Composite electrode material and preparation method thereof

Abstract

This invention discloses a composite electrode material and its preparation method, belonging to the field of functional materials technology. The composite electrode material is composed of metal oxides, alkaline phenolic resin, phytic acid, monolayer graphene oxide, coupling agent KH5500, alkaline silica sol, and niobium ammonium oxalate. A continuous carbon network carbonized from phenolic resin serves as the substrate, monolayer graphene oxide as the conductive framework, and niobium pentoxide from the pyrolysis of niobium ammonium oxalate as the interfacial conductive bridging structure. These three components crosslink to form a three-dimensional conductive network. The preparation method includes KH550-modified graphene oxide, construction of the phytic acid composite system, ball milling of the main slurry, low-temperature introduction of phenolic resin for molding, and curing and sintering. This invention possesses high conductivity, high heat resistance, corrosion resistance, and high mechanical strength. The three-dimensional conductive network effectively reduces internal resistance and exhibits excellent cycle stability, making it widely applicable to supercapacitors and lithium-ion batteries. It solves the problems of poor heat resistance, weak interfacial bonding, and easy corrosion of traditional electrode materials.

Description

Technical Field

[0001] This invention belongs to the field of functional materials technology, specifically relating to a composite electrode material and its preparation method. Background Technology

[0002] With the rapid development of new energy technologies, electrochemical devices are placing higher demands on the comprehensive performance of electrode materials, making high-performance electrode materials a research hotspot. Traditional electrode materials often use polyvinylidene fluoride (PVDF) as a binder, but it has poor heat resistance, is prone to decomposition at high temperatures, and has a low carbon residue rate, which cannot meet the application requirements of high-temperature or high-safety scenarios. Moreover, PVDF is an inert polymer that does not participate in electrochemical reactions, and its bonding effect relies solely on physical adsorption, resulting in weak interfacial bonding. During long-term cycling, this can easily lead to the shedding of active materials, reducing the lifespan of the device.

[0003] Phenolic resins, due to their high char residue, excellent thermal stability, and char-forming ability, have become ideal carbon source binders to replace PVDF. However, using phenolic resins alone results in defects such as high brittleness, easy cracking, and insufficient conductivity after carbonization. Graphene oxide possesses a high specific surface area and excellent conductivity, which can effectively improve the conductivity of materials. However, it tends to agglomerate in organic resins, exhibiting poor interfacial compatibility and making it difficult to fully exert its conductivity-enhancing effect. Furthermore, electrode materials are prone to corrosion in complex working environments such as acidic, alkaline, and salt spray conditions, further shortening the service life of electrochemical devices.

[0004] In the existing technology, there is no systematic solution for the synergistic application of phytic acid, monolayer graphene oxide, silane coupling agent KH550 and phenolic resin in metal oxide-based electrode materials. In particular, there is a lack of technical solutions for integrated optimization of material interface compatibility, flame retardancy, corrosion resistance and conductivity, and it is impossible to achieve a comprehensive improvement in the high-temperature stability, electrochemical performance and long-term cycle life of electrode materials at the same time. Summary of the Invention

[0005] The purpose of this invention is to provide a composite electrode material and its preparation method, which solves the technical problems of existing electrode materials such as poor heat resistance, insufficient conductivity, easy corrosion, low mechanical strength and weak interfacial bonding. Through multi-component synergistic design, a structurally stable three-dimensional conductive network is constructed, which significantly improves the material's high-temperature stability, electrochemical performance, corrosion resistance and long-term cycle life, while taking into account environmental protection and preparation cost advantages.

[0006] To address the problems mentioned in the background section, the present invention adopts the following technical solution.

[0007] A composite electrode material is composed of the following components: Metal oxides: 60-63 parts Alkaline phenolic resin: 10-12 parts Phytic acid: 3-5 parts Single-layer graphene oxide: 0.5-1.5 parts Coupling agent KH550: 0.5-1 part Alkaline silica sol: 10-12 parts Niobium oxalate ammonium: 3-4 parts; The composite electrode material possesses a three-dimensional conductive network, a limiting oxygen index ≥30%, a weight loss ≤3% after immersion in 1M H₂SO₄ for 72 hours, and a volume resistivity ≤0.2. The alkaline phenolic resin has a solid content of ≥70%, which carbonizes during sintering to form a continuous carbon network, providing a substrate for the three-dimensional conductive network. The thickness of the monolayer graphene oxide is 0.8-1.2 nm, which is confirmed to be a monolayer structure by atomic force microscopy. It is distributed interspersed in the continuous carbon network as a conductive framework. The content of SiO2 in the alkaline silica sol is 20-30%, which is used to provide a silicon-oxygen network structure and enhance the corrosion resistance and bonding strength of the material. The phytic acid is a natural phosphorus-containing organic acid that promotes the formation of an expanded carbon layer at high temperature, thereby improving the flame retardancy and corrosion resistance of the material.

[0008] Preferably, the metal oxide is any one or two or more of manganese dioxide, vanadium pentoxide, ferric oxide, and cobalt tetroxide mixed in any proportion as transition metal oxides; the coupling agent KH550 is γ-aminopropyltriethoxysilane, which improves the interfacial bonding between the inorganic and organic phases and promotes the uniform formation of the three-dimensional conductive network; phytic acid is a natural phosphorus-containing organic acid; and ammonium niobate oxalate can be completely pyrolyzed at 300-350℃ to generate niobium pentoxide, forming a conductive bridging structure at the interface between the metal oxide and the continuous carbon network.

[0009] Preferably, the three-dimensional conductive network is formed by cross-linking a continuous carbon network formed by carbonization of alkaline phenolic resin, a conductive framework composed of interwoven monolayer graphene oxide, and an interfacial conductive bridging structure formed by niobium pentoxide generated by the pyrolysis of niobium ammonium oxalate. Niobium pentoxide is specifically distributed at the interface between the metal oxide and the continuous carbon network, and monolayer graphene oxide is interwoven into the pores and surface of the continuous carbon network to form a continuous conductive path.

[0010] Preferably, one end of the coupling agent KH550 forms an inorganic phase chemical bond with the metal oxide and alkaline silica sol, and the other end forms an organic phase chemical bond with the continuous carbon network and monolayer graphene oxide. The alkaline silica sol is sintered to form a continuous Si-O-Si silicon oxide network structure. Phytic acid complexes with metal ions in the metal oxide to form a dense protective film. The Si-O-Si silicon oxide network and the phytic acid metal complex film cross-link and coat the surface and pores of the three-dimensional conductive network.

[0011] Preferably, the composite electrode material is used as an electrode active material in any electrochemical device such as a supercapacitor, lithium-ion battery, or fuel cell, and can be coated on any current collector substrate such as titanium mesh, copper foil, or aluminum foil.

[0012] A method for preparing a composite electrode, comprising the above-mentioned composite electrode material, including the following steps: S1. Preparation of KH550 modified graphene oxide dispersion: KH550 was added to an ethanol-water mixed solvent, the pH of the system was adjusted to 4-5 and hydrolyzed for 30 min, and monolayer graphene oxide was added and ultrasonically dispersed for 1-2 h to obtain a uniform and non-agglomerated modified dispersion. S2. Constructing a phytic acid composite system: Add phytic acid to the modified dispersion of S1 and stir at room temperature until the mixture is homogeneous to form a phytic acid-graphene oxide-KH550 composite solution. S3. Mixing the main slurry: Add the metal oxide and niobium ammonium oxalate to the composite liquid of S2, and disperse by ball milling for 2-4 hours to form a uniform suspension; S4. Introducing phenolic resin and molding: In an environment with a temperature ≤30℃, slowly add alkaline phenolic resin to the suspension of S3 and stir continuously, then add alkaline silica sol and mix evenly, and obtain a molded blank by coating or pressing. S5. Curing and sintering: The molded blank is dried and cured at 80-100℃ for 2-4 hours, and then sintered at a constant temperature of 300-350℃ in air for 2 hours to obtain the composite electrode material.

[0013] Preferably, the ethanol-water mixed solvent in S1 is anhydrous ethanol and deionized water mixed in a volume ratio of 1:1 to 3:1, the ultrasonic dispersion power is 300-500W, and the dispersed particle size of monolayer graphene oxide in the modified dispersion is ≤5μm.

[0014] Preferably, in S3, a planetary ball mill is used for ball milling dispersion, the ball milling media is zirconia balls, the ball-to-material ratio is 10:1-15:1, the ball milling speed is 300-400 r / min, and the ball milling process is room temperature sealed ball milling.

[0015] Preferably, the alkaline phenolic resin is slowly added to S4 at a rate of 1-5 g / min, and after addition, it is continuously stirred for 30-60 min to form a viscous slurry with a solid content of 50-60%; after adding alkaline silica sol, it is stirred at a speed of 300-500 r / min for 20-30 min to ensure that all components are mixed evenly.

[0016] Preferably, in S5, drying and curing is carried out by forced air drying. During the curing process, the alkaline phenolic resin undergoes preliminary cross-linking with a cross-linking degree of ≥40%. During the sintering process, the carbonization rate of the alkaline phenolic resin is ≥70%, and phytic acid participates in the carbonization reaction to form a dense expanded carbon layer. Furthermore, the sintered material exhibits no cracking or peeling.

[0017] Compared with the prior art, the beneficial effects of the present invention are as follows: (1) In this invention, a continuous carbon network carbonized with phenolic resin is used as the substrate, a single layer of graphene oxide is used as the conductive framework, and niobium pentoxide is used as the interfacial conductive bridging structure. The three-dimensional conductive network formed by the cross-linking of the three has good connectivity, effectively reduces the volume resistivity of the material, improves the charge transport efficiency, and solves the problem of insufficient conductivity of traditional materials. Furthermore, alkaline phenolic resin is used to replace PVDF as the carbon source, and combined with the phosphorus-based flame retardant effect of phytic acid, a "phosphorus-carbon" synergistic carbonization system is formed. The limiting oxygen index (LOI) of the material is increased to more than 30%, and it is not easy to burn or decompose at high temperature. After sintering at 350℃, there is no cracking, and the thermal stability is significantly improved.

[0018] (2) In this invention, alkaline silica sol provides a Si–O–Si silicon-oxygen network structure, and phytic acid complexes with metal ions to form a dense protective film. The two work synergistically to make the material have excellent stability in acid, alkali and salt spray environments, effectively reducing the corrosion weight loss rate. In addition, the monolayer graphene oxide constructs an enhanced skeleton structure, and the coupling agent KH550 improves the interfacial compatibility between the inorganic phase and the organic phase, effectively alleviating stress concentration during the carbonization process, preventing material cracking or peeling of active substances, and improving structural integrity.

[0019] (3) In this invention, KH550 and niobium oxalate work together to achieve strong chemical bonding at the organic-inorganic multiphase interface. Combined with the structural stability of the three-dimensional conductive network, the capacity retention rate of the material after 1000 cycles can reach more than 93%, which is far superior to the traditional PVDF system. The amount of alkaline phenolic resin used is lower than that of the traditional PVDF binder system. Phytic acid is a natural renewable resource. The preparation process has no toxic or harmful byproducts, which is in line with the trend of green manufacturing. Moreover, all raw materials are conventional industrial raw materials, which are readily available and the preparation process is simple, making them suitable for large-scale production. In summary, by adjusting the ultrasonic power, ball milling parameters, sintering temperature and other process conditions, the molding effect of the three-dimensional conductive network and the comprehensive performance of the material can be precisely controlled to meet the needs of different electrochemical devices. Detailed Implementation

[0020] To make the above-mentioned objects, features and advantages of the present invention more apparent and understandable, the specific embodiments of the present invention will be described in detail below.

[0021] Many specific details are set forth in the following description in order to provide a full understanding of the invention. However, the invention may also be practiced in other ways different from those described herein, and those skilled in the art can make similar extensions without departing from the spirit of the invention. Therefore, the invention is not limited to the specific embodiments disclosed below.

[0022] Secondly, the term "one embodiment" or "embodiment" as used herein refers to a specific feature, structure, or characteristic that may be included in at least one implementation of the present invention. The phrase "in one embodiment" appearing in different places throughout this specification does not necessarily refer to the same embodiment, nor is it a single or selective embodiment that mutually excludes other embodiments. The present invention provides the following embodiments.

[0023] Raw material preparation Metal oxide: Manganese dioxide, industrial grade; Alkaline phenolic resin: 75% solids content, industrial grade; Phytic acid: Food grade, natural phosphorus-containing organic acid; Monolayer graphene oxide: 0.8-1.2 nm thick, verified by atomic force microscopy as a monolayer structure; Coupling agent KH550: γ-aminopropyltriethoxysilane, industrial grade; Alkaline silica sol: SiO2 content 25%, industrial grade; Ammonium niobate oxalate: Industrial grade; Anhydrous ethanol and deionized water: analytical grade.

[0024] Instruments and equipment Ultrasonic processing equipment: CNC ultrasonic cell disruptor, power adjustable range 0-800W; Ball milling equipment: planetary ball mill, equipped with zirconia ball milling media (3mm and 6mm in a 1:1 mass ratio); Drying equipment: blower drying oven, temperature control accuracy ±1℃; Sintering equipment: Programmable temperature muffle furnace, temperature control accuracy ±2℃, heating rate adjustable from 0-10℃ / min; Mixing equipment: Digital display magnetic stirrer, speed adjustable from 0-800r / min.

[0025] Example 1 A composite electrode material is composed of the following components: manganese dioxide: 62.0 parts, alkaline phenolic resin: 11.0 parts, phytic acid: 4.0 parts, monolayer graphene oxide: 1.0 parts, KH550: 0.8 parts, alkaline silica sol: 11.2 parts, and niobium ammonium oxalate: 3.0 parts.

[0026] Its preparation method includes the following steps: S1. Preparation of KH550 modified graphene oxide dispersion: 0.8 parts of KH550 were added to a mixed solvent of anhydrous ethanol and deionized water in a volume ratio of 2:1, the pH was adjusted to 4.5 with dilute acetic acid, and hydrolyzed for 30 min; 1.0 part of monolayer graphene oxide was added, and ultrasonic dispersion was carried out at 400W for 1.5 h to obtain the modified dispersion.

[0027] S2. Construction of phytic acid composite system: Add 4.0 parts of phytic acid to the modified dispersion and stir magnetically at room temperature for 15 min to form phytic acid-graphene oxide-KH550 composite solution.

[0028] S3. Mixing the main slurry: Add 62.0 parts of manganese dioxide and 3.0 parts of niobium ammonium oxalate, and use a planetary ball mill with a ball-to-material ratio of 12:1 and a rotation speed of 350 r / min to disperse the mixture for 3 hours to form a uniform suspension.

[0029] S4. Introduce phenolic resin and form: Under low temperature conditions of 25℃, slowly add 11.0 parts of alkaline phenolic resin and stir continuously for 45 minutes to form a viscous slurry; add 11.2 parts of alkaline silica sol and stir for 25 minutes until uniformly mixed. Coat the slurry onto the titanium mesh substrate to form a molded blank.

[0030] S5. Curing and sintering: The molded blank is placed in a forced-air drying oven and dried and cured at 90°C for 3 hours; then sintered at 350°C for 2 hours in an air atmosphere in a muffle furnace to obtain the composite electrode material.

[0031] During the sintering process, the alkaline phenolic resin undergoes pyrolysis and carbonization to form a continuous carbon network substrate. Niobium ammonium oxalate is completely pyrolyzed to generate niobium pentoxide, which forms a conductive bridging structure at the interface between manganese dioxide and the carbon network. Phytic acid, phenolic resin, and alkaline silica sol synergistically undergo a carbonization reaction to form a dense expanded carbon layer on the surface and inside of the material, ultimately constructing a three-dimensional interconnected conductive network structure.

[0032] Comparative Example 1 The alkaline phenolic resin in Example 1 was replaced with polyvinylidene fluoride (PVDF). The amount of PVDF added was 12.0%, and the remaining components and their mass percentages were: manganese dioxide: 61.0 parts, phytic acid: 4.0 parts, monolayer graphene oxide: 1.0 parts, KH550: 0.8 parts, alkaline silica sol: 11.2%, and niobium ammonium oxalate: 3.0 parts. The preparation process was exactly the same as in Example 1.

[0033] Performance testing The materials of Example 1 and Comparative Example 1 were subjected to performance tests, including volume resistivity, cracking after sintering at 350℃, limiting oxygen index (LOI), weight loss after immersion in 1M H₂SO₄ for 72 hours, and capacity retention after 1000 cycles. The test results are shown in Table 1. Table 1 Performance test results of Example 1 and Comparative Example 1 .

[0034] Test Result Analysis As shown in Table 1, the composite electrode material of Example 1 of the present invention is significantly superior to the conventional PVDF system of Comparative Example 1 in all aspects of performance. Its volume resistivity is only 0.18. The resistance is much lower than that of Comparative Example 1, indicating that the three-dimensional conductive network constructed in this invention effectively reduces the internal resistance of the material and improves its conductivity. No cracking occurred after sintering at 350℃, while obvious cracking appeared in Comparative Example 1, indicating that the thermal stability and mechanical strength of the material of the present invention are greatly improved. With a limiting oxygen index of 32%, it exhibits excellent flame retardancy, solving the problem of traditional materials being easily combustible at high temperatures. The weight loss rate in acidic environments is only 2.1%, and the corrosion resistance is significantly improved. The capacity retention rate reached 93.5% after 1000 cycles, demonstrating excellent cycle stability and solving the problems of weak interfacial bonding and easy shedding of active substances in traditional materials.

[0035] The above test results demonstrate that the present invention, through multi-component synergistic design and the construction of a three-dimensional conductive network, achieves a comprehensive performance improvement in composite electrode materials, including high conductivity, high heat resistance, corrosion resistance, and high cycle stability, fully meeting the high-performance requirements of electrochemical devices.

[0036] The above description, in conjunction with specific embodiments, provides a further detailed explanation of the present invention. It should not be construed that the specific implementation of the present invention is limited to these descriptions. For those skilled in the art, several simple deductions or substitutions can be made without departing from the concept of the present invention, and all such deductions or substitutions should be considered to fall within the scope of protection defined by the claims submitted herein.

Claims

1. A composite electrode material, characterized in that, It consists of the following components: Metal oxides: 60-63 parts Alkaline phenolic resin: 10-12 parts Phytic acid: 3-5 parts 0.5-1.5 parts of monolayer graphene oxide Coupling agent KH550: 0.5-1 part Alkaline silica sol: 10-12 parts Niobium oxalate ammonium: 3-4 parts; The alkaline phenolic resin has a solid content ≥70%, the single-layer graphene oxide has a thickness of 0.8-1.2 nm, and the alkaline silica sol has a SiO2 content of 20-30%. The composite electrode material has a three-dimensional conductive network, a limiting oxygen index ≥30%, a weight loss of ≤3% after immersion in 1 M H₂SO₄ for 72 h, and a volume resistivity ≤0.

2. .

2. The composite electrode material according to claim 1, characterized in that, The metal oxide is any one or two or more of the following transition metal oxides: manganese dioxide, vanadium pentoxide, ferric oxide, and cobalt tetroxide, mixed in any proportion; the coupling agent KH550 is γ-aminopropyltriethoxysilane; the phytic acid is a natural phosphorus-containing organic acid; and the ammonium niobate oxalate can be completely pyrolyzed at 300-350℃ to generate niobium pentoxide.

3. The composite electrode material according to claim 1, characterized in that, The three-dimensional conductive network is formed by cross-linking a continuous carbon network formed by carbonization of alkaline phenolic resin, a conductive framework composed of interwoven monolayer graphene oxide, and an interfacial conductive bridging structure formed by niobium pentoxide generated by the pyrolysis of niobium ammonium oxalate. The niobium pentoxide is specifically distributed at the phase interface between the metal oxide and the continuous carbon network, and the monolayer graphene oxide is interwoven into the pores and surface of the continuous carbon network to form a continuous conductive path.

4. The composite electrode material according to claim 1, characterized in that, The coupling agent KH550 forms an inorganic phase chemical bond with metal oxides and alkaline silica sol at one end, and an organic phase chemical bond with a continuous carbon network and monolayer graphene oxide at the other end. The alkaline silica sol is sintered to form a continuous Si-O-Si silicon oxide network structure. Phytic acid complexes with metal ions in the metal oxide to form a dense protective film. The Si-O-Si silicon oxide network and the phytic acid-metal complex film cross-link and coat the surface and pores of the three-dimensional conductive network.

5. The composite electrode material according to any one of claims 1-4, characterized in that, The composite electrode material is used as an electrode active material in any electrochemical device such as supercapacitors, lithium-ion batteries, and fuel cells, and can be coated on any current collector substrate such as titanium mesh, copper foil, and aluminum foil.

6. A method for preparing a composite electrode, comprising preparing the composite electrode material as described in any one of claims 1-4, characterized in that, Includes the following steps: S1. Preparation of KH550 modified graphene oxide dispersion: KH550 was added to an ethanol-water mixed solvent, the pH of the system was adjusted to 4-5 and hydrolyzed for 30 min, and monolayer graphene oxide was added and ultrasonically dispersed for 1-2 h to obtain a uniform and non-agglomerated modified dispersion. S2. Constructing a phytic acid composite system: Add phytic acid to the modified dispersion of S1 and stir at room temperature until the mixture is homogeneous to form a phytic acid-graphene oxide-KH550 composite solution. S3. Mixing the main slurry: Add the metal oxide and niobium ammonium oxalate to the composite liquid of S2, and disperse by ball milling for 2-4 hours to form a uniform suspension; S4. Introducing phenolic resin and molding: In an environment with a temperature ≤30℃, slowly add alkaline phenolic resin to the suspension of S3 and stir continuously, then add alkaline silica sol and mix evenly, and obtain a molded blank by coating or pressing. S5. Curing and sintering: The molded blank is dried and cured at 80-100℃ for 2-4 hours, and then sintered at a constant temperature of 300-350℃ in air for 2 hours to obtain the composite electrode material.

7. The method for preparing the composite electrode material according to claim 6, characterized in that, The ethanol-water mixed solvent in S1 is anhydrous ethanol and deionized water mixed in a volume ratio of 1:1 to 3:

1. The ultrasonic dispersion power is 300-500W, and the dispersed particle size of monolayer graphene oxide in the modified dispersion is ≤5μm.

8. The method for preparing the composite electrode material according to claim 6, characterized in that, The ball milling dispersion in S3 uses a planetary ball mill, the ball milling media is zirconia balls, the ball-to-material ratio is 10:1-15:1, the ball milling speed is 300-400 r / min, and the ball milling process is room temperature sealed ball milling.

9. The method for preparing the composite electrode material according to claim 6, characterized in that, The alkaline phenolic resin is slowly added at a rate of 1-5 g / min in step S4, and then stirred continuously for 30-60 min to form a viscous slurry with a solid content of 50-60%. After adding the alkaline silica sol, the mixture is stirred at a speed of 300-500 r / min for 20-30 min to ensure that all components are mixed evenly.

10. The method for preparing the composite electrode material according to claim 6, characterized in that, The drying and curing described in S5 is blower drying. During the curing process, the alkaline phenolic resin undergoes preliminary cross-linking with a cross-linking degree of ≥40%. During the sintering process, the carbonization rate of the alkaline phenolic resin is ≥70%, and phytic acid participates in the carbonization reaction to form a dense expanded carbon layer. The sintered material exhibits no cracking or peeling.