A lithium metal anode based on a gradient solid-state electrolyte and a preparation method and application thereof

Abstract

This invention discloses a lithium metal anode based on a gradient solid-state electrolyte, its preparation method, and its application. The lithium metal anode sequentially comprises: a current collector, a porous lithium-zinc alloy interface layer, a lithium metal layer, and a gradient solid-state electrolyte layer. The gradient solid-state electrolyte layer includes a polymer matrix and a high-dielectric filler layer distributed in a gradient within the polymer matrix. In this invention, the porous lithium-zinc alloy interface layer and the gradient high-dielectric filler polymer layer work synergistically to effectively guide uniform lithium-ion deposition, suppress dendrite growth, and reduce tip effects, thereby improving cycle life, reducing interface impedance and polarization voltage, and minimizing volume expansion.

Description

Technical Field

[0001] This invention belongs to the field of lithium-ion battery technology, and more specifically, relates to a lithium metal anode based on a gradient solid electrolyte, its preparation method, and its application. Background Technology

[0002] In recent years, with the rapid increase in the demand for high energy density in power batteries and energy storage batteries, lithium metal anodes have been regarded as the core material for next-generation battery technology due to their extremely high theoretical specific capacity (3860 mAh / g), low electrochemical potential (-3.04 V vs. SHE), and low density (0.534 g / cm³). They have important application prospects in new battery systems such as solid-state batteries, lithium-sulfur batteries, and lithium-air batteries. However, lithium metal anodes face key challenges in practical applications, such as dendrite growth (uniform lithium deposition / stripping can cause dendrites to pierce the separator, leading to short circuits or even thermal runaway), volume expansion (the huge volume change of more than 300% during lithium deposition / stripping destroys the integrity of the electrode structure), and interface instability (lithium continuously reacts with the electrolyte, consuming active lithium and thickening the solid electrolyte interphase (SEI), leading to increased impedance and capacity decay). These challenges result in short battery cycle life and poor safety, seriously restricting their commercialization process.

[0003] Existing solutions mainly improve the performance of lithium metal anodes through surface coatings, three-dimensional current collectors, or electrolyte modification, but limitations remain. For example, single-functional coatings (such as LiF and polymers) cannot simultaneously address dendrite suppression and interface stability requirements; homogeneous solid electrolytes (such as LLZO and PEO) are difficult to adapt to lithium deposition stress, cannot maintain structural integrity over a long period, and are prone to cracking; traditional porous current collectors (such as copper foam) have disordered pore distribution, making it impossible to precisely control the lithium deposition path. Summary of the Invention

[0004] The purpose of this invention is to provide a lithium metal anode based on a gradient solid electrolyte, its preparation method, and its application. In this invention, the porous lithium-zinc alloy interface layer and the gradient high-dielectric filler polymer layer work synergistically to effectively guide the uniform deposition of lithium ions, inhibit dendrite growth, and reduce tip effects, thereby improving cycle life, reducing interface impedance and polarization voltage, and reducing volume expansion.

[0005] To achieve the above objectives, a first aspect of the present invention provides a lithium metal anode based on a gradient solid electrolyte, the lithium metal anode comprising, in sequence: a current collector, a porous lithium-zinc alloy interface layer, a lithium metal layer, and a gradient solid electrolyte layer; the gradient solid electrolyte layer comprises a polymer matrix and a high-dielectric filler that is gradient-distributed in the polymer matrix.

[0006] According to the present invention, preferably, the porous lithium-zinc alloy interface layer is prepared by a method comprising the following steps: (1) forming a polystyrene nanosphere template on the surface of the current collector; then performing zinc electroplating in an electroplating solution to fill the gaps between the templates; finally removing the template to obtain a porous zinc layer; (2) using a stepwise hot pressing process to composite the lithium metal foil with the porous zinc layer, wherein the part in contact with the porous zinc layer forms a porous lithium-zinc alloy interface layer, and the part not in contact is the lithium metal layer.

[0007] According to the present invention, preferably, in step (1), a polystyrene nanosphere colloidal solution is coated on the surface of the current collector and annealed to form a template; the diameter of the polystyrene nanospheres in the polystyrene nanosphere colloidal solution is 200-600 nm; the annealing temperature is 60-90℃. The electrolyte is a zinc plating electrolyte with a pH value of 4.0. The electroplating parameters are: pulse peak current density of 5-20 mA / cm² and electroplating time of 60-300 s. The porous zinc layer has a pore size of 200-500 nm, a porosity of 55%-80%, and a thickness of 0.5-5 μm.

[0008] In this invention, in step (1), the coating is preferably spin coating, scraping coating, dip coating, spray coating or gravure coating.

[0009] In this invention, preferably, the method for removing the template includes: soaking and dissolving the PS template in toluene and then ultrasonically treating it for 5-15 minutes.

[0010] According to the present invention, preferably, in step (2), the stepwise hot pressing process includes the following steps: a. First stage: Pre-compress for 1-3 minutes at 50-80℃ and 2-5MPa; b. Second stage: Final pressure is applied for 3-8 minutes at 100-120℃ and 8-15MPa. During the hot pressing process, the heating rate is 5-10℃ / min, and the pressure gradient change does not exceed 3MPa / min. Preferably, the thickness of the lithium metal foil is 20-50 μm.

[0011] According to the present invention, preferably, the concentration of the high dielectric filler in the solid electrolyte layer decreases from the near current collector side to the surface side along the thickness direction of the gradient solid electrolyte layer; Preferably, the gradient distribution of the high dielectric filler in the solid electrolyte layer is achieved by centrifugation; the centrifugation speed is 2000-4000 rpm and the time is 3-10 min; during centrifugation, the collector side is brought close to the inner wall of the centrifuge.

[0012] According to the present invention, preferably, in the gradient solid electrolyte layer, the polymer matrix is ​​a polyethylene oxide-lithium bis(trifluoromethanesulfonyl)imide system (PEO-LiTFSI system); in the polymer matrix, the molar ratio of polyethylene oxide to Li is (14-16):1; The high dielectric filler is selected from at least one of barium titanate (BaTiO3), barium strontium titanate, strontium titanate (SrTiO3), titanium dioxide (TiO2), and lead magnesium niobate (PMN-PT); The particle size of the high dielectric filler is 50-200 nm; The filler content is 15-35 wt% based on the total weight of polyethylene oxide and lithium bis(trifluoromethanesulfonyl)imide.

[0013] In this invention, the general formula for barium strontium titanate is Ba. 1-x Sr x TiO3, where 0 < x < 1.

[0014] According to the present invention, preferably, the gradient solid electrolyte layer is prepared by a method comprising the following steps: coating a uniform slurry containing a polymer matrix and a high dielectric filler onto the surface of a lithium metal layer, then centrifuging the negative electrode semi-finished product coated with the slurry to form a filler concentration gradient; finally, drying and hot pressing are performed to form a gradient solid electrolyte layer.

[0015] In this invention, the negative electrode semi-finished product coated with slurry sequentially includes: a current collector, a porous lithium-zinc alloy interface layer, a lithium metal layer, and a uniform slurry layer containing a polymer matrix and a high-dielectric filler.

[0016] According to the present invention, preferably, the centrifugation speed is 2000-4000 rpm and the time is 3-10 min; the drying is vacuum drying; the drying temperature is 60-80℃ and the time is 10-15 h; the hot pressing is carried out in an argon atmosphere; the hot pressing temperature is 80-120℃, the pressure is 5-15 MPa, and the time is 5-15 min.

[0017] A second aspect of the present invention provides a method for preparing the above-described lithium metal anode, the method comprising: S1. A polystyrene nanosphere template is formed on the surface of the current collector; then zinc electroplating is performed in the electroplating solution to fill the gaps between the templates; finally, the template is removed to obtain a porous zinc layer; S2. A step-by-step hot pressing process is used to composite lithium metal foil with a porous zinc layer. The part in contact with the porous zinc layer forms a porous lithium-zinc alloy interface layer, and the part not in contact is the lithium metal layer. S3. A uniform slurry containing a polymer matrix and a high-dielectric filler is coated onto the surface of a lithium metal layer. Then, the negative electrode semi-finished product coated with the slurry is placed in a centrifuge with the current collector side close to the inner wall of the centrifuge for centrifugation to form a filler concentration gradient. Finally, after drying and hot pressing, a gradient solid electrolyte layer is formed.

[0018] In this invention, the outer lithium-conducting layer employs a gradient distribution design of high-dielectric filler. Through centrifugation, a gradient distribution of high-dielectric filler is formed from top to bottom, with the filler quantity increasing. First, the gradient distribution creates dielectric force, driving Li+ to preferentially deposit towards the current collector, forming a bottom-preferred deposition mode. Second, the gradient distribution causes the electric field to decrease from the outside to the inside, creating a non-uniform electric field. The inner high-dielectric region is equivalent to an "electrostatic shielding layer," reducing the electric field intensity at the lithium deposition tip and inhibiting lithium dendrite growth. Third, the dielectric gradient matches the mechanical gradient of lithium deposition expansion (greater expansion in the inner layer), forming a dense lithium deposition from the current collector outwards, reducing interfacial shear stress and minimizing interfacial peeling and cracking. Simultaneously, using a polymer as a substrate provides elastic buffer space, cushioning the expansion and contraction of metallic lithium and optimizing the interface.

[0019] A third aspect of the present invention provides the application of the above-described lithium metal anode or the lithium metal anode prepared by the above-described preparation method in lithium-ion batteries.

[0020] The technical solution of the present invention has the following beneficial effects: The lithium metal anode of the present invention, with its porous lithium-zinc alloy interface layer and gradient high dielectric filler polymer layer working synergistically, can effectively guide the uniform deposition of lithium ions, suppress dendrite growth, and reduce tip effect, thereby improving cycle life, reducing interface impedance and polarization voltage, and reducing volume expansion.

[0021] This invention forms a composite lithium metal anode with an "ilene-lithiophilic-lithi-conducting" structure from the inside out through structural regulation (nanopores → alloy layer → gradient dielectric) and process innovation (template electroplating → stepwise hot pressing composite → centrifugation).

[0022] In this invention, a template-based porous zinc plating method is used to form a high-porosity substrate, precisely controlling the pore structure. After the zinc plating layer is lithiated, the high porosity of the original zinc layer is transformed into a large number of nanoscale LiZn4 grain boundaries, guiding the uniform and rapid deposition of lithium ions.

[0023] In this invention, the outer lithium-conducting layer is designed with a high dielectric filler gradient distribution to guide the rapid and uniform transfer of lithium ions.

[0024] Other features and advantages of the present invention will be described in detail in the following detailed description section. Attached Figure Description

[0025] The above and other objects, features and advantages of the present invention will become more apparent from the more detailed description of exemplary embodiments of the invention in conjunction with the accompanying drawings, wherein the same reference numerals generally represent the same components in the exemplary embodiments of the invention.

[0026] Figure 1 A flowchart illustrating a method for preparing a lithium metal anode based on a gradient solid electrolyte according to an embodiment of the present invention is shown.

[0027] Figure 2 A schematic structural diagram of a lithium metal anode based on a gradient solid electrolyte according to an embodiment of the present invention is shown.

[0028] Explanation of reference numerals in the attached figures: 1. Current collector; 2. Porous lithium-zinc alloy interface layer; 3. Lithium metal layer; 4. Gradient solid electrolyte layer. Detailed Implementation

[0029] Preferred embodiments of the invention will now be described in more detail. While preferred embodiments of the invention are described below, it should be understood that the invention can be implemented in various forms and should not be limited to the embodiments set forth herein. Rather, these embodiments are provided so that the invention will be thorough and complete, and will fully convey the scope of the invention to those skilled in the art.

[0030] The present invention is further illustrated by the following examples: In the following examples and comparative examples: the polystyrene nanospheres used were purchased from Xi'an Qiyue Biotechnology Co., Ltd.; the polyethylene oxide (PEO) used was purchased from Aoke Chemical, with a molecular weight Mw = 500,000 g / mol and a purity ≥99%; and the polyvinylpyrrolidone used was purchased from Wuxi Yatai United Chemical Co., Ltd., with the brand name K30.

[0031] Example 1

[0032] like Figure 2 As shown, this embodiment provides a lithium metal anode based on a gradient solid electrolyte, which sequentially includes: a current collector 1, a porous lithium-zinc alloy interface layer 2, a lithium metal layer 3, and a gradient solid electrolyte layer 4; the gradient solid electrolyte layer 4 includes a polymer matrix and a high-dielectric filler that is gradient distributed in the polymer matrix.

[0033] like Figure 1 As shown, the specific preparation method is as follows: 1. Current collector pretreatment (1) Take an electrolytic copper foil with a thickness of 10 μm and clean it by ultrasonication for 15 minutes each in acetone, ethanol and deionized water. (2) After being dried with nitrogen, place it in a vacuum oven at 120°C for 2 hours.

[0034] 2. Preparation of porous zinc layer

[0035] (1) Prepare a 10% polystyrene nanosphere colloidal solution (polystyrene nanosphere particle size 300±20nm); the specific preparation method is as follows: mix polystyrene nanospheres, polyvinylpyrrolidone and deionized water evenly to obtain a polystyrene nanosphere colloidal solution; wherein, based on the total weight of the polystyrene nanosphere colloidal solution, the content of the polystyrene nanospheres is 10wt%, the content of polyvinylpyrrolidone is 0.3wt%, and the balance is deionized water.

[0036] (2) Spin coat the copper foil surface at 3000 rpm for 30 seconds, and anneal at 70°C for 30 minutes to form a hexagonal close-packed template; (3) Electroplating solution composition: Deionized water is used as solvent, containing 0.1 mol / L zinc sulfate (ZnSO4·7H2O), 0.05 mol / L boric acid (H3BO3) and 0.01 mol / L sodium dodecyl sulfate (SDS). The pH value of the electroplating solution is adjusted to 4.0 with 1 mol / L dilute sulfuric acid. (4) Zinc electroplating is performed in the electroplating solution to fill the gaps in the template; pulse electroplating is used: on time 10ms, off time 20ms, peak current density 15mA / cm², and electroplating time 180 seconds. (5) The sample was immersed in toluene solvent and ultrasonically treated for 5 minutes to remove the template, and a porous zinc layer with a thickness of 1.2 micrometers, a pore size of 300 nm and a porosity of 65% was obtained.

[0037] 3. Lithium layer composite

[0038] (1) Operate in an argon glove box (H2O<0.1ppm, O2<0.1ppm); (2) A 25 μm thick lithium foil is coated onto a porous zinc layer; a. First stage: Pre-compression at 60℃ and 3MPa for 2 minutes; b. Second stage: The temperature is increased to 110℃ at 10℃ / min, and the pressure is linearly increased to 12MPa at 3MPa / min, and held for 5 minutes; finally, the part in contact with the porous zinc layer forms a porous lithium-zinc alloy interface layer 2, and the part not in contact is a metallic lithium layer 3.

[0039] 4. Gradient electrolyte preparation

[0040] (1) Base solution: PEO and LiTFSI are dissolved in acetonitrile at a molar ratio of PEO:Li = 15:1. The mass ratio of acetonitrile to the total mass of PEO+LiTFSI is 9. (2) Based on the total weight of polyethylene oxide and lithium bis(trifluoromethanesulfonyl)imide, add 15wt% BaTiO3 nanoparticles (particle size 100±20nm), and ball mill and mix for 4 hours to obtain a uniform slurry containing polymer matrix and high dielectric filler. (3) Coating a uniform slurry containing a polymer matrix and a high dielectric filler onto the surface of a lithium metal layer with a coating thickness of 20 μm, and then placing the negative electrode semi-finished product coated with the slurry into a centrifuge, with the current collector side close to the inner wall of the centrifuge, and centrifuging at 3000 rpm for 5 minutes to form a filler concentration gradient. (4) After vacuum drying at 60°C for 12 hours, hot pressing is carried out in an argon atmosphere. The hot pressing is carried out at 80°C and 5MPa for 5 minutes to form a gradient solid electrolyte layer 4. The concentration of high dielectric filler in the solid electrolyte layer decreases from the near current collector side to the surface side along the thickness direction of the gradient solid electrolyte layer.

[0041] Example 2

[0042] like Figure 2 As shown, this embodiment provides a lithium metal anode based on a gradient solid electrolyte, which sequentially includes: a current collector 1, a porous lithium-zinc alloy interface layer 2, a lithium metal layer 3, and a gradient solid electrolyte layer 4; the gradient solid electrolyte layer 4 includes a polymer matrix and a high-dielectric filler that is gradient distributed in the polymer matrix.

[0043] The lithium metal anode based on a gradient solid electrolyte was prepared according to the method in Example 1, with the only difference being as follows: In step 2, the polystyrene nanospheres have a particle size of 500±20nm; the annealing temperature is 85℃; the peak current density is 20mA / cm²; and the electroplating time is 300 seconds; finally, a porous zinc layer with a thickness of 4.5 micrometers, a pore size of 500nm, and a porosity of 80% is obtained.

[0044] In step 3, the hot pressing process is adjusted as follows: a. First stage: pre-press for 2 minutes at 80℃ and 5MPa pressure; b. Second stage: heat up to 120℃ at 10℃ / min, and simultaneously linearly pressurize to 15MPa at 3MPa / min, and hold for 3 minutes; In step 4, 20 wt% Ba is added based on the total weight of polyethylene oxide and lithium bis(trifluoromethanesulfonyl)imide. 0.7 Sr 0.3 TiO3 filler (particle size 70±20nm).

[0045] Example 3

[0046] like Figure 2As shown, this embodiment provides a lithium metal anode based on a gradient solid electrolyte, which sequentially includes: a current collector 1, a porous lithium-zinc alloy interface layer 2, a lithium metal layer 3, and a gradient solid electrolyte layer 4; the gradient solid electrolyte layer 4 includes a polymer matrix and a high-dielectric filler that is gradient distributed in the polymer matrix.

[0047] The lithium metal anode based on a gradient solid electrolyte was prepared according to the method in Example 1, with the only difference being as follows: In step 2, the polystyrene nanospheres have a particle size of 200±20nm; the peak current density is 5mA / cm²; and the electroplating time is 60 seconds. Finally, a porous zinc layer with a thickness of 0.6 micrometers, a pore size of 200nm, and a porosity of 65% is obtained.

[0048] In step 3, the hot pressing process is adjusted as follows: a. First stage: pre-press for 3 minutes at 50℃ and 2MPa pressure; b. Second stage: heat up to 100℃ at 10℃ / min, and simultaneously linearly pressurize to 8MPa at 3MPa / min, and hold for 8 minutes; In step 4, 15 wt% TiO2 (particle size 100 ± 20 nm) is added based on the total weight of polyethylene oxide and lithium bis(trifluoromethanesulfonyl)imide.

[0049] Comparative Example 1

[0050] The specific preparation method of the lithium metal anode in this comparative example is as follows: Steps 1-3 are the same as in Example 1. The only difference between step 4 and Example 1 is step (3), in which centrifugation is not performed during electrolyte preparation; that is, step (3) specifically involves coating a uniform slurry containing a polymer matrix and a high dielectric filler onto the surface of a lithium metal layer with a coating thickness of 20 μm.

[0051] Comparative Example 2

[0052] The specific preparation method of the lithium metal anode in this comparative example is as follows: The only difference between this comparative example and Example 1 is that the electrolyte layer is not coated, i.e., step 4 is removed.

[0053] Comparative Example 3

[0054] This comparative example provides a pure lithium anode, and the specific preparation method is as follows: 1. Current collector pretreatment (1) Take a 10μm electrolytic copper foil and ultrasonically clean it for 15 minutes each in acetone, ethanol and deionized water. (2) After being dried with nitrogen, place it in a vacuum oven at 120°C for 2 hours.

[0055] 2. Lithium layer composite

[0056] (1) Operate in an argon glove box (H2O<0.1ppm, O2<0.1ppm); (2) A 25μm thick lithium foil is directly applied to the surface of the copper foil. (3) Single-step hot pressing: maintain at 100℃ and 10MPa pressure for 5 minutes; The pure lithium anode structure prepared in this comparative example has the following characteristics: (1) no interface modification layer; (2) the lithium / copper interface is a physical contact without alloying reaction.

[0057] Comparative Example 4

[0058] This comparative example provides a homogeneous electrolyte lithium anode, and the specific preparation method is as follows: 1. The current collector and lithium layer composite process is the same as steps 1-2 of Comparative Example 3; 2. Preparation of homogeneous electrolytes (1) Base solution: PEO and LiTFSI are dissolved in acetonitrile at a molar ratio of PEO:Li = 15:1. The mass ratio of acetonitrile to the total mass of PEO+LiTFSI is 9. (2) Based on the total weight of polyethylene oxide and lithium bis(trifluoromethanesulfonyl)imide, add 15wt% BaTiO3 nanoparticles (particle size 100±20nm), and ball mill and mix for 4 hours to obtain a uniform slurry containing polymer matrix and high dielectric filler. (3) A uniform slurry containing a polymer matrix and a high dielectric filler is coated on the surface of the lithium metal layer with a coating thickness of 20 μm; then, after vacuum drying at 60 °C for 12 hours, it is hot-pressed in an argon atmosphere at 80 °C and 5 MPa for 5 minutes to form a homogeneous electrolyte layer.

[0059] The homogeneous electrolyte lithium anode structure prepared in this comparative example is characterized by: uniform distribution of BaTiO3 nanoparticles without gradient control.

[0060] Test case

[0061] 1. Battery assembly

[0062] (1) Button cell assembly (CR2032)

[0063] Negative electrode: The lithium metal negative electrode prepared in the examples / comparative examples was punched into a disc with a diameter of 12 mm; Positive electrode: Lithium iron phosphate (LiFePO4) is used. The active material: conductive carbon black: PVDF = 8:1:1 (weight ratio) is homogenized into a slurry, coated on aluminum foil (area capacity 1mAh / cm²), dried, and then punched into round pieces with a diameter of 10mm. The pieces are then vacuum dried at 120℃ for 12h. Electrolyte: 1M LiPF6 in EC:DMC (1:1 vol%); Membrane: Standard 9μm PE membrane; Assembly: Button cells were fabricated in an argon glove box (H2O < 0.1 ppm, O2 < 0.1 ppm); (2) Symmetrical battery assembly Positive and Negative Electrodes: The lithium metal negative electrode prepared in the examples / comparative examples was punched into a disc with a diameter of 12 mm; Electrolyte: 1M LiPF6 in EC:DMC (1:1 vol%); Membrane: Standard 9μm PE membrane; Assembly: Symmetric cells were prepared in an argon glove box (H2O < 0.1 ppm, O2 < 0.1 ppm); 2. Testing (1) Cyclic performance test Equipment: Xinwei Battery Testing System (CT-4008) Method: The above-mentioned button cells were charged at a constant current and constant voltage of 0.1C and discharged at a constant current of 0.1C, and cycled at a voltage of 2.5-3.8V. The test was terminated when the capacity decayed to 80%. (2) Interface impedance (EIS) test Equipment: Electrochemical workstation Method: The above button cells were tested for EIS at a frequency range of 100kHz to 0.1Hz and an amplitude of 10mV. The data were compared with the interface impedance (Rct) corresponding to the semicircle in the high-frequency region. (3) Polarization voltage test Equipment: Xinwei Battery Testing System (CT-4008) Method: The above symmetrical battery was charged and discharged 10 times at a constant current density of 1 mA / cm², with the capacity limited to 1 mAh / cm². The voltage-time curve of the 10th cycle was taken, and the charging plateau voltage (V) was read. charge ) and discharge platform voltage (V discharge ), calculate the polarization voltage ΔV = |V charge - V discharge | (4) Expansion rate test Equipment: Micrometer Method: First, the thickness (T0) of the composite lithium metal anode was measured. Then, the assembled coin cell was subjected to a cyclic test, and after 50 cycles, the thickness (T0) of the composite lithium metal anode was measured again. 50 ), calculate the expansion rate = ((T) 50 -T0) / T0) 100%; (5) Data comparison is shown in the table below. Table 1

[0064] The test results of Examples 1-3 and Comparative Examples 1-4 show that the Li-Zn alloy layer and the gradient high dielectric filler polymer layer work together to effectively guide the uniform deposition of lithium ions, inhibit dendrite growth, and reduce the tip effect, thereby improving cycle life, reducing interface impedance and polarization voltage, and reducing volume expansion.

[0065] The various embodiments of the present invention have been described above. These descriptions are exemplary and not exhaustive, nor are they limited to the disclosed embodiments. Many modifications and variations will be apparent to those skilled in the art without departing from the scope and spirit of the described embodiments.

Claims

1. A lithium metal anode based on a gradient solid-state electrolyte, characterized in that, The lithium metal anode comprises, in sequence: a current collector, a porous lithium-zinc alloy interface layer, a lithium metal layer, and a gradient solid electrolyte layer; the gradient solid electrolyte layer comprises a polymer matrix and a high-dielectric filler that is gradient distributed in the polymer matrix.

2. The lithium metal anode of claim 1, wherein, The porous lithium-zinc alloy interface layer is prepared by a method including the following steps: (1) forming a polystyrene nanosphere template on the surface of the current collector; then performing zinc electroplating in the electroplating solution to fill the gaps between the templates; finally removing the template to obtain a porous zinc layer; (2) using a stepwise hot pressing process to combine the lithium metal foil with the porous zinc layer, the part in contact with the porous zinc layer forming a porous lithium-zinc alloy interface layer, and the part not in contact being the lithium metal layer.

3. The lithium metal anode of claim 2, wherein, In step (1), a polystyrene nanosphere colloidal solution is coated on the surface of the current collector and annealed to form a template; the diameter of the polystyrene nanospheres in the polystyrene nanosphere colloidal solution is 200-600 nm; the annealing temperature is 60-90℃. The electrolyte is a zinc plating electrolyte with a pH value of 4.

0. The electroplating parameters are: pulse peak current density of 5-20 mA / cm² and electroplating time of 60-300 s. The porous zinc layer has a pore size of 200-500 nm, a porosity of 55%-80%, and a thickness of 0.5-5 μm.

4. The lithium metal anode of claim 2, wherein, In step (2), the stepwise hot pressing process includes the following steps: a. First stage: Pre-compress for 1-3 minutes at 50-80℃ and 2-5MPa; b. Second stage: Final pressure is applied for 3-8 minutes at 100-120℃ and 8-15MPa. During the hot pressing process, the heating rate is 5-10℃ / min, and the pressure gradient change does not exceed 3MPa / min. Preferably, the thickness of the lithium metal foil is 20-50 μm.

5. The lithium metal anode of claim 1, wherein, The concentration of the high dielectric filler in the solid electrolyte layer decreases from the near current collector side to the surface side along the thickness direction of the gradient solid electrolyte layer. Preferably, the gradient distribution of the high dielectric filler in the solid electrolyte layer is achieved by centrifugation; the centrifugation speed is 2000-4000 rpm and the time is 3-10 min; during centrifugation, the collector side is brought close to the inner wall of the centrifuge.

6. The lithium metal anode of claim 1, wherein, In the gradient solid electrolyte layer, the polymer matrix is ​​a lithium bis(trifluoromethanesulfonyl)imide system; in the polymer matrix, the molar ratio of polyethylene oxide to Li is (14-16):1; The high dielectric filler is selected from at least one of barium titanate, barium strontium titanate, strontium titanate, titanium dioxide, and lead magnesium niobate; The particle size of the high dielectric filler is 50-200 nm; The filler content is 15-35 wt% based on the total weight of polyethylene oxide and lithium bis(trifluoromethanesulfonyl)imide.

7. The lithium metal anode according to claim 1, wherein, The gradient solid electrolyte layer is prepared by a method comprising the following steps: coating a uniform slurry containing a polymer matrix and a high dielectric filler onto the surface of a lithium metal layer; then placing the negative electrode semi-finished product coated with the slurry into a centrifuge, with the current collector side close to the inner wall of the centrifuge, and centrifuging it to form a filler concentration gradient; finally, drying and hot pressing are performed to form a gradient solid electrolyte layer.

8. The lithium metal anode according to claim 7, wherein, Centrifugation is performed at 2000-4000 rpm for 3-10 min; drying is done under vacuum at 60-80℃ for 10-15 h; hot pressing is carried out in an argon atmosphere at 80-120℃ at 5-15 MPa for 5-15 min.

9. The method for preparing the lithium metal anode according to any one of claims 1-8, characterized in that, The preparation method includes: S1. A polystyrene nanosphere template is formed on the surface of the current collector; then zinc electroplating is performed in the electroplating solution to fill the gaps between the templates; finally, the template is removed to obtain a porous zinc layer; S2. A step-by-step hot pressing process is used to composite lithium metal foil with a porous zinc layer. The part in contact with the porous zinc layer forms a porous lithium-zinc alloy interface layer, and the part not in contact is the lithium metal layer. S3. A uniform slurry containing a polymer matrix and a high-dielectric filler is coated onto the surface of a lithium metal layer. Then, the negative electrode semi-finished product coated with the slurry is placed in a centrifuge with the current collector side close to the inner wall of the centrifuge for centrifugation to form a filler concentration gradient. Finally, after drying and hot pressing, a gradient solid electrolyte layer is formed.

10. The application of the lithium metal anode according to any one of claims 1-8 or the lithium metal anode prepared by the preparation method according to claim 9 in a lithium-ion battery.

Images