A water-based crown ether electrolyte capable of chelating stannous ions and preparation and application thereof

Abstract

The application belongs to the technical field of electrochemical cells, and particularly relates to a water-based crown ether electrolyte capable of chelating stannous ions and a preparation and application thereof. The electrolyte comprises deionized water, acid, soluble stannous salt and crown ether with a specific internal cavity size. The application introduces crown ether as a functional additive in a conventional acidic stannous salt electrolyte, chelates stannous ions through the specific internal cavity size, the special chemical confinement effect can regulate the nucleation kinetics of stannous ions, induce uniform tin deposition, prevent the formation of large tin particles and "dead tin", and further improve the deposition / dissolution reversibility of the tin negative electrode. The double-deposition type tin-manganese full cell assembled by using the electrolyte has a high discharge platform of 1.68 V and a long cycle stability of more than 300 cycles. The preparation method of the electrolyte is simple, the H-type double-deposition type tin-manganese full cell has low requirements on equipment conditions, raw materials are abundant, the production cost is low, and the application has a large practical application prospect.

Description

Technical Field

[0001] This invention belongs to the field of electrochemical battery technology, specifically relating to an aqueous crown ether electrolyte capable of chelating stannous ions and its preparation and application. Background Technology

[0002] Rechargeable aqueous batteries have gained attention as a promising alternative to lithium-ion batteries due to their low cost, environmental friendliness, and high safety, and are used for storing renewable energy by avoiding the use of toxic and flammable organic electrolytes. Among these, zinc-ion batteries with zinc metal as the negative electrode have become a current research hotspot. However, since most currently used electrolytes are acidic, they inevitably exacerbate the hydrogen evolution reaction. Simultaneously, parasitic byproducts and corrosion make the zinc metal surface more uneven, making it prone to dendrite formation during deposition. In severe cases, this can puncture the separator and cause a short circuit. These problems hinder the further development of zinc negative electrodes. Therefore, exploring a negative electrode that can cycle stably under acidic conditions is of great significance.

[0003] Compared to zinc, tin exhibits stronger acid resistance, higher hydrogen evolution overpotential, and a higher theoretical specific capacity (451 mAh / g), making it a highly promising next-generation anode material for aqueous batteries. However, despite these advantages, tin faces several challenges in practical applications. Due to the similar surface energies of tin's crystal planes, it tends to preferentially nucleate at sites with lower nucleation barriers during deposition, continuing growth at these sites. As the deposition capacity increases, large tin particles easily form, which can fall off the current collector, becoming "dead tin," resulting in poor coulombic efficiency and significantly shortened cycle life. In severe cases, the sharp edges of large tin particles may puncture the separator, causing a short circuit. This is also why large-area capacity deposition / stripping is difficult to achieve in coin cells. Currently, researchers have adopted an interface modification strategy, using coatings to induce uniform deposition of tin subions on the electrode surface, effectively improving the reversibility of Sn deposition / dissolution. However, the problems of "dead tin" formation in tin metal anodes and poor cycle stability at high areal capacities remain difficult to solve. Therefore, improving the problems of "dead tin" formation and poor cycle stability at high areal capacities in tin metal anodes is a technical problem that this invention urgently needs to solve. Summary of the Invention

[0004] To overcome the shortcomings of the prior art, this invention provides an aqueous crown ether electrolyte capable of chelating stannous ions, its preparation, and its application. Starting with electrolyte modification, this invention, based on the stannous ion diameter of approximately 162 μm, for the first time utilizes crown ethers with specific internal cavity dimensions as functional additives. Crown ethers are stable under acidic conditions. By utilizing the specific internal cavity dimensions of crown ethers to chelate stannous ions, the nucleation kinetics of stannous ions are effectively controlled, resulting in more nucleation sites during deposition. This promotes uniform deposition of stannous ions, effectively avoiding the formation of large tin particles, significantly reducing the formation of "dead tin," and greatly improving the cycle stability of the tin anode.

[0005] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0006] The first aspect of the present invention provides an aqueous crown ether electrolyte capable of chelating stannous ions, the aqueous crown ether electrolyte capable of chelating stannous ions comprising deionized water, acid, soluble stannous salt, and crown ether having a specific internal cavity size.

[0007] Preferably, the acid is one of hydrochloric acid and sulfuric acid.

[0008] Preferably, the soluble stannous salt is one of stannous sulfate and stannous chloride.

[0009] Preferably, the crown ether is one of 12-crown ether-4, 15-crown ether-5, 18-crown ether-6, or 21-crown ether-7; the cavity diameter of 12-crown ether-4 is 120-150 pm, the cavity diameter of 15-crown ether-5 is 170-220 pm, the cavity diameter of 18-crown ether-6 is 260-320 pm, and the cavity diameter of 21-crown ether-7 is 340-430 pm.

[0010] Preferably, the ratio of the inner diameter of the crown ether to the diameter of the stannous ion is 0.7 to 2.5.

[0011] More preferably, the ratio of the inner diameter of the crown ether to the diameter of the stannous ion is 1 to 2.

[0012] Preferably, the concentration of crown ether in the electrolyte is 0.01–5 mol / L, the amount of acid used is 1–5 times the amount of crown ether used, and the amount of soluble stannous salt used is 1–5 times the amount of crown ether used.

[0013] The second aspect of the present invention provides a method for preparing the above-mentioned aqueous crown ether electrolyte capable of chelating stannous ions. The preparation method includes the following steps: mixing deionized water and acid and stirring for the first time, then adding soluble stannous salt and stirring for the second time, and then adding crown ether with a specific inner cavity size and stirring for the third time to obtain the aqueous crown ether electrolyte capable of chelating stannous ions.

[0014] A third aspect of the present invention provides an H-type dual-deposition tin-manganese full cell, the tin-manganese full cell comprising a positive electrode current collector, a negative electrode current collector, a proton exchange membrane, a positive electrode side electrolyte, and the above-mentioned aqueous crown ether electrolyte capable of chelating tin ions.

[0015] Preferably, the preparation method of the positive electrode side electrolyte is as follows: deionized water and acid are mixed, then stannous salt is added, and finally manganese salt is added and stirred evenly to obtain the positive electrode side electrolyte of H-type double-deposition tin-manganese full cell.

[0016] More preferably, the manganese salt is manganese sulfate with a concentration of 0.01 to 2 mol / L.

[0017] Preferably, the proton exchange membrane is polybenzimidazole; the negative electrode current collector is one of copper foil, carbon paper, carbon felt, and titanium mesh; and the positive electrode current collector is one of carbon paper, carbon felt, carbon cloth, titanium mesh, and stainless steel mesh.

[0018] Compared with the prior art, the beneficial effects of the present invention are:

[0019] This invention provides an aqueous crown ether electrolyte capable of chelating stannous ions, its preparation, and its application. The electrolyte comprises deionized water, acid, soluble stannous salt, and a crown ether with a specific internal cavity size. This invention introduces a crown ether as a functional additive into a traditional acidic stannous salt electrolyte. Through its specific internal cavity size, the crown ether chelates stannous ions. This unique chemical confinement effect can regulate the nucleation kinetics of stannous ions, induce uniform tin deposition, prevent the formation of large tin particles and "dead tin," and thus improve the deposition / dissolution reversibility of the tin anode. A dual-deposition tin-manganese full cell assembled using this electrolyte exhibits a high discharge plateau of 1.68V and long-term cycle stability exceeding 300 cycles. The electrolyte preparation method provided by this invention is simple, the H-type dual-deposition tin-manganese full cell has low equipment requirements, abundant raw materials, and low production costs, making it promising for practical applications. Specifically:

[0020] (1) This invention is the first to use crown ether with a specific internal cavity size as a functional additive. Crown ether is stable in acidic conditions. By utilizing the specific internal cavity size of crown ether to chelate tin ions, the nucleation kinetics of tin ions are effectively regulated, so that tin ions have more nucleation sites during the deposition process, promoting uniform deposition of tin ions, effectively avoiding the generation of large tin particles, effectively reducing the generation of "dead tin", and greatly improving the cycle stability of tin anode.

[0021] (2) This invention assembles a simple H-type dual-deposition tin-manganese full cell with only a current collector. The positive electrode reaction of this cell is Mn 2+ and Mn 3+The reversible process involves the deposition / stripping of tin ions in the negative electrode reaction. The aqueous crown ether electrolyte proposed in this invention, which can chelate tin ions, has a longer cycle life for the tin negative electrode due to its inhibitory effect on "dead tin," thereby extending the cycle life of the assembled H-type double-deposition tin-manganese full cell. This H-type double-deposition tin-manganese full cell, which only allows proton exchange, can achieve both high power density and good safety, and has broad application prospects in the field of large-scale energy storage. Attached Figure Description

[0022] Figure 1 A symmetrical cell assembled using the aqueous crown ether electrolyte capable of chelating stannous ions from Example 1 and the blank electrolyte from Comparative Example 1 was tested at a current density of 10 mA cm⁻¹. -2 The deposition / stripping capacity is 1 mAh cm⁻¹ -2 A comparison of time-voltage curves.

[0023] Figure 2 A symmetrical cell assembled using the aqueous crown ether electrolyte capable of chelating stannous ions from Example 1 and the blank electrolyte from Comparative Example 1 was tested at a current density of 1 mA cm⁻¹. -2 The deposition / stripping capacity is 5 mAh cm⁻¹ -2 A comparison of time-voltage curves.

[0024] Figure 3 The coulombic efficiency versus cycle count diagram of the asymmetric button cell assembled with the aqueous crown ether electrolyte capable of chelating stannous ions in Example 1.

[0025] Figure 4 Coulomb efficiency versus cycle count plot of an asymmetric coin cell assembled with the blank electrolyte of Comparative Example 1.

[0026] Figure 5 The linear sweep voltammetry curve is shown for the aqueous crown ether electrolyte capable of chelating stannous ions in Example 1.

[0027] Figure 6 The image shows the linear sweep voltammetry curve of the blank electrolyte in Comparative Example 1.

[0028] Figure 7 An optical photograph of the tin deposition morphology on copper foil after linear scanning voltammetry of the aqueous crown ether electrolyte capable of chelating tin ions in Example 1.

[0029] Figure 8 An optical photograph of the tin deposition morphology on copper foil after linear scanning voltammetry of the blank electrolyte in Comparative Example 1.

[0030] Figure 9 The image shows the Tafel curve of the aqueous crown ether electrolyte capable of chelating stannous ions in Example 1.

[0031] Figure 10 The image shows the Tafel curve of the blank electrolyte in Comparative Example 1.

[0032] Figure 11 The capacity-voltage curves for constant current charge-discharge of the H-type double-deposition tin-manganese full cell in Example 6 are shown.

[0033] Figure 12 The diagram shows the constant current charge-discharge cycle of the H-type double-deposition tin-manganese full cell in Example 6.

[0034] Figure 13 The capacity-voltage curve of the H-type double-deposition tin-manganese full cell at a constant voltage of 1.9V is shown in Example 6.

[0035] Figure 14 The circuit diagram shows the H-type double-deposition tin-manganese full cell of Example 6 at a constant voltage of 1.9V. Detailed Implementation

[0036] The specific embodiments of the present invention will be further described below. It should be noted that these descriptions are for the purpose of aiding understanding the present invention, but do not constitute a limitation thereof. Furthermore, the technical features involved in the various embodiments of the present invention described below can be combined with each other as long as they do not conflict with each other.

[0037] Unless otherwise specified, the experimental methods used in the following embodiments are conventional methods, and the experimental materials used in the following embodiments are all available through conventional commercial channels.

[0038] Example 1: Preparation of an aqueous crown ether electrolyte capable of chelating stannous ions

[0039] 1.09 mL of concentrated sulfuric acid was added to 7.92 mL of ultrapure water, followed by the addition of 0.2147 g of stannous sulfate and stirring to dissolve. Then, 0.99 mL of 15-crown ether-5 was added to prepare 10 mL of an aqueous crown ether electrolyte capable of chelating stannous ions. The concentrations of sulfuric acid, stannous sulfate, and 15-crown ether-5 were 2 mol / L, 0.1 mol / L, and 0.5 mol / L, respectively.

[0040] Comparative Example 1: Preparation of Blank Electrolyte

[0041] 1.09 mL of concentrated sulfuric acid was added to 8.91 mL of ultrapure water, and then 0.2147 g of stannous sulfate was added and stirred to dissolve, thus preparing 10 mL of blank electrolyte containing 2 mol / L sulfuric acid and 0.1 mol / L stannous sulfate.

[0042] Example 2: Assembling a symmetric battery with an aqueous crown ether electrolyte capable of chelating stannous ions.

[0043] High-purity tin foil (99.99%) with a thickness of 100 μm was cut into circular pieces with a diameter of 12 mm. After cleaning the tin foil with alcohol, it was used as the positive and negative electrodes of the button cell. First, the negative electrode was placed in the negative electrode shell, followed by a 16 mm diameter circular glass fiber separator. 120 μL of the aqueous crown ether electrolyte from Example 1, which can chelate tin ions, was added, then the positive electrode was placed, followed by a gasket and spring sheet. Finally, the positive electrode shell was placed on top, and the battery was sealed using a battery packaging machine to obtain a button cell symmetric battery, labeled as BE(2 mol / L H2SO4 + 0.1 mol / L LnSO4) + 15-crown-5 symmetric button cell.

[0044] Comparative Example 2: Assembly of Symmetrical Cells with Blank Electrolyte

[0045] The difference from Example 2 is that the electrolyte was replaced with the blank electrolyte prepared in Comparative Example 1, and a button symmetric cell was assembled and labeled as BE (2mol / L H2SO4+0.1mol / L SnSO4) symmetric button cell.

[0046] Figure 1 This is a comparison of the time-voltage curves of the symmetrical button cells assembled in Example 2 and Comparative Example 2 under 10⁻¹ conditions. Figure 2 This is a comparison of the time-voltage curves of the symmetrical button cells assembled in Example 2 and Comparative Example 2 under conditions 1-5. Figure 1 The comparison shows that at a current density of 10 mA cm⁻¹ -2 Under high current, the polarization of the battery without crown ether suddenly increases after less than 20 cycles, which is a result of the formation of large tin particles. In contrast, the battery assembled with the electrolyte containing crown ether can stably cycle for over 1700 cycles. Figure 2 The comparison shows that at a current density of 1 mA cm⁻¹ -2 The area capacity is 5mAh cm -2 Under the same conditions, the symmetric button cell of Comparative Example 2, assembled using a blank electrolyte without 15-crown ether-5, only had a cycle time of 120 hours, after which the polarization suddenly and drastically increased. This indicates that large tin particles were generated on the tin anode surface during deposition, eventually detaching from the tin foil surface and causing the battery to short-circuit and fail. Under the same test conditions, the Sn-Sn symmetric cell of Example 2 achieved a cycle time of 5 mAh cm⁻¹. -2 Under large capacity conditions, the cycle time can exceed 800 hours, indicating that the aqueous crown ether electrolyte that can chelate tin ions in Example 1 can greatly improve the cycle life of the battery. This is because the specific internal cavity size of 15-crown ether-5 chelates tin ions, thereby playing a role in the nucleation of tin ions, regulating the uniform deposition of tin anode, making the tin ion deposition more uniform, and effectively reducing the generation of "dead tin".

[0047] Example 3: Assembling an asymmetric button cell with an aqueous crown ether electrolyte capable of chelating stannous ions.

[0048] After cleaning tin foil and copper foil cut into 12mm diameter circular pieces with alcohol, the tin foil is used as the negative electrode of the button cell, and the copper foil as the positive electrode. First, the tin foil negative electrode is placed in the negative electrode shell, followed by a glass fiber separator. Then, 120μL of the aqueous crown ether electrolyte from Example 1, which can chelate tin ions, is added. Next, the copper foil positive electrode is placed, and a spacer and spring are placed on top. Finally, the positive electrode shell is placed on top, and the battery is packaged using a battery packaging machine to assemble an asymmetric button cell, labeled as BE(2mol / L H2SO4+0.1mol / L SnSO4)+15-crown-5 asymmetric button cell.

[0049] Comparative Example 3: Assembling Asymmetric Button Cells with Blank Electrolyte

[0050] The difference from Example 3 is that the electrolyte was replaced with the blank electrolyte prepared in Comparative Example 1, and an asymmetric button cell was assembled and labeled as BE(2mol / L H2SO4+0.1mol / L SnSO4) asymmetric button cell.

[0051] Figure 3 The coulombic efficiency-cycle count plot is shown for the asymmetric button cell (BE+15-crown-5 asymmetric button cell) of Example 3. Figure 4 This is a coulombic efficiency-cycle count plot for the asymmetric coin cell (BE asymmetric coin cell) of Comparative Example 3. Figure 3 and Figure 4 The comparison shows that at a current density of 2 mA cm⁻¹ -2 The surface area capacity is 2mAh cm -2 Under the same conditions, the BE asymmetric button cell of Comparative Example 3 could only cycle about 12 times, and the average coulombic efficiency was only 61.94%. However, the BE+15-crown-5 asymmetric button cell using an aqueous crown ether electrolyte that can chelate tin ions could cycle stably for more than 200 times, and the coulombic efficiency could reach 99.12%. This indicates that the aqueous crown ether electrolyte that can chelate tin ions of the present invention is beneficial to the uniform transport of tin ions at the negative electrode / electrolyte interface and the uniform deposition / stripping of tin ions, thereby increasing the stability of the battery cycle.

[0052] Example 4: Linear Scan Voltammetry

[0053] Three-electrode assemblies were assembled using the aqueous crown ether electrolyte capable of chelating stannous ions prepared in Example 1 and the blank electrolyte of Comparative Example 1, respectively. Tin foil was used as the counter electrode, copper foil as the working electrode, and Hg / Hg₂SO₄ as the reference electrode. Linear sweep voltammetry was performed, and the obtained linear sweep voltammetry curves are shown below. Figure 5 and Figure 6 As shown, from Figure 5 , Figure 6 As can be seen from the comparison, the aqueous crown ether electrolyte prepared in Example 1, which can chelate tin ions, gives the tin anode a more negative hydrogen evolution potential. This is evident from the optical photographs of the tin deposition morphology on the copper foil after the hydrogen evolution test. Figure 7 and Figure 8 It is evident that the aqueous crown ether electrolyte prepared in Example 1, which can chelate stannous ions, enables uniform deposition of stannous ions on the copper foil. In contrast, the electrolyte without crown ether produces a large amount of "dead tin" during the deposition process and is more prone to hydrogen evolution reaction.

[0054] Example 5: Tafel Test

[0055] Three electrodes were assembled using the aqueous crown ether electrolyte capable of chelating stannous ions prepared in Example 1 and the blank electrolyte of Comparative Example 1, respectively. Tin foil was used as the working electrode, a platinum sheet electrode as the counter electrode, and Hg / Hg₂SO₄ as the reference electrode. Tafel tests were performed. Figure 9 and Figure 10 As can be seen from the comparison, the aqueous crown ether electrolyte that can chelate tin ions prepared in Example 1 gives the tin anode a more positive corrosion potential, that is, it has higher corrosion resistance.

[0056] Example 6: Preparation of H-type dual-deposition tin-manganese full cell

[0057] Using 100μm carbon paper as the positive current collector and copper foil as the negative current collector, 1.635mL of concentrated sulfuric acid was added to 11.88mL of deionized water and stirred evenly. Then, 0.3221g of stannous sulfate was added and stirred a second time. Then, 1.2676g of manganese sulfate was added and stirred a third time. Finally, 1.485mL of 15-crown ether-5 was added to prepare 15mL of positive side electrolyte. 15mL of the aqueous crown ether electrolyte that can chelate stannous ions from Example 1 was used as the negative side electrolyte. A polybenzimidazole proton exchange membrane was placed between the two electrolyte tanks to assemble an H-type double-deposition tin-manganese full cell.

[0058] The capacity-voltage curves of the H-type double-deposition tin-manganese full cell under constant current charge-discharge were obtained after testing, as shown below. Figure 11 As shown, the constant current charge-discharge cycle diagram of the H-type double-deposition tin-manganese full cell is as follows: Figure 12 As shown, the capacity-voltage curve of the H-type double-deposited tin-manganese full cell at a constant voltage of 1.9V is as follows. Figure 13 As shown, the cycling diagram of the H-type double-deposition tin-manganese full cell at a constant voltage of 1.9V is as follows. Figure 14 As shown.

[0059] from Figure 11 , 12 As shown in 13 and 14, the assembled H-type double-deposition tin-manganese full cell can not only perform constant current charge-discharge in the range of 0.2-1.9V with a stable coulombic efficiency of 98.19%, but also achieve stable cycling for more than 300 cycles at a high voltage of 1.9V with a stable coulombic efficiency of 97.04%. This indicates that the aqueous crown ether electrolyte that can chelate tin ions effectively reduces the formation of "dead tin," resulting in better cycle stability of the tin anode and the assembled H-type double-deposition tin-manganese full cell. This is of great significance for the subsequent research on tin-ion batteries.

[0060] In summary, the aqueous crown ether electrolyte that can chelate tin ions provided by this invention has a significant inhibitory effect on the formation of "dead tin," a significant effect on the deposition / stripping regulation of tin anodes, and can achieve stable cycling with high areal capacity in coin cells, stable cycling with high coulombic efficiency in asymmetric cells, a significant inhibitory effect on hydrogen evolution and corrosion, and a significant improvement effect on the deposition morphology of tin ions. It is of great significance for improving tin anodes.

[0061] This invention assembles a simple H-type double-deposition tin-manganese full cell with only a current collector. The aqueous crown ether electrolyte that can chelate tin ions has a longer cycle life of the tin anode due to its suppression of "dead tin," which in turn makes the assembled H-type double-deposition tin-manganese full cell have a longer cycle life. Even at a high voltage of 1.9V, it can achieve high coulombic efficiency. This H-type double-deposition tin-manganese full cell that only allows proton exchange is beneficial to the development of subsequent energy storage technologies.

[0062] The embodiments of the present invention have been described in detail above, but the present invention is not limited to the described embodiments. For those skilled in the art, various changes, modifications, substitutions, and variations can be made to these embodiments without departing from the principles and spirit of the present invention, and these variations still fall within the protection scope of the present invention.

Claims

1. An aqueous crown ether electrolyte capable of chelating stannous ions, characterized in that, The aqueous crown ether electrolyte capable of chelating stannous ions includes deionized water, acid, soluble stannous salt, and crown ether with a specific internal cavity size. The acid is either hydrochloric acid or sulfuric acid; The soluble stannous salt is one of stannous sulfate and stannous chloride; The crown ether is one of 12-crown ether-4, 15-crown ether-5, 18-crown ether-6, or 21-crown ether-7; the cavity diameter of 12-crown ether-4 is 120~150 pm, the cavity diameter of 15-crown ether-5 is 170~220 pm, the cavity diameter of 18-crown ether-6 is 260~320 pm, and the cavity diameter of 21-crown ether-7 is 340~430 pm. The ratio of the inner diameter of the crown ether to the diameter of the stannous ion is 1 to 2.

2. The aqueous crown ether electrolyte capable of chelating stannous ions according to claim 1, characterized in that, The concentration of crown ether in the electrolyte is 0.01~5 mol / L, and the amount of acid used is 1~5 times the amount of crown ether used; the amount of soluble stannous salt used is 1~5 times the amount of crown ether used.

3. A method for preparing an aqueous crown ether electrolyte capable of chelating stannous ions as described in any one of claims 1-2, characterized in that, The preparation method includes the following steps: mixing deionized water and acid and stirring for the first time, then adding soluble stannous salt and stirring for the second time, and then adding crown ether with a specific inner cavity size and stirring for the third time to obtain the aqueous crown ether electrolyte that can chelate stannous ions.

4. An H-type dual-deposition tin-manganese full cell, characterized in that, The tin-manganese full cell includes a positive electrode current collector, a negative electrode current collector, a proton exchange membrane, a positive electrode side electrolyte, and an aqueous crown ether electrolyte capable of chelating tin ions as described in any one of claims 1-2.

5. The H-type dual-deposition tin-manganese full cell according to claim 4, characterized in that, The preparation method of the positive electrode side electrolyte is as follows: deionized water and acid are mixed, then stannous salt is added, and finally manganese salt is added and stirred evenly to obtain the positive electrode side electrolyte of H-type double-deposition tin-manganese full cell.

6. The H-type dual-deposition tin-manganese full cell according to claim 5, characterized in that, The manganese salt is manganese sulfate with a concentration of 0.01~2 mol / L.

7. The H-type dual-deposition tin-manganese full cell according to claim 4, characterized in that, The proton exchange membrane is polybenzimidazole; the negative electrode current collector is one of copper foil, carbon paper, carbon felt, and titanium mesh; the positive electrode current collector is one of carbon paper, carbon felt, carbon cloth, titanium mesh, and stainless steel mesh.

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