Electrodes, secondary batteries, battery packs, and vehicles

Abstract

To provide electrodes that can realize a secondary battery with high input / output density, a secondary battery and battery pack with high input / output density, and a vehicle including this battery pack. [Solution] According to the embodiment, an electrode is provided that includes a plurality of active material particles and fibrous carbon. The fibrous carbon includes a first portion having a fiber diameter W1 in the range of 60 nm to 500 nm, and a second portion having a fiber diameter W2 smaller than the fiber diameter W1. At least a portion of at least the second portion is in contact with the plurality of active material particles.

Description

[Technical Field]

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

[0002] Lithium-ion batteries, such as non-aqueous electrolyte batteries, which charge and discharge by the movement of lithium ions between the negative and positive electrodes, are being actively researched as high-energy-density batteries.

[0003] Typical electrodes in secondary batteries such as lithium-ion batteries contain an electrode active material that contributes to charging and discharging through the insertion and removal of lithium ions, as well as a conductive agent to enhance the electrical conductivity of the electrodes. Carbon materials are widely used as conductive agents to be included in electrodes. [Prior art documents] [Patent Documents]

[0004] [Patent Document 1] Japanese Patent Publication No. 2020-47437 [Patent Document 2] International Publication No. 2024 / 070095 [Non-patent literature]

[0005] [Non-Patent Document 1] "Practical Aspects of Powder X-ray Radiation Analysis," First Edition (2002), edited by the X-ray Radiation Analysis Research Group of the Japan Society for Analytical Chemistry, authored by Izumi Nakai and Fujio Izumi (Asakura Shoten). [Overview of the project] [Problems that the invention aims to solve]

[0006] The objective is to provide electrodes that can realize a secondary battery with high input / output density, a secondary battery and battery pack with high input / output density, and a vehicle including this battery pack. [Means for solving the problem]

[0007] According to the embodiment, an electrode is provided that includes a plurality of active material particles and fibrous carbon. The fibrous carbon includes a first portion having a fiber diameter W1 in the range of 60 nm to 500 nm, and a second portion having a fiber diameter W2 smaller than the fiber diameter W1. At least a portion of at least the second portion is in contact with the plurality of active material particles.

[0008] In another embodiment, a secondary battery is provided that comprises a positive electrode, a negative electrode, and an electrolyte. At least one of the positive electrode and the negative electrode is the electrode according to the above embodiment.

[0009] According to another embodiment, a battery pack comprising a secondary battery according to the above embodiment is provided.

[0010] According to other embodiments, a vehicle is provided that is equipped with the battery pack according to the above embodiment. [Brief explanation of the drawing]

[0011] [Figure 1] A schematic cross-sectional view showing an example of an electrode according to the embodiment. [Figure 2] An enlarged cross-sectional view of part A of the electrode shown in Figure 1. [Figure 3] A schematic cross-sectional view showing an example of a conventional electrode. [Figure 4] A schematic cross-sectional view showing an example of a secondary battery according to this embodiment. [Figure 5] An enlarged cross-sectional view of section B of the secondary battery shown in Figure 4. [Figure 6] A schematic partial cutaway perspective view showing another example of a secondary battery according to the embodiment. [Figure 7] An enlarged cross-sectional view of section C of the secondary battery shown in Figure 6. [Figure 8] A schematic perspective view showing an example of a battery pack according to this embodiment. [Figure 9] An exploded perspective view schematically showing an example of a battery pack according to this embodiment. [Figure 10]A block diagram showing an example of the electrical circuit of the battery pack shown in Figure 9. [Figure 11] A partially transparent view schematically showing an example of a vehicle according to the embodiment. [Figure 12] 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]

[0012] To obtain low-resistance electrodes, large amounts of carbon materials such as granular carbon or fibrous carbon are generally added. However, adding large amounts of granular or fibrous carbon increases the volume ratio of carbon in the electrode body. In electrodes using metal oxides as the active material, the proportion of the active material is small, making it difficult to obtain electrodes with high input / output density per unit volume. It is conceivable to increase the input / output density while suppressing the carbon ratio of the electrode body by using a small amount of fibrous carbon with a fine fiber diameter, but fine fibrous carbon is difficult to disperse and form into electrodes, making it difficult to obtain sufficient input / output density.

[0013] The embodiments will be described below with reference to the drawings. Common components throughout the embodiments will be denoted by the same reference numerals, and redundant explanations will be omitted. Furthermore, each drawing is a schematic diagram intended to illustrate the embodiments and facilitate understanding; their shapes, dimensions, and ratios may differ from those of the actual device. These can be appropriately modified in accordance with the following description and known technology.

[0014] (First embodiment) According to the first embodiment, an electrode is provided. The electrode comprises active material particles and fibrous carbon. The fibrous carbon comprises a first portion and a second portion. The first portion has a fiber diameter W1 in the range of 60 nm to 500 nm. The second portion has a fiber diameter W2 smaller than the fiber diameter W1 of the first portion. The electrode contains a plurality of active material particles, and at least a portion of the second portion of the fibrous carbon is in contact with the plurality of active material particles.

[0015] In this electrode, both good conductive paths and high density can be achieved. Therefore, the input / output density of the electrode is high. Specifically, by including fibrous carbon materials with different fiber diameters as a conductive agent, the electrical resistance of the electrode is low and conductive paths can be easily formed. Furthermore, even when the electrode is made high-density, voids can be secured within the electrode, so the diffusion of the liquid within the electrode is not easily hindered. Therefore, the diffusion of the liquid electrolyte, i.e., electrolyte solution, within the electrode is good, which also contributes to the excellent input / output performance of the secondary battery.

[0016] The electrode in question may include a current collector and an active material-containing layer. The active material-containing layer may be formed on one or both sides of the current collector. The active material-containing layer may include an active material and a conductive agent, and optionally include a binder. The conductive agent may include fibrous carbon containing at least the first and second parts described above. The conductive agent may further include other materials described later, such as granular carbon. The current collector may include portions on its surface where the active material-containing layer is not formed. These portions can function as current-collecting tabs.

[0017] Figures 1 and 2 show an example of an electrode according to the embodiment. Figure 1 schematically shows a cross-section of the electrode, and Figure 2 is an enlarged cross-sectional view of part A in Figure 1.

[0018] The example electrode 10 includes a current collector 10a and active material-containing layers 10b provided on both its front and back surfaces. A portion of the current collector 10a does not have the active material-containing layers 10b provided on either its front or back surface, and this portion can function as a current-collecting tab 10c. The active material-containing layers 10b contain a plurality of active material particles 11 and fibrous carbon 12.

[0019] The fibrous carbon 12 contains a first portion C1 with a thick fiber diameter and a second portion C2 with a thin fiber diameter. By including fibrous carbon 12 containing both the thick first portion C1 and the thin second portion C2, good conductive paths can be formed in the active material-containing layer 10b, so the electrode 10 can realize a secondary battery with excellent input / output performance. Furthermore, since conductive paths can be formed with a small amount of fibrous carbon 12, the fibrous carbon 12 does not become bulky, and the density of the active material-containing layer 10b can be increased while maintaining the voids between the active material particles 11. Therefore, the electrode 10 can realize a secondary battery with high input / output density.

[0020] As shown in the figure, the first part C1 and the second part C2 may be different fibrous carbon 12, or different parts of the same fibrous carbon 12 may be the first part C1 and the second part C2, as shown in Figure 2 where multiple second parts C2 branch off from the first part C1 on the right. Including fibrous carbon 12 in which the first part C1 and the second part C2 are integrated, as in the latter case, makes it easier to form a stronger conductive path. In the active material-containing layer 10b which includes both the first part C1 and the second part C2 as shown in the figure, both the first part C1 and the second part C2 can come into contact with multiple active material particles 11, but the second part C2, which is thinner and more easily dispersed, can come into contact with more active material particles 11 more reliably.

[0021] In the illustrated example, the active material-containing layer 10b further contains fine oxide particles 13 on the surface of the active material particles 11. The fine oxide particles 13 can be generated, for example, by adjusting the synthesis conditions during active material synthesis, as described later, or by generating them on the particle surface after active material synthesis. By having the fine oxide particles 13 on the particle surface of the active material particles 11, the contact between the fibrous carbon 12 and the active material particles 11 is improved.

[0022] For comparison, an example of a conventional electrode is shown in Figure 3. Figure 3 shows a magnified cross-section similar to that in Figure 2. The conventional electrode 14 shown also includes a current collector 14a and an active material-containing layer 14b provided on top of it, which contains active material particles 11. However, in the conventional example, the active material-containing layer 14b contains granular carbon 15 as a conductive agent instead of fibrous carbon 12.

[0023] Unlike fibrous carbon 12, granular carbon 15 is bulky. Electrodes containing a large amount of bulky granular carbon 15 to enhance conductivity, such as the electrode 14 shown in the example, are thick, making it difficult to obtain a good input / output density. In addition, there is a concern that the large amount of granular carbon 15 will aggregate, as shown in the figure. When granular carbon 15 aggregates, the electrode density further decreases, or the formation of conductive paths becomes poor. Thus, attempting to obtain high conductivity using only granular carbon 15 requires the use of a large amount of granular carbon 15, resulting in a large electrode volume and making it difficult to obtain a good input / output density.

[0024] Fibrous carbon is, for example, carbon nanotubes (CNTs). The first part C1 may be, for example, a bundled portion of single-walled carbon nanotubes (SWCNTs). The second part C2 may be, for example, unbundled SWCNTs. Fibrous carbon in which the first part C1 and the second part C2 are integrated may be, for example, a bundle of the first part C1 that has partially unraveled and separated into the second part C2. CNTs are not limited to SWCNTs; carbon nanotubes with two or more layers (for example, few-walled carbon nanotubes (FWCNTs)) can also be used.

[0025] By including a first portion C1, such as bundled carbon nanotubes (CNTs), in the active material-containing layer, the current efficiency in the active material-containing layer is locally improved, leading to a reduction in the overall resistance of the electrode. The second portion C2 can be dispersed more effectively within the active material-containing layer than the first portion C1, and at least a portion of it comes into contact with multiple active material particles. The dispersion of the second portion C2 allows fibrous carbon to be distributed throughout the entire active material-containing layer, eliminating localized unreacted or high-resistance areas within the electrode. Note that if the second portion C2 is included alone as fibrous carbon without the first portion C1, it is difficult to disperse the second portion C2. By using the second portion C2 in combination with the first portion C1, dispersion in the active material-containing layer can be improved, and a good conductive path can be formed.

[0026] The fiber diameter W1 of the first part C1 is within the range of 60 nm or more and 500 nm or less. The first part C1 with a fiber diameter W1 of 60 nm or more has a high above-described effect of reducing the electrical resistance of the electrode. By keeping the fiber diameter W1 at 500 nm or less, the first part C1 does not become bulky, so that the density of the active material-containing layer can be increased, and the ratio of the active material particles in the active material-containing layer can be increased, thus increasing the energy density of the electrode.

[0027] The fiber diameter W2 of the second part C2 is smaller than the fiber diameter W1. The fiber diameter W2 can be, for example, within the range of 1 nm or more and 15 nm or less. When the fiber diameter W2 is within this range, the aggregation of the second part C2 is less and the dispersion is better, so a fiber diameter W2 of 1 nm or more and 15 nm or less is preferable.

[0028] The ratio between the first part C1 and the second part C2 of the fibrous carbon can be, for example, a ratio such that the area ratio between the area A1 occupied by the first part C1 and the area A2 occupied by the second part C2 on the electrode surface is 0.5 < A1 / A2 < 50. That is, the ratio occupied by the first part C1 of the fibrous carbon may be larger, or the ratio occupied by the second part C2 may be larger. It is desirable that each exists in a well-balanced manner and neither is extremely small. Since the first part C1 with a thicker diameter has a larger area per unit length, when the first part C1 and the second part C2 exist on the electrode surface for the same fiber length, the area ratio A1 / A2 exceeds 1.

[0029] The longer the fiber length of the fibrous carbon, the more it can span over many active material particles in the electrode and form a better conductive path. For example, the fibrous carbon on the electrode surface may include those in which the ratio of the length L to the fiber diameter W2 of the second part C2 is 100 < L / W2. The method for measuring the length L of the fibrous carbon will be described later.

[0030] The electrode in question can be, for example, at least one of the positive and negative electrodes of a battery. In a battery that includes such an electrode as the negative electrode, the positive electrode may be other than the electrode according to the embodiment. Conversely, in a battery that includes such an electrode as the positive electrode, the negative electrode may be other than the electrode according to the first embodiment. Both the negative electrode and the positive electrode included in the battery can be the electrodes according to the first embodiment.

[0031] Hereinafter, the electrode according to the embodiment will be described in detail.

[0032] The active material-containing layer may contain one type of active material alone, or may contain two or more types of active materials. Such an electrode can include, for example, the following negative electrode active material in the active material-containing layer (negative electrode active material-containing layer) in the aspect as a negative electrode, and can include the following positive electrode active material in the active material-containing layer (positive electrode active material-containing layer) in the aspect as a positive electrode.

[0033] Examples of the negative electrode active material include titanium oxide, lithium titanium oxide, niobium titanium oxide, niobium oxide, etc. Specifically, lithium titanate having a lamellar 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, niobium pentoxide (Nb2O5), hollandite-type titanium composite oxide, orthorhombic titanium composite oxide, and monoclinic niobium titanium oxide. Among the above, examples of more preferable compounds as the negative electrode active material include lithium titanate having a spinel structure and monoclinic niobium titanium oxide.

[0034] Examples of the above orthorhombic titanium-containing composite oxide include compounds represented by Li 2+a M I 2-b Ti 6-c M II d O 14+σ Here, M IIt 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.

[0035] As an example of the above monoclinic type niobium titanium oxide, Li x Ti 1-y M1 y Nb 2-z M2 z O 7+δ Examples of compounds represented by the formula are: Here, M1 is at least one selected from the group consisting of Zr, Si, and Sn. M2 is at least one selected from the group consisting of V, Ta, and Bi. The subscripts in the compositional formula are 0≦x≦5, 0≦y<1, 0≦z<2, and -0.3≦δ≦0.3. A specific example of monoclinic niobium titanium oxide is Li x Nb2TiO7 (0≦x≦5) is one example.

[0036] Another example of monoclinic niobium titanium oxide is Li x Ti 1-y M3 y+z Nb 2-z O 7-δ A compound represented by the formula is shown below. Here, M3 is at least one selected from Mg, Fe, Ni, Co, W, Ta, and Mo. In the compositional formula, each subscript represents 0≦x≦5, 0≦y<1, 0≦z<2, and -0.3≦δ≦0.3.

[0037] As the positive electrode active material, for example, an oxide or a sulfide can be used. The positive electrode may contain, as the positive electrode active material, one type of compound alone, or may contain a combination of two or more types of compounds. Examples of the oxide and the sulfide include compounds into which Li or Li ions can be inserted and extracted.

[0038] Examples of such compounds include manganese dioxide (MnO2), iron oxide, copper oxide, nickel oxide, lithium manganese composite oxide (for example, Li x Mn2O4 or Li x MnO2; 0 < x ≦ 1), lithium nickel composite oxide (for example, Li x NiO2; 0 < x ≦ 1), lithium cobalt composite oxide (for example, Li x CoO2; 0 < x ≦ 1), lithium nickel cobalt composite oxide (for example, Li x Ni 1-y Co y O2; 0 < x ≦ 1, 0 < y < 1), lithium manganese cobalt composite oxide (for example, Li x Mn y Co 1-y O2; 0 < x ≦ 1, 0 < y < 1), lithium nickel manganese composite oxide having a spinel structure (for example, Li x Ni y Mn 2-y O4; 0 < x ≦ 1, 0 < y < 2), lithium phosphate having an olivine structure (for example, Li x FePO4; 0 < x ≦ 1, Li x MnPO4; 0 < x ≦ 1, Li x Fe 1-y Mn y PO4; 0 < x ≦ 1, 0 < y ≦ 1, Li x CoPO4; 0 < x ≦ 1), iron sulfate (Fe2(SO4)3), vanadium oxide (for example, V2O5), and lithium nickel cobalt manganese composite oxide (Li x Ni 1-y-z Co y Mn z O2; 0 < x ≦ 1, 0 < y < 1, 0 < z < 1, y + z < 1) are included.

[0039] Among the above, examples of more preferable compounds as the positive electrode active material include lithium manganese composite oxides having a spinel structure (for example, Li x Mn2O4; 0 < x ≦ 1), lithium nickel composite oxides (for example, Li x NiO2; 0 < x ≦ 1), lithium cobalt composite oxides (for example, Li x CoO2; 0 < x ≦ 1), lithium nickel cobalt composite oxides (for example, Li x Ni 1-y Co y O2; 0 < x ≦ 1, 0 < y < 1), lithium nickel manganese composite oxides having a spinel structure (for example, Li x Ni y Mn 2-y O4; 0 < x ≦ 1, 0 < y < 2), lithium manganese cobalt composite oxides (for example, Li x Mn y Co 1-y O2; 0 < x ≦ 1, 0 < y < 1), lithium iron phosphate (for example, Li x FePO4; 0 < x ≦ 1), lithium nickel cobalt manganese composite oxides (Li x Ni 1-y-z Co y Mn z O2; 0 < x ≦ 1, 0 < y < 1, 0 < z < 1, y + z < 1), and lithium phosphates having an olivine structure (for example, Li x FePO4; 0 < x ≦ 1, Li x MnPO4; 0 < x ≦ 1, Li x Mn 1-y Fe y PO4; 0 < x ≦ 1, 0 < y ≦ 1, Li x CoPO4; 0 < x ≦ 1) are included. When these compounds are used as the positive electrode active material, the positive electrode potential can be increased. As a specific example, a positive electrode active material containing one or more selected from the group consisting of the above lithium nickel cobalt manganese composite oxide, lithium phosphate, and lithium nickel manganese composite oxide can be mentioned.

[0040] When a room temperature molten salt is used as the electrolyte of the battery, lithium iron phosphate, Li xIt is preferable to use a positive electrode active material containing VPO4F (0 ≤ x ≤ 1), lithium manganese composite oxide, lithium nickel composite oxide, lithium nickel cobalt composite oxide, or a mixture thereof. These compounds have low reactivity with room-temperature molten salts, thus improving cycle life. Details of the room-temperature molten salts will be described later in the second embodiment.

[0041] The primary particle size of the positive electrode active material is preferably between 100 nm and 1 μm. Positive electrode active material with a primary particle size of 100 nm or more is easy to handle in industrial production. Positive electrode active material with a primary particle size of 1 μm or less allows for smooth diffusion of lithium ions within the solid.

[0042] The specific surface area of ​​the positive electrode active material is 0.1 m². 2 / g or more 10m 2 It is preferable that it is less than or equal to / g. 0.1m 2 A positive electrode active material with a specific surface area of ​​10m or more can adequately secure sites for Li ion intercalation and release. 2 Positive electrode active materials with a specific surface area of ​​less than / g are easy to handle in industrial production and can ensure good charge-discharge cycle performance.

[0043] The conductive agent is formulated to enhance current collection performance and reduce contact resistance between the active material and the current collector. The conductive agent comprises at least fibrous carbon containing a first part C1 and a second part C2. In addition to the fibrous carbon, other conductive agents may be further included. Examples of other conductive agents include carbonaceous materials such as vapor-grown carbon fiber (VGCF), carbon black such as acetylene black, graphite, multi-walled carbon nanotubes (MWCNTs), and carbon nanofibers. One of these may be used as the other conductive agent, or two or more may be used in combination as the other conductive agent. Alternatively, instead of using other conductive agents, the surface of the active material particles may be coated with a carbon coating or an electronically conductive inorganic material coating.

[0044] 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.

[0045] The proportions of active material, fibrous carbon, other conductive agents, and binders in the active material-containing layer can be appropriately changed depending on the application of the electrode. For example, in the case of a negative electrode, it is preferable to blend the active material (negative electrode active material), fibrous carbon, other conductive agents, and binders in the active material-containing layer in proportions of 68% to 97% by mass, 0.1% to 1% by mass, 0% to 1% by mass, and 2% to 30% by mass, respectively. In the case of a positive electrode, it is preferable to blend the active material (positive electrode active material), fibrous carbon, other conductive agents, and binders in the active material-containing layer in proportions of 77% to 97% by mass, 0.15% to 1% by mass, 0% to 1% by mass, and 2% to 15% by mass, respectively. 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. To increase the volume, it is preferable to limit the amount of binder to 30% by mass or less.

[0046] In both positive and negative electrode configurations, it is preferable that the total amount of carbon material included as a conductive agent, i.e., the total amount of fibrous carbon and other carbon materials used as conductive agents, be 2% by mass or less. By including fibrous carbon containing a first part C1 and a second part C2 as at least a portion of the conductive agent, the current collection performance of the active material-containing layer can be improved while reducing the total amount of conductive agent. By reducing the amount of carbon material included in the active material-containing layer, the amount of active material can be increased, and a high-capacity electrode can be obtained. Furthermore, it is preferable to have a low content of granular carbon such as carbon black and graphite, and more preferably to have no granular carbon at all. By reducing or eliminating bulky granular carbon, an electrode with high energy density can be obtained.

[0047] 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, in the case of a negative electrode, 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.

[0048] In the case of the positive electrode configuration, the 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.

[0049] 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.

[0050] The density of the negative electrode active material layer (excluding the current collector) is 1.8 g / cm³. 3 More than 2.8g / cm3 The following is preferable: The density of the negative electrode active material-containing layer is 2.1 g / cm³. 3 More than 2.7g / cm 3 The following is more preferable: The density of the positive electrode active material-containing layer (excluding the current collector) is 1.8 g / cm³. 3 More than 3.5g / cm 3 The following is preferable: The density of the positive electrode active material-containing layer is 2.1 g / cm³. 3 More than 3.3g / cm 3 The following is more preferable: Electrodes in which the density of the active material-containing layer is within this range exhibit excellent energy density and electrolyte retention.

[0051] <Manufacturing method> Electrodes can be manufactured, for example, by the following method. First, an active material, a conductive agent, and a binder are suspended in a solvent to prepare a slurry. This slurry is applied to one or both sides of a current collector. Next, the applied slurry is dried to obtain a laminate of the active material-containing layer and the current collector. After that, this laminate is pressed. In this way, electrodes are manufactured.

[0052] Alternatively, electrodes may be manufactured by the following method: First, an active material, a conductive agent, and a binder are mixed to obtain a mixture. Next, this mixture is formed into pellets. Then, electrodes can be obtained by placing these pellets on a current collector.

[0053] When using an active material that has fine oxide particles on its particle surface, it is possible to generate these fine particles after or during the synthesis of the active material particles. For example, when generating fine particles on the surface of monoclinic titanium niobium oxide (TNO) particles after synthesis, fine oxide particles of about 100 nm are mixed with the calcined TNO active material particles and heat-treated at 300°C to 400°C. This generates fine particles on the surface of the TNO active material particles.

[0054] For example, when generating fine particles during the synthesis of TNO active material particles, TiO2 and Nb2O5 are used as raw materials. After mixing these, the particles are refined by grinding before firing. Grinding is performed to a particle size D such that the cumulative volume frequency from the smallest particle size side is 10% in the particle size distribution measurement of the powder. 10 It is preferable to continue until the wavelength reaches approximately 10 nm to 100 nm.

[0055] <Measurement method> Next, we will explain the electrode measurement method. Specifically, we will describe the observation and measurement of the electrode surface using a scanning electron microscope (SEM), as well as the measurement method for the carbon material and active material contained in the electrode.

[0056] For measurement, electrodes that are not incorporated into a battery or electrodes removed from a battery can be used as samples. When removing electrodes from a battery, they should be washed with an organic solvent to ensure no lithium salt remains. First, impregnate the electrodes in a cyclic carbonate with high lithium salt solubility, then impregnate them in a chain carbonate and wash them to sufficiently reduce the amount of lithium salt remaining. After impregnation, remove the solvent by reducing the pressure under vacuum.

[0057] (SEM observation of electrodes) By observing the surface of the electrode sample with a scanning electron microscope (SEM), the presence of fibrous carbon containing the first portion C1 and the second portion C2 can be confirmed. Furthermore, the diameter W1 and area A1 of the first portion C1, the diameter W2 and area A2 of the second portion C2, and the length L of the fibrous carbon can be measured.

[0058] SEM images of the electrode surface are acquired, and the obtained SEM images are binarized. During binarization, thresholds are set to distinguish between active material particles and carbon materials such as fibrous carbon and granular carbon. Software such as Image-J can be used for this purpose.

[0059] Fibrous carbon and granular carbon differ in shape. Fibrous carbon has a high aspect ratio, possesses length relative to its fiber diameter, and can have straight or curved sections. If the aspect ratio is 5 or greater, it is considered fibrous carbon. Fibrous carbon can come into contact with multiple active material particles or granular carbon particles. Granular carbon has a low aspect ratio, and irregularly shaped particles can exist individually or in clusters. If the aspect ratio is 3 or less, it is considered granular carbon. Furthermore, the diameter of granular carbon is defined as the diameter of the largest circle inscribed within the particle; for example, the diameter of a single granular particle may be 800 nm or less. Moreover, the diameter of a single granular particle may be 400 nm or less.

[0060] The fiber diameter of fibrous carbon is estimated from the binarized image. The first part C1 is the region in the binarized image where the fiber diameter W1 is between 60 nm and 500 nm. Regions with fiber diameters close to 60 nm and 500 nm can be detected from the image. The fiber diameter W1 is defined by drawing a 50 nm straight line along one side of the fiber, drawing a perpendicular line from it, and measuring the distance from end to end of the fiber along the perpendicular line. Fibrous carbon can exist on active material particles, on granular particles, and between particles.

[0061] The second portion C2 is a portion with a smaller fiber diameter than the first portion C1, and a fiber diameter of 1 nm to 15 nm is preferred. Portions smaller than 60 nm can be detected from the image. Similar to the measurement of the fiber diameter W1 of the first portion C1, the fiber diameter W2 is determined by drawing a 50 nm straight line along one side of the fiber, drawing a perpendicular line, and taking the distance from the perpendicular line to the end of the fiber as the fiber diameter W2.

[0062] From the binarized image, the area A1 of the first part C1 and the area A2 of the second part C2 can be determined using image analysis software.

[0063] The fibrous carbon confirmed by SEM image preferably satisfies 100 < L / W2. The length L is determined for the fibrous carbon that at least partially satisfies W2. The length L does not have to be a straight line. For fibrous carbon including a curve, the length L is determined from image analysis software. The fibrous carbon may exist across a plurality of active material particles. Further, the fibrous carbon may be branched. When branched, any branch may be selected to determine the length L.

[0064] (Measurement method of carbon material) The amount of the carbon material contained in the electrode can be measured by thermogravimetry (TG). Since the ablation temperature is different between fibrous carbon and granular carbon, the amounts of fibrous carbon and granular carbon can be measured by TG, respectively. Specifically, TG measurement is performed in air, held at 500 °C for 1 hour, and the reduced weight is taken as the weight of the binder. Then, the temperature is raised, held at 650 °C for 1 hour, and the reduced weight loss is taken as the weight of the fibrous carbon. Then, the temperature is raised again, held at 800 °C for 1 hour, and the reduced weight loss is taken as the weight of the granular carbon.

[0065] (Measurement method of active material) The composition of the active material contained in the electrode can be determined by measuring as follows.

[0066] By combining elemental analysis using a scanning electron microscope (SEM-EDX) equipped with an energy-dispersive X-ray analyzer, X-ray diffraction (XRD) measurement, and inductively coupled plasma (ICP) emission spectroscopy, the composition of the active material contained in the electrode, for example, the active material-containing layer, can be confirmed. SEM-EDX analysis allows us to determine the shape of the components contained in the active material-containing layer and the composition of those components (elements B to U in the periodic table). ICP measurement allows for the quantitative determination of elements in the active material-containing layer. Finally, XRD measurement allows us to confirm the crystal structure of the material contained in the active material-containing layer.

[0067] The cross-section of the electrode extracted as described above is cut out by Ar ion milling. The cut-out cross-section is observed using a scanning electron microscope (SEM). Sample sampling is also carried out in an inert atmosphere such as argon or nitrogen, without exposure to air. Several particles are selected from the 3000x SEM image. At this time, the selection is made so that the particle size distribution of the selected particles is as broad as possible.

[0068] Next, elemental analysis is performed on each selected particle using EDX. This allows us to identify the types and amounts of elements other than Li contained in each selected particle.

[0069] Regarding Li, information about the Li content in the entire active material can be obtained by ICP emission spectroscopy. ICP emission spectroscopy is performed according to the following procedure.

[0070] From the dried electrodes, a powder sample is prepared as follows: The active material-containing layer is peeled off the current collector and ground in a mortar. The ground sample is dissolved in acid to prepare a liquid sample. Hydrochloric acid, nitric acid, sulfuric acid, or hydrogen fluoride can be used as the acid. By subjecting this liquid sample to ICP emission spectroscopy, the concentrations of elements contained in the active material being measured can be determined.

[0071] The crystal structure of the compound contained in each particle selected by SEM can be determined by XRD measurement. The XRD measurement is performed using CuKα radiation as the source in the measurement range of 2θ = 5° to 90°. This measurement allows us to obtain the X-ray diffraction pattern of the compound contained in the selected particle.

[0072] For XRD measurements, we will use the Rigaku SmartLab. The measurement conditions will be as follows: X-ray source: Cu target Output: 45kV, 200mA Solar slit: 5° for both incident and received light. Step size (2θ): 0.02deg Scan speed: 20deg / min Semiconductor detector: D / teX Ultra 250 Sample plate holder: Flat glass sample plate holder (thickness 0.5 mm) Measurement range: 5° ≤ 2θ ≤ 90°.

[0073] If other equipment is used, measurements should be performed using standard Si powder for powder X-ray diffraction to find conditions that yield peak intensity, full width at half maximum, and diffraction angle equivalent to those obtained with the above equipment, and then the sample should be measured under those conditions.

[0074] The XRD measurement conditions should be such that an XRD pattern suitable for Rietveld analysis can be obtained. Specifically, to collect data for Rietveld analysis, the step size should be set to 1 / 3 to 1 / 5 of the minimum full width at half maximum of the diffraction peak, and the measurement time or X-ray intensity should be adjusted as appropriate so that the intensity at the peak position of the most intense reflection is 5000 cps or more.

[0075] The XRD patterns obtained as described above are analyzed using the Rietveld method. In the Rietveld method, the diffraction pattern is calculated from a pre-estimated crystal structure model. The crystal structure model is estimated here based on the analysis results from EDX and ICP. By fitting all of these calculated values ​​with the measured values, parameters related to the crystal structure (lattice constants, atomic coordinates, occupancy, etc.) can be precisely analyzed.

[0076] Rietveld analysis can be used to estimate the content of titanium niobium composite oxide, for example, when the negative electrode contains multiple active materials. A fitting parameter S is used as a measure to estimate the degree of agreement between the observed intensity and the calculated intensity in Rietveld analysis. The analysis must be performed so that S is less than 1.8. In addition, the standard deviation σj must be taken into consideration when determining the occupancy rate of each site. The fitting parameter S and standard deviation σj defined here shall be estimated using the formula described in Non-Patent Literature 1 ("Practical Aspects of Powder X-ray Analysis," edited by the X-ray Analysis Research Group of the Japan Society for Analytical Chemistry, Izumi Nakai and Fujio Izumi (Asakura Shoten)).

[0077] XRD measurements can be performed by directly attaching the electrode sample to the glass holder of a wide-angle X-ray diffractometer. In this process, it is necessary to pre-measure the XRD spectrum according to the type of metal foil used for the electrode current collector to determine where peaks originating from the current collector appear. It is also important to pre-determine the presence or absence of peaks from conductive agents and binders. If the current collector peak and the active material peak overlap, it is desirable to peel the active material-containing layer from the current collector before measurement. This is to separate the overlapping peaks when quantitatively measuring the peak intensity. Of course, if these factors are known in advance, this step can be omitted.

[0078] For example, if the particles observed by the aforementioned SEM-EDX measurement contain Ti, Nb, and O, and furthermore, if the aforementioned XRD measurement yields an X-ray diffraction pattern attributed to a monoclinic type from the electrode being measured, it can be determined that the active material being measured contains particles of monoclinic titanium niobium composite oxide. If the EDX measurement reveals particles with significantly different Ti and Nb content, it is possible that multiple active materials are present. The amount of elements contained in the active material in the electrode can be determined by ICP emission spectroscopy following the procedure described earlier.

[0079] The amount of active material in the active material-containing layer can be estimated using the following method.

[0080] After cleaning and drying the electrodes removed from the battery using the procedure described earlier, the active material-containing layer is peeled off the current collector and ground in a mortar. The ground sample is placed on a glass sample plate and leveled so that the surface of the sample matches the surface of the glass sample plate. A Si standard sample may also be added to correct the peak position.

[0081] XRD measurements and Rietveld analysis are performed on the powder sample packed into a glass sample plate under the conditions described above. SEM-EDX measurements and ICP measurements are also performed on the powder sample using the procedure described above. Considering the results of the XRD, SEM-EDX, and ICP measurements, the types and proportions of active materials present can be estimated.

[0082] The electrode according to the first embodiment includes a plurality of active material particles and fibrous carbon comprising a first portion (C1) with a fiber diameter of 60 nm to 500 nm and a second portion (C2) with a smaller fiber diameter, at least a portion of which is in contact with the plurality of active material particles. Such an electrode can provide a secondary battery and battery pack with high input / output density.

[0083] (Second embodiment) According to the second embodiment, a secondary battery is provided that includes a positive electrode, a negative electrode, and an electrolyte. This secondary battery includes an electrode according to the first embodiment as at least one of the positive electrode and the negative electrode. When the electrode according to the first embodiment is included as the negative electrode, the positive electrode may be a different electrode from that of the first embodiment. When the electrode according to the first embodiment is included as the positive electrode, the negative electrode may be a different electrode from that of the first embodiment. The secondary battery according to the second embodiment may also include both the negative electrode and positive electrode embodiments of the electrode according to the first embodiment, respectively, as the negative electrode and the positive electrode.

[0084] The secondary battery may further include a separator positioned between the positive electrode and the negative electrode. The negative electrode, positive electrode, and separator can constitute an electrode group. The electrolyte can be held within the electrode group.

[0085] Furthermore, the secondary battery may further comprise an outer casing that houses the electrode group and the electrolyte.

[0086] 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.

[0087] 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.

[0088] The following provides a detailed explanation of the negative electrode, positive electrode, electrolyte, separator, outer casing, negative electrode terminal, and positive electrode terminal.

[0089] 1) Negative electrode The negative electrode may include a negative electrode current collector and a negative electrode active material-containing layer. The negative electrode may be an embodiment of the negative electrode of the electrode according to the first embodiment. Therefore, 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.

[0090] Regarding the details of the negative electrode, any parts that overlap with the details described regarding the negative electrode configuration of the electrode according to the first embodiment are omitted. For example, other negative electrodes that can be used in a battery containing the electrode according to the first embodiment as the positive electrode differ from the electrode according to the first embodiment in that they do not contain fibrous carbon containing both the first portion C1 and the second portion C2 as a conductive agent.

[0091] In the negative electrode active material-containing layer of the other negative electrode, it is preferable to blend the negative electrode active material, conductive agent, and binder in proportions of 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 negative electrode 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 in order to achieve high capacity.

[0092] Other negative electrodes can be manufactured by the same method as the electrode according to the first embodiment, except that, for example, fibrous carbon containing both the first portion C1 and the second portion C2 as a conductive agent is not used.

[0093] 2) Positive electrode The positive electrode may include a positive electrode current collector and a positive electrode active material-containing layer. The positive electrode may be an embodiment of the positive electrode of the electrode according to the first embodiment. Therefore, the positive electrode current collector and the positive 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.

[0094] Regarding the details of the positive electrode, any parts that overlap with the details described regarding the positive electrode configuration of the electrode according to the first embodiment are omitted. For example, other positive electrodes that can be used in a battery containing the electrode according to the first embodiment as the negative electrode differ from the electrode according to the first embodiment in that they do not contain fibrous carbon containing both the first portion C1 and the second portion C2 as a conductive agent.

[0095] In the positive electrode active material-containing layer of the other positive electrode, 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.

[0096] 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.

[0097] When a conductive agent is added, it is preferable that the positive electrode active material, binder, and conductive agent are blended in proportions of 77% to 95% by mass, 2% to 20% by mass, and 3% to 15% by mass, respectively.

[0098] The above-mentioned effects can be achieved by increasing the amount of conductive agent to 3% by mass or more. Furthermore, by reducing the amount of conductive agent to 15% by mass or less, the proportion of conductive agent in contact with the electrolyte can be reduced. This lower proportion reduces the decomposition of the electrolyte under high-temperature storage conditions.

[0099] The positive electrode can be manufactured by the same method as the electrode according to the first embodiment, except that, for example, fibrous carbon containing both the first portion C1 and the second portion C2 as a conductive agent is not used.

[0100] 3) Electrolyte As the electrolyte, for example, a liquid non-aqueous electrolyte or a gel-type non-aqueous electrolyte can be used. A liquid non-aqueous electrolyte is prepared by dissolving an electrolyte salt as a solute in an organic solvent. The concentration of the electrolyte salt is preferably 0.5 mol / L or more and 2.5 mol / L or less.

[0101] 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.

[0102] 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.

[0103] 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.

[0104] 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.

[0105] 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.

[0106] Polymeric solid electrolytes are prepared by dissolving an electrolyte salt in a polymer material and then solidifying it.

[0107] 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.

[0108] 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.

[0109] 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.

[0110] 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.

[0111] 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.

[0112] 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.

[0113] 5) Exterior components For example, the outer packaging material can be a container made of laminate film or a metal container.

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

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

[0116] The thickness of the 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.

[0117] 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.

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

[0119] 6) Negative terminal The negative electrode terminal can be formed from a material that is electrochemically stable at the Li absorption / release potential of the negative electrode active material described above, and is also conductive. Specifically, the material for the negative electrode terminal can be copper, nickel, stainless steel, or aluminum, or an aluminum alloy containing at least one element selected from the group consisting of Mg, Ti, Zn, Mn, Fe, Cu, and Si. It is preferable to use aluminum or an aluminum alloy as the material for the negative electrode terminal. It is preferable that the negative electrode terminal be made of the same material as the negative electrode current collector in order to reduce contact resistance with the negative electrode current collector.

[0120] 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.

[0121] Next, the secondary battery according to the embodiment will be described in more detail with reference to the drawings.

[0122] Figure 4 is a schematic cross-sectional view showing an example of a secondary battery. Figure 5 is an enlarged cross-sectional view of section B of the secondary battery shown in Figure 4.

[0123] The secondary battery 100 shown in Figures 4 and 5 comprises a bag-shaped outer casing member 2 shown in Figure 4, an electrode group 1 shown in Figures 4 and 5, 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.

[0124] The bag-shaped outer packaging member 2 consists of a laminate film comprising two resin layers and a metal layer interposed between them.

[0125] As shown in Figure 4, electrode group 1 is a flat, wound electrode group. As shown in Figure 5, 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.

[0126] 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 5. 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.

[0127] The positive electrode 5 includes a positive electrode current collector 5a and positive electrode active material-containing layers 5b formed on both sides thereof.

[0128] As shown in Figure 4, the negative electrode terminal 6 and the positive electrode terminal 7 are located near the outer edge of the wound electrode group 1. The negative electrode terminal 6 is connected to the outermost part of the negative electrode current collector 3a. The positive electrode terminal 7 is connected to the outermost part of the positive electrode current collector 5a. These negative electrode terminals 6 and positive electrode terminals 7 extend outward from the opening of the bag-shaped outer casing member 2. A thermoplastic resin layer is installed on the inner surface of the bag-shaped outer casing member 2, and the opening is closed by heat-sealing this layer.

[0129] The secondary battery according to this embodiment is not limited to the secondary battery with the configuration shown in Figures 4 and 5, but may also be a battery with the configuration shown in Figures 6 and 7, for example.

[0130] Figure 6 is a schematic partially cutaway perspective view showing another example of a secondary battery. Figure 7 is an enlarged cross-sectional view of section C of the secondary battery shown in Figure 6.

[0131] The secondary battery 100 shown in Figures 6 and 7 comprises an electrode group 1 shown in Figures 6 and 7, an outer casing member 2 shown in Figure 6, 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.

[0132] The exterior component 2 consists of a laminate film comprising two resin layers and a metal layer interposed between them.

[0133] As shown in Figure 7, 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.

[0134] 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.

[0135] 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 7, 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.

[0136] 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.

[0137] The secondary battery according to the second embodiment includes the electrodes according to the first embodiment. Therefore, this secondary battery has a high input / output density.

[0138] (Third embodiment) According to the third embodiment, a battery pack is provided. This battery pack comprises a plurality of secondary batteries according to the second embodiment.

[0139] 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.

[0140] Next, an example of a battery pack according to the embodiment will be described with reference to the drawings.

[0141] Figure 8 is a schematic perspective view showing an example of a battery pack. The battery pack 200 shown in Figure 8 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.

[0142] 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 8 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.

[0143] 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.

[0144] The battery pack according to the third embodiment comprises a secondary battery according to the second embodiment. Therefore, the battery pack has a high input / output density.

[0145] (Fourth embodiment) According to the fourth embodiment, a battery pack is provided. This battery pack comprises a battery pack according to the third embodiment. This battery pack may also comprise a single secondary battery according to the second embodiment instead of the battery pack according to the third embodiment.

[0146] 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.

[0147] Furthermore, such a battery pack may also be equipped with 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.

[0148] Next, an example of a battery pack according to the embodiment will be described with reference to the drawings.

[0149] Figure 9 is an exploded perspective view schematically showing an example of a battery pack. Figure 10 is a block diagram showing an example of the electrical circuit of the battery pack shown in Figure 9.

[0150] The battery pack 300 shown in Figures 9 and 10 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).

[0151] The container 31 shown in Figure 9 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.

[0152] The battery pack 200 comprises multiple individual cells 100, a positive electrode lead 22, a negative electrode lead 23, and an adhesive tape 24.

[0153] 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 10. 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.

[0154] 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.

[0155] 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.

[0156] 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.

[0157] 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.

[0158] 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.

[0159] 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.

[0160] 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.

[0161] 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.

[0162] 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.

[0163] 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.

[0164] 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.).

[0165] 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.

[0166] 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.

[0167] 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.

[0168] The battery pack according to the fourth embodiment comprises a secondary battery according to the second embodiment or a battery pack according to the third embodiment. Therefore, the battery pack has a high input / output density.

[0169] (Fifth embodiment) According to the fifth embodiment, a vehicle is provided, which is equipped with the battery pack according to the fourth embodiment.

[0170] 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.

[0171] 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.

[0172] 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.

[0173] 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.

[0174] Next, an example of a vehicle according to the embodiment will be described with reference to the drawings.

[0175] Figure 11 is a schematic partial transparency drawing showing an example of a vehicle.

[0176] The vehicle 400 shown in Figure 11 includes a vehicle body 40 and a battery pack 300 according to the fourth embodiment. In the example shown in Figure 11, the vehicle 400 is a four-wheeled automobile.

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

[0178] Figure 11 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.

[0179] Next, an embodiment of the vehicle according to the embodiment will be described with reference to Figure 12.

[0180] Figure 12 is a schematic diagram illustrating an example of a control system for the electrical system in a vehicle. The vehicle 400 shown in Figure 12 is an electric vehicle.

[0181] The vehicle 400 shown in Figure 12 comprises a vehicle body 40, a vehicle power supply 41, a vehicle ECU (ECU: Electric Control Unit) 42 which is a control device above 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.

[0182] Vehicle 400 has a 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 vehicle 400 shown in Figure 12, the mounting location of the vehicle power supply 41 is shown in a schematic manner.

[0183] 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.

[0184] 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.

[0185] 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.

[0186] 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.

[0187] 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.

[0188] The battery pack monitoring devices 301a to 301c measure the voltage and temperature of each individual cell constituting the battery packs 200a to 200c based on commands communicated from the battery management device 411. However, temperature can be measured at only a few locations per battery pack, and it is not necessary to measure the temperature of all individual cells.

[0189] The vehicle power supply 41 may also have an electromagnetic contactor (for example, a switch device 415 shown in Figure 12) that switches the presence or absence of an electrical connection between the positive terminal 413 and the negative terminal 414. The switch device 415 includes a pre-charge switch (not shown) that turns on when charging is performed on the battery packs 200a to 200c, and a main switch (not shown) that turns on when the output from the battery packs 200a to 200c is supplied to the load. Each of the pre-charge switch and the main switch includes a relay circuit (not shown) that is switched on or off by a signal supplied to a coil located near the switch element. Electromagnetic contactors such as the switch device 415 are controlled based on a control signal from the battery management device 411 or the vehicle ECU 42 that controls the operation of the entire vehicle 400.

[0190] The inverter 44 converts the input DC voltage into a high voltage of three-phase alternating current (AC) for motor drive. The three-phase output terminals of the inverter 44 are connected to the three-phase input terminals of the drive motor 45. The inverter 44 is controlled based on control signals from the battery management device 411 or the vehicle ECU 42 for controlling the operation of the entire vehicle. By controlling the inverter 44, the output voltage from the inverter 44 is adjusted.

[0191] The drive motor 45 rotates using power supplied from the inverter 44. The driving force generated by the rotation of the drive motor 45 is transmitted to the axle and drive wheels W, for example, via a differential gear unit.

[0192] 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.

[0193] 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.

[0194] 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.

[0195] External terminal 43 is connected to battery management device 411. External terminal 43 can be connected to an external power supply, for example.

[0196] 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.

[0197] The vehicle according to the fifth embodiment is equipped with the battery pack according to the fourth embodiment. Therefore, a high-performance vehicle can be provided. [Examples]

[0198] Examples are described below, but the present invention is not limited to the examples listed below unless it exceeds the spirit of the invention.

[0199] (Example 1) In Example 1, a non-aqueous electrolyte battery was manufactured using the following procedure.

[0200] <Fabrication of the negative electrode> As the negative electrode active material, monoclinic niobium titanium oxide particles having a composition represented by the formula TiNb2O7 were prepared. Carbon nanotubes (CNTs) were prepared as a conductive agent, and carboxymethylcellulose (CMC) and styrene butadiene rubber (SBR) were prepared as binders. The CNTs were prepared with fiber diameters of approximately 1 nm to 30 nm in some areas and approximately 60 nm to 500 nm in others. These were mixed in pure water in a mass ratio of negative electrode active material:CNT:CMC:SBR of 96.6:0.4:1:2 to obtain a slurry. This slurry was applied to both the front and back main surfaces of a strip-shaped current collector made of aluminum foil with a thickness of 15 μm, and the coating was dried. Here, an uncoated area was left on one side along the longitudinal direction of the current collector, where the slurry was not applied to both the front and back surfaces. Thus, a composite was obtained containing the current collector and a negative electrode active material-containing layer formed on both sides of the current collector. The coating amount per side of the negative electrode active material layer is 100 g / m². 2 The mixture was then adjusted to achieve the following: Next, the resulting composite was prepared so that the density of the negative electrode active material-containing layer was 2.7 g / cm³. 3 The material was subjected to a roll press to obtain the desired shape. When the resulting electrode was observed by SEM, it was confirmed that the CNT had a fiber diameter (W1) of 480 nm and a fiber diameter (W2) of 15 nm. The former was designated as the C1 portion and the latter as the C2 portion. Subsequently, the electrode was punched out into a strip shape with an uncoated current collector portion along one side in the short direction of the electrode, and then subjected to vacuum drying to obtain the negative electrode.

[0201] <Fabrication of the positive electrode> As the positive electrode active material, Formula LiNi0.5 Co 0.2 Mn 0.3 Particles of lithium nickel cobalt manganese composite oxide represented by O2 were prepared. Acetylene black (AB) was prepared as a conductive agent, and polyvinylidene fluoride (PVdF) was prepared as a binder. These were mixed in a mass ratio of positive electrode active material:AB:PVdF of 90:5:5 to obtain a mixture. Next, the obtained mixture was dispersed in n-methylpyrrolidone (NMP) solvent to prepare a positive electrode slurry. This slurry was applied to both the front and back main surfaces of a strip-shaped current collector made of aluminum foil with a thickness of 15 μm, and the coating was dried. Here, an uncoated area was left on one side along the longitudinal direction of the current collector, where the slurry was not applied to both the front and back surfaces. Thus, a composite was obtained containing the current collector and a positive electrode active material-containing layer formed on both sides of the current collector. The coating amount per side of the positive electrode active material-containing layer was 125 g / m². 2 The mixture was then adjusted so that the density of the positive electrode active material-containing layer of the resulting composite was 3.05 g / cm³. 3 The electrodes were subjected to a roll press in this manner. The resulting electrodes were punched out into strips with an uncoated portion of the current collector along one side in the shorter direction, and then subjected to vacuum drying to obtain the positive electrode.

[0202] <Manufacturing of electrode groups> A polyethylene (PE) separator with a thickness of 15 μm was prepared. Next, the prepared separator was folded in a zigzag pattern, and the separator, along with six negative electrodes and five positive electrodes, were stacked in the order of negative electrode, separator, positive electrode, and separator to obtain a laminate. Specifically, the negative and positive electrodes were alternately inserted into the space defined by the zigzag-folded separator. The negative and positive electrodes were arranged so that their respective areas overlapped by 50 mm vertically and 50 mm horizontally. Furthermore, the negative and positive electrodes were stacked in opposite directions so that the uncoated portions of the current collectors of the negative and positive electrodes were located on opposite sides of the laminate. Next, this laminate was pressed. The pressing of the laminate was carried out at room temperature (25°C) by applying a load of 80 kN for 1 minute. Thus, the electrode group was manufactured.

[0203] <Preparation of non-aqueous electrolytes> A non-aqueous electrolyte was prepared using the following procedure. First, propylene carbonate (PC) and diethyl carbonate (DEC) were mixed in a volume ratio of PC:DEC 1:2 to obtain a mixed solvent. Lithium hexafluoride phosphate (LiPF6) was dissolved in this mixed solvent at a concentration of 1 M to obtain a liquid non-aqueous electrolyte.

[0204] <Battery assembly> The electrode group was housed in a laminate film pack and vacuum-dried at 80°C for 10 hours. The laminate film used was 0.1 mm thick, consisting of a 40 μm thick aluminum foil with polypropylene layers on both sides. The above non-aqueous electrolyte was injected. After injection, the laminate film pack was heat-sealed under reduced pressure to manufacture the battery.

[0205] (Example 2) In Example 2, a non-aqueous electrolyte battery was manufactured using the same procedure as in Example 1, except that the negative electrode prepared as described below was used instead.

[0206] <Fabrication of the negative electrode> As the negative electrode active material, the formula is Li4Ti5O 12 Lithium titanate particles having the composition represented by [formula] were prepared. CNTs were prepared as a conductive agent and PVdF as a binder. The CNTs were prepared with fiber diameters of approximately 1 nm to 30 nm in some areas and approximately 60 nm to 500 nm in others. These were mixed in NMP so that the mass ratio of negative electrode active material:CNT:PVdF was 96.6:0.4:3 to obtain a slurry. This slurry was applied to both the front and back main surfaces of a strip-shaped current collector made of aluminum foil with a thickness of 15 μm, and the coating was dried. Here, an uncoated area was left on one side along the longitudinal direction of the current collector, where the slurry was not applied to both the front and back surfaces. Thus, a composite was obtained containing the current collector and a negative electrode active material-containing layer formed on both sides of the current collector. The coating amount per side of the negative electrode active material-containing layer was 135 g / m². 2 The mixture was then adjusted to achieve the following: Next, the resulting composite was prepared so that the density of the negative electrode active material-containing layer was 2.3 g / cm³. 3The material was subjected to a roll press in the manner described. When the resulting electrode was observed by SEM, it was confirmed that the CNT had a portion C1 with a fiber diameter W1 of 480 nm and a portion C2 with a fiber diameter W2 of 15 nm. Subsequently, the electrode was punched out into a strip shape with an uncoated portion of the current collector along one side in the short direction of the electrode, and then subjected to vacuum drying to obtain the negative electrode.

[0207] (Example 3) In Example 3, a non-aqueous electrolyte battery was manufactured using the same procedure as in Example 1, except that the negative and positive electrodes prepared as described below were used instead.

[0208] <Fabrication of the negative electrode> As the negative electrode active material, monoclinic niobium titanium oxide particles having a composition represented by the formula TiNb2O7 were prepared. AB was prepared as a conductive agent, and CMC and SBR were prepared as binders. These were mixed in pure water in a mass ratio of negative electrode active material:AB:CMC:SBR of 94:3:1:2 to obtain a slurry. This slurry was applied to both the front and back main surfaces of a strip-shaped current collector made of aluminum foil with a thickness of 15 μm, and the coating was dried. Here, an uncoated area was left on one side along the longitudinal direction of the current collector, where the slurry was not applied to both the front and back surfaces. Thus, a composite was obtained containing the current collector and a negative electrode active material-containing layer formed on both sides of the current collector. The coating amount per side of the negative electrode active material-containing layer was 100 g / m². 2 The adjustments were made so that the density of the negative electrode active material-containing layer was 2.55 g / cm³. 3 The electrodes were subjected to a roll press in this manner. The resulting electrodes were punched out into strips with an uncoated portion of the current collector along one side in the shorter direction, and then subjected to vacuum drying to obtain the negative electrode.

[0209] <Fabrication of the positive electrode> As the positive electrode active material, Formula LiNi 0.5 Co 0.2 Mn 0.3Particles of lithium nickel cobalt manganese composite oxide represented by O2 were prepared. CNTs were prepared as a conductive agent, and PVdF as a binder. The CNTs were prepared with fiber diameters of approximately 1 nm to 30 nm in some areas and 60 nm to 500 nm in others. These were mixed to obtain a mixture with a mass ratio of positive electrode active material:CNT:PVdF of 94.5:0.5:5. Next, the obtained mixture was dispersed in NMP solvent to prepare a positive electrode slurry. This slurry was applied to both the front and back main surfaces of a strip-shaped current collector made of 15 μm thick aluminum foil, and the coating was dried. Here, an uncoated area was left on one side along the longitudinal direction of the current collector, where the slurry was not applied to both the front and back surfaces. Thus, a composite was obtained containing the current collector and a positive electrode active material-containing layer formed on both sides of the current collector. The coating amount per side of the positive electrode active material-containing layer was 125 g / m². 2 The adjustments were made so that the density of the positive electrode active material-containing layer of the resulting composite was 3.25 g / cm³. 3 The material was subjected to a roll press in the manner described. When the obtained electrode was observed by SEM, it was confirmed that the CNT had a portion C1 with a fiber diameter W1 of 480 nm and a portion C2 with a fiber diameter W2 of 15 nm. Subsequently, the electrode was punched out into a strip shape with an uncoated portion of the current collector along one side in the short direction of the electrode, and then subjected to vacuum drying to obtain the positive electrode.

[0210] (Example 4) In Example 4, a non-aqueous electrolyte battery was manufactured using the same procedure as in Example 1, except that the negative electrode manufactured in the same manner as in Example 3 and the positive electrode manufactured as described below were used instead.

[0211] <Fabrication of the positive electrode> As the positive electrode active material, formula LiMn 0.7 Fe 0.3Particles of lithium iron manganese phosphate, represented as PO4, were prepared. CNTs were prepared as a conductive agent, and PVdF as a binder. The CNTs were prepared with fiber diameters of approximately 1 nm to 30 nm in some areas and 60 nm to 500 nm in others. These were mixed to obtain a mixture with a mass ratio of positive electrode active material:CNT:PVdF of 94.5:0.5:5. Next, the obtained mixture was dispersed in NMP solvent to prepare a positive electrode slurry. This slurry was applied to both the front and back main surfaces of a strip-shaped current collector made of 15 μm thick aluminum foil, and the coating was dried. Here, an uncoated area was left on one side along the longitudinal direction of the current collector, where the slurry was not applied to both the front and back surfaces. Thus, a composite was obtained containing the current collector and a positive electrode active material-containing layer formed on both sides of the current collector. The coating amount per side of the positive electrode active material-containing layer was 140 g / m². 2 The adjustments were made so that the resulting composite had a positive electrode active material-containing layer density of 2.3 g / cm³. 3 The material was subjected to a roll press in the manner described. When the obtained electrode was observed by SEM, it was confirmed that the CNT had a portion C1 with a fiber diameter W1 of 480 nm and a portion C2 with a fiber diameter W2 of 15 nm. Subsequently, the electrode was punched out into a strip shape with an uncoated portion of the current collector along one side in the short direction of the electrode, and then subjected to vacuum drying to obtain the positive electrode.

[0212] (Example 5) In Example 5, a non-aqueous electrolyte battery was manufactured using the same procedure as in Example 1, except that the negative electrode manufactured in the same manner as in Example 3 and the positive electrode manufactured as described below were used instead.

[0213] <Fabrication of the positive electrode> As the positive electrode active material, Formula LiNi 0.5 Mn 1.5Particles of a lithium nickel manganese composite oxide represented by O4 were prepared. Also, CNT as a conductive agent and PVdF as a binder were prepared. Among the CNTs, those having a fiber diameter of about 1 nm to 30 nm in part and a fiber diameter of about 60 nm to 500 nm in part were prepared. These were mixed so that the mass ratio of the positive electrode active material:CNT:PVdF was 94.5:0.5:5 to obtain a mixture. Next, the obtained mixture was dispersed in an NMP solvent to prepare a positive electrode slurry. This slurry was applied onto both main surfaces of a current collector made of an aluminum foil having a thickness of 15 μm and having a strip shape, and the coating film was dried. Here, on one side along the longitudinal direction of the current collector, an uncoated portion where the slurry was not applied was left on both the front and back surfaces. Thus, a composite including the current collector and a positive electrode active material-containing layer formed on both surfaces of the current collector was obtained. The coating amount per side of the positive electrode active material-containing layer was adjusted to be 170 g / m 2 so as to be. Next, the obtained composite was subjected to roll pressing so that the density of the positive electrode active material-containing layer was 2.75 g / cm 3 so as to be. When the obtained electrode was observed by SEM, it was confirmed that there were a portion C1 where the fiber diameter W1 of the CNT was 480 nm and a portion C2 where the fiber diameter W2 was 15 nm. Thereafter, it was punched into a strip shape having an uncoated portion of the current collector on one side along the short side direction of the electrode, and further subjected to vacuum drying to obtain a positive electrode.

[0214] (Example 6) In Example 6, a non-aqueous electrolyte battery was manufactured in the same procedure as in Example 1, except that particles of a monoclinic niobium titanate having a composition represented by the formula TiNb2O7 in which fine oxide particles of about 100 nm are present on the particle surface were used instead as the negative electrode active material.

[0215] (Example 7) In Example 7, a non-aqueous electrolyte battery was manufactured in the same procedure as in Example 1, except that CNT in which a portion C1 having a fiber diameter W1 of about 1 nm to 30 nm and a portion C2 having a fiber diameter W2 of about 60 nm to 500 nm are integrally formed in a partially bundled shape was used instead as the conductive agent for the negative electrode.

[0216] (Example 8) In Example 8, a non-aqueous electrolyte battery was manufactured using the same procedure as in Example 1, except that the negative electrode was prepared in the same manner as in Example 1, but the positive electrode prepared in the same manner as in Example 3 was used instead.

[0217] (Example 9) In Example 9, a non-aqueous electrolyte battery was manufactured using the same procedure as in Example 1, except that the negative electrode prepared as described below was used instead.

[0218] <Fabrication of the negative electrode> As the negative electrode active material, monoclinic niobium titanium oxide particles having a composition represented by the formula TiNb2O7 were prepared. CNTs and AB were prepared as conductive agents, and CMC and SBR were prepared as binders. The CNTs were prepared with fiber diameters of approximately 1 nm to 30 nm in some parts and approximately 60 nm to 500 nm in others. These were mixed in pure water to obtain a slurry, with a mass ratio of negative electrode active material:CNT:AB:CMC:SBR of 95.9:0.4:0.7:1:2. This slurry was applied to both the front and back main surfaces of a strip-shaped current collector made of aluminum foil with a thickness of 15 μm, and the coating was dried. Here, an uncoated area was left on one side along the longitudinal direction of the current collector, where the slurry was not applied to both the front and back surfaces. Thus, a composite was obtained containing the current collector and a negative electrode active material-containing layer formed on both sides of the current collector. The coating amount per side of the negative electrode active material layer is 100 g / m². 2 The adjustments were made so that the density of the negative electrode active material-containing layer of the resulting composite was 2.7 g / cm³. 3 The material was subjected to a roll press in the manner described. When the resulting electrode was observed by SEM, it was confirmed that the CNT had a portion C1 with a fiber diameter W1 of 480 nm and a portion C2 with a fiber diameter W2 of 15 nm. Subsequently, the electrode was punched out into a strip shape with an uncoated portion of the current collector along one side in the short direction of the electrode, and then subjected to vacuum drying to obtain the negative electrode.

[0219] (Comparative Example 1) In Comparative Example 1, a non-aqueous electrolyte battery was manufactured using the same procedure as in Example 1, except that a single-walled carbon nanotube (WNT) containing only portions with a fiber diameter of approximately 1 nm to 30 nm was used as the conductive agent for the negative electrode.

[0220] (Comparative Example 2) In Comparative Example 2, a non-aqueous electrolyte battery was manufactured using the same procedure as in Example 1, except that a multilayer CNT containing only portions with a fiber diameter of approximately 60 nm to 500 nm was used as the conductive agent for the negative electrode.

[0221] Table 1 below summarizes the designs of the non-aqueous electrolyte batteries manufactured in Examples 1 to 9 and Comparative Examples 1 and 2. Specifically, it summarizes the electrode designs of each battery. In detail, it shows the electrode active materials and conductive agents used for the positive and negative electrodes, as well as the basis weight and density of the electrode active material-containing layer. Furthermore, Table 1 shows the form in which the fibrous carbon (CNT) used as the conductive agent is contained, specifically the first portion C1 with a fiber diameter of 60 nm to 500 nm and the second portion C2 with a finer fiber diameter. Note that for the positive electrode active material, "NCM" stands for lithium nickel cobalt manganese composite oxide LiNi 0.5 Co 0.2 Mn 0.3 O2, “LMFP” is LiMn 0.7 Fe 0.3 PO4, “LNMO” is lithium nickel manganese composite oxide LiNi 0.5 Mn 1.5 These refer to O4 respectively. Regarding the negative electrode active material, "TNO" is monoclinic niobium titanium oxide TiNb2O7, and "TLO" is lithium titanium oxide Li4Ti5O 12 These terms refer to the following: Regarding conductive materials, "AB" refers to acetylene black, "CNT" to carbon nanotubes, "SWCNT" to single-walled carbon nanotubes, and "MWCNT" to multi-walled carbon nanotubes.

[0222] [Table 1]

[0223] <Rating> For each battery manufactured in Examples 1 to 9 and Comparative Examples 1 and 2, discharge was performed at 0.2C and 5C respectively as an indicator of rapid discharge performance, and the ratio of the 5C discharge capacity to the 0.2C capacity was determined. The test results are shown in Table 2 below.

[0224] [Table 2]

[0225] As shown in Table 2, each of the non-aqueous electrolyte batteries manufactured in Examples 1 to 9 achieved a higher rapid discharge capacity than the non-aqueous electrolyte batteries manufactured in Comparative Examples 1 and 2. The test results indicate that high input / output performance was obtained by using fibrous carbon, which includes both a first portion C1 with a thicker fiber diameter and a second portion C2 with a thinner fiber diameter, as the electrode conductive material.

[0226] An electrode is provided according to one or more embodiments and examples described above. The electrode comprises a plurality of active material particles and fibrous carbon. The fibrous carbon comprises a first portion C1 having a fiber diameter W1 in the range of 60 nm to 500 nm and a second portion C2 having a fiber diameter W2 smaller than the fiber diameter W1. At least the second portion C2 includes active material particles that are in contact with a plurality of particles. The electrode provides a secondary battery and battery pack exhibiting high input / output density, as well as a vehicle equipped with this battery pack.

[0227] 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.

[0228] Several embodiments of the present invention are described below. [1] Multiple active material particles, A first portion having a fiber diameter W1 within a range of 60 nm or more and 500 nm or less, and a second portion having a fiber diameter W2 smaller than the fiber diameter W1, wherein at least a part of at least the second portion is fibrous carbon in contact with a plurality of the active material particles An electrode comprising: [2] The electrode according to [1], wherein at least a part of the fibrous carbon has the first portion and the second portion integrated therewith. [3] The electrode according to [1] or [2], wherein an area ratio between an area A1 of the first portion and an area A2 of the second portion on the surface thereof is 0.5 < A1 / A2 < 50. [4] The electrode according to any one of [1] to [3], wherein the fiber diameter W2 of the second portion is within a range of 1 nm or more and 15 nm or less. [5] The electrode according to any one of [1] to [4], wherein a ratio of a length L of the fibrous carbon to the fiber diameter W2 of the second portion on the surface thereof is 100 < L / W2. [6] The electrode according to any one of [1] to [5], wherein the active material particles include at least one selected from the group consisting of lithium titanate and niobium titanate. [7] The electrode according to any one of [1] to [5], wherein the active material particles include at least one selected from the group consisting of lithium nickel cobalt manganese composite oxide, lithium phosphate oxide, and lithium nickel manganese composite oxide. [8] A positive electrode, A negative electrode, An electrolyte A secondary battery comprising: The secondary battery, wherein at least one of the positive electrode and the negative electrode is the electrode according to any one of [1] to [7]. [9] A battery pack comprising the secondary battery according to [8].

[10] An external terminal for energization, A protection circuit The battery pack according to [9], further comprising:

[11] The battery pack comprising a plurality of the secondary batteries, The battery pack described in [9] or

[10] , wherein the secondary batteries are electrically connected in series, in parallel, or in a combination of series and parallel. A vehicle equipped with a battery pack as described in any one of

[12] [8] through

[11] .

[13] The vehicle according to

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

[0229] 1…Electrode group, 2…Outer material, 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, 10…Electrode, 10a…Current collector, 10b…Active material containing layer, 10c…Current collector tab, 11…Active material particles, 12…Fibrous carbon, 13…Fine oxide particles, 14…Electrode, 14a…Current collector, 14 b...Active material-containing layer, 15...Granular carbon, 21...Bus bar, 22...Positive electrode lead, 22a...Other end, 23...Negative electrode 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, 300a...Battery pack, 300b...Battery pack, 300c...Battery pack, 301a...Battery pack monitoring device, 301b...Battery pack monitoring device, 301c...Battery pack monitoring device, 342...Positive side connector, 343...Negative side connector, 345...Thermistor, 346...Protection circuit, 342a...Wiring, 343a...Wiring, 350...For energizing External terminals, 352...positive terminal, 353...negative terminal, 348a...positive wiring, 348b...negative wiring, 400...vehicle, 411...battery management device, 412...communication bus, 413...positive terminal, 414...negative terminal, 415...switch device, 416...current detection unit, 417...negative input terminal, 418...positive input terminal, L1...connection line, L2...connection line, W...drive wheel, C1...first part, C2...second part.

Claims

1. Multiple active material particles, It comprises a first portion having a fiber diameter W1 in the range of 60 nm to 500 nm and a second portion having a fiber diameter W2 smaller than the fiber diameter W1, and at least a portion of the second portion is fibrous carbon in contact with a plurality of active material particles. An electrode containing an electrode.

2. The electrode according to claim 1, wherein at least a portion of the fibrous carbon is integrated with the first portion and the second portion.

3. The electrode according to claim 1 or 2, wherein the area ratio between the area A1 of the first part and the area A2 of the second part on its surface is 0.5 < A1 / A2 < 50.

4. The electrode according to claim 1 or 2, wherein the fiber diameter W2 of the second portion is in the range of 1 nm to 15 nm.

5. The electrode according to claim 1 or 2, wherein the ratio of the length L of the fibrous carbon to the fiber diameter W2 of the second portion on the surface is 100 < L / W2.

6. The electrode according to claim 1 or 2, wherein the active material particles include at least one selected from the group consisting of lithium titanate and titanium niobium oxide.

7. The electrode according to claim 1 or 2, wherein the active material particles include at least one selected from the group consisting of lithium nickel cobalt manganese composite oxide, lithium phosphorus oxide, and lithium nickel manganese composite oxide.

8. Positive electrode and, The negative electrode and, Electrolytes and A secondary battery comprising, A secondary battery in which at least one of the positive electrode and the negative electrode is the electrode described in claim 1 or 2.

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

10. External terminals for power supply, Protection circuit and The battery pack according to claim 9, further comprising the above.

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

12. A vehicle comprising the battery pack described in claim 9.

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

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