Multifunctional mixed ion electrolyte capable of remarkably improving discharge depth of aluminum metal negative electrode

Abstract

The invention relates to a multifunctional mixed ion electrolyte capable of remarkably improving the discharge depth of an aluminum metal negative electrode, and belongs to the field of metal-air batteries. The electrolyte can be directly used for a water-based aluminum air battery. The process is simple, preparation is convenient, and the green chemical requirement is met. Under the condition of room temperature, two cation salts of ammonium ions (NH4 +) and manganese ions (Mn < 2 + >) are used for preparing a mixed solution with a certain concentration, so that the preparation of the electrolyte can be completed. The obtained electrolyte is applied to the aluminum air battery, and compared with a traditional neutral aluminum air battery electrolyte (sodium chloride), the energy density is obviously improved. Under the current density of 1mA cm <-2 >, the discharge depth of the aluminum air battery using the material is 84.5%, and the specific capacity can reach 2516.5 mAh / g. And the discharge depth of the aluminum air battery using the traditional neutral aluminum air electrolyte (sodium chloride) is 47.23%, and the specific capacity is lower than 1500mAh / g. The discharge depth of the aluminum negative electrode is greatly improved, so that the aluminum air battery based on the mixed electrolyte shows excellent discharge capacity. The mixed ion 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 a neutral electrolyte that can significantly improve the discharge depth of an aluminum metal negative electrode (i.e., the utilization rate of an aluminum metal negative electrode) and its application, which 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 discharge potential, abundant raw material reserves, and green environmental protection. Therefore, they have become one of the strong candidates for the next generation of energy storage devices. In neutral aluminum-air batteries, sodium chloride is widely used as neutral aluminum-air battery electrolyte due to its abundance and safety. However, based on the sodium chloride neutral electrolyte system, a dense passivation layer will be generated on the surface of the aluminum negative electrode to hinder ion diffusion and the subsequent discharge process. In addition, as the discharge continues, the low-solubility discharge product aluminum hydroxide will produce a large amount of precipitation on the electrode surface and in the electrolyte, and the discharge solid phase product will accumulate. The above problems will lead to problems such as unstable discharge voltage of aluminum-air batteries and serious insufficient utilization of aluminum negative electrodes. Therefore, how to effectively regulate the interface reaction of aluminum negative electrode electrolyte and achieve uniform stripping of aluminum is the key to improving the energy density of neutral aluminum-air batteries. Although some studies have shown that alloying pure aluminum with specific elements can effectively destroy the original passivation layer and improve the electrochemical activity of aluminum negative electrodes. However, the alloying method is complex and energy consuming, which is not conducive to the commercial production and application of aluminum-air batteries. In contrast, the use of electrolyte regulation to suppress the side reactions at the aluminum metal negative electrode interface and achieve stable aluminum metal stripping has very important application value and research significance. Summary of the invention

[0003] The present invention aims to solve the above existing technical problems and to provide a method for preparing a multifunctional mixed ion electrolyte and its application that significantly improves the discharge depth of aluminum metal negative electrodes. The preparation process is simple and meets the requirements of green chemistry. The obtained electrolyte exhibits excellent discharge potential and specific capacity and is an aqueous aluminum-air battery electrolyte with application prospects.

[0004] A multifunctional mixed ion electrolyte which can significantly improve the discharge depth of an aluminum metal negative electrode. The electrolyte is a mixed ion solution formed by dissolving an ammonium salt and a manganese salt in deionized water.

[0005] Furthermore, the concentration of ammonium ions in the mixed ion solution is 0.1 to 10 mol / L, and the concentration of manganese ions is 0.1 to 10 mol / L.

[0006] Further, the ratio of ammonium ions to manganese ions is 0.5 to 5.

[0007] Furthermore, the types of the ammonium salt and the manganese salt are one or more of acetate, chloride, sulfate, nitrate, and trifluoromethylsulfonate.

[0008] Furthermore, the aluminum metal negative electrode is a pure aluminum sheet, an aluminum rod or an aluminum alloy.

[0009] Furthermore, the electrolyte is applied to aqueous aluminum-air batteries, including liquid flow aluminum-air batteries and Swagelok aluminum-air batteries.

[0010] Different from the widely used sodium chloride electrolyte, the present invention modifies the neutral aluminum-air battery electrolyte cations. Based on the mixed hydrolysis of ammonium ions and manganese ions, the composite electrolyte has high ionic conductivity, which can fully activate the aluminum negative electrode in an open system, prevent the appearance of a 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 1mA cm -2 At a current density of , the energy density of the aluminum-air battery based on the electrolyte can reach 2433.5Wh / kg, while the energy density of the aluminum-air battery based on the traditional electrolyte sodium chloride is only 1071.09Wh / 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 the activation mechanism of the composite electrolyte with high energy density in Example 1 of the present invention;

[0012] Figure 2 This is a comparison of the discharge depth of the aluminum-air battery using the mixed electrolyte in Example 1 of the present invention;

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

[0014] Figure 4 This is a scanning electron microscope test image of the aluminum negative electrode after using the mixed electrolyte aluminum-air battery in Example 1 of the present invention;

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

[0017] Figure 7 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;

[0018] Figure 8 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;

[0019] Fig. 9 1 is a comparison of the discharge depth of the Swagelok type aluminum-air battery using the mixed electrolyte in Example 1 of the present invention.

[0020] Specific Examples In order to better understand the present invention, the present invention is described below with reference to specific examples, but the present invention is not limited to the following examples.

[0021] Example 1

[0022] A preparation method and application of a multifunctional mixed ion electrolyte that significantly improves the discharge depth of an aluminum metal negative electrode, comprising:

[0023] (1) A 2 mol / L manganese ion-containing clarified salt solution and a 2 mol / L ammonium ion-containing clarified salt solution are prepared respectively, wherein the added ionic salt is chloride.

[0024] (2) The two prepared cationic solutions are uniformly mixed to form an aqueous aluminum-air battery electrolyte.

[0025] (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.

[0026] Taking this embodiment as an example, the schematic diagram of the activation mechanism of the aluminum negative electrode in the aluminum-air battery of the present invention is shown in the attached figure. Figure 1 As shown. In the traditional neutral electrolyte, a dense aluminum hydroxide passivation layer will be formed on the surface of the aluminum negative electrode. The protons generated by the double hydrolysis of the mixed electrolyte of manganese ions and ammonium ions can effectively destroy the passivation layer on the surface of the negative electrode 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 1mAcm -2At a current density of , the aluminum-air battery based on the mixed electrolyte can achieve deep discharge in the electrolyte (84.51%). The stable discharge is 102h, and the specific capacity is 2516.5mAh / g, which is close to the theoretical specific capacity. The continuous discharge time of the traditional sodium chloride electrolyte is only 63h (discharge depth 47.23%), and the pure ammonium chloride can also achieve an increase in the discharge depth (63.8%). Therefore, it can be proved that the mixed electrolyte composed of manganese ions and ammonium ions effectively alleviates the passivation of the aluminum negative electrode and significantly improves the discharge depth of the aluminum negative electrode, achieving excellent discharge performance. It is an aqueous aluminum-air battery electrolyte with application prospects.

[0027] Figure 3 This is the X-ray diffraction diagram of the aluminum negative electrode after discharge of the aluminum-air battery using a composite electrolyte. 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) produced 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 using a mixed electrolyte aluminum-air battery. It can be seen that there are only loose and fine solid products on the surface of the aluminum negative electrode, and the surface of the aluminum negative electrode is smooth. This phenomenon shows that the mixed electrolyte can reduce the solid byproducts generated by the neutral aluminum-air battery during the discharge process and avoid the resulting passivation layer that hinders the discharge depth of the aluminum negative electrode. Figure 5 As shown in Figure 2, for comparison, the X-ray diffraction pattern of the single ammonium chloride electrolyte after discharge is similar to that of the mixed electrolyte, with no obvious Al(OH)3 diffraction peak. Figure 6 As shown in the scanning electron microscope test image, it can be seen that the Al(OH)3 generated on the surface of the aluminum negative electrode has increased significantly, and the morphology is flaky and densely distributed. The X-ray diffraction of the aluminum negative electrode of the aluminum-air battery based on sodium chloride electrolyte after discharge ( Figure 7 ) and scanning test graph, it can be seen that there is a strong Al(OH)3 characteristic peak in the X-ray diffraction peak, and the scanning microscope shows that there are more dense solid phase products on the surface of the aluminum negative electrode, which is consistent with the problems of the traditional neutral aluminum-air battery mentioned above. Fig. 9 As shown, in the lean-liquid-based Swagelok battery, the mixed-ion electrolyte also has the effect of increasing the depth of discharge, from 14% to 24%, indicating a wide range of applicability in different types of batteries.

[0028] Example 2

[0029] A preparation method and application of a multifunctional mixed ion electrolyte that significantly improves the discharge depth of an aluminum metal negative electrode, comprising:

[0030] (1) A clear salt solution containing manganese ions at a concentration of 0.5 mol / L and a clear salt solution containing ammonium ions at a concentration of 1 mol / L are prepared respectively, wherein the ionic salt added is acetate.

[0031] (2) The two prepared cationic solutions are uniformly mixed to form an aqueous aluminum-air battery electrolyte.

[0032] (3) Take 10 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 0.2 mm and an active area of ​​1 cm 2 .

[0033] The air positive electrode preparation process and the flow battery discharge test process are consistent with those in Example 1.

[0034] 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.

[0035] Example 3

[0036] A preparation method and application of a multifunctional mixed ion electrolyte that significantly improves the discharge depth of an aluminum metal negative electrode, comprising:

[0037] (1) A clear salt solution containing manganese ions at a concentration of 2 mol / L and a clear salt solution containing ammonium ions at a concentration of 0.5 mol / L are prepared respectively, wherein the added ion salt is nitrate.

[0038] (2) The two prepared cationic solutions are uniformly mixed to form an aqueous aluminum-air battery electrolyte.

[0039] (3) Take 3 ml of the prepared electrolyte and add it to the aluminum-air battery. The negative electrode is a polished pure aluminum metal sheet with a thickness of 0.2 mm and an active area of ​​1 cm 2 .

[0040] The air positive electrode preparation process and the flow battery discharge test process are consistent with those in Example 1.

[0041] 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.

[0042] Example 4

[0043] A preparation method and application of a multifunctional mixed ion electrolyte that significantly improves the discharge depth of an aluminum metal negative electrode, comprising:

[0044] (1) A clear salt solution containing manganese ions at a concentration of 0.5 mol / L and a clear salt solution containing ammonium ions at a concentration of 0.5 mol / L are prepared respectively, wherein the added ionic salt is chloride.

[0045] (2) The two prepared cationic solutions are uniformly mixed to form an aqueous aluminum-air battery electrolyte.

[0046] (3) Take 5 ml of the prepared electrolyte and add it to the aluminum-air battery. The negative electrode is a polished pure aluminum metal sheet with a thickness of 0.25 mm and an active area of ​​1 cm 2 .

[0047] The air positive electrode preparation process and the flow battery discharge test process are consistent with those in Example 1.

[0048] 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.

[0049] Example 5

[0050] A preparation method and application of a multifunctional mixed ion electrolyte that significantly improves the discharge depth of an aluminum metal negative electrode, comprising:

[0051] (1) A clear salt solution containing manganese ions at a concentration of 0.2 mol / L and a clear salt solution containing ammonium ions at a concentration of 0.2 mol / L are prepared respectively, wherein the added ionic salt is trifluoromethanesulfonate.

[0052] (2) The two prepared cationic solutions are uniformly mixed to form an aqueous aluminum-air battery electrolyte.

[0053] (3) Take 3 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 .

[0054] The air positive electrode preparation process and the flow battery discharge test process are consistent with those in Example 1.

[0055] 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.

[0056] Example 6

[0057] A preparation method and application of a multifunctional mixed ion electrolyte that significantly improves the discharge depth of an aluminum metal negative electrode, comprising:

[0058] (1) A clear salt solution containing manganese ions at a concentration of 0.5 mol / L and a clear salt solution containing ammonium ions at a concentration of 0.5 mol / L are prepared respectively, wherein the added ionic salt is sulfate.

[0059] (2) The two prepared cationic solutions are uniformly mixed to form an aqueous aluminum-air battery electrolyte.

[0060] (3) Take 3 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 .

[0061] The air positive electrode preparation process and the flow battery discharge test process are consistent with those in Example 1.

[0062] 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.

[0063] 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 multifunctional mixed ion electrolyte that significantly improves the discharge depth of aluminum metal negative electrodes, the electrolyte being a mixed ion solution formed by dissolving ammonium salt and manganese salt in deionized water.

2. A multifunctional mixed ion electrolyte for significantly improving the discharge depth of aluminum metal negative electrode as claimed in claim 1, characterized in that: The concentration of ammonium ions in the mixed ion solution is 0.1 to 10 mol / L, and the concentration of manganese ions is 0.1 to 10 mol / L.

3. The multifunctional mixed ion electrolyte for significantly improving the discharge depth of aluminum metal negative electrode according to claim 1, characterized in that: The ratio of ammonium ion to manganese ion is 0.5 to 5.

4. The multifunctional mixed ion electrolyte for significantly improving the discharge depth of aluminum metal negative electrode according to claim 1, characterized in that: The types of the ammonium salt and the manganese salt are one or more of acetate, chloride, sulfate, nitrate and trifluoromethylsulfonate.

5. The multifunctional mixed ion electrolyte for significantly improving the discharge depth of aluminum metal negative electrode according to claim 1, characterized in that: The aluminum metal negative electrode is pure aluminum sheet, aluminum rod or aluminum alloy.

6. The multifunctional mixed ion electrolyte for significantly improving the discharge depth of aluminum metal negative electrode according to claim 1, characterized in that: The electrolyte is applied to aqueous aluminum-air batteries, including liquid flow aluminum-air batteries and Swagelok aluminum-air batteries.

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