An artificial interfacial layer material, its preparation method and application in lithium metal and negative electrode-free batteries

Abstract

This invention discloses an artificial interface layer material, its preparation method, and its application in lithium metal and electrodeless batteries. The material is a narrow-pore covalent organic framework containing nitrogen sites. By introducing metal ions such as Co / Ni / Fe to form M-Nx coordination sites, it achieves 0.5-1.2 nm sub-nanopores and negative surface charges, enabling selective transport and uniform nucleation of lithium ions. The material can form a continuous interface layer with a thickness of 0.1-10 μm on the surface of copper current collectors or metallic lithium, improving electrolyte wettability, reducing nucleation overpotential and interfacial transport impedance, and suppressing dendrites and side reactions. When current collectors using the interface layer of this invention are used in electrodeless batteries, uniform lithium deposition can be achieved during the first charge, and coulombic efficiency can be improved. When used in lithium metal anodes, it can significantly extend the life of symmetrical batteries and improve the rate capability and cycle stability of the full battery.

Description

Technical Field

[0001] This invention belongs to the field of secondary battery interface regulation technology, specifically relating to a metal-coordinated narrow-pore covalent organic framework artificial interface layer material and its preparation method, and to the application of this material / interface layer in the modification of the negative electrode interface of lithium metal batteries and anode-free batteries. Background Technology

[0002] Lithium metal possesses extremely high theoretical specific capacity and the lowest electrochemical potential, making it a crucial anode system for achieving high-energy-density secondary batteries. However, during charge and discharge, lithium metal is prone to uneven deposition / stripping, leading to dendrite growth, dead lithium accumulation, and persistent side reactions, which in turn cause reduced coulombic efficiency, increased polarization, and even internal short circuits.

[0003] Electrodeless batteries represent a further pursuit of high energy density: during battery assembly, the negative electrode side only contains a current collector (usually copper foil) without pre-placed metallic lithium; the lithium source comes entirely from the positive electrode. During the first charge, lithium ions deposit on the surface of the negative electrode current collector to form metallic lithium. This configuration can significantly reduce the ineffective mass on the negative electrode side, but it also places more stringent requirements on the reversibility of lithium deposition: any irreversible lithium loss will directly consume the positive electrode lithium source and rapidly lead to capacity decay. Therefore, electrodeless batteries especially require the construction of an efficient and stable interface modification layer on the current collector surface to induce uniform nucleation and suppress side reactions.

[0004] Existing interface control strategies include constructing artificial SEIs, introducing lithiophilic coatings, using porous hosts, or adjusting electrolyte systems. However, these strategies generally suffer from insufficient ion transport selectivity, difficulty in simultaneously achieving mechanical and chemical stability of the interface layer, and poor adaptability to anode-free systems. Therefore, developing an interface layer material that can simultaneously achieve "lithium-ion selective transport + uniform nucleation and templating + structural stability support" is of great significance for improving the cycle life and rate performance of lithium metal and anode-free batteries. Summary of the Invention

[0005] This invention aims to provide a metal-coordinated narrow-pore covalent organic framework artificial interface layer material and its preparation method. By constructing a nitrogen-rich coordination microenvironment in sub-nanometer channels and anchoring dispersed metal-nitrogen coordination sites, the selective migration of lithium ions and interfacial reaction kinetics are enhanced, thereby suppressing dendrites and side reactions. Furthermore, the scope of protection is extended to the modification of current collector interfaces in negative electrode-free batteries.

[0006] To achieve the above objectives, the present invention provides the following technical solution: (1) An artificial interface layer material for modifying the negative electrode interface of lithium metal batteries and negative electrodeless batteries is provided: the artificial interface layer material is a metal-coordinated narrow-pore covalent organic framework material, the covalent organic framework material having pores mainly at the sub-nanometer scale; the inner wall of the pore contains nitrogen-containing coordination units and anchors metal-nitrogen coordination sites M-Nx formed by metal ions, wherein the metal M is one or more of Co, Ni, Fe, Mn, Cu, and Zn, and x is a number from 2 to 6. x represents the number of nitrogen atoms coordinated with the metal ions.

[0007] Structural Basis: This COF material possesses sub-nanometer pores (e.g., pore sizes in the range of 0.5 nm to 1.2 nm, preferably 0.7–0.9 nm). This narrow-pore structure provides a geometrically confined basis for subsequent ion transport modulation. Pore size < 0.5 nm: Excessive geometric confinement will significantly increase Li... + (And some solvated clusters) migration resistance and desolvation energy barriers lead to increased interfacial transport impedance, intensified polarization, and decreased rate / cycling performance; at the same time, it is more prone to pore blockage due to byproduct accumulation. Pore size > 1.2 nm: ion sieving effect is weakened, anions / solvents pass through more easily, ion association and side reactions at the interface are more difficult to suppress, weakening "Li + The ability to regulate "selective migration + uniform flux" can improve the risk of uneven deposition / dendritic formation and the probability of dead lithium accumulation. Therefore, a pore size of 0.5-1.2 nm (preferably 0.7-0.9 nm) is a compromise window to balance the contradiction between ion sieving selectivity and low impedance / low polarization.

[0008] Functional center: Highly dispersed M atoms are anchored on the inner wall of the COF pores through chemical coordination. + This forms a well-defined coordination center. The coordination center is formed by a nitrogen-containing aromatic heterocyclic structural unit (e.g., pyrazine and / or bipyridine unit) in the COF backbone interacting with M... + It is formed by coordination.

[0009] Synergistic mechanism: The sub-nanometer narrow pores and the M–Nx coordination centers on the pore walls work synergistically to reconstruct the interfacial microenvironment of the lithium metal anode. This material enables preferential transport of lithium ions and hinders anion migration, thereby reducing concentration polarization and the risk of side reactions.

[0010] Preferably, the mass percentage of the metal element is 5% to 40% based on the total mass of the covalent organic framework material.

[0011] Preferably, the dominant pore size of the sub-nanopores is 0.7-0.9 nm.

[0012] Preferably, the nitrogen-containing coordinating unit is selected from one or more of pyridyl, pyrazinyl, bipyridyl, imidazoleyl, and triazineyl.

[0013] More preferably, the metal-nitrogen coordination site is a Co-Nx coordination site.

[0014] More preferably, the covalent organic framework material is composed of a conjugated skeleton formed by the condensation of 3,3'-bipyridine-6,6'-dicarboxaldehyde (BPDC) and 2,3,5,6-tetramethylpyrazine (Pz) with vinylidene bonds, and is obtained by coordination with Co ions.

[0015] (2) An artificial interface layer is provided: the artificial interface layer material is constructed as a coating on the surface of the negative electrode substrate (e.g., a copper foil current collector or a lithium metal surface), typically forming a continuous and dense interface layer with a thickness of 0.1-10 μm. The artificial interface layer is a continuous coating formed on the surface of the negative electrode substrate by the aforementioned artificial interface layer material. The interface layer can simultaneously provide ion-selective transport channels and uniform lithiophilic nucleation sites, and also possesses certain mechanical support and surface leveling functions. The thickness of the interface layer is preferably 0.2-3 μm, more preferably 0.5-2 μm.

[0016] (3) A negative electrode current collector / negative electrode and battery are provided: the negative electrode current collector includes a negative electrode substrate and an artificial interface layer disposed on the surface of the negative electrode substrate. The negative electrode substrate is selected from one or more of copper foil, copper alloy, nickel foil, stainless steel foil, titanium foil, and carbon-based current collector. The negative electrode includes the aforementioned negative electrode current collector, and optionally further includes a lithium metal layer and / or a lithium-containing alloy layer on the surface of the artificial interface layer; wherein, when the negative electrode does not contain the lithium metal layer and / or the lithium-containing alloy layer during battery assembly, the negative electrode is a negative electrode of a negative electrodeless battery. When the interface layer is disposed on a current collector such as copper foil, it can be used for current collector interface modification of lithium metal batteries, or directly as a negative electrode of a negative electrodeless battery (it does not contain lithium metal during assembly, and the lithium source is provided by the positive electrode for deposition during charging); when the interface layer is disposed on the surface of lithium metal, it can be used for artificial SEI modification of lithium metal negative electrodes. Accordingly, the present invention also provides a lithium metal secondary battery containing the above-mentioned negative electrode, including a positive electrode, a negative electrode, an electrolyte, and a separator. When the lithium metal secondary battery is a negative electrode-less battery, the negative electrode side does not contain metallic lithium during battery assembly. During the first charge, the positive electrode provides the lithium source, and metallic lithium is deposited on the surface of the negative electrode current collector through the artificial interface layer. Typically, the active material of the positive electrode is one or more of lithium iron phosphate, layered lithium-containing transition metal oxides, lithium-rich manganese-based materials, sulfur, or sulfur-containing compounds. When the current collector using the interface layer of this invention is used in a negative electrode-less battery, it can achieve uniform lithium deposition and improve coulombic efficiency during the first charge; when used in a lithium metal negative electrode, it can significantly extend the life of symmetrical cells and improve the rate capability and cycle stability of the entire cell.

[0017] (4) A method for preparing the artificial interface layer material is provided, comprising the following steps: S1, providing a nitrogen-containing monomer and an aldehyde-containing monomer, and performing a solvothermal reaction under an inert atmosphere or vacuum sealing conditions to obtain a narrow-pore covalent organic framework; S2, contacting the covalent organic framework obtained in step S1 with a metal salt solution for post-coordination treatment, so that the metal ions coordinate with the nitrogen-containing coordination unit to form M-Nx coordination sites, thereby obtaining a metal-coordinated narrow-pore covalent organic framework material.

[0018] (5) A method for preparing the artificial interface layer, comprising the following steps: dispersing the artificial interface layer material according to any one of claims 1-5 in a solvent to form a dispersion; coating the dispersion onto the surface of a negative electrode substrate and drying it to form a continuous coating. The coating method may be selected from one or more of the following: drop coating, blade coating, spin coating, spray coating, or dip coating.

[0019] (6) The application of the artificial interface layer material in the preparation of a negative electrode interface modification layer for lithium metal batteries or negative electrode-free batteries is provided. The negative electrode interface modification layer is the interface modification layer described above.

[0020] Compared with the prior art, the present invention has at least the following beneficial effects: (a) By leveraging the “ion sieving” effect of sub-nanometer pores and the regulation of ion association states by nitrogen-rich pore walls / metal coordination sites, the contribution of lithium ions in cross-interface migration can be enhanced, the interfacial transport energy barrier can be reduced, and the interfacial reaction kinetics can be improved, thereby reducing polarization and improving reversibility. (b) By providing a uniform lithium-affinity nucleation template through dispersed M-Nx coordination sites, and combined with the leveling and mechanical support of the continuous coating, local current density hotspots and tip effects can be suppressed, dendrite triggering probability can be reduced and dead lithium accumulation can be reduced. (c) For batteries without a negative electrode, the interface layer of the present invention can be directly applied to the surface of the current collector to induce uniform lithium deposition and improve deposition / stripping reversibility during the first charge, thereby slowing down the consumption of positive electrode lithium source and extending cycle life. (d) The results of the embodiments show that the interface layer of the present invention can significantly reduce nucleation overpotential and polarization, improve coulombic efficiency and extend the life of symmetric cells, while achieving better rate capability and long cycle stability in full cells. Attached Figure Description

[0021] Figure 1 This is a schematic diagram of the material structure of the artificial interface layer of the metal-coordinated narrow-pore covalent organic framework (M-Nx@COF) of the present invention; Figure 2 Contact angle test of bare copper with electrolyte on PzB-COF-Co-Cu surface; Figure 3The coulombic efficiency test results for the Li||Cu half-cell (1 mA cm⁻¹) -2 Capacity 1 mAh cm -2 ); Figure 4 The results of constant current lithium plating / stripping cycle tests for Li||Li symmetric cells (2 mA cm⁻¹) -2 2 mAh cm -2 ); Figure 5 Rate performance of Li||LFP full cells (0.1C to 5C); Figure 6 Long-cycle stability test of Li||LFP full cell (5C condition); Figure 7 The pore size distribution curve of PzB-COF-Co; Figure 8 For the Li||Cu half-cell at 5 mV s -1 The cyclic voltammetry curve below; Figure 9 1 mA cm -2 Under the given conditions, the nucleation overpotential of the Li||Cu half-cell is determined. Detailed Implementation

[0022] To make the objectives, technical solutions, and beneficial effects of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the described embodiments are only for explaining the invention and are not intended to limit the scope of protection of the invention.

[0023] Definitions and abbreviations: BPDC: 3,3'-Bipyridine-6,6'-Dicarboxaldehyde.

[0024] Pz: 2,3,5,6-Tetramethylpyrazine.

[0025] PzB-COF: A covalent organic framework material constructed from narrow-pore vinylene bonds of BPDC and Pz.

[0026] PzB-COF-Co: A metal-coordinated narrow-pore covalent organic framework material obtained by coordinating PzB-COF with Co ions.

[0027] PzB-COF-Ni: A metal-coordinated narrow-pore covalent organic framework material obtained by coordinating PzB-COF with Ni ions.

[0028] PzB-COF-Fe: A metal-coordinated narrow-pore covalent organic framework material obtained by coordinating PzB-COF with Fe ions.

[0029] M-Nx@COF: A metal-coordinated narrow-pore covalent organic framework material obtained by coordinating COF with M metal ions. In this material, the metal ions coordinate with the nitrogen-containing coordination units of COF to form M-Nx coordination sites.

[0030] Artificial interface layer / artificial SEI: A functional layer set on the surface of the negative electrode substrate to regulate ion transport and interfacial reactions.

[0031] Anode-less battery: During battery assembly, metallic lithium is not pre-placed on the negative electrode side, but only contains a current collector (the current collector surface has an artificial interface layer); during charging, lithium is provided by the positive electrode and metallic lithium is deposited on the negative electrode side to form a battery configuration.

[0032] Unless otherwise stated, the terms “comprising” and “including” as used herein are open-ended and may include, but are not limited to, the listed components or steps.

[0033] Example 1: Preparation of metal-coordinated narrow-pore covalent organic framework materials The COF material is dispersed in a polar solvent (e.g., ethanol, methanol, acetonitrile, N,N-dimethylformamide DMF, or mixtures thereof), and a metal salt solution is added. The reaction is stirred within the range of room temperature to reflux temperature. The reaction time can be 2–24 h (preferably 6–12 h). The molar ratio of the metal salt to the coordinating sites (e.g., N sites) in the COF can be adjusted within the range of 0.01–1.0 (preferably 0.05–0.5) to achieve controllable metal loading and coordination degree. After the reaction is complete, the material is centrifuged / filtered and washed with solvent until the filtrate shows no obvious metal ion characteristics (which can be determined by UV / ion colorimetry or conductivity changes). Then, it is dried under vacuum or an inert atmosphere to obtain M-Nx@COF materials (e.g., PzB-COF-Co, PzB-COF-Ni, PzB-COF-Fe, etc.). The structural schematic diagram of the M-Nx@COF material is shown below. Figure 1 As shown.

[0034] (1) Preparation of narrow-pore covalent organic framework PzB-COF BPDC (84.9 mg, 0.4 mmol), Pz (27.25 mg, 0.2 mmol), and benzoic anhydride (181.0 mg, 0.8 mmol) were added to a 5 mL glass reaction tube. After degassing by vacuuming, freezing, and thawing three times, the tube was sealed and heated at 200 °C for 5 days to obtain a solid product. Subsequently, the solid product was soaked in 1 M NaOH / methanol (volume ratio 1:1) for 24 h to remove residual anhydride and activate the pores. Then, it was ground, Soxhlet extracted (acetone / methanol volume ratio 1:1, 24 h), and vacuum dried (60 °C overnight) to obtain PzB-COF powder.

[0035] After the PzB-COF matrix (or other covalent organic frameworks containing nitrogen-containing coordination sites) is prepared, a metal ion M can be introduced by post-treatment coordination. M is selected from one or more of Co, Ni, Fe, Mn, Cu, and Zn. Preferably, the metal salt for introducing the metal ion M is selected from: acetates: Co(OAc)₂·4H₂O, Ni(OAc)₂·4H₂O, Cu(OAc)₂·H₂O, Zn(OAc)₂·2H₂O, Mn(OAc)₂·4H₂O; chlorides / nitrates: FeCl₂ / FeCl₃, NiCl₂, CoCl₂, Cu(NO₃)₂, Zn(NO₃)₂, etc.

[0036] (2) PzB-COF-Co is obtained by post-coordination of metal ions. 30 mg of PzB-COF powder and 30 mg of cobalt acetate tetrahydrate were added to 30 mL of methanol. The mixture was microwaved to 150 °C and held at this temperature for 30 min to initiate a post-coordination reaction. After the reaction, the mixture was washed with methanol and deionized water, centrifuged three times, and dried at 60 °C for 24 h to obtain PzB-COF-Co powder. N2 adsorption-desorption testing showed that the prepared PzB-COF-Co material exhibited a single-peak narrow pore distribution with a dominant pore size of 0.720 nm. Figure 7 It has a typical sub-nanometer confined pore structure.

[0037] Note: The above are merely feasible example processes. This invention is not limited to the specific amounts and conditions of the raw materials mentioned above. The molar ratio of monomers such as BPDC and Pz, the type of solvent (e.g., alcohols, nitriles, aromatic hydrocarbons or mixtures thereof), the reaction temperature (e.g., 120-250 °C), and the time (e.g., 12 h-10 days) can be adjusted according to the target pore size and crystallinity. Metal ions such as Ni, Fe, Mn, Cu, and Zn, which can coordinate with nitrogen-containing sites, can also be selected.

[0038] Example 2: Preparation of artificial interface layer (current collector / lithium anode) (1) Constructing an artificial interface layer on the surface of the current collector (Cu foil) 1.5 mg of PzB-COF or PzB-COF-Co powder was added to 1.5 mL of N-methylpyrrolidone (NMP), and the mixture was ultrasonically dispersed at 25 °C for 30 min, followed by stirring for 24 h to obtain a uniform dispersion. The dispersion was then drop-coated / coated onto the surface of a copper foil and dried at 60 °C to obtain a PzB-COF-Cu or PzB-COF-Co-Cu current collector with a continuous coating. The coating thickness can be controlled by adjusting the concentration of the dispersion and the coating amount, for example, from 0.1 to 10 μm; in this embodiment, the typical thickness is on the order of approximately 1 μm.

[0039] The electrolyte (1 M LiTFSI dissolved in a DOL / DME (volume ratio 1:1) mixed solvent, with 1 wt% LiNO3 added) showed a contact angle of approximately 63.1° on bare Cu and approximately 34.2° on PzB-COF-Co-Cu. Figure 2 This indicates a significant improvement in wettability.

[0040] (2) Constructing an artificial interface layer on the surface of lithium metal The above-mentioned framework material dispersion was uniformly coated on the surface of the lithium metal sheet to achieve complete coverage, and dried in an argon glove box environment (O2 / H2O<0.1 ppm) for 24 h to obtain PzB-COF-Li or PzB-COF-Co-Li anodes.

[0041] Note: The coating method is not limited to drip coating, but can also be scraping, spraying, dip coating, spin coating, etc.; the dispersion medium can be NMP, acetonitrile, alcohols, ethers or their mixtures; if necessary, a small amount of binder (such as PVDF, PVA, CMC, etc.) can be introduced to enhance adhesion.

[0042] Example 3: Li||Cu half-cell (simulating negative electrode side deposition / stripping of a negative electrode-less cell) This embodiment is used to evaluate the effect of the interface layer on the regulation of "lithium deposition on the current collector". This process is consistent with the lithium deposition process on the negative electrode side during the first charge of a battery without a negative electrode. Therefore, it can be used as a direct simulation of the interface modification on the negative electrode side of a battery without a negative electrode.

[0043] (1) Battery assembly Assemble coin cells in an argon-filled glove box: using bare Cu, PzB-COF-Cu, or PzB-COF-Co-Cu as the working electrode, lithium metal sheets as the counter / reference electrode, glass fiber (GF / D) as the separator, and 70 μL of electrolyte. The electrolyte formulation is: 1 M LiTFSI dissolved in a DOL / DME (volume ratio 1:1) mixed solvent, with 1 wt% LiNO3 added.

[0044] (2) Test content, results and discussion Perform constant current deposition / stripping tests and coulombic efficiency (CE) tests. For example, at 1 mA cm⁻¹. -2 Capacity 1 mAh cm -2 Under these conditions, in a Li||Cu half-cell, PzB-COF-Co-Cu can maintain an average coulombic efficiency of approximately 98.67% over more than 270 cycles. Figure 3 This indicates that its deposition stability is excellent. Therefore, it can be inferred that when this interface layer is used on the surface of the current collector in a negative electrodeless battery, it can achieve more uniform lithium nucleation and a higher proportion of reversible deposition during the first charge deposition stage, thereby slowing down the consumption of the positive electrode lithium source and improving cycle stability.

[0045] Perform cyclic voltammetry testing. For example, at 5 mV s. -1 CV comparison results at different scanning speeds ( Figure 8 The results showed that bare Cu exhibited only a weak current response and a broad passivation oxidation peak, indicating limited reversibility of the stripping process. The introduction of PzB-COF significantly increased the current density and clarified the oxidation / reduction peaks, suggesting that the lithium-affinity sites in the COF framework promote more reversible deposition / dissolution. Further Co coordination resulted in PzB-COF-Co-Cu exhibiting a higher peak current density and sharper oxidation / reduction peaks, with peak positions closer to Li / Li. + Thermodynamic potential reflects a decrease in interfacial polarization and a significant enhancement in charge transfer and nucleation / dissolution kinetics.

[0046] Perform constant current deposition tests. For example, at 1 mA cm⁻¹. -2 Under these conditions, in a Li||Cu half-cell, the nucleation overpotential of PzB-COF-Co-Cu is 35 mV, lower than that of bare Cu (53 mV) and PzB-COF-Cu (46 mV). Figure 9 This demonstrates that the interface layer of the present invention can significantly reduce the nucleation overpotential.

[0047] Example 4: Li||Li symmetric battery (lithium anode interface stability) (1) Battery assembly Two lithium metal sheets were used as the electrodes of a symmetrical battery; one set consisted of bare lithium sheet to bare lithium sheet, and the other set consisted of PzB-COF or PzB-COF-Co modified lithium sheet to the same modified lithium sheet. A coin cell symmetrical battery was assembled in an argon glove box using a polypropylene membrane (e.g., Celgard 2325) or a glass fiber membrane as the separator, and an electrolyte with the same formulation as in Example 3 was injected.

[0048] (2) Test content, results and discussion Constant current lithium plating / stripping cycle tests can be performed under different current densities and areal capacities (e.g., 2 mA cm⁻¹). -2 2mAh cm -2 Under conditions of ; or higher current density), the polarization voltage was recorded over time to evaluate interfacial impedance accumulation and deposition morphology stability. In symmetric cells, PzB-COF-Co-Li significantly reduced polarization and prolonged stable cycling time compared to bare lithium symmetric cells, achieving stable cycling times exceeding 900 h. Figure 4 This demonstrates its role in improving the long-term stability of the lithium metal interface.

[0049] Example 5: Li||LFP Full Cell (Rate and Long Cycle Validation) (1) Preparation of positive electrode Lithium iron phosphate (LFP) powder, conductive carbon black and PVDF were dispersed in NMP at a mass ratio of 7:2:1 to obtain a uniform slurry. The slurry was then coated onto an aluminum foil current collector using a doctor blade and vacuum dried to obtain the LFP cathode.

[0050] (2) Battery assembly The LFP cathode was paired with bare Li metal or COF-modified Li anode, and 120 μL of electrolyte (1 M LiTFSI in DOL / DME, volume ratio 1:1, with 1 wt% LiNO3 added) was injected into the GF / D membrane. The coin cells were then assembled in an argon glove box.

[0051] (3) Test content, results and discussion Rate performance of the full cell (e.g., 0.1C to 5C) was evaluated. Figure 5 ) and long-cycle stability testing (e.g., 5C conditions, Figure 6 In Li||LFP full cells, stable cycling at 5C for approximately 1000 cycles is achieved, demonstrating a balance between high rate capability and long cycle life. Full cells employing a metal-coordinated narrow-pore COF interface layer exhibit even higher rate response and longer cycle life, indicating that this interface strategy effectively suppresses negative electrode-side side reactions and maintains interface stability in full-cell systems.

[0052] Application example: Anode-free lithium metal battery construction method This application example illustrates an implementable construction method of the interface layer of the present invention in a negative electrode-free battery.

[0053] (1) Anode preparation A continuous PzB-COF-Co coating was constructed on the surface of a copper foil current collector according to Example 2(1) to obtain PzB-COF-Co-Cu. No additional lithium metal or pre-lithiation material was introduced during battery assembly.

[0054] (2) Battery assembly A lithium source cathode (such as lithium iron phosphate (LFP), layered lithium-containing transition metal oxides, etc.) is positioned opposite the aforementioned PzB-COF-Co-Cu anode, with a separator placed in between and an electrolyte injected, to assemble a cathode-free battery. During the first charge, lithium ions are extracted from the cathode and deposited on the surface of the anode current collector through an artificial interface layer to form metallic lithium; in subsequent cycles, more uniform deposition / stripping is achieved under the control of this interface layer.

[0055] (3) Explanation of mechanism of action Since the lithium deposition behavior on the negative electrode side of a negative electrodeless battery is essentially equivalent to lithium deposition on the current collector, the Li||Cu results in Example 3 can directly reflect the ability of the interface layer of the present invention to regulate the negative electrode side of the negative electrodeless battery. That is, by working together with sub-nano pores and M-Nx sites, selective lithium-ion transport, desolvation and uniform nucleation are achieved, thereby improving the reversibility and lifespan of the negative electrodeless battery.

[0056] The above embodiments are merely illustrative of preferred embodiments of the present invention. Those skilled in the art can make various modifications or substitutions without departing from the spirit and substance of the present invention, and all such modifications or substitutions should fall within the protection scope of the present invention.

Claims

1. An artificial interface layer material for modifying the negative electrode interface of lithium metal batteries and negative electrodeless batteries, characterized in that: The artificial interface layer material is a metal-coordinated narrow-pore covalent organic framework material, which has pores mainly at the sub-nanometer scale; the inner wall of the pore contains nitrogen-containing coordination units and is anchored with metal-nitrogen coordination sites M-Nx formed by metal ions, wherein M is one or more of Co, Ni, Fe, Mn, Cu, and Zn, and x is a number from 2 to 6.

2. The artificial interface layer material according to claim 1, characterized in that, The dominant pore size of the sub-nano pores is 0.5-1.2 nm, preferably 0.7-0.9 nm.

3. The artificial interface layer material according to claim 1 or 2, characterized in that, The nitrogen-containing coordinating unit is selected from one or more of pyridyl, pyrazinyl, bipyridyl, imidazoleyl, and triazineyl.

4. The artificial interface layer material according to any one of claims 1-3, characterized in that, The metal-nitrogen coordination site is a Co-Nx coordination site.

5. The artificial interface layer material according to claim 4, characterized in that, The covalent organic framework material is obtained by condensing 3,3'-bipyridine-6,6'-dicarboxaldehyde (BPDC) and 2,3,5,6-tetramethylpyrazine (Pz) to form a conjugated framework with vinylidene bonds, and then coordinating with Co ions.

6. An artificial interface layer, characterized in that, The artificial interface layer is a continuous coating formed on the surface of the negative electrode substrate by the artificial interface layer material according to any one of claims 1-5.

7. The artificial interface layer according to claim 6, characterized in that, The thickness of the continuous coating is 0.1-10 μm, preferably 0.2-3 μm.

8. A negative electrode current collector, characterized in that, It includes a negative electrode substrate and an artificial interface layer as described in claim 6 or 7 disposed on the surface of the negative electrode substrate; the negative electrode substrate is selected from one or more of copper foil, copper alloy, nickel foil, stainless steel foil, titanium foil, and carbon-based current collector.

9. A negative electrode, characterized in that, The negative electrode current collector includes the negative electrode current collector as described in claim 8, and optionally further includes a lithium metal layer and / or a lithium-containing alloy layer on the surface of the artificial interface layer; wherein, when the negative electrode does not include the lithium metal layer and / or the lithium-containing alloy layer during battery assembly, the negative electrode is a negative electrode of a battery without a negative electrode.

10. A lithium metal secondary battery, characterized in that, It includes a positive electrode, a negative electrode, an electrolyte, and a separator, wherein the negative electrode is the negative electrode as described in claim 9.

11. The lithium metal secondary battery according to claim 10, characterized in that, The lithium metal secondary battery is a negative electrode-free battery. When the battery is assembled, the negative electrode side does not contain metallic lithium. During the first charge, the positive electrode provides the lithium source, and metallic lithium is deposited on the surface of the negative electrode current collector through the artificial interface layer.

12. The lithium metal secondary battery according to claim 10 or 11, characterized in that, The active material of the positive electrode is one or more of lithium iron phosphate, layered lithium-containing transition metal oxides, lithium-rich manganese-based materials, sulfur or sulfur-containing compounds.

13. A method for preparing the artificial interface layer material according to any one of claims 1-5, characterized in that, The process includes the following steps: S1, providing a nitrogen-containing monomer and an aldehyde-containing monomer, and performing a solvothermal reaction under an inert atmosphere or vacuum sealing conditions to obtain a narrow-pore covalent organic framework; S2, contacting the covalent organic framework obtained in step S1 with a metal salt solution for post-coordination treatment, so that the metal ions coordinate with the nitrogen-containing coordination unit to form M-Nx coordination sites, thereby obtaining a metal-coordinated narrow-pore covalent organic framework material.

14. A method for preparing the artificial interface layer according to any one of claims 6-7, characterized in that, The method includes the following steps: dispersing the artificial interface layer material according to any one of claims 1-5 in a solvent to form a dispersion; coating the dispersion onto the surface of a negative electrode substrate and drying it to form a continuous coating.

15. The use of the artificial interface layer material according to any one of claims 1-5 in the preparation of a negative electrode interface modification layer for lithium metal batteries or negative electrode-free batteries.

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