Tin-based interface layer protection potassium metal negative electrode and preparation method and application thereof

Abstract

The invention provides a tin-based interface layer protection potassium metal negative electrode and a preparation method and application thereof, and belongs to the technical field of electrochemistry. The preparation method comprises the following steps: uniformly coating the surface of a potassium metal sheet with tin fluoride powder, so that the tin fluoride powder and potassium metal are subjected to an in-situ reaction to generate a multifunctional interface layer consisting of potassium-tin alloy and potassium fluoride; the multifunctional interface layer can homogenize K < + > flow, induce the K < + > flow to uniformly nucleate and inhibit the growth of potassium dendrites, so that the cycle life of the battery is prolonged. In addition, the preparation method is simple and convenient to operate and low in cost, and has great industrialization potential.

Description

Technical Field

[0001] The invention belongs to the field of electrochemical technology, and in particular relates to a tin-based interface layer protecting a potassium metal negative electrode, a preparation method and an application thereof. Background Art

[0002] The statements in this section merely provide 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. With their high operating voltage and long cycle life, they play an important role in all aspects of our lives. However, with the rise and popularity of electric vehicles, people have put forward higher requirements for the energy density and power density of batteries. In addition, limited lithium resources have also restricted its development in the field of large-scale energy storage. It is imperative to develop a battery system with lower cost and higher energy density. Sodium and potassium are in the same main group as lithium and have similar physical and chemical properties, but their reserves are almost a thousand times that of lithium, making them strong candidates for large-scale energy storage. Among them, potassium metal batteries have a capacity of up to 687 mAh g -1 It has a theoretical specific capacity and a lower redox potential than sodium (-2.93 V vs. standard hydrogen electrode), making it a research hotspot for low-cost, high-energy-density alkali metal batteries.

[0004] However, potassium metal anodes face severe challenges in practical applications. Potassium metal with high reactivity will have serious side reactions with the electrolyte, thus forming a solid electrolyte interface (SEI) layer mainly composed of organic matter. The SEI layer has low electronic conductivity and poor mechanical strength, resulting in uneven K + In addition, due to the huge volume expansion during the potassium metal deposition / stripping process, the SEI layer will continue to break, exposing fresh potassium metal, and the side reactions will continue until the active potassium is completely consumed and the battery fails.

[0005] In order to solve the above problems, researchers have adopted a variety of strategies. For example, constructing a three-dimensional current collector to alleviate the volume expansion of potassium metal, optimizing the electrolyte composition to form a multifunctional SEI layer, and constructing an artificial SEI protective layer. Among them, the directionally regulated artificial SEI layer is an effective strategy to protect the potassium metal interface. In existing technologies, researchers mainly regulate K by constructing an SEI layer with high ionic conductivity and high mechanical strength. + flow and inhibit the growth of dendrites, but less attention is paid to the potassium affinity of the SEI layer and the subsequent uniform deposition. Summary of the invention

[0006] In order to overcome the above-mentioned deficiencies of the prior art, the present invention provides a tin-based interface layer protecting a potassium metal negative electrode and a preparation method and application thereof.

[0007] The purpose of the present invention is to solve the problem of uneven deposition of potassium metal batteries without potassium-affinity protective layer modification, by constructing a protective layer with high potassium affinity, high ionic conductivity and high mechanical strength, regulating potassium nucleation and uniform K + flow and inhibit the growth of potassium dendrites, thereby improving the cycle stability and service life of the battery.

[0008] To achieve the above objectives, one or more embodiments of the present invention provide the following technical solutions: In a first aspect of the present invention, there is provided a potassium metal negative electrode, comprising a potassium metal sheet and a multifunctional interface layer; The multifunctional interface layer includes potassium tin alloy and potassium fluoride. The multifunctional interface layer is generated in situ and can homogenize K + flow, induce uniform nucleation, and inhibit the growth of potassium dendrites, thereby improving the cycle life of the battery.

[0009] In one or more specific embodiments of the present invention, the thickness of the multifunctional interface layer is about 20-50 μm, preferably 35 μm.

[0010] A second aspect of the present invention provides a method for preparing the above-mentioned potassium metal negative electrode, comprising the following steps: S1, rolling and pressing a potassium metal block into a potassium metal sheet in a glove box filled with argon; S2, weighing tin fluoride powder and evenly coating it on the surface of the potassium metal flakes with a brush and reacting in situ; S3, the two react to form a uniform black interface layer on the surface of potassium metal, that is, a potassium metal negative electrode material protected by a multifunctional interface layer is obtained.

[0011] In one or more specific embodiments of the present invention, the oxygen content in the glove box filled with argon in step S1 is less than 0.1 ppm; the potassium metal flakes are 25-35 cm 2 .

[0012] 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.

[0013] In one or more specific embodiments of the present invention, the reaction temperature in step S3 is room temperature.

[0014] The third aspect of the present invention provides the use of the above-mentioned potassium metal negative electrode or its preparation method in the preparation of an alkali metal battery; Preferably, the alkali metal battery comprises a button cell.

[0015] According to a fourth aspect of the present invention, a button-type battery is provided, comprising a positive electrode, a negative electrode, a separator and an electrolyte, wherein the negative electrode is the potassium metal negative electrode as described in the first aspect.

[0016] In one or more specific embodiments of the present invention, the electrolyte used is KFSI-EC-DEC or KPF6-EC-DEC; preferably 1M.

[0017] In one or more specific embodiments of the present invention, the electrolyte is prepared 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 to form a 1 mol L -1 prepared by a solution of.

[0018] One or more of the above technical solutions have the following beneficial effects: 1. The present invention uses a simple physical method to make tin fluoride powder react with potassium metal in situ. Compared with other existing modification technologies, the operation is simple and the cost is low.

[0019] 2. The multifunctional interface layer composed of potassium-tin alloy and potassium fluoride generated by the in-situ reaction of the present invention has high potassium affinity and high ionic conductivity, and achieves subsequent uniform deposition of potassium by inducing uniform nucleation of potassium; in addition, the multifunctional interface layer has high mechanical strength, and can effectively inhibit the growth of dendrites during the battery cycle, protect the potassium metal negative electrode, and improve the cycle life of the potassium metal battery.

[0020] Advantages of additional aspects of the present invention will be given in part in the following description, and in part will become obvious from the following description, or will be learned through practice of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] The accompanying drawings in the specification, which constitute a part of the present invention, are used to provide a further understanding of the present invention. The exemplary embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute improper limitations on the present invention.

[0022] Figure 1 This is a comparison diagram before and after the surface of potassium metal is coated with tin fluoride powder in Example 1 of the present invention, a is potassium metal, and b is potassium metal after the surface is coated with tin fluoride powder; Figure 2 This is a scanning electron microscope photograph of a cross section of a multifunctional interface layer of Example 1 of the present invention; Figure 3 The symmetrical battery assembled from the potassium metal sheet coated with tin fluoride powder in Example 1 of the present invention at 1 mAcm -2 Current density, 1 mAh cm -2 Time-voltage curve under surface capacity; Figure 4 This is a comparison chart of the cycle performance of a full battery assembled with a potassium metal sheet covered with a multifunctional interface layer and a potassium metal sheet not covered with a multifunctional interface layer and a 3,4,9,10-perylenetetracarboxylic dianhydride (PTCDA) positive electrode in Example 1 of the present invention. DETAILED DESCRIPTION

[0023] It should be noted that the following detailed descriptions are exemplary and are intended to provide further explanation of the present invention. Unless otherwise specified, all technical and scientific terms used herein have the same meanings as those commonly understood by those skilled in the art to which the present invention belongs.

[0024] It should be noted that the terms used herein are for describing specific embodiments only and are not intended to be limiting of exemplary embodiments according to the present invention.

[0025] Embodiment 1 This embodiment discloses a tin-based interface layer protecting a potassium metal negative electrode, and its preparation method and application.

[0026] (1) In a glove box, weigh 25 mg of tin fluoride powder and evenly apply it on the surface of a rectangular potassium metal sheet with a length of 10 cm and a width of 3 cm. Use a brush to evenly apply the powder to allow it to fully react with potassium metal. The reaction temperature is room temperature. When the surface of the potassium metal changes from bright silver-white to uniform black, the reaction is complete and a multifunctional interface layer is generated. The optical photographs of the potassium metal sheet before and after the multifunctional interface layer is modified are shown in the figure below. Figure 1 As shown in the figure, it can be seen that the initial potassium metal sheet is silvery white with metallic luster, and the surface of the potassium metal modified by the multifunctional interface layer turns black, indicating that the potassium metal and the tin fluoride powder have chemically reacted. The cross-sectional scanning electron microscope photo of the multifunctional interface layer is shown in the figure. Figure 2 As shown, a uniform and dense modification layer with a thickness of about 35 μm can be observed on the surface of potassium metal.

[0027] (2) Use a punch with a diameter of 10 mm to punch potassium metal into small discs to serve as the positive and negative electrodes of the symmetrical battery. Assemble the battery in the order of negative electrode shell, negative electrode sheet, glass fiber separator, positive electrode sheet, steel sheet, shrapnel, and positive electrode shell, and inject 1 MKFSI-EC-DEC electrolyte. The assembled button cell has a current of 1 mA cm -2 Current density, 1 mAh cm -2 The battery was cycled under the condition of surface capacity to test the cycle stability of the charge and discharge process.

[0028] (3) The potassium metal sheet modified with the multifunctional interface layer in (1) was used as the negative electrode and assembled with the PTCDA positive electrode to form a full battery. The positive electrode was prepared into a slurry with 70% PTCDA, 20% conductive carbon black, 10% polytetrafluoroethylene binder and an appropriate amount of N-methylpyrrolidone solvent, and the above percentages are all weight percentages. The mixed slurry was coated on a carbon-coated aluminum foil, and after drying, it was cut into small discs with a diameter of 10 mm as the positive electrode sheet, and assembled with the potassium metal negative electrode modified with the above multifunctional interface layer, and 1 MKFSI-EC-DEC electrolyte was injected to form a full battery. The assembled button cell was tested at 1 mA cm -2 Current density, 1 mAh cm -2 The cycle stability of the charge and discharge process was tested under the condition of surface capacity. Figure 3 , Figure 4 shown.

[0029] Figure 3 It can be seen that compared with the unmodified potassium metal anode, the cycle life is extended from 120 h to more than 420 h when protected by the multifunctional interface layer, indicating that the multifunctional interface layer has a uniform K + The initial potassium sheet and the potassium metal sheet protected by the multifunctional interface layer are used as the negative electrode, and the full battery assembled with PTCDA as the positive electrode is assembled in the same way as above. The cycle performance diagram is shown in Figure 4 The discharge capacity of the full cell with a multifunctional interface layer reached 131 mAh g -1 The capacity retention rate after 400 cycles is 90%, and it can be stably cycled for more than 2000 cycles. The discharge capacity of the full battery with the initial potassium sheet as the negative electrode is about 125 mAh g -1 , and after more than 650 cycles, there will be violent fluctuations, and the capacity will decay rapidly until the battery fails.

[0030] Embodiment 2 This embodiment discloses a tin-based interface layer protecting a potassium metal negative electrode, and its preparation method and application. Specifically, 10 mg of tin fluoride powder is weighed in a glove box and evenly coated on the surface of a rectangular potassium metal sheet with a length of 10 cm and a width of 3 cm with a brush. An in-situ reaction is carried out during the brushing process, and the reaction temperature is room temperature. When the potassium metal completely changes color, it is punched into discs with a diameter of 10 mm, which are used as positive and negative electrodes to assemble button symmetrical batteries. The electrolyte used is 1 M KFSI-EC-DEC electrolyte. After assembly, the button battery is charged at 1 mA cm -2 Current density, 1 mAh cm -2 The battery was cycled under the condition of surface capacity to test the cycle stability of the charge and discharge process.

[0031] Embodiment 3 This embodiment discloses a tin-based interface layer protecting a potassium metal negative electrode, and its preparation method and application. Specifically, 50 mg of tin fluoride powder is weighed in a glove box and evenly coated on the surface of a rectangular potassium metal sheet with a length of 10 cm and a width of 3 cm with a brush. An in-situ reaction is carried out during the brushing process, and the reaction temperature is room temperature. When the potassium metal completely changes color, it is punched into discs with a diameter of 10 mm, which are used as positive and negative electrodes to assemble button symmetrical batteries. The electrolyte used is 1 M KFSI-EC-DEC electrolyte. After assembly, the button battery is charged at 1 mA cm -2 Current density, 1 mAh cm -2 The battery was cycled under the condition of surface capacity to test the cycle stability of the charge and discharge process.

[0032] Although the above describes the specific implementation mode of the present invention in conjunction with the accompanying drawings, it 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 on the basis of the technical solution of the present invention without creative work are still within the scope of protection of the present invention.

Claims

1. A potassium metal negative electrode, characterized in that including potassium metal flakes and a multifunctional interfacial layer; The multifunctional interface layer comprises potassium tin alloy and potassium fluoride.

2. The potassium metal negative electrode according to claim 1, characterized in that The thickness of the multifunctional interface layer is about 20-50 μm, preferably 35 μm.

3. A method for preparing a potassium metal negative electrode as claimed in claim 1 or 2, characterized in that: The following steps are involved: S1, rolling and pressing a potassium metal block into a potassium metal sheet in a glove box filled with argon; S2, weighing tin fluoride powder and evenly coating it on the surface of the potassium metal flakes with a brush and reacting in situ; S3, the two react to form a uniform black interface layer on the surface of potassium metal, that is, a potassium metal negative electrode material protected by a multifunctional interface layer is obtained.

4. The method for preparing a potassium metal negative electrode according to claim 3, characterized in that: The oxygen content in the glove box filled with argon in step S1 is less than 0.1 ppm; the potassium metal flakes are 25-35 cm 2 .

5. The method for preparing a potassium metal negative electrode according to claim 3, characterized in that: The amount of tin fluoride powder used in step S2 is 10-50 mg, preferably 10 mg, 25 mg or 50 mg.

6. The method for preparing a potassium metal negative electrode according to claim 3, characterized in that: The reaction temperature in step S3 is room temperature.

7. Use of the potassium metal negative electrode according to claims 1-2 or the method for preparing the potassium metal negative electrode according to claims 3-6 in preparing an alkali metal battery; Preferably, the alkali metal battery comprises a button cell.

8. A button battery, characterized in that: The button-type battery comprises a positive electrode, a negative electrode, a separator and an electrolyte, and the positive electrode and the negative electrode are the potassium metal negative electrode according to claim 1 or 2.

9. A button cell battery as claimed in claim 8, characterized in that: The electrolyte used is KFSI-EC-DEC; preferably 1M.

10. A button cell battery as claimed in claim 8, 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 in a volume ratio of 1 / 1 to form a 1 mol L -1 prepared by a solution of.

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