Wide-temperature-range high-rate lithium battery ester-based electrolyte and application
By optimizing the solvent and lithium salt composition of the lithium battery electrolyte, the problems of lithium dendrite growth and interface instability in lithium batteries under wide temperature range and high rate conditions were solved, achieving high-efficiency lithium battery performance and safety.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- CENT SOUTH UNIV
- Filing Date
- 2026-02-09
- Publication Date
- 2026-05-08
AI Technical Summary
Existing lithium batteries suffer from lithium dendrite growth, interface instability, and low conductivity under wide temperature range and high rate conditions, leading to safety hazards and performance degradation.
Using propylene carbonate, fluoroethylene carbonate, and isopropyl trifluoroacetate as solvents, and combining lithium bis(trifluoromethanesulfonyl)imide and lithium difluorooxalate borate as lithium salts, the ratio and concentration were optimized to form an electrolyte with high oxidation stability and low viscosity, which promotes the desolvation of lithium ions and the formation of a stable interface film.
Stable charge and discharge performance was achieved in a wide temperature range of -40 to 60 °C, with a capacity retention rate of 94.2% at low temperatures and excellent cycle stability at high temperatures. Lithium dendrite growth was suppressed, improving the charge and discharge efficiency and safety of the battery.
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Figure CN122000473A_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the field of battery technology, and in particular to a wide-temperature-range, high-rate lithium battery ester-based electrolyte and its application. Background Technology
[0002] With the global energy crisis and environmental pollution becoming increasingly severe, lithium batteries have become an important component of the new energy field. The theoretical limit of the energy density of lithium-ion batteries is approximately 350 Wh / kg. -1 Therefore, the demand for higher energy density energy storage systems is increasingly urgent for electric vehicles and portable devices. Lithium metal anodes, due to their low density (0.535 g / cm³), are a suitable choice. -3 ) and high theoretical capacity (3860 mAh g) -1 Lithium metal (LiMH) batteries are considered an ideal high-energy-density material to replace existing graphite anodes. However, the solid electrolyte interface (SEI) formed in commercial carbonate electrolytes exhibits poor electrochemical and mechanical stability. The unstable SEI structure continuously exposes new active lithium surfaces during cycling, leading to uncontrolled lithium dendrite growth, which may penetrate the separator and cause short circuits and thermal runaway. This problem can be exacerbated when batteries operate at high and low temperatures and at high rates. This critical safety issue severely restricts the practical application of lithium metal batteries under wide temperature ranges and high-rate conditions.
[0003] Regarding solvents, propylene carbonate is widely used in lithium metal batteries due to its wide liquidus temperature range (−49~240 °C), strong solvation ability, and high oxidation stability. However, its high viscosity leads to low conductivity at low temperatures, thus limiting its application at high rates in low-temperature environments. Furthermore, the strong binding force between propylene carbonate solvent and lithium ions results in a high lithium-ion desolvation barrier, leading to severe dendrite growth. Additionally, the solvation sheath composed of solvent molecules and lithium salt is prone to decomposition at the interface, forming an unstable interfacial film, thus degrading performance. The key is to lower the lithium-ion desolvation barrier and adjust the solvation sheath to form a more stable inorganic-rich SEI. As for lithium salts, commercially available LiPF6 exhibits low conductivity at low temperatures and thermal instability, easily generating HF, which leads to SEI film damage and transition metal dissolution, making it unsuitable as a lithium salt for a wide-temperature-range electrolyte. Based on the above issues, the key is to weaken the binding force between lithium ions and the solvent to accelerate the lithium ion desolvation process, thereby inhibiting the growth of lithium dendrites and forming a stable, inorganic-rich SEI layer. Competitive coordination to regulate the solvation sheath structure is a simple and effective way to improve ion transport kinetics and control the composition, structure, and morphology of the SEI layer. Fluorinated solvents typically have low melting points and viscosities, which is beneficial for maintaining high ionic conductivity at low temperatures. They also have low LUMO energy levels, allowing for preferential decomposition at the negative electrode interface. Furthermore, their moderate molecular polarity can regulate the lithium-ion solvation sheath structure, promote the formation of anion-derived interfaces, and improve ion transport kinetics. Therefore, selecting fluorinated solvents with moderate coordination ability with lithium ions and strong antioxidant properties is a superior method for regulating the solvation sheath layer and stabilizing the interfacial film.
[0004] It should be noted that the information disclosed in the background section above is only for understanding the background of this application, and therefore may include information that does not constitute prior art known to those skilled in the art. Summary of the Invention
[0005] The purpose of this invention is to provide a method for preparing and applying a wide-temperature-range, high-rate ester-based electrolyte. This electrolyte has an oxidation potential greater than 5.5 V, and batteries prepared using this electrolyte can undergo stable and reversible charge-discharge within a wide temperature range of -40 to 60 °C. Furthermore, the prepared batteries exhibit a capacity retention rate of up to 94.2% after 120 cycles at -30 °C and 1 C rate, and 82.79% after 200 cycles at 25 °C and 4.5 V. They also demonstrate excellent cycle stability at a high temperature of 60 °C, thus solving the problems existing in the prior art.
[0006] Existing technologies suffer from several problems. Low temperatures significantly increase electrolyte viscosity and decrease ionic conductivity, leading to increased battery polarization and a sharp drop in capacity. Simultaneously, the desolvation process of lithium ions at the electrode / electrolyte interface becomes difficult, and the increased desolvation energy barrier becomes the main source of interfacial impedance, severely impacting charge and discharge efficiency. Currently, the main solvents in commercial electrolytes have high freezing points and viscosities, resulting in a decrease in lithium ion migration rate at low temperatures. Furthermore, increased polarization leads to a significant decrease in discharge capacity, especially at higher rates; high temperatures significantly exacerbate interfacial side reactions between the electrolyte and the lithium metal anode and high-voltage cathode. Conventional carbonate solvents have limited thermal stability and are prone to decomposition at high temperatures, leading to continuous electrolyte consumption and gas production (such as CO2 and olefins). Simultaneously, high temperatures accelerate the decomposition of lithium salts (such as LiPF6), producing corrosive substances such as HF, which damage the cathode material structure and corrode the SEI film of the anode. For lithium metal anodes, high temperatures exacerbate lithium dendrite growth and the formation of "dead lithium," leading to repeated rupture and reconstruction of the SEI film, a sharp decline in coulombic efficiency, and an increased risk of thermal runaway and explosion.
[0007] The technical solution adopted in this invention is,
[0008] A wide-temperature-range, high-rate lithium battery ester-based electrolyte and its application, comprising a soluble lithium salt and a liquid component; the liquid component is a solvent; the solvent comprises at least three of propylene carbonate, fluoroethylene carbonate, isopropyl trifluoroacetate, ethyl trifluoroacetate, ethyl acetate, methyl acetate, and methyl trifluoroacetate.
[0009] This invention relates to a wide-temperature-range, high-rate lithium battery ester-based electrolyte and its application. The soluble lithium salt includes at least one of lithium bis(trifluoromethanesulfonyl)imide, lithium bis(fluorosulfonyl)imide, lithium tetrafluoroborate, lithium difluorooxalate borate, lithium dioxalate borate, lithium hexafluorophosphate, lithium difluorophosphate, lithium perchlorate, and lithium nitrate.
[0010] As preferred options, soluble lithium salts include lithium bis(trifluoromethanesulfonyl)imide (LiTFSI) and lithium difluorooxalate borate (LiDFOB).
[0011] In the electrolyte, the molar concentration of soluble lithium salt is 0.8~1.5 mol / L, more preferably 0.9~1.2 mol / L.
[0012] As a preferred option, the selected solvent includes at least one of propylene carbonate, fluoroethylene carbonate, and isopropyl trifluoroacetate.
[0013] Preferably, the solvent is at least one of propylene carbonate, fluoroethylene carbonate, and isopropyl trifluoroacetate; more preferably, the solvent is composed of propylene carbonate, fluoroethylene carbonate, and isopropyl trifluoroacetate; and even more preferably, the liquid component is composed of propylene carbonate, fluoroethylene carbonate, and isopropyl trifluoroacetate in a volume ratio of 3~10:0.2~4:0.2~6.
[0014] As a further preferred option, the volume ratio of propylene carbonate, fluoroethylene carbonate and isopropyl trifluoroacetate is 4~8:1~3.5:3; this includes schemes of 3~6:2~3.5:3.
[0015] The present invention controls the volume ratio of propylene carbonate, fluoroethylene carbonate, and isopropyl trifluoroacetate to be propylene carbonate: fluoroethylene carbonate: isopropyl trifluoroacetate = 3~10:0.2~4:0.2~6, preferably 4~8:1~3.5:3. This is because it ensures both complete dissociation of the lithium salt and a suitable desolvation energy barrier. If the proportion of propylene carbonate is too low, the degree of lithium salt dissociation will be insufficient; if it is too high, the desolvation of lithium ions will be difficult and the solvent will be co-intercalated into graphite. If the proportion of fluoroethylene carbonate is too low, the interface film on the negative electrode side will be unstable; if it is too high, the viscosity will be high. If the proportion of isopropyl trifluoroacetate is too low, the solvation structure will be insufficient to control, making lithium ion desolvation difficult; if it is too high, the degree of lithium salt dissociation will be insufficient.
[0016] As a preferred embodiment, the selected soluble lithium salt is composed of LiTFSI and LiDFOB in a molar ratio of 3.8 to 4.2:1; more preferably, the molar ratio of LiTFSI and LiDFOB is 3.9 to 4.1:1. The present invention controls the soluble lithium salt to have a molar ratio of LiTFSI to LiDFOB of 3.8 to 4.2:1 because an appropriate amount of LiDFOB can form a passivation layer on the aluminum foil surface and participate in the solvation structure. If the LiDFOB content is too high, it will lead to problems such as difficulty in lithium salt dissociation; if the LiDFOB content is too low, it will lead to problems such as corrosion of the current collector aluminum foil by LiTFSI.
[0017] As a further preferred option, the volume ratio of propylene carbonate, fluoroethylene carbonate, and isopropyl trifluoroacetate is 4.8~5.2:1.8~2.2:2.8~3.2. Based on this, it can be further optimized to a volume ratio of propylene carbonate, fluoroethylene carbonate, and isopropyl trifluoroacetate of 5:2:3.
[0018] A method for preparing a wide-temperature-range, high-rate lithium-ion battery ester-based electrolyte and its applications includes the following steps:
[0019] According to the set ratio, the lithium salt is dissolved in a pre-dehydrated solvent and stirred until a homogeneous electrolyte is formed. In the electrolyte, the molar concentration of the soluble lithium salt is 0.8~1.5 mol / L, more preferably 0.9~1.2 mol / L.
[0020] Further, the method specifically includes the following steps: taking lithium salts LiDFOB and LiTFSI, as well as propylene carbonate, fluoroethylene carbonate and isopropyl trifluoroacetate, and preparing the solution according to the molar ratio of LiTFSI and LiDFOB being 3.9~4.1:1, and the volume ratio of propylene carbonate, fluoroethylene carbonate and isopropyl trifluoroacetate being 3~10:0.2~4:0.2~6, preferably 4~8:1~3.5:3, and more preferably 3~6:2~3.5:3, and stirring until a uniform electrolyte is formed, wherein the molar concentration of soluble lithium salt in the electrolyte is 0.95~1.05 mol / L.
[0021] This invention relates to a wide-temperature-range, high-rate lithium battery ester-based electrolyte and its application. The application includes using the electrolyte in a lithium battery, wherein the lithium battery comprises the wide-temperature-range, high-rate lithium battery electrolyte, a negative electrode, and a high-voltage positive electrode material.
[0022] Furthermore, the high-voltage cathode material is selected from at least one of nickel cobalt manganese oxide (NCM), lithium cobalt oxide (LiCoO2), and nickel-based oxide (NiO).
[0023] Furthermore, the high-voltage positive electrode material is NCM811.
[0024] The beneficial effects of this invention are:
[0025] This invention discloses an ester-based electrolyte designed for high-rate operation over a wide temperature range. From the perspective of competitive coordination between electrolyte solvents, a novel ester-based electrolyte with high rate performance and a wide operating temperature range is designed. A sulfonamide lithium salt with high stability and good conductivity is selected as the main lithium salt, and its concentration is adjusted. Propylene carbonate solvent, which has a wide liquidus temperature range, strong solvation ability, and high oxidation stability, is selected as the main solvent (optimized propylene carbonate accounts for 48-52% of the total solvent), ensuring sufficient dissociation of the lithium salt. Simultaneously, appropriate amounts of isopropyl trifluoroacetate solvent (optimized isopropyl trifluoroacetate accounts for 28-32% of the total solvent) and fluoroethylene carbonate solvent (optimized fluoroethylene carbonate accounts for 18-22% of the total solvent) with lower melting points, viscosity, and lower LUMO levels are introduced to adjust the lithium-ion solvation sheath structure. This weakens the binding force between the solvent and lithium ions, accelerates the desolvation process of lithium ions, promotes the formation of anion-derived interfaces, improves ion transport kinetics, and inhibits the formation of lithium dendrites. The final designed electrolyte lowers the desolvation energy barrier of lithium ions, effectively suppresses lithium dendrite growth and electrode-electrolyte interface side reactions at low temperatures, and promotes the formation of a solid interface film rich in inorganic matter and with low interfacial impedance. This enables lithium batteries with fast charge-discharge, stable cycling, and excellent performance over a wide temperature range, suitable for high-nickel cathode materials. Attached Figure Description
[0026] Figure 1 These are electrochemical window diagrams for Comparative Example 1 and Example 1;
[0027] Figure 2 The graph shows the rate performance of the NCM811||Li batteries prepared in Comparative Example 1 and Example 1 at −30 °C and 2.8–4.5 V.
[0028] Figure 3 The graph shows the rate performance of NCM811||Li batteries prepared with electrolytes from Comparative Example 1 and Example 1 at −40 °C and 2.8–4.5 V.
[0029] Figure 4 The graph shows the cycle performance of NCM811||Li batteries prepared with electrolytes from Comparative Example 1 and Example 1 at −30 °C, 1 C, and 2.8–4.5 V.
[0030] Figure 5 The graph shows the rate performance of NCM811||Li batteries prepared with electrolytes from Comparative Example 1 and Example 1 under conditions of 25 °C, 2.8-4.5 V, and 1 C.
[0031] Figure 6The graph shows the cycle performance of NCM811||Li batteries prepared with electrolytes from Comparative Example 1 and Example 1 under conditions of 25 °C, 2.8-4.5 V, and 1 C.
[0032] Figure 7 This is a graph showing the cycle performance of NCM811||Li batteries prepared with electrolytes from Comparative Example 1 and Example 1 under conditions of 60 °C, 2.8–4.3 V, and 1 C. Detailed Implementation
[0033] The embodiments of the present invention will be described in detail below. It should be emphasized that the following description is merely exemplary and is not intended to limit the scope and application of the present invention.
[0034] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature. In the description of embodiments of the present invention, "a plurality of" means two or more, unless otherwise explicitly specified.
[0035] This application provides a wide-temperature-range, high-rate lithium battery ester-based electrolyte and its application, comprising the following components: lithium difluorooxalate borate (LiDFOB) and lithium bis(trifluoromethanesulfonyl)imide (LiTFSI) as lithium salts; and propylene carbonate, fluoroethylene carbonate, and isopropyl trifluoroacetate as the main solvents.
[0036] The separator of the NCM811||Li battery in the embodiments and comparative examples of the present invention is a polypropylene (PP) separator.
[0037] The NCM811||Li batteries in the embodiments and comparative examples of this invention use the corresponding electrolytes developed in the specific embodiments and comparative examples.
[0038] Example 1:
[0039] A wide-temperature-range, high-rate lithium-ion battery ester-based electrolyte and its application are disclosed, using LiTFSI and LiDFOB as lithium salts and propylene carbonate, fluoroethylene carbonate, and isopropyl trifluoroacetate as solvents. The preparation method is as follows: First, lithium salts LiDFOB and LiTFSI, along with solutions of propylene carbonate, fluoroethylene carbonate, and isopropyl trifluoroacetate pre-dried in molecular sieves, are prepared according to a molar ratio of LiTFSI to LiDFOB of 0.8 M:0.2 M and a volume ratio of propylene carbonate, fluoroethylene carbonate, and isopropyl trifluoroacetate of 5:2:3. The solution is then stirred in a glove box for 12 h. The concentration of Li in the electrolyte is 1 mol / L.
[0040] The upper limit of the electrochemical window for the electrolyte obtained in Example 1 is 5.71 V;
[0041] The NCM811||Li battery prepared using the electrolyte of Example 1 was tested for 1C cycle performance at -30 °C, 25 °C, and 60 °C. At -30 °C, the battery retained 94.8% of its capacity after 120 cycles at 4.5 V. At 25 °C, the battery retained 82.82% of its capacity after 200 cycles at 4.5 V. At a higher temperature of 60 °C, the NCM811||Li battery prepared using the electrolyte of Example 1 retained 77.17% of its capacity after 100 cycles at 1 C and 4.3 V.
[0042] Example 2:
[0043] A wide-temperature-range, high-rate lithium-ion battery ester-based electrolyte and its application are disclosed, using LiTFSI and LiDFOB as lithium salts and propylene carbonate, fluoroethylene carbonate, and isopropyl trifluoroacetate as solvents. The preparation method is as follows: First, lithium salts LiDFOB and LiTFSI, along with solutions of propylene carbonate, fluoroethylene carbonate, and isopropyl trifluoroacetate pre-dried in molecular sieves, are prepared according to a molar ratio of LiTFSI to LiDFOB of 0.8 M:0.2 M and a volume ratio of propylene carbonate, fluoroethylene carbonate, and isopropyl trifluoroacetate of 6:2:2. The mixture is then stirred in a glove box for 12 h. The concentration of Li in the electrolyte is 1 mol / L.
[0044] The NCM811||Li battery prepared using the electrolyte of Example 2 was tested for 1C cycle performance at -30 °C, 25 °C, and 60 °C. At -30 °C, the battery retained 62.12% of its capacity after 120 cycles at 4.5 V. At 25 °C, the battery retained 72.62% of its capacity after 200 cycles at 4.5 V. At a higher temperature of 60 °C, the NCM811||Li battery prepared using the electrolyte of Example 1 retained 63.16% of its capacity after 100 cycles at 1 C and 4.3 V.
[0045] Example 3:
[0046] A wide-temperature-range, high-rate lithium-ion battery ester-based electrolyte and its application are disclosed, using LiTFSI and LiDFOB as lithium salts and propylene carbonate, fluoroethylene carbonate, and isopropyl trifluoroacetate as solvents. The preparation method is as follows: First, lithium salts LiDFOB and LiTFSI, along with solutions of propylene carbonate, fluoroethylene carbonate, and isopropyl trifluoroacetate pre-dried in molecular sieves, are prepared according to a molar ratio of LiTFSI to LiDFOB of 0.8 M:0.2 M and a volume ratio of propylene carbonate, fluoroethylene carbonate, and isopropyl trifluoroacetate of 4:2:4. The solution is then stirred in a glove box for 12 h. The concentration of Li in the electrolyte is 1 mol / L.
[0047] The NCM811||Li battery prepared using the electrolyte of Example 3 was tested for 1C cycle performance at -30 °C, 25 °C, and 60 °C. At -30 °C, the battery retained 66.65% of its capacity after 120 cycles at 4.5 V. At 25 °C, the battery retained 79.45% of its capacity after 200 cycles at 4.5 V. At a higher temperature of 60 °C, the NCM811||Li battery prepared using the electrolyte of Example 3 showed overcharge after 61 cycles at 1 C and 4.3 V, with a capacity retention of 47.39%.
[0048] Example 4:
[0049] A wide-temperature-range, high-rate lithium-ion battery ester-based electrolyte and its application are disclosed, using LiTFSI and LiDFOB as lithium salts and propylene carbonate, fluoroethylene carbonate, and isopropyl trifluoroacetate as solvents. The preparation method is as follows: First, lithium salts LiDFOB and LiTFSI, along with solutions of propylene carbonate, fluoroethylene carbonate, and isopropyl trifluoroacetate pre-dried in molecular sieves, are prepared according to a molar ratio of LiTFSI to LiDFOB of 0.8 M:0.2 M, and a volume ratio of propylene carbonate, fluoroethylene carbonate, and isopropyl trifluoroacetate of 5:1:4. The mixture is then stirred in a glove box for 12 h. The concentration of Li in the electrolyte is 1 mol / L.
[0050] The NCM811||Li battery prepared using the electrolyte of Example 4 was tested for 1C cycle performance at -30 °C, 25 °C, and 60 °C. At -30 °C, the battery retained 63.92% of its capacity after 120 cycles at 4.5 V, indicating extremely rapid capacity decay. At 25 °C, the battery retained 78.45% of its capacity after 200 cycles at 4.5 V. At a higher temperature of 60 °C, the NCM811||Li battery prepared using the electrolyte of Example 1 retained 85.69% of its capacity after 60 cycles at 1 C and 4.3 V, after which the battery exhibited severe overcharging.
[0051] Example 5:
[0052] A wide-temperature-range, high-rate lithium-ion battery ester-based electrolyte and its application are disclosed, using LiTFSI and LiDFOB as lithium salts and propylene carbonate, fluoroethylene carbonate, and isopropyl trifluoroacetate as solvents. The preparation method is as follows: First, lithium salts LiDFOB and LiTFSI, along with solutions of propylene carbonate, fluoroethylene carbonate, and isopropyl trifluoroacetate pre-dried in molecular sieves, are prepared according to a molar ratio of LiTFSI to LiDFOB of 0.8 M:0.2 M, and a volume ratio of propylene carbonate, fluoroethylene carbonate, and isopropyl trifluoroacetate of 6:1:3. The solution is then stirred in a glove box for 12 h. The concentration of Li in the electrolyte is 1 mol / L.
[0053] The NCM811||Li battery prepared using the electrolyte of Example 5 was tested for 1C cycle performance at -30 °C, 25 °C, and 60 °C. At -30 °C, the battery retained 44.2% of its capacity after 120 cycles at 4.5 V. At 25 °C, the battery retained 66.58% of its capacity after 200 cycles at 4.5 V. At a higher temperature of 60 °C, the NCM811||Li battery prepared using the electrolyte of Example 1 retained 74.31% of its capacity after 85 cycles at 1 C and 4.3 V, after which the battery exhibited severe overcharging.
[0054] Comparative Example 1:
[0055] LiTFSI and LiDFOB were used as lithium salts, and propylene carbonate and fluoroethylene carbonate were used as solvents. The preparation method was as follows: First, lithium salts LiDFOB and LiTFSI, along with solutions of propylene carbonate and fluoroethylene carbonate pre-dried in molecular sieves, were prepared according to a molar ratio of LiTFSI to LiDFOB of 0.8 M:0.2 M and a volume ratio of propylene carbonate to fluoroethylene carbonate of 8:2. The mixture was then stirred in a glove box for 12 h. The concentration of Li in the electrolyte was 1 mol / L.
[0056] Comparative Example 2:
[0057] LiTFSI and LiDFOB were used as lithium salts, and propylene carbonate and fluoroethylene carbonate were used as solvents. The preparation method was as follows: First, lithium salts LiDFOB and LiTFSI, along with solutions of propylene carbonate and fluoroethylene carbonate pre-dried in molecular sieves, were prepared according to a molar ratio of LiTFSI to LiDFOB of 0.8 M:0.2 M and a volume ratio of propylene carbonate to fluoroethylene carbonate of 9:1. The mixture was then stirred in a glove box for 12 h. The concentration of Li in the electrolyte was 1 mol / L.
[0058] The NCM811||Li battery prepared using the electrolyte of Comparative Example 2 was tested for 1 C cycling performance at -30 °C and 25 °C. At -30 °C, the battery retained 50.2% of its capacity after 100 cycles at 4.5 V, and at 25 °C, the battery retained 61.89% of its capacity after 200 cycles at 4.5 V.
[0059] Electrolyte performance testing:
[0060] The upper limit of the electrochemical window of the electrolyte was obtained by linear voltammetry.
[0061] Battery low temperature test:
[0062] The electrochemical performance of NMC811||Li batteries prepared using the electrolytes of the above examples and comparative examples was tested using the Xinwei Battery Testing System. The batteries were activated at room temperature and their room temperature capacity was tested. They were then placed in a low-temperature oven and left to stand at the test temperature for 2 hours before undergoing charge-discharge tests at different rates and cycle tests.
[0063] Battery room temperature cycle test:
[0064] The electrochemical performance of NMC811||Li batteries prepared using the electrolytes of the above examples and comparative examples was tested using the Xinwei Battery Testing System. The batteries were activated at room temperature and then subjected to charge-discharge tests at different rates. Long-cycle testing was performed using a 1 C constant current charge-discharge cycle test, and the capacity retention rate after each cycle compared to the first cycle was recorded.
[0065] Battery high-temperature cycle test:
[0066] The electrochemical performance of NMC811||Li batteries prepared using the electrolytes of the above examples and comparative examples was tested using the Xinwei Battery Testing System. After activation at room temperature, the batteries were placed in a high-temperature 60 °C oven and left to stand at the measured temperature for 2 hours before undergoing a 1 C constant current charge-discharge cycle test. The capacity retention rate after each cycle compared to the first cycle was recorded.
[0067] The upper limit of the electrochemical window at 25 °C was tested for Comparative Example 1 and Example 1. Figure 1 The electrochemical windows of the two electrolytes at 25 °C are shown. The upper limits of the electrochemical windows of Comparative Example 1 and Example 1 are 5.48 V and 5.71 V, respectively. Compared with conventional commercial carbonate electrolytes, the antioxidant properties of the electrolytes are increased.
[0068] from Figure 2 and Figure 3 As can be seen, the NCM811||Li battery prepared with the electrolyte of Example 1 exhibits excellent rate performance at low temperatures. Its discharge specific capacity at -30 °C, 1 C, and 4 C rates is 76.37% and 62.83% of the room temperature discharge specific capacity, respectively; while the NCM811||Li battery prepared with the electrolyte of Comparative Example 1 has a discharge specific capacity of only 63.23% and 10.76% of the room temperature capacity at 1 C and 4 C rates, respectively. The comparison at -40 °C is even more significant; the NCM811||Li battery prepared with the electrolyte of Comparative Example 1 has a discharge specific capacity of only 32.11% of the room temperature capacity at 1 C, while the battery of Example 1 has a discharge specific capacity of 55.79% of the room temperature capacity at the same rate.
[0069] To verify the cycling performance at low temperatures, the NCM811||Li battery prepared with the electrolyte from Example 1 was subjected to long-term cycling tests at −30 °C and 1C. Figure 4 As can be seen, Example 1 exhibits excellent low-temperature high-rate cycling stability, with the battery retaining 94.8% of its capacity after 120 cycles at 4.5 V.
[0070] To test the wide-temperature performance of the electrolyte, the NCM811||Li battery prepared using the electrolyte of Example 1 was subjected to rate testing at 25°C and 1C long-cycle testing. Additionally, a 1C long-cycle test was performed at 60°C. The test results are as follows: Figure 5 , Figure 6 and Figure 7 As shown. From Figure 5 It can be seen that at 25 °C, even at a 10 C rate, the battery prepared with the electrolyte of Example 1 still has a discharge specific capacity of 157.41 mAh / g, while the battery assembled with the electrolyte of Comparative Example 1 has a discharge specific capacity of 144.89 mAh / g at a 10 C rate. Figure 6 and Figure 7It can be seen that the electrolyte of Example 1 has excellent wide temperature performance: at 25°C, the battery retains 82.82% of its capacity after 200 cycles at 4.5 V. At a higher temperature of 60°C, the NCM811||Li battery prepared using the electrolyte of Example 1 retains 77.17% of its capacity after 100 cycles at 1 C and 4.3 V. In contrast, the battery using the electrolyte of Comparative Example 1 retains only 49.85% of its capacity after 100 cycles.
[0071] As can be seen, this invention vividly demonstrates the excellent wide-temperature-range and high-rate performance of wide-temperature-range battery electrolytes.
[0072] The above description is only a preferred embodiment of the present invention. Given that those skilled in the art can make appropriate changes and modifications to the above embodiments, the present invention is not limited to the specific embodiments described above, and some modifications and changes to the present invention should also fall within the protection scope of the claims of the present invention.
Claims
1. A wide-temperature-range, high-rate lithium battery ester-based electrolyte, characterized in that: The electrolyte comprises a soluble lithium salt and a liquid component; the liquid component is a solvent; the solvent comprises at least three of the following: propylene carbonate, fluoroethylene carbonate, isopropyl trifluoroacetate, ethyl trifluoroacetate, ethyl acetate, methyl acetate, and methyl trifluoroacetate.
2. The wide-temperature-range, high-rate lithium battery ester-based electrolyte according to claim 1, characterized in that: Soluble lithium salts include at least two of lithium bis(trifluoromethanesulfonyl)imide, lithium bis(fluorosulfonyl)imide, lithium tetrafluoroborate, lithium difluorooxalate borate, lithium dioxalate borate, lithium hexafluorophosphate, lithium difluorophosphate, lithium perchlorate, and lithium nitrate.
3. The wide-temperature-range, high-rate lithium battery ester-based electrolyte according to claim 2, characterized in that: Soluble lithium salts include lithium bis(trifluoromethanesulfonylimide) and lithium difluorooxalateborate.
4. The wide-temperature-range, high-rate lithium battery ester-based electrolyte according to claim 1, characterized in that: In the electrolyte, the molar concentration of soluble lithium salt is 0.8~1.5 mol / L, more preferably 0.9~1.2 mol / L.
5. The wide-temperature-range, high-rate lithium battery ester-based electrolyte and its application according to claim 1, characterized in that: The selected solvent includes at least one of propylene carbonate, fluoroethylene carbonate, and isopropyl trifluoroacetate.
6. The wide-temperature-range, high-rate lithium battery ester-based electrolyte according to claim 3, characterized in that: The selected soluble lithium salt is composed of LiTFSI and LiDFOB in a molar ratio of 3.8 to 4.2:1; more preferably, the molar ratio of LiTFSI and LiDFOB is 3.9 to 4.1:
1.
7. The wide-temperature-range, high-rate lithium battery ester-based electrolyte according to claim 1, characterized in that: The solvent is at least one of propylene carbonate, fluoroethylene carbonate, and isopropyl trifluoroacetate; more preferably, the solvent is composed of propylene carbonate, fluoroethylene carbonate, and isopropyl trifluoroacetate; even more preferably, the liquid component is composed of propylene carbonate, fluoroethylene carbonate, and isopropyl trifluoroacetate in a volume ratio of 3~10:0.2~4:0.2~6.
8. The wide-temperature-range, high-rate lithium battery ester-based electrolyte according to claim 7, characterized in that: The volume ratio of propylene carbonate, fluoroethylene carbonate and isopropyl trifluoroacetate is 4~8:1~3.5:
3. As a further preferred option, the volume ratio of propylene carbonate, fluoroethylene carbonate and isopropyl trifluoroacetate is 4.8~5.2:1.8~2.2:2.8~3.
2.
9. A wide-temperature-range, high-rate lithium battery ester-based electrolyte as described in any one of claims 1-8 and its application, characterized in that: The applications include the use of electrolytes in lithium batteries.
10. The application of the wide-temperature-range high-rate lithium battery ester-based electrolyte according to claim 9, characterized in that: The lithium battery includes the wide-temperature-range high-rate lithium battery ester-based electrolyte, a lithium metal negative electrode, and a high-voltage positive electrode material. The high-voltage cathode material is selected from at least one of nickel cobalt manganese oxide, lithium cobalt oxide, and nickel-based oxide.