Electrodes, secondary batteries, and battery packs

Abstract

To provide an electrode capable of realizing a secondary battery and a battery pack having high rate performance and long life performance, and a secondary battery and a battery pack having high rate performance and long life performance 【Solution means】According to an embodiment, an electrode is provided that includes a foil-shaped current collector containing a metal and an active material-containing layer on the current collector. The current collector has a plurality of through-holes with a diameter of 10 μm or more and 1000 μm or less, which are opened at a pitch of 3.0 mm or more and 100 mm or less. The atomic weight of oxygen O P to the atomic weight of metal Me P in the hole peripheral portion within 5% of the diameter of the through-hole from the outer periphery of the through-hole P ratio O P / Me U is 1.2 times or more than the ratio O U of the atomic weight of oxygen O U to the atomic weight of metal Me U in the non-opening portion more than 1.5 times the diameter of the through-hole from the outer periphery of the through-hole.

Description

[Technical Field]

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

[0002] Lithium-ion batteries, such as non-aqueous electrolyte batteries, which charge and discharge by the movement of lithium ions between the negative and positive electrodes, are being actively researched as high-energy-density batteries. It is known that using porous current collector foil as the core material of the electrodes greatly improves the rate performance because Li ions can be supplied from the back of the current collector foil during charging and discharging. [Prior art documents] [Patent Documents]

[0003] [Patent Document 1] Japanese Patent Publication No. 2017-117731 [Non-patent literature]

[0004] [Non-Patent Document 1] Dr. Michael et al., Image Processing with ImageJ, Reprinted from the July 2004 issue of Biophotonics International copyrighted by Laurin Publishing Co. INC. [Overview of the project] [Problems that the invention aims to solve]

[0005] The objective is to provide electrodes that enable secondary batteries and battery packs with high rate performance and longevity performance, as well as secondary batteries and battery packs with high rate performance and longevity performance. [Means for solving the problem]

[0006] According to the embodiment, an electrode is provided comprising a foil-shaped current collector containing metal and an active material-containing layer on the current collector. The current collector has a plurality of through holes with diameters of 10 μm to 1000 μm, opened at a pitch of 3.0 mm to 100 mm. The amount of metal atomic weight Me in the area around the hole, within 5% of the diameter of the through hole from the outer circumference of the through hole. P Oxygen atomic weight relative to O P Ratio O P / Me P However, the amount of metal atomic weight Me in non-opening areas that are more than 1.5 times the diameter of the through-hole from the outer circumference of the through-hole is... U Oxygen atomic weight relative to O U Ratio O U / Me U This is more than 1.2 times the other value.

[0007] In another embodiment, a secondary battery is provided that comprises a positive electrode, a negative electrode, and an electrolyte. At least one of the positive electrode and the negative electrode is the electrode according to the above embodiment.

[0008] According to another embodiment, a battery pack comprising a secondary battery according to the above embodiment is provided. [Brief explanation of the drawing]

[0009] [Figure 1] A schematic cross-sectional view showing an example of an electrode according to the embodiment. [Figure 2] A schematic plan view showing the current collector included in the electrode according to the embodiment. [Figure 3] A schematic cross-sectional view showing an example of a secondary battery according to this embodiment. [Figure 4] Figure 3 shows an enlarged cross-sectional view of section A of the secondary battery. [Figure 5] A schematic partial cutaway perspective view showing another example of a secondary battery according to the embodiment. [Figure 6] Figure 5 shows an enlarged cross-sectional view of section B of the secondary battery. [Figure 7] A schematic perspective view showing an example of a battery pack according to this embodiment. [Figure 8] An exploded perspective view schematically showing an example of a battery pack according to this embodiment. [Figure 9] A block diagram showing an example of an electric circuit of a battery pack shown in FIG. 8.

Mode for Carrying Out the Invention

[0010] In an electrode using a porous current collector foil as a current collector, it is known that the rate performance is greatly improved. However, the manufacturing cost of the porous current collector foil is high, and in addition, current concentrates on the processing edge, increasing the resistance due to the generation of excessive AlF3 or the like by corrosion. In addition, since the rigidity of the porous current collector foil is lowered, when using the porous current collector foil, there are problems such as breakage of the current collector foil during the pressing process when manufacturing the electrode, or damage to the current collector foil due to volume changes of the electrode accompanying charge and discharge. A method of processing each active material supported on the current collector foil is also known, but in that case, there is a problem that the energy density decreases.

[0011] Hereinafter, embodiments will be described with reference to the drawings. In the embodiments, the same reference numerals are given to common configurations, and redundant explanations are omitted. In addition, each figure is a schematic diagram for facilitating the explanation and understanding of the embodiments, and there are parts where the shape, dimensions, ratio, etc. are different from the actual device, but these can be appropriately designed and changed in consideration of the following explanation and known techniques.

[0012] (First Embodiment) According to the first embodiment, an electrode is provided. Such an electrode includes a current collector in the form of a foil containing a metal, and an active material-containing layer on the current collector. The current collector has a plurality of through-holes opened. The diameter of the through-holes is 10 μm or more and 1000 μm or less, and the pitch on the current collector is 3.0 mm or more and 100 mm or less. The ratio O P of the oxygen atomic weight O P to the metal atomic weight Me P / Me P at the periphery of the through-hole is the ratio O U of the oxygen atomic weight O U to the metal atomic weight Me U / Me UIt is 1.2 times or more. The area around the hole refers to the region within 5% of the diameter of the through hole, extending outward from the outer circumference of the through hole. The non-opening area refers to a location that is 1.5 times or more the diameter of the through hole from the outer circumference.

[0013] The above electrode is equipped with a porous current collector foil as a current collector. Since charge carrier ions such as Li ions can pass through the porous current collector foil, the movement of carrier ions is not hindered by the current collector in such an electrode. Therefore, a battery using such an electrode can exhibit high rate performance.

[0014] In this electrode, although multiple through holes are opened into the current collector, the increase in resistance due to the excessive generation of by-products such as AlF3 at the edges of the through holes is suppressed, and the strength around the through holes is increased, thereby mitigating damage to the current collector due to the expansion and contraction of the electrode. As described above, the ratio of oxygen atoms in the area around the through holes is higher than in the area without openings. Specifically, the ratio of the atomic weight of oxygen to the atomic weight of metal (oxygen atomic weight / metal atomic weight) is more than 1.2 times higher in the area around the holes compared to the area without openings, which is significantly higher than the naturally formed protective film. In other words, the area around the through holes is composed of metal acid hydroxide, thereby protecting the current collector from the generation of by-products such as AlF3 and increasing the strength around the holes.

[0015] The active material-containing layer can be formed on one or both sides of the current collector. It is preferable that the active material-containing layer is provided 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 provided on both sides can be utilized to its fullest potential. The active material-containing layer may optionally contain an active material, a conductive agent, and a binder.

[0016] It is preferable that the active material-containing layer does not have through holes. By not providing through holes and instead including the active material in the corresponding spaces, the energy density of the electrode can be increased accordingly. Furthermore, the porosity of the active material-containing layer is preferably 36% or less. By reducing the voids and including more active material, the energy density per unit volume of the electrode can be increased.

[0017] A current collector may include portions on its surface where the active material-containing layer is not formed. These portions can function as current-collecting tabs.

[0018] Figure 1 shows an example of an electrode according to the embodiment. Figure 1 schematically shows a cross-section of the electrode. Figure 2 shows an example of a current collector included in the electrode. Figure 2 schematically shows a plan view of the current collector.

[0019] The illustrated electrode 10 includes a current collector 10a and active material-containing layers 10b provided on both its front and back surfaces. A portion of the current collector 10a does not have the active material-containing layers 10b on either its front or back surface, and this portion can function as a current collector tab 10c. The active material-containing layers 10b contain an active material (not shown).

[0020] Multiple through-holes 11 are arranged in the portion of the current collector 10a that supports the active material-containing layer 10b. That is, the current collector 10a is a porous current collector foil. The portion of the current collector tab 10c that does not support the active material-containing layer 10b does not contain through-holes 11. As shown in Figure 1, lithium ions (Li + Charge carrier ions such as ) can move back and forth between the active material-containing layers 10b located on both sides of the current collector 10a through the through-hole 11. Therefore, a battery using the electrode 10 can exhibit high rate performance.

[0021] The through-holes 11 have a diameter of 10 μm to 1000 μm. The through-holes 11 are spaced apart from each other at intervals of 3.0 mm to 100 mm, and are not necessarily uniformly arranged as shown in Figure 2. A current collector 10a with through-holes of this size arranged at the above pitch can improve the rate performance of the electrodes while maintaining strength. In Figure 2, the size of the through-holes 11 is uniform, but the diameters of multiple through-holes 11 are not necessarily the same. The largest diameter, measured by the method described later, falls within the above range. Also, in Figure 2, the through-holes 11 are drawn as circles, but the shape of the through-holes 11 is not limited to circles, and the shapes of multiple through-holes 11 are not necessarily uniform.

[0022] When comparing the area surrounding the through-hole 11, within 5% of the diameter of the through-hole 11, with the non-opening area, which is located at least 1.5 times the diameter of the through-hole 11, the amount of metal atomic weight Me in the area surrounding the hole 12 is... P Oxygen atomic weight relative to O P Ratio O P / Me P This is the metal atomic weight Me at the non-opening 13. U Oxygen atomic weight relative to O U Ratio O U / Me U This is more than 1.2 times greater. This means that at least the portion of the hole perimeter 12 contains metal acid hydroxide. Therefore, the hole perimeter 12, which is the area surrounding the through hole 11, is protected and has high strength.

[0023] In the illustrated example, the active material-containing layer 10b does not have through holes. Therefore, the through hole 11 of the current collector 10a is covered by the active material-containing layer 10b. By providing through holes only in the current collector 10a, rate performance can be improved without reducing the energy density of the electrode 10.

[0024] The electrode in question may be, for example, at least one of the positive and negative electrodes of a battery. In a battery that includes such an electrode as the negative electrode, the positive electrode may be an electrode other than the one according to the embodiment. Conversely, in a battery that includes such an electrode as the positive electrode, the negative electrode may be an electrode other than the one according to the first embodiment. Both the negative and positive electrodes included in a battery may be electrodes according to the first embodiment.

[0025] The active material-containing layer may contain one type of active material alone, or it may contain two or more types of active materials. As the active material, for example, an electrode active material whose solubility when dispersed in water is less than 0.2 wt% can be used. Furthermore, an electrode active material whose pH is between 5 and 9 during the electrode material washing process described later can be suitably used.

[0026] In the embodiment of the electrode as a negative electrode, the active material-containing layer (negative electrode active material-containing layer) may contain an oxide as the negative electrode active material, for example, an oxide containing at least one selected from the group consisting of titanium, niobium, tungsten, molybdenum, vanadium, iron, tin, and silicon. Specific examples include niobium-containing oxides and titanium dioxide (TiO2). Niobium-containing oxides include niobium pentoxide (Nb2O5), Nb 12 O 29 FeNb 11 O 29 This includes monoclinic titanium niobium oxide (TNO), tetragonal titanium-niobium-tungsten composite oxide, and tetragonal titanium-niobium-molybdenum composite oxide, among others.

[0027] As an example of the above monoclinic type niobium titanium oxide, Li x Ti 1-y M1 y Nb 2-z M2 z O 7+δCompounds represented by the following are included. Here, M1 is at least one selected from the group consisting of Zr, Si, and Sn. M2 is at least one selected from the group consisting of V, Ta, and Bi. Each subscript in the composition formula satisfies 0 ≦ x ≦ 5, 0 ≦ y < 1, 0 ≦ z < 2, and -0.3 ≦ δ ≦ 0.3. As a specific example of the monoclinic niobium titanate, Li x Nb2TiO7 (0 ≦ x ≦ 5) is included.

[0028] As another example of the monoclinic niobium titanate, compounds represented by Li x Ti 1-y M3 y+z Nb 2-z O 7-δ are included. Here, M3 is at least one selected from Mg, Fe, Ni, Co, W, Ta, and Mo. Each subscript in the composition formula satisfies 0 ≦ x ≦ 5, 0 ≦ y < 1, 0 ≦ z < 2, and -0.3 ≦ δ ≦ 0.3.

[0029] In the aspect as the positive electrode of the electrode according to the first embodiment, the active material-containing layer (positive electrode active material-containing layer) can contain at least one selected from the group consisting of phosphate salts and pyrophosphate salts as the positive electrode active material. The phosphate salts include iron phosphate, manganese phosphate, nickel phosphate, cobalt phosphate, and their lithium salts. Specific examples include lithium phosphates having an olivine structure (e.g., Li x FePO4; 0 < x ≦ 1, Li x Fe 1-y Mn y PO4; 0 < x ≦ 1, 0 < y ≦ 1, Li x CoPO4; 0 < x ≦ 1). The pyrophosphate salts include iron pyrophosphate, manganese pyrophosphate, nickel pyrophosphate, cobalt pyrophosphate, and their lithium salts.

[0030] Conductive agents are added to enhance current collection performance and reduce contact resistance between the active material and the current collector. Examples of conductive agents include carbonaceous materials such as vapor-grown carbon fiber (VGCF), carbon black such as acetylene black, graphite, carbon nanotubes, and carbon nanofibers. One of these may be used as a conductive agent, or two or more may be used in combination. Alternatively, instead of using a conductive agent, a carbon coating or an electronically conductive inorganic material coating may be applied to the surface of the active material particles. Furthermore, in the positive electrode configuration, the conductive agent may be omitted.

[0031] A binder is added to fill the gaps between dispersed active materials and to bond the active materials to the current collector. It is desirable that the binder contains a water-soluble binder. As will be described in detail later, through-holes can be formed in the current collector by a porosity reaction in a hydrated environment. Therefore, using a water-soluble binder during electrode manufacturing can accelerate the porosity reaction of the current collector. As a water-soluble binder, cellulose-based materials such as sodium carboxymethyl cellulose (CMC), fluororubber, or styrene-butadiene rubber can be used, but are not limited to these.

[0032] The mixing ratios of the active material, conductive agent, and binder in the active material-containing layer can be appropriately changed depending on the application of the electrode. For example, when the electrode is used as the negative electrode of a secondary battery, it is preferable to mix the active material (negative electrode active material), conductive agent, and binder in the following proportions: 68% to 96% by mass, 2% to 30% by mass, and 2% to 30% by mass, respectively. By setting the amount of conductive agent to 2% by mass or more, the current collection performance of the active material-containing layer can be improved. Furthermore, by setting the amount of binder to 2% by mass or more, sufficient bonding between the active material-containing layer and the current collector can be achieved, and excellent cycle performance can be expected. On the other hand, it is preferable to set the amount of conductive agent and binder to 30% by mass or less each in order to achieve high capacity.

[0033] In the case of a positive electrode, it is preferable that the active material (positive electrode active material) and the binder are blended in the active material-containing layer in proportions of 80% to 98% by mass and 2% to 20% by mass, respectively. By using 2% or more by mass of the binder, sufficient strength of the active material-containing layer can be obtained. Furthermore, the binder can function as an insulator. Therefore, by using 20% ​​or less by mass of the binder, the amount of insulator contained in the electrode is reduced, thereby reducing the internal resistance.

[0034] When a conductive agent is added, it is preferable that the active material (positive electrode active material), binder, and conductive agent are blended in proportions of 77% to 95% by mass, 2% to 20% by mass, and 3% to 15% by mass, respectively. By increasing the amount of conductive agent to 3% by mass or more, the effects described above can be achieved. Furthermore, by reducing the amount of conductive agent to 15% by mass or less, the proportion of conductive agent in contact with the electrolyte can be reduced. A lower proportion reduces the decomposition of the electrolyte under high-temperature storage conditions.

[0035] The material of the current collector is 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 containing one or more elements selected from Mg, Ti, Zn, Mn, Fe, Cu, Si, Cr, V, and Ga. It is preferable that the current collector contains aluminum. In other words, it is preferable that the current collector is made of aluminum or an aluminum alloy. Furthermore, if the current collector contains aluminum, the impurity concentration of that aluminum may be greater than 0.15% but less than 4%.

[0036] <<Manufacturing method>> The electrode can be manufactured, for example, by the following method. First, a slurry is prepared by suspending an electrode composite material containing an active material, a conductive agent, and a binder in a solvent. For the solvent, a solvent containing water, for example, is used. The solvent may be pure water or a mixed solvent of water and another solvent. This slurry is applied to one or both sides of a foil serving as a current collector. Next, the applied slurry is dried, and pressure is applied to the coating film formed on the current collector foil. The thus obtained electrode precursor is held in a state of being exposed to an environment with a relatively high humidity such as in the atmosphere. By exposing the foil in a water-containing environment while in contact with the electrode composite material and oxygen, a reaction for making the foil porous proceeds. Next, the coating film is completely dried to form an active material-containing layer on the current collector. In this way, the electrode is manufactured.

[0037] For the foil serving as the current collector, the above-described material of the current collector, that is, 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 elute due to the potential difference between the active material, the conductive agent, and the metal of the current collector foil, and through-holes are formed in the current collector foil. The eluted metal ions react with oxygen and water in the air, and metal oxyhydroxide is formed around the holes. For example, when a foil containing aluminum (Al) is used, aluminum oxyhydroxide represented by x (OH) y and satisfying 0 < x ≦ 1.5, 0 < y ≦ 3, and 2x + y = 3 can be generated. Specifically, first, through-holes are generated due to the formation of aluminum oxide, and aluminum oxyhydroxide is generated by the electrolysis reaction of oxygen and water using aluminum oxide as a reactant. Therefore, by subjecting the electrode precursor to a porous treatment by holding it in a water-containing environment, through-holes protected and reinforced with metal oxyhydroxide at the edges can be provided in the current collector.

[0038] It is desirable to use a compound that is slightly acidic to weakly basic as the active material. Specifically, for example, it is desirable to use an active material whose pH during electrode material washing, as determined by the method described later, is between 5 and 9. Using a more acidic active material tends to result in larger diameters and a greater number of through-holes. Using a more basic active material tends to result in smaller diameters and a fewer number of through-holes. For example, when using a strongly basic active material, through-holes formed during the production of aluminum oxide may become blocked during the production of aluminum hydroxide oxide. When using an active material whose pH during electrode material washing is between 5 and 9, it is easier to obtain an electrode with a current collector having through-holes with diameters and pitches within the above-mentioned range.

[0039] The electrode precursor should be held in a humid environment, for example, in air with a dew point between 10°C and 35°C. The holding time should be, for example, between 1 hour and 72 hours. However, moisture may be absorbed into the coating on the current collector foil during the holding period; it is desirable to keep the maximum amount of moisture at this time below 10,000 ppm. By holding the electrode precursor under these conditions, an electrode equipped with a current collector having through holes with diameters and pitches within the above-mentioned range can be obtained.

[0040] From the viewpoint of promoting the porosity reaction, it is desirable to use a water-soluble binder as a binder. In a slurry coating using a water-soluble binder, moisture can easily reach the interface between the coating and the foil, that is, the area where the active material or conductive agent comes into contact with the metal.

[0041] Since the formation of through-holes in the current collector is carried out after pressing to increase the density of the active material-containing layer, the size and number of through-holes can be made relatively large without worrying about the current collector breaking during pressing. Furthermore, as mentioned above, the area around the holes is protected and reinforced with metal acid hydroxide, which increases the durability of the electrode itself and the battery life. As a result, such electrodes can realize secondary batteries with excellent rate performance and lifespan performance. In addition, since there is no need to separately manufacture porous current collector foil, electrodes can be manufactured at a low cost.

[0042] <<Measurement method>> Various measurement methods related to the electrode according to the embodiment will be described. Specifically, methods for analyzing the aperture in the electrode, measuring the ratio of oxygen atomic weight to metal atomic weight in the current collector, confirming the water-soluble binder, measuring the pH during water washing of the electrode material, measuring the porosity of the active material-containing layer, and confirming the electrode active material will be described.

[0043] If the electrode to be measured is integrated into the battery, remove the electrode from the battery as follows: First, discharge the battery to 0.0V to induce an over-discharge state. Next, disassemble the battery in a glove box filled with argon and remove the electrode. If the electrode forms an electrode group together with the opposite electrode and separator, remove and disassemble the electrode group and separate the electrode to be measured from the electrode group.

[0044] <Analysis of the opening> By immersing the electrodes in water or a solvent such as N-methylpyrrolidone for 24 hours, the active material-containing layer on the current collector can be removed without damaging the current collector. Afterward, ultrasonic cleaning is performed for 5 seconds if necessary. After drying the current collector, analysis is performed under an electron microscope.

[0045] For the analysis of apertures in current collectors, we use SEM-EDS (Scanning Electron Microscope - Energy Dispersive X-ray Spectroscopy), which combines scanning electron microscopy and energy dispersive X-ray spectroscopy. First, the entire current collector is analyzed qualitatively, and the element with the highest abundance among the detected metal elements is defined as the current collector material. Then, SEM-EDS analysis is performed to map the metal element in question, and areas where this metal is not detected are defined as apertures formed by through holes. However, it is confirmed in advance that the SEM-EDS equipment does not contain the metal element in question.

[0046] After the mapping process, the mapped image is binarized using image processing software, and the widest portion of the diameter of the missing area where the element is absent is recorded as the diameter of the through-hole.

[0047] For binarization, image analysis software such as Image J (Non-Patent Document 1) can be used. Image J is public domain software. Version 1.52a of Image J will be used.

[0048] Furthermore, the impurity concentration in the current collector can be calculated based on the relative abundance of the metal elements identified as current collector material and other elements detected.

[0049] SEM-EDS analysis is also used to determine the presence or absence of openings in the active material layer. However, instead of removing the active material layer from the current collector, cleaning is performed by immersing the electrode in a solvent that does not dissolve the binder of the active material layer, such as dimethyl carbonate, for 24 hours. The presence or absence of through holes can be confirmed by analyzing the most abundant transition metal contained in the electrode active material, instead of the metal of the current collector.

[0050] <Ratio of oxygen atomic weight to metal atomic weight> From the mapping images obtained by SEM-EDS analysis to confirm the opening in the current collector described above, the ratio of oxygen atomic weight to metal atomic weight can be determined for both the area around the hole and the non-opening area. Oxygen atomic weight around the hole: P and metal atomic weight Me P For this analysis, the field of view should be centered on the area extending from the edge of the target through-hole outward to a distance of 1 / 20th of the diameter of the through-hole. When analyzing the area surrounding the hole, it is desirable to select one of the two closest adjacent through-holes from among multiple through-holes. Non-opening oxygen atomic weight O U and metal atomic weight Me UFor this purpose, the analysis is performed by centering the field of view at the midpoint of the straight line connecting the two nearest adjacent holes among the multiple through holes, and at a distance of at least 1.5 times the diameter of the nearest adjacent hole from the outer circumference of the nearest adjacent hole. For example, in the example shown in Figure 2, measurement point 13a is set as the center of the non-aperture analysis field of view. Pairs of through holes where the midpoint of the straight line connecting the two through holes is less than 1.5 times the diameter from either hole are excluded from the pair of nearest adjacent holes. Also, if the diameters of the two nearest adjacent holes are different, the distance of 1.5 times or more is based on the diameter of the larger through hole. Furthermore, the atomic weight of the metal around the hole Me P Oxygen atomic weight relative to O P This value is taken as the position on the straight line connecting the two through holes that pass through the measurement point 13a of the non-opening mentioned above.

[0051] <Water-soluble binder> Whether or not the active material-containing layer contains a water-soluble binder can be analyzed, for example, by extracting and analyzing the binder from the electrode. The electrode is washed with dimethyl carbonate, dried at 120°C, then immersed in water, ultrasonically dispersed, and filtered to extract the water-soluble binder. The filtered clear liquid may contain the water-soluble binder. The water-soluble binder can be separated by air-drying the solid residue of the remaining liquid at room temperature and analyzing it. The presence of remaining organic molecules in this solid residue can be confirmed using methods such as infrared spectroscopy (IR), nuclear magnetic resonance (NMR) analysis, or mass spectrometry, or by combining multiple methods as needed.

[0052] <pH during water washing of electrode materials> The acidity and basicity of the active material contained in the electrode can be evaluated by measuring the pH during the washing of the electrode material, as follows.

[0053] The electrodes removed from the battery are washed with dimethyl carbonate. After drying at 120°C, the active material-containing layer is separated from the current collector using a spatula or similar tool. 1 g of the active material-containing layer separated from the current collector is placed in 10 mL of water, and the resulting suspension is left to stand for 24 hours. Next, the supernatant of the suspension is separated by centrifugation. The pH of the separated supernatant is measured. The pH measured here is referred to as the "pH during electrode material washing."

[0054] <Porosity of the active material-containing layer> The porosity of the active material-containing layer is measured using a three-dimensional scanning electron microscope (3D-SEM) image. The electrode removed from the battery is washed with dimethyl carbonate solvent and dried. A sample approximately 5 mm x 5 mm in size is cut out. 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 is cut out using a focused ion beam (FIB), and observed with a scanning electron microscope (SEM). Subsequently, the cross-sectional processing with FIB and observation with SEM are repeated, and the porosity is measured by three-dimensional reconstruction of the SEM observation image. For example, the FIB processing pitch is set to approximately 150 nm, and the number of repetitions of FIB processing and SEM observation is set to 100.

[0055] <Active material> The active material can be identified by analyzing its crystal structure using X-ray diffraction spectroscopy (XRD spectroscopy) and by analyzing its composition using inductively coupled plasma (ICP) emission spectroscopy.

[0056] XRD measurements can be performed, for example, as follows:

[0057] First, to understand the crystalline state of the active material, the lithium ions must be completely removed from the active material. For example, in the case of electrodes used as the negative electrode of a battery, the battery must be completely discharged. For example, the battery can be discharged by repeatedly discharging it at a current of 0.1C in a 25°C environment until the rated termination voltage or battery voltage reaches 1.0V, ensuring that the discharge current is less than 1 / 100 of the rated capacity. Even in the discharged state, residual lithium ions may still be present.

[0058] Next, the battery is disassembled in a glove box filled with argon, the electrodes are removed, and washed with a suitable solvent. Dimethyl carbonate can be used as a suitable solvent, for example. If the electrodes are not washed thoroughly, impurity phases such as lithium carbonate and lithium fluoride may be introduced due to the influence of lithium ions remaining in the electrodes. In that case, it is advisable to use an airtight container that allows the measurement to be performed in an inert gas atmosphere. The washed electrodes are cut to an area approximately the same as the area of ​​the holder of the powder X-ray diffractometer to prepare the measurement sample. This sample is then directly attached to the glass holder and the measurement is performed.

[0059] At this time, the peaks originating from the current collector (metal foil), conductive agent, and binder should be measured and identified in advance using XRD. Of course, if these can be identified in advance, this step can be omitted. If the peaks of the current collector and the active material overlap, it is desirable to peel off the active material-containing layer from the current collector and measure it. This is to separate the overlapping peaks 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 mixture (including the active material, conductive agent, and binder) can be recovered by volatilizing the solvent. The recovered electrode mixture can then be packed into a capillary tube made of Lindemann glass, for example, and measured to perform powder X-ray diffraction measurement of the active material.

[0060] For powder X-ray diffraction measurements, we will use, for example, the SmartLab manufactured by Rigaku. The measurement conditions will be as follows: X-ray source: Cu target Output: 45kV 200mA Solar slit: 5° for both incident and received light. Step size (2θ): 0.02deg Scan speed: 20deg / min Semiconductor detector: D / teX Ultra 250 Measurement range: 5°≦2θ≦90° Sample plate holder: Flat glass sample plate holder (thickness 0.5 mm).

[0061] If other equipment is used, measurements should be performed using standard Si powder for powder X-ray diffraction to obtain measurement results equivalent to those described above, and the conditions should be adjusted so that the peak intensity and peak top position match those of the above equipment.

[0062] The composition of the active material is measured by ICP emission spectroscopy using the following procedure.

[0063] The active material-containing layer is peeled off the electrodes, which have been removed from the battery and cleaned, using the method described above. Next, the peeled portion is heated briefly in the air (for example, at 500°C for about 1 hour) to burn off unwanted components such as binders and conductive agents. By dissolving this residue with acid, a liquid sample containing the active material can be prepared. Hydrochloric acid, nitric acid, sulfuric acid, or hydrogen fluoride can be used as the acid. By subjecting this liquid sample to ICP analysis, the average composition of the active material can be determined.

[0064] The electrode according to the first embodiment comprises a foil-shaped current collector containing metal and an active material-containing layer thereon, wherein the current collector has a plurality of through holes with a diameter of 10 μm to 1000 μm opened at a pitch of 3.0 mm to 100 mm, and the atomic weight of the metal around the holes of the current collector is Me P Oxygen atomic weight relative to O P Ratio O P / Me P This is the amount of metal atomic weight Me at the non-opening of the current collector.U Oxygen atomic weight relative to O U Ratio O U / Me U This is more than 1.2 times greater. This electrode enables the realization of secondary batteries and battery packs exhibiting high rate performance and long lifespan.

[0065] (Second embodiment) According to the second embodiment, a secondary battery is provided that includes a negative electrode, a positive electrode, and an electrolyte. This secondary battery includes an electrode according to the first embodiment as at least one of the positive electrode and the negative electrode. When the electrode according to the first embodiment is included as the negative electrode, the positive electrode may be a different electrode from that of the first embodiment. When the electrode according to the first embodiment is included as the positive electrode, the negative electrode may be a different electrode from that of the first embodiment. The secondary battery according to the second embodiment may also include both the negative electrode and positive electrode embodiments of the electrode according to the first embodiment, respectively, as the negative electrode and the positive electrode.

[0066] The secondary battery may further include a separator positioned between the positive electrode and the negative electrode. The negative electrode, positive electrode, and separator can constitute an electrode group. The electrolyte can be held within the electrode group.

[0067] Furthermore, the secondary battery may further comprise an outer casing that houses the electrode group and the electrolyte.

[0068] Furthermore, the secondary battery may further include a negative terminal electrically connected to the negative electrode and a positive terminal electrically connected to the positive electrode.

[0069] The secondary battery in question may be, for example, a lithium secondary battery. Furthermore, the secondary battery may include a non-aqueous electrolyte secondary battery containing a non-aqueous electrolyte.

[0070] The following provides a detailed explanation of the negative electrode, positive electrode, electrolyte, separator, outer casing, negative electrode terminal, and positive electrode terminal.

[0071] 1) Negative electrode The negative electrode may include a negative electrode current collector and a negative electrode active material-containing layer. The negative electrode may be an embodiment of the negative electrode of the electrode according to the first embodiment. Therefore, the negative electrode current collector and the negative electrode active material-containing layer may be a current collector and an active material-containing layer that can be included in the electrode according to the first embodiment, respectively. The negative electrode active material-containing layer may include, for example, the negative electrode active material described in the first embodiment or other negative electrode active materials listed below.

[0072] Details of the negative electrode that overlap with the details described regarding the negative electrode configuration of the electrode according to the first embodiment will be omitted. Below, we will explain the differences between the electrode according to the first embodiment and other negative electrodes that can be used in a battery that includes the electrode according to the first embodiment as the positive electrode.

[0073] Other negative electrodes may include as negative electrode active materials the negative electrode embodiments of the electrode according to the first embodiment may include. Other negative electrodes may further include other negative electrode active materials together with the negative electrode active materials described in the first embodiment. Other negative electrodes may include one or more negative electrode active materials alone as described in the first embodiment, or one or more negative electrode active materials and other negative electrode active materials, or one or more other negative electrode active materials alone.

[0074] Other examples of active materials include lithium titanate (e.g., Li) which has a ramsdelite structure. 2+y Li3O7 (0≦y≦3), lithium titanate having a spinel structure (e.g., Li 4+x Ti5O 12 Examples include titanium dioxide (TiO2), anatase-type titanium dioxide, rutile-type titanium dioxide, hollandite-type titanium composite oxides, and orthorhombic titanium composite oxides.

[0075] As an example of the above orthorhombic titanium-containing composite oxide, Li 2+a M I 2-b Ti 6-c M II d O 14+σExamples of compounds represented by are given. Here, M I It is at least one selected from the group consisting of Sr, Ba, Ca, Mg, Na, Cs, Rb, and K. II is at least one selected from the group consisting of Zr, Sn, V, Nb, Ta, Mo, W, Y, Fe, Co, Cr, Mn, Ni, and Al. In the composition formula, each subscript has the following properties: 0≦a≦6, 0≦b<2, 0≦c<6, 0≦d<6, -0.5≦σ≦0.5. As a specific example of an orthorhombic titanium-containing composite oxide, Li 2+a Na2Li6O 14 (0 ≤ a ≤ 6) is one example.

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

[0077] The density of the negative electrode active material layer (excluding the current collector) is 1.8 g / cm³. 3 More than 2.8g / cm 3 The following is preferable. A negative electrode with a density of the negative electrode active material-containing layer within this range exhibits excellent energy density and electrolyte retention. The density of the negative electrode active material-containing layer is 2.1 g / cm³. 3 More than 2.6g / cm 3 The following is more preferable:

[0078] The negative electrode current collector, which includes other negative electrodes, has through holes with a diameter of 10 μm to 1000 μm, as described in the first embodiment, with a pitch of 3.0 mm to 100 mm. P / Me P is ratio O U / MeU This differs from current collectors that are 1.2 times or more in thickness. 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 containing one or more elements selected from Mg, Ti, Zn, Mn, Fe, Cu, and Si. The thickness of the current collector is preferably 5 μm to 20 μm. Current collectors with such thickness can balance electrode strength and weight reduction.

[0079] Furthermore, the negative electrode current collector may include portions on its surface where the negative electrode active material-containing layer is not formed. These portions can function as negative electrode current collector tabs.

[0080] Other negative electrodes can be manufactured, 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 applied to one or both sides of a current collector. The solvent is not limited to water, but can be, for example, other water-soluble solvents or organic solvents. Next, the applied slurry is dried to obtain a laminate of the negative electrode active material-containing layer and the current collector. Then, this laminate is pressed. In this way, a negative electrode is manufactured.

[0081] Alternatively, the negative electrode may be manufactured by the following method: First, a negative electrode active material, a conductive agent, and a binder are mixed to obtain a mixture. Next, this mixture is formed into pellets. Then, these pellets are placed on a current collector to obtain the negative electrode.

[0082] 2) Positive electrode The positive electrode may include a positive electrode current collector and a positive electrode active material-containing layer. The positive electrode active material-containing layer may be formed on one or both sides of the positive electrode current collector. The positive electrode active material-containing layer may optionally include a positive electrode active material and a conductive agent and a binder.

[0083] Among the details of the positive electrode, the parts overlapping with the details described for the positive electrode as an aspect according to the first embodiment are omitted. Hereinafter, for example, in a battery including the electrode according to the first embodiment as a negative electrode, the differences from the electrode according to the first embodiment for other positive electrodes that can be used will be described.

[0084] Other positive electrodes can include an active material that can be included in the aspect as the positive electrode of the electrode according to the first embodiment as the positive electrode active material. Other positive electrodes can further include other positive electrode active materials together with the positive electrode active material described in the first embodiment. Other positive electrodes may include one or more of the positive electrode active materials described in the first embodiment alone, or may include one or more of each of the positive electrode active materials described in the first embodiment and other positive electrode active materials, or may include one or more of other positive electrode active materials alone.

[0085] As other positive electrode active materials, for example, oxides or sulfides can be used. The positive electrode may include a single type of compound alone as the positive electrode active material, or may include a combination of two or more types of compounds. Examples of oxides and sulfides can include compounds into which Li or Li ions can be inserted and desorbed.

[0086] Such compounds include, for example, manganese dioxide (MnO2), iron oxide, copper oxide, nickel oxide, lithium manganese composite oxide (e.g., Li x Mn2O4 or Li x MnO2; 0 < x ≤ 1), lithium nickel composite oxide (e.g., Li x NiO2; 0 < x ≤ 1), lithium cobalt composite oxide (e.g., Li x CoO2; 0 < x ≤ 1), lithium nickel cobalt composite oxide (e.g., Li x Ni 1-y Co y O2; 0 < x ≤ 1, 0 < y < 1), lithium manganese cobalt composite oxide (e.g., Li x Mn y Co 1-y O2; 0 < x ≤ 1, 0 < y < 1), lithium manganese nickel composite oxide having a spinel structure (e.g., Lix Mn 2-y Ni y O4; 0 < x ≤ 1, 0 < y < 2), iron sulfate (Fe2(SO4)3), vanadium oxide (e.g., V2O5), and lithium nickel cobalt manganese composite oxide (Li x Ni 1-y-z Co y Mn z O2; 0 < x ≤ 1, 0 < y < 1, 0 < z < 1, y + z < 1) is included.

[0087] Among the above, examples of more preferable compounds as the positive electrode active material include lithium manganese composite oxide having a spinel structure (e.g., Li x Mn2O4; 0 < x ≤ 1), lithium nickel composite oxide (e.g., Li x NiO2; 0 < x ≤ 1), lithium cobalt composite oxide (e.g., Li x CoO2; 0 < x ≤ 1), lithium nickel cobalt composite oxide (e.g., Li x Ni 1-y Co y O2; 0 < x ≤ 1, 0 < y < 1), lithium manganese nickel composite oxide having a spinel structure (e.g., Li x Mn 2-y Ni y O4; 0 < x ≤ 1, 0 < y < 2), lithium manganese cobalt composite oxide (e.g., Li x Mn y Co 1-y O2; 0 < x ≤ 1, 0 < y < 1), lithium iron phosphate (e.g., Li x FePO4; 0 < x ≤ 1), and lithium nickel cobalt manganese composite oxide (Li x Ni 1-y-z Co y Mn z O2; 0 < x ≤ 1, 0 < y < 1, 0 < z < 1, y + z < 1) is included. When these compounds are used as the positive electrode active material, the positive electrode potential can be increased.

[0088] When a room temperature molten salt is used as the electrolyte of the battery, lithium iron phosphate, Li xIt is preferable to use a positive electrode active material containing VPO4F (0 ≤ x ≤ 1), lithium manganese composite oxide, lithium nickel composite oxide, lithium nickel cobalt composite oxide, or a mixture thereof. These compounds have low reactivity with room-temperature molten salts, thus improving cycle life. Details of room-temperature molten salts will be described later.

[0089] The primary particle size of the positive electrode active material is preferably between 100 nm and 1 μm. Positive electrode active material with a primary particle size of 100 nm or more is easy to handle in industrial production. Positive electrode active material with a primary particle size of 1 μm or less allows for smooth diffusion of lithium ions within the solid.

[0090] The specific surface area of ​​the positive electrode active material is 0.1 m². 2 / g or more 10m 2 It is preferable that it is less than or equal to / g. 0.1m 2 A positive electrode active material with a specific surface area of ​​10m or more can adequately secure sites for Li ion intercalation and release. 2 Positive electrode active materials with a specific surface area of ​​less than / g are easy to handle in industrial production and can ensure good charge-discharge cycle performance.

[0091] A binder is added to fill the gaps between dispersed positive electrode active materials and to bond the positive electrode active materials to the positive electrode current collector. Examples of binders include polytetrafluoroethylene (PTFE), polyvinylidene fluoride (PVdF), fluororubber, polyacrylic acid compounds, imide compounds, carboxymethyl cellulose (CMC), and salts of CMC. One of these may be used as a binder, or two or more may be used in combination.

[0092] The positive electrode current collector, which includes other positive electrodes, has through holes with a diameter of 10 μm to 1000 μm, as described in the first embodiment, with a pitch of 3.0 mm to 100 mm. P / Me Pis ratio O U / Me U This differs from current collectors that have a ratio of 1.2 or more. Other positive electrode current collectors may be, for example, current collector foils without through holes. The positive electrode current collector is preferably an aluminum foil, or an aluminum alloy foil containing one or more elements selected from Mg, Ti, Zn, Ni, Cr, Mn, Fe, Cu, and Si.

[0093] The thickness of the aluminum foil or aluminum alloy foil is preferably 5 μm or more and 20 μm or less, and more preferably 15 μm or less. The purity of the aluminum foil is preferably 99% by mass or more. The content of transition metals such as iron, copper, nickel, and chromium in the aluminum foil or aluminum alloy foil is preferably 1% by mass or less.

[0094] Furthermore, the positive electrode current collector may include portions on its surface where the positive electrode active material-containing layer is not formed. These portions can function as positive electrode current collector tabs.

[0095] Other positive electrodes can be fabricated, for example, by using the same method as other negative electrodes, but with the positive electrode active material instead of the negative electrode active material.

[0096] 3) Electrolyte As the electrolyte, for example, a liquid non-aqueous electrolyte or a gel-type non-aqueous electrolyte can be used. A liquid non-aqueous electrolyte is prepared by dissolving an electrolyte salt as a solute in an organic solvent. The concentration of the electrolyte salt is preferably 0.5 mol / L or more and 2.5 mol / L or less.

[0097] Examples of electrolyte salts include lithium salts such as lithium perchlorate (LiClO4), lithium hexafluoride phosphate (LiPF6), lithium tetrafluoroborate (LiBF4), lithium arsenide hexafluoride (LiAsF6), lithium trifluoromethanesulfonate (LiCF3SO3), and lithium bistrifluoromethylsulfonylimide (LiN(CF3SO2)2), as well as mixtures thereof. The electrolyte salt is preferably resistant to oxidation even at high potentials, with LiPF6 being the most preferred.

[0098] Examples of organic solvents include cyclic carbonates such as propylene carbonate (PC), ethylene carbonate (EC), and vinylene carbonate (VC); linear carbonates such as diethyl carbonate (DEC), dimethyl carbonate (DMC), and methyl ethyl carbonate (MEC); cyclic ethers such as tetrahydrofuran (THF), 2-methyl tetrahydrofuran (2MeTHF), and dioxolane (DOX); linear ethers such as dimethoxyethane (DME) and diethoxyethane (DEE); and γ-butyrolactone (GBL), acetonitrile (AN), and sulfolane (SL). These organic solvents can be used alone or as mixed solvents.

[0099] Gel-like non-aqueous electrolytes are prepared by compounding a liquid non-aqueous electrolyte with a polymer material. Examples of polymer materials include polyvinylidene fluoride (PVdF), polyacrylonitrile (PAN), polyethylene oxide (PEO), or mixtures thereof.

[0100] Alternatively, in addition to liquid nonaqueous electrolytes and gel-type nonaqueous electrolytes, room-temperature molten salts (ionic melts) containing lithium ions, polymer solid electrolytes, and inorganic solid electrolytes may be used as nonaqueous electrolytes.

[0101] Room temperature molten salts (ionic melts) refer to organic salts consisting of a combination of organic cations and anions that can exist as liquids at room temperature (15°C to 25°C). Room temperature molten salts include room temperature molten salts that exist as liquids on their own, room temperature molten salts that become liquid when mixed with an electrolyte salt, room temperature molten salts that become liquid when dissolved in an organic solvent, or mixtures thereof. Generally, the melting point of room temperature molten salts used in secondary batteries is 25°C or lower. Also, organic cations generally have a quaternary ammonium skeleton.

[0102] Polymeric solid electrolytes are prepared by dissolving an electrolyte salt in a polymer material and then solidifying it.

[0103] Inorganic solid electrolytes are solid materials that have lithium ion conductivity. Here, lithium ion conductivity means 1 × 10⁻⁶ at 25°C. -6 This refers to exhibiting a lithium ion conductivity of S / cm or higher. Examples of inorganic solid electrolytes include oxide-based solid electrolytes and sulfide-based solid electrolytes. Specific examples of inorganic solid electrolytes are as follows.

[0104] As an oxide-based solid electrolyte, it has a NASICON (Sodium (Na) Super Ionic Conductor) type structure, and its general formula is Li 1+x It is preferable to use a lithium phosphate solid electrolyte represented by Mα2(PO4)3. In the above general formula, Mα is one or more selected from the group consisting of, for example, titanium (Ti), germanium (Ge), strontium (Sr), zirconium (Zr), tin (Sn), aluminum (Al), and calcium (Ca). The subscript x is in the range of 0 ≤ x ≤ 2.

[0105] A specific example of a lithium phosphate solid electrolyte having a NASICON-type structure is Li 1+x Al x Ti 2-x LATP compounds represented as (PO4)3 where 0.1 ≤ x ≤ 0.5; Li 1+x Al y Mβ 2-yA compound represented by (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; Li 1+x Al x Ge 2-x A compound represented by (PO4)3, where 0 ≦ x ≦ 2; and, Li 1+x Al x Zr 2-x A compound represented by (PO4)3, where 0 ≦ x ≦ 2; Li 1+x+y Al x Mγ 2-x Si y P 3-y O 12 A compound represented by, where Mγ is one or more selected from the group consisting of Ti and Ge, 0 < x ≦ 2, and 0 ≦ y < 3; Li 1+2x Zr 1-x Ca x Examples of compounds represented by (PO4)3, where 0 ≦ x < 1, can be given.

[0106] In addition, as the oxide-based solid electrolyte, in addition to the above lithium phosphate solid electrolyte, Li x PO y N z An amorphous LIPON compound represented by, where 2.6 ≦ x ≦ 3.5, 1.9 ≦ y ≦ 3.8, and 0.1 ≦ z ≦ 1.3 (for example, Li 2.9 PO 3.3 N 0.46 ); A garnet-type structure of La 5+x A x La 3-x Mδ2O 12 A compound represented by, 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; Li3Mδ 2-x L2O 12 A compound represented by, where Mδ is one or more selected from the group consisting of Nb and Ta, L may contain Zr, and 0 ≦ x ≦ 0.5; Li 7-3x Al x A compound represented by La3Zr3O 12 where 0 ≦ x ≦ 0.5; Li 5+x La3Mδ 2-x Zr x O12 Represented by , where Mδ is 1 or more selected from the group consisting of Nb and Ta, and 0 ≤ x ≤ 2, it is an LLZ compound (e.g., Li7La3Zr2O 12 ); and having a perovskite-type structure La 2 / 3-x Li x Examples include compounds represented as TiO3 where 0.3 ≤ x ≤ 0.7.

[0107] One or more of the above compounds can be used as a solid electrolyte. Two or more of the above solid electrolytes may also be used.

[0108] 4) Separator The separator is formed from a porous film containing, for example, polyethylene (PE), polypropylene (PP), cellulose, or polyvinylidene fluoride (PVdF), or from a synthetic resin nonwoven fabric. From a safety standpoint, it is preferable to use a porous film made of polyethylene or polypropylene. This is because these porous films can melt at a certain temperature and interrupt the electric current.

[0109] 5) Exterior components For example, the outer packaging material can be a container made of laminate film or a metal container.

[0110] The thickness of the laminating film is, for example, 0.5 mm or less, and preferably 0.2 mm or less.

[0111] As the laminate film, a multilayer film is used that includes multiple resin layers and a metal layer interposed between these resin layers. The resin layers include polymer materials such as polypropylene (PP), polyethylene (PE), nylon, and polyethylene terephthalate (PET). The metal layer is preferably made of aluminum foil or aluminum alloy foil for weight reduction. The laminate film can be molded into the shape of an exterior component by sealing it by heat fusion.

[0112] The thickness of the metal container wall is, for example, 1 mm or less, more preferably 0.5 mm or less, and even more preferably 0.2 mm or less.

[0113] Metal containers are made from, for example, aluminum or aluminum alloys. Aluminum alloys preferably contain elements such as magnesium, zinc, and silicon. If aluminum alloys contain transition metals such as iron, copper, nickel, and chromium, their content is preferably 100 ppm by mass or less.

[0114] The shape of the exterior components is not particularly limited. For example, the exterior components may be flat (thin), rectangular, cylindrical, coin-shaped, or button-shaped. The exterior components can be appropriately selected according to the battery dimensions and intended use.

[0115] 6) Negative terminal The negative electrode terminal can be formed from a material that is electrochemically stable at the Li absorption / release potential of the negative electrode active material described above, and is also conductive. Specifically, the material for the negative electrode terminal can be copper, nickel, stainless steel, or aluminum, or an aluminum alloy containing at least one element selected from the group consisting of Mg, Ti, Zn, Mn, Fe, Cu, and Si. It is preferable to use aluminum or an aluminum alloy as the material for the negative electrode terminal. It is preferable that the negative electrode terminal be made of the same material as the negative electrode current collector in order to reduce contact resistance with the negative electrode current collector.

[0116] 7) Positive terminal The positive terminal has a potential range of 3V to 4.5V relative to the oxidation-reduction potential of lithium (vs.Li / Li + The positive electrode terminal can be formed from an electrically stable and conductive material. Examples of positive electrode terminal materials include aluminum, or an aluminum alloy containing at least one element selected from the group consisting of Mg, Ti, Zn, Mn, Fe, Cu, and Si. It is preferable that the positive electrode terminal be formed from the same material as the positive electrode current collector in order to reduce contact resistance with the positive electrode current collector.

[0117] Next, the secondary battery according to the embodiment will be described in more detail with reference to the drawings.

[0118] Figure 3 is a schematic cross-sectional view showing 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.

[0119] The secondary battery 100 shown in Figures 3 and 4 comprises a bag-shaped outer casing member 2 shown in Figure 3, an 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 bag-shaped outer casing member 2. The electrolyte (not shown) is held by the electrode group 1.

[0120] The bag-shaped outer packaging member 2 consists of a laminate film comprising two resin layers and a metal layer interposed between them.

[0121] As shown in Figure 3, electrode group 1 is a flat, wound electrode group. As shown in Figure 4, the flat, wound electrode group 1 includes a negative electrode 3, a separator 4, and a positive electrode 5. The separator 4 is interposed between the negative electrode 3 and the positive electrode 5.

[0122] The negative electrode 3 includes a negative electrode current collector 3a and a negative electrode active material containing layer 3b. In the portion of the negative electrode 3 located in the outermost shell of the wound electrode group 1, the negative electrode active material containing layer 3b is formed only on the inner surface side of the negative electrode current collector 3a, as shown in Figure 4. In the other portions of the negative electrode 3, the negative electrode active material containing layer 3b is formed on both sides of the negative electrode current collector 3a.

[0123] The positive electrode 5 includes a positive electrode current collector 5a and positive electrode active material-containing layers 5b formed on both sides thereof.

[0124] As shown in Figure 3, the negative electrode terminal 6 and the positive electrode terminal 7 are located near the outer edge of the wound electrode group 1. The negative electrode terminal 6 is connected to the outermost part of the negative electrode current collector 3a. The positive electrode terminal 7 is connected to the outermost part of the positive electrode current collector 5a. These negative electrode terminals 6 and positive electrode terminals 7 extend outward from the opening of the bag-shaped outer casing member 2. A thermoplastic resin layer is installed on the inner surface of the bag-shaped outer casing member 2, and the opening is closed by heat-sealing this layer.

[0125] The secondary battery according to this embodiment is not limited to the secondary battery with the configuration shown in Figures 3 and 4, but may also be a battery with the configuration shown in Figures 5 and 6, for example.

[0126] Figure 5 is a schematic partially cutaway perspective view showing another example of a secondary battery. Figure 6 is an enlarged cross-sectional view of section B of the secondary battery shown in Figure 5.

[0127] The secondary battery 100 shown in Figures 5 and 6 comprises an electrode group 1 shown in Figures 5 and 6, an outer casing member 2 shown in Figure 5, and an electrolyte (not shown). The electrode group 1 and the electrolyte are housed within the outer casing member 2. The electrolyte is held within the electrode group 1.

[0128] The exterior component 2 consists of a laminate film comprising two resin layers and a metal layer interposed between them.

[0129] As shown in Figure 6, electrode group 1 is a stacked electrode group. The stacked electrode group 1 has a structure in which negative electrodes 3 and positive electrodes 5 are stacked alternately with a separator 4 interposed between them.

[0130] The electrode group 1 includes a plurality of negative electrodes 3. Each of the plurality of negative electrodes 3 comprises a negative electrode current collector 3a and a negative electrode active material-containing layer 3b supported on both sides of the negative electrode current collector 3a. The electrode group 1 also includes a plurality of positive electrodes 5. Each of the plurality of positive electrodes 5 comprises a positive electrode current collector 5a and a positive electrode active material-containing layer 5b supported on both sides of the positive electrode current collector 5a.

[0131] Each negative electrode 3's negative electrode current collector 3a includes a portion on one side where the negative electrode active material-containing layer 3b is not supported on any surface. This portion functions as a negative electrode current collector tab 3c. As shown in Figure 6, the negative electrode current collector tab 3c does not overlap with the positive electrode 5. Furthermore, multiple negative electrode current collector tabs 3c are electrically connected to a strip-shaped negative electrode terminal 6. The tip of the strip-shaped negative electrode terminal 6 is extended to the outside of the outer casing member 2.

[0132] Although not shown in the diagram, the positive electrode current collector 5a of each positive electrode 5 includes a portion on one side where the positive electrode active material-containing layer 5b is not supported on any surface. This portion functions as a positive electrode current collector tab. The positive electrode current collector tab, like the negative electrode current collector tab 3c, does not overlap with the negative electrode 3. Furthermore, the positive electrode current collector tab is located on the opposite side of the electrode group 1 from the negative electrode current collector tab 3c. The positive electrode current collector tab is electrically connected to a strip-shaped positive electrode terminal 7. The tip of the strip-shaped positive electrode terminal 7 is located on the opposite side from the negative electrode terminal 6 and is extended to the outside of the outer casing member 2.

[0133] The secondary battery according to the second embodiment includes the electrodes according to the first embodiment. Therefore, such a secondary battery can exhibit high rate performance and high lifespan performance.

[0134] (Third embodiment) According to the third embodiment, a battery pack is provided. This battery pack comprises a plurality of secondary batteries according to the second embodiment.

[0135] In such a battery pack, each individual cell may be arranged in series or parallel connections, or a combination of series and parallel connections may be used.

[0136] Next, an example of a battery pack according to the embodiment will be described with reference to the drawings.

[0137] Figure 7 is a schematic perspective view showing an example of a battery pack. The battery pack 200 shown in Figure 7 comprises five single cells 100a to 100e, four busbars 21, a positive electrode lead 22, and a negative electrode lead 23. Each of the five single cells 100a to 100e is a secondary battery according to the second embodiment.

[0138] The busbar 21 connects, for example, the negative terminal 6 of one cell 100a to the positive terminal 7 of the adjacent cell 100b. In this way, the five cells 100 are connected in series by four busbars 21. That is, the battery pack 200 in Figure 7 is a battery pack with five cells in series. Although not illustrated, in a battery pack containing multiple cells that are electrically connected in parallel, the multiple cells can be electrically connected, for example, by connecting multiple negative terminals to each other and multiple positive terminals to each other by busbars.

[0139] The positive terminal 7 of at least one of the five single cells 100a to 100e is electrically connected to the positive lead 22 for external connection. In addition, the negative terminal 6 of at least one of the five single cells 100a to 100e is electrically connected to the negative lead 23 for external connection.

[0140] The battery pack according to the third embodiment comprises the secondary battery according to the second embodiment. Therefore, it can exhibit high rate performance and long life performance.

[0141] (Fourth embodiment) According to the fourth embodiment, a battery pack is provided. This battery pack comprises a battery pack according to the third embodiment. This battery pack may also comprise a single secondary battery according to the second embodiment instead of the battery pack according to the third embodiment.

[0142] The battery pack may further include a protection circuit. The protection circuit has the function of controlling the charging and discharging of the secondary battery. Alternatively, a circuit included in a device that uses the battery pack as a power source (e.g., electronic equipment, automobile, etc.) may be used as the protection circuit for the battery pack.

[0143] Furthermore, such a battery pack may also be equipped with external terminals for power supply. These external terminals are for outputting current from the secondary battery to the outside and / or for inputting current from the outside to the secondary battery. In other words, when the battery pack is used as a power source, current is supplied to the outside through the external terminals. Also, when charging the battery pack, the charging current (including regenerative energy from the power of an automobile, etc.) is supplied to the battery pack through the external terminals.

[0144] Next, an example of a battery pack according to the embodiment will be described with reference to the drawings.

[0145] Figure 8 is an exploded perspective view schematically showing an example of a battery pack. Figure 9 is a block diagram showing an example of the electrical circuit of the battery pack shown in Figure 8.

[0146] The battery pack 300 shown in Figures 8 and 9 comprises a housing container 31, a lid 32, a protective sheet 33, a battery pack 200, a printed circuit board 34, wiring 35, and an insulating plate (not shown).

[0147] The container 31 shown in Figure 8 is a rectangular-bottomed rectangular container. The container 31 is configured to accommodate a protective sheet 33, a battery pack 200, a printed circuit board 34, and wiring 35. The lid 32 has a rectangular shape. The lid 32 covers the container 31, thereby housing the battery pack 200 and the other components. The container 31 and the lid 32 are provided with openings or connection terminals for connecting to external devices, etc., although these are not shown in the figures.

[0148] The battery pack 200 comprises multiple individual cells 100, a positive electrode lead 22, a negative electrode lead 23, and an adhesive tape 24.

[0149] At least one of the multiple single cells 100 is a secondary battery according to the second embodiment. Each of the multiple single cells 100 is electrically connected in series as shown in Figure 9. The multiple single cells 100 may also be electrically connected in parallel, or they may be connected in a combination of series and parallel connections. When the multiple single cells 100 are connected in parallel, the battery capacity increases compared to when they are connected in series.

[0150] The adhesive tape 24 fastens multiple single cells 100 together. Alternatively, heat-shrinkable tape may be used to secure the multiple single cells 100 instead of the adhesive tape 24. In this case, protective sheets 33 are placed on both sides of the battery pack 200, the heat-shrinkable tape is wrapped around it, and then the heat-shrinkable tape is heat-shrinked to bundle the multiple single cells 100 together.

[0151] One end of the positive lead 22 is connected to the battery pack 200. One end of the positive lead 22 is electrically connected to the positive terminal of one or more single cells 100. One end of the negative lead 23 is connected to the battery pack 200. One end of the negative lead 23 is electrically connected to the negative terminal of one or more single cells 100.

[0152] The printed circuit board 34 is installed along one of the shorter sides of the inner surface of the housing container 31. The printed circuit board 34 includes a positive terminal connector 342, a negative terminal connector 343, a thermistor 345, a protection circuit 346, wiring 342a and 343a, an external terminal 350 for energization, a positive side wiring (positive wiring) 348a, and a negative side wiring (negative wiring) 348b. One main surface of the printed circuit board 34 faces one side of the battery pack 200. An insulating plate (not shown) is interposed between the printed circuit board 34 and the battery pack 200.

[0153] 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.

[0154] The thermistor 345 is fixed to one main surface of the printed circuit board 34. The thermistor 345 detects the temperature of each of the single cells 100 and transmits the detection signal to the protection circuit 346.

[0155] The external power supply terminal 350 is fixed to the other main surface of the printed circuit board 34. The external power supply terminal 350 is electrically connected to equipment located outside the battery pack 300. The external power supply terminal 350 includes a positive terminal 352 and a negative terminal 353.

[0156] The protection circuit 346 is fixed to the other main surface of the printed circuit board 34. The protection circuit 346 is connected to the positive terminal 352 via the positive side wiring 348a. The protection circuit 346 is connected to the negative terminal 353 via the negative side wiring 348b. The protection circuit 346 is also electrically connected to the positive side connector 342 via wiring 342a. The protection circuit 346 is also electrically connected to the negative side connector 343 via wiring 343a. Furthermore, the protection circuit 346 is electrically connected to each of the multiple single cells 100 via wiring 35.

[0157] The protective sheet 33 is positioned on both inner surfaces in the long-side direction of the housing container 31 and on the inner surface in the short-side direction facing the printed circuit board 34 via the battery pack 200. The protective sheet 33 is made of, for example, resin or rubber.

[0158] The protection circuit 346 controls the charging and discharging of multiple single cells 100. The protection circuit 346 also disconnects the electrical connection between the protection circuit 346 and the external terminals 350 (positive terminal 352, negative terminal 353) for supplying power to external devices, based on a detection signal transmitted from the thermistor 345 or a detection signal transmitted from an individual single cell 100 or a battery pack 200.

[0159] An example of a detection signal transmitted from the thermistor 345 is a signal indicating that the temperature of a single cell 100 is above a predetermined temperature. An example of a detection signal transmitted from an individual single cell 100 or a battery pack 200 is a signal indicating that overcharging, over-discharging, or overcurrent has been detected in a single cell 100. When detecting overcharging, etc., in an individual single cell 100, the battery voltage may be detected, or the positive electrode potential or negative electrode potential may be detected. In the latter case, a lithium electrode to be used as a reference electrode is inserted into each individual single cell 100.

[0160] Furthermore, the protection circuit 346 may be a circuit included in a device that uses the battery pack 300 as a power source (for example, an electronic device, an automobile, etc.).

[0161] Furthermore, as described above, the battery pack 300 is equipped with an external terminal 350 for power supply. Therefore, the battery pack 300 can output current from the battery pack 200 to an external device and input current from an external device to the battery pack 200 via the external terminal 350. In other words, when the battery pack 300 is used as a power source, current from the battery pack 200 is supplied to the external device through the external terminal 350. Also, when charging the battery pack 300, charging current from an external device is supplied to the battery pack 300 through the external terminal 350. When this battery pack 300 is used as an on-board battery, the regenerative energy of the vehicle's power can be used as the charging current from the external device.

[0162] The battery pack 300 may have multiple battery packs 200. In this case, the multiple battery packs 200 may be connected in series, in parallel, or in a combination of series and parallel connections. The printed circuit board 34 and wiring 35 may also be omitted. In this case, the positive lead 22 and the negative lead 23 may be used as the positive terminal 352 and negative terminal 353 of the external terminal 350 for energization, respectively.

[0163] Such battery packs are used in applications where excellent cycle performance is required, for example, when drawing high currents. Specifically, these battery packs are used as power supplies for electronic devices, stationary batteries, and on-board batteries for various vehicles. Examples of electronic devices include digital cameras. These battery packs are particularly suitable for use as on-board batteries.

[0164] The battery pack according to the fourth embodiment comprises a secondary battery according to the second embodiment or a battery pack according to the third embodiment. Therefore, the battery pack has high rate performance and lifespan performance. [Examples]

[0165] Examples are described below, but the embodiments are not limited to those described below.

[0166] (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 carboxymethylcellulose and styrene butadiene rubber (SBR) as a binder were added to water and mixed to obtain a slurry. This slurry was applied to one side of a current collector made of 12 μm thick aluminum foil, dried, and then pressed to produce an electrode precursor with a porosity of 25% (excluding the current collector). The impurity concentrations in the current collector were as shown in Table 1.

[0167] The obtained electrode precursor was subjected to a porous current collector treatment by holding it in a hydrated environment with the dew point shown in Table 1 for the time shown in Table 1. For example, in Example 1, the precursor was held in a hydrated environment with a dew point of 15°C for 6 hours. After being held in the hydrated environment, the coating film was completely dried under vacuum to form an active material-containing layer and obtain the electrode.

[0168] (Example 10) An electrode precursor was obtained in the same manner as in Example 1, except that the current collector was changed from aluminum foil to copper foil. The obtained electrode precursor was subjected to a current collector porosity treatment under the moisture-containing environment conditions shown in Table 1. After being kept in a moisture-containing environment, the coating film was completely dried under vacuum to form an active material-containing layer and obtain an electrode.

[0169] (Comparative Example 1) Electrodes were fabricated in the same manner as in Example 1, except that aluminum foil with the impurity concentrations shown in Table 1 was used as the current collector, and the conditions for holding the precursor were changed to longer holding in a dry environment as shown in Table 1.

[0170] (Comparative Example 2) An electrode precursor was obtained in the same manner as in Example 1, except that aluminum foil with the impurity concentrations shown in Table 1 was used as the current collector. The obtained electrode precursor was subjected to a current collector porosity treatment under the moisture-containing environment conditions shown in Table 1. After being kept in a moisture-containing environment, the coating film was completely dried under vacuum to form an active material-containing layer and obtain an electrode.

[0171] (Comparative Example 3) An electrode precursor was obtained in the same manner as in Example 1, except that aluminum foil with the impurity concentrations shown in Table 1 was used as the current collector. The obtained electrode precursor was subjected to a current collector porosity treatment under the moisture-containing environment conditions shown in Table 1. After being kept in a moisture-containing environment, the coating film was completely dried under vacuum to form an active material-containing layer and obtain an electrode.

[0172] (Comparative Example 4) An electrode precursor was obtained in the same manner as in Example 1, except that the current collector was replaced with aluminum foil that had been pre-porousized by mechanical treatment, and the pressing conditions were adjusted so that the void ratio (excluding the current collector) was 38%. The obtained electrode precursor was held under the dry conditions shown in Table 1. After being held in a dry environment, the coating film was completely dried under vacuum to form an active material-containing layer and obtain an electrode.

[0173] (Examples 11 to 13) An electrode precursor was obtained in the same manner as in Example 1, except that aluminum foil with the impurity concentrations shown in Table 2 was used as the current collector, and the active material was changed to an oxide having the composition shown in Table 2. The obtained electrode precursor was subjected to a current collector porosity treatment under the moisture-containing environment conditions shown in Table 2. After being kept in a moisture-containing environment, the coating film was completely dried under vacuum to form an active material-containing layer, and an electrode was obtained.

[0174] (Example 14) An electrode precursor was obtained in the same manner as in Example 1, except that aluminum foil with the impurity concentrations shown in Table 3 was used as the current collector, and the active material was changed to an oxide having the composition shown in Table 3. The obtained electrode precursor was subjected to a current collector porosity treatment under the moisture-containing environment conditions shown in Table 3. After being kept in a moisture-containing environment, the coating film was completely dried under vacuum to form an active material-containing layer, and an electrode was obtained.

[0175] (Comparative Examples 5 and 6) An electrode precursor was obtained in the same manner as in Example 14, except that aluminum foil with the impurity concentrations shown in Table 3 was used as the current collector, and the active material was changed to an oxide having the composition shown in Table 3. The obtained electrode precursor was held in a hydrated environment under the conditions shown in Table 3. After being held in a hydrated environment, the coating film was completely dried under vacuum to form an active material-containing layer, and an electrode was obtained.

[0176] (Examples 15 and 16) First, 100 parts by mass of lithium iron phosphate (LiFePO4) 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 carboxymethylcellulose and polyurethane as a binder were added to water and mixed to obtain a slurry. This slurry was applied to one side of a current collector made of 12 μm thick aluminum foil, dried, and then pressed to produce an electrode precursor with a porosity of 25% (excluding the current collector). The impurity concentrations in the current collector were as shown in Table 4.

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

[0178] (Comparative Example 7) First, as the active material, lithium nickel cobalt manganese composite oxide (LiNi 0.8 Co 0.1 Mn 0.1 A slurry was obtained by mixing 100 parts by mass of O2 powder, 5 parts by mass of acetylene black as a conductive agent, and 5 parts by mass of a mixture of carboxymethylcellulose and polyurethane as a binder with water. This slurry was applied to one side of a current collector made of 12 μm thick aluminum foil, and after drying, it was pressed to produce an electrode precursor with a porosity of 25% (excluding the current collector). The impurity concentrations in the current collector were as shown in Table 4.

[0179] The obtained electrode precursor was subjected to a current collector porosity treatment under the moisture-containing environment conditions shown in Table 4. After being maintained in a moisture-containing environment, the coating film was completely dried under vacuum to form an active material-containing layer, and the electrode was obtained.

[0180] [Table 1]

[0181] [Table 2]

[0182] [Table 3]

[0183] [Table 4]

[0184] <Checking the electrodes> The obtained electrodes were observed and various measurements were taken using the method described above. Specifically, the diameter of the through-holes on the current collector, the pitch, and the ratio of oxygen atoms to metal atoms in the area around the holes and in the non-opening areas were measured. P / Me P and O U / Me U The pH of the electrode material constituting the active material-containing layer after washing with water, and the porosity of the active material-containing layer were measured. The measurement results are summarized in Tables 5 to 8.

[0185] [Table 5]

[0186] [Table 6]

[0187] [Table 7]

[0188] [Table 8]

[0189] <Electrochemical Measurement> The electrodes obtained in each of the above examples were used as the working electrode, Li metal as the counter electrode and reference electrode, and coin cells were fabricated using the electrolyte to evaluate their electrochemical performance.

[0190] The electrolyte was prepared as follows: Ethylene carbonate (EC) and diethyl carbonate (DEC) were mixed in a volume ratio of 1:2 to obtain a mixed solvent. The electrolyte was then prepared by dissolving a LiPF6-supporting salt in the obtained mixed solvent at a concentration of 1 mol / L.

[0191] In this embodiment, since lithium metal is used as the counter electrode in this measurement coin cell, the electrode potential of the embodiment and comparative example is nobler than that of the counter electrode and therefore functions as the positive electrode. The definition of charge and discharge is reversed when the electrodes of Embodiments 1 to 14 and Comparative Examples 1 to 6 are used as the negative electrode. To avoid confusion, in this embodiment, the direction in which lithium ions are inserted into the electrode is called charging, and the direction in which they are removed is called discharging. Note that the electrodes of Embodiments 1 to 14 and Comparative Examples 1 to 6 function as negative electrodes when combined with known positive electrode materials.

[0192] Furthermore, the fabricated electrochemical measurement cell was used to measure 1.0V to 3.0V (Li / Li) relative to a metallic lithium electrode. + The batteries were charged and discharged within a specific potential range. To investigate the rapid discharge performance, after confirming the discharge capacity at 0.2C (time discharge rate), the batteries were charged again with a charging current of 0.2C, and the rapid discharge capacity at 5C was confirmed at room temperature. The discharge capacity retention rate (%) was then calculated by dividing the 5C discharge capacity by the 0.2C discharge capacity and multiplying by 100. The 5C / 0.2C discharge capacity retention rate (%) serves as an indicator for evaluating rapid charge and discharge performance.

[0193] Furthermore, the cells of the examples and comparative examples were subjected to a voltage of 1.0V to 3.0V (Li / Li) relative to the metallic lithium electrode. +A life test was conducted at 25°C by repeating 0.2C charge and discharge within the potential range of ( ). Under this condition, 1000 cycles of repeated charge and discharge were performed (one cycle consists of charge and discharge), and the discharge capacity retention rate after 1000 cycles was examined. To confirm the discharge capacity retention rate after 1000 cycles, charge and discharge were performed again at 0.2C, and the cycle capacity retention rate (%) when the initial discharge capacity was set to 100% was calculated by dividing the discharge capacity after 1000 cycles by the initial discharge capacity and multiplying by 100. The discharge capacity retention rate after 1000 cycles serves as an indicator for evaluating the cycle life performance. The above results are summarized in Tables 9 to 12.

[0194] <Durability confirmation> Regarding the electrodes obtained in each of the above examples, the durability of the current collector against roll pressing was evaluated. Specifically, continuous pressing was performed at a pressing pressure such that the porosity of the active material-containing layer was 25%, and the presence or absence of breakage of the current collector was confirmed during that time. The confirmed results are shown in Tables 9 to 12. When no breakage of the current collector occurred, it was judged that there was durability, and it was indicated by a white circle (for example, Examples 1 to 10). When it was confirmed that breakage of the current collector occurred, it was judged that there was no durability, and it was indicated by a cross (for example, Comparative Examples 2 to 4).

[0195]

Table 9

[0196]

Table 10

[0197]

Table 11

[0198]

Table 12

[0199] As shown in Table 9, in Examples 1 to 10, which used niobium titanium oxide (Nb2TiO7) as the active material, higher rapid charge / discharge performance was obtained compared to Comparative Examples 1 to 3, and higher lifespan performance was obtained compared to Comparative Examples 2 to 4. In Comparative Example 4, the current collector could not withstand the pressing to increase the density of the electrodes and broke.

[0200] In Comparative Example 1, the electrode precursor was held under dry conditions, preventing the current collector from becoming porous, and thus the rapid charge-discharge performance was not improved. In Comparative Examples 2 and 3, although through holes were formed in the current collector, only a few large-diameter through holes were formed, resulting in an uneven distribution of charge and discharge within the electrode, which in turn reduced the rapid charge-discharge performance. Furthermore, the large through holes reduced the lifespan performance. In Comparative Example 4, instead of performing porosification treatment in a humid environment, a pre-porous current collector was used. Because porosification treatment was not performed, the area around the holes was not protected by metal acid hydroxide, and the effect of improving lifespan performance was not obtained. In addition, because a current collector with low strength was used, it was not possible to increase the density of the active material-containing layer.

[0201] As shown in Table 10, in Examples 11 to 13, where various niobium oxides were used as the active material, good rapid charge / discharge performance and lifespan performance were obtained.

[0202] As shown in Table 11, in Example 14, which used titanium oxide as the active material, higher rapid charge / discharge performance was obtained compared to Comparative Examples 5 and 6, and higher lifespan performance was obtained compared to Comparative Example 6. In Comparative Example 5, the current collector could not withstand the pressing process to increase the density of the electrodes and broke.

[0203] Active material H used in Comparative Example 5 0.11 TiO 2.11 The acidity was strong, and when held in a hydrated environment, the porosity of the current collector became excessive. Conversely, the active material Li4Ti5O used in Comparative Example 6 12 It is highly basic, and even when held in a hydrated environment, it was not possible to make the current collector porous.

[0204] As shown in Table 12, in Examples 15 and 16, which used lithium iron phosphate, a typical cathode active material, as the active material, higher rapid charge-discharge performance and lifespan were obtained compared to Comparative Example 7, which used lithium nickel cobalt manganese composite oxide, another typical cathode active material.

[0205] The nickel-cobalt-manganese composite oxide used in Comparative Example 7 was strongly basic, and even when held in a hydrated environment, it was not possible to create a porous current collector.

[0206] According to the one or more embodiments and examples described above, an electrode is provided. The electrode comprises a foil-shaped current collector containing metal and an active material-containing layer on the current collector. The current collector has a plurality of through holes with diameters of 10 μm to 1000 μm, opened at a pitch of 3.0 mm to 100 mm. The amount of metal atomic weight Me in the area around the hole, within 5% of the diameter of the through hole from the outer circumference of the through hole. P Oxygen atomic weight relative to O P Ratio O P / Me P However, the amount of metal atomic weight Me in non-opening areas that are more than 1.5 times the diameter of the through-hole from the outer circumference of the through-hole is... U Oxygen atomic weight relative to O U Ratio O U / Me U This is more than 1.2 times. The electrodes with the above configuration can provide secondary batteries and battery packs with high rate performance and lifespan performance.

[0207] While several embodiments of the present invention have been described, these embodiments are presented as examples only and are not intended to limit the scope of the invention. These novel embodiments can be carried out in a variety of other forms, and various omissions, substitutions, and modifications can be made without departing from the spirit of the invention. These embodiments and their variations are included in the scope and spirit of the invention, as well as in the claims of the invention and its equivalents.

[0208] Several embodiments of the present invention are described below. [1] A current collector in the shape of a foil containing metal, the active material-containing layer on the current collector and comprises: the current collector has a plurality of through-holes with a diameter of 10 μm or more and 1000 μm or less, which are opened at a pitch of 3.0 mm or more and 100 mm or less, the ratio O P of oxygen atomic weight O P to metal atomic weight Me P / Me P in the hole peripheral portion within 5% of the diameter of the through-hole from the outer periphery of the through-hole is 1.2 times or more than the ratio O U of oxygen atomic weight O U to metal atomic weight Me U / Me U in the non-opening portion more than 1.5 times the diameter of the through-hole from the outer periphery of the through-hole, and an electrode. [2] The electrode according to [1], wherein the current collector contains aluminum. [3] The electrode according to [1], wherein the current collector contains aluminum with an impurity concentration exceeding 0.15% and less than 4%. [4] The electrode according to any one of [1] to [3], wherein the active material-containing layer has no through-holes. [5] The electrode according to any one of [1] to [4], wherein the porosity of the active material-containing layer is 36% or less. [6] The electrode according to any one of [1] to [5], wherein the active material-containing layer is provided on both main surfaces of the front side and the back side of the current collector. [7] The electrode according to any one of [1] to [6], wherein the active material-containing layer contains a water-soluble binder. [8] The electrode according to any one of [1] to [7], wherein the active material-containing layer contains an oxide containing at least one selected from the group consisting of titanium, niobium, tungsten, molybdenum, vanadium, iron, tin, and silicon. [9] The electrode according to any one of [1] to [7], wherein the active material-containing layer contains at least one active material selected from the group consisting of phosphoric acid salts and pyrophosphates. [[ID=4))

[10] A positive electrode, a negative electrode, and an electrolyte A secondary battery comprising, A secondary battery in which at least one of the positive electrode and the negative electrode is an electrode described in any one of [1] to [9]. A battery pack comprising the rechargeable batteries described in

[11] and

[10] .

[12] External terminals for power supply, Protection circuit and The battery pack described in

[11] further comprises the following:

[13] comprising a plurality of the aforementioned secondary batteries, The battery pack described in

[11] or

[12] , wherein the secondary batteries are electrically connected in series, in parallel, or in a combination of series and parallel. [Explanation of Symbols]

[0209] 1…Electrode group, 2…Outer casing, 3…Negative electrode, 3a…Negative electrode current collector, 3b…Negative electrode active material-containing layer, 3c…Negative electrode current collector tab, 4…Separator, 5…Positive electrode, 5a…Positive electrode current collector, 5b…Positive electrode active material-containing layer, 6…Negative electrode terminal, 7…Positive electrode terminal, 10…Electrode, 10a…Current collector, 10b…Active material-containing layer, 10c…Current collector tab, 11…Through hole, 12…Around the hole, 13…Non-opening, 13a…Measurement point, 21…Bus bar, 22…Positive electrode side lead, 22a…Other end, 23…Negative electrode side Lead, 23a...other end, 24...adhesive tape, 31...container, 32...lid, 33...protective sheet, 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. A foil-shaped current collector containing metal, The active material-containing layer on the current collector and It is equipped with, The current collector has multiple through holes with a diameter of 10 μm or more and 1000 μm or less, opened at a pitch of 3.0 mm or more and 100 mm or less. The amount of metal atomic weight Me in the area surrounding the through hole, from the outer circumference of the through hole to within 5% of the diameter of the through hole. P Oxygen atomic weight relative to O P Ratio O P / Me P However, the amount of metal atomic weight Me in the non-opening area, which is located at a distance of 1.5 times or more the diameter of the through-hole from the outer circumference of the through-hole, is... U Oxygen atomic weight relative to O U Ratio O U / Me U An electrode that is 1.2 times or more in proportion to the given value.

2. The electrode according to claim 1, wherein the current collector comprises aluminum.

3. The electrode according to claim 1, wherein the current collector contains aluminum with an impurity concentration of more than 0.15% and less than 4%.

4. The electrode according to any one of claims 1 to 3, wherein the active material-containing layer does not have through holes.

5. The electrode according to any one of claims 1 to 3, wherein the porosity of the active material-containing layer is 36% or less.

6. The electrode according to any one of claims 1 to 3, wherein the active material-containing layer is provided on both the front and back main surfaces of the current collector.

7. The electrode according to any one of claims 1 to 3, wherein the active material-containing layer comprises a water-soluble binder.

8. The electrode according to any one of claims 1 to 3, wherein the active material-containing layer contains an oxide comprising at least one selected from the group consisting of titanium, niobium, tungsten, molybdenum, vanadium, iron, tin, and silicon.

9. The electrode according to any one of claims 1 to 3, wherein the active material-containing layer contains at least one selected from the group consisting of phosphoric acid salts and pyrophosphate salts.

10. Positive electrode and, The negative electrode and, Electrolytes and A secondary battery comprising, A secondary battery in which at least one of the positive electrode and the negative electrode is the electrode described in any one of claims 1 to 3.

11. A battery pack comprising the secondary battery described in claim 10.

12. External terminals for power supply, Protection circuit and The battery pack according to claim 11, further comprising the above.

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

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