Inactivation method and inactivation device

Abstract

To provide novel inactivation method and device for inactivating nickel-metal hydride batteries.SOLUTION: A deactivation method according to the present disclosure includes a deactivation step of reacting a deactivating solution in which anions containing N and O and / or cations containing N and H are dissolved with the positive electrode and / or negative electrode of a nickel-metal hydride battery to deactivate the nickel-metal hydride battery.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present disclosure relates to a deactivation method and a deactivation device. [Background technology]

[0002] A conventional electricity storage device proposed is a sealed metal-hydrogen alkaline storage battery having a negative electrode mainly made of a hydrogen storage alloy and a positive electrode, and provided with an oxidant supply means for supplying an oxidant that oxidizes hydrogen stored in the negative electrode (see Patent Document 1). It is claimed that this electricity storage device can provide a sealed metal-hydrogen alkaline storage battery with improved cycle characteristics by improving the utilization rate of the negative electrode. Another proposed method for stabilizing a dissolved and pulverized hydrogen storage alloy involves exposing the pulverized hydrogen storage alloy powder to a carbon dioxide atmosphere and then removing it from the atmosphere (see Patent Document 2). It is claimed that this stabilization method can stabilize the hydrogen storage alloy without forming an oxide film on the surface. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 5-251108 [Patent Document 2] Japanese Patent Application Publication No. 10-195503 Summary of the Invention [Problem to be solved by the invention]

[0004] When recycling commonly used nickel-metal hydride batteries, it has been necessary to inactivate the batteries in order to ensure safer recycling. In the stabilization method of Patent Document 2, a process for stabilizing the hydrogen storage alloy has been considered, but the process for treating the batteries has not yet been fully considered.

[0005] The present disclosure has been made to solve such problems, and a main object of the present disclosure is to provide a novel deactivation method and deactivation device for deactivating nickel-metal hydride batteries. [Means for solving the problem]

[0006] As a result of extensive research to achieve the above-mentioned object, the present inventors have discovered that by using a nitrogen-containing anion and a nitrogen-containing cation, nickel-metal hydride batteries can be more efficiently inactivated through their oxidation-reduction cycle, and have thus completed the invention of the present disclosure.

[0007] That is, the inactivation method of the present disclosure comprises: a deactivation step in which a deactivating solution in which anions containing N and O and / or cations containing N and H are dissolved is reacted with the positive electrode and / or negative electrode of the nickel-metal hydride battery to deactivate the nickel-metal hydride battery; It includes:

[0008] In addition, the deactivation device of the present disclosure includes: A deactivation device for deactivating a nickel-metal hydride battery, comprising: a processing unit that performs a deactivation process to deactivate the nickel-metal hydride battery by reacting a deactivating solution in which anions containing N and O and / or cations containing N and H are dissolved with the positive electrode and / or negative electrode of the nickel-metal hydride battery; It is equipped with the following. [Effects of the Invention]

[0009] This deactivation method and deactivation device can provide a novel deactivation method and deactivation device for deactivating nickel-metal hydride batteries. The reason for this effect is presumably due to, for example, an oxidation-reduction reaction of nitrogen-containing cations and nitrogen-containing anions contained in the deactivation solution, which causes the deactivation reaction to proceed at the positive and negative electrodes. [Brief explanation of the drawings]

[0010] [Figure 1]10 is a flowchart showing an example of a battery recycling process routine. [Figure 2] 1 is a cross-sectional view showing the outline of the configuration of a Ni-MH secondary battery 20. FIG. [Figure 3] Five-cycle discharge curve of a small Ni-MH battery. [Figure 4] Deactivation behavior of a small Ni-MH battery in KNO2 and ammonia detection results. [Figure 5] Deactivation behavior of a small Ni-MH battery with NaNO2. [Figure 6] Deactivation behavior of a small Ni-MH battery in KNO3 and detection results of ammonia and nitrite. [Figure 7] Deactivation behavior of a small Ni-MH battery with (NH4)2SO4 and nitrite detection results. [Figure 8] Deactivation behavior of small Ni-MH batteries with K3Fe(CN)6. [Figure 9] Deactivation behavior of a small Ni-MH battery with 1,5-dihydroanthraquinone. [Figure 10] Deactivation behavior of small Ni-MH batteries with sodium 1,2-naphthoquinone-4-sulfonate. [Figure 11] FIG. 1 is a graph showing the relationship between nitrite ion concentration and inactivation time in Experimental Examples 10 to 13. [Figure 12] FIG. 1 is a graph showing the relationship between the injection amount of aqueous sodium nitrite solution and the inactivation time in Examples 11, 13, and 14. [Figure 13] FIG. 1 is a graph showing the relationship between the concentration of aqueous sodium nitrite solution and ammonium nitrate solution and the inactivation time in Experimental Examples 11 and 16 to 19. [Figure 14] FIG. 1 is a graph showing the relationship between the inactivation index and the inactivation time of the inactivating agents in Experimental Examples 10 to 19. DETAILED DESCRIPTION OF THE INVENTION

[0011] (Inactivation method) The deactivation method disclosed herein is a process for deactivating nickel-metal hydride batteries that is performed during the process of recycling nickel-metal hydride batteries. FIG. 1 is a flowchart showing an example of a nickel-metal hydride battery recycling process routine. This recycling process is an example of a process for recycling automotive batteries, such as those used in HEVs. In this routine, a battery pack is collected from an HEV (S10), disassembled (S20), deactivated by injecting a deactivating solution (S30), oxidized (S40), crushed (S50), and dissolved to recover elements (S60). The recovered elements are used to synthesize active materials (S70), and the cells are reassembled (S80). This deactivation process may be performed in S30 of this routine.

[0012] In the deactivation step, a deactivating solution containing dissolved anions containing N and O and / or cations containing N and H is reacted with the positive and / or negative electrodes of the nickel-metal hydride battery to deactivate the nickel-metal hydride battery. The deactivating solution may be a solution capable of a shuttle reaction in which H is desorbed from Ni-MH, resulting in a substance that inserts H into the positive electrode and then desorbs H from the negative electrode again. Here, for convenience, a compound containing either anions containing N and O and / or cations containing N and H is referred to as a "nitrogen-containing salt." This deactivating solution is preferably an aqueous solution using water as the solvent. Furthermore, this deactivating solution is preferably alkaline, and may be made alkaline by dissolving an alkali metal hydroxide. Examples of alkali metals include Li, Na, and K, with K and Na being preferred. The deactivating solution preferably contains, as nitrogen-containing salts, nitrate anions, nitrite anions, and one or more of primary ammonium cations, secondary ammonium cations, tertiary ammonium cations, and quaternary ammonium cations. In each ammonium cation, hydrogen may be substituted with an alkyl group or an aryl group. Examples of alkyl groups include methyl, ethyl, and propyl groups. Examples of aryl groups include phenyl, tolyl, and xyl groups. This inactivating solution may contain an alkali cation as a counter cation for the nitrate anion and the nitrite anion. This inactivating solution may also contain a sulfate anion and / or a halogen as a counter anion for the ammonium cation. Examples of nitrogen-containing salts contained in this inactivating solution include sodium nitrate, potassium nitrate, lithium nitrate, sodium nitrite, potassium nitrite, and lithium nitrite. Of these, sodium nitrite and potassium nitrite are more preferred from the viewpoint of solubility, etc. This inactivating solution may also contain ammonium sulfate, etc.

[0013] The concentration of the nitrogen-containing salt contained in the deactivation solution is preferably higher, preferably 0.1 mol / L (M) or higher, more preferably 0.2 M or higher, and may be 0.5 M or higher or 1 M or higher. This concentration is determined appropriately depending on the solubility in the alkaline electrolyte in the cell, but may be 6 M or lower, or may be higher depending on the composition of the alkaline electrolyte. Furthermore, if the deactivation solution is not dissolved in the alkaline electrolyte at the injection stage, the concentration may be higher, such as 6 M or higher, 10 M or higher, or 30 M or lower. Furthermore, the pH of the deactivation solution is preferably 3 or higher, and may be 8 or 9 or higher. In this deactivation step, the deactivation treatment may be performed at room temperature, for example, in the range of 20°C to 25°C. The treatment temperature may be in the range of -20°C to 100°C. In this step, the amount of deactivation solution added may be appropriately selected depending on the concentration of the nitrogen-containing salt, the treatment temperature, and the size of the nickel-metal hydride battery. The treatment time for the deactivation treatment may be appropriately selected depending on the size of the nickel-metal hydride battery, the amount and concentration of the deactivation solution added, and the type of salt. This treatment time may be, for example, in the range of 1 hour to 24 hours. In the deactivation treatment, after the deactivation solution is injected into the nickel-metal hydride battery, the battery may be left to stand, or may be held while being vibrated. This treatment does not require any special processing, and the battery may simply be left to stand.

[0014] In the deactivation step, a deactivation solution may be used whose deactivation index, calculated by dividing the capacity (mAh) of the nickel-metal hydride battery to be deactivated by the number of reactions of protons at the positive and negative electrodes multiplied by the amount (mol) of the deactivation substance containing an anion containing N and O and / or a cation containing N and H, falls within a predetermined range. In this step, it is preferable to use a deactivation solution in which the solvent and deactivation substance are selected and their concentrations and amounts are adjusted so that the deactivation index falls within the predetermined range. Here, the reaction number is the amount of hydrogen that reacts with one molecule of the deactivation substance. The reaction number can be determined by whether any of the following formulas (1) to (3) occurs. For example, the reaction number is "6" for NaNO2 or KNO2, and "14" for NH4NO3. This deactivation index is preferably smaller, for example, within the range of 4 Ah / mol to 75 Ah / mol, more preferably 50 Ah / mol or less, and even more preferably 40 Ah / mol or less.

[0015] In the deactivation step, a deactivating solution may be injected into the electrolyte while the electrodes of the nickel-metal hydride battery are constrained. In this deactivation step, a deactivating solution containing ammonium nitrate as a deactivating substance in the range of 2 mol / L to 8 mol / L is preferably used. Ammonium nitrate is preferred because it has a relatively high solubility in water as a solvent, making it easy to increase the concentration, is relatively inexpensive, and is easier to handle. The concentration of the deactivating substance in the deactivating solution has an appropriate range, taking into account the functionality after injection into the cell, with 2 mol / L or more being more preferable and 8 mol / L or less being more preferable.

[0016] During the passivation treatment, the reactions represented by the following formulas (1) to (3) are presumed to occur at the positive and negative electrodes. For example, in a passivation solution containing ammonia cations, the reaction represented by formula (1) occurs at the positive electrode, causing Ni to be passivated and nitrite anions to be produced. In a passivation solution containing nitrate anions, the reaction represented by formula (2) occurs at the negative electrode, causing the hydrogen storage alloy to be passivated and nitrite anions to be produced. Furthermore, in the presence of nitrite anions at the negative electrode, the reaction represented by formula (3) occurs, causing the hydrogen storage alloy to be passivated and ammonium salts to be produced. Therefore, it is presumed that the presence of any of the nitrogen-containing salts in the passivation solution will cause the reactions represented by formulas (1) to (3) to proceed cyclically at the positive and negative electrodes, resulting in efficient battery passivation.

[0017] [ka]

[0018] [Nickel-metal hydride battery] The nickel-metal hydride battery to be deactivated will now be described. The nickel-metal hydride battery includes a positive electrode having a positive electrode active material, a negative electrode having a negative electrode active material, and an ion-conducting medium interposed between the positive and negative electrodes and conducting carrier ions. The positive electrode active material may be, for example, a nickel oxide compound such as nickel oxyhydroxide. The negative electrode active material may be a hydrogen-storing alloy or a hydrogen compound containing hydrogen. The ion-conducting medium may be an alkaline solution such as a concentrated potassium hydroxide aqueous solution as an electrolyte. The shape of this nickel-metal hydride battery is not particularly limited, and examples include coin, button, sheet, laminated, cylindrical, flat, and rectangular types. Large nickel-metal hydride batteries for use in electric vehicles and the like may also be used. An example of a nickel-metal hydride battery is shown in FIG. 2. FIG. 2 is a cross-sectional view showing the schematic configuration of a coin-shaped nickel-metal hydride battery 20. As shown in FIG. 2, the nickel-metal hydride battery 20 includes a cup-shaped battery case 21, a positive electrode 22 having a positive electrode active material and provided at the bottom of the battery case 21, a negative electrode 23 having a negative electrode active material and provided in a position opposite the positive electrode 22 with a separator 24 interposed therebetween, a gasket 25 made of an insulating material, and a sealing plate 26 disposed at the opening of the battery case 21 and sealing the battery case 21 via the gasket 25.

[0019] [Inactivation device] The deactivation device is configured as a device for carrying out the above-described deactivation method. This device includes, for example, a processing unit that carries out deactivation treatment to deactivate a nickel-metal hydride battery by reacting a deactivating solution in which anions containing N and O and / or cations containing N and H are dissolved with the positive electrode and / or negative electrode of the nickel-metal hydride battery. The processing unit may include an injection unit that injects the deactivating solution into the nickel-metal hydride battery, and a setting unit that sets the nickel-metal hydride battery.

[0020] The deactivation method and deactivation device described above can provide a novel deactivation method and deactivation device for deactivating nickel-metal hydride batteries. The reason for this effect is presumably due to, for example, an oxidation-reduction reaction of nitrogen-containing cations and nitrogen-containing anions contained in the deactivation solution, which causes the deactivation reaction to proceed at the positive and negative electrodes.

[0021] It goes without saying that the present disclosure is not limited to the above-described embodiments, and can be implemented in various forms as long as they fall within the technical scope of the present disclosure.

[0022] The present disclosure may be any of the following [1] to [6]. [1] A deactivation method including a deactivation step in which a deactivating solution in which anions containing N and O and / or cations containing N and H are dissolved is reacted with the positive electrode and / or negative electrode of a nickel-metal hydride battery to deactivate the nickel-metal hydride battery. [2] The deactivation method according to [1], wherein the deactivating solution is a solution capable of a shuttle reaction in which a substance generated after desorbing H from Ni-MH inserts H into the positive electrode and then desorbs H from the negative electrode again. [3] The inactivation method according to [1] or [2], wherein the inactivation solution contains one or more of nitrate anions, nitrite anions, and primary ammonium cations, secondary ammonium cations, tertiary ammonium cations, and quaternary ammonium cations. [4] The inactivation method according to [3], wherein the inactivation solution contains an alkali cation for nitrate anions and nitrite anions, and a sulfate anion and / or a halogen for ammonium cations. [5] The inactivation method according to any one of [1] to [4], wherein the inactivation liquid is alkaline. [6] The deactivation method according to any one of [1] to [5], wherein the deactivation step uses the deactivation solution in which the solvent and the deactivation substance are selected and the concentration and amount thereof are adjusted so that the deactivation index, obtained by dividing the capacity (mAh) of the nickel-metal hydride battery to be deactivated by the number obtained by multiplying the amount (mol) of the deactivation substance containing an anion containing N and O and / or a cation containing N and H by the number of reactions of protons at the positive and negative electrodes, is in the range of 4 Ah / mol to 75 Ah / mol. [7] The inactivation method according to any one of [1] to [6], wherein the inactivation solution contains ammonium nitrate as an inactivating substance in a range of 2 mol / L to 8 mol / L. [8] A deactivation device for deactivating a nickel-metal hydride battery, comprising: A deactivation device including a processing unit that performs deactivation processing to deactivate a nickel-metal hydride battery by reacting a deactivating solution in which anions containing N and O and / or cations containing N and H are dissolved with the positive electrode and / or negative electrode of the nickel-metal hydride battery. [Example]

[0023] Below, specific examples of the inactivation method for a nonaqueous secondary battery according to the present disclosure are described as experimental examples. Experimental Examples 1 to 4 and 10 to 19 correspond to working examples of the present disclosure, and Experimental Examples 5 to 9 correspond to reference examples.

[0024] (Experimental Example 1) (Making small batteries) A commercially available automotive Ni-MH battery module was disassembled before filling to obtain the positive electrode, negative electrode, and separator. One side of the negative electrode was peeled off to create a single-sided coated product. The positive and negative electrodes were cut to a design capacity of 125 mAh. The positive electrode was placed in a separator bag and sandwiched between two single-sided coated negative electrodes, and Ni metal tabs were attached to each of the positive and negative electrodes to form a small cell. The small cell was then clamped in a restraining device and vacuum-impregnated with a model alkaline electrolyte (KOH: 6M, NaOH: 1M, LiOH: 1M) to form a small cell.

[0025] (Small battery activation and pre-deactivation charging) The small cells were initially charged at a current of 6.25 mA (1 / 20 C) for 24 hours, i.e., to a capacity equivalent to 120% SOC. After a 10-minute rest, they were discharged at a current of 12.5 mA (1 / 10 C) to a voltage limit of 1 V. From the second cycle onward, they were charged at a current of 12.5 mA (1 / 10 C) for 12 hours, i.e., to a capacity equivalent to 120% SOC, and after a 10-minute rest, they were discharged at a current of 12.5 mA (1 / 10 C) to a voltage limit of 1 V. This cycle was repeated up to five times to obtain activated Ni-MH small cells. In the next test, to evaluate the deactivation solution, the small cells were charged at a current of 12.5 mA (1 / 10 C) for 12 hours, i.e., to a capacity equivalent to 120% SOC. Figure 3 shows the discharge curves (N = 2) of a five-cycle small Ni-MH battery.

[0026] (Preparation of inactivation solution) KNO2 was dissolved in a model alkaline electrolyte (KOH: 6M, NaOH: 1M, LiOH: 1M) to a concentration of 1M to obtain a deactivation solution.

[0027] (Inactivation test, confirmation of reaction products) After pouring the deactivating solution into a polytetrafluoroethylene beaker, the small cell was removed from the restraint and transferred to the beaker. The voltage between the positive and negative electrodes was then monitored in a thermostatic chamber at 20°C. Figure 4 shows the behavior of the deactivation of a small Ni-MH battery with KNO2 (N number = 2). As shown in Figure 4, it was found that injecting this deactivating solution into the electrolyte can reduce the battery voltage over time. In addition, the solution after deactivation was removed and an attempt was made to detect ammonia using the Nessler method. As a result, ammonium ions were detected in the KNO2 deactivating solution. This suggests that a reaction is progressing in which NO2 in the deactivating solution is reduced.

[0028] (Experimental Example 2) Experimental Example 2 was conducted in the same manner as in Experimental Example 1, except that the salt dissolved in the model electrolyte was changed to NaNO2 and the solution was not analyzed. This experiment evaluated the deactivation behavior of NaNO2. Figure 5 shows the behavior of deactivation of a small Ni-MH battery with NaNO2. As shown in Figure 5, it was found that injecting this deactivation solution into the electrolyte reduced the battery voltage over time.

[0029] (Experimental Example 3) Experimental Example 3 was conducted in the same manner as in Experimental Example 1, except that the salt dissolved in the model electrolyte was changed to KNO3, the KNO3 concentration was set to 0.2 M, and the solution analysis was performed as described below. Figure 6 shows the deactivation behavior of a small Ni-MH battery using KNO3 (N = 2). For the analysis of the solution in Experimental Example 3, the solution after deactivation was removed and nitrite ions were detected using the naphthylethylenediamine colorimetric method and ammonium ions using the Nessler method. As shown in Figure 6, injecting this deactivation solution into the electrolyte reduced the battery voltage over time. Furthermore, analysis of the solution after deactivation detected ammonium ions and nitrite ions in the KNO3 deactivation solution. This suggests that a reduction reaction of NO3 in the deactivation solution was occurring.

[0030] (Experimental Example 4) The deactivation solution used in Experimental Example 1 was prepared and analyzed as follows. The deactivation solution was prepared by mixing the model electrolyte with a 0.5 M (NH4)2SO4 solution in a volume ratio of 2:1 to obtain the deactivation solution. The solution was analyzed by extracting the deactivated solution and detecting nitrite ions using naphthylethylenediamine colorimetry. Figure 7 shows the deactivation behavior of a small Ni-MH battery with (NH4)2SO4 (N number = 2). As shown in Figure 7, injecting this deactivation solution into the electrolyte reduced the battery voltage in two stages over time. Furthermore, analysis of the solution after deactivation revealed that nitrite ions were detected in the (NH4)2SO4 deactivation solution. This suggests that the ammonium ions in the deactivation solution were oxidized.

[0031] (Experimental Examples 5 and 6) The deactivation solution used in Experimental Example 1 was modified as follows: Experimental Example 5 was performed in the same manner as Experimental Example 1, except that K3Fe(CN)6 was adjusted to 10 mM in 6 M KOH. The deactivation behavior of K3Fe(CN)6 was evaluated. Experimental Example 6 was also evaluated by adding the following deactivation solution to the evaluation cell of Experimental Example 5. A deactivation solution was prepared by adjusting K3Fe(CN)6 to 100 mM in 1 M KOH. After adding the deactivation solution, the cell was left for 150 hours or more. The state of the solution and the cell was then visually observed in a glove box under an Ar atmosphere. Figure 8 shows the deactivation behavior of small Ni-MH batteries using K3Fe(CN)6 in Experimental Examples 5 and 6. As shown in Figure 8, 0.01 M K3Fe(CN)6 did not sufficiently reduce the battery voltage. Furthermore, even 0.1 M K3Fe(CN)6 did not achieve sufficient deactivation effects. Furthermore, yellow crystals were found to have precipitated on the negative electrode after deactivation.

[0032] (Experimental Example 7) Experimental Example 7 was conducted in the same manner as Experimental Example 1, except that the molecule dissolved in the model electrolyte was 1,5-dihydroanthraquinone, the concentration of 1,5-dihydroanthraquinone was 0.01 M, and the solution was not analyzed. The same test was conducted to evaluate the deactivation behavior of 1,5-dihydroanthraquinone. Figure 9 shows the behavior of deactivation of a small Ni-MH battery with 1,5-dihydroanthraquinone (N=2). As shown in Figure 9, 1,5-dihydroanthraquinone was unable to achieve sufficient battery deactivation effects.

[0033] (Experimental Example 8) Experimental Example 8 was conducted in the same manner as Experimental Example 1, except that the molecules dissolved in the model electrolyte solution in the deactivation solution preparation were changed to sodium 1,2-naphthoquinone-4-sulfonate, the concentration of sodium 1,2-naphthoquinone-4-sulfonate was set to 0.1 M, and the solution analysis was not performed. The same test was conducted to evaluate the deactivation behavior of sodium 1,2-naphthoquinone-4-sulfonate. Figure 10 shows the behavior of deactivation of a small Ni-MH battery with sodium 1,2-naphthoquinone-4-sulfonate (N=2). As shown in Figure 10, sodium 1,2-naphthoquinone-4-sulfonate was unable to achieve sufficient battery deactivation effects.

[0034] (Experimental Example 9) The solubilities of nitric acid and nitrite salts in model alkaline electrolytes (6M KOH, 1M NaOH, 1M LiOH) were quantified using the following procedure. For the lithium and calcium nitrite and nitrite salts, 2 mmol of the lithium salt and 0.04 mmol of the calcium salt were weighed, and 1000 μL of electrolyte was added dropwise and stirred. If any residue remained, an equal amount of electrolyte was added dropwise. If no residue remained, the volume was measured and the solubility was calculated. For the sodium and potassium nitrite and nitrite salts, 20 mmol of the lithium salt and nitrite salt were added dropwise and stirred. If any residue remained, an equal amount of electrolyte was added dropwise. If no residue remained, the volume was measured and the solubility was calculated. Note that Ca(NO2)2 did not completely dissolve in the above test, so the upper limit of solubility was evaluated. The quantified solubilities are summarized in Table 1. Regarding salt solubilities (mol / L), sodium and potassium nitrite showed high solubility.

[0035] [Table 1]

[0036] (Results and Discussion) In solutions containing NO2, NO3, and NH4 ions, the battery voltage dropped below 1 V, confirming that the battery was discharging due to the effects of the solution. In analyses of the solutions in Experiments 1 and 4, conducted to confirm the reactions in the above solutions, ammonia was detected in Experiment 1 and nitrite in Experiment 4. Thus, it is inferred that a shuttle reaction involving these ions occurred between the positive and negative electrodes of the Ni-MH battery, causing the battery to discharge. Furthermore, because ammonia and nitrite were detected in the analysis of the solution in Experiment 3, it is inferred that nitrate ions were reduced to nitrite ions, which were then further reduced by MH to produce ammonia, which then reduced the positive electrode. From these results, it is inferred that discharge due to the passivation solution is due to the chemical reactions derived from the above-mentioned reaction equations (1) to (3). Experiments 1 and 2 demonstrated that passivation of NO2 proceeds regardless of the cation species combined. However, it is believed that the cation species affects its solubility in the electrolyte. Therefore, the solubility of various nitrites and nitrates was quantified. The solubility of monovalent cations with nitrates and nitrites is higher than 0.1 M, making them preferable as they can be quickly discharged as a passivating solution. When comparing different anions, nitrites have a higher solubility than nitrates, and among them, Na and K salts have the highest solubility and are the most preferable. On the other hand, the solubility of salts of nitrites with divalent cations is significantly lower, making them unpreferable.

[0037] In Experiments 5 and 6, we considered a method for discharging a battery by using a shuttle reaction between the positive and negative electrodes, such as a chemical substance capable of utilizing transition metal valence changes or a chemical substance capable of utilizing stable radicals, collectively known as a redox mediator (RM), in addition to the shuttle reactions described above. Therefore, we investigated whether discharge was possible using potassium hexacyanoferrate (Examples 5 and 6), a common aqueous RM. First, in Experiment 5, potassium hexacyanoferrate was dissolved in the same high-concentration alkaline solution as the electrolyte to evaluate deactivation. However, the solubility of potassium hexacyanoferrate in alkaline solution was low, at only 0.01 M. Therefore, the concentration of reactive species was too low to allow discharge reactions to proceed, and the battery voltage barely dropped even after 250 hours. Reducing the alkaline concentration to increase the concentration of reactive species increased the solubility of potassium hexacyanoferrate. Therefore, a deactivating solution prepared by dissolving 0.1 M potassium hexacyanoferrate in 1 M KOH was dropped into the cell. However, even after 150 h, only one of the two samples reached 1 V. Visual observation of the cell revealed the formation of yellow potassium hexacyanoferrate crystals on the electrode surface and in the beaker. This suggests that even if an RM with low solubility in alkaline electrolyte is dissolved in a low-concentration alkaline solution and added, the salt crystallizes upon contact with the high-concentration alkaline solution present in the cell. The crystals obstruct the flow path of the solution, diluting the RM concentration in the solution and inhibiting the shuttle reaction, resulting in a significantly longer reaction time. This phenomenon is presumed to be due to the low solubility of the salt in alkaline electrolyte.

[0038] Among the molecules that function as RMs in alkaline solutions, Experimental Example 7 shows an RM that has low solubility in the model electrolyte but undergoes a reversible reaction, while Experimental Example 8 shows an RM that has high solubility in the model electrolyte but undergoes an irreversible reaction. As with Experimental Example 5, the discharge reaction did not proceed with the low-solubility RM, and no voltage drop was observed. On the other hand, Experimental Example 8, which includes an irreversible reaction, saw the voltage drop slow down midway through the discharge, and the battery was not discharged to 1 V. From these results, it was inferred that in order to achieve passivation, in addition to the shuttle reaction occurring between the positive and negative electrodes of Ni-MH, it is desirable for the RM to have high solubility in the electrolyte and to have no reactions other than the shuttle reaction.

[0039] [Table 2]

[0040] Next, a small test battery was fabricated, and the process of injecting a deactivator into this small battery was investigated. The above test results were obtained by using an aqueous solution of salt dissolved in the electrolyte as a deactivating solution to release the constrained state of the cell, while the following test was performed by injecting a deactivating solution of salt dissolved in ion-exchange water into the electrolyte of a constrained cell. The small battery was the same as in Experimental Examples 1 to 8 described above.

[0041] (Small battery activation and pre-deactivation charging) The small cells were initially charged at a current of 6.25 mA (1 / 20 C) for 24 hours, i.e., to a capacity equivalent to 120% SOC. After a 10-minute rest, they were discharged at a current of 125 mA (1 C) to a voltage limit of 1 V. From the second cycle onwards, they were charged at a current of 125 mA (1 C) for 1.2 hours, i.e., to a capacity equivalent to 120% SOC, and after a 10-minute rest, they were discharged at a current of 125 mA (1 C) to a voltage limit of 1 V. This cycle was repeated up to five times to obtain an active Ni-MH small cell. In the next test, to evaluate the deactivation solution, the small cells were charged at a current of 125 mA (1 C) for 12 hours, i.e., to a capacity equivalent to 120% SOC.

[0042] (Preparation of inactivation solution) NaNO2 was dissolved in ion-exchanged water to a concentration of 5M to obtain an inactivation solution.

[0043] (Inactivation test) (Experimental Examples 10-19) The cell's inlet was opened, and 62.4 μL of 5M NaNO2 aqueous solution was injected into the separator. The voltage between the positive and negative electrodes was then monitored in a thermostatic chamber at 20°C, and the discharge time to 1 V was measured. This was designated Experimental Example 1. A battery was deactivated using the same procedure as in Experimental Example 10, except that the concentration of the deactivation solution was adjusted to 7M. ​​This was designated Experimental Example 11. A battery was deactivated using the same procedure as in Experimental Example 10, except that the nitrite in the deactivation solution was changed to KNO2 at a concentration of 10M. This was designated Experimental Example 12. A battery was deactivated using the same procedure as in Experimental Example 12, except that the concentration of the deactivation solution was adjusted to 13M. This was designated Experimental Example 13. This was designated Experimental Example 14. This was designated Experimental Example 15. This was designated Experimental Example 16. Experimental Example 14 was a result of measuring the discharge time when a battery was deactivated using the same procedure as Experimental Example 11, except that the amount of deactivating solution injected was 124.8 μL, and the deactivating solution was doubled (N=3). Experimental Example 15 was a result of measuring the discharge time when a battery was deactivated using the same procedure as Experimental Example 11, except that the amount of deactivating solution injected was 187.4 μL, and the deactivating solution was tripled (N=3). Experimental Example 16 was a result of measuring the discharge time to 1 V when a battery was deactivated using the same procedure as Experimental Example 15, except that the deactivating solution was dissolved in ion-exchanged water to a concentration of 4 M NH4NO3. Experimental Example 17 was a result of measuring the discharge time to 1 V when a battery was deactivated using the same procedure as Experimental Example 16, except that the concentration of the deactivating solution was changed to 5 M. Experimental Example 18 was a result of measuring the discharge time to 1 V when a battery was deactivated using the same procedure as Experimental Example 16, except that the concentration of the deactivating solution was changed to 6 M. In addition, Experimental Example 19 was obtained by measuring the discharge time to 1 V when the battery was deactivated using the same procedure as in Experimental Example 18, except that the concentration of the deactivating solution was changed to 8M.

[0044] (Results and Discussion) Table 3 summarizes the type of deactivating substance, concentration (mol / L) of the deactivating solution, amount (μL) injected, test method, time (hr) until cell voltage reached 1 V or less, and deactivation index (Ah / mol) for Experimental Examples 10 to 19. The deactivation index is a value obtained by dividing the capacity (mAh) of the nickel-metal hydride battery to be deactivated by the amount (mol) of the deactivating substance multiplied by the number of proton reactions at the positive and negative electrodes. FIG. 11 is a graph showing the relationship between nitrite ion concentration and deactivation time for Experimental Examples 10 to 13. FIG. 12 is a graph showing the relationship between the injection amount of sodium nitrite aqueous solution and deactivation time for Examples 11, 13, and 14. FIG. 13 is a graph showing the relationship between the concentration of sodium nitrite aqueous solution and ammonium nitrate and deactivation time for Experimental Examples 11 and 16 to 19. FIG. 14 is a graph showing the relationship between the deactivation index and deactivation time for the deactivating agent for Experimental Examples 10 to 19.

[0045] As shown in Figure 11, the deactivation of nickel-metal hydride batteries was confirmed using aqueous solutions of NaNO2 or KNO2. Furthermore, as shown in Figure 12, it was found that by increasing the amount of deactivating solution injected, the deactivation time using NaNO2, which is cheaper and easier to use, can be further shortened. Furthermore, as shown in Figure 13, it was found that by using NH4NO3 as the deactivating substance, the time required for deactivation can be further shortened compared to NaNO2. This is presumed as follows: The deactivation reaction formulas for nitrite, nitrate, and ammonium salt used in the deactivating solution proceed, for example, according to the above-mentioned formulas (1) to (3). Here, in Experimental Examples 10 to 15, the deactivating substance injected was NO2 - Only anions react with each other, and the reaction starts from equation (3). On the other hand, in Experimental Examples 16 to 19, the ammonium ion, which is a cation, reacts with equation (1), and the nitrate ion, which is an anion, reacts with equation (2), and the anion reacts with equation (3), which is presumably why deactivation proceeds more efficiently. It is presumed that the reason the deactivation time did not shorten at NH4NO3 concentrations of 5M or higher is because the NH4NO3 concentration in the solution did not rise above 5M due to crystallization.

[0046] To compare the deactivation functions of different deactivating substances side-by-side using the above-mentioned reaction equations (1) to (3), we introduced the deactivation index (battery capacity) / (amount of deactivating substance) × (number of reactions). The number of reactions is the amount of hydrogen reacting with one molecule of deactivating substance. As shown in Figure 14, a relatively good linear relationship was obtained between the deactivation index and deactivation time. The battery capacity was introduced into the denominator because it is expected that the input amount range will vary depending on the battery type. In this disclosure, using the deactivation index as the axis, we inferred that the desirable range for deactivating ammonium ions, nitrate ions, and nitrite ions is 4 Ah / mol to 75 Ah / mol, more preferably 50 Ah / mol or less, and even more preferably 40 Ah / mol or less. The above results revealed that nickel-metal hydride batteries can be deactivated by using nitrogen-containing ions, such as nitrate-based anions and ammonium-based cations, as deactivation solutions.

[0047] [Table 3]

[0048] It goes without saying that the present disclosure is not limited to the above-described embodiments, and can be implemented in various forms as long as they fall within the technical scope of the present disclosure. [Industrial Applicability]

[0049] The present invention is applicable to the field of the battery industry. [Explanation of symbols]

[0050] 20 non-aqueous secondary battery, 21 battery case, 22 positive electrode, 23 negative electrode, 24 separator, 25 gasket, 26 sealing plate, 27 ion conductive medium.

Claims

1. a passivation step of causing a passivation solution in which anions containing N and O and / or cations containing N and H are dissolved to react with the positive electrode and / or negative electrode of the nickel-metal hydride battery to passivate the nickel-metal hydride battery; An inactivation method comprising:

2. The inactivation method according to claim 1, wherein the inactivation solution is a solution capable of a shuttle reaction in which a substance generated after desorbing H from Ni-MH inserts H into the positive electrode and then desorbs H from the negative electrode again.

3. 3. The inactivation method according to claim 1, wherein the inactivation solution contains at least one of nitrate anions, nitrite anions, and primary ammonium cations, secondary ammonium cations, tertiary ammonium cations, and quaternary ammonium cations.

4. 4. The method of claim 3, wherein the deactivating solution contains alkali cations for nitrate and nitrite anions, and sulfate anions and / or halogens for ammonium cations.

5. The inactivation method according to claim 1 or 2, wherein the inactivation liquid is alkaline.

6. 3. The deactivation method according to claim 1 or 2, wherein the deactivation step uses the deactivating solution in which a solvent and the deactivating substance are selected and their concentrations and amounts are adjusted so that a deactivation index, obtained by dividing the capacity (mAh) of the nickel-metal hydride battery to be deactivated by the number obtained by multiplying the amount of substance (mol) of the deactivating substance containing an anion containing N and O and / or a cation containing N and H by the number of reactions of protons at the positive and negative electrodes, falls within a range of 4 Ah / mol to 75 Ah / mol.

7. 3. The inactivation method according to claim 1, wherein the inactivation solution contains ammonium nitrate as an inactivating substance in a range of 2 mol / L to 8 mol / L.

8. A deactivation device for deactivating a nickel-metal hydride battery, comprising: a processing unit that performs a deactivation process to deactivate the nickel-metal hydride battery by reacting a deactivating solution in which anions containing N and O and / or cations containing N and H are dissolved with a positive electrode and / or a negative electrode of the nickel-metal hydride battery; An inactivation device comprising:

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