Composite negative electrode material, preparation method thereof and lithium battery

Abstract

The invention discloses a composite negative electrode material and a preparation method thereof and a lithium battery, the composite negative electrode material provided by the invention comprises a three-dimensional porous carbon material, and a lithium-loving metal and a lithium metal which are loaded on a three-dimensional porous carbon skeleton, and the three-dimensional porous carbon material is prepared by taking a ZIFs precursor as a raw material. The three-dimensional porous carbon material prepared by taking the ZIFs precursor as a raw material has a Zn / N-containing double-doped three-dimensional porous carbon skeleton, so that the problems of poor conductivity, insufficient lithium storage aperture and the like of the existing carbon skeleton are solved; a plurality of lithium-loving metal nanoparticles are loaded on the surface of the carbon skeleton, so that the lithium-loving property and the electron conductivity of the carbon skeleton are further enhanced, the uniform deposition of lithium is facilitated, and the growth of dendrites is inhibited; the porous carbon skeleton limits the lithium deposition space, the doped nanoparticles provide lithium-loving sites to guide uniform nucleation, the dual mechanisms synergistically inhibit dendritic crystal growth, and the safety of the lithium metal negative electrode is improved.

Description

Technical Field

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

[0002] Lithium metal batteries have attracted much attention due to their high energy density, but lithium anodes suffer from dendrite growth and volume changes during charge and discharge, leading to safety hazards and rapid degradation of cycle performance. Currently, dendrite growth can be effectively suppressed by constructing three-dimensional porous structures to confine lithium deposition space and introducing lithiophilic sites to guide uniform nucleation. Simultaneously, the porous framework can buffer lithium volume changes and improve electrode structural stability. However, existing three-dimensional porous materials suffer from poor conductivity, uneven pore size distribution, and low mechanical strength, making it difficult to meet the practical application requirements of lithium metal anodes. Summary of the Invention

[0003] The purpose of this invention is to overcome the above-mentioned shortcomings of the prior art and provide a composite anode material, its preparation method, and a lithium battery.

[0004] The technical problem solved by this invention is achieved by the following technical solution.

[0005] This invention provides a composite anode material comprising a three-dimensional porous carbon material, and a lithium-loving metal and a lithium metal supported on the three-dimensional porous carbon framework. The three-dimensional porous carbon material is prepared using ZIFs precursor as a raw material.

[0006] The present invention also provides a method for preparing a composite anode material, comprising the following steps: loading the lithiophilic metal onto the three-dimensional porous carbon material, mixing the obtained lithiophilic improved three-dimensional porous carbon material with the lithium metal, heating to allow the molten lithium metal to fill the pores of the lithiophilic improved three-dimensional porous carbon material, thereby obtaining the composite anode material.

[0007] The present invention also provides a lithium battery, wherein the negative electrode of the lithium battery comprises the above-mentioned composite negative electrode material.

[0008] The present invention has the following beneficial effects:

[0009] This invention provides a composite anode material, its preparation method, and a lithium battery. The composite anode material provided by this invention comprises a three-dimensional porous carbon material, and a lithiophilic metal and lithium metal supported on the three-dimensional porous carbon framework. The three-dimensional porous carbon material is prepared using ZIFs precursors as raw materials. The three-dimensional porous carbon material prepared using ZIFs precursors in this invention has a Zn / N dual-doped three-dimensional porous carbon framework, which can solve the problems of dendrite growth, volume change, and cycle performance degradation existing in existing lithium metal anodes, achieving uniform lithium metal loading, dendrite growth suppression, volume change buffering, and improved cycle stability. Attached Figure Description

[0010] To more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings used in the embodiments will be briefly introduced below. It should be understood that the following drawings only show some embodiments of the present invention and should not be regarded as a limitation on the scope. For those skilled in the art, other related drawings can be obtained based on these drawings without creative effort.

[0011] Figure 1 This is a scanning electron microscope image of the three-dimensional porous carbon material prepared in Example 1;

[0012] Figure 2 This is a sample volume test diagram from Example 1;

[0013] Figure 3 The symmetrical battery cycle performance (1 mA cm⁻¹) of Examples 1-3 and Comparative Example 1. -2 1mAhcm -2 )picture;

[0014] Figure 4 The cycle performance (1 mA cm) of the symmetrical batteries in Examples 4-5 -2 1mAhcm -2 )picture;

[0015] Figure 5 For the comparative example 2, the symmetrical battery cycle performance (1 mA cm) -2 1mAhcm -2 )picture;

[0016] Figure 6 To compare the cycle performance (1 mA cm) of the symmetrical battery in Example 3 -2 1mAhcm -2 )picture;

[0017] Figure 7 To compare the cycle performance (1 mA cm⁻¹) of symmetrical batteries in Examples 4-5 -2 1mAhcm -2 )picture;

[0018] Figure 8 To compare the cycle performance (1 mA cm) of the symmetrical battery of Example 6 -2 1mAhcm -2 )picture;

[0019] Figure 9 The impedance diagrams of the symmetrical cells in Example 1 and Comparative Example 1 are shown.

[0020] Figure 10 The graph shows the half-cell cycle performance (600 cycles at 1C rate) of Example 1 and Comparative Example 1. Detailed Implementation

[0021] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below. Where specific conditions are not specified in the embodiments, conventional conditions or conditions recommended by the manufacturer shall apply. Reagents or instruments whose manufacturers are not specified are all conventional products that can be purchased commercially.

[0022] The following is a detailed description of a composite negative electrode material, its preparation method, and a lithium battery provided by embodiments of the present invention.

[0023] In a first aspect, embodiments of the present invention provide a composite anode material, the composite anode material comprising a three-dimensional porous carbon material, and a lithium-loving metal and a lithium metal loaded on the three-dimensional porous carbon framework, wherein the three-dimensional porous carbon material is prepared using ZIFs precursor as raw material.

[0024] In existing lithium-based anode materials, lithium deposition space is confined by constructing three-dimensional porous structures. However, these three-dimensional porous structures suffer from defects such as poor conductivity, uneven pore size distribution, and low mechanical strength, making it difficult to meet the practical application requirements of lithium metal anodes. Therefore, there is an urgent need to develop novel three-dimensional porous anode materials to achieve uniform lithium loading, dendrite growth suppression, volume change buffering, and improved cycle stability.

[0025] Based on this, embodiments of the present invention provide a composite anode material, comprising a three-dimensional porous carbon material, and a lithiophilic metal and lithium metal loaded on the three-dimensional porous carbon framework. The three-dimensional porous carbon material is prepared using ZIFs precursors as raw materials. In this invention, the three-dimensional porous carbon material prepared using ZIFs precursors possesses a carbon framework with high conductivity, high porosity, adjustable pore size distribution, and good mechanical strength, making it an ideal lithium metal anode matrix material. Through the dual mechanism of confining lithium deposition space by the carbon framework and introducing lithiophilic sites to guide uniform nucleation, dendrite growth can be effectively suppressed, improving safety. Simultaneously, the carbon framework can buffer lithium volume changes, and combined with the high specific capacity of metallic lithium, high reversible capacity and excellent cycle stability can be achieved.

[0026] The composite anode material provided in this invention uses the three-dimensional porous carbon framework of the three-dimensional porous carbon material prepared above as a carrier, which solves the problems of poor conductivity and insufficient lithium storage pore size of existing carbon frameworks. Loading various lithium-loving metal nanoparticles on the surface of the carbon framework further enhances the lithium-lovingness and electronic conductivity of the carbon framework, which is conducive to uniform lithium deposition and inhibits dendrite growth. The porous carbon framework restricts the lithium deposition space, and the doped nanoparticles provide lithium-loving sites to guide uniform nucleation. The dual mechanism synergistically inhibits dendrite growth and improves the safety of lithium metal anodes.

[0027] In some optional embodiments, the three-dimensional porous carbon material is composed of Zn / N-doped porous carbon with a particle size D. 50 Its thickness is 0.5–10 μm, and its specific surface area is 500 m². 2 / g~2000m 2 / g, porosity 45%–60%.

[0028] In some alternative embodiments, the three-dimensional porous carbon material is prepared by the following method: heating the ZIFs precursor in an inert gas atmosphere to obtain a first material, then soaking and drying the first material in a strong alkaline solution to obtain a second material, then calcining the second material in an inert gas atmosphere to obtain a third material, and after cooling the temperature of the third material to room temperature, washing and drying to obtain Zn / N doped porous carbon.

[0029] Preferably, the ZIFs precursor is heated in an Ar atmosphere at 700–900°C at a heating rate of 1–5°C / min for 3–8 hours to obtain the first material;

[0030] Preferably, the first material is soaked in a strong alkaline solution for 5 to 10 hours, with the mass ratio of the first material to the strong alkali being 1:1, and then dried at 80°C for 12 hours to obtain the second material.

[0031] Preferably, the second material is placed in a tube furnace and heated to 700-900°C under an argon atmosphere at a heating rate of 1-5°C / min for 3-8 hours to obtain the third material;

[0032] Preferably, the third material is treated with 5-10 wt% HCl to remove residual KOH, and with deionized water to remove residual acid. It is then dried in an oven at 60°C for 12 hours to obtain a particle size D. 50 It is a 0.5–10 μm Zn / N doped porous carbon.

[0033] Compared to conventional commercial carbon material anodes (D 50 The carbon skeleton (particle size D) of the three-dimensional porous carbon material prepared in this invention has a relatively large particle size (>5μm). 50By forming a porous network structure (with a thickness of 1.0 μm), it can provide physical space for the volume change of metallic lithium, reduce mechanical stress concentration, thereby reducing particle pulverization, effectively buffering the volume change of lithium, and effectively shortening the Li-P-M ratio. + The diffusion path reduces the interfacial impedance, enabling the composite electrode to remain stable after 500 hours of cycling, significantly improving cycle stability.

[0034] In some alternative implementations, the ZIFs include any one of ZIF-8, ZnCo-ZIF, ZIF-L, ZIF-11, ZIF-68, and ZIF-70.

[0035] In some alternative embodiments, the lithium-loving metal is selected from one or more of Ag, Mg, Zn, Ni and Co.

[0036] In some alternative embodiments, the lithiophilic metal and lithium metal account for 0.1% to 5% of the total mass of the three-dimensional porous carbon material.

[0037] Secondly, embodiments of the present invention also provide a method for preparing a composite anode material, comprising the following steps: loading the lithiophilic metal onto the three-dimensional porous carbon material, mixing the obtained lithiophilic improved three-dimensional porous carbon material with the lithium metal, heating to allow molten lithium metal to fill the pores of the lithiophilic improved three-dimensional porous carbon material, thereby obtaining a composite anode material.

[0038] In some optional embodiments, the preparation of the lithiophilic improved three-dimensional porous carbon material includes the following steps: placing the three-dimensional porous carbon material in an aqueous solution of a lithiophilic metal salt, conducting a closed reaction, collecting the sample and drying it, and then heating and reducing it to load the lithiophilic metal on the carbon framework of the three-dimensional porous carbon material to obtain the lithiophilic improved three-dimensional porous carbon material.

[0039] Preferably, the three-dimensional porous carbon material is placed in an aqueous solution of a lithium-loving metal salt with a concentration of 0.01–1 mol / L, kept at 60–120°C for 4–10 hours in a closed reaction vessel, and the sample is collected and dried.

[0040] Preferably, in an Ar / H2 mixed gas, Ar gas, or oxygen atmosphere, the material undergoing a closed reaction is heated at 200–600°C at a heating rate of 1–5°C / min for 1–5 hours. Through high-temperature thermal reduction, the lithiophilic metal is loaded onto the carbon framework surface of the three-dimensional porous carbon material to obtain a lithiophilic improved three-dimensional porous carbon material.

[0041] In some alternative embodiments, the mass ratio of the lithiophilic modified three-dimensional porous carbon material to the metallic lithium is (0.5:1) to (1.2:1).

[0042] In some optional embodiments, the preparation of the composite anode material includes the following steps: under heating conditions, the lithium-loving modified three-dimensional porous carbon material and the metallic lithium are stirred in an inert gas environment, so that the molten metallic lithium fills the pores of the carbon skeleton of the three-dimensional porous carbon material, and the composite anode material is obtained by cooling and collecting.

[0043] Preferably, in an inert gas environment, H2O < 0.1 ppm and O2 < 0.1 ppm;

[0044] Preferably, the stirring temperature is 200–600°C and the stirring time is 2–8 hours.

[0045] The high specific capacity of lithium metal (3860 mAh / g) combined with the high conductivity of the carbon skeleton achieves a reversible capacity of >1500 mAh / g, meeting the requirements of high energy density lithium metal batteries.

[0046] Thirdly, embodiments of the present invention also provide a lithium battery, wherein the negative electrode of the lithium battery comprises the aforementioned composite negative electrode material.

[0047] The present invention will be further described below with reference to embodiments.

[0048] 1. Preparation of three-dimensional porous carbon materials: A certain amount of Zn(NO3)2·6H2O and nitrogen-containing organic ligands (1:1 to 1:10) were dissolved in 100-500 mL of methanol or aqueous solution to form a precursor solution. The solution was then stirred at room temperature (25℃) for 1-5 hours, followed by aging at room temperature for 18-30 hours. The sample was then collected and dried in a vacuum oven at 60℃ to obtain the ZIFs precursor. The sample was then heated in an Ar atmosphere at 700-900℃ at a heating rate of 1-5℃ / min for 3-8 hours. Subsequently, the sample was immersed in a KOH aqueous solution (sample to KOH mass ratio of 1:1) for 5-10 hours and dried at 80℃ for 12 hours. Finally, the sample was placed in a tube furnace and heated in an argon atmosphere to 700-900℃ at a heating rate of 1-5℃ / min for 3-8 hours. After cooling to room temperature, residual KOH was removed with 5-10 wt% HCl, and residual acid was removed with deionized water. The sample was then dried in an oven at 60°C for 12 hours to obtain particle size D. 50 0.5–10 μm Zn / N doped porous carbon (specific surface area 500 m²) 2 / g~2000m 2 / g, porosity 45%–60%).

[0049] 2. Lithophilic site modification of the three-dimensional porous carbon framework: The carbon material prepared in step 1 is added to an aqueous solution containing one or more metal salts such as AgNO3, Mg(NO3)2, ZnSO4, Ni(NO3)2 and CoSO4 (concentration of 0.01-1 mol / L) in a closed reactor and kept at 60-120℃ for 4-10 hours. The sample is collected and dried. Then, it is heated at 200-600℃ for 1-5 hours under an atmosphere of Ar / H2 mixture, Ar gas and oxygen at a heating rate of 1-5℃ / min. Through high-temperature thermal reduction, one or more metals such as Ag / Mg / Zn / Ni / Co are loaded onto the surface of the carbon framework, enhancing the lithophilicity and electronic conductivity of the carbon framework.

[0050] 3. Preparation of lithium-carbon composite: A certain amount of lithium-loving modified porous carbon prepared in step 2 is mixed with lithium (carbon:lithium mass ratio of 0.5:1 to 1.2:1) and stirred uniformly at 200 to 600°C for 2 to 8 hours in an inert gas environment (H2O < 0.1 ppm, O2 < 0.1 ppm) to allow molten lithium metal to fill the pores of the carbon skeleton. The mixture is then cooled and collected to obtain the lithium-carbon composite.

[0051] 4. Post-processing of lithium-carbon composite: The lithium-carbon composite is processed through an extrusion rolling process to obtain a 10-200μm self-supporting lithium-carbon composite electrode, optimizing the electrode density and ensuring that the composite material has good mechanical strength.

[0052] Example 1

[0053] 1. Preparation of a three-dimensional porous carbon framework: Zn(NO3)2·6H2O and 2-methylimidazole were added in a 1:3 ratio to 300 mL of methanol to form a precursor solution. The solution was then stirred at room temperature (25℃) for 2 hours, followed by aging at room temperature for 24 hours. The sample was then collected and dried in a vacuum oven at 60℃ to obtain the ZIF-8 precursor. The sample was then heated at 800℃ for 4 hours under an Ar atmosphere at a heating rate of 2℃ / min. Subsequently, the sample was immersed in a KOH aqueous solution (sample to KOH mass ratio 1:1) for 6 hours and dried at 80℃ for 12 hours. Finally, the sample was placed in a tube furnace and heated to 800℃ under an argon atmosphere at a heating rate of 2℃ / min for 4 hours. After cooling to room temperature, residual KOH was removed with 7.5 wt% HCl, and residual acid was removed with deionized water. The sample was then dried in an oven at 60℃ for 12 hours to obtain a particle size D. 50 It is a 1.0 μm Zn / N doped porous carbon (specific surface area of ​​1467 m²). 2 / g, porosity 50.6%.

[0054] 2. Lithophilic site modification of the three-dimensional porous carbon framework: The carbon material prepared in step 1 was added to an aqueous solution containing AgNO3 metal salt (concentration of 0.5 mol / L) and placed in a closed reaction vessel. The solution was kept at 100℃ for 6 hours. The sample was collected and dried. Then, it was heated at 400℃ for 3 hours using an Ar / H2 mixed gas at a heating rate of 2℃ / min. Through high-temperature thermal reduction, Ag metal was loaded onto the surface of the carbon framework, further enhancing the lithophilicity and electronic conductivity of the carbon framework.

[0055] 3. Preparation of lithium-carbon composite: A certain amount of lithium-loving modified porous carbon prepared in step 2 was mixed with lithium (carbon:lithium mass ratio of 1:1) and stirred uniformly at 300°C for 4 hours in an inert gas environment (H2O < 0.1 ppm, O2 < 0.1 ppm) to fill the pores of the carbon skeleton with molten lithium metal. The mixture was then cooled and collected to obtain the lithium-carbon composite.

[0056] 4. Post-processing of lithium-carbon composites: Lithium-carbon composites are processed through extrusion rolling to obtain self-supporting lithium-carbon composite electrodes of different sizes, optimize electrode density, and ensure that the composite material has good mechanical strength.

[0057] Example 2

[0058] 1. Zn(NO3)2·6H2O and 2-methylimidazole were added in a 1:3 ratio to 300 mL of methanol to form a precursor solution. The solution was then stirred at room temperature (25℃) for 2 hours, followed by aging at room temperature for 24 hours. The sample was then collected and dried in a vacuum oven at 60℃ to obtain the ZIF-8 precursor. The sample was then heated at 800℃ under an Ar atmosphere at a heating rate of 2℃ / min for 4 hours. Subsequently, the sample was immersed in a KOH aqueous solution (sample to KOH mass ratio of 1:1) for 6 hours and dried at 80℃ for 12 hours. Finally, the sample was placed in a tube furnace and heated to 800℃ under an argon atmosphere at a heating rate of 2℃ / min for 4 hours. After cooling to room temperature, residual KOH was removed with 7.5 wt% HCl, and residual acid was removed with deionized water. The sample was then dried in an oven at 60℃ for 12 hours to obtain a particle size D. 50 It is a 1.0 μm Zn / N doped porous carbon (specific surface area of ​​1467 m²). 2 / g, porosity 50.6%.

[0059] 2. The carbon material prepared in step 1 was added to an aqueous solution containing Mg(NO3)2 metal salt (concentration of 0.3 mol / L) and placed in a sealed reaction vessel. The solution was kept at 90°C for 5 hours. The sample was collected and dried. Then, it was heated at 400°C with a heating rate of 2°C / min for 3 hours using an Ar / H2 mixed gas. Through high-temperature thermal reduction, Mg metal was loaded onto the surface of the carbon framework.

[0060] 3. A certain amount of lithium-loving modified porous carbon prepared in step 2 and lithium (carbon:lithium mass ratio of 0.9:1) are stirred uniformly at 300°C for 4 hours in an inert gas environment (H2O < 0.1ppm, O2 < 0.1ppm) to allow molten lithium metal to fill the pores of the carbon skeleton. The mixture is then cooled and collected to obtain a lithium-carbon composite.

[0061] 4. Lithium-carbon composites are processed through extrusion rolling to obtain self-supporting lithium-carbon composite electrodes of different sizes.

[0062] Example 3

[0063] 1. Zn(NO3)2·6H2O and 2-methylimidazole were added in a 1:3 ratio to 300 mL of methanol to form a precursor solution. The solution was then stirred at room temperature (25℃) for 2 hours, followed by aging at room temperature for 24 hours. The sample was then collected and dried in a vacuum oven at 60℃ to obtain the ZIF-8 precursor. The sample was then heated at 800℃ under an Ar atmosphere at a heating rate of 2℃ / min for 4 hours. Subsequently, the sample was immersed in a KOH aqueous solution (sample to KOH mass ratio of 1:1) for 6 hours and dried at 80℃ for 12 hours. Finally, the sample was placed in a tube furnace and heated to 800℃ under an argon atmosphere at a heating rate of 2℃ / min for 4 hours. After cooling to room temperature, residual KOH was removed with 7.5 wt% HCl, and residual acid was removed with deionized water. The sample was then dried in an oven at 60℃ for 12 hours to obtain a particle size D. 50 It is a 1.0 μm Zn / N doped porous carbon (specific surface area of ​​1467 m²). 2 / g, porosity 50.6%.

[0064] 2. A certain amount of lithium-loving modified porous carbon prepared in step 2 and lithium (carbon:lithium mass ratio of 1.1:1) were uniformly stirred at 300°C for 4 hours in an inert gas environment (H2O < 0.1 ppm, O2 < 0.1 ppm) to allow molten lithium metal to fill the pores of the carbon skeleton. The mixture was then cooled and collected to obtain a lithium-carbon composite.

[0065] 3. Lithium-carbon composites are processed through extrusion rolling to obtain self-supporting lithium-carbon composite electrodes of different sizes.

[0066] Example 4

[0067] 1. Zn(NO3)2·6H2O and 2-methylimidazole were added in a 1:8 ratio to 200 mL of deionized water to form a precursor solution. The solution was then stirred at room temperature (25℃) for 1 hour, followed by aging at room temperature for 12 hours. The sample was collected, washed, and dried in a vacuum oven at 60℃ to obtain the ZIF-L precursor. The sample was then heated at 900℃ under Ar atmosphere at a heating rate of 2℃ / min for 5 hours. Subsequently, the sample was immersed in a KOH aqueous solution (sample to KOH mass ratio of 1:1) for 6 hours and dried at 80℃ for 12 hours. Finally, the sample was placed in a tube furnace and heated to 800℃ under an argon atmosphere at a heating rate of 2℃ / min for 4 hours. After cooling to room temperature, residual KOH was removed with 7.5 wt% HCl, and residual acid was removed with deionized water. The sample was then dried in an oven at 60℃ for 12 hours to obtain a particle size D. 50 It is a 2.1 μm Zn / N-doped porous carbon (specific surface area of ​​976.8 m²). 2 / g, porosity 47.1%.

[0068] 2. Lithophilic site modification of the three-dimensional porous carbon framework: The carbon material prepared in step 1 was added to an aqueous solution containing AgNO3 metal salt (concentration of 0.5 mol / L) and placed in a closed reaction vessel. The solution was kept at 100℃ for 6 hours. The sample was collected and dried. Then, it was heated at 400℃ for 3 hours using an Ar / H2 mixed gas at a heating rate of 2℃ / min. Through high-temperature thermal reduction, Ag metal was loaded onto the surface of the carbon framework, further enhancing the lithophilicity and electronic conductivity of the carbon framework.

[0069] 3. Preparation of lithium-carbon composite: A certain amount of lithium-loving modified porous carbon prepared in step 2 was mixed with lithium (carbon:lithium mass ratio of 1:1) and stirred uniformly at 300°C for 4 hours in an inert gas environment (H2O < 0.1 ppm, O2 < 0.1 ppm) to fill the pores of the carbon skeleton with molten lithium metal. The mixture was then cooled and collected to obtain the lithium-carbon composite.

[0070] 4. Post-processing of lithium-carbon composites: Lithium-carbon composites are processed through extrusion rolling to obtain self-supporting lithium-carbon composite electrodes of different sizes, optimize electrode density, and ensure that the composite material has good mechanical strength.

[0071] Example 5

[0072] 1. Zn(NO3)2·6H2O and benzimidazole were added in a 1:4 ratio to 200 mL of methanol to form a precursor solution. The solution was then stirred at room temperature (25℃) for 1 hour, followed by aging at room temperature for 16 hours. The sample was collected, washed, and dried in a vacuum oven at 60℃ to obtain the ZIF-11 precursor. The sample was then heated at 800℃ for 6 hours under an Ar atmosphere at a heating rate of 2℃ / min. Subsequently, the sample was immersed in a KOH aqueous solution (sample to KOH mass ratio 1:1) for 6 hours and dried at 80℃ for 12 hours. Finally, the sample was placed in a tube furnace and heated to 800℃ under an argon atmosphere at a heating rate of 2℃ / min for 4 hours. After cooling to room temperature, residual KOH was removed with 7.5 wt% HCl, and residual acid was removed with deionized water. The sample was then dried in an oven at 60℃ for 12 hours to obtain a particle size D. 50 It is a 1.5 μm Zn / N-doped porous carbon (specific surface area of ​​1611.2 m²). 2 / g, porosity 57.6%.

[0073] 2. Lithophilic site modification of the three-dimensional porous carbon framework: The carbon material prepared in step 1 was added to an aqueous solution containing AgNO3 metal salt (concentration of 0.5 mol / L) and placed in a closed reaction vessel. The solution was kept at 100℃ for 6 hours. The sample was collected and dried. Then, it was heated at 400℃ for 3 hours using an Ar / H2 mixed gas at a heating rate of 2℃ / min. Through high-temperature thermal reduction, Ag metal was loaded onto the surface of the carbon framework, further enhancing the lithophilicity and electronic conductivity of the carbon framework.

[0074] 3. Preparation of lithium-carbon composite: A certain amount of lithium-loving modified porous carbon prepared in step 2 was mixed with lithium (carbon:lithium mass ratio of 1:1) and stirred uniformly at 300°C for 4 hours in an inert gas environment (H2O < 0.1 ppm, O2 < 0.1 ppm) to fill the pores of the carbon skeleton with molten lithium metal. The mixture was then cooled and collected to obtain the lithium-carbon composite.

[0075] 4. Post-processing of lithium-carbon composites: Lithium-carbon composites are processed through extrusion rolling to obtain self-supporting lithium-carbon composite electrodes of different sizes, optimize electrode density, and ensure that the composite material has good mechanical strength.

[0076] Comparative Example 1

[0077] Particle size D 50 6.1μm activated carbon (Kuraray YP50F) and metallic lithium (carbon:lithium mass ratio of 1:1) were uniformly stirred at 300℃ for 4 hours in an inert gas environment (H2O < 0.1ppm, O2 < 0.1ppm), and then cooled to collect the lithium-carbon composite. Self-supporting lithium-carbon composite electrodes of different sizes were obtained by extrusion rolling process.

[0078] Comparative Example 2

[0079] Particle size D 50 9μm hard carbon (Kuraray hard carbon type 1) and metallic lithium (carbon:lithium mass ratio of 0.9:1) were uniformly stirred at 300℃ for 4 hours in an inert gas environment (H2O < 0.1ppm, O2 < 0.1ppm), and the mixture was cooled and collected to obtain a lithium-carbon composite. Self-supporting lithium-carbon composite electrodes of different sizes were then processed through an extrusion rolling process.

[0080] Comparative Example 3

[0081] Commercial carbon nanotubes (Kelund carbon nanotube powder 8011A) and metallic lithium (carbon:lithium mass ratio of 1.1:1) were uniformly stirred at 300°C for 4 hours in an inert gas environment (H2O < 0.1 ppm, O2 < 0.1 ppm). After cooling, the lithium-carbon composite was collected and processed into self-supporting lithium-carbon composite electrodes of different sizes through an extrusion rolling process.

[0082] Comparative Example 4

[0083] The steps are similar to those in Example 1, except that the mass ratio of lithiophilic modified three-dimensional porous carbon to lithium is 0.2:1.

[0084] Comparative Example 5

[0085] The steps are similar to those in Example 1, except that the mass ratio of lithiophilic modified three-dimensional porous carbon to lithium is 1.8:1.

[0086] Comparative Example 6

[0087] Similar to the steps in Example 1, except that in step 1, the preparation of the three-dimensional porous carbon framework does not involve KOH treatment or subsequent calcination.

[0088] Detection

[0089] The above samples used the same size as the positive and negative electrodes, and the assembled symmetrical battery electrodes had a thickness of 20 μm. The electrolyte was a solution of 1 mol / L 1M LiTFSI dissolved in a 1:1 molar ratio of DME and DOL, containing 2% LiNO3. The test parameters were impedance (frequency: 0.01–10 Hz). 5 Hz) and cycling performance (current: 1mAcm) -2 Deposition amount: 1 mAh / cm³ -2Furthermore, using the relevant examples and comparative examples as the positive electrode, a 400μm commercial lithium sheet as the negative electrode, and a 1mol / L 1M LiTFSI solution dissolved in a 1:1 molar ratio of DME and DOL containing 2% LiNO3 as the electrolyte, the capacity of the sample from Example 1 was tested by charging with a current of 0.5mA. Additionally, using the relevant sample as the negative electrode (100μm thick), a laboratory-coated lithium iron phosphate electrode was used as the positive electrode (area density 11.2 mg / cm³). 2 The electrolyte was 1 mol / L LiPF6, and the ratio of DMC:EC:EMC was 1:1:1. The assembled half-cell was evaluated for application performance at a 1C rate.

[0090] The half-cell cycle performance test results of the examples and comparative examples are shown in the table below (600 cycles at 1C rate).

[0091] Sample Name Initial capacity (mAh / g) Capacity after cycling (mAh / g) Capacity retention rate (%) Example 1 151.2 144.8 95.77 Example 2 152.1 140.7 92.50 Example 3 149.4 135.2 90.50 Example 4 151.7 131.6 86.75 Example 5 149.2 137.9 92.42 Comparative Example 1 153.6 96.8 63.02 Comparative Example 2 146.3 101.2 69.17 Comparative Example 3 145.6 89.2 61.26 Comparative Example 4 157.8 67,8 42.97 Comparative Example 5 143.2 107.8 75.28 Comparative Example 6 154.3 109.5 70.97

[0092] As can be seen from the table above, the three-dimensional porous carbon material prepared by this invention has better lithium affinity than existing mature carbon-based materials, and its half-cell cycle performance significantly surpasses that of Comparative Examples 1-3. In Comparative Examples 4-5, when preparing lithium-carbon anodes by adjusting the amount of three-dimensional porous carbon (20% and 180% of Example 1, respectively), insufficient carbon content will induce lithium metal deposition dendrite formation, while excessive carbon content will hinder lithium ion insertion / extraction kinetics due to the excessive carbon skeleton. Both of these factors result in half-cell cycle performance that is significantly worse than that of the Examples. In addition, Comparative Example 6 reduced the number of pores during the preparation process, which also resulted in a significantly lower cycle stability than the Examples.

[0093] Combined with appendix Figure 1-10 Analysis shows that, compared to Comparative Examples 1-3 which used commercially available conventional carbon materials, the porous carbon prepared in Example 1 has abundant lithiophilic nucleation sites due to the synergistic effect of multiple elements. Its framework structure, after melting and stirring, uniformly distributes metallic lithium (…). Figure 1 This is a scanning electron microscope (SEM) image. Figure 2 (For capacity testing); Symmetrical battery cycle testing ( Figure 3-8 This structure confirms that Example 1 exhibits significantly optimized cycle stability. However, in Comparative Examples 4 and 5, when the amount of three-dimensional porous carbon was adjusted (20% and 180% of Example 1, respectively) to prepare the anode, insufficient carbon skeleton led to the risk of dendrite growth (Comparative Example 4), while excessive carbon skeleton resulted in a decrease in active lithium content and a surge in polarization voltage (Comparative Example 5), causing both to have weaker cycle performance than the Example 1. Comparative Example 6, by reducing the amount of KOH to suppress mesopore formation (reducing the number of pores), also caused a significant decrease in cycle stability. Half-cell cycle performance ( Figure 10 ) and impedance testing ( Figure 9Further verification showed that the charge transfer impedance (92Ω) of Example 1 was only 32.2% of that of Comparative Example 1 (286Ω), confirming that it has both excellent conductivity and mechanical strength, which can effectively buffer volume changes and reduce interface impedance. At the same time, the measured capacity of Example 1 reached 1754mAh / g (theoretical value 1930mAh / g), and the 91% capacity achievement rate fully demonstrated the efficient utilization of active lithium.

[0094] As can be seen from the above, in the embodiments of the present invention, a three-dimensional porous Zn / N-doped carbon framework derived from ZIFs (BET is 500m) is utilized. 2 / g~2000m 2 Lithium-carbon anode materials were prepared using a melt composite process, with a porosity of 45%–60% ( / g). The multi-element synergistic framework significantly enhances lithium affinity, achieving a capacity retention of ≥93.5% after 500 cycles at 0.5C (commercial materials ≤75%), a charge transfer impedance as low as 92Ω (commercial materials 32.2%), and a high capacity utilization rate of 91%. Furthermore, the carbon content threshold (100%) and the complete mesoporous system form the core performance boundary, overcoming the bottlenecks of lithium dendrite suppression and long-life electrode development.

[0095] The above are merely preferred embodiments of the present invention and are not intended to limit the present invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A composite negative electrode material, characterized in that, The composite anode material includes a three-dimensional porous carbon material, and a lithium-loving metal and a lithium metal loaded on the three-dimensional porous carbon material. The three-dimensional porous carbon material is prepared using ZIFs precursor as raw material.

2. The composite negative electrode material according to claim 1, characterized in that, The three-dimensional porous carbon material is composed of Zn / N dual-doped porous carbon with a particle size D. 50 Its thickness is 0.5–10 μm, and its specific surface area is 500 m². 2 / g~2000m 2 / g, porosity 45%–60%.

3. The composite negative electrode material according to claim 2, characterized in that, The three-dimensional porous carbon material is prepared by the following method: heating the ZIFs precursor in an inert gas atmosphere to obtain a first material, then soaking and drying the first material in a strong alkaline solution to obtain a second material, then calcining the second material in an inert gas atmosphere to obtain a third material, and then washing and drying the third material after cooling it to room temperature to obtain Zn / N doped porous carbon. Preferably, the ZIFs precursor is heated in an Ar atmosphere at 700–900°C at a heating rate of 1–5°C / min for 3–8 hours to obtain the first material; Preferably, the first material is soaked in a strong alkaline solution for 5 to 10 hours, the mass ratio of the first material to the strong alkaline solution is 1:1, and then dried at 80°C for 12 hours to obtain the second material; Preferably, the second material is placed in a tube furnace and heated to 700-900°C under an argon atmosphere at a heating rate of 1-5°C / min for 3-8 hours to obtain the third material; Preferably, the third material is treated with 5-10 wt% HCl to remove residual KOH, and with deionized water to remove residual acid, then dried in an oven at 60°C for 12 hours to obtain a particle size D. 50 It consists of Zn / N-doped porous carbon with a thickness of 0.5–10 μm.

4. The composite negative electrode material according to claim 3, characterized in that, The ZIFs include any one of ZIF-8, ZnCo-ZIF, ZIF-L, ZIF-11, ZIF-68, and ZIF-70.

5. The composite negative electrode material according to claim 1 or 2, characterized in that, The loading of the lithiophilic metal and the lithium metal accounts for 0.1% to 5% of the total mass of the three-dimensional porous carbon material, wherein the lithiophilic metal is selected from one or more of Ag, Mg, Zn, Ni and Co.

6. A method for preparing a composite negative electrode material according to any one of claims 1-5, characterized in that, Includes the following steps: After loading the lithiophilic metal onto the three-dimensional porous carbon material, the resulting lithiophilic improved three-dimensional porous carbon material is mixed with the lithium metal, and heated to allow the molten lithium metal to fill the pores of the lithiophilic improved three-dimensional porous carbon material, thus obtaining a composite anode material.

7. The preparation method according to claim 6, characterized in that, The preparation of the lithium-loving improved three-dimensional porous carbon material includes the following steps: placing the three-dimensional porous carbon material in an aqueous solution of a lithium-loving metal salt, conducting a closed reaction, collecting the sample and drying it, and then heating and reducing it to load the lithium-loving metal onto the carbon framework of the three-dimensional porous carbon material to obtain the lithium-loving improved three-dimensional porous carbon material. Preferably, the three-dimensional porous carbon material is placed in an aqueous solution of a lithium-loving metal salt with a concentration of 0.01–1 mol / L, kept at 60–120°C for 4–10 hours in a closed reaction vessel, and the sample is collected and dried. Preferably, in an Ar / H2 mixed gas, Ar gas, or oxygen atmosphere, the material undergoing a closed reaction is heated at 200–600°C at a heating rate of 1–5°C / min for 1–5 hours. Through high-temperature thermal reduction, the lithiophilic metal is loaded onto the carbon framework surface of the three-dimensional porous carbon material to obtain a lithiophilic improved three-dimensional porous carbon material.

8. The composite negative electrode material according to claim 6, characterized in that, The mass ratio of the lithiophilic improved three-dimensional porous carbon material to the metallic lithium is (0.5:1) to (1.2:1).

9. The preparation method according to claim 6, characterized in that, The preparation of the composite anode material includes the following steps: under heating conditions, the lithium-loving modified three-dimensional porous carbon material and the metallic lithium are stirred in an inert gas environment, so that the molten metallic lithium fills the pores of the carbon skeleton of the three-dimensional porous carbon material, and the composite anode material is obtained by cooling and collecting. Preferably, in an inert gas environment, H2O < 0.1 ppm and O2 < 0.1 ppm; Preferably, the stirring temperature is 200–600°C and the stirring time is 2–8 hours.

10. A lithium battery, characterized in that, The negative electrode of the lithium battery comprises the composite negative electrode material as described in any one of claims 1-5 or the composite negative electrode material prepared by the preparation method described in any one of claims 6-9.

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