A water-based battery electrolyte for inhibiting dendrite growth, and a preparation method and application thereof

Abstract

This invention belongs to the field of aqueous batteries and discloses an aqueous battery electrolyte that inhibits dendrite growth, its preparation method, and its application. The aqueous battery electrolyte includes an alkaline electrolyte and electrolyte additives; the electrolyte additives include an organic base and an organic zinc salt. In the aqueous battery electrolyte, the concentration of the alkaline electrolyte solute is 3-8 mol / L, the concentration of the organic base is 0.1-2 mol / L, and the concentration of the organic zinc salt is 0.1-1 mol / L. Unmodified electrolytes show obvious dendrites after two cycles. The aqueous battery electrolyte of this invention can effectively inhibit dendrite growth, and no large dendrites appear after 50 cycles, greatly reducing the risk of internal short circuits caused by dendrites piercing the separator, and significantly improving electrochemical reversibility and cycle stability. Moreover, the preparation process of this electrolyte is simple, cost-controllable, reproducible, and easy to industrialize, with broad application prospects.

Description

Technical Field

[0001] This invention relates to the field of aqueous batteries, and more particularly to an aqueous battery electrolyte that inhibits dendrite growth, its preparation method, and its application. Background Technology

[0002] With the increasing proportion of intermittent renewable energy sources such as wind and solar power, large-scale energy storage systems with high efficiency, long lifespan, and low environmental impact are needed for peak shaving and valley filling. Traditional organic electrolyte lithium-ion batteries pose a risk of thermal runaway, which may lead to fires or even explosions, especially in large-scale energy storage power stations or high-temperature environments. Aqueous alkaline nickel-zinc batteries, however, use a non-flammable aqueous solution as the electrolyte, fundamentally eliminating the risk of combustion and explosion. In addition, alkaline aqueous nickel-zinc batteries have a series of other advantages, including abundant and low-cost raw materials, high energy density, and high environmental friendliness, making them promising for large-scale energy storage applications. However, alkaline aqueous nickel-zinc batteries, especially their zinc anode, still face severe challenges from a series of side reactions such as uncontrolled dendrite growth and hydrogen evolution reaction surface passivation, which seriously restrict the battery's cycle life and safety. Besides the influence of interfacial reaction kinetics, the growth of zinc dendrites is also significantly affected by macroscopic physical fields (such as gravity) on deposition uniformity. Gravity causes the discharge product zincate ions (Zn(OH)4) to grow. 2- Zinc dendrites settle and form a vertical concentration gradient in the electrolyte, thereby inducing preferential deposition of zinc at the bottom of the electrode and the growth of giant dendrites. CN117832753A prepared a paper-based separator for aqueous zinc-ion batteries resistant to dendrite penetration to prevent short circuits caused by zinc dendrites, but it did not fundamentally solve the problem of zinc dendrite formation. CN119491179A used a laser cutting machine to perform surface laser texturing on zinc foil to increase the number of surface active sites, thereby obtaining the zinc foil used to inhibit zinc dendrite growth. However, it has high equipment requirements and is limited to the inhibition of zinc dendrites in weakly acidic electrolytes, without mentioning the effect of inhibiting dendrites in alkaline electrolytes. Therefore, there is an urgent need to develop a new method that is universal, has low equipment requirements, and can inhibit zinc dendrite growth at its source. Summary of the Invention

[0003] In order to solve the above-mentioned technical problems and make up for the deficiencies in the prior art, the primary objective of the present invention is to provide an electrolyte for an aqueous battery that inhibits dendrite growth.

[0004] Another objective of this invention is to provide a method for preparing an aqueous battery electrolyte that inhibits dendrite growth. This method is simple, inexpensive, and can significantly inhibit the formation of dendrites in alkaline aqueous zinc-ion batteries.

[0005] Another object of the present invention is to provide the application of the electrolyte in the above-mentioned aqueous battery for inhibiting dendrite growth.

[0006] Another objective of this invention is to provide an aqueous zinc-ion battery.

[0007] To achieve the above objectives, the present invention adopts the following technical solution:

[0008] An aqueous battery electrolyte for inhibiting dendrite growth includes an alkaline electrolyte and an electrolyte additive.

[0009] The electrolyte additives include organic bases and organic zinc salts.

[0010] Preferably, in the aqueous battery electrolyte, the concentration of the alkaline electrolyte solute is 3~8 mol / L, the concentration of the organic base is 0.1~2 mol / L, and the concentration of the organic zinc salt is 0.1~1 mol / L.

[0011] Preferably, in the aqueous battery electrolyte, the concentration of the alkaline electrolyte solute is 5~7 mol / L, the concentration of the organic base is 0.5~1 mol / L, and the concentration of the organic zinc salt is 0.2~0.75 mol / L.

[0012] Preferably, the molar ratio of the organic base to the organic zinc salt is 1~10:1, more preferably 1.5~5:1.

[0013] Preferably, the alkaline electrolyte is an aqueous solution of lithium hydroxide, potassium hydroxide, or sodium hydroxide.

[0014] Preferably, the organic base is at least one of tetramethylammonium hydroxide or tetraethylammonium hydroxide;

[0015] The organic zinc salt is at least one of zinc acetate or zinc oxalate.

[0016] A method for preparing an aqueous battery electrolyte that inhibits dendrite growth includes the following steps:

[0017] (1) Dissolve the inorganic base in water and stir to obtain an alkaline electrolyte;

[0018] (2) Dissolve organic zinc and organic base in the alkaline electrolyte described in step (1), and then pass nitrogen or inert gas through to obtain an aqueous battery electrolyte that inhibits dendrite growth.

[0019] Preferably, the inert gas in step (2) is argon, and the introduction time is ≥10 min.

[0020] The above-mentioned aqueous battery electrolyte for inhibiting dendrite growth is applied in aqueous zinc-ion batteries.

[0021] An aqueous zinc-ion battery includes the above-mentioned aqueous battery electrolyte that inhibits dendrite growth.

[0022] Compared with the prior art, the present invention has the following advantages and beneficial effects:

[0023] 1. This invention introduces organic zinc salts (such as zinc acetate (Zn(Ac)2)) and organic bases (such as tetramethylammonium hydroxide (TMAOH)) as electrolyte additives into an alkaline electrolyte. The preparation process is simple, cost-controllable, reproducible, and easy to industrialize, achieving dual regulation from the bulk electrolyte to the electrode interface.

[0024] 2. The electrolyte of this invention can inhibit dendrite growth and improve safety. It does not produce large dendrites after 50 cycles, which is superior to KOH electrolyte, TMA electrolyte and KOH-Ac electrolyte, and greatly reduces the risk of internal short circuit caused by dendrites piercing the diaphragm.

[0025] 3. The electrolyte of the present invention can significantly improve electrochemical reversibility and cycle stability. Attached Figure Description

[0026] Figure 1 The results are from CV tests with different electrolytes.

[0027] Figure 2 Tafel polarization curves of zinc foil in electrolytes with different additives.

[0028] Figure 3 Symmetrical battery cycle performance of batteries assembled with different electrolytes.

[0029] Figure 4 Rate performance of symmetrical batteries assembled with different electrolytes.

[0030] Figure 5 In-situ optical microscopy images of batteries assembled with different electrolytes, from top to bottom: KOH, TMA, KOH-Ac, and TMA-0.5Ac solutions.

[0031] Figure 6 Figure showing dendrite growth on the surface of the zinc anode in batteries assembled with different electrolytes. Detailed Implementation

[0032] The present invention will be further described in detail below with reference to the embodiments and accompanying drawings. However, the implementation of the present invention is not limited thereto. For process parameters not specifically noted, conventional techniques can be referred to.

[0033] Example 1

[0034] The method for preparing aqueous battery electrolyte in this scheme includes the following steps:

[0035] (1) Preparation of alkaline solution: Take 336.65g of KOH and put it into a beaker. Add ultrapure water to dissolve it and prepare 1L of 6MKOH solution.

[0036] (2) Preparation of modified electrolyte: Weigh 109.8 g of zinc acetate dihydrate and 91.15 g of tetramethylammonium hydroxide and dissolve them in the KOH solution prepared in step (1). Stir until the solution is clear to obtain the modified electrolyte. The molar concentration of zinc acetate is 0.5 M and the molar concentration of tetramethylammonium hydroxide is 1 M, denoted as TMA-0.5Ac.

[0037] (3) Introduce protective gas: Introduce argon gas into the TMA-Ac solution prepared in step (2) for 15 minutes to create an oxygen-free and inert chemical environment.

[0038] Example 2

[0039] (1) Preparation of alkaline solution: Take 240.06g of KOH and dissolve it in a beaker to prepare 1L of 6M KOH solution.

[0040] (2) Preparation of modified electrolyte: Weigh 109.8g of zinc acetate dihydrate and 68.36g of tetramethylammonium hydroxide and dissolve them in the KOH solution prepared in (1). Stir the solution until it is clear to obtain the modified electrolyte. The molar concentration of zinc acetate is 0.5M and the molar concentration of tetramethylammonium hydroxide is 0.75M, which is denoted as 0.75TMA-0.5Ac.

[0041] (3) Introduce protective gas: Introduce argon gas into the prepared TMA-Ac solution in step (2) for 10 min.

[0042] Example 3

[0043] (1) Preparation of alkaline solution: Take 240.06g of KOH and dissolve it in a beaker to prepare 1L of 6M KOH solution.

[0044] (2) Preparation of modified electrolyte: Weigh 43.92 g of zinc acetate dihydrate and 91.15 g of tetramethylammonium hydroxide and dissolve them in the KOH solution prepared in (1). Stir the solution until it is clear to obtain the modified electrolyte. The molar concentration of zinc acetate is 0.2 M and the molar concentration of tetramethylammonium hydroxide is 1 M, denoted as TMA-0.2Ac.

[0045] Comparative Example 1

[0046] The electrolyte is a KOH solution. A 6M KOH solution is prepared using ultrapure water and analytical grade KOH (95% Maclean). After preparation, argon gas is introduced as a protective gas for later use.

[0047] Comparative Example 2

[0048] The electrolyte is a TMA solution, prepared by mixing 1M TMAOH solution and analytical grade KOH (95% Maclean). KOH powder is added to the 1M TMAOH solution, resulting in a TMAOH concentration of 1M and a KOH concentration of 6M. After preparation, argon gas is introduced as a protective gas for later use.

[0049] Comparative Example 3

[0050] The electrolyte is prepared by adding 0.5 mol Zn(Ac)2 powder to 1 L of 6M KOH solution and allowing it to stand to degas before use.

[0051] Comparative Example 4

[0052] The electrolyte used is KOH-SO4 2- The solution is prepared by adding 0.5 mol ZnSO4 powder to each 1 L of 6M KOH solution, and is allowed to stand to degas before use.

[0053] Test case

[0054] Performance tests were conducted on Examples 1-3 and Comparative Examples 1, 2, and 3, where:

[0055] The CV test conditions were as follows: the working electrode was zinc foil, the reference electrode was mercuric oxide electrode, and the counter electrode was platinum electrode. The test parameters on the electrochemical workstation were set as follows: the test potential window was -1.0 to -1.8 V (vs. mercuric oxide electrode), and the scan rate was 5 mV / s.

[0056] The Tafel test conditions were as follows: the working electrode was zinc foil, the reference electrode was a mercuric oxide electrode, and the counter electrode was a platinum electrode. The test parameters on the electrochemical workstation were set as follows: the test potential window was -1.4 to -1.65 V (vs. mercuric oxide electrode), and the scan rate was 1 mV / s.

[0057] The test conditions for the charge-discharge curves of the symmetrical electrode are as follows: the symmetrical cell is a coin cell assembled with zinc sheets for both positive and negative electrodes, and the test current density is 5 mA cm⁻¹. -2 The charge / discharge capacity is 1 mAh cm⁻¹ -2 .

[0058] The in-situ optical microscope testing conditions were as follows: the battery casing was an acrylic mold, with two acrylic plates at each end and an acrylic plate of the same size as the ends but with a cavity in the middle. Two zinc sheets were placed in the middle of the acrylic plates, and each plate was tightened with screws. Zinc sheets were used for both the positive and negative electrodes. The test current density was 5 mA cm⁻¹. -2 The charge / discharge capacity is 1 mAhcm -2During battery testing, an optical microscope was used to observe the surface morphology of the electrodes inside the battery in situ.

[0059] Figure 1 The results of CV tests with different electrolytes are presented. During the forward scan, the test systems using KOH, TMA, and KOH-Ac solutions as electrolytes exhibited an oxidation peak corresponding to zinc dissolution at approximately -1.08 V. The oxidation peak of the TMA-Ac test system shifted to a more negative potential value, at approximately -1.13 V. This shift in the oxidation peak position to a negative potential indicates a lower activation barrier for the oxidation reaction: the substances on the electrode surface begin to oxidize at a lower potential than before. This demonstrates that the addition of TMAOH and zinc acetate can favorablely alter the kinetic environment of the electrode / electrolyte interface. During the negative scan, another large oxidation peak appeared at approximately -1.16 V, corresponding to the re-oxidation of zinc in the presence of some early-formed oxides. Comparison revealed that the intensity of this oxidation peak significantly decreased after the addition of zinc acetate, indicating that the increased zinc ion concentration inhibited the re-oxidation process. The reduction peak between -1.6 and -1.7 V represents the reduction process of zinc ions. It was found that the KOH solution had the smallest reduction peak intensity, indicating poor reversibility. The peak intensities of the electrolyte with TMAOH or zinc acetate added alone were significantly increased compared to the initial solution without additives. The electrolyte with both additives added simultaneously showed the largest reduction peak intensity, indicating that the addition of additives enhanced the cycle stability of the zinc anode in the electrochemical process.

[0060] Figure 2 Tafel polarization curves of zinc foil in electrolytes with different additives were obtained. It was found that regardless of which additive was added, the corrosion potential shifted significantly to the positive potential, indicating that it inhibited the corrosion of zinc electrodes in alkaline electrolytes. The TMA-Ac electrolyte showed a lower corrosion potential. The co-addition of TMA and zinc acetate can enhance the corrosion resistance of zinc, and there may be a certain synergistic effect between the two.

[0061] Figure 3 For alkaline zinc-zinc symmetric cells at a current density of 5 mA cm⁻¹ -2 1 mAh cm -2The charge-discharge curves for different cycle numbers are shown. In the basic KOH electrolyte, the initial cycle overpotential is high (approximately 600 mV), which gradually decreases and stabilizes with each cycle. This is related to the dynamic reconstruction of the passivation layer on the electrode surface and the accumulation of zinc ion concentration in the solution, consistent with previous test results. Adding TMAOH alone (TMA electrolyte) has a limited effect on reducing the overpotential. However, with the addition of zinc acetate (KOH-Ac electrolyte), the overpotential is very low from the first cycle due to the increased zinc ion concentration, and this low overpotential trend is maintained throughout the cycle. The electrolyte containing both zinc acetate and TMAOH (TMA-Ac) exhibits a lower overpotential from the first cycle due to the significantly increased initial zinc ion concentration and reduced charge transfer resistance, and remains stable throughout the cycle.

[0062] To evaluate the performance of different electrolytes at high rates, zinc-zinc symmetric batteries were fabricated. The fabrication method is similar to... Figure 3 The battery structures used in all tests were identical, and rate tests were conducted. The rate conditions, from first to last, were 0.25, 0.5, 1, 2, 5, 10, and 0.5 mAh / cm³. -2 ( Figure 4 The results show that the addition of additives can significantly reduce the deposition overpotential, whether under low-rate testing conditions (overpotential controlled by activation polarization and initial ohmic resistance) or high-rate testing conditions (concentration polarization begins to dominate, exposing mass transfer limitations). This indicates that the additives synergistically improve ion transport kinetics and alleviate mass transfer limitations.

[0063] The effects of different electrolytes on dendrite suppression were tested in situ using optical microscopy. Figure 5 It was found that the electrode surfaces were smooth and flat in the initial state. However, significant dendrites appeared in the unmodified electrolyte after two cycles. Adding TMAOH did not effectively reduce the tendency of dendrite formation; significant dendrites also appeared at the beginning of the second cycle. However, because TMA ions adsorb onto the zinc anode surface, the deposition became more uniform compared to the unmodified electrolyte surface, and the dendrite shape changed from severe dendritic dendrites to relatively less harmful moss-like dendrites. After adding sufficient zinc acetate to eliminate the concentration gradient in the solution, the dendrite phenomenon during cycling was greatly alleviated, and more significant dendrites appeared only after 20 cycles. The electrolyte with both added simultaneously showed superior performance, and it could withstand 50 cycles without the appearance of large dendrites.

[0064] For a current density of 5 mA cm -2 The charge / discharge capacity is 1 mAh cm⁻¹ -2The zinc anode was photographed after cycling, and the degree of dendrite growth on the surface of the zinc anode after the reaction was directly observed. Figure 6 The photos from left to right are Example 1, Example 2, Example 3 (top row) and Comparative Examples 1, 2, 3 and 4 (bottom row). It can be clearly observed that no obvious zinc dendrites appeared on the surface of the zinc negative electrode after the reaction in the examples, while obvious zinc dendrites appeared on the electrode after the reaction in the comparative examples, proving that the electrolyte used in the examples has a good effect on inhibiting the formation of zinc dendrites.

[0065] The above embodiments are preferred embodiments of the present invention, but the embodiments of the present invention are not limited to the above embodiments. Any changes, modifications, substitutions, combinations, or simplifications made without departing from the spirit and principle of the present invention shall be considered equivalent substitutions and shall be included within the protection scope of the present invention.

Claims

1. An aqueous battery electrolyte that suppresses dendrite growth, characterized by, It includes an alkaline electrolyte and electrolyte additives; the electrolyte additives include organic bases and organic zinc salts.

2. The aqueous battery electrolyte for inhibiting dendrite growth according to claim 1, characterized in that, In the aqueous battery electrolyte, the concentration of alkaline electrolyte solute is 3~8 mol / L, the concentration of organic base is 0.1~2 mol / L, and the concentration of organic zinc salt is 0.1~1 mol / L.

3. The aqueous battery electrolyte for inhibiting dendrite growth according to claim 1, characterized in that, In the aqueous battery electrolyte, the concentration of alkaline electrolyte solute is 5~7 mol / L, the concentration of organic base is 0.5~1 mol / L, and the concentration of organic zinc salt is 0.2~0.75 mol / L.

4. The aqueous battery electrolyte for inhibiting dendrite growth according to claim 1, characterized in that, The molar ratio of the organic base to the organic zinc salt is 1 to 10:

1.

5. The aqueous battery electrolyte for inhibiting dendrite growth according to claim 1, characterized in that, The alkaline electrolyte is an aqueous solution of lithium hydroxide, potassium hydroxide, or sodium hydroxide.

6. The aqueous battery electrolyte for inhibiting dendrite growth according to claim 1, characterized in that, The organic base is at least one of tetramethylammonium hydroxide or tetraethylammonium hydroxide; The organic zinc salt is at least one of zinc acetate or zinc oxalate.

7. A method for preparing an aqueous battery electrolyte for inhibiting dendrite growth as described in any one of claims 1 to 6, characterized in that, Includes the following steps: (1) Dissolve the inorganic base in water and stir to obtain an alkaline electrolyte; (2) Dissolve organic zinc and organic base in the alkaline electrolyte described in step (1), and then pass nitrogen or inert gas through to obtain an aqueous battery electrolyte that inhibits dendrite growth.

8. The method for preparing an aqueous battery electrolyte that inhibits dendrite growth according to claim 7, characterized in that, The inert gas in step (2) is argon, and the introduction time is ≥10min.

9. The application of the aqueous battery electrolyte for inhibiting dendrite growth as described in any one of claims 1 to 6 in an aqueous zinc-ion battery.

10. An aqueous zinc-ion battery, characterized in that, Includes the electrolyte as described in any one of claims 1 to 6.

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