Method for manufacturing electrodes, method for manufacturing energy storage devices, electrodes for energy storage devices, doping method

Abstract

This invention provides a method for manufacturing electrodes with high Coulomb efficiency that can rapidly and uniformly dope charge carriers into a composite layer without using electrolytes or solid electrolytes, and that exhibit excellent cycle characteristics. [Solution] A method for manufacturing an electrode for an energy storage device, comprising: step A, pressing a carrier coating having a carrier source on a substrate onto an asphalt layer; step B, releasing the pressure to dope the asphalt layer with charge carriers; and step C, removing the substrate from the asphalt layer.

Description

Technical Field

[0001] The present invention relates to a method for manufacturing an electrode doped with charge carriers, a method for manufacturing a power storage device, an electrode for a power storage device, and a method for doping charge carriers.

Background Art

[0002] Power storage devices play an important role in mobile bodies such as hybrid vehicles, plug-in hybrid vehicles, and electric vehicles, as well as in power storage systems. These are being positioned as important key devices from the perspective of economic growth, and with the recent increase in demand, there is a strong demand for improving the productivity of power storage devices. The main types of power storage devices are secondary batteries and capacitors (condensers).

[0003] Commonly used secondary batteries include lead-acid batteries, nickel-metal hydride (Ni-MH) batteries, nickel-cadmium (Ni-Cd) batteries, lithium-ion batteries, etc., which are generally in circulation. In particular, lithium-ion batteries fall under non-aqueous electrolyte secondary batteries, and due to their characteristics of being small, lightweight, high voltage, and having no memory effect, their demand is increasing rapidly.

[0004] A non-aqueous electrolyte secondary battery is a general term for a battery system that uses an electrolyte that does not contain water as the main component and is a rechargeable power storage device. Specific examples include lithium-ion batteries, lithium polymer batteries, lithium all-solid-state batteries, lithium-air batteries, lithium-sulfur batteries, sodium-ion batteries, sodium-sulfur batteries, potassium-ion batteries, polyvalent ion batteries, fluoride ion batteries, etc. These batteries are composed of a positive electrode, a negative electrode, an electrolyte, and an exterior body (housing case), and when the electrolyte has fluidity, a separator is interposed between the positive electrode and the negative electrode.

[0005] Other typical capacitors include aluminum electrolytic capacitors, ceramic capacitors, electric double-layer capacitors, and lithium-ion capacitors. Of these, lithium-ion capacitors are energy storage devices that, while based on the basic principle of electric double-layer capacitors, use an active material that enables the absorption and release of lithium ions in either the positive or negative electrode material, and a non-aqueous electrolyte.

[0006] In recent years, development has progressed on energy storage devices that use sodium ions, potassium ions, magnesium ions, calcium ions, and other elements as alternatives to lithium ions, which act as charge carriers. Such ion capacitors consist of a positive electrode, a negative electrode, a separator, an electrolyte solution or electrolyte, and an outer casing (also called a battery case, storage case, or casing).

[0007] Typical electrode components include a current collector and an assortment layer (active material layer). For example, in lithium-ion batteries, aluminum foil or copper foil is used as the current collector, and an assortment layer containing active materials such as lithium transition metal oxide or graphite is provided on top of these.

[0008] Electrodes come in various types, including positive electrodes, negative electrodes, reference electrodes, and bipolar electrodes. All can be manufactured using an active material, a binder, and a current collector. Conductive additives can also be added to increase the conductivity of the electrode. In a typical electrode manufacturing process, a slurry (a paste-like, fluid mixture) is applied to or filled into a current collector. After the dispersion medium contained in the slurry is vaporized and removed (dried), the mixture layer is pressure-regulated using a roll press or similar device. This slurry consists of liquid and solid components, and during electrode manufacturing, the active material, conductive additive, binder, etc., are mixed with the dispersion medium to create a fluid state.

[0009] The above-mentioned energy storage devices require improved energy density. A technique that pre-dops the active material with alkali metal ions, which act as charge carriers, during the manufacturing process of the energy storage device is effective in improving energy density.

[0010] By pre-doping the composite layer with charge carriers before assembling the energy storage device, it is possible to offset the capacity reduction of the energy storage device caused by the irreversible capacitance of the active material, binder, and conductive additive contained in the electrode active material. Furthermore, it is possible to increase the average voltage of the energy storage device. As electrode materials, active materials that do not originally have active charge carriers, active materials that are deficient in charge carriers, and binders and conductive additives with large irreversible capacitances can be used. In other words, by doping with charge carriers, the shortcomings of various electrode materials can be overcome and their advantages can be maximized. Therefore, the performance of the energy storage device can be improved.

[0011] For example, Patent Document 1 discloses an organic electrolyte battery in which lithium is pre-doped into an insoluble, infusible substrate containing a polyacene-based skeleton structure, which is the negative electrode active material. According to this, it is possible to support (dope) lithium, which will become a charge carrier, by assembling an electrochemical cell using the pre-doped electrode as the working electrode and metallic lithium as the counter electrode, and applying an electrochemical voltage.

[0012] Patent Document 2 discloses a technique for doping lithium ions into the positive and negative electrodes from a third electrode different from the opposing positive and negative electrodes before a charging operation is performed between the positive and negative electrodes.

[0013] Patent Document 3 discloses a non-aqueous secondary battery characterized by having a lithium-based metal foil pre-attached to the negative electrode sheet. Even if the positive electrode does not contain lithium, which acts as a charge carrier, it is possible to supply the charge carriers (lithium) necessary for charging and discharging by providing a carrier source (metallic lithium foil) on the negative electrode.

[0014] Incidentally, since doping with charge carriers is a reaction equivalent to charging or discharging, there is a problem in the doping process where the composite layer expands. To address this problem, a technique of doping under pressure is being considered.

[0015] For example, Patent Document 4 discloses a method for manufacturing a lithium-ion secondary battery comprising a cell having a negative electrode having a negative electrode active material layer (negative electrode composite layer) and a positive electrode, the method comprising a pre-doping step in which lithium pre-doping is performed after adjusting the volume density of the negative electrode active material layer, and a charging step in which the initial charge is performed while pressurizing the cell, wherein in the pre-doping step, the cell is pressurized at a predetermined pressure. [Prior art documents] [Patent Documents]

[0016] [Patent Document 1] Japanese Patent Application Publication No. 3-233860 [Patent Document 2] US-A1-2010 / 0255356 [Patent Document 3] Japanese Patent Publication No. 2000-182602 [Patent Document 4] Japanese Patent Publication No. 2016-110777 [Overview of the project] [Problems that the invention aims to solve]

[0017] Patent Document 1 requires the step of removing the charge carrier-doped electrode from the electrochemical system and reassembling it into an energy storage device. In the method of doping via an electrolyte, SEI (Solid Electrolyte Interface) and decomposition gases originating from the electrolyte are generated on the surface of the active material. Furthermore, the step of removing the electrode from the electrochemical system is time-consuming and has the drawback of making the electrode prone to degradation.

[0018] Patent Document 2 requires a third electrode having a carrier source for doping charge carriers different from those of the positive and negative electrodes within the cell. Therefore, its installation and management involve additional processes and costs. Furthermore, the presence of the third electrode within the cell results in a decrease in the energy density of the energy storage device.

[0019] In Patent Document 3, the carrier source (metallic lithium) attached to the negative electrode sheet needs to be absorbed into the electrode material by discharge and aging. This process has the drawback that decomposition gases originating from the electrolyte are generated on the surface of the active material, making it easy for the metallic lithium foil to peel off from the attached electrode and for metallic lithium to remain in the cell.

[0020] Patent Document 4 describes a lithium-ion secondary battery using silicon oxide as the negative electrode active material, in which lithium pre-doping causes the negative electrode active material layer (negative electrode composite layer) to expand and deform the cell's outer casing, and also causes the negative electrode composite layer and the cell to expand significantly during the first charge.

[0021] Furthermore, the prior art described in Patent Document 4 requires pressurizing the cell. This pressurization can cause the battery to short-circuit, posing a risk of thermal runaway. In particular, when charging cells containing materials that expand significantly in volume during doping, the separator is more likely to be damaged, increasing the likelihood of a short circuit.

[0022] Furthermore, Patent Documents 1 to 4 all require an electrolyte in their manufacturing process, and since the doping reaction proceeds via the electrolyte, they utilize electrochemical reactions. For this reason, the composite layer must be electrically conductive, and the reaction rate due to the movement of charge carriers becomes the rate-limiting factor, which presents challenges in terms of industrial productivity.

[0023] As described in Patent Documents 1-4, when charge carriers are doped via an electrolyte, the electrolyte also decomposes, resulting in the formation of electrolyte-derived decomposition products on the surface of the active material. When these decomposition products form at the interface of the active material and exhibit alkali metal ion conductivity, they are referred to as SEI. This SEI is known to be a composite of an organolithium salt compound and an inorganic lithium salt compound.

[0024] Methods for doping charge carriers via an electrolyte can be broadly classified into two types: the doping method, in which electrodes to which alkali metals serving as carrier sources are attached are immersed in the electrolyte (attachment method), and the doping method, in which a voltage is applied to an electrochemical cell with alkali metals serving as the counter electrodes (voltage application method).

[0025] The bonding method involves bonding alkali metals to the asphalt mixture layer and electronically conductive parts (for example, the asphalt mixture layer containing conductive additives or current collectors), and then immersing the mixture in an electrolyte or ionic liquid. This causes a short circuit between the asphalt mixture layer and the alkali metals, promoting doping. The voltage application method involves applying an external voltage or creating an external short circuit to an electrochemical cell with at least an alkali metal as the counter electrode, thereby promoting doping. In either method, doping of charge carriers and the generation of decomposition products derived from the electrolyte occur simultaneously.

[0026] Incidentally, it is known that adding organic substances such as vinylene carbonate (VC), fluoroethylene carbonate (FEC), and ethylene sulfite (ES) to the electrolyte improves battery characteristics. These additives include VC at 1.35V (vs.Li + / Li), FEC is 1.15V (vs.Li + / Li), ES is 1.05V (vs.Li + It is reduced and decomposed by (Li).

[0027] For example, when lithium ions are doped into a Si electrode via an electrolyte containing these three types of additives, generally, VC is reduced and decomposed first, followed by FEC, then ES, and finally the lithiumation reaction of Si occurs. Exceptionally, by performing an operation that lowers the potential below that of the Si lithiumation reaction, the order of the reduction and decomposition described above can be ignored to some extent, but the priority order in which the reactions occur remains unchanged. In any case, as volume expansion accompanies Si lithiumation and SEI is formed, defects and uneven thickness can occur in the SEI film formed on the surface of Si particles, resulting in a non-uniform film. [Means for solving the problem]

[0028] Therefore, in light of the above issues, the inventors conducted diligent research and found that proceeding with doping without maintaining a pressurized state is effective in bringing out the excellent features and effects of the invention.

[0029] Furthermore, once doping of the asphalt mixture layer with charge carriers is initiated by pressurization, the activation energy required for the reaction between the asphalt mixture layer and the carrier source decreases, allowing the doping reaction to proceed continuously even without external load. In other words, doping can proceed even when the pressurization is released and the mixture is unpressurized. By allowing the doping reaction to proceed without external load, the asphalt mixture layer becomes more prone to expanding in the thickness direction of the electrode, reducing the stress on the asphalt mixture layer and the current collector. Moreover, if the pressurization time is short, the energy consumption during pressurization is temporary, resulting in higher energy efficiency in the electrode manufacturing process. In addition, the temporary burden on the pressurizing equipment makes it easier to maintain the durability of the pressurizing equipment.

[0030] Furthermore, by physically pressurizing the asphalt mixture layer and the carrier coating (carrier source and substrate) together, the pressure is uniformly transmitted from the substrate to the carrier source and the asphalt mixture layer. This allows the carrier source to be evenly pressed onto the surface of the asphalt mixture layer in contact with the carrier source, and the doping reaction can be initiated simultaneously across the entire pressed surface. As a result, rapid and uniform doping can be achieved. In addition, since the charge carriers diffuse uniformly into the asphalt mixture layer, the carrier source disappears uniformly on the asphalt mixture layer, and the substrate can be easily peeled off and removed from the asphalt mixture layer.

[0031] Based on the above discovery, the present invention provides a method for rapidly and uniformly obtaining electrodes doped with charge carriers, regardless of whether the composite layer has electronic or ionic conductivity.

[0032] A method for manufacturing an electrode for an energy storage device according to one aspect of the present invention provides a method for manufacturing an electrode, comprising: step A of pressing a carrier coating onto an asphalt layer; step B of releasing the pressure and doping the asphalt layer with charge carriers; and step C of removing the substrate from the asphalt layer.

[0033] This configuration allows for rapid and uniform doping of charge carriers into the composite layer without the need for an electrolyte solution. In other words, it is possible to obtain an active electrode before charging or discharging operations occur between the positive and negative electrodes. Other methods will be described later. Furthermore, since it can be manufactured without using an electrolyte solution and no excess electrolyte-derived compounds are included in the composite layer, it results in an electrode for energy storage devices that exhibits excellent cycle characteristics and input / output characteristics. Moreover, this doping method can be used not only for electrodes in energy storage devices but also for doping charge carriers in other applications.

[0034] Furthermore, the method for manufacturing electrodes for this energy storage device is such that the carrier coating has a carrier source on a substrate, and the substrate has an insulating material that does not react with the carrier source on the surface that is in direct contact with the carrier source, or a release agent on the surface that is in direct contact with the carrier source.

[0035] This configuration makes it easier to peel the substrate from the asphalt mixture layer after doping, suppresses metal contamination of the electrodes, and reduces damage to the asphalt mixture layer during peeling.

[0036] Furthermore, in the method for manufacturing electrodes for this energy storage device, in step A, the carrier coating has a first region on the substrate where the carrier source is present and a second region where the carrier source is absent or the amount of the carrier source is less than in the first region, and in step B, only the charge carriers in the first region are doped into the composite layer, or the amount of charge carriers doped into the composite layer is greater at the position corresponding to the first region than at the position corresponding to the second region.

[0037] In this configuration, the carrier sources pressed onto the asphalt layer on the substrate are not arranged in a continuous surface, but rather at predetermined intervals. In this case, the substrate has a first region where carrier sources exist and a second region where carrier sources exist, resulting in a shape where carrier sources are intermittently present, such as stripes, a grid, or dots. The second region can also have fewer carrier sources than the first region, in addition to having no carrier sources at all. By doing so, it is possible to create thick and thin asphalt layers after doping (see Figure 11), and this difference in thickness allows for the creation of channels for the electrolyte of the energy storage device and channels for gases generated from the electrodes when these electrodes are used in a laminated or reassembled energy storage device. These channels eventually disappear as charge carriers diffuse in the planar direction of the asphalt layer (for example, in both the MD and TD directions of the current collector) during charging and discharging, resulting in a flat asphalt layer (see Figure 12). In other words, while the initial manufacturing process may create pathways for gas escape and electrolyte penetration, charging or discharging the energy storage device ultimately equalizes the thickness of the undoped and doped composite layers facing the counter electrode. This reduces the likelihood of localized current concentration caused by uneven thickness in the composite layer facing the counter electrode. The charging or discharging to eliminate these pathways should be performed under conditions that meet the specifications of the energy storage device (current, voltage, temperature, pressure, etc.).

[0038] An electrode for an energy storage device according to one aspect of the present invention comprises an asphalt mixture layer in which charge carriers are doped into the asphalt mixture, and the asphalt mixture layer has a surface layer containing a carbonate on its surface.

[0039] In this configuration, a surface layer containing carbonate exists on the surface of the composite material layer. Since this carbonate layer is not electrically conductive, it has the effect of suppressing internal short circuits in the battery caused by dendrites generated during overcharging or rapid charging, as well as internal short circuits caused by nails. In addition, because the carbonate layer suppresses direct contact between the electrolyte and the active material, it improves the high-temperature durability and cycle characteristics of energy storage devices using electrolytes, and suppresses the deterioration of the solid electrolyte in energy storage devices using solid electrolytes.

[0040] Furthermore, the electrodes for this energy storage device have a first group of composite materials doped with charge carriers in the composite material layer, and a second group of composite materials that are undoped with charge carriers or have less doping than the first group of composite materials.

[0041] This configuration allows for the formation of a thick first asphalt mixture layer doped with charge carriers and a thin second asphalt mixture layer (see Figure 11). This results in an electrode that exhibits the effects described in paragraph 0039 above.

[0042] Furthermore, in this energy storage device electrode, multiple first and second regions exist on the substrate, and the first and second regions are arranged alternately in the width direction and / or length direction of the substrate.

[0043] According to this configuration, a thick first asphalt mixture layer doped with charge carriers and a thin second asphalt mixture layer can be alternately formed in the width and / or length directions of the substrate. This results in an electrode with enhanced effects compared to paragraph 0039 above. The first and second regions may alternately exist in an oblique direction that is neither perpendicular nor parallel to the width and length directions of the substrate. Furthermore, if the first or second region is a dot, it may be arranged in a grid (aligned), staggered, or random pattern, and the shape of the dots is not particularly limited. [Effects of the Invention]

[0044] According to the electrode manufacturing method of the present invention, charge carriers can be rapidly and uniformly doped into the composite layer without the need for an electrolyte solution or other electrolytes. Therefore, the electrode impregnation step in an electrolyte solution for doping is unnecessary, and even composite layers that do not contain solid electrolytes can be doped with charge carriers into the active material or binder contained in the composite layer.

[0045] Furthermore, the electrode of the present invention exhibits superior cycle characteristics and input / output characteristics compared to conventional electrodes. [Brief explanation of the drawing]

[0046] [Figure 1] A schematic diagram, viewed from the electrode thickness direction, illustrating a method for manufacturing an electrode for an energy storage device according to the first embodiment of the present invention. [Figure 2] A schematic diagram, viewed from above, illustrating the manufacturing method for an electrode for an energy storage device according to the first embodiment. [Figure 3] A schematic diagram, viewed from above, illustrating the manufacturing method of an intermittent electrode for an energy storage device according to the first embodiment. [Figure 4] A schematic diagram, viewed from above, illustrating the manufacturing method of a stripe electrode for an energy storage device according to the first embodiment. [Figure 5] Schematic diagram of the configuration of a manufacturing apparatus for a single-sided electrode for an energy storage device according to the first embodiment. [Figure 6] Schematic diagram of the configuration of a manufacturing apparatus for double-sided electrodes for energy storage devices according to the first embodiment. [Figure 7] Diagram to explain the angle of holding [Figure 8] A schematic diagram showing an electrode for an energy storage device according to the first embodiment of the present invention. [Figure 9] A schematic diagram, viewed from the electrode thickness direction, illustrating a method for manufacturing a single-sided electrode for an energy storage device according to a second embodiment of the present invention. [Figure 10] A schematic diagram, viewed from the electrode thickness direction, illustrating the manufacturing method of a double-sided electrode for an energy storage device according to the second embodiment of this present invention. [Figure 11] A schematic diagram showing the cross-sectional structure of an energy storage device according to one embodiment of the present invention (before charging and discharging). [Figure 12] A schematic diagram showing the cross-sectional structure of an energy storage device according to one embodiment of the present invention (after charging and discharging). [Figure 13] A graph showing the XRD patterns of an electrode for an energy storage device and other electrodes according to one embodiment of the present invention. [Figure 14] A schematic diagram showing an example of a method for manufacturing electrodes for energy storage devices according to one embodiment of the present invention. [Modes for carrying out the invention]

[0047] The following describes one embodiment of the present invention in detail with reference to the drawings. Although there are various types of electrodes, such as positive electrodes, negative electrodes, reference electrodes, and bipolar electrodes, the basic manufacturing process and equipment are common to all of them, differing only in the current collector and active material used.

[0048] [Electrodes to be doped] First, the electrode to be doped (electrode before doping) usable in this embodiment will be described. This electrode consists of at least an assortment layer (active material layer) and a current collector. The assortment layer is manufactured, for example, by applying or filling a current collector with a slurry containing the active material and binder, pre-drying, then applying pressure to regulate the pressure, and finally drying.

[0049] There are no restrictions on the application method of the asphalt mixture layer; known application patterns such as continuous application, intermittent application, and stripe application can be selected.

[0050] One example is a method in which a slurry is discharged from a coating head to the surface of a current collector being transported in one direction at a predetermined speed and applied to it with a uniform thickness. Known devices such as bar coaters, knife coaters, comma coaters, lip coaters, gravure coaters, die coaters, air knives, reverse coaters, and doctor blades can be used as coating heads. After application, the dispersion medium contained in the slurry is vaporized and removed to form an asphalt layer on the surface of the current collector.

[0051] In terms of the composition of the composite layer, when the total of the active material, binder, conductive additive, and electrolyte is considered to be 100% by mass, it is preferable that the active material is 50% to 99.9% by mass, the binder is 0.1% to 35% by mass, the conductive additive is 0% to 30% by mass, and the electrolyte is 0% to 30% by mass. In other words, the conductive additive and electrolyte are included as needed. The active material is essential because without it, the electrode cannot function. The binder is essential to suppress the peeling of the composite layer during charge carrier doping.

[0052] If the active material content is less than 50% by mass, the amount of active material relative to the electrode is too small, making it impossible to obtain an energy storage device with high energy density. Furthermore, the process described in the embodiment below alone takes several days to complete the doping process. In such cases, it is effective to impregnate the electrode with electrolyte or to pre-include a solid electrolyte in the composite layer.

[0053] A slurry obtained by mixing an active material, a binder, a conductive additive, and an electrolyte with a dispersion medium to form a composite layer of a predetermined composition can be applied to or filled into a current collector to provide a composite layer on the current collector.

[0054] The dispersion medium can be any fluid substance, such as water, organic solvents, electrolytes, ionic liquids, or molten salts. In the case of water or organic solvents, the dispersion medium can be vaporized (dried) using a known method after coating or filling. In the case of slurries using electrolytes, ionic liquids, or molten salts as the dispersion medium, vaporization of the dispersion medium is not required.

[0055] After applying an asphalt mixture layer to the current collector, the electrode to be doped can be manufactured by applying pressure to the asphalt mixture layer using an external load such as a roll press or a uniaxial press to densify it.

[0056] However, the embodiments described later include a step of applying an external load to the asphalt mixture layer, which densifies the asphalt mixture layer, so the pressure adjustment step for the asphalt mixture layer may be unnecessary or simplified.

[0057] The porosity of the composite material layer of the electrode to be doped is preferably 5% to 80%. Furthermore, the thickness of the composite material layer of the electrode to be doped is preferably 1 μm to 500 μm. By keeping the dimensions within these ranges, the composite material layer can react uniformly in the thickness direction in the embodiments described later. As the thickness of the composite material layer increases, it tends to take longer for charge carriers to diffuse to the vicinity of the current collector. In composite material layers of 500 μm or less, the distance over which charge carriers diffuse from the surface to the interior is short, so the time required for diffusion is reduced. When the thickness exceeds 500 μm, the surface of the composite material layer expands first, and the interior expands later, making non-uniform deformation more likely. Below 1 μm, the energy density of the electrode is low.

[0058] An active material refers to a material that can be alloyed with alkali metals or a material that can absorb alkali metal ions. For example, if sodium ions are used as charge carriers, the active material refers to a material that can be alloyed with sodium or a material that can absorb sodium ions. If doping speed and homogeneity are not required, known active materials used in energy storage devices that use alkali metal ions as charge carriers can be used.

[0059] In other words, graphite, hard carbon, soft carbon, and activated carbon, which are widely used as active materials for electrodes in energy storage devices such as lithium-ion batteries, sodium-ion batteries, potassium-ion batteries, electric double-layer capacitors, and alkali metal-ion capacitors, can also be used.

[0060] In embodiments of the present invention, the active material that yields high effectiveness is a material containing at least one element selected from P, S, Fe, Co, Ni, Cu, Zn, Ga, Ge, Ag, In, Sn, Sb, Au, Pb, and Bi, or a compound, alloy, or modified form containing one of these elements. The more of these materials present as active material in the composite layer, the faster the doping reaction tends to be.

[0061] In particular, SiO x (0≦x≦1.6), Si-M xAn alloy (M is any one or more of B, Mg, Al, P, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zr, Al, Y, Zr, Nb, Sn; 0 < x ≤ 5), GeO x (0 ≤ x ≤ 1.5), SnO x (0 ≤ x ≤ 2), SnS x (0 ≤ x ≤ 2), S8, sulfur-modified organic substances (e.g., sulfur-modified polyacrylonitrile, sulfur-modified rubber, sulfur-modified polyethylene glycol, etc.), sulfur composite carbon (e.g., a composite of activated carbon and sulfur, etc.), and other sulfides have a fast doping reaction rate and are likely to achieve uniform doping.

[0062] Moreover, generally, regardless of the composition of these materials, when the charge carriers are doped into the composite layer, they have the property that the conductivity is improved compared to the composite layer before doping. As the doping amount increases, the electrical resistivity tends to decrease.

[0063] Also, the doping reaction of the active material is faster in the form of a single substance than in compounds or alloys. For example, the doping reaction is faster for SiO 1.2 than for SiO 0.7 , and faster for Si than for SiO 0.7 . In the case of sulfur-modified substances or sulfur composites, etc., the tendency is that the higher the sulfur content, the faster the reaction.

[0064] Note that two or more active materials may be mixed or combined for use. In this case, it is preferably to contain at least 5% by mass or more, more preferably 10% by mass or more, and even more preferably 20% by mass or more of the active material that can obtain the high effects of the present invention described above with respect to the composite layer.

[0065] On the other hand, carbon materials such as graphite, hard carbon, soft carbon, activated carbon, acetylene black (AB), furnace black (FB), carbon nanotube (CNT), graphene, etc. tend to have a slower doping reaction as the content increases. Particularly, highly crystalline graphite has a slow doping reaction rate.

[0066] The doping rate can be increased by raising the pressure or temperature during the crimping process. However, if the pressure is too high, the asphalt layer becomes excessively dense, making it prone to delamination from the current collector. If the temperature is too high, thermal decomposition of the materials in the asphalt layer occurs, and if the process is not carried out in an inert atmosphere, the electrodes will oxidize.

[0067] Therefore, from the standpoint of accelerating the doping reaction, it is preferable to have a lower carbon material content in the composite layer. However, if there is too little carbon material, the internal resistance of the electrode will increase in the low state of charge (low SOC) region.

[0068] Carbon materials can be used not only as active materials but also as conductive additives. In either application, when carbon materials are included, it is preferable to adjust the carbon material content in the composite layer to 0.1% by mass or more and 90% by mass or less, more preferably 0.15% by mass or more and 70% by mass or less, and even more preferably 0.2% by mass or more and 60% by mass or less.

[0069] In the embodiments of the present invention described above, if the active material content that yields high effectiveness is less than 5% by mass, or if the carbon material content exceeds 90% by mass, it takes several days to completely dope the carrier source even after the pressure is released following compression. In such cases, the doping time can be significantly shortened by impregnating the carrier source with an electrolyte after compression, or by incorporating an electrolyte into the composite layer. In this disclosure, a completely doped state means a state in which 90% or more of the carrier source has been utilized for its intended purpose, unless otherwise specified.

[0070] The shape of the active material is not particularly limited as long as it is a shape that can be used as the active material for an energy storage device. That is, it may be spherical, elliptical, faceted, strip-shaped, fibrous, needle-shaped, flake-shaped, donut-shaped, hollow, fragmented, or amorphous particles. The median diameter (D) of the active material. 50 The particle size is preferably between 10 nm and 100 μm. Granulated active material is also acceptable.

[0071] Here, the median diameter (D 50) is the particle size at which the cumulative frequency reaches 50% when converted to volume based on the volume standard, as determined using the laser diffraction-scattering particle size distribution method, and the particle size in this application refers to this.

[0072] For active materials that can be etched with alkaline or acidic aqueous solutions, it is preferable to use materials that have been brought into contact with an alkaline aqueous solution with a pH of 9 or higher, or an acidic aqueous solution with a pH of 5 or lower, and then dried.

[0073] In particular, active materials with a crystalline structure often exhibit different etching rates and hardness depending on the crystal orientation. Generally, planes with higher atomic density are less etchable and have higher hardness. For example, in the case of Si and Ge, the Miller index (100) plane has a lower atomic density than the (111) plane, and is therefore known to be more easily etched by alkali. When an alkaline aqueous solution comes into contact with it, the (110) plane is etched preferentially over the (111) plane. Lithiumation also reacts preferentially at the (110) plane. SiC has higher etching resistance to alkaline aqueous solutions compared to Si and Ge, but it can be etched with hydrofluoric acid and phosphoric acid, and certain crystal planes are etched more easily than others. In Ga, Sn, Sb, Bi, Al, Zn, etc., certain crystal planes are also etched more easily than others.

[0074] When the active material is a material with a crystalline structure, etching the active material with an alkaline or acidic aqueous solution exposes the surface where the carrier source reacts, allowing for rapid and uniform doping of the active material with charge carriers at relatively low pressure.

[0075] The etching treatment may be performed on the active material powder or on the composite layer.

[0076] The alkaline aqueous solution used in the etching process may be aqueous ammonia, an aqueous alkali metal hydroxide solution, or an aqueous silicate solution. Of these, an aqueous silicate solution is preferred. An aqueous silicate solution can be obtained, for example, by dissolving a silicate represented by A2O·nSiO2 in water. Here, A is at least one of Li, Na, K, triethanolammonium group, tetramethanolammonium group, tetraethanolammonium group, or granidine group, and n is preferably 0.1 to 15. In particular, when A is Li, n is preferably 2.0 to 12, and when A is Na or K, n is preferably 1.0 to 7. By bringing the active material into contact with the aqueous silicate solution, the active material is alkali-etched, and by further drying, an active material or composite layer coated with silicate can be obtained.

[0077] The acidic aqueous solution used in the etching process may be an organic acid aqueous solution, a hydrofluoric acid aqueous solution, a phosphoric acid aqueous solution, a phosphate aqueous solution, or the like. Of these, a phosphate aqueous solution is preferred. A phosphate aqueous solution can be obtained, for example, by dissolving a phosphate represented by Al2O3·nP2O5 in water. Here, n is preferably between 1 and 7. By bringing the active material into contact with the phosphate aqueous solution, the active material is acid-etched, and by further drying, an active material or composite layer coated with phosphate can be obtained.

[0078] When using silicates or phosphates, it is preferable to coat the entire composite layer rather than only the active material powder. By coating the composite layer, not only the active material but also the binder and conductive additive can be coated. In this case, the amount of silicate or phosphate per unit area of ​​the composite layer is 0.01 mg / cm². 2 More than 6mg / cm 2The amount of silicate or phosphate contained in the composite layer should be between 0.1% by mass and 40% by mass. The composite layer obtained in this way is less susceptible to the disruption of the electrode's conductive path due to the volume expansion of the active material that occurs during compression with the carrier source, and does not impair the doping time after compression. As a result, it becomes an electrode with excellent cycle characteristics. In particular, when silicate is used, the electrode also exhibits improved high-temperature and low-temperature durability.

[0079] Generally, active materials doped with charge carriers expand in volume compared to the active material before doping. Materials that can alloy with alkali metals or absorb large amounts of alkali metal ions, such as Si, Ge, Ga, Al, Sn, Sb, Bi, and S, exhibit particularly large volume expansion. While coating with silicates or phosphates still causes volume expansion due to doping, this can suppress the expansion of the composite layer and increase mechanical strength. This is especially effective when the volume expansion of the active material exceeds 30%.

[0080] The volume expansion rate of the active material differs depending on the type of active material, the amount of charge carrier doping, and the type of charge carrier, but if the active material is completely doped with lithium, then Li4Ti5O 12 It is believed that lithium expands in volume by approximately 0.2%, LiFePO4 and LiMn2O4 by about 6-7%, graphite by about 10%, Al by about 200%, Sb by 200-300%, and Si and Sn by 300-400%. Furthermore, sodium, which has about twice the ionic volume of lithium, is thought to undergo an even greater volume expansion.

[0081] For the electrodes, known binders that can be used for electrodes in energy storage devices can be used. For example, polyvinylidene fluoride (PVdF), polyvinylidene fluoride-co-hexafluoropropylene (PVdF-HFP), polytetrafluoroethylene (PTFE), tetrafluoroethylene-hexafluoropropylene copolymer (FEP), tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer (PFA), ethylene-tetrafluoroethylene copolymer (ETFE), chlorotrifluoroethylene-ethylene copolymer (ECTFE), polychlorotrifluoroethylene (PCTFE), polyvinyl fluoride (PVF), polyethylene (PE), polypropylene (PP), styrene-butadiene rubber (SBR), polyacrylic Examples include polyacid (PAA), polyacrylates, polymethyl methacrylate (PMMA), butyl methacrylate (BMA), ethyl methacrylate (EMA), ethyl acrylate, methyl acrylate, polyurethane, polyurea, polyvinyl alcohol (PVA), polyvinylpyrrolidone (PVP), polyamide (PA), polyamide-imide (PAI), polyimide (PI), ethylene-vinyl acetate copolymer (EVA), styrene-ethylene-butylene-styrene copolymer (SEBS), silicates, phosphates, etc. These may be used individually or in combination of two or more. In addition, thickeners, surfactants, defoamers, SEI-forming agents, etc. may be added.

[0082] However, the doping reaction rate varies greatly depending on the type of binder, and this also significantly affects the cycle characteristics, making binder selection crucial. For most binders, the doping rate tends to decrease significantly as the amount of binder relative to the asphalt mixture increases.

[0083] However, in the case of fluoropolymer resins such as PVDF, PVDF-HFP, and PTFE, or acrylic polymer resins such as PAA, sodium polyacrylate, and PMMA, or acrylic monomers, urethane resins, silicates, and phosphates, the doping rate does not decrease significantly even with a large amount of binder. In particular, the doping tends to be faster the higher the flexibility of the binder. The reason for this is not clear, but it is thought that flexible binders deform more in response to pressure, increasing the contact area between the active material and alkali metals, etc., thereby promoting the diffusion of charge carriers.

[0084] In the embodiments described later, charge carriers can be doped regardless of the electronic conductivity of the composite layer, so the composite layer does not need to contain any conductive additives. However, in order to improve the input / output characteristics of the energy storage device, and especially the input / output characteristics in the low SOC region, it is preferable to include 0.1% by mass or more of a conductive additive relative to the composite layer.

[0085] As for conductive additives, there are no particular restrictions as long as they have electronic conductivity, and known materials can be used. Specifically, examples include AB, Ketjenblack (KB), FB, thermal black, lamp black, channel black, roller black, disc black, carbon black (CB), carbon fiber (e.g., vapor-grown carbon fiber VGCF®), CNT, carbon nanohorn, graphite, graphene, glassy carbon, amorphous carbon, etc., and one or more of these can be used.

[0086] In the embodiments described later, the composite layer does not need to contain any electrolyte, such as an electrolyte solution or a solid electrolyte. However, when using an electrolyte with poor fluidity in the energy storage device, it is preferable to contain 1% by mass or more and less than 50% by mass of the electrolyte relative to the composite layer.

[0087] As for the electrolyte, there are no particular limitations as long as it has ionic conductivity, and known materials can be used. Specifically, examples include electrolytes, ionic liquids, molten salts, gel electrolytes, polymer electrolytes, sulfide-based solid electrolytes, oxide-based solid electrolytes, and hydride-based solid electrolytes (including complexes), and one or more of these can be used. Here, an electrolyte refers to a state in which the electrolyte is dissolved in a solvent.

[0088] The current collector used in the electrode is not particularly limited as long as it is an electronically conductive material capable of conducting electricity to the active material in the composite layer.

[0089] For example, conductive materials such as C, Ti, Cr, Ni, Cu, Mo, Ru, Rh, Ta, W, Os, Ir, Pt, Al, and Au, or alloys containing two or more of these conductive materials (e.g., stainless steel, Al-Fe alloy, etc.) can be used. If materials other than the above conductive materials are used, for example, a multilayer structure such as a resin coated with Cu, Ni, or Al may be used.

[0090] When the electrode is used as the negative electrode, C, Cu, Ni, Fe, and stainless steel are preferred. If Fe is used as the current collector, it is preferable that it be coated with Ni or Cu to prevent surface oxidation. For the positive electrode, C, Au, Ti, Al, Al alloy, and stainless steel are preferred. For bipolar electrodes, C, Al, Al alloy, and stainless steel are preferred. Alternatively, a multilayer structure consisting of two materials with resistance to oxidation on the surface and reduction on the back surface of the current collector is preferred. In other words, materials capable of maintaining the applied positive and negative electrode potentials should be selected.

[0091] Current collectors can take the form of wire, rod, plate, foil, or porous, and all of these are usable. Porous materials include mesh, woven fabric, nonwoven fabric, embossed material, perforated material, expanded material, perforated foil, or foam.

[0092] The high effectiveness of the present invention can be obtained by using the doped electrode described above. Specifically, by pressing a carrier source onto the composite layer described above, an electrode for an energy storage device doped with charge carriers can be obtained.

[0093] [Carrier covering] In this embodiment, the carrier source refers to a substance that is pressed together with the asphalt layer using a press machine, thereby supplying charge carriers to the asphalt layer. The carrier coating is a structure provided on a substrate that supports the carrier source.

[0094] Here, a charge carrier refers to a free particle that carries electric charge, and in particular, to a particle that carries electric current in an electrical conductor. For example, a proton (H + ), hydride ions (OH - ), alkali metal ions (Li + na + , K + , Rb + (etc.), alkaline earth metal ions (Be 2+ Mg 2+ Ca 2+ Sr 2+ Ba 2+ ), Al 3+ , Ga 3+ , halide ions (F - Cl - , Br - , I - PF6 - BF4 - AlCl4 - , TfO - Tf2N - TF3C - FSA - Examples of cations and anions include ) and others. Of these, alkali metal ions are preferable because they allow for rapid doping of charge carriers through compression. In addition, lithium ions, sodium ions, and potassium ions are preferable because they provide a high electromotive force for the battery.

[0095] A carrier source refers to a substance that possesses charge carriers. When the charge carrier is an alkali metal ion, the carrier source is at least one element of the alkali metal, or an alloy or compound thereof. For example, if the charge carrier is a sodium ion, the carrier source refers to sodium metal and sodium alloys, or sodium compounds.

[0096] The carrier source is preferably an alkali metal with zero valency, from the viewpoint that it disappears after doping and the substrate can be easily peeled off from the composite layer.

[0097] Alkali metals are the Group 1 elements excluding hydrogen: Li, Na, K, Rb, Cs, and Fr. Of these, elements selected from Li, Na, and K, or alloys containing one of these elements, are preferred due to their ease of handling, low cost, and readily available availability. Here, an alkali metal alloy is a metal composed of two or more elements formed by fusing an alkali metal with another metal (In, Mg, Al, Sn, Si, Zn, Ga, Ge, Ag, Cd, Sb, Bi, Pb, Au, Tl, Pb, Hg, Cd, Pt, Co, Rh, Ir, Ru, Ca, Sr, Ba). The alloy may be fully solid solution type, eutectic type, peritectic type, or two-phase separation type (petechnical type). Furthermore, the compounds are preferably alkali metal hydrides (LiH, NaH, KH, LiAlH4, LiAlH4, LiAlH4, LiBH4, NaBH4, KBH4) or nitrides (Li3N, Na3N, K3N).

[0098] In the bonding of the composite layer and the carrier source described later, if the temperature of the carrier source exceeds its melting point, the carrier source liquefies, and although the doping rate becomes faster than that of a solid, the cycle characteristics and input / output characteristics deteriorate. For this reason, the carrier source used in this manufacturing method is preferably a solid such as foil or powder.

[0099] In particular, it is preferable to use an element selected from Li, Na, and K, or an alloy containing one of them, because it can be doped rapidly and uniformly at low pressure. It is also preferable to use Li or a lithium alloy because it does not degrade the carrier source easily and can be carried out with good reproducibility, even in non-oxygen environments. The flexibility of the carrier source allows it to deform more in response to pressure, increasing the contact area with the active material contained in the composite layer, which improves the diffusion of charge carriers into the composite layer and enables rapid and uniform doping.

[0100] Although not as effective as liquefied zero-valent alkali metals, the carrier source is preferably a soft material that is easily deformable under pressure, as it enables rapid and uniform doping. Specifically, a carrier source with a Mohs hardness of 2 or less is preferred. If the Mohs hardness exceeds 2, the pressure required for doping tends to increase, and the composite layer is more likely to break during compression.

[0101] The thickness of the carrier source is preferably 0.1 μm to 500 μm, preferably 0.5 μm to 200 μm, and more preferably 1 μm to 50 μm. Furthermore, the carrier source is preferably flat and dense.

[0102] The carrier source may have its surface covered with carbonates or oxides. That is, carbonates or oxides may be present between the carrier source and the composite layer, or between the substrate and the carrier source. However, since doping becomes difficult if the thickness of the carbonate or oxide exceeds 500 nm, it is preferable that it be 500 nm or less. When the surface of the carrier source is covered with carbonates or oxides, a layer of carbonates or oxides can be provided on the surface of the composite layer. By providing an electrode with a layer of carbonates or oxides with a thickness of 1 nm or more on the surface of the composite layer, the carbonate or oxide layer suppresses direct contact between the electrolyte and the active material. In the case of an energy storage device using an electrolyte, high-temperature durability and cycle characteristics are improved, and in the case of an energy storage device using a solid electrolyte, the effect of suppressing deterioration of the solid electrolyte is enhanced.

[0103] To create a carrier source covered with a layer of carbonate or oxide of the thickness described above, the carrier source can be reacted with carbon dioxide or oxygen. For example, alkali metal carbonates can be formed on the surface of alkali metals by exposing them to carbon dioxide. The carbonate or oxide layer grows more rapidly with higher concentrations, temperatures, and pressures of the exposure gas, and longer exposure times. The thickness of the carbonate or oxide layer can be measured, for example, in an environment without exposure to air, using X-ray photoelectron spectroscopy (XPS), glow discharge emission spectrometry (GD-OES), or SIMS. XPS is suitable for thicknesses of 1 nm to 50 nm, while GD-OES and SIMS are suitable for thicknesses of 10 nm or more.

[0104] When comparing the carbonates and oxides described above, carbonates offer superior high-temperature durability and improved cycle characteristics, while oxides exhibit better power output characteristics. Furthermore, the carbonate and oxide layers may also be composed of resins, solid electrolytes, ceramics, or carbon.

[0105] A carrier source with a thickness within the above-mentioned range can be obtained, for example, by providing an alkali metal or alkali metal alloy rolled to a predetermined thickness on a substrate, or by vapor-phase formation (e.g., sputtering, vapor deposition, etc.) of an alkali metal on a substrate in an inert environment. Since the substrate plays a role in supporting the carrier source, it is preferable that its strength is at least greater than that of the carrier source.

[0106] In the embodiments described later, depending on the type of substrate, it may be difficult to peel the substrate from the asphalt mixture layer after the pressure is released. In particular, when the carrier source is an alkali metal or alkali metal alloy, the adhesion between the carrier source and the substrate is strong, making it difficult to peel the substrate from the asphalt mixture layer during or after doping. The stronger the adhesion between the carrier source and the substrate, the more tensile force is applied to the asphalt mixture layer when peeling the substrate during or after doping, making peeling and cracking more likely.

[0107] Furthermore, this point applies not only to electrolytes but also to solid electrolytes. The inventors of this application doped the surface of the negative electrode that was not in contact with the solid electrolyte by contacting a lithium source such as lithium foil or lithium powder. However, alkali metals such as metallic lithium are very soft and have very low mechanical strength, making them difficult to handle. For example, when metallic lithium with uneven thickness due to wrinkles, folds, or cracks is used, doping becomes concentrated in one part of the composite layer, while doping is delayed in other parts. In such a state, even if the lithium diffuses and becomes uniform over time, it takes time. In addition, because the volume expansion proceeds unevenly, the electrode tends to become distorted.

[0108] As a countermeasure, it was thought that providing alkali metals on a substrate with higher strength than alkali metals would be effective, and therefore lithium foil bonded to a Cu foil substrate was used for the negative electrode containing a solid electrolyte. However, with thin conductive metal foils, the substrate was difficult to peel off from the composite layer after doping. In addition, since metal contamination of the electrode is undesirable, it was found that not only was peeling laborious, but the composite layer was also easily damaged during the peeling process.

[0109] Furthermore, simple metal foils are harder and less flexible than typical resin films, so the alkali metals cannot flexibly adapt to the surface roughness of the composite layer. As a result, areas may lift, areas may not adhere properly, and pressure may concentrate in specific areas. This is especially likely to occur when the active material contains large particle sizes, has high porosity, or when the composite layer undergoes significant volume expansion due to doping.

[0110] Therefore, the inventors conducted extensive research on the substrate surface that directly contacts the carrier source and found that improving the peelability from the carrier source is effective. It is preferable that the substrate surface that directly contacts the carrier source be an insulator that does not react with the carrier source, or have a release agent on the surface that directly contacts the carrier source. This configuration makes it possible to easily peel and remove the substrate from the composite layer after the pressure is released. When the composite layer expands significantly in volume due to doping, stress is applied to the contact surface between the substrate and the composite layer, which promotes peeling. In addition, a smaller tensile force when peeling the substrate has the advantage of reducing the amount of substrate-derived material that adversely affects the battery. Furthermore, this embodiment allows doping of charge carriers even via a solid electrolyte. While conventional doping methods required both electronic conductivity and ionic conductivity in the composite layer, this embodiment does not require these properties, and doping is possible.

[0111] Examples of insulating substrates that do not react with the carrier source include resins such as PE, PP, polybutene, ethylene-propylene copolymer, polyethylene terephthalate (PET), EVA, ethylene-methyl acrylate copolymer, ethylene-acrylic acid copolymer (EAA), PA, PAI, PI, polycarbonate, nylon, polyetheretherketone (PEEK), PVdF, ECTFE, PTFE, and FEP, as well as polymer alloys of these resins with rubber (e.g., shock-absorbing nylon). PET, PE, or PP are particularly preferred.

[0112] The substrate may be a resin or a metal having a release agent on its surface. The metal may be, for example, a metal such as Ni, Cu, Al, Fe, or Cr, or an alloy or composite containing at least one of these.

[0113] The release layer should function to reduce adhesion at the bonding surface between the carrier source and the substrate. In other words, by interposing a release layer between the carrier source and the substrate, the carrier source does not adhere strongly to the substrate after pressing, making it easy and simple to peel off. For example, release agents used in packaging materials for food, clothing, and industrial products, as well as release paper, sealing materials, and laminate films, may be used.

[0114] Specifically, these include silicone-based paint removers, fluorine-based paint removers, water-based paint removers, olefin-based paint removers, and hot-melt paint removers.

[0115] Silicone-based release agents are release agents that contain silicon as an ingredient. Examples include dimethylpolysiloxane, organosiloxane, methylphenyl silicone oil, aminosiloxane, alkyl silicone, epoxyloxane, polymethylhydrosiloxane, vinylsiloxane, or siloxanes having methyl or trimethylsilyl groups.

[0116] Fluorine-based stripping agents are stripping agents that contain fluorine as a component. Examples include PTEF, fluorinated ethylene propylene, fluorinated polyethylene propylene, copolymers of tetrafluoroethylene and perfluoroalkoxyethylene, ETFE, PVdF, PCTFE, PVF, and fluorocarbon compounds.

[0117] Aqueous release agents are release agents that use water as the main solvent, for example, in the form of dissolved or dispersed in water. Examples include acrylic acid esters, acrylate salts, polyacrylics, aliphatic polyurethanes, aromatic polyurethanes, aqueous epoxys, PVA, carboxymethylcellulose (CMC), hydroxyethylcellulose, polyvinyl acetate, polyvinylpyrrolidone, and polycarbonate.

[0118] Olefin-based release agents are release agents based on polyolefins. Examples include PP, PE, ethylene-vinyl acetate copolymer, ethylene-butene copolymer, ethylene-methacrylic acid copolymer, and laminate films for pouches.

[0119] Hot melt release agents are release agents based on thermoplastic materials that are applied in a molten state after heating and solidify upon cooling. Examples include ethylene-vinyl acetate copolymer, polyvinyl acetate, PP, PE, polyurethane, polyvinyl acetate, and SBR.

[0120] Other release agents include wax, boron nitride (BN), graphite, graphene, molybdenum sulfide, tungsten sulfide, alumina, boehmite, silica, and zirconia. Other release agents include those with a median diameter (D 50 A powder with a particle size of 10 nm to 3 μm is preferred. The release layer is preferably formed with a particle size of 0.01 μm to 3 μm.

[0121] To more reliably separate the substrate from the composite layer, it is preferable to use a resin substrate with the aforementioned release layer rather than a metal substrate. Furthermore, in the crimping process described later, a flexible material is more suitable for the substrate than a hard material, but if it is too soft, the thickness of the substrate will need to be increased to maintain strength.

[0122] To facilitate the separation of the substrate from the asphalt mixture layer during or after doping, it is desirable that the adhesive strength between the asphalt mixture layer and the carrier source be higher than the adhesive strength between the substrate and the carrier source. In the asphalt mixture layer, the adhesive strength between the asphalt mixture layer and the carrier source varies depending on the composition ratio, material type, density, etc., so the adhesive strength is not particularly limited. On the other hand, the adhesive strength between the substrate and the carrier source is 0.001 N / cm². 2 More than 20N / cm 2 The following is preferable. Within this range, the adhesive strength between the asphalt layer and the carrier source will be higher than the adhesive strength between the substrate and the carrier source, making it easier to peel the substrate from the asphalt layer after pressurization. 0.001 N / cm 2Below 20 N / cm², the carrier source is more likely to detach from the substrate, and wrinkles, cracks, and detachment of the carrier source are more likely to occur. 2 If the value exceeds a certain limit, the doping of charge carriers into the composite layer becomes uneven because the carrier source is strongly pulled by the substrate during the doping process. In addition, some of the carrier source may remain in the substrate, or the substrate may be damaged, making delamination difficult.

[0123] Furthermore, the substrate may have the same area as the carrier source, but it is preferable that it has a larger area. Here, area refers to the quantity calculated as the product of the width and length dimensions, excluding the thickness.

[0124] When the surface area of ​​the base material is larger than the surface area of ​​the carrier source, the composite layer that is not intended to be doped can also be pressed through the base material during bonding, making it less likely for defects such as wrinkles and peeling to occur. More preferably, the surface area of ​​the base material is the same as or larger than that of the composite layer.

[0125] Furthermore, the substrate is preferably transparent rather than opaque. If light is transmitted through the substrate without being absorbed, the doping state can be easily observed. For example, in addition to visual observation, the color, gloss, and texture of the asphalt layer can be inspected after the pressure is released, or the spectrum of reflected light can be analyzed by shining light on the asphalt layer, simplifying the manufacturing process and quality control.

[0126] The substrate may be in the form of fibers, nonwoven fabrics, foils, films, or sheets. A flat substrate such as a foil, film, or sheet is preferred because it has high strength, is flexible, and allows for uniform doping of charge carriers by compression. A film with numerous through-holes, like a separator for secondary batteries, is also acceptable.

[0127] If the substrate is too thin, its mechanical strength is low, causing the carrier source to deform during the bonding process. This makes it vulnerable to tension and tearing, and prone to wrinkles and cracks. Furthermore, wrinkles easily form in the carrier source when it is bonded to the asphalt layer, making it susceptible to damage during removal. On the other hand, while increasing the substrate thickness improves mechanical strength, flexibility tends to decrease. Lack of flexibility in the charge carrier source makes it difficult to uniformly distribute force during bonding, resulting in uneven doping. For these reasons, the substrate thickness is preferably between 2 μm and 500 μm, and more preferably between 5 μm and 300 μm. Within this range, the charge carrier source maintains the flexibility necessary for uniform doping during the bonding process, while also improving physical vulnerability. Additionally, the process of removing the substrate after doping becomes easier.

[0128] The strength of the substrate should be higher than that of the carrier source. More specifically, a substrate with a tensile strength of 50 MPa or higher, a tensile elongation at break of 60% or higher, and a tensile modulus of elasticity of 500 MPa or higher, as measured by a method compliant with JIS K7127, is preferred.

[0129] The carrier source placed on the substrate may have the same area as the substrate, but it is preferable that the substrate is larger. In other words, it is preferable that the dimensions of the substrate be the same as or larger than the carrier source and the same as or smaller than the electrodes. This allows the undoped composite layer to be pressurized simultaneously because the substrate is larger than the carrier source.

[0130] Furthermore, the carrier sources may be located on both sides or one side of the substrate, and may be arranged in shapes such as off-center, central, continuous, intermittent, or striped. While the carrier sources pressed onto the asphalt layer may be continuous, an intermittent or striped shape is preferred. Specifically, it is preferable that the carrier sources pressed onto the asphalt layer be arranged in an intermittent, striped, or dotted pattern with spacings of 1 mm to 20 mm between the carrier sources. By using carrier sources of this structure, as shown in Figure 11, a thick and a thin asphalt layer can be created in the doped asphalt layer. This difference in thickness becomes a channel for the electrolyte and a channel for gases generated from the electrodes of the laminated or re-laid energy storage device. Also, as shown in Figure 12, repeated charging and discharging of the battery causes charge carriers to diffuse in the plane of the asphalt layer facing the opposite electrode, and these channels eventually disappear, resulting in a flat asphalt layer. Note that if the above spacing is less than 1 mm or greater than 20 mm, the channels will not function adequately as liquid or gas channels.

[0131] On the other hand, during the doping process, if the asphalt layer is pressurized as it expands in volume, the asphalt layer becomes denser, but conversely, the stress on the asphalt layer and the current collector increases. As a result, the asphalt layer is prone to delamination or detachment from the current collector after the pressure is released, and if the current collector does not have sufficient strength, wrinkles or cracks may develop in the current collector. In other words, maintaining a pressurized state to allow doping to proceed has the drawback of degrading cycle characteristics and input / output characteristics.

[0132] The higher the capacity of the active material, the greater the volume expansion of the active material during charging or discharging, and this is also true for the volume change that occurs during bonding with alkali metals. When doping is performed under pressure using a press, the force that causes the active material to expand is counteracted by the pressure from the press. In other words, when charge carriers are doped into the asphalt layer, a force that causes expansion is generated, but the pressure from the press suppresses this, thus suppressing expansion and slowing down the doping reaction.

[0133] Therefore, the inventors conducted extensive research on pressurization during the doping process and found that the above problems could be suppressed by pressurizing a carrier coating containing a carrier source onto the composite layer, then releasing the pressurization to dope the composite layer with charge carriers. By releasing the pressurization during the doping process and doping without applying external load, the composite layer becomes more prone to expanding in the thickness direction of the electrode, reducing the stress on the composite layer and the current collector. As a result, an electrode with excellent cycle characteristics and input / output characteristics is obtained.

[0134] Furthermore, by releasing the pressure after the carrier source is pressed into the asphalt layer, the energy consumption required to maintain the pressure is reduced, resulting in higher energy efficiency in the electrode manufacturing process. In addition, since the load on the pressurizing device is temporary, it is easier to maintain the durability of the pressurizing device. Moreover, it is possible to adjust the productivity of the electrodes by increasing the transport speed. It is also acceptable to create a reduced pressure environment after releasing the pressure. Several specific embodiments will be described below.

[0135] [First Embodiment (Crimping by Line Pressure)] Figure 1 is a schematic diagram viewed from the electrode thickness direction to illustrate the manufacturing method of the electrode for the energy storage device according to this embodiment. Figures 2 to 4 are schematic diagrams viewed from the top to illustrate the manufacturing method of the electrode for the energy storage device. Figures 5 and 6 are schematic diagrams of the configuration of the manufacturing apparatus for the electrode for the energy storage device.

[0136] As shown in Figures 1-4, the manufacturing method for electrodes for energy storage devices according to this embodiment includes a step of doping charge carriers into the electrode mixture layer by applying pressure to a carrier coating (carrier source and base material) being conveyed at a predetermined speed in the same direction with a work roll or the like, pressing the mixture layer and carrier source together, and then releasing the pressure. The method also includes a step of peeling and removing the base material from the mixture layer after releasing the pressure.

[0137] For example, a doped electrode is prepared by providing a 50 μm thick composite layer on a 10 μm thick metal foil wound into a roll, while a carrier coating is prepared by providing a 10 μm thick alkali metal on a 10 μm thick PET film wound into a roll. Then, the electrode and the carrier coating are pressed together so that the carrier source is in contact with the surface of the composite layer, and the pressure is released to manufacture the electrode. In this pressing process, the composite layer, current collector, carrier source, and substrate are all pressed together, but if a current collector is provided on the composite layer in a later step, the composite layer, carrier source, and substrate may be pressed together.

[0138] Here, "pressure release" means removing the pressure applied to the electrode and the carrier coating. For example, in this embodiment, the process of releasing pressure occurs after the work roll has passed.

[0139] In the case of electrodes where the composite layer is provided in a continuous shape, or in the case of carrier coatings where the carrier source is provided in a continuous shape, continuous doping is possible as shown in Figure 2. If either or both are intermittent, intermittent doping is possible as shown in Figure 3. If either or both are striped, striped doping is possible as shown in Figure 4.

[0140] As shown in Figures 5 and 6, the manufacturing apparatus for electrodes for energy storage devices of this embodiment mainly comprises an electrode unwinding mechanism for unwinding a roll-shaped electrode to be doped, a carrier coating unwinding mechanism for unwinding a carrier coating having a carrier source on a roll-shaped substrate, a pressurizing mechanism for pressing the composite layer and the carrier source, an electrode winding mechanism for winding the doped electrode, and a substrate winding mechanism for winding the substrate of the carrier coating. When the composite layer is provided on both the front and back surfaces of the current collector, or when the current collector is a porous body with through holes, the materials can be pressed simultaneously as shown in Figure 6, or one side at a time as shown in Figure 5.

[0141] Furthermore, the manufacturing apparatus for electrodes for energy storage devices preferably includes multiple support rolls to assist in the transport of the doped electrode unwound from the electrode unwinding mechanism as it passes through the pressurizing mechanism, and a back roll that contacts the back surface of the electrode to support it and bond it to the carrier source. By providing support rolls and a back roll, misalignment between the composite layer and the carrier source during bonding can be suppressed. The gripping angle of the support rolls and back rolls that contact the electrode should be between 10 degrees and 180 degrees. Here, the gripping angle refers to the angle of the portion where the electrode or substrate is in contact with the surface of the roll, as shown in Figure 7.

[0142] The following describes in detail an example of application to battery electrodes using alkali metal ions as charge carriers, but various additions, modifications, or deletions are possible without departing from the spirit of the present invention.

[0143] Known methods such as the roll-to-roll method, belt conveyor method, chain conveyor method, roller conveyor method, and lifting method can be used to transport the electrodes to be doped and the carrier coating. The roll-to-roll method is a technique in which the doped electrode is unwound from one roll while the doped electrode is wound back into a roll on the other. The belt conveyor method is a technique in which electrodes are placed on a flat belt and transported by the movement of the belt. The chain conveyor method is a technique in which electrodes are placed on a platform attached to a chain and transported. The roller conveyor method is a technique in which electrodes are placed on a series of rollers and transported by the rotation of the rollers. The lifting method is a technique in which electrodes are suspended from above and transported while being lifted up. Of these, the roll-to-roll method is preferred because it is easy to mass-produce and allows for high-speed, continuous production under the same conditions.

[0144] Furthermore, if the electrode and carrier coating are not transported, the pressurizing mechanism must move to press the carrier source against the composite layer, which is disadvantageous for producing large-area electrodes.

[0145] When transporting electrodes and carrier coatings, the electrodes and carrier coatings are supported by back rolls and support rolls, and the tension is adjusted as needed, allowing the carrier source to be uniformly pressed onto the asphalt layer.

[0146] Here, the back roll is a roller located near where the asphalt mixture layer and the carrier source are bonded together, and it supports the electrode by contacting the back surface of the electrode or the back surface of the substrate. This ensures that the asphalt mixture layer evenly receives the carrier source. The support roll is a roller provided between each unwinding mechanism and each winding mechanism, and multiple rollers can support the electrode or carrier coating. Note that the back roll and support roll may also be dancer rolls, and they may be equipped with a heating mechanism.

[0147] In the charge carrier doping process, electrodes doped with charge carriers can be manufactured by continuously applying pressure to the asphalt layer and the carrier source, as the alkali metals in the charge carrier source will eventually disappear over time. However, with this method, adjusting the pressure is extremely difficult when the asphalt layer undergoes significant volume expansion during the doping process. Specifically, if the pressure is too low, a dense asphalt layer cannot be obtained, and doping will take a long time; if it is too high, the asphalt layer will peel off or detach from the current collector. Furthermore, when using an active material that exhibits large volume expansion during doping, the force of the active material trying to expand will be opposed by the pressure from the press, resulting in a decrease in the doping speed.

[0148] For the reasons that the above problems are less pronounced, it is preferable to dope the charge carriers without applying pressure after crimping. By doping without applying external load, the composite layer expands more easily in the thickness direction of the electrode, and the stress on the composite layer and current collector can be reduced. As a result, an electrode with excellent cycle characteristics and input / output characteristics is obtained.

[0149] Furthermore, by releasing the pressure after the carrier source is pressed into the asphalt layer, the energy consumption required to maintain pressure is reduced, resulting in higher energy efficiency in the electrode manufacturing process. In addition, since the load on the pressurizing device is temporary, it is easier to maintain the durability of the pressurizing device. It is also possible to adjust the productivity of electrodes by increasing the transport speed. Note that a reduced pressure environment may be maintained after the pressure is released.

[0150] The pressurizing time during the bonding of the composite layer and the carrier source is preferably 10 seconds or less. More preferably 1 second or less, and more preferably 0.001 seconds or more and less than 1 second. In particular, when the composite layer contains an active material with an electrical capacitance of 500 mAh / g or more, an electrode with excellent cycle characteristics can be obtained when the pressurizing time is 0.001 seconds or more and less than 1 second.

[0151] Furthermore, it is preferable to sustain the doping reaction for at least 1 second after releasing the pressure to expand the composite layer in the thickness direction. More preferably, it should be 5 seconds or more, and more preferably 10 seconds or more.

[0152] The doping reaction after release of pressure tends to accelerate at higher temperatures, but rapid doping reactions due to temperature can easily degrade the electrodes. In particular, if the composite layer undergoes rapid expansion, the electrode's cycle characteristics deteriorate. For this reason, it is preferable to carry out the reaction at a temperature between -20°C and 120°C. More preferably, it is between -20°C and 80°C. After the doping reaction is complete, heat treatment, UV irradiation, etc., may be performed to the extent that the electrodes do not undergo thermal decomposition.

[0153] The completion of doping can be determined by the degree of color change in the asphalt mixture layer or the rate of volume change in the asphalt mixture layer. For example, when no change in the color of the asphalt mixture layer occurs or no change in volume occurs even after time has passed, it can be determined that an equilibrium state has been reached, and the doping reaction can be considered complete at this point.

[0154] Although it varies depending on the diameter of the work roll and the electrode thickness, the transport speed (feed speed) of the electrode and carrier coating is preferably 0.001 m / min or more and 100 m / min or less, more preferably 0.01 m / min or more and 80 m / min or less, and even more preferably 0.02 m / min or more and 50 m / min or less.

[0155] The pressurizing mechanism is not particularly limited as long as it can apply a predetermined linear pressure. Linear pressure is the value obtained by dividing the total load acting on the cylinder by the contact length with the conveyed object. For example, existing pressurizing mechanisms such as roll presses, calender presses, laminator presses, and belt presses can be selected. Among these, it is preferable to select a roll press or belt press that can apply pressure to two or more work rolls or work belts through electrodes and carrier coverings. These may be equipped with a heating mechanism for the work rolls or work belts as needed.

[0156] When crimping using a roll press, the appropriate linear pressure changes based on several factors such as the work roll diameter, roll material, gap between rolls, electrode type, and tension applied to the electrodes. However, at the above-mentioned transport speed, the high effectiveness of the present invention can be obtained by applying a linear pressure of 5 kgf / cm (0.5 N / cm) to 1000 kgf / cm (10² N / cm) when crimping.

[0157] When the linear pressure is less than 5 kgf / cm, it is difficult to press the asphalt layer and the carrier source together, or even if they do adhere, the doping reaction is extremely slow, resulting in an electrode with uneven doping in the thickness direction. Effective countermeasures include introducing a process to impregnate the asphalt layer and carrier source with an electrolyte, or pre-containing a solid electrolyte in the asphalt layer. However, these methods dope the charge carriers via the electrolyte or electrolyte solution.

[0158] On the other hand, when the line pressure exceeds 1000 kgf / cm, the composite material layer is more likely to peel off from the current collector. Even if peeling does not occur, the electrodes tend to have inferior cycle characteristics and input / output characteristics.

[0159] It is preferable to adjust the linear pressure to 7 kgf / cm to 800 kgf / cm, and more preferably 10 kgf / cm to 500 kgf / cm, because this allows for rapid doping of charge carriers into the composite layer and results in electrodes with excellent cycle characteristics and input / output characteristics.

[0160] The gripping angle between the work roll and the electrode is not particularly limited. For example, it is sufficient for the work roll to simply be in contact with the electrode without wrapping around it. In other words, the gripping angle includes 0 degrees.

[0161] If the temperature during crimping is too low, the doping reaction will be slow, and if it is too high, the doping reaction will be too fast. However, if the doping reaction is too fast, cracks will form in the composite layer, and the composite layer will be more likely to peel off from the current collector, resulting in poor cycle characteristics and input / output characteristics of the electrode. For this reason, it is preferable to carry out the crimping process at a temperature below the melting point of the carrier source and between -20°C and 120°C.

[0162] The work roll diameter is preferably 2 cm or larger. If it is less than 2 cm, the electrode and carrier coating tend to bend during crimping, making it difficult to maintain uniformity during crimping, and resulting in wrinkles and peeling of the resulting electrode. To prevent such defects and to keep the equipment from becoming too large, it is recommended to select a work roll with a diameter of 5 cm to 200 cm.

[0163] The material of the work roll is not particularly limited as long as it can withstand the application of the specified linear pressure; for example, tool steel, high-speed steel, alloy steel, and cemented carbide can be used. Furthermore, these materials may be covered with resin or rubber, or metal plating may be applied.

[0164] The gap between the rolls is preferably 10% to 200% of the thickness of the composite layer. The gap is preferably 20% to less than 100% of the total thickness of the electrode and carrier coating, more preferably 30% to 99%, and even more preferably 40% to 98%.

[0165] Maintaining uniform tension on electrodes and carrier coatings allows for the manufacture of electrodes with less waviness and wrinkles, and also prevents wrinkles, loosening, and meandering of electrodes during winding. For this reason, it is preferable to introduce a tension maintenance mechanism capable of maintaining a constant tension on conveyed materials such as electrodes and substrates. The tension maintenance mechanism is not particularly limited as long as it can maintain tension on the electrodes and carrier coatings, and known mechanisms can be used. Examples include load cells, dancer arms, and edge position controls. The preferred values ​​vary depending on the width, thickness, and material of the conveyed material, so the tension setting is not particularly limited. For example, if the current collector is 5 μm to 50 μm thick and 5 cm to 300 cm wide, and the material of the current collector is Cu, Cu alloy, Ni, Al, Al alloy, steel, or stainless steel, or if the carrier coating is of the same dimensions, it is preferable to set the tension to 0.5 N to 200 N. Tension control can be achieved by either torque control or speed control. The unwinding section, winding section, or even individual parts may each have a mechanism for individual tension control. These tensions can be measured using existing tension detectors.

[0166] The timing for peeling the substrate from the asphalt mixture layer can be during or after doping. Since the substrate tends to peel more easily as the carrier source is doped, it is preferable to peel it after doping. If peeled before doping, the carrier source may deform or disappear during the doping process, making it prone to wrinkles and cracks, and making rapid and uniform doping difficult. In addition, the carrier source tends to stick to the pressurizing device. Here, "before doping" means the stage before the charge carriers are incorporated into the asphalt mixture layer, "after doping" means the stage after the charge carriers have been incorporated into the asphalt mixture layer, and "during doping" means the stage while the charge carriers are being incorporated into the asphalt mixture layer.

[0167] In this embodiment, when peeling the substrate from the asphalt layer, it is preferable to peel it at a constant speed while maintaining an angle of 10 degrees to 180 degrees with respect to the electrode to which the substrate is attached. This angle is called the peeling angle. When this angle is 0 degrees, it means that the substrate is pulled in the transport direction, completely parallel to the electrode to which the substrate is attached. 90 degrees means that the substrate is pulled in the direction perpendicular (thickness direction) to the electrode to which the substrate is attached. 180 degrees means that the direction in which the substrate is pulled is completely opposite to the transport direction of the electrode. If the angle is too acute, the carrier source is likely to remain on the substrate, making it difficult to peel off, and because it is peeled along the substrate, the substrate is easily damaged by tensile stress. If the angle is too obtuse, the asphalt layer is easily damaged. In the case of 90 degrees, force is applied in the vertical direction, making it easy for the pressed carrier source to peel off from the asphalt layer, or for the asphalt layer to detach from the current collector. From this perspective, a more preferable angle is 10 degrees to 80 degrees or 100 degrees to 180 degrees, even more preferably 12 degrees to 70 degrees or 110 degrees to 160 degrees, and most preferably 15 degrees to 50 degrees.

[0168] The above angle is preferably achieved by adjusting the gripping angle of the substrate gripping roll. When conveying using a single gripping roll, the peeling angle and the gripping angle coincide. In this case, it is preferable to peel the substrate at a constant speed while keeping it in contact with the gripping roll so that the surface of the substrate is at the above peeling angle against the outer surface of the peeling gripping roll.

[0169] When transporting using two or more grabbing rolls, the process involves multiple stages, so the peeling angle and the grabbing angle do not necessarily have to match.

[0170] In any case, for the reason that the substrate can be cleanly peeled from the asphalt layer with minimal damage to the asphalt layer, the gripping angle of the initial gripping roll used to peel the substrate is preferably 10 degrees or more and 180 degrees or less. More preferably, it is 12 degrees or more and 160 degrees or less.

[0171] As the gripping angle increases, the contact area widens, improving the stability of transport and doping. However, the tensile stress also increases, making the substrate more prone to elongation and cracking in the carrier source. Conversely, as the gripping angle decreases, the contact area narrows, making the electrode and carrier coating more likely to slip during transport. From this perspective, more preferable gripping angles are between 12 degrees and 160 degrees, and between 15 degrees and 150 degrees.

[0172] The above process is preferably carried out in a dry environment, as moisture would deactivate the carrier source if performed in the atmosphere. Specifically, it is preferable to carry it out in an environment with a dew point temperature of -10°C or lower. Preferably, it is -20°C or lower, and more preferably -40°C or lower. If manufacturing costs are not a consideration, the lower the temperature, the better. The dew point temperature is a value that expresses the amount of moisture in terms of temperature, and it is the temperature at which condensation occurs when a gas is cooled.

[0173] Equipment that can achieve a dry environment with a dew point temperature of -10°C or lower includes dry rooms, dry booths, and glove boxes. Specifically, a dry environment can be achieved by passing air through a desiccant such as silica gel, zeolite, or alkali metal chloride, and supplying this dry air to the electrode manufacturing area. Alternatively, dry air can be produced by removing moisture from compressed air generated by a compressor.

[0174] Furthermore, if the carrier source is a spontaneously combustible substance such as sodium or potassium, it is preferable to carry out the process in an inert gas atmosphere such as a noble gas.

[0175] In this embodiment, the doping reaction is initiated by pressurization, and then the pressurization is released to promote the doping reaction. Therefore, it is not necessary to include a step to dopate charge carriers via an electrolyte, gel electrolyte, ionic liquid, molten salt, or other electrolyte. In this case, no decomposition products originating from the electrolyte are generated in the doping step.

[0176] In this embodiment, the composite layer may be brought into contact with an electrolyte, gel electrolyte, ionic liquid, molten salt, or other electrolyte during or after doping. In this case, decomposition products derived from the electrolyte will be generated.

[0177] In any case, when the charge carrier is an alkali metal ion, the electrode approaches the potential of a zero-valent alkali metal as the doping amount increases. Therefore, when the electrode obtained in this embodiment is brought into contact with an electrolyte, decomposition products of the electrolyte can be formed on the surface of the active material without applying an external voltage. Furthermore, since SEI can be formed without causing volume expansion associated with alkali metalization of the active material, an SEI of uniform thickness is formed on the surface of the active material. By making the thickness of the SEI uniform, the cycle characteristics, input / output characteristics, and self-discharge characteristics are improved.

[0178] Furthermore, the electrodes obtained in this embodiment may be pressurized again to densify or smooth the composite layer.

[0179] According to this embodiment, electrodes can be manufactured in which charge carriers are doped into the composite layer.

[0180] For example, if the charge carrier is an alkali metal ion, an electrode can be manufactured that contains an alloy with an alkali metal or a material that has absorbed alkali metal ions as an active material. Furthermore, if the binder or conductive additive contained in the composite layer has irreversible capacitance, these materials are simultaneously doped with charge carriers, reducing their irreversible capacitance.

[0181] These electrodes, without exception, have a higher potential than zero-valent alkali metals, and therefore can be applied to solid electrolytes that react in contact with alkali metals. For this reason, the electrodes obtained in this embodiment have the advantage of offering a wider range of solid electrolyte options for use in energy storage devices compared to electrodes made solely of zero-valent alkali metals. Solid electrolytes that readily undergo side reactions with zero-valent alkali metals include sulfide-based solid electrolytes and oxide-based solid electrolytes.

[0182] Furthermore, compared to electrodes composed solely of zero-valent alkali metals, these electrodes offer advantageous features such as less dendrite formation during charging and higher mechanical strength. For these reasons, the energy storage device using the electrodes and solid electrolyte obtained in this embodiment exhibits superior cycle characteristics, self-discharge characteristics, high-temperature characteristics, and low-temperature characteristics.

[0183] Furthermore, in electrochemical methods where an external voltage is applied to an electrochemical cell or an external short circuit is used to dope charge carriers, if the electrical resistivity of the composite layer is low, the doping process takes a long time. However, in the manufacturing method of this embodiment, charge carriers can be doped quickly and uniformly, regardless of the conductivity of the composite layer. That is, even composite layers that do not contain any conductive additives, or composite layers that do not contain any electrolytes, can be suitably doped. In addition, uniform doping is achieved by uniformly pressing alkali metals onto the composite layer. Moreover, the substrate can be easily peeled off after doping with minimal damage to the composite layer. Furthermore, in electrochemical methods, the active material after doping tends to be amorphous, but with the method of this disclosure, a crystalline active material doped with charge carriers is easily obtained.

[0184] An example of an electrode manufactured as described above is shown in Figure 8. As shown in Figure 8, this electrode comprises a current collector and a composite layer doped with charge carriers. The composite layer also has a surface layer containing a carbonate or oxide. Here, the carbonate or oxide is lithium carbonate or lithium oxide if the charge carrier is lithium, sodium carbonate or sodium oxide if it is sodium, and potassium carbonate or potassium oxide if it is potassium.

[0185] Because this electrode does not use an electrolyte in its manufacturing process, for example, if the charge carrier is lithium, the surface layer is composed of lithium carbonate, or a small amount of lithium oxide, and there are no electrolyte-derived compounds or decomposition products. Furthermore, since this manufacturing method involves doping the composite layer by pressing the carrier source from above, lithium carbonate is not present below the composite layer or near the current collector.

[0186] Because this electrode does not use an electrolyte in its manufacturing process, it does not contain excess electrolyte-derived compounds or decomposition products in the composite layer, resulting in an electrode for energy storage devices that exhibits excellent cycle characteristics and input / output characteristics. For example, it is known that electrolyte-derived SEI formed on the surface of graphite negative electrodes decomposes at temperatures above 80°C, causing undesirable exothermic reactions, but this invention does not contain such substances.

[0187] Furthermore, X-ray diffraction analysis of this electrode revealed that a crystalline material consisting of active material and charge carriers was formed in the composite layer. For example, if the charge carrier is lithium and the active material is a material that can alloy with the charge carrier, a crystalline Li alloy is formed in the composite layer. In contrast, electrodes produced by conventional electrochemical doping showed amorphous material rather than a crystalline alloy.

[0188] Furthermore, this electrode can also be manufactured using the following process.

[0189] [Second Embodiment (Crimping by Surface Pressure)] Figures 9 and 10 are schematic diagrams viewed from the electrode thickness direction to illustrate the method for manufacturing an electrode for an energy storage device according to this embodiment.

[0190] As shown in Figures 9 and 10, the manufacturing method for electrodes for energy storage devices of this embodiment includes the steps of doping the charge carrier into the asphalt layer by placing the electrode to be doped and the carrier coating (carrier source and substrate) into a die, sandwiching them between an upper punch and a lower punch so that the carrier source is in contact with the asphalt layer, applying pressure to the electrode to be doped and the carrier coating to press the carrier source into the asphalt layer, and then releasing the pressure. Furthermore, the method includes the steps of peeling off and removing the substrate on the asphalt layer after the pressure is released using tweezers, a blower, a suction device, an electrostatic chuck, etc.

[0191] When the asphalt mixture layer is provided on both the front and back surfaces of the current collector, or when the current collector is a porous body with through holes, carrier coatings can be provided above and below the electrode and simultaneously crimped together so that the carrier source contacts the asphalt mixture layer, as shown in Figure 10, or crimped one side at a time as needed, as shown in Figure 9. Furthermore, if the base material has carrier sources on both sides, the electrodes may be crimped together so that the carrier sources are in contact with the electrodes from above and below.

[0192] When crimping using a uniaxial press, the appropriate surface pressure changes based on several factors such as the die material and electrode type, but 20 kgf / cm² is the appropriate pressure. 2 (196N / cm 2 , 1.96MPa) or more 30000kgf / cm 2 (294kN / cm 2 The high effectiveness of the present invention can be obtained by applying a surface pressure of 2942 MPa or less. Here, a uniaxial press means a device that can apply a pressing force along a single axis to at least a carrier source and press it against the asphalt layer.

[0193] For example, any device with a mechanism that applies pressure from one or both sides of a single shaft can dope charge carriers into the asphalt layer by compression. Specifically, this includes hydraulic presses that use hydraulic pressure, mechanical presses that use mechanical cams or cranks, servo presses that use servo motors, screw presses that apply pressure by the rotation of a screw, hand presses that apply pressure manually, electric presses that use electric motors, and air presses that apply pressure using pneumatic pressure.

[0194] However, the surface pressure is 10 kgf / cm². 2 If the concentration is less than the specified value, it becomes difficult to press the carrier source and the asphalt mixture layer together, the doping reaction is extremely slow, and the doping of the asphalt mixture layer becomes uneven in the thickness direction. To address this, it is effective to impregnate the asphalt mixture layer and carrier source with an electrolyte solution, or to pre-incorporate the electrolyte into the asphalt mixture layer. However, these methods involve doping via an electrolyte solution or similar substance.

[0195] On the other hand, the surface pressure is 30,000 kgf / cm².2 If the value exceeds this, the composite material layer is more likely to peel off from the current collector, resulting in electrodes with inferior cycle characteristics and input / output characteristics.

[0196] A surface pressure of 20 kgf / cm² is chosen because it allows for rapid doping of charge carriers into the composite layer and results in an electrode with excellent cycle characteristics and input / output characteristics. 2 More than 10000kgf / cm 2 It is preferable to adjust the pressure as follows, with a more preferable surface pressure being 30 kgf / cm². 2 More than 300kgf / cm 2 The following applies:

[0197] The materials of the die, upper punch, and lower punch are not particularly limited as long as they can withstand the required surface pressure. For example, tool steel, high-speed steel, alloy steel, and cemented carbide are suitably used. Furthermore, these materials may be coated with resin or rubber, metal plating, or a release agent.

[0198] Similar to the first embodiment, the pressurizing time during the bonding of the asphalt layer and the carrier source is preferably 10 seconds or less. More preferably 1 second or less, and more preferably 0.001 seconds or more and less than 1 second. In particular, when the asphalt layer contains an active material with an electrical capacitance of 500 mAh / g or more, an electrode with excellent cycle characteristics can be obtained when the pressurizing time is 0.001 seconds or more and less than 1 second. When applying surface pressure with a uniaxial press, preferred pressurizing mechanisms that can achieve a pressurizing time of 10 seconds or less include hydraulic presses, servo presses, and air presses.

[0199] Furthermore, similar to the first embodiment, it is preferable to sustain the doping reaction for 1 second or more after releasing the pressure to expand the composite layer in the thickness direction. A more preferable duration is 10 seconds or more, and even more preferably 30 seconds or more.

[0200] In this embodiment, the peeling angle when peeling the substrate from the composite layer is preferably 10 degrees to 80 degrees or 100 degrees to 180 degrees with respect to the electrode to which the substrate is attached. It is preferable to peel at a constant speed while maintaining this angle. More preferable angles are 12 degrees to 70 degrees or 110 degrees to 160 degrees, and preferably 15 degrees to 50 degrees. In this embodiment, a peeling angle near 90 degrees is not very preferable.

[0201] For conditions not specifically mentioned, the preferred conditions are the same as those in the first embodiment, and the characteristics of the resulting electrodes are generally consistent.

[0202] Compared to the first embodiment, this embodiment lacks industrial productivity, but it can effectively dope clay-like composite layers containing electrolytes or ionic liquids, or brittle composite layers that crumble easily.

[0203] On the other hand, when the thickness of the asphalt layer is 200 μm or more, it is preferable to use the cold isostatic pressing (CIP) method as the pressing mechanism. In the CIP method, the electrode to be doped and the carrier coating are pressed in a non-directional manner via a fluid, and after the asphalt layer and carrier source are pressed together, the pressure is released, thereby doping the asphalt layer with charge carriers. With this method, the electrode is uniformly subjected to a pressure equal to its fluid pressure, so it can be pressed in a non-directional manner. In the CIP method as well, the preferred surface pressure, pressing time, duration after pressure release, and peeling angle are the same as when pressing using a uniaxial press.

[0204] [Third embodiment (area ratio of asphalt layer to alkali metal)] A drawback of asphalt mixture layers doped with charge carriers is that their mechanical strength is reduced compared to the asphalt mixture layer before doping. This is because the mechanical strength of the asphalt mixture layer tends to decrease as the amount of doping increases. When mechanical strength decreases, the asphalt mixture layer becomes more prone to cracking, making it more likely to detach or peel off from the current collector, and making it difficult to obtain stable cycle characteristics.

[0205] From the perspective of obtaining an electrode with high mechanical strength, rather than doping charge carriers over the entire surface of the composite layer, it is preferable that the area (S1) of the composite layer is larger than the area (S2) of the carrier source (S2 < S1). Here, the area refers to the quantity calculated as the product of the horizontal dimension and the vertical dimension, excluding the thickness of the electrode.

[0206] However, if S1 is too large or S2 is too small, the doping amount of charge carriers is small, and the improvement effect of battery characteristics by doping cannot be sufficiently expected. By increasing the thickness of the carrier source, the doping amount of charge carriers can be increased. However, if the thickness of the carrier source is too large, in the crimping process, the pressure tends to be easily dispersed within the carrier source, and the required pressure tends to increase. If the pressure in the crimping process is too high, the composite layer becomes overly dense, is easily peeled off from the current collector, and the cycle characteristics also deteriorate. Also, due to crimping, the carrier source is likely to stretch, the contact area becomes large, and it is difficult to adjust the dimensions.

[0207] For these reasons, it is preferable that S1 is larger than S2 and is the same as or smaller than 1.3 times S2, and more preferably the same as or smaller than 1.2 times S2. And S2 is smaller than S1 and is the same as or larger than 0.7 times S1, and more preferably the same as or larger than 0.8 times S1. That is, it is preferable that S1 and S2 satisfy the relationship of (Equation 1). Desirably, S1 and S2 satisfy the relationship of (Equation 1-2). 0.7×S1 ≦ S2 < S1 ≦ 1.3×S2 ···· (Equation 1) 0.8×S1 ≦ S2 < S1 ≦ 1.2×S2 ···· (Equation 1-2)

[0208] Also, when in a relationship satisfying (Equation 1), by arranging the carrier source inside in the plane direction of the electrode and applying pressure, the doping amount of charge carriers inside in the plane direction of the electrode can be made more than the doping amount of charge carriers outside in the plane direction.

[0209] That is, an electrode can be manufactured in which the outer side in the plane direction of the electrode has better mechanical strength than the inner side in the plane direction. When the doping amount per electrode is equal, this electrode has better cycle characteristics than an electrode with the same charge doping amount on the inner and outer sides in the plane direction. And it has better output characteristics than an electrode in which the doping amount of charge carriers on the inner side in the plane direction is less than that on the outer side in the plane direction.

[0210] Also, in this embodiment, since the mechanical strength of the electrode can be made higher on the outer side in the plane direction than on the inner side in the plane direction, when cutting the electrode, it is preferable to cut the outer side in the plane direction. By cutting the outer side in the plane direction, an electrode in which the peeling or cracking of the composite material layer is suppressed can be obtained.

[0211] [Fourth Embodiment (Method for Manufacturing a Power Storage Device)] The composite material layer doped with charge carriers has a problem that its mechanical strength decreases compared to the composite material layer before doping. As a countermeasure, as described in the third embodiment, it is effective to make the area (S1) of the composite material layer larger than the area (S2) of the carrier source. To form a power storage device, a counter electrode composite material layer of the counter electrode facing the composite material layer of the electrode obtained in this embodiment is also required.

[0212] When the area (S3) of the counter electrode composite material layer is larger than S1, charge carriers are likely to precipitate as solids near the end face of the counter electrode during the charging process, making the power storage device likely to short-circuit. For example, when the charge carriers are lithium ions, they precipitate as metallic lithium. Also, when S3 is larger than S2, there is a problem that the Coulomb efficiency of the power storage device decreases and the energy density of the power storage device decreases.

[0213] To solve these problems, it is preferable that the area S3 of the counter electrode composite material layer is the same as or larger than S2 and smaller than S1. That is, it is preferable that S1, S2, and S3 satisfy the relationship of (Equation 2). S3≦S2<S1·····(Equation 2)

[0214] Here, if S3 is too small, the doping amount of charge carriers is low, and various advantages brought by doping the charge carriers cannot be utilized.

[0215] By increasing the thickness of the carrier source, the doping amount of charge carriers can be increased. However, if the thickness of the carrier source is too large, in the crimping process, the pressure tends to be dispersed within the carrier source, and the required pressure tends to increase.

[0216] If the pressure in the crimping process is too high, the composite material layer is likely to peel off from the current collector. Also, due to crimping, the carrier source is likely to stretch, the contact area becomes large, and it is difficult to adjust the dimensions.

[0217] For these reasons, it is desirable to satisfy both (Equation 1) and (Equation 2). In addition, the area S1 of the composite material layer is the sum of the area S ' 1 of the composite material layer with a large doping amount of charge carriers and the area S " 1 of the composite material layer with a small doping amount of charge carriers, and it is preferably in a relationship that satisfies (Equation 3). S " 1 < S3 ≤ S2 ≤ S ' 1 < S1 = S ' 1 + S " 1 ····· (Equation 3)

[0218] With this manufacturing method, since the doping amount of charge carriers in the composite material layer (S ' 1) facing the counter electrode is large, the effect of improving the battery characteristics due to the doping of charge carriers can be sufficiently obtained, and since the doping of the composite material layer (S " 1) not facing the counter electrode is small, a decrease in the strength of the composite material layer not facing the counter electrode can be suppressed, resulting in a power storage device with excellent cycle characteristics.

[0219] It is preferable that the thickness T1 of the carrier source, the thickness T2 of the counter electrode composite material layer, and the thickness T3 of the composite material layer satisfy the relationship of (Equation 3). T1 ≤ T3 < T2 ····· (Equation 3) Here, the thickness T1 of the carrier source is preferably 0.1 μm or more and 500 μm or less.

[0220] The conditions of the composite layer and counter electrode composite layer (active material, composition, dimensions, etc.) and the amount of charge carrier doping affect the thickness of the carrier source. If the carrier source is too thin, the amount of doping is small, making it difficult to obtain the effect of doping on improving the characteristics of the energy storage device. If it is too thick, the carrier source tends to remain on the surface of the composite layer, which reduces the cycle characteristics and increases the risk of short circuits in the energy storage device.

[0221] Therefore, T1, T2, and T3 are related in a way that satisfies (Equation 3), and it is preferable that T1 is between 0.1 μm and 600 μm. It is more preferable that T1 is between 0.5 μm and 200 μm, and even more preferable that it is between 1 μm and 100 μm.

[0222] The amount of charge carriers that can be doped varies depending on the carrier source, but for example, in the case of metallic lithium, it is 10 μm / cm². 2 Approximately 2mAh / cm² 2 , 50 μm / cm 2 Approximately 10mAh / cm² 2 The electrode to be doped can be doped with charge carriers. Preferably, the capacitance per unit area of ​​the composite layer is such that it can accept a carrier source of a predetermined thickness.

[0223] An energy storage device comprises a positive electrode, a negative electrode, and an electrolyte or solid electrolyte interposed between the positive and negative electrodes. Examples include lithium-ion batteries, sodium-ion batteries, potassium-ion batteries, lithium-ion capacitors, sodium-ion capacitors, and potassium-ion capacitors.

[0224] When this electrode is used as the positive electrode of an energy storage device, the device can be fabricated by combining it with an electrode whose charge / discharge potential is lower than that of this electrode. On the other hand, when this electrode is used as the negative electrode of an energy storage device, the device can be fabricated by combining it with an electrode whose charge / discharge potential is higher than that of this electrode.

[0225] For example, when the electrode of this disclosure is used as a positive electrode, a known negative electrode used in energy storage devices can be used as the counter electrode. Also, when the electrode of this disclosure is used as a bipolar electrode, the counter electrode corresponds to the back surface of the electrode of this disclosure.

[0226] The non-aqueous electrolyte used in energy storage devices can be any liquid or solid that can move charge carriers in response to an externally applied electric field. Examples include electrolytes, gel electrolytes, ionic liquids, molten salts, polymer electrolytes, and solid electrolytes. In other words, known electrolytes used in energy storage devices using non-aqueous electrolytes can be used. In particular, it is preferable that the non-aqueous electrolyte be a polymer electrolyte or a solid electrolyte alone, or a non-aqueous electrolyte containing either of these.

[0227] The structure of the energy storage device is not particularly limited, but existing forms and structures such as stacked and wound types can be adopted. That is, an electrode group in which the positive and negative electrodes are stacked or wound with a separator between them, is immersed in an electrolyte and sealed to form an energy storage device. Alternatively, an electrode group in which the positive and negative electrodes are stacked or wound with a solid electrolyte between them is sealed to form an energy storage device.

[0228] In terms of the structure of an energy storage device using bipolar electrodes, multiple cells are stacked in series via bipolar electrodes, each cell independently contains an electrolyte, and the devices are sealed to form an energy storage device.

[0229] [Fifth Embodiment (Inspection Method)] Alkali metals and alkali metal alloys have a metallic luster, but when doped into an asphalt mixture layer, the alkali metals eventually disappear, and the metallic luster is no longer visible. Even other carrier sources that do not have a metallic luster will show a change in color when doped into an asphalt mixture layer.

[0230] The color of the composite layer varies depending on its composition, materials, and density. The color changes when doped with charge carriers. For example, if silicon is present, it approaches black, and if graphite is present, it approaches yellow.

[0231] By examining the color, gloss, and texture of the asphalt mixture layer or carrier source after the pressure is released, the degree of doping can be determined from this change in color. This is particularly easy to determine if the carrier source is an alkali metal or an alkali metal alloy.

[0232] For example, if a metallic luster is observed on the asphalt mixture layer after the pressure is released, it means that alkali metals are present, and it can be inferred that doping is incomplete or that there is excessive doping.

[0233] If the composite layer approaches black as the amount of charge carrier doping increases, then when quantified in the CIE Lab* color space, the lightness (L*) decreases as the doping amount increases, and the red-green axis (a*) and yellow-blue axis (b*) approach 0. Conversely, if the color becomes more vivid or a specific color depending on the doping amount, the values ​​of a* and b* will take values ​​corresponding to each color. For example, in the case of yellow, a* will be around 0, and b* will be a large positive value.

[0234] In addition to methods that inspect color, gloss, and texture, the degree of doping can also be determined by irradiating the asphalt layer after pressure release with light and measuring the spectrum of the reflected light in the visible light range (300nm to 800nm) using a spectrophotometer. With this method, the degree of doping can be determined by comparing the reflection spectra before and after doping and observing the changes in peak position and intensity.

[0235] The electrodes obtained by this manufacturing method tend to have lower electrical resistivity (higher conductivity) in the composite layer as the amount of charge carrier doping increases. Therefore, in the electrodes obtained in the first and second embodiments, it is possible to estimate the amount of charge carrier doping from the electrical resistivity of the composite layer. The electrical resistivity of the composite layer can be determined by known measurement methods such as the four-terminal method and the four-point needle method.

[0236] Furthermore, it is preferable to perform all of the above-mentioned inspection methods in a dry environment at -10°C or below. [Examples]

[0237] [Electrode (1)] Si(median diameter D) 50 A slurry consisting of PVdF (Kureha, #1120), AB (Denka, Denka Black), and carbon fiber (Showa Denko, VGCH-H) (solid content composition 90:6:3:1 by mass%) was coated onto stainless steel foil (Nippon Steel, 8 μm thick), then vacuum dried (150°C, 5 hours) on both sides of the current collector, resulting in an electrode capacity of 4 mAh / cm² per unit area on one side. 2 This formed a composite layer.

[0238] [Electrode (2)] Electrode (2) was prepared by spraying an aqueous sodium silicate solution (Na2O·3SiO2 aq., concentration 10% by mass) onto the composite layer of electrode (1) using a spray gun, followed by vacuum drying (150°C, 5 hours). The amount of sodium silicate (Na2O·3SiO2) present in the composite layer was 0.35 mg / cm³. 2 That's what I decided.

[0239] [Electrode (3)] Electrode (3) is the same as electrode (1), except that PVdF has been replaced with PI (UBE, U-varnish).

[0240] [Electrode (4)] Electrode (4) is the same as electrode (1), except that PVdF is replaced with SBR (JSR, 2001) and CMC (Daicel, 2260). The weight ratio of SBR to CMC was set to 5.5:0.5.

[0241] [Electrode (5)] Electrode (5) is the same as electrode (4), except that the SBR has been changed to an acrylic resin (JSR, TRD202A).

[0242] [Electrode (6)] The electrode (6) is the same as the electrode (5), except that Si is changed to Sn (median diameter D 50 = 10 μm).

[0243] [Electrode (7)] The electrode (7) is the same as the electrode (5), except that Si is changed to SiO x (x = 0.7, median diameter D 50 = 3 μm).

[0244] [Electrode (8)] The electrode (8) is the same as the electrode (5), except that Si is changed to natural graphite (median diameter D 50 = 10 μm).

[0245] [Electrode (9)] The electrode (9) is the same as the electrode (2), except that Si is changed to a mixture of Si and artificial graphite. The mass ratio of Si to artificial graphite is 5:95.

[0246] [Electrode (10)] The electrode (10) is the same as the electrode (2), except that the mass ratio of Si to artificial graphite is changed to 20:80.

[0247] [Electrode (11)] The electrode (11) is the same as the electrode (2), except that the mass ratio of Si to artificial graphite is changed to 50:50.

[0248] [Electrode (12)] The electrode (12) is composed of a slurry (solid content composition 9.2:82.8:1:2:5 mass%) of Si (median diameter D 50 = 74 nm), Si (median diameter D 50 = 3 μm), SBR, CMC, and AB. After coating and drying on one side of a Ni-plated steel foil (manufactured by Nippon Steel, thickness 8 μm), potassium silicate (K2Si2O·1.7SiO2) dissolved in water is gravure-coated so that the solid content is 5.2 mg / cm 2 , and then vacuum dried (160 °C, 10 hours) to make the capacitance per unit area of the electrode 5.5 mAh / cm 2 .

[0249] [Carrier covering (1)] A carrier coating was used, in which metallic lithium (10 μm thick) was deposited on one side of a colorless, transparent PET film (50 μm thick) by vapor deposition.

[0250] [Carrier covering (2)] Carrier coating (2) is the same as carrier coating (1), except that the PET film is replaced with copper foil (10 μm thick) and the thickness of the metallic lithium is changed to 15 μm.

[0251] [Carrier covering 3] Carrier coating (3) is the same as carrier coating (2), except that a BN powder layer approximately 0.1 μm thick is provided on the copper foil. The BN powder layer was formed by spraying the contents of an aerosol can containing BN (manufactured by Fine Chemical Japan, B·N Spray) onto the copper foil and vacuum drying (110°C, 10 hours).

[0252] [Carrier covering (4)] The carrier coating (4) is the same as the carrier coating (4), except that the copper foil is replaced with a colorless transparent PP film (200 μm thick).

[0253] [Carrier covering (5)] Carrier coating (5) is the same as carrier coating (1), except that metallic lithium is replaced with metallic sodium. When using carrier coating (5), the doping operation described later was performed in an argon environment (room temperature 20°C, dew point temperature -80°C, atmospheric pressure 0.1 MPa).

[0254] [Dope operation (1)] Under conditions of room temperature (20°C), dew point (-80°C), and atmospheric pressure (0.1 MPa), a roll press machine (manufactured by Hosen, tabletop thermal roll press HSRP-60150H) with two work rolls (material: stainless steel, roll diameter: 60 mm, roll length: 150 mm, roll temperature: 20°C) was used to press-bond metallic lithium to the asphalt layer on both sides by sandwiching the electrode between carrier coverings so that the alkali metal was in contact with the asphalt layer, and passing it through work rolls rotating at 1.5 rpm. The load during pressing was set to 30-35 kgf / cm. After 30 seconds, the substrate was peeled off from the asphalt layer. When peeling the substrate from the asphalt layer, the substrate was brought into contact with a stainless steel roll at a 35-degree angle, and peeled off by winding it at a speed of 0.283 m / min while maintaining an angle of approximately 35 degrees with respect to the electrode to which the substrate was attached.

[0255] [Dope operation (2)] Doping operation (2) is the same as doping operation (1), except that the load during compression is set to 1-5 kgf / cm.

[0256] [Doping operation (3)] Doping operation (3) is the same as doping operation (1), except that the load during compression is set to 200-250 kgf / cm.

[0257] [Dope operation (4)] Doping operation (4) is the same as doping operation (1), except that the load during compression is set to 1100-1200 kgf / cm.

[0258] [Dope operation (5)] Doping operation (5) is the same as doping operation (1), except that the load during compression is set to 10-15 kgf / cm.

[0259] [Dope operation (6)] In an environment with a room temperature of 20°C, a dew point temperature of -80°C, and a pressure of 0.1 MPa, an electrode (φ10 mm) was sandwiched between a carrier coating (substrate φ10 mm, metallic lithium φ9 mm) so that the alkali metal contacted the composite material layer. After placing this in a die made of die steel with a diameter of φ10 mm, punches were inserted above and below the die. Using a uniaxial press, a surface pressure of 883 kgf / cm 2 (approx. 86.6 MPa, approx. 8659 N / cm 2 ) was applied for 1 second to crimp metallic lithium to the front and back composite material layers. Then, 30 seconds after the start, the substrate was peeled off and removed from the composite material layer. When peeling the substrate from the composite material layer, first, the edge of the substrate was lifted with tweezers, and while maintaining an angle of approximately 45 degrees with respect to the electrode to which the substrate was adhered, it was peeled at a speed of 0.01 - 0.02 m / min.

[0260] [Doping operation (7)] The surface pressure was continuously applied for 600 seconds. After crimping metallic lithium to one-sided composite material layer, immediately, the substrate was peeled off and removed from the composite material layer. Otherwise, it was the same as the doping operation (6).

[0261] [Fabrication of doped electrode] Electrodes for Test Examples 1 - 23 were fabricated with the combinations shown in Table 1.

[0262]

Table 1

[0263] (Test Example 1) As time passed from when it passed through the work roll, the metallic luster derived from metallic lithium gradually disappeared. 50 seconds after the pressure was released, visually, the metallic luster derived from metallic lithium completely disappeared, and only the transparent film of the substrate remained on the composite material layer. Thus, it was confirmed that charge carriers could be doped. However, the strength of the composite material layer was low, countless cracks occurred, and it fell off from the current collector.

[0264] (Test Example 2) As time elapsed from the time the work roll passed, the metallic luster derived from metallic lithium gradually disappeared. After 30 seconds from the release of pressure, the metallic luster derived from metallic lithium was completely gone to the naked eye, and only the transparent film of the substrate remained on the asphalt layer, confirming that charge carriers could be doped. Compared to Test Example 1, the strength of the asphalt layer was dramatically increased, and the shedding of the asphalt layer was suppressed.

[0265] (Test Example 3) Even after 60 seconds had elapsed since the pressure was released, no change was observed in the metallic lithium on the asphalt layer. Visually, the metallic luster derived from the metallic lithium completely disappeared 420 seconds after the pressure was released. Compared to Test Example 1, the strength of the asphalt layer was dramatically increased, and the shedding of the asphalt layer was suppressed.

[0266] (Test Example 4) Even after 60 seconds had elapsed since the pressure was released, no change was observed in the metallic lithium on the asphalt mixture layer. Visually, the metallic luster derived from the metallic lithium completely disappeared 300 seconds after the pressure was released. However, the strength of the asphalt mixture layer was low, and numerous cracks formed, causing it to detach from the current collector.

[0267] (Test Example 5) As time elapsed from the time the material passed through the work roll, the metallic luster derived from metallic lithium gradually disappeared, and 40 seconds after the pressure was released, only the transparent film of the substrate remained on the asphalt layer, confirming that charge carriers could be doped. The strength of the asphalt layer after doping was higher than that of Test Examples 1 and 4, but lower than that of Test Examples 2 and 3.

[0268] (Test Example 6) As time elapsed after the work roll passed, the metallic luster derived from metallic lithium gradually disappeared, and 40 seconds after the pressure was released, only the transparent film of the substrate remained on the composite layer, confirming that charge carriers could be doped into the material.

[0269] (Test Example 7) Even after more than 72 hours had elapsed since the pressure was released, no change was observed in the metallic sodium on the composite layer. When Si is used as the active material, sodium cannot act as a charge carrier, which is likely why no change occurred in the metallic sodium.

[0270] (Test Example 8) As time elapsed after the work roll passed, the metallic luster derived from metallic sodium gradually disappeared, and 50 seconds after the pressure was released, only the transparent film of the substrate remained on the asphalt layer, confirming that charge carriers could be doped. When comparing the asphalt layers before and after doping, the strength of the doped layer was lower.

[0271] (Test Example 9) Although lithium metal adhered to the asphalt layer after passing through the work roll, the metallic luster derived from metallic lithium did not change easily, and the metallic lithium did not completely disappear even after 24 hours.

[0272] (Test Example 10) As time elapsed after the work roll passed, the metallic luster derived from metallic lithium gradually disappeared, and 10 seconds after the pressure was released, only the transparent film of the substrate remained on the composite layer, confirming that charge carriers could be doped. The strength of the composite layer was slightly lower than that of Test Example 2.

[0273] (Test Example 11) As time passed after the work roll passed, the metallic luster derived from metallic lithium gradually disappeared, and within 10 seconds of pressure release, only the transparent film of the base material remained on the asphalt layer. However, as doping progressed, countless cracks appeared in the asphalt layer, causing it to detach from the current collector.

[0274] (Test Example 12) As time passed after the work roll, the metallic luster derived from metallic lithium gradually disappeared, and 50 seconds after the pressure was released, only the transparent film of the substrate remained on the asphalt layer. Compared to Test Example 2, the doping reaction was slightly slower, but the strength of the asphalt layer was slightly higher.

[0275] (Test Example 13) Although metallic lithium could not be observed because the substrate was Cu foil, when the substrate was peeled off from the composite layer 60 seconds after the pressure was released, the metallic lithium had almost completely disappeared. However, metallic lithium remained locally on the substrate surface that had been in contact with the composite layer. In addition, the substrate was difficult to peel off from the composite layer.

[0276] (Test Example 14) Similar to Test Example 13, metallic lithium could not be observed. After 60 seconds from the release of pressure, the substrate on the asphalt layer was peeled off, and the metallic lithium had almost completely disappeared. Furthermore, the substrate was significantly easier to peel from the asphalt layer than in Test Example 13.

[0277] (Test Example 15) As time elapsed from the time the material passed through the work roll, the metallic luster derived from metallic lithium gradually disappeared, and 20 seconds after the pressure was released, only the transparent film of the substrate remained on the asphalt layer. The strength of the asphalt layer was higher than that of Test Examples 13 and 14.

[0278] (Test Example 16) When the pressure from the uniaxial press was released and the electrode, integrated with the carrier coating, was removed from the die, the metallic luster derived from the lithium metal gradually disappeared over time. Sixty seconds after the pressure was released, only the transparent film of the substrate remained on the composite layer. The substrate could be easily peeled off.

[0279] (Test Example 17) Similar to Test Example 16, the metallic luster disappeared over time, and 300 seconds after the pressure was released, only the transparent film of the substrate remained on the composite layer. The substrate could be easily peeled off. The doping reaction was slower compared to Test Example 16.

[0280] (Test Example 18) Similar to Test Example 16, no change was observed in the metallic lithium even after 1800 seconds. After 1800 seconds from the release of pressure, when the substrate was peeled off the electrode, some of the metallic lithium adhered to the substrate.

[0281] (Test Example 19) The results are similar to those of Test Example 18.

[0282] (Test Example 20) Similar to Test Example 16, the metallic luster disappeared over time, and 900 seconds after the pressure was released, only the transparent film of the substrate remained on the composite layer. The substrate could be easily peeled off.

[0283] (Test Example 21) Similar to Test Example 16, the metallic luster disappeared over time, and 180 seconds after the pressure was released, only the transparent film of the substrate remained on the composite layer. The substrate could be easily peeled off.

[0284] (Test Example 22) In Test Example 22, the results were the same as in Test Example 2.

[0285] (Test Example 23) When the pressure was released and the electrode, which was integrated with the carrier coating, was removed from the die, the metallic luster derived from the metallic lithium had completely disappeared to the naked eye. However, the composite layer had peeled off from the current collector.

[0286] [Charge / Discharge Test] Using electrode (12) and the electrode from test example 22 as test electrodes, a coin-type battery (R2032) was fabricated using a metallic lithium counter electrode (made of metal from this company, lithium foil with a thickness of 500 μm), a PP / PE / PP three-layer microporous membrane (Celgard Co., Ltd., 2325), a glass filter (Advantec Co., Ltd., GA100), and 1 mol / L LiPF6 / ethylene carbonate (EC):diethyl carbonate (DEC) = 1:1 vol., + vinylene carbonate (VC) 1 wt.%.

[0287] The charge-discharge cycle test was conducted at 30°C with a cutoff voltage of 0.001 to 1.5V and a 0.1C rate (0.55mA / cm²). 2 The test was conducted under conditions of repeated charging and discharging.

[0288] Table 2 shows a comparison of the charge-discharge cycle characteristics of electrode (12) and the electrode of test example 22. Here, charging is defined as the reaction in which charge carriers are inserted into the test electrode, and discharging is defined as the reaction in which charge carriers are removed from the test electrode. Coulomb efficiency is the ratio of discharge capacity to charge capacity, expressed as a percentage.

[0289] [Table 2]

[0290] As is clear from Table 2, the electrode in test example 22 has a higher initial Coulomb efficiency and better cycle characteristics compared to electrode (12). Furthermore, as the internal resistance increases with the progression of the charge-discharge cycle, it is thought that not only does the capacity decrease, but the discharge rate characteristics, charge rate characteristics, and temperature characteristics also change.

[0291] [X-ray diffraction pattern] The X-ray diffraction (XRD) patterns of electrodes obtained by the method of this embodiment and the electrochemical method were compared. A Cu-Kα line (1.54 Å) was used as the X-ray source, with an output of 40 kV and 40 mA.

[0292] In the electrochemical method, electrode (2) was used as the test electrode, and a coin-type battery (R2032) was fabricated using a metallic lithium counter electrode (made of this metal, lithium foil with a thickness of 500 μm), a PP / PE / PP three-layer microporous membrane (Celgard, 2325), a glass filter (Advantec, GA100), and 1 mol / L LiPF6 / EC:DEC = 1:1 vol., + VC 1 wt.%. The resulting battery was doped with lithium ions at a temperature of 30°C and a rate of 0.1C to an electrical capacity equivalent to that of Test Example 2 with the same amount of Li metal. After that, the coin-type battery was disassembled, electrode (2) was removed, and washed with dimethyl carbonate.

[0293] Figure 13 shows the XRD patterns of electrode (2), the electrode from test example 2, and electrode (2) that was Li-doped using an electrochemical method.

[0294] As is clear from Figure 13, the electrode in Test Example 2 and the electrode (2) doped with Li by electrochemical method show lower intensity of crystalline Si diffraction peaks compared to the undoped electrode (2). This is thought to be because the Si became amorphous due to Li alloying. Furthermore, comparing the electrode in Test Example 2 with the electrode (2) doped with Li by electrochemical method, the electrode in Test Example 2 shows lower intensity of crystalline Li x A diffraction peak for Si (1 ≤ x ≤ 4.4) is observed, but it is not clearly confirmed by electrochemical methods. x Si is, for example, Li 22 Si5, Li 13 Si4, Li7Si3, Li 12 It was a Li-Si alloy with a crystalline structure such as Si7.

[0295] The method for manufacturing electrodes according to the present invention has been described above based on embodiments thereof. However, the present invention is not limited to the contents described above embodiments, and its configuration can be modified as appropriate without departing from the spirit of the invention. In particular, alkali metals were used as an example of a carrier source in the description, but the invention is not limited to this, and alkali metal alloys (for example, Li-In, Na-K, etc.) and lithium nitride can also be applied to this embodiment.

[0296] Furthermore, although the above embodiments mainly describe examples of continuous coating and stripe coating of carrier sources, the method can also be applied to other methods, such as intermittent coating, intermittent stripe coating, diagonal coating, and dot-pattern coating (see Figure 14). In addition, although the above embodiments describe a method for manufacturing electrodes for energy storage devices, this doping method can also be applied to doping other than electrodes. Therefore, such applications are also included within the scope of the present invention.

Claims

1. A method for manufacturing electrodes for energy storage devices, Step A involves pressing and adhering a carrier coating having a carrier source on a substrate to the composite layer. Step B involves releasing the pressure and doping the composite layer with charge carriers. The process includes step C of removing the substrate from the composite layer. A method for manufacturing electrodes.

2. The substrate has an insulating material on the surface that is in direct contact with the carrier source that does not react with the carrier source. Alternatively, the surface that comes into direct contact with the carrier source has a release agent, A method for manufacturing an electrode according to claim 1.

3. Area S of the aforementioned composite layer 1 and the area S of the carrier source 2 However, the relationship satisfies (Equation 1), 0.7×S 1 ≦S 2 <S 1 ≤1.3×S 2 ...(Form 1) A method for manufacturing an electrode according to claim 1.

4. Step A is performed with the carrier source positioned on the inside in the plane direction of the asphalt layer. The amount of charge carrier doping on the inner side of the electrode in the plane direction is The amount of doping of charge carriers on the outer side in the planar direction of the electrode is made greater than the amount of doping of charge carriers on the outer side in the planar direction of the electrode. The method for manufacturing an electrode according to claim 3.

5. The thickness of the substrate is 2 μm or more and 500 μm or less. A method for manufacturing an electrode according to any one of claims 1 to 4.

6. The pressure applied in step A is 20 kgf / cm². 2 More than 30000kgf / cm 2 Apply the following surface pressure: A method for manufacturing an electrode according to any one of claims 1 to 4.

7. The crimping in step A above involves applying a linear pressure of 5 kgf / cm to 1000 kgf / cm. The feed rate of the electrode at the aforementioned line pressure is 0.001 m / min or more and 100 m / min or less. A method for manufacturing an electrode according to any one of claims 1 to 4.

8. Step A is performed in which the charge carriers are present on the composite layer. A method for manufacturing an electrode according to any one of claims 1 to 4.

9. The time for maintaining the pressure in step A is 10 seconds or less. A method for manufacturing an electrode according to any one of claims 1 to 4.

10. After releasing the pressure in step B, the doping reaction is sustained for at least one second to promote the expansion of the asphalt layer. A method for manufacturing an electrode according to any one of claims 1 to 4.

11. The aforementioned step C involves peeling at a constant speed while maintaining an angle of 10 degrees or more and 180 degrees or less. A method for manufacturing an electrode according to any one of claims 1 to 4.

12. The aforementioned composite layer contains an active material, The active material includes at least one element selected from P, S, Fe, Co, Ni, Cu, Zn, Ga, Ge, In, Sn, Sb, Pb, and Bi, or a compound, alloy, or modified form containing one of these elements. A method for manufacturing an electrode according to any one of claims 1 to 4.

13. The electrical resistivity of the aforementioned composite layer is, Process A is lower than process B, and process C is lower than process B. A method for manufacturing an electrode according to any one of claims 1 to 4.

14. Before step A, The active material is brought into contact with an alkaline aqueous solution with a pH of 9 or higher, or an acidic aqueous solution with a pH of 5 or lower, and then dried. A method for manufacturing an electrode according to any one of claims 1 to 4.

15. The aforementioned composite layer is further coated with silicate or phosphate, A method for manufacturing an electrode according to any one of claims 1 to 4.

16. The carbon-based material content in the aforementioned composite layer is 0.1% by mass or more and 90% by mass or less. A method for manufacturing an electrode according to any one of claims 1 to 4.

17. The binder included in the aforementioned composite layer includes a fluororesin, an acrylic resin, or a urethane resin. A method for manufacturing an electrode according to any one of claims 1 to 4.

18. The outer side of the electrode in the planar direction is cut. A method for manufacturing an electrode according to any one of claims 1 to 4.

19. In step A, The carrier covering is private The substrate has a first region where the carrier source is present, and a second region where the carrier source is absent or where the amount of the carrier source is less than in the first region. In step B, Only the charge carriers in the first region are doped into the composite layer. Alternatively, the amount of charge carriers doped into the composite layer is such that the doping amount at the location corresponding to the first region is greater than the doping amount at the location corresponding to the second region. A method for manufacturing an electrode according to any one of claims 1 to 4.

20. Multiple first regions and second regions exist on the substrate, The first region and the second region are alternately located in the width direction and / or length direction of the substrate. The method for manufacturing an electrode according to claim 19.

21. A method for manufacturing an energy storage device comprising an asphalt mixture layer, a counter asphalt mixture layer for the asphalt mixture layer, and a non-aqueous electrolyte, Before a charging operation is performed between the asphalt mixture layer and the counter electrode asphalt mixture layer, the asphalt mixture layer is doped with charge carriers using the method described in any one of claims 1 to 4. The area S of the carrier source 2 , the area S of the counter electrode composite layer 3 , and the area S of the composite layer 1 are in a relationship that satisfies (Equation 2). A method for manufacturing energy storage devices. S 3 ≦S 2 <S 1 ・・・・・(Form 2)

22. Area S of the aforementioned composite layer 1 teeth, Area S of the asphalt mixture layer with a high amount of charge carrier doping ' 1 and, Area S of the asphalt mixture layer with a low amount of charge carrier doping " 1 It is a sum of, The relationship satisfies (Equation 3), S " 1 <S 3 ≦S 2 ≦S ' 1 <S 1 =S ' 1 +S " 1 ... (Formula 3) A method for manufacturing an energy storage device according to claim 21.

23. The thickness T of the aforementioned carrier source 1 , the thickness T of the counter electrode composite layer 2 , and the thickness T of the composite layer 3 The relationship satisfies (Equation 3), T 1 ≦T 3 <T 2 ... (Formula 3) The thickness T of the aforementioned carrier source 1 However, it is between 0.1 μm and 500 μm. A method for manufacturing an energy storage device according to claim 21.

24. The carrier source has a Mohs hardness of 2 or less. A method for manufacturing an energy storage device according to claim 21.

25. An electrode for an energy storage device, The system comprises a current collector and an asphalt mixture layer in which charge carriers are doped into the asphalt mixture. The aforementioned composite layer has a surface layer containing carbonate on its surface. Electrodes for energy storage devices.

26. An electrode for an energy storage device, While carbonates are present in the aforementioned surface layer, carbonates are not present in the current collector and the composite material layer below the current collector. Electrode for energy storage device according to claim 25.

27. The aforementioned composite layer does not contain halogen compounds derived from electrolytes. Electrode for energy storage device according to claim 25.

28. The aforementioned composite layer does not contain electrolyte-derived SEI. Electrode for energy storage device according to claim 25.

29. The surface layer of the composite material layer consists only of carbonates or oxides. Electrode for energy storage device according to claim 25.

30. The composite layer contains a crystalline alloy derived from an active material doped with charge carriers. Electrode for energy storage device according to claim 25.

31. The surface layer has a thickness of 1 nm to 500 nm. An electrode for an energy storage device according to any one of claims 25 to 30.

32. The aforementioned asphalt mixture layer contains a first group of asphalt mixtures doped with charge carriers, and a second group of asphalt mixtures that are undoped with charge carriers or have less doping than the first group of asphalt mixtures. An electrode for an energy storage device according to any one of claims 25 to 30.

33. The aforementioned asphalt layer contains multiple first asphalt groups and second asphalt groups, The first group of composite materials and the second group of composite materials are arranged alternately in the width direction and / or length direction of the electrode. Electrode for energy storage device according to claim 32.

34. A method for doping charge carriers, Step A involves pressing and adhering a carrier coating body, which has a carrier source on the substrate, to the composite layer. Step B involves releasing the pressure and doping the composite layer with charge carriers. The process includes step C of removing the substrate from the composite layer. Methods for doping charge carriers.

35. The base material of the carrier coating has an insulating material that does not react with the carrier source on the surface that is in direct contact with the carrier source, or a release agent on the surface that is in direct contact with the carrier source. The method for doping charge carriers according to claim 34.

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