Lithium carbon fluoride battery electrolyte, preparation method and lithium carbon fluoride battery

Abstract

The invention relates to a lithium carbon fluoride battery electrolyte and preparation thereof, and a lithium carbon fluoride battery, the lithium carbon fluoride battery electrolyte comprises a lithium salt and a solvent, and also comprises an additive metallocene, and the metallocene is one or two of cobaltocene and ferrocene; according to the electrolyte, on the premise that the capacity is not lost, the heat yield of the battery is reduced, and the voltage platform of the battery under different discharge rates is widened.

Description

Technical Field

[0001] This invention belongs to the field of lithium battery heat generation technology, specifically relating to a lithium fluoride carbon battery electrolyte and a low-heat-generating lithium fluoride carbon battery. Background Technology

[0002] Because lithium metal has an extremely high theoretical specific capacity (3860 mAh g⁻¹) -1 The high energy density (>1000 Wh / kg) of lithium primary batteries, achieved by combining high electrode potential (-3.04 V vs. SHE), with electrode potential (-3.04 V vs. SHE), results in energy density nearly twice that of lithium-ion batteries. -1 Therefore, lithium primary batteries are still widely used in primary battery applications such as portable electronic devices, automotive products, wearable devices, medical devices, and aerospace and marine equipment. Among different types of lithium primary batteries, lithium fluoride carbon batteries (Li / CF2) are... x Because of its high energy density (2180Wh / kg) -1 Lithium fluoride batteries have become a promising primary battery energy storage device due to their advantages such as stable discharge platform, low self-discharge rate, wide operating temperature range, and long storage life. However, despite these advantages, thermal runaway becomes a significant problem under high-rate discharge conditions, directly impacting the battery pack's structural design and operational safety. Therefore, resolving the thermal runaway issue is the primary challenge facing lithium fluoride batteries.

[0003] The thermal runaway problem in lithium-carbon fluoride batteries occurs because, during discharge, the carbon-fluorine bonds break and react with lithium ions, causing voltage hysteresis and the formation of large amounts of lithium fluoride, generating significant heat. Even without thermal runaway, the high-temperature environment of the cell negatively impacts battery components, shortening battery life. Simultaneously, the activity of electrode materials decreases at high temperatures, and the diffusion rate of lithium ions in the electrolyte also slows down, leading to a sharp decline in battery performance. Therefore, despite the challenges of Li / CF4 batteries... x While batteries boast high capacity and high voltage, their performance remains unsatisfactory. Therefore, there is an urgent need to develop a low-heat-generating lithium-carbon fluoride battery to meet the demands of future applications and achieve thermal stability and safety during high-rate discharge. Summary of the Invention

[0004] To address the thermal runaway problem in lithium-carbon fluoride batteries, this invention proposes an electrolyte that reduces the heat generated during the lithium fluoride crystallization process by pre-generating a large number of crystal nuclei through a chemical reaction of lithium fluoride before battery discharge, thereby reducing the heat generated during the Li / CF battery's thermal runaway. xRegulation of battery heat generation process. This invention utilizes the addition of metallocene to the electrolyte to reduce the cathode material, inducing a pre-chemical reaction in the cathode material before discharge and generating free lithium fluoride nuclei on the cathode material surface. This reduces the nucleation barrier of lithium fluoride, lowers the surface formation energy of lithium fluoride, and reduces the Li / CF ratio. x The purpose of this electrolyte is to reduce the large amount of heat released by lithium fluoride at high discharge rates. Furthermore, this electrolyte also reduces the battery's voltage plateau at different discharge rates without sacrificing capacity.

[0005] This invention relates to a lithium fluoride carbon battery electrolyte, comprising a lithium salt and a solvent, and further comprising a metallocene additive, wherein the metallocene is one or both of cobalt dicene and ferrocene, preferably cobalt dicene.

[0006] Furthermore, the content of the metallocene additive is 0.1-1.5 wt% of the total mass of the electrolyte, preferably 0.5-1.0 wt%, and more preferably 0.6-0.8 wt%.

[0007] Furthermore, the solvent is at least one or more of the following lipid electrolytes: ethylene carbonate (EC), ethyl methyl carbonate (EMC), fluoroethylene carbonate (FEC), propylene carbonate (PC), and dimethyl carbonate (DMC). Preferably, the added solvent is at least one or more of the following: ethylene carbonate (EC), ethyl methyl carbonate (EMC), and fluoroethylene carbonate (FEC). More preferably, EC / EMC / FEC is mixed in a volume ratio of (40-50) / (40-50) / (5-15).

[0008] Furthermore, the lithium salt is one or more of lithium salts such as lithium hexafluorophosphate (LiPF6), lithium tetrafluoroborate (LiBF4), lithium bis(fluorosulfonyl)imide (LiFSI), and lithium bis(trifluoromethanesulfonyl)imide (LiTFSI). Preferably, the added lithium salt is lithium hexafluorophosphate (LiPF6). The concentration of the lithium salt in the electrolyte is 0.5-2M, preferably 0.8-1.5M, and more preferably 1-1.2M.

[0009] The present invention also relates to a method for preparing the electrolyte, comprising the following steps:

[0010] 1) The solvent and lithium salt are mixed and stirred under an inert atmosphere to obtain the electrolyte;

[0011] 2) Under an inert atmosphere, the metallocene is mixed with the electrolyte from step 1), and the mixture is stirred to obtain the electrolyte with added metallocene.

[0012] The stirring time for the electrolyte is 0–4 hours;

[0013] Inert gases are classified as high-purity argon, with a purity greater than 99.999%, and oxygen and water content less than 0.01 ppm.

[0014] The present invention also relates to a lithium fluoride carbon battery, comprising a positive electrode, a negative electrode, an electrolyte, and a separator;

[0015] The positive electrode uses carbon fluoride (CF2) x The active substance is , and the electrolyte is the electrolyte.

[0016] Preferably, the lithium fluoride carbon battery of the present invention includes a pouch battery or a button lithium metal battery.

[0017] Furthermore, the positive electrode uses an aluminum sheet as the current collector with a thickness of 10-30 μm; a composite electrode with fluorinated carbon as the active material is loaded on it;

[0018] Preferably, the diameter of the aluminum current collector is 12-16 mm.

[0019] The conductive agent used in the composite electrode is SuperP, which accounts for 5-10 wt% of the total amount of the composite electrode.

[0020] The binder used in the composite electrode is PVDF, and the content of the binder accounts for 5 to 10 wt% of the total amount of the composite electrode.

[0021] Fluorocarbon (CF) x The carrying capacity is 1.5–12.5 mg / cm³. 2 .

[0022] Preferably, when assembling coin cells, fluorinated carbon (CF4) is used. x The carrying capacity is 1.5–2.5 mg / cm³. 2 When assembling pouch cells, carbon fluoride (CF3) x The dosage is 10.5–12.5 mg / cm³. 2 .

[0023] Preferably, fluorocarbon (CF) x The diameter of the fluorocarbon is 12-16 mm. The fluorocarbon used is CF2. x The carbon-fluorine ratio x value in the sample is 0.5 to 1.5, with the optimal value being 0.9.

[0024] Furthermore, the battery uses Celgard 2325 as the separator;

[0025] The negative electrode is a lithium metal sheet. When assembling a coin cell battery, the thickness of the lithium sheet is 500-800μm; when assembling a pouch cell battery, the thickness of the lithium sheet is 50-100μm.

[0026] Preferably, when assembling a button cell battery, the diameter of the lithium metal sheet is 14-18 mm and the thickness is 500-800 μm; when assembling a pouch cell battery, the length and width of the lithium metal sheet are (20-200):(10-50) mm.

[0027] Under an inert atmosphere, lithium sheets, electrolyte with added metallocene, separator, and positive electrode are assembled in sequence to form a lithium metal battery.

[0028] The electrolyte is injected into the battery of the equipment.

[0029] Furthermore, the mass ratio of the metallocene to the positive electrode active material in the battery is 0.023 to 0.572.

[0030] More specifically, this invention relates to a lithium fluoride carbon battery electrolyte and a low-heat-generating lithium fluoride carbon battery. The battery assembly method includes the following steps:

[0031] (1) Mix the solvent and lithium salt under an inert atmosphere and stir thoroughly to obtain an electrolyte;

[0032] (2) Mix the metallocene with the electrolyte from step (1) under an inert atmosphere and stir thoroughly to obtain the electrolyte with added metallocene;

[0033] (3) Under the protection of an inert atmosphere, lithium sheet, electrolyte with added metallocene, separator and positive electrode are assembled into a coin cell lithium metal battery in sequence.

[0034] (4) Apply double-sided coated CF in a drying chamber x Cathode and bare lithium anode assembly 0.5AhLi / CF x The soft-pack battery has a dew point that is kept constant at 25°C. The assembly sequence of the soft-pack battery includes material preparation, electrode coating, cutting, stacking assembly, injection of the electrolyte prepared in step (2), and encapsulation.

[0035] The beneficial effects of this invention are as follows:

[0036] (1) The electrolyte of the present invention can reduce the heat generated during discharge. Metallocene is added to reduce the positive electrode material and induce the positive electrode material to undergo a chemical reaction to generate free lithium fluoride crystal nuclei on the surface of the positive electrode material. This can reduce the nucleation barrier of newly generated lithium fluoride during discharge, reduce the surface generation energy of lithium fluoride, and thus reduce the heat released when lithium fluoride is generated at high rate in lithium fluoride carbon batteries.

[0037] (2) The lithium fluoride carbon battery electrolyte of the present invention improves the electrode electromotive force and exhibits a small nucleation overpotential, thus broadening the voltage plateau at high rates.

[0038] (3) The lithium fluoride carbon battery electrolyte of the present invention effectively reduces the heat generated during discharge, avoids negative impact on battery components, thereby extending the battery's service life, improving the diffusion rate of lithium ions in the electrolyte and the activity of electrode materials, and improving battery performance.

[0039] (4) The cathode material described in this invention uses metallocene as an additive, which avoids the loss of capacity caused by the large consumption of fluorinated carbon compared with the use of other reducing additives. Attached Figure Description

[0040] Figure 1 The discharge curves are for Example 1, Example 5, and Comparative Example 5.

[0041] Figure 2 The X-ray diffraction patterns of Example 1, Comparative Example 1, and Comparative Example 2 are shown below.

[0042] Figure 3 The discharge curves (A) and percentage accumulation diagrams (B) for Examples 1, 2, 3, 4, and Comparative Example 1 are shown.

[0043] Figure 4 Tafel curves for Example 1, Comparative Example 1, and Comparative Example 2;

[0044] Figure 5 The GITT curve (A) and lithium-ion diffusion map (B) are for Example 1 and Comparative Example 1;

[0045] Figure 6 Temperature-time graphs of pouch cells under isothermal conditions in Example 1 and Comparative Example 1;

[0046] Figure 7 The temperature-time graphs for pouch cells under adiabatic conditions are shown for Example 1 (A) and Comparative Example 1 (B). Detailed Implementation

[0047] The present invention will be described in detail below with reference to the embodiments. However, the implementation of the present invention is not limited thereto. Obviously, the embodiments described below are only some embodiments of the present invention. For those skilled in the art, other similar embodiments can be obtained without creative effort and all fall within the protection scope of the present invention.

[0048] Take 0.1g of polyvinylidene fluoride (PVDF, number average molecular weight 600,000), 0.1g of SuperP, and 0.8g of fluorinated carbon (CF). 0.9The fluorinated carbon was dissolved in N-methylpyrrolidone and stirred for 5 hours. The mixture was then coated onto aluminum foil using a scraper adjusted to a thickness of 150 μm. The coated film was then dried in a 60°C oven for 8 hours. The resulting electrode was bonded to the aluminum foil, yielding a positive electrode sheet with fluorinated carbon as the positive electrode active material. When assembling a coin cell, the one-sided carrying capacity of the positive electrode material, fluorinated carbon, was 2.2 mg / cm³. -2 When constructing a pouch cell, the one-sided carrying capacity of the positive electrode material, carbon fluoride, is 11.6 mg / cm². -2 .

[0049] For assembled batteries, the cutoff voltage window is 1.5V. Specific capacity calculation is based on the overall CF... x The mass and 1C = 829 mA / g.

[0050] 0.5AhLi / CF x The battery was discharged at 30°C in a constant temperature chamber, and the battery temperature data was monitored by an infrared thermal imager.

[0051] 0.5AhLi / CF x The discharge process of the pouch battery was conducted using a LakeShore 340 temperature controller to provide an adiabatic environment, and the discharge temperature was monitored by a KEYSIGHT (DAQ970A) temperature monitoring system. To prevent deformation and thermal runaway during discharge under adiabatic conditions, the adiabatic test was performed in several stages. Furthermore, the maximum temperature set for each test stage was 70℃. (Li / CF) x The battery is discharged at 0.5C. When the surface temperature reaches 70°C, the discharge process stops (step 1), and then the surface temperature is reduced to approximately 30°C (step 2). Steps 1 and 2 are repeated until the voltage drops to 1.5V.

[0052] Example 1

[0053] The initial electrolyte was prepared by uniformly mixing 1M LiPF6 in EC / EMC / FEC (v / v / v = 45 / 45 / 10) for 1 h in an inert gas atmosphere of high-purity argon (purity greater than 99.999%) with oxygen and water content less than 0.01 ppm for 1 h. A metallocene, specifically cobalt-dioctenosene (Co(C5H5)2), was added to the obtained electrolyte, with the metallocene additive content accounting for 0.75 wt% of the total electrolyte mass. The mixture was then uniformly mixed for 2 h to obtain the final electrolyte.

[0054] Electrolyte was injected into a lithium battery casing consisting of a positive electrode with fluorinated carbon as the positive electrode active material, a lithium metal sheet as the negative electrode (700µm thick), and a Celgard 2325 separator (the positive electrode, separator, and negative electrode are stacked sequentially in the casing, with the electrolyte filling between the positive and negative electrodes). The assembled coin cell was then placed in the Blue Electric electrochemical testing system for constant current charge-discharge testing.

[0055] Assemble a 9cm*4.5cm*1mm 0.5AhLi / CF1 electrode with one positive and two negative electrodes (negative electrode, separator, positive electrode, separator, and negative electrode stacked in sequence). x In the pouch cell, the unilateral carrying capacity of the positive electrode material, carbon fluoride, is 11.6 mg / cm². -2 The pouch cell was connected to the Blue Electrochemical testing system, and the heat generation during the battery discharge process was tested under constant temperature (30℃).

[0056] Assemble a 9cm*4.5cm*1mm 0.5AhLi / CF1 electrode with one positive and two negative electrodes (negative electrode, separator, positive electrode, separator, and negative electrode stacked in sequence). x The single-sided carrying capacity of carbon fluoride, the positive electrode material, in a pouch cell is 11.6 mg / cm². -2 The soft-pack battery is connected to the Blue Electrochemical testing system to avoid heat exchange with the external environment, and the heat generation during the battery discharge process is tested in an adiabatic environment.

[0057] The prepared electrode was immersed in an electrolyte containing cobalt diacene for 10 minutes. After removal, the electrode material on the electrode was scraped off for XRD testing. The results showed that lithium fluoride was formed on the surface, indicating that cobalt diacene promoted the nucleation and growth of lithium fluoride in the electrolyte, which helps to improve the interfacial stability and electrochemical performance of the electrode.

[0058] Example 2

[0059] In a gaseous atmosphere with high-purity argon as the inert gas (purity greater than 99.999%) and oxygen and water content less than 0.01 ppm, according to 1M LiPF6 in EC / EMC / FEC...

[0060] The initial electrolyte was prepared by uniformly mixing (v / v / v = 45 / 45 / 10) for 1 h. A metallocene, specifically cobalt-dicyclopentadiene (Co(C5H5)2), was added to the resulting electrolyte at a mass percentage of 0.25 wt%. The mixture was then uniformly mixed for 2 h to obtain the final electrolyte.

[0061] Electrolyte was injected into a lithium battery with fluorinated carbon as the positive electrode active material, lithium metal as the negative electrode, and Celgard 2325 as the separator. The assembled battery was then placed in the Blue Electric electrochemical testing system for constant current charge-discharge testing, using the same testing method as in Example 1.

[0062] Example 3

[0063] In an inert gas atmosphere of high-purity argon (purity greater than 99.999%) with oxygen and water content less than 0.01 ppm, 1 M LiPF6 in EC / EMC / FEC (v / v / v = 45 / 45 / 10) was uniformly mixed for 1 h to prepare the initial electrolyte. A metallocene, specifically cobalt-disperse (Co(C5H5)2), was added to the obtained electrolyte at a concentration of 0.5 wt% of the total electrolyte mass. The mixture was then uniformly mixed for 2 h to obtain the electrolyte solution. This electrolyte solution was injected into a lithium-ion battery with fluorinated carbon as the positive electrode active material, lithium metal as the negative electrode, and Celgard 2325 as the separator. The assembled battery was then subjected to constant current charge-discharge testing using a Blue Electric electrochemical testing system, following the same testing method as in Example 1.

[0064] Example 4

[0065] In an inert gas atmosphere of high-purity argon (purity greater than 99.999%) with oxygen and water content less than 0.01 ppm, 1 M LiPF6 in EC / EMC / FEC (v / v / v = 45 / 45 / 10) was uniformly mixed for 1 h to prepare the initial electrolyte. A metallocene, specifically cobalt-disperse (Co(C5H5)2), was added to the obtained electrolyte at a concentration of 1.25 wt% of the total electrolyte mass. The mixture was then uniformly mixed for 2 h to obtain the electrolyte solution. This electrolyte solution was injected into a lithium-ion battery with fluorinated carbon as the positive electrode active material, lithium metal as the negative electrode, and Celgard 2325 as the separator. The assembled battery was then subjected to constant current charge-discharge testing using a Blue Electric electrochemical testing system, following the same testing method as in Example 1.

[0066] Example 5

[0067] In an inert gas atmosphere of high-purity argon (purity greater than 99.999%) with oxygen and water content less than 0.01 ppm, 1 M LiPF6 in EC / EMC / FEC (v / v / v = 45 / 45 / 10) was uniformly mixed for 1 h to prepare the initial electrolyte. A metallocene, specifically ferrocene (Fe(C5H5)2), was added to the obtained electrolyte at a concentration of 0.75 wt% of the total electrolyte mass. The mixture was then uniformly mixed for 2 h to obtain the electrolyte solution. This electrolyte solution was injected into a lithium-ion battery with fluorinated carbon as the positive electrode active material, lithium metal as the negative electrode, and Celgard 2325 as the separator. The assembled battery was then subjected to constant current charge-discharge testing using a Blue Electric electrochemical testing system, following the same testing method as in Example 1.

[0068] Example 6

[0069] In an inert gas atmosphere of high-purity argon (purity greater than 99.999%) with oxygen and water content less than 0.01 ppm, 1 M LiPF6 in EC / EMC (v / v = 1 / 1) was uniformly mixed for 1 h to prepare the initial electrolyte. A metallocene, specifically Co(C5H5)2, was added to the obtained electrolyte at a concentration of 0.75 wt% of the total electrolyte mass. The mixture was then uniformly mixed for 2 h to obtain the electrolyte solution. This electrolyte solution was injected into a lithium-ion battery with fluorinated carbon as the positive electrode active material, lithium metal as the negative electrode, and Celgard 2325 as the separator. The assembled battery was then subjected to constant current charge-discharge testing using a Blue Electric electrochemical testing system, following the same testing method as in Example 1.

[0070] Comparative Example 1

[0071] The initial electrolyte was prepared by uniformly mixing 1M LiPF6 in EC / EMC / FEC (v / v / v = 45 / 45 / 10) for 1 hour in an inert gas atmosphere of high-purity argon (purity greater than 99.999%) with oxygen and water content less than 0.01 ppm. The electrolyte was then injected into a coin cell lithium battery with fluorinated carbon as the positive electrode active material, lithium metal as the negative electrode (700 μm thickness), and Celgard 2325 as the separator. The assembled battery was then subjected to constant current charge-discharge testing using a Blue Electric electrochemical testing system.

[0072] Assemble a 9cm*4.5cm*1mm 0.5AhLi / CF1 electrode with one positive and two negative electrodes (negative electrode, separator, positive electrode, separator, and negative electrode stacked in sequence). x In the pouch cell, the unilateral carrying capacity of the positive electrode material, carbon fluoride, is 11.6 mg / cm². 2 The pouch battery was connected to the Blue Electric Electrochemical Testing System, and the heat generation during the battery discharge process was tested under constant temperature (30℃).

[0073] Assemble a 9cm*4.5cm*1mm 0.5AhLi / CF1 electrode with one positive and two negative electrodes (negative electrode, separator, positive electrode, separator, and negative electrode stacked in sequence). x In the pouch cell, the unilateral carrying capacity of the positive electrode material, carbon fluoride, is 11.6 mg / cm². 2 The soft-pack battery is connected to the Blue Electrochemical testing system to avoid heat exchange with the external environment, and the heat generation during the battery discharge process is tested in an adiabatic environment.

[0074] The prepared electrode was transferred to an electrolyte without metallocene additives and immersed for 10 minutes. After removal, the electrode material on the electrode was scraped off and XRD test was performed.

[0075] Comparative Example 2

[0076] The same amount of fluorinated carbon as in Comparative Example 1 was used, with a single-sided loading of 11.6 mg / cm². 2 The positive electrode is scraped off, and the electrode material is then subjected to XRD testing.

[0077] Comparative Example 3

[0078] In an inert gas atmosphere of high-purity argon (purity greater than 99.999%) with oxygen and water content less than 0.01 ppm, 1 M LiPF6 in EC / EMC / FEC (v / v / v = 45 / 45 / 10) was uniformly mixed for 1 h without the addition of metallocenes to prepare the initial electrolyte. Lithium fluoride (LiF) was added to the obtained electrolyte at a concentration of 0.75 wt% of the total electrolyte mass, and the mixture was uniformly mixed for 2 h to obtain the electrolyte solution. The electrolyte solution was then injected into a lithium battery with fluorinated carbon as the positive electrode active material, lithium metal as the negative electrode, and Celgard 2325 as the separator. The assembled battery was placed in the Blue Electric electrochemical testing system for constant current charge-discharge testing, using the same testing method as Comparative Example 1.

[0079] Comparative Example 4

[0080] In an inert gas atmosphere of high-purity argon (purity greater than 99.999%) with oxygen and water content less than 0.01 ppm, a commercial electrolyte was uniformly mixed with 1 M LiBF4 in PC / DME (v / v = 1 / 1) for 1 h to prepare the initial electrolyte. A metallocene, specifically cobalt-disperse (Co(C5H5)2), was added to the obtained electrolyte at a content of 0.75 wt% of the total electrolyte mass. The mixture was uniformly mixed for 2 h to obtain the electrolyte. The electrolyte was then injected into a lithium-ion battery with fluorinated carbon as the positive electrode active material, lithium metal as the negative electrode, and Celgard 2325 as the separator. The assembled battery was placed in a Blue Electric electrochemical testing system for constant current charge-discharge testing, using the same testing method as Comparative Example 1.

[0081] Comparative Example 5

[0082] In an inert gas atmosphere of high-purity argon (purity greater than 99.999%) with oxygen and water content less than 0.01 ppm, 1 M LiPF6 in EC / EMC / FEC (v / v / v = 45 / 45 / 10) was uniformly mixed for 1 h to prepare the initial electrolyte. A metallocene, specifically nickel-cadmium (Ni(C5H5)2), was added to the obtained electrolyte at a concentration of 0.75 wt%, and the mixture was uniformly mixed for 2 h to obtain the electrolyte solution. This electrolyte solution was then injected into a lithium-ion battery with fluorinated carbon as the positive electrode active material, lithium metal as the negative electrode, and Celgard 2325 as the separator. The assembled battery was placed in a Blue Electric electrochemical testing system for constant current charge-discharge testing, using the same testing method as Comparative Example 1.

[0083] Analysis of experimental results:

[0084] During the constant current discharge test at room temperature (25°C) on the electrode materials prepared in Examples 1, 5, and Comparative Example 5 using the LandCT2001A battery testing system, such as... Figure 1 As shown, the following phenomena were observed: the electrode material of Example 1 exhibited good performance, with a discharge capacity roughly the same as that of Comparative Example 1. This demonstrates that the relatively stable metallocene can increase the electromotive force of the electrode, thereby increasing its nucleation overpotential and facilitating nucleation. During discharge, newly formed LiF adheres to and grows on the surface of pre-formed LiF nuclei, thus reducing the entropy increase associated with LiF nucleation. This will lead to a Li / CF ratio... x The electromotive force (EMF) of the battery increased. However, because the oxidation potential of ferrocene is higher than that of carbon fluoride, the reaction of carbon fluoride is more intense, resulting in more severe side reactions. The discharge capacity of the electrode material in Example 5 decreased significantly during cycling. Further observation of Comparative Example 5 revealed that due to the poor chemical stability of the nickel ferrocene used in the electrolyte, its discharge capacity during 5C high-rate discharge was 264.5 mAh / g, a sharp decrease compared to the 693.7 mAh / g discharge capacity of Example 1. The decrease was very significant, and the electromotive force of the electrode decreased. The interaction between nickel ferrocene and the electrolyte may lead to instability of the solid electrolyte interface (SEI), further limiting the migration efficiency of lithium ions.

[0085] Furthermore, Comparative Example 3, by directly adding lithium fluoride to the electrolyte, aimed to induce nucleation without a chemical reaction. However, its discharge specific capacity at a high rate of 5C was only 696.8 mAh / g, and the nucleation overpotential remained as high as 250 mV. This result indicates that this strategy did not bring the expected significant improvement, demonstrating that directly adding lithium fluoride did not effectively improve the nucleation behavior of lithium ions, resulting in a still high nucleation overpotential. Comparative Example 4, by adding metallocene to a commercial electrolyte (1M LiBF4 in PC / DME (v / v = 1 / 1)), caused a short circuit in the battery. This is likely due to the interaction between the metallocene and the ether electrolyte, leading to electrolyte degradation and the generation of non-conductive byproducts, which reduces electrolyte stability and negatively impacts battery performance. This demonstrates that lipid electrolytes generally exhibit higher stability in chemical environments, better resisting adverse reactions with metallocenes and reducing the risk of degradation. It can be seen that the three lipid-based electrolytes in Example 1 can enhance the stability of the system, thereby improving battery safety, reducing the risk of thermal runaway, and thus improving overall battery performance. Furthermore, FEC can increase the lithium-ion conductivity of the electrolyte, enhancing overall battery performance, especially at high-rate discharge. In contrast, Example 6 showed a capacity of 567.6 mAh / g at a 5C high-rate discharge, indicating a significant decrease in discharge capacity. These results demonstrate that additives and electrolytes have a decisive influence on electrochemical performance.

[0086] XRD tests were performed on the electrodes prepared in Example 1 and Comparative Example 1. The electrodes used for characterization were obtained by disassembling the battery in an argon-filled glove box, then cleaning the electrodes, and drying them in a vacuum drying oven at 80°C for 12 hours. The test results are as follows. Figure 2 As shown. Example 1 exhibits an amorphous structure, with lithium fluoride displaying broad and small peaks, indicating small grain size and significant internal distortion and stress, leading to the enrichment of a large number of lithium fluoride particles. In contrast, the untreated electrode in Comparative Example 2 showed no change. The addition of metallocene can generate lithium fluoride nuclei on the electrode surface through a chemical reaction, indicating that metallocene can undergo redox reactions with fluorinated carbon, causing the carbon-fluorine bonds in the fluorinated carbon to break, generating graphitized carbon and a small amount of free lithium fluoride nuclei.

[0087] Electrochemical performance tests were conducted on batteries assembled with electrolytes containing different concentrations of cobalt-ceramic as an additive used in Examples 1-4, and on batteries assembled with an electrolyte without cobalt-ceramic used in Comparative Example 1. The results are as follows: Figure 3As shown, with the increase of cobalt-ceramic electrolyte concentration, the voltage hysteresis of the battery decreased, and the electrode electromotive force of the battery after adding cobalt-ceramic electrolyte significantly increased compared to that of Comparative Example 1. Example 4 showed the highest electrode electromotive force, but its capacity exhibited significant decay. This demonstrates that the preferred percentage of cobalt-ceramic addition to the total electrolyte mass is 0.75 wt%.

[0088] The Tafel curves of the prepared cathode materials from Examples 1, 5, and Comparative Example 1 were tested using different electrolytes on a CHI660 electrochemical workstation. The results are as follows: Figure 4 As shown. From Figure 4 It can be seen that the exchange current density of Examples 1 and 5 is higher than that of Comparative Example 1, showing stronger interfacial reaction kinetics; indicating that the introduction of metallocene can reduce the surface generation energy of lithium fluoride by free lithium fluoride nuclei induced by the carbon fluoride interface, promote the interfacial reaction, and accelerate the reaction kinetics.

[0089] The batteries prepared in Example 1 and Comparative Example 1 were subjected to GITT testing, Li / CF x Discharge the battery at 0.1C for 10 minutes (step 1), then let it rest for half an hour (step 2). Repeat steps 1 and 2 until the voltage drops to 1.5V, as shown in the following figure. Figure 5 As shown. In the initial stage of discharge, the addition of cobalt-cene can lower the nucleation barrier of lithium fluoride, thereby promoting lithium-ion diffusion. The addition of cobalt-cene can accelerate the dispersion of LiF in the electrolyte, forming a rapid ion transport channel and promoting lithium-ion diffusion. When the voltage drops below 2.0V, excessive LiF is generated in the electrode, leading to Li... + The diffusion channels were blocked, causing D Li+ The value decreased.

[0090] The 0.5AhLi / CF with one positive and two negative atoms prepared in Example 1 x The heat generation of the pouch battery during discharge under constant temperature conditions of 30℃ was tested, with a discharge rate of 1C. The obtained maximum temperature versus time curves are shown below. Figure 6 As shown. From Figure 6 It can be seen that the heating rate and the highest temperature of the battery in Example 1 are lower than those in Comparative Example 1, indicating that the addition of metallocene electrolyte can significantly reduce the heat generation rate and heat output of the battery.

[0091] Example 1 and Comparative Example 1 were assembled with one positive and two negative 0.5AhLi / CF x The soft-pack battery underwent a heat generation test in a 0.5C, adiabatic environment, and the results are as follows: Figure 7As shown. When the battery surface temperature reaches 70°C, discharge is paused (step 1), and the battery surface temperature is allowed to cool naturally to 30°C (step 2). Steps 1 and 2 are repeated until the battery voltage drops to 1.5V. Under adiabatic conditions, Example 1 reached 70°C for the first time 535 seconds later than Comparative Example 1, indicating that the temperature rise rate of Example 1 is much lower than that of Comparative Example 1 before discharge begins, i.e., during the nucleation of lithium fluoride. This demonstrates that controlling the thermal runaway process of the battery through pre-nucleation significantly improves the heat released during the formation of lithium fluoride in lithium-carbon fluoride batteries at high rates.

Claims

1. A lithium fluoride carbon battery electrolyte, comprising a lithium salt and a solvent, characterized in that: It also includes metallocene additives, wherein the metallocene is one or two of cobalt cadmium and ferrocene, preferably cobalt cadmium.

2. The electrolyte according to claim 1, characterized in that: The content of the metallocene additive is 0.1-1.5 wt% of the total mass of the electrolyte, preferably 0.5-1.0 wt%, and more preferably 0.6-0.8 wt%.

3. The electrolyte according to claim 1, characterized in that: The solvent is one or more of ethylene carbonate, methyl ethyl carbonate, fluoroethylene carbonate, propylene carbonate, and dimethyl carbonate; preferably, the solvent is one or more of ethylene carbonate, methyl ethyl carbonate, and fluoroethylene carbonate; more preferably, ethylene carbonate / methyl ethyl carbonate / fluoroethylene carbonate is mixed in a volume ratio of (40-50) / (40-50) / (5-15).

4. The electrolyte according to claim 1, characterized in that: The lithium salt is one or more of lithium hexafluorophosphate, lithium tetrafluoroborate, lithium bis(fluorosulfonyl)imide, and lithium bis(trifluoromethylsulfonyl)imide; preferably, the lithium salt is lithium hexafluorophosphate; the concentration of the lithium salt in the electrolyte is 0.5-2M, preferably 0.8-1.5M, and more preferably 1-1.2M.

5. A method for preparing the electrolyte according to any one of claims 1-4, characterized in that, Includes the following steps: 1) The solvent and lithium salt are mixed and stirred under an inert atmosphere to obtain the electrolyte; 2) Under an inert atmosphere, the metallocene is mixed with the electrolyte from step 1), and the mixture is stirred to obtain the electrolyte with added metallocene. The stirring time for the electrolyte is 0–4 hours; Inert gases are classified as high-purity argon, with a purity greater than 99.999%, and oxygen and water content less than 0.01 ppm.

6. A lithium fluoride carbon battery, comprising a positive electrode, a negative electrode, an electrolyte, and a separator, characterized in that: The positive electrode uses carbon fluoride (CF) x The active material is the electrolyte as described in any one of claims 1-4.

7. The battery according to claim 6, characterized in that: The positive electrode uses an aluminum sheet as the current collector, on which a composite electrode with fluorinated carbon as the active material is loaded. The conductive agent used in the composite electrode is SuperP, which accounts for 5-10 wt% of the total amount of the composite electrode. The binder used in the composite electrode is PVDF, and the content of the binder accounts for 5 to 10 wt% of the total amount of the composite electrode. Fluorinated carbon CF x The carrying capacity is 1.5–12.5 mg / cm³. 2 .

8. The battery according to claim 6, characterized in that: The battery uses Celgard 2325 as the separator; The negative electrode is a lithium metal sheet; Under an inert atmosphere, lithium sheets, electrolyte with added metallocene, separator, and positive electrode are assembled in sequence to form a lithium metal battery. The electrolyte is injected into the battery of the equipment.

9. The battery according to claim 6, characterized in that: The mass ratio of the metallocene to the positive electrode active material in the battery is 0.023 to 0.572.

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