Gradient composite lithium alloy negative electrode material, preparation method thereof and lithium metal battery

Abstract

The invention discloses a gradient composite lithium alloy negative electrode material, a preparation method thereof and a lithium metal battery, and the gradient composite lithium alloy negative electrode material provided by the invention comprises a current collector and a lithium alloy gradient material layer arranged on at least one side of the current collector, the lithium intercalation potential and / or alloy element concentration of the lithium alloy gradient material layer are / is changed in a gradient manner along the direction vertical to the surface of the current collector, so that the lithium alloy gradient material layer has continuous component concentration gradient and / or potential gradient. The gradient structure design effectively optimizes immigration and nucleation behaviors of lithium ions, inhibits dendritic crystal growth, is hopeful to effectively eliminate the nucleation risk of dendritic crystals on the surface of an electrode, alleviates volume expansion, and significantly improves the safety performance and cycle stability of the lithium metal negative electrode.

Description

Technical Field

[0001] This invention relates to the field of battery materials technology, and more specifically, to a gradient composite lithium alloy anode material, its preparation method, and a lithium metal battery. Background Technology

[0002] Lithium metal anodes are considered ideal candidate materials for building next-generation high-energy-density energy storage systems due to their theoretical specific capacity of up to 3860 mAh / g and extremely low electrochemical potential of -3.04 V (relative to the standard hydrogen electrode). However, their practical application still faces four key challenges: uncontrolled growth of lithium dendrites poses serious safety hazards; high volume changes during cycling lead to electrode structure damage; continuous side reactions between active lithium and the electrolyte cause a decrease in coulombic efficiency; and the continuous accumulation of non-conductive "dead lithium" causes rapid capacity decay. To address these issues, researchers have proposed various surface modification strategies; however, due to limitations in design concepts and implementation paths, no fundamental breakthroughs have yet been achieved. Summary of the Invention

[0003] The purpose of this invention is to overcome the above-mentioned shortcomings of the prior art and provide a gradient composite lithium alloy anode material, its preparation method, and a lithium metal battery.

[0004] The technical problem solved by this invention is achieved by the following technical solution.

[0005] The present invention provides a gradient composite lithium alloy anode material, comprising: a current collector and a lithium alloy gradient material layer disposed on at least one side of the current collector, wherein the lithium intercalation potential and / or alloy element concentration of the lithium alloy gradient material layer varies in a gradient direction perpendicular to the surface of the current collector, so that the lithium alloy gradient material layer has a continuous composition concentration gradient and / or potential gradient.

[0006] The present invention also provides a method for preparing the above-mentioned gradient composite lithium alloy anode material, which includes: composite a lithium alloy gradient material layer onto the surface of the current collector to obtain the gradient composite lithium alloy anode material.

[0007] The present invention also provides a lithium metal battery comprising the above-described gradient composite lithium alloy anode material.

[0008] The present invention has the following beneficial effects: This invention provides a gradient composite lithium alloy anode material, comprising: a current collector and a lithium alloy gradient material layer disposed on at least one side of the current collector. The lithium intercalation potential and / or alloy element concentration of the lithium alloy gradient material layer vary gradientally along a direction perpendicular to the surface of the current collector, so that the lithium alloy gradient material layer has a continuous composition concentration gradient and / or potential gradient. This gradient structure design effectively optimizes the migration and nucleation behavior of lithium ions, suppresses dendrite growth, and thus synergistically improves the rate performance and cycle stability of the battery. This type of structure design is expected to effectively eliminate the risk of dendrite nucleation on the electrode surface, alleviate volume expansion, significantly improve the safety performance and cycle stability of lithium metal anodes, and provide a new solution for the practical application of high-energy-density battery systems. Attached Figure Description

[0009] To more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings used in the embodiments will be briefly introduced below. It should be understood that the following drawings only show some embodiments of the present invention and should not be regarded as a limitation on the scope. For those skilled in the art, other related drawings can be obtained based on these drawings without creative effort.

[0010] Figure 1 Electrochemical impedance spectroscopy of the gradient composite lithium alloy anode material prepared for the example; Figure 2 Electrochemical impedance spectroscopy of lithium alloy anode materials prepared for comparison; Figure 3 The critical current density test diagram of the gradient composite lithium alloy anode material prepared in Example 3; Figure 4 The critical current density test diagram of the gradient composite lithium alloy anode material prepared in Example 4; Figure 5 The critical current density test diagram of the gradient composite lithium alloy anode material prepared in Example 7; Figure 6 The critical current density test diagram is for the lithium alloy anode material prepared in Comparative Example 5. Detailed Implementation

[0011] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below. Where specific conditions are not specified in the embodiments, conventional conditions or conditions recommended by the manufacturer shall apply. Reagents or instruments whose manufacturers are not specified are all conventional products that can be purchased commercially.

[0012] The following is a detailed description of a gradient composite lithium alloy anode material, its preparation method, and a lithium metal battery provided by the present invention.

[0013] In a first aspect, the present invention provides a gradient composite lithium alloy anode material, comprising: a current collector and a lithium alloy gradient material layer disposed on at least one side of the current collector, wherein the lithium intercalation potential and / or alloy element concentration of the lithium alloy gradient material layer varies in a gradient direction perpendicular to the surface of the current collector, so that the lithium alloy gradient material layer has a continuous composition concentration gradient and / or potential gradient.

[0014] Current research largely focuses on constructing concentration gradient alloy layers, where the lithium content gradually increases from the surface inwards, while simultaneously creating a chemical potential gradient to guide the migration of high-content lithium at the bottom outwards to compensate for lithium loss from the surface. However, these methods generally suffer from slow lithium-ion transport rates, dendrite growth on the surface, and complex fabrication processes with high energy consumption. Therefore, developing a layered alloy anode structure with a simple fabrication process, potential gradient control, and good interfacial bonding is of great significance.

[0015] This invention addresses the issue of lithium alloy gradient material layers on the surface of a current collector. The lithium intercalation potential and / or alloy element concentration of this gradient material layer vary along a direction perpendicular to the current collector surface. This gradient structure design effectively optimizes lithium-ion migration and nucleation behavior, suppresses dendrite growth, and thus synergistically improves the rate performance and cycle stability of the battery. This type of structure design is expected to effectively eliminate the risk of dendrite nucleation on the electrode surface, alleviate volume expansion, and significantly improve the safety performance and cycle stability of lithium metal anodes, providing a new solution for the practical application of high-energy-density battery systems.

[0016] In some alternative embodiments, the lithium intercalation potential of the lithium alloy gradient material layer decreases from the inside out, and / or the concentration of alloying elements increases from the inside out.

[0017] In some alternative embodiments, the lithium alloy gradient material layer is at least two layers, including a first alloy layer disposed on the surface of the current collector and a second alloy layer located on the surface of the first alloy layer, wherein the lithium intercalation potential of the first alloy layer is higher than that of the second alloy layer, and / or the lithium content of the first alloy layer is lower than that of the second alloy layer.

[0018] In some alternative embodiments, the first alloy layer is a low-lithium-content, high-lithium-intercalation-potential alloy layer, and the second alloy layer is a high-lithium-content, low-lithium-intercalation-potential alloy layer.

[0019] This invention provides a gradient composite lithium alloy anode material. A low-defect interface structure is formed by combining a high-lithium-intercalation potential alloy layer and a low-lithium-intercalation potential alloy layer using a stacking composite process. The intrinsic lithium-intercalation potential difference between the two layers creates a stable potential difference, reconstructing the lithium-ion deposition path. This design guides lithium ions to preferentially pass through the surface low-lithium-intercalation potential alloy region during charging, directionally migrating to the bottom alloy layer for deposition, thus eliminating the basis for dendrite nucleation on the electrode surface from a thermodynamic perspective. Simultaneously, the bulk deposition mode significantly reduces the volume change, and combined with the three-dimensional stress buffering characteristics of the interface, effectively overcomes the interface failure problem caused by the drastic volume expansion of traditional electrodes. While completely avoiding the introduction of inactive materials, it maintains high areal capacity and ensures long-term cycle stability, ultimately providing a breakthrough solution for high-safety, high-energy-density lithium metal battery systems.

[0020] In some optional embodiments, the first alloy layer and the second alloy layer comprise ≥50% by mass of battery-grade metallic lithium, and at least one alloying element selected from Mg, Ca, Si, Ge, Sn, Bi, Sb, B, Al, Ga, In, Cu, Zn, Ag, and rare earth metals, and the sum of the mass percentages of lithium and the alloying element is ≥99.9 wt%. Preferably, the alloying elements in the first alloy layer and the second alloy layer include at least one alloying element selected from Mg, Si, Al, In, Cu, Zn, and Ag.

[0021] In some alternative embodiments, the thickness of the first alloy layer and the second alloy layer is each independently 5-50 μm, preferably 5-20 μm; Preferably, the first alloy layer and the second alloy layer have the same thickness, and the tensile strength of both the first alloy layer and the second alloy layer is greater than 1 MPa.

[0022] In some alternative embodiments, the current collector is any one of copper foil, modified copper foil, composite copper foil, and stainless steel foil, with a thickness of 3-12 μm.

[0023] Secondly, the present invention provides a method for preparing the above-mentioned gradient composite lithium alloy anode material, which includes: composite a lithium alloy gradient material layer onto the surface of the current collector to obtain the gradient composite lithium alloy anode material.

[0024] In some optional embodiments, the method includes the following steps: extruding and rolling a lithium alloy ingot to obtain a lithium alloy foil; after bonding a first lithium alloy foil onto the surface of the current collector, bonding a second lithium alloy foil onto the surface of the first lithium alloy foil away from the current collector by a stacking method.

[0025] In some optional embodiments, the preparation of the lithium alloy foil includes: melting and stirring to prepare lithium alloy material in a vacuum environment or inert atmosphere at a melting temperature of 200-1000℃, a stirring speed of 20rpm / min-1000rpm / min, and a melting time of 0.5-10h; then casting the molten lithium alloy into a mold and cooling it at 5℃ / min-100℃ / min to obtain a lithium alloy ingot; placing the lithium alloy ingot in a drying room and extruding and rolling it to obtain a lithium alloy foil; Preferably, the preparation of molten lithium metal alloy includes: controlling the melting temperature to be 300-800℃, the stirring speed to be 50rpm / min-500rpm / min, and the melting time to be 2-6h; Preferably, the stacking pressure of both the first lithium alloy foil and the second lithium alloy foil is 1000-5000 N / cm. 2 .

[0026] Thirdly, the present invention provides a lithium metal battery comprising the aforementioned gradient composite lithium alloy anode material.

[0027] The following detailed description, in conjunction with embodiments, illustrates a gradient composite lithium alloy anode material, its preparation method, and a lithium metal battery provided by the present invention. However, these descriptions should not be construed as limiting the scope of protection of the present invention.

[0028] Example 1 1. In a vacuum environment or inert atmosphere (dew point -50℃), lithium metal ingots and metallic Al are reacted in a LiAl mixture. 0.1wt% The proportions were added to a melting crucible and melted and stirred at 300°C and 100 rpm for 1 hour. Then, the mixture was poured into a custom mold and cooled at a rate of 70°C / min to obtain an alloy ingot. 2. LiAl 0.1wt% The alloy ingot is placed in a drying room (dew point -50℃) and thinned to a thickness of 20μm by a precision rolling mill to form an initial alloy foil; 3. At 3000 N / cm 2 Under the action of force, the alloy foil is transferred to the surface of the current collector through a mechanical composite process to form the first alloy layer; 4. Repeat steps (1)-(3) to prepare LiAl 0.3wt% Alloy foil, and under the same pressure parameters, LiAl 0.3wt% Alloy foil is stacked on the first alloy layer to form the second alloy layer, ultimately forming a lithium alloy anode material with a continuous composition gradient.

[0029] Example 2 1. Prepare LiAl according to the method in Example 1 0.1wt% and LiAl 1.5wt% Alloy ingots; 2. LiAl 0.1wt% The alloy ingot is placed in a drying room (dew point -50℃) and thinned to a thickness of 20μm by a precision rolling mill to form an initial alloy foil; 3. At 3000 N / cm 2 Under the action of force, the alloy foil is transferred to the surface of the current collector through a mechanical composite process to form the first alloy layer; 4. Repeat steps (1)-(3) to prepare LiAl 1.5wt% Alloy foil, and under the same pressure parameters, LiAl 1.5wt% Alloy foil is stacked on the first alloy layer to form the second alloy layer, ultimately forming a lithium alloy anode material with a continuous composition gradient.

[0030] Example 3 1. Prepare LiAl according to the method in Example 1 0.1wt% and LiAl 10wt% Alloy ingots;

[0031] 2. LiAl 0.1wt% The alloy ingot is placed in a drying room (dew point -50℃) and thinned to a thickness of 20μm by a precision rolling mill to form an initial alloy foil; 3. At 3000 N / cm 2 Under the action of force, the alloy foil is transferred to the surface of the current collector through a mechanical composite process to form the first alloy layer; 4. Repeat steps (1)-(3) to prepare LiAl 10wt% Alloy foil, and under the same pressure parameters, LiAl 10wt% Alloy foil is stacked on the first alloy layer to form the second alloy layer, ultimately forming a lithium alloy anode material with a continuous composition gradient.

[0032] Example 4 1. Prepare LiAl according to the method in Example 1 10wt% and LiAl 0.1wt% Alloy ingots; 2. LiAl 10wt% The alloy ingot is placed in a drying room (dew point -50℃) and thinned to a thickness of 20μm by a precision rolling mill to form an initial alloy foil; 3. At 3000 N / cm 2 Under the action of force, the alloy foil is transferred to the surface of the current collector through a mechanical composite process to form the first alloy layer; 4. Repeat steps (1)-(3) to prepare LiAl 0.1wt% Alloy foil, and under the same pressure parameters, LiAl 0.1wt% Alloy foil is stacked on the first alloy layer to form the second alloy layer, ultimately forming a lithium alloy anode material with a continuous composition gradient.

[0033] Example 5 1. Prepare LiAl according to the method in Example 1 10wt% and LiAl 0.3wt% Alloy ingots; 2. LiAl 10wt% The alloy ingot is placed in a drying room (dew point -50℃) and thinned to a thickness of 20μm by a precision rolling mill to form an initial alloy foil; 3. At 3000 N / cm 2 Under the action of force, the alloy foil is transferred to the surface of the current collector through a mechanical composite process to form the first alloy layer; 4. Repeat steps (1)-(3) to prepare LiAl 0.3wt% Alloy foil, and under the same pressure parameters, LiAl 0.3wt% Alloy foil is stacked on the first alloy layer to form the second alloy layer, ultimately forming a lithium alloy anode material with a continuous composition gradient.

[0034] Example 6 1. Prepare LiAl according to the method in Example 1 10wt% and LiAl 1.5wt% Alloy ingots; 2. LiAl 10wt% The alloy ingot is placed in a drying room (dew point -50℃) and thinned to a thickness of 20μm by a precision rolling mill to form an initial alloy foil; 3. At 3000 N / cm 2 Under the action of force, the alloy foil is transferred to the surface of the current collector through a mechanical composite process to form the first alloy layer; 4. Repeat steps (1)-(3) to prepare LiAl 1.5wt% Alloy foil, and under the same pressure parameters, LiAl 1.5wt% Alloy foil is stacked on the first alloy layer to form the second alloy layer, ultimately forming a lithium alloy anode material with a continuous composition gradient.

[0035] Example 7 1. Melting LiIn under vacuum or inert atmosphere (dew point -50°C): 5wt% Alloy: Lithium ingots and In were stirred at 100 rpm for 1 hour at 400°C and cooled at 75°C / min; LiMg was then smelted. 10wt% Alloy: Lithium ingots and Mg were stirred at 400℃ and 90 rpm for 1 h, and then cooled at 75℃ / min; 2. LiIn 5wt% The alloy ingot is placed in a drying room (dew point -50℃) and thinned to a thickness of 20μm by a precision rolling mill to form an initial alloy foil; 3. At 3000 N / cm2 Under the action of force, the alloy foil is transferred to the surface of the current collector through a mechanical composite process to form the first alloy layer; 4. Repeat steps (1)-(3) to prepare LiMg 10wt% Alloy foil, and under the same pressure parameters, LiMg 10wt% Alloy foil is stacked on the first alloy layer to form the second alloy layer, ultimately forming a lithium alloy anode material with a continuous composition gradient.

[0036] Comparative Example 1 1. Prepare LiAl according to the method in Example 1 0.1wt% Single-component alloy ingots; 2. LiAl 0.1wt% The alloy ingot is placed in a drying room (dew point -50℃) and thinned to a thickness of 40μm by a precision rolling mill to form an alloy foil; 3. At 3000 N / cm 2 Under the action of force, the alloy foil is transferred to the surface of the current collector through a mechanical composite process, serving as a lithium anode material.

[0037] Comparative Example 2 1. Prepare LiAl according to the method in Example 1 0.3wt% Single-component alloy ingots; 2. LiAl 0.3wt% The alloy ingot is placed in a drying room (dew point -50℃) and thinned to a thickness of 40μm by a precision rolling mill to form an initial alloy foil; 3. At 3000 N / cm 2 Under the action of force, the alloy foil is transferred to the surface of the current collector through a mechanical composite process, serving as a lithium anode material.

[0038] Comparative Example 3 1. Prepare LiAl according to the method in Example 1 1.5wt% Single-component alloy ingots; 2. LiAl 1.5wt% The alloy ingot is placed in a drying room (dew point -50℃) and thinned to a thickness of 40μm by a precision rolling mill to form an initial alloy foil; 3. At 3000 N / cm 2 Under the action of force, the alloy foil is transferred to the surface of the current collector through a mechanical composite process, serving as a lithium anode material.

[0039] Comparative Example 4 1. Prepare LiAl according to the method in Example 1 10wt% Single-component alloy ingots; 2. LiAl 10wt% The alloy ingot is placed in a drying room (dew point -50℃) and thinned to a thickness of 40μm by a precision rolling mill to form an initial alloy foil; 3. At 3000 N / cm 2 Under the action of force, the alloy foil is transferred to the surface of the current collector through a mechanical composite process, serving as a lithium anode material.

[0040] Comparative Example 5 1. Prepare pure Li ingots according to the method of Example 1; 2. The Li ingot is placed in a drying room (dew point -50℃) and thinned to a thickness of 40μm using a precision rolling mill to form the initial lithium foil; 3. At 3000 N / cm 2 Under the action of force, the lithium foil is transferred to the surface of the current collector through a mechanical composite process, serving as a lithium anode material.

[0041] Comparative Example 6 1. Smelting LiMg 10wt% Alloy: Lithium ingots and Mg were stirred at 400℃ and 90 rpm for 1 h, and then cooled at 75℃ / min; 2. LiMg 10wt% The alloy ingot is placed in a drying room (dew point -50℃) and thinned to a thickness of 40μm by a precision rolling mill to form an initial alloy foil; 3. At 3000 N / cm 2 Under the action of force, the alloy foil is transferred to the surface of the current collector through a mechanical composite process, serving as a lithium anode material.

[0042] Comparative Example 7 1. Melting LiIn under vacuum or inert atmosphere (dew point -50°C): 5wt% Alloy: Lithium ingots and In were stirred at 100 rpm for 1 hour at 400°C and then cooled at 75°C / min; 2. LiIn 5wt% The alloy ingot is placed in a drying room (dew point -50℃) and thinned to a thickness of 40μm by a precision rolling mill to form an initial alloy foil; 3. At 3000 N / cm 2 Under the action of force, the alloy foil is transferred to the surface of the current collector through a mechanical composite process, serving as a lithium anode material.

[0043] Testing method: The electrodes prepared in the above examples and comparative examples were cut to the same size and used as the positive and negative electrodes, respectively, and assembled into a symmetrical cell. Two electrolyte systems were used for testing: (1) Used for impedance testing (test frequency range: 0.01-10) 5 (Hz) and cycling performance (current density: 0.5 mA·cm⁻¹) -2 Deposition capacity: 0.5 mAh·cm -2The electrolyte composition for the test was: 19 wt% LiTFSI dissolved in a mixed solvent consisting of 11 wt% DME and 70 wt% HFE; (2) The electrolyte used for the critical current density test was: 1 mol / L LiTFSI dissolved in a mixed solvent of DME and DOL in a 1:1 molar ratio, with 2 wt% LiNO3 added. This test selected some examples and comparative examples, first at 0.5 mA·cm⁻¹. -2 0.5mAh·cm -2 Under these conditions, the system was cycled for 5 weeks, and then the current density and deposition capacity were increased by 0.25 mA·cm² per cycle thereafter. -2 and 0.25mAh·cm -2 Observe whether the battery has short-circuited.

[0044] Table 1

[0045] Table 2

[0046] Table 3

[0047] As can be seen from Tables 1-3, compared with single-component lithium alloys (Comparative Examples 1-7), the multi-component gradient alloy anodes of the present invention (Examples 1-7) exhibit significantly improved electrochemical performance. Electrochemical impedance spectroscopy (EIS) tests show that, except for Example 2 which exhibits fluctuations due to specific composition, the interfacial impedance of the other multi-component alloys is lower than that of the single-component alloys. Example 4 has the lowest impedance value (228.5 Ω), which is approximately 25% lower than the optimal comparative example. This is attributed to the low-defect interfacial structure formed by mechanical lamination.

[0048] Constant current deposition / stripping tests further confirmed that the lithium deposition nucleation overpotential of multi-component alloys is generally superior to that of single-component alloys (Example 7: only 104.5 mV vs. the best value of 123.7 mV in the comparative example), especially for the top layer (such as LiAl). 0.1wt% The alloy layer, acting as an "ion migration layer," possesses a relatively low lithium equilibrium potential and exhibits strong lithiophilicity, providing adsorption sites for lithium ions and promoting their migration into the bulk phase; the bottom layer (such as LiAl) 10wt% The alloy layer, acting as a "uniform nucleation layer," possesses a relatively high lithium equilibrium potential, and its electrochemical inertness significantly reduces the nucleation barrier for lithium atoms at this location. This achieves a reduction in the lithium deposition nucleation overpotential to 105.3 mV (the optimal comparative example shows a reduction of 123.7 mV), significantly optimizing lithium-ion insertion / extraction kinetics and cycle stability.

[0049] Cycle life tests showed that the multi-component alloy electrode exhibited superior overall cycle durability. For example, Example 6 achieved a cycle time of 2129 hours, the best among all samples. This is because the high-aluminum-content bottom layer has a higher lithium intercalation potential, which can induce lithium ions to migrate directionally to the bottom, effectively mitigating the growth of interface dendrites. Critical current density tests further showed that Example 4 achieved a critical current density of 3.25 mA·cm⁻¹. -2 It still operates stably under the conditions, which is better than Comparative Example 7 (1.75 mA·cm). -2 ) and Example 3 (2.75 mA·cm -2 This indicates that it possesses superior rate performance. In contrast, because the Li-Mg alloy is a solid solution phase, the lithium-ion diffusion rate is low, resulting in poor rate performance.

[0050] In summary, the multi-component gradient alloy anode provided by this invention, by constructing a composite structure of "ion migration layer / uniform nucleation layer" with compositional and functional gradients, significantly outperforms single-component lithium alloys in key electrochemical performance indicators such as interfacial charge transfer impedance, lithium deposition nucleation overpotential, cycle life, and critical current density. This gradient structure design effectively optimizes lithium-ion migration and nucleation behavior, suppresses dendrite growth, and thus synergistically improves the rate performance and cycle stability of the battery, demonstrating outstanding comprehensive advantages and application potential.

[0051] As can be seen from the above, the present invention provides a gradient composite lithium alloy anode material, its preparation method, and a lithium metal battery, which have the following characteristics and advantages compared with the prior art: (1) By constructing a potential difference, the lithium intercalation potential of the bottom alloy layer (first alloy layer) is higher than that of the top alloy layer (second alloy layer), driving lithium ions to diffuse and deposit into the bulk phase of the bottom alloy layer (first alloy layer), preventing the growth of lithium dendrites on the surface, and significantly improving the cycle life of the lithium metal anode.

[0052] (2) Constructing a concentration gradient and combining the synergistic effect of high and low lithium content layers: The first alloy layer (low lithium content, high potential alloy layer) constructs a highly conductive network to accelerate charge transfer; the second alloy layer (high lithium content, low potential alloy layer) provides low-barrier ion channels, reducing the lithium-ion migration energy barrier. The synergistic effect reduces the nucleation overpotential to 105.3 mV (a 15% reduction compared to the optimal comparative example of 123.7 mV), significantly optimizing the lithium-ion insertion / extraction dynamics and further reducing the risk of dendrite growth.

[0053] (3) Significantly reduced interface impedance: The first alloy layer and the second alloy layer are laminated to form a low-defect interface structure, which reduces the interface charge transfer impedance (Rct) to as low as 228.5 Ω (Example 4), which is 25% lower than the optimal single-component alloy, effectively improving ion transport efficiency.

[0054] (4) Advantages of process compatibility: The layered composite process forms a layered alloy anode structure with good interface bonding by roll-to-roll lamination at room temperature, avoiding high-energy-consuming and high-risk processes such as high-temperature evaporation or high-temperature coating. At the same time, the alloy composition of each layer is controlled with an accuracy of ±0.05wt%, which is suitable for large-scale production.

[0055] The above are merely preferred embodiments of the present invention and are not intended to limit the present invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A gradient composite lithium alloy anode material, characterized in that, include: A current collector and a lithium alloy gradient material layer disposed on at least one side of the current collector, wherein the lithium intercalation potential and / or alloy element concentration of the lithium alloy gradient material layer vary in a gradient direction perpendicular to the surface of the current collector, so that the lithium alloy gradient material layer has a continuous composition concentration gradient and / or potential gradient.

2. The gradient composite lithium alloy anode material according to claim 1, characterized in that, The lithium intercalation potential of the lithium alloy gradient material layer decreases from the inside out, and / or the concentration of alloy elements increases from the inside out.

3. The gradient composite lithium alloy anode material according to claim 2, characterized in that, The lithium alloy gradient material layer comprises at least two layers, including a first alloy layer disposed on the surface of the current collector and a second alloy layer disposed on the surface of the first alloy layer, wherein the lithium intercalation potential of the first alloy layer is higher than that of the second alloy layer, and / or the lithium content of the first alloy layer is lower than that of the second alloy layer. Preferably, the first alloy layer is a low-lithium-content, high-lithium-intercalation-potential alloy layer, and the second alloy layer is a high-lithium-content, low-lithium-intercalation-potential alloy layer.

4. The gradient composite lithium alloy anode material according to claim 3, characterized in that, The first alloy layer and the second alloy layer contain ≥50% by mass of battery-grade metallic lithium, and at least one alloying element selected from Mg, Ca, Si, Ge, Sn, Bi, Sb, B, Al, Ga, In, Cu, Zn, Ag and rare earth metals, and the sum of the mass percentages of lithium and alloying elements is ≥99.9 wt%. Preferably, the alloying elements in the first alloy layer and the second alloy layer include at least one alloying element selected from Mg, Si, Al, In, Cu, Zn, and Ag.

5. The gradient composite lithium alloy anode material according to claim 3, characterized in that, The thickness of the first alloy layer and the second alloy layer is independently 5-50 μm, preferably 5-20 μm; Preferably, the first alloy layer and the second alloy layer have the same thickness, and the tensile strength of both the first alloy layer and the second alloy layer is greater than 1 MPa.

6. The gradient composite lithium alloy anode material according to claim 1, characterized in that, The current collector is any one of copper foil, modified copper foil, composite copper foil, and stainless steel foil, with a thickness of 3-12 μm.

7. A method for preparing a gradient composite lithium alloy anode material according to any one of claims 1-6, characterized in that, It includes: The gradient composite lithium alloy anode material is prepared by laminating a lithium alloy gradient material layer onto the surface of the current collector.

8. The preparation method according to claim 7, characterized in that, Includes the following steps: Lithium alloy ingots are extruded and rolled to obtain lithium alloy foil. After a first lithium alloy foil is laminated onto the surface of the current collector, a second lithium alloy foil is laminated onto the surface of the first lithium alloy foil away from the current collector by a stacking method.

9. The preparation method according to claim 8, characterized in that, The preparation of the lithium alloy foil includes: melting and stirring to prepare lithium alloy material in a vacuum environment or inert atmosphere at a melting temperature of 200-1000℃, a stirring speed of 20rpm / min-1000rpm / min, and a melting time of 0.5-10h; then casting the molten lithium alloy into a mold and cooling it at 5℃ / min-100℃ / min to obtain a lithium alloy ingot; placing the lithium alloy ingot in a drying room and extruding and rolling it to obtain lithium alloy foil; Preferably, the preparation of molten lithium metal alloy includes: controlling the melting temperature to be 300-800℃, the stirring speed to be 50rpm / min-500rpm / min, and the melting time to be 2-6h; Preferably, the stacking pressure of both the first lithium alloy foil and the second lithium alloy foil is 1000-5000 N / cm. 2 .

10. A lithium metal battery, characterized in that, The gradient composite lithium alloy anode material included in any one of claims 1-6.

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