetary mixer. The carbon fibers used were carbon nanotubes with an average diameter S1 of 0.1 μm and an average length L1 of 20 μm, measured perpendicular to the length. These carbon fibers will be referred to as the first carbon fibers. Active material and granular carbon were added to the mixture of carbon fibers, the first binder, and pure water and stirred using a planetary mixer and a bead mill. During stirring, the planetary mixer was set to a stirring speed of 40 rpm and a stirring time of 60 minutes. The bead mill flow rate was 30 mL / min and the rotation speed was 2000 rpm. Niobium titanium composite oxide (Nb2TiO7) particles with an average particle size of 1 μm were used as the active material. These active material will be referred to as NTO. Acetylene black with an average particle size of 0.2 μm was used as the granular carbon. These granular carbon will be referred to as AB. Subsequently, a second binder was added and the mixture was stirred using a planetary mixer to prepare a dispersed slurry. During stirring, the stirring speed was set to 50 rpm and the stirring time to 30 minutes. Styrene-butadiene rubber was used as the second binder. Hereafter, this binder will be referred to as SBR.

[0145] In the dispersed slurry, the amounts of carbon fibers, granular carbon, first binder, and second binder per 100 parts by mass of active material were 2 parts by mass, 2 parts by mass, 1 part by mass, and 1 part by mass, respectively.

[0146] Next, the dispersed slurry was applied to one or both sides of the current collector, and the coating was dried to obtain a laminate of the active material-containing layer and the current collector.

[0147] A 12 μm thick aluminum alloy foil was used as the current collector. This laminate was subjected to a press treatment to obtain electrodes. During the press treatment, a roll press was used to adjust the pressure to achieve the desired film density. In this embodiment, the density of the active material-containing layer was 2.6 g / cm³. 3 It was pressed in that manner.

[0148] (Example 2) The electrodes were fabricated in the same manner as in Example 1, except that the pressing conditions were changed. The density of the active material-containing layer was 2.7 g / cm³. 3 It was pressed in that manner.

[0149] (Example 3) The electrodes were fabricated in the same manner as in Example 1, except that the pressing conditions were changed. The density of the active material-containing layer was 2.55 g / cm³. 3 It was pressed in that manner.

[0150] (Example 4) The electrodes were fabricated in the same manner as in Example 1, except that the rotation speed of the bead mill and the pressing conditions were changed. The rotation speed of the bead mill was set to 700 rpm. The density of the active material-containing layer was 2.75 g / cm³. 3 It was pressed in that manner.

[0151] (Example 5) The electrodes were fabricated in the same manner as in Example 1, except that the rotation speed of the bead mill and the pressing conditions were changed. The rotation speed of the bead mill was set to 1200 rpm. The density of the active material-containing layer was 2.55 g / cm³. 3 It was pressed in that manner.

[0152] (Example 6) The electrodes were prepared in the same manner as in Example 1, except that the amount of granular carbon AB was changed and the rotation speed of the bead mill was changed. The rotation speed of the bead mill was set to 700 rpm. In the dispersion slurry, the amounts of carbon fiber, granular carbon, first binder, and second binder per 100 parts by mass of active material were 2 parts by mass, 4 parts by mass, 1 part by mass, and 1 part by mass, respectively.

[0153] (Example 7) The electrodes were fabricated in the same manner as in Example 1, except that the amount of granular carbon AB was changed, the rotation speed of the bead mill was changed, and the pressing conditions were changed. The rotation speed of the bead mill was set to 1200 rpm. The density of the active material-containing layer was 2.75 g / cm³. 3 The material was pressed in this manner. In the dispersed slurry, the amounts of carbon fibers, granular carbon, first binder, and second binder per 100 parts by mass of active material were 2 parts by mass, 4 parts by mass, 1 part by mass, and 1 part by mass, respectively.

[0154] (Example 8) The electrodes were fabricated in the same manner as in Example 1, except that the type of carbon fiber and the pressing conditions were changed. As the carbon fiber, carbon nanotubes were used, with an average thickness S1 of 0.005 μm and an average length L1 of 50 μm in the cross-sectional diameter perpendicular to the length direction. Hereafter, this carbon fiber will be referred to as the second carbon fiber. The density of the active material-containing layer was 2.75 g / cm³. 3 It was pressed in that manner.

[0155] (Example 9) The electrodes were fabricated in the same manner as in Example 8, except that the pressing conditions were changed. The density of the active material-containing layer was 2.8 g / cm³. 3 It was pressed in that manner.

[0156] (Example 10) The electrodes were fabricated in the same manner as in Example 8, except that the rotation speed of the bead mill and the pressing conditions were changed. The rotation speed of the bead mill was set to 1200 rpm. The density of the active material-containing layer was 2.7 g / cm³. 3 It was pressed in that manner.

[0157] (Example 11) The electrodes were prepared in the same manner as in Example 8, except that the amount of granular carbon AB was changed and the pressing conditions were changed. The density of the active material-containing layer was 2.6 g / cm³. 3The material was pressed in this manner. In the dispersed slurry, the amounts of carbon fibers, granular carbon, first binder, and second binder per 100 parts by mass of active material were 2 parts by mass, 1 part by mass, 1 part by mass, and 1 part by mass, respectively.

[0158] (Example 12) The electrodes were fabricated in the same manner as in Example 1, except that the type of active material was changed, the amount of granular carbon AB was changed, the rotation speed of the bead mill was changed, and the pressing conditions were changed. The active material used was a sodium-containing niobium-titanium composite compound (Li2Na) with an average particle size of 5 μm. 1.5 Ti 5.5 Nb 0.5 O 14 The particle used was ). Hereafter, this active material will be referred to as LNT. The rotation speed of the bead mill was set to 700 rpm. The density of the active material-containing layer was 2.5 g / cm³. 3 The material was pressed in this manner. In the dispersed slurry, the amounts of carbon fibers, granular carbon, first binder, and second binder per 100 parts by mass of active material were 2 parts by mass, 1 part by mass, 1 part by mass, and 1 part by mass, respectively.

[0159] (Example 13) The electrodes were fabricated in the same manner as in Example 1, except that the type of active material, the type of carbon fiber, the rotation speed of the bead mill, and the pressing conditions were changed. LNT was used as the active material. Secondary carbon fiber was used as the carbon fiber. The rotation speed of the bead mill was set to 1200 rpm. The density of the active material-containing layer was 2.7 g / cm³. 3 It was pressed in that manner.

[0160] (Example 14) The electrodes were fabricated in the same manner as in Example 1, except that the type of active material was changed, the amount of granular carbon AB was changed, the rotation speed of the bead mill was changed, and the pressing conditions were changed. The active material was a titanium composite oxide (Li4Ti5O) with an average particle size of 3 μm. 12The active material used was LTO. The rotation speed of the bead mill was set to 700 rpm. The density of the active material-containing layer was 2.3 g / cm³. 3 The material was pressed in this manner. In the dispersed slurry, the amounts of carbon fibers, granular carbon, first binder, and second binder per 100 parts by mass of active material were 2 parts by mass, 4 parts by mass, 1 part by mass, and 1 part by mass, respectively.

[0161] (Comparative Example 1) The electrodes were prepared in the same manner as in Example 1, except that the amount of granular carbon AB was changed and the pressing conditions were changed. The density of the active material-containing layer was 2.9 g / cm³. 3 The material was pressed in this manner. In the dispersed slurry, the amounts of carbon fibers, granular carbon, first binder, and second binder per 100 parts by mass of active material were 2 parts by mass, 4 parts by mass, 1 part by mass, and 1 part by mass, respectively.

[0162] (Comparative Example 2) The electrodes were fabricated in the same manner as in Example 1, except that the amount of carbon fiber was set to 0, the rotation speed of the bead mill was changed, and the pressing conditions were changed. The rotation speed of the bead mill was set to 2200 rpm. The density of the active material-containing layer was 2.8 g / cm³. 3 The material was pressed in this manner. In the dispersed slurry, the amounts of carbon fibers, granular carbon, first binder, and second binder per 100 parts by mass of active material were 0 parts by mass, 2 parts by mass, 1 part by mass, and 1 part by mass, respectively.

[0163] (Comparative Example 3) The electrodes were fabricated in the same manner as in Example 1, except that the type of carbon fiber was changed, the amount of granular carbon AB was changed, the rotation speed of the bead mill was changed, and the pressing conditions were changed. Secondary carbon fiber was used as the carbon fiber. The rotation speed of the bead mill was set to 2200 rpm. The density of the active material-containing layer was 2.8 g / cm³. 3The material was pressed in this manner. In the dispersed slurry, the amounts of carbon fibers, granular carbon, first binder, and second binder per 100 parts by mass of active material were 2 parts by mass, 4 parts by mass, 1 part by mass, and 1 part by mass, respectively.

[0164] (Comparative Example 4) The electrodes were fabricated in the same manner as in Example 1, except that the type of active material and the pressing conditions were changed. LNT was used as the active material. The density of the active material-containing layer was 2.7 g / cm³. 3 It was pressed in that manner.

[0165] (Comparative Example 5) The electrodes were fabricated in the same manner as in Example 1, except that the type of active material, the type of carbon fiber, the amount of granular carbon AB added, and the pressing conditions were changed. LTO was used as the active material. Secondary carbon fibers were used as the carbon fibers. The density of the active material-containing layer was 2.8 g / cm³. 3 The material was pressed in this manner. In the dispersed slurry, the amounts of carbon fibers, granular carbon, first binder, and second binder per 100 parts by mass of active material were 2 parts by mass, 1 part by mass, 1 part by mass, and 1 part by mass, respectively.

[0166] (Measurement of logarithmic differential pore volume distribution curve) Using the method described above, the logarithmic differential pore volume distribution curves of the electrodes prepared in Examples 1-14 and Comparative Examples 1-5 were measured.

[0167] (Cycle performance evaluation) Cycle performance was evaluated using a three-electrode glass cell. The battery was charged at a current density of 1C at 70°C until the State of Charge (SOC) reached 100%. Then, it was discharged at a current density of 1C until the SOC reached 0%, and the discharge capacity was measured. This charge-discharge cycle was considered one cycle, and this process was repeated until the discharge capacity retention rate relative to the initial discharge capacity reached 80%. The results are shown in Table 3.

[0168] The methods for manufacturing electrodes for Examples 1-14 and Comparative Examples 1-5 are summarized in Tables 1 and 2 below.

[0169] [Table 1]

[0170] In Table 1, the column labeled "Composition" under the heading "Active Material" lists the composition of the active material. The columns labeled "Type," "Thickness S1," "Length L1," "L1 / S1," and "Amount (parts by mass)" under the heading "Carbon Fiber" list the type of carbon fiber, average thickness S, average length L, the ratio of average length L to average thickness S, and the amount of carbon fiber per 100 parts by mass of active material, respectively. The columns labeled "Type" and "Amount" under the heading "Granular Carbon" list the type of granular carbon and the amount of granular carbon per 100 parts by mass of active material, respectively.

[0171] [Table 2]

[0172] In Table 2, the column labeled "Rotation Speed" shows the rotation speed of the bead mill when the carbon fibers, primary binder, pure water, active material, and granular carbon were stirred. The column labeled "Density" shows the density of the active material-containing layer when the laminate of the active material-containing layer and current collector was pressed using a roll press machine.

[0173] The performance of the electrodes used in Examples 1-14 and Comparative Examples 1-5, and the secondary batteries using these electrodes, are summarized in Table 3 and Figure 12 below.

[0174] [Table 3]

[0175] In Table 3, under the heading "Electrode," the columns labeled "Pore Surface Area TA," "Peak Pore Diameter PD," "Median Diameter MD," "MD-PD," and "Full Width at Half Max" show the total pore surface area TA, peak pore diameter PD, median diameter MD, median diameter MD-PD (MD minus peak pore diameter PD), and peak full width at half maximum, respectively, for electrodes obtained by the mercury intrusion method. In addition, under the heading "Battery," the column labeled "Cycle Count Ratio" shows the ratio of the number of cycles of the secondary battery in each example or comparative example to the number of cycles of Example 1. Here, the number of cycles is the number of cycles at which the discharge capacity retention rate relative to the discharge capacity of the first cycle reaches 80% under conditions of 70°C.

[0176] Figure 12 is a graph showing the relationship between peak pore diameter PD and total pore volume TA. Plots for Examples 1 to 15 are shown as black circles, and plots for Comparative Examples 1 to 5 are shown as white circles. In addition, dotted lines corresponding to PD=0.1, TA=-17×PD+10.6 (in equation (1), a=-17, b=10.6), TA=-17×PD+8 (in equation (1), a=-17, b=8), and TA=-17×PD+7 (in equation (1), a=-17, b=7) are drawn in the figure.

[0177] As is clear from the comparison between Examples 1-14 and Comparative Examples 1-5, electrodes with a peak pore size PD greater than 0.1 μm and plotted within the range of 0.3 μm or less exhibit superior high-temperature cycling performance compared to electrodes outside this range. Furthermore, many electrodes with plots within the range enclosed by TA=-17×PD+10.6, TA=-17×PD+7, PD=0.1, and PD=0.3 (the light and dark hatched areas in Figure 12) have higher high-temperature cycling performance compared to electrodes outside this range. Moreover, many electrodes with plots within the range enclosed by TA=-17×PD+10.6, TA=-17×PD+8, PD=0.1, and PD=0.3 (the dark hatched areas in Figure 12) have even higher high-temperature cycling performance compared to electrodes outside this range.

[0178] The electrode according to at least one embodiment described above comprises an active material and an active material-containing layer containing carbon fibers. In the logarithmic differential pore volume distribution curve of the active material-containing layer obtained by the mercury intrusion method, the pore diameter PD of the peak indicating the maximum logarithmic differential pore volume is greater than 0.1 μm and less than or equal to 0.3 μm, and the full width at half maximum of the peak is less than or equal to 0.06 μm. Using this electrode, a secondary battery with excellent high-temperature cycle performance can be realized.

[0179] While several embodiments of the present invention have been described, these embodiments are presented as examples only and are not intended to limit the scope of the invention. These novel embodiments can be carried out in a variety of other forms, and various omissions, substitutions, and modifications can be made without departing from the spirit of the invention. These embodiments and their variations are included in the scope and spirit of the invention, as well as in the claims of the invention and its equivalents. [Explanation of Symbols]

[0180] 1…Electrode group, 2…Outer casing, 3…Negative electrode, 3a…Negative electrode current collector, 3b…Negative electrode active material containing layer, 3c…Negative electrode current collector tab, 4…Separator, 5…Positive electrode, 5a…Positive electrode current collector, 5b…Positive electrode active material, 6…Negative electrode terminal, 7…Positive electrode terminal, 21…Bus bar, 22…Positive electrode side lead, 22a…Other end, 23…Negative electrode side lead, 23a…Other end, 24…Adhesive tape, 31…Housing container, 3 2...Lid, 33...Protective sheet, 34...Printed circuit board, 35...Wiring, 40...Vehicle body, 41...Vehicle power supply, 42...Electrical control device, 43...External terminals, 44...Inverter, 45...Drive motor, 50...Active material particles, 51...Carbon fiber, 52...Granular carbon, 100...Secondary battery, 200...Battery pack, 200a...Battery pack, 200b...Battery pack, 200c...Battery pack, 3 00...Battery pack, 300a...Battery pack, 300b...Battery pack, 300c...Battery pack, 301a...Battery pack monitoring device, 301b...Battery pack monitoring device, 301c...Battery pack monitoring device, 342...Positive side connector, 343...Negative side connector, 345...Thermistor, 344...Protection circuit, 342a...Wiring, 343a...Wiring, 350...External terminal for energization, 352...Positive side terminal, 353...Negative side terminal, 348a...Positive side wiring, 348b...Negative side wiring, 400...Vehicle, 411...Battery management device, 412...Communication bus, 413...Positive terminal, 414...Negative terminal, 415...Switching device, 416...Current detection unit, 417...Negative input terminal, 418...Positive input terminal, L1...Connection line, L2...Connection line, W...Drive wheel.

Claims

1. The active material includes a titanium-containing composite oxide and an active material-containing layer containing carbon fibers. The active material-containing layer shows a peak in the logarithmic differential pore volume distribution curve obtained by the mercury intrusion method, indicating the maximum logarithmic differential pore volume. The pore size PD of the aforementioned peak is greater than 0.1 μm and less than or equal to 0.3 μm. The total pore surface area TA of the active material-containing layer and the peak pore diameter PD obtained by the mercury intrusion method described above. The relationship is expressed by the following equation (1), The aforementioned titanium-containing composite oxide is A ｘ TiM ｙ Nb ２－ｙ O ７±ｚ (0 ≤ x ≤ 5, 0 ≤ y ≤ 0.5, -0.3 ≤ z ≤ 0.3, M is at least one metallic element other than Ti and Nb, A is at least one of Li and Na), Li ２＋ａ No ２ Today ６ O １４ (0≦a≦6) Li ｘ TO ２ (0≦+≦1), Li ２＋ａ M(I) ２－ｂ Ti ６－ｃ M(II)dO １４＋σ (M(I) is at least one element selected from the group consisting of Sr, Ba, Ca, Mg, Na, Cs, Rb, and K; M(II) is at least one element selected from the group consisting of Zr, Sn, V, Nb, Ta, Mo, W, Y, Fe, Co, Cr, Mn, Ni, and Al; 0 ≤ a ≤ 6, 0 ≤ b < 2, 0 ≤ c < 6, 0 ≤ d < 6, -0.5 ≤ σ ≤ 0.5) Li ｘ Ti １－ｙ M1 ｙ Nb ２－ｚ M2 ｚ O ７＋δ (M1 is at least one element selected from the group consisting of Zr, Si, and Sn; M2 is at least one element selected from the group consisting of V, Ta, and Bi; 0 ≤ x ≤ 5, 0 ≤ y < 1, 0 ≤ z < 2, -0.3 ≤ δ ≤ 0.3), and, Li ｘ Ti １－ｙ M3 ｙ＋ｚ Nb ２－ｚＯ７－δ (M3 is at least one element selected from Mg, Fe, Ni, Co, W, Ta, and Mo, 0 ≤ x < 5, 0 ≤ y < 1, 0 ≤ z < 2, -0.3 ≤ δ ≤ 0.3) At least one compound represented by a general formula selected from the group consisting of, An electrode in a battery using at least one of a non-aqueous electrolyte or a non-aqueous electrolyte solution as the electrolyte. TA=a×PD+b (1) Here, in the equation, a = -17 and b = 7 ≤ b ≤ 10.

6.

2. The active material includes a titanium-containing composite oxide and an active material-containing layer containing carbon fibers. The active material-containing layer, in the logarithmic differential pore volume distribution curve obtained by the mercury intrusion method, shows the maximum logarithmic differential It shows a peak indicating pore volume, The pore size PD of the aforementioned peak is greater than 0.1 μm and less than or equal to 0.3 μm. The aforementioned titanium-containing composite oxide is A ｘ TiM ｙ Nb ２－ｙ O ７±ｚ (0 ≤ x ≤ 5, 0 ≤ y ≤ 0.5, -0.3 ≤ z ≤ 0.3, M is at least one metallic element other than Ti and Nb, A is at least one of Li and Na), Li ２＋ａ No ２ Today ６ O １４ (0≦a≦6) Li ｘ TO ２ (0≦+≦1), Li ２＋ａ M(I) ２－ｂ Ti ６－ｃ M(II)dO １４＋σ (M(I) is at least one element selected from the group consisting of Sr, Ba, Ca, Mg, Na, Cs, Rb, and K; M(II) is at least one element selected from the group consisting of Zr, Sn, V, Nb, Ta, Mo, W, Y, Fe, Co, Cr, Mn, Ni, and Al; 0 ≤ a ≤ 6, 0 ≤ b < 2, 0 ≤ c < 6, 0 ≤ d < 6, -0.5 ≤ σ ≤ 0.5) Li ｘ Ti １－ｙ M1 ｙ Nb ２－ｚ M2 ｚ O ７＋δ (M1 is at least one element selected from the group consisting of Zr, Si, and Sn; M2 is at least one element selected from the group consisting of V, Ta, and Bi; 0 ≤ x ≤ 5, 0 ≤ y < 1, 0 ≤ z < 2, -0.3 ≤ δ ≤ 0.3), and, Li ｘ Ti １－ｙ M3 ｙ＋ｚ Nb ２－ｚＯ７－δ (M3 is at least one element selected from Mg, Fe, Ni, Co, W, Ta, and Mo, 0 ≤ x < 5, 0 ≤ y < 1, 0 ≤ z < 2, -0.3 ≤ δ ≤ 0.3) At least one compound represented by a general formula selected from the group consisting of, From the median diameter MD of the active material-containing layer by the mercury intrusion method, the pore diameter of the peak The value obtained by subtracting PD, MD-PD, is between -0.02 μm and 0.02 μm. An electrode in a battery using at least one of a non-aqueous electrolyte or a non-aqueous electrolyte solution as the electrolyte.

3. The total pore surface area TA of the active material-containing layer obtained by the mercury injection method is 4 m ２ The electrode according to claim 1, wherein the amount is 1g or more.

4. The electrode according to any one of claims 1 to 3, wherein the total pore volume TV of the active material-containing layer by the mercury intrusion method is 0.15 mL / g or less.

5. The electrode according to any one of claims 1 to 3, wherein the diameter of the cross-section perpendicular to the longitudinal direction of the carbon fiber is 1 nm or more and 200 nm or less.

6. The electrode according to any one of claims 1 to 3, wherein the length of the carbon fiber is 5 μm or more and 50 μm or less.

7. It comprises a positive electrode, a negative electrode, and an electrolyte. A secondary battery in which at least one of the positive electrode and the negative electrode is the electrode described in any one of claims 1 to 3.

8. A battery pack comprising the secondary battery described in claim 7.

9. External terminals, Protection circuit and The battery pack according to claim 8, comprising the following:

10. The device comprises multiple secondary batteries, The battery pack according to claim 8, wherein the secondary batteries are electrically connected in series, parallel, or a combination of series and parallel.

11. A vehicle equipped with the battery pack described in claim 8.

12. The vehicle according to claim 11, which includes a mechanism for converting the kinetic energy of the vehicle into regenerative energy.

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