Cellulose nanocrystal-based artificial protective layer for zinc negative electrode and preparation method and application thereof

Abstract

This invention belongs to the field of zinc-ion battery technology, specifically relating to a cellulose nanocrystalline-based artificial protective layer for zinc anodes, its preparation method, and its application. This invention utilizes the good dispersion of cellulose nanocrystals (CNCs) in water, their inherent negative charge, and their ability to self-assemble through evaporation. MTC and CNCs are uniformly mixed and assembled into a layered structure with the aid of vacuum filtration, resulting in an MTC / CNC composite material for use in zinc anodes. This fully leverages the conductivity and abundant pore structure of MTC to effectively promote the desolvation process and create a uniform electric field, overcoming the shortcomings of CNCs as electrical insulators. Furthermore, the inherent negative charge and sulfonic acid groups of CNCs allow for the regulation of Zn... 2+ Deposition, uniform electric field, suppression of hydrogen evolution corrosion, and repulsion of SO4 2‑ This invention effectively prevents side reactions and significantly improves the cycle stability and coulombic efficiency of the zinc anode. It is low-cost, environmentally friendly, and its preparation process is simple, time-saving, and labor-saving, effectively solving the problems associated with zinc anodes.

Description

Technical Field

[0001] This invention belongs to the field of zinc-ion battery technology, specifically relating to a cellulose nanocrystalline-based zinc anode artificial protective layer, its preparation method, and its application. Background Technology

[0002] Aqueous zinc-ion batteries offer advantages such as high safety, low cost, and environmental friendliness, and have broad application prospects in large-scale energy storage and other fields. However, their commercialization is still severely constrained by the performance of the zinc anode, mainly manifested in uncontrollable zinc dendrite growth, severe hydrogen evolution, corrosion, and side reactions, resulting in short battery cycle life and low coulombic efficiency.

[0003] To improve the performance of zinc anodes, various strategies have been employed, including electrolyte regulation, structural design, separator modification, and anode surface modification. Among these, constructing an artificial protective layer on the zinc anode surface is considered a promising solution due to its ability to effectively regulate zinc deposition behavior, suppress side reactions, and relatively simple process. Cellulose nanocrystals (CNCs) are widely available and inexpensive, and their surface is rich in hydrophilic and zinc-loving oxygen-containing functional groups. Theoretically, this could enhance the water-locking capacity and zinc ion affinity of the protective layer, potentially guiding uniform zinc deposition and improving cycle stability.

[0004] However, existing cellulose-based protective layers still have the following problems in practical applications: Traditional cellulose materials (such as micron-sized cellulose fibers) are prone to forming macroscopic pores and gaps during film formation, making it difficult to achieve complete and effective coverage of water molecules and ion flow on the negative electrode surface. This leads to local electric field concentration, allowing zinc dendrites to still penetrate and grow, and water molecule contact triggers hydrogen evolution and corrosion reactions; Strong hydrogen bonding exists between cellulose molecular chains, which easily forms highly crystalline regions, resulting in a large number of oxygen-containing functional groups being buried and difficult to fully expose to the electrode interface, weakening its ability to uniformly induce zinc ion deposition; Cellulose itself is an electrically insulating material, and if it is used directly as a protective layer, it will significantly increase the interfacial impedance, hinder charge transport, and reduce the rate performance and electrochemical kinetics of the battery. Summary of the Invention

[0005] The purpose of this invention is to provide a cellulose nanocrystal-based artificial protective layer for zinc anodes, its preparation method, and its application, thereby overcoming the shortcomings of existing technologies. This invention combines carbon derived from *Tetrapanax papyriferus* with cellulose nanocrystals (CNC) to prepare an artificial protective layer, constructing a continuous and efficient electron transport channel and achieving a homogeneous distribution of the interfacial electric field. It can effectively regulate zinc ion flux and deposition kinetics, inducing uniform nucleation and dense deposition of zinc ions. Simultaneously, it suppresses zinc dendrite growth and side reactions at both the kinetic and interfacial structural levels, thereby significantly improving the interfacial stability and long-cycle performance of the zinc anode.

[0006] To achieve the above objectives, the technical solution of the present invention is as follows: In a first aspect, the present invention provides a cellulose nanocrystal-based zinc anode artificial protective layer, comprising a polymer matrix and a filler dispersed in the polymer matrix, wherein the filler is composed of carbon derived from Tetrapanax papyriferus and cellulose nanocrystals in a mass ratio of (1-2):(1-2); The carbon derived from Tetrapanax papyriferus and the cellulose nanocrystals are connected by a network of hydrogen bonds and van der Waals forces.

[0007] This invention uses a mixture of tetrapanax papyriferus-derived carbon and cellulose nanocrystals as a filler, forming a stable structure with hydrogen bonds and van der Waals forces in a polymer matrix. While retaining the zinc-loving properties of cellulose, it introduces conductive carbon materials to construct a rapid zinc ion transport channel. This effectively overcomes the problems of uneven zinc deposition and severe side reactions caused by the insulation and loose structure of traditional cellulose protective layers, achieving uniform protection of the zinc anode and significantly improving the cycle stability and rate performance of aqueous zinc-ion batteries.

[0008] In a second aspect, the present invention provides a method for preparing the cellulose nanocrystalline-based zinc anode artificial protective layer as described in the first aspect, comprising the following steps: The dried Tetrapanax papyriferus was cut into slices perpendicular to its growth direction, and after being acid-washed and water-washed until neutral, it was dried and ground to obtain precursor powder. The precursor powder was then carbonized under a protective atmosphere to obtain Tetrapanax papyriferus-derived carbon. Cellulose nanocrystals were dispersed in water, and carbon derived from Tetrapanax papyriferus was added and stirred to obtain a mixed dispersion. The dispersion was then filtered, dried, and ground to make a filler. The cellulose nanocrystalline zinc anode artificial protective layer is obtained by mixing and drying the filler, polymer matrix and N-methylpyrrolidone.

[0009] This invention combines carbon derived from Tetrapanax papyriferus with cellulose nanocrystals after pre-dispersion in solution and filtration. This allows the two materials to be tightly bound together through hydrogen bonding networks and van der Waals forces, forming a composite filler with both effectively exposed functional groups and a conductive network. This filler is then uniformly mixed with a polymer matrix to form a slurry. The resulting protective layer possesses both excellent ion affinity and conductivity, effectively solving a series of problems associated with traditional cellulose protective layers, such as loose structure, low accessibility of functional groups, and intrinsic insulation. The process is simple and easily scalable.

[0010] Thirdly, the present invention provides a zinc anode, comprising a zinc foil anode and a cellulose nanocrystalline-based zinc anode artificial protective layer as described in the first aspect, which is coated on the surface of the zinc foil anode.

[0011] By coating the zinc foil anode surface with a protective layer composed of carbon derived from tetrapanax papyriferus and cellulose nanocrystals, a stable and dense protective interface is constructed while retaining the zinc affinity of cellulose materials. This effectively inhibits the disordered growth of zinc dendrites and the occurrence of side reactions, significantly improving the cycle stability and rate performance of the anode.

[0012] Fourthly, this invention provides an aqueous zinc-ion battery, comprising the negative electrode and electrolyte described in the third aspect; the concentration of the electrolyte is 1-3 mol / L, and the amount added is 60-100 μL, wherein the electrolyte is an aqueous solution of zinc sulfate. This invention can achieve stable and uniform zinc deposition while effectively controlling the activity of water molecules at the interface and ion transport behavior, thereby significantly improving the battery's cycle life, coulombic efficiency, and rate performance.

[0013] The beneficial effects of this invention are: This invention uses the natural biomass material Tetrapanax papyriferus as a carbon source and combines it with biodegradable, environmentally friendly, and low-cost cellulose nanocrystals (CNC), embodying the concept of green and sustainable development. The preparation process requires no complex chemical reactions; material composites are achieved solely through carbonization and physical mixing based on an aqueous system, followed by vacuum filtration. The process is simple, process parameters are easy to control, and no cumbersome post-processing is needed, significantly reducing preparation costs and balancing economic efficiency and practicality.

[0014] The MTC / CNC composite artificial protective layer prepared by this invention fully leverages the synergistic advantages of MTC and CNC. On one hand, MTC, as a conductive framework, effectively improves the overall conductivity of the protective layer, promotes uniform electron transport at the interface and homogenization of the electric field distribution, which is beneficial for guiding Zn... 2+ Uniform deposition. On the other hand, the CNC surface is rich in zinc-loving and negatively charged functional groups such as hydroxyl and sulfonic acid groups, which can selectively adsorb Zn from the electrolyte. 2+ And it rejects SO4 2- Thus optimizing Zn 2+ The transport behavior and deposition kinetics of the zinc anode are studied. Their synergistic effect achieves dual homogenization of the electrode interface electric field and zinc ion flux, effectively suppressing zinc dendrite growth, hydrogen evolution reaction, and other harmful interfacial side reactions. This significantly improves the coulombic efficiency, deposition / dissolution reversibility, and long-term cycle stability of the battery. Attached Figure Description

[0015] The accompanying drawings, which form part of this invention, are used to provide a further understanding of the invention. The illustrative embodiments of the invention and their descriptions are used to explain the invention and do not constitute an improper limitation of the invention.

[0016] Figure 1 This is a schematic diagram of the MTC / CNC composite material preparation process in Example 1 of the present invention; Figure 2The images shown are SEM images of the MTC / CNC composite materials prepared in Examples 1-3 of this invention at different magnifications. Specifically, a is the SEM image of Example 1 at a scale of 10 μm, b is the SEM image of Example 1 at a scale of 2 μm, c is the SEM image of Example 2 at a scale of 10 μm, b is the SEM image of Example 2 at a scale of 2 μm, e is the SEM image of Example 3 at a scale of 10 μm, and f is the SEM image of Example 3 at a scale of 2 μm. Figure 3 This is a TEM image of the MTC / CNC composite material in Example 1 of the present invention; Figure 4 This is a TEM image of the MTC / CNC=2:1 composite material in Example 2 of the present invention; Figure 5 This is a TEM image of the MTC / CNC=1:2 composite material in Example 3 of the present invention; Figure 6 The graphs show the cycle performance of the zinc anodes prepared in Examples 1-3 and Comparative Examples 1-3 of this invention and the assembled zinc symmetric batteries. Figure 7 The graphs show the cycle performance of zinc-manganese batteries assembled from the negative electrodes obtained in Examples 1-3 and Comparative Examples 1-3 of this invention. Figure 8 The coulomb efficiency of the negative electrode assembly prepared in Examples 1-3 and Comparative Examples 1-3 of this invention; Figure 9 The infrared spectra of the MTC / CNC composite material and the MTC and CNC obtained in Examples 1-3 of this invention are shown. Figure 10 The zeta potential diagrams of the MTC / CNC composite material and CNC obtained in Examples 1-3 of this invention are shown. Detailed Implementation

[0017] Those skilled in the art will understand that the following embodiments are for illustrative purposes only and should not be construed as limiting the scope of the invention. Specific conditions not specified in the embodiments are performed under conventional conditions or conditions recommended by the manufacturer. Components not specifying their manufacturers are all commercially available conventional products. The method for preparing cellulose nanocrystals (CNC) is as follows: Cellulose pulp (17 g) was thoroughly pulverized in a grinder and then added to a 64 wt.% sulfuric acid solution (300 mL). The mixture was vigorously stirred at 45°C for 45 minutes. The hydrolysis reaction was terminated by dilution with 1.5 L of cold water. After standing overnight, a turbid layer formed at the bottom of the beaker, which was then purified by centrifugation at 10,000 rpm 2-3 times. The resulting white slurry was then redispersed in deionized water and dialyzed against deionized water for one week. The resulting dialyzed CNC suspension was further centrifuged at 10,000 rpm to remove large aggregates, and then sonicated in an ultrasonic cell disruptor (1800 W, 25% power) for 10 minutes to obtain a stable and well-dispersed suspension. Finally, the prepared CNC suspension was concentrated to a concentration of 2 wt.% at room temperature. The resulting nanocellulose suspension was then freeze-dried at -60°C and 0.1 mbar (under this pressure, the cellulose nanostructure is not affected) to obtain a powdered sample.

[0018] To address the problems of existing cellulose-based zinc anode protective layers, such as their porous structure (failing to completely isolate moisture and dendrite penetration), strong hydrogen bonds leading to functional group burial and hindering efficient zinc deposition, and the material's inherent insulation significantly increasing interfacial impedance and impairing rate performance, this invention utilizes CNC material prepared by sulfuric acid hydrolysis. The crystalline regions derived from cellulose possess extremely high mechanical strength and lightweight properties, effectively improving the strength of the artificial protective layer and thus effectively preventing layer cracking caused by zinc dendrite formation or unevenness. Furthermore, the abundant hydroxyl and sulfonic acid groups exposed on the CNC surface effectively attract Zn. 2+ Promote Zn 2+ Uniform deposition, especially the presence of sulfonic acid groups, can effectively repel SO4. 2- This mitigates the occurrence of side reactions. Furthermore, an MTC / CNC composite artificial protective layer for the zinc anode is prepared by combining MTC and CNC, constructing a continuous and efficient electron transport channel and achieving a homogenized distribution of the interfacial electric field. The synergistic effect between the two can effectively regulate zinc ion flux and deposition kinetics, inducing uniform nucleation and dense deposition of zinc ions. This simultaneously suppresses zinc dendrite growth and side reactions at both the kinetic and interfacial structural levels, thereby significantly improving the interfacial stability and long-cycle performance of the zinc anode.

[0019] In a first aspect, the present invention provides a cellulose nanocrystal-based zinc anode artificial protective layer, comprising a polymer matrix and a filler dispersed in the polymer matrix, wherein the filler is composed of carbon derived from Tetrapanax papyriferus and cellulose nanocrystals in a mass ratio of (1-2):(1-2); The carbon derived from Tetrapanax papyriferus and the cellulose nanocrystals are connected by a network of hydrogen bonds and van der Waals forces.

[0020] In some other embodiments, the polymer matrix comprises polyvinylidene fluoride; The filler content in the cellulose nanocrystalline zinc anode artificial protective layer is 80-90 wt%.

[0021] In some other embodiments, the carbon derived from Tetrapanax papyriferus has a micron-sized porous layered structure and contains oxygen-containing functional groups. The surface of the cellulose nanocrystals contains hydroxyl and sulfonic acid groups, and is negatively charged.

[0022] In a second aspect, the present invention provides a method for preparing the cellulose nanocrystalline-based zinc anode artificial protective layer as described in the first aspect, comprising the following steps: The dried *Tetrapanax papyrifer* was cut into slices perpendicular to its growth direction, then acid-washed and water-washed until neutral, dried and ground to obtain precursor powder. The precursor powder was then carbonized under a protective atmosphere to obtain *Tetrapanax papyrifer*-derived carbon.

[0023] Cellulose nanocrystals were dispersed in water, and carbon derived from tetrapanax papyriferus was added and stirred to obtain a mixed dispersion. After filtration, drying, and grinding, the mixture was made into a filler.

[0024] The filler, polymer matrix and N-methylpyrrolidone are mixed and dried to obtain the cellulose nanocrystalline zinc anode artificial protective layer.

[0025] In some other embodiments, the pickling is performed by washing with acid solution for 5-8 hours, and the carbonization treatment is carried out at a temperature of 800-1000℃ for 2-3 hours with a heating rate of 3-10℃ / min.

[0026] Specifically, the pickling is performed by washing with hydrochloric acid for 5, 6, 7 or 8 hours, the carbonization treatment is performed at a temperature of 800, 900 or 1000°C for 2 or 3 hours, and the heating rate is 3, 5, 8 or 10°C / min.

[0027] In some other embodiments, the preparation method of cellulose nanocrystals (CNC) includes the following steps: pulverizing cellulose wood pulp and adding it to a sulfuric acid solution for hydrolysis; after the hydrolysis reaction is complete, adding cold water to dilute and terminate the reaction, allowing it to settle and precipitate, then separating and purifying to obtain a white slurry; redispersing the white slurry in deionized water for dialysis until the system is neutral; centrifuging the dialyzed suspension to remove large particle aggregates, followed by ultrasonic treatment to obtain a stable CNC suspension; concentrating the CNC suspension and freeze-drying to obtain cellulose nanocrystals. Specifically, the concentration of the sulfuric acid solution is 60-70 wt%.

[0028] In some other embodiments, the mass ratio of the tetrapanax papyrifer-derived carbon to the cellulose nanocrystals is (1-2):(1-2); The mass ratio of the filler to the polymer matrix is ​​(8-9):1.

[0029] Thirdly, the present invention provides a zinc anode, comprising a zinc foil anode and a cellulose nanocrystalline-based zinc anode artificial protective layer as described in the first aspect, which is coated on the surface of the zinc foil anode.

[0030] In some other embodiments, the thickness of the cellulose nanocrystalline zinc anode artificial protective layer is 8-15 μm.

[0031] Fourthly, the present invention provides an aqueous zinc-ion battery, comprising the negative electrode and electrolyte described in the third aspect; the concentration of the electrolyte is 1~3 mol / L, the amount added is 60~100μL, and the electrolyte is an aqueous solution of zinc sulfate.

[0032] In other embodiments, the aqueous zinc-ion battery includes zinc-zinc symmetric batteries and zinc-manganese full batteries. Specifically, a zinc anode with a surface coated with a cellulose nanocrystalline zinc anode artificial protective layer can be assembled with a zinc salt electrolyte and a battery casing to form a zinc-zinc symmetric battery; or a zinc anode with a surface coated with a cellulose nanocrystalline zinc anode artificial protective layer can be assembled with a manganese dioxide cathode to form a zinc-manganese full battery.

[0033] More specifically, for symmetrical cells: zinc anodes with a cellulose nanocrystalline zinc anode artificial protective layer on their surface are used as positive and negative electrodes to assemble symmetrical cells; for full cell testing: zinc anodes with a cellulose nanocrystalline zinc anode artificial protective layer on their surface are used as positive electrodes, and MnO2 is used as positive electrodes; the assembly sequence for both symmetrical cells and full cell testing is: negative electrode shell, gasket, spring, negative electrode, glass fiber separator, positive electrode and positive electrode shell.

[0034] The solution of the present invention will be further described below with reference to specific embodiments: Example 1 This embodiment provides a cellulose nanocrystalline-based zinc anode artificial protective layer and its preparation method, such as... Figure 1 As shown, the specific steps include: (1) At room temperature, the dried Tetrapanax papyriferus is first cut into thin slices of uniform thickness (<1 mm) with a blade perpendicular to the growth direction. Then it is placed in a tube furnace and heated from room temperature to 900°C at a rate of 5°C / min under nitrogen atmosphere and held for 2 hours. The Tetrapanax papyriferus-derived carbon (MTC) is obtained after the furnace temperature drops to room temperature.

[0035] (2) First, 0.05g of CNC powder is evenly dispersed in water, then 0.05g of MTC is added and homogenized for 30 min, followed by sonication for 15 min to prepare a mixture. Then, the mixture is poured into a vacuum filtration device for vacuum filtration, and then dried in a vacuum dryer at 60℃ for 8 h. The dried material is then placed in an agate mortar and ground into a fine powder to obtain the prepared MTC / CNC composite material (marked as MTC / CNC=1:1).

[0036] (3) Preparation of zinc anode with MTC / CNC artificial protective layer: 0.01 g of PVDF binder was placed in a weighing bottle, and an appropriate amount of N-methylpyrrolidone (NMP) was added dropwise. The mixture was magnetically stirred for 30 min to obtain a transparent and uniform solution. After adding 0.09 g of MTC / CNC composite powder, the mixture was stirred for another 6 h to obtain a uniform slurry. A 30 μm thick zinc foil was placed on a glass plate. After cleaning the surface with anhydrous ethanol and lint-free paper, the slurry was uniformly coated onto the zinc foil surface (the purity of the zinc foil was not less than 99.9%, and the coating thickness was 100 μm). The coating was dried in an oven at 80℃ for 10 h to allow the solvent to evaporate completely, and finally a zinc anode with an artificial protective layer of about 10 μm thickness (MTC / CNC @ Zn, abbreviated as MCC11) was obtained.

[0037] (4) Preparation of electrolyte: Dissolve zinc sulfate heptahydrate (ZnSO4·7H2O) in deionized water to prepare a zinc sulfate electrolyte with a concentration of 2 mol / L.

[0038] (5) Preparation of positive electrode: Weigh 0.01 g of PVDF binder into a weighing bottle, add an appropriate amount of NMP dropwise, and stir magnetically for 30 min to obtain a transparent slurry. Then take 0.07 g of manganese dioxide (MnO2) powder and 0.02 g of conductive carbon black, mix and grind for 30 min, add to the above slurry and stir for 12 h to obtain a uniform black slurry. Use a 100 μm coating tool to coat the slurry onto a PE conductive film, and dry at 80℃ for 10 h to obtain a MnO2 positive electrode.

[0039] (6) Electrochemical performance testing: Symmetrical cell test: MTC / CNC @ Zn electrode sheets were cut into 1cm diameter circular pieces and used as positive and negative electrodes to assemble a symmetrical cell. The assembly sequence was: negative electrode shell, gasket, spring, negative electrode, glass fiber separator, positive electrode and positive electrode shell. Full cell test: MTC / CNC @ Zn electrode sheets and MnO2 positive electrode sheets were assembled into a full cell with the same structure as above.

[0040] Example 2 This embodiment provides a cellulose nanocrystalline-based zinc anode artificial protective layer and its preparation method, specifically including the following steps: (1) The preparation process of MTC is the same as in Example 1.

[0041] (2) In the preparation of the MTC / CNC composite material, the MTC / CNC ratio is 2:1. Specifically, the CNC powder is first uniformly dispersed in water, and then MTC with a mass of 2 times that of CNC is added and stirred for 30 min, followed by sonication for 15 min. Then, the uniformly dispersed aqueous dispersion is poured into a vacuum filtration device for vacuum filtration, and then dried in a vacuum dryer at 60°C for 8 h. The dried material is then placed in an agate mortar and ground into a fine powder, which is the prepared MTC / CNC (2:1) composite material.

[0042] (3) The preparation of the zinc anode with an artificial protective layer of MTC / CNC = 2:1 is the same as in the above example. Specifically, 0.01 g of polyvinylidene fluoride (PVDF) binder is placed in a weighing bottle, and an appropriate amount of N-methylpyrrolidone (NMP) is added dropwise. The mixture is magnetically stirred for 30 min to obtain a transparent and uniform solution. After adding 0.09 g of MTC / CNC=2:1 composite powder, stirring is continued for 6 h to obtain a uniform slurry. A 30 μm thick zinc foil is placed on a glass plate, and the surface is cleaned with anhydrous ethanol and lint-free paper. The slurry is then uniformly coated onto the zinc foil surface (the purity of the zinc foil is not less than 99.9%, and the coating thickness is 100 μm). The foil is dried in an oven at 80 °C for 10 h to allow the solvent to evaporate completely, and finally, a zinc anode with an artificial protective layer of about 10 μm thickness (MTC / CNC=2:1 @ Zn, abbreviated as MCC21) is obtained.

[0043] (4) Assemble the battery according to the same assembly steps: Assemble a zinc-manganese full cell with MTC / CNC=2:1 @ Zn as the negative electrode, MnO2 as the positive electrode, and 2mol / L ZnSO4 solution as the electrolyte; The symmetrical cell is composed of bare zinc as the positive and negative electrodes.

[0044] Example 3 This embodiment provides a cellulose nanocrystalline-based zinc anode artificial protective layer and its preparation method, specifically including the following steps: (1) The preparation process of MTC is the same as in Example 1.

[0045] (2) In the preparation of the MTC / CNC composite material, the MTC / CNC ratio is 1:2. Specifically, the CNC powder is first uniformly dispersed in water, and then 1 / 2 of the mass of CNC is added to MTC and stirred for 30 min, followed by sonication for 15 min. Then, the uniformly dispersed aqueous dispersion is poured into a vacuum filtration device for vacuum filtration, and then dried in a vacuum dryer at 60°C for 8 h. The dried material is then placed in an agate mortar and ground into a fine powder, which is the prepared MTC / CNC 1:2 composite material.

[0046] (3) Preparation of zinc anode with MTC / CNC=1:2 artificial protective layer: 0.01 g of polyvinylidene fluoride (PVDF) binder was placed in a weighing bottle, and an appropriate amount of N-methylpyrrolidone (NMP) was added dropwise. The mixture was magnetically stirred for 30 min to obtain a transparent and uniform solution. 0.09 g of MTC / CNC=1:2 composite powder was added and stirring was continued for 6 h to obtain a uniform slurry. A 30 μm thick zinc foil was placed on a glass plate, and the surface was cleaned with anhydrous ethanol and lint-free paper. The slurry was then uniformly coated onto the zinc foil surface (the purity of the zinc foil was not less than 99.9%, and the coating thickness was 100 μm). The foil was dried in an oven at 80℃ for 10 h to allow the solvent to evaporate completely, and finally a zinc anode with an artificial protective layer of about 10 μm thickness (MTC / CNC=1:2 @ Zn, abbreviated as MCC12) was obtained.

[0047] (4) Assemble the battery according to the same assembly steps: use MTC / CNC=1:2 @ Zn as the negative electrode, MnO2 as the positive electrode, and 2mol / L ZnSO4 solution as the electrolyte to assemble a zinc-manganese full cell; the symmetrical cell is composed of bare zinc as the positive and negative electrodes.

[0048] Comparative Example 1 This comparative example provides an artificial protective layer for a zinc anode and its preparation method, specifically including the following steps: (1) At room temperature, the dried Tetrapanax papyriferus is first cut into thin slices of uniform thickness (<1 mm) with a blade perpendicular to the growth direction. Then, it is placed in a tube furnace and heated from room temperature to 900°C at a rate of 5°C / min under nitrogen atmosphere and held at that temperature for 2 hours. The prepared MTC is then removed after the furnace temperature drops to room temperature.

[0049] (2) A slurry was prepared in the same ratio (MTC:PVDF = 9:1) and coated onto the surface of zinc foil. After drying at 80℃ for 10 h, an MTC@Zn negative electrode (coating thickness 10 μm) was obtained. A zinc-manganese full cell was assembled using this MTC@Zn as the negative electrode, MnO2 as the positive electrode, and 2 mol / L ZnSO4 solution as the electrolyte; the symmetrical cell was composed of MTC@Zn as the positive and negative electrodes.

[0050] Comparative Example 2 This comparative example provides an artificial protective layer for a zinc anode and its preparation method, specifically including the following steps: A 30 μm thick zinc foil, after cleaning, was used directly as the electrode and denoted as bare zinc (Bare Zn). The batteries were assembled using the same assembly steps: a zinc-manganese full cell was assembled using this bare zinc as the negative electrode, MnO2 as the positive electrode, and a 2 mol / L ZnSO4 solution as the electrolyte; the symmetrical cell consisted of bare zinc as both the positive and negative electrodes.

[0051] Comparative Example 3 Unlike Example 1, only CNC was used as the filler, and the other preparations were the same as in Example 1, resulting in an artificial protective zinc anode (CNC @ Zn, abbreviated as CNC) with a thickness of about 10 μm.

[0052] Performance testing Figure 9 The images show the infrared spectra of the MTC / CNC composite materials and the MTC and CNC obtained in Examples 1-3 of this invention. Figure 9 It can be seen that pure CNC is available in the range of 3200–3500 cm. -1 A strong and broad absorption peak appears at 1000–1100 cm⁻¹, which is attributed to the stretching vibration of the hydroxyl group (-OH) in the cellulose molecule. -1 The characteristic peaks at 1600–1750 cm⁻¹ correspond to the COC and CO stretching vibrations of cellulose, indicating that CNC possesses typical cellulose structural characteristics. Pure MTC exhibits peaks at 1600–1750 cm⁻¹. -1 The presence of a distinct carbonyl (C=O) characteristic absorption peak in the region reflects the structural characteristics of the matrix material. The infrared spectra of the MTC / CNC composites (MCC12, MCC11, MCC21) simultaneously contain the main characteristic absorption peaks of both CNC and MTC, indicating that the composite process did not significantly disrupt the basic chemical structures of the two components. Furthermore, the 3200–3500 cm⁻¹ region of the composite material exhibits... -1 The hydroxyl peak at the CNC surface showed a slight shift and broadening with the change in CNC content, indicating that hydrogen bond interactions were formed between the hydroxyl groups on the CNC surface and the MTC matrix. This proves that the two components are not simply physically mixed, but rather there is an interfacial interaction, which is beneficial to improving the interfacial compatibility of the composite material.

[0053] Figure 10 This is a zeta potential diagram of the MTC / CNC composite material and CNC obtained in Examples 1-3 of this invention. Figure 10 The zeta potential of pure CNC is -42.88 mV, which is relatively high in absolute value, indicating that its surface is rich in negative charges and it has excellent colloidal stability in the aqueous phase. The zeta potentials of the MTC / CNC composites (MCC21, MCC11, and MCC12) are -33.06 mV, -38.78 mV, and -39.97 mV, respectively. All of these are negative and their absolute values ​​are greater than the critical value of colloidal stability of 30 mV, indicating that the composites still have good aqueous dispersion stability. Compared with pure CNC, the absolute value of the zeta potential of the composites is slightly lower overall. This is due to the partial shielding effect of the inert MTC on the negative charge on the CNC surface, which also corresponds to the weakening of the hydroxyl peak intensity in the infrared spectrum.

[0054] SEM images of the product from Example 1 are shown below. Figure 2 As shown in Figures a and b, the composite material exhibits a relatively uniform blocky or sheet-like aggregate. The nanoscale fiber structure of CNC and the micron-scale porous sheets of MTC interweave to form a relatively dense yet still porous composite structure. At this ratio, the high specific surface area and abundant surface hydroxyl groups of CNC may interact with the functional groups on the surface of MTC through hydrogen bonds or van der Waals forces, promoting the compatibility and interfacial bonding between the two phases. This allows CNC to adhere to or embed in the pores of the MTC sheets, forming a relatively uniform composite.

[0055] Figure 3 TEM characterization of the material in Example 1 revealed that the widespread presence of oxygen and its high spatial correlation with carbon indicate that the CNC and MTC layers are not simply physically stacked. A dense network of hydrogen bonds and van der Waals forces likely formed between the numerous hydroxyl groups on the CNC surface and the oxygen-containing functional groups on the MTC surface. This effectively suppressed excessive self-aggregation of the CNC and disordered stacking of the MTC sheets, promoting the formation of these two interpenetrating networks.

[0056] In the symmetric cell testing system, at 1 mAh cm⁻¹ -1 and 1 mA cm -1 Under the test conditions, the MTC / CNC @ Zn symmetric cell can maintain a stable voltage plateau within 1600 h without significant polarization or fluctuations. In full cell cycling, it can still retain 91.6% of its capacity after 1000 cycles.

[0057] Depend on Figure 2 As can be seen from the CD, the composite material prepared in Example 2 is mainly composed of MTC, exhibiting more obvious open pores and blocky lamellar stacking morphology. The overall structure is relatively loose, and the aggregation tendency of MTC itself leads to the formation of a porous structure with MTC as the skeleton. Figure 2 As can be seen from ef in Example 3, when the CNC content is dominant, the morphology of the composite material is dominated by CNC. Due to its high aspect ratio, high specific surface area, and strong hydrophilicity, CNC is easy to self-assemble through hydrogen bonds and van der Waals forces when in excess, forming an entangled nanofiber network. The MTC sheets are dispersed in this network or encapsulated by CNC, and their original macroscopic morphology of the sheets is no longer significant.

[0058] The amount of CNC added has a significant impact on the morphology of the composite material. Figure 4 and Figure 5 This demonstrates that adding too much or too little CNC has an adverse effect on the composite material. For example, from Example 2... Figure 4 It is evident that when too little CNC is added, the carbon flakes of the MTC are exposed, and the attached CNC is insufficient to completely cover the carbon flakes. Therefore, it can be inferred that adding too little CNC cannot achieve uniform carbon dispersion in the water; Example 3 Figure 5 It is evident that adding too much CNC will cause the CNC to agglomerate on the carbon sheet, making it impossible to uniformly coat the carbon sheet, thus affecting the properties of the composite material.

[0059] In summary, the addition of CNC to regulate morphology mainly stems from the competitive interaction between oxygen-containing functional groups on the surfaces of CNC and MTC and the spatial competition of their own morphological characteristics. The content of CNC directly determines the density and continuity of the hydrogen bond network in the system, thereby regulating the final phase structure: from continuous carbon skeleton to interpenetration between the two, and then to continuous cellulose network morphology changes.

[0060] like Figures 6-8 The battery performance of the examples and comparative examples is shown in Table 1. Specific performance characterization data are shown in Table 1.

[0061] Table 1 Performance Characterization

[0062] The above are merely preferred embodiments of the present invention and are not intended to limit the present invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A cellulose nanocrystalline-based zinc anode artificial protective layer, characterized in that, It includes a polymer matrix and a filler dispersed in the polymer matrix, wherein the filler is composed of carbon derived from Tetrapanax papyriferus and cellulose nanocrystals in a mass ratio of (1-2):(1-2); The carbon derived from Tetrapanax papyriferus and the cellulose nanocrystals are connected by a network of hydrogen bonds and van der Waals forces.

2. The cellulose nanocrystalline zinc anode artificial protective layer according to claim 1, characterized in that, The polymer matrix includes polyvinylidene fluoride; The filler content in the cellulose nanocrystalline zinc anode artificial protective layer is 80-90 wt%.

3. The cellulose nanocrystalline zinc anode artificial protective layer according to claim 1, characterized in that, The carbon derived from Tetrapanax papyrifer has a micron-sized porous layered structure and contains oxygen-containing functional groups. The surface of the cellulose nanocrystals contains hydroxyl and sulfonic acid groups, and is negatively charged.

4. A method for preparing a cellulose nanocrystalline zinc anode artificial protective layer according to any one of claims 1-3, characterized in that, Includes the following steps: The dried Tetrapanax papyriferus was cut into slices perpendicular to its growth direction, and after being acid-washed and water-washed until neutral, it was dried and ground to obtain precursor powder. The precursor powder was then carbonized under a protective atmosphere to obtain Tetrapanax papyriferus-derived carbon. Cellulose nanocrystals were dispersed in water, and carbon derived from Tetrapanax papyriferus was added and stirred to obtain a mixed dispersion. The dispersion was then filtered, dried, and ground to make a filler. The cellulose nanocrystalline zinc anode artificial protective layer is obtained by mixing and drying the filler, polymer matrix and N-methylpyrrolidone.

5. The method for preparing the cellulose nanocrystalline zinc anode artificial protective layer according to claim 4, characterized in that, The pickling process involves washing with acid solution for 5-8 hours, and the carbonization treatment is carried out at a temperature of 800-1000℃ for 2-3 hours with a heating rate of 3-10℃ / min.

6. The method for preparing the cellulose nanocrystalline-based zinc anode artificial protective layer according to claim 4, characterized in that, The mass ratio of the carbon derived from Tetrapanax papyriferus to cellulose nanocrystals is (1-2):(1-2); The mass ratio of the filler to the polymer matrix is ​​(8-9):

1.

7. A zinc negative electrode, characterized in that, The artificial protective layer for the cellulose nanocrystalline zinc anode as described in any one of claims 1-3 includes a zinc foil anode and its surface coating.

8. The zinc negative electrode according to claim 7, characterized in that, The thickness of the artificial protective layer for the cellulose nanocrystalline zinc anode is 8-15 μm.

9. An aqueous zinc-ion battery, characterized in that, It includes the negative electrode and electrolyte as described in claim 7 or 8; the concentration of the electrolyte is 1~3 mol / L, the amount added is 60~100μL, and the electrolyte is an aqueous solution of zinc sulfate.

10. The aqueous zinc-ion battery according to claim 8, characterized in that, The aqueous zinc-ion battery includes zinc-zinc symmetric cells and zinc-manganese full cells.

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