An electrolyte additive for a lithium metal battery, a preparation method thereof, a lithium metal battery electrolyte, and a lithium metal battery

Abstract

The application discloses an electrolyte additive for a lithium metal battery, a preparation method thereof, a lithium metal battery electrolyte and a lithium metal battery and belongs to the technical field of lithium ion batteries. The electrolyte additive is specifically a fluoroazocyanamide derivative. The fluoroazocyanamide derivative can be preferentially decomposed in a lithium salt and a solvent in an electrolyte. A large amount of free radicals can be generated in a decomposition process of azo salts with different electron densities. The free radicals can be grafted to an electrode surface. In the presence of an amide group, nitrogen-containing free radicals can react with lithium metal to generate lithium nitride. After fluorine substitution, the above-mentioned free radicals can simultaneously derive lithium fluoride on the surface of the lithium metal, participate in in-situ construction to form a dense, stable and high-ionic-conductivity composite inorganic interface layer, further improve the stability of the interface layer, reduce the direct contact area of the metal lithium and the electrolyte, inhibit the growth of lithium dendrites and effectively improve the long cycle and high-rate performance of the lithium metal battery.

Description

Technical Field

[0001] This invention relates to the field of lithium-ion battery technology, and particularly to an electrolyte additive for lithium metal batteries and its preparation method, a lithium metal battery electrolyte, and a lithium metal battery. Background Technology

[0002] With the rapid expansion of the electronic devices and electric vehicle markets, the demand for high-energy-density and high-power-density lithium batteries is increasing. However, the traditional graphite anode has a low theoretical capacity, which is insufficient to meet the needs of modern development. To replace graphite anodes, lithium metal anodes are a promising anode material with high theoretical capacity. Moreover, lithium metal has excellent properties such as the lowest standard electrode potential and good conductivity.

[0003] However, lithium metal anodes still present numerous problems. Due to the difficulty in controlling the lithium-ion deposition process and the high reactivity of lithium metal, a fragile and unstable solid electrolyte interphase (SEI) film and uncontrolled lithium dendrites can form on the lithium metal surface. This can lead to battery capacity loss, volume expansion, and short circuits. Using electrolyte additives is one of the efficient and simple methods to optimize the SEI composition and structure and solve these problems.

[0004] An ideal SEI (Sediment Injection Layer) not only needs excellent mechanical properties and fast ion transport capabilities, but also a dense structure to provide long-term protection for lithium metal. Among the components of an SEI, lithium fluoride can improve its mechanical properties and stability, and inhibit dendrite growth, while lithium nitride has high lithium-ion conductivity, which can improve the ion transport performance of lithium ions within the SEI film, thereby optimizing the battery's rate performance. Chinese patent CN118553984A describes a method of generating an SEI rich in lithium fluoride and lithium nitride on the surface of the lithium metal anode through a redox reaction of electrolyte additives, aiming to balance the stability and rate performance of lithium metal batteries. However, relying solely on redox reactions to generate the SEI can lead to uneven local reactions, resulting in inconsistent SEI layer thickness and composition, making it difficult to provide long-term protection for the lithium metal anode. Previous studies have reported adjusting the electron density distribution of azo salts and using them as electrolyte additives to generate a large number of nitrogen-containing free radicals in the electrolyte. These free radicals adsorb onto the lithium metal surface to form a dense layer, which then derives into a dense lithium nitride-containing SEI. However, this strategy generates relatively little lithium fluoride, resulting in limited improvement in SEI film stability. Therefore, this invention uses different fluorine-containing groups to adjust the electron density distribution of azo amides to generate free radicals containing both fluorine and nitrogen. These free radicals adsorb onto the lithium metal surface and derive into a dense SEI rich in lithium fluoride and lithium nitride. This not only improves the uniformity, stability, and ion transport performance of the SEI but also provides long-term protection for the lithium metal anode. It should be noted that Chinese patent CN120565816B provides an electrolyte containing fluorinated monomers of the amide type, which aims to improve the storage stability of the battery at high temperatures. However, the fluorinated monomers of the amide type have long fluorine chains (more than 5 carbon atoms), high stability, and are difficult to derive stable SEI. They also bind solvent molecules, which increases the viscosity of the electrolyte, disrupts the solvation of lithium ions, hinders the transport of lithium ions in the electrolyte, and reduces the long-cycle stability and rate performance of the battery. Summary of the Invention

[0005] This invention provides an electrolyte additive for lithium metal batteries and its preparation method, a lithium metal battery electrolyte, and a lithium metal battery, aiming to solve the problem that existing electrolyte additives cannot simultaneously achieve a uniform and dense SEI structure, high mechanical strength, and excellent lithium-ion transport performance.

[0006] The objective of this invention can be achieved through the following technical solutions: In a first aspect, the present invention provides an electrolyte additive for lithium metal batteries, having a structure as shown in Formula A:

[0007] Formula A R1 and R2 are each independently selected from -CHF2, -CH2F, -CF3 or -CH3; and at least one of R1 and R2 is selected from -CHF2, -CH2F or -CF3.

[0008] Furthermore, the electrolyte additive for lithium metal batteries is selected from any one of formulas (I) to (IX):

[0009] Formula (I) Formula (II) Formula (III)

[0010] Formula (Ⅳ) Formula (Ⅴ) Formula (Ⅵ)

[0011] Formula (VII) Formula (VIII) Formula (IX) Secondly, the present invention provides a method for preparing an electrolyte additive for lithium metal batteries, comprising the following steps: S1. Under the action of an active catalyst, fluorinated methanol having the structure shown in Formula a is reacted with ammonia to obtain a reaction intermediate having the structure shown in Formula b. The structural formulas for formula a or formula b are as follows: Formula a; Formula b; R1 is selected from -CHF2, -CH2F or -CF3; S2. Mix one or two reaction intermediates with diethyl azodicarbonate to carry out a second reaction to obtain an electrolyte additive for lithium metal batteries. Specifically, when a reaction intermediate is used and the molar ratio of the reaction intermediate to diethyl azodicarbonate is (1-1.25):1, dimethylamine is added to the reaction system to participate in the reaction together; when two reaction intermediates are mixed, or when a reaction intermediate is used and the molar ratio of it to diethyl azodicarbonate is (2-2.5):1, dimethylamine is not added to the reaction system.

[0012] Further, in step S1, the molar ratio of fluorinated methanol to ammonia is (0.8~1.2):1.

[0013] Furthermore, in step S1, the amount of the active catalyst is 1 wt% to 2 wt% of ammonia.

[0014] Further, in step S1, the active catalyst includes activated alumina or activated carbon.

[0015] Furthermore, in step S1, the temperature of the first reaction is 400℃~450℃, the pressure is 2MPa~3MPa, and the time is 4~6h.

[0016] Furthermore, in step S1, the first reaction is followed by the following steps: After the first reaction between fluorinated methanol and ammonia is completed, the resulting reaction system is condensed, extracted, and distilled to obtain a reaction intermediate.

[0017] Furthermore, the extractant used for extraction includes anhydrous diethyl ether or ethyl acetate.

[0018] Furthermore, the distillation temperature is 50–80°C.

[0019] Further, in step S2, when dimethylamine is added, the total molar amount of the reaction intermediate and dimethylamine to the molar ratio of diethyl azodicarbonate is (2-2.5):1; When dimethylamine is not added, the total molar amount of the one or two reaction intermediates to the molar ratio of diethyl azodicarbonate is (2-2.5):1.

[0020] Furthermore, in step S2, the temperature of the second reaction is 200℃~300℃, the pressure is 1.5MPa~2.0MPa, and the time is 8~12h.

[0021] Furthermore, in step S2, the second reaction is followed by the following steps: After the second reaction between the reaction intermediate and diethyl azodicarbonate is completed, the cooled product is added to an alkaline catalyst and stirred until homogeneous. Then, it is filtered and rotary evaporated to obtain an electrolyte additive for lithium metal batteries.

[0022] Furthermore, the amount of alkaline catalyst used is 0.5wt% to 1wt% of diethyl azodicarbonate.

[0023] Furthermore, the alkaline catalyst includes calcium hydroxide or potassium hydroxide.

[0024] Furthermore, the rotary evaporation temperature is 80–100°C, and the rotation speed is 100–200 rpm.

[0025] Thirdly, the present invention provides a lithium metal battery electrolyte, comprising lithium salt, organic solvent and the electrolyte additives for lithium metal batteries mentioned in the above technical solutions.

[0026] Furthermore, based on a mass percentage of 100% for the lithium metal battery electrolyte, the lithium metal battery electrolyte comprises the following components: 8%–20% lithium salt, 1%–15% electrolyte additives for lithium metal batteries, and the remainder being organic solvents.

[0027] Furthermore, the lithium salt includes any one or more of lithium hexafluorophosphate, lithium bis(fluorosulfonyl)imide, lithium bis(trifluoromethanesulfonyl)imide, lithium tetrafluoroborate, lithium bis(oxalateborate)borate, or lithium di(fluorooxalateborate).

[0028] Further, the organic solvent includes any one or more of ethylene carbonate, propylene carbonate, dimethyl carbonate, diethyl carbonate, methyl ethyl carbonate, methyl propyl carbonate, γ-butyrolactone, methyl formate, methyl acetate, ethylene glycol dimethyl ether, or ethylene glycol diethyl ether and diethylene glycol dimethyl ether.

[0029] Fourthly, the present invention provides a lithium metal battery, comprising a positive electrode, a negative electrode, an electrolyte, and a separator disposed between the positive electrode and the negative electrode; The electrolyte is the lithium metal battery electrolyte involved in the above technical solution.

[0030] Furthermore, the active material of the positive electrode includes any one or more of the following: lithium-ion intercalated transition metal oxide with a layered structure, lithium-ionized transition metal mixed oxide with a spinel structure, or lithium-ionized transition metal phosphate with an olivine structure, preferably any one or more of lithium nickel cobalt manganese oxide, lithium manganese oxide, lithium cobalt oxide, lithium iron phosphate, or sulfur-carbon composite material.

[0031] Furthermore, the active material of the negative electrode includes any one or more of lithium, lithium alloys, or materials capable of forming lithium alloys.

[0032] Furthermore, the diaphragm includes any one or more of polyvinylidene fluoride, polyethylene, polypropylene, or surface-modified composite diaphragms.

[0033] The beneficial effects of this invention are: This invention provides an electrolyte additive for lithium metal batteries, specifically a fluoroazoamide derivative. The fluoroazoamide derivative preferentially decomposes before lithium salts and solvents in the electrolyte. During decomposition, azo salts with different electron densities generate a large number of free radicals. These free radicals can graft onto the electrode surface. In the presence of the amide group, nitrogen-containing free radicals can react with lithium metal to generate lithium nitride. After fluorine substitution, these free radicals can simultaneously derive lithium fluoride on the lithium metal surface, participating in the in-situ construction of a dense, stable, and highly ionicly conductive composite inorganic interface layer. This further improves the stability of the interface layer, reduces the direct contact area between lithium metal and the electrolyte, inhibits the growth of lithium dendrites, and effectively improves the long-cycle and high-rate performance of lithium metal batteries. Detailed Implementation

[0034] To make the above-mentioned objects, features and advantages of the present invention more apparent and understandable, specific embodiments of the present invention will be described in detail below.

[0035] In a first aspect, the present invention provides an electrolyte additive for lithium metal batteries, having a structure as shown in Formula A:

[0036] Formula A R1 and R2 are each independently selected from -CHF2, -CH2F, -CF3 or -CH3; and at least one of R1 and R2 is selected from -CHF2, -CH2F or -CF3.

[0037] In this fluoroazoamide structure, the introduction of fluorinated substituents such as -CHF2, -CH2F, or -CF3 can effectively regulate the electron cloud distribution and redox stability of the molecule, enabling it to decompose preferentially on the lithium metal anode surface before the main electrolyte components. The azo group in the molecule can generate nitrogen-containing free radicals in situ. In the presence of the amide group, the nitrogen-containing free radicals can react with lithium metal to generate lithium nitride. At the same time, the fluorinated group can generate lithium fluoride in situ. The two work together to construct a dense, stable, and highly ionicly conductive inorganic composite interface film on the anode surface, thereby significantly inhibiting lithium dendrite growth and continuous electrolyte decomposition, reducing interface impedance, and improving the cycle stability and high-rate discharge performance of lithium metal batteries.

[0038] In some embodiments, the electrolyte additive for lithium metal batteries is selected from any one of formulas (I) to (IX):

[0039] Formula (I) Formula (II) Formula (III)

[0040] Formula (Ⅳ) Formula (Ⅴ) Formula (Ⅵ)

[0041] Formula (VII) Formula (VIII) Formula (IX) Secondly, the present invention provides a method for preparing an electrolyte additive for lithium metal batteries, comprising the following steps: S1. Under the action of an active catalyst, fluorinated methanol having the structure shown in Formula a is reacted with ammonia to obtain a reaction intermediate having the structure shown in Formula b. The structural formulas for formula a or formula b are as follows: Formula a; Formula b; R1 is selected from -CHF2, -CH2F or -CF3; In the above reaction steps, under the action of an active catalyst, fluorinated methanol first undergoes dehydrogenation to generate an aldehyde intermediate. Subsequently, the aldehyde undergoes nucleophilic addition with ammonia and further oxidative rearrangement to finally generate a fluoroamide. The catalyst provides active sites, promotes the breaking of CO bonds and the formation of CN bonds, while the strong electron-withdrawing effect of the fluorinated groups regulates the electron density of the reaction intermediate, enabling the reaction to proceed smoothly towards the formation of the target amide under high temperature and high pressure conditions.

[0042] S2. Mix one or two reaction intermediates with diethyl azodicarbonate to carry out a second reaction to obtain an electrolyte additive for lithium metal batteries. Specifically, when a reaction intermediate is used and the molar ratio of the reaction intermediate to diethyl azodicarbonate is (1-1.25):1, dimethylamine is added to the reaction system to participate in the reaction together; when two reaction intermediates are mixed, or when a reaction intermediate is used and the molar ratio of it to diethyl azodicarbonate is (2-2.5):1, dimethylamine is not added to the reaction system.

[0043] In the second reaction step described above, the amide group in the reaction intermediate acts as a nucleophile, launching a nucleophilic attack on the ester group of diethyl azodicarbonate under high temperature and pressure, resulting in an aminolysis reaction that removes ethanol and generates a fluoroalkyl-substituted azobisamide structure. When dimethylamine is added to the reaction system, it also acts as a nucleophile, introducing a methyl group onto the amide nitrogen, yielding an N-methyl-substituted fluoroazoamide derivative. This reaction design allows for flexible control of the substitution mode on the nitrogen in the product, thereby regulating the electron density distribution and reduction stability of the molecule. This enables the resulting additive to preferentially decompose on the lithium metal anode surface and generate free radicals containing both fluorine and nitrogen, synergistically constructing a dense, stable, and highly ionicly conductive lithium fluoride / lithium nitride composite interface layer in situ. This effectively inhibits lithium dendrite growth and significantly improves the cycle life and high-rate performance of lithium metal batteries.

[0044] In some embodiments, in step S1, the molar ratio of fluorinated methanol to ammonia is (0.8–1.2):1. This is beneficial for the complete conversion of fluorinated methanol and the improvement of intermediate yield. If the molar ratio is too high, excess fluorinated methanol may lead to raw material waste and subsequent separation burden. If the molar ratio is too low, excess ammonia may lead to an increase in side reactions and reduce the purity of the target intermediate.

[0045] In some embodiments, in step S1, the amount of the active catalyst is 1wt% to 2wt% of the ammonia gas. This ensures moderate catalytic efficiency and accelerates the reaction rate. If too much catalyst is used, it is easy to increase reaction by-products, increase costs, and increase separation difficulty. If too little catalyst is used, the catalytic effect is insufficient, the reaction rate is slow, and the conversion is incomplete.

[0046] In some embodiments, in step S1, the active catalyst comprises activated alumina or activated carbon. Using activated alumina or activated carbon as the active catalyst allows for efficient catalysis of the substitution reaction between fluorinated methanol and ammonia under mild conditions, exhibiting high selectivity and few side reactions.

[0047] In some embodiments, in step S1, the temperature of the first reaction is 400℃~450℃, the pressure is 2MPa~3MPa, and the time is 4~6h. Controlling the temperature, pressure, and time of the first reaction within the above range can ensure the reaction rate and complete conversion of raw materials, while avoiding side reactions, excessive energy consumption, and volatilization loss of reactants, resulting in better yield and purity of intermediates.

[0048] In some embodiments, step S1 further includes the following step after the first reaction: After the initial reaction of fluorinated methanol and ammonia, the resulting reaction system is condensed, extracted, and distilled to obtain a reaction intermediate. Sequentially performing condensation, extraction, and distillation on the reaction system effectively separates and removes unreacted raw materials and byproducts, resulting in a purified fluoroalkylamine intermediate with higher purity and fewer impurities.

[0049] In some embodiments, the extractant used for extraction includes anhydrous diethyl ether or ethyl acetate. It has moderate polarity, good extraction selectivity, and can efficiently separate and purify intermediates, which are then easily removed subsequently.

[0050] In some embodiments, the distillation temperature is 50–80°C. This allows for the purification of intermediates under mild conditions, avoiding decomposition or volatilization losses due to high temperatures.

[0051] In some embodiments, in step S2, when dimethylamine is added, the molar ratio of the total molar amount of the reaction intermediate and dimethylamine to diethyl azodicarbonate is (2-2.5):1; when dimethylamine is not added, the molar ratio of the total molar amount of one or both reaction intermediates to diethyl azodicarbonate is (2-2.5):1. This ensures complete reaction conversion and yields a high-purity target product; an excessively high ratio will result in excessive waste of intermediates and increased costs; an excessively low ratio will lead to incomplete reaction and residual impurities.

[0052] In some embodiments, in step S2, the temperature of the second reaction is 200℃~300℃, the pressure is 1.5MPa~2.0MPa, and the time is 8~12h. Controlling the temperature, pressure, and time of the second reaction within the above ranges can ensure a moderate reaction rate and sufficient conversion of raw materials, thereby improving the yield and purity of the target additive. Excessive temperature and pressure can easily cause the decomposition of azo groups and increase side reactions, while excessively low temperatures result in a slow reaction rate and incomplete conversion. Excessively long time will increase energy consumption and produce by-products, while excessively short time will result in incomplete reaction, affecting the product yield and purity.

[0053] In some embodiments, step S2 further includes the following step after the second reaction: After the second reaction between the reaction intermediate and diethyl azodicarbonate is completed, the cooled product is added to an alkaline catalyst and stirred until homogeneous. The mixture is then filtered and rotary evaporated to obtain an electrolyte additive for lithium metal batteries. Cooling, adding an alkaline catalyst, stirring, filtering, and rotary evaporating the product after the second reaction neutralizes the reaction system, promotes the decomposition and removal of byproducts, and effectively removes unreacted raw materials, organic impurities, and solvents, thereby improving the purity and electrochemical stability of the electrolyte additive.

[0054] In some embodiments, the amount of alkaline catalyst used is 0.5wt% to 1wt% of diethyl azodicarbonate. This can effectively promote the removal of by-products and ensure post-processing efficiency; excessive use will lead to excessive alkalinity in the system, causing hydrolysis or decomposition of the product; insufficient use will result in inadequate catalytic neutralization and incomplete removal of impurities.

[0055] In some embodiments, the alkaline catalyst comprises calcium hydroxide or potassium hydroxide. It can efficiently neutralize the reaction system, promote the removal of byproducts, and is easily removed in subsequent separation; however, if the alkalinity is too weak, post-treatment will be insufficient, while if the alkalinity is too strong, the additive structure will be easily damaged.

[0056] In some embodiments, the rotary evaporation temperature is 80–100°C and the rotation speed is 100–200 rpm. This method can quickly and gently remove solvents and volatile impurities; however, excessively high temperatures or rotation speeds can cause thermal decomposition or loss of the product; conversely, excessively low temperatures or rotation speeds result in incomplete solvent removal and low purification efficiency.

[0057] Thirdly, the present invention provides a lithium metal battery electrolyte, comprising lithium salt, organic solvent and the electrolyte additives for lithium metal batteries mentioned in the above technical solutions.

[0058] In some embodiments, the lithium metal battery electrolyte, based on a mass percentage of 100%, comprises the following components: 8%–20% lithium salt, 1%–15% electrolyte additives for lithium metal batteries, and the balance being organic solvents. Controlling the lithium salt, electrolyte additives, and organic solvents within the aforementioned content range ensures that the electrolyte possesses suitable ionic conductivity, interfacial film-forming effect, and electrochemical stability, while also considering the battery's cycle and rate performance. Excessive lithium salt or additive content can increase viscosity, generate side reactions, and deteriorate battery safety; conversely, insufficient content results in inadequate ionic conductivity, poor film-forming effect, and an inability to effectively suppress lithium dendrite growth.

[0059] In some embodiments, the lithium salt includes any one or more of lithium hexafluorophosphate, lithium bis(fluorosulfonyl)imide, lithium bis(trifluoromethanesulfonyl)imide, lithium tetrafluoroborate, lithium bis(oxalate-borate), or lithium di(fluorooxalate-borate). Selecting the above lithium salts can provide the electrolyte with stable and high ionic conductivity, ensuring moderate internal resistance and stable charge-discharge performance of the battery.

[0060] In some embodiments, the organic solvent includes any one or more of ethylene carbonate, propylene carbonate, dimethyl carbonate, diethyl carbonate, methyl ethyl carbonate, methyl propyl carbonate, γ-butyrolactone, methyl formate, methyl acetate, ethylene glycol dimethyl ether, or ethylene glycol diethyl ether and diethylene glycol dimethyl ether. Using the above solvents can balance the solubility, volatility, viscosity, and electrochemical stability of the electrolyte, and has good compatibility with additives, thus synergistically improving the overall performance of the electrolyte.

[0061] Fourthly, the present invention provides a lithium metal battery, comprising a positive electrode, a negative electrode, an electrolyte, and a separator disposed between the positive electrode and the negative electrode; The electrolyte is the lithium metal battery electrolyte involved in the above technical solution.

[0062] In some embodiments, the active material of the positive electrode includes any one or more of the following: lithium-ion intercalated transition metal oxides with a layered structure, lithium-ionized transition metal mixed oxides with a spinel structure, or lithium-ionized transition metal phosphates with an olivine structure; preferably, any one or more of the following: lithium nickel cobalt manganese oxide, lithium manganese oxide, lithium cobalt oxide, lithium iron phosphate, or sulfur-carbon composite materials. Using the above-mentioned active material of the positive electrode provides structural stability, good reversibility of lithium intercalation / deintercalation, and excellent capacity and cycle performance. It can also be well-matched with the electrolyte additives of the present invention, thereby improving the overall electrochemical performance of the battery.

[0063] In some embodiments, the active material of the negative electrode includes any one or more of lithium, lithium alloys, or materials capable of forming lithium alloys. Using the above-mentioned active material of the negative electrode can leverage the high specific capacity advantage of lithium metal to meet high energy density requirements, while simultaneously forming a stable interface film with electrolyte additives to suppress lithium dendrite formation.

[0064] In some embodiments, the separator comprises any one or more of polyvinylidene fluoride, polyethylene, polypropylene, or surface-modified composite separators. Using the above-mentioned separator materials results in high mechanical strength, good chemical and electrochemical stability, and excellent ion permeability, effectively preventing direct contact between the positive and negative electrodes and improving the safety and reliability of the battery.

[0065] The specific embodiments of the present invention will be described in detail below, but it should be understood that the scope of protection of the present invention is not limited to the specific embodiments.

[0066] Example Example 1 This embodiment provides an electrolyte additive for lithium metal batteries, and the preparation method includes the following steps: Fluorinated methanol with the structure shown in formula (a-1) and ammonia were mixed and reacted at a temperature of 425°C and a pressure of 2.5 MPa for 5 hours under the action of activated alumina. The synthesized substance was condensed and extracted with anhydrous diethyl ether, followed by distillation at 65°C under normal pressure to obtain a reaction intermediate with the structure shown in formula (b-1), wherein the molar ratio of fluorinated methanol to ammonia was 0.8:1 and the amount of activated alumina was 1.5 wt% of ammonia.

[0067]

[0068] Equation (a-1) Equation (b-1) S2: The intermediate (b-1) and dimethylamine were passed into diethyl azodicarbonate and reacted for 10 hours under heating and pressure (temperature 250℃, pressure 1.8MPa). The cooled product was added to a calcium hydroxide solution, stirred evenly, and then filtered. The filtered liquid was subjected to rotary evaporation (temperature 90℃, rotation speed 150rpm) to obtain an electrolyte additive with the structure shown in formula (Ⅰ). The molar ratio of (b-1) to dimethylamine to diethyl azodicarbonate was 1.1:1.1:1, and the amount of calcium hydroxide was 0.8wt% of diethyl azodicarbonate.

[0069]

[0070] Equation (I) Its proton NMR spectrum data are as follows: 1 H-NMR (400 MHz, CDCl3, δ / ppm): δ 2.92 (6H, s), 5.30-5.40 (4H, 5.35 (s), 5.35 (s)).

[0071] The electrolyte is prepared using the above-mentioned electrolyte additives. Based on the mass percentage of 100% of the lithium metal battery electrolyte, it includes the following components: 10% lithium bis(fluorosulfonyl)imide, 5% of the above-mentioned electrolyte additives, and 85% of the solvent ethylene glycol dimethyl ether.

[0072] Example 2 This embodiment provides an electrolyte additive for lithium metal batteries, and the preparation method includes the following steps: S1: Fluorinated methanol with the structure shown in formula (a-2) and ammonia were mixed. The reaction conditions were 400°C and 2 MPa. The reaction was initiated for 4 hours under the action of activated alumina. The resulting substance was condensed and extracted with anhydrous diethyl ether. Then, it was distilled at 50°C under normal pressure to obtain a reaction intermediate with the structure shown in formula (b-2), wherein the molar ratio of fluorinated methanol to ammonia was 0.8:1 and the amount of activated alumina was 1 wt% of ammonia.

[0073]

[0074] Equation (a-2) Equation (b-2) S2: The intermediate (b-2) and dimethylamine were passed into diethyl azodicarbonate and reacted for 8 hours under heating and pressure (temperature 200℃, pressure 1.5MPa). The cooled product was added to a calcium hydroxide solution, stirred evenly, and then filtered. The extracted liquid was subjected to rotary evaporation (temperature 80℃, rotation speed 100rpm) to obtain an electrolyte additive with the structure shown in formula (II). The molar ratio of (b-2) to dimethylamine to diethyl azodicarbonate was 1:1:1, and the amount of calcium hydroxide was 0.5wt% of diethyl azodicarbonate.

[0075]

[0076] Formula (II) Its proton NMR spectrum data are as follows: 1 H-NMR (400 MHz, CDCl3, δ / ppm): δ 2.93 (6H, s), 6.61 (2H, s).

[0077] The electrolyte is prepared using the above-mentioned electrolyte additives. Based on the mass percentage of 100% of the lithium metal battery electrolyte, it includes the following components: 15% lithium difluorosulfonyl imide, 5% of the above-mentioned electrolyte additives, and 80% ethylene glycol dimethyl ether solvent.

[0078] Example 3 This embodiment provides an electrolyte additive for lithium metal batteries, and the preparation method includes the following steps: S1: Fluorinated methanol with the structure shown in formula (a-3) and ammonia were mixed. The reaction conditions were 450°C and 3 MPa. The reaction was started for 6 hours under the action of activated alumina. The synthesized substance was condensed and extracted with ethyl acetate. Then, it was distilled at 80°C under normal pressure to obtain a reaction intermediate with the structure shown in formula (b-3). The molar ratio of fluorinated methanol to ammonia was 1.2:1, and the amount of activated alumina was 2 wt% of ammonia.

[0079]

[0080] Equation (a-3) Equation (b-3) S2: The intermediate (b-3) and dimethylamine were passed into diethyl azodicarbonate and reacted for 12 hours under heating and pressure (temperature 300℃, pressure 2MPa). The cooled product was added to a calcium hydroxide solution, stirred evenly, and then filtered. The extracted liquid was subjected to rotary evaporation (temperature 100℃, speed 200rpm) to obtain an electrolyte additive with the structure shown in formula (Ⅲ). The molar ratio of (b-3) to dimethylamine to diethyl azodicarbonate was 1.25:1.25:1, and the amount of potassium hydroxide was 1wt% of diethyl azodicarbonate.

[0081]

[0082] Formula (III) Its proton NMR spectrum data are as follows: 1 H-NMR (400 MHz, CDCl3, δ / ppm): δ 2.93 (6H, s).

[0083] The electrolyte is prepared using the above-mentioned electrolyte additives. Based on the mass percentage of 100% of the lithium metal battery electrolyte, it includes the following components: 15% lithium difluorosulfonyl imide, 5% of the above-mentioned electrolyte additives, and 80% ethylene glycol dimethyl ether solvent.

[0084] Example 4 This embodiment provides an electrolyte additive for lithium metal batteries, and the preparation method includes the following steps: The b-1 obtained in Example 1 was passed into diethyl azodicarbonate and reacted for 10 hours under heating and pressurization (temperature 250°C, pressure 2 MPa). The cooled product was added to a calcium hydroxide solution, stirred evenly, and then filtered. The extracted liquid was subjected to rotary evaporation (temperature 90°C, rotation speed 200 rpm) to obtain an electrolyte additive with the structure shown in Formula (IV). The molar ratio of b-1 to diethyl azodicarbonate was 2.1:1, and the amount of potassium hydroxide was 0.8 wt% of diethyl azodicarbonate.

[0085]

[0086] Equation (Ⅳ) Its proton NMR spectrum data are as follows: 1 H-NMR (400 MHz, CDCl3, δ / ppm): δ 5.30-5.40 (8H, 5.35 (s), 5.35 (s), 5.35 (s), 5.35 (s), 5.35 (s)).

[0087] The electrolyte is prepared using the above-mentioned electrolyte additives. Based on the mass percentage of 100% of the lithium metal battery electrolyte, it includes the following components: 18% lithium difluorosulfonylimide, 2% of the above-mentioned electrolyte additives, and 80% ethylene glycol dimethyl ether solvent.

[0088] Example 5 This embodiment provides an electrolyte additive for lithium metal batteries, and the preparation method includes the following steps: The b-1 obtained in Example 1 and the b-2 obtained in Example 2 were passed into diethyl azodicarbonate and reacted for 10 hours under heating and pressurization (temperature 300℃, pressure 1.8MPa). The cooled product was added to a calcium hydroxide solution, stirred evenly, and then filtered. The extracted liquid was subjected to rotary evaporation (temperature 100℃, rotation speed 150rpm) to obtain an electrolyte additive with the structure shown in formula (V). The molar ratio of b-1, b-2 to diethyl azodicarbonate was 1.25:1.25:1, and the amount of potassium hydroxide was 1 wt% of diethyl azodicarbonate.

[0089]

[0090] Formula (V) Its proton NMR spectrum data are as follows: 1 H-NMR (400 MHz, CDCl3, δ / ppm): δ 5.30-5.40 (4H, 5.35 (s), 5.35 (s), 5.35 (s)), 6.56-6.66 (2H, 6.61 (s), 6.61 (s)).

[0091] The electrolyte is prepared using the above-mentioned electrolyte additives. Based on the mass percentage of 100% of the lithium metal battery electrolyte, it includes the following components: 10% lithium bis(fluorosulfonyl)imide, 5% of the above-mentioned electrolyte additives, and 85% of the solvent ethylene glycol dimethyl ether.

[0092] Example 6 This embodiment provides an electrolyte additive for lithium metal batteries, and the preparation method includes the following steps: The above-mentioned b-1 and b-3 were passed into diethyl azodicarbonate and reacted for 10 hours under heating and pressurization (temperature 280℃, pressure 1.8MPa). The cooled product was added to calcium hydroxide solution, stirred evenly, and then filtered. The extracted liquid was subjected to rotary evaporation (temperature 90℃, rotation speed 150rpm) to obtain an electrolyte additive with the structure shown in formula (VI). The molar ratio of b-1, b-3 to diethyl azodicarbonate was 1.1:1.1:1, and the amount of potassium hydroxide was 0.5wt% of diethyl azodicarbonate.

[0093]

[0094] Formula (VI) Its proton NMR spectrum data are as follows: 1 H-NMR (400 MHz, CDCl3, δ / ppm): δ 5.30-5.40 (4H, 5.35 (s), 5.35 (s)).

[0095] The electrolyte is prepared using the above-mentioned electrolyte additives. Based on the mass percentage of 100% of the lithium metal battery electrolyte, it includes the following components: 18% lithium difluorosulfonylimide, 2% of the above-mentioned electrolyte additives, and 80% ethylene glycol dimethyl ether solvent.

[0096] Example 7 This embodiment provides an electrolyte additive for lithium metal batteries, and the preparation method includes the following steps: The above-mentioned b-2 was passed into diethyl azodicarbonate and reacted for 8 hours under heating and pressurization (temperature 300℃, pressure 1.8MPa). The cooled product was added to a calcium hydroxide solution, stirred evenly, and then filtered. The extracted liquid was subjected to rotary evaporation (temperature 90℃, rotation speed 150rpm) to obtain an electrolyte additive with the structure shown in formula (VII). The molar ratio of b-2 to diethyl azodicarbonate was 2.5:1, and the amount of potassium hydroxide was 1 wt% of diethyl azodicarbonate.

[0097]

[0098] Formula (VII) Its proton NMR spectrum data are as follows: 1 H-NMR (400 MHz, CDCl3, δ / ppm): δ 6.56-6.66 (4H, 6.61 (s), 6.61 (s)).

[0099] The electrolyte is prepared using the above-mentioned electrolyte additives. Based on the mass percentage of 100% of the lithium metal battery electrolyte, it includes the following components: 10% lithium difluorosulfonyl imide, 10% of the above-mentioned electrolyte additives, and 80% ethylene glycol dimethyl ether solvent.

[0100] Example 8 This embodiment provides an electrolyte additive for lithium metal batteries, and the preparation method includes the following steps: The above-mentioned b-2 and b-3 were passed into diethyl azodicarbonate and reacted for 9 hours under heating and pressurization (temperature 300℃, pressure 1.9MPa). The cooled product was added to a calcium hydroxide solution, stirred evenly, and then filtered. The extracted liquid was subjected to rotary evaporation (temperature 90℃, rotation speed 200rpm) to obtain an electrolyte additive with the structure shown in formula (VIII). The molar ratio of b-2, b-3 to diethyl azodicarbonate was 1.2:1.2:1, and the amount of potassium hydroxide was 0.8wt% of diethyl azodicarbonate.

[0101]

[0102] Formula (VIII) Its proton NMR spectrum data are as follows: 1 H-NMR (400 MHz, CDCl3, δ / ppm): δ 6.56-6.66 (2H, 6.61 (s), 6.61 (s)).

[0103] The electrolyte is prepared using the above-mentioned electrolyte additives. Based on the mass percentage of 100% of the lithium metal battery electrolyte, it includes the following components: 10% lithium bis(fluorosulfonyl)imide, 2% of the above-mentioned electrolyte additives, and 88% ethylene glycol dimethyl ether as solvent.

[0104] Example 9 This embodiment provides an electrolyte additive for lithium metal batteries, and the preparation method includes the following steps: The above-mentioned b-3 was passed into diethyl azodicarbonate and reacted under heating and pressure (temperature 280℃, pressure 1.9MPa) for 8.5 h. The cooled product was added to a calcium hydroxide solution, stirred evenly, and then filtered. The extracted liquid was subjected to rotary evaporation (temperature 100℃, speed 200 rpm) to obtain an electrolyte additive with the structure shown in formula (IX). The molar ratio of b-3 to diethyl azodicarbonate was 2.2:1, and the amount of potassium hydroxide was 1 wt% of diethyl azodicarbonate.

[0105]

[0106] Formula (IX) Its proton NMR spectrum data are as follows:1 H-NMR (400 MHz, CDCl3, δ / ppm): δ 0.00 (1H, m).

[0107] The electrolyte is prepared using the above-mentioned electrolyte additives. Based on the mass percentage of 100% of the lithium metal battery electrolyte, it includes the following components: 11% lithium bis(fluorosulfonyl)imide, 4% of the above-mentioned electrolyte additives, and 85% of the solvent ethylene glycol dimethyl ether.

[0108] Example 10 The electrolyte was prepared using the electrolyte additive obtained in Example 9. Based on the mass percentage of 100% of the lithium metal battery electrolyte, it included the following components: 10% lithium difluorosulfonylimide, 5% electrolyte additive in this invention, and the remaining 85% was an organic solvent, which was a mixture of ethylene carbonate and methyl ethyl carbonate in a mass ratio of 3:7.

[0109] Example 11 The electrolyte was prepared using the electrolyte additive of Example 9. Based on the mass percentage of 100% of the lithium metal battery electrolyte, it includes the following components: 10% lithium hexafluorophosphate, 5% electrolyte additive in this invention, and the balance 85% is organic solvent, which is a mixture of propylene carbonate and dimethyl carbonate in a mass ratio of 3:7.

[0110] Example 12 The electrolyte was prepared using the electrolyte additive from Example 9. Based on a mass percentage of 100% for lithium metal battery electrolyte, it included the following components: 12% lithium bis(trifluoromethanesulfonyl)imide, 5% electrolyte additive in this invention, and the remaining 83% was an organic solvent, which was a mixture of diethyl carbonate and methyl propyl carbonate in a mass ratio of 3:7.

[0111] Example 13 The electrolyte was prepared using the electrolyte additive from Example 9. Based on a mass percentage of 100% for lithium metal battery electrolyte, it included the following components: 15% lithium tetrafluoroborate, 5% electrolyte additive in this invention, and the remaining 80% was an organic solvent, which was a mixture of γ-butyrolactone and methyl formate in a mass ratio of 3:7.

[0112] Example 14 The electrolyte was prepared using the electrolyte additive from Example 9. Based on a mass percentage of 100% for lithium metal battery electrolyte, it included the following components: 5% lithium dioxolane borate, 5% lithium difluorooxolane borate, 5% electrolyte additive, and the remaining 85% was an organic solvent, which was a mixture of ethylene glycol diethyl ether and diethylene glycol dimethyl ether in a mass ratio of 3:7.

[0113] Comparative Example Comparative Example 1 The electrolyte composition of this comparative example is based on a 100% mass percentage of lithium metal battery electrolyte, and includes the following components: 10% lithium bis(fluorosulfonyl)imide, 5% lithium nitrate as electrolyte additive, and the balance 85% is ethylene glycol dimethyl ether as solvent.

[0114] Comparative Example 2 The electrolyte composition of this comparative example is based on a 100% mass percentage of lithium metal battery electrolyte, and includes the following components: 10% lithium difluorosulfonylimide, 5% lithium difluorooxalate borate (an electrolyte additive), and the balance 85% is ethylene glycol dimethyl ether (the solvent).

[0115] Comparative Example 3 The electrolyte composition of this comparative example is based on a 100% mass percentage of lithium metal battery electrolyte, and includes the following components: 10% lithium bis(fluorosulfonyl)imide, 5% fluoroethylene carbonate as an electrolyte additive, and the balance 85% is ethylene glycol dimethyl ether as a solvent.

[0116] Comparative Example 4 The electrolyte composition of this comparative example is based on a 100% mass percentage of lithium metal battery electrolyte, and includes the following components: 10% lithium difluorosulfonyl imide, 5% electrolyte additive CF3CF2CF2CF2CF2CF2CF2CF2-CO-NH2 obtained from patent CN120565816B, and the balance 85% is solvent ethylene glycol dimethyl ether.

[0117] Comparative Example 5 The electrolyte composition of this comparative example is based on a 100% mass percentage of lithium metal battery electrolyte, and includes the following components: 10% lithium bisfluorosulfonamide, 5% N,N,N',N'-tetramethylazodicarbonamide added to the electrolyte, and the balance 85% is ethylene glycol dimethyl ether solvent.

[0118] Test case (1) Take the electrolytes prepared in Examples 1-14 and Comparative Examples 1-5 respectively and measure the ionic conductivity of each electrolyte using a conductivity meter, and record the measurement data; (2) The cathode material selected is LiNi 0.8 Co 0.1 Mn 0.1O2 was used as the negative electrode material, which was a 100μm thick lithium metal foil. A PP separator was used to fabricate the cells, and the electrolytes prepared in Examples 1-14 and Comparative Examples 1-5 were injected into each cell. After formation and capacity testing, 3.8Ah pouch batteries were obtained. The internal resistance of each of the 3.8Ah pouch batteries was measured using an internal resistance meter, and the measurement data was recorded. The 3.8Ah pouch batteries were cycled at room temperature with a charge / discharge current of 0.2 / 0.5C, with a test voltage range of 3-4.3V. The number of cycles when the capacity retention rate was 80% was recorded. The 3.8Ah pouch batteries were also cycled 5 times at room temperature with charge / discharge currents of 0.2 / 0.2C, 0.2 / 0.5C, 0.2 / 1C, 0.2 / 3C, and 0.2 / 5C, with a test voltage range of 3-4.3V. The capacity retention rate at 0.2 / 5C charge / discharge was recorded.

[0119] The test results are shown in Table 1: Table 1

[0120] As shown in Table 1, the fluoroazoamide additive provided by this invention does not affect the ionic conductivity of the electrolyte itself and has good compatibility with the electrolyte. Due to the strong reducing properties of lithium metal anodes, in the comparative examples, regardless of whether the electrolyte is ester-based or ether-based, side reactions continuously occur at the anode / electrolyte interface, and the continuous breakdown of the SEI leads to an increase in battery polarization impedance. However, in Examples 1-14, the fluoroazoamide derivative additive of this invention was used, which not only maintains the ionic conductivity of the electrolyte itself, but also generates a large number of free radicals during the decomposition of azo salts with different electron densities. These free radicals can be grafted onto the electrode surface and participate in the in-situ construction of a uniform interface layer, significantly reducing impedance. Furthermore, the optimization effect on the interface is significant when using different lithium salts and solvents.

[0121] In the structure of the fluoroazoamide derivatives of this invention, due to the strong electron-withdrawing effect of fluorine, the symmetrical fluoroazoamide derivatives of this invention have a lower lowest unoccupied molecular orbital energy level, making them easier to reduce on the negative electrode side. During charge and discharge, they are preferentially and thoroughly reduced, forming a more stable electrode / electrolyte interface. Furthermore, the enrichment of fluorine and nitrogen elements results in higher mechanical strength of the formed inorganic SEI, and Examples 4, 7, and 9 exhibit lower interfacial impedance. Fluoroazoamide derivatives can generate free radicals containing both fluorine and nitrogen, which can be grafted onto the electrode surface to form a dense, stable interface with high ionic conductivity. This significantly reduces side reactions between the electrolyte and electrode materials, reduces battery impedance, and allows batteries to cycle for more than 360 cycles in general, with symmetrical additives even exceeding 400 cycles. Simultaneously, in high-rate discharge performance tests, the fluoroazoamide derivative electrolyte exhibits higher capacity retention (>85%), and compared to conventional electrolyte additives in the comparative examples, the fluoroazoamide derivative additives demonstrate superior electrochemical performance.

[0122] In Comparative Example 3, fluoroethylene carbonate was used as an electrolyte additive, which can induce the formation of a stable lithium fluoride interface during battery cycling. Compared with the example, Comparative Example 3 has a higher impedance. This is because the thickness of the fluoroethylene carbonate-derived lithium fluoride is uneven. In addition, the lithium fluoride layer has low ionic conductivity, resulting in a low capacity retention rate at high discharge rates.

[0123] In Comparative Example 4, the fluorinated amide monomers in patent CN120565816B were compared with the additives of this invention and conventional additives. The results showed that the electrolyte used in Comparative Example 4 had lower ionic conductivity, higher impedance, and lower cycle performance and high-rate discharge performance. This is because long fluorine chains are difficult to generate a stable and uniform interface and cannot optimize the transport behavior of lithium ions in the electrolyte and interface.

[0124] In Comparative Example 5, N,N,N',N'-tetramethylazodicarbonamide was used as an additive. The results showed that Comparative Example 5 had higher high-rate discharge performance than other comparative examples, but its cycle performance was significantly lower than that of the examples. This is because N,N,N',N'-tetramethylazodicarbonamide was not fluorinated, and it can generate nitrogen-containing free radicals in the electrolyte, which can be grafted onto the electrode surface and partially react to derive a lithium nitride interface, which can improve the rate performance of the cell to a certain extent. However, the lack of lithium fluoride leads to interface instability. Therefore, after cycling, the electrode-electrolyte interface breaks down and side reactions intensify.

[0125] In summary, this invention, by substituting azodicarbonamide with varying degrees and amounts of fluorine atoms, produces a lithium metal electrolyte with excellent positive and negative electrode stability. Simultaneously, it improves the stability of lithium ions at the electrode / electrolyte interface, enhancing the cycle performance and capacity retention of lithium metal batteries under high-rate conditions and extending cycle life. The mechanism lies in the fact that azo salts with different electron densities generate a large number of free radicals during decomposition. These free radicals can graft onto the electrode surface, participating in the in-situ construction of a uniform interface layer. Furthermore, the abundant fluorine and nitrogen compounds generate large amounts of lithium nitride and lithium fluoride, forming a dense composite inorganic interface layer, further improving the stability of the interface layer. This effectively improves the cycle performance and high-rate performance of lithium metal batteries, effectively avoiding serious side reactions between the electrolyte and lithium metal.

[0126] The above-disclosed embodiments are merely a few specific examples of the present invention. However, the embodiments of the present invention are not limited thereto, and any variations that can be conceived by those skilled in the art should fall within the protection scope of the present invention.

Claims

1. An electrolyte additive for lithium metal batteries, characterized in that, It has a structure as shown in Equation A: Formula A R1 and R2 are each independently selected from -CHF2, -CH2F, -CF3 or -CH3; and at least one of R1 and R2 is selected from -CHF2, -CH2F or -CF3.

2. A method for preparing an electrolyte additive for lithium metal batteries, used to prepare the electrolyte additive of claim 1, characterized in that, Includes the following steps: S1. Under the action of an active catalyst, fluorinated methanol having the structure shown in Formula a is reacted with ammonia to obtain a reaction intermediate having the structure shown in Formula b. The structural formulas for formula a or formula b are as follows: Formula a; Formula b; R1 is selected from -CHF2, -CH2F or -CF3; The active catalyst includes activated alumina or activated carbon; S2. Mix one or two reaction intermediates with diethyl azodicarbonate to carry out a second reaction to obtain an electrolyte additive for lithium metal batteries. Specifically, when a reaction intermediate is used and the molar ratio of the reaction intermediate to diethyl azodicarbonate is (1-1.25):1, dimethylamine is added to the reaction system to participate in the reaction together; when two reaction intermediates are mixed, or when a reaction intermediate is used and the molar ratio of it to diethyl azodicarbonate is (2-2.5):1, dimethylamine is not added to the reaction system.

3. The preparation method of the electrolyte additive for lithium metal batteries as described in claim 2, characterized in that, In step S1, the molar ratio of fluorinated methanol to ammonia is (0.8-1.2):1; The amount of the active catalyst used is 1 wt% to 2 wt% of ammonia. The temperature of the first reaction is 400℃~450℃, the pressure is 2MPa~3MPa, and the time is 4~6h.

4. The preparation method of the electrolyte additive for lithium metal batteries as described in claim 2, characterized in that, In step S1, the first reaction is followed by the following steps: After the first reaction of fluorinated methanol and ammonia is completed, the resulting reaction system is condensed, extracted, and distilled to obtain a reaction intermediate. The extractant used for extraction includes anhydrous diethyl ether or ethyl acetate; The distillation temperature is 50–80℃.

5. The method for preparing the electrolyte additive for lithium metal batteries as described in claim 2, characterized in that, In step S2, when dimethylamine is added, the total molar amount of the reaction intermediate and dimethylamine is in the molar ratio of diethyl azodicarbonate to (2-2.5):

1. When dimethylamine is not added, the total molar amount of the one or two reaction intermediates to the molar ratio of diethyl azodicarbonate is (2-2.5):1; The second reaction is carried out at a temperature of 200℃~300℃, a pressure of 1.5MPa~2.0MPa, and a time of 8~12h.

6. The method for preparing the electrolyte additive for lithium metal batteries as described in claim 2, characterized in that, In step S2, the second reaction is followed by the following steps: After the second reaction between the reaction intermediate and diethyl azodicarbonate is completed, the cooled product is added to an alkaline catalyst and stirred until homogeneous. Then, it is filtered and rotary evaporated to obtain an electrolyte additive for lithium metal batteries. The amount of alkaline catalyst used is 0.5wt% to 1wt% of diethyl azodicarbonate; The alkaline catalyst includes calcium hydroxide or potassium hydroxide; The rotary evaporation temperature is 80–100°C, and the rotation speed is 100–200 rpm.

7. A lithium metal battery electrolyte, characterized in that, It includes lithium salts, organic solvents, and the electrolyte additives according to claim 1 or prepared by any one of claims 2-6.

8. The lithium metal battery electrolyte as described in claim 7, characterized in that, Based on a mass percentage of 100% for lithium metal battery electrolyte, the lithium metal battery electrolyte comprises the following components: 8%–20% lithium salt, 1%–15% electrolyte additives for lithium metal batteries, and the remainder being organic solvents. The lithium salt includes any one or more of lithium hexafluorophosphate, lithium bis(fluorosulfonyl)imide, lithium bis(trifluoromethanesulfonyl)imide, lithium tetrafluoroborate, lithium bis(oxalateborate) or lithium di(fluorooxalateborate). The organic solvent includes any one or more of ethylene carbonate, propylene carbonate, dimethyl carbonate, diethyl carbonate, methyl ethyl carbonate, methyl propyl carbonate, γ-butyrolactone, methyl formate, methyl acetate, ethylene glycol dimethyl ether, or ethylene glycol diethyl ether and diethylene glycol dimethyl ether.

9. A lithium metal battery, characterized in that, It includes a positive electrode, a negative electrode, an electrolyte, and a diaphragm disposed between the positive and negative electrodes; The electrolyte is the lithium metal battery electrolyte according to any one of claims 7-8.

10. The lithium metal battery as described in claim 9, characterized in that, The active material of the positive electrode includes any one or more of the following: lithium-ion intercalated transition metal oxide with a layered structure, lithium-ionized transition metal mixed oxide with a spinel structure, or lithium-ionized transition metal phosphate with an olivine structure. The active material of the negative electrode includes any one or more of lithium, lithium alloys, or materials capable of forming lithium alloys. The diaphragm includes any one or more of polyvinylidene fluoride, polyethylene, polypropylene, or surface-modified composite diaphragms.

Images