Novel polyhydroxy electrolyte additive and application thereof in aqueous zinc ion battery

Abstract

The invention relates to the technical field of water-based battery energy storage, in particular to a novel polyhydroxy electrolyte additive and application thereof in a water-based zinc ion battery. The polyhydroxy electrolyte additive is a water-soluble organic compound, and is a D-raphanin pentahydrate. According to the invention, the electrolyte additive regulates the interaction between zinc ion water molecules and sulfate radicals by virtue of the polyhydroxy structure of the electrolyte additive through the directional reconstruction effect of hydrogen bonds, further regulates the solvation structure of hydrated zinc ions, repels water molecules and sulfate anions at an electrode-electrolyte interface, and improves the electrochemical performance of the electrolyte. And interface corrosion and hydrogen evolution side reaction participated by water and sulfate radicals are avoided. Besides, the D-lanolin pentahydrate can stabilize a metal-electrolyte interface through chemical adsorption and guide uniform planar zinc deposition, so that formation and growth of zinc dendrites are inhibited, and the service life of the battery is prolonged.

Description

Technical Field

[0001] The invention relates to a novel polyhydroxy electrolyte additive and application thereof in an aqueous zinc ion battery, belonging to the technical field of aqueous energy storage batteries. Background Art

[0002] In recent years, lithium-ion batteries have dominated the electronics industry and energy storage market due to their high energy density. However, the shortage of lithium resources and safety issues have questioned its use and development. Therefore, it is urgent to develop low-cost, safe and reliable energy storage technology. Aqueous zinc-ion batteries have the advantages of safety, environmental protection, abundant zinc reserves, and high theoretical capacity of zinc metal (820mAh g -1 / 5855mAh cm -2 ), low redox potential (-0.76V vs SHE), so aqueous zinc-ion batteries are regarded as favorable competitors in the field of large-scale energy storage and are expected to be widely used. However, in neutral / weakly acidic electrolytes, zinc metal is prone to parasitic side reactions such as hydrogen evolution and corrosion passivation due to its inherent thermodynamic instability, which promotes uneven zinc deposition and induces disordered dendrite growth, resulting in unstable electrode / electrolyte interface, reduced battery capacity, low coulombic efficiency, and short cycle life. Therefore, inhibiting dendrite growth and limiting the occurrence of side reactions are of great significance to the further development of zinc-ion batteries.

[0003] In order to solve the above problems, researchers have proposed a variety of improvement strategies, such as constructing an artificial interface protective layer, designing the zinc negative electrode structure, and introducing electrolyte additives. The construction of an artificial interface protective layer and the design of the zinc negative electrode structure often require tedious and complicated synthesis steps, and the synthesis process also involves a variety of unstable factors. Therefore, adding functional additives to aqueous electrolytes is seen as a simple and practical solution. However, the existing electrolyte additives still have some shortcomings, such as organic polymer additives that increase ion transfer resistance, or other additives have a single function such as inhibiting side reactions or inhibiting dendrite growth. Therefore, it is still necessary to further find a new type of excellent additive that can improve ion transfer kinetics and inhibit side reactions and dendrite growth at the same time, so as to further improve the electrochemical performance of aqueous zinc-ion batteries. Summary of the invention

[0004] The invention relates to a novel polyhydroxy electrolyte additive and application thereof in an aqueous zinc ion battery.

[0005] The purpose of the present invention is to provide a novel polyhydroxy electrolyte additive with the scientific name of D-raffinose pentahydrate, which regulates the interaction between zinc ions, water molecules and sulfate groups through the directional reconstruction effect of hydrogen bonds, further regulates the solvation structure of hydrated zinc ions, repels water molecules and sulfate anions at the electrode-electrolyte interface, avoids interfacial corrosion and hydrogen evolution side reactions involving water and sulfate groups, and the additive can stabilize the metal-electrolyte interface through chemical adsorption, guide uniform planar zinc deposition, thereby inhibiting the formation and growth of zinc dendrites and extending the service life of the battery.

[0006] The technical scheme of the present invention is as follows: a novel polyhydroxy electrolyte additive is D-raffinose pentahydrate.

[0007] An aqueous zinc ion battery electrolyte containing the novel polyhydroxy electrolyte additive, the electrolyte uses a soluble zinc salt as an electrolyte salt, D-raffinose pentahydrate as an additive, and high-purity deionized water as a solvent.

[0008] The aqueous zinc ion battery electrolyte has a concentration of D-raffinose pentahydrate of 0.1 mol L -1 .

[0009] In the above-mentioned aqueous zinc ion battery electrolyte, the soluble zinc salt is one or more of zinc sulfate, zinc chloride, zinc acetate, and zinc trifluoromethanesulfonate.

[0010] The aqueous zinc ion battery electrolyte has a soluble zinc salt concentration of 2 mol L -1 .

[0011] An aqueous zinc ion battery comprises a positive electrode, a negative electrode, a diaphragm and the aqueous zinc ion battery electrolyte.

[0012] The above-mentioned aqueous zinc ion battery is a symmetrical battery composed of zinc foil, glass fiber separator and electrolyte; or a full battery composed of zinc foil as negative electrode, vanadium oxide as positive electrode and electrolyte.

[0013] In the above-mentioned aqueous zinc ion battery, the vanadium oxide is one or a combination of two or more of ammonium vanadate, vanadium dioxide or vanadium pentoxide.

[0014] An aqueous zinc ion full battery comprises a positive electrode, a negative electrode, a separator and the above-mentioned electrolyte.

[0015] The positive electrode of the aqueous zinc ion full battery is prepared by mixing vanadium pentoxide, Super P and polyvinylidene fluoride in a mass ratio of 7:2:1, grinding them evenly, using N-methylpyrrolidone as a solvent to prepare a positive electrode slurry, coating it on a titanium foil with a scraper and drying it in a vacuum to obtain a positive electrode with a loading of 1 to 2 mg cm -2 .

[0016] The beneficial effects that the present invention can produce include:

[0017] 1. The electrolyte additive provided by the present invention has a polyhydroxy structure, which regulates the interaction between zinc ions, water molecules and sulfate groups through the directional reconstruction effect of hydrogen bonds, further regulates the solvation structure of hydrated zinc ions, repels water molecules and sulfate anions at the electrode-electrolyte interface, avoids interfacial corrosion and hydrogen evolution side reactions involving water and sulfate groups, and thus improves the electrochemical performance of zinc ion batteries.

[0018] 2. The electrolyte additive provided by the present invention can stabilize the metal-electrolyte interface through chemical adsorption, guide uniform planar zinc deposition, thereby inhibiting the formation and growth of zinc dendrites and extending the service life of the battery.

[0019] 3. The electrolyte additive provided by the present invention has inherent advantages such as low price, safety, environmental protection, simple preparation method, and wide application range. It has great application prospects and research value in the field of new energy batteries. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 A comparison diagram of charge and discharge curves of a Zn||Zn symmetric battery with different electrolyte systems in Example 3 of the present invention;

[0021] Figure 2 This is a comparison chart of the rate performance of Zn||Zn symmetric batteries with different electrolyte systems in Example 4 of the present invention;

[0022] Figure 3 This is a SEM comparison of the zinc negative electrode surface of the Zn||Zn symmetric battery with different electrolyte systems in Example 5 of the present invention after 20 cycles;

[0023] Figure 4 The Zn||V of different electrolyte systems in Example 6 of the present invention 2 O 5 Full battery at 0.5Ag -1 Comparison of constant current charge and discharge curves under current density;

[0024] Figure 5 The Zn||V of different electrolyte systems in Example 6 of the present invention 2 O 5 Full battery at 3Ag -1Comparison of constant current charge and discharge curves under current density. DETAILED DESCRIPTION

[0025] In order to make the purpose, technical solution and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the accompanying drawings and embodiments. The specific embodiments described in the present invention are only used to explain the present invention and are not used to limit the present invention.

[0026] Unless otherwise defined, the professional terms used below have the same meanings as those understood by professionals in the field; unless otherwise specified, the raw materials and reagents in the examples of the present invention are purchased through commercial channels or prepared by known methods.

[0027] The analysis method in the embodiment of the present invention is as follows:

[0028] Using the Blue Electric battery testing instrument, constant current charge and discharge tests were carried out at different current densities to analyze the cycle life and coulomb efficiency under different test conditions.

[0029] The present invention provides a novel polyhydroxy electrolyte additive, which is applied to aqueous zinc ion battery electrolyte and is prepared by the following method steps:

[0030] At room temperature, add 5.75 g zinc sulfate to 10 mL deionized water and stir ultrasonically until the solution is clear to obtain 2 mol L -1 Zinc sulfate solution (abbreviated as ZS).

[0031] In the above zinc sulfate electrolyte, 0.59 g of D-raffinose was added to obtain a D-raffinose concentration of 0.1 mol / L -1 electrolyte (abbreviated as ZS-RP).

[0032] The button battery model used in this embodiment is CR2032.

[0033] A high-purity zinc foil (purity of 99.99%) with a thickness of 100 μm was cut into discs with a diameter of 12 mm for later use; a glass fiber diaphragm was cut into discs with a diameter of 16 mm for later use; and a titanium foil was cut into discs with a diameter of 12 mm for later use.

[0034] Experimental Example 1 Aqueous Zinc Ion Symmetric Button Cell (Zn||Zn Symmetric Cell)

[0035] Assembly: Use zinc foil as the positive and negative electrodes of the button battery. First, put the positive electrode into the positive electrode shell, then put in the glass fiber separator, and then drop 100μL of the above ZS and ZS-RP electrolytes respectively, and then put in the negative electrode, and then put in the gasket and shrapnel in turn, and finally buckle the negative electrode shell, and use the battery packaging machine to package the battery, and you can get two Zn||Zn symmetrical batteries with zinc sulfate as the electrolyte and zinc sulfate mixed solution containing D-raffinose additive as the electrolyte.

[0036] Experimental Example 2 Aqueous Zinc Ion Full Battery (Zn||V 2 O 5 Battery)

[0037] Aqueous zinc ion full battery, the positive electrode active material is vanadium pentoxide, and the assembly method includes the following steps:

[0038] (1) Electrolyte: ZS and ZS-RP electrolytes were used as aqueous zinc ion full battery electrolytes.

[0039] (2) Preparation of positive electrode sheet: Vanadium pentoxide, Super P and polyvinylidene fluoride were mixed in a mass ratio of 7:2:1, ground evenly in a mortar, and prepared into positive electrode slurry using N-methylpyrrolidone as solvent. The slurry was coated onto titanium foil using a scraper and dried in a vacuum at 60°C for 12 hours to obtain a positive electrode sheet with a loading of 1-2 mg cm -2 .

[0040] (3) Assembly of aqueous zinc ion full battery: The aqueous zinc ion full battery is composed of the positive electrode sheet prepared in step (2), ZS and ZS-RP electrolytes, a glass fiber separator and a zinc foil negative electrode. The battery is assembled in the order of the positive electrode, the separator and the negative electrode to obtain two kinds of Zn||V batteries with zinc sulfate as the electrolyte and with a zinc sulfate mixed solution containing D-raffinose as the electrolyte. 2 O 5 Battery.

[0041] Example 3

[0042] The Zn||Zn symmetric cell of Example 1 is -2 / 1mAh cm -2 The constant current charge and discharge cycle test was carried out under the conditions, and the respective cycle time was as follows Figure 1 As shown in the figure, the Zn||Zn symmetric battery without D-raffinose had a short circuit after less than 100 hours of cycling; while the Zn||Zn symmetric battery with D-raffinose additive had a cycle time of up to 1500 hours, significantly extending the battery's cycle life.

[0043] Example 4

[0044] The Zn||Zn symmetric cell obtained in Example 1 was subjected to the test from 0.5 to 20 mA cm -2 Carry out rate cycle test, and the respective cycle time is as follows Figure 2 The Zn||Zn symmetric battery containing only zinc sulfate has a current density of less than 5 mA cm -2 When the Zn||Zn symmetric battery with D-raffinose added can fully cycle to 20 mA cm -2 The current density is high and it has good rate cycling performance.

[0045] Example 5

[0046] The Zn||Zn symmetric cell obtained in Example 1 was tested at 1 mA cm -2 / 1mAh cm -2 The constant current charge and discharge cycle test was carried out for 20 cycles under the conditions. Figure 3 The surface SEM image of the zinc negative electrode after cycling. It can be seen that the zinc negative electrode of the Zn||Zn symmetric battery with D-raffinose added has a smooth and flat surface, indicating that the electrolyte containing D-raffinose additive can induce uniform zinc ion deposition and inhibit corrosion and hydrogen evolution side reactions. However, the surface of the zinc negative electrode of the Zn||Zn symmetric battery without additives shows a large number of anisotropic square plate-like dendrites, which will further lead to battery short circuit.

[0047] Example 6

[0048] At a current density of 0.5A g -1 and 3A g -1 Next, for the Zn||V 2 O 5 The battery is tested for constant current charge and discharge. The results are as follows: Figure 4 , Figure 5 The results show that during the cycling process at two current densities, the Zn||V 2 O 5 Batteries are always more stable than those without additives, and Zn||V containing D-raffinose 2 O 5 The battery has a higher capacity retention rate.

[0049] It can be seen from the above implementation methods and test data that the method of the present invention is simple, low-cost, and effective, and is of great significance for inhibiting dendrite growth and side reactions in aqueous zinc ion batteries and promoting the long-life application of aqueous zinc ion batteries in the future.

[0050] The above are only several embodiments of the present invention and are not intended to limit the present invention in any form. Although the present invention is disclosed as above in the form of a preferred embodiment, it is not intended to limit the present invention. Any technician familiar with the profession, without departing from the scope of the technical solution of the present invention, using the above disclosed technical content to make slight changes or modifications are equivalent to equivalent implementation cases and fall within the scope of the technical solution.

Claims

1. A novel polyhydroxy electrolyte additive, characterized in that: It is D-raffinose pentahydrate.

2. An aqueous zinc ion battery electrolyte comprising the novel polyhydroxy electrolyte additive according to claim 1, characterized in that: The electrolyte solution uses soluble zinc salt as electrolyte salt, D-raffinose pentahydrate as additive, and high-purity deionized water as solvent.

3. The aqueous zinc ion battery electrolyte according to claim 2, characterized in that: The concentration of D-raffinose pentahydrate is 0.1 mol L -1 .

4. The aqueous zinc ion battery electrolyte according to claim 2, characterized in that The soluble zinc salt is one or more of zinc sulfate, zinc chloride, zinc acetate and zinc trifluoromethanesulfonate.

5. The aqueous zinc ion battery electrolyte according to claim 2, characterized in that The concentration of soluble zinc salt is 2 mol L -1 .

6. An aqueous zinc ion battery, characterized in that: The invention comprises a positive electrode, a negative electrode, a separator and the aqueous zinc ion battery electrolyte according to any one of claims 2 to 5.

7. An aqueous zinc ion battery according to claim 6, characterized in that: The aqueous zinc ion battery is a symmetrical battery composed of zinc foil, glass fiber separator and electrolyte; or a full battery composed of zinc foil as negative electrode, vanadium oxide as positive electrode and electrolyte.

8. An aqueous zinc ion battery according to claim 7, characterized in that: The vanadium oxide is one or a combination of two or more of ammonium vanadate, vanadium dioxide or vanadium pentoxide.

9. An aqueous zinc ion full battery, characterized in that: The invention comprises a positive electrode, a negative electrode, a separator and the electrolyte according to any one of claims 2 to 5.

10. An aqueous zinc ion full battery according to claim 9, characterized in that: The positive electrode is prepared by mixing vanadium pentoxide, Super P and polyvinylidene fluoride in a mass ratio of 7:2:1, grinding them evenly, using N-methylpyrrolidone as a solvent to prepare a positive electrode slurry, coating it on a titanium foil with a scraper and drying it in a vacuum to obtain a positive electrode sheet with a loading of 1 to 2 mg cm -2 .

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