Electrodes, electrode groups, secondary batteries, battery packs, and vehicles

Abstract

To provide: an electrode and an electrode group that can realize a secondary battery with excellent electrolyte penetration into electrodes and retention at electrodes and excellent lifetime performance; a secondary battery and a battery pack with excellent electrolyte penetration into electrodes and retention at electrodes and excellent lifetime performance; and a vehicle equipped with such a battery pack.SOLUTION: According to an embodiment, an electrode 10 is provided including an active material-containing layer 10b and a current collector 10a. The active material-containing layer contains electrode active material, and includes a first side and a second side on an opposite side in a first direction that intersects the first side. The current collector includes an active material carrying portion 10d carrying the active material-containing layer, and an active material non-carrying portion 10e that is adjacent to the active material carrying portion and the first side and is not provided with the active material-containing layer. The electrode has an uneven portion including a plurality of ridges 8 and a plurality of grooves 9, each provided along the first direction. A first pitch a of the uneven portions along the first side and a second pitch b of the uneven portions along the second side satisfy a relationship of a<b.SELECTED DRAWING: Figure 1

Description

[Technical Field]

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

[0002] In recent years, rechargeable batteries such as lithium-ion batteries have been increasingly incorporated into battery-powered devices such as smartphones, vehicles, stationary power supplies, robots, and drones. Furthermore, to enable prolonged use of these devices, there is a demand for higher capacity individual batteries. Recently, oxides containing niobium and titanium have been used as negative electrode active materials to increase charging capacity and enable rapid charging. For example, titanium niobium oxide, represented as Nb2TiO7, has a high theoretical capacity exceeding 380 mAh / g.

[0003] While niobium titanium oxide has high capacity, on the other hand, electrodes using niobium titanium oxide as the active material require a large amount of conductive additive to ensure conductivity. Furthermore, a large amount of binder is used to prevent electrode collapse due to the expansion and contraction of niobium titanium oxide during battery charging and discharging. Increasing the capacity per unit volume of electrodes with a large amount of electrode composite material other than the active material can be achieved by increasing the electrode density. Increasing the capacity per unit weight of a single cell can be achieved by increasing the electrode area. Therefore, energy density can be improved by increasing electrode density and expanding electrode area. [Prior art documents] [Patent Documents]

[0004] [Patent Document 1] Japanese Patent Publication No. 2001-76711 [Patent Document 2] Japanese Patent Publication No. 2012-174434 [Patent Document 3] Japanese Patent Publication No. 2013-73690 [Overview of the project] [Problems that the invention aims to solve]

[0005] Provided are an electrode and an electrode group capable of realizing a secondary battery excellent in the permeability of an electrolyte to an electrode and the retention in the electrode, and excellent in life performance, a secondary battery and a battery pack excellent in the permeability of an electrolyte to an electrode and the retention in the electrode, and excellent in life performance, and a vehicle equipped with this battery pack.

Means for Solving the Problem

[0006] According to an embodiment, an electrode including an active material-containing layer and a current collector is provided. The active material-containing layer includes a second side on the opposite side in a first direction intersecting the first side, and contains an electrode active material. The current collector includes an active material-supported portion supporting the active material-containing layer, and an active material non-supported portion adjacent to the active material-supported portion and the first side and where the active material-containing layer is not provided. The electrode has a concavo-convex portion including a plurality of ridges and a plurality of grooves respectively along the first direction. The concavo-convex portion along the first side This is the average distance between adjacent pairs of ridges in a given area. The first pitch a and the concavo-convex portion along the second side This is the average distance between adjacent pairs of ridges in a given area. The second pitch b satisfies the relationship a < b.

[0007] According to another embodiment, an electrode group including a plurality of positive electrodes and a plurality of negative electrodes is provided. The negative electrode is the above electrode. The electrode group has a laminated structure in which the positive electrode and the negative electrode are laminated.

[0008] According to still another embodiment, a secondary battery including the above electrode group and an electrolyte is provided.

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

[0010] Also, according to an embodiment, a vehicle equipped with the above battery pack is provided.

Brief Description of the Drawings

[0011] [Figure 1]A partially cutaway plan view schematically showing an example of an electrode according to the embodiment. [Figure 2] A conceptual diagram showing an example of a partial cross-sectional shape of an electrode according to the embodiment, determined by a 3D laser displacement meter. [Figure 3] A conceptual diagram showing an example of another cross-sectional shape of the electrode according to the embodiment, as determined by a 3D laser displacement meter. [Figure 4] A plan view schematically showing one step in the manufacturing of an electrode according to the embodiment. [Figure 5] A plan view schematically showing other steps in the manufacturing of an electrode according to the embodiment. [Figure 6] A schematic cross-sectional view showing an example of an electrode group according to the embodiment. [Figure 7] An exploded perspective view schematically showing another example of the electrode group according to the embodiment. [Figure 8] A schematic partial cutaway perspective view showing an example of a secondary battery according to the embodiment. [Figure 9] An enlarged cross-sectional view of section E of the secondary battery shown in Figure 8. [Figure 10] A schematic perspective view showing an example of a battery pack according to this embodiment. [Figure 11] An exploded perspective view schematically showing an example of a battery pack according to this embodiment. [Figure 12] A block diagram showing an example of the electrical circuit of the battery pack shown in Figure 11. [Figure 13] A partially transparent view schematically showing an example of a vehicle according to the embodiment. [Figure 14] A schematic diagram showing an example of a control system for the electrical system in a vehicle according to this embodiment. [Modes for carrying out the invention]

[0012] In a battery using a negative electrode active material containing niobium titanate oxide, there are many additive components such as a conductive agent and a binder contained in the negative electrode, and the electrode density is also high. Therefore, in a battery using niobium titanate oxide, the poor permeability of the electrolytic solution (liquid electrolyte) due to the large area of the electrode becomes a problem. This not only lengthens the time required to impregnate the electrolytic solution into the electrode during manufacturing, but also makes the impregnation of the electrolytic solution in the electrode non-uniform, which may cause a decrease in battery performance. Furthermore, in a battery cell containing niobium titanate oxide, the electrolytic solution may be extruded from the electrode due to the volume change (expansion and contraction) of the electrode during charge and discharge, which may lead to a decrease in input / output performance and lifespan. Therefore, a method for improving the electrolytic solution permeability of an electrode body and a battery containing niobium titanate oxide is required.

[0013] Hereinafter, embodiments will be described with reference to the drawings as appropriate. In the embodiments, the same reference numerals are assigned to common configurations, and redundant descriptions are omitted. In addition, each drawing is a schematic diagram for explaining the embodiments and facilitating their understanding. Although there are parts where the shape, dimensions, ratio, etc. are different from the actual device, these can be appropriately modified in design in consideration of the following description and known techniques.

[0014] (First Embodiment) According to the first embodiment, an electrode is provided. Such an electrode includes an active material-containing layer containing an electrode active material and a current collector. The active material-containing layer includes a first side and a second side. The second side is on the opposite side in the first direction that intersects the first side in the active material-containing layer. The current collector includes an active material-supported portion and an active material-non-supported portion. The active material-supported portion supports the active material-containing layer. The active material-non-supported portion is adjacent to the active material-supported portion and the second side. The active material-containing layer is not provided in the active material-non-supported portion. The electrode has a concavo-convex portion including a plurality of ridges and a plurality of grooves respectively along the first direction. The first pitch a of the concavo-convex portion along the first side and the second pitch b of the concavo-convex portion along the second side satisfy the relationship a < b.

[0015] The electrode in question may be a battery electrode. An electrode used as a battery electrode may, for example, be a negative electrode for a secondary battery. The secondary battery referred to here includes, for example, lithium-ion secondary batteries and non-aqueous electrolyte batteries.

[0016] Electrodes having the above configuration exhibit high impregnation properties for liquid electrolytes. That is, the electrolyte penetrates the electrode well, and the electrode also has high electrolyte retention capabilities. Therefore, by using these electrodes, it is possible to manufacture batteries that achieve their design capacity in a short time, as well as obtain batteries with excellent lifespan performance.

[0017] The electrode according to the embodiment will be described with reference to the drawings.

[0018] Figure 1 is a partially cutaway plan view schematically showing an example of an electrode according to the embodiment. The electrode 10 shown in Figure 1 comprises a current collector 10a and an active material-containing layer 10b supported on at least one of its front and back main surfaces. The current collector 10a includes an active material-supporting portion 10d on which the active material-containing layer 10b is provided, and an active material-non-supporting portion 10e on which the active material-containing layer 10b is not provided on either surface. The active material-non-supporting portion 10e functions as a current collector tab 10c. One side of the active material-containing layer 10b on the side of the active material-non-supporting portion 10e of the current collector 10a is designated as the first side 11a, and one side of the active material-containing layer 10b on the opposite side of the first direction 11 intersecting this first side is designated as the second side 11b. As shown in the figure, the current collector tab 10c (non-active material supporting portion 10e) is a narrow portion in which the width intersecting the first direction 11 is narrower than the first length Xa of the first side 11a and the second length Xb of the second side 11b of the active material containing layer 10b.

[0019] Each electrode 10 has an uneven surface that includes multiple ridges 8 and multiple grooves 9 along the first direction 11. That is, the electrode 10 does not have a flat plate shape, and the cross-section of the electrode 10 intersecting the first direction 11 has a wave shape. Also, the first pitch a of the wave shape on the first side 11a is narrower than the second pitch b of the wave shape on the second side 11b. The wave shape of the uneven surface extends across both the current collector 10a and the active material containing layer 10b in the thickness direction (depth direction of the wave shape) of the electrode 10.

[0020] Figures 2 and 3 show the waveforms of the electrode cross-sections on the first side 11a side and the second side 11b side, respectively. Both Figures 2 and 3 are conceptual diagrams showing an example of the cross-sectional shape of the electrode 10 obtained by a three-dimensional laser displacement meter. Although the detailed calculation method will be described later, the average value of the distances between the maximum values in the curve representing the concavo-convex shape of the cross-section of the electrode 10 is taken as the pitch at that position.

[0021] For example, the curve c0 representing the cross-sectional shape of the first side 11a shown in FIG. 2 includes a plurality of maximum values. Among the plurality of maximum values, the distance between a pair of adjacent ones is a n Let it be, and the distances a n for the plurality of pairs are taken as the first pitch a. Similarly, the curve c 100 representing the cross-sectional shape of the second side 11b shown in FIG. 3 includes a plurality of maximum values. Among the plurality of maximum values, the distance between a pair of adjacent ones is b n Let it be, and the distances b n for the plurality of pairs are taken as the second pitch b. Note that the maximum values in the curve c0 and the curve c 100 correspond to the positions of the ridges 8 of the concavo-convex portions on the first side 11a and the second side 11b, respectively. The minimum values in the respective curves correspond to the positions of the grooves 9 of the concavo-convex portions on the first side 11a and the second side 11b, respectively.

[0022] [[ID=2,2]]The first pitch a of the waveform on the first side 11a side may be within the range of 0.01X ≤ a ≤ 0.1X with respect to the average length X of the first length Xa of the active material-containing layer 10b and the second length Xb of the second side 11b. Also, the second pitch b of the waveform on the second side 11b side may be within the range of 0.05X ≤ b ≤ 0.5X with respect to the average length X. However, the first pitch a and the second pitch b satisfy the relationship a < b.

[0023] The electrode 10 shown in FIG. 1 is an example of a preferred form of the electrode according to the embodiment, and the ridges 8 and the grooves 9 in the concavo-convex portions are arranged so that the interval widens from the first side 11a toward the second side 11b. Specifically, starting from the current collector tab 10c, the ridges 8 and the grooves 9 extend radially. For example, the first side 11a side of the active material-containing layer 10b is Y0, and the second side 11b side is Y 100Let it be so. Taking the length of the active material-containing layer 10b along the first direction 11 from the first side 11a to the second side 11b (or the length of the active material-supported portion 10d of the current collector 10a) as Y, the midpoints every Y / 4 are Y 25 , Y 50 , and Y 75 Let it be so. At the concavo-convex portion of the electrode 10, from the position Y0 on the first side 11a side, Y 25 , Y 50 , Y 75 , and as it proceeds to the position Y on the second side 11b side 100 , the pitch of the waveform of the electrode cross-section gradually becomes wider. The orientation of the ridges 8 and grooves 9 included in the concavo-convex portion is not limited to the radial shape as shown in FIG. 1. For example, each ridge 8 and each groove 9 can be arranged substantially parallel to each other. Or, the ridges 8 and grooves 9 can meander in the path from the first side 11a to the second side 11b.

[0024] Also, at the concavo-convex portion of the electrode 10, the undulation of the concavo-convex due to the ridges 8 and grooves 9 is larger on the first side 11a side than on the second side 11b side. That is, the difference D0 between the minimum value and the maximum value of the curve c0 representing the cross-sectional shape on the first side 11a side (Y0) shown in FIG. 2 is the curve c representing the cross-sectional shape on the second side 11b side (Y 100 ) shown in FIG. 3 100 of the minimum value and the maximum value of the difference D[[ID=:23]] 100 is larger. More specifically, the undulation of the ridges 8 and grooves 9 is the largest on the first side 11a side, and the undulation gradually decreases toward the second side 11b side. Therefore, from the position Y0 on the first side 11a side, Y 25 , Y 50 , Y 75 , and as it proceeds to the position Y on the second side 11b side 100 , the depth of the concavo-convex decreases.

[0025] As described above, the electrode in question has a wavy, uneven surface. This uneven surface facilitates the penetration of the electrolyte into the active material-containing layer from the first edge. Therefore, for example, in a stacked electrode group where electrodes are stacked together with a counter electrode, although the main electrode surface cannot be used for electrolyte introduction, the high permeability of the electrolyte from the first edge promotes electrolyte impregnation into the electrode. This improves the utilization rate of the electrodes in the battery, allowing the design capacity to be achieved in a shorter time. Furthermore, because the movement of the electrolyte due to volume fluctuations in the electrodes during charging and discharging of the battery becomes reversible, performance degradation due to electrolyte depletion in the electrodes is prevented.

[0026] The uneven portion preferably has a scallop-shell-like radial wave shape, as shown in the example in Figure 1. When a liquid electrolyte is introduced during the manufacture of a battery using electrodes with such a structure, liquid electrolyte tends to accumulate on the first edge of the active material-containing layer and on the adjacent current-collecting tab (the part of the current collector that does not support the active material). Therefore, the electrolyte can be efficiently distributed throughout the entire electrode, starting from the part of the first edge along which the current-collecting tab runs.

[0027] The active material-containing layer and the current collector will be described in detail below.

[0028] The active material-containing layer may be supported on one side or on both the front and back main surfaces of the current collector. The active material-containing layer contains electrode active material and may optionally also contain a conductive agent and a binder.

[0029] As the electrode active material, for example, carbon materials or metal oxides can be used. It is desirable that the electrode active material contains a metal oxide because it can increase the density of the electrode. Examples of metal oxides that can be used as electrode active materials include lithium titanate (e.g., Li) which has a ramsdelite structure. 2+y Li3O7 (0≦y≦3), lithium titanate having a spinel structure (e.g., Li 4+x Ti5O 12Examples include monoclinic titanium dioxide (TiO2), anatase titanium dioxide, rutile titanium dioxide, niobium pentoxide (Nb2O5), hollandite titanium composite oxide, orthorhombic titanium composite oxide, and monoclinic niobium titanium oxide. Hereafter, electrode active materials will simply be referred to as active materials.

[0030] As an example of the above orthorhombic titanium-containing composite oxide, Li 2+a M I 2-b Ti 6-c M II d O 14+σ Examples of compounds represented by are given. Here, M I It is at least one selected from the group consisting of Sr, Ba, Ca, Mg, Na, Cs, Rb, and K. II is at least one selected from the group consisting of Zr, Sn, V, Nb, Ta, Mo, W, Y, Fe, Co, Cr, Mn, Ni, and Al. In the composition formula, each subscript has the following properties: 0≦a≦6, 0≦b<2, 0≦c<6, 0≦d<6, -0.5≦σ≦0.5. As a specific example of an orthorhombic titanium-containing composite oxide, Li 2+a Na2Li6O 14 (0 ≤ a ≤ 6) is one example.

[0031] As an example of the above monoclinic type niobium titanium oxide, Li x Ti 1-y M1 y Nb 2-z M2 z O 7+δ Examples of compounds represented by the formula are: Here, M1 is at least one selected from the group consisting of Zr, Si, and Sn. M2 is at least one selected from the group consisting of V, Ta, and Bi. The subscripts in the compositional formula are 0≦x≦5, 0≦y<1, 0≦z<2, and -0.3≦δ≦0.3. A specific example of monoclinic niobium titanium oxide is Li x Nb2TiO7 (0≦x≦5) is one example.

[0032] Another example of monoclinic niobium titanium oxide particles is Lix Ti 1-y M3 y+z Nb 2-z O 7-δ A compound represented by the formula is shown below. Here, M3 is at least one selected from Mg, Fe, Ni, Co, W, Ta, and Mo. In the compositional formula, each subscript represents 0≦x≦5, 0≦y<1, 0≦z<2, and -0.3≦δ≦0.3.

[0033] From the viewpoint of energy density, it is desirable to include monoclinic niobium titanium oxide as the active material. In the active material-containing layer, it is preferable that the content ratio of niobium titanium oxide to the total mass of niobium titanium oxide and other active materials be 50% by mass or more and 100% by mass or less.

[0034] Conductive agents are added to enhance current collection performance and reduce contact resistance between the active material and the current collector. Examples of conductive agents include carbonaceous materials such as vapor-grown carbon fiber (VGCF), carbon black such as acetylene black, graphite, carbon nanotubes, and carbon nanofibers. One of these may be used as a conductive agent, or two or more may be used in combination. Alternatively, instead of using a conductive agent, the surface of the active material particles may be coated with a carbon coating or an electronically conductive inorganic material coating.

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

[0036] The mixing ratios of the active material, conductive agent, and binder in the active material-containing layer can be appropriately changed depending on the application of the electrode. For example, when the electrode is used as the negative electrode of a secondary battery, it is preferable to mix the active material (negative electrode active material), conductive agent, and binder in the following proportions: 68% to 96% by mass, 2% to 30% by mass, and 2% to 30% by mass, respectively. By setting the amount of conductive agent to 2% by mass or more, the current collection performance of the active material-containing layer can be improved. Furthermore, by setting the amount of binder to 2% by mass or more, sufficient bonding between the active material-containing layer and the current collector can be achieved, and excellent cycle performance can be expected. On the other hand, it is preferable to set the amount of conductive agent and binder to 30% by mass or less each in order to achieve high capacity.

[0037] The density of the active material-containing layer (excluding the current collector) is 2.3 g / cm³. 3 More than 3.5g / cm 3 The following is preferable. A negative electrode with an active material-containing layer density within this range exhibits excellent energy density and electrolyte retention. The density of the active material-containing layer is 2.5 g / cm³. 3 More than 2.9g / cm 3 The following is more preferable:

[0038] The main surface area of ​​the active material-containing layer is, for example, 150 cm². 2 More than 500cm 2 The following applies: Conventional electrodes have an electrode area of ​​150 cm². 2 In the above cases, the impregnation of electrolytes was the problem. Therefore, 150cm 2 For electrodes having the above area, the promotion of electrolyte permeability due to the uneven surface of the electrode according to the embodiment is effectively demonstrated. Electrode area: 500 cm² 2 If the following conditions are met, for example, the distortion of the laminated structure caused by unevenness when constructing a stacked electrode group can be minimized, and an electrode group or battery with the shape as designed can be obtained. Therefore, energy density can be ensured in the battery.

[0039] The current collector is made of a material that is electrochemically stable at the potential at which lithium (Li) is inserted into and removed from the active material. For example, when the electrode is used as a negative electrode, the current collector is preferably made of copper, nickel, stainless steel, or aluminum, or an aluminum alloy containing one or more elements selected from Mg, Ti, Zn, Mn, Fe, Cu, and Si. The thickness of the current collector is preferably 5 μm to 20 μm. A current collector with such a thickness can balance the strength of the electrode with weight reduction.

[0040] <Manufacturing method> The electrodes can be manufactured by the following method. First, a slurry is prepared by suspending the active material, conductive agent, and binder in a solvent. This slurry is applied to one or both sides of the current collector. When applying the slurry, a certain width is left uncoated along one side of the current collector and the opposite side. The width of these two uncoated areas is also made to differ. Next, the applied slurry is dried to obtain a laminate of the active material-containing layer and the current collector.

[0041] Next, this laminate is used as an electrode precursor and subjected to rolling either without tension or with a weak tension of 15kN or less. By making the width of the uncoated portion asymmetrical and rolling with little or no tension, the pitch of the unevenness can be made different on the current-collecting tab side (first side) and the opposite side (second side) of the resulting electrode. This is because the elongation rate of the uncoated portion differs between the two sides of the current collector during rolling. The wider uncoated portion shows a higher elongation rate than the narrower uncoated portion. Furthermore, the difference in elongation rates between these uncoated portions becomes more pronounced at higher rolling pressures. In addition, the density of the active material-containing layer increases at higher pressures. In this way, an electrode precursor is obtained that has a pair of active material-uncoated portions with different elongation rates of the current collector at both ends.

[0042] Next, electrodes are formed by punching them out using a die (Thomson die) from electrode precursors with different elongation rates in the uncoated active material areas. Here, the electrode is punched out so that the narrower uncoated active material area becomes the unsupported active material area (current-collecting tab). Alternatively, the electrode may be punched out so that the wider uncoated active material area does not remain on the opposite side (second side), or the unnecessary uncoated active material area may be cut off after punching. Alternatively, the uncoated active material area may be left on the second side. When punching out the electrode, the current-collecting tab side (first side) is made the uncoated area with a low elongation rate, and the opposite side (second side) is made the uncoated area with a high elongation rate, thereby making the elongation rates during molding different between the first and second sides. As a result, when forming the electrode, an uneven surface is obtained in which the pitch is narrow on the current-collecting tab side and wide on the opposite side. These pitches and the depth of the irregularities can be controlled by adjusting the rolling pressure and the width of the uncoated areas on both sides.

[0043] Furthermore, when removing the electrodes, it is preferable to use a die-cut type in which the portion that will become the non-active material-supporting portion (current-collecting tab) is a convex narrow section with a narrower width along the first side than the portion that will become the active material-supporting portion. When punching out electrodes in which the non-active material-supporting portion is a narrow section, stress concentrates around the non-active material-supporting portion, making it easy to obtain uneven surfaces that radiate outwards from that point. Instead of punching out electrodes from an electrode precursor, it is also possible to cut out electrodes, for example. Punching out is more preferable because it is easier for uneven surfaces to be formed radially due to stress.

[0044] In this way, electrodes are fabricated.

[0045] Referring to Figures 4 and 5, we will explain a part of the electrode fabrication process.

[0046] Figure 4 is a schematic plan view illustrating an example of the rolling process for an electrode precursor. Figure 5 is a schematic plan view illustrating the extraction of electrodes from the electrode precursor.

[0047] The electrode precursor sheet 12 shown in Figure 4 includes a current collector and an active material-containing layer 12b formed on the current collector. The current collector includes a first uncoated active material portion 12a and a second uncoated active material portion 12c along one side and the opposite side, respectively, where the active material-containing layer 12b is not formed.

[0048] The electrode precursor sheet 12 may be subjected to a weak tension 13 by roll-to-roll transport between rolls (not shown), including press rolls, but the tension 13 is kept below 15kN. When the electrode precursor sheet 12 is rolled by press rolls (not shown) with little to no tension applied, the elongation rate 14a on the wider first uncoated active material portion 12a side is higher than the elongation rate 14c on the narrower second uncoated active material portion 12c side, depending on the above-mentioned factors such as the difference in width between the first uncoated active material portion 12a and the second uncoated active material portion 12c.

[0049] As shown in Figure 5, the electrode is removed such that a portion of the second uncoated active material portion 12c, which has a lower elongation rate, becomes the non-supported active material portion 10e (current collector tab), and the adjacent active material-containing layer 12b becomes the supported active material portion 10d. Because the elongation rate of the current collector on the second uncoated active material portion 12c side is lower than that on the first uncoated active material portion 12a side, when removed, an electrode is formed on the non-supported active material portion 10e side (first side) which has a narrower pitch and deeper unevenness than on the opposite side (second side).

[0050] <Measurement method> 3D laser displacement meter measurement For measuring the shape of the uneven surfaces of electrodes, the use of a 3D laser displacement meter is effective. Specifically, the pitch of the uneven surfaces on the electrode can be measured using a 3D laser displacement meter. Furthermore, the depth of the uneven surfaces can also be measured.

[0051] The electrodes are placed on a surface plate and allowed to rest under their own weight. No weights or frames are used to hold the electrodes in place or correct their shape. Three-dimensional information of the entire electrode is collected using a 3D laser displacement sensor.

[0052] Next, as shown in Figure 1, the first side 11a of the active material-containing layer 10b adjacent to the current collector tab 10c is Y0, and the second side 11b on the opposite side is Y 100 As such, the midpoints that divide the length Y between these two points along the first direction 11 into 1 / 4 are Y 25 ,Y 50 , and Y 75 Let's assume that these five points (Y0, Y) are at 1 / 4 intervals from the first side 11a to the second side 11b. 25 ,Y 50 ,Y 75 ,Y 100 The cross-sectional shape of each of the ) is extracted as two-dimensional information. From each cross-sectional shape, the highest and lowest points of the unevenness caused by the ridges 8 and grooves 9 are found, and the difference between them is taken as the depth of the unevenness. Next, the distance between two adjacent maximum values ​​in the unevenness, that is, for each adjacent ridge 8, is measured, and the average distance between them is taken for the cross-section (from Y0 to Y 100 The pitch will be one of the following.

[0053] For example, consider the cross-sectional shape extracted from the curve c0 shown in Figure 2 at position Y0 of the first side 11a. For each of the multiple pairs of adjacent local maximums contained in the curve c0, the distance a between those positions is... n We find the distance a. n The average value is calculated to obtain the first pitch a on the first side 11a. Also, the curve c shown in Figure 3. 100 Position Y of the second side 11b 100 Let's consider an example of a cross-sectional shape extracted for curve c. 100 For each pair of adjacent local maxima that the function contains, the distance b between their positions n We find the distance b. n The average value is calculated to obtain the second pitch b on the second side 11b. Midpoint Y 25 ,Y 50 , and Y 75 Similarly, the pitch is obtained by calculating the average distance between adjacent local maximums in the curve showing the unevenness from the extracted cross-sectional shape.

[0054] Powder X-ray diffraction measurement The active material contained in the active material-containing layer can be identified by powder X-ray diffraction (XRD) measurement. XRD measurement can be performed, for example, as follows.

[0055] If the electrode to be measured is contained within the battery, remove the sample from the battery using, for example, the method described below.

[0056] First, to understand the crystalline state of the active material, the lithium ions must be completely removed from the active material. For example, if the electrode is used as the negative electrode, the battery must be completely discharged. For instance, the battery can be discharged by repeatedly discharging it at a current of 0.1C in a 25°C environment until the rated cutoff voltage or battery voltage reaches 1.0V, ensuring that the discharge current is less than 1 / 100th of the rated capacity. Even in a discharged state, residual lithium ions may still be present.

[0057] Next, the battery is disassembled in a glove box filled with argon and the electrodes are removed. Then, the removed electrodes are washed with a suitable solvent. For example, ethyl methyl carbonate can be used as a washing solvent. If the electrodes are not washed thoroughly, impurity phases such as lithium carbonate and lithium fluoride may be introduced due to the influence of lithium ions remaining in the electrodes. In that case, it is advisable to use an airtight container that allows the measurement to be performed in an inert gas atmosphere.

[0058] The cleaned electrode is cut to a size approximately the same as the area of ​​the powder X-ray diffractometer holder to prepare the sample for measurement. This sample is then directly attached to the glass holder, and an X-ray diffraction (XRD) pattern is acquired using Cu-Kα rays.

[0059] At this time, the position of the peak originating from the electrode substrate, such as metal foil, should be measured in advance. The peaks of other components, such as conductive agents and binders, should also be measured in advance. If the substrate peak and the active material peak overlap, it is desirable to peel off the active material-containing layer before measurement. This is to separate the overlapping peaks when quantitatively measuring the peak intensity. While the active material-containing layer can be physically peeled off, it is easier to peel it off by applying ultrasound in a solvent. When ultrasound treatment is performed, the electrode material powder (including active material, conductive agent, and binder) can be recovered by volatilizing the solvent. The recovered electrode material powder can then be packed into, for example, a Lindemann glass capillary and measured to perform powder X-ray diffraction measurement of the active material. For example, a Lindemann glass capillary with a diameter of 1 mm to 6 mm can be used.

[0060] Furthermore, the orientation of particles may increase depending on the particle shape of the sample. If the orientation of the sample is high, the position of the peak may shift or the intensity ratio may change depending on how the sample is packed. Samples with such significantly high orientation should be measured using a glass capillary. Specifically, the sample is inserted into the capillary, and this capillary is placed on a rotating sample stage for measurement. This measurement method can mitigate the effects of orientation.

[0061] For powder X-ray diffraction measurements, for example, a SmartLab manufactured by Rigaku will be used. The measurement conditions will be as follows: X-ray source: Cu target Output: 45kV, 200mA Solar slit: 5° for both incident and received light. Step size (2θ): 0.01deg Scan speed: 2 degrees / minute Semiconductor detector: D / teX Ultra 250 Sample plate holder: Flat glass sample plate holder (thickness 0.5 mm) Measurement range: 5°≦2θ≦90°.

[0062] When using other devices, perform measurements using standard Si powder for powder X-ray diffraction to find the conditions under which measurement results of peak intensity, full width at half maximum, and diffraction angle equivalent to those obtained by the above device can be obtained, and measure the sample under those conditions.

[0063] The conditions for XRD measurement shall be those under which an XRD pattern applicable to Rietveld analysis can be obtained. Specifically, to collect data for Rietveld analysis, set the step width to 1 / 3 - 1 / 5 of the minimum full width at half maximum of the diffraction peak, and appropriately adjust the measurement time or X-ray intensity so that the intensity at the peak position of the strongest reflection is 500 cps or more.

[0064] The electrode according to the first embodiment includes an active material-containing layer and a current collector. The active material-containing layer includes a first side and a second side on the opposite side in the first direction intersecting the first side. The current collector includes an active material-supported portion and an active material-unsupported portion adjacent to the active material-supported portion and the first side. The electrode has concavo-convex portions composed of ridges and grooves along the first direction, and the first pitch a and the second pitch b of the concavo-convex portions along the first side and the second side respectively satisfy the relationship a < b. By using this electrode, a secondary battery excellent in the permeability of the electrolyte to the electrode and the retention in the electrode, as well as excellent in life performance, can be provided.

[0065] (Second Embodiment) According to the second embodiment, an electrode group is provided. The electrode group includes a plurality of positive electrodes and a plurality of negative electrodes. The negative electrode is the electrode according to the first embodiment. The electrode group has a laminated structure in which a plurality of positive electrodes and negative electrodes are laminated respectively.

[0066] Such an electrode group may further include a separator disposed between the positive electrode and the negative electrode. The laminated structure of the electrode group is configured such that, for example, a plurality of positive electrodes and a plurality of negative electrodes are alternately laminated with a separator sandwiched therebetween. In the laminated structure, for example, a plurality of separators can be interposed between the positive electrode and the negative electrode respectively. Alternatively, each member can be laminated such that a single separator is folded into ninety-nine folds, and the positive electrode and the negative electrode are alternately arranged within the space defined by the folded separator.

[0067] Hereinafter, the negative electrode, the positive electrode, and the separator will be described in detail.

[0068] 1) Negative electrode The negative electrode can include a negative electrode current collector and a negative electrode active material-containing layer. The negative electrode current collector and the negative electrode active material-containing layer respectively correspond to the current collector and the active material-containing layer included in the electrode according to the first embodiment. Since the details of the negative electrode overlap with the details according to the first embodiment, they will be omitted.

[0069] 2) Positive electrode The positive electrode can include a positive electrode current collector and a positive electrode active material-containing layer. The positive electrode active material-containing layer can be formed on one or both sides of the positive electrode current collector. The positive electrode active material-containing layer can include a positive electrode active material, and optionally a conductive agent and a binder.

[0070] As the positive electrode active material, for example, an oxide or a sulfide can be used. The positive electrode may contain one kind of compound alone or a combination of two or more kinds of compounds as the positive electrode active material. Examples of the oxide and the sulfide include compounds into which Li or Li ions can be inserted and desorbed.

[0071] Such compounds include, for example, manganese dioxide (MnO2), iron oxide, copper oxide, nickel oxide, lithium manganese composite oxide (e.g., Li x Mn2O4 or Li x MnO2; 0 < x ≦ 1), lithium nickel composite oxide (e.g., Li x NiO2; 0 < x ≦ 1), lithium cobalt composite oxide (e.g., Li x CoO2; 0 < x ≦ 1), lithium nickel cobalt composite oxide (e.g., Li x Ni 1-y Co y O2; 0 < x ≦ 1, 0 < y < 1), lithium manganese cobalt composite oxide (e.g., Li x Mn y Co 1-yO2; 0 < x ≤ 1, 0 < y < 1), a lithium manganese nickel composite oxide having a spinel structure (e.g., Li x Mn 2-y Ni y O4; 0 < x ≤ 1, 0 < y < 2), a lithium phosphate having an olivine structure (e.g., Li x FePO4; 0 < x ≤ 1, Li x Fe 1-y Mn y PO4; 0 < x ≤ 1, 0 < y ≤ 1, Li x CoPO4; 0 < x ≤ 1), iron sulfate (Fe2(SO4)3), vanadium oxide (e.g., V2O5), and a 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) is included.

[0072] Among the above, examples of more preferable compounds as the positive electrode active material include a lithium manganese composite oxide having a spinel structure (e.g., Li x Mn2O4; 0 < x ≤ 1), a lithium nickel composite oxide (e.g., Li x NiO2; 0 < x ≤ 1), a lithium cobalt composite oxide (e.g., Li x CoO2; 0 < x ≤ 1), a lithium nickel cobalt composite oxide (e.g., Li x Ni 1-y Co y O2; 0 < x ≤ 1, 0 < y < 1), a lithium manganese nickel composite oxide having a spinel structure (e.g., Li x Mn 2-y Ni y O4; 0 < x ≤ 1, 0 < y < 2), a lithium manganese cobalt composite oxide (e.g., Li x Mn y Co 1-y O2; 0 < x ≤ 1, 0 < y < 1), lithium iron phosphate (e.g., Li x FePO4; 0 < x ≤ 1), and a lithium nickel cobalt manganese composite oxide (Li x Ni 1-y-z Co y Mn zO2; where 0 < x ≤ 1, 0 < y < 1, 0 < z < 1, and y + z < 1 is included. When these compounds are used as the positive electrode active material, the positive electrode potential can be increased.

[0073] When a room-temperature molten salt is used as the electrolyte of the battery, it is preferable to use a positive electrode active material containing lithium iron phosphate, Li x VPO4F (0 ≤ x ≤ 1), a lithium manganese composite oxide, a lithium nickel composite oxide, a lithium nickel cobalt composite oxide, or a mixture thereof. Since these compounds have low reactivity with the room-temperature molten salt, the cycle life can be improved. Details of the room-temperature molten salt will be described later.

[0074] The primary particle size of the positive electrode active material is preferably 100 nm or more and 1 μm or less. A positive electrode active material with a primary particle size of 100 nm or more is easy to handle in industrial production. A positive electrode active material with a primary particle size of 1 μm or less can allow smooth solid-state diffusion of lithium ions.

[0075] The specific surface area of the positive electrode active material is preferably 0.1 m 2 / g or more and 10 m 2 / g or less. A positive electrode active material with a specific surface area of 0.1 m 2 / g or more can sufficiently secure insertion / desorption sites for Li ions. A positive electrode active material with a specific surface area of 10 m 2 / g or less is easy to handle in industrial production and can ensure good charge / discharge cycle performance.

[0076] A binder is added to fill the gaps between dispersed positive electrode active materials and to bond the positive electrode active materials to the positive electrode current collector. Examples of binders include polytetrafluoroethylene (PTFE), polyvinylidene fluoride (PVdF), fluororubber, polyacrylic acid compounds, imide compounds, carboxymethyl cellulose (CMC), and salts of CMC. One of these may be used as a binder, or two or more may be used in combination.

[0077] Conductive agents are added to enhance current collection performance and reduce contact resistance between the positive electrode active material and the positive electrode current collector. Examples of conductive agents include vapor-grown carbon fiber (VGCF), carbon black such as acetylene black, and carbonaceous materials such as graphite. One of these may be used as a conductive agent, or two or more may be used in combination. Conductive agents may also be omitted.

[0078] In the positive electrode active material-containing layer, it is preferable that the positive electrode active material and the binder are blended in proportions of 80% to 98% by mass and 2% to 20% by mass, respectively.

[0079] Sufficient electrode strength can be obtained by using a binder amount of 2% by mass or more. Furthermore, the binder can function as an insulator. Therefore, reducing the binder amount to 20% by mass or less reduces the amount of insulator contained in the electrode, thereby reducing internal resistance.

[0080] When a conductive agent is added, it is preferable that the positive electrode active material, binder, and conductive agent are blended in proportions of 77% to 95% by mass, 2% to 20% by mass, and 3% to 15% by mass, respectively.

[0081] The above-mentioned effects can be achieved by increasing the amount of conductive agent to 3% by mass or more. Furthermore, by reducing the amount of conductive agent to 15% by mass or less, the proportion of conductive agent in contact with the electrolyte can be reduced. This lower proportion reduces the decomposition of the electrolyte under high-temperature storage conditions.

[0082] The positive electrode current collector is preferably an aluminum foil, or an aluminum alloy foil containing one or more elements selected from Mg, Ti, Zn, Ni, Cr, Mn, Fe, Cu, and Si.

[0083] The thickness of the aluminum foil or aluminum alloy foil is preferably 5 μm or more and 20 μm or less, and more preferably 15 μm or less. The purity of the aluminum foil is preferably 99% by mass or more. The content of transition metals such as iron, copper, nickel, and chromium in the aluminum foil or aluminum alloy foil is preferably 1% by mass or less.

[0084] Furthermore, the positive electrode current collector may include portions on its surface where the positive electrode active material-containing layer is not formed. These portions can function as positive electrode current collector tabs.

[0085] The positive electrode can be manufactured, for example, by the following method. First, a slurry is prepared by suspending the positive electrode active material, conductive agent, and binder in a solvent. This slurry is applied to one or both sides of the current collector. Next, the applied slurry is dried to obtain a laminate of the positive electrode active material-containing layer and the current collector. After that, this laminate is pressed. In this way, the positive electrode is manufactured.

[0086] Alternatively, the electrodes may be manufactured by the following method: First, a positive electrode active material, a conductive agent, and a binder are mixed to obtain a mixture. Next, this mixture is formed into pellets. Then, these pellets are placed on a current collector to obtain a positive electrode.

[0087] 3) Separator The separator is formed from a porous film containing, for example, polyethylene (PE), polypropylene (PP), cellulose, or polyvinylidene fluoride (PVdF), or from a synthetic resin nonwoven fabric. From a safety standpoint, it is preferable to use a porous film made of polyethylene or polypropylene. This is because these porous films can melt at a certain temperature and interrupt the electric current.

[0088] Next, the electrode group according to the embodiment will be described in more detail with reference to the drawings.

[0089] Figure 6 is a schematic cross-sectional view showing an example of an electrode group according to the embodiment.

[0090] The electrode group 1 shown in Figure 6 is a stacked electrode group. The stacked electrode group 1 has a structure in which negative electrodes 3 and positive electrodes 5 are stacked alternately with a separator 4 interposed between them.

[0091] The electrode group 1 includes a plurality of negative electrodes 3. Each of the plurality of negative electrodes 3 comprises a negative electrode current collector 3a and a negative electrode active material-containing layer 3b supported on both sides of the negative electrode current collector 3a. Each negative electrode 3 may be, for example, the electrode 10 shown in Figure 1. The electrode group 1 also includes a plurality of positive electrodes 5. Each of the plurality of positive electrodes 5 comprises a positive electrode current collector 5a and a positive electrode active material-containing layer 5b supported on both sides of the positive electrode current collector 5a.

[0092] Each negative electrode 3's negative electrode current collector 3a includes an active material-free portion on one side, where the negative electrode active material-containing layer 3b is not supported on any surface. This active material-free portion functions as a negative electrode current collector tab 3c. As shown in Figure 6, the negative electrode current collector tab 3c does not overlap with the positive electrode 5. Each positive electrode 5's positive electrode current collector 5a includes a portion on one side, where the positive electrode active material-containing layer 5b is not supported on any surface. This portion functions as a positive electrode current collector tab 5c. The positive electrode current collector tab 5c, like the negative electrode current collector tab 3c, does not overlap with the negative electrode 3. Furthermore, the positive electrode current collector tab 5c is located on the opposite side of the electrode group 1 from the negative electrode current collector tab 3c.

[0093] The electrode group in question is not limited to the electrode group with the structure shown in Figure 6, but may also be, for example, an electrode group with the configuration shown in Figure 7. Figure 7 is an exploded perspective view schematically showing another example of an electrode group according to the embodiment.

[0094] The electrode group 1 shown in Figure 7 includes a zigzag-folded separator 4 and a plurality of positive electrodes 5 and negative electrodes 3, each having a strip-like shape. A negative electrode 31 is placed on top of the uppermost layer of the separator 4. In addition, positive electrodes 51, 32, 52, and 33 are inserted from top to bottom between the folded separator 4. In this figure, the positive electrodes 5 and 3 are represented in a simplified manner, and detailed depictions of the active material-containing layers and current collectors (both the active material-carrying and non-active material-carrying parts) of each are omitted.

[0095] The electrode group according to the second embodiment includes the electrodes according to the first embodiment. Therefore, this electrode group has excellent electrolyte permeability and retention properties, enabling the realization of a secondary battery with excellent lifespan performance.

[0096] (Third embodiment) According to the third embodiment, a secondary battery is provided. The secondary battery comprises an electrode group and an electrolyte. The electrode group is the electrode group according to the second embodiment.

[0097] The electrolyte can be held in the electrode group.

[0098] Furthermore, the secondary battery may further comprise an outer casing that houses the electrode group and the electrolyte.

[0099] Furthermore, the secondary battery may further include a negative terminal electrically connected to the negative electrode and a positive terminal electrically connected to the positive electrode.

[0100] The secondary battery in question may be, for example, a lithium secondary battery. Furthermore, the secondary battery may include a non-aqueous electrolyte secondary battery containing a non-aqueous electrolyte.

[0101] The electrolyte, casing components, negative electrode terminal, and positive electrode terminal will be described in detail below.

[0102] I. Electrolytes As the electrolyte, for example, a liquid non-aqueous electrolyte or a gel-type non-aqueous electrolyte can be used. A liquid non-aqueous electrolyte is prepared by dissolving an electrolyte salt as a solute in an organic solvent. The concentration of the electrolyte salt is preferably 0.5 mol / L or more and 2.5 mol / L or less.

[0103] Examples of electrolyte salts include lithium salts such as lithium perchlorate (LiClO4), lithium hexafluoride phosphate (LiPF6), lithium tetrafluoroborate (LiBF4), lithium arsenide hexafluoride (LiAsF6), lithium trifluoromethanesulfonate (LiCF3SO3), and lithium bistrifluoromethylsulfonylimide (LiN(CF3SO2)2), as well as mixtures thereof. The electrolyte salt is preferably resistant to oxidation even at high potentials, with LiPF6 being the most preferred.

[0104] Examples of organic solvents include cyclic carbonates such as propylene carbonate (PC), ethylene carbonate (EC), and vinylene carbonate (VC); linear carbonates such as diethyl carbonate (DEC), dimethyl carbonate (DMC), and methyl ethyl carbonate (MEC); cyclic ethers such as tetrahydrofuran (THF), 2-methyl tetrahydrofuran (2MeTHF), and dioxolane (DOX); linear ethers such as dimethoxyethane (DME) and diethoxyethane (DEE); and γ-butyrolactone (GBL), acetonitrile (AN), and sulfolane (SL). These organic solvents can be used alone or as mixed solvents.

[0105] Gel-like non-aqueous electrolytes are prepared by compounding a liquid non-aqueous electrolyte with a polymer material. Examples of polymer materials include polyvinylidene fluoride (PVdF), polyacrylonitrile (PAN), polyethylene oxide (PEO), or mixtures thereof.

[0106] Alternatively, in addition to liquid non-aqueous electrolytes and gel-type non-aqueous electrolytes, room-temperature molten salts (ionic melts) containing lithium ions may be used as non-aqueous electrolytes.

[0107] Room temperature molten salts (ionic melts) refer to organic salts consisting of a combination of organic cations and anions that can exist as liquids at room temperature (15°C to 25°C). Room temperature molten salts include room temperature molten salts that exist as liquids on their own, room temperature molten salts that become liquid when mixed with an electrolyte salt, room temperature molten salts that become liquid when dissolved in an organic solvent, or mixtures thereof. Generally, the melting point of room temperature molten salts used in secondary batteries is 25°C or lower. Also, organic cations generally have a quaternary ammonium skeleton.

[0108] In addition to the non-aqueous electrolytes mentioned above, polymer solid electrolytes and inorganic solid electrolytes may be used in combination.

[0109] Polymeric solid electrolytes are prepared by dissolving an electrolyte salt in a polymer material and then solidifying it.

[0110] Inorganic solid electrolytes are solid materials that have lithium ion conductivity. Here, lithium ion conductivity means 1 × 10⁻⁶ at 25°C. -6 This refers to exhibiting a lithium ion conductivity of S / cm or higher. Examples of inorganic solid electrolytes include oxide-based solid electrolytes and sulfide-based solid electrolytes. Specific examples of inorganic solid electrolytes are as follows.

[0111] As an oxide-based solid electrolyte, it has a NASICON (Sodium (Na) Super Ionic Conductor) type structure, and its general formula is Li 1+x It is preferable to use a lithium phosphate solid electrolyte represented by Mα2(PO4)3. In the above general formula, Mα is one or more selected from the group consisting of, for example, 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.

[0112] A specific example of a lithium phosphate solid electrolyte having a NASICON-type structure is Li 1+x Al x Ti 2-xThe LATP compound represented by (PO4)3 where 0.1 ≦ x ≦ 0.5; Li 1+x Al y Mβ 2-y The compound represented by (PO4)3 where Mβ is one or more selected from the group consisting of Ti, Ge, Sr, Zr, Sn, and Ca and 0 ≦ x ≦ 1 and 0 ≦ y ≦ 1; Li 1+x Al x Ge 2-x The compound represented by (PO4)3 where 0 ≦ x ≦ 2; and, Li 1+x Al x Zr 2-x The compound represented by (PO4)3 where 0 ≦ x ≦ 2; Li 1+x+y Al x Mγ 2-x Si y P 3-y O 12 The compound represented by where Mγ is one or more selected from the group consisting of Ti and Ge and 0 < x ≦ 2, 0 ≦ y < 3; Li 1+2x Zr 1-x Ca x Examples of the compound represented by (PO4)3 where 0 ≦ x < 1 can be given.

[0113] In addition, as the oxide-based solid electrolyte, in addition to the above lithium phosphate solid electrolyte, Li x PO y N z The amorphous LIPON compound represented by where 2.6 ≦ x ≦ 3.5, 1.9 ≦ y ≦ 3.8, and 0.1 ≦ z ≦ 1.3 (for example, Li 2.9 PO 3.3 N 0.46 ); The garnet-type structure La 5+x A x La 3-x Mδ2O 12 The compound represented by where A is one or more selected from the group consisting of Ca, Sr, and Ba and Mδ is one or more selected from the group consisting of Nb and Ta and 0 ≦ x ≦ 0.5; Li3Mδ 2-x L2O 12 The compound represented by where Mδ is one or more selected from the group consisting of Nb and Ta and L may contain Zr and 0 ≦ x ≦ 0.5; Li 7-3x Al x La3Zr3O 12Compounds represented by 0 ≤ x ≤ 0.5; Li 5+x La3MCSR 2-x Zr x O 12 Represented by , where Mδ is 1 or more selected from the group consisting of Nb and Ta, and 0 ≤ x ≤ 2, it is an LLZ compound (e.g., Li7La3Zr2O 12 ); and having a perovskite-type structure La 2 / 3-x Li x Examples include compounds represented as TiO3 where 0.3 ≤ x ≤ 0.7.

[0114] One or more of the above compounds can be used as a solid electrolyte. Two or more of the above solid electrolytes may also be used.

[0115] Alternatively, a liquid aqueous electrolyte or a gel-type aqueous electrolyte can be used as the electrolyte instead of a non-aqueous electrolyte. A liquid aqueous electrolyte is prepared by dissolving, for example, the following electrolyte salt in an aqueous solvent as the solute. A gel-type aqueous electrolyte is prepared by compounding a liquid aqueous electrolyte with the above polymer material. As the aqueous solvent, a solution containing water may be used. The solution containing water may be pure water or a mixed solvent of water and an organic solvent.

[0116] Examples of electrolyte salts that can be used in aqueous electrolyte systems include lithium salts, sodium salts, or mixtures thereof.

[0117] Examples of lithium salts include lithium chloride (LiCl), lithium bromide (LiBr), lithium hydroxide (LiOH), lithium sulfate (Li2SO4), lithium nitrate (LiNO3), lithium acetate (CH3COOLi), lithium oxalate (Li2C2O4), lithium carbonate (Li2CO3), and lithium bis(trifluoromethanesulfonyl)imide (LiTFSI;LiN(SO2CF)). 3)2 ), lithium bis(fluorosulfonyl)imide (LiFSI;LiN(SO2F)2), and lithium bisoxalate borate (LiBOB:LiB[(OCO)2]2) can be used.

[0118] Examples of sodium salts that can be used include sodium chloride (NaCl), sodium sulfate (Na2SO4), sodium hydroxide (NaOH), sodium nitrate (NaNO3), and sodium trifluoromethanesulfonylamide (NaTFSA).

[0119] The molar concentration of lithium ions or sodium ions in the aqueous electrolyte is preferably 3 mol / L or higher, preferably 6 mol / L or higher, and preferably 12 mol / L or higher. When an aqueous electrolyte is used, electrolysis of the aqueous solvent occurs at the negative electrode, which can lead to self-discharge and hydrogen generation. When the concentration of lithium ions or sodium ions in the aqueous electrolyte is high, the electrolysis of the aqueous solvent at the negative electrode is easily suppressed, and hydrogen generation from the negative electrode tends to be low.

[0120] The higher the concentration of carrier ions such as lithium ions and sodium ions, the lower the wettability of the aqueous electrolyte to the electrode tends to be. Therefore, aqueous electrolytes with high carrier ion concentrations have low impregnation properties into the electrode. In the secondary battery described above, by including the electrode according to the first embodiment, which has excellent electrolyte permeability, good impregnation properties into the electrode can be achieved even with aqueous electrolytes with high ion concentrations.

[0121] In addition to lithium salts and sodium salts, zinc salts such as zinc chloride and zinc sulfate may also be added to the aqueous electrolyte. By adding such compounds to the aqueous electrolyte, a zinc-containing coating layer and / or zinc oxide-containing region can be formed on the negative electrode in a battery using the electrode according to the first embodiment. These zinc-containing components have the effect of suppressing hydrogen generation on the negative electrode where they are formed.

[0122] II. Exterior Components For example, the outer packaging material can be a container made of laminate film or a metal container.

[0123] The thickness of the laminating film is, for example, 0.5 mm or less, and preferably 0.2 mm or less.

[0124] As the laminate film, a multilayer film is used that includes multiple resin layers and a metal layer interposed between these resin layers. The resin layers include polymer materials such as polypropylene (PP), polyethylene (PE), nylon, and polyethylene terephthalate (PET). The metal layer is preferably made of aluminum foil or aluminum alloy foil for weight reduction. The laminate film can be molded into the shape of an exterior component by sealing it by heat fusion.

[0125] The thickness of the metal container wall is, for example, 1 mm or less, more preferably 0.5 mm or less, and even more preferably 0.2 mm or less.

[0126] Metal containers are made from, for example, aluminum or aluminum alloys. Aluminum alloys preferably contain elements such as magnesium, zinc, and silicon. If aluminum alloys contain transition metals such as iron, copper, nickel, and chromium, their content is preferably 100 ppm by mass or less.

[0127] The shape of the exterior components is not particularly limited. For example, the exterior components may be flat (thin), rectangular, cylindrical, coin-shaped, or button-shaped. The exterior components can be appropriately selected according to the battery dimensions and intended use.

[0128] III. Negative terminal The negative terminal has a potential range of 1V to 3V relative to the oxidation-reduction potential of lithium (vs.Li / Li +The negative electrode terminal can be formed from a material that is electrochemically stable and conductive in the field. Specifically, examples of materials for the negative electrode terminal include copper, nickel, stainless steel, or aluminum, or an aluminum alloy containing at least one element selected from the group consisting of Mg, Ti, Zn, Mn, Fe, Cu, and Si. It is preferable to use aluminum or an aluminum alloy as the material for the negative electrode terminal. It is preferable that the negative electrode terminal be made of the same material as the negative electrode current collector in order to reduce contact resistance with the negative electrode current collector.

[0129] IV. Positive terminal The positive terminal has a potential range of 3V to 4.5V relative to the oxidation-reduction potential of lithium (vs.Li / Li + The positive electrode terminal can be formed from an electrically stable and conductive material. Examples of positive electrode terminal materials include aluminum, or an aluminum alloy containing at least one element selected from the group consisting of Mg, Ti, Zn, Mn, Fe, Cu, and Si. It is preferable that the positive electrode terminal be formed from the same material as the positive electrode current collector in order to reduce contact resistance with the positive electrode current collector.

[0130] Next, the secondary battery according to the embodiment will be described in more detail with reference to the drawings.

[0131] Figure 8 is a schematic partially cutaway perspective view showing an example of a secondary battery according to the embodiment. Figure 9 is an enlarged cross-sectional view of section E of the secondary battery shown in Figure 8.

[0132] The secondary battery 100 shown in Figures 8 and 9 comprises an electrode group 1 shown in Figures 8 and 9, an outer casing member 2 shown in Figure 8, and an electrolyte (not shown). The electrode group 1 and the electrolyte are housed within the outer casing member 2. The electrolyte is held within the electrode group 1.

[0133] The exterior component 2 consists of a laminate film comprising two resin layers and a metal layer interposed between them.

[0134] Electrode group 1 has a structure similar to electrode group 1 shown in Figure 6 as an example of an electrode group according to the second embodiment. In the secondary battery 100 shown in Figures 8 and 9, each negative electrode current collector tab 3c of the plurality of negative electrodes 3 is electrically connected to a strip-shaped negative electrode terminal 6. The tip of the strip-shaped negative electrode terminal 6 is drawn out to the outside of the outer casing member 2. Similarly, although not shown, each positive electrode current collector tab (5c) of the plurality of positive electrodes 5 is electrically connected to a strip-shaped positive electrode terminal 7. The tip of the strip-shaped positive electrode terminal 7 is located on the opposite side from the negative electrode terminal 6 and is drawn out to the outside of the outer casing member 2.

[0135] The secondary battery according to the third embodiment includes the electrode group according to the second embodiment. Therefore, the secondary battery according to the third embodiment has excellent electrolyte permeability to the electrodes and electrolyte retention in the electrodes, and can exhibit excellent lifespan performance.

[0136] (Fourth embodiment) According to the fourth embodiment, a battery pack is provided. This battery pack comprises a plurality of secondary batteries according to the third embodiment.

[0137] In such a battery pack, each individual cell may be arranged in series or parallel connections, or a combination of series and parallel connections may be used.

[0138] Next, an example of a battery pack according to the embodiment will be described with reference to the drawings.

[0139] Figure 10 is a schematic perspective view showing an example of such a battery pack. The battery pack 200 shown in Figure 10 comprises five single cells 100a to 100e, four busbars 21, a positive electrode lead 22, and a negative electrode lead 23. Each of the five single cells 100a to 100e is a secondary battery according to the third embodiment.

[0140] The busbar 21 connects, for example, the negative terminal 6 of one cell 100a to the positive terminal 7 of the adjacent cell 100b. In this way, the five cells 100 are connected in series by four busbars 21. That is, the battery pack 200 in Figure 10 is a battery pack with five cells in series. Although not illustrated, in a battery pack containing multiple cells that are electrically connected in parallel, the multiple cells can be electrically connected, for example, by connecting multiple negative terminals to each other and multiple positive terminals to each other by busbars.

[0141] The positive terminal 7 of at least one of the five single cells 100a to 100e is electrically connected to the positive lead 22 for external connection. In addition, the negative terminal 6 of at least one of the five single cells 100a to 100e is electrically connected to the negative lead 23 for external connection.

[0142] The battery pack according to the fourth embodiment comprises a secondary battery according to the third embodiment. Therefore, it has excellent electrolyte permeability and retention properties, and can exhibit excellent lifespan performance.

[0143] (Fifth embodiment) According to the fifth embodiment, a battery pack is provided. This battery pack comprises a battery pack according to the fourth embodiment. This battery pack may also comprise a single secondary battery according to the third embodiment instead of the battery pack according to the fourth embodiment.

[0144] The battery pack according to the fifth embodiment may further include a protection circuit. The protection circuit has the function of controlling the charging and discharging of the secondary battery. Alternatively, a circuit included in a device that uses the battery pack as a power source (e.g., an electronic device, an automobile, etc.) may be used as the protection circuit for the battery pack.

[0145] Furthermore, such a battery pack may also be equipped with external terminals for power supply. These external terminals are for outputting current from the secondary battery to the outside and / or for inputting current from the outside to the secondary battery. In other words, when the battery pack is used as a power source, current is supplied to the outside through the external terminals. Also, when charging the battery pack, the charging current (including regenerative energy from the power of an automobile, etc.) is supplied to the battery pack through the external terminals.

[0146] Next, an example of a battery pack according to the embodiment will be described with reference to the drawings.

[0147] Figure 11 is an exploded perspective view schematically showing an example of a battery pack. Figure 12 is a block diagram showing an example of the electrical circuit of the battery pack shown in Figure 11.

[0148] The battery pack 300 shown in Figures 11 and 12 comprises a housing 31, a lid 32, a protective sheet 33, a battery pack 200, a printed circuit board 34, wiring 35, and an insulating plate (not shown).

[0149] The container 31 shown in Figure 11 is a rectangular-bottomed rectangular container. The container 31 is configured to accommodate a protective sheet 33, a battery pack 200, a printed circuit board 34, and wiring 35. The lid 32 has a rectangular shape. The lid 32 covers the container 31, thereby housing the battery pack 200 and the other components. The container 31 and the lid 32 are provided with openings or connection terminals for connecting to external devices, etc., although these are not shown in the figures.

[0150] The battery pack 200 comprises multiple individual cells 100, a positive electrode lead 22, a negative electrode lead 23, and an adhesive tape 24.

[0151] At least one of the multiple single cells 100 is a secondary battery according to the third embodiment. Each of the multiple single cells 100 is electrically connected in series as shown in Figure 12. The multiple single cells 100 may also be electrically connected in parallel, or they may be connected in a combination of series and parallel connections. When the multiple single cells 100 are connected in parallel, the battery capacity increases compared to when they are connected in series.

[0152] The adhesive tape 24 fastens multiple single cells 100 together. Alternatively, heat-shrinkable tape may be used to secure the multiple single cells 100 instead of the adhesive tape 24. In this case, protective sheets 33 are placed on both sides of the battery pack 200, the heat-shrinkable tape is wrapped around it, and then the heat-shrinkable tape is heat-shrinked to bundle the multiple single cells 100 together.

[0153] One end of the positive lead 22 is connected to the battery pack 200. One end of the positive lead 22 is electrically connected to the positive terminal of one or more single cells 100. One end of the negative lead 23 is connected to the battery pack 200. One end of the negative lead 23 is electrically connected to the negative terminal of one or more single cells 100.

[0154] The printed circuit board 34 is installed along one of the shorter sides of the inner surface of the housing container 31. The printed circuit board 34 includes a positive terminal connector 342, a negative terminal connector 343, a thermistor 345, a protection circuit 346, wiring 342a and 343a, an external terminal 350 for energization, a positive side wiring (positive wiring) 348a, and a negative side wiring (negative wiring) 348b. One main surface of the printed circuit board 34 faces one side of the battery pack 200. An insulating plate (not shown) is interposed between the printed circuit board 34 and the battery pack 200.

[0155] 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.

[0156] The thermistor 345 is fixed to one main surface of the printed circuit board 34. The thermistor 345 detects the temperature of each of the single cells 100 and transmits the detection signal to the protection circuit 346.

[0157] The external power supply terminal 350 is fixed to the other main surface of the printed circuit board 34. The external power supply terminal 350 is electrically connected to equipment located outside the battery pack 300. The external power supply terminal 350 includes a positive terminal 352 and a negative terminal 353.

[0158] The protection circuit 346 is fixed to the other main surface of the printed circuit board 34. The protection circuit 346 is connected to the positive terminal 352 via the positive side wiring 348a. The protection circuit 346 is connected to the negative terminal 353 via the negative side wiring 348b. The protection circuit 346 is also electrically connected to the positive side connector 342 via wiring 342a. The protection circuit 346 is also electrically connected to the negative side connector 343 via wiring 343a. Furthermore, the protection circuit 346 is electrically connected to each of the multiple single cells 100 via wiring 35.

[0159] The protective sheet 33 is positioned on both inner surfaces in the long-side direction of the housing container 31 and on the inner surface in the short-side direction facing the printed circuit board 34 via the battery pack 200. The protective sheet 33 is made of, for example, resin or rubber.

[0160] The protection circuit 346 controls the charging and discharging of multiple single cells 100. The protection circuit 346 also disconnects the electrical connection between the protection circuit 346 and the external terminals 350 (positive terminal 352, negative terminal 353) for supplying power to external devices, based on a detection signal transmitted from the thermistor 345 or a detection signal transmitted from an individual single cell 100 or a battery pack 200.

[0161] An example of a detection signal transmitted from the thermistor 345 is a signal indicating that the temperature of a single cell 100 is above a predetermined temperature. An example of a detection signal transmitted from an individual single cell 100 or a battery pack 200 is a signal indicating that overcharging, over-discharging, or overcurrent has been detected in a single cell 100. When detecting overcharging, etc., in an individual single cell 100, the battery voltage may be detected, or the positive electrode potential or negative electrode potential may be detected. In the latter case, a lithium electrode to be used as a reference electrode is inserted into each individual single cell 100.

[0162] Furthermore, the protection circuit 346 may be a circuit included in a device that uses the battery pack 300 as a power source (for example, an electronic device, an automobile, etc.).

[0163] Furthermore, as described above, the battery pack 300 is equipped with an external terminal 350 for power supply. Therefore, the battery pack 300 can output current from the battery pack 200 to an external device and input current from an external device to the battery pack 200 via the external terminal 350. In other words, when the battery pack 300 is used as a power source, current from the battery pack 200 is supplied to the external device through the external terminal 350. Also, when charging the battery pack 300, charging current from an external device is supplied to the battery pack 300 through the external terminal 350. When this battery pack 300 is used as an on-board battery, the regenerative energy of the vehicle's power can be used as the charging current from the external device.

[0164] The battery pack 300 may have multiple battery packs 200. In this case, the multiple battery packs 200 may be connected in series, in parallel, or in a combination of series and parallel connections. The printed circuit board 34 and wiring 35 may also be omitted. In this case, the positive lead 22 and the negative lead 23 may be used as the positive terminal 352 and negative terminal 353 of the external terminal 350 for energization, respectively.

[0165] Such battery packs are used in applications where excellent cycle performance is required, for example, when drawing high currents. Specifically, these battery packs are used as power supplies for electronic devices, stationary batteries, and on-board batteries for various vehicles. Examples of electronic devices include digital cameras. These battery packs are particularly suitable for use as on-board batteries.

[0166] The battery pack according to the fifth embodiment comprises a secondary battery according to the third embodiment or a battery pack according to the fourth embodiment. Therefore, it has excellent electrolyte permeability and retention to the electrodes, and can exhibit excellent lifespan performance.

[0167] (Sixth embodiment) According to the sixth embodiment, a vehicle is provided, which is equipped with a battery pack according to the fifth embodiment.

[0168] In such a vehicle, the battery pack, for example, recovers regenerative energy from the vehicle's power. The vehicle may also include a mechanism (regenerator) that converts the vehicle's kinetic energy into regenerative energy.

[0169] Examples of vehicles include, for example, two-wheeled or four-wheeled hybrid electric vehicles, two-wheeled or four-wheeled electric vehicles, electric assist bicycles, and railway vehicles.

[0170] The mounting location of the battery pack in a vehicle is not particularly limited. For example, when a battery pack is installed in an automobile, it can be mounted in the engine compartment, at the rear of the vehicle, or under the seats.

[0171] A vehicle may be equipped with multiple battery packs. In this case, the batteries contained in each battery pack may be electrically connected in series, in parallel, or a combination of series and parallel connections. For example, if each battery pack contains a battery pack, the battery packs may be electrically connected in series, in parallel, or a combination of series and parallel connections. Alternatively, if each battery pack contains a single battery, the batteries may be electrically connected in series, in parallel, or a combination of series and parallel connections.

[0172] Next, an example of a vehicle according to the embodiment will be described with reference to the drawings.

[0173] Figure 13 is a schematic partial transparency drawing showing an example of a vehicle.

[0174] The vehicle 400 shown in Figure 13 includes a vehicle body 40 and a battery pack 300 according to the fifth embodiment. In the example shown in Figure 13, the vehicle 400 is a four-wheeled automobile.

[0175] This vehicle 400 may be equipped with multiple battery packs 300. In this case, the batteries contained in the battery pack 300 (for example, single cells or battery packs) may be connected in series, in parallel, or in a combination of series and parallel connections.

[0176] Figure 13 illustrates an example in which the battery pack 300 is mounted in the engine compartment located in front of the vehicle body 40. As described above, the battery pack 300 may also be mounted, for example, in the rear of the vehicle body 40 or under the seats. This battery pack 300 can be used as a power source for the vehicle 400. In addition, this battery pack 300 can recover regenerative energy from the vehicle 400's power.

[0177] Next, an embodiment of the vehicle according to the embodiment will be described with reference to Figure 14.

[0178] Figure 14 is a schematic diagram illustrating an example of a control system for the electrical system in a vehicle. The vehicle 400 shown in Figure 14 is an electric vehicle.

[0179] The vehicle 400 shown in Figure 14 comprises a vehicle body 40, a vehicle power supply 41, a vehicle ECU (ECU: Electric Control Unit) 42 which is a control device above the vehicle power supply 41, an external terminal (terminal for connecting to an external power supply) 43, an inverter 44, and a drive motor 45.

[0180] Vehicle 400 has its vehicle power supply 41 mounted, for example, in the engine compartment, at the rear of the vehicle body, or under the seats. Note that in the vehicle 400 shown in Figure 14, the mounting location of the vehicle power supply 41 is shown in a schematic manner.

[0181] The vehicle power supply 41 comprises a plurality (for example, three) of battery packs 300a, 300b, and 300c, a battery management unit (BMU) 411, and a communication bus 412.

[0182] Battery pack 300a comprises a battery pack 200a and a battery pack monitoring device 301a (e.g., VTM: Voltage Temperature Monitoring). Battery pack 300b comprises a battery pack 200b and a battery pack monitoring device 301b. Battery pack 300c comprises a battery pack 200c and a battery pack monitoring device 301c. Battery packs 300a to 300c are similar to the aforementioned battery pack 300, and battery packs 200a to 200c are similar to the aforementioned battery pack 200. Battery packs 200a to 200c are electrically connected in series. Battery packs 300a, 300b, and 300c can each be independently removed and replaced with another battery pack 300.

[0183] Each of the battery packs 200a to 200c comprises multiple single cells connected in series. At least one of the multiple single cells is a secondary battery according to the third embodiment. Each of the battery packs 200a to 200c is charged and discharged through a positive terminal 413 and a negative terminal 414.

[0184] The battery management device 411 communicates with the battery pack monitoring devices 301a to 301c and collects information such as voltage and temperature for each of the single cells 100 included in the battery packs 200a to 200c included in the vehicle power supply 41. In this way, the battery management device 411 collects information related to the maintenance of the vehicle power supply 41.

[0185] The battery management device 411 and the battery pack monitoring devices 301a to 301c are connected via a communication bus 412. On the communication bus 412, one set of communication lines is shared by multiple nodes (the battery management device 411 and one or more battery pack monitoring devices 301a to 301c). The communication bus 412 is a communication bus configured, for example, based on the CAN (Control Area Network) standard.

[0186] The battery pack monitoring devices 301a to 301c measure the voltage and temperature of each individual cell constituting the battery packs 200a to 200c based on commands communicated from the battery management device 411. However, temperature can be measured at only a few locations per battery pack, and it is not necessary to measure the temperature of all individual cells.

[0187] The vehicle power supply 41 may also have an electromagnetic contactor (for example, a switch device 415 shown in Figure 14) that switches the presence or absence of an electrical connection between the positive terminal 413 and the negative terminal 414. The switch device 415 includes a pre-charge switch (not shown) that turns on when charging is performed on the battery packs 200a to 200c, and a main switch (not shown) that turns on when the output from the battery packs 200a to 200c is supplied to the load. Each of the pre-charge switch and the main switch includes a relay circuit (not shown) that is switched on or off by a signal supplied to a coil located near the switch element. Electromagnetic contactors such as the switch device 415 are controlled based on a control signal from the battery management device 411 or the vehicle ECU 42 that controls the operation of the entire vehicle 400.

[0188] The inverter 44 converts the input DC voltage into a high voltage of three-phase alternating current (AC) for motor drive. The three-phase output terminals of the inverter 44 are connected to the three-phase input terminals of the drive motor 45. The inverter 44 is controlled based on control signals from the battery management device 411 or the vehicle ECU 42 for controlling the operation of the entire vehicle. By controlling the inverter 44, the output voltage from the inverter 44 is adjusted.

[0189] The drive motor 45 rotates using power supplied from the inverter 44. The driving force generated by the rotation of the drive motor 45 is transmitted to the axle and drive wheels W, for example, via a differential gear unit.

[0190] Although not shown in the diagram, vehicle 400 is also equipped with a regenerative braking mechanism (regenerator). The regenerative braking mechanism rotates the drive motor 45 when vehicle 400 is braked, converting kinetic energy into regenerative energy as electrical energy. The regenerative energy recovered by the regenerative braking mechanism is input to the inverter 44 and converted into a DC current. The converted DC current is input to the vehicle power supply 41.

[0191] One terminal of connection line L1 is connected to the negative terminal 414 of the vehicle power supply 41. The other terminal of connection line L1 is connected to the negative input terminal 417 of the inverter 44. A current detection unit (current detection circuit) 416 within the battery management device 411 is provided on connection line L1 between the negative terminal 414 and the negative input terminal 417.

[0192] One terminal of connection line L2 is connected to the positive terminal 413 of the vehicle power supply 41. The other terminal of connection line L2 is connected to the positive input terminal 418 of the inverter 44. A switch device 415 is provided between the positive terminal 413 and the positive input terminal 418 of connection line L2.

[0193] External terminal 43 is connected to battery management device 411. External terminal 43 can be connected to an external power supply, for example.

[0194] The vehicle ECU 42, in response to operational inputs from the driver and others, coordinates control of the vehicle power supply 41, switch device 415, inverter 44, etc., together with other management and control devices, including the battery management device 411. Through the coordinated control of the vehicle ECU 42, etc., the output of power from the vehicle power supply 41 and the charging of the vehicle power supply 41 are controlled, and the entire vehicle 400 is managed. Data related to the maintenance of the vehicle power supply 41, such as the remaining capacity of the vehicle power supply 41, is transferred between the battery management device 411 and the vehicle ECU 42 via a communication line.

[0195] The vehicle according to the sixth embodiment is equipped with the battery pack according to the fifth embodiment. Therefore, a high-performance and highly reliable vehicle can be provided. [Examples]

[0196] Examples are described below. However, the present invention is not limited to the examples listed below, unless it exceeds the spirit of the invention.

[0197] <Electrode fabrication> (Example 1) Niobium titanium oxide was synthesized by the solid-phase synthesis method described below.

[0198] First, Nb2O5 particles and TiO2 particles were prepared to obtain niobium titanium oxide (Nb2TiO7). To obtain the desired crystalline phase, the molar ratio of Nb2O5 to TiO2 was 1:1, and the particles were weighed and mixed using a dry ball mill. The resulting powder was placed in an alumina crucible and calcined (first calcination) at 800°C for 12 hours. After calcination, the powder was placed in a platinum crucible and calcined (second calcination) at 1200°C for 5 hours. After calcination, the powder was crushed and mixed in an agate mortar, and coarse particles were removed by passing it through a 25 μm mesh sieve to obtain niobium titanium oxide powder consisting of primary Nb2TiO7 particles.

[0199] A slurry was obtained by adding 100 parts by mass of niobium titanium oxide powder obtained as the active material, 10 parts by mass of acetylene black as a conductive agent, 5 parts by mass of carbon nanofiber, and 10 parts by mass of polyvinylidene fluoride (PVdF) as a binder to N-methylpyrrolidone (NMP) and mixing. This slurry was applied to both sides of a strip-shaped current collector made of 12 μm thick aluminum foil. The slurry coating width was set to 400 mm, leaving uncoated areas of 15 mm and 30 mm widths on either side. Next, the slurry coating was dried under vacuum at 130°C for 12 hours to obtain a laminate. Subsequently, using a roll-to-roll press, the winding tension during rolling was set to 10 kN, and the density of the target active material-containing layer (excluding the current collector) was set to 2.7 g / cm³. 3 The laminate was rolled in such a manner. In this way, an electrode precursor sheet was obtained in which the elongation rate of the uncoated active material portion differed between the two ends.

[0200] Next, electrodes were molded by punching them out of the electrode precursor sheet using a die. A die was used that included a portion corresponding to the active material carrying area, which had a rectangular shape with dimensions of 330 mm (Y) and 150 mm (X), and a portion corresponding to the current collecting tab, which was adjacent to the short side of this area and had a strip shape with a width of 50 mm on the adjacent side. The die was pressed onto an unpainted area with a low elongation rate of 15 mm in width, overlapping the portion corresponding to the current collecting tab, to punch out the electrode. As a result, stress was concentrated during the punching out of the tab portion, and an electrode was obtained in which radial irregularities were formed centered on the tab portion.

[0201] (Example 2) In Example 2, an electrode with radially shaped irregularities centered on the tab portion was obtained using the same method as in Example 1, except that the punching size of the electrode was changed to 150 mm vertically (Y) and 100 mm horizontally (X) for the active material support portion, and the width of the adjacent side of the current-collecting tab to the active material support portion was changed to 30 mm.

[0202] (Example 3) In Example 3, the width of the uncoated slurry section was changed to 20 mm and 50 mm, the winding tension was reduced to 5 kN, and the electrode density was 2.4 g / cm³. 3 Except for the rolling process being carried out in the same manner as in Example 1, an electrode precursor sheet was obtained in which the elongation rate of the uncoated active material portion differed between the two ends. By removing the electrode with the same punching size as in Example 2, an electrode was obtained in which radial irregularities were formed centered on the tab portion.

[0203] (Example 4) In Example 4, an electrode precursor sheet was obtained using the same method as in Example 3, in which the elongation rate of the uncoated active material portion differed between the two ends. The dimensions of the active material-supporting portion in the punched-out size were changed to 330 mm (Y) and 70 mm (X), and the electrode was extracted to obtain an electrode with radially shaped irregularities centered on the tab portion.

[0204] (Example 5) In Example 5, an electrode precursor sheet was obtained using the same method as in Example 1, in which the elongation rate of the uncoated active material portion differed between the two ends, and the electrode was shaped using a laser cutter. The electrode size was set to a vertical (Y) of 300 mm and a horizontal (X) of 100 mm for the active material supporting portion, with a width of 50 mm for the adjacent side of the current collecting tab. The electrode was cut out at the position where the current collecting tab was cut out from the uncoated portion with a low elongation rate of 15 mm width. By shaping the electrode without applying stress, the unevenness did not become radial, and a randomly formed electrode was obtained.

[0205] (Comparative Example 1) In Comparative Example 1, the electrodes were obtained in the same manner as in Example 1, except that the dimensions of the aluminum foil used as the current collector were changed, the slurry coating width was set to 400 mm, and the width of the uncoated slurry area was set to 15 mm evenly on both sides. The electrodes obtained in Comparative Example 1 were flat, punched electrodes without any curvature or irregularities.

[0206] (Comparative Example 2) In Comparative Example 2, the electrode density was 2.2 g / cm³. 3 The electrode was obtained in the same manner as in Example 1, except that the rolling process was carried out in the same way. The electrode obtained in Comparative Example 2 was a flat, punched electrode without any curvature or irregularities.

[0207] <Electrode measurement> For each electrode fabricated in Examples 1-5, the pitch and depth of the uneven surface were measured using the method described above. Specifically, the positions of five points along the first direction shown in Figure 1 (Y0, Y) were measured. 25 ,Y 50 ,Y 75 ,Y 100 The average pitch and average depth were determined in the cross-sectional waveform of the ). The measurement results are shown in Table 1 below. Table 1 shows the pitch and depth values ​​obtained for each cross-section at five points in the first direction, as well as the cross-sections along the first and second sides (positions Y0 and Y 100 The values ​​of the first pitch a and second pitch b in the cross-section are shown as ratios (a / X, b / X) to the average length X of the first and second sides. The electrode density (excluding the current collector) and electrode area (excluding the current collector tab) of each electrode are also shown.

[0208]

Table 1

[0209] As shown in Table 1, in any of Examples 1 - 5, electrodes having uneven portions with a wavy shape throughout were obtained. Also, in any of Examples 1 - 5, the first pitch a of the uneven portions on the first side of the active material-containing layer on the current collector side was narrower than the second pitch b of the uneven portions on the second side.

[0210] In Comparative Example 1, since the widths of the slurry-uncoated portions at both ends of the electrode precursor sheet were equal, the elongation rates of those uncoated portions were equivalent. Therefore, a flat electrode without curvature was obtained. Also, since the electrode fabricated in Comparative Example 2 was a low-density electrode, the pressure during rolling was low. Therefore, although the widths of the slurry-uncoated portions at both ends of the electrode precursor sheet were different from each other, there was almost no difference in their elongation rates, and the precursor sheet did not get distorted and became flat. As a result, a flat electrode without curvature was obtained. For Comparative Examples 1 and 2 where flat electrodes were obtained, the above measurements were not performed, so the corresponding values for the pitch and depth of the uneven portions are denoted as “-”, indicating that there are no applicable values.

[0211] <Battery fabrication> Using the electrodes obtained in Examples 1 - 5 and Comparative Examples 1 - 2 as the negative electrode, a non-aqueous electrolyte battery was fabricated according to the following procedure.

[0212] (Fabrication of the positive electrode) Commercial lithium cobalt oxide (LiCoO2) was mixed with acetylene black as a conductive agent at a ratio of 5% by mass to obtain a mixture. Next, this mixture was dispersed in NMP to obtain a dispersion. To this dispersion, PVdF as a binder was mixed with lithium cobalt oxide at a ratio of 5% by mass to prepare a positive electrode slurry. This slurry was applied to both sides of a current collector made of 12-μm aluminum foil using a blade. This was dried at 130 °C under vacuum for 12 hours to obtain a laminate. Thereafter, the density of the active material-containing layer (excluding the current collector) was 2.2 g / cm 3The laminate was rolled in such a manner to obtain the positive electrode.

[0213] (Fabrication of electrode groups) The negative and positive electrodes prepared as described above were stacked with a polyethylene separator in between to obtain a stacked electrode group. The number of stacked negative electrodes was 40, and the number of stacked positive electrodes was 39. Next, the negative electrode terminals were electrically connected to the current collection tabs of each negative electrode, and the positive electrode terminals were electrically connected to the current collection tabs of each positive electrode.

[0214] A mixed solvent of EC and DEC (volume ratio 1:1) was prepared. Lithium hexafluoride phosphate (LiPF6) was dissolved in this solvent at a concentration of 1 M. Thus, a non-aqueous electrolyte was prepared.

[0215] (Assembly of non-aqueous electrolyte batteries) The electrode group prepared as described above was placed in a battery casing made of aluminum-containing laminate film. After injecting a non-aqueous electrolyte into the casing, the casing was sealed with heat seal to produce a laminate-type non-aqueous electrolyte battery.

[0216] <Rating> For each non-aqueous electrolyte battery, the impregnation state of the non-aqueous electrolyte into the electrode group after injection into the outer casing was confirmed. The impregnation state of the non-aqueous electrolyte inside the battery was evaluated using a non-contact ultrasonic measuring device (manufactured by Japan Probe Co., Ltd.), model number: NAUT-21. Specifically, the unimpregnated and impregnated areas in the negative electrode were visualized by ultrasonic measurement, and measurements were taken every 4 hours until the unimpregnated area was less than 5% of the area of ​​the main surface of the negative electrode.

[0217] Next, these batteries underwent several formation cycles in a 25°C environment and were subjected to 24-hour aging. After aging, capacity verification was performed at a charge / discharge rate of 0.2C to confirm that the design capacity was obtained. Subsequently, AC impedance measurement (R) was performed at full charge. iniNext, the device was placed in a constant temperature chamber set to an ambient temperature of 45°C and left to stand for 2 hours. Then, a 500-cycle charge-discharge test was performed at a charge-discharge rate of 1C. After the 500 cycles were completed, the capacity was checked again at 0.2C in a 25°C environment, and then the AC impedance measurement (R) at full charge was performed. after ) was performed. From these results, the resistance increase rate (=R) before and after the 500-cycle test was calculated. after / R ini We calculated (×100%).

[0218] The evaluation results are shown in Table 2 below. Specifically, it shows the electrolyte penetration time required until the unimpregnated area became less than 5% of the negative electrode main surface area after injection of the non-aqueous electrolyte, and the resistance increase rate during a 500-cycle charge-discharge test.

[0219] [Table 2]

[0220] As shown in Table 2, in batteries using the electrodes prepared in Examples 1-5 as the negative electrode, the electrolyte penetrated almost the entire negative electrode within a few hours to 12 hours. In contrast, in batteries using the electrodes prepared in Comparative Examples 1 and 2 as the negative electrode, it took nearly a full day for the electrolyte to penetrate the negative electrode. This indicates that electrodes with a corrugated surface and a pitch on the current collector tab side that is narrower than the pitch on the opposite side have high electrolyte penetration.

[0221] Furthermore, in batteries using the electrodes fabricated in Examples 1-5 as the negative electrode, the rate of resistance increase after repeated charging and discharging was lower compared to batteries using the batteries fabricated in Comparative Examples 1 and 2. Therefore, it can be seen that by using electrodes with the above-described uneven surface configuration, it is possible to realize batteries with less performance degradation and superior lifespan.

[0222] According to one or more of the embodiments and examples described above, an electrode including an active material-containing layer and a current collector is provided. The active material-containing layer includes a second side on the opposite side in the first direction intersecting the first side, and contains an electrode active material. The current collector includes an active material-supported portion that supports the active material-containing layer, and an active material non-supported portion that is adjacent to the active material-supported portion and the first side and on which the active material-containing layer is not provided. The electrode has uneven portions including ridges and grooves along the first direction, and a first pitch a and a second pitch b of the uneven portions along the first side and the second side respectively satisfy the relationship a < b. By using this electrode, it is possible to provide a secondary battery and a battery pack excellent in the permeability of the electrolyte to the electrode and the retention in the electrode, excellent in life performance, and a vehicle equipped with this battery pack.

[0223] Some embodiments according to the present invention are appended below.

[0224] [1] An active material-containing layer including a second side on the opposite side in the first direction intersecting the first side and containing an electrode active material, An electrode comprising an active material-supported portion that supports the active material-containing layer, and a current collector including an active material non-supported portion that is adjacent to the active material-supported portion and the first side and on which the active material-containing layer is not provided, Having uneven portions including a plurality of ridges and a plurality of grooves respectively along the first direction, and a first pitch a and a second pitch b of the uneven portions along the first side and the second side respectively satisfy the relationship a < b.

[0225] [2] With respect to the average length X of the first length of the first side and the second length of the second side, the first pitch a is within the range of 0.01X ≤ a ≤ 0.1X, and the second pitch b is within the range of 0.05X ≤ b ≤ 0.5X. The electrode according to [1].

[0226] [3] The electrode according to [1] or [2], wherein the ridges and the grooves are arranged so as to radially expand from the first side toward the second side.

[0227] [4] The electrode active material contains a metal oxide, and the active material-containing layer has a density of 2.3 g / cm 3 or more and 3.5 g / cm 3 or less, and the electrode according to any one of [1]-[3].

[0228] [5] The active material-containing layer has a main surface area of 150 cm 2 or more and 500 cm 2 or less, and the electrode according to any one of [1]-[4].

[0229] [6] An electrode group including a plurality of positive electrodes and a plurality of negative electrodes, wherein the negative electrode is the electrode according to any one of [1]-[5], and the electrode group has a laminated structure in which the positive electrode and the negative electrode are laminated.

[0230] [7] A secondary battery including the electrode group according to [6] and an electrolyte.

[0231] [8] A battery pack including the secondary battery according to [7].

[0232] [9] The battery pack according to [8], further including an external terminal for energization and a protection circuit.​​​​​​​​​​​​​​​​​​​​ While several embodiments of the present invention have been described, these embodiments are presented as examples only and are not intended to limit the scope of the invention. These novel embodiments can be carried out in a variety of other forms, and various omissions, substitutions, and modifications can be made without departing from the spirit of the invention. These embodiments and their variations are included in the scope and spirit of the invention, as well as in the claims of the invention and its equivalents. [Explanation of symbols]

[0237] 1…Electrode group, 2…Outer material, 3…Negative electrode, 3a…Negative electrode current collector, 3b…Negative electrode active material containing layer, 3c…Negative electrode current collector tab, 4…Separator, 5…Positive electrode, 5a…Positive electrode current collector, 5b…Positive electrode active material containing layer, 5c…Positive electrode current collector tab, 6…Negative electrode terminal, 7…Positive electrode terminal, 8…Ridge, 9…Groove, 10…Electrode, 10a…Current collector, 10b…Active material containing layer, 10c…Current collector tab, 10d…Active material supporting part, 10e…Active material non-supporting part, 12… Electrode precursor sheet, 12a...Uncoated area of ​​first active material, 12b...Active material-containing layer, 12c...Uncoated area of ​​second active material, 21...Bus bar, 22...Positive electrode lead, 23...Negative electrode lead, 24...Adhesive tape, 31...Container container, 32...Lid, 33...Protective sheet, 34...Printed circuit board, 35...Wiring, 40...Vehicle body, 41...Vehicle power supply, 42...Electrical control device, 43...External terminals, 44...Inverter, 45...Drive motor 100...Secondary battery, 200...Battery pack, 200a...Battery pack, 200b...Battery pack, 200c...Battery pack, 300...Battery pack, 300a...Battery pack, 300b...Battery pack, 300c...Battery pack, 301a...Battery pack monitoring device, 301b...Battery pack monitoring device, 301c...Battery pack monitoring device, 342...Positive side connector, 343...Negative side connector, 345...Thermistor, 346...Protection circuit, 342a...Wiring 343a...Wiring, 350...External terminal for power supply, 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...Connection line, L2...Connection line, W...Drive wheel.

Claims

1. An active material-containing layer comprising a first side and a second side on the opposite side in a first direction intersecting the first side, and containing an electrode active material, The current collector comprises an active material supporting portion that supports the active material-containing layer, and an active material non-supporting portion adjacent to the active material-supporting portion and the first side, where the active material-containing layer is not provided. An electrode having a surface with a plurality of ridges and a plurality of grooves along the first direction, wherein the relationship a < b is satisfied between a first pitch a, which is the average value of the distance between adjacent pairs of ridges in the surface with a plurality of ridges along the first side, and a second pitch b, which is the average value of the distance between adjacent pairs of ridges in the surface with a plurality of ridges along the second side.

2. The electrode according to claim 1, wherein, with respect to the average length X of the first length of the first side and the second length of the second side, the first pitch a is in the range of 0.01X ≤ a ≤ 0.1X and the second pitch b is in the range of 0.05X ≤ b ≤ 0.5X.

3. The electrode according to claim 1 or 2, wherein the ridges and grooves are arranged to spread radially from the first side to the second side.

4. The electrode active material contains a metal oxide, and the active material-containing layer is 2.3 g / cm³. 3 3.5g / cm or more 3 The electrode according to claim 1 or 2, having the following density.

5. The active material-containing layer is 150 cm 2 More than 500cm 2 The electrode according to claim 1 or 2, having a main surface with the following area.

6. Multiple positive electrodes, Multiple negative electrodes, A group of electrodes comprising, The negative electrode is the electrode described in claim 1 or 2. An electrode group having a stacked structure in which the positive electrode and the negative electrode are stacked.

7. The electrode group according to claim 6, Electrolytes and A secondary battery equipped with the following features.

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

9. External terminals for power supply, Protection circuit and The battery pack according to claim 8, further comprising the above.

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

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

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

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