Method for restoring electrodes and method for manufacturing electrodes for energy storage devices

Abstract

This electrode recovery method is a method for recovering an electrode from a used power storage device, the recovery method comprising: a first step (S1) for evaluating the state of the electrode; and a second step (S2) for compressing the electrode in the thickness direction of the electrode.

Description

Technical Field

[0001] The present invention relates to a method for restoring an electrode 、 for a power storage device and the manufacturing method thereof and relates thereto. This application claims priority based on Japanese Patent Application No. 2023-057930 filed in Japan on March 31, 2023, and incorporates the content herein by reference.

Background Art

[0002] In recent years, in order to enable more people to access affordable, reliable, sustainable, and advanced energy, research and development have been conducted on the reuse of secondary batteries that contribute to energy efficiency (see, for example, Patent Document 1).

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] By the way, in the technology related to the reuse of secondary batteries such as Patent Document 1, although it is possible to remove surface degradation products of the active material, it has been a problem that an increase in resistance due to a decrease in the adhesion density of particles cannot be achieved.

[0005] This application aims to solve the above problems and aims to restore an increase in resistance due to a decrease in the adhesion density of particles. And, by extension, it contributes to energy efficiency.

Means for Solving the Problems

[0006] In order to solve the above problems, the present invention proposes the following means. <1>The method for restoring an electrode according to Embodiment 1 of the present invention is A method for restoring the electrodes of a used energy storage device, A first step of evaluating the state of the electrode, A second step of compressing the electrode in the thickness direction of the electrode, It may include. <2> Aspect 2 of the present invention relates to the electrode recovery method of Aspect 1, The first step further includes a step of measuring the resistance component of the electrode. <3> A third aspect of the present invention is the electrode recovery method of aspect 1 or aspect 2, wherein the resistance component may be the composite layer resistance or interfacial resistance of the electrode. <4> Aspect 4 of the present invention relates to a method for recovering one of the electrodes described in aspects 1 to 3, In the second step described above, compression may be performed while heating. <5> Aspect 5 of the present invention is a method for restoring an electrode according to any one of aspects 1 to 4, wherein the second step further includes a calculation step of measuring the thickness of the electrode and calculating the difference from the estimated pre-use thickness, In the second step, the electrode may be compressed in the thickness direction so as to reduce its thickness by the difference obtained in the calculation step. <6> Aspect 6 of the present invention is a method for restoring an electrode according to any one of aspects 1 to 5, wherein the second step may further include a coating step of applying a conductive agent to the surface of the electrode. <7> Aspect 7 of the present invention is a method for restoring an electrode according to any one of aspects 1 to 6, wherein the conductive agent may be carbon fiber. <8> Aspect 8 of the present invention is a method for restoring an electrode according to any one of aspects 1 to 7, wherein the coating step may be a step of applying a dispersion in which the conductive agent is dispersed and drying it. <9> Aspect 9 of the present invention is a method for restoring an electrode according to any one of aspects 1 to 8, wherein ultrasonic waves may be applied to the electrode during the coating step. <10> The electrode for the energy storage device according to embodiment 10 of the present invention is obtained by the recovery method of any one of the electrodes from embodiments 1 to 9. [Effects of the Invention]

[0007] According to each of the above aspects of the present invention, it is possible to recover the increase in resistance due to the decrease in the adhesion of particles. And, by extension, it contributes to the efficiency of energy.

Brief Description of the Drawings

[0008] [Figure 1] It is a flowchart of a method for recovering an electrode according to a first embodiment of the present invention. [Figure 2] It is a schematic diagram showing the configuration of an electrode. [Figure 3] It is a diagram for explaining an example of a dV / dQ curve for each single electrode of a positive electrode and a negative electrode in an initial state. [Figure 4] It is a diagram for explaining an example of a measured curve and a fitted curve of a dV / dQ curve of a power storage device. [Figure 5] It is a diagram for explaining a comparison between a dV / dQ curve in an initial state and a diagnostic dV / dQ curve. [Figure 6] It is a flowchart of a method for recovering an electrode according to a second embodiment of the present invention.

Modes for Carrying Out the Invention

[0009] Hereinafter, referring to the drawings, a method for recovering an electrode according to an embodiment of the present invention will be described. FIG. 1 is a flowchart of a method for recovering an electrode according to an embodiment of the present invention. The method for recovering an electrode of the present disclosure is a method for recovering an electrode of a used power storage device, and includes a first step S1 of evaluating the state of the electrode and a second step S2 of compressing the electrode in the thickness direction of the electrode. Hereinafter, each step will be described.

[0010] (First Step S1) In the first step S1, the state of the electrode of the used power storage device is evaluated. In the first step S1, the state of the electrode of the used power storage device may be evaluated based on physical quantity data obtained during charging and discharging of the used power storage device. The physical quantity data is, for example, a voltage value and a current value during charging.

[0011] (Used Power Storage Device) The used energy storage device has an electrode including an active material, a binder, and a current collector. The energy storage device is not particularly limited as long as it can store electricity and has an electrode including an active material, a binder, and a current collector. The energy storage device is, for example, a lithium ion secondary battery. FIG. 2 is a schematic diagram showing the configuration of the electrode. The electrodes targeted by the method for separating the active material of the present disclosure are the positive electrode 10 and the negative electrode 20. Hereinafter, the configuration of the electrode will be described.

[0012] "Positive electrode" The positive electrode 10, which is an electrode, includes a positive electrode active material 11, a positive electrode conductive assistant 12, a positive electrode binder 13, and a positive electrode current collector 14. A layer composed of the positive electrode active material 11, the positive electrode conductive assistant 12, and the positive electrode binder 13 is defined as the positive electrode composite material layer. The positive electrode composite material layer may be formed on one or both sides of the positive electrode current collector 14. In addition, if the positive electrode active material 11 has conductivity, the positive electrode composite material layer may not contain the positive electrode conductive assistant 12.

[0013] The positive electrode active material 11, which is the active material used in the positive electrode, is not particularly limited as long as it can occlude and release Li ions. Examples of the positive electrode active material 11 include lithium nickel oxide (e.g., LiNiO2), lithium cobalt oxide (e.g., LiCoO2), lithium nickel cobalt oxide, lithium nickel cobalt manganese oxide, LiFePO4, LiMn 1-x Fe x PO4, LiMnPO4, LiCoPO4, LiNiPO4, etc. The positive electrode active material 11 preferably contains one or more selected from the group consisting of manganese, nickel, and cobalt.

[0014] The positive electrode conductive assistant 12, which is the conductive assistant used in the positive electrode 10, assists in forming a conductive path between the positive electrode active material 11 and the positive electrode current collector 14. The positive electrode conductive assistant 12 is not particularly limited as long as it has conductivity, and examples thereof include carbon black such as acetylene black, carbon nanotubes, and graphite (graphite) such as artificial graphite.

[0015] The positive electrode binder 13, which is a binder for the positive electrode active material 11, binds the positive electrode active material 11, the positive electrode conductive additive 12, and the positive electrode current collector 14, respectively. Examples of positive electrode binders 13 include polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), polyamide (PA), polyimide (PI), polyacrylic acid and its copolymers, polyamideimide (PAI), polybenzimidazole, polyethersulfone (PES), maleic anhydride-modified polypropylene, and mixtures thereof. It is preferable that the positive electrode binder 13 contains a crystalline polymer with a melting point. It is preferable that the positive electrode binder 13 is a polymer containing fluorine. Examples of polymers containing fluorine include PVDF and PTFE.

[0016] Examples of positive electrode current collectors 14 include metal foils such as aluminum foil, stainless steel foil, and nickel foil. A carbon coating layer may be formed on the positive electrode current collector 14. The positive electrode current collector 14 may also be processed into a mesh shape.

[0017] "Negative electrode" The negative electrode 20, which is an electrode, includes a negative electrode active material 21, a negative electrode conductive additive 22, a negative electrode binder 23, and a negative electrode current collector 24. The layer consisting of the negative electrode active material 21, the negative electrode conductive additive 22, and the negative electrode binder 23 is called the negative electrode composite layer. The negative electrode composite layer may be formed on one or both sides of the negative electrode current collector 24. Note that if the negative electrode active material 21 is conductive, the negative electrode composite layer does not need to contain the negative electrode conductive additive 22.

[0018] The negative electrode active material 21, which is the active material of the negative electrode 20, is not particularly limited as long as it is capable of intercalating and releasing Li ions. Examples of negative electrode active material 21 include graphite (artificial graphite, natural graphite), amorphous carbon (hard carbon), mesocarbon microbeads, carbon fibers, and Si materials (silicon, Si alloys, Si oxides).

[0019] The negative electrode conductive additive 22, which is a conductive additive for the negative electrode 20, assists in the formation of a conductive path between the negative electrode active material 21 and the negative electrode current collector 24. The negative electrode conductive additive 22 is not particularly limited as long as it has conductivity, and examples include carbon black such as acetylene black, carbon nanotubes, and graphite such as artificial graphite.

[0020] The negative electrode binder 23, which is the binder for the negative electrode 20, binds the negative electrode active material 21, the negative electrode conductive additive 22, and the negative electrode current collector 24, respectively. Examples of negative electrode binders 23 include carboxymethylcellulose, polyvinylidene fluoride, polytetrafluoroethylene, polyacrylic acid, fluororubber, and diene rubbers such as styrene-butadiene rubber. It is preferable that the negative electrode binder 23 contains a crystalline polymer with a melting point. It is preferable that the negative electrode binder 23 is a polymer containing fluorine. Examples of polymers containing fluorine include PVDF, PTFE, and fluororubber.

[0021] Examples of materials that can be used as the negative electrode current collector 24 for the negative electrode 20 include metal foils such as copper foil, stainless steel foil, and nickel foil. The negative electrode current collector 24 may have a carbon coating layer formed on it. The negative electrode current collector 24 may also be processed into a mesh shape.

[0022] (Preparation) More specifically, as a preliminary step to the first step S1, for example, first, a storage device with the same specifications as the target storage device is disassembled, and unipolar data at the coin cell level is obtained, that is, dV / dQ curves for the initial state of the positive and negative electrodes, as illustrated in Figure 3. Furthermore, these unipolar dV / dQ curves are added together and fitted to the measured curve of the storage device (the dashed curve in Figure 4), as shown in Figure 4. In Figure 4, the fitted curve is shown as a solid line. This allows each pole value of the measured curve to be assigned to the positive and negative electrodes. In this way, the dV / dQ curve in the initial state of the used storage device is obtained in advance. Then, the peak positions based on the positive and negative electrodes in the dV / dQ curve are determined, and the peak widths in the initial state of the positive and negative electrodes are determined.

[0023] In Figures 3 and 4, the horizontal axis represents the cell capacity (Ah), and the vertical axis represents the change in voltage in response to a change in the reference capacity (dV / dQ).

[0024] Here, if the peak position can be detected between 5% and 95% of the charge rate or State of Charge (SOC), with a fully charged state being 100%, differential capacitance analysis becomes possible. Specifically, in the dV / dQ curve in the initial state, two peaks based on the positive electrode are identified, and the width between these peaks is determined. In Figures 3 and 4, the two peaks based on the positive electrode are located at the intersection with the dashed line. Also, in the dV / dQ curve in the initial state, two peaks based on the negative electrode are identified, and the width between these peaks is determined. In Figures 3 and 4, the two peaks based on the negative electrode are located at the intersection with the dashed line.

[0025] For example, as a guideline, two peaks between 0 and 30% on the lower end of the SOC range may be identified as the positive electrode peaks, two peaks between 30 and 60% as the negative electrode peaks (graphite in this embodiment) (intersection with the dashed line Gr), and two peaks between 60 and 100% on the higher end of the SOC range as the silicon oxide (SiO) peaks in the negative electrode (intersection with the dashed line SiO). Alternatively, the positive electrode peaks may be convex towards the negative side of dV / dQ, and the negative electrode peaks may be convex towards the positive side of dV / dQ. Although peaks originating from the materials constituting the electrodes will appear, if, for example, the negative electrode does not contain SiO, then peaks originating from SiO will not appear.

[0026] (After battery use begins) After the battery is put into use, the voltage and current are obtained over time by charging under low current. It is important that the current is relatively low. The capacity is obtained by integrating the current value with respect to time, and from this, a voltage curve with respect to capacity can be obtained. Furthermore, the differential capacitance curve (dV / dQ curve) with respect to capacity can be obtained by differentiating the voltage value with respect to capacity.

[0027] The charging rate can be analyzed even at a typical rate of 0.2 to 0.5 C. However, using a lower rate, such as 0.02 to 0.07 C, allows for more accurate analysis. Furthermore, once charging has progressed to a certain extent and the voltage has stabilized, the charging current may be gradually reduced.

[0028] As described above, the dV / dQ curve is obtained by calculating the derivative of the voltage in the charge / discharge curve of the energy storage device with respect to the reference capacity. This method allows for accurate recognition of the voltage fluctuation characteristics of the energy storage device being assessed for degradation relative to its reference capacity. By comparing the generated dV / dQ curve for degradation assessment with the dV / dQ curve obtained in the initial state of the energy storage device, it becomes possible to evaluate and determine how much the battery has degraded from its initial state at that point in time.

[0029] The dV / dQ curve obtained for a used energy storage device is called a diagnostic dV / dQ curve, which shows the change in voltage in response to a change in the reference capacity of the used energy storage device.

[0030] Next, based on the obtained diagnostic dV / dQ curve and the dV / dQ curve in the initial state, the first capacity reduction rate due to positive electrode degradation, the second capacity reduction rate due to negative electrode degradation, and the amount of capacity reduction due to other factors are evaluated, respectively.

[0031] Specifically, for the cells of a used energy storage device, two peaks originating from each electrode are identified, and the change in the width between these two peaks (peak width) between the initial state and the state after battery use begins is evaluated. That is, the peak widths of the positive and negative electrodes in the state after battery use begins are determined, and the change in peak width due to the use of the energy storage device is evaluated by comparing them with the peak width in the initial state described above.

[0032] (First capacity reduction rate and second capacity reduction rate) The dV / dQ curve in the initial state is compared with the diagnostic dV / dQ curve, and the rate of change in the width between the two peaks based on the positive and negative electrodes is calculated. The rate of change in the width between the two peaks based on the positive electrode of the diagnostic dV / dQ curve relative to the initial state dV / dQ curve is defined as the first capacity reduction rate, and the rate of change in the width between the two peaks based on the negative electrode of the diagnostic dV / dQ curve relative to the initial state dV / dQ curve is defined as the second capacity reduction rate.

[0033] Figure 5 shows a comparison between the initial dV / dQ curve and the diagnostic dV / dQ curve. In Figure 5, the solid line represents the initial dV / dQ curve, and the dashed line represents the diagnostic dV / dQ curve. The diagnostic dV / dQ curve is also shifted along the vertical axis to avoid overlap. As shown in Figure 5, comparing the initial dV / dQ curve and the diagnostic dV / dQ curve reveals that the width between the two peaks based on the positive and negative electrodes has changed.

[0034] (Amount of capacity reduction due to other factors) The shift in the diagnostic dV / dQ curve relative to the initial dV / dQ curve is defined as the amount of capacity reduction due to factors other than the degradation of the positive or negative electrode (other factors). The shift in the diagnostic dV / dQ curve relative to the initial dV / dQ curve is judged to be mainly due to a decrease in the amount of Li involved in charging and discharging, caused by the deposition of a Li-containing negative electrode coating due to the swelling and contraction of the active material. For example, the amount by which the midpoint of the two peaks based on the negative electrode shifts is defined as the amount of capacity reduction due to other factors.

[0035] It is determined whether the conditions are met where both the obtained first capacity reduction rate and the second capacity reduction rate are below a predetermined threshold (e.g., 5%) and the amount of capacity reduction exceeds the predetermined threshold. The threshold can be set for each energy storage device.

[0036] If it is confirmed that the first and second capacity degradation rates are below a threshold, it is preferable to analyze the state of the electrodes in more detail. Specifically, the resistance component of the electrodes is measured. That is, it is preferable that the electrode recovery method further includes a step of measuring the resistance component of the electrodes in the first step S1. The resistance component of the electrodes can be measured using the AC impedance method or the multi-point probe method. However, for example, when replenishing lithium in an energy storage device, the AC impedance method and multi-point probe method may be omitted, and the electrodes described later may be removed and the second step S2 may be performed.

[0037] When measuring the resistance component using the AC impedance method, it can be measured in the following way, for example: The AC impedance is measured using a commercially available AC impedance measuring device, for example, in the state of a power storage device (cell). For example, an AC voltage with an amplitude of 10mV superimposed on the OCV (open-circuit voltage) is applied from 1MHz to 1mHz, and the internal resistance can be determined from the response current. The obtained results are plotted using a Cole-Cole plot. Examples of the resistance component of the electrode to be measured include the composite layer resistance or the interface resistance. Each resistance component can be separated based on a time constant. The measurement conditions are set appropriately by the power storage device. Separation of each resistance component based on the time constant can be achieved, for example, by considering the measurement results from 1MHz to 1kHz as the high-frequency resistance, determining it as metal resistance and resistance due to the film at the battery interface and degradation of electrolyte components; determining it as ion conduction resistance between active materials from 1kHz to 1Hz; and determining it as solid ion diffusion within particles below 1Hz.

[0038] When determining the state of the electrodes using the AC impedance method, for example, a reference curve obtained from the AC impedance of a newly manufactured energy storage device is compared with the curve of a used energy storage device. For example, in the cole-cole plot of a used energy storage device, if the region in which the impedance component increases almost linearly with increasing frequency (upward sloping region) is larger than that of the initial energy storage device, it is determined that the conduction resistance has increased, and the second step S2 is performed.

[0039] In the case of the multi-point probe measurement method, the electrodes extracted from the energy storage layer are evaluated. The method for extracting the positive electrode 10 and negative electrode 20, which are electrodes, from the energy storage device is not particularly limited, and known methods can be used. The electrode to be evaluated is preferably the positive electrode 10. Since it is dangerous to dismantle the energy storage device while it is charged, it is preferable to fully discharge the energy storage device. After discharge, the outer material of the energy storage device is cut, and the positive electrode 10 and negative electrode 20 are extracted from the energy storage device.

[0040] In the multi-point probe measurement method, a fine probe is applied to the electrode surface, a constant current is passed through it, and the potential at multiple points is measured. Furthermore, a modeling is performed to calculate the potential generated on the surface by assuming a virtual electrode. Then, using the resistance of the composite layer and the interfacial resistance as variables, measurements are repeated until the measured potential matches the actual measured potential. If the obtained resistance of the composite layer and the interfacial resistance are determined to be higher than a predetermined threshold, the second step S2 is performed. For example, if the resistance of the composite layer of the electrode increases by more than 10% compared to before use, it is determined that the resistance of the composite layer has increased, and the second step S2 is performed. As a multi-point probe measurement system, for example, the HIOKI RM2610 electrode resistance measurement system can be used.

[0041] (2nd process S2) In the second step S2, the electrode is compressed in the thickness direction of the electrode. Compression can be performed by known means such as a roll press. Either the positive electrode 10 or the negative electrode 20 may be used, but the positive electrode 10 is preferred. In the second step S2, it is preferable to compress while heating. By pressing while heating, the binders 13 and 23 can be softened, making it easier to restore adhesion. The heating temperature is, for example, above the melting point of the binder and below 200°C.

[0042] The second step S2 preferably further includes a calculation step of measuring the thickness of electrodes 10 and 20 and calculating the difference from the estimated pre-use thickness. In the second step S2, it is preferable to compress the electrodes in the thickness direction so that the thickness of electrodes 10 and 20 decreases by the difference obtained in the calculation step. By compressing in this way, it is possible to restore the inter-particle contact that has decreased due to the expansion and contraction of the active material accompanying charging and discharging. If information on the thickness of the electrodes at the time of manufacture of the energy storage device is available, that information should be used for the estimated pre-use thickness. If there is no information on the initial manufacturing thickness, for example, the thickness obtained by subtracting the void portion of the electrode from the thickness of the used electrode may be used as the estimated pre-use thickness.

[0043] The electrode recovery method according to the first embodiment has been described above. According to the electrode recovery method according to this embodiment, it is possible to recover from the increase in resistance caused by a decrease in particle adhesion. By the electrode recovery method of this embodiment, a recovered electrode for an energy storage device can be obtained.

[0044] Next, a method for restoring an electrode according to a second embodiment of the present invention will be described. Figure 6 is a flowchart of the electrode restoration method according to the second embodiment of the present invention. The electrode restoration method of this disclosure is a method for restoring an electrode of a used energy storage device, and includes a first step S1 for evaluating the state of the electrode and a second step S2A for compressing the electrode in the thickness direction of the electrode. In the following description, the same reference numerals are used for components that are the same as in the first embodiment, and their descriptions may be omitted. The following describes each step.

[0045] (2nd process S2) In the second step S2A, it is preferable to further include a coating step of applying a conductive agent to the surfaces of electrodes 10 and 20. The electrodes can be either the positive electrode 10 or the negative electrode 20, but the positive electrode 10 is preferred. The conductive agent is not particularly limited, but for example, it can be a carbonaceous material such as acetylene black or carbon nanotubes. Carbon fiber is preferred as the conductive agent. By applying the conductive agent, conductivity can be supplemented by the addition of the conductive agent, and the resistance of the composite layer and interfacial resistance can be reduced.

[0046] The method of applying the conductive agent in the coating process is not particularly limited. For example, in the coating process, a dispersion of the conductive agent may be applied and dried. That is, the coating process may be a process of applying a dispersion of the conductive agent and drying it. Furthermore, it is preferable to apply ultrasound in the coating process. By applying ultrasound, the conductive agent can penetrate into the gaps in the electrodes 10 and 20, and the resistance can be further reduced. This can further improve and restore the condition of the electrodes.

[0047] In the second step S2A, the electrodes 10 and 20 after the coating process are compressed in the thickness direction of the electrodes 10 and 20. Compression can be performed by known means such as a roll press. In the second step S2A, it is preferable to compress the electrodes 10 and 20 while heating them. By pressing while heating, the binders 13 and 23 can be softened, making it easier to restore adhesion. The heating temperature is, for example, above the melting point of the binder and below 200°C.

[0048] The second step S2A preferably further includes a calculation step of measuring the thickness of electrodes 10 and 20 and calculating the difference from the estimated pre-use thickness. In the second step S2A, it is preferable to compress the electrodes in the thickness direction so that the thickness of electrodes 10 and 20 decreases by the difference obtained in the calculation step. By compressing in this way, it is possible to restore the inter-particle contact that has decreased due to the expansion and contraction of the active material accompanying charging and discharging.

[0049] As described above, the method for separating active material according to the second embodiment makes it possible to recover from the increased resistance caused by a decrease in particle adhesion.

[0050] It should be noted that the technical scope of the present invention is not limited to the embodiments described above, and various modifications can be made without departing from the spirit of the invention. Furthermore, it is possible to replace the components in the embodiments with well-known components as appropriate, without departing from the spirit of the invention. [Industrial applicability]

[0051] The recovery method described herein makes it possible to recover from the increased resistance caused by a decrease in particle adhesion, and therefore has high potential for industrial application. [Explanation of symbols]

[0052] 10 Positive electrode, 11 Positive electrode active material, 12 Positive electrode conductive additive, 13 Positive electrode binder, 14 Positive electrode current collector, 20 Negative electrode, 21 Negative electrode active material, 22 Negative electrode conductive additive, 23 Negative electrode binder, 24 Negative electrode current collector, S1 First process, S2 Second process

Claims

1. A method for restoring the electrodes of a used energy storage device, A first step of evaluating the state of the electrode, A second step of compressing the electrode in the thickness direction of the electrode, Includes, The first step further includes a step of measuring the resistance component of the electrode, The aforementioned resistance component is the resistance of the composite layer or the interfacial resistance of the electrode. How to restore electrodes.

2. A method for restoring the electrodes of a used energy storage device, A first step of evaluating the state of the electrode, A second step of compressing the electrode in the thickness direction of the electrode, Includes, In the second step described above, the material is compressed while being heated. How to restore electrodes.

3. A method for restoring the electrodes of a used energy storage device, A first step of evaluating the state of the electrode, A second step of compressing the electrode in the thickness direction of the electrode, Includes, The second step further includes a calculation step of measuring the thickness of the electrode and calculating the difference from the estimated thickness before use. In the second step, the electrode is compressed in the thickness direction so that the thickness is reduced by the difference obtained in the calculation step. How to restore electrodes.

4. A method for restoring the electrodes of a used energy storage device, A first step of evaluating the state of the electrode, A second step of compressing the electrode in the thickness direction of the electrode, Includes, The second step further includes a coating step of applying a conductive agent to the surface of the electrode. How to restore electrodes.

5. The electrode recovery method according to claim 4, wherein the conductive agent is carbon fiber.

6. The method for restoring an electrode according to claim 4, wherein the coating step is a step of applying a dispersion in which the conductive agent is dispersed and drying it.

7. The electrode recovery method according to claim 6, wherein ultrasonic waves are applied to the electrode in the coating step.

8. A step of preparing electrodes for a used energy storage device, A step of restoring the electrode using the method according to any one of claims 1 to 7, A method for manufacturing electrodes for energy storage devices, comprising the same components.

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