JP2018160409A - Separator evaluation method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method of quantitatively and quickly evaluating dendrite deterrence performance of a separator.SOLUTION: A separator evaluation method includes checking a short circuit between two electrodes separated from each other by a separator and causing a form change accompanying charging and discharging in an electrolytic cell vessel that holds an electrolyte such that charging reaction and discharging reaction are alternately and inversely carried out at the two electrodes.SELECTED DRAWING: Figure 1

Description

The present invention relates to a separator evaluation method. More specifically, the present invention relates to a separator evaluation method that can be suitably used for a secondary battery that includes an electrode that undergoes a change in shape with charge and discharge.

In recent years, the importance of batteries has increased rapidly in many industries, from small portable devices to large-scale applications such as automobiles. New battery systems that have advantages mainly in terms of capacity, energy density, and secondary battery use. Have been developed and improved. For example, zinc negative electrodes using zinc species as negative electrode active materials have been studied for a long time with the spread of batteries, and in particular, air / zinc primary batteries, manganese / zinc primary batteries, silver / zinc primary batteries have been put into practical use, Widely used in the world.

However, for secondary batteries composed of a zinc negative electrode, if charging / discharging is repeated for a long time, a dendritic electrode active material tree is formed in the process of metal dissolution and precipitation in the vicinity of the active material layer of the electrode. However, it has not been put into practical use because of the problem that a battery life is shortened due to short circuit between electrodes caused by this dendrite. There is a similar problem with a secondary battery including an electrode that undergoes a change in shape with charge / discharge of a cadmium negative electrode, a lithium negative electrode, or the like.

Many technical developments have been made to deal with such problems. For example, a separator for the purpose of suppressing dendrite is disclosed (for example, see Patent Documents 1 to 4).
In the present situation where such separators are being developed in various ways, methods and indicators for appropriately evaluating the separator's dendrite suppression performance are required, and these methods and indicators are also being studied from many technical viewpoints. . As the evaluation method, for example, a first zinc electrode and a second zinc electrode are provided in a container, and a separator is disposed in the container, and a first section including the first zinc electrode and a second zinc electrode are included. The step of isolating the two compartments, and the alkali metal hydroxide aqueous solution is injected into the container or the first compartment and the second compartment at a water level not exceeding the height of the separator or the separator structure including the separator. A step of immersing in an aqueous metal hydroxide solution, a step of adding ZnO to the first compartment, a continuous application of a direct current between the first zinc electrode and the second zinc electrode, the first zinc electrode and the second zinc electrode A method for evaluating a separator for a zinc secondary battery including a step of confirming whether or not there is a sudden voltage drop due to a zinc dendrite short circuit between the two (see Patent Document 5).

International Publication No. 2016/121168 JP, 2006-152082, A Japanese Patent Laid-Open No. 2006-146263 International Publication No. 2014/119665 JP 2006-170946 A

The method described in Patent Document 5 has room for further contrivance in quantitatively and rapidly evaluating the dendrite suppression performance of the separator.

This invention is made | formed in view of the said present condition, and it aims at providing the method of evaluating the dendrite suppression performance of a separator quantitatively and rapidly.

The present inventors have studied various methods for quantitatively and rapidly evaluating the dendrite deterring performance of the separator, and in the electrolytic cell container holding the electrolyte, in order to be separated from each other by the separator, the form is associated with charging / discharging. Two electrodes were placed where the change occurred. And the present inventors solve the above-mentioned problem by confirming the short circuit between the two electrodes by alternately performing the charge reaction and the discharge reaction with the two electrodes so as to be opposite to each other. The present inventors have arrived at the present invention.

That is, the present invention is a method for evaluating a separator, which comprises a charge reaction between two electrodes separated from each other by a separator and undergoing a change in shape with charge and discharge in an electrolytic cell container holding an electrolyte. A separator evaluation method characterized by including a step of performing a discharge reaction alternately and in a reverse reaction with each other and confirming a short circuit between two electrodes.

By using the separator evaluation method of the present invention, the dendrite suppression performance of the separator can be quantitatively and rapidly evaluated.

It is a cross-sectional schematic diagram of the measuring apparatus which concerns on one Embodiment of this invention. It is a schematic diagram of the electrode surface which concerns on one Embodiment of this invention. It is a schematic diagram of the electrode surface which concerns on one Embodiment of this invention.

The present invention is described in detail below.
A combination of two or more preferred embodiments of the present invention described below is also a preferred embodiment of the present invention.

In the evaluation method described in Patent Document 5, a direct current is applied between the electrodes like a primary battery. In this case, there were the following disadvantages.
(1) Although durability against a dendrite that is permanently generated by direct current can be quantified, consistency with the cycle life of an actual secondary battery that repeats a charge / discharge cycle cannot be obtained.
(2) Since the electrode reaction interface becomes wider as the charge / discharge time elapses, the substantial current density decreases with the elapse of time, the dendrite shape changes greatly, and evaluation can be performed under stable conditions over a long period of time. The dendrite deterring performance cannot be quantitatively evaluated (see, for example, J. Phys. Chem. C 2007, 111, 1150-116).
(3) Since dendrite grows from only one of the two electrodes, the measurement time is prolonged and the dendrite suppression performance cannot be evaluated quickly.
(4) In the evaluation method described in Patent Document 5, since only the reaction in which zinc or the like is changed to ions, when a separator having a high dendrite deterring performance is evaluated over a long period of time, raw materials necessary for the reaction from the outside ( Zinc, electrolyte, etc.) must be replenished, or a large measuring device must be used to mount a large amount of raw materials, and the evaluation cannot be performed easily. Further, if the raw material is replenished later as described in paragraph [0075] of Patent Document 5, the conditions in the measuring device change, and there is a possibility that continuous and stable evaluation cannot be performed.

<The evaluation method of the separator of this invention>
According to the separator evaluation method of the present invention, the charge reaction and the discharge reaction are alternately performed with each other in the two electrodes separated from each other by the separator and undergoing a change in shape with charge and discharge in the electrolytic cell container holding the electrolyte. The process includes performing a reverse reaction and confirming a short circuit between the two electrodes.
Since the evaluation method of the present invention repeats charging and discharging like an actual secondary battery, it has the following advantages.
(1) Evaluation consistent with the cycle life of an actual secondary battery is possible.
(2) Since the reaction interface of the electrode does not become very wide even after the charge / discharge time has elapsed, the degree of decrease in the current density with the passage of time is small, and the dendrite shape does not change greatly. Measurements are possible below, and as a result, dendrite suppression performance can be quantitatively evaluated.
(3) Since dendrite grows from each of the two electrodes, the measurement time until a short circuit occurs can be shortened, and rapid evaluation is possible.
(4) In the evaluation method of the present invention, since charging and discharging are alternately performed with two electrodes, even when a separator with high dendrite suppression performance is evaluated, raw materials necessary for the reaction are further supplemented from the outside, or a large amount Therefore, it is not necessary to use a large measuring device for mounting the raw materials, and simple evaluation is possible. Moreover, when the raw material is not further supplied from the outside, the conditions in the measuring apparatus are prevented from changing, and continuous and stable evaluation is possible. Therefore, it is possible to perform an excellent evaluation with quantitative properties.

In the separator evaluation method of the present invention, the means for confirming the short circuit between the two electrodes is not particularly limited, and examples include confirmation of a decrease in voltage or resistance and other physical property fluctuations, visual recognition of the short circuit itself, and the like. In the confirmation step, it is preferable to confirm a short circuit between the two electrodes by a decrease in voltage or resistance. Due to the short circuit between the two electrodes, the voltage and resistance clearly decrease suddenly and discontinuously, so it can be easily confirmed that the short circuit has occurred due to the dendrites breaking through the separator.

In the separator evaluation method of the present invention, the charge / discharge capacity in the confirmation step is preferably ½ or less of the capacity of the active material possessed by at least one of the two electrodes.
In other words, the utilization factor of the active material possessed by at least one of the two electrodes in the confirmation step (the proportion of the maximum amount of active material used for the battery reaction and dissolved in the amount of active material possessed by the electrode [mass proportion] In the present specification, it is also referred to as an electrode utilization rate.) Is preferably 50% or less. As a result, the base of the battery is maintained during the battery reaction, and the electrode does not change greatly in shape, enabling a more continuous and stable evaluation, and the dendrite suppression performance of the separator is more quantitative. Can be evaluated.
In particular, the charge / discharge capacity in the confirmation step is more preferably ½ or less of the capacity of the active material of each of the two electrodes.

The charge / discharge capacity in the confirmation step is more preferably 以下 or less of the active material capacity of at least one of the two electrodes or the active material capacity of each of the two electrodes. More preferably, it is more preferably 1/5 or less.

In the confirmation step, it is preferable to switch between the charging reaction and the discharging reaction at regular time intervals using two electrodes.
The time interval is more preferably 40 minutes or less, more preferably 30 minutes or less, still more preferably 20 minutes or less, and further preferably 12 minutes or less from the viewpoint of more continuous and stable evaluation. It is particularly preferred that The lower limit of the time interval is not particularly limited, but is usually 1 minute or longer, preferably 3 minutes or longer, and more preferably 5 minutes or longer. In addition, a time during which no current flows (resting time) may be provided between the switching from the charging reaction to the discharging reaction, the switching from the discharging reaction to the charging reaction, or both. The pause time is preferably shorter from the viewpoint of shortening the evaluation time, but is preferably 0.1 to 10 times the last reaction time from the viewpoint of eliminating the ion bias accompanying the charge / discharge reaction. More preferably, they are 0.5 times-5 times, More preferably, they are 0.8 times-1.2 times.

In the evaluation method of the present invention, it is preferable that at least one of the two electrodes has a surface area of a portion facing the separator that is smaller than a current-carrying area of the separator. Also, from the viewpoint of flowing a uniform current between the electrodes, it is desirable to insulate at least the outer peripheral portion (edge portion) of the electrode (for example, the case where only the outer peripheral portion is insulated along the electrode outer peripheral portion is shown in FIG. FIG. 3 shows a case where a wider portion including the outer peripheral portion of the electrode is insulated and an opening having a specific shape is provided. Insulation treatment of the edge part includes, for example, a method of applying an insulating paint to form a coating film and a method of disposing an insulating film, but the end part is electrically insulated while providing an energized opening. If it does, it will not specifically limit. Thereby, a uniform current density can be applied to the entire electrode, and a continuous and stable evaluation can be performed. Especially, it is more preferable that the surface area of each of the two electrodes facing the separator is smaller than the current-carrying area of the separator and is arranged in parallel to the separator surface.

In the evaluation method of this invention, it is preferable that the charging / discharging current density in the said confirmation process is 1-100 mA / cm < ² > with respect to the electricity supply area of the said separator. When the charge / discharge current density is 1 mA / cm ² or more, the evaluation can be performed more quickly. Moreover, it can fully prevent that the decomposition reaction of water arises because this charging / discharging current density is 100 mA / cm < ² > or less.
The charge and discharge current density is more preferably 10 mA / cm ² or more, still more preferably 25mA / cm ² or more, and particularly preferably 40 mA / cm ² or more. The charge / discharge current density is more preferably 90 mA / cm ² or less.

In the separator evaluation method of the present invention, the two electrodes are not particularly limited as long as they change in shape with charge and discharge, and the materials include a positive electrode active material and a negative electrode active material of a primary battery and a secondary battery. Although a substance normally used as a substance can be used, it is preferable to include a zinc species, a cadmium species, or a lithium species, and from the viewpoint of performing a quicker evaluation, it is more preferable to include a zinc species.
In the separator evaluation method of the present invention, for example, the two electrodes are particularly preferably an electrode having zinc and an electrode having zinc oxide. The electrode containing zinc is on the discharge side, and the electrode containing zinc oxide is on the charge side. The electrode having zinc may further have zinc oxide as long as it has zinc as a main component of the active material, and the electrode having zinc oxide may further have zinc oxide as the main component of the active material. You may have zinc.
The main component of the active material means that the mass ratio is the largest as the content ratio of the active material. In the above confirmation step, the electrode having zinc and the electrode having zinc oxide are usually interchanged.

The two electrodes can be manufactured by forming the material layer on a current collector.
Current collectors that make up the electrode include (electrolytic) copper foil, copper mesh (expanded metal), foamed copper, punched copper, copper alloys such as brass, brass foil, brass mesh (expanded metal), foamed brass, punched brass , Nickel foil, corrosion-resistant nickel, nickel mesh (expanded metal), punching nickel, metallic zinc, corrosion-resistant metallic zinc, zinc foil, zinc mesh (expanded metal), (punched) steel sheet, non-woven fabric with conductivity; Ni · Zn · Copper, copper foil, copper mesh (expanded metal), copper foil, punched copper, brass and other copper alloys, brass foil, brass mesh (expanded metal) with Sn, Pb, Hg, Bi, In, Tl, brass, etc. added ) ・ Foamed brass ・ Punching brass ・ Nickel foil ・ Corrosion resistant nickel ・ Nickel mesh (Expanded) Tal), punched nickel, metallic zinc, corrosion resistant metallic zinc, zinc foil, zinc mesh (expanded metal), (punched) steel sheet, non-woven fabric; plated with Ni, Zn, Sn, Pb, Hg, Bi, In, Tl, brass, etc. (Electrolytic) copper foil, copper mesh (expanded metal), foamed copper, punched copper, copper alloys such as brass, brass foil, brass mesh (expanded metal), foamed brass, punched brass, nickel foil, corrosion-resistant nickel, nickel Mesh (expanded metal), punched nickel, metallic zinc, corrosion-resistant metal zinc, zinc foil, zinc mesh (expanded metal), (punched) steel sheet, non-woven fabric; silver; current collectors and containers for alkaline (storage) batteries and zinc-air batteries The material etc. which are used as are mentioned.

The two electrodes are separated by a separator, but may or may not be in direct contact with the separator. Further, when not in direct contact with the separator, a porous member can be inserted in order to align the distance from the separator. The porous member is not particularly limited as long as it has the air permeability normally possessed by the porous member, but a porous substrate such as a nonwoven fabric or a microporous membrane is desirable, and has a higher air permeability than the separator to be measured. It is preferable. The distance between the electrode and the separator is preferably 1000 μm or less, more preferably 700 μm or less, and still more preferably 500 μm or less. When the electrode is separated from the separator beyond 1000 μm, the dendrite does not reach the separator, and there is a possibility that measurement cannot be performed correctly.

In the separator evaluation method of the present invention, the electrolyte is preferably an electrolytic solution, more preferably an aqueous electrolytic solution, and particularly preferably an alkaline electrolytic solution. Since dendrites are easy to grow in an alkaline electrolyte, more rapid evaluation is possible. Moreover, the dendrite suppression performance of the separator when used for a battery configured to contain an alkaline electrolyte can be more accurately evaluated. The type, concentration, and the like of the alkaline electrolyte can be set as appropriate, but are preferably set to the same conditions as the alkaline electrolyte of the battery using the separator. Examples of the alkaline electrolyte include potassium hydroxide aqueous solution, sodium hydroxide aqueous solution, lithium hydroxide aqueous solution, zinc sulfate aqueous solution, zinc nitrate aqueous solution, zinc phosphate aqueous solution, and zinc acetate aqueous solution. The aqueous electrolyte solution can be used alone or in combination of two or more.

Moreover, the water-containing electrolyte solution may contain an organic solvent used for the organic solvent-based electrolyte solution. Examples of the organic solvent include ethylene carbonate, propylene carbonate, dimethyl carbonate, diethyl carbonate, γ-butyrolactone, dimethoxymethane, diethoxymethane, dimethoxyethane, tetrahydrofuran, methyltetrahydrofuran, diethoxyethane, dimethyl sulfoxide, sulfolane, acetonitrile, Examples include benzonitrile, ionic liquid, fluorine-containing carbonates, fluorine-containing ethers, polyethylene glycols, fluorine-containing polyethylene glycols and the like. The organic solvent electrolyte can be used alone or in combination of two or more. The electrolyte of the organic solvent-based electrolytic solution is not particularly limited, but LiPF ₆ , LiBF ₄ , LiB (CN) ₄ , lithium bis (fluorosulfonyl) imide (LiFSI), lithium bis (trifluoromethylsulfonyl) imide ( LiTFSI) and the like are preferable.
In the case of a water-containing electrolyte containing an organic solvent-based electrolyte, the content of the water-based electrolyte is preferably 10-99.9% by mass with respect to a total of 100% by mass of the water-based electrolyte and the organic solvent-based electrolyte. More preferably, it is 20-99.9 mass%.

In the evaluation method of the present invention, the following formula (1) in the above confirmation step;
^{X = A 2 / (100-} B) (1)
(In the formula, A represents a cycle life (number of cycles), B represents an electrode utilization rate (%)), and a separator having X of 100 or more is preferably a good product. Thereby, a more accurate quantitative evaluation becomes possible. Moreover, it is more preferable that the separator having X of 150 or more is a non-defective product.
The upper limit of X is not particularly limited, and the larger the value, the better the performance, but it is usually 50000 or less.
In addition, it is a non-defective product if X is equal to or higher than the reference at any electrode utilization rate, but it is preferable that X is equal to or higher than the reference at any electrode utilization rate of 50% or less.

<Separator of the present invention>
This invention is also a separator which becomes a non-defective product by the evaluation method of this invention including the composite_body | complex of a polymer and an inorganic particle.
Since the separator of the present invention includes a composite of a polymer and inorganic particles, it is an anion conductive membrane. Such an anion-conducting membrane allows sufficient diffusion of hydroxide ions but metal ions having a large ionic radius (for example, zincate ions generated by the electrode reaction of a zinc negative electrode) even though they are anions. Since it can prevent, the battery obtained by using this as a separator can exhibit favorable performance. In addition, since the separator of the present invention becomes a non-defective product by the evaluation method of the present invention, a short circuit between the positive electrode and the negative electrode by a dendrite of a battery that includes an electrode that undergoes a change in shape with charge / discharge. This can further suppress the battery life.
Below, the polymer and inorganic particle which the separator of this invention contains are demonstrated in order. The separator of the present invention may contain one kind or two or more kinds of polymers and inorganic particles described later.

(polymer)
The polymer may be any polymer as long as it can thicken the separator-forming material and bind the components in the material, for example, an aliphatic hydrocarbon group-containing polymer such as polyethylene, aromatic such as polystyrene, etc. Group-containing polymer; ether group-containing polymer such as alkylene glycol; hydroxyl group-containing polymer such as polyvinyl alcohol; amide group-containing polymer such as polyacrylamide; imide group-containing polymer such as polymaleimide; (meth) acrylic polymer; polyvinylidene fluoride; Halogen atom-containing polymers such as polytetrafluoroethylene; ammonium salt-containing polymers; phosphonium salt-containing polymers; ion-exchangeable polymers; natural rubbers; conjugated diene-based polymers; hydroxyalkylcelluloses (eg, hydroxyethylcellulose) S; amino group-containing polymers such as polyethyleneimine and the like, may be used one of these, or two or more may be used. When these polymers have a functional group, they may be present in the main chain and / or side chain, and may exist as a binding site with a crosslinking agent. The polymer may be crosslinked with an organic crosslinking agent compound.

The polymer is preferably a conjugated diene polymer and / or a (meth) acrylic polymer.
The separator of the present invention containing a conjugated diene polymer and / or a (meth) acrylic polymer suppresses permeation of metal ions such as zincate ions, and selectively transmits good hydroxide ions. Since the film has permeability and has few voids, the battery can have a longer life. In addition, since the anion conductive film formed using the conjugated diene polymer has alkali resistance, it can be suitably used as a material for a battery separator in contact with an alkaline electrolyte.

The polymer preferably further has a structural unit derived from an acid group-containing vinyl monomer. As the acid group-containing vinyl monomer, for example, itaconic acid, acrylic acid, methacrylic acid, and fumaric acid are more preferable.
In 100 mass% of all the structural units constituting the polymer, the mass ratio of the structural unit derived from the acid group-containing vinyl monomer is preferably 0.1 mass% or more. The mass ratio is preferably 10% by mass or less.

The polymer preferably has a weight average molecular weight of 10,000 or more and 6.5 million or less. The weight average molecular weight is more preferably 20,000 or more. The said weight average molecular weight can be measured as a weight average molecular weight converted into polystyrene by gel permeation chromatography (GPC) under the following conditions.
Device: HCL-8220GPC manufactured by Tosoh Corporation
Column: TSKgel Super AWM-H
Eluent (LiBr · H ₂ O, phosphoric acid-containing NMP): 0.01 mol / L

The polymer preferably has a glass transition temperature (Tg) of −40 ° C. or higher and 50 ° C. or lower. When the Tg of the polymer is less than −40 ° C., the mechanical strength of the separator is insufficient, and the dendrite suppressing effect may be lowered. In addition, when Tg exceeds 50 ° C., the separator becomes too hard and brittle, and cracks or the like may enter the separator when forming the battery, which may reduce the life performance of the battery.
The polymer Tg was determined by applying a polymer to a glass plate and drying at 120 ° C. for 1 hour to form a polymer film. The resulting polymer film was subjected to a differential scanning calorimeter (device name: thermal analyzer DSC3100S, BRVKER). ).

The said polymer can be manufactured by polymerizing the monomer component which forms the structural unit which the polymer mentioned above contains, for example.
The method for polymerizing the monomer component is not particularly limited, and examples thereof include an aqueous solution polymerization method, an emulsion polymerization method, a reverse phase suspension polymerization method, a suspension polymerization method, a solution polymerization method, and a bulk polymerization method. Among these methods, the emulsion polymerization method is preferably used from the viewpoint of easy production. For emulsion polymerization, for example, an anionic surfactant such as sodium dodecylbenzenesulfonate can be suitably used.

A polymerization initiator can be used for the polymerization of each monomer component. As the polymerization initiator, one or more commonly used ones can be used.
The amount of the polymerization initiator used is preferably 0.02% by mass or more and 2% by mass or less with respect to 100% by mass of all monomer components used as a raw material for the polymer.

For the polymerization of each monomer component, a chain transfer agent such as t-dodecyl mercaptan may be used for the purpose of adjusting the weight average molecular weight. When using a chain transfer agent, the amount used may be appropriately set according to the type and amount of monomers used, polymerization reaction conditions such as polymerization temperature and concentration, the molecular weight of the target polymer, etc. Although not particularly limited, for example, it is preferably 10% by mass or less with respect to 100% by mass of all monomer components used as a raw material for the conjugated diene polymer. From the viewpoint of adjusting the weight average molecular weight, it is preferably 0.01% by mass or more.

The temperature of the polymerization reaction for producing the polymer is not particularly limited as long as the polymerization reaction proceeds, but it is preferably 20 ° C. or higher and 100 ° C. or lower. The temperature is more preferably 40 ° C. or higher and 90 ° C. or lower.
The polymerization reaction time is not particularly limited, but preferably 1 hour or more and 10 hours or less in consideration of productivity.

The content of the polymer is preferably 10% by mass or more, more preferably 15% by mass or more, and more preferably 20% by mass in 100% by mass of the separator from the viewpoint of mechanical strength and ion conductivity of the separator. More preferably, it is more preferably 25% by mass or more. Moreover, it is preferable that this content is 70 mass% or less, It is more preferable that it is 50 mass% or less, It is still more preferable that it is 40 mass% or less.

(Inorganic particles)
The elements contained in the inorganic particles include alkali metals, alkaline earth metals, Sc, Y, lanthanoids, Ti, Zr, Hf, V, Nb, Ta, Cr, Mo, W, Mn, Fe, Ru, Co, Ni , Pd, Cu, Au, Zn, Cd, B, Al, Ga, In, Tl, C, Si, Ge, Sn, Pb, N, P, Sb, Bi, S, Se, Te, F, Cl, and , Br is preferably at least one element selected from the group consisting of Br.

Examples of the inorganic particles include oxides, hydroxides, layered double hydroxides, clay compounds, solid solutions, alloys, zeolites, halides, carboxylate compounds, carbonate compounds, bicarbonate compounds, nitrate compounds, sulfate compounds, and the like. Examples thereof include sulfonic acid compounds; phosphoric acid compounds such as hydroxyapatite; phosphorous compounds; hypophosphorous acid compounds and boric acid compounds; silicic acid compounds; aluminate compounds; sulfides; Among these, the inorganic particles preferably include at least one selected from the group consisting of oxides, hydroxides, layered inorganic compounds, and sulfides.

As the oxide, for example, cerium oxide and zirconium oxide are preferable. More preferably, it is cerium oxide. Further, the cerium oxide may be a solid solution with a metal oxide such as samarium oxide, gadolinium oxide, bismuth oxide, zirconium oxide or the like. It may have an oxygen defect.
As the hydroxide, for example, magnesium hydroxide, cerium hydroxide, and zirconium hydroxide are preferable.

The layered inorganic compound may be a single layer or a laminate of two or more layers. Examples of the layered inorganic compound include layered double hydroxides.
The layered double hydroxide is represented by the following formula:
[M ¹ _1-x M ² _x (OH) ₂ ] (A ⁿ⁻ ) _{x / n} · mH ₂ O
(M ¹ represents a divalent metal ion that is ^one of Mg, Fe, Zn, Ca, Li, Ni, Co, Cu, and Mn. M ² represents Al, Fe, Mn, Co, Cr, In the ^.A n-representing a trivalent metal ion is _{^{either, OH -, Cl -, NO}} 3 -, CO 3 2-, COO - .m representing a 1-3-valent anion such as 0 or more N is a number of 1 to 3. x is a number of 0.20 to 0.40). In addition, it is preferable that An <- ^> is a bivalent or less anion.
Such layered double hydroxides are naturally occurring (eg, Hydrotalcite, Manassite, Motucoreite, Stichtite, Sjogrenite, Barbertite). , Pyroaurite, Iomite, Chlormagalminite, Hydrocalmite, Green Last 1, Bertierine, Tacobe, Tacoit Reevesite, Honesite In addition to Yardlite, Meixnerite, and the like, it may be artificially synthesized, and may be dehydrated by firing at 150 ° C. to 900 ° C. The compound which decomposed | disassembled the anion and the compound which replaced | exchanged the anion in an interlayer for the hydroxide ion etc. may be sufficient. Among these layered double hydroxides, Mg—Al-based layered double hydroxides such as hydrotalcite are preferable. A compound having a functional group such as a hydroxyl group, an amino group, a carboxyl group, or a silanol group may be coordinated with the layered double hydroxide.
As the sulfide, for example, cerium sulfide and zirconium sulfide are preferable.

Examples of the shape of the inorganic particles include fine powder, powder, granule, granule, scale, polyhedron, rod, and curved surface.

The inorganic particles preferably have an average particle diameter of 10 nm to 100 μm. When the average particle diameter is 100 μm or less, the surface area of the separator with respect to the mass of the metal and / or metal compound is increased, and dendrites are further prevented from penetrating the separator. The lower limit of the average particle diameter is not particularly limited, but the average particle diameter is usually 10 nm or more.
The average particle size is determined by LA-920 (Horiba, Ltd.), a laser diffraction / scattering particle size distribution measuring device obtained by dispersing a suitable amount of metal and / or metal compound in a 0.2 mass% sodium hexametaphosphate aqueous solution. It is measured using.

The proportion of the inorganic particles is preferably 25% by mass or more in 100% by mass of the separator of the present invention. More preferably, it is 35 mass% or more, More preferably, it is 40 mass% or more. Moreover, it is preferable that it is 80 mass% or less. More preferably, it is 70 mass% or less.

The separator of the present invention may further contain other components. Examples of other components include carbon.
The content of the other components is preferably 5% by mass or less in 100% by mass of the separator of the present invention. More preferably, it is 1 mass% or less, More preferably, it is 0.2 mass% or less.

Examples of the method for preparing the separator forming material for forming the separator in the present invention include the following methods.
Together with the separator forming material (preferably, the polymer, the inorganic particles, and, if necessary, the other components), the other components are mixed as necessary. For mixing, a mixer, blender, kneader, bead mill, ready mill, ball mill, or the like can be used. Prior to mixing, water, an organic solvent such as methanol, ethanol, propanol, isopropanol, butanol, hexanol, tetrahydrofuran, N-methylpyrrolidone, or a mixed solvent of water and an organic solvent may be added.

The method for producing the separator from the separator forming material is not particularly limited as long as a film is formed. The separator forming material is formed into a film by rolling it with a roll, or is formed into a film by rolling with a flat plate press or the like. For example, a method such as an injection molding method, an extrusion molding method, or a casting method can be used. These molding methods may be used alone, or two or more methods may be used in combination.
The said manufacturing method may include the process of drying a film | membrane other than the process of shape | molding a separator formation material in a film form. The drying temperature may be set as appropriate, but can be performed at 60 ° C to 160 ° C.

It is preferable that the separator of the present invention further includes a porous material, and the composite is impregnated in the porous material.
Examples of the porous material include nonwoven fabrics, filter paper, polymers containing hydrocarbon moieties such as polyethylene and polypropylene, polymers containing polytetrafluoroethylene moieties, polymers containing polyvinylidene fluoride moieties, cellulose, fibrillated cellulose, and viscose. Rayon, cellulose acetate, hydroxyalkyl cellulose, carboxymethyl cellulose, polyvinyl alcohol-containing polymer, cellophane, polystyrene-containing aromatic ring-containing polymer, polyacrylonitrile-containing polymer, polyacrylamide-containing polymer, polyvinyl halide-containing polymer Polymer, polyamide site-containing polymer, polyimide site-containing polymer, ester site-containing polymer such as nylon, poly (meth) acrylic acid site-containing polymer, poly (meth) acrylate site-containing polymer, Hydroxyl group-containing polymers such as isoprenol and poly (meth) allyl alcohol, carbonate group-containing polymers such as polycarbonate, ester group-containing polymers such as polyester, carbamate and carbamide group site-containing polymers such as polyurethane, agar, gel compounds, Organic-inorganic hybrid (composite) compounds, ion-exchange membrane polymers, cyclized polymers, sulfonate-containing polymers, quaternary ammonium salt-containing polymers, quaternary phosphonium salt polymers, cyclic hydrocarbon group-containing heavy compounds A film made of an inorganic substance such as a coalescence, an ether group-containing polymer, or a ceramic, and has a porous structure. These separators may be used alone or in combination of two or more.

The porous material in the porous material may be any material as long as it can be said to be porous in the technical field of the present invention. Among them, Asahi Seiko Co., Ltd. Wangken air permeability smoothness measuring device KY-55 is used for measurement. The air permeability value obtained by calculating the average value is preferably 1000 s or more, for example. The upper limit of the air permeability value is not particularly limited, but is usually 100,000 s or less.

The separator made a non-defective product by the evaluation method of the present invention is particularly preferably used as a battery separator such as a battery including a negative electrode containing a lithium species, a zinc species, or a cadmium species as a negative electrode active material. By using the evaluation method of the present invention, a short circuit between electrodes due to dendrites can be sufficiently suppressed, and a separator capable of extending the battery life can be selected accurately, simply and quickly.

A battery to which the separator of the present invention is applied is a primary battery; a chargeable / dischargeable secondary battery (storage battery); a mechanical charge type battery (a battery in which a zinc negative electrode is mechanically replaced); a third pole type battery ( The battery may be in any form such as a negative electrode, an electrode suitable for charging, and an electrode suitable for discharging, and a fuel cell, but a secondary battery or a fuel cell is preferred.
The configuration of the battery is not particularly limited, but is preferably a battery that uses an alkaline electrolyte, such as an alkaline dry battery, a silver oxide battery, a manganese-zinc battery, a nickel-zinc battery, a fuel battery, and an air battery.

The present invention will be described in more detail with reference to the following examples. However, the present invention is not limited to these examples. Unless otherwise specified, “part” means “part by weight” and “%” means “mass%”.

In the electrolytic cell container holding the following electrolyte solution, the following two electrodes are arranged so as to be separated from each other by the following separator, and a measuring device is constructed. A charge / discharge test was conducted so that the reverse reaction occurred.

(electrode)
A zinc plate (0.5 mm thick) is welded onto a current collector (Sn / Ni plated punched steel plate) cut into 2 cm × 2 cm, and a mass ratio of ZnO: PTFE (polytetrafluoroethylene) = 97: 3 is formed thereon. The zinc active material mixed in (1) was pressed by a flat plate press to produce a zinc / zinc oxide mixture electrode. Here, the theoretical active material amount of the zinc mixture electrode was 80 mAh / cm ² .
Epoxy resin (Million Clear manufactured by Kansai Paint Co., Ltd.) was applied as an insulation treatment of the outer peripheral portion so as to have a width of 1 mm along the outer peripheral portion of the electrode (see FIG. 2).

(Electrolyte)
A solution obtained by dissolving zinc oxide to a saturated concentration in an aqueous potassium hydroxide solution adjusted to 6.7 mol / L was used as an electrolytic solution.

(Separator)
[Preparation Example of Conjugated Diene Copolymer]
After charging 0.5 parts by mass of sodium dodecylbenzenesulfonate and 57 parts by mass of deionized water into a flask equipped with a dropping funnel, a stirrer, a nitrogen gas inlet tube, a thermometer, and a reflux condenser, the inside of the flask was Replaced with nitrogen gas.
Meanwhile, sodium dodecylbenzenesulfonate 0.5 parts by mass, styrene 58 parts by mass, 1,3-butadiene 40 parts by mass, fumaric acid 2 parts by mass, t-dodecyl mercaptan 0.5 parts by mass and deionized water 38 were added to the dropping funnel. A pre-emulsion was prepared by charging mass parts. Thereafter, the temperature was raised to 65 ° C. with stirring while gently blowing nitrogen gas into the flask, 6 parts by mass of 5% aqueous ammonium persulfate solution was added, and then the pre-emulsion obtained above was uniformly added to the flask over 5 hours. It was dripped in. After completion of dropping, the dropping funnel was washed with 5 parts by mass of deionized water, and the resulting cleaning solution was dropped into the flask. Thereafter, the contents in the flask were maintained at 65 ° C. for 2 hours to complete the polymerization. The obtained reaction liquid was cooled to room temperature to obtain an aqueous dispersion of a conjugated diene copolymer having a nonvolatile content of 48.1% by mass.

[Example of preparation of separator]
100 parts by mass of hydrotalcite (trade name: DHT-6, manufactured by Kyowa Chemical Industry Co., Ltd., average particle size 0.20 μm), 100 parts by mass of an aqueous dispersion of the conjugated diene copolymer prepared in the above preparation example, and pure water 25 parts by mass were weighed and kneaded until a uniform state was obtained using a kneader, and then the obtained kneaded product was roll-pressed to a thickness of 100 μm to produce a separator.

The following three types of separators were examined.
(1) Microporous membrane: (1-1) Nylon nonwoven fabric (thickness 160 μm), (1-2) Polyolefin hydrophilic microporous membrane (thickness 25 μm), respectively.
(2) Anion conductive membrane: The anion conductive membrane prepared in the above separator preparation example (same as the anion conductive membrane of Example 1 described in Japanese Patent Application No. 2015-213144, thickness: 101 μm) was used.
(3) Porous body-impregnated membrane: a separator integrated with a fiber material by rolling a kneaded material of the above separator preparation example (same as the kneaded material of Example 1 described in Japanese Patent Application No. 2015-213144) with a nylon nonwoven fabric Was used.

(Charge / discharge test equipment)
A charge / discharge test apparatus (HJ-1005SD8) manufactured by Hokuto Denko Corporation was used.
(Measuring instrument)
The short circuit between the electrodes was confirmed by measuring the resistance between the two electrodes using a battery tester (BT3554) manufactured by HIOKI, and rapidly decreasing the resistance. The rapid decrease in resistance refers to a case where there is a decrease rate of 10% or more in comparison with the interelectrode resistance in the previous cycle when the interelectrode resistance is measured for each cycle. This measurement can be performed by the battery high tester, but can also be calculated from the measured current-voltage value in the charge / discharge test apparatus.

<Evaluation by direct current>
(Comparative Example 1)
As a result of applying a direct current having a current density of 10 mA / cm ^2, the test results shown in Table 1 below were obtained.

As the measurement time elapses, dendrite grows from one zinc electrode, and the metal zinc species mounted on the other electrode is oxidized. For this reason, if the metal zinc which was originally mounted is consumed, it will change into a hydrogen generation reaction by electrolysis of water (measurable time is short). In the above test, a 0.5 mm-thick zinc metal plate was pasted on the current collector, but the substantial amount of dischargeable electricity was about 30 mAh / cm ² due to oxidation of the contacts with the current collector. .
Thus, in order to perform separator evaluation by direct current for a long period of time, it is necessary to mount a large amount of metal zinc species as a raw material for discharging in advance.

<Evaluation by AC measurement>
Example 1
Next, a measuring apparatus was constructed with the same configuration as in Comparative Example 1, and a charge / discharge test was performed with a predetermined amount of electricity instead of applying a direct current.
Here, the current density was fixed at 80 mA / cm ² , and the measurement was performed by switching the direction of the charge / discharge current every 10 minutes, 15 minutes, 30 minutes, and 48 minutes.
Tables 2 and 3 below show the number of cycles and X values obtained by each measurement.
In addition, X value is the following general formula (1);
^{X = A 2 / (100-} B) (1)
(In the formula, A represents the cycle life (number of cycles), and B represents the electrode utilization rate (%)). A separator having an X value of 100 or more is regarded as a good product.

From the results of Example 1, (2) the anion conductive membrane and (3) the porous material-impregnated membrane have an X value of 100 or more at any electrode utilization rate of 50% or less, and can be evaluated as good products.
In Example 1, stable evaluation for a long time is possible without mounting a large amount of metal zinc species on the electrode or adding a metal zinc species. (2) Anion conductive membrane, (3 ) It was possible to quantitatively and rapidly evaluate the superior dendrite suppression ability of the porous material impregnated film. Moreover, since the measurement method of Example 1 performs charging / discharging reaction like an actual secondary battery, it is thought that the evaluation result consistent with the cycle life of an actual secondary battery is obtained.

When the electrode utilization rate exceeds 50%, the zinc electrode undergoes a great change in shape, and there is a risk of performance degradation regardless of the separator performance. For this reason, this test is preferably evaluated with a utilization rate of 50% or less of the capacity mounted on the electrode.

1: separators 2a, 2b, 12a, 12b: electrode lead portions 3a, 3b: current collector 5a: zinc layer 5b before dendrite formation: zinc oxide layers 7a, 7b before dendrite formation: dendrite 9: electrolytic vessel container 10: Measuring device 15a, 15b: Electrode reaction part (zinc layer or zinc oxide layer)
16a, 16b: Insulation processing part (insulating member)

Claims (10)

A separator evaluation method,
In this method, in the electrolytic cell container holding the electrolyte, the charge reaction and the discharge reaction are alternately and reversely performed by the two electrodes that are separated from each other by the separator and undergo a shape change with charge and discharge. And a step for confirming a short circuit between the two electrodes. The separator evaluation method according to claim 1, wherein the two electrodes are an electrode having zinc and an electrode having zinc oxide. The separator evaluation method according to claim 1 or 2, wherein the confirmation step confirms a short circuit between the two electrodes by a decrease in voltage or resistance. 4. The separator evaluation method according to claim 1, wherein a charge / discharge capacity in the confirmation step is ½ or less of an active material capacity of at least one of the two electrodes. 5. The separator evaluation method according to claim 1, wherein at least one of the two electrodes has a surface area of a portion facing the separator that is smaller than a current-carrying area of the separator. The method for evaluating a separator according to claim 1, wherein a charge / discharge current density in the confirmation step is 1 to 100 mA / cm ² with respect to a current-carrying area of the separator. In the confirmation step, the following general formula (1);
^{X = A 2 / (100-} B) (1)
(Wherein A represents cycle life (number of cycles), B represents electrode utilization rate (%)), and X is 100 or more. Item 7. The method for evaluating a separator according to any one of Items 1 to 6. The separator which becomes a non-defective product by the evaluation method according to claim 7 including a composite of a polymer and inorganic particles. The separator according to claim 8, further comprising a porous material, wherein the composite is impregnated in the porous material. The separator according to claim 8 or 9, wherein the inorganic particles include at least one selected from the group consisting of oxides, hydroxides, layered inorganic compounds, and sulfides.

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