A high-load porous carbon integrated electrode constructed by ultrafast joule heating in one step and a preparation method and application thereof

Abstract

The application discloses a high-load porous carbon-coated integrated electrode constructed by one-step super-fast Joule heating and a preparation method and application thereof. The electrode comprises a current collector and an active material layer, and the active material layer has a three-dimensional porous carbon-coated integrated structure composed of an active material, a conductive agent and an in-situ generated carbon layer. The preparation method is to perform super-fast Joule heating treatment on the current collector coated with an electrode precursor wet film, and to synchronously complete solvent evaporation pore forming, binder / conductive agent carbonization coating and interface fusion in one step within a second. The method greatly simplifies the process, and the prepared electrode has high active material loading (active material surface loading≥20 mg / cm 2 ), rich ion transmission channels and excellent interface electron / ion conductivity, effectively solves the problem of slow charge transmission kinetics in high-load electrodes, and significantly improves the rate performance and unit area capacity of the battery.

Description

Technical Field

[0001] This invention belongs to the field of electrochemical energy storage device technology, specifically relating to a high-load porous carbon-coated integrated electrode constructed in one step by ultra-fast Joule heating, its preparation method and application. Background Technology

[0002] With the rapid development of electric vehicles, large-scale energy storage, and portable electronic devices, higher demands are being placed on the energy density, power density, and cycle life of electrochemical energy storage devices (especially secondary batteries). As a core component of the battery, the performance of the electrode directly determines the overall performance of the device. Traditional electrodes are typically manufactured by mixing active materials, conductive agents, and binders to form a slurry, coating it onto a current collector, and then undergoing time-consuming processes such as stepped temperature drying and rolling. Electrodes prepared using this conventional method have a dense structure and limited ion transport channels. Especially in high-load, thick electrodes aiming for high areal capacity, the thickness of the active material layer increases significantly, leading to longer ion diffusion paths, slower charge transport kinetics, and increased interfacial impedance, severely limiting the battery's rate performance and capacity per unit area.

[0003] To improve the charge transport performance of high-load electrodes, existing technologies typically employ strategies such as constructing three-dimensional porous electrode structures, introducing highly conductive networks, or surface coating modifications to active materials. For example, porous electrodes are prepared by introducing pore-forming templates into the electrode, freeze-drying, or electrospinning to increase electrolyte wetting and ion transport channels; or by using highly conductive materials such as carbon nanotubes and graphene to construct long-range conductive networks and reduce electron transport impedance; or by coating the surface of active materials with carbon layers through chemical vapor deposition or hydrothermal carbonization to enhance interfacial stability and electronic conductivity. However, these methods are often complex, time-consuming, and costly, and the multi-step processing can easily introduce impurities or damage the structural integrity. Especially when integrating multiple functions such as porous structure construction, conductive network formation, and surface coating, existing technologies usually require step-by-step execution, making it difficult to achieve rapid, efficient, and structurally controllable integrated fabrication while ensuring high load capacity. Summary of the Invention

[0004] The purpose of this invention is to develop a new method for the efficient, rapid, low-cost, and scalable preparation of high-load electrodes. This method can simultaneously complete solvent evaporation and pore formation, binder carbonization and coating, and interface fusion in a very short time, thereby constructing an integrated electrode structure with a three-dimensional interconnected porous network and a uniform carbon coating layer in one step. This solves the key problem of slow charge transport dynamics in high-load electrodes and significantly improves the rate performance and capacity per unit area of ​​the battery.

[0005] The specific plan is as follows: I. Electrode Structure Design This invention provides a high-load porous carbon-coated integrated electrode for energy storage batteries (including aqueous batteries), comprising a current collector and an active material layer grown on the surface of the current collector. The active material layer consists of active material particles, a conductive agent, and an in-situ generated carbon layer. The active material layer has a three-dimensional interconnected porous network structure, and the surface of the active material is coated by the in-situ generated carbon layer, forming a continuous and rapid electron transport interface; the surface loading of the active material of the electrode is not less than 20 mg / cm³. 2 The in-situ generated carbon layer has a thickness of 1 nm to 50 nm, and the porous network structure has a pore size distribution of 10 nm to 5 μm. This structure ensures high loading capacity while also exhibiting excellent ion and electron conductivity.

[0006] II. Innovation in Preparation Methods The present invention correspondingly provides a method for preparing the above-mentioned electrode, comprising the following steps: S1. Electrode precursor preparation: The active material, conductive agent, binder and solvent are mixed to form a slurry, which is then coated onto the current collector to form a wet film; S2. Pre-drying: Place the current collector with wet film obtained in step S1 in an oven for a certain period of time to partially remove the solvent; S3. Ultra-fast Joule heating treatment: The current collector with wet film obtained in step S2 is placed in an inert atmosphere or vacuum, and a pulsed or continuous high current is applied to it, so that the wet film is rapidly heated to 600°C~1200°C within 0.1 seconds to 10 seconds, and then naturally cooled.

[0007] This heating process simultaneously achieves three key transformations: 1. The binder and / or some conductive agents are carbonized to form an in-situ generated carbon layer; 2. Solvent evaporates or decomposes, forming a three-dimensional interconnected porous network structure; 3. Interfacial fusion is achieved between the active material, the conductive agent, and the carbon layer.

[0008] Preferably, the surface loading of the active material in the electrode is 20 mg / cm³. 2 Up to 100 mg / cm 2 .

[0009] Preferably, the thickness of the in-situ generated carbon layer is 1 nm to 50 nm.

[0010] Preferably, the pore size distribution of the three-dimensional interconnected porous network structure is from 10 nm to 5 μm.

[0011] Preferably, the conductive agent includes at least one of carbon nanotubes, graphene, and conductive carbon black; the binder is a carbonizable polymer at the heating temperature in step S3, including at least one of polyvinylidene fluoride, polyacrylonitrile, and polyvinyl alcohol. The solvent is a substance that volatilizes / decomposes at the heating temperature in step S3 to achieve pore formation, including at least one of NMP and water.

[0012] Preferably, in step S2, the oven temperature is 50-95℃ and the heating time is 5-20 min.

[0013] Preferably, in step S3, if the applied current is a DC pulse current, the pulse width is 1 ms to 500 ms.

[0014] Preferably, in step S3, the current density is 10 A / cm². 2 ~100A / cm 2 .

[0015] The present invention also proposes an aqueous battery comprising a positive electrode, a negative electrode, an electrolyte, and a separator, wherein the positive electrode and / or the negative electrode are made of a high-load porous carbon-coated integrated electrode prepared by any of the methods described above.

[0016] Compared with the prior art, the beneficial effects of this invention are as follows: One-step integrated process: Through ultra-fast Joule heating, volatilization pore formation, carbonization coating and interface fusion are completed simultaneously in seconds, which greatly simplifies the process and improves production efficiency.

[0017] Precise and controllable structure: Rapid high-temperature processing suppresses material coarsening, enabling precise control of the porous structure and carbon coating layer, forming a continuous conductive network and rapid ion channels.

[0018] Excellent electrochemical performance: The electrode also features high loading (area loading ≥ 20 mg / cm²). 2 With excellent rate performance, it effectively solves the problem of slow charge transport dynamics in thick electrodes.

[0019] Wide applicability: This method is applicable to a variety of active material systems, especially aqueous batteries that require high interface stability, and can significantly improve the battery's capacity per unit area and cycle life.

[0020] This invention provides a practical and feasible technical solution for the development of high-energy-density and high-power-density energy storage devices through collaborative innovation in materials, processes, and structural design. Attached Figure Description

[0021] Figure 1 The preparation process of the high-load porous carbon-coated integrated electrode of the present invention is as follows; Figure 2This is a comparison of the electrochemical cycling performance of the integrated sodium titanium phosphate electrode prepared in Example 1 and the electrode prepared by the conventional method. Figure 3 This is a comparison chart of the electrochemical rate performance of the integrated lithium manganese oxide electrode prepared in Example 2 and the electrode prepared by the conventional method. Detailed Implementation

[0022] The present invention will now be described in further detail with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and not intended to limit it.

[0023] Example 1 I. Preparation of precursor slurry: Active material: sodium titanium phosphate (NaTi2PO4)3, NTP, with an average particle size of approximately 200 nm; Conductive agent: Carbon black (Super P); Adhesive: Polyvinylidene fluoride (PVDF); Solvent: N-methylpyrrolidone (NMP); Mass ratio: NTP:carbon black:PVDF=80:10:10; Solid content: 25 wt% Slurry preparation: Mix the above materials in proportion and stir at 2000 rpm for 4 hours in a planetary mixer to make a uniform slurry; II. Electrode Coating and Pre-drying: Current collector: Aluminum foil (15 μm thick); Coating method: Use a doctor blade coater to evenly coat the slurry onto the aluminum foil surface; Wet film thickness: approximately 300 μm; Pre-drying: Place in an 80°C oven for 10 minutes to partially remove NMP solvent and prevent structural damage caused by violent solvent evaporation during subsequent heating. III. Ultra-fast Joule heating treatment: Atmosphere: Argon protection; Heating method: DC pulsed current, pulse width 100 ms, current density approximately 50 A / cm² 2 ; Peak temperature: 800℃; Holding time: Approximately 2 seconds (including heating and holding); Cooling: Allow to cool naturally to room temperature; IV. Explanation of the structure formation mechanism: During ultra-rapid Joule heating: PVDF carbonization: PVDF decomposes and carbonizes rapidly at high temperature, forming an in-situ carbon layer with a thickness of about 5~20 nm, which uniformly coats the surface of NTP particles. Solvent evaporation and pore formation: The residual NMP evaporates rapidly, forming a three-dimensional interconnected porous network with a pore size distribution of 50 nm ~ 2 μm; Interface fusion: A tight electronic contact interface is formed between carbon black, PVDF carbonized layer and NTP particles, constructing a continuous conductive network; V. Electrode structural features: Active substance surface loading: approximately 35 mg / cm³ 2 ; Carbon layer thickness: approximately 5~20 nm; Porosity: Approximately 45%; Pore ​​size distribution: mainly concentrated in the range of 100 nm to 1 μm; Interface resistance: reduced by approximately 60% compared to electrodes prepared using traditional drying methods; VI. Traditional Drying Method for Electrode Preparation: The precursor slurry was prepared using the same method as in Example 1. The slurry was uniformly coated onto the surface of the aluminum foil using a doctor blade coater, and then placed in an 80°C oven for 8 hours to ensure complete electrode drying.

[0024] VII. Battery Manufacturing Methods The system was tested using a three-electrode electrolytic cell. The working electrode was the prepared electrode, the counter electrode was a platinum sheet electrode, and the reference electrode was a mercury / mercurous sulfate electrode. The electrolyte was a 1 M Na₂SO₄ aqueous solution.

[0025] VIII. Electrochemical Performance Testing: like Figure 2 As shown, it can be seen that the integrated electrode prepared by Joule heating, compared with the electrode prepared by the traditional method, exhibits a significant improvement in the initial specific capacity and cycle performance of the battery under the same rate of cycling.

[0026] Example 2 I. Preparation of precursor slurry Active material: Lithium manganese oxide (LiMn2O4, LMO), with an average particle size of approximately 5 μm; Conductive agent: Conductive carbon black (Super P); Adhesive: Polyvinylidene fluoride (PVDF); Solvent: N-methylpyrrolidone (NMP); Mass ratio: LMO:carbon black:PVDF=90:5:5; Solid content: 30 wt% Slurry preparation: Mix the above materials in proportion and stir at 1800 rpm for 3 hours in a planetary mixer to make a uniform slurry; II. Electrode Coating and Pre-drying: Current collector: Aluminum foil (20 μm thick); Coating method: Use a doctor blade coater to evenly coat the slurry onto the aluminum foil surface; Wet film thickness: approximately 400 μm; Pre-drying: Place in a 90°C oven for 15 minutes to partially remove NMP solvent; III. Ultra-fast Joule heating treatment: Atmosphere: Argon protection; Heating method: continuous direct current, current density approximately 30 A / cm² 2 ; Peak temperature: 700℃; Holding time: Approximately 3 seconds (including heating and holding); Cooling: Allow to cool naturally to room temperature; IV. Explanation of the structure formation mechanism: During ultra-rapid Joule heating: PVDF carbonization: PVDF is rapidly carbonized at high temperature to form a uniform carbon layer with a thickness of about 3~15 nm, which partially coats the surface of LMO particles and forms a conductive network with carbon black. Solvent evaporation and pore formation: NMP evaporates rapidly, forming a three-dimensional porous structure with a pore size distribution of 100 nm to 3 μm; Interface integration: Carbon black and PVDF carbonization layer together construct a continuous conductive path, and LMO particles and carbon layer form a good electronic contact interface; V. Electrode structural features: Active substance surface loading: approximately 45 mg / cm³ 2 ; Carbon layer thickness: approximately 3~15 nm; Porosity: Approximately 40%; Pore ​​size distribution: mainly concentrated in the range of 200 nm to 1.5 μm; Electronic conductivity: approximately 50% higher than that of traditional dry electrodes; VI. Traditional Drying Method for Electrode Preparation: The precursor slurry was prepared using the same method as in Example 2. The slurry was uniformly coated onto the surface of the aluminum foil using a doctor blade coater, and then placed in an 80°C oven for 8 hours to ensure complete electrode drying.

[0027] VII. Battery Manufacturing Methods The system was tested using a three-electrode electrolytic cell. The working electrode was the prepared electrode, the counter electrode was a platinum sheet electrode, and the reference electrode was a mercury / mercurous sulfate electrode. The electrolyte was a 1 M Li₂SO₄ aqueous solution.

[0028] VIII. Electrochemical Performance Testing: like Figure 3 As shown, the lithium manganese oxide integrated electrode prepared by Joule heating significantly improves the rate performance of the battery compared to the electrode prepared by the traditional method.

Claims

1. A high-load porous carbon-coated integrated electrode for energy storage batteries, characterized in that, The electrode includes a current collector and an active material layer grown on the surface of the current collector. The active material layer consists of an active material, a conductive agent, and an in-situ generated carbon layer. The active material layer has a three-dimensional interconnected porous network structure, and the surface of the active material is coated by the in-situ generated carbon layer, forming a continuous and rapid electron transport interface. The areal loading of the active material in the electrode is not less than 20 mg / cm³. 2 .

2. A method for preparing a high-load porous carbon-coated integrated electrode as described in claim 1, characterized in that, Includes the following steps: S1. Electrode precursor preparation: The active material, conductive agent, binder and solvent are mixed to form a slurry, which is then coated onto the current collector to form a wet film; S2. Pre-drying: Place the current collector with wet film obtained in step S1 in an oven for a certain period of time to partially remove the solvent; S3. Ultra-fast Joule heating treatment: The current collector with wet film obtained in step S2 is placed in an inert atmosphere or vacuum, and a pulsed or continuous high current is applied to it to rapidly heat the wet film to 600°C to 1200°C within 0.1 to 10 seconds, followed by natural cooling. During the ultrafast Joule heating process, the following are simultaneously achieved: carbonization of the binder and / or part of the conductive agent to form the in-situ generated carbon layer; evaporation or decomposition of the solvent to form the three-dimensional interconnected porous network structure; and interfacial fusion between the active material, the conductive agent, and the carbon layer.

3. The method according to claim 2, characterized in that, The surface loading of the active material in the electrode is 20 mg / cm². 2 Up to 100 mg / cm 2 .

4. The method according to claim 2, characterized in that, The thickness of the in-situ generated carbon layer is 1 nm to 50 nm.

5. The method according to claim 2, characterized in that, The pore size distribution of the three-dimensional interconnected porous network structure is from 10 nm to 5 μm.

6. The method according to claim 2, characterized in that, The conductive agent includes at least one of carbon nanotubes, graphene, and conductive carbon black; the binder is a carbonizable polymer at the heating temperature in step S3, including at least one of polyvinylidene fluoride, polyacrylonitrile, and polyvinyl alcohol.

7. The method according to claim 2, characterized in that, In step S2, the oven temperature is 50-95℃ and the heating time is 5-20 min.

8. The method according to claim 2, characterized in that, In step S3, if the applied current is a DC pulse current, the pulse width is 1 ms to 500 ms.

9. The method according to claim 2, characterized in that, In step S3, the current density is 10 A / cm². 2 ~100A / cm 2 .

10. An aqueous battery, comprising a positive electrode, a negative electrode, an electrolyte, and a separator, characterized in that, The positive electrode and / or the negative electrode are high-load porous carbon-coated integrated electrodes prepared by the method described in any one of claims 2-9.

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