A tin-based interface layer protects the potassium metal negative electrode and its preparation method and application

Abstract

The application provides a tin-based interface layer for protecting a potassium metal negative electrode and a preparation method and application thereof, and belongs to the technical field of electrochemistry. + The tin fluoride powder is uniformly coated on the surface of the potassium metal sheet, so that the potassium metal is in-situ reacted to generate a multifunctional interface layer composed of potassium-tin alloy and potassium fluoride; the multifunctional interface layer can homogenize K + current, induce uniform nucleation thereof, and inhibit the growth of potassium dendrites, so that the cycle life of the battery is improved. In addition, the preparation method is simple in operation, low in cost, and has great industrialization potential.

Description

Technical Field

[0001] This invention belongs to the field of electrochemical technology, and particularly relates to a tin-based interface layer protecting potassium metal anode, its preparation method and application. Background Technology

[0002] The statements in this section are merely background information related to the present invention and do not necessarily constitute prior art.

[0003] After decades of development, lithium-ion batteries have become the most widely used energy storage system, playing a vital role in all aspects of our lives due to their high operating voltage and long cycle life. However, with the rise and popularization of electric vehicles, people have placed higher demands on the energy density and power density of batteries; in addition, limited lithium resources also restrict its development in the field of large-scale energy storage, making the development of battery systems with lower cost and higher energy density imperative. Sodium and potassium belong to the same group as lithium and have similar physicochemical properties, but their reserves are almost thousands of times that of lithium, making them strong candidates for large-scale energy storage. Among them, potassium metal batteries have a high energy density of up to 687 mAh g⁻¹. -1 With its theoretical specific capacity and lower redox potential than sodium (-2.93 V vs. standard hydrogen electrode), it has become a research hotspot for low-cost, high-energy-density alkali metal batteries.

[0004] However, potassium metal anodes face severe challenges in practical applications. The highly reactive potassium metal undergoes serious side reactions with the electrolyte, generating a solid electrolyte interface (SEI) layer dominated by organic matter. This SEI layer has low electronic conductivity and poor mechanical strength, leading to uneven Ka content. + The flow and dendrite growth; in addition, due to the huge volume expansion generated during the potassium metal deposition / stripping process, the SEI layer will continuously break, exposing fresh potassium metal, and the side reactions will continue until the active potassium is completely consumed, and the battery will fail.

[0005] To address these issues, researchers have employed various strategies. These include constructing three-dimensional current collectors to mitigate potassium metal volume expansion, optimizing electrolyte composition to form a multifunctional SEI layer, and building artificial SEI protective layers. Among these, directionally tunable artificial SEI layers are an effective strategy for protecting the potassium metal interface. In existing technologies, researchers primarily regulate potassium metal exchange by constructing SEI layers with high ionic conductivity and high mechanical strength. + Flow and inhibit dendrite growth, but less attention is paid to the potassium affinity of the SEI layer and subsequent uniform deposition. Summary of the Invention

[0006] To overcome the shortcomings of the prior art, the present invention provides a tin-based interface layer protected potassium metal anode, its preparation method and application.

[0007] The purpose of this invention is to solve the problem of uneven deposition in potassium metal batteries without a potassium-affinity protective layer. This is achieved by constructing a protective layer that combines high potassium affinity, high ionic conductivity, and high mechanical strength, thereby regulating potassium nucleation and achieving uniform K deposition. + It can reduce flow and inhibit potassium dendrite growth, thereby improving the cycle stability and lifespan of the battery.

[0008] To achieve the above objectives, one or more embodiments of the present invention provide the following technical solutions:

[0009] In a first aspect, the present invention provides a potassium metal anode, comprising a potassium metal sheet and a multifunctional interface layer;

[0010] The multifunctional interface layer comprises a potassium-tin alloy and potassium fluoride. This multifunctional interface layer is generated in situ and can homogenize K. + The flow induces uniform nucleation and inhibits the growth of potassium dendrites, thereby improving the cycle life of the battery.

[0011] In one or more specific embodiments of the present invention, the thickness of the multifunctional interface layer is approximately 20-50 μm; preferably 35 μm.

[0012] A second aspect of the present invention provides a method for preparing the above-described potassium metal anode, comprising the following steps:

[0013] S1, In an argon-filled glove box, the potassium metal block is rolled into a thin potassium metal sheet;

[0014] S2, Weigh out tin fluoride powder and coat it evenly on the surface of potassium metal sheet with a brush and react in situ;

[0015] S3, the two react to form a uniform black interface layer on the potassium metal surface, thus obtaining a potassium metal anode material with multifunctional interface layer protection.

[0016] In one or more specific embodiments of the present invention, the oxygen content in the argon-filled glove box in step S1 is less than 0.1 ppm; the potassium metal sheet is 25-35 cm thick. 2 .

[0017] In one or more specific embodiments of the present invention, the amount of tin fluoride powder used in step S2 is 10-50 mg, preferably, such as 10 mg, 25 mg or 50 mg.

[0018] In one or more specific embodiments of the present invention, the reaction temperature in step S3 is room temperature.

[0019] A third aspect of the present invention provides the application of the above-described potassium metal anode or its preparation method in the preparation of alkali metal batteries;

[0020] Preferably, the alkali metal battery includes a button cell.

[0021] In a fourth aspect, the present invention provides a button cell battery comprising a positive electrode, a negative electrode, a separator, and an electrolyte, wherein the negative electrode is the potassium metal negative electrode described in the first aspect.

[0022] In one or more specific embodiments of the present invention, the electrolyte used is KFSI-EC-DEC or KPF6-EC-DEC; preferably 1M.

[0023] In one or more specific embodiments of the present invention, the electrolyte is formed by dissolving potassium bis(fluorosulfonyl)imide or potassium hexafluorophosphate in a mixed solvent of ethylene carbonate and diethyl carbonate in a volume ratio of 1:1, resulting in a concentration of 1 mol / L. -1 It was prepared from a solution.

[0024] The above one or more technical solutions have the following beneficial effects:

[0025] 1. This invention enables tin fluoride powder to react with potassium metal in situ using a simple physical method. Compared with other existing modification technologies, it is simple to operate and low in cost.

[0026] 2. The multifunctional interface layer composed of potassium-tin alloy and potassium fluoride generated in situ by the present invention has high potassium affinity and high ionic conductivity, and achieves uniform potassium deposition by inducing uniform potassium nucleation. In addition, the multifunctional interface layer has high mechanical strength, which can effectively suppress dendrite growth during battery cycling, protect the potassium metal anode, and improve the cycle life of potassium metal batteries.

[0027] Advantages of additional aspects of the invention will be set forth in part in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. Attached Figure Description

[0028] The accompanying drawings, which form part of this invention, are used to provide a further understanding of the invention. The illustrative embodiments of the invention and their descriptions are used to explain the invention and do not constitute an improper limitation of the invention.

[0029] Figure 1 The images show a comparison of potassium metal before and after coating with tin fluoride powder in Embodiment 1 of the present invention. a is potassium metal, and b is potassium metal after coating with tin fluoride powder.

[0030] Figure 2 This is a cross-sectional scanning electron microscope image of the multifunctional interface layer according to Embodiment 1 of the present invention;

[0031] Figure 3 The symmetrical battery assembled from potassium metal sheets coated with tin fluoride powder in Embodiment 1 of this invention operates at 1 mAcm. -2 Current density, 1 mAh cm -2 Time-voltage curves under areal capacity;

[0032] Figure 4 This is a comparison chart of the cycle performance of full cells assembled with potassium metal sheets covered with a multifunctional interface layer and potassium metal sheets without a multifunctional interface layer and 3,4,9,10-perylenetetracarboxylic dianhydride (PTCDA) cathodes in Embodiment 1 of the present invention. Detailed Implementation

[0033] It should be noted that the following detailed descriptions are exemplary and intended to provide further illustration of the invention. Unless otherwise specified, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains.

[0034] It should be noted that the terminology used herein is for the purpose of describing particular implementations only and is not intended to limit the exemplary implementations of the present invention.

[0035] Example 1

[0036] This embodiment discloses a method for preparing and applying a tin-based interface layer to protect a potassium metal anode.

[0037] (1) Weigh 25 mg of tin fluoride powder in a glove box and evenly coat it onto the surface of a rectangular potassium metal sheet (10 cm long and 3 cm wide) with a brush. Brush the powder evenly to ensure a thorough reaction with the potassium metal. The reaction temperature is room temperature. When the potassium metal surface changes from a bright silvery-white to a uniform black, the reaction is complete, forming a multifunctional interface layer. Comparison of optical photographs of the potassium metal sheet before and after the multifunctional interface layer modification is shown below. Figure 1 As shown, the initial potassium metal sheet is silvery-white with a metallic luster. After being modified with the multifunctional interface layer, the potassium metal surface turns black, indicating a chemical reaction between the potassium metal and the tin fluoride powder. A cross-sectional scanning electron microscope image of the multifunctional interface layer is shown below. Figure 2 As shown, a uniform and dense modification layer with a thickness of approximately 35 μm can be observed on the potassium metal surface.

[0038] (2) Potassium metal was punched into small discs using a 10 mm diameter punch, which were used as the positive and negative electrodes of the symmetrical battery. The battery was assembled in the following order: negative electrode shell, negative electrode sheet, glass fiber separator, positive electrode sheet, steel sheet, spring sheet, and positive electrode shell, and 1 MKFSI-EC-DEC electrolyte was injected. The assembled coin cell measured 1 mA cm⁻¹. -2 Current density, 1 mAh cm -2The system was cycled under conditions of surface capacity to test its cyclic stability during charge and discharge processes.

[0039] (3) The potassium metal sheet modified with the multifunctional interface layer in (1) was used as the negative electrode and assembled into a full cell with the PTCDA positive electrode. The positive electrode was prepared by mixing 70% PTCDA, 20% conductive carbon black, 10% polytetrafluoroethylene binder, and an appropriate amount of N-methylpyrrolidone solvent. All percentages were by mass. The uniformly mixed slurry was coated onto carbon-coated aluminum foil, dried, and cut into small circular pieces with a diameter of 10 mm as the positive electrode. These were then combined with the potassium metal negative electrode modified with the multifunctional interface layer and injected with 1 MKFSI-EC-DEC electrolyte to assemble the full cell. The assembled coin cell was tested at 1 mA cm⁻¹. -2 Current density, 1 mAh cm -2 The cycle stability of the device during charge and discharge was tested under conditions of its areal capacity. The results are as follows: Figure 3 , Figure 4 As shown.

[0040] Figure 3 As can be seen from the data, compared to the unmodified potassium metal anode, the cycle life with the protection of the multifunctional interface layer is extended from 120 h to over 420 h, indicating that the multifunctional interface layer has homogenized K + This process helps to control the flow of potassium and inhibit potassium dendrite growth, thereby improving the cycle life of the battery. A full cell was assembled using an initial potassium sheet and a potassium metal sheet protected by a multifunctional interface layer as the negative electrode, and PTCDA as the positive electrode. The assembly method was the same as above, and its cycle performance diagram is shown in [Figure number missing]. Figure 4 The discharge specific capacity reaches 131 mAh g in a full cell with a multifunctional interface layer. -1 The capacity retention rate after 400 cycles is 90%, and it can be stably cycled for more than 2000 cycles. The discharge specific capacity of the full cell using the initial potassium sheet as the negative electrode is approximately 125 mAh g. -1 Furthermore, after more than 650 cycles, the battery exhibits drastic fluctuations, with rapid capacity decay until it fails.

[0041] Example 2

[0042] This embodiment discloses a method for preparing and applying a tin-based interface layer to protect a potassium metal anode. Specifically, 10 mg of tin fluoride powder is weighed in a glove box and uniformly coated onto the surface of a rectangular potassium metal sheet (10 cm long and 3 cm wide) using a brush. An in-situ reaction is carried out during the brushing process at room temperature. After the potassium metal completely changes color, it is punched into a 10 mm diameter disc, which is then used as the positive and negative electrodes to assemble a coin cell. The electrolyte used is a 1 M KFSI-EC-DEC electrolyte. After assembly, the coin cell is heated to 1 mA cm⁻¹. -2 Current density, 1 mAh cm-2 The system was cycled under conditions of surface capacity to test its cyclic stability during charge and discharge processes.

[0043] Example 3

[0044] This embodiment discloses a method for preparing and applying a tin-based interface layer to protect a potassium metal anode. Specifically, 50 mg of tin fluoride powder is weighed in a glove box and uniformly coated onto the surface of a rectangular potassium metal sheet (10 cm long and 3 cm wide) using a brush. An in-situ reaction is carried out during the brushing process at room temperature. After the potassium metal completely changes color, it is punched into a 10 mm diameter disc, which is then used as the positive and negative electrodes to assemble a coin cell. The electrolyte used is a 1 M KFSI-EC-DEC electrolyte. After assembly, the coin cell is heated to 1 mA cm⁻¹. -2 Current density, 1 mAh cm -2 The system was cycled under conditions of surface capacity to test its cyclic stability during charge and discharge processes.

[0045] While the specific embodiments of the present invention have been described above in conjunction with the accompanying drawings, this is not intended to limit the scope of protection of the present invention. Those skilled in the art should understand that various modifications or variations that can be made by those skilled in the art without creative effort based on the technical solutions of the present invention are still within the scope of protection of the present invention.

Claims

1. A method for preparing a potassium metal anode, characterized in that, The reaction temperature is room temperature; the potassium metal anode comprises a potassium metal sheet and a multifunctional interface layer, the thickness of which is 20-50 μm; the multifunctional interface layer comprises a potassium-tin alloy and potassium fluoride. The specific method for preparing the potassium metal anode is as follows: S1, In an argon-filled glove box, the potassium metal block is rolled into a thin potassium metal sheet; S2, Weigh out tin fluoride powder and coat it evenly on the surface of potassium metal sheet with a brush and react in situ; In step S3, the two react to form a uniform black interface layer on the potassium metal surface, thus obtaining a potassium metal anode material with a multifunctional interface layer protection; the oxygen content in the argon-filled glove box in step S1 is less than 0.1 ppm; the potassium metal sheet is 25-35 cm thick. 2 The amount of tin fluoride powder used in step S2 is 10-50 mg.

2. The application of the potassium metal anode prepared by the method of claim 1 in the preparation of alkali metal batteries, characterized in that, The alkali metal battery includes a button cell.

3. A button cell battery, characterized in that, The button cell includes a positive electrode, a negative electrode, a separator, and an electrolyte, wherein the negative electrode is a potassium metal negative electrode prepared by the preparation method of claim 1.

4. The button cell battery according to claim 3, characterized in that, The electrolyte used is KFSI-EC-DEC.

5. The button cell battery according to claim 3, characterized in that, The electrolyte is prepared by dissolving potassium bis(fluorosulfonyl)imide or potassium hexafluorophosphate in a mixed solvent of ethylene carbonate and diethyl carbonate at a volume ratio of 1:1, resulting in a concentration of 1 mol / L. -1 It was prepared from a solution.

Images