Preparation method of sulfur functionalized quaternary ammonium salt ionic liquid and solid-state battery
By introducing sulfur-functionalized quaternary ammonium salt ionic liquids as interface wetting agents into solid-state batteries, the problem of poor solid-solid interface contact in solid-state batteries is solved, achieving high ionic conductivity, thermal stability, and electrochemical stability, thereby improving the charge-discharge performance and cycle life of the battery.
Patent Information
- Application Number
- CN202511019943.3
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-07-23
- Publication Date
- 2025-11-18
AI Technical Summary
In solid-state batteries, poor solid-solid interface contact between electrode materials and electrolyte leads to incomplete ion transport pathways, limiting battery capacity and rate performance. Furthermore, existing interface wetting agents are flammable or chemically reactive, affecting battery safety and performance.
Sulfur-functionalized quaternary ammonium salt ionic liquids are used as interface wetting agents. By introducing sulfur functional groups on the cationic side chains, specific adsorption capacity for electrolytes is provided, a uniform ion transport channel is constructed, and operation is carried out under low stack pressure.
It significantly improves the charge/discharge performance and cycle life of solid-state batteries, reduces operating stress, and enhances battery safety and electrochemical performance.
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Figure CN120965613A_ABST
Abstract
Description
Technical Field
[0001] This invention belongs to the field of solid-state battery technology, specifically relating to a method for preparing sulfur-functionalized quaternary ammonium salt ionic liquids and their application in solid-state batteries. Background Technology
[0002] Solid-state batteries, as a representative of next-generation energy storage technology, have become a key technology in fields such as electric vehicles, large-scale energy storage systems, and special equipment due to their higher energy density, superior safety, and longer cycle life. However, in practical applications, solid-state batteries still face several technical challenges. Because the solid-solid interface between the electrode materials and the electrolyte is less extensive, with a contact area much smaller than the solid / liquid interface in traditional liquid batteries, the incomplete solid-solid interface makes it difficult for the active materials inside the electrode to build effective ion transport pathways, resulting in the capacity and rate performance of all-solid-state batteries not being fully realized. To solve the problem of solid-solid interface separation during cycling, current solid-state batteries need to operate under high stacking pressures, which greatly limits their commercial application.
[0003] Introducing liquid ion-conducting components (interface wetting agents) into the cathode / electrolyte interface to construct ion channels can effectively solve the problem of poor solid-solid interface contact in solid-state batteries. However, most existing quasi-solid-state batteries use flammable carbonate electrolytes to improve solid-solid contact. Although this effectively improves the electrochemical performance of solid-state batteries, the flammability of carbonates weakens their high safety characteristics. Meanwhile, common solid-state electrolytes such as halide and sulfide electrolytes are chemically reactive and prone to chemical reactions that generate low-conductivity byproducts, significantly impacting battery performance. Therefore, developing a novel interface wetting agent with high safety and compatibility is an effective way to reduce battery operating stress, improve battery electrochemical performance, and realize the commercialization of solid-state batteries. Summary of the Invention
[0004] To address the problems existing in the background art, one of the objectives of this invention is to provide a method for preparing sulfur-functionalized quaternary ammonium salt ionic liquids, applicable to sulfide electrolytes and halide electrolytes;
[0005] The second objective of this invention is to provide a solid-state battery with a long cycle life that can operate at low stack pressure.
[0006] To achieve the above objectives, the present invention adopts the following technical solution:
[0007] A method for preparing a sulfur-functionalized quaternary ammonium salt ionic liquid includes the following steps:
[0008] Step 1: After mixing nitrogen heterocyclic compounds, halothioether compounds, organic solvents, and catalysts, a deoxygenation treatment is performed.
[0009] Step 2: Stir the deoxygenated mixed solution at 100℃-150℃ for 12-48 hours;
[0010] Step 3: After the reaction is complete, cool the solution to room temperature, add alkali metal salt, stir and mix thoroughly, filter the precipitate, and further purify the product by vacuum distillation to obtain sulfur-functionalized quaternary ammonium salt ionic liquid.
[0011] Furthermore, in step one, the nitrogen heterocyclic compound includes one of N-methylpyrrolidine, N-ethylpyrrolidine, N-methylpiperidinidine, and N-ethylpiperidinidine; the halothioether compound includes one of 2-chloroethylmethyl sulfide, 1-chloromethylmethyl sulfide, 1-chloromethylethyl sulfide, and 2-chloroethylethyl sulfide.
[0012] Furthermore, in step one, the deoxygenation process involves freezing the mixed solution, applying a vacuum, and thawing it, repeating this cycle several times to achieve a vacuum-free, oxygen-free reaction system.
[0013] Furthermore, the cation of the alkali metal salt is Li. + Na + K + One of the following: the anion of the alkali metal salt is one of bis(trifluoromethanesulfonyl)imide anion, bis(fluorosulfonyl)imide anion, trifluoroacetate, tetrafluoroborate, difluorooxalate-borate, hexafluorophosphate, perchlorate, nitrate, difluorophosphate, and dioxalate-borate.
[0014] Furthermore, the molar ratio of the nitrogen heterocyclic compound, the halothioether compound, and the alkali metal salt is 1:(0.5-0.9):(0.5-1.1).
[0015] Furthermore, in step one, the organic solvent includes at least one of diethyl ether, tetrahydrofuran, n-hexane, benzene, toluene, and chloroform; the catalyst includes one of potassium iodide, potassium bromide, sodium dodecyl sulfate, and hexadecyltrimethylammonium bromide.
[0016] A solid-state lithium battery, comprising a positive electrode, an electrolyte, a negative electrode, and an interface wetting agent, wherein the interface wetting agent comprises a sulfur-functionalized quaternary ammonium salt ionic liquid and a lithium salt prepared by the preparation method described above.
[0017] The concentration of the lithium salt in the interface wetting agent is 0.5-3.0 mol / L; the lithium salt includes one or more combinations of lithium bis(trifluoromethanesulfonyl)imide, lithium bis(fluorosulfonyl)imide, lithium trifluoroacetate, lithium tetrafluoroborate, lithium difluorooxalate borate, lithium hexafluorophosphate, lithium perchlorate, lithium nitrate, lithium difluorophosphate, and lithium dioxalate borate.
[0018] A solid-state sodium battery, comprising a positive electrode, an electrolyte, a negative electrode, and an interface wetting agent, wherein the interface wetting agent comprises a sulfur-functionalized quaternary ammonium salt ionic liquid prepared by the aforementioned preparation method and a sodium salt. The concentration of the sodium salt in the interface wetting agent is 0.5-3.0 mol / L; the sodium salt comprises one or more combinations of sodium bis(trifluoromethanesulfonyl)imide, sodium bis(fluorosulfonyl)imide, sodium trifluoroacetate, sodium tetrafluoroborate, sodium difluorooxalateborate, sodium hexafluorophosphate, sodium perchlorate, sodium nitrate, sodium difluorophosphate, and sodium dioxalateborate.
[0019] Compared with the prior art, the beneficial effects of the present invention are:
[0020] The sulfur-functionalized quaternary ammonium salt ionic liquid synthesized in this invention possesses high ionic conductivity, high thermal stability, high electrochemical stability, and sufficient interfacial wettability. Compared with other types of ionic liquids, the sulfur-functionalized quaternary ammonium salt ionic liquid synthesized in this invention provides the ability to specifically adsorb electrolytes by introducing sulfur functional groups on the cation branches, enabling uniform distribution on the surface of solid electrolytes. Compared with ionic liquids that rely solely on capillary action and preparation processes for dispersion, it achieves a more uniform distribution effect in composite cathodes, thus achieving superior interfacial wettability with a smaller dosage. Introducing the sulfur-functionalized quaternary ammonium salt ionic liquid described in this invention into the cathode region of solid-state batteries during electrode preparation transforms the solid-solid interface into a solid-liquid interface, constructing new ion transport channels, which can significantly improve the charge-discharge performance of the battery at high rates. Simultaneously, this ionic liquid can fill the interfacial stratification caused by volume changes during battery cycling, improving the battery's cycle life. These effects are even more significant in low-density operating environments, greatly improving the discharge specific capacity and cycle stability of solid-state batteries under low-density conditions. Attached Figure Description
[0021] Figure 1 The 1H NMR spectrum of the quaternary ammonium salt-based sulfur-functionalized ionic liquid synthesized in Example 1 is shown below.
[0022] Figure 2 Figures (a) and (b) show the charge-discharge curves of sulfide solid-state lithium batteries with a packaging pressure of 100 MPa in Example 2 and Comparative Example 1, respectively, at a current density of 0.2C.
[0023] Figure 3 Figures (a) and (b) show the long-cycle curves of halide solid-state lithium batteries with a packaging pressure of 100 MPa in Example 4 and Comparative Example 2, respectively, at a current density of 1C.
[0024] Figure 4 Figures (a) and (b) show the long-cycle curves of the sulfide solid lithium battery with a packaging pressure of 25 MPa in Example 5 and Comparative Example 3, respectively, at a current density of 1C.
[0025] Figure 5 Figures (a) and (b) show the long-cycle curves of the sulfide solid sodium battery with a packaging pressure of 100 MPa in Example 7 and Comparative Example 4, respectively, at a current density of 1C.
[0026] Figure 6 The long-cycle curve of the sulfide solid-state lithium battery with a packaging pressure of 100 MPa (Comparative Example 5) at a current density of 0.5C is shown. Detailed Implementation
[0027] The technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings and embodiments. Obviously, the described embodiments are only some embodiments of the invention, not all embodiments. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are within the scope of protection of the present invention.
[0028] Example 1:
[0029] A method for preparing a sulfur-functionalized quaternary ammonium salt ionic liquid includes the following steps: weighing 12 mmol of N-methylpyrrolidine, 10 mmol of 2-chloroethyl methyl sulfide and 0.1 mmol of potassium bromide into a 50 mL Schlenk flask, adding 5 mL of diethyl ether, and stirring thoroughly to mix evenly; performing three freeze-vacuum-thaw operations, using liquid nitrogen-ethanol with a volume ratio of 2:1 as the cold trap coolant, and using high-purity argon as the vacuum release gas; stirring the reaction at 120℃ for 24 h to obtain a yellowish-brown oily mixed solution; naturally cooling the reaction vessel to room temperature, adding 10 mmol of lithium bis(trifluoromethanesulfonyl)imide (LiTFSI) under a water- and oxygen-free condition, mixing thoroughly, filtering the precipitate, and further purifying the solvent using a vacuum distillation apparatus to obtain the sulfur-functionalized quaternary ammonium salt ionic liquid N-methylthioethyl-N-methyl-pyrrolidine bis(trifluoromethanesulfonyl)imide.
[0030] Example 2
[0031] A solid-state lithium battery, wherein the interface wetting agent includes the sulfur-functionalized quaternary ammonium salt ionic liquid and LiTFSI prepared in Example 1, the concentration of LiTFSI is 1.0 mol / L, NCM811 material is used as the positive electrode active material, LiP6S5Cl is used as the solid electrolyte, and vapor-grown carbon fiber is used as the conductive carbon. The composite electrode material prepared by ball milling and mixing under argon protection for 24 hours in a mass ratio of positive electrode active material: solid electrolyte: interface wetting agent: conductive carbon = 60:30:5:5 is used to prepare the positive electrode material, and LiP6S5Cl is used as the electrolyte and lithium indium alloy sheet is used as the negative electrode to prepare the solid-state lithium battery.
[0032] The specific electrochemical testing methods are as follows:
[0033] The solid-state lithium battery prepared in Example 2 was subjected to a constant pressure of 100 MPa and charge-discharge cycles at a current density of 0.2 C. The results of the first charge-discharge curve are as follows: Figure 2 As shown in (a), the initial discharge capacity is 217.05 mAh / g.
[0034] Example 3
[0035] A method for preparing a sulfur-functionalized quaternary ammonium salt ionic liquid differs from Example 1 in that the lithium salt added under arid and oxygen-free conditions is LiFSI, while the remaining steps are the same as in Example 1.
[0036] Example 4
[0037] A solid-state lithium battery uses an interface wetting agent comprising a sulfur-functionalized quaternary ammonium salt ionic liquid and LiFSI prepared in Example 3, with a LiFSI concentration of 2.0 mol / L. NCM811 material is used as the positive electrode active material, Li3InCl6 as the solid electrolyte, and vapor-grown carbon fiber as the conductive carbon. The composite electrode material prepared by ball milling and mixing the materials under argon protection for 24 hours in a mass ratio of positive electrode active material: solid electrolyte: interface wetting agent: conductive carbon = 60:30:5:5 is used to prepare the positive electrode material, and LiP6S5Cl is used as the electrolyte, with a lithium indium alloy sheet as the negative electrode to prepare the solid-state lithium battery.
[0038] The specific electrochemical testing methods are as follows:
[0039] The battery prepared in Example 4 was subjected to a constant pressure of 100 MPa, activated at a current density of 0.2 C, and then subjected to charge-discharge cycles at a current density of 1 C. The experimental results are as follows: Figure 3 As shown in (a), the reversible specific capacity of the battery is 181.49 mAh / g.
[0040] Example 5
[0041] The difference between this embodiment and Embodiment 2 lies in the specific electrochemical testing method: a constant pressure of 25 MPa is applied to the battery, activation is performed at a current density of 0.2 C, and charge-discharge cycles are conducted at a current density of 1 C. All other steps are the same as in Embodiment 2. Experimental results are as follows: Figure 4 As shown in (a), the reversible specific capacity of the battery is 170.60 mAh / g.
[0042] Example 6
[0043] A method for preparing a sulfur-functionalized quaternary ammonium salt ionic liquid differs from Example 1 in that sodium hexafluorophosphate (NaPF6) is added under arid and oxygen-free conditions, while the remaining steps are the same as in Example 1.
[0044] Example 7
[0045] A solid-state sodium battery is disclosed. The interface wetting agent includes the sulfur-functionalized quaternary ammonium salt ionic liquid prepared in Example 6 and sodium hexafluorophosphate, with a sodium hexafluorophosphate concentration of 2.0 mol / L. Na3V2(PO4)3 material is used as the positive electrode active material, Na3PS4 as the solid electrolyte, and vapor-grown carbon fiber as the conductive carbon. The composite electrode material prepared by ball milling and mixing under argon protection for 24 hours in a mass ratio of positive electrode active material: solid electrolyte: interface wetting agent: conductive carbon = 60:30:5:5 is used to prepare the positive electrode material for the positive electrode sheet. Na3PS4 is used as the electrolyte, and Na-SiO2 composite electrode is used as the negative electrode to prepare the solid-state sodium battery.
[0046] The specific electrochemical testing methods are as follows:
[0047] The solid sodium battery prepared in Example 7 was subjected to a constant pressure of 100 MPa, activated at a current density of 0.2 C, and then subjected to charge-discharge cycles at a current density of 1 C. The experimental results are as follows: Figure 5 As shown in (a), the reversible specific capacity is 85 mAh / g.
[0048] Comparative Example 1
[0049] The difference between this comparative example and Example 2 is that the mass ratio of the composite cathode components is 60:35:0:5 for the positive electrode active material, solid electrolyte, interfacial wetting agent, and conductive carbon. All other steps and electrochemical testing methods are the same as in Example 2. The experimental results are as follows: Figure 2 As shown in (b), the initial discharge capacity is 146.63 mAh / g.
[0050] Comparative Example 2
[0051] The difference between this comparative example and Example 4 is that the mass ratio of the composite cathode components is 60:35:0:5 for the positive electrode active material, solid electrolyte, interfacial wetting agent, and conductive carbon. All other steps and electrochemical testing methods are the same as in Example 4. The experimental results are as follows: Figure 3 As shown in (b), the reversible specific capacity is 143.92 mAh / g.
[0052] Comparative Example 3
[0053] The difference between this comparative example and Example 5 is that the mass ratio of the composite cathode components is 60:35:0:5 for the positive electrode active material, solid electrolyte, interfacial wetting agent, and conductive carbon. All other steps and electrochemical testing methods are the same as in Example 5. The experimental results are as follows: Figure 4 As shown in (b), the reversible specific capacity is 30.92 mAh / g.
[0054] Comparative Example 4
[0055] The difference between this comparative example and Example 7 is that the mass ratio of the composite cathode components is 60:35:0:5 for the positive electrode active material, solid electrolyte, interfacial wetting agent, and conductive carbon. All other steps and electrochemical testing methods are the same as in Example 7. The experimental results are as follows: Figure 5 As shown in (b), the battery has virtually no capacity.
[0056] Comparative Example 5
[0057] The difference between this comparative example and Example 2 is that the interface wetting agent used is a 1 mol / L LiTFSI carbonate electrolyte, which is composed of equal volumes of EC, PC, and EMC. Electrochemical testing was performed using charge-discharge cycles at a current density of 0.5 C. All other steps and electrochemical testing methods are the same as in Example 2. Experimental results are as follows: Figure 6 As shown, after 37 cycles, the capacity dropped sharply, and the battery failed.
[0058] Furthermore, it should be understood that although this specification describes embodiments, not every embodiment contains only one independent technical solution. This narrative style is merely for clarity. Those skilled in the art should consider the specification as a whole, and the technical solutions in each embodiment can also be appropriately combined to form other embodiments that can be understood by those skilled in the art.
Claims
1. A method for preparing a sulfur-functionalized quaternary ammonium salt ionic liquid, characterized in that, Includes the following steps: Step 1: After mixing nitrogen heterocyclic compounds, halothioether compounds, organic solvents, and catalysts, a deoxygenation treatment is performed. Step 2: Stir the deoxygenated mixed solution at 100℃-150℃ for 12-48 hours; Step 3: After the reaction is complete, cool the solution to room temperature, add alkali metal salt, stir and mix thoroughly, filter the precipitate, and further purify the product by vacuum distillation to obtain sulfur-functionalized quaternary ammonium salt ionic liquid.
2. The preparation method according to claim 1, characterized in that: In step one, the nitrogen heterocyclic compound includes one of N-methylpyrrolidine, N-ethylpyrrolidine, N-methylpiperidinidine, and N-ethylpiperidinidine; the halothioether compound includes one of 2-chloroethylmethyl sulfide, 1-chloromethylmethyl sulfide, 1-chloromethylethyl sulfide, and 2-chloroethylethyl sulfide.
3. The preparation method according to claim 1, characterized in that: In step one, the deoxygenation process involves freezing the mixed solution, vacuuming it, and thawing it, repeating this cycle several times to achieve a vacuum-free, oxygen-free reaction system.
4. The preparation method according to claim 1, characterized in that: The cation of the alkali metal salt is Li + Na + K + One of the following: the anion of the alkali metal salt is one of bis(trifluoromethanesulfonyl)imide anion, bis(fluorosulfonyl)imide anion, trifluoroacetate, tetrafluoroborate, difluorooxalate-borate, hexafluorophosphate, perchlorate, nitrate, difluorophosphate, and dioxalate-borate.
5. The preparation method according to claim 1, characterized in that: The molar ratio of the nitrogen heterocyclic compound, the halothioether compound, and the alkali metal salt is 1:(0.5-0.9):(0.5-1.1).
6. The preparation method according to claim 1, characterized in that: In step one, the organic solvent includes at least one of diethyl ether, tetrahydrofuran, n-hexane, benzene, toluene, and chloroform; the catalyst includes one of potassium iodide, potassium bromide, sodium dodecyl sulfate, and hexadecyltrimethylammonium bromide.
7. A solid-state lithium battery, characterized in that: The solid-state lithium battery includes a positive electrode, an electrolyte, a negative electrode, and an interface wetting agent, wherein the interface wetting agent includes a sulfur-functionalized quaternary ammonium salt ionic liquid and a lithium salt prepared by the preparation method according to any one of claims 1-6.
8. The solid-state lithium battery according to claim 7, characterized in that: The concentration of the lithium salt in the interface wetting agent is 0.5-3.0 mol / L; the lithium salt includes one or more combinations of lithium bis(trifluoromethanesulfonyl)imide, lithium bis(fluorosulfonyl)imide, lithium trifluoroacetate, lithium tetrafluoroborate, lithium difluorooxalate borate, lithium hexafluorophosphate, lithium perchlorate, lithium nitrate, lithium difluorophosphate, and lithium dioxalate borate.
9. A solid-state sodium battery, characterized in that: The solid sodium battery includes a positive electrode, an electrolyte, a negative electrode, and an interface wetting agent, wherein the interface wetting agent includes a sulfur-functionalized quaternary ammonium salt ionic liquid and a sodium salt prepared by the preparation method according to any one of claims 1-6.
10. The solid-state sodium battery according to claim 9, characterized in that: The concentration of the sodium salt in the interfacial wetting agent is 0.5-3.0 mol / L; the sodium salt includes one or more combinations of sodium bis(trifluoromethanesulfonyl)imide, sodium bis(fluorosulfonyl)imide, sodium trifluoroacetate, sodium tetrafluoroborate, sodium difluorooxalate borate, sodium hexafluorophosphate, sodium perchlorate, sodium nitrate, sodium difluorophosphate, and sodium dioxalate borate.