Electrolyte and zinc ion battery

Abstract

The invention relates to the technical field of aqueous zinc ion batteries, in particular to an electrolyte and a zinc ion battery. The electrolyte comprises water, a zinc salt and a cellulose-based material. Wherein the zinc salt is dissolved in water, and the molar concentration range of the zinc salt in the electrolyte is 1M-2M; the average polymerization degree range of the cellulose-based material is 2-1000, the surface of the cellulose-based material is charged, and the mass concentration range of the cellulose-based material in the electrolyte is 0.1-100 mg / mL. The zinc ion battery composed of the electrolyte provided by the invention can realize a good low-temperature anti-freezing effect, so that the zinc ion battery can still work stably in a low-temperature environment; and the growth of dendritic crystals in the zinc negative electrode can be effectively inhibited, and the service life and the overall performance of the zinc ion battery are further improved. In addition, the zinc ion battery also has the characteristics of low cost, high safety, environmental friendliness and the like.

Description

Technical Field

[0001] This invention relates to the field of aqueous zinc-ion battery technology, specifically to an electrolyte and a zinc-ion battery. Background Technology

[0002] As the global energy transition moves towards low-carbon development, energy storage technology plays a crucial role in the large-scale application of renewable energy. Compared to traditional lithium-ion batteries, aqueous zinc-ion batteries offer greater advantages in terms of safety and environmental friendliness. Furthermore, aqueous zinc-ion batteries (ZIBs) have become a hot topic in research and development due to their low cost, environmental friendliness, and high theoretical specific capacity.

[0003] However, since water's freezing point is 0°C, the viscosity of electrolytes in traditional aqueous zinc-ion batteries tends to increase at low temperatures. Furthermore, freezing occurs below 0°C, reducing the conductivity of zinc ions in the electrolyte and even preventing their effective migration, thus significantly degrading the battery's charge-discharge performance. These issues severely limit the performance of aqueous zinc-ion batteries at low temperatures, particularly regarding the electrolyte's antifreeze properties, restricting their application in cold regions. Currently, those skilled in the art are attempting to improve the low-temperature performance of zinc-ion battery electrolytes by adding high-concentration electrolytes, hydrogels, or antifreeze agents. However, most of these methods suffer from high costs, environmental unfriendliness, or poor chemical stability.

[0004] In addition to the above, zinc-ion batteries also suffer from the problem of zinc dendrite growth on the anode. The growth of zinc dendrites can lead to internal short circuits and capacity decay, negatively impacting the performance and safety of the zinc-ion battery. Currently, methods such as surface modification or the addition of additives are used to alter the properties of the electrolyte and regulate the kinetics of zinc ion deposition, thereby suppressing dendrite growth. However, these methods have limited effectiveness in suppressing dendrite growth on the zinc anode and can negatively affect the long-term stability of the battery. Summary of the Invention

[0005] To address the above problems, this invention provides an electrolyte and a zinc-ion battery that can ensure the zinc-ion battery maintains its basic performance under low-temperature conditions while solving the dendrite growth problem of its zinc electrode to a certain extent.

[0006] The first aspect of the present invention provides an electrolyte comprising water, a zinc salt and a cellulose-based material, wherein the zinc salt is dissolved in the water and the molar concentration of the zinc salt in the electrolyte ranges from 1M to 2M; the cellulose-based material has an average degree of polymerization ranging from 2 to 1000 and is surface-charged, and the mass concentration of the cellulose-based material in the electrolyte ranges from 0.1 to 100 mg / mL.

[0007] Alternatively, the zinc salt may be one or more combinations of zinc trifluoromethanesulfonate, zinc sulfate, zinc perchlorate, and zinc chloride.

[0008] Optionally, the functional groups in the cellulose-based material include one or a combination of ester groups and amino groups.

[0009] Optionally, the cellulose-based material is one or more combinations of cellulose, 2,3-epoxypropyltrimethylammonium chloride modified cellulose, phosphorylated cellulose, sulfated cellulose, carboxymethylated cellulose, tetramethylpiperidine oxide oxidized cellulose, nitrocellulose, citric acid modified cellulose, acrylic acid modified cellulose, and pyridine modified cellulose.

[0010] Optionally, the average degree of polymerization of the cellulose-based material ranges from 2 to 600.

[0011] Optionally, the mass concentration of the cellulose-based material in the electrolyte ranges from 0.1 to 10 mg / mL.

[0012] A second aspect of the present invention provides a zinc-ion battery comprising a positive electrode, a negative electrode, a separator, and the electrolyte described above.

[0013] Optionally, the positive electrode includes:

[0014] Positive current collector; and

[0015] The positive electrode active material is made of ammonium intercalated vanadium oxide.

[0016] Optionally, the negative electrode is made of zinc; the separator is made of glass fiber.

[0017] This invention, by adding a specific type of cellulose-based material to the electrolyte of a zinc-ion battery, not only inhibits ice crystal formation and controls morphology at low temperatures, but also effectively regulates the electrolyte structure and expands the liquid region within the electrolyte at low temperatures. This ensures uniform deposition and migration of zinc ions, maintaining the normal operation of the zinc-ion battery. Furthermore, it enhances the transport efficiency of zinc ions, significantly improving the capacity and cycle performance of aqueous zinc-ion batteries. In addition, the electrolyte provided by this invention is economical and environmentally friendly, exhibiting good biodegradability and environmental friendliness, and its manufacturing process is convenient and reliable. Moreover, by adding cellulose-based materials with different average degrees of polymerization, surface charges, and chemical group modifications to the electrolyte, this invention enables the electrolyte to achieve different antifreeze effects, allowing zinc-ion batteries composed of this electrolyte to meet the performance requirements of various application scenarios. Attached Figure Description

[0018] Figure 1 This is a flowchart illustrating the preparation process of an electrolyte containing a specific type of cellulose-based material, provided by an embodiment of the present invention.

[0019] Figure 2 These are ice crystal morphology diagrams of pure water and aqueous solutions of cellulose-based materials provided in Examples 1-6, respectively, in the embodiments of the present invention.

[0020] Figure 3 This is a graph showing the growth rate of ice crystals at different cooling temperatures, formed by pure water in Comparative Example 1 and aqueous solutions of cellulose-based materials provided in Examples 2-6, respectively, in an embodiment of the present invention.

[0021] Figure 4 These are morphological images of ice crystals recrystallized from pure water and aqueous solutions of cellulose-based materials provided in Examples 1-6, respectively, in embodiments of the present invention.

[0022] Figure 5 This is a bar chart showing the average maximum grain size (MLGS) after recrystallization of ice crystals formed by pure water in Comparative Example 1 and aqueous solutions of cellulose-based materials provided in Examples 1-6, respectively, in an embodiment of the present invention.

[0023] Figure 6 This is a long-term cyclic charge-discharge specific capacity curve of a zinc-ion battery composed of the electrolytes provided in Comparative Example 1 and Example 2 in an embodiment of the present invention.

[0024] Figure 7 This is a scanning electron microscope image of the zinc negative electrode of a zinc-ion battery composed of the electrolytes provided in Comparative Example 1 and Example 2, according to an embodiment of the present invention. Detailed Implementation

[0025] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0026] Unless otherwise stated or in case of contradiction, the terms or phrases used herein shall have the following meanings:

[0027] Ice recrystallization inhibition (IRI) refers to the ability of a specific substance (such as antifreeze proteins, modified polymers, oligosaccharides, etc.) to inhibit or slow down the ice recrystallization process under low temperature conditions.

[0028] Zeta potential refers to the potential difference at the shear plane between the surface of colloidal particles and the surrounding dispersion medium (usually a liquid) in a colloidal dispersion system; it is also called "electrokinetic potential".

[0029] In this document, when referring to numerical ranges, unless otherwise specified, the distribution of selectable values ​​within a numerical range is considered continuous, including the two endpoints of the range (i.e., the minimum and maximum values), and every value between these two endpoints. When multiple numerical ranges are provided to describe a feature or property, these numerical ranges can be combined.

[0030] The first aspect of this embodiment provides an electrolyte comprising water, a zinc salt, and a cellulose-based material. The zinc salt is dissolved in the water, and its molar concentration in the electrolyte ranges from 1M to 2M. The cellulose-based material has an average degree of polymerization ranging from 2 to 1000 and carries a surface charge; its mass concentration in the electrolyte ranges from 0.1 to 100 mg / mL.

[0031] In this embodiment, when the zinc salt is completely dissolved in water, it releases a large number of active zinc ions. These zinc ions serve as the main source of charge carriers in the electrolyte, participating in redox reactions occurring at the positive and negative electrodes through migration within the electrolyte, thereby achieving charge transfer and energy conversion. The electrolyte formed in this way is an aqueous zinc ion electrolyte.

[0032] In electrolytes, ionic conductivity, a key indicator of ion migration capability, determines the charge transport efficiency of the electrolyte, as well as the energy conversion efficiency and system stability of the zinc-ion battery. The ionic conductivity of the electrolyte is related to the zinc salt concentration. If the zinc salt concentration is too low, zinc ions migrate freely in the electrolyte with a high diffusion coefficient, but the overall migration rate of zinc ions is limited due to the low number of charge carriers. Conversely, if the zinc salt concentration is too high, the viscosity of the electrolyte increases sharply, hindering the migration of zinc ions and resulting in a decrease in ionic conductivity. Considering the impact of zinc salt concentration on the electrolyte and other performance aspects of the zinc-ion battery composed of the electrolyte, in this embodiment, the molar concentration range of zinc salt in the electrolyte is 1M-2M. More preferably, the molar concentration range of zinc salt in the electrolyte is 1M.

[0033] To ensure the zinc salt dissolves quickly and completely in water and exhibits good chemical stability after dissolution, the zinc salt selected in this embodiment includes one or more combinations of zinc trifluoromethanesulfonate, zinc sulfate, zinc perchlorate, and zinc chloride. The zinc ions generated by these zinc salts provide high ionic conductivity to the electrolyte, while the generated anions can also suppress side reactions in the electrolyte to some extent. Furthermore, the above-mentioned zinc salts are all commercially available and inexpensive, thus reducing the manufacturing cost of zinc-ion batteries. In other embodiments, other types of zinc salts besides those mentioned above can be selected based on the actual application scenario and performance requirements of the electrolyte; no specific limitations are imposed here.

[0034] To address the potential issues of increased electrolyte viscosity and even freezing in aqueous zinc-ion batteries used at low temperatures, as well as the possible growth of zinc anode dendrites, this embodiment addresses these problems to some extent by adding cellulose-based materials to the electrolyte. The presence of hydroxyl groups in cellulose's chemical structure allows for stronger interactions with water molecules through hydrogen bonds, reducing the number of free water molecules in the electrolyte. Simultaneously, the hydrated sugar clusters formed by the combination of cellulose and water molecules further reduce the diffusion coefficient of water molecules, thereby inhibiting the formation and growth of ice crystals and dendrites, ensuring the normal migration of zinc ions within the electrolyte.

[0035] To enable cellulose-based materials to dissolve more effectively in aqueous electrolytes, allowing small cellulose molecules to rapidly and extensively bind to water molecules under strong hydration, thereby forming a uniform and stable dispersion system in the electrolyte, in this embodiment, based on NMR and mass spectrometry test results, the average degree of polymerization of the selected cellulose-based material ranges from 2 to 1000. If the average degree of polymerization of the cellulose-based material is too low, it indicates that the individual molecule size is too small and the number of hydroxyl groups is limited, making it difficult to form continuous hydrogen bond structures. This results in weak hydration between the cellulose-based material and water molecules, making it difficult to effectively suppress the freezing phenomenon of the aqueous electrolyte at low temperatures and the dendrite growth of the zinc anode in zinc-ion batteries. Conversely, if the average degree of polymerization of the cellulose-based material is too high, it indicates that the cellulose molecular chains are too long, potentially leading to problems such as molecular chain entanglement and local aggregation, resulting in a decrease in the effective surface area for contacting water molecules, thus reducing the antifreeze activity of the cellulose-based material in the electrolyte. In some embodiments provided in this embodiment, it is more preferably that the average degree of polymerization of the cellulose-based material ranges from 2 to 600. In the embodiments provided in this embodiment, the addition of a cellulose-based material with an average polymerization of 6 to the electrolyte exhibits excellent antifreeze effect and inhibition of zinc anode dendrite growth.

[0036] To further improve the antifreeze properties of the electrolyte containing cellulose-based materials and enhance the transport efficiency of zinc ions, in this embodiment, the mass concentration of the cellulose-based material in the electrolyte ranges from 0.1 to 100 mg / mL. More preferably, its mass concentration ranges from 0.1 to 10 mg / mL.

[0037] To enable water molecules in the electrolyte to form a more stable interaction with cellulose molecules, in addition to utilizing the hydroxyl groups inherent in cellulose molecules to form hydrogen bonds with water molecules, in some embodiments provided in this example, other highly hydrophilic groups can be introduced into the cellulose molecular chain through chemical modification, so that the functional groups in the cellulose-based material include one or a combination of ester groups and amino groups. In some embodiments provided in this example, the modified cellulose materials formed by introducing ester groups or amino groups include 2,3-epoxypropyltrimethylammonium chloride modified cellulose, phosphorylated cellulose, sulfated cellulose, tetramethylpiperidine oxide oxidized cellulose, and carboxymethylated cellulose. The specific functional groups introduced can be selected according to the requirements of different antifreeze performance and inhibition of zinc anode dendrite growth in the actual application scenarios of aqueous zinc-ion batteries. In other embodiments, the cellulose-based materials also include cellulose, nitrocellulose, citric acid modified cellulose, acrylic acid modified cellulose, and pyridine modified cellulose. In other embodiments, the cellulose-based material added to the electrolyte may be one or more of the cellulose-based materials mentioned above, or other types of cellulose-based materials, without specific limitations.

[0038] For ions, the higher the charge density, the easier it is for them to remain at the ice-water interface, resulting in higher ice recrystallization inhibition (IRI) activity. However, in this embodiment, the test results of zeta potential and IRI activity of the cellulose-based material provided in the comparative examples show that the effect of charged groups on ice crystal recrystallization differs from that of ions. Cellulose-based materials with higher surface charge density exhibit lower IRI activity, while cellulose with lower surface charge density exhibits significant IRI activity.

[0039] A second aspect of the present invention also provides a zinc-ion battery, comprising a positive electrode, a negative electrode, a separator, and the electrolyte provided in this embodiment. During the charging and discharging process, zinc ions repeatedly insert and extract between the positive and negative electrode. The separator is disposed between the positive and negative electrode to provide isolation, and the electrolyte conducts ions between the positive and negative electrode.

[0040] In this embodiment, the positive electrode of the zinc-ion battery includes a positive current collector and a positive active material. The positive current collector acts as a carrier for electron conduction, conducting electrons generated by the active material out of or into the external circuit. Typically, the positive current collector is made of a material with good conductivity and mechanical strength; no specific limitations are imposed here. In this embodiment, titanium foil is preferably used as the positive current collector, and ammonium intercalated vanadium oxide is preferably used as the positive active material. Furthermore, the negative electrode of the zinc-ion battery is preferably made of pure zinc, and the separator is preferably made of glass fiber.

[0041] The technical solution of the present invention will be described in detail below through specific embodiments and comparative examples. Unless otherwise stated, the raw materials and reagents used in the following embodiments are all commercially available products, or can be prepared by conventional methods in the art, and the instruments used in the embodiments are all commercially available.

[0042] Figure 1 This is a flowchart illustrating the preparation process of an electrolyte containing cellulose-based materials according to an embodiment of this invention. First, high molecular weight cellulose is hydrolyzed. Through different cellulose modification methods, the resulting cellulose-based materials exhibit different degrees of polymerization, different surface charges, and different chemical groups. By adding different cellulose-based materials to the electrolyte and utilizing the density differences of their binding sites on the ice crystal surface, the antifreeze properties of the electrolyte can be controllably adjusted.

[0043] The types and properties of the cellulose-based materials prepared in the different groups of examples and comparative examples are specifically referred to in Table 1.

[0044] Example 1

[0045] This embodiment provides an electrolyte for assembling zinc-ion batteries. The preparation process of the zinc salt solution used in this electrolyte is as follows:

[0046] Add 3.6353g of zinc trifluoromethanesulfonate (ZOTf) to 10mL of ultrapure water and sonicate for 15min to ensure that the zinc salt is completely dissolved in the water.

[0047] The preparation method of the cellulose-based material added to the electrolyte is as follows:

[0048] (1) Add 20g of α-cellulose to a beaker containing 200g of 96% sulfuric acid while stirring. This process is carried out in an ice bath.

[0049] (2) The solution obtained above was placed in an oven at 40°C for 2 hours for hydrolysis reaction, and finally the hydrolyzed cellulose sulfuric acid solution was obtained.

[0050] (3) The hydrolyzed cellulose sulfuric acid solution was mixed with an equal mass of water, stored at 4°C for 24 hours, and then centrifuged to obtain cellulose precipitate A.

[0051] (4) The cellulose precipitate A was washed until neutral and then freeze-dried to obtain the product, namely sulfated cellulose A, which has an average degree of polymerization of 20 and a Zeta potential of -20.1mV.

[0052] After the zinc salt solution and sulfated cellulose A were prepared, 5 mg of sulfated cellulose A was added to the zinc salt solution, and the mixture was sonicated for another 30 minutes to obtain the electrolyte of this embodiment.

[0053] Example 2

[0054] Similar to the zinc salt solution provided in Example 1, the method for preparing the cellulose-based material added to the zinc salt solution is as follows:

[0055] (1) Take out the supernatant of the mixed solution centrifuged in step (3) of the preparation of cellulose-based material in Example 1, mix it with three times the volume of isopropanol, store it at 4°C for 24 hours, and then centrifuge it again to obtain cellulose precipitate B.

[0056] (2) The cellulose precipitate B was washed until neutral and then freeze-dried to obtain the product, namely sulfated cellulose B, which has an average degree of polymerization of 6 and a Zeta potential of -17.6mV.

[0057] Add 5 mg of sulfated cellulose B to the zinc salt solution and continue sonication for 30 min to obtain the electrolyte of this embodiment.

[0058] Example 3

[0059] Similar to the zinc salt solution provided in Example 1, the method for preparing the cellulose-based material added to the zinc salt solution is as follows:

[0060] (1) Add 20g of α-cellulose to a beaker containing 380g of 83% phosphoric acid while stirring. Dissolve the above solution at 60°C for 5 minutes, stirring with a glass rod. Repeat this process several times until the solution becomes clear and transparent.

[0061] (2) Hydrolyze in an oven at 60℃ for 8 hours to obtain a hydrolyzed cellulose phosphoric acid solution;

[0062] (3) The hydrolyzed cellulose phosphoric acid solution was mixed with an equal mass of water, stored at 4°C for 24 h, and then centrifuged to obtain cellulose precipitate C with an average degree of polymerization of 20. The supernatant was mixed with three times the volume of isopropanol, stored at 4°C for 24 h, and then centrifuged to obtain precipitate D.

[0063] (4) Take out more than 1g of the cellulose precipitate C obtained in step (3) into a beaker, then add 11g of 77% NaOH aqueous solution and stir at room temperature for 30 minutes;

[0064] (5) Add 2.81 g of 2,3-epoxypropyltrimethylammonium chloride (EPTMAC) to the solution obtained in step (4) and react for 5 hours in a water bath at 65°C.

[0065] (6) The solution obtained in step (5) is washed with water until neutral, and then freeze-dried to obtain the product, namely 2,3-epoxypropyltrimethylammonium chloride modified cellulose, whose average degree of polymerization is still 20 and whose Zeta potential is 11.7mV.

[0066] Add 5 mg of 2,3-epoxypropyltrimethylammonium chloride-modified cellulose to the zinc salt solution and continue sonication for 30 min to obtain the electrolyte of this embodiment.

[0067] Example 4

[0068] Similar to the zinc salt solution provided in Example 1, the method for preparing the cellulose-based material added to the zinc salt solution is as follows:

[0069] (1) Take 1g of cellulose precipitate C prepared in step (3) of Example 3, disperse it in a beaker containing 100mL of water, then add 0.016g of tetramethylpiperidine oxide (TEMPO) and 0.1g of NaBr, and stir until TEMPO is completely dissolved;

[0070] (2) Add 15 mL of saturated NaClO solution to the solution after completing step (1) above, and then adjust the pH of the solution to 10 with 12 M HCl under stirring at 150 rpm.

[0071] (3) As the reaction proceeds, the pH of the above mixed solution decreases continuously. Under stirring at 150 rpm, 0.5 M NaOH solution is added dropwise to the solution to maintain its pH at 10. After reacting for 1 hour, a small amount of ethanol is added to terminate the reaction.

[0072] (4) The product was obtained by centrifugation and washing with ethanol four times and drying at 60°C. The product was tetramethylpiperidine oxide oxidized cellulose with an average degree of polymerization of 20 and a zeta potential of -27.5mV.

[0073] Add 5 mg of tetramethylpiperidine oxide to the zinc salt solution and continue sonication for 30 min to obtain the electrolyte of this embodiment.

[0074] Example 5

[0075] Similar to the zinc salt solution provided in Example 1, the method for preparing the cellulose-based material added to the zinc salt solution is as follows:

[0076] (1) Take out 1g of cellulose precipitate C prepared in step (3) of Example 3, transfer it to a glass bottle with a cap and add 15mL of isopropanol, then add 1.5mL of 20% NaOH aqueous solution and stir magnetically at room temperature for 1 hour;

[0077] (2) Add 0.46g of chloroacetic acid to the glass bottle, then seal it with a parafilm membrane and react at 55°C for 3 hours;

[0078] (3) Add 30 ml of ethanol to the solution after completing step (2), and then neutralize the solution to neutral with acetic acid;

[0079] (4) Add 3 times the volume of isopropanol to the solution after completing step (3), and then wash the precipitated solid by centrifugation with ethanol 4 times. After drying at 60°C, the product, namely carboxymethyl cellulose A, is obtained. Its average degree of polymerization is 20 and its Zeta potential is -21.4mV.

[0080] 5 mg of carboxymethyl cellulose A was added to the zinc salt solution, and the mixture was sonicated for another 30 minutes to obtain the electrolyte of this embodiment.

[0081] Example 6

[0082] Similar to the zinc salt solution provided in Example 1, the cellulose-based material added to the zinc salt solution is selected as high molecular weight carboxymethyl cellulose B, with an average degree of polymerization of 600 and a Zeta potential of -59.25mV.

[0083] Comparative Example 1

[0084] Similar to the zinc salt solution provided in Example 1, no cellulose-based materials were added, and the zinc salt solution was used directly as the electrolyte.

[0085] Compare with Example 1

[0086] This Comparative Example 1 contains only pure water and is used to compare the freezing process and ice crystal morphology of pure water with an aqueous solution (10 mg / mL) prepared from the cellulose-based materials in Examples 1-6.

[0087] Table 1. Types and properties of cellulose-based materials in different groups of examples and comparative examples

[0088]

[0089]

[0090] The electrolytes from Examples 1 to 6 and Comparative Example 1 were used in the preparation of zinc-ion batteries.

[0091] In this embodiment of the invention, the zinc-ion battery includes a positive electrode, a negative electrode, a separator located between the positive and negative electrodes, and an electrolyte. The preparation method of the zinc-ion battery in this embodiment of the invention is as follows:

[0092] (1) Preparation of the positive electrode sheet:

[0093] 1 g of NH4VO3 was placed in a tube furnace at 300 °C and calcined for 2 h under argon atmosphere to obtain black powder NH4. + -V₂O₅. (The NH₄) + V₂O₅, Super P, and polyvinylidene fluoride (PVDF) were added to a mortar in a ratio of 7:2:1 and ground for 15 minutes. After grinding, 260 μL of N-methylpyrrolidone (NMP) was added, and grinding was continued for another 15 minutes to obtain a black slurry, which is the positive electrode active material. The slurry was evenly coated onto a 15 μm thick titanium foil using a 60 μm coater and dried in an oven at 80 °C for 12 hours to obtain the positive electrode sheet. The sheet was cut into 12 mm diameter circles for later use. The positive electrode active material loading was 0.75–1.25 mg / cm³. 2 .

[0094] (2) Preparation of negative electrode sheet:

[0095] Commercial zinc sheets with a thickness of 100 μm were cut into 12 mm circles, ultrasonically washed with isopropanol for 15 min, and then air-dried for later use.

[0096] (3) Preparation of electrolyte:

[0097] 3.6353 g of zinc trifluoromethanesulfonate (ZOTf) was added to 10 mL of ultrapure water and sonicated for 15 min to ensure complete dissolution of the zinc salt. After complete dissolution, 5 mg of the cellulose-based material provided in Examples 1-5 was added, and sonication was continued for 30 min to obtain the cellulose-based modified electrolyte.

[0098] (4) Preparation of zinc-ion batteries:

[0099] The CR2032 model negative electrode battery casing, spring sheet, gasket, negative electrode plate, glass fiber separator, positive electrode plate, and positive electrode battery casing are assembled sequentially, and finally packaged using a button cell battery packaging machine to obtain a button cell battery for battery performance testing. 75 μL of the electrolyte provided in Examples 1-6 is dropped onto the glass fiber.

[0100] The modification morphology and grain size of ice crystals by the cellulose-based materials provided in Examples 1-6 were monitored, and the performance of zinc-ion batteries assembled using the electrolytes provided in Examples 1-6 and Comparative Example 1 were tested. The monitoring and test results are detailed in [link to relevant documentation]. Figures 2-7The testing method is as follows:

[0101] (1) Evaluation of antifreeze performance:

[0102] The cellulose-based materials provided in Examples 1-6 were dissolved in pure water to form a 10 mg / mL aqueous solution of the cellulose-based materials. Nanoliter-level aqueous solutions of the cellulose-based materials provided in Examples 1-6 were injected into the silicone oil of the sample holder using a microsyringe equipped with a capillary tube. The solution was then rapidly cooled to freeze the droplets, followed by slow heating to allow the droplets to melt gradually. When only a small ice crystal remained, the temperature was adjusted to maintain this small ice crystal for 20 seconds without growth or melting. This temperature was recorded as the melting point temperature (T0). m Then the temperature is lowered to a target temperature (T). f That is, the degree of subcooling ΔT = T m -T f The entire process was observed and recorded using a high-speed camera, capturing the morphology and growth rate of the ice crystals. A control example (Example 1) using pure water as the test subject was also included in the experiment.

[0103] Figure 2 The morphological characteristics of individual ice crystals are shown in untreated water and in pure water after modification with equal amounts of the cellulose-based materials provided in Examples 1-6. The cellulose-based materials can selectively adsorb onto the ice crystal surface through hydrogen bonding or hydrophobic interactions, disrupting the inherent hexagonal crystal system symmetry growth path of pure water during freezing. Specifically, the ice crystal growth mechanism is as follows: the adsorbed cellulose-based material molecules cover the active growth sites of the ice crystals (such as edges, crystal faces, etc.), thereby inducing the ice crystals to grow in thermodynamically unfavorable directions, forming non-equilibrium morphologies such as forked structures. Therefore, the more non-circular the ice crystal morphology, i.e., the more the growth rate is inhibited, the stronger the antifreeze activity of the cellulose-based material. (Reference) Figure 2 Comparing the growth morphology of ice crystals, Example 6 showed the most significant regulation of ice crystal structure, exhibiting the most obvious asymmetric and non-circular characteristics. Furthermore, compared to the regular circular ice crystals formed in the pure water system, Examples 1-5 showed locally protruding structures, indicating that the cellulose-based antifreeze agent had been adsorbed onto the ice crystal surface to a certain extent and had a regulatory effect on its morphology.

[0104] Figure 3 The ice crystal growth rate of pure water and 10 mg / mL cellulose-based material aqueous solutions from Examples 1-6 were compared under different supercooling conditions. Linear fitting of the data revealed that the ice crystal growth rate in pure water was 434.92 μm·s. -1 ·℃ -1 The growth rate of Example 5 decreased significantly to 198.14 μm·s. -1 ·℃ -1This indicates that it has the strongest inhibitory ability on ice crystal growth. In addition, the growth rates of Examples 2-4 and Example 6 are also lower than those of the pure water system in Control Example 1, further verifying the effectiveness of the cellulose-based aqueous solution in antifreeze and its ability to significantly reduce the ice crystal growth rate.

[0105] (2) Evaluation of Ice Recrystallization Inhibition (IRI):

[0106] A square glass slide was fixed on a cooling stage, which was pre-cooled to -60°C. A 10 μL aqueous solution of cellulose-based material (10 mg / mL) was dropped onto the glass slide from a height of 1.4 meters. The temperature was rapidly increased to -10°C, and the slide was annealed at -10°C for 30 minutes. Then, the ice crystal size was observed and photographed using an optical microscope equipped with a digital camera (OLYMPUS, model BX63). Image processing was performed using ImageJ software, and the ten largest ice crystal sizes (longest length on any axis) were measured from each photograph. The experiment was repeated three times, and the average value was calculated to obtain the Mean Largest Grain Size (MLGS).

[0107] Figure 4 The image shows the recrystallization morphology of ice crystals formed by pure water in Comparative Example 1 and an aqueous solution (10 mg / mL) of cellulose-based material prepared from the cellulose-based materials provided in Examples 1-6. Figure 5 This is a bar chart for quantitative analysis of the crystal size formed by recrystallization of pure water (Comparative Example 1) and an aqueous solution (10 mg / mL) of cellulose-based material prepared from the cellulose-based materials provided in Examples 1-6. The average maximum crystal size (MLGS) is used as the evaluation index; a smaller MLGS indicates a stronger ability to inhibit recrystallization, i.e., higher ice crystal recrystallization inhibition (IRI) activity.

[0108] Combination Figure 4 and Figure 5 A comparison of the recrystallization morphology and grain size of pure water in Examples 1-6 and Control Example 1 revealed that the grains in pure water exhibited relatively regular hexagonal crystals with a MLGS of 121.87 ± 11.62 μm, indicating that ice crystals easily grow freely in the absence of cellulose-based materials. In contrast, the MLGS of the grains in Examples 1-5 were all reduced, and the recrystallization morphology exhibited irregular morphologies such as fragmented nanocrystals or fractal dendrites. This demonstrates that after adding cellulose-based materials to water, the cellulose-based materials can effectively adsorb onto the surface of ice crystals, restricting the rearrangement and growth of crystals, thereby significantly reducing the ice crystal size and giving the solution high IRI activity. Especially under low concentration conditions, a significant grain refinement effect can still be observed, further verifying that the cellulose-based materials prepared in Examples 1-5 have excellent inhibitory effects on ice crystal recrystallization.

[0109] (2) Low-temperature performance evaluation of aqueous zinc-ion batteries:

[0110] All full-cell performance tests were conducted in a LAND CT3002A 5V system under the following conditions: current density 1 A / g and charge / discharge voltage window 0.2–1.6 V. All low-temperature tests were performed in a high / low temperature and humidity chamber (SME-64PF-70, -70–150℃). After battery operation, the battery was disassembled using a tablet press and the full-cell assembly was removed. The zinc anode was then extracted for scanning electron microscopy to observe its surface morphology after battery operation.

[0111] Figure 6 The graphs show the long-term charge-discharge specific capacity of aqueous zinc-ion batteries assembled using the electrolytes provided in Example 2 and Comparative Example 1, respectively. (Reference) Figure 6 The test results shown indicate that, in Comparative Example 1, the electrolyte without cellulose-based material was not added, and the aqueous zinc-ion battery composed of this electrolyte rapidly failed at -30°C due to electrolyte freezing. However, in the electrolyte provided in Example 2, with the addition of cellulose-based material at a mass concentration of 0.5 mg / mL, the zinc-ion battery composed of this electrolyte exhibited excellent low-temperature performance at -30°C. Specifically, the zinc-ion battery composed of the electrolyte in Example 2 could cycle for over 2500 times (approximately 45 days) at a current density of 1 A / g.

[0112] Figure 7 Scanning electron microscopy (SEM) images of the zinc anode of aqueous zinc-ion batteries assembled with the electrolytes provided in Example 2 and Comparative Example 1, respectively, are shown after 20 hours of operation. The comparison reveals that the aqueous zinc-ion battery using the electrolyte without added cellulose-based material (Comparative Example 1) develops a large number of dendrites on the zinc anode after 20 hours of operation, significantly reducing battery life and affecting battery performance. In contrast, the zinc-ion battery using the electrolyte with added cellulose-based material (Example 2) shows significantly suppressed dendrite growth on the zinc anode after 20 hours of operation, exhibiting a relatively smooth surface. This indicates that the cellulose-based material can effectively modify the zinc anode, thereby mitigating battery short circuits caused by zinc dendrites and optimizing battery performance.

[0113] The above are merely preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. An electrolyte, characterized in that, include: water; A zinc salt, dissolved in water, wherein the molar concentration of the zinc salt in the electrolyte is in the range of 1M-2M; The cellulose-based material has an average degree of polymerization ranging from 2 to 1000 and is surface-charged. The mass concentration of the cellulose-based material in the electrolyte ranges from 0.1 to 100 mg / mL.

2. The electrolyte according to claim 1, characterized in that, The zinc salt is one or more combinations of zinc trifluoromethanesulfonate, zinc sulfate, zinc perchlorate, and zinc chloride.

3. The electrolyte according to claim 1, characterized in that, The functional groups in the cellulose-based material include one or a combination of two of ester groups and amino groups.

4. The electrolyte according to claim 1, characterized in that, The cellulose-based material is one or more combinations of cellulose, 2,3-epoxypropyltrimethylammonium chloride modified cellulose, phosphorylated cellulose, sulfated cellulose, carboxymethylated cellulose, tetramethylpiperidine oxide oxidized cellulose, nitrocellulose, citric acid modified cellulose, acrylic acid modified cellulose, and pyridine modified cellulose.

5. The electrolyte according to claim 1, characterized in that, The average degree of polymerization of the cellulose-based material ranges from 2 to 600.

6. The electrolyte according to claim 1, characterized in that, The mass concentration of the cellulose-based material in the electrolyte ranges from 0.1 to 10 mg / mL.

7. A zinc-ion battery, characterized in that, The zinc-ion battery includes a positive electrode, a negative electrode, a separator, and an electrolyte as described in any one of claims 1 to 6.

8. The zinc-ion battery according to claim 7, characterized in that, The positive electrode sheet includes: Positive current collector; and The positive electrode active material is ammonium intercalated vanadium oxide.

9. The zinc-ion battery according to claim 7, characterized in that, The negative electrode is made of zinc; the separator is made of glass fiber.

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