Lithium-oxygen battery electrolyte for regulating and controlling solvation structure as well as preparation method and application of lithium-oxygen battery electrolyte

Abstract

The invention relates to a lithium-oxygen battery electrolyte for regulating and controlling a solvation structure as well as a preparation method and application of the lithium-oxygen battery electrolyte, and belongs to the technical field of lithium-oxygen batteries. The problem that an existing electrolyte cannot give consideration to positive electrode reaction kinetics and negative electrode stability is solved. The electrolyte comprises a lithium salt, an organic solvent and a functional additive, and is characterized in that the functional additive is an indole compound or a derivative thereof, and the concentration is 20 mM to 150 mM. The additive can be coordinated with lithium ions to form a unique [additive... Li < + >] solvated structure, a lithium ion desolvating energy barrier is reduced at a negative electrode, lithium dendrite growth is inhibited, a stable SEI film is formed, and lithium peroxide is guided to grow into annular granular lithium peroxide through a solution mediation way at a positive electrode. The positive and negative electrode interface reaction is synergistically optimized through the single additive, the charge and discharge overpotential is reduced, the discharge capacity and energy efficiency of the battery are improved, the cycle life is prolonged, the additive raw materials are easy to obtain, and the preparation method is simple.

Description

Technical Field

[0001] This invention belongs to the field of lithium-oxygen battery technology, specifically relating to a lithium-oxygen battery electrolyte with a controlled solvation structure, its preparation method, and its application. Background Technology

[0002] Lithium-oxygen (Li-O2 or Li-Air) batteries have a high efficiency of approximately 3500 Wh / kg. -1 With its theoretical energy density, lithium peroxide (Li₂O₂) is considered a promising next-generation high-specific-energy storage system. Its core electrochemical reaction relies on the reversible generation and decomposition of Li₂O₂. However, the practical application of this system faces two major challenges: first, the uncontrolled deposition of the insulating and insoluble discharge product Li₂O₂ easily leads to positive electrode passivation, sluggish reaction kinetics, and a surge in charge / discharge overpotential; second, the lithium metal anode is prone to lithium dendrite growth during cycling, accompanied by severe side reactions, causing battery short circuits, capacity decay, and safety hazards.

[0003] The growth pathway of Li2O2 directly determines battery performance, and is mainly divided into two types: surface-mediated and solution-mediated. The surface-mediated pathway tends to form a dense Li2O2 film on the positive electrode surface, leading to electrode passivation and capacity limitation; while the solution-mediated pathway allows Li2O2 to deposit in a ring-like morphology, significantly improving discharge capacity. Therefore, guiding Li2O2 growth through the solution-mediated pathway is a key strategy for improving battery performance. Current research mostly relies on high donor number (DN) solvents or soluble redox media (RMs), but the former is prone to side reactions with the lithium metal anode, and the latter exhibits a "shuttle effect" that corrodes the lithium anode, both leading to rapid battery degradation during cycling.

[0004] Therefore, developing a novel electrolyte regulation strategy that can effectively induce Li₂O₂ growth via a solution-mediated pathway without compromising anode stability is crucial for advancing lithium-oxygen batteries. Recent studies have shown that introducing specific functional additives into conventional ether-based electrolytes can precisely regulate Li₂O₂ growth. + The primary solvation sheath structure is a feasible approach to simultaneously optimize the reactions at the positive and negative electrode interfaces. However, how to design or find additive molecular structures that are efficient, stable, and cost-effective, and elucidate their synergistic mechanisms, remains a key technical problem to be solved. Summary of the Invention

[0005] This invention addresses the technical problem of existing lithium-oxygen battery electrolytes failing to simultaneously achieve optimal positive electrode reaction kinetics and negative electrode stability. It provides a lithium-oxygen battery electrolyte with a controlled solvation structure, its preparation method, and its applications. The electrolyte of this invention introduces specific indole derivatives as multifunctional additives, effectively guiding Li₂O₂ growth via a solution-mediated pathway while simultaneously achieving uniform lithium-ion deposition and inhibiting dendrite growth, thereby synergistically enhancing the overall electrochemical performance of the battery.

[0006] To solve the above-mentioned technical problems, the technical solution of the present invention is as follows:

[0007] A lithium-oxygen battery electrolyte with a controlled solvation structure includes a lithium salt, an organic solvent, and a functional additive.

[0008] The functional additive is one of indole, 5-boronide, 7-aminoindole, 4-methylindole, 4,7-difluoroindole, 7-bromo-4-fluoroindole, 5-chloro-6-fluoroindole, 6-bromoindole, and 6-fluoroindole.

[0009] The concentration of the functional additive in the electrolyte is 20 mM to 150 mM;

[0010] The organic solvent is an ether solvent.

[0011] Preferably, the lithium salt is selected from one or more of lithium bis(trifluoromethanesulfonyl)imide (LiTFSI), lithium hexafluorophosphate (LiPF6), lithium perchlorate (LiClO4), lithium dioxolaneborate (LiBOB), and lithium bis(fluorosulfonyl)imide (LiFSI).

[0012] Preferably, the organic solvent is one or more of tetraethylene glycol dimethyl ether (TEGDME), 1,2-dimethoxyethane (DME), and dimethyl sulfoxide (DMSO).

[0013] A method for preparing a lithium-oxygen battery electrolyte with regulated solvation structure includes the following steps:

[0014] (1) Under an inert atmosphere, lithium salt is dissolved in an organic solvent and stirred to form a homogeneous basic electrolyte;

[0015] (2) Add functional additives to the basic electrolyte in step (1) and continue stirring until completely dissolved and mixed evenly to obtain the lithium-oxygen battery electrolyte with controlled solvation structure.

[0016] Preferably, a pretreatment step is included before step (1): the organic solvent is dried through a 4Å molecular sieve for 1-8 days, and the lithium salt and functional additives are dried in a vacuum drying oven at 50-120 °C for 12-48 hours.

[0017] Preferably, in step (1), the molar concentration of the lithium salt in the organic solvent is 0.5-1.5 M, the stirring speed is 300-600 rpm, and the stirring time is 6-36 hours.

[0018] Preferably, in step (2), the stirring speed is 400-700 rpm and the stirring time is 6-24 hours.

[0019] The application of a lithium-oxygen battery electrolyte with a regulated solvation structure according to the present invention in lithium-oxygen batteries.

[0020] Preferably, the lithium-oxygen battery includes a positive electrode, a separator, a lithium metal negative electrode, an electrolyte, and a battery casing, wherein the electrolyte is the lithium-oxygen battery electrolyte with controlled solvation structure described in this invention.

[0021] The application of a lithium-oxygen battery electrolyte with a regulated solvation structure according to the present invention in lithium|lithium symmetric batteries.

[0022] The beneficial effects of this invention are:

[0023] The electrolyte provided by this invention, by introducing specific indole compounds as functional additives, can react with Li + Coordination occurs, forming a unique [additive...Li] + [Solvation structure. This structure effectively weakens Li] + Strong interactions with conventional solvent molecules.

[0024] On the negative electrode side, the aforementioned solvation structure can significantly reduce Li + The desolvation energy barrier promotes rapid lithium-ion transport and uniform deposition, effectively suppressing lithium dendrite growth. Simultaneously, specific groups in the additive molecules (such as Br and F) can participate in the formation of a stable solid-state electrolyte interface (SEI) film rich in inorganic substances (such as LiBr and LiF), further protecting the lithium anode.

[0025] On the positive electrode side, [additive···Li + The solvated structure is stabilized and promotes superoxide (O2) formation through electrostatic interactions. - The dissolution of intermediates transforms the growth mechanism of Li2O2 from a surface-mediated pathway to a solution-mediated pathway, generating highly active cyclic product morphologies, significantly reducing reaction overpotential, and improving discharge capacity and energy efficiency.

[0026] This invention achieves synergistic optimization of the reaction kinetics of the positive and negative electrodes of the battery through a single functional additive, overcoming the side reaction and shuttle effect problems caused by traditional high DN solvents or RMs, and significantly improving the cycle life of lithium-oxygen batteries without sacrificing safety and negative electrode stability.

[0027] The functional additives used in this invention are readily available, the preparation method is simple, and they are easy to integrate with existing battery production processes, thus showing good application prospects. Attached Figure Description

[0028] To more clearly illustrate the technical solutions in the embodiments of the present invention, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some specific embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0029] Figure 1 The CV curves of the lithium-oxygen battery electrolytes provided in Example 1 and Comparative Example 1 of the present invention under argon (left) and oxygen (right) environments are shown.

[0030] Figure 2 The first discharge-charge curves of the lithium-oxygen batteries assembled with the lithium-oxygen battery electrolytes provided in Example 1 and Comparative Example 1 of the present invention are shown.

[0031] Figure 3 SEM images of the positive electrode of the lithium-oxygen battery assembled with the lithium-oxygen battery electrolyte provided in Embodiment 1 and Comparative Example 1 of the present invention after discharge.

[0032] Figure 4 For testing the long-cycle performance of lithium-lithium symmetric batteries assembled using the lithium-oxygen battery electrolytes prepared in Example 1 and Comparative Example 1 of this invention;

[0033] Figure 5 The image shows the SEM images of the lithium anode of lithium-ion symmetric batteries assembled using the lithium-oxygen battery electrolytes prepared in Example 1 and Comparative Example 1 of this invention after 50 cycles. Detailed Implementation

[0034] This invention provides a lithium-oxygen battery electrolyte with a controlled solvation structure, comprising a lithium salt, an organic solvent, and a functional additive; the functional additive is one of indole, 5-boronide, 7-aminoindole, 4-methylindole, 4,7-difluoroindole, 7-bromo-4-fluoroindole, 5-chloro-6-fluoroindole, 6-bromoindole, and 6-fluoroindole; the concentration of the functional additive in the electrolyte is from 20 mM to 150 mM; the organic solvent is an ether solvent (including thioether solvents, such as dimethyl sulfoxide).

[0035] In the lithium-oxygen battery electrolyte of the present invention, preferably, the lithium salt is selected from one or more of lithium bis(trifluoromethanesulfonyl)imide (LiTFSI), lithium hexafluorophosphate (LiPF6), lithium perchlorate (LiClO4), lithium dioxolane borate (LiBOB), and lithium bis(fluorosulfonyl)imide (LiFSI). The organic solvent is one or more of tetraethylene glycol dimethyl ether (TEGDME), 1,2-dimethoxyethane (DME), and dimethyl sulfoxide (DMSO).

[0036] The lithium-oxygen battery electrolyte of the present invention is an electrolyte system in which the lithium-ion solvation structure is regulated by functional additives to simultaneously improve the lithium metal anode deposition behavior and the oxygen reaction kinetics at the cathode.

[0037] This invention also provides a method for preparing a lithium-oxygen battery electrolyte with a controlled solvation structure, comprising the following steps:

[0038] (1) Under an inert atmosphere, lithium salt is dissolved in an organic solvent and stirred to form a homogeneous basic electrolyte;

[0039] (2) Add functional additives to the basic electrolyte in step (1) and continue stirring until completely dissolved and mixed evenly to obtain the lithium-oxygen battery electrolyte with controlled solvation structure.

[0040] In the preparation method of the lithium-oxygen battery electrolyte of the present invention, a pretreatment step is included before step (1). The specific steps of the preparation method of the present invention are as follows:

[0041] The selected organic solvent is dried through a 4Å molecular sieve to remove trace amounts of moisture. The drying time is preferably 1 to 8 days, more preferably 2 to 6 days, and even more preferably 3 to 4 days.

[0042] Lithium salts and functional additives are dried in a vacuum drying oven at 50-120 °C for 12-48 hours to completely remove crystal water and adsorbed water.

[0043] For the preparation of the basic electrolyte, in a glove box filled with inert protective gas and where the water and oxygen content are both below 0.1 ppm, accurately weigh the dried lithium salt according to the predetermined molar concentration, preferably 0.5-1.5 M, and add it to a dry organic solvent. Place the mixture on a magnetic stirrer and stir continuously at 300-600 rpm for 6-36 hours until the lithium salt is completely dissolved, forming a clear and homogeneous basic electrolyte.

[0044] The functional electrolyte (i.e., the lithium-oxygen battery electrolyte with controlled solvation structure) is prepared by accurately adding dried functional additives to the prepared base electrolyte at the designed concentration, preferably 20-150 mM. The mixture is then stirred in a glove box at 400-700 rpm for 6-24 hours to ensure complete dissolution of the functional additives and full interaction with the electrolyte system, ultimately obtaining a homogeneous and stable target functional electrolyte—the lithium-oxygen battery electrolyte with controlled solvation structure.

[0045] The present invention also provides an application of the lithium-oxygen battery electrolyte with regulated solvation structure of the present invention in lithium-oxygen batteries.

[0046] In the application of the present invention, the lithium-oxygen battery includes a positive electrode, a separator, a lithium metal negative electrode, an electrolyte, and a battery casing, wherein the electrolyte is the lithium-oxygen battery electrolyte with regulated solvation structure described in the present invention.

[0047] In this invention, the positive electrode comprises carbon paper and a positive electrode material coated on the surface of the carbon paper; the positive electrode material comprises a binder and a conductive carbon material; the binder is polyvinylidene fluoride; the conductive carbon material is Super P; the loading of the positive electrode material on the carbon paper is preferably 0.1~1 mg / cm³. 2 More preferably, it is 0.3~0.8 mg / cm³. 2 More preferably 0.5~0.7 mg / cm³ 2 The mass ratio of the binder to the conductive carbon material is 1:9.

[0048] In this invention, the diaphragm is preferably a glass fiber diaphragm, and the lithium metal anode is preferably a lithium sheet with a thickness of 0.5 mm.

[0049] The present invention does not have any special limitation on the source of the separator and lithium sheet. Conventional commercial products known to those skilled in the art or qualified products made in the laboratory can be used, as long as they meet the requirements for battery assembly and charging and discharging.

[0050] This invention also provides the application of a lithium-oxygen battery electrolyte with a controlled solvation structure in a lithium|lithium symmetric battery.

[0051] The present invention will now be described in detail with reference to embodiments thereof. The described embodiments are only a part of the present invention, and not all of it. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without inventive effort are within the scope of protection of the present invention.

[0052] In the embodiments, all operations were carried out in an argon-protected glove box (H2O < 0.1 ppm, O2 < 0.1 ppm), and all reagents used were dried.

[0053] In the following examples, lithium-oxygen batteries are assembled using the lithium-oxygen battery electrolyte prepared in the previous examples. The positive electrode used includes carbon paper and a positive electrode material coated on the surface of the carbon paper. The positive electrode material includes a binder and a conductive carbon material. The binder is polyvinylidene fluoride (PVDF). The conductive carbon material is Super P. The loading of the positive electrode material on the carbon paper is 0.6 mg / cm³. 2 The mass ratio of the binder to the conductive carbon material is 1:9. The negative electrode is a lithium sheet with a thickness of 0.5 mm. The separator is a glass fiber separator. The battery casing (negative electrode casing and positive electrode casing) can be any battery casing commonly used in the art.

[0054] Example 1:

[0055] The tetraethylene glycol dimethyl ether solvent was dried for one week using a 4 Å molecular sieve. Lithium bis(trifluoromethanesulfonyl)imide and 6-bromoindole were then dried in a vacuum oven at 60 °C for 24 hours. In a glove box, lithium bis(trifluoromethanesulfonyl)imide was dissolved in the dried tetraethylene glycol dimethyl ether at a molar concentration of 1.0 M in the organic solvent. The solution was stirred at 500 r / min for 12 hours to obtain the basic electrolyte. Subsequently, 6-bromoindole was added to this basic electrolyte at a concentration of 20 mM, and the solution was stirred at 500 r / min for another 24 hours until completely dissolved, yielding the target electrolyte.

[0056] Inside a glove box under an argon atmosphere, a 2025-type coin cell lithium-oxygen battery is assembled in the following order: negative electrode shell, metallic lithium negative electrode, separator, lithium-oxygen battery electrolyte prepared in this embodiment, positive electrode, and positive electrode shell. The positive electrode shell has a circular window with a diameter of 10 mm.

[0057] Example 2:

[0058] Dimethyl sulfoxide solvent was dried with a 4 Å molecular sieve for 3 days, and lithium perchlorate and 6-fluoroindole were dried in a vacuum drying oven at 60 °C for 12 hours. In a glove box, lithium perchlorate was dissolved in the dried dimethyl sulfoxide at a molar concentration of 1.0 M in the organic solvent, and stirred at 400 r / min for 5 hours to obtain the basic electrolyte. Subsequently, 6-fluoroindole was added to the basic electrolyte at a concentration of 20 mM, and stirring was continued at 400 r / min for 12 hours until completely dissolved to obtain the target electrolyte.

[0059] Inside a glove box under an argon atmosphere, a 2025-type coin cell lithium-oxygen battery is assembled in the following order: negative electrode shell, metallic lithium negative electrode, separator, lithium-oxygen battery electrolyte prepared in this embodiment, positive electrode, and positive electrode shell. The positive electrode shell has a circular window with a diameter of 10 mm.

[0060] Example 3:

[0061] Dimethyl sulfoxide solvent was dried with a 4 Å molecular sieve for 3 days, and lithium dioxaborate and indole 5-boronate were dried in a vacuum drying oven at 110 °C for 36 hours. In a glove box, lithium dioxaborate was dissolved in the dried dimethyl sulfoxide at a molar concentration of 1.0 M in the organic solvent, and stirred at 300 r / min for 24 hours to obtain the basic electrolyte. Subsequently, indole 5-boronate was added to the basic electrolyte at a concentration of 50 mM, and stirring was continued at 700 r / min for 24 hours until completely dissolved to obtain the target electrolyte.

[0062] Inside a glove box under an argon atmosphere, a 2025-type coin cell lithium-oxygen battery is assembled in the following order: negative electrode shell, metallic lithium negative electrode, separator, lithium-oxygen battery electrolyte prepared in this embodiment, positive electrode, and positive electrode shell. The positive electrode shell has a circular window with a diameter of 10 mm.

[0063] Example 4:

[0064] The tetraethylene glycol dimethyl ether solvent was dried with a 4 Å molecular sieve for 7 days, and lithium difluorosulfonyl imide and 7-aminoindole were dried in a vacuum drying oven at 60 °C for 48 hours. In a glove box, lithium difluorosulfonyl imide was dissolved in the dried tetraethylene glycol dimethyl ether at a molar concentration of 1.0 M in the organic solvent, and stirred at 600 r / min for 36 hours to obtain the basic electrolyte. Subsequently, 7-aminoindole was added to the basic electrolyte at a concentration of 60 mM, and stirring was continued at 500 r / min for 24 hours until completely dissolved to obtain the target electrolyte.

[0065] Inside a glove box under an argon atmosphere, a 2025-type coin cell lithium-oxygen battery is assembled in the following order: negative electrode shell, metallic lithium negative electrode, separator, lithium-oxygen battery electrolyte prepared in this embodiment, positive electrode, and positive electrode shell. The positive electrode shell has a circular window with a diameter of 10 mm.

[0066] Example 5:

[0067] 1,2-Dimethoxyethane solvent was dried with a 4 Å molecular sieve for 7 days, and lithium difluorosulfonylimide and 4-methylindole were dried in a vacuum drying oven at 60 °C for 48 hours. In a glove box, lithium difluorosulfonylimide was dissolved in the dried 1,2-dimethoxyethane at a molar concentration of 1.0 M in the organic solvent, and stirred at 450 r / min for 24 hours to obtain the basic electrolyte. Subsequently, 4-methylindole was added to the basic electrolyte at a concentration of 30 mM, and stirring was continued at 500 r / min for 24 hours until completely dissolved to obtain the target electrolyte.

[0068] Inside a glove box under an argon atmosphere, a 2025-type coin cell lithium-oxygen battery is assembled in the following order: negative electrode shell, metallic lithium negative electrode, separator, lithium-oxygen battery electrolyte prepared in this embodiment, positive electrode, and positive electrode shell. The positive electrode shell has a circular window with a diameter of 10 mm.

[0069] Example 6:

[0070] 1,2-Dimethoxyethane solvent was dried using a 4 Å molecular sieve for 5 days. Lithium hexafluorophosphate and 4,7-difluoroindole were dried in a vacuum drying oven at 60 °C for 48 hours. In a glove box, lithium hexafluorophosphate was dissolved in the dried 1,2-dimethoxyethane at a molar concentration of 1.0 M in the organic solvent, and stirred at 450 r / min for 24 hours to obtain the basic electrolyte. Subsequently, 4,7-difluoroindole was added to this basic electrolyte at a concentration of 50 mM, and stirring was continued at 500 r / min for 12 hours until completely dissolved to obtain the target electrolyte.

[0071] Inside a glove box under an argon atmosphere, a 2025-type coin cell lithium-oxygen battery is assembled in the following order: negative electrode shell, metallic lithium negative electrode, separator, lithium-oxygen battery electrolyte prepared in this embodiment, positive electrode, and positive electrode shell. The positive electrode shell has a circular window with a diameter of 10 mm.

[0072] Example 7:

[0073] The tetraethylene glycol dimethyl ether solvent was dried with a 4 Å molecular sieve for 7 days. Lithium bis(trifluoromethanesulfonyl)imide and 7-bromo-4-fluoroindole were dried in a vacuum drying oven at 60 °C for 12 hours. In a glove box, lithium bis(trifluoromethanesulfonyl)imide was dissolved in the dried tetraethylene glycol dimethyl ether at a molar concentration of 0.5 M in the organic solvent. The solution was stirred at 400 r / min for 12 hours to obtain the basic electrolyte. Subsequently, 7-bromo-4-fluoroindole was added to the basic electrolyte at a concentration of 30 mM, and the solution was stirred at 500 r / min for 12 hours until completely dissolved to obtain the target electrolyte.

[0074] Inside a glove box under an argon atmosphere, a 2025-type coin cell lithium-oxygen battery is assembled in the following order: negative electrode shell, metallic lithium negative electrode, separator, lithium-oxygen battery electrolyte prepared in this embodiment, positive electrode, and positive electrode shell. The positive electrode shell has a circular window with a diameter of 10 mm.

[0075] Example 8:

[0076] Dimethyl sulfoxide solvent was dried with a 4 Å molecular sieve for 7 days. Lithium perchlorate and 5-chloro-6-fluoroindole were dried in a vacuum drying oven at 60 °C for 15 hours. In a glove box, lithium perchlorate was dissolved in the dried dimethyl sulfoxide at a molar concentration of 1.5 M in the organic solvent and stirred at 300 r / min for 15 hours to obtain the basic electrolyte. Subsequently, 5-chloro-6-fluoroindole was added to the basic electrolyte at a concentration of 100 mM, and stirring was continued at 500 r / min for 6 hours until completely dissolved to obtain the target electrolyte.

[0077] Inside a glove box under an argon atmosphere, a 2025-type coin cell lithium-oxygen battery is assembled in the following order: negative electrode shell, metallic lithium negative electrode, separator, lithium-oxygen battery electrolyte prepared in this embodiment, positive electrode, and positive electrode shell. The positive electrode shell has a circular window with a diameter of 10 mm.

[0078] Comparative Example 1:

[0079] The lithium-oxygen battery electrolyte and the lithium-oxygen battery were prepared according to Example 1, the difference being that the electrolyte did not contain 6-bromoindole.

[0080] Comparative Example 2:

[0081] The lithium-oxygen battery electrolyte and the lithium-oxygen battery were prepared according to Example 2, the difference being that the electrolyte did not contain 6-fluoroindole.

[0082] Comparative Example 3:

[0083] The lithium-oxygen battery electrolyte and the lithium-oxygen battery were prepared according to Example 3, the difference being that the electrolyte did not contain 5-boronyl indole.

[0084] Comparative Example 4:

[0085] The lithium-oxygen battery electrolyte and the lithium-oxygen battery were prepared according to Example 4, the difference being that the electrolyte did not contain 7-aminoindole.

[0086] Comparative Example 5:

[0087] The lithium-oxygen battery electrolyte and the lithium-oxygen battery were prepared according to Example 5, the difference being that the electrolyte did not contain 4-methylindole.

[0088] Comparative Example 6:

[0089] The lithium-oxygen battery electrolyte and the lithium-oxygen battery were prepared according to Example 6, the difference being that the electrolyte did not contain 4,7-difluoroindole.

[0090] Comparative Example 7:

[0091] The lithium-oxygen battery electrolyte and the lithium-oxygen battery were prepared according to Example 7, the difference being that the electrolyte did not contain 7-bromo-4-fluoroindole.

[0092] Comparative Example 8:

[0093] The lithium-oxygen battery electrolyte and the lithium-oxygen battery were prepared according to Example 8, the difference being that the electrolyte did not contain 5-chloro-6-fluoroindole.

[0094] The following are performance tests of the product of this invention.

[0095] Test Example 1:

[0096] Using the electrolytes of Example 1 and Comparative Example 1, cyclic voltammetry curves were measured under argon and oxygen atmospheres using a three-electrode system. A lithium iron phosphate electrode was used as the reference electrode, a platinum sheet electrode as the counter electrode, and a glassy carbon electrode as the working electrode. The scan rate was 1 mV / s. -1 The results are shown Figure 1 The test results show that the indole compounds in the electrolyte provided in Example 1 underwent a deprotonation reaction during electrochemical cycling and combined with lithium ions to form a stable solvated structure.

[0097] Test Example 2:

[0098] Using the electrolytes of Example 2 and Comparative Example 2, cyclic voltammetry curves were measured under argon and oxygen atmospheres using a three-electrode system. A lithium iron phosphate electrode was used as the reference electrode, a platinum sheet electrode as the counter electrode, and a glassy carbon electrode as the working electrode. The scan rate was 1 mV / s. -1The test results are consistent with those of Test Example 1, indicating that the electrolyte provided in Example 2 of this invention combines with lithium ions to form a stable solvation structure.

[0099] Test Example 3:

[0100] Using the electrolytes of Example 3 and Comparative Example 3, cyclic voltammetry curves were measured under argon and oxygen atmospheres using a three-electrode system. A lithium iron phosphate electrode was used as the reference electrode, a platinum sheet electrode as the counter electrode, and a glassy carbon electrode as the working electrode. The scan rate was 1 mV / s. -1 The test results are consistent with those of Test Example 1, indicating that the electrolyte provided in Example 3 of this invention combines with lithium ions to form a stable solvated structure.

[0101] Test Example 4:

[0102] Using the electrolytes of Example 4 and Comparative Example 4, cyclic voltammetry curves were measured under argon and oxygen atmospheres using a three-electrode system. A lithium iron phosphate electrode was used as the reference electrode, a platinum sheet electrode as the counter electrode, and a glassy carbon electrode as the working electrode. The scan rate was 1 mV / s. -1 The test results are consistent with those of Test Example 1, indicating that the electrolyte provided in Example 4 of this invention combines with lithium ions to form a stable solvation structure.

[0103] Test Example 5:

[0104] Using the electrolytes of Example 5 and Comparative Example 5, cyclic voltammetry curves were measured under argon and oxygen atmospheres using a three-electrode system. A lithium iron phosphate electrode was used as the reference electrode, a platinum sheet electrode as the counter electrode, and a glassy carbon electrode as the working electrode. The scan rate was 1 mV / s. -1 The test results are consistent with those of Test Example 1, indicating that the electrolyte provided in Example 5 of this invention combines with lithium ions to form a stable solvated structure.

[0105] Test Example 6:

[0106] Using the electrolytes of Example 6 and Comparative Example 6, cyclic voltammetry curves were measured under argon and oxygen atmospheres using a three-electrode system. A lithium iron phosphate electrode was used as the reference electrode, a platinum sheet electrode as the counter electrode, and a glassy carbon electrode as the working electrode. The scan rate was 1 mV / s. -1 The test results are consistent with those of Test Example 1, indicating that the electrolyte provided in Example 6 of this invention combines with lithium ions to form a stable solvated structure.

[0107] Test Example 7:

[0108] Using the electrolytes of Example 7 and Comparative Example 7, cyclic voltammetry curves were measured under argon and oxygen atmospheres using a three-electrode system. A lithium iron phosphate electrode was used as the reference electrode, a platinum sheet electrode as the counter electrode, and a glassy carbon electrode as the working electrode. The scan rate was 1 mV / s. -1 The test results are consistent with those of Test Example 1, indicating that the electrolyte provided in Example 7 of this invention combines with lithium ions to form a stable solvated structure.

[0109] Test Example 8:

[0110] Using the electrolytes of Example 8 and Comparative Example 8, cyclic voltammetry curves were measured under argon and oxygen atmospheres using a three-electrode system. A lithium iron phosphate electrode was used as the reference electrode, a platinum sheet electrode as the counter electrode, and a glassy carbon electrode as the working electrode. The scan rate was 1 mV / s. -1 The test results are consistent with those of Test Example 1, indicating that the electrolyte provided in Example 8 of this invention combines with lithium ions to form a stable solvated structure.

[0111] Test Example 9:

[0112] In an oxygen-filled glove box, the lithium-oxygen batteries assembled in Example 1 and Comparative Example 1 were subjected to constant current charge-discharge tests using the Newwell battery testing system. The test conditions were: current density 100 mA g. -1 Limited capacity 500 mAh g -1 The results are shown Figure 2 It can be seen that the lithium-oxygen battery provided in Embodiment 1 of the present invention exhibits a lower charge-discharge overpotential.

[0113] Test 10:

[0114] Lithium-oxygen batteries were assembled using the electrolytes of Example 1 and Comparative Example 1, respectively, and constant current discharge tests were conducted in the Newwell battery testing system under the conditions of a current density of 200 mA g. -1 Limited capacity 1000 mAh g -1 After discharge, the battery was disassembled, and the positive electrode was characterized using scanning electron microscopy. The results are as follows: Figure 3 As shown, the lithium-oxygen battery using the electrolyte of Example 1 of this invention exhibits a typical annular particle morphology on the positive electrode after discharge, indicating that the solvation structure constructed by the electrolyte effectively promotes the growth of lithium peroxide through a solution-mediated pathway.

[0115] Test Example 11:

[0116] Lithium-lithium symmetric batteries were assembled using the electrolytes of Example 1 and Comparative Example 1, respectively, and constant current cycling tests were performed using the Xinwei Battery Testing System. The test conditions were: current density 0.2 mA cm⁻¹. -2Limited capacity 0.2 mAh cm -2 The result is as follows Figure 4 As shown, the battery using the electrolyte of Example 1 of the present invention exhibits a lower polarization voltage and a longer cycle life, indicating that the electrolyte has better interfacial stability with the lithium metal anode.

[0117] Test Example 12:

[0118] Lithium-lithium symmetric batteries were assembled using the electrolytes of Example 1 and Comparative Example 1, respectively. Constant current cycling tests were performed using a Newway battery testing system under the condition of a current density of 0.5 mA cm⁻¹. -2 Limited capacity 1 mAh cm -2 After 50 cycles, the battery was disassembled, and the lithium anode was observed using a scanning electron microscope. The results are as follows: Figure 5 As shown, after 50 cycles, the lithium anode surface in Example 1 was smooth and flat, while the lithium anode surface in Comparative Example 1 showed a large number of dendrites and dead lithium. This result indicates that the electrolyte provided in Example 1 of the present invention can effectively promote uniform lithium ion deposition and inhibit dendrite growth, thereby significantly improving the cycle performance of the battery.

[0119] Obviously, the above embodiments, comparative examples, and test cases are merely illustrative examples for clear explanation and are not intended to limit the embodiments. Those skilled in the art can make other variations or modifications based on the above description. It is neither necessary nor possible to exhaustively list all embodiments here. However, obvious variations or modifications derived therefrom are still within the scope of protection of this invention.

Claims

1. A lithium-oxygen battery electrolyte with a controlled solvation structure, comprising a lithium salt, an organic solvent, and a functional additive; Its features are, The functional additive is one of indole, 5-boronide, 7-aminoindole, 4-methylindole, 4,7-difluoroindole, 7-bromo-4-fluoroindole, 5-chloro-6-fluoroindole, 6-bromoindole, and 6-fluoroindole. The concentration of the functional additive in the electrolyte is 20 mM to 150 mM; The organic solvent is an ether solvent.

2. The lithium-oxygen battery electrolyte according to claim 1, characterized in that, The lithium salt is selected from one or more of lithium bis(trifluoromethanesulfonyl)imide, lithium hexafluorophosphate, lithium perchlorate, lithium dioxaborate, and lithium bis(fluorosulfonyl)imide.

3. The lithium-oxygen battery electrolyte according to claim 1, characterized in that, The organic solvent is one or more of tetraethylene glycol dimethyl ether, 1,2-dimethoxyethane, and dimethyl sulfoxide.

4. A method for preparing a lithium-oxygen battery electrolyte with a controlled solvation structure as described in claim 1, characterized in that, Includes the following steps: (1) Under an inert atmosphere, lithium salt is dissolved in an organic solvent and stirred to form a homogeneous basic electrolyte; (2) Add functional additives to the basic electrolyte in step (1) and continue stirring until completely dissolved and mixed evenly to obtain the lithium-oxygen battery electrolyte with controlled solvation structure.

5. The preparation method according to claim 4, characterized in that, Before step (1), a pretreatment step is also included: the organic solvent is dried through a 4Å molecular sieve for 1-8 days, and the lithium salt and functional additives are dried in a vacuum drying oven at 50-120 °C for 12-48 hours respectively.

6. The preparation method according to claim 4, characterized in that, In step (1), the molar concentration of the lithium salt in the organic solvent is 0.5-1.5 M, the stirring speed is 300-600 rpm, and the stirring time is 6-36 hours.

7. The preparation method according to claim 4, characterized in that, In step (2), the stirring speed is 400-700 rpm and the stirring time is 6-24 hours.

8. The application of the lithium-oxygen battery electrolyte according to any one of claims 1-3 or the lithium-oxygen battery electrolyte prepared by the preparation method according to any one of claims 4-7 in a lithium-oxygen battery.

9. The application according to claim 8, characterized in that, The lithium-oxygen battery includes a positive electrode, a separator, a lithium metal negative electrode, an electrolyte, and a battery casing. The electrolyte is the lithium-oxygen battery electrolyte according to any one of claims 1-3 or the lithium-oxygen battery electrolyte prepared by the preparation method according to any one of claims 4-7.

10. The application of a lithium-oxygen battery electrolyte according to any one of claims 1-3 or a lithium-oxygen battery electrolyte prepared by the preparation method according to any one of claims 4-7 in a lithium|lithium symmetric battery.

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