Composite lithium-magnesium alloy negative electrode and preparation and application thereof
By combining a three-dimensional conductive framework with a fluorinated copolymer to form a lithium-magnesium alloy anode, the problems of interface instability and dendrite growth in lithium metal batteries were solved, enabling stable cycling and rapid charge-discharge of high-energy-density batteries.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- SHANGHAI JIAOTONG UNIV
- Filing Date
- 2024-07-17
- Publication Date
- 2026-06-26
AI Technical Summary
The existing intercalation graphite anodes for lithium-ion batteries are approaching their theoretical limit. The lithium metal anode, due to its high activity, reacts with the electrolyte, resulting in an unstable interface, producing side reactions and lithium dendrites, which affect cycle stability and safety.
A composite lithium-magnesium alloy anode is formed by combining a three-dimensional conductive framework material with a fluorinated copolymer. The composite is then mechanically rolled to reduce the local current density, provide space for lithium deposition, and form a LiF-rich elastic adaptive layer at the interface to promote lithium-ion transport and uniform deposition.
Stable cycling of lithium metal batteries under high current and high capacity conditions was achieved, dendrite growth was suppressed, interface stability and electrode structure stability were improved, and cycle life was extended.
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Figure CN118800867B_ABST
Abstract
Description
Technical Field
[0001] This invention relates to a technology in the field of lithium-magnesium alloys, specifically a composite lithium-magnesium alloy anode and its preparation and application. Background Technology
[0002] With the rapid development of portable electronic products and new energy vehicles, the demand for high-energy-density rechargeable batteries is increasing. However, lithium-ion batteries based on embedded graphite anodes are approaching their theoretical energy density limit, making the development of new high-energy-density rechargeable battery systems urgent. Lithium metal anodes, due to their high theoretical specific capacity (3860 mAh g / g), are a promising option. -1 Low density (0.53g cm⁻¹) -3 Lithium metal is considered an ideal negative electrode for high-energy-density secondary batteries due to its low electrochemical potential (-3.04V vs. standard hydrogen electrode). However, the highly reactive metallic lithium exhibits severe side reactions with the electrolyte, resulting in an unstable solid-state electrolyte interface that continuously breaks down and rebuilds with each cycle. This leads to a series of problems, including intensified side reactions, lithium dendrite growth, and the formation of "dead lithium," severely hindering its practical application. Summary of the Invention
[0003] This invention addresses the shortcomings of existing technologies, such as insufficient mechanical strength to withstand local pressure changes caused by uneven lithium metal deposition, inability to guarantee interface stability during cycling, and inability to fundamentally solve the problem of uneven electrode deposition / dissolution. It proposes a composite lithium-magnesium alloy anode, its preparation, and its application. The three-dimensional conductive framework material effectively reduces the local current density and provides sufficient space for lithium metal deposition. The LiF-rich elastic adaptive interface formed by fluorinated copolymers accelerates ion transport at the interface and maintains stability during long-term cycling. The lithium-philic lithium-magnesium alloy induces uniform lithium ion deposition and inhibits dendrite growth, thus constructing a composite lithium-magnesium alloy anode material with a lithium fluoride-rich elastic adaptive interface.
[0004] This invention is achieved through the following technical solution:
[0005] This invention relates to a method for preparing a composite lithium-magnesium alloy anode material, which involves uniformly loading a fluorinated copolymer solution onto the surface of a three-dimensional conductive framework, and then combining it with lithium-magnesium alloy foil in a sandwich arrangement by mechanical rolling.
[0006] The three-dimensional conductive framework material is one of conductive polyurethane, nickel foam, copper foam, carbon felt, or carbon-based materials.
[0007] The fluorinated copolymer described herein uses methyl methacrylate, 2-(perfluorobutyl)ethyl methacrylate, polyurethane methacrylate, heptadecanyl methacrylate, ethylene carbonate, trifluoroethyl methacrylate, or a combination thereof as monomer materials.
[0008] The fluorinated copolymer is obtained by copolymerizing monomer materials through photo-initiated polymerization, thermal initiated polymerization, or initiator-initiated polymerization.
[0009] The lithium-magnesium alloy foil is obtained by mixing metallic lithium and metallic magnesium, firing them in an argon atmosphere, and then rolling them, wherein the atomic ratio of metallic lithium to metallic magnesium is 1:1-10:1.
[0010] The preferred firing temperature is 150-400℃.
[0011] The foil is preferably in the range of ten micrometers or hundreds of micrometers in thickness.
[0012] The fluorinated copolymer solution is provided in the form of tetrahydrofuran and / or dichloromethane as solvents; the concentration of the solution is 3wt%-10wt%.
[0013] The uniform loading involves immersing the three-dimensional skeleton material in the above-mentioned fluorinated copolymer solution and then drying it in a vacuum oven, wherein the mass ratio of the fluorinated copolymer to the three-dimensional conductive skeleton is 1:1 to 1:10.
[0014] The drying process is preferably carried out at 80-100℃ for 24 hours;
[0015] This invention relates to a composite lithium-magnesium alloy anode material prepared by the above method, specifically a three-dimensional framework material of a fluorinated copolymer uniformly distributed in a lithium-magnesium alloy material.
[0016] This invention relates to the application of the above-mentioned composite lithium-magnesium alloy anode material, which is used as the anode material and matched with the cathode and electrolyte to assemble a lithium metal battery.
[0017] The positive electrode includes lithium nickel cobalt manganese oxide, lithium cobalt oxide, lithium manganese oxide, and lithium iron phosphate positive electrode.
[0018] The electrolyte may be, but is not limited to, any one of the following: a mixed solution of 1M lithium bis(trifluoromethanesulfonyl)imide (LiTFSI) in dioxolane (DOL) / ethylene glycol dimethyl ether (DME) and 2% LiNO3; a mixed solution of 0.2M LiPF6, 0.2M LiBF4, and 0.8M lithium difluorooxalate borate (LiDFOB) in diethyl carbonate (DEC): fluoroethylene carbonate (FEC) = 2:1 vol%; a mixed solution of 1M LiTFSI in DME:DOL = 1:1 vol%; or a mixed solution of 1M LiPF6 in ethylene carbonate (EC):DEC = 1:1 vol%.
[0019] Technical effect
[0020] This invention utilizes mechanical rolling to uniformly composite lithium-magnesium alloy materials and a three-dimensional framework material supported on fluorinated copolymers. The three-dimensional conductive framework material reduces local current density, thereby ensuring stable cycling of the electrode under high current conditions. Simultaneously, its abundant porous structure provides sufficient space for lithium metal deposition, ensuring structural stability of the electrode at high cycle capacities. Therefore, a symmetrical battery constructed from this composite negative electrode achieves high cycle capacity at 3 mA / cm². -2 -3mAh cm -2 Under certain conditions, it can stably cycle for over 550 cycles. Secondly, the fluorinated copolymer can form a lithium-fluoride-rich solid electrolyte interface layer at the electrode interface during the electrochemical reaction, which facilitates faster ion transport at the interface and improves interface stability during cycling. Simultaneously, the highly viscoelastic fluorinated copolymer provides better conformability to the interface, adapting to volume fluctuations in the electrode during lithium metal deposition / dissolution. Finally, compared to lithium metal anodes, lithium-rich lithium-magnesium alloy solid solution undergoes alloying and dealloying processes during lithium metal insertion and extraction. During this process, the lithium-magnesium alloy experiences only minor structural changes, ensuring the material's structural stability at 3 mA / cm². -2 -3mAh cm -2 Under these conditions, the single-cycle volume expansion rate of the electrode after 200 cycles is only 0.16%. Furthermore, the lithium-magnesium alloy exhibits better lithium affinity, promoting uniform lithium deposition and inhibiting dendrite growth. Therefore, the anode material prepared using this method plays a crucial role in suppressing lithium dendrite growth and improving interface stability, effectively enhancing the cycle stability of lithium metal batteries under high current and high capacity conditions, and advancing the practical application of lithium metal batteries. Attached Figure Description
[0021] Figure 1 The images shown are SEM and optical images of the composite lithium-magnesium alloy anode prepared in Example 1.
[0022] Figure 2 As in Example 1, the symmetrical cells in Comparative Examples 1, 2, and 3 were used at 1 mA cm⁻¹. -2 -1mAh cm -2 A comparison of voltage-time curves under cyclic conditions;
[0023] Figure 3 The full-cell capacity retention curve is shown in Example 1 and Comparative Example 1. Detailed Implementation
[0024] Example 1
[0025] This embodiment relates to the preparation of a composite lithium-magnesium alloy anode material (CPU+MPP@Li-Mg) with an adaptive interface layer rich in lithium fluoride (CPU+MPP@Li-Mg) and its application in lithium metal batteries, including:
[0026] Step 1) Dissolve 1.0g of methyl methacrylate, 2.0g of polyurethane methacrylate and 1.2g of 2-(perfluorobutyl)ethyl methacrylate in 20ml of tetrahydrofuran solvent and stir for 24h until the three monomer materials are completely dissolved; then add 0.42g of 2-hydroxy-2-methyl-1-phenyl-1-propanone as a photoinitiator to the solution; place the above solution under a 400nm ultraviolet lamp for polymerization and react for 4h.
[0027] The reaction equation for step 1 is as follows:
[0028]
[0029] Where: R1 is R2 is R3 is
[0030]
[0031] Step 2) After the polymerization reaction is completed, the solvent in the solution is removed by rotary evaporator to obtain a yellow fluorinated copolymer material;
[0032] Step 3) Weigh 1.0g of the fluorinated copolymer and dissolve it in 3.0ml of tetrahydrofuran solvent; use a dropper to evenly drop the solution onto the conductive polyurethane skeleton, and then place it in a vacuum oven to dry at 100℃ for 12h to obtain a conductive polyurethane material uniformly loaded with the fluorinated copolymer; repeat this operation several times until the mass of the loaded fluorinated copolymer and the mass of the conductive polyurethane are 1:1.
[0033] Step 4) Weigh lithium magnesium alloy and conductive polyurethane material loaded with fluorinated copolymer in a mass ratio of 3:1; combine the two by mechanical rolling to finally obtain a composite lithium magnesium alloy anode material (CPU+MPP@Li-Mg) with a thickness of 50μm.
[0034] Step 5) Roll the CPU+MPP@Li-Mg obtained by rolling into a circular sheet with a diameter of 12mm for use in assembling symmetrical cells and full cells;
[0035] Step 6) Using the CPU+MPP@Li-Mg obtained in Step 5, assemble a lithium metal battery and perform electrochemical testing; use 0.2M LiPF6, 0.2M LiBF4, and 0.8M LiDFOB in DEC:FEC = 2:1 (Vol%) as the electrolyte; use Celgard 2400 as the separator; assemble a symmetrical battery at 1 mA cm⁻¹. -2 -1mAh cm -2 Long-cycle testing was conducted under these conditions; with a loading capacity of 4.1 mAh cm⁻¹. -2 The NCM811 cathode was used to assemble full cells, which were then subjected to long-cycle testing at a rate of 0.2C-0.5C.
[0036] In the above steps, except for steps 1-3, all other steps are carried out in a glove box where the water content and oxygen content are both below 0.1 ppm.
[0037] like Figure 1 The image shown is a SEM image and an optical image of the CPU+MPP@Li-Mg prepared in this embodiment. The mechanical rolling method can not only achieve precise control of electrode thickness, but also enable large-scale production.
[0038] Comparative Example 1
[0039] This comparative example relates to the preparation of a lithium metal anode and its application in lithium metal batteries. The specific preparation process includes the following steps:
[0040] Step 1) Press a 50μm thick lithium foil into a 12mm diameter disc;
[0041] Step 2) Using the lithium metal anode obtained in Step 1, assemble a lithium metal battery and perform electrochemical testing; use 0.2M LiPF6, 0.2M LiBF4, and 0.8M LiDFOB in DEC:FEC = 2:1 (Vol%) as the electrolyte; use Celgard 2400 as the separator; assemble a symmetrical battery at 1 mA cm⁻¹. -2 -1mAh cm -2 Long-cycle testing was conducted under these conditions; with a loading capacity of 4.1 mAh cm⁻¹. -2The NCM811 cathode was used to assemble full cells, which were then subjected to long-cycle testing at a rate of 0.2C-0.5C.
[0042] All the above steps were carried out in a glove box with both water and oxygen content below 0.1 ppm.
[0043] Comparative Example 2
[0044] This comparative example relates to the preparation of a composite anode material (CPU@Li-Mg) based on conductive polyurethane and lithium-magnesium alloy and its application in lithium metal batteries. The specific preparation process includes the following steps:
[0045] Step 1) Weigh lithium-magnesium alloy and conductive polyurethane material in a mass ratio of 3:1; combine the two by mechanical rolling to obtain a composite lithium-magnesium alloy anode material (CPU@Li-Mg) with a thickness of 50μm.
[0046] Step 2) The CPU@Li-Mg obtained by rolling is rolled into a circular sheet with a diameter of 12mm for use in assembling symmetrical cells and full cells;
[0047] Step 3) Using the CPU@Li-Mg obtained in Step 2, assemble a lithium metal battery and perform electrochemical tests; use 0.2M LiPF6, 0.2M LiBF4, and 0.8M LiDFOB in DEC:FEC = 2:1 (Vol%) as the electrolyte; use Celgard 2400 as the separator; assemble a symmetrical battery at 1 mA / cm². -2 -1mAh cm -2 Long-cycle testing was conducted under these conditions; with a loading capacity of 4.1 mAh cm⁻¹. -2 The NCM811 cathode was used to assemble full cells, which were then subjected to long-cycle testing at a rate of 0.2C-0.5C.
[0048] All the above steps were carried out in a glove box with both water and oxygen content below 0.1 ppm.
[0049] Comparative Example 3
[0050] This comparative example relates to the preparation of a composite anode material (MPP@Li-Mg) based on fluorinated copolymers and lithium-magnesium alloys and its application in lithium metal batteries. The specific preparation process includes the following steps:
[0051] Step 1) Weigh 2.0 g of the fluorinated copolymer obtained in Step 2 of Example, and then dissolve it in 5 ml of tetrahydrofuran solvent, stirring for 24 h until completely dissolved;
[0052] Step 2) Use a dropper to spread the solution obtained in step 1 evenly on the surface of the lithium-magnesium alloy, and let it stand until the solvent completely evaporates; repeat the above operation to control the mass ratio of fluorinated copolymer to lithium-magnesium alloy to 3:1.
[0053] Step 3) The lithium-magnesium alloy uniformly loaded with the fluorinated copolymer obtained in Step 2 is repeatedly folded and rolled 5 times to finally obtain a composite lithium-magnesium alloy material (MPP@Li-Mg) with a thickness of 50μm.
[0054] Step 4) Using the MPP@Li-Mg obtained in Step 3, assemble a lithium metal battery and perform electrochemical tests; use 0.2M LiPF6, 0.2M LiBF4, and 0.8M LiDFOB in DEC:FEC = 2:1 (Vol%) as the electrolyte; use Celgard 2400 as the separator; assemble a symmetrical battery at 1 mA / cm². -2 -1mAh cm -2 Long-cycle testing was conducted under these conditions; with a loading capacity of 4.1 mAh cm⁻¹. -2 The NCM811 cathode was used to assemble full cells, which were then subjected to long-cycle testing at a rate of 0.2C-0.5C.
[0055] All of the above steps were carried out in a glove box with both water and oxygen content below 0.1 ppm.
[0056] like Figure 2 As shown, the symmetrical cells composed of Example 1, Comparative Example 1, Comparative Example 2, and Comparative Example 3 are tested at 1 mA cm⁻¹. -2 -1mAh cm -2 The test results under the specified conditions are as follows: For Comparative Example 1, the battery short-circuited after only 240 cycles; for Comparative Example 2, the voltage increased sharply after 670 cycles with a small overpotential; for Comparative Example 3, it could be stably cycled for 780 cycles with an overpotential of approximately 55 mV; and for the comparative example, it could be stably cycled for 1300 cycles with an extremely small overpotential. These results indicate that the composite lithium-magnesium alloy anode prepared in these examples plays an important role in improving the cycle stability of lithium metal batteries.
[0057] like Figure 3 The figures show the test results of the full cells assembled in the Examples and Comparative Example 1. For Comparative Example 1, the battery capacity decayed to 80% of its initial value after 100 cycles; however, for the Examples, it still retained 80% of its capacity after 268 cycles. The results indicate that the composite lithium-magnesium alloy anode prepared in the Examples can effectively improve the stability of the electrode under practical application conditions.
[0058] Compared with existing technologies, this method utilizes a composite lithium-magnesium alloy anode with a lithium-fluoride-rich adaptive interface layer, constructed from a three-dimensional conductive framework material, a fluorinated copolymer, and a lithium-magnesium alloy, to achieve stable cycling under high current and high capacity conditions. First, the introduction of the three-dimensional framework material reduces the local current density, and its abundant porosity provides sufficient space for lithium metal, effectively suppressing electrode volume expansion under high cycling capacity conditions. Second, the lithium-fluoride-rich elastic adaptive interface layer formed by the fluorinated copolymer accelerates ion transport and maintains stability during long cycling. Finally, the lithium-magnesium alloy exhibits excellent lithiophilicity, thereby inducing uniform lithium metal deposition and suppressing lithium dendrite growth. Simultaneously, the lithium-magnesium alloy acts as a framework during lithium metal deposition / dissolution, thus endowing the composite electrode with excellent structural stability. Therefore, this invention can effectively improve the cycling stability of lithium metal batteries. Compared to pure lithium anodes, the composite anode exhibits better performance in both symmetrical and full-cell batteries.
[0059] In summary, the composite lithium-magnesium alloy anode prepared in this invention, when applied to lithium metal batteries, achieves a more stable solid-state electrolyte interface, effectively suppressing electrode volume fluctuations and lithium dendrite growth. Therefore, this composite lithium-magnesium alloy anode exhibits excellent cycle stability under high current density and large areal specific capacity conditions, while also enabling rapid charge-discharge cycling of high-energy-density full cells.
[0060] The above-described specific implementations can be partially adjusted by those skilled in the art in different ways without departing from the principles and purpose of the present invention. The scope of protection of the present invention is defined by the claims and is not limited to the above-described specific implementations. All implementation schemes within the scope of the claims are bound by the present invention.
Claims
1. A method for preparing a composite lithium-magnesium alloy anode material, characterized in that, After uniformly loading the fluorinated copolymer solution onto the surface of the three-dimensional conductive framework, it is composited with lithium magnesium alloy foil in a sandwich arrangement by mechanical rolling. The three-dimensional conductive framework material is made of conductive polyurethane, nickel foam, copper foam, carbon felt, or carbon-based material. The fluorinated copolymer is obtained by copolymerizing methyl methacrylate, 2-(perfluorobutyl)ethyl methacrylate, and methacrylic polyurethane through photo-initiated polymerization, thermally initiated polymerization, and initiator-initiated polymerization. The lithium-magnesium alloy foil is obtained by mixing metallic lithium and metallic magnesium, firing them in an argon atmosphere at 150-400℃, and then rolling them. The foil has a thickness of ten micrometers or hundreds of micrometers, wherein the atomic ratio of metallic lithium to metallic magnesium is 1:1-10:
1. The fluorinated copolymer solution is provided in the presence of tetrahydrofuran and / or dichloromethane as a solvent; the concentration of the solution is 3 wt%-10 wt%. The uniform loading involves immersing the three-dimensional skeleton material in the above-mentioned fluorinated copolymer solution and then drying it in a vacuum oven, wherein the mass ratio of the fluorinated copolymer to the three-dimensional conductive skeleton is 1:1 to 1:
10.
2. The method for preparing the composite lithium-magnesium alloy anode material according to claim 1, characterized in that, The drying process involves drying at 80-100 °C for 24 hours.
3. An application of a composite lithium-magnesium alloy anode material prepared according to the method of claim 1 or 2, characterized in that, As a negative electrode material, it is matched with the positive electrode and electrolyte to assemble lithium metal batteries.
4. The application according to claim 3, characterized in that, The positive electrode includes any one of lithium nickel manganese cobalt oxide, lithium cobalt oxide, lithium manganese oxide, and lithium iron phosphate positive electrode. The electrolyte may be any one of the following: a mixed solution of 1 M lithium bis(trifluoromethanesulfonyl)imide (LiTFSI) in dioxolane (DOL) / ethylene glycol dimethyl ether (DME) and 2% LiNO3; a mixed solution of 0.2 M LiPF6, 0.2 M LiBF4, and 0.8 M lithium difluorooxalate borate (LiDFOB) in diethyl carbonate (DEC): fluoroethylene carbonate (FEC) = 2:1 Vol%; a mixed solution of 1 M LiTFSI in DME:DOL = 1:1 Vol%; or a mixed solution of 1 M LiPF6 in ethylene carbonate (EC):DEC = 1:1 Vol%.