High-pressure-resistant non-flammable electrolyte, preparation method and application thereof in preparation of lithium metal battery

Abstract

The application relates to a high-pressure-resistant non-flammable electrolyte, a preparation method thereof and application of the electrolyte in preparation of lithium metal batteries, and belongs to the technical field of lithium metal battery preparation. The electrolyte is composed of a lithium salt, an electrolyte solvent and a fluoroalkane diluent, the molar ratio of the lithium salt to the electrolyte solvent is 1:1-5, and the molar ratio of the electrolyte solvent to the fluoroalkane diluent is 0.2-5:1; the fluoroalkane diluent includes cyclic fluoroalkane and chain fluoroalkane, the lithium salt can be one or more of organic or inorganic lithium salts such as lithium bisfluorosulfonylimide, lithium bis(trifluoromethanesulfonyl)imide, lithium hexafluorophosphate or lithium chloride, and the electrolyte solvent is an ether-based electrolyte suitable for a lithium metal negative electrode. The electrolyte has the characteristics of non-flammability, high-pressure resistance, high stability and wide temperature adaptability (-20-60 DEG C), and the electrolyte is suitable for high-specific-energy lithium metal batteries, and has remarkable application value in the fields of new energy automobile power batteries and energy storage batteries.

Description

Technical Field

[0001] This invention belongs to the field of lithium metal battery preparation technology, specifically relating to a high-voltage resistant non-flammable electrolyte, its preparation method, and its application in the preparation of lithium metal batteries. Background Technology

[0002] Lithium metal batteries have a relatively high theoretical capacity (3860 mAh g) due to their negative electrode. -1 With its lowest operating voltage (-3.04V vs SHE), it is considered to have broken the 500Wh / kg energy density barrier. -1 The ideal system for lithium-ion batteries holds promise for replacing commercial lithium-ion batteries in power batteries for new energy vehicles and large-scale energy storage. However, due to the strong side reactions between the traditional electrolyte and the negative electrode, the unstable solid electrolyte interphase (SEI) film leads to continuous electrolyte consumption and lithium dendrite growth, as well as safety hazards such as short circuits and thermal runaway caused by lithium dendrites. To address these issues, researchers have proposed a high-concentration electrolyte scheme. By adjusting the lithium-ion solvation structure, a dense SEI film rich in inorganic substances (such as LiF) is induced, thereby suppressing dendrite growth and improving cycle stability. However, high-concentration electrolytes suffer from serious drawbacks such as high cost, high self-discharge, low energy density, and low environmental adaptability.

[0003] To address the aforementioned issues, researchers further proposed a locally high-concentration electrolyte. By introducing a low-polarity, low-viscosity diluent, a solvation structure with high salt concentration can be maintained in localized regions. Fluoride diluents, primarily fluoroethers, are ideal choices due to their low dielectric constant and high fluorine content. They can promote the formation of locally high-concentration structures and generate a LiF-rich SEI film on the lithium metal surface, significantly improving interfacial stability. Furthermore, fluoride diluents lower the desolvation energy barrier by regulating the solvation structure, enhancing the stability of the SEI / CEI film, and are compatible with both lithium metal anode and high-voltage cathode materials (such as NCM811). While locally high-concentration electrolytes improve battery performance through a "high-concentration lithium salt + diluent" strategy, they suffer from significant core disadvantages: 1. High-purity fluorinated ether diluents are expensive; 2. High concentrations cause a surge in viscosity; although diluents reduce system viscosity, they easily disrupt the solvation structure, weakening stability to the lithium anode / high-voltage cathode; 3. Some fluorinated ether diluents (such as TTE) may decompose under high temperature or overcharge conditions, producing harmful gases (such as HF), and insufficient compatibility between the diluent and the main solvent can easily lead to phase separation; 4. Poor low-temperature performance; viscosity rebound in locally high-concentration areas causes a sharp drop in ionic conductivity; 5. The degradation mechanism (lithium salt decomposition, diluent consumption) is not yet clear, long-term reliability is questionable, and large-scale scalability risks are high. Therefore, developing novel non-fluorinated ether-based diluents to enhance their own stability and improve system performance without altering the solvation structure has become an important direction for future research. Summary of the Invention

[0004] To address the key problems associated with locally high-concentration lithium metal electrolytes, the present invention aims to provide a high-voltage resistant, non-flammable electrolyte, its preparation method, and its application in the fabrication of lithium metal batteries. This invention uses fluoroalkanes (including chain-like and cyclic fluoroalkanes) as a diluent for the high-concentration electrolyte, which possesses advantages such as non-flammability, high voltage resistance, high lithium metal content, and compatibility with ternary electrolytes, thus contributing to improved battery energy density, cycle stability, and safety.

[0005] To achieve the above-mentioned objectives, the present invention discloses the following technical solution:

[0006] The first objective of this invention is to provide a high-voltage resistant, non-flammable electrolyte, which comprises three parts: a lithium salt, an electrolyte solvent, and a fluoroalkane diluent. The lithium salt can be one or more organic or inorganic lithium salts such as lithium bis(fluorosulfonyl)imide, lithium bis(trifluoromethanesulfonyl)imide, lithium hexafluorophosphate, or lithium chloride. The electrolyte solvent is an ether-based electrolyte suitable for lithium metal anodes (one or more of monooxyethers, dioxyethers, or polyoxyethers such as diethyl ether, diethylene glycol dimethyl ether, or ethylene glycol dimethyl ether). The fluoroalkane diluent is a cyclic or chain-like fluoroalkane, wherein the cyclic fluoroalkane has a cyclic structure as shown in formula (I) or (II), and the chain-like fluoroalkane has a chain structure as shown in formula (III).

[0007] ;

[0008] In formula (I), the cyclic structure is a saturated five-membered cycloalkanes, R1~R 10 Each is independently selected from H, F, and C 1~10 Fluoroalkyl groups, and R1~R 10 Not simultaneously H; in formula (II), the cyclic structure is a saturated six-membered cycloalkanes, R 11 ~R 22 Each is independently selected from H, F, and C 1~10 Fluoroalkyl groups, and R 11 ~R 22 Not both H; in equation (III), R 23 ~R 25 Each is independently selected from H, F, and C 1~10 Fluoroalkyl groups, and R 23 ~R 25 They are not both H.

[0009] The C of this invention 1～10 Fluoroalkyl groups, i.e., C 1～10The alkyl group in which the H atom is replaced by at least one F atom can be monofluoromethyl, difluoromethyl, trifluoromethyl, 2-fluoroethyl, 3-fluoropropyl, 2-fluoropropyl, 4-fluorobutyl, 1-fluoro-2-methylpropyl, 1,1-dimethyl-2-fluoroethyl, 2,2,3,3,4,4,5,5,5-nonafluoropentyl, 5-fluoropentyl, 4-fluoro-2-methylbutyl, 2,2-dimethyl-1-fluoropropyl, 6-fluorohexyl, 1-fluoro-2-methylpentyl, 1-fluoro-3-methylpentyl, 1-fluoro-2,3-dimethylpentyl, 1-fluoro-2,2-dimethylpentyl, 7-fluoroheptyl, 1-fluoro-2-methylhexyl, 1-fluoro-3-methylhexyl, 1-fluoro-3,3-dimethylpentyl, 1-fluoro-2,4-dimethylpentyl, 1-fluoro-3-ethylpentyl, 1-fluoro-2,2 3-Trimethylbutyl, 8-Fluoroctyl, 1-Fluoro-2-methylheptyl, 1-Fluoro-3-methylheptyl, 1-Fluoro-4-methylheptyl, 1-Fluoro-2,2-dimethylhexyl, 1-Fluoro-3,3-dimethylhexyl, 1-Fluoro-2-ethylhexyl, 1-Fluoro-2,2,3-trimethylpentyl, 9-Fluoronyl, 1-Fluoro-2-methyloctyl, 1-Fluoro-3-methyloctyl, 1-Fluoro- 2,2-Dimethylheptyl, 1-fluoro-3,3-dimethylheptyl, 1-fluoro-2-ethylheptyl, 1-fluoro-2,2,3-trimethylhexyl, 10-fluorodecyl, 1-fluoro-2-methylnonyl, 1-fluoro-3-methylnonyl, 1-fluoro-2,2-dimethyloctyl, 1-fluoro-3,3-dimethyloctyl, 1-fluoro-2-ethyloctyl, 1-fluoro-2,2,3-trimethylheptyl, etc.

[0010] In the electrolyte formulation of this invention, the molar ratio of lithium salt to electrolyte solvent is 1:1 to 5 (preferably 1:2), and the molar ratio of electrolyte solvent to fluorocarbon diluent is 0.2 to 5:1 (preferably 1:1).

[0011] The fluoroalkane diluent selected in this invention should be miscible with the electrolyte solvent. Further, the chain-like fluoroalkane includes, but is not limited to, perfluorohexylethane, 1,1,1,3,3-pentafluorobutane, 1,1,1,2,4,4,4-heptafluorobutane, 1,1,1,2,3,4,4,4-octafluorobutane, 1,1,2,2,3,3,4,4-octafluorobutane, 2,2,3,3-tetrafluoropentane, 1,1,1,2,2,3,4,5,5,5-decafluoropentane, 1,1,1,2,2,3,3-heptafluorohexane, 1,1,1,2,2,3,3,4,4,5,5,6,6-tridecaffluorohexane, 1,1,1,2,2,3,3,4,4,5,5,6 The cyclic fluoroalkane includes, but is not limited to, 6,7,7,8,8-heptadecane, 1,1,1,2,2,3,3,4,4-nonafluorononane, 1,1,1,2,2,3,3,4,4,5,5,6,6,7,7,8,8,9,9,10,10-tetrafluorodecane, etc.; the cyclic fluoroalkane includes, but is not limited to, fluorocyclopentane, 1,1,2,2,3-pentafluorocyclopentane, 1,1,2,2,3-pentafluorocyclohexane, fluorocyclohexane, 1,1-difluorocyclohexane, perfluorocyclopentane, perfluorocyclohexane, perfluoromethylcyclohexane, perfluorodimethylcyclohexane, 1,1,2,2-tetrafluorocyclohexane, 1,1,2,2,3,3,4,4-octafluorocyclopentane, 1H,2H-octafluorocyclopentane, etc.

[0012] A second objective of this invention is to provide a method for preparing the above-mentioned high-voltage resistant, non-flammable electrolyte, the steps of which are as follows:

[0013] (1) One or more of the following dehydration operations are performed on the electrolyte solvent, fluoroalkane diluent and lithium salt: distillation, addition of drying material or high-temperature drying;

[0014] (2) Dissolve the lithium salt after the dehydration operation in step (1) in the electrolyte solvent, heat to 50~70℃ and stir for 1~3 hours; then dissolve the fluorocarbon diluent after the dehydration operation in it, heat to 50~70℃ and stir for 1~6 hours, and finally let it stand at room temperature to obtain the high-voltage resistant non-flammable electrolyte.

[0015] Preferably, the drying material is one or more of 4A molecular sieve, calcium hydride, calcium oxide, magnesium sulfate, phosphorus pentoxide, alkali metal, alkaline earth metal, activated carbon, or calcium chloride; high-temperature drying is vacuum drying at 80~95℃ for 10~15 hours.

[0016] Preferably, steps (1) to (2) are performed in a glove box with an oxygen content of less than 0.1 ppm.

[0017] The third objective of this invention is to provide the application of the above-mentioned high-voltage resistant non-flammable electrolyte in the preparation of high-energy-density and high-stability lithium metal batteries (lithium metal batteries are primary lithium metal batteries or secondary lithium metal batteries), which has significant application value, especially in the fields of power batteries for new energy vehicles and energy storage batteries.

[0018] The lithium metal batteries described in this invention include a lithium metal half-cell based on a lithium metal anode and a copper cathode (Example 2), a lithium metal symmetric cell based on a lithium metal anode and a lithium metal cathode (Example 3), and a lithium metal anode based on a nickel-cobalt-manganese ternary layered oxide cathode (LiNi). x Mn y Co 1-x-y A lithium metal full cell (O2, ternary cathode) (Examples 4-5, 7); the voltage range of the cathode is 3-4.5V, and the voltage range of the anode is 0.001-2V; the lithium metal battery has high capacity retention and cycle stability in the range of -20 to 60℃, and the electrolyte prepared by this invention is completely non-flammable in the combustion test.

[0019] This invention employs a specific fluoroalkane as an electrolyte diluent. This diluent exhibits excellent chemical and electrochemical stability, along with a high flash point and high dielectric constant. It is miscible with other solvents but not with lithium salts. It not only possesses a certain flame-retardant effect but also improves the battery's safety performance under heated and overcharged conditions. The fluoroalkane electrolyte of this invention does not participate in lithium-ion solvation, helping to maintain the solvation structure of the high-concentration electrolyte, increasing the reduction potential of anions at the lithium metal interface and decreasing the oxidation potential of anions at the ternary cathode interface, optimizing the properties of the SEI / CEI film at the interface, and improving the compatibility between the electrolyte and the electrode.

[0020] The electrolyte of the present invention has the following advantages:

[0021] (1) The electrolyte of the present invention has a high flash point and is non-flammable compared with the currently commercial electrolyte. According to the experimental data of the present invention, compared with the self-extinguishing time of ~120 seconds / gram of ordinary electrolyte (4.3M lithium difluorosulfonyl imide solution in ethylene glycol dimethyl ether), the electrolyte of the present invention can achieve the effect of being completely non-flammable.

[0022] (2) The fluoroalkane diluent does not participate in solvation, allowing lithium ions to maintain a solvation structure at a high concentration, thus enabling the formation of a high-performance SEI film and improving the cycle stability, coulombic efficiency, and utilization rate of the battery anode at 1 mA cm⁻¹. -2 and 1mAh cm -2 Under these conditions, the lithium metal deposition stripping coulombic efficiency is higher than 99.0%, which is much higher than that using ordinary electrolytes;

[0023] (3) Compared with the electrolytes currently on the market (the highest charging voltage does not exceed 4V, usually between 1 and 3V), the electrolyte of the present invention has the function of high voltage resistance and can be used in the new 4.5V-level high nickel ternary materials, thereby greatly improving the energy density of the battery, with high positive electrode capacity retention and good cycle stability (greater than 80% after 500 cycles). Attached Figure Description

[0024] The accompanying drawings, which form part of this application, are used to provide a further understanding of this application. The illustrative embodiments and descriptions of this application are used to explain this application and do not constitute an undue limitation of this application. Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings. The common high-concentration electrolyte (comparative sample) is a 4.3M bis(fluorosulfonyl)imide lithium salt solution in ethylene glycol dimethyl ether.

[0025] Figure 1 This is a comparison chart of the deposition stripping coulombic efficiency of the lithium metal battery prepared in Example 2 in a common high-concentration electrolyte (comparative sample) and the electrolyte of the present invention (target samples 1-5);

[0026] Figure 2 The graph shows a comparison of the cycle life of the lithium metal battery prepared in Example 3 in a common high-concentration electrolyte (comparative sample) and the electrolyte of the present invention (target samples 1-5).

[0027] Figure 3 Comparative scanning electron microscope images of the morphology of the lithium metal electrode surface after 10 cycles in a conventional high-concentration electrolyte (comparative sample) and the electrolyte of the present invention (target samples 1-5) for the lithium metal battery prepared in Example 3.

[0028] Figure 4 The lithium metal full cell prepared in Example 4 (positive electrode 2.5 mAh cm⁻¹) -2 Comparison of cycle performance of NCM811 (with a negative electrode of 50μm thick lithium metal) in ordinary high-concentration electrolyte (comparative sample) and electrolyte of the present invention (target samples 1-5);

[0029] Figure 5 The graph shows the cycling performance of the lithium metal pouch battery (nominal capacity 2Ah) prepared in Example 5 in a common high-concentration electrolyte (comparative sample) and the electrolyte of the present invention (target samples 1-5).

[0030] Figure 6 The image shows a comparison of the ignition test results of the ordinary high-concentration electrolyte (comparative sample) and the electrolyte of the present invention (target sample 1 and target sample 3) in Example 6.

[0031] Figure 7 The capacity of the assembly using the electrolyte of the present invention in Example 7. Charging and discharging performance of a 6.0Ah high-energy-density lithium metal pouch battery. Detailed Implementation

[0032] The present invention will be further illustrated below with reference to specific embodiments. It should be understood that these embodiments are for illustrative purposes only and are not intended to limit the scope of the invention. Experimental methods in the following embodiments that do not specify specific conditions are generally performed under conventional conditions or as recommended by the manufacturer. Unless otherwise specified, the materials and reagents used in this invention can be obtained through ordinary means or purchasing platforms. And, unless otherwise indicated, they are used in a manner familiar to those skilled in the art.

[0033] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as are familiar to those skilled in the art. Furthermore, any methods and materials similar to or equivalent to those described herein may be applied to the methods of this invention. The preferred embodiments and materials described herein are for illustrative purposes only.

[0034] Example 1

[0035] This embodiment provides a high-voltage resistant, non-flammable electrolyte, which is composed of lithium salt, electrolyte solvent and fluoroalkane diluent;

[0036] The lithium salt used is lithium bis(fluorosulfonyl)imide, the electrolyte solvent is ethylene glycol dimethyl ether, and the fluoroalkyl diluents are 1,1,2,2,3-pentafluorocyclopentane (target sample 1, one of the compounds with structure I), fluorocyclohexane (target sample 2, one of the compounds with structure II), 2,2,3,3-tetrafluoropentane (target sample 3, one of the compounds with structure III), 1H,2H-octafluorocyclopentane (target sample 4, one of the compounds with structure I), and 1,1,1,2,4,4,4-heptafluorobutane (target sample 5, one of the compounds with structure III), mixed in a molar ratio of 1:2:2; the high-voltage resistant non-flammable electrolyte is prepared by the following steps:

[0037] 1) In a glove box with an oxygen content below 0.1 ppm, the purchased lithium difluorosulfonamide, ethylene glycol dimethyl ether, and fluoroalkane diluent were subjected to dehydration treatment. Specifically, the lithium salt was placed in a vacuum drying system and dried at 90°C for 12 hours; then, 4A molecular sieves were added to the ethylene glycol dimethyl ether and fluoroalkane diluent, and the mixture was allowed to stand and dry in the glove box for 24 hours.

[0038] (2) In a glove box with an oxygen value of less than 0.1 ppm, lithium difluorosulfonamide was dissolved in ethylene glycol dimethyl ether electrolyte solvent, heated to 60°C and magnetically stirred for 1 hour, and finally allowed to stand at room temperature to obtain the high-concentration electrolyte (comparative sample).

[0039] (3) In a glove box with an oxygen value of less than 0.1 ppm, add fluorocarbon diluent to the high-concentration electrolyte (comparative sample) that was stirred evenly in step (2), heat to 60°C and stir magnetically for 3 hours, and finally let stand at room temperature to obtain the high-voltage resistant non-flammable electrolyte (target sample 1~5).

[0040] Example 2

[0041] This embodiment provides a Li||Cu lithium metal battery with two electrodes consisting of 50µm thick lithium metal foil and copper foil. The electrolytes are the comparative sample and target samples 1-5 prepared in steps (2) and (3) of Example 1, respectively, thus obtaining 6 types of Li||Cu lithium metal batteries. Then, the Aurbach method lithium metal deposition stripping coulomb efficiency test is performed to compare the utilization rate of the lithium metal anode.

[0042] like Figure 1 As shown, the Coulomb efficiency was tested using the Aurbach method: first, at a current density of 0.5 mA cm⁻¹ -2 Under these conditions, a 5mAh cm⁻¹ deposit was performed on the Cu anode of a Li||Cu lithium metal battery. -2 The areal capacity of lithium metal was completely stripped to form an SEI film. Subsequently, a 5 mAh cm⁻¹ anode was pre-deposited on the Cu anode. -2 The areal capacity of lithium metal (the capacity of the initially deposited Li metal is denoted as Q) i Then, the "stripping-deposition" cycle was repeated ten times, with each cycle performed at 0.5 mA cm⁻¹. -2 The current density was used for stripping for 2 hours (the total capacity of ten strippings is denoted as Q). s ), then with 0.5mA cm -2 The current density was deposited for 2 hours (the total capacity of ten depositions is denoted as Q). p Finally, the remaining lithium metal was completely stripped away (the final capacity of stripped Li metal is denoted as Q). f The formula for calculating the coulombic efficiency of deposition stripping is as follows:

[0043]

[0044] The values ​​of each parameter in the formula and the deposition stripping coulombic efficiency are shown in Table 1.

[0045] Table 1: Specific values ​​of each parameter in the formula and deposition / exfoliation coulombic efficiency

[0046]

[0047] This represents the utilization rate of lithium metal in 10 "stripping-deposition" cycles. The coulombic efficiency comparison data in Table 1 shows that the addition of fluorocarbon diluent helps improve the utilization rate of the lithium metal anode.

[0048] Example 3

[0049] This embodiment provides a Li||Li lithium metal battery, with both electrodes being 50µm thick lithium metal foils. The electrolytes are the comparative sample and target samples 1-5 prepared in steps (2) and (3) of Example 1, respectively, thus obtaining 6 types of Li||Li lithium metal batteries. After 10 cycles, scanning electron microscopy tests are performed on the surface of the lithium metal anode to compare the cycling stability of the lithium metal anode deposition stripping and the morphology after deposition.

[0050] like Figure 2 As shown, at a current density of 1 mA cm⁻¹ -2 Surface capacity is 1mAh cm -2 Under the given cycling conditions, the symmetrical battery using the electrolyte of this invention exhibited a cycle life exceeding 800 hours, with no significant increase in voltage curve; whereas the control sample showed a significant increase in voltage curve after 400 hours of cycling. The cycling curves indicate that the addition of the fluoroalkane diluent helps suppress side reactions such as dendrite formation, thereby improving the cycle life of the lithium metal anode.

[0051] like Figure 3 As shown in the scanning electron microscope images, the lithium electrode surface of the control sample exhibits a rough and uneven morphology after cycling, with a large number of irregular lithium dendrites and a loose deposition structure, indicating severe side reactions and significant dendrite growth during cycling in ordinary high-concentration electrolytes. In contrast, the target samples 1-5, using the electrolyte of this invention, show significantly improved electrode surfaces, with an overall smooth and dense surface and no significant dendrites. No large amounts of dendrites or loose deposits were observed in any of the target samples, as seen in the control samples. This indicates that the addition of the fluorocarbon diluent helps suppress side reactions such as dendrite formation, thereby improving the cycle life of the lithium metal anode.

[0052] Example 4

[0053] This embodiment provides a high-voltage Li|| ternary lithium metal battery, with a high-area-capacity LiNi cathode. 0.8 Co 0.1 Mn 0.1 O2 (NCM811) ternary lithium electrode sheet, with an area capacity of 2.5 mAh cm⁻¹ -2 The negative electrode was a 50µm thick lithium metal foil, and the electrolyte was the same as in Example 2, thus preparing six 2.5mAh / cm³ electrolytes. -2 NCM811||50μm Li lithium metal full cell; used to test the cycle performance of high-voltage ternary cathodes and compare the compatibility of different electrolytes with the cathode and anode.

[0054] like Figure 4 As shown, the results indicate that the capacity of the control sample decreased to 150 mAh g after 300 cycles. -1Below this, the capacity retention rate is less than 80%; however, the target samples 1-5 using the electrolyte of this invention still maintain a capacity of 150 mAhg after 600 stable cycles. -1 The cycle life exceeded 600 cycles with slow degradation. This indicates that the addition of fluoroalkane diluent helps to construct a stable cathode electrolyte interface (CEI) protective layer, thereby significantly improving the cycle life of ternary cathode / lithium metal full cells.

[0055] Example 5

[0056] This embodiment provides a high-voltage Li|| ternary lithium metal pouch battery (nominal capacity 2Ah), with a high areal capacity LiNi cathode. 0.8 Co 0.1 Mn 0.1 O2 (NCM811) ternary lithium electrode sheet, with an area capacity of 4.5 mAh cm⁻¹ -2 The negative electrode is a 20µm thick lithium metal foil, and the electrolyte is the same as in Example 2. The practicality of the electrolyte is tested.

[0057] like Figure 5 As shown, the results indicate that the control sample exhibited significant capacity decay after 16 cycles, with a capacity retention rate below 80% after 20 cycles. In contrast, the pouch cells using target samples 1-5 electrolytes showed no capacity decay after 50 stable cycles, with each target sample maintaining a capacity retention rate above 99%. This demonstrates that the addition of fluoroalkane diluent helps construct a stable solid-state electrolyte interface (SEI) and cathode electrolyte interface (CEI) protective layer, thereby simultaneously improving the cycle stability of both the lithium metal anode and the ternary cathode, meeting the application requirements in the power battery field.

[0058] Example 6

[0059] This embodiment tests the flammability of the prepared electrolyte. The method is as follows: 1g of ordinary high-concentration electrolyte (comparative sample) and 1g of the electrolyte of this invention (target sample 1 and target sample 3) are taken respectively, and ignition tests are performed, with self-extinguishing times recorded. The comparative sample ignites and the flame continues to burn, with a self-extinguishing time of 118 seconds; while the target samples cannot ignite, with a self-extinguishing time of 0 seconds. This indicates that the electrolyte of this invention has non-flammable properties, significantly improving battery safety performance and meeting the requirements of high-safety applications.

[0060] like Figure 6 As shown in the figure, the photos before and after ignition and the corresponding self-extinguishing time are shown. The self-extinguishing time of the control sample is 118 seconds, and the self-extinguishing time of the target sample is 0 seconds.

[0061] Example 7

[0062] This embodiment provides a high-energy-density lithium metal battery. A high-energy-density lithium metal pouch battery (capacity) is assembled using the electrolyte of this invention (target sample). A 6Ah high-voltage Li|| ternary lithium metal pouch battery was assembled as in Example 5, and its charge-discharge performance was tested. The battery was discharged at a 0.1C rate, and the energy density was... 510Wh kg -1 The results demonstrate that high-energy-density lithium metal batteries using the electrolyte of this invention exhibit excellent energy density and are suitable for high-energy-density energy storage applications.

[0063] like Figure 7 As shown in the figure, the horizontal axis represents the discharge capacity (Ah), and the left vertical axis represents the voltage (V). Figure 7 (a), (b), (c), (d), and (e) in the figure show the charge-discharge curves of target samples 1, 2, 3, 4, and 5, respectively. The battery capacity is... At 6Ah, with a discharge rate of 0.1C, the energy density can reach 510Wh / kg. -1 above.

[0064] The above description is merely a specific embodiment of the present invention. Any feature disclosed in this specification may be replaced by other equivalent or similar features unless otherwise specified. All disclosed features, or steps in all methods or processes, may be combined in any way except for mutually exclusive features and / or steps.

Claims

1. A high-voltage resistant, non-flammable electrolyte, characterized in that: The high-voltage resistant, non-flammable electrolyte consists of three parts: lithium salt, electrolyte solvent, and fluoroalkane diluent. The fluoroalkane diluent is a cyclic fluoroalkane or a chain fluoroalkane, wherein the cyclic fluoroalkane has a cyclic structure as shown in formula (I) or (II), and the chain fluoroalkane has a chain structure as shown in formula (III). ； In formula (I), the cyclic structure is a saturated five-membered cycloalkanes, R1~R 10 Each is independently selected from H, F, and C 1~10 Fluoroalkyl groups, and R1~R 10 Not simultaneously H; in formula (II), the cyclic structure is a saturated six-membered cycloalkanes, R 11 ~R 22 Each is independently selected from H, F, and C 1~10 Fluoroalkyl groups, and R 11 ~R 22 Not both H; in equation (III), R 23 ~R 25 Each is independently selected from H, F, and C 1~10 Fluoroalkyl groups, and R 23 ~R 25 They are not both H.

2. The high-voltage resistant, non-flammable electrolyte as described in claim 1, characterized in that: The lithium salt is one or more of lithium bis(fluorosulfonyl)imide, lithium bis(trifluoromethanesulfonyl)imide, lithium hexafluorophosphate, or lithium chloride; the electrolyte solvent is one or more of diethyl ether, diethylene glycol dimethyl ether, or ethylene glycol dimethyl ether, which are suitable for lithium metal anodes.

3. The high-voltage resistant, non-flammable electrolyte as described in claim 2, characterized in that: C 1～10 The fluorinated alkyl groups are monofluoromethyl, difluoromethyl, trifluoromethyl, 2-fluoroethyl, 3-fluoropropyl, 2-fluoropropyl, 4-fluorobutyl, 1-fluoro-2-methylpropyl, 1,1-dimethyl-2-fluoroethyl, 2,2,3,3,4,4,5,5,5-nonafluoropentyl, 5-fluoropentyl, 4-fluoro-2-methylbutyl, 2,2-dimethyl-1-fluoropropyl, 6-fluorohexyl, 1-fluoro-2-methylpentyl, 1-fluoro-3-methylpentyl, 1-fluoro-2,3-dimethylpentyl, 1-fluoro-2,2-dimethylpentyl, 7-fluoroheptyl, 1-fluoro-2-methylhexyl, 1-fluoro-3-methylhexyl, 1-fluoro-3,3-dimethylpentyl, 1-fluoro-2,4-dimethylpentyl, 1-fluoro-3-ethylpentyl, 1-fluoro-2,2,3-trimethylbutyl, 8 One of the following: -fluorooctyl, 1-fluoro-2-methylheptyl, 1-fluoro-3-methylheptyl, 1-fluoro-4-methylheptyl, 1-fluoro-2,2-dimethylhexyl, 1-fluoro-3,3-dimethylhexyl, 1-fluoro-2-ethylhexyl, 1-fluoro-2,2,3-trimethylpentyl, 9-fluorononyl, 1-fluoro-2-methyloctyl, 1-fluoro-3-methyloctyl, 1-fluoro-2,2-dimethylheptyl, 1-fluoro-3,3-dimethylheptyl, 1-fluoro-2-ethylheptyl, 1-fluoro-2,2,3-trimethylhexyl, 10-fluorodecyl, 1-fluoro-2-methylnonyl, 1-fluoro-3-methylnonyl, 1-fluoro-2,2-dimethyloctyl, 1-fluoro-3,3-dimethyloctyl, 1-fluoro-2-ethyloctyl, 1-fluoro-2,2,3-trimethylheptyl.

4. The high-voltage resistant, non-flammable electrolyte as described in claim 1, characterized in that: The molar ratio of lithium salt to electrolyte solvent is 1:1 to 5, and the molar ratio of electrolyte solvent to fluorocarbon diluent is 0.2 to 5:

1.

5. The high-voltage resistant, non-flammable electrolyte as described in claim 1, characterized in that: Chain-like fluoroalkanes include perfluorohexylethane, 1,1,1,3,3-pentafluorobutane, 1,1,1,2,4,4,4-heptafluorobutane, 1,1,1,2,3,4,4,4-octafluorobutane, 1,1,2,2,3,3,4,4-octafluorobutane, 2,2,3,3-tetrafluoropentane, 1,1,1,2,2,3,4,5,5,5-decafluoropentane, 1,1,1,2,2,3,3-heptafluorohexane, 1,1,1,2,2,3,3,4,4,5,5,6,6-tridecaffluorohexane, and 1,1,1,2,2,3,3,4,4,5,5,6,6,7,7,8,8-heptafluorooctane. One of the following: 1,1,1,2,2,3,3,4,4-nonafluorononane, 1,1,1,2,2,3,3,4,4,5,5,6,6,7,7,8,8,9,9,10,10-tetrafluorodecane; and one of the following: fluorocyclopentane, 1,1,2,2,3-pentafluorocyclopentane, 1,1,2,2,3-pentafluorocyclohexane, fluorocyclohexane, 1,1-difluorocyclohexane, perfluorocyclopentane, perfluorocyclohexane, perfluoromethylcyclohexane, perfluorodimethylcyclohexane, 1,1,2,2-tetrafluorocyclohexane, 1,1,2,2,3,3,4,4-octafluorocyclopentane, and 1H,2H-octafluorocyclopentane.

6. A method for preparing a high-voltage resistant, non-flammable electrolyte according to any one of claims 1 to 5, characterized in that: The steps are as follows: (1) One or more of the following dehydration operations are performed on the electrolyte solvent, fluoroalkane diluent and lithium salt: distillation, addition of drying material or high-temperature drying; (2) Dissolve the lithium salt after the dehydration operation in step (1) in the electrolyte solvent, heat to 50~70℃ and stir for 1~3 hours; then dissolve the fluorocarbon diluent after the dehydration operation in it, heat to 50~70℃ and stir for 1~6 hours, and finally let it stand at room temperature to obtain a high-voltage resistant non-flammable electrolyte.

7. The method for preparing a high-voltage resistant, non-flammable electrolyte as described in claim 6, characterized in that: The drying material is one or more of the following: 4A molecular sieve, calcium hydride, calcium oxide, magnesium sulfate, phosphorus pentoxide, alkali metal, alkaline earth metal, activated carbon, or calcium chloride; high-temperature drying is vacuum drying at 80~95℃ for 10~15 hours.

8. The application of the high-voltage resistant, non-flammable electrolyte according to any one of claims 1 to 5 in the preparation of high-energy-density, high-stability lithium metal batteries, characterized in that: Lithium metal batteries are either primary lithium metal batteries or secondary lithium metal batteries.

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