Liquid organic electrolyte, method for preparing the same, and zinc metal battery

Abstract

The application provides a liquid organic electrolyte of a zinc metal battery, comprising a zinc salt and an organic solvent, wherein the organic solvent comprises a sulfone compound. The application also provides a preparation method of the liquid organic electrolyte of the zinc metal battery and a zinc metal battery. The liquid organic electrolyte provided by the application realizes dendrite-free growth of a negative electrode of the zinc metal battery, so that the zinc negative electrode has high reversibility and coulombic efficiency, thereby improving the electrochemical performance and safety of the zinc metal battery and achieving excellent full battery performance. The preparation method is simple, has no special requirement on equipment, and is low in cost, can solve the safety problem of the zinc metal battery, and can be used as an efficient and low-cost organic electrolyte of a zinc metal battery negative electrode.

Description

Technical Field

[0001] This invention relates to the field of zinc metal battery technology, and more particularly to a liquid organic electrolyte, its preparation method, and a zinc metal battery. Background Technology

[0002] With the development of high-energy-density portable electronic devices and the increasing demand for new energy storage technologies, the development of new energy storage devices is crucial. In the energy storage field, metal-based batteries have attracted significant attention due to their high energy density. Currently, lithium-ion batteries are the most widely used energy storage devices in industry; however, the depletion of lithium resources and the ever-increasing energy demand have spurred the development of other metal-based batteries, among which zinc metal batteries are particularly noteworthy. Zinc metal possesses high theoretical capacity and energy density, and has abundant reserves, making it possible to develop zinc metal batteries with high cycle performance and high energy density.

[0003] However, the practical application of zinc metal batteries faces significant challenges, particularly in terms of cycle life and cycle performance. Currently, zinc metal batteries primarily use aqueous electrolytes. Aqueous zinc metal batteries are highly susceptible to uncontrolled zinc dendrite growth and severe water desorption hydrogen side reactions during use, leading to rapid performance degradation and potential safety hazards. Therefore, developing low-cost, efficient, and safe organic electrolytes has become a hot topic in zinc metal battery research to improve their cycle performance and safety.

[0004] In recent years, researchers have successfully prepared organic electrolytes for zinc metal batteries based on solvents such as trimethyl phosphate (TMP), triethyl phosphate (TEP), and propylene carbonate (PC), which can be used to improve the stability of the negative electrode in zinc metal batteries. However, these electrolytes are expensive, limiting their large-scale application. Furthermore, pure organic electrolytes based on these solvents often fail to achieve stable cycling in zinc metal full-cell batteries. Therefore, developing organic electrolytes suitable for high-performance, low-cost zinc metal full-cell batteries is crucial. Summary of the Invention

[0005] The technical problem solved by this invention is to provide a low-cost, high-efficiency, and safe liquid organic electrolyte for zinc metal batteries, which has good compatibility with zinc metal anodes and conversion-type cathodes, and can ensure that the battery has excellent long-cycle stability.

[0006] In view of this, this application provides a liquid organic electrolyte for zinc metal batteries, comprising a zinc salt and an organic solvent, wherein the organic solvent comprises sulfone compounds.

[0007] Preferably, the zinc salt is selected from one or both of anhydrous zinc acetate and zinc trifluoromethanesulfonate.

[0008] Preferably, the sulfone compound is selected from dimethyl sulfoxide.

[0009] Preferably, the concentration of the zinc salt in the organic solvent is 0.2 to 2.5 mol / L.

[0010] Preferably, the sulfone compound has a volume fraction of 20% to 100% in the organic solvent.

[0011] This application also provides a method for preparing the liquid organic electrolyte of the zinc metal battery, comprising the following steps:

[0012] The zinc salts were dried, and the sulfone compounds were dehydrated.

[0013] The dried zinc salt and the dehydrated sulfone compound were mixed and allowed to stand to obtain a liquid organic electrolyte.

[0014] Preferably, the dehydration is performed using molecular sieve dehydration.

[0015] This application also provides a zinc metal battery, including a positive electrode, a negative electrode, and an electrolyte, wherein the electrolyte is the liquid organic electrolyte described above or the liquid organic electrolyte prepared by the preparation method described above.

[0016] This application provides a liquid electrolyte for zinc metal batteries, comprising a zinc salt and a solvent, wherein the solvent comprises a sulfone compound. The liquid organic electrolyte provided in this application achieves dendrite-free growth of the zinc metal battery anode, resulting in higher recoverability and coulombic efficiency of the zinc anode, thereby improving the electrochemical performance and safety of the zinc metal battery and enabling excellent full-cell performance. Attached Figure Description

[0017] Figure 1 This describes the morphology of the electrolyte prepared in step 3 of Example 1 of the present invention deposited on the substrate;

[0018] Figure 2 This is a coulombic efficiency-cycle count curve of the electrolyte prepared in step 3 as the working electrolyte in Example 1 of the present invention;

[0019] Figure 3 This is a voltage-current density curve of the electrolyte prepared in step 3 as the working electrolyte in Example 1 of the present invention;

[0020] Figure 4 This is the surface morphology of the substrate after being stripped from the electrolyte prepared in step 3 in Example 1 of the present invention after being charged and discharged.

[0021] Figure 5 The material morphology after charging and discharging with Mo6S8 as the positive electrode in Embodiment 1 of the present invention;

[0022] Figure 6 This is a comparison curve of coulombic efficiency of different anhydrous zinc acetate concentrations in this invention.

[0023] Figure 7 This invention presents the deposition morphology of the electrolyte formed by zinc trifluoromethanesulfonate on a copper substrate. Detailed Implementation

[0024] To further understand the present invention, preferred embodiments of the present invention are described below in conjunction with examples. However, it should be understood that these descriptions are only for further illustrating the features and advantages of the present invention, and not for limiting the scope of the claims of the present invention.

[0025] In view of the technical problem that organic electrolytes in existing zinc metal batteries affect the performance of zinc metal batteries, this application provides a liquid organic electrolyte for zinc metal batteries, which uses sulfone compounds as pure solvents to match zinc salts, resulting in zinc metal batteries with better cycle performance. Specifically, the embodiments of this invention first disclose a liquid organic electrolyte for zinc metal batteries, comprising zinc salts and an organic solvent, wherein the organic solvent includes sulfone compounds.

[0026] The zinc salts and sulfone compounds provided in this application can achieve good compatibility with zinc metal anodes, improve the stability of zinc metal anodes, and inhibit zinc dendrite growth.

[0027] In this application, the zinc salt is selected from one or both of anhydrous zinc acetate and zinc trifluoromethanesulfonate, more specifically, the zinc salt is selected from anhydrous zinc acetate or zinc trifluoromethanesulfonate. The solvent is specifically selected from dimethyl sulfoxide. In a specific embodiment, the zinc salt is selected from anhydrous zinc acetate, and the solvent is selected from dimethyl sulfoxide. The concentration of the zinc salt in the liquid organic electrolyte is 0.2–2.5 mol / L. In a specific embodiment, the total concentration of the zinc salt in the organic electrolyte is 0.2 mol / L, 0.5 mol / L, 0.75 mol / L, 1.0 mol / L, 1.2 mol / L, 1.5 mol / L, 1.8 mol / L, 2.0 mol / L, 2.2 mol / L, or 2.5 mol / L; the concentration of the zinc salt is the molar concentration of the zinc salt in the organic solvent. The dimethyl sulfoxide has a volume fraction of 20% to 100% in the organic solvent, where the volume fraction is the volume fraction of the dimethyl sulfoxide in the total volume of the organic solvent; that is, the organic solvent may consist entirely of dimethyl sulfoxide or may contain other organic solvents.

[0028] This application also provides a method for preparing a liquid organic electrolyte for zinc metal batteries, including the following steps:

[0029] The zinc salts were dried, and the sulfone compounds were dehydrated.

[0030] The dried zinc salt and the dehydrated sulfone compound were mixed and allowed to stand to obtain a liquid organic electrolyte.

[0031] In this application, the dehydration is carried out using a dehydration method well known to those skilled in the art, specifically, the dehydration is molecular sieve dehydration.

[0032] This application also provides a zinc metal battery, which includes a positive electrode, a negative electrode, and an electrolyte, wherein the electrolyte is the liquid organic electrolyte described in the above-mentioned scheme.

[0033] The liquid electrolyte provided in this application has excellent compatibility with the zinc metal anode due to the addition of sulfone compounds, which ensures that the Zn||Mo6S8 full cell has excellent long-cycle performance.

[0034] To further understand the present invention, the following detailed description of the liquid organic electrolyte provided by the present invention, its preparation method and its application are provided in conjunction with the embodiments. The scope of protection of the present invention is not limited by the following embodiments.

[0035] Example

[0036] Step 1: Dry the anhydrous zinc acetate powder required for preparing the electrolyte: Weigh a certain amount of anhydrous zinc acetate, put it into a container and place it in a vacuum environment, set the drying temperature to 100℃ and continue for 24 hours.

[0037] Step 2: Dehydrate the organic reagent dimethyl sulfoxide using a molecular sieve: Add the dimethyl sulfoxide reagent to the reagent bottle, add a molecular sieve to absorb the water in the reagent, and continue for more than 24 hours;

[0038] Step 3: Prepare electrolyte: Weigh 2 mmol of dried anhydrous zinc acetate powder and dissolve it in 1 mL of dehydrated dimethyl sulfoxide solvent. Stir for 1 h to ensure uniform mixing and let stand for 12 h to obtain 2 M Zn(OAc)2-DMSO electrolyte.

[0039] Step 4: Apply the electrolyte prepared in Step 3 to a zinc metal battery via electrochemical deposition at a current density of 0.5 mA cm⁻¹. -2 The capacity is 0.25mAh cm -2 Deposited on a copper substrate, such as Figure 1 It is evident that a sedimentary morphology with a close-packed structure and no dendrite growth can be obtained.

[0040] Step 5: Using the electrolyte prepared in Step 3 as the working electrolyte, the zinc sheet as the negative electrode, and the copper sheet as the current collector, under constant current charge-discharge test conditions, the charge-discharge current density is 0.5 mA cm⁻¹. -2 The discharge capacity is 0.25mAh cm⁻¹ -2 The charging cutoff voltage is 0.6V, and the cycle life is 300 times. For example... Figure 2 It is evident that a high coulombic efficiency of zinc anodes can be achieved on a copper substrate.

[0041] Step 6: Using the electrolyte prepared in Step 3, assemble a zinc metal battery and test it using a linear sweep voltammetry method at 2 mV / s. -1 The scanning speed was used to detect zinc deposition and stripping behavior at room temperature, and the final results are shown in [reference needed]. Figure 3 .

[0042] Step 7: Using the electrolyte prepared in Step 3, assemble a zinc metal battery with a zinc plate as the negative electrode and a copper plate as the current collector. Under constant current charge-discharge test conditions, the charge-discharge current density is 0.5 mA cm⁻¹. -2 The discharge capacity is 0.25mAh cm⁻¹ -2 After completing the deposition process, the charging cutoff voltage was set to 0.6V. The morphology of the substrate surface after peeling is as follows: Figure 4 It is evident that it still exhibits a dendrite-free morphology.

[0043] Step 8: Assemble a zinc metal full battery using the electrolyte prepared in Step 4, with the zinc metal sheet as the negative electrode and Mo6S8 as the positive electrode. Cycle the battery under constant current charge-discharge conditions at a charge-discharge rate of 0.2C. Set the charging cutoff voltage to 1.1V and the discharging cutoff voltage to 0.2V. Figure 5 The image shows the morphology of the Mo6S8 cathode material used.

[0044] Step 9: Weigh out 0.2 mmol, 1 mmol, 1.5 mmol, and 2.5 mmol of dried anhydrous zinc acetate powder, respectively, and dissolve them in 1 mL of dehydrated dimethyl sulfoxide. Stir for 1 h to ensure uniform mixing, and let stand for 12 h to obtain the concentration comparison ratio. Figure 6 The figure shows a comparison of the coulombic efficiency of zinc acetate at different concentrations. It can be seen that the electrolyte performance increases from 0.2M to 2M concentrations. Lower concentrations result in fewer ion transport numbers in the electrolyte, leading to lower performance. However, as the concentration further increases to 2.5M, the electrolyte viscosity becomes too high, limiting the Zn... 2+ Conduction.

[0045] Step 10: Weigh 0.2 mmol of dried zinc trifluoromethanesulfonate powder and dissolve it in 1 mL of dehydrated dimethyl sulfoxide. Stir for 1 hour to ensure uniform mixing, and let stand for 12 hours to obtain the zinc salt comparison sample. Figure 7 The figure shows the deposition morphology of this comparative example on a copper substrate. During the deposition process, small zinc particles were formed, which not only tended to grow dendrites, but also had a weak bond with the substrate. They were easy to detach from the substrate and could easily be released into the electrolyte onto the diaphragm or electrode, causing a short circuit.

[0046] Table 1 Electrolyte composition and battery capacity retention data

[0047]

[0048]

[0049] As demonstrated by the above examples, high-performance zinc metal batteries can be obtained using a liquid electrolyte made from low-cost raw materials, anhydrous zinc acetate and dimethyl sulfoxide. However, there is no simple correlation between the proportion of dimethyl sulfoxide in the electrolyte and battery performance; it depends on the amount present.

[0050] The applicant's research concluded that among common zinc salts, only zinc acetate and zinc trifluoromethanesulfonate can achieve a certain degree of solubility in DMSO; among them, the solubility of zinc trifluoromethanesulfonate is less than 0.2M; zinc sulfate, zinc nitrate, and other zinc salts are almost insoluble in DMSO.

[0051] The applicant experimented with several sulfone compounds, including dimethyl sulfoxide, dimethyl sulfone, diphenyl sulfone, and sulfolane. The experiments revealed that dimethyl sulfone and diphenyl sulfone have high melting points and are solid at room temperature; even with heating to promote dissolution, they still solidify and precipitate salts upon cooling. Sulfolane is liquid at room temperature, but its melting point is also close to room temperature (20–26°C), allowing it to dissolve anhydrous zinc acetate. However, the concentration is limited to below 0.5 M; further increases cause the electrolyte to solidify due to the forces between solvent and salt molecules. Therefore, considering all factors, only the synergistic combination of anhydrous zinc acetate and DMSO can yield this high-performance, stable liquid electrolyte with good compatibility with both positive and negative electrodes.

[0052] The above description of the embodiments is only for the purpose of helping to understand the method and core ideas of the present invention. It should be noted that those skilled in the art can make several improvements and modifications to the present invention without departing from the principles of the present invention, and these improvements and modifications also fall within the protection scope of the claims of the present invention.

[0053] The above description of the disclosed embodiments enables those skilled in the art to make or use the invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the invention. Therefore, the invention is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A liquid organic electrolyte for a zinc metal battery, characterized in that, It is composed of anhydrous zinc acetate and dimethyl sulfoxide, wherein the concentration of anhydrous zinc acetate in the dimethyl sulfoxide is 0.2~2.5 mol / L.

2. The method for preparing the liquid organic electrolyte of the zinc metal battery according to claim 1, comprising the following steps: Dry anhydrous zinc acetate and dehydrate dimethyl sulfoxide; The dried anhydrous zinc acetate and the dehydrated dimethyl sulfoxide were mixed and allowed to stand to obtain a liquid organic electrolyte.

3. The preparation method according to claim 2, characterized in that, The dehydration is performed using molecular sieves.

4. A zinc metal battery, comprising a positive electrode, a negative electrode, and an electrolyte, characterized in that, The electrolyte is the liquid organic electrolyte of claim 1 or the liquid organic electrolyte prepared by the preparation method of any one of claims 2 to 3.

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