Electrolyte additive and application thereof in aqueous zinc battery

Abstract

The invention discloses an electrolyte additive and application thereof, and particularly relates to application in an aqueous zinc battery. The electrolyte additive is trans-aconitic acid (TAA), the trans-aconitic acid and electrolyte salt are added into water to form an electrolyte, and the electrolyte is applied to the aqueous zinc battery. The trans-aconitic acid is used as an electrolyte additive, so that the electrolyte is safe and environment-friendly; the trans-aconitic acid molecule contains three carboxylic acid groups and one unsaturated double bond, has strong coordination ability with metal ions, can effectively regulate and control the solvation structure of the metal ions, and can participate in formation of a stable solid electrolyte interface, inhibition of side reaction and the like; the electrolyte containing the trans-aconitic acid as the additive is applied to the water-based zinc battery and has remarkable effects on hydrogen evolution reaction, corrosion inhibition, zinc dendrite growth and the like of the battery, and the water-based zinc battery with super-long cycle life is obtained.

Description

Technical Field

[0001] The present invention belongs to the field of new energy batteries, and particularly relates to an electrolyte additive and its application in aqueous zinc batteries. Background Art

[0002] With the advancement of global energy transformation, efficient and safe energy storage technology has become one of the hottest research areas. Lithium batteries have been widely used in many fields, such as electric vehicles and electronic equipment markets. However, lithium batteries also face a series of severe challenges such as poor safety performance and shortage of lithium resources. Aqueous batteries have gradually attracted attention because they use aqueous electrolytes with high safety, low cost, and simple assembly process (no need to use a glove box). Rechargeable aqueous zinc ion batteries (AZIBs) have the following advantages: (1) High theoretical specific capacity (820mAh g -1 ); (2) low reduction potential (-0.76V vs. SHE); (3) zinc is more abundant on Earth than lithium and has a lower cost. Therefore, AZIBs have attracted extensive attention from researchers at home and abroad in recent years.

[0003] Although the aqueous electrolyte used in aqueous zinc batteries offers advantages such as low cost, good safety, and high ionic conductivity, the presence of a large amount of active water in the aqueous electrolyte causes the water to decompose into hydrogen ions and hydroxide ions. The hydrogen ions undergo a hydrogen evolution reaction during charging, producing hydrogen gas, which can cause battery bulging and pose a safety hazard. The hydrogen evolution reaction causes the pH to rise, and the hydroxide ions react with zinc ions, sulfate ions, and water molecules to form corrosion products such as Zn4SO4(OH)6·xH2O. Furthermore, the uneven distribution of nucleation sites easily forms zinc tips. Due to the strong electric field at the tips, zinc ions are attracted to continue depositing at the tips, causing them to grow and form zinc dendrites. These dendrites can then pierce the separator, causing the battery to short-circuit. Therefore, addressing the hydrogen evolution reaction, corrosion reaction, and dendrite issues at the zinc anode is particularly urgent.

[0004] The electrolyte acts as a bridge connecting the cathode and anode, providing the necessary channels for ion transport. The key issues of aqueous zinc batteries are closely related to the performance of the electrolyte. Therefore, in order to solve these problems and ensure that the battery has good electrochemical performance, researchers have carried out research on the modification of aqueous zinc battery electrolytes, including the selection and optimization of electrolyte salts, high-concentration electrolytes and electrolyte additives. Among them, electrolyte additives have gradually become one of the most promising modification measures due to their wide selection, low cost and simple process. Electrolyte additives are required to solve the problems of hydrogen evolution reaction, corrosion reaction and dendrites of the zinc negative electrode while retaining the advantages of aqueous electrolytes such as low cost, safety and environmental protection. Summary of the Invention

[0005] The purpose of the present invention is to provide an electrolyte additive and obtain a low-cost electrolyte containing the additive by a simple method, and apply the electrolyte additive to aqueous zinc batteries to solve the dendrite problem and side reaction problems existing in the negative electrode of aqueous zinc batteries, thereby obtaining aqueous zinc batteries with long cycle life.

[0006] The present invention achieves the purpose of the invention through the following technical solutions.

[0007] The present invention first provides an electrolyte additive, which is a food additive trans-aconitic acid (TAA for short), and has a chemical formula of C6H6O6.

[0008] The present invention also provides an electrolyte containing the above additive, wherein the electrolyte comprises the above additive trans-aconitic acid, an electrolyte salt and water.

[0009] Preferably, the concentration of the additive trans-aconitic acid in the electrolyte is 0.0006-0.05 M. Furthermore, the electrolyte salt includes one or more of zinc sulfate, zinc bromide, zinc chloride, zinc trifluoromethanesulfonate, and zinc nitrate.

[0010] Preferably, the concentration of the electrolyte salt in the electrolyte is 1-6M.

[0011] Furthermore, the present invention proposes the use of the aforementioned electrolyte containing the additive trans-aconitic acid in an aqueous zinc battery, achieving a long cycle life for the aqueous zinc battery. Specifically, the aforementioned electrolyte is used as the electrolyte for an aqueous zinc battery and assembled with a positive electrode, a negative electrode, and a separator to form an aqueous zinc battery.

[0012] Preferably, in a specific application example of the present invention, the positive electrode of the aqueous zinc battery is manganese-based oxide, vanadium-based oxide, organic compound, Prussian blue analogue, carbon felt or graphite felt; the negative electrode is metallic zinc or a zinc metal alloy.

[0013] The trans-aconitic acid used in the present invention as an electrolyte additive is safe and environmentally friendly: trans-aconitic acid is an intermediate metabolite of the tricarboxylic acid cycle and is a C6 unsaturated tricarboxylic acid that is safe for consumption. It is naturally present in many plants, such as sugarcane and wheat, or exists in certain foods as a natural ingredient. For example, it can be detected in by-products of the sugar industry, such as molasses.

[0014] The present invention applies trans-aconitic acid as an additive in an electrolyte for the first time. The trans-aconitic acid molecule contains three carboxylic acid groups (-COOH) and one unsaturated double bond, which has a strong coordination ability with metal ions, regulates the solvation structure of metal ions, and can also participate in the formation of a stable solid electrolyte interface (SEI), inhibit side reactions, etc.; and when trans-aconitic acid is used as an additive in the electrolyte of an aqueous battery, the carboxyl group interacts with water molecules through hydrogen bonding, etc., so that it plays a role in the battery's hydrogen evolution reaction, corrosion inhibition, etc. For example, in an application example of the present invention, an electrolyte containing the additive trans-aconitic acid is used in an aqueous zinc battery. The specific role of the electrolyte in the operation of the aqueous zinc battery can be summarized as follows: the additive trans-aconitic acid TAA contains a carboxyl functional group, which has a large binding energy with zinc ions and replaces part of the water molecules in the solvation structure of the zinc ions, reducing the number of water molecules in the solvation structure of the zinc ions, inhibiting the hydrogen evolution reaction of the zinc negative electrode, alleviating the corrosion of the zinc negative electrode, and facilitating the desolvation process; the carboxyl functional group in the additive TAA bonds to the water molecules through hydrogen bonds, destroying the hydrogen bond network between water molecules, and preventing hydrogen ions from being transported to the surface of the zinc negative electrode through the hydrogen bond network to undergo a hydrogen evolution reaction; The additive TAA is adsorbed on the surface of the zinc negative electrode by virtue of the high affinity of the carboxyl functional group with zinc. During the charging process, it accepts electrons and partially decomposes the TAA to generate a solid electrolyte intermediate phase (SEI layer) in situ. The SEI layer protects the zinc electrode; while other undecomposed additives TAA will be adsorbed on the SEI layer to protect the SEI layer and maximize the effect of the SEI layer; in addition, those undecomposed additives TAA adsorbed on the SEI layer can also interact with water molecules, bind the water molecules to the TAA surface, prevent direct contact between the water molecules and the zinc electrode, and inhibit side reactions; at the same time, the undecomposed additives TAA adsorbed on the SEI layer can also make Zn 2+ When passing through TAA adsorbed on SEI, the diffusion mode at the solid / liquid interface is three-dimensional diffusion. TAA induces uniform zinc deposition and effectively inhibits the generation and growth of zinc dendrites.

[0015] The technical solution of the present invention embodies the following beneficial effects:

[0016] The trans-aconitic acid used in the present invention as an electrolyte additive is safe and environmentally friendly. Moreover, the electrolyte containing the additive is simple to prepare, does not require a complicated process, and has high repeatability.

[0017] The present invention uses an electrolyte containing trans-aconitic acid as an additive in an aqueous zinc battery, effectively inhibiting zinc dendrite growth and hydrogen evolution reaction, alleviating zinc negative electrode corrosion, and achieving an aqueous zinc battery with a long cycle life. For example, in one embodiment of the present invention, the cycle life of the aqueous zinc battery reaches 7,400 hours. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 The figure is a scanning electron microscopy (SEM) image of surface zinc deposition of an aqueous zinc symmetric battery prepared using the electrolyte of Example 1 after cycling.

[0019] Figure 2 This is a scanning electron microscopy (SEM) image of surface zinc deposition of an aqueous zinc symmetric battery prepared using the electrolyte of Comparative Example 1 after cycling.

[0020] Figure 3 This is a cycle life diagram of an aqueous zinc symmetric battery prepared using the electrolyte of Example 1.

[0021] Figure 4 This is a cycle life diagram of an aqueous zinc symmetric battery prepared using the electrolyte of Example 2.

[0022] Figure 5 This is a cycle life diagram of an aqueous zinc symmetric battery prepared using the electrolyte of Comparative Example 1. DETAILED DESCRIPTION

[0023] The present invention is further described below with reference to specific embodiments, but the scope of the present invention is not limited thereto.

[0024] Example 1

[0025] 1) Preparation of electrolyte: Dissolve 0.0006 mol of trans-aconitic acid and 0.2 mol of zinc sulfate in 100 mL of deionized water, and then ultrasonically disperse for 10 minutes to completely dissolve the solution to obtain 100 mL of electrolyte containing 2 M zinc sulfate and 0.006 M trans-aconitic acid.

[0026] 2) Preparation of zinc electrode: Clean the surface of commercial zinc foil (thickness 100 μm) and cut into φ

[0027] 11.3mm discs are made into zinc electrodes.

[0028] 3) Assembling an aqueous zinc battery: Place the positive electrode shell on the laboratory bench with the inner surface facing up, and place the zinc electrode, separator, zinc electrode, and gasket in order. Then, drip the above-mentioned electrolyte to completely wet the separator. Then, cover the negative electrode shell and package it on a button cell packaging machine to obtain an aqueous zinc symmetrical battery.

[0029] Example 2

[0030] 0.00015 mol of trans-aconitic acid and 0.2 mol of zinc sulfate were dissolved in 100 mL of deionized water, and then ultrasonically dispersed for 10 minutes to completely dissolve them, thereby obtaining 100 mL of an electrolyte solution containing 2 M zinc sulfate and 0.0015 M of trans-aconitic acid.

[0031] The surface of commercial zinc foil was cleaned and cut into discs to make zinc electrodes.

[0032] Place the positive electrode shell with the inner surface facing up on the laboratory bench, and place the zinc electrode, diaphragm, zinc electrode and gasket in sequence. Then drip the above-mentioned electrolyte to completely wet the diaphragm. Then cover the negative electrode shell and package it on a button battery packaging machine to obtain an aqueous zinc symmetrical battery.

[0033] Example 3

[0034] 0.0015 mol of trans-aconitic acid and 0.2 mol of zinc sulfate were dissolved in 100 mL of deionized water, and then ultrasonically dispersed for 10 minutes to completely dissolve them, thereby obtaining 100 mL of an electrolyte solution containing 2 M zinc sulfate and 0.015 M of trans-aconitic acid.

[0035] The surface of commercial zinc foil was cleaned and cut into discs to make zinc electrodes.

[0036] Place the positive electrode shell with the inner surface facing up on the laboratory bench, and place the zinc electrode, diaphragm, zinc electrode and gasket in sequence. Then drip the above-mentioned electrolyte to completely wet the diaphragm. Then cover the negative electrode shell and package it on a button battery packaging machine to obtain an aqueous zinc symmetrical battery.

[0037] Example 4

[0038] 0.005 mol of trans-aconitic acid and 0.2 mol of zinc sulfate were dissolved in 100 mL of deionized water, and then ultrasonically dispersed for 10 minutes to completely dissolve them, thereby obtaining 100 mL of an electrolyte solution containing 2 M zinc sulfate and 0.05 M trans-aconitic acid.

[0039] The surface of commercial zinc foil was cleaned and cut into discs to make zinc electrodes.

[0040] Place the positive electrode shell with the inner surface facing up on the laboratory bench, and place the zinc electrode, diaphragm, zinc electrode and gasket in sequence. Then drip the above-mentioned electrolyte to completely wet the diaphragm. Then cover the negative electrode shell and package it on a button battery packaging machine to obtain an aqueous zinc symmetrical battery.

[0041] Example 5

[0042] 0.00006 mol of trans-aconitic acid and 0.2 mol of zinc sulfate were dissolved in 100 mL of deionized water, and then ultrasonically dispersed for 10 minutes to completely dissolve them, thereby obtaining 100 mL of an electrolyte solution containing 2 M zinc sulfate and 0.0006 M of trans-aconitic acid.

[0043] The surface of commercial zinc foil was cleaned and cut into discs to make zinc electrodes.

[0044] Place the positive electrode shell with the inner surface facing up on the laboratory bench, and place the zinc electrode, diaphragm, zinc electrode and gasket in sequence. Then drip the above-mentioned electrolyte to completely wet the diaphragm. Then cover the negative electrode shell and package it on a button battery packaging machine to obtain an aqueous zinc symmetrical battery.

[0045] Example 6

[0046] 0.0006 mol of trans-aconitic acid and 0.1 mol of zinc sulfate were dissolved in 100 mL of deionized water, and then ultrasonically dispersed for 10 minutes to completely dissolve them, thereby obtaining 100 mL of an electrolyte solution containing 1 M zinc sulfate and 0.006 M of trans-aconitic acid.

[0047] The surface of commercial zinc foil was cleaned and cut into discs to make zinc electrodes.

[0048] Place the positive electrode shell with the inner surface facing up on the laboratory bench, and place the zinc electrode, diaphragm, zinc electrode and gasket in sequence. Then drip the above-mentioned electrolyte to completely wet the diaphragm. Then cover the negative electrode shell and package it on a button battery packaging machine to obtain an aqueous zinc symmetrical battery.

[0049] Example 7

[0050] 0.0006 mol of trans-aconitic acid and 0.6 mol of zinc sulfate were dissolved in 100 mL of deionized water, and then ultrasonically dispersed for 10 minutes to completely dissolve them, thereby obtaining 100 mL of an electrolyte solution containing 6 M zinc sulfate and 0.006 M of trans-aconitic acid.

[0051] The surface of commercial zinc foil was cleaned and cut into discs to make zinc electrodes.

[0052] Place the positive electrode shell with the inner surface facing up on the laboratory bench, and place the zinc electrode, diaphragm, zinc electrode and gasket in sequence. Then drip the above-mentioned electrolyte to completely wet the diaphragm. Then cover the negative electrode shell and package it on a button battery packaging machine to obtain an aqueous zinc symmetrical battery.

[0053] Example 8

[0054] 0.0006 mol of trans-aconitic acid, 0.2 mol of zinc sulfate and 0.01 mol of manganese sulfate were dissolved in 100 mL of deionized water, and then ultrasonically dispersed for 10 minutes to completely dissolve them, thereby obtaining 100 mL of an electrolyte solution containing 2 M zinc sulfate, 0.1 M manganese sulfate and 0.006 M of trans-aconitic acid.

[0055] The surface of commercial zinc foil is cleaned and cut into discs to make zinc electrodes. MnO2, Super P carbon and polyvinylidene fluoride are mixed in N-methylpyrrolidone solvent to prepare a slurry. The resulting slurry is then scraped onto carbon paper and dried to obtain a MnO2 positive electrode. The positive electrode is cut into discs. The inner surface of the positive electrode shell is placed on the laboratory bench with the upper surface facing up. The MnO2 positive electrode, diaphragm, zinc electrode and gasket are placed in order. The above-mentioned electrolyte is then dripped in to completely wet the diaphragm. The negative electrode shell is then covered and packaged on a button cell packaging machine to obtain an aqueous zinc full battery.

[0056] Comparative Example 1

[0057] 1) Dissolve 0.2 mol of zinc sulfate in 100 mL of deionized water, and then ultrasonically disperse it for 10 minutes to completely dissolve it, to obtain 100 mL of electrolyte containing 2 M zinc sulfate.

[0058] 2) Clean the surface of commercial zinc foil and cut it into discs to make zinc electrodes.

[0059] 3) Place the positive electrode shell with the inner surface facing up on the laboratory bench, and place the zinc electrode, separator, zinc electrode and gasket in order. Then, drip the above-mentioned electrolyte to completely wet the separator. Then, cover the negative electrode shell and package it on a button cell packaging machine to obtain the aqueous zinc symmetrical battery of this comparative example.

[0060] The aqueous zinc symmetrical batteries of the above-mentioned embodiments and comparative examples were subjected to cycle tests. Under the same test conditions, the surface of the zinc electrode after the cycle was observed using SEM. The observation results clearly show that: the conventional electrolyte used in the comparative example will form a large number of zinc dendrites on the surface of the zinc electrode after the cycle; while the aqueous zinc electrode batteries of the embodiments, due to the addition of different concentrations of trans-aconitic acid TAA in their electrolytes, the growth of zinc dendrites on the surface of the zinc electrode after the cycle is significantly suppressed. Figure 1 This is a scanning electron microscopy (SEM) image of surface zinc deposition in an aqueous zinc symmetric battery prepared using the electrolyte of Example 1 after cycling. It can be seen that the surface is smooth and zinc dendrites are effectively suppressed. Figure 2 This is a scanning electron micrograph (SEM) of zinc deposition on the surface of an aqueous zinc symmetric battery prepared using the electrolyte from Comparative Example 1 after cycling. The image shows the presence of numerous dendrites on the zinc electrode surface. This demonstrates that trans-aconitic acid (TAA) attached to the SEI in the electrolyte induces uniform zinc ion deposition across the solid-liquid interface, effectively suppressing the formation and growth of zinc dendrites.

[0061] The aqueous zinc symmetrical batteries of the above embodiments and comparative examples were subjected to cycle life tests. Figure 3 、 Figure 4 , respectively, the aqueous zinc symmetric battery of Example 1 and Example 2 at 1 mA cm -2 The current density and 1 mAh cm-2 The cycle life test diagram under the area capacity of 10000 h is shown in the figure. It can be seen that the aqueous zinc symmetric battery in Example 1 has a cycle life of more than 7400 h, and the aqueous zinc symmetric battery in Example 2 has a stable cycle life of more than 7100 h. Figure 5 The cycle life of the aqueous zinc symmetric battery of Comparative Example 1 is shown in Figure 1. -2 The current density and 1 mAh cm -2 At an area capacity of 1.5 Å, the battery in Comparative Example 1 short-circuited after less than 90 hours of cycling. This demonstrates that trans-aconitic acid (TAA) in the electrolyte effectively inhibits zinc dendrite growth and side reactions, confirming the effectiveness of the trans-aconitic acid additive in improving zinc battery performance and achieving a long cycle life for aqueous zinc batteries.

[0062] In summary, the present invention proposes the introduction of trans-aconitic acid as an additive into aqueous zinc battery electrolytes, demonstrating remarkable effectiveness in suppressing zinc dendrites and side reactions. This method is simple to operate, safe, and environmentally friendly, and aqueous zinc batteries prepared using the electrolyte of the present invention exhibit high cycling stability.

Claims

1. An electrolyte additive, characterized in that: The additive is trans-aconitic acid, and its chemical formula is C6H6O6.

2. An electrolyte, characterized in that: The electrolyte comprises the additive trans-aconitic acid according to claim 1, an electrolyte salt and water.

3. An electrolyte according to claim 2, characterized in that: The concentration of the additive trans-aconitic acid in the electrolyte is 0.0006-0.05M.

4. An electrolyte according to claim 2, characterized in that: The electrolyte salt includes one or more of zinc sulfate, zinc bromide, zinc chloride, zinc trifluoromethanesulfonate, and zinc nitrate.

5. An electrolyte according to claim 4, characterized in that: The concentration of the electrolyte salt in the electrolyte solution is 1-6M.

6. An aqueous zinc battery, characterized in that: The components of the aqueous zinc battery include the electrolyte according to any one of claims 2 to 5.

7. The aqueous zinc battery according to claim 6, characterized in that: The aqueous zinc battery further includes a positive electrode, a negative electrode and a separator.

8. The aqueous zinc battery according to claim 7, characterized in that: The positive electrode is a manganese-based oxide, a vanadium-based oxide, an organic compound, a Prussian blue analogue, carbon felt or graphite felt.

9. The aqueous zinc battery according to claim 7, characterized in that: The negative electrode is metallic zinc or a metal alloy of zinc.

10. The aqueous zinc battery according to claim 7, characterized in that: The aqueous zinc battery has a long cycle life, and the long cycle life means that the aqueous Zn||Zn symmetrical battery has a cycle life of 1 mA cm -2 The current density and 1 mAh cm -2 The cycle life under the area capacity reaches more than 7000 hours.

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