High-temperature-resistant electrolyte for supercapacitor as well as preparation method and application of high-temperature-resistant electrolyte
By using composite multifunctional additives TFEB, TTC, and VC in supercapacitors, the positive and negative electrode interface films were optimized, solving the problem of performance degradation of hybrid supercapacitors at high temperatures and achieving a more stable electrolyte system and a longer cycle life.
Patent Information
- Application Number
- CN202511643222.X
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-11-11
- Publication Date
- 2026-02-13
AI Technical Summary
Hybrid supercapacitors exhibit significant performance degradation at high temperatures, particularly in capacity retention and energy efficiency. This is primarily due to the aging of the interface between the electrolyte system and electrode materials, leading to weakened SEI film stability and intensified side reactions.
By employing composite multifunctional additives, including fluoroboronic acid ester TFEB, organosiloxane TTC, and vinylene carbonate VC, the formation of the positive and negative electrode interface films is optimized to construct a wide bandgap CEI film and a stable SEI film, thereby improving the high-temperature stability of the electrolyte.
It significantly improves the performance stability of supercapacitors in high-temperature environments, extends cycle life and capacity retention, and suppresses capacity decay during high-temperature cycling.
Smart Images
Figure CN121528772A_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the field of hybrid supercapacitors, specifically to a high-temperature resistant electrolyte for supercapacitors, its preparation method, and its application. Background Technology
[0002] Hybrid supercapacitors have shown great potential in energy storage due to their high power density, long cycle life, and fast charge / discharge characteristics. However, their insufficient adaptability to high-temperature environments has become a core bottleneck restricting their commercialization. Studies have shown that the performance of these devices degrades significantly at high temperatures (>45°C), especially during long-cycle or calendar-life testing, where capacity retention and energy efficiency drop dramatically. The root cause of this phenomenon lies in the interfacial aging mechanism between the electrolyte system and the electrode materials. Under high-temperature conditions, the reactivity of the electrolyte at the electrode / electrolyte interface increases dramatically, leading to a significant weakening of the stability of the solid electrolyte interphase (SEI) film. The dissolution and reconstruction process of the SEI film continuously consumes active lithium and triggers a chain reaction of interfacial side reactions, including solvent molecule co-intercalation, gas evolution, and transition metal ion dissolution, ultimately resulting in electrode structure damage and increased internal resistance.
[0003] The thermal stability of the electrolyte system is a key factor determining the high-temperature performance of hybrid supercapacitors. Traditional carbonate solvents (such as EC and DMC) are volatile at high temperatures, leading to fluctuations in electrolyte concentration and local overpotentials, exacerbating side reactions at the electrode / electrolyte interface. More critically, lithium hexafluorophosphate (LiPF6) undergoes irreversible decomposition at high temperatures, generating acidic products such as PF5 and HF. PF5 catalyzes further solvent decomposition, while HF directly corrodes the SEI film and the positive electrode electrolyte interphase (CEI) film, destroying their compositional and structural integrity. The dissolution of the SEI film on the negative electrode side leads to continuous consumption of active lithium, while the damage to the CEI film on the positive electrode side triggers the dissolution of transition metal elements (such as Ni and Co), forming metal fluoride precipitates and accelerating solvent oxidation and decomposition. These chemically driven interfacial degradation processes are coupled together, forming a vicious cycle that ultimately leads to device capacity decay and a sharp reduction in cycle life. Summary of the Invention
[0004] To address the aforementioned problem of accelerated degradation in high-temperature environments in hybrid capacitor systems, this invention proposes a multi-dimensional composite solution. Based on high-temperature modified electrolytes and the addition of functional additives, it focuses on solving the degradation problem caused by interface defects between positive and negative electrode materials and electrolytes. Fluoroboronic acid ester TFEB, organosiloxane TTC, and unsaturated carbonate VC are used. On the positive electrode side, TFEB is preferentially selected to construct a wide bandgap CEI film, while on the negative electrode side, TTC and VC are used to optimize and modify the SEI film formation.
[0005] Specifically, the present invention provides a high-temperature resistant electrolyte for supercapacitors, wherein the high-temperature resistant electrolyte contains a composite multifunctional additive, which includes fluoroboronate TFEB (tris(2,2,2-trifluoroethyl)boronate, 1,3,5-trimethyl-1,3,5-tris(3,3,3-trifluoropropyl)cyclotrisiloxane) and vinylene carbonate.
[0006] The mass ratio of the fluoroboronic ester TFEB (tris(2,2,2-trifluoroethyl)boronic ester, 1,3,5-trimethyl-1,3,5-tris(3,3,3-trifluoropropyl)cyclotrisiloxane) to vinylene carbonate is (8-10):(5-8):(82-87).
[0007] The high-temperature resistant electrolyte also contains a basic solvent and lithium salt.
[0008] The base solvent is a mixture of ethylene carbonate, ethyl butyrate, and methyl ethyl carbonate in a volume ratio of 0.5-2: 0.5-2: 1-5.
[0009] The lithium salt is at least one of lithium hexafluorophosphate and lithium difluorosulfonylimide, and its volume ratio with ethylene carbonate is 1:4 to 1:7.
[0010] This invention also provides a method for preparing a high-temperature resistant electrolyte for supercapacitors, comprising the following steps: S1: Mix ethylene carbonate, ethyl butyrate and methyl ethyl carbonate in a volume ratio of 1:2:2 and stir until the three liquids are completely miscible to form a compound multifunctional additive mixture. S2: Cool the mixture obtained in step S1 to 5-12℃; S3: Add lithium salt to the cooled mixture in step S2, with a volume ratio of lithium salt to ethylene carbonate of 1:4 to 1:7, and stir until all components in the solution are completely miscible and the solution is clear and transparent. S4: Add a multifunctional additive to the mixture after treatment in step S3, with a volume ratio of 1:7 to 1:8 of ethylene carbonate, and stir to obtain the high-temperature resistant electrolyte.
[0011] In step S2, the mixture is cooled to 9-11℃.
[0012] In step S4, the mixture is stirred until all components are completely miscible and the mixture is clear and transparent.
[0013] Compared with the prior art, the present invention has the following beneficial effects: This invention significantly improves the performance stability of hybrid supercapacitors under high-temperature environments through the synergistic design of composite multifunctional additives and optimized solvent systems. Among them, the fluoroboronate TFEB (tris(2,2,2-trifluoroethyl)boronate) exhibits remarkable high-temperature stability and interface regulation capabilities, addressing the electrode / electrolyte interface failure problem under high temperature and high pressure through molecular design. Furthermore, the boron atoms in TFEB possess empty orbitals, exhibiting strong Lewis acidity, which can capture anions or bind to Lewis basic substances such as polysulfides, optimizing ion transport pathways. The electrolyte additive TTC (1,3,5-trimethyl-1,3,5-tris(3,3,3-trifluoropropyl)cyclotrisiloxane) forms an effective protective layer on the electrode surface, suppressing side reactions induced by the nickel-rich cathode at high temperatures, enhancing the electronic barrier capability of the interfacial film, and thus reducing capacity decay during high-temperature cycling. Ethylene carbonate (VEC), as a film-forming additive, acts on the surface of the negative electrode to form a dense solid electrolyte interface (SEI) film. This film allows lithium ions to pass freely but blocks solvent molecules, significantly inhibiting electrolyte decomposition and improving cycle life and capacity retention. Attached Figure Description
[0014] Figure 1 Comparison chart of float charge test results for electrolytes prepared in Comparative Example 1(a), Example 1(b), and Example 2(c). Detailed Implementation
[0015] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the protection scope of the present invention.
[0016] Example 1 The method for preparing the high-temperature resistant electrolyte in this embodiment includes the following steps: Step 1: Mix ethylene carbonate EC, ethyl butyrate EB, and methyl ethyl carbonate EMC in a volume ratio of 1:1:2 and stir until the three solvents are completely miscible. Step 2: Cool the mixture obtained in Step 1 to 10°C; Step 3: Add lithium hexafluorophosphate (LiPF6) to the cooled solution from Step 2, with a volume ratio of 1:4 to ethylene carbonate (EC), and stir until all components in the solution are completely miscible and the solution is clear and transparent. Step 4: Mix fluoroboronic acid ester TFEB (tris(2,2,2-trifluoroethyl)boronic acid ester), 1,3,5-trimethyl-1,3,5-tris(3,3,3-trifluoropropyl)cyclotrisiloxane) and vinylene carbonate in a volume ratio of 1:1:2 and stir until the three solvents are completely miscible. Step 5: Add the compound multifunctional additive prepared in Step 4 to the solution obtained in Step 3. The volume ratio of the additive to ethylene carbonate EC is 1:7. Stir until all components in the solution are completely miscible and the solution is clear and transparent.
[0017] Example 2 The method for preparing the high-temperature resistant electrolyte in this embodiment includes the following steps: Step 1: Mix ethylene carbonate EC, ethyl butyrate EB, and methyl ethyl carbonate EMC in a volume ratio of 1:1:2 and stir until the three solvents are completely miscible. Step 2: Cool the mixture obtained in Step 1 to 10℃; Step 3: Add lithium hexafluorophosphate (LiPF6) to the cooled solution from Step 2, with a volume ratio of 1:4 to ethylene carbonate (EC), and stir until all components in the solution are completely miscible and the solution is clear and transparent. Step 4: Mix fluoroboronate TFEB (tris(2,2,2-trifluoroethyl)boronate), 1,3,5-trimethyl-1,3,5-tris(3,3,3-trifluoropropyl)cyclotrisiloxane, and vinylene carbonate in a volume ratio of 1:1:2 and stir until the three solvents are completely miscible. Step 5: Add the compound multifunctional additive prepared in Step 4 (the amount is doubled compared to that in Example 1) to the solution obtained in Step 3. The volume ratio of the additive to ethylene carbonate EC is 2:7. Stir until all components in the solution are completely miscible and the solution is clear and transparent.
[0018] Comparative Example 1 The method for preparing the electrolyte in this comparative example includes the following steps: (1) Mix ethyl acetate (EA), dimethyl carbonate (DMC), diethyl carbonate (DEC), and ethylene carbonate (EC) in proportion and stir until completely miscible; (2) Electrolyte salts LiPF6, LiFSI and additives ethylene sulfate DTD and fluoroethylene carbonate FEC are added to the above mixed solvent to form an electrolyte. The mass ratio of each substance in the electrolyte is: EA 45%, DMC 10%, DEC 9%, EC (15%), LiPF6 (15%), LiFSI (2%), DTD (2%), FEC (2%).
[0019] Characterization To demonstrate the advantages of the high-temperature electrolyte prepared in Example 1, a common electrolyte was used as a comparison, and float charge life was used as a reference guide. The two electrolytes were injected into cylindrical monomers and float charge tests were conducted at 70°C and 4.2V high temperature and high pressure.
[0020] Figure 1 To characterize the results, and by Figure 1 a. As can be seen, the capacity of the ordinary electrolyte prepared in Comparative Example 1 had already decreased to 36% after only 1080 hours of float charging; Figure 1 b. As can be seen, the high-temperature resistant electrolyte formulation 1 prepared in Example 1 can achieve a capacity retention rate of 60% after 2950 hours of float charging; Figure 1 As can be seen, the high-temperature resistant electrolyte formulation 2 prepared in Example 2 achieved a capacity retention rate of 82% after 4400 hours of float charging. This means that both high-temperature resistant electrolytes 1 and 2 significantly improved high-temperature performance. Among them, high-temperature resistant electrolyte formulation 2, with its increased amount of composite multifunctional additives, maximized the improvement in high-temperature float charging life. The reason for this is that a dense CEI film forms on the surface of the positive electrode, while a more stable SEI film forms on the negative electrode. This effectively isolates the electrolyte byproduct HF from corroding the electrode, reduces the lithium consumption due to the dissolution and regeneration of the negative electrode SEI film, and thus improves the electrochemical performance of the cell at high temperatures.
[0021] The embodiments described above are preferred embodiments of the present invention, but the present invention is not limited to the above embodiments. Any obvious improvements, substitutions or modifications that can be made by those skilled in the art without departing from the essence of the present invention shall fall within the protection scope of the present invention.
Claims
1. A high-temperature resistant electrolyte for supercapacitors, characterized in that, The high-temperature resistant electrolyte contains a complex multifunctional additive, which includes fluoroboronic acid ester TFEB (tris(2,2,2-trifluoroethyl)boronic acid ester), 1,3,5-trimethyl-1,3,5-tris(3,3,3-trifluoropropyl)cyclotrisiloxane and vinylene carbonate.
2. The high-temperature resistant electrolyte according to claim 1, characterized in that, The mass ratio of the fluoroboronic ester TFEB (tris(2,2,2-trifluoroethyl)boronic ester, 1,3,5-trimethyl-1,3,5-tris(3,3,3-trifluoropropyl)cyclotrisiloxane) to vinylene carbonate is (8-10):(5-8):(82-87).
3. The high-temperature resistant electrolyte according to claim 1, characterized in that, The high-temperature resistant electrolyte also contains a basic solvent and lithium salt.
4. The high-temperature resistant electrolyte according to claim 3, characterized in that, The base solvent is a mixture of ethylene carbonate, ethyl butyrate, and methyl ethyl carbonate in a volume ratio of 0.5-2: 0.5-2: 1-5.
5. The high-temperature resistant electrolyte according to claim 3, characterized in that, The lithium salt is at least one of lithium hexafluorophosphate and lithium difluorosulfonylimide, and its volume ratio with ethylene carbonate is 1:4 to 1:
7.
6. A method for preparing a high-temperature resistant electrolyte for a supercapacitor according to claim 1, characterized in that, Includes the following steps: S1: Mix ethylene carbonate, ethyl butyrate, and methyl ethyl carbonate in a volume ratio of 0.5-2: 0.5-2: 1-5 and stir until the three solvents are completely miscible to form a mixture; S2: Cool the mixture obtained in step S1 to 5-12℃; S3: Add lithium salt to the cooled mixture in step S2, with a volume ratio of lithium salt to ethylene carbonate of 1:4 to 1:7, and stir until all components in the solution are completely miscible and the solution is clear and transparent. S4: Add a multifunctional additive to the mixture after treatment in step S3, with a volume ratio of 1:7 to 1:8 of ethylene carbonate, and stir to obtain the high-temperature resistant electrolyte.
7. The method according to claim 6, characterized in that, In step S2, the mixture is cooled to 9-11℃.
8. The method according to claim 6, characterized in that, In step S4, the mixture is stirred until all components are completely miscible and the mixture is clear and transparent.
9. The application of the high-temperature resistant electrolyte according to claim 1 in supercapacitors.