A method for preparing and applying a dual-cation deep eutectic electrolyte

Abstract

This invention belongs to the field of electrochemical energy storage technology and discloses a method for preparing and applying a dual-cation deep eutectic electrolyte. The dual-cation deep eutectic electrolyte comprises at least two different metal salts and a Lewis base, wherein the metal salts provide the first metal cation (M1x). + ) and the second metal cation (M2y) + ), of which M1x + With M2y + The preparation method involves mixing the raw materials and stirring them at 80°C to form a transparent liquid, resulting in a dual-cation deep eutectic electrolyte. Through the synergistic coordination of the two metal cations with the Lewis base, the long-standing contradiction between interfacial stability and ion transport in existing deep eutectic electrolytes is resolved. The electrolyte obtained by this invention possesses advantages such as low melting point, environmental friendliness, flame retardancy, high ionic conductivity, and a wide electrochemical stability window, significantly improving the cycle stability and safety of the battery and providing a new path for the development of high-performance battery technology.

Description

Technical Field

[0001] This invention belongs to the field of electrochemical energy storage technology, specifically relating to a method for preparing and applying a dual-cation deep eutectic electrolyte. Background Technology

[0002] With the ever-increasing demand for consumer electronics and electric vehicles, developing next-generation safe energy storage systems has become an urgent task. As a core component of batteries, the electrolyte's performance directly affects the battery's charge-discharge efficiency, cycle life, and safety. In traditional battery systems, the electrolyte is typically liquid, mainly composed of carbonate-based organic solvents and salts. However, the inherent flammability and poor electrode compatibility of traditional carbonate electrolytes cause problems such as uneven metal ion deposition, positive electrode structure degradation, and even catastrophic safety hazards, severely restricting the battery's cycle stability and greatly limiting its application. Therefore, developing novel electrolyte systems that combine non-flammability and interfacial stability is crucial for achieving long-term cycle stability and safety in energy storage devices.

[0003] Deep eutectic electrolytes (DEEs) are a class of eutectic mixtures composed of Lewis acids and Lewis bases in specific proportions. The strong interactions between the components in DEEs, such as hydrogen bonding, Lewis acid-base interactions, and van der Waals forces, result in a melting point lower than that of the individual components. As analogs to ionic liquids, DEEs possess advantages such as high ionic conductivity, low vapor pressure, good thermal and chemical stability, and non-flammability. Currently, most deep eutectic electrolytes based on nitrogen-containing Lewis bases, such as lithium succinate / bis(fluorosulfonyl)imide (SN / LiFSI) and lithium N-methylacetamide / bis(trifluoromethanesulfonyl)imide (NMA / LiTFSI), exhibit high ionic conductivity. This is attributed to the strong electron-donating ability of nitrogen atoms, which enables them to form strong coordination with metal cations. However, nitrogen-containing Lewis bases often undergo side reactions with the negative electrode, leading to poor interfacial stability and low coulombic efficiency. Furthermore, the activity of Lewis bases can also react with the positive electrode, forming a high-impedance CEI through oxidative decomposition, and the polar groups of Lewis bases can accelerate the decay and dissolution of the positive electrode structure. In existing technologies, lithium difluorooxalate borate (LiDFOB) is introduced into the SN / LiFSI system, through DFOB... - The decomposition of lithium trifluoromethanesulfonylimide forms a stable solid-state electrolyte interface (SEI film) to enhance the interfacial stability of the eutectic electrolyte. Existing techniques further introduce polyvinylidene fluoride (PVDF) into the lithium bis(trifluoromethanesulfonylimide) / 1,2-dimethylimidazole (LiTFSI / DMIm) system, using the strong electron-withdrawing properties of the -CF functional group to reduce the activity of the Lewis base and improve the interfacial stability between the electrolyte and lithium metal. However, the introduction of high-content PVDF is detrimental to the interfacial stability of Li... +Rapid ion transport is crucial. Although these strategies have improved the side reaction problem between DEEs and the negative electrode to some extent, the interfacial compatibility between the electrode and electrolyte remains unresolved under long-term cycling conditions. Introducing functional additives, such as fluoroethylene carbonate (FEC) and lithium nitrate (LiNO3), can enhance oxidation resistance and broaden the electrochemical stability window, thereby suppressing interfacial side reactions and stabilizing the positive electrode structure. However, the introduction of inorganic components leads to increased viscosity and decreased ionic conductivity of DEEs. Overall, constructing DEEs with high ionic conductivity and high interfacial compatibility still faces many challenges. Therefore, developing new methods that can balance ion transport kinetics and interfacial stability is essential for achieving high-performance battery applications. Summary of the Invention

[0004] In view of the above-mentioned technical problems in the prior art, the present invention overcomes the shortcomings of the prior art and provides a method for preparing and applying a dual-cation deep eutectic electrolyte. The electrolyte exhibits high ionic conductivity, wide electrochemical stability window and flame retardancy, which is expected to promote the development of high-performance energy storage systems.

[0005] The objective of this invention is achieved through the following technical solution.

[0006] A dual-cation deep eutectic electrolyte comprising at least two different metal salts and a Lewis base; the metal salts provide the first metal cation (M1x). + ) and the second metal cation (M2y) + ), of which M1x + With M2y + The metal cations are different metal cations and satisfy the following conditions: the ratio of the total molar amount of all metal salts to the molar amount of Lewis bases is 1.005:4-6; the molar amount of the metal salt providing the second metal cation is 0.5% of the molar amount of the metal salt providing the first metal cation.

[0007] The present invention also provides a method for preparing the above-mentioned dual-cation deep eutectic electrolyte, comprising the following steps: Step 1: Mix the metal salt that provides the first metal cation with a Lewis base at a molar ratio of 1:4-6, heat to 80°C, and stir for 4 h to obtain a mixed solution; Step 2: Add a metal salt that provides a second metal cation to the mixed solution obtained in Step 1. The molar amount of the metal salt that provides the second metal cation is 0.5% of the molar amount of the metal salt that provides the first metal cation. Heat to 80°C and stir for 4 h to prepare a dication deep eutectic electrolyte.

[0008] Preferably, the metal salt providing the first metal cation is selected from at least one of lithium hexafluorophosphate, lithium trifluoromethanesulfonate, lithium bis(trifluoromethanesulfonyl)imide, lithium bis(fluorosulfonyl)imide, lithium dioxoborate, lithium difluorooxalateborate, zinc trifluoromethanesulfonate, sodium trifluoromethanesulfonate, zinc bis(trifluoromethanesulfonyl)imide, sodium bis(trifluoromethanesulfonyl)imide, zinc bis(fluorosulfonyl)imide, and sodium bis(fluorosulfonyl)imide.

[0009] Preferably, the metal salt providing the second metal cation is selected from perchlorate M(ClO4)n, tetrafluoroborate M(BF4)n, metal chloride MCln, metal iodide MCln, metal bromide MCln, trifluoromethanesulfonate M(OTf)n, acetate M(Ac)n, sulfate M(SO4)n, and nitrate M(NO3)n (M = Li, Na, Mg). 2 Zn 2 Ca 2+ Al 3+ (where n is the valence of M), lithium hexafluorophosphate, lithium bis(trifluoromethanesulfonyl)imide, sodium bis(trifluoromethanesulfonyl)imide, lithium bis(trifluoromethanesulfonyl)imide, lithium bis(trifluoromethanesulfonyl)imide, lithium bis(trifluoromethanesulfonyl)imide, lithium bis(trifluoromethanesulfonyl)imide, lithium bis(trifluoromethanesulfonyl)imide, lithium bis(trifluoromethanesulfonyl)imide, and zinc bis(trifluoromethanesulfonyl)imide.

[0010] Preferably, the Lewis base is selected from at least one of succinic anionyl nitrile, acetamide, urea, tetrahydropyran, propenyl-1,3-sulfonyl lactone, vinyl sulfate, 2,6-dimethylpyrazine, 2-cyanopyridine, 2-cyano-5-fluoropyridine, 2-cyano-3-fluoropyridine, 2-cyano-5-trifluoromethylpyridine, and 3-cyano-6-trifluoromethylpyridine.

[0011] The present invention also provides the application of the aforementioned dual-cation deep eutectic electrolyte in the preparation of energy storage devices, wherein the energy storage devices are lithium-ion batteries, zinc-ion batteries or sodium-ion batteries.

[0012] Preferably, the dual-cation deep eutectic electrolyte is used as a component of the lithium-ion battery, which includes: a positive electrode, a negative electrode, a separator, and the dual-cation deep eutectic electrolyte; wherein, the positive electrode material is selected from any one of lithium metal, lithium iron phosphate, lithium cobalt oxide, lithium manganese oxide, NCM622 type positive electrode material, NCM613 type positive electrode material, NCM811 type positive electrode material, and NCM523 type positive electrode material; the negative electrode is selected from any one of lithium metal sheet, graphite, hard carbon, and soft carbon; and the separator is selected from any one of PVDF membrane, glass fiber membrane, PE, and PP separator.

[0013] Preferably, the dual-cation deep eutectic electrolyte is used as a component of the zinc-ion battery, which includes: a positive electrode, a negative electrode, a separator, and the dual-cation deep eutectic electrolyte; wherein, the positive electrode material is selected from any one of vanadium pentoxide, vanadium oxide, sodium vanadate, ammonium vanadate, manganese vanadate, magnesium vanadate, calcium vanadate, and aluminum vanadate; the negative electrode is selected from any one of zinc sheet and zinc powder; and the separator is selected from any one of PVDF membrane, glass fiber membrane, PE, and PP separator.

[0014] Preferably, the dual-cation deep eutectic electrolyte is used as a component of the sodium-ion battery, which includes: a positive electrode, a negative electrode, a separator, and the dual-cation deep eutectic electrolyte; wherein, the positive electrode material is selected from any one of sodium vanadium phosphate, sodium iron pyrophosphate, sodium nickel manganate, and sodium nickel iron manganate; the negative electrode is selected from any one of metallic sodium sheet, hard carbon, soft carbon, and silicon carbide; and the separator is selected from any one of PVDF membrane, glass fiber membrane, PE, and PP separator.

[0015] The present invention has the following beneficial effects: Compared with existing technologies, this invention provides a dual-cation deep eutectic electrolyte, its preparation method, and its applications. The bimetallic cation system achieves a balance between interfacial chemical stability and ion transport kinetics through coordination competition-induced solvation structure reconstruction. High charge density cations preferentially chelate Lewis base ligands due to their strong Lewis acidity, forming a kinetically inert solvation structure to passivate parasitic reactions at the electrode / electrolyte interface. Meanwhile, low charge density cations form coordination ion pairs with specific anions, reducing ion migration activation energy and increasing carrier dissociation. This resolves, at the molecular scale, the inherent contradiction in traditional single-cation deep eutectic electrolytes where "strong coordination between Lewis bases and cations facilitates ion transport, but interfacial side reactions between Lewis bases and negative electrode metals hinder stable battery operation." The dual-cation deep eutectic electrolyte prepared by this invention has the characteristics of low melting point, green and environmentally friendly, flame retardant, excellent ionic conductivity (reaching 2.48 mS / cm), and wide electrochemical stability window (reaching 0.2-5.2 V), which significantly improves the cycle stability and safety of the battery and can meet the practical application window of lithium-ion batteries, zinc-ion batteries and sodium-ion batteries, providing a new path for the development of high-performance battery technology.

[0016] When the dual-cation deep eutectic electrolyte is applied to lithium metal batteries, the Li||Li symmetric cell achieves a speed of 0.1 mA / cm². 2The device achieves 800 h of dendrite-free cycling at a given current density with a polarization voltage of only 65 mV. The Li||LFP battery exhibits excellent electrochemical performance, maintaining a specific capacity of 80 mAh / g after 1000 cycles at 0.5 C. The dual-cation deep eutectic electrolyte prepared in this invention also demonstrates enhanced rate performance and cycling stability in high-voltage systems; the NCM613||Li battery retains 90% of its capacity after 200 cycles at 4.3 V.

[0017] The preparation process of this invention is simple, and the required raw materials are inexpensive, meeting the needs of large-scale production. This invention provides a design paradigm for resolving the long-standing contradiction between interfacial stability and ion transport in traditional eutectic electrolytes, thereby promoting the development of high-performance battery technology. Attached Figure Description

[0018] Figure 1 These are physical images of the dual-cation deep eutectic electrolytes used in Examples 1-3 of this invention; Figure 2 The diagram shows the flammability of the monocation deep eutectic electrolyte in Comparative Example 1 of this invention (wherein... Figure 2 (a) is a picture of the device ignited at 2 seconds. Figure 2 (b) is a picture of combustion in 1 second. Figure 2 (c) is a picture of the second 2-second ignition. Figure 2 (d) is a picture of the second 1-second burn). Figure 3 The diagram shows the flammability of the dual-cation deep eutectic electrolyte in Example 1 of this invention (wherein... Figure 3 (a) is a picture of the device ignited at 2 seconds. Figure 3 (b) is a picture of combustion in 1 second. Figure 3 (c) is a picture of the second 2-second ignition. Figure 3 (d) is a picture of the second 1-second burn). Figure 4 The impedance spectra of the dual-cation deep eutectic electrolyte and the monocation deep eutectic electrolyte in Example 1 and Comparative Example 1 of the present invention are compared. Figure 5 This is a comparison of the electrochemical stability windows of the dication deep eutectic electrolyte and the monocation deep eutectic electrolyte in Example 1 and Comparative Example 1 of the present invention; Figure 6 This is a comparison of the thermal stability of the dual-cation deep eutectic electrolyte and the monocation deep eutectic electrolyte corresponding to Example 1 and Comparative Example 1 of the present invention, respectively. Figure 7 Comparison of long-cycle performance test graphs of lithium metal symmetric batteries corresponding to Example 1 and Comparative Example 1 of the present invention; Figure 8This is a charge-discharge curve of the LFP||Li battery at 0.5 C corresponding to Embodiment 1 of the present invention; Figure 9 This is a charge-discharge curve of the NCM613||Li battery at 0.5 C corresponding to Embodiment 1 of the present invention; Figure 10 This is a charge-discharge curve of the NVP||Na battery at 0.2 C in Embodiment 11 of the present invention; Figure 11 This is a charge-discharge curve of the CNT@NVO||Zn battery at 0.5 A / g in Example 15 of the present invention. Detailed Implementation

[0019] The present invention will be further illustrated below with reference to specific embodiments. It should be understood that these embodiments are only used to illustrate the present invention and not to limit the scope of the present invention. After reading the present invention, any modifications of the present invention in various equivalent forms by those skilled in the art will fall within the scope defined by the appended claims.

[0020] Example 1

[0021] Weigh 0.2871 g of lithium bis(trifluoromethanesulfonyl)imide, add 0.3204 g of succinate, mix at a molar ratio of 1:4, and stir at 80 °C for 4 hours to obtain a uniform and transparent liquid; add 0.0018 g of zinc trifluoromethanesulfonate (the molar amount of the metal salt providing the second metal cation is 0.5% of the molar amount of the metal salt providing the first metal cation), heat to 80 °C, and stir for 4 h to obtain the dual-cation deep eutectic electrolyte of Example 1 of this invention.

[0022] Example 2

[0023] Weigh 0.2871 g of lithium bis(trifluoromethanesulfonyl)imide, add 0.236 g of acetamide, mix at a molar ratio of 1:4, and stir at 80 °C for 4 hours to obtain a uniform and transparent liquid; add 0.0009 g of sodium trifluoromethanesulfonate (the molar amount of the metal salt providing the second metal cation is 0.5% of the molar amount of the metal salt providing the first metal cation), heat to 80 °C, and stir for 4 h to obtain the dual-cation deep eutectic electrolyte of Example 2 of this invention.

[0024] Example 3

[0025] Weigh 0.2871 g of lithium bis(trifluoromethanesulfonyl)imide, add 0.2402 g of urea, mix at a molar ratio of 1:4, heat to 80 °C, and stir for 4 h to obtain a uniform and transparent liquid; add 0.0005 g of zinc fluoride (the molar amount of the metal salt providing the second metal cation is 0.5% of the molar amount of the metal salt providing the first metal cation), heat to 80 °C, and stir for 4 h to obtain the dual-cation deep eutectic electrolyte of Example 3 of the present invention.

[0026] Comparative Example 1 Weigh 0.2871 g of lithium bis(trifluoromethanesulfonyl)imide and add 0.3204 g of succinate. Mix them at a molar ratio of 1:4 and stir at 80 °C for 4 hours to obtain a uniform and transparent liquid, which is the monocation deep eutectic electrolyte of Comparative Example 1 of this invention.

[0027] Figure 1 These are physical images of the dual-cation deep eutectic electrolytes used in lithium metal batteries in Examples 1-3, which are uniform and transparent solutions.

[0028] Figure 2 The flammability diagram of the single-cation deep eutectic electrolyte used in lithium metal batteries in Comparative Example 1 is shown (where...). Figure 2 (a) is a picture of the device ignited at 2 seconds. Figure 2 (b) is a picture of combustion in 1 second. Figure 2 (c) is a picture of the second 2-second ignition. Figure 2 (d) is a picture of the second 1s combustion). It can be seen from the picture that the electrolyte exhibits excellent flame retardancy after continuous combustion for a certain period of time.

[0029] Figure 3 This is a flammability diagram of the dual-cation deep eutectic electrolyte used in lithium metal batteries in Example 1 (wherein) Figure 3 (a) is a picture of the device ignited at 2 seconds. Figure 3 (b) is a picture of combustion in 1 second. Figure 3 (c) is a picture of the second 2-second ignition. Figure 3 (d) is a picture of the second 1s combustion). It can be seen from the picture that the electrolyte exhibits excellent flame retardancy after continuous combustion for a certain period of time.

[0030] Figure 4 The impedance comparison spectra of the dual-cation deep eutectic electrolyte in Example 1 and the monocation deep eutectic electrolyte in Comparative Example 1 are shown. Based on the conductivity formula ( The conductivity of the dual-cation deep eutectic electrolyte can reach 2.48 mS / cm, which is calculated by denoted as d (where d is the thickness of the electrolyte membrane, S is the area of ​​the electrolyte membrane, and R is the ohmic resistance obtained from the impedance spectrum). When the molar amount of the metal salt providing the second metal cation is 0.5% of the molar amount of the metal salt providing the first metal cation, the conductivity of the dual-cation deep eutectic electrolyte can reach 2.48 mS / cm, which shows high conductivity performance.

[0031] Figure 5 The figure shows a comparison of the electrochemical stability windows of the dual-cation deep eutectic electrolyte in Example 1 and the monocation deep eutectic electrolyte in Comparative Example 1. As shown in the figure, the electrochemical stability window of the dual-cation deep eutectic electrolyte in Example 1 can reach 0.2-5.2 V, which meets the practical application window requirements of lithium-ion batteries, sodium-ion batteries and zinc-ion batteries.

[0032] Figure 6 The graphs show the thermal stability comparison of the dication deep eutectic electrolyte and the monocation deep eutectic electrolyte corresponding to Example 1 and Comparative Example 1, respectively. Differential scanning calorimetry was performed from -100 °C to 100 °C at a heating rate of 10 °C / min.

[0033] In conjunction with Examples 1-3 and Comparative Example 1, the dioxygen ion deep eutectic electrolyte of the present invention can be used in an energy storage device, namely a lithium-ion battery, which will be further explained below.

[0034] Example 4

[0035] Example 4 is a lithium metal symmetric battery, utilizing the dual-cation deep eutectic electrolytes corresponding to Examples 1-3. The preparation process of the lithium metal symmetric battery corresponding to Example 4 includes the following steps: Lithium metal (Li) with a diameter of 16 mm was selected as the positive and negative electrodes. 15 μL of dual-cation deep eutectic electrolyte was added to a polypropylene (PP) separator. The positive electrode, electrolyte layer, separator, and negative electrode were then encapsulated in sequence with a battery case (CR2025) to obtain a lithium metal symmetric battery.

[0036] Example 5

[0037] Example 5 is a lithium metal symmetric battery using the single-cation deep eutectic electrolyte corresponding to Comparative Example 1. The preparation process of the lithium metal symmetric battery corresponding to Example 5 includes the following steps: Lithium metal with a diameter of 16 mm was selected as the positive and negative electrodes. 15 μL of single-cation deep eutectic electrolyte was added to the PP separator. The positive electrode, electrolyte layer, separator and negative electrode were then encapsulated in sequence with a battery case CR2025 to obtain a lithium metal symmetric battery.

[0038] Example 6

[0039] Example 6 is a lithium-ion battery that utilizes the dual-cation deep eutectic electrolytes of Examples 1-3. The preparation process of the lithium-ion battery in Example 6 includes the following steps: Commercial-grade lithium iron phosphate (LFP), super carbon black, and polyvinylidene fluoride (PVDF) were mixed in N-methylpyrrolidone at a mass ratio of 7:2:1 to form a homogeneous slurry, which was then coated onto aluminum foil. The prepared electrode film was dried under vacuum at 80°C for 24 hours before battery assembly, with the LFP positive electrode having an active material loading of 1.0–1.5 mg / cm³. 2 Finally, the dual-cation deep eutectic electrolyte was sandwiched between the LFP cathode and the lithium metal anode, and the LFP||Li battery was assembled in a glove box. Electrochemical tests of the LFP||Li battery were conducted at 30°C, with a voltage range of 2.5–4.0 V.

[0040] Example 7

[0041] Example 7 is a lithium-ion battery under high voltage system, using the dual-cation deep eutectic electrolytes corresponding to Examples 1-3. The preparation process of the lithium-ion battery corresponding to Example 7 includes the following steps: Commercial-grade nickel-cobalt-manganese (NCM613), super carbon black, and polyvinylidene fluoride (PVDF) were mixed in N-methylpyrrolidone at a mass ratio of 8:1:1 to form a homogeneous slurry, which was then coated onto aluminum foil. The prepared electrode film was dried under vacuum at 80°C for 24 hours before battery assembly, with the NCM613 positive electrode having an active material loading of 1.0–2.0 mg / cm³. 2 Finally, a dual-cation deep eutectic electrolyte was sandwiched between the NCM613 cathode and the lithium metal anode to assemble an NCM613||Li battery. Electrochemical tests of the NCM613||Li battery were conducted at 30°C, with a voltage range of 2.8–4.3 V.

[0042] Figure 7 For Example 1 and Comparative Example 1, the corresponding dication deep eutectic electrolyte and monocation deep eutectic electrolyte were respectively tested at 0.1 mA / cm 2 A comparison of the galvanostatic cycling curves of the assembled Li||Li symmetric cells at different current densities. The Li||Li symmetric cell assembled using a dual-cation deep eutectic cell operates at 0.1 mA / cm². 2 After 800 hours of testing, the polarization voltage decreased significantly to 65 mV, while the polarization voltage of the Li||Li symmetric cell assembled with a single-cation deep eutectic electrolyte was 86 mV. The increase in polarization voltage indicates that its interface transfer kinetics are slower.

[0043] Figure 8The charge-discharge curve of LFP||Li assembled at 0.5 C is shown for the dual-cation deep eutectic electrolyte corresponding to Example 1.

[0044] Figure 9 The charge-discharge curves of NCM613||Li assembled at 0.5 C for the dual-cation deep eutectic electrolytes corresponding to Examples 1-3.

[0045] Example 8

[0046] Weigh 0.1721 g of sodium trifluoromethanesulfonate, add 0.4805 g of propylene-1,3-sulfonyl lactone, mix at a molar ratio of 1:4, and stir at 80 °C for 4 hours to obtain a uniform and transparent liquid. Add 0.0008 g of lithium trifluoromethanesulfonate (the molar amount of the metal salt providing the second metal cation is 0.5% of the molar amount of the metal salt providing the first metal cation), heat to 80 °C, and stir for 4 h to obtain the dual-cation deep eutectic electrolyte of Example 8 of this invention.

[0047] Example 9

[0048] Weigh 0.1721 g of sodium trifluoromethanesulfonate, add 0.4805 g of propylene-1,3-sulfonyl lactone, mix at a molar ratio of 1:4, stir at 80 °C for 4 hours to obtain a uniform and transparent liquid, add 0.0005 g of magnesium chloride (the molar amount of the metal salt providing the second metal cation is 0.5% of the molar amount of the metal salt providing the first metal cation), heat to 80 °C, and stir for 4 h to obtain the dication deep eutectic electrolyte of Example 9 of the present invention.

[0049] Example 10

[0050] Weigh 0.1721 g of sodium trifluoromethanesulfonate, add 0.4805 g of propylene-1,3-sulfonyl lactone, mix at a molar ratio of 1:4, and stir at 80 °C for 4 hours to obtain a uniform and transparent liquid. Add 0.0009 g of zinc perchlorate (the molar amount of the metal salt providing the second metal cation is 0.5% of the molar amount of the metal salt providing the first metal cation), heat to 80 °C, and stir for 4 h to obtain the dual-cation deep eutectic electrolyte of Example 10 of this invention.

[0051] Comparative Example 2 Weigh 0.1721 g of sodium bis(trifluoromethanesulfonyl)imide and add 0.4805 g of propenyl-1,3-sulfonyl lactone. Mix them at a molar ratio of 1:4 and stir at 80 °C for 4 hours to obtain a uniform and transparent liquid, which is the monocation deep eutectic electrolyte of Comparative Example 2 of this invention.

[0052] In conjunction with Examples 8-10 and Comparative Example 2, the dual-cation deep eutectic electrolyte described in this invention can be used in an energy storage device, namely a sodium-ion battery, which will be further explained below.

[0053] Example 11

[0054] Example 11 is a sodium-ion battery that utilizes the dual-cation deep eutectic electrolytes of Examples 8-10. The preparation process of the sodium-ion battery in Example 11 includes the following steps: Commercial-grade sodium vanadium phosphate, super carbon black, and polyvinylidene fluoride were mixed in N-methylpyrrolidone at a mass ratio of 8:1:1 to form a homogeneous slurry, which was then coated onto aluminum foil. The prepared electrode film was dried under vacuum at 80°C for 24 hours before battery assembly, with the active material loading of the vinylpyrrolidone (NVP) cathode being 1.0–2.0 mg / cm³. 2 Finally, the dual-cation deep eutectic electrolyte was sandwiched between the NVP positive electrode and the sodium metal negative electrode, and an NVP||Na battery was assembled in a glove box. Electrochemical tests of the NVP||Na battery were conducted at 30°C, with a voltage range of 2.5–3.8 V.

[0055] Figure 10 The figures show the charge-discharge curves of the dual-cation deep eutectic electrolytes in Examples 8-10 at 0.2 C in an NVP||Na battery. As shown, this sodium-ion battery exhibits good electrochemical performance, with a constant current charge-discharge curve showing a discharge voltage plateau of 3.2 V.

[0056] Example 12

[0057] Weigh 0.3635 g of zinc trifluoromethanesulfonate, add 0.3544 g of acetamide, mix at a molar ratio of 1:6, stir at 80 °C for 4 hours to obtain a uniform and transparent liquid, add 0.0003 g of lithium nitrate (the molar amount of the metal salt providing the second metal cation is 0.5% of the molar amount of the metal salt providing the first metal cation), heat to 80 °C, and stir for 4 h to obtain the dual-cation deep eutectic electrolyte of Example 12 of this invention.

[0058] Example 13

[0059] Weigh 0.3635 g of zinc trifluoromethanesulfonate, add 0.3544 g of acetamide, mix at a molar ratio of 1:6, and stir at 80 °C for 4 hours to obtain a uniform and transparent liquid. Add 0.0009 g of sodium trifluoromethanesulfonate (the molar amount of the metal salt providing the second metal cation is 0.5% of the molar amount of the metal salt providing the first metal cation), heat to 80 °C, and stir for 4 h to obtain the dual-cation deep eutectic electrolyte of Example 13 of this invention.

[0060] Example 14

[0061] Weigh 0.3635 g of zinc trifluoromethanesulfonate, add 0.3544 g of acetamide, mix at a molar ratio of 1:6, stir at 80 °C for 4 hours to obtain a uniform and transparent liquid, add 0.0007 g of aluminum chloride (the molar amount of the metal salt providing the second metal cation is 0.5% of the molar amount of the metal salt providing the first metal cation), heat to 80 °C, and stir for 4 h to obtain the dual-cation deep eutectic electrolyte of Example 14 of this invention.

[0062] Comparative Example 3 Weigh 0.3635 g of zinc trifluoromethanesulfonate, add 0.3544 g of acetamide, mix at a molar ratio of 1:6, and stir at 80 °C for 4 hours to obtain a uniform and transparent liquid, which is the monocation deep eutectic electrolyte of Comparative Example 3 of this invention.

[0063] In conjunction with Examples 12-14 and Comparative Example 3, the dual-cation deep eutectic electrolyte of the present invention can be used in an energy storage device, namely a lithium-ion battery, which will be further explained below.

[0064] Example 15

[0065] Example 15 is a zinc-ion battery that utilizes the dual-cation deep eutectic electrolytes of Examples 12-14. The preparation process of the zinc-ion battery in Example 15 includes the following steps: Preparation of carbon nanotube dispersion Weigh 1 g of sodium dodecyl sulfate, add 100 mL of deionized water, stir to dissolve, add 50 mg of carbon nanotubes, and sonicate for 15 min to obtain a carbon nanotube dispersion of 0.5 mg / mL.

[0066] Preparation of sodium vanadate slurry Weigh 2 g of vanadium oxide, add 30 mL of 2 M sodium chloride solution, stir at room temperature for 96 h, wash several times with ethanol by centrifugation, and vacuum dry at 80 ℃ for 12 h to obtain a dark brown solid powder. Add deionized water to quantitatively prepare a sodium vanadate solution with a concentration of 0.0102 g / mL.

[0067] Preparation of electrode paste for sodium vanadate composite carbon nanotubes (CNT@NVO) 20 mL of a 0.5 mg / mL carbon nanotube (CNT) dispersion was transferred, and 2.5 mL of a 0.0102 g / mL sodium vanadate (NVO) solution was slowly added dropwise. The mixture was stirred for 2 h, then vacuum filtered and dried at 45 °C for 2 h to obtain a sodium vanadate composite carbon nanotube electrode film. The prepared electrode film was perforated into small discs with a diameter of 12 mm, which were used as the positive electrode material for zinc-ion full cells. The average loading of the electrode discs was 2 mg / cm². 2 .

[0068] Finally, the dual-cation deep eutectic electrolyte was sandwiched between the positive electrode and the zinc negative electrode, and a CNT@NVO||Zn battery was assembled in a glove box. Electrochemical tests of the CNT@NVO||Zn battery were conducted at 30°C, with a voltage range of 0.3–1.5 V.

[0069] Example 16

[0070] Example 16 is a lithium-ion battery that uses the single-cation deep eutectic solution corresponding to Comparative Example 1 as the electrolyte. The preparation methods of other materials and the assembly process of the battery are the same as those in Example 15.

[0071] Example 17

[0072] Example 17 is a sodium-ion battery that uses the monocation deep eutectic solution corresponding to Comparative Example 2 as the electrolyte. The preparation methods of other materials and the assembly process of the battery are the same as those in Example 15.

[0073] Example 18

[0074] Example 18 is a zinc-ion battery that uses the monocation deep eutectic solution corresponding to Comparative Example 3 as the electrolyte. The preparation methods of other materials and the assembly process of the battery are the same as those in Example 15.

[0075] Figure 11 The CNT@NVO||Zn battery assembled at 0.5 C using the dual-cation deep eutectic electrolyte in Examples 12-14 is 0.5 A·g. -1 The following is a charge-discharge curve. As shown in the figure, this zinc-ion battery exhibits good electrochemical performance.

[0076] As demonstrated by the above embodiments, this invention prepares a dual-cation deep eutectic electrolyte via a simple and efficient thermal dissolution method. Compared to the preparation of traditional deep eutectic electrolytes, the introduction of a metal salt providing the second cation through the synergistic coordination of the two cations with Lewis acids and bases facilitates the regulation of the coordination environment of the other metal cation, thereby promoting ion transport and anchoring Lewis base molecules. This simultaneously optimizes ionic conductivity and interfacial stability, making it suitable for the development of high-energy-density energy storage systems. This breakthrough directly resolves the long-standing contradiction between interfacial stability and ion transport in traditional eutectic electrolytes, paving the way for the practical application of high-performance energy storage systems.

[0077] The above are merely preferred embodiments of the present invention. It should be noted that, for those skilled in the art, numerous improvements and modifications can be made without departing from the principles of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A dual-cation deep eutectic electrolyte, characterized in that, It comprises at least two different metal salts and a Lewis base, wherein the metal salts provide the first metal cation M1x. + The second metal cation M2y + M1x + With M2y + They are different metal cations, and satisfy the following condition: the ratio of the total molar amount of all metal salts to the molar amount of Lewis bases is 1.005:4-6.

2. The dual-cation deep eutectic electrolyte according to claim 1, characterized in that, The molar amount of the metal salt providing the second metal cation is 0.5% of the molar amount of the metal salt providing the first metal cation.

3. The dual-cation deep eutectic electrolyte according to claim 1, characterized in that, The metal salt providing the first metal cation is selected from at least one of lithium hexafluorophosphate, lithium trifluoromethanesulfonate, lithium bis(trifluoromethanesulfonyl)imide, lithium bis(fluorosulfonyl)imide, lithium dioxoborate, lithium difluorooxalateborate, zinc trifluoromethanesulfonate, sodium trifluoromethanesulfonate, zinc bis(trifluoromethanesulfonyl)imide, sodium bis(trifluoromethanesulfonyl)imide, zinc bis(fluorosulfonyl)imide, and sodium bis(fluorosulfonyl)imide.

4. The dual-cation deep eutectic electrolyte according to claim 1, characterized in that, The metal salt providing the second metal cation is selected from at least one of the following: perchlorate M(ClO4)n, tetrafluoroborate M(BF4)n, metal chloride MCln, metal iodide MCln, metal bromide MCln, trifluoromethanesulfonate M(OTf)n, acetate M(Ac)n, sulfate M(SO4)n, nitrate M(NO3)n, lithium hexafluorophosphate, lithium bis(trifluoromethanesulfonyl)imide, sodium bis(trifluoromethanesulfonyl)imide, lithium bis(trifluoromethanesulfonyl)imide, lithium bis(trifluoromethanesulfonyl)imide, lithium bis(trifluoromethanesulfonyl)imide, lithium dioxoborate, lithium difluorooxalate borate, zinc bis(trifluoromethanesulfonyl)imide, sodium bis(trifluoromethanesulfonyl)imide, and zinc bis(trifluoromethanesulfonyl)imide, wherein M = Li + Na + , M g 2+ Zn 2+ Ca 2+ Or Al 3+ , where n is the valence of M.

5. The dual-cation deep eutectic electrolyte according to claim 1, characterized in that, The Lewis acid or base is selected from at least one of succinic acid, acetamide, urea, tetrahydropyran, propenyl-1,3-sulfonyl lactone, vinyl sulfate, 2,6-dimethylpyrazine, 2-cyanopyridine, 2-cyano-5-fluoropyridine, 2-cyano-3-fluoropyridine, 2-cyano-5-trifluoromethylpyridine, and 3-cyano-6-trifluoromethylpyridine.

6. A method for preparing a dual-cation deep eutectic electrolyte as described in any one of claims 1-5, characterized in that, Includes the following steps: Step 1: Mix the metal salt that provides the first metal cation with a Lewis base at a molar ratio of 1:4-6, heat to 80°C, and stir for 4 h to obtain a mixed solution; Step 2: Add a metal salt that provides a second metal cation to the mixed solution obtained in Step 1. The molar amount of the metal salt that provides the second metal cation is 0.5% of the molar amount of the metal salt that provides the first metal cation. Heat to 80°C and stir for 4 h to prepare a dication deep eutectic electrolyte.

7. The application of a dual-cation deep eutectic electrolyte as described in claims 1-5 in energy storage devices, characterized in that, The energy storage device is a lithium-ion battery, a zinc-ion battery, or a sodium-ion battery.

8. The application of the dual-cation deep eutectic electrolyte according to claim 7 in energy storage devices, characterized in that, The dual-cation deep eutectic electrolyte is used as a component of the lithium-ion battery. The lithium metal battery includes: a positive electrode, a negative electrode, a separator, and the dual-cation deep eutectic electrolyte. The positive electrode material is selected from any one of lithium metal, lithium iron phosphate, lithium cobalt oxide, lithium manganese oxide, NCM622 type positive electrode material, NCM613 type positive electrode material, NCM811 type positive electrode material, and NCM523 type positive electrode material. The negative electrode is selected from lithium metal sheet, graphite, hard carbon, and soft carbon. The separator is selected from any one of PVDF membrane, glass fiber membrane, PE, and PP separator.

9. The application of the dual-cation deep eutectic electrolyte according to claim 7 in energy storage devices, characterized in that, The dual-cation deep eutectic electrolyte is used as a component of the sodium-ion battery, which includes a positive electrode, a negative electrode, a separator, and the dual-cation deep eutectic electrolyte. The positive electrode material is selected from any one of sodium vanadium phosphate, sodium iron pyrophosphate, sodium nickel manganate, and sodium nickel iron manganate. The negative electrode is selected from any one of sodium metal sheet, hard carbon, soft carbon, and silicon carbide. The separator is selected from any one of PVDF membrane, glass fiber membrane, PE, and PP separator.

10. The application of the dual-cation deep eutectic electrolyte according to claim 7 in energy storage devices, characterized in that, The dual-cation deep eutectic electrolyte is used as a component of the zinc-ion battery. The zinc metal battery includes: a positive electrode, a negative electrode, a separator, and the dual-cation deep eutectic electrolyte. The positive electrode material is selected from any one of vanadium pentoxide, vanadium oxide, sodium vanadate, ammonium vanadate, manganese vanadate, magnesium vanadate, calcium vanadate, and aluminum vanadate. The negative electrode is selected from any one of zinc sheet and zinc powder. The separator is selected from any one of PVDF membrane, glass fiber membrane, PE membrane, and PP membrane.

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