JP6296542B2 - Electrolyte for zinc secondary battery and zinc secondary battery - Google Patents

Description

  The present invention relates to an electrolyte for a zinc secondary battery and a zinc secondary battery. More specifically, the present invention relates to a zinc secondary battery electrolyte capable of improving charge / discharge cycle characteristics and a zinc secondary battery using the same.

  In recent years, in order to cope with air pollution and global warming, reduction of carbon dioxide emissions has been strongly desired. In the automobile industry, there are high expectations for the reduction of carbon dioxide emissions by introducing electric vehicles (EV), plug-in hybrid electric vehicles (PHEV), hybrid electric vehicles (HEV), etc., and these are the keys to commercialization of these. The development of secondary batteries for motor driving is actively performed. As a secondary battery for driving a motor, a lithium ion secondary battery having a high energy density has attracted attention, and is currently being developed rapidly. In addition, for further popularization of electric vehicles, plug-in hybrid electric vehicles, and hybrid electric vehicles, it is urgent to reduce the cost of secondary batteries.

  However, electric vehicles are required to have a cruising distance per charge comparable to that of gasoline vehicles, as well as performance equivalent to that of gasoline vehicles. The technological improvement of conventional lithium-ion secondary batteries has greatly reached the target. It has been pointed out that it is difficult.

Therefore, metal-air batteries are attracting attention as batteries that can achieve higher energy density than lithium ion secondary batteries.
In particular, in-vehicle secondary batteries are required to have a high energy density per volume, and zinc-air secondary batteries are considered promising among metal-air batteries.
Further, nickel-metal hydride secondary batteries currently used in some hybrid electric vehicles have a high cost for the hydrogen storage alloy used as the negative electrode, and the cost of the negative electrode is required to be reduced.
And from a viewpoint of cost reduction of a negative electrode, the request | requirement with respect to practical use of a nickel zinc secondary battery is high.
Thus, there is a high demand for practical use of a secondary battery in which zinc or zinc oxide is applied to the negative electrode.

  Conventionally, as a secondary battery in which zinc or zinc oxide is applied to the negative electrode, a secondary battery using an electrolytic solution containing potassium hydroxide is known (see Patent Document 1).

JP-T-2007-515863

  However, the secondary battery in which zinc or zinc oxide described in Patent Document 1 is applied to the negative electrode has a problem in that the measures for dendrite precipitation of dissolved zinc are not sufficient and the life of the charge / discharge cycle is very short. there were.

  The present invention has been made in view of such problems of the prior art. And an object of this invention is to provide the electrolyte for zinc secondary batteries which can suppress thru | or prevent the dendrite precipitation of zinc, and can improve charging / discharging cycling characteristics, and a zinc secondary battery using the same.

The inventors of the present invention have made extensive studies in order to achieve the above object. As a result, seen containing a solvent consisting of an organic substance and water having a structure represented by the general formula (1), a hydroxide, a salt comprising an alkali metal cation and an anion, and the general formula (1) It has been found that the above object can be achieved when the content of the organic substance having the structure represented is 30% by mass or more, and the present invention has been completed.

（式中、Ｘはアルキル基、ハロゲン基、ヒドロキシル基、カルボキシル基及びアミノ基からなる群より選ばれるいずれか１種の官能基を示し、Ｙは水素原子及びアルキル基からなる群より選ばれるいずれか１種の官能基を示す。）

(In the formula, X represents any one functional group selected from the group consisting of an alkyl group, a halogen group, a hydroxyl group, a carboxyl group and an amino group, and Y represents any one selected from the group consisting of a hydrogen atom and an alkyl group. Or a single functional group.)

That is, the electrolyte for a zinc secondary battery of the present invention comprises a solvent comprising an organic substance having a structure represented by the general formula (1) and water, a hydroxide, a salt comprising an alkali metal cation and an anion, only containing the content of the organic substance having the structure represented by the general formula (1) is what is at least 30 mass%.

（式中、Ｘはアルキル基、ハロゲン基、ヒドロキシル基、カルボキシル基及びアミノ基からなる群より選ばれるいずれか１種の官能基を示し、Ｙは水素原子及びアルキル基からなる群より選ばれるいずれか１種の官能基を示す。）

(In the formula, X represents any one functional group selected from the group consisting of an alkyl group, a halogen group, a hydroxyl group, a carboxyl group and an amino group, and Y represents any one selected from the group consisting of a hydrogen atom and an alkyl group. Or a single functional group.)

  Moreover, the zinc secondary battery of this invention is equipped with the electrolyte for zinc secondary batteries of the said this invention.

According to the present invention, seen containing a solvent consisting of an organic substance and water having a structure represented by the general formula (1), a hydroxide, a salt comprising an alkali metal cation and an anion, the general formula ( It was set as the structure whose content of the organic substance which has a structure represented by 1) is 30 mass% or more .

（式中、Ｘはアルキル基、ハロゲン基、ヒドロキシル基、カルボキシル基及びアミノ基からなる群より選ばれるいずれか１種の官能基を示し、Ｙは水素原子及びアルキル基からなる群より選ばれるいずれか１種の官能基を示す。）

(In the formula, X represents any one functional group selected from the group consisting of an alkyl group, a halogen group, a hydroxyl group, a carboxyl group and an amino group, and Y represents any one selected from the group consisting of a hydrogen atom and an alkyl group. Or a single functional group.)

  Therefore, it is possible to provide a zinc secondary battery electrolyte capable of suppressing or preventing zinc dendrite precipitation and improving charge / discharge cycle characteristics, and a zinc secondary battery using the same.

FIG. 1 is a cross-sectional view schematically showing a test cell or battery of each example. FIG. 2 is a graph showing the evaluation results of the solubility of the zinc discharge product of each example. FIG. 3 is a graph showing the results of the charge / discharge cycle test of each example. FIG. 4 is a scanning electron micrograph of the surface of the zinc negative electrode after the charge / discharge cycle test in Example 1. FIG. 5 is a scanning electron micrograph of the surface of the zinc negative electrode after the charge / discharge cycle test in Example 2. 6 is a scanning electron micrograph of the surface of the zinc negative electrode after the charge / discharge cycle test in Example 3. FIG. FIG. 7 is a scanning electron micrograph of the surface of the zinc negative electrode after the charge / discharge cycle test in Comparative Example 2. FIG. 8 is a graph showing the results of the charge / discharge cycle test of each example. FIG. 9 is a graph showing the results in the charge / discharge cycle test of each example. FIG. 10 is a graph showing the results of the charge / discharge cycle test of each example.

  Hereinafter, an electrolyte for a zinc secondary battery and a zinc secondary battery using the same according to an embodiment of the present invention will be described.

  First, an electrolyte for a zinc secondary battery according to an embodiment of the present invention will be described in detail. The electrolyte for a zinc secondary battery of the present embodiment comprises a solvent comprising an organic substance having a structure represented by the general formula (1) and water, a hydroxide, and a salt comprising an alkali metal cation and an anion. Is included.

（式中、Ｘはアルキル基、ハロゲン基、ヒドロキシル基、カルボキシル基及びアミノ基からなる群より選ばれるいずれか１種の官能基を示し、Ｙは水素原子及びアルキル基からなる群より選ばれるいずれか１種の官能基を示す。）

(In the formula, X represents any one functional group selected from the group consisting of an alkyl group, a halogen group, a hydroxyl group, a carboxyl group and an amino group, and Y represents any one selected from the group consisting of a hydrogen atom and an alkyl group. Or a single functional group.)

  With such a configuration, dissolution of the zinc discharge product is controlled, and when applied to a zinc secondary battery, the dendrite precipitation of zinc is suppressed or prevented, and the charge / discharge cycle characteristics are improved. Moreover, when it is set as such a structure, when it applies to a zinc secondary battery, it will become what was excellent in charging / discharging efficiency.

In addition, since an electrolyte having hydroxide and an alkali metal cation and anion and having OH ^- conductivity can be obtained, a charge / discharge reaction in a negative electrode to which zinc or zinc oxide is applied is possible. It becomes.
In addition, it is thought that the charging / discharging reaction of zinc or zinc oxide in this invention is based on reaction of following formula (2)-(4).
Here, zinc is zero-valent zinc, and the oxide of zinc is presumed to be divalent zinc. However, zinc oxide other than divalent may be generated in the charge / discharge process. It goes without saying that the case of the oxide is included in the scope of the present invention.

Examples of the alkali metal cation include lithium cation (Li ⁺ ), sodium cation (Na ⁺ ), potassium cation (K ⁺ ), rubidium cation (Rb ⁺ ), and cesium cation (Cs ⁺ ). . Further, an alkaline earth metal cation may be applied instead of the alkali metal cation. Examples of the alkaline earth metal cation include beryllium cation (Be ²⁺ ), magnesium cation (Mg ²⁺ ), and calcium cation (Ca ²⁺ ). Strontium cation (Sr ²⁺ ), barium cation (Ba ²⁺ ) and the like.

  Furthermore, the solvent is composed of an organic substance having a structure represented by the general formula (1) and water, and a typical example of the organic substance is polyethylene glycol (PEG). Polyethylene glycol (PEG) usually has a hydroxyl group at the end. In addition, it is preferable that the terminal of organic substance is a hydroxyl group. With such a configuration, the compatibility of the salt composed of an alkali metal cation or alkaline earth metal cation and an anion is improved, and it becomes possible to arbitrarily change the content of organic matter and salt in the electrolyte. Can be effectively suppressed or prevented. Thereby, charge / discharge cycle characteristics can be improved.

  At present, we believe that the effect is obtained by the following mechanism.

Conventionally, an electrolyte applied to a secondary battery having a negative electrode to which zinc or zinc oxide is applied is generally obtained by adding water as a solvent and a hydroxide as a salt. However, when such an electrolyte is used, dissolution of the zinc discharge product is not controlled. Therefore, when the charge / discharge reaction of zinc is repeated in this state, the shape change of zinc and the dendrite precipitation accompanying charge / discharge are not suppressed, and the cycle life is short. Furthermore, only potassium hydroxide (KOH), which is an example of a hydroxide, is added as a salt to a solvent composed of polyethylene glycol (PEG), which is an example of an organic substance having a structure represented by the general formula (1), and water. In the electrolyte, the solubility of the zinc discharge product increases as the concentration of PEG increases. In this state, when the charge / discharge reaction of zinc is repeated as in the conventional case, the shape change of zinc and the dendrite precipitation accompanying charge / discharge are not suppressed, and the cycle life cannot be improved. This is because the potassium cation (K ⁺ ) of potassium hydroxide (KOH) is coordinated to the ether oxygen in the general formula (1) to form PEG-K ⁺ / OH ⁻ (chelating effect). The dissociated OH ⁻ reacts with the zinc discharge product, and Zn (OH) ₄ ²⁻ re-coordinates with PEG-K ⁺ so as to maintain electrical neutrality, so that the solubility of the zinc discharge product is increased. I guess.
Therefore, for example, as a salt composed of an alkali metal cation and an anion, an irrelevant salt such as potassium carbonate (K ₂ CO ₃ ) is allowed to coexist, whereby potassium carbonate (KOH) is originally coordinated with ether carbonate (KOH). It is presumed that potassium hydroxide (KOH) has escaped from PEG restraint by K ₂ CO ₃ ) coordinating first. The basis for potassium carbonate (K ₂ CO ₃ ) to be coordinated first is the HSAB rule. By adding PEG to a high concentration, the water activity is reduced, and complexation of potassium hydroxide (KOH) and ether oxygen consists of an alkali metal cation such as potassium carbonate (K ₂ CO ₃ ) and an anion. The combined effect of the mixture of PEG and salt, which is prevented by salt, makes it possible to control the solubility of zinc discharge products, suppress or prevent zinc dendrite precipitation, and improve charge / discharge cycle characteristics. ing.

  However, the above mechanism is based on estimation. Therefore, it goes without saying that even if the above-described effect is obtained by a mechanism other than the above-described mechanism, it is included in the scope of the present invention.

  Moreover, in this embodiment, it is preferable that the molecular weight of organic substance is 50000 g / mol or less, It is more preferable that it is 2000 g / mol or less, It is still more preferable that it is 1000 g / mol or less. When the molecular weight of the organic substance is 50000 g / mol or less, it becomes a liquid state when a salt containing an alkali metal cation is mixed, and thus has high ionic conductivity. Further, when the molecular weight of the organic substance is 2000 g / mol or less, the affinity with the alkaline aqueous solution increases, and it becomes possible to mix a high concentration organic substance with the alkaline aqueous solution. Thereby, the activity of water in the aqueous alkaline electrolyte can be reduced, the solubility of the zinc discharge product can be effectively controlled, and the charge / discharge cycle characteristics can be effectively improved. . In particular, the effect is significant when the molecular weight of the organic substance is 1000 g / mol or less. However, it is not limited to such a numerical range.

  Here, “molecular weight” means a weight average molecular weight that can be determined by, for example, a light scattering method.

  Furthermore, in this embodiment, it is preferable that content of organic substance is 30 mass% or more, and it is more preferable that it is 60 mass% or more. When the content of the organic substance is 30% by mass or more, the activity of water in the aqueous electrolyte solution can be reduced, and further, the potassium cation is coordinated to the ether oxygen of the organic substance, so that the electrolyte of the zinc discharge product can be obtained. Can be controlled. In particular, when the content of the organic substance is 60% by mass or more, the effect is remarkable. However, it is not limited to such a numerical range.

In the present embodiment, the alkali metal cation is preferably a potassium cation (K ⁺ ). With such a configuration, a salt containing potassium cations (K ⁺ ) can be dissolved in an aqueous electrolyte at a high concentration, and the salt cations are inhibited from coordinating with organic substances, thereby effectively discharging zinc. It becomes possible to control the solubility of the product. As a result, the electrolyte has high ionic conductivity.

Furthermore, in this embodiment, it is preferable that the anion which becomes a pair of alkali metal cations is a softer base than the hydroxide ions. Specifically, CH ₃ COO ⁻ , Cl ⁻ , ClO ₄ ⁻ , NO ₃ ⁻ , SO ₄ ²⁻ , CO ₃ ²⁻ , PO ₄ ^{3− and the} like can be mentioned. With such a configuration, the organic substance has higher coordination ability than hydroxide ions in a state where cations are coordinated. As a result, free hydroxide ions in the electrolyte can be reduced, the solubility of the zinc discharge product can be effectively controlled, and the charge / discharge cycle characteristics can be effectively improved. .

In the present embodiment, salt comprising an alkali metal cation and an anion is preferably potassium carbonate (K 2 _{CO 3).} Since potassium carbonate (K ₂ CO ₃ ) exhibits high compatibility with an alkaline aqueous solution, it can be mixed with an organic substance at an arbitrary ratio, and the solubility of zinc discharge products can be effectively controlled. . As a result, the charge / discharge cycle characteristics can be effectively improved.
In addition, as described in the examples described later, it is generally preferable to add a salt composed of an alkali metal cation of about 0.5M to 1M and an anion, but the basic electrolyte solution such as viscosity and ionic conductivity is preferred. In consideration of performance, an electrolytic solution having an optimum concentration for the rate characteristics and capacity required for the battery is used.

Next, a zinc secondary battery according to an embodiment of the present invention will be described in detail.
The zinc secondary battery of this embodiment includes, for example, a negative electrode to which zinc or zinc oxide is applied, a positive electrode to which an air electrode is applied, and the above-described electrolyte for a zinc secondary battery. When such a zinc-air secondary battery is configured, it becomes a secondary battery having a high energy density, suppresses or prevents zinc dendrite precipitation, and improves charge / discharge cycle characteristics.
The zinc secondary battery of the present embodiment includes, for example, a negative electrode to which zinc or zinc oxide is applied, a positive electrode to which a nickel electrode (Ni (OH) ₂ , NiOOH) is applied, and the above-described electrolyte for a zinc secondary battery. Are provided. Such a nickel-zinc secondary battery has a secondary battery that is less expensive than a nickel-hydrogen secondary battery used as a secondary battery for a hybrid electric vehicle and suppresses zinc dendrite deposition. And charge / discharge cycle characteristics are improved.

  Hereinafter, each component other than the electrolyte described above will be described in detail.

As the air electrode (positive electrode), for example, an air electrode composed of an oxygen reduction catalyst, a binder contained as necessary, and a current collector can be suitably used. As the oxygen reduction catalyst, it is preferable to apply manganese dioxide, perovskite oxide, noble metal, nickel metal, etc. from the viewpoint of catalytic activity. Examples of the current collector include a carbon-based current collector and a metal-based current collector. However, it is not limited to these, The conventionally well-known material used for the air electrode (positive electrode) of a zinc air battery can be used suitably.
Further, the nickel electrode (positive electrode) is composed of, for example, Ni (OH) ₂ or Ni (OOH) in the positive electrode active material, an electron conductive auxiliary agent, a binder, and a current collector that are included as necessary. A nickel electrode can be suitably used. As the positive electrode active material, it is preferable to apply a metal hydroxide containing nickel oxyhydroxide (Ni (OOH)) as a main component from the viewpoint of durability and the like. Examples of the current collector include nickel foam. However, it is not limited to these, The conventionally well-known material used for the nickel electrode (positive electrode) of a nickel zinc secondary battery can be used suitably.

  In consideration of energy density, charge / discharge efficiency, and cycle life, the negative electrode preferably contains one or both of zinc and zinc oxide (for example, zinc oxide, zinc hydroxide) as the negative electrode active material. However, it is not limited to these, The conventionally well-known material used for the zinc negative electrode of a zinc air battery or a nickel zinc secondary battery can be used suitably.

  Hereinafter, the present invention will be described in more detail with reference to examples and comparative examples.

Example 1
<Production of electrolyte (1M potassium hydroxide (KOH) + 60% by mass polyethylene glycol (PEG, molecular weight: 1000 g / mol) + 0.5M potassium carbonate (K ₂ CO ₃ ) aqueous solution)>
8M potassium hydroxide (KOH) was prepared so as to be a mixed aqueous solution of 1M potassium hydroxide (KOH), 60% by mass polyethylene glycol (PEG, molecular weight: 1000 g / mol), and 0.5M potassium carbonate (K ₂ CO ₃ ). ) Aqueous solution, polyethylene glycol (PEG, molecular weight: 1000 g / mol), potassium carbonate (K ₂ CO ₃ ) and ion-exchanged water were weighed and mixed in a volumetric flask to obtain the electrolyte of this example.

<Assembly of electrochemical measurement cell (1M potassium hydroxide (KOH) +60 mass% polyethylene glycol (PEG, molecular weight: 1000 g / mol) +0.5 M potassium carbonate (K ₂ CO ₃ ) aqueous solution)>
First, a working electrode was produced. A zinc plate (thickness: 1 mm) was cut into a predetermined size, and the surface was washed with ethanol to obtain a working electrode used in this example. Next, a counter electrode was produced. Nickel foam was used as a current collector, and a nickel oxyhydroxide paste was fixed to the current collector and molded into a counter electrode used in this example. The Hg / HgO electrode was used as a reference electrode. Thereafter, using these, a test cell of this example as shown in FIG. 1 was produced.

  FIG. 1 is a cross-sectional view schematically showing a test cell. 1 is a working electrode, 2 is a counter electrode, 3 is an electrolyte, and 4 is a reference electrode. In the test cell, the working electrode 1 was placed on the bottom of a cylindrical housing 5 and the bottom holder 6 was tightened. Next, the inside of the cylindrical casing 5 on which the working electrode 1 was mounted was filled with the electrolyte 3, and the lid 7 on which the counter electrode 2 and the reference electrode 4 were mounted was rotated on the cylindrical casing 5 and mounted and assembled.

[Anode polarization test (evaluation of solubility of zinc discharge products)]
In the anodic reaction (discharge reaction) of zinc, Zn (OH) ₄ ²⁻ is generated as an intermediate soluble component during the reaction (the following formula [1]), and Zn (OH) ₄ ²⁻ on the electrode surface as the reaction proceeds. This is a dissolution precipitation reaction that precipitates on the electrode surface as ZnO (the following formula [2]). Accordingly, the solubility of the zinc discharge product was evaluated by measuring the reaction time of the following formula [1] by conducting a constant current anodic polarization test, and evaluating the time as the solubility of the zinc discharge product.

Zn + 4OH ⁻ = Zn (OH) ₄ ² + 2e ⁻ (E ₀ = −1.25 V) [1]
Zn (OH) ₄ ²⁻ = ZnO + H ₂ O + 2OH ⁻ [2]

  A specific anodic polarization test waits for the open circuit voltage of the test cell to stabilize, then performs anodic polarization with a constant current of ± 0.5 mA using an electrochemical measurement system, and the potential of the working electrode is -1. The test was terminated when the voltage reached 18 V (vs. Hg / HgO), and the time until that time was measured. FIG. 2 shows the evaluation results of the solubility of the zinc discharge product in this example when the solubility of the zinc discharge product calculated from the anodic polarization test with the electrolyte of Comparative Example 1 is 1.

[Charge / discharge cycle test]
The charge / discharge cycle test was carried out under conditions that defined the capacity of the zinc negative electrode. Specifically, a copper plate was used as a current collector, and a certain amount of zinc was electrodeposited on the surface to produce a zinc negative electrode with a known capacity. Using this zinc negative electrode, a charge / discharge cycle test was conducted using a test cell as shown in FIG. The charge / discharge cycle test was carried out under conditions using a zinc capacity of 25% with respect to the total capacity of the zinc negative electrode (charge / discharge depth 25%). The charge / discharge cycle test was performed at a constant current, and the current value was 1.25 at the C rate. The cut-off potential during charging / discharging is -2.0 V vs. charging. Hg / HgO, during discharge -1.1 V vs. Hg / HgO. The results of the charge / discharge cycle test are shown in FIG.

[Scanning electron microscope observation]
A charge / discharge cycle test was performed under the same conditions as described above, and after 100 charge / discharge cycle tests, the battery was disassembled, and the zinc negative electrode was taken out and washed with ion-exchanged water. After washing, the zinc negative electrode was dried under reduced pressure, and the shape of the zinc negative electrode surface was observed with a scanning electron microscope. A scanning electron micrograph is shown in FIG.

(Example 2)
<Preparation of electrolyte (1M potassium hydroxide (KOH) +60 mass% polyethylene glycol (PEG, molecular weight: 1000 g / mol) + 1M potassium fluoride (KF) aqueous solution)>
1M potassium hydroxide (KOH), 60% by mass polyethylene glycol (PEG, molecular weight: 1000 g / mol) and 1M potassium fluoride (KF) so as to be a mixed aqueous solution, 8M potassium hydroxide (KOH) aqueous solution, polyethylene Glycol (PEG, molecular weight: 1000 g / mol), potassium fluoride (KF) and ion-exchanged water were weighed and mixed in a volumetric flask to obtain the electrolyte of this example.

<Assembly of electrochemical measurement cell (1M potassium hydroxide (KOH) +60 mass% polyethylene glycol (PEG, molecular weight: 1000 g / mol) + 1M potassium fluoride (KF) aqueous solution)>
A cell configuration similar to that of Example 1 was used except that the electrolyte of this example was used instead of the electrolyte of Example 1.

[Anode polarization test (evaluation of solubility of zinc discharge products)]
An anodic polarization test was carried out in the same manner as in Example 1. FIG. 2 shows the evaluation results of the solubility of the zinc discharge product in this example when the solubility of the zinc discharge product calculated from the anodic polarization test with the electrolyte of Comparative Example 1 is 1.

[Scanning electron microscope observation]
A charge / discharge cycle test was performed under the same conditions as in Example 1. After 100 cycles of the charge / discharge cycle test, the battery was disassembled, and the zinc negative electrode was taken out and washed with ion-exchanged water. After washing, the zinc negative electrode was dried under reduced pressure, and the shape of the zinc negative electrode surface was observed with a scanning electron microscope. A scanning electron micrograph is shown in FIG.

(Example 3)
<Preparation of electrolyte (1M potassium hydroxide (KOH) +60 mass% polyethylene glycol (PEG, molecular weight: 1000 g / mol) + 1M potassium chloride (KCl) aqueous solution)>
1M potassium hydroxide (KOH), 60% by weight polyethylene glycol (PEG, molecular weight: 1000 g / mol) and 1M potassium chloride (KCl) so as to be a mixed aqueous solution, 8M potassium hydroxide (KOH) aqueous solution, polyethylene glycol (PEG, molecular weight: 1000 g / mol), potassium chloride (KCl) and ion-exchanged water were weighed and mixed in a volumetric flask to obtain the electrolyte of this example.

<Assembly of electrochemical measurement cell (1 M potassium hydroxide (KOH) +60 mass% polyethylene glycol (PEG, molecular weight: 1000 g / mol) +1 M potassium chloride (KCl) aqueous solution)>
A cell configuration similar to that of Example 1 was used except that the electrolyte of this example was used instead of the electrolyte of Example 1.

[Anode polarization test (evaluation of solubility of zinc discharge products)]
An anodic polarization test was carried out in the same manner as in Example 1. FIG. 2 shows the evaluation results of the solubility of the zinc discharge product in this example when the solubility of the zinc discharge product calculated from the anodic polarization test with the electrolyte of Comparative Example 1 is 1.

[Scanning electron microscope observation]
A charge / discharge cycle test was performed under the same conditions as in Example 1. After 100 cycles of the charge / discharge cycle test, the battery was disassembled, and the zinc negative electrode was taken out and washed with ion-exchanged water. After washing, the zinc negative electrode was dried under reduced pressure, and the shape of the zinc negative electrode surface was observed with a scanning electron microscope. A scanning electron micrograph is shown in FIG.

Example 4
<Production of electrolyte (1M potassium hydroxide (KOH) + 60% by mass polyethylene glycol (PEG, molecular weight: 600 g / mol) + 0.5M potassium carbonate (K ₂ CO ₃ ) aqueous solution)>
8M potassium hydroxide (KOH) was prepared so as to be a mixed aqueous solution of 1M potassium hydroxide (KOH), 60% by mass polyethylene glycol (PEG, molecular weight: 600 g / mol), and 0.5M potassium carbonate (K ₂ CO ₃ ). ) Aqueous solution, polyethylene glycol (PEG, molecular weight: 600 g / mol), potassium carbonate (K ₂ CO ₃ ) and ion-exchanged water were weighed and mixed in a volumetric flask to obtain the electrolyte of this example.

<Assembly of electrochemical measurement cell (1M potassium hydroxide (KOH) +60 mass% polyethylene glycol (PEG, molecular weight: 600 g / mol) +0.5 M potassium carbonate (K ₂ CO ₃ ) aqueous solution)>

[Charge / discharge cycle test]
A charge / discharge cycle test was carried out in the same manner as in Example 1. The results of the charge / discharge cycle test are shown in FIG.

(Example 5)
<Preparation of electrolyte (1M potassium hydroxide (KOH) +60 mass% polyethylene glycol (PEG, molecular weight: 600 g / mol) + 1M potassium fluoride (KF) aqueous solution)>
1M potassium hydroxide (KOH), 60% by weight polyethylene glycol (PEG, molecular weight: 600 g / mol) and 1M potassium fluoride (KF) so as to be a mixed aqueous solution, 8M potassium hydroxide (KOH) aqueous solution, polyethylene Glycol (PEG, molecular weight: 600 g / mol), potassium fluoride (KF) and ion-exchanged water were weighed and mixed in a volumetric flask to obtain the electrolyte of this example.

<Assembly of electrochemical measurement cell (1M potassium hydroxide (KOH) +60 mass% polyethylene glycol (PEG, molecular weight: 600 g / mol) + 1M potassium fluoride (KF) aqueous solution)>
A cell configuration similar to that of Example 1 was used except that the electrolyte of this example was used instead of the electrolyte of Example 1.

[Charge / discharge cycle test]
A charge / discharge cycle test was carried out in the same manner as in Example 1. The results of the charge / discharge cycle test are shown in FIG.

(Example 6)
<Production of electrolyte (1M potassium hydroxide (KOH) + 60% by mass polyethylene glycol (PEG, molecular weight: 600 g / mol) + 1M potassium chloride (KCl) aqueous solution)>
8M potassium hydroxide (KOH) aqueous solution, polyethylene glycol so as to be a mixed aqueous solution of 1M potassium hydroxide (KOH), 60% by mass polyethylene glycol (PEG, molecular weight: 600 g / mol) and 1M potassium chloride (KCl) (PEG, molecular weight: 600 g / mol), potassium chloride (KCl) and ion-exchanged water were weighed and mixed in a volumetric flask to obtain the electrolyte of this example.

<Assembly of electrochemical measurement cell (1M potassium hydroxide (KOH) +60 mass% polyethylene glycol (PEG, molecular weight: 600 g / mol) + 1M potassium chloride (KCl) aqueous solution)>
A cell configuration similar to that of Example 1 was used except that the electrolyte of this example was used instead of the electrolyte of Example 1.

[Charge / discharge cycle test]
A charge / discharge cycle test was carried out in the same manner as in Example 1. The results of the charge / discharge cycle test are shown in FIG.

(Example 7)
<Preparation of electrolyte (1M potassium hydroxide (KOH) +60 mass% polyethylene glycol (PEG, molecular weight: 200 g / mol) + 1M potassium carbonate (K ₂ CO ₃ ) aqueous solution)>
8M potassium hydroxide (KOH) aqueous solution so as to be a mixed aqueous solution of 1M potassium hydroxide (KOH), 60% by mass polyethylene glycol (PEG, molecular weight: 200 g / mol) and 1M potassium carbonate (K ₂ CO ₃ ). , Polyethylene glycol (PEG, molecular weight: 200 g / mol), potassium carbonate (K ₂ CO ₃ ) and ion-exchanged water were weighed and mixed in a volumetric flask to obtain the electrolyte of this example.

<Assembly of electrochemical measurement cell (1M potassium hydroxide (KOH) +60 mass% polyethylene glycol (PEG, molecular weight: 200 g / mol) + 1M potassium carbonate (K ₂ CO ₃ ) aqueous solution)>
A cell configuration similar to that of Example 1 was used except that the electrolyte of this example was used instead of the electrolyte of Example 1.

[Charge / discharge cycle test]
A charge / discharge cycle test was carried out in the same manner as in Example 1. The results of the charge / discharge cycle test are shown in FIG.

(Example 8)
<Preparation of electrolyte (1M potassium hydroxide (KOH) + 30% by mass polyethylene glycol (PEG, molecular weight: 1000 g / mol) + 0.5M potassium carbonate (K ₂ CO ₃ ) aqueous solution)>
1M potassium hydroxide (KOH), 30% by mass polyethylene glycol (PEG, molecular weight: 1000 g / mol), and 8M potassium hydroxide (KOH) so as to be a mixed aqueous solution of 0.5M potassium carbonate (K ₂ CO ₃ ). ) Aqueous solution, polyethylene glycol (PEG, molecular weight: 1000 g / mol), potassium carbonate (K ₂ CO ₃ ) and ion-exchanged water were weighed and mixed in a volumetric flask to obtain the electrolyte of this example.

<Assembly of electrochemical measurement cell (1 M potassium hydroxide (KOH) +30 mass% polyethylene glycol (PEG, molecular weight: 1000 g / mol) +0.5 M potassium carbonate (K ₂ CO ₃ ) aqueous solution)>
A cell configuration similar to that of Example 1 was used except that the electrolyte of this example was used instead of the electrolyte of Example 1.

[Charge / discharge cycle test]
A charge / discharge cycle test was carried out in the same manner as in Example 1. The results of the charge / discharge cycle test are shown in FIG.

( Reference Example 9 )
<Preparation of electrolyte (1M potassium hydroxide (KOH) +10 mass% polyethylene glycol (PEG, molecular weight: 1000 g / mol) + 0.5M potassium carbonate (K ₂ CO ₃ ) aqueous solution)>
8M potassium hydroxide (KOH) was prepared so as to be a mixed aqueous solution of 1M potassium hydroxide (KOH), 10% by mass polyethylene glycol (PEG, molecular weight: 1000 g / mol), and 0.5M potassium carbonate (K ₂ CO ₃ ). ) Aqueous solution, polyethylene glycol (PEG, molecular weight: 1000 g / mol), potassium carbonate (K ₂ CO ₃ ) and ion-exchanged water were weighed and mixed in a volumetric flask to obtain the electrolyte of this example.

<Assembly of electrochemical measurement cell (1M potassium hydroxide (KOH) +10 mass% polyethylene glycol (PEG, molecular weight: 1000 g / mol) + 0.5M potassium carbonate (K ₂ CO ₃ ) aqueous solution)>
A cell configuration similar to that of Example 1 was used except that the electrolyte of this example was used instead of the electrolyte of Example 1.

[Charge / discharge cycle test]
A charge / discharge cycle test was carried out in the same manner as in Example 1. The result of the charge / discharge cycle test is shown in FIG.

(Comparative Example 1)
<Production of electrolyte (1M potassium hydroxide (KOH) aqueous solution)>
An 8M potassium hydroxide (KOH) aqueous solution and ion-exchanged water were weighed and mixed in a volumetric flask so as to be 1M potassium hydroxide (KOH) to obtain the electrolyte of this example.

<Assembly of electrochemical measurement cell (1M potassium hydroxide (KOH) aqueous solution)>
A cell configuration similar to that of Example 1 was used except that the electrolyte of this example was used instead of the electrolyte of Example 1.

[Anode polarization test (evaluation of solubility of zinc discharge products)]
An anodic polarization test was carried out in the same manner as in Example 1. FIG. 2 shows the evaluation results of the solubility of the zinc discharge product of this example when the solubility of the zinc discharge product calculated from the anodic polarization test with the electrolyte of Comparative Example 1 is 1.

[Charge / discharge cycle test]
A charge / discharge cycle test was carried out in the same manner as in Example 1. The results of the charge / discharge cycle test are shown in FIG.

(Comparative Example 2)
<Production of electrolyte (1M potassium hydroxide (KOH) + 60% by mass polyethylene glycol (PEG, molecular weight: 1000 g / mol) aqueous solution)>
8M potassium hydroxide (KOH) aqueous solution, polyethylene glycol (PEG, molecular weight: 1000 g / mol) so as to be a mixed aqueous solution of 1M potassium hydroxide (KOH) and 60% by mass polyethylene glycol (PEG, molecular weight: 1000 g / mol). ) And ion-exchanged water were weighed and mixed in a volumetric flask to obtain the electrolyte of this example.

<Assembly of electrochemical measurement cell (1M potassium hydroxide (KOH) aqueous solution)>
A cell configuration similar to that of Example 1 was used except that the electrolyte of this example was used instead of the electrolyte of Example 1.

[Anode polarization test (evaluation of solubility of zinc discharge products)]
An anodic polarization test was carried out in the same manner as in Example 1. FIG. 2 shows the evaluation results of the solubility of the zinc discharge product of this example when the solubility of the zinc discharge product calculated from the anodic polarization test with the electrolyte of Comparative Example 1 is 1.

[Charge / discharge cycle test]
A charge / discharge cycle test was carried out in the same manner as in Example 1. The results of the charge / discharge cycle test are shown in FIG.

[Scanning electron microscope observation]
A charge / discharge cycle test was performed under the same conditions as in Example 1. After 100 cycles of the charge / discharge cycle test, the battery was disassembled, and the zinc negative electrode was taken out and washed with ion-exchanged water. After washing, the zinc negative electrode was dried under reduced pressure, and the shape of the zinc negative electrode surface was observed with a scanning electron microscope. A scanning electron micrograph is shown in FIG.

(Comparative Example 3)
<Preparation of electrolyte (1M potassium hydroxide (KOH) + 0.5M potassium carbonate (K ₂ CO ₃ ) aqueous solution)>
To obtain a mixed aqueous solution of 1M potassium hydroxide (KOH) and 0.5M potassium carbonate (K ₂ CO ₃ ), 8M potassium hydroxide (KOH) aqueous solution, potassium carbonate (K ₂ CO ₃ ) and ion-exchanged water were added. And weighed and mixed in a volumetric flask to obtain the electrolyte of this example.

<Assembly of electrochemical measurement cell (1M potassium hydroxide (KOH) + 0.5M potassium carbonate (K ₂ CO ₃ ) aqueous solution)>
A cell configuration similar to that of Example 1 was used except that the electrolyte of this example was used instead of the electrolyte of Example 1.

[Charge / discharge cycle test]
A charge / discharge cycle test was carried out in the same manner as in Example 1. The results of the charge / discharge cycle test are shown in FIG.

(Comparative Example 4)
<Preparation of electrolyte (1M potassium hydroxide (KOH) +60 mass% polyethylene glycol (PEG, molecular weight: 600 g / mol) aqueous solution)>
8M potassium hydroxide (KOH) aqueous solution, polyethylene glycol (PEG, molecular weight: 600 g / mol) so as to be a mixed aqueous solution of 1M potassium hydroxide (KOH) and 60% by mass polyethylene glycol (PEG, molecular weight: 600 g / mol). ) And ion-exchanged water were weighed and mixed in a volumetric flask to obtain the electrolyte of this example.

<Assembly of electrochemical measurement cell (1M potassium hydroxide (KOH) +60 mass% polyethylene glycol (PEG, molecular weight: 600 g / mol) aqueous solution)>
A cell configuration similar to that of Example 1 was used except that the electrolyte of this example was used instead of the electrolyte of Example 1.

[Charge / discharge cycle test]
A charge / discharge cycle test was carried out in the same manner as in Example 1. The results of the charge / discharge cycle test are shown in FIG.

As shown in FIG. 2, Examples 1 to 3 belonging to the scope of the present invention effectively control the solubility of zinc discharge products as compared with Comparative Examples 1 and 2 outside the present invention. I understand that For this reason, it turns out that the electrolyte for zinc secondary batteries of this invention can improve charging / discharging cycling characteristics compared with the electrolyte for zinc secondary batteries outside this invention. Among them, Example 1 to which 0.5 M potassium carbonate (K ₂ CO ₃ ) is applied and Example 2 to which 1 M potassium chloride (KCl) is applied more effectively control the solubility of zinc discharge products. I understand that. For this reason, it turns out that the electrolyte for zinc secondary batteries of Example 1 and Example 2 can improve a charge / discharge cycle characteristic compared with the electrolyte for zinc secondary batteries of Example 3.

  Further, FIG. 3 shows that Example 1 belonging to the scope of the present invention has excellent charge / discharge cycle characteristics as compared with Comparative Examples 1 to 3 outside the present invention.

Furthermore, from FIG. 4 to FIG. 7, no dendrite precipitation is confirmed in Examples 1 to 3 belonging to the scope of the present invention, but in Comparative Example 1 outside the present invention, the portion surrounded by the encircling line a is shown. Dendritic precipitation is confirmed.
In addition, the maintenance factor calculated from (Zinc negative electrode volume after charge / discharge cycle test) / (Zinc negative electrode volume before charge / discharge cycle test) × 100 is 98% in Example 1 and 62% in Example 2. Example 3 is 80% and Comparative Example 1 is 58%. This maintenance rate is an index of charge / discharge efficiency, and the higher the maintenance rate, the higher the charge / discharge efficiency.

Further, FIG. 8 shows that Examples 4 to 6 belonging to the scope of the present invention have excellent charge / discharge cycle characteristics as compared with Comparative Example 4 outside the present invention. Among them, examples of applying the 0.5M potassium carbonate (K 2 _{CO 3)} 4 it can be seen to have better charge-discharge cycle characteristics.

  Furthermore, FIG. 9 shows that Example 7 belonging to the scope of the present invention also has excellent charge / discharge cycle characteristics.

Furthermore, from FIG. 10, Example 8 to which 30% by mass or more of PEG (1000) is applied and Example 1 to which 60% by mass or more of PEG (1000) is applied have more excellent charge / discharge cycle characteristics. I understand.

  As mentioned above, although this invention was demonstrated with some embodiment and an Example, this invention is not limited to these, A various deformation | transformation is possible within the range of the summary of this invention.

  For example, the configuration described in each embodiment or example described above is not limited to each embodiment or example, for example, the configuration of each embodiment may be a combination other than each embodiment described above, Details such as an air electrode (positive electrode), a nickel electrode (positive electrode), a negative electrode to which zinc or zinc oxide is applied, and an electrolyte for a zinc secondary battery can be changed.

1 Working electrode (or negative electrode)
2 Counter electrode (or positive electrode)
3 Electrolyte 4 Reference Electrode 5 Housing 6 Bottom Holder 7 Lid

Claims (7)

A solvent comprising an organic substance having a structure represented by the general formula (1) and water;
Hydroxide,
And salt consisting of alkali metal cations and anions, only contains,
The electrolyte for a zinc secondary battery, wherein the content of the organic substance is 30% by mass or more .

(In the formula, X represents any one functional group selected from the group consisting of an alkyl group, a halogen group, a hydroxyl group, a carboxyl group and an amino group, and Y represents any one selected from the group consisting of a hydrogen atom and an alkyl group. Or a single functional group.) The electrolyte for a zinc secondary battery according to claim 1 , wherein the alkali metal cation is a potassium cation. The electrolyte for a zinc secondary battery according to claim 1 or 2 , wherein the anion is a base softer than a hydroxide ion. The electrolyte for a zinc secondary battery according to claim 1 or 2 , wherein the anion is a carbonate ion or a chloride ion. The electrolyte for a zinc secondary battery according to any one of claims 1 to 3 , wherein the salt is potassium carbonate. The electrolyte for a zinc secondary battery according to any one of claims 1 to 5 , wherein the hydroxide is potassium hydroxide. A zinc secondary battery comprising the electrolyte for a zinc secondary battery according to any one of claims 1 to 6 .

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