Electrode, secondary battery, battery pack, and vehicle

Abstract

The embodiment of the invention relates to a secondary battery, a battery pack and a vehicle. Provided are an electrode capable of realizing a secondary battery having a high input / output density, a secondary battery and a battery pack having a high input / output density, and a vehicle including the battery pack. According to one embodiment, an electrode including a plurality of active material particles and fibrous carbon is provided. 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 the second portion is in contact with the plurality of active material particles.

Description

TECHNICAL FIELD

[0001] Embodiments of the present application relate to an electrode, a secondary battery, a battery pack, and a vehicle. BACKGROUND

[0002] A lithium ion battery, such as a nonaqueous electrolyte battery, which performs charge and discharge by moving lithium ions between a negative electrode and a positive electrode, is being actively researched as a high-energy-density battery.

[0003] In a typical electrode of a secondary battery such as a lithium ion battery, in addition to an electrode active material that contributes to charge and discharge by performing intercalation and deintercalation of lithium ions, a conductive agent for improving the conductivity of the electrode is included. As the conductive agent included in the electrode, a carbon material is widely used. SUMMARY

[0004] Provided is an electrode capable of realizing a secondary battery with a high input and output density, a secondary battery and a battery pack with a high input and output density, and a vehicle including the battery pack.

[0005] According to an embodiment, an electrode including a plurality of active material particles and a fibrous carbon is provided. The fibrous carbon includes a first portion having a fiber diameter W1 in 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. At least a portion of at least the second portion is in contact with the plurality of active material particles.

[0006] According to another embodiment, a secondary battery including a positive electrode, a negative electrode, and an electrolyte is provided. At least one of the positive electrode and the negative electrode is the electrode of the above-described embodiment.

[0007] According to another embodiment, a battery pack including the secondary battery of the above-described embodiment is provided.

[0008] According to another embodiment, a vehicle including the battery pack related to the above-described embodiment is provided.

[0009] According to the electrode configured as described above, a secondary battery and a battery pack with a high input and output density, and a vehicle including the battery pack can be provided. BRIEF DESCRIPTION OF DRAWINGS

[0010] Figure 1 is a cross-sectional view schematically showing an example of the electrode of the embodiment.

[0011] Figure 2 is a cross-sectional view schematically showing an example of the electrode of the embodiment. Figure 1 is a cross-sectional view schematically showing an example of the electrode of the embodiment.

[0012] Figure 3 is a cross-sectional view schematically showing an example of the electrode of the embodiment.

[0013] Figure 4 is a cross-sectional view schematically showing an example of a secondary battery of the embodiment.

[0014] Figure 5 is Figure 4 is an enlarged cross-sectional view of a portion B of the secondary battery shown in FIG. 2.

[0015] Figure 6 is a partial cutaway perspective view schematically showing another example of a secondary battery of the embodiment.

[0016] Figure 7 is an enlarged cross-sectional view of a portion C of the secondary battery shown in FIG. 2. Figure 6

[0017] Figure 8 is a perspective view schematically showing an example of a battery pack of the embodiment.

[0018] Figure 9 is an exploded perspective view schematically showing an example of a battery pack of the embodiment.

[0019] Figure 10 is a block diagram showing an example of a circuit of the battery pack shown in FIG. 5. Figure 9

[0020] Figure 11 is a partial perspective view schematically showing an example of a vehicle of the embodiment.

[0021] Figure 12 is a diagram schematically showing an example of a control system related to an electrical system in the vehicle of the embodiment.

[0022] [EXPLANATION OF REFERENCE NUMERALS]

[0023] ​​1…Electrode assembly, 2…Outer packaging component, 3…Negative electrode, 3a…Negative electrode current collector, 3b…Layer containing negative electrode active material, 3c…Negative electrode current collector tab, 4…Separator, 5…Positive electrode, 5a…Positive electrode current collector, 5b…Layer containing positive electrode active material, 6…Negative terminal, 7…Positive terminal, 10…Electrode, 10a…Current collector, 10b…Layer containing active material, 10c…Current collector tab, 11…Active material particles, 12…Fiber-like carbon, 13…Fine oxide particles, 14…Electrode, 14a …current collector, 14b…layer containing active material, 15…granular carbon, 21…busbar, 22…positive electrode side lead, 22a…the other end, 23…negative electrode side lead, 23a…the other end, 24…adhesive tape, 31…container, 32…lid, 33…protective sheet, 34…printed wiring board, 35…wiring, 40…vehicle body, 41…vehicle power supply, 42…electrical control device, 43…external terminal, 44…inverter, 45…drive motor, 100…secondary battery, 200 …battery pack, 200a…battery pack, 200b…battery pack, 200c…battery pack, 300…battery pack, 300a…battery pack, 300b…battery pack, 300c…battery pack, 301a…battery monitoring device, 301b…battery monitoring device, 301c…battery monitoring device, 342…positive side connector, 343…negative side connector, 345…thermistor, 346…protection circuit, 342a…wiring, 343a…wiring, 350…pass External terminals for electrical use, 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…switching device, 416…current detection unit, 417…negative input terminal, 418…positive input terminal, L1…connecting wire, L2…connecting wire, W…drive wheel, C1…first part, C2…second part. Detailed Implementation

[0024] According to an embodiment, an electrode comprising a plurality of active material particles and fibrous carbon is provided. The fibrous carbon comprises a first portion having a fiber diameter W1 in the 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. At least a portion of the second portion is in contact with the plurality of active material particles.

[0025] According to other embodiments, a secondary battery comprising a positive electrode, a negative electrode, and an electrolyte is provided. At least one of the positive electrode and the negative electrode is an electrode as described in the above embodiments.

[0026] According to other embodiments, a battery pack having the secondary battery described above is provided.

[0027] According to other embodiments, a vehicle equipped with the battery pack described in the above embodiments is provided.

[0028] To obtain electrodes with low resistance, large amounts of carbon materials such as granular carbon and fibrous carbon are typically added. However, if large amounts of granular or fibrous carbon are added, the volume ratio of carbon in the electrode body increases. In electrodes using metal oxides as active materials, the proportion of active material decreases, making it difficult to obtain electrodes with high input / output density per unit volume. It has also been considered to use a small amount of fibrous carbon with a fine fiber diameter to suppress the carbon ratio of the electrode body and increase the input / output density, but fine fibrous carbon is difficult to disperse and polarize, making it difficult to obtain sufficient input / output density.

[0029] Hereinafter, embodiments will be described with reference to the accompanying drawings. Furthermore, common structures in the embodiments will be labeled with the same reference numerals, and repeated descriptions will be omitted. Additionally, the drawings are schematic diagrams intended to facilitate the explanation and understanding of the embodiments; their shapes, dimensions, proportions, etc., may differ from those of the actual device, but these can be appropriately modified with reference to the following description and known techniques.

[0030] (First Implementation)

[0031] According to a 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 or more and 500 nm or less. The second portion has a fiber diameter W2 smaller than the fiber diameter W1 of the first portion. The electrode comprises 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.

[0032] This electrode achieves a balance between good conductive pathways and high density, resulting in high input-output density. Specifically, by using fibrous carbon materials with varying fiber diameters as conductive agents, the electrode exhibits low resistance and facilitates the formation of conductive pathways. Furthermore, even with high electrode density, porosity within the electrode is maintained, thus minimizing obstruction to liquid diffusion. Consequently, the diffusion of the liquid electrolyte within the electrode is optimized, leading to excellent input-output performance in the secondary battery.

[0033] The electrode may comprise a current collector and an active material layer. The active material layer may be formed on one or both sides of the current collector. The active material layer comprises an active material and a conductive agent, and may optionally include a binder. As a conductive agent, it at least comprises fibrous carbon containing the first and second portions described above. The conductive agent may further comprise other materials described later, such as granular carbon. The current collector may be included in the portion of its surface where the active material layer is not formed. This portion is capable of functioning as a current collector tab.

[0034] Figure 1 and Figure 2 An example of an electrode according to an embodiment is shown. Figure 1 The cross-section of the electrode is roughly represented. Figure 2 yes Figure 1 An enlarged sectional view of part A in the image.

[0035] The illustrated electrode 10 includes a current collector 10a and active material layers 10b disposed on both its surface and back surface. A portion of the current collector 10a lacks the active material layers 10b on both its surface and back surface; this portion functions as a current collector tab 10c. The active material layers 10b comprise a plurality of active material particles 11 and fibrous carbon 12.

[0036] The fibrous carbon 12 comprises a first portion C1 with a large fiber diameter and a second portion C2 with a small fiber diameter. By including both the large first portion C1 and the small second portion C2 in the fibrous carbon 12, a good conductive path can be formed in the active material layer 10b, thus enabling the electrode 10 to achieve a secondary battery with excellent input-output performance. Furthermore, since a small amount of fibrous carbon 12 can be used to form the conductive path, the volume of the fibrous carbon 12 does not increase, allowing for increased density of the active material layer 10b while maintaining sufficient spacing between the active material particles 11. Therefore, the electrode 10 can achieve a secondary battery with high input-output density.

[0037] As shown in the figure, the first part C1 and the second part C2 can be different fibrous carbon-12, or they can be as follows: Figure 2 Just as multiple second parts C2 branch off from the first part C1 on the right, different portions of the same fibrous carbon 12 are designated as the first part C1 and the second part C2. When the fibrous carbon 12, which includes the first part C1 and the second part C2 as a whole, is as follows, it is easier to form a more robust conductive path. As shown in the figure, in the active material layer 10b containing both the first part C1 and the second part C2, both the first part C1 and the second part C2 can contact multiple active material particles 11, but the finer and better dispersed second part C2 can more reliably contact more active material particles 11.

[0038] In the illustrated example, the active material layer 10b further comprises 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 the synthesis of the active material as described later, or by being generated on the particle surface after the synthesis of the active material. By having the fine oxide particles 13 present 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.

[0039] In contrast, an example of a conventional electrode is shown below.Figure 3 .exist Figure 3 In the middle, it is shown that... Figure 2 The same magnified cross-section. The conventional electrode 14 also includes a current collector 14a and an active material layer 14b containing active material particles 11 disposed thereon. However, in the conventional example, the active material layer 14b contains granular carbon 15 as a conductive agent instead of fibrous carbon 12.

[0040] Unlike fibrous carbon 12, granular carbon 15 has a large volume. Electrodes containing a large amount of bulky granular carbon 15, such as the illustrated electrode 14, to improve conductivity, are thick and difficult to achieve good input-output density. Furthermore, the abundant granular carbon 15 may aggregate as shown in the figure. If the granular carbon 15 aggregates, the electrode density further decreases, or the formation of conductive pathways becomes poor. Thus, if high conductivity is desired using only granular carbon 15, a large amount of granular carbon 15 is required, resulting in a large electrode volume and making it difficult to achieve good input-output density.

[0041] Fibrous carbon can be, for example, carbon nanotubes (CNTs). The first part, C1, can be, for example, a bundle of single-walled carbon nanotubes (SWCNTs). The second part, C2, can be, for example, SWCNTs that are not bundled. Fibrous carbon formed by the integration of the first part, C1, and the second part, C2 can be, for example, fibrous carbon where the bundle of the first part, C1, has partially dispersed and branched into the second part, C2. CNTs are not limited to SWCNTs; two or more layers of carbon nanotubes can also be used (e.g., few-walled carbon nanotubes; FWCNTs), etc.

[0042] By including a first portion C1, such as bundled CNTs, in the active material layer, the local current efficiency within the active material layer is improved, resulting in a decrease in the overall resistance of the electrode. The second portion C2, compared to the first portion C1, is better dispersed within the active material layer, with at least a portion contacting multiple active material particles. Through the dispersion of the second portion C2, fibrous carbon can reach the entire active material layer, eliminating localized unreacted or high-resistance areas within the electrode. Furthermore, if the second portion C2 is included solely in the form of fibrous carbon without the first portion C1, it is difficult to disperse the second portion C2. By using the second portion C2 in conjunction with the first portion C1, good dispersion within the active material layer is achieved, forming a good conductive path.

[0043] The fiber diameter W1 of the first part C1 is in the range of 60 nm or more and 500 nm or less. The above effect of reducing the resistance of the electrode by the first part C1 with a fiber diameter W of 60 nm or more is high. By limiting the fiber diameter W1 to 500 nm or less, the volume of the first part C1 does not increase, so the density of the active material-containing layer can be increased, and in addition, the ratio of active material particles in the active material-containing layer can be increased, so the energy density of the electrode can be increased.

[0044] The fiber diameter W2 of the second part C2 is smaller than the fiber diameter W1. The fiber diameter W2 can be, for example, in the range of 1 nm or more and 15 nm or less. If the fiber diameter W2 is in 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 preferred.

[0045] The ratio of the first part C1 to the second part C2 in the fibrous carbon can be, for example, 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 proportion of the first part C1 in the fibrous carbon can be relatively large, and the proportion of the second part C2 can also be relatively large. It is preferably present in a well-balanced manner, and neither side should be extremely small. In addition, since the area per unit length of the first part C1 with a larger diameter is large, when the first part C1 and the second part C2 exist in the same amount of fiber length on the electrode surface, the area ratio A1 / A2 is greater than 1.

[0046] The fibrous carbon with a longer fiber length 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 can include fibrous carbon with a ratio of its length L to the fiber diameter W2 of the second part C2 being 100 < L / W2. The method for measuring the length L of the fibrous carbon is described later.

[0047] This electrode can be, for example, at least one of the positive electrode and the negative electrode of a battery. In a battery including this electrode as the negative electrode, the positive electrode can also be an electrode other than the electrode of the embodiment. On the contrary, in a battery including this electrode as the positive electrode, the negative electrode can also be an electrode other than the electrode of the first embodiment. Both the negative electrode and the positive electrode included in the battery can be the electrodes according to the first embodiment.

[0048] Hereinafter, the electrode of the embodiment will be described in detail.

[0049] The active material layer may contain only one type of active material or two or more types of active materials. For example, when the electrode is used as a negative electrode, the active material layer (containing a negative electrode active material layer) may contain the following negative electrode active material, and when it is used as a positive electrode, the active material layer (containing a positive electrode active material layer) may contain the following positive electrode active material.

[0050] Examples of anode active materials include titanium oxide, lithium titanium oxide, niobium titanium oxide, and niobium oxide. Specifically, lithium titanate (e.g., Lithium titanate with an orthorhombic manganese oxide structure) can be cited. 2+y Ti3O7, 0≤y≤3), lithium titanate with spinel structure (e.g., Li) 4+x Ti5O 12 The compounds include, but are not limited to, 0≤x≤3), titanium dioxide (TiO2), anatase titanium dioxide, rutile titanium dioxide, niobium pentoxide (Nb2O5), manganese barium ore titanium composite oxide, orthorhombic titanium composite oxide, and monoclinic niobium titanium oxide. Among these, examples of compounds more preferred as negative electrode active materials include lithium titanate having a spinel structure and monoclinic niobium titanium oxide.

[0051] As an example of the orthorhombic titanium-containing composite oxides mentioned above, Li can be cited. 2+a M I 2-b Ti 6-c M II d O 14+σ The compound represented. Here, M I It is selected from at least one of Sr, Ba, Ca, Mg, Na, Cs, Rb, and K. M II It is selected from at least one of Zr, Sn, V, Nb, Ta, Mo, W, Y, Fe, Co, Cr, Mn, Ni, and Al. The subscripts in the composition formula are 0 ≤ a ≤ 6, 0 ≤ b < 2, 0 ≤ c < 6, 0 ≤ d < 6, and -0.5 ≤ σ ≤ 0.5. As a specific example of an orthorhombic titanium-containing composite oxide, Li can be cited. 2+ a Na2Ti6O 14 (0≤a≤6).

[0052] As an example of the aforementioned monoclinic niobium titanium oxide, Li can be cited as an example. x Ti 1-y M1 y Nb 2-z M2 z O 7+δThe compound is represented by M1, which is selected from at least one of Zr, Si, and Sn. M2 is selected from at least one of V, Ta, and Bi. The subscripts in the composition formula are 0 ≤ x ≤ 5, 0 ≤ y < 1, 0 ≤ z < 2, and -0.3 ≤ δ ≤ 0.3. Li can be cited as a specific example of a monoclinic niobium titanium oxide. x Nb2TiO7 (0≤x≤5).

[0053] Other examples of monoclinic niobium titanium oxides include Li x Ti 1-y M3 y+z Nb 2-z O 7-δ The compound is represented by M3, which is selected from at least one of Mg, Fe, Ni, Co, W, Ta, and Mo. The subscripts in the composition formula are 0 ≤ x ≤ 5, 0 ≤ y < 1, 0 ≤ z < 2, and -0.3 ≤ δ ≤ 0.3.

[0054] As positive electrode active materials, oxides or sulfides can be used, for example. The positive electrode, as a positive electrode active material, can contain only one compound, or it can contain two or more compounds in combination. Examples of oxides and sulfides include compounds capable of intercalating and deintercalating Li or Li ions.

[0055] Such compounds include, for example, manganese dioxide (MnO2), iron oxide, copper oxide, nickel oxide, and lithium manganese composite oxides (e.g., Li). x Mn2O4 or Li x MnO2: 0 < x ≤ 1), lithium-nickel composite oxides (e.g., Li) x NiO2, 0 < x ≤ 1), lithium-cobalt composite oxides (e.g., Li) x CoO2, 0 < x ≤ 1), lithium nickel cobalt composite oxides (e.g., Li) x Ni 1-y Co y O2, 0 < x ≤ 1, 0 < y < 1), lithium manganese cobalt composite oxides (e.g., Li) x Mn y Co 1-y O2, 0 < x ≤ 1, 0 < y < 1), lithium nickel manganese composite oxides with spinel structure (e.g., Li) x Ni y Mn 2-y O4, 0 < x ≤ 1, 0 < y < 2), lithium phosphates with olivine structures (e.g., Li) x FePO4, 0 < x ≤ 1, Li x MnPO4, 0 < x ≤ 1, Li x Fe 1-y Mn yPO4, where 0 < x ≤ 1, 0 < y ≤ 1, Li x CoPO4, where 0 < x ≤ 1), iron sulfate (Fe2(SO4)3), vanadium oxide (such as V2O5), and lithium nickel cobalt manganese composite oxide (Li x Ni 1-y-z Co y Mn z O2, where 0 < x ≤ 1, 0 < y < 1, 0 < z < 1, y + z < 1).

[0056] Among the above, examples of more preferred compounds as the positive electrode active material include: lithium manganese composite oxide with a spinel structure (such as Li x Mn2O4; 0 < x ≤ 1), lithium nickel composite oxide (such as Li x NiO2; 0 < x ≤ 1), lithium cobalt composite oxide (such as Li x CoO2; 0 < x ≤ 1), lithium nickel cobalt manganese composite oxide (such as Li x Ni 1-y Co y O2; 0 < x ≤ 1, 0 < y < 1), lithium nickel manganese composite oxide with a spinel structure (such as Li x Ni y Mn 2-y O4; 0 < x ≤ 1, 0 < y < 2), lithium manganese cobalt composite oxide (such as Li x Mn y Co 1-y O2; 0 < x ≤ 1, 0 < y < 1), lithium iron phosphate (such as Li x FePO4; 0 < x ≤ 1), 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) and lithium phosphide with an olivine structure (such as 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). If 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 above lithium nickel cobalt manganese composite oxide, lithium phosphide, and lithium nickel manganese composite oxide can be cited.

[0057] When using a room-temperature molten salt as the electrolyte of the battery, it is preferable to use a composition containing lithium iron phosphate, Lix Positive electrode active materials include VPO4F (0≤x≤1), lithium manganese composite oxide, lithium nickel composite oxide, lithium nickel cobalt composite oxide, or mixtures thereof. These compounds exhibit low reactivity with room-temperature molten salts, thus improving cycle life. Details regarding room-temperature molten salts will be described later in the description of the second embodiment.

[0058] The primary particle size of the positive electrode active material is preferably above 100 nm and below 1 μm. Positive electrode active materials with a primary particle size of above 100 nm are easy to process in industrial production. Positive electrode active materials with a primary particle size of below 1 μm can smoothly undergo solid-state internal diffusion of lithium ions.

[0059] The specific surface area of ​​the positive electrode active material is preferably 0.1 m². 2 / g or more and 10m 2 / g or less. Has 0.1m 2 Positive electrode active materials with a specific surface area of ​​over / g can adequately ensure the insertion and extraction sites of Li ions. (The last part, "10m," appears to be an unrelated fragment and is omitted from the translation.) 2 Positive electrode active materials with a specific surface area of ​​less than 1 g are easy to process in industrial production and can ensure good charge-discharge cycle performance.

[0060] The conductive agent is formulated to improve current collection performance and suppress the contact resistance between the active material and the current collector. The conductive agent comprises at least fibrous carbon containing a first portion C1 and a second portion 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, multilayer carbon nanotubes (MWCNTs), and carbon nanofibers. One of these can be used as another conductive agent, or two or more can be combined. Alternatively, instead of using other conductive agents, the surface of the active material particles can be coated with carbon or an electronically conductive inorganic material.

[0061] Binders are used 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 can be used as a binder, or two or more can be used in combination.

[0062] The proportions of the active material, fibrous carbon, other conductive agents, and binder in the active material layer can be appropriately varied depending on the application of the electrode. For example, in the case of a negative electrode, it is preferable to combine the active material (negative electrode active material), fibrous carbon, other conductive agents, and binder 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 combine the active material (positive electrode active material), fibrous carbon, other conductive agents, and binder 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 making the amount of binder 2% or more by mass, the adhesion between the active material layer and the current collector becomes sufficient, and excellent cycle performance can be expected. To achieve high capacity, it is preferable to make the binder 30% or less by mass.

[0063] For either the positive or negative electrode, 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, is preferably 2% by mass or less. By including at least a portion of fibrous carbon containing a first portion of C1 and a second portion of C2 as a conductive agent, the current-collecting performance of the active material layer can be improved while reducing the total amount of conductive agent. By reducing the amount of carbon material contained in the active material layer, the amount of active material can be increased, resulting in a high-capacity electrode. Furthermore, it is preferable to have a low content of granular carbon such as carbon black and graphite, and more preferably, no granular carbon. By reducing or eliminating bulky granular carbon, a high-energy-density electrode can be obtained.

[0064] The current collector uses an electrochemically stable material at the potential for lithium (Li) insertion and extraction into 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 or more and 20 μm or less. A current collector with such a thickness achieves a balance between electrode strength and lightweight.

[0065] In the case of a positive electrode, 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.

[0066] The thickness of the aluminum foil or aluminum alloy foil is preferably 5 μm or more and 20 μm or less, more preferably 15 μm or less. The purity of the aluminum foil is preferably 99% by mass or more. The content of transition metals such as iron, copper, nickel, and chromium contained in the aluminum foil or aluminum alloy foil is preferably 1% by mass or less.

[0067] The density of the negative electrode active material layer (excluding the current collector) is preferably 1.8 g / cm³. 3 Above and 2.8g / cm 3 The density of the layer containing the negative electrode active material is more preferably 2.1 g / cm³. 3 Above and 2.7g / cm 3 The density of the positive electrode active material layer (excluding the current collector) is preferably 1.8 g / cm³. 3 Above and 3.5g / cm 3 The density of the layer containing the negative electrode active material is more preferably 2.1 g / cm³. 3 Above and 3.3g / cm 3 The following electrodes, with an active material layer density within this range, exhibit excellent energy density and electrolyte retention.

[0068] <Manufacturing Method>

[0069] Electrodes can be fabricated, 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 then coated onto one or both sides of a current collector. Next, the coated slurry is dried to obtain a laminate containing the active material layer and the current collector. Then, pressure is applied to the laminate. This process fabricates the electrode.

[0070] Alternatively, the electrode can be fabricated using the following method: First, an active material, a conductive agent, and a binder are mixed to obtain a mixture. Next, this mixture is granulated. Then, these granules are disposed on a current collector, thereby obtaining the positive electrode.

[0071] When using active materials with fine particles having oxides on their particle surfaces, 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 approximately 100 nm are mixed into calcined TNO active material particles, and then heat-treated at 300°C to 400°C. This generates fine particles on the surface of the TNO active material particles.

[0072] For example, in the synthesis of TNO active material particles, where fine particles are generated, TiO2 and Nb2O5 are used as raw materials. After mixing them and before calcination, the particles are finely ground. Grinding is preferably performed until the cumulative frequency of the volume from the smallest particle size side in the particle size distribution measurement reaches 10% for particle size D. 10 It will become around 10nm to 100nm.

[0073] <Determination Method>

[0074] Next, the measurement methods for the electrodes will be explained. Specifically, the methods for observing and measuring the electrode surface using a scanning electron microscope (SEM), as well as the methods for measuring the carbon materials and active substances contained in the electrodes, will be explained.

[0075] The test sample can be an electrode that is not inserted into the battery or an electrode removed from a disassembled battery. If removed from the battery, the sample is cleaned with an organic solvent to remove any lithium salt residue. First, the sample is immersed in a cyclic carbonate, which has high lithium salt solubility, followed by immersion in a chain carbonate for cleaning; this significantly reduces the amount of residual lithium salt. After immersion, the solvent is removed under reduced pressure in a vacuum.

[0076] (SEM observation of the electrodes)

[0077] By observing the surface of the electrode sample using SEM, the presence of fibrous carbon comprising a first part C1 and a second part C2 can be confirmed. Furthermore, the diameter W1 and area A1 of the first part C1, the diameter W2 and area A2 of the second part C2, and the length L of the fibrous carbon can be measured.

[0078] SEM images of the electrode surface are obtained and then binarized. During binarization, a threshold is set to distinguish active material particles from carbon materials such as fibrous carbon and granular carbon. Software examples include Image-J.

[0079] Fibrous carbon and granular carbon differ in shape. Fibrous carbon has a high aspect ratio, possessing length relative to its fiber diameter, and can have straight or curved portions. If the aspect ratio is 5 or higher, it is considered fibrous carbon. Fibrous carbon can contact multiple active material particles or granular carbon particles. Granular carbon has a low aspect ratio; amorphous particles can exist individually or continuously. If the aspect ratio is 3 or lower, it is considered granular carbon. It should be noted that 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 can be 800 nm or less. Furthermore, the diameter of a single granular particle can be 400 nm or less.

[0080] Based on the binarized image, the fiber diameter of fibrous carbon is estimated. The first part, C1, is based on the binarized image where the fiber diameter W1 ranges from 60 nm to 500 nm. The portion of the fiber with a diameter close to 60 nm to 500 nm can be detected from the image. Regarding the fiber diameter W1, a 50 nm straight line is drawn along one side of the fiber, and its perpendicular line is drawn. The distance along this perpendicular line from end to end of the fiber is taken as the fiber diameter. Fibrous carbon can exist on active material particles, on granular particles, and between particles.

[0081] The second part C2 is a part with a smaller fiber diameter than the first part C1, preferably having a fiber diameter of 1 nm to 15 nm. A part smaller than 60 nm can be detected from the image. Similar to the measurement of the fiber diameter W1 of the first part C1, regarding the fiber diameter W2, draw a 50-nm straight line along one side of the fiber, draw a perpendicular line to it, and set the distance from the perpendicular line to the end of the fiber as the fiber diameter W2.

[0082] Based on the binarized image, the area A1 of the first part C1 and the area A2 of the second part C2 can be obtained using image analysis software.

[0083] The fibrous carbon confirmed in the SEM image preferably satisfies 100 < L / W2. The length L is obtained in at least some of the fibrous carbon that satisfies W2. The length L may not be a straight line. For fibrous carbon containing curves, the length L is obtained by image analysis software. The fibrous carbon sometimes exists across multiple active material particles. Furthermore, the fibrous carbon may branch and exist. In the case of branching, any branch can be selected to obtain the length L.

[0084] (Measurement method of carbon material)

[0085] The amount of carbon material contained in the electrode can be measured by thermogravimetric analysis (Thermo Gravimetry; TG). Since the burnout temperatures are different between fibrous carbon and granular carbon, the amounts of fibrous carbon and granular carbon can be measured separately by TG. Specifically, perform TG measurement in air, hold at 500 °C for 1 hour, and take the reduced weight as the weight of the binder. Then, raise the temperature, hold at 650 °C for 1 hour, and take the reduction in the reduced weight as the weight of the fibrous carbon. Then, raise the temperature again, hold at 800 °C for 1 hour, and take the reduction in the reduced weight as the weight of the granular carbon.

[0086] (Measurement method of active material)

[0087] By the following measurement, the composition of the active material contained in the electrode can be obtained.

[0088] By combining elemental analysis using a scanning electron microscope (SEM-EDX) equipped with an energy-dispersive X-ray spectrometry (SEM-EDX) device, X-ray diffraction (XRD) measurements, and inductively coupled plasma (ICP) luminescence spectrometry, the composition of active materials, such as those contained in an active material layer, can be identified within an electrode. SEM-EDX analysis reveals the shape and composition (elements from B to U in the periodic table) of the components within the active material layer. ICP measurements allow for the quantification of elements within the active material layer. Finally, XRD measurements confirm the crystal structure of the material contained in the active material layer.

[0089] The cross-section of the electrode, as described above, was cut using Ar ion milling. The cut cross-section was observed using SEM. Sample collection was conducted in an inert atmosphere, such as argon or nitrogen, without contact with the atmosphere. Several particles were selected from the SEM image at 3000x magnification. Selection was performed in a manner that maximized the particle size distribution of the selected particles.

[0090] Next, elemental analysis based on EDX is performed on each selected particle. This allows us to determine the types and amounts of elements other than Li contained in each selected particle.

[0091] Regarding Li, information about the overall Li content in the active substance can be obtained through ICP-luminescence spectrometry. ICP-luminescence spectrometry is performed according to the following steps.

[0092] The powder sample is prepared from the dried electrode as follows: The active material layer is peeled off from 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, hydrofluoric acid, etc., can be used as the acid. By performing ICP-based spectral analysis on this liquid sample, the concentration of elements in the active material of the analyte can be determined.

[0093] The crystal structure of the compounds contained in each particle selected by SEM can be determined by XRD. XRD is performed using CuKα rays as the X-ray source within a measurement range of 2θ = 5° to 90°. This measurement yields the X-ray diffraction pattern of the compounds contained in the selected particles.

[0094] The Rigaku SmartLab was used as the XRD apparatus. The measurement conditions were as follows:

[0095] X-ray source: Cu target

[0096] Output: 45kV, 200mA

[0097] Slatter slit: both incident and received light angles are 5°.

[0098] Step size (2θ): 0.02 deg

[0099] Scanning speed: 20 deg / minute

[0100] Semiconductor detector: D / teX Ultra 250

[0101] Sample plate holder: Flat glass sample plate holder (0.5mm thick)

[0102] Measurement range: 5°≤2θ≤90°.

[0103] When other apparatus was used, measurements were performed using standard Si powder for powder X-ray diffraction. It was found that the results of peak intensity, half-maximum amplitude, and diffraction angle were equivalent to those obtained by the apparatus described above. The measurements of the sample were performed under these conditions.

[0104] The XRD measurement conditions were set to obtain XRD patterns suitable for Rietveld analysis. Specifically, to collect data for Rietveld analysis, the measurement time or X-ray intensity was appropriately adjusted such that the step size was 1 / 3 to 1 / 5 of the minimum half-maximum amplitude of the diffraction peak, and the intensity at the position of the most intense reflection peak was 5000 cps or higher.

[0105] The XRD pattern obtained above was 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 here is estimated based on the analysis results of EDX and ICP. By fitting all the calculated values ​​to the measured values, parameters related to the crystal structure (lattice constant, atomic coordinates, occupancy, etc.) can be precisely analyzed.

[0106] Rietveld analysis can be used to estimate the content of titanium-niobium composite oxides, for example, in cases where the negative electrode contains multiple active materials. A fitting parameter S is used as a measure of the consistency between observed and calculated intensities in Rietveld analysis. Analysis must be performed with S less than 1.8. Furthermore, the standard deviation σj must be considered when determining the occupancy of each point. The fitting parameter S and standard deviation σj, as defined here, are derived from mathematical formulas described in non-patent literature ("Practical Applications of Powder X-ray Analysis," edited by Izumi Nakai and Fujio Izumi, Japan Society for Analytical Chemistry X-ray Analysis Research Symposium (Asakura Shoten)).

[0107] XRD measurements can be performed by directly attaching the electrode sample to a glass support in a wide-angle X-ray diffractometer. In this case, the XRD spectrum is pre-measured based on the type of metal foil used as the current collector to determine the location of peaks originating from the current collector. Additionally, the presence or absence of peaks from conductive agents, binders, or other additives is also pre-determined. If the current collector peak overlaps with the active material peak, it is preferable to peel off the active material layer from the current collector before measurement. This is to separate the overlapping peaks when quantitatively measuring peak intensity. Of course, if these factors are known beforehand, this step can be omitted.

[0108] For example, the particles observed by previous SEM-EDX measurements contain Ti, Nb, and O. Furthermore, when X-ray diffraction patterns belonging to the monoclinic crystal type were obtained from the electrode of the test object in previous XRD measurements, it was known that monoclinic titanium-niobium composite oxide particles are present in the active material of the test object. According to EDX measurements, in cases where the content of Ti and Nb varies greatly, multiple active materials may be present. The amount of elements contained in the active material of the electrode can be determined by ICP-luminescence spectrophotometry following the previously described procedure.

[0109] The content of active substances in the active substance layer can be estimated using the following methods.

[0110] After washing and drying the electrodes removed from the battery following the previously described steps, peel off the active material layer from the current collector and grind it using a mortar. Place the ground sample into a glass sample plate and grind it so that the surface of the glass sample plate is flush with the sample surface. Additionally, a Si standard sample can be added to correct the peak position.

[0111] For the powder sample filled into a glass sample plate, XRD and Rietveld analysis were performed under the conditions described above. Additionally, SEM-EDX and ICP analyses were performed using the powder sample following the same procedure. Based on the results of the XRD, SEM-EDX, and ICP analyses, the types and proportions of active substances contained within can be estimated.

[0112] The electrode according to the first embodiment comprises a plurality of active material particles and fibrous carbon, wherein the fibrous carbon comprises a first portion (C1) with a fiber diameter of 60 nm or more and 500 nm or less, 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. This electrode is capable of providing secondary batteries and battery packs with high input-output density.

[0113] (Second Implementation)

[0114] According to a second embodiment, a secondary battery comprising a positive electrode, a negative electrode, and an electrolyte is provided. This secondary battery includes at least one of the electrodes described in the first embodiment as a positive electrode and a negative electrode. When the electrode described in the first embodiment is included as the negative electrode, the positive electrode may be a different electrode than that described in the first embodiment. When the electrode described in the first embodiment is included as the positive electrode, the negative electrode may be a different electrode than that described in the first embodiment. The secondary battery according to the second embodiment may also include both the electrode described in the first embodiment as a negative electrode and as a positive electrode, respectively.

[0115] The secondary battery can also be further equipped with a separator disposed between the positive and negative electrodes. The negative electrode, positive electrode, and separator can constitute an electrode assembly. The electrolyte can be retained within the electrode assembly.

[0116] In addition, the secondary battery can be further equipped with an outer packaging component that houses the electrode assembly and electrolyte.

[0117] Furthermore, the secondary battery can further have a negative terminal electrically connected to the negative electrode and a positive terminal electrically connected to the positive electrode.

[0118] The secondary battery can be, for example, a lithium secondary battery. Alternatively, secondary batteries include non-aqueous electrolyte secondary batteries containing a non-aqueous electrolyte.

[0119] The following provides a detailed description of the negative electrode, positive electrode, electrolyte, diaphragm, outer packaging components, negative terminal, and positive terminal.

[0120] 1) Negative electrode

[0121] The negative electrode may include a negative current collector and a layer containing a negative active material. The negative electrode may be the electrode according to the first embodiment. Therefore, the negative current collector and the layer containing the negative active material may be the current collector and the active material layer included in the electrode according to the first embodiment, respectively.

[0122] In the details of the negative electrode, portions that repeat the details already described regarding the method of using the electrode according to the first embodiment as the negative electrode 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.

[0123] In the negative electrode containing the negative electrode active material layer, the negative electrode active material, conductive agent, and binder are preferably combined 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-collecting performance of the negative electrode active material layer can be improved. In addition, by setting the amount of binder to 2% by mass or more, the adhesion between the active material layer and the current collector becomes sufficient, and excellent cycle performance can be expected. On the other hand, setting the amount of conductive agent and binder to 30% by mass or less is preferred for achieving high capacity.

[0124] Other negative electrodes, for example, can be manufactured using the same method as the electrodes involved in the first embodiment, except that they do not use fibrous carbon containing both the first portion C1 and the second portion C2 as a conductive agent.

[0125] 2) Positive electrode

[0126] The positive electrode may include a positive current collector and a layer containing a positive active material. The positive electrode may be the electrode according to the first embodiment. Therefore, the positive current collector and the layer containing the positive active material may be the current collector and the active material layer that the electrode according to the first embodiment can include.

[0127] In the details of the positive electrode, portions that repeat the details already described regarding the method of using the electrode according to the first embodiment as the positive electrode 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.

[0128] In other positive electrodes containing positive electrode active material layers, positive electrode active material and binder are preferably combined in proportions of 80% to 98% by mass and 2% to 20% by mass, respectively.

[0129] Sufficient electrode strength can be obtained by making the amount of binder 2% by mass or more. Furthermore, the binder functions as an insulator. Therefore, if the amount of binder is 20% by mass or less, the amount of insulator contained in the electrode is reduced, thus reducing internal resistance.

[0130] When adding the conductive agent, it is preferable that the positive electrode active material, binder and conductive agent are mixed in proportions of 77% or more and 95% or less by mass, 2% or more and 20% or less by mass, and 3% or more and 15% or less by mass, respectively.

[0131] The aforementioned effects can be achieved by ensuring that the amount of the conductive agent is 3% by mass or more. Furthermore, by ensuring that the amount of the conductive agent is 15% by mass or less, the proportion of the conductive agent in contact with the electrolyte can be reduced. If this proportion is low, electrolyte decomposition can be reduced under high-temperature storage conditions.

[0132] The positive electrode, for example, can be manufactured in the same way as the electrode involved in the first embodiment, except that it does not use fibrous carbon containing both the first part C1 and the second part C2 as a conductive agent.

[0133] 3) Electrolytes

[0134] As the electrolyte, for example, a liquid non-aqueous electrolyte or a gel-like non-aqueous electrolyte can be used. A liquid non-aqueous electrolyte is prepared by dissolving an electrolyte salt, which is the 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.

[0135] Examples of electrolyte salts include lithium salts such as lithium perchlorate (LiClO4), lithium hexafluorophosphate (LiPF6), lithium tetrafluoroborate (LiBF4), lithium hexafluoroarsenate (LiAsF6), lithium trifluoromethanesulfonate (LiCF3SO3), and lithium bis(trifluoromethanesulfonyl)imide (LiN(CF3SO2)2), as well as mixtures thereof. The electrolyte salt is preferably a salt that is difficult to oxidize even at high potentials, with LiPF6 being the most preferred.

[0136] Examples of organic solvents include: cyclic carbonates such as propylene carbonate (PC), ethylene carbonate (EC), and vinylene carbonate (VC); chain carbonates such as diethyl carbonate (DEC), dimethyl carbonate (DMC), and methyl ethyl carbonate (MEC); cyclic ethers such as tetrahydrofuran (THF), 2-methyl tetrahydrofuran (2MeTHF), and dioxolane (DOX); chain ethers such as dimethoxyethane (DME) and diethoxyethane (DEE); γ-butyrolactone (GBL), acetonitrile (AN), and sulfolane (SL). These organic solvents can be used alone or as mixed solvents.

[0137] Gel-like nonaqueous electrolytes can be modulated by combining liquid nonaqueous electrolytes with polymeric materials. Examples of polymeric materials include polyvinylidene fluoride (PVdF), polyacrylonitrile (PAN), polyethylene oxide (PEO), or mixtures thereof.

[0138] Alternatively, as a non-aqueous electrolyte, in addition to liquid non-aqueous electrolytes and gel non-aqueous electrolytes, room-temperature molten salts (ionic melts) containing lithium ions, polymeric solid electrolytes, and inorganic solid electrolytes can also be used.

[0139] Room-temperature molten salts (ionic melts) refer to compounds of organic salts composed of a combination of organic cations and anions that exist as liquids at room temperature (above 15°C and below 25°C). Room-temperature molten salts include those that exist as liquids alone, those that become liquid by mixing with electrolyte salts, those that become liquid by dissolving in organic solvents, or mixtures thereof. Typically, the melting point of room-temperature molten salts used in secondary batteries is below 25°C. Furthermore, the organic cations usually possess a quaternary ammonium framework.

[0140] Polymer solid electrolytes are prepared by dissolving electrolyte salts in polymer materials and then solidifying them.

[0141] Inorganic solid electrolytes are solid substances that exhibit Li-ion conductivity. Here, Li-ion conductivity refers to a conductivity of 1×10⁻⁶ at 25°C. -6 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 described below.

[0142] As an oxide-based solid electrolyte, it is preferable to use an electrolyte with a NASICON (Sodium(Na) Super Ionic Conductor) type structure and composed of the general formula Li 1+x Mα2(PO4)3 represents a lithium phosphate solid electrolyte. In the above formula, Mα is, for example, selected from one or more of titanium (Ti), germanium (Ge), strontium (Sr), zirconium (Zr), tin (Sn), aluminum (Al), and calcium (Ca). The subscript x is in the range of 0 ≤ x ≤ 2.

[0143] As a specific example of a lithium phosphate solid electrolyte with a NASICON-type structure, one could cite Li... 1+x Al x Ti 2-xAn LATP compound represented by (PO4)3 and where 0.1 ≤ x ≤ 0.5; composed of Li 1+x Al y Mβ 2-y (PO4)3, where Mβ is one or more selected from Ti, Ge, Sr, Zr, Sn, and Ca and the compound has 0 ≤ x ≤ 1 and 0 ≤ y ≤ 1; composed of Li 1+x Al x Ge 2-x (PO4)3 and the compound has 0 ≤ x ≤ 2; and composed of Li 1+x Al x Zr 2-x (PO4)3 and the compound has 0 ≤ x ≤ 2; composed of Li 1+x+y Al x Mγ 2- x Si y P 3-y O 12 and where Mγ is one or more selected from Ti and Ge and the compound has 0 < x ≤ 2, 0 ≤ y < 3; composed of Li 1+2x Zr 1- x Ca x (PO4)3 and the compound has 0 ≤ x < 1.

[0144] In addition, as the oxide-based solid electrolyte, in addition to the above lithium phosphate solid electrolyte, an amorphous LIPON compound represented by Li x PO y N z can also be cited, where 2.6 ≤ x ≤ 3.5, 1.9 ≤ y ≤ 3.8, and 0.1 ≤ z ≤ 1.3 (for example, Li 2.9 PO<了 3.3 N 0.46 ); a compound represented by garnet-type structure La 5+x A x La 3-x Mδ2O 12 where A is one or more selected from the group consisting of Ca, Sr, and Ba, Mδ is one or more selected from the group consisting of Nb and Ta, and 0 ≤ x ≤ 0.5; a compound represented by Li3Mδ 2- x L2O 12 where Mδ is one or more selected from the group consisting of Nb and Ta, L may contain Zr, and 0 ≤ x ≤ 0.5; a compound represented by Li 7-3x Al x La3Zr3O 12 and 0 ≤ x ≤ 0.5; a compound represented by Li 5+x La3Mδ 2-x It should be noted that there seems to be an error in the tag where it says "<了 3.3 ", which should probably be corrected for a proper translation.Zr x O 12 Mδ represents one or more LLZ compounds selected from the group consisting of Nb and Ta, with 0 ≤ x ≤ 2 (e.g., Li7La3Zr2O). 12 ); and having a perovskite-type structure and composed of La 2 / 3-x Li x TiO3 represents compounds in which 0.3 ≤ x ≤ 0.7.

[0145] One or more of the above-mentioned compounds may be used as a solid electrolyte. Two or more of the above-mentioned solid electrolytes may also be used.

[0146] 4) Diaphragm

[0147] The diaphragm can be formed, for example, from a porous membrane containing polyethylene (PE), polypropylene (PP), cellulose, or polyvinylidene fluoride (PVdF) or a nonwoven fabric made of synthetic resin. From a safety point of view, a porous membrane made of polyethylene or polypropylene is preferred. This is because these porous membranes melt at a certain temperature, which can interrupt the current.

[0148] 5) Outer packaging components

[0149] As an outer packaging component, containers formed of laminated film or metal containers can be used, for example.

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

[0151] As a laminated film, a multilayer film comprising multiple resin layers and a metal layer sandwiched between these resin layers can be used. The resin layers may contain polymers such as polypropylene (PP), polyethylene (PE), nylon, and polyethylene terephthalate (PET). For weight reduction, the metal layer is preferably formed of aluminum foil or aluminum alloy foil. The laminated film can be sealed by hot-melt bonding to form the shape of an outer packaging component.

[0152] The wall thickness of the metal container is preferably 1 mm or less, more preferably 0.5 mm or less, and even more preferably 0.2 mm or less.

[0153] Metal containers can be made of materials such as aluminum or aluminum alloys. Preferably, the aluminum alloy contains elements such as magnesium, zinc, and silicon. When the aluminum alloy contains transition metals such as iron, copper, nickel, and chromium, their content is preferably less than 100 ppm by mass.

[0154] The shape of the outer packaging component is not particularly limited. The outer packaging component can be, for example, flat (thin), square, cylindrical, coin-shaped, or button-shaped. The outer packaging component can be selected appropriately according to the battery size and intended use.

[0155] 6) Negative extremes

[0156] The negative terminal can be formed of a material that is electrochemically stable and conductive at the Li insertion / deintercalation potential of the aforementioned negative electrode active material. Specifically, examples of materials for the negative terminal include copper, nickel, stainless steel, or aluminum, or an aluminum alloy containing at least one element selected from Mg, Ti, Zn, Mn, Fe, Cu, and Si. Aluminum or an aluminum alloy is preferred as the material for the negative terminal. To reduce the contact resistance with the negative electrode current collector, the negative terminal is preferably formed of the same material as the negative electrode current collector.

[0157] 7) Positive extreme

[0158] The positive terminal can be in a potential range of 3V or higher and 4.5V or lower relative to the redox potential of lithium (vs. Li / Li). + The positive terminal is formed of a material that is electrically stable and conductive. Examples of materials for the positive terminal include aluminum or aluminum alloys containing at least one element selected from Mg, Ti, Zn, Mn, Fe, Cu, and Si. To reduce the contact resistance with the positive current collector, the positive terminal is preferably formed of the same material as the positive current collector.

[0159] Next, the secondary battery of the embodiment will be described in more detail with reference to the accompanying drawings.

[0160] Figure 4 This is a cross-sectional view that roughly represents an example of a secondary battery. Figure 5 yes Figure 4 An enlarged cross-sectional view of part B of the secondary battery shown.

[0161] Figure 4 and Figure 5 The secondary battery 100 shown has Figure 4 The bag-shaped outer packaging component 2 shown is shown. Figure 4 and Figure 5 Electrode assembly 1 and electrolyte (not shown) are shown. Electrode assembly 1 and electrolyte are housed within a bag-shaped outer packaging component 2. The electrolyte (not shown) is held within electrode assembly 1.

[0162] The bag-shaped outer packaging component 2 is formed of a laminate containing two resin layers and a metal layer between them.

[0163] like Figure 4 As shown, electrode group 1 is a flat, wound electrode group. Figure 5As shown, the flat and coiled electrode assembly 1 includes a negative electrode 3, a diaphragm 4, and a positive electrode 5. The diaphragm 4 is located between the negative electrode 3 and the positive electrode 5.

[0164] The negative electrode 3 includes a negative current collector 3a and a layer 3b containing a negative active material. In the negative electrode 3, the outermost portion located in the wound electrode assembly 1 is as follows... Figure 5 As shown, a layer 3b containing negative electrode active material is formed only on the inner surface of the negative electrode current collector 3a. In other parts of the negative electrode 3, layers 3b containing negative electrode active material are formed on both sides of the negative electrode current collector 3a.

[0165] The positive electrode 5 includes a positive current collector 5a and a layer 5b containing positive active material formed on both sides of it.

[0166] like Figure 4 As shown, the negative terminal 6 and the positive terminal 7 are located near the outer periphery of the wound electrode assembly 1. The negative terminal 6 is connected to the outermost portion of the negative current collector 3a. The positive terminal 7 is connected to the outermost portion of the positive current collector 5a. These negative terminals 6 and positive terminals 7 extend outward from the opening of the bag-shaped outer packaging member 2. A thermoplastic resin layer is provided on the inner surface of the bag-shaped outer packaging member 2, and the opening is sealed by thermally melting and bonding it.

[0167] The secondary batteries involved in the implementation methods are not limited to Figure 4 and Figure 5 The secondary battery shown can also be, for example, a... Figure 6 and Figure 7 The battery configuration shown.

[0168] Figure 6 This is a partial cutaway perspective view schematically representing other examples of secondary batteries. Figure 7 It is Figure 6 An enlarged cross-sectional view of section C of the secondary battery shown.

[0169] Figure 6 and Figure 7 The secondary battery 100 shown has Figure 6 and Figure 7 Electrode group 1 shown Figure 6 The outer packaging component 2 and the electrolyte (not shown) are shown. The electrode assembly 1 and the electrolyte are housed within the outer packaging component 2. The electrolyte is held within the electrode assembly 1.

[0170] The outer packaging component 2 is formed of a laminated film comprising two resin layers and a metal layer sandwiched between them.

[0171] Electrode group 1 as follows Figure 7The electrode assembly shown is a stacked type. The stacked type electrode assembly 1 has a structure in which a membrane 4 is sandwiched between the negative electrode 3 and the positive electrode 5, and the negative electrode 3 and the positive electrode 5 are stacked alternately.

[0172] The electrode assembly 1 includes multiple negative electrodes 3. Each negative electrode 3 has a negative current collector 3a and a layer 3b containing a negative active material supported on both sides of the negative current collector 3a. Furthermore, the electrode assembly 1 includes multiple positive electrodes 5. Each positive electrode 5 has a positive current collector 5a and a layer 5b containing a positive active material supported on both sides of the positive current collector 5a.

[0173] Each negative electrode 3's negative current collector 3a comprises a portion on one side of which does not support a layer 3b containing the negative electrode active material on any surface. This portion functions as a negative current collector tab 3c. Figure 7 As shown, the negative collector tab 3c does not overlap with the positive electrode 5. Furthermore, multiple negative collector tabs 3c are electrically connected to the strip-shaped negative terminal 6. The front end of the strip-shaped negative terminal 6 extends to the outside of the outer packaging component 2.

[0174] Furthermore, although not illustrated, the positive current collector 5a of each positive electrode 5 also includes a portion on one side where no layer of positive active material 5b is supported on either surface. This portion functions as a positive current collector tab. The positive current collector tab, like the negative current collector tab 3c, does not overlap with the negative electrode 3. Moreover, the positive current collector tab is located on the opposite side of the electrode group 1 relative to the negative current collector tab 3c. The positive current collector tab is electrically connected to the strip-shaped positive terminal 7. The front end of the strip-shaped positive terminal 7 is located on the opposite side of the negative terminal 6, extending to the outside of the outer packaging member 2.

[0175] The secondary battery according to the second embodiment includes the electrodes according to the first embodiment. Therefore, the input-output density of this secondary battery is high.

[0176] (Third Implementation)

[0177] According to a third embodiment, a battery pack is provided. This battery pack includes a plurality of secondary batteries according to a second embodiment.

[0178] In this battery pack, the individual cells can be configured to be connected in series or in parallel, or a combination of series and parallel connections can be configured.

[0179] Next, an example of a battery pack according to the embodiment will be described with reference to the accompanying drawings.

[0180] Figure 8 This is a three-dimensional diagram that roughly represents an example of a battery pack. Figure 8The battery pack 200 shown includes five individual cells 100a to 100e, four busbars 21, a positive electrode lead 22, and a negative electrode lead 23. The five individual cells 100a to 100e are secondary batteries according to the second embodiment.

[0181] Bus 21 connects, for example, the negative terminal 6 of a single cell 100a to the positive terminal 7 of the adjacent single cell 100b. Thus, five single cells 100 are connected in series via four buses 21. Figure 8 The battery pack 200 is a battery pack of 5 connected in series. Although no example is illustrated, in a battery pack containing multiple individual cells connected in parallel, for example, multiple negative terminals are connected to each other via a bus, and multiple positive terminals are connected to each other via a bus, so that multiple individual cells can be electrically connected.

[0182] The positive terminal 7 of at least one of the five individual cells 100a to 100e is electrically connected to the positive terminal lead 22 for external connection. In addition, the negative terminal 6 of at least one of the five individual cells 100a to 100e is electrically connected to the negative terminal lead 23 for external connection.

[0183] The battery pack according to the third embodiment includes the secondary battery according to the second embodiment. Therefore, the input-output density of this battery pack is high.

[0184] (Fourth Implementation)

[0185] According to a fourth embodiment, a battery pack is provided. This battery pack includes the battery pack according to the third embodiment. Alternatively, the battery pack may include a single secondary battery according to the second embodiment instead of the battery pack according to the third embodiment.

[0186] The battery pack can be further equipped with a protection circuit. This protection circuit controls the charging and discharging of the secondary battery. Alternatively, the protection circuitry within a device that uses the battery pack as a power source (such as electronic devices, automobiles, etc.) can be used as the battery pack's protection circuitry.

[0187] Furthermore, the battery pack may also include external terminals for power supply. These external terminals are used to supply current from the secondary battery to the external source and / or to the secondary battery from the external source. In other words, when the battery pack is used as a power source, current is supplied to the external source through the external terminals. Additionally, when charging the battery pack, charging current (including regenerative energy from the power source of a vehicle, etc.) is supplied to the battery pack through the external terminals.

[0188] Next, an example of the battery pack according to the embodiments will be described with reference to the accompanying drawings.

[0189] Figure 9This is an exploded perspective view that roughly represents an example of a battery pack. Figure 10 It means Figure 9 A block diagram of an example of the circuitry for the battery pack shown.

[0190] Figure 9 and Figure 10 The battery pack 300 shown includes a housing 31, a cover 32, a protective sheet 33, a battery pack 200, a printed circuit board 34, wiring 35, and an insulating plate (not shown).

[0191] Figure 9 The container 31 shown is a square container with a rectangular base. The container 31 is configured to accommodate the protective sheet 33, the battery pack 200, the printed circuit board 34, and the wiring 35. The cover 32 has a rectangular shape. The cover 32 covers the container 31 to accommodate the battery pack 200 and the like. Although not shown, the container 31 and the cover 32 are provided with openings or connection terminals for connecting to external devices.

[0192] The battery pack 200 includes multiple individual cells 100, a positive electrode lead 22, a negative electrode lead 23, and an adhesive tape 24.

[0193] At least one of the multiple single cells 100 is a secondary battery according to the second embodiment. For example... Figure 10 As shown, multiple individual cells 100 are connected in series with ground. Multiple individual cells 100 can also be connected in parallel with ground, or a combination of series and parallel connections. When multiple individual cells 100 are connected in parallel, the battery capacity increases compared to a series connection.

[0194] Adhesive tape 24 is used to secure multiple individual cells 100 together. Alternatively, heat shrinkable tape can be used instead of adhesive tape 24 to secure multiple individual cells 100. In this case, protective sheets 33 are placed on both sides of the battery pack 200, and after the heat shrinkable tape is wrapped around it, the heat shrinkable tape is heat-shrinked to secure the multiple individual cells 100 together.

[0195] One end of the positive electrode lead 22 is connected to the battery pack 200. One end of the positive electrode lead 22 is electrically connected to the positive electrode of one or more individual cells 100. One end of the negative electrode lead 23 is connected to the battery pack 200. One end of the negative electrode lead 23 is electrically connected to the negative electrode of one or more individual cells 100.

[0196] The printed circuit board 34 is disposed along one of the width directions of the inner surface of the receiving container 31. The printed circuit board 34 includes a positive-side connector 342, a negative-side connector 343, a thermistor 345, a protection circuit 346, wirings 342a and 343a, an external terminal 350 for power supply, positive-side wiring 348a, and negative-side 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 located between the printed circuit board 34 and the battery pack 200.

[0197] 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.

[0198] A thermistor 345 is fixed to one main surface of the printed circuit board 34. The thermistor 345 detects the temperature of each individual cell 100 and sends its detection signal to the protection circuit 346.

[0199] An external terminal 350 for power supply is fixed to another main surface of the printed circuit board 34. The external terminal 350 for power supply is electrically connected to a device located outside the battery pack 300. The external terminal 350 for power supply includes a positive terminal 352 and a negative terminal 353.

[0200] The protection circuit 346 is fixed to another main surface of the printed circuit board 34. The protection circuit 346 is connected to the positive terminal 352 via a positive side wiring 348a. The protection circuit 346 is connected to the negative terminal 353 via a negative side wiring 348b. Additionally, the protection circuit 346 is electrically connected to the positive connector 342 via wiring 342a. The protection circuit 346 is electrically connected to the negative connector 343 via wiring 343a. Furthermore, the protection circuit 346 is electrically connected to each of the multiple individual cells 100 via wiring 35.

[0201] The protective sheet 33 is disposed on the two inner sides of the housing 31 along its length and on the inner side of the housing 31 along its width, which is opposite to the printed circuit board 34 across the battery pack 200. The protective sheet 33 is formed, for example, from resin or rubber.

[0202] The protection circuit 346 controls the charging and discharging of multiple individual batteries 100. In addition, based on the detection signal sent from the thermistor 345, or the detection signal sent from each individual battery 100 or battery pack 200, the protection circuit 346 disconnects the electrical connection between the protection circuit 346 and the external terminals 350 (positive terminal 352, negative terminal 353) used to power external devices.

[0203] As a detection signal sent from the thermistor 345, an example could be a signal indicating that the temperature of a single cell 100 is above a predetermined temperature. As a detection signal sent from each single cell 100 or the battery pack 200, examples could be signals indicating overcharging, over-discharging, and overcurrent of a single cell 100. When detecting overcharging in each single cell 100, the battery voltage, or the positive or negative electrode potential, can be detected. In the latter case, a lithium electrode used as a reference electrode is inserted into each single cell 100.

[0204] In addition, as a protection circuit 346, a circuit contained in a device that uses the battery pack 300 as a power source (such as an electronic device, a car, etc.) can also be used.

[0205] Furthermore, as described above, the battery pack 300 includes 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. Additionally, when charging the battery pack 300, charging current from the external device is supplied to the battery pack 300 through the external terminal 350. When the battery pack 300 is used as a vehicle battery, the regenerative energy from the vehicle's power source can be used as the charging current from the external device.

[0206] Furthermore, the battery pack 300 may also include multiple battery groups 200. In this case, the multiple battery groups 200 may be connected in series, in parallel, or in a combination of series and parallel connections. Additionally, the printed circuit board 34 and wiring 35 may be omitted. In this case, the positive lead 22 and the negative lead 23 may be used as the positive terminal 352 and negative terminal 353 of the external terminal 350 for power supply, respectively.

[0207] Such battery packs are used in applications requiring excellent cycle performance when drawing high currents. Specifically, they are used as power sources for electronic devices, stationary batteries, and in-vehicle batteries for various vehicles. Examples of electronic devices include digital cameras. This battery pack is particularly suitable for use as an in-vehicle battery.

[0208] The battery pack according to the fourth embodiment includes 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.

[0209] (Fifth Implementation)

[0210] According to a fifth embodiment, a vehicle is provided. This vehicle is equipped with a battery pack according to a fourth embodiment.

[0211] In this vehicle, the battery pack, for example, recovers regenerative energy from the vehicle's kinetic energy. The vehicle may also include a mechanism (Regenerator) that converts the vehicle's kinetic energy into regenerative energy.

[0212] Examples of vehicles include two- to four-wheeled hybrid electric vehicles, two- to four-wheeled electric vehicles, electric bicycles, and railway vehicles.

[0213] There are no particular restrictions on the location of the battery pack in a vehicle. For example, when mounting the battery pack in a car, it can be installed in the engine compartment, at the rear of the vehicle, or under the seats.

[0214] The vehicle can also be equipped with multiple battery packs. In this case, the batteries contained in each battery pack can be electrically connected in series, in parallel, or a combination of series and parallel connections. For example, when each battery pack contains battery groups, the battery groups can be electrically connected in series, in parallel, or a combination of series and parallel connections. Alternatively, when each battery pack contains a single battery, the individual batteries can be electrically connected in series, in parallel, or a combination of series and parallel connections.

[0215] Next, an example of a vehicle according to the embodiments will be described with reference to the accompanying drawings.

[0216] Figure 11 It is a partial perspective view that roughly represents an example of a vehicle.

[0217] Figure 11 The vehicle 400 shown includes a vehicle body 40 and a battery pack 300 according to the fourth embodiment. Figure 11 In the example shown, vehicle 400 is a four-wheeled car.

[0218] The vehicle 400 can be equipped with multiple battery packs 300. In this case, the batteries (e.g., single cells or groups of cells) contained in the battery pack 300 can be connected in series, in parallel, or in a combination of series and parallel connections.

[0219] exist Figure 11 The illustration shows an example of a battery pack 300 mounted in the engine compartment located at the front of the vehicle body 40. As mentioned above, the battery pack 300 can be mounted, for example, at 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. Furthermore, this battery pack 300 can recover regenerative energy from the power source of the vehicle 400.

[0220] Next, refer to Figure 12 The implementation method of the vehicle in the implementation method will be described.

[0221] Figure 12 This is a diagram that roughly illustrates an example of a control system associated with the electrical system in a vehicle. Figure 12 The vehicle shown, 400, is an electric car.

[0222] Figure 12 The vehicle 400 shown includes a vehicle body 40, a vehicle power supply 41, a vehicle ECU (Electric Control Unit) 42 which serves as a higher-level control device for the vehicle power supply 41, external terminals (terminals for connecting to an external power source) 43, an inverter 44, and a drive motor 45.

[0223] The vehicle 400 mounts the vehicle power supply 41 in, for example, the engine compartment, the rear of the vehicle body, or under the seats. It should be noted that... Figure 12 The vehicle 400 shown here has a schematic diagram of the mounting location of the vehicle power supply 41.

[0224] The vehicle power supply 41 includes multiple (e.g., three) battery packs 300a, 300b and 300c, a battery management unit (BMU) 411 and a communication bus 412.

[0225] Battery pack 300a includes battery pack 200a and battery pack monitoring device 301a (e.g., VTM: Voltage Temperature Monitoring). Battery pack 300b includes battery pack 200b and battery pack monitoring device 301b. Battery pack 300c includes battery pack 200c and battery pack monitoring device 301c. Battery packs 300a to 300c are the same battery packs as the aforementioned battery pack 300, and battery packs 200a to 200c are the same battery packs as the aforementioned battery pack 200. Battery packs 200a to 200c are electrically connected in series. Battery packs 300a, 300b, and 300c can be disassembled independently and can be exchanged with other battery packs 300.

[0226] Each of the battery packs 200a to 200c comprises a plurality of individual cells connected in series. At least one of the plurality of individual cells is a secondary battery according to the second embodiment. The battery packs 200a to 200c are charged and discharged respectively through the positive terminal 413 and the negative terminal 414.

[0227] The battery management device 411 communicates with the battery pack monitoring devices 301a-301c to collect information related to voltage and temperature for each individual cell 100 in the battery packs 200a-200c included in the vehicle power supply 41. Thus, the battery management device 411 collects information related to the maintenance of the vehicle power supply 41.

[0228] The battery management device 411 and the battery monitoring devices 301a-301c are connected via a communication bus 412. In the communication bus 412, one communication line is shared by multiple nodes (the battery management device 411 and one or more battery monitoring devices 301a-301c). The communication bus 412 is, for example, a communication bus based on the CAN (Control Area Network) standard.

[0229] Based on instructions from the battery management device 411, the battery monitoring devices 301a to 301c measure the voltage and temperature of each individual cell constituting the battery packs 200a to 200c. However, the temperature may be measured at only a few points for a single battery pack, or it may not be necessary to measure the temperature of all individual cells.

[0230] The vehicle power supply 41 may also have an electromagnetic contactor (e.g., to switch the electrical connection between the positive terminal 413 and the negative terminal 414) to enable or disable the connection. Figure 12 The switching device 415 shown includes a pre-charge switch (not shown) that is turned on when charging the battery packs 200a-200c, and a main switch (not shown) that is turned on when supplying output from the battery packs 200a-200c to a load. The pre-charge switch and the main switch each have a relay circuit (not shown) that switches on or off according to a signal supplied to a coil disposed near the switching element. The electromagnetic contactor, such as the switching device 415, is controlled based on a control signal from the vehicle ECU 42, which controls the operation of the battery management device 411 or the vehicle 400 as a whole.

[0231] Inverter 44 converts the input DC voltage into a high-voltage three-phase AC voltage for motor drive. The three-phase output terminals of inverter 44 are connected to the three-phase input terminals of drive motor 45. Inverter 44 is controlled based on control signals from vehicle ECU 42, which controls the operation of battery management device 411 or the vehicle as a whole. The output voltage from inverter 44 is adjusted by controlling inverter 44.

[0232] The drive motor 45 rotates using electricity supplied from the inverter 44. The driving force generated by the rotation of the drive motor 45 is transmitted to the axle and drive wheel W, for example, via a differential gear unit.

[0233] Additionally, although not shown, vehicle 400 is equipped with a regenerative braking mechanism (regenerator). When braking vehicle 400, the regenerative braking mechanism causes drive motor 45 to rotate, converting kinetic energy into regenerative energy as electrical energy. The regenerative energy recovered through the regenerative braking mechanism is input to inverter 44, where it is converted into direct current. The converted direct current is then input to vehicle power supply 41.

[0234] One terminal of the connecting line L1 is connected to the negative terminal 414 of the vehicle power supply 41. The other terminal of the connecting line L1 is connected to the negative input terminal 417 of the inverter 44. A current detection unit (current detection circuit) 416 of the battery management device 411 is provided on the connecting line L1 between the negative terminal 414 and the negative input terminal 417.

[0235] A terminal of a connecting wire L2 is connected to the positive terminal 413 of the vehicle power supply 41. The other terminal of the connecting wire L2 is connected to the positive input terminal 418 of the inverter 44. A switching device 415 is provided on the connecting wire L2 between the positive terminal 413 and the positive input terminal 418.

[0236] External terminal 43 is connected to battery management device 411. External terminal 43 can be connected to an external power source, for example.

[0237] The vehicle ECU 42, in response to input from the driver or other operators, coordinates with other management and control devices, including the battery management device 411, to control the vehicle power supply 41, switching device 415, and inverter 44. Through the coordinated control of the vehicle ECU 42 and others, it manages the overall operation of the vehicle 400, including controlling the power output from the vehicle power supply 41 and its charging. Data related to the maintenance of the vehicle power supply 41, such as its remaining capacity, is transmitted between the battery management device 411 and the vehicle ECU 42 via a communication line.

[0238] 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.

[0239] Example

[0240] The following describes the embodiments, but the present invention is not limited to the embodiments described below as long as it does not depart from the spirit of the present invention.

[0241] (Example 1)

[0242] In Example 1, a non-aqueous electrolyte battery was manufactured according to the following steps.

[0243] <Making the Negative Electrode>

[0244] As the negative electrode active material, monoclinic niobium titanium oxide particles with a composition represented by the formula TiNb2O7 were prepared. Carbon nanotubes (CNTs) were prepared as conductive agents, carboxymethyl cellulose (CMC) and styrene-butadiene rubber (SBR) were prepared as binders. For CNTs, samples with fiber diameters of approximately 1 nm to 30 nm and approximately 60 nm to 500 nm were prepared. They were mixed in pure water at a mass ratio of negative electrode active material:CNT:CMC:SBR of 96.6:0.4:1:2 to obtain a slurry. The slurry was coated on both sides of the front and back surfaces of a strip-shaped current collector formed from an aluminum foil with a thickness of 15 μm, and the coating was dried. Here, uncoated portions of the slurry remained on both sides of the front and back surfaces along one side of the current collector along the length direction. Thus, a composite containing a current collector and layers containing negative electrode active material formed on both sides of the current collector was obtained. The coating amount on each side containing the negative electrode active material layer was adjusted to 100 g / m². 2 Next, the resulting composite was prepared with a density of 2.7 g / cm³ containing the negative electrode active material layer. 3 The electrodes were then subjected to rolling. SEM observation revealed two portions for CNTs: a 480 nm fiber diameter (W1) and a 15 nm fiber diameter (W2). The former was designated as portion C1, and the latter as portion C2. The electrodes were then punched into strips with an uncoated current collector along one side of the electrode's width, and subsequently vacuum-dried to obtain the negative electrode.

[0245] <The Making of the Positive Electrode>

[0246] As the positive electrode active material, LiNi is prepared. 0.5 Co 0.2 Mn 0.3 O2 represents lithium nickel cobalt manganese composite oxide particles. Additionally, acetylene black (AB) is prepared as a conductive agent, and polyvinylidene fluoride (PVdF) is prepared as a binder. These are mixed in a mass ratio of positive electrode active material:AB:PVdF of 90:5:5 to obtain a mixture. Next, the obtained mixture is dispersed in N-methylpyrrolidone (NMP) solvent to prepare a positive electrode slurry. This slurry is coated onto the main surfaces of both sides of the front and back of a strip-shaped current collector formed from an aluminum foil with a thickness of 15 μm, and the coating is dried. Here, uncoated portions of the slurry remain on both sides of the front and back of the current collector along its length. Thus, a composite containing a current collector and positive electrode active material layers formed on both sides of the current collector is obtained. The coating amount on each side containing the positive electrode active material layer is adjusted to 125 g / m². 2 Next, the resulting composite was prepared with a density of 3.05 g / cm³ containing the positive electrode active material layer. 3The electrode is then subjected to rolling. The resulting electrode is punched into a strip shape with an uncoated portion of a current collector on one side along the width direction, and then subjected to vacuum drying to obtain a positive electrode.

[0247] <Electrode Assembly Manufacturing>

[0248] A polyethylene (PE) diaphragm with a thickness of 15 μm was prepared. Next, the prepared diaphragm was bent, and the diaphragm, six negative electrodes, and five positive electrodes were stacked in the order of negative electrode, diaphragm, positive electrode, and diaphragm to obtain a laminate. Specifically, the negative and positive electrodes were alternately inserted into the spaces defined by the bent diaphragm. The negative and positive electrodes were arranged to overlap by a range of 50 mm vertically and 50 mm horizontally. Furthermore, the negative and positive electrodes were overlapped in opposite directions, with the uncoated portions of their respective current collectors located on opposite sides of the laminate. Next, the laminate was pressed. The pressing of the laminate was performed at room temperature (25°C) under a load of 80 kN for 1 minute. This produced the electrode assembly.

[0249] <Preparation of Non-Aqueous Electrolytes>

[0250] The non-aqueous electrolyte was prepared according to the following steps. First, propylene carbonate (PC) and diethyl carbonate (DEC) were mixed in a volume ratio of PC:DEC of 1:2 to obtain a mixed solvent. Lithium hexafluorophosphate (LiPF6) was then dissolved in this mixed solvent at a concentration of 1M to obtain a liquid non-aqueous electrolyte.

[0251] <Battery Assembly>

[0252] The electrode assembly was housed in a package formed by a laminated film and vacuum-dried at 80°C for 10 hours. The laminated film was a 0.1 mm thick laminate with polypropylene layers formed on both sides of a 40 μm thick aluminum foil. The aforementioned non-aqueous electrolyte was injected. After injection, the laminated film was heat-sealed under reduced pressure, thereby manufacturing the battery.

[0253] (Example 2)

[0254] In Example 2, a non-aqueous electrolyte battery was manufactured following the same steps as in Example 1, except that a negative electrode was used instead of the one prepared as described below.

[0255] <Making the Negative Electrode>

[0256] As the negative electrode active material, a material with the formula Li4Ti5O is prepared. 12The composition of lithium titanate particles is shown. CNTs were prepared as conductive agents and PVdF as binders. For CNTs, samples were prepared with some having fiber diameters of approximately 1 nm to 30 nm and others having fiber diameters of approximately 60 nm to 500 nm. They were mixed in NMP at a mass ratio of negative electrode active material:CNT:PVdF of 96.6:0.4:3 to obtain a slurry. This slurry was coated onto the main surfaces of both sides of a strip-shaped current collector formed from an aluminum foil with a thickness of 15 μm, and the coating was allowed to dry. Here, uncoated portions of the slurry remain on both sides of the front and back sides along one length of the current collector. Thus, a composite containing a current collector and layers containing negative electrode active material formed on both sides of the current collector was obtained. The coating weight on each side containing the negative electrode active material layer was adjusted to 135 g / m². 2 Next, the resulting composite was prepared with a density of 2.3 g / cm³ containing the negative electrode active material layer. 3 The electrodes were then subjected to rolling. SEM observation revealed that, for CNTs, a portion C1 with a fiber diameter W1 of 480 nm and a portion C2 with a fiber diameter W2 of 15 nm were identified. The electrodes were then punched into strips with an uncoated current collector on one side along the width of the electrode, and subsequently vacuum-dried to obtain the negative electrode.

[0257] (Example 3)

[0258] In Example 3, a non-aqueous electrolyte battery was manufactured using the same steps as in Example 1, except that the negative and positive electrodes prepared as described below were used instead.

[0259] <Making the Negative Electrode>

[0260] As the negative electrode active material, particles of monoclinic niobium titanium oxide with a composition represented by the formula TiNb2O7 were prepared. AB was prepared as a conductive agent, CMC as a binder, and SBR as a binder. These were mixed in pure water at a mass ratio of negative electrode active material:AB:CMC:SBR of 94:3:1:2 to obtain a slurry. This slurry was coated onto the main surfaces of both sides of a strip-shaped current collector formed from an aluminum foil with a thickness of 15 μm, and the coating was allowed to dry. Here, uncoated portions of the slurry remained on both sides of the front and back surfaces along one length of the current collector. Thus, a composite containing a current collector and negative electrode active material layers formed on both sides of the current collector was obtained. The coating amount on each side of the negative electrode active material layer was adjusted to 100 g / m². 2 Next, the resulting composite was prepared with a density of 2.55 g / cm³ containing the negative electrode active material layer. 3 The electrode is then subjected to rolling. The resulting electrode is punched into a strip shape with an uncoated portion of a current collector on one side along the width direction, and then subjected to vacuum drying to obtain a negative electrode.

[0261] <The Making of the Positive Electrode>

[0262] As the positive electrode active material, LiNi is prepared. 0.5 Co 0.2 Mn 0.3 O2 represents lithium nickel cobalt manganese composite oxide particles. Additionally, CNTs were prepared as a conductive agent and PVdF as a binder. For the CNTs, samples were prepared with some having a fiber diameter of approximately 1 nm to 30 nm and others having a fiber diameter of approximately 60 nm to 500 nm. These were mixed with a positive electrode active material:CNT:PVdF mass ratio of 94.5:0.5:5 to obtain a mixture. Next, the obtained mixture was dispersed in NMP solvent to prepare a positive electrode slurry. This slurry was coated onto the main surfaces of both sides of a strip-shaped current collector formed from an aluminum foil with a thickness of 15 μm, and the coating was dried. Here, uncoated portions of the slurry remained on both sides of the main surface along one length of the current collector. Thus, a composite containing a current collector and positive electrode active material layers formed on both sides of the current collector was obtained. The coating amount on each side containing the positive electrode active material layer was adjusted to 125 g / m². 2 Next, the resulting composite was prepared with a density of 3.25 g / cm³ containing the positive electrode active material layer. 3 The electrodes were rolled using a rolling process. SEM observation of the resulting electrodes confirmed the presence of a portion C1 with a fiber diameter W1 of 480 nm and a portion C2 with a fiber diameter W2 of 15 nm for CNTs. The electrodes were then punched into strips with an uncoated current collector on one side along the width direction of the electrode, and subsequently vacuum dried to obtain the positive electrode.

[0263] (Example 4)

[0264] In Example 4, a non-aqueous electrolyte battery was manufactured following the same steps as in Example 1, except that a negative electrode made in the same manner as in Example 3 and a positive electrode made as described below were used instead.

[0265] <The Making of the Positive Electrode>

[0266] As the positive electrode active material, LiMn is prepared. 0.7 Fe 0.3PO4 represents lithium manganese iron phosphate particles. Additionally, CNTs were prepared as a conductive agent and PVdF as a binder. For the CNTs, samples were prepared with some having a fiber diameter of approximately 1 nm to 30 nm and others having a fiber diameter of approximately 60 nm to 500 nm. These were mixed with a positive electrode active material:CNT:PVdF mass ratio of 94.5:0.5:5 to obtain a mixture. Next, the obtained mixture was dispersed in NMP solvent to prepare a positive electrode slurry. This slurry was coated onto both sides of the front and back surfaces of a strip-shaped current collector formed from an aluminum foil with a thickness of 15 μm, and the coating was allowed to dry. Here, uncoated portions of the slurry remained on both sides of the front and back surfaces along one length of the current collector. Thus, a composite containing a current collector and positive electrode active material layers formed on both sides of the current collector was obtained. The coating weight of each side containing the positive electrode active material layer was adjusted to 140 g / m². 2 Next, the resulting composite was prepared with a density of 2.3 g / cm³ containing the positive electrode active material layer. 3 The electrodes were rolled using a rolling process. SEM observation of the resulting electrodes confirmed the presence of a portion C1 with a fiber diameter W1 of 480 nm and a portion C2 with a fiber diameter W2 of 15 nm for CNTs. The electrodes were then punched into strips with an uncoated current collector on one side along the width direction of the electrode, and subsequently vacuum dried to obtain the positive electrode.

[0267] (Example 5)

[0268] In Example 5, a non-aqueous electrolyte battery was manufactured following the same steps as in Example 1, except that a negative electrode made in the same manner as in Example 3 and a positive electrode made as described below were used instead.

[0269] <The Making of the Positive Electrode>

[0270] As the positive electrode active material, LiNi was prepared. 0.5 Mn 1.5Particles of lithium nickel manganese composite oxide (O4) were prepared. Additionally, CNTs were prepared as a conductive agent, and PVdF as a binder. For the CNTs, samples were prepared with some having a fiber diameter of approximately 1 nm to 30 nm and others having a fiber diameter of approximately 60 nm to 500 nm. These were mixed with a positive electrode active material:CNT:PVdF mass ratio of 94.5:0.5:5 to obtain a mixture. Next, the obtained mixture was dispersed in NMP solvent to prepare a positive electrode slurry. This slurry was coated onto the main surfaces of both sides of a strip-shaped current collector formed from an aluminum foil with a thickness of 15 μm, and the coating was allowed to dry. Here, uncoated portions of the slurry remained on both sides of the front and back sides along one length of the current collector. Thus, a composite containing a current collector and positive electrode active material layers formed on both sides of the current collector was obtained. The coating weight on each side containing the positive electrode active material layer was adjusted to 170 g / m². 2 Next, the resulting composite was prepared with a density of 2.75 g / cm³ containing the positive electrode active material layer. 3 The electrodes were rolled using a rolling process. SEM observation of the resulting electrodes confirmed the presence of a portion C1 with a fiber diameter W1 of 480 nm and a portion C2 with a fiber diameter W2 of 15 nm for CNTs. The electrodes were then punched into strips with an uncoated current collector on one side along the width direction of the electrode, and subsequently vacuum dried to obtain the positive electrode.

[0271] (Example 6)

[0272] In Example 6, instead of using particles of monoclinic niobium titanium oxide with a composition represented by the formula TiNb2O7, which have fine oxide particles of about 100 nm on their surface, a non-aqueous electrolyte battery was manufactured using the same steps as in Example 1.

[0273] (Example 7)

[0274] In Example 7, instead of using CNTs that are partially bundled and have a fiber diameter W1 of about 1 nm to 30 nm and a fiber diameter W2 of about 60 nm to 500 nm as the conductive agent of the negative electrode, a non-aqueous electrolyte battery is manufactured by the same steps as in Example 1.

[0275] (Example 8)

[0276] In Example 8, the negative electrode was made in the same manner as in Example 1, and the positive electrode was made in the same manner as in Example 3. Otherwise, the non-aqueous electrolyte battery was manufactured according to the same steps as in Example 1.

[0277] (Example 9)

[0278] In Example 9, a non-aqueous electrolyte battery was manufactured following the same steps as in Example 1, except that a negative electrode made as described below was used instead.

[0279] <Making the Negative Electrode>

[0280] As the negative electrode active material, particles of monoclinic niobium titanium oxide with 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. For CNTs, samples with fiber diameters of approximately 1 nm to 30 nm and approximately 60 nm to 500 nm were prepared. They were mixed in pure water at a mass ratio of negative electrode active material:CNT:AB:CMC:SBR of 95.9:0.4:0.7:1:2 to obtain a slurry. This slurry was coated onto the main surfaces of both sides of a strip-shaped current collector formed from an aluminum foil with a thickness of 15 μm, and the coating was dried. Here, uncoated portions of the slurry remained on both sides of the front and back sides along one length of the current collector. Thus, a composite containing a current collector and layers of negative electrode active material formed on both sides of the current collector was obtained. The coating amount on each side containing the negative electrode active material layer was adjusted to 100 g / m². 2 Next, the resulting composite was prepared with a density of 2.7 g / cm³ containing the negative electrode active material layer. 3 The electrodes were then subjected to rolling. SEM observation revealed that, for CNTs, a portion C1 with a fiber diameter W1 of 480 nm and a portion C2 with a fiber diameter W2 of 15 nm were identified. The electrodes were then punched into strips with an uncoated current collector on one side along the width of the electrode, and subsequently vacuum-dried to obtain the negative electrode.

[0281] (Comparative Example 1)

[0282] In Comparative Example 1, a non-aqueous electrolyte battery was manufactured using a non-aqueous electrolyte battery instead of a single-layer CNT containing only a portion with a fiber diameter of about 1 nm to 30 nm as the conductive agent for the negative electrode, except that the same steps as in Example 1 were followed.

[0283] (Comparative Example 2)

[0284] In Comparative Example 2, instead of using a multilayer CNT containing only a portion with a fiber diameter of about 60 nm to 500 nm as the conductive agent for the negative electrode, a non-aqueous electrolyte battery was manufactured according to the same steps as in Example 1.

[0285] Table 1 below summarizes the designs of the non-aqueous electrolyte batteries manufactured in Examples 1-9 and Comparative Examples 1 and 2. Specifically, the electrode designs of each battery are summarized. In detail, the electrode active materials and conductive agents used for the positive and negative electrodes, respectively, as well as the weight per unit area and density of the electrode active material layer, are shown. Furthermore, for the fibrous carbon (CNT) used in the conductive agent, Table 1 shows the morphology in which it comprises a first portion C1 having a fiber diameter of 60 nm to 500 nm and a second portion C2 having a finer fiber diameter. Moreover, regarding the positive electrode active material, "NCM" refers to lithium nickel cobalt manganese composite oxide LiNi 0.5 Co 0.2 Mn 0.3 O2, "LMFP" refers to lithium manganese iron phosphate (LiMn). 0.7 Fe 0.3 PO4, "LNMO" refers to lithium nickel manganese composite oxide LiNi 0.5 Mn 1.5 O4. Regarding the negative electrode active material, "TNO" refers to monoclinic titanium niobium oxide TiNb2O7, and "TLO" refers to titanium lithium oxide Li4Ti5O. 12 Regarding conductive agents, "AB" refers to acetylene black, "CNT" refers to carbon nanotubes, "SWCNT" refers to single-layer carbon nanotubes, and "MWCNT" refers to multilayer carbon nanotubes.

[0286]

[0287] <Evaluation>

[0288] For each battery manufactured in Examples 1-9 and Comparative Examples 1 and 2, as an indicator of rapid discharge performance, they were discharged at 0.2C and 5C respectively, and the 5C discharge capacity ratio relative to the 0.2C capacity was determined. The test results are shown in Table 2 below.

[0289] Table 2

[0290]

[0291] As shown in Table 2, higher fast discharge capacity was obtained in each of the non-aqueous electrolyte batteries manufactured in Examples 1 to 9 compared to the non-aqueous electrolyte batteries manufactured in Comparative Examples 1 and 2. The experimental results show that high input / output performance can be obtained by using fibrous carbon comprising a first portion C1 with a coarse fiber diameter and a second portion C2 with a fine fiber diameter as the electrode conductive agent.

[0292] 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 or more and 500 nm or less, and a second portion C2 having a fiber diameter W2 smaller than the fiber diameter W1. At least the second portion C2 comprises contacts with a plurality of particles in the active material particles. According to the electrode described above, a secondary battery and battery pack exhibiting high input / output density, as well as a vehicle equipped with the battery pack, can be provided.

[0293] Several embodiments of the present invention have been described, but these embodiments are given by way of example and are not intended to limit the scope of the invention. These novel embodiments can be implemented in various other ways, 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 invention as described in the claims and its equivalents.

[0294] Furthermore, the above-described implementation methods can be summarized into the following technical solutions.

[0295] (Technical Solution 1) An electrode comprising a plurality of active material particles and fibrous carbon, the fibrous carbon comprising a first portion having a fiber diameter W1 in the 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, at least a portion of the second portion being in contact with the plurality of active material particles.

[0296] (Technical Solution 2) According to the above technical solution 1, in at least a portion of the fibrous carbon, the first portion and the second portion are integral.

[0297] (Technical Solution 3) According to Technical Solution 1 or 2 above, on its surface, the area ratio between the area A1 of the first portion and the area A2 of the second portion is 0.5. <A1 / A2<50。

[0298] (Technical Solution 4) According to any one of the above technical solutions 1 to 3, the fiber diameter W2 of the second part is in the range of 1 nm or more and 15 nm or less.

[0299] (Technical Solution 5) According to any one of the above technical solutions 1 to 4, the ratio of the length L of the fibrous carbon on its surface to the fiber diameter W2 of the second part is 100. <L / W2。

[0300] (Technical Solution 6) According to any one of the above technical solutions 1 to 5, the active material particles contain at least one selected from lithium titanate and niobium titanium oxide.

[0301] (Technical Solution 7) According to any one of the above technical solutions 1 to 5, the active material particles contain at least one selected from lithium nickel cobalt manganese composite oxide, lithium phosphate and lithium nickel manganese composite oxide.

[0302] (Technical Solution 8) A secondary battery comprising a positive electrode, a negative electrode, and an electrolyte.

[0303] Wherein, at least one of the positive electrode and the negative electrode is the electrode described in any one of the above technical solutions 1 to 7.

[0304] (Technical Solution 9) A battery pack comprising the secondary battery described in Technical Solution 8 above.

[0305] (Technical Solution 10) According to the above technical solution 9, it also has an external terminal for power supply and a protection circuit.

[0306] (Technical Solution 11) According to the above technical solution 9 or 10, it comprises a plurality of the aforementioned secondary batteries.

[0307] The secondary batteries are electrically connected in series, parallel, or a combination of series and parallel connections.

[0308] (Technical Solution 12) A vehicle having a battery pack as described in any one of the above-described technical solutions 9 to 11.

[0309] (Technical Solution 13) According to the above technical solution 12, it includes a mechanism for converting the kinetic energy of the vehicle into renewable energy.

Claims

1. An electrode comprising a plurality of active material particles and fibrous carbon, the fibrous carbon comprising a first portion having a fiber diameter W1 in the 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 portion of the second portion is in contact with the plurality of active material particles.

2. The electrode according to claim 1, wherein, In at least a portion of the fibrous carbon, the first portion and the second portion are integral.

3. The electrode according to claim 1 or 2, wherein, On its surface, the area ratio between the area A1 of the first portion and the area A2 of the second portion is 0.

5. <A1 / A2<50。 4. The electrode according to any one of claims 1 to 3, wherein, The fiber diameter W2 of the second part is in the range of 1 nm or more and 15 nm or less.

5. The electrode according to any one of claims 1 to 4, wherein the ratio of the length L of the fibrous carbon on its surface to the fiber diameter W2 of the second portion is 100. <L / W2。 6. The electrode according to any one of claims 1 to 5, wherein, The active material particles comprise at least one selected from lithium titanate and niobium titanium oxide.

7. The electrode according to any one of claims 1 to 5, wherein, The active material particles comprise at least one of the following: lithium nickel cobalt manganese composite oxide, lithium phosphorus oxide, and lithium nickel manganese composite oxide.

8. A secondary battery comprising a positive electrode, a negative electrode, and an electrolyte. in, At least one of the positive electrode and the negative electrode is an electrode as described in any one of claims 1 to 7.

9. A battery pack comprising the secondary battery of claim 8.

10. The battery pack according to claim 9, further comprising an external terminal for power supply and a protection circuit.

11. The battery pack according to claim 9 or 10, wherein, Equipped with multiple of the aforementioned secondary batteries, The secondary batteries are electrically connected in series, parallel, or a combination of series and parallel connections.

12. A vehicle comprising the battery pack of any one of claims 9 to 11.

13. The vehicle according to claim 12, wherein, It includes a mechanism for converting the kinetic energy of the vehicle into renewable energy.

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