Alkali metal-air chargeable battery

Abstract

The present application relates to an alkali metal-air rechargeable battery, comprising a battery cavity, the battery cavity is filled with an electrolyte, the electrolyte is selected from the group consisting of working temperature which can keep water in gaseous state, and is an alkali metal salt non-aqueous solution or molten alkali metal salt. The alkali metal-air rechargeable battery of the present application can prevent the contact between the alkali metal in the battery and oxygen and water, thereby avoiding the unnecessary chemical reaction of the alkali metal with active chemical properties after the contact, thereby threatening the use safety of the battery.

Description

Technical Field

[0001] This invention mainly relates to the structure of high-temperature chemical batteries, specifically to an alkali metal-air rechargeable battery. Background Technology

[0002] Most air batteries currently use aqueous electrolytes, such as aqueous solutions of alkaline metal hydroxides like KOH / NaOH or chlorides like KCl / NaCl. During the battery discharge reaction, air and water react at the positive terminal to produce OH-. - ion:

[0003] O2 + 2H2O + 4e - →4OH -

[0004] At the negative electrode of the battery, the metallic element M loses electrons and becomes the corresponding ion M. x+ (X is the valence charge of metal M), then in the electrolyte, the elemental M of the metal... x+ Ions and OH - Ion bonding. Metals such as aluminum, magnesium, zinc, iron, and tin combine with OH groups. - The products of these metals precipitate in water and have a very low degree of ionization, making it difficult to achieve complete reverse charging through ionization. Furthermore, the discharge process of air batteries containing these metals is mostly irreversible. Additionally, hydroxides of alkaline metals such as lithium, sodium, and potassium are highly soluble in water, but these metals are more reactive than elemental hydrogen. Electrolysis of aqueous solutions of these alkaline metal hydroxides only produces H2 at the negative electrode of the battery, without producing the corresponding elemental metal, making reversible charging of these air batteries difficult to achieve as well. Summary of the Invention

[0005] The main objective of this invention is to prevent the alkali metal elements generated during the charging process of alkali metal-air batteries from coming into contact with oxygen and water.

[0006] To achieve the above objectives, the present invention provides an alkali metal-air rechargeable battery, comprising a battery cavity filled with an electrolyte, wherein the electrolyte used is:

[0007] Selected from those with an operating temperature that keeps water in a gaseous state, and

[0008] It is an alkali metal salt in a non-aqueous solution or a molten alkali metal salt.

[0009] In some embodiments of the present invention, the battery cavity includes a negative electrode portion, a connecting portion, and a positive electrode portion. The lower portion of the negative electrode portion and the lower portion of the positive electrode portion are connected through the connecting portion. The upper portion of the negative electrode portion and the upper portion of the positive electrode portion are separated. The negative electrode is disposed in the upper portion of the negative electrode portion, and the positive electrode is disposed in the upper portion of the positive electrode portion.

[0010] In some embodiments of the present invention, the height of the positive electrode portion is higher than the height of the negative electrode portion, and the height of the electrolyte filling portion is higher than the height of the negative electrode portion, and the electrolyte fills both the negative electrode portion and the connecting portion.

[0011] In some embodiments of the present invention, the height of the electrolyte filling is also lower than the height of the positive electrode portion, so that a cavity is formed above the liquid surface of the electrolyte in the positive electrode portion.

[0012] In some embodiments of the present invention, an air inlet and an exhaust outlet are provided on the top of the positive electrode portion.

[0013] In some embodiments of the present invention, the positive and negative electrodes have porous structures.

[0014] In some embodiments of the present invention, a diaphragm body with OH- ion conduction properties is further included. The diaphragm body is disposed in conjunction with the lower part of the positive electrode portion and covers the communication position between the connecting portion and the positive electrode portion.

[0015] In some embodiments of the present invention, the diaphragm is a solid hydrotalcite.

[0016] In some embodiments of the present invention, the alkali metal salt includes an alkali metal hydroxide.

[0017] In some embodiments of the present invention, the alkali metal salt further includes one or more of alkali metal nitrates, alkali metal carbonates, alkali metal formates, and alkali metal acetates.

[0018] In some embodiments of the present invention, the solvent for the non-aqueous solution of the alkali metal salt is selected from one or more of ethylene carbonate, dimethyl sulfoxide, and sulfolane.

[0019] In some embodiments of the present invention, a heating mechanism is also included, which is thermally disposed with the battery cavity.

[0020] In some embodiments of the present invention, a heat insulation layer is provided outside the battery cavity.

[0021] The alkali metal-air rechargeable battery of the present invention can prevent the alkali metal in the battery from coming into contact with oxygen and water, thereby avoiding unnecessary chemical reactions that would threaten the safety of the battery after contact with the alkali metal, which has active chemical properties. Attached Figure Description

[0022] Figure 1 This is a schematic diagram of the structure of an alkali metal-air rechargeable battery.

[0023] In the diagram: 1. Negative electrode, 2. Positive electrode, 3. Separator, 4. Electrolyte, 110. Negative electrode section, 120. Connecting section, 130. Positive electrode section, 131. Air inlet, 132. Exhaust port, 133. Feed inlet. Detailed Implementation

[0024] The chemical principle of alkali metal-air rechargeable batteries is known. They mainly involve charge and discharge reactions at their respective electrode positions according to Formulas I to III, where the forward direction of Formulas I to III represents the discharge reaction and the reverse direction represents the charge reaction.

[0025] Negative electrode reaction:

[0026] Positive electrode reaction:

[0027] Overall reaction equation:

[0028] In the above reaction, M represents an alkali metal element.

[0029] During the charging process of alkali metal-air batteries, alkali metals, water, and oxygen are generated at the negative and positive electrodes, respectively. Alkali metals readily react with the water and oxygen produced, posing a safety hazard to the battery. For example, sodium reacts violently with water, generating sodium hydroxide and hydrogen gas. This reaction alone is enough to damage the battery, and the resulting hydrogen gas is flammable and explosive, making it equally dangerous.

[0030] To address the aforementioned problems, this invention provides a different internal battery structure to prevent the reaction of alkali metals with water and oxygen. The structure includes a battery chamber filled with an electrolyte, specifically:

[0031] Selected from those with an operating temperature that keeps water in a gaseous state, and

[0032] It is an alkali metal salt in a non-aqueous solution or a molten alkali metal salt.

[0033] The “operating temperature” of the electrolyte mentioned in this application refers to the temperature at which the electrolyte can stably perform its function as an electrolyte.

[0034] For the sake of brevity, "alkali metal-air rechargeable battery" will be referred to simply as "battery".

[0035] When the battery is in operation, the electrolyte keeps the water at the positive electrode in a gaseous state, thus preventing it from forming an aqueous solution with the alkali metal salt and then coming into contact with the alkali metal element at the negative electrode, causing a violent reaction and posing a danger to the battery.

[0036] To prevent alkali metals from contacting water and oxygen, a specific structure of the battery cavity includes a negative electrode section, a connecting section, and a positive electrode section. The lower parts of the negative electrode section and the lower parts of the positive electrode section are connected through the connecting section, while the upper parts of the negative electrode section and the upper parts of the positive electrode section are separated. The negative electrode is located at the upper part of the negative electrode section, and the positive electrode is located at the upper part of the positive electrode section. This battery cavity structure prevents alkali metals from contacting and reacting with water and oxygen by restricting the location where the positive and negative electrode reactions occur. During charging, alkali metals are generated at the upper part of the negative electrode section, while water and oxygen are generated at the upper part of the positive electrode section. Because the positive and negative electrode sections are connected at the bottom and separated at the top, the generated alkali metals are confined in the negative electrode section, while the water and oxygen are confined in the positive electrode section, thus effectively preventing contact and reaction between the two and ensuring battery safety.

[0037] The battery may further include a separator. In relevant chemical battery examples, the separator is generally used to separate the positive and negative electrodes to prevent short circuits within the battery; it is typically positioned between the positive and negative electrodes within the battery cavity. Based on this, the selection of the separator in this application is limited to separators with ion-conducting properties. Suitable separators include, but are not limited to, garnet-type solid electrolytes, NASICON-type solid electrolytes, and β-alumina solid electrolytes with alkali metal ion conductivity, and those with OH... - Solid hydrotalcites with ion conductivity and related known modified materials.

[0038] Furthermore, when using OH - In the case of a membrane with ion-conducting properties, one specific arrangement of the membrane is as follows: the membrane is fitted to the lower part of the positive electrode portion and covers the connection position between the connecting portion and the positive electrode portion. This type of membrane allows OH- to pass through during charging and discharging. - Ions can migrate freely and prevent water from flowing from the positive electrode to the negative electrode. One type of membrane with the above properties is solid hydrotalcite.

[0039] In this battery, both the positive and negative electrodes can have porous structures. Possible negative electrodes include, but are not limited to, electrodes made of foamed copper, graphite felt, or foamed nickel. The porous structure of the negative electrode provides a sufficiently large surface area for contact with the electrolyte, thereby increasing the rate of the negative electrode reaction. Possible positive electrodes include, but are not limited to, mesh or foam electrodes made of carbon nanotubes, carbon fibers, graphite felt, nickel, copper, silver, gold, or platinum. Based on the same principle as the porous negative electrode, the porous positive electrode can also increase the rate of the positive electrode reaction. The surface of the positive electrode can be further doped with small amounts of nitrogen (N), sulfur (S), phosphorus (P), or halogens (Cl), or with transition metal oxides such as nickel oxide (NiO) or cobalt oxide (CoO), or with catalysts such as iron-nickel (FeNi) or iron-cobalt (FeCo) metal hydroxides grown in situ on the surface. In addition, a certain amount of water-retaining materials such as sodium polyacrylate can be added to the positive electrode. This allows the material to absorb water vapor generated during charging and provide the necessary water vapor reaction raw materials during discharging.

[0040] In this battery, based on the required operating temperature and the limitations of the electrolyte category range proposed in this application (i.e., alkali metal salt non-aqueous solutions and molten and fused alkali metal salts), those skilled in the art can select the appropriate electrolyte according to its physicochemical properties. The following are some examples of selectable electrolytes: The alkali metal salt in the electrolyte generally includes alkali metal hydroxides, such as sodium hydroxide, potassium hydroxide, and lithium hydroxide. Since the discharge products of the battery are also alkali metal hydroxides, electrolytes containing this component can be well compatible with the discharge products and, as a supplement to the alkali metal source, improve the charge-discharge performance of the battery. Furthermore, the alkali metal salt may also include one or more of alkali metal nitrates, alkali metal carbonates, alkali metal formates, and alkali metal acetates. The above-mentioned alkali metal salts can improve the overall chemical stability of the electrolyte. When using an alkali metal salt non-aqueous solution as the electrolyte, the selected solvent includes, but is not limited to, one or more of ethylene carbonate, dimethyl sulfoxide, and sulfolane. These solvents have high boiling points and can meet the battery's operating temperature requirements. Furthermore, when the selected electrolyte's acceptable operating range includes the melting point of alkali metals, the alkali metal element generated at the negative electrode during charging can also be kept in a molten state by setting the battery's operating temperature, thereby preventing crystallization.

[0041] To prevent the battery temperature from dropping, heating mechanisms, insulation layers, etc., can be incorporated into the battery. The specific implementation methods are well understood by those skilled in the art. For example, the heating mechanism can be thermally integrated with the battery cavity. When the heating mechanism heats up, the heat is conducted through the battery cavity to the internal electrolyte, further ensuring that the electrolyte operates at the required temperature. The insulation layer can generally be formed or applied to the outer surface of the battery cavity through coating, encapsulation, or other methods to maintain the battery's temperature.

[0042] Figure 1 The figure illustrates one feasible structure of the aforementioned battery. The battery includes a battery cavity, which in this embodiment is made of 304 stainless steel. As shown, the battery cavity includes a negative electrode portion 110, a connecting portion 120, and a positive electrode portion 130. The lower part of the negative electrode portion 110 and the lower part of the positive electrode portion 130 are connected by the connecting portion 120. The upper part of the negative electrode portion is separated from the upper part of the positive electrode portion. The height of the negative electrode portion 110 is lower than the height of the positive electrode portion 130, so that the cross-section of the battery cavity in this example presents a U-shaped cavity with a lower left side and a higher right side. An air inlet 131, an exhaust outlet 132, and a feed inlet 133 are provided at the top of the positive electrode portion of the battery cavity. A foamed copper negative electrode 1 is provided in the upper part of the negative electrode portion 110 of the battery cavity. A separator 3, made of solid hydrotalcite material, is provided in the positive electrode portion 130. The separator 3 is positioned at the lower part of the positive electrode portion 130 and covers the communication position between the connecting portion 120 and the positive electrode portion 130. A graphite felt positive electrode 2 is provided above the separator 3. Molten sodium hydroxide is filled in the battery cavity, filling the negative electrode portion and the connecting portion. The liquid level in the positive electrode portion is slightly higher than that of the separator, so that the foamed copper negative electrode 1, the separator 3, and the graphite felt positive electrode 2 are wetted by electrolyte 4. A cavity is formed above the liquid surface of the electrolyte in the positive electrode portion. Molten sodium hydroxide can be poured in through the feed inlet 133, which is normally closed during battery operation. The air inlet can be connected in parallel with a pressure gas source for water vapor or oxygen, and the exhaust port is connected to a gas collection container. To ensure the battery's operating temperature, an electric heating element can be installed on the battery cavity to heat it. The electric heating element and the battery cavity can be further coated with polyimide resin foam material for insulation.

[0043] During battery charging, sodium ions from molten sodium hydroxide form molten sodium metal at the negative electrode, while hydroxide ions, through ion conduction via the separator, generate water and oxygen at the positive electrode. The molten sodium metal, due to the buoyancy of the molten sodium hydroxide, floats above the negative electrode portion of the battery cavity after its formation. The molten sodium hydroxide keeps the water generated at the positive electrode in a gaseous state, allowing it to escape through the upper vent. The separation between the upper portions of the positive and negative electrodes prevents water and oxygen from contacting and reacting.

[0044] The alkali metal-air rechargeable battery described in this application effectively prevents alkali metals from contacting water and air, ensuring the safety and stability of the battery. The battery structure of this application is easy to manufacture and has good prospects for electrochemical static energy storage applications.

[0045] The embodiments described in this invention are for illustrative purposes only and do not constitute a limitation on the scope of the claims. Other substantially equivalent substitutions that can be conceived by those skilled in the art are all within the scope of protection of this invention.

Claims

1. An alkali metal-air rechargeable battery, characterized in that... Includes a battery cavity, which is filled with electrolyte. The electrolyte used is: Selected from those with an operating temperature that keeps water in a gaseous state, and It is an alkali metal salt in a non-aqueous solution or a molten alkali metal salt. The battery cavity includes a negative electrode portion, a connecting portion, and a positive electrode portion. The lower part of the negative electrode portion and the lower part of the positive electrode portion are connected through the connecting portion. The upper part of the negative electrode portion and the upper part of the positive electrode portion are separated. The negative electrode is located in the upper part of the negative electrode portion, and the positive electrode is located in the upper part of the positive electrode portion. The height of the positive electrode portion is higher than the height of the negative electrode portion, and the electrolyte filling height is higher than the height of the negative electrode portion, filling both the negative electrode portion and the connecting portion.

2. The alkali metal-air rechargeable battery as described in claim 1, characterized in that... The electrolyte filling height is also lower than the height of the positive electrode, so that a cavity is formed above the electrolyte surface in the positive electrode.

3. The alkali metal-air rechargeable battery as described in claim 2, characterized in that... The top of the positive electrode is equipped with an air inlet and an exhaust outlet.

4. The alkali metal-air rechargeable battery as described in claim 1, characterized in that... The positive and negative electrodes have porous structures.

5. The alkali metal-air rechargeable battery as described in claim 1, characterized in that... It also includes a diaphragm, which has OH - Regarding ion conduction performance, the membrane body is disposed in conjunction with the lower part of the positive electrode portion and covers the connection position between the connecting portion and the positive electrode portion.

6. The alkali metal-air rechargeable battery as described in claim 5, characterized in that... The diaphragm is a solid hydrotalcite.

7. The alkali metal-air rechargeable battery as described in claim 1, characterized in that... Alkali metal salts include alkali metal hydroxides.

8. The alkali metal-air rechargeable battery as described in claim 7, characterized in that... Alkali metal salts also include one or more of alkali metal nitrates, alkali metal carbonates, alkali metal formates, and alkali metal acetates.

9. The alkali metal-air rechargeable battery as described in claim 1, characterized in that... The solvent for non-aqueous solutions of alkali metal salts is selected from one or more of ethylene carbonate, dimethyl sulfoxide, and sulfolane.

10. The alkali metal-air rechargeable battery as described in claim 1, characterized in that... It also includes a heating mechanism, which is arranged to transfer heat between the heating mechanism and the battery cavity.

11. The alkali metal-air rechargeable battery as described in claim 1, characterized in that... The battery cavity is provided with an insulation layer.

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