Aqueous zinc ion battery electrolyte containing additive, preparation method of aqueous zinc ion battery electrolyte and zinc ion battery

Abstract

The invention discloses an additive-containing aqueous zinc ion battery electrolyte, a preparation method thereof and a zinc ion battery, and belongs to the field of aqueous zinc ion batteries. The invention aims to solve the technical problems that zinc dendrite growth and battery short circuit influence the cycling stability and the service life of the battery. The electrolyte is an aqueous solution of a zinc salt and an organic aluminum salt, the concentration of the zinc salt is 0.2 M-3M, and the concentration of the organic aluminum salt is 0.01 M-0. 1M. The organic aluminum salt (such as aluminum lactate and the like) is used as an electrolyte additive. By adding the aluminum salt, the ionic conductivity of the electrolyte is also improved, uniform deposition of Zn < 2 + > is promoted, zinc dendrite growth and battery short circuit are prevented, and finally, the cycle stability and the service life of the battery are remarkably improved.

Description

Technical Field

[0001] The present invention belongs to the field of aqueous zinc ion batteries, and in particular relates to an aqueous zinc ion battery electrolyte containing an additive and a preparation method thereof, and a zinc ion battery. Background Art

[0002] With the continuous growth of energy demand and the increasing prominence of environmental problems, the development of efficient, safe, and low-cost energy storage devices has become a top priority. Aqueous zinc-ion batteries (ZIBs) are considered to be a highly promising next-generation energy storage technology due to their high safety, low cost, and environmental friendliness. The theoretical capacity of zinc is as high as 820 mAh g -1 , and its redox potential is moderate (-0.76 V vs. SHE), and it shows good stability in alkaline, neutral and weakly acidic aqueous solutions, giving it broad application prospects in large-scale energy storage systems.

[0003] However, the further application of ZIBs still faces many challenges. The zinc negative electrode has a serious problem of dendrite growth during the charge and discharge process. The dendrites formed by this uneven deposition will pierce the separator, causing the battery to short-circuit. In addition, direct contact between zinc and water molecules in the electrolyte will lead to hydrogen evolution reaction, corrosion and the formation of by-products (such as Zn4SO4(OH)6·xH2O), which will cause a decrease in coulombic efficiency and battery expansion. Finally, Zn 2+ [Zn(H2O)6] formed with strongly coordinated water molecules 2+ The solvated structure needs to overcome a high energy barrier during the desolvation process, which exacerbates the hysteresis of the interface dynamics. All of the above problems will seriously affect the cycle stability and service life of the battery. Summary of the Invention

[0004] The present invention aims to solve the technical problem that zinc dendrite growth and battery short circuit affect the cycle stability and service life of the battery, and provides an aqueous zinc ion battery electrolyte containing additives, a preparation method thereof, and a zinc ion battery.

[0005] In order to solve the above problems, the present invention proposes to use organic aluminum salts (such as aluminum lactate) as electrolyte additives. 3+ It can spontaneously form a uniform zinc-aluminum alloy layer on the surface of the zinc negative electrode, guide zinc ions to deposit uniformly along specific crystal planes, and effectively inhibit the formation and growth of zinc dendrites.

[0006] In order to solve the above technical problems, the present invention adopts the following technical solutions: The present invention aims to provide an aqueous zinc ion battery electrolyte containing an additive. The electrolyte is an aqueous solution of a zinc salt and an organic aluminum salt, wherein the concentration of the zinc salt is 0.2M-3M, and the concentration of the organic aluminum salt is 0.01M-0.1M.

[0007] The concentrations of zinc salt and organoaluminum salt should be controlled within the above range. Too high a concentration will significantly increase the acidity of the solution, making hydrogen evolution reaction more likely to occur on the zinc foil surface; too low a concentration will fail to inhibit dendrite growth and side reactions.

[0008] It is further defined that the zinc salt is one of zinc sulfate, zinc trifluoromethanesulfonate, zinc nitrate, zinc chloride or a combination of any of them in any ratio. It is further defined that the organic aluminum salt is one of aluminum lactate, aluminum citrate, aluminum acetate, aluminum oleate, and aluminum isopropoxide, or a combination of several of them in any ratio.

[0009] Preferably, the electrolyte is a zinc sulfate solution. The additive is an aluminum lactate solution. Compared with other common aluminum salts (such as aluminum citrate, aluminum acetate, aluminum oleate, aluminum isopropoxide, etc.), aluminum lactate exhibits unique advantages in aqueous zinc ion battery electrolytes. The dual coordination properties can effectively weaken the [Zn(H2O)6] 2+ The solvation structure reduces the activity of water molecules and inhibits the hydrogen evolution side reaction from the root; Al 3+ The formed zinc-aluminum alloy layer can guide the uniform deposition of zinc ions and has a better dendrite inhibition effect than other aluminum salts.

[0010] Another object of the present invention is to provide a method for preparing the above-mentioned aqueous zinc ion battery electrolyte containing additives; the method comprises the following steps: dissolving zinc salt and organic aluminum salt in deionized water, stirring and then ultrasonically dispersing, and degassing to obtain the electrolyte.

[0011] It is further defined that the stirring speed is 200 rpm-800 rpm for 2 min-5 min.

[0012] It is further defined that the ultrasonic dispersion time is 2 min-10 min.

[0013] It is further defined that the degassing treatment time is 2 minutes to 10 minutes, the purpose of which is to remove oxygen in the solution, reduce oxygen absorption corrosion with the zinc foil, and reduce interface impedance.

[0014] Another object of the present invention is to provide an aqueous zinc ion battery comprising a positive electrode, a zinc negative electrode and a separator, and also comprising the above-mentioned electrolyte.

[0015] It is further defined that the positive electrode is hydrated sodium vanadate, vanadium pentoxide, manganese dioxide or Prussian blue analogues.

[0016] It is further defined that the separator can be made of one or more of GF / A, F, D specifications of glass fiber, cotton fiber filter paper, and polyolefin porous membrane.

[0017] It is further defined that zinc foil is used as a negative electrode, and the surface oxide layer needs to be removed before use. First, the zinc foil is placed in deionized water and acetone in turn, ultrasonically cleaned for 30-60 minutes, and then dried in a blast drying oven. Next, use 400-2000 mesh sandpaper to polish the surface of the zinc foil in a cross-polishing manner until the surface becomes relatively smooth, and then polish it to make the surface of the zinc foil uniform. After polishing, the zinc foil is ultrasonically cleaned again, and then washed with deionized water and acetone for 5-10 minutes in turn, and the surface is quickly blown dry with argon gas to obtain a zinc sheet with the oxide layer removed. Finally, the polished zinc sheet is transferred to a vacuum dryer for standby use.

[0018] It is further defined that the zinc foil has a mass purity of 98%-99.99% and a thickness of 0.02mm-0.2mm.

[0019] It is further specified that 400 mesh, 800 mesh, 1200 mesh and 2000 mesh sandpaper are used in sequence for grinding, with each grinding time being 2 minutes to 5 minutes, and the sandpaper needs to be replaced perpendicular to the grinding direction; during the grinding process of the zinc foil, when changing sandpaper of different specifications, the surface of the zinc foil should be cleaned to ensure better grinding effect.

[0020] Preferably, the battery size is CR2025 or CR2032. The amount of electrolyte added is 20 μL-200 μL. Too little electrolyte cannot wet the electrode material, and too much electrolyte wastes raw materials and increases the risk of battery expansion during charging and discharging.

[0021] When aluminum lactate is used as an additive, a zinc-aluminum alloy layer can be spontaneously formed on the surface of the zinc negative electrode during the charge and discharge process. At the same time, the carboxyl and hydroxyl groups in the lactate ions react with the Zn 2+ Coordinate, weaken [Zn(H2O)6] 2+ The solvation structure of ZnO2 reduces the activity of water and the occurrence of hydrogen evolution reaction. In addition, the addition of aluminum salt also improves the ionic conductivity of the electrolyte and promotes the 2+ The uniform deposition of zinc prevents zinc dendrite growth and battery short circuit, ultimately significantly improving the cycle stability and service life of the battery.

[0022] Compared with the prior art, the present invention has the following beneficial effects: The present invention uses aluminum lactate as an additive to achieve multiple functions. 3+ It can spontaneously form a uniform zinc-aluminum alloy layer on the surface of the zinc negative electrode, guide the zinc ions to deposit uniformly along a specific crystal plane, and effectively inhibit the formation and growth of zinc dendrites; lactate ions react with Zn through -COOH and -OH 2+ Coordination reduces the activity of water molecules and inhibits the formation of by-products and hydrogen evolution reaction.

[0023] In order to further understand the features and technical contents of the present invention, please refer to the following detailed description of the present invention and the accompanying drawings. However, the accompanying drawings are provided for reference and illustration only and are not intended to limit the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 1 is a rate performance diagram of a zinc-zinc symmetrical battery in Example 1 of the method of the present invention; Figure 2 The zinc-zinc symmetrical battery in Example 1 of the present invention is subjected to a current density of 0.2 mA cm -2 , areal capacity of 0.1 mAh cm -2 Long cycle performance diagram under conditions; Figure 3 The zinc-zinc symmetrical battery in Example 1 of the present invention is subjected to a current density of 8 mA cm -2 , surface capacity of 4 mAh cm -2 Long cycle performance diagram under conditions; Figure 4 is the surface optical image of the zinc foil after being immersed in different electrolytes in Example 2 of the method of the present invention; Figure 5 is the XRD pattern of the surface of the zinc foil after being immersed in different electrolytes in Example 2 of the method of the present invention; Figure 6 is an XRD pattern of the zinc surface of the zinc-zinc symmetric battery after 20 cycles in Example 3 of the method of the present invention; Figure 7 is a grazing incidence XRD pattern of the zinc surface of the zinc-zinc symmetric battery after 20 cycles in Example 3 of the method of the present invention; Figure 8 This is the XPS spectrum of the zinc surface of the zinc-zinc symmetric battery after 20 cycles in Example 3 of the method of the present invention; Figure 9 are SEM and AFM images of zinc deposition in zinc sulfate / aluminum lactate solution in Example 3 of the method of the present invention; Figure 10 are SEM and AFM images of zinc deposition in zinc sulfate solution in Comparative Example 2 of the method of the present invention; Figure 11 is the LSV curve of zinc in zinc sulfate and zinc sulfate / aluminum lactate electrolyte in Example 4 of the method of the present invention; Figure 12 is an AC impedance diagram of a zinc-zinc symmetrical battery in zinc sulfate and zinc sulfate / aluminum lactate electrolytes in Example 5 of the method of the present invention; Figure 13 This is a long cycle performance diagram of the full battery in Example 6 of the method of the present invention. DETAILED DESCRIPTION

[0025] The present invention will be described in detail below with reference to specific embodiments. The following embodiments will help those skilled in the art further understand the present invention and are not intended to limit the present invention in any way. It should be noted that those skilled in the art may make various modifications and improvements without departing from the scope of the present invention. These modifications and improvements are all within the scope of protection of the present invention.

[0026] The following embodiment uses zinc foil as the negative electrode. The surface oxide layer is removed before use. The specific steps are as follows: the zinc foil is placed in deionized water and acetone in turn, ultrasonically cleaned for 300 minutes, and then dried in a blast drying oven. Next, 400 mesh, 800 mesh, 1200 mesh, and 2000 mesh sandpaper are used for polishing in turn. Each polishing time is 2min-5min, and the sandpaper needs to be replaced perpendicular to the polishing direction; during the polishing process of the zinc foil, when changing sandpaper of different specifications, the surface of the zinc foil should be cleaned and polished in a cross-polishing manner until the surface becomes relatively flat, and then polished to make the surface of the zinc foil uniform. After polishing, the zinc foil is ultrasonically cleaned again, and then washed with deionized water and acetone for 5-10 minutes in turn. The surface is quickly blown dry with argon gas to obtain a zinc sheet with the oxide layer removed. Finally, the polished zinc sheet is transferred to a vacuum dryer for standby use.

[0027] Example 1: Zinc sulfate and aluminum lactate were added to deionized water to create an aqueous solution containing 2M zinc sulfate and 0.01-0.1M aluminum lactate as the electrolyte. Zinc-zinc symmetric cells were assembled, using zinc foil as the electrode and glass fiber as the separator. The electrolytes were 2M zinc sulfate / 0.01M aluminum lactate, 2M zinc sulfate / 0.05M aluminum lactate, and 2M zinc sulfate / 0.1M aluminum lactate, respectively. Rate performance was tested at 0.1mA cm -2 The current density gradually increased to 8 mA cm -2 The long cycle performance test selected two conditions, namely 0.2mA cm -2 , 0.1mAh cm -2 and 8 mA cm -2 , 4mAh cm -2 .like Figure 1 As shown in Figure 2, the Zn-Zn symmetric battery with 0.05 M aluminum lactate additive exhibits the best cycling stability and the smallest nucleation overpotential at different current densities. -2 , 0.1mAh cm -2 Under these conditions, the battery's cycle stability performance is as follows: Figure 2 As shown, its service life exceeds 1400 hours; especially at high current density (8mA cm -2),like Figure 3 As shown, its cycle life exceeds 300 hours.

[0028] Comparative Example 1: (does not contain aluminum lactate) Zinc sulfate was added to deionized water to prepare a 2M zinc sulfate aqueous solution as the electrolyte. A zinc-zinc symmetrical battery was assembled, using zinc foil as the electrode, glass fiber as the separator, and 2M zinc sulfate as the electrolyte. The rate performance was also improved from 0.1 mA cm -2 The current density gradually increased to 8 mA cm -2 The long cycle performance test also has two conditions, namely 0.2mA cm -2 , 0.1mAh cm -2 and 8 mA cm -2 , 4mAh cm -2 .like Figure 1 As shown, the additive-free Zn-Zn symmetric battery has a current density ranging from 0.1 mA cm -2 Increase to 5 mA cm -2 During the process, the voltage fluctuated violently, indicating that the battery had a short circuit. -2 , 0.1mAh cm -2 The cycling stability of the battery under these conditions is as follows: Figure 2 As shown in Figure 2, its service life is only 1000 hours, and the voltage fluctuation range is also large; especially at high current density (8mA cm -2 ),like Figure 3 As shown, its cycle life is only 65 hours.

[0029] Example 2: Add zinc sulfate and aluminum lactate to deionized water to prepare an aqueous solution containing 2M zinc sulfate and 0.05M aluminum lactate. Immerse zinc foil in 2M zinc sulfate and 2M zinc sulfate / 0.05M aluminum lactate solutions for 14 days. Figure 4 As shown in the figure, when the zinc foil is immersed in the zinc sulfate solution, a large number of block crystals grow on the surface of the zinc foil, and the growth is uneven. However, in the zinc sulfate / aluminum lactate solution, the surface of the zinc foil does not produce dendrites and is relatively smooth. Figure 5 The XRD pattern shows that in the zinc sulfate solution, a strong diffraction peak of Zn4SO4(OH)6·H2O appears on the zinc foil surface. This is attributed to a side reaction between the zinc foil surface and the zinc sulfate solution. However, in the zinc sulfate / 0.05M aluminum lactate solution, no additional diffraction peaks are generated, demonstrating that aluminum lactate has excellent ability to inhibit side reactions.

[0030] Example 3: Zinc sulfate and aluminum lactate were added to deionized water to prepare an aqueous solution containing 2M zinc sulfate and 0.05M aluminum lactate as the electrolyte. A zinc-zinc symmetric cell was assembled, using zinc foil as the electrode and glass fiber as the separator. The electrolyte was 2M zinc sulfate / 0.05M aluminum lactate. -2 , 1mAh cm -2 Under the conditions of , the zinc-zinc symmetric battery was cycled 20 times, and the zinc electrode was tested by XRD. Figure 6 As shown in the figure, in the zinc sulfate / aluminum lactate solution, the (002) crystal plane of zinc gradually grows into the dominant crystal plane, and the diffraction peak position shifts to the left, which proves the formation of the zinc-aluminum alloy layer. In the grazing incidence XRD pattern ( Figure 7 ), it can be seen that the alloy layer on the surface of the zinc foil mainly consists of zinc and aluminum elements. At the same time, the XPS spectrum also proves the presence of aluminum elements ( Figure 8 ).like Figure 9 As shown, the zinc-aluminum alloy layer on the surface of the zinc foil grows uniformly, has low roughness, and a relatively smooth surface.

[0031] Comparative Example 2: (does not contain aluminum lactate) Zinc sulfate was added to deionized water to prepare a 2M aqueous zinc sulfate solution as the electrolyte. A zinc-zinc symmetric battery was assembled, using zinc foil as the electrode and glass fiber as the separator. -2 , 1mAh cm -2 Under the conditions of , the Zn-Zn symmetric battery was cycled 20 times, and then the Zn electrode was tested by XRD. Figure 6 As shown in the figure, during the cycle of the symmetrical battery, side reactions begin to occur on the surface, forming the diffraction peak of Zn4SO4(OH)6·H2O. Figure 10 As shown, a large number of dendrites were generated on the surface of the zinc foil at the same time, and the surface roughness increased significantly, which made it easy for them to pierce the separator and cause a short circuit in the battery.

[0032] Example 4: Zinc sulfate and aluminum lactate were added to deionized water to prepare an aqueous solution containing 2M zinc sulfate and 0.05M aluminum lactate. Zinc foil was used as the working electrode, platinum sheet as the counter electrode, and saturated calomel electrode as the reference electrode to form a three-electrode system. Figure 11 As shown in the figure, after the introduction of aluminum lactate, the hydrogen evolution potential of the electrolyte is significantly higher than that of the pure zinc sulfate electrolyte, which proves that aluminum lactate can effectively inhibit the occurrence of hydrogen evolution side reaction in aqueous electrolyte.

[0033] Example 5: Zinc sulfate and aluminum lactate were added to deionized water to prepare an aqueous solution containing 2M zinc sulfate and 0.05M aluminum lactate as the electrolyte. A stainless steel sheet-stainless steel sheet symmetrical battery was assembled, with stainless steel sheets as the pole pieces and glass fiber as the diaphragm. The electrolytes were 2M zinc sulfate and 2M zinc sulfate / 0.05M aluminum lactate, respectively. The AC impedance spectra of different electrolytes were measured by electrochemical impedance spectroscopy, and the ionic conductivity was calculated. Figure 12 As shown, the ionic conductivity of zinc sulfate solution is 49.63 mS cm -1 After adding aluminum lactate, the ionic conductivity increased to 60.27mS cm -1 , which proves that aluminum lactate has a significant improvement effect on the transport of zinc ions.

[0034] Example 6: Zinc sulfate and aluminum lactate were added to deionized water to prepare an aqueous solution containing 2M zinc sulfate and 0.05M aluminum lactate as the electrolyte. A full battery was assembled, using zinc foil as the negative electrode, hydrated sodium vanadate as the positive electrode, and glass fiber as the separator. The electrolytes were 2M zinc sulfate and 2M zinc sulfate / 0.05M aluminum lactate, respectively. -1 At a current density of 2000, a constant current charge and discharge test was conducted ( Figure 13 ), the full battery capacity of the pure zinc sulfate electrolyte decays rapidly, while the full battery with the added aluminum lactate electrolyte still provides more than 100 mAh g after cycling. -1 Discharge specific capacity.

[0035] The above describes the specific embodiments of the present invention. It should be noted that the present invention is not limited to the above specific embodiments, and those skilled in the art may make various variations or modifications within the scope of the claims, which do not affect the essence of the present invention.

Claims

1. An aqueous zinc ion battery electrolyte containing an additive, characterized in that: The electrolyte is an aqueous solution of zinc salt and organic aluminum salt, the concentration of the zinc salt is 0.2M-3M, and the concentration of the organic aluminum salt is 0.01M-0.1M.

2. The electrolyte according to claim 1, characterized in that The zinc salt is one of zinc sulfate, zinc trifluoromethanesulfonate, zinc nitrate, and zinc chloride, or a combination of several of them in any ratio; the organic aluminum salt is one of aluminum lactate, aluminum citrate, aluminum acetate, aluminum oleate, and aluminum isopropoxide, or a combination of several of them in any ratio.

3. The method for preparing an electrolyte according to claim 1 or 2, wherein: The method comprises the following steps: dissolving zinc salt and organic aluminum salt in deionized water, stirring, ultrasonically dispersing, and degassing to obtain an electrolyte.

4. The method according to claim 3, characterized in that Stir at a speed of 200rpm-800rpm for 2min-5min; ultrasonic dispersion time is 2min-10min; degassing time is 2min-10min.

5. An aqueous zinc ion battery comprising a positive electrode, a negative electrode and a separator, characterized in that: Also includes the electrolyte according to claim 1 or 2.

6. The battery according to claim 5, characterized in that: The positive electrode is hydrated sodium vanadate, vanadium pentoxide, manganese dioxide or Prussian blue analogues.

7. The battery according to claim 5, characterized in that: The separator is one or more of glass fiber, cotton fiber filter paper, and polyolefin porous membrane of GF / A, F, and D specifications.

8. The battery according to claim 5, characterized in that: Zinc foil is used as the negative electrode, and the surface oxide layer needs to be removed before use: the zinc foil is ultrasonically cleaned in deionized water and acetone in turn, and then dried; next, the surface of the zinc foil is polished with sandpaper in a cross-grinding manner until the surface becomes relatively flat, and then polished, and then ultrasonically cleaned with deionized water and acetone in turn, and the surface is quickly blown dry with argon gas.

9. The battery according to claim 8, characterized in that: The purity of zinc foil is 98%-99.99% and the thickness is 0.02mm-0.2mm.

10. The battery according to claim 8, characterized in that: Use 400 mesh, 800 mesh, 1200 mesh, and 2000 mesh sandpaper in turn. Each sanding time is 2 minutes to 5 minutes, and the sandpaper needs to be replaced perpendicular to the sanding direction.

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