Electrodes, secondary batteries, battery packs, and vehicles

Abstract

The objective is to provide an electrode that suppresses gas generation and has high output performance. [Solution] According to the embodiment, an electrode is provided. The electrode comprises a niobium-containing oxide and a carbon-containing material. The hydroxyl group content of the niobium-containing oxide is 0.25 mmol / g or less. The functional group content of the carbon-containing material is 5 mmol / g or less.

Description

[Technical Field]

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

[0002] In recent years, research and development of secondary batteries, such as lithium-ion batteries and other non-aqueous electrolyte secondary batteries, has been actively pursued as high-energy-density batteries. Secondary batteries, including non-aqueous electrolyte secondary batteries, are expected to be used as power sources for vehicles such as hybrid electric vehicles and electric vehicles, and for uninterruptible power supplies in mobile phone base stations. Therefore, secondary batteries are required to excel not only in high energy density but also in other performance aspects such as rapid charge / discharge performance and long-term reliability. For example, secondary batteries capable of rapid charge / discharge not only significantly reduce charging time but also enable improved power performance in vehicles such as hybrid electric vehicles and efficient recovery of regenerative energy.

[0003] To enable rapid charging and discharging, electrons and lithium ions must be able to move quickly between the positive and negative electrodes. However, in batteries using carbon-based negative electrodes, repeated rapid charging and discharging can cause dendrite deposition of metallic lithium on the electrodes, potentially leading to internal short circuits, overheating, and ignition.

[0004] Therefore, batteries using metal composite oxides as the negative electrode instead of carbonaceous materials have been developed. In particular, batteries using titanium oxide as the negative electrode have the characteristics of enabling stable rapid charging and discharging, and having a longer lifespan compared to those using carbon-based negative electrodes.

[0005] However, titanium oxide has a higher potential relative to metallic lithium than carbonaceous materials, meaning it is nobler. Furthermore, titanium oxide has a low capacity per unit weight. For this reason, batteries using titanium oxide as the negative electrode suffer from a problem of low energy density.

[0006] For example, the electrode potential of titanium oxide is approximately 1.5V (vs. Li / Li) relative to metallic lithium.+ ) is higher (more noble) than the potential of the carbon-based anode. The potential of titanium oxide is Ti when lithium is electrochemically inserted and removed. 3+ and Tire 4+ Because it is caused by a redox reaction between them, it is electrochemically constrained. Also, 1.5V (vs.Li / Li + There is also the fact that rapid charging and discharging of lithium ions can be performed stably at high electrode potentials. Therefore, it has been difficult to lower the electrode potential in order to improve energy density.

[0007] On the other hand, regarding capacity per unit weight, the theoretical capacity of titanium dioxide (anatase structure) is about 165 mAh / g, while Li4Ti5O 12 The theoretical capacity of spinel-type lithium-titanium composite oxides like the one shown is also around 180 mAh / g. On the other hand, the theoretical capacity of typical graphite-based electrode materials is 385 mAh / g or more. Thus, the capacity density of titanium oxide is significantly lower compared to that of carbon-based anodes. This is because titanium oxide has fewer sites for intercalating lithium in its crystal structure, and lithium is easily stabilized within the structure, resulting in a decrease in effective capacity.

[0008] In light of the above, new electrode materials containing Nb are being investigated. Such niobium-containing oxide materials are expected to have high charge / discharge capacities. In particular, the composite oxide represented by TiNb2O7 has a high theoretical capacity exceeding 380 mAh / g. Therefore, Li4Ti5O 12 The use of niobium-containing oxides is being considered as an alternative material. [Prior art documents] [Patent Documents]

[0009] [Patent Document 1] Japanese Patent Publication No. 2024-038914 [Overview of the project] [Problems that the invention aims to solve]

[0010] The objective is to provide an electrode that suppresses gas generation and has high output performance, a secondary battery containing the electrode, a battery pack containing the secondary battery, and a vehicle containing the battery pack. [Means for solving the problem]

[0011] According to the embodiment, an electrode is provided. The electrode comprises a niobium-containing oxide and a carbon-containing material. The hydroxyl group content of the niobium-containing oxide is 0.25 mmol / g or less. The functional group content of the carbon-containing material is 5 mmol / g or less.

[0012] According to another embodiment, a secondary battery is provided which includes a positive electrode, a negative electrode, and an electrolyte. The negative electrode is the electrode according to the above embodiment.

[0013] According to another embodiment, a battery pack including a secondary battery according to the above embodiment is provided.

[0014] According to other embodiments, a vehicle including the battery pack according to the above embodiment is provided. [Brief explanation of the drawing]

[0015] [Figure 1] A schematic cross-sectional view showing an example of a secondary battery according to this embodiment. [Figure 2] An enlarged cross-sectional view of section A of the secondary battery shown in Figure 1. [Figure 3] A schematic partial cutaway perspective view showing another example of a secondary battery according to the embodiment. [Figure 4] Figure 3 shows an enlarged cross-sectional view of section B of the secondary battery. [Figure 5] A schematic perspective view showing an example of a battery pack according to this embodiment. [Figure 6] An exploded perspective view schematically showing an example of a battery pack according to this embodiment. [Figure 7] A block diagram showing an example of the electrical circuit of the battery pack shown in Figure 6. [Figure 8] A partially transparent view schematically showing an example of a vehicle according to the embodiment. [Figure 9] A schematic diagram showing an example of a control system for the electrical system in a vehicle according to this embodiment. [Modes for carrying out the invention]

[0016] (First embodiment) According to the first embodiment, an electrode is provided. The electrode comprises a niobium-containing oxide and a carbon-containing material. The hydroxyl group content of the niobium-containing oxide is 0.25 mmol / g or less. The functional group content of the carbon-containing material is 5 mmol / g or less.

[0017] As a result of diligent research, the inventors have found that the lower the hydroxyl group content of the niobium-containing oxide, the more likely it is that gas generation from the electrode can be reduced. The niobium-containing oxide contained in the electrode according to this embodiment has a low hydroxyl group content of 0.25 mmol / g or less, thus reducing the amount of gas generated. Furthermore, niobium-containing oxides with a low hydroxyl group content are highly hydrophobic.

[0018] Carbon-containing materials with a functional group content of 5 mmol / g or less are highly hydrophobic. Therefore, they are less likely to repel niobium-containing oxides, which are also highly hydrophobic and have a hydroxyl group content of 0.25 mmol / g or less. Consequently, carbon-containing materials and niobium-containing oxides tend to aggregate easily. This allows for the maintenance of good conductive paths within the electrode. Furthermore, it reduces the likelihood of delamination between the carbon-containing material and the niobium-containing oxide. As a result, output performance can be increased.

[0019] The electrode according to the embodiment will be described further.

[0020] In this specification, the composition, structure, chemical formula, etc., of niobium-containing oxides and carbon-containing materials may be described. However, unless otherwise specified, the elements contained in the hydroxyl groups that niobium-containing oxides may contain and the functional groups that carbon-containing materials may contain will not be described. In other words, niobium-containing oxides may have further hydroxyl groups added to the compositions shown in this specification. Carbon-containing materials may have further functional groups added to the compositions shown in this specification.

[0021] Niobium-containing oxides may be present in the electrode, for example, in particulate form. The particles may be primary particles or secondary particles formed by aggregation of primary particles.

[0022] Niobium-containing oxides may contain both a crystalline phase and an amorphous phase (defects). However, since hydroxyl groups readily attach to the amorphous phase, it is preferable that niobium-containing oxides consist only of a crystalline phase or have a small amount of amorphous phase. In other words, it is preferable that niobium-containing oxides have high crystallinity. Niobium-containing oxides with low crystallinity may, for example, have an elemental ratio in the amorphous phase that differs from the atomic composition (elemental ratio) that constitutes the crystal of the niobium-containing oxide. When particles containing niobium-containing oxide have an amorphous phase, the amorphous phase may be present on the surface of the particles.

[0023] The hydroxyl group content of niobium-containing oxides can be, for example, 0.00 mmol / g or more and 0.25 mmol / g or less. The hydroxyl group content of niobium-containing oxides can be expressed as the amount of hydroxyl groups (mmol) per mass (g) of the niobium-containing oxide.

[0024] Carbon-containing materials contain carbon atoms. Preferably, carbon-containing materials have a composition consisting of carbon atoms. While carbon-containing materials may contain functional groups containing atoms other than carbon atoms, as explained above, carbon-containing materials preferably have a low functional group content, and more preferably do not contain functional groups at all. If a carbon-containing material does not contain functional groups, it may consist only of carbon atoms.

[0025] Carbon-containing materials may contain both crystalline and amorphous phases (defects). However, since functional groups readily attach to amorphous phases, it is preferable that carbon-containing materials consist only of crystalline phases or have a small amount of amorphous phase. In other words, it is preferable that carbon-containing materials have high crystallinity.

[0026] The functional group content of a carbon-containing material can be, for example, between 0 mmol / g and 5 mmol / g. The functional group content of a carbon-containing material can be expressed as the amount of substance (mmol) of the functional group per mass (g) of the carbon-containing material. Examples of functional groups that a carbon-containing material may contain include hydroxyl groups, carboxyl groups, carbonyl groups, ether bonds, and hydrocarbon bonds. These functional groups are highly hydrophilic. The higher the content of such functional groups, the lower the hydrophobicity of the carbon-containing material tends to be.

[0027] The carbon-containing material may include, for example, at least one selected from the group consisting of fibrous carbon-containing material, granular carbon-containing material, and plate-shaped carbon-containing material. The type of carbon-containing material can be one or two or more.

[0028] The carbon-containing material preferably includes fibrous carbon-containing material. Fibrous carbon-containing material is a carbon-containing material with a shape that has a high aspect ratio in one dimension. Among carbon-containing materials, those with an aspect ratio (ratio of fiber length to fiber diameter) of 5 or more can be considered fibrous carbon-containing material.

[0029] Examples of fibrous carbon-containing materials include carbon nanotubes (CNTs). Specific examples of CNTs include multi-walled carbon nanotubes (MWCNTs), few-walled carbon nanotubes (FWCNTs), single-walled carbon nanotubes (SWCNTs), vapor-grown carbon fibers (VGCFs), and carbon nanofibers (CNFs). The types of fibrous carbon-containing materials can be one or more.

[0030] The average fiber diameter of the fibrous carbon-containing material is preferably small, less than 10 nm. Fibrous carbon-containing materials with a small average fiber diameter tend to have high crystallinity. Since the hydrophobicity of carbon-containing materials improves with higher crystallinity, fibrous carbon-containing materials with a small average fiber diameter are preferable because they readily aggregate with hydrophobic niobium-containing oxides to maintain good conductive paths. This also contributes to reducing side reactions of the electrodes.

[0031] Examples of fibrous carbon-containing materials with an average fiber diameter of 10 nm or less include FWCNTs and SWCNTs. From the viewpoint of further reducing the average fiber diameter, carbon nanotubes having a tubular structure with a thin wall thickness are preferred, and SWCNTs are the most preferred.

[0032] Granular carbon-containing materials may have particle shapes with a low aspect ratio. The particle shape may be amorphous. Granular carbon-containing materials may contain particles with a low aspect ratio, either individually or in groups of two or more particles. A carbon-containing material having a particle shape with an aspect ratio of 3 or less can be considered a granular carbon-containing material. More specifically, a particle can be said to have an aspect ratio of 3 or less if there is no combination of three lengths obtained by measuring the length in three directions: the thickness direction, the longitudinal direction perpendicular to the thickness direction, and the transverse direction perpendicular to both the thickness direction and the longitudinal direction, that results in an aspect ratio greater than 3.

[0033] Specific examples of granular carbon-containing materials include carbon black such as acetylene black and furnace black. From the viewpoint of reducing the functional group content of carbon-containing materials, crystalline carbon black is preferred among carbon blacks. An example of crystalline carbon black is acetylene black. A specific example of acetylene black is Denka Black (registered trademark) manufactured by Denka. A flat carbon-containing material may have a two-dimensional structure. A carbon-containing material can be considered a flat carbon-containing material if, when the lengths in three directions—the thickness direction, the longitudinal direction perpendicular to the thickness direction, and the transverse direction perpendicular to both the thickness direction and the longitudinal direction—are measured, the ratio of the length in the longitudinal direction to the length in the thickness direction is 5 or greater, and the ratio of the length in the transverse direction to the length in the thickness direction is also 5 or greater. In other words, a flat carbon-containing material may have a plane with an aspect ratio of 5 × 5 or greater with respect to the thickness direction. The portion of this plane with the maximum width is defined as the maximum width.

[0034] Examples of plate-shaped carbon-containing materials include multilayer graphene and graphite. Of these, multilayer graphene is preferable because its high crystallinity allows for a lower functional group content.

[0035] When the carbon-containing material includes both fibrous carbon-containing material and granular carbon-containing material, it is preferable that the average fiber diameter of the fibrous carbon-containing material and the average particle size of the granular carbon-containing material satisfy the following formula A.

[0036] Formula A: db<10da In formula A, da is the average fiber diameter of the fibrous carbon-containing material, and db is the average particle size of the granular carbon-containing material.

[0037] When the carbon-containing material includes both fibrous carbon-containing material and plate-shaped carbon-containing material, it is preferable that the average fiber diameter of the fibrous carbon-containing material and the average thickness of the plate-shaped carbon-containing material satisfy the following formula B.

[0038] Formula B: ta<20da In formula B, da is the average fiber diameter of the fibrous carbon-containing material, and ta is the average thickness of the plate-like carbon-containing material.

[0039] Fibrous carbon-containing materials and granular carbon-containing materials satisfying formula A are unlikely to aggregate with each other. Furthermore, fibrous carbon-containing materials and plate-shaped carbon-containing materials satisfying formula B are unlikely to aggregate with each other.

[0040] When granular carbon-containing material and / or plate-shaped carbon-containing material aggregates with fibrous carbon-containing material, the fibrous carbon-containing material may coat the granular carbon-containing material and / or plate-shaped carbon-containing material. In this case, the fibrous carbon-containing material becomes less likely to disperse within the electrode, making it difficult to secure a conductive path for the electrode through the fibrous carbon-containing material, which can lead to a decrease in output and is therefore undesirable.

[0041] The electrode according to the embodiment will be described in more detail.

[0042] In the electrode according to this embodiment, a niobium-containing oxide may be included as an active material. A carbon-containing material may be included as a conductive agent.

[0043] The electrode can be an electrode for a battery containing a niobium-containing oxide as an active material for the battery. The electrode is preferably an electrode for a secondary battery. Since the niobium-containing oxide and the carbon-containing material are difficult to separate, a good conductive path is likely to be maintained in the electrode even after charge-discharge cycles. The electrode as an electrode for a battery can be, for example, a negative electrode containing a niobium-containing oxide as a negative electrode active material.

[0044] Such an electrode can include a current collector and an active material-containing layer. The active material-containing layer can be formed on one or both sides of the current collector. The active material-containing layer can include an active material, a conductive agent, and a binder.

[0045] The active material-containing layer may contain the niobium-containing oxide alone, or may contain a mixture of the niobium-containing oxide and one or more other active materials.

[0046] Specific compositions of the niobium-containing oxide are exemplified below. In each composition formula, hydroxyl groups that the niobium-containing oxide may contain are not considered.

[0047] Examples of the niobium-containing oxide include, for example, monoclinic niobium titanate, niobium pentoxide (Nb2O5), and compounds represented by Nb 1-x W x O 2.5+0.5x (where x is, for example, 0 < x ≦ 0.5). The type of the niobium-containing oxide can be one or more.

[0048] Examples of the above monoclinic niobium titanate include compounds represented by Li x Ti 1-y M1 y Nb 2-z M2 z O 7+δ 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. Each subscript in the composition formula is 0 ≦ x ≦ 5, 0 ≦ y < 1, 0 ≦ z < 2, -0.3 ≦ δ ≦ 0.3. Specific examples of the monoclinic niobium titanate include Lix Examples include Nb2TiO7 (0 ≦ x ≦ 5).

[0049] As other examples of monoclinic niobium titanate oxides, Li x Ti 1-y M3 y+z Nb 2-z O 7-δ compounds represented by are included. Here, M3 is at least one selected from Mg, Fe, Ni, Co, W, Ta, and Mo. Each subscript in the composition formula is 0 ≦ x ≦ 5, 0 ≦ y < 1, 0 ≦ z < 2, -0.3 ≦ δ ≦ 0.3.

[0050] Nb 1-x W x O 2.5+3x As specific examples of the compounds represented by, for example, Nb 12 WO 33 and Nb 16 W5O 55 can be mentioned. These compositions are represented by Nb 1-x W x O 2.5+3x and satisfy 0 < x ≦ 0.5. In other words, the formulas Nb 12 WO 33 and Nb 16 W5O 55 each show the composition formula satisfying Nb 1-x W x O 2.5+3x with each subscript being an integer.

[0051] When a niobium-containing oxide is included as the negative electrode active material, examples of other active materials include lithium titanate having a lamellarite structure (for example, Li 2+y Ti3O7, 0 ≦ y ≦ 3), lithium titanate having a spinel structure (for example, Li 4+x Ti5O 12 , 0 ≦ x ≦ 3), titanium dioxide (TiO2), anatase-type titanium dioxide, rutile-type titanium dioxide, hollandite-type titanium composite oxide, and orthorhombic titanium composite oxide.

[0052] As an example of the above orthorhombic titanium-containing composite oxide, Li 2+a M I 2-b Ti 6-c M II d O 14+σ Examples of compounds represented by are given. Here, M I It is at least one selected from the group consisting of Sr, Ba, Ca, Mg, Na, Cs, Rb, and K. 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. In the composition formula, each subscript has the following properties: 0≦a≦6, 0≦b<2, 0≦c<6, 0≦d<6, -0.5≦σ≦0.5. As a specific example of an orthorhombic titanium-containing composite oxide, Li 2+a Na2Li6O 14 (0 ≤ a ≤ 6) is one example.

[0053] The conductive agent is added to enhance current collection performance and reduce contact resistance between the active material and the current collector. Examples of conductive agents include the carbon-containing materials described earlier. When the electrode according to this embodiment is used as a negative electrode, the carbon-containing material may be referred to as the negative electrode carbon-containing material. In addition to using the carbon-containing materials described earlier as the conductive agent, a carbon coating or an electronically conductive inorganic material coating may be applied to the surface of the active material particles.

[0054] A binder is added to fill the gaps between dispersed active materials and to bond the active materials to the current collector. Examples of binders include polytetrafluoroethylene (PTFE), polyvinylidene fluoride (PVdF), fluororubber, styrene-butadiene rubber, polyacrylic acid compounds, imide compounds, carboxymethyl cellulose (CMC), and salts of CMC. One of these may be used as a binder, or two or more may be used in combination.

[0055] The mixing ratios of the active material, conductive agent, and binder in the active material-containing layer can be appropriately changed depending on the application of the electrode. For example, when the electrode is used as the negative electrode of a secondary battery, it is preferable to mix the active material (negative electrode active material), conductive agent, and binder in the following proportions: 68% to 96% by mass, 2% to 30% by mass, and 2% to 30% by mass, respectively. By setting the amount of conductive agent to 2% by mass or more, the current collection performance of the active material-containing layer can be improved. Furthermore, by setting the amount of binder to 2% by mass or more, sufficient bonding between the active material-containing layer and the current collector can be achieved, and excellent cycle performance can be expected. On the other hand, it is preferable to set the amount of conductive agent and binder to 30% by mass or less each in order to achieve high capacity.

[0056] The current collector is made of a material that is electrochemically stable at the potential at which lithium (Li) is inserted into and removed from the active material. For example, when the active material is used as the negative electrode active material, the current collector is preferably made of copper, nickel, stainless steel, or aluminum, or an aluminum alloy containing one or more elements selected from 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.

[0057] Furthermore, the current collector may include portions on its surface where the negative electrode active material-containing layer is not formed. These portions can function as negative electrode current collector tabs.

[0058] (Manufacturing method) The method for manufacturing an electrode according to this embodiment includes, for example, synthesizing a niobium-containing oxide, preparing a slurry containing the niobium-containing oxide and a carbon-containing material, and applying the slurry to a current collector.

[0059] Each step that the above method may include is described below.

[0060] The hydroxyl group content of niobium-containing oxides is affected by the synthesis conditions. For example, niobium-containing oxides can be synthesized by mixing starting materials and heating the resulting mixture. The mixing method and heating temperature in such synthesis can affect the hydroxyl group content of the resulting niobium-containing oxide. Furthermore, niobium-containing oxides may contain impurities such as alkali residues derived from the starting materials. Potassium can be an example of an alkali. Alkali residues can also increase the hydroxyl group content of niobium-containing oxides.

[0061] To obtain a niobium-containing oxide with a low hydroxyl group content, it is preferable to synthesize the niobium-containing oxide by, for example, performing an annealing treatment on an intermediate obtained by a liquid-phase method.

[0062] The liquid-phase method is a method of synthesizing a target substance using a mixture (mixture) obtained by melting or dissolving / suspending the starting materials in a solvent and then mixing them until they are homogeneous at the atomic level. Alternatively, granular precursors may be prepared from the mixture, and the target substance may be synthesized from the precursors.

[0063] Examples of liquid-phase methods include spray drying, spray pyrolysis, and hydrothermal synthesis. Spray drying is a method in which a mixture is sprayed, and the sprayed droplets are dried in hot air to obtain an intermediate, which is then heated to synthesize the target substance. Spray pyrolysis is a method in which droplets of a mixture are sprayed and introduced into a high-temperature field such as a reactor using a carrier gas, and heated to synthesize the target substance through reaction with the gas or thermal decomposition. Hydrothermal synthesis is a method in which a mixture with water as a solvent is heated and pressurized to synthesize the target substance in the presence of hot water at high temperature and pressure.

[0064] As starting materials, oxides or salts containing niobium and other metallic elements (e.g., titanium) that are present in the target niobium-containing oxide can be used. The salts used as starting materials are preferably salts that decompose at relatively low temperatures to produce oxides, such as carbonates and nitrates. These starting materials can be mixed in a molar ratio that results in the desired composition. It is preferable to use starting materials with a low alkali content.

[0065] Intermediate products may be obtained by methods other than the liquid-phase method described above. An example of a method other than the liquid-phase method is the solid-phase method. The solid-phase method is a method of synthesizing the target substance by heating a mixture obtained by mixing starting materials such as metal oxides in a solid phase.

[0066] From the viewpoint of obtaining niobium-containing oxides with a low hydroxyl group content, the liquid phase method is preferred. Niobium-containing oxides obtained via the liquid phase method are preferred because they are less prone to a decrease in crystallinity and a change in the elemental ratio of the surface during the grinding process, which will be explained later.

[0067] The intermediate obtained as described above may contain a niobium-containing oxide with low crystallinity. By performing an annealing treatment by heating such an intermediate, the crystallinity of the niobium-containing oxide can be improved, which is preferable.

[0068] To obtain a niobium-containing oxide with high crystallinity, it is preferable to increase the annealing temperature. The higher the annealing temperature and the longer the annealing time, the more the crystalline phase of the niobium-containing oxide can be developed. However, if the annealing temperature is too high or the time is too long, sintering may occur, and the niobium-containing oxide may form coarse secondary particles. To obtain a niobium-containing oxide with a desired particle size, these secondary particles must be crushed using a ball mill or the like. However, if the shear force during crushing is too high, an amorphous phase may form on the surface of the niobium-containing oxide. As a result, the hydroxyl group content may end up being high.

[0069] From the viewpoint of synthesizing niobium-containing oxides with high crystallinity, it is preferable to perform the annealing treatment at a temperature of 400°C to 1100°C for 1 to 12 hours. It is more preferable to set the annealing temperature to 800°C or lower.

[0070] After annealing, grinding can be performed to obtain niobium-containing oxides as particles with a desired particle size. For grinding, a ball mill can be used, for example. A specific example of a ball mill is a dry ball mill. The ball milling conditions can be, for example, a ball diameter of 1 mm to 10 mm, a rotation speed of 120 rpm to 450 rpm, and a grinding time of 3 hours to 24 hours. The smaller the ball diameter, the lower the rotation speed, or the shorter the ball milling time, the lower the shear force during grinding tends to be. The lower the shear force, the higher the crystallinity of the niobium-containing oxide particles obtained by grinding tends to be.

[0071] After grinding, re-annealing may be performed. Re-annealing can be carried out by heating the niobium-containing oxide particles obtained by grinding at a temperature of 400°C to 700°C for 0.5 hours to 12 hours. The re-annealing time is preferably 6 hours or less. Niobium-containing oxide particles immediately after grinding may have reduced crystallinity on the particle surface due to grinding, and may contain an amorphous phase on the particle surface. By re-annealing such niobium-containing oxide particles, the crystallinity of the particle surface can be improved, making it more difficult for hydroxyl groups to be added to the niobium-containing oxide. As a result, the hydroxyl group content of the niobium-containing oxide can be reduced. If the crystallinity of the niobium-containing oxide particles obtained by grinding is sufficiently high, re-annealing may be omitted.

[0072] Furthermore, when ball milling is performed at rotational speeds exceeding 450 rpm, the amorphization of niobium-containing oxides tends to progress significantly. As a result, the niobium-containing oxide particles obtained after grinding may have a fluctuating elemental ratio on the particle surface. Even if re-annealing is performed on such significantly amorphized niobium-containing oxides, there is a limit to how much the hydroxyl group content can be reduced. Therefore, it becomes difficult to reduce the hydroxyl group content of niobium-containing oxides to 0.25 mmol / g or less, which is undesirable.

[0073] The niobium-containing oxide synthesized as described above is dispersed in a solvent together with a carbon-containing material. Specifically, the active material containing the niobium-containing oxide, the carbon-containing material, and the binder are dispersed in a solvent. For example, water can be used as the solvent.

[0074] For dispersion, for example, a bead mill can be used. If the shear force applied by the bead mill is too high, the crystallinity of the carbon-containing material may decrease. Furthermore, the parts of the carbon-containing material whose crystallinity has decreased may react with the solvent. As a result, functional groups are more likely to be added to the carbon-containing material, which is undesirable. From the viewpoint of reducing the functional group content of the carbon-containing material, the dispersion conditions using a bead mill are preferably low peripheral speed and high flow rate. In dispersion using a bead mill, the peripheral speed can be, for example, 10 m / s or less. The peripheral speed is preferably, for example, 6 m / s. The peripheral speed is preferably, for example, 3000 rpm or less, and can be, for example, 2000 rpm. The flow rate can be 10 mL / min or more. The flow rate can be, for example, 40 mL / min. In this way, a slurry can be prepared.

[0075] Prior to dispersion by bead milling, the active material containing niobium oxide, the carbon-containing material, and the binder may be pre-mixed. Pre-mixing allows for obtaining an electrode slurry in which the materials are sufficiently dispersed in the solvent without excessively increasing the shear force of the bead mill. For pre-mixing, a planetary mixer can be used, for example. If the shear force of the planetary mixer is too high, the crystallinity of the carbon-containing material decreases, making it easier for functional groups to be added to the carbon-containing material, which is undesirable. From the viewpoint of reducing the functional group content of the carbon-containing material, it is preferable to lower the peripheral speed of the planetary mixer. The peripheral speed can be, for example, 3 m / s or less.

[0076] The slurry prepared as described above is applied to one or both sides of the 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, an electrode can be manufactured.

[0077] In addition to the methods described above, electrodes may also be manufactured by the following method. First, a mixture is obtained by mixing (kneading) a niobium-containing oxide, a carbon-containing material, and a binder. A constrained fluid mixer (Henschel mixer) can be used for kneading. However, if the shear force of the Henschel mixer is too high, it is undesirable because it will reduce the crystallinity of the carbon-containing material and make it easier for functional groups to be added to the carbon-containing material. When mixing using a Henschel mixer, the kneading environment can be adjusted along with the shear force. From the viewpoint of reducing the functional group content of the carbon-containing material, it is preferable to adjust the rotation speed of the Henschel mixer and the kneading atmosphere as the kneading environment. The rotation speed can be set to, for example, 120 rpm or less. As for the kneading environment, it is preferable to carry out kneading in an atmosphere that does not contain oxygen. Specifically, an argon atmosphere can be selected. Next, this mixture is formed into pellets. Then, electrodes can be obtained by placing these pellets on a current collector.

[0078] (Measurement method) The following describes methods for measuring the hydroxyl group content of niobium-containing oxides and the functional group content of carbon-containing materials. Furthermore, methods for identifying the type and measuring the size of carbon-containing materials are also described.

[0079] If the electrode to be measured is incorporated into a battery, the battery should be disassembled in a glove box maintained at a dew point of -80°C or below before measurement, and the electrode to be measured (e.g., the negative electrode) should be removed.

[0080] (Preparation of the sample for measurement) From the electrode to be measured, prepare a TG-MS sample for measuring the hydroxyl group content of niobium-containing oxides, and a TPD-MS sample for measuring the functional group content of carbon-containing materials, using the following method.

[0081] First, a coin cell is assembled using the electrode to be measured, with Li metal as the counter electrode. This coin cell is then charged at 1 mA / g until it reaches 3.2 V vs. Li, completely detaching Li from the electrode to be measured. This process is repeated three times.

[0082] The coin cell is disassembled in a glove box where the dew point is controlled to -80°C or below, and the electrode to be measured is removed. Using a spatula, the active material-containing layer of the electrode to be measured is peeled off from the current collector to obtain a powdered active material-containing layer (electrode powder). The obtained electrode powder is placed in water and ultrasonic dispersion is performed. The precipitate that settles after dispersion is separated from the suspension on top. This ultrasonic dispersion and separation operation is repeated three times to obtain the precipitate and suspension. Of the active material-containing layer, the niobium-containing oxide tends to precipitate after ultrasonic dispersion. Therefore, the precipitate may contain the niobium-containing oxide. The suspension may contain carbon-containing material.

[0083] (Measurement of hydroxyl group content in niobium-containing oxides) Samples for thermogravimetric mass spectrometry (TG-MS) used to measure the hydroxyl group content of niobium-containing oxides can be obtained by drying the precipitate obtained by the method described above at 130°C for 24 hours or more, and then allowing it to stand for 24 hours in an environment with a dew point of 10°C or higher.

[0084] The hydroxyl group content of niobium-containing oxides can be measured by subjecting the TG-MS sample to TG-MS as follows.

[0085] Using a thermogravimetric-mass spectrometer, measurements are performed in an inert environment, for example, under nitrogen flow, at a heating rate of 3°C per minute up to 600°C. During this process, hydroxyl groups are quantified by MS analysis with m / z=18. The quantification of hydroxyl groups is performed using the cumulative value in the range of 150°C to 400°C.

[0086] (Measurement of functional group content in carbon-containing materials) Samples for Temperature Programmed Desorption-Mass Spectrometry (TPD-MS), used to measure the functional group content of carbon-containing materials, can be obtained by the following method. First, the suspension obtained by the above method is centrifuged. The precipitated phase is placed back into water and allowed to stand for 10 minutes, after which the precipitate is removed. The resulting liquid is centrifuged again, causing the carbon-containing material-containing phase to precipitate. Next, the obtained carbon-containing material-containing phase is washed. Washing is performed by placing the carbon-containing material-containing phase back into water and allowing it to stand for 10 minutes, removing the precipitate, and then centrifuging again to obtain the precipitated phase. After repeating the washing of the carbon-containing material-containing phase three times, the sample for TPD-MS is obtained by drying it in an inert atmosphere at 150°C for 24 hours or more.

[0087] The functional group content of carbon-containing materials can be measured by subjecting a TPD-MS sample to TPD-MS as follows.

[0088] Using a heating-generated gas mass spectrometer, the amount of substance of CO, CO2, H2O, and H2 gases generated in an inert gas stream at temperatures between 200°C and 800°C is quantified. These gases may be generated when carbon-containing materials contain hydroxyl groups, carboxyl groups, carbonyl groups, ether bonds, or hydrocarbon bonds.

[0089] The amount of substance of the quantified gas is obtained as the amount of functional groups contained in the carbon-containing material. It is preferable to perform the heating-generated gas mass spectrometry in a dehumidified environment to prevent the re-adsorption of moisture.

[0090] (Identification of carbon-containing material type and measurement of size) The type of carbon-containing material in the electrode can be determined by analysis using a scanning electron microscope (SEM). Among the particles, fibers, or plates observed in the secondary electron image of the electrode, the smallest size (particle size, fiber length, or maximum width) is considered the carbon-containing material. The largest particle size is considered the active material particle.

[0091] Backscattered electron image analysis is performed in a field of view that includes both the active material particles and carbon-containing material identified as described above. The field of view acquisition conditions are set so that the brightness of the active material particles and carbon-containing material identified by the method described above can be distinguished by their brightness. For example, measurements at 1kV-10uA in backscattered electron images are performed, but this is not limited to the type of active material.

[0092] The fiber diameter of a fibrous carbon-containing material is defined as the distance from one end of the fiber to the point where a perpendicular line drawn along that end intersects the other end of the fiber. The average fiber diameter can be measured by taking the fiber diameter of 10 randomly selected fibrous carbon-containing materials within the field of view and calculating the average value. The fiber length of a fibrous carbon-containing material can be measured by extrapolating a curve along one end of the fiber within the field of view until it is interrupted, and measuring the length of the resulting curve. The average fiber length can be measured by selecting the 10 longest extrapolated curves and calculating the average value of their lengths.

[0093] The thickness of a flat carbon-containing material is measured at the thinnest part of the material. Specifically, when observing the thickness of a flat carbon-containing material, a straight line perpendicular to the plane with an aspect ratio of 5x5 or more relative to the thickness direction is drawn at the thinnest part. The distance between the two points where this line intersects with the contour line of the flat carbon-containing material is defined as the thickness of the flat carbon-containing material. The average thickness can be measured by measuring the thickness of 10 randomly selected flat carbon-containing materials within the field of view and calculating the average value.

[0094] The particle size of granular carbon-containing material is defined as the diameter of the largest circle inscribed within the particle. The average particle size can be measured by randomly selecting 10 granular carbon-containing materials from within the field of view, measuring their diameters, and calculating their average value.

[0095] (Identification of crystalline carbon black) The presence of crystalline carbon black in an electrode can be identified using a transmission electron microscope (TEM). A TEM sample is prepared from the electrode being measured using the same method as for TPD-MS. When this TEM sample is analyzed by TEM, carbon-containing materials with two or more layered structures can be identified as crystalline carbon black.

[0096] The electrode according to the first embodiment comprises a niobium-containing oxide and a carbon-containing material. The hydroxyl group content of the niobium-containing oxide is 0.25 mmol / g or less. The functional group content of the carbon-containing material is 5 mmol / g or less. Therefore, an electrode can be provided that suppresses gas generation and has high output performance.

[0097] (Second embodiment) According to a second embodiment, a secondary battery is provided that includes a negative electrode, a positive electrode, and an electrolyte. This secondary battery includes the electrode according to the first embodiment as the negative electrode.

[0098] The secondary battery may further include a separator positioned between the positive electrode and the negative electrode. The negative electrode, positive electrode, and separator may constitute an electrode group. The electrolyte may be held within the electrode group.

[0099] Furthermore, the secondary battery may further include an outer casing that houses the electrode group and the electrolyte.

[0100] Furthermore, the secondary battery may further include a negative terminal electrically connected to the negative electrode and a positive terminal electrically connected to the positive electrode.

[0101] The secondary battery in question may be, for example, a lithium secondary battery. Furthermore, the secondary battery may include a non-aqueous electrolyte secondary battery containing a non-aqueous electrolyte.

[0102] The following provides a detailed explanation of the negative electrode, positive electrode, electrolyte, separator, outer casing, negative electrode terminal, and positive electrode terminal.

[0103] 1) Negative electrode The negative electrode may include a negative electrode current collector and a negative electrode active material-containing layer. The negative electrode current collector and the negative electrode active material-containing layer may be a current collector and an active material-containing layer that can be included in the electrode according to the first embodiment, respectively.

[0104] Details of the negative electrode that overlap with the details described in the first embodiment will be omitted.

[0105] The density of the negative electrode active material layer (excluding the current collector) is 1.8 g / cm³. 3 More than 3.5g / cm 3 The following is preferable. A negative electrode with a density of the negative electrode active material-containing layer within this range exhibits excellent energy density and electrolyte retention. The density of the negative electrode active material-containing layer is 2.1 g / cm³. 3 More than 3.0g / cm 3 The following is more preferable:

[0106] The negative electrode can be manufactured, for example, by the same method as the electrode according to the first embodiment.

[0107] 2) Positive electrode The positive electrode can include a positive electrode current collector and a positive electrode active material-containing layer. The positive electrode active material-containing layer can be formed on one or both sides of the positive electrode current collector. The positive electrode active material-containing layer can contain a positive electrode active material, and optionally a conductive agent and a binder.

[0108] 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 or a combination of two or more types of compounds as the positive electrode active material. Examples of the oxide and the sulfide include compounds into which Li or Li ions can be inserted and desorbed.

[0109] Examples of such compounds include, for example, manganese dioxide (MnO2), iron oxide, copper oxide, nickel oxide, lithium manganese composite oxide (e.g., Li x Mn2O4 or Li x MnO2; 0 < x ≦ 1), lithium nickel composite oxide (e.g., Li x NiO2; 0 < x ≦ 1), lithium cobalt composite oxide (e.g., Li x CoO2; 0 < x ≦ 1), lithium nickel cobalt composite oxide (e.g., Li x Ni 1-y Co y O2; 0 < x ≦ 1, 0 < y < 1), lithium manganese cobalt composite oxide (e.g., Li x Mn y Co 1-y O2; 0 < x ≦ 1, 0 < y < 1), lithium manganese nickel composite oxide having a spinel structure (e.g., Li x Mn 2-y Ni y O4; 0 < x ≦ 1, 0 < y < 2), lithium phosphate having an olivine structure (e.g., Li x FePO4; 0 < x ≦ 1, Li x Fe 1-y Mn y PO4; 0 < x ≦ 1, 0 < y ≦ 1, Li xCoPO4; 0 < x ≦ 1), iron sulfate (Fe2(SO4)3), vanadium oxide (e.g., V2O5), and lithium nickel cobalt manganese composite oxide (Li x Ni 1-y-z Co y Mn z O2; 0 < x ≦ 1, 0 < y < 1, 0 < z < 1, y + z < 1) are included.

[0110] Among the above, examples of more preferable compounds as the positive electrode active material include lithium manganese composite oxide having a spinel structure (e.g., Li x Mn2O4; 0 < x ≦ 1), lithium nickel composite oxide (e.g., Li x NiO2; 0 < x ≦ 1), lithium cobalt composite oxide (e.g., Li x CoO2; 0 < x ≦ 1), lithium nickel cobalt composite oxide (e.g., Li x Ni 1-y Co y O2; 0 < x ≦ 1, 0 < y < 1), lithium manganese nickel composite oxide having a spinel structure (e.g., Li x Mn 2-y Ni y O4; 0 < x ≦ 1, 0 < y < 2), lithium manganese cobalt composite oxide (e.g., Li x Mn y Co 1-y O2; 0 < x ≦ 1, 0 < y < 1), lithium iron phosphate (e.g., Li x FePO4; 0 < x ≦ 1), and lithium nickel cobalt manganese composite oxide (Li x Ni 1-y-z Co y Mn z O2; 0 < x ≦ 1, 0 < y < 1, 0 < z < 1, y + z < 1) are included. When these compounds are used as the positive electrode active material, the positive electrode potential can be increased.

[0111] 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), a lithium manganese composite oxide, a lithium nickel composite oxide, a lithium nickel cobalt composite oxide, or a mixture thereof. Since these compounds have low reactivity with room temperature molten salts, the cycle life can be improved. Details of the room temperature molten salts will be described later.

[0112] The primary particle size of the positive electrode active material is preferably 100 nm or more and 1 μm or less. A positive electrode active material with a primary particle size of 100 nm or more is easy to handle in industrial production. A positive electrode active material with a primary particle size of 1 μm or less can smoothly progress the solid-state diffusion of lithium ions.

[0113] The specific surface area of the positive electrode active material is 2 preferably 0.1 m 2 / g or more and 10 m 2 / g or less. A positive electrode active material having a specific surface area of 0.1 m 2 / g or more can sufficiently secure the Li ion storage and release sites. A positive electrode active material having a specific surface area of 10 m

[0114] The binder is blended to fill the gaps between the dispersed positive electrode active materials and to bind the positive electrode active material and the positive electrode current collector. Examples of the binder include polytetrafluoroethylene (PTFE), polyvinylidene fluoride (PVdF), fluorine rubber, polyacrylic acid compounds, imide compounds, carboxymethyl cellulose (CMC), and salts of CMC. One of these may be used as the binder, or two or more of them may be combined and used as the binder.

[0115] 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.

[0116] 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.

[0117] 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.

[0118] 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, 0.2% to 20% by mass, and 0.5% to 15% by mass, respectively.

[0119] The above-mentioned effects can be achieved by increasing the amount of conductive agent to 0.5% 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.

[0120] 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.

[0121] 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.

[0122] 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.

[0123] The positive electrode can be manufactured, for example, by the following method. First, a slurry is prepared by suspending the positive electrode active material, conductive agent, and binder in a solvent. This slurry is applied to one or both sides of the positive electrode current collector. Next, the applied slurry is dried to obtain a laminate of the positive electrode active material-containing layer and the positive electrode current collector. After that, this laminate is pressed. In this way, the positive electrode is manufactured.

[0124] Alternatively, the positive electrode may be manufactured by the following method: First, a positive electrode active material, a conductive agent, and a binder are mixed to obtain a mixture. Next, this mixture is formed into pellets. Then, these pellets are placed on a positive electrode current collector to obtain the positive electrode.

[0125] 3) Electrolyte As electrolytes, for example, non-aqueous electrolytes, aqueous electrolytes, or a combination of non-aqueous and aqueous electrolytes can be used.

[0126] As the non-aqueous electrolyte, for example, a liquid non-aqueous electrolyte or a gel-type non-aqueous electrolyte can be used. The liquid non-aqueous electrolyte is prepared by dissolving the 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.

[0127] 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.

[0128] 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.

[0129] 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.

[0130] 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.

[0131] 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.

[0132] Polymeric solid electrolytes are prepared by dissolving an electrolyte salt in a polymer material and then solidifying it.

[0133] Inorganic solid electrolytes are solid materials that have lithium ion conductivity. Here, lithium ion conductivity means 1 × 10⁻⁶ at 25°C. -6 This refers to exhibiting a lithium ion conductivity of S / cm or higher. Examples of inorganic solid electrolytes include oxide-based solid electrolytes and sulfide-based solid electrolytes. Specific examples of inorganic solid electrolytes are as follows.

[0134] As an oxide-based solid electrolyte, it has a NASICON (Sodium (Na) Super Ionic Conductor) type structure, and its general formula is Li 1+xIt is preferable to use a lithium phosphate solid electrolyte represented by Mα2(PO4)3. Mα in the above general formula is, for example, one or more selected from the group consisting of titanium (Ti), germanium (Ge), strontium (Sr), zirconium (Zr), tin (Sn), aluminum (Al), and calcium (Ca). The subscript x is within the range of 0 ≦ x ≦ 2.

[0135] Specific examples of the lithium phosphate solid electrolyte having a NASICON-type structure include LATP compounds represented by Li 1+x Al x Ti 2-x (PO4)3 with 0.1 ≦ x ≦ 0.5; Li 1+x Al y Mβ 2-y (PO4)3 where Mβ is one or more selected from the group consisting of Ti, Ge, Sr, Zr, Sn, and Ca and 0 ≦ x ≦ 1 and 0 ≦ y ≦ 1; Li 1+x Al x Ge 2-x (PO4)3 with 0 ≦ x ≦ 2; and Li 1+x Al x Zr 2-x (PO4)3 with 0 ≦ x ≦ 2; Li 1+x+y Al x Mγ 2-x Si y P 3-y O 12 represented by where Mγ is one or more selected from the group consisting of Ti and Ge and 0 < x ≦ 2, 0 ≦ y < 3; Li 1+2x Zr 1-x Ca x (PO4)3 with 0 ≦ x < 1 can be mentioned.

[0136] In addition, as the oxide-based solid electrolyte, in addition to the above lithium phosphate solid electrolyte, there is also an amorphous LIPON compound represented by Li x PO y N z where 2.6 ≦ x ≦ 3.5, 1.9 ≦ y ≦ 3.8, and 0.1 ≦ z ≦ 1.3 (for example, Li 2.9 PO 3.3 N 0.46); Garnet-type structure La 5+x A x La 3-x Mδ2O 12 A compound represented as follows: A is one or more selected from the group consisting of Ca, Sr, and Ba, and Mδ is one or more selected from the group consisting of Nb and Ta, and 0 ≤ x ≤ 0.5; Li3Mδ 2-x L2O 12 A compound represented by where Mδ is 1 or more selected from the group consisting of Nb and Ta, and L may contain Zr, with 0 ≤ x ≤ 0.5; Li 7-3x Al x La3Zr3O 12 Compounds represented by 0 ≤ x ≤ 0.5; Li 5+x La3MCSR 2-x Zr x O 12 Represented by , where Mδ is 1 or more selected from the group consisting of Nb and Ta, and 0 ≤ x ≤ 2, it is an LLZ compound (e.g., Li7La3Zr2O 12 ); and having a perovskite-type structure La 2 / 3-x Li x Examples include compounds represented as TiO3 where 0.3 ≤ x ≤ 0.7.

[0137] One or more of the above compounds can be used as a solid electrolyte. Two or more of the above solid electrolytes may also be used.

[0138] Aqueous electrolytes contain an aqueous solvent and an electrolyte salt. Aqueous electrolytes are, for example, liquid. A liquid aqueous electrolyte is a solution prepared by dissolving an electrolyte salt as a solute in an aqueous solvent. The solution preferably contains 1 mole or more of aqueous solvent per 1 mole of salt (the solute), and more preferably 3.5 moles or more.

[0139] As an aqueous solvent, a solution containing water can be used. The solution containing water may be pure water or a mixed solvent of water and an organic solvent. For example, the aqueous solvent contains water in a proportion of 50% by volume or more.

[0140] The presence of water in an aqueous electrolyte can be confirmed by GC-MS (Gas Chromatography-Mass Spectrometry). Furthermore, the salt concentration and water content in the aqueous electrolyte can be measured, for example, by ICP (Inductively Coupled Plasma) emission spectrometry. By weighing a specified amount of the aqueous electrolyte and calculating the salt concentration, the molar concentration (mol / L) can be determined. Additionally, by measuring the specific gravity of the aqueous electrolyte, the number of moles of solute and solvent can be calculated.

[0141] The aqueous electrolyte may also be a gel-type electrolyte. The gel-type electrolyte is prepared by mixing and compounding the liquid aqueous electrolyte described above with a polymer material. As the polymer material, the polymer materials described for gel-type non-aqueous electrolytes can be used.

[0142] Examples of electrolyte salts that can be contained in an aqueous electrolyte include lithium chloride (LiCl), lithium bromide (LiBr), lithium hydroxide (LiOH), lithium sulfate (Li2SO4), lithium nitrate (LiNO3), lithium acetate (CH3COOLi), lithium oxalate (Li2C2O4), lithium carbonate (Li2CO3), lithium bis(trifluoromethanesulfonyl)imide (LiTFSI; LiN(SO2CF3)2), lithium bis(fluorosulfonyl)imide (LiFSI; LiN(SO2F)2), and lithium bisoxalate borate (LiBOB: LiB[(OCO)2]2). The aqueous electrolyte may contain one or more types of electrolyte salts. It is preferable that the aqueous electrolyte contains LiCl. Using LiCl can increase the lithium ion concentration of the aqueous electrolyte. It is also preferable that the lithium salt contains at least one of LiSO4 and LiOH in addition to LiCl.

[0143] The molar concentration of lithium ions in an aqueous electrolyte may be 3 mol / L or higher, 6 mol / L or higher, or 12 mol / L or higher. For example, the molar concentration of lithium ions in an aqueous electrolyte is 14 mol / L or lower. When the concentration of lithium ions in an aqueous electrolyte is high, the electrolysis of the aqueous solvent at the negative electrode tends to be suppressed, and hydrogen generation from the negative electrode tends to be low.

[0144] Aqueous electrolytes include chloride ions (Cl) as anion species. - ), hydroxide ion (OH - ), sulfate ions (SO4 2- ), nitrate ion (NO3 - Preferably, it includes at least one selected from ).

[0145] The pH of the aqueous electrolyte is preferably between 3 and 14, and more preferably between 4 and 13. When different electrolytes are used for the negative electrode and the positive electrode, the pH of the negative electrode electrolyte is preferably within the range of 3 to 14, and the pH of the positive electrode electrolyte is preferably within the range of 1 to 8.

[0146] When the pH of the negative electrode electrolyte is within the above range, the hydrogen evolution potential at the negative electrode decreases, thereby suppressing hydrogen evolution at the negative electrode. This improves the battery's storage performance and cycle life performance. When the pH of the positive electrode electrolyte is within the above range, the oxygen evolution potential at the positive electrode increases, thus reducing oxygen evolution at the positive electrode. This improves the battery's storage performance and cycle life performance. It is more preferable that the pH of the positive electrode electrolyte be within the range of 3 to 7.5.

[0147] The aqueous electrolyte may contain a surfactant. Examples of surfactants include polyoxyalkylene alkyl ethers, polyethylene glycol, polyvinyl alcohol, thiourea, 3,3'-dithiobis(1-propanephosic acid) disodium, dimercaptothiadiazole, boric acid, oxalic acid, malonic acid, saccharin, sodium naphthalene sulfonate, gelatin, potassium nitrate, aromatic aldehydes, heterocyclic aldehydes, and other nonionic surfactants. Surfactants may be used individually or in combination of two or more types.

[0148] 4) 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.

[0149] 5) Exterior components For example, the outer packaging material can be a container made of laminate film or a metal container.

[0150] The thickness of the laminating film is, for example, 0.5 mm or less, and preferably 0.2 mm or less.

[0151] 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.

[0152] 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.

[0153] 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.

[0154] 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.

[0155] 6) Negative terminal The negative electrode terminal can be formed from a material that is electrochemically stable at the Li absorption / desorption potential of the negative electrode active material and is also conductive. For example, the negative electrode terminal can be formed from a material with a potential range of 1V to 3V relative to the oxidation-reduction potential of lithium (vs. Li / Li +The negative electrode terminal can be formed from an electrically stable and conductive material. Specifically, examples of materials for the negative electrode terminal include copper, nickel, stainless steel, or aluminum, or an aluminum alloy containing at least one element selected from the group consisting of Mg, Ti, Zn, Mn, Fe, Cu, and Si. It is preferable to use aluminum or an aluminum alloy as the material for the negative electrode terminal. It is preferable that the negative electrode terminal be made of the same material as the negative electrode current collector in order to reduce contact resistance with the negative electrode current collector.

[0156] 7) Positive terminal The positive terminal has a potential range of 3V to 4.5V relative to the oxidation-reduction potential of lithium (vs.Li / Li + The positive electrode terminal can be formed from an electrically stable and conductive material. Examples of positive electrode terminal materials include aluminum, or an aluminum alloy containing at least one element selected from the group consisting of Mg, Ti, Zn, Mn, Fe, Cu, and Si. It is preferable that the positive electrode terminal be formed from the same material as the positive electrode current collector in order to reduce contact resistance with the positive electrode current collector.

[0157] Next, the secondary battery according to the embodiment will be described in more detail with reference to the drawings.

[0158] Figure 1 is a schematic cross-sectional view showing an example of a secondary battery. Figure 2 is an enlarged cross-sectional view of part A of the secondary battery shown in Figure 1.

[0159] The secondary battery 100 shown in Figures 1 and 2 includes a bag-shaped outer casing member 2 shown in Figure 1, an electrode group 1 shown in Figures 1 and 2, and an electrolyte (not shown). The electrode group 1 and the electrolyte are housed within the bag-shaped outer casing member 2. The electrolyte (not shown) is held by the electrode group 1.

[0160] The bag-shaped outer packaging member 2 consists of a laminate film comprising two resin layers and a metal layer interposed between them.

[0161] As shown in Figure 1, electrode group 1 is a flat, wound electrode group. As shown in Figure 2, the flat, wound electrode group 1 includes a negative electrode 3, a separator 4, and a positive electrode 5. The separator 4 is interposed between the negative electrode 3 and the positive electrode 5.

[0162] The negative electrode 3 includes a negative electrode current collector 3a and a negative electrode active material containing layer 3b. In the portion of the negative electrode 3 located in the outermost shell of the wound electrode group 1, the negative electrode active material containing layer 3b is formed only on the inner surface side of the negative electrode current collector 3a, as shown in Figure 2. In the other portions of the negative electrode 3, the negative electrode active material containing layer 3b is formed on both sides of the negative electrode current collector 3a.

[0163] The positive electrode 5 includes a positive electrode current collector 5a and positive electrode active material-containing layers 5b formed on both sides thereof.

[0164] As shown in Figure 1, the negative electrode terminal 6 and the positive electrode terminal 7 are located near the outer edge of the wound electrode group 1. The negative electrode terminal 6 is connected to the outermost part of the negative electrode current collector 3a. The positive electrode terminal 7 is connected to the outermost part of the positive electrode current collector 5a. These negative electrode terminals 6 and positive electrode terminals 7 extend outward from the opening of the bag-shaped outer casing member 2. A thermoplastic resin layer is installed on the inner surface of the bag-shaped outer casing member 2, and the opening is closed by heat fusion of this layer.

[0165] The secondary battery according to this embodiment is not limited to the secondary battery with the configuration shown in Figures 1 and 2, but may also be a battery with the configuration shown in Figures 3 and 4, for example.

[0166] Figure 3 is a schematic partially cutaway perspective view showing another example of a secondary battery. Figure 4 is an enlarged cross-sectional view of section B of the secondary battery shown in Figure 3.

[0167] The secondary battery 100 shown in Figures 3 and 4 includes an electrode group 1 shown in Figures 3 and 4, an outer casing member 2 shown in Figure 3, and an electrolyte (not shown). The electrode group 1 and the electrolyte are housed within the outer casing member 2. The electrolyte is held within the electrode group 1.

[0168] The exterior component 2 consists of a laminate film comprising two resin layers and a metal layer interposed between them.

[0169] As shown in Figure 4, electrode group 1 is a stacked electrode group. The stacked electrode group 1 has a structure in which negative electrodes 3 and positive electrodes 5 are alternately stacked with separators 4 interposed between them.

[0170] 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.

[0171] Each negative electrode 3's negative electrode current collector 3a includes a portion on one side where the negative electrode active material-containing layer 3b is not supported on any surface. This portion functions as a negative electrode current collector tab 3c. As shown in Figure 4, the negative electrode current collector tab 3c does not overlap with the positive electrode 5. Furthermore, multiple negative electrode current collector tabs 3c are electrically connected to a strip-shaped negative electrode terminal 6. The tip of the strip-shaped negative electrode terminal 6 is extended to the outside of the outer casing member 2.

[0172] 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 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 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.

[0173] The secondary battery according to the second embodiment includes the electrodes according to the first embodiment. Therefore, it is possible to provide a secondary battery that suppresses gas generation and has high output performance.

[0174] (Third embodiment) According to the third embodiment, a battery pack is provided, which includes a plurality of secondary batteries according to the second embodiment.

[0175] In such a battery pack, each individual cell may be arranged in series or parallel connections, or a combination of series and parallel connections may be used.

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

[0177] Figure 5 is a schematic perspective view showing an example of a battery pack. The battery pack 200 shown in Figure 5 comprises five single cells 100a to 100e, four busbars 21, a positive electrode lead 22, and a negative electrode lead 23. Each of the five single cells 100a to 100e is a secondary battery according to the second embodiment.

[0178] The busbar 21 connects, for example, the negative terminal 6 of one cell 100a to the positive terminal 7 of the adjacent cell 100b. In this way, the five cells 100 are connected in series by four busbars 21. That is, the battery pack 200 in Figure 5 is a battery pack with five cells in series. Although not illustrated, in a battery pack containing multiple cells that are electrically connected in parallel, the multiple cells can be electrically connected, for example, by connecting multiple negative terminals to each other and multiple positive terminals to each other by busbars.

[0179] 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.

[0180] The battery pack according to the third embodiment includes the secondary battery according to the second embodiment. Therefore, it is possible to provide a battery pack that suppresses gas generation and has high output performance.

[0181] (Fourth embodiment) According to a fourth embodiment, a battery pack is provided. This battery pack includes a battery pack according to the third embodiment. This battery pack may include a single secondary battery according to the second embodiment instead of the battery pack according to the third embodiment.

[0182] The battery pack may further include a protection circuit. The protection circuit has the function of controlling the charging and discharging of the secondary battery. Alternatively, a circuit included in a device that uses the battery pack as a power source (e.g., electronic equipment, automobile, etc.) may be used as the protection circuit for the battery pack.

[0183] Furthermore, such a battery pack may also include external terminals for power supply. These external terminals are for outputting current from the secondary battery to the outside and / or for inputting current from the outside to the secondary battery. In other words, when the battery pack is used as a power source, current is supplied to the outside through the external terminals. Also, when charging the battery pack, the charging current (including regenerative energy from the power of an automobile, etc.) is supplied to the battery pack through the external terminals.

[0184] Next, an example of a battery pack according to the embodiment will be described with reference to the drawings.

[0185] Figure 6 is an exploded perspective view schematically showing an example of a battery pack. Figure 7 is a block diagram showing an example of the electrical circuit of the battery pack shown in Figure 6.

[0186] The battery pack 300 shown in Figures 6 and 7 comprises a housing 31, a lid 32, a protective sheet 33, a battery pack 200, a printed circuit board 34, wiring 35, and an insulating plate (not shown).

[0187] The container 31 shown in Figure 6 is a bottomed rectangular container with a rectangular base. 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.

[0188] The battery pack 200 comprises multiple individual cells 100, a positive electrode lead 22, a negative electrode lead 23, and an adhesive tape 24.

[0189] 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 7. 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.

[0190] 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.

[0191] 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.

[0192] The printed circuit board 34 is installed along one of the shorter sides of the inner surface of the housing container 31. The printed circuit board 34 includes a positive terminal connector 342, a negative terminal connector 343, a thermistor 345, a protection circuit 346, wiring 342a and 343a, an external terminal 350 for energization, 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.

[0193] 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.

[0194] The thermistor 345 is fixed to one main surface of the printed circuit board 34. The thermistor 345 detects the temperature of each of the single cells 100 and transmits the detection signal to the protection circuit 346.

[0195] 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.

[0196] 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 side wiring 348a. The protection circuit 346 is connected to the negative terminal 353 via the negative side wiring 348b. The protection circuit 346 is also electrically connected to the positive side connector 342 via wiring 342a. The protection circuit 346 is also electrically connected to the negative side connector 343 via wiring 343a. Furthermore, the protection circuit 346 is electrically connected to each of the multiple single cells 100 via wiring 35.

[0197] The protective sheet 33 is positioned on both inner surfaces in the long-side direction of the housing container 31 and on the inner surface in the short-side direction facing the printed circuit board 34 via the battery pack 200. The protective sheet 33 is made of, for example, resin or rubber.

[0198] The protection circuit 346 controls the charging and discharging of 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 a detection signal transmitted from the thermistor 345 or a detection signal transmitted from an individual single cell 100 or a battery pack 200.

[0199] 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.

[0200] 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.).

[0201] 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.

[0202] The battery pack 300 may have 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 terminal 352 and negative terminal 353 of the external terminal 350 for energization, respectively.

[0203] Such battery packs are used in applications where excellent cycle performance is required, for example, when drawing high currents. Specifically, these battery packs are used as power supplies for electronic devices, stationary batteries, and on-board batteries for various vehicles. Examples of electronic devices include digital cameras. These battery packs are particularly suitable for use as on-board batteries.

[0204] 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, it is possible to provide a battery pack that suppresses gas generation and has high output performance.

[0205] (Fifth embodiment) According to the fifth embodiment, a vehicle is provided, which is equipped with the battery pack according to the fourth embodiment.

[0206] In such a vehicle, 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.

[0207] Examples of vehicles include, for example, two-wheeled or four-wheeled hybrid electric vehicles, two-wheeled or four-wheeled electric vehicles, electric assist bicycles, and railway vehicles.

[0208] The mounting location of the battery pack in a vehicle is not particularly limited. For example, when a battery pack is installed in an automobile, it can be mounted in the engine compartment, at the rear of the vehicle, or under the seats.

[0209] A vehicle may be equipped with multiple battery packs. In this case, the batteries contained in each battery pack may be electrically connected in series, in parallel, or a combination of series and parallel connections. For example, if each battery pack contains a battery pack, the battery packs may be electrically connected in series, in parallel, or a combination of series and parallel connections. Alternatively, if each battery pack contains a single battery, the batteries may be electrically connected in series, in parallel, or a combination of series and parallel connections.

[0210] Next, an example of a vehicle according to the embodiment will be described with reference to the drawings.

[0211] Figure 8 is a schematic partial transparency drawing showing an example of a vehicle.

[0212] The vehicle 400 shown in Figure 8 includes a vehicle body 40 and a battery pack 300 according to the fourth embodiment. In the example shown in Figure 8, the vehicle 400 is a four-wheeled automobile.

[0213] This vehicle 400 may be equipped with multiple battery packs 300. In this case, the batteries contained in the battery pack 300 (for example, single cells or battery packs) may be connected in series, in parallel, or in a combination of series and parallel connections.

[0214] Figure 8 illustrates an example in which the battery pack 300 is mounted in the engine compartment located in front of the vehicle body 40. As described above, the battery pack 300 may also be mounted, for example, in the rear of the vehicle body 40 or under the seats. This battery pack 300 can be used as a power source for the vehicle 400. In addition, this battery pack 300 can recover regenerative energy from the vehicle 400's power.

[0215] Next, an embodiment of the vehicle according to the embodiment will be described with reference to Figure 9.

[0216] Figure 9 is a schematic diagram illustrating an example of a control system for the electrical system in a vehicle. The vehicle 400 shown in Figure 9 is an electric vehicle.

[0217] The vehicle 400 shown in Figure 9 comprises a vehicle body 40, a vehicle power supply 41, a vehicle ECU (ECU: Electric Control Unit) 42 which is a higher-level control device for the vehicle power supply 41, an external terminal (terminal for connecting to an external power supply) 43, an inverter 44, and a drive motor 45.

[0218] Vehicle 400 has its vehicle power supply 41 mounted, for example, in the engine compartment, at the rear of the vehicle body, or under the seats. Note that in the vehicle 400 shown in Figure 9, the mounting location of the vehicle power supply 41 is shown in a schematic manner.

[0219] 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.

[0220] 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.

[0221] 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.

[0222] 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.

[0223] 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.

[0224] The battery pack monitoring devices 301a to 301c measure the voltage and temperature of individual single cells that make up the battery packs 200a to 200c based on commands received through communication from the battery management device 411. However, the temperature can be measured at only a few locations for each battery pack, and it is not necessary to measure the temperature of all single cells.

[0225] The vehicle power supply 41 can also have an electromagnetic contactor (for example, the switch device 415 shown in FIG. 9) that switches the presence or absence of an electrical connection between the positive terminal 413 and the negative terminal 414. The switch device 415 includes a pre-charge switch (not shown) that turns on when charging is performed on the battery packs 200a to 200c, and a main switch (not shown) that turns on when the output from the battery packs 200a to 200c is supplied to the load. Each of the pre-charge switch and the main switch includes a relay circuit (not shown) that is switched on or off by a signal supplied to a coil disposed near the switch element. The electromagnetic contactor such as the switch device 415 is controlled based on a control signal from the vehicle ECU 42 that controls the operation of the battery management device 411 or the entire vehicle 400.

[0226] The inverter 44 converts the input DC voltage into a three-phase alternating current (AC) high voltage for motor driving. The three-phase output terminals of the inverter 44 are connected to the respective three-phase input terminals of the drive motor 45. The inverter 44 is controlled based on a control signal from the vehicle ECU 42 for controlling the operation of the battery management device 411 or the entire vehicle. By controlling the inverter 44, the output voltage from the inverter 44 is adjusted.

[0227] The drive motor 45 rotates by the power supplied from the inverter 44. The driving force generated by the rotation of the drive motor 45 is transmitted to the axle and the drive wheels W through, for example, a differential gear unit.

[0228] Although not shown in the diagram, vehicle 400 is also equipped with a regenerative braking mechanism (regenerator). The regenerative braking mechanism rotates the drive motor 45 when vehicle 400 is braked, converting kinetic energy into regenerative energy as electrical energy. The regenerative energy recovered by the regenerative braking mechanism is input to the inverter 44 and converted into a DC current. The converted DC current is input to the vehicle power supply 41.

[0229] 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.

[0230] 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.

[0231] External terminal 43 is connected to battery management device 411. External terminal 43 can be connected to an external power supply, for example.

[0232] 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.

[0233] The vehicle according to the fifth embodiment is equipped with the battery pack according to the fourth embodiment. Because gas generation from the battery pack is suppressed and output performance is high, a high-performance vehicle can be provided. [Examples]

[0234] The present invention will be further explained with examples below, but the present invention is not limited to the embodiments listed below unless it exceeds the spirit of the invention.

[0235] (Example 1) (Fabrication of the negative electrode) First, TiNb2O7, a niobium-containing oxide, was synthesized by spray drying followed by annealing. The annealing was performed at 1100°C for 6 hours. Subsequently, it was ground in a dry ball mill with a ball diameter of 2 mm and a rotation speed of 200 rpm for 12 hours, and then re-annealed at 600°C for 12 hours. The TiNb2O7 particles thus obtained were used as the negative electrode active material.

[0236] As the carbon-containing material, acetylene black with a particle size of 31 nm was prepared as a granular carbon-containing material. As the binder, a mixture of carboxymethylcellulose and styrene-butadiene rubber in a mass ratio of 1:1 was prepared.

[0237] Niobium-containing oxide, acetylene black, and a binder were mixed in a mass ratio of 96:2:2 and dispersed in water as a solvent. A planetary mixer was used for the preliminary mixing of the electrode materials. Dispersion was carried out using a bead mill at 2000 rpm and a flow rate of 40 mL / min. The negative electrode slurry thus prepared was applied to a negative electrode current collector made of aluminum foil and dried. Thus, a negative electrode was obtained.

[0238] (Fabrication of the positive electrode) Lithium nickel cobalt manganese composite oxide (LiNi) is used as the positive electrode active material. 0.8 Co 0.1 Mn 0.1A slurry was prepared by adding 100 parts by mass of O2 (NCM811), 5 parts by mass of acetylene black as a conductive agent, and 5 parts by mass of polyvinylidene fluoride (PVdF) as a binder to N-methylpyrrolidone (NMP) and mixing. This slurry was applied to both sides of a current collector made of 12 μm thick aluminum foil, dried, and pressed to obtain an electrode density (excluding the current collector) of 3.2 g / cm³. 3 The positive electrode was fabricated.

[0239] (Preparation of electrolytes) Under an argon atmosphere, lithium hexafluoride phosphate (LiPF6) was dissolved in propylene carbonate (PC) at a concentration of 1.0 mol / L to prepare a liquid non-aqueous electrolyte (electrolyte).

[0240] (Battery assembly) The positive electrode prepared as described above, a separator made of cellulose with a thickness of 15 μm, the negative electrode prepared as described above, and the separator were stacked in this order, and then wound in a spiral shape so that the negative electrode was located on the outermost periphery to create an electrode group. By heating and pressing this at 90°C, a flat electrode group with a width of 58 mm and a thickness of 3.0 mm was prepared. The obtained electrode group was placed in an outer casing made of a laminate film with a thickness of 0.1 mm, which consisted of an aluminum foil with a thickness of 40 μm and polypropylene layers formed on both sides of the aluminum foil, and vacuum dried at 120°C for 24 hours. After vacuum drying, the electrolyte was poured into the electrode group placed in the laminate film under an argon atmosphere. Then, the top of the laminate film was sealed under reduced pressure to obtain a secondary battery.

[0241] (Example 2) A secondary battery was fabricated in the same manner as in Example 1, except that furnace black with a particle size of 45 nm was used as the negative electrode carbon-containing material.

[0242] (Example 3) A secondary battery was fabricated in the same manner as in Example 1, except that a multilayer graphene with a thickness of 52 nm as a flat carbon-containing material was used as the negative electrode carbon-containing material.

[0243] (Example 4) A secondary battery was fabricated in the same manner as in Example 1, except that SWCNT having a fiber diameter of 4 nm as a fibrous carbon-containing material was used as the negative electrode carbon-containing material.

[0244] (Example 5) A secondary battery was fabricated in the same manner as in Example 1, except that MWCNT having a fiber diameter of 15 nm as a fibrous carbon-containing material was used as the negative electrode carbon-containing material.

[0245] (Example 6) As the negative electrode carbon-containing material, SWCNT having a fiber diameter of 4 nm as a fibrous carbon-containing material and acetylene black having a particle shape (particle diameter) of 31 nm as a granular carbon-containing material were prepared. In the preparation of the negative electrode slurry, niobium-containing oxide, SWCNT, acetylene black and the binder were mixed so that the mass ratio was 96:1.99:0.01:2. A secondary battery was fabricated in the same manner as in Example 1, except for the above.

[0246] (Example 7) As the negative electrode carbon-containing material, SWCNT having a fiber diameter of 4 nm as a fibrous carbon-containing material and multilayer graphene having a thickness of 55 nm as a flat carbon-containing material were prepared. In the preparation of the negative electrode slurry, niobium-containing oxide, SWCNT, multilayer graphene and the binder were mixed so that the mass ratio was 96:0.1:1.9:2. A secondary battery was fabricated in the same manner as in Example 1, except for the above.

[0247] (Example 8) As the negative electrode carbon-containing material, SWCNT having a fiber diameter of 4 nm as a fibrous carbon-containing material and acetylene black having a particle shape of 49 nm as a granular carbon-containing material were prepared. In the preparation of the negative electrode slurry, niobium-containing oxide, SWCNT, acetylene black and the binder were mixed so that the mass ratio was 96:1.99:0.01:2. A secondary battery was fabricated in the same manner as in Example 1, except for the above.

[0248] (Example 9) As the negative electrode carbon-containing material, we prepared SWCNTs with a fiber diameter of 4 nm as a fibrous carbon-containing material and graphite with a thickness of 582 nm as a plate-shaped carbon-containing material. Refined natural graphite was used as the graphite. In preparing the negative electrode slurry, the niobium-containing oxide, SWCNTs, graphite, and binder were mixed in a mass ratio of 96:0.1:1.9:2. Except for the above, a secondary battery was prepared in the same manner as in Example 1.

[0249] (Example 10) The niobium-containing oxide was changed to Nb2O5. Nb2O5 was synthesized by spray drying followed by annealing. The annealing was performed at 1100°C for 6 hours. After that, it was ground in a dry ball mill with a ball diameter of 2 mm and a rotation speed of 200 rpm for 12 hours, and then re-annealed at 600°C for 12 hours. The Nb2O5 particles thus obtained were used as the negative electrode active material. Except for the above, a secondary battery was fabricated in the same manner as in Example 6.

[0250] (Example 11) Niobium-containing oxides are Nb 16 W5O 55 Changed to Nb. 16 W5O 55 It was synthesized by spray drying followed by annealing. The annealing was carried out at 1100°C for 6 hours. After that, it was ground in a dry ball mill with a ball diameter of 2 mm and a rotation speed of 200 rpm for 12 hours, and then re-annealed at 600°C for 12 hours. The Nb thus obtained 16 W5O 55 Particles were used as the negative electrode active material. Except for the above, a secondary battery was fabricated in the same manner as in Example 6.

[0251] (Example 12) Niobium-containing oxides are FeNb 11 O 29 Changed to FeNb. 11 O 29It was synthesized by spray drying followed by annealing. The annealing was carried out at 1100°C for 6 hours. After that, it was ground in a dry ball mill with a ball diameter of 2 mm and a rotation speed of 200 rpm for 12 hours, and then re-annealed at 600°C for 12 hours. The FeNb thus obtained 11 O 29 Particles were used as the negative electrode active material. Except for the above, a secondary battery was fabricated in the same manner as in Example 6.

[0252] (Comparative Example 1) In the synthesis of TiNb2O7 as a niobium-containing oxide, the grinding conditions using a dry ball mill were changed to a ball diameter of 10 mm, a rotation speed of 300 rpm, and a grinding time of 48 hours. Furthermore, re-annealing was not performed. Aside from these changes, a secondary battery was fabricated in the same manner as in Example 6.

[0253] (Comparative Example 2) A secondary battery was fabricated in the same manner as in Example 6, except that the conditions for the bead mill used for dispersion in the preparation of the negative electrode slurry were changed to 3600 rpm and a flow rate of 5 mL / min.

[0254] (Comparative Example 3) As negative electrode carbon-containing materials, MWCNTs with a fiber diameter of 17 nm as fibrous carbon-containing materials and furnace black with a particle size of 46 nm as granular carbon-containing materials were prepared. In preparing the negative electrode slurry, the niobium-containing oxide, MWCNTs, furnace black, and binder were mixed in a mass ratio of 92:2:4:2. Except for the above, a secondary battery was prepared in the same manner as in Example 6.

[0255] (measurement) For the negative electrodes of the secondary batteries in each example and comparative example, the hydroxyl group content of the niobium-containing oxide, the functional group content of the carbon-containing material, and the size of the carbon-containing material (average fiber diameter of fibrous carbon, average thickness of plate-like carbon-containing material, and average particle size of granular carbon-containing material) were measured using the method described above.

[0256] (evaluation) For each example and comparative example of secondary battery, the amount of gas generated, the 5C / 0.2C discharge capacity retention rate, and the cycle capacity retention rate were tested as follows.

[0257] (Gas generation amount) The secondary batteries of the examples and comparative examples were kept at a state of charge (SOC) of 100% and at an ambient temperature of 80°C for 10 days. Afterward, the amount of gas generated in the secondary batteries (cc) was measured. The measured amount of gas generated was divided by the battery capacity (Ah) to calculate the gas generation rate (cc / Ah) relative to the battery capacity.

[0258] (5C / 0.2C discharge capacity maintenance rate) The secondary batteries of the examples and comparative examples were charged and discharged within a potential range of 1.0V to 3.0V. To investigate the discharge rate performance, after confirming the 0.2C discharge capacity, the batteries were charged again with a charging current of 0.2C, and the 5C rapid discharge capacity was confirmed at room temperature. The discharge capacity retention rate (%) was then calculated by dividing the 5C discharge capacity by the 0.2C discharge capacity and multiplying by 100. The 5C / 0.2C discharge capacity retention rate (%) serves as an indicator for evaluating output performance.

[0259] (Cycle capacity maintenance rate) Life tests were conducted on the secondary batteries of the examples and comparative examples, involving repeated 1C charge-discharge cycles within a potential range of 1.0V to 3.0V at 25°C. Under these conditions, 1000 charge-discharge cycles were performed (one cycle consisted of charging and discharging), and the discharge capacity retention rate after 1000 cycles was investigated. To confirm the discharge capacity retention rate after 1000 cycles, charging and discharging were performed again at 0.2C (time discharge rate), and the cycle capacity retention rate (%) was calculated by dividing the discharge capacity after 1000 cycles by the initial discharge capacity and multiplying by 100, with the initial discharge capacity set to 100%. The discharge capacity retention rate after 1000 cycles serves as an indicator for evaluating cycle life performance.

[0260] The materials, measurement results, and test results for each example and comparative example described above are summarized in the table below. Table 1 shows the type of negative electrode active material, the hydroxyl group content of the niobium-containing oxide, the type of carbon-containing material, and the functional group content of the carbon-containing material. Table 2 shows the size of the carbon-containing material (average fiber diameter of fibrous carbon-containing material, average thickness of plate-like carbon-containing material, average particle size of granular carbon-containing material), gas generation amount, 5C / 0.2C discharge capacity maintenance rate, and cycle capacity maintenance rate. Among the sizes of the carbon-containing material, carbon-containing materials not included in the secondary battery being measured are indicated with "-".

[0261] [Table 1]

[0262] [Table 2]

[0263] In Examples 1 to 12, the hydroxyl group content of the niobium-containing oxide in the negative electrode was 0.25 mmol / g or less, and the functional group content of the carbon-containing material was 5 mmol / g or less. In all of these examples, the amount of gas generated was small, and the 5C / 0.2C discharge capacity maintenance rate was high. In other words, it was clear that gas generation was suppressed and output performance was high. This is thought to be because the low hydroxyl group content of the niobium-containing oxide in the electrode suppressed gas generation, and the niobium-containing oxide with a low hydroxyl group content and the carbon-containing material with a low functional group content were able to form a good conductive path.

[0264] Furthermore, all of the secondary batteries in the examples showed high cycle capacity retention rates. This is thought to be because the hydroxyl group content of the niobium-containing oxide in the electrodes was low, and the functional group content of the carbon-containing material was also low, making it difficult for the niobium-containing oxide and the carbon-containing material to separate even after charge-discharge cycles, thus improving cycle life performance.

[0265] Examples 1 to 9 demonstrate that even when various types of carbon-containing materials are changed or carbon-containing materials with different shapes are combined, secondary batteries with low gas generation, high 5C / 0.2C discharge capacity retention, and high cycle capacity retention can be obtained.

[0266] Comparing Examples 1 and 2, which contain granular carbon-containing materials, Example 1, which contains acetylene black (a crystalline carbon black), was superior in terms of gas generation amount, 5C / 0.2C discharge capacity maintenance rate, and cycle capacity maintenance rate.

[0267] Comparing Examples 4 and 5, which include fibrous carbon-containing materials, Example 4, which includes a fibrous carbon-containing material with an average fiber diameter of 10 nm or less, was superior in gas generation amount, 5C / 0.2C discharge capacity maintenance rate, and cycle capacity maintenance rate.

[0268] Comparing Examples 6 and 8, which include fibrous carbon-containing materials and granular carbon-containing materials, Example 6, in which the fibrous carbon-containing material and granular carbon-containing material satisfy db < 10da when the average fiber diameter of the fibrous carbon-containing material is da and the average particle size of the granular carbon-containing material is db, showed superior gas generation rate, 5C / 0.2C discharge capacity maintenance rate, and cycle capacity maintenance rate. This is thought to be because the average particle size of the granular carbon-containing material is not too large compared to the average fiber diameter of the fibrous carbon-containing material, thus suppressing the coating of the fibrous carbon-containing material on the granular carbon-containing material, and as a result, the dispersibility of the fibrous carbon-containing material in the electrode was good.

[0269] Comparing Examples 7 and 9, which include fibrous carbon-containing materials and plate-shaped carbon-containing materials, Example 7, in which the fibrous carbon-containing material and the plate-shaped carbon-containing material satisfy ta < 20da (where da is the average fiber diameter of the fibrous carbon-containing material and ta is the average thickness of the plate-shaped carbon-containing material), showed superior gas generation rate, 5C / 0.2C discharge capacity maintenance rate, and cycle capacity maintenance rate. This is thought to be because the average thickness of the plate-shaped carbon-containing material was not too large relative to the average fiber diameter of the fibrous carbon-containing material, thus suppressing the coating of the plate-shaped carbon-containing material by the fibrous carbon-containing material, and as a result, the dispersibility of the fibrous carbon-containing material in the electrode was good.

[0270] Examples 1, 10, and 12 revealed that even when the type of niobium-containing oxide in the negative electrode active material was varied, secondary batteries with low gas generation, high 5C / 0.2C discharge capacity retention, and high cycle capacity retention could be obtained.

[0271] Comparative Example 1, like Example 6, used a liquid-phase spray drying method for the synthesis of niobium-containing oxide. However, the grinding conditions using a dry ball mill were more shear-forced than in Example 6, and the process was carried out for a longer period of 48 hours, resulting in excessively high shear force. Consequently, the crystallinity of the niobium-containing oxide particle surface decreased, leading to a higher hydroxyl group content in the niobium-containing oxide, which is thought to have resulted in a higher gas generation rate.

[0272] Comparative Example 2 was a secondary battery made using the same materials as Example 6, but it had a higher functional group content in the carbon-containing material. This is thought to be because, in the preparation of the negative electrode slurry, the peripheral speed of the bead mill used for dispersion was too high and the flow rate was too low, resulting in excessive shear force. This reduced the crystallinity of the carbon-containing material and caused a reaction between the solvent and the carbon-containing material, leading to the addition of functional groups to the carbon-containing material. Comparative Example 2 was inferior to Example 6 in terms of gas generation amount, 5C / 0.2C discharge capacity maintenance rate, and cycle capacity maintenance rate.

[0273] Comparative Example 3 was inferior to the Examples in terms of gas generation amount, 5C / 0.2C discharge capacity retention rate, and cycle capacity retention rate. The negative electrode of the secondary battery in Comparative Example 3 contains MWCNTs as a fibrous carbon-containing material and furnace black as granular carbon. MWCNTs tend to have a higher functional group content compared to SWCNTs, which are also fibrous carbons. Furnace black also tends to have a higher functional group content compared to acetylene black, which is also a granular carbon. As a result of using carbon-containing materials with such high functional group content, the total functional group content of the carbon-containing material exceeded 5 mmol / g, which is thought to have increased gas generation and reduced the 5C / 0.2C discharge capacity retention rate and cycle capacity retention rate.

[0274] An electrode is provided according to at least one embodiment or example described above. The electrode comprises a niobium-containing oxide and a carbon-containing material. The hydroxyl group content of the niobium-containing oxide is 0.25 mmol / g or less. The functional group content of the carbon-containing material is 5 mmol / g or less. The electrode has suppressed gas generation and high output performance.

[0275] The invention according to the embodiment is described below.

[0276] [1] comprising a niobium-containing oxide and a carbon-containing material, The hydroxyl group content of the niobium-containing oxide is 0.25 mmol / g or less. An electrode in which the functional group content of the carbon-containing material is 5 mmol / g or less.

[0277] [2] The electrode according to [1], wherein the carbon-containing material comprises a fibrous carbon-containing material having an average fiber diameter of 10 nm or less.

[0278] [3] The electrode according to [1] or [2], wherein the carbon-containing material comprises crystalline carbon black.

[0279] [4] The carbon-containing material comprises the fibrous carbon-containing material and the granular carbon-containing material, satisfying formula A, Formula A: db<10da The electrode according to [2] or [3], wherein in formula A, da is the average fiber diameter and db is the average particle size of the granular carbon-containing material.

[0280] [5] The carbon-containing material includes the fibrous carbon-containing material and the plate-shaped carbon-containing material, and satisfies formula B, Formula B: ta<20da The electrode according to any one of [2] to [4], wherein in formula B, da is the average fiber diameter and ta is the average thickness of the flat carbon-containing material.

[0281] [6] comprising a positive electrode, a negative electrode, and an electrolyte, The negative electrode is a secondary battery having the electrode described in any one of items [1] to [5].

[0282] A battery pack including the rechargeable batteries described in [7] [6].

[0283] [8] The battery pack described in [7] further includes an external terminal for power supply and a protection circuit.

[0284] [9] Including a plurality of the aforementioned secondary batteries, The battery pack described in [7] or [8], wherein the secondary batteries are electrically connected in series, in parallel, or in a combination of series and parallel.

[0285] A vehicle equipped with a battery pack as described in any one of the following items:

[10] [7] to [9].

[0286]

[11] The vehicle according to

[10] , which includes a mechanism for converting the kinetic energy of the vehicle into regenerative energy.

[0287] 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]

[0288] 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 containing layer, 6…Negative electrode terminal, 7…Positive electrode terminal, 21…Bus bar, 22…Positive electrode side lead, 22a…Other end, 23…Negative electrode side lead, 23a…Other end, 24…Adhesive tape, 31…Housing container, 32…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, 100…Secondary battery, 200…Battery pack, 200a…Battery pack, 200b…Battery pack, 200c…Battery pack, 300…Battery pack, 30 0a...Battery pack, 300b...Battery pack, 300c...Battery pack, 301a...Battery pack monitoring device, 301b...Battery pack monitoring device, 301c...Battery pack monitoring device, 342...Positive side connector, 343...Negative side connector, 345...Thermistor, 346...Protection circuit, 342a...Wiring, 343a...Wiring, 350...External terminal for 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. It contains niobium-containing oxide and carbon-containing material, The hydroxyl group content of the niobium-containing oxide is 0.25 mmol / g or less. An electrode having a functional group content of 5 mmol / g or less in the carbon-containing material.

2. The electrode according to claim 1, wherein the carbon-containing material includes a fibrous carbon-containing material having an average fiber diameter of 10 nm or less.

3. The electrode according to claim 1, wherein the carbon-containing material includes crystalline carbon black.

4. The carbon-containing material comprises the fibrous carbon-containing material and the granular carbon-containing material, and satisfies formula A. Formula A: db<10da The electrode according to claim 2, wherein in formula A, da is the average fiber diameter and db is the average particle size of the granular carbon-containing material.

5. The carbon-containing material includes the fibrous carbon-containing material and the plate-shaped carbon-containing material, and satisfies formula B. Formula B: ta<20da The electrode according to claim 2, wherein in formula B, da is the average fiber diameter and ta is the average thickness of the flat carbon-containing material.

6. It includes a positive electrode, a negative electrode, and an electrolyte. The negative electrode is the electrode described in any one of claims 1 to 5, in a secondary battery.

7. A battery pack including the secondary battery described in claim 6.

8. The battery pack according to claim 7, further comprising an external terminal for power supply and a protection circuit.

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

10. A vehicle equipped with the battery pack described in claim 7.

11. The vehicle according to claim 10, which includes a mechanism for converting the kinetic energy of the vehicle into regenerative energy.

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