Aqueous zinc metal battery electrolyte and applications thereof

Abstract

The application discloses a kind of aqueous zinc metal battery electrolyte and application thereof, belong to new energy battery field.The electrolyte of the application is composed of soluble zinc salt, succinic acid and water, the concentration of the soluble zinc salt is 1~5mol / kg, the concentration of the succinic acid is 0.01~0.5mol / kg.The aqueous zinc metal battery electrolyte provided by the application first uses succinic acid as electrolyte additive, which has strong adsorption and desolvation between zinc ions in electrolyte Dual role, both solve the hydrogen evolution, corrosion, passivation and dendrite and other problems existing in zinc negative electrode in aqueous electrolyte, also improve the charge-discharge efficiency of battery, battery capacity and electrochemical performance such as cycle stability.

Description

Technical Field

[0001] This invention belongs to the field of new energy batteries, specifically relating to an aqueous zinc metal battery electrolyte and its application. Background Technology

[0002] In recent years, aqueous zinc-ion batteries have been widely studied by researchers as a next-generation energy storage system. Compared with traditional organic energy storage systems, aqueous electrolyte systems offer strong competitiveness, with the following main advantages: (1) Low cost: Due to the characteristics of aqueous electrolytes, the assembly of aqueous zinc-ion batteries does not require oxygen-free drying conditions, resulting in lower electrolyte costs; (2) Green and environmentally friendly: Using water as a solvent can effectively avoid environmental pollution problems caused by organic solutions; (3) High ionic conductivity: The ionic conductivity of aqueous electrolytes is ~0.1 S cm⁻¹. −1 The ionic conductivity of non-aqueous electrolytes is ~1-10 mS / cm. −1 (4) High safety. Because water-based electrolyte has a flame-retardant effect, water-based zinc-ion batteries will not cause violent explosions and combustion like organic electrolytes even when short circuits or other faults occur, thus effectively ensuring the safety of the energy storage system.

[0003] On the negative electrode side of zinc-ion batteries, metallic zinc is an ideal negative electrode material for aqueous zinc-ion batteries, exhibiting a low redox potential (-0.762V vs. standard hydrogen electrode) and a high theoretical capacity (820 mAh g⁻¹). -1 5855 mAh cm -3 Zinc electrodes, with their high reserves and low toxicity, have been extensively studied by researchers. However, their severe irreversibility in aqueous electrolytes leads to low coulombic efficiency and significant capacity loss. Generally, zinc electrodes in aqueous electrolytes mainly suffer from hydrogen evolution, corrosion, and passivation problems. The best approach to solving these problems is to develop a suitable electrolyte system, and additives are a convenient and simple method. Currently, commonly used additives include organic additives and metal ion additives.

[0004] Patent application number 201810208545.X discloses an electrolyte for an aqueous zinc-ion secondary battery, comprising soluble zinc salt, nickel salt, pH buffer, and deionized water. Patent application number 202110075837.2 discloses a low-cost aqueous zinc-ion battery electrolyte, including soluble zinc salt and fluoride salt additives. Patent application number 202111481938.6 discloses an aqueous zinc-ion battery electrolyte, comprising monosodium glutamate, zinc salt, and water. While these electrolytes can inhibit zinc dendrite growth to some extent, they do not effectively solve problems such as hydrogen evolution, corrosion, and passivation of the zinc electrode in aqueous electrolytes. Summary of the Invention

[0005] In view of the shortcomings of the prior art, the purpose of this invention is to provide an aqueous zinc metal battery electrolyte for application in the field of new energy batteries.

[0006] The specific technical solution is as follows:

[0007] An aqueous zinc metal battery electrolyte is composed of soluble zinc salt, succinic acid and water.

[0008] Existing organic additives mainly adsorb onto the zinc electrode surface through adsorption, forming an organic molecular interface layer. However, while this interface layer suppresses zinc dendrite formation, it also typically inhibits the kinetics of zinc ions at the electrolyte-zinc electrode interface, exhibiting a large polarization voltage and reducing conductivity. In this invention, succinic acid, a carboxylic acid-containing organic compound, is used as an electrolyte additive. This gives the zinc ion solvation shell a negative electrostatic potential, enabling it to adsorb zinc ions during the electrochemical deposition process. This improves the kinetics of zinc ions in the electrolyte, and the strong adsorption also prevents the two-dimensional diffusion of zinc ions on the zinc electrode surface, causing them to be reduced to metallic zinc upon arrival at the zinc electrode surface, thus enhancing the kinetics of zinc ions at the electrolyte-zinc electrode interface.

[0009] As a preferred embodiment of the above technical solution, the concentration of the soluble zinc salt is 1~5 mol / kg; the concentration of the succinic acid is 0.01~0.5 mol / kg.

[0010] Furthermore, the concentration of the soluble zinc salt is 1.5~4 mol / kg; the concentration of the succinic acid is 0.05~0.3 mol / kg.

[0011] Furthermore, the concentration of the soluble zinc salt is preferably 2 mol / kg; the concentration of the succinic acid is preferably 0.1 mol / kg.

[0012] As a preferred embodiment of the above technical solution, the soluble zinc salt is one or more selected from zinc sulfate, zinc trifluoromethanesulfonate, zinc bis[bis(trifluoromethanesulfonyl)imide], zinc tetrafluoroborate, and zinc acetate. Preferably, the soluble zinc salt is zinc sulfate.

[0013] Another objective of this invention is to provide the application of the above-mentioned aqueous electrolyte in zinc metal batteries.

[0014] The zinc metal battery of the present invention comprises a positive electrode, a negative electrode, a separator, and an electrolyte, wherein the electrolyte is the aqueous zinc metal battery electrolyte described above.

[0015] As a preferred embodiment of the above technical solution, the positive electrode is composed of an active material, a conductive agent, and a binder; the negative electrode is any one of zinc foil, zinc powder, or elemental zinc; and the diaphragm is any one of glass fiber or a porous filter membrane.

[0016] Furthermore, the active material of the positive electrode is K. 0.27 Any one of MnO2·0.54H2O, V2O5, MnO2, or Na3VO4.

[0017] In summary, the present invention has the following beneficial effects:

[0018] 1. This invention introduces succinic acid as an additive into the electrolyte, which can effectively adjust the solvation shell structure of zinc ions in the aqueous electrolyte, changing the solvation shell structure of zinc ions in the aqueous electrolyte to [Zn(H2O)4(succinic acid)]. 2+ The reduction of water molecules can alleviate the hydrogen evolution reaction in aqueous electrolytes, and at the same time, it has a significant inhibitory effect on the corrosion and passivation reaction on the surface of zinc metal anode, thereby improving the deposition / stripping efficiency of zinc metal anode (>99%).

[0019] 2. The addition of succinic acid molecules changes the electrostatic potential of the zinc ion solvation shell, resulting in a more negative potential at the location of the succinic acid molecules. This makes the solvation shell structure containing succinic acid molecules have a stronger adsorption capacity for zinc ions. During the zinc ion deposition process, it can induce zinc ions to be uniformly deposited on the zinc metal surface. At the same time, the strong adsorption also inhibits the two-dimensional diffusion of zinc ions on the zinc metal anode surface, causing the reduction reaction to occur at the original deposition location. This achieves the purpose of inhibiting the formation of zinc dendrites, obtaining a dendrite-free zinc metal anode, and extending the cycle life of the zinc metal anode.

[0020] 3. This invention provides an aqueous zinc metal battery electrolyte, which for the first time uses succinic acid as an electrolyte additive. Succinic acid has a strong adsorption effect and a desolvation effect with zinc ions in the electrolyte. It can solve the problems of hydrogen evolution, corrosion, passivation and dendrite formation of zinc anode in aqueous electrolyte, and improve the electrochemical performance of battery such as charge and discharge efficiency, battery capacity and cycle stability. Attached Figure Description

[0021] Figure 1 This is a comparison chart of the voltage windows of the electrolyte in Example 1;

[0022] Figure 2 Comparison of linear polarization curves of zinc metal anode in the electrolyte of Example 1;

[0023] Figure 3 In-situ optical images of the zinc ion deposition process in the electrolyte of Example 1, (a) target electrolyte, (b) blank electrolyte;

[0024] Figure 4 This is a comparison chart of the chronoampere readings of the zinc metal negative electrode in the electrolyte of Example 1;

[0025] Figure 5 SEM images of the zinc anode surface after the Zn||Zn symmetric cell was circulated 10 times in the electrolyte of Example 1: (a) target electrolyte; (b) blank electrolyte.

[0026] Figure 6 A comparison of the coulombic efficiency of the Zn||Cu half-cell in the electrolyte of Example 1;

[0027] Figure 7 A comparison of cycle time and voltage for Zn||Zn symmetric cells in the electrolyte of Example 1;

[0028] Figure 8 For Zn||K 0.27 Cyclic capacity and coulombic efficiency of MnO2·0.54H2O full cell in the target electrolyte of Example 1. Detailed Implementation

[0029] The technical solution of the present invention will be further described below with reference to specific embodiments. However, the specific details of the embodiments are only for illustrating the present invention and do not represent all technical methods under the concept of the present invention. Therefore, they should not be construed as limiting the overall technical solution of the present invention.

[0030] Example 1

[0031] An aqueous zinc metal battery electrolyte is prepared by dissolving 2 mol of zinc sulfate and 0.1 mol of succinic acid in ultrapure water to prepare a target electrolyte containing 2 mol / kg zinc sulfate and 0.1 mol / kg succinic acid.

[0032] To prepare the blank electrolyte, 2 mol of zinc sulfate was dissolved in ultrapure water to prepare a blank electrolyte containing 2 mol / kg zinc sulfate.

[0033] a. Electrolyte performance analysis

[0034] 1) Hydrogen evolution capability. A standard CR2032 coin cell was fabricated using titanium foil as the working electrode, zinc foil as the counter and reference electrodes, and glass fiber as the separator, with 80 μL of electrolyte added. Cyclic scanning voltammetry (CV) was used to test the cell, with a scan rate set to 1 mV / s and a test voltage range of -0.1 to 0.5 V. Data was recorded using an Autolab electrochemical workstation, and the test results are as follows: Figure 1 As shown.

[0035] The results show that the target electrolyte can effectively inhibit the hydrogen evolution reaction in the aqueous electrolyte. This is mainly because the addition of maleic succinic acid can regulate the solvation shell structure of zinc ions in the aqueous electrolyte. In the blank electrolyte, the solvation shell structure of zinc ions is [Zn(H₂O)₆]. 2+ The structure, with a high water molecule content, tends to undergo hydrogen evolution reaction at low potentials. By adding succinic acid to the electrolyte, the solvation shell structure of zinc ions changes to [Zn(H₂O)₄(succinic acid)] 2+ The number of water molecules is reduced from 6 to 4, which inhibits the hydrogen evolution reaction at low potential, thereby achieving the purpose of inhibiting the hydrogen evolution reaction.

[0036] 2) Corrosion resistance. A three-electrode system was used for testing, with zinc foil as the working and counter electrodes, and an Ag / AgCl electrode as the reference electrode. Cyclic scanning voltammetry (CV) was employed to test the battery, with a scan rate set to 1 mV / s and a test voltage range of -1.2 to -0.8 V. Data was recorded using an Autolab electrochemical workstation, and the test results are as follows: Figure 2 As shown.

[0037] It can be seen that the corrosion current of the zinc metal anode in the target electrolyte decreased from 2.4 mA to 1.5 mA, indicating that the corrosion reaction of the zinc metal anode in the target electrolyte was significantly inhibited in the presence of succinic acid. Furthermore, based on the results in 1) above, it can be found that the zinc ion solvation shell structure in the electrolyte changed from the original [Zn(H₂O)₆] 2+ It transforms into [Zn(H₂O)₄(succinic acid)] 2+The corrosion reaction of the zinc metal anode mainly involves the reaction between metallic zinc and water in the electrolyte, as well as sulfate ions contained in the electrolyte salt. The reaction equation is shown below:

[0038]

[0039] As can be seen from the above corrosion reaction equation, when the content of water molecules decreases, the second step of the reaction is inhibited, which in turn inhibits the entire corrosion reaction.

[0040] b. Analysis of zinc ion deposition behavior

[0041] 1) In-situ observation of zinc ion deposition behavior in electrolyte. A battery was assembled using a battery device (Zhongyan Environmental Technology LIB-MS-R), with zinc foil used as the working electrode, counter electrode, and reference electrode. 200 μL of electrolyte was added. The deposition behavior of zinc ions in the electrolyte was recorded using an optical microscope (Cewei Guangdian, LW750LJT) at a current density of 3 mA / cm². 2 The deposition process of zinc ions under certain conditions, and the test results are as follows: Figure 3 As shown.

[0042] In-situ optical images revealed that zinc ions were uniformly deposited on the surface of metallic zinc in the target electrolyte, and no dendritic crystals were observed. Figure 3 a); while in the blank electrolyte, the formation of dendritic crystals of varying sizes can be clearly observed ( Figure 3 b) indicates that adding succinic acid to the electrolyte can induce uniform deposition of zinc ions and inhibit the formation of zinc dendrites.

[0043] 2) Deposition model test of zinc ions in electrolyte. A zinc deposition model was obtained using a Zn||Zn symmetric cell test. Zinc foil was used as the working electrode, counter electrode, and reference electrode, and glass fiber was used as the separator. 80 μL of electrolyte was added to fabricate a standard CR2032 coin cell. The cell was tested using chronoamperometry, with a voltage set to -150 mV and a test time set to 150 s. The test results are as follows: Figure 4 As shown.

[0044] pass Figure 4 The test results show that in the target electrolyte, the current density tends to stabilize after 50 seconds, while in the blank electrolyte, the current density continues to decrease. This indicates that the two-dimensional diffusion of zinc ions on the zinc metal anode surface is suppressed in the target electrolyte, and zinc ions tend to deposit at the original adsorption site, effectively avoiding the dendrite growth problem caused by two-dimensional diffusion.

[0045] 3) Surface morphology analysis of the zinc metal anode. Zinc foil and electrolyte were assembled into a Zn||Zn symmetric cell, with the zinc foil serving as both the working and counter electrodes, and glass fiber as the separator. 80 μL of electrolyte was added to fabricate a standard CR2032 coin cell. Testing was performed using a LAND-CT2001A battery testing system with a current density set to 1 mA / cm². 2 In each cycle, constant current discharge was performed for 1 hour, followed by constant current charging for 1 hour. After 10 cycles, the battery was disassembled, the working electrode was removed, and the surface morphology was analyzed using a scanning electron microscope (SEM). The results are as follows: Figure 5 As shown.

[0046] In the blank electrolyte, the zinc metal surface was covered with dense zinc dendrites; however, in the target electrolyte, it exhibited a smooth and dense morphology with no obvious dendrite formation. This result is consistent with... Figure 3 They match perfectly.

[0047] c. Electrochemical performance analysis

[0048] 1) Deposition / stripping efficiency test of zinc in electrolyte. Using zinc foil as the counter and reference electrode, copper foil as the working electrode, and glass fiber as the separator, 80 μL of electrolyte was added to assemble a Zn||Cu half-cell, forming a standard CR2032 coin cell. The test was conducted using a LAND-CT2001A battery testing system with a current density set to 1 mA / cm². 2 The discharge cycle time was set to 1 hour, and the charging cycle cutoff voltage was 0.5V. The test results are as follows: Figure 6 As shown.

[0049] The comparison chart of coulombic efficiency shows that the average coulombic efficiency in the target electrolyte reaches 99.7%, which is much higher than that in the blank electrolyte. This indicates that the side reactions occurring on the zinc metal anode surface are effectively suppressed, demonstrating good chemical stability.

[0050] 2) Cycle stability. Using zinc foil as the working and counter electrodes, and glass fiber as the separator, 80 μL of electrolyte was added to assemble a Zn||Zn symmetric cell, thus fabricating a standard CR2032 coin cell. Testing was conducted using a LAND-CT2001A battery testing system, with the charge / discharge current density set to 1 mA / cm² during the test. 2 The time was set to 1 hour. The test results are as follows: Figure 7 As shown.

[0051] The cycle time-voltage plot shows a significant voltage drop at the zinc metal anode after 100 hours of cycling in the blank electrolyte, indicating a short circuit. This is likely due to the continuous growth of zinc dendrites during prolonged cycling, which puncture the separator and cause contact with the counter electrode. In the target electrolyte, however, continuous cycling for 5500 hours without significant voltage changes indicates that zinc dendrite growth was significantly suppressed during cycling, thus greatly improving the battery's cycle stability.

[0052] 3) Full battery performance. K 0.27 MnO2·0.54H2O, conductive carbon, and PVDF are mixed in a mass ratio of 8:1:1, with N,N-dimethylpyrrolidine as a diluent, and thoroughly ground to ensure uniform mixing. The uniformly mixed slurry is then evenly coated onto the surface of a stainless steel foil, vacuum dried at 80℃ for 12 hours, and then cut into 10mm diameter discs as positive electrodes. Each electrode surface is loaded with K... 0.27 The mass of MnO2·0.54H2O was controlled at 3.3 mg; zinc foil with a diameter of 10 mm and a thickness of 10 μm was used as the negative electrode, glass fiber as the separator, and 80 μL of electrolyte was added to assemble a standard CR2032 battery, which was tested using a LAND-CT2001A battery testing system. Zn||K 0.27 The MnO2·0.54H2O full cell has a voltage range of 0.8~1.8 V (vs. Zn). 2+ Charge-discharge tests were performed within the voltage range of / Zn, with a current density of 1 A g. -1 The test results are as follows Figure 8 As shown.

[0053] The full cell with the target electrolyte still yielded 89 mAh g⁻¹ after 3000 cycles. -1 The high reversible capacity and high coulombic efficiency demonstrate the long-term cycling stability of the zinc metal anode. This indicates that when succinic acid is present as an additive in the electrolyte, the corrosion reaction of the zinc metal anode and the hydrogen evolution reaction of the electrolyte are effectively suppressed, while the formation of zinc dendrites is also alleviated. Therefore, the zinc metal-based full cell exhibits high capacity.

[0054] Example 2

[0055] An electrolyte containing 2 mol / kg zinc sulfate and 0.01 mol / kg succinic acid was prepared using the same method as in Example 1.

[0056] Example 3

[0057] An electrolyte containing 2 mol / kg zinc sulfate and 0.5 mol / kg succinic acid was prepared using the same method as in Example 1.

[0058] Example 4

[0059] An electrolyte containing 1 mol / kg zinc sulfate and 0.1 mol / kg succinic acid was prepared using the same method as in Example 1.

[0060] Example 5

[0061] An electrolyte containing 5 mol / kg zinc sulfate and 0.1 mol / kg succinic acid was prepared using the same method as in Example 1.

[0062] Example 6

[0063] An electrolyte containing 2 mol / kg zinc acetate and 0.1 mol / kg succinic acid was prepared using the same method as in Example 1.

[0064] The performance of the electrolytes prepared in the examples was evaluated:

[0065] The specific method is as follows: Using zinc foil as the working and counter electrodes, and glass fiber as the separator, 80 μL of electrolyte is added dropwise to assemble a Zn||Zn symmetrical cell, thus producing a standard CR2032 coin cell. Testing is conducted using a LAND-CT2001A battery testing system, with the charge / discharge current density set to 1 mA / cm² during the test. 2 The test time was set to 1 hour. The test results are shown in the table below.

[0066]

Claims

1. An aqueous zinc metal battery electrolyte, characterized in that: It is composed of zinc sulfate, succinic acid and water; the concentration of zinc sulfate is 2 mol / kg; the concentration of succinic acid is 0.1 mol / kg.

2. The application of the aqueous zinc metal battery electrolyte as described in claim 1 in zinc metal batteries.

3. A zinc metal battery, characterized in that: Includes the aqueous zinc metal battery electrolyte as described in claim 1.

4. The zinc metal battery according to claim 3, characterized in that: It also includes the positive electrode, negative electrode, and separator.

5. The zinc metal battery according to claim 4, characterized in that: The positive electrode is composed of an active material, a conductive agent, and a binder.

6. The zinc metal battery according to claim 5, characterized in that: The active material of the positive electrode is K. 0.27 Any one of MnO2·0.54H2O, V2O5, MnO2, or Na3VO4.

Images