A corrosion-resistant lithium-based negative electrode material and its synthesis method and application

Abstract

A corrosion-resistant lithium-based negative electrode material and its synthesis method and application, wherein the method comprises: weighing the following raw materials according to atomic ratio: nickel powder 0.08-4at%, molybdenum powder or / and chromium powder 0.02-2at%, the balance being metallic lithium, and the impurity content in the raw materials not exceeding 0.05at%; placing the weighed and mixed raw materials into the cabin of a smelting and throwing belt device, smelting the raw materials at a heating temperature of 600-1200°C under an argon protective atmosphere, and spray-casting the smelted product, which is collected by a copper roller at a linear speed of 40-50m / s; the product is rolled into a thin sheet with a thickness of 100-300μm, and cut to form a corrosion-resistant lithium-based negative electrode material. The present invention successfully prepares a corrosion-resistant lithium-based alloy material using a simple one-step synthesis method, introduces high-melting-point corrosion-resistant elements Ni, and Mo or Cr into the lithium metal bulk phase, thereby improving the corrosion resistance of the lithium metal, and when the alloy is applied to a battery negative electrode material, the dendrite growth during the battery cycle is suppressed, thereby improving the stability during the battery cycle.

Description

Technical Field

[0001] The present invention relates to the field of lithium metal batteries, and in particular to a corrosion-resistant lithium-based negative electrode material, a synthesis method thereof, and applications thereof. Background Art

[0002] In recent years, the energy crisis and greenhouse effect have intensified. Electrochemical energy storage can effectively alleviate the energy gap and reduce carbon emissions, and its market share has increased year by year. The development of new high-energy-density power batteries is in line with the "National Medium- and Long-Term Science and Technology Development Plan" and meets the needs of "promoting the transformation of energy development methods as the main line and building a safe, green, and efficient energy system." The lithium metal negative electrode has a low density (0.534g cm 3 ), the lowest redox potential (-3.04 V vs. standard hydrogen electrode) and an ultra-high theoretical specific capacity (3860 mAh g -1 ) has attracted much attention. When lithium metal is matched with an ideal cathode material, high-energy-density lithium metal secondary batteries can be obtained. However, the practical application of lithium metal batteries (LMBs) still faces problems such as increased voltage polarization, rapid capacity decay, and short circuits. The main reasons are the growth of lithium dendrites caused by uneven lithium metal deposition and stripping, large volume expansion during electrochemical reactions, and unstable solid electrolyte interface (SEI) caused by side reactions between highly active lithium metal and the electrolyte.

[0003] In order to solve the above problems, inhibit the growth of lithium dendrites, and obtain a stable lithium metal anode, scientists have conducted research from multiple angles, including alloy anode, interface protection, anode structure design, and solid electrolyte, and have made important progress. It is well known that nickel has excellent resistance to corrosion by reducing media and a high tolerance for elements such as chromium and molybdenum that improve the corrosion resistance of alloys. It is expected to be used in lithium-based alloys to optimize the performance of metal lithium anodes, promote the application of lithium metal anodes and the development of high-energy lithium metal batteries. However, since the melting points of Ni and Mo are 1435°C and 2617°C, respectively, which are higher than the boiling point of lithium (1347°C), a large amount of lithium volatilizes during the preparation process. Therefore, in the existing lithium alloy anode material preparation technology, it is difficult to prepare a micro-nanostructured corrosion-resistant lithium-based alloy with high melting point elements introduced into the bulk phase. Summary of the Invention

[0004] Based on this, the present invention provides a corrosion-resistant lithium-based negative electrode material, its synthesis method and application, to solve the problem that lithium metal is highly active and easily reacts with electrolytes, resulting in unlimited consumption of electrode materials and electrolytes until they are exhausted, thereby improving the cycle stability of lithium metal negative electrodes.

[0005] To achieve the above object, the present invention provides a method for synthesizing a corrosion-resistant lithium-based negative electrode material, which comprises the following steps:

[0006] (1) Weigh the following raw materials according to atomic ratio: nickel powder 0.08-4at%, molybdenum powder and / or chromium powder 0.02-2at%, and the balance being metallic lithium;

[0007] (2) Select a smelting and throwing belt equipment with a closed cabin, put the weighed and mixed raw materials into the cabin of the smelting and throwing belt equipment, smelt the raw materials at a heating temperature of 600-1200°C under an argon protective atmosphere, spray-cast the molten liquid alloy, and collect the materials by a copper roller at a linear speed of 40-50m / s;

[0008] (3) The product collected on the copper roller in step (2) is rolled into a thin sheet with a thickness of 100-300 μm, and cut to form a corrosion-resistant lithium-based negative electrode material.

[0009] As a further preferred technical solution of the present invention, in step (1), the metallic lithium is in block, granular, ribbon or flake form; the nickel powder has a particle size of 100 nm to 500 μm; and the molybdenum powder or chromium powder has a particle size of 100 nm to 500 μm.

[0010] As a further preferred technical solution of the present invention, in step (2), the raw materials are carried in a crucible and placed in the cabin of the smelting and belt-spinning equipment.

[0011] As a further preferred technical solution of the present invention, in step (2), after the raw materials are placed in the chamber and before heating for smelting, the chamber vacuum of the smelting stripping equipment is pumped to 6*10 -3 After the pressure drops below Pa, argon is filled into the cabin to create an argon atmosphere.

[0012] As a further preferred technical solution of the present invention, in step (2), when heating for smelting, the heating device increases the temperature by 0.1 kW every 6 to 8 seconds until the power reaches 1.2 kW.

[0013] As a further preferred embodiment of the present invention, the copper roller is a single copper wheel having a thickness of 50 mm and a diameter of 300 mm. In step (2), during the smelting process and before spray casting, the copper roller rotates at a speed of 1000 rpm; during spray casting and collection, the copper roller rotates at a speed of 3000 rpm. In step (2), the spray casting pressure is 0.1 to 0.4 MPa.

[0014] According to another aspect of the present invention, the present invention also provides a corrosion-resistant lithium-based negative electrode material, which is prepared by the above method.

[0015] According to another aspect of the present invention, the present invention also provides an application of a corrosion-resistant lithium-based negative electrode material in a lithium metal battery.

[0016] Compared with the prior art, the present invention can achieve the following beneficial effects:

[0017] 1) This invention proposes for the first time the design of a corrosion-resistant lithium-based negative electrode material with a micro-nanostructure. The micro-nanostructured lithium-based negative electrode has a larger specific surface area, thereby increasing the lithium ion exchange current density, placing the electrode in a quasi-equilibrium state during the charge and discharge process, thereby inhibiting dendrite growth and alleviating volume expansion. At the same time, nickel (Ni) and corrosion-resistant elements such as molybdenum (Mo) or chromium (Cr) are introduced into the bulk phase of the lithium metal negative electrode to construct a highly stable lithium-based composite negative electrode material, enhancing the corrosion resistance of the electrode material's bulk and interface, thereby improving the stability of the electrode material during long-term cycling. This also addresses the problem of corrosion of the lithium metal electrode caused by the generation of trace water during the battery's charge and discharge process, which causes LiPF6 in the electrolyte to decompose upon contact with water to produce hydrofluoric acid.

[0018] 2) The present invention successfully prepares corrosion-resistant lithium-based negative electrode materials (lithium nickel-molybdenum alloy or lithium nickel-chromium alloy) using a simple one-step synthesis method. The raw materials are selected from high-melting-point corrosion-resistant elements Ni and Mo, or Ni and Cr, which are not in phase with lithium but in phase with each other. Since Ni, Mo and Cr are slightly soluble in liquid lithium metal at a relatively low temperature (below the boiling point of lithium), their respective melting temperatures are reduced, which greatly reduces the preparation temperature of the alloy, thereby successfully preparing a corrosion-resistant lithium-based negative electrode material with a micro-nano structure.

[0019] 3) The present invention successfully prepares corrosion-resistant lithium-based negative electrode materials using a simple one-step synthesis method, and improves the corrosion resistance of lithium metal by introducing high-melting-point corrosion-resistant elements Ni and Mo, or Ni and Cr, into the lithium metal bulk phase. When the alloy is applied to the battery negative electrode material, the dendrite growth during the battery cycle is suppressed, thereby improving the stability of the battery during the cycle. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] The present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0021] Figure 1 SEM image of lithium nickel molybdenum alloy (Li-Ni-Mo at% = 98.5:1.2:0.3).

[0022] Figure 2 EDS pattern of lithium nickel molybdenum alloy (Li-Ni-Mo at% = 98.5:1.2:0.3).

[0023] Figure 3 XRD spectrum of lithium nickel molybdenum alloy (Li-Ni-Mo at% = 98.5:1.2:0.3).

[0024] Figure 4 EIS graph of a symmetrical battery assembled with lithium nickel molybdenum alloy (Li-Ni-Mo at% = 98.5:1.2:0.3).

[0025] Figure 5 Critical current density (CCD) diagram of a symmetrical battery assembled with lithium nickel molybdenum alloy (Li-Ni-Mo at% = 98.5:1.2:0.3).

[0026] Figure 6 Lithium nickel molybdenum alloy (Li-Ni-Mo at% = 98.5:1.2:0.3) was assembled into a symmetrical battery at 1 mA cm -2 , 1mAh cm -2 Cycling performance under .

[0027] Figure 7 SEM image of lithium nickel chromium alloy (Li-Ni-Cr at% = 98.5:1:0.5);

[0028] Figure 8 EDS pattern of lithium nickel chromium alloy (Li-Ni-Cr at% = 98.5:1:0.5);

[0029] Figure 9 XRD spectrum of lithium nickel chromium alloy (Li-Ni-Cr at% = 98.5:1:0.5);

[0030] Figure 10 EIS graph of a symmetrical battery assembled with lithium nickel-chromium alloy (Li-Ni-Cr at% = 98.5:1:0.5);

[0031] Figure 11 Coulombic efficiency diagram of Li-Ni-Cr‖Cu half-cell assembled with lithium nickel-chromium alloy (Li-Ni-Cr at% = 98.5:1:0.5);

[0032] Figure 12 Critical current density (CCD) diagram of a symmetrical battery assembled with lithium nickel-chromium alloy (Li-Ni-Cr at% = 98.5:1:0.5);

[0033] Figure 13 The symmetrical battery assembled with lithium nickel chromium alloy (Li-Ni-Cr at% = 98.5:1:0.5) was -2 , 1mAh cm -2 Cycling performance under .

[0034] The purpose, features and advantages of the present invention will be further described with reference to the accompanying drawings and in conjunction with the embodiments. DETAILED DESCRIPTION

[0035] The following describes the specific embodiments of the present invention in detail with reference to the accompanying drawings. It should be understood that the specific embodiments described herein are only used to illustrate and explain the present invention and are not intended to limit the present invention.

[0036] Unless otherwise defined, the technical terms used in the following examples have the same meanings as commonly understood by those skilled in the art to which this invention belongs. The experimental reagents used in the following examples, unless otherwise specified, are conventional biochemical reagents; the experimental methods described, unless otherwise specified, are conventional methods.

[0037] Example 1

[0038] This embodiment provides the preparation and application of a lithium nickel molybdenum alloy (Li-Ni-Mo at% = 98.5:1.2:0.3) negative electrode material.

[0039] Step 1: Use an electronic balance to weigh metallic lithium, nickel powder, and molybdenum powder as raw materials, with an atomic ratio of at% = 98.5:1.2:0.3, wherein the metallic lithium is in block form, and the particle size of the nickel powder and the molybdenum powder are both 50 μm;

[0040] Step 2: Lithium nickel molybdenum alloy (Li-Ni-Mo) is prepared by using a melting and spinning belt equipment.

[0041] Put the weighed raw materials into the smelting and throwing belt cabin in advance (the cabin is a closed space), start the smelting and throwing belt system, and wait until the vacuum degree in the cabin drops to 6*10 -3 Pa, then fill with argon to normal pressure, then put the raw materials into the crucible through the cabin glove box, and install the crucible to the designated spray casting position. Then start to increase the power to heat the sample, and start the copper roller at the same time (set the initial speed to 1000rpm, the linear speed to 10m / s), the power is increased by 0.1kw every 6 to 8 seconds, and when the power reaches 1.2kw (the temperature is about 900℃), the raw materials melt to form liquid alloy, and the speed of the copper roller is adjusted to 3000rpm (the linear speed is 50m / s). At the same time, lower the crucible to the appropriate position, and use a spray casting pressure of 0.2Mpa for spray casting. After the cabin cools down, collect the samples on the copper roller through the cabin glove box. The obtained samples were characterized by scanning electron microscopy (SEM), X-ray energy spectrum analysis (EDS) and X-ray diffraction (XRD), respectively. Figure 1-3 shown.

[0042] Step 3: Use a roller press to roll and cut the sample into discs approximately 200 μm thick and 10 mm in diameter. These discs are then used as electrodes to assemble CR2025 button cells. The battery components primarily include the positive electrode shell, negative electrode shell, electrode sheet, separator, electrolyte, spring, and gasket. Battery assembly is performed in an argon-filled glove box with H₂O and O₂ concentrations below 0.01 ppm. 2325 lithium battery separator was used as the separator; the electrolyte consisted of 1.0 M LiPF₆-EC / DEC + 5 wt% FEC, with a 1:1 volume ratio of EC to DEC. The electrolyte volume in the cell ranged from 80 to 150 μL. The battery was allowed to rest at room temperature for 6 hours before testing to ensure that the electrolyte fully penetrated the electrodes and formed a relatively stable interface.

[0043] Depend on Figure 1 It can be clearly observed from the SEM image that the construction of a micro-nanostructured lithium nickel-molybdenum alloy negative electrode material was achieved by utilizing the rapid quenching process of melting and stripping. The prepared lithium nickel-molybdenum alloy (Li-Ni-Mo at% = 98.5:1.2:0.3) presents a nanoparticle structure. The negative electrode material with this micro-nano structure is applied to lithium metal batteries. During the charge and discharge process of the battery, the nano-sized lithium alloy negative electrode material increases the lithium ion exchange current density due to its large specific surface area, so that the electrode is in a quasi-equilibrium state during the charge and discharge process. A higher exchange current density means that the reaction rate on the electrode surface is faster, which means that too much overpotential is not required to drive the electrochemical reaction, making lithium deposition and stripping more uniform, thereby inhibiting dendrite growth and alleviating volume expansion.

[0044] from Figure 2 The EDS image shows that nickel and molybdenum are evenly distributed in the lithium alloy. During battery cycling, the highly active lithium metal easily reacts with the electrolyte to form an unstable solid electrolyte interface (SEI), resulting in uneven lithium deposition and stripping, leading to continuous electrolyte consumption. The addition of corrosion-resistant elements like nickel and molybdenum enhances the corrosion resistance of the lithium metal anode in the electrolyte and improves the battery's cycling stability.

[0045] from Figure 3 The XRD spectrum shows that the prepared lithium nickel chromium alloy sample is composed of four substances: Li, Ni, Mo and MoNi4.

[0046] The wafer samples were assembled into symmetrical batteries to test their electrochemical performance. The impedance spectroscopy (EIS) showed that the charge transfer resistance was 40Ω (e.g. Figure 4 ), the critical current density (CCD) test result is 11mA cm -2 (like Figure 5 ), at 1 mA cm -2 , 1mAh cm -2Under the conditions of stable circulation for 600h (such as Figure 6 ).

[0047] In summary, alloys are prepared by adding corrosion-resistant elements Ni and Mo to obtain better corrosion resistance. Among them, molybdenum improves the corrosion resistance of nickel in reducing acidic media. In hydrochloric acid, wet-process phosphoric acid, hydrofluoric acid, and concentration ≤60% H2SO4, it is an important alloying element that makes nickel alloys have good corrosion resistance. The introduction of high-melting-point corrosion-resistant elements Ni and Mo into the lithium metal bulk improves the corrosion resistance of lithium metal. When the alloy is applied to the battery negative electrode material, it can effectively inhibit the growth of dendrites during the battery cycle and improve the stability of the battery cycle.

[0048] Example 2

[0049] This embodiment provides the preparation and application of a lithium nickel-chromium alloy (Li-Ni-Cr at% = 98.5:1:0.5) negative electrode material.

[0050] The difference from Example 1 is that lithium metal Li, nickel powder and chromium powder with an atomic ratio of at% = 98.5:1:0.5 are used as raw materials, wherein the lithium metal is in flake form, and the particle size of the nickel powder or chromium powder is 50 μm, and the other process parameters remain unchanged.

[0051] In this embodiment, the microstructure and phase composition of the samples obtained by melting and spinning strips were characterized by scanning electron microscopy (SEM), X-ray energy dispersive spectroscopy (EDS) and X-ray diffraction (XRD), respectively. Figure 7-9 shown.

[0052] Figure 7 The SEM photos clearly show that the lithium nickel chromium alloy (Li-Ni-Crat% = 98.5:1:0.5) prepared by the melting and stripping equipment presents a nano-particle structure, and the nickel and chromium elements are evenly distributed in the lithium alloy (such as Figure 8 From Figure 9 It can be seen from the XRD spectrum that the prepared lithium nickel chromium alloy sample is composed of four substances: Li element, Ni element, Cr element and Cr3Cr2.

[0053] Referring to Example 1, the sample was rolled and cut into discs with a thickness of about 200 μm and a diameter of φ10 mm, and then assembled into a Li-Ni-Cr||Cu half-cell. The electrochemical performance was tested, and the average coulombic efficiency was 91.69% and it could be cycled for 60 cycles (e.g. Figure 10 The samples were assembled into symmetrical batteries to test the electrochemical performance. The impedance spectroscopy (EIS) showed that the charge transfer resistance was 36Ω (as shown in Figure 2). Figure 11 The critical current density (CCD) test result is 11mA cm -2 (like Figure 12 shown), at 1 mA cm -2 , 1mAh cm -2 Under the conditions of stable circulation for 600h (such as Figure 13 shown).

[0054] Although specific embodiments of the present invention are described above, those skilled in the art should understand that these are merely examples and that various changes or modifications may be made to the embodiments without departing from the principles and essence of the present invention. The scope of protection of the present invention is limited only by the appended claims.

Claims

1. A method for synthesizing a corrosion-resistant lithium-based negative electrode material, characterized in that: The following steps are involved: (1) Weigh the following raw materials according to atomic ratio: nickel powder 0.08-4 at%, molybdenum powder and / or chromium powder 0.02-2 at%, and the balance is metallic lithium; (2) Select a melting and spinning belt equipment with a closed cabin, place the weighed and mixed raw materials into the cabin of the melting and spinning belt equipment, melt the raw materials at a heating temperature of 600~1200℃ under an argon protective atmosphere, spray-cast the melted liquid alloy, and collect the materials by a copper roller at a linear speed of 40~50 m / s; (3) rolling the product collected on the copper roller in step (2) into a sheet with a thickness of 100-300 μm, and cutting it to form a corrosion-resistant lithium-based negative electrode material; wherein, In step (1), the metallic lithium is in the form of blocks, granules, strips or flakes; the particle size of the nickel powder is 100 nm to 500 μm; the particle size of the molybdenum powder or chromium powder is 100 nm to 500 μm; In step (2), after placing the raw materials into the chamber and before heating for smelting, the chamber vacuum of the smelting stripping equipment is pumped to After that, fill the cabin with argon gas to create an argon atmosphere; In step (2), during the smelting process and before spray casting, the rotation speed of the copper roller is 1000 rpm; during spray casting and collecting, the rotation speed of the copper roller is 3000 rpm.

2. The method for synthesizing the corrosion-resistant lithium-based negative electrode material according to claim 1, characterized in that: In step (2), the raw materials are carried in a crucible and placed in the chamber of the smelting and belt-spinning equipment.

3. The method for synthesizing the corrosion-resistant lithium-based negative electrode material according to claim 1, characterized in that: In step (2), when heating for smelting, the heating device increases the temperature by 0.1 kW every 6 to 8 seconds until the power reaches 1.2 kW.

4. The method for synthesizing the corrosion-resistant lithium-based negative electrode material according to claim 1, wherein: The copper roller is a single copper wheel with a thickness of 50 mm and a diameter of 300 mm.

5. The method for synthesizing the corrosion-resistant lithium-based negative electrode material according to claim 1, characterized in that: In step (2), the injection molding pressure is 0.1~0.4 MPa.

6. A corrosion-resistant lithium-based negative electrode material, characterized in that: The method according to any one of claims 1 to 5 is used for preparation.

7. Use of the corrosion-resistant lithium-based negative electrode material prepared by the method according to any one of claims 1 to 5, or the corrosion-resistant lithium-based negative electrode material according to claim 6 in a lithium metal battery.

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