Lithium-oxygen battery electrolyte and preparation method and application thereof

Abstract

The invention discloses a lithium-oxygen battery electrolyte and a preparation method and application thereof. The lithium-oxygen battery electrolyte comprises a lithium salt, an additive and a solvent, the additive is 1, 3-dimethylimidazole iodized salt. The redox medium (organic iodized salt) is added into the ether electrolyte of the lithium oxygen battery, anions of the redox medium can reduce the charge-discharge overpotential of the lithium oxygen battery, cations of the redox medium can form an in-situ protection layer on a lithium negative electrode, the redox medium is prevented from reacting with the lithium negative electrode, lithium corrosion and lithium dendrite growth are effectively inhibited, and the service life of the lithium oxygen battery is prolonged. And the lithium-oxygen battery has excellent electrochemical performance and long cycle stability.

Description

Technical Field

[0001] The present application relates to an electrolyte for a lithium-oxygen battery, a preparation method thereof, and an application thereof, belonging to the technical field of electrolytes for lithium-oxygen batteries. Background Art

[0002] In the past few decades, fossil fuels have been the main source of energy production. Overconsumption to meet high energy demands has brought them to the brink of exhaustion, resulting in insufficient battery life. Adopting cleaner energy production methods is essential. Electrochemical energy storage devices, especially lithium batteries, have revolutionized the electronics industry. Lithium-oxygen batteries have become potential candidates and better alternatives to lithium-ion batteries due to their extremely high theoretical energy density. However, the development of lithium-oxygen batteries still faces many obstacles, such as high overpotential, low energy efficiency, poor reversibility, and short cycle life. These problems are mainly caused by the thermodynamic inertness of the discharge products and slow chemical reaction kinetics. The conductivity between the solid-state catalyst, discharge products, and the electrode is relatively low, making it difficult for the catalyst to fully exert its advantages. Soluble redox mediators can not only catalyze the decomposition of discharge products through a homogeneous catalytic reaction mechanism in the electrolyte but also provide more reactive sites for the charge and discharge processes of the battery through solid-liquid contact. Therefore, they can replace solid-state catalysts in lithium-oxygen batteries to catalyze the charge and discharge reactions. Summary of the Invention

[0003] The purpose of the present invention is to provide an application of an electrolyte redox additive in a lithium-oxygen battery. The anion of this additive reduces the charge and discharge overpotential of the lithium-oxygen battery and accelerates the oxidation kinetics of lithium peroxide. The cation can form a protective layer on the lithium negative electrode to prevent lithium corrosion and the growth of lithium dendrites, enabling the lithium-oxygen battery to have excellent electrochemical performance and long cycle stability.

[0004] According to one aspect of the present application, there is provided an electrolyte for a lithium-oxygen battery, and the electrolyte for a lithium-oxygen battery includes a lithium salt, an additive, and a solvent;

[0005] The additive is 1,3-dimethylimidazolium iodide;

[0006] The lithium salt is selected from at least one of LiTFSI, LiBF4, LiCLO4, and LiCF3SO3;

[0007] The solvent is selected from at least one of TEGDME, DMSO, and DME.

[0008] Optionally, the 1,3-dimethylimidazolium iodide has a bifunctional redox mediator.

[0009] Optionally, in the lithium-oxygen battery electrolyte, the concentration of 1,3-dimethylimidazolium iodide is 0.02 to 0.2 mol L -1 .

[0010] According to another aspect of the present application, there is provided a method for preparing the lithium-oxygen battery electrolyte described above, the preparation method comprising:

[0011] Under anhydrous and anaerobic conditions, a mixture containing a lithium salt, a solvent, and 1,3-dimethylimidazolium iodide is stirred to obtain the lithium-oxygen battery electrolyte.

[0012] Optionally, the 1,3-dimethylimidazolium iodide needs to be pretreated, and the pretreatment method is vacuum drying.

[0013] Optionally, the temperature of the vacuum drying is 60 to 80 °C, and the time of the vacuum drying is 20 to 24 h.

[0014] Optionally, the concentration of the mixture of the lithium salt and the solvent is 0.02 M to 0.2 M.

[0015] Optionally, the concentration of the mixture of the lithium salt and the solvent is independently selected from any value of 0.02 M, 0.05 M, 0.1 M, 0.2 M or the range value between any two of the above.

[0016] Optionally, the temperature of the stirring is 20 to 25 °C, and the time of the stirring is 1 to 2 h.

[0017] Optionally, the temperature of the stirring is independently selected from any value of 20 °C, 21 °C, 22 °C, 23 °C, 24 °C, 25 °C or the range value between any two of the above.

[0018] Optionally, the time of the stirring is independently selected from any value of 1 h, 1.2 h, 1.4 h, 1.5 h, 1.6 h, 1.8 h, 2 h or the range value between any two of the above.

[0019] According to yet another aspect of the present application, there is provided an application of the lithium-oxygen battery electrolyte described above in a lithium-oxygen battery.

[0020] Optionally, the lithium-oxygen battery includes a positive electrode, a negative electrode, and a lithium-oxygen battery electrolyte.

[0021] Optionally, the positive electrode includes a positive electrode active material, and the negative electrode is a lithium sheet.

[0022] Optionally, the preparation method of the positive electrode of the lithium-oxygen battery includes the following steps:

[0023] A mixture containing a positive electrode active material, a conductive agent, and a binder is mixed evenly and coated on a substrate to obtain the positive electrode.

[0024] Optionally, the conductive agent is carbon black.

[0025] Optionally, the binder includes polyvinylidene fluoride (PVDF).

[0026] Optionally, the substrate is carbon paper.

[0027] Optionally, the size of the carbon paper is 16 mm.

[0028] Optionally, in the mixture of the conductive agent and the binder, the mass ratio of the conductive agent to the binder is 9:1.

[0029] The present application provides an organic additive for solving the problems of large charge-discharge overpotential and unstable lithium anode in lithium-oxygen batteries. Specifically, by adding a redox mediator (organic iodide salt) to the ether-based electrolyte of the lithium-oxygen battery, its anion can reduce the charge-discharge overpotential of the lithium-oxygen battery, and its cation can form an in-situ protective layer on the lithium anode to prevent the redox mediator from reacting with the lithium anode, effectively inhibiting lithium corrosion and lithium dendrite growth, and enabling the lithium-oxygen battery to have excellent electrochemical performance and long cycle stability.

[0030] The beneficial effects that can be produced by the present application include:

[0031] 1) The additive provided by the present application can be used as a redox mediator to increase the discharge capacity of the lithium-oxygen battery and reduce the charge potential.

[0032] 2) The cation of the additive provided by the present application generates a "self-defense" SEI layer on the lithium anode to inhibit lithium corrosion and lithium dendrite growth.

[0033] 3) The lithium-oxygen battery provided by the present application has excellent electrochemical performance and long cycle stability. Description of the Drawings

[0034] Figure 1 This is the charge-discharge curve in the electrolyte of the LiI system lithium-oxygen battery prepared in Comparative Example 1 of the present application, with a current density of 500 mA g -1 , and a capacity limit of 1000 mAh g -1 .

[0035] Figure 2 This is the charge-discharge curve in the electrolyte of the DMII system lithium-oxygen battery prepared in Example 1 of the present application, with a current density of 500 mA g -1 , and a capacity limit of 1000 mAh g -1 .

[0036] Figure 3 This is the deep charge-discharge curve of Comparative Example 1 and Example 1 of the present application, with a current density of 500 mA g-1 with a capacity limit of 1000 mAh g -1 .

[0037] Figure 4 The long - cycle curve current density of Comparative Example 1 of this application is 500 mA g -1 with a capacity limit of 1000 mAh g -1 .

[0038] Figure 5 The long - cycle curve current density of Example 1 of this application is 500 mA g -1 with a capacity limit of 1000 mAh g -1 . Detailed implementation manners

[0039] The following describes this application in detail with reference to the examples, but this application is not limited to these examples.

[0040] Unless otherwise specified, the raw materials in the examples of this application are all purchased through commercial channels.

[0041] The chemical reagents used in the examples, such as lithium - oxygen battery electrolyte LiTFSI - TEGDME, lithium iodide (LiI), 1,3 - dimethylimidazolium iodide (DMII), etc., are all purchased from Kasma Mall, and the manufacturers are Kelude and Macklin.

[0042] Use the LAND CT3001A battery system (Wuhan Blue Electronic Co., Ltd.) to conduct constant - current charge / discharge tests (current density is 500 mA g -1 with a limited capacity of 1000 mAh g -1 ).

[0043] In this article, "LiTFSI" refers to lithium bis(trifluoromethanesulfonyl)imide.

[0044] "TEGDME" refers to tetraethylene glycol dimethyl ether.

[0045] "DMII" refers to 1,3 - dimethylimidazolium iodide.

[0046] Comparative Example 1

[0047] 1) Vacuum - dry the additive LiI at 60 °C for 24 h.

[0048] 2) Take 0.0268 g of LiI in a sample bottle, use a pipette to take 2 ml of 1 M LiTFSI - TEGDME in the sample bottle, put in a clean magnetic stir bar, and stir on a magnetic stirrer at room temperature for 1 h. Prepare a 1 M LiTFSI - TEGDME + 0.1 M LiI electrolyte, and place it with molecular sieves for static storage.

[0049] 3) Assemble the battery using the prepared positive electrode, the prepared electrolyte, and a lithium metal negative electrode, and compact it.

[0050] All of the above steps are carried out in an argon-filled glove box.

[0051] 4) Test the electrochemical performance of the assembled battery in an oxygen-filled glove box.

[0052] Example 1

[0053] 1) Vacuum dry the additive DMII at 60 °C for 24 h.

[0054] 2) Take 0.0448 g of DMII in a sample bottle, use a pipette to add 2 ml of 1 M LiTFSI-TEGDME to the sample bottle, add a clean magnetic stir bar, and stir on a magnetic stirrer at room temperature for 1 h. Prepare a 1 M LiTFSI-TEGDME + 0.1 M DMII electrolyte, and let it stand with molecular sieves for later use.

[0055] 3) Assemble the battery using the prepared positive electrode, the prepared electrolyte, and a lithium metal negative electrode, and compact it.

[0056] All of the above steps are carried out in an argon-filled glove box.

[0057] Test the electrochemical performance of the assembled battery in an oxygen-filled glove box.

[0058] Performance Test of Example 2

[0059] Assemble the batteries using the electrolytes prepared in Comparative Example 1 and Example 1, and conduct electrical performance tests. Preparation method of the positive electrode: Mix carbon black material and PVDF in a mass ratio of 9:1, use the dispersant NMP to obtain a slurry, coat the slurry on a substrate, with an active material mass of 0.1 - 0.15 mg, and the substrate is carbon paper to obtain the positive electrode. Battery assembly: Then, combine the negative lithium metal sheet with the positive electrode to obtain the test battery.

[0060] Charge and Discharge Performance Test

[0061] The test parameters are: 500 mA g -1 Constant current charge and discharge, with a limited capacity of 1000 mAh g -1 . The voltage range is 2 V to 5 V. The test results are as Figure 1 shown for the LiI system prepared in Comparative Example 1, and as Figure 2 shown for the DMII system prepared in Example 1. In terms of charge and discharge overpotential and cycle stability, both the system using DMII and the LiI system can reduce the charge and discharge overpotential, but the DMII system has higher cycle stability. Figure 3 This is the deep charge and discharge curve of Comparative Example 1 and Example 1 of the present invention. The LOBs containing DMII and LiI at a current density of 500 mA g-1 For the deep charge-discharge curve, the LOBs discharge capacity of DMII is approximately 16000 mAh g -1 , and the LOBs discharge capacity of LiI is approximately 9000 mAh g -1 , and the LOBs containing DMII have excellent rate performance.

[0062] Figure 4 For Comparative Example 1 of the present invention and Figure 5 The long cycle curve current density of Example 1 is 500 mA g -1 , and the capacity limit is 1000 mAh g -1 The LOBs containing DMII exhibit excellent cycle stability. The charging potential of the battery with the LiI system gradually increases, and the cycle performance is improved after adding DMII, indicating that the protective layer on the lithium metal inhibits the RM shuttle effect.

[0063] As described above, the above are only several embodiments of the present application, and do not impose any form of limitation on the present application. Although the present application is disclosed as above with preferred embodiments, it is not intended to limit the present application. Any person skilled in the art, without departing from the scope of the technical solution of the present application, makes some changes or modifications using the technical content disclosed above, which are equivalent to equivalent embodiments and all fall within the scope of the technical solution.

Claims

1. A lithium-oxygen battery electrolyte, characterized in that, The electrolyte of the lithium-oxygen battery includes a lithium salt, an additive, and a solvent; The additive is 1,3-dimethylimidazolium iodide; The lithium salt is selected from at least one of LiTFSI, LiBF4, LiCLO4, and LiCF3SO3; The solvent is selected from at least one of TEGDME, DMSO, and DME.

2. The lithium-oxygen battery electrolyte according to claim 1, characterized in that, In the electrolyte of the lithium-oxygen battery, the concentration of the 1,3-dimethylimidazolium iodide is 0.02 to 0.2 mol / L -1 .

3. A method for preparing the lithium-oxygen battery electrolyte according to any one of claims 1 to 2, characterized in that, The preparation method includes: Under anhydrous and anaerobic conditions, a mixture containing a lithium salt, a solvent, and 1,3-dimethylimidazolium iodide is stirred to obtain the electrolyte of the lithium-oxygen battery.

4. The preparation method according to claim 3, characterized in that, The 1,3-dimethylimidazolium iodide needs to be pretreated, and the pretreatment method is vacuum drying.

5. The preparation method according to claim 4, characterized in that, The temperature of the vacuum drying is 60-80°C, and the time of the vacuum drying is 20-24h.

6. The preparation method according to claim 3, characterized in that, The concentration of the mixture of the lithium salt and the solvent is 0.02M-0.2M.

7. The preparation method according to claim 3, characterized in that, The temperature of the stirring is 20-25°C, and the time of the stirring is 1-2h.

8. Application of the lithium-oxygen battery electrolyte according to any one of claims 1 to 2 in a lithium-oxygen battery.

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