Preparation method of double-lithium-salt electrolyte with shear thickening characteristic

Abstract

The invention discloses a preparation method of a double-lithium-salt electrolyte with a shear thickening characteristic, and relates to the technical field of preparation of intelligent materials and new energy battery electrolytes. The preparation method comprises the following steps: preparing surface amino modified mesoporous silica, dispersing the surface amino modified mesoporous silica in a basic electrolyte, adding a lithium salt additive, stirring again to uniformly disperse the lithium salt additive, and finally preparing the double-lithium-salt electrolyte with the shear thickening characteristic. The viscosity of the double-lithium-salt electrolyte can be sharply increased along with the increase of the shearing speed, so that short circuit under physical impact can be protected, and combustion is avoided. Moreover, the lithium salt additive is added to form a double-lithium-salt electrolyte system, so that the ionic conductivity of the electrolyte can be improved, and the battery has excellent electrochemical performance.

Description

Technical Field

[0001] The present invention relates to the technical field of intelligent materials and new energy battery electrolyte preparation, and in particular to a method for preparing a double lithium salt electrolyte with shear thickening properties. Background Art

[0002] Lithium / sodium ion batteries have the characteristics of high energy density, strong environmental adaptability and low environmental impact, which make them widely used in portable electronic devices, electric vehicles and energy storage systems.

[0003] Currently, commercial lithium-ion and sodium-ion batteries mostly use liquid organic electrolytes, including ester- and ether-based electrolytes. These electrolytes offer high ionic conductivity and excellent electrochemical performance. However, when a liquid battery system is subjected to a high-speed external impact, a short circuit may occur within the battery, causing a rapid increase in system temperature, melting of the separator, and the heat and gas generated by electrolyte decomposition, which can trigger thermal runaway, ultimately leading to fire or even explosion. While solid-state electrolytes offer advantages such as non-volatility, safety, and mechanical strength compared to liquid electrolytes, they suffer from poor interfacial contact between the solid electrolyte and the electrodes, low ionic conductivity, and poor solid-solid interface stability, far inferior to liquid electrolytes. Therefore, there is an urgent need to develop liquid electrolytes with impact resistance and high electrochemical performance.

[0004] In light of this, the present invention proposes a dilithium salt electrolyte with shear-thickening properties and a method for preparing the same. The shear-thickening property refers to the rapid aggregation of inorganic particles in a liquid electrolyte battery when subjected to an external force, increasing the electrolyte viscosity and improving the mechanical strength of the liquid electrolyte battery, thereby dissipating the energy impact caused by the external force. When the external force is removed, the inorganic particles remain evenly dispersed in the electrolyte system, and the electrolyte returns to a steady state. This imparts shear-thickening properties to the liquid electrolyte. The selected dilithium salt can impart high ionic conductivity to the electrolyte, improving the battery's cycle stability and rate capability. The dilithium salt electrolyte with shear-thickening properties not only exhibits high electrochemical performance but also enhances the battery's impact safety. Summary of the Invention

[0005] The purpose of the present invention is to provide a method for preparing a dilithium salt electrolyte with shear thickening properties, so that the dilithium salt electrolyte has the high electrochemical properties of a conventional electrolyte and also has shear thickening properties, which can alleviate the impact force generated by external collisions. In addition, amino-modified mesoporous silica is uniformly dispersed in the electrolyte as inorganic particles, so that the electrolyte has shear thickening properties and high electrochemical properties.

[0006] In order to achieve the above object, the technical solution adopted by the present invention is:

[0007] A method for preparing a dilithium salt electrolyte having shear thickening properties comprises the following steps:

[0008] Step 1: Preparation of mesoporous silica:

[0009] Anhydrous ethanol, deionized water, ammonia water, tetraethyl orthosilicate and hexadecyltrimethylammonium bromide were mixed, stirred and reacted completely, centrifuged and diluted with anhydrous ethanol, and then etched with hydrochloric acid. Finally, the mixture was centrifuged, washed, dried, calcined and ground to obtain a white mesoporous silica powder.

[0010] Step 2: Preparation of surface amino-modified mesoporous silica:

[0011] The white mesoporous silica powder was mixed with 3-aminopropyltriethoxysilane and an appropriate amount of toluene, stirred and reacted completely, and then centrifuged, washed, and dried to obtain surface amino-modified mesoporous silica.

[0012] Step 3: Preparation of electrolyte with shear thickening properties:

[0013] Dispersing surface amino-modified mesoporous silica into a basic electrolyte, stirring and mixing uniformly to obtain an electrolyte with shear thickening properties;

[0014] Step 4: Preparation of a dilithium salt electrolyte with shear thickening properties:

[0015] Add an appropriate amount of lithium salt additive to the electrolyte prepared in step 3, stir and mix evenly to obtain a double lithium salt electrolyte with shear thickening properties.

[0016] As a preferred technical solution of the present invention, in step 1, the volume ratio of anhydrous ethanol, deionized water, ammonia water, and tetraethyl orthosilicate is 10-20:30-35:1:1-2, and the mass ratio of hexadecyltrimethylammonium bromide to deionized water is 1:50-150. The stirring reaction is carried out at 40-60°C for 12-36 hours. After the addition of hydrochloric acid, the etching is carried out by stirring at 50-70°C for 3-6 hours. The surfactant is removed by high-temperature calcination in a muffle furnace at a temperature of 520-580°C for 6-8 hours, and the heating time is 80-110 minutes.

[0017] As a preferred technical solution of the present invention, in step 2, the mass ratio of the surface amino-modified mesoporous silica to 3-aminopropyltriethoxysilane is 1:0.15-0.25. The stirring reaction temperature is 60-80°C, and the reaction time is 3-6 hours. After centrifugal washing, the mixture is dried at 60-80°C for 5-10 hours.

[0018] As a preferred technical solution of the present invention, in step 3, the added mass of the surface amino-modified mesoporous silica is 10-15% of the mass of the basic electrolyte, the basic electrolyte contains 1 mol / L lithium hexafluorophosphate (LiPF6), and the solvent is a mixture of ethylene carbonate (EC), ethyl methyl carbonate (EMC) and dimethyl carbonate (DMC), and the volume ratio of the three is 1:1:1.

[0019] As a preferred technical solution of the present invention, in step 4, the lithium salt additive is lithium bis(difluorosulfonyl)imide, and its addition amount is 3-5% of the mass of the basic electrolyte in step 3.

[0020] The shear-thickening dilithium salt electrolyte prepared by the present invention is composed of a lithium salt, an organic solvent, and surface-amino-modified mesoporous silica. Based on the total mass of the electrolyte, the mass percentage of the lithium salt is 15-25%, the mass percentage of the organic solvent is 60-77%, and the mass percentage of the surface-amino-modified mesoporous silica is 8-15%. Compared with the prior art, the present invention has the following beneficial effects:

[0021] (1) The dual lithium salt system prepared by the present invention can make the liquid electrolyte have a higher lithium ion concentration, improve the ionic conductivity of the electrolyte, and make the battery have better cycle performance and rate performance.

[0022] (2) The shear-thickening dilithium salt electrolyte prepared by the present invention is prepared by adding amino-modified mesoporous silica to a conventional electrolyte to impart shear-thickening properties. This can increase the viscosity of the conventional liquid electrolyte when subjected to impact force, thereby alleviating the impact of the impact force on the battery and improving the safety of the battery during collisions. Simultaneously, a dilithium salt electrolyte system is formed, which improves the electrolyte ion conductivity and imparts excellent electrochemical performance to the battery. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 This is a flow chart for the preparation of surface amino-modified mesoporous silica.

[0024] Figure 2 This is a scanning electron microscope image of the prepared surface amino-modified mesoporous silica.

[0025] Figure 3 Shear rate-viscosity test graphs of different electrolytes prepared for Examples 3 and 4.

[0026] Figure 4 The cycling performance diagram shows the effect of different lithium salt additive addition ratios on the electrochemical performance of the battery. DETAILED DESCRIPTION

[0027] The present invention is further described below in conjunction with embodiments and drawings.

[0028] Example 1 Preparation of mesoporous silica:

[0029] See also Figure 1 As shown, 150 mL of anhydrous ethanol, 300 mL of deionized water, 9.6 mL of aqueous ammonia (14.79 mol / L), and 3.0 g of hexadecyltrimethylammonium bromide were mixed and stirred at 45°C for 3 minutes at a speed of 650 rpm. Then, 15 mL of tetraethyl orthosilicate was added and stirring continued at 45°C for 24 hours to obtain a white suspension.

[0030] The white suspension was washed three times by centrifugation with deionized water and ethanol to obtain white particles, which were dispersed in 400 mL of anhydrous ethanol and etched with 10 mL of hydrochloric acid (0.1 mol / L). The mixture was stirred at 60°C for 4.5 h at a stirring speed of 400 r / min to obtain a suspension.

[0031] The resulting suspension was washed three times with deionized water and three times with ethanol by centrifugation at a speed of 8,000 to 10,000 rpm for 4 to 6 minutes. Finally, it was dried, calcined at 560°C for 6 hours, and ground to obtain mesoporous silica as a white granular powder.

[0032] Example 2 Preparation of surface amino-modified mesoporous silica:

[0033] See also Figure 1 As shown, 2 g of the mesoporous silica particles prepared in Example 1 were uniformly dispersed in a mixed solution of 8 g of toluene solution and 0.4 mL of 3-aminopropyltriethoxysilane, and heated and stirred at 70° C. for 5 h at a stirring speed of 500 r / min to obtain a suspension.

[0034] After the suspension is centrifuged, it is washed with methanol three times and dried at a constant temperature of 80°C for 8 h to obtain surface amino-modified mesoporous silica.

[0035] See also Figure 2 As shown, the surface amino-modified mesoporous silica prepared in this embodiment is combined with Figure 2 The morphology of the prepared amino-modified mesoporous silica is described. It can be seen that the prepared amino-modified mesoporous silica is evenly dispersed, and its surface is relatively rough due to the hydrochloric acid etching and surface amino modification.

[0036] Example 3 Preparation of an electrolyte with shear thickening properties:

[0037] 1.2 g of the surface amino-modified mesoporous silica particles obtained in Example 2 were dispersed in 10 g of the basic electrolyte and magnetically stirred for 10 min at a stirring speed of 500 r / min to prepare an electrolyte with shear thickening properties.

[0038] The above-mentioned basic electrolyte comes from a commercial electrolyte, containing 1 mol / L lithium hexafluorophosphate (LiPF6), and the solvent is a mixture of ethylene carbonate (EC), ethyl methyl carbonate (EMC) and dimethyl carbonate (DMC), with a volume ratio of 1:1:1.

[0039] Example 4 Preparation of a dilithium salt electrolyte with shear thickening properties:

[0040] 0.4 g of lithium salt additive, lithium bis(fluorosulfonyl)imide, was added to the electrolyte prepared in Example 3, and the mixture was magnetically stirred for 10 min at a stirring speed of 500 r / min to obtain a dilithium salt electrolyte with shear thickening properties.

[0041] The electrolyte with shear thickening properties prepared in Example 3 was compared with the lithium salt electrolyte with shear thickening properties prepared in Example 4. The results are as follows: Figure 3 As shown, the viscosity of the dual lithium salt electrolyte increases dramatically with increasing shear rate, alleviating the impact of impact on the battery. Simultaneously, with the addition of lithium salt additives, a dual lithium salt electrolyte system is formed, improving the electrolyte's ionic conductivity and giving the battery excellent electrochemical performance.

[0042] Example 5 Effects of different lithium salt additive ratios on battery electrochemical performance:

[0043] Research has found that when a lithium salt additive is added at a mass ratio of 4% of the conventional base electrolyte, the battery performance reaches its best. Figure 4 As shown, it can stably cycle for 500 cycles. At this time, the prepared double lithium salt electrolyte with shear thickening properties has a surface amino-modified mesoporous silica content of 10% by weight, a lithium salt content of 17% by weight, and the rest being an organic solvent.

[0044] The above content is merely an example and explanation of the concept of the present invention. Those skilled in the art may make various modifications or additions to the described specific embodiments or replace them in a similar manner. As long as they do not deviate from the concept of the invention or exceed the scope defined by the claims, they should all fall within the scope of protection of the present invention.

Claims

1. A method for preparing a dilithium salt electrolyte having shear thickening properties, characterized in that: The following steps are involved: Step 1: Preparation of mesoporous silica: Anhydrous ethanol, deionized water, ammonia water, tetraethyl orthosilicate and hexadecyltrimethylammonium bromide were mixed, stirred and reacted completely, centrifuged and diluted with anhydrous ethanol, and then etched with hydrochloric acid. Finally, the mixture was centrifuged, washed, dried, calcined and ground to obtain a white mesoporous silica powder. Step 2: Preparation of surface amino-modified mesoporous silica: The white mesoporous silica powder was mixed with 3-aminopropyltriethoxysilane and an appropriate amount of toluene, stirred and reacted completely, and then centrifuged, washed, and dried to obtain surface amino-modified mesoporous silica. Step 3: Preparation of electrolyte with shear thickening properties: Dispersing surface amino-modified mesoporous silica into a basic electrolyte, stirring and mixing uniformly to obtain an electrolyte with shear thickening properties; Step 4: Preparation of a dilithium salt electrolyte with shear thickening properties: Add an appropriate amount of lithium salt additive to the electrolyte prepared in step 3, stir and mix evenly to obtain a double lithium salt electrolyte with shear thickening properties.

2. The preparation method according to claim 1, wherein In step 1, the volume ratio of anhydrous ethanol, deionized water, ammonia water and tetraethyl orthosilicate is 10-20:30-35:1:1-2, and the mass ratio of hexadecyltrimethylammonium bromide to deionized water is 1:50-150.

3. The preparation method according to claim 1, wherein In step 1, the stirring reaction is carried out at 40-60° C. for 12-36 hours, and after the addition of hydrochloric acid, the etching is carried out by continuously stirring at 50-70° C. for 3-6 hours.

4. The preparation method according to claim 1, wherein In step 1, the surfactant is removed by high-temperature calcination in a muffle furnace. The calcination temperature is 520-580°C, the calcination time is 6-8 h, and the heating time is 80-110 min.

5. The preparation method according to claim 1, wherein The mass ratio of the surface amino-modified mesoporous silica to 3-aminopropyltriethoxysilane in step 2 is 1:0.15-0.

25.

6. The preparation method according to claim 1, wherein In step 2, the stirring reaction temperature is 60-80° C., and the reaction time is 3-6 h. After centrifugal washing, the mixture is dried at 60-80° C. for 5-10 h.

7. The preparation method according to claim 1, wherein The added mass of the surface amino-modified mesoporous silica in step 3 is 10-15% of the mass of the basic electrolyte. The basic electrolyte contains 1 mol / L lithium hexafluorophosphate (LiPF6), and the solvent is a mixture of ethylene carbonate (EC), ethyl methyl carbonate (EMC) and dimethyl carbonate (DMC), with a volume ratio of 1:1:

1.

8. The preparation method according to claim 1, wherein The lithium salt additive in step 4 is lithium bis(fluorosulfonyl)imide, and its addition amount is 3-5% of the mass of the basic electrolyte in step 3.

9. The dilithium salt electrolyte having shear thickening properties prepared by the method according to any one of claims 1 to 8, characterized in that: The electrolyte comprises lithium salt, organic solvent and surface amino-modified mesoporous silica; based on the total mass of the electrolyte, the mass percentage of the lithium salt is 15-25%, the mass percentage of the organic solvent is 60-77%, and the mass percentage of the surface amino-modified mesoporous silica is 8-15%.

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