Aqueous electrolyte, preparation method thereof and aqueous battery

Abstract

The invention discloses an aqueous electrolyte, a preparation method thereof and an aqueous battery, belongs to the technical field of aqueous batteries, and solves the problems of high polarization potential and short cycle life of an aqueous zinc ion battery in the prior art. The aqueous electrolyte comprises the following components: zinc salt, an additive and water; wherein the additive comprises sulfonate, acetate and halide. The aqueous battery adopting the aqueous electrolyte is long in cycle life and low in polarization potential.

Description

Technical Field

[0001] The present invention relates to the technical field of aqueous batteries, and particularly relates to an aqueous electrolyte, a preparation method thereof, and an aqueous battery. Background Art

[0002] Aqueous zinc-ion batteries have the characteristics of high safety, rich zinc reserves, high theoretical capacity, low electrochemical oxidation-reduction potential of metallic zinc, and simple preparation process. They are a promising energy storage device. However, during the operation of the battery, the growth of zinc dendrites and the instability of metallic zinc in aqueous solutions (side reactions such as corrosion, passivation, and hydrogen evolution) will lead to poor reversibility of the zinc negative electrode and limited cycle life, seriously hindering the commercialization process of aqueous zinc-ion batteries.

[0003] In recent years, researchers have developed a series of approaches to alleviate the dendrite growth and side reactions of the zinc negative electrode to improve the reversibility of the negative electrode, such as constructing a zinc negative electrode protection layer, optimizing the electrolyte, and modifying the separator. Among them, the electrolyte optimization strategy is a convenient, economical, and general method. By introducing electrolyte additives, an interfacial layer can be formed in-situ, or zinc can be induced to deposit directionally, or the zinc ion solvation structure can be changed, thereby regulating the zinc deposition / dissolution process and improving the cycle life and reversibility of the negative electrode. However, the current research mainly focuses on the optimization mechanism of the introduction of a single additive to the negative electrode. This optimization effect is limited and difficult, and it can only optimize a specific problem and is difficult to solve the numerous problems faced by the negative electrode. Summary of the Invention

[0004] In view of the above situation, the present invention aims to provide an aqueous electrolyte, a preparation method thereof, and an aqueous battery for at least solving one of the following technical problems: the polarization potential of the existing aqueous zinc-ion battery is high, and the cycle life is short.

[0005] The object of the present invention is mainly achieved by the following technical solutions:

[0006] On the one hand, the present invention provides an aqueous electrolyte. The components of the aqueous electrolyte include: zinc salt, additive, and water; wherein, the additive includes sulfonate, acetate, and halide.

[0007] Further, the zinc salt includes one or more of zinc sulfate, zinc chloride, zinc trifluoromethanesulfonate, zinc acetate, zinc nitrate, zinc perchlorate, and tetraaquaboric acid zinc hydroxide.

[0008] Further, the sulfonate includes one or more of sodium 3-mercapto-1-propanesulfonate, sodium diphenylamine sulfonate, sodium aminosulfonate, potassium aminosulfonate, zinc aminosulfonate, sodium lignosulfonate, and sodium dodecylbenzenesulfonate.

[0009] Further, the acetate salt includes one or more of sodium acetate, ammonium acetate, potassium acetate, zinc acetate, magnesium acetate, and calcium acetate.

[0010] Further, the halide includes one or more of fluoride salts, chloride salts, bromide salts, and iodide salts.

[0011] Further, the concentration of the sulfonate is 5 - 100 mmol / L.

[0012] Further, the concentration of the acetate salt is 1 - 1000 mmol / L.

[0013] Further, the concentration of the halide is 0.05 - 2 mol / L.

[0014] The present invention also provides a method for preparing the above aqueous electrolyte, including:

[0015] Mixing and stirring zinc salt, sulfonate, and halide with water, and after dissolution, adding acetate salt to adjust the pH value of the system to obtain the aqueous electrolyte.

[0016] The present invention also provides an aqueous battery, and the aqueous battery includes the above aqueous electrolyte.

[0017] Compared with the prior art, the present invention can at least achieve one of the following beneficial effects:

[0018] a) The aqueous electrolyte provided by the present invention introduces three additives with different functions, namely sulfonate, acetate salt, and halide. The three substances act synergistically to simultaneously inhibit the growth of zinc dendrites and alleviate the occurrence of side reactions at the negative electrode, thereby improving the performance of the aqueous zinc-ion battery. The aqueous zinc-ion battery based on this aqueous electrolyte exhibits a low polarization potential and a long service life.

[0019] b) In the aqueous electrolyte of the present invention, the introduction of fluoride salt can in-situ form an inorganic interfacial layer with high zinc affinity on the surface of the zinc negative electrode, and the introduction of sodium 3-mercapto-1-propanesulfonate can form a uniform anion adsorption layer on the surface of zinc metal. The two interact with each other to form an inorganic-organic hybrid interfacial layer with high zinc ion flux and low water activity, which not only inhibits the occurrence of side reactions such as hydrogen evolution and corrosion at the negative electrode, but also can induce the uniform deposition of zinc ions with the (002) crystal plane; in addition, ammonium acetate acts as a pH regulator and buffer in the system, which not only avoids the decrease of the system pH caused by the introduction of sodium 3-mercapto-1-propanesulfonate and triggers side reactions, but also can maintain the concentration of OH - and H + at the interface during charge and discharge, and inhibits the formation of by-product basic zinc sulfate and the occurrence of hydrogen evolution reaction.

[0020] c) The aqueous electrolyte of the present invention has high cost-effectiveness, a simple process, and can be mass-produced.

[0021] d) Benefiting from the synergistic effect of three additives, the aqueous zinc-ion battery of the present invention exhibits a low polarization potential and a long lifespan. For example, the symmetric battery using the above-mentioned aqueous electrolyte has a long cycle stability of more than 700 h, and the polarization potential of the symmetric battery is below -45 to +49 mV.

[0022] Other features and advantages of the present invention will be described in the following specification, and some of them will become obvious from the specification or be understood by implementing the present invention. The objectives and other advantages of the present invention can be achieved and obtained by the content specifically pointed out in the written specification and the attached drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] The drawings are only for the purpose of showing specific embodiments and are not considered as limitations on the present invention. Throughout the drawings, the same reference numerals represent the same components.

[0024] Figure 1 Cycling performance of the symmetric battery assembled with the electrolyte of Example 1;

[0025] Figure 2 SEM-EDS surface scan of the zinc foil after 5 cycles in the electrolyte of Example 2;

[0026] Figure 3 XRD pattern of the zinc foil after cycling of the symmetric battery based on the electrolyte of Example 2;

[0027] Figure 4 Cycling performance of the symmetric battery assembled with the electrolyte of Example 2;

[0028] Figure 5 Cycling performance of the symmetric battery assembled with the electrolyte of Example 3;

[0029] Figure 6 Hydrogen evolution performance of the zinc foil in the electrolytes prepared in different cases;

[0030] Figure 7 Cycling performance of the symmetric battery assembled with the electrolyte of Comparative Example 1;

[0031] Figure 8 XRD pattern of the zinc foil before cycling in the electrolyte of Comparative Example 1;

[0032] Figure 9 XRD pattern of the zinc foil after cycling in the electrolyte of Comparative Example 1;

[0033] Figure 10 Cycling performance of the symmetric battery assembled with the electrolyte of Comparative Example 2;

[0034] Figure 11Cycling performance of the symmetric cell assembled with the electrolyte of Comparative Example 3;

[0035] Figure 12 Cycling performance of the symmetric cell assembled with the electrolyte of Comparative Example 4;

[0036] Figure 13 XRD pattern of the zinc foil after cycling in the electrolyte of Comparative Example 4;

[0037] Figure 14 Cycling performance of the symmetric cell assembled with the electrolyte of Comparative Example 5. Detailed Description of the Invention

[0038] The preferred embodiments of the present invention will be specifically described below with reference to the accompanying drawings, in which the drawings form a part of the present invention and are used together with the embodiments of the present invention to explain the principles of the present invention.

[0039] The present invention provides an aqueous electrolyte, and the components of the aqueous electrolyte include: zinc salt, additive and water; wherein, the additive includes sulfonate, acetate and halide.

[0040] Specifically, water as a solvent can provide a site for the electrochemical reaction and ensure the normal progress of the redox reaction during charge and discharge.

[0041] Specifically, in order to prevent impurity contamination, deionized water can be used for water.

[0042] Specifically, the above zinc salts include one or more of zinc sulfate, zinc chloride, zinc trifluoromethanesulfonate, zinc acetate, zinc nitrate, zinc perchlorate, and tetraaquaboric acid zinc oxide.

[0043] Specifically, considering that too high a concentration of zinc salt will increase the viscosity of the electrolyte, thus hindering ion migration, reducing the conductivity, and even possibly causing salting-out phenomenon, affecting the performance of the battery; too low a concentration of zinc salt will result in a small number of carriers in the system, leading to low solution conductivity, increasing the internal resistance of the battery, and affecting the electrochemical performance of the battery. Therefore, the concentration of the zinc salt is controlled to be 0.1 - 3 mol / L. Preferably, the zinc salt is zinc sulfate, and the concentration of the zinc salt is 0.5 - 2 mol / L, such as 0.8 mol / L, 1 mol / L, 1.2 mol / L, 1.4 mol / L, 1.6 mol / L, 1.8 mol / L.

[0044] Specifically, the above sulfonates include one or more of sodium 3-mercapto-1-propanesulfonate, sodium diphenylamine sulfonate, sodium aminosulfonate, potassium aminosulfonate, zinc aminosulfonate, sodium lignosulfonate, and sodium dodecylbenzenesulfonate.

[0045] Preferably, the above sulfonate is sodium 3-mercapto-1-propanesulfonate.

[0046] Sodium 3-mercapto-1-propanesulfonate contains -SH and -SO3 - The zincophilic group can not only complex with zinc ions to regulate the desolvation process, but also chemically adsorb on the zinc metal surface, inducing dense and flat deposition of Zn along the (002) crystal plane, thereby inhibiting the growth of zinc dendrites. Considering that the addition concentration of sulfonate is too low, the distribution of sodium 3-mercapto-1-propanesulfonate at the negative electrode interface is uneven, resulting in insufficient modification effect; if the concentration is too high, it will not only increase the cost of the electrolyte, but also reduce the conductivity of the electrolyte, thereby increasing the polarization voltage of the battery and affecting the battery performance. Therefore, the concentration of sulfonate is controlled to be 5-100 mmol / L, such as 10 mmol / L, 20 mmol / L, 30 mmol / L, 40 mmol / L, 50 mmol / L, 60 mmol / L, 70 mmol / L, 80 mmol / L, 90 mmol / L; preferably, the concentration of sulfonate is 10-40 mmol / L.

[0047] Specifically, the above-mentioned acetate salts include one or more of sodium acetate, ammonium acetate, potassium acetate, zinc acetate, magnesium acetate, calcium acetate. The introduction of acetate salts can regulate the pH value of the electrolyte, and the concentration of acetate salts is controlled to be 1-1000 mmol / L. Preferably, the concentration of acetate salts is 5-100 mmol / L, so as to regulate the pH value of the aqueous electrolyte in the range of 4-5. For example, the concentration of acetate salts is 10 mmol / L, 20 mmol / L, 30 mmol / L, 40 mmol / L, 50 mmol / L, 60 mmol / L, 70 mmol / L, 80 mmol / L, 90 mmol / L. More preferably, the concentration of acetate salts is 25-50 mmol / L.

[0048] Preferably, ammonium acetate is selected as the acetate salt. It can not only regulate the pH value of the original aqueous electrolyte to maintain it between pH = 4-5, inhibiting the occurrence of hydrogen evolution side reactions caused by too low pH value, but also act as a pH buffer during the operation of the battery to maintain the concentrations of OH - and H + at the negative electrode / electrolyte interface, thereby inhibiting the formation of by-products.

[0049] Specifically, the above-mentioned halides include one or more of fluorides, chlorides, bromides and iodides. The concentration of the halides is 0.05-2 mol / L.

[0050] Preferably, the halide is a fluoride salt. During the electrochemical process, the fluoride salt can in-situ form a zincophilic inorganic interface layer composed of ZnF2 and ZnO on the surface of the zinc negative electrode, which can not only effectively isolate the direct contact between the zinc negative electrode and the electrolyte, inhibit the occurrence of parasitic side reactions related to water, but also promote the rapid transport of zinc ions, which is beneficial to reducing the polarization potential of the battery.

[0051] Considering that the concentration of fluoride salt is too low, resulting in a low concentration of F in the electrolyte - and it is impossible to form an inorganic interface layer or the formed inorganic interface layer is insufficient in thickness and cannot play the role of interface modification; the aqueous solution of fluoride is weakly alkaline, and if the concentration is too high, it will cause the pH value of the electrolyte to increase, and side products are likely to be generated during the charge and discharge process. Therefore, the concentration of fluoride salt is controlled to be 0.05 - 2 mol / L, such as 0.1 mol / L, 0.2 mol / L, 0.3 mol / L, 0.5 mol / L, 0.7 mol / L, 1 mol / L, 1.2 mol / L, 1.3 mol / L, 1.5 mol / L, 1.7 mol / L. Preferably, the concentration of fluoride salt is controlled to be 0.1 - 0.5 mol / L.

[0052] Compared with the prior art, the aqueous electrolyte provided by the present invention introduces three additives with different functions, namely sulfonate, acetate and halide. The three substances act synergistically, and based on this aqueous electrolyte, the aqueous zinc-ion battery exhibits a low polarization potential and a long service life.

[0053] In the aqueous electrolyte of the present invention, the introduction of fluoride salt can in-situ form an inorganic interface layer with high zinc affinity on the surface of the zinc negative electrode, while the introduction of sodium 3-mercapto-1-propanesulfonate can form a uniform anion adsorption layer on the surface of zinc metal. The two interact to form an inorganic-organic hybrid interface layer with high zinc ion flux and low water activity, which not only inhibits the occurrence of side reactions such as hydrogen evolution and corrosion at the negative electrode, but also can induce the uniform deposition of zinc ions with the (002) crystal plane; in addition, ammonium acetate acts as a pH regulator and buffer in the system, which not only avoids the decrease of the system pH caused by the introduction of sodium 3-mercapto-1-propanesulfonate and triggers side reactions, but also can maintain the concentration of OH- and H at the interface during the charge and discharge process + to inhibit the formation of by-product basic zinc sulfate and the occurrence of hydrogen evolution reaction.

[0054] The aqueous electrolyte of the present invention has high cost-effectiveness, simple process and can be mass-produced.

[0055] Benefiting from the synergistic effect of the three additives, the aqueous zinc-ion battery of the present invention exhibits a low polarization potential and a long service life.

[0056] The present invention also provides a preparation method of the above aqueous electrolyte, which includes the following steps:

[0057] Mix zinc salt, sulfonate and halide with water and stir. After dissolution, add acetate to adjust the pH value of the system to obtain the aqueous electrolyte.

[0058] Specifically, the pH of the aqueous electrolyte of the present invention is 4 - 5.

[0059] The present invention also provides an aqueous battery, which includes the above aqueous electrolyte.

[0060] Specifically, the aqueous battery may be an aqueous zinc ion battery.

[0061] Compared with the prior art, the aqueous battery of the present invention adopts a compound aqueous electrolyte including zinc salt, sulfonate, acetate and halide, and the aqueous battery exhibits a low polarization potential and a long service life.

[0062] The following further explains the technical solution of the present invention in conjunction with specific embodiments. It should be noted that the data in the embodiments are all exemplary descriptions, and during the production process, the dosage can be determined according to actual needs.

[0063] Example 1

[0064] This example provides an aqueous electrolyte, its preparation method and an aqueous battery.

[0065] The preparation method of the aqueous electrolyte in this example includes the following steps:

[0066] Weigh 2.8756 g of ZnSO4·7H2O, 0.0360 g of sodium 3-mercapto-1-propanesulfonate and 0.0420 g of sodium fluoride and add them to 10 mL of deionized water, stir until dissolved, and then add 0.0193 g of ammonium acetate to adjust the pH value of the system, and then an ZnSO4 electrolyte containing 20 mmol / L of sodium 3-mercapto-1-propanesulfonate + 25 mmol / L of ammonium acetate + 0.1 mol / L of sodium fluoride can be prepared.

[0067] The pH of the aqueous electrolyte in this example is 4.40, within the range of 4 to 5, which is beneficial to inhibiting the occurrence of negative electrode side reactions.

[0068] This example also provides a symmetric battery assembled with the aqueous electrolyte of Example 1. Symmetric battery assembly and electrochemical performance test conditions: Using the electrode prepared from zinc powder, zinc foil or electrodeposited zinc as the working electrode and the counter electrode (where the area of the working electrode is 24 cm 2 ), an Zn( counter electrode ) / / Zn( working electrode ) / / Zn( counter electrode ) square shell type symmetric aqueous zinc ion battery is assembled. This symmetric battery is first activated for 2 cycles under the conditions of 0.5 mA cm -2 , and the areal capacity is 2.5 mAh cm -2 , and then the electrochemical performance is tested under the conditions of a current density of 1 mA cm -2 , and the areal capacity is 5 mAh cm -2 .

[0069] Figure 1For the cycling performance of the symmetric cell assembled with the electrolyte of Example 1, it can be seen that the symmetric cell of this example has a long cycling stability of more than 800 h, and its polarization potential is -38 to 35 mV. The concentration of sodium fluoride in the electrolyte is relatively low, which results in an insufficient thickness of the formed inorganic layer and unstable interface optimization effect. Therefore, after cycling for 600 h, there is a slight increase in the polarization potential of the cell.

[0070] Example 2

[0071] This example provides an aqueous electrolyte, its preparation method, and an aqueous battery.

[0072] The preparation method of the aqueous electrolyte of this example includes the following steps:

[0073] Weigh 2.8756 g of ZnSO4·7H2O, 0.0360 g of sodium 3-mercapto-1-propanesulfonate, and 0.0840 g of sodium fluoride and add them to 10 mL of deionized water, stir until dissolved, and then add 0.0193 g of ammonium acetate to adjust the pH value of the system, and then the ZnSO4 electrolyte containing 20 mmol / L sodium 3-mercapto-1-propanesulfonate + 25 mmol / L ammonium acetate + 0.2 mol / L sodium fluoride can be prepared.

[0074] The pH of the aqueous electrolyte of this example is 4.61, within the range of 4 - 5, which is beneficial to inhibiting the occurrence of negative electrode side reactions.

[0075] This example also provides a symmetric cell assembled with the aqueous electrolyte of Example 2. The assembly and electrochemical performance test conditions of the symmetric cell are the same as those of Example 1, and will not be elaborated here.

[0076] Figure 2 It is the EDS surface scan diagram of the zinc foil after cycling 5 times in the electrolyte of Example 2. It is found that during the electrochemical process, sodium fluoride can in-situ form an inorganic interface layer composed of ZnF2 and ZnO on the surface of the zinc foil, effectively isolating the direct contact between the zinc negative electrode and the electrolyte and inhibiting the occurrence of parasitic side reactions related to water. Therefore, in the electrolyte of Example 2, the hydrogen evolution current density of the zinc foil at -1.30 V vs. Ag / AgCl potential is only 9.45 mA / cm -2 . Since the inorganic interface layer composed of ZnF2 and ZnO has high zinc affinity, it is beneficial to promote the rapid transfer of zinc ions, thereby reducing the cell polarization potential. In addition, further XRD testing was carried out on the cycled zinc foil (as Figure 3 shown), and it was found that this complex electrolyte can efficiently induce zinc to deposit along the (002) crystal plane. Thanks to the synergistic effect of the 3 additives, the symmetric cell assembled based on the electrolyte of Example 2 can stably cycle for more than 850 h and exhibits the lowest polarization potential (-30 - 36 mV, asFigure 4 as shown

[0077] Example 3

[0078] This example provides an aqueous electrolyte, a preparation method thereof, and an aqueous battery.

[0079] The preparation method of the aqueous electrolyte in this example includes the following steps:

[0080] Weigh 2.8756 g of ZnSO4·7H2O, 0.0360 g of sodium 3-mercapto-1-propanesulfonate, and 0.1260 g of sodium fluoride and add them to 10 mL of deionized water. Stir until dissolved, and then add 0.0193 g of ammonium acetate to adjust the pH value of the system. Then, a ZnSO4 electrolyte containing 20 mmol / L of sodium 3-mercapto-1-propanesulfonate + 25 mmol / L of ammonium acetate + 0.3 mol / L of sodium fluoride can be prepared.

[0081] The pH of the aqueous electrolyte in this example is 4.84, within the range of 4 - 5, which is beneficial to inhibiting the occurrence of negative electrode side reactions.

[0082] This example also provides a symmetric battery assembled with the aqueous electrolyte of Example 3. The assembly and electrochemical performance test conditions of the symmetric battery are the same as those of Example 1, and will not be elaborated here.

[0083] Figure 5 For the cycling performance of the symmetric battery assembled with the electrolyte of Example 3, it can be seen that the symmetric battery has a cycling stability of more than 800 h, and its polarization potential is -45 - 42 mV.

[0084] Example 4

[0085] This example provides an aqueous electrolyte, a preparation method thereof, and an aqueous battery.

[0086] The preparation method of the aqueous electrolyte in this example includes the following steps:

[0087] Weigh 2.8756 g of ZnSO4·7H2O, 0.0180 g of sodium 3-mercapto-1-propanesulfonate, and 0.0840 g of sodium fluoride and add them to 10 mL of deionized water. Stir until dissolved, and then add 0.0193 g of ammonium acetate to adjust the pH value of the system. Then, a ZnSO4 electrolyte containing 10 mmol / L of sodium 3-mercapto-1-propanesulfonate + 25 mmol / L of ammonium acetate + 0.2 mol / L of sodium fluoride can be prepared.

[0088] The pH of the aqueous electrolyte in this example is 4.4, within the range of 4 - 5, which is beneficial to inhibiting the occurrence of negative electrode side reactions.

[0089] This example also provides a symmetric battery assembled using the aqueous electrolyte of Example 4. The assembly of the symmetric battery and the test conditions for its electrochemical performance are the same as those in Example 1, and will not be elaborated here.

[0090] The symmetric battery of this example has a long cycle stability of more than 700 h, and its polarization potential is -45 to 49 mV.

[0091] Example 5

[0092] This example provides an aqueous electrolyte, its preparation method, and an aqueous battery.

[0093] The preparation method of the aqueous electrolyte of this example includes the following steps:

[0094] Weigh 2.8756 g of ZnSO4·7H2O, 0.0360 g of sodium 3-mercapto-1-propanesulfonate, and 0.0840 g of sodium fluoride and add them to 10 mL of deionized water, stir until dissolved, and then add 0.0385 g of ammonium acetate to adjust the pH value of the system, thus obtaining a ZnSO4 electrolyte containing 20 mmol / L of sodium 3-mercapto-1-propanesulfonate + 50 mmol / L of ammonium acetate + 0.2 mol / L of sodium fluoride.

[0095] The pH of the aqueous electrolyte of this example is 4.1, within the range of 4 to 5, which is beneficial to inhibiting the occurrence of negative electrode side reactions.

[0096] This example also provides a symmetric battery assembled using the aqueous electrolyte of Example 5. The assembly of the symmetric battery and the test conditions for its electrochemical performance are the same as those in Example 1, and will not be elaborated here.

[0097] The symmetric battery of this example has a long cycle stability of more than 750 h, and its polarization potential is -37 to 43 mV.

[0098] Example 6

[0099] This example provides an aqueous electrolyte, its preparation method, and an aqueous battery.

[0100] The preparation method of the aqueous electrolyte of this example includes the following steps:

[0101] Weigh 2.8756 g of ZnSO4·7H2O, 0.0720 g of sodium 3-mercapto-1-propanesulfonate, and 0.0840 g of sodium fluoride and add them to 10 mL of deionized water, stir until dissolved, and then add 0.0385 g of ammonium acetate to adjust the pH value of the system, thus obtaining a ZnSO4 electrolyte containing 40 mmol / L of sodium 3-mercapto-1-propanesulfonate + 50 mmol / L of ammonium acetate + 0.2 mol / L of sodium fluoride.

[0102] This example also provides a symmetric battery assembled using the aqueous electrolyte of Example 6. The assembly of the symmetric battery and the test conditions for its electrochemical performance are the same as those in Example 1 and will not be elaborated here.

[0103] The symmetric battery of this example has a long cycle stability of more than 700 h, and its polarization potential is -33 to 39 mV.

[0104] Example 7

[0105] This example provides an aqueous electrolyte, its preparation method, and an aqueous battery.

[0106] The preparation method of the aqueous electrolyte of this example includes the following steps:

[0107] Weigh 2.8756 g of ZnSO4·7H2O, 0.0547 g of sodium diphenylamine sulfonate, and 0.0840 g of sodium fluoride and add them to 10 mL of deionized water. Stir until dissolved, and then add 0.0385 g of ammonium acetate to adjust the pH value of the system. Thus, a ZnSO4 electrolyte containing 20 mmol / L of sodium diphenylamine sulfonate + 50 mmol / L of ammonium acetate + 0.2 mol / L of sodium fluoride can be prepared.

[0108] This example also provides a symmetric battery assembled using the aqueous electrolyte of Example 7. The assembly of the symmetric battery and the test conditions for its electrochemical performance are the same as those in Example 1 and will not be elaborated here.

[0109] The symmetric battery of this example has a long cycle stability of more than 800 h, and its polarization potential is -44 to 49 mV.

[0110] Example 8

[0111] This example provides an aqueous electrolyte, its preparation method, and an aqueous battery.

[0112] The preparation method of the aqueous electrolyte of this example includes the following steps:

[0113] Weigh 2.8756 g of ZnSO4·7H2O, 0.0360 g of 3-mercapto-1-propanesulfonic acid sodium salt, and 0.0840 g of sodium fluoride and add them to 10 mL of deionized water. Stir until dissolved, and then add 0.0205 g of sodium acetate to adjust the pH value of the system. Thus, a ZnSO4 electrolyte containing 20 mmol / L of 3-mercapto-1-propanesulfonic acid sodium salt + 25 mmol / L of sodium acetate + 0.2 mol / L of sodium fluoride can be prepared.

[0114] This example also provides a symmetric battery assembled using the aqueous electrolyte of Example 8. The assembly of the symmetric battery and the test conditions for its electrochemical performance are the same as those in Example 1 and will not be elaborated here.

[0115] The symmetric battery of this embodiment has a long cycle stability of more than 800 h, and its polarization potential is -40 to 45 mV.

[0116] During the research process, the inventors conducted a large number of experimental studies and now use some solutions with poor performance as comparative examples.

[0117] Comparative Example 1

[0118] A preparation method of an aqueous electrolyte is as follows: Weigh 2.8756 g of ZnSO4·7H2O and add it to 10 mL of deionized water, stir until dissolved, and then ZnSO4 electrolyte can be prepared.

[0119] Figure 6 For the hydrogen evolution performance of zinc foil in the electrolytes prepared in different cases, it can be seen that serious hydrogen evolution reaction occurs on the zinc foil in the electrolyte prepared in Comparative Example 1, and its hydrogen evolution reaction current density at -1.30 V vs. Ag / AgCl potential is 24.53 mAcm -2 . In addition, the pH value of the electrolyte in Comparative Example 1 is 3.72. The lower pH value will exacerbate the occurrence of side reactions such as corrosion and hydrogen evolution at the negative electrode. Therefore, the symmetric battery assembled based on the electrolyte prepared in Comparative Example 1 short-circuited after 300 h of cycling (as Figure 7 shown). In addition, this symmetric battery has a polarization potential as high as -80 to 54 mV, and its polarization potential increases significantly with the extension of the cycling time. The polarization potential at 300 h of cycling is as high as -120 to 80 mV. Figure 8 and 9 are the XRD patterns of the zinc foil before and after cycling in the electrolyte of Comparative Example 1 respectively. The characteristic peak of zinc hydroxide sulfate (Zn4(OH)6SO4·5H2O, PDF#39-0688) appears on the surface of the negative electrode after cycling, which indicates that the zinc foil is prone to react with the pure ZnSO4 electrolyte during cycling, thus affecting the performance of the battery.

[0120] Comparative Example 2

[0121] A preparation method of an aqueous electrolyte is as follows: Weigh 2.8756 g of ZnSO4·7H2O and 0.0180 g of 3-mercapto-1-propanesulfonic acid sodium salt respectively and add them to 10 mL of deionized water, stir until dissolved, and then ZnSO4 electrolyte containing 10 mmol / L 3-mercapto-1-propanesulfonic acid sodium salt can be prepared.

[0122] Figure 10For the cycling performance of the symmetric cell assembled with the electrolyte prepared in Comparative Example 2, it can be seen that after adding only 10 mmol / L sodium 3-mercapto-1-propanesulfonate, the cycling life of the cell can only be extended to 600 h. However, the optimization effect of this comparative example is not significant, so the polarization potential of the cell increases significantly to -86 to 86 mV after 350 h.

[0123] Comparative Example 3

[0124] A preparation method of an aqueous electrolyte is as follows: Weigh 2.8756 g of ZnSO4·7H2O, 0.0360 g of sodium 3-mercapto-1-propanesulfonate and 0.0193 g of ammonium acetate and add them to 10 mL of deionized water, stir until dissolved, and then an ZnSO4 electrolyte containing 20 mmol / L sodium 3-mercapto-1-propanesulfonate + 25 mmol / L ammonium acetate can be prepared.

[0125] The introduction of ammonium acetate raises the pH value of the electrolyte to 4.26, inhibiting the hydrogen evolution reaction caused by too low pH value. Therefore, the zinc foil has a low hydrogen evolution current density in the electrolyte of Comparative Example 3, and its hydrogen evolution reaction current density at -1.30 V vs. Ag / AgCl potential is 12.12 mA cm -2 . Figure 11 For the cycling performance of the symmetric cell assembled with the electrolyte prepared in Comparative Example 3, it can be seen that after adding only 20 mmol / L sodium 3-mercapto-1-propanesulfonate + 25 mmol / L ammonium acetate, the cycling life of the cell can only be extended to 700 h. However, the optimization effect of this comparative example is not significant, and the polarization potential of the cell is -51 to 49 mV.

[0126] Comparative Example 4

[0127] A preparation method of an aqueous electrolyte is as follows: Weigh 2.8756 g of ZnSO4·7H2O and 0.0840 g of sodium fluoride and add them to 10 mL of deionized water, stir until dissolved, and then an ZnSO4 electrolyte containing 0.2 mol / L sodium fluoride can be prepared.

[0128] Figure 12 For the cycling performance of the symmetric cell assembled with the electrolyte of Comparative Example 4, it can be seen that the introduction of 0.2 mol / L of sodium fluoride additive alone can reduce the polarization potential of the cell (-37 to 39 mV), and this symmetric cell can stably cycle for more than 600 h. Figure 13 For the XRD pattern of the zinc foil after cycling in the electrolyte of Comparative Example 4, it is found that the intensity of the (002) / (101) crystal plane on the negative electrode surface after cycling is 0.70, which is close to 0.72 of the original zinc foil, indicating that the introduction of the sodium fluoride additive cannot induce the directional deposition of zinc.

[0129] Comparative Example 5

[0130] A preparation method of an aqueous electrolyte, the specific steps are as follows: Weigh 2.8756 g of ZnSO4·7H2O, 0.0018 g of sodium 3-mercapto-1-propanesulfonate and 0.8398 g of sodium fluoride and add them to 10 mL of deionized water, stir until dissolved, and then add 0.6167 g of ammonium acetate to adjust the pH value of the system, and then a ZnSO4 electrolyte containing 1 mmol / L of sodium 3-mercapto-1-propanesulfonate + 0.8 mol / L of ammonium acetate + 2 mol / L of sodium fluoride can be prepared.

[0131] Figure 14 For the cycle performance of the symmetric battery assembled with the electrolyte prepared in Comparative Example 5, it can be seen that after adding 1 mmol / L of sodium 3-mercapto-1-propanesulfonate + 0.8 mol / L of ammonium acetate + 2 mol / L of sodium fluoride, the cycle life of the battery can only be extended to 500 h. However, the optimization effect of this comparative example is not significant, and the polarization potential of the battery is -88 to 67 mV.

[0132] As mentioned above, it is only the preferred specific embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Any changes or substitutions that can be easily thought of by those skilled in the art within the technical scope disclosed by the present invention should be covered by the protection scope of the present invention.

Claims

1. An aqueous electrolyte, characterized in that, The components of the aqueous electrolyte include: zinc salts, additives and water; wherein, the additives include sulfonates, acetates and halides.

2. The aqueous electrolyte according to claim 1, characterized in that, The zinc salts include one or more of zinc sulfate, zinc chloride, zinc trifluoromethanesulfonate, zinc acetate, zinc nitrate, zinc perchlorate, zinc tetraaquaborate hydroxide.

3. The aqueous electrolyte according to claim 1, wherein The sulfonates include one or more of sodium 3-mercapto-1-propanesulfonate, sodium diphenylamine sulfonate, sodium aminosulfonate, potassium aminosulfonate, zinc aminosulfonate, sodium lignosulfonate, sodium dodecylbenzenesulfonate.

4. The aqueous electrolyte according to claim 1, characterized in that, The acetates include one or more of sodium acetate, ammonium acetate, potassium acetate, zinc acetate, magnesium acetate, calcium acetate.

5. The aqueous electrolyte according to claim 1, wherein The halides include one or more of fluorides, chlorides, bromides and iodides.

6. The aqueous electrolyte according to claim 1, wherein The concentration of the sulfonates is 5 to 100 mmol / L.

7. The aqueous electrolyte according to claim 1, characterized in that, The concentration of the acetates is 1 to 1000 mmol / L.

8. The aqueous electrolyte according to any one of claims 1 to 7, characterized in that, The concentration of the halides is 0.05 to 2 mol / L.

9. A method for preparing the aqueous electrolyte according to any one of claims 1 to 8, characterized in that, Comprising: Mix zinc salts, sulfonates and halides with water and stir. After dissolution, add acetate to adjust the pH value of the system to obtain the aqueous electrolyte.

10. A water-based battery, characterized in that, The aqueous battery includes the aqueous electrolyte according to any one of claims 1 to 8 or the aqueous electrolyte prepared by the preparation method according to claim 9.

Images