High-discharge-potential neutral aluminum air battery electrolyte based on iron ion additive

Abstract

The invention relates to a high-discharge-potential neutral aluminum-air battery electrolyte based on an iron ion additive, and belongs to the field of metal-air batteries. The electrolyte is prepared by mixing an additive and a sodium chloride solution, and can be directly used for the aqueous aluminum air battery. The process is simple, preparation is convenient, and the green chemical requirement is met. Under the condition of room temperature, the preparation of the electrolyte can be completed by dissolving iron ion (Fe < 3 + >) salt with a certain concentration in a sodium chloride solution. The obtained electrolyte is applied to an aluminum air battery, and compared with a traditional neutral aluminum air battery electrolyte (sodium chloride), the discharge potential is obviously improved. Under the current density of 1mA cm <-2 >, the discharge voltage of the aluminum air battery using the aluminum air battery is 1.25 V, and the energy density can reach 2190.3 Wh kg <-1 >. And the discharge voltage of the aluminum air battery using the traditional neutral aluminum air electrolyte (sodium chloride) is only 0.75 V, and the energy density of the aluminum air battery is only 1055.59 Wh kg <-1 >. The discharge potential of an aluminum negative electrode is greatly improved, and the aluminum air battery based on the electrolyte shows excellent energy density, so that the multifunctional mixed electrolyte provided by the invention has a remarkable application prospect.

Description

Technical Field

[0001] The present invention belongs to the field of metal-air batteries, and specifically relates to a method for preparing and applying a multifunctional electrolyte that can significantly improve the discharge potential of an aluminum-air battery, and the multifunctional electrolyte can be used as an electrolyte for a high-energy-density neutral aluminum-air battery. Background Art

[0002] Aluminum-air batteries are mainly composed of three basic parts: aluminum negative electrode, air positive electrode and electrolyte. They have many advantages such as high theoretical energy density, abundant raw material reserves and low cost, and environmental friendliness. Therefore, they have broad application prospects in many fields, such as electric vehicles, portable power supplies and distributed power generation. However, in practical applications, neutral aluminum-air batteries face a series of problems that need to be solved. Sodium chloride is widely used in neutral aluminum-air battery electrolytes due to its abundance and safety. However, based on the sodium chloride neutral electrolyte system, a dense aluminum hydroxide passivation layer will be generated on the surface of the aluminum negative electrode. This passivation layer seriously hinders the further dissolution of aluminum and the electron transfer process, causing the battery to produce serious polarization, the working voltage drops sharply, and the discharge efficiency also decreases significantly. In addition, during the continuous discharge of aluminum-air batteries, due to the appearance of low-solubility discharge products such as aluminum hydroxide, a large amount of precipitation will gradually form on the electrode surface and in the electrolyte. At the same time, the discharge solid phase products will continue to accumulate. These situations will cause a series of problems, such as the instability of the discharge voltage of aluminum-air batteries and the serious lack of utilization of aluminum negative electrodes.

[0003] The key to improving the energy density of neutral aluminum-air batteries is to effectively regulate the aluminum negative electrode electrolyte interface reaction, so as to achieve uniform stripping of aluminum. At present, some studies have pointed out that alloying pure aluminum with specific elements can effectively destroy the original passivation layer and enhance the electrochemical activity of the aluminum negative electrode. However, this alloying method has obvious drawbacks. Its process is complicated and the energy consumption is high during the production process, which is extremely unfavorable for the commercial production and application of aluminum-air batteries. In contrast, the method of suppressing the side reactions at the aluminum metal negative electrode interface through electrolyte regulation and thus achieving stable aluminum metal stripping has important application value and research significance. Summary of the invention

[0004] The present invention aims to solve the above existing technical problems and aims to provide a method for preparing a neutral aluminum-air battery electrolyte with high discharge potential based on iron ion additives and its application. The preparation process is simple and meets the requirements of green chemistry. The obtained electrolyte exhibits excellent discharge potential and is an aqueous aluminum-air battery electrolyte with application prospects.

[0005] The high discharge potential neutral aluminum-air battery electrolyte based on iron ion additive is a mixed solution of iron ion salt and sodium chloride, wherein the iron ion in the iron ion salt is Fe3+ .

[0006] Furthermore, the iron ions Fe 3+ The concentration of sodium chloride solution is 0.005-0.5 mol / L, and the concentration of sodium chloride solution is 1-10 mol / L.

[0007] Furthermore, the iron ion salt is one or more of acetate, chloride, sulfate, nitrate, and trifluoromethylsulfonate.

[0008] Furthermore, the negative electrode of the aluminum-air battery is a pure aluminum sheet, an aluminum rod or an aluminum alloy; the positive electrode is biomass activated carbon or porous carbon.

[0009] Furthermore, the types of aluminum-air batteries include: liquid flow aluminum-air batteries, button batteries, and Swagelok batteries.

[0010] Different from the widely used sodium chloride electrolyte, the present invention regulates the inorganic additives of the neutral aluminum-air battery electrolyte, based on the hydrolysis and oxidation of iron ions, so that the composite electrolyte has high ionic conductivity, which can fully activate the aluminum negative electrode in an open system, alleviate the problem of increased internal polarization of the battery caused by the passivation layer, and accelerate the electrochemical reaction rate. The prepared electrolyte can be directly used in different types of aluminum-air battery devices and shows significant performance improvement. At 1mAcm -2 At a current density of , the energy density of the aluminum-air battery based on the electrolyte can reach 2190.3Wh / kg, while the energy density of the aluminum-air battery based on the traditional electrolyte sodium chloride is only 1055.59Wh / kg under the same conditions. The process of the present invention is simple, the preparation speed is fast and it meets the requirements of green chemistry, and it effectively improves the discharge depth of the aluminum metal negative electrode and the energy density of the aluminum-air battery. Therefore, the present invention has significant economic value and practical application potential. BRIEF DESCRIPTION OF THE DRAWINGS

[0011] Figure 1 Schematic diagram of a multifunctional electrolyte aluminum-air battery with high discharge potential in Example 1 of the present invention.

[0012] Figure 2 1 is a comparison of the discharge voltage of aluminum-air batteries using a multifunctional electrolyte in Example 1 of the present invention.

[0013] Figure 3 This is the X-ray diffraction test diagram of the aluminum negative electrode after discharge of the multifunctional electrolyte aluminum-air battery in Example 1 of the present invention.

[0014] Figure 4 This is a scanning electron microscope test image of the rear aluminum negative electrode of the multifunctional electrolyte aluminum-air battery in Example 1 of the present invention.

[0015] Figure 5 This is an X-ray diffraction test diagram of the aluminum negative electrode after discharge of the aluminum-air battery using sodium chloride electrolyte in Example 1 of the present invention.

[0016] Figure 6 This is a scanning electron microscope test image of the aluminum negative electrode after discharge of the aluminum-air battery using sodium chloride electrolyte in Example 1 of the present invention.

[0017] Figure 7 Graph showing the discharge voltage comparison of aluminum-air batteries using a multifunctional electrolyte in Example 2 of the present invention.

[0018] Figure 8 Graph showing the discharge voltage comparison of aluminum-air batteries using a multifunctional electrolyte in Example 3 of the present invention.

[0019] Specific example method

[0020] Example 1

[0021] A method for preparing a neutral aluminum-air battery electrolyte with a high discharge potential based on an iron ion additive and its application, comprising:

[0022] (1) Prepare a clear sodium chloride solution with a concentration of 2 mol / L, weigh a certain amount of iron ion salt and dissolve it in the sodium chloride solution so that the iron ion concentration is 0.1 mol / L. The added ion salt is chloride salt.

[0023] (2) The prepared orange-yellow solution is evenly mixed to serve as an electrolyte for aqueous aluminum-air batteries.

[0024] (3) Take 5 ml of the prepared electrolyte and add it to the aluminum-air battery. The negative electrode is a polished pure aluminum sheet with a thickness of 0.15 mm and an active area of ​​1 cm 2 The positive electrode is a homemade air electrode, which is mainly composed of activated carbon YP50, carbon paper, waterproof and breathable membrane, and nickel foam. After the battery is assembled, an electrochemical test is carried out, and the discharge depth is calculated based on the mass change of the aluminum sheet before and after discharge.

[0025] Taking this embodiment as an example, the schematic diagram of the optimization mechanism of the battery system in the aluminum-air battery of the present invention is shown in the attached figure. Figure 1 As shown. In the traditional neutral electrolyte sodium chloride, a dense aluminum hydroxide passivation layer will be formed on the surface of the aluminum negative electrode. The electrolyte after adding the iron ion additive can effectively destroy the passivation layer on the surface of the negative electrode through the protons generated by the hydrolysis of iron ions, and reduce the generation of solid phase products. When the electrolyte prepared in this embodiment is used as the electrolyte of the aluminum-air battery, Figure 2 It can be seen that at 1 mA cm -2At a current density of 1.26 V, the aluminum-air battery based on the mixed electrolyte can achieve a discharge potential of 1.26 V in the electrolyte and can stably discharge for 70 h (discharge depth of 58.3%) with a specific capacity of 1738.3 mAh g -1 , the energy density can reach 2190.3Wh kg -1 The continuous discharge time of the traditional sodium chloride electrolyte is only 60h (discharge depth 47.23%), and the discharge voltage is as low as 0.75V. Its energy density is 1055.59Wh kg -1 Therefore, it can be proved that the mixed electrolyte with the addition of iron ions effectively alleviates the passivation of the aluminum negative electrode and significantly improves the discharge potential of the aluminum negative electrode, achieving excellent discharge performance, and is an aqueous aluminum-air battery electrolyte with application prospects.

[0026] Figure 3 It is the X-ray diffraction diagram of the aluminum negative electrode after discharge of the aluminum-air battery using the electrolyte of the present invention. All characteristic diffraction peaks belong to aluminum metal (JCPDS No.001-1176), and there is no obvious passivation layer of solid phase product Al(OH)3 (JCPDS No.077-0117) generated by discharge on the electrode surface. Figure 4 This is a scanning electron microscope test image of the aluminum negative electrode after 20 hours of discharge of the aluminum-air battery using the electrolyte of the present invention. It can be seen that the surface of the aluminum negative electrode is stable and flat, and there is no excess solid phase product. This phenomenon shows that the electrolyte of the present invention can reduce the solid phase byproducts generated during the discharge process of the neutral aluminum-air battery and reduce the polarization of the aluminum negative electrode caused by the passivation layer. Figure 5 As shown in the figure, in contrast, the X-ray diffraction pattern of the single sodium chloride electrolyte after discharge has a strong Al(OH)3 diffraction peak, and the scanning microscope image shows that there are more dense solid phase products on the surface of the aluminum negative electrode ( Figure 6 ), which is consistent with the problems existing in traditional neutral aluminum-air batteries mentioned above.

[0027] Example 2

[0028] A method for preparing a neutral aluminum-air battery electrolyte with a high discharge potential based on an iron ion additive and its application, comprising:

[0029] (1) Prepare a clear sodium chloride solution with a concentration of 2 mol / L, weigh a certain amount of iron ion salt and dissolve it in the sodium chloride solution so that the iron ion concentration is 0.05 mol / L. The added ion salt is chloride salt.

[0030] (2) The prepared light yellow solution is evenly mixed to serve as an electrolyte for aqueous aluminum-air batteries.

[0031] (3) Take 5 ml of the prepared electrolyte and add it to the aluminum-air battery. The negative electrode is a polished aluminum alloy sheet with a thickness of 0.15 mm and an active area of ​​1 cm 2 .

[0032] The air positive electrode preparation process and the flow battery discharge test process are consistent with those in Example 1.

[0033] Taking the multifunctional electrolyte obtained in this embodiment as an example, the discharge performance is compared with Figure 7 The discharge potential of the aluminum-air battery using the electrolyte of this example is 0.8V, which is only 0.05V higher than that of the traditional sodium chloride electrolyte. This is because the concentration of iron ions is insufficient, the protons produced by hydrolysis are limited, and the activation of the aluminum negative electrode is insufficient, resulting in a limited increase in the discharge potential.

[0034] Example 3

[0035] A method for preparing a neutral aluminum-air battery electrolyte with a high discharge potential based on an iron ion additive and its application, comprising:

[0036] (1) Prepare a clear sodium chloride solution with a concentration of 2 mol / L, weigh a certain amount of iron ion salt and dissolve it in the sodium chloride solution so that the iron ion concentration is 0.5 mol / L. The added ion salt is chloride salt.

[0037] (2) The prepared deep red solution is evenly mixed to serve as an electrolyte for aqueous aluminum-air batteries.

[0038] (3) Take 5 ml of the prepared electrolyte and add it to the aluminum-air battery. The negative electrode is a polished aluminum alloy sheet with a thickness of 0.15 mm and an active area of ​​1 cm 2 .

[0039] The air positive electrode preparation process and the flow battery discharge test process are consistent with those in Example 1.

[0040] Taking the multifunctional electrolyte obtained in this embodiment as an example, the performance improvement effect of aqueous aluminum-air battery is as follows: Figure 8 It can be seen that although the initial discharge voltage is 1.2V, its discharge potential is unstable. This is because too many iron ions cause the solution pH to be lower than the pH at which aluminum metal can exist stably, resulting in a strong hydrogen evolution reaction at its interface and insufficient utilization of the aluminum negative electrode. The traditional sodium chloride electrolyte also confirms the above view.

[0041] Example 4

[0042] A method for preparing a neutral aluminum-air battery electrolyte with a high discharge potential based on an iron ion additive and its application, comprising:

[0043] (1) Prepare a clear sodium chloride solution with a concentration of 2 mol / L, weigh a certain amount of iron ion salt and dissolve it in the sodium chloride solution so that the iron ion concentration is 0.1 mol / L. The added ion salt is sulfate.

[0044] (2) The prepared orange-yellow solution is evenly mixed to serve as an electrolyte for aqueous aluminum-air batteries.

[0045] (3) Take 5 ml of the prepared electrolyte and add it to the aluminum-air battery. The negative electrode is a polished pure aluminum sheet with a thickness of 0.15 mm and an active area of ​​1 cm 2 The positive electrode is a homemade air electrode, which is mainly composed of activated carbon YP50, carbon paper, waterproof and breathable membrane, and nickel foam. After the battery is assembled, an electrochemical test is carried out, and the discharge depth is calculated based on the mass change of the aluminum sheet before and after discharge.

[0046] Taking the multifunctional mixed ion electrolyte obtained in this embodiment as an example, the performance improvement effect of the aqueous aluminum-air battery is similar to that in Embodiment 1.

[0047] Example 5

[0048] A method for preparing a neutral aluminum-air battery electrolyte with a high discharge potential based on an iron ion additive and its application, comprising:

[0049] (1) Prepare a clear sodium chloride solution with a concentration of 2 mol / L, weigh a certain amount of iron ion salt and dissolve it in the sodium chloride solution so that the iron ion concentration is 0.1 mol / L. The added ion salt is trifluoromethanesulfonate.

[0050] (2) The prepared orange-yellow solution is evenly mixed to serve as an electrolyte for aqueous aluminum-air batteries.

[0051] (3) Take 5 ml of the prepared electrolyte and add it to the aluminum-air battery. The negative electrode is a polished aluminum-magnesium metal sheet with a thickness of 0.25 mm and an active area of ​​1 cm 2 .

[0052] The air positive electrode preparation process and the flow battery discharge test process are consistent with those in Example 1.

[0053] Taking the multifunctional mixed ion electrolyte obtained in this embodiment as an example, the performance improvement effect of the aqueous aluminum-air battery is similar to that in Embodiment 1.

[0054] Example 6

[0055] A method for preparing a neutral aluminum-air battery electrolyte with a high discharge potential based on an iron ion additive and its application, comprising:

[0056] (1) Prepare a clear sodium chloride solution with a concentration of 2 mol / L, weigh a certain amount of iron ion salt and dissolve it in the sodium chloride solution so that the iron ion concentration is 0.1 mol / L. The added ion salt is acetate.

[0057] (2) The two prepared cationic solutions are uniformly mixed to form an electrolyte for an aqueous aluminum-air battery.

[0058] (3) Take 5 ml of the prepared electrolyte and add it to the aluminum-air battery. The negative electrode is a polished aluminum-zinc metal sheet with a thickness of 0.25 mm and an active area of ​​2 cm 2 .

[0059] The air positive electrode preparation process and the flow battery discharge test process are consistent with those in Example 1.

[0060] Taking the multifunctional mixed ion electrolyte obtained in this embodiment as an example, the performance improvement effect of the aqueous aluminum-air battery is similar to that in Embodiment 1.

[0061] Although implementation cases have been listed and described in detail here, those skilled in the art will appreciate that various improvements, additions, substitutions, etc. may be made without departing from the core content of the present invention, and these contents are considered to be within the scope of the present invention as defined by the claims.

Claims

1. A high discharge potential neutral aluminum-air battery electrolyte based on an iron ion additive, the electrolyte being a mixed solution of an iron ion salt and sodium chloride, wherein the iron ion in the iron ion salt is Fe 3+ .

2. A high discharge potential neutral aluminum-air battery electrolyte based on iron ion additives as claimed in claim 1, characterized in that: The iron ions Fe 3+ The concentration of sodium chloride solution is 0.005-0.5 mol / L, and the concentration of sodium chloride solution is 1-10 mol / L.

3. The high discharge potential neutral aluminum-air battery electrolyte based on iron ion additive according to claim 1, characterized in that: The iron ion salt is one or more of acetate, chloride, sulfate, nitrate and trifluoromethylsulfonate.

4. The high discharge potential neutral aluminum-air battery electrolyte based on iron ion additive according to claim 1, characterized in that: The negative electrode of the aluminum-air battery is a pure aluminum sheet, an aluminum rod or an aluminum alloy; the positive electrode is biomass activated carbon or porous carbon.

5. The high discharge potential neutral aluminum-air battery electrolyte based on iron ion additive according to claim 1, characterized in that: The types of aluminum-air batteries include: liquid flow aluminum-air batteries, button batteries, and Swagelok batteries.

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