High-voltage-resistant flame-retardant electrolyte and application thereof in preparation of negative-electrode-free lithium metal battery with long cycle life
By designing an electrolyte containing lithium salt and an organic solvent with specific coordination capabilities, the flammability and cycle life issues of lithium metal batteries have been solved, achieving efficient lithium deposition/stripping and stable battery cycle performance, thus improving the safety and commercial potential of electrodeless lithium metal batteries.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2026-01-06
- Publication Date
- 2026-03-13
AI Technical Summary
Existing lithium metal battery electrolytes suffer from problems such as high flammability, poor thermal stability, and unstable SEI, leading to uncontrollable lithium dendrite growth, affecting battery safety and cycle life, and limiting the commercial application of negative electrode-free lithium metal batteries.
An electrolyte composed of lithium salt, phosphate solvent with flame retardancy and strong coordination ability, cyclic ester solvent with medium coordination ability, and chain ester solvent with weak coordination ability is used to form an anion-dominated solvation structure, forming a stable SEI, reducing desolvation energy, and improving lithium deposition/stripping efficiency.
It achieves high oxidation stability and flame retardancy of electrolyte, improves cycle life and safety of lithium metal battery, reduces cost, the formed SEI is stable under high pressure, lithium deposition/stripping efficiency reaches 99.01%, and the whole cell exhibits excellent cycle performance and flame retardancy under high load cathode.
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Figure CN121662901A_ABST
Abstract
Description
Technical Field
[0001] This invention belongs to the field of energy battery technology, specifically relating to a high-voltage resistant flame-retardant electrolyte and its application in the preparation of long-cycle-life negative electrode-free lithium metal batteries. Background Technology
[0002] The ever-growing demand for high-performance rechargeable batteries is driving the development of advanced battery technologies. Lithium-metal batteries (LMBs) are particularly popular due to their extremely high specific capacity (3860 mAh g⁻¹). −1 Lithium metal batteries (AFLMBs) have attracted widespread attention due to their extremely low electrochemical potential (−3.04 V vs. standard hydrogen electrode). AFLMBs significantly improve the mass and volumetric energy density of batteries by eliminating traditional anode materials and utilizing fully lithiated cathodes and current collectors. During charging, lithium metal is deposited directly on the current collector, significantly increasing the battery's mass and volumetric energy density, and are considered the ideal state for lithium metal batteries. Due to the elimination of anode materials, AFLMBs exhibit specific energy exceeding 450 Wh / kg, and possess good compatibility with existing production processes and low cost, which is conducive to large-scale commercial applications and promotes the sustainable development of the battery industry. Unfortunately, severe side reactions easily occur between the highly active deposited lithium layer and the traditional electrolyte. The loss of active Li during cycling cannot be replenished, leading to a limited cycle life for AFLMBs. Uneven lithium deposition results in uncontrolled lithium dendrite growth, and the high flammability of the electrolyte seriously affects battery safety, severely hindering the practical application of AFLMBs.
[0003] Electrolytes are considered the "blood" of batteries, directly affecting battery safety and cycle stability. However, conventional electrolytes composed of traditional carbonate or ether solvents typically suffer from poor thermal stability, high flammability, and unstable SEI formation. To promote the commercialization of "negative electrode-free" lithium metal batteries, electrolytes must meet several key requirements: (1) high oxidation stability, matching high-voltage cathode materials to fully leverage the advantages of AFLMBs; (2) moderate lithium salt concentration and low cost; (3) good compatibility with lithium metal, forming a stable SEI, thus enabling the battery to have a high CE value and long cycle life; (4) flame retardancy, as the high flammability of most electrolytes seriously affects lithium battery safety. When the battery is subjected to thermal, mechanical, and electrical abuse conditions, it is highly likely to lead to thermal runaway, violent combustion of the electrolyte, or even serious fire and explosion. Currently, new electrolytes mainly consist of high-concentration electrolytes and locally high-concentration electrolytes. These electrolytes reduce the Li-to-Li ratio by increasing the concentration of lithium salts. +The free solvent molecules in the solvation structure form an electrolyte layer (SEI) dominated by inorganic components, improving the battery's cycle performance, but also facing problems such as high viscosity and high cost. Although a large amount of fluorinated diluent can impart some flame retardancy to the electrolyte, its high cost and low ionic conductivity limit its practical application. While phosphorus-containing solvents exhibit good flame retardancy, their continuous side reactions with lithium metal and strong solvation often lead to extremely low coulombic efficiency and cycle life.
[0004] Therefore, it is essential to design an electrolyte that simultaneously achieves anion-dominated solvation structure, a stable and reliable SEI, low desolvation energy, stability to lithium metal, and low cost, while ensuring the flame retardant effect of the electrolyte. Summary of the Invention
[0005] The purpose of this section is to outline some aspects of the embodiments of the present invention and to briefly describe some preferred embodiments.
[0006] In view of the problems existing in the above and / or prior art, the present invention is proposed.
[0007] Therefore, the purpose of this invention is to overcome the shortcomings of the prior art and provide a high-pressure resistant flame-retardant electrolyte.
[0008] To solve the above-mentioned technical problems, the present invention provides the following technical solution: a high-voltage resistant flame-retardant electrolyte, comprising lithium salt and organic solvent;
[0009] The organic solvent is composed of phosphate solvents with flame retardancy and strong coordination ability, cyclic ester solvents with moderate coordination ability, and chain ester solvents with weak coordination ability.
[0010] As a preferred embodiment of the high-voltage flame-retardant electrolyte of the present invention, the lithium salt is at least one of lithium bis(fluorosulfonyl)imide, lithium bis(trifluoromethanesulfonyl)imide, lithium difluorooxalateborate, lithium hexafluorophosphate, lithium nitrate, lithium perchlorate, and lithium tetrafluoroborate.
[0011] As a preferred embodiment of the high-voltage flame-retardant electrolyte of the present invention, the phosphate solvent with flame retardancy and strong coordination ability is at least one of ethyl 2,2,2-trifluoroacetate, γ-butyrolactone, dimethyl methylphosphonate, diethyl ethyl phosphonate, trimethyl phosphate, triethyl phosphate, and tributyl phosphate.
[0012] As a preferred embodiment of the high-voltage flame-retardant electrolyte of the present invention, the cyclic ester solvent with moderate coordination ability is at least one of ethylene carbonate, vinylene carbonate, fluoroethylene carbonate, and propylene carbonate.
[0013] As a preferred embodiment of the high-voltage flame-retardant electrolyte of the present invention, the chain ester solvent with weak coordination ability is at least one of methyl ethyl carbonate, dimethyl carbonate, diethyl carbonate, methyl trifluoroethyl carbonate, ethyl trifluoroethyl carbonate and di(2,2,2-trifluoroethyl) carbonate.
[0014] In a preferred embodiment of the high-voltage resistant flame-retardant electrolyte of the present invention, the molar concentration of the lithium salt in the electrolyte is 0.5~3 mol / L;
[0015] The volume content of the phosphate ester solvent with flame retardancy and strong coordination ability is 0.01% to 100%, the volume content of the cyclic ester solvent with medium coordination ability is 0.01% to 50%, and the volume content of the chain ester solvent with weak coordination ability is 0.01% to 60%.
[0016] Another objective of this invention is to overcome the shortcomings of the prior art and provide an application of a high-voltage resistant flame-retardant electrolyte in the preparation of a long-cycle-life, electrodeless lithium metal battery.
[0017] As a preferred embodiment of the application described in this invention, the negative electrode of the non-negative electrode lithium metal battery consists only of a copper foil current collector and no active material, and the positive electrode is at least one of lithium iron phosphate, lithium cobalt oxide, ternary positive electrode material or lithium-rich manganese-based positive electrode material.
[0018] As a preferred embodiment of the application described in this invention, the negative electrode-free lithium metal battery further includes a separator, which includes at least one of a polypropylene separator, a polyethylene separator, a glass fiber separator, a polytetrafluoroethylene separator, and a cellulose separator.
[0019] In a preferred embodiment of the application described in this invention, the negative electrode-free lithium metal battery is a button cell battery or a pouch cell battery.
[0020] Beneficial effects of this invention:
[0021] (1) The electrolyte of the present invention has successfully achieved an anion-dominant solvation structure through this gradient coordination design, forming an anion-derived stable SEI, which improves the lithium metal deposition / stripping efficiency to 99.01% and can be stably cycled for more than 200 cycles; moreover, compared with the currently common high-concentration electrolytes and local high-concentration electrolytes used to construct anion-dominant solvation structures, the electrolyte design of this invention eliminates the use of expensive highly fluorinated diluents, which greatly reduces costs.
[0022] (2) A large number of anions react with Li in the first shell. +Coordination reduces the desolvation energy and accelerates the desolvation process, thus enabling the "negative electrode-free" battery to have excellent rate performance. The full cell matched with the high-load NCM811 positive electrode has a high specific capacity of 150.7 mAh / g at 3C.
[0023] (3) The electrolyte has high oxidation stability (>4.5V), good compatibility with high-nickel ternary cathodes, excellent high-voltage cycling performance at 4.35V, and good compatibility with high-load NCM811 cathodes (8.69mg / cm³). 2 The matched button cell battery can stably cycle 76 times with a capacity retention of 80%, and the Cu||NCM811 pouch cell with a capacity of 1.22Ah can achieve 53 cycles with a capacity retention of 80% under practical conditions.
[0024] (4) The electrolyte described in this invention has good flame retardant properties and achieves excellent self-extinguishing effect in 0s after the ignition device is removed in the ignition experiment. Attached Figure Description
[0025] To more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings used in the description of the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort. Wherein:
[0026] Figure 1 The CV spectra of Li|Cu half-cells in Example 1 and Comparative Examples 1-3 of this invention are shown.
[0027] Figure 2 The images show the Aurbach coulomb efficiency spectra of Li|Cu half-cells in Examples 1-5 and Comparative Examples 1-3 of this invention.
[0028] Figure 3 The graphs show the long-cycle performance of Li|Cu half-cells in Example 1 and Comparative Examples 2-3 of this invention.
[0029] Figure 4 The images show the rate performance of Cu|NCM811 full cells in Example 1 and Comparative Examples 2-3 of this invention.
[0030] Figure 5 The images show the cycling performance of Cu||NCM811 full cells in Example 1 and Comparative Examples 2-3 of this invention.
[0031] Figure 6 The graph shows the voltage withstand performance test results of the Li||Al battery in Example 1 of this invention.
[0032] Figure 7 The figure shows the ignition test results of Example 1 of the present invention and a commercial electrolyte. Detailed Implementation
[0033] To make the above-mentioned objects, features and advantages of the present invention more apparent and understandable, the specific embodiments of the present invention will be described in detail below with reference to the examples in the specification.
[0034] In the embodiments of this invention, all materials were used as is without additional purification treatment; wherein, triethyl phosphate (TEP), trimethyl phosphate (TMP), fluoroethylene carbonate (FEC), methyl trifluoroethyl carbonate (FEMC), ethylene carbonate (EC), methyl ethyl carbonate (EMC), and di(2,2,2-trifluoroethyl) carbonate (ETFEC) were all purchased from Suzhou Duoduo Chemical Technology Co., Ltd.
[0035] Lithium nitrate (LiNO3), lithium hexafluorophosphate (LiPF6), and lithium tetrafluoroborate (LiBF4) were purchased from Shanghai Aladdin Biochemical Technology Co., Ltd.
[0036] Battery-grade copper foil, lithium foil, loading capacity of 8.69 mg / cm³ 2 All NCM811 electrodes were purchased from Dongguan Kelude Experimental Equipment Technology Co., Ltd.
[0037] Example 1
[0038] Electrolyte preparation: LiNO3 was selected as the lithium salt. 3， The phosphate solvent is triethyl phosphate (TEP), the cyclic carbonate solvent is fluoroethylene carbonate (FEC), and the chain carbonate solvent is methyltrifluoroethyl carbonate (FEMC). The volume ratio of TEP, FEC and FEMC is 5:1:4 (total volume is 1 ml).
[0039] In an atmosphere filled with argon gas and where the oxygen and water content is below 0.01 ppm, the above solvents are mixed evenly in proportion, and then 1.6 M LiNO3 is added and stirred until completely dissolved to obtain the target electrolyte.
[0040] Example 2
[0041] Electrolyte preparation: LiNO3 is used as the lithium salt, trimethyl phosphate (TMP) is used as the phosphate solvent, fluoroethylene carbonate (FEC) is used as the cyclic carbonate solvent, and methyl trifluoroethyl carbonate (FEMC) is used as the chain carbonate solvent. The volume ratio of TMP, FEC and FEMC is 5:1:4 (total volume is 1 ml).
[0042] In an atmosphere filled with argon gas and where the oxygen and water content is below 0.01 ppm, the above solvents are mixed evenly in proportion, and then 1.6 M LiNO3 is added and stirred until completely dissolved to obtain the target electrolyte.
[0043] Example 3
[0044] Electrolyte preparation: LiNO3 was selected as the lithium salt. 3， The phosphate solvent used is triethyl phosphate (TEP), the cyclic carbonate solvent is ethylene carbonate (EC), and the chain carbonate solvent is methyltrifluoroethyl carbonate (FEMC). The volume ratio of TEP, EC and FEMC is 5:1:4 (total volume is 1 ml).
[0045] In an atmosphere filled with argon gas and where the oxygen and water content is below 0.01 ppm, the above solvents are mixed evenly in proportion, and then 1.6 M LiNO3 is added and stirred until completely dissolved to obtain the target electrolyte.
[0046] Example 4
[0047] Electrolyte preparation: LiNO3 was selected as the lithium salt. 3， The phosphate solvent used is triethyl phosphate (TEP), the cyclic carbonate solvent is fluoroethylene carbonate (FEC), and the chain carbonate solvent is methyl ethyl carbonate (EMC). The volume ratio of TEP, FEC and EMC is 5:1:4 (total volume is 1 ml).
[0048] In an atmosphere filled with argon gas and where the oxygen and water content is below 0.01 ppm, the above solvents are mixed evenly in proportion, and then 1.6 M LiNO3 is added and stirred until completely dissolved to obtain the target electrolyte.
[0049] Example 5
[0050] Electrolyte preparation: LiNO3 was selected as the lithium salt. 3， The phosphate solvent used is triethyl phosphate (TEP), the cyclic carbonate solvent is fluoroethylene carbonate (FEC), and the chain carbonate solvent is di(2,2,2-trifluoroethyl) carbonate (ETFEC). The volume ratio of TEP, FEC and ETFEC is 5:1:4 (total volume is 1 ml).
[0051] In an atmosphere filled with argon gas and where the oxygen and water content is below 0.01 ppm, the above solvents are mixed evenly in proportion, and then 1.6 M LiNO3 is added and stirred until completely dissolved to obtain the target electrolyte.
[0052] Example 6
[0053] Electrolyte preparation: Lithium tetrafluoroborate is selected as the lithium salt. ，The phosphate solvent used is triethyl phosphate (TEP), the cyclic carbonate solvent is fluoroethylene carbonate (FEC), and the chain carbonate solvent is di(2,2,2-trifluoroethyl) carbonate (ETFEC). The volume ratio of TEP, FEC and ETFEC is 5:1:4 (total volume is 1 ml).
[0054] In an atmosphere where the oxygen and water content is below 0.01 ppm in an argon-filled glove box, the above solvents are mixed evenly in proportion, and then 1.6 moles of lithium tetrafluoroborate are added and stirred until completely dissolved to obtain the target electrolyte.
[0055] Example 7
[0056] Electrolyte preparation: Lithium hexafluorophosphate is selected as the lithium salt. ， The phosphate solvent used is triethyl phosphate (TEP), the cyclic carbonate solvent is fluoroethylene carbonate (FEC), and the chain carbonate solvent is methyltrifluoroethyl carbonate (FEMC). The volume ratio of TEP, FEC and FEMC is 5:1:4 (total volume is 1 ml).
[0057] In an atmosphere filled with argon gas and where the oxygen and water content is below 0.01 ppm, the above solvents are mixed evenly in proportion, and then 1.6 M LiPF6 is added and stirred until completely dissolved to obtain the target electrolyte.
[0058] Comparative Example 1
[0059] Electrolyte preparation: LiNO3 was selected as the lithium salt. 3， Triethyl phosphate (TEP) was selected as the phosphate solvent. In an argon-filled glove box with oxygen and water concentrations below 0.01 ppm, 1.6 M LiNO3 was added to the TEP solvent and stirred until completely dissolved to obtain the target electrolyte.
[0060] Comparative Example 2
[0061] Electrolyte preparation: LiNO3 was selected as the lithium salt. 3， The phosphate solvent used is triethyl phosphate (TEP), and the cyclic carbonate solvent is fluoroethylene carbonate (FEC). The volume ratio of TEP to FEC is 5:1 (total volume is 1 ml).
[0062] In an atmosphere filled with argon gas and where the oxygen and water content is below 0.01 ppm, the above solvents are mixed evenly in proportion, and then 1.6 M LiNO3 is added and stirred until completely dissolved to obtain the target electrolyte.
[0063] Comparative Example 3
[0064] Electrolyte preparation: LiNO3 was selected as the lithium salt. 3，The phosphate solvent used is triethyl phosphate (TEP), and the cyclic carbonate solvent is fluoroethylene carbonate (FEC). The volume ratio of TEP to FEC is 5:5 (total volume is 1 ml).
[0065] In an atmosphere filled with argon gas and where the oxygen and water content is below 0.01 ppm, the above solvents are mixed evenly in proportion, and then 1.6 M LiNO3 is added and stirred until completely dissolved to obtain the target electrolyte.
[0066] Comparative Example 4
[0067] Electrolyte preparation: LiNO3 was selected as the lithium salt. 3， The phosphate solvent used is triethyl phosphate (TEP), and the chain carbonate solvent is methyltrifluoroethyl carbonate (FEMC). The volume ratio of TEP to FEMC is 5:5 (total volume is 1 ml).
[0068] In an atmosphere filled with argon gas and where the oxygen and water content is below 0.01 ppm, the above solvents are mixed evenly in proportion, and then 1 M LiNO3 is added and stirred until completely dissolved to obtain the target electrolyte.
[0069] Performance testing:
[0070] (1) Cyclic voltammetry (CV) tests were performed on Li||Cu half-cells assembled with the electrolytes of Example 1 and Comparative Examples 1-3. The assembly steps of the Li||Cu half-cells were as follows: In an argon-filled glove box, polypropylene (PP) was used as the separator, copper foil for batteries was used as the positive electrode, and lithium metal was used as the negative electrode. The electrolyte was added, and the battery was assembled according to the following order: positive electrode shell, copper foil, electrolyte, separator, electrolyte, lithium sheet, gasket, spring, and negative electrode shell. After assembly, the battery was tested at 0.5 mV s using an electrochemical workstation. -1 CV tests were performed at the scan rate. The results are as follows: Figure 1 As shown.
[0071] The lithium deposition / stripping current in Example 1 is significantly greater than that in Comparative Examples 1-3, demonstrating the excellent rapid kinetic performance of the electrolyte designed in this invention. Furthermore, Example 1 also exhibits the lowest nucleation initiation potential, further confirming the rapid reaction kinetics of lithium deposition.
[0072] (2) The Li||Cu half-cells assembled with the electrolytes of Examples 1-5 and Comparative Examples 2 and 3 were tested using the Aurbach coulomb efficiency measurement method. Figure 2As shown, the coulombic efficiencies measured in Comparative Examples 2 and 3 were only 95.59% and 97.82%, respectively. However, the electrolyte designed in this invention achieves high coulombic efficiency, with Examples 1 and 5 even reaching over 99%. These examples fully demonstrate that the electrolyte design principle of this invention is a universal and highly adaptable "negative electrode-free" lithium metal electrolyte design, providing a powerful solution for achieving high coulombic efficiency "negative electrode-free" lithium metal batteries.
[0073] (3) The performance of Example 1 and Comparative Examples 2 and 3 was tested using a long-cycle lithium copper half-cell test. The results are as follows: Figure 3 As shown, Example 1 exhibits the highest initial coulombic efficiency (88.3%), maintaining stable cycling for 200 cycles without significant fluctuations, with an average coulombic efficiency exceeding 98%. This contrasts sharply with the batteries used in Comparative Examples 2 and 3, whose coulombic efficiency rapidly declined after only a few dozen cycles, with the average coulombic efficiency in the initial few dozen cycles falling below 97%. This further demonstrates the advantages of the electrolyte of this invention for long-term cycling of lithium metal anodes.
[0074] (4) The electrolytes of Example 1 and Comparative Examples 2 and 3 were assembled into Cu||NCM811 full cells and the rate was tested. The Cu||NCM811 full cell assembly steps were as follows: In a glove box filled with argon, polypropylene (PP) was used as the separator, copper foil for batteries was used as the negative electrode, and NCM811 was used as the positive electrode. The above electrolyte was added, and the battery was assembled according to the following order: positive electrode shell, NCM811, electrolyte, separator, electrolyte, copper foil, gasket, spring, and negative electrode shell. After assembly, the battery was tested on a battery tester.
[0075] The results are as follows Figure 4 As shown. Within the current density range, the battery based on Example 1 consistently outperforms the batteries based on Comparative Examples 2 and 3. The battery based on Example 1 exhibits the highest initial discharge specific capacity of 195.9 mAh g. -1 Even at high rates of 3C, it still has 150.7 mAh g. -1 The specific capacity is high, while Comparative Examples 2 and 3 only have 56.7 mAhg under 3C conditions. -1 and 4.2 mAh g -1 The specific capacity. The high rate performance of the electrodeless full cell based on Example 1 is attributed to the gradient solvation design, which forms an anion-dominant solvation structure in the electrolyte. This structure has a low desolvation energy and a fast lithium deposition / stripping rate. The resulting SEI can suppress lithium dendrite growth even at high rates.
[0076] (5) The electrolytes of Example 1 and Comparative Examples 2 and 3 were used to assemble Cu||NCM811 full cells for cycle performance testing. The results are as follows: Figure 5 As shown, at charge / discharge rates of 0.2C / 0.5C, the battery based on Example 1 can also achieve a stable 76-cycle cycle with 80% capacity retention, which is far superior to the electrodeless full cells based on Comparative Examples 2 and 3, further demonstrating the positive role of the present invention in achieving long cycle life of electrodeless lithium metal batteries.
[0077] (6) To verify the oxidative stability of the electrolyte of the present invention, the electrolyte withstand voltage performance was tested by assembling a Li||Al battery. Except for replacing the copper foil with aluminum foil, the assembly steps were the same as those for the Li||Cu battery. Figure 6 In Example 1, the electrolyte can withstand a high voltage of at least 4.7V, which is perfectly compatible with ternary cathode materials with high specific capacity, thus giving full play to the high energy density advantage of "negative electrode-free" lithium metal batteries.
[0078] (7) Electrolyte flammability test: Immerse a certain amount of electrolyte into the glass fiber diaphragm and ignite it using an igniter. Figure 7 As shown, the glass fiber diaphragm using commercial electrolyte burned violently upon ignition and continued to burn violently even after the igniter was removed, while Example 1 showed superior flame retardancy, with the glass fiber diaphragm not burning upon ignition or after removal.
[0079] It should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit it. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the spirit and scope of the technical solutions of the present invention, and all such modifications or substitutions should be covered within the scope of the present invention.
Claims
1. A high-voltage resistant flame-retardant electrolyte, characterized in that: Including lithium salts and organic solvents; The organic solvent is composed of phosphate solvents with flame retardancy and strong coordination ability, cyclic ester solvents with moderate coordination ability, and chain ester solvents with weak coordination ability.
2. The high-voltage resistant flame-retardant electrolyte as described in claim 1, characterized in that: The lithium salt is at least one of lithium bis(fluorosulfonyl)imide, lithium bis(trifluoromethyl)sulfonyl)imide, lithium difluorooxalate borate, lithium hexafluorophosphate, lithium nitrate, lithium perchlorate, and lithium tetrafluoroborate.
3. The high-voltage resistant flame-retardant electrolyte as described in claim 1 or 2, characterized in that: The phosphate solvent with flame retardancy and strong coordination ability is at least one selected from ethyl 2,2,2-trifluoroacetate, γ-butyrolactone, dimethyl methylphosphonate, diethyl ethylphosphonate, trimethyl phosphate, triethyl phosphate, and tributyl phosphate.
4. The high-voltage resistant flame-retardant electrolyte as described in claim 3, characterized in that: The cyclic ester solvent with moderate coordination ability is at least one of ethylene carbonate, vinylene carbonate, fluoroethylene carbonate, and propylene carbonate.
5. The high-voltage resistant flame-retardant electrolyte as described in claim 1 or 4, characterized in that: The chain ester solvent with weak coordination ability is at least one of methyl ethyl carbonate, dimethyl carbonate, diethyl carbonate, methyl trifluoroethyl carbonate, ethyl trifluoroethyl carbonate, and di(2,2,2-trifluoroethyl) carbonate.
6. The high-voltage resistant flame-retardant electrolyte as described in claim 1, characterized in that: The molar concentration of the lithium salt in the electrolyte is 0.5~3 mol / L; The volume content of the phosphate ester solvent with flame retardancy and strong coordination ability is 0.01% to 100%, the volume content of the cyclic ester solvent with medium coordination ability is 0.01% to 50%, and the volume content of the chain ester solvent with weak coordination ability is 0.01% to 60%.
7. The application of the high-voltage resistant flame-retardant electrolyte according to any one of claims 1 to 6 in the preparation of a long-cycle-life negative electrode-free lithium metal battery.
8. The application as described in claim 7, characterized in that: The negative electrode of the non-negative electrode lithium metal battery consists only of copper foil current collector and no active material, while the positive electrode is at least one of lithium iron phosphate, lithium cobalt oxide, ternary cathode material or lithium-rich manganese-based cathode material.
9. The application as described in claim 7, characterized in that: The negative electrode-free lithium metal battery also includes a separator, which includes at least one of polypropylene separator, polyethylene separator, glass fiber separator, polytetrafluoroethylene separator and cellulose separator.
10. The application as described in claim 7, characterized in that: The negative electrode-free lithium metal battery is a button cell or a pouch cell.