Additive for secondary battery, non-aqueous electrolyte and secondary battery
By using oxalate sulfonamide compounds and fluorinated sulfonamide salts to form a stable SEI film in secondary batteries, the problem of impedance growth during long-term storage and use of secondary batteries is solved, thereby improving the power performance and safety of the batteries.
Patent Information
- Application Number
- CN202410572951.X
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2024-05-10
- Publication Date
- 2025-11-11
AI Technical Summary
During long-term storage and use, the internal impedance of existing secondary batteries increases, leading to a decrease in battery power performance and reduced safety. In particular, overpotential and irreversible lithium plating are prone to occur during high-rate charging.
Using oxalic acid sulfonamide compounds as additives, combined with fluorinated sulfonamide salts, a kinetically and thermally stable SEI film is formed. During long-term cycling, the broken SEI film is continuously repaired, impedance growth is suppressed, and the electrolyte solvation structure is optimized to improve lithium ion distribution.
Maintaining low impedance in the initial state of the battery, as well as during long-term storage and cycling, improves battery power performance, suppresses side reactions, and enhances overall battery performance.
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Figure CN120933466A_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the field of electrolytes, and in particular to the application of an oxalate sulfonamide compound that achieves stable input or output power during long-term storage or long-term cycling as an additive for secondary battery electrolytes, as well as a non-aqueous electrolyte containing the oxalate sulfonamide compound and its application in secondary batteries. Background Technology
[0002] In recent years, the stability of new energy vehicles during long-term use has become a core concern for car owners. Therefore, the stability of battery input / output power during long-term storage and use is receiving increasing attention. Battery internal impedance is one of the important standards for evaluating the power performance of lithium-ion batteries. Excessive internal impedance can lead to significant internal polarization during charging and discharging, thus affecting battery power output and generating more side reactions under extreme conditions. For example, if the internal polarization is large during high-rate charging, overpotential can easily occur, leading to irreversible lithium plating at the negative electrode, further reducing battery capacity and safety.
[0003] Therefore, it is both necessary and urgent to propose an additive that can achieve low initial impedance of secondary batteries and effectively suppress impedance growth during long-term storage / use, and to apply it to secondary batteries to improve battery power performance. Summary of the Invention
[0004] To address the aforementioned technical problems, this invention proposes a secondary battery additive, a non-aqueous electrolyte for secondary batteries, and a secondary battery thereof, which improves the initial power performance and power performance during long-term storage or cycling.
[0005] The objective of this invention is achieved through the following technical solution:
[0006] An additive for secondary batteries comprises at least one of the oxalic acid sulfonamide compounds shown in structural formulas (I) to (IV):
[0007]
[0008] In formulas (I) to (IV), R is a hydrogen atom, a substituted or unsubstituted C1-C6 alkyl group, a substituted or unsubstituted C2-C6 alkenyl group, a substituted or unsubstituted C2-C6 alkynyl group, a substituted or unsubstituted C3-C7 cycloalkyl group, or a substituted or unsubstituted C3-C7 cycloalkenyl group; M is H, Li, Na, or K.
[0009] Preferably, R is a hydrogen atom, a substituted or unsubstituted C1-C3 alkyl group, a substituted or unsubstituted C2-C4 alkenyl group, or a substituted or unsubstituted C2-C4 alkynyl group; M is H, Li, or Na.
[0010] Preferably, the oxalic acid sulfonamide compound represented by structural formulas (I) to (IV) is at least one of the compounds shown in the following structures:
[0011]
[0012]
[0013] A non-aqueous electrolyte for secondary batteries comprises any of the oxalic acid sulfonamide compounds shown in structural formulas (I) to (IV) above, wherein the amount of the compound is 0.001 to 3.0 wt% of the total mass of the electrolyte.
[0014] Although the mechanism of action of the additive proposed in this invention is still not fully understood, characterization by gas chromatography (GC), X-ray photoelectron spectroscopy (XPS), and electrochemical performance testing suggest that the additive can alter the main components and thickness of the electrolyte-electrode interface (SEI) film during battery formation and capacity testing, thereby forming an SEI film with superior kinetic and thermal stability. Furthermore, it is speculated that this compound is a consumable additive and will not completely react during the initial stages of battery fabrication and testing. Instead, it continuously repairs ineffective components of the SEI film during long-term battery cycling, ensuring a low impedance effect throughout the initial battery state and during long-term storage and cycling, thus improving battery power performance.
[0015] The non-aqueous electrolyte for the secondary battery also contains fluorosulfonyl imide salt, with a dosage of 0.2 to 18.0 wt% of the total electrolyte mass.
[0016] Preferably, the fluorosulfonyl imide salt is at least one of lithium bis(fluorosulfonyl imide) (LiFSI), lithium bis(trifluoromethanesulfonyl imide) (LiTFSI), sodium bis(fluorosulfonyl imide) (NaFSI), or sodium bis(trifluoromethanesulfonyl imide) (NaTFSI), and is used in an amount of 0.5 to 15.0 wt% of the total mass of the electrolyte.
[0017] Although the interaction mechanism between the fluorosulfonyl imide salt and the additive proposed in this invention is still not fully understood, extensive experimental data have revealed that the fluorosulfonyl imide salt itself, as a compound that inhibits impedance growth during battery use and storage, can further suppress impedance growth when used in conjunction with the oxalic acid sulfonamide compound, achieving an effect exceeding that of using a single compound. It is speculated that the simultaneous presence of the two alters the overall solvation structure of the electrolyte, thereby changing the ion / compound distribution in the double-layer liquid phase (electrolyte diffusion layer) during charging and discharging, effectively suppressing side reactions in this process, and inhibiting SEI interface and impedance growth.
[0018] The non-aqueous electrolyte for the secondary battery also contains a non-aqueous solvent, which is selected from at least one of C3-C6 carbonate or fluorocarbonate compounds, C3-C8 carboxylic acid esters or fluorocarboxylic acid ester compounds, sulfone compounds or ether compounds;
[0019] Preferably, the C3-C6 carbonate or fluorocarbonate compound is selected from at least one of ethylene carbonate, fluoroethylene carbonate, propylene carbonate, butenyl carbonate, dimethyl carbonate, methyl ethyl carbonate, diethyl carbonate, dipropyl carbonate, methyl propyl carbonate, or ethyl propyl carbonate; the C3-C8 carboxylic acid ester or fluorocarboxylic acid ester compound is selected from at least one of γ-butyrolactone, methyl acetate, methyl propionate, methyl butyrate, ethyl acetate, ethyl propionate, ethyl butyrate, propyl acetate, or propyl propionate; the sulfone compound is selected from at least one of sulfolane, dimethyl sulfoxide, dimethyl sulfone, or diethyl sulfone; and the ether compound is selected from at least one of triethylene glycol dimethyl ether, tetraethylene glycol dimethyl ether, ethylene glycol dimethyl ether, or dioxolane.
[0020] The non-aqueous electrolyte for the secondary battery also contains other electrolyte salts, which are selected from at least one of lithium hexafluorophosphate (LiPF6), lithium tetrafluoroborate, lithium hexafluoroarsenate, lithium perchlorate, lithium bis(oxalate)borate, lithium difluorooxalateborate, lithium tetrafluorooxalate phosphate, lithium tri(oxalate) phosphate, lithium difluorodi(oxalate) phosphate, sodium hexafluorophosphate (NaPF6), sodium tetrafluoroborate, sodium perchlorate, and sodium difluorophosphate.
[0021] The non-aqueous electrolyte for the secondary battery further contains a basic additive selected from at least one of vinylene carbonate (VC), fluoroethylene carbonate, vinyl sulfate, vinyl sulfite, 4,4'-ethylene bisulfate, 1,4-dioxane disulfate, tris(trimethylsilyl) phosphate, tris(trimethylsilyl) borate, 1,3-propane sulpholol (PS), 1,3-propene sulpholol, adiponitrile (ADN), cyclohexylbenzene, lithium difluorophosphate, lithium difluorodioxolane phosphate, lithium dioxolane borate, lithium difluorodioxolane borate (LiDFOB), sodium difluorophosphate, sodium difluorodioxolane phosphate, sodium dioxolane borate, and sodium difluorodioxolane borate, such that any one basic additive accounts for 0.1 to 5.0 wt% of the total mass of the electrolyte.
[0022] In one specific embodiment, a lithium-ion battery electrolyte is provided, wherein the electrolyte salt is preferably LiFSI and LiPF6, accounting for 12.5 wt% of the total mass of the electrolyte; the non-aqueous solvent is preferably at least one of ethylene carbonate (EC), ethyl methyl carbonate (EMC), and diethyl carbonate (DEC), more preferably a mixed solvent of EC, EMC, and DEC, and the mass ratio of the three is EC:EMC:DEC = 3:5:2; the additives include: vinylene carbonate, 1,3-propanesulfonyl lactone, and lithium difluorooxalate borate, accounting for 0.5 to 2 wt% of the total mass of the electrolyte.
[0023] In another specific embodiment, a sodium-ion battery electrolyte is provided, wherein the electrolyte salt is preferably NaFSI and NaPF6, accounting for 14 wt% of the total mass of the electrolyte; the non-aqueous solvent is preferably at least one of diethyl carbonate (DEC), ethyl methyl carbonate (EMC), and propylene carbonate (PC), more preferably a mixed solvent of DEC, EMC, and PC, and the mass ratio of the three is PC:EMC:DMC = 3:5:2; the additive includes 1,3-propenyl sulfonyl lactone, accounting for 0.5 to 2 wt% of the total mass of the electrolyte.
[0024] A secondary battery includes a positive electrode, a negative electrode, and a separator, characterized in that: the secondary battery is filled with any of the above-mentioned non-aqueous electrolytes for secondary batteries.
[0025] Specifically, the positive electrode is selected from at least one of lithium cobalt oxide, lithium iron phosphate, lithium nickel manganese oxide, lithium nickel cobalt manganese oxide ternary materials, other lithium-containing layered oxides, sodium-containing layered oxides, Prussian blue / white, and polyanions (sodium iron phosphate, sodium vanadium phosphate, etc.), and the negative electrode is selected from graphite, silicon-carbon composite materials, lithium titanate, lithium metal, hard carbon, anthracite soft carbon, hard-soft composite carbon, etc.
[0026] Compared with the prior art, the beneficial effects of the present invention are as follows:
[0027] 1. By using the oxalate sulfonamide compound described in this invention, the main components and thickness of the electrolyte-electrode interface (SEI) film can be changed during battery formation and capacity testing, thereby forming an SEI film with superior kinetic and thermal stability. At the same time, it is speculated that this compound is a consumable additive and will not completely react in the early stages of battery manufacturing and testing. Instead, it has a continuous repair function for the broken SEI film during long-term battery cycling, thereby ensuring that the battery maintains a low impedance effect in the initial state and during long-term storage and cycling, thus improving the battery power performance.
[0028] 2. The combined use of fluorosulfonyl imide salt and the oxalic acid sulfonamide compound can further suppress impedance growth, achieving an effect beyond that of using a single compound. It is speculated that the simultaneous presence of the two alters the overall solvation structure of the electrolyte, thereby changing the ion / compound distribution in the double-layer liquid phase (electrolyte diffusion layer) during charging and discharging, effectively suppressing side reactions in this process, and inhibiting SEI interface and impedance growth.
[0029] 3. When selecting different positive and negative electrode materials, this invention requires matching different combinations of solvents, lithium salts and additives to achieve better interface optimization and ensure the reversible cycling of lithium ions during the charging and discharging process, thereby improving the overall performance of the battery. Detailed Implementation
[0030] The present invention will be further described below with reference to specific embodiments, but the invention is not limited to these specific embodiments. Those skilled in the art should recognize that the present invention covers all alternatives, improvements, and equivalents that may be included within the scope of the claims.
[0031] I. Electrolyte and Battery Preparation
[0032] The solvents were mixed uniformly according to the data in Table 1 below. Then, the electrolyte was slowly added to the mixed solution and mixed evenly. After mixing evenly, the additive compound was added quantitatively and mixed evenly to form an electrolyte.
[0033] Table 1 Electrolyte Formulation
[0034]
[0035]
[0036] The electrolytes from Examples 1-15 and Comparative Examples 1-6 were used to fabricate 3600mA pouch-type secondary batteries. Each secondary battery includes a positive electrode, a negative electrode, a separator, an electrolyte, and battery auxiliary materials. Details of the positive and negative active materials are shown in Table 2 below. The preparation process is as follows: The positive electrode, separator, and negative electrode are wound together into a core, sealed with an aluminum-plastic film, and then baked to ensure the electrode moisture content meets requirements. After baking, the cell is injected with electrolyte, and after standing, formation, capacity testing, and aging processes, the finished pouch-type secondary battery cell is obtained.
[0037] II. Electrochemical Performance Testing
[0038] The performance of the secondary batteries prepared above was tested, mainly including:
[0039] (1) Initial impedance test:
[0040] During the battery capacity grading stage: At room temperature (25℃), charge the battery with a constant current of 0.2C until the charging cutoff voltage, and then charge it with a constant voltage until the current drops to 0.05C; then discharge the battery with a constant current of 0.2C until the discharge cutoff voltage, and record the discharge capacity C1, which is the initial capacity of the battery.
[0041] Then charge at a constant current of 0.2C until the charging cutoff voltage, and charge at a constant voltage until the current drops to 0.05C; then discharge at a constant current of 0.2C until the capacity reaches 0.5*C1, which is 50% SOC state of charge, let stand for 2 hours, and record the voltage U1.
[0042] Finally, discharge the battery at a constant current of 4C for 30 seconds, record the voltage U2, and calculate the initial impedance R1 of the battery:
[0043] Initial impedance R1 = (U1 - U2) / (4 × C1)
[0044] (2) Impedance test after long-term storage / cycling:
[0045] Batteries that have been stored at 100SOC and 60℃ for 60 days, or have undergone high-temperature cycling for 500 cycles, are charged at room temperature (25℃) with a constant current of 0.2C to the charging cutoff voltage, and then charged at a constant voltage until the current drops to 0.05C; then discharged at a constant current of 0.2C to the discharge cutoff voltage, and the discharge capacity C2 is recorded, which is the battery cutoff capacity.
[0046] Then charge at a constant current of 0.2C until the charging cutoff voltage, and charge at a constant voltage until the current drops to 0.05C; then discharge at a constant current of 0.2C until the capacity reaches 0.5*C2, which is 50% SOC state of charge, let stand for 2 hours, and record the voltage U3.
[0047] Discharge the battery at a constant current of 4C for 30 seconds, record the voltage U4, and calculate the battery cutoff impedance R2 and impedance growth rate R%.
[0048] Cut-off impedance R2 = (U3 - U4) / (4 × C2)
[0049] Impedance growth rate R% = (R2 / R1-1) × 100%
[0050] The specific test results are shown in Table 2 below:
[0051] Table 2. Results of positive and negative electrode materials and electrochemical tests
[0052]
[0053]
[0054] By comparing Examples 1 and 2 with Comparative Example 1, or Examples 3-7 with Comparative Example 2, or Examples 8-11 with Comparative Example 3, or Examples 13 with Comparative Example 4, or Examples 14 and 15 with Comparative Example 6, it can be seen that the oxalic acid sulfonamide-based additive proposed in this invention can suppress the problem of initial impedance and impedance growth after long-term storage or cycling in secondary battery systems with different positive and negative electrode materials, thereby improving the power performance of the battery.
[0055] Comparing Examples 3-7 and Comparative Example 2, it can be seen that the use of this additive in the range of 0.001-3% by mass has a better effect.
[0056] Comparing Examples 8 and 12 with Comparative Examples 3 and 5, it can be seen that when fluorosulfonamide salts are used alone, they have only a limited inhibitory effect on impedance growth. However, when fluorosulfonamide salts are used in electrolytes containing oxalate sulfonamide additives, the impedance inhibition effect can be significantly enhanced, thus demonstrating the interaction between the two.
[0057] By comparing Examples 1, 2, 8-11, 14, and 15, it can be seen that when different positive and negative electrode materials are selected, the selection of corresponding solvents, lithium salts, and additives can improve the interface stability of the corresponding battery system, thereby improving battery performance.
Claims
1. The application of an oxalic acid sulfonamide compound as an additive in secondary battery electrolytes, characterized in that: The structures of the oxalic acid sulfonamide compounds are shown in formulas (I) to (IV) below: In formulas (I) to (IV), R is selected from hydrogen atom, substituted or unsubstituted C1-C6 alkyl, substituted or unsubstituted C2-C6 alkenyl, substituted or unsubstituted C2-C6 alkynyl, substituted or unsubstituted C3-C7 cycloalkyl, and substituted or unsubstituted C3-C7 cycloalkenyl; M is selected from H, Li, Na, or K.
2. The application of the oxalate sulfonamide compound according to claim 1 as an additive in secondary battery electrolytes, characterized in that: R is selected from hydrogen atom, substituted or unsubstituted C1-C3 alkyl, substituted or unsubstituted C2-C4 alkenyl, substituted or unsubstituted C2-C4 alkynyl; M is selected from H, Li or Na.
3. The application of the oxalate sulfonamide compound according to claim 2 as an additive in secondary battery electrolytes, characterized in that: The oxalic acid sulfonamide compound is selected from compounds with the following structures:
4. A non-aqueous electrolyte for secondary batteries, comprising an electrolyte salt and a non-aqueous solvent, characterized in that: The non-aqueous electrolyte includes at least one of the oxalic acid sulfonamide compounds according to any one of claims 1-3, and the amount of the compound is 0.001 to 3.0 wt% of the total mass of the electrolyte.
5. The non-aqueous electrolyte for secondary batteries according to claim 4, characterized in that: The non-aqueous electrolyte also contains fluorosulfonyl imide salt, accounting for 0.2 to 18.0 wt% of the total mass of the electrolyte.
6. The non-aqueous electrolyte for secondary batteries according to claim 5, characterized in that: The fluorosulfonyl imide salt is selected from at least one of lithium bis(fluorosulfonyl imide), lithium bis(trifluoromethylsulfonyl imide), sodium bis(fluorosulfonyl imide), or sodium bis(trifluoromethylsulfonyl imide), and is used in an amount of 0.5 to 15.0 wt% of the total mass of the electrolyte.
7. The non-aqueous electrolyte for secondary batteries according to claim 4, characterized in that: The non-aqueous solvent in the non-aqueous electrolyte is selected from at least one of C3-C6 carbonate or fluorocarbonate compounds, C3-C8 carboxylic acid esters or fluorocarboxylic acid ester compounds, sulfone compounds or ether compounds; Preferably, the C3-C6 carbonate or fluorocarbonate compound is selected from at least one of ethylene carbonate, fluoroethylene carbonate, propylene carbonate, butenyl carbonate, dimethyl carbonate, methyl ethyl carbonate, diethyl carbonate, dipropyl carbonate, methyl propyl carbonate, or ethyl propyl carbonate; the C3-C8 carboxylic acid ester or fluorocarboxylic acid ester compound is selected from at least one of γ-butyrolactone, methyl acetate, methyl propionate, methyl butyrate, ethyl acetate, ethyl propionate, ethyl butyrate, propyl acetate, or propyl propionate; the sulfone compound is selected from at least one of sulfolane, dimethyl sulfoxide, dimethyl sulfone, or diethyl sulfone; and the ether compound is selected from at least one of triethylene glycol dimethyl ether, tetraethylene glycol dimethyl ether, ethylene glycol dimethyl ether, or dioxolane.
8. The non-aqueous electrolyte for secondary batteries according to claim 4, characterized in that: The electrolyte salt in the non-aqueous electrolyte is selected from at least one of lithium hexafluorophosphate, lithium tetrafluoroborate, lithium hexafluoroarsenate, lithium perchlorate, lithium bis(oxalate)borate, lithium difluorooxalateborate, lithium tetrafluorooxalate phosphate, lithium tri(oxalate) phosphate, lithium difluorodi(oxalate) phosphate, sodium hexafluorophosphate, sodium tetrafluoroborate, sodium perchlorate, and sodium difluorophosphate.
9. The non-aqueous electrolyte for secondary batteries according to any one of claims 4-8, characterized in that: The non-aqueous electrolyte further includes a basic additive selected from at least one of vinylene carbonate, fluoroethylene carbonate, vinyl sulfate, vinyl sulfite, 4,4'-diethylene sulfate, 1,4-dioxane disulfate, tris(trimethylsilyl)phosphate, tris(trimethylsilyl)borate, 1,3-propanesulfonyl lactone, 1,3-propenesulfonyl lactone, adiponitrile, cyclohexylbenzene, lithium difluorophosphate, lithium difluorodioxalate phosphate, lithium dioxalate borate, lithium difluorodioxalate borate, sodium difluorophosphate, sodium difluorodioxalate phosphate, sodium dioxalate borate, and sodium difluorodioxalate borate, such that any one basic additive accounts for 0.1 to 5.0 wt% of the total mass of the electrolyte.
10. A secondary battery, comprising a positive electrode, a negative electrode, and a separator, characterized in that: The secondary battery is filled with the non-aqueous electrolyte for secondary batteries as described in any one of claims 4-9.
11. The secondary battery according to claim 10, characterized in that: The active material of the positive electrode is selected from lithium cobalt oxide, lithium iron phosphate, lithium nickel manganese oxide, lithium nickel cobalt manganese oxide ternary materials, other lithium-containing layered oxides, sodium-containing layered oxides, Prussian blue / white or polyanionic oxides; the active material of the negative electrode is selected from graphite, silicon-carbon composite material, lithium titanate, lithium metal, hard carbon, anthracite soft carbon or hard-soft composite carbon.