Additive-containing difunctional aqueous electrolyte and zinc ion battery

Abstract

The invention discloses a difunctional aqueous electrolyte containing an additive and a zinc ion battery, and belongs to the technical field of aqueous batteries, the electrolyte of the battery is composed of the additive, a zinc salt and water; the additive is a compound composed of acyl choline cations and iodine anions. Acylcholine cations in the additive can form a positive charge layer on the surface of a zinc negative electrode in the charging and discharging process of the battery, so that the distribution of zinc ions in the deposition process is more uniform, and the formation and growth of zinc dendrites are further inhibited; iodine anions can form triiodide ions in the charging process, when the battery is in the discharging process, the triiodide ions in the electrolyte react with dead zinc through oxidation reduction, the dead zinc can be converted into zinc ions with electrochemical activity, and the zinc ions return to the battery cycle again. The coulombic efficiency and the cycle life of the aqueous zinc ion battery are greatly improved.

Description

Technical Field

[0001] The present invention belongs to the technical field of aqueous batteries, and particularly relates to a bifunctional aqueous electrolyte containing additives and a zinc-ion battery. Background Art

[0002] Developing a new battery system based on aqueous electrolytes is an effective strategy to improve battery safety. Among them, aqueous zinc-ion batteries have shown broad application prospects in the fields of distributed energy storage, home energy storage, etc. due to their safe and efficient charge and discharge processes, inexpensive and non-toxic battery raw materials, simple preparation process, and the characteristics of both high energy and high power. Metallic zinc has advantages such as high theoretical specific capacity (5855 mAh cm -3 and 820 mAh g -1 ), low redox potential (-0.762 V vs. SHE), and rich crustal content, and is an ideal anode material for zinc-ion batteries and has been widely studied. However, zinc metal anodes are prone to form dendrites during the charging process and "dead zinc" during the discharging process, resulting in rapid deterioration of the cycling performance and potential safety hazards, which restricts the practical application of aqueous zinc-ion batteries.

[0003] To stabilize the zinc anode and improve the cycling performance of zinc-ion batteries, numerous scholars at home and abroad have proposed a large number of solutions, mainly including anode structure design, functional electrolyte additives, separator optimization design, and interface modification. Among them, the electrolyte additive strategy can adjust the solvation structure and transport properties of zinc ions and the electrode-electrolyte interface properties, thereby effectively suppressing dendrites on the zinc anode and side reactions at the interface. In addition, additives are usually inexpensive and have a low addition amount, and the electrolyte engineering based on additives does not change the existing battery manufacturing process, so it has lower costs and better application advantages and potential.

[0004] However, at present, the molecular structures and components of the vast majority of electrolyte additives are relatively single, making their functions single and limited, and it is difficult to simultaneously solve the problems of dendrite growth and "dead zinc" formation faced by the zinc anode during the charging and discharging processes respectively. Most of the proposed additives have been proven to be beneficial to the flat deposition of zinc ions, thus alleviating the growth of zinc dendrites during the charging process of zinc-ion batteries. However, there is no improvement in the problem that the deposited zinc during the discharging process is prone to dissolution and form "dead zinc", resulting in a significant decrease in the reversibility and cycle life of the zinc anode. Therefore, there is an urgent need to develop a bifunctional electrolyte additive that inhibits dendrite growth during the charging process of the zinc anode and forms "dead zinc" during the discharging process to improve the stability and cycle life of zinc-ion batteries. Summary of the Invention

[0005] The object of the present invention is to overcome the above-mentioned disadvantages of the prior art, and to provide a dual-functional aqueous electrolyte containing additives and a zinc-ion battery, so as to solve the problems of zinc dendrite growth during the charging process of the zinc negative electrode and the formation of "dead zinc" during the discharging process in the prior art of aqueous zinc-ion batteries.

[0006] To achieve the above object, the present invention adopts the following technical solutions:

[0007] A dual-functional aqueous electrolyte containing additives, comprising additives, zinc salts and water; the additives are compounds composed of acylcholine cations and iodide anions.

[0008] A further improvement of the present invention lies in:

[0009] Preferably, the molar concentration of the additives in the electrolyte is 0.35 - 0.75 mol / L.

[0010] Preferably, the molar concentration of the additives is 0.5 mol / L.

[0011] Preferably, the molar concentration of the zinc salt is 0.5 - 3 mol / L.

[0012] Preferably, the additives are one or more of acetylcholine iodide, benzoylcholine iodide, benzoylthiocholine iodide, S-butyrylthiocholine iodide and acetylthiocholine iodide.

[0013] Preferably, the zinc salts are one or more of zinc sulfate, zinc trifluoromethanesulfonate, zinc bis(trifluoromethanesulfonyl)imide, zinc acetate, zinc chloride, zinc perchlorate.

[0014] A zinc-ion battery, comprising a zinc negative electrode, a positive electrode and a separator; both the zinc negative electrode and the positive electrode are placed in the above-mentioned dual-functional aqueous electrolyte; the zinc negative electrode and the positive electrode are isolated by a separator.

[0015] Preferably, the zinc negative electrode is a zinc foil or a current collector plated with zinc; the current collector is a copper foil or a titanium foil.

[0016] Preferably, the positive electrode is an iodine-activated carbon composite positive electrode.

[0017] Preferably, the separator is a mixed cellulose filter membrane or a glass fiber separator.

[0018] Compared with the prior art, the present invention has the following beneficial effects:

[0019] The present invention discloses a dual-functional aqueous electrolyte containing additives. The compound additive composed of acylcholine cations and iodide anions in the electrolyte has dual-functional characteristics. Among them, during the charge and discharge process of the zinc battery, the acylcholine cations will spontaneously adsorb on the surface of the zinc negative electrode, and a positively charged protective layer can be formed on the surface of the zinc negative electrode to evenly distribute the zinc ions on the surface of the zinc negative electrode and inhibit the formation and growth of zinc dendrites; while the iodide anions can form oxidizing triiodide ions during the charging process, oxidize the "dead zinc" formed during the discharging process into electrochemically active zinc ions and return them to the battery cycle. Therefore, this additive can effectively solve the problems of zinc dendrite growth during the charging process of the zinc negative electrode and the formation of "dead zinc" during the discharging process.

[0020] Furthermore, the molar concentration of the additive in the electrolyte is 0.35 - 0.75 mol / L. This concentration can ensure that the acylcholine cations have a sufficient concentration to form a complete protective layer, and the iodide ions can form triiodide ions during the charging process and play a role in the subsequent discharging process.

[0021] Furthermore, the additive is one or more of acetylcholine iodide, benzoylcholine iodide, benzoylthiocholine iodide, S-butrylthiocholine iodide, and acetylthiocholine iodide; the choline of the cations all carry acyl groups, and the acyl groups help the choline cations form a protective layer on the surface of the zinc negative electrode.

[0022] Furthermore, the zinc salt is a common zinc salt in zinc ion batteries, and the application range of this electrolyte is relatively wide.

[0023] The present invention also discloses a zinc ion battery. The electrolyte used in this zinc ion battery applies this aqueous electrolyte in the aqueous zinc ion battery, and high coulombic efficiency and cycle life are obtained under conditions such as high current density and high areal capacity. At a current density of 1 mA / cm 2 , the average coulombic efficiency of the zinc negative electrode reaches 99.6%; the assembled zinc ion full battery has a cycle life of more than 10,000 cycles at a current density of 2 A / g. Description of the Drawings

[0024] Figure 1 It is a graph of the mass change caused by the adsorption of ions on the gold sheet electrode in the aqueous solution obtained in Comparative Example 4.

[0025] Figure 2 It is an in-situ optical microscope observation diagram of the zinc deposition process in the electrolytes obtained in Example 1 and Comparative Example 1.

[0026] Figure 3 It is a scanning electron microscope diagram of the zinc deposition morphology at different deposition times in the electrolytes obtained in Example 1 and Comparative Example 1.

[0027] Figure 4Curves of "dead zinc" formation and recovery in the electrolytes obtained in Example 1 and Comparative Example 1.

[0028] Figure 5 Cycling performance graphs of zinc-titanium half-cells assembled with the electrolytes obtained in Example 1 and Comparative Example 1.

[0029] Figure 6 Cycling performance graphs of zinc-zinc symmetric cells assembled with the electrolytes obtained in Example 1, Comparative Example 1, Comparative Example 2, and Comparative Example 3.

[0030] Figure 7 Cycling performance graphs of zinc-iodine full cells assembled with the electrolytes obtained in Example 1 and Comparative Example 1. Detailed implementation modes

[0031] The present invention will be further described in detail below with reference to the accompanying drawings:

[0032] To enable those skilled in the art to understand the features and effects of the present invention, the following is a general description and definition of the terms and phrases mentioned in the specification and claims. Unless otherwise specified, all technical and scientific terms used herein shall have the ordinary meaning understood by those skilled in the art for the present invention. In case of conflict, the definition in this specification shall prevail.

[0033] In this article, unless otherwise specified, "comprising", "including", "containing", "having" or similar terms cover the meanings of "consisting of" and "consisting essentially of". For example, "A comprises a" covers the meanings of "A comprises a and others" and "A consists only of a".

[0034] The present invention will be further illustrated with specific examples below. It should be understood that these examples are only used to illustrate the present invention and not to limit the scope of the present invention. In addition, it should be understood that after reading the content taught by the present invention, those skilled in the art can make various changes or modifications to the present invention, and these equivalent forms also fall within the scope defined by the appended claims of this application.

[0035] Conventional instrument equipment in the art is used in the following examples. The experimental methods without specific conditions noted in the following examples are usually carried out under conventional conditions or according to the conditions recommended by the manufacturer. Various raw materials are used in the following examples. Unless otherwise stated, commercially available products are used, and their specifications are the conventional specifications in the art. In the specification of the present invention and the following examples, unless otherwise specified, "%" represents weight percentage, "parts" represents weight parts, and the ratio represents weight ratio.

[0036] The first aspect of the present invention discloses a bifunctional aqueous electrolyte containing additives, comprising additives, zinc salt and water; the additive is a compound composed of an acylcholine cation and an iodide anion.

[0037] The bifunctional aqueous electrolyte containing additives provided by the present invention is composed of additives, zinc salt and water; the additive is a compound composed of an acylcholine cation and an iodide anion. During the charge and discharge process of the battery, the acylcholine cation in the additive can form a positive charge layer on the surface of the zinc negative electrode, making the distribution of zinc ions more uniform during the deposition process, thereby inhibiting the formation and growth of zinc dendrites; the iodide anion can form triiodide ions during the charging process. When the battery is in the discharge process, the triiodide ions in the electrolyte react with "dead zinc" through redox, and can convert the "dead zinc" into electrochemically active zinc ions and return them to the battery cycle, greatly improving the Coulomb efficiency and cycle life of the aqueous zinc ion battery.

[0038] In some embodiments of the present invention, the molar concentration of the additive in the electrolyte is 0.35 - 0.75 mol / L. Limiting the concentration of the additive in the electrolyte within this range enables the acylcholine cation to have a sufficient concentration to form a complete protective layer. Especially for the iodide anion, a sufficient concentration ensures that iodide ions can form triiodide ions during the charging process and play a role in the subsequent discharge process.

[0039] As a preferred solution, the molar concentration of the additive is 0.5 mol / L; at this concentration value, the zinc ion battery has a high Coulomb efficiency and cycle life.

[0040] In some embodiments of the present invention, the additive is one or more of acetylcholine iodide, benzoylcholine iodide, benzoylthiocholine iodide, S-butyrylthiocholine iodide and acetylthiocholine iodide. The method of the present invention directly uses a compound composed of an acylcholine cation and an iodide anion, rather than a compound composed of an iodide anion and other cations, or a compound composed of an acylcholine cation and other anions, so that the electrolyte itself does not contain other impurities, improving the overall battery cycle performance. Due to the presence of acyl groups, the acylcholine cation is more likely to deposit on the surface of the zinc negative electrode to form a protective layer.

[0041] In some embodiments of the present invention, the zinc salt is one or more of zinc sulfate, zinc trifluoromethanesulfonate, zinc bis(trifluoromethanesulfonyl)imide, zinc acetate, zinc chloride, zinc perchlorate. The electrolyte system of the present invention is applicable to most zinc salt electrolytes and has a wide applicability.

[0042] The second aspect of the present invention discloses a zinc-ion battery, comprising a zinc negative electrode, a positive electrode, and a separator; the zinc negative electrode and the positive electrode are both placed in the above-mentioned bifunctional aqueous electrolyte; the zinc negative electrode and the positive electrode are isolated by the separator. It also includes a seal for the battery.

[0043] In this zinc-ion battery, since the electrolyte contains additives, in the zinc-ion battery system, the functional additives in the electrolyte play a synergistic effect: among them, the acylcholine cation component can be directionally adsorbed on the surface of the zinc negative electrode during the charge-discharge cycle to form a cation enrichment layer with an electrostatic regulation effect. This dynamic interface layer effectively guides the uniform nucleation and directional deposition of zinc ions through the charge repulsion effect, thereby significantly inhibiting the problem of heterogeneous growth of zinc dendrites. At the same time, the iodine-based additive in the electrolyte can be converted into oxidizing-active I3 - ions during the charging process. This substance reacts with the electrochemically inactive "dead zinc" on the electrode surface through a reversible redox reaction during the discharging stage, reactivating it and converting it into Zn 2+ to re-participate in the electrochemical cycle. This self-repair mechanism effectively improves the utilization rate of zinc metal and extends the battery cycle life.

[0044] In some embodiments of the present invention, the zinc negative electrode includes but is not limited to zinc foil (with a thickness of 10 - 500 μm), and the zinc negative electrode obtained by electroplating zinc on a current collector. Zinc metal as the negative electrode has a low electrode potential and can remain basically stable in an aqueous solution environment.

[0045] Furthermore, the negative electrode current collector includes but is not limited to copper foil and titanium foil, with a thickness of 5 - 50 μm, and has the characteristics of stable physical and chemical properties and not participating in electrochemical reactions.

[0046] In some embodiments of the present invention, the positive electrode is selected from an iodine-activated carbon composite positive electrode, which is prepared according to the following method: Activated carbon, a conductive agent, and a binder are evenly dispersed in powder form and pressed on a positive electrode current collector to obtain an activated carbon film, and then an appropriate amount of ethanol solution containing iodine is dropped and dried to obtain an iodine-activated carbon composite positive electrode; the mass ratio of the activated carbon, the conductive agent, and the binder is (7 - 9.5):(0 - 1.5):(0.5 - 1.5), more preferably 8:1:1; the conductive agent is a conductive agent well-known to those skilled in the art, and acetylene black is preferably used in the present invention; the binder is a binder well-known to those skilled in the art, and polytetrafluoroethylene is preferably used in the present invention; the positive electrode current collector is a positive electrode current collector well-known to those skilled in the art, and titanium mesh is preferably used in the present invention; the surface loading of iodine is 1 - 100 mg / cm 2 .

[0047] In some embodiments of the present invention, the separator includes, but is not limited to, a mixed cellulose filter membrane or a glass fiber separator, which has high hydrophilicity, liquid absorption, liquid retention, electronic insulation, and high ion conductivity. The thickness of the separator is 50 - 500 μm, and in the present invention, a glass fiber separator is preferably used.

[0048] The following is a further description in combination with specific examples.

[0049] Comparative Example 1

[0050] Under the condition that the zinc ion molar concentration is 1 mol / L, 36.353 g of zinc trifluoromethanesulfonate powder was weighed into a 100 - milliliter volumetric flask, and an appropriate amount of deionized water was added to dissolve the zinc trifluoromethanesulfonate and make the volume up to 100 mL to obtain a 1 - mol / L zinc trifluoromethanesulfonate basic electrolyte, which was used as a comparative example.

[0051] Comparative Example 2

[0052] Under the condition that the zinc ion molar concentration is 1 mol / L, 36.353 g of zinc trifluoromethanesulfonate powder was weighed into a 100 - milliliter volumetric flask, and an appropriate amount of deionized water was added to dissolve the zinc trifluoromethanesulfonate and make the volume up to 100 mL to obtain a 1 - mol / L zinc trifluoromethanesulfonate basic electrolyte. Then, acetylcholine iodide was added to the 1 - mol / L zinc trifluoromethanesulfonate basic electrolyte, and the molar concentration of acetylcholine iodide was 0.1 mol / L to obtain an aqueous electrolyte containing a compound additive composed of acylcholine - type cations and iodide anions.

[0053] Comparative Example 3

[0054] Under the condition that the zinc ion molar concentration is 1 mol / L, 36.353 g of zinc trifluoromethanesulfonate powder was weighed into a 100 - milliliter volumetric flask, and an appropriate amount of deionized water was added to dissolve the zinc trifluoromethanesulfonate and make the volume up to 100 mL to obtain a 1 - mol / L zinc trifluoromethanesulfonate basic electrolyte. Then, acetylcholine iodide was added to the 1 - mol / L zinc trifluoromethanesulfonate basic electrolyte, and the molar concentration of acetylcholine iodide was 0.25 mol / L to obtain an aqueous electrolyte containing a compound additive composed of acylcholine - type cations and iodide anions.

[0055] Comparative Example 4

[0056] This example provides a solution for testing adsorption, which specifically includes the following steps:

[0057] Under the condition that the molar concentration of Na2SO4 is 0.2 mol / L, weigh 2.84 g of sodium sulfate powder into a 100 mL volumetric flask, add an appropriate amount of deionized water to dissolve the sodium sulfate and make up the volume to 100 mL to obtain a 0.2 mol / L Na2SO4 aqueous solution. On the basis of the above aqueous solution, add acetylcholine iodide to ensure that the molar concentration of acetylcholine iodide is 0.5 mol / L to obtain a solution for testing adsorption containing a compound additive composed of choline-based cations and iodide anions.

[0058] Example 1

[0059] This example provides a method for preparing an aqueous electrolyte containing a compound additive composed of acylcholine-based cations and iodide anions, which specifically includes the following steps:

[0060] Under the condition that the molar concentration of zinc ions is 1 mol / L, weigh 36.353 g of zinc trifluoromethanesulfonate powder into a 100 mL volumetric flask, add an appropriate amount of deionized water to dissolve the zinc trifluoromethanesulfonate and make up the volume to 100 mL to obtain a 1 mol / L zinc trifluoromethanesulfonate basic electrolyte. Add acetylcholine iodide to the 1 mol / L zinc trifluoromethanesulfonate basic electrolyte, and the molar concentration of acetylcholine iodide is 0.5 mol / L to obtain an aqueous electrolyte containing a compound additive composed of acylcholine-based cations and iodide anions.

[0061] Example 2

[0062] This example provides a method for preparing an aqueous electrolyte containing a compound additive composed of acylcholine-based cations and iodide anions, which specifically includes the following steps:

[0063] Under the condition that the molar concentration of zinc ions is 2 mol / L, weigh zinc trifluoromethanesulfonate powder into a 100 mL volumetric flask, add an appropriate amount of deionized water to dissolve the zinc trifluoromethanesulfonate and make up the volume to 100 mL to obtain a 2 mol / L zinc trifluoromethanesulfonate basic electrolyte. Add benzoylthiocholine iodide to the 2 mol / L zinc trifluoromethanesulfonate basic electrolyte, and the molar concentration of benzoylthiocholine iodide is 0.6 mol / L to obtain an aqueous electrolyte containing a compound additive composed of acylcholine-based cations and iodide anions.

[0064] Example 3

[0065] This example provides a method for preparing an aqueous electrolyte containing a compound additive composed of acylcholine-based cations and iodide anions, which specifically includes the following steps:

[0066] Under the condition that the molar concentration of zinc ions is 1.5 mol / L, weigh zinc acetate powder into a 100-milliliter volumetric flask, add an appropriate amount of deionized water to dissolve the zinc acetate and make up the volume to 100 mL to obtain a 1.5 mol / L zinc acetate basic electrolyte. Add S-butyrylthiocholine iodide to the 1.5 mol / L zinc acetate basic electrolyte, and the molar concentration of S-butyrylthiocholine iodide is 0.7 mol / L to obtain an aqueous electrolyte containing a compound additive composed of acylcholine cations and iodide anions.

[0067] Example 4

[0068] This example provides a preparation method of an aqueous electrolyte containing a compound additive composed of acylcholine cations and iodide anions, which specifically includes the following steps:

[0069] Under the condition that the molar concentration of zinc ions is 0.5 mol / L, weigh zinc chloride powder into a 100-milliliter volumetric flask, add an appropriate amount of deionized water to dissolve the zinc chloride and make up the volume to 100 mL to obtain a 0.5 mol / L zinc chloride basic electrolyte. Add acetylthiocholine iodide to the 0.5 mol / L zinc chloride basic electrolyte, and the molar concentration of acetylthiocholine iodide is 0.35 mol / L to obtain an aqueous electrolyte containing a compound additive composed of acylcholine cations and iodide anions.

[0070] Test Example 1

[0071] This test example provides a test for the formation of an adsorption layer of an electrolyte additive on the negative electrode surface:

[0072] Measure the adsorption of choline cation additives on the negative electrode surface by in-situ electrochemical quartz crystal microbalance. The specific test is carried out in a three-electrode cell composed of a gold working electrode, a titanium counter electrode and an Ag / AgCl reference electrode. The aqueous solution prepared in Comparative Example 4 is used as the electrolyte. Verify the adsorption of acylcholine cations on its surface by monitoring the mass change on the gold sheet during the linear sweep voltammetry test. As Figure 1 shown, when the potential is scanned from 0.1 V to -0.3 V, the maximum mass increase in Na2SO4 is 1.1 ng; however, when acetylcholine is added, the mass increase reaches 46.4 ng. This shows that the large increase in mass is mainly attributed to the adsorption of acetylcholine cations, rather than the adsorption of sodium ions or water molecules, proving that acylcholine cations can adsorb on the metal surface.

[0073] Test Example 2

[0074] This test example provides a test for an electrolyte additive to regulate zinc deposition behavior:

[0075] The electrolytes prepared in Example 1 and Comparative Example 1 were added to a three - electrode system with a volume of approximately 1 mL. A titanium wire with a diameter of 0.5 mm was used as the working electrode, and two zinc wires with a diameter of 1 mm were used as the reference electrode and the counter electrode respectively. Electro - deposition was carried out at a current density of 1 mA / cm 2 for different times, and the zinc deposition process was recorded by an optical microscope. After deposition, the titanium wire with deposited zinc was taken out, washed with deionized water, and its deposition morphology was characterized by scanning electrochemical microscopy after drying. As can be seen from the in - situ optical observation as shown in Figure 2 , in Comparative Example 1, the electrolyte initially deposited bright - white massive zinc, and then deposited in a fluffy moss - like form. While for the electrolyte of Example 1, the zinc deposition showed a flat and dense morphology throughout the process. Figure 3 The results of scanning electron microscopy are consistent with the optical observation results. The results of in - situ optical observation and scanning electron microscopy illustrate that choline - based cations have the function of inhibiting zinc dendrite growth.

[0076] Test Example 3

[0077] This test example provides a test on the restoration of "dead zinc" by an electrolyte additive:

[0078] The electrolytes prepared in Example 1 and Comparative Example 1 were added to a zinc - titanium two - electrode system. In the first cycle, zinc was first electro - deposited on the titanium substrate at 4 mAh / cm 2 , and then the zinc was stripped with a cut - off voltage of 0.5 V. Subsequently, a cycle was carried out with a capacity of 1 mAh / cm 2 , and the remaining zinc was stripped from the titanium substrate to obtain the corresponding coulombic efficiency. As shown in Figure 4 , in the first cycle, Example 1 and Comparative Example 1 produced 0.28 and 0.87 mAh / cm 2 of "dead zinc" respectively. In the subsequent cycles, the electrolyte of Example 1 stripped 1.12 mAh / cm 2 of zinc, and the coulombic efficiency reached 111.6%, indicating that the "dead zinc" formed in the first cycle dissolved in the subsequent cycles, so the coulombic efficiency was greater than 100%. In contrast, Comparative Example 1 still could only strip 0.85 mAh / cm 2 of zinc, corresponding to a coulombic efficiency of 85.3%, indicating that it does not have the function of restoring "dead zinc".

[0079] Example 5

[0080] This example provides an application of an electrolyte additive in an aqueous zinc - ion battery and its performance test:

[0081] (1) Battery assembly: For the first type of battery, a zinc-titanium half-cell, the positive electrode uses titanium foil and the negative electrode uses zinc foil; for the second type of battery, a zinc-zinc symmetric cell, both the positive and negative electrodes use zinc foil; for the third type of battery, a zinc-iodine full cell, the negative electrode uses zinc foil and the positive electrode uses an iodine-activated carbon composite positive electrode. The sizes of the positive and negative electrodes are circular wafers with a diameter of 12 mm. The separator is preferably a glass fiber filter membrane with a diameter of 16 mm. The electrolytes all use the aqueous electrolytes prepared in Example 1, Comparative Example 1, Comparative Example 2, and Comparative Example 3 of the present invention to assemble an aqueous zinc-ion battery. The battery assembly sequence is: positive electrode case, positive electrode sheet, electrolyte, separator, electrolyte, negative electrode sheet, gasket, shrapnel, negative electrode case.

[0082] (2) Electrochemical tests: Electrochemical performance tests were carried out on the assembled batteries in a constant temperature chamber. The specific test methods are as follows: The zinc-titanium half-cell was discharged for one hour at a current density of 1 mA / cm 2 , and then charged to 0.5 V, and the above steps were repeated for cyclic testing; the zinc-zinc symmetric cell was first discharged for one hour and then charged for one hour at a current density of 1 mA / cm 2 , and the above steps were repeated for cyclic testing; the zinc-iodine full cell was charged and discharged at a current density of 2 A / g, and the charge-discharge voltage range was 0.5 - 1.6 V (vs. Zn / Zn2+), and the above steps were repeated for cyclic testing. The coulombic efficiency of the zinc-titanium half-cell is as Figure 5 shown. Under this condition, the average coulombic efficiency of the electrolyte in Example 1 was as high as 99.7% after 1500 cycles, far higher than that of Comparative Example 1. The cycle stability of the zinc-zinc symmetric cell is as Figure 6 shown. Under this condition, the electrolyte in Example 1 could be stably cycled for more than 4000 hours, higher than that of Comparative Example 1, Comparative Example 2, and Comparative Example 3, indicating that the additives of the present invention can form a complete inert protective layer and triiodide ions only when they have a sufficient concentration in the electrolyte, so as to play a role in the subsequent discharge process and improve the cycle stability of the battery. The cycle life of the zinc-iodine full cell is as Figure 7 shown. Under this condition, the electrolyte in Example 1 could be stably cycled for more than 10000 cycles, far higher than that of Comparative Example 1.

[0083] The above are only the preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principles of the present invention shall be included within the protection scope of the present invention.

Claims

1. A dual-functional aqueous electrolyte containing additives, characterized in that, It includes an additive, a zinc salt and water; the additive is a compound composed of an acylcholine cation and an iodide anion.

2. The bifunctional aqueous electrolyte containing an additive according to claim 1, wherein, The molar concentration of the additive in the electrolyte is 0.35 - 0.75 mol / L.

3. A dual-functional aqueous electrolyte containing an additive according to claim 1, wherein The molar concentration of the additive is 0.5 mol / L.

4. A bifunctional aqueous electrolyte containing additives according to claim 1, characterized in that, The molar concentration of the zinc salt is 0.5 - 3 mol / L.

5. A bifunctional aqueous electrolyte containing an additive according to claim 1, characterized in that, The additive is one or more of acetylcholine iodide, benzoylcholine iodide, benzoylthiocholine iodide, S-butylthiocholine iodide and acetylthiocholine iodide.

6. The bifunctional aqueous electrolyte containing an additive according to claim 1, wherein, The zinc salt is one or more of zinc sulfate, zinc trifluoromethanesulfonate, zinc bis(trifluoromethanesulfonyl)imide, zinc acetate, zinc chloride, zinc perchlorate.

7. A zinc-ion battery, characterized in that, It includes a zinc negative electrode, a positive electrode, and a separator; both the zinc negative electrode and the positive electrode are placed in the bifunctional aqueous electrolyte described in claim 1; the zinc negative electrode and the positive electrode are isolated by the separator.

8. The zinc ion battery according to claim 7, characterized in that, The zinc negative electrode is a zinc foil or a current collector electroplated with zinc; the current collector is a copper foil or a titanium foil.

9. The zinc ion battery according to claim 7, characterized in that, The positive electrode is an iodine-activated carbon composite positive electrode.

10. The zinc ion battery according to claim 7, characterized in that, The separator is a mixed cellulose filter membrane or a glass fiber separator.

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