Zinc-silver battery electrolyte additive, zinc-silver battery electrolyte and zinc-silver secondary battery

Abstract

The invention relates to the technical field of zinc-silver batteries, in particular to a zinc-silver battery electrolyte additive, a zinc-silver battery electrolyte and a zinc-silver secondary battery. A trace amount of negatively-charged surfactant N-ethyl-N-(3-sulfopropyl)-3-methylaniline sodium salt is added into the traditional KOH electrolyte of the zinc-silver secondary battery, and the problem of deformation of a zinc negative electrode caused by the existence of a free-state charge-discharge intermediate product Zn (OH) 4 < 2-> is inhibited by utilizing specific adsorption of amphoteric molecules and a negatively-charged functional group. The additive not only can stabilize the zinc negative electrode structure and improve the cycle performance of the zinc-silver battery, but also can enable the active substances in the zinc-silver battery to give full play to the capacity, and prolongs the service life of the zinc-silver secondary battery for repeated and stable discharge and energy supply.

Description

Technical Field

[0001] This invention relates to the field of zinc-silver battery technology, specifically to a zinc-silver battery electrolyte additive, a zinc-silver battery electrolyte, and a zinc-silver secondary battery. Background Technology

[0002] Zinc-silver batteries, as a widely used aqueous zinc-based battery, maintain an extremely important position in specialized fields such as aerospace, military, and medical applications due to their outstanding characteristics such as high energy density, stable discharge voltage, and superior safety. However, traditional zinc-silver rechargeable batteries experience structural deformation and severe side reactions on the negative electrode side during cyclic charging and discharging, leading to unexpected losses of the negative electrode active material and significantly limiting the battery's cycle life and effective discharge capacity.

[0003] To improve battery performance, researchers have begun using electrolyte additives. Chinese patent CN102790239A discloses a method for preparing an alkaline zinc-silver battery electrolyte. This method reduces electrolyte corrosion of the zinc electrode and improves electrolyte conductivity by compounding various inorganic and organic additives such as aluminum silicate, polyethylene glycol, polyacrylamide, sodium alkylammonium, zinc molybdate, and sodium stannate. However, this system mainly forms a physical barrier or improves the overall electrolyte environment. It lacks effectiveness in inhibiting the crucial process of zinc active material migration and dissolution outside the electrode bulk phase. Furthermore, the complexity of the system increases the difficulty and cost of process control, potentially leading to fluctuations in battery performance and failing to fundamentally solve the structural deformation problem of the zinc anode during cycling.

[0004] Therefore, it is necessary to develop a new type of electrolyte additive to fundamentally suppress negative electrode deformation during charging and discharging, and improve the cycle life and discharge capacity of zinc-silver batteries. Summary of the Invention

[0005] To overcome the shortcomings of existing technologies, this invention provides a zinc-silver battery electrolyte additive, a zinc-silver battery electrolyte, and a zinc-silver secondary battery. By adding sodium N-ethyl-N-(3-sulfopropyl)-3-methylaniline to the electrolyte, adsorption occurs at the zinc anode interface, suppressing the Zn(OH)4 content in the anode bulk phase. 2- The migration and dissolution process to the outside of the electrode ultimately yields a relatively complete zinc anode, improving the structural deformation problem that occurs on the anode side.

[0006] To achieve the above-mentioned objectives, the technical solution of this invention is as follows: The first aspect of this invention provides an additive for zinc-silver battery electrolytes. This additive is a negatively charged surfactant, and its molecular structure contains a negatively charged sulfonic acid group, a tertiary amine nitrogen atom, and an electron-rich benzene ring. The additive is N-ethyl-N-(3-sulfopropyl)-3-methylaniline sodium salt (TOPS), and its chemical structure is shown in Formula 1. .

[0007] Furthermore, the concentration of the additive in the electrolyte is 0.01-0.20 g·L. -1 Further optimization was performed using 0.05-0.15 g·L⁻¹. -1 .

[0008] A second aspect of the present invention provides a zinc-silver battery electrolyte comprising an aqueous KOH solution and a TOPS additive.

[0009] Furthermore, the concentration of the KOH aqueous solution in the electrolyte is 5-7 mol·L⁻¹. -1 Further optimization of 6 mol·L -1 .

[0010] A third aspect of the present invention provides a zinc-silver secondary battery, comprising a positive electrode, a negative electrode, a separator, and the zinc-silver battery electrolyte.

[0011] Furthermore, the active material of the negative electrode is zinc powder, and the active material of the positive electrode is silver oxide (Ag2O).

[0012] Furthermore, the negative electrode preparation method is as follows: zinc powder, polyvinylidene fluoride (PVDF) and conductive carbon (Super P) are mixed in a mass ratio of 8:1:1, N-methyl-2-pyrrolidone (NMP) is added dropwise to obtain a slurry, which is then coated on a foamed copper current collector and dried to obtain the negative electrode.

[0013] Furthermore, the positive electrode preparation method is as follows: Ag2O powder and graphite powder are mixed, polytetrafluoroethylene emulsion is added dropwise to the mixed powder, and then isopropanol is added dropwise to obtain a slurry, which is then pressed onto a silver mesh current collector and dried at room temperature for 4 hours to obtain the positive electrode.

[0014] The fourth aspect of this invention provides the application of the zinc-silver battery electrolyte additive in the preparation of zinc-silver secondary batteries with high cycle life and high discharge capacity.

[0015] The advantages and beneficial effects of this invention are as follows: (1) This invention adds a trace amount of the negatively charged surfactant TOPS to the traditional KOH electrolyte of a zinc-silver secondary battery. By utilizing the specific adsorption of its amphipathic molecules and the negatively charged functional groups (negatively charged sulfonic acid groups, tertiary amine nitrogen atoms, and electron-rich benzene rings) in its structure, TOPS adsorbs at the zinc anode interface, thereby stabilizing the zinc anode structure and suppressing the Zn(OH)4 in the anode bulk phase. 2- The migration and dissolution process to the outside of the electrode ultimately yields a relatively complete zinc anode, solving the problem of free intermediate product Zn(OH)4 during the charging and discharging process of the zinc anode. 2- The problem of drastic deformation caused by its existence.

[0016] (2) The electrolyte of the present invention not only extends the cycle life of zinc-silver batteries for stable discharge and energy supply, but also enables the negative electrode active material in zinc-silver secondary batteries to fully utilize its capacity, thereby improving the discharge capacity and efficiency of zinc-silver secondary batteries. Attached Figure Description

[0017] Figure 1 This is a schematic diagram showing the discharge test results of the zinc-silver secondary batteries in Examples 1-3 and Comparative Example 1.

[0018] Figure 2 The long-cycle performance of the zinc-silver secondary batteries in Examples 1-3 and Comparative Example 1 at a charge-discharge rate of 0.1 C is shown.

[0019] Figure 3 This is a schematic diagram showing the discharge test results of the zinc-silver secondary batteries in Example 2 and Comparative Examples 2-4.

[0020] Figure 4 The long-cycle performance of the zinc-silver secondary batteries in Example 2 and Comparative Examples 2-4 at a charge-discharge rate of 0.1 C is shown.

[0021] Figure 5 The SEM planar morphology of the zinc anode in the zinc-silver secondary batteries of Examples 1-3 and Comparative Example 1 after 100 cycles at a charge-discharge rate of 0.1 C.

[0022] Figure 6 The SEM cross-sectional morphology of the zinc anode in the zinc-silver secondary batteries of Examples 1-3 and Comparative Example 1 after 100 cycles at a charge-discharge rate of 0.1 C.

[0023] Figure 7 The SEM planar morphology of the zinc anode in the zinc-silver secondary batteries of Examples 2 and Comparative Examples 2-4 after 100 cycles at a charge-discharge rate of 0.1 C.

[0024] Figure 8 The SEM cross-sectional morphology of the zinc anode in the zinc-silver secondary batteries of Examples 2 and Comparative Examples 2-4 after 100 cycles at a charge-discharge rate of 0.1 C. Detailed Implementation

[0025] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0026] Unless otherwise defined, all technical terms used herein have the same meaning as commonly understood by those skilled in the art. The technical terms used herein are for the purpose of describing particular embodiments only and are not intended to limit the scope of the invention.

[0027] Example 1 A method for preparing a zinc-silver secondary battery, comprising the following steps: (1) Preparation of zinc negative electrode sheet: Zinc powder, polyvinylidene fluoride (PVDF) and conductive carbon (Super P) are mixed in a mass ratio of 8:1:1, N-methyl-2-pyrrolidone (NMP) is added dropwise to prepare a slurry, which is then coated on a copper foam current collector and dried at 60 °C for 4 h to obtain a zinc negative electrode sheet.

[0028] (2) Preparation of silver positive electrode: The positive electrode is prepared by pressing a slurry onto a current collector. The positive electrode slurry consists of 80 wt.% Ag2O, 10 wt.% graphite powder, and 10 wt.% polytetrafluoroethylene emulsion (60 wt.% diluted emulsion, diluted with water). Ag2O powder and graphite powder are mixed at a mass ratio of 8:1. Polytetrafluoroethylene emulsion (60 wt.%) is added dropwise to the mixed powder, followed by the addition of isopropanol to obtain a slurry. This slurry is then pressed onto a silver mesh current collector and dried at room temperature for 4 h to prepare the silver positive electrode for the zinc-silver battery.

[0029] (3) Preparation of zinc-silver battery electrolyte: Sodium N-ethyl-N-(3-sulfopropyl)-3-methylaniline (TOPS) was added to 6 mol·L⁻¹ -1 TOPS with a concentration of 0.05 g·L⁻¹ was prepared in KOH solution. -1 The KOH solution is used, which is the electrolyte for zinc-silver secondary batteries. The structure of the additive is shown in Formula 1: .

[0030] (4) Preparation of the diaphragm: Two layers of hydrophilic polypropylene microporous membrane and one layer of glass fiber diaphragm are stacked between the positive and negative electrode plates.

[0031] (5) Assemble the battery: Stack the zinc negative electrode, glass fiber separator and silver positive electrode in sequence, add zinc-silver battery electrolyte and encapsulate it into a zinc-silver secondary battery.

[0032] Example 2 The difference from Example 1 lies in step (3), where the TOPS concentration in the zinc-silver battery electrolyte is 0.10 g·L⁻¹. -1 .

[0033] Example 3 The difference from Example 1 lies in step (3), where the TOPS concentration in the zinc-silver battery electrolyte is 0.15 g·L⁻¹. -1 .

[0034] Comparative Example 1 The difference from Example 1 is in step (3), where TOPS is not added to the electrolyte, but only 6 mol·L⁻¹ is used. -1 KOH solution was used as the electrolyte.

[0035] Comparative Example 2 The difference from Example 2 is in step (3), where TOPS is not added to the electrolyte, but 0.10 g L is added. -1 DMDS (N,N-dimethyldithiocarbamate propanesulfonate sodium, CAS: 18880-36-9) up to 6 mol·L -1 in KOH solution.

[0036] Comparative Example 3 The difference from Example 2 is in step (3), where TOPS is not added to the electrolyte, but 0.10 g·L⁻¹ is added. -1 SBS (sodium benzenesulfonate, CAS: 515-42-4) up to 6 mol·L -1 in KOH solution.

[0037] Comparative Example 4 The difference from Example 2 is in step (3), where TOPS is not added to the electrolyte, but 0.10 g·L⁻¹ is added. -1 DMAn (N,N-dimethylaniline, CAS: 121-69-7) up to 6 mol·L -1 in KOH solution.

[0038] The zinc-silver secondary batteries of Examples 1-3 and Comparative Example 1 were subjected to a 0.1 C single constant current discharge test at 22 °C. The test results are as follows: Figure 1 As shown. The results show that, compared with the traditional alkaline electrolyte in the battery of Comparative Example 1, the discharge time (discharge capacity) of the battery was improved after the addition of TOPS, and the discharge capacity of Example 2 (adding 0.10 g·L) was also improved. -1 The zinc-silver secondary battery prepared with TOPS exhibited the highest discharge capacity. This indicates that the addition of TOPS can suppress the loss of active species in the zinc anode, improve the integrity of the connection between the active material and the conductive network, and thus enhance the effective discharge capacity of the zinc-silver battery.

[0039] The zinc-silver secondary batteries in Examples 1-3 and Comparative Example 1 were subjected to a 0.1 C constant current charge-discharge test, and the test results are as follows: Figure 2 As shown. The results indicate that the cycle life of the zinc-silver battery was improved to a certain extent after the addition of TOPS, and the degree of improvement was as follows: Example 2 (adding 0.10 g·L⁻¹) -1 TOPS) > Example 1 (add 0.05 g·L) -1 TOPS) > Example 3 (add 0.15g·L -1 TOPS).

[0040] A single discharge test was conducted on the zinc-silver secondary batteries of Example 2 and Comparative Examples 2-4. The test results are as follows: Figure 3 As shown in the figure. The results show that, compared with the battery assembled with TOPS added in Example 2, the discharge time (discharge capacity) of the batteries in Comparative Examples 2-4 decreased, and some hydrogen evolution was generated, indicating that, compared with the additive TOPS, other types of additives are less effective in inhibiting the loss of active materials.

[0041] The zinc-silver secondary batteries in Example 2 and Comparative Examples 2-4 were subjected to a 0.1 C constant current charge-discharge test, and the test results are as follows: Figure 4 As shown, the results indicate that the cycle life of the zinc-silver secondary batteries in Comparative Examples 2-4 is reduced to some extent compared to Example 2. The above data demonstrate that when the tertiary amine group is missing, the risk of hydrogen evolution from the sulfonic acid group cannot be suppressed, and the adsorption effect of the benzene ring is insufficient to compensate. Furthermore, when the electron-rich benzene ring is missing, the interfacial directional adsorption capacity weakens, and the dendrite suppression effect drops sharply.

[0042] The zinc-silver secondary batteries of the examples and comparative examples were disassembled after 100 constant current charge-discharge cycles at a charge-discharge rate of 0.1 C. The negative electrode was removed and its microstructure was characterized. Its planar morphology and cross-sectional morphology are shown below. Figures 5-8 As shown, the planar and cross-sectional SEM images of Comparative Example 1 indicate that a large amount of Zn(OH)4 has appeared at its negative electrode. 2- The porosity caused by migration was less pronounced on the negative electrode surface after cycles in Examples 2-4, but cross-sectional SEM images showed slight volumetric deformation of the negative electrode. In contrast, the zinc negative electrode structures in Examples 1-3 were relatively dense with fewer pores, corroborating that the addition of TOPS suppresses the formation of Zn(OH)4 in the bulk phase of the negative electrode. 2- The migration of the zinc anode reduces the deformation of the negative electrode and obtains a relatively complete zinc anode, ultimately resulting in a zinc-silver secondary battery with both high discharge capacity and long cycle life.

[0043] In summary, this invention designs the electrolyte for zinc-silver batteries by employing a modification strategy using electrolyte additives. Through the specific adsorption of surfactant amphoteric molecules and the presence of negatively charged functional groups in the molecular structure, the intermediate charge-discharge product Zn(OH)4 is suppressed. 2- The migration of these molecules allows for the production of zinc anodes with higher structural stability. This additive addresses the problem of zinc anode structural deformation under alkaline conditions to some extent, and has led to the development of a zinc-silver battery with longer cycle life and higher discharge capacity, thus deepening and promoting the application of zinc-silver batteries in multiple industries.

[0044] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several modifications and improvements can be made without departing from the inventive concept, and these all fall within the protection scope of the present invention.

Claims

1. A zinc-silver battery electrolyte additive, characterized in that, The additive is sodium N-ethyl-N-(3-sulfopropyl)-3-methylaniline, and its chemical structure is shown in Formula 1: 。 2. The zinc-silver battery electrolyte additive according to claim 1, characterized in that, The concentration of the additive in the electrolyte is 0.01-0.20 g·L. -1 .

3. A zinc-silver battery electrolyte, characterized in that, It comprises an aqueous solution of KOH and the additives described in any one of claims 1-2.

4. The zinc-silver battery electrolyte according to claim 3, characterized in that, The concentration of the KOH aqueous solution is 5-7 mol·L⁻¹. -1 .

5. A zinc-silver secondary battery, characterized in that, It includes the electrolyte according to any one of claims 3-4.

6. The zinc-silver secondary battery according to claim 5, characterized in that, The active material of the negative electrode sheet of the zinc-silver secondary battery is zinc powder.

7. The zinc-silver secondary battery according to claim 6, characterized in that, The active material of the positive electrode of the zinc-silver secondary battery is silver oxide.

8. The application of the zinc-silver battery electrolyte additive as described in any one of claims 1-2 in the preparation of zinc-silver secondary batteries with high cycle life and high discharge capacity.

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