High-dielectric / solvophobic synergistic artificial interface protection layer as well as preparation method and application thereof

Abstract

The invention provides a high-dielectric / solvophobic synergistic artificial interface protective layer and a preparation method and application thereof. The protective layer sequentially comprises a high-dielectric composite matrix layer and a solvophobic surface layer from inside to outside, wherein the high-dielectric composite matrix layer contains 40-60 wt% of a solid electrolyte matrix, 10-25 wt% of a high-dielectric polymer, 20-30 wt% of high-dielectric inorganic particles and 5-10 wt% of a LiF stabilizing phase; the hydrophobic agent surface layer is made of Al2O3 / SiO2 nano-particles which are subjected to coupling modification by fluorosilane; the protective layer can realize lithium metal negative electrode side electric field homogenization and interface chemical passivation, induce lithium ions to uniformly deposit from bottom to top, and inhibit electrolyte side reaction and H2S release at the same time, when the protective layer is applied to a lithium metal battery, the lithium metal battery can stably circulate for more than or equal to 500h under 0.5-1.0 mA * cm <-2 >, and the 100-time circulation capacity retention rate of the all-solid-state battery is more than or equal to 93%.

Description

Technical Field

[0001] This invention relates to the field of lithium metal battery interface modification technology, and in particular to a high dielectric / solvent-repellent synergistic artificial interface protective layer, its preparation method and application. Background Technology

[0002] Lithium metal batteries, with their high energy density (theoretical energy density can reach over 500Wh / kg), have become the core direction of next-generation energy storage devices, while sulfide-based solid electrolytes, due to their high room-temperature ionic conductivity (10... -3 ~10 -2 With its high S / cm (S / cm) and good interfacial compatibility, sulfide-based solid electrolytes are considered ideal electrolyte systems for lithium metal batteries. However, two key issues still exist at the interface between sulfide-based solid electrolytes and lithium metal anodes:

[0003] 1. Uneven lithium-ion deposition: Differences in the electric field distribution on the surface of lithium metal anodes cause lithium ions to preferentially deposit in local areas, forming lithium dendrites. Dendrites piercing the electrolyte layer can cause battery short circuits. At the same time, dendrite growth is accompanied by repeated rupture of the SEI film, which aggravates the consumption of active lithium and electrolyte (Jeong et al., Adv. Funct. Mater. 2025, 35, 2408612).

[0004] 2. Electrolyte / electrolyte side reactions: S in sulfide electrolytes 2- PS4 3- It readily reacts with ambient moisture or electrolyte to generate H2S gas, which corrodes battery components and damages the stability of the SEI film. At the same time, direct contact between the electrolyte and lithium metal will trigger continuous decomposition, generating insulating byproducts (such as Li2CO3 and LiF aggregates), leading to a sharp increase in interfacial impedance (Wan et al., ACS Energy Lett. 2023, 8, 4215-4224).

[0005] At present, the solutions to the above problems have obvious limitations:

[0006] Modification with a single high-dielectric material: such as the "boron-rich single-ion polymer artificial SEI film" disclosed in CN115692710A, which uses a borate ester polymer (ε≈12) with a uniform electric field, but the interfacial binding energy is only -3.0eV (measured data from CNKI patent database), and the coating peeling rate reaches 25% after 50 cycles; and no solvent-repellent layer is introduced, with H2S release of 0.8~1.0ppm at 85%RH, and side reactions continue to occur;

[0007] Single hydrophobic surface modification: such as the "fluorinated polymer coated lithium anode" disclosed in US20230155021A1, although it achieves a contact angle of 118°, it lacks electric field control, the lithium ion deposition uniformity is only 68%, and the dendrite penetration time is only 50 hours, which is far below the actual application requirements.

[0008] Traditional artificial protective layers, such as the "LiF / polymer composite SEI" disclosed in US11004567B2, only focus on improving mechanical strength (elastic modulus 2.5 GPa), without combining the synergistic properties of high dielectric and solvent repellency. Therefore, they cannot simultaneously solve the two major problems of "uneven deposition" and "side reactions," and their interfacial impedance is as high as 200 Ω·cm. 2 This is far above the practical application threshold (≤80Ω·cm). 2 ).

[0009] In summary, existing technologies suffer from core defects such as "single function and poor synergy," and there is an urgent need to develop an artificial solid electrolyte interphase (SEI) material that integrates "electric field homogenization, electrolyte barrier, and H2S suppression" to achieve a comprehensive improvement in the interface performance of lithium metal batteries. Summary of the Invention

[0010] The technical problem to be solved by the present invention is to provide a high dielectric / solvent-repellent synergistic artificial interface protective layer.

[0011] Another technical problem to be solved by the present invention is to provide a method for preparing the above-mentioned high dielectric / solvent-repellent synergistic artificial interface protective layer.

[0012] Another technical problem to be solved by the present invention is to provide the application of the above-mentioned high dielectric / solvent-repellent synergistic artificial interface protective layer.

[0013] To solve the above-mentioned technical problems, the technical solution of the present invention is as follows:

[0014] A high-dielectric / solubilizing synergistic artificial interface protective layer comprises, from the inside out, a high-dielectric composite matrix layer and a solvent-repellent surface layer, wherein the mass percentage of the high-dielectric composite matrix layer and the solvent-repellent surface layer is 85-95 wt% : 5-15 wt%.

[0015] The high-dielectric composite matrix layer comprises, by mass percentage: 40–60 wt% solid electrolyte matrix, 10–25 wt% high-dielectric polymer, 20–30 wt% high-dielectric inorganic particles, and 5–10 wt% LiF stabilizing phase, with the sum of the mass percentages of each component being 100 wt%. The solid electrolyte matrix is ​​a sulfide, Li6PS5Cl, Li3PS4, or an oxide, Li7La3Zr2O. 12At least one of the following: and its composites; the high dielectric polymer is PVDF or PVDF-HFP (poly(vinylidene fluoride-hexafluoropropylene) copolymer); the high dielectric inorganic particles are at least one of BaTiO3, SrTiO3, TiO2-Rutile, SrTaO2N, LaTiO2N, and CeTaN3 with a room temperature dielectric constant εr≥50;

[0016] The solvent-repellent surface layer consists of Al2O3 or SiO2 nanoparticles modified with fluorosilane coupling, with a particle size of 5–15 nm. The fluorosilane coupling agent is perfluorooctyltriethoxysilane or perfluorohexylethyltrimethoxysilane.

[0017] Preferably, the above-mentioned high-dielectric / solubilizing synergistic artificial interface protective layer has an in-plane ionic conductivity ≥1.0×10⁻⁶ at 25°C. -4 S·cm -1 The total thickness is 3-20 μm. It has not been subjected to external high voltage electric field polarization treatment and is used in an unpolarized state.

[0018] Preferably, in the above-mentioned high dielectric / solvent-repellent synergistic artificial interface protective layer, the solid electrolyte matrix is ​​a sulfide electrolyte Li6PS5Cl with a particle size of 1-3 μm and a purity of 99.9%, which is used to provide lithium-ion transport channels.

[0019] Preferably, in the above-mentioned high-dielectric / solubilizing synergistic artificial interface protective layer, the mass ratio of the high-dielectric inorganic particles to the solid electrolyte matrix is ​​0.4–0.6:1, with a mass ratio between 1 and 10. 5 The overall effective dielectric constant ε of the protective layer in the Hz frequency range r Effective dielectric response ≥30.

[0020] Preferably, in the above-mentioned high dielectric / solvent-repellent synergistic artificial interface protective layer, the high dielectric inorganic particles are CeTaN3 with a dielectric constant of 50-60 and a particle size of 30-80 nm, which are used to uniformly shape the interfacial electric field and suppress lithium dendrites.

[0021] Preferably, in the above-mentioned high dielectric / solvent-repellent synergistic artificial interface protective layer, the high dielectric polymer is PVDF-HFP, wherein the mass fraction of HFP is 10-15%, and the film-forming solvent used is composed of acetone and methyl ethyl ketone, wherein the volume ratio of acetone to methyl ethyl ketone is 1:1.

[0022] Preferably, in the above-mentioned high dielectric / solvent-repellent synergistic artificial interface protective layer, the high dielectric polymer is PVDF with a dielectric constant of 10-12 and a number-average molecular weight of 50,000, and the film-forming solvent used is N-methylpyrrolidone (NMP).

[0023] The aforementioned high-dielectric polymer is used to bind particles and enhance the mechanical strength of the SEI.

[0024] Preferably, in the above-mentioned high dielectric / solvent-repellent synergistic artificial interface protective layer, the particle size of the LiF stabilizing phase is 30-40 nm (addition amount 8 wt%), which is used to form a F-rich stable interface phase, reduce interfacial side reactions, and uniformly distribute space charge, thereby improving lithium-ion conductivity.

[0025] Preferably, in the above-mentioned high dielectric / solvent-repellent synergistic artificial interface protective layer, the solvent-repellent surface layer is Al2O3 nanoparticles modified by fluorinated silane coupling, with an Al2O3 particle size of 10-12 nm and a fluorine content of 18-20 at%, used to block electrolyte / water and inhibit H2S generation.

[0026] The specific steps for preparing the above-mentioned high-dielectric / solvent-repellent synergistic artificial interface protective layer are as follows:

[0027] S1. Preparation of high-dielectric composite matrix precursor: Solid electrolyte matrix, high-dielectric inorganic particles (CeTaN3) and high-dielectric polymer are added to film-forming solvent and ball-milled at a ball-to-particle ratio of (10-12):1 at 350-450 rpm for 2-3 hours. LiF is added in the later stage of ball milling (1.5-2 hours), and ball milling is continued for 0.5-1 hours to obtain mixed powder A;

[0028] S2. Preparation of solvent-repellent modified particles: Al2O3 or SiO2 nanoparticles were dispersed in anhydrous ethanol, and 0.5-1.0 vol% deionized water and 0.05-0.10 vol% acetic acid were added. The mixture was heated to 50-60℃ and then a fluorosilane coupling agent was added. The mixture was stirred and reacted for 1.5-2 h. After centrifugation at 6000-8000 rpm for 5-8 min, the mixture was vacuum dried at 80-100℃ for 2-3 h to obtain solvent-repellent modified particles B.

[0029] S3. Coating and molding: Mix the mixed powder A and the solvent-modified particles B at a mass ratio of (85-95):(5-15), add anhydrous ethanol to form a suspension with a solid content of 20-30%, ultrasonically disperse at 300-500W for 30-40 minutes, and then coat it onto the surface of lithium metal foil (lithium foil thickness 50-100μm) using slit coating or spraying method. Control the wet film thickness of the coating to 30-80μm, and dry it at 60-70℃ while coating to initially obtain a pre-formed protective layer with a thickness of 3-20μm.

[0030] S4. Densification treatment: The pre-formed protective layer is transferred to an Ar atmosphere tube furnace for stepwise heat treatment. First, it is pre-dried at 70-90℃ for 1-2 hours to remove residual solvent, and then heated to 110-120℃ for 1 hour to achieve interfacial bonding. Subsequently, it is thermally pressed at 50-60℃ and 5-15MPa for 0.5 hours to improve the adhesion between the protective layer and the lithium metal foil and its own density, thus obtaining the artificial interface protective layer.

[0031] Preferably, in the above-mentioned method for preparing the high dielectric / solvent-repellent synergistic artificial interface protective layer, the high dielectric inorganic particles (CeTaN3) in step S1 are pretreated with Ar plasma (power 100-150W, time 10-15min), and then placed in an Ar glove box (water and oxygen content ≤0.1ppm) for 30-45min to prevent surface oxidation from affecting the dielectric properties.

[0032] Preferably, in the above-mentioned method for preparing a high dielectric / solvent-repellent synergistic artificial interface protective layer, the solid electrolyte substrate in step S1 is prepared by grinding a sulfide electrolyte to a particle size of 1-3 μm in an Ar glove box to avoid introducing moisture.

[0033] Preferably, in the above-mentioned method for preparing the high dielectric / solvent-repellent synergistic artificial interface protective layer, the process parameters of the spraying method in step S3 are: nozzle diameter 0.5-1 mm, spraying distance 10-15 cm, spraying rate 5-8 mL / min; the coating speed of the slit coating method is 5-10 mm / s, and the wet film thickness is controlled to be 30-60 μm.

[0034] Preferably, in the above-mentioned method for preparing the high dielectric / solvent-repellent synergistic artificial interface protective layer, step S4 involves pre-drying at 80-90°C for 1.5-2 hours to remove residual solvent.

[0035] The above-mentioned high dielectric / solvent-repellent synergistic artificial interface protective layer is used as a negative electrode in lithium metal batteries.

[0036] Preferably, in the above applications, the lithium metal battery includes, but is not limited to, lithium-sulfur, high-nickel layered oxide cathode lithium metal batteries, or all-solid-state lithium metal batteries.

[0037] Preferably, in the above application, the lithium metal battery is a lithium metal battery with a sulfide-based solid electrolyte system.

[0038] A lithium metal battery comprising a lithium metal anode modified with the aforementioned high dielectric / solvent-repellent synergistic artificial interface protective layer.

[0039] Preferably, the above-mentioned lithium metal battery has the following stacked structure: positive electrode composite electrode | solid electrolyte layer | lithium metal negative electrode modified by the high dielectric / solvent-repellent synergistic artificial interface protective layer.

[0040] Preferably, in the above-mentioned lithium metal battery, the active material of the positive electrode composite electrode is LiNi. x Co yMn_zO2 (NCM, x+y+z=1), LiFePO4 (LFP), or a sulfur-carbon complex; the solid electrolyte layer is a sulfide solid electrolyte (Li6PS5Cl or Li3PS4) with a thickness of 50-100 μm.

[0041] Preferably, the N / P ratio (negative electrode capacity / positive electrode capacity) of the above-mentioned lithium metal battery is 1.2 to 2.0.

[0042] Preferably, the above-mentioned lithium metal battery has an efficiency of 0.5 to 1.0 mA·cmw. 2 Current density, 1.0–2.0 mAh·cm -2 Under the condition of areal capacity, the Li|protective layer|Li symmetric cell (test method is the general test method) can be stably cycled for ≥500h with an average overpotential ≤25mV; in the range of 25~50℃, the capacity retention rate of the whole cell after 100 cycles is ≥93%.

[0043] Preferably, in the above-mentioned lithium metal battery, when the artificial interface protective layer is in contact with the solid electrolyte layer (sulfide solid electrolyte), the H2S release within 24 hours is ≤0.5ppm / 24h·g (measured by GC-PFPD or GC-SCD method, with N2 as the carrier gas, and the detection limit LOD ≤0.01ppm).

[0044] Beneficial effects:

[0045] The aforementioned high-dielectric / solubilizing synergistic artificial interface protective layer, through a triple synergistic design of "high-dielectric CeTaN3 regulating the electric field + solvent-repellent layer blocking the interface + LiF stabilizing phase optimization," simultaneously solves the problems of uneven lithium-ion deposition, interfacial side reactions, and H2S release. It improves the interfacial compatibility between the protective layer and the sulfide electrolyte, providing a key interface material for high-stability lithium metal batteries, especially suitable for lithium metal batteries with sulfide-based solid electrolyte systems, significantly improving battery cycle stability and safety. Specifically:

[0046] 1. Multifunctional synergistic improvement: CeTaN3 improves the uniformity of lithium-ion deposition by 75% (coefficient of variation CV≤8.5%), the solvent-repellent layer reduces the side reaction rate of electrolyte by 80%, and the H2S release at 85% RH for 24h is ≤0.5ppm / 24h·g, thus solving the three core problems of "dendrites, side reactions, and H2S".

[0047] 2. High interfacial compatibility and ion transport efficiency: CeTaN3 exhibits a high interfacial binding energy (-3.5 eV) with the sulfide electrolyte, with an interfacial impedance increase of ≤15% after 100 cycles; the in-plane ionic conductivity at room temperature is ≥1.0×10⁻⁶. -4 S·cm -1The lithium-ion transference number is ≥0.75, which is superior to the traditional BaTiO3 system (impedance increase ≥30%, conductivity ≤8×10). -5 S·cm -1 );

[0048] 3. Excellent stability over a wide temperature range: ionic conductivity ≥1.0×10⁻⁶ at -20℃ -5 S·cm -1 The capacity retention rate is ≥93% after 100 cycles at 45℃, making it suitable for high and low temperature applications such as electric vehicles and energy storage power stations.

[0049] 4. Strong industrial compatibility: It adopts conventional equipment such as ball milling, slot coating, and tube furnace, without the need for complex processes such as vacuum evaporation, reducing production costs by more than 50% compared to existing technologies, and can be directly adapted to lithium metal battery dry forming production lines. Attached Figure Description

[0050] Figure 1 This is a schematic diagram of an artificial SEI with synergistic effects of high dielectric and solvent repellency. In the diagram, 1-lithium metal anode; 2-high dielectric composite matrix; 3-solvent repellent surface layer; 4-separation layer; the arrows indicate the uniform lithium ion transport path and the electrolyte barrier effect.

[0051] Figure 2 The schematic diagram of the synergistic mechanism is shown in two steps: ① The high dielectric component (BaTiO3 / PVDF) forms a uniform interfacial electric field, guiding the uniform deposition of lithium ions; ② The solvent-repellent layer blocks the electrolyte / water, inhibiting side reactions and H2S generation.

[0052] Figure 3 Photographs of the electrodes of the full cell without SEI and Example 1 after 100 cycles at 25°C.

[0053] Figure 4 This is a comparison chart of the capacity retention rates of full cells in Example 1, Comparative Examples A, B, and C after 100 cycles at 25°C. Detailed Implementation

[0054] To enable those skilled in the art to better understand the technical solution of the present invention, the technical solution of the present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0055] All the following examples were carried out in an Ar glove box with a water and oxygen content ≤0.1ppm and an ambient temperature of 25±1℃.

[0056] Example 1

[0057] A CeTaN3-Li6PS5Cl-PVDF-LiF / F-SiO2 surface layer is prepared by the following method:

[0058] 1. Raw material preparation

[0059] High dielectric composite matrix raw materials: Li6PS5Cl (particle size 2μm, purity 99.9%, Aladdin), CeTaN3 (ε r =55, particle size 50nm, purity 99.5%, Maclean), PVDF (number average molecular weight 5×10 4 BASF), LiF (particle size 30nm, purity 99.5%, TISHIAL);

[0060] Raw materials for the solvent-repellent surface layer: SiO2 (particle size 10nm, Aladdin), perfluorooctyltriethoxysilane (analytical grade, Sinopharm Group);

[0061] Solvents: NMP (analytical grade, water content ≤0.005%), anhydrous ethanol (analytical grade, Sinopharm Group).

[0062] 2. Preparation steps:

[0063] S1. Preparation of high dielectric composite matrix precursor: 50g Li6PS5Cl, 22g CeTaN3 (treated with Ar plasma: 120W, 12min → stand in glove box for 40min), and 18g PVDF were added to an agate ball mill jar with a ball-to-material ratio of 11:1 and ball milled at 400rpm for 2h; 8g LiF was added and ball milled for another 0.5h to obtain mixed powder A (Note: the total amount of all components is 98g, and the proportions of each component are: Li6PS5Cl 51.0%, CeTaN3 22.4%, PVDF 18.4%, and LiF 8.2%).

[0064] S2. Preparation of solvent-repellent modified particles: 10g SiO2 was dispersed in 200mL anhydrous ethanol, 0.8vol% deionized water and 0.05vol% acetic acid were added, the temperature was raised to 55℃, and 1.2g perfluorooctyltriethoxysilane was added. The mixture was stirred for 1.8h. After centrifugation at 7000rpm for 6min, the mixture was vacuum dried at 90℃ for 2.5h to obtain solvent-repellent modified particles B (X-ray photoelectron spectroscopy detection showed a fluorine content of 19.2at%).

[0065] S3. Coating and molding: Mix 90g of mixed powder A with 10g of solvent-modified particles B, add 300mL of anhydrous ethanol to form a suspension with a solid content of 25%, and ultrasonically disperse at 400W for 35min; coat the 10×10mm lithium metal foil (thickness 50μm) surface using the slit coating method at a coating speed of 8mm / s and a wet film thickness of 20μm, and dry while coating at 65℃ to initially obtain a pre-formed protective layer with a thickness of 10μm.

[0066] S4. Densification treatment: The preformed protective layer is transferred to an Ar atmosphere tube furnace, pre-dried at 75℃ for 1.5h, and then heated to 115℃ for 1h; subsequently, it is thermally pressed at 55℃ and 10MPa for 0.5h and naturally cooled to room temperature to obtain the artificial interface protective layer (CeTaN3-Li6PS5Cl-PVDF-LiF / F-SiO2 surface layer), named Sample-1.

[0067] The entire process described above does not involve external high-voltage polarization or directional polarization treatment.

[0068] 3. Performance Testing

[0069] Dielectric and solvent-repellent properties: tested with an LCR meter (Agilent E4980A), 1-10 5 ε at Hz frequency r =38 (due to dilution of the Li6PS5Cl matrix, lower than 55 for pure CeTaN3); the contact angle of 1M LiPF6 / EC:EMC (1:1) electrolyte was 115° as measured by an optical contact angle meter (Krüss DSA100).

[0070] Ion transport performance: Employs a "stainless steel|Sample-1|stainless steel" blocking electrode structure, AC impedance method (Solartron 1260, 10 -1 ~10 6 (Hz) test, in-plane ionic conductivity at 25℃ is 1.8×10⁻⁶. -4 S·cm -1 The lithium-ion transference number measured by the Bruce-Vincent method was 0.78 (0.62 at -20℃ and 0.81 at 45℃).

[0071] H2S release: Weigh 1.0g Sample-1 and mix with 0.5g Li6PS5Cl, place in a 1L sealed container (85%RH±2%), place at 25℃ for 24h, and detect by GC-PFPD (Agilent 7890A, carrier gas N2, detection limit 0.01ppm). The H2S release was 0.30ppm / 24h·g.

[0072] Battery performance: Assembled "Li|Sample-1|Li6PS5Cl|NCM811" full cell (cathode: NCM811 / SuperP / PVDF = 8∶1∶1, N / P ratio 1.5), tested with LAND CT2001A testing system under 0.1C (1C = 200mA / g) and 2.7–4.3V conditions, initial discharge capacity was 193mAh / g, initial coulombic efficiency was 92.5%; Li|Sample-1|Li symmetric cell under 0.8mA·cm -2 1.5mAh·cm-2 Under the given conditions, after 500 hours of cycling, the average overpotential was 22mV; at 25℃, the full cell retained 94.1% of its capacity after 100 cycles (n=3), and at 45℃, the capacity retention was 90.2%.

[0073] Example 2

[0074] A CeTaN3-LLZO-PVDF-HFP / F-Al2O3 surface layer is prepared by the following method:

[0075] The difference from Example 1 is as follows:

[0076] High dielectric composite matrix layer: Solid electrolyte replaced with Li7La3Zr2O 12 (LLZO, particle size 1μm) is prepared as follows: LiOH·H2O (10% excess to compensate for lithium volatilization), La2O3 and ZrO2 powders are mixed in stoichiometric ratio, ball-milled in isopropanol for 12 hours, dried and pre-calcined at 900℃ for 12 hours; the pre-calcined powder is ball-milled again, pressed into tablets, sintered at 1150℃ for 24 hours, crushed, ground and sieved to obtain cubic phase LLZO powder, the high dielectric polymer is replaced with PVDF-HFP (HFP mass fraction 12%), and the solvent is replaced with acetone / methyl ethyl ketone = 1:1;

[0077] Solvent-repellent surface layer: nanoparticles are replaced with Al2O3 (particle size 12nm), and fluorosilanes are replaced with perfluorohexylethyltrimethoxysilane;

[0078] Preparation parameters: S3 slit coating wet film thickness 16μm, final protective layer thickness 8μm;

[0079] Performance testing: In-plane ionic conductivity at 25℃: 2.1 × 10⁻⁶ -4 S·cm -1 The H2S release was 0.34 ppm / 24 h·g; the assembled “Li|Sample-2|LLZO|LFP” full cell had an initial discharge capacity of 168 mAh / g at 0.1c and a capacity retention of 94.5% after 100 cycles (n=3).

[0080] Comparative Example A

[0081] The high-dielectric composite matrix (without a solvent-repellent surface layer) was prepared by the following method:

[0082] The solvent-modified particles B in steps S2 to S3 above are omitted. The mixed powder A is treated with the coating and densification process of Example 1 to obtain Sample-A with a thickness of 12 μm (BaTiO3 replaces CeTaN3, and the rest is the same as in Example 1).

[0083] Performance testing: Electrolyte contact angle 70°, H2S release 1.85ppm / 24h·g at 85%RH; Overpotential rises to 50mV after 350h cycling of Li|Sample-A|Li symmetric cell; Capacity retention of the full cell after 100 cycles is 82.3% (side reactions cause increased impedance).

[0084] Comparative Example B

[0085] Uncontrolled water coupling (F-SiO2) is prepared by the following method:

[0086] In step S2, the addition of "0.8 vol% deionized water and 0.05 vol% acetic acid" is omitted, and the rest is the same as in Example 1, to obtain Sample-B.

[0087] Performance testing: The fluorine content of the solvent-repellent modified particle B is only 12.5 at, and the electrolyte contact angle is 95°; the lithium-ion deposition uniformity CV = 14.3%; the capacity retention rate of the full cell after 100 cycles is 88.6% (insufficient solvent-repellent effect, aggravated side reactions).

[0088] Comparative Example C

[0089] BaTiO3, replacing CeTaN3 (retaining the bilayer), is prepared by the following method:

[0090] In step S1, BaTiO3(ε r =80, particle size 50nm) replaced CeTaN3, the rest is the same as in Example 1, to obtain Sample-C.

[0091] Performance testing: Interface binding energy -3.2 eV, interface impedance increase of 32% after 100 cycles; H2S release of 0.58 ppm / 24 h-g; capacity retention of the full cell after 100 cycles of 86.5% (dielectric-interface synergy is weaker than that of the CeTaN3 system).

[0092] Comparative Example D

[0093] The material, which contains no high-dielectric particles and no solvent-repellent surface layer (basic protective layer), is prepared by the following method:

[0094] Only Li6PS5Cl and LiF (mass ratio 50:8) were mixed and coated and densified according to the process of Example 1 to obtain Sample-D with a thickness of 10 μm.

[0095] Performance testing: Ionic conductivity at room temperature 8.5 × 10⁻⁶ -5 S·cm -1Electrolyte contact angle 55°; lithium ion deposition uniformity CV = 45%; Li|Sample-D|Li symmetric cell failed due to dendrite short circuit after 30 cycles; H2S release 1.5ppm / 24h·g.

[0096] The test results, obtained using a general testing method, are shown in Table 1-2.

[0097] In-plane ionic conductivity: Four-probe impedance method (1~10) 6 Hz, 25°C), converted according to thickness and effective area; Lithium-ion transference number tLi + Bruce-Vincent polarization method (DC 10mV, EIS correction before and after); symmetric cell cycling: Li|protective layer|Li, 0.5~1.0mA·cm -2 1.0~2.0mAh·cm -2 EIS: 5MHz~0.1Hz, 5mV; H2S release: GC-PFPD or GC-SCD (carrier gas N2), providing chamber volume (L), sample mass (g), limit of detection (LOD) and normalized units (ppm / 24h·g).

[0098] Table 1 Comparison of Sample Performance

[0099]

[0100] Table 2 Comparison of Sample Performance

[0101]

[0102]

[0103] Note: The data for "Materials of the Invention (CeTaN3 System)" in Table 2 above are derived from Examples 1-2 and Table 1; the data for "SEI of the Traditional BaTiO3 System" are derived from Comparative Example C and Table 1; the data for "Single Soluble SEI" can be obtained by comparing Comparative Example B with publicly available data from the cited prior art. All performance indicators were tested using the standards described in the general test methods.

[0104] in conclusion

[0105] 1. High dielectric / solvent-repellent synergistic artificial interface protective layer (CeTaN3 system, structure as shown in Examples 1-2) Figure 1 (As shown) It performed best in all core indicators: lithium-ion deposition uniformity CV≤8.5%, room temperature conductivity≥1.8×10 -4 S·cm -1H2S release ≤0.34ppm / 24h·g, symmetric battery cycling ≥500h, and retention rate ≥93.5% after 100 cycles fully demonstrate that the triple synergistic mechanism of "CeTaN3 high dielectric + solvent-repellent layer + LiF stable phase" can comprehensively solve the lithium metal anode interface problem.

[0106] 2. Comparative Examples A to D: A single high-dielectric layer (A) cannot block side reactions and H2S; the solvent-repellent layer (B) without water and acid control is insufficient; replacing CeTaN3 with BaTiO3 (C) leads to a decrease in synergy; and the base layer without high dielectric / solvent-repellent properties (D) performs the worst. This further proves the necessity of the core innovation of this invention (the synergistic mechanism is as follows). Figure 2 (as shown);

[0107] 3. For example Figure 3 As shown, the test results indicate that, compared to a full cell without SEI protection, the full cell of Example 1 retains its cycle capacity after 100 cycles at 25°C as follows: Figure 4 As shown, the electrode surface is in excellent condition with almost no lithium deposition, fully demonstrating the optimization effect of this invention on lithium metal deposition behavior.

[0108] 4. The protective layer described in this invention is compatible with sulfide / oxide solid electrolytes, and the preparation process does not require special equipment. The high compatibility and stability of CeTaN3 ensure the consistency of battery performance, providing key technical support for the industrialization of lithium metal batteries.

[0109] In summary, the high dielectric / solvent-repellent synergistic artificial interface protective layer of this invention:

[0110] 1. Synergistic Mechanism: CeTaN3-led dual-function integration of "electric field uniformity - interface barrier"

[0111] The triple synergistic mechanism of CeTaN3 as the core high-dielectric component: Electric field homogenization: CeTaN3, through ε r The dielectric polarization effect of ≥50 weakens the local strong electric field on the surface of the lithium metal anode, reduces the electric field distortion rate by more than 60%, guides lithium ions to be deposited uniformly from bottom to top, and suppresses lithium dendrites from the source.

[0112] Interface barrier: The solvent-repellent surface layer (fluorosilane-modified Al2O3 / SiO2) reduces the direct contact between the electrolyte / water and lithium metal and sulfide electrolyte through an electrolyte contact angle of ≥110°, thus inhibiting side reactions;

[0113] Phase stability: LiF nanoparticles form an F-rich interface phase, reducing S 2-The reactivity with Li and the uniform space charge distribution further optimize the lithium-ion transport path. These three factors work synergistically to achieve a three-in-one function of "dendritic suppression, side reaction prevention, and H2S suppression," overcoming the shortcomings of existing single-function modifications.

[0114] 2. Material Combination: High compatibility design between CeTaN3 and sulfide electrolytes

[0115] The selected CeTaN3 as a high dielectric particle exhibits excellent interfacial compatibility: the nitride crystal structure of CeTaN3 has an interfacial binding energy of -3.5 eV with sulfide electrolytes (such as Li6PS5Cl), which is significantly better than that of traditional BaTiO3 (-3.2 eV), effectively preventing interfacial delamination.

[0116] High chemical stability: CeTaN3 reacts with S in sulfide electrolytes 2- Without chemical reaction, nanoparticles with a size of 30–80 nm can be uniformly dispersed in high-dielectric polymers (dispersion ≥95%), solving the problems of "uneven dispersion and poor compatibility" of existing high-dielectric particles;

[0117] Dielectric response adaptation: The volume ratio of CeTaN3 to the solid electrolyte matrix is ​​controlled at (0.3~0.8):1, within the range of 1~10. 5 It can stably maintain ε within the Hz frequency range r ≥30, to ensure the long-term effectiveness of electric field homogenization.

[0118] 3. Process: CeTaN3-compatible integrated "ball milling-coating-warm pressing" process

[0119] Optimize the preparation process based on the characteristics of CeTaN3 to ensure the consistency of the protective layer performance: Pretreatment stage: Ar plasma treatment of CeTaN3 followed by glove box stabilization to prevent surface oxidation;

[0120] Coating stage: Use slot coating / spraying method to control water and oxygen content ≤0.1ppm to avoid moisture absorption by the suspension, which could cause coating blistering;

[0121] Densification stage: The three-step process of "low temperature pre-drying - high temperature bonding - warm pressure setting" not only achieves interfacial cross-linking between CeTaN3 and polymer, but also improves the density of the protective layer (relative density ≥92%), avoiding the coating peeling problem of traditional processes.

[0122] Example 3

[0123] A type of lithium metal battery, such as Figure 1As shown, a lithium metal anode 1 is modified with either the CeTaN3-Li6PS5Cl-PVDF-LiF / F-SiO2 surface layer described in Example 1 or the CeTaN3-LLZO-PVDF-HFP / F-Al2O3 surface layer described in Example 2 as a high-dielectric composite matrix 2 and a solvent-repellent surface layer 3. The specific stacked structure is: positive electrode composite electrode - separator layer - solid electrolyte layer - separator layer 4 - lithium metal anode 1 modified with high-dielectric composite matrix 2 and solvent-repellent surface layer 3. The active material of the positive electrode composite electrode is LiFePO4; the solid electrolyte layer is Li6PS5Cl with a thickness of 80 μm. The N / P ratio (anode capacity / positive electrode capacity) of the battery is approximately 1.6. At 0.8 mA·cm⁻¹... -2 Current density, 1.5 mAh·cm -2 Under the condition of areal capacity, the battery (test method is the general test method) can be stably cycled for ≥500h with an average overpotential ≤25mV; within the range of 25~50℃, the capacity retention rate of the whole battery after 100 cycles is ≥93%.

[0124] In the aforementioned lithium metal battery, when the artificial interface protective layer is in contact with the solid electrolyte layer (sulfide solid electrolyte), the H2S release within 24 hours is ≤0.5ppm / 24h·g (measured by GC-PFPD or GC-SCD method, with N2 as the carrier gas, and a detection limit LOD ≤0.01ppm).

[0125] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A high-dielectric / solvent-repellent synergistic artificial interface protective layer, characterized in that: From the inside out, it comprises a high-dielectric composite matrix layer and a solvent-repellent surface layer, wherein the mass percentage of the high-dielectric composite matrix layer and the solvent-repellent surface layer is 85-95 wt% : 5-15 wt%. The high-dielectric composite matrix layer comprises, by mass percentage: 40–60 wt% solid electrolyte matrix, 10–25 wt% high-dielectric polymer, 20–30 wt% high-dielectric inorganic particles, and 5–10 wt% LiF stabilizing phase; the solid electrolyte matrix is ​​a sulfide Li6PS5Cl, Li3PS4, or an oxide Li7La3Zr2O. 12 At least one of the following: and its complex; the high dielectric polymer is PVDF or PVDF-HFP; the high dielectric inorganic particles are at least one of BaTiO3, SrTiO3, TiO2-Rutile, SrTaO2N, LaTiO2N, and CeTaN3 with a room temperature dielectric constant εr ≥ 50; The solvent-repellent surface layer consists of Al2O3 or SiO2 nanoparticles modified with fluorosilane coupling, with a particle size of 5–15 nm. The fluorosilane coupling agent is perfluorooctyltriethoxysilane or perfluorohexylethyltrimethoxysilane.

2. The high dielectric / solvent-repellent synergistic artificial interface protective layer according to claim 1, characterized in that: In-plane ionic conductivity ≥1.0×10 at 25℃ -4 S·cm -1 The total thickness is 3-20 μm.

3. The high dielectric / solvent-repellent synergistic artificial interface protective layer according to claim 1, characterized in that: The mass ratio of the high-dielectric inorganic particles to the solid electrolyte matrix is ​​0.4–0.6:

1.

4. The high dielectric / solvent-repellent synergistic artificial interface protective layer according to claim 1, characterized in that: The solid electrolyte matrix is ​​a sulfide electrolyte Li6PS5Cl with a particle size of 1-3 μm and a purity of 99.9%; the high-dielectric inorganic particles are CeTaN3 with a dielectric constant of 50-60 and a particle size of 30-80 nm; when the high-dielectric polymer is PVDF-HFP, the film-forming solvent is composed of acetone and methyl ethyl ketone, with a volume ratio of acetone to methyl ethyl ketone of 1:1; when the high-dielectric polymer is PVDF, the film-forming solvent is N-methylpyrrolidone.

5. The high dielectric / solvent-repellent synergistic artificial interface protective layer according to claim 1, characterized in that: The solvent-repellent surface layer consists of Al2O3 nanoparticles modified with fluorinated silane coupling, with an Al2O3 particle size of 10–12 nm and a fluorine content of 18–20 at%.

6. The method for preparing the high dielectric / solvent-repellent synergistic artificial interface protective layer according to any one of claims 1-5, characterized in that: The specific steps are as follows: S1. Preparation of high dielectric composite matrix precursor: Solid electrolyte matrix, high dielectric inorganic particles and high dielectric polymer are added to film-forming solvent and ball-milled at a ball-to-material ratio of (10-12):1 at 350-450 rpm for 2-3 hours. LiF is added in the later stage of ball milling and ball milling is continued for 0.5-1 hours to obtain mixed powder A. S2. Preparation of solvent-repellent modified particles: Al2O3 or SiO2 nanoparticles were dispersed in anhydrous ethanol, and 0.5-1.0 vol% deionized water and 0.05-0.10 vol% acetic acid were added. The mixture was heated to 50-60℃ and then a fluorosilane coupling agent was added. The mixture was stirred and reacted for 1.5-2 h. After centrifugation at 6000-8000 rpm for 5-8 min, the mixture was vacuum dried at 80-100℃ for 2-3 h to obtain solvent-repellent modified particles B. S3. Coating and molding: Mix the mixed powder A and the solvent-modified particles B at a mass ratio of (85-95):(5-15), add anhydrous ethanol to form a suspension with a solid content of 20-30%, ultrasonically disperse at 300-500W for 30-40 minutes, and then coat it onto the surface of lithium metal foil by slit coating or spraying. Control the wet film thickness of the coating to 30-80μm, and dry it at 60-70℃ while coating to obtain a pre-formed protective layer with a thickness of 3-20μm. S4. Densification treatment: The preformed protective layer is transferred to an Ar atmosphere tube furnace for stepwise heat treatment. First, it is pre-dried at 70-90℃ for 1-2 hours to remove residual solvent, and then heated to 110-120℃ for 1 hour to achieve interfacial bonding. Subsequently, it is thermally pressed at 50-60℃ and 5-15MPa for 0.5 hours to obtain the artificial interface protective layer.

7. The method for preparing the high dielectric / solvent-repellent synergistic artificial interface protective layer according to claim 6, characterized in that: In step S1, the high-dielectric inorganic particles are pretreated with Ar plasma and then left to stand in an Ar glove box for 30–45 min. In step S3, the process parameters for the spraying method are: nozzle diameter 0.5–1 mm, spraying distance 10–15 cm, and spraying rate 5–8 mL / min. The coating speed for the slit coating method is 5–10 mm / s, and the wet film thickness is controlled to be 30–60 μm.

8. The application of the high dielectric / solvent-repellent synergistic artificial interface protective layer as a negative electrode in lithium metal batteries.

9. A lithium metal battery, characterized in that: The lithium metal anode modified with a high dielectric / solvent-repellent synergistic artificial interface protective layer as described in any one of claims 1-5.

10. The lithium metal battery according to claim 9, characterized in that: It has the following stacked structure: positive electrode composite electrode | solid electrolyte layer | lithium metal anode modified by the high dielectric / solvent-repellent synergistic artificial interface protective layer; the active material of the positive electrode composite electrode is LiNi. x Co y Mn₂O₂, LiFePO₄, or a sulfur-carbon complex; the solid electrolyte layer is a sulfide solid electrolyte with a thickness of 50–100 μm.

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