Spiro-based ionic liquid electrolyte for low-temperature supercapacitor and manufacturing method thereof
By using spiro-based ionic liquid electrolytes in supercapacitors, the problems of low energy density and temperature limitation in the prior art are solved, and the efficient energy storage and stable operation of supercapacitors over a wide temperature range are achieved.
Patent Information
- Application Number
- CN202380073129.2
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Priority Date
- 2022-09-07
- Filing Date
- 2023-09-07
- Publication Date
- 2025-05-27
AI Technical Summary
Existing supercapacitors have problems with degradation in performance in low energy density and temperature limitations, making it difficult to maintain efficient energy storage in different seasons and ambient temperature changes.
Using a spiro-based ionic liquid electrolyte, the spiro-based liquid electrolyte with specific cations or anions is produced by synthesizing intermediate spiro-based products and applying an ion exchange method to use the separator layer of a supercapacitor.
The stable operation of supercapacitors over a wide temperature range (such as 60℃ to -60℃), improves energy storage performance and charge transfer efficiency, and extends the cycle life of the equipment.
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Figure CN120051842A_ABST
Abstract
Description
[0001] Cross - Reference to Related Applications
[0002] This application claims the benefit of U.S. Provisional Patent Application Serial No. 63 / 404,409, filed on September 7, 2022, which is incorporated herein by reference in its entirety. Field of the Invention
[0003] The present disclosure generally relates to supercapacitors and, more particularly, to their spiro-based ionic liquid electrolytes and methods of making the same. Background of the Invention
[0004] Current interest in reducing global emissions that impact climate change and transitioning to a greener and more sustainable energy production and lifestyle has led to a surge in the demand for reliable and safe energy storage technologies. Supercapacitors have generated significant interest due to their surface-related electrochemistry, which enables fast charge and discharge rates, long cycle life, low maintenance, a less restricted operating temperature range, and safety compared to batteries. These properties make supercapacitors ideal for direct integration into renewable energy generation systems, such as solar technologies, where ambient temperatures can vary significantly during the day and across different seasons of the year. However, compared to batteries, the low energy density of supercapacitors limits their ability to store energy. Since the electrolyte plays a major role in energy density and temperature limitations, it is important that supercapacitors can have electrolytes with enhanced chemical and physical properties to mitigate issues that could otherwise degrade their performance. Summary of the Invention
[0005] Embodiments disclosed herein relate to electrochemical energy storage devices and methods of making the same. In some embodiments, the electrochemical energy storage device is a high-energy volumetric capacitor (also referred to as a "supercapacitor") for storing electrical energy therein that can be used as a power source.
[0006] According to one aspect of the present disclosure, there is provided a supercapacitor including a cathode layer, an anode layer, and a separator layer disposed between the cathode layer and the anode layer. The separator layer contains an ionic liquid electrolyte.
[0007] According to one aspect of the present disclosure, there is provided an electrochemical energy storage device including: an ionic liquid electrolyte containing an ionic liquid salt having the following cations:
[0008]
[0009] In some embodiments, the ionic liquid electrolyte is a spiro-based ionic liquid electrolyte.
[0010] In some embodiments, the ionic liquid electrolyte is spiro-1,1'-dipyrrolidinium bromide (SBPBr):
[0011]
[0012] According to one aspect of the present disclosure, there is provided an electrochemical energy storage device, the electrochemical energy storage device comprising: an ionic liquid electrolyte, the ionic liquid electrolyte comprising an ionic liquid salt having the following anions:
[0013]
[0014] In some embodiments, the ionic liquid electrolyte is a spiro-based ionic liquid electrolyte.
[0015] In some embodiments, the ionic liquid electrolyte is spiro-1,1'-dipyrrolidinium tetrafluoroborate (SBPBF 4 ):
[0016]
[0017] According to one aspect of the present disclosure, there is provided a method for manufacturing an ionic liquid electrolyte, the method comprising: synthesizing an intermediate spiro product; and applying an ion exchange method to the intermediate spiro product to obtain the ionic liquid electrolyte.
[0018] In some embodiments, the synthesizing the intermediate spiro product comprises: adding a plurality of precursors to an organic solvent (such as isopropanol or acetonitrile) to obtain a mixture, and stirring the mixture at a temperature of 340 Kelvin (K) for a period of time to obtain the intermediate spiro product; and purifying the intermediate spiro product; the plurality of precursors includes alkylation of a cyclic amine and a dihaloalkane.
[0019] In some embodiments, the organic solvent includes isopropanol or acetonitrile.
[0020] In some embodiments, the period of time is about 6 hours (h), 12 h, 18 h or 24 h.
[0021] In some embodiments, the purifying the intermediate spiro product comprises: washing the intermediate spiro product with acetone.
[0022] In some embodiments, the applying the ion exchange method to the intermediate spiro product to obtain the ionic liquid electrolyte comprises: reacting the intermediate spiro product with hydrofluoro boric acid or an alkali metal tetrafluoroborate in ethanol. Description of the Drawings
[0023] To more fully understand the present disclosure, reference is made to the following description and drawings, wherein:
[0024] Figure 1A is a schematic perspective view of a supercapacitor;
[0025] Figure 1B is Figure 1A a schematic exploded view of the supercapacitor shown;
[0026] Figure 2 is a diagram showing Figure 1A the self-discharge curve of the supercapacitor shown in, which is used to show the low-temperature voltage leakage of the supercapacitor; and
[0027] Figure 3 is a diagram showing Figure 1A the voltage retention test curve of the supercapacitor shown in, which is used to show the capacitance retention of the supercapacitor over time. DETAILED DESCRIPTION
[0028] The detailed description of Subsection F lists the references cited in this disclosure. The content of each of these references is incorporated herein by reference in its entirety.
[0029] A. Supercapacitors and Spiro-Based Ionic Liquid Electrolytes
[0030] Referring now to Figure 1A and 1B , there is shown an electrochemical energy storage device in the form of a high-energy volumetric capacitor (also referred to as a "supercapacitor"), and it is generally identified by the reference numeral 100. In these embodiments, the supercapacitor is a highly stable low-temperature supercapacitor that can operate at temperatures much lower than the operating temperatures of most prior art supercapacitors.
[0031] As Figure 1A and 1B shown, the supercapacitor 100 includes a pair of cell housings 102 in which a cathode layer 104, an anode layer 106, and a separator layer 108 sandwiched between the cathode layer 104 and the anode layer 106 are encapsulated. A cathode tab or electrode 110 and an anode tab or electrode are electrically connected to the cathode layer 104 and the anode layer 106, respectively, for electrically connecting the supercapacitor 100 to various electrical components or devices (not shown). For example, the cathode electrode 110 and the anode electrode 112 can be electrically connected to a power source, such as a solar panel, for storing electrical energy received from the solar panel. The cathode electrode 110 and the anode electrode 112 can be electrically connected to a power-consuming device to serve as a power source for the power-consuming device and supply power to the power-consuming device.
[0032] In some embodiments, the separator layer 108 includes an ionic liquid electrolyte, and the ionic liquid electrolyte includes an ionic liquid salt having the following cations:
[0033]
[0034] In some embodiments, the ionic liquid electrolyte comprises an ionic liquid salt having the following anions:
[0035]
[0036] In some embodiments, the ionic liquid electrolyte is a spiro-based ionic liquid electrolyte, wherein an electrolyte having ions of a specific size classification is used as a charge transport and storage agent within the carbon pores of a supercapacitor electrode. In some embodiments, the spiro-based ionic liquid electrolyte is in the form of a spiro-based ionic liquid salt that is highly soluble in an organic solvent.
[0037] As used herein, the term "ionic liquid salt" refers to a solid white precipitate that is then dissolved in a suitable solvent to obtain a liquid form referred to as an "ionic liquid electrolyte". In various embodiments, the solvent can be any organic solvent such as acetonitrile (AN), propylene carbonate (PC), or a combination of organic solvents in different volume ratios.
[0038] The ionic kinetics employed in the spiro-based ionic liquid electrolytes disclosed herein and the nature of the solvents enable supercapacitors to operate at low temperatures. For example, the ionic liquid electrolyte provides energy storage in a carbon electrode supercapacitor operating over a wide temperature range such as 60 °C to -60 °C, while most prior art commercial supercapacitors are only rated up to -45 °C. Within this wide operating temperature range, the ionic liquid electrolytes disclosed herein provide various benefits to energy storage devices such as hybrid supercapacitors (containing both supercapacitor-type and battery-type active electrode materials), electric double layer capacitors with carbon active electrode materials, lithium-ion capacitors, etc. These devices have been used as energy storage components in a variety of applications such as electric vehicles, outdoor lighting and displays, smart devices, etc.
[0039] In some embodiments, the spiro-based ionic liquid salts disclosed herein can be combined with a polymer gel for the production of a solid-state freestanding supercapacitor that can be integrated into other device structures such as next-generation flexible quantum dot light-emitting diode (QLED) panels and QLED passive matrix displays.
[0040] B. Method for Manufacturing Spiro-Based Ionic Liquid Electrolytes
[0041] In some embodiments, a two-step process or method is used to manufacture the spiro-based ionic liquid electrolyte.
[0042] Step I: Synthesis of Intermediate Spiro Product
[0043] In this step, various precursors including the alkylation of cyclic amine and dihaloalkane are added to an organic solvent (such as isopropanol or acetonitrile), and the mixture is stirred at a temperature of 340 Kelvin (K) for a period of time, such as 6 hours (h), 12 h, 18 h or 24 h, to cause a synthesis reaction and produce a spiroquaternary ammonium intermediate (such as spiroammonium halide). Then, the produced spiroquaternary ammonium intermediate is purified by thoroughly washing with acetone to obtain a pure intermediate product (i.e., spiroquaternary ammonium halide). The purification ensures that the pure intermediate compound is used for the ion exchange to produce the final product.
[0044] This step produces a high yield of about 96% of the intermediate.
[0045] Step II: Ion exchange method to the final ionic liquid salt
[0046] In this step, the halide intermediate obtained in Step I is further reacted with hydrofluoroboric acid or alkali metal tetrafluoroborate in ethanol to produce a spiroquaternary ammonium salt.
[0047] In some embodiments, the halide intermediate can be treated in an alkaline medium to form a spiroammonium hydroxide solution (to facilitate the reaction with the tetrafluoroborate anion precursor). Then, the spiroammonium hydroxide solution is mixed with hydrofluoroboric acid in ethanol at room temperature and stirred for 18 h. After the reaction, the precipitate is removed by filtration. Then, a spiroquaternary ammonium salt (i.e., spiro-based ionic liquid salt) is obtained.
[0048] Using the two-step method, no additional purification step may be required before integrating the spiro-based tetrafluoroborate ionic salt into the activated carbon supercapacitor. More specifically, the synthesis using hydrofluoroboric acid in an alkaline medium reduces the need for an additional purification step by repeated evaporation to remove the halide-based by-products (which are impurities) (see References [1] and [2]).
[0049] Therefore, the two-step method is a simple, economical and scalable synthesis method, which can greatly facilitate the large-scale manufacture of high-purity spiro-based ionic liquid salts under ambient conditions.
[0050] As will be shown in the following examples, although isopropanol or acetonitrile can be used in Step I, using isopropanol (instead of acetonitrile) in Step I can increase the yield of the final product. In addition, using isopropanol (instead of acetonitrile) and ethanol in the two-step method can reduce the total cost of synthesizing this ionic liquid salt on a larger commercial scale.
[0051] C. Examples
[0052] Example 1: Synthesis of spiro-1,1'-dipyrrolidinium bromide (SBPBr), yield 40%:
[0053] Approximately 50.0 grams (g) (i.e., 0.23 moles (mol)) of 1,4-dibromobutane and 34.9 g (0.23 mol) of potassium carbonate were mixed in 200 milliliters (mL) of acetonitrile. 15.0 g (0.21 mol) of pyrrolidine was added dropwise to this solution over 30 minutes. The solution was mixed and heated at 340 K for 6 h. Then, potassium bromide was filtered off, and the acetonitrile was rotary evaporated at 350 K. The powder was washed with acetone and dried in a vacuum oven for 12 h.
[0054] Through 1 H NMR (500 MHz, CD 3 OD) identified the sample: δ = 2.23 (t, 8H), δ = 3.63 (d, 8H).
[0055] The reaction in this example is as follows:
[0056]
[0057] The yield of SBPBr was approximately 40%.
[0058] Example 2: Synthesis of spiro-1,1'-dipyrrolidinium bromide (SBPBr), yield 46%:
[0059] Approximately 50.0 g (0.23 mol) of 1,4-dibromobutane and 34.9 g (0.23 mol) of potassium carbonate were mixed in 200 mL of acetonitrile. 15.0 g (0.21 mol) of pyrrolidine was added dropwise to this solution over 30 minutes. The solution was mixed and heated at 340 K for 12 hours. Then, potassium bromide was filtered off, and the acetonitrile was rotary evaporated at 350 K. The powder was washed with acetone and dried in a vacuum oven for 12 hours.
[0060] Through 1 H NMR (500 MHz, CD 3 OD) identified the sample: δ = 2.23 (t, 8H), δ = 3.63 (d, 8H).
[0061] The reaction of this example is as follows:
[0062]
[0063] The yield of SBPBr was approximately 46%.
[0064] Example 3: Synthesis of spiro-1,1'-dipyrrolidinium bromide (SBPBr), yield 75%:
[0065] About 50.0 g (0.23 mol) of 1,4-dibromobutane and 34.9 g (0.23 mol) of potassium carbonate were mixed in 200 mL of acetonitrile. 15.0 g (0.21 mol) of pyrrolidine was added dropwise to this solution over 30 minutes. The solution was mixed and heated at 340 K for 18 hours. Then, potassium bromide was filtered off, and the acetonitrile was rotary evaporated at 350 K. The powder was washed with acetone and dried in a vacuum oven for 12 hours.
[0066] By 1 H NMR (500 MHz, CD 3 OD) The sample was identified as: δ = 2.23 (t, 8H), δ = 3.63 (d, 8H).
[0067] The reaction of this example is shown below:
[0068]
[0069] The yield of SBPBr was approximately 75%.
[0070] Example 4: Synthesis of spiro-1,1'-dipyrrolidinium bromide (SBPBr), yield 45%:
[0071] About 50.0 g (0.23 mol) of 1,4-dibromobutane and 34.9 g (0.23 mol) of potassium carbonate were mixed in 200 mL of acetonitrile. 15.0 g (0.21 mol) of pyrrolidine was added dropwise to this solution over 30 minutes. The solution was mixed and heated at 340 K for 24 hours. Then, potassium bromide was filtered off, and the acetonitrile was rotary evaporated at 350 K. The powder was washed with acetone and dried in a vacuum oven for 12 hours.
[0072] By 1 H NMR (500 MHz, CD 3 OD) The sample was identified as: δ = 2.23 (t, 8H), δ = 3.63 (d, 8H).
[0073] The reaction of this example is shown below:
[0074]
[0075] The yield of SBPBr was approximately 45%.
[0076] Example 5: Synthesis of spiro-1,1'-dipyrrolidinium bromide (SBPBr), yield 96%:
[0077] Approximately 50.0 g (0.23 mol) of 1,4-dibromobutane and 34.9 g (0.23 mol) of potassium carbonate were mixed in 200 mL of isopropanol. 15.0 g (0.21 mol) of pyrrolidine was added dropwise to this solution over 30 minutes. The solution was mixed and heated at 340 K for 18 hours. Then, potassium bromide was filtered off, and the isopropanol was rotary evaporated at 350 K. The powder was washed with acetone and dried in a vacuum oven for 12 hours.
[0078] The sample was identified by 1 1H NMR (500 MHz, CD 3 OD): δ = 2.23 (t, 8H), δ = 3.63 (d, 8H).
[0079] The reaction of this example is shown below:
[0080]
[0081] The yield of SBPBr was approximately 96%.
[0082] Example 6: Synthesis of spiro-1,1'-dipyrrolidinium tetrafluoroborate (SBPBF 4 ) 4 :
[0083] 40.0 g (0.21 mol) of SBPBr and 30.0 g (0.21 mol) of sodium tetrafluoroborate were added to 200 mL of ethanol and the solution was stirred at room temperature for 18 hours. After filtration, the filtrate solution was evaporated and the product was recrystallized from ethanol. The SBPBF 4 was washed several times with ethanol and dried in a vacuum oven for 12 hours.
[0084] The sample was identified by 1 1H NMR (500 MHz, CD 3 OD): δ = 2.23 (m, 8H), δ = 3.55 (m, 8H).
[0085] The reaction of this example is shown below:
[0086]
[0087] The yield of SBPBF 4 was approximately 35%.
[0088] Example 7: Synthesis of spiro-1,1'-dipyrrolidinium tetrafluoroborate (SBPBF 4 ) 4 :
[0089] 40.0 g (0.21 mol) of SBPBr and 27.6 g (0.16 mol) of 40% tetrafluoroboric acid were added to 200 mL of ethanol and the solution was stirred at room temperature for 18 h. The solution was evaporated repeatedly with ethanol (greater than or equal to 3 times) to remove hydrobromic acid and water. The product was recrystallized from ethanol. SBPBF was washed several times with ethanol and dried in a vacuum oven for 12 h. 4 The sample was identified by
[0090] H NMR (500 MHz, CD 1 OD): δ = 2.23 (m, 8H), δ = 3.55 (m, 8H). 3 The reaction of this example is shown below:
[0091] The reaction of this example is as follows:
[0092]
[0093] The yield of SBPBF 4 was approximately 45%.
[0094] Example 8: Synthesis of spiro-1,1'-dipyrrolidinium tetrafluoroborate (SBPBF 4 ) in an alkaline (OH - ) medium: 4 40.0 g (0.21 mol) of SBPBr and 10.6 g (0.19 mol) of potassium hydroxide were added to 200 mL of ethanol and the solution was stirred at room temperature for 6 h. The solution was filtered and 40% tetrafluoroboric acid was added dropwise to the filtrate until a pH of 5 to 6 was recorded. The solution was evaporated and the final product was recrystallized from ethanol. SBPBF was washed several times with ethanol and dried in a vacuum oven for 12 h.
[0095] By using an alkaline medium for the synthesis, the repeated evaporation of hydrobromic acid with ethanol was overcome. 4 The sample was identified by
[0096] H NMR (500 MHz, CD
[0097] OD): δ = 2.23 (m, 8H), δ = 3.55 (m, 8H). 1 The reaction of this example is as follows: 3 The sample was identified by
[0098] H NMR (500 MHz, CD
[0099]
[0100] The yield of SBPBF 4 was approximately 60% and the purity was high.
[0101] A summary of all the synthesis steps implemented is shown in Table 1 below.
[0102] Table 1
[0103]
[0104]
[0105] D. Application of Spiro-Based Ionic Liquid Electrolytes in Low-Temperature Supercapacitors
[0106] Using the synthesized electrolytes described in Examples 1 to 8, activated carbon electrodes coated on etched aluminum and separated from each other by a surfactant-coated polypropylene separator were assembled in a pouch package. Aluminum and nickel tabs were ultrasonically welded as the positive and negative terminals, respectively, to prevent excessive degradation during operation (see reference [3]).
[0107] In some embodiments, a freestanding solid-state gel electrolyte can be fabricated by encapsulating the ionic liquid electrolyte in a gel. The freestanding solid-state gel electrolyte can also be used as the separator layer 108 of a supercapacitor 100, which can be a flexible and stretchable supercapacitor.
[0108] As will be understood by those skilled in the art, the supercapacitors fabricated as described above are stable and include commercially available porous activated carbon electrodes that work with the low-temperature ionic liquid electrolyte described above, which has a much lower concentration compared to commercial electrolytes. More specifically, precise control of the ion kinetics within the electrolyte can result in effective charge transport and storage performance, even at ultra-low temperatures, such as -60 °C. In some embodiments, the ionic liquid electrolyte has a low concentration of about 0.1 M.
[0109] The self-discharge tests showed that the supercapacitors fabricated as described above had excellent device voltage retention (low voltage leakage) at room temperature. The full capacitance recovery of supercapacitors fabricated using the electrolytes described above was tested at ultra-low temperatures. The test results showed that the supercapacitors fabricated as described above provided improved self-discharge characteristics even after extended ultra-low temperature operation using the ionic liquid electrolyte.
[0110] E. Testing of Supercapacitors
[0111] The initial degassing of the supercapacitor is carried out before the final vacuum sealing after the initial cycle. A supercapacitor rated at 100 farads (F) is placed in an environmental chamber with programmable temperature test conditions. The performance of the test device is tested in the temperature range from 25 °C to -60 °C and from -60 °C to 25 °C. In addition, a leakage test is carried out at a fixed temperature of -60 °C for up to 24 hours and compared with the normal leakage test at room temperature. After continuous low-temperature testing at a maximum operating voltage of 2.7 volts (V) for up to 90 hours, a voltage holding test is also carried out, which is a better form of testing the stability of the test device (see reference [4]). Table 2 as well as Figure 2 and 3 show the results.
[0112] Table 2
[0113] Temperature (°C) Capacitance (F) 25 120 0 105 -25 90 -50 60 -60 45 25 119
[0114] F. References
[0115] [1] Zhou, Hm., Sun, Wj. & Li, J. Preparation of spiro-type quaternary ammonium salt via economical and efficient synthetic route as electrolyte for electric double-layer capacitor. J. Cent. South Univ. 22, (2015) 2435–2439.
[0116] [2] Chiba, Kazumi, Tsukasa Ueda, and Hideo Yamamoto. "Performance of electrolyte composed of spiro-type quaternary ammonium salt and electric double-layer capacitor using it." Electrochemistry 75.8 (2007): 664-667.
[0117] [3]Liu, Yinghui, et al. "Understanding ageing mechanisms of porouscarbons in non-aqueous electrolytes for supercapacitors applications." Journalof Power Sources 434(2019):226734.
[0118] [4]Weingarth, D., A. Foelske-Schmitz, and R. "Cycle versus voltagehold–Which is the better stability test for electrochemical double layercapacitors?." Journal of Power Sources 225(2013):84-88.
[0119] Although the embodiments have been described above with reference to the accompanying drawings, those skilled in the art will understand that changes and modifications can be made without departing from its scope as defined by the appended claims.
Claims
1. An electrochemical energy storage device, comprising: an ionic liquid electrolyte, the ionic liquid electrolyte comprising an ionic liquid salt having the following cations:
2. The ionic liquid electrolyte according to claim 1, wherein, the ionic liquid electrolyte is a spiro-based ionic liquid electrolyte.
3. The ionic liquid electrolyte according to claim 1, wherein, the ionic liquid electrolyte is spiro-1,1'-dipyrrolidinium bromide (SBPBr):
4. An electrochemical energy storage device, comprising: an ionic liquid electrolyte, the ionic liquid electrolyte comprising an ionic liquid salt having the following anions:
5. The ionic liquid electrolyte according to claim 4, wherein, the ionic liquid electrolyte is a spiro-based ionic liquid electrolyte.
6. The ionic liquid electrolyte according to claim 4, wherein, The ionic liquid electrolyte is spiro-1,1'-dipyrrolidinium tetrafluoroborate (SBPBF 4 ):
7. A method for manufacturing an ionic liquid electrolyte, the method comprising: synthesizing an intermediate spiro-based product; and applying an ion exchange method to the intermediate spiro-based product to obtain an ionic liquid electrolyte.
8. The method according to claim 7, wherein, the synthesizing of the intermediate spiro-based product comprises: adding a plurality of precursors to an organic solvent to obtain a mixture, and stirring the mixture at a temperature of 340 Kelvin (K) for a period of time to obtain the intermediate spiro-based product; and purifying the intermediate spiro-based product; wherein the plurality of precursors includes the alkylation of a cyclic amine and a dihaloalkane.
9. The method according to claim 7, wherein, the organic solvent includes isopropyl alcohol or acetonitrile.
10. The method according to claim 8 or 9, wherein, the period of time is about 6 hours, 12 hours, 18 hours or 24 hours.
11. The method according to claim 8 or 10, wherein, the purifying of the intermediate spiro-based product comprises: washing the intermediate spiro-based product with acetone.
12. The method according to any one of claims 8 to 11, wherein, the applying of the ion exchange method to the intermediate spiro-based product to obtain an ionic liquid electrolyte comprises: reacting the intermediate spiro-based product with hydrofluoro boric acid or an alkali metal tetrafluoroborate in ethanol.