High-voltage low-temperature electrolyte and application thereof in sodium-ion battery

Abstract

The invention provides a high-voltage low-temperature electrolyte and application thereof in a sodium-ion battery. The high-voltage low-temperature electrolyte has excellent electrochemical performance in a low-temperature environment and is high in low-temperature adaptability; the electrochemical window can reach 4.95 V, the oxidation resistance is excellent, the long-acting oxidation resistance and interface stabilization protection under the high-voltage working condition can be realized, and the adaptation with a high-voltage positive electrode material can be realized; the sodium ion battery assembled by using the high-voltage low-temperature electrolyte and a high-voltage positive electrode material provided by the invention circulates for 100 circles under the conditions of 2.0-4.5 V and 1 C, the capacity retention ratio is more than 80%, and the sodium ion battery has excellent high-voltage stability. The sodium ion battery containing the high-voltage low-temperature electrolyte has high first-circle discharge specific capacity and excellent low-temperature cycling stability, room-temperature cycling stability and capacity retention ratio. In addition, the high-voltage low-temperature electrolyte is simple in preparation process, low in raw material cost and suitable for large-scale production.

Description

Technical Field

[0001] This invention relates to the field of battery energy storage technology, and in particular to a high-voltage low-temperature electrolyte and its application in sodium-ion batteries. Background Technology

[0002] Sodium-ion batteries, with their abundant sodium resources, low raw material costs, and "rocking chair" insertion / extraction mechanism similar to lithium-ion batteries, are considered an ideal choice for replacing lithium-ion battery systems and realizing large-scale energy storage industrialization. However, the performance defects of sodium-ion batteries under extreme conditions severely restrict their practical application: (1) In low-temperature environments (e.g., ≤-20 ℃), the viscosity of traditional carbonate-based electrolytes surges due to the enhanced intermolecular forces of solvent molecules, leading to a decrease in ionic conductivity, which significantly hinders sodium ion migration kinetics and causes the battery discharge specific capacity to decrease by more than 60%; (2) Under high-voltage conditions (>4 V vs. Na), + Under conditions of / Na), electrolyte components are prone to oxidative decomposition (e.g., ethylene carbonate (EC) produces gas violently above 4.3 V), leading to problems such as transition metal dissolution and repeated rupture / reconstruction of the positive electrode interface film (CEI film), resulting in severe degradation of battery cycle life.

[0003] To address the aforementioned issues, current research primarily focuses on improving performance through electrolyte composition optimization. For instance, low-freezing-point ether solvents (such as dimethyl glycol ether (DME) and diethylene glycol dimethyl ether (DEGDME)) are used to reduce electrolyte viscosity; however, their upper limit for oxidation resistance is generally below 4.0 V, making them difficult to match with high-voltage cathode materials (such as O3-type layered oxides). Introducing fluorinated solvents (such as fluoroethylene carbonate (FEC) and fluoroethyl methyl carbonate (FEMC)) can suppress interfacial side reactions by forming a fluorine-rich CEI film, raising the electrochemical window to above 4.2 V. However, the synthesis processes for these solvents are complex and costly, and fluorine-containing compounds pose environmental pollution risks. Furthermore, optimization strategies relying on a single additive (such as fluoroethylene carbonate) tend to result in excessively thick CEI films (>20 nm), exacerbating ion transport resistance and creating a contradiction between "high stability and low kinetics." Therefore, developing a novel electrolyte system that combines strong low-temperature adaptability, a wide electrochemical window, excellent high voltage stability, and low cost is of great significance for promoting the practical application of sodium-ion batteries in extreme environment energy storage and electric vehicles in cold regions. Summary of the Invention

[0004] This invention provides a high-voltage, low-temperature electrolyte, which features strong low-temperature adaptability, a wide electrochemical window, and excellent high-voltage stability. Sodium-ion batteries containing this high-voltage, low-temperature electrolyte exhibit high capacity retention, excellent low-temperature cycling stability, and room-temperature cycling stability. Furthermore, the preparation process of this high-voltage, low-temperature electrolyte is simple, the raw material cost is low, and it is suitable for large-scale production.

[0005] The present invention also provides a sodium-ion battery comprising the above-mentioned high-voltage low-temperature electrolyte. This sodium-ion battery has both high capacity retention and excellent low-temperature cycle stability and room-temperature cycle stability, and has broad application prospects in extreme environment energy storage, electric vehicles in cold regions and other fields.

[0006] A first aspect of the present invention provides a high-voltage, low-temperature electrolyte, comprising a sodium salt solution and a hydrogen-bonded framework material additive containing amino and sulfonic acid groups; the hydrogen-bonded framework material additive containing amino and sulfonic acid groups comprises guanidine monomer structural units and sulfonic acid monomer structural units, the guanidine monomer structural units and the sulfonic acid monomer structural units being connected by hydrogen bonds to form a network structure; the morphology of the hydrogen-bonded framework material additive containing amino and sulfonic acid groups includes a composite structure of plate-like and needle-like structures;

[0007] The structural formula of the guanidine monomer structural unit is shown in formula (1):

[0008]

[0009] In equation (1), Indicates the center of positive charge;

[0010] The sulfonic acid monomer structural unit is one of formulas (2), (3), (4), and (5):

[0011]

[0012] In equations (2) to (5), It represents the center of negative charge.

[0013] The high-voltage, low-temperature electrolyte described above, wherein the hydrogen-bonded framework material additive containing amino and sulfonic acid groups is obtained by a preparation method comprising the following steps:

[0014] The guanidine monomer solution was added dropwise to the sulfonic acid monomer solution at room temperature with continuous stirring to obtain the reaction system;

[0015] The reaction system was allowed to stand, and the solvent was evaporated at room temperature. The solid product was collected by decantation. The solid product was washed and dried to obtain the hydrogen-bonded framework material additive containing amino and sulfonic acid groups.

[0016] In the high-voltage, low-temperature electrolyte described above, the guanidine monomer solution is prepared by dissolving the guanidine monomer in an aqueous ethanol solution; the structural formula of the guanidine monomer is as follows:

[0017] ;

[0018] The sulfonic acid monomer solution is prepared by dissolving the sulfonic acid monomer in an aqueous ethanol solution; the sulfonic acid monomer has one of the following structures:

[0019] .

[0020] In the high-voltage, low-temperature electrolyte described above, the molar ratio of guanidine monomer to sulfonic acid monomer in the reaction system is 1:1.

[0021] In the high-voltage low-temperature electrolyte described above, the concentration of the hydrogen-bonded framework material additive containing amino and sulfonic acid groups is 1-5 mg / mL.

[0022] The high-voltage low-temperature electrolyte described above, wherein the sodium salt solution is composed of sodium salt and organic solvent;

[0023] The concentration of the sodium salt is 0.5-2 mol / L.

[0024] In the high-voltage low-temperature electrolyte described above, the sodium salt is at least one of sodium hexafluorophosphate, sodium perchlorate, sodium bis(fluorosulfonyl)imide, sodium bis(trifluoromethanesulfonyl)imide, sodium trifluoromethanesulfonate, sodium bis(oxalato)borate, and sodium difluorooxalato)borate.

[0025] In the high-voltage, low-temperature electrolyte described above, the organic solvent is at least one selected from ethylene carbonate, fluoroethylene carbonate, vinylene carbonate, propylene carbonate, butene carbonate, dimethyl carbonate, diethyl carbonate, methyl ethyl carbonate, methyl propyl carbonate, methyl formate, methyl acetate, methyl butyrate, ethyl propionate, ethyl butyrate, butyl acetate, methyl propionate, propyl butyrate, trimethyl phosphate, triethyl phosphate, sulfolane, dimethyl sulfoxide, dimethyl sulfoxide, ethyl methyl sulfone, ethylene sulfite, propylene sulfite, dimethyl sulfite, diethyl sulfite, methyl (2,2,2-trifluoroethyl) carbonate, methyl trifluoroacetate, acetonitrile, and 1,3-dioxolane.

[0026] A second aspect of the present invention provides a sodium-ion battery, comprising a positive electrode, a negative electrode, and the aforementioned high-voltage low-temperature electrolyte.

[0027] In the sodium-ion battery described above, the positive electrode is one of a transition metal layered oxide, a polyanionic compound, Prussian blue, or a Prussian blue analogue.

[0028] And / or, the negative electrode is one of carbon materials, metallic sodium, alloy materials, transition metal oxides, transition metal sulfides, transition metal phosphides, and transition metal selenides.

[0029] The solution of the present invention has at least the following effects:

[0030] (1) The high-voltage low-temperature electrolyte provided by the present invention has excellent electrochemical performance in low-temperature environment and strong low-temperature adaptability; its electrochemical window can reach 4.95 V, and it has excellent anti-oxidation ability, which can realize long-term anti-oxidation and interface stabilization protection under high voltage conditions, and can be adapted to high-voltage cathode materials; the sodium-ion battery assembled with the high-voltage low-temperature electrolyte and high-voltage cathode material provided by the present invention can retain more than 80% of its capacity after 100 cycles under 2.0-4.5 V and 1 C conditions, and has excellent high-voltage stability.

[0031] (2) Compared with traditional electrolytes, the high-voltage low-temperature electrolyte provided by the present invention creatively solves the problems of slow ion transport kinetics at low temperatures and oxidative decomposition of electrolytes under high voltage.

[0032] (3) Compared with traditional electrolytes, the present invention introduces hydrogen bond framework material additives containing amino and sulfonic acid groups, so that the prepared high voltage low temperature electrolyte can reduce the ion-dipole interaction between the solvent and sodium ions in the high voltage low temperature electrolyte through the anchoring effect of hydrogen bonds with the solvent, promote the desolvation process of sodium ions, and improve the low temperature transport dynamics of the electrolyte.

[0033] (4) Compared with traditional electrolytes, the present invention introduces hydrogen bond framework material additives containing amino and sulfonic acid groups, so that the prepared high voltage low temperature electrolyte can anchor the solvent through hydrogen bonding, promote more solvent to participate in the sodium ion solvation structure, reduce solvent decomposition and improve the oxidative stability of the electrolyte.

[0034] (5) Compared with low freezing point ether solvents (such as ether solvents) or fluorinated solvents with a wide electrochemical window, the preparation process of the high voltage low temperature electrolyte provided by the present invention is simpler, more effective, and more economical.

[0035] (6) The high-voltage low-temperature electrolyte provided by the present invention is mixed with an O3-type layered oxide cathode (such as Na). 0.85 Li 0.12 Ni 0.22 Mn 0.66 Sodium-ion batteries are assembled using O2 or polyanionic cathodes (such as Na3V2(PO4)2F3): based on Na 0.85 Li 0.12 Ni 0.22 Mn 0.66 A sodium-ion battery with O2 as the positive electrode, under conditions of -20 ℃, a current density of 1 C, and a voltage window of 2.0-4.5 V, exhibits an initial discharge specific capacity of 91.5 mAh / g and a capacity retention rate of 85.8% after 100 cycles. Based on Na... 0.85 Li 0.12 Ni 0.22 Mn0.66 Sodium-ion batteries using O2 as the positive electrode exhibit an initial discharge specific capacity of 104-118.8 mAh / g under conditions of 25 ℃, a current density of 1 C, and a voltage window of 2.0-4.5 V, with a capacity retention rate of 80.3%-87.6% after 100 cycles. Sodium-ion batteries using Na3V2(PO4)2F3 as the positive electrode exhibit an initial discharge specific capacity of 88.1-104.6 mAh / g under conditions of -20 ℃, a current density of 1 C, and a voltage window of 2.0-4.5 V, with a capacity retention rate of 82.5%-91.1% after 100 cycles. Furthermore, sodium-ion batteries using Na3V2(PO4)2F3 as the positive electrode exhibit an initial discharge specific capacity of 102.7 mAh / g under conditions of 25 ℃, a current density of 1 C, and a voltage window of 2.0-4.5 V, with a capacity retention rate of 95.7% after 100 cycles. It is evident that the high-voltage, low-temperature electrolyte provided by this invention can be adapted to high-voltage cathode materials, and the assembled sodium-ion battery possesses both high capacity retention and excellent low-temperature cycling stability and room-temperature cycling stability. Attached Figure Description

[0036] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0037] Figure 1 The image shows the XRD pattern of the hydrogen-bonded framework material additive in Example 1 of this invention.

[0038] Figure 2 This is a SEM image of the hydrogen-bonded framework material additive in Example 1 of the present invention;

[0039] Figure 3 The infrared spectrum of the hydrogen-bonded framework material additive in Example 1 of this invention;

[0040] Figure 4 The image shows the Raman spectrum of the hydrogen-bonded framework material additive in Example 1 of this invention.

[0041] Figure 5 The ionic conductivity of the high-voltage low-temperature electrolyte in Example 1 and the electrolyte in Comparative Example 1 at different temperatures;

[0042] Figure 6 The electrochemical window test results are for the high-voltage low-temperature electrolyte in Example 1 and the electrolyte in Comparative Example 1 of this invention. Detailed Implementation

[0043] To make the objectives, technical solutions, and advantages of this invention clearer, the technical solutions in the embodiments of this invention will be clearly and completely described below in conjunction with the embodiments of this invention. Obviously, the described embodiments are only some embodiments of this invention, not all embodiments. Based on the embodiments of this invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this invention. Where specific techniques or conditions are not specified in the embodiments, they shall be performed in accordance with the techniques or conditions described in the literature in this art or in accordance with the product instructions. Reagents or instruments used without specified manufacturers are all conventional products that can be obtained commercially.

[0044] It should be noted that in this invention, "and / or" means at least one of the connected objects, and the character " / " generally indicates that the preceding and following objects are in an "or" relationship.

[0045] In this invention, the use of terms such as "first" and "second" is for distinguishing similar objects and not for describing a specific order or sequence, and therefore should not be construed as a limitation of this invention.

[0046] In the following description, the terms “including,” “containing,” “having,” and “containing” are open-ended terms, meaning that they include but are not limited to.

[0047] Those skilled in the art should understand that, in the following description of the embodiments of the present invention, the sequence of numbers does not imply the order of execution. Some or all steps may be executed in parallel or sequentially. The execution order of each process should be determined by its function and internal logic, and should not constitute any limitation on the implementation process of the embodiments of the present invention.

[0048] Those skilled in the art will understand that the numerical ranges in the embodiments of the present invention should be understood to specifically disclose each intermediate value between the upper and lower limits of the range. Any stated value or intermediate value within a stated range, as well as each smaller range between any other stated value or intermediate value within said range, are also included in the present invention. The upper and lower limits of these smaller ranges may be independently included or excluded from the range.

[0049] Unless otherwise stated, the technical / scientific terms used herein have the same meanings as commonly understood by one of ordinary skill in the art to which this invention pertains. While only preferred methods and materials are described herein, any methods and materials similar or equivalent to those described herein may be used in the implementation or testing of this invention. All references to this specification are incorporated by way of citation to disclose and describe methods and / or materials associated with those references. In the event of any conflict with any incorporated reference, the content of this specification shall prevail.

[0050] A first aspect of the present invention provides a high-voltage, low-temperature electrolyte, comprising a sodium salt solution and a hydrogen-bonded framework material additive containing amino and sulfonic acid groups; the hydrogen-bonded framework material additive containing amino and sulfonic acid groups comprises guanidine monomer structural units and sulfonic acid monomer structural units, the guanidine monomer structural units and the sulfonic acid monomer structural units being connected by hydrogen bonds to form a network structure; the morphology of the hydrogen-bonded framework material additive containing amino and sulfonic acid groups includes a composite structure of plate-like and needle-like structures;

[0051] The structural formula of the guanidine monomer structural unit is shown in formula (1):

[0052]

[0053] In equation (1), Indicates the center of positive charge;

[0054] The sulfonic acid monomer structural unit is one of formulas (2), (3), (4), and (5):

[0055]

[0056] In equations (2) to (5), It represents the center of negative charge.

[0057] This invention introduces hydrogen-bonded framework material additives containing amino and sulfonic acid groups, enabling the prepared high-voltage low-temperature electrolyte to weaken the ion-dipole interaction between the solvent and sodium ions in the high-voltage low-temperature electrolyte through the anchoring effect of hydrogen bonds with the solvent, thereby promoting the desolvation process of sodium ions and improving the low-temperature transport kinetics of the electrolyte.

[0058] This invention introduces hydrogen-bonded framework material additives containing amino and sulfonic acid groups, enabling the prepared high-voltage low-temperature electrolyte to anchor the solvent through hydrogen bonding, thereby promoting more solvent participation in the sodium ion solvation structure, reducing solvent decomposition, and improving the oxidative stability of the electrolyte.

[0059] In some embodiments, the hydrogen-bonded framework material additive containing amino and sulfonic acid groups is obtained by a preparation method comprising the following steps: adding a guanidine monomer solution dropwise to a sulfonic acid monomer solution at room temperature with continuous stirring to obtain a reaction system; allowing the reaction system to stand and allowing solvent evaporation at room temperature, collecting the solid product by decantation or vacuum filtration; washing and drying the solid product to obtain the hydrogen-bonded framework material additive containing amino and sulfonic acid groups.

[0060] The principle of preparing hydrogen-bonded framework material additives containing amino and sulfonic acid groups in this invention is explained as follows: The guanidinium group in the guanidinium monomer acts as a strong hydrogen bond donor, and the hydrogen atom attached to its nitrogen atom carries a strong partial positive charge; while the sulfonic acid group in the sulfonic acid monomer can act as both a hydrogen bond donor and a hydrogen bond acceptor (the oxygen atom in the sulfonic acid group is an excellent hydrogen bond acceptor, carrying a strong partial negative charge); based on the strong electrostatic attraction between the positive and negative charges, multiple and strong intermolecular hydrogen bonds can be formed between the two. These hydrogen bonds spontaneously and orderly extend and assemble in three-dimensional space, thereby constructing a long-range ordered and stable hydrogen bond network structure, thus obtaining the desired hydrogen-bonded framework material additive.

[0061] In some embodiments, the guanidinyl monomer solution is prepared by dissolving the guanidinyl monomer in an aqueous ethanol solution; the structural formula of the guanidinyl monomer is as follows:

[0062] .

[0063] In some embodiments, the sulfonic acid monomer solution is prepared by dissolving the sulfonic acid monomer in an aqueous ethanol solution; the sulfonic acid monomer has one of the following structures:

[0064] .

[0065] In this invention, the ethanol aqueous solution is prepared by water and ethanol in a volume ratio of 1:1.

[0066] In some embodiments, the molar ratio of guanidine monomer to sulfonic acid monomer in the reaction system is 1:1.

[0067] In some embodiments, the concentration of the hydrogen-bonded framework material additive containing amino and sulfonic acid groups in the high-voltage low-temperature electrolyte is 1-5 mg / mL.

[0068] In some embodiments, the sodium salt solution consists of a sodium salt and an organic solvent; the concentration of the sodium salt is 0.5-2 mol / L.

[0069] In some embodiments, the sodium salt is at least one of sodium hexafluorophosphate, sodium perchlorate, sodium bis(fluorosulfonyl)imide, sodium bis(trifluoromethanesulfonyl)imide, sodium trifluoromethanesulfonate, sodium bis(oxalateborate), and sodium difluorooxalateborate, preferably sodium hexafluorophosphate.

[0070] In some embodiments, the organic solvent is at least one selected from ethylene carbonate, fluoroethylene carbonate, vinylene carbonate, propylene carbonate, butene carbonate, dimethyl carbonate, diethyl carbonate, methyl ethyl carbonate, methyl propyl carbonate, methyl formate, methyl acetate, methyl butyrate, ethyl propionate, ethyl butyrate, butyl acetate, methyl propionate, propyl butyrate, trimethyl phosphate, triethyl phosphate, sulfolane, dimethyl sulfone, dimethyl sulfoxide, ethyl methyl sulfone, ethylene sulfite, propylene sulfite, dimethyl sulfite, diethyl sulfite, methyl (2,2,2-trifluoroethyl) carbonate, methyl trifluoroacetate, acetonitrile, and 1,3-dioxolane, preferably at least one selected from ethylene carbonate and methyl ethyl carbonate.

[0071] A second aspect of the present invention provides a sodium-ion battery, comprising a positive electrode, a negative electrode, and the aforementioned high-voltage low-temperature electrolyte.

[0072] In some embodiments, the positive electrode is one of a transition metal layered oxide, a polyanionic compound, Prussian blue, or a Prussian blue analogue.

[0073] In some embodiments, the negative electrode is one of carbon material, metallic sodium, alloy material, transition metal oxide, transition metal sulfide, transition metal phosphide, and transition metal selenide.

[0074] The present invention will be further described below through specific embodiments.

[0075] In the following examples, Na 0.85 Li 0.12 Ni 0.22 Mn 0.66 O2 was purchased from Youyan platform; Na3V2(PO4)2F3 was purchased from Kelude.

[0076] Example 1

[0077] The high-voltage, low-temperature electrolyte provided in this embodiment is obtained through a preparation method including the following process:

[0078] (1) Preparation of hydrogen-bonded framework material additives:

[0079] S1. Dissolve 1.0 mmol of guanidine monomer in an aqueous ethanol solution to prepare a guanidine monomer solution; wherein the aqueous ethanol solution is obtained by mixing water and ethanol in a volume ratio of 1:1.

[0080] The structural formula of the guanidine monomer is as follows:

[0081] ;

[0082] S2. Dissolve 1.0 mmol of sulfonic acid monomer in an aqueous ethanol solution to prepare a sulfonic acid monomer solution; wherein the aqueous ethanol solution is obtained by mixing water and ethanol in a volume ratio of 1:1.

[0083] The structural formula of the sulfonic acid monomer is as follows:

[0084] ;

[0085] S3. Under constant stirring at room temperature, the guanidine monomer solution is added dropwise to the sulfonic acid monomer solution to obtain the reaction system;

[0086] S4. Allow the reaction system to stand, allow the solvent to evaporate at room temperature, and collect the solid product by vacuum filtration.

[0087] S5. After washing the solid product with ethanol, dry it in a vacuum drying oven at 50 °C for 12 h to obtain a hydrogen bond framework material additive.

[0088] (2) In a glove box, sodium hexafluorophosphate (NaPF6) is added to a mixed solvent to prepare a sodium salt solution; the concentration of NaPF6 in the sodium salt solution is 1.0 mol / L; wherein the mixed solvent is obtained by mixing ethylene carbonate (EC) and ethyl methyl carbonate (EMC) in a volume ratio of 3:7;

[0089] (3) Add the hydrogen bond framework material additive to the sodium salt solution to make the final concentration of the hydrogen bond framework material additive 1.0 mg / mL, stir at room temperature for 12 h, mix evenly, and obtain a high voltage low temperature electrolyte.

[0090] Example 2

[0091] The high-voltage, low-temperature electrolyte provided in this embodiment is basically the same as that in Example 1, except that:

[0092] In step (3), the final concentration of the hydrogen bond framework material additive is 2 mg / mL.

[0093] Example 3

[0094] The high-voltage, low-temperature electrolyte provided in this embodiment is basically the same as that in Example 1, except that:

[0095] In step (1), the structural formula of the sulfonic acid monomer is as follows:

[0096] .

[0097] Example 4

[0098] The high-voltage, low-temperature electrolyte provided in this embodiment is basically the same as that in Example 3, except that:

[0099] In step (3), the final concentration of the hydrogen bond framework material additive is 2 mg / mL.

[0100] Example 5

[0101] The high-voltage low-temperature electrolyte provided in this embodiment is basically the same as that in Example 1, except that:

[0102] In step (2), the concentration of NaPF6 in the sodium salt solution is 1.2 mol / L.

[0103] Example 6

[0104] The high-voltage, low-temperature electrolyte provided in this embodiment is basically the same as that in Example 1, except that:

[0105] In step (3), the final concentration of the hydrogen bond framework material additive is 3 mg / mL.

[0106] Example 7

[0107] The high-voltage, low-temperature electrolyte provided in this embodiment is basically the same as that in Example 3, except that:

[0108] In step (2), the final concentration of NaPF6 in the sodium salt solution is 1.2 mol / L.

[0109] Example 8

[0110] The high-voltage, low-temperature electrolyte provided in this embodiment is basically the same as that in Example 3, except that:

[0111] In step (3), the final concentration of the hydrogen bond framework material additive is 3 mg / mL.

[0112] Comparative Example 1

[0113] The electrolyte provided in this comparative example is obtained by a preparation method including the following process:

[0114] In a glove box, sodium hexafluorophosphate (NaPF6) is added to a mixed solvent to prepare an electrolyte; the concentration of NaPF6 in the electrolyte is 1.0 mol / L; wherein the mixed solvent is obtained by mixing ethylene carbonate (EC) and ethyl methyl carbonate (EMC) in a volume ratio of 3:7.

[0115] Comparative Example 2

[0116] The electrolyte provided in this comparative example is obtained by a preparation method including the following process:

[0117] In a glove box, sodium hexafluorophosphate (NaPF6) is added to a mixed solvent to prepare an electrolyte; the concentration of NaPF6 in the electrolyte is 1.2 mol / L; wherein the mixed solvent is obtained by mixing ethylene carbonate (EC) and ethyl methyl carbonate (EMC) in a volume ratio of 3:7.

[0118] Performance testing

[0119] 1. The hydrogen-bonded framework material additive in Example 1 of this invention was subjected to X-ray diffraction (XRD) and scanning electron microscopy (SEM) tests, such as... Figure 1 and Figure 2 As shown; Figure 1 The image shows the XRD pattern of the hydrogen-bonded framework material additive in Example 1 of this invention. Figure 2 This is a SEM image of the hydrogen-bonded framework material additive in Example 1 of the present invention.

[0120] Depend on Figure 1 It can be seen that hydrogen-bonded framework material additives have significant crystal structure characteristics.

[0121] Depend on Figure 2 It can be seen that the hydrogen bond framework material additive has a composite structure with plate-like and needle-like morphologies.

[0122] 2. Infrared and Raman spectroscopy tests were performed on the hydrogen-bonded framework material additive in Example 1 of this invention, such as... Figure 3 and Figure 4 As shown; Figure 3 The infrared spectrum of the hydrogen-bonded framework material additive in Example 1 of this invention; Figure 4 This is the Raman spectrum of the hydrogen-bonded framework material additive in Example 1 of the present invention.

[0123] Depend on Figure 3 It can be seen that in the infrared spectrum corresponding to the hydrogen-bonded framework material additive, at 1200 cm⁻¹... -1 A characteristic peak representing the stretching vibration of the S=O bond in the sulfonic acid group is present nearby, at 3250 cm⁻¹. -1 The region exhibits characteristic peaks representing the stretching vibrations of the NH bond in amino groups, and characteristic peaks for C=C and CH in the aromatic skeleton were also observed. Figure 4 It can be seen that in the Raman spectrum corresponding to the hydrogen-bonded framework material additive, at 1100 cm⁻¹... -1 The characteristic peak representing the stretching vibration of the S=O bond in the sulfonic acid group is present at 1350 cm⁻¹. -1The presence of a characteristic peak representing the stretching vibration of the NH bond in the amino group indicates that the hydrogen-bonded framework material additive prepared using guanidine monomers and sulfonic acid monomers does not alter the framework of either monomer. The inventors analyzed that this is because there is a strong electrostatic attraction between the positively charged nitrogen atom of the guanidine monomer and the negatively charged oxygen atom of the sulfonic acid monomer, allowing them to be connected via intermolecular hydrogen bonds, rather than through a chemical reaction of their covalent frameworks. This strong electrostatic attraction enables the two monomers to construct a long-range ordered and stable hydrogen bond network structure, forming a hydrogen-bonded framework material additive with a hydrogen bond network structure.

[0124] 3. The ionic conductivity of the high-voltage low-temperature electrolyte in Example 1 and the electrolyte in Comparative Example 1 were tested respectively. Figure 5 As shown; Figure 5 The ionic conductivity of the high-voltage low-temperature electrolyte in Example 1 and the electrolyte in Comparative Example 1 at different temperatures.

[0125] Depend on Figure 5 It can be seen that, in an environment with a temperature of -20 ℃, the ionic conductivity of the high-voltage low-temperature electrolyte in Example 1 is 4.43 mS cm⁻¹. -1 The ionic conductivity of the electrolyte in Comparative Example 1 was 1.61 mS / cm. -1 In an environment with a temperature of 25 °C, the ionic conductivity of the high-voltage low-temperature electrolyte in Example 1 is 7.92 mS / cm. -1 The ionic conductivity of the electrolyte in Comparative Example 1 was 4.63 mS / cm. -1 The above results show that, compared with Comparative Example 1, the low-temperature ionic conductivity and room-temperature ionic conductivity of the high-voltage low-temperature electrolyte in Example 1 of the present invention are significantly improved. The inventors analyzed that the reason may be that the hydrogen bond network structure of the hydrogen bond framework material additive can promote the dissolution of sodium salt (sodium hexafluorophosphate) and the dissociation of ion pairs (such as sodium ions and anions), thereby increasing the concentration of freely moving sodium ions and improving the ionic conductivity.

[0126] 4. Electrochemical window tests were performed on the high-voltage low-temperature electrolyte in Example 1 and the electrolyte in Comparative Example 1, respectively. Figure 6 As shown; Figure 6 The electrochemical window test results are for the high-voltage low-temperature electrolyte in Example 1 and the electrolyte in Comparative Example 1 of this invention.

[0127] Depend on Figure 6It can be seen that the electrochemical window of the electrolyte in Comparative Example 1 is 4.29 V, while the electrochemical window of the high-voltage low-temperature electrolyte in Example 1 of the present invention can reach 4.95 V. This indicates that the high-voltage low-temperature electrolyte provided by the present invention has excellent antioxidant capacity, can achieve long-term antioxidant and interface stabilization protection under high voltage conditions, and can be adapted to high-voltage cathode materials.

[0128] 6. To illustrate the electrochemical performance of the high-voltage, low-temperature electrolyte provided in the embodiments of the present invention, the high-voltage, low-temperature electrolytes in Examples 1-8 and the electrolytes in Comparative Examples 1-2 were used as electrolyte samples for the assembly of sodium-ion batteries: the positive electrode material, conductive agent Super P, and binder PVDF were prepared into a working electrode at a mass ratio of 8:1:1, and a sodium sheet was used as the counter electrode. The electrolyte samples were then assembled together to form a coin-type sodium-ion battery; the positive electrode material was Na. 0.85 Li 0.12 Ni 0.22 Mn 0.66 O2 (denoted as cathode material 1) or Na3V2(PO4)2F3 (denoted as cathode material 2).

[0129] Test conditions: Constant current charge and discharge were performed at room temperature (25 ℃) or low temperature (-20 ℃), with a voltage range of 2.0-4.5 V. The assembled coin cell sodium-ion battery was pre-cycled for 3 cycles at a current density of 0.1 C, and then subjected to cyclic charge and discharge tests at a current density of 1 C. The test results are shown in Table 1.

[0130] Table 1. Electrochemical performance test results of Examples 1-8 and Comparative Examples 1-2

[0131]

[0132] As shown in Table 1, the sodium-ion battery assembled using the high-voltage low-temperature electrolyte provided in this embodiment of the invention exhibits higher low-temperature cycle stability, room-temperature cycle stability, and capacity retention than Comparative Examples 1-2. Compared to Comparative Example 1, under conditions of -20 ℃ or 25 ℃, current density of 1 C, and voltage window of 2.0-4.5 V, the high-voltage low-temperature electrolyte and Na+ provided in Example 1 demonstrate superior performance. 0.85 Li 0.12 Ni 0.22 Mn 0.66The sodium-ion battery assembled with O2 exhibits superior low-temperature cycling stability, room-temperature cycling stability, and capacity retention. Compared to Comparative Example 1, the sodium-ion battery assembled using the high-voltage low-temperature electrolyte and Na3V2(PO4)2F3 in Example 2 exhibits superior low-temperature cycling stability, room-temperature cycling stability, and capacity retention under conditions of -20 ℃ or 25 ℃, a current density of 1C, and a voltage window of 2.0-4.5 V. These results demonstrate that the high-voltage low-temperature electrolyte provided by this invention can be adapted to high-voltage cathode materials and exhibits excellent electrochemical performance under both low-temperature and room-temperature conditions.

[0133] In summary, the high-voltage low-temperature electrolyte provided in this embodiment of the invention exhibits excellent electrochemical performance and strong low-temperature adaptability under low-temperature conditions. Its electrochemical window can reach 4.95 V, and it has excellent antioxidant capacity, enabling long-term antioxidant and interface stabilization protection under high-voltage conditions. It can also be adapted to high-voltage cathode materials. Sodium-ion batteries assembled using the high-voltage low-temperature electrolyte and high-voltage cathode materials provided in this invention retain more than 80% of their capacity after 100 cycles at 2.0-4.5 V and 1 C, demonstrating excellent high-voltage stability.

[0134] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A high-voltage, low-temperature electrolyte, characterized in that, The additive includes a sodium salt solution and a hydrogen-bonded framework material containing amino and sulfonic acid groups; the hydrogen-bonded framework material containing amino and sulfonic acid groups includes guanidine monomer structural units and sulfonic acid monomer structural units, which are connected by hydrogen bonds to form a network structure; the morphology of the hydrogen-bonded framework material containing amino and sulfonic acid groups includes a composite structure of plate-like and needle-like structures. The structural formula of the guanidine monomer structural unit is shown in formula (1): ； In equation (1), Indicates the center of positive charge; The sulfonic acid monomer structural unit is one of formulas (2), (3), (4), and (5): ； In equations (2) to (5), It represents the center of negative charge.

2. The high-voltage low-temperature electrolyte according to claim 1, characterized in that, The hydrogen-bonded framework material additive containing amino and sulfonic acid groups is obtained by a preparation method including the following process: The guanidine monomer solution was added to the sulfonic acid monomer solution at room temperature with continuous stirring to obtain the reaction system; The reaction system was allowed to stand, and the solvent was evaporated at room temperature. The solid product was then collected by decantation or vacuum filtration. The solid product is washed and dried to obtain the hydrogen-bonded framework material additive containing amino and sulfonic acid groups.

3. The high-voltage low-temperature electrolyte according to claim 2, characterized in that, The guanidine monomer solution is prepared by dissolving the guanidine monomer in an aqueous ethanol solution; the structural formula of the guanidine monomer is as follows: ； The sulfonic acid monomer solution is prepared by dissolving the sulfonic acid monomer in an aqueous ethanol solution; the sulfonic acid monomer has one of the following structures: 。 4. The high-voltage low-temperature electrolyte according to claim 2, characterized in that, In the reaction system, the molar ratio of guanidine monomer to sulfonic acid monomer is 1:

1.

5. The high-voltage low-temperature electrolyte according to claim 1, characterized in that, In the high-voltage low-temperature electrolyte, the concentration of the hydrogen-bonded framework material additive containing amino and sulfonic acid groups is 1-5 mg / mL.

6. The high-voltage low-temperature electrolyte according to claim 1, characterized in that, The sodium salt solution is composed of sodium salt and organic solvent; The concentration of the sodium salt is 0.5-2 mol / L.

7. The high-voltage low-temperature electrolyte according to claim 6, characterized in that, The sodium salt is at least one of sodium hexafluorophosphate, sodium perchlorate, sodium bis(fluorosulfonyl)imide, sodium bis(trifluoromethanesulfonyl)imide, sodium trifluoromethanesulfonate, sodium bis(oxalateborate), and sodium difluorooxalateborate.

8. The high-voltage low-temperature electrolyte according to claim 6, characterized in that, The organic solvent is at least one of ethylene carbonate, fluoroethylene carbonate, vinylene carbonate, propylene carbonate, butene carbonate, dimethyl carbonate, diethyl carbonate, methyl ethyl carbonate, methyl propyl carbonate, methyl formate, methyl acetate, methyl butyrate, ethyl propionate, ethyl butyrate, butyl acetate, methyl propionate, propyl butyrate, trimethyl phosphate, triethyl phosphate, sulfolane, dimethyl sulfone, dimethyl sulfoxide, ethyl methyl sulfone, ethylene sulfite, propylene sulfite, dimethyl sulfite, diethyl sulfite, methyl (2,2,2-trifluoroethyl) carbonate, methyl trifluoroacetate, acetonitrile, and 1,3-dioxolane.

9. A sodium-ion battery, characterized in that, It includes a positive electrode, a negative electrode, and the high-voltage low-temperature electrolyte as described in any one of claims 1-8.

10. The sodium-ion battery according to claim 9, characterized in that, The positive electrode is one of the following: a transition metal layered oxide, a polyanionic compound, Prussian blue, or a Prussian blue analogue; And / or, the negative electrode is one of carbon materials, metallic sodium, alloy materials, transition metal oxides, transition metal sulfides, transition metal phosphides, and transition metal selenides.

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