JP2022060727A - Separator for zinc secondary battery - Google Patents

Abstract

To provide a separator for a zinc secondary battery, capable of suppressing a short circuit of a zinc secondary battery.SOLUTION: A separator for a zinc secondary battery according to the present disclosure includes a gallium oxide-containing porous layer and a porous base material layer which are stacked on each other. The porous base material layer, the gallium oxide-containing porous layer, and the porous base material layer may be stacked in this order. The porous base material layer may be a resin porous layer. A zinc secondary battery according to the present disclosure includes the separator for a zinc secondary battery according to the present disclosure.SELECTED DRAWING: Figure 1

Description

The present disclosure relates to a separator for a zinc secondary battery.

It is known that in a zinc secondary battery such as a nickel-zinc secondary battery or an air-zinc secondary battery, zinc constituting a negative electrode electrode body forms dendrite when charging and discharging are repeated. When this dendrite grows and reaches the positive electrode body beyond the separator, it may cause a short circuit. Therefore, in zinc secondary batteries, there is a demand for a technique for suppressing a short circuit due to the growth of dendrites.

Regarding the above problem, Patent Document 1 is a porous film arranged between a positive electrode body and a negative electrode body of a zinc battery, which contains a metal oxide having an isoelectric point of 5 to 11. Is disclosed. The document also cites titanium dioxide, aluminum oxide and beryllium oxide as examples of metal oxides contained in porous membranes.

Japanese Unexamined Patent Publication No. 2019-216857

As described above, in the zinc secondary battery, it is required to suppress a short circuit caused by the zinc dendrite grown from the negative electrode body reaching the positive electrode body.

Patent Document 1 describes that a short circuit can be suppressed by the porous membrane disclosed in the same document. However, it is required to further suppress the short circuit of the zinc secondary battery.

It is an object of the present disclosure to provide a separator for a zinc secondary battery capable of suppressing a short circuit of the zinc secondary battery.

The Discloser has found that the above task can be achieved by the following means:
A separator for a zinc secondary battery having a gallium oxide-containing porous layer and a porous substrate layer laminated on each other.

According to the present disclosure, it is possible to provide a separator for a zinc secondary battery capable of suppressing a short circuit of the zinc secondary battery.

FIG. 1 is a schematic view showing a separator 10 for a zinc secondary battery according to the first embodiment of the present disclosure. FIG. 2 is a schematic view showing a zinc secondary battery separator 10'according to the second embodiment of the present disclosure. FIG. 3 is a schematic view showing a zinc secondary battery separator 10'according to the third embodiment of the present disclosure. FIG. 4 is a schematic diagram showing a zinc secondary battery 100 according to the first embodiment of the present disclosure.

Hereinafter, embodiments of the present disclosure will be described in detail. It should be noted that the present disclosure is not limited to the following embodiments, but can be variously modified and implemented within the scope of the main purpose of the disclosure.

<< Separator for zinc secondary battery >>
The zinc secondary battery separator of the present disclosure is a zinc secondary battery separator having a gallium oxide-containing porous layer and a porous base material layer laminated on each other.

In the zinc secondary battery to which the separator for a zinc secondary battery of the present disclosure can be applied, for example, the negative electrode body, the separator, and the positive electrode body are housed in the battery case in this order, and the electrolytic solution is contained in the battery case. It may be a filled zinc secondary battery. Specific examples of the zinc secondary battery that can adopt the separator for the zinc secondary battery of the present disclosure include a nickel zinc secondary battery, a silver zinc oxide secondary battery, a manganese zinc oxide secondary battery, and a zinc air secondary battery. Batteries and various other alkaline zinc secondary batteries can be mentioned.

Although not limited by the principle, the principle that the short circuit of the zinc secondary battery can be suppressed by the separator for the zinc secondary battery of the present disclosure is considered as follows.

In a zinc secondary battery, zinc dendrite may grow from the negative electrode body and reach the positive electrode body beyond the separator by repeating charging and discharging, causing a short circuit of the zinc secondary battery.

Zinc dendrite is considered to be one of the causes that ^Zn (OH) _4-2 in the electrolytic solution is reduced and the generated Zn is unevenly deposited on the negative electrode body. Therefore, it is conceivable to suppress the growth of zinc dendrite by suppressing the supply of ^Zn ₍ OH) 42 to the zinc dendrite, thereby suppressing the short circuit of the zinc secondary battery.

Here, as a means for suppressing the supply of Zn ₍ OH) ⁴²² to zinc dendrite, a separator having a porous layer of a material that tends to repel electrostatically with ^Zn (OH) _4-2 is used as a zinc secondary. It is conceivable to use it as a battery separator.

Here, as a means for suppressing the supply of Zn ₍ OH) ⁴²² to zinc dendrite, a separator having a porous layer of a material that tends to repel electrostatically with ^Zn (OH) _4-2 is used as a zinc secondary. It is conceivable to use it as a battery separator. As a result, it is considered that Zn (OH) ₄₂ ^2- existing on the positive electrode body side can be suppressed from approaching the separator, and zinc dendrite can be suppressed from penetrating the separator and growing toward the positive electrode body side. ..

In this regard, Patent Document 1 discloses that a metal oxide having an isoelectric point in the range of 5 to 11 is contained in the separator, and the present disclosed person has an isoelectric point in such a range. When a plurality of types of metal oxides were compared, the degree of the effect of suppressing the short circuit of the zinc secondary battery varied even among the metal oxides having close isoelectric points. Then, they have found that the durability of the zinc secondary battery can be particularly improved by adopting the gallium oxide-containing porous layer, that is, the gallium oxide-containing porous layer as a component of the separator.

The isoelectric point of gallium oxide measured according to JIS R 1638 is about 9.0. Examples of the metal oxide having a similar isoelectric point include bismuth trioxide having an isoelectric point of about 9.4 and zinc oxide having an isoelectric point of about 9.0.

However, when a separator having a porous layer containing gallium oxide, bismuth trioxide, and zinc oxide as a constituent element was formed and incorporated into a zinc secondary battery, the durability of the zinc secondary battery was measured. Only when a separator having a porous layer containing gallium as a constituent element was used, a high short-circuit suppressing effect, that is, high durability of a zinc secondary battery was obtained.

Gallium has a higher valence than zinc and has a smaller ionic radius than bismuth. Therefore, it is considered that gallium oxide easily attracts OH ⁻ in the strongly alkaline electrolytic solution used for the zinc secondary battery and is strongly negatively charged in the electrolytic solution. As a result, it is considered that the gallium oxide ^{-containing porous layer can suppress the supply of Zn (OH) 42-} _from the positive electrode body side by electrostatic repulsion.

For this reason, it is considered that a zinc secondary battery using a separator having a porous layer containing gallium oxide as a component has a high short-circuit suppressing effect, that is, a high durability of the zinc secondary battery.

FIG. 1 is a zinc secondary battery separator 10 according to the first embodiment of the present disclosure.

As shown in FIG. 1, the zinc secondary battery separator 10 according to the first embodiment of the present disclosure has a gallium oxide-containing porous layer 11 and a porous substrate layer 12 laminated on each other.

Note that FIG. 1 is not intended to limit the separator for a zinc secondary battery of the present disclosure.

The separator for a zinc secondary battery of the present disclosure may have a structure in which a porous base material layer, a gallium oxide-containing porous layer, and a porous base material layer are laminated in this order.

When the separator for a zinc secondary battery of the present disclosure has such a configuration, it is possible to prevent gallium oxide from slipping off from the gallium oxide-containing porous layer. Thereby, the durability of the gallium oxide-containing porous layer can be improved, and therefore the short circuit of the zinc secondary battery can be further suppressed. Further, by interposing the porous base material layer between the gallium oxide-containing porous layer and the positive electrode body, it is possible to suppress the direct contact between the gallium oxide-containing porous layer and the positive electrode body.

FIG. 2 is a zinc secondary battery separator 10'according to the second embodiment of the present disclosure.

As shown in FIG. 2, the zinc secondary battery separator 10'according to the second embodiment of the present disclosure includes a porous base material layer 13, a gallium oxide-containing porous layer 11, and a porous base material layer 12. They are stacked in order.

Note that FIG. 2 is not intended to limit the separator for a zinc secondary battery of the present disclosure.

Further, the separator for a zinc secondary battery of the present disclosure may have a structure in which a nonwoven fabric layer, a porous base material layer, a gallium oxide-containing porous layer, and a porous base material layer are laminated in this order. ..

When the separator for a zinc secondary battery of the present disclosure has such a configuration, a non-woven layer is arranged between the negative electrode body and the porous base material layer of the separator for a zinc secondary battery of the present disclosure. Therefore, it is easy to hold the electrolytic solution between the negative electrode body and the porous base material layer.

FIG. 3 is a zinc secondary battery separator 10 ″ according to the third embodiment of the present disclosure.

As shown in FIG. 3, the zinc secondary battery separator 10 ″ according to the third embodiment of the present disclosure includes a nonwoven fabric layer 14, a porous base material layer 13, a gallium oxide-containing porous layer 11, and a porous group. The material layers 12 are laminated in this order.

Note that FIG. 3 is not intended to limit the separator for a zinc secondary battery of the present disclosure.

<Porous layer containing gallium oxide>
The gallium oxide-containing porous layer is a porous layer containing gallium oxide. Gallium oxide can be contained in the gallium oxide-containing porous layer as particles, for example.

The gallium oxide-containing porous layer is "porous", which means that it has a plurality of through holes penetrating the front and back surfaces of the layer.

Further, in the present disclosure, the gallium oxide may be gallium oxide (III).

The gallium oxide-containing porous layer can be formed, for example, by adhering and drying a slurry in which gallium oxide particles are dispersed in a dispersion medium on the porous layer, for example, the porous base material layer described below. The method of adhering the slurry to the porous layer is not particularly limited, and can be performed by a known method such as screen printing, immersion, and coating, and more specifically, doctor blade coating. The gallium oxide-containing porous layer may be partially or wholly integrated with the porous layer.

In addition to gallium oxide, the slurry may contain a binder such as styrene-butadiene rubber (SBR), a thickener such as carboxymethyl cellulose (CMC), and the like.

When the gallium oxide-containing porous layer contains gallium oxide particles, the average primary particle diameter of the gallium oxide particles may be 10 nm to 1000 μm.

The average primary particle diameter of the gallium oxide particles may be 10 nm or more, 100 nm or more, 10 μm or more, 50 μm or more, and may be 1000 μm or less, 500 μm or less, 250 μm or less, or 100 μm or less.

The average primary particle diameter of the gallium oxide particles can be determined as an area circle equivalent diameter by observation with a scanning electron microscope (SEM). The number of samples is preferably large, for example, 20 or more, 50 or more, or 100 or more.

The average primary particle diameter of the gallium oxide particles may be appropriately determined by those skilled in the art according to the porosity and the pore diameter required for the gallium oxide-containing porous layer. The larger the average primary particle size of the gallium oxide particles, the higher the porosity and the average pore size of the gallium oxide-containing porous layer, and the smaller the average primary particle size of the gallium oxide particles, the higher the porosity of the gallium oxide-containing porous layer. And it is considered that the average pore diameter tends to decrease.

The porosity and average pore diameter required for the gallium oxide-containing porous layer may be the porosity and average pore diameter generally required for a zinc secondary battery separator.

The thickness of the gallium oxide-containing porous layer may be, for example, 10 μm to 1000 μm. The thickness of the gallium oxide-containing porous layer may be 10 μm or more, 50 μm or more, or 100 μm or more, and may be 1000 μm or less, 500 μm or less, or 200 μm or less.

<Porous medium layer>
The porous base material layer is a porous layer that is insulating and has through holes penetrating both sides of the membrane. The porous substrate layer may be hydrophobic or hydrophilic.

The porosity and average pore diameter of the porous substrate layer may be the porosity and pore diameter generally required for a separator for a zinc secondary battery.

The thickness of the porous substrate layer may be, for example, 10 μm to 1000 μm. The thickness of the porous substrate layer may be 10 μm or more, 50 μm or more, or 100 μm or more, and may be 1000 μm or less, 500 μm or less, or 200 μm or less.

The porous base material layer may be, for example, a resin porous layer, more specifically, a polyolefin-based porous layer, a polyamide-based porous layer, or a nylon-based porous layer, but is not limited thereto.

Here, the porous resin film may be hydrophilized, for example, by imparting a hydrophilic functional group.

In addition, the fact that the porous base material layer is "porous" means that it has a plurality of through holes penetrating the front and back surfaces of the layer. Therefore, the porous substrate layer may be, for example, a sponge-like layer.

<Non-woven fabric layer>
The nonwoven fabric layer may be, for example, a cellulosic nonwoven fabric.

《Zinc secondary battery》
The zinc secondary battery of the present disclosure has the separator for the zinc secondary battery of the present disclosure.

The zinc secondary battery of the present disclosure may have a known configuration except that the separator for the zinc secondary battery of the present disclosure is adopted as the separator.

The zinc secondary battery of the present disclosure has, for example, a negative electrode body, a separator for a zinc secondary battery, and a positive electrode body in this order, and the negative electrode body, the separator for a zinc secondary battery, and the positive electrode body have the negative electrode body. It may be a zinc secondary battery impregnated with an electrolytic solution.

Typically, in the zinc secondary battery of the present disclosure, the negative electrode body, the separator, and the positive electrode body are housed in the battery case in this order, and the battery case is filled with the electrolytic solution. It may be the next battery. More specifically, the zinc secondary battery of the present disclosure includes a nickel zinc secondary battery, a silver zinc oxide secondary battery, a manganese oxide zinc secondary battery, a zinc air secondary battery, and various other alkaline zinc secondary batteries. Batteries can be mentioned.

FIG. 4 is a zinc secondary battery 100 according to the first embodiment of the present disclosure.

As shown in FIG. 4, the zinc secondary battery 100 according to the first embodiment of the present disclosure includes a negative electrode body 20, a zinc secondary battery separator 10'' according to the third embodiment of the present disclosure, and a positive electrode. The bodies 30 are laminated in this order. Then, these are housed in the battery case 50 filled with the electrolytic solution 40.

The negative electrode body 20 has a structure in which the negative electrode active material layer 22 is formed on the negative electrode current collector 21. Further, the positive electrode body 30 has a structure in which the positive electrode active material layer 32 is formed on the positive electrode current collector 31.

<Negative electrode body>
Examples of the negative electrode body include those in which the surface of the negative electrode current collector is covered with a zinc-based negative electrode active material layer.

Here, the negative electrode current collector may be, but is not limited to, a conductive material, for example, a metal such as stainless steel, aluminum, copper, nickel, iron, or titanium, or carbon. The material of the negative electrode current collector may be copper.

The shape of the current collector is not particularly limited, and examples thereof include a rod shape, a foil shape, a plate shape, a mesh shape, and a porous body. The current collector may be a metal celmet.

The zinc-based negative electrode active material layer contains zinc and zinc oxide, and optionally binders and other additives. The zinc-based negative electrode active material layer can further contain a zinc compound such as calcium zincate.

Examples of the binder include, but are not limited to, styrene-butadiene rubber (SBR) and the like.

<Separator for zinc secondary battery>
The zinc secondary battery of the present disclosure has the separator for the zinc secondary battery of the present disclosure.

<Positive electrode body>
Examples of the positive electrode body include those in which the surface of the positive electrode current collector is covered with a zinc-based negative electrode active material layer.

Here, as the positive electrode current collector, the description regarding the negative electrode current collector can be referred to by replacing the negative electrode current collector with the positive electrode current collector. The material of the positive electrode current collector may be aluminum. When the material of the positive electrode current collector is nickel, the positive electrode current collector may be nickel celmet.

The positive electrode active material layer contains a positive electrode active material and optionally binders and other additives. The positive electrode active material can be appropriately selected depending on the type of the zinc secondary battery. For example, when the zinc secondary battery is a nickel-zinc secondary battery, the positive electrode active material may contain nickel hydroxide and / or nickel oxyhydroxide.

The binder can refer to the description regarding the negative electrode body.

<Electrolytic solution>
The electrolytic solution can be an aqueous solution, more specifically an alkaline electrolytic solution. Examples of the alkaline electrolytic solution include an electrolytic solution containing an alkali metal hydroxide, more specifically, potassium hydroxide, sodium hydroxide, lithium hydroxide, ammonium hydroxide and the like. Potassium hydroxide is preferable as the electrolytic solution. The electrolytic solution may further contain other inorganic / organic additives.

Zinc oxide can be further dissolved in the electrolytic solution. Zinc oxide may be dissolved in the electrolytic solution in a saturated state at room temperature.

<< Example 1 and Comparative Examples 1 to 9 >>
<Example 1>
The separator for the zinc secondary battery of Example 1 was prepared as follows.

(Ink preparation)
The mass ratio of gallium oxide powder, styrene-butadiene rubber (SBR), and carboxymethyl cellulose (CMC) in the gallium oxide-containing porous layer to be formed is gallium oxide powder: SBR: CMC = 97: 2.5: 0. Each was weighed so as to be 5. The isoelectric point of gallium oxide measured according to JIS R 1638 is about 9.0.

Gallium oxide powder and CMC were placed in a mortar and kneaded. Then, the kneaded material was put into a container, and the mixture was stirred with Awatori Rentaro (manufactured by Shinky Co., Ltd.) for 1 minute at 2000 rpm. Next, SBR was added to the kneaded material, and the ink was prepared by stirring with Awatori Rentaro (manufactured by Shinky Co., Ltd.) for 3 minutes at 2000 rpm.

(Formation of gallium oxide-containing porous layer)
A polypropylene separator as a porous substrate layer was attached onto a glass substrate with masking tape in a state of being pulled from both ends in the vertical direction while applying a slight tension. The polypropylene separator was previously hydrophilized.

Ink was applied to the surface of the polypropylene separator by the doctor blade coating method. The blade gap was 125 μm. Then, the applied ink was naturally dried, and further dried in a vacuum dryer at 40 ° C. for 10 hours. As a result, a gallium oxide-containing porous layer was formed on the polypropylene separator.

(Assembly of separator)
Another hydrophilicized polypropylene separator was placed on the gallium oxide-containing porous layer, and a hydrophilicized nonwoven fabric separator was further placed on the hydrophilicized polypropylene separator to prepare the separator of Example 1.

The separator of Example 1 had a structure in which a nonwoven fabric separator, a polypropylene separator, a gallium oxide-containing porous layer, and a polypropylene separator were laminated in this order.

<Comparative Example 1>
The separator of Comparative Example 1 was prepared in the same manner as in Example 1 except that the gallium oxide-containing porous layer was not formed on the polypropylene separator.

The separator of Example 1 had a structure in which a nonwoven fabric separator, a polypropylene separator, and a polypropylene separator were laminated in this order.

<Reference Examples 1 to 3>
Separator of Reference Examples 1 to 3 was prepared in the same manner as in Example 1 except that hafnium oxide, bismuth trioxide, and zinc oxide were used in order instead of gallium oxide. The isoelectric points of hafnium oxide, bismuth trioxide, and zinc oxide measured in accordance with JIS R 1638 are, respectively, about 5.0, about 9.4, and about 9.0, respectively.

That is, the separator of Reference Example 1 had a structure in which a nonwoven fabric separator, a polypropylene separator, a hafnium oxide-containing porous layer, and a polypropylene separator were laminated in this order.

Further, the separator of Reference Example 2 had a structure in which a nonwoven fabric separator, a polypropylene separator, a porous layer containing bismuth trioxide, and a polypropylene separator were laminated in this order.

Further, the separator of Reference Example 3 had a structure in which a nonwoven fabric separator, a polypropylene separator, a zinc oxide-containing porous layer, and a polypropylene separator were laminated in this order.

<Manufacturing of zinc secondary battery>
Nickel-zinc secondary batteries using the separators of each example were produced as follows.

(Positive electrode body)
Ni (OH) ₂ , SBR, and CMC were weighed so that the mass ratio was Ni (OH) ₂ : SBR: CMC = 97: 2.5: 0.5. Ni (OH) ₂ contained an auxiliary agent.

These materials were kneaded in a mortar and water was added to adjust the hardness, and then the mixture was stirred with Awatori Rentaro (manufactured by Shinky Co., Ltd.) for 1 minute at 2000 rpm to prepare a positive electrode active material slurry.

By the doctor blade coating method, the positive electrode active material slurry was applied to the surface of the nickel foil as the positive electrode current collector. Then, the applied positive electrode active material slurry was naturally dried, and further dried at 80 ° C. overnight under a reduced pressure environment. As a result, a positive electrode body was formed.

(Negative electrode body)
ZnO, Zn, SBR, and CMC were weighed so that the mass ratio was ZnO: Zn: SBR: CMC = 76: 21: 2.5: 0.5.

These materials were kneaded in a mortar and water was added to adjust the hardness, and then the mixture was stirred with Awatori Rentaro (manufactured by Shinky Co., Ltd.) for 1 minute at 2000 rpm to prepare a negative electrode active material slurry.

The negative electrode active material slurry was applied to the surface of the copper foil as the negative electrode current collector by the doctor blade coating method. Then, the applied negative electrode active material slurry was naturally dried, and further dried at 80 ° C. overnight under a reduced pressure environment. As a result, a negative electrode body was formed.

(Assembly of zinc secondary battery)
The positive electrode body, the separator, and the negative electrode body were laminated in this order and housed in the battery case. Then, the battery case was filled with an electrolytic solution to obtain a zinc secondary battery. The separator was arranged so that the nonwoven fabric layer faced the negative electrode body side. The electrolytic solution was a 6 mol / L KOH aqueous solution in which ZnO was dissolved in a saturated state at 25 ° C.

<Cycle stability evaluation>
A cycle test was performed on each of the nickel-zinc secondary batteries using the separators of each example, and the number of cycles until a short circuit was measured was measured.

An electrochemical measurement system (VMP3, manufactured by Biologic) and a constant temperature bath (SU-642, manufactured by ESPEC) were used for the cycle test. The temperature of each nickel-zinc secondary battery at the time of measurement was 25 ° C.

The cycle test was carried out in the charge / discharge range with a charge state (SOC) of 0% to 50% when the theoretical charge capacity of the positive electrode active material layer was 100%. The C rate was 3.5 mA / cm 2. The cut voltage was 2V at the time of charging and 1.3V at the time of discharging. The cycle test was performed at intervals of 5 minutes for each cycle.

<result>
The configurations of the separators and the results of cycle stability evaluation of each example are shown in Table 1 below. In the cycle stability evaluation result, the number of cycles until a short circuit in Comparative Example 1 is described as 100%.

As shown in Table 1, in Example 1 having the gallium oxide-containing porous layer, the durability was 209%, and the durability was significantly improved from Comparative Example 1.

In Reference Examples 1 to 3, the durability was 82%, 20%, and 99%, respectively, which were lower than those in Comparative Example 1.

10, 10', and 10'' Separator 11 Gallium oxide-containing porous layer 12 and 13 Porous base material layer 14 Non-woven electrode layer 20 Negative electrode body 21 Negative electrode current collector 22 Negative electrode active material layer 30 Positive electrode body 31 Positive electrode current collector Body 32 Positive electrode active material layer 40 Electrolytic solution 50 Battery case 100 Zinc secondary battery

Claims (1)

A separator for a zinc secondary battery having a gallium oxide-containing porous layer and a porous substrate layer laminated on each other.

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