Carbon composites, methods of making and using the same

Abstract

This application relates to a carbon composite material, its preparation method, and its application. The carbon composite material comprises porous carbon material and nickel-containing particles doped into the porous carbon material; the carbon composite material satisfies the following synergistic effect relationship: SE=d Ni +S ass Furthermore, the carbon composite material satisfies the following conditions: 36≤SE≤200; 6≤d Ni ≤100; 30≤S ass ≤100. The solution provided in this application, in which the carbon composite material serves as the iodine host material, enables the zinc-iodine battery to exhibit excellent specific capacity, cycle durability, and catalytic conversion performance of iodine species.

Description

Technical Field

[0001] This application relates to the field of battery technology, and in particular to carbon composite materials, their preparation methods, and applications. Background Technology

[0002] Aqueous zinc-iodine batteries are considered a highly promising alternative to next-generation energy storage systems due to the world's abundant iodine resources, safe reaction mechanism, high energy density, and excellent redox reversibility.

[0003] However, the large-scale application of aqueous zinc-iodine batteries is still limited by slow redox kinetics and the dissolution and shuttle effect of polyiodide intermediates in the electrolyte, which leads to negative electrode corrosion and rapid capacity decay.

[0004] Various strategies have been explored in related technologies to address the aforementioned challenges, among which the design of iodine host materials is widely recognized as crucial for improving battery performance. For example, porous carbon is widely used as a cathode host due to its well-developed pore structure, excellent conductivity, and chemical stability. However, relying solely on the weak interaction between the physical channels of porous carbon and iodine species makes it difficult to effectively suppress the shuttle of polyiodides, thus limiting the electrochemical performance of zinc-iodine batteries.

[0005] Therefore, there is an urgent need to develop a new type of high-performance iodine host material to significantly optimize the specific capacity, cycle durability, and catalytic conversion performance of iodine species in zinc-iodine batteries. Summary of the Invention

[0006] To address or partially address the problems existing in related technologies, this application provides a carbon composite material, its preparation method, and its application. This carbon composite material, as an iodine host material, enables zinc-iodine batteries to exhibit excellent specific capacity, cycle durability, and catalytic conversion performance of iodine species.

[0007] The first aspect of this application provides a carbon composite material, wherein the carbon composite material comprises a porous carbon material and nickel-containing particles doped in the porous carbon material; The carbon composite material satisfies the following synergistic effect relationship: SE=d Ni +S ass ; The synergistic effect index of the carbon composite material is SE; the particle size of the nickel-containing particles is d. Ni , defined as d Ni =D Ni / ω Ni The particle size of the nickel-containing particles is D. Ni The unit is nm; the mass content of nickel in the nickel-containing particles is ω. Ni The unit is %; the active specific surface area of ​​the porous carbon material is S.ass Defined as S ass =S BET / I dis The specific surface area of ​​the porous carbon material is S. BET The unit is cm. 2 / g; the disorder degree of the porous carbon material is I. dis ; And the carbon composite material satisfies the following conditions: 36≤SE≤200; 6≤d Ni ≤100; 30≤S ass ≤100.

[0008] As described in the first aspect, for carbon composite materials, 50 ≤ S BET ≤100; And / or, 0.5≤I dis ≤1.

[0009] As described in the first aspect, for carbon composite materials, where 100 ≤ D Ni ≤300; And / or, 3≤ω Ni ≤50.

[0010] A second aspect of this application provides a method for preparing a carbon composite material as described in the first aspect, comprising the following steps: S1. The porous carbon material, the natural polyphenolic acid compound solution, and the divalent nickel metal salt are mixed and subjected to a hydrothermal reaction to obtain a composite precursor. The hydrothermal treatment temperature is 80℃~120℃, and the hydrothermal time is 12h~24h. S2. The composite precursor is subjected to carbonization treatment to obtain the carbon composite material; wherein the divalent nickel metal salt is converted into the nickel-containing particles, and the nickel-containing particles are doped into the porous carbon material. The carbonization process is carried out under an inert atmosphere, with a heating rate of 2℃ / min to 20℃ / min, a carbonization temperature of 700℃ to 900℃, and a carbonization time of 60min to 240min.

[0011] The method for preparing carbon composite materials as described in the second aspect, wherein the natural polyphenolic acid compound includes at least one of ellagic acid, tea polyphenols, proanthocyanidins and gallic acid; And / or, divalent nickel metal salts include at least one of nickel chloride, nickel acetate, nickel nitrate, nickel sulfate, nickel chloride hydrate, nickel acetate hydrate, nickel nitrate hydrate, and nickel sulfate hydrate.

[0012] The method for preparing the carbon composite material as described in the second aspect, wherein the mass ratio of the natural polyphenolic acid compound to the porous carbon material is (2.4~5.6):1; And / or, the mass ratio of the porous carbon material to the divalent nickel metal salt is (1~2.62):1.

[0013] The method for preparing carbon composite materials as described in the second aspect further includes, before step S2, the following step: cleaning the composite precursor, wherein the cleaning process includes washing with an acidic solution; Preferably, the acidic solution includes at least one of hydrochloric acid, sulfuric acid, phosphoric acid, and nitric acid; preferably, the molar concentration of the acidic solution is 0.1 mol / L to 3 mol / L.

[0014] The method for preparing carbon composite materials as described in the second aspect, wherein the method for preparing porous carbon materials includes the following steps: subjecting a biomass precursor to high-temperature heat treatment, acid washing treatment, and drying treatment in sequence; Preferably, the biomass precursor comprises sawdust; more preferably, the sawdust comprises at least one type of broadleaf wood. Preferably, the high-temperature heat treatment is carried out under an inert atmosphere, the heating rate of the high-temperature heat treatment is 2℃ / min to 20℃ / min, the temperature of the high-temperature heat treatment is 1000℃ to 1300℃, and the time of the high-temperature heat treatment is 60min to 240min.

[0015] A third aspect of this application provides a positive electrode sheet, wherein the positive electrode sheet includes a positive current collector and a positive electrode coating coated on at least one side of the positive current collector, the positive electrode coating comprising a carbon composite material as described in the first aspect or a carbon composite material prepared by a method for preparing a carbon composite material as described in the second aspect.

[0016] A fourth aspect of this application provides a zinc-iodine battery, wherein the zinc-iodine battery includes a positive electrode as described in the third aspect.

[0017] The technical solution provided in this application can include the following beneficial effects: by regulating the synergistic effect index of carbon composite materials, the particle size of nickel-containing particles, and the active specific surface area of ​​porous carbon materials, a bifunctional coupling mechanism of physical adsorption and chemical catalysis is constructed. Among them, the porous carbon framework with high specific surface area serves as an efficient physical adsorption site, which not only provides sufficient iodine storage space but also constructs a continuous electron transport network. Meanwhile, the uniformly doped nickel-containing particles serve as active centers for chemical adsorption and catalysis, significantly inhibiting the shuttle of polyiodides and accelerating the reversible transformation between iodine species. The two produce a significant synergistic effect in terms of spatial structure and functional characteristics. That is, by optimizing the particle size of nickel-containing particles to optimize the exposure of active sites, and matching the pore structure of porous carbon materials to expand the iodine storage capacity, a deep synergy between physical confinement and chemical catalysis is achieved, significantly improving the overall electrochemical performance of zinc-iodine batteries.

[0018] It should be understood that the above general description and the following detailed description are exemplary and explanatory only, and do not limit this application. Detailed Implementation

[0019] To facilitate understanding of this application, it will be described in detail below. However, before describing this application in detail, it should be understood that this application is not limited to the specific embodiments described. It should also be understood that the terminology used herein is for the purpose of describing specific embodiments only and is not intended to be restrictive.

[0020] Where a numerical range is provided, it should be understood that every intermediate value between the upper and lower limits of the range and any other specified or intermediate value within the specified range is covered within this application. The upper and lower limits of these smaller ranges may be independently included in the smaller range and are also covered within this application, subject to any explicitly excluded limits within the specified range. Where the specified range includes one or two limits, the range excluding any or both of those included limits is also included within this application.

[0021] Unless otherwise defined, all terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application pertains. While the methods and materials described herein, or any equivalent methods and materials, may also be used in the implementation or testing of this application, preferred methods and materials are now described.

[0022] The large-scale application of aqueous zinc-iodine batteries remains limited by slow redox kinetics and the dissolution and shuttle effect of polyiodide intermediates in the electrolyte, leading to negative electrode corrosion and rapid capacity decay. Various strategies have been explored to address these challenges, with the design of iodine-host materials being widely recognized as crucial for improving battery performance. For example, porous carbon materials are widely used as positive electrode hosts due to their well-developed pore structure, excellent conductivity, and chemical stability. However, relying solely on the weak interaction between the physical channels of porous carbon and iodine species is insufficient to effectively suppress polyiodide shuttle, thus limiting the electrochemical performance of zinc-iodine batteries.

[0023] To address the aforementioned issues, this application provides a carbon composite material comprising porous carbon material and nickel-containing particles doped into the porous carbon material.

[0024] The main framework of the carbon composite material of this application is composed of three-dimensional interconnected porous carbon material, with nickel-containing particles uniformly dispersed within the porous carbon skeleton, forming a tight interlocking relationship between the nickel-containing particles and the porous carbon. Preferably, the nickel-containing particles are uniformly embedded in the porous carbon skeleton. The nickel-containing particles are firmly confined within the pore cavities or interlayer regions of the porous carbon material, with numerous contact interfaces between them. This special spatial configuration allows the nickel-containing particles to be exposed on accessible surfaces to perform their iodine catalytic conversion function, while being physically confined and protected by the surrounding carbon pore walls, preventing them from detaching or migrating during cycling or use, thus constructing a composite system with good electronic conductivity, strong structural stability, and abundant active sites.

[0025] This application does not limit the specific selection of porous carbon materials. The porous carbon materials of this application possess a highly developed pore network, forming a high specific surface area and abundant mass transfer channels. The carbon framework of the porous carbon materials not only provides excellent conductive pathways for rapid electron transport, but also provides ample physical space and anchoring points for the subsequent loading of active components.

[0026] This application does not limit the specific parameters of the nickel-containing particles. The nickel-containing particles of this application are spherical or nearly spherical, with small size and high dispersion, thus avoiding agglomeration.

[0027] The carbon composite material of this application satisfies the following synergistic effect relationship: SE=d Ni +S ass ; Among them, the synergistic effect index of the carbon composite material is SE; the particle size of the nickel-containing particles is d. Ni , defined as d Ni =D Ni / ω Ni The particle size of the nickel-containing particles is D. Ni The unit is nm; the mass content of nickel metal in the nickel-containing particles is ω.Ni The unit is %; the active specific surface area of ​​porous carbon materials is S. ass Defined as S ass =S BET / I dis The specific surface area of ​​porous carbon materials is S. BET The unit is cm. 2 / g; The disorder degree of porous carbon materials is I dis .

[0028] It is understandable that the synergistic effect relationship is SE=d Ni +S ass A dimension for quantitatively evaluating the comprehensive performance of carbon composite materials was constructed, where d Ni (D) Ni / ω Ni The equivalent particle size of nickel-containing particles per unit mass content was characterized, reflecting the dispersion efficiency and the degree of exposure of active sites; S ass (S) BET / I dis The effective specific surface area under unit disorder is defined to balance the physical adsorption capacity and structural conductivity of porous carbon materials. The physical essence of this synergistic effect relationship lies in revealing the two-component matching mechanism between the nickel-containing particle catalytic component and the porous carbon host structure. That is, when the dispersion state of the nickel-containing particles and the pore characteristics of the porous carbon reach a specific equilibrium, the carbon composite material can simultaneously exert the chemical adsorption and efficient catalytic effect of nickel on iodides and the strong physical adsorption capacity of porous carbon materials on iodides, thereby forming a stable anchoring-catalytic synergistic system. Ultimately, this significantly suppresses the shuttle effect of zinc-iodine batteries, achieving high specific capacity, excellent cycle stability, and iodine catalytic conversion performance.

[0029] The carbon composite material of this application meets the following conditions: 36≤SE≤200; 6≤d Ni ≤100; 30≤S ass ≤100.

[0030] For example, SE can be 36, 40, 50, 60, 70, 80, 90, 100, 110, 120, 130, 140, 150, 160, 170, 180, 190, 200, etc.

[0031] For example, d Ni It can be 6, 10, 20, 30, 40, 50, 60, 70, 80, 90, 100, etc.

[0032] For example, S ass It can be 30, 40, 50, 60, 70, 80, 90, 100, etc.

[0033] This application modulates the synergistic effect index of carbon composite materials, the particle size of nickel-containing particles, and the active specific surface area of ​​porous carbon materials to construct a bifunctional coupling mechanism of physical adsorption and chemical catalysis. The high specific surface area of ​​the porous carbon framework serves as an efficient physical adsorption site, providing ample iodine storage space and constructing a continuous electron transport network. Meanwhile, the uniformly doped nickel-containing particles act as active centers for chemical adsorption and catalysis, significantly inhibiting the shuttle movement of polyiodides and accelerating the reversible transformation between iodine species. The two exhibit a significant synergistic effect in spatial structure and functional characteristics. By optimizing the particle size of nickel-containing particles to optimize the exposure of active sites, and simultaneously matching the pore structure of the porous carbon material to expand the iodine storage capacity, a deep synergy between physical confinement and chemical catalysis is achieved, significantly improving the overall electrochemical performance of the zinc-iodine battery.

[0034] Specifically, the particle size of nickel-containing particles can be obtained by transmission electron microscopy; the nickel metal mass content in the nickel-containing particles can be obtained by inductively coupled plasma atomic emission spectrometry (ICP) of the carbon composite material; the specific surface area of ​​the porous carbon material can be obtained by BET (Brunauer-Emmett-Teller analysis) of the carbon composite material; and the disorder of the porous carbon material can be obtained by Raman spectroscopy of the carbon composite material.

[0035] In one specific implementation, 50 ≤ S BET ≤100, for example, S BET The specific surface area can be 50, 60, 70, 80, 90, 100, etc. When the specific surface area of ​​porous carbon materials is within the above range, it can provide sufficient and reasonably distributed pore structures for carbon composite materials. As efficient physical adsorption sites, it can firmly capture iodine molecules through strong van der Waals forces, while constructing unobstructed ion transport channels to accelerate reaction kinetics. This ensures both high iodine loading and strong physical confinement, as well as rapid electron conduction. It avoids insufficient iodine storage capacity and severe shuttle effect due to excessively low specific surface area, or decreased conductivity and increased side reactions due to excessively high specific surface area. This results in a better match between the physical adsorption function of porous carbon materials and the chemical catalytic function of nickel-containing particles, significantly improving the specific capacity, cycle performance, and iodine catalytic conversion performance of zinc-iodine batteries.

[0036] In one specific implementation, 0.5 ≤ I dis ≤1, for example, I disThe disorder can be 0.5, 0.6, 0.7, 0.8, 0.9, 1, etc. The disorder within this range indicates that the porous carbon material framework retains an appropriate amount and uniformly distributed lattice defects and edge sites. These structural defects, acting as highly active physical adsorption centers, can significantly enhance the capture capacity of iodine molecules and polyiodides, effectively suppressing the shuttle effect of iodides. Simultaneously, the graphitized microcrystalline regions within this range maintain good connectivity, constructing an efficient electron transport network and ensuring the excellent conductivity of the carbon composite material. This moderate disorder structure avoids both the scarcity of adsorption sites and chemical inertness caused by excessive order, and the sharp decline in conductivity and increase in internal resistance caused by excessive disorder, thereby significantly improving the specific capacity and cycle performance of the battery.

[0037] In one specific implementation, 100 ≤ D Ni ≤300, for example, D Ni The particle size can be 100, 150, 200, 250, 300, etc. When the particle size of nickel-containing particles is within the above range, the surface atomic ratio and active site exposure of the nickel-containing particles can be optimized, significantly enhancing their chemical adsorption energy for iodine species and reducing the activation energy barrier of iodine redox reaction, thereby promoting the conversion kinetics of polyiodides. At the same time, the nickel-containing particles can be uniformly dispersed and stably anchored in the pore structure of porous carbon materials, avoiding the reduction of specific surface area, burial of active sites and poor contact with porous carbon materials caused by excessively large particles, and preventing agglomeration or excessive catalytic side reactions caused by excessively small particles. This ensures the matching of the high catalytic activity of nickel-containing particles with the physical confinement iodine storage function of porous carbon materials, thereby effectively improving the specific capacity, long-cycle stability and iodine catalytic conversion performance of the battery.

[0038] In one specific implementation, 3≤ω Ni ≤50, for example, ω Ni The values ​​can be 3, 5, 10, 15, 20, 25, 30, 35, 40, 45, 50, etc. When the nickel metal content of the nickel-containing particles is within the above range, it ensures that a sufficient amount of nickel-containing particles are uniformly distributed on the surface of the porous carbon material, forming a high-density chemical adsorption and catalytic active center. This significantly enhances the chemical capture capacity of polyiodides and greatly accelerates the kinetics of the iodine oxidation-reduction reaction. At the same time, the nickel-containing particles can maintain an ideal ratio with the porous carbon framework, avoiding the problems of insufficient catalytic sites and sluggish reaction kinetics caused by too low nickel content, or particle agglomeration and pore blockage caused by too high nickel content, which reduces the effective specific surface area and weakens the physical iodine storage space of the porous carbon material. This optimizes the synergistic effect of physical adsorption and chemical catalysis, achieving high specific capacity, long cycle life, and iodine catalytic conversion performance of zinc-iodine batteries at high rates.

[0039] A second aspect of this application provides a method for preparing a carbon composite material, comprising the following steps: S1. A composite precursor is obtained by mixing porous carbon material, natural polyphenolic acid compound solution and divalent nickel metal salt and then carrying out a hydrothermal reaction. The hydrothermal treatment temperature is 80℃~120℃, and the hydrothermal time is 12h~24h. S2. The composite precursor is carbonized to obtain a carbon composite material; wherein, the divalent nickel metal salt is converted into nickel-containing particles, and the nickel-containing particles are doped into the porous carbon material. The carbonization process is carried out under an inert atmosphere, with a heating rate of 2℃ / min to 20℃ / min, a carbonization temperature of 700℃ to 900℃, and a carbonization time of 60min to 240min.

[0040] Specifically, in step S1, a natural polyphenolic acid compound is dissolved in an alkaline solution to form a natural polyphenolic acid compound solution. Then, a porous carbon material is mixed with the natural polyphenolic acid compound solution in a solid-liquid mixture, allowing the natural polyphenolic acid compound to permeate into the pores of the porous carbon material. Subsequently, a divalent nickel metal salt is dissolved in water to form a divalent nickel metal salt solution. The divalent nickel metal salt solution is then mixed with the aforementioned mixture in a solid-liquid mixture, allowing the divalent nickel metal salt to permeate into the pores of the porous carbon material. Then, a hydrothermal reaction is carried out, using the porous carbon material as a template, and the natural polyphenolic acid compound and the divalent nickel metal salt are assembled on the porous carbon material to form a natural polyphenolic acid nickel metal-organic framework (MOF), thus obtaining a composite precursor.

[0041] This application does not limit the specific selection of porous carbon materials, but can select them according to actual needs, such as biomass-derived porous carbon, polymer-derived porous carbon, fossil fuel-derived porous carbon, etc.

[0042] This application does not limit the specific selection of natural polyphenolic acid compounds; they can be selected according to actual needs.

[0043] This application does not limit the specific choice of alkaline solvent, which can be selected according to actual needs, such as potassium hydroxide.

[0044] This application does not limit the specific parameters of solid-liquid mixing; as long as the solid and liquid are thoroughly mixed, it is acceptable.

[0045] This application does not limit the specific selection of divalent nickel metal salts; selection can be made according to actual needs.

[0046] The hydrothermal treatment in this application uses a hydrothermal temperature of 80℃ to 120℃ and a hydrothermal time of 12h to 24h. For example, the hydrothermal temperature can be 80℃, 90℃, 100℃, 110℃, 120℃, etc., and the hydrothermal time can be 12h, 13h, 14h, 15h, 16h, 17h, 18h, 19h, 20h, 21h, 22h, 23h, 24h, etc. Adjusting the hydrothermal treatment parameters within the above range can ensure the growth of natural nickel polyphenolate metal-organic frameworks on porous carbon materials.

[0047] In step S2, the composite precursor is carbonized to carbonize the natural nickel polyphenolic metal-organic framework in the composite precursor into nickel-containing particles, and the nickel-containing particles are then doped into the porous carbon material to obtain a carbon composite material.

[0048] The carbonization treatment in this application is carried out under an inert atmosphere. The heating rate of the carbonization treatment is 2℃ / min to 20℃ / min, the carbonization temperature is 700℃ to 900℃, and the carbonization time is 60min to 240min. For example, the heating rate can be 2℃ / min, 3℃ / min, 4℃ / min, 5℃ / min, 6℃ / min, 7℃ / min, 8℃ / min, 9℃ / min, 10℃ / min, 11℃ / min, 12℃ / min, 13℃ / min, 14℃ / min, 15℃ / min, 16℃ / min, 17℃ / min, etc. The carbonization rates can be 18℃ / min, 19℃ / min, 20℃ / min, etc., and the carbonization temperatures can be 700℃, 750℃, 800℃, 850℃, 900℃, etc., with carbonization times of 60min, 70min, 80min, 90min, 100min, 110min, 120min, 130min, 140min, 150min, 160min, 170min, 180min, 190min, 200min, 210min, 220min, 230min, 240min, etc. By controlling the parameters of the carbonization treatment, the graphitization degree, specific surface area, and nucleation growth of nickel-containing particles in porous carbon materials can be regulated, ultimately obtaining carbon composite materials with high specific surface area, excellent conductivity, and uniformly dispersed nickel active sites, thereby improving the specific capacity, cycle life, and iodine catalytic conversion performance of zinc-iodine batteries. Preferably, the inert atmosphere includes nitrogen and / or argon.

[0049] This application first enables in-situ coordination self-assembly of porous carbon materials, natural polyphenolic acid compounds, and divalent nickel metal salts under hydrothermal conditions. The abundant oxygen-containing functional groups on the porous carbon surface serve as nucleation sites, inducing uniform growth of the natural polyphenolic acid nickel metal-organic framework on its surface and within its pores, effectively suppressing the free aggregation and stacking of the natural polyphenolic acid nickel metal-organic framework. Subsequently, high-temperature carbonization treatment precisely inherits the pre-dispersed natural polyphenolic acid nickel metal-organic framework, promoting the in-situ reduction and confined precipitation of nickel species into highly dispersed small-sized particles, avoiding the excessively large particles caused by direct pyrolysis of bulk natural polyphenolic acid nickel metal-organic framework crystals. This carbon composite structure significantly increases the exposure density of nickel active sites, not only enabling the firm capture of iodine species through enhanced surface chemisorption to suppress the shuttle effect, but also lowering the activation energy barrier of the iodine redox reaction, thereby significantly improving the specific capacity, cycle stability, and iodine catalytic conversion performance of zinc-iodine batteries. Furthermore, the preparation process is clear in steps, with controllable parameters, requires no complex equipment, is easy to scale up, and is suitable for large-scale production.

[0050] In one specific embodiment, the natural polyphenolic acid compound includes at least one of ellagic acid, tea polyphenols, proanthocyanidins, and gallic acid. These natural polyphenolic acid compounds are rich in adjacent phenolic hydroxyl groups, possessing extremely strong electron-donating ability and multidentate coordination characteristics. They can undergo rapid and stable chelation reactions with divalent nickel ions under hydrothermal conditions, forming a well-structured natural polyphenolic nickel metal-organic framework through in-situ self-assembly. Simultaneously, the aromatic ring structure of the natural polyphenolic acid compound can serve as a carbon source during high-temperature carbonization, transforming into a highly graphitized carbon framework through aromatization and condensation. This ensures that nickel-containing particles are uniformly dispersed in the porous carbon material, thereby significantly improving the electrochemical performance of the zinc-iodine battery.

[0051] In one specific embodiment, the divalent nickel metal salt includes at least one of nickel chloride, nickel acetate, nickel nitrate, nickel sulfate, nickel chloride hydrate, nickel acetate hydrate, nickel nitrate hydrate, and nickel sulfate hydrate. These divalent nickel metal salts can efficiently dissociate into highly active divalent nickel ions in aqueous solution. These ions have a suitable coordination constant and undergo rapid and stable coordination reactions with the ortho-phenolic hydroxyl groups in natural polyphenolic acid compounds. This allows for the in-situ construction of a uniform natural polyphenolic acid nickel metal-organic framework under hydrothermal conditions, thereby obtaining the target carbon composite material and ultimately improving the electrochemical performance of the zinc-iodine battery.

[0052] In one specific embodiment, the mass ratio of the natural polyphenolic acid compound to the porous carbon material is (2.4~5.6):1, for example, the mass ratio of the natural polyphenolic acid compound to the porous carbon material can be 2.4:1, 2.5:1, 3:1, 3.5:1, 4:1, 4.5:1, 5:1, 5.6:1, etc. When the mass ratio of the natural polyphenolic acid compound to the porous carbon material is within the above range, the abundant oxygen-containing functional groups on the surface of the porous carbon material can provide sufficient heterogeneous nucleation sites, inducing uniform growth of the natural polyphenolic acid nickel metal-organic framework. This avoids the homogeneous nucleation dominance caused by excessive natural polyphenolic acid compound (i.e., the natural polyphenolic acid nickel metal-organic framework grows freely in the solution, detaches from the porous carbon material, and thus leads to coarse agglomeration of nickel-containing particles after carbonization), and also prevents the low loading of active sites and sparse distribution of catalytic centers caused by insufficient natural polyphenolic acid compound, thereby successfully optimizing the structure of the carbon composite material.

[0053] In one specific embodiment, the mass ratio of porous carbon material to divalent nickel metal salt is (1~2.62):1, for example, the mass ratio of porous carbon material to divalent nickel metal salt can be 1:1, 1.5:1, 2:1, 2.5:1, 2.62:1, etc. This mass ratio range can ensure the uniform dispersion of nickel-containing particles in the porous carbon material, avoiding excessive accumulation, and at the same time avoiding the problem of low catalytic active site density and inability to form a continuous catalytic network due to insufficient nickel salt. Ultimately, it achieves the synergy of high-density chemical catalysis and efficient physical adsorption, improving the electrochemical performance of zinc-iodine batteries.

[0054] In one specific embodiment, prior to step S2, the method further includes the following step: cleaning the composite precursor, which includes washing with an acidic solution. Washing the composite precursor with an acidic solution can precisely remove physically adsorbed free nickel salts, avoid the appearance of nickel oxide impurities after carbonization, improve the purity of the carbon composite material, and ensure the electrochemical performance of the carbon composite material.

[0055] In one specific embodiment, the acidic solution includes at least one of hydrochloric acid, sulfuric acid, phosphoric acid, and nitric acid. This acidic solution effectively removes free nickel salts and is widely available and inexpensive, thus facilitating the large-scale preparation of carbon composite materials.

[0056] In one specific embodiment, the molar concentration of the acidic solution is 0.1 mol / L to 3 mol / L, for example, the molar concentration of the acidic solution can be 0.1 mol / L, 0.5 mol / L, 1 mol / L, 1.5 mol / L, 2 mol / L, 2.5 mol / L, 3 mol / L, etc. When the concentration of the acidic solution is within the above range, the complete removal of free nickel salt can be ensured, and the negative impact of the strongly acidic environment on the natural nickel polyphenolate metal-organic framework can be avoided, thus ensuring the successful preparation of carbon composite materials.

[0057] In one specific embodiment, after the cleaning treatment of the composite precursor, water washing, filtration treatment, and drying treatment are performed sequentially. This application does not limit the specific parameters of the water washing; as long as the composite precursor is thoroughly cleaned, it is acceptable. This application does not limit the specific parameters of the filtration treatment; they can be selected according to actual needs. This application does not limit the specific parameters of the drying treatment; they can be selected according to actual needs.

[0058] In one specific embodiment, the method for preparing porous carbon materials includes the following steps: subjecting a biomass precursor to high-temperature heat treatment, acid washing, and drying sequentially. Specifically, the biomass precursor is subjected to high-temperature heat treatment to carbonize it and construct a porous carbon framework with rich pore structure in situ. Then, impurities in the crude product are washed with an acidic solution, and finally dried to obtain a high-purity porous carbon material with a high specific surface area.

[0059] In one specific embodiment, the biomass precursor includes wood chips.

[0060] In one embodiment, the wood chips include at least one type of broadleaf wood. Preferably, the broadleaf wood includes beech.

[0061] In one specific embodiment, the high-temperature heat treatment is carried out under an inert atmosphere. The heating rate of the high-temperature heat treatment is 2℃ / min to 20℃ / min, the temperature of the high-temperature heat treatment is 1000℃ to 1300℃, and the time of the high-temperature heat treatment is 60min to 240min. For example, the heating rate can be 2℃ / min, 3℃ / min, 4℃ / min, 5℃ / min, 6℃ / min, 7℃ / min, 8℃ / min, 9℃ / min, 10℃ / min, 11℃ / min, 12℃ / min, 13℃ / min, 14℃ / min, 15℃ / min, or 16℃ / min. The heat treatment parameters can be set at speeds of 17℃ / min, 18℃ / min, 19℃ / min, 20℃ / min, etc., with temperatures ranging from 1000℃, 1050℃, 1100℃, 1150℃, 1200℃, 1250℃, 1300℃, etc., and durations ranging from 60min, 70min, 80min, 90min, 100min, 110min, 120min, 130min, 140min, 150min, 160min, 170min, 180min, 190min, 200min, 210min, 220min, 230min, 240min, etc. When the high-temperature heat treatment parameters are within the above ranges, the biomass precursor is fully carbonized and a porous carbon framework with abundant pores is constructed in situ, laying the foundation for the successful preparation of subsequent carbon composite materials.

[0062] A third aspect of this application provides a positive electrode sheet, which includes a positive current collector and a positive electrode coating coated on at least one side of the positive current collector. The positive electrode coating includes a positive electrode active material, which includes the aforementioned carbon composite material.

[0063] In this application, there is no particular limitation on the type of positive electrode current collector; it can be any known material suitable for use as a positive electrode current collector. In one embodiment, the positive electrode current collector includes metallic materials such as aluminum, stainless steel, nickel plating, titanium, and tantalum.

[0064] In one specific embodiment, the positive electrode coating further includes a positive electrode conductive agent and a positive electrode binder. The positive electrode conductive agent includes at least one of carbon materials such as natural graphite, artificial graphite, acetylene black, needle coke, carbon nanotubes, graphene, and carbon fiber. The positive electrode binder includes at least one of cellulose nanocrystals, polyvinylidene fluoride, hydroxypropyl methylcellulose, sodium carboxymethyl cellulose, and styrene-butadiene rubber.

[0065] A fourth aspect of this application provides a zinc-iodine battery comprising the aforementioned positive electrode. This zinc-iodine battery exhibits excellent specific capacity, cycle stability, and iodine catalytic conversion performance.

[0066] In one specific embodiment, the zinc-iodine battery of this application includes a negative electrode sheet, which includes a zinc foil sheet.

[0067] In one specific embodiment, the battery of this application further includes an electrolyte, which is an electrolyte known in the art that can be used in batteries and makes the battery have excellent electrochemical performance, including aqueous solutions of zinc sulfate and / or aqueous solutions of zinc chloride, which can be specifically set as needed.

[0068] In one specific embodiment, the zinc-iodine battery also includes a separator. The embodiments of this application do not have any particular restrictions on the material and shape of the separator, as long as it does not significantly impair the effect of this application. The material may include porous sheet-like or non-woven fabric-like substances with excellent liquid retention, including but not limited to polypropylene, polyethylene, etc., which can be set as needed.

[0069] In one embodiment, the battery may include an outer packaging that can be used to encapsulate the electrode assembly and electrolyte.

[0070] In one specific embodiment, the outer packaging of the battery can be a hard shell, such as a hard plastic shell, an aluminum shell, or a steel shell. The outer packaging of the secondary battery can also be a soft pack, such as a pouch-type soft pack. The material of the soft pack can be plastic; examples of plastics include polypropylene, polybutylene terephthalate, and polybutylene succinate.

[0071] This application does not impose any particular restrictions on the shape of the secondary battery; it can be cylindrical, square, or any other arbitrary shape.

[0072] The present application will be further described in detail below through specific embodiments.

[0073] Example 1 1. Preparation of carbon composite materials Beech sawdust was sieved through a 100-mesh sieve, and then calcined at 1000℃ for 60 min under a nitrogen atmosphere at a heating rate of 5℃ / min, and then ground into carbon powder. The obtained carbon powder was soaked in 500 mL of 2M HCl solution, stirred for 12 h, washed 6 times with deionized water, and dried at 80℃ to obtain porous carbon material.

[0074] 0.68 g of gallic acid was dissolved in 20 mL of 0.16 M KOH solution, followed by the addition of 0.26 g of NiCl2 and 0.2 g of porous carbon material. The mixture was sonicated for 30 minutes and then transferred to a 100 mL stainless steel autoclave equipped with polytetrafluoroethylene. The autoclave was sealed and subjected to a hydrothermal reaction at 120 °C for 24 h, followed by natural cooling to room temperature. The resulting mixture was centrifuged and washed twice with deionized water, dried at 60 °C for 12 h, and then calcined at 800 °C for 120 min under a nitrogen atmosphere at a heating rate of 5 °C / min. The resulting product was washed three times with deionized water and dried at 80 °C to obtain the carbon composite material.

[0075] The mass ratio of gallic acid to porous carbon material is 3.4:1; the mass ratio of porous carbon material to NiCl2 is 2.62:1.

[0076] S BET =100, I dis =1,D Ni =300, ω Ni =3, therefore, S ass =100, d Ni =100, SE=200.

[0077] 2. Preparation of the positive electrode sheet The carbon composite material and I2 were mixed at a mass ratio of 1:1 and transferred to a sealed glass bottle. The mixture was heated at 60°C for 12 hours to collect the iodine-carbon composite. The prepared iodine composite material, PVDF (polyvinylidene fluoride), and Ketjen black were dispersed in N-methylpyrrolidone (NMP) at a weight ratio of 8:1:1 and ground into a uniform slurry. The slurry was then uniformly coated onto carbon paper and dried at 60°C for 4 hours to obtain the iodine cathode material. The three types of circular carbon paper were placed in 10 mL sealed tubes with an equal amount of iodine powder and dried at 80°C for 2 hours to obtain the button cell cathode sheet.

[0078] 3. Manufacturing of zinc-iodine batteries A CR2025 coin cell was assembled in a 2M ZnSO4 electrolyte using an iodine positive electrode, a 19mm diameter glass fiber separator (GF / C, Whatman), and a 0.1mm thick zinc foil negative electrode.

[0079] Comparative Example 1 The preparation method of the zinc-iodine battery in this comparative example is largely the same as that in Example 1, except that: beech wood sawdust is passed through a 100-mesh sieve, and then the sieved sawdust is calcined at 1000°C for 60 min under a nitrogen atmosphere at a heating rate of 5°C / min, and then ground into carbon powder. The obtained carbon powder is soaked in 500 mL of 2M HCl solution, stirred for 12 h, washed 6 times with deionized water, and dried at 80°C to obtain porous carbon material; the porous carbon material is used as the positive electrode material to prepare a zinc-iodine battery.

[0080] Comparative Example 2 The preparation method of the zinc-iodine battery in this comparative example is roughly the same as that in Example 1, except that porous carbon materials are not used.

[0081] Examples 2-17 and Comparative Examples 3-7 are used to illustrate the zinc-iodine battery of this application, including most of the operations in Example 1, except that: the mass ratio of natural polyphenolic acid compound to porous carbon material, the mass ratio of porous carbon material to divalent nickel metal salt, the parameters of hydrothermal treatment, the parameters of carbonization treatment, and the parameters of high-temperature heat treatment are based on Table 1 and Table 2, respectively.

[0082] Table 1

[0083] Table 2

[0084] Test case The following performance tests were performed on the batteries prepared in the examples and comparative examples: 1. Specific capacity test The zinc-iodine button cell was placed in a 30°C constant temperature chamber and constant current charge-discharge test was performed using the Xinwei Battery Testing System. The voltage range was 0.6V to 1.6V. The specific capacity of the first discharge cycle at current densities of 2A / g and 10A / g was recorded.

[0085] 2. Cyclic performance The zinc-iodine button cell was placed in a 30°C constant temperature chamber and subjected to constant current charge-discharge testing using the Xinwei Battery Testing System, with a voltage range of 0.6V to 1.6V. The discharge specific capacity of the first cycle at current densities of 2A / g and 10A / g was recorded as the initial capacity C1. Subsequently, constant current charge-discharge cycles were continuously performed at current densities of 2A / g and 10A / g until a total of 1200 and 1000 cycles were reached, respectively. The discharge specific capacity C2 of the 1200th and 1000th cycles was recorded. The capacity retention rate of the zinc-iodine button cell after cycling at current densities of 2A / g and 10A / g was calculated based on the capacity retention rate = (C2 / C1) × 100%.

[0086] 3. Iodine catalytic conversion performance Zinc-iodine button cells were placed in a 30°C constant temperature chamber and subjected to constant current charge-discharge tests using a Newway battery testing system, with a voltage range of 0.6V to 1.6V. The I² / I² / I² / C ... The characteristic flat region of the redox reaction (i.e., the voltage plateau region) was used to read the average voltage value (V) of the charging plateau. charge ) and the average voltage value of the discharge platform (V discharge ), calculate the difference between the two ΔV = |V charge V discharge |, and this difference is the plateau polarization voltage.

[0087] Table 3

[0088] As shown in Table 3, based on the comparison between Examples 1-17 and Comparative Examples 1 and 2, when the carbon composite material is composed of porous carbon material and nickel-containing particles doped in the porous carbon material, the porous carbon material and the nickel-containing particles work synergistically to improve the overall electrochemical performance of the zinc-iodine battery.

[0089] Based on the comparison of Examples 1-17 and Comparative Examples 3-7, it can be seen that when 36≤SE≤200, 6≤d Ni ≤100, 30≤S ass When the value is ≤100, the synergistic effect of porous carbon materials and nickel-containing particles is better, which makes zinc-iodine batteries exhibit excellent specific capacity and cycle durability.

[0090] Based on the comparison of Examples 1-3, 8, and 9, it can be seen that 50≤S BET ≤100, and 0.5≤I dis When the value is ≤1, carbon composite materials can provide sufficient and reasonably distributed pore structure, which is beneficial to improving the specific capacity, cycle performance and iodine catalytic conversion performance of zinc-iodine batteries.

[0091] According to the comparison of Examples 1, 8, and 9, when the biomass precursor is subjected to high-temperature heat treatment at a heating rate of 5℃ / min to 10℃ / min, a temperature of 1000℃ to 1300℃, and a time of 60min to 240min, a porous carbon skeleton with rich pore structure can be prepared, the structure of carbon composite material can be optimized, and the specific capacity, cycle performance and iodine catalytic conversion performance of the battery can be further improved.

[0092] According to the comparison of Examples 1, 10-12, when ellagic acid, tea polyphenols and gallic acid are selected as natural polyphenolic acid compounds, the zinc-iodine battery has better specific capacity, cycle performance and iodine catalytic conversion performance.

[0093] As can be seen from the comparison of Examples 1, 13, and 14, when nickel chloride and nickel acetate are selected as divalent nickel metal salts, zinc-iodine batteries exhibit higher specific capacity, cycle performance, and iodine catalytic conversion performance.

[0094] According to the comparison of Examples 1 and 15, when the hydrothermal temperature is 80℃~120℃ and the hydrothermal time is 12h~24h, the specific capacity, cycle performance and iodine catalytic conversion performance of zinc-iodine batteries can be guaranteed.

[0095] According to the comparison of Examples 1 to 5, when the mass ratio of natural polyphenolic acid compound to porous carbon material is (2.4~5.6):1, the structure of the carbon composite material is better, thereby improving the specific capacity, cycle performance and iodine catalytic conversion performance of zinc-iodine battery.

[0096] According to the comparison of Examples 1, 4 to 7, when the mass ratio of porous carbon material to divalent nickel metal salt is (1.5 to 2.62): 1, the nickel-containing particles are uniformly dispersed in the porous carbon material, which can improve the electrochemical performance of zinc-iodine batteries.

[0097] According to the comparison of Examples 1 and 16-17, the zinc-iodine battery exhibits excellent electrochemical performance when the heating rate of the carbonization treatment is 2℃ / min to 20℃ / min, the carbonization temperature is 700℃ to 900℃, and the carbonization time is 60min to 240min.

[0098] The various embodiments of this application have been described above. These descriptions are exemplary and not exhaustive, nor are they limited to the disclosed embodiments. Many modifications and variations will be apparent to those skilled in the art without departing from the scope and spirit of the described embodiments. The terminology used herein is chosen to best explain the principles, practical application, or improvement of the technology in the market, or to enable others skilled in the art to understand the embodiments disclosed herein.

Claims

1. A carbon composite material, characterized in that, The carbon composite material includes porous carbon material and nickel-containing particles doped in the porous carbon material; The carbon composite material satisfies the following synergistic effect relationship: SE=d Ni +S ass ; The synergistic effect index of the carbon composite material is SE; the particle size of the nickel particles is d. Ni , defined as d Ni =D Ni / ω Ni The particle size of the nickel-containing particles is D. Ni The unit is nm; the mass content of nickel in the nickel-containing particles is ω. Ni The unit is %; the active specific surface area of ​​the porous carbon material is S. ass Defined as S ass =S BET / I dis The specific surface area of ​​the porous carbon material is S. BET The unit is cm. 2 / g; the disorder degree of the porous carbon material is I. dis ; Furthermore, the carbon composite material satisfies the following conditions: 36≤SE≤200; 6≤d Ni ≤100； 30≤S ass ≤100。 2. The carbon composite material according to claim 1, characterized in that, 50≤S BET ≤100； And / or, 0.5≤I dis ≤1.

3. The carbon composite material according to claim 1, characterized in that, 100≤D Ni ≤300； And / or, 3≤ω Ni ≤50.

4. A method for preparing a carbon composite material according to any one of claims 1 to 3, characterized in that, Includes the following steps: S1. The porous carbon material, the natural polyphenolic acid compound solution, and the divalent nickel metal salt are mixed and subjected to a hydrothermal reaction to obtain a composite precursor. The hydrothermal treatment temperature is 80℃~120℃, and the hydrothermal time is 12h~24h. S2. The composite precursor is subjected to carbonization treatment to obtain the carbon composite material; wherein the divalent nickel metal salt is converted into the nickel-containing particles, and the nickel-containing particles are doped into the porous carbon material; The carbonization process is carried out under an inert atmosphere, with a heating rate of 2℃ / min to 20℃ / min, a carbonization temperature of 700℃ to 900℃, and a carbonization time of 60min to 240min.

5. The method for preparing the carbon composite material according to claim 4, characterized in that, The natural polyphenolic acid compounds include at least one of ellagic acid, tea polyphenols, proanthocyanidins, and gallic acid; And / or, divalent nickel metal salts include at least one of nickel chloride, nickel acetate, nickel nitrate, nickel sulfate, nickel chloride hydrate, nickel acetate hydrate, nickel nitrate hydrate, and nickel sulfate hydrate.

6. The method for preparing the carbon composite material according to claim 4, characterized in that, The mass ratio of the natural polyphenolic acid compound to the porous carbon material is (2.4~5.6):1; And / or, the mass ratio of the porous carbon material to the divalent nickel metal salt is (1~2.62):

1.

7. The method for preparing the carbon composite material according to claim 4, characterized in that, Before step S2, the method further includes the following step: cleaning the composite precursor, the cleaning process including washing with an acidic solution; Preferably, the acidic solution includes at least one of hydrochloric acid, sulfuric acid, phosphoric acid, and nitric acid; preferably, the molar concentration of the acidic solution is 0.1 mol / L to 3 mol / L.

8. The method for preparing the carbon composite material according to claim 4, characterized in that, The method for preparing the porous carbon material includes the following steps: subjecting the biomass precursor to high-temperature heat treatment, acid washing treatment, and drying treatment in sequence; Preferably, the biomass precursor comprises sawdust; more preferably, the sawdust comprises at least one type of broadleaf wood. Preferably, the high-temperature heat treatment is carried out under an inert atmosphere, the heating rate of the high-temperature heat treatment is 2℃ / min to 20℃ / min, the temperature of the high-temperature heat treatment is 1000℃ to 1300℃, and the time of the high-temperature heat treatment is 60min to 240min.

9. A positive electrode plate, characterized in that, The positive electrode sheet includes a positive current collector and a positive electrode coating coated on at least one side of the positive current collector. The positive electrode coating includes a carbon composite material as described in any one of claims 1 to 3 or a carbon composite material prepared by the method of preparing the carbon composite material as described in any one of claims 4 to 8.

10. A zinc-iodine battery, characterized in that, The zinc-iodine battery includes the positive electrode as described in claim 9.

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