Lithium-philic porous interface functional layer and preparation method and application thereof

Abstract

The invention discloses a lithium-loving porous interface functional layer as well as a preparation method and application thereof. The preparation method comprises the following steps: dissolving a binder in a non-polar solvent to form a solution A; adding a lithium-loving porous framework material and an electronic conductor into the solution A through a water bath synthesis method, and stirring and reacting to form a solution B; adding a small amount of ionic conductor into the solution B for multiple times to form a solution C; and coating a current collector with the solution C, and drying to form the lithium-loving porous interface functional layer on the current collector. The invention also discloses a lithium-loving porous interface functional layer prepared by the preparation method, and a lithium negative electrode containing the functional layer. The lithium-loving porous interface functional layer comprises the lithium-loving framework, the hole wall of the lithium-loving framework comprises the electronic conductor, and the hole internally comprises the ionic conductor, so that the infinite volume expansion of lithium can be limited, the lithium ion flow is homogenized, the effective current density on the surface is reduced, and the growth of lithium dendrites is inhibited; and the high-capacity and long-cycle performance of the all-solid-state lithium metal battery is realized.

Description

Technical Field

[0001] This invention relates to the field of lithium battery technology, and more specifically, to a lithium-loving porous interface functional layer, its preparation method, and its application. Background Technology

[0002] While graphite anodes offer high safety and long cycle life, their theoretical capacity is limited, resulting in a relatively low energy density (approximately 150-250 Wh·kg⁻¹). -1 However, lithium metal anodes are relatively heavy and thick. Compared to graphite anodes, lithium metal anodes have a higher theoretical specific capacity (3860 mAh / g) and a lower electrochemical potential, making them one of the most promising anode materials. The application of lithium metal anodes can significantly improve the energy density of solid-state batteries, giving them broad application prospects in electric vehicles, energy storage systems, and other fields. Furthermore, lithium metal anodes also feature high charge-discharge efficiency and strong safety in solid-state batteries. Meanwhile, thin lithium metal anodes and anode-free configurations further reduce weight and thickness, significantly improving battery energy density (reaching >400 Wh·kg⁻¹). -1 and >500 Wh·kg -1 ).

[0003] However, lithium metal anodes still present several challenges. The SEI film formed during cycling exhibits significant inhomogeneity in chemical composition, microstructure, and ion conductivity. This leads to uneven lithium-ion flux distribution and chaotic nucleation site distribution, inducing lithium dendrite growth and, in severe cases, "dead lithium," resulting in internal short circuits within the battery. Therefore, constructing an SEI layer with a stable structure and uniform properties is crucial for suppressing side reactions and dendrite growth. Furthermore, lithium metal undergoes creep under high pressure, easily triggering battery short circuits; while under low pressure, poor contact occurs at the solid-solid interface. The lithium metal anode itself suffers from severe volume expansion, and interface degradation during cycling is prominent, significantly reducing battery cycle life. Summary of the Invention

[0004] To address the aforementioned technical problems, the present invention aims to provide a lithiophilic porous interface functional layer, its preparation method, and its application. This invention modifies lithium metal anodes using a lithiophilic porous interface functional layer with a lithiophilic porous framework structure. The pore walls of this lithiophilic porous framework structure are electronic conductors, while the interior of the pores is an ion conductor. The resulting porous lithiophilic framework can homogenize lithium-ion flux and form a rapid lithium diffusion path, transforming the surface lithium "deposition / stripping" process into lithium diffusion transport along the lithiophilic framework.

[0005] The porous lithiophilic framework of this invention, used as a pre-storage lithium matrix, not only restricts the unlimited volume expansion of lithium but also homogenizes the lithium-ion flow, reduces the effective surface current density, and constructs a stable surface solid-electrolyte interface (SEI) with fast ion transport characteristics, thereby suppressing lithium dendrite growth. Further increases in current density and lithium plating capacity would raise more safety concerns. When lithium metal is matched with a solid electrolyte, both safety issues can be resolved, and the specific energy of the battery system can be improved.

[0006] The objective of this invention is achieved through the following technical solution: In a first aspect, the present invention provides a method for preparing a lithium-loving porous interface functional layer, comprising the following steps: S1. Dissolve the adhesive in a non-polar solvent to form solution A; S2. By means of water bath synthesis, a lithiophilic porous framework material and an electronic conductor are added to solution A and stirred to react, forming solution B; S3. Add the ionic conductor to solution B in small amounts multiple times to form solution C; S4. Apply solution C onto the current collector, and after drying, a lithium-loving porous interface functional layer is formed on the current collector.

[0007] As some specific embodiments of the present invention, in step S1, the binder is selected from at least one of styrene-butadiene rubber (BR), polypropylene carbonate (PPC), polyisobutylene (PIB), and polyvinylidene fluoride (PVDF). The binder has good flexibility to buffer the volume change of the active material during charging and discharging; it does not react harmfully with highly active solid electrolytes (especially sulfide electrolytes); it has a certain lithium-ion conductivity to optimize the ion transport path inside the electrode; and it has good process adaptability to be suitable for different electrode preparation processes (such as dry or wet coating).

[0008] As some specific embodiments of the present invention, in step S1, the nonpolar solvent is selected from at least one of p-xylene (PX), toluene (TL), tetrahydrofuran (THF), and butyl ether (DBE).

[0009] As some specific embodiments of the present invention, in step S1, the concentration of the binder in solution A is 0.5wt%-1.5wt%.

[0010] As some specific embodiments of the present invention, in step S2, the lithium-loving porous framework material includes a carbon-based porous framework material or a metal-based porous framework material.

[0011] Furthermore, the carbon-based porous framework material is selected from any one of porous carbon fibers, three-dimensional porous graphene, three-dimensional porous carbon nanotubes, and biomass-derived porous carbon.

[0012] Specifically, the porous carbon fiber is spun from a spinning solution composed of a pore-forming agent, a polymer, and an organic solvent, and then pre-oxidized and carbonized; the polymer is selected from any one of polyimide, polyacrylonitrile, cellulose, and polyvinyl alcohol; the pore-forming agent is selected from polyvinylpyrrolidone or polymethyl methacrylate; and the organic solvent is selected from N,N-dimethylformamide (DMF), dimethyl sulfoxide (DMSO), or N-methylpyrrolidone (NMP).

[0013] Specifically, the three-dimensional porous graphene (3D-PG) is prepared by first preparing graphene oxide (GO) using a modified Hummers method, and then using polystyrene (PS) as a sacrificial template. The three-dimensional porous graphene has a porous network structure and exhibits high mechanical strength.

[0014] Furthermore, the metal-based porous framework material is selected from metal oxide porous framework materials or metal sulfide porous framework materials; the metal oxide porous framework material is selected from any one of aluminosilicates with microporous structures, mesoporous TiO2, and mesoporous ZrO2; the metal sulfide porous framework material is selected from any one of MoS2, Zn4S, and Mn4S porous framework materials.

[0015] Specifically, the metal sulfide porous framework material is obtained by chemical vapor deposition. First, a transition metal oxide nanowire array is grown on the surface of carbon cloth, and MOF material is grown in situ on this substrate. Then, the metal sulfide porous framework material is obtained by sulfidation.

[0016] By using the aforementioned metal compounds that are inherently electrochemically active to create porous structures, and then using them as electrode materials, the pores facilitate the insertion and extraction of ions.

[0017] As some specific embodiments of the present invention, in step S2, the electronic conductor is a metal conductor, and the metal conductor is selected from at least one of aluminum (Al), magnesium (Mg), indium (In), tungsten (W), silver (Ag), and tin (Sn).

[0018] As some specific embodiments of the present invention, in step S2, the temperature of the stirring reaction is 50~60℃ and the time is 4-8h.

[0019] As some specific embodiments of the present invention, in step S3, the ion conductor includes an oxide solid electrolyte or a sulfide solid electrolyte.

[0020] Specifically, the oxide solid electrolyte is selected from Li7La3Zr2O 12 (LLZO), Li 1+x Al x Ti2-x (PO4)3(LATP), Li 1+x Al x Ge 2-x At least one of (PO4)3(LAGP); And / or, the sulfide solid electrolyte is selected from Li 10 GeP2S 12 Li7P3S 11 At least one of Li6PS5Cl.

[0021] As some specific embodiments of the present invention, in step S4, the coating method is selected from any one of spin coating, spraying, and magnetron sputtering.

[0022] As some specific embodiments of the present invention, in step S4, the current collector is selected from copper foil or stainless steel foil.

[0023] In a second aspect, the present invention provides a lithium-loving porous interface functional layer, which is prepared by any of the preparation methods described above, and includes a lithium-loving porous framework, an electronic conductor and an ionic conductor, wherein the electronic conductor is uniformly dispersed on the pore walls of the lithium-loving porous framework and the ionic conductor is dispersed in the pores of the lithium-loving porous framework.

[0024] As some specific embodiments of the present invention, the mass percentage of the electronic conductor in the lithiophilic porous interface functional layer is 5%-20%; The ionic conductor constitutes 20%-50% of the mass of the lithiophilic porous interface functional layer.

[0025] As some specific embodiments of the present invention, the average pore size D of the lithiophilic porous framework is 0.1~5 μm, and the pore volume V is 0.1~0.5 cc / g; The average particle size of the electronic conductor is d1 = 0.01~1 μm, and d1 / D = 0.2~0.5; The average particle size of the ionic conductor is d2 = 0.05~2μm, and d2 / D = 0.5~0.8.

[0026] As some specific embodiments of the present invention, the lithium-loving porous interface functional layer further includes a binder, wherein the mass percentage of the binder in the lithium-loving porous interface functional layer is 0.5wt%-2wt%.

[0027] Thirdly, the present invention provides a lithium metal anode modified with a lithium-loving porous framework, comprising a lithium-loving porous interface functional layer as described in any of the above claims, and further comprising a lithium foil.

[0028] As some specific embodiments of the present invention, the thickness of the lithium-loving porous interface functional layer is 1µm-30µm; the thickness of the lithium foil is 5µm-20µm.

[0029] Compared with the prior art, the present invention has the following beneficial effects: 1) The SEI film formed by the lithium anode during cycling exhibits significant inhomogeneity in chemical composition, microstructure, and ion conductivity, resulting in uneven lithium-ion flux distribution and chaotic nucleation site distribution. The porous lithiophilic framework of this invention can uniformly distribute lithium-ion flux, forming a rapid lithium diffusion path. This transforms the surface lithium "deposition / stripping" process into lithium diffusion transport along the lithiophilic framework, thereby constructing an SEI layer with a stable structure and uniform properties.

[0030] 2) Poor contact is common at the solid-solid interface between lithium metal and the solid electrolyte, resulting in low ion transport efficiency. In the framework structure of this invention, the pore walls contain electronic conductors, and the pores contain ion conductors, with the ion conductors being the solid electrolyte. The resulting ion-conducting / electron framework not only restricts the unlimited volume expansion of lithium but also homogenizes the lithium ion flow, reduces the effective surface current density, and thus inhibits the growth of lithium dendrites; thereby achieving high-capacity, long-cycle performance in all-solid-state lithium metal batteries. Detailed Implementation

[0031] The present invention will now be described in detail with reference to specific embodiments. These embodiments will help those skilled in the art to further understand the present invention, but do not limit the invention in any way. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention. These all fall within the scope of protection of the present invention.

[0032] Example 1 1. Preparation of the positive electrode: Take lithium nickel cobalt manganese oxide (LiNiO) as the positive electrode active material. 0.8 Co 0.1 Mn 0.1 O2 (NCM811), sulfide electrolyte Li6PS5Cl, and conductive agent VGCF were mixed in a mass ratio of 70:28:2 and ball-milled at 300 r / min for 2 h. The mixture was ball-milled three times to prepare a composite cathode.

[0033] 2. Preparation of electrolyte: Weigh LiCl, Li2S, and P2S5 into a mortar according to the stoichiometric ratio of Li6PS5Cl, and grind manually until the powder is evenly mixed to obtain the precursor. Place the precursor in a muffle furnace, introduce argon gas to remove impurity gases in the reaction zone, heat to 650℃, and ensure that the argon gas flows at a low speed to remove excess S and avoid contaminating the product to prepare the sulfide electrolyte.

[0034] 3. Preparation of porous lithiophilic interface functional layer: (1) Polyimide is spun into fibers, and then pre-oxidized and carbonized to produce porous carbon fibers, so that the particle size D of the porous carbon fibers is 2µm and the pore volume V is 0.5 cc / g. (2) Prepare a 1.5 wt% p-xylene solution containing styrene-butadiene rubber (BR) to form solution A; (3) By water bath synthesis method, porous carbon fiber and Al powder with a particle size d1 of 0.8µm are first added to solution A, the stirring temperature is 60℃, and the stirring is carried out for 4-8h to make Al uniformly dispersed on the pore wall of carbon fiber to form mixed solution B. (4) Add small amounts of Li6PS5Cl with a particle size d2 of 1µm to mixed solution B to form mixed solution C; (5) The mixed solution C is sprayed onto the copper foil and dried to obtain a porous lithium-loving interface functional layer.

[0035] In the prepared lithiophilic interface functional layer, the mass percentage of the lithiophilic porous framework is 65%, the mass percentage of the ionic conductor is 26 wt%, the mass percentage of the electronic conductor is 8 wt%, and the mass percentage of the binder is 1 wt%.

[0036] 4. Battery assembly After cleaning and drying the battery mold, place it in a glove box filled with Ar gas. First, weigh 100 mg of sulfide electrolyte into the mold and pressurize it at 200 MPa for 1 min. Then, weigh 28.5 mg of composite positive electrode material and add it to the current collector (aluminum foil), and pressurize it at 300 MPa for 1 min. The negative electrode side consists of a porous lithium-loving interface functional layer, lithium foil, and current collector (copper foil), and is pressurized at 200 MPa for 1 min. Place the assembled pressure battery mold on a pressure device, pressurize it to 1 ton, and then place it in a constant temperature chamber at 25°C to stand.

[0037] Comparative Examples 1-7 Comparative Examples 1-7 were prepared according to the method of Example 1. Compared with Example 1, one or more of the following parameters of porous framework were adjusted: particle size D, pore volume V, electronic conductor particle size d1, electronic conductor particle size d2, d1 / D, d2 / D, as shown in Table 1.

[0038] Comparative Example 8 The difference from Example 1 is that it does not contain a lithiophilic porous framework, and the interface functional layer only contains electronic and ionic conductors. The remaining steps are the same as in Example 1.

[0039] Comparative Example 9 In preparing the porous lithiophilic interface functional layer, only the porous framework is used as the raw material, and no ionic conductors or electronic conductors are set. The remaining steps are carried out in accordance with Example 1.

[0040] Comparative Example 10 In preparing the porous lithiophilic interface functional layer, a porous framework and electronic conductors are used, but no ionic conductors are provided. The remaining steps are carried out in accordance with Example 1.

[0041] Comparative Example 11 In preparing the porous lithiophilic interface functional layer, a porous framework and ionic conductors are used, but no electronic conductors are provided. The remaining steps are carried out in accordance with Example 1.

[0042] Comparative Example 12 Without a porous lithium-loving interface functional layer, the remaining steps are performed as described in Example 1.

[0043] The parameters for the embodiments and comparative examples are shown in Table 1 below: Table 1

[0044] The assembled batteries from the above embodiments and comparative examples were subjected to full-cell cycle performance tests. The cycle steps were set to 0.1C for 3 cycles and 0.5C for 1000 cycles, with a voltage range of 2.5V-4.3V. The test results are shown in Table 2 below: Table 2 Battery Cycle Performance Test Results

[0045] As shown in Table 2 above, this invention forms a functional layer at the lithium metal interface. This functional layer is dominated by a lithium-philic porous framework, with the pore walls acting as conductors of electrons and the pores themselves acting as conductors of ions. By limiting the pore size, pore volume, and particle size of the electronic and ionic conductors of the framework, the resulting lithium-philic porous interface functional layer is composed of a lithium-philic porous framework, with the pore walls acting as electronic conductors and the pores themselves acting as ionic conductors. This interface functional layer can uniformly distribute lithium-ion flux, and the framework forms a rapid lithium diffusion path, transforming the surface lithium "deposition / stripping" process into lithium diffusion transport along the lithium-philic framework, thereby increasing the number of cycles and achieving high-capacity, long-cycle performance in all-solid-state lithium metal batteries.

[0046] The specific embodiments of the present invention have been described above. It should be understood that the present invention is not limited to the specific embodiments described above, and those skilled in the art can make various modifications or variations within the scope of the claims, which do not affect the essence of the present invention.

Claims

1. A method for preparing a lithiophilic porous interface functional layer, characterized in that, Includes the following steps: S1. Dissolve the adhesive in a non-polar solvent to form solution A; S2. By means of water bath synthesis, a lithiophilic porous framework material and an electronic conductor are added to solution A and stirred to react, forming solution B; S3. Add the ionic conductor to solution B in small amounts multiple times to form solution C; S4. Apply solution C onto the current collector, and after drying, a lithium-loving porous interface functional layer is formed on the current collector.

2. The preparation method according to claim 1, characterized in that, In step S1, the adhesive is selected from at least one of styrene-butadiene rubber, polypropylene carbonate, polyisobutylene, and polyvinylidene fluoride; And / or, the nonpolar solvent is selected from at least one of p-xylene, toluene, tetrahydrofuran, and butyl ether; In solution A, the concentration of the binder is 0.5wt%-1.5wt%.

3. The preparation method according to claim 1, characterized in that, In step S2, the lithiophilic porous framework material includes a carbon-based porous framework material or a metal-based porous framework material. The carbon-based porous framework material is selected from any one of porous carbon fiber, three-dimensional porous graphene, three-dimensional porous carbon nanotubes, and biomass-derived porous carbon. The metal-based porous framework material is selected from metal oxide porous framework materials or metal sulfide porous framework materials; the metal oxide porous framework material is selected from any one of aluminosilicates with microporous structures, mesoporous TiO2, and mesoporous ZrO2; the metal sulfide porous framework material is selected from any one of MoS2, Zn4S, and Mn4S porous framework materials.

4. The preparation method according to claim 1, characterized in that, In step S2, the electronic conductor is a metallic conductor, and the metallic conductor is selected from at least one of aluminum, magnesium, indium, tungsten, silver, and tin; And / or, in step S2, the temperature of the stirring reaction is 50~60℃ and the time is 4-8h.

5. The preparation method according to claim 1, characterized in that, In step S3, the ion conductor includes an oxide solid electrolyte or a sulfide solid electrolyte; The oxide solid electrolyte is selected from Li7La3Zr2O 12 Li 1+x Al x Ti 2-x (PO4)3, Li 1+x Al x Ge 2-x At least one of (PO4)3; The sulfide solid electrolyte is selected from Li 10 GeP2S 12 Li7P3S 11 At least one of Li6PS5Cl.

6. The preparation method according to claim 1, characterized in that, In step S4, the coating method is selected from any one of spin coating, spray coating, and magnetron sputtering; And / or, in step S4, the current collector is selected from copper foil or stainless steel foil.

7. A lithiophilic porous interface functional layer, characterized in that, Prepared by the preparation method according to any one of claims 1-6, comprising a lithium-loving porous framework, an electronic conductor, and an ionic conductor, wherein the electronic conductor is uniformly dispersed on the pore walls of the lithium-loving porous framework, and the ionic conductor is dispersed in the pores of the lithium-loving porous framework.

8. The lithiophilic porous interface functional layer according to claim 7, characterized in that, The electronic conductor constitutes 5%-20% of the mass of the lithium-loving porous interface functional layer; the ionic conductor constitutes 20%-50% of the mass of the lithium-loving porous interface functional layer. And / or, the lithiophilic porous interface functional layer further includes a binder, wherein the mass percentage of the binder in the lithiophilic porous interface functional layer is 0.5wt%-2wt%.

9. The lithiophilic porous interface functional layer according to claim 7, characterized in that, The average pore size D of the lithiophilic porous framework is 0.1~5 μm, and the pore volume V is 0.1~0.5 cc / g; The average particle size of the electronic conductor is d1 = 0.01~1 μm, and d1 / D = 0.2~0.5; The average particle size of the ionic conductor is d2 = 0.05~2μm, and d2 / D = 0.5~0.

8.

10. A lithium metal anode modified with a lithiophilic porous framework, characterized in that, The material includes a lithium-loving porous interface functional layer as described in any one of claims 7-9, and further includes a lithium foil; The thickness of the lithium-loving porous interface functional layer is 1µm-30µm; the thickness of the lithium foil is 5µm-20µm.

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