A lithium-silicon alloy anode material with a micro-nano structure, a preparation method thereof, and an application thereof

Abstract

A micro-nanostructured lithium-silicon alloy negative electrode material and its preparation method and application, wherein the method comprises: weighing lithium metal and silicon in an atomic ratio of 99.5:0.5 to 97.5:1.5 as raw materials; placing the weighed and mixed raw materials into the cabin of a smelting and stripping device, melting the raw materials by heating under an argon protective atmosphere to form a liquid alloy, then spray-casting the liquid alloy, and collecting the material by a copper roller at a linear speed of 35-40m / sec; rolling the product collected on the copper roller into a thin sheet with a thickness of 100-300um, and cutting it to obtain a micro-nanostructured lithium-silicon alloy negative electrode material. The present invention introduces silicon element and utilizes a smelting and stripping rapid quenching process to construct a lithium-silicon alloy negative electrode material with a micro-nanostructure. The lithium-silicon alloy exhibits a unique three-dimensional network skeleton with good structural organization. This micro-nanostructure provides a large specific surface area, which is conducive to improving the mechanical strength and stability of the electrode material as a whole.

Description

Technical Field

[0001] The present invention relates to the field of lithium metal batteries, and in particular to a lithium-silicon alloy negative electrode material with a micro-nano structure, a preparation method thereof, and applications thereof. Background Art

[0002] Lithium metal has a high theoretical specific capacity (3860 mAh g -1 ) and a low redox potential (-3.04V vs. standard hydrogen electrode), making lithium metal anode materials of great interest. However, lithium metal faces several challenges in practical applications, including uncontrollable lithium dendrite formation, large volume changes during deposition / stripping, and side reactions with the electrolyte.

[0003] In order to solve the above problems faced by lithium metal anodes, researchers have developed a variety of modification strategies. They mainly focus on current collector modification, construction of stable electrode / electrolyte interface, and construction of lithium-based alloy anodes. Among them, lithium silicon alloy, as a potential candidate for lithium-ion battery anode materials, has the advantages of high capacity and high energy density, but there are still some challenges and shortcomings in its preparation and application. The following are some possible problems: (1) Volume expansion problem: Lithium silicon alloy will undergo significant volume expansion during lithium ion deposition and stripping, which may lead to particle breakage of the material, electrode failure or structural damage. This volume change will cause delamination and deactivation of the electrode material, reducing the cycle stability of the battery; (2) Conductive properties: Silicon is a semiconductor material with relatively poor electrical conductivity. This will lead to a decrease in the electronic conductivity of the electrode material, affecting the discharge and charging rate of the battery; (3) Design challenges: The design of lithium silicon alloy needs to overcome its volume expansion and electrical conductivity problems, so it requires clever structural and composite material design, which increases the difficulty of research and development. Scientists and engineers have been conducting research and trying to overcome these problems through nanostructure design, coating technology, alloying treatment and other means.

[0004] Here we propose a micro-nanostructured lithium-silicon alloy negative electrode material and its preparation. The micro-nanostructured lithium-silicon alloy has many advantages: (1) increasing the electrode specific surface area, improving the exchange current density, maintaining the bidirectional (net zero) current in a quasi-equilibrium state, balancing the oxidation and reduction reaction rates on the electrode, thereby inhibiting dendrite growth and improving the safety performance of the battery. (2) slowing down the volume change during the lithium ion deposition / stripping process. The micro-nanostructured lithium-silicon alloy negative electrode material can slow down the volume shrinkage / expansion of lithium during stripping / deposition, thereby improving the cycle stability of the battery. (3) improving the mechanical and electrochemical stability of the electrode material. By introducing silicon to construct a micro-nanostructured lithium-silicon alloy negative electrode material, the electrode material can have stronger mechanical and electrochemical stability, thereby improving the battery life. With the advancement of technology, we may see more solutions in the future to improve the performance and availability of lithium-silicon alloy materials. Summary of the Invention

[0005] Based on this, the present invention provides a micro-nanostructured lithium-silicon alloy anode material, its preparation method, and its application. This approach addresses the structural issues in lithium-ion batteries caused by uncontrolled lithium dendrite formation, volume changes in the electrode material, and electrolyte interface corrosion due to side reactions in the electrolyte. These factors affect battery performance and lifespan, and urgently require technological improvements and material design to address them.

[0006] To achieve the above objectives, the present invention provides a micro-nanostructured lithium-silicon alloy negative electrode material, which is composed of Li and Li 22 Si5, wherein the atomic ratio of lithium element to silicon element is 99.5:0.5 to 97.5:1.5, the lithium silicon alloy has a cross-linked structure to form a stable network skeleton, and the grain size is between 200nm and 2μm.

[0007] According to another aspect of the present invention, the present invention also provides a method for preparing a micro-nanostructured lithium-silicon alloy negative electrode material, characterized in that it comprises the following steps:

[0008] (1) lithium metal and silicon are weighed and mixed as raw materials in an atomic ratio of 99.5:0.5 to 97.5:1.5;

[0009] (2) Select a smelting and throwing belt equipment with a closed cabin, place the weighed and mixed raw materials into the cabin of the smelting and throwing belt equipment, melt the raw materials by heating under an argon protective atmosphere to form a liquid alloy, then spray-cast the liquid alloy, and collect the material by a copper roller at a linear speed of 35-40m / sec;

[0010] (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 obtain a lithium-silicon alloy negative electrode material with a micro-nano structure.

[0011] As a further preferred technical solution of the present invention, in step (2), the raw materials are contained in a crucible with a stainless steel lining and placed in the cabin of the smelting and stripping equipment.

[0012] 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 vacuum degree of the chamber of the smelting stripping equipment is pumped to 6*10 -2 After the pressure drops below Pa, argon is filled into the cabin to create an argon protective atmosphere.

[0013] As a further preferred embodiment of the present invention, the copper roller is a single copper wheel with a thickness of 50 mm and a diameter of 300 mm. During the smelting process and before spray casting, the copper roller rotates at a speed of 1500 rpm; during spray casting and material collection, the copper roller rotates at a speed of 3500 rpm.

[0014] As a further preferred technical solution of the present invention, in step (2), the pressure of the spray casting is 0.1-0.5 MPa.

[0015] According to another aspect of the present invention, the present invention also provides an application of a micro-nanostructured lithium-silicon alloy negative electrode material in a lithium metal battery.

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

[0017] The present invention introduces silicon elements and utilizes a rapid quenching process of melting and spinning to construct a lithium-silicon alloy negative electrode material with a micro-nano structure. The lithium-silicon alloy exhibits a stable micro-nano structure with a three-dimensional network skeleton and has a good structural organization. This micro-nano structure provides a large specific surface area, which is beneficial to improving the overall mechanical strength and stability of the electrode material. In a lithium metal battery using the lithium-silicon alloy negative electrode material, the electrode is in a quasi-equilibrium state during the reaction process, thereby inhibiting dendrite growth and volume expansion and improving stability. Through this method, the safety and stability of the lithium metal battery can be effectively improved. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] The present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0019] Figure 1 This is the SEM image of the lithium-silicon alloy (Li-Si at% = 99:1) of Example 1.

[0020] Figure 2 This is the EDS graph of the lithium-silicon alloy (Li-Si at%=99:1) of Example 1.

[0021] Figure 3 This is the XRD spectrum of the lithium-silicon alloy (Li-Si at% = 99:1) of Example 1.

[0022] Figure 4 This is the coulombic efficiency diagram of the Li-Si||Cu half-cell assembled with the lithium-silicon alloy (Li-Si at%=99:1) of Example 1.

[0023] Figure 5 This is the EIS graph of a symmetrical battery assembled with the lithium-silicon alloy (Li-Si at% = 99:1) of Example 1.

[0024] Figure 6This is a critical current density (CCD) diagram of a symmetrical battery assembled with the lithium-silicon alloy (Li-Si at% = 99:1) of Example 1.

[0025] Figure 7 The symmetrical battery assembled from the lithium-silicon alloy (Li-Si at% = 99:1) of Example 1 was tested at 1 mA cm -2 , 1mAh cm -2 Cycling performance under .

[0026] Figure 8 This is the SEM image of the lithium-silicon alloy (Li-Si at% = 96:4) of Comparative Example 1.

[0027] 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

[0028] 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.

[0029] 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.

[0030] Example 1

[0031] This embodiment provides the preparation and application of lithium silicon alloy (Li-Si at% = 99:1) negative electrode material:

[0032] In the first step, lithium metal and silicon (at% = 99:1) as raw materials are weighed using an electronic balance.

[0033] The second step is to put the weighed raw materials into the closed chamber of the melting and stripping equipment in advance, start the melting and stripping system that isolates water and oxygen, and wait until the vacuum degree drops to 6*10 -2Pa, fill the cabin with argon, and then load the raw materials into the crucible through the glove device of the smelting and throwing equipment and install the crucible to the designated position; start to increase the power to heat the raw materials, and start the copper roller at the same time, set the speed of the copper roller to 1500rpm (the linear speed is 15m / sec), and after the power reaches 1.2kw (about 600-800℃), the raw materials melt to form liquid alloy, adjust the speed of the copper roller to 3500rpm (the linear speed is 35m / sec), lower the crucible for spray casting, and the spray casting pressure is 0.2Mpa. After the cabin is cooled, collect the samples on the copper roller. The copper roller is a single copper wheel with a thickness of 50mm and a diameter of 300mm. The obtained samples were characterized by scanning electron microscopy (SEM), X-ray energy spectrum analysis (EDS) and X-ray diffraction (XRD), respectively, as shown below. Figure 1-3 shown.

[0034] In the third step, the sample was rolled into a thin sheet with a thickness of about 200 μm using a roller press, and cut into discs with a diameter of φ10 mm, which were then used as electrodes in lithium metal batteries.

[0035] Figure 1 The SEM images clearly demonstrate that the lithium-silicon alloy (atomic ratio of 99:1) produced using a smelting and spinning process isolated from water and oxygen exhibits a unique three-dimensional skeleton with a well-defined structural organization. This micro-nanostructure provides a large specific surface area, enhancing the overall mechanical strength and stability of the electrode material. The microstructural features revealed by the SEM images emphasize the effectiveness of the silicon element and the smelting and spinning process for rapid quenching in constructing this micro-nanostructure.

[0036] Figure 2 The EDS element mapping diagram clearly shows the uniformity of element distribution in the micro-nano structure, further illustrating the consistency of lithium and silicon element distribution in the entire electrode material.

[0037] Figure 3 The XRD patterns of the prepared samples were analyzed in detail. Clear Li and Li 22 The peaks of the Si5 phase are relatively uniform, indicating that the dispersion of lithium metal and silicon alloy in the sample is quite uniform. This is crucial for the uniform distribution of battery materials, as it helps improve electrochemical performance and increase the cycle life of the battery while mitigating problems that may arise during cycling, such as volume expansion and structural damage of the electrode materials.

[0038] According to the above step 3, the prepared wafer samples were assembled into Li-Si alloy||Cu half-cells and the electrochemical performance was tested. The cells could be cycled for 50 cycles with an average coulombic efficiency of 91.21% (see Figure 4Similarly, the wafer samples were assembled into a symmetrical battery to test the electrochemical performance, and the impedance spectroscopy (EIS) showed that the charge transfer resistance was about 400Ω (see Figure 5 ), CCD value is 13mAcm -2 (See Figure 6 ), and at 1 mA cm -2 , 1mAh cm -2 Under the conditions of Figure 7 ).

[0039] Comparative Example 1

[0040] As a control experiment of Example 1, the difference is that only the atomic ratio of lithium metal and silicon as raw materials is changed to at%=96:4.

[0041] like Figure 8 The SEM image of the lithium-silicon alloy (Li-Si at% = 96:4) shows that as the Si content increases, it becomes granular, and the phase changes from lithium-silicon alloy and lithium to silicon alone, showing a granular structure. The lithium-silicon alloy is cross-linked and no longer forms a stable network skeleton. Referring to the electrochemical performance test method of Example 1, the silicon alloy (Li-Si at% = 96:4) disc sample was assembled into a Li-Si alloy||Cu half-cell. At 1 mA cm -2 , 1mAh cm -2 Under the conditions of , the battery can be stably cycled for less than 500 hours.

[0042] Furthermore, based on Comparative Example 1, a large number of experimental comparisons show that if the Si content is further increased, the presence of silicon increases, presenting a granular structure. When the alloy is used in a battery, the stable cycle time is further shortened.

[0043] 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 micro-nanostructured lithium-silicon alloy negative electrode material, characterized in that: Li and Li 22 Si5, in which the atomic ratio of lithium to silicon is 99.5:0.5~97.5:1.

5. The lithium-silicon alloy has a cross-linked structure to form a stable network skeleton, and the grain size is between 200 nm and 2 µm. The method for preparing the micro-nanostructured lithium-silicon alloy negative electrode material comprises the following steps: (1) Lithium metal and silicon are weighed and mixed as raw materials in an atomic ratio of 99.5:0.5 to 97.5:1.5; (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, and heat the raw materials at 600-800 °C in an argon protective atmosphere to melt the raw materials to form a liquid alloy. The liquid alloy is then spray-casted and collected by a copper roller at a linear speed of 35-40 m / sec. (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 obtain a micro-nanostructured lithium-silicon alloy negative electrode material.

2. The micro-nanostructured lithium-silicon alloy negative electrode material according to claim 1, characterized in that: In step (2), the raw materials are contained in a crucible with a stainless steel lining and placed in the chamber of the smelting and stripping equipment.

3. The micro-nanostructured lithium-silicon alloy negative electrode material according to claim 1, characterized in that: In step (2), after placing the raw materials into the chamber and before heating for smelting, the vacuum degree of the chamber of the smelting stripping equipment is pumped to After the pressure drops below Pa, argon is filled into the cabin to create an argon protective atmosphere.

4. The micro-nanostructured lithium-silicon alloy negative electrode material according to claim 1, characterized in that: The copper roller is a single copper wheel with a thickness of 50 mm and a diameter of 300 mm.

5. The micro-nanostructured lithium-silicon alloy negative electrode material according to claim 4, characterized in that: During the smelting process and before spray casting, the copper roller rotates at a speed of 1500 rpm; during spray casting and collecting, the speed of the copper roller is 3500 rpm.

6. The micro-nanostructured lithium-silicon alloy negative electrode material according to claim 1, characterized in that: In step (2), the pressure of the spray casting is 0.1-0.5 MPa.

7. Use of the micro-nanostructured lithium-silicon alloy negative electrode material according to claim 1 in lithium metal batteries.

Images