KR101720417B1 - Zinc air battery comprising alkaline electrolyte containing zinc and tin ions - Google Patents

Abstract

The present invention relates to a negative electrode comprising a zinc plate or a metal zinc powder; A cathode made of air or oxygen; And an alkaline electrolyte containing zinc and tin ions.

Description

TECHNICAL FIELD [0001] The present invention relates to a zinc air battery including an alkaline electrolyte containing zinc and tin ions,

The present invention relates to an additive for suppressing dendritic growth of zinc during charging of a zinc air cell.

Despite the technical completion of the zinc air cell, the commercialization of electrically rechargeable zinc air cells has not yet been successful, mainly due to the poor charge / discharge performance of the zinc air battery. Possible causes of the low electrical charging capacity of the zinc air secondary battery, such as zinc corrosion, water consumption during charging and discharging, zinc oxide deposition, zinc dendritic growth, have been raised. Dendritic growth of the double zinc is a decisive factor.

Several inorganic additives such as CdO, PbO, Pb ₃ O ₄ , In ₂ O ₃ and Bi ₂ O ₃ have been tested for inhibiting dendritic growth during electrolytic plating of zinc. Dissolving this additive in water produces metal ions with a higher reduction potential than zinc. Thus, the metal elements in the additive can easily bind to zinc during the electrochemical reduction process and affect the zinc growth pattern. In particular, the effect of Pb is known to be large. Even very small amounts of Pb ions greatly inhibit both the resinous growth of zinc and the hydrogen evolution reaction. However, due to the potential hazards of Pb-containing materials, attempts to find suitable alternatives are ongoing.

The metal Sn has the reduction potential higher than that of Zn as well as the inorganic additives, and is environmentally friendly and economical. Sn ion is present in the electrolyte of the air zinc battery and it is possible to suppress the dendritic growth of Zn which occurs upon charging, it is possible to substitute existing additive having toxicity at low cost.

The present inventors have found that SnO is added to an alkali solution to successfully inhibit unstable dendritic growth when Zn is electroplated.

The present invention aims to suppress the dendritic growth of Zn during charging / discharging of a zinc air cell.

The present invention relates to a negative electrode comprising a zinc plate or a metal zinc powder; A cathode comprising a porous carbon material and an oxygen oxidation / reduction reaction catalyst; And an alkaline electrolyte containing zinc and tin ions.

The tin ions are obtained by adding SnO to the electrolyte, and the SnO is added by 10 < ^-3 > M or more. Preferably, the SnO 2 is added in an amount of 10 ^-3 M to 5 × 10 ^-3 M.

The zinc plate or powder of the negative electrode is characterized in that a tin atom partially forms a solid solution, and the tin has a tetragonal structure, and the zinc has a hexavalent dendritic structure.

The zinc air cell of the present invention adds a very small amount of SnO to the alkaline electrolyte to inhibit the resinous growth of zinc upon charging.

FIG. 1A shows the results of a cyclic voltammetry method obtained in an electrolyte having a different SnO content.
FIG. 1B is a graph showing that the increase in the amount of charge in the oxidized region and the increase in the amount of charge in the reduction region are similar in the cyclic voltammetry method of the embodiment of the present invention.
Figures 2a to d are the results as a microscope image of a Zn electrolytic thin film obtained by applying a constant current density of 40mA / cm ^2, showing the change in shape of the electrolytic Zn thin film according to the content of SnO is added in the electrolyte.
3A is a graph showing the relationship between the chemical depth profile and the chemical depth profile of the electrolytic plating layer prepared in an electrolyte containing 3 x 10 < ^-3 > M SnO, using dynamic SIMS analysis to further analyze the electrolytic plating layer produced when SnO was added. ).
FIG. 3B shows an X-ray diffraction pattern, showing a tetragonal structure of Sn and a typical hexavalent structure of Zn.
4 is a microscope image of the plated layer obtained in Example 7. Fig.

Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings. The present invention is capable of various modifications and various forms, and specific embodiments are illustrated in the drawings and described in detail in the text. It is to be understood, however, that the invention is not intended to be limited to the particular forms disclosed, but on the contrary, is intended to cover all modifications, equivalents, and alternatives falling within the spirit and scope of the invention. Like reference numerals are used for like elements in describing each drawing.

The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. The singular expressions include plural expressions unless the context clearly dictates otherwise. In this application, the terms "comprise", "having", and the like are used to specify that a feature, step, operation, element, component, or combination of features described in the specification is to be included and that one or more other features, And does not preclude the presence or addition of one or more other elements, components, components, parts, or combinations thereof.

Unless otherwise defined, all terms used herein, including technical or scientific terms, have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. Terms such as those defined in commonly used dictionaries should be construed in a manner consistent with meaning in the context of the relevant art and are not to be construed as an ideal or overly formal sense unless expressly defined in the present application.

All electrochemical experiments of the present invention were performed with a three-electrode electrochemical beaker cell. Nickel foil (Alfa Aeser, 99,9%) was polished with a 600 grid emery paper and rinsed with distilled water to serve as the working electrode substrate. This substrate was masked so that an area of 1 cm < ² > was exposed to the electrolyte. Pt wire and Hg / HgO electrode were used as the opposite electrode and reference electrode, respectively.

An electrolyte was prepared in which 0.4 M ZnO (Alfa Aeser, 99.99%) was dissolved in an aqueous solution of 6 M KOH (Junsei, 85%) and SnO (Alfa Aeser, 99.9%) was not added. -0.5 to -1.7 V vs. Cyclic voltammetry was performed at a scan rate of 1 mV / s in the voltage range of Hg / HgO. In addition, Zn electroplating was performed for 900 seconds at a constant current density of 40 mA / cm < ^{2 &} gt ;.

An electrolyte was prepared by dissolving 0.4 M ZnO (Alfa Aeser, 99.99%) in an aqueous solution of 6 M KOH (Junsei, 85%) and adding 10 ^-4 M SnO (Alfa Aeser, 99.9%). -0.5 to -1.7 V vs. Cyclic voltammetry was performed at a scan rate of 1 mV / s in the voltage range of Hg / Hgo. In addition, Zn electroplating was performed for 900 seconds at a constant current density of 40 mA / cm < ^{2 &} gt ;.

An electrolyte was prepared by dissolving 0.4 M ZnO (Alfa Aeser, 99.99%) in an aqueous solution of 6 M KOH (Junsei, 85%) and adding 10 ^-3 M SnO (Alfa Aeser, 99.9%). -0.5 to -1.7 V vs. Cyclic voltammetry was performed at a scan rate of 1 mV / s in the voltage range of Hg / Hgo. In addition, Zn electroplating was performed for 900 seconds at a constant current density of 40 mA / cm < ^{2 &} gt ;.

An electrolyte was prepared by dissolving 0.4 M ZnO (Alfa Aeser, 99.99%) in an aqueous solution of 6 M KOH (Junsei, 85%) and adding 2 × 10 ^-3 M SnO (Alfa Aeser, 99.9%). -0.5 to -1.7 V vs. Cyclic voltammetry was performed at a scan rate of 1 mV / s in the voltage range of Hg / Hgo. In addition, Zn electroplating was performed for 900 seconds at a constant current density of 40 mA / cm < ^{2 &} gt ;.

An electrolyte was prepared by dissolving 0.4 M ZnO (Alfa Aeser, 99.99%) in an aqueous solution of 6 M KOH (Junsei, 85%) and adding 3 × 10 ^-3 M SnO (Alfa Aeser, 99.9%). -0.5 to -1.7 V vs. Cyclic voltammetry was performed at a scan rate of 1 mV / s in the voltage range of Hg / Hgo. In addition, Zn electroplating was performed for 900 seconds at a constant current density of 40 mA / cm < ^{2 &} gt ;.

An electrolyte was prepared by dissolving 0.4 M ZnO (Alfa Aeser, 99.99%) in an aqueous solution of 6 M KOH (Junsei, 85%) and adding 5 × 10 ^-3 M SnO (Alfa Aeser, 99.9%). -0.5 to -1.7 V vs. Cyclic voltammetry was performed at a scan rate of 1 mV / s in the voltage range of Hg / Hgo. In addition, Zn electroplating was performed for 900 seconds at a constant current density of 40 mA / cm < ^{2 &} gt ;.

An electrolyte was prepared by dissolving 0.4 M ZnO (Alfa Aeser, 99.99%) in an aqueous solution of 6 M KOH (Junsei, 85%) and adding 10 ^-2 M SnO (Alfa Aeser, 99.9%). -0.5 to -1.7 V vs. Cyclic voltammetry was performed at a scan rate of 1 mV / s in the voltage range of Hg / Hgo. In addition, Zn electroplating was performed for 900 seconds at a constant current density of 40 mA / cm < ^{2 &} gt ;.

1. Evaluation Method

Iviumstat (Ivium Technologies, Netherlands) was used for all electrochemical experiments. The shape of the Zn plating layer was observed with a field emission scanning electron microscope (FESEM, MIRA3, TESCAN, Czech Republic), and its crystal structure was observed with an X-ray diffractometer (XRD, D8 Advance , Bruker, Germany). The chemical depth profile was measured using a dynamic secondary ion mass spectrometer (CAMECA IMS-6f Magnetic Sector SIMS, CAMECA, France), and the composition of the plated layer was confirmed by energy dispersive X-ray spectroscopy (EDS, APOLLO X, AMETEK, USA) , And its detection limit is in ppm-ppb range.

2. Results

FIG. 1A shows the results of a cyclic voltammetry method obtained in an electrolyte having a different SnO content. On the reduction side, when 10 ^-4 M SnO was added to the electrolyte, there was no significant difference from the results of the cyclic voltammetry method in the case where SnO 2 was not added. However, it can be seen that the electrochemical reaction (reduction reaction) is promoted when the addition amount of SnO is 10 ^-3 M or more.

At this time, the reaction in the reduction region is caused by the reduction of the metal ion (mainly zinc salt ion Zn (OH) ₄ ^2- and tin sulfate ion, Sn (OH) ₃ ^- ), hydrogen evolution and generation of hydroxyl ion As a result, it is confirmed that the electrochemical reaction in the reduction region is promoted as the amount of SnO is increased from 10 < ^-3 > However, it is not easy to determine which of the above-mentioned reduction of metal ions, hydrogen release, and reduction of hydroxyl ions is more dominant. However, it can be seen that as the content of SnO is increased from 10 ^-3 M, the oxidation reaction increases as well as the reduction reaction. This means that the reduction amount of the metal ion is increased. The comparison of the increase in the amount of charge in the oxidizing region and the amount of charge in the reducing region can be seen in FIG.

If SnO is added at a concentration equal to or greater than 10 ^-3 M, the reduction reaction of the metal ion is accelerated. If the SnO 2 content is less than 10 ^-3 M, the effect of the addition is almost zero.

Figures 2a to d are the results shows a microscope image of a Zn electrolytic thin film obtained by applying a constant current density of 40mA / cm ^2, the shape change of the electrolytic Zn thin film according to the content of SnO is added in the electrolyte. In the case of the Zn electrolytic thin film obtained in the case where SnO was not added (Example 1, Fig. 2A) and the electrolyte in which 10 ^-4 M SnO was added (Example 2, Fig. 2B), Zn resinous phases were unevenly grown . However, in the case of adding 10 ^-3 M SnO 2, it was confirmed that the prepared thin film (Example 3) was suppressed to a certain degree of heterogeneous resin phase (FIG. 2C). The inserted image in FIG. 2C shows a simplified rod shape. It can be confirmed that a relatively more uniform and flat electrolytic thin film layer was formed in the case of adding 3 × 10 ^-3 M SnO ² (Example 5, FIG. 2 d). 2 × 10 ^-3 and 5 × 10 ^-3 M SnO was added to the thin film of the same shape as in the case of adding 3 × 10 ^-3 M SnO although not shown in the figure.

In order to further analyze the electrolytic thin film in which dendritic growth of Zn is suppressed, a chemical depth profile is performed on a thin film formed in an electrolyte doped with 3 x 10 ^-3 M SnO ² using dynamic SIMS analysis , And the result is confirmed in Fig. 3A. The thin film is composed of plated Zn and Sn, and the measured content of Sn is 0.3 to 1.5 at%. Since the solid solubility of Zn in Zn is known to be extremely low (0.04 at%), it can be concluded that Sn atom partially forms a solid solution in the Zn matrix upon electrochemical reduction and at the same time forms a pure Sn phase. The X-ray diffraction pattern shows a typical hexagonal close-packed structure of Zn (see FIG. 3B), as well as a crystalline structure of Sn and a tetragonal structure of Sn. From these experimental results, it can be seen that the Sn plated with different metals has a considerable influence on the shape of zinc.

On the other hand, if the amount of SnO added is increased, it may be detrimental to the uniform growth of the Zn thin film. For example, it can be seen that the shape of the thin film (Example 7) made from an electrolyte doped with 10 ^-3 M SnO 2 is rough and porous over the entire surface (FIG. 4B). Due to the weak adhesion and strength of the thin film, the plating layer was completely broken or separated during washing and drying. From the compositional analysis (FIG. 4B), it can be seen that a large amount of Sn in the Zn thin film was detected at 7 at%. This shows that there is a large amount of secondary phase in the thin film, i.e., pure Sn, which can also be confirmed by an X-ray diffraction analysis pattern (FIG. 3B). The excessive amount of Sn phase formed in this electrolytic thin film is deduced to interfere conclusively with the uniform and dense formation of the Zn electrolytic thin film.

It will be apparent to those skilled in the art that various modifications and variations can be made in the present invention without departing from the spirit or scope of the present invention as defined by the following claims. It can be understood that it is possible.

Claims (5)

As the zinc ion, stannous ion and an alkaline electrolyte for a zinc-air electrode containing KOH, the tin ion is obtained by adding to the electrolyte a SnO, SnO is the addition of 10 ^-3 M to 5 × 10 ^-3 M, An alkaline electrolyte for a zinc air electrode, which inhibits formation of a zinc resin phase on a cathode during charge and discharge of the zinc air electrode, and simultaneously increases the reduction and oxidation reaction compared to the case where there is no Sn ion. A negative electrode made of zinc plate or metal zinc powder;
A cathode comprising a porous carbon material and an oxygen oxidation / reduction reaction catalyst;
A method for producing an alkaline electrolyte comprising the steps of:
Zinc air battery. delete 3. The method of claim 2,
Characterized in that in the zinc plate or powder of the negative electrode partly the tin atoms partially form solid solution,
Zinc air battery. 5. The method of claim 4,
The tin has a tetragonal structure,
Characterized in that the zinc has a hexavalent densified structure,
Zinc air battery.

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