A zinc-enriched carbon nanoflower current collector with a double inorganic passivation layer for a negative electrode-free lithium metal battery

Abstract

The application discloses a zinc-rich carbon nanoflower current collector with a double inorganic passivation layer constructed in situ and a preparation method thereof, and belongs to the technical field of negative electrode-free lithium metal battery current collector materials. A ZnNCN / ZnF2 double inorganic passivation layer is constructed in situ on a Zn-MOF derived zinc-rich carbon nanoflower three-dimensional framework, zinc is highly dispersed in the nitrogen-containing carbon framework in the form of Zn-N / Zn-O coordination, and the carbon nanoflower has dense scale units and a through-hole network. The modified carbon nanoflower is prepared through hydrothermal synthesis, high-temperature carbonization and NH4F hydrothermal modification, and is coated on a copper foil to obtain a finished product. The current collector can be directly used as a negative electrode-free lithium metal battery current collector, can control lithium deposition and SEI interface evolution, can inhibit lithium dendrite growth and volume expansion, can improve battery interface stability and cycle performance, and is suitable for high-energy-density energy storage fields.

Description

Technical Field

[0001] This invention belongs to the technical field of lithium-free metal battery anode current collector materials, specifically relating to a zinc-enriched carbon nanoflower current collector with an in-situ constructed dual inorganic passivation layer for use in anode-free lithium metal batteries. Background Technology

[0002] High-energy-density energy storage technology is the core support for new energy vehicles, portable electronic devices, and large-scale grid energy storage. Electrodeless lithium metal batteries, because they do not require pre-loading of lithium metal, can significantly improve battery energy density, simplify manufacturing processes, and reduce safety risks, making them an important development direction for next-generation high-energy-density energy storage devices. Lithium metal, with its ultra-high theoretical specific capacity of 3860 mAh / g and extremely low electrochemical potential of -3.04V (relative to the standard hydrogen electrode), is the core active component of electrodeless systems. However, problems such as dendrite growth, unstable and easily broken solid electrolyte interphase (SEI) films, severe volume expansion, and low coulombic efficiency during lithium metal deposition / stripping processes severely restrict the industrial application of electrodeless lithium metal batteries.

[0003] Constructing three-dimensional carbon-based modified current collectors is a key strategy for solving the above problems. Copper foil, as a traditional current collector substrate for lithium metal batteries, possesses good conductivity and mechanical properties, but its surface has poor lithiophilicity, easily leading to uneven lithium deposition and dendrite formation. Furthermore, direct contact with the electrolyte can easily trigger side reactions, generating a thick and porous SEI film, exacerbating interfacial impedance accumulation and dead lithium formation. To optimize the performance of copper foil current collectors, existing technologies mostly employ carbon-based material coating modification. Among these, metal-organic framework (MOF)-derived carbon-based materials have become a research hotspot due to their porous structure, high specific surface area, and tunable surface chemistry. Zinc-enriched carbon nanoflowers, as Zn-MOF-derived carbon materials, provide space for lithium deposition through their porous framework, and the presence of zinc species is expected to regulate lithium nucleation behavior.

[0004] Invention patent CN108767263A provides a method for in-situ growth of Zn-MOF nanosheet arrays on the surface of copper foil for modifying lithium metal anode copper foil current collectors. Invention patent CN121709629A provides a method for constructing a metal nanoparticle@metal-organic framework composite layer and a dense lithium-loving metal oxide layer on the surface of copper foil to improve lithium deposition uniformity and cycling stability. Jiang et al. reported in *Energy Storage Materials*, 2019, 23: 181-189, on the in-situ growth of MOF-derived Co3O4 / N-doped carbon nanosheet arrays on carbon cloth as a host material for stable lithium deposition. Luo et al. reported in *Chem. Commun.*, 2026, 62, 7598-7602, on the development of Ni / CoO modified carbon cloth based on bimetallic NiCo-MOFs as a multi-site functional current collector for regulating lithium ion nucleation and growth. While the aforementioned approaches improve lithium deposition uniformity and cycle stability of electrodeless lithium-ion batteries to some extent, they primarily employ uncarbonized MOF arrays, MOF composite layers, or host / current collector structures based on carbon cloth. Their interface regulation mechanisms are relatively simple, making it difficult to simultaneously achieve efficient electron transport, three-dimensional framework buffering, uniform lithium nucleation, and ordered SEI film evolution. Therefore, there is an urgent need to develop a composite current collector that combines a three-dimensional conductive framework with efficient interface regulation capabilities. This current collector could achieve effective decoupling of lithium nucleation behavior and interfacial side reactions through multi-component synergy, thereby further improving the interfacial stability and cycle performance of electrodeless lithium-ion metal batteries.

[0005] Due to the synergistic function of its components, the dual inorganic passivation layer exhibits unique advantages in interface regulation, simultaneously achieving the control of Li nucleation, SEI film optimization, and enhanced structural stability. Therefore, developing a composite current collector with a copper foil substrate and an in-situ construction of a dual inorganic passivation layer on Zn-MOF-derived zinc-rich carbon nanoflowers, and achieving tight bonding between the passivation layer and the carbon nanoflowers, and between the carbon nanoflowers and the copper foil substrate through precise control of the preparation process, utilizes the synergistic effect of the dual inorganic passivation layer to guide uniform lithium nucleation and deposition and regulate the generation of inorganic-rich SEI. This is of great significance for solving problems such as uneven lithium deposition, dendrite growth, and interface instability in electrodeless lithium metal batteries, and can provide key material support for the research and development of high-safety, high-cycle-stability electrodeless lithium metal batteries. Summary of the Invention

[0006] The purpose of this invention is to overcome the defects of existing copper foil current collectors for electrodeless lithium metal batteries, such as poor surface lithiophilicity, uneven lithium deposition, difficulty in suppressing dendrite growth, unstable SEI film, and easy detachment of carbon-based modified layer. The invention provides a zinc-enriched carbon nanoflower current collector with in-situ constructed dual inorganic passivation layer, its preparation method, and its application. By coating ZnNCN / ZnF2 composite carbon nanoflowers on copper foil, the structural layers are tightly bonded, which can effectively guide uniform and dense lithium deposition, promote the formation of inorganic SEI, and improve the cycle stability and coulombic efficiency of electrodeless lithium metal batteries.

[0007] To achieve the above objectives, the present invention adopts the following technical solution: A zinc-enriched carbon nanoflower current collector with an in-situ constructed dual inorganic passivation layer is disclosed. The current collector is constructed in-situ on a three-dimensional framework of zinc-enriched carbon nanoflowers with a ZnNCN / ZnF2 dual inorganic passivation layer. The zinc-enriched three-dimensional carbon nanoflowers are flower-shaped porous carbon frameworks derived from Zn-MOF. Zn is highly dispersed in the nitrogen-containing carbon framework in the form of Zn-N / Zn-O coordination. The diameter of the ZnNCN / ZnF2 composite carbon nanoflowers is 1.5-2.5 μm, which are composed of thinned and dense scaly units and have a network of interconnected pores.

[0008] The above-mentioned method for preparing zinc-enriched carbon nanoflower current collectors with in-situ constructed dual inorganic passivation layers includes the following steps: a) Add dimethylimidazolium and 5-aminotetrazole to 30 mL of methanol in a certain proportion, and stir at 25-30°C for 10-15 min until dissolved to obtain solution A; add zinc salt to 30 mL of methanol, and stir at 25-30°C for 10-15 min to obtain solution B; then add solution A to solution B, and stir at 25-30°C for 5-10 min to obtain a homogeneous mixture; b) Add the mixture obtained in step a) to a hydrothermal reactor and hydrothermally heat it at 70~90°C for 4~6 hours. After centrifugation, washing and drying, the Zn-MOF precursor is obtained. c) The Zn-MOF precursor obtained in step b) is carbonized at 800℃ under inert gas protection and kept at that temperature for 2-3 h to obtain Zn-MOF-derived zinc-rich carbon nanoflowers. d) The zinc-enriched carbon nanoflowers, zinc nitrate hexahydrate, and NH4F obtained in step c) were added to 60 mL of anhydrous ethanol in a certain proportion and stirred at 25-30°C for 40-60 min. Then, the mixture was added to a hydrothermal reactor and hydrothermally heated at 100-120°C for 10-14 h. After centrifugation, washing, and drying, ZnNCN / ZnF2 composite carbon nanoflowers were obtained. e) The ZnNCN / ZnF2 composite carbon nanoflowers obtained in step d) are mixed with the binder and solvent in a certain proportion. The slurry after grinding is coated onto copper foil with a scraper and then vacuum dried at 120~130°C for 10~12h.

[0009] Preferably, the zinc salt in step a) is any one of zinc nitrate hexahydrate, zinc acetate dihydrate, anhydrous zinc sulfate, and zinc chloride.

[0010] Preferably, in step a), the molar ratio of dimethylimidazolium to 5-aminotetrazole is 3:1 to 4:1, and the molar ratio of imidazole ligand to zinc salt is 2:1 to 3:1. The ratio of zinc salt to imidazole ligand has a significant impact on the nucleation, growth, and final structure formation of Zn-MOF precursors. An excessively high zinc salt ratio can lead to rapid nucleation, particle aggregation, and localized enrichment of zinc species, while an excessively low ratio can result in insufficient ligand scaffold construction and a lack of zinc active sites, which is detrimental to the formation of zinc-enriched carbon nanoflowers with complete structures, abundant pores, and uniform zinc dispersion.

[0011] Preferably, in step d), the molar ratio of NH4F to zinc nitrate hexahydrate is 2:1 to 4:1, and the total mass ratio of the two to the zinc-enriched carbon nanoflowers is 1:1 to 3:2. If the molar ratio of NH4F to zinc nitrate hexahydrate is too high, it can easily lead to excessive fluorination, excessive deposition of inorganic components, and damage to the pore structure, thereby affecting the conductivity and structural integrity of the carbon framework. Conversely, if the molar ratio of NH4F to zinc nitrate hexahydrate is too low, insufficient fluorine source will result in inadequate formation of the ZnNCN / ZnF2 composite layer and limited interfacial active sites, making it difficult to effectively improve the synergistic regulation of lithium nucleation behavior and interfacial stability.

[0012] Preferably, in step e), the adhesive is any one of polyvinylidene fluoride, polyacrylic acid, lithium carboxymethyl cellulose, and styrene-butadiene rubber, and the solvent is N-methylpyrrolidone or water.

[0013] Preferably, in step e), the mass ratio of ZnNCN / ZnF2 composite carbon nanoflowers to binder is 90:10~95:5, and the coating thickness is 10-20 μm.

[0014] This invention also protects the application of the zinc-enriched carbon nanoflower current collector with the above-mentioned in-situ constructed dual inorganic passivation layer in current collectors of negative electrode-free lithium metal batteries.

[0015] Inventive Principles This invention uses copper foil as a substrate and employs a combined process of hydrothermal synthesis, high-temperature carbonization, and secondary hydrothermal modification to achieve in-situ construction of a ZnNCN / ZnF2 dual inorganic passivation layer on Zn-MOF-derived zinc-enriched carbon nanoflowers and its tight integration with copper foil. The core technology achieves precise control of lithium deposition and interfacial reactions through the synergistic effect of multiple structural layers. Using dimethylimidazolium and 5-aminotetrazolium as ligands and nitrogen sources, and zinc salt as the zinc source, a Zn-MOF precursor is synthesized hydrothermally. After high-temperature carbonization, it forms highly dispersed Zn in a Zn-N / Zn-O coordinated form, creating flower-like porous carbon nanoflowers that provide highly active reaction sites and interconnected channels for the construction of the dual passivation layer. Furthermore, during the secondary hydrothermal process, zinc-enriched carbon nanoflowers, zinc nitrate hexahydrate, and NH4F are introduced into the reaction system. Using an external zinc and fluorine source, ZnF2 is generated in-situ on the surface of the carbon nanoflowers, while NH4F... + Nitrogen species rearrangement is induced, and the resulting reaction with zinc forms ZnNCN, thereby constructing a continuous, uniform, and firmly bonded ZnNCN / ZnF2 dual inorganic passivation layer on the surface of carbon nanoflowers. Finally, the modified carbon nanoflower slurry is coated onto copper foil to form a composite current collector. ZnF2 guides the formation of a stable LiF-enriched SEI, ZnNCN reduces the lithium nucleation overpotential, and the porous structure of the carbon nanoflowers homogenizes the LiF content. + The three factors work together to achieve uniform and dense lithium deposition, suppress dendrite growth and interfacial side reactions, thereby improving flux, mitigating volume expansion, and reducing density.

[0016] Beneficial effects This invention constructs a composite structure of ZnNCN / ZnF2 double passivation layer composite zinc-enriched carbon nanoflowers. Zn is highly dispersed in the carbon framework in the form of Zn-N / Zn-O coordination. The double inorganic passivation layer is grown in situ on the surface of the carbon nanoflowers. The structural layers are tightly bonded. ZnF2 and ZnNCN work synergistically to reduce the lithium nucleation overpotential and guide the formation of a stable LiF-enriched SEI film, thereby inhibiting lithium dendrite growth and interfacial side reactions from the source. This invention achieves the directional synthesis of Zn-MOF precursor, zinc-enriched carbon nanoflowers and ZnNCN / ZnF2 double passivation layer by precisely controlling the process parameters of each step. The resulting ZnNCN / ZnF2 composite carbon nanoflowers have uniform particle size, dense flake units and interconnected channels, strong adhesion to the composite coating of copper foil, no peeling phenomenon, and good repeatability of electrochemical and mechanical properties of the current collector. The porous structure of zinc-enriched carbon nanoflowers provides ample space for lithium deposition. The interconnected pore network can homogenize the lithium ion flux and local current density. Combined with the interfacial constraint of the ZnNCN / ZnF2 double passivation layer, it effectively alleviates the volume expansion during lithium deposition / stripping, avoids repeated rupture and regeneration of the SEI film, and significantly improves the cycle stability of the current collector. The current collector of this invention uses traditional copper foil as the substrate, and the preparation process is simple and has good compatibility with existing battery production processes. This current collector can be adapted to various positive electrode materials such as LiFePO4 and NCM811. The electrolyte system of the assembled negative electrode-free lithium metal battery can be selected from conventional ether electrolytes without special modification, and has a wide range of practical application adaptability. When the current collector prepared by this invention is applied to a cathode-free lithium metal battery, it can achieve uniform and dense lithium deposition, significantly improving the coulombic efficiency and cycle life of the battery. At the same time, the preparation process uses conventional equipment and reagents throughout, the steps are simple, easy to scale up, and the production cost is controllable. It has important promotional value in the industrial application of high energy density cathode-free lithium metal batteries. Attached Figure Description

[0017] Figure 1 (a, b) are SEM and HRTEM images of the material prepared in Example 1 of the present invention, respectively.

[0018] Figure 2 (a, b, c) are SEM images of the materials prepared in Examples 2, 3 and 4 of this invention, respectively.

[0019] Figure 3 (a, b) are SEM and HRTEM images of the material prepared in Comparative Example 1 of the present invention, respectively.

[0020] Figure 4 The XRD patterns are of the materials prepared in Example 1 and Comparative Example 1 of this invention.

[0021] Figure 5 The images show the FTIR spectra of the materials prepared in Example 1 and Comparative Example 1 of this invention.

[0022] Figure 6 The current collector assembled half-cell prepared for Test Example 1 of this invention operates at 1 mA cm⁻¹. -2 1mAhcm -2 The Coulomb efficiency curve is shown below.

[0023] Figure 7 Cycling curves of a full cell without a negative electrode assembled with a current collector and LFP prepared for Test Example 2 of the present invention at 1C rate. Detailed Implementation

[0024] Example 1 Preparation of zinc-enriched carbon nanoflowers with an in-situ dual inorganic passivation layer: a) 15 mmol dimethylimidazole and 5 mmol 5-Aminotetrazole was added to 30 mL of methanol and stirred at 25°C for 10 min until dissolved, yielding solution A; 10 mmol of zinc acetate dihydrate was added to 30 mL of methanol and stirred at 25°C for 10 min, yielding solution B; then solution A was added to solution B and stirred at 25°C for 10 min to obtain a homogeneous mixture; b) the mixture obtained in step a) was added to a hydrothermal reactor and hydrothermally heated at 80°C for 5 h, then centrifuged, washed three times with ethanol, and dried at 80°C for 12 h to obtain the Zn-MOF precursor; c) the Zn-MOF precursor obtained in step b) was carbonized at 800°C for 2 h under argon protection to obtain Zn-MOF-derived zinc-enriched carbon nanoflowers; d) 0.5 g of the zinc-enriched carbon nanoflowers obtained in step c) and 5 mmol NH4F and 2 mmol of zinc nitrate hexahydrate were added to 60 mL of anhydrous ethanol and stirred at 25°C for 60 min. The mixture was then added to a hydrothermal reactor and hydrothermally heated at 120°C for 12 h. After centrifugation, the mixture was washed three times with ethanol and water, and dried at 80°C for 12 h to obtain ZnNCN / ZnF2 composite carbon nanoflowers (ZCNF@ZNZF).

[0025] Example 2 Preparation of zinc-enriched carbon nanoflowers with an in-situ dual inorganic passivation layer (compared to Example 1, this example mainly changes the molar ratio of the ligands): a) 16 mmol dimethylimidazole and 4 mmol 5-Aminotetrazole was added to 30 mL of methanol and stirred at 25°C for 10 min until dissolved, yielding solution A; 8 mmol of zinc nitrate hexahydrate was added to 30 mL of methanol and stirred at 25°C for 10 min, yielding solution B; then solution A was added to solution B and stirred at 25°C for 10 min to obtain a homogeneous mixture; b) the mixture obtained in step a) was added to a hydrothermal reactor and hydrothermally heated at 80°C for 5 h, then centrifuged, washed three times with ethanol, and dried at 80°C for 12 h to obtain the Zn-MOF precursor; c) the Zn-MOF precursor obtained in step b) was carbonized at 800°C for 2 h under argon protection to obtain Zn-MOF-derived zinc-enriched carbon nanoflowers; d) 0.5 g of the zinc-enriched carbon nanoflowers obtained in step c) and 5 mmol NH4F and 2 mmol of zinc nitrate hexahydrate were added to 60 mL of anhydrous ethanol and stirred at 25°C for 60 min. The mixture was then added to a hydrothermal reactor and hydrothermally heated at 120°C for 12 h. After centrifugation, the mixture was washed three times with ethanol and water, and dried at 80°C for 12 h to obtain ZnNCN / ZnF2 composite carbon nanoflowers.

[0026] Example 3 Preparation of zinc-enriched carbon nanoflowers with an in-situ dual inorganic passivation layer (compared to Example 1, this example mainly changes the feeding ratio of zinc-enriched carbon nanoflowers to NH4F in the secondary hydrothermal modification stage): a) 15 mmol dimethylimidazole and 5 mmol 5-Aminotetrazole was added to 30 mL of methanol and stirred at 25°C for 10 min until dissolved, yielding solution A; 10 mmol of anhydrous zinc sulfate was added to 30 mL of methanol and stirred at 25°C for 10 min, yielding solution B; then solution A was added to solution B and stirred at 25°C for 10 min to obtain a homogeneous mixture; b) the mixture obtained in step a) was added to a hydrothermal reactor and hydrothermally heated at 80°C for 5 h, then centrifuged, washed three times with ethanol, and dried at 80°C for 12 h to obtain the Zn-MOF precursor; c) the Zn-MOF precursor obtained in step b) was carbonized at 800°C for 2 h under argon protection to obtain Zn-MOF-derived zinc-enriched carbon nanoflowers; d) 0.6 g of the zinc-enriched carbon nanoflowers obtained in step c) and 8 mmol NH4F and 2 mmol of zinc nitrate hexahydrate were added to 60 mL of anhydrous ethanol and stirred at 25°C for 60 min. The mixture was then added to a hydrothermal reactor and hydrothermally heated at 120°C for 12 h. After centrifugation, the mixture was washed three times with ethanol and water, and dried at 80°C for 12 h to obtain ZnNCN / ZnF2 composite carbon nanoflowers.

[0027] Example 4 Preparation of zinc-enriched carbon nanoflowers with an in-situ dual inorganic passivation layer (compared to Example 1, this example also changes the ligand molar ratio and the feeding ratio of zinc-enriched carbon nanoflowers to NH4F in the secondary hydrothermal modification stage): a) 16 mmol dimethylimidazole and 4 mmol 5-Aminotetrazole was added to 30 mL of methanol and stirred at 25°C for 10 min until dissolved, yielding solution A; 8 mmol of zinc chloride was added to 30 mL of methanol and stirred at 25°C for 10 min, yielding solution B; then solution A was added to solution B and stirred at 25°C for 10 min to obtain a homogeneous mixture; b) the mixture obtained in step a) was added to a hydrothermal reactor and hydrothermally heated at 80°C for 5 h, then centrifuged, washed three times with ethanol, and dried at 80°C for 12 h to obtain the Zn-MOF precursor; c) the Zn-MOF precursor obtained in step b) was carbonized at 800°C for 2 h under argon protection to obtain Zn-MOF-derived zinc-enriched carbon nanoflowers; d) 0.6 g of the zinc-enriched carbon nanoflowers obtained in step c) and 8 mmol of... NH4F and 2 mmol of zinc nitrate hexahydrate were added to 60 mL of anhydrous ethanol and stirred at 25°C for 60 min. The mixture was then added to a hydrothermal reactor and hydrothermally heated at 120°C for 12 h. After centrifugation, the mixture was washed three times with ethanol and water, and dried at 80°C for 12 h to obtain ZnNCN / ZnF2 composite carbon nanoflowers.

[0028] Comparative Example 1 Preparation of zinc-enriched carbon nanoflowers (compared to Example 1, this comparative example does not have a secondary hydrothermal modification step): a) 15 mmol of dimethylimidazole and 5 mmol of 5-aminotetrazazole were added to 30 mL of methanol and stirred at 25°C for 10 min until dissolved to obtain solution A; 10 mmol of zinc acetate dihydrate was added to 30 mL of methanol and stirred at 25°C for 10 min to obtain solution B; then solution A was added to solution B and stirred at 25°C for 10 min to obtain a homogeneous mixture; b) the mixture obtained in step a) was added to a hydrothermal reactor and hydrothermally heated at 80°C for 5 h, then centrifuged, washed three times with ethanol, and dried at 80°C for 12 h to obtain the Zn-MOF precursor; c) the Zn-MOF precursor obtained in step b) was carbonized at 800°C for 2 h under argon protection to obtain Zn-MOF-derived zinc-enriched carbon nanoflowers (ZCNF).

[0029] Depend on Figures 1-5It can be seen that the ZCNF@ZNZF obtained in Example 1 maintains the three-dimensional flower-like porous framework of Zn-MOF-derived carbon nanoflowers, and forms a relatively continuous and uniform composite coating layer on the surface. The scale units are more dense and the pore structure remains interconnected. In contrast, although the ZCNF in Comparative Example 1 has a flower-like carbon framework morphology, it lacks an obvious inorganic composite layer coating on the surface. The SEM images of Examples 2-4 further illustrate that composite carbon nanoflowers with relatively uniform morphology can be successfully obtained under different zinc salt conditions. At the same time, XRD and FTIR results show that ZnNCN / ZnF2 related structures and chemical bonds were successfully introduced in Example 1, while Comparative Example 1 mainly exhibits the intrinsic characteristics of Zn-MOF-derived carbon framework. This indicates that the secondary hydrothermal modification strategy adopted in this invention can effectively construct a ZnNCN / ZnF2 dual inorganic composite layer on the surface of zinc-enriched carbon nanoflowers.

[0030] Test Example 1 To test the lithium deposition / stripping efficiency of ZCNF@ZNZF in Example 1, ZCNF in Comparative Example 1, and copper foil (Bare Cu), half-cells were assembled for testing. The materials obtained in Example 1 and Comparative Example 1 were mixed with PVDF and NMP in a 9:1 ratio. The resulting slurry was coated onto copper foil using a doctor blade and dried under vacuum at 120°C for 12 hours to obtain a current collector. The current collector or Bare Cu was used as the positive electrode, lithium metal as the negative electrode, and the electrolyte was 1M LiTFSI dissolved in DOL / DME = 1:1 with 2wt% lithium nitrate added. The separator was Celgard 2500. Battery assembly was performed using a Model 2032 button cell in an argon-protected glove box. The test conditions were 1 mA / cm². -2 1mAhcm -2 Its Coulomb efficiency curve is as follows Figure 5 As shown. Depend on Figure 5 It is evident that ZCNF@ZNZF exhibits significantly superior cycling stability and electrochemical reversibility compared to ZCNF and Bare Cu. Bare Cu, due to its poor lithiophilicity and uneven lithium deposition, experiences drastic fluctuations in coulombic efficiency and fails after only 50 cycles. While ZCNF benefits from improved lithiophilicity due to zinc species, the lack of an inorganic passivation layer to regulate the interface results in significant efficiency fluctuations and degradation after 200 cycles, with repeated SEI film rupture and regeneration leading to a continuous decline in interface stability. In contrast, ZCNF@ZNZF utilizes the synergistic effect of dual inorganic passivation layers: ZnNCN reduces the lithium nucleation overpotential, ZnF2 induces the formation of a stable LiF-enriched SEI film, and the porous structure of carbon nanoflowers homogenizes the Li... + Flux. At 1 mA cm - ²、1mAhcm -It can cycle stably for 1200 cycles under certain conditions, with an average coulombic efficiency of 98.5%. It can still cycle stably under high load, effectively suppressing interfacial side reactions and significantly improving the reversibility of lithium deposition / stripping.

[0031] Test Example 2 The materials obtained in Example 1 and Comparative Example 1 were mixed with lithium carboxymethyl cellulose and deionized water at a ratio of 9:1. The resulting slurry was coated onto copper foil using a scraper and dried under vacuum at 100°C for 12 hours to obtain a current collector. The current collector or Bare Cu was used as the negative electrode to assemble a full cell with an LFP. The electrolyte was 1M LiTFSI dissolved in DOL / DME = 1:1, with 2wt% lithium nitrate added. The separator was Celgard 2500. Battery assembly was performed using a 2032 button cell in an argon-protected glove box. Charge-discharge tests were conducted at 1C rate, and the results are as follows: Figure 6 As shown.

[0032] Depend on Figure 6 and Figure 7 It is evident that, compared to ZCNF current collectors and Bare Cu, the ZCNF@ZNZF current collector exhibits superior coulombic efficiency and cycling stability in half-cell lithium deposition / stripping tests, and also demonstrates higher capacity retention and a more stable cycling curve in electrodeless LFP full cells. This is because the synergistic effect of the ZnNCN / ZnF2 dual inorganic composite layer and the zinc-enriched carbon nanoflower three-dimensional framework reduces the lithium nucleation overpotential and induces uniform lithium deposition. Furthermore, it facilitates the construction of a stable inorganic-rich SEI film and suppresses interfacial side reactions, thereby significantly improving the electrochemical reversibility of the current collector and the cycling performance of the full cell.

[0033] The above description is a specific illustration of the present invention, and not a limitation thereof. Those skilled in the art can make various equivalent technical solutions without departing from the scope of the present invention; therefore, all equivalent technical solutions should be included within the protection scope of the present invention.

Claims

1. A zinc-enriched carbon nanoflower current collector with an in-situ constructed dual inorganic passivation layer, characterized in that, The current collector is a ZnNCN / ZnF2 dual inorganic passivation layer constructed in situ on a three-dimensional framework of zinc-enriched carbon nanoflowers. The zinc-enriched three-dimensional carbon nanoflowers are flower-shaped porous carbon frameworks derived from Zn-MOF. Zn is highly dispersed in the nitrogen-containing carbon framework in the form of Zn-N / Zn-O coordination. The diameter of the ZnNCN / ZnF2 composite carbon nanoflowers is 1.5-2.5 μm, which are composed of thinned and dense scaly units and have a network of interconnected pores.

2. The method for preparing a zinc-enriched carbon nanoflower current collector with an in-situ constructed dual inorganic passivation layer according to claim 1, characterized in that, Includes the following steps: a) Add dimethylimidazolium and 5-aminotetrazole to 30 mL of methanol in a certain proportion, and stir at 25-30°C for 10-15 min until dissolved to obtain solution A; add zinc salt to 30 mL of methanol, and stir at 25-30°C for 10-15 min to obtain solution B; then add solution A to solution B, and stir at 25-30°C for 5-10 min to obtain a homogeneous mixture; b) Add the mixture obtained in step a) to a hydrothermal reactor and hydrothermally heat it at 70~90°C for 4~6 hours. After centrifugation, washing and drying, the Zn-MOF precursor is obtained. c) The Zn-MOF precursor obtained in step b) is carbonized at 800℃ under inert gas protection and kept at that temperature for 2-3 h to obtain Zn-MOF-derived zinc-enriched carbon nanoflowers. d) The zinc-enriched carbon nanoflowers, zinc nitrate hexahydrate and NH4F obtained in step c) are added to 60 mL of anhydrous ethanol in a certain proportion and stirred at 25-30°C for 40-60 min. Then, the mixture is added to a hydrothermal reactor and hydrothermally heated at 100-120°C for 10-14 h. After centrifugation, washing and drying, ZnNCN / ZnF2 composite carbon nanoflowers are obtained. e) The ZnNCN / ZnF2 composite carbon nanoflowers obtained in step d) are mixed with the binder and solvent in a certain proportion. The slurry after grinding is coated onto copper foil with a scraper and then vacuum dried at 120~130°C for 10~12h.

3. The preparation method according to claim 2, characterized in that, In step a), the zinc salt is any one of zinc nitrate hexahydrate, zinc acetate dihydrate, anhydrous zinc sulfate, and zinc chloride.

4. The preparation method according to claim 2, characterized in that, In step a), the molar ratio of dimethylimidazole to 5-aminotetrazole is 3:1 to 4:1, and the molar ratio of imidazole ligand to zinc salt is 2:1 to 3:

1.

5. The preparation method according to claim 2, characterized in that, In step d), the molar ratio of NH4F to zinc nitrate hexahydrate is 2:1 to 4:1, and the total mass of the two is 1:1 to 3:2 compared with the mass of zinc-enriched carbon nanoflowers.

6. The preparation method according to claim 2, characterized in that, In step e), the adhesive is any one of polyvinylidene fluoride, polyacrylic acid, lithium carboxymethyl cellulose, and styrene-butadiene rubber, and the solvent is N-methylpyrrolidone or water.

7. The preparation method according to claim 2, characterized in that, In step e), the mass ratio of ZnNCN / ZnF2 composite carbon nanoflowers to binder is 90:10~95:5, and the coating thickness is 10-20 μm.

8. The application of the zinc-enriched carbon nanoflower current collector with in-situ constructed dual inorganic passivation layer according to claim 1 or the ZnNCN / ZnF2 composite carbon nanoflower prepared by any of the preparation methods according to claims 2 to 7 in the current collector of a negative electrode-free lithium metal battery.

Images