Electrodes, secondary cells, and battery packs

Abstract

Electrodes are provided for secondary batteries and battery packs that achieve high rate performance and long lifespan. According to one embodiment, an electrode is provided having a current collector in the shape of a foil containing metal, and an electrode having an active material layer on the current collector. The current collector has a plurality of through holes with a diameter of 10 μm to 1000 μm at a spacing of 3.0 mm to 100 mm. The ratio of oxygen atomic weight OU to metal atomic weight MeU in the non-opening portion at a distance of 1.5 times or more from the outer periphery of the through hole to the ratio OU / MeU, and the ratio of oxygen atomic weight OP to metal atomic weight MeP in the portion surrounding the holes at a distance of 5% or less from the outer periphery of the through hole to the ratio OP / MeP, is 1.2 times or more.

Description

Technical Field

[0001] The embodiments of the present invention relate to electrodes, secondary batteries, and battery packs. Prior Technology

[0002] Lithium-ion batteries, which charge and discharge by the movement of lithium ions between the negative and positive electrodes, such as non-aqueous electrolyte batteries, are being actively researched as high-energy-density batteries. It is known that using porous current-collecting foil as the electrode core material can significantly improve rate performance by supplying Li ions from the back side of the current-collecting foil during charging and discharging. Summary of the Invention

[0003] It provides electrodes for secondary batteries and battery packs that achieve high rate performance and long lifespan, as well as secondary batteries and battery packs that achieve high rate performance and long lifespan.

[0004] According to an embodiment, a current collector having a foil shape containing metal is provided, and an electrode having an active material layer on the current collector. The current collector has a plurality of through holes with a diameter of 10 μm to 1000 μm with openings at a spacing of 3.0 mm to 100 mm. The ratio of oxygen atomic weight OU to metal atomic weight MeU in the non-opening portion at a distance of 1.5 times or more from the outer periphery of the through hole to the metal atomic weight MeU is OU / MeU, and the ratio of oxygen atomic weight OP to metal atomic weight MeP in the portion surrounding the holes at a distance of 5% or less from the outer periphery of the through hole is OP / MeP, which is 1.2 times or more.

[0005] According to other embodiments, a secondary battery comprising a positive electrode, a negative electrode, and an electrolyte is provided. At least one of the positive electrode and the negative electrode is an electrode related to the above embodiments.

[0006] According to other embodiments, a battery pack having the secondary battery related to the above embodiments is provided. Simple Explanation of the Diagram

[0007] [Figure 1] is a cross-sectional view schematically showing an example of an electrode related to an embodiment. [Figure 2] is a top view schematically showing the current collector including electrodes related to the implementation configuration. [Figure 3] is a cross-sectional view of one example of a secondary battery with a schematic embodiment. [Figure 4] is an enlarged cross-sectional view of part A of the secondary battery shown in Figure 3. [Figure 5] is a partial cross-sectional perspective view schematically showing another example of a secondary battery related to the embodiment. [Figure 6] is an enlarged cross-sectional view of part B of the secondary battery shown in Figure 5. [Figure 7] is a perspective view of one example of a battery pack related to an embodiment. [Figure 8] is an exploded perspective view that schematically presents one example of a battery pack related to an implementation configuration. [Figure 9] is a block diagram showing an example of the electrical circuit of the battery pack shown in Figure 8. Implementation

[0008] It is known that using porous current collector foil in the electrodes of current collectors significantly improves rate performance. However, porous current collector foils are expensive to manufacture, and the current concentrates at the processing edges, leading to increased resistance due to the formation of excessive AlF3 and other substances caused by corrosion. Furthermore, the rigidity of porous current collector foils is reduced, resulting in problems such as foil breakage during pressure processing in electrode manufacturing, or damage due to volume changes in the electrodes accompanying charge and discharge. Methods involving processing the foil along with active materials also exist, but these methods suffer from reduced energy density.

[0009] The embodiments will be described below with reference to the drawings. Furthermore, common components in the embodiments will be marked with the same symbols, and repeated explanations will be omitted. Also, the drawings are schematic diagrams used to facilitate the explanation and understanding of the embodiments; their shapes, dimensions, proportions, etc., may differ from the actual device. In such cases, please refer to the following explanation and conventional techniques, and appropriate design modifications may be made.

[0010] (First Implementation) According to the first embodiment, an electrode is provided. The electrode system comprises a current collector in the shape of a foil containing metal, and an active material layer on the current collector. The current collector system has a plurality of through holes. The diameter of the through holes is 10 μm to 1000 μm, and the spacing on the current collector is 3.0 mm to 100 mm. The ratio of oxygen atomic mass OU to metal atomic mass MeU (OU / MeU) of the non-opening portion, the ratio of oxygen atomic mass OP to metal atomic mass MeP (OP / MeP) of the portion surrounding the through holes is 1.2 times or more. The portion surrounding the holes refers to the area within 5% of the diameter of the through hole from its outer periphery. The non-opening portion refers to a position at least 1.5 times the diameter of the through hole from its outer periphery.

[0011] The aforementioned electrode system incorporates a porous current collector foil. Charge carrier ions, such as Li ions, can pass through the porous current collector foil, thus the movement of carrier ions within the electrode is not hindered by the current collector. Therefore, batteries using this electrode system can exhibit high-rate performance.

[0012] In the relevant electrodes, although there are multiple through-holes in the current collector opening, the resistance increase caused by the excessive formation of byproducts such as AlF3 at the edges of the through-holes is suppressed, and the strength around the through-holes is improved. Therefore, the damage to the current collector caused by the expansion and contraction of the electrodes can be mitigated. As mentioned above, the ratio of oxygen atoms around the through-holes is higher than that in the non-opening areas. Specifically, the ratio of oxygen atomic weight to metal atomic weight (oxygen atomic weight / metal atomic weight) is more than 1.2 times higher in the area around the hole than in the non-opening areas, which is a significantly higher ratio than that of naturally formed protective films. That is, the area around the through-holes is composed of metal acid hydroxide, thereby protecting the current collector from the effects of the formation of byproducts such as AlF3, and improving the strength around the hole.

[0013] The active material containing layer can be formed on one or both sides of the current collector. Preferably, the active material containing layer is disposed on both the front and back main surfaces of the current collector. By using a porous current collector foil as the current collector, the active material containing layer disposed on both sides can be utilized to the maximum extent. The active material containing layer may contain an active material and selectively contain a conductive agent and an adhesive.

[0014] The active material containing layer preferably does not have through-pores. By not providing through-pores, but containing active material in the corresponding spaces, the energy density of the electrode can be increased by an equal amount. Furthermore, the porosity of the active material containing layer is preferably 36% or less. By reducing porosity and containing an equal amount of active material, the energy density per unit volume of the electrode can be increased.

[0015] The current collector may include a portion on which an active material layer is not formed on its surface. This portion can be used as a current collector tongue.

[0016] Figure 1 shows an example of an electrode related to an embodiment. Figure 1 is a schematic cross-section of the electrode. Figure 2 shows an example of a current collector including the electrode. Figure 2 is a schematic planar view of the current collector.

[0017] The illustrated electrode 10 includes a current collector 10a and active material containing layers 10b disposed on both its front and back sides. The active material containing layer 10b is not disposed on either the front or back side of a portion of the current collector 10a; this portion can be used as a current collector tongue 10c. The active material containing layer 10b contains an active material not shown.

[0018] In the portion of the current collector 10a that does not support the active material containing layer 10b, a plurality of through holes 11 are disposed. That is, the current collector 10a is a porous current collector foil. In the portion of the current collector tongue 10c that does not support the active material containing layer 10b, there are no through holes 11. As shown in Figure 1, charge carrier ions such as lithium ions (Li+) can pass through the through holes 11 and move back and forth between the active material containing layers 10b located on both sides of the current collector 10a. Therefore, the battery using electrode 10 can exhibit high rate performance.

[0019] The through-holes 11 have a diameter of 10 μm to 1000 μm. The through-holes 11 are arranged with a spacing of 3.0 mm to 100 mm between them, as shown in Figure 2, and are not necessarily arranged uniformly. The current collector 10a with through-holes of this size arranged at the aforementioned spacing can improve the rate performance of the electrode while maintaining strength. In Figure 2, the through-holes 11 are of uniform size, but the diameters of the multiple through-holes 11 are not necessarily uniform. The maximum diameter measured by the method described later is within the aforementioned range. Furthermore, while the through-holes 11 are depicted as circular in Figure 2, the shape of the through-holes 11 is not limited to a circle, and the shapes of the multiple through-holes 11 are not necessarily uniform.

[0020] Comparing the periphery 12 of the through hole 11, which faces outward and is within 5% of the diameter of the through hole 11 at a distance from its outer periphery, with the non-opening portion 13, which faces outward and is at least 1.5 times the diameter of the through hole 11 at a distance from its outer periphery, the ratio of oxygen atomic weight OU to metal atomic weight MeU in the non-opening portion 13 (OU / MeU) is greater than 1.2 times. This refers to the presence of a metal acid hydroxide in at least a portion of the periphery 12. Therefore, the periphery 12, which is the peripheral region of the through hole 11, is protected and has high strength.

[0021] In the illustrated example, no through-holes are provided in the active material containing layer 10b. Therefore, the through-holes 11 of the current collector 10a are covered by the active material containing layer 10b. By providing through-holes only in the current collector 10a, the rate performance of the electrode 10 can be improved without reducing its energy density.

[0022] The relevant electrode system can be, for example, at least one of the positive and negative electrodes of the battery. In a battery that includes the relevant electrode as the negative electrode, the positive electrode can also be something other than the electrode related to the embodiment. Conversely, in a battery that includes the relevant electrode as the positive electrode, the negative electrode can be something other than the electrode related to the first embodiment. Both the negative and positive electrodes included in the battery can be the electrodes related to the first embodiment.

[0023] The active material containing layer may contain only one type of active material, or it may contain two or more types of active materials. For example, an electrode active material whose solubility in water is less than 0.2 wt% can be used. Furthermore, an electrode active material with a pH of 5 to 9 when the electrode material is washed with water can be suitable.

[0024] As for the negative electrode of the electrode related to the first embodiment, the active material containing layer (negative electrode active material containing layer) may contain, for example, an oxide selected from the group consisting of titanium, niobium, tungsten, molybdenum, vanadium, iron, tin, and silicon as the negative electrode active material. Specific examples include niobium oxide and titanium dioxide (TiO2). Niobium oxides include niobium pentoxide (Nb2O5), Nb12O29, FeNb11O29, monoclinic titanium niobium oxide (TNO), tetragonal titanium-niobium-tungsten composite oxide, and tetragonal titanium-niobium-molybdenum composite oxide, etc.

[0025] Examples of monoclinic niobium titanium oxides include compounds denoted as LixTi1-yM1yNb2-zM2zO7+δ. Here, M1 is selected from at least one of the groups consisting of Zr, Si, and Sn. M2 is selected from at least one of the groups consisting of V, Ta, and Bi. The subscripts in the formulas are 0≦x≦5, 0≦y<1, 0≦z<2, and -0.3≦δ≦0.3. A specific example of a monoclinic niobium titanium oxide is LixNb2TiO7 (0≦x≦5).

[0026] Other examples of monoclinic niobium titanium oxides include compounds represented as LixTi1-yM3y+zNb2-zO7-δ. Here, M3 is selected from at least one of Mg, Fe, Ni, Co, W, Ta, and Mo. The subscripts in the formulas are 0≦x≦5, 0≦y<1, 0≦z<2, and -0.3≦δ≦0.3.

[0027] As an aspect of the positive electrode of the electrode related to the first embodiment, as the positive electrode active material in the active material-containing layer (positive electrode active material-containing layer), it may contain at least one selected from the group consisting of phosphoric acid oxide salts and pyrophosphates. The phosphoric acid oxide salts include iron phosphate, manganese phosphate, nickel phosphate, cobalt phosphate, and lithium salts thereof. As a specific example, a lithium phosphoric acid oxide having an olivine structure (for example, LixFePO4; 0 < x ≦ 1, LixFe1-yMnyPO4; 0 < x ≦ 1, 0 < y ≦ 1, LixCoPO4; 0 < x ≦ 1) can be cited. The pyrophosphates include iron pyrophosphate, manganese pyrophosphate, nickel pyrophosphate, cobalt pyrophosphate, and lithium salts thereof.

[0028] The conductive agent is blended to improve the current collection performance and suppress the contact resistance between the active material and the current collector. Among examples of the conductive agent, carbonaceous materials such as vapor grown carbon fiber (VGCF), carbon black such as acetylene black, graphite, carbon nanotubes, and carbon nanofibers can be included. One of these can be used as the conductive agent, or two or more of them can be combined and used as the conductive agent. Alternatively, carbon coating or coating with an electronically conductive inorganic material can be performed on the surface of the active material particles instead of using the conductive agent. Also, in the aspect of the positive electrode, the conductive agent can be omitted.

[0029] The binder is blended to fill the gaps between the dispersed active materials and bond the active materials to the current collector. As the binder, it is preferably a water-soluble binder. Although it will be described in detail later, through-hole pores can be formed in the current collector by a porous reaction in an aqueous environment. Therefore, by using a water-soluble binder during electrode manufacturing, the porous reaction of the current collector can be promoted. As the water-soluble binder, for example, sodium carboxymethyl cellulose (CMC), fluorine-based rubber, or styrene-butadiene rubber can be used as the cellulose-based component, but it is not limited to these.

[0030] The blending ratios of the active material, conductive agent, and binder in the active material-containing layer can be appropriately changed according to the use of the electrode. For example, when using the electrode as the negative electrode of a secondary battery, it is preferable to blend the active material (negative electrode active material), conductive agent, and binder at ratios of 68% by mass or more and 96% by mass or less, 2% by mass or more and 30% by mass or less, and 2% by mass or more and 30% by mass or less, respectively. By setting the amount of the conductive agent to 2% by mass or more, the current collection performance of the active material-containing layer can be improved. Also, by setting the amount of the binder to 2% by mass or more, the adhesion between the active material-containing layer and the current collector is sufficient, and excellent cycle performance can be expected. On the other hand, it is preferable that the conductive agent and the binder are each 30% by mass or less to achieve a high capacity.

[0031] In the case of the positive electrode, the active material (positive electrode active material) and binder in the active material containing layer are preferably blended in proportions of 80% to 98% by mass and 2% to 20% by mass, respectively. By setting the amount of binder to 2% by mass or more, sufficient strength of the active material containing layer can be obtained. Furthermore, the binder can function as an insulator. Therefore, if the amount of binder is set to 20% by mass or less, the amount of insulator contained in the electrode is reduced, thereby reducing internal resistance.

[0032] When a conductive agent is added, the active material (positive electrode active material), binder, and conductive agent are preferably blended in proportions of 77% to 95% by mass, 2% to 20% by mass, and 3% to 15% by mass, respectively. The aforementioned effects are achieved by setting the amount of conductive agent to 3% by mass or more. Furthermore, by setting the amount of conductive agent to 15% by mass or less, the proportion of conductive agent in contact with the electrolyte can be reduced. If this proportion is low, the decomposition of the electrolyte can be reduced during high-temperature storage.

[0033] The current collector is made of a metal or alloy, with a metallic element other than titanium (Ti) as the main component. Specific examples include aluminum, aluminum alloys, copper, nickel, or stainless steel (SUS, etc.). Examples of aluminum alloys include aluminum alloys selected from one or more elements selected from Mg, Ti, Zn, Mn, Fe, Cu, Si, Cr, V, and Ga. Preferably, the current collector contains aluminum. That is, it is preferable that the current collector is made of aluminum or an aluminum alloy. Furthermore, when the current collector contains aluminum, the aluminum impurity concentration can be greater than 0.15% but less than 4%.

[0034] <<Manufacturing Methods>> Electrodes can be fabricated by, for example, the following method. First, an electrode composite containing an active material, a conductive agent, and a binder is suspended in a solvent to prepare a slurry. For example, a solvent containing water is used. The solvent can be pure water or a mixture of water and other solvents. This slurry is coated onto one or both sides of a foil serving as a current collector. Next, the coated slurry is dried, and pressure is applied to the coating formed on the current collector foil. The electrode precursor thus obtained is kept in an environment with moderate humidity, exposed to the atmosphere. The foil is exposed to a water-containing environment while in contact with the electrode composite and oxygen, causing a reaction that makes the foil porous. Next, the coating is completely dried, forming an active material-containing layer on the current collector. Thus, the electrode is fabricated.

[0035] In the foil serving as a current collector, the material of the above-described current collector, namely, a foil of a metal or an alloy, is used. When the electrode precursor is exposed to an environment containing air and water, metal ions are dissolved due to the potential difference between the active material or the conductive agent and the metal of the current collector foil, and through-holes are formed in the current collector foil. By the reaction of the dissolved metal ions with oxygen and water in the air, metal hydrogen hydroxides are formed around the holes. For example, when a foil containing aluminum (Al) is used, aluminum oxyhydroxide represented by AlOx(OH)y can be generated, where 0 < x ≤ 1.5, 0 < y ≤ 3, and 2x + y = 3. Specifically, first, through-holes are generated by the formation of aluminum oxide, and aluminum oxide is used as a reactant, and aluminum oxyhydroxide is generated by the electrolytic reaction of oxygen and water. Therefore, by maintaining it in a water-containing environment and subjecting the electrode precursor to a porous treatment, through-holes protected and reinforced by metal hydrogen hydroxides at the edges can be provided in the current collector.

[0036] Preferably, a compound with a slightly acidic to weakly basic property is used as the active material. Specifically, preferably, for example, an active material with a pH of 5 or more and 9 or less when the electrode material obtained by the method described later is washed with water is used. When an active material with a more acidic property is used, the diameter or the number of through-holes tends to increase. When an active material with a more basic property is used, the diameter or the number of through-holes tends to decrease. For example, when an active material with a strong basic property is used, the through-holes generated during the formation of aluminum oxide may be blocked during the formation of aluminum oxyhydroxide. When an active material with a pH of 5 or more and 9 or less when the electrode material is washed with water is used, an electrode having a current collector with through-holes having diameters and spacings within the above ranges can be easily obtained.

[0037] The holding of the electrode precursor in a water-containing environment is carried out, for example, in the atmosphere in an environment with a dew point of 10°C or more and 35°C or less. The holding time is set, for example, to 1 hour or more and 72 hours or more. However, during the holding process, moisture may be absorbed into the coating film on the current collector foil. Preferably, for example, the maximum value of the moisture content at this time is controlled to be 10,000 ppm or less. By holding under the above conditions, an electrode having a current collector with through-holes having diameters and spacings within the above ranges can be obtained.

[0038] From the viewpoint of promoting the porous reaction, it is preferable to use a water-soluble binder as the binder. In the coating film of the slurry using a water-soluble binder, moisture can easily reach the interface between the coating film and the foil, that is, the part where the active material or the conductive agent contacts the metal.

[0039] The formation of through-holes on the current collector is carried out under pressure to increase the density of the active material layer, thus eliminating concerns about current collector breakage during pressure application and allowing for a relative increase in the size and number of through-holes. Furthermore, as mentioned above, the area around the holes is protected and reinforced by a metal acid hydroxide, thereby improving the electrode's durability and battery life. Consequently, the related electrode can achieve a secondary battery with excellent rate performance and battery life. Moreover, since a porous current collector foil is not required, the electrode can be manufactured at a low cost.

[0040] <<Determination Methods>> This document describes various measurement methods for electrodes related to their implementation forms. Specifically, it describes analytical methods for openings in the electrode, methods for determining the ratio of oxygen atomic weight to metal atomic weight on the current collector, methods for identifying water-soluble binders, methods for measuring the pH of the electrode material during water washing, methods for measuring the porosity of the active material containing the layer, and methods for identifying the active material of the electrode.

[0041] When the electrode to be measured is assembled into the battery, the electrode is removed from the battery as follows: First, the battery is discharged to 0.0V to achieve an over-discharge state. Next, the battery is disassembled in a glove box filled with argon, and the electrode is removed. If the electrode, along with the counter electrode and separator, forms an electrode group, the electrode group is removed and disassembled, and the electrode to be measured is separated from the electrode group.

[0042] <Analysis of the opening> By immersing the electrode in water or a solvent such as N-methylpyrrolidone for 24 hours, the active material layer on the current collector can be peeled off without damaging it. Afterward, if necessary, it is ultrasonically cleaned for 5 seconds. Once the current collector is dried, it is analyzed under an electron microscope.

[0043] The analysis of openings on the current collector was performed using a combination of scanning electron microscopy and energy dispersive x-ray spectroscopy (SEM-EDS). First, a qualitative analysis was conducted on the entire current collector, defining the material containing the most abundant detected metallic elements as the current collector material. Then, SEM-EDS analysis was used to map these metallic elements, designating locations where the metal was not detected as the openings of the through-holes. However, it was necessary to confirm beforehand that the SEM-EDS mechanical material did not contain the required metallic element.

[0044] After mapping, the mapped image is binarized using image processing software, and the widest part of the diameter of the missing part where the element does not exist is recorded as the diameter of the through hole.

[0045] For binarization, image analysis software such as ImageJ (non-patent literature: Dr. Michael et al., Image Processing with ImageJ, Reprinted from the July 2004 issue of Biophotonics International, copyrighted by Laurin Publishing Co. INC.) can be used. ImageJ is a public software. The version of ImageJ used is 1.52a.

[0046] Furthermore, based on the presence ratio of the metal elements identified as current collector materials and other elements detected, the impurity concentration in the current collector can be calculated.

[0047] The presence or absence of openings in the active material layer was also analyzed using SEM-EDS. However, instead of stripping the active material layer from the current collector, the electrode was immersed in a solvent that would not dissolve the adhesive of the active material layer, such as dimethyl carbonate, for 24 hours, followed by washing. The presence or absence of through-holes was confirmed by analyzing the transition metal most abundant in the electrode active material, rather than analyzing the metal of the current collector.

[0048] <Ratio of oxygen atomic weight to metal atomic weight> To confirm the openings on the current collector, the ratio of oxygen atomic mass to metal atomic mass for the area surrounding the hole and the non-opening area can be determined from the mapping image obtained by SEM-EDS analysis. For the oxygen atomic mass OP and metal atomic mass MeP around the hole, the area at the center of the field of view is analyzed, extending outward from the edge of the through-hole to a distance of 1 / 20th of the diameter of the through-hole. The through-hole used for analysis of the area surrounding the hole is one of the two nearest through-holes, ideally the closest one. For the oxygen atomic mass OU and metal atomic mass MeU of the non-opening area, the midpoint of the straight line connecting the two nearest holes, at a distance of at least 1.5 times the diameter of the nearest hole from its outer perimeter, is placed at the center of the field of view and analyzed. For example, in the example shown in Figure 2, measurement point 13a is used as the center of the analysis field of view for the non-opening area. Furthermore, pairs of through holes whose midpoint on the straight line connecting the two through holes is not more than 1.5 times the diameter of either hole are excluded from the nearest neighbor pairs. Also, when the diameters of the nearest neighbor pairs are different, the diameter of the larger through hole is used as the reference for a distance of more than 1.5 times. Furthermore, the oxygen atomic weight OP relative to the metal atomic weight MeP around the hole is also set as the value of the position on the straight line connecting the two through holes through the aforementioned measurement point 13a at the non-opening portion.

[0049] Water-soluble adhesives Whether the active material layer contains water-soluble binders can be analyzed, for example, by extracting and analyzing the binder from the electrode. The electrode is cleaned with dimethyl carbonate, dried at 120°C, then immersed in water, ultrasonically dispersed, and filtered to extract the water-soluble binder. That is, the filtered clear liquid may contain water-soluble binders. The water-soluble binder can be separated by air-drying at room temperature and analyzing the solid residue. The presence of residual organic molecules in the solid residue can be confirmed using methods such as infrared spectroscopy (IR), nuclear magnetic resonance (NMR), mass spectrometry, or a combination of methods as needed.

[0050] <pH during electrode material washing> The acidity and alkalinity of the active material contained in the electrode can be assessed by measuring the pH of the electrode material during water washing, as follows.

[0051] The electrodes removed from the battery were washed with dimethyl carbonate. After drying at 120°C, the active material layer was peeled off from the current collector using a scraper or similar tool. 1 g of the active material layer separated from the current collector was added to 10 mL of water, and the resulting suspension was allowed to stand for 24 hours. Next, the supernatant of the suspension was separated by centrifugation. The pH of the separated supernatant was measured. This measured pH is referred to as the "pH of the electrode material during washing."

[0052] <Porosity of the layer containing active substances> The porosity of the active material containing layer was measured using three-dimensional measurement scanning electron microscopy (3D-SEM). Electrodes removed from the battery were cleaned with dimethyl carbonate solvent and dried. Samples approximately 5 mm × 5 mm in size were cut. After depositing a tungsten protective film on the main surface of the active material containing layer of the sample, a cross-section in the thickness direction of the active material containing layer was cut using focused ion beam (FIB) and observed using SEM. Subsequently, the cross-section processing using FIB and the SEM observation were repeated, and the porosity was determined by three-dimensional reconstruction of the SEM images. For example, the FIB processing spacing was set to approximately 150 nm, and the number of repetitions of FIB processing and SEM observation was set to 100.

[0053] <Active Substances> For active substances, crystal structure analysis by X-ray diffraction spectroscopy and compositional analysis by inductively coupled plasma (ICP) luminescence spectrometry can be used for identification.

[0054] XRD measurements can be performed, for example, as follows.

[0055] First, to determine the crystallization state of the active material, it is necessary to ensure that lithium ions are completely detached from the active material. For example, when used as the negative electrode of a battery, the battery is brought to a fully discharged state. For instance, the battery is repeatedly discharged at 0.1C at 25°C until the rated termination voltage or the battery voltage reaches 1.0V, with the discharge current being less than 1 / 100 of the rated capacity. This allows the battery to be brought to a discharged state. Even in a discharged state, residual lithium ions may remain.

[0056] Next, the battery is disassembled in an argon-filled glove box, and the electrodes are removed and cleaned with a suitable solvent. For example, dimethyl carbonate can be used as a suitable solvent. If the electrodes are not cleaned sufficiently, impurities such as lithium carbonate or lithium fluoride may be introduced due to the influence of residual lithium ions in the electrodes. In this case, it is preferable to use an airtight container that can be used in an inert gas environment. The cleaned electrodes are cut to a size equal to the area of ​​the fixture in the powder X-ray diffraction apparatus to serve as the test sample. This sample is attached to a direct glass fixture and the measurement is performed.

[0057] At this point, XRD is used to pre-determine and control the peak values ​​from the metal foil, conductive agent, and binder, which serve as current collectors. Of course, if these can be controlled in advance, this step can be omitted. When the peak value of the current collector overlaps with the peak value of the active material, it is ideal to peel off the active material containing layer from the current collector for measurement. This is to separate the overlapping peak values ​​when quantitatively measuring the peak intensity. The active material containing layer can be peeled off physically, as described above, or by immersion in a solvent such as water. In the latter case, the electrode assembly (including the active material, conductive agent, and binder) can be recovered by evaporating the solvent. By filling the recovered electrode assembly into, for example, a Lindemann glass capillary tube, powder X-ray diffraction measurement of the active material can be performed.

[0058] As an apparatus for powder X-ray diffraction measurement, for example, the SmartLab manufactured by Rigaku Corporation is used. The measurement conditions are set as follows: X-ray source: Cu target material Output: 45kV 200mA Soller slit: 5° for both incident and received light. Step size (2θ): 0.02 degrees Scanning speed: 20 degrees / minute Semiconductor detector: D / teX Ultra 250 Measurement range: 5°≦2θ≦90° Sample plate holder: Flat glass sample plate holder (thickness 0.5mm). When using other devices, in order to obtain the same measurement results as above, measurements were performed using standard Si powder for powder X-ray diffraction, adjusting the conditions to make the peak intensity and peak position consistent with the above-mentioned devices, and then the measurements were performed. The determination of the composition of active substances by ICP luminescence spectrometry is carried out by the following steps.

[0059] The electrodes, removed from the battery and cleaned, are stripped of their active material layer using the method described above. Next, the stripped portion is briefly heated in air (e.g., at approximately 500°C for 1 hour) to burn off unwanted components such as adhesives and conductive agents. The residue is then dissolved in acid to prepare a liquid sample containing the active material. Hydrochloric acid, nitric acid, sulfuric acid, or hydrogen fluoride can be used as the acid. By supplying this liquid sample to ICP analysis, the average composition of the active material can be determined.

[0060] The electrode system of the first embodiment includes a current collector in the shape of a metal foil and an active material layer thereon. The current collector has multiple through holes with a diameter of 10 μm to 1000 μm, spaced at intervals of 3.0 mm to 100 mm. The ratio of oxygen atomic weight OU to metal atomic weight MeU (OU / MeU) relative to the non-opening portion of the current collector, and the ratio of oxygen atomic weight OP to metal atomic weight MeP (OP / MeP) around the holes in the current collector, is 1.2 times or more. This electrode enables the development of secondary batteries and battery packs exhibiting high rate performance and long lifespan.

[0061] (Second Implementation)

[0062] According to a second embodiment, a secondary battery comprising a negative electrode, a positive electrode, and an electrolyte is provided. This secondary battery includes at least one of the electrodes related to the first embodiment as a positive electrode and a negative electrode. When the electrode related to the first embodiment is included as the negative electrode, the positive electrode may be an electrode different from that in the first embodiment. When the electrode related to the first embodiment is included as the positive electrode, the negative electrode may be an electrode different from that in the first embodiment. The secondary battery according to the second embodiment may also include both the state where the electrode related to the first embodiment serves as a negative electrode and the state where it serves as a positive electrode, respectively, as both the negative and positive electrodes.

[0063] The related secondary battery can further incorporate a separator positioned between the positive and negative electrodes. The negative electrode, positive electrode, and separator can form an electrode array. The electrolyte can be retained within the electrode array.

[0064] Furthermore, the related secondary batteries can have external components that house the electrode array and electrolyte.

[0065] Furthermore, the related secondary battery can have a negative terminal that is electrically connected to the negative electrode and a positive terminal that is electrically connected to the positive electrode.

[0066] The relevant secondary battery may be, for example, a lithium secondary battery. Furthermore, secondary batteries include those containing a non-aqueous electrolyte.

[0067] The following details the negative electrode, positive electrode, electrolyte, separator, external components, negative terminal, and positive terminal.

[0068] 1) Negative electrode The negative electrode may include a negative current collector and a negative active material containing layer. The negative electrode may be the negative electrode of the electrode related to the first embodiment. Therefore, the negative current collector and the negative active material containing layer may be the current collector and active material containing layer respectively included in the electrode related to the first embodiment. The negative active material containing layer includes, for example, the negative active material described in the first embodiment, and other negative active materials described below.

[0069] In the details of the negative electrode, the parts that are repeated in the description of the negative electrode as the electrode related to the first embodiment are omitted. The following describes the differences between other negative electrodes that can be used in a battery, for example, including the electrode related to the first embodiment as the positive electrode, and the electrode related to the first embodiment.

[0070] Other negative electrodes may include active materials that are present in the state of the negative electrode associated with the electrode of the first embodiment as negative electrode active materials. Other negative electrodes may include the negative electrode active material described in the first embodiment, and may further include other negative electrode active materials. Other negative electrodes may individually include one or more negative electrode active materials described in the first embodiment, or may each contain one or more of the negative electrode active materials described in the first embodiment and other negative electrode active materials, or may individually include one or more other negative electrode active materials.

[0071] Other examples of active materials include lithium titanate with a straight manganese oxide structure (e.g., Li2+yTi3O7, 0≦y≦3), lithium titanate with a spinel structure (e.g., Li4+xTi5O12, 0≦x≦3), titanium dioxide (TiO2), anatase titanium dioxide, rutile titanium dioxide, manganese barite titanium composite oxides, and orthorhombic titanium composite oxides.

[0072] As an example of orthorhombic titanium containing a complex oxide, a compound represented by Li2+aMI 2-bTi6-CMII dO14+σ can be cited. Here, MI is selected from at least one of the group consisting of Sr, Ba, Ca, Mg, Na, Cs, Rb, and K. MII is selected from at least one of the group consisting of Zr, Sn, V, Nb, Ta, Mo, W, Y, Fe, Co, Cr, Mn, Ni, and Al. The subscripts in the composition formula are 0≦a≦6, 0≦b<2, 0≦c<6, 0≦d<6, -0.5≦σ≦0.5. As a specific example of orthorhombic titanium containing a complex oxide, Li2+aNa2Ti6O14 (0≦a≦6) can be cited.

[0073] Adhesives are incorporated to fill the gaps between dispersed active materials and to bind the active materials to the current collector. Examples of adhesives may include polytetrafluoroethylene (PTFE), polyvinylidene fluoride (PVdF), fluororubber, styrene-butadiene rubber, polyacrylate compounds, amide compounds, carboxymethyl cellulose (CMC), and salts of CMC. One of these can be used as an adhesive, or a combination of two or more can be used as an adhesive.

[0074] The density of the negative electrode active material containing the layer (excluding the current collector) is preferably between 1.8 g / cm³ and 2.8 g / cm³. A negative electrode system with a negative electrode active material containing the layer within this density range exhibits excellent energy density and electrolyte retention. The density of the negative electrode active material containing the layer is preferably between 2.1 g / cm³ and 2.6 g / cm³.

[0075] Other negative electrode current collectors differ from those described in the first embodiment, which have through holes with a diameter of 10 μm to 1000 μm and an opening spacing of 3.0 mm to 100 mm, and whose current collector ratio is 1.2 times or more than that of OP / MeP compared to OU / MeU. Other negative electrode current collectors may be, for example, current collector foils without through holes. The negative electrode current collector is preferably made of copper, nickel, stainless steel, or aluminum, or an aluminum alloy selected from 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 achieves a balance between electrode strength and lightweight design.

[0076] Furthermore, the negative current collector may include a portion on its surface where no negative active material layer is formed. This portion can be used as a negative current collector tongue.

[0077] Other negative electrode systems can be fabricated, for example, by the following method. First, a slurry is prepared by suspending the negative electrode active material, conductive agent, and binder in a solvent. This slurry is then coated onto one or both sides of the current collector. The solvent is not limited to water; for example, other water-soluble solvents or organic solvents can be used. Next, the coated slurry is dried to obtain a laminate containing the negative electrode active material layer and the current collector. Subsequently, pressure is applied to the laminate. Thus, the negative electrode is fabricated.

[0078] Alternatively, the negative electrode can be made by the following method: First, a negative electrode active material, a conductive agent, and a binder are mixed to obtain a mixture. Next, the mixture is shaped into granules. Then, by placing these granules on a current collector, the negative electrode can be obtained.

[0079] 2) Positive electrode The positive electrode may include a positive current collector and a positive active material containing layer. The positive active material containing layer may be formed on one or both sides of the positive current collector. The positive active material containing layer may include positive active material, and selectively include conductive agents and binders.

[0080] In the details of the positive electrode, the parts that are repeated in the description of the positive electrode as described in the first embodiment are omitted. The following description includes, for example, the differences between other positive electrodes and the electrodes related to the first embodiment that can be used in a battery in which the electrode related to the first embodiment is used as the negative electrode.

[0081] Other positive electrodes may include active materials that can be included in the positive electrode state of the electrode related to the first embodiment as positive electrode active materials. Other positive electrodes may include, in addition to the positive electrode active material described in the first embodiment, other positive electrode active materials. Other positive electrodes may individually include one or more positive electrode active materials described in the first embodiment, or may each include one or more of the positive electrode active materials described in the first embodiment and other positive electrode active materials, or may individually include one or more other positive electrode active materials.

[0082] Other positive electrode active materials may include, for example, oxides or sulfides. The positive electrode system, as the positive electrode active material, may contain only one compound or may contain a combination of two or more compounds. Examples of oxides and sulfides include compounds that allow for the insertion and removal of Li or Li ions.

[0083] As such compounds, for example, it may include manganese dioxide (MnO2), iron oxide, copper oxide, nickel oxide, lithium manganese composite oxide (such as LixMn2O4 or LixMnO2; 0 < x ≦ 1), lithium nickel composite oxide (such as LixNiO2; 0 < x ≦ 1), lithium cobalt composite oxide (such as LixCoO2; 0 < x ≦ 1), lithium nickel cobalt composite oxide (such as LixNi1-yCoyO2; 0 < x ≦ 1, 0 < y < 1), lithium manganese cobalt composite oxide (such as LixMnyCo1-yO2; 0 < x ≦ 1, 0 < y < 1), lithium manganese nickel composite oxide with spinel structure (such as LixMn2-yNiyO4; 0 < x ≦ 1, 0 < y < 2), iron sulfate (Fe2(SO4)3), vanadium oxide (such as V2O5), and lithium nickel cobalt manganese composite oxide (LixNi1-y-zCoyMnzO2; 0 < x ≦ 1, 0 < y < 1, 0 < z < 1, y + z < 1).

[0084] Among the above, as examples of better compounds for the positive electrode active material, it may include lithium manganese composite oxide with spinel structure (such as LixMn2O4; 0 < x ≦ 1), lithium nickel composite oxide (such as LixNiO2; 0 < x ≦ 1), lithium cobalt composite oxide (such as LixCoO2; 0 < x ≦ 1), lithium nickel cobalt composite oxide (such as LixNi1-yCoyO2; 0 < x ≦ 1, 0 < y < 1), lithium manganese nickel composite oxide with spinel structure (such as LixMn2-yNiyO4; 0 < x ≦ 1, 0 < y < 2), lithium manganese cobalt composite oxide (such as LixMnyCo1-yO2; 0 < x ≦ 1, 0 < y < 1), lithium iron phosphate (such as LixFePO4; 0 < x ≦ 1), and lithium nickel cobalt manganese composite oxide (LixNi1-y-zCoyMnzO2; 0 < x ≦ 1, 0 < y < 1, 0 < z < 1, y + z < 1). If these compounds are used as the positive electrode active material, the positive electrode potential can be increased.

[0085] When using a room temperature molten salt as the electrolyte of the battery, it is preferably to use a positive electrode active material of lithium iron phosphate, LixVPO4F (0 ≦ x ≦ 1), lithium manganese composite oxide, lithium nickel composite oxide, lithium nickel cobalt composite oxide, or a mixture containing these. These compounds have low reactivity with the room temperature molten salt, so the cycle life can be improved. Details of the room temperature molten salt will be described later.

[0086] The primary particle size of the positive electrode active material is preferably between 100 nm and 1 μm. Positive electrode active materials with a primary particle size of 100 nm or more are easier to handle in industrial production. Positive electrode active materials with a primary particle size of less than 1 μm allow for smooth diffusion of lithium ions within the solid.

[0087] The specific surface area of ​​the positive electrode active material is preferably between 0.1 m² / g and 10 m² / g. A specific surface area of ​​0.1 m² / g or higher ensures sufficient storage and release sites for Li ions. A specific surface area of ​​10 m² / g or lower is easier to process in industrial production and ensures good charge-discharge cycle performance.

[0088] The binder is incorporated to fill the gaps between the dispersed positive electrode active material and to bond the positive electrode active material to the positive electrode current collector. Examples of binders may include polytetrafluoroethylene (PTFE), polyvinylidene fluoride (PVdF), fluororubber, polyacrylate compounds, amide compounds, carboxymethyl cellulose (CMC), and salts of CMC. One of these can be used as a binder, or two or more can be combined as a binder.

[0089] Other positive electrode current collectors differ from those described in the first embodiment, which have through holes with a diameter of 10 μm to 1000 μm at a spacing of 3.0 mm to 100 mm, and whose OP / MeP ratio is 1.2 times or more than the OU / MeU ratio. Other positive electrode current collectors may be, for example, current collector foils without through holes. Preferably, the positive electrode current collector is 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.

[0090] The thickness of the aluminum foil or aluminum alloy foil is preferably 5 μm to 20 μm, 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 contained in the aluminum foil or aluminum alloy foil is preferably 1% by mass or less.

[0091] Furthermore, the positive current collector may include a portion on its surface where no layer of positive active material is formed. This portion can be used as a positive current collector tongue.

[0092] Other positive electrode systems can use positive electrode active materials instead of negative electrode active materials, and can be manufactured using the same methods as other negative electrodes.

[0093] 3) Electrolytes As the electrolyte, for example, a liquid non-aqueous electrolyte or a colloidal non-aqueous electrolyte can be used. A liquid non-aqueous electrolyte is prepared by dissolving an electrolyte salt, which is the solute, in an organic solvent. The concentration of the electrolyte salt is preferably between 0.5 mol / L and 2.5 mol / L.

[0094] Examples of electrolyte salts may include lithium salts such as lithium perchlorate (LiClO4), lithium hexafluorophosphate (LiPF6), lithium tetrafluoroborate (LiBF4), lithium hexafluoroarsenate (LiAsF6), lithium trifluoromethanesulfonate (LiCF3SO3), and bis(trifluoromethylsulfonyl)imide (LiN(CF3SO2)2), as well as mixtures thereof. Preferably, the electrolyte salt is difficult to oxidize even at high potentials, and LiPF6 is the most preferred.

[0095] Examples of organic solvents may include cyclic carbonates such as propylene carbonate (PC), ethylene carbonate (EC), and vinylene carbonate (VC); chain carbonates such as diethyl carbonate (DEC), dimethyl carbonate (DMC), and methyl ethyl carbonate (MEC); cyclic ethers such as tetrahydrofuran (THF), 2-methyl tetrahydrofuran (2MeTHF), and dioxolane (DOX); chain ethers such as dimethoxyethane (DME) and diethoxyethane (DEE); γ-butyrolactone (GBL), acetonitrile (AN), and sulfolane (SL). These organic solvents may be used alone or as mixed solvents.

[0096] The colloidal non-aqueous electrolyte is formulated by compounding a liquid non-aqueous electrolyte with a polymer material. Examples of polymer materials may include polyvinylidene fluoride (PVdF), polyacrylonitrile (PAN), polyethylene oxide (PEO), or mixtures thereof.

[0097] Alternatively, as a non-aqueous electrolyte, in addition to liquid non-aqueous electrolytes and colloidal non-aqueous electrolytes, room-temperature molten salts (ionic melts) containing lithium ions, polymeric solid electrolytes, and inorganic solid electrolytes can be used.

[0098] Room-temperature molten salts (ionic melts) refer to compounds that exist as liquids at room temperature (between 15°C and 25°C) within an organic salt composed of a combination of organic cations and anions. Room-temperature molten salts can include those existing as liquid monomers, those that become liquid by mixing with electrolyte salts, those that become liquid by dissolving in organic solvents, or mixtures thereof. Typically, room-temperature molten salts used in secondary batteries have a melting point below 25°C. Furthermore, the organic cations usually possess a quaternary ammonium framework.

[0099] Polymer solid electrolytes are formulated by dissolving electrolyte salts in polymer materials and then solidifying them.

[0100] Inorganic solid electrolytes are solid substances that exhibit Li-ion conductivity. Here, Li-ion conductivity refers to a lithium-ion conductivity of 1 × 10⁻⁶ S / cm or higher at 25°C. Examples of inorganic solid electrolytes include oxide-based solid electrolytes and sulfide-based solid electrolytes. Specific examples of inorganic solid electrolytes are as follows.

[0101] As an oxide-based solid electrolyte, a lithium phosphate solid electrolyte with a NASICON (Sodium (Na) Super Ionic conductor) type structure and represented by the general formula Li1+xMα2(PO4)3 is preferred. The Mα group in the above formula is selected from, for example, one or more elements in the group consisting of titanium (Ti), germanium (Ge), strontium (Sr), zirconium (Zr), tin (Sn), aluminum (Al), and calcium (Ca). The subscript x is in the range of 0 ≤ x ≤ 2.

[0102] As a specific example of a lithium phosphate solid electrolyte having a NASICON-type structure, examples include an LATP compound represented by Li1+xAlxTi2-x(PO4)3, where 0.1 ≦ x ≦ 0.5; a compound represented by Li1+xAlyMβ2-y(PO4)3, where Mβ is one or more selected from the group consisting of Ti, Ge, Sr, Zr, Sn, and Ca, 0 ≦ x ≦ 1, and 0 ≦ y ≦ 1; a compound represented by Li1+xAlxGe2-x(PO4)3, where 0 ≦ x ≦ 2; and a compound represented by Li1+xAlxZr2-x(PO4)3, where 0 ≦ x ≦ 2; a compound represented by Li1+x+yAlxMγ2-xSiyP3-yO12, where Mγ is one or more selected from the group consisting of Ti and Ge, 0 < x ≦ 2, and 0 ≦ y < 3; a compound represented by Li1+2xZr1-xCax(PO4)3, where 0 ≦ x < 1.

[0103] Further, as an oxide-based solid electrolyte, in addition to the above lithium phosphate solid electrolyte, examples include an amorphous LIPON compound represented by LixPOyNz, where 2.6 ≦ x ≦ 3.5, 1.9 ≦ y ≦ 3.8, and 0.1 ≦ z ≦ 1.3 (for example, Li2.9PO3.3N0.46); a compound represented by La5+xAxLa3-xMδ2O12 having a garnet-type structure, where A is one or more selected from the group consisting of Ca, Sr, and Ba, Mδ is one or more selected from the group consisting of Nb and Ta, and 0 ≦ x ≦ 0.5; a compound represented by Li3Mδ2-xL2O12, where Mδ is one or more selected from the group consisting of Nb and Ta, and L may include Zr, and 0 ≦ x ≦ 0.5; a compound represented by Li7-3xAlxLaZrxO12, where 0 ≦ x ≦ 0.5; a LLZ compound represented by Li5+xLa3Mδ2-xZrxO1, where Mδ is one or more selected from the group consisting of Nb and Ta, and 0 ≦ x ≦ 2 (for example, Li7La3Zr2O12); and a compound having a perovskite-type structure and represented by La2 / 3-xLixTiO3, where 0.3 ≦ x ≦ 0.7.

[0104] One or more of the above compounds can be used as the solid electrolyte. Two or more of the above solid electrolytes can also be used. <00^00351> 4) Separator The separator is formed, for example, from a porous membrane containing polyethylene (PE), polypropylene (PP), cellulose, or polyvinylidene fluoride (PVdF), or a non-woven fabric made of synthetic resin. From a safety point of view, it is preferable to use a porous membrane formed of polyethylene or polypropylene, because such porous membranes melt at a certain temperature and can block the current.

[0106] 5) External components As an outer component, a container made of laminated film or a metal container can be used, for example.

[0107] The thickness of the laminated film is, for example, less than 0.5 mm, preferably less than 0.2 mm.

[0108] As a laminated film, a multilayer film containing multiple resin layers and a metal layer between these resin layers can be used. The resin layers may include polymeric materials such as polypropylene (PP), polyethylene (PE), nylon, and polyethylene terephthalate (PET). For weight reduction, the metal layer is preferably made of aluminum foil or aluminum alloy foil. The laminated film is sealed by heat welding, thus forming the shape of an external component.

[0109] The wall thickness of the metal container is preferably less than 1 mm, more preferably less than 0.5 mm, and even more preferably less than 0.2 mm.

[0110] Metal containers are made of materials such as aluminum or aluminum alloys. The aluminum alloy preferably contains elements such as magnesium, zinc, and silicon. When the aluminum alloy contains transition metals such as iron, copper, nickel, and chromium, their content is preferably below 100 ppm by mass.

[0111] There are no particular restrictions on the shape of the outer casing. The outer casing can be, for example, flat (thin), angular, cylindrical, coin-shaped, or button-shaped. The outer casing can be appropriately selected based on the battery size or intended use.

[0112] 6) Negative extremes The negative terminal can be formed of a material that is electrochemically stable at the Li adsorption-release potential of the aforementioned negative electrode active material and is conductive. Specifically, materials for the negative terminal include copper, nickel, stainless steel, or aluminum, or aluminum alloys containing at least one element selected from the group consisting of Mg, Ti, Zn, Mn, Fe, Cu, and Si. Aluminum or aluminum alloys are preferred as the material for the negative terminal. To reduce the contact resistance with the negative current collector, the negative terminal is preferably made of the same material as the negative current collector.

[0113] 7) Positive extreme The positive terminal may be formed of a material that is electrically stable and conductive in a potential range of 3V to 4.5V relative to the redox potential of lithium (vs. Li / Li+). Examples of materials for the positive terminal include aluminum, or aluminum alloys comprising at least one element selected from the group consisting of Mg, Ti, Zn, Mn, Fe, Cu, and Si. To reduce the contact resistance with the positive current collector, the positive terminal is preferably formed of the same material as the positive current collector.

[0114] Next, the secondary battery related to the implementation will be explained in more detail while referring to the illustration.

[0115] Figure 3 is a schematic cross-sectional view of an example of a secondary battery. Figure 4 is an enlarged cross-sectional view of part A of the secondary battery shown in Figure 3.

[0116] The secondary battery 100 shown in Figures 3 and 4 includes the pouch-shaped outer casing 2 shown in Figure 3, the electrode group 1 shown in Figures 3 and 4, and an electrolyte (not shown). The electrode group 1 and the electrolyte are housed within the pouch-shaped outer casing 2. The electrolyte (not shown) is held in the electrode group 1.

[0117] The bag-shaped outer component 2 is composed of a laminated film comprising two resin layers and a metal layer between them.

[0118] As shown in Figure 3, electrode group 1 is a flat, wound electrode group. The flat, wound electrode group 1, as shown in Figure 4, includes a negative electrode 3, a separator 4, and a positive electrode 5. The separator 4 is located between the negative electrode 3 and the positive electrode 5.

[0119] The negative electrode 3 includes a negative current collector 3a and a negative active material containing layer 3b. In the negative electrode 3, the outermost portion of the wound electrode group 1, as shown in Figure 4, has the negative active material containing layer 3b formed only on the inner surface of the negative current collector 3a. In other portions of the negative electrode 3, the negative active material containing layer 3b is formed on both sides of the negative current collector 3a.

[0120] The positive electrode 5 includes a positive current collector 5a, and a layer 5b is formed on both sides of the positive electrode active material.

[0121] As shown in Figure 3, the negative terminal 6 and the positive terminal 7 are located near the outer periphery of the wound electrode group 1. The negative terminal 6 is connected to the outermost portion of the negative current collector 3a. Similarly, the positive terminal 7 is connected to the outermost portion of the positive current collector 5a. These negative terminals 6 and 7 extend outward from the opening of the bag-shaped outer casing 2. A thermoplastic resin layer is provided on the inner surface of the bag-shaped outer casing 2, and the opening is closed by heat-welding it.

[0122] The secondary battery configuration related to the implementation is not limited to the secondary battery configuration shown in Figures 3 and 4, but can also be a battery configuration shown in Figures 5 and 6.

[0123] Figure 5 is a schematic partial cross-sectional perspective view illustrating other examples of secondary batteries. Figure 6 is an enlarged cross-sectional view of part B of the secondary battery shown in Figure 5.

[0124] The secondary battery 100 shown in Figures 5 and 6 includes an electrode group 1 as shown in Figures 5 and 6, an external mounting component 2 as shown in Figure 5, and an electrolyte (not shown). The electrode group 1 and the electrolyte are housed within the external mounting component 2. The electrolyte is held within the electrode group 1.

[0125] The outer component 2 is composed of a laminate containing two resin layers and a metal layer between them.

[0126] As shown in Figure 6, electrode group 1 is a stacked electrode group. The stacked electrode group 1 has a structure in which the negative electrode 3 and the positive electrode 5 are stacked alternately with a separator 4 between them.

[0127] Electrode group 1 includes a plurality of negative electrodes 3. Each of the plurality of negative electrodes 3 has 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. Electrode group 1 also includes a plurality of positive electrodes 5. Each of the plurality of positive electrodes 5 has 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.

[0128] Each negative electrode 3 has a negative current collector 3a on one side, including a portion containing a layer 3b on any surface where no negative electrode active material is supported. This portion serves as a negative current collector tongue 3c. As shown in Figure 6, the negative current collector tongue 3c does not overlap with the positive electrode 5. Furthermore, the plurality of negative current collector tongues 3c are electrically connected to a strip-shaped negative terminal 6. The front end of the strip-shaped negative terminal 6 is led out to the outside of the outer casing 2.

[0129] Furthermore, although not illustrated, the positive current collector 5a of each positive electrode 5 has a portion on one side containing a layer 5b on which no positive active material is supported on any surface. This portion serves as a positive current collector tongue. The positive current collector tongue is the same as the negative current collector tongue 3c and does not overlap with the negative electrode 3. The positive current collector tongue is located on the opposite side of the electrode group 1 relative to the negative current collector tongue 3c. The positive current collector tongue is electrically connected to the strip-shaped positive terminal 7. The front end of the strip-shaped positive terminal 7 is located on the opposite side of the negative terminal 6 and is led out to the outside of the outer casing 2.

[0130] The secondary battery of the second embodiment includes the electrodes of the first embodiment. Therefore, the related secondary battery can exhibit high rate performance and long lifespan performance.

[0131] (Third Implementation)

[0132] According to the third embodiment, a battery pack is provided. The battery pack includes a plurality of secondary batteries as described in the second embodiment.

[0133] In the relevant battery packs, the individual cells can be electrically connected in series or in parallel, or they can be combined in series and in parallel.

[0134] Next, an example of a battery pack related to the implementation configuration will be described with reference to the illustration.

[0135] Figure 7 is a perspective view schematically illustrating one example of a battery pack. The battery pack 200 shown in Figure 7 includes five individual cells 100a to 100e, four busbars 21, a positive electrode lead 22, and a negative electrode lead 23. The five individual cells 100a to 100e are secondary cells related to the second embodiment.

[0136] Bus 21 connects, for example, the negative terminal 6 of a single cell 100a to the positive terminal 7 of a single cell 100b located adjacent to it. Thus, five single cells 100 are connected in series via four bus 21s. That is, the battery pack 200 in Figure 7 is a pack of five connected in series. Although not illustrated, in a battery pack containing multiple single cells connected in parallel, for example, multiple single cells can be electrically connected by connecting multiple negative terminals to each other via bus 21 while simultaneously connecting multiple positive terminals to each other via bus 21.

[0137] The positive terminal 7 of at least one of the five individual cells 100a to 100e is electrically connected to the positive side lead 22 for external connection. Also, the negative terminal 6 of at least one of the five individual cells 100a to 100e is electrically connected to the negative side lead 23 for external connection.

[0138] The battery pack system related to the third embodiment includes the secondary battery related to the second embodiment. Therefore, it can exhibit high rate performance and long lifespan performance.

[0139] (Fourth Implementation) According to the fourth embodiment, a battery pack is provided. This battery pack includes the battery pack of the third embodiment. The battery pack may include a single secondary battery of the second embodiment instead of the battery pack of the third embodiment.

[0140] The battery pack can be further equipped with protection circuitry. This protection circuitry controls the charging and discharging of the secondary battery. Alternatively, the circuitry within a device that uses the battery pack as a power source (e.g., electronic devices, automobiles, etc.) can be used as the battery pack's protection circuitry.

[0141] Furthermore, the battery pack may also have external terminals for power supply. These external terminals are used to output current from the secondary battery to the outside and / or to input 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 the battery pack is being charged, charging current (including regenerative energy from the power source of the vehicle, etc.) is supplied to the battery pack through the external terminals.

[0142] Next, an example of a battery pack related to the implementation will be described while referring to the illustration.

[0143] Figure 8 is an exploded perspective view schematically showing one example of a battery pack. Figure 9 is a block diagram showing one example of the electrical circuit of the battery pack shown in Figure 8.

[0144] The battery pack 300 shown in Figures 8 and 9 includes a housing 31, a cover 32, a protective sheet 33, a battery pack 200, a printed circuit board 34, wiring 35, and an insulating plate not shown.

[0145] The container 31 shown in Figure 8 is a rectangular container with corners. The container 31 is configured to house the protective sheet 33, the battery pack 200, the printed circuit board 34, and the wiring 35. The cover 32 has a rectangular shape. The cover 32 houses the battery pack 200 and other components by covering the container 31. Although not shown, both the container 31 and the cover 32 have openings or connection terminals for connecting to external machines or the like.

[0146] The battery pack 200 series includes multiple individual cells 100, a positive electrode lead 22, a negative electrode lead 23, and adhesive tape 24.

[0147] At least one of the plurality of single cells 100 is a secondary battery related to the second embodiment. The plurality of single cells 100 are electrically connected in series as shown in FIG9. The plurality of single cells 100 can be electrically connected in parallel, or can be connected in a combination of series and parallel connections. If the plurality of single cells 100 are connected in parallel, the battery capacity increases compared to the case of series connection.

[0148] Adhesive tape 24 is used to connect the multiple individual cells 100. Alternatively, heat shrinkable tape can be used instead of adhesive tape 24 to fix the multiple individual cells 100. In this case, protective sheet 33 is placed on both sides of the battery pack 200, and after the heat shrinkable tape is wrapped around it, the heat shrinkable tape is heat-shrinked to bind the multiple individual cells 100 together.

[0149] One end of the positive electrode lead 22 is connected to the battery pack 200. One end of the positive electrode lead 22 is electrically connected to the positive electrode of one or more individual cells 100. One end of the negative electrode lead 23 is connected to the battery pack 200. One end of the negative electrode lead 23 is electrically connected to the negative electrode of one or more individual cells 100.

[0150] The printed circuit board 34 is disposed along one of the shorter sides of the inner surface of the receiving container 31. The printed circuit board 34 includes a positive-side connector 342, a negative-side connector 343, a thermistor 345, a protection circuit 346, wirings 342a and 343a, an external terminal 350 for power supply, a positive-side wiring (positive side wiring) 348a, and a negative-side wiring (negative side wiring) 348b. One main surface of the printed circuit board 34 faces the side of the battery pack 200. An insulating plate (not shown) separates the printed circuit board 34 from the battery pack 200.

[0151] 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.

[0152] Thermistor 345 is fixed on one of the main surfaces of the printed circuit board 34. Thermistor 345 detects the temperature of each cell 100 and sends the detection signal to the protection circuit 346.

[0153] The external terminal 350 for power supply is fixed to another main surface of the printed circuit board 34. The external terminal 350 for power supply is electrically connected to a machine located outside the battery pack 300. The external terminal 350 for power supply includes a positive terminal 352 and a negative terminal 353.

[0154] The protection circuit 346 is fixed to another main surface of the printed circuit board 34. The protection circuit 346 is connected to the positive terminal 352 via positive side wiring 348a. The protection circuit 346 is connected to the negative terminal 353 via negative side wiring 348b. Furthermore, the protection circuit 346 is electrically connected to the positive connector 342 via wiring 342a. The protection circuit 346 is electrically connected to the negative connector 343 via wiring 343a. Moreover, the protection circuit 346 is electrically connected to each of the plurality of individual cells 100 via wiring 35.

[0155] The protective sheet 33 is disposed on the two inner sides of the long side of the housing 31, and on the inner side of the short side of the housing 31, which is separated from the battery pack 200 from the printed circuit board 34. The protective sheet 33 is made of, for example, resin or rubber.

[0156] The protection circuit 346 controls the charging and discharging of the plurality of individual batteries 100. Furthermore, the protection circuit 346 disconnects the electrical connection between the protection circuit 346 and the external terminals 350 (positive terminal 352, negative terminal 353) for powering external machines based on the detection signal sent from the thermistor 345, or the detection signal sent from each individual battery 100 or the battery pack 200.

[0157] As a detection signal sent from the thermistor 345, examples include signals indicating that the temperature of a single cell 100 is above a specific temperature. As a detection signal sent from each single cell 100 or the battery pack 200, examples include signals indicating overcharging, over-discharging, and overcurrent of a single cell 100. When detecting overcharging in each single cell 100, the battery voltage can be detected, as well as the positive or negative electrode potential. In the latter case, a lithium electrode used as a reference electrode is inserted into each single cell 100.

[0158] Alternatively, as a protection circuit 346, a circuit included in a device that uses the battery pack 300 as a power source (e.g., electronic equipment, automobiles, etc.) can be used.

[0159] Furthermore, the battery pack 300, as described above, has an external terminal 350 for power supply. Therefore, the battery pack 300, via the external terminal 350, can simultaneously output current from the battery pack 200 to an external device and input current from the external device to the battery pack 200. 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 the battery pack 300 is charged, charging current from the external device is supplied to the battery pack 300 through the external terminal 350. When the battery pack 300 is used as a vehicle battery, the regenerative energy from the vehicle's power source can be utilized as charging current from the external device.

[0160] Additionally, the battery pack 300 may include multiple battery cells 200. In this case, the multiple battery cells 200 can be connected in series, in parallel, or a combination of series and parallel connections. Furthermore, the printed circuit board 34 and wiring 35 may be omitted. In this case, the positive terminal lead 22 and the negative terminal lead 23 can be used as the positive terminal 352 and negative terminal 353 of the external terminal 350 for power supply, respectively.

[0161] Such a battery pack can be used, for example, in applications requiring excellent cycle performance when drawing high currents. Specifically, this battery pack can be used as a power source for electronic devices, a stationary battery, and an onboard battery for various vehicles. Examples of electronic devices include digital cameras. This battery pack is particularly suitable for use as an onboard battery in vehicles.

[0162] The battery pack according to the fourth embodiment includes either the secondary battery according to the second embodiment or the battery pack according to the third embodiment. Therefore, the battery pack has high rate performance and longevity performance.

[0163] [Example] The following describes embodiments, but the implementation is not limited to the embodiments described below.

[0164] (Examples 1 to 9) First, 100 parts by mass of niobium titanium oxide (TiNb2O7) powder as the active material, 10 parts by mass of acetylene black as the conductive agent, 5 parts by mass of carbon nanofiber, and 5 parts by mass of a mixture of carboxymethyl cellulose and styrene-butadiene rubber (SBR) as a binder were added to water and mixed to obtain a slurry. This slurry was coated onto one side of a current collector made of aluminum foil with a thickness of 12 μm, and after drying, pressure was applied to produce an electrode precursor with a porosity of 25% (excluding the current collector). The impurity concentration in the current collector is shown in Table 1.

[0165] The obtained electrode precursor was kept in an aqueous environment with dew points as shown in Table 1 for the times listed in Table 1 below, and the current collector was porousized. For example, for Example 1, the precursor was kept in an aqueous environment with a dew point of 15°C for 6 hours. After being kept in an aqueous environment, the coating was completely dried under vacuum to form an active material containing layer, and the electrode was obtained.

[0166] (Example 10) The current collector was changed from aluminum foil to copper foil, and the electrode precursor was obtained in the same manner as in Example 1. The obtained electrode precursor was then subjected to a porosimetry treatment of the current collector under the aqueous environment conditions shown in Table 1. After being kept in an aqueous environment, the coating was completely dried under vacuum to form an active material containing layer, and the electrode was obtained.

[0167] (Comparative Example 1) Using aluminum foil with the impurity concentrations shown in Table 1 as the current collector, the electrode was fabricated in the same manner as in Example 1, except that the conditions for maintaining the precursor were changed to a longer period of maintenance in a dry environment as shown in Table 1.

[0168] (Comparative Example 2) Using aluminum foil with the impurity concentrations shown in Table 1 as the current collector, an electrode precursor was obtained in the same manner as in Example 1. The obtained electrode precursor was then subjected to a current collector porosimetry treatment under the aqueous environment conditions shown in Table 1. After being kept in an aqueous environment, the coating was completely dried under vacuum to form an active material containing layer, and the electrode was obtained.

[0169] (Comparative Example 3) Using aluminum foil with the impurity concentrations shown in Table 1 as the current collector, an electrode precursor was obtained in the same manner as in Example 1. The obtained electrode precursor was then subjected to a current collector porosimetry treatment under the aqueous environment conditions shown in Table 1. After being kept in an aqueous environment, the coating was completely dried under vacuum to form an active material containing layer, and the electrode was obtained.

[0170] (Comparative Example 4) The current collector was replaced with a mechanically treated, pre-porous aluminum foil. The pressure conditions were adjusted so that the porosity (excluding the current collector) was more than 38%, and the electrode precursor was obtained in the same manner as in Example 1. The obtained electrode precursor was kept under the dry conditions shown in Table 1. After being kept in a dry environment, the coating was completely dried under vacuum to form an active material containing layer, and the electrode was obtained.

[0171] (Examples 11 to 13) Using aluminum foil with impurity concentrations as shown in Table 2 as the current collector, and changing the active material to an oxide other than the one shown in Table 2, an electrode precursor was obtained in the same manner as in Example 1. The obtained electrode precursor was then subjected to a current collector porosimetry treatment under the aqueous environment conditions shown in Table 2. After being kept in an aqueous environment, the coating was completely dried under vacuum to form an active material containing layer, and the electrode was obtained.

[0172] (Example 14) Using aluminum foil with the impurity concentrations shown in Table 3 as the current collector, and changing the active material to an oxide other than the one shown in Table 3, an electrode precursor was obtained in the same manner as in Example 1. The obtained electrode precursor was then subjected to a current collector porosimetry treatment under the aqueous environment conditions shown in Table 3. After being kept in an aqueous environment, the coating was completely dried under vacuum to form an active material containing layer, and the electrode was obtained.

[0173] (Compare Examples 5 and 6) Using aluminum foil with the impurity concentrations shown in Table 3 as the current collector, and changing the active material to an oxide other than the one shown in Table 3, an electrode precursor was obtained in the same manner as in Example 14. The obtained electrode precursor was then held in an aqueous environment under the conditions shown in Table 3. After holding in the aqueous environment, the coating was completely dried under vacuum to form an active material containing layer, and an electrode was obtained.

[0174] (Examples 15 and 16) First, a mixture of 100 parts by weight of lithium iron phosphate (LiFePO4) powder as the active material, 5 parts by weight of acetylene black as the conductive agent, and 5 parts by weight of a mixture of carboxymethyl cellulose and polyurethane as the binder was added to water and mixed to obtain a slurry. This slurry was coated onto one side of a current collector made of aluminum foil with a thickness of 12 μm, and then dried and pressurized to produce an electrode precursor with a porosity of 25% (excluding the current collector). The impurity concentration in the current collector is shown in Table 4.

[0175] The obtained electrode precursor was subjected to a porous current collector treatment under the aqueous environment conditions shown in Table 4. After being kept in an aqueous environment, the coating was completely dried under vacuum to form an active material containing layer, and the electrode was obtained.

[0176] (Comparative Example 7) First, 100 parts by mass of lithium nickel cobalt manganese composite oxide (LiNi0.8Co0.1Mn0.1O2) powder as the active material, 5 parts by mass of acetylene black as the conductive agent, and 5 parts by mass of a mixture of carboxymethyl cellulose and polyurethane as the binder were added to water and mixed to obtain a slurry. This slurry was coated onto one side of a current collector made of aluminum foil with a thickness of 12 μm, and after drying, pressure was applied to produce an electrode precursor with a porosity of 25% (excluding the current collector). The impurity concentration in the current collector is shown in Table 4.

[0177] The obtained electrode precursor was subjected to a porous current collector treatment under the aqueous environment conditions shown in Table 4. After being kept in an aqueous environment, the coating was completely dried under vacuum to form an active material containing layer, and the electrode was obtained.

[0178]

[0179]

[0180]

[0181]

[0182] <Electrode Confirmation> The obtained electrodes were observed and various measurements were performed on the current collector using the methods described above. Specifically, the diameter and spacing of the through holes on the current collector, the oxygen atomic weight ratios (OP / MeP and OU / MeU) of the surrounding and non-opening portions of the holes, the pH of the electrode material constituting the active material layer after water washing, and the porosity of the active material layer were measured. The measurement results are summarized in Tables 5 to 8.

[0183]

[0184]

[0185]

[0186]

[0187] <Electrochemical Measurement> Using the electrodes obtained in the above examples as active electrodes and Li metal as the relative and reference electrodes, a coin cell using an electrolyte was fabricated and its electrochemical performance was evaluated.

[0188] The electrolyte was prepared as follows: Ethyl carbonate (EC) and diethyl carbonate (DEC) were mixed in a volume ratio of 1:2 to obtain a mixed solvent. The LiPF6 supporting salt was dissolved in the obtained mixed solvent at a concentration of 1 mol / L to prepare the electrolyte.

[0189] In this embodiment, lithium metal is used as the counter electrode in the coin cell used for the measurement. Therefore, the electrode potential of the embodiments and comparative examples is higher than that of the counter electrode, and thus they operate as positive electrodes. When the electrodes of embodiments 1 to 14 and comparative examples 1 to 6 are used as negative electrodes, the definitions of charging and discharging are reversed. Here, to avoid confusion, in this embodiment, the direction in which lithium ions insert into the electrode is uniformly referred to as charging, and the direction in which they detach is referred to as discharging. In addition, the electrodes of embodiments 1 to 14 and comparative examples 1 to 6 are combined with conventional positive electrode materials to operate as negative electrodes.

[0190] Furthermore, the fabricated electrochemical measurement unit was charged and discharged within a potential range of 1.0V to 3.0V (Li / Li+) using a lithium metal electrode as a reference. To test the fast discharge performance, after confirming the discharge capacity at 0.2C (time-based discharge rate), the charging current was set to 0.2C again, and the fast discharge capacity at 5C was confirmed at room temperature. Then, the discharge capacity retention rate (%) was obtained by dividing the 5C discharge capacity by the 0.2C discharge capacity and multiplying by 100. The 5C / 0.2C discharge capacity retention rate (%) is used as an indicator for evaluating fast charge and discharge performance.

[0191] Furthermore, in the units of the embodiments and comparative examples, a 0.2C charge-discharge cycle was repeatedly performed with a lithium metal electrode reference in a potential range of 1.0V to 3.0V (Li / Li+), and a life test was conducted at 25°C. Under these conditions, 1000 charge-discharge cycles were repeated (with one charge and discharge cycle defined as one cycle), and the discharge capacity retention rate after 1000 cycles was measured. To confirm the discharge capacity retention rate after 1000 cycles, a 0.2C charge-discharge cycle was performed again, and the discharge capacity after 1000 cycles was divided by the initial discharge capacity and then multiplied by 100 to calculate the cycle capacity retention rate (%) with the initial discharge capacity set to 100%. The discharge capacity retention rate after 1000 cycles is used as an indicator for evaluating cycle life performance. The above results are summarized in Tables 9 to 12.

[0192] <Durability Confirmation> For the electrodes obtained in the above examples, the durability of the current collector relative to rolling was evaluated. Specifically, continuous pressurization was performed under a pressure that brought the porosity of the active material containing layer to 25%, and the presence or absence of current collector breakage was confirmed. The confirmed results are shown in Tables 9 to 12. No current collector breakage was considered durable and indicated by a white circle (e.g., Examples 1 to 10). The presence or absence of current collector breakage was considered non-durable and indicated by an cross (e.g., Comparative Examples 2 to 4).

[0193]

[0194]

[0195]

[0196]

[0197] As shown in Table 9, in Examples 1 to 10, where niobium titanium oxide (Nb₂TiO₇) was used as the active material, higher fast charge / discharge performance was achieved compared to Comparative Examples 1 to 3, and higher lifetime performance was achieved compared to Comparative Examples 2 to 4. Furthermore, in Comparative Example 4, the current collector could not withstand the pressure applied to increase electrode density and fractured.

[0198] In Comparative Example 1, the current collector could not be porousized because the electrode precursor was kept under dry conditions, thus failing to improve fast charge / discharge performance. In Comparative Examples 2 and 3, the current collector had through-holes, but only a few large-diameter through-holes, resulting in uneven charge / discharge distribution within the electrode and reduced fast charge / discharge performance. Furthermore, the large through-holes also reduced lifetime performance. In Comparative Example 4, a pre-porousized current collector was used instead of the porousization treatment performed in an aqueous environment. Because no porousization treatment was performed, the pores were not protected by metal hydroxide, thus failing to improve lifetime performance. Additionally, because a current collector with lower strength was used, a high-density active material layer could not be achieved.

[0199] As shown in Table 10, in Examples 11 to 13, which use various niobates as active materials, good fast charge / discharge performance and lifetime performance can be obtained.

[0200] As shown in Table 11, in Example 14, which uses titanium oxide as the active material, higher fast charge / discharge performance is achieved compared to Comparative Examples 5 and 6, while higher lifetime performance is achieved compared to Comparative Example 6. Furthermore, in Comparative Example 5, the current collector could not withstand the pressure applied to increase electrode density and broke.

[0201] The active material H0.11TiO2.11 used in Comparative Example 5 is highly acidic, resulting in excessive porosity of the current collector when kept in an aqueous environment. Conversely, the active material Li4Ti5O12 used in Comparative Example 6 is highly alkaline, and it cannot make the current collector porous even when kept in an aqueous environment.

[0202] As shown in Table 12, in Examples 15 and 16, where lithium iron phosphate, which is typically used as a positive electrode active material, is used as the active material, higher fast charge / discharge performance and lifespan performance can be obtained compared to Comparative Example 7, which uses other typical positive electrode active materials, lithium nickel cobalt manganese composite oxide.

[0203] The nickel-cobalt-manganese composite oxide used in Comparative Example 7 is highly alkaline and cannot make the current collector porous even when kept in an aqueous environment.

[0204] An electrode is provided according to one or more embodiments and examples described above. The electrode comprises a current collector in the shape of a metal foil and an active material layer on the current collector. The current collector has a plurality of through holes with a diameter of 10 μm to 1000 μm at intervals of 3.0 mm to 100 mm. The ratio of oxygen atomic weight OU to metal atomic weight MeU in the non-opening portion at a distance of 1.5 times or more from the outer periphery of the through hole to the non-opening portion is OU / MeU, and the ratio of oxygen atomic weight OP to metal atomic weight MeP in the portion surrounding the holes at a distance of 5% or less from the outer periphery of the through hole is OP / MeP, which is 1.2 times or more. The electrode constructed as described above can provide a secondary battery and battery pack with high rate performance and high lifespan performance.

[0205] Several embodiments of the present invention are described, but these embodiments are provided as examples and are not intended to limit the scope of the invention. These novel embodiments can be implemented in various other forms, with various omissions, substitutions, and modifications made without departing from the spirit of the invention. These embodiments or variations thereof are included in the scope and spirit of the invention, as well as in the scope of the invention described in the claims and their equivalents.

[0206] The following are some embodiments of the present invention. [1] An electrode comprising: Current collectors including those in the shape of metal foils, and The active material on the aforementioned current collector contains a layer, The aforementioned current collector has multiple through holes with a diameter of 10μm to 1000μm, spaced 3.0mm to 100mm apart. The ratio of oxygen atomic weight OU to metal atomic weight MeU in the non-opening portion that is at least 1.5 times the diameter of the aforementioned through hole from the outer periphery of the aforementioned through hole is OU / MeU. The ratio of oxygen atomic weight OP to metal atomic weight MeP in the hole periphery that is at least 5% the diameter of the aforementioned through hole from the outer periphery of the aforementioned through hole is OP / MeP, which is at least 1.2 times. [2] The electrode as described in [1], wherein the aforementioned current collector comprises aluminum. [3] The electrode as described in [1], wherein the aforementioned current collector contains aluminum with an impurity concentration of more than 0.15% but less than 4%. [4] An electrode as described in any of [1] to [3], wherein the aforementioned active material contains a layer that does not have through-pores. [5] An electrode as described in any of [1] to [4], wherein the porosity of the aforementioned active material containing layer is less than 36%. [6] An electrode as described in any of [1] to [5], wherein the aforementioned active material comprises layers disposed on the front and back surfaces of the aforementioned current collector. [7] An electrode as described in any of [1] to [6], wherein the aforementioned active material contains a layer comprising a water-soluble binder. [8] An electrode as described in any of [1] to [7], wherein the aforementioned active material contains an oxide layer comprising at least one of the group consisting of titanium, niobium, tungsten, molybdenum, vanadium, iron, tin and silicon. [9] An electrode as described in any of [1] to [7], wherein the aforementioned active material contains an active material comprising at least one of the group consisting of phosphates and pyrophosphates.

[10] A secondary battery, comprising: positive electrode, Negative electrode, and Electrolytes At least one of the aforementioned positive electrode and the aforementioned negative electrode is an electrode described in any of [1] to [9].

[11] A battery pack comprising the secondary battery described in

[10] .

[12] The battery pack as described in

[11] further comprises: External terminals for power supply, and Protection circuit.

[13] The battery pack as described in

[11] or

[12] comprises a plurality of the aforementioned secondary batteries, The aforementioned secondary batteries are electrically connected in series, parallel, or a combination of series and parallel connections.

[0207] 1: Electrode Group 2: External components 3: Negative electrode 3a: Negative current collector 3b: The negative electrode active material contains a layer 3c: Negative electrode current collector tongue 4: Separator 5: Positive electrode 5a: Positive current collector 5b: The positive electrode active material contains a layer 6: Negative extremes 7: Positive extreme 10: Electrode 10a: Collector 10b: The active substance contains a layer 10c: Collector Tongue 11: Through hole 12: Surrounding area of ​​the hole 13: Non-opening section 13a: Measurement point 21: Busbar 22: Positive side lead 22a: The other end 23: Negative side lead 23a: The other end 24: Applying tape 31: Containment Container 32: Cover 33: Protective film 34: Printed Circuit Board 35: Wiring 100: Secondary battery 300: Battery Pack 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 side terminal 353: Negative side terminal 348a: Positive side wiring 348b: Negative side wiring

Claims

1. An electrode for a secondary battery, comprising: a current collector in the shape of a foil containing metal, and an active material containing layer on the current collector, wherein the current collector has a plurality of through holes with a diameter of 10 μm to 1000 μm at a spacing of 3.0 mm to 100 mm, wherein the ratio of oxygen atomic weight OU to metal atomic weight MeU of the non-opening portion at a distance of 1.5 times or more from the outer periphery of the through hole is OU / MeU, and the ratio of oxygen atomic weight OP to metal atomic weight MeP of the hole periphery at a distance of 5% or less from the outer periphery of the through hole is OP / MeP, which is 1.2 times or more.

2. The electrode for a secondary battery as described in claim 1, wherein, The aforementioned current collector contains aluminum.

3. The electrode for a secondary battery as described in claim 1, wherein, The aforementioned current collector contains aluminum with an impurity concentration of more than 0.15 atomic% but less than 4 atomic%.

4. The electrode for a secondary battery as described in any one of claims 1 to 3, wherein, The aforementioned active material contains a layer that does not have through-pores.

5. The electrode for a secondary battery as described in any one of claims 1 to 3, wherein, The porosity of the aforementioned active material containing the layer is less than 36%.

6. The electrode for a secondary battery as described in any one of claims 1 to 3, wherein, The aforementioned active material contains a layered structure disposed on the two main surfaces of the aforementioned current collector, on the front and back sides.

7. The electrode for a secondary battery as described in any one of claims 1 to 3, wherein, The aforementioned active substance contains a layer containing a water-soluble binder.

8. The electrode for a secondary battery as described in any one of claims 1 to 3, wherein, The aforementioned active material contains an oxide layer, which includes at least one of the group consisting of titanium, niobium, tungsten, molybdenum, vanadium, iron, tin and silicon.

9. The electrode for a secondary battery as described in any one of claims 1 to 3, wherein, The aforementioned active substance contains at least one of the group consisting of phosphates and pyrophosphates.

10. A secondary battery comprising: a positive electrode, a negative electrode, and an electrolyte, wherein at least one of the aforementioned positive electrode and the aforementioned negative electrode is an electrode for a secondary battery as described in any one of claims 1 to 3.

11. A battery pack comprising a secondary battery as described in claim 10.

12. The battery pack as described in claim 11 further includes: an external terminal for power supply and a protection circuit.

13. The battery pack as described in claim 11 comprises a plurality of the aforementioned secondary batteries, which are electrically connected in series, in parallel, or in a combination of series and parallel.

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