A negative electrode material, a preparation method thereof, and a battery

Abstract

This invention discloses an anode material, its preparation method, and a battery, belonging to the technical field of battery anode materials. The anode material of this invention comprises a regularly grown array of LDH nanosheets on a substrate, LDH nanosheets containing vacancy defects, uniformly attached silver nanoparticles on the LDH nanosheets, and conjugated organic ligands inserted between the LDH nanosheet layers. The unique three-dimensional array composite porous structure of this invention effectively buffers the volume change of lithium metal during repeated charge-discharge processes. The loaded Ag nanoparticles increase the number of active sites and conductivity, while also guiding uniform lithium deposition to inhibit dendrite growth. The d-π conjugated structure formed by the conjugated organic ligands and the metal not only improves the overall conductivity of the material but also optimizes the electronic structure of the metal sites. Simultaneously, the strong coordination chelation effectively ensures the stability of the Ag nanoparticles during charge-discharge processes, inhibiting interlayer aggregation and effectively improving electrochemical performance.

Description

Technical Field

[0001] This invention relates to the field of battery anode material technology, specifically to an anode material, its preparation method, and a battery. Background Technology

[0002] Lithium metal is widely considered an ideal anode material for high-energy-density batteries due to its ultra-high theoretical specific capacity (3860 mAh g⁻¹) and low redox potential (-3.04 V, relative to the standard hydrogen electrode). However, due to its lack of a stable matrix structure, it exhibits uncontrolled volume changes during cycling, leading to instability of the solid electrolyte interface film and poor battery cycle stability. Furthermore, the irregular deposition / dissolution behavior of lithium metal can cause lithium dendrite growth. As cycling progresses, the continuously growing dendrites may penetrate the separator, triggering internal short circuits, causing not only a sharp decline in battery performance but also safety issues.

[0003] Layered dihydroxy hydroxides (LDHs) are a class of inorganic functional materials with a layered structure. They possess unique advantages such as tunable structure and controllable surface properties, making them one of the ideal candidate materials for constructing lithium metal anode host materials. However, due to their poor intrinsic conductivity, tendency to stack, and poor lithium affinity, LDHs can lead to problems such as large polarization during charge and discharge, uneven lithium deposition, lithium dendrite growth, and poor battery cycle stability. Summary of the Invention

[0004] One of the objectives of this invention is to provide a negative electrode material to solve the problems of large polarization, uneven lithium deposition, lithium dendrite growth, and poor battery cycle stability of existing LDHs materials during charging and discharging.

[0005] The technical solution of the present invention to solve the above-mentioned technical problems is as follows:

[0006] A negative electrode material includes an LDH nanosheet array on a substrate, the LDH nanosheet array having a three-dimensional structure, the LDH nanosheets containing vacancy defects, uniformly attached silver nanoparticles on the LDH nanosheets, and conjugated organic ligands inserted between the LDH nanosheet layers; the LDH nanosheet array is a NiCo-LDH nanosheet array, the LDH nanosheets containing oxygen vacancy defects, and the conjugated organic ligand is 2,3,6,7,10,11-hexahydroxytriphenyl.

[0007] Furthermore, the particle size of the silver nanoparticles is 2~4nm.

[0008] A second objective of this invention is to provide a method for preparing the negative electrode material used in one of the objectives, the method comprising the following steps:

[0009] Step 1: The pretreated substrate is placed in a reaction solution containing nickel salt, cobalt salt and hexadecyltrimethylammonium bromide, and then a solvothermal reaction is carried out to obtain a NiCo-LDH nanosheet array grown on the substrate; the NiCo-LDH nanosheet array is placed in a strong alkaline solution for etching reaction to obtain a NiCo-LDH nanosheet array containing vacancy defects.

[0010] Step 2: Immerse the NiCo-LDH nanosheet array containing vacancy defects into an aqueous solution of silver nitrate to carry out an auto-oxidation-reduction reaction. The silver particles generated by the reduction are loaded onto the surface of the NiCo-LDH nanosheet containing vacancy defects to obtain a NiCo-LDH / Ag array composite material.

[0011] Step 3: Place the NiCo-LDH / Ag array composite material in a mixed solvent containing dissolved conjugated organic ligands, and obtain a negative electrode material with conjugated organic ligands inserted between the NiCo-LDH / Ag layers after intercalation reaction.

[0012] Furthermore, the reaction solution in step 1 also includes ethanol and water;

[0013] The molar ratio of nickel salt to cobalt salt is 2:1-2:3, and the sum of the masses of nickel salt and cobalt salt is in the molar ratio of hexadecyltrimethylammonium bromide to 1:2-1:4.

[0014] The solvothermal reaction conditions are: temperature 110-130°C, reaction time 5-7h;

[0015] The etching reaction conditions are: place it in a strong alkaline solution with a concentration of 1-3M and react at 50-70°C for 0.5-1.5h.

[0016] Furthermore, the nickel salt is nickel chloride or nickel nitrate, and the cobalt salt is cobalt chloride or cobalt nitrate;

[0017] The strong alkaline solution is either sodium hydroxide solution or potassium hydroxide solution.

[0018] Furthermore, the concentration of silver nitrate in the silver nitrate aqueous solution is 35-45 mM;

[0019] The self-oxidation-reduction reaction takes 30-50 minutes.

[0020] Furthermore, the mixed solvent in step 3 is composed of dimethylformamide, ethanol, and water in a volume ratio of 2:1:1 to 4:1:1;

[0021] In step 3, the amount of conjugated organic ligands is 0.05-0.15 mol;

[0022] The conditions for the intercalation reaction in step 3 are: a reaction temperature of 90-110°C and a reaction time of 6-8 hours.

[0023] Furthermore, the conjugated organic ligand is 2,3,6,7,10,11-hexahydroxytriphenyl.

[0024] A third objective of this invention is to provide a battery comprising a negative electrode, wherein the negative electrode comprises the negative electrode material described in one objective.

[0025] The present invention has the following beneficial effects:

[0026] 1. The negative electrode material in this invention has a unique three-dimensional array composite porous structure, which provides a certain space for lithium metal storage, effectively buffers the volume change of lithium metal during repeated charging and discharging, and its large specific surface area reduces the effective current density.

[0027] 2. This invention introduces Ag nanoparticles with excellent lithiophilicity and conductivity, solving the problems of insufficient electron conduction and inability to guide uniform lithium deposition in pure NiCo-LDH. Simultaneously, the uniform loading of Ag nanoparticles onto the defect-rich NiCo-LDH nanosheet surface effectively increases the number of active sites due to the constructed heterostructure and vacancy defects.

[0028] 3. The conjugated organic ligands in this invention form a d-π conjugated structure with the metal, which not only increases conductivity and promotes electron transfer, but also optimizes the electron cloud density of the active site. At the same time, the ligands can also inhibit the interlayer aggregation of NiCo-LDH nanosheets, and the strong anchoring effect effectively prevents the aggregation and dissolution of Ag nanoparticles, stabilizes the active site structure, and greatly enhances the long-term cycle stability of lithium metal batteries, forming a synergistic system of "structural support-electron acceleration-interface optimization" to achieve simultaneous improvement in capacity, rate capability, and cycle performance. Attached Figure Description

[0029] Figure 1 This is a schematic diagram of the negative electrode material.

[0030] Figure 2 X-ray photoelectron spectrum of NiCo-LDH / Ag / HHTP array composite material;

[0031] Figure 3 Here are scanning electron microscope images, in which, Figure 3 Figure (a) shows a SEM image of the NiCo-LDH array material containing vacancy defects. Figure 3 Figure (b) in the figure is a SEM image of the NiCo-LDH / Ag / HHTP array composite material;

[0032] Figure 4 Transmission electron microscope image;

[0033] Figure 5 This is an X-ray diffraction analysis diagram;

[0034] Figure 6This is a graph showing the results of the electrical test.

[0035] Figure 7 This is a Coulomb efficiency diagram;

[0036] Figure 8 This is a graph showing the electrochemical performance test results;

[0037] Figure 9 This is a graph showing the performance of the magnification.

[0038] Figure 10 Figure 1 shows the charge / discharge curves, where Figure 2a is the charge / discharge curve at a rate of 0.5C and Figure 3b is the charge / discharge curve at a rate of 2C. Detailed Implementation

[0039] The principles and features of the present invention are described below with reference to the accompanying drawings. The examples given are only for explaining the present invention and are not intended to limit the scope of the present invention.

[0040] According to the inventors' research, when using LDHs to construct lithium anode carriers, there are problems such as poor conductivity, easy stacking, and poor lithium affinity, which can lead to problems such as large polarization during charging and discharging, uneven lithium deposition, lithium dendrite growth, and reduced battery cycle stability.

[0041] Based on this, an embodiment of the first aspect of the present invention provides a negative electrode material, including an LDHs nanosheet array located on a substrate, the LDHs nanosheet array having a three-dimensional structure, the LDHs nanosheets containing vacancy defects, uniformly attached silver nanoparticles on the LDHs nanosheets, and conjugated organic ligands inserted between the LDHs nanosheet layers; the LDHs nanosheet array is a NiCo-LDH nanosheet array, the LDHs nanosheets containing oxygen vacancy defects.

[0042] In the embodiments, the negative electrode material of the present invention mainly addresses the problems of large polarization during charging, uneven lithium deposition, lithium dendrite growth, and poor cycle stability from the following aspects:

[0043] First, the negative electrode material in this invention possesses a unique three-dimensional array composite porous structure. This structure provides sufficient space for lithium metal storage, effectively buffering the volume changes of lithium metal during repeated charge-discharge processes. The larger specific surface area reduces the effective current density. Furthermore, the three-dimensional array composite porous structure enhances the lithium affinity of the negative electrode material, inducing lithium metal nucleation and uniform deposition while inhibiting dendrite growth.

[0044] Second, the LDHs nanosheets selected in this invention contain vacancy defects, which increase the number of active sites in the negative electrode material. Secondly, silver nanoparticles uniformly distributed on the vacancy-defect-containing LDHs nanosheets can form heterostructures with the LDHs nanosheets, which also increase the number of active sites to some extent, thereby improving the effective electrochemical active area and conductivity. Finally, conjugated organic ligands form d-π conjugated structures with metals (including silver, nickel, and cobalt), which optimize the electronic structure of the active sites. Strong coordination chelation effectively prevents the aggregation and dissolution of Ag nanoparticles, while also improving conductivity to some extent. Based on this, this invention first increases the number and stability of active sites in the negative electrode material from three different directions. The abundant and uniformly distributed active sites distribute the total current evenly across the entire electrode surface, resulting in a low local current density at each site. This promotes the stable and uniform deposition or embedding of lithium ions, reducing polarization and inhibiting dendrite formation, thus improving cycle stability.

[0045] Third, the d-π conjugated structure formed by the conjugated organic ligands and the metals (including silver, cobalt, and nickel) in the LDHs nanosheet array in this invention has a strong chelating effect that effectively ensures the stability of the active sites of the nanoscale dispersed Ag particles during charge and discharge, inhibiting interlayer aggregation and improving the stability of the negative electrode material to a certain extent. In addition, the relationship between the organic ligands and the metals on the LDHs layers is no longer a simple electrostatic adsorption of inorganic anions, but a d-π conjugated coordination structure. Since the bond energy of the coordination bond is much higher than that of the electrostatic attraction, the conjugated organic ligands can firmly anchor the ligands in the interlayer, balance the positive charge of the layers, and prevent the layers from peeling off due to charge imbalance, which further improves the stability of the negative electrode material. The stability of the negative electrode material, battery polarization, and battery stability have a stepwise transmission relationship of "cause-characterization-result". It can be seen that this invention fundamentally improves the stability of the material by introducing conjugated organic ligands, thereby reducing polarization and improving battery cycle stability.

[0046] In addition, the d-π conjugated structure itself is a special heterojunction interface, which has the combined effect of increased active sites and improved conductivity, which can effectively reduce charge and discharge polarization; and its stable structure and high conductivity ultimately ensure the cycle stability of the battery and suppress the occurrence of problems such as lithium dendrites.

[0047] In summary, this invention achieves the goals of reducing polarization and improving battery cycle stability from three different directions: increasing the number of active sites, inhibiting dendrite growth, and improving the stability of the anode material.

[0048] Preferably, the conjugated organic ligand in this embodiment is 2,3,6,7,10,11-hexahydroxytriphenyl (HHTP). This embodiment further illustrates the structure of the negative electrode material (NiCo-LDH / Ag / HHTP array composite material) of the present invention with 2,3,6,7,10,11-hexahydroxytriphenyl as the conjugated organic ligand, as shown in the schematic diagram below. Figure 1 As shown, Figure 1 This is a schematic diagram of the structure of the negative electrode material (NiCo-LDH / Ag / HHTP array composite material). From... Figure 1 As can be seen, HHTP is inserted into the interlayer of LDH nanosheets. In this invention, the HHTP conjugated organic ligand contains multiple hydroxyl functional groups. Under solvothermal conditions, the solvated HHTP molecules enter the NiCo-LDH / Ag interlayer and form a d-π conjugated coordination structure with the metal in the NiCo-LDH / Ag structure. Therefore, the anode material is not simply subjected to electrostatic adsorption of inorganic anions. In addition, the bond energy of the coordination bond is much higher than that of the electrostatic attraction, and the ligand can firmly anchor the ligand in the interlayer, balancing the positive charge of the layers and preventing the layers from peeling off due to charge imbalance. It is evident that the constructed d-π conjugated structure can significantly improve the overall conductivity of NiCo-LDH / Ag and stabilize the metal active sites, preventing them from falling off and dissolving during charging and discharging.

[0049] Furthermore, the introduction of HHTP ligands leads to the formation of numerous intermolecular hydrogen bonds. This hydrogen bond network connects adjacent layers to the ligands, enhancing interlayer binding and preventing layer collapse. Simultaneously, the significantly increased interlayer spacing not only exposes more adsorption active sites but also accelerates the transport process, thereby improving the overall battery performance.

[0050] In some embodiments, the particle size of the silver nanoparticles is 2-4 nm.

[0051] A second aspect of the present invention provides a method for preparing the negative electrode material of the first aspect embodiment, comprising the following steps:

[0052] Step 1: The pretreated substrate is placed in a reaction solution containing nickel salt, cobalt salt and hexadecyltrimethylammonium bromide, and then a solvothermal reaction is carried out to obtain a NiCo-LDH nanosheet array grown on the substrate; the NiCo-LDH nanosheet array is placed in a strong alkaline solution for etching reaction to obtain a NiCo-LDH nanosheet array containing vacancy defects.

[0053] Step 2: Immerse the NiCo-LDH nanosheet array containing vacancy defects into an aqueous solution of silver nitrate to carry out an auto-oxidation-reduction reaction. The silver particles generated by the reduction are loaded onto the surface of the NiCo-LDH nanosheet containing vacancy defects to obtain a NiCo-LDH / Ag array composite material.

[0054] Step 3: Place the NiCo-LDH / Ag array composite material in a mixed solvent containing dissolved conjugated organic ligands, and obtain a negative electrode material with conjugated organic ligands inserted between the NiCo-LDH / Ag layers after intercalation reaction.

[0055] In this embodiment of the invention, a NiCo-LDH nanosheet array containing vacancy defects is first prepared by solvothermal reaction and alkaline etching. Then, through spontaneous redox reaction, silver ions are reduced in situ to form Ag nanoparticles, which are uniformly loaded onto the surface of NiCo-LDH nanosheets. Subsequently, conjugated organic ligands are introduced to enhance the conductivity of the material and regulate the electronic structure of the metal sites, thus preparing a NiCo-LDH composite array electrode material co-modified by conjugated organic ligands and Ag nanoparticles, which is then used as a multifunctional host material for lithium metal anodes. In this invention, the uniform loading of Ag nanoparticles onto a NiCo-LDH nanosheet array containing vacancy defects increases the effective electrochemical active area. The interface structure guides the redistribution of lithium and promotes rapid and uniform deposition / dissolution of lithium, effectively reducing the volume change of lithium metal during repeated charge and discharge processes. The conjugated organic ligands form a d-π conjugated structure with the metal, which can improve the overall conductivity of the material and optimize the electronic structure of the metal sites. The strong chelation effect can effectively ensure that the active sites of Ag nanoparticles remain stable and do not fall off during charge and discharge processes, inhibiting interlayer aggregation and forming a synergistic system of "structural support-electron acceleration-interface optimization". This effectively improves electrochemical performance and greatly enhances the capacity, rate capability, and long-cycle stability of lithium metal batteries.

[0056] Preferably, the substrate in this embodiment is nickel foam, and the substrate pretreatment method is as follows: the substrate is subjected to dilute hydrochloric acid, ultrapure water, and acetone in sequence to remove the surface oxide layer and organic matter by ultrasonic treatment, wherein the concentration of dilute hydrochloric acid is 1M.

[0057] In some embodiments, the reaction solution in step 1 further includes ethanol and water. Preferably, the volume ratio of ethanol to water is 2:1 to 1:2. More preferably, the volume ratio of the two is 2:1, 1:1 or 1:2.

[0058] The molar ratio of nickel salt to cobalt salt is 2:1-2:3, and the sum of the amounts of nickel and cobalt salts to the amount of hexadecyltrimethylammonium bromide is 1:2-1:4. In this embodiment of the invention, the selection of the molar ratio range of nickel salt to cobalt salt ensures the thermodynamic stability of the LDH layered structure and the absence of impurity phases, which is beneficial for the formation of ultrathin nanosheet arrays. Hexadecyltrimethylammonium bromide can regulate the solution pH, achieving mild and controllable LDH precipitation, avoiding morphological loss of control caused by rapid precipitation, and enabling uniform nucleation and growth of LDH nanosheets on the substrate. Preferably, the molar ratio of nickel salt to cobalt salt is 2:1, 2:2, or 2:3, and preferably, the sum of the amounts of nickel and cobalt salts to the amount of hexadecyltrimethylammonium bromide is 1:2, 1:3, or 1:4.

[0059] The solvothermal reaction conditions are: temperature 110-130°C, reaction time 5-7 h; the etching reaction conditions are: placed in a 1-3M strong alkaline solution and reacted at 50-70°C for 0.5-1.5 h. In the embodiments of this invention, during the preparation of NiCo-LDH, temperature and time must be controlled within a specific range. The temperature and time range selected in this invention can ensure that NiCo-LDH undergoes heterogeneous nucleation on the substrate, avoiding rapid nucleation in solution and growth into uniform and regular ultrathin nanosheets; at the same time, it avoids the corrosion of the substrate caused by increased temperature and longer time, resulting in severe nanosheet stacking; and it also avoids the inability to grow a regular nanosheet structure on the substrate due to decreased temperature and shortened time. Preferably, the solvothermal reaction conditions are: temperature 110°C, 120°C, or 130°C, reaction time 5 h, 6 h, or 7 h. The alkaline etching concentration and time selected in this invention can maintain the NiCo-LDH structure and generate appropriate vacancy defects; avoiding situations where the alkaline etching concentration and time are outside this range will damage the original NiCo-LDH array structure or result in a small number of vacancy defects. Preferably, the etching reaction conditions are: placing the sample in a strong alkaline solution with a concentration of 1M (or 2M, or 3M) at 50°C (or 60°C, or 70°C) for 0.5h (or 1h, or 1.5h).

[0060] In some embodiments, the nickel salt is nickel chloride or nickel nitrate, and the cobalt salt is cobalt chloride or cobalt nitrate; the strong alkaline solution is sodium hydroxide solution or potassium hydroxide solution.

[0061] In some embodiments, the concentration of silver nitrate in the aqueous solution is 35-45 mM; the autoreduction reaction time is 30-50 min. Preferably, the concentration of silver nitrate is 35, 40, or 45 mM, and the autoreduction reaction time is 30, 40, or 50 min.

[0062] In some embodiments, the mixed solvent in step 3 consists of dimethylformamide (DMF), ethanol, and water in a volume ratio of 2:1:1 to 4:1:1. The use of these three solvents in this invention ensures sufficient dissolution of the metal salt and hexadecyltrimethylammonium bromide, and the resulting water-organic solvent interface promotes the formation of ultrathin nanosheets. Preferably, the volume ratio of DMF, ethanol, and water is 2:1:1, 3:1:1, and 4:1:1.

[0063] In step 3, the amount of conjugated organic ligand is 0.05-0.15 mol. In this embodiment of the invention, too little conjugated organic ligand will not have a good synergistic promoting effect, while too much will destroy the structure and morphology of NiCo-LDH, generate new metal-organic framework materials, and lead to reduced activity. Preferably, the amount of conjugated organic ligand is 0.05 mol, 0.1 mol, or 0.15 mol.

[0064] The intercalation reaction conditions in step 3 are: a reaction temperature of 90-110°C and a reaction time of 6-8 hours. In this embodiment of the invention, this temperature range is chosen to avoid situations where the temperature is too low, resulting in slow ligand diffusion and adsorption only on the surface without truly entering the interlayer to form stable coordination bonds. It also avoids situations where excessively high temperatures can easily damage the morphology and structure of LDHs. This is because ligands require diffusion time from the solution to the LDH surface / interlayer; a short reaction time only completes rapid surface adsorption without achieving a stable coordination structure, resulting in poor overall uniformity; while a long time leads to thickening of the nanosheets, severe stacking, and structural damage. Preferably, the intercalation reaction conditions are: a reaction temperature of 90°C, 100°C, or 110°C, and a reaction time of 6 hours, 7 hours, or 8 hours.

[0065] In some embodiments, the conjugated organic ligand is 2,3,6,7,10,11-hexahydroxytriphenyl. In this embodiment, 2,3,6,7,10,11-hexahydroxytriphenyl contains multiple hydroxyl functional groups, which can form a d-π conjugated coordination structure with the metal in the NiCo-LDH / Ag structure. This improves the stability of the NiCo-LDH / Ag structure while also increasing the number of active sites, reducing the polarization of the battery assembled from the negative electrode material prepared in this invention, and improving its cycle stability. Furthermore, HHTP contains multiple hydroxyl groups. After being introduced into the interlayer of LDHs, it forms numerous intermolecular hydrogen bonds with the hydroxyl groups on the LDHs layers and the residual anions in the interlayer, thus forming a hydrogen bond network. This hydrogen bond network connects adjacent layers to the ligand, enhancing the interlayer binding force and preventing layer structure collapse. Simultaneously, the introduction of HHTP into the interlayer of LDHs, due to its molecular length of 1.5-1.6 nm, can increase the interlayer spacing of LDHs, exposing more adsorption active sites, which is beneficial for accelerating the transport process and thus improving the overall battery performance.

[0066] A third aspect of the present invention provides a battery including a negative electrode comprising the negative electrode material described in the first aspect embodiment. For example, when used as the negative electrode of a full cell, it typically requires electrochemical deposition of lithium metal before it can be used as the negative electrode of the full cell.

[0067] The present invention will be further described below through specific embodiments.

[0068] Example 1

[0069] A method for preparing a negative electrode material includes the following steps:

[0070] Step 1: First, the nickel foam (2cm×4cm) is ultrasonically cleaned for 15 minutes each with 1M dilute hydrochloric acid solution, ultrapure water and acetone to remove the oxide layer and organic matter on the surface. After drying, it is used for the next reaction.

[0071] Then, 0.436g Ni(NO3)2·6H2O, 0.437g Co(NO3)2·6H2O and 3.28g hexadecyltrimethylammonium bromide were dissolved in a mixed solvent consisting of 15mL deionized water and 15mL anhydrous ethanol. After thorough ultrasonic dissolution, the solution was loaded into a 50mL reactor, and pretreated nickel foam was added vertically. The reactor was then reacted at 120°C for 6 hours. After the reaction was completed, NiCo-LDH nanosheet array material grown on a nickel foam substrate was obtained. The material was then rinsed with deionized water and anhydrous ethanol before being used in the next reaction.

[0072] Finally, the synthesized NiCo-LDH nanosheet array material was placed in a 1M potassium hydroxide solution and reacted at 70°C for 1 hour to obtain NiCo-LDH nanosheet array material containing vacancy defects. After cleaning and drying, it was used for the next step of the reaction.

[0073] Step 2: The NiCo-LDH nanosheet array material containing vacancy defects is immersed in a 45mM silver nitrate aqueous solution for 40min for an auto-oxidation-reduction reaction. The Ag nanoparticles generated by the reduction are uniformly loaded on the surface of the NiCo-LDH nanosheet containing vacancy defects to obtain the NiCo-LDH / Ag array composite material. Then, it is rinsed several times with deionized water and anhydrous ethanol, and after drying, it is used for the next step of the reaction.

[0074] Step 3: 32.4 mg (0.1 mmol) of 2,3,6,7,10,11-hexahydroxytriphenyl (HHTP) conjugated organic ligand was ultrasonically dissolved in a mixed solvent consisting of N,N-dimethylformamide DMF (18 mL), ethanol (6 mL), and water (6 mL). The well-mixed solution was placed in a polytetrafluoroethylene-lined reactor, and the NiCo-LDH / Ag composite array material synthesized in Step 2 was added. After intercalation reaction at 100°C for 7 h, the negative electrode material with HHTP inserted into the NiCo-LDH / Ag interlayer (NiCo-LDH / Ag / HHTP array composite material) was obtained.

[0075] Example 2

[0076] A method for preparing a negative electrode material includes the following steps:

[0077] Step 1: First, the nickel foam (2cm×4cm) is ultrasonically cleaned for 15 minutes each with 1M dilute hydrochloric acid solution, ultrapure water and acetone to remove the oxide layer and organic matter on the surface. After drying, it is used for the next reaction.

[0078] Then, 0.356g NiCl2·6H2O, 0.357g CoCl2·6H2O and 3.28g hexadecyltrimethylammonium bromide were dissolved in a mixed solvent consisting of 15mL deionized water and 15mL anhydrous ethanol. After thorough ultrasonic dissolution, the solution was loaded into a 50mL reaction vessel, and pretreated nickel foam was added vertically. The reaction was then carried out at 110°C for 7 hours. After the reaction was completed, NiCo-LDH nanosheet array material grown on a nickel foam substrate was obtained. The material was then rinsed with deionized water and anhydrous ethanol before being used in the next reaction.

[0079] Finally, the synthesized NiCo-LDH nanosheet array material was placed in a 2M potassium hydroxide solution and reacted at 60°C for 1 hour to obtain NiCo-LDH nanosheet array material containing vacancy defects. After cleaning and drying, it was used for the next step of the reaction.

[0080] Step 2: Immerse the NiCo-LDH nanosheet array material containing vacancy defects in a 35mM silver nitrate aqueous solution for 30 min for an auto-oxidation-reduction reaction. The Ag nanoparticles generated by the reduction are uniformly loaded on the surface of the NiCo-LDH nanosheet containing vacancy defects to obtain the NiCo-LDH / Ag composite array material. Then, rinse it several times with deionized water and anhydrous ethanol, and dry it for the next step of the reaction.

[0081] Step 3: 16.2 mg (0.05 mmol) of 2,3,6,7,10,11-hexahydroxytriphenyl (HHTP) conjugated organic ligand was ultrasonically dissolved in a mixed solvent consisting of N,N-dimethylformamide DMF (18 mL), ethanol (6 mL), and water (6 mL). The well-mixed solution was placed in a polytetrafluoroethylene-lined reactor, and the NiCo-LDH / Ag composite array material synthesized in Step 2 was added. After intercalation reaction at 90°C for 8 h, the negative electrode material with HHTP inserted into the NiCo-LDH / Ag interlayer (NiCo-LDH / Ag / HHTP array composite material) was obtained.

[0082] Example 3

[0083] A method for preparing a negative electrode material includes the following steps:

[0084] Step 1: First, the nickel foam (2cm×4cm) is ultrasonically cleaned for 15 minutes each with 1M dilute hydrochloric acid solution, ultrapure water and acetone to remove the oxide layer and organic matter on the surface. After drying, it is used for the next reaction.

[0085] Then, 0.356g NiCl2·6H2O, 0.357g CoCl2·6H2O and 3.28g hexadecyltrimethylammonium bromide were dissolved in a mixed solvent consisting of 15mL deionized water and 15mL anhydrous ethanol. After thorough ultrasonic dissolution, the solution was loaded into a 50mL reaction vessel, and pretreated nickel foam was added vertically. The reaction was then carried out at 130°C for 5 hours. After the reaction was completed, NiCo-LDH nanosheet array material grown on a nickel foam substrate was obtained. The material was then rinsed with deionized water and anhydrous ethanol before being used in the next reaction.

[0086] Finally, the synthesized NiCo-LDH nanosheet array material was placed in a 3M potassium hydroxide solution and reacted at 50°C for 0.5 h to obtain NiCo-LDH nanosheet array material containing vacancy defects. After cleaning and drying, it was used for the next reaction.

[0087] Step 2: The NiCo-LDH nanosheet array material containing vacancy defects is immersed in a 40mM silver nitrate aqueous solution for 40min for an auto-oxidation-reduction reaction. The Ag nanoparticles generated by the reduction are uniformly loaded on the surface of the NiCo-LDH nanosheet containing vacancy defects to obtain NiCo-LDH / Ag composite array material. Then, it is rinsed several times with deionized water and anhydrous ethanol, and after drying, it is used for the next step of the reaction.

[0088] Step 3: 48.6 mg (0.15 mmol) of 2,3,6,7,10,11-hexahydroxytriphenyl (HHTP) conjugated organic ligand was ultrasonically dissolved in a mixed solvent consisting of N,N-dimethylformamide DMF (18 mL), ethanol (6 mL), and water (6 mL). The well-mixed solution was placed in a polytetrafluoroethylene-lined reactor, and the NiCo-LDH / Ag composite array material synthesized in Step 2 was added. After intercalation reaction at 110°C for 6 h, the negative electrode material with HHTP inserted into the NiCo-LDH / Ag interlayer (NiCo-LDH / Ag / HHTP array composite material) was obtained.

[0089] Comparative Example 1

[0090] A method for preparing a negative electrode material includes the following steps:

[0091] First, the nickel foam (2cm×4cm) was ultrasonically cleaned for 15 minutes each with 1M dilute hydrochloric acid solution, ultrapure water and acetone to remove the oxide layer and organic matter on the surface. After drying, it was used for the next reaction.

[0092] Then, 0.436g Ni(NO3)2·6H2O, 0.437g Co(NO3)2·6H2O and 3.28g hexadecyltrimethylammonium bromide were dissolved in a mixed solvent consisting of 15mL deionized water and 15mL anhydrous ethanol. After thorough ultrasonic dissolution, the solution was loaded into a 50mL reactor, and pretreated nickel foam was added vertically. The reactor was then reacted at 120°C for 6 hours. After the reaction was completed, NiCo-LDH nanosheet array material grown on a nickel foam substrate was obtained. The material was then rinsed with deionized water and anhydrous ethanol before being used in the next reaction.

[0093] Finally, the synthesized NiCo-LDH nanosheet array material was placed in a 1M potassium hydroxide solution and reacted at 70°C for 1 h to obtain NiCo-LDH nanosheet array material containing vacancy defects.

[0094] Comparative Example 2

[0095] A method for preparing a negative electrode material includes the following steps:

[0096] Step 1: First, the nickel foam (2cm×4cm) is ultrasonically cleaned for 15 minutes each with 1M dilute hydrochloric acid solution, ultrapure water and acetone to remove the oxide layer and organic matter on the surface. After drying, it is used for the next reaction.

[0097] Then, 0.436g Ni(NO3)2·6H2O, 0.437g Co(NO3)2·6H2O and 3.28g hexadecyltrimethylammonium bromide were dissolved in a mixed solvent consisting of 15mL deionized water and 15mL anhydrous ethanol. After thorough ultrasonic dissolution, the solution was loaded into a 50mL reaction vessel, and pretreated nickel foam was added vertically. The reaction was carried out at 120°C for 6 hours. After the reaction was completed, NiCo-LDH nanosheet array material grown on a nickel foam substrate was obtained. The material was then rinsed with deionized water and anhydrous ethanol before being used in the next reaction.

[0098] Finally, the synthesized NiCo-LDH nanosheet array material was placed in a 2M potassium hydroxide solution and reacted at 70°C for 1 hour to obtain NiCo-LDH nanosheet array material containing vacancy defects. After cleaning and drying, it was used for the next step of the reaction.

[0099] Step 2: Immerse the NiCo-LDH nanosheet array material containing vacancy defects in a 45mM silver nitrate aqueous solution for 40 minutes for an auto-oxidation-reduction reaction. The Ag nanoparticles generated by the reduction are uniformly loaded on the surface of the NiCo-LDH nanosheet containing vacancy defects to obtain the NiCo-LDH / Ag composite array material.

[0100] Test Analysis:

[0101] I. Structural Analysis

[0102] 1. The NiCo-LDH / Ag / HHTP array composite material obtained in Example 1 was subjected to X-ray photoelectron energy analysis, and the test results are as follows: Figure 2 As shown, Figure 2 The image shows the X-ray photoelectron spectrum of the NiCo-LDH / Ag / HHTP array composite material.

[0103] from Figure 2 As can be seen, the binding energy of 531.5 eV corresponds to an oxygen vacancy defect, which is the oxygen vacancy defect in the NiCo-LDH / Ag / HHTP array composite material prepared in this invention.

[0104] 2. Scanning electron microscopy (SEM) testing and analysis

[0105] The NiCo-LDH nanosheet array material with vacancy defects and the NiCo-LDH / Ag / HHTP array composite material obtained in Example 1 were analyzed by scanning electron microscopy (SEM), and the results are as follows: Figure 3 As shown, where, Figure 3 This is a scanning electron microscope image. Figure 3 Figure (a) shows a SEM image of the NiCo-LDH nanosheet array material containing vacancy defects. Figure 3 Figure (b) in the figure is a SEM image of the NiCo-LDH / Ag / HHTP array composite material.

[0106] from Figure 3 As can be seen, both the NiCo-LDH nanosheet array material with vacancy defects and the NiCo-LDH / Ag / HHTP array composite material have the morphology of regularly arranged nanosheets.

[0107] 3. Transmission electron microscopy (TEM) analysis

[0108] The negative electrode material (NiCo-LDH / Ag / HHTP array composite material) prepared in Example 1 was analyzed by high-magnification transmission electron microscopy, and the results are as follows: Figure 4 As shown, Figure 4 This is a transmission electron microscope (TEM) image.

[0109] from Figure 4 As can be seen from the figure, the Ag nanoparticles in the NiCo-LDH / Ag / HHTP array composite material are uniformly loaded onto the surface of the NiCo-LDH nanosheets without agglomeration; and the particle size of the silver nanoparticles is 2~4nm.

[0110] 4. X-ray diffraction analysis (XRD)

[0111] X-ray diffraction analysis was performed on the NiCo-LDH nanosheet array material with vacancy defects, the NiCo-LDH / Ag array composite material, and the NiCo-LDH / Ag / HHTP array composite material obtained in Example 1. The results are as follows: Figure 5 As shown, where, Figure 5 This is an X-ray diffraction analysis diagram.

[0112] from Figure 5 As can be seen, after the introduction of the HHTP ligand, the characteristic peak of NiCo-LDH shifts to a lower angle at 11.6°, which to some extent proves that the HHTP ligand has been successfully inserted into the NiCo-LDH interlayer; at the same time, combined with Figure 3 As can be seen from Figure (b), the NiCo-LDH / Ag / HHTP array composite material with HHTP inserted between LDH layers still maintains the morphology and structure of NiCo-LDH nanosheets.

[0113] II. Performance Analysis

[0114] 1. Conductivity test

[0115] The NiCo-LDH nanosheet array material, NiCo-LDH / Ag array composite material, and NiCo-LDH / Ag / HHTP array composite material with vacancy defects obtained in Example 1 were tested and analyzed using the two-needle method. The results are as follows: Figure 6 As shown; Figure 6 The image shows the results of the electrical test.

[0116] from Figure 6 The IV test results and the conductivity calculation formula σ=L / (R×S) (where L is the distance, R is the resistance, and S is the area) show that the conductivity of NiCo-LDH nanosheet array material with vacancy defects, NiCo-LDH / Ag array composite material and NiCo-LDH / Ag / HHTP array composite material are 1.0×10-5Scm-1, 7.0×10-5Scm-1 and 10.0×10-5Scm-1, respectively. It can be seen that modifying Ag and conjugated HHTP ligands can significantly enhance the conductivity of LDHs.

[0117] 2. Coulomb efficiency test

[0118] Using the NiCo-LDH nanosheet array material with vacancy defects, the NiCo-LDH / Ag array composite material, and the NiCo-LDH / Ag / HHTP array composite material obtained in Example 1 as negative electrodes, LIPF6 was dissolved in ethylene carbonate / ethyl methyl carbonate (volume ratio 1:1) with 5 wt% fluoroethylene carbonate added as an additive to prepare a 1M electrolyte. Half-cells were assembled, and their coulombic efficiency was tested at a current density of 1 mA cm⁻² and a deposition capacity of 1 mAh cm⁻² to evaluate the reversibility and stability of the electrode during lithium deposition / dissolution. The test results are as follows: Figure 7 As shown; Figure 7 This is a Coulomb efficiency diagram.

[0119] from Figure 7 As can be seen, the anode of the NiCo-LDH / Ag / HHTP array composite material exhibits the best cycling stability and the longest cycle life, maintaining a high coulombic efficiency of 98.17% after 160 cycles. In contrast, the anode of the NiCo-LDH / Ag array composite material shows a coulombic efficiency drop to 97.16% after 140 cycles, while the NiCo-LDH nanosheet array material has the worst coulombic efficiency, rapidly dropping to 96.57% after 60 cycles.

[0120] 3. Cyclic performance, rate performance testing, and typical charge / discharge voltage curves

[0121] Half-cells were assembled using the NiCo-LDH nanosheet array material with vacancy defects, the NiCo-LDH / Ag array composite material, and the NiCo-LDH / Ag / HHTP array composite material obtained in Example 1, respectively. Electrochemical deposition of lithium metal was performed to obtain NiCo-LDH@Li. NiCo-LDH / Ag@Li and NiCo-LDH / Ag / HHTP@Li were used as the negative electrodes of the full cell, respectively. NCM622 with a loading of 10 mg cm⁻² was used as the positive electrode of the full cell. The electrolyte was the same as that in the aforementioned half-cells. Then, a full cell with an N / P ratio of 5:1 was assembled and its cycle performance and rate performance were tested. The full cell test voltage range was 3-4.3V. The cycle performance test procedure was as follows: the battery was first activated by cycling at 0.1C for three cycles, and then cycled at 0.5C.

[0122] The test results are as follows: Figure 8 , Figure 9 and Figure 10 As shown; where, Figure 8 This is a graph showing the electrochemical performance test results. Figure 9 This is a graph showing the performance of the magnification. Figure 10 Figure 1 shows the charge / discharge curves, where Figure 2a is the charge / discharge curve at a rate of 0.5C and Figure 3b is the charge / discharge curve at a rate of 2C.

[0123] from Figure 8 It can be seen that the full cell based on the NiCo-LDH / Ag / HHTP array composite material exhibits excellent cycle stability, with a capacity retention of 76% after 150 cycles, corresponding to a discharge capacity of 146.5 mAh·g⁻¹. The full cell based on the NiCo-LDH / Ag array composite material shows the second best cycle performance, with a capacity retention of 62.5% after 150 cycles and a discharge capacity decay to 121.8 mAh·g⁻¹. The battery based on the NiCo-LDH array material exhibits a significantly faster capacity decay rate and the worst cycle stability, with a sharp drop in discharge capacity to 58.23 mAh·g⁻¹ after 150 cycles.

[0124] Combination Figure 9 and Figure 10 It can be seen that the full cell based on the NiCo-LDH / Ag / HHTP array composite material exhibits the best rate performance, showing the highest discharge specific capacity at rates from 0.1C to 2C. Furthermore, typical charge-discharge capacity-voltage curves at 0.5C and 2C rates are shown (…). Figure 10 This also shows that the battery based on the NiCo-LDH / Ag / HHTP array composite material has higher discharge capacity and lower polarization, indicating that the synergistic effect significantly enhances the electrochemical kinetics.

[0125] The comparative examples and comparative tests revealed that the NiCo-LDH / Ag / HHTP array composite material of the present invention exhibits significant battery performance advantages as a negative electrode host material for lithium metal batteries. This is because: the uniform loading of Ag nanoparticles onto the NiCo-LDH nanosheet array material with vacancy defects increases the effective electrochemical active area and conductivity; the improved interface structure enhances lithiophilic properties, promotes uniform lithium deposition / dissolution, inhibits dendrite growth, effectively reduces the volume change of lithium metal during repeated charge-discharge cycles, and improves coulombic efficiency; the d-π conjugated structure formed by the conjugated organic ligands and the metal not only improves the overall conductivity of the material and optimizes the electronic structure of the metal sites, but also, the strong coordination chelation effectively ensures the stability of the Ag nanoparticle active sites during charge-discharge processes, inhibiting interlayer aggregation and forming a synergistic system of "structural support - electron acceleration - interface optimization," effectively improving electrochemical performance and achieving simultaneous improvements in capacity, rate capability, and cycle performance.

[0126] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A negative electrode material, characterized in that, The invention includes an array of LDH nanosheets on a substrate, the LDH nanosheet array being a three-dimensional structure containing vacancy defects, uniformly attached silver nanoparticles on the LDH nanosheets, and conjugated organic ligands inserted between the LDH nanosheet layers; the LDH nanosheet array is a NiCo-LDH nanosheet array, the LDH nanosheets containing oxygen vacancy defects, and the conjugated organic ligand is 2,3,6,7,10,11-hexahydroxytriphenyl.

2. The negative electrode material according to claim 1, characterized in that, The particle size of the silver nanoparticles is 2~4 nm.

3. The method for preparing the negative electrode material according to claim 1 or 2, characterized in that, Includes the following steps: Step 1: The pretreated substrate is placed in a reaction solution containing nickel salt, cobalt salt and hexadecyltrimethylammonium bromide, and then a solvothermal reaction is carried out to obtain a NiCo-LDH nanosheet array grown on the substrate; the NiCo-LDH nanosheet array is placed in a strong alkaline solution for etching reaction to obtain a NiCo-LDH nanosheet array containing vacancy defects. Step 2: Immerse the NiCo-LDH nanosheet array containing vacancy defects into an aqueous solution of silver nitrate to carry out an auto-oxidation-reduction reaction. The silver particles generated by the reduction are loaded onto the surface of the NiCo-LDH nanosheet containing vacancy defects to obtain a NiCo-LDH / Ag array composite material. Step 3: Place the NiCo-LDH / Ag array composite material in a mixed solvent containing dissolved conjugated organic ligands, and obtain a negative electrode material with conjugated organic ligands inserted between the NiCo-LDH / Ag layers after intercalation reaction.

4. The preparation method according to claim 3, characterized in that, The reaction solution in step 1 also includes ethanol and water; The molar ratio of the nickel salt to the cobalt salt is 2:1-2:3, and the sum of the masses of the nickel salt and the cobalt salt is in a mass ratio of 1:2-1:4 to the mass of hexadecyltrimethylammonium bromide. The solvothermal reaction conditions are: temperature 110-130°C, reaction time 5-7h; The etching reaction is performed under the following conditions: the sample is placed in a strong alkaline solution with a concentration of 1-3M and reacted at 50-70°C for 0.5-1.5 hours.

5. The preparation method according to claim 4, characterized in that, The nickel salt is nickel chloride or nickel nitrate, and the cobalt salt is cobalt chloride or cobalt nitrate; The strong alkaline solution is a sodium hydroxide solution or a potassium hydroxide solution.

6. The preparation method according to claim 5, characterized in that, The concentration of silver nitrate in the silver nitrate aqueous solution is 35-45 mM; The self-oxidation-reduction reaction takes 30-50 minutes.

7. The preparation method according to claim 6, characterized in that, The mixed solvent in step 3 is composed of dimethylformamide, ethanol and water in a volume ratio of 2:1:1 to 4:1:

1. The amount of conjugated organic ligand in step 3 is 0.05-0.15 mol; The conditions for the intercalation reaction in step 3 are: a reaction temperature of 90-110°C and a reaction time of 6-8 hours.

8. The preparation method according to any one of claims 3 to 7, characterized in that, The conjugated organic ligand is 2,3,6,7,10,11-hexahydroxytriphenyl.

9. A battery, characterized in that, The battery includes a negative electrode, which includes the negative electrode material according to any one of claims 1 or 2.

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