A three-dimensional NiS / Ni-modified copper-based current collector for lithium metal anodes and its preparation method.

Abstract

This invention provides a three-dimensional NiS / Ni modified copper-based current collector for lithium metal anodes and its preparation method. The method includes: immersing foamed copper in an aqueous solution containing NiCl2·6H2O, NaClO, and ammonia; loading metallic nickel onto the surface of the foamed copper using a hydrothermal chemical deposition method to obtain a CN current collector; immersing the CN current collector in an aqueous solution containing NiCl2·6H2O, NaKC4H4O6·4H2O, NaOH, N2H4·H2O, and CH4N2S; loading nickel sulfide onto the surface of the CN current collector using a hydrothermal chemical deposition method to obtain the three-dimensional NiS / Ni modified copper-based current collector. The three-dimensional lithiophilic copper-based current collector of this invention effectively reduces local current density, increases the specific surface area of ​​the anode, and effectively inhibits lithium dendrite growth; the uniformly deposited metallic nickel and nickel sulfide enhance the lithiophilicity of the current collector, provide a large number of nucleation sites, reduce the lithium nucleation overpotential, and provide necessary conditions for uniform lithium deposition.

Description

Technical Field

[0001] This invention belongs to the field of lithium metal battery technology, and particularly relates to a three-dimensional NiS / Ni modified copper-based current collector for lithium metal anodes and its preparation method. Background Technology

[0002] Lithium metal anodes are known for their unparalleled theoretical specific capacity (3860 mAh g⁻¹). -1 With its lowest electrochemical potential (-3.04 V relative to the standard hydrogen electrode), lithium metal anodes are widely considered the "holy grail" of next-generation high-energy-density batteries. However, in practical applications, lithium metal anodes face two core challenges: first, the uncontrollable growth of lithium dendrites. The local current density distribution of traditional planar current collectors is extremely uneven, and the "sharp effect" during electrodeposition causes lithium to preferentially deposit at protrusions, forming dendrites. Dendrites penetrating the separator can lead to internal short circuits, causing thermal runaway or even explosions. Second, poor interface stability. Lithium metal reacts violently with the electrolyte, making it difficult to form a stable solid electrolyte interphase (SEI) film. Repeated rupture and regeneration of the SEI during cycling cause continuous electrolyte consumption and the accumulation of "dead lithium," resulting in rapid capacity decay.

[0003] To reduce local current density and mitigate volume expansion, researchers have developed various three-dimensional current collectors. Three-dimensional porous structures, by increasing specific surface area, can significantly reduce the effective local current density at the same surface current density, while simultaneously providing a physically confined space for lithium deposition. Copper-based three-dimensional current collectors, such as copper foam and copper mesh, have attracted considerable attention due to their low cost and good conductivity. However, pure copper surfaces have poor affinity for lithium, and copper has a high lithiation potential. The nucleation overpotential of lithium on copper surfaces is typically greater than 50 mV, leading to preferential nucleation of lithium at defects and uneven deposition. Therefore, a simple three-dimensional copper framework cannot chemically control the nucleation behavior of lithium, and relying solely on structural modification has significant limitations.

[0004] To improve the lithiophilicity of copper-based current collectors, researchers have developed various surface modification strategies. Metal oxide modifications such as NiO, CoO, and ZnO can reduce the nucleation overpotential through alloying or conversion reactions with lithium. However, metal oxides generally suffer from low electronic conductivity; large oxide loading increases interfacial impedance, and volume changes during cycling can easily lead to coating cracking and peeling. Metal sulfide modifications such as NiS, CoS, and MoS2 typically exhibit better electronic conductivity and higher lithium affinity than oxides, with Li-S bond energies higher than Li-O bond energies. However, directly loading sulfides onto the copper surface presents problems such as weak bonding, easy aggregation, and discontinuous conductive networks in a single sulfide layer. Metal or alloy modifications such as Ag, Zn, and Au can reduce the nucleation overpotential by forming alloys with lithium. However, Ag and Au are expensive, Zn exhibits large volume changes in its alloy phase during cycling, and the improvement in lithiophilicity of a single metal layer is limited.

[0005] In recent years, researchers have attempted to construct composite lithiophilic layers to balance lithiophilicity and conductivity. CN104993131A discloses a method for preparing NiS / Ni composite structures in one step via hydrothermal reaction using nickel foam as a substrate. This method utilizes thiourea and hydrogen peroxide at 90-150°C for 4-10 hours and is used as a negative electrode in lithium-ion batteries. However, this method, using nickel foam as a substrate and leveraging the nickel inherent in the substrate as the reaction source, cannot be directly applied to nickel-free substrates such as copper foam. Furthermore, the one-step reaction makes it difficult to control the ratio and distribution of NiS to Ni. CN118448638A discloses a method for constructing a Co@CoO core-shell framework on copper foam, employing in-situ growth via hydrothermal reaction and hydrogen reduction strategies. However, the lithiophilicity of Co@CoO, based on Li-Co alloys and Li₂O formation, is weaker than that of sulfide systems, and the cost of the Co source is higher than that of the Ni source.

[0006] In summary, existing technologies for constructing efficient lithiophilic interfaces on copper foam-based three-dimensional current collectors face the following unresolved technical challenges. First, there is a lack of methods for constructing NiS / Ni composite lithiophilic layers suitable for copper foam. Existing NiS / Ni composite structures mostly use nickel foam as a substrate, utilizing the substrate nickel as a reaction source, or employing a one-step reaction on a copper substrate, making it difficult to control the product composition. There is no clear solution for how to controllably construct a NiS / Ni composite layer on the surface of copper foam, ensuring that metallic nickel forms a continuous conductive framework and nickel sulfide is uniformly distributed on the framework surface to provide lithiophilic sites. Second, existing preparation processes lack compatibility and controllability. Electrochemical deposition methods exhibit weak bonding, high-temperature vapor phase methods are costly, and one-step hydrothermal methods have uncontrollable product composition. A mild, low-cost preparation method with controllable product composition is needed. Therefore, there is an urgent need in this field for a copper-based current collector that combines three-dimensional structural support, a highly conductive framework, and a highly lithiophilic surface, along with a simple and controllable preparation method to complement it. Summary of the Invention

[0007] The technical problem to be solved by this invention is to controllably construct a NiS / Ni composite interface layer with both high conductivity and high lithiophilicity on a nickel-free copper-based three-dimensional framework such as copper foam, so that metallic nickel forms a continuous conductive network and nickel sulfide is uniformly distributed on the network surface to provide lithiophilic sites, thereby simultaneously controlling the physical space and chemical nucleation behavior of lithium deposition, and obtaining a mild and controllable preparation method.

[0008] To solve the above-mentioned technical problems, the technical solution adopted by the present invention is as follows:

[0009] A method for preparing a three-dimensional NiS / Ni-modified copper-based current collector for a lithium metal anode includes the following steps:

[0010] (1) Immerse copper foam in an aqueous solution containing NiCl2·6H2O, NaClO and ammonia, and load metallic nickel onto the surface of copper foam using a hydrothermal chemical deposition method to obtain a CN current collector;

[0011] (2) The CN current collector is immersed in an aqueous solution containing NiCl2·6H2O, NaKC4H4O6·4H2O, NaOH, N2H4·H2O and CH4N2S. Nickel sulfide is loaded on the surface of the CN current collector by hydrothermal chemical deposition. After washing and drying, the three-dimensional NiS / Ni modified copper-based current collector is obtained.

[0012] Preferably, the thickness of the copper foam is 0.5-1.5 mm, more preferably 0.8-1.5 mm, and even more preferably 1 mm; the porosity is 90-98%, the pore size is 0.10-0.20 mm, and the density is 0.28-0.32 g / cm³. -3 .

[0013] Preferably, in step (1), the foamed copper is sequentially cleaned with dilute hydrochloric acid, anhydrous ethanol, and distilled water and then dried.

[0014] Preferably, in the aqueous solution containing NiCl2·6H2O, NaClO and ammonia, each 100 mL of the aqueous solution contains 3.0-4.0 g of NiCl2·6H2O, 1-2.0 g of NaClO, and 2-6 mL of ammonia.

[0015] Preferably, in step (1), the conditions for the hydrothermal chemical deposition method are: reaction temperature 110-130 ℃, preferably 120 ℃, and reaction time 4-8 hours. The above-mentioned surface deposition process of metallic nickel, combined with copper foam, can uniformly deposit a dense layer of metallic nickel on the surface of the current collector, resulting in a product with better performance.

[0016] Preferably, in the aqueous solution containing NiCl2·6H2O, NaKC4H4O6·4H2O, NaOH, N2H4·H2O and CH4N2S, each 100 mL of the aqueous solution contains 3.0-4.0 g of NiCl2·6H2O, 4.0-6.0 g of NaKC4H4O6·4H2O, 0.4-1.0 g of NaOH, 2-6 mL of N2H4·H2O, and 0.4-0.8 g of CH4N2S.

[0017] Preferably, in step (2), the conditions for the hydrothermal chemical deposition method are: reaction temperature 140-160 ℃, preferably 150 ℃, and reaction time 8-12 hours.

[0018] In the above preparation method, the first step, hydrothermal chemical deposition, preferentially forms a nickel layer on the surface of the copper foam. This nickel layer serves two purposes: firstly, it acts as a conductive framework to reduce interfacial resistance; secondly, it provides heterogeneous nucleation sites for the deposition of nickel sulfide in the second step, guiding the uniform growth of nickel sulfide rather than localized accumulation. The second step, hydrothermal chemical deposition, forms a lithium-affinity active layer of nickel sulfide on the surface of the nickel framework. The sulfur atoms in nickel sulfide have a strong chemical affinity for lithium, which can reduce the overpotential for lithium nucleation. Simultaneously, during lithiation, nickel sulfide can generate lithium-sulfur compounds in situ, participating in the construction of a stable solid electrolyte interfacial film. The reaction conditions for the two steps are optimized independently, avoiding the problem of mutual constraints between the reduction and sulfidation processes in a single reaction system, and achieving controllable adjustment of the composition and spatial distribution of the NiS / Ni composite layer.

[0019] This invention also provides a three-dimensional NiS / Ni modified copper-based current collector for lithium metal anodes, prepared using the method described above. The current collector comprises a three-dimensional porous copper framework and a NiS / Ni composite lithiophilic layer loaded on the surface of the copper framework. In the composite lithiophilic layer, metallic nickel forms a continuous conductive network, and nickel sulfide is uniformly distributed on the surface of the conductive network.

[0020] The present invention also provides a lithium metal coin cell battery, comprising a positive electrode shell, a negative electrode current collector, a separator, a lithium sheet, and a negative electrode shell, wherein the negative electrode current collector is the aforementioned three-dimensional NiS / Ni modified copper-based current collector.

[0021] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0022] 1) This invention forms a NiS / Ni composite lithiophilic layer on the surface of copper foam through a stepwise construction strategy. The spatially ordered distribution of the conductive framework of metallic nickel and the lithiophilic sites of nickel sulfide enables the current collector to have both high electronic conductivity and low lithium nucleation overpotential, effectively suppressing lithium dendrite growth and volume expansion. At the same time, the stable solid electrolyte interface film formed in situ reduces electrolyte consumption and dead lithium accumulation, significantly improving the cycle stability and safety of lithium metal batteries.

[0023] 2) This invention utilizes the unique structure of three-dimensional foamed copper to uniformly deposit a dense nickel sulfide and metallic nickel lithiophilic layer of a certain size on its surface. The lithiophilic layer provides a large number of nucleation sites and spatial structures for lithium deposition, effectively suppressing the growth and volume change of lithium dendrites. At the same time, the lithiophilicity of the loaded material is structurally modified, further increasing the specific surface area of ​​the current collector, which can effectively weaken the negative impact of lithium metal volume expansion, thereby effectively improving the energy density and effective capacity of the battery. This is an innovative method and effective strategy to solve the problem of limiting the practical application of lithium metal batteries and improve battery energy density.

[0024] 3) This invention constructs a three-dimensional, lithium-loving copper-based current collector with a high specific surface area through structural modification and loading of lithium-loving materials. This optimizes lithium insertion / extraction behavior, improves electrochemical performance, and can accommodate more lithium deposition, thus broadening the application prospects of high-load lithium batteries. This three-dimensional lithium-loving copper-based current collector design effectively achieves uniform lithium deposition and long-term cycling of the anode, providing a reference for the design of lithium metal anodes and representing an innovation in lithium anode research methods. Attached Figure Description

[0025] Figure 1 The image shows the surface morphology of the copper foam disc (CF) in Comparative Example 1.

[0026] Figure 2 This is a surface morphology diagram of the nickel-loaded copper foam disc (CN) in Comparative Example 3.

[0027] Figure 3 This is a surface morphology diagram of the copper foam disc (CNS) loaded with nickel sulfide and metal in Example 4.

[0028] Figure 4 The chart shows a comparison of coulomb efficiency tests for Examples 1-4.

[0029] Figure 5 This is a comparison chart of coulomb efficiency tests for Comparative Examples 1-5.

[0030] Figure 6 This is a comparison chart of the long-cycle tests of symmetrical batteries in Comparative Examples 1, 3, and 4.

[0031] Figure 7 This is a comparison chart of the full-cell long-cycle test results for Comparative Example 1, Comparative Example 3, and Example 4.

[0032] Figure 8 This is a comparison chart of the full-cell rate performance tests of Comparative Example 1, Comparative Example 3, and Example 4.

[0033] Figure 9 This is a comparison chart showing the long-cycle performance of full cells of Comparative Example 1, Comparative Example 3, and Example 4 compared to high-load lithium iron phosphate. Detailed Implementation

[0034] To facilitate understanding of the present invention, the present invention will be described more fully and in detail below with reference to the accompanying drawings and preferred embodiments, but the scope of protection of the present invention is not limited to the following specific embodiments.

[0035] Unless otherwise defined, all technical terms used herein have the same meaning as commonly understood by those skilled in the art. The technical terms used herein are for the purpose of describing particular embodiments only and are not intended to limit the scope of the invention.

[0036] Unless otherwise specified, all raw materials, reagents, instruments and equipment used in this invention can be purchased from the market or prepared by existing methods.

[0037] This invention provides a three-dimensional NiS / Ni modified copper-based current collector for lithium metal anodes and its preparation method. The current collector uses foamed copper as a three-dimensional conductive framework. A metallic nickel layer and a nickel sulfide layer are sequentially constructed on its surface through a two-step hydrothermal chemical deposition method, forming a NiS / Ni composite lithiophilic interface. The porous three-dimensional structure of the foamed copper provides a high specific area physical scaffold, effectively reducing local current density and providing sufficient space for lithium deposition to alleviate volume expansion problems. In the first step, the deposited metallic nickel forms a continuous conductive network on the surface of the copper framework. This enhances the electronic conductivity of the current collector and provides heterogeneous nucleation sites for the second step of nickel sulfide deposition, guiding uniform growth of nickel sulfide rather than localized accumulation. The nickel sulfide deposited in the second step is distributed on the surface of the metallic nickel framework, providing a high density of lithiophilic active sites, reducing the lithium nucleation overpotential, and promoting uniform lithium metal deposition. Simultaneously, during electrochemical cycling, the nickel sulfide participates in the formation of a stable solid electrolyte interface film rich in lithium-sulfur compounds, inhibiting continuous electrolyte decomposition and the accumulation of dead lithium. This three-dimensional framework provides spatial support, while the surface lithiophilic material guides the uniform deposition of lithium, thus accelerating the diffusion rate of lithium ions in the electrode, reducing the lithium ion concentration difference during charging and discharging, and forming a rapid lithium ion transport channel. This effectively improves the lithium insertion / extraction efficiency and enhances the electrochemical performance and safety of lithium metal batteries.

[0038] Example 1

[0039] A method for preparing a three-dimensional NiS / Ni-modified copper-based current collector for a lithium metal anode includes the following steps:

[0040] (1) Cut the foamed copper into round pieces with a diameter of 14 mm and a thickness of 0.5 mm, and wash them in sequence with 0.1 mol L-1 dilute hydrochloric acid, anhydrous ethanol and distilled water, and place them in a vacuum oven at 80 ℃ for 1 hour to dry them;

[0041] (2) Immerse three pieces of foamed copper pretreated in step (1) into 50 mL of an aqueous solution containing NiCl2·6H2O (1.66 g), NaClO (0.75 g) and ammonia (2 mL), and heat the mixture in an oven at 120 °C for 6 hours to obtain CN current collector.

[0042] (3) Place the three CN current collectors into a 50 mL aqueous solution containing NiCl2·6H2O (1.66 g), NaKC4H4O6·4H2O (2.8 g), NaOH (0.4 g), N2H4·H2O (2 mL) and CH4N2S (0.38 g), and heat the reaction system at 150 °C for 12 hours.

[0043] (4) Take out the disc after the above reaction, wash it with deionized water 3 times, dry it in vacuum at 60 °C for 12 hours and set it aside for use to prepare a foamed copper disc loaded with nickel sulfide and metallic nickel, that is, the lithium metal anode copper-based current collector modified with three-dimensional NiS / Ni (CNS current collector).

[0044] This embodiment uses a 0.5 mm thin foamed copper substrate, which achieves effective loading of the NiS / Ni composite layer while ensuring the current collector is lightweight. It is suitable for application scenarios with high battery energy density requirements but relatively moderate cycle life requirements.

[0045] Example 2

[0046] A method for preparing a three-dimensional NiS / Ni-modified copper-based current collector for a lithium metal anode includes the following steps:

[0047] (1) Cut the foamed copper into circular pieces with a diameter of 14 mm and a thickness of 1 mm, and wash them in sequence with 0.1 mol L-1 dilute hydrochloric acid, anhydrous ethanol and distilled water, and place them in a vacuum oven at 80 ℃ for 1 hour to dry them;

[0048] (2) Immerse three pieces of foamed copper pretreated in step (1) into 50 mL of an aqueous solution containing NiCl2·6H2O (1.5 g), NaClO (0.5 g) and ammonia (1 mL), and heat the mixture in an oven at 120 °C for 4 hours to obtain CN current collector.

[0049] (3) Place the three CN current collectors into a 50 mL aqueous solution containing NiCl2·6H2O (1.66 g), NaKC4H4O6·4H2O (2.8 g), NaOH (0.4 g), N2H4·H2O (2 mL) and CH4N2S (0.38 g), and heat the reaction system at 150 °C for 12 hours.

[0050] (4) Take out the disc after the above reaction, wash it with deionized water 3 times, dry it under vacuum at 60 °C for 12 hours and prepare the CNS current collector.

[0051] This embodiment shortens the reaction time of the first step and improves the preparation efficiency while ensuring the basic formation of the NiS / Ni composite layer, making it suitable for large-scale application scenarios with high production efficiency requirements.

[0052] Example 3

[0053] A method for preparing a three-dimensional NiS / Ni-modified copper-based current collector for a lithium metal anode includes the following steps:

[0054] (1) Cut the foamed copper into circular pieces with a diameter of 14 mm and a thickness of 1 mm, and wash them in sequence with 0.1 mol L-1 dilute hydrochloric acid, anhydrous ethanol and distilled water, and place them in a vacuum oven at 80 ℃ for 1 hour to dry them;

[0055] (2) Three pieces of pretreated copper foam were immersed in 50 mL of an aqueous solution containing NiCl2·6H2O (1.66 g), NaClO (0.75 g) and ammonia (2 mL), and the mixture was heated in an oven at 120 °C for 6 hours to obtain CN current collector.

[0056] (3) Place the three CN current collectors into a 50 mL aqueous solution containing NiCl2·6H2O (1.5 g), NaKC4H4O6·4H2O (2.0 g), NaOH (0.2 g), N2H4·H2O (2 mL) and CH4N2S (0.2 g), and heat the reaction system at 150 °C for 8 hours.

[0057] (4) Take out the disc after the above reaction, wash it with deionized water 3 times, dry it under vacuum at 60 °C for 12 hours and prepare the CNS current collector.

[0058] This embodiment reduces the amount of reactants and reaction time in the second step, thereby reducing raw material costs and energy consumption while ensuring the functionality of the NiS / Ni composite layer. It is suitable for large-scale commercial applications that are sensitive to production costs.

[0059] Example 4

[0060] A method for preparing a three-dimensional NiS / Ni-modified copper-based current collector for a lithium metal anode includes the following steps:

[0061] (1) Cut the copper foam into circular pieces with a diameter of 14 mm and a thickness of 1 mm, and then use 0.1 mol L... -1 Clean with dilute hydrochloric acid, anhydrous ethanol, and distilled water, and then place in a vacuum oven at 80 ℃ for 1 hour to dry.

[0062] (2) Three pieces of pretreated copper foam were immersed in 50 mL of an aqueous solution containing NiCl2·6H2O (1.66 g), NaClO (0.75 g) and ammonia (2 mL), and the mixture was heated in an oven at 120 °C for 6 hours to obtain CN current collector.

[0063] (3) Place the three CN current collectors into a 50 mL aqueous solution containing NiCl2·6H2O (1.66 g), NaKC4H4O6·4H2O (2.8 g), NaOH (0.4 g), N2H4·H2O (2 mL) and CH4N2S (0.38 g), and heat the reaction system at 150 °C for 12 hours.

[0064] (4) Take out the disc after the above reaction, wash it with deionized water 3 times, dry it under vacuum at 60 °C for 12 hours and prepare the CNS current collector.

[0065] The surface morphology of the CNS current collector is as follows: Figure 3 As shown, after further loading nickel sulfide onto the surface of the copper foam loaded with nano-nickel particles, the morphology of the original nickel particles is transformed, and composite particles of nickel sulfide and metallic nickel with high lithiophilic properties are formed on the surface of the copper foam, further increasing the specific surface area. In this embodiment, after comprehensively optimizing the substrate thickness, the first-step reaction conditions, and the second-step reaction conditions, the loading amount, distribution density, and spatial structure of the NiS / Ni composite layer are optimally matched, resulting in the best cycle performance. This represents a preferred implementation method of the present invention that balances cycle life and overall performance. Compared with current traditional lithiophilic material loading methods, this method not only introduces highly lithiophilic materials but also physically modifies the copper foam, effectively increasing the specific surface area of ​​the current collector. This method, which combines chemical modification and physical modification, is innovative and helps to expand the commercial application prospects of three-dimensional current collectors in the field of lithium metal anodes.

[0066] Comparative Example 1

[0067] Cut copper foam into circular pieces with a diameter of 14 mm and a thickness of 1 mm, and then sequentially apply 0.1 mol L... -1 The sample was washed with dilute hydrochloric acid, anhydrous ethanol, and distilled water, and then dried in a vacuum oven at 80 ℃ for 1 hour to serve as a blank control sample.

[0068] Comparative Example 2

[0069] The preparation method of Comparative Example 2 includes the following steps:

[0070] Nickel foam was cut into circular pieces with a diameter of 14 mm and a thickness of 1 mm, and then sequentially treated with 0.1 mol L... -1 The sample was washed with dilute hydrochloric acid, anhydrous ethanol, and distilled water, and then dried in a vacuum oven at 80 °C for 1 hour to serve as a base control sample.

[0071] Comparative Example 3

[0072] A method for preparing a three-dimensional Ni-modified copper-based current collector for a lithium metal anode includes the following steps:

[0073] (1) Cut the copper foam into circular pieces with a diameter of 14 mm and a thickness of 1 mm, and then use 0.1 mol L... -1 Wash with dilute hydrochloric acid, anhydrous ethanol, and distilled water, and then place in a vacuum oven at 80 ℃ for 1 hour to dry.

[0074] (2) Immerse three pieces of pretreated copper foam in 50 mL of an aqueous solution containing NiCl2·6H2O (1.66 g), NaClO (0.75 g) and ammonia (2 mL), and heat the mixture in an oven at 120 °C for 6 hours.

[0075] (3) Take out the disc after the above reaction, wash it with deionized water 3 times, and dry it under vacuum at 60 °C for 12 hours to prepare nickel-loaded copper foam disc (CN current collector).

[0076] The surface morphology diagram of the CN current collector is shown below. Figure 2 As shown, flower-shaped nickel nanoparticles were loaded onto the surface of copper foam via a hydrothermal method, which significantly increased the specific surface area and lithiophilicity of the current collector. This comparative example only underwent the first step of the reaction to verify the effect of a single nickel layer.

[0077] Comparative Example 4

[0078] A method for preparing a lithium metal anode using a three-dimensional NiS-modified copper-based current collector includes the following steps:

[0079] (1) Cut the copper foam into circular pieces with a diameter of 14 mm and a thickness of 1 mm, and then use 0.1 mol L... -1 Clean with dilute hydrochloric acid, anhydrous ethanol, and distilled water, and then place in a vacuum oven at 80 ℃ for 1 hour to dry.

[0080] (2) Place the three pretreated copper foam pieces into a 50 mL aqueous solution containing NiCl2·6H2O (1.66 g), NaKC4H4O6·4H2O (2.8 g), NaOH (0.4 g), N2H4·H2O (2 mL) and CH4N2S (0.38 g), and heat the reaction system at 150 °C for 12 hours.

[0081] (3) Take out the disc after the above reaction, wash it with deionized water 3 times, dry it in vacuum at 60 °C for 12 hours and then use it to prepare the foamed copper disc loaded with nickel sulfide (CS current collector).

[0082] This comparative example omits the first nickel deposition step and directly performs the second reaction on copper foam to verify the role of a single nickel sulfide layer and the necessity of the two-step method.

[0083] Comparative Example 5

[0084] A method for preparing a three-dimensional NiS / Ni-modified nickel-based current collector for a lithium metal anode includes the following steps:

[0085] (1) Cut the nickel foam into circular pieces with a diameter of 14 mm and a thickness of 1 mm, and then use 0.1 mol L... -1 Clean with dilute hydrochloric acid, anhydrous ethanol, and distilled water, and then place in a vacuum oven at 80 ℃ for 1 hour to dry.

[0086] (2) Three pieces of pretreated nickel foam were immersed in 50 mL of an aqueous solution containing NiCl2·6H2O (1.66 g), NaClO (0.75 g) and ammonia (2 mL), and the mixture was heated in an oven at 120 °C for 6 hours to obtain NN current collector.

[0087] (3) Place the three NN current collectors into a 50 mL aqueous solution containing NiCl2·6H2O (1.66 g), NaKC4H4O6·4H2O (2.8 g), NaOH (0.4 g), N2H4·H2O (2 mL) and CH4N2S (0.38 g), and heat the reaction system at 150 °C for 12 hours.

[0088] (4) Take out the disc after the above reaction, wash it with deionized water 3 times, dry it in vacuum at 60 °C for 12 hours and set it aside for use, thus preparing the foam nickel disc loaded with nickel sulfide and metallic nickel (NNS current collector).

[0089] The surface morphology of the NNS current collector described above is basically consistent with that of the CNS current collector obtained in Example 4. This comparative example uses nickel foam instead of copper foam as the substrate to verify the influence of the substrate material on performance.

[0090] Electrochemical performance testing:

[0091] The current collectors prepared in Examples 1-4 and Comparative Examples 1-5 were assembled into coin cells for electrochemical performance testing. The tests included coulombic efficiency, symmetric cell testing, and full cell testing. All cell assembly was performed in a glove box under an argon atmosphere. The electrolyte was a non-aqueous electrolyte containing lithium salts. After assembly, the cells were allowed to stand for 12 hours to allow for full electrolyte wetting before testing began.

[0092] Half-cell assembly: Using lithium metal foil as the counter electrode and the current collector prepared in each embodiment or comparative example as the working electrode, the cells are packaged into coin cells for coulombic efficiency testing.

[0093] Symmetrical cell assembly: Using two identical pre-deposited lithium metal current collectors prepared in the above-described embodiments or comparative examples as electrodes on both sides, they are packaged into coin cell symmetrical cells to evaluate voltage stability and long-term cycle durability during lithium deposition and stripping processes.

[0094] Full cell assembly: Using the current collector of each embodiment or comparative example with a pre-deposited lithium metal of a certain capacity as the negative electrode and lithium iron phosphate as the positive electrode, they are packaged into coin cell full cells. The capacity of the pre-deposited lithium metal corresponds to twice the capacity of the lithium iron phosphate positive electrode. The full cell is used to evaluate the actual cycle performance, rate performance, and capacity retention under high load conditions of the complete battery system.

[0095] (1) Coulomb efficiency test

[0096] After the coin cell has been left to stand, apply 1 mA cm⁻¹ water to it. -2 Current density at 1 mAh cm⁻¹ -2 Coulomb efficiency tests were conducted at the specified capacity, and the results are shown in Table 1. Figure 4 and Figure 5 .

[0097] Depend on Figure 4 As shown in Table 1, in Comparative Example 1, the pure copper foam exhibited poor lithiophilicity and high local current density, resulting in drastic fluctuations in coulombic efficiency and failure after only 100 cycles. In Comparative Example 2, although the pure nickel foam showed improved lithiophilicity, its high substrate cost and insufficient specific surface area advantage led to failure after 160 cycles. In Comparative Example 3, the copper foam loaded only with metallic nickel increased its cycle life to 200 cycles by increasing the specific surface area and introducing lithiophilic sites, but the limited lithiophilicity of a single nickel layer caused the coulombic efficiency to rapidly decline to below 90%, indicating insufficient long-term stability. In Comparative Example 4, the copper foam loaded only with nickel sulfide suffered from insufficient conductivity of nickel sulfide and weak bonding with the copper substrate, resulting in a coulombic efficiency of 83% after 360 cycles. In Comparative Example 5, the sample loaded with NiS and Ni on nickel foam achieved a cycle life of 560 cycles, but under the same reaction conditions, Example 4, using copper foam as a substrate, achieved a cycle life of 810 cycles, significantly better than Comparative Example 5. Furthermore, the copper foam had lower cost, lower density, and better conductivity.

[0098] Depend on Figure 5As can be seen, all embodiments exhibit superior cycling performance compared to the blank substrate, demonstrating the effectiveness of the two-step method for constructing NiS / Ni composite layers. Embodiment 4, after comprehensive parameter optimization, demonstrates the most outstanding cycling performance, maintaining a coulombic efficiency of 97% after 810 cycles, significantly outperforming all comparative examples and representing the best performance of this invention in maximizing cycle life. Embodiment 1 utilizes a thin substrate, achieving lightweight current collectors while ensuring basic cycling performance. Embodiment 2 shortens the reaction time, improving preparation efficiency while maintaining a cycling level comparable to Comparative Example 3. Embodiment 3 reduces reactant usage, maintaining a high coulombic efficiency of 98% within 480 cycles while reducing raw material costs, exhibiting a good cost-effectiveness ratio. These results indicate that the two-step stepwise construction strategy has flexible parameter adjustability, allowing for optimized selection among cycle life, energy density, production efficiency, and cost according to different application requirements.

[0099] (2) Symmetrical cell test

[0100] After the button cell has been left to stand, it is first charged with a small current of 0.5 mA cm -2 Lithium is deposited on the current collector at a current density of 2 mA h cm⁻¹ -2 Then with 1mA cm -2 Current density at 1 mAh cm⁻¹ -2 Cyclic testing was conducted at a capacity of [capacity value missing] to demonstrate the voltage stability of the composite lithium metal anode of the present invention. The results of the symmetrical cell tests on coin cells in Comparative Example 1, Comparative Example 2, and Example 4 are compared as follows: Figure 6 As shown.

[0101] The symmetric cell in Example 4 maintained very stable cycling for over 860 hours, with the overpotential consistently remaining at a low level of approximately 20 mV. In stark contrast, the overpotential of the Comparative Example 3 cell increased rapidly after 465 hours, indicating that lithium dendrites began to grow uncontrollably, while the Comparative Example 1 cell failed after only 140 hours of stable operation. These results demonstrate that the NiS / Ni composite layer effectively stabilizes lithium deposition and stripping behavior and inhibits dendrite growth.

[0102] (3) Full battery test

[0103] The current collector, after pre-deposited lithium metal in the above half-cell, was removed and assembled with a lithium iron phosphate cathode to form a full cell. A loading of 2.5 mg cm⁻¹ was selected. -2 Using lithium iron phosphate as the positive electrode, cycle tests were conducted at a current density of 1 C. The corresponding results are shown in Table 2, with test results for several representative examples as follows. Figure 7 As shown.

[0104] The pure copper foam full cell of Comparative Example 1 has an initial discharge capacity of 148 mAh g at a 1 C rate. -1 However, its capacity fluctuated significantly during cycling, rapidly dropping to 110 mAh g after only 200 cycles. -1 This indicates poor interfacial stability on the negative electrode side and uneven lithium stripping / deposition behavior. The performance of the copper foam full cell in Comparative Example 3, which only loads metallic nickel, is improved, retaining 110 mAh g⁻¹ after 350 cycles. -1 The capacity is attributed to the enhanced lithium affinity resulting from nickel modification. Most notably, the full cell of Example 4 exhibits best-in-class performance, retaining over 125 mAh g⁻¹ after 610 long cycles. -1 The high capacity corresponds to an extremely low average capacity decay rate of only 0.033% per cycle, with a coulombic efficiency consistently maintained at around 99.9%. This excellent cycling stability stems directly from the synergistic effect of the three-dimensional high specific surface area framework and the lithiophilic NiS sites, which together regulate lithium-ion flux and promote uniform nucleation.

[0105] A loading capacity of 2.5 mg cm was selected. -2 Using lithium iron phosphate as the positive electrode and the aforementioned material as the negative electrode, cyclic testing was conducted at different current densities, and the results are as follows: Figure 8 As shown, at various rate limits, the capacity of the full cell in Example 4 was consistently higher than that in Comparative Examples 1 and 3, demonstrating excellent rate performance and good lithium insertion / extraction performance.

[0106] The loading capacity was selected as 11.5 mg cm. -2 Using lithium iron phosphate as the positive electrode and the above material as the negative electrode, a cycle test was conducted at a current density of 1 C, and the results are as follows. Figure 9 As shown. At a 1C rate, Comparative Example 1 battery retained only 80 mAh g after 90 cycles. -1 The capacity of the battery in Comparative Example 3 was 90 mAh g after 300 cycles. -1 However, the full cell of Example 4 still maintained a capacity of over 110 mAh g after 510 cycles. -1 The capacity exhibits extremely low capacity decay (0.052% per cycle) and high coulombic efficiency.

[0107] Table 1

[0108]

[0109] Table 2

[0110]

[0111] In summary, the three-dimensional NiS / Ni-modified copper-based current collector provided in this application not only alleviates local charge accumulation and the stress effect caused by volume expansion during lithium deposition / stripping, but also significantly reduces the lithium-ion nucleation barrier and optimizes lithium deposition behavior due to the lithium-lithium sulfide and metallic nickel loaded on the three-dimensional metal substrate framework. Furthermore, structural modification further increases the specific surface area of ​​the current collector, reduces local current density, and suppresses the negative impact of lithium volume expansion. The preparation method is simple, easy to mass-produce, and has great potential for practical applications.

[0112] The above description is merely a specific embodiment of this application. Any variations or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in this application should be included within the protection scope of this application. The protection scope of this application should be determined by the protection scope of the claims.

Claims

1. A method for preparing a three-dimensional NiS / Ni-modified copper-based current collector for lithium metal anodes, characterized in that, Includes the following steps: (1) Immerse copper foam in an aqueous solution containing NiCl2·6H2O, NaClO and ammonia, and load metallic nickel onto the surface of copper foam using a hydrothermal chemical deposition method to obtain a CN current collector; (2) The CN current collector is immersed in an aqueous solution containing NiCl2·6H2O, NaKC4H4O6·4H2O, NaOH, N2H4·H2O and CH4N2S, and nickel sulfide is loaded on the surface of the CN current collector by hydrothermal chemical deposition to obtain the three-dimensional NiS / Ni modified copper-based current collector.

2. The method for preparing a three-dimensional NiS / Ni-modified copper-based current collector for a lithium metal anode according to claim 1, characterized in that, The copper foam has a thickness of 0.5-1.5 mm, a porosity of 90-98%, a pore size of 0.10-0.20 mm, and a density of 0.28-0.32 g / cm³. -3 .

3. The method for preparing a three-dimensional NiS / Ni-modified copper-based current collector for a lithium metal anode according to claim 1, characterized in that, The thickness of the copper foam is 0.8-1.5 mm.

4. The method for preparing a three-dimensional NiS / Ni-modified copper-based current collector for a lithium metal anode according to claim 1, characterized in that, In step (1), the foamed copper is washed with dilute hydrochloric acid, anhydrous ethanol and distilled water in sequence and then dried.

5. The method for preparing a three-dimensional NiS / Ni-modified copper-based current collector for a lithium metal anode according to claim 1, characterized in that, The aqueous solution containing NiCl2·6H2O, NaClO, and ammonia contains 3.0-4.0 g of NiCl2·6H2O, 1.0-2.0 g of NaClO, and 2-6 mL of ammonia per 100 mL.

6. The method for preparing a three-dimensional NiS / Ni-modified copper-based current collector for a lithium metal anode according to claim 1, characterized in that, In step (1), the conditions for the hydrothermal chemical deposition method are: reaction temperature 110-130 ℃, reaction time 4-8 hours.

7. The method for preparing a three-dimensional NiS / Ni-modified copper-based current collector for a lithium metal anode according to claim 1, characterized in that, The aqueous solution containing NiCl2·6H2O, NaKC4H4O6·4H2O, NaOH, N2H4·H2O, and CH4N2S contains, per 100 mL, 3.0-4.0 g of NiCl2·6H2O, 4.0-6.0 g of NaKC4H4O6·4H2O, 0.4-1.0 g of NaOH, 2-6 mL of N2H4·H2O, and 0.4-0.8 g of CH4N2S.

8. The method for preparing a three-dimensional NiS / Ni-modified copper-based current collector for a lithium metal anode according to claim 1, characterized in that, In step (2), the conditions for the hydrothermal chemical deposition method are: reaction temperature 140-160 ℃, reaction time 8-12 hours.

9. A three-dimensional NiS / Ni-modified copper-based current collector for lithium metal anodes, characterized in that, Prepared using the method described in any one of claims 1-8.

10. A lithium metal button battery, characterized in that, It includes a positive electrode shell, a negative electrode current collector, a separator, a lithium sheet, and a negative electrode shell, wherein the negative electrode current collector is the three-dimensional NiS / Ni modified copper-based current collector as described in claim 9.

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