A composite zinc negative electrode based on single-molecule in-situ polymerization and a preparation method and application thereof

Abstract

The application discloses a kind of composite zinc negative electrode based on single molecule in-situ polymerization and its preparation method and application, and the composite zinc negative electrode is sequentially arranged from bottom to top by bottom zinc metal layer and top modification layer;Bottom zinc metal layer is zinc metal film;Top modification layer is fullerene-based polymer film;Fullerene-based polymer film is the cross-linked film of fullerene-based molecular polymerization;Preparation method includes: fullerene-based molecule is dissolved in selected solvent, and fullerene-based molecule solution is obtained;Fullerene-based molecule solution is coated to the surface of zinc metal layer by liquid phase film forming method;Fullerene-based molecule solution coated zinc metal layer is polymerized, and composite zinc negative electrode is obtained.The above-mentioned composite zinc negative electrode can effectively promote the desolvation process of zinc metal negative electrode surface hydrated zinc ion and the uniform distribution of surface electric field, significantly prolong the cycle life of zinc metal negative electrode, and has higher practical value and popularization value in water-based zinc metal battery field.

Description

Technical Field

[0001] This invention relates to the field of aqueous zinc metal batteries, and in particular to a composite zinc anode based on monomolecular in-situ polymerization, its preparation method, and its application. Background Technology

[0002] With the increasing demand for electrochemical energy storage, the development of battery systems that combine high safety, low cost, and environmental friendliness has become a research hotspot. Aqueous zinc metal batteries, which use an aqueous electrolyte instead of a traditional organic electrolyte, fundamentally avoid the risks of combustion and explosion. They possess outstanding advantages such as high intrinsic safety, low raw material cost, and environmental friendliness, and are considered a strong candidate for next-generation large-scale energy storage technology.

[0003] Zinc, as a metal abundant in the Earth's crust, with mature mining technology and low price, provides a solid resource foundation for the large-scale application of aqueous zinc metal batteries. This system not only demonstrates significant safety but also exhibits good potential in power output and rate performance, making it suitable for various applications such as large-scale energy storage, portable electronic devices, and low-speed electric vehicles.

[0004] However, aqueous zinc metal batteries still face severe challenges in the stability of the negative electrode interface during actual operation, which greatly restricts their cycle life and commercialization. Specifically, this manifests as: uneven deposition of zinc ions on the electrode surface, easily forming zinc dendrites that can pierce the separator and cause a short circuit; under common electrolyte conditions, hydrogen evolution side reactions easily occur on the zinc metal negative electrode surface, resulting in loss of active material and decreased charge utilization; and the presence of anions (SO4) in the electrolyte... 2- and OH - The reaction with zinc ions produces an insoluble passivation product (Zn4SO4(OH)6·xH2O), which covers the electrode surface, increases interfacial impedance, and hinders reaction kinetics.

[0005] To address these issues, constructing a modification layer on the surface of the zinc metal anode has become a widely adopted strategy.

[0006] Chinese patent application CN108520985A discloses a method for extending the cycle life of zinc batteries and its application. The core of this method is to create a porous coating between the zinc anode and the battery separator. This coating is composed of nanomaterials and a binder in a specific ratio, with a thickness ranging from 0.02 to 500 μm and an average pore size of less than 1 μm. The nanomaterials can be selected from carbon particles, acetylene black, carbon nanotubes, graphene, fullerenes, or various metal oxides, while the binder includes various polymers such as polytetrafluoroethylene, polyvinylidene fluoride, and styrene-butadiene rubber. This porous structure aims to guide the uniform deposition of zinc ions and inhibit dendrite formation, thereby improving the battery's cycle stability. However, the non-conductive binder and the relatively thick modification layer structure introduced into the coating (typically, the appropriate thickness of the modification layer should be 0.1–1000 nm) significantly increase the difficulty of interfacial charge transfer, hindering the rapid migration and desolvation process of hydrated zinc ions. Furthermore, the simple mechanical mixing and coating process used in this technology easily leads to uneven distribution of nanomaterials in the coating, affecting the uniformity and consistency of the structure.

[0007] Chinese patent application CN119208610A discloses a negative electrode coating material for aqueous zinc-ion batteries, its preparation method, and its application. This coating material is synthesized by reacting coumarin hydrazine with benzyl isothiocyanate to form a compound LXB containing polynitrogen, oxygen, and sulfur heteroatoms. This compound is then mixed with polyvinylidene fluoride (PVDF) and coated onto the surface of zinc foil to form a composite coating LXB@Zn. The preparation method mainly includes the stepwise synthesis of compound LXB and a composite coating process with a binder. This coating utilizes the imino groups in its molecular structure to bind with hydrogen ions in the electrolyte, thus suppressing hydrogen evolution side reactions. Simultaneously, it leverages the lone pairs of electrons from heteroatoms such as S, O, and N to coordinate with zinc ions, promoting ion transport and uniform deposition, thereby suppressing dendrite growth and interfacial side reactions, and improving the cycle stability and electrochemical performance of the battery. However, the proportion of heteroatoms (S, O, N) in the overall molecular structure of this coating is relatively low, and the effect achieved solely by their lone pairs of electrons coordinating with zinc ions is relatively limited. Furthermore, the zinc affinity of polyvinylidene fluoride introduced into the coating differs significantly from that of compound LXB, resulting in a decrease in the uniformity of zinc affinity in the coating and affecting the deposition kinetics of zinc ions.

[0008] To suppress dendrite growth and related side reactions in zinc anodes, researchers have proposed a strategy of constructing a protective layer on the surface of the zinc anode. For example, Professor Ji Xiaobo's research group at Central South University (Chemical Engineering Journal 2023, 466, 143054) prepared fullerene C on the surface of zinc foil using a blade coating method. 60 / Carboxymethyl cellulose (CMC) composite protective layer (denoted as Zn@C 60 This protective layer utilizes fullerene C. 60The high electric field homogenization capability and the high lowest unoccupied molecular orbital energy level (LUMO, approximately 4.0 eV) of Zn@C form an ohmic contact interface with the zinc anode, effectively homogenizing the electric field on the electrode surface and reducing the zinc nucleation overpotential. This guides zinc ions to preferentially deposit along the (002) crystal plane of metallic zinc, suppressing dendrites and side reactions. Experiments show that based on Zn@C... 60 A full cell with negative electrode (Zn@C) 60 ||NVO) in 3 A g -1 After 1500 cycles at current density, the specific capacity remains at 135 mAh g⁻¹. -1 However, the CMC binder introduced by this method is incompatible with fullerene C... 60 Significant differences in zinc affinity not only reduce battery energy density but also decrease the uniformity of zinc affinity in the zinc anode, thus exacerbating the kinetic differences in the zinc ion deposition process. Furthermore, simple mechanical mixing and coating processes easily lead to weak film adhesion and uneven composition distribution, causing coating peeling or decreased functional consistency when the zinc anode undergoes volume changes, affecting the reliability of its long-term protection.

[0009] To address the shortcomings of existing technologies, there is an urgent need to develop a high-functionality composite zinc anode, its preparation method, and related applications. This composite zinc anode significantly improves its overall electrochemical performance by constructing a structurally stable and functionally integrated modification layer on the zinc surface using a polymerization process. It must meet the following key requirements: First, the preparation process should be simple and efficient, enabling uniform anchoring and dispersion of functional components in the modification layer through polymerization. Second, the dense and continuous structure formed by polymerization should ensure that the modification layer as a whole possesses good zinc ion conductivity. Most importantly, the ordered molecular arrangement and synergistic enhancement effect promoted by polymerization can significantly increase the delocalized electron density of the modification layer, thereby strengthening the coordination of zinc ions and optimizing their interfacial migration kinetics. Simultaneously, it effectively homogenizes the electric field distribution on the zinc anode surface, suppressing the formation and growth of zinc dendrites at the source. Summary of the Invention

[0010] To address the above problems, the present invention aims to provide a composite zinc anode based on monomolecular in-situ polymerization, its preparation method, and its application. The technical solution adopted by the present invention is as follows:

[0011] A composite zinc anode based on monomolecular in-situ polymerization consists of a bottom zinc metal layer and a top modification layer arranged sequentially from bottom to top; the bottom zinc metal layer is a zinc metal thin film; and the top modification layer is a fullerene-based polymer thin film.

[0012] Furthermore, the fullerene-based polymer film refers to a cross-linked network film obtained by intermolecular polymerization between fullerene molecules.

[0013] Furthermore, the polymerization is achieved through at least one of annealing and radiation treatment.

[0014] Furthermore, the fullerene-based molecule is composed of a fullerene carbon cage portion, a bridging portion, and a terminal group portion, and its general structural formula is:

[0015]

[0016] The fullerene carbon cage portion is C 60 C 70 C 76 C 78 C 80 C 84 One of the following: the bridging part is at least one of chain-like and cyclic structures; the terminal part is at least one of alkenyl, alkynyl, carbonyl, ester, ether, thioether, amino, carboxyl, phosphorus nitrogen group, lactam group and lactone group that can undergo cross-linking polymerization; n1 is any integer between 1 and 3; n2 is any integer between 1 and 30.

[0017] A method for preparing a composite zinc anode based on monomolecular in-situ polymerization includes the following steps:

[0018] Step 1: Dissolve the fullerene molecules in a selected solvent to obtain a fullerene molecule solution;

[0019] Step 2: Cut the purchased zinc sheet into pieces. After ultrasonic cleaning in acetone, place the cut zinc sheet in isopropanol for later use.

[0020] Step 3: The fullerene-based molecular solution is coated onto the surface of the bottom zinc metal layer using a liquid-phase film formation method;

[0021] Step 4: Perform polymerization treatment on the coated bottom zinc metal layer to promote the polymerization of fullerene molecular end groups to form a top fullerene polymer modification layer, and obtain a composite zinc anode.

[0022] Furthermore, the selected solvent in step one is at least one of aromatic solvents such as benzene, anisole, chlorobenzene, o-dichlorobenzene, and toluene.

[0023] Furthermore, the concentration of the fullerene-based molecular solution in step one is 0.1~100 mg / mL.

[0024] Furthermore, the liquid phase film formation method in step three includes at least one of dip coating, screen printing, roll coating, slot coating, spray coating, spin coating, or inkjet printing.

[0025] Furthermore, the polymerization treatment in step four is either annealing or radiation treatment.

[0026] Furthermore, the annealing temperature is 60~200℃, and the annealing time is 5~180 min.

[0027] Furthermore, the wavelength of the radiation treatment is 170~950 nm, and the power of the radiation treatment is 5~500 mW / cm². 2 The radiation treatment time is 1~180 min.

[0028] Furthermore, the thickness of the top fullerene-based polymer modification layer formed in step four is 10~1000 nm.

[0029] Application of a composite zinc anode based on monomolecular in-situ polymerization in an aqueous zinc metal battery.

[0030] Compared with the prior art, the present invention has the following beneficial effects:

[0031] The fullerene-based polymer modification layer of this invention employs a process combining liquid-phase film formation and in-situ polymerization to achieve uniform spreading and cross-linking polymerization of fullerene molecules on a zinc metal surface, thereby forming a modification layer with a consistent structure and controllable thickness. This film formation method not only allows for flexible adjustment of the modification layer thickness within the range of 10~1000 nm, but also enables the fullerene functional components to be highly ordered distributed at the interface through in-situ polymerization, greatly improving the overall functional performance of the modification layer, specifically in the following aspects:

[0032] (1) The uniform and dense polymer layer relies on the efficient electron acceptor properties of the fullerene carbon cage to promote the uniform delocalization of free electrons during the charging and discharging process, effectively homogenize the electric field on the zinc negative electrode surface, and inhibit the formation and growth of zinc dendrites from the source.

[0033] (2) Based on the high-density delocalized electron system formed by a large number of fullerene carbon cages in the polymer layer, the hydrated zinc ions in the electrolyte are strongly attracted by the Coulomb effect, which significantly accelerates the desolvation process and thus improves the reversibility and cycle stability of zinc ion deposition / stripping.

[0034] (3) The inherent hydrophobic properties of fullerene carbon cages are fully utilized in the uniform polymer layer, which can effectively block the direct contact between water molecules in the electrolyte and the zinc negative electrode, significantly inhibit hydrogen evolution reaction, reduce corrosion and surface passivation, and maintain the battery coulombic efficiency at a high level.

[0035] (4) The modified layer is a single-component system that does not require non-conductive additives. With its own good electronic and ionic conductivity, it effectively reduces the interfacial charge transfer impedance, reduces the overpotential of zinc ion deposition / stripping, and further enhances the cycle stability of the battery.

[0036] In summary, this invention constructs a fullerene-based polymer modification layer with uniform structure and adjustable thickness through liquid phase film formation and in-situ polymerization processes. This design integrates interfacial electric field homogenization, ion desolvation promotion, moisture barrier, and high interfacial conductivity, significantly optimizing the conductivity uniformity and functional integration of the zinc anode, thereby greatly improving the cycle life and overall stability of the battery. Attached Figure Description

[0037] To more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings used in the embodiments will be briefly introduced below. It should be understood that the following drawings only show some embodiments of the present invention and should not be regarded as a limitation on the scope of protection. For those skilled in the art, other related drawings can be obtained based on these drawings without creative effort.

[0038] Figure 1 This is a schematic diagram of the molecular structure of the fullerene-based molecule F1.

[0039] Figure 2 This is a schematic diagram of the composite zinc anode PF1 / Zn.

[0040] Figure 3 The images show the surface morphology of the bare zinc anode (Zn) and the composite zinc anode (PF1 / Zn).

[0041] Figure 4 The figure shows the cycle stability test results of aqueous zinc-iodine batteries based on bare zinc anode (Zn) and composite zinc anode (PF1 / Zn).

[0042] Figure 5 This is a schematic diagram of the molecular structure of the fullerene-based molecule F2.

[0043] Figure 6 The surface potential distribution of bare zinc (Zn) and fullerene-based polymer-modified layer PF2 is shown.

[0044] Figure 7 The figure shows the cycle stability test results of aqueous zinc-iodine batteries based on bare zinc anode (Zn) and composite zinc anode (PF2 / Zn).

[0045] Figure 8 The diagram shows the molecular structures of fullerene molecules F3-1 and F3-2.

[0046] Figure 9 The contact angle test results are shown for a 2 M zinc sulfate aqueous solution on the surface of bare zinc (Zn) and a fullerene-based polymer-modified PF3 layer.

[0047] Figure 10 The figure shows the cycle stability test results of aqueous zinc-iodine batteries based on bare zinc anode (Zn) and composite zinc anode (PF3 / Zn).

[0048] Figure 11 The figure shows the cycle stability test results of aqueous zinc-iodine batteries based on bare zinc anode (Zn) and composite zinc anode (PF1 / Zn, thick coating). Detailed Implementation

[0049] The technical solution of the present invention will be further described clearly and completely below with reference to the embodiments and accompanying drawings.

[0050] Example 1

[0051] This embodiment provides a composite zinc anode (named PF1 / Zn), consisting of a bottom zinc metal layer and a top fullerene-based polymer modification layer arranged sequentially from bottom to top. The bottom zinc metal layer is made of commercially available zinc sheet. The top fullerene-based polymer modification layer (named PF1) is made of... Figure 1 The fullerene-based molecule shown is (N-phenyl-2-[4-(4-vinylbenzyloxycarbonyl)phenyl]C 70 Fullerene pyrrolidine (named F1) was obtained by polymerization. The synthesis of the fullerene-based molecule F1 was commissioned to Fujian Fuerjin Biotechnology Co., Ltd.

[0052] In this embodiment, the preparation process of the composite zinc anode is as follows:

[0053] (1) Zinc sheet treatment: Commercially available zinc sheets with a thickness of 200 μm are cut into round zinc sheets with a diameter of 12 mm. The cut round zinc sheets are placed in 200 mL of acetone solution for ultrasonic cleaning for 30 min. The ultrasonically cleaned round zinc sheets are placed in isopropanol solution for later use.

[0054] (2) Solution preparation: Dissolve 5 mg of fullerene molecules F1 in 1 mL of anisole solvent and sonicate for 30 min to obtain an anisole solution with a concentration of 5 mg / mL of fullerene molecules F1.

[0055] (3) Spin coating: Take out the round zinc sheet from step (1) and dry it with a nitrogen gun. Place it in a spin coater and add 0.1 mL of the anisole solution of fullerene molecule F1 from step (2) to the center of the round zinc sheet at a speed of 2000 rpm. After adding the solution, keep the spin coater rotating at 2000 rpm for 30 s.

[0056] (4) Polymerization treatment: The round zinc sheets from step (3) are placed on a 150°C flat plate heater and annealed for 1 h to obtain a composite zinc anode.

[0057] (5) Drying and storage: The composite zinc anode from step (4) is treated in a vacuum oven at 110°C for 12 h and then vacuum stored for later use.

[0058] In this embodiment, the preparation process of the zinc metal battery is as follows:

[0059] (1) The zinc-iodine cathode is prepared into a self-supporting thin film by roll forming process. The composite cathode is composed of zinc iodide, activated carbon, and polytetrafluoroethylene in a mass ratio of 50:40:10, wherein the areal loading of zinc iodide is 10~15 mg / cm³. 2 .

[0060] (2) The battery is assembled using a CR2032 button cell casing, a 304 stainless steel outer shell, gaskets, spring contacts, an electrolyte-wetted separator, and electrodes. Unless otherwise specified, a glass fiber membrane (thickness: 675 μm) is used as the separator, and a 2 M zinc sulfate aqueous solution is used as the electrolyte.

[0061] (3) In the full cell, bare zinc negative electrode Zn and composite zinc negative electrode PF1 / Zn were paired with zinc iodide-based positive electrode to construct control sample and target sample, respectively.

[0062] like Figure 1 As shown, the fullerene carbon cage portion, bridging portion, and terminal group portion of the fullerene-based molecule F1 are composed of fullerene C1, C2, C3, and C4, respectively. 70 Structure, benzoic acid-like benzoyl ester structure, vinyl structure.

[0063] like Figure 2 As shown, the vinyl structure undergoes cross-linking polymerization under annealing, polymerizing the fullerene-based molecule F1 into a fullerene-based polymer modification layer PF1. Combined with the bottom zinc sheet, this forms a composite zinc anode PF1 / Zn.

[0064] like Figure 3 As shown, the surface morphology of the bare zinc anode (Zn) and the composite zinc anode (PF1 / Zn) was characterized using scanning electron microscopy at a scale bar of 400 nm. It is clearly visible that the surface of the bare zinc anode (Zn) is uneven, easily leading to a non-uniform distribution of surface potential, resulting in non-uniformity of the electric field on the surface of the bare zinc anode. This also causes non-uniformity of the zinc ion concentration field at the interface between the electrolyte and the bare zinc anode, inducing the growth of zinc dendrites during charge and discharge. Compared to the bare zinc anode (Zn), the surface of the composite zinc anode (PF1 / Zn) is uniform and dense, which can effectively improve the uniformity of the electric field and concentration field at the interface between the composite zinc anode (PF1 / Zn) and the electrolyte, thereby effectively improving the cycle stability of the aqueous zinc metal battery.

[0065] like Figure 4 As shown, calculations were performed using the mass of zinc iodide in the zinc iodide cathode at 200 mA g. -1The battery was charged and discharged at a mass current density with discharge and charge cutoff voltages of 0.6 V and 1.6 V, respectively, for 1000 cycles. The effects of the bare zinc anode (Zn) and the composite zinc anode (PF1 / Zn) on battery performance were tested using an aqueous zinc-iodine battery system. The aqueous zinc-iodine battery using the bare zinc anode (Zn) achieved an initial discharge specific capacity of 137.49 mAh g⁻¹. -1 After 611 cycles, the concentration decreased to 100.59 mAh g. -1 The capacity rapidly decayed to 73% (1-611 cycles), reaching the standard for retired conventional batteries. This decay was mainly due to side reactions such as dendrite growth, hydrogen evolution at the interface, and passivation that occurred in the zinc anode during cycling. In contrast, the aqueous zinc-iodine battery using the composite zinc anode PF1 / Zn had an initial discharge specific capacity of 140.58 mAh g⁻¹. -1 After 1000 cycles, it still has 125.64 mAh g. -1 The capacity decay rate is only 14.94 μAh / cycle (1~1000 cycles), and the overall capacity retention reaches 89%. The coulombic efficiency is still close to 100% after 1000 cycles.

[0066] Therefore, it can be seen that the composite zinc anode PF1 / Zn with the top fullerene-based polymer modification layer PF1 can effectively suppress the occurrence of side reactions and improve the cycle stability of aqueous zinc-iodine batteries.

[0067] Example 2

[0068] This embodiment provides a composite zinc anode (named PF2 / Zn), consisting of a bottom zinc metal layer and a top fullerene-based polymer modification layer arranged sequentially from bottom to top. The bottom zinc metal layer is made of commercially available zinc sheet. The top fullerene-based polymer modification layer (named PF2) is composed of... Figure 5 The fullerene molecule shown is bis[1-(pent-4-en-1-yl)-1-phenyl]C 62 The fullerene-based molecule F2 was synthesized by polymerization. The synthesis of F2 was commissioned to Fujian Fuerjin Biotechnology Co., Ltd.

[0069] In this embodiment, the preparation process of the composite zinc anode is as follows:

[0070] (1) Zinc sheet treatment: A commercially available zinc sheet (100 mm * 100 mm) with a thickness of 200 μm was placed in 500 mL of acetone solution for ultrasonic cleaning for 30 min. The ultrasonically cleaned zinc sheet was then placed in isopropanol solution for later use.

[0071] (2) Solution preparation: Dissolve 50 mg of fullerene molecules F2 in 10 mL of anisole solvent and sonicate for 30 min to obtain anisole solution with a concentration of 5 mg / mL of fullerene molecules F2.

[0072] (3) Slit coating: Take out the zinc sheet from step (1) and dry it with a nitrogen gun. Place it on the slit coating table and drop 0.5 mL of the anisole solution of fullerene molecule F2 from step (2) onto the side of the zinc sheet close to the scraper. Coat the zinc sheet to form a film under the condition that the slit width is 5 μm.

[0073] (4) Polymerization treatment: The zinc sheet from step (3) is placed on a flat plate heater at 150°C and annealed for 1 h. It is then further cut into round zinc sheets with a diameter of 12 mm to obtain a composite zinc anode.

[0074] (5) Drying and storage: The composite zinc anode from step (4) is treated in a vacuum oven at 110°C for 12 h and then vacuum stored for later use.

[0075] In this embodiment, the preparation process of the zinc metal battery is as follows:

[0076] (1) The zinc-iodine cathode is prepared into a self-supporting thin film by roll forming process. The composite cathode is composed of zinc iodide, activated carbon, and polytetrafluoroethylene in a mass ratio of 50:40:10, wherein the areal loading of zinc iodide is 10~15 mg / cm³. 2 .

[0077] (2) The battery is assembled using a CR2032 button cell casing, a 304 stainless steel outer shell, gaskets, spring contacts, an electrolyte-wetted separator, and electrodes. Unless otherwise specified, a glass fiber membrane (thickness: 675 μm) is used as the separator, and a 2 M zinc sulfate aqueous solution is used as the electrolyte.

[0078] (3) In the full cell, bare zinc negative electrode and composite zinc negative electrode were paired with zinc iodide-based positive electrode to construct control sample and target sample, respectively.

[0079] like Figure 5 As shown, the fullerene carbon cage portion, bridging portion, and terminal group portion of the fullerene-based molecule F2 are composed of fullerene C164, C164, C2 ... 60 The structure includes propyl-like and acetylene-based structures. The acetylene-based structure undergoes cross-linking polymerization under thermal annealing, polymerizing the fullerene-based molecules F2 into a fullerene-based polymer modification layer PF2. Combined with the bottom zinc sheet, this forms a composite zinc anode PF2 / Zn.

[0080] like Figure 6As shown, the surface potential of the bare zinc anode (Zn) and the composite zinc anode (PF2 / Zn) was characterized using Kelvin probe force microscopy within a 10 μm * 10 μm area on the scale bar. It is clearly visible that the bare zinc anode (Zn) exhibits varying surface colors and a significant non-uniform surface potential distribution. This indicates that the non-uniformity of the electric field on the surface of the bare zinc anode easily induces the growth of zinc dendrites during charge and discharge. Compared to the bare zinc anode (Zn), the composite zinc anode (PF2 / Zn) shows a more uniform surface potential distribution, effectively improving the electric field uniformity at the interface between the composite zinc anode (PF2 / Zn) and the electrolyte, thereby effectively enhancing the cycle stability of the aqueous zinc metal battery.

[0081] like Figure 7 As shown, calculations were performed using the mass of zinc iodide in the zinc iodide cathode at 200 mA g. -1 The battery was charged and discharged at a mass current density with discharge and charge cutoff voltages of 0.6 V and 1.6 V, respectively, for 1000 cycles. The effects of the bare zinc anode (Zn) and the composite zinc anode (PF2 / Zn) on battery performance were tested using an aqueous zinc-iodine battery system. The aqueous zinc-iodine battery using the bare zinc anode (Zn) had an initial discharge specific capacity of 137.55 mAh g⁻¹. -1 After 599 cycles, the concentration decreased to 97.46 mAh g. -1 The capacity rapidly decayed to 71% (1-599 cycles), reaching the standard for retirement of commonly used batteries. This decay was mainly due to side reactions such as dendrite growth, interface hydrogen evolution, and passivation that occurred on the zinc anode during cycling. In contrast, the aqueous zinc-iodine battery using the composite zinc anode PF2 / Zn had an initial discharge specific capacity of 138.94 mAh g⁻¹. -1 After 1000 cycles, it still has 125.63 mAh g. -1 The capacity decay rate is only 13.31 μAh / cycle (1~1000 cycles), and the overall capacity retention reaches 90%. The coulombic efficiency remains close to 100% after 1000 cycles.

[0082] Therefore, it can be seen that the composite zinc anode PF2 / Zn with a top fullerene-based polymer modification layer PF2 can effectively improve the cycle stability of aqueous zinc-iodine batteries.

[0083] Example 3

[0084] This embodiment provides a composite zinc anode (named PF3 / Zn), consisting of a bottom zinc metal layer and a top fullerene-based polymer modification layer arranged sequentially from bottom to top. The bottom zinc metal layer is made of commercially available zinc sheet. The top fullerene-based polymer modification layer (named PF3) is composed of... Figure 8 The fullerene molecule shown is (bis[N-phenyl-2-(4-(4-hydroxypent-4-en-1-yl)phenyl)]C 76Fullerene pyrrolidine) F3-1 and fullerene-based molecules (bis[N-phenyl-2-(4-(3-aminopropyl)phenyl)]C 76 The fullerene-pyrrolidine (F3-2) was obtained by polymerization. The synthesis of fullerene-based molecules F3-1 and F3-2 was commissioned to Fujian Fuerjin Biotechnology Co., Ltd.

[0085] In this embodiment, the preparation process of the composite zinc anode is as follows:

[0086] (1) Zinc sheet treatment: A commercially available zinc sheet (50 mm * 50 mm) with a thickness of 200 μm was placed in 300 mL of acetone solution for ultrasonic cleaning for 30 min. The ultrasonically cleaned zinc sheet was then placed in isopropanol solution for later use.

[0087] (2) Solution preparation: Dissolve 10 mg of fullerene molecules F3-1 and 10 mg of fullerene molecules F3-2 in 10 mL of anisole solvent and sonicate for 60 min to obtain anisole solutions of fullerene molecules F3-1 and F3-2 with a concentration of 1 mg / mL.

[0088] (3) Spraying film: Take out the zinc sheet from step (1) and dry it with a nitrogen gun, then place it on a 150°C flat plate heater in a fume hood; put 5 mL of the anisole solution of fullerene molecules F3-1 and F3-2 from step (2) into the liquid carrier bottle of the spray gun and spray it at a rate of 1 mL / min to form a film.

[0089] (4) Polymerization treatment: The zinc sheet from step (3) is placed flat on a 150°C flat plate heater and annealed for 1 h. It is then further cut into round zinc sheets with a diameter of 12 mm as composite zinc negative electrode.

[0090] (5) Drying and storage: The composite zinc anode from step (4) is treated in a vacuum oven at 110°C for 12 h and then vacuum stored for later use.

[0091] In this embodiment, the preparation process of the zinc metal battery is as follows:

[0092] (1) The zinc-iodine cathode is prepared into a self-supporting thin film by roll forming process. The composite cathode is composed of zinc iodide, activated carbon, and polytetrafluoroethylene in a mass ratio of 50:40:10, wherein the areal loading of zinc iodide is 10~15 mg / cm³. 2 .

[0093] (2) The battery is assembled using a CR2032 button cell casing, a 304 stainless steel outer shell, gaskets, spring contacts, an electrolyte-wetted separator, and electrodes. Unless otherwise specified, a glass fiber membrane (thickness: 675 μm) is used as the separator, and a 2 M zinc sulfate aqueous solution is used as the electrolyte.

[0094] (3) In the full cell, bare zinc negative electrode and composite zinc negative electrode were paired with zinc iodide-based positive electrode to construct control sample and target sample, respectively.

[0095] like Figure 8 As shown, the fullerene carbon cage, bridging, and terminal groups of the fullerene-based molecule F3-1 are composed of fullerene C1, C2, C3, C4, C5, C6, C7, C8, C9, C1, C 76 Structure, ethylbenzene-like structure, carboxylic acid structure; the fullerene carbon cage, bridging moiety, and terminal group of the fullerene molecule F3-2 are composed of fullerene C 76 The structure includes ethylbenzene-like and amino structures. The carboxylic acid and amino structures undergo cross-linking polymerization under thermal annealing, polymerizing fullerene molecules F3-1 and F3-2 into a fullerene-based polymer modification layer PF3. Combined with the bottom zinc sheet, this forms a composite zinc anode PF3 / Zn.

[0096] like Figure 9 As shown, the contact angle (θ) between a 2 M zinc sulfate aqueous solution and the surface of bare zinc (Zn) and the fullerene-based polymer-modified PF3 layer is... c The φ values ​​are 96.2° and 112.6°, respectively. Compared with the bare zinc anode (Zn), the composite zinc anode (PF3 / Zn) has stronger hydrophobic properties. This is beneficial in two ways: firstly, it facilitates the desolvation process of hydrated zinc ions at the interface between the anode and the electrolyte, promoting the kinetics of zinc ion deposition; secondly, it helps reduce the hydrogen evolution reaction at the interface between the composite zinc anode and the electrolyte, reducing corrosion and passivation of the zinc anode, thereby effectively improving the cycle stability of aqueous zinc metal batteries.

[0097] like Figure 10 As shown, calculations were performed using the mass of zinc iodide in the zinc iodide cathode at 200 mA g. -1 The battery was charged and discharged at a mass current density with discharge and charge cutoff voltages of 0.6 V and 1.6 V, respectively, for 1000 cycles. The effects of the bare zinc anode (Zn) and the composite zinc anode (PF2 / Zn) on battery performance were tested using an aqueous zinc-iodine battery system. The aqueous zinc-iodine battery using the bare zinc anode (Zn) had an initial discharge specific capacity of 138.46 mAh g⁻¹. -1 After 625 cycles, the concentration decreased to 103.59 mAh g. -1 The capacity rapidly decayed to 75% (1~625 cycles), reaching the standard for retired common batteries. This decay was mainly due to side reactions such as dendrite growth, interface hydrogen evolution, and passivation that occurred on the zinc anode during cycling. In contrast, an aqueous zinc-iodine battery using a composite zinc anode PF3 / Zn had an initial discharge specific capacity of 139.48 mAh g. -1 After 1000 cycles, it still has 124.96 mAh g. -1The capacity decay rate is only 14.52 μAh / cycle (1~1000 cycles), and the overall capacity retention reaches 90%. The coulombic efficiency is still close to 100% after 1000 cycles.

[0098] Example 4

[0099] The fullerene molecule used in this embodiment is the same as the fullerene molecule F1 in Example 1.

[0100] In this embodiment, the preparation process of the composite zinc anode is as follows:

[0101] (1) Zinc sheet treatment: Commercially available zinc sheets with a thickness of 200 μm are cut into round zinc sheets with a diameter of 12 mm. The cut round zinc sheets are placed in 200 mL of acetone solution for ultrasonic cleaning for 30 min. The ultrasonically cleaned round zinc sheets are placed in isopropanol solution for later use.

[0102] (2) Solution preparation: Dissolve 5 mg of fullerene molecules F1 in 1 mL of anisole solvent and sonicate for 30 min to obtain an anisole solution with a concentration of 5 mg / mL of fullerene molecules F1.

[0103] (3) Spin coating: Take out the round zinc sheet from step (1) and dry it with a nitrogen gun. Place it in a spin coater and add 0.1 mL of the anisole solution of fullerene molecule F1 from step (2) to the center of the round zinc sheet at a speed of 2000 rpm. After adding the solution, keep the spin coater rotating at 2000 rpm for 30 s.

[0104] (4) Polymerization treatment: Place the round zinc sheets from step (3) on a 150°C flat plate heater and anneal for 1 h.

[0105] (5) Thickness improvement: The sample obtained in step (4) is subjected to spin coating-polymerization process 9 times to obtain composite zinc anode.

[0106] (6) Drying and storage: The composite zinc anode from step (5) is treated in a vacuum oven at 110°C for 12 h and then vacuum stored for later use.

[0107] In this embodiment, the preparation process of the zinc metal battery is as follows:

[0108] (1) The zinc-iodine cathode is prepared into a self-supporting thin film by roll forming process. The composite cathode is composed of zinc iodide, activated carbon, and polytetrafluoroethylene in a mass ratio of 50:40:10, wherein the areal loading of zinc iodide is 10~15 mg / cm³. 2 .

[0109] (2) The battery is assembled using a CR2032 button cell casing, a 304 stainless steel outer shell, gaskets, spring contacts, an electrolyte-wetted separator, and electrodes. Unless otherwise specified, a glass fiber membrane (thickness: 675 μm) is used as the separator, and a 2 M zinc sulfate aqueous solution is used as the electrolyte.

[0110] (3) In the full cell, bare zinc negative electrode Zn and composite zinc negative electrode PF1 / Zn were paired with zinc iodide-based positive electrode to construct control sample and target sample, respectively.

[0111] like Figure 11 As shown, this study used the mass of zinc iodide in the zinc iodide cathode as a baseline, at 200 mA g -1 Charge-discharge tests were conducted at a mass current density, with discharge and charge cutoff voltages set at 0.6 V and 1.6 V, respectively. The test cycle count was 1000 cycles. The effects of bare zinc (Zn) and spray-coated composite zinc (PF1 / Zn) anodes on battery performance were compared using an aqueous zinc-iodine battery system. The battery using the bare zinc anode had an initial discharge specific capacity of 136.45 mAh g⁻¹. -1 After 509 cycles, it decreased to 101.68 mAh g. -1 The capacity decayed rapidly, dropping to 75% of its initial capacity by the 509th cycle, reaching the retirement standard for common batteries. This degradation was mainly attributed to side reactions such as dendrite growth, hydrogen evolution at the interface, and surface passivation that occurred on the zinc anode during cycling.

[0112] In contrast, the battery assembled using a composite zinc anode (PF1 / Zn) prepared by 10 spin-coating-polymerization processes had an initial discharge specific capacity of 137.13 mAh g⁻¹. -1 It remained at 112.99 mAh g after 1000 cycles. -1 The average capacity decay rate per cycle was 24.14 μAh / cycle (1~1000 cycles), and the overall capacity retention rate was 82%.

[0113] Compared to the composite zinc anode of Example 1, the capacity retention of the composite zinc anode in this example decreased due to the increased thickness of the modification layer. This result indicates that the thickness of the modification layer has a significant impact on the performance of the composite zinc anode: an excessively thick modification layer prolongs the desolvation path of hydrated zinc ions, thereby increasing the kinetic resistance to zinc deposition. The advantage of this invention is that the thickness of the modification layer can be controlled within the range of 10–1000 nm using various liquid-phase film deposition techniques, thus avoiding the performance degradation caused by an excessively thick modification layer.

[0114] Table 1 Test results of Examples 1-4

[0115] Example Number of cycles <![CDATA[Initial specific capacity (mAh g -1 ).]]> <![CDATA[Specific capacity after cycling (mAh g -1 )]]> Example 1: Control Sample 611 137.49 100.59 Example 1 Target Sample 1000 140.58 125.64 Example 2 Control Sample 599 137.55 97.46 Example 2 Target Sample 1000 138.94 125.63 Example 3 Control Sample 625 138.46 103.59 Example 3 Target Sample 1000 139.48 124.96 Example 4 Control Sample 509 136.45 101.68 Example 4 Target Sample 1000 137.13 112.99

[0116] As shown in Table 1, thanks to the uniform and dense fullerene-based polymer layer formed by in-situ polymerization, the inherent electric field homogenization, Coulomb attraction, and physical hydrophobicity of the fullerene carbon cage are synergistically enhanced, enabling the target samples of Examples 1 to 3 to achieve stable cycling of over 1000 cycles with a discharge capacity retention rate of over 89%. In contrast, the unmodified control sample failed after only 625 cycles due to aggravated side reactions, resulting in a short circuit and a capacity retention rate of only 75%.

[0117] The above results demonstrate that the composite zinc anode constructed using the polymerization process of this invention, based on monomolecular in-situ polymerization, significantly enhances the functional integration and stability of the interface, thereby substantially improving the cycle life and electrochemical performance of the battery. Furthermore, although both Examples 1 and 4 completed 1000 cycles, their capacity retention differed by approximately 8%, indicating that the thickness of the modified layer has a controllable impact on performance. Based on the combination of liquid-phase film formation and in-situ polymerization, this invention can precisely control the thickness of the modified layer within the range of 10–1000 nm, while ensuring the uniform distribution of fullerene functional components in the polymer structure and avoiding the introduction of non-conductive additives, thus further optimizing the overall performance and lifespan of the battery.

Claims

1. A composite zinc anode based on monomolecular in-situ polymerization, characterized in that, It consists of a bottom zinc metal layer and a top decorative layer arranged sequentially from bottom to top; the bottom zinc metal layer is a zinc metal film; the top decorative layer is a fullerene-based polymer film.

2. The composite zinc anode based on monomolecular in-situ polymerization according to claim 1, characterized in that, The fullerene-based polymer film is a cross-linked network film obtained by intermolecular polymerization between fullerene molecules.

3. The composite zinc anode based on monomolecular in-situ polymerization according to claim 2, characterized in that, The fullerene-based molecule consists of a fullerene carbon cage portion, a bridging portion, and a terminal group portion, and its general structural formula is: The fullerene carbon cage portion is C 60 C 70 C 76 C 78 C 80 C 84 One of the following: the bridging part is at least one of chain-like and cyclic structures; the terminal part is at least one of alkenyl, alkynyl, carbonyl, ester, ether, thioether, amino, carboxyl, phosphorus nitrogen group, lactam group and lactone group that can undergo cross-linking polymerization; n1 is any integer between 1 and 3; n2 is any integer between 1 and 30.

4. A method for preparing a composite zinc anode based on monomolecular in-situ polymerization according to any one of claims 1 to 3, characterized in that, Includes the following steps: Step 1: Dissolve the fullerene molecules in a selected solvent to obtain a fullerene molecule solution; Step 2: Cut the purchased zinc sheet into pieces. After ultrasonic cleaning in acetone, place the cut zinc sheet in isopropanol for later use. Step 3: Using a liquid phase film formation method, the fullerene-based molecular solution is coated onto the cleaned bottom zinc metal layer surface; Step 4: Perform polymerization treatment on the coated bottom zinc metal layer to promote the polymerization of the fullerene molecular end groups, form the top fullerene polymer modification layer, and obtain the composite zinc anode.

5. The method for preparing a composite zinc anode based on monomolecular in-situ polymerization according to claim 4, characterized in that, The selected solvent in step one is at least one of the aromatic solvents such as benzene, anisole, chlorobenzene, o-dichlorobenzene, and toluene.

6. The method for preparing a composite zinc anode based on monomolecular in-situ polymerization according to claim 4, characterized in that, The concentration of the fullerene-based molecular solution in step one is 0.1~100 mg / mL.

7. The method for preparing a composite zinc anode based on monomolecular in-situ polymerization according to claim 5, characterized in that, The thickness of the top fullerene-based polymer modification layer formed in step four is 10~1000 nm.

8. The method for preparing a composite zinc anode based on monomolecular in-situ polymerization according to claim 5, characterized in that, The polymerization process in step four is an annealing process.

9. The method for preparing a composite zinc anode based on monomolecular in-situ polymerization according to claim 5, characterized in that, The polymerization process in step four is a radiation treatment.

10. The application of a composite zinc anode based on monomolecular in-situ polymerization according to any one of claims 1 to 3 in an aqueous zinc metal battery.

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