KR102491114B1 - All Solid State Metal Air Battery - Google Patents

Abstract

The present invention is a negative electrode; anode; and a solid electrolyte-based metal-air battery having a solid electrolyte disposed between the negative electrode and the positive electrode and a deliquescent material included in the positive electrode.
An all-solid metal-air battery according to the present invention includes a positive electrode provided to be in contact with external air, a negative electrode disposed at a predetermined distance from the positive electrode and containing a metal, and disposed between the positive electrode and the negative electrode. It includes a solid electrolyte, and the anode is characterized in that it contains a deliquescent material.

Description

All Solid State Metal Air Battery {All Solid State Metal Air Battery}

The present invention uses a deliquescent material included in an air electrode (anode) to reduce the polarization of hydroxide, carbonate, or hydrate generated by reaction with air, and to implement an all-solid metal-air that can realize stability and high capacity. It's about batteries.

Lithium secondary batteries have been widely used as energy storage devices for electronic devices such as mobile phones and laptops, but recently, demand for large-capacity energy storage devices such as electric vehicles and grid energy systems is rapidly increasing. Accordingly, the development of a next-generation battery having a high energy density has become very important.

Metal-air batteries have a much higher energy density than conventional lithium-ion secondary batteries, and are attracting attention as a storage device that can theoretically realize the highest energy capacity by using air and metal with the highest energy density among cathode and anode materials.

Among several types of metal-air systems, research on organic liquid electrolyte-based lithium-oxygen batteries, which are most similar to conventional lithium-ion secondary batteries, is being intensively conducted, but commercialization is difficult. In addition, since the lithium-oxygen system uses oxygen rather than air, a storage device for this and a separation device for reacting only oxygen are required. There are downsides.

Therefore, many studies are being conducted to use air instead of oxygen in metal-oxygen batteries. However, when air is used instead of oxygen, it causes high polarization rather than metal oxides (MO ₂ , M ₂ O ₂ , M ₂ O, M=Li/Na) that are previously produced due to water and carbon dioxide in the air. Hydroxides, carbonates, and hydrates (MOH, M ₂ CO ₂ , MOH·xH ₂ O, M ₂ CO ₂ ·xH ₂ O, M=Li/Na) are produced as reaction products.

When these reaction products having a high charge polarization are generated in an organic liquid electrolyte having a low electrochemical window of 5V or less, a high charge polarization occurs and the electrolyte is decomposed, causing rapid degradation of performance. In addition, in the case of an organic liquid electrolyte, the chemical stability of the material itself against air is not excellent, so it is not suitable for long-term operation of an air battery.

Therefore, in order to develop a high-performance metal-air battery powered by air, a material that is stable in air is required. As an example, a metal-air battery can be implemented through an all-solid-state battery constructed using a solid electrolyte material that is stable to air disclosed in the following patent documents. In addition, it is necessary to develop technologies for lowering the polarization of hydroxides, carbonates, and hydrates, which are types of products produced by the reaction of a reaction product with air, and securing high capacity.

Publication No. 2018-0089809

An object of the present invention is an all-solid metal-air battery capable of realizing stability and high capacity by using a solid electrolyte that is stable in air and at the same time lowering the polarization of hydroxide, carbonate, or hydrate generated by reaction with air. is providing

In order to achieve the above object, the present invention provides a positive electrode provided to be in contact with external air, a negative electrode disposed at a predetermined distance from the positive electrode and containing a metal, and a solid disposed between the positive electrode and the negative electrode. An all-solid metal-air battery is provided, comprising an electrolyte and the positive electrode comprising a deliquescent material.

In the solid electrolyte-based all-solid metal-air battery according to the present invention, a deliquescent material is formed on the air electrode using an electrochemical reaction or injected (added) from the outside to adsorb moisture in the air to the air electrode so that the discharge product is conventionally By changing into a dissolved form rather than a particle form to act as a new ion conductor, it is possible to charge and discharge carbonates or hydroxides at low polarization, which was previously impossible.

In addition, the 2M + CO ₂ + 0.5O ₂ + xH ₂ O ↔ M ₂ CO ₃ xH ₂ O, M=Li/Na, x≥0 reaction with a high discharge voltage is activated by the water adsorbed on the electrode surface. , high capacity energy can be realized, and high energy efficiency is possible due to a low charge/discharge voltage difference due to the same reaction path during charge/discharge. Accordingly, the solid electrolyte-based all-solid metal-air battery according to the present invention can provide a metal-air battery having high energy and excellent output characteristics and energy efficiency.

In addition, the solid electrolyte-based all-solid metal-air battery according to the present invention applies an oxide solid electrolyte that has no reaction with air and is chemically stable, and thus an air atmosphere containing moisture, carbon dioxide, etc., which was difficult to apply in a liquid electrolyte-based battery. and can be applied to high temperature conditions.

In addition, in the solid electrolyte-based all-solid metal-air battery according to the present invention, the water adsorbed on the deliquescent material dissolves the discharge product to generate a new cathode secondary electrolyte (catholyte), thereby improving energy capacity and efficiency , Long life characteristics can be secured unlike conventional solid electrolyte-based batteries.

In addition, according to one embodiment of the present invention, since the deliquescent material can dissolve the discharge product to form a metal ion (Li ⁺ /Na ⁺ ) conductive solution during charging and discharging, a metal-air battery that is easy to charge and discharge quickly can provide

In addition, according to one embodiment of the present invention, the water adsorbed to the air electrode by the deliquescent material has a high discharge voltage (~3.4V) 2Na + CO ₂ + 0.5O ₂ + xH ₂ O ↔ Na ₂ CO ₃ · Since a high energy capacity can be realized by activating the xH ₂ O reaction and the same reaction path is followed during charge/discharge, a metal-air battery having high energy efficiency can be provided.

1 is a schematic diagram of a metal-air battery according to an embodiment of the present invention.
2 is a graph showing the first charge and discharge results of a sodium (Na)-air battery in various gas atmospheres.
3 is a view showing changes in the microstructure of an air electrode in a sodium (Na)-air battery by charging and discharging processes in an air atmosphere at 25° C. and 70% relative humidity.
FIG. 4 shows a charge/discharge graph of a sodium (Na)-air battery in an air atmosphere at 25° C. and 70% relative humidity, and the precipitation and removal of discharge products during the first cycle charge/discharge.
5 is a graph showing the results of a cycle test, energy efficiency, and coulombic efficiency of a sodium (Na)-air battery in an air atmosphere at 25° C. and 70% relative humidity.

Hereinafter, the configuration and operation of embodiments of the present invention will be described with reference to the accompanying drawings.

In describing the present invention, if it is determined that a detailed description of a related known function or configuration may unnecessarily obscure the gist of the present invention, the detailed description will be omitted. In addition, when a part "includes" a certain component, it means that it may further include other components without excluding other components unless otherwise stated.

The present invention is formed by an electrochemical reaction during initial charge/discharge or by adsorbing moisture (water) in the air to an anode using a deliquescent material included in an air electrode before the electrochemical reaction to improve ionic conductivity and electrochemical reaction. form a cathode secondary electrolyte (catholyte) that can be used to improve the electrochemical performance of an all-solid-state metal-air battery, and M ₂ CO ₃ xH ₂ O (M=Li/Na, x≥0) It is about activating a reversible charge and discharge reaction.

An all-solid metal-air battery according to the present invention includes a positive electrode provided to be in contact with external air, a negative electrode disposed at a predetermined distance from the positive electrode and containing a metal, and disposed between the positive electrode and the negative electrode. It includes a solid electrolyte, and the anode is characterized in that it contains a deliquescent material.

An electron current collector may be disposed on one surface of the positive electrode not in contact with the solid electrolyte, and a current collector may be disposed on one surface of the negative electrode not in contact with the solid electrolyte.

In addition, the all-solid-state metal-air battery may further include an air exposure port through which air may pass so that an oxidation-reduction reaction occurs by passing the active material through the electron current collector.

In addition, the deliquescent material may be a material having deliquescent property formed by reaction of a charge/discharge product of the positive electrode with air in the all-solid metal-air battery, or a deliquescent material injected (or added) to the positive electrode. Injecting (or adding) a deliquescent material is more preferable because it can stably improve electrochemical performance to implement a high-capacity/high-output/high-efficiency all-solid-state metal-air battery.

In addition, the deliquescent material may adsorb water in the air to at least partially dissolve discharge products generated during the driving of the all-solid-state metal-air battery so that the discharge products act as ion conductors.

In addition, the reversible reaction of the following [Reaction Formula 1] can be activated by the water adsorbed by the deliquescent substance. This reversible reaction can realize high capacity energy with high discharge voltage, and can implement high energy efficiency by low charge/discharge voltage difference because the reaction path is the same during charge/discharge.

[Scheme 1]

2M + CO ₂ + 0.5O ₂ + xH ₂ O ↔ M ₂ CO ₃ xH ₂ O

(M is at least one selected from Li and Na, x≥0)

In addition, the reversible reaction of the following [Reaction Formula 2] can be activated by the water adsorbed by the deliquescent substance. The material produced by this reversible reaction adsorbs water in the air and dissolves itself to act as a cathode secondary electrolyte (catholyte), which contributes to charge/discharge reactions and improvements in usable capacity, output speed, and efficiency.

[Scheme 2]

M + 0.5H ₂ O + 0.25O ₂ + xH ₂ O ↔ MOH xH ₂ O

(M is at least one selected from Li and Na, x≥0)

In addition, by the water adsorbed by the deliquescent material, the discharge product generated during the driving process of the all-solid-state metal-air battery is ionized to form a cathode secondary electrolyte (catholyte), and the ionized discharge product is MOH xH ₂ O or M ₂ CO ₃ xH ₂ O (M is at least one selected from Li and Na, x≥0).

In addition, as the deliquescent material, for example, at least one selected from sodium hydroxide (NaOH), potassium hydroxide (KOH), calcium chloride (CaCl ₂ ), magnesium chloride (MgCl ₂ ), and zinc chloride (ZnCl ₂ ) may be used. there is. However, the deliquescent material of the present invention is not limited to the above types, and is not particularly limited as long as it can perform the above functions.

In addition, the negative electrode may be one or more metals selected from lithium (Li), sodium (Na), and alloys thereof.

In addition, the solid electrolyte may be made of a ceramic, a polymer, or a composite thereof having an ionic conductivity of 10 ⁻⁴ S/cm or more.

In addition, the positive electrode may include a composite of a porous conductive material and the solid electrolyte.

In addition, the anode is made of Super P, carbon nanofibers, carbon nanotubes, graphene, nickel, cobalt, titanium, iron, copper, gold, platinum, silver, and transition metal oxides (AB1 _1-xyz B2 _x B3 _y B4 _z O ₂ , A is Li or Na, B is Al, Fe, V, Cr, Ti, W, Ta, and Mo, 0≤x<1, 0≤y<1, 0≤z< 1, 0 ≤ x + y + z ≤ 1) may include one or more selected from the particles.

[Example]

1 is a schematic diagram of a metal-air battery according to an embodiment of the present invention.

As shown in FIG. 1, a metal-air battery 1 according to an embodiment of the present invention has a negative electrode 10, and the negative electrode 10 and the negative electrode 10 are disposed to face each other at a predetermined interval. It includes a positive electrode 20 and a solid electrolyte layer 30 disposed between the negative electrode 10 and the positive electrode 20 . A current collector 12 is disposed on one side of the negative electrode 10, an electron collector 22 is disposed on one side of the positive electrode 20, and air exposure holes for contacting air on both sides of the positive electrode ( 40) is formed, and a housing 50 made of non-conductor is disposed on both sides of the negative electrode 10, the positive electrode 20, and the solid electrolyte layer 30 to block the outside.

Specifically, in the embodiment of the present invention, a sodium (Na) negative electrode made of sodium (Na) was used as the negative electrode 10, and NaSicon (Na ₃ Zr ₂ Si ₂ PO ₁₂ ) was used as the solid electrolyte layer 20 A solid electrolyte layer was used, and the positive electrode 20 used a composite having a porous structure composed of Nasicon (Na ₃ Zr ₂ Si ₂ PO ₁₂ ) and nickel (Ni) particles used as the solid electrolyte layer.

Since the solid electrolyte layer 30 made of Nasicon (Na ₃ Zr ₂ Si ₂ PO ₁₂ ) is chemically stable to water and carbon dioxide (CO ₂ ), it is resistant to moisture adsorption by deliquescent substances and the presence of CO ₂ in the air. It can be operated stably without any decomposition reaction of the electrolyte.

2 is a graph showing the first charge and discharge results of a sodium (Na)-air battery in various gas atmospheres. As shown in FIG. 2, when the sodium-air battery 1 according to an embodiment of the present invention is driven in a state in which air containing high concentration of moisture and single/mixed gases of high purity oxygen, nitrogen, and carbon dioxide flow, It can be confirmed that the charge/discharge reaction occurs only in the atmosphere containing moisture.

The sodium-air battery was charged and discharged at a current density of 0.02 mA/cm ² and in the range of 0.2 mAh/cm ² discharge - 3.85 V charge. In an oxygen (O ₂ ) atmosphere, NaO ₂ , Na ₂ O ₂ , and Na ₂ O can be formed, and in the case of an O ₂ /CO ₂ mixed gas, Na ₂ CO ₃ can be formed. However, since the polarization of these reactions is high in a state in which moisture in the air is not included, the charge/discharge reaction itself does not occur.

On the other hand, when moisture is contained in the air, NaOH is generated by the following reaction (1) at around 2.7V.

Na + 0.5H ₂ O + 0.25O ₂ → NaOH (1)

Since the produced NaOH is highly deliquescent, it adsorbs water in the air and dissolves itself to act as a cathode secondary electrolyte (catholyte), which greatly affects charge/discharge reactions, usable capacity, output speed, and efficiency.

A substance in which NaOH and water are reacted can also react with CO ₂ in the air to form Na ₂ CO ₃ xH ₂ O (x = 0 or 1). Na ₂ CO ₃ xH ₂ O is charged around 3.4V / Discharge reaction is possible. In general, it is known that charging Na ₂ CO ₃ is difficult, but in this embodiment, charging/discharging occurs at an operating voltage close to the theoretical voltage, which is an effect of increasing output by the cathode secondary electrolyte (catholyte).

3 is a view showing changes in the microstructure of an air electrode in a sodium (Na)-air battery by charging and discharging processes in an air atmosphere at 25° C. and 70% relative humidity (RH). Looking at the microstructure of the cathode in the sodium-air battery driven in the air, as shown in FIG. 3, it is confirmed that the discharge product is formed in the form of a film rather than a particle form, which is It means that the discharge product is dissolved because of the deliquescent property of NaOH adsorbing moisture.

FIG. 4 shows a charge/discharge graph of a sodium (Na)-air battery in an air atmosphere at 25° C. and 70% relative humidity, and the precipitation and removal of discharge products during the first cycle charge/discharge. As confirmed in FIG. 4, when the cycle test of the sodium-air battery is performed, the generation of NaOH and Na ₂ CO ₃ H ₂ O is observed after discharging, and as the cycle is repeated [2Na + CO ₂ + 0.5O ₂ ↔ Na ₂ CO ₃ xH ₂ O, E= 3.37 V(x=0) or 3.43 V(x=1)] It can be seen that the discharge reaction is activated. Considering that the concentration of CO ₂ in the air is extremely low and the discharge capacity of Na ₂ CO ₃ .xH ₂ O gradually increases, it can be seen that the concentration of CO ₂ in the positive electrode gradually increases as the cycle is repeated.

5 is a graph showing the results of a cycle test, energy efficiency, and coulombic efficiency of a sodium (Na)-air battery in an air atmosphere at 25° C. and 70% relative humidity. As shown in FIG. 5 , the sodium-air battery 1 according to an embodiment of the present invention was subjected to a current density of 0.2 mA/cm ² and a discharge of 0.2 mAh/cm ² - 3.85 V in an atmosphere of 25° C. and 70% relative humidity. As a result of the cycle test in the range of charge, stable electrochemical performance is expressed even when charge and discharge are repeated for 50 cycles. That is, since the battery according to the embodiment of the present invention uses a material that is stable in air, excellent charge and discharge characteristics can be obtained.

As described above, in the sodium (Na)-air battery according to an embodiment of the present invention, the deliquescent material dissolves the discharge product to generate a cathode secondary electrolyte (catholyte) capable of electrochemical reaction with a new type of ion conduction Through this, the all-solid-state metal-air battery can implement high performance.

In addition, the generated positive secondary electrolyte (catholyte) activates the discharge reaction of 2Na + CO ₂ + 0.5O ₂ + xH ₂ O → Na ₂ CO ₃ xH ₂ O at around 3.4V from the second cycle, and the charge and discharge reaction By reducing the voltage difference between them, energy efficiency can be improved and high energy capacity can be realized.

1: metal-air cell
10: cathode
12: current collector
20: anode
22: electronic current collector
30: solid electrolyte layer
40: air exposure port
50: non-conductive housing

Claims (11)

A positive electrode provided to be in contact with external air, a negative electrode disposed at a predetermined distance from the positive electrode and containing a metal, and a solid electrolyte disposed between the positive electrode and the negative electrode,
The anode contains a deliquescent material,
By the water adsorbed by the deliquescent material, the discharge product generated during the driving process of the all-solid-state metal-air battery is ionized to form a cathode secondary electrolyte (catholyte),
The discharge product is MOH·xH ₂ O or M ₂ CO ₃ ·xH ₂ O (M is at least one selected from Li and Na, x≥0), an all-solid-state metal-air battery. According to claim 1,
The deliquescent material is generated through an electrochemical discharge reaction,
All-solid metal-air battery added to the positive electrode. According to claim 1,
The deliquescent material adsorbs water in the air so that the discharge product generated during the driving process of the all-solid metal-air battery is at least partially dissolved so that the discharge product acts as an ion conductor. According to claim 3,
An all-solid metal-air battery in which the reaction of [Reaction Formula 1] is activated by the water adsorbed by the deliquescent material.
[Scheme 1]
2M + CO ₂ + 0.5O ₂ + xH ₂ O ↔ M ₂ CO ₃ xH ₂ O
(M is at least one selected from Li and Na, x≥0) According to claim 3,
An all-solid metal-air battery in which the reaction of [Reaction Formula 2] is activated by the water adsorbed by the deliquescent material.
[Scheme 2]
M + 0.5H ₂ O + 0.25O ₂ + xH ₂ O ↔ MOH xH ₂ O
(M is at least one selected from Li and Na, x≥0) delete According to any one of claims 1 to 5,
The deliquescent material is at least one selected from sodium hydroxide (NaOH), potassium hydroxide (KOH), calcium chloride (CaCl ₂ ), magnesium chloride (MgCl ₂ ), and zinc chloride (ZnCl ₂ ) All-solid-state metal-air battery. According to any one of claims 1 to 5,
The all-solid-state metal-air battery, wherein the negative electrode is at least one metal selected from lithium (Li), sodium (Na), and alloys thereof. According to any one of claims 1 to 5,
The solid electrolyte is an all-solid metal-air battery made of a ceramic, a polymer, or a composite thereof having an ionic conductivity of 10 ⁻⁴ S/cm or more. According to any one of claims 1 to 5,
The positive electrode comprises a composite of a porous conductive material and the solid electrolyte, the all-solid metal-air battery. According to any one of claims 1 to 5,
The anode is made of Super P, carbon nanofibers, carbon nanotubes, graphene, nickel, cobalt, titanium, iron, copper, gold, platinum, silver, and transition metal oxides (AB1 _1-xyz B2 _x B3 _y B4 _z O ₂ , A is Li or Na, B is Al, Fe, V, Cr, Ti, W, Ta, and Mo, 0≤x<1, 0≤y<1, 0≤z<1, An all-solid metal-air battery comprising at least one selected from particles of 0≤ x + y + z ≤ 1).

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