Ultrasonic cavitation device and method for assisting entropy of electrolyte of lithium-sulfur battery by ultrasonic cavitation device

Abstract

The invention provides an ultrasonic cavitation device and a lithium-sulfur battery electrolyte entropy assisting method thereof, and belongs to the technical field of lithium-sulfur batteries. The device comprises a cabinet body, a cabinet door, an ultrasonic mechanism and a heat exchange mechanism, the cabinet door is connected with the cabinet body; the ultrasonic mechanism is arranged in the cabinet body; the heat exchange mechanism is connected with the ultrasonic mechanism; wherein the ultrasonic mechanism comprises an amplitude-change pole, an ultrasonic transducer, a cooling pond and a battery clamping device; the cooling pool is of a double-layer structure, the inner layer is an oil bath pool, and the outer layer is a water bath pool; the amplitude-change pole penetrates through the cabinet body and is in contact connection with the ultrasonic transducer; the upper end of the ultrasonic transducer is fixed on the cabinet body, and the lower end of the ultrasonic transducer is arranged in the oil bath and connected with the battery clamping device. The invention also provides a method for assisting the entropy of the electrolyte of the lithium-sulfur battery by using the ultrasonic cavitation device. The ultrasonic cavitation device is used for assisting entropy of the electrolyte of the lithium-sulfur battery, so that the relative mass transfer of liquid in the lithium-sulfur battery can be enhanced, the oxidation-reduction reaction process is promoted, the sulfur utilization rate is increased, and the application prospect is wide.

Description

Technical Field

[0001] The invention belongs to the technical field of lithium-sulfur batteries, and particularly relates to an ultrasonic cavitation device and a method thereof for assisting entropy conversion of lithium-sulfur battery electrolyte. Background Art

[0002] As an emerging rechargeable battery technology, lithium-sulfur (Li-S) batteries have shown great application potential and market prospects in the field of energy storage due to their many significant advantages, including ultra-high theoretical energy density (several times higher than traditional lithium-ion batteries), low raw material costs, and environmental friendliness. However, the actual commercialization process of lithium-sulfur batteries has encountered many technical bottlenecks.

[0003] First, lithium-sulfur batteries use lithium metal as the negative electrode, but lithium metal is prone to uneven deposition during the charge and discharge process, which not only accelerates the consumption of lithium and reduces the coulombic efficiency, but may also puncture the diaphragm, causing an internal short circuit in the battery and causing serious safety problems such as thermal runaway or even explosion.

[0004] Secondly, sulfur and its discharge product polysulfide have high solubility in the electrolyte, and the conversion reaction kinetics between these polysulfides are slow, especially under high sulfur loading. This problem is particularly prominent. This not only limits the utilization of sulfur, but also exacerbates the shuttle effect, that is, polysulfide migrates from the positive electrode to the negative electrode and is reduced at the negative electrode, and then returns to the positive electrode to be oxidized. This process will cause the loss of active materials and the attenuation of battery capacity; in addition, the shuttle effect not only leads to the irreversible loss of active materials and reduces the battery cycle stability, but also forms a non-conductive lithium sulfide (Li2S2 / Li2S) deposition layer on the negative electrode surface, which hinders the transmission of lithium ions and further deteriorates the battery performance. In addition, the shuttle effect will increase the self-discharge rate of the battery and shorten the storage life of the battery. Summary of the invention

[0005] The problem to be solved by the present invention is to provide an ultrasonic cavitation device and a method for assisting entropy conversion of lithium-sulfur battery electrolyte, so as to solve the problem of low sulfur utilization rate caused by slow redox reaction process and severe shuttle effect in lithium-sulfur battery.

[0006] The technical solution adopted to solve the technical problem is to provide an ultrasonic cavitation device, including a cabinet, a cabinet door, an ultrasonic mechanism and a heat exchange mechanism; the cabinet door is connected to the cabinet; the ultrasonic mechanism is arranged inside the cabinet; the heat exchange mechanism is connected to the ultrasonic mechanism; The ultrasonic mechanism includes a variable amplitude rod, an ultrasonic transducer, a cooling pool and a battery clamp; the cooling pool is a double-layer structure, the inner layer is an oil bath, and the outer layer is a water bath; the variable amplitude rod penetrates the cabinet and is in contact with the ultrasonic transducer; the upper end of the ultrasonic transducer is fixed on the cabinet, and the lower end is arranged in the oil bath and connected to the battery clamp.

[0007] The beneficial effects of the above technical solution adopted by the present invention are as follows: the ultrasonic cavitation device of the present invention can provide a controllable high-energy ultrasonic cavitation field environment, and has a plurality of sound wave enhanced network channels; the sound wave promotes the high entropy of the convective mass transfer enhancement system through the liquid phase, and realizes the catalysis of polysulfide ions in the electrolyte by enhancing the probability of ion-electron collision, and has a certain guiding effect on electrons or metal ions; at the same time, it can also enhance the electrode interface contact and directly improve the electrode surface environment. The cabinet body and the cabinet door provide overall interlayer sound insulation, and are connected to the ultrasonic mechanism through a heat exchange mechanism to realize external liquid circulation cooling and heat preservation; the ultrasonic transducer and the amplitude transformer directly apply ultrasonic waves to the lithium-sulfur battery fixed by the battery clamp in the oil bath through a given adjustable ultrasonic cavitation field, and enhance the redox reaction activity of the active substance through the high entropy electrolyte. The ultrasonic cavitation module is simple and easy to use, and exhibits high efficiency and high entropy characteristics.

[0008] Preferably, the heat exchange mechanism comprises an external water heat exchange inlet pipe and an external water heat exchange outlet pipe which are arranged in parallel, and the external water heat exchange inlet pipe is located below the external water heat exchange outlet pipe.

[0009] The beneficial effects of the above technical solution adopted in the present invention are as follows: the external water heat exchange inlet pipe is located below the external water heat exchange outlet pipe, and the "bottom-in and top-out" circulating water flow mode helps to maintain the stability of the water flow, reduce the resistance of the water flow and the occurrence of water accumulation in dead corners, and help improve the heat exchange efficiency.

[0010] More preferably, the heat exchange mechanism also includes a water cooling device, which can be a compressor, a refrigerator, etc.; the external water heat exchange inlet pipe and the external water heat exchange outlet pipe are simultaneously connected to the water bath and pass through the cabinet to be connected to the water cooling device.

[0011] Preferably, the water cooling device is a compressor or a refrigerator.

[0012] More preferably, the volume of the oil bath is 100 mL to 1000 mL.

[0013] The present invention also provides a method for entropy treatment of lithium-sulfur battery electrolyte assisted by the ultrasonic cavitation device, comprising the following steps: S1. Place a non-conductive solvent in an oil bath and adjust the liquid level. Insert the horn and use a heat exchange mechanism to perform low-temperature heating treatment. S2. Prepare a lithium-sulfur battery, use a battery clamp to clamp the lithium-sulfur battery and place it under the ultrasonic transducer, and close the cabinet door; S3, turn on the ultrasonic transducer and adjust the power of the amplitude transformer to perform entropy conversion of the lithium-sulfur battery electrolyte.

[0014] The beneficial effects of the above technical solution of the present invention are as follows: the ultrasonic cavitation device of the present invention triggers ultrasonic waves to be transmitted to the lithium-sulfur battery through the constant temperature oil bath, and polysulfide ions in the electrolyte are adsorbed, and the electrons or metal ions are guided, thereby effectively enhancing the convective mass transfer, slowing down the volume expansion of the electrode, and regulating the influence of the electrochemical reaction kinetics on the battery cycle performance, thereby improving the defects of the lithium-sulfur battery in that the capacity is low due to the shuttle effect and the electrochemical reaction kinetics, and the cycle performance deteriorates due to the volume expansion of the active material sulfur redox process. In the present invention, the ultrasonic cavitation technology is used, and the ultrasonic cavitation control is performed by controlling the ultrasonic cavitation power of the ultrasonic cavitation device. By changing the power parameters of the ultrasonic transducer, the overall high entropy environment of the lithium-sulfur battery redox reaction system is regulated and the convective mass transfer is enhanced, so that the lithium-sulfur battery suitable for special application environments can be constructed in a simple, convenient and scalable manner.

[0015] Preferably, in step S1, the non-conductive solvent is olive oil, silicone oil or paraffin oil; the low-temperature heating temperature is 10-50° C., and the time is 1-6 hours; the liquid level is adjusted so that the ultrasonic transducer is immersed in the liquid to a depth of 1-5 cm.

[0016] More preferably, in step S1, the non-conductive solvent is olive oil; the low-temperature heating temperature is 28° C., and the time is 2 h.

[0017] Preferably, the lithium-sulfur battery in step S2 is a button cell or a soft pack cell; the positive electrode surface loading of the lithium-sulfur battery is 2-6 mg / cm 2 The thickness of the positive electrode is 5~50μm, and the sulfur content of the positive electrode is 50~70%; the thickness of the negative electrode lithium of the lithium-sulfur battery is 100~1000μm.

[0018] More preferably, the lithium-sulfur battery in step S2 is a button cell; the positive electrode surface loading of the lithium-sulfur battery is 3.53 mg / cm 2 The thickness of the positive electrode is 25μm and the sulfur content of the positive electrode is 66.6%; the thickness of the negative electrode lithium of the lithium-sulfur battery is 200μm.

[0019] Preferably, the electrolyte used for assembling the lithium-sulfur battery during the preparation of the lithium-sulfur battery in step S2 is a mixture of lithium bis(trifluoromethylsulfonyl)imide containing lithium nitrate, ethylene glycol dimethyl ether and 1,3-dioxolane.

[0020] More preferably, the electrolyte is prepared by dissolving 1M lithium bis(trifluoromethanesulfonyl)imide) containing 2 wt % lithium nitrate in a mixture of ethylene glycol dimethyl ether and 1,3-dioxolane in a volume ratio of 1:1.

[0021] More preferably, the liquid to electrolyte ratio of sulfur in the positive electrode of the lithium-sulfur battery is 5-20 μL:1 mg.

[0022] More preferably, the preparation of the lithium-sulfur battery in step S2 comprises the following steps: Active material sulfur, conductive carbon nanotubes and polyvinylidene fluoride are mixed, N-methylpyrrolidone is added and stirred evenly to obtain positive electrode slurry; the positive electrode slurry is coated on the surface of aluminum foil and vacuum dried, and cut into positive electrode sheets; and the lithium-sulfur battery is assembled in a glove box filled with argon and dry in the order of positive electrode, interlayer, diaphragm, lithium sheet, gasket and shrapnel with the aid of electrolyte.

[0023] Preferably, in step S3, the power of the amplitude transformer is 50-900W; and the working duty ratio of the amplitude transformer is 2:2-8:2.

[0024] More preferably, the operating duty cycle of the amplitude transformer is 6:2.

[0025] More preferably, the temperature protection parameter of the horn is 30-35°C.

[0026] The present invention has the following beneficial effects: (1) The cabinet body and cabinet door in the ultrasonic cavitation device of the present invention provide overall interlayer sound insulation, and ultrasonic waves are released through the ultrasonic transducer. The ultrasonic transducer and the horn provide an adjustable ultrasonic cavitation field to achieve ultrasonic external field-assisted high-entropy conversion of lithium-sulfur batteries, and are connected to the ultrasonic mechanism through a heat exchange mechanism to achieve external liquid circulation cooling. The ultrasonic cavitation module of the present invention is simple and easy to use, and exhibits high-efficiency and high-entropy characteristics.

[0027] (2) In the present invention, after the traditional lithium-sulfur battery is assembled, it is placed in an ultrasonic cavitation cooling pool, and after adding a non-conductive solvent, an ultrasonic cavitation device is used for ultrasonic treatment, and a transducer coolant is configured; ultrasonic waves are released by the transducer to achieve ultrasonic external field assisted high entropy of the lithium-sulfur battery, and external liquid circulation cooling technology and layer sound insulation technology are used to ultrasonically generate the battery in a constant temperature non-conductive solvent to achieve external field assisted high entropy of the lithium-sulfur battery electrolyte; the method of using the ultrasonic cavitation device of the present invention to assist the entropy of the lithium-sulfur battery electrolyte can enhance the liquid phase relative mass transfer in the lithium-sulfur battery while effectively promoting the redox reaction process and improving the utilization rate of the active substance sulfur, and has good application prospects in the external field assisted application of lithium-sulfur batteries in special environments. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 It is a schematic diagram of the overall structure of the ultrasonic cavitation device; Figure 2 It is a schematic diagram of the structure of the cooling pool and the heat exchange mechanism connected thereto; Figure 3 The electrochemical impedance test diagram of the lithium-sulfur battery obtained in Examples 1 to 3 and the comparative example; Figure 4 The cyclic voltammetry test diagram of the lithium-sulfur battery obtained in Examples 1 to 3 and the comparative example; Figure 5The peak current analysis diagrams of lithium-sulfur batteries obtained in Examples 1 to 3 and the comparative example; wherein A is the peak current diagram at 2.35 to 2.55 V; B is the peak current diagram at 2.02 to 2.10 V; and C is the peak current diagram at 2.10 to 2.35 V; Figure 6 The nucleation-decomposition scanning electron microscope test diagram of lithium sulfide in the lithium-sulfur battery obtained in Examples 1 to 3 and the comparative example; Figure 7 The figures are the 0.5C voltage-discharge specific capacity test figures of the lithium-sulfur battery obtained in Examples 1 to 3 and the comparative example; wherein A is the overall figure of the 0.5C voltage-discharge specific capacity test of the lithium-sulfur battery; B is the partial enlarged figure of the I area in A; C is the partial enlarged figure of the II area in A; Figure 8 : is a comparison chart of the platform discharge specific capacity of the lithium-sulfur battery obtained in Examples 1 to 3 and the comparative example; wherein, Q L For low discharge platform, Q H It is a high discharge platform; Among them, 1. Ultrasonic transducer; 2. Amplitude transformer; 3. Cooling pool; 4. External water heat exchange outlet pipe; 5. External water heat exchange inlet pipe; 6. Battery clamp; 7. Lithium-sulfur battery; 8. Cabinet; 9. Cabinet door; 10. Water cooling device; 11. Water bath; 12. Oil bath. DETAILED DESCRIPTION

[0029] The specific implementation modes of the present invention are further described in detail below with reference to the accompanying drawings.

[0030] like Figure 1 As shown, an ultrasonic cavitation device includes a cabinet 8, a cabinet door 9, an ultrasonic mechanism and a heat exchange mechanism; the cabinet door 9 is connected to the cabinet 8; the ultrasonic mechanism is arranged inside the cabinet 8; the heat exchange mechanism is connected to the ultrasonic mechanism; Among them, the ultrasonic mechanism includes a transformer 2, an ultrasonic transducer 1, a cooling pool 3 and a battery clamp 6; the cooling pool 3 is a double-layer structure, the inner layer is an oil bath 12, and the outer layer is a water bath 11. The volume of the oil bath 12 is 100~1000mL, which can accommodate lithium-sulfur batteries of different sizes; the transformer 2 passes through the cabinet 8 and is in contact with the ultrasonic transducer 1; the upper end of the ultrasonic transducer 1 is fixed on the cabinet 8, and the lower end is arranged in the oil bath 12 and connected to the battery clamp 6.

[0031] like Figure 2 As shown, the heat exchange mechanism includes an external water heat exchange inlet pipe 5 and an external water heat exchange outlet pipe 4 arranged in parallel, and the external water heat exchange inlet pipe 5 is located below the external water heat exchange outlet pipe 4; the heat exchange mechanism also includes a water cooling device 10, and the external water heat exchange inlet pipe 5 and the external water heat exchange outlet pipe 4 are simultaneously connected to the water bath 11 and pass through the cabinet 8 to be connected to the water cooling device 10.

[0032] In a preferred embodiment of the present invention, the water cooling device is a refrigerator.

[0033] In another preferred embodiment of the present invention, the water cooling device is a compressor.

[0034] Example 1 The method of using the ultrasonic cavitation device to assist entropy treatment of lithium-sulfur battery electrolyte comprises the following steps: S1. 500 mL of olive oil is measured and placed in an oil bath. The liquid level is adjusted to a depth of 3 cm when the ultrasonic transducer is immersed in the liquid. The horn is inserted into the liquid to a depth of 1 cm. The oil is then subjected to low-temperature heating treatment at 28° C. for 2 h using circulating water from an external water heat exchange inlet pipe and an external water heat exchange outlet pipe connected to a refrigerator to obtain an olive oil bath at a temperature of 28° C.; S2. Prepare a lithium-sulfur battery, mix active material sulfur, conductive carbon nanotubes (MWCNT) and polyvinylidene fluoride (PVDF) in a mass ratio of 6:3:1, wherein sulfur and MWCNT are packaged in a weighing bottle before mixing and placed in an oven at 155°C for 6 hours to achieve sulfur melting, and after mixing, 2 g of N-methylpyrrolidone is added dropwise thereto, and stirred for 6 hours to obtain a positive electrode slurry; the positive electrode slurry is coated on the surface of an aluminum foil, and the thickness of the wet film formed by the positive electrode slurry on the surface of the aluminum foil is 250 μm, and it is placed at 60°C for vacuum drying for 12 hours to form a positive electrode with a thickness of 25 μm, and is cut into positive electrode sheets with a diameter of 13 mm using a cutting machine; wherein the positive electrode surface loading is 3.53 mg / cm 2 , the sulfur content of the positive electrode is 66.6%; the thickness of the negative electrode lithium is 200μm; the lithium-sulfur battery is assembled in the order of positive electrode, interlayer, diaphragm, lithium sheet, gasket and shrapnel in a MIKROUNA glove box filled with argon and dry; the battery accessories are 2032 button batteries, and the diaphragm is Celgrad2500; the electrolyte used for battery assembly is a lithium-sulfur electrolyte prepared by dissolving 1M lithium bistrifluoromethylsulfonimide (LiTFSI) containing 2wt% LiNO3 in ethylene glycol dimethyl ether and 1,3-dioxolane in a volume ratio of 1:1; the liquid ratio of the electrolyte to the active substance sulfur is 8μL:1mg; S3. After the lithium-sulfur battery is assembled, use a battery gripper to grip the lithium-sulfur battery and place it under the ultrasonic transducer, and close the cabinet door; S4. Turn on the ultrasonic transducer and adjust the power of the amplitude transformer to 90W at 28°C to perform entropy treatment on the electrolyte of the lithium-sulfur battery; wherein the working duty ratio of the amplitude transformer is 6:2.

[0035] Example 2 The method of using the ultrasonic cavitation device to assist entropy treatment of lithium-sulfur battery electrolyte comprises the following steps: S1. 500 mL of olive oil is measured and placed in an oil bath. The liquid level is adjusted to a depth of 3 cm when the ultrasonic transducer is immersed in the liquid. The horn is inserted into the liquid to a depth of 1 cm. The oil is then subjected to low-temperature heating treatment at 28° C. for 2 h using circulating water from an external water heat exchange inlet pipe and an external water heat exchange outlet pipe connected to a refrigerator to obtain an olive oil bath at a temperature of 28° C.; S2. Prepare a lithium-sulfur battery, mix active materials sulfur, MWCNT and PVDF in a mass ratio of 6:3:1, wherein sulfur and MWCNT are packaged in a weighing bottle before mixing and placed in an oven at 155°C for 6 hours to achieve sulfur melting, and after mixing, 2g of N-methylpyrrolidone is added dropwise thereto, and stirred for 6 hours using a mixing degassing machine to obtain a positive electrode slurry; the positive electrode slurry is coated on the surface of an aluminum foil, and the thickness of the wet film formed by the positive electrode slurry on the surface of the aluminum foil is 250μm, and the positive electrode is placed at 60°C and vacuum dried for 12 hours to form a positive electrode with a thickness of 25μm, and the positive electrode is cut into a positive electrode sheet with a diameter of 13mm using a sheet cutter; wherein the positive electrode surface loading is 3.53mg / cm 2 , the sulfur content of the positive electrode is 66.6%; the thickness of the negative electrode lithium is 200μm; the lithium-sulfur battery is assembled in the order of positive electrode, interlayer, diaphragm, lithium sheet, gasket and shrapnel in a MIKROUNA glove box filled with argon and dry; the battery accessories are 2032 button batteries, and the diaphragm is Celgrad2500; the electrolyte used for battery assembly is a lithium-sulfur electrolyte prepared by dissolving 1MLiTFSI containing 2wt% LiNO3 in ethylene glycol dimethyl ether and 1,3-dioxolane in a volume ratio of 1:1; the liquid ratio of the electrolyte to the active substance sulfur is 10μL:1mg; S3. After the lithium-sulfur battery is assembled, use a battery gripper to grip the lithium-sulfur battery and place it under the ultrasonic transducer, and close the cabinet door; S4. Turn on the ultrasonic transducer and adjust the power of the amplitude transformer to 360W at 28°C to perform entropy treatment on the electrolyte of the lithium-sulfur battery; wherein the working duty ratio of the amplitude transformer is 6:2.

[0036] Example 3 The method of using the ultrasonic cavitation device to assist entropy treatment of lithium-sulfur battery electrolyte comprises the following steps: S1. 500 mL of olive oil is measured and placed in an oil bath. The liquid level is adjusted to a depth of 3 cm when the ultrasonic transducer is immersed in the liquid. The horn is inserted into the liquid to a depth of 1 cm. The oil is then subjected to low-temperature heating treatment at 28° C. for 2 h using circulating water from an external water heat exchange inlet pipe and an external water heat exchange outlet pipe connected to a refrigerator to obtain an olive oil bath at a temperature of 28° C.; S2. Prepare a lithium-sulfur battery, mix active materials sulfur, MWCNT and PVDF in a mass ratio of 6:3:1, wherein sulfur and MWCNT are packaged in a weighing bottle before mixing and placed in an oven at 155°C for 6 hours to achieve sulfur melting, and after mixing, 2 g of N-methylpyrrolidone is added dropwise thereto, and stirred for 6 hours to obtain a positive electrode slurry; the positive electrode slurry is coated on the surface of an aluminum foil, and the thickness of the wet film formed by the positive electrode slurry on the surface of the aluminum foil is 250 μm, and it is placed at 60°C and vacuum dried for 12 hours to form a positive electrode with a thickness of 25 μm, and cut into positive electrode sheets with a diameter of 13 mm using a cutting machine; wherein the positive electrode surface loading is 3.53 mg / cm 2 , the sulfur content of the positive electrode is 66.6%; the thickness of the negative electrode lithium is 200μm; the lithium-sulfur battery is assembled in the order of positive electrode, interlayer, diaphragm, lithium sheet, gasket and shrapnel in a MIKROUNA glove box filled with argon and dry; the battery accessories are 2032 button batteries, and the diaphragm is Celgrad2500; the electrolyte used for battery assembly is a lithium-sulfur electrolyte prepared by dissolving 1M lithium bistrifluoromethylsulfonimide (LiTFSI) containing 2wt% LiNO3 in a volume ratio of 1:1 ethylene glycol dimethyl ether and 1,3-dioxolane; the liquid ratio of the electrolyte to the active substance sulfur is 12μL:1mg; S3. After the lithium-sulfur battery is assembled, use a battery gripper to grip the lithium-sulfur battery and place it under the ultrasonic transducer, and close the cabinet door; S4. Turn on the ultrasonic transducer and adjust the power of the amplitude transformer to 720W at 28°C to perform entropy treatment on the electrolyte of the lithium-sulfur battery; wherein the working duty ratio of the amplitude transformer is 6:2.

[0037] Comparative Example 1 A method for preparing a lithium-sulfur battery comprises the following steps: The active materials sulfur, MWCNT and PVDF were mixed in a mass ratio of 6:3:1, 2 g of N-methylpyrrolidone was added thereto after mixing, and stirred for 6 hours to obtain a positive electrode slurry; the positive electrode slurry was coated on the surface of aluminum foil, and the thickness of the wet film formed by the positive electrode slurry on the surface of the aluminum foil was 250 μm. After being placed at 60°C and vacuum dried for 12 hours, a positive electrode with a thickness of 25 μm was formed, and a positive electrode sheet with a diameter of 13 mm was cut with a sheet cutting machine; wherein, the positive electrode surface loading was 3.53 mg / cm 2The sulfur content of the positive electrode is 66.6%; the thickness of the negative electrode lithium is 200μm; the lithium-sulfur battery is assembled in the order of positive electrode, interlayer, diaphragm, lithium sheet, gasket and shrapnel in an argon-filled and dry MIKROUNA glove box; among them, the battery accessories are 2032 button batteries, and the diaphragm is Celgrad2500; the electrolyte used for battery assembly is a lithium-sulfur electrolyte prepared by dissolving 1M lithium bistrifluoromethylsulfonimide (LiTFSI) containing 2wt% LiNO3 in ethylene glycol dimethyl ether and 1,3-dioxolane in a volume ratio of 1:1; the liquid ratio of the electrolyte to the active substance sulfur is 10μL:1mg.

[0038] Experimental example The lithium-sulfur batteries obtained in Examples 1 to 3 and Comparative Example 1 were collected and tested for electrochemical properties; the test methods and test results are as follows: 1. Electrochemical impedance test: Electrochemical impedance (EIS) is measured by an electrochemical workstation. The kinetic process and mechanism involved in the electrode reaction can be inferred by analyzing the combination of linear elements in the equivalent circuit. The present invention uses the French Bio-Logic VSP multi-channel constant potential instrument to perform electrochemical AC impedance characterization on the simulated battery. The amplitude is 10mV and the frequency range is between 100kHz and 0.01Hz. Before the EIS test, the simulated battery is activated 3 to 5 times at a small current density to determine the impedance spectrum at the open circuit voltage; the results are as follows: Figure 3 As shown. Figure 3 It can be seen that the test results of electrochemical impedance spectroscopy of high-entropy lithium-sulfur batteries enhanced by ultrasonic cavitation field and lithium-sulfur batteries without ultrasound show that the addition of ultrasound reduces the overall interface charge transfer resistance and improves the ion transfer rate to a certain extent. This effect is further enhanced with the increase of ultrasonic power.

[0039] 2. Cyclic voltammetry test: Cyclic voltammetry (CV) is used to study and analyze the current-voltage (iE) curve (i.e., CV curve). Cyclic voltammetry obtains the corresponding current through the linear change of voltage. Based on the relationship between the response current and the voltage potential, it can be determined whether a redox reaction has occurred (the cyclic voltammetry curve of a pure capacitor material is a complete rectangle) and whether the redox reaction is reversible. The results are as follows: Figure 4 shown.

[0040] 3. Peak current analysis: According to the test results of cyclic voltammetry test, use origin software to perform peak current analysis. The results are as follows: Figure 5 As shown. Figures 4 and 5It can be seen that the electrochemical test results of high-entropy lithium-sulfur batteries enhanced by ultrasonic cavitation field and lithium-sulfur batteries without ultrasound using cyclic voltammetry show that the addition of ultrasound reduces the overall redox reaction potential while also improving the peak current to a certain extent. This effect is further enhanced with the increase of ultrasonic power.

[0041] 4. Nucleation-decomposition scanning electron microscopy test of lithium sulfide in lithium-sulfur batteries: Scanning electron microscope (SEM) analysis is used to directly observe the basic microscopic morphology of the sample; the basic principle is to focus the electron beam and scan it in a grating manner within a depth of 10nm on the sample surface, and interact with the surface atoms to generate a large amount of information such as backscattered electrons, X-rays and secondary electrons, etc. This information is collected and analyzed to obtain the microscopic morphology information of the sample surface. The present invention uses a JEOL JSM-6700F scanning electron microscope from Japan Electronics, with an acceleration voltage of 30kV and a resolution of 1nm. The test results are as follows: Figure 6 As shown in the figure, the nucleation-decomposition test results of lithium sulfide observed using scanning electron microscopy in high-entropy lithium-sulfur batteries enhanced by ultrasonic cavitation field and lithium-sulfur batteries without ultrasound showed that the addition of ultrasound made the overall lithium sulfide nucleation more uniform and the degree of lithium sulfide decomposition was also improved to a certain extent. This effect was further enhanced with the increase of ultrasonic power.

[0042] 5. Voltage-discharge specific capacity test: The present invention uses Wuhan LAND CT2001A battery test system to perform constant current charge and discharge test. The system can test the energy density and rate performance of electrode materials in the battery system, and actually reflects the advantages and disadvantages of the electrochemical performance of electrode materials. The results are as follows: Figure 7-8 As shown. Figure 7-8 It can be seen that the high-entropy lithium-sulfur battery enhanced by ultrasonic cavitation field and the lithium-sulfur battery without ultrasound use 0.5C constant current charge and discharge electrochemical test results show that the addition of ultrasound improves the effective specific capacity of the overall redox reaction while the voltage of the charge and discharge platform is also optimized to a certain extent. Combined with the statistical platform capacity, it can be seen that the ultrasonic cavitation field can effectively enhance the capacity of each platform of the whole battery, and this effect is further enhanced with the increase of ultrasonic power.

[0043] The ultrasonic cavitation device of the present invention exhibits the characteristics of high efficiency and high entropy, and can construct an ultrasonic cavitation field environment for lithium-sulfur batteries. The ultrasonic cavitation field directly applies ultrasonic waves to the lithium-sulfur battery, and enhances the redox reaction activity of the active substance through the high entropy electrolyte. The lithium-sulfur battery after the entropy treatment of the electrolyte of the present invention not only exhibits the overall enhanced activity of the positive and negative electrode surfaces, but also has the functions of enhancing convective mass transfer and improving ion and electron transmission, and has good application prospects in the external field assisted enhancement of lithium-sulfur batteries.

[0044] The present invention has been described according to the above embodiments. It should be understood that the above embodiments do not limit the present invention in any form. Any technical solutions obtained by equivalent replacement or equivalent transformation shall fall within the scope of the present invention.

Claims

1. An ultrasonic cavitation device, characterized in that: It comprises a cabinet (8), a cabinet door (9), an ultrasonic mechanism and a heat exchange mechanism; the cabinet door (9) is connected to the cabinet (8); the ultrasonic mechanism is arranged inside the cabinet (8); and the heat exchange mechanism is connected to the ultrasonic mechanism; The ultrasonic mechanism comprises a horn (2), an ultrasonic transducer (1), a cooling pool (3) and a battery clamp (6); the cooling pool (3) is a double-layer structure, the inner layer is an oil bath (12), and the outer layer is a water bath (11); the horn (2) passes through the cabinet (8) and is in contact with the ultrasonic transducer (1); the upper end of the ultrasonic transducer (1) is fixed on the cabinet (8), and the lower end is arranged in the oil bath (12) and is connected to the battery clamp (6).

2. The ultrasonic cavitation device according to claim 1, characterized in that: The heat exchange mechanism comprises an external water heat exchange inlet pipe (5) and an external water heat exchange outlet pipe (4) arranged in parallel; the external water heat exchange inlet pipe (5) is located below the external water heat exchange outlet pipe (4).

3. The ultrasonic cavitation device according to claim 2, characterized in that: The heat exchange mechanism also includes a water cooling device (10); the external water heat exchange inlet pipe (5) and the external water heat exchange outlet pipe (4) are simultaneously connected to the water bath (11) and pass through the cabinet (8) to be connected to the water cooling device (10).

4. A method for assisted entropy treatment of lithium-sulfur battery electrolyte using the ultrasonic cavitation device according to any one of claims 1 to 3, characterized in that: The following steps are involved: S1. Place a non-conductive solvent in an oil bath and adjust the liquid level. Insert the horn and use a heat exchange mechanism to perform low-temperature heating treatment. S2. Prepare a lithium-sulfur battery, use a battery clamp to clamp the lithium-sulfur battery and place it under the ultrasonic transducer, and close the cabinet door; S3, turn on the ultrasonic transducer and adjust the power of the amplitude transformer to perform entropy conversion of the lithium-sulfur battery electrolyte.

5. The method according to claim 4, characterized in that In the step S1, the non-conductive solvent is olive oil, silicone oil or paraffin oil; the low-temperature heating temperature is 10-50° C., and the time is 1-6 hours; the liquid level is adjusted so that the ultrasonic transducer is immersed in the liquid to a depth of 1-5 cm.

6. The method according to claim 4, characterized in that The lithium-sulfur battery in step S2 is a button cell or a soft pack cell; the positive electrode surface loading of the lithium-sulfur battery is 2-6 mg / cm 2 The thickness of the positive electrode is 5-50 μm, and the sulfur content of the positive electrode is 50-70%; the thickness of the negative electrode lithium of the lithium-sulfur battery is 100-1000 μm.

7. The method according to claim 4, characterized in that In the process of preparing the lithium-sulfur battery in step S2, the electrolyte used for assembling the lithium-sulfur battery is prepared by mixing lithium bis(trifluoromethylsulfonyl)imide) containing lithium nitrate, ethylene glycol dimethyl ether and 1,3-dioxolane.

8. The method according to claim 6 or 7, characterized in that The liquid-to-electrolyte ratio of the electrolyte to the sulfur in the positive electrode of the lithium-sulfur battery is 5-20 μL:1 mg.

9. The method according to claim 4, characterized in that In step S3, the power of the horn is 50-900W; the working duty ratio of the horn is 2:2-8:

2.

10. The method according to claim 9, characterized in that The temperature protection parameter of the horn is 30~35℃.

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