Zinc ion battery electrolyte and preparation method and application thereof

Abstract

The invention discloses a zinc ion battery electrolyte as well as a preparation method and application thereof, and belongs to the technical field of aqueous zinc ion batteries. The electrolyte comprises deionized water, soluble zinc salt and an ionic liquid additive, preferably, the ionic liquid is 1-ethyl-3-methylimidazole ethyl sulfate salt, and the adding concentration is 0.02-0.5 mol / L <-1 >. The additive can be preferentially adsorbed on the surface of the zinc negative electrode to form a protective layer, contact between free water and the zinc negative electrode is effectively blocked, and hydrogen evolution reaction and by-product generation are remarkably inhibited; meanwhile, zinc ions are guided to be uniformly deposited along a flat crystal face, and dendritic crystal growth is inhibited. The cycle life of the zinc symmetric battery assembled by adopting the electrolyte is prolonged by about 18 times, the coulombic efficiency of the zinc-copper asymmetric battery reaches 99.8%, and the capacity retention ratio is improved to 84% after the whole battery is circulated for 1000 times. The method is simple in process, low in cost, environment-friendly and suitable for large-scale energy storage application.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of aqueous zinc ion battery electrolyte, and particularly relates to an aqueous zinc ion battery electrolyte and a preparation method and application thereof. BACKGROUND

[0002] The development of energy storage technology has a crucial impact on future energy supply systems and will become a key link in building a safe, low-carbon and clean modern energy system. Lithium ion batteries are the most widely used energy storage system at present, but the safety hazards and high costs caused by the flammability of organic electrolytes limit the further development of lithium ion batteries. In recent years, zinc ion batteries have become one of the most promising alternatives due to their high safety, low cost and abundant resources.

[0003] Zinc metal can provide a high theoretical capacity (820 mAh·g -1 ) and a low redox potential (-0.76 V vs. SHE), however, the zinc anode also faces many challenges, mainly including the following aspects, firstly, the uneven Zn 2+ transfer, local nucleation and cumulative growth process occur on the zinc metal anode side, gradually evolving into rough zinc dendrites. Secondly, the local pH value of the interface increases due to the uncontrollable hydrogen evolution reaction, and the hydroxyl ion reacts with zinc ions and anions to generate inert byproducts, increasing the interface impedance. Dendrites and byproducts seriously damage the stability of the zinc metal anode, leading to low coulombic efficiency and short cycle life of zinc ion batteries, which seriously hinders the market application of aqueous zinc ion batteries.

[0004] In order to cope with the above challenges, various advanced strategies including interface modification, electrode structure design, electrolyte optimization, and separator modification are proposed. Among them, electrolyte optimization is considered as the most feasible method due to its simple preparation process and low cost, and suitable electrolyte additives are sought to optimize the electrolyte, regulate the deposition behavior of the anode / electrolyte interface, inhibit the occurrence of zinc dendrites, hydrogen evolution and byproducts, and thus improve the stability and cycle life of the zinc anode. SUMMARY

[0005] The purpose of the present application is to provide a zinc ion battery electrolyte and a preparation method and application thereof to solve the problems of dendrite and byproduct generation existing in the zinc anode of the existing aqueous zinc ion battery.

[0006] In order to achieve the above purpose, the present application adopts the following technical solutions:

[0007] A zinc ion battery electrolyte and a preparation method and application thereof, characterized in that the aqueous zinc ion electrolyte comprises deionized water, a soluble zinc salt and an ionic liquid additive.

[0008] Preferably, the soluble zinc salt is zinc sulfate.

[0009] Preferably, the ionic liquid is 1-ethyl-3-methylimidazolium ethyl sulfate.

[0010] Preferably, the concentration of zinc sulfate is 1-2 mol·L -1 .

[0011] Preferably, the concentration of the electrolyte additive is 0.02-0.5 mol·L -1 .

[0012] The optimized electrolyte in the application is used to assemble zinc-zinc symmetric batteries, zinc-copper asymmetric batteries, and zinc-sodium vanadate full batteries.

[0013] Compared with the prior art, the application has the following beneficial effects:

[0014] (1) The ionic liquid is selected as an electrolyte additive in the application, which is preferentially adsorbed on the surface of the zinc negative electrode during zinc deposition, prevents free water from directly contacting the zinc negative electrode, reduces hydrogen evolution and the occurrence of by-products, and at the same time, the ionic liquid can induce zinc ions to uniformly deposit along flat crystal faces, achieving the purpose of inhibiting dendrite growth.

[0015] (2) The optimized electrolyte in the application improves the stability and cycle life of the zinc negative electrode, and the zinc ion battery assembled with the electrolyte has good capacity retention rate and cycle stability.

[0016] (3) The ionic liquid is a green solvent with low cost and reproducibility, and the electrolyte optimization process is simple, which is suitable for large-scale scene use. BRIEF DESCRIPTION OF DRAWINGS

[0017] Figure 1 is the X-ray diffraction comparison chart of the zinc sheets of the application comparative example 1 and example 1 after being immersed in different electrolytes for 5 days;

[0018] Figure 2 is the scanning electron microscope photo of the zinc negative electrode of the Zn / / Zn symmetric battery assembled using the zinc sulfate electrolyte of the comparative example 1 after being cycled at a current density of 5 mA·cm -2

[0019] Figure 3 is the scanning electron microscope photo of the zinc negative electrode of the Zn / / Zn symmetric battery assembled using the electrolyte with the additive of example 1 after being cycled at a current density of 5 mA·cm -2

[0020] Figure 4 is the scanning electron microscope photo of the zinc negative electrode of the Zn / / Zn symmetric battery assembled using the electrolyte with the additive of example 1 and the zinc sulfate electrolyte of the comparative example 1 after being cycled at a current density of 1 mA·cm -2 ​​current density of 2 mA·cm-2 and 1 mAh·cm-2 specific capacity. -2 a comparison chart of cycle performance at a current density of 2 mA·cm

[0021] Figure 5 Zn / / Cu asymmetric batteries assembled using the electrolyte of Example 1 with the additive and the zinc sulfate electrolyte of Comparative Example 1 at a current density of 2 mA·cm -2 current density of 2 mA·cm-2 and 1 mAh·cm-2 specific capacity. -2 a comparison chart of coulombic efficiency at a current density of 2 mA·cm

[0022] Figure 6 Zn / / NVO full batteries assembled using the electrolyte of Example 1 with the additive and the zinc sulfate electrolyte of Comparative Example 1 at a current density of 1 A·g -1 a comparison chart of cycle performance at a current density of 2 mA·cm. DETAILED DESCRIPTION

[0023] The technical solutions in the embodiments of the present application will be clearly and completely described below in combination with the prior known technology. Obviously, the described embodiments are only some of the embodiments of the present application, but not all the embodiments.

[0024] The selected ionic liquid additive of the present application can improve the stability of the zinc negative electrode, and the X-ray diffraction and scanning electron microscope characterization show that the generation of zinc dendrites and by-products can be inhibited after adding the additive. By comparing the performance of Zn / / Zn symmetric batteries, Zn / / Cu asymmetric batteries and Zn / / NVO full batteries assembled using different electrolytes, the stability of the zinc negative electrode can be improved after adding the additive, thereby improving the overall performance of the zinc ion battery, which embodies the effectiveness of the electrolyte additive proposed in the present application.

[0025] Part IV:

[0026] I. Raw material preparation:

[0027] Preparation Example 1: Preparation of electrolyte containing additive

[0028] The present embodiment provides a water-based zinc ion battery electrolyte containing an ionic liquid additive, and the preparation method comprises the following steps:

[0029] (1) 5.75 g of zinc sulfate heptahydrate is weighed and added to 6 mL of deionized water, and stirred thoroughly until completely dissolved. After being diluted with a 10 mL volumetric flask, 2 mol·L -1 of zinc sulfate solution is obtained.

[0030] (2) 1-ethyl-3-methylimidazole ethyl sulfate salt is weighed and added to the above solution, and stirred thoroughly until dissolved, to obtain an electrolyte containing 0.2 mol·L -1 of 1-ethyl-3-methylimidazole ethyl sulfate additive.

[0031] Preparation Example 2:

[0032] Based on the preparation in Example 1, the concentration of 1-ethyl-3-methylimidazolium ethyl sulfate in the electrolyte was changed to 0.02 mol·L⁻¹. -1 The concentration of zinc sulfate is 1 mol·L⁻¹ -1 .

[0033] Preparation Example 3:

[0034] Based on the preparation in Example 1, the concentration of 1-ethyl-3-methylimidazolium ethyl sulfate in the electrolyte was changed to 0.5 mol·L⁻¹. -1 The concentration of zinc sulfate is 1.5 mol·L⁻¹. -1 .

[0035] Comparative Preparation Example 1: Preparation of Zinc Sulfate Electrolyte

[0036] Using zinc sulfate solution as the electrolyte, the procedure is as follows: Weigh 5.75 g of zinc sulfate heptahydrate and add it to 6 mL of deionized water. Stir thoroughly until completely dissolved. Dilute to volume with a 10 mL volumetric flask to obtain 2 mol·L⁻¹. -1 Zinc sulfate solution. The sample prepared in Comparative Example 1 was used to compare its performance with that of the sample prepared in Example 1 with the electrolyte containing 1-ethyl-3-methylimidazolium sulfate additive, in order to illustrate the beneficial effects of the present invention.

[0037] Preparation Example 4: Preparation of the diaphragm

[0038] Commercial fiberglass diaphragms were cut into circles with a diameter of 19 mm using a custom mold. All operations in this implementation were performed at room temperature.

[0039] Preparation Example 5: Preparation of Sodium Vanadate as a Cathode Material

[0040] Weigh 3 g of commercial vanadium pentoxide powder and add it to 2 mol·L⁻¹ -1 The precipitate was collected by centrifugation after stirring in sodium chloride solution for 72 h at room temperature. The precipitate was washed with water and ethanol and dried at 60 °C for 12 h to obtain sodium vanadate cathode material, which was labeled as NVO.

[0041] The positive electrode of the Zn / / NVO full cell is composed of 70 wt% NVO active material, 10 wt% binder (polyvinylidene fluoride), and 20 wt% conductive agent (Super P). The three components are mixed thoroughly in a mortar, and a solvent (N-methylpyrrolidone) is added dropwise while continuously stirring until the mixture becomes a homogeneous viscous liquid. This viscous liquid is then uniformly coated onto a current collector (titanium sheet). The coated sheet is placed in a vacuum oven at 80 °C for 12 h. After 12 h, it is removed and cut into electrode discs with a diameter of 10 mm using a custom mold.

[0042] II. Assembly and Performance Testing of Different Types of Batteries

[0043] The principle of this invention is as follows:

[0044] This invention uses ionic liquid as a bifunctional electrolyte additive. First, the additive preferentially adsorbs onto the surface of the zinc anode, forming an adsorption layer in situ on the surface. This layer occupies the decomposition sites of active water, preventing free water from directly contacting the zinc anode and reducing hydrogen evolution and the occurrence of byproducts. At the same time, the ionic liquid additive increases the nucleation overpotential, which is conducive to the formation of a small and uniform zinc deposition layer. This induces zinc ions to be uniformly deposited along the flat crystal surface, thereby achieving the purpose of inhibiting dendrite growth.

[0045] Example 1

[0046] Different batteries were made using the electrolyte from Preparation Example 1, the separator from Preparation Example 4, and the sodium vanadate cathode material from Preparation Example 5.

[0047] Example 2

[0048] The electrolyte was prepared in Example 2, and the rest was the same as in Example 1.

[0049] Example 3

[0050] The electrolyte was prepared in Example 3, and the rest was the same as in Example 1.

[0051] Comparative Example 1

[0052] The electrolyte was prepared in Comparative Preparation Example 1, and the rest was the same as in Example 1.

[0053] The following effects were verified:

[0054] (1) Characterizing byproducts on the surface of zinc sheets

[0055] The surface of zinc sheets after immersion in different electrolytes for 5 days was characterized using X-ray diffraction. Figure 1 As shown, zinc sheets immersed in zinc sulfate electrolyte exhibit obvious byproduct characteristic peaks, while zinc sheets immersed in electrolyte containing additives do not have byproduct peaks. This indicates that ionic liquids preferentially adsorb onto the zinc anode surface during zinc deposition, reducing direct contact between free water and the zinc anode, and preventing hydrogen evolution and side reactions.

[0056] (2) Characterization of the zinc anode surface using zinc sulfate electrolyte

[0057] The Zn / / Zn symmetric cells assembled using zinc sulfate electrolyte were studied using scanning electron microscopy at 5 mA·cm⁻¹. -2 The zinc anode was characterized after 50 cycles of current density cycling. For example... Figure 2As shown, a large number of zinc dendrites and byproducts were observed on the zinc anode surface using zinc sulfate electrolyte of Comparative Example 1.

[0058] (3) Characterization of the zinc anode surface using an electrolyte containing additives

[0059] The Zn / / Zn symmetric cells assembled using an electrolyte containing additives were studied using scanning electron microscopy at 5 mA·cm⁻¹. -2 The zinc anode was characterized after 50 cycles of current density cycling. For example... Figure 3 As shown, the zinc anode surface using the electrolyte containing additives in Example 1 is smooth, and zinc grows along a specific crystal plane, indicating that ionic liquids can induce zinc ions to deposit uniformly along a flat crystal plane, thereby inhibiting dendrite growth.

[0060] (4) Battery testing system for testing Zn / / Zn symmetric cells

[0061] The Blue Electric Battery testing system was used to test Zn / / Zn symmetric cells assembled with different electrolytes at 1 mA·cm⁻¹. -2 Current density and 1 mAh·cm -2 Constant current cycling test was performed at specific capacitance. For example... Figure 4 As shown, the cycle life of the symmetric battery using the additive electrolyte in Example 1 is close to 2500 h, which is 18 times that of the symmetric battery using zinc sulfate electrolyte in Comparative Example 1 (135 h), indicating that the ionic liquid additive enhances the stability of the zinc anode.

[0062] (5) Battery testing system for testing Zn / / Cu asymmetric cells

[0063] The Blue Battery testing system was used to test Zn / / Cu asymmetric cells assembled with different electrolytes at 2 mA·cm⁻¹. -2 Current density and 1 mAh·cm -2 The reversibility of zinc ion deposition / stripping was studied at specific capacity. For example... Figure 5 As shown, the asymmetric battery using the additive electrolyte of Example 1 can cycle 850 times with an average coulombic efficiency of 99.8%. In contrast, the asymmetric battery using zinc sulfate electrolyte of Comparative Example 1 shows significant coulombic efficiency fluctuations around 265 cycles, indicating that the side reactions reduce cycle reversibility.

[0064] (6) Battery testing system for Zn / / NVO full cell testing

[0065] The Blue Battery testing system was used at 1 A·g -1 Cyclic stability tests were conducted on Zn / / NVO full cells assembled using different electrolytes at different current densities. Figure 6As shown, the full cell using the additive electrolyte of Example 1 can cycle 1000 times with a capacity retention of 84.0%. In contrast, the full cell using zinc sulfate electrolyte of Comparative Example 1 has a lower reversible capacity and a capacity retention of 62.2% throughout the cycle.

[0066] Battery products:

[0067] For Zn / / Zn symmetric cells, the positive and negative electrodes are zinc plates; for Zn / / Cu asymmetric cells, the positive electrode is a copper plate and the negative electrode is a zinc plate; for Zn / / NVO full cells, the positive electrode is an NVO electrode and the negative electrode is a zinc plate. The zinc-ion batteries used are CR-2032 button cells. The matching battery positive and negative electrode casings, gaskets, springs, separators, electrolytes, and electrode plates are assembled in an orderly manner, and the batteries are sealed. All operations are performed at room temperature.

[0068] Battery performance test:

[0069] The assembled Zn / / Zn symmetric cell, Zn / / Cu asymmetric cell, and Zn / / NVO full cell were tested using the Blue Electric Battery testing system. The test was conducted at 5 mA·cm⁻¹. -2 and 5 mAh·cm -2 The zinc-zinc symmetric cells assembled with electrolytes before and after optimization were tested under the following conditions: at 2 mA·cm -2 and 1 mAh·cm -2 The zinc-copper symmetric cells assembled with electrolytes before and after optimization were tested under the following conditions; at 1 A·g -1 At a current density of 0.4-1.6V, fully symmetrical batteries assembled with electrolytes before and after optimization were subjected to cyclic charge-discharge tests.

[0070] The above description is only a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any equivalent substitutions or modifications made by those skilled in the art within the scope of the technology disclosed in the present invention, based on the technical solution and inventive concept of the present invention, should be covered within the scope of protection of the present invention.

Claims

1. A zinc-ion battery electrolyte, characterized in that, It includes deionized water, soluble zinc salts, and ionic liquid additives.

2. The zinc-ion battery electrolyte according to claim 1, characterized in that, The soluble zinc salt is zinc sulfate.

3. The zinc-ion battery electrolyte according to claim 1, characterized in that, The concentration of zinc sulfate in the zinc-ion battery electrolyte is 1-2 mol·L⁻¹. -1 .

4. The zinc-ion battery electrolyte according to claim 1, characterized in that, The ionic liquid additive is ethyl 1-ethyl-3-methylimidazolium sulfate.

5. The zinc-ion battery electrolyte according to claim 1, characterized in that, The concentration of electrolyte additives in the zinc-ion battery electrolyte is 0.02-0.5 mol·L⁻¹. -1 It is an additive for ionic liquids.

6. A method for preparing a zinc-ion battery electrolyte according to any one of claims 1-5, characterized in that, Includes the following steps: (1) Weigh out zinc sulfate heptahydrate and add it to deionized water. Stir thoroughly until completely dissolved. Dilute to volume with a volumetric flask to obtain zinc sulfate solution. (2) Weigh 1-ethyl-3-methylimidazolium sulfate ethyl salt and add it to the above solution. Stir thoroughly until dissolved to obtain an electrolyte containing 1-ethyl-3-methylimidazolium sulfate ethyl salt additive.

7. The zinc-ion battery electrolyte according to any one of claims 1-5 is used to assemble a zinc / / zinc symmetric battery, a zinc / / copper asymmetric battery, or a zinc / / sodium vanadate full battery.

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