Recovering method for active material

Abstract

To provide a recovering method for an active material capable of suppressing the generation of hydrogen fluoride by thermal decomposition of a binder while improving the activity of active material whose activity has been reduced.SOLUTION: A recovery method for an active material is for improving the reduced activity of the active material included in a lithium-ion battery and has a heating process for mixing a lithium compound with the active material or an electrode mixture containing the active material and heating the mixture under a temperature lower than the thermal decomposition temperature of the binder included in the lithium-ion battery. Further, the mixture amount of the lithium compound is such that a value obtained by dividing the total surface area of the lithium compound by the total surface area of the active material is 0.05 or more.SELECTED DRAWING: None

Description

Technical Field

[0001] The present invention relates to a method for recovering an active material.

Background Art

[0002] The active material included in a lithium-ion battery decreases in activity due to the desorption of lithium ions during the use of the lithium-ion battery, but the activity can be improved by performing a recovery treatment. For example, Patent Document 1 discloses a technique for improving the activity of a reduced positive electrode active material by mixing a lithium compound into an electrode mixture containing a positive electrode active material and a binder and heating the mixture to a temperature equal to or higher than the melting start temperature of the lithium compound (for example, 750°C). In the technique disclosed in Patent Document 1, since the lithium compound is melted, lithium ions are inserted into the positive electrode active material by the reaction at the solid-liquid interface between the positive electrode active material and the lithium compound, thereby improving the activity of the positive electrode active material.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] In the technique disclosed in Patent Document 1, the binder is also heated to a high temperature together with the positive electrode active material and the lithium compound. Polyvinylidene fluoride (PVDF) is often used as the binder, but when polyvinylidene fluoride is thermally decomposed at a high temperature, hydrogen fluoride (HF) is generated, so that the active material reacts with hydrogen fluoride to form lithium fluoride (LiF). As a result, the amount of lithium in the active material decreases, the performance of the active material deteriorates, and the charge-discharge capacity of the lithium-ion battery may decrease. An object of the present invention is to provide a method for recovering an active material that can improve the activity of a degraded active material while suppressing the generation of hydrogen fluoride due to thermal decomposition of a binder.

Means for Solving the Problems

[0005] A method for recovering an active material according to one aspect of the present invention is a method for improving the activity of a degraded active material included in a lithium-ion battery, the method including a heating step of mixing a lithium compound with an active material or an electrode binder containing the active material and performing heat treatment at a temperature lower than the thermal decomposition temperature of a binder included in the lithium-ion battery, wherein the mixing amount of the lithium compound is an amount such that a value obtained by dividing the total surface area of the lithium compound by the total surface area of the active material is 0.05 or more.

Advantages of the Invention

[0006] According to the present invention, it is possible to improve the activity of a degraded active material while suppressing the generation of hydrogen fluoride due to thermal decomposition of a binder.

Brief Description of the Drawings

[0007]

Figure 1

Figure 2

Figure 3

Embodiments for Carrying Out the Invention

[0008] One embodiment of the present invention will be described below. Note that this embodiment shows an example of the present invention, and the present invention is not limited to this embodiment. Further, various changes or improvements can be made to this embodiment, and forms with such changes or improvements can also be included in the present invention.

[0009] The method for recovering an active material according to this embodiment is a method for improving the reduced activity of the active material included in a lithium-ion battery. The method includes a heating step of mixing a lithium compound with the active material or an electrode binder containing the active material and performing a heat treatment at a temperature lower than the thermal decomposition temperature of the binder included in the lithium-ion battery. The mixing amount of the lithium compound is an amount such that the value obtained by dividing the total surface area of the lithium compound by the total surface area of the active material is 0.05 or more.

[0010] The method for recovering an active material according to this embodiment can improve the reduced activity of the active material while suppressing the generation of hydrogen fluoride due to the thermal decomposition of the binder. The operation and effect of the method for recovering an active material according to this embodiment will be described in more detail. In the method for recovering an active material according to this embodiment, since there is a heating step of performing a heat treatment at a temperature lower than the thermal decomposition temperature of the binder (for example, lower than 350°C), even when a lithium compound is mixed with the electrode binder and the heat treatment is performed, thermal decomposition of the binder contained in the electrode binder hardly occurs, and hydrogen fluoride is hardly generated. Therefore, the formation of lithium fluoride due to the reaction between the active material and hydrogen fluoride is suppressed, and a decrease in the amount of lithium in the active material is suppressed. That is, when the lithium contained in the active material becomes lithium fluoride, the amount of lithium constituting the active material decreases, and the amount of operating lithium inside the active material required for charge and discharge decreases, but such a reaction is suppressed. As a result, a decrease in the performance of the active material during the heating step is suppressed, and thus the reduced activity of the active material can be sufficiently improved.

[0011] In addition, in the method for recovering the active material according to the present embodiment, since the temperature of the heat treatment is low and the lithium compound is not melted, the reaction between the active material and the lithium compound is a reaction at the solid-solid interface. The reaction at the solid-solid interface is less likely to occur than the reaction at the solid-liquid interface. However, since the mixing amount of the lithium compound with respect to the amount of the active material is set to an amount such that the value obtained by dividing the total surface area of the lithium compound by the total surface area of the active material is 0.05 or more, there are many solid-solid interfaces where the reaction between the active material and the lithium compound occurs. Therefore, since the reaction in which lithium ions are inserted into the active material is likely to occur, even if the temperature of the heat treatment is low, the activity of the deteriorated active material can be sufficiently improved. In the present invention, the electrode binder means a mixture containing an active material, a conductive assistant, a binder, and the like.

[0012] Since the amount of lithium in the active material is reflected in the crystal structure of the active material, the activity of the active material can be evaluated by the c-axis lattice constant calculated from the X-ray diffraction pattern obtained by the X-ray diffraction method (XRD). For example, when an unused lithium-ion battery is used (discharged), the amount of lithium in the active material decreases, and the c-axis lattice constant calculated from the X-ray diffraction pattern increases. Therefore, when the recovery treatment according to the method for recovering the active material according to the present embodiment is performed on the active material with a reduced lithium amount, the lithium amount of the active material is recovered, and the c-axis lattice constant calculated from the X-ray diffraction pattern becomes smaller.

[0013] For example, for the positive electrode active material included in an unused lithium-ion secondary battery, the positive electrode active material included in a used lithium-ion secondary battery, and the positive electrode active material after the recovery treatment, an X-ray diffraction pattern is acquired, and the c-axis lattice constant of the positive electrode active material is calculated. Then, it can be confirmed that in the deteriorated lithium-ion secondary battery after use, the c-axis lattice constant of the positive electrode active material increases, but by performing the recovery treatment, the c-axis lattice constant of the positive electrode active material becomes smaller and can be made comparable to the c-axis lattice constant of the positive electrode active material included in the unused lithium-ion secondary battery.

[0014] The method for recovering the active material according to this embodiment will be further described in detail below. 〔Lithium-ion battery〕 The active material to which the method for recovering the active material according to this embodiment can be applied is the active material included in a lithium-ion battery. However, the type of the lithium-ion battery is not particularly limited. For example, a lithium-ion secondary battery can be mentioned. Examples of the type of the lithium-ion secondary battery include a cobalt-based lithium-ion secondary battery, a nickel-based lithium-ion secondary battery, a NAC (nickel-cobalt-aluminum) -based lithium-ion secondary battery, a manganese-based lithium-ion secondary battery, a lithium iron phosphate-based lithium-ion secondary battery, a ternary (nickel-manganese-cobalt) -based lithium-ion secondary battery, a titanate-based lithium-ion secondary battery, a lithium polymer-based lithium-ion secondary battery, and the like.

[0015] 〔Active material〕 The type of the active material to which the method for recovering the active material according to this embodiment can be applied is not particularly limited as long as it is an active material used in a lithium-ion battery. For example, the following compounds used as a positive electrode active material can be mentioned. That is, examples of the active material include composite compounds having lithium as a constituent element. Examples of the composite compounds include lithium transition metal composite oxides. The composite compounds may be used alone or in combination of two or more.

[0016] Examples of the lithium transition metal composite oxide include LiCoO2, LiNiO2, Li(Ni,Co)O2, Li(Ni,Co,Al)O2, Li(Ni,Mn)O2, Li(Ni,Mn,Co)O2, LiMn2O4, Li(Mn,Fe)2O4, Li2MnO3, Li2NiO3, Li2(Ni,Mn)O3, LiFePO4, LiMnPO4. Examples of Li(Ni,Mn,Co)O2 include LiNi 1 / 3 Mn 1 / 3 Co 1 / 3 O2, LiNi 0.5 Mn 0.3 Co 0.2 O2.

[0017] [Binder] The type of electrode binder to which the method for recovering active material according to this embodiment can be applied is not particularly limited as long as it is an electrode binder used in a lithium-ion battery. Although the electrode binder contains a binder together with the active material, the type of the binder is not particularly limited, and examples thereof include thermoplastic resins. The binder may be used alone or in combination of two or more kinds.

[0018] Examples of the thermoplastic resin include fluororesins such as polyvinylidene fluoride, polytetrafluoroethylene (PTFE), ethylene tetrafluoride - hexafluoropropylene - vinylidene fluoride copolymer, hexafluoropropylene - vinylidene fluoride copolymer, and ethylene tetrafluoride - perfluorovinyl ether copolymer, polyolefin resins such as polyethylene and polypropylene, and styrene - butadiene copolymer.

[0019] [Lithium Compound] The lithium compound that can be used in the method for recovering active material according to this embodiment is not particularly limited as long as it is a compound having lithium as a constituent element. Examples thereof include lithium hydroxide (LiOH), lithium carbonate (Li2CO3), lithium oxide (Li2O), lithium sulfate (Li2SO4), lithium nitrate (LiNO3), and lithium salts of organic acids.

[0020] In the method for recovering active material according to this embodiment, the mixing amount of the lithium compound to be mixed with the active material or the electrode binder containing the active material needs to be an amount such that the value obtained by dividing the total surface area of the lithium compound by the total surface area of the active material is 0.05 or more.

[0021] The greater the mixing amount of the lithium compound, the more solid-solid interfaces where reactions occur between the active material and the lithium compound, so it is preferable to increase the amount of the lithium compound used. In particular, in the case of an active material with degraded performance, since the lithium content is less than the theoretical amount, the lithium compound in an equimolar amount to the shortage of the lithium amount or in a molar amount in excess of the shortage is mixed with the active material or the electrode binder containing the active material so that the lithium amount increases to the theoretical amount by inserting lithium into the active material by the recovery treatment. However, even if the mixing amount of the lithium compound is less than the equimolar amount of the shortage of the lithium amount, the activity of the active material can be improved according to the mixing amount.

[0022] Also, the smaller the diameter of the particles of the lithium compound, the higher the reactivity. However, particles with a particle size of less than 10 μm may react with carbon dioxide in the air, etc. due to their high reactivity. For example, when the lithium compound is lithium hydroxide, particles with a particle size of less than 10 μm are likely to react with carbon dioxide in the air, and as a result, lithium carbonate and water are generated. When water is generated, the particles of lithium hydroxide aggregate, so the total surface area of the lithium compound may change.

[0023] Therefore, the total surface area of the lithium compound may be the sum of the surface areas of all the particles of the lithium compound, or may be the sum of the surface areas of the particles with a particle size of 10 μm or more among all the particles of the lithium compound. When calculating the total surface area of the lithium compound excluding particles with a particle size of less than 10 μm, the mixing amount of the lithium compound to be mixed with the active material or the electrode binder containing the active material can be calculated more accurately.

[0024] 〔Removal step〕 In the method for recovering the active material according to this embodiment, a removal step of removing the binder from the electrode binder may be performed before the heating step. When the binder is removed from the electrode binder, the amounts of the binder and the conductive assistant covering the surface of the active material decrease, so the number of solid-solid interfaces where reactions occur between the active material and the lithium compound increases.

[0025] The amount of the binder remaining in the electrode mixture after the removal step is preferably 1.2% by mass or less of the entire electrode mixture after the removal step. When the binder connecting the active materials is removed from the electrode mixture, the electrode mixture changes from a slurry state in which the active materials are connected by the binder to a powdery state in which the active materials are not connected to each other. As a result, the active material and the lithium compound are easily mixed, so that the number of solid-solid interfaces where the reaction between the active material and the lithium compound occurs increases.

[0026] 〔Heating step〕 When heat-treating the active material in the heating step, the temperature is lower than the thermal decomposition temperature of the binder included in the lithium ion battery, and for example, it can be less than 350°C, or can also be 250°C or lower.

[0027] Also, the atmosphere when heat-treating the active material in the heating step is a gas containing an oxidizing gas such as air or oxygen gas, but the concentration of the oxidizing gas is not particularly limited. That is, the oxygen partial pressure of the atmosphere of the heat treatment in the heating step may be 0.2 atm or more. Since the method for recovering the active material according to the present embodiment can be carried out even in air, it is a low-cost method.

[0028] As the valence of the transition metal (especially nickel) in the active material decreases due to the decrease in the activity of the active material, the surface structure of the active material changes from a layered rock salt structure (the international symbol of the space group representing the crystal structure is R-3m) to a rock salt structure (the international symbol of the space group representing the crystal structure is Fm-3m). When the heating step is carried out in the presence of oxygen gas, the oxidation of the transition metal is promoted, so that the surface structure of the active material returns from the rock salt structure to the layered rock salt structure, and thus the insertion reaction of lithium ions into the active material proceeds easily. The change in the surface structure from the rock salt structure to the layered rock salt structure can occur even in air, but is more likely to occur in oxygen gas.

[0029] 〔Washing step〕 In the heating process, when a lithium compound in an amount excessive rather than insufficient in lithium content is used, the active material after the completion of the heating process will contain the excess lithium compound. If the lithium compound is mixed in the active material, in addition to leading to an increase in the resistance of the lithium-ion battery, there is a risk that a binder such as polyvinylidene fluoride will gel. Therefore, the residual lithium compound may be removed after the completion of the heating process. That is, after the heating process, a washing process for removing the lithium compound may be performed.

[0030] The method for removing the lithium compound is not particularly limited. However, if the lithium compound is water-soluble, a method of dissolving the lithium compound in water and removing it can be used. However, when the active material comes into contact with water in the washing process, there is a risk that lithium ions will elute from the active material. If the water used in the washing process is alkaline, the elution of lithium ions from the active material is suppressed. Therefore, it is preferable that the aqueous solution of the lithium compound exhibits alkalinity. That is, when the residual lithium compound to be washed dissolves in the water used in the washing process, the water exhibits alkalinity, so the elution of lithium ions from the active material is suppressed.

Example

[0031] Examples and comparative examples are shown below to more specifically explain the present invention. 〔Example 1〕 An unused lithium-ion secondary battery was prepared. The positive electrode active material of this lithium-ion secondary battery is a lithium transition metal composite oxide LiNi 0.5 Mn 0.3 Co 0.2 O2, and the binder is polyvinylidene fluoride. The thermal decomposition temperature of polyvinylidene fluoride is 350°C.

[0032] This unused lithium-ion secondary battery was repeatedly charged and discharged, resulting in a degradation of the performance of the positive electrode active material. Then, an electrode mixture containing the positive electrode active material and the binder was taken out from the used lithium-ion secondary battery. Due to degradation during use, lithium ions were desorbed from the positive electrode active material. When the lithium transition metal composite oxide is represented by a chemical formula, it is Li 1-x Ni 0.5 Mn 0.3 Co 0.2 O2. Here, x in the above chemical formula is a number greater than 0 and less than 1.

[0033] The lithium content (molar amount) was measured for the positive electrode active material taken out from the unused lithium-ion secondary battery (hereinafter sometimes referred to as "unused positive electrode active material") and the positive electrode active material taken out from the used lithium-ion secondary battery (hereinafter sometimes referred to as "used positive electrode active material"). As a result, when the lithium content of the unused positive electrode active material was 1.00 mol, the lithium content of the used positive electrode active material was 0.86 mol. That is, x in the above chemical formula was 0.14. These results are shown in Table 1.

[0034] The method for measuring the lithium content of the positive electrode active material is as follows. The contents of lithium, nickel, manganese, and cobalt in the active material were measured by ICP emission spectrometry (Inductively Coupled Plasma Atomic Emission Spectroscopy: ICP-AES), and the molar ratio of lithium to the total amount of transition metals (nickel, manganese, cobalt) was calculated.

[0035] In addition, the unused positive electrode active material and the used positive electrode active material were analyzed by X-ray diffraction method, and the c-axis lattice constants were calculated from the obtained X-ray diffraction patterns. As a result, the c-axis lattice constant of the unused positive electrode active material was 14.236 Å, while the c-axis lattice constant of the used positive electrode active material was 14.299 Å. That is, the crystal structure had changed due to the decrease in the lithium content of the positive electrode active material. These results are shown in Table 1.

[0036] Lithium hydroxide was mixed with the electrode binder taken out from the used lithium-ion secondary battery, and heat treatment was carried out at 250 °C in air to insert lithium ions into the positive electrode active material and improve the activity of the deteriorated positive electrode active material. The mixing amount of lithium hydroxide is as follows. When the lithium deficiency amount of the positive electrode active material after use (that is, the positive electrode active material before heat treatment) is 0.14 mol, lithium hydroxide containing 0.79 mol of lithium was mixed into the electrode binder.

[0037] At this time, the value obtained by dividing the total surface area of all the particles of the mixed lithium hydroxide by the total surface area of the positive electrode active material to be subjected to the recovery treatment is 0.81. Further, the value obtained by dividing the total sum of the surface areas of the particles having a particle size of 10 μm or more among all the particles of the mixed lithium hydroxide by the total surface area of the positive electrode active material to be subjected to the recovery treatment is 0.05.

[0038] The total surface areas of lithium hydroxide and the positive electrode active material were measured using the Morphologi 4, an image-based particle size distribution measuring device manufactured by Malvern Panalytical. Specifically, the particle size distribution was obtained by static image analysis, and the total volumes of lithium hydroxide and the positive electrode active material were calculated from the volume fraction and the particle size, respectively. Then, the number of particles of each particle size was calculated from the total volume and the volume fraction, and the total surface area was calculated by multiplying the surface area of the particles of each particle size by the number of particles.

[0039] The positive electrode active material of Example 1 subjected to heat treatment was analyzed by X-ray diffraction method, and the c-axis lattice constant was calculated from the obtained X-ray diffraction pattern. As a result, the c-axis lattice constant was 14.239 Å. The results are shown in Table 1 and the graph of FIG. 1. The graph of FIG. 1 shows the c-axis lattice constants of the unused positive electrode active material, the positive electrode active material after use, and the positive electrode active material of Example 1 subjected to the recovery treatment. As can be seen from the graph of FIG. 1, the c-axis lattice constant of the positive electrode active material increases due to the use of the lithium ion secondary battery, but by performing the recovery treatment, the c-axis lattice constant of the positive electrode active material decreases and becomes approximately the same as the c-axis lattice constant of the unused positive electrode active material. From this result, it can be understood that the activity is improved by subjecting the used positive electrode active material to the recovery treatment and the activity has recovered to near that of the unused positive electrode active material.

[0040] Note that by the recovery treatment, a reaction occurs in which lithium ions are inserted into the positive electrode active material from which lithium ions have desorbed, and the reaction formula representing the insertion reaction is as follows. Li 1-x Ni 0.5 Mn 0.3 Co 0.2 O2 + LiOH → LiNi 0.5 Mn 0.3 Co 0.2 O2 + (1 - x)LiOH + 0.5xH2O + 0.25xO2

[0041]

Table 1

[0042] 〔Examples 2 and 3〕 Except that the mixing amount of lithium hydroxide was different as shown in Table 1, the used positive electrode active material was subjected to the recovery treatment in the same manner as in Example 1. The results are shown in Table 1 and the graph of FIG. 1. As can be seen from the graph of FIG. 1, by performing the recovery treatment, the c-axis lattice constant of the positive electrode active material decreases and becomes approximately the same as the c-axis lattice constant of the unused positive electrode active material. From this result, it can be understood that the activity is improved by subjecting the used positive electrode active material to the recovery treatment and the activity has recovered to near that of the unused positive electrode active material.

[0043] 〔Example 4〕 Except for the points of changing the type of lithium compound from lithium hydroxide to lithium carbonate and setting the mixing amount of lithium carbonate as shown in Table 1, the used positive electrode active material was subjected to a recovery treatment in the same manner as in Example 1. The results are shown in Table 1 and the graph of FIG. 1. As can be seen from the graph of FIG. 1, by performing the recovery treatment, the c-axis lattice constant of the positive electrode active material becomes smaller and is comparable to that of the unused positive electrode active material. From this result, it can be seen that the activity is improved by subjecting the used positive electrode active material to the recovery treatment, and the activity has recovered to near that of the unused positive electrode active material.

[0044] [Example 5] Except for the point that the mixing amount of lithium hydroxide was different as shown in Table 1, the used positive electrode active material was subjected to a recovery treatment in the same manner as in Example 1. The results are shown in Table 1 and the graph of FIG. 2. As can be seen from the graph of FIG. 2, by performing the recovery treatment, the c-axis lattice constant of the positive electrode active material becomes smaller and is comparable to that of the unused positive electrode active material. From this result, it can be seen that the activity is improved by subjecting the used positive electrode active material to the recovery treatment, and the activity has recovered to near that of the unused positive electrode active material.

[0045] However, for Example 5, since the mixing amount of lithium hydroxide was relatively small and the value obtained by dividing the total surface area of the particles with a particle size of 10 μm or more among all the particles of the mixed lithium hydroxide by the total surface area of the positive electrode active material was 0.03, the degree of improvement in activity was smaller compared to Example 1.

[0046] [Example 6] Except for the point of changing the atmosphere during the heat treatment of the positive electrode active material from air to oxygen gas, the used positive electrode active material was subjected to a recovery treatment in the same manner as in Example 1. The results are shown in Table 1 and the graph of FIG. 3. As can be seen from the graph of FIG. 3, by performing the recovery treatment, the c-axis lattice constant of the positive electrode active material becomes smaller and is comparable to that of the unused positive electrode active material. From this result, it can be seen that the activity is improved by subjecting the used positive electrode active material to the recovery treatment, and the activity has recovered to near that of the unused positive electrode active material.

[0047] In addition, since the transition metal of the positive electrode active material is oxidized by oxygen gas, the surface structure of the positive electrode active material returns from the rock salt type structure to the layered rock salt type structure, so that the insertion reaction of lithium ions into the active material proceeds more easily. The change in the surface structure from the rock salt type structure to the layered rock salt type structure occurs even in air with an oxygen partial pressure of 0.2 atm, but it is more likely to occur in oxygen gas, so the insertion reaction of lithium ions into the positive electrode active material proceeds more easily. As a result, as can be seen from the graph of FIG. 3, it can be seen that the activity has been improved compared to the unused positive electrode active material.

[0048] [Comparative Example 1] A recovery treatment was performed on the used positive electrode active material in the same manner as in Example 1, except that the temperature during the heat treatment of the positive electrode active material was changed from 250°C to 850°C. The results are shown in Table 1 and the graph of FIG. 1. As can be seen from the graph of FIG. 1, the c-axis lattice constant of the positive electrode active material has become smaller by performing the recovery treatment, and it is considered that the activity has been improved. However, compared with Example 1, since the c-axis lattice constant is large, it can be seen that the recovery of the activity is insufficient and the activity has not recovered to near that of the unused positive electrode active material.

Claims

1. A method for improving the reduced activity of an active material included in a lithium-ion battery, comprising: a heating step of mixing a lithium compound with the active material or an electrode binder containing the active material and performing a heat treatment at a temperature lower than the thermal decomposition temperature of a binder included in the lithium-ion battery; wherein the mixing amount of the lithium compound is an amount such that a value obtained by dividing the total surface area of the lithium compound by the total surface area of the active material is 0.05 or more, the method for recovering the active material.

2. The method for recovering the active material according to Claim 1, wherein the total surface area of the lithium compound is the total sum of the surface areas of particles having a particle size of 10 μm or more among all the particles of the lithium compound.

3. The method for recovering the active material according to Claim 1 or Claim 2, wherein the lithium compound is water-soluble.

4. The method for recovering the active material according to Claim 1 or Claim 2, wherein an aqueous solution of the lithium compound is alkaline.

5. The method for recovering the active material according to Claim 1 or Claim 2, wherein the lithium compound is lithium hydroxide.

6. The method for recovering the active material according to Claim 1 or Claim 2, wherein the oxygen partial pressure in the atmosphere of the heat treatment in the heating step is 0.2 atm or more.

7. The method for recovering the active material according to Claim 1 or Claim 2, further comprising a removing step of removing the binder from the electrode binder before the heating step.

8. The method for recovering the active material according to Claim 7, wherein the amount of the binder remaining in the electrode binder after the removing step is 1.2% by mass or less of the entire electrode binder after the removing step.

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