Preparation method of a suspension electrolyte and application thereof

Abstract

The application relates to a preparation method of a suspension electrolyte and application thereof, and aims to solve the problems of high impedance, high viscosity and high cost of the existing high-concentration electrolyte. The preparation method of the suspension electrolyte is as follows: main salt powder is added into a solvent, magnetic stirring is carried out until the main salt particles are fully dispersed, trace water is added according to the molar ratio of water to metal ions in the main salt powder, the magnetic stirring is continuously carried out, a suspension electrolyte in which the main salt is not fully dissolved is obtained, and the concentration of the main salt in the system is controlled to be 1-5 mol / L. The double-ion battery using the suspension electrolyte of the application reduces the high-concentration electrolyte impedance, maintains good fluidity, and can realize the effect of the high-concentration electrolyte by using a small amount of main salt; when the double-ion battery using the suspension electrolyte of the application uses graphite for the positive and negative electrodes, the effective cycle number can reach 1200 times, and the coulomb efficiency can be above 90%.

Description

Technical Field

[0001] This invention belongs to the field of battery electrolytes, specifically relating to a method for preparing a suspension electrolyte and its application. Background Technology

[0002] Currently, most conventionally available airborne water-based single ions (such as Li) can be assembled. + Na + K + Zn 2+ In traditional dual-ion batteries, only cations are inserted / deintercalated at both the positive and negative electrodes. The positive electrode has a low potential, and the operating voltage is mostly less than 1.2V, limiting the improvement of energy density and restricting its application in large-scale energy storage. Recently, dual-ion batteries using anion insertion / deintercalation have gradually attracted researchers' attention due to their higher operating voltage and energy density. Since neither the positive nor negative electrodes provide anions, the type, concentration, and composition of the electrolyte directly affect the electrochemical performance of the dual-ion battery. Currently, high-concentration electrolytes that can provide a large number of anions play an important role in dual-ion batteries. However, electrolytes with concentrations often greater than 5 mol / L or higher have higher costs, greater weight, higher viscosity, higher impedance, and lower ion utilization. This not only reduces the utilization of the main salt and weakens battery performance but also raises the commercialization threshold for dual-ion batteries. If the effect of a high-concentration electrolyte could be achieved using a relatively low concentration of main salt, these problems could be solved.

[0003] Recently, "suspension electrolytes" with slightly soluble salts have begun to attract researchers' attention. For example, Cui's research group used slightly soluble Li₂O nanoparticles contained in the lithium metal SEI as additives to ester or ether electrolytes to form suspension electrolytes. This optimized the solvation structure, the SEI composition on the lithium metal surface, and the nucleation overpotential, improving the coulombic efficiency of the lithium metal anode and the cycle performance of the NCM811 / Li full cell. Although this suspension electrolyte formed using inorganic additives has many interesting properties, it is not suitable for direct use in dual-ion batteries because the concentration of the main salt involved in intercalation remains unchanged, and the electrolyte cannot mitigate the simultaneous consumption of cations and anions by the positive and negative electrodes of dual-ion batteries during charge and discharge. Therefore, suspension electrolytes need further improvement to meet the requirements of dual-ion batteries. Summary of the Invention

[0004] The present invention aims to address the problems of high impedance, high viscosity, and high cost of existing high-concentration electrolytes, and thus provides a method for preparing a suspension electrolyte and its application.

[0005] The method for preparing the suspension electrolyte of the present invention is carried out according to the following steps:

[0006] Add the main salt powder to the solvent and stir magnetically until the main salt particles are fully dispersed. Add a trace amount of water at a molar ratio of 1:1 to the metal ions in the main salt powder and continue stirring magnetically to obtain a suspension electrolyte in which the main salt is not completely dissolved. Control the concentration of the main salt in the system to be 1-5 mol / L.

[0007] The solvent is one or a mixture of two of the following: fluorinated solvents (such as HFE), dimethyl carbonate (DMC), diethyl carbonate (DEC), ethylene glycol dimethyl ether (DME), N,N-dimethylformamide (DMF), dimethyl sulfoxide (DMSO), ethyl methyl carbonate (EMC), polycarbonate (PC), tetrahydrofuran (THF), 1,3-dioxolane (DOL), and trimethyl phosphate (TMP).

[0008] The application of the suspended electrolyte of this invention is to use it as an electrolyte in dual-ion batteries.

[0009] This invention utilizes the slight solubility of the main salt in a solvent to prepare a novel suspension electrolyte suitable for dual-ion batteries. The concentration only needs to be controlled between 1 and 3 mol / L to achieve the effect of an ultra-high concentration electrolyte. Research results show that this electrolyte exhibits excellent fluidity, particle adsorption, high charge-discharge voltage, and is suitable for both zinc and graphite anodes. This suspension electrolyte, without additive modification, can achieve satisfactory electrochemical performance when directly used in battery assembly under atmospheric conditions. This creates favorable conditions for the low-cost industrial production of dual-ion batteries and other types of batteries in the future.

[0010] The saturated solubility of the main salt in the system is approximately less than 0.2 mol / L. This invention controls the concentration of the main salt in the system to be 1–5 mol / L. Undissolved particles do not hinder ion migration and adsorption on the electrode surface. When ion intercalation occurs and the electrode is depleted, the suspended particles dissolve to replenish the electrolyte. When there is excess ion deintercalation, the suspended particles precipitate again. A dynamic equilibrium exists between the suspended particles and the system, thereby maintaining the beneficial effects of the ultra-high concentration electrolyte.

[0011] The preparation method of the suspension electrolyte of the present invention and its application have the following beneficial effects:

[0012] 1. The dual-ion battery using the suspension electrolyte of this invention reduces the impedance of high-concentration electrolytes, maintains good fluidity, and achieves the effect of high-concentration electrolytes with less main salt, thus significantly saving battery manufacturing costs.

[0013] 2. When the dual-ion battery using the suspension electrolyte of this invention uses graphite for both the positive and negative electrodes, its effective cycle count can reach 1200 times, and its coulombic efficiency can reach more than 90%.

[0014] 3. The suspended electrolyte of this invention can participate in battery assembly in an atmospheric environment and can be stored in the air for a long time; compared with traditional high-concentration electrolytes, it is low in cost and simple in preparation process. Attached Figure Description

[0015] Figure 1 Impedance spectrum of a dual-ion battery assembled with 2 mol / L zinc trifluoromethanesulfonate / dimethyl carbonate suspension electrolyte in Example 1;

[0016] Figure 2 This is a charge-discharge curve of a dual-ion battery assembled using a 2 mol / L zinc trifluoromethanesulfonate / dimethyl carbonate suspension electrolyte from Example 1.

[0017] Figure 3 The graph shows the constant current cycling curve of the dual-ion battery assembled using the 2 mol / L zinc trifluoromethanesulfonate / dimethyl carbonate suspension electrolyte in Example 1. Detailed Implementation

[0018] Specific Implementation Method 1: The preparation method of the suspension electrolyte in this implementation method is carried out according to the following steps:

[0019] Add the main salt powder to the solvent and stir magnetically until the main salt particles are fully dispersed. Add a trace amount of water at a molar ratio of 1:1 to the metal ions in the main salt powder and continue stirring magnetically to obtain a suspension electrolyte in which the main salt is not completely dissolved. Control the concentration of the main salt in the system to be 1-5 mol / L.

[0020] The solvent is one or a mixture of two of the following: fluorinated solvents (such as HFE), dimethyl carbonate (DMC), diethyl carbonate (DEC), ethylene glycol dimethyl ether (DME), N,N-dimethylformamide (DMF), dimethyl sulfoxide (DMSO), ethyl methyl carbonate (EMC), polycarbonate (PC), tetrahydrofuran (THF), 1,3-dioxolane (DOL), and trimethyl phosphate (TMP).

[0021] This embodiment develops a low-cost and simple method for preparing a suspension electrolyte, utilizing the slight solubility of the main salt powder in a solvent to obtain a highly fluid suspension electrolyte containing suspended particles. The dual-ion battery based on the suspension electrolyte proposed in this invention has a high discharge voltage plateau and a large specific capacity, and the battery can be directly assembled in an atmospheric environment.

[0022] Specific Implementation Method Two: This implementation method differs from Specific Implementation Method One in that the main salt powder is lithium bis(trifluoromethanesulfonyl)imide powder, magnesium bis(trifluoromethanesulfonyl)imide powder, lithium bis(fluorosulfonyl)imide powder, or lithium hexafluorophosphate powder.

[0023] Specific Implementation Method 3: This implementation method differs from Specific Implementation Method 1 or 2 in that it involves magnetic stirring for 20 to 26 hours until the main salt particles are fully dispersed.

[0024] Specific Implementation Method Four: This implementation method differs from Specific Implementation Methods One to Three in that the concentration of the main salt in the system is controlled to be 1 to 3 mol / L.

[0025] Specific Implementation Method 5: This implementation method differs from Specific Implementation Method 4 in that the concentration of the main salt in the solvent is controlled to be 2 mol / L.

[0026] Specific Implementation Method Six: This implementation method differs from Specific Implementation Method Four in that the solvent used is dimethyl carbonate (DMC).

[0027] Specific Implementation Method Seven: This implementation method differs from Specific Implementation Methods One to Six in that the main salt powder is added to the solvent at room temperature.

[0028] Specific implementation method eight: The application of the suspended electrolyte in this implementation method is to use the suspended electrolyte as an electrolyte in a dual-ion battery.

[0029] Specific Implementation Method Nine: This implementation method differs from Specific Implementation Method Nine in that the negative electrode in the dual-ion battery is a negative electrode metal electrode material or a negative electrode non-metal electrode material. The negative electrode metal electrode material is a lithium metal negative electrode, a zinc metal negative electrode, a sodium metal negative electrode, a magnesium metal negative electrode, or an aluminum metal negative electrode, and the negative electrode non-metal electrode material is a graphite negative electrode, a metal oxide negative electrode, a bimetallic oxide negative electrode, a metal sulfide negative electrode, a metal selenide negative electrode, or a silicon-based negative electrode.

[0030] Specific Implementation Method 10: This implementation method differs from Specific Implementation Method 9 in that the positive electrode material in the dual-ion battery is graphite, expanded graphite, natural graphite flakes, spherical graphite, or modified graphite.

[0031] Example 1: The preparation method of the suspension electrolyte in this example is carried out according to the following steps:

[0032] At room temperature, 0.01 mol of zinc trifluoromethanesulfonate powder was added to 5 mL of dimethyl carbonate (DMC) and magnetically stirred for 24 hours until the particles were fully dispersed. Then, 30 μL of trace water was added at a molar ratio of water to zinc ions of 1:1, and magnetic stirring was continued for another 24 hours to obtain a suspension electrolyte in which the main salt was not completely dissolved.

[0033] Example 2: The preparation method of the suspension electrolyte in this example is carried out according to the following steps:

[0034] At room temperature, 0.005 mol of zinc trifluoromethanesulfonate powder and 0.005 mol of bis(trifluoromethanesulfonyl)imide zinc powder were added to 5 mL of dimethyl carbonate (DMC) and magnetically stirred for 24 hours until the particles were fully dispersed. Then, 30 μL of trace water was added at a water to zinc ion molar ratio of 1:1, and magnetic stirring was continued for another 24 hours to obtain a suspension electrolyte in which the main salt was not completely dissolved.

[0035] Example 3: The preparation method of the suspension electrolyte in this example is carried out according to the following steps:

[0036] At room temperature, 0.01 mol of zinc trifluoromethanesulfonate powder was added to 2.5 mL of diethyl carbonate (DEC) and 2.5 mL of N,N-dimethylformamide (DMF), and the mixture was magnetically stirred for 24 hours until the particles were fully dispersed. Then, 30 μL of water was added at a molar ratio of water to zinc ions of 1:1, and the mixture was magnetically stirred for another 24 hours to obtain a suspension electrolyte in which the main salt was not completely dissolved.

[0037] Electrochemical testing:

[0038] Impedance spectroscopy of dual-ion batteries using a suspended electrolyte was tested using a Shanghai Chenhua CHI760E electrochemical workstation. The bias voltage was set to the open-circuit voltage, and the frequency range was 0.1–100,000 Hz. The negative electrode was a graphite or zinc metal negative electrode, and the positive electrode was expanded graphite. The battery was assembled directly in an atmospheric environment, and the data were collected.

[0039] Figure 1 The electrochemical impedance spectroscopy (EIS) of the suspension electrolyte prepared in Example 1 and assembled into a dual-ion battery is shown. Compared to conventional high-concentration electrolytes, the figure exhibits a lower ion transport impedance, and the calculated ion diffusion coefficient is 6.68 × 10⁻⁶. -12 cm 2 / s.

[0040] Figure 2 The graph shows the charge-discharge curves of the suspension electrolyte prepared in Example 1 and assembled into a dual-ion battery. The current density is 50 mA / g, and the cutoff charge-discharge voltage range is 0.2–2.5 V. The graph shows a relatively high discharge plateau of around 2.0 V and a relatively large specific capacity of 116 mAh / g.

[0041] Figure 3 The graph shows the cycle stability test curves of the suspension electrolyte prepared in Example 1 and assembled into a dual-ion battery. The current density is 100 mA / g, and the cutoff charge / discharge voltage range is 0.2–2.5 V. The graph shows that the battery can operate stably for at least 1200 cycles, and the coulombic efficiency can reach over 90%.

[0042] The discharge voltage plateau, specific capacity, and coulombic efficiency stability of dual-ion batteries during charge-discharge cycles are important indicators for evaluating their performance. The above results demonstrate that the suspension electrolyte developed in this invention significantly improves the stability and coulombic efficiency of dual-ion batteries. The anions in the electrolyte can be well inserted and extracted into the graphite lattice. The suspension electrolyte proposed in this invention achieves the effects of a high-concentration electrolyte with a relatively low concentration.

Claims

1. A method for the preparation of a suspension electrolyte, characterized in that The preparation method is carried out according to the following steps: The main salt powder is added to the solvent and magnetically stirred until the main salt particles are fully dispersed. A trace amount of water is added at a molar ratio of water to metal ions in the main salt powder of 1:

1. Magnetic stirring is continued to obtain a suspension electrolyte in which the main salt is not completely dissolved. The concentration of the main salt in the system is controlled at 1~3 mol / L. This suspension electrolyte is used in dual-ion batteries. The solvent is one or a mixture of two of the following: HFE, dimethyl carbonate, diethyl carbonate, ethylene glycol dimethyl ether, N,N-dimethylformamide, dimethyl sulfoxide, ethyl methyl carbonate, polycarbonate, tetrahydrofuran, 1,3-dioxolane, and trimethyl phosphate; the main salt powder is zinc trifluoromethanesulfonate powder or zinc trifluoromethanesulfonate powder and bis(trifluoromethanesulfonyl)imide zinc powder.

2. The method of claim 1, wherein Stir magnetically for 20-26 hours until the main salt particles are fully dispersed.

3. The method of claim 1, wherein Add the main salt powder to the solvent at room temperature.

4. The application of the suspension electrolyte prepared according to claim 1, characterized in that... This suspended electrolyte was used as an electrolyte in a dual-ion battery.

5. The application of the suspension electrolyte according to claim 4, characterized in that... In a dual-ion battery, the negative electrode is either a metal electrode material or a non-metal electrode material.

6. The application of the suspension electrolyte according to claim 4, characterized in that... The positive electrode material in a dual-ion battery is graphite.

Images