Low-temperature and low-internal-resistance supercapacitor and electrolyte and manufacturing method thereof

Abstract

The invention relates to a low-temperature and low-internal-resistance supercapacitor and an electrolyte and a manufacturing method thereof, the electrolyte comprises a mixed solvent and a mixed electrolyte salt, the molar concentration of the mixed electrolyte salt is 1-2M, the mixed solvent is formed by mixing acetonitrile, 1-tert-butoxy-2, 3-epoxypropane and a diluent, the mixed electrolyte salt is formed by mixing an electrolyte salt and a competitive solvation regulator, and the competitive solvation regulator is formed by mixing the electrolyte salt and the diluent. The composition of the electrolyte is limited, the 1-tert-butoxy-2, 3-epoxypropane, the acetonitrile and the diluent are introduced to be compounded as the solvent, and the competitive solvation regulator and the electrolyte salt are introduced to be compounded as the mixed electrolyte salt, so that the prepared electrolyte has the characteristics of low temperature and low internal resistance; therefore, the prepared super capacitor can work at the temperature of-60 DEG C while keeping the characteristic of low internal resistance, and the lower limit working temperature of the super capacitor is greatly widened.

Description

Technical Field

[0001] The present invention belongs to the field of supercapacitor manufacturing, and in particular relates to a low-temperature, low-internal-resistance supercapacitor, an electrolyte thereof, and a manufacturing method thereof. Background Art

[0002] Supercapacitors, as energy storage devices with high power density and long cycle life, are showing significant application value in new energy vehicles, smart grids, and electronic devices in extreme environments. The electrolyte, a core component that determines the operating temperature range and internal resistance of supercapacitors, has a direct impact on the device's energy transfer efficiency and adaptability to low-temperature environments.

[0003] Currently, organic electrolytes (such as propylene carbonate systems) suffer from a sharp increase in viscosity at low temperatures (viscosity > 200 mPa·s at -40°C) and a decrease in ionic dissociation. This leads to a significant increase in device internal resistance (ESR), severely restricting their application in cold regions and low-temperature applications such as aerospace. Recent studies have proposed using low-freezing-point solvents or introducing ionic liquids (such as EMIM-BF4) to improve low-temperature performance. However, the former often comes with safety risks caused by a decrease in decomposition voltage (<2.7 V), while the latter, due to its high viscosity (viscosity > 40 mPa·s at 25°C), degrades rate performance, requiring further improvement. Summary of the Invention

[0004] The purpose of the present invention is to overcome the shortcomings of the prior art and provide a low-temperature, low-internal-resistance supercapacitor and its electrolyte, and a manufacturing method.

[0005] The present invention adopts the following technical solutions: A low-temperature, low-internal-resistance electrolyte comprises a mixed solvent and a mixed electrolyte salt, wherein the molar concentration of the mixed electrolyte salt is 1-2M, the mixed solvent is composed of acetonitrile, 1-tert-butoxy-2,3-propylene oxide, and a diluent in a volume ratio of 60-70:20-30:10, and the mixed electrolyte salt is composed of an electrolyte salt and a competitive solvation regulator, and the molar concentration ratio of the electrolyte salt to the competitive solvation regulator is 1:0.1-0.3.

[0006] Furthermore, the competitive solvation regulator is Li + , K + , Ca + Or Na + A salt composed of cations and anions.

[0007] Furthermore, the electrolyte salt includes one or more of spirocyclic quaternary ammonium tetrafluoroborate, tetraethylammonium tetrafluoroborate, and triethylmethylammonium tetrafluoroborate.

[0008] Furthermore, the diluent includes one or more of 1,1,2,2-tetrafluoroethyl-2,2,3,3-tetrafluoropropyl ether, 1,1,2,2-tetrafluoroethyl-2,2,2-trifluoroethyl ether, and 2,2,2-trifluoroethyl trifluoromethanesulfonate.

[0009] A method for preparing a low-temperature, low-internal-resistance electrolyte comprises the following steps: Step 1, acetonitrile, 1-tert-butoxy-2,3-propylene oxide, and a diluent are mixed in a volume ratio and stirred to obtain a mixed solvent; Step 2, weighing a certain mass of electrolyte salt and a competitive solvation regulator according to the molar concentration ratio of the mixed electrolyte salt, and dissolving them in the mixed solvent obtained in step 1 to obtain a precursor electrolyte; Step 3: using a molecular sieve to remove water from the obtained precursor electrolyte to obtain the low-temperature, low-internal-resistance electrolyte.

[0010] Furthermore, in step 3, the water content of the obtained low-temperature, low-internal-resistance electrolyte is less than 10 ppm.

[0011] Furthermore, step 1, step 2 and step 3 are all carried out in a glove box.

[0012] Furthermore, nitrogen is used as an inert gas in the glove box, and the water and oxygen index is less than 0.1 ppm.

[0013] A low-temperature, low-internal-resistance supercapacitor is prepared using any of the above-mentioned electrolytes.

[0014] Furthermore, the lower limit operating temperature of the supercapacitor is -60°C.

[0015] From the above description of the present invention, it can be seen that compared with the prior art, the beneficial effects of the present invention are as follows: the present application limits the composition of the electrolyte, introduces 1-tert-butoxy-2,3-propylene oxide, acetonitrile, and a diluent compound as a solvent, and introduces a competitive solvation regulator and an electrolyte salt compound as a mixed electrolyte salt, so that the prepared electrolyte has the characteristics of low temperature and low internal resistance, thereby enabling the prepared supercapacitor to operate at -60°C while maintaining the characteristics of low internal resistance, greatly broadening the lower limit operating temperature of the supercapacitor; wherein, the added competitive solvation regulator cation has a high charge density (small radius, concentrated charge) giving it a strong polarization ability (easier to combine with solvent molecules), weakening the interaction between the cations and solvent molecules in the electrolyte salt, and increasing the number of free ions; the presence of the diluent reduces the viscosity of the overall electrolyte and increases the ion migration rate. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1The capacitance and DC internal resistance of the supercapacitor assembled with each electrolyte at 25°C; Figure 2 The capacitance and DC internal resistance of supercapacitors assembled with various electrolytes at -60°C; Figure 3 The graph shows the capacitance and DC internal resistance change rate of supercapacitors assembled with different electrolytes. DETAILED DESCRIPTION

[0017] The present invention is further described below through specific embodiments.

[0018] A low-temperature, low-internal-resistance supercapacitor is prepared using a low-temperature, low-internal-resistance electrolyte, wherein the lower limit operating temperature is -60°C.

[0019] A low-temperature, low-internal-resistance electrolyte comprises a mixed solvent and a mixed electrolyte salt, wherein the molar concentration of the mixed electrolyte salt is 1-2M.

[0020] The mixed solvent is composed of acetonitrile, 1-tert-butoxy-2,3-propylene oxide and a diluent in a volume ratio of 60-70:20-30:10, wherein the diluent includes one or more of 1,1,2,2-tetrafluoroethyl-2,2,3,3-tetrafluoropropyl ether, 1,1,2,2-tetrafluoroethyl-2,2,2-trifluoroethyl ether and 2,2,2-trifluoroethyl trifluoromethanesulfonate.

[0021] A mixed electrolyte salt is composed of an electrolyte salt and a competitive solvation regulator, wherein the molar concentration ratio of the electrolyte salt to the competitive solvation regulator is 1:0.1-0.3; the competitive solvation regulator is Li + , K + , Ca + Or Na + A salt composed of a cation and an anion; the electrolyte salt includes one or more of spirocyclic quaternary ammonium tetrafluoroborate, tetraethylammonium tetrafluoroborate, and triethylmethylammonium tetrafluoroborate; specifically, the competitive solvation regulator can be selected from lithium tetrafluoroborate, potassium tetrafluoroborate, calcium tetrafluoroborate, and sodium tetrafluoroborate.

[0022] The method for preparing a low-temperature, low-internal-resistance electrolyte specifically comprises the following steps: Step 1, acetonitrile, 1-tert-butoxy-2,3-propylene oxide, and a diluent are mixed in a volume ratio and stirred to obtain a mixed solvent; Step 2, weighing a certain mass of electrolyte salt and a competitive solvation regulator according to the molar concentration ratio of the mixed electrolyte salt, and dissolving them in the mixed solvent obtained in step 1 to obtain a precursor electrolyte; Step 3: using a molecular sieve to remove water from the obtained precursor electrolyte to obtain the low-temperature, low-internal-resistance electrolyte.

[0023] Furthermore, in step 3, the water content of the obtained low-temperature, low-internal-resistance electrolyte is less than 10 ppm.

[0024] Wherein, step 1, step 2 and step 3 are all carried out in a glove box; nitrogen is used as an inert gas in the glove box, and the water oxygen index is less than 0.1 ppm.

[0025] Example 1 A method for preparing a low-temperature, low-internal-resistance electrolyte comprises the following steps: Step 1: Mix acetonitrile, 1-tert-butoxy-2,3-propylene oxide, and 1,1,2,2-tetrafluoroethyl-2,2,3,3-tetrafluoropropyl ether in a volume ratio of 65:25:10 and stir to obtain a mixed solvent with a total volume of 100 mL; Step 2: Weigh 21.303 g of tetrafluoroborate spirocyclic quaternary ammonium salt and 1.259 g of potassium tetrafluoroborate, and dissolve them in the mixed solvent obtained in step 1 using a magnetic stirrer to obtain a precursor electrolyte at a speed of 500 r·min. -1 , stirring time is 3 h; Step 3: The precursor electrolyte obtained in step 2 is dehydrated using a molecular sieve and the moisture content is detected using a moisture meter. The precursor electrolyte is treated with a 3Å molecular sieve for 24 hours to control the moisture content to <10 ppm, thereby obtaining the low-temperature, low-internal-resistance electrolyte.

[0026] Example 2 A method for preparing a low-temperature, low-internal-resistance super electrolyte comprises the following steps: Step 1: Mix acetonitrile, 1-tert-butoxy-2,3-propylene oxide, and 1,1,2,2-tetrafluoroethyl-2,2,3,3-tetrafluoropropyl ether in a volume ratio of 65:25:10 and stir to obtain a mixed solvent with a total volume of 100 mL; Step 2: Weigh 21.303 g of tetrafluoroborate spirocyclic quaternary ammonium salt and 1.0979 g of sodium tetrafluoroborate, and dissolve them in the mixed solvent obtained in step 1 using a magnetic stirrer to obtain a precursor electrolyte at a speed of 500 r / min. -1 , stirring time is 3 h; Step 3: The precursor electrolyte obtained in step 2 is dehydrated using a molecular sieve and the moisture content is detected using a moisture meter. The precursor electrolyte is treated with a 3Å molecular sieve for 24 hours to control the moisture content to <10 ppm, thereby obtaining the low-temperature, low-internal-resistance electrolyte.

[0027] Comparative Example 1 A method for preparing a low-temperature, low-internal-resistance super electrolyte comprises the following steps: Step 1: Mix acetonitrile and 1-tert-butoxy-2,3-propylene oxide in a volume ratio of 70:30 and stir evenly to obtain a mixed solvent with a total volume of 100 mL; Step 2: Weigh 21.303 g of tetrafluoroborate spirocyclic quaternary ammonium salt and 1.259 g of potassium tetrafluoroborate, and dissolve them in the mixed solvent obtained in step 1 using a magnetic stirrer to obtain a precursor electrolyte at a speed of 500 r / min. -1 , stirring time is 3 h; Step 3: The precursor electrolyte obtained in step 2 is dehydrated using a molecular sieve and the moisture content is detected using a moisture meter. The precursor electrolyte is treated with a 3Å molecular sieve for 24 hours and the moisture content is controlled to be less than 10 ppm to obtain the electrolyte.

[0028] Comparative Example 2 A method for preparing a low-temperature, low-internal-resistance super electrolyte comprises the following steps: Step 1: Mix acetonitrile, 1-tert-butoxy-2,3-propylene oxide, and 1,1,2,2-tetrafluoroethyl-2,2,3,3-tetrafluoropropyl ether in a volume ratio of 65:25:10 and stir to obtain a mixed solvent with a total volume of 100 mL; Step 2: Weigh 21.303 g of tetrafluoroborate spirocyclic quaternary ammonium salt and dissolve it in the mixed solvent obtained in step 1 using a magnetic stirrer to obtain a precursor electrolyte at a speed of 500 r·min. -1 , stirring time is 3 h; Step 3: The precursor electrolyte obtained in step 2 is dehydrated using a molecular sieve and the moisture content is detected using a moisture meter. The precursor electrolyte is treated with a 3Å molecular sieve for 24 hours and the moisture content is controlled to be less than 10 ppm to obtain the electrolyte.

[0029] Comparative Example 3 A method for preparing a low-temperature, low-internal-resistance super electrolyte comprises the following steps: Step 1: Mix acetonitrile and 1-tert-butoxy-2,3-propylene oxide in a volume ratio of 70:30 and stir evenly to obtain a mixed solvent with a total volume of 100 mL; Step 2: Weigh 21.303 g of tetrafluoroborate spirocyclic quaternary ammonium salt and dissolve it in the mixed solvent obtained in step 1 using a magnetic stirrer to obtain a precursor electrolyte at a speed of 500 r·min. -1 , stirring time is 3 h; Step 3: The precursor electrolyte obtained in step 2 is dehydrated using a molecular sieve and the moisture content is detected using a moisture meter. The precursor electrolyte is treated with a 3Å molecular sieve for 24 hours and the moisture content is controlled to be less than 10 ppm to obtain the electrolyte.

[0030] The electrolytes obtained from Examples 1-2 and Comparative Examples 1-3 were used to prepare supercapacitors, and the obtained capacitors were tested accordingly. Figure 1-3 .

[0031] From the attached Figure 1 It can be seen that at 25°C, the capacitance of supercapacitor products assembled with electrolytes containing competitive solvation modifiers and diluents is normal, and their capacitance performance is not damaged. In terms of DC internal resistance, the electrolyte containing competitive solvation modifiers and diluents has a low DC internal resistance. This is because the cations in the competitive solvation modifiers have a high charge density (small radius and concentrated charge), which gives them strong polarization ability (easier to bind to solvent molecules), weakening the interaction between cations and solvent molecules in the electrolyte salt, while increasing the number of free ions. The presence of the diluent reduces the viscosity of the overall electrolyte and increases the ion migration rate.

[0032] By the attached Figure 2 The low internal resistance characteristics of the competitive solvation regulator and diluent electrolyte are also reflected in the -60°C environment.

[0033] From the attached Figure 3 It can be seen that the electrolyte strategy adopted in the present invention enables the supercapacitor to have lower internal resistance and internal resistance change rate at -60°C, while meeting the requirements of low temperature and low internal resistance.

[0034] The above description is merely a preferred embodiment of the present invention and therefore cannot be used to limit the scope of the present invention. In other words, equivalent changes and modifications made according to the scope of the present invention and the contents of the specification should still fall within the scope of the present invention.

Claims

1. A low-temperature, low-internal-resistance electrolyte, characterized by: The invention comprises a mixed solvent and a mixed electrolyte salt, wherein the molar concentration of the mixed electrolyte salt is 1-2M, the mixed solvent is composed of acetonitrile, 1-tert-butoxy-2,3-propylene oxide, and a diluent in a volume ratio of 60-70:20-30:10, and the mixed electrolyte salt is composed of an electrolyte salt and a competitive solvation regulator, and the molar concentration ratio of the electrolyte salt to the competitive solvation regulator is 1:0.1-0.

3.

2. The low-temperature, low-internal-resistance electrolyte according to claim 1, characterized in that: The competitive solvation modifier is Li + , K + , Ca + Or Na + A salt composed of cations and anions.

3. The low-temperature, low-internal-resistance electrolyte according to claim 1, characterized in that: The electrolyte salt includes one or more of spirocyclic quaternary ammonium tetrafluoroborate, tetraethylammonium tetrafluoroborate, and triethylmethylammonium tetrafluoroborate.

4. The low-temperature, low-internal-resistance electrolyte according to claim 1, characterized in that: The diluent includes one or more of 1,1,2,2-tetrafluoroethyl-2,2,3,3-tetrafluoropropyl ether, 1,1,2,2-tetrafluoroethyl-2,2,2-trifluoroethyl ether, and 2,2,2-trifluoroethyl trifluoromethanesulfonate.

5. The method for preparing a low-temperature, low-internal-resistance electrolyte according to claim 1, characterized in that: The specific steps include: Step 1, acetonitrile, 1-tert-butoxy-2,3-propylene oxide, and a diluent are mixed in a volume ratio and stirred to obtain a mixed solvent; Step 2, weighing a certain mass of electrolyte salt and a competitive solvation regulator according to the molar concentration ratio of the mixed electrolyte salt, and dissolving them in the mixed solvent obtained in step 1 to obtain a precursor electrolyte; Step 3: using a molecular sieve to remove water from the obtained precursor electrolyte to obtain the low-temperature, low-internal-resistance electrolyte.

6. The method for producing a low-temperature, low-internal-resistance electrolyte according to claim 5, characterized in that: In step 3, the water content of the obtained low-temperature, low-internal-resistance electrolyte is less than 10 ppm.

7. The method for producing a low-temperature, low-internal-resistance electrolyte according to claim 5, characterized in that: Step 1, step 2 and step 3 are all carried out in a glove box.

8. The method for producing a low-temperature, low-internal-resistance electrolyte according to claim 7, characterized in that: Nitrogen is used as an inert gas in the glove box, and the water and oxygen index is less than 0.1 ppm.

9. A low-temperature, low-internal-resistance supercapacitor, characterized by: The electrolyte is prepared using the electrolyte according to any one of claims 1 to 4.

10. The low-temperature, low-internal-resistance supercapacitor according to claim 9, characterized in that: The lower limit operating temperature of the supercapacitor is -60°C.

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