Non-aqueous electrolyte for secondary battery and secondary battery
By using a non-aqueous electrolyte of sulfonamide compounds and bis(fluorosulfonyl)imide salt in a secondary battery, a stable SEI film is formed, which solves the problem of capacity loss and power reduction caused by interfacial reactions at high temperatures in secondary batteries, and achieves better high-temperature cycling and storage performance.
Patent Information
- Application Number
- CN202410572952.4
- 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
Under high temperature and high voltage, the interfacial reaction between the positive electrode material and the electrolyte in secondary batteries intensifies, leading to battery capacity loss and power performance degradation, and affecting high-temperature storage and cycle performance.
A non-aqueous electrolyte containing sulfonamide compounds and bis(fluorosulfonyl)imide salt is used to form an SEI membrane with low interfacial impedance. The SEI component, which combines inorganic LiF and organic components, improves the stability of the membrane and the high-temperature cycling performance of the battery.
It effectively suppresses solvent decomposition and gas production, reduces initial impedance, improves high-temperature cycling performance and storage performance, and enhances the overall performance of the battery.
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Abstract
Description
Technical Field
[0001] This invention relates to the field of electrolytes, and in particular to a non-aqueous electrolyte for secondary batteries that can suppress solvent decomposition and gas production and improve the high-temperature cycle performance of full batteries, as well as its application in secondary batteries. Background Technology
[0002] In recent years, rechargeable batteries, as a new type of energy source, have been widely used in important fields such as next-generation information and communication, electric vehicles, energy storage power stations, and the energy internet. With the continuous deepening of research and technological development of rechargeable batteries, to achieve their widespread application in various fields, they need to simultaneously meet requirements such as high specific energy, long cycle life, high safety, high power, and low cost, possessing excellent comprehensive performance. Numerous studies have found that interfacial reactions occur between high-specific-energy cathode materials and electrolytes, especially under high temperature and high voltage conditions. Side reactions between the cathode surface and electrolyte intensify. For example, taking layered cathode materials NCM or NFM as examples, the dissolution of transition metal ions Ni and Mn is intensified, and the release of singlet oxygen from the cathode leads to the oxidative decomposition of the electrolyte and the loss of active lithium / sodium. This is reflected in the battery's electrochemical performance as phenomena such as gas generation and a continuous increase in DC impedance (DCIR), resulting in battery capacity loss and decreased power performance, severely affecting high-temperature storage and high-temperature cycling performance. Therefore, researching suitable high-temperature electrolytes and improving the interfacial stability between high-specific-energy electrodes and electrolytes has always been a hot topic in electrolyte development. Summary of the Invention
[0003] To address the aforementioned technical problems, this invention proposes a lithium / sodium ion battery electrolyte that can construct a low interfacial impedance SEI in secondary batteries. Furthermore, this SEI component exhibits superior thermal and mechanical stability, suppressing solvent decomposition and gas generation, and improving the high-temperature cycling performance of the full battery.
[0004] The objective of this invention is achieved through the following technical solution:
[0005] A non-aqueous electrolyte for secondary batteries, comprising an electrolyte salt, a non-aqueous solvent, and additives, characterized in that: the additives include at least:
[0006] The first additive is a sulfonamide compound with the structure shown in formula (I) and is used in an amount of 0.01 to 3.0 wt% of the total mass of the electrolyte.
[0007]
[0008] In formula (I), R is a halogen, a substituted or unsubstituted C1-C6 alkyl, a substituted or unsubstituted C2-C6 alkenyl, a substituted or unsubstituted C2-C6 alkynyl, a substituted or unsubstituted C3-C7 cycloalkyl, a substituted or unsubstituted C3-C7 cycloalkenyl, or -OR; M is H, Li, Na, or K.
[0009] The second additive is bis(fluorosulfonyl)imide salt, used in an amount of 0.05–18.0 wt% of the total electrolyte mass.
[0010] Regarding the structure of the first additive and the second additive, preferably, in formula (I), R is a halogen, a substituted or unsubstituted C1-C3 alkyl group or -OR; M is H, Li or Na.
[0011] More preferably, the sulfonamide compound represented by structural formula (I) is selected as at least one of the compounds shown in the following structures, and is used in an amount of 0.2 to 2.0 wt% of the total mass of the electrolyte.
[0012]
[0013]
[0014] When the electrolyte is used in a lithium-ion battery, the second additive, bis(fluorosulfonyl)imide salt, is preferably lithium bis(fluorosulfonyl)imide; when the electrolyte is used in a sodium-ion battery, the bis(fluorosulfonyl)imide salt is preferably sodium bis(fluorosulfonyl)imide. The amount of the bis(fluorosulfonyl)imide salt is 0.1 to 15.0 wt% of the total mass of the electrolyte.
[0015] The first additive of this invention, as a good film-forming additive, can preferentially decompose on the negative electrode surface to form a low-impedance electrolyte interface film. However, the SEI component generated by the decomposition of the above-mentioned substances is mainly organic, which generally has poor resistance to swelling by electrolyte solvents and poor high-temperature thermal stability, resulting in gas generation during high-temperature battery storage. By adding bis(fluorosulfonyl)imide salt, the generation of inorganic components LiF and Li2O can be promoted. Compared with the organic component SEI, LiF has a higher Young's modulus and is more lithium-repellent, thereby improving the stability of the SEI component. Experiments show that although LiFSI alone can improve the mechanical stability of the SEI and the high-temperature cycle performance of the battery, when the LiFSI addition is higher than 1%, the gas generation during high-temperature battery storage increases. The combined use of the two additives can solve the problems of insufficient gas generation during high-temperature storage and insufficient high-temperature capacity retention when using a single additive, while also achieving lower DCIR impedance and high-temperature cycle performance.
[0016] Preferably, the non-aqueous solvent 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;
[0017] More preferably, the C3-C6 carbonate or fluorocarbonate compound is selected from at least one of ethylene carbonate, propylene carbonate, butene 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.
[0018] When the electrolyte salt is used in lithium-ion batteries, it further includes at least one of lithium hexafluorophosphate, lithium tetrafluoroborate, lithium perchlorate, lithium bis(oxalato)borate, lithium difluorooxalato)borate, lithium bis(trifluoromethanesulfonyl)imide, lithium tetrafluorooxalatophosphate, lithium tri(oxalato)phosphate, and lithium difluorobis(oxalato)phosphate. When the electrolyte salt is used in sodium-ion batteries, it further includes at least one of sodium hexafluorophosphate, sodium tetrafluoroborate, sodium perchlorate, sodium bis(trifluoromethanesulfonyl)imide, and sodium difluorophosphate, in an amount accounting for 0.1% to 15.0 wt% of the total mass of the electrolyte.
[0019] The additives further include a base additive selected from at least one of vinylene carbonate, fluoroethylene carbonate, vinyl sulfate, vinyl sulfite, 4,4'-diethylene sulfate, pentaerythritol bicyclic sulfate, tris(trimethylsilyl)phosphate, tris(trimethylsilyl)borate, 1,3-propanesulfonyl lactone, 1,3-propenesulfonyl lactone, adiponitrile, 1,3,6-hexanetrionitrile, cyclohexylbenzene, tetravinylsilane, 1,3,5-triallyl isocyanurate, and 2,4,6-(allyloxy)-1,3,5-triazine, and such that any one base additive accounts for 0.1 to 5.0 wt% of the total mass of the electrolyte.
[0020] In one specific embodiment, a lithium-ion battery electrolyte is provided, wherein the electrolyte salt is preferably LiPF6, and the amount used accounts for 3.0 to 15.0 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), diethyl carbonate (DEC), ethyl propionate (EP), and propyl propionate (PP). When the cathode material is a ternary material of NCM and LNMO, the solvent is 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 are the first additives I-1 and I-4 and LiFSI, and the base additives are preferably 1% VC, 1% PS, and 1% LiDFP. When the cathode material is LCO material, the solvent is more preferably PC, FEC, EP, DEC, and the mass ratio of the four is PC, FEC, EP, DEC = 1:3:3:3. The additives are preferably I-4 and LiFSI; the basic additives are 4% PS, 2% AND and 0.5% LiDFOB.
[0021] In another specific embodiment, a sodium-ion battery electrolyte is provided, wherein the electrolyte salt is preferably NaPF6, and the amount used accounts for 3.0 to 18.0 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:DEC = 3:5:2; the first additive containing an N-cyclic compound is preferably I-3, the second additive is preferably NaFSI, and the basic film-forming additive is preferably FEC and PS.
[0022] A lithium / sodium-ion secondary battery includes a positive electrode, a negative electrode, and a separator. The active material of the positive electrode is selected from lithium cobalt oxide, lithium iron phosphate, lithium nickel manganese oxide, ternary materials of nickel cobalt manganese lithium, sodium-containing layered oxides, Prussian blue / white or polyanionic materials. 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.
[0023] Compared with the prior art, the beneficial effects of the present invention are as follows:
[0024] 1. Through the synergistic effect of the first additive and the second additive in the electrolyte of the present invention, the problem of high gas production during high-temperature storage when using a single additive can be solved, while taking into account low initial impedance and better high-temperature cycling performance.
[0025] 2. Based on the addition of the first additive and the second additive, the present invention further introduces a basic film-forming additive, which has better high-temperature cycling and high-temperature storage performance. Detailed Implementation
[0026] 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.
[0027] I. Electrolyte Preparation
[0028] 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.
[0029] Table 1 Electrolyte Formulation
[0030]
[0031] II. Electrochemical Performance Testing
[0032] The electrolytes from Examples 1-18 and Comparative Examples 1-6 were used to prepare 1000mAh soft-pack lithium-ion batteries. Each lithium-ion battery includes a positive electrode, a negative electrode, a separator, an electrolyte, and battery auxiliary materials. The positive and negative electrode materials are shown in Table 2. 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 lithium-ion battery soft-pack cell is obtained.
[0033] The performance of the lithium-ion and sodium-ion batteries prepared above was tested, mainly including:
[0034] (1) Initial impedance test:
[0035] 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.
[0036] 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.
[0037] Finally, discharge the battery at a constant current of 4C for 30 seconds, record the voltage U2, and calculate the initial impedance of the battery:
[0038] Initial impedance = (U1 - U2) / 4 * 1000
[0039] (2) High-temperature storage performance test
[0040] At room temperature (25℃), the battery was charged at a constant current of 1C to the charging cutoff voltage (4.4V), and then charged at a constant voltage until the current dropped to 0.05C. It was then placed in a 60℃ constant temperature oven for 60 days. After storage, the battery was cooled to room temperature, and the initial volume V1 and the volume V2 after storage were recorded. The battery was then discharged at a constant current of 1C to the discharge cutoff voltage, and the initial discharge capacity C1 and the discharge capacity C2 after storage were recorded. The high-temperature storage volume expansion rate and capacity retention rate were calculated using the following formula:
[0041] High-temperature storage volume expansion rate = (V2 / V1-1)*100%
[0042] High-temperature storage capacity retention rate = C2 / C1 * 100%
[0043] (3) High-temperature cycling performance test
[0044] The battery was cycled in an oven at 45±1℃ with a charge / discharge current of 1C / 1C. The discharge capacity was calculated per cycle. The cycle was stopped after 500 cycles, and the capacity retention rate after the cycle was calculated.
[0045] The specific test results are shown in Table 2 below:
[0046] Table 2. Results of positive and negative electrode materials and electrochemical tests
[0047]
[0048]
[0049] By comparing Example 2 and Comparative Example 7, and Example 17 and Comparative Example 6, it can be seen that using the first additive alone or in combination with other basic additives results in higher initial battery impedance and poorer high-temperature storage and high-temperature cycling stability compared to using the first additive and the second additive together.
[0050] By comparing Examples 1-6 with Comparative Examples 1-2, or Examples 14, 16 with Comparative Examples 4-5, it can be seen that the combination of sulfonamide compound and difluorosulfonyl imide salt shown in the (I) structure of the present invention can effectively suppress the problem of increased gas generation during high-temperature storage of a single additive, while taking into account the initial impedance and cycle performance of the battery.
[0051] By comparing Examples 1-18 and Comparative Examples 1-7, it can be seen that the composition proposed in this invention can reduce initial impedance, suppress gas generation during long-term storage, and improve capacity retention and cycle life in secondary battery systems with different positive and negative electrode materials.
[0052] By comparing Examples 1-5 with Example 6 and Comparative Example 2, it can be seen that in the NCM622 positive electrode and graphite negative electrode system, the sulfonamide compound shown in Formula (I) has better performance in the mass concentration range of 0.2% to 2%.
[0053] By comparing Example 7 with Examples 1-6, it can be seen that adding basic film-forming additives such as VC, PS and LiDFP composition to the formulation can further improve the battery's high-temperature storage and high-temperature cycling performance.
Claims
1. A non-aqueous electrolyte for secondary batteries, comprising an electrolyte salt, a non-aqueous solvent, and additives, characterized in that: The additives include at least: The first additive is a sulfonamide compound with the structure shown in formula (I) and is used in an amount of 0.01 to 3.0 wt% of the total mass of the electrolyte. In formula (I), R is selected from halogen, substituted or unsubstituted C1-C6 alkyl, substituted or unsubstituted C2-C6 alkenyl, substituted or unsubstituted C2-C6 alkynyl, substituted or unsubstituted C3-C7 cycloalkyl, substituted or unsubstituted C3-C7 cycloalkenyl, or -OR; M is H, Li, Na or K. The second additive is bis(fluorosulfonyl)imide salt, used in an amount of 0.05–18.0 wt% of the total electrolyte mass.
2. The non-aqueous electrolyte for secondary batteries according to claim 1, characterized in that: R is selected from halogen, C1-C3 alkyl, C1-C3 haloalkyl or C1-C3 alkoxy; M is H, Li or Na.
3. The non-aqueous electrolyte for secondary batteries according to claim 2, characterized in that: The first additive is selected from at least one of the compounds shown in the following structures:
4. The non-aqueous electrolyte for secondary batteries according to claim 1, characterized in that: When the electrolyte is used in a lithium-ion battery, the bis(fluorosulfonyl)imide salt is lithium bis(fluorosulfonyl)imide; When the electrolyte is used in a sodium-ion battery, the difluorosulfonamide salt is sodium difluorosulfonamide.
5. The non-aqueous electrolyte for secondary batteries according to claim 1, characterized in that: The amount of the first additive is 0.2 to 2.0 wt% of the total mass of the electrolyte.
6. The non-aqueous electrolyte for secondary batteries according to claim 1, characterized in that: The amount of the bis(fluorosulfonyl)imide salt is 0.1 to 15.0 wt% of the total mass of the electrolyte.
7. The non-aqueous electrolyte for secondary batteries according to claim 1, characterized in that: The non-aqueous solvent 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, propylene carbonate, butene 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 any one of claims 1-7, characterized in that: When the electrolyte is used in a lithium-ion battery, the electrolyte salt is selected from at least one of lithium hexafluorophosphate, lithium tetrafluoroborate, lithium perchlorate, lithium bis(oxalate)borate, lithium difluorooxalateborate, lithium bis(trifluoromethanesulfonyl)imide, lithium tetrafluorooxalate phosphate, lithium tri(oxalate) phosphate, and lithium difluorobis(oxalate) phosphate. When the electrolyte is used in a sodium-ion battery, the electrolyte salt is selected from at least one of sodium hexafluorophosphate, sodium tetrafluoroborate, sodium perchlorate, sodium bis(trifluoromethanesulfonyl)imide, and sodium difluorophosphate. The amount of the electrolyte salt used is 0.1% to 15.0 wt% of the total mass of the electrolyte.
9. The non-aqueous electrolyte for secondary batteries according to any one of claims 1-8, characterized in that: The additives further include a base additive selected from at least one of vinylene carbonate, fluoroethylene carbonate, vinyl sulfate, vinyl sulfite, 4,4'-diethylene sulfate, pentaerythritol bicyclic sulfate, tris(trimethylsilyl)phosphate, tris(trimethylsilyl)borate, 1,3-propanesulfonyl lactone, 1,3-propenesulfonyl lactone, adiponitrile, 1,3,6-hexanetrionitrile, cyclohexylbenzene, tetravinylsilane, 1,3,5-triallyl isocyanurate, and 2,4,6-(allyloxy)-1,3,5-triazine, and such that any one base 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 1-9.
11. A 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, ternary materials of nickel cobalt manganese lithium, sodium-containing layered oxides, Prussian blue / white or polyanionic oxides, and 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.